649 files changed, 125255 insertions, 0 deletions

diff --git a/toolkit/components/extensions/test/browser/.eslintrc.js b/toolkit/components/extensions/test/browser/.eslintrc.js
new file mode 100644
index 0000000000..ef228570e3
--- /dev/null
+++ b/toolkit/components/extensions/test/browser/.eslintrc.js
@@ -0,0 +1,11 @@
+"use strict";
+
+module.exports = {
+  env: {
+    webextensions: true,
+  },
+
+  rules: {
+    "no-shadow": "off",
+  },
+};
diff --git a/toolkit/components/extensions/test/browser/browser-serviceworker.ini b/toolkit/components/extensions/test/browser/browser-serviceworker.ini
new file mode 100644
index 0000000000..58e9082f7b
--- /dev/null
+++ b/toolkit/components/extensions/test/browser/browser-serviceworker.ini
@@ -0,0 +1,9 @@
+[DEFAULT]
+support-files =
+  head_serviceworker.js
+  data/**
+
+prefs =
+  extensions.backgroundServiceWorker.enabled=true
+
+[browser_ext_background_serviceworker.js]
diff --git a/toolkit/components/extensions/test/browser/browser.ini b/toolkit/components/extensions/test/browser/browser.ini
new file mode 100644
index 0000000000..a26e73ee37
--- /dev/null
+++ b/toolkit/components/extensions/test/browser/browser.ini
@@ -0,0 +1,56 @@
+[DEFAULT]
+support-files =
+  head.js
+  data/**
+
+[browser_ext_background_serviceworker_pref_disabled.js]
+[browser_ext_downloads_filters.js]
+[browser_ext_downloads_referrer.js]
+https_first_disabled = true
+[browser_ext_eventpage_disableResetIdleForTest.js]
+[browser_ext_extension_page_tab_navigated.js]
+[browser_ext_management_themes.js]
+skip-if = verify
+[browser_ext_process_crash_handling.js]
+skip-if = !crashreporter
+[browser_ext_test_mock.js]
+[browser_ext_themes_additional_backgrounds_alignment.js]
+[browser_ext_themes_alpha_accentcolor.js]
+[browser_ext_themes_arrowpanels.js]
+[browser_ext_themes_autocomplete_popup.js]
+[browser_ext_themes_chromeparity.js]
+[browser_ext_themes_dynamic_getCurrent.js]
+[browser_ext_themes_dynamic_onUpdated.js]
+[browser_ext_themes_dynamic_updates.js]
+[browser_ext_themes_experiment.js]
+[browser_ext_themes_findbar.js]
+[browser_ext_themes_getCurrent_differentExt.js]
+[browser_ext_themes_highlight.js]
+[browser_ext_themes_incognito.js]
+[browser_ext_themes_lwtsupport.js]
+[browser_ext_themes_multiple_backgrounds.js]
+[browser_ext_themes_ntp_colors.js]
+[browser_ext_themes_ntp_colors_perwindow.js]
+[browser_ext_themes_pbm.js]
+[browser_ext_themes_persistence.js]
+[browser_ext_themes_reset.js]
+[browser_ext_themes_sanitization.js]
+[browser_ext_themes_separators.js]
+[browser_ext_themes_sidebars.js]
+[browser_ext_themes_static_onUpdated.js]
+[browser_ext_themes_tab_line.js]
+[browser_ext_themes_tab_loading.js]
+[browser_ext_themes_tab_selected.js]
+[browser_ext_themes_tab_text.js]
+[browser_ext_themes_theme_transition.js]
+[browser_ext_themes_toolbar_fields.js]
+[browser_ext_themes_toolbar_fields_focus.js]
+[browser_ext_themes_toolbarbutton_colors.js]
+[browser_ext_themes_toolbarbutton_icons.js]
+[browser_ext_themes_toolbars.js]
+[browser_ext_themes_warnings.js]
+[browser_ext_thumbnails_bg_extension.js]
+support-files = !/toolkit/components/thumbnails/test/head.js
+[browser_ext_webNavigation_eventpage.js]
+[browser_ext_webRequest_redirect_mozextension.js]
+[browser_ext_windows_popup_title.js]
diff --git a/toolkit/components/extensions/test/browser/browser_ext_background_serviceworker.js b/toolkit/components/extensions/test/browser/browser_ext_background_serviceworker.js
new file mode 100644
index 0000000000..153818f4de
--- /dev/null
+++ b/toolkit/components/extensions/test/browser/browser_ext_background_serviceworker.js
@@ -0,0 +1,285 @@
+/* -*- Mode: indent-tabs-mode: nil; js-indent-level: 2 -*- */
+/* vim: set sts=2 sw=2 et tw=80: */
+"use strict";
+
+/* globals getBackgroundServiceWorkerRegistration, waitForServiceWorkerTerminated */
+
+Services.scriptloader.loadSubScript(
+  new URL("head_serviceworker.js", gTestPath).href,
+  this
+);
+
+add_task(assert_background_serviceworker_pref_enabled);
+
+add_task(async function test_serviceWorker_register_guarded_by_pref() {
+  // Test with backgroundServiceWorkeEnable set to true and the
+  // extensions.serviceWorkerRegist.allowed pref set to false.
+  // NOTE: the scenario with backgroundServiceWorkeEnable set to false
+  // is part of "browser_ext_background_serviceworker_pref_disabled.js".
+
+  await SpecialPowers.pushPrefEnv({
+    set: [["extensions.serviceWorkerRegister.allowed", false]],
+  });
+
+  let extensionData = {
+    files: {
+      "page.html": "<!DOCTYPE html><script src='page.js'></script>",
+      "page.js": async function () {
+        browser.test.assertEq(
+          undefined,
+          navigator.serviceWorker,
+          "navigator.serviceWorker should be undefined"
+        );
+        browser.test.sendMessage("test-serviceWorker-register-disallowed");
+      },
+      "sw.js": "",
+    },
+  };
+
+  let extension = ExtensionTestUtils.loadExtension(extensionData);
+  await extension.startup();
+
+  // Verify that an extension page can't register a moz-extension url
+  // as a service worker.
+  await BrowserTestUtils.withNewTab(
+    {
+      gBrowser,
+      url: `moz-extension://${extension.uuid}/page.html`,
+    },
+    async () => {
+      await extension.awaitMessage("test-serviceWorker-register-disallowed");
+    }
+  );
+
+  await extension.unload();
+
+  await SpecialPowers.popPrefEnv();
+
+  // Test again with the pref set to true.
+
+  await SpecialPowers.pushPrefEnv({
+    set: [["extensions.serviceWorkerRegister.allowed", true]],
+  });
+
+  extension = ExtensionTestUtils.loadExtension({
+    files: {
+      ...extensionData.files,
+      "page.js": async function () {
+        try {
+          await navigator.serviceWorker.register("sw.js");
+        } catch (err) {
+          browser.test.fail(
+            `Unexpected error on registering a service worker: ${err}`
+          );
+          throw err;
+        } finally {
+          browser.test.sendMessage("test-serviceworker-register-allowed");
+        }
+      },
+    },
+  });
+  await extension.startup();
+
+  // Verify that an extension page can register a moz-extension url
+  // as a service worker if enabled by the related pref.
+  await BrowserTestUtils.withNewTab(
+    {
+      gBrowser,
+      url: `moz-extension://${extension.uuid}/page.html`,
+    },
+    async () => {
+      await extension.awaitMessage("test-serviceworker-register-allowed");
+    }
+  );
+
+  await extension.unload();
+
+  await SpecialPowers.popPrefEnv();
+});
+
+add_task(async function test_cache_api_allowed() {
+  // Verify that Cache API support for moz-extension url availability is
+  // conditioned only by the extensions.backgroundServiceWorker.enabled pref.
+  // NOTE: the scenario with backgroundServiceWorkeEnable set to false
+  // is part of "browser_ext_background_serviceworker_pref_disabled.js".
+  const extension = ExtensionTestUtils.loadExtension({
+    async background() {
+      try {
+        let cache = await window.caches.open("test-cache-api");
+        browser.test.assertTrue(
+          await window.caches.has("test-cache-api"),
+          "CacheStorage.has should resolve to true"
+        );
+
+        // Test that adding and requesting cached moz-extension urls
+        // works as well.
+        let url = browser.runtime.getURL("file.txt");
+        await cache.add(url);
+        const content = await cache.match(url).then(res => res.text());
+        browser.test.assertEq(
+          "file content",
+          content,
+          "Got the expected content from the cached moz-extension url"
+        );
+
+        // Test that deleting the cache storage works as expected.
+        browser.test.assertTrue(
+          await window.caches.delete("test-cache-api"),
+          "Cache deleted successfully"
+        );
+        browser.test.assertTrue(
+          !(await window.caches.has("test-cache-api")),
+          "CacheStorage.has should resolve to false"
+        );
+      } catch (err) {
+        browser.test.fail(`Unexpected error on using Cache API: ${err}`);
+        throw err;
+      } finally {
+        browser.test.sendMessage("test-cache-api-allowed");
+      }
+    },
+    files: {
+      "file.txt": "file content",
+    },
+  });
+
+  await extension.startup();
+  await extension.awaitMessage("test-cache-api-allowed");
+  await extension.unload();
+});
+
+function createTestSWScript({ postMessageReply }) {
+  return `
+    self.onmessage = msg => {
+      dump("Background ServiceWorker - onmessage handler\\n");
+      msg.ports[0].postMessage("${postMessageReply}");
+      dump("Background ServiceWorker - postMessage\\n");
+    };
+    dump("Background ServiceWorker - executed\\n");
+  `;
+}
+
+async function testServiceWorker({ extension, expectMessageReply }) {
+  // Verify that the WebExtensions framework has successfully registered the
+  // background service worker declared in the extension manifest.
+  const swRegInfo = getBackgroundServiceWorkerRegistration(extension);
+
+  // Activate the background service worker by exchanging a message
+  // with it.
+  await BrowserTestUtils.withNewTab(
+    {
+      gBrowser,
+      url: `moz-extension://${extension.uuid}/page.html`,
+    },
+    async browser => {
+      let msgFromV1 = await SpecialPowers.spawn(
+        browser,
+        [swRegInfo.scriptURL],
+        async url => {
+          const { active } = await content.navigator.serviceWorker.ready;
+          const { port1, port2 } = new content.MessageChannel();
+
+          return new Promise(resolve => {
+            port1.onmessage = msg => resolve(msg.data);
+            active.postMessage("test", [port2]);
+          });
+        }
+      );
+
+      Assert.deepEqual(
+        msgFromV1,
+        expectMessageReply,
+        "Got the expected reply from the extension service worker"
+      );
+    }
+  );
+}
+
+function loadTestExtension({ version }) {
+  const postMessageReply = `reply:sw-v${version}`;
+
+  return ExtensionTestUtils.loadExtension({
+    useAddonManager: "temporary",
+    manifest: {
+      version,
+      background: {
+        service_worker: "sw.js",
+      },
+      browser_specific_settings: { gecko: { id: "test-bg-sw@mochi.test" } },
+    },
+    files: {
+      "page.html": "<!DOCTYPE html><body></body>",
+      "sw.js": createTestSWScript({ postMessageReply }),
+    },
+  });
+}
+
+async function assertWorkerIsRunningInExtensionProcess(extension) {
+  // Activate the background service worker by exchanging a message
+  // with it.
+  await BrowserTestUtils.withNewTab(
+    {
+      gBrowser,
+      url: `moz-extension://${extension.uuid}/page.html`,
+    },
+    async browser => {
+      const workerScriptURL = `moz-extension://${extension.uuid}/sw.js`;
+      const workerDebuggerURLs = await SpecialPowers.spawn(
+        browser,
+        [workerScriptURL],
+        async url => {
+          await content.navigator.serviceWorker.ready;
+          const wdm = Cc[
+            "@mozilla.org/dom/workers/workerdebuggermanager;1"
+          ].getService(Ci.nsIWorkerDebuggerManager);
+
+          return Array.from(wdm.getWorkerDebuggerEnumerator())
+            .map(wd => {
+              return wd.url;
+            })
+            .filter(swURL => swURL == url);
+        }
+      );
+
+      Assert.deepEqual(
+        workerDebuggerURLs,
+        [workerScriptURL],
+        "The worker should be running in the extension child process"
+      );
+    }
+  );
+}
+
+add_task(async function test_background_serviceworker_with_no_ext_apis() {
+  const extensionV1 = loadTestExtension({ version: "1" });
+  await extensionV1.startup();
+
+  const swRegInfo = getBackgroundServiceWorkerRegistration(extensionV1);
+  const { uuid } = extensionV1;
+
+  await assertWorkerIsRunningInExtensionProcess(extensionV1);
+  await testServiceWorker({
+    extension: extensionV1,
+    expectMessageReply: "reply:sw-v1",
+  });
+
+  // Load a new version of the same addon and verify that the
+  // expected worker script is being executed.
+  const extensionV2 = loadTestExtension({ version: "2" });
+  await extensionV2.startup();
+  is(extensionV2.uuid, uuid, "The extension uuid did not change as expected");
+
+  await testServiceWorker({
+    extension: extensionV2,
+    expectMessageReply: "reply:sw-v2",
+  });
+
+  await Promise.all([
+    extensionV2.unload(),
+    // test extension v1 wrapper has to be unloaded explicitly, otherwise
+    // will be detected as a failure by the test harness.
+    extensionV1.unload(),
+  ]);
+  await waitForServiceWorkerTerminated(swRegInfo);
+  await waitForServiceWorkerRegistrationsRemoved(extensionV2);
+});
diff --git a/toolkit/components/extensions/test/browser/browser_ext_background_serviceworker_pref_disabled.js b/toolkit/components/extensions/test/browser/browser_ext_background_serviceworker_pref_disabled.js
new file mode 100644
index 0000000000..0194cd237f
--- /dev/null
+++ b/toolkit/components/extensions/test/browser/browser_ext_background_serviceworker_pref_disabled.js
@@ -0,0 +1,126 @@
+/* -*- Mode: indent-tabs-mode: nil; js-indent-level: 2 -*- */
+/* vim: set sts=2 sw=2 et tw=80: */
+"use strict";
+
+add_task(async function assert_background_serviceworker_pref_disabled() {
+  is(
+    WebExtensionPolicy.backgroundServiceWorkerEnabled,
+    false,
+    "Expect extensions.backgroundServiceWorker.enabled to be false"
+  );
+});
+
+add_task(async function test_background_serviceworker_disallowed() {
+  const id = "test-disallowed-worker@test";
+
+  const extensionData = {
+    manifest: {
+      background: {
+        service_worker: "sw.js",
+      },
+      applicantions: { gecko: { id } },
+      useAddonManager: "temporary",
+    },
+  };
+
+  SimpleTest.waitForExplicitFinish();
+  let waitForConsole = new Promise(resolve => {
+    SimpleTest.monitorConsole(resolve, [
+      {
+        message:
+          /Reading manifest: Error processing background: background.service_worker is currently disabled/,
+      },
+    ]);
+  });
+
+  const extension = ExtensionTestUtils.loadExtension(extensionData);
+  await Assert.rejects(
+    extension.startup(),
+    /startup failed/,
+    "Startup failed with background.service_worker while disabled by pref"
+  );
+
+  SimpleTest.endMonitorConsole();
+  await waitForConsole;
+});
+
+add_task(async function test_serviceWorker_register_disallowed() {
+  // Verify that setting extensions.serviceWorkerRegist.allowed pref to false
+  // doesn't allow serviceWorker.register if backgroundServiceWorkeEnable is
+  // set to false
+
+  await SpecialPowers.pushPrefEnv({
+    set: [["extensions.serviceWorkerRegister.allowed", true]],
+  });
+
+  let extensionData = {
+    files: {
+      "page.html": "<!DOCTYPE html><script src='page.js'></script>",
+      "page.js": async function () {
+        try {
+          await navigator.serviceWorker.register("sw.js");
+          browser.test.fail(
+            `An extension page should not be able to register a serviceworker successfully`
+          );
+        } catch (err) {
+          browser.test.assertEq(
+            String(err),
+            "SecurityError: The operation is insecure.",
+            "Got the expected error on registering a service worker from a script"
+          );
+        }
+        browser.test.sendMessage("test-serviceWorker-register-disallowed");
+      },
+      "sw.js": "",
+    },
+  };
+
+  let extension = ExtensionTestUtils.loadExtension(extensionData);
+  await extension.startup();
+
+  // Verify that an extension page can't register a moz-extension url
+  // as a service worker.
+  await BrowserTestUtils.withNewTab(
+    {
+      gBrowser,
+      url: `moz-extension://${extension.uuid}/page.html`,
+    },
+    async () => {
+      await extension.awaitMessage("test-serviceWorker-register-disallowed");
+    }
+  );
+
+  await extension.unload();
+
+  await SpecialPowers.popPrefEnv();
+});
+
+add_task(async function test_cache_api_disallowed() {
+  // Verify that Cache API support for moz-extension url availability is also
+  // conditioned by the extensions.backgroundServiceWorker.enabled pref.
+  const extension = ExtensionTestUtils.loadExtension({
+    async background() {
+      try {
+        const cache = await window.caches.open("test-cache-api");
+        let url = browser.runtime.getURL("file.txt");
+        await browser.test.assertRejects(
+          cache.add(url),
+          new RegExp(`Cache.add: Request URL ${url} must be either`),
+          "Got the expected rejections on calling cache.add with a moz-extension:// url"
+        );
+      } catch (err) {
+        browser.test.fail(`Unexpected error on using Cache API: ${err}`);
+        throw err;
+      } finally {
+        browser.test.sendMessage("test-cache-api-disallowed");
+      }
+    },
+    files: {
+      "file.txt": "file content",
+    },
+  });
+
+  await extension.startup();
+  await extension.awaitMessage("test-cache-api-disallowed");
+  await extension.unload();
+});
diff --git a/toolkit/components/extensions/test/browser/browser_ext_downloads_filters.js b/toolkit/components/extensions/test/browser/browser_ext_downloads_filters.js
new file mode 100644
index 0000000000..18d68d2061
--- /dev/null
+++ b/toolkit/components/extensions/test/browser/browser_ext_downloads_filters.js
@@ -0,0 +1,138 @@
+/* -*- Mode: indent-tabs-mode: nil; js-indent-level: 2 -*- */
+/* vim: set sts=2 sw=2 et tw=80: */
+
+"use strict";
+
+async function testAppliedFilters(ext, expectedFilter, expectedFilterCount) {
+  let tempDir = FileUtils.getDir(
+    "TmpD",
+    [`testDownloadDir-${Math.random()}`],
+    true
+  );
+
+  let filterCount = 0;
+
+  let MockFilePicker = SpecialPowers.MockFilePicker;
+  MockFilePicker.init(window);
+  MockFilePicker.displayDirectory = tempDir;
+  MockFilePicker.returnValue = MockFilePicker.returnCancel;
+  MockFilePicker.appendFiltersCallback = function (fp, val) {
+    const hexstr = "0x" + ("000" + val.toString(16)).substr(-3);
+    filterCount++;
+    if (filterCount < expectedFilterCount) {
+      is(val, expectedFilter, "Got expected filter: " + hexstr);
+    } else if (filterCount == expectedFilterCount) {
+      is(val, MockFilePicker.filterAll, "Got all files filter: " + hexstr);
+    } else {
+      is(val, null, "Got unexpected filter: " + hexstr);
+    }
+  };
+  MockFilePicker.showCallback = function (fp) {
+    const filename = fp.defaultString;
+    info("MockFilePicker - save as: " + filename);
+  };
+
+  let manifest = {
+    description: ext,
+    permissions: ["downloads"],
+  };
+
+  const extension = ExtensionTestUtils.loadExtension({
+    manifest: manifest,
+
+    background: async function () {
+      let ext = chrome.runtime.getManifest().description;
+      await browser.test.assertRejects(
+        browser.downloads.download({
+          url: "http://any-origin/any-path/any-resource",
+          filename: "any-file" + ext,
+          saveAs: true,
+        }),
+        "Download canceled by the user",
+        "expected request to be canceled"
+      );
+      browser.test.sendMessage("canceled");
+    },
+  });
+
+  await extension.startup();
+  await extension.awaitMessage("canceled");
+  await extension.unload();
+
+  is(
+    filterCount,
+    expectedFilterCount,
+    "Got correct number of filters: " + filterCount
+  );
+
+  MockFilePicker.cleanup();
+
+  tempDir.remove(true);
+}
+
+// Missing extension
+add_task(async function testDownload_missing_All() {
+  await testAppliedFilters("", null, 1);
+});
+
+// Unrecognized extension
+add_task(async function testDownload_unrecognized_All() {
+  await testAppliedFilters(".xxx", null, 1);
+});
+
+// Recognized extensions
+add_task(async function testDownload_html_HTML() {
+  await testAppliedFilters(".html", Ci.nsIFilePicker.filterHTML, 2);
+});
+
+add_task(async function testDownload_xhtml_HTML() {
+  await testAppliedFilters(".xhtml", Ci.nsIFilePicker.filterHTML, 2);
+});
+
+add_task(async function testDownload_txt_Text() {
+  await testAppliedFilters(".txt", Ci.nsIFilePicker.filterText, 2);
+});
+
+add_task(async function testDownload_text_Text() {
+  await testAppliedFilters(".text", Ci.nsIFilePicker.filterText, 2);
+});
+
+add_task(async function testDownload_jpe_Images() {
+  await testAppliedFilters(".jpe", Ci.nsIFilePicker.filterImages, 2);
+});
+
+add_task(async function testDownload_tif_Images() {
+  await testAppliedFilters(".tif", Ci.nsIFilePicker.filterImages, 2);
+});
+
+add_task(async function testDownload_webp_Images() {
+  await testAppliedFilters(".webp", Ci.nsIFilePicker.filterImages, 2);
+});
+
+add_task(async function testDownload_xml_XML() {
+  await testAppliedFilters(".xml", Ci.nsIFilePicker.filterXML, 2);
+});
+
+add_task(async function testDownload_aac_Audio() {
+  await testAppliedFilters(".aac", Ci.nsIFilePicker.filterAudio, 2);
+});
+
+add_task(async function testDownload_mp3_Audio() {
+  await testAppliedFilters(".mp3", Ci.nsIFilePicker.filterAudio, 2);
+});
+
+add_task(async function testDownload_wma_Audio() {
+  await testAppliedFilters(".wma", Ci.nsIFilePicker.filterAudio, 2);
+});
+
+add_task(async function testDownload_avi_Video() {
+  await testAppliedFilters(".avi", Ci.nsIFilePicker.filterVideo, 2);
+});
+
+add_task(async function testDownload_mp4_Video() {
+  await testAppliedFilters(".mp4", Ci.nsIFilePicker.filterVideo, 2);
+});
+
+add_task(async function testDownload_xvid_Video() {
+  await testAppliedFilters(".xvid", Ci.nsIFilePicker.filterVideo, 2);
+});
diff --git a/toolkit/components/extensions/test/browser/browser_ext_downloads_referrer.js b/toolkit/components/extensions/test/browser/browser_ext_downloads_referrer.js
new file mode 100644
index 0000000000..9690df6376
--- /dev/null
+++ b/toolkit/components/extensions/test/browser/browser_ext_downloads_referrer.js
@@ -0,0 +1,91 @@
+/* -*- Mode: indent-tabs-mode: nil; js-indent-level: 2 -*- */
+/* vim: set sts=2 sw=2 et tw=80: */
+
+"use strict";
+
+const URL_PATH = "browser/toolkit/components/extensions/test/browser/data";
+const TEST_URL = `http://example.com/${URL_PATH}/test_downloads_referrer.html`;
+const DOWNLOAD_URL = `http://example.com/${URL_PATH}/test-download.txt`;
+
+async function triggerSaveAs({ selector }) {
+  const contextMenu = window.document.getElementById("contentAreaContextMenu");
+  const popupshown = BrowserTestUtils.waitForEvent(contextMenu, "popupshown");
+  await BrowserTestUtils.synthesizeMouseAtCenter(
+    selector,
+    { type: "contextmenu", button: 2 },
+    gBrowser.selectedBrowser
+  );
+  await popupshown;
+  let saveLinkCommand = window.document.getElementById("context-savelink");
+  contextMenu.activateItem(saveLinkCommand);
+}
+
+add_setup(() => {
+  const tempDir = Services.dirsvc.get("TmpD", Ci.nsIFile);
+  tempDir.append("test-download-dir");
+  if (!tempDir.exists()) {
+    tempDir.create(Ci.nsIFile.DIRECTORY_TYPE, 0o755);
+  }
+
+  let MockFilePicker = SpecialPowers.MockFilePicker;
+  MockFilePicker.init(window);
+  registerCleanupFunction(function () {
+    MockFilePicker.cleanup();
+
+    if (tempDir.exists()) {
+      tempDir.remove(true);
+    }
+  });
+
+  MockFilePicker.displayDirectory = tempDir;
+  MockFilePicker.showCallback = function (fp) {
+    info("MockFilePicker: shown");
+    const filename = fp.defaultString;
+    info("MockFilePicker: save as " + filename);
+    const destFile = tempDir.clone();
+    destFile.append(filename);
+    MockFilePicker.setFiles([destFile]);
+    info("MockFilePicker: showCallback done");
+  };
+});
+
+add_task(async function test_download_item_referrer_info() {
+  const extension = ExtensionTestUtils.loadExtension({
+    manifest: {
+      permissions: ["downloads"],
+    },
+    async background() {
+      browser.downloads.onCreated.addListener(async downloadInfo => {
+        browser.test.sendMessage("download-on-created", downloadInfo);
+      });
+      browser.downloads.onChanged.addListener(async downloadInfo => {
+        // Wait download to be completed.
+        if (downloadInfo.state?.current !== "complete") {
+          return;
+        }
+        browser.test.sendMessage("download-completed");
+      });
+
+      // Call an API method implemented in the parent process to make sure
+      // registering the downloas.onCreated event listener has been completed.
+      await browser.runtime.getBrowserInfo();
+
+      browser.test.sendMessage("bg-page:ready");
+    },
+  });
+
+  await extension.startup();
+  await extension.awaitMessage("bg-page:ready");
+
+  await BrowserTestUtils.withNewTab({ gBrowser, url: TEST_URL }, async () => {
+    await triggerSaveAs({ selector: "a.test-link" });
+    const downloadInfo = await extension.awaitMessage("download-on-created");
+    is(downloadInfo.url, DOWNLOAD_URL, "Got the expected download url");
+    is(downloadInfo.referrer, TEST_URL, "Got the expected referrer");
+  });
+
+  // Wait for the download to have been completed and removed.
+  await extension.awaitMessage("download-completed");
+
+  await extension.unload();
+});
diff --git a/toolkit/components/extensions/test/browser/browser_ext_eventpage_disableResetIdleForTest.js b/toolkit/components/extensions/test/browser/browser_ext_eventpage_disableResetIdleForTest.js
new file mode 100644
index 0000000000..8178411e80
--- /dev/null
+++ b/toolkit/components/extensions/test/browser/browser_ext_eventpage_disableResetIdleForTest.js
@@ -0,0 +1,83 @@
+"use strict";
+
+const { PromiseTestUtils } = ChromeUtils.importESModule(
+  "resource://testing-common/PromiseTestUtils.sys.mjs"
+);
+
+const { AppUiTestDelegate } = ChromeUtils.importESModule(
+  "resource://testing-common/AppUiTestDelegate.sys.mjs"
+);
+
+// Ignore error "Actor 'Conduits' destroyed before query 'RunListener' was resolved"
+PromiseTestUtils.allowMatchingRejectionsGlobally(
+  /Actor 'Conduits' destroyed before query 'RunListener'/
+);
+
+async function run_test_disableResetIdleForTest(options) {
+  const extension = ExtensionTestUtils.loadExtension({
+    manifest: {
+      manifest_version: 3,
+      action: {},
+    },
+    background() {
+      browser.action.onClicked.addListener(async () => {
+        browser.test.notifyPass("action-clicked");
+        // Deliberately keep this listener active to simulate a still active listener
+        // callback, while calling extension.terminateBackground().
+        await new Promise(() => {});
+      });
+
+      browser.test.sendMessage("background-ready");
+    },
+  });
+
+  await extension.startup();
+  await extension.awaitMessage("background-ready");
+  // After startup, the listener should be persistent but not primed.
+  assertPersistentListeners(extension, "browserAction", "onClicked", {
+    primed: false,
+  });
+
+  // Terminating the background should prime the persistent listener.
+  await extension.terminateBackground();
+  assertPersistentListeners(extension, "browserAction", "onClicked", {
+    primed: true,
+  });
+
+  // Wake up the background, and verify the listener is no longer primed.
+  await AppUiTestDelegate.clickBrowserAction(window, extension.id);
+  await extension.awaitFinish("action-clicked");
+  await AppUiTestDelegate.closeBrowserAction(window, extension.id);
+  await extension.awaitMessage("background-ready");
+  assertPersistentListeners(extension, "browserAction", "onClicked", {
+    primed: false,
+  });
+
+  // Terminate the background again, while the onClicked listener is still
+  // being executed.
+  // With options.disableResetIdleForTest = true, the termination should NOT
+  // be skipped and the listener should become primed again.
+  // With options.disableResetIdleForTest = false or unset, the termination
+  // should be skipped and the listener should not become primed.
+  await extension.terminateBackground(options);
+  assertPersistentListeners(extension, "browserAction", "onClicked", {
+    primed: !!options?.disableResetIdleForTest,
+  });
+
+  await extension.unload();
+}
+
+// Verify default behaviour when terminating a background while a
+// listener is still running: The background should not be terminated
+// and the listener should not become primed. Not specifyiny a value
+// for disableResetIdleForTest defauls to disableResetIdleForTest:false.
+add_task(async function test_disableResetIdleForTest_default() {
+  await run_test_disableResetIdleForTest();
+});
+
+// Verify that disableResetIdleForTest:true is honoured and terminating
+// a background while a listener is still running is enforced: The
+// background should be terminated and the listener should become primed.
+add_task(async function test_disableResetIdleForTest_true() {
+  await run_test_disableResetIdleForTest({ disableResetIdleForTest: true });
+});
diff --git a/toolkit/components/extensions/test/browser/browser_ext_extension_page_tab_navigated.js b/toolkit/components/extensions/test/browser/browser_ext_extension_page_tab_navigated.js
new file mode 100644
index 0000000000..b2fb9484c2
--- /dev/null
+++ b/toolkit/components/extensions/test/browser/browser_ext_extension_page_tab_navigated.js
@@ -0,0 +1,226 @@
+/* Any copyright is dedicated to the Public Domain.
+ * http://creativecommons.org/publicdomain/zero/1.0/ */
+
+"use strict";
+
+const { AddonTestUtils } = ChromeUtils.importESModule(
+  "resource://testing-common/AddonTestUtils.sys.mjs"
+);
+
+// The test tasks in this test file tends to trigger an intermittent
+// exception raised from JSActor::AfterDestroy, because of a race between
+// when the WebExtensions API event is being emitted from the parent process
+// and the navigation triggered on the test extension pages.
+const { PromiseTestUtils } = ChromeUtils.importESModule(
+  "resource://testing-common/PromiseTestUtils.sys.mjs"
+);
+PromiseTestUtils.allowMatchingRejectionsGlobally(
+  /Actor 'Conduits' destroyed before query 'RunListener' was resolved/
+);
+
+AddonTestUtils.initMochitest(this);
+
+const server = AddonTestUtils.createHttpServer({
+  hosts: ["example.com", "anotherwebpage.org"],
+});
+
+server.registerPathHandler("/", (request, response) => {
+  response.write(`<!DOCTYPE html>
+    <html>
+      <head>
+       <meta charset="utf-8">
+       <title>test webpage</title>
+      </head>
+    </html>
+  `);
+});
+
+function createTestExtPage({ script }) {
+  return `<!DOCTYPE html>
+    <html>
+      <head>
+       <meta charset="utf-8">
+       <script src="${script}"></script>
+      </head>
+    </html>
+  `;
+}
+
+function createTestExtPageScript(name) {
+  return `(${function (pageName) {
+    browser.webRequest.onBeforeRequest.addListener(
+      details => {
+        browser.test.log(
+          `Extension page "${pageName}" got a webRequest event: ${details.url}`
+        );
+        browser.test.sendMessage(`event-received:${pageName}`);
+      },
+      { types: ["main_frame"], urls: ["http://example.com/*"] }
+    );
+    /* eslint-disable mozilla/balanced-listeners */
+    window.addEventListener("pageshow", () => {
+      browser.test.log(`Extension page "${pageName}" got a pageshow event`);
+      browser.test.sendMessage(`pageshow:${pageName}`);
+    });
+    window.addEventListener("pagehide", () => {
+      browser.test.log(`Extension page "${pageName}" got a pagehide event`);
+      browser.test.sendMessage(`pagehide:${pageName}`);
+    });
+    /* eslint-enable mozilla/balanced-listeners */
+  }})("${name}");`;
+}
+
+// Triggers a WebRequest listener registered by the test extensions by
+// opening a tab on the given web page URL and then closing it after
+// it did load.
+async function triggerWebRequestListener(webPageURL, pause) {
+  let webPageTab = await BrowserTestUtils.openNewForegroundTab(
+    {
+      gBrowser,
+      url: webPageURL,
+    },
+    true /* waitForLoad */,
+    true /* waitForStop */
+  );
+  BrowserTestUtils.removeTab(webPageTab);
+}
+
+// The following tests tasks are testing the expected behaviors related to same-process and cross-process
+// navigations for an extension page, similarly to test_ext_extension_page_navigated.js, but unlike its
+// xpcshell counterpart this tests are only testing that after navigating back to an extension page
+// previously stored in the BFCache the WebExtensions events subscribed are being received as expected.
+
+add_task(async function test_extension_page_sameprocess_navigation() {
+  const extension = ExtensionTestUtils.loadExtension({
+    manifest: {
+      permissions: ["webRequest", "http://example.com/*"],
+    },
+    files: {
+      "extpage1.html": createTestExtPage({ script: "extpage1.js" }),
+      "extpage1.js": createTestExtPageScript("extpage1"),
+      "extpage2.html": createTestExtPage({ script: "extpage2.js" }),
+      "extpage2.js": createTestExtPageScript("extpage2"),
+    },
+  });
+
+  await extension.startup();
+
+  const policy = WebExtensionPolicy.getByID(extension.id);
+
+  const extPageURL1 = policy.extension.baseURI.resolve("extpage1.html");
+  const extPageURL2 = policy.extension.baseURI.resolve("extpage2.html");
+
+  info("Opening extension page in a new tab");
+  const extPageTab = await BrowserTestUtils.addTab(gBrowser, extPageURL1);
+  let browser = gBrowser.getBrowserForTab(extPageTab);
+  info("Wait for the extension page to be loaded");
+  await extension.awaitMessage("pageshow:extpage1");
+
+  await triggerWebRequestListener("http://example.com");
+  await extension.awaitMessage("event-received:extpage1");
+  ok(true, "extpage1 got a webRequest event as expected");
+
+  info("Load a second extension page in the same tab");
+  BrowserTestUtils.loadURIString(browser, extPageURL2);
+
+  info("Wait extpage1 to receive a pagehide event");
+  await extension.awaitMessage("pagehide:extpage1");
+  info("Wait extpage2 to receive a pageshow event");
+  await extension.awaitMessage("pageshow:extpage2");
+
+  info(
+    "Trigger a web request event and expect extpage2 to be the only one receiving it"
+  );
+  await triggerWebRequestListener("http://example.com");
+  await extension.awaitMessage("event-received:extpage2");
+  ok(true, "extpage2 got a webRequest event as expected");
+
+  info(
+    "Navigating back to extpage1 and expect extpage2 to be the only one receiving the webRequest event"
+  );
+
+  browser.goBack();
+  info("Wait for extpage1 to receive a pageshow event");
+  await extension.awaitMessage("pageshow:extpage1");
+  info("Wait for extpage2 to receive a pagehide event");
+  await extension.awaitMessage("pagehide:extpage2");
+
+  // We only expect extpage1 to be able to receive API events.
+  await triggerWebRequestListener("http://example.com");
+  await extension.awaitMessage("event-received:extpage1");
+  ok(true, "extpage1 got a webRequest event as expected");
+
+  BrowserTestUtils.removeTab(extPageTab);
+  await extension.awaitMessage("pagehide:extpage1");
+
+  await extension.unload();
+});
+
+add_task(async function test_extension_page_context_navigated_to_web_page() {
+  const extension = ExtensionTestUtils.loadExtension({
+    manifest: {
+      permissions: ["webRequest", "http://example.com/*"],
+    },
+    files: {
+      "extpage.html": createTestExtPage({ script: "extpage.js" }),
+      "extpage.js": createTestExtPageScript("extpage"),
+    },
+  });
+
+  await extension.startup();
+
+  const policy = WebExtensionPolicy.getByID(extension.id);
+
+  const extPageURL = policy.extension.baseURI.resolve("extpage.html");
+  // NOTE: this test will navigate the extension page to a webpage url that
+  // isn't matching the match pattern the test extension is going to use
+  // in its webRequest event listener, otherwise the extension page being
+  // navigated will be intermittently able to receive an event before it
+  // is navigated to the webpage url (and moved into the BFCache or destroyed)
+  // and trigger an intermittent failure of this test.
+  const webPageURL = "http://anotherwebpage.org/";
+  const triggerWebRequestURL = "http://example.com/";
+
+  info("Opening extension page in a new tab");
+  const extPageTab1 = await BrowserTestUtils.addTab(gBrowser, extPageURL);
+  let browserForTab1 = gBrowser.getBrowserForTab(extPageTab1);
+  info("Wait for the extension page to be loaded");
+  await extension.awaitMessage("pageshow:extpage");
+
+  info("Navigate the tab from the extension page to a web page");
+  let promiseLoaded = BrowserTestUtils.browserLoaded(
+    browserForTab1,
+    false,
+    webPageURL
+  );
+  BrowserTestUtils.loadURIString(browserForTab1, webPageURL);
+  info("Wait the tab to have loaded the new webpage url");
+  await promiseLoaded;
+  info("Wait the extension page to receive a pagehide event");
+  await extension.awaitMessage("pagehide:extpage");
+
+  // Trigger a webRequest listener, the extension page is expected to
+  // not be active, if that isn't the case a test message will be queued
+  // and will trigger an explicit test failure.
+  await triggerWebRequestListener(triggerWebRequestURL);
+
+  info("Navigate back to the extension page");
+  browserForTab1.goBack();
+  info("Wait for extension page to receive a pageshow event");
+  await extension.awaitMessage("pageshow:extpage");
+
+  await triggerWebRequestListener(triggerWebRequestURL);
+  await extension.awaitMessage("event-received:extpage");
+  ok(
+    true,
+    "extpage got a webRequest event as expected after being restored from BFCache"
+  );
+
+  info("Cleanup and exit test");
+  BrowserTestUtils.removeTab(extPageTab1);
+
+  info("Wait the extension page to receive a pagehide event");
+  await extension.awaitMessage("pagehide:extpage");
+
+  await extension.unload();
+});
diff --git a/toolkit/components/extensions/test/browser/browser_ext_management_themes.js b/toolkit/components/extensions/test/browser/browser_ext_management_themes.js
new file mode 100644
index 0000000000..d3cfa536b8
--- /dev/null
+++ b/toolkit/components/extensions/test/browser/browser_ext_management_themes.js
@@ -0,0 +1,177 @@
+/* -*- Mode: indent-tabs-mode: nil; js-indent-level: 2 -*- */
+/* vim: set sts=2 sw=2 et tw=80: */
+"use strict";
+
+const { PromiseTestUtils } = ChromeUtils.importESModule(
+  "resource://testing-common/PromiseTestUtils.sys.mjs"
+);
+const { BuiltInThemes } = ChromeUtils.importESModule(
+  "resource:///modules/BuiltInThemes.sys.mjs"
+);
+PromiseTestUtils.allowMatchingRejectionsGlobally(
+  /Message manager disconnected/
+);
+
+add_task(async function test_management_themes() {
+  await BuiltInThemes.ensureBuiltInThemes();
+
+  const TEST_ID = "test_management_themes@tests.mozilla.com";
+
+  let theme = ExtensionTestUtils.loadExtension({
+    manifest: {
+      name: "Simple theme test",
+      version: "1.0",
+      description: "test theme",
+      theme: {
+        images: {
+          theme_frame: "image1.png",
+        },
+      },
+    },
+    files: {
+      "image1.png": BACKGROUND,
+    },
+    useAddonManager: "temporary",
+  });
+
+  async function background(TEST_ID) {
+    browser.management.onInstalled.addListener(info => {
+      if (info.name == TEST_ID) {
+        return;
+      }
+      browser.test.log(`${info.name} was installed`);
+      browser.test.assertEq(info.type, "theme", "addon is theme");
+      browser.test.sendMessage("onInstalled", info.name);
+    });
+    browser.management.onDisabled.addListener(info => {
+      browser.test.log(`${info.name} was disabled`);
+      browser.test.assertEq(info.type, "theme", "addon is theme");
+      browser.test.sendMessage("onDisabled", info.name);
+    });
+    browser.management.onEnabled.addListener(info => {
+      browser.test.log(`${info.name} was enabled`);
+      browser.test.assertEq(info.type, "theme", "addon is theme");
+      browser.test.sendMessage("onEnabled", info.name);
+    });
+    browser.management.onUninstalled.addListener(info => {
+      browser.test.log(`${info.name} was uninstalled`);
+      browser.test.assertEq(info.type, "theme", "addon is theme");
+      browser.test.sendMessage("onUninstalled", info.name);
+    });
+
+    async function getAddon(type) {
+      let addons = await browser.management.getAll();
+      let themes = addons.filter(addon => addon.type === "theme");
+      const STANDARD_BUILTIN_THEME_IDS = [
+        "default-theme@mozilla.org",
+        "firefox-compact-light@mozilla.org",
+        "firefox-compact-dark@mozilla.org",
+        "firefox-alpenglow@mozilla.org",
+      ];
+      // Check that management.getAll returns the built-in themes and our test
+      // extension.
+      for (let id of [...STANDARD_BUILTIN_THEME_IDS, TEST_ID]) {
+        let builtInExtension = addons.find(addon => {
+          return addon.id === id;
+        });
+        browser.test.assertTrue(
+          !!builtInExtension,
+          `The extension with id ${id} was returned by getAll.`
+        );
+      }
+      let found;
+      for (let addon of themes) {
+        browser.test.assertEq(addon.type, "theme", "addon is theme");
+        if (type == "theme" && addon.id.includes("temporary-addon")) {
+          found = addon;
+        } else if (type == "enabled" && addon.enabled) {
+          found = addon;
+        }
+      }
+      return found;
+    }
+
+    browser.test.onMessage.addListener(async msg => {
+      let theme = await getAddon("theme");
+      browser.test.assertEq(
+        theme.description,
+        "test theme",
+        "description is correct"
+      );
+      browser.test.assertTrue(theme.enabled, "theme is enabled");
+      await browser.management.setEnabled(theme.id, false);
+
+      theme = await getAddon("theme");
+
+      browser.test.assertTrue(!theme.enabled, "theme is disabled");
+      let addon = getAddon("enabled");
+      browser.test.assertTrue(addon, "another theme was enabled");
+
+      await browser.management.setEnabled(theme.id, true);
+      theme = await getAddon("theme");
+      addon = await getAddon("enabled");
+      browser.test.assertEq(theme.id, addon.id, "theme is enabled");
+
+      browser.test.sendMessage("done");
+    });
+  }
+
+  let extension = ExtensionTestUtils.loadExtension({
+    manifest: {
+      browser_specific_settings: {
+        gecko: {
+          id: TEST_ID,
+        },
+      },
+      name: TEST_ID,
+      permissions: ["management"],
+    },
+    background: `(${background})("${TEST_ID}")`,
+    useAddonManager: "temporary",
+  });
+  await extension.startup();
+
+  await theme.startup();
+  is(
+    await extension.awaitMessage("onInstalled"),
+    "Simple theme test",
+    "webextension theme installed"
+  );
+  is(
+    await extension.awaitMessage("onDisabled"),
+    "System theme — auto",
+    "default disabled"
+  );
+
+  extension.sendMessage("test");
+  is(
+    await extension.awaitMessage("onEnabled"),
+    "System theme — auto",
+    "default enabled"
+  );
+  is(
+    await extension.awaitMessage("onDisabled"),
+    "Simple theme test",
+    "addon disabled"
+  );
+  is(
+    await extension.awaitMessage("onEnabled"),
+    "Simple theme test",
+    "addon enabled"
+  );
+  is(
+    await extension.awaitMessage("onDisabled"),
+    "System theme — auto",
+    "default disabled"
+  );
+  await extension.awaitMessage("done");
+
+  await Promise.all([theme.unload(), extension.awaitMessage("onUninstalled")]);
+
+  is(
+    await extension.awaitMessage("onEnabled"),
+    "System theme — auto",
+    "default enabled"
+  );
+  await extension.unload();
+});
diff --git a/toolkit/components/extensions/test/browser/browser_ext_process_crash_handling.js b/toolkit/components/extensions/test/browser/browser_ext_process_crash_handling.js
new file mode 100644
index 0000000000..09ded0bcc1
--- /dev/null
+++ b/toolkit/components/extensions/test/browser/browser_ext_process_crash_handling.js
@@ -0,0 +1,116 @@
+/* Any copyright is dedicated to the Public Domain.
+ * http://creativecommons.org/publicdomain/zero/1.0/ */
+
+"use strict";
+
+const { AddonTestUtils } = ChromeUtils.importESModule(
+  "resource://testing-common/AddonTestUtils.sys.mjs"
+);
+
+const { ExtensionProcessCrashObserver, Management } =
+  ChromeUtils.importESModule("resource://gre/modules/Extension.sys.mjs");
+
+AddonTestUtils.initMochitest(this);
+
+add_task(async function test_ExtensionProcessCrashObserver() {
+  let mv2Extension = ExtensionTestUtils.loadExtension({
+    useAddonManager: "temporary",
+    manifest: {
+      manifest_version: 2,
+    },
+    background() {
+      browser.test.sendMessage("background_running");
+    },
+  });
+
+  await mv2Extension.startup();
+  await mv2Extension.awaitMessage("background_running");
+
+  let { currentProcessChildID, lastCrashedProcessChildID } =
+    ExtensionProcessCrashObserver;
+
+  Assert.notEqual(
+    currentProcessChildID,
+    undefined,
+    "Expect ExtensionProcessCrashObserver.currentProcessChildID to be set"
+  );
+
+  Assert.equal(
+    ChromeUtils.getAllDOMProcesses().find(
+      pp => pp.childID == currentProcessChildID
+    )?.remoteType,
+    "extension",
+    "Expect a child process with remoteType extension to be found for the process childID set"
+  );
+
+  Assert.notEqual(
+    lastCrashedProcessChildID,
+    currentProcessChildID,
+    "Expect lastCrashedProcessChildID to not be set to the same value that currentProcessChildID is set"
+  );
+
+  let mv3Extension = ExtensionTestUtils.loadExtension({
+    useAddonManager: "temporary",
+    manifest: {
+      manifest_version: 3,
+    },
+    background() {
+      browser.test.sendMessage("background_running");
+    },
+  });
+
+  const waitForExtensionBrowserInserted = () =>
+    new Promise(resolve => {
+      const listener = (_eventName, browser) => {
+        if (!browser.getAttribute("webextension-view-type") === "background") {
+          return;
+        }
+        Management.off("extension-browser-inserted", listener);
+        resolve(browser);
+      };
+      Management.on("extension-browser-inserted", listener);
+    });
+
+  const waitForExtensionProcessCrashNotified = () =>
+    new Promise(resolve => {
+      Management.once("extension-process-crash", (_evt, data) => resolve(data));
+    });
+
+  const promiseBackgroundBrowser = waitForExtensionBrowserInserted();
+
+  const promiseExtensionProcessCrashNotified =
+    waitForExtensionProcessCrashNotified();
+
+  await mv3Extension.startup();
+  await mv3Extension.awaitMessage("background_running");
+  const bgPageBrowser = await promiseBackgroundBrowser;
+
+  info("Force extension process crash");
+  // NOTE: shouldShowTabCrashPage option needs to be set to false
+  // to make sure crashFrame method resolves without waiting for a
+  // tab crash page (which is not going to be shown for a background
+  // page browser element).
+  await BrowserTestUtils.crashFrame(
+    bgPageBrowser,
+    /* shouldShowTabCrashPage */ false
+  );
+
+  info("Verify ExtensionProcessCrashObserver after extension process crash");
+  Assert.equal(
+    ExtensionProcessCrashObserver.lastCrashedProcessChildID,
+    currentProcessChildID,
+    "Expect ExtensionProcessCrashObserver.lastCrashedProcessChildID to be set to the expected childID"
+  );
+
+  info("Expect the same childID to have been notified as a Management event");
+  Assert.deepEqual(
+    await promiseExtensionProcessCrashNotified,
+    { childID: currentProcessChildID },
+    "Got the expected childID notified as part of the extension-process-crash Management event"
+  );
+
+  info("Wait for mv3 extension shutdown");
+  await mv3Extension.unload();
+  info("Wait for mv2 extension shutdown");
+  await mv2Extension.unload();
+});
diff --git a/toolkit/components/extensions/test/browser/browser_ext_test_mock.js b/toolkit/components/extensions/test/browser/browser_ext_test_mock.js
new file mode 100644
index 0000000000..de496b7631
--- /dev/null
+++ b/toolkit/components/extensions/test/browser/browser_ext_test_mock.js
@@ -0,0 +1,47 @@
+/* -*- Mode: indent-tabs-mode: nil; js-indent-level: 2 -*- */
+/* vim: set sts=2 sw=2 et tw=80: */
+"use strict";
+
+// This test verifies that the extension mocks behave consistently, regardless
+// of test type (xpcshell vs browser test).
+// See also toolkit/components/extensions/test/xpcshell/test_ext_test_mock.js
+
+// Check the state of the extension object. This should be consistent between
+// browser tests and xpcshell tests.
+async function checkExtensionStartupAndUnload(ext) {
+  await ext.startup();
+  Assert.ok(ext.id, "Extension ID should be available");
+  Assert.ok(ext.uuid, "Extension UUID should be available");
+  await ext.unload();
+  // Once set nothing clears the UUID.
+  Assert.ok(ext.uuid, "Extension UUID exists after unload");
+}
+
+add_task(async function test_MockExtension() {
+  // When "useAddonManager" is set, a MockExtension is created in the main
+  // process, which does not necessarily behave identically to an Extension.
+  let ext = ExtensionTestUtils.loadExtension({
+    // xpcshell/test_ext_test_mock.js tests "temporary", so here we use
+    // "permanent" to have even more test coverage.
+    useAddonManager: "permanent",
+    manifest: {
+      browser_specific_settings: { gecko: { id: "@permanent-mock-extension" } },
+    },
+  });
+
+  Assert.ok(!ext.id, "Extension ID is initially unavailable");
+  Assert.ok(!ext.uuid, "Extension UUID is initially unavailable");
+  await checkExtensionStartupAndUnload(ext);
+  Assert.ok(ext.id, "Extension ID exists after unload");
+});
+
+add_task(async function test_generated_Extension() {
+  let ext = ExtensionTestUtils.loadExtension({
+    manifest: {},
+  });
+
+  Assert.ok(!ext.id, "Extension ID is initially unavailable");
+  Assert.ok(!ext.uuid, "Extension UUID is initially unavailable");
+  await checkExtensionStartupAndUnload(ext);
+  Assert.ok(ext.id, "Extension ID exists after unload");
+});
diff --git a/toolkit/components/extensions/test/browser/browser_ext_themes_additional_backgrounds_alignment.js b/toolkit/components/extensions/test/browser/browser_ext_themes_additional_backgrounds_alignment.js
new file mode 100644
index 0000000000..cc814b4ae8
--- /dev/null
+++ b/toolkit/components/extensions/test/browser/browser_ext_themes_additional_backgrounds_alignment.js
@@ -0,0 +1,119 @@
+"use strict";
+
+// Case 1 - When there is a theme_frame image and additional_backgrounds_alignment is not specified.
+// So background-position should default to "right top"
+add_task(async function test_default_additional_backgrounds_alignment() {
+  const RIGHT_TOP = "100% 0%";
+
+  let extension = ExtensionTestUtils.loadExtension({
+    manifest: {
+      theme: {
+        images: {
+          theme_frame: "image1.png",
+          additional_backgrounds: ["image1.png", "image1.png"],
+        },
+        colors: {
+          frame: ACCENT_COLOR,
+          tab_background_text: TEXT_COLOR,
+        },
+      },
+    },
+    files: {
+      "image1.png": BACKGROUND,
+    },
+  });
+
+  await extension.startup();
+
+  let toolbox = document.querySelector("#navigator-toolbox");
+  let toolboxCS = window.getComputedStyle(toolbox);
+  if (backgroundColorSetOnRoot()) {
+    let docEl = document.documentElement;
+    let rootCS = window.getComputedStyle(docEl);
+
+    Assert.equal(
+      rootCS.getPropertyValue("background-position"),
+      `${RIGHT_TOP}, ${RIGHT_TOP}`,
+      "root contains theme_frame and lwt-background-alignment properties"
+    );
+    Assert.equal(
+      toolboxCS.getPropertyValue("background-position"),
+      RIGHT_TOP,
+      toolbox.id + " contains lwt-background-alignment properties"
+    );
+  } else {
+    /**
+     * We expect duplicate background-position values because we apply `right top`
+     * once for theme_frame, and again as the default value of
+     * --lwt-background-alignment.
+     */
+    Assert.equal(
+      toolboxCS.getPropertyValue("background-position"),
+      `${RIGHT_TOP}, ${RIGHT_TOP}`,
+      toolbox.id +
+        " contains theme_frame and default lwt-background-alignment properties"
+    );
+  }
+
+  await extension.unload();
+});
+
+// Case 2 - When there is a theme_frame image and additional_backgrounds_alignment is specified.
+add_task(async function test_additional_backgrounds_alignment() {
+  const LEFT_BOTTOM = "0% 100%";
+  const CENTER_CENTER = "50% 50%";
+  const RIGHT_TOP = "100% 0%";
+
+  let extension = ExtensionTestUtils.loadExtension({
+    manifest: {
+      theme: {
+        images: {
+          theme_frame: "image1.png",
+          additional_backgrounds: ["image1.png", "image1.png", "image1.png"],
+        },
+        colors: {
+          frame: ACCENT_COLOR,
+          tab_background_text: TEXT_COLOR,
+        },
+        properties: {
+          additional_backgrounds_alignment: [
+            "left bottom",
+            "center center",
+            "right top",
+          ],
+        },
+      },
+    },
+    files: {
+      "image1.png": BACKGROUND,
+    },
+  });
+
+  await extension.startup();
+
+  let toolbox = document.querySelector("#navigator-toolbox");
+  let toolboxCS = window.getComputedStyle(toolbox);
+  if (backgroundColorSetOnRoot()) {
+    let docEl = document.documentElement;
+    let rootCS = window.getComputedStyle(docEl);
+    Assert.equal(
+      rootCS.getPropertyValue("background-position"),
+      `${RIGHT_TOP}, ${LEFT_BOTTOM}, ${CENTER_CENTER}, ${RIGHT_TOP}`,
+      "root contains theme_frame and additional_backgrounds alignment properties"
+    );
+    Assert.equal(
+      toolboxCS.getPropertyValue("background-position"),
+      LEFT_BOTTOM + ", " + CENTER_CENTER + ", " + RIGHT_TOP,
+      toolbox.id + " contains additional_backgrounds alignment properties"
+    );
+  } else {
+    Assert.equal(
+      toolboxCS.getPropertyValue("background-position"),
+      RIGHT_TOP + ", " + LEFT_BOTTOM + ", " + CENTER_CENTER + ", " + RIGHT_TOP,
+      toolbox.id +
+        " contains theme_frame and additional_backgrounds alignment properties"
+    );
+  }
+
+  await extension.unload();
+});
diff --git a/toolkit/components/extensions/test/browser/browser_ext_themes_alpha_accentcolor.js b/toolkit/components/extensions/test/browser/browser_ext_themes_alpha_accentcolor.js
new file mode 100644
index 0000000000..2799d37551
--- /dev/null
+++ b/toolkit/components/extensions/test/browser/browser_ext_themes_alpha_accentcolor.js
@@ -0,0 +1,39 @@
+"use strict";
+
+add_task(async function test_alpha_frame_color() {
+  let extension = ExtensionTestUtils.loadExtension({
+    manifest: {
+      theme: {
+        images: {
+          theme_frame: "image1.png",
+        },
+        colors: {
+          frame: "rgba(230, 128, 0, 0.1)",
+          tab_background_text: TEXT_COLOR,
+        },
+      },
+    },
+    files: {
+      "image1.png": BACKGROUND,
+    },
+  });
+
+  await extension.startup();
+
+  let computedStyle;
+  if (backgroundColorSetOnRoot()) {
+    let docEl = window.document.documentElement;
+    computedStyle = window.getComputedStyle(docEl);
+  } else {
+    let toolbox = document.querySelector("#navigator-toolbox");
+    computedStyle = window.getComputedStyle(toolbox);
+  }
+
+  Assert.equal(
+    computedStyle.backgroundColor,
+    "rgb(230, 128, 0)",
+    "Window background color should be opaque"
+  );
+
+  await extension.unload();
+});
diff --git a/toolkit/components/extensions/test/browser/browser_ext_themes_arrowpanels.js b/toolkit/components/extensions/test/browser/browser_ext_themes_arrowpanels.js
new file mode 100644
index 0000000000..6665fb3092
--- /dev/null
+++ b/toolkit/components/extensions/test/browser/browser_ext_themes_arrowpanels.js
@@ -0,0 +1,82 @@
+"use strict";
+
+function openIdentityPopup() {
+  let promise = BrowserTestUtils.waitForEvent(
+    window,
+    "popupshown",
+    true,
+    event => event.target == gIdentityHandler._identityPopup
+  );
+  gIdentityHandler._identityIconBox.click();
+  return promise;
+}
+
+function closeIdentityPopup() {
+  let promise = BrowserTestUtils.waitForEvent(
+    gIdentityHandler._identityPopup,
+    "popuphidden"
+  );
+  gIdentityHandler._identityPopup.hidePopup();
+  return promise;
+}
+
+// This test checks applied WebExtension themes that attempt to change
+// popup properties
+
+add_task(async function test_popup_styling(browser, accDoc) {
+  const POPUP_BACKGROUND_COLOR = "#FF0000";
+  const POPUP_TEXT_COLOR = "#008000";
+  const POPUP_BORDER_COLOR = "#0000FF";
+
+  let extension = ExtensionTestUtils.loadExtension({
+    manifest: {
+      theme: {
+        images: {
+          theme_frame: "image1.png",
+        },
+        colors: {
+          frame: ACCENT_COLOR,
+          tab_background_text: TEXT_COLOR,
+          popup: POPUP_BACKGROUND_COLOR,
+          popup_text: POPUP_TEXT_COLOR,
+          popup_border: POPUP_BORDER_COLOR,
+        },
+      },
+    },
+    files: {
+      "image1.png": BACKGROUND,
+    },
+  });
+
+  await BrowserTestUtils.withNewTab(
+    { gBrowser, url: "https://example.com" },
+    async function (browser) {
+      await extension.startup();
+
+      // Open the information arrow panel
+      await openIdentityPopup();
+
+      let arrowContent = gIdentityHandler._identityPopup.panelContent;
+      let arrowContentComputedStyle = window.getComputedStyle(arrowContent);
+      // Ensure popup background color was set properly
+      Assert.equal(
+        arrowContentComputedStyle.getPropertyValue("background-color"),
+        `rgb(${hexToRGB(POPUP_BACKGROUND_COLOR).join(", ")})`,
+        "Popup background color should have been themed"
+      );
+
+      // Ensure popup text color was set properly
+      Assert.equal(
+        arrowContentComputedStyle.getPropertyValue("color"),
+        `rgb(${hexToRGB(POPUP_TEXT_COLOR).join(", ")})`,
+        "Popup text color should have been themed"
+      );
+
+      // Ensure popup border color was set properly
+      testBorderColor(arrowContent, POPUP_BORDER_COLOR);
+
+      await closeIdentityPopup();
+      await extension.unload();
+    }
+  );
+});
diff --git a/toolkit/components/extensions/test/browser/browser_ext_themes_autocomplete_popup.js b/toolkit/components/extensions/test/browser/browser_ext_themes_autocomplete_popup.js
new file mode 100644
index 0000000000..d2baf6157b
--- /dev/null
+++ b/toolkit/components/extensions/test/browser/browser_ext_themes_autocomplete_popup.js
@@ -0,0 +1,173 @@
+"use strict";
+
+// This test checks whether applied WebExtension themes that attempt to change
+// popup properties are applied correctly to the autocomplete bar.
+const POPUP_COLOR_DARK = "#00A400";
+const POPUP_COLOR_BRIGHT = "#85A4FF";
+const POPUP_TEXT_COLOR_DARK = "#000000";
+const POPUP_TEXT_COLOR_BRIGHT = "#ffffff";
+const POPUP_SELECTED_COLOR = "#9400ff";
+const POPUP_SELECTED_TEXT_COLOR = "#09b9a6";
+
+const POPUP_URL_COLOR_DARK = "#0061e0";
+const POPUP_ACTION_COLOR_DARK = "#5b5b66";
+const POPUP_URL_COLOR_BRIGHT = "#00ddff";
+const POPUP_ACTION_COLOR_BRIGHT = "#bfbfc9";
+
+const SEARCH_TERM = "urlbar-reflows-" + Date.now();
+
+ChromeUtils.defineESModuleGetters(this, {
+  PlacesTestUtils: "resource://testing-common/PlacesTestUtils.sys.mjs",
+  UrlbarTestUtils: "resource://testing-common/UrlbarTestUtils.sys.mjs",
+});
+
+add_setup(async function () {
+  await PlacesUtils.history.clear();
+  const NUM_VISITS = 10;
+  let visits = [];
+
+  for (let i = 0; i < NUM_VISITS; ++i) {
+    visits.push({
+      uri: `http://example.com/urlbar-reflows-${i}`,
+      title: `Reflow test for URL bar entry #${i} - ${SEARCH_TERM}`,
+    });
+  }
+
+  await PlacesTestUtils.addVisits(visits);
+
+  registerCleanupFunction(async function () {
+    await PlacesUtils.history.clear();
+  });
+});
+
+add_task(async function test_popup_url() {
+  // Load a manifest with popup_text being dark (bright background). Test for
+  // dark text properties.
+  let extension = ExtensionTestUtils.loadExtension({
+    manifest: {
+      theme: {
+        images: {
+          theme_frame: "image1.png",
+        },
+        colors: {
+          frame: ACCENT_COLOR,
+          tab_background_text: TEXT_COLOR,
+          toolbar_field_focus: POPUP_COLOR_BRIGHT,
+          toolbar_field_text_focus: POPUP_TEXT_COLOR_DARK,
+          popup_highlight: POPUP_SELECTED_COLOR,
+          popup_highlight_text: POPUP_SELECTED_TEXT_COLOR,
+        },
+      },
+    },
+    files: {
+      "image1.png": BACKGROUND,
+    },
+  });
+
+  await extension.startup();
+
+  let maxResults = Services.prefs.getIntPref("browser.urlbar.maxRichResults");
+  let tab = await BrowserTestUtils.openNewForegroundTab(
+    gBrowser,
+    "about:mozilla"
+  );
+  registerCleanupFunction(async function () {
+    await PlacesUtils.history.clear();
+    await BrowserTestUtils.removeTab(tab);
+  });
+
+  let visits = [];
+
+  for (let i = 0; i < maxResults; i++) {
+    visits.push({ uri: makeURI("http://example.com/autocomplete/?" + i) });
+  }
+
+  await PlacesTestUtils.addVisits(visits);
+  await UrlbarTestUtils.promiseAutocompleteResultPopup({
+    window,
+    waitForFocus,
+    value: "example.com/autocomplete",
+  });
+  await UrlbarTestUtils.waitForAutocompleteResultAt(window, maxResults - 1);
+
+  Assert.equal(
+    UrlbarTestUtils.getResultCount(window),
+    maxResults,
+    "Should get maxResults=" + maxResults + " results"
+  );
+
+  // Set the selected attribute to true to test the highlight popup properties
+  UrlbarTestUtils.setSelectedRowIndex(window, 1);
+  let actionResult = await UrlbarTestUtils.getDetailsOfResultAt(window, 0);
+  let urlResult = await UrlbarTestUtils.getDetailsOfResultAt(window, 1);
+  let resultCS = window.getComputedStyle(urlResult.element.row);
+
+  Assert.equal(
+    resultCS.backgroundColor,
+    `rgb(${hexToRGB(POPUP_SELECTED_COLOR).join(", ")})`,
+    `Popup highlight background color should be set to ${POPUP_SELECTED_COLOR}`
+  );
+
+  Assert.equal(
+    resultCS.color,
+    `rgb(${hexToRGB(POPUP_SELECTED_TEXT_COLOR).join(", ")})`,
+    `Popup highlight color should be set to ${POPUP_SELECTED_TEXT_COLOR}`
+  );
+
+  // Now set the index to somewhere not on the first two, so that we can test both
+  // url and action text colors.
+  UrlbarTestUtils.setSelectedRowIndex(window, 2);
+
+  Assert.equal(
+    window.getComputedStyle(urlResult.element.url).color,
+    `rgb(${hexToRGB(POPUP_URL_COLOR_DARK).join(", ")})`,
+    `Urlbar popup url color should be set to ${POPUP_URL_COLOR_DARK}`
+  );
+
+  Assert.equal(
+    window.getComputedStyle(actionResult.element.action).color,
+    `rgb(${hexToRGB(POPUP_ACTION_COLOR_DARK).join(", ")})`,
+    `Urlbar popup action color should be set to ${POPUP_ACTION_COLOR_DARK}`
+  );
+
+  await extension.unload();
+
+  // Load a manifest with popup_text being bright (dark background). Test for
+  // bright text properties.
+  extension = ExtensionTestUtils.loadExtension({
+    manifest: {
+      theme: {
+        images: {
+          theme_frame: "image1.png",
+        },
+        colors: {
+          frame: ACCENT_COLOR,
+          tab_background_text: TEXT_COLOR,
+          toolbar_field_focus: POPUP_COLOR_DARK,
+          toolbar_field_text_focus: POPUP_TEXT_COLOR_BRIGHT,
+          popup_highlight: POPUP_SELECTED_COLOR,
+          popup_highlight_text: POPUP_SELECTED_TEXT_COLOR,
+        },
+      },
+    },
+    files: {
+      "image1.png": BACKGROUND,
+    },
+  });
+
+  await extension.startup();
+
+  Assert.equal(
+    window.getComputedStyle(urlResult.element.url).color,
+    `rgb(${hexToRGB(POPUP_URL_COLOR_BRIGHT).join(", ")})`,
+    `Urlbar popup url color should be set to ${POPUP_URL_COLOR_BRIGHT}`
+  );
+
+  Assert.equal(
+    window.getComputedStyle(actionResult.element.action).color,
+    `rgb(${hexToRGB(POPUP_ACTION_COLOR_BRIGHT).join(", ")})`,
+    `Urlbar popup action color should be set to ${POPUP_ACTION_COLOR_BRIGHT}`
+  );
+
+  await extension.unload();
+});
diff --git a/toolkit/components/extensions/test/browser/browser_ext_themes_chromeparity.js b/toolkit/components/extensions/test/browser/browser_ext_themes_chromeparity.js
new file mode 100644
index 0000000000..e88c78fa93
--- /dev/null
+++ b/toolkit/components/extensions/test/browser/browser_ext_themes_chromeparity.js
@@ -0,0 +1,213 @@
+"use strict";
+
+add_task(async function test_support_theme_frame() {
+  const FRAME_COLOR = [71, 105, 91];
+  const TAB_TEXT_COLOR = [0, 0, 0];
+  let extension = ExtensionTestUtils.loadExtension({
+    manifest: {
+      theme: {
+        images: {
+          theme_frame: "face.png",
+        },
+        colors: {
+          frame: FRAME_COLOR,
+          tab_background_text: TAB_TEXT_COLOR,
+        },
+      },
+    },
+    files: {
+      "face.png": imageBufferFromDataURI(ENCODED_IMAGE_DATA),
+    },
+  });
+
+  await extension.startup();
+
+  let docEl = window.document.documentElement;
+  Assert.ok(docEl.hasAttribute("lwtheme"), "LWT attribute should be set");
+
+  Assert.ok(
+    docEl.hasAttribute("lwtheme-image"),
+    "LWT image attribute should be set"
+  );
+
+  Assert.equal(
+    docEl.getAttribute("lwtheme-brighttext"),
+    null,
+    "LWT text color attribute should not be set"
+  );
+
+  let toolbox = document.querySelector("#navigator-toolbox");
+  let toolboxCS = window.getComputedStyle(toolbox);
+
+  if (backgroundColorSetOnRoot()) {
+    let rootCS = window.getComputedStyle(docEl);
+    Assert.ok(
+      rootCS.backgroundImage.includes("face.png"),
+      `The backgroundImage should use face.png. Actual value is: ${toolboxCS.backgroundImage}`
+    );
+    Assert.equal(
+      rootCS.backgroundColor,
+      "rgb(" + FRAME_COLOR.join(", ") + ")",
+      "Expected correct background color"
+    );
+  } else {
+    Assert.ok(
+      toolboxCS.backgroundImage.includes("face.png"),
+      `The backgroundImage should use face.png. Actual value is: ${toolboxCS.backgroundImage}`
+    );
+    Assert.equal(
+      toolboxCS.backgroundColor,
+      "rgb(" + FRAME_COLOR.join(", ") + ")",
+      "Expected correct background color"
+    );
+  }
+  Assert.equal(
+    toolboxCS.color,
+    "rgb(" + TAB_TEXT_COLOR.join(", ") + ")",
+    "Expected correct text color"
+  );
+
+  await extension.unload();
+
+  Assert.ok(!docEl.hasAttribute("lwtheme"), "LWT attribute should not be set");
+
+  Assert.ok(
+    !docEl.hasAttribute("lwtheme-image"),
+    "LWT image attribute should not be set"
+  );
+
+  Assert.ok(
+    !docEl.hasAttribute("lwtheme-brighttext"),
+    "LWT text color attribute should not be set"
+  );
+});
+
+add_task(async function test_support_theme_frame_inactive() {
+  const FRAME_COLOR = [71, 105, 91];
+  const FRAME_COLOR_INACTIVE = [255, 0, 0];
+  const TAB_TEXT_COLOR = [207, 221, 192];
+  let extension = ExtensionTestUtils.loadExtension({
+    manifest: {
+      theme: {
+        images: {
+          theme_frame: "image1.png",
+        },
+        colors: {
+          frame: FRAME_COLOR,
+          frame_inactive: FRAME_COLOR_INACTIVE,
+          tab_background_text: TAB_TEXT_COLOR,
+        },
+      },
+    },
+    files: {
+      "image1.png": BACKGROUND,
+    },
+  });
+
+  await extension.startup();
+
+  let docEl = window.document.documentElement;
+  let toolbox = document.querySelector("#navigator-toolbox");
+  let toolboxCS = window.getComputedStyle(toolbox);
+
+  if (backgroundColorSetOnRoot()) {
+    let rootCS = window.getComputedStyle(docEl);
+    Assert.equal(
+      rootCS.backgroundColor,
+      "rgb(" + FRAME_COLOR.join(", ") + ")",
+      "Window background is set to the colors.frame property"
+    );
+  } else {
+    Assert.equal(
+      toolboxCS.backgroundColor,
+      "rgb(" + FRAME_COLOR.join(", ") + ")",
+      "Window background is set to the colors.frame property"
+    );
+  }
+
+  // Now we'll open a new window to see if the inactive browser accent color changed
+  let window2 = await BrowserTestUtils.openNewBrowserWindow();
+  if (backgroundColorSetOnRoot()) {
+    let rootCS = window.getComputedStyle(docEl);
+    Assert.equal(
+      rootCS.backgroundColor,
+      "rgb(" + FRAME_COLOR_INACTIVE.join(", ") + ")",
+      `Inactive window root background color should be ${FRAME_COLOR_INACTIVE}`
+    );
+  } else {
+    Assert.equal(
+      toolboxCS.backgroundColor,
+      "rgb(" + FRAME_COLOR_INACTIVE.join(", ") + ")",
+      `Inactive window background color should be ${FRAME_COLOR_INACTIVE}`
+    );
+  }
+
+  await BrowserTestUtils.closeWindow(window2);
+  await extension.unload();
+
+  Assert.ok(!docEl.hasAttribute("lwtheme"), "LWT attribute should not be set");
+});
+
+add_task(async function test_lack_of_theme_frame_inactive() {
+  const FRAME_COLOR = [71, 105, 91];
+  const TAB_TEXT_COLOR = [207, 221, 192];
+  let extension = ExtensionTestUtils.loadExtension({
+    manifest: {
+      theme: {
+        images: {
+          theme_frame: "image1.png",
+        },
+        colors: {
+          frame: FRAME_COLOR,
+          tab_background_text: TAB_TEXT_COLOR,
+        },
+      },
+    },
+    files: {
+      "image1.png": BACKGROUND,
+    },
+  });
+
+  await extension.startup();
+
+  let docEl = window.document.documentElement;
+  let toolbox = document.querySelector("#navigator-toolbox");
+  let toolboxCS = window.getComputedStyle(toolbox);
+
+  if (backgroundColorSetOnRoot()) {
+    let rootCS = window.getComputedStyle(docEl);
+    Assert.equal(
+      rootCS.backgroundColor,
+      "rgb(" + FRAME_COLOR.join(", ") + ")",
+      "Window background is set to the colors.frame property"
+    );
+  } else {
+    Assert.equal(
+      toolboxCS.backgroundColor,
+      "rgb(" + FRAME_COLOR.join(", ") + ")",
+      "Window background is set to the colors.frame property"
+    );
+  }
+
+  // Now we'll open a new window to make sure the inactive browser accent color stayed the same
+  let window2 = await BrowserTestUtils.openNewBrowserWindow();
+  if (backgroundColorSetOnRoot()) {
+    let rootCS = window.getComputedStyle(docEl);
+    Assert.equal(
+      rootCS.backgroundColor,
+      "rgb(" + FRAME_COLOR.join(", ") + ")",
+      "Inactive window background should not change if colors.frame_inactive isn't set"
+    );
+  } else {
+    Assert.equal(
+      toolboxCS.backgroundColor,
+      "rgb(" + FRAME_COLOR.join(", ") + ")",
+      "Inactive window background should not change if colors.frame_inactive isn't set"
+    );
+  }
+
+  await BrowserTestUtils.closeWindow(window2);
+  await extension.unload();
+
+  Assert.ok(!docEl.hasAttribute("lwtheme"), "LWT attribute should not be set");
+});
diff --git a/toolkit/components/extensions/test/browser/browser_ext_themes_dynamic_getCurrent.js b/toolkit/components/extensions/test/browser/browser_ext_themes_dynamic_getCurrent.js
new file mode 100644
index 0000000000..4a379edfbf
--- /dev/null
+++ b/toolkit/components/extensions/test/browser/browser_ext_themes_dynamic_getCurrent.js
@@ -0,0 +1,203 @@
+"use strict";
+
+// This test checks whether browser.theme.getCurrent() works correctly in different
+// configurations and with different parameter.
+
+// PNG image data for a simple red dot.
+const BACKGROUND_1 =
+  "data:image/png;base64,iVBORw0KGgoAAAANSUhEUgAAAAUAAAAFCAYAAACNbyblAAAAHElEQVQI12P4//8/w38GIAXDIBKE0DHxgljNBAAO9TXL0Y4OHwAAAABJRU5ErkJggg==";
+// PNG image data for the Mozilla dino head.
+const BACKGROUND_2 =
+  "data:image/png;base64,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";
+
+add_task(async function test_get_current() {
+  let extension = ExtensionTestUtils.loadExtension({
+    async background() {
+      const ACCENT_COLOR_1 = "#a14040";
+      const TEXT_COLOR_1 = "#fac96e";
+
+      const ACCENT_COLOR_2 = "#03fe03";
+      const TEXT_COLOR_2 = "#0ef325";
+
+      const theme1 = {
+        images: {
+          theme_frame: "image1.png",
+        },
+        colors: {
+          frame: ACCENT_COLOR_1,
+          tab_background_text: TEXT_COLOR_1,
+        },
+      };
+
+      const theme2 = {
+        images: {
+          theme_frame: "image2.png",
+        },
+        colors: {
+          frame: ACCENT_COLOR_2,
+          tab_background_text: TEXT_COLOR_2,
+        },
+      };
+
+      function ensureWindowFocused(winId) {
+        browser.test.log("Waiting for focused window to be " + winId);
+        // eslint-disable-next-line no-async-promise-executor
+        return new Promise(async resolve => {
+          let listener = windowId => {
+            if (windowId === winId) {
+              browser.windows.onFocusChanged.removeListener(listener);
+              resolve();
+            }
+          };
+          // We first add a listener and then check whether the window is
+          // focused using .get(), because the .get() Promise resolving
+          // could race with the listener running, in which case we'd
+          // never be notified.
+          browser.windows.onFocusChanged.addListener(listener);
+          let { focused } = await browser.windows.get(winId);
+          if (focused) {
+            browser.windows.onFocusChanged.removeListener(listener);
+            resolve();
+          }
+        });
+      }
+
+      function testTheme1(returnedTheme) {
+        browser.test.assertTrue(
+          returnedTheme.images.theme_frame.includes("image1.png"),
+          "Theme 1 theme_frame image should be applied"
+        );
+        browser.test.assertEq(
+          ACCENT_COLOR_1,
+          returnedTheme.colors.frame,
+          "Theme 1 frame color should be applied"
+        );
+        browser.test.assertEq(
+          TEXT_COLOR_1,
+          returnedTheme.colors.tab_background_text,
+          "Theme 1 tab_background_text color should be applied"
+        );
+      }
+
+      function testTheme2(returnedTheme) {
+        browser.test.assertTrue(
+          returnedTheme.images.theme_frame.includes("image2.png"),
+          "Theme 2 theme_frame image should be applied"
+        );
+        browser.test.assertEq(
+          ACCENT_COLOR_2,
+          returnedTheme.colors.frame,
+          "Theme 2 frame color should be applied"
+        );
+        browser.test.assertEq(
+          TEXT_COLOR_2,
+          returnedTheme.colors.tab_background_text,
+          "Theme 2 tab_background_text color should be applied"
+        );
+      }
+
+      function testEmptyTheme(returnedTheme) {
+        browser.test.assertEq(
+          JSON.stringify({ colors: null, images: null, properties: null }),
+          JSON.stringify(returnedTheme),
+          JSON.stringify(returnedTheme, null, 2)
+        );
+      }
+
+      browser.test.log("Testing getCurrent() with initial unthemed window");
+      const firstWin = await browser.windows.getCurrent();
+      testEmptyTheme(await browser.theme.getCurrent());
+      testEmptyTheme(await browser.theme.getCurrent(firstWin.id));
+
+      browser.test.log("Testing getCurrent() with after theme.update()");
+      await browser.theme.update(theme1);
+      testTheme1(await browser.theme.getCurrent());
+      testTheme1(await browser.theme.getCurrent(firstWin.id));
+
+      browser.test.log(
+        "Testing getCurrent() with after theme.update(windowId)"
+      );
+      const secondWin = await browser.windows.create();
+      await ensureWindowFocused(secondWin.id);
+      await browser.theme.update(secondWin.id, theme2);
+      testTheme2(await browser.theme.getCurrent());
+      testTheme1(await browser.theme.getCurrent(firstWin.id));
+      testTheme2(await browser.theme.getCurrent(secondWin.id));
+
+      browser.test.log("Testing getCurrent() after window focus change");
+      let focusChanged = ensureWindowFocused(firstWin.id);
+      await browser.windows.update(firstWin.id, { focused: true });
+      await focusChanged;
+      testTheme1(await browser.theme.getCurrent());
+      testTheme1(await browser.theme.getCurrent(firstWin.id));
+      testTheme2(await browser.theme.getCurrent(secondWin.id));
+
+      browser.test.log(
+        "Testing getCurrent() after another window focus change"
+      );
+      focusChanged = ensureWindowFocused(secondWin.id);
+      await browser.windows.update(secondWin.id, { focused: true });
+      await focusChanged;
+      testTheme2(await browser.theme.getCurrent());
+      testTheme1(await browser.theme.getCurrent(firstWin.id));
+      testTheme2(await browser.theme.getCurrent(secondWin.id));
+
+      browser.test.log("Testing getCurrent() after theme.reset(windowId)");
+      await browser.theme.reset(firstWin.id);
+      testTheme2(await browser.theme.getCurrent());
+      testTheme1(await browser.theme.getCurrent(firstWin.id));
+      testTheme2(await browser.theme.getCurrent(secondWin.id));
+
+      browser.test.log(
+        "Testing getCurrent() after reset and window focus change"
+      );
+      focusChanged = ensureWindowFocused(firstWin.id);
+      await browser.windows.update(firstWin.id, { focused: true });
+      await focusChanged;
+      testTheme1(await browser.theme.getCurrent());
+      testTheme1(await browser.theme.getCurrent(firstWin.id));
+      testTheme2(await browser.theme.getCurrent(secondWin.id));
+
+      browser.test.log("Testing getCurrent() after theme.update(windowId)");
+      await browser.theme.update(firstWin.id, theme1);
+      testTheme1(await browser.theme.getCurrent());
+      testTheme1(await browser.theme.getCurrent(firstWin.id));
+      testTheme2(await browser.theme.getCurrent(secondWin.id));
+
+      browser.test.log("Testing getCurrent() after theme.reset()");
+      await browser.theme.reset();
+      testEmptyTheme(await browser.theme.getCurrent());
+      testEmptyTheme(await browser.theme.getCurrent(firstWin.id));
+      testEmptyTheme(await browser.theme.getCurrent(secondWin.id));
+
+      browser.test.log("Testing getCurrent() after closing a window");
+      await browser.windows.remove(secondWin.id);
+      testEmptyTheme(await browser.theme.getCurrent());
+      testEmptyTheme(await browser.theme.getCurrent(firstWin.id));
+
+      browser.test.log("Testing update calls with invalid window ID");
+      await browser.test.assertRejects(
+        browser.theme.reset(secondWin.id),
+        /Invalid window/,
+        "Invalid window should throw"
+      );
+      await browser.test.assertRejects(
+        browser.theme.update(secondWin.id, theme2),
+        /Invalid window/,
+        "Invalid window should throw"
+      );
+      browser.test.notifyPass("get_current");
+    },
+    manifest: {
+      permissions: ["theme"],
+    },
+    files: {
+      "image1.png": BACKGROUND_1,
+      "image2.png": BACKGROUND_2,
+    },
+  });
+
+  await extension.startup();
+  await extension.awaitFinish("get_current");
+  await extension.unload();
+});
diff --git a/toolkit/components/extensions/test/browser/browser_ext_themes_dynamic_onUpdated.js b/toolkit/components/extensions/test/browser/browser_ext_themes_dynamic_onUpdated.js
new file mode 100644
index 0000000000..34c7162810
--- /dev/null
+++ b/toolkit/components/extensions/test/browser/browser_ext_themes_dynamic_onUpdated.js
@@ -0,0 +1,154 @@
+"use strict";
+
+// This test checks whether browser.theme.onUpdated works correctly with different
+// types of dynamic theme updates.
+
+// PNG image data for a simple red dot.
+const BACKGROUND_1 =
+  "data:image/png;base64,iVBORw0KGgoAAAANSUhEUgAAAAUAAAAFCAYAAACNbyblAAAAHElEQVQI12P4//8/w38GIAXDIBKE0DHxgljNBAAO9TXL0Y4OHwAAAABJRU5ErkJggg==";
+// PNG image data for the Mozilla dino head.
+const BACKGROUND_2 =
+  "data:image/png;base64,iVBORw0KGgoAAAANSUhEUgAAABAAAAAQCAYAAAAf8/9hAAAABGdBTUEAAK/INwWK6QAAABl0RVh0U29mdHdhcmUAQWRvYmUgSW1hZ2VSZWFkeXHJZTwAAAHWSURBVHjaYvz//z8DJQAggJiQOe/fv2fv7Oz8rays/N+VkfG/iYnJfyD/1+rVq7ffu3dPFpsBAAHEAHIBCJ85c8bN2Nj4vwsDw/8zQLwKiO8CcRoQu0DxqlWrdsHUwzBAAIGJmTNnPgYa9j8UqhFElwPxf2MIDeIrKSn9FwSJoRkAEEAM0DD4DzMAyPi/G+QKY4hh5WAXGf8PDQ0FGwJ22d27CjADAAIIrLmjo+MXA9R2kAHvGBA2wwx6B8W7od6CeQcggKCmCEL8bgwxYCbUIGTDVkHDBia+CuotgACCueD3TDQN75D4xmAvCoK9ARMHBzAw0AECiBHkAlC0Mdy7x9ABNA3obAZXIAa6iKEcGlMVQHwWyjYuL2d4v2cPg8vZswx7gHyAAAK7AOif7SAbOqCmn4Ha3AHFsIDtgPq/vLz8P4MSkJ2W9h8ggBjevXvHDo4FQUQg/kdypqCg4H8lUIACnQ/SOBMYI8bAsAJFPcj1AAEEjwVQqLpAbXmH5BJjqI0gi9DTAAgDBBCcAVLkgmQ7yKCZxpCQxqUZhAECCJ4XgMl493ug21ZD+aDAXH0WLM4A9MZPXJkJIIAwTAR5pQMalaCABQUULttBGCCAGCnNzgABBgAMJ5THwGvJLAAAAABJRU5ErkJggg==";
+
+add_task(async function test_on_updated() {
+  let extension = ExtensionTestUtils.loadExtension({
+    async background() {
+      const ACCENT_COLOR_1 = "#a14040";
+      const TEXT_COLOR_1 = "#fac96e";
+
+      const ACCENT_COLOR_2 = "#03fe03";
+      const TEXT_COLOR_2 = "#0ef325";
+
+      const theme1 = {
+        images: {
+          theme_frame: "image1.png",
+        },
+        colors: {
+          frame: ACCENT_COLOR_1,
+          tab_background_text: TEXT_COLOR_1,
+        },
+      };
+
+      const theme2 = {
+        images: {
+          theme_frame: "image2.png",
+        },
+        colors: {
+          frame: ACCENT_COLOR_2,
+          tab_background_text: TEXT_COLOR_2,
+        },
+      };
+
+      function testTheme1(returnedTheme) {
+        browser.test.assertTrue(
+          returnedTheme.images.theme_frame.includes("image1.png"),
+          "Theme 1 theme_frame image should be applied"
+        );
+        browser.test.assertEq(
+          ACCENT_COLOR_1,
+          returnedTheme.colors.frame,
+          "Theme 1 frame color should be applied"
+        );
+        browser.test.assertEq(
+          TEXT_COLOR_1,
+          returnedTheme.colors.tab_background_text,
+          "Theme 1 tab_background_text color should be applied"
+        );
+      }
+
+      function testTheme2(returnedTheme) {
+        browser.test.assertTrue(
+          returnedTheme.images.theme_frame.includes("image2.png"),
+          "Theme 2 theme_frame image should be applied"
+        );
+        browser.test.assertEq(
+          ACCENT_COLOR_2,
+          returnedTheme.colors.frame,
+          "Theme 2 frame color should be applied"
+        );
+        browser.test.assertEq(
+          TEXT_COLOR_2,
+          returnedTheme.colors.tab_background_text,
+          "Theme 2 tab_background_text color should be applied"
+        );
+      }
+
+      const firstWin = await browser.windows.getCurrent();
+      const secondWin = await browser.windows.create();
+
+      const onceThemeUpdated = () =>
+        new Promise(resolve => {
+          const listener = updateInfo => {
+            browser.theme.onUpdated.removeListener(listener);
+            resolve(updateInfo);
+          };
+          browser.theme.onUpdated.addListener(listener);
+        });
+
+      browser.test.log("Testing update with no windowId parameter");
+      let updateInfo1 = onceThemeUpdated();
+      await browser.theme.update(theme1);
+      updateInfo1 = await updateInfo1;
+      testTheme1(updateInfo1.theme);
+      browser.test.assertTrue(
+        !updateInfo1.windowId,
+        "No window id on first update"
+      );
+
+      browser.test.log("Testing update with windowId parameter");
+      let updateInfo2 = onceThemeUpdated();
+      await browser.theme.update(secondWin.id, theme2);
+      updateInfo2 = await updateInfo2;
+      testTheme2(updateInfo2.theme);
+      browser.test.assertEq(
+        secondWin.id,
+        updateInfo2.windowId,
+        "window id on second update"
+      );
+
+      browser.test.log("Testing reset with windowId parameter");
+      let updateInfo3 = onceThemeUpdated();
+      await browser.theme.reset(firstWin.id);
+      updateInfo3 = await updateInfo3;
+      browser.test.assertEq(
+        0,
+        Object.keys(updateInfo3.theme).length,
+        "Empty theme given on reset"
+      );
+      browser.test.assertEq(
+        firstWin.id,
+        updateInfo3.windowId,
+        "window id on third update"
+      );
+
+      browser.test.log("Testing reset with no windowId parameter");
+      let updateInfo4 = onceThemeUpdated();
+      await browser.theme.reset();
+      updateInfo4 = await updateInfo4;
+      browser.test.assertEq(
+        0,
+        Object.keys(updateInfo4.theme).length,
+        "Empty theme given on reset"
+      );
+      browser.test.assertTrue(
+        !updateInfo4.windowId,
+        "no window id on fourth update"
+      );
+
+      browser.test.log("Cleaning up test");
+      await browser.windows.remove(secondWin.id);
+      browser.test.notifyPass("onUpdated");
+    },
+    manifest: {
+      permissions: ["theme"],
+    },
+    files: {
+      "image1.png": BACKGROUND_1,
+      "image2.png": BACKGROUND_2,
+    },
+  });
+
+  await extension.startup();
+  await extension.awaitFinish("onUpdated");
+  await extension.unload();
+});
diff --git a/toolkit/components/extensions/test/browser/browser_ext_themes_dynamic_updates.js b/toolkit/components/extensions/test/browser/browser_ext_themes_dynamic_updates.js
new file mode 100644
index 0000000000..c6af66b5e5
--- /dev/null
+++ b/toolkit/components/extensions/test/browser/browser_ext_themes_dynamic_updates.js
@@ -0,0 +1,217 @@
+"use strict";
+
+// PNG image data for a simple red dot.
+const BACKGROUND_1 =
+  "data:image/png;base64,iVBORw0KGgoAAAANSUhEUgAAAAUAAAAFCAYAAACNbyblAAAAHElEQVQI12P4//8/w38GIAXDIBKE0DHxgljNBAAO9TXL0Y4OHwAAAABJRU5ErkJggg==";
+const ACCENT_COLOR_1 = "#a14040";
+const TEXT_COLOR_1 = "#fac96e";
+
+// PNG image data for the Mozilla dino head.
+const BACKGROUND_2 =
+  "data:image/png;base64,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";
+const ACCENT_COLOR_2 = "#03fe03";
+const TEXT_COLOR_2 = "#0ef325";
+
+function hexToRGB(hex) {
+  hex = parseInt(hex.indexOf("#") > -1 ? hex.substring(1) : hex, 16);
+  return (
+    "rgb(" + [hex >> 16, (hex & 0x00ff00) >> 8, hex & 0x0000ff].join(", ") + ")"
+  );
+}
+
+function validateTheme(backgroundImage, accentColor, textColor, isLWT) {
+  let docEl = window.document.documentElement;
+  let rootCS = window.getComputedStyle(docEl);
+
+  let toolbox = document.querySelector("#navigator-toolbox");
+  let toolboxCS = window.getComputedStyle(toolbox);
+
+  if (isLWT) {
+    Assert.ok(docEl.hasAttribute("lwtheme"), "LWT attribute should be set");
+    Assert.equal(
+      docEl.getAttribute("lwtheme-brighttext"),
+      "true",
+      "LWT text color attribute should be set"
+    );
+  }
+
+  if (accentColor.startsWith("#")) {
+    accentColor = hexToRGB(accentColor);
+  }
+  if (textColor.startsWith("#")) {
+    textColor = hexToRGB(textColor);
+  }
+  if (backgroundColorSetOnRoot()) {
+    Assert.ok(
+      rootCS.backgroundImage.includes(backgroundImage),
+      "Expected correct background image"
+    );
+    Assert.equal(
+      rootCS.backgroundColor,
+      accentColor,
+      "Expected correct accent color"
+    );
+  } else {
+    Assert.ok(
+      toolboxCS.backgroundImage.includes(backgroundImage),
+      "Expected correct background image"
+    );
+    Assert.equal(
+      toolboxCS.backgroundColor,
+      accentColor,
+      "Expected correct accent color"
+    );
+  }
+
+  Assert.equal(rootCS.color, textColor, "Expected correct text color");
+}
+
+add_task(async function test_dynamic_theme_updates() {
+  let extension = ExtensionTestUtils.loadExtension({
+    manifest: {
+      permissions: ["theme"],
+    },
+    files: {
+      "image1.png": BACKGROUND_1,
+      "image2.png": BACKGROUND_2,
+    },
+    background() {
+      browser.test.onMessage.addListener((msg, details) => {
+        if (msg === "update-theme") {
+          browser.theme.update(details).then(() => {
+            browser.test.sendMessage("theme-updated");
+          });
+        } else {
+          browser.theme.reset().then(() => {
+            browser.test.sendMessage("theme-reset");
+          });
+        }
+      });
+    },
+  });
+
+  let rootCS = window.getComputedStyle(window.document.documentElement);
+  let toolboxCS = window.getComputedStyle(
+    window.document.documentElement.querySelector("#navigator-toolbox")
+  );
+  await extension.startup();
+
+  extension.sendMessage("update-theme", {
+    images: {
+      theme_frame: "image1.png",
+    },
+    colors: {
+      frame: ACCENT_COLOR_1,
+      tab_background_text: TEXT_COLOR_1,
+    },
+  });
+
+  await extension.awaitMessage("theme-updated");
+
+  validateTheme("image1.png", ACCENT_COLOR_1, TEXT_COLOR_1, true);
+
+  // Check with the LWT aliases (to update on Firefox 69, because the
+  // LWT aliases are going to be removed).
+  extension.sendMessage("update-theme", {
+    images: {
+      theme_frame: "image2.png",
+    },
+    colors: {
+      frame: ACCENT_COLOR_2,
+      tab_background_text: TEXT_COLOR_2,
+    },
+  });
+
+  await extension.awaitMessage("theme-updated");
+
+  validateTheme("image2.png", ACCENT_COLOR_2, TEXT_COLOR_2, true);
+
+  extension.sendMessage("reset-theme");
+
+  await extension.awaitMessage("theme-reset");
+
+  let { color } = rootCS;
+  let { backgroundImage, backgroundColor } = toolboxCS;
+  if (backgroundColorSetOnRoot()) {
+    backgroundImage = rootCS.backgroundImage;
+    backgroundColor = rootCS.backgroundColor;
+  }
+  validateTheme(backgroundImage, backgroundColor, color, false);
+
+  await extension.unload();
+
+  let docEl = window.document.documentElement;
+  Assert.ok(!docEl.hasAttribute("lwtheme"), "LWT attribute should not be set");
+});
+
+add_task(async function test_dynamic_theme_updates_with_data_url() {
+  let extension = ExtensionTestUtils.loadExtension({
+    manifest: {
+      permissions: ["theme"],
+    },
+    background() {
+      browser.test.onMessage.addListener((msg, details) => {
+        if (msg === "update-theme") {
+          browser.theme.update(details).then(() => {
+            browser.test.sendMessage("theme-updated");
+          });
+        } else {
+          browser.theme.reset().then(() => {
+            browser.test.sendMessage("theme-reset");
+          });
+        }
+      });
+    },
+  });
+
+  let rootCS = window.getComputedStyle(window.document.documentElement);
+  let toolboxCS = window.getComputedStyle(
+    window.document.documentElement.querySelector("#navigator-toolbox")
+  );
+  await extension.startup();
+
+  extension.sendMessage("update-theme", {
+    images: {
+      theme_frame: BACKGROUND_1,
+    },
+    colors: {
+      frame: ACCENT_COLOR_1,
+      tab_background_text: TEXT_COLOR_1,
+    },
+  });
+
+  await extension.awaitMessage("theme-updated");
+
+  validateTheme(BACKGROUND_1, ACCENT_COLOR_1, TEXT_COLOR_1, true);
+
+  extension.sendMessage("update-theme", {
+    images: {
+      theme_frame: BACKGROUND_2,
+    },
+    colors: {
+      frame: ACCENT_COLOR_2,
+      tab_background_text: TEXT_COLOR_2,
+    },
+  });
+
+  await extension.awaitMessage("theme-updated");
+
+  validateTheme(BACKGROUND_2, ACCENT_COLOR_2, TEXT_COLOR_2, true);
+
+  extension.sendMessage("reset-theme");
+
+  await extension.awaitMessage("theme-reset");
+
+  let { color } = rootCS;
+  let { backgroundImage, backgroundColor } = toolboxCS;
+  if (backgroundColorSetOnRoot()) {
+    backgroundImage = rootCS.backgroundImage;
+    backgroundColor = rootCS.backgroundColor;
+  }
+  validateTheme(backgroundImage, backgroundColor, color, false);
+
+  await extension.unload();
+
+  let docEl = window.document.documentElement;
+  Assert.ok(!docEl.hasAttribute("lwtheme"), "LWT attribute should not be set");
+});
diff --git a/toolkit/components/extensions/test/browser/browser_ext_themes_experiment.js b/toolkit/components/extensions/test/browser/browser_ext_themes_experiment.js
new file mode 100644
index 0000000000..02156b6cd8
--- /dev/null
+++ b/toolkit/components/extensions/test/browser/browser_ext_themes_experiment.js
@@ -0,0 +1,450 @@
+"use strict";
+
+const { AddonSettings } = ChromeUtils.importESModule(
+  "resource://gre/modules/addons/AddonSettings.sys.mjs"
+);
+
+// This test checks whether the theme experiments work
+add_task(async function test_experiment_static_theme() {
+  let extension = ExtensionTestUtils.loadExtension({
+    useAddonManager: "temporary",
+    manifest: {
+      theme: {
+        colors: {
+          some_color_property: "#ff00ff",
+        },
+        images: {
+          some_image_property: "background.jpg",
+        },
+        properties: {
+          some_random_property: "no-repeat",
+        },
+      },
+      theme_experiment: {
+        colors: {
+          some_color_property: "--some-color-property",
+        },
+        images: {
+          some_image_property: "--some-image-property",
+        },
+        properties: {
+          some_random_property: "--some-random-property",
+        },
+      },
+    },
+  });
+
+  const root = window.document.documentElement;
+
+  is(
+    root.style.getPropertyValue("--some-color-property"),
+    "",
+    "Color property should be unset"
+  );
+  is(
+    root.style.getPropertyValue("--some-image-property"),
+    "",
+    "Image property should be unset"
+  );
+  is(
+    root.style.getPropertyValue("--some-random-property"),
+    "",
+    "Generic Property should be unset."
+  );
+
+  await extension.startup();
+
+  const testExperimentApplied = rootEl => {
+    if (AddonSettings.EXPERIMENTS_ENABLED) {
+      is(
+        rootEl.style.getPropertyValue("--some-color-property"),
+        hexToCSS("#ff00ff"),
+        "Color property should be parsed and set."
+      );
+      ok(
+        rootEl.style
+          .getPropertyValue("--some-image-property")
+          .startsWith("url("),
+        "Image property should be parsed."
+      );
+      ok(
+        rootEl.style
+          .getPropertyValue("--some-image-property")
+          .endsWith("background.jpg)"),
+        "Image property should be set."
+      );
+      is(
+        rootEl.style.getPropertyValue("--some-random-property"),
+        "no-repeat",
+        "Generic Property should be set."
+      );
+    } else {
+      is(
+        rootEl.style.getPropertyValue("--some-color-property"),
+        "",
+        "Color property should be unset"
+      );
+      is(
+        rootEl.style.getPropertyValue("--some-image-property"),
+        "",
+        "Image property should be unset"
+      );
+      is(
+        rootEl.style.getPropertyValue("--some-random-property"),
+        "",
+        "Generic Property should be unset."
+      );
+    }
+  };
+
+  info("Testing that current window updated with the experiment applied");
+  testExperimentApplied(root);
+
+  info("Testing that new window initialized with the experiment applied");
+  const newWindow = await BrowserTestUtils.openNewBrowserWindow();
+  const newWindowRoot = newWindow.document.documentElement;
+  testExperimentApplied(newWindowRoot);
+
+  await extension.unload();
+
+  info("Testing that both windows unapplied the experiment");
+  for (const rootEl of [root, newWindowRoot]) {
+    is(
+      rootEl.style.getPropertyValue("--some-color-property"),
+      "",
+      "Color property should be unset"
+    );
+    is(
+      rootEl.style.getPropertyValue("--some-image-property"),
+      "",
+      "Image property should be unset"
+    );
+    is(
+      rootEl.style.getPropertyValue("--some-random-property"),
+      "",
+      "Generic Property should be unset."
+    );
+  }
+  await BrowserTestUtils.closeWindow(newWindow);
+});
+
+add_task(async function test_experiment_dynamic_theme() {
+  let extension = ExtensionTestUtils.loadExtension({
+    useAddonManager: "temporary",
+    manifest: {
+      permissions: ["theme"],
+      theme_experiment: {
+        colors: {
+          some_color_property: "--some-color-property",
+        },
+        images: {
+          some_image_property: "--some-image-property",
+        },
+        properties: {
+          some_random_property: "--some-random-property",
+        },
+      },
+    },
+    background() {
+      const theme = {
+        colors: {
+          some_color_property: "#ff00ff",
+        },
+        images: {
+          some_image_property: "background.jpg",
+        },
+        properties: {
+          some_random_property: "no-repeat",
+        },
+      };
+      browser.test.onMessage.addListener(msg => {
+        if (msg === "update-theme") {
+          browser.theme.update(theme).then(() => {
+            browser.test.sendMessage("theme-updated");
+          });
+        } else {
+          browser.theme.reset().then(() => {
+            browser.test.sendMessage("theme-reset");
+          });
+        }
+      });
+    },
+  });
+
+  await extension.startup();
+
+  const root = window.document.documentElement;
+
+  is(
+    root.style.getPropertyValue("--some-color-property"),
+    "",
+    "Color property should be unset"
+  );
+  is(
+    root.style.getPropertyValue("--some-image-property"),
+    "",
+    "Image property should be unset"
+  );
+  is(
+    root.style.getPropertyValue("--some-random-property"),
+    "",
+    "Generic Property should be unset."
+  );
+
+  extension.sendMessage("update-theme");
+  await extension.awaitMessage("theme-updated");
+
+  const testExperimentApplied = rootEl => {
+    if (AddonSettings.EXPERIMENTS_ENABLED) {
+      is(
+        rootEl.style.getPropertyValue("--some-color-property"),
+        hexToCSS("#ff00ff"),
+        "Color property should be parsed and set."
+      );
+      ok(
+        rootEl.style
+          .getPropertyValue("--some-image-property")
+          .startsWith("url("),
+        "Image property should be parsed."
+      );
+      ok(
+        rootEl.style
+          .getPropertyValue("--some-image-property")
+          .endsWith("background.jpg)"),
+        "Image property should be set."
+      );
+      is(
+        rootEl.style.getPropertyValue("--some-random-property"),
+        "no-repeat",
+        "Generic Property should be set."
+      );
+    } else {
+      is(
+        rootEl.style.getPropertyValue("--some-color-property"),
+        "",
+        "Color property should be unset"
+      );
+      is(
+        rootEl.style.getPropertyValue("--some-image-property"),
+        "",
+        "Image property should be unset"
+      );
+      is(
+        rootEl.style.getPropertyValue("--some-random-property"),
+        "",
+        "Generic Property should be unset."
+      );
+    }
+  };
+  testExperimentApplied(root);
+
+  const newWindow = await BrowserTestUtils.openNewBrowserWindow();
+  const newWindowRoot = newWindow.document.documentElement;
+
+  testExperimentApplied(newWindowRoot);
+
+  extension.sendMessage("reset-theme");
+  await extension.awaitMessage("theme-reset");
+
+  for (const rootEl of [root, newWindowRoot]) {
+    is(
+      rootEl.style.getPropertyValue("--some-color-property"),
+      "",
+      "Color property should be unset"
+    );
+    is(
+      rootEl.style.getPropertyValue("--some-image-property"),
+      "",
+      "Image property should be unset"
+    );
+    is(
+      rootEl.style.getPropertyValue("--some-random-property"),
+      "",
+      "Generic Property should be unset."
+    );
+  }
+
+  extension.sendMessage("update-theme");
+  await extension.awaitMessage("theme-updated");
+
+  testExperimentApplied(root);
+  testExperimentApplied(newWindowRoot);
+
+  await extension.unload();
+
+  for (const rootEl of [root, newWindowRoot]) {
+    is(
+      rootEl.style.getPropertyValue("--some-color-property"),
+      "",
+      "Color property should be unset"
+    );
+    is(
+      rootEl.style.getPropertyValue("--some-image-property"),
+      "",
+      "Image property should be unset"
+    );
+    is(
+      rootEl.style.getPropertyValue("--some-random-property"),
+      "",
+      "Generic Property should be unset."
+    );
+  }
+
+  await BrowserTestUtils.closeWindow(newWindow);
+});
+
+add_task(async function test_experiment_stylesheet() {
+  let extension = ExtensionTestUtils.loadExtension({
+    useAddonManager: "temporary",
+    manifest: {
+      theme: {
+        colors: {
+          menu_button_background: "#ff00ff",
+        },
+      },
+      theme_experiment: {
+        stylesheet: "experiment.css",
+        colors: {
+          menu_button_background: "--menu-button-background",
+        },
+      },
+    },
+    files: {
+      "experiment.css": `#PanelUI-menu-button {
+        background-color: var(--menu-button-background);
+        fill: white;
+      }`,
+    },
+  });
+
+  const root = window.document.documentElement;
+  const menuButton = document.getElementById("PanelUI-menu-button");
+  const computedStyle = window.getComputedStyle(menuButton);
+  const expectedColor = hexToCSS("#ff00ff");
+  const expectedFill = hexToCSS("#ffffff");
+
+  is(
+    root.style.getPropertyValue("--menu-button-background"),
+    "",
+    "Variable should be unset"
+  );
+  isnot(
+    computedStyle.backgroundColor,
+    expectedColor,
+    "Menu button should not have custom background"
+  );
+  isnot(
+    computedStyle.fill,
+    expectedFill,
+    "Menu button should not have stylesheet fill"
+  );
+
+  await extension.startup();
+
+  if (AddonSettings.EXPERIMENTS_ENABLED) {
+    // Wait for stylesheet load.
+    await BrowserTestUtils.waitForCondition(
+      () => computedStyle.fill === expectedFill
+    );
+
+    is(
+      root.style.getPropertyValue("--menu-button-background"),
+      expectedColor,
+      "Variable should be parsed and set."
+    );
+    is(
+      computedStyle.backgroundColor,
+      expectedColor,
+      "Menu button should be have correct background"
+    );
+    is(
+      computedStyle.fill,
+      expectedFill,
+      "Menu button should be have correct fill"
+    );
+  } else {
+    is(
+      root.style.getPropertyValue("--menu-button-background"),
+      "",
+      "Variable should be unset"
+    );
+    isnot(
+      computedStyle.backgroundColor,
+      expectedColor,
+      "Menu button should not have custom background"
+    );
+    isnot(
+      computedStyle.fill,
+      expectedFill,
+      "Menu button should not have stylesheet fill"
+    );
+  }
+
+  await extension.unload();
+
+  is(
+    root.style.getPropertyValue("--menu-button-background"),
+    "",
+    "Variable should be unset"
+  );
+  isnot(
+    computedStyle.backgroundColor,
+    expectedColor,
+    "Menu button should not have custom background"
+  );
+  isnot(
+    computedStyle.fill,
+    expectedFill,
+    "Menu button should not have stylesheet fill"
+  );
+});
+
+// This test checks whether the theme experiments are allowed for non privileged
+// theme installed non-temporarily if AddonSettings.EXPERIMENTS_ENABLED is true.
+add_task(async function test_experiment_installed_non_temporarily() {
+  await SpecialPowers.pushPrefEnv({
+    set: [["extensions.experiments.enabled", true]],
+  });
+
+  if (!AddonSettings.EXPERIMENTS_ENABLED) {
+    info(
+      "Skipping test case on build where AddonSettings.EXPERIMENTS_ENABLED is false"
+    );
+    return;
+  }
+
+  let extension = ExtensionTestUtils.loadExtension({
+    manifest: {
+      theme: {
+        colors: {
+          some_color_property: "#ff00ff",
+        },
+      },
+      theme_experiment: {
+        colors: {
+          some_color_property: "--some-color-property",
+        },
+      },
+    },
+  });
+
+  const root = window.document.documentElement;
+
+  is(
+    root.style.getPropertyValue("--some-color-property"),
+    "",
+    "Color property should be unset"
+  );
+
+  await extension.startup();
+
+  is(
+    root.style.getPropertyValue("--some-color-property"),
+    hexToCSS("#ff00ff"),
+    "Color property should be parsed and set."
+  );
+
+  await extension.unload();
+
+  await SpecialPowers.popPrefEnv();
+});
diff --git a/toolkit/components/extensions/test/browser/browser_ext_themes_findbar.js b/toolkit/components/extensions/test/browser/browser_ext_themes_findbar.js
new file mode 100644
index 0000000000..a24c90615b
--- /dev/null
+++ b/toolkit/components/extensions/test/browser/browser_ext_themes_findbar.js
@@ -0,0 +1,227 @@
+"use strict";
+
+// This test checks whether applied WebExtension themes that attempt to change
+// the toolbar and toolbar_field properties also theme the findbar.
+
+function assertHasNoBorders(element) {
+  let cs = window.getComputedStyle(element);
+  Assert.equal(cs.borderTopWidth, "0px", "should have no top border");
+  Assert.equal(cs.borderRightWidth, "0px", "should have no right border");
+  Assert.equal(cs.borderBottomWidth, "0px", "should have no bottom border");
+  Assert.equal(cs.borderLeftWidth, "0px", "should have no left border");
+}
+
+add_task(async function test_support_toolbar_properties_on_findbar() {
+  const TOOLBAR_COLOR = "#ff00ff";
+  const TOOLBAR_TEXT_COLOR = "#9400ff";
+  const ACCENT_COLOR_INACTIVE = "#ffff00";
+  // The TabContextMenu initializes its strings only on a focus or mouseover event.
+  // Calls focus event on the TabContextMenu early in the test.
+  gBrowser.selectedTab.focus();
+  let extension = ExtensionTestUtils.loadExtension({
+    manifest: {
+      theme: {
+        colors: {
+          frame: ACCENT_COLOR,
+          frame_inactive: ACCENT_COLOR_INACTIVE,
+          tab_background_text: TEXT_COLOR,
+          toolbar: TOOLBAR_COLOR,
+          bookmark_text: TOOLBAR_TEXT_COLOR,
+        },
+      },
+    },
+  });
+
+  await extension.startup();
+  await gBrowser.getFindBar();
+
+  let findbar_button = gFindBar.getElement("highlight");
+
+  info("Checking findbar background is set as toolbar color");
+  Assert.equal(
+    window.getComputedStyle(gFindBar).backgroundColor,
+    hexToCSS(ACCENT_COLOR),
+    "Findbar background color should be the same as toolbar background color."
+  );
+
+  info("Checking findbar and checkbox text color use toolbar text color");
+  const rgbColor = hexToCSS(TOOLBAR_TEXT_COLOR);
+  Assert.equal(
+    window.getComputedStyle(gFindBar).color,
+    rgbColor,
+    "Findbar text color should be the same as toolbar text color."
+  );
+  Assert.equal(
+    window.getComputedStyle(findbar_button).color,
+    rgbColor,
+    "Findbar checkbox text color should be toolbar text color."
+  );
+
+  // Open a new window to check frame_inactive
+  let window2 = await BrowserTestUtils.openNewBrowserWindow();
+  Assert.equal(
+    window.getComputedStyle(gFindBar).backgroundColor,
+    hexToCSS(ACCENT_COLOR_INACTIVE),
+    "Findbar background changed in inactive window."
+  );
+  await BrowserTestUtils.closeWindow(window2);
+
+  await extension.unload();
+});
+
+add_task(async function test_support_toolbar_field_properties_on_findbar() {
+  let findbar_prev_button = gFindBar.getElement("find-previous");
+  let findbar_next_button = gFindBar.getElement("find-next");
+
+  assertHasNoBorders(findbar_prev_button);
+  assertHasNoBorders(findbar_next_button);
+
+  const TOOLBAR_FIELD_COLOR = "#ff00ff";
+  const TOOLBAR_FIELD_TEXT_COLOR = "#9400ff";
+  const TOOLBAR_FIELD_BORDER_COLOR = "#ffffff";
+  // The TabContextMenu initializes its strings only on a focus or mouseover event.
+  // Calls focus event on the TabContextMenu early in the test.
+  gBrowser.selectedTab.focus();
+  let extension = ExtensionTestUtils.loadExtension({
+    manifest: {
+      theme: {
+        colors: {
+          frame: ACCENT_COLOR,
+          tab_background_text: TEXT_COLOR,
+          toolbar_field: TOOLBAR_FIELD_COLOR,
+          toolbar_field_text: TOOLBAR_FIELD_TEXT_COLOR,
+          toolbar_field_border: TOOLBAR_FIELD_BORDER_COLOR,
+        },
+      },
+    },
+  });
+
+  await extension.startup();
+  await gBrowser.getFindBar();
+
+  let findbar_textbox = gFindBar.getElement("findbar-textbox");
+
+  info(
+    "Checking findbar textbox background is set as toolbar field background color"
+  );
+  Assert.equal(
+    window.getComputedStyle(findbar_textbox).backgroundColor,
+    hexToCSS(TOOLBAR_FIELD_COLOR),
+    "Findbar textbox background color should be the same as toolbar field color."
+  );
+
+  info("Checking findbar textbox color is set as toolbar field text color");
+  Assert.equal(
+    window.getComputedStyle(findbar_textbox).color,
+    hexToCSS(TOOLBAR_FIELD_TEXT_COLOR),
+    "Findbar textbox text color should be the same as toolbar field text color."
+  );
+  testBorderColor(findbar_textbox, TOOLBAR_FIELD_BORDER_COLOR);
+
+  assertHasNoBorders(findbar_prev_button);
+  assertHasNoBorders(findbar_next_button);
+
+  await extension.unload();
+});
+
+// Test that theme properties are applied with a theme_frame
+add_task(async function test_toolbar_properties_on_findbar_with_theme_frame() {
+  const TOOLBAR_COLOR = "#ff00ff";
+  const TOOLBAR_TEXT_COLOR = "#9400ff";
+  // The TabContextMenu initializes its strings only on a focus or mouseover event.
+  // Calls focus event on the TabContextMenu early in the test.
+  gBrowser.selectedTab.focus();
+  let extension = ExtensionTestUtils.loadExtension({
+    manifest: {
+      theme: {
+        images: {
+          theme_frame: "image1.png",
+        },
+        colors: {
+          frame: ACCENT_COLOR,
+          tab_background_text: TEXT_COLOR,
+          toolbar: TOOLBAR_COLOR,
+          bookmark_text: TOOLBAR_TEXT_COLOR,
+        },
+      },
+    },
+    files: {
+      "image1.png": BACKGROUND,
+    },
+  });
+
+  await extension.startup();
+  await gBrowser.getFindBar();
+
+  let findbar_button = gFindBar.getElement("highlight");
+
+  info("Checking findbar background is set as toolbar color");
+  Assert.equal(
+    window.getComputedStyle(gFindBar).backgroundColor,
+    hexToCSS(ACCENT_COLOR),
+    "Findbar background color should be set by theme."
+  );
+
+  info("Checking findbar and button text color is set as toolbar text color");
+  Assert.equal(
+    window.getComputedStyle(gFindBar).color,
+    hexToCSS(TOOLBAR_TEXT_COLOR),
+    "Findbar text color should be set by theme."
+  );
+  Assert.equal(
+    window.getComputedStyle(findbar_button).color,
+    hexToCSS(TOOLBAR_TEXT_COLOR),
+    "Findbar button text color should be set by theme."
+  );
+
+  await extension.unload();
+});
+
+add_task(
+  async function test_toolbar_field_properties_on_findbar_with_theme_frame() {
+    const TOOLBAR_FIELD_COLOR = "#ff00ff";
+    const TOOLBAR_FIELD_TEXT_COLOR = "#9400ff";
+    const TOOLBAR_FIELD_BORDER_COLOR = "#ffffff";
+    // The TabContextMenu initializes its strings only on a focus or mouseover event.
+    // Calls focus event on the TabContextMenu early in the test.
+    gBrowser.selectedTab.focus();
+    let extension = ExtensionTestUtils.loadExtension({
+      manifest: {
+        theme: {
+          images: {
+            theme_frame: "image1.png",
+          },
+          colors: {
+            frame: ACCENT_COLOR,
+            tab_background_text: TEXT_COLOR,
+            toolbar_field: TOOLBAR_FIELD_COLOR,
+            toolbar_field_text: TOOLBAR_FIELD_TEXT_COLOR,
+            toolbar_field_border: TOOLBAR_FIELD_BORDER_COLOR,
+          },
+        },
+      },
+      files: {
+        "image1.png": BACKGROUND,
+      },
+    });
+
+    await extension.startup();
+    await gBrowser.getFindBar();
+
+    let findbar_textbox = gFindBar.getElement("findbar-textbox");
+
+    Assert.equal(
+      window.getComputedStyle(findbar_textbox).backgroundColor,
+      hexToCSS(TOOLBAR_FIELD_COLOR),
+      "Findbar textbox background color should be set by theme."
+    );
+
+    Assert.equal(
+      window.getComputedStyle(findbar_textbox).color,
+      hexToCSS(TOOLBAR_FIELD_TEXT_COLOR),
+      "Findbar textbox text color should be set by theme."
+    );
+
+    await extension.unload();
+  }
+);
diff --git a/toolkit/components/extensions/test/browser/browser_ext_themes_getCurrent_differentExt.js b/toolkit/components/extensions/test/browser/browser_ext_themes_getCurrent_differentExt.js
new file mode 100644
index 0000000000..587c5d4efe
--- /dev/null
+++ b/toolkit/components/extensions/test/browser/browser_ext_themes_getCurrent_differentExt.js
@@ -0,0 +1,151 @@
+"use strict";
+
+// This test checks whether browser.theme.getCurrent() works correctly when theme
+// does not originate from extension querying the theme.
+const THEME = {
+  manifest: {
+    theme: {
+      images: {
+        theme_frame: "image1.png",
+      },
+      colors: {
+        frame: ACCENT_COLOR,
+        tab_background_text: TEXT_COLOR,
+      },
+    },
+  },
+  files: {
+    "image1.png": BACKGROUND,
+  },
+};
+
+add_task(async function test_getcurrent() {
+  const theme = ExtensionTestUtils.loadExtension(THEME);
+  const extension = ExtensionTestUtils.loadExtension({
+    background() {
+      browser.theme.onUpdated.addListener(() => {
+        browser.theme.getCurrent().then(theme => {
+          browser.test.sendMessage("theme-updated", theme);
+          if (!theme?.images) {
+            return;
+          }
+
+          // Try to access the theme_frame image
+          fetch(theme.images.theme_frame)
+            .then(() => {
+              browser.test.sendMessage("theme-image", { success: true });
+            })
+            .catch(e => {
+              browser.test.sendMessage("theme-image", {
+                success: false,
+                error: e.message,
+              });
+            });
+        });
+      });
+    },
+  });
+
+  await extension.startup();
+
+  info("Testing getCurrent after static theme startup");
+  let updatedPromise = extension.awaitMessage("theme-updated");
+  let imageLoaded = extension.awaitMessage("theme-image");
+  await theme.startup();
+  let receivedTheme = await updatedPromise;
+  Assert.ok(
+    receivedTheme.images.theme_frame.includes("image1.png"),
+    "getCurrent returns correct theme_frame image"
+  );
+  Assert.equal(
+    receivedTheme.colors.frame,
+    ACCENT_COLOR,
+    "getCurrent returns correct frame color"
+  );
+  Assert.equal(
+    receivedTheme.colors.tab_background_text,
+    TEXT_COLOR,
+    "getCurrent returns correct tab_background_text color"
+  );
+  Assert.deepEqual(await imageLoaded, { success: true }, "theme image loaded");
+
+  info("Testing getCurrent after static theme unload");
+  updatedPromise = extension.awaitMessage("theme-updated");
+  await theme.unload();
+  receivedTheme = await updatedPromise;
+  Assert.equal(
+    JSON.stringify({ colors: null, images: null, properties: null }),
+    JSON.stringify(receivedTheme),
+    "getCurrent returns empty theme"
+  );
+
+  await extension.unload();
+});
+
+add_task(async function test_getcurrent_privateBrowsing() {
+  const theme = ExtensionTestUtils.loadExtension(THEME);
+
+  const extension = ExtensionTestUtils.loadExtension({
+    incognitoOverride: "spanning",
+    manifest: {
+      sidebar_action: {
+        default_panel: "sidebar.html",
+      },
+    },
+    // We don't want the sidebar to automatically open on extension startup.
+    startupReason: "APP_STARTUP",
+    files: {
+      "sidebar.html": `<!DOCTYPE html>
+        <html>
+          <body>
+            Test Extension Sidebar
+            <script src="sidebar.js"></script>
+          </body>
+        </html>
+      `,
+      "sidebar.js": function () {
+        browser.theme.getCurrent().then(theme => {
+          if (!theme?.images) {
+            browser.test.fail(
+              `Missing expected images from theme.getCurrent result`
+            );
+            return;
+          }
+
+          // Try to access the theme_frame image
+          fetch(theme.images.theme_frame)
+            .then(() => {
+              browser.test.sendMessage("theme-image", { success: true });
+            })
+            .catch(e => {
+              browser.test.sendMessage("theme-image", {
+                success: false,
+                error: e.message,
+              });
+            });
+        });
+      },
+    },
+  });
+
+  await extension.startup();
+  await theme.startup();
+
+  const privateWin = await BrowserTestUtils.openNewBrowserWindow({
+    private: true,
+  });
+
+  const { ExtensionCommon } = ChromeUtils.importESModule(
+    "resource://gre/modules/ExtensionCommon.sys.mjs"
+  );
+  const { makeWidgetId } = ExtensionCommon;
+  privateWin.SidebarUI.show(`${makeWidgetId(extension.id)}-sidebar-action`);
+
+  let imageLoaded = extension.awaitMessage("theme-image");
+  Assert.deepEqual(await imageLoaded, { success: true }, "theme image loaded");
+
+  await extension.unload();
+  await theme.unload();
+
+  await BrowserTestUtils.closeWindow(privateWin);
+});
diff --git a/toolkit/components/extensions/test/browser/browser_ext_themes_highlight.js b/toolkit/components/extensions/test/browser/browser_ext_themes_highlight.js
new file mode 100644
index 0000000000..5a0d1c7a8d
--- /dev/null
+++ b/toolkit/components/extensions/test/browser/browser_ext_themes_highlight.js
@@ -0,0 +1,63 @@
+"use strict";
+
+// This test checks whether applied WebExtension themes that attempt to change
+// the color of the font and background in a selection are applied properly.
+const { CustomizableUITestUtils } = ChromeUtils.importESModule(
+  "resource://testing-common/CustomizableUITestUtils.sys.mjs"
+);
+let gCUITestUtils = new CustomizableUITestUtils(window);
+add_setup(async function () {
+  await gCUITestUtils.addSearchBar();
+  await gFindBarPromise;
+  registerCleanupFunction(() => {
+    gFindBar.close();
+    gCUITestUtils.removeSearchBar();
+  });
+});
+
+add_task(async function test_support_selection() {
+  const HIGHLIGHT_TEXT_COLOR = "#9400FF";
+  const HIGHLIGHT_COLOR = "#F89919";
+  let extension = ExtensionTestUtils.loadExtension({
+    manifest: {
+      theme: {
+        colors: {
+          toolbar_field_highlight: HIGHLIGHT_COLOR,
+          toolbar_field_highlight_text: HIGHLIGHT_TEXT_COLOR,
+        },
+      },
+    },
+  });
+  await extension.startup();
+
+  let fields = [
+    gURLBar.inputField,
+    document.querySelector("#searchbar .searchbar-textbox"),
+    document.querySelector(".findbar-textbox"),
+  ].filter(field => {
+    let bounds = field.getBoundingClientRect();
+    return bounds.width > 0 && bounds.height > 0;
+  });
+
+  Assert.equal(fields.length, 3, "Should be testing three elements");
+
+  info(
+    `Checking background colors and colors for ${fields.length} toolbar input fields.`
+  );
+  for (let field of fields) {
+    info(`Testing ${field.id || field.className}`);
+    field.focus();
+    Assert.equal(
+      window.getComputedStyle(field, "::selection").backgroundColor,
+      hexToCSS(HIGHLIGHT_COLOR),
+      "Input selection background should be set."
+    );
+    Assert.equal(
+      window.getComputedStyle(field, "::selection").color,
+      hexToCSS(HIGHLIGHT_TEXT_COLOR),
+      "Input selection color should be set."
+    );
+  }
+
+  await extension.unload();
+});
diff --git a/toolkit/components/extensions/test/browser/browser_ext_themes_incognito.js b/toolkit/components/extensions/test/browser/browser_ext_themes_incognito.js
new file mode 100644
index 0000000000..d9beb0f9a8
--- /dev/null
+++ b/toolkit/components/extensions/test/browser/browser_ext_themes_incognito.js
@@ -0,0 +1,77 @@
+"use strict";
+
+add_task(async function test_theme_incognito_not_allowed() {
+  let windowExtension = ExtensionTestUtils.loadExtension({
+    incognitoOverride: "spanning",
+    async background() {
+      const theme = {
+        colors: {
+          frame: "black",
+          tab_background_text: "black",
+        },
+      };
+      let window = await browser.windows.create({ incognito: true });
+      browser.test.onMessage.addListener(async message => {
+        if (message == "update") {
+          browser.theme.update(window.id, theme);
+          return;
+        }
+        await browser.windows.remove(window.id);
+        browser.test.sendMessage("done");
+      });
+      browser.test.sendMessage("ready", window.id);
+    },
+    manifest: {
+      permissions: ["theme"],
+    },
+  });
+  await windowExtension.startup();
+  let wId = await windowExtension.awaitMessage("ready");
+
+  async function background(windowId) {
+    const theme = {
+      colors: {
+        frame: "black",
+        tab_background_text: "black",
+      },
+    };
+
+    browser.theme.onUpdated.addListener(info => {
+      browser.test.log("got theme onChanged");
+      browser.test.fail("theme");
+    });
+    await browser.test.assertRejects(
+      browser.theme.getCurrent(windowId),
+      /Invalid window ID/,
+      "API should reject getting window theme"
+    );
+    await browser.test.assertRejects(
+      browser.theme.update(windowId, theme),
+      /Invalid window ID/,
+      "API should reject updating theme"
+    );
+    await browser.test.assertRejects(
+      browser.theme.reset(windowId),
+      /Invalid window ID/,
+      "API should reject reseting theme on window"
+    );
+
+    browser.test.sendMessage("start");
+  }
+
+  let extension = ExtensionTestUtils.loadExtension({
+    background: `(${background})(${wId})`,
+    manifest: {
+      permissions: ["theme"],
+    },
+  });
+
+  await extension.startup();
+  await extension.awaitMessage("start");
+  windowExtension.sendMessage("update");
+
+  windowExtension.sendMessage("close");
+  await windowExtension.awaitMessage("done");
+  await windowExtension.unload();
+  await extension.unload();
+});
diff --git a/toolkit/components/extensions/test/browser/browser_ext_themes_lwtsupport.js b/toolkit/components/extensions/test/browser/browser_ext_themes_lwtsupport.js
new file mode 100644
index 0000000000..4293e5eb19
--- /dev/null
+++ b/toolkit/components/extensions/test/browser/browser_ext_themes_lwtsupport.js
@@ -0,0 +1,69 @@
+"use strict";
+
+const DEFAULT_THEME_BG_COLOR = "rgb(255, 255, 255)";
+const DEFAULT_THEME_TEXT_COLOR = "rgb(0, 0, 0)";
+
+add_task(async function test_deprecated_LWT_properties_ignored() {
+  // This test uses deprecated theme properties, so warnings are expected.
+  ExtensionTestUtils.failOnSchemaWarnings(false);
+
+  let extension = ExtensionTestUtils.loadExtension({
+    manifest: {
+      theme: {
+        images: {
+          headerURL: "image1.png",
+        },
+        colors: {
+          accentcolor: ACCENT_COLOR,
+          textcolor: TEXT_COLOR,
+        },
+      },
+    },
+    files: {
+      "image1.png": BACKGROUND,
+    },
+  });
+
+  await extension.startup();
+
+  let docEl = window.document.documentElement;
+  let docStyle = window.getComputedStyle(docEl);
+  let navigatorStyle = window.getComputedStyle(
+    docEl.querySelector("#navigator-toolbox")
+  );
+
+  Assert.ok(docEl.hasAttribute("lwtheme"), "LWT attribute should be set");
+  Assert.ok(
+    !docEl.hasAttribute("lwtheme-image"),
+    "LWT image attribute should not be set on deprecated headerURL alias"
+  );
+  Assert.ok(
+    !docEl.getAttribute("lwtheme-brighttext"),
+    "LWT text color attribute should not be set on deprecated textcolor alias"
+  );
+
+  if (backgroundColorSetOnRoot()) {
+    let rootCS = window.getComputedStyle(docEl);
+    Assert.equal(
+      rootCS.backgroundColor,
+      DEFAULT_THEME_BG_COLOR,
+      "Expected default theme background color"
+    );
+  } else {
+    Assert.equal(
+      navigatorStyle.backgroundColor,
+      DEFAULT_THEME_BG_COLOR,
+      "Expected default theme background color"
+    );
+  }
+
+  Assert.equal(
+    docStyle.color,
+    DEFAULT_THEME_TEXT_COLOR,
+    "Expected default theme text color"
+  );
+
+  await extension.unload();
+
+  Assert.ok(!docEl.hasAttribute("lwtheme"), "LWT attribute should not be set");
+});
diff --git a/toolkit/components/extensions/test/browser/browser_ext_themes_multiple_backgrounds.js b/toolkit/components/extensions/test/browser/browser_ext_themes_multiple_backgrounds.js
new file mode 100644
index 0000000000..58088ce6a0
--- /dev/null
+++ b/toolkit/components/extensions/test/browser/browser_ext_themes_multiple_backgrounds.js
@@ -0,0 +1,287 @@
+"use strict";
+
+add_task(async function test_support_backgrounds_position() {
+  let extension = ExtensionTestUtils.loadExtension({
+    manifest: {
+      theme: {
+        images: {
+          theme_frame: "face1.png",
+          additional_backgrounds: ["face2.png", "face2.png", "face2.png"],
+        },
+        colors: {
+          frame: `rgb(${FRAME_COLOR.join(",")})`,
+          tab_background_text: `rgb(${TAB_BACKGROUND_TEXT_COLOR.join(",")})`,
+        },
+        properties: {
+          additional_backgrounds_alignment: [
+            "left top",
+            "center top",
+            "right bottom",
+          ],
+        },
+      },
+    },
+    files: {
+      "face1.png": imageBufferFromDataURI(ENCODED_IMAGE_DATA),
+      "face2.png": imageBufferFromDataURI(ENCODED_IMAGE_DATA),
+    },
+  });
+
+  await extension.startup();
+
+  let docEl = window.document.documentElement;
+  let toolbox = document.querySelector("#navigator-toolbox");
+
+  Assert.ok(docEl.hasAttribute("lwtheme"), "LWT attribute should be set");
+  Assert.equal(
+    docEl.getAttribute("lwtheme-brighttext"),
+    "true",
+    "LWT text color attribute should be set"
+  );
+
+  let toolboxCS = window.getComputedStyle(toolbox);
+  let toolboxBgImage = toolboxCS.backgroundImage.split(",")[0].trim();
+  if (backgroundColorSetOnRoot()) {
+    let rootCS = window.getComputedStyle(docEl);
+    let rootBgImage = rootCS.backgroundImage.split(",")[0].trim();
+    Assert.ok(
+      rootBgImage.includes("face1.png"),
+      `The backgroundImage should use face1.png. Actual value is: ${rootBgImage}`
+    );
+    Assert.equal(
+      toolboxCS.backgroundImage,
+      Array(3).fill(toolboxBgImage).join(", "),
+      "The backgroundImage should use face2.png three times."
+    );
+    Assert.equal(
+      toolboxCS.backgroundPosition,
+      "0% 0%, 50% 0%, 100% 100%",
+      "The backgroundPosition should use the three values provided."
+    );
+  } else {
+    Assert.equal(
+      toolboxCS.backgroundImage,
+      [1, 2, 2, 2]
+        .map(num => toolboxBgImage.replace(/face[\d]*/, `face${num}`))
+        .join(", "),
+      "The backgroundImage should use face1.png once and face2.png three times."
+    );
+    Assert.equal(
+      toolboxCS.backgroundPosition,
+      "100% 0%, 0% 0%, 50% 0%, 100% 100%",
+      "The backgroundPosition should use the three values provided, preceded by the default for theme_frame."
+    );
+    /**
+     * We expect duplicate background-repeat values because we apply `no-repeat`
+     * once for theme_frame, and again as the default value of
+     * --lwt-background-tiling.
+     */
+    Assert.equal(
+      toolboxCS.backgroundRepeat,
+      "no-repeat, no-repeat",
+      "The backgroundPosition should use the default value."
+    );
+  }
+
+  await extension.unload();
+
+  Assert.ok(!docEl.hasAttribute("lwtheme"), "LWT attribute should not be set");
+  toolboxCS = window.getComputedStyle(toolbox);
+
+  // Styles should've reverted to their initial values.
+  if (backgroundColorSetOnRoot()) {
+    let rootCS = window.getComputedStyle(docEl);
+    Assert.equal(rootCS.backgroundImage, "none");
+    Assert.equal(rootCS.backgroundPosition, "0% 0%");
+    Assert.equal(rootCS.backgroundRepeat, "repeat");
+  }
+  Assert.equal(toolboxCS.backgroundImage, "none");
+  Assert.equal(toolboxCS.backgroundPosition, "0% 0%");
+  Assert.equal(toolboxCS.backgroundRepeat, "repeat");
+});
+
+add_task(async function test_support_backgrounds_repeat() {
+  let extension = ExtensionTestUtils.loadExtension({
+    manifest: {
+      theme: {
+        images: {
+          theme_frame: "face0.png",
+          additional_backgrounds: ["face1.png", "face2.png", "face3.png"],
+        },
+        colors: {
+          frame: FRAME_COLOR,
+          tab_background_text: TAB_BACKGROUND_TEXT_COLOR,
+        },
+        properties: {
+          additional_backgrounds_tiling: ["repeat-x", "repeat-y", "repeat"],
+        },
+      },
+    },
+    files: {
+      "face0.png": imageBufferFromDataURI(ENCODED_IMAGE_DATA),
+      "face1.png": imageBufferFromDataURI(ENCODED_IMAGE_DATA),
+      "face2.png": imageBufferFromDataURI(ENCODED_IMAGE_DATA),
+      "face3.png": imageBufferFromDataURI(ENCODED_IMAGE_DATA),
+    },
+  });
+
+  await extension.startup();
+
+  let docEl = window.document.documentElement;
+  let toolbox = document.querySelector("#navigator-toolbox");
+
+  Assert.ok(docEl.hasAttribute("lwtheme"), "LWT attribute should be set");
+  Assert.equal(
+    docEl.getAttribute("lwtheme-brighttext"),
+    "true",
+    "LWT text color attribute should be set"
+  );
+
+  let toolboxCS = window.getComputedStyle(toolbox);
+  if (backgroundColorSetOnRoot()) {
+    let rootCS = window.getComputedStyle(docEl);
+    let rootImage = rootCS.backgroundImage.split(",")[0].trim();
+    Assert.ok(
+      rootImage.includes("face0.png"),
+      `The backgroundImage should use face.png. Actual value is: ${rootImage}`
+    );
+    Assert.equal(
+      [1, 2, 3]
+        .map(num => rootImage.replace(/face[\d]*/, `face${num}`))
+        .join(", "),
+      toolboxCS.backgroundImage,
+      "The backgroundImage should use face.png three times."
+    );
+    Assert.equal(
+      rootCS.backgroundPosition,
+      "100% 0%, 100% 0%",
+      "The backgroundPosition should use the default value for root."
+    );
+    Assert.equal(
+      toolboxCS.backgroundPosition,
+      "100% 0%",
+      "The backgroundPosition should use the default value for navigator-toolbox."
+    );
+    Assert.equal(
+      rootCS.backgroundRepeat,
+      "no-repeat, repeat-x, repeat-y, repeat",
+      "The backgroundRepeat should use the default values for root."
+    );
+    Assert.equal(
+      toolboxCS.backgroundRepeat,
+      "repeat-x, repeat-y, repeat",
+      "The backgroundRepeat should use the three values provided for navigator-toolbox."
+    );
+  } else {
+    let toolboxImage = toolboxCS.backgroundImage.split(",")[0].trim();
+    Assert.equal(
+      [0, 1, 2, 3]
+        .map(num => toolboxImage.replace(/face[\d]*/, `face${num}`))
+        .join(", "),
+      toolboxCS.backgroundImage,
+      "The backgroundImage should use face.png four times."
+    );
+    /**
+     * We expect duplicate background-position values because we apply `right top`
+     * once for theme_frame, and again as the default value of
+     * --lwt-background-alignment.
+     */
+    Assert.equal(
+      toolboxCS.backgroundPosition,
+      "100% 0%, 100% 0%",
+      "The backgroundPosition should use the default value for navigator-toolbox."
+    );
+    Assert.equal(
+      toolboxCS.backgroundRepeat,
+      "no-repeat, repeat-x, repeat-y, repeat",
+      "The backgroundRepeat should use the three values provided for --lwt-background-tiling, preceeded by the default for theme_frame."
+    );
+  }
+
+  await extension.unload();
+
+  Assert.ok(!docEl.hasAttribute("lwtheme"), "LWT attribute should not be set");
+});
+
+add_task(async function test_additional_images_check() {
+  let extension = ExtensionTestUtils.loadExtension({
+    manifest: {
+      theme: {
+        images: {
+          theme_frame: "face.png",
+        },
+        colors: {
+          frame: FRAME_COLOR,
+          tab_background_text: TAB_BACKGROUND_TEXT_COLOR,
+        },
+        properties: {
+          additional_backgrounds_tiling: ["repeat-x", "repeat-y", "repeat"],
+        },
+      },
+    },
+    files: {
+      "face.png": imageBufferFromDataURI(ENCODED_IMAGE_DATA),
+    },
+  });
+
+  await extension.startup();
+
+  let docEl = window.document.documentElement;
+  let toolbox = document.querySelector("#navigator-toolbox");
+
+  Assert.ok(docEl.hasAttribute("lwtheme"), "LWT attribute should be set");
+  Assert.equal(
+    docEl.getAttribute("lwtheme-brighttext"),
+    "true",
+    "LWT text color attribute should be set"
+  );
+
+  let toolboxCS = window.getComputedStyle(toolbox);
+  if (backgroundColorSetOnRoot()) {
+    let rootCS = window.getComputedStyle(docEl);
+    let bgImage = rootCS.backgroundImage.split(",")[0].trim();
+    Assert.ok(
+      bgImage.includes("face.png"),
+      `The backgroundImage should use face.png. Actual value is: ${bgImage}`
+    );
+    Assert.equal(
+      "none",
+      toolboxCS.backgroundImage,
+      "The backgroundImage should not use face.png."
+    );
+    Assert.equal(
+      rootCS.backgroundPosition,
+      "100% 0%, 100% 0%",
+      "The backgroundPosition should use the default value."
+    );
+    Assert.equal(
+      rootCS.backgroundRepeat,
+      "no-repeat, no-repeat",
+      "The backgroundPosition should use only one (default) value for the header and the default additional images."
+    );
+  } else {
+    let bgImage = toolboxCS.backgroundImage.split(",")[0].trim();
+    Assert.ok(
+      bgImage.includes("face.png"),
+      `The backgroundImage should use face.png. Actual value is: ${bgImage}`
+    );
+    Assert.ok(
+      bgImage.includes("face.png"),
+      `The backgroundImage should use face.png. Actual value is: ${bgImage}`
+    );
+    Assert.equal(
+      toolboxCS.backgroundPosition,
+      "100% 0%, 100% 0%",
+      "The backgroundPosition should use the default value."
+    );
+    Assert.equal(
+      toolboxCS.backgroundRepeat,
+      "no-repeat, no-repeat",
+      "The backgroundRepeat should use the default value."
+    );
+  }
+
+  await extension.unload();
+
+  Assert.ok(!docEl.hasAttribute("lwtheme"), "LWT attribute should not be set");
+});
diff --git a/toolkit/components/extensions/test/browser/browser_ext_themes_ntp_colors.js b/toolkit/components/extensions/test/browser/browser_ext_themes_ntp_colors.js
new file mode 100644
index 0000000000..8e2f5446c9
--- /dev/null
+++ b/toolkit/components/extensions/test/browser/browser_ext_themes_ntp_colors.js
@@ -0,0 +1,203 @@
+"use strict";
+// This test checks whether the new tab page color properties work.
+
+function waitForAboutNewTabReady(browser, url) {
+  // Stop-gap fix for https://bugzilla.mozilla.org/show_bug.cgi?id=1697196#c24
+  return SpecialPowers.spawn(browser, [url], async url => {
+    let doc = content.document;
+    await ContentTaskUtils.waitForCondition(
+      () => doc.querySelector(".outer-wrapper"),
+      `Waiting for page wrapper to be initialized at ${url}`
+    );
+  });
+}
+
+/**
+ * Test whether the selected browser has the new tab page theme applied
+ *
+ * @param {object} theme that is applied
+ * @param {boolean} isBrightText whether the brighttext attribute should be set
+ */
+async function test_ntp_theme(theme, isBrightText) {
+  let extension = ExtensionTestUtils.loadExtension({
+    manifest: {
+      theme,
+    },
+  });
+
+  let browser = gBrowser.selectedBrowser;
+
+  let { originalBackground, originalCardBackground, originalColor } =
+    await SpecialPowers.spawn(browser, [], function () {
+      let doc = content.document;
+      ok(
+        !doc.documentElement.hasAttribute("lwt-newtab"),
+        "New tab page should not have lwt-newtab attribute"
+      );
+      ok(
+        !doc.documentElement.hasAttribute("lwt-newtab-brighttext"),
+        `New tab page should not have lwt-newtab-brighttext attribute`
+      );
+
+      return {
+        originalBackground: content.getComputedStyle(doc.body).backgroundColor,
+        originalCardBackground: content.getComputedStyle(
+          doc.querySelector(".top-site-outer .tile")
+        ).backgroundColor,
+        originalColor: content.getComputedStyle(
+          doc.querySelector(".outer-wrapper")
+        ).color,
+        // We check the value of --newtab-link-primary-color directly because the
+        // elements on which it is applied are hard to test. It is most visible in
+        // the "learn more" link in the Pocket section. We cannot show the Pocket
+        // section since it hits the network, and the usual workarounds to change
+        // its backend only work in browser/. This variable is also used in
+        // the Edit Top Site modal, but showing/hiding that is very verbose and
+        // would make this test almost unreadable.
+        originalLinks: content
+          .getComputedStyle(doc.documentElement)
+          .getPropertyValue("--newtab-link-primary-color"),
+      };
+    });
+
+  await extension.startup();
+
+  Services.ppmm.sharedData.flush();
+
+  await SpecialPowers.spawn(
+    browser,
+    [
+      {
+        isBrightText,
+        background: hexToCSS(theme.colors.ntp_background),
+        card_background: hexToCSS(theme.colors.ntp_card_background),
+        color: hexToCSS(theme.colors.ntp_text),
+      },
+    ],
+    async function ({ isBrightText, background, card_background, color }) {
+      let doc = content.document;
+      ok(
+        doc.documentElement.hasAttribute("lwt-newtab"),
+        "New tab page should have lwt-newtab attribute"
+      );
+      is(
+        doc.documentElement.hasAttribute("lwt-newtab-brighttext"),
+        isBrightText,
+        `New tab page should${
+          !isBrightText ? " not" : ""
+        } have lwt-newtab-brighttext attribute`
+      );
+
+      is(
+        content.getComputedStyle(doc.body).backgroundColor,
+        background,
+        "New tab page background should be set."
+      );
+      is(
+        content.getComputedStyle(doc.querySelector(".top-site-outer .tile"))
+          .backgroundColor,
+        card_background,
+        "New tab page card background should be set."
+      );
+      is(
+        content.getComputedStyle(doc.querySelector(".outer-wrapper")).color,
+        color,
+        "New tab page text color should be set."
+      );
+    }
+  );
+
+  await extension.unload();
+
+  Services.ppmm.sharedData.flush();
+
+  await SpecialPowers.spawn(
+    browser,
+    [
+      {
+        originalBackground,
+        originalCardBackground,
+        originalColor,
+      },
+    ],
+    function ({ originalBackground, originalCardBackground, originalColor }) {
+      let doc = content.document;
+      ok(
+        !doc.documentElement.hasAttribute("lwt-newtab"),
+        "New tab page should not have lwt-newtab attribute"
+      );
+      ok(
+        !doc.documentElement.hasAttribute("lwt-newtab-brighttext"),
+        `New tab page should not have lwt-newtab-brighttext attribute`
+      );
+
+      is(
+        content.getComputedStyle(doc.body).backgroundColor,
+        originalBackground,
+        "New tab page background should be reset."
+      );
+      is(
+        content.getComputedStyle(doc.querySelector(".top-site-outer .tile"))
+          .backgroundColor,
+        originalCardBackground,
+        "New tab page card background should be reset."
+      );
+      is(
+        content.getComputedStyle(doc.querySelector(".outer-wrapper")).color,
+        originalColor,
+        "New tab page text color should be reset."
+      );
+    }
+  );
+}
+
+add_task(async function test_support_ntp_colors() {
+  await SpecialPowers.pushPrefEnv({
+    set: [
+      // BrowserTestUtils.withNewTab waits for about:newtab to load
+      // so we disable preloading before running the test.
+      ["browser.newtab.preload", false],
+      // Force prefers-color-scheme to "light", as otherwise it might be
+      // derived from the theme, but we hard-code the light styles on this
+      // test.
+      ["layout.css.prefers-color-scheme.content-override", 1],
+      // Override the system color scheme to light so this test passes on
+      // machines with dark system color scheme.
+      ["ui.systemUsesDarkTheme", 0],
+    ],
+  });
+  NewTabPagePreloading.removePreloadedBrowser(window);
+  for (let url of ["about:newtab", "about:home"]) {
+    info("Opening url: " + url);
+    await BrowserTestUtils.withNewTab({ gBrowser, url }, async browser => {
+      await waitForAboutNewTabReady(browser, url);
+      await test_ntp_theme(
+        {
+          colors: {
+            frame: ACCENT_COLOR,
+            tab_background_text: TEXT_COLOR,
+            ntp_background: "#add8e6",
+            ntp_card_background: "#ffffff",
+            ntp_text: "#00008b",
+          },
+        },
+        false,
+        url
+      );
+
+      await test_ntp_theme(
+        {
+          colors: {
+            frame: ACCENT_COLOR,
+            tab_background_text: TEXT_COLOR,
+            ntp_background: "#00008b",
+            ntp_card_background: "#000000",
+            ntp_text: "#add8e6",
+          },
+        },
+        true,
+        url
+      );
+    });
+  }
+});
diff --git a/toolkit/components/extensions/test/browser/browser_ext_themes_ntp_colors_perwindow.js b/toolkit/components/extensions/test/browser/browser_ext_themes_ntp_colors_perwindow.js
new file mode 100644
index 0000000000..9d28cf50c8
--- /dev/null
+++ b/toolkit/components/extensions/test/browser/browser_ext_themes_ntp_colors_perwindow.js
@@ -0,0 +1,240 @@
+"use strict";
+
+// This test checks whether the new tab page color properties work per-window.
+
+function waitForAboutNewTabReady(browser, url) {
+  // Stop-gap fix for https://bugzilla.mozilla.org/show_bug.cgi?id=1697196#c24
+  return SpecialPowers.spawn(browser, [url], async url => {
+    let doc = content.document;
+    await ContentTaskUtils.waitForCondition(
+      () => doc.querySelector(".outer-wrapper"),
+      `Waiting for page wrapper to be initialized at ${url}`
+    );
+  });
+}
+
+/**
+ * Test whether a given browser has the new tab page theme applied
+ *
+ * @param {object} browser to test against
+ * @param {object} theme that is applied
+ * @param {boolean} isBrightText whether the brighttext attribute should be set
+ * @returns {Promise} The task as a promise
+ */
+function test_ntp_theme(browser, theme, isBrightText) {
+  Services.ppmm.sharedData.flush();
+  return SpecialPowers.spawn(
+    browser,
+    [
+      {
+        isBrightText,
+        background: hexToCSS(theme.colors.ntp_background),
+        card_background: hexToCSS(theme.colors.ntp_card_background),
+        color: hexToCSS(theme.colors.ntp_text),
+      },
+    ],
+    function ({ isBrightText, background, card_background, color }) {
+      let doc = content.document;
+      ok(
+        doc.documentElement.hasAttribute("lwt-newtab"),
+        "New tab page should have lwt-newtab attribute"
+      );
+      is(
+        doc.documentElement.hasAttribute("lwt-newtab-brighttext"),
+        isBrightText,
+        `New tab page should${
+          !isBrightText ? " not" : ""
+        } have lwt-newtab-brighttext attribute`
+      );
+
+      is(
+        content.getComputedStyle(doc.body).backgroundColor,
+        background,
+        "New tab page background should be set."
+      );
+      is(
+        content.getComputedStyle(doc.querySelector(".top-site-outer .tile"))
+          .backgroundColor,
+        card_background,
+        "New tab page card background should be set."
+      );
+      is(
+        content.getComputedStyle(doc.querySelector(".outer-wrapper")).color,
+        color,
+        "New tab page text color should be set."
+      );
+    }
+  );
+}
+
+/**
+ * Test whether a given browser has the default theme applied
+ *
+ * @param {object} browser to test against
+ * @param {string} url being tested
+ * @returns {Promise} The task as a promise
+ */
+function test_ntp_default_theme(browser, url) {
+  Services.ppmm.sharedData.flush();
+  return SpecialPowers.spawn(
+    browser,
+    [
+      {
+        background: hexToCSS("#F9F9FB"),
+        color: hexToCSS("#15141A"),
+      },
+    ],
+    function ({ background, color }) {
+      let doc = content.document;
+      ok(
+        !doc.documentElement.hasAttribute("lwt-newtab"),
+        "New tab page should not have lwt-newtab attribute"
+      );
+      ok(
+        !doc.documentElement.hasAttribute("lwt-newtab-brighttext"),
+        `New tab page should not have lwt-newtab-brighttext attribute`
+      );
+
+      is(
+        content.getComputedStyle(doc.body).backgroundColor,
+        background,
+        "New tab page background should be reset."
+      );
+      is(
+        content.getComputedStyle(doc.querySelector(".outer-wrapper")).color,
+        color,
+        "New tab page text color should be reset."
+      );
+    }
+  );
+}
+
+add_task(async function test_per_window_ntp_theme() {
+  let extension = ExtensionTestUtils.loadExtension({
+    manifest: {
+      permissions: ["theme"],
+    },
+    async background() {
+      function promiseWindowChecked() {
+        return new Promise(resolve => {
+          let listener = msg => {
+            if (msg == "checked-window") {
+              browser.test.onMessage.removeListener(listener);
+              resolve();
+            }
+          };
+          browser.test.onMessage.addListener(listener);
+        });
+      }
+
+      function removeWindow(winId) {
+        return new Promise(resolve => {
+          let listener = removedWinId => {
+            if (removedWinId == winId) {
+              browser.windows.onRemoved.removeListener(listener);
+              resolve();
+            }
+          };
+          browser.windows.onRemoved.addListener(listener);
+          browser.windows.remove(winId);
+        });
+      }
+
+      async function checkWindow(theme, isBrightText, winId) {
+        let windowChecked = promiseWindowChecked();
+        browser.test.sendMessage("check-window", {
+          theme,
+          isBrightText,
+          winId,
+        });
+        await windowChecked;
+      }
+
+      const darkTextTheme = {
+        colors: {
+          frame: "#add8e6",
+          tab_background_text: "#000",
+          ntp_background: "#add8e6",
+          ntp_card_background: "#ff0000",
+          ntp_text: "#000",
+        },
+      };
+
+      const brightTextTheme = {
+        colors: {
+          frame: "#00008b",
+          tab_background_text: "#add8e6",
+          ntp_background: "#00008b",
+          ntp_card_background: "#00ff00",
+          ntp_text: "#add8e6",
+        },
+      };
+
+      let { id: winId } = await browser.windows.getCurrent();
+      // We are opening about:blank instead of the default homepage,
+      // because using the default homepage results in intermittent
+      // test failures on debug builds due to browser window leaks.
+      // A side effect of testing on about:blank is that
+      // test_ntp_default_theme cannot test properties used only on
+      // about:newtab, like ntp_card_background.
+      let { id: secondWinId } = await browser.windows.create({
+        url: "about:blank",
+      });
+
+      browser.test.log("Test that single window update works");
+      await browser.theme.update(winId, darkTextTheme);
+      await checkWindow(darkTextTheme, false, winId);
+      await checkWindow(null, false, secondWinId);
+
+      browser.test.log("Test that applying different themes on both windows");
+      await browser.theme.update(secondWinId, brightTextTheme);
+      await checkWindow(darkTextTheme, false, winId);
+      await checkWindow(brightTextTheme, true, secondWinId);
+
+      browser.test.log("Test resetting the theme on one window");
+      await browser.theme.reset(winId);
+      await checkWindow(null, false, winId);
+      await checkWindow(brightTextTheme, true, secondWinId);
+
+      await removeWindow(secondWinId);
+      await checkWindow(null, false, winId);
+      browser.test.notifyPass("perwindow-ntp-theme");
+    },
+  });
+
+  extension.onMessage(
+    "check-window",
+    async ({ theme, isBrightText, winId }) => {
+      let win = Services.wm.getOuterWindowWithId(winId);
+      win.NewTabPagePreloading.removePreloadedBrowser(win);
+      // These pages were initially chosen because LightweightThemeChild.sys.mjs
+      // treats them specially.
+      for (let url of ["about:newtab", "about:home"]) {
+        info("Opening url: " + url);
+        await BrowserTestUtils.withNewTab(
+          { gBrowser: win.gBrowser, url },
+          async browser => {
+            await waitForAboutNewTabReady(browser, url);
+            if (theme) {
+              await test_ntp_theme(browser, theme, isBrightText);
+            } else {
+              await test_ntp_default_theme(browser, url);
+            }
+          }
+        );
+      }
+      extension.sendMessage("checked-window");
+    }
+  );
+
+  // BrowserTestUtils.withNewTab waits for about:newtab to load
+  // so we disable preloading before running the test.
+  await SpecialPowers.setBoolPref("browser.newtab.preload", false);
+  registerCleanupFunction(() => {
+    SpecialPowers.clearUserPref("browser.newtab.preload");
+  });
+
+  await extension.startup();
+  await extension.awaitFinish("perwindow-ntp-theme");
+  await extension.unload();
+});
diff --git a/toolkit/components/extensions/test/browser/browser_ext_themes_pbm.js b/toolkit/components/extensions/test/browser/browser_ext_themes_pbm.js
new file mode 100644
index 0000000000..f830e55294
--- /dev/null
+++ b/toolkit/components/extensions/test/browser/browser_ext_themes_pbm.js
@@ -0,0 +1,439 @@
+/* -*- Mode: indent-tabs-mode: nil; js-indent-level: 2 -*- */
+/* vim: set sts=2 sw=2 et tw=80: */
+"use strict";
+
+/**
+ * Tests that we apply dark theme variants to PBM windows where applicable.
+ */
+
+const { BuiltInThemes } = ChromeUtils.importESModule(
+  "resource:///modules/BuiltInThemes.sys.mjs"
+);
+const { PromptTestUtils } = ChromeUtils.importESModule(
+  "resource://testing-common/PromptTestUtils.sys.mjs"
+);
+
+const IS_LINUX = AppConstants.platform == "linux";
+
+const LIGHT_THEME_ID = "firefox-compact-light@mozilla.org";
+const DARK_THEME_ID = "firefox-compact-dark@mozilla.org";
+
+// This tests opens many chrome windows which is slow on debug builds.
+requestLongerTimeout(2);
+
+/**
+ * Test a window's theme color scheme.
+ *
+ * @param {*} options - Test options.
+ * @param {Window} options.win - Window object to test.
+ * @param {boolean} options.colorScheme - Whether expected chrome color scheme
+ * is dark (true) or light (false).
+ * @param {boolean} options.expectLWTAttributes - Whether the window  should
+ * have the LWT attributes set matching the color scheme.
+ * @param {boolean} options.expectDefaultDarkAttribute - Whether the window
+ * should have the "lwt-default-theme-in-dark-mode" attribute.
+ */
+async function testWindowColorScheme({
+  win,
+  expectDark,
+  expectLWTAttributes,
+  expectDefaultDarkAttribute,
+}) {
+  let docEl = win.document.documentElement;
+
+  is(
+    docEl.hasAttribute("lwt-default-theme-in-dark-mode"),
+    expectDefaultDarkAttribute,
+    `Window should${
+      expectDefaultDarkAttribute ? "" : " not"
+    } have lwt-default-theme-in-dark-mode attribute.`
+  );
+
+  if (expectLWTAttributes) {
+    ok(docEl.hasAttribute("lwtheme"), "Window should have LWT attribute.");
+    is(
+      docEl.getAttribute("lwtheme-brighttext"),
+      expectDark ? "true" : null,
+      "LWT text color attribute should be set."
+    );
+  } else {
+    ok(!docEl.hasAttribute("lwtheme"), "Window should not have LWT attribute.");
+    ok(
+      !docEl.hasAttribute("lwtheme-brighttext"),
+      "LWT text color attribute should not be set."
+    );
+  }
+}
+
+/**
+ * Match the prefers-color-scheme media query and return the results.
+ *
+ * @param {object} options
+ * @param {Window} options.win - If chrome=true, window to test, otherwise
+ * parent window of the content window to test.
+ * @param {boolean} options.chrome - If true the media queries will be matched
+ * against the supplied chrome window. Otherwise they will be matched against
+ * the content window.
+ * @returns  {Promise<{light: boolean, dark: boolean}>} - Resolves with an
+ * object of the media query results.
+ */
+function getPrefersColorSchemeInfo({ win, chrome = false }) {
+  let fn = async windowObj => {
+    // If called in the parent, we use the supplied win object. Otherwise use
+    // the content window global.
+    let win = windowObj || content;
+
+    // LookAndFeel updates are async.
+    await new Promise(resolve => {
+      win.requestAnimationFrame(() => win.requestAnimationFrame(resolve));
+    });
+    return {
+      light: win.matchMedia("(prefers-color-scheme: light)").matches,
+      dark: win.matchMedia("(prefers-color-scheme: dark)").matches,
+    };
+  };
+
+  if (chrome) {
+    return fn(win);
+  }
+
+  return SpecialPowers.spawn(win.gBrowser.selectedBrowser, [], fn);
+}
+
+add_setup(async function () {
+  // Set system theme to light to ensure consistency across test machines.
+  await SpecialPowers.pushPrefEnv({
+    set: [
+      ["browser.theme.dark-private-windows", true],
+      ["ui.systemUsesDarkTheme", 0],
+    ],
+  });
+  // Ensure the built-in themes are initialized.
+  await BuiltInThemes.ensureBuiltInThemes();
+
+  // The previous test, browser_ext_themes_ntp_colors.js has side effects.
+  // Switch to a theme, then switch back to the default theme to reach a
+  // consistent themeData state. Without this, themeData in
+  // LightWeightConsumer#_update does not contain darkTheme data and PBM windows
+  // don't get themed correctly.
+  let lightTheme = await AddonManager.getAddonByID(LIGHT_THEME_ID);
+  await lightTheme.enable();
+  await lightTheme.disable();
+});
+
+// For the default theme with light color scheme, private browsing windows
+// should be themed dark.
+// The PBM window's content should not be themed dark.
+add_task(async function test_default_theme_light() {
+  info("Normal browsing window should not be in dark mode.");
+  await testWindowColorScheme({
+    win: window,
+    expectDark: false,
+    expectLWTAttributes: false,
+    expectDefaultDarkAttribute: false,
+  });
+
+  let windowB = await BrowserTestUtils.openNewBrowserWindow();
+
+  info("Additional normal browsing window should not be in dark mode.");
+  await testWindowColorScheme({
+    win: windowB,
+    expectDark: false,
+    expectLWTAttributes: false,
+    expectDefaultDarkAttribute: false,
+  });
+
+  let pbmWindowA = await BrowserTestUtils.openNewBrowserWindow({
+    private: true,
+  });
+
+  info("Private browsing window should be in dark mode.");
+  await testWindowColorScheme({
+    win: pbmWindowA,
+    expectDark: true,
+    expectLWTAttributes: true,
+    expectDefaultDarkAttribute: true,
+  });
+
+  let prefersColorScheme = await getPrefersColorSchemeInfo({ win: pbmWindowA });
+  ok(
+    prefersColorScheme.light && !prefersColorScheme.dark,
+    "Content of dark themed PBM window should still be themed light"
+  );
+
+  let pbmWindowB = await BrowserTestUtils.openNewBrowserWindow({
+    private: true,
+  });
+  info("Additional private browsing window should be in dark mode.");
+  await testWindowColorScheme({
+    win: pbmWindowB,
+    expectDark: true,
+    expectLWTAttributes: true,
+    expectDefaultDarkAttribute: true,
+  });
+
+  await BrowserTestUtils.closeWindow(windowB);
+  await BrowserTestUtils.closeWindow(pbmWindowA);
+  await BrowserTestUtils.closeWindow(pbmWindowB);
+});
+
+// For the default theme with dark color scheme, normal and private browsing
+// windows should be themed dark.
+add_task(async function test_default_theme_dark() {
+  // Set the system theme to dark. The default theme will follow this color
+  // scheme.
+  await SpecialPowers.pushPrefEnv({ set: [["ui.systemUsesDarkTheme", 1]] });
+
+  info("Normal browsing window should be in dark mode.");
+  await testWindowColorScheme({
+    win: window,
+    expectDark: true,
+    expectLWTAttributes: !IS_LINUX,
+    expectDefaultDarkAttribute: !IS_LINUX,
+  });
+
+  let pbmWindow = await BrowserTestUtils.openNewBrowserWindow({
+    private: true,
+  });
+
+  info("Private browsing window should be in dark mode.");
+  await testWindowColorScheme({
+    win: pbmWindow,
+    expectDark: true,
+    expectLWTAttributes: !IS_LINUX,
+    expectDefaultDarkAttribute: !IS_LINUX,
+  });
+
+  await BrowserTestUtils.closeWindow(pbmWindow);
+
+  await SpecialPowers.popPrefEnv();
+});
+
+// For the light theme both normal and private browsing windows should have a
+// bright color scheme applied.
+add_task(async function test_light_theme_builtin() {
+  let lightTheme = await AddonManager.getAddonByID(LIGHT_THEME_ID);
+  await lightTheme.enable();
+
+  info("Normal browsing window should not be in dark mode.");
+  await testWindowColorScheme({
+    win: window,
+    expectDark: false,
+    expectLWTAttributes: true,
+    expectDefaultDarkAttribute: false,
+  });
+
+  let pbmWindow = await BrowserTestUtils.openNewBrowserWindow({
+    private: true,
+  });
+  info("Private browsing window should not be in dark mode.");
+  await testWindowColorScheme({
+    win: pbmWindow,
+    expectDark: false,
+    expectLWTAttributes: true,
+    expectDefaultDarkAttribute: false,
+  });
+
+  await BrowserTestUtils.closeWindow(pbmWindow);
+  await lightTheme.disable();
+});
+
+// For the dark theme both normal and private browsing should have a dark color
+// scheme applied.
+add_task(async function test_dark_theme_builtin() {
+  let darkTheme = await AddonManager.getAddonByID(DARK_THEME_ID);
+  await darkTheme.enable();
+
+  info("Normal browsing window should be in dark mode.");
+  await testWindowColorScheme({
+    win: window,
+    expectDark: true,
+    expectLWTAttributes: true,
+    expectDefaultDarkAttribute: false,
+  });
+
+  let pbmWindow = await BrowserTestUtils.openNewBrowserWindow({
+    private: true,
+  });
+
+  info("Private browsing window should be in dark mode.");
+  await testWindowColorScheme({
+    win: pbmWindow,
+    expectDark: true,
+    expectLWTAttributes: true,
+    expectDefaultDarkAttribute: false,
+  });
+
+  await BrowserTestUtils.closeWindow(pbmWindow);
+  await darkTheme.disable();
+});
+
+// When switching between default, light and dark theme the private browsing
+// window color scheme should update accordingly.
+add_task(async function test_theme_switch_updates_existing_pbm_win() {
+  let windowB = await BrowserTestUtils.openNewBrowserWindow();
+  let pbmWindow = await BrowserTestUtils.openNewBrowserWindow({
+    private: true,
+  });
+
+  info("Normal browsing window should not be in dark mode.");
+  await testWindowColorScheme({
+    win: window,
+    expectDark: false,
+    expectLWTAttributes: false,
+    expectDefaultDarkAttribute: false,
+  });
+
+  info("Private browsing window should be in dark mode.");
+  await testWindowColorScheme({
+    win: pbmWindow,
+    expectDark: true,
+    expectLWTAttributes: true,
+    expectDefaultDarkAttribute: true,
+  });
+
+  info("Enabling light theme.");
+  let lightTheme = await AddonManager.getAddonByID(LIGHT_THEME_ID);
+  await lightTheme.enable();
+
+  info("Normal browsing window should not be in dark mode.");
+  await testWindowColorScheme({
+    win: window,
+    expectDark: false,
+    expectLWTAttributes: true,
+    expectDefaultDarkAttribute: false,
+  });
+
+  info("Private browsing window should not be in dark mode.");
+  await testWindowColorScheme({
+    win: pbmWindow,
+    expectDark: false,
+    expectLWTAttributes: true,
+    expectDefaultDarkAttribute: false,
+  });
+
+  await lightTheme.disable();
+
+  info("Enabling dark theme.");
+  let darkTheme = await AddonManager.getAddonByID(DARK_THEME_ID);
+  await darkTheme.enable();
+
+  info("Normal browsing window should be in dark mode.");
+  await testWindowColorScheme({
+    win: window,
+    expectDark: true,
+    expectLWTAttributes: true,
+    expectDefaultDarkAttribute: false,
+  });
+
+  info("Private browsing window should be in dark mode.");
+  await testWindowColorScheme({
+    win: pbmWindow,
+    expectDark: true,
+    expectLWTAttributes: true,
+    expectDefaultDarkAttribute: false,
+  });
+
+  await darkTheme.disable();
+
+  await BrowserTestUtils.closeWindow(windowB);
+  await BrowserTestUtils.closeWindow(pbmWindow);
+});
+
+// pageInfo windows should inherit the PBM window dark theme.
+add_task(async function test_pbm_dark_page_info() {
+  for (let isPBM of [false, true]) {
+    let win = await BrowserTestUtils.openNewBrowserWindow({
+      private: isPBM,
+    });
+    let windowTypeStr = isPBM ? "private" : "normal";
+
+    info(`Opening pageInfo from ${windowTypeStr} browsing.`);
+
+    await BrowserTestUtils.withNewTab(
+      { gBrowser: win.gBrowser, url: "https://example.com" },
+      async () => {
+        let pageInfo = win.BrowserPageInfo(null, "securityTab");
+        await BrowserTestUtils.waitForEvent(pageInfo, "page-info-init");
+
+        let prefersColorScheme = await getPrefersColorSchemeInfo({
+          win: pageInfo,
+          chrome: true,
+        });
+        if (isPBM) {
+          ok(
+            !prefersColorScheme.light && prefersColorScheme.dark,
+            "pageInfo from private window should be themed dark."
+          );
+        } else {
+          ok(
+            prefersColorScheme.light && !prefersColorScheme.dark,
+            "pageInfo from normal window should be themed light."
+          );
+        }
+
+        pageInfo.close();
+      }
+    );
+
+    await BrowserTestUtils.closeWindow(win);
+  }
+});
+
+// Prompts should inherit the PBM window dark theme.
+add_task(async function test_pbm_dark_prompts() {
+  const { MODAL_TYPE_TAB, MODAL_TYPE_CONTENT } = Services.prompt;
+
+  for (let isPBM of [false, true]) {
+    let win = await BrowserTestUtils.openNewBrowserWindow({
+      private: isPBM,
+    });
+
+    // TODO: Once Bug 1751953 has been fixed, we can also test MODAL_TYPE_WINDOW
+    // here.
+    for (let modalType of [MODAL_TYPE_TAB, MODAL_TYPE_CONTENT]) {
+      let windowTypeStr = isPBM ? "private" : "normal";
+      let modalTypeStr = modalType == MODAL_TYPE_TAB ? "tab" : "content";
+
+      info(`Opening ${modalTypeStr} prompt from ${windowTypeStr} browsing.`);
+
+      let openPromise = PromptTestUtils.waitForPrompt(
+        win.gBrowser.selectedBrowser,
+        {
+          modalType,
+          promptType: "alert",
+        }
+      );
+      let promptPromise = Services.prompt.asyncAlert(
+        win.gBrowser.selectedBrowser.browsingContext,
+        modalType,
+        "Hello",
+        "Hello, world!"
+      );
+
+      let dialog = await openPromise;
+
+      let prefersColorScheme = await getPrefersColorSchemeInfo({
+        win: dialog.ui.prompt,
+        chrome: true,
+      });
+
+      if (isPBM) {
+        ok(
+          !prefersColorScheme.light && prefersColorScheme.dark,
+          "Prompt from private window should be themed dark."
+        );
+      } else {
+        ok(
+          prefersColorScheme.light && !prefersColorScheme.dark,
+          "Prompt from normal window should be themed light."
+        );
+      }
+
+      await PromptTestUtils.handlePrompt(dialog);
+      await promptPromise;
+    }
+
+    await BrowserTestUtils.closeWindow(win);
+  }
+});
diff --git a/toolkit/components/extensions/test/browser/browser_ext_themes_persistence.js b/toolkit/components/extensions/test/browser/browser_ext_themes_persistence.js
new file mode 100644
index 0000000000..526c3a0883
--- /dev/null
+++ b/toolkit/components/extensions/test/browser/browser_ext_themes_persistence.js
@@ -0,0 +1,64 @@
+"use strict";
+
+// This test checks whether applied WebExtension themes are persisted and applied
+// on newly opened windows.
+
+add_task(async function test_multiple_windows() {
+  let extension = ExtensionTestUtils.loadExtension({
+    manifest: {
+      theme: {
+        images: {
+          theme_frame: "image1.png",
+        },
+        colors: {
+          frame: ACCENT_COLOR,
+          tab_background_text: TEXT_COLOR,
+        },
+      },
+    },
+    files: {
+      "image1.png": BACKGROUND,
+    },
+  });
+
+  await extension.startup();
+
+  let docEl = window.document.documentElement;
+  let toolbox = document.querySelector("#navigator-toolbox");
+  let computedStyle = window.getComputedStyle(
+    backgroundColorSetOnRoot() ? docEl : toolbox
+  );
+
+  Assert.ok(docEl.hasAttribute("lwtheme"), "LWT attribute should be set");
+  Assert.equal(
+    docEl.getAttribute("lwtheme-brighttext"),
+    "true",
+    "LWT text color attribute should be set"
+  );
+  Assert.ok(
+    computedStyle.backgroundImage.includes("image1.png"),
+    "Expected background image"
+  );
+
+  // Now we'll open a new window to see if the theme is also applied there.
+  let window2 = await BrowserTestUtils.openNewBrowserWindow();
+  docEl = window2.document.documentElement;
+  toolbox = window2.document.querySelector("#navigator-toolbox");
+  computedStyle = window.getComputedStyle(
+    backgroundColorSetOnRoot() ? docEl : toolbox
+  );
+
+  Assert.ok(docEl.hasAttribute("lwtheme"), "LWT attribute should be set");
+  Assert.equal(
+    docEl.getAttribute("lwtheme-brighttext"),
+    "true",
+    "LWT text color attribute should be set"
+  );
+  Assert.ok(
+    computedStyle.backgroundImage.includes("image1.png"),
+    "Expected background image"
+  );
+
+  await BrowserTestUtils.closeWindow(window2);
+  await extension.unload();
+});
diff --git a/toolkit/components/extensions/test/browser/browser_ext_themes_reset.js b/toolkit/components/extensions/test/browser/browser_ext_themes_reset.js
new file mode 100644
index 0000000000..d8b3b14073
--- /dev/null
+++ b/toolkit/components/extensions/test/browser/browser_ext_themes_reset.js
@@ -0,0 +1,112 @@
+"use strict";
+
+add_task(async function theme_reset_global_static_theme() {
+  let global_theme_extension = ExtensionTestUtils.loadExtension({
+    manifest: {
+      theme: {
+        colors: {
+          frame: "#123456",
+          tab_background_text: "#fedcba",
+        },
+      },
+    },
+  });
+
+  let extension = ExtensionTestUtils.loadExtension({
+    manifest: {
+      permissions: ["theme"],
+    },
+    async background() {
+      await browser.theme.reset();
+      let theme_after_reset = await browser.theme.getCurrent();
+
+      browser.test.assertEq(
+        "#123456",
+        theme_after_reset.colors.frame,
+        "Theme from other extension should not be cleared upon reset()"
+      );
+
+      let theme = {
+        colors: {
+          frame: "#CF723F",
+        },
+      };
+
+      await browser.theme.update(theme);
+      await browser.theme.reset();
+      let final_reset_theme = await browser.theme.getCurrent();
+
+      browser.test.assertEq(
+        JSON.stringify({ colors: null, images: null, properties: null }),
+        JSON.stringify(final_reset_theme),
+        "Should reset when extension had replaced the global theme"
+      );
+      browser.test.sendMessage("done");
+    },
+  });
+  await global_theme_extension.startup();
+  await extension.startup();
+  await extension.awaitMessage("done");
+
+  await global_theme_extension.unload();
+  await extension.unload();
+});
+
+add_task(async function theme_reset_by_windowId() {
+  let extension = ExtensionTestUtils.loadExtension({
+    manifest: {
+      permissions: ["theme"],
+    },
+    async background() {
+      let theme = {
+        colors: {
+          frame: "#CF723F",
+        },
+      };
+
+      let { id: winId } = await browser.windows.getCurrent();
+      await browser.theme.update(winId, theme);
+      let update_theme = await browser.theme.getCurrent(winId);
+
+      browser.test.onMessage.addListener(async () => {
+        let current_theme = await browser.theme.getCurrent(winId);
+        browser.test.assertEq(
+          update_theme.colors.frame,
+          current_theme.colors.frame,
+          "Should not be reset by a reset(windowId) call from another extension"
+        );
+
+        browser.test.sendMessage("done");
+      });
+
+      browser.test.sendMessage("ready", winId);
+    },
+  });
+
+  let anotherExtension = ExtensionTestUtils.loadExtension({
+    manifest: {
+      permissions: ["theme"],
+    },
+    background() {
+      browser.test.onMessage.addListener(async winId => {
+        await browser.theme.reset(winId);
+        browser.test.sendMessage("done");
+      });
+    },
+  });
+
+  await extension.startup();
+  let winId = await extension.awaitMessage("ready");
+
+  await anotherExtension.startup();
+
+  // theme.reset should be ignored if the theme was set by another extension.
+  anotherExtension.sendMessage(winId);
+  await anotherExtension.awaitMessage("done");
+
+  extension.sendMessage();
+  await extension.awaitMessage("done");
+
+  await anotherExtension.unload();
+  await extension.unload();
+});
diff --git a/toolkit/components/extensions/test/browser/browser_ext_themes_sanitization.js b/toolkit/components/extensions/test/browser/browser_ext_themes_sanitization.js
new file mode 100644
index 0000000000..2e7359ce29
--- /dev/null
+++ b/toolkit/components/extensions/test/browser/browser_ext_themes_sanitization.js
@@ -0,0 +1,187 @@
+"use strict";
+
+// This test checks color sanitization in various situations
+
+add_task(async function test_sanitization_invalid() {
+  // This test checks that invalid values are sanitized
+  let extension = ExtensionTestUtils.loadExtension({
+    manifest: {
+      theme: {
+        colors: {
+          frame: ACCENT_COLOR,
+          tab_background_text: TEXT_COLOR,
+          bookmark_text: "ntimsfavoriteblue",
+        },
+      },
+    },
+  });
+
+  await extension.startup();
+
+  let navbar = document.querySelector("#nav-bar");
+  Assert.equal(
+    window.getComputedStyle(navbar).color,
+    "rgb(0, 0, 0)",
+    "All invalid values should always compute to black."
+  );
+
+  await extension.unload();
+});
+
+add_task(async function test_sanitization_css_variables() {
+  // This test checks that CSS variables are sanitized
+  let extension = ExtensionTestUtils.loadExtension({
+    manifest: {
+      theme: {
+        colors: {
+          frame: ACCENT_COLOR,
+          tab_background_text: TEXT_COLOR,
+          bookmark_text: "var(--arrowpanel-dimmed)",
+        },
+      },
+    },
+  });
+
+  await extension.startup();
+
+  let navbar = document.querySelector("#nav-bar");
+  Assert.equal(
+    window.getComputedStyle(navbar).color,
+    "rgb(0, 0, 0)",
+    "All CSS variables should always compute to black."
+  );
+
+  await extension.unload();
+});
+
+add_task(async function test_sanitization_important() {
+  // This test checks that the sanitizer cannot be fooled with !important
+  let stylesheetAttr = `href="data:text/css,*{color:red!important}" type="text/css"`;
+  let stylesheet = document.createProcessingInstruction(
+    "xml-stylesheet",
+    stylesheetAttr
+  );
+  let load = BrowserTestUtils.waitForEvent(stylesheet, "load");
+  document.insertBefore(stylesheet, document.documentElement);
+  await load;
+
+  let extension = ExtensionTestUtils.loadExtension({
+    manifest: {
+      theme: {
+        colors: {
+          frame: ACCENT_COLOR,
+          tab_background_text: TEXT_COLOR,
+          bookmark_text: "green",
+        },
+      },
+    },
+  });
+
+  await extension.startup();
+
+  let navbar = document.querySelector("#nav-bar");
+  Assert.equal(
+    window.getComputedStyle(navbar).color,
+    "rgb(255, 0, 0)",
+    "Sheet applies"
+  );
+
+  stylesheet.remove();
+
+  Assert.equal(
+    window.getComputedStyle(navbar).color,
+    "rgb(0, 128, 0)",
+    "Shouldn't be able to fool the color sanitizer with !important"
+  );
+
+  await extension.unload();
+});
+
+add_task(async function test_sanitization_transparent() {
+  // This test checks whether transparent values are applied properly
+  let extension = ExtensionTestUtils.loadExtension({
+    manifest: {
+      theme: {
+        colors: {
+          frame: ACCENT_COLOR,
+          tab_background_text: TEXT_COLOR,
+          toolbar_top_separator: "transparent",
+        },
+      },
+    },
+  });
+
+  await extension.startup();
+
+  let navbar = document.querySelector("#nav-bar");
+  Assert.ok(
+    window.getComputedStyle(navbar).boxShadow.includes("rgba(0, 0, 0, 0)"),
+    "Top separator should be transparent"
+  );
+
+  await extension.unload();
+});
+
+add_task(async function test_sanitization_transparent_frame_color() {
+  // This test checks whether transparent frame color falls back to white.
+  let extension = ExtensionTestUtils.loadExtension({
+    manifest: {
+      theme: {
+        colors: {
+          frame: "transparent",
+          tab_background_text: TEXT_COLOR,
+        },
+      },
+    },
+  });
+
+  await extension.startup();
+
+  let toolbox = document.querySelector("#navigator-toolbox");
+  let toolboxCS = window.getComputedStyle(toolbox);
+
+  if (backgroundColorSetOnRoot()) {
+    let docEl = document.documentElement;
+    let rootCS = window.getComputedStyle(docEl);
+    Assert.equal(
+      rootCS.backgroundColor,
+      "rgb(255, 255, 255)",
+      "Accent color should be white"
+    );
+  } else {
+    Assert.equal(
+      toolboxCS.backgroundColor,
+      "rgb(255, 255, 255)",
+      "Accent color should be white"
+    );
+  }
+
+  await extension.unload();
+});
+
+add_task(
+  async function test_sanitization_transparent_tab_background_text_color() {
+    // This test checks whether transparent textcolor falls back to black.
+    let extension = ExtensionTestUtils.loadExtension({
+      manifest: {
+        theme: {
+          colors: {
+            frame: ACCENT_COLOR,
+            tab_background_text: "transparent",
+          },
+        },
+      },
+    });
+
+    await extension.startup();
+
+    let docEl = document.documentElement;
+    Assert.equal(
+      window.getComputedStyle(docEl).color,
+      "rgb(0, 0, 0)",
+      "Text color should be black"
+    );
+
+    await extension.unload();
+  }
+);
diff --git a/toolkit/components/extensions/test/browser/browser_ext_themes_separators.js b/toolkit/components/extensions/test/browser/browser_ext_themes_separators.js
new file mode 100644
index 0000000000..4da4927ccf
--- /dev/null
+++ b/toolkit/components/extensions/test/browser/browser_ext_themes_separators.js
@@ -0,0 +1,76 @@
+"use strict";
+
+// This test checks whether applied WebExtension themes that attempt to change
+// the separator colors are applied properly.
+
+add_task(async function test_support_separator_properties() {
+  const SEPARATOR_TOP_COLOR = "#ff00ff";
+  const SEPARATOR_VERTICAL_COLOR = "#f0000f";
+  const SEPARATOR_FIELD_COLOR = "#9400ff";
+  const SEPARATOR_BOTTOM_COLOR = "#3366cc";
+
+  let extension = ExtensionTestUtils.loadExtension({
+    manifest: {
+      theme: {
+        images: {
+          theme_frame: "image1.png",
+        },
+        colors: {
+          frame: ACCENT_COLOR,
+          tab_background_text: TEXT_COLOR,
+          toolbar_top_separator: SEPARATOR_TOP_COLOR,
+          toolbar_vertical_separator: SEPARATOR_VERTICAL_COLOR,
+          // This property is deprecated, but left in to check it doesn't
+          // unexpectedly break the theme installation.
+          toolbar_field_separator: SEPARATOR_FIELD_COLOR,
+          toolbar_bottom_separator: SEPARATOR_BOTTOM_COLOR,
+        },
+      },
+    },
+    files: {
+      "image1.png": BACKGROUND,
+    },
+  });
+
+  // Test the deprecated color property.
+  let deprecatedMessagePromise = new Promise(resolve => {
+    Services.console.registerListener(function listener(msg) {
+      if (msg.message.includes("toolbar_field_separator")) {
+        resolve();
+        Services.console.unregisterListener(listener);
+      }
+    });
+  });
+  ExtensionTestUtils.failOnSchemaWarnings(false);
+  await extension.startup();
+  ExtensionTestUtils.failOnSchemaWarnings(true);
+  info("Wait for property deprecation message");
+  await deprecatedMessagePromise;
+
+  let navbar = document.querySelector("#nav-bar");
+  Assert.ok(
+    window
+      .getComputedStyle(navbar)
+      .boxShadow.includes(`rgb(${hexToRGB(SEPARATOR_TOP_COLOR).join(", ")})`),
+    "Top separator color properly set"
+  );
+
+  let panelUIButton = document.querySelector("#PanelUI-button");
+  // Bug 1712334: This should test bookmark item toolbar separators instead
+  Assert.equal(
+    window
+      .getComputedStyle(panelUIButton)
+      .getPropertyValue("border-image-source"),
+    "none",
+    "No vertical separator on app menu"
+  );
+
+  let toolbox = document.querySelector("#navigator-toolbox");
+  Assert.equal(
+    window.getComputedStyle(toolbox).borderBottomColor,
+    `rgb(${hexToRGB(SEPARATOR_BOTTOM_COLOR).join(", ")})`,
+    "Bottom separator color properly set"
+  );
+
+  await extension.unload();
+});
diff --git a/toolkit/components/extensions/test/browser/browser_ext_themes_sidebars.js b/toolkit/components/extensions/test/browser/browser_ext_themes_sidebars.js
new file mode 100644
index 0000000000..35a7955f9f
--- /dev/null
+++ b/toolkit/components/extensions/test/browser/browser_ext_themes_sidebars.js
@@ -0,0 +1,275 @@
+"use strict";
+
+// This test checks whether the sidebar color properties work.
+
+/**
+ * Test whether the selected browser has the sidebar theme applied
+ *
+ * @param {object} theme that is applied
+ * @param {boolean} isBrightText whether the brighttext attribute should be set
+ */
+async function test_sidebar_theme(theme, isBrightText) {
+  let extension = ExtensionTestUtils.loadExtension({
+    manifest: {
+      theme,
+    },
+  });
+
+  const sidebarBox = document.getElementById("sidebar-box");
+  const content = SidebarUI.browser.contentWindow;
+  const root = content.document.documentElement;
+
+  ok(
+    !sidebarBox.hasAttribute("lwt-sidebar"),
+    "Sidebar box should not have lwt-sidebar attribute"
+  );
+  ok(
+    !root.hasAttribute("lwt-sidebar"),
+    "Sidebar should not have lwt-sidebar attribute"
+  );
+  ok(
+    !root.hasAttribute("lwt-sidebar-brighttext"),
+    "Sidebar should not have lwt-sidebar-brighttext attribute"
+  );
+  ok(
+    !root.hasAttribute("lwt-sidebar-highlight"),
+    "Sidebar should not have lwt-sidebar-highlight attribute"
+  );
+
+  const rootCS = content.getComputedStyle(root);
+  const originalBackground = rootCS.backgroundColor;
+  const originalColor = rootCS.color;
+
+  // ::-moz-tree-row(selected, focus) computed style can't be accessed, so we create a fake one.
+  const highlightCS = {
+    get backgroundColor() {
+      // Standardize to rgb like other computed style.
+      let color = rootCS.getPropertyValue(
+        "--lwt-sidebar-highlight-background-color"
+      );
+      let [r, g, b] = color
+        .replace("rgba(", "")
+        .split(",")
+        .map(channel => parseInt(channel, 10));
+      return `rgb(${r}, ${g}, ${b})`;
+    },
+
+    get color() {
+      let color = rootCS.getPropertyValue("--lwt-sidebar-highlight-text-color");
+      let [r, g, b] = color
+        .replace("rgba(", "")
+        .split(",")
+        .map(channel => parseInt(channel, 10));
+      return `rgb(${r}, ${g}, ${b})`;
+    },
+  };
+  const originalHighlightBackground = highlightCS.backgroundColor;
+  const originalHighlightColor = highlightCS.color;
+
+  await extension.startup();
+
+  Services.ppmm.sharedData.flush();
+
+  const actualBackground = hexToCSS(theme.colors.sidebar) || originalBackground;
+  const actualColor = hexToCSS(theme.colors.sidebar_text) || originalColor;
+  const actualHighlightBackground =
+    hexToCSS(theme.colors.sidebar_highlight) || originalHighlightBackground;
+  const actualHighlightColor =
+    hexToCSS(theme.colors.sidebar_highlight_text) || originalHighlightColor;
+  const isCustomHighlight = !!theme.colors.sidebar_highlight_text;
+  const isCustomSidebar = !!theme.colors.sidebar_text;
+
+  is(
+    sidebarBox.hasAttribute("lwt-sidebar"),
+    isCustomSidebar,
+    `Sidebar box should${
+      !isCustomSidebar ? " not" : ""
+    } have lwt-sidebar attribute`
+  );
+  is(
+    root.hasAttribute("lwt-sidebar"),
+    isCustomSidebar,
+    `Sidebar should${!isCustomSidebar ? " not" : ""} have lwt-sidebar attribute`
+  );
+  is(
+    root.hasAttribute("lwt-sidebar-brighttext"),
+    isBrightText,
+    `Sidebar should${
+      !isBrightText ? " not" : ""
+    } have lwt-sidebar-brighttext attribute`
+  );
+  is(
+    root.hasAttribute("lwt-sidebar-highlight"),
+    isCustomHighlight,
+    `Sidebar should${
+      !isCustomHighlight ? " not" : ""
+    } have lwt-sidebar-highlight attribute`
+  );
+
+  if (isCustomSidebar) {
+    const sidebarBoxCS = window.getComputedStyle(sidebarBox);
+    is(
+      sidebarBoxCS.backgroundColor,
+      actualBackground,
+      "Sidebar box background should be set."
+    );
+    is(
+      sidebarBoxCS.color,
+      actualColor,
+      "Sidebar box text color should be set."
+    );
+  }
+
+  is(
+    rootCS.backgroundColor,
+    actualBackground,
+    "Sidebar background should be set."
+  );
+  is(rootCS.color, actualColor, "Sidebar text color should be set.");
+
+  is(
+    highlightCS.backgroundColor,
+    actualHighlightBackground,
+    "Sidebar highlight background color should be set."
+  );
+  is(
+    highlightCS.color,
+    actualHighlightColor,
+    "Sidebar highlight text color should be set."
+  );
+
+  await extension.unload();
+
+  Services.ppmm.sharedData.flush();
+
+  ok(
+    !sidebarBox.hasAttribute("lwt-sidebar"),
+    "Sidebar box should not have lwt-sidebar attribute"
+  );
+  ok(
+    !root.hasAttribute("lwt-sidebar"),
+    "Sidebar should not have lwt-sidebar attribute"
+  );
+  ok(
+    !root.hasAttribute("lwt-sidebar-brighttext"),
+    "Sidebar should not have lwt-sidebar-brighttext attribute"
+  );
+  ok(
+    !root.hasAttribute("lwt-sidebar-highlight"),
+    "Sidebar should not have lwt-sidebar-highlight attribute"
+  );
+
+  is(
+    rootCS.backgroundColor,
+    originalBackground,
+    "Sidebar background should be reset."
+  );
+  is(rootCS.color, originalColor, "Sidebar text color should be reset.");
+  is(
+    highlightCS.backgroundColor,
+    originalHighlightBackground,
+    "Sidebar highlight background color should be reset."
+  );
+  is(
+    highlightCS.color,
+    originalHighlightColor,
+    "Sidebar highlight text color should be reset."
+  );
+}
+
+add_task(async function test_support_sidebar_colors() {
+  for (let command of ["viewBookmarksSidebar", "viewHistorySidebar"]) {
+    info("Executing command: " + command);
+
+    await SidebarUI.show(command);
+
+    await test_sidebar_theme(
+      {
+        colors: {
+          sidebar: "#fafad2", // lightgoldenrodyellow
+          sidebar_text: "#2f4f4f", // darkslategrey
+        },
+      },
+      false
+    );
+
+    await test_sidebar_theme(
+      {
+        colors: {
+          sidebar: "#8b4513", // saddlebrown
+          sidebar_text: "#ffa07a", // lightsalmon
+        },
+      },
+      true
+    );
+
+    await test_sidebar_theme(
+      {
+        colors: {
+          sidebar: "#fffafa", // snow
+          sidebar_text: "#663399", // rebeccapurple
+          sidebar_highlight: "#7cfc00", // lawngreen
+          sidebar_highlight_text: "#ffefd5", // papayawhip
+        },
+      },
+      false
+    );
+
+    await test_sidebar_theme(
+      {
+        colors: {
+          sidebar_highlight: "#a0522d", // sienna
+          sidebar_highlight_text: "#fff5ee", // seashell
+        },
+      },
+      false
+    );
+  }
+});
+
+add_task(async function test_support_sidebar_border_color() {
+  const LIGHT_SALMON = "#ffa07a";
+  const extension = ExtensionTestUtils.loadExtension({
+    manifest: {
+      theme: {
+        colors: {
+          sidebar_border: LIGHT_SALMON,
+        },
+      },
+    },
+  });
+
+  await extension.startup();
+
+  const sidebarHeader = document.getElementById("sidebar-header");
+  const sidebarHeaderCS = window.getComputedStyle(sidebarHeader);
+
+  is(
+    sidebarHeaderCS.borderBottomColor,
+    hexToCSS(LIGHT_SALMON),
+    "Sidebar header border should be colored properly"
+  );
+
+  if (AppConstants.platform !== "linux") {
+    const sidebarSplitter = document.getElementById("sidebar-splitter");
+    const sidebarSplitterCS = window.getComputedStyle(sidebarSplitter);
+
+    is(
+      sidebarSplitterCS.borderInlineEndColor,
+      hexToCSS(LIGHT_SALMON),
+      "Sidebar splitter should be colored properly"
+    );
+
+    SidebarUI.reversePosition();
+
+    is(
+      sidebarSplitterCS.borderInlineStartColor,
+      hexToCSS(LIGHT_SALMON),
+      "Sidebar splitter should be colored properly after switching sides"
+    );
+
+    SidebarUI.reversePosition();
+  }
+
+  await extension.unload();
+});
diff --git a/toolkit/components/extensions/test/browser/browser_ext_themes_static_onUpdated.js b/toolkit/components/extensions/test/browser/browser_ext_themes_static_onUpdated.js
new file mode 100644
index 0000000000..4a6d9a92f6
--- /dev/null
+++ b/toolkit/components/extensions/test/browser/browser_ext_themes_static_onUpdated.js
@@ -0,0 +1,126 @@
+"use strict";
+
+// This test checks whether browser.theme.onUpdated works
+// when a static theme is applied
+
+add_task(async function test_on_updated() {
+  const theme = ExtensionTestUtils.loadExtension({
+    manifest: {
+      theme: {
+        images: {
+          theme_frame: "image1.png",
+        },
+        colors: {
+          frame: ACCENT_COLOR,
+          tab_background_text: TEXT_COLOR,
+        },
+      },
+    },
+    files: {
+      "image1.png": BACKGROUND,
+    },
+  });
+
+  const extension = ExtensionTestUtils.loadExtension({
+    background() {
+      browser.theme.onUpdated.addListener(updateInfo => {
+        browser.test.sendMessage("theme-updated", updateInfo);
+      });
+    },
+  });
+
+  await extension.startup();
+
+  info("Testing update event on static theme startup");
+  let updatedPromise = extension.awaitMessage("theme-updated");
+  await theme.startup();
+  const { theme: receivedTheme, windowId } = await updatedPromise;
+  Assert.ok(!windowId, "No window id in static theme update event");
+  Assert.ok(
+    receivedTheme.images.theme_frame.includes("image1.png"),
+    "Theme theme_frame image should be applied"
+  );
+  Assert.equal(
+    receivedTheme.colors.frame,
+    ACCENT_COLOR,
+    "Theme frame color should be applied"
+  );
+  Assert.equal(
+    receivedTheme.colors.tab_background_text,
+    TEXT_COLOR,
+    "Theme tab_background_text color should be applied"
+  );
+
+  info("Testing update event on static theme unload");
+  updatedPromise = extension.awaitMessage("theme-updated");
+  await theme.unload();
+  const updateInfo = await updatedPromise;
+  Assert.ok(!windowId, "No window id in static theme update event on unload");
+  Assert.equal(
+    Object.keys(updateInfo.theme),
+    0,
+    "unloading theme sends empty theme in update event"
+  );
+
+  await extension.unload();
+});
+
+add_task(async function test_on_updated_eventpage() {
+  await SpecialPowers.pushPrefEnv({
+    set: [["extensions.eventPages.enabled", true]],
+  });
+  const theme = ExtensionTestUtils.loadExtension({
+    manifest: {
+      theme: {
+        images: {
+          theme_frame: "image1.png",
+        },
+        colors: {
+          frame: ACCENT_COLOR,
+          tab_background_text: TEXT_COLOR,
+        },
+      },
+    },
+    files: {
+      "image1.png": BACKGROUND,
+    },
+  });
+
+  const extension = ExtensionTestUtils.loadExtension({
+    useAddonManager: "permanent",
+    manifest: {
+      browser_specific_settings: { gecko: { id: "watcher@mochitest" } },
+      background: { persistent: false },
+    },
+    background() {
+      browser.theme.onUpdated.addListener(updateInfo => {
+        browser.test.sendMessage("theme-updated", updateInfo);
+      });
+    },
+  });
+
+  await extension.startup();
+  assertPersistentListeners(extension, "theme", "onUpdated", {
+    primed: false,
+  });
+
+  await extension.terminateBackground();
+  assertPersistentListeners(extension, "theme", "onUpdated", {
+    primed: true,
+  });
+
+  info("Testing update event on static theme startup");
+  let updatedPromise = extension.awaitMessage("theme-updated");
+  await theme.startup();
+  const { theme: receivedTheme, windowId } = await updatedPromise;
+  Assert.ok(!windowId, "No window id in static theme update event");
+  Assert.ok(
+    receivedTheme.images.theme_frame.includes("image1.png"),
+    "Theme theme_frame image should be applied"
+  );
+  await theme.unload();
+  await extension.awaitMessage("theme-updated");
+
+  await extension.unload();
+  await SpecialPowers.popPrefEnv();
+});
diff --git a/toolkit/components/extensions/test/browser/browser_ext_themes_tab_line.js b/toolkit/components/extensions/test/browser/browser_ext_themes_tab_line.js
new file mode 100644
index 0000000000..e4bd8cb99b
--- /dev/null
+++ b/toolkit/components/extensions/test/browser/browser_ext_themes_tab_line.js
@@ -0,0 +1,39 @@
+"use strict";
+
+// This test checks whether applied WebExtension themes that attempt to change
+// the color of the tab line are applied properly.
+
+add_task(async function test_support_tab_line() {
+  let newWin = await BrowserTestUtils.openNewBrowserWindow();
+
+  const TAB_LINE_COLOR = "#ff0000";
+  let extension = ExtensionTestUtils.loadExtension({
+    manifest: {
+      theme: {
+        colors: {
+          frame: ACCENT_COLOR,
+          tab_background_text: "#000",
+          tab_line: TAB_LINE_COLOR,
+        },
+      },
+    },
+  });
+
+  await extension.startup();
+
+  info("Checking selected tab line color");
+  let selectedTab = newWin.document.querySelector(".tabbrowser-tab[selected]");
+  let tab = selectedTab.querySelector(".tab-background");
+  let element = tab;
+  let property = "outline-color";
+  let computedValue = newWin.getComputedStyle(element)[property];
+  let expectedColor = `rgb(${hexToRGB(TAB_LINE_COLOR).join(", ")})`;
+
+  Assert.ok(
+    computedValue.includes(expectedColor),
+    `Tab line should be displayed in the box shadow of the tab: ${computedValue}`
+  );
+
+  await extension.unload();
+  await BrowserTestUtils.closeWindow(newWin);
+});
diff --git a/toolkit/components/extensions/test/browser/browser_ext_themes_tab_loading.js b/toolkit/components/extensions/test/browser/browser_ext_themes_tab_loading.js
new file mode 100644
index 0000000000..1e402dbcc6
--- /dev/null
+++ b/toolkit/components/extensions/test/browser/browser_ext_themes_tab_loading.js
@@ -0,0 +1,51 @@
+"use strict";
+
+add_task(async function test_support_tab_loading_filling() {
+  const TAB_LOADING_COLOR = "#FF0000";
+
+  // Make sure we use the animating loading icon
+  await SpecialPowers.pushPrefEnv({
+    set: [["ui.prefersReducedMotion", 0]],
+  });
+
+  let extension = ExtensionTestUtils.loadExtension({
+    manifest: {
+      theme: {
+        images: {
+          theme_frame: "image1.png",
+        },
+        colors: {
+          frame: "#000",
+          toolbar: "#124455",
+          tab_background_text: "#9400ff",
+          tab_loading: TAB_LOADING_COLOR,
+        },
+      },
+    },
+    files: {
+      "image1.png": BACKGROUND,
+    },
+  });
+
+  await extension.startup();
+
+  info("Checking selected tab loading indicator colors");
+
+  let selectedTab = document.querySelector(
+    ".tabbrowser-tab[visuallyselected=true]"
+  );
+
+  selectedTab.setAttribute("busy", "true");
+  selectedTab.setAttribute("progress", "true");
+
+  let throbber = selectedTab.throbber;
+  Assert.equal(
+    window.getComputedStyle(throbber, "::before").fill,
+    `rgb(${hexToRGB(TAB_LOADING_COLOR).join(", ")})`,
+    "Throbber is filled with theme color"
+  );
+
+  selectedTab.removeAttribute("busy");
+  selectedTab.removeAttribute("progress");
+  await extension.unload();
+});
diff --git a/toolkit/components/extensions/test/browser/browser_ext_themes_tab_selected.js b/toolkit/components/extensions/test/browser/browser_ext_themes_tab_selected.js
new file mode 100644
index 0000000000..21f3c6d38b
--- /dev/null
+++ b/toolkit/components/extensions/test/browser/browser_ext_themes_tab_selected.js
@@ -0,0 +1,54 @@
+"use strict";
+
+// This test checks whether applied WebExtension themes that attempt to change
+// the background color of selected tab are applied correctly.
+
+add_task(async function test_tab_background_color_property() {
+  const TAB_BACKGROUND_COLOR = "#9400ff";
+  let extension = ExtensionTestUtils.loadExtension({
+    manifest: {
+      theme: {
+        colors: {
+          frame: ACCENT_COLOR,
+          tab_background_text: TEXT_COLOR,
+          tab_selected: TAB_BACKGROUND_COLOR,
+        },
+      },
+    },
+  });
+
+  await extension.startup();
+
+  info("Checking selected tab color");
+
+  let openTab = document.querySelector(
+    ".tabbrowser-tab[visuallyselected=true]"
+  );
+  let openTabBackground = openTab.querySelector(".tab-background");
+
+  let selectedTab = await BrowserTestUtils.openNewForegroundTab(
+    gBrowser,
+    "about:blank"
+  );
+  let selectedTabBackground = selectedTab.querySelector(".tab-background");
+
+  let openTabGradient = window
+    .getComputedStyle(openTabBackground)
+    .getPropertyValue("background-image");
+  let selectedTabGradient = window
+    .getComputedStyle(selectedTabBackground)
+    .getPropertyValue("background-image");
+
+  let rgbRegex = /rgb\((\d{1,3}), (\d{1,3}), (\d{1,3})\)/g;
+  let selectedTabColors = selectedTabGradient.match(rgbRegex);
+
+  Assert.equal(
+    selectedTabColors[0],
+    "rgb(" + hexToRGB(TAB_BACKGROUND_COLOR).join(", ") + ")",
+    "Selected tab background color should be set."
+  );
+  Assert.equal(openTabGradient, "none");
+
+  gBrowser.removeTab(selectedTab);
+  await extension.unload();
+});
diff --git a/toolkit/components/extensions/test/browser/browser_ext_themes_tab_text.js b/toolkit/components/extensions/test/browser/browser_ext_themes_tab_text.js
new file mode 100644
index 0000000000..d819f3a5f1
--- /dev/null
+++ b/toolkit/components/extensions/test/browser/browser_ext_themes_tab_text.js
@@ -0,0 +1,70 @@
+"use strict";
+
+// This test checks whether applied WebExtension themes that attempt to change
+// the text color of the selected tab are applied properly.
+
+add_task(async function test_support_tab_text_property_css_color() {
+  const TAB_TEXT_COLOR = "#9400ff";
+  let extension = ExtensionTestUtils.loadExtension({
+    manifest: {
+      theme: {
+        images: {
+          theme_frame: "image1.png",
+        },
+        colors: {
+          frame: ACCENT_COLOR,
+          tab_background_text: TEXT_COLOR,
+          tab_text: TAB_TEXT_COLOR,
+        },
+      },
+    },
+    files: {
+      "image1.png": BACKGROUND,
+    },
+  });
+
+  await extension.startup();
+
+  info("Checking selected tab colors");
+  let selectedTab = document.querySelector(".tabbrowser-tab[selected]");
+  Assert.equal(
+    window.getComputedStyle(selectedTab).color,
+    "rgb(" + hexToRGB(TAB_TEXT_COLOR).join(", ") + ")",
+    "Selected tab text color should be set."
+  );
+
+  await extension.unload();
+});
+
+add_task(async function test_support_tab_text_chrome_array() {
+  const TAB_TEXT_COLOR = [148, 0, 255];
+  let extension = ExtensionTestUtils.loadExtension({
+    manifest: {
+      theme: {
+        images: {
+          theme_frame: "image1.png",
+        },
+        colors: {
+          frame: FRAME_COLOR,
+          tab_background_text: TAB_BACKGROUND_TEXT_COLOR,
+          tab_text: TAB_TEXT_COLOR,
+        },
+      },
+    },
+    files: {
+      "image1.png": BACKGROUND,
+    },
+  });
+
+  await extension.startup();
+
+  info("Checking selected tab colors");
+  let selectedTab = document.querySelector(".tabbrowser-tab[selected]");
+  Assert.equal(
+    window.getComputedStyle(selectedTab).color,
+    "rgb(" + TAB_TEXT_COLOR.join(", ") + ")",
+    "Selected tab text color should be set."
+  );
+
+  await extension.unload();
+});
diff --git a/toolkit/components/extensions/test/browser/browser_ext_themes_theme_transition.js b/toolkit/components/extensions/test/browser/browser_ext_themes_theme_transition.js
new file mode 100644
index 0000000000..39934200ac
--- /dev/null
+++ b/toolkit/components/extensions/test/browser/browser_ext_themes_theme_transition.js
@@ -0,0 +1,48 @@
+"use strict";
+
+// This test checks whether the applied theme transition effects are applied
+// correctly.
+
+add_task(async function test_theme_transition_effects() {
+  const TOOLBAR = "#f27489";
+  const TEXT_COLOR = "#000000";
+  const TRANSITION_PROPERTY = "background-color";
+
+  let extension = ExtensionTestUtils.loadExtension({
+    manifest: {
+      theme: {
+        colors: {
+          tab_background_text: TEXT_COLOR,
+          toolbar: TOOLBAR,
+          bookmark_text: TEXT_COLOR,
+        },
+      },
+    },
+  });
+
+  await extension.startup();
+
+  // check transition effect for toolbars
+  let navbar = document.querySelector("#nav-bar");
+  let navbarCS = window.getComputedStyle(navbar);
+
+  Assert.ok(
+    navbarCS
+      .getPropertyValue("transition-property")
+      .includes(TRANSITION_PROPERTY),
+    "Transition property set for #nav-bar"
+  );
+
+  let bookmarksBar = document.querySelector("#PersonalToolbar");
+  setToolbarVisibility(bookmarksBar, true, false, true);
+  let bookmarksBarCS = window.getComputedStyle(bookmarksBar);
+
+  Assert.ok(
+    bookmarksBarCS
+      .getPropertyValue("transition-property")
+      .includes(TRANSITION_PROPERTY),
+    "Transition property set for #PersonalToolbar"
+  );
+
+  await extension.unload();
+});
diff --git a/toolkit/components/extensions/test/browser/browser_ext_themes_toolbar_fields.js b/toolkit/components/extensions/test/browser/browser_ext_themes_toolbar_fields.js
new file mode 100644
index 0000000000..aa0446c453
--- /dev/null
+++ b/toolkit/components/extensions/test/browser/browser_ext_themes_toolbar_fields.js
@@ -0,0 +1,183 @@
+"use strict";
+
+// This test checks whether applied WebExtension themes that attempt to change
+// the background color and the color of the navbar text fields are applied properly.
+
+const { CustomizableUITestUtils } = ChromeUtils.importESModule(
+  "resource://testing-common/CustomizableUITestUtils.sys.mjs"
+);
+let gCUITestUtils = new CustomizableUITestUtils(window);
+
+add_setup(async function () {
+  await gCUITestUtils.addSearchBar();
+  registerCleanupFunction(() => {
+    gCUITestUtils.removeSearchBar();
+  });
+});
+
+add_task(async function test_support_toolbar_field_properties() {
+  const TOOLBAR_FIELD_BACKGROUND = "#ff00ff";
+  const TOOLBAR_FIELD_COLOR = "#00ff00";
+  const TOOLBAR_FIELD_BORDER = "#aaaaff";
+  let extension = ExtensionTestUtils.loadExtension({
+    manifest: {
+      theme: {
+        images: {
+          theme_frame: "image1.png",
+        },
+        colors: {
+          frame: ACCENT_COLOR,
+          tab_background_text: TEXT_COLOR,
+          toolbar_field: TOOLBAR_FIELD_BACKGROUND,
+          toolbar_field_text: TOOLBAR_FIELD_COLOR,
+          toolbar_field_border: TOOLBAR_FIELD_BORDER,
+        },
+      },
+    },
+    files: {
+      "image1.png": BACKGROUND,
+    },
+  });
+
+  await extension.startup();
+
+  let root = document.documentElement;
+  // Remove the `remotecontrol` attribute since it interferes with the urlbar styling.
+  root.removeAttribute("remotecontrol");
+  registerCleanupFunction(() => {
+    root.setAttribute("remotecontrol", "true");
+  });
+
+  let fields = [
+    document.querySelector("#urlbar-background"),
+    BrowserSearch.searchBar,
+  ].filter(field => {
+    let bounds = field.getBoundingClientRect();
+    return bounds.width > 0 && bounds.height > 0;
+  });
+
+  Assert.equal(fields.length, 2, "Should be testing two elements");
+
+  info(
+    `Checking toolbar background colors and colors for ${fields.length} toolbar fields.`
+  );
+  for (let field of fields) {
+    info(`Testing ${field.id || field.className}`);
+    Assert.equal(
+      window.getComputedStyle(field).backgroundColor,
+      hexToCSS(TOOLBAR_FIELD_BACKGROUND),
+      "Field background should be set."
+    );
+    Assert.equal(
+      window.getComputedStyle(field).color,
+      hexToCSS(TOOLBAR_FIELD_COLOR),
+      "Field color should be set."
+    );
+    testBorderColor(field, TOOLBAR_FIELD_BORDER);
+  }
+
+  await extension.unload();
+});
+
+add_task(async function test_support_toolbar_field_brighttext() {
+  let root = document.documentElement;
+  // Remove the `remotecontrol` attribute since it interferes with the urlbar styling.
+  root.removeAttribute("remotecontrol");
+  registerCleanupFunction(() => {
+    root.setAttribute("remotecontrol", "true");
+  });
+  let urlbar = gURLBar.textbox;
+
+  let extension = ExtensionTestUtils.loadExtension({
+    manifest: {
+      theme: {
+        colors: {
+          frame: ACCENT_COLOR,
+          tab_background_text: TEXT_COLOR,
+          toolbar_field: "#fff",
+          toolbar_field_text: "#000",
+        },
+      },
+    },
+  });
+
+  await extension.startup();
+
+  Assert.equal(
+    window.getComputedStyle(urlbar).color,
+    hexToCSS("#000000"),
+    "Color has been set"
+  );
+  Assert.ok(
+    !root.hasAttribute("lwt-toolbar-field-brighttext"),
+    "Brighttext attribute should not be set"
+  );
+
+  await extension.unload();
+
+  extension = ExtensionTestUtils.loadExtension({
+    manifest: {
+      theme: {
+        colors: {
+          frame: ACCENT_COLOR,
+          tab_background_text: TEXT_COLOR,
+          toolbar_field: "#000",
+          toolbar_field_text: "#fff",
+        },
+      },
+    },
+  });
+
+  await extension.startup();
+
+  Assert.equal(
+    window.getComputedStyle(urlbar).color,
+    hexToCSS("#ffffff"),
+    "Color has been set"
+  );
+  Assert.ok(
+    root.hasAttribute("lwt-toolbar-field-brighttext"),
+    "Brighttext attribute should be set"
+  );
+
+  await extension.unload();
+});
+
+// Verifies that we apply the lwt-toolbar-field-brighttext attribute when
+// toolbar fields are dark text on a dark background.
+add_task(async function test_support_toolbar_field_brighttext_dark_on_dark() {
+  let root = document.documentElement;
+  // Remove the `remotecontrol` attribute since it interferes with the urlbar styling.
+  root.removeAttribute("remotecontrol");
+  registerCleanupFunction(() => {
+    root.setAttribute("remotecontrol", "true");
+  });
+  let urlbar = gURLBar.textbox;
+
+  let extension = ExtensionTestUtils.loadExtension({
+    manifest: {
+      theme: {
+        colors: {
+          frame: ACCENT_COLOR,
+          tab_background_text: TEXT_COLOR,
+          toolbar_field: "#000",
+          toolbar_field_text: "#111111",
+        },
+      },
+    },
+  });
+
+  await extension.startup();
+
+  Assert.equal(
+    window.getComputedStyle(urlbar).color,
+    hexToCSS("#111111"),
+    "Color has been set"
+  );
+  Assert.ok(
+    root.hasAttribute("lwt-toolbar-field-brighttext"),
+    "Brighttext attribute should be set"
+  );
+
+  await extension.unload();
+});
diff --git a/toolkit/components/extensions/test/browser/browser_ext_themes_toolbar_fields_focus.js b/toolkit/components/extensions/test/browser/browser_ext_themes_toolbar_fields_focus.js
new file mode 100644
index 0000000000..ff6af3ade7
--- /dev/null
+++ b/toolkit/components/extensions/test/browser/browser_ext_themes_toolbar_fields_focus.js
@@ -0,0 +1,107 @@
+"use strict";
+
+add_setup(async function () {
+  // Remove the `remotecontrol` attribute since it interferes with the urlbar styling.
+  document.documentElement.removeAttribute("remotecontrol");
+  registerCleanupFunction(() => {
+    document.documentElement.setAttribute("remotecontrol", "true");
+  });
+});
+
+add_task(async function test_toolbar_field_focus() {
+  const TOOLBAR_FIELD_BACKGROUND = "#FF00FF";
+  const TOOLBAR_FIELD_COLOR = "#00FF00";
+  const TOOLBAR_FOCUS_BACKGROUND = "#FF0000";
+  const TOOLBAR_FOCUS_TEXT = "#9400FF";
+  const TOOLBAR_FOCUS_BORDER = "#FFFFFF";
+
+  let extension = ExtensionTestUtils.loadExtension({
+    manifest: {
+      theme: {
+        colors: {
+          frame: "#FF0000",
+          tab_background_color: "#ffffff",
+          toolbar_field: TOOLBAR_FIELD_BACKGROUND,
+          toolbar_field_text: TOOLBAR_FIELD_COLOR,
+          toolbar_field_focus: TOOLBAR_FOCUS_BACKGROUND,
+          toolbar_field_text_focus: TOOLBAR_FOCUS_TEXT,
+          toolbar_field_border_focus: TOOLBAR_FOCUS_BORDER,
+        },
+      },
+    },
+  });
+
+  await extension.startup();
+
+  info("Checking toolbar field's focus color");
+
+  let urlBar = document.querySelector("#urlbar-background");
+  gURLBar.textbox.setAttribute("focused", "true");
+  let style = window.getComputedStyle(urlBar);
+
+  Assert.equal(
+    style.backgroundColor,
+    `rgb(${hexToRGB(TOOLBAR_FOCUS_BACKGROUND).join(", ")})`,
+    "Background Color is changed"
+  );
+  Assert.equal(
+    style.color,
+    `rgb(${hexToRGB(TOOLBAR_FOCUS_TEXT).join(", ")})`,
+    "Text Color is changed"
+  );
+  Assert.equal(
+    style.outlineColor,
+    `rgb(${hexToRGB(TOOLBAR_FOCUS_BORDER).join(", ")})`,
+    "Focus ring color"
+  );
+
+  gURLBar.textbox.removeAttribute("focused");
+
+  Assert.equal(
+    style.backgroundColor,
+    `rgb(${hexToRGB(TOOLBAR_FIELD_BACKGROUND).join(", ")})`,
+    "Background Color is set back to initial"
+  );
+  Assert.equal(
+    style.color,
+    `rgb(${hexToRGB(TOOLBAR_FIELD_COLOR).join(", ")})`,
+    "Text Color is set back to initial"
+  );
+  await extension.unload();
+});
+
+add_task(async function test_toolbar_field_focus_low_alpha() {
+  let extension = ExtensionTestUtils.loadExtension({
+    manifest: {
+      theme: {
+        colors: {
+          frame: "#FF0000",
+          tab_background_color: "#ffffff",
+          toolbar_field: "#FF00FF",
+          toolbar_field_text: "#00FF00",
+          toolbar_field_focus: "rgba(0, 0, 255, 0.4)",
+          toolbar_field_text_focus: "red",
+          toolbar_field_border_focus: "#FFFFFF",
+        },
+      },
+    },
+  });
+
+  await extension.startup();
+  gURLBar.textbox.setAttribute("focused", "true");
+
+  let urlBar = document.querySelector("#urlbar-background");
+  Assert.equal(
+    window.getComputedStyle(urlBar).backgroundColor,
+    `rgba(0, 0, 255, 0.9)`,
+    "Background color has minimum opacity enforced"
+  );
+  Assert.equal(
+    window.getComputedStyle(urlBar).color,
+    `rgb(255, 255, 255)`,
+    "Text color has been overridden to match background"
+  );
+
+  gURLBar.textbox.removeAttribute("focused");
+  await extension.unload();
+});
diff --git a/toolkit/components/extensions/test/browser/browser_ext_themes_toolbarbutton_colors.js b/toolkit/components/extensions/test/browser/browser_ext_themes_toolbarbutton_colors.js
new file mode 100644
index 0000000000..37c082b36f
--- /dev/null
+++ b/toolkit/components/extensions/test/browser/browser_ext_themes_toolbarbutton_colors.js
@@ -0,0 +1,63 @@
+"use strict";
+
+/* globals InspectorUtils */
+
+// This test checks whether applied WebExtension themes that attempt to change
+// the button background color properties are applied correctly.
+
+add_task(async function setup_home_button() {
+  CustomizableUI.addWidgetToArea("home-button", "nav-bar");
+  registerCleanupFunction(() =>
+    CustomizableUI.removeWidgetFromArea("home-button")
+  );
+});
+
+add_task(async function test_button_background_properties() {
+  const BUTTON_BACKGROUND_ACTIVE = "#FFFFFF";
+  const BUTTON_BACKGROUND_HOVER = "#59CBE8";
+
+  let extension = ExtensionTestUtils.loadExtension({
+    manifest: {
+      theme: {
+        images: {
+          theme_frame: "image1.png",
+        },
+        colors: {
+          frame: ACCENT_COLOR,
+          tab_background_text: TEXT_COLOR,
+          button_background_active: BUTTON_BACKGROUND_ACTIVE,
+          button_background_hover: BUTTON_BACKGROUND_HOVER,
+        },
+      },
+    },
+    files: {
+      "image1.png": BACKGROUND,
+    },
+  });
+
+  await extension.startup();
+
+  let toolbarButton = document.querySelector("#home-button");
+  let toolbarButtonIcon = toolbarButton.icon;
+  let toolbarButtonIconCS = window.getComputedStyle(toolbarButtonIcon);
+
+  InspectorUtils.addPseudoClassLock(toolbarButton, ":hover");
+
+  Assert.equal(
+    toolbarButtonIconCS.getPropertyValue("background-color"),
+    `rgb(${hexToRGB(BUTTON_BACKGROUND_HOVER).join(", ")})`,
+    "Toolbar button hover background is set."
+  );
+
+  InspectorUtils.addPseudoClassLock(toolbarButton, ":active");
+
+  Assert.equal(
+    toolbarButtonIconCS.getPropertyValue("background-color"),
+    `rgb(${hexToRGB(BUTTON_BACKGROUND_ACTIVE).join(", ")})`,
+    "Toolbar button active background is set!"
+  );
+
+  InspectorUtils.clearPseudoClassLocks(toolbarButton);
+
+  await extension.unload();
+});
diff --git a/toolkit/components/extensions/test/browser/browser_ext_themes_toolbarbutton_icons.js b/toolkit/components/extensions/test/browser/browser_ext_themes_toolbarbutton_icons.js
new file mode 100644
index 0000000000..2802c6ac33
--- /dev/null
+++ b/toolkit/components/extensions/test/browser/browser_ext_themes_toolbarbutton_icons.js
@@ -0,0 +1,109 @@
+"use strict";
+
+// This test checks applied WebExtension themes that attempt to change
+// icon color properties
+
+add_task(async function setup_home_button() {
+  CustomizableUI.addWidgetToArea("home-button", "nav-bar");
+  registerCleanupFunction(() =>
+    CustomizableUI.removeWidgetFromArea("home-button")
+  );
+});
+
+add_task(async function test_icons_properties() {
+  const ICONS_COLOR = "#001b47";
+  const ICONS_ATTENTION_COLOR = "#44ba77";
+
+  let extension = ExtensionTestUtils.loadExtension({
+    manifest: {
+      theme: {
+        images: {
+          theme_frame: "image1.png",
+        },
+        colors: {
+          frame: ACCENT_COLOR,
+          tab_background_text: TEXT_COLOR,
+          icons: ICONS_COLOR,
+          icons_attention: ICONS_ATTENTION_COLOR,
+        },
+      },
+    },
+    files: {
+      "image1.png": BACKGROUND,
+    },
+  });
+
+  await extension.startup();
+
+  let toolbarbutton = document.querySelector("#home-button");
+  Assert.equal(
+    window.getComputedStyle(toolbarbutton).getPropertyValue("fill"),
+    `rgb(${hexToRGB(ICONS_COLOR).join(", ")})`,
+    "Buttons fill color set!"
+  );
+
+  let starButton = document.querySelector("#star-button");
+  starButton.setAttribute("starred", "true");
+
+  let starComputedStyle = window.getComputedStyle(starButton);
+  Assert.equal(
+    starComputedStyle.getPropertyValue(
+      "--lwt-toolbarbutton-icon-fill-attention"
+    ),
+    `rgb(${hexToRGB(ICONS_ATTENTION_COLOR).join(", ")})`,
+    "Variable is properly set"
+  );
+  Assert.equal(
+    starComputedStyle.getPropertyValue("fill"),
+    `rgb(${hexToRGB(ICONS_ATTENTION_COLOR).join(", ")})`,
+    "Starred icon fill is properly set"
+  );
+
+  starButton.removeAttribute("starred");
+
+  await extension.unload();
+});
+
+add_task(async function test_no_icons_properties() {
+  let extension = ExtensionTestUtils.loadExtension({
+    manifest: {
+      theme: {
+        images: {
+          theme_frame: "image1.png",
+        },
+        colors: {
+          frame: ACCENT_COLOR,
+          tab_background_text: TEXT_COLOR,
+        },
+      },
+    },
+    files: {
+      "image1.png": BACKGROUND,
+    },
+  });
+
+  await extension.startup();
+
+  let toolbarbutton = document.querySelector("#home-button");
+  let toolbarbuttonCS = window.getComputedStyle(toolbarbutton);
+  let currentColor = toolbarbuttonCS.getPropertyValue("color");
+  Assert.equal(
+    window.getComputedStyle(toolbarbutton).getPropertyValue("fill"),
+    currentColor,
+    "Button fill color should be currentColor when no icon color specified."
+  );
+
+  let starButton = document.querySelector("#star-button");
+  starButton.setAttribute("starred", "true");
+  let starComputedStyle = window.getComputedStyle(starButton);
+  Assert.equal(
+    starComputedStyle.getPropertyValue(
+      "--lwt-toolbarbutton-icon-fill-attention"
+    ),
+    "",
+    "Icon attention fill should not be set when the value is not specified in the manifest."
+  );
+  starButton.removeAttribute("starred");
+
+  await extension.unload();
+});
diff --git a/toolkit/components/extensions/test/browser/browser_ext_themes_toolbars.js b/toolkit/components/extensions/test/browser/browser_ext_themes_toolbars.js
new file mode 100644
index 0000000000..ee31d80888
--- /dev/null
+++ b/toolkit/components/extensions/test/browser/browser_ext_themes_toolbars.js
@@ -0,0 +1,105 @@
+"use strict";
+
+// This test checks whether applied WebExtension themes that attempt to change
+// the background color of toolbars are applied properly.
+
+add_task(async function test_support_toolbar_property() {
+  const TOOLBAR_COLOR = "#ff00ff";
+  const TOOLBAR_TEXT_COLOR = "#9400ff";
+  let extension = ExtensionTestUtils.loadExtension({
+    manifest: {
+      theme: {
+        colors: {
+          frame: ACCENT_COLOR,
+          tab_background_text: TEXT_COLOR,
+          toolbar: TOOLBAR_COLOR,
+          toolbar_text: TOOLBAR_TEXT_COLOR,
+        },
+      },
+    },
+  });
+
+  let toolbox = document.querySelector("#navigator-toolbox");
+  let toolbars = [
+    ...toolbox.querySelectorAll("toolbar:not(#TabsToolbar)"),
+  ].filter(toolbar => {
+    let bounds = toolbar.getBoundingClientRect();
+    return bounds.width > 0 && bounds.height > 0;
+  });
+
+  let transitionPromise = waitForTransition(toolbars[0], "background-color");
+  await extension.startup();
+  await transitionPromise;
+
+  info(`Checking toolbar colors for ${toolbars.length} toolbars.`);
+  for (let toolbar of toolbars) {
+    info(`Testing ${toolbar.id}`);
+    Assert.equal(
+      window.getComputedStyle(toolbar).backgroundColor,
+      hexToCSS(TOOLBAR_COLOR),
+      "Toolbar background color should be set."
+    );
+    Assert.equal(
+      window.getComputedStyle(toolbar).color,
+      hexToCSS(TOOLBAR_TEXT_COLOR),
+      "Toolbar text color should be set."
+    );
+  }
+
+  info("Checking selected tab colors");
+  let selectedTab = document.querySelector(".tabbrowser-tab[selected]");
+  Assert.equal(
+    window.getComputedStyle(selectedTab).color,
+    hexToCSS(TOOLBAR_TEXT_COLOR),
+    "Selected tab text color should be set."
+  );
+
+  await extension.unload();
+});
+
+add_task(async function test_bookmark_text_property() {
+  const TOOLBAR_COLOR = [255, 0, 255];
+  const TOOLBAR_TEXT_COLOR = [48, 0, 255];
+  let extension = ExtensionTestUtils.loadExtension({
+    manifest: {
+      theme: {
+        colors: {
+          frame: ACCENT_COLOR,
+          tab_background_text: TEXT_COLOR,
+          toolbar: TOOLBAR_COLOR,
+          bookmark_text: TOOLBAR_TEXT_COLOR,
+        },
+      },
+    },
+  });
+
+  await extension.startup();
+
+  let toolbox = document.querySelector("#navigator-toolbox");
+  let toolbars = [
+    ...toolbox.querySelectorAll("toolbar:not(#TabsToolbar)"),
+  ].filter(toolbar => {
+    let bounds = toolbar.getBoundingClientRect();
+    return bounds.width > 0 && bounds.height > 0;
+  });
+
+  info(`Checking toolbar colors for ${toolbars.length} toolbars.`);
+  for (let toolbar of toolbars) {
+    info(`Testing ${toolbar.id}`);
+    Assert.equal(
+      window.getComputedStyle(toolbar).color,
+      rgbToCSS(TOOLBAR_TEXT_COLOR),
+      "bookmark_text should be an alias for toolbar_text"
+    );
+  }
+
+  info("Checking selected tab colors");
+  let selectedTab = document.querySelector(".tabbrowser-tab[selected]");
+  Assert.equal(
+    window.getComputedStyle(selectedTab).color,
+    rgbToCSS(TOOLBAR_TEXT_COLOR),
+    "Selected tab text color should be set."
+  );
+
+  await extension.unload();
+});
diff --git a/toolkit/components/extensions/test/browser/browser_ext_themes_warnings.js b/toolkit/components/extensions/test/browser/browser_ext_themes_warnings.js
new file mode 100644
index 0000000000..025a4073dd
--- /dev/null
+++ b/toolkit/components/extensions/test/browser/browser_ext_themes_warnings.js
@@ -0,0 +1,144 @@
+"use strict";
+
+const { AddonSettings } = ChromeUtils.importESModule(
+  "resource://gre/modules/addons/AddonSettings.sys.mjs"
+);
+
+// This test checks that theme warnings are properly emitted.
+
+function waitForConsole(task, message) {
+  // eslint-disable-next-line no-async-promise-executor
+  return new Promise(async resolve => {
+    SimpleTest.monitorConsole(resolve, [
+      {
+        message: new RegExp(message),
+      },
+    ]);
+    await task();
+    SimpleTest.endMonitorConsole();
+  });
+}
+
+add_setup(async function () {
+  SimpleTest.waitForExplicitFinish();
+});
+
+add_task(async function test_static_theme() {
+  for (const property of ["colors", "images", "properties"]) {
+    const extension = ExtensionTestUtils.loadExtension({
+      manifest: {
+        theme: {
+          [property]: {
+            such_property: "much_wow",
+          },
+        },
+      },
+    });
+    await waitForConsole(
+      extension.startup,
+      `Unrecognized theme property found: ${property}.such_property`
+    );
+    await extension.unload();
+  }
+});
+
+add_task(async function test_dynamic_theme() {
+  let extension = ExtensionTestUtils.loadExtension({
+    manifest: {
+      permissions: ["theme"],
+    },
+    background() {
+      browser.test.onMessage.addListener((msg, details) => {
+        if (msg === "update-theme") {
+          browser.theme.update(details).then(() => {
+            browser.test.sendMessage("theme-updated");
+          });
+        } else {
+          browser.theme.reset().then(() => {
+            browser.test.sendMessage("theme-reset");
+          });
+        }
+      });
+    },
+  });
+
+  await extension.startup();
+
+  for (const property of ["colors", "images", "properties"]) {
+    extension.sendMessage("update-theme", {
+      [property]: {
+        such_property: "much_wow",
+      },
+    });
+    await waitForConsole(
+      () => extension.awaitMessage("theme-updated"),
+      `Unrecognized theme property found: ${property}.such_property`
+    );
+  }
+
+  await extension.unload();
+});
+
+add_task(async function test_experiments_enabled() {
+  info("Testing that experiments are handled correctly on nightly and deved");
+
+  const extension = ExtensionTestUtils.loadExtension({
+    useAddonManager: "temporary",
+    manifest: {
+      theme: {
+        properties: {
+          such_property: "much_wow",
+          unknown_property: "very_unknown",
+        },
+      },
+      theme_experiment: {
+        properties: {
+          such_property: "--such-property",
+        },
+      },
+    },
+  });
+  if (!AddonSettings.EXPERIMENTS_ENABLED) {
+    await waitForConsole(
+      extension.startup,
+      "This extension is not allowed to run theme experiments"
+    );
+  } else {
+    await waitForConsole(
+      extension.startup,
+      "Unrecognized theme property found: properties.unknown_property"
+    );
+  }
+  await extension.unload();
+});
+
+add_task(async function test_experiments_disabled() {
+  await SpecialPowers.pushPrefEnv({
+    set: [["extensions.experiments.enabled", false]],
+  });
+
+  info(
+    "Testing that experiments are handled correctly when experiements pref is disabled"
+  );
+
+  const extension = ExtensionTestUtils.loadExtension({
+    manifest: {
+      theme: {
+        properties: {
+          such_property: "much_wow",
+        },
+      },
+      theme_experiment: {
+        properties: {
+          such_property: "--such-property",
+        },
+      },
+    },
+  });
+  await waitForConsole(
+    extension.startup,
+    "This extension is not allowed to run theme experiments"
+  );
+  await extension.unload();
+  await SpecialPowers.popPrefEnv();
+});
diff --git a/toolkit/components/extensions/test/browser/browser_ext_thumbnails_bg_extension.js b/toolkit/components/extensions/test/browser/browser_ext_thumbnails_bg_extension.js
new file mode 100644
index 0000000000..96a2216067
--- /dev/null
+++ b/toolkit/components/extensions/test/browser/browser_ext_thumbnails_bg_extension.js
@@ -0,0 +1,94 @@
+"use strict";
+
+/* import-globals-from ../../../thumbnails/test/head.js */
+loadTestSubscript("../../../thumbnails/test/head.js");
+
+// The service that creates thumbnails of webpages in the background loads a
+// web page in the background (with several features disabled). Extensions
+// should be able to observe requests, but not run content scripts.
+add_task(async function test_thumbnails_background_visibility_to_extensions() {
+  const iframeUrl = "http://example.com/?iframe";
+  const testPageUrl = bgTestPageURL({ iframe: iframeUrl });
+  // ^ testPageUrl is http://mochi.test:8888/.../thumbnails_background.sjs?...
+
+  let extension = ExtensionTestUtils.loadExtension({
+    manifest: {
+      content_scripts: [
+        {
+          // ":8888" omitted due to bug 1362809.
+          matches: [
+            "http://mochi.test/*/thumbnails_background.sjs*",
+            "http://example.com/?iframe*",
+          ],
+          js: ["contentscript.js"],
+          run_at: "document_start",
+          all_frames: true,
+        },
+      ],
+      permissions: [
+        "webRequest",
+        "webRequestBlocking",
+        "http://example.com/*",
+        "http://mochi.test/*",
+      ],
+    },
+    files: {
+      "contentscript.js": () => {
+        // Content scripts are not expected to be run in the page of the
+        // thumbnail service, so this should never execute.
+        new Image().src = "http://example.com/?unexpected-content-script";
+        browser.test.fail("Content script ran in thumbs, unexpectedly.");
+      },
+    },
+    background() {
+      let requests = [];
+      browser.webRequest.onBeforeRequest.addListener(
+        ({ url, tabId, frameId, type }) => {
+          browser.test.assertEq(-1, tabId, "Thumb page is not a tab");
+          // We want to know if frameId is 0 or non-negative (or possibly -1).
+          if (type === "sub_frame") {
+            browser.test.assertTrue(frameId > 0, `frame ${frameId} for ${url}`);
+          } else {
+            browser.test.assertEq(0, frameId, `frameId for ${type} ${url}`);
+          }
+          requests.push({ type, url });
+        },
+        {
+          types: ["main_frame", "sub_frame", "image"],
+          urls: ["*://*/*"],
+        },
+        ["blocking"]
+      );
+      browser.test.onMessage.addListener(msg => {
+        browser.test.assertEq("get-results", msg, "expected message");
+        browser.test.sendMessage("webRequest-results", requests);
+      });
+    },
+  });
+
+  await extension.startup();
+
+  ok(!thumbnailExists(testPageUrl), "Thumbnail should not be cached yet.");
+
+  await bgCapture(testPageUrl);
+  ok(thumbnailExists(testPageUrl), "Thumbnail should be cached after capture");
+  removeThumbnail(testPageUrl);
+
+  extension.sendMessage("get-results");
+  Assert.deepEqual(
+    await extension.awaitMessage("webRequest-results"),
+    [
+      {
+        type: "main_frame",
+        url: testPageUrl,
+      },
+      {
+        type: "sub_frame",
+        url: iframeUrl,
+      },
+    ],
+    "Expected requests via webRequest"
+  );
+
+  await extension.unload();
+});
diff --git a/toolkit/components/extensions/test/browser/browser_ext_webNavigation_eventpage.js b/toolkit/components/extensions/test/browser/browser_ext_webNavigation_eventpage.js
new file mode 100644
index 0000000000..d898cb96a4
--- /dev/null
+++ b/toolkit/components/extensions/test/browser/browser_ext_webNavigation_eventpage.js
@@ -0,0 +1,72 @@
+"use strict";
+
+add_task(async function webnav_test_eventpage() {
+  await SpecialPowers.pushPrefEnv({
+    set: [["extensions.eventPages.enabled", true]],
+  });
+
+  let extension = ExtensionTestUtils.loadExtension({
+    manifest: {
+      permissions: ["webNavigation", "*://mochi.test/*"],
+      background: { persistent: false },
+    },
+    background() {
+      const EVENTS = [
+        "onTabReplaced",
+        "onBeforeNavigate",
+        "onCommitted",
+        "onDOMContentLoaded",
+        "onCompleted",
+        "onErrorOccurred",
+        "onReferenceFragmentUpdated",
+        "onHistoryStateUpdated",
+      ];
+
+      for (let event of EVENTS) {
+        browser.webNavigation[event].addListener(() => {});
+      }
+      browser.test.sendMessage("ready");
+    },
+  });
+
+  // onTabReplaced is never persisted, it is an empty event handler.
+  const EVENTS = [
+    "onBeforeNavigate",
+    "onCommitted",
+    "onDOMContentLoaded",
+    "onCompleted",
+    "onErrorOccurred",
+    "onReferenceFragmentUpdated",
+    "onHistoryStateUpdated",
+  ];
+
+  await extension.startup();
+  await extension.awaitMessage("ready");
+  for (let event of EVENTS) {
+    assertPersistentListeners(extension, "webNavigation", event, {
+      primed: false,
+    });
+  }
+
+  await extension.terminateBackground();
+  for (let event of EVENTS) {
+    assertPersistentListeners(extension, "webNavigation", event, {
+      primed: true,
+    });
+  }
+
+  // wake up the background, we don't really care which event does it,
+  // we're just verifying the state after.
+  let newWin = await BrowserTestUtils.openNewBrowserWindow();
+  await extension.awaitMessage("ready");
+  for (let event of EVENTS) {
+    assertPersistentListeners(extension, "webNavigation", event, {
+      primed: false,
+    });
+  }
+
+  await BrowserTestUtils.closeWindow(newWin);
+
+  await extension.unload();
+  await SpecialPowers.popPrefEnv();
+});
diff --git a/toolkit/components/extensions/test/browser/browser_ext_webRequest_redirect_mozextension.js b/toolkit/components/extensions/test/browser/browser_ext_webRequest_redirect_mozextension.js
new file mode 100644
index 0000000000..674a10a5ef
--- /dev/null
+++ b/toolkit/components/extensions/test/browser/browser_ext_webRequest_redirect_mozextension.js
@@ -0,0 +1,48 @@
+"use strict";
+
+// See: https://bugzilla.mozilla.org/show_bug.cgi?id=1573456
+add_task(async function test_mozextension_page_loaded_in_extension_process() {
+  let extension = ExtensionTestUtils.loadExtension({
+    manifest: {
+      permissions: [
+        "webRequest",
+        "webRequestBlocking",
+        "https://example.com/*",
+      ],
+      web_accessible_resources: ["test.html"],
+    },
+    files: {
+      "test.html": '<!DOCTYPE html><script src="test.js"></script>',
+      "test.js": () => {
+        browser.test.assertTrue(
+          browser.webRequest,
+          "webRequest API should be available"
+        );
+
+        browser.test.sendMessage("test_done");
+      },
+    },
+    background: () => {
+      browser.webRequest.onBeforeRequest.addListener(
+        () => {
+          return {
+            redirectUrl: browser.runtime.getURL("test.html"),
+          };
+        },
+        { urls: ["*://*/redir"] },
+        ["blocking"]
+      );
+    },
+  });
+  await extension.startup();
+
+  let tab = await BrowserTestUtils.openNewForegroundTab(
+    gBrowser,
+    "https://example.com/redir"
+  );
+
+  await extension.awaitMessage("test_done");
+
+  await extension.unload();
+  BrowserTestUtils.removeTab(tab);
+});
diff --git a/toolkit/components/extensions/test/browser/browser_ext_windows_popup_title.js b/toolkit/components/extensions/test/browser/browser_ext_windows_popup_title.js
new file mode 100644
index 0000000000..666d4f324f
--- /dev/null
+++ b/toolkit/components/extensions/test/browser/browser_ext_windows_popup_title.js
@@ -0,0 +1,133 @@
+"use strict";
+
+// Check that extension popup windows contain the name of the extension
+// as well as the title of the loaded document, but not the URL.
+add_task(async function test_popup_title() {
+  const name = "custom_title_number_9_please";
+  const docTitle = "popup-test-title";
+
+  const extensionWithImplicitHostPermission = ExtensionTestUtils.loadExtension({
+    manifest: {
+      name,
+    },
+    async background() {
+      let popup;
+
+      // Called after the popup loads
+      browser.runtime.onMessage.addListener(async ({ docTitle }) => {
+        const name = browser.runtime.getManifest().name;
+        const { id } = await popup;
+        const { title } = await browser.windows.get(id);
+
+        browser.test.assertTrue(
+          title.includes(name),
+          "popup title must include extension name"
+        );
+        browser.test.assertTrue(
+          title.includes(docTitle),
+          "popup title must include extension document title"
+        );
+        browser.test.assertFalse(
+          title.includes("moz-extension:"),
+          "popup title must not include extension URL"
+        );
+
+        // share window data with other extensions
+        browser.test.sendMessage("windowData", {
+          id: id,
+          fullTitle: title,
+        });
+
+        browser.test.onMessage.addListener(async message => {
+          if (message === "cleanup") {
+            await browser.windows.remove(id);
+            browser.test.sendMessage("finishedCleanup");
+          }
+        });
+
+        browser.test.sendMessage("done");
+      });
+
+      popup = browser.windows.create({
+        url: "/index.html",
+        type: "popup",
+      });
+    },
+    files: {
+      "index.html": `<!doctype html>
+        <meta charset="utf-8">
+        <title>${docTitle}</title>,
+        <script src="index.js"></script>
+      `,
+      "index.js": `addEventListener(
+          "load",
+          () => browser.runtime.sendMessage({docTitle: document.title})
+         );`,
+    },
+  });
+
+  const extensionWithoutPermissions = ExtensionTestUtils.loadExtension({
+    async background() {
+      const { id } = await new Promise(resolve => {
+        browser.test.onMessage.addListener(message => {
+          resolve(message);
+        });
+      });
+
+      const { title } = await browser.windows.get(id);
+
+      browser.test.assertEq(
+        title,
+        undefined,
+        "popup window must not include title"
+      );
+
+      browser.test.sendMessage("done");
+    },
+  });
+
+  const extensionWithTabsPermission = ExtensionTestUtils.loadExtension({
+    manifest: {
+      permissions: ["tabs"],
+    },
+    async background() {
+      const { id, fullTitle } = await new Promise(resolve => {
+        browser.test.onMessage.addListener(message => {
+          resolve(message);
+        });
+      });
+
+      const { title } = await browser.windows.get(id);
+
+      browser.test.assertEq(
+        title,
+        fullTitle,
+        "popup title equals expected title"
+      );
+
+      browser.test.sendMessage("done");
+    },
+  });
+
+  await extensionWithoutPermissions.startup();
+  await extensionWithTabsPermission.startup();
+  await extensionWithImplicitHostPermission.startup();
+
+  const windowData = await extensionWithImplicitHostPermission.awaitMessage(
+    "windowData"
+  );
+
+  extensionWithoutPermissions.sendMessage(windowData);
+  extensionWithTabsPermission.sendMessage(windowData);
+
+  await extensionWithoutPermissions.awaitMessage("done");
+  await extensionWithTabsPermission.awaitMessage("done");
+  await extensionWithImplicitHostPermission.awaitMessage("done");
+
+  extensionWithImplicitHostPermission.sendMessage("cleanup");
+  await extensionWithImplicitHostPermission.awaitMessage("finishedCleanup");
+
+  await extensionWithoutPermissions.unload();
+  await extensionWithTabsPermission.unload();
+  await extensionWithImplicitHostPermission.unload();
+});
diff --git a/toolkit/components/extensions/test/browser/data/test-download.txt b/toolkit/components/extensions/test/browser/data/test-download.txt
new file mode 100644
index 0000000000..f416e0e291
--- /dev/null
+++ b/toolkit/components/extensions/test/browser/data/test-download.txt
@@ -0,0 +1 @@
+test download content
diff --git a/toolkit/components/extensions/test/browser/data/test_downloads_referrer.html b/toolkit/components/extensions/test/browser/data/test_downloads_referrer.html
new file mode 100644
index 0000000000..85410abfcd
--- /dev/null
+++ b/toolkit/components/extensions/test/browser/data/test_downloads_referrer.html
@@ -0,0 +1,10 @@
+<!DOCTYPE html>
+<html>
+  <head>
+    <meta charset="utf-8">
+    <title>Test downloads referrer</title>
+  </head>
+  <body>
+    <a href="test-download.txt" class="test-link">test link</a>
+  </body>
+</html>
diff --git a/toolkit/components/extensions/test/browser/head.js b/toolkit/components/extensions/test/browser/head.js
new file mode 100644
index 0000000000..e25d4cb594
--- /dev/null
+++ b/toolkit/components/extensions/test/browser/head.js
@@ -0,0 +1,126 @@
+/* exported ACCENT_COLOR, BACKGROUND, ENCODED_IMAGE_DATA, FRAME_COLOR, TAB_TEXT_COLOR,
+   TEXT_COLOR, TAB_BACKGROUND_TEXT_COLOR, imageBufferFromDataURI, hexToCSS, hexToRGB, testBorderColor,
+   waitForTransition, loadTestSubscript, backgroundColorSetOnRoot, assertPersistentListeners */
+
+"use strict";
+
+const { ClientEnvironmentBase } = ChromeUtils.importESModule(
+  "resource://gre/modules/components-utils/ClientEnvironment.sys.mjs"
+);
+
+const BACKGROUND =
+  "data:image/png;base64,iVBORw0KGgoAAAANSUhEUgAAAAUAAAAFCAYAAACNbyblAAAAHElEQVQI12P4//8/w38GIAXDIBKE0" +
+  "DHxgljNBAAO9TXL0Y4OHwAAAABJRU5ErkJggg==";
+const ENCODED_IMAGE_DATA =
+  "iVBORw0KGgoAAAANSUhEUgAAABkAAAAZCAYAAADE6YVjAAAABGdBTUEAALGPC/xhBQAAAAFzUkdCAK7OHOkAAAAgY0h" +
+  "STQAAeiYAAICEAAD6AAAAgOgAAHUwAADqYAAAOpgAABdwnLpRPAAAAAZiS0dEAP8A/wD/oL2nkwAAAAlwSFlzAAAdhwAAHYcBj+XxZQAAB5dJREFUSMd" +
+  "91vmTlEcZB/Bvd7/vO+/ce83O3gfLDUsC4VgIghBUEo2GM9GCFTaQBEISA1qIEVNQ4aggJDGIgAGTlFUKKcqKQpVHaQyny7FrCMiywp4ze+/Mzs67M/P" +
+  "O+3a3v5jdWo32H/B86vv0U083weecV3+0C8lkEh6PhzS3tuLkieMSAKo3fW9Mb1eoUtM0jemerukLllzrbGlKheovUpeqkmt113hPfx/27tyFF7+/bbg" +
+  "e+U9g20s7kEwmMXXGNLrp2fWi4V5z/tFjJ3fWX726INbfU2xx0yelkJAKdJf3Xl5+2QcPTpv2U0JZR+u92+xvly5ygKDm20/hlX17/jvB6VNnIKXEOyd" +
+  "O0iFh4PLVy0XV1U83Vk54QI7JK+bl+UE5vjRfTCzJ5eWBTFEayBLjisvljKmzwmtWrVkEAPNmVrEZkyfh+fU1n59k//7X4Fbz8MK2DRSAWLNq/Yc36y9" +
+  "+3UVMsyAYVPMy/MTvdBKvriJhphDq6xa9vf0i1GMwPVhM5s9bsLw/EvtN2kywwnw/nzBuLDZs2z4auXGjHuvWbmBQdT5v7qytn165fLCyyGtXTR6j5GV" +
+  "kIsvlBCwTVNgQhMKCRDQ2iIbmJv7BpU+Ykl02UFOzdt6gkbzTEQ5Rl2KL3W8eGUE+/ssFXK+rJQ8vWigLgjk5z9ZsvpOniJzVi+ZKTUhCuATTKCjhoLA" +
+  "hhQAsjrSZBJcm7rZ22O+ev6mMmTLj55eu1T+jU8GOH/kJf2TZCiifIQsXfwEbN2yktxoaeYbf93DKSORMnTOZE0aZaVlQGYVKJCgjEJSCcgLB0xDERjI" +
+  "NFBUEaXmuB20t95eEutr0xrufpo4eepMAkMPIxx+dx9at25EWQNXsh77q0Bzwen0ShEF32HCrCpjksAWHFAKqokFhgEJt2DKJeFoQv8eDuz3duaseXZY" +
+  "dixthaQ+NRlRCcKO+FgCweP68wswMF/yZWcTkNpLJFAZEGi6XC07NCUIIoqaNSLQfFALCEpCSEL/bK/wuw+12sKlDQzKs6k5yZt+rI+2aNKUSNdUbSSQ" +
+  "Wh2mJP46rGPeYrjtkY0M7jFgciUQCiqqgrCAfBTle3G9rR1NHN3SnDq9Lg49QlBQEcbfbQCKZlhQEDkXBih27RpDOrmacfP8YB4CfHT7uNXrCMFM2FdD" +
+  "BVQ5TE/A5HbDSJoSpQXAbXm8A4b5+gKrwulU4KKEBnwuzHpiQu+n1jQoQsM+9cYQMT9fvf/FLBYTaDqdzbfgft95PKzbPyQqwnlAXGkJtGIgNYnJpMfw" +
+  "OghLG0GJE0ZdiaOnsQ16OD6XZLkiRROdAgud5sxk8ridsy/pQU1VlOIkZN6QtAGnx0FA0AtXvIA4C5OX4kOWbiLRhQBDApTmgJuLwEonMgBvjgpmgjIE" +
+  "hhX7DAIVKNeqE05/dJbgEgRy5eOJ1ieXr1gJA7ZNLTrVVlAZLyopLJAUlHsrAMrwwrRQ4t6E5VHgSBExjcGpO0JQNizCE05a41dhOi+cXXVm144e1AHD" +
+  "1vXfFMOLy+KSHEDoEJLZ8s+ZWKpUusWwpFKiMUQ4jbiAaj8Hp9oExBsMCUpEIfD6JLKZjKJVGV3RIZGdm0qxA5qmz+/cgMhBVuuMRewRRGF7fe4BYHMg" +
+  "N5LxdV3vhy1EjrrjA5GAyTuKpFHricfS0dSDNCQRPoSyQgSSPI+UBEtwShiWUQEHw5mMvbz4JRcXvDr3B3dBG1sq5X53GlMcX4JWVTyvRQcOumDD2vfK" +
+  "cjOqiQDZPGBF2ryUEnjRhJlP4d6/BiQ1TABPKiyQhgtzvjPCJlQ/OGRwauqESSUPX68U3Vi4fGeH83Hwc3bYHBWUV0m0k4HB6z7aGu6sznDos00R3exg" +
+  "l5ZMwc+FMaJoKKxHFnbo6DMYiELBlqLOXDBq8dsvuPTfKALpwdbX42iMLsHjLd0Zv4RNvvY1wZxdZunyVDGZm6D/47sv12RqbmOPVhG5LGnAH4S8sgu7" +
+  "1oK/pn2BWAoYw0dDbaTd19iqlZROejwzEjqgMSuXUifak8jF49JnNI0kAoGrBfET7+uXOrS+y5ta21JzZsw7faW45XJaXxSvyAtTpkOi483fwtAWP1wt" +
+  "vrhvd/VFx+26zojr9Les2PnfaTNu4cuGvvKe9BVv3/RgARiNTpk/Hod17MWikxcqzzfhK/+1jL2xc+YQAX1ISDHLV7WTpQQaLcASzPEiB41ZrmEeHkrT" +
+  "Q49uz/aXn+iilLKXq/MmlS0e/jFcuX4SmaQAAKSXlnIvVy1aQ6EBMFgRyCznDpfGFwdKqirF2tu5SdIeGrkiP+KS5yb7dHtIKsnI++kP9rS8RQvjmxxe" +
+  "jePxD2HHwwP9FdCllurGhUbx14CAbiMc4Y2qVJqwLbo0qfpdLSilILB4Xg0mT6h7vnSWzZn9RoaynobWF3K6rk1NmzMWZ83/+37+V4a1cVg5JACYF45b" +
+  "FGVVWOFS2V1HUCjOdBqW0Q9fYb7N9/tcSptnldjpott8rFEXBO+f+NKrWMHL9Wu1nSUAIAaUUa59aAyE43E4X3bD8W6K5K6x1h1snRaMDJDuQf7+vrzf" +
+  "eG+mgfrcLHh3C79bx6wttGEqERiH/AjPohWMouv2ZAAAAAElFTkSuQmCC";
+const ACCENT_COLOR = "#a14040";
+const TEXT_COLOR = "#fac96e";
+// For testing aliases of the colors above:
+const FRAME_COLOR = [71, 105, 91];
+const TAB_BACKGROUND_TEXT_COLOR = [207, 221, 192, 0.9];
+
+function hexToRGB(hex) {
+  if (!hex) {
+    return null;
+  }
+  hex = parseInt(hex.indexOf("#") > -1 ? hex.substring(1) : hex, 16);
+  return [hex >> 16, (hex & 0x00ff00) >> 8, hex & 0x0000ff];
+}
+
+function rgbToCSS(rgb) {
+  return `rgb(${rgb.join(", ")})`;
+}
+
+function hexToCSS(hex) {
+  if (!hex) {
+    return null;
+  }
+  return rgbToCSS(hexToRGB(hex));
+}
+
+function imageBufferFromDataURI(encodedImageData) {
+  let decodedImageData = atob(encodedImageData);
+  return Uint8Array.from(decodedImageData, byte => byte.charCodeAt(0)).buffer;
+}
+
+function waitForTransition(element, propertyName) {
+  return BrowserTestUtils.waitForEvent(
+    element,
+    "transitionend",
+    false,
+    event => {
+      return event.target == element && event.propertyName == propertyName;
+    }
+  );
+}
+
+function testBorderColor(element, expected) {
+  let computedStyle = window.getComputedStyle(element);
+  Assert.equal(
+    computedStyle.borderLeftColor,
+    hexToCSS(expected),
+    "Element left border color should be set."
+  );
+  Assert.equal(
+    computedStyle.borderRightColor,
+    hexToCSS(expected),
+    "Element right border color should be set."
+  );
+  Assert.equal(
+    computedStyle.borderTopColor,
+    hexToCSS(expected),
+    "Element top border color should be set."
+  );
+  Assert.equal(
+    computedStyle.borderBottomColor,
+    hexToCSS(expected),
+    "Element bottom border color should be set."
+  );
+}
+
+function loadTestSubscript(filePath) {
+  Services.scriptloader.loadSubScript(new URL(filePath, gTestPath).href, this);
+}
+
+/**
+ * Windows 7 and 8 set the window's background-color on :root instead of
+ * #navigator-toolbox to avoid bug 1695280. When that bug is fixed, this
+ * function and the assertions it gates can be removed.
+ *
+ * @returns {boolean} True if the window's background-color is set on :root
+ *   rather than #navigator-toolbox.
+ */
+function backgroundColorSetOnRoot() {
+  const os = ClientEnvironmentBase.os;
+  if (!os.isWindows) {
+    return false;
+  }
+  return os.windowsVersion < 10;
+}
+
+// Persistent Listener test functionality
+const { assertPersistentListeners } = ExtensionTestUtils.testAssertions;
diff --git a/toolkit/components/extensions/test/browser/head_serviceworker.js b/toolkit/components/extensions/test/browser/head_serviceworker.js
new file mode 100644
index 0000000000..b2f9512e5a
--- /dev/null
+++ b/toolkit/components/extensions/test/browser/head_serviceworker.js
@@ -0,0 +1,119 @@
+"use strict";
+
+/* exported assert_background_serviceworker_pref_enabled,
+ *          getBackgroundServiceWorkerRegistration,
+ *          getServiceWorkerInfo, getServiceWorkerState,
+ *          waitForServiceWorkerRegistrationsRemoved, waitForServiceWorkerTerminated
+ */
+
+async function assert_background_serviceworker_pref_enabled() {
+  is(
+    WebExtensionPolicy.backgroundServiceWorkerEnabled,
+    true,
+    "Expect extensions.backgroundServiceWorker.enabled to be true"
+  );
+}
+
+// Return the name of the enum corresponding to the worker's state (ex: "STATE_ACTIVATED")
+// because nsIServiceWorkerInfo doesn't currently provide a comparable string-returning getter.
+function getServiceWorkerState(workerInfo) {
+  const map = Object.keys(workerInfo)
+    .filter(k => k.startsWith("STATE_"))
+    .reduce((map, name) => {
+      map.set(workerInfo[name], name);
+      return map;
+    }, new Map());
+  return map.has(workerInfo.state)
+    ? map.get(workerInfo.state)
+    : "state: ${workerInfo.state}";
+}
+
+function getServiceWorkerInfo(swRegInfo) {
+  const { evaluatingWorker, installingWorker, waitingWorker, activeWorker } =
+    swRegInfo;
+  return evaluatingWorker || installingWorker || waitingWorker || activeWorker;
+}
+
+async function waitForServiceWorkerTerminated(swRegInfo) {
+  info(`Wait all ${swRegInfo.scope} workers to be terminated`);
+
+  try {
+    await BrowserTestUtils.waitForCondition(
+      () => !getServiceWorkerInfo(swRegInfo)
+    );
+  } catch (err) {
+    const workerInfo = getServiceWorkerInfo(swRegInfo);
+    if (workerInfo) {
+      ok(
+        false,
+        `Error while waiting for workers for scope ${swRegInfo.scope} to be terminated. ` +
+          `Found a worker in state: ${getServiceWorkerState(workerInfo)}`
+      );
+      return;
+    }
+
+    throw err;
+  }
+}
+
+function getBackgroundServiceWorkerRegistration(extension) {
+  const policy = WebExtensionPolicy.getByHostname(extension.uuid);
+  const expectedSWScope = policy.getURL("/");
+  const expectedScriptURL = policy.extension.backgroundWorkerScript || "";
+
+  ok(
+    expectedScriptURL.startsWith(expectedSWScope),
+    `Extension does include a valid background.service_worker: ${expectedScriptURL}`
+  );
+
+  const swm = Cc["@mozilla.org/serviceworkers/manager;1"].getService(
+    Ci.nsIServiceWorkerManager
+  );
+
+  let swReg;
+  let regs = swm.getAllRegistrations();
+
+  for (let i = 0; i < regs.length; i++) {
+    let reg = regs.queryElementAt(i, Ci.nsIServiceWorkerRegistrationInfo);
+    if (reg.scriptSpec === expectedScriptURL) {
+      swReg = reg;
+      break;
+    }
+  }
+
+  ok(swReg, `Found service worker registration for ${expectedScriptURL}`);
+
+  is(
+    swReg.scope,
+    expectedSWScope,
+    "The extension background worker registration has the expected scope URL"
+  );
+
+  return swReg;
+}
+
+async function waitForServiceWorkerRegistrationsRemoved(extension) {
+  info(`Wait ${extension.id} service worker registration to be deleted`);
+  const swm = Cc["@mozilla.org/serviceworkers/manager;1"].getService(
+    Ci.nsIServiceWorkerManager
+  );
+  let baseURI = Services.io.newURI(`moz-extension://${extension.uuid}/`);
+  let principal = Services.scriptSecurityManager.createContentPrincipal(
+    baseURI,
+    {}
+  );
+
+  await BrowserTestUtils.waitForCondition(() => {
+    let regs = swm.getAllRegistrations();
+
+    for (let i = 0; i < regs.length; i++) {
+      let reg = regs.queryElementAt(i, Ci.nsIServiceWorkerRegistrationInfo);
+      if (principal.equals(reg.principal)) {
+        return false;
+      }
+    }
+
+    info(`All ${extension.id} service worker registrations are gone`);
+    return true;
+  }, `All ${extension.id} service worker registrations should be deleted`);
+}
diff --git a/toolkit/components/extensions/test/marionette/data/extension-with-bg-sw/manifest.json b/toolkit/components/extensions/test/marionette/data/extension-with-bg-sw/manifest.json
new file mode 100644
index 0000000000..38a5c3f027
--- /dev/null
+++ b/toolkit/components/extensions/test/marionette/data/extension-with-bg-sw/manifest.json
@@ -0,0 +1,11 @@
+{
+  "manifest_version": 2,
+  "name": "Test Extension with Background Service Worker",
+  "version": "1",
+  "browser_specific_settings": {
+    "gecko": { "id": "extension-with-bg-sw@test" }
+  },
+  "background": {
+    "service_worker": "sw.js"
+  }
+}
diff --git a/toolkit/components/extensions/test/marionette/data/extension-with-bg-sw/sw.js b/toolkit/components/extensions/test/marionette/data/extension-with-bg-sw/sw.js
new file mode 100644
index 0000000000..2282e6a64b
--- /dev/null
+++ b/toolkit/components/extensions/test/marionette/data/extension-with-bg-sw/sw.js
@@ -0,0 +1,3 @@
+"use strict";
+
+dump("extension-with-bg-sw: sw.js loaded");
diff --git a/toolkit/components/extensions/test/marionette/manifest.ini b/toolkit/components/extensions/test/marionette/manifest.ini
new file mode 100644
index 0000000000..8073096b9e
--- /dev/null
+++ b/toolkit/components/extensions/test/marionette/manifest.ini
@@ -0,0 +1,2 @@
+[test_extension_serviceworkers_purged_on_pref_disabled.py]
+[test_temporary_extension_serviceworkers_not_persisted.py]
diff --git a/toolkit/components/extensions/test/marionette/service_worker_testutils.py b/toolkit/components/extensions/test/marionette/service_worker_testutils.py
new file mode 100644
index 0000000000..b1fda926c0
--- /dev/null
+++ b/toolkit/components/extensions/test/marionette/service_worker_testutils.py
@@ -0,0 +1,48 @@
+# This Source Code Form is subject to the terms of the Mozilla Public
+# License, v. 2.0. If a copy of the MPL was not distributed with this
+# file, You can obtain one at http://mozilla.org/MPL/2.0/.
+
+from marionette_harness import MarionetteTestCase
+
+EXT_ID = "extension-with-bg-sw@test"
+EXT_DIR_PATH = "extension-with-bg-sw"
+PREF_BG_SW_ENABLED = "extensions.backgroundServiceWorker.enabled"
+PREF_PERSIST_TEMP_ADDONS = (
+    "dom.serviceWorkers.testing.persistTemporarilyInstalledAddons"
+)
+
+
+class MarionetteServiceWorkerTestCase(MarionetteTestCase):
+    def get_extension_url(self, path="/"):
+        with self.marionette.using_context("chrome"):
+            return self.marionette.execute_script(
+                """
+              let policy = WebExtensionPolicy.getByID(arguments[0]);
+              return policy.getURL(arguments[1])
+            """,
+                script_args=(self.test_extension_id, path),
+            )
+
+    @property
+    def is_extension_service_worker_registered(self):
+        with self.marionette.using_context("chrome"):
+            return self.marionette.execute_script(
+                """
+                let serviceWorkerManager = Cc["@mozilla.org/serviceworkers/manager;1"].getService(
+                    Ci.nsIServiceWorkerManager
+                );
+
+                let serviceWorkers = serviceWorkerManager.getAllRegistrations();
+                for (let i = 0; i < serviceWorkers.length; i++) {
+                    let sw = serviceWorkers.queryElementAt(
+                        i,
+                        Ci.nsIServiceWorkerRegistrationInfo
+                    );
+                    if (sw.scope == arguments[0]) {
+                        return true;
+                    }
+                }
+                return false;
+            """,
+                script_args=(self.test_extension_base_url,),
+            )
diff --git a/toolkit/components/extensions/test/marionette/test_extension_serviceworkers_purged_on_pref_disabled.py b/toolkit/components/extensions/test/marionette/test_extension_serviceworkers_purged_on_pref_disabled.py
new file mode 100644
index 0000000000..ff2184c692
--- /dev/null
+++ b/toolkit/components/extensions/test/marionette/test_extension_serviceworkers_purged_on_pref_disabled.py
@@ -0,0 +1,56 @@
+# This Source Code Form is subject to the terms of the Mozilla Public
+# License, v. 2.0. If a copy of the MPL was not distributed with this
+# file, You can obtain one at http://mozilla.org/MPL/2.0/.
+
+import os
+import sys
+
+from marionette_driver import Wait
+from marionette_driver.addons import Addons
+
+# Add this directory to the import path.
+sys.path.append(os.path.dirname(__file__))
+
+from service_worker_testutils import (
+    EXT_DIR_PATH,
+    EXT_ID,
+    PREF_BG_SW_ENABLED,
+    PREF_PERSIST_TEMP_ADDONS,
+    MarionetteServiceWorkerTestCase,
+)
+
+
+class PurgeExtensionServiceWorkersOnPrefDisabled(MarionetteServiceWorkerTestCase):
+    def setUp(self):
+        super(PurgeExtensionServiceWorkersOnPrefDisabled, self).setUp()
+        self.test_extension_id = EXT_ID
+        # Flip the "mirror: once" pref and restart Firefox to be able
+        # to run the extension successfully.
+        self.marionette.set_pref(PREF_BG_SW_ENABLED, True)
+        self.marionette.set_pref(PREF_PERSIST_TEMP_ADDONS, True)
+        self.marionette.restart(in_app=True)
+
+    def tearDown(self):
+        self.marionette.restart(in_app=False, clean=True)
+        super(PurgeExtensionServiceWorkersOnPrefDisabled, self).tearDown()
+
+    def test_unregistering_service_worker_when_clearing_data(self):
+        self.install_extension_with_service_worker()
+
+        # Flip the pref to false and restart again to verify that the
+        # service worker registration has been removed as expected.
+        self.marionette.set_pref(PREF_BG_SW_ENABLED, False)
+        self.marionette.restart(in_app=True)
+        self.assertFalse(self.is_extension_service_worker_registered)
+
+    def install_extension_with_service_worker(self):
+        addons = Addons(self.marionette)
+        test_extension_path = os.path.join(
+            os.path.dirname(self.filepath), "data", EXT_DIR_PATH
+        )
+        addons.install(test_extension_path, temp=True)
+        self.test_extension_base_url = self.get_extension_url()
+        Wait(self.marionette).until(
+            lambda _: self.is_extension_service_worker_registered,
+            message="Wait the extension service worker to be registered",
+        )
diff --git a/toolkit/components/extensions/test/marionette/test_temporary_extension_serviceworkers_not_persisted.py b/toolkit/components/extensions/test/marionette/test_temporary_extension_serviceworkers_not_persisted.py
new file mode 100644
index 0000000000..57c0696385
--- /dev/null
+++ b/toolkit/components/extensions/test/marionette/test_temporary_extension_serviceworkers_not_persisted.py
@@ -0,0 +1,54 @@
+# This Source Code Form is subject to the terms of the Mozilla Public
+# License, v. 2.0. If a copy of the MPL was not distributed with this
+# file, You can obtain one at http://mozilla.org/MPL/2.0/.
+
+import os
+import sys
+
+from marionette_driver import Wait
+from marionette_driver.addons import Addons
+
+# Add this directory to the import path.
+sys.path.append(os.path.dirname(__file__))
+
+from service_worker_testutils import (
+    EXT_DIR_PATH,
+    EXT_ID,
+    PREF_BG_SW_ENABLED,
+    MarionetteServiceWorkerTestCase,
+)
+
+
+class TemporarilyInstalledAddonServiceWorkerNotPersisted(
+    MarionetteServiceWorkerTestCase
+):
+    def setUp(self):
+        super(TemporarilyInstalledAddonServiceWorkerNotPersisted, self).setUp()
+        self.test_extension_id = EXT_ID
+        # Flip the "mirror: once" pref and restart Firefox to be able
+        # to run the extension successfully.
+        self.marionette.set_pref(PREF_BG_SW_ENABLED, True)
+        self.marionette.restart(in_app=True)
+
+    def tearDown(self):
+        self.marionette.restart(in_app=False, clean=True)
+        super(TemporarilyInstalledAddonServiceWorkerNotPersisted, self).tearDown()
+
+    def test_temporarily_installed_addon_serviceWorkers_not_persisted(self):
+        self.install_temporary_extension_with_service_worker()
+        # Make sure the extension worker registration is persisted
+        # across restarts when the pref stays set to true.
+        self.marionette.restart(in_app=True)
+        self.assertFalse(self.is_extension_service_worker_registered)
+
+    def install_temporary_extension_with_service_worker(self):
+        addons = Addons(self.marionette)
+        test_extension_path = os.path.join(
+            os.path.dirname(self.filepath), "data", EXT_DIR_PATH
+        )
+        addons.install(test_extension_path, temp=True)
+        self.test_extension_base_url = self.get_extension_url()
+        Wait(self.marionette).until(
+            lambda _: self.is_extension_service_worker_registered,
+            message="Wait the extension service worker to be registered",
+        )
diff --git a/toolkit/components/extensions/test/mochitest/.eslintrc.js b/toolkit/components/extensions/test/mochitest/.eslintrc.js
new file mode 100644
index 0000000000..a776405c9d
--- /dev/null
+++ b/toolkit/components/extensions/test/mochitest/.eslintrc.js
@@ -0,0 +1,12 @@
+"use strict";
+
+module.exports = {
+  env: {
+    browser: true,
+    webextensions: true,
+  },
+
+  rules: {
+    "no-shadow": 0,
+  },
+};
diff --git a/toolkit/components/extensions/test/mochitest/chrome.ini b/toolkit/components/extensions/test/mochitest/chrome.ini
new file mode 100644
index 0000000000..30781a8759
--- /dev/null
+++ b/toolkit/components/extensions/test/mochitest/chrome.ini
@@ -0,0 +1,38 @@
+[DEFAULT]
+support-files =
+  chrome_cleanup_script.js
+  head.js
+  head_cookies.js
+  file_image_good.png
+  file_image_great.png
+  file_sample.html
+  file_with_images.html
+  webrequest_chromeworker.js
+  webrequest_test.sys.mjs
+prefs =
+  security.mixed_content.upgrade_display_content=false
+tags = webextensions in-process-webextensions
+
+# NO NEW TESTS.  mochitest-chrome does not run under e10s, avoid adding new
+# tests here unless absolutely necessary.
+
+[test_chrome_ext_contentscript_data_uri.html]
+[test_chrome_ext_contentscript_telemetry.html]
+[test_chrome_ext_contentscript_unrecognizedprop_warning.html]
+[test_chrome_ext_downloads_open.html]
+[test_chrome_ext_downloads_saveAs.html]
+skip-if = (verify && !debug && (os == 'win')) || (os == 'android') || (os == 'win' && os_version == '10.0') # Bug 1695612
+[test_chrome_ext_downloads_uniquify.html]
+skip-if = os == 'win' && os_version == '10.0' # Bug 1695612
+[test_chrome_ext_permissions.html]
+skip-if = os == 'android' # Bug 1350559
+[test_chrome_ext_svg_context_fill.html]
+[test_chrome_ext_trackingprotection.html]
+[test_chrome_ext_webnavigation_resolved_urls.html]
+[test_chrome_ext_webrequest_background_events.html]
+[test_chrome_ext_webrequest_host_permissions.html]
+skip-if = verify
+[test_chrome_ext_webrequest_mozextension.html]
+skip-if = true # Bug 1404172
+[test_chrome_native_messaging_paths.html]
+skip-if = os != "mac" && os != "linux"
diff --git a/toolkit/components/extensions/test/mochitest/chrome_cleanup_script.js b/toolkit/components/extensions/test/mochitest/chrome_cleanup_script.js
new file mode 100644
index 0000000000..9afa95f302
--- /dev/null
+++ b/toolkit/components/extensions/test/mochitest/chrome_cleanup_script.js
@@ -0,0 +1,65 @@
+/* eslint-env mozilla/chrome-script */
+
+"use strict";
+
+const { AppConstants } = ChromeUtils.importESModule(
+  "resource://gre/modules/AppConstants.sys.mjs"
+);
+
+let listener = msg => {
+  void (msg instanceof Ci.nsIConsoleMessage);
+  dump(`Console message: ${msg}\n`);
+};
+
+Services.console.registerListener(listener);
+
+let getBrowserApp, getTabBrowser;
+if (AppConstants.MOZ_BUILD_APP === "mobile/android") {
+  getBrowserApp = win => win.BrowserApp;
+  getTabBrowser = tab => tab.browser;
+} else {
+  getBrowserApp = win => win.gBrowser;
+  getTabBrowser = tab => tab.linkedBrowser;
+}
+
+function* iterBrowserWindows() {
+  for (let win of Services.wm.getEnumerator("navigator:browser")) {
+    if (!win.closed && getBrowserApp(win)) {
+      yield win;
+    }
+  }
+}
+
+let initialTabs = new Map();
+for (let win of iterBrowserWindows()) {
+  initialTabs.set(win, new Set(getBrowserApp(win).tabs));
+}
+
+addMessageListener("check-cleanup", extensionId => {
+  Services.console.unregisterListener(listener);
+
+  let results = {
+    extraWindows: [],
+    extraTabs: [],
+  };
+
+  for (let win of iterBrowserWindows()) {
+    if (initialTabs.has(win)) {
+      let tabs = initialTabs.get(win);
+
+      for (let tab of getBrowserApp(win).tabs) {
+        if (!tabs.has(tab)) {
+          results.extraTabs.push(getTabBrowser(tab).currentURI.spec);
+        }
+      }
+    } else {
+      results.extraWindows.push(
+        Array.from(win.gBrowser.tabs, tab => getTabBrowser(tab).currentURI.spec)
+      );
+    }
+  }
+
+  initialTabs = null;
+
+  sendAsyncMessage("cleanup-results", results);
+});
diff --git a/toolkit/components/extensions/test/mochitest/chrome_head.js b/toolkit/components/extensions/test/mochitest/chrome_head.js
new file mode 100644
index 0000000000..3918c74e44
--- /dev/null
+++ b/toolkit/components/extensions/test/mochitest/chrome_head.js
@@ -0,0 +1 @@
+"use strict";
diff --git a/toolkit/components/extensions/test/mochitest/file_WebNavigation_page1.html b/toolkit/components/extensions/test/mochitest/file_WebNavigation_page1.html
new file mode 100644
index 0000000000..663ebc6112
--- /dev/null
+++ b/toolkit/components/extensions/test/mochitest/file_WebNavigation_page1.html
@@ -0,0 +1,12 @@
+<!DOCTYPE HTML>
+
+<html>
+<body>
+
+<iframe src="file_WebNavigation_page2.html" width="200" height="200"></iframe>
+
+<form>
+</form>
+
+</body>
+</html>
diff --git a/toolkit/components/extensions/test/mochitest/file_WebNavigation_page2.html b/toolkit/components/extensions/test/mochitest/file_WebNavigation_page2.html
new file mode 100644
index 0000000000..cc1acc83d6
--- /dev/null
+++ b/toolkit/components/extensions/test/mochitest/file_WebNavigation_page2.html
@@ -0,0 +1,7 @@
+<!DOCTYPE HTML>
+
+<html>
+<body>
+
+</body>
+</html>
diff --git a/toolkit/components/extensions/test/mochitest/file_WebNavigation_page3.html b/toolkit/components/extensions/test/mochitest/file_WebNavigation_page3.html
new file mode 100644
index 0000000000..a0a26a2e9d
--- /dev/null
+++ b/toolkit/components/extensions/test/mochitest/file_WebNavigation_page3.html
@@ -0,0 +1,9 @@
+<!DOCTYPE HTML>
+
+<html>
+<body>
+
+<a id="elt" href="file_WebNavigation_page3.html#ref">click me</a>
+
+</body>
+</html>
diff --git a/toolkit/components/extensions/test/mochitest/file_WebRequest_page3.html b/toolkit/components/extensions/test/mochitest/file_WebRequest_page3.html
new file mode 100644
index 0000000000..24c7a42986
--- /dev/null
+++ b/toolkit/components/extensions/test/mochitest/file_WebRequest_page3.html
@@ -0,0 +1,10 @@
+<!DOCTYPE HTML>
+
+<html>
+<head>
+<meta charset="utf-8">
+<script>
+"use strict";
+</script>
+</head>
+</html>
diff --git a/toolkit/components/extensions/test/mochitest/file_contains_iframe.html b/toolkit/components/extensions/test/mochitest/file_contains_iframe.html
new file mode 100644
index 0000000000..e905b5a224
--- /dev/null
+++ b/toolkit/components/extensions/test/mochitest/file_contains_iframe.html
@@ -0,0 +1,13 @@
+<!DOCTYPE HTML>
+<html>
+<head>
+<meta charset="utf-8">
+<title>file contains iframe</title>
+</head>
+<body>
+
+<iframe src="//example.org/tests/toolkit/components/extensions/test/mochitest/file_contains_img.html">
+</iframe>
+
+</body>
+</html>
diff --git a/toolkit/components/extensions/test/mochitest/file_contains_img.html b/toolkit/components/extensions/test/mochitest/file_contains_img.html
new file mode 100644
index 0000000000..2b0c3137d6
--- /dev/null
+++ b/toolkit/components/extensions/test/mochitest/file_contains_img.html
@@ -0,0 +1,12 @@
+<!DOCTYPE HTML>
+<html>
+<head>
+<meta charset="utf-8">
+<title>file contains img</title>
+</head>
+<body>
+
+<img src="file_image_good.png"/>
+
+</body>
+</html>
diff --git a/toolkit/components/extensions/test/mochitest/file_contentscript_activeTab.html b/toolkit/components/extensions/test/mochitest/file_contentscript_activeTab.html
new file mode 100644
index 0000000000..6c1675cb47
--- /dev/null
+++ b/toolkit/components/extensions/test/mochitest/file_contentscript_activeTab.html
@@ -0,0 +1,11 @@
+<!DOCTYPE HTML>
+
+<html>
+<head>
+  <meta charset="utf-8">
+</head>
+<body>
+  <iframe id="emptyframe"></iframe>
+  <iframe id="regularframe" src="http://test1.example.com/"></iframe>
+</body>
+</html>
diff --git a/toolkit/components/extensions/test/mochitest/file_contentscript_activeTab2.html b/toolkit/components/extensions/test/mochitest/file_contentscript_activeTab2.html
new file mode 100644
index 0000000000..3b102b3d67
--- /dev/null
+++ b/toolkit/components/extensions/test/mochitest/file_contentscript_activeTab2.html
@@ -0,0 +1,10 @@
+<!DOCTYPE HTML>
+
+<html>
+<head>
+  <meta charset="utf-8">
+</head>
+<body>
+  <iframe srcdoc="<iframe src='http://test1.example.com/'&gt;</iframe&gt;"></iframe>
+</body>
+</html>
diff --git a/toolkit/components/extensions/test/mochitest/file_contentscript_iframe.html b/toolkit/components/extensions/test/mochitest/file_contentscript_iframe.html
new file mode 100644
index 0000000000..670bad1360
--- /dev/null
+++ b/toolkit/components/extensions/test/mochitest/file_contentscript_iframe.html
@@ -0,0 +1,10 @@
+<!DOCTYPE HTML>
+
+<html>
+<head>
+  <meta charset="utf-8">
+</head>
+<body>
+  <iframe id="frame" src="https://test2.example.com/"></iframe>
+</body>
+</html>
diff --git a/toolkit/components/extensions/test/mochitest/file_green.html b/toolkit/components/extensions/test/mochitest/file_green.html
new file mode 100644
index 0000000000..20755c5b56
--- /dev/null
+++ b/toolkit/components/extensions/test/mochitest/file_green.html
@@ -0,0 +1,3 @@
+<meta charset=utf-8>
+<title>Super green test page</title>
+<body style="background: #0f0">
diff --git a/toolkit/components/extensions/test/mochitest/file_green_blue.html b/toolkit/components/extensions/test/mochitest/file_green_blue.html
new file mode 100644
index 0000000000..9266b637ba
--- /dev/null
+++ b/toolkit/components/extensions/test/mochitest/file_green_blue.html
@@ -0,0 +1,16 @@
+<meta charset=utf-8>
+<title>Upper square green, rest blue</title>
+<style>
+  div {
+    position: absolute;
+    width: 50vw;
+    height: 50vh;
+    top: 0;
+    left: 0;
+    background-color: lime;
+  }
+  :root {
+    background-color: blue;
+  }
+</style>
+<div></div>
diff --git a/toolkit/components/extensions/test/mochitest/file_image_bad.png b/toolkit/components/extensions/test/mochitest/file_image_bad.png
new file mode 100644
index 0000000000..4c3be50847
--- /dev/null
+++ b/toolkit/components/extensions/test/mochitest/file_image_bad.png
diff --git a/toolkit/components/extensions/test/mochitest/file_image_good.png b/toolkit/components/extensions/test/mochitest/file_image_good.png
new file mode 100644
index 0000000000..769c636340
--- /dev/null
+++ b/toolkit/components/extensions/test/mochitest/file_image_good.png
diff --git a/toolkit/components/extensions/test/mochitest/file_image_great.png b/toolkit/components/extensions/test/mochitest/file_image_great.png
new file mode 100644
index 0000000000..769c636340
--- /dev/null
+++ b/toolkit/components/extensions/test/mochitest/file_image_great.png
diff --git a/toolkit/components/extensions/test/mochitest/file_image_redirect.png b/toolkit/components/extensions/test/mochitest/file_image_redirect.png
new file mode 100644
index 0000000000..4c3be50847
--- /dev/null
+++ b/toolkit/components/extensions/test/mochitest/file_image_redirect.png
diff --git a/toolkit/components/extensions/test/mochitest/file_indexedDB.html b/toolkit/components/extensions/test/mochitest/file_indexedDB.html
new file mode 100644
index 0000000000..65b7e0ad2f
--- /dev/null
+++ b/toolkit/components/extensions/test/mochitest/file_indexedDB.html
@@ -0,0 +1,28 @@
+<!DOCTYPE html>
+<html lang="en">
+  <head>
+    <meta charset="utf-8">
+    <script>
+"use strict";
+
+const objectStoreName = "Objects";
+
+let test = {key: 0, value: "test"};
+
+let request = indexedDB.open("WebExtensionTest", 1);
+request.onupgradeneeded = event => {
+  let db = event.target.result;
+  let objectStore = db.createObjectStore(objectStoreName,
+                                         {autoIncrement: 0});
+  request = objectStore.add(test.value, test.key);
+  request.onsuccess = event => {
+    db.close();
+    window.postMessage("indexedDBCreated", "*");
+  };
+};
+    </script>
+  </head>
+  <body>
+    This is a test page.
+  </body>
+<html>
diff --git a/toolkit/components/extensions/test/mochitest/file_mixed.html b/toolkit/components/extensions/test/mochitest/file_mixed.html
new file mode 100644
index 0000000000..f3c7dda580
--- /dev/null
+++ b/toolkit/components/extensions/test/mochitest/file_mixed.html
@@ -0,0 +1,13 @@
+<!DOCTYPE HTML>
+
+<html>
+<head>
+<meta charset="utf-8">
+</head>
+<body>
+
+<div id="test">Sample text</div>
+<img id="bad-image" src="http://example.com/tests/toolkit/components/extensions/test/mochitest/file_image_bad.png" />
+
+</body>
+</html>
diff --git a/toolkit/components/extensions/test/mochitest/file_redirect_cors_bypass.html b/toolkit/components/extensions/test/mochitest/file_redirect_cors_bypass.html
new file mode 100644
index 0000000000..b8fda2369a
--- /dev/null
+++ b/toolkit/components/extensions/test/mochitest/file_redirect_cors_bypass.html
@@ -0,0 +1,30 @@
+<!DOCTYPE HTML>
+<html>
+<head>
+  <title>1450965 Skip Cors Check for Early WebExtention Redirects</title>
+</head>
+<body>
+  <pre id="c">
+    Fetching ...
+  </pre>
+  <script>
+    "use strict";
+    let c = document.querySelector("#c");
+    const channel = new BroadcastChannel("test_bus");
+    function l(t) { c.innerText += `${t}\n`; }
+
+    fetch("https://example.org/tests/toolkit/components/extensions/test/mochitest/file_cors_blocked.txt")
+      .then(r => r.text())
+      .then(t => {
+        // This Request should have been redirected to /file_sample.txt in
+        // onBeforeRequest. So the text should be 'Sample'
+        l(`Loaded: ${t}`);
+        channel.postMessage(t);
+      }).catch(e => {
+        // The Redirect Failed, most likly due to a CORS Error
+        l(`e`);
+        channel.postMessage(e.toString());
+      });
+  </script>
+</body>
+</html>
diff --git a/toolkit/components/extensions/test/mochitest/file_redirect_data_uri.html b/toolkit/components/extensions/test/mochitest/file_redirect_data_uri.html
new file mode 100644
index 0000000000..fe8e5bea44
--- /dev/null
+++ b/toolkit/components/extensions/test/mochitest/file_redirect_data_uri.html
@@ -0,0 +1,9 @@
+<!DOCTYPE HTML>
+<html>
+<head>
+  <title>Bug 1434357: Allow Web Request API to redirect to data: URI</title>
+</head>
+<body>
+  <div id="testdiv">foo</div>
+</body>
+</html>
diff --git a/toolkit/components/extensions/test/mochitest/file_remote_frame.html b/toolkit/components/extensions/test/mochitest/file_remote_frame.html
new file mode 100644
index 0000000000..f1b9240092
--- /dev/null
+++ b/toolkit/components/extensions/test/mochitest/file_remote_frame.html
@@ -0,0 +1,20 @@
+<!DOCTYPE>
+<html>
+  <head>
+    <meta charset="utf-8">
+    <script>
+      "use strict";
+      var response = {
+        tabs: false,
+        cookie: document.cookie,
+      };
+      try {
+        browser.tabs.create({url: "file_sample.html"});
+        response.tabs = true;
+      } catch (e) {
+        // ok
+      }
+      window.parent.postMessage(response, "*");
+    </script>
+  </head>
+</html>
diff --git a/toolkit/components/extensions/test/mochitest/file_sample.html b/toolkit/components/extensions/test/mochitest/file_sample.html
new file mode 100644
index 0000000000..aa1ef6e6f4
--- /dev/null
+++ b/toolkit/components/extensions/test/mochitest/file_sample.html
@@ -0,0 +1,13 @@
+<!DOCTYPE HTML>
+
+<html>
+<head>
+<meta charset="utf-8">
+<title>file sample</title>
+</head>
+<body>
+
+<div id="test">Sample text</div>
+
+</body>
+</html>
diff --git a/toolkit/components/extensions/test/mochitest/file_sample.txt b/toolkit/components/extensions/test/mochitest/file_sample.txt
new file mode 100644
index 0000000000..c02cd532b1
--- /dev/null
+++ b/toolkit/components/extensions/test/mochitest/file_sample.txt
@@ -0,0 +1 @@
+Sample
\ No newline at end of file
diff --git a/toolkit/components/extensions/test/mochitest/file_sample.txt^headers^ b/toolkit/components/extensions/test/mochitest/file_sample.txt^headers^
new file mode 100644
index 0000000000..cb762eff80
--- /dev/null
+++ b/toolkit/components/extensions/test/mochitest/file_sample.txt^headers^
@@ -0,0 +1 @@
+Access-Control-Allow-Origin: *
diff --git a/toolkit/components/extensions/test/mochitest/file_script_bad.js b/toolkit/components/extensions/test/mochitest/file_script_bad.js
new file mode 100644
index 0000000000..c425122c71
--- /dev/null
+++ b/toolkit/components/extensions/test/mochitest/file_script_bad.js
@@ -0,0 +1,3 @@
+"use strict";
+
+window.failure = true;
diff --git a/toolkit/components/extensions/test/mochitest/file_script_good.js b/toolkit/components/extensions/test/mochitest/file_script_good.js
new file mode 100644
index 0000000000..14e959aa5c
--- /dev/null
+++ b/toolkit/components/extensions/test/mochitest/file_script_good.js
@@ -0,0 +1,12 @@
+"use strict";
+
+window.success = window.success ? window.success + 1 : 1;
+
+{
+  let scripts = document.getElementsByTagName("script");
+  let url = new URL(scripts[scripts.length - 1].src);
+  let flag = url.searchParams.get("q");
+  if (flag) {
+    window.postMessage(flag, "*");
+  }
+}
diff --git a/toolkit/components/extensions/test/mochitest/file_script_redirect.js b/toolkit/components/extensions/test/mochitest/file_script_redirect.js
new file mode 100644
index 0000000000..c425122c71
--- /dev/null
+++ b/toolkit/components/extensions/test/mochitest/file_script_redirect.js
@@ -0,0 +1,3 @@
+"use strict";
+
+window.failure = true;
diff --git a/toolkit/components/extensions/test/mochitest/file_script_xhr.js b/toolkit/components/extensions/test/mochitest/file_script_xhr.js
new file mode 100644
index 0000000000..ad01f74253
--- /dev/null
+++ b/toolkit/components/extensions/test/mochitest/file_script_xhr.js
@@ -0,0 +1,9 @@
+"use strict";
+
+var request = new XMLHttpRequest();
+request.open(
+  "get",
+  "http://mochi.test:8888/tests/toolkit/components/extensions/test/mochitest/xhr_resource",
+  false
+);
+request.send();
diff --git a/toolkit/components/extensions/test/mochitest/file_serviceWorker.html b/toolkit/components/extensions/test/mochitest/file_serviceWorker.html
new file mode 100644
index 0000000000..d2b99769cc
--- /dev/null
+++ b/toolkit/components/extensions/test/mochitest/file_serviceWorker.html
@@ -0,0 +1,16 @@
+<!DOCTYPE html>
+<html lang="en">
+  <head>
+    <meta charset="utf-8">
+    <script>
+      "use strict";
+
+      navigator.serviceWorker.register("serviceWorker.js").then(() => {
+        window.postMessage("serviceWorkerRegistered", "*");
+      });
+    </script>
+  </head>
+  <body>
+    This is a test page.
+  </body>
+<html>
diff --git a/toolkit/components/extensions/test/mochitest/file_simple_iframe_worker.html b/toolkit/components/extensions/test/mochitest/file_simple_iframe_worker.html
new file mode 100644
index 0000000000..2ecc24e648
--- /dev/null
+++ b/toolkit/components/extensions/test/mochitest/file_simple_iframe_worker.html
@@ -0,0 +1,26 @@
+<!DOCTYPE HTML>
+
+<html>
+<head>
+<meta charset="utf-8">
+</head>
+<body>
+
+<script type="application/javascript">
+"use strict";
+
+fetch("file_simple_iframe.txt");
+const worker = new Worker("file_simple_worker.js?iniframe=true");
+worker.onmessage = (msg) => {
+  worker.postMessage("file_simple_iframe_worker.txt");
+}
+
+const sharedworker = new SharedWorker("file_simple_sharedworker.js?iniframe=true");
+sharedworker.port.onmessage = (msg) => {
+  sharedworker.port.postMessage("file_simple_iframe_sharedworker.txt");
+}
+sharedworker.port.start();
+
+</script>
+</body>
+</html>
diff --git a/toolkit/components/extensions/test/mochitest/file_simple_sandboxed_frame.html b/toolkit/components/extensions/test/mochitest/file_simple_sandboxed_frame.html
new file mode 100644
index 0000000000..909a1f9e36
--- /dev/null
+++ b/toolkit/components/extensions/test/mochitest/file_simple_sandboxed_frame.html
@@ -0,0 +1,23 @@
+<!DOCTYPE HTML>
+
+<html>
+<head>
+<meta charset="utf-8">
+</head>
+<body>
+
+<script>
+"use strict";
+
+let req = new XMLHttpRequest();
+req.open("GET", "/xhr_sandboxed");
+req.send();
+
+let sandbox = document.createElement("iframe");
+sandbox.setAttribute("sandbox", "allow-scripts");
+sandbox.setAttribute("src", "file_simple_sandboxed_subframe.html");
+document.documentElement.appendChild(sandbox);
+</script>
+<img src="file_image_great.png"/>
+</body>
+</html>
diff --git a/toolkit/components/extensions/test/mochitest/file_simple_sandboxed_subframe.html b/toolkit/components/extensions/test/mochitest/file_simple_sandboxed_subframe.html
new file mode 100644
index 0000000000..a0a437d0eb
--- /dev/null
+++ b/toolkit/components/extensions/test/mochitest/file_simple_sandboxed_subframe.html
@@ -0,0 +1,10 @@
+<!DOCTYPE HTML>
+
+<html>
+<head>
+<meta charset="utf-8">
+</head>
+<body>
+
+</body>
+</html>
diff --git a/toolkit/components/extensions/test/mochitest/file_simple_sharedworker.js b/toolkit/components/extensions/test/mochitest/file_simple_sharedworker.js
new file mode 100644
index 0000000000..e8776216f1
--- /dev/null
+++ b/toolkit/components/extensions/test/mochitest/file_simple_sharedworker.js
@@ -0,0 +1,11 @@
+"use strict";
+
+self.onconnect = async evt => {
+  const port = evt.ports[0];
+  port.onmessage = async message => {
+    await fetch(message.data);
+    self.close();
+  };
+  port.start();
+  port.postMessage("loaded");
+};
diff --git a/toolkit/components/extensions/test/mochitest/file_simple_webrequest_worker.html b/toolkit/components/extensions/test/mochitest/file_simple_webrequest_worker.html
new file mode 100644
index 0000000000..a90c4509be
--- /dev/null
+++ b/toolkit/components/extensions/test/mochitest/file_simple_webrequest_worker.html
@@ -0,0 +1,28 @@
+<!DOCTYPE HTML>
+
+<html>
+<head>
+<meta charset="utf-8">
+</head>
+<body>
+
+<script type="application/javascript">
+"use strict";
+
+fetch("file_simple_toplevel.txt");
+const worker = new Worker("file_simple_worker.js");
+worker.onmessage = (msg) => {
+  worker.postMessage("file_simple_worker.txt");
+}
+
+const sharedworker = new SharedWorker("file_simple_sharedworker.js");
+sharedworker.port.onmessage = (msg) => {
+  dump(`postMessage to sharedworker\n`);
+  sharedworker.port.postMessage("file_simple_sharedworker.txt");
+}
+sharedworker.port.start();
+
+</script>
+<iframe src="file_simple_iframe_worker.html"></iframe>
+</body>
+</html>
diff --git a/toolkit/components/extensions/test/mochitest/file_simple_worker.js b/toolkit/components/extensions/test/mochitest/file_simple_worker.js
new file mode 100644
index 0000000000..9638a8e9c2
--- /dev/null
+++ b/toolkit/components/extensions/test/mochitest/file_simple_worker.js
@@ -0,0 +1,8 @@
+"use strict";
+
+self.onmessage = async message => {
+  await fetch(message.data);
+  self.close();
+};
+
+self.postMessage("loaded");
diff --git a/toolkit/components/extensions/test/mochitest/file_simple_xhr.html b/toolkit/components/extensions/test/mochitest/file_simple_xhr.html
new file mode 100644
index 0000000000..1b43f804d9
--- /dev/null
+++ b/toolkit/components/extensions/test/mochitest/file_simple_xhr.html
@@ -0,0 +1,19 @@
+<!DOCTYPE HTML>
+
+<html>
+<head>
+<meta charset="utf-8">
+</head>
+<body>
+
+<script>
+"use strict";
+
+let req = new XMLHttpRequest();
+req.open("GET", "https://example.org/example.txt");
+req.send();
+</script>
+<img src="file_image_good.png"/>
+<iframe src="file_simple_xhr_frame.html"/>
+</body>
+</html>
diff --git a/toolkit/components/extensions/test/mochitest/file_simple_xhr_frame.html b/toolkit/components/extensions/test/mochitest/file_simple_xhr_frame.html
new file mode 100644
index 0000000000..7f38247ac0
--- /dev/null
+++ b/toolkit/components/extensions/test/mochitest/file_simple_xhr_frame.html
@@ -0,0 +1,19 @@
+<!DOCTYPE HTML>
+
+<html>
+<head>
+<meta charset="utf-8">
+</head>
+<body>
+
+<script>
+"use strict";
+
+let req = new XMLHttpRequest();
+req.open("GET", "/xhr_resource");
+req.send();
+</script>
+<img src="file_image_bad.png"/>
+<iframe src="file_simple_xhr_frame2.html"/>
+</body>
+</html>
diff --git a/toolkit/components/extensions/test/mochitest/file_simple_xhr_frame2.html b/toolkit/components/extensions/test/mochitest/file_simple_xhr_frame2.html
new file mode 100644
index 0000000000..6174a0b402
--- /dev/null
+++ b/toolkit/components/extensions/test/mochitest/file_simple_xhr_frame2.html
@@ -0,0 +1,23 @@
+<!DOCTYPE HTML>
+
+<html>
+<head>
+<meta charset="utf-8">
+</head>
+<body>
+
+<script>
+"use strict";
+
+let req = new XMLHttpRequest();
+req.open("GET", "/xhr_resource_2");
+req.send();
+
+let sandbox = document.createElement("iframe");
+sandbox.setAttribute("sandbox", "allow-scripts");
+sandbox.setAttribute("src", "file_simple_sandboxed_frame.html");
+document.documentElement.appendChild(sandbox);
+</script>
+<img src="file_image_redirect.png"/>
+</body>
+</html>
diff --git a/toolkit/components/extensions/test/mochitest/file_slowed_document.sjs b/toolkit/components/extensions/test/mochitest/file_slowed_document.sjs
new file mode 100644
index 0000000000..8c42fcc966
--- /dev/null
+++ b/toolkit/components/extensions/test/mochitest/file_slowed_document.sjs
@@ -0,0 +1,49 @@
+/* -*- Mode: indent-tabs-mode: nil; js-indent-level: 2 -*- */
+/* vim: set sts=2 sw=2 et tw=80 ft=javascript: */
+"use strict";
+
+// This script slows the load of an HTML document so that we can reliably test
+// all phases of the load cycle supported by the extension API.
+
+/* eslint-disable no-unused-vars */
+
+const URL = "file_slowed_document.sjs";
+
+const DELAY = 2 * 1000; // Delay two seconds before completing the request.
+
+let nsTimer = Components.Constructor(
+  "@mozilla.org/timer;1",
+  "nsITimer",
+  "initWithCallback"
+);
+
+let timer;
+
+function handleRequest(request, response) {
+  response.processAsync();
+
+  response.setHeader("Content-Type", "text/html", false);
+  response.setHeader("Cache-Control", "no-cache", false);
+  response.write(`<!DOCTYPE html>
+    <html lang="en">
+    <head>
+      <meta charset="UTF-8">
+      <title></title>
+    </head>
+    <body>
+  `);
+
+  // Note: We need to store a reference to the timer to prevent it from being
+  // canceled when it's GCed.
+  timer = new nsTimer(
+    () => {
+      if (request.queryString.includes("with-iframe")) {
+        response.write(`<iframe src="${URL}?r=${Math.random()}"></iframe>`);
+      }
+      response.write(`</body></html>`);
+      response.finish();
+    },
+    DELAY,
+    Ci.nsITimer.TYPE_ONE_SHOT
+  );
+}
diff --git a/toolkit/components/extensions/test/mochitest/file_streamfilter.txt b/toolkit/components/extensions/test/mochitest/file_streamfilter.txt
new file mode 100644
index 0000000000..56cdd85e1d
--- /dev/null
+++ b/toolkit/components/extensions/test/mochitest/file_streamfilter.txt
@@ -0,0 +1 @@
+Middle
diff --git a/toolkit/components/extensions/test/mochitest/file_style_bad.css b/toolkit/components/extensions/test/mochitest/file_style_bad.css
new file mode 100644
index 0000000000..8dbc8dc7a4
--- /dev/null
+++ b/toolkit/components/extensions/test/mochitest/file_style_bad.css
@@ -0,0 +1,3 @@
+#test {
+  color: green !important;
+}
diff --git a/toolkit/components/extensions/test/mochitest/file_style_good.css b/toolkit/components/extensions/test/mochitest/file_style_good.css
new file mode 100644
index 0000000000..46f9774b5f
--- /dev/null
+++ b/toolkit/components/extensions/test/mochitest/file_style_good.css
@@ -0,0 +1,3 @@
+#test {
+  color: red;
+}
diff --git a/toolkit/components/extensions/test/mochitest/file_style_redirect.css b/toolkit/components/extensions/test/mochitest/file_style_redirect.css
new file mode 100644
index 0000000000..8dbc8dc7a4
--- /dev/null
+++ b/toolkit/components/extensions/test/mochitest/file_style_redirect.css
@@ -0,0 +1,3 @@
+#test {
+  color: green !important;
+}
diff --git a/toolkit/components/extensions/test/mochitest/file_tabs_permission_page1.html b/toolkit/components/extensions/test/mochitest/file_tabs_permission_page1.html
new file mode 100644
index 0000000000..63f503ad3c
--- /dev/null
+++ b/toolkit/components/extensions/test/mochitest/file_tabs_permission_page1.html
@@ -0,0 +1,10 @@
+<!DOCTYPE HTML>
+
+<html>
+<head>
+    <title>The Title</title>
+</head>
+<body>
+
+</body>
+</html>
diff --git a/toolkit/components/extensions/test/mochitest/file_tabs_permission_page2.html b/toolkit/components/extensions/test/mochitest/file_tabs_permission_page2.html
new file mode 100644
index 0000000000..87ac7a2f64
--- /dev/null
+++ b/toolkit/components/extensions/test/mochitest/file_tabs_permission_page2.html
@@ -0,0 +1,11 @@
+<!DOCTYPE HTML>
+
+<html>
+<head>
+    <title>Another Title</title>
+    <link href="file_image_great.png" rel="icon" type="image/png" />
+</head>
+<body>
+
+</body>
+</html>
diff --git a/toolkit/components/extensions/test/mochitest/file_third_party.html b/toolkit/components/extensions/test/mochitest/file_third_party.html
new file mode 100644
index 0000000000..fc5a326297
--- /dev/null
+++ b/toolkit/components/extensions/test/mochitest/file_third_party.html
@@ -0,0 +1,21 @@
+<!DOCTYPE HTML>
+
+<html>
+<head>
+<meta charset="utf-8">
+</head>
+<body>
+
+<script>
+
+"use strict"
+
+let url = new URL(location);
+let img = new Image();
+img.src = `http://${url.searchParams.get("domain")}/tests/toolkit/components/extensions/test/mochitest/file_image_bad.png`;
+document.body.appendChild(img);
+
+</script>
+
+</body>
+</html>
diff --git a/toolkit/components/extensions/test/mochitest/file_to_drawWindow.html b/toolkit/components/extensions/test/mochitest/file_to_drawWindow.html
new file mode 100644
index 0000000000..6ebd54d9a3
--- /dev/null
+++ b/toolkit/components/extensions/test/mochitest/file_to_drawWindow.html
@@ -0,0 +1,9 @@
+<!doctype html>
+<html>
+<head>
+  <meta charset="utf-8">
+</head>
+<body style="background: #ff9">
+  &nbsp;
+</body>
+</html>
diff --git a/toolkit/components/extensions/test/mochitest/file_webNavigation_clientRedirect.html b/toolkit/components/extensions/test/mochitest/file_webNavigation_clientRedirect.html
new file mode 100644
index 0000000000..cba3043f71
--- /dev/null
+++ b/toolkit/components/extensions/test/mochitest/file_webNavigation_clientRedirect.html
@@ -0,0 +1,9 @@
+<!DOCTYPE HTML>
+
+<html>
+  <head>
+    <meta http-equiv="refresh" content="1;dummy_page.html">
+  </head>
+  <body>
+  </body>
+</html>
diff --git a/toolkit/components/extensions/test/mochitest/file_webNavigation_clientRedirect_httpHeaders.html b/toolkit/components/extensions/test/mochitest/file_webNavigation_clientRedirect_httpHeaders.html
new file mode 100644
index 0000000000..c5b436979f
--- /dev/null
+++ b/toolkit/components/extensions/test/mochitest/file_webNavigation_clientRedirect_httpHeaders.html
@@ -0,0 +1,8 @@
+<!DOCTYPE HTML>
+
+<html>
+  <head>
+  </head>
+  <body>
+  </body>
+</html>
diff --git a/toolkit/components/extensions/test/mochitest/file_webNavigation_clientRedirect_httpHeaders.html^headers^ b/toolkit/components/extensions/test/mochitest/file_webNavigation_clientRedirect_httpHeaders.html^headers^
new file mode 100644
index 0000000000..574a392a15
--- /dev/null
+++ b/toolkit/components/extensions/test/mochitest/file_webNavigation_clientRedirect_httpHeaders.html^headers^
@@ -0,0 +1 @@
+Refresh: 1;url=dummy_page.html
diff --git a/toolkit/components/extensions/test/mochitest/file_webNavigation_frameClientRedirect.html b/toolkit/components/extensions/test/mochitest/file_webNavigation_frameClientRedirect.html
new file mode 100644
index 0000000000..d360bcbb13
--- /dev/null
+++ b/toolkit/components/extensions/test/mochitest/file_webNavigation_frameClientRedirect.html
@@ -0,0 +1,12 @@
+<!DOCTYPE HTML>
+
+<html>
+<body>
+
+<iframe src="file_webNavigation_clientRedirect.html" width="200" height="200"></iframe>
+
+<form>
+</form>
+
+</body>
+</html>
diff --git a/toolkit/components/extensions/test/mochitest/file_webNavigation_frameRedirect.html b/toolkit/components/extensions/test/mochitest/file_webNavigation_frameRedirect.html
new file mode 100644
index 0000000000..06dbd43741
--- /dev/null
+++ b/toolkit/components/extensions/test/mochitest/file_webNavigation_frameRedirect.html
@@ -0,0 +1,12 @@
+<!DOCTYPE HTML>
+
+<html>
+<body>
+
+<iframe src="redirection.sjs" width="200" height="200"></iframe>
+
+<form>
+</form>
+
+</body>
+</html>
diff --git a/toolkit/components/extensions/test/mochitest/file_webNavigation_manualSubframe.html b/toolkit/components/extensions/test/mochitest/file_webNavigation_manualSubframe.html
new file mode 100644
index 0000000000..307990714b
--- /dev/null
+++ b/toolkit/components/extensions/test/mochitest/file_webNavigation_manualSubframe.html
@@ -0,0 +1,12 @@
+<!DOCTYPE HTML>
+
+<html>
+<body>
+
+<iframe src="file_webNavigation_manualSubframe_page1.html" width="200" height="200"></iframe>
+
+<form>
+</form>
+
+</body>
+</html>
diff --git a/toolkit/components/extensions/test/mochitest/file_webNavigation_manualSubframe_page1.html b/toolkit/components/extensions/test/mochitest/file_webNavigation_manualSubframe_page1.html
new file mode 100644
index 0000000000..55bb7aa6ae
--- /dev/null
+++ b/toolkit/components/extensions/test/mochitest/file_webNavigation_manualSubframe_page1.html
@@ -0,0 +1,8 @@
+<!DOCTYPE html>
+
+<html>
+  <body>
+    <h1>page1</h1>
+    <a href="file_webNavigation_manualSubframe_page2.html">page2</a>
+  </body>
+</html>
diff --git a/toolkit/components/extensions/test/mochitest/file_webNavigation_manualSubframe_page2.html b/toolkit/components/extensions/test/mochitest/file_webNavigation_manualSubframe_page2.html
new file mode 100644
index 0000000000..8f589f8bbd
--- /dev/null
+++ b/toolkit/components/extensions/test/mochitest/file_webNavigation_manualSubframe_page2.html
@@ -0,0 +1,7 @@
+<!DOCTYPE html>
+
+<html>
+  <body>
+    <h1>page2</h1>
+  </body>
+</html>
diff --git a/toolkit/components/extensions/test/mochitest/file_with_about_blank.html b/toolkit/components/extensions/test/mochitest/file_with_about_blank.html
new file mode 100644
index 0000000000..af51c2e52a
--- /dev/null
+++ b/toolkit/components/extensions/test/mochitest/file_with_about_blank.html
@@ -0,0 +1,10 @@
+<!doctype html>
+<html>
+<head>
+  <meta charset="utf-8">
+</head>
+<body>
+  <iframe id="a_b" src="about:blank"></iframe>
+  <iframe srcdoc="galactica actual" src="adama"></iframe>
+</body>
+</html>
diff --git a/toolkit/components/extensions/test/mochitest/file_with_images.html b/toolkit/components/extensions/test/mochitest/file_with_images.html
new file mode 100644
index 0000000000..6a3c090be2
--- /dev/null
+++ b/toolkit/components/extensions/test/mochitest/file_with_images.html
@@ -0,0 +1,10 @@
+<!doctype html>
+<html>
+<head>
+  <meta charset="utf-8">
+</head>
+<body>
+  <img src="https://example.com/chrome/toolkit/components/extensions/test/mochitest/file_image_good.png">
+  <img src="http://mochi.test:8888/chrome/toolkit/components/extensions/test/mochitest/file_image_great.png">
+</body>
+</html>
diff --git a/toolkit/components/extensions/test/mochitest/file_with_subframes_and_embed.html b/toolkit/components/extensions/test/mochitest/file_with_subframes_and_embed.html
new file mode 100644
index 0000000000..348c51f16c
--- /dev/null
+++ b/toolkit/components/extensions/test/mochitest/file_with_subframes_and_embed.html
@@ -0,0 +1,21 @@
+<!DOCTYPE HTML>
+<meta charset="utf-8">
+
+Load a bunch of iframes with subframes.
+<p>
+<iframe src="file_contains_iframe.html"></iframe>
+<iframe src="file_WebNavigation_page1.html"></iframe>
+<iframe src="file_with_xorigin_frame.html"></iframe>
+
+<p>
+Load an embed frame.
+<p>
+<embed type="text/html" src="file_sample.html"></embed>
+
+<p>
+And an object.
+<p>
+<object type="text/html" data="file_contains_img.html"></embed>
+
+<p>
+Done.
diff --git a/toolkit/components/extensions/test/mochitest/file_with_xorigin_frame.html b/toolkit/components/extensions/test/mochitest/file_with_xorigin_frame.html
new file mode 100644
index 0000000000..25c60df078
--- /dev/null
+++ b/toolkit/components/extensions/test/mochitest/file_with_xorigin_frame.html
@@ -0,0 +1,6 @@
+<!DOCTYPE HTML>
+<meta charset="utf-8">
+
+<img src="file_image_great.png"/>
+Load a cross-origin iframe from example.net <p>
+<iframe src="https://example.net/tests/toolkit/components/extensions/test/mochitest/file_sample.html"></iframe>
diff --git a/toolkit/components/extensions/test/mochitest/head.js b/toolkit/components/extensions/test/mochitest/head.js
new file mode 100644
index 0000000000..ad8fb2052f
--- /dev/null
+++ b/toolkit/components/extensions/test/mochitest/head.js
@@ -0,0 +1,117 @@
+"use strict";
+
+/* exported AppConstants, Assert, AppTestDelegate */
+
+var { AppConstants } = SpecialPowers.ChromeUtils.importESModule(
+  "resource://gre/modules/AppConstants.sys.mjs"
+);
+var { AppTestDelegate } = SpecialPowers.ChromeUtils.importESModule(
+  "resource://specialpowers/AppTestDelegate.sys.mjs"
+);
+
+{
+  let chromeScript = SpecialPowers.loadChromeScript(
+    SimpleTest.getTestFileURL("chrome_cleanup_script.js")
+  );
+
+  SimpleTest.registerCleanupFunction(async () => {
+    await new Promise(resolve => setTimeout(resolve, 0));
+
+    chromeScript.sendAsyncMessage("check-cleanup");
+
+    let results = await chromeScript.promiseOneMessage("cleanup-results");
+    chromeScript.destroy();
+
+    if (results.extraWindows.length || results.extraTabs.length) {
+      ok(
+        false,
+        `Test left extra windows or tabs: ${JSON.stringify(results)}\n`
+      );
+    }
+  });
+}
+
+let Assert = {
+  // Cut-down version based on Assert.sys.mjs. Only supports regexp and objects as
+  // the expected variables.
+  rejects(promise, expected, msg) {
+    return promise.then(
+      () => {
+        ok(false, msg);
+      },
+      actual => {
+        let matched = false;
+        if (Object.prototype.toString.call(expected) == "[object RegExp]") {
+          if (expected.test(actual)) {
+            matched = true;
+          }
+        } else if (actual instanceof expected) {
+          matched = true;
+        }
+
+        if (matched) {
+          ok(true, msg);
+        } else {
+          ok(false, `Unexpected exception for "${msg}": ${actual}`);
+        }
+      }
+    );
+  },
+};
+
+/* exported waitForLoad */
+
+function waitForLoad(win) {
+  return new Promise(resolve => {
+    win.addEventListener(
+      "load",
+      function () {
+        resolve();
+      },
+      { capture: true, once: true }
+    );
+  });
+}
+
+/* exported loadChromeScript */
+function loadChromeScript(fn) {
+  let wrapper = `
+(${fn.toString()})();`;
+
+  return SpecialPowers.loadChromeScript(new Function(wrapper));
+}
+
+/* exported consoleMonitor */
+let consoleMonitor = {
+  start(messages) {
+    this.chromeScript = SpecialPowers.loadChromeScript(
+      SimpleTest.getTestFileURL("mochitest_console.js")
+    );
+    this.chromeScript.sendAsyncMessage("consoleStart", messages);
+  },
+
+  async finished() {
+    let done = this.chromeScript.promiseOneMessage("consoleDone").then(done => {
+      this.chromeScript.destroy();
+      return done;
+    });
+    this.chromeScript.sendAsyncMessage("waitForConsole");
+    let test = await done;
+    ok(test.ok, test.message);
+  },
+};
+/* exported waitForState */
+
+function waitForState(sw, state) {
+  return new Promise(resolve => {
+    if (sw.state === state) {
+      return resolve();
+    }
+    sw.addEventListener("statechange", function onStateChange() {
+      if (sw.state === state) {
+        sw.removeEventListener("statechange", onStateChange);
+        resolve();
+      }
+    });
+  });
+}
diff --git a/toolkit/components/extensions/test/mochitest/head_cookies.js b/toolkit/components/extensions/test/mochitest/head_cookies.js
new file mode 100644
index 0000000000..610c800c94
--- /dev/null
+++ b/toolkit/components/extensions/test/mochitest/head_cookies.js
@@ -0,0 +1,287 @@
+/* -*- Mode: indent-tabs-mode: nil; js-indent-level: 2 -*- */
+/* vim: set sts=2 sw=2 et tw=80: */
+"use strict";
+
+/* exported testCookies */
+/* import-globals-from head.js */
+
+async function testCookies(options) {
+  // Changing the options object is a bit of a hack, but it allows us to easily
+  // pass an expiration date to the background script.
+  options.expiry = Date.now() / 1000 + 3600;
+
+  async function background(backgroundOptions) {
+    // Ask the parent scope to change some cookies we may or may not have
+    // permission for.
+    let awaitChanges = new Promise(resolve => {
+      browser.test.onMessage.addListener(msg => {
+        browser.test.assertEq("cookies-changed", msg, "browser.test.onMessage");
+        resolve();
+      });
+    });
+
+    let changed = [];
+    browser.cookies.onChanged.addListener(event => {
+      changed.push(`${event.cookie.name}:${event.cause}`);
+    });
+    browser.test.sendMessage("change-cookies");
+
+    // Try to access some cookies in various ways.
+    let { url, domain, secure } = backgroundOptions;
+
+    let failures = 0;
+    let tallyFailure = error => {
+      failures++;
+    };
+
+    try {
+      await awaitChanges;
+
+      let cookie = await browser.cookies.get({ url, name: "foo" });
+      browser.test.assertEq(
+        backgroundOptions.shouldPass,
+        cookie != null,
+        "should pass == get cookie"
+      );
+
+      let cookies = await browser.cookies.getAll({ domain });
+      if (backgroundOptions.shouldPass) {
+        browser.test.assertEq(2, cookies.length, "expected number of cookies");
+      } else {
+        browser.test.assertEq(0, cookies.length, "expected number of cookies");
+      }
+
+      await Promise.all([
+        browser.cookies
+          .set({
+            url,
+            domain,
+            secure,
+            name: "foo",
+            value: "baz",
+            expirationDate: backgroundOptions.expiry,
+          })
+          .catch(tallyFailure),
+        browser.cookies
+          .set({
+            url,
+            domain,
+            secure,
+            name: "bar",
+            value: "quux",
+            expirationDate: backgroundOptions.expiry,
+          })
+          .catch(tallyFailure),
+        browser.cookies.remove({ url, name: "deleted" }),
+      ]);
+
+      if (backgroundOptions.shouldPass) {
+        // The order of eviction events isn't guaranteed, so just check that
+        // it's there somewhere.
+        let evicted = changed.indexOf("evicted:evicted");
+        if (evicted < 0) {
+          browser.test.fail("got no eviction event");
+        } else {
+          browser.test.succeed("got eviction event");
+          changed.splice(evicted, 1);
+        }
+
+        browser.test.assertEq(
+          "x:explicit,x:overwrite,x:explicit,x:explicit,foo:overwrite,foo:explicit,bar:explicit,deleted:explicit",
+          changed.join(","),
+          "expected changes"
+        );
+      } else {
+        browser.test.assertEq("", changed.join(","), "expected no changes");
+      }
+
+      if (!(backgroundOptions.shouldPass || backgroundOptions.shouldWrite)) {
+        browser.test.assertEq(2, failures, "Expected failures");
+      } else {
+        browser.test.assertEq(0, failures, "Expected no failures");
+      }
+
+      browser.test.notifyPass("cookie-permissions");
+    } catch (error) {
+      browser.test.fail(`Error: ${error} :: ${error.stack}`);
+      browser.test.notifyFail("cookie-permissions");
+    }
+  }
+
+  let extension = ExtensionTestUtils.loadExtension({
+    manifest: {
+      permissions: options.permissions,
+    },
+
+    background: `(${background})(${JSON.stringify(options)})`,
+  });
+
+  let stepOne = loadChromeScript(() => {
+    const { addMessageListener, sendAsyncMessage } = this;
+    addMessageListener("options", options => {
+      let domain = options.domain.replace(/^\.?/, ".");
+      // This will be evicted after we add a fourth cookie.
+      Services.cookies.add(
+        domain,
+        "/",
+        "evicted",
+        "bar",
+        options.secure,
+        false,
+        false,
+        options.expiry,
+        {},
+        Ci.nsICookie.SAMESITE_NONE,
+        options.url.startsWith("https")
+          ? Ci.nsICookie.SCHEME_HTTPS
+          : Ci.nsICookie.SCHEME_HTTP
+      );
+      // This will be modified by the background script.
+      Services.cookies.add(
+        domain,
+        "/",
+        "foo",
+        "bar",
+        options.secure,
+        false,
+        false,
+        options.expiry,
+        {},
+        Ci.nsICookie.SAMESITE_NONE,
+        options.url.startsWith("https")
+          ? Ci.nsICookie.SCHEME_HTTPS
+          : Ci.nsICookie.SCHEME_HTTP
+      );
+      // This will be deleted by the background script.
+      Services.cookies.add(
+        domain,
+        "/",
+        "deleted",
+        "bar",
+        options.secure,
+        false,
+        false,
+        options.expiry,
+        {},
+        Ci.nsICookie.SAMESITE_NONE,
+        options.url.startsWith("https")
+          ? Ci.nsICookie.SCHEME_HTTPS
+          : Ci.nsICookie.SCHEME_HTTP
+      );
+      sendAsyncMessage("done");
+    });
+  });
+  stepOne.sendAsyncMessage("options", options);
+  await stepOne.promiseOneMessage("done");
+  stepOne.destroy();
+
+  await extension.startup();
+
+  await extension.awaitMessage("change-cookies");
+
+  let stepTwo = loadChromeScript(() => {
+    const { addMessageListener, sendAsyncMessage } = this;
+    addMessageListener("options", options => {
+      let domain = options.domain.replace(/^\.?/, ".");
+
+      Services.cookies.add(
+        domain,
+        "/",
+        "x",
+        "y",
+        options.secure,
+        false,
+        false,
+        options.expiry,
+        {},
+        Ci.nsICookie.SAMESITE_NONE,
+        options.url.startsWith("https")
+          ? Ci.nsICookie.SCHEME_HTTPS
+          : Ci.nsICookie.SCHEME_HTTP
+      );
+      Services.cookies.add(
+        domain,
+        "/",
+        "x",
+        "z",
+        options.secure,
+        false,
+        false,
+        options.expiry,
+        {},
+        Ci.nsICookie.SAMESITE_NONE,
+        options.url.startsWith("https")
+          ? Ci.nsICookie.SCHEME_HTTPS
+          : Ci.nsICookie.SCHEME_HTTP
+      );
+      Services.cookies.remove(domain, "x", "/", {});
+      sendAsyncMessage("done");
+    });
+  });
+  stepTwo.sendAsyncMessage("options", options);
+  await stepTwo.promiseOneMessage("done");
+  stepTwo.destroy();
+
+  extension.sendMessage("cookies-changed");
+
+  await extension.awaitFinish("cookie-permissions");
+  await extension.unload();
+
+  let stepThree = loadChromeScript(() => {
+    const { addMessageListener, sendAsyncMessage, assert } = this;
+    let cookieSvc = Services.cookies;
+
+    function getCookies(host) {
+      let cookies = [];
+      for (let cookie of cookieSvc.getCookiesFromHost(host, {})) {
+        cookies.push(cookie);
+      }
+      return cookies.sort((a, b) => a.name.localeCompare(b.name));
+    }
+
+    addMessageListener("options", options => {
+      let cookies = getCookies(options.domain);
+
+      if (options.shouldPass) {
+        assert.equal(cookies.length, 2, "expected two cookies for host");
+
+        assert.equal(cookies[0].name, "bar", "correct cookie name");
+        assert.equal(cookies[0].value, "quux", "correct cookie value");
+
+        assert.equal(cookies[1].name, "foo", "correct cookie name");
+        assert.equal(cookies[1].value, "baz", "correct cookie value");
+      } else if (options.shouldWrite) {
+        // Note: |shouldWrite| applies only when |shouldPass| is false.
+        // This is necessary because, unfortunately, websites (and therefore web
+        // extensions) are allowed to write some cookies which they're not allowed
+        // to read.
+        assert.equal(cookies.length, 3, "expected three cookies for host");
+
+        assert.equal(cookies[0].name, "bar", "correct cookie name");
+        assert.equal(cookies[0].value, "quux", "correct cookie value");
+
+        assert.equal(cookies[1].name, "deleted", "correct cookie name");
+
+        assert.equal(cookies[2].name, "foo", "correct cookie name");
+        assert.equal(cookies[2].value, "baz", "correct cookie value");
+      } else {
+        assert.equal(cookies.length, 2, "expected two cookies for host");
+
+        assert.equal(cookies[0].name, "deleted", "correct second cookie name");
+
+        assert.equal(cookies[1].name, "foo", "correct cookie name");
+        assert.equal(cookies[1].value, "bar", "correct cookie value");
+      }
+
+      for (let cookie of cookies) {
+        cookieSvc.remove(cookie.host, cookie.name, "/", {});
+      }
+      // Make sure we don't silently poison subsequent tests if something goes wrong.
+      assert.equal(getCookies(options.domain).length, 0, "cookies cleared");
+      sendAsyncMessage("done");
+    });
+  });
+  stepThree.sendAsyncMessage("options", options);
+  await stepThree.promiseOneMessage("done");
+  stepThree.destroy();
+}
diff --git a/toolkit/components/extensions/test/mochitest/head_notifications.js b/toolkit/components/extensions/test/mochitest/head_notifications.js
new file mode 100644
index 0000000000..bba3f59d49
--- /dev/null
+++ b/toolkit/components/extensions/test/mochitest/head_notifications.js
@@ -0,0 +1,171 @@
+"use strict";
+
+/* exported MockAlertsService */
+
+function mockServicesChromeScript() {
+  /* eslint-env mozilla/chrome-script */
+
+  const MOCK_ALERTS_CID = Components.ID(
+    "{48068bc2-40ab-4904-8afd-4cdfb3a385f3}"
+  );
+  const ALERTS_SERVICE_CONTRACT_ID = "@mozilla.org/alerts-service;1";
+
+  const { setTimeout } = ChromeUtils.importESModule(
+    "resource://gre/modules/Timer.sys.mjs"
+  );
+  const registrar = Components.manager.QueryInterface(Ci.nsIComponentRegistrar);
+
+  let activeNotifications = Object.create(null);
+
+  const mockAlertsService = {
+    showPersistentNotification: function (
+      persistentData,
+      alert,
+      alertListener
+    ) {
+      this.showAlert(alert, alertListener);
+    },
+
+    showAlert: function (alert, listener) {
+      activeNotifications[alert.name] = {
+        listener: listener,
+        cookie: alert.cookie,
+        title: alert.title,
+      };
+
+      // fake async alert show event
+      if (listener) {
+        setTimeout(function () {
+          listener.observe(null, "alertshow", alert.cookie);
+        }, 100);
+      }
+    },
+
+    showAlertNotification: function (
+      imageUrl,
+      title,
+      text,
+      textClickable,
+      cookie,
+      alertListener,
+      name
+    ) {
+      this.showAlert(
+        {
+          name: name,
+          cookie: cookie,
+          title: title,
+        },
+        alertListener
+      );
+    },
+
+    closeAlert: function (name) {
+      let alertNotification = activeNotifications[name];
+      if (alertNotification) {
+        if (alertNotification.listener) {
+          alertNotification.listener.observe(
+            null,
+            "alertfinished",
+            alertNotification.cookie
+          );
+        }
+        delete activeNotifications[name];
+      }
+    },
+
+    QueryInterface: ChromeUtils.generateQI(["nsIAlertsService"]),
+
+    createInstance: function (iid) {
+      return this.QueryInterface(iid);
+    },
+  };
+
+  registrar.registerFactory(
+    MOCK_ALERTS_CID,
+    "alerts service",
+    ALERTS_SERVICE_CONTRACT_ID,
+    mockAlertsService
+  );
+
+  function clickNotifications(doClose) {
+    // Until we need to close a specific notification, just click them all.
+    for (let [name, notification] of Object.entries(activeNotifications)) {
+      let { listener, cookie } = notification;
+      listener.observe(null, "alertclickcallback", cookie);
+      if (doClose) {
+        mockAlertsService.closeAlert(name);
+      }
+    }
+  }
+
+  function closeAllNotifications() {
+    for (let alertName of Object.keys(activeNotifications)) {
+      mockAlertsService.closeAlert(alertName);
+    }
+  }
+
+  const { addMessageListener, sendAsyncMessage } = this;
+
+  addMessageListener("mock-alert-service:unregister", () => {
+    closeAllNotifications();
+    activeNotifications = null;
+    registrar.unregisterFactory(MOCK_ALERTS_CID, mockAlertsService);
+    sendAsyncMessage("mock-alert-service:unregistered");
+  });
+
+  addMessageListener(
+    "mock-alert-service:click-notifications",
+    clickNotifications
+  );
+
+  addMessageListener(
+    "mock-alert-service:close-notifications",
+    closeAllNotifications
+  );
+
+  sendAsyncMessage("mock-alert-service:registered");
+}
+
+const MockAlertsService = {
+  async register() {
+    if (this._chromeScript) {
+      throw new Error("MockAlertsService already registered");
+    }
+    this._chromeScript = SpecialPowers.loadChromeScript(
+      mockServicesChromeScript
+    );
+    await this._chromeScript.promiseOneMessage("mock-alert-service:registered");
+  },
+  async unregister() {
+    if (!this._chromeScript) {
+      throw new Error("MockAlertsService not registered");
+    }
+    this._chromeScript.sendAsyncMessage("mock-alert-service:unregister");
+    return this._chromeScript
+      .promiseOneMessage("mock-alert-service:unregistered")
+      .then(() => {
+        this._chromeScript.destroy();
+        this._chromeScript = null;
+      });
+  },
+  async clickNotifications() {
+    // Most implementations of the nsIAlertsService automatically close upon click.
+    await this._chromeScript.sendAsyncMessage(
+      "mock-alert-service:click-notifications",
+      true
+    );
+  },
+  async clickNotificationsWithoutClose() {
+    // The implementation on macOS does not automatically close the notification.
+    await this._chromeScript.sendAsyncMessage(
+      "mock-alert-service:click-notifications",
+      false
+    );
+  },
+  async closeNotifications() {
+    await this._chromeScript.sendAsyncMessage(
+      "mock-alert-service:close-notifications"
+    );
+  },
+};
diff --git a/toolkit/components/extensions/test/mochitest/head_unlimitedStorage.js b/toolkit/components/extensions/test/mochitest/head_unlimitedStorage.js
new file mode 100644
index 0000000000..dfec90b3e0
--- /dev/null
+++ b/toolkit/components/extensions/test/mochitest/head_unlimitedStorage.js
@@ -0,0 +1,45 @@
+/* -*- Mode: indent-tabs-mode: nil; js-indent-level: 2 -*- */
+/* vim: set sts=2 sw=2 et tw=80: */
+"use strict";
+
+/* exported checkSitePermissions */
+
+const { Services } = SpecialPowers;
+const { NetUtil } = SpecialPowers.ChromeUtils.import(
+  "resource://gre/modules/NetUtil.jsm"
+);
+
+function checkSitePermissions(uuid, expectedPermAction, assertMessage) {
+  if (!uuid) {
+    throw new Error(
+      "checkSitePermissions should not be called with an undefined uuid"
+    );
+  }
+
+  const baseURI = NetUtil.newURI(`moz-extension://${uuid}/`);
+  const principal = Services.scriptSecurityManager.createContentPrincipal(
+    baseURI,
+    {}
+  );
+
+  const sitePermissions = {
+    webextUnlimitedStorage: Services.perms.testPermissionFromPrincipal(
+      principal,
+      "WebExtensions-unlimitedStorage"
+    ),
+    persistentStorage: Services.perms.testPermissionFromPrincipal(
+      principal,
+      "persistent-storage"
+    ),
+  };
+
+  for (const [sitePermissionName, actualPermAction] of Object.entries(
+    sitePermissions
+  )) {
+    is(
+      actualPermAction,
+      expectedPermAction,
+      `The extension "${sitePermissionName}" SitePermission ${assertMessage} as expected`
+    );
+  }
+}
diff --git a/toolkit/components/extensions/test/mochitest/head_webrequest.js b/toolkit/components/extensions/test/mochitest/head_webrequest.js
new file mode 100644
index 0000000000..9e6b5cc910
--- /dev/null
+++ b/toolkit/components/extensions/test/mochitest/head_webrequest.js
@@ -0,0 +1,481 @@
+"use strict";
+
+let commonEvents = {
+  onBeforeRequest: [{ urls: ["<all_urls>"] }, ["blocking"]],
+  onBeforeSendHeaders: [
+    { urls: ["<all_urls>"] },
+    ["blocking", "requestHeaders"],
+  ],
+  onSendHeaders: [{ urls: ["<all_urls>"] }, ["requestHeaders"]],
+  onBeforeRedirect: [{ urls: ["<all_urls>"] }],
+  onHeadersReceived: [
+    { urls: ["<all_urls>"] },
+    ["blocking", "responseHeaders"],
+  ],
+  // Auth tests will need to set their own events object
+  // "onAuthRequired":      [{urls: ["<all_urls>"]}, ["blocking", "responseHeaders"]],
+  onResponseStarted: [{ urls: ["<all_urls>"] }],
+  onCompleted: [{ urls: ["<all_urls>"] }, ["responseHeaders"]],
+  onErrorOccurred: [{ urls: ["<all_urls>"] }],
+};
+
+function background(events) {
+  const IP_PATTERN = /^\d{1,3}\.\d{1,3}\.\d{1,3}\.\d{1,3}$/;
+
+  let expect;
+  let ignore;
+  let defaultOrigin;
+  let watchAuth = Object.keys(events).includes("onAuthRequired");
+  let expectedIp = null;
+
+  browser.test.onMessage.addListener((msg, expected) => {
+    if (msg !== "set-expected") {
+      return;
+    }
+    expect = expected.expect;
+    defaultOrigin = expected.origin;
+    ignore = expected.ignore;
+    let promises = [];
+    // Initialize some stuff we'll need in the tests.
+    for (let entry of Object.values(expect)) {
+      // a place for the test infrastructure to store some state.
+      entry.test = {};
+      // Each entry in expected gets a Promise that will be resolved in the
+      // last event for that entry.  This will either be onCompleted, or the
+      // last entry if an events list was provided.
+      promises.push(
+        new Promise(resolve => {
+          entry.test.resolve = resolve;
+        })
+      );
+      // If events was left undefined, we're expecting all normal events we're
+      // listening for, exclude onBeforeRedirect and onErrorOccurred
+      if (entry.events === undefined) {
+        entry.events = Object.keys(events).filter(
+          name => name != "onErrorOccurred" && name != "onBeforeRedirect"
+        );
+      }
+      if (entry.optional_events === undefined) {
+        entry.optional_events = [];
+      }
+    }
+    // When every expected entry has finished our test is done.
+    Promise.all(promises).then(() => {
+      browser.test.sendMessage("done");
+    });
+    browser.test.sendMessage("continue");
+  });
+
+  // Retrieve the per-file/test expected values.
+  function getExpected(details) {
+    let url = new URL(details.url);
+    let filename = url.pathname.split("/").pop();
+    if (ignore && ignore.includes(filename)) {
+      return;
+    }
+    let expected = expect[filename];
+    if (!expected) {
+      browser.test.fail(`unexpected request ${filename}`);
+      return;
+    }
+    // Save filename for redirect verification.
+    expected.test.filename = filename;
+    return expected;
+  }
+
+  // Process any test header modifications that can happen in request or response phases.
+  // If a test includes headers, it needs a complete header object, no undefined
+  // objects even if empty:
+  // request: {
+  //   add: {"HeaderName": "value",},
+  //   modify: {"HeaderName": "value",},
+  //   remove: ["HeaderName",],
+  // },
+  // response: {
+  //   add: {"HeaderName": "value",},
+  //   modify: {"HeaderName": "value",},
+  //   remove: ["HeaderName",],
+  // },
+  function processHeaders(phase, expected, details) {
+    // This should only happen once per phase [request|response].
+    browser.test.assertFalse(
+      !!expected.test[phase],
+      `First processing of headers for ${phase}`
+    );
+    expected.test[phase] = true;
+
+    let headers = details[`${phase}Headers`];
+    browser.test.assertTrue(
+      Array.isArray(headers),
+      `${phase}Headers array present`
+    );
+
+    let { add, modify, remove } = expected.headers[phase];
+
+    for (let name in add) {
+      browser.test.assertTrue(
+        !headers.find(h => h.name === name),
+        `header ${name} to be added not present yet in ${phase}Headers`
+      );
+      let header = { name: name };
+      if (name.endsWith("-binary")) {
+        header.binaryValue = Array.from(add[name], c => c.charCodeAt(0));
+      } else {
+        header.value = add[name];
+      }
+      headers.push(header);
+    }
+
+    let modifiedAny = false;
+    for (let header of headers) {
+      if (header.name.toLowerCase() in modify) {
+        header.value = modify[header.name.toLowerCase()];
+        modifiedAny = true;
+      }
+    }
+    browser.test.assertTrue(
+      modifiedAny,
+      `at least one ${phase}Headers element to modify`
+    );
+
+    let deletedAny = false;
+    for (let j = headers.length; j-- > 0; ) {
+      if (remove.includes(headers[j].name.toLowerCase())) {
+        headers.splice(j, 1);
+        deletedAny = true;
+      }
+    }
+    browser.test.assertTrue(
+      deletedAny,
+      `at least one ${phase}Headers element to delete`
+    );
+
+    return headers;
+  }
+
+  // phase is request or response.
+  function checkHeaders(phase, expected, details) {
+    if (!/^https?:/.test(details.url)) {
+      return;
+    }
+
+    let headers = details[`${phase}Headers`];
+    browser.test.assertTrue(
+      Array.isArray(headers),
+      `valid ${phase}Headers array`
+    );
+
+    let { add, modify, remove } = expected.headers[phase];
+    for (let name in add) {
+      let value = headers.find(
+        h => h.name.toLowerCase() === name.toLowerCase()
+      ).value;
+      browser.test.assertEq(
+        value,
+        add[name],
+        `header ${name} correctly injected in ${phase}Headers`
+      );
+    }
+
+    for (let name in modify) {
+      let value = headers.find(
+        h => h.name.toLowerCase() === name.toLowerCase()
+      ).value;
+      browser.test.assertEq(
+        value,
+        modify[name],
+        `header ${name} matches modified value`
+      );
+    }
+
+    for (let name of remove) {
+      let found = headers.find(
+        h => h.name.toLowerCase() === name.toLowerCase()
+      );
+      browser.test.assertFalse(
+        !!found,
+        `deleted header ${name} still found in ${phase}Headers`
+      );
+    }
+  }
+
+  let listeners = {
+    onBeforeRequest(expected, details, result) {
+      // Save some values to test request consistency in later events.
+      browser.test.assertTrue(
+        details.tabId !== undefined,
+        `tabId ${details.tabId}`
+      );
+      browser.test.assertTrue(
+        details.requestId !== undefined,
+        `requestId ${details.requestId}`
+      );
+      // Validate requestId if it's already set, this happens with redirects.
+      if (expected.test.requestId !== undefined) {
+        browser.test.assertEq(
+          "string",
+          typeof expected.test.requestId,
+          `requestid ${expected.test.requestId} is string`
+        );
+        browser.test.assertEq(
+          "string",
+          typeof details.requestId,
+          `requestid ${details.requestId} is string`
+        );
+        browser.test.assertEq(
+          "number",
+          typeof parseInt(details.requestId, 10),
+          "parsed requestid is number"
+        );
+        browser.test.assertEq(
+          expected.test.requestId,
+          details.requestId,
+          "redirects will keep the same requestId"
+        );
+      } else {
+        // Save any values we want to validate in later events.
+        expected.test.requestId = details.requestId;
+        expected.test.tabId = details.tabId;
+      }
+      // Tests we don't need to do every event.
+      browser.test.assertTrue(
+        details.type.toUpperCase() in browser.webRequest.ResourceType,
+        `valid resource type ${details.type}`
+      );
+      if (details.type == "main_frame") {
+        browser.test.assertEq(
+          0,
+          details.frameId,
+          "frameId is zero when type is main_frame, see bug 1329299"
+        );
+      }
+    },
+    onBeforeSendHeaders(expected, details, result) {
+      if (expected.headers && expected.headers.request) {
+        result.requestHeaders = processHeaders("request", expected, details);
+      }
+      if (expected.redirect) {
+        browser.test.log(`${name} redirect request`);
+        result.redirectUrl = details.url.replace(
+          expected.test.filename,
+          expected.redirect
+        );
+      }
+    },
+    onBeforeRedirect() {},
+    onSendHeaders(expected, details, result) {
+      if (expected.headers && expected.headers.request) {
+        checkHeaders("request", expected, details);
+      }
+    },
+    onResponseStarted() {},
+    onHeadersReceived(expected, details, result) {
+      let expectedStatus = expected.status || 200;
+      // If authentication is being requested we don't fail on the status code.
+      if (watchAuth && [401, 407].includes(details.statusCode)) {
+        expectedStatus = details.statusCode;
+      }
+      browser.test.assertEq(
+        expectedStatus,
+        details.statusCode,
+        `expected HTTP status received for ${details.url} ${details.statusLine}`
+      );
+      if (expected.headers && expected.headers.response) {
+        result.responseHeaders = processHeaders("response", expected, details);
+      }
+    },
+    onAuthRequired(expected, details, result) {
+      result.authCredentials = expected.authInfo;
+    },
+    onCompleted(expected, details, result) {
+      // If we have already completed a GET request for this url,
+      // and it was found, we expect for the response to come fromCache.
+      // expected.cached may be undefined, force boolean.
+      if (typeof expected.cached === "boolean") {
+        let expectCached =
+          expected.cached &&
+          details.method === "GET" &&
+          details.statusCode != 404;
+        browser.test.assertEq(
+          expectCached,
+          details.fromCache,
+          "fromCache is correct"
+        );
+      }
+      // We can only tell IPs for non-cached HTTP requests.
+      if (!details.fromCache && /^https?:/.test(details.url)) {
+        browser.test.assertTrue(
+          IP_PATTERN.test(details.ip),
+          `IP for ${details.url} looks IP-ish: ${details.ip}`
+        );
+
+        // We can't easily predict the IP ahead of time, so just make
+        // sure they're all consistent.
+        expectedIp = expectedIp || details.ip;
+        browser.test.assertEq(
+          expectedIp,
+          details.ip,
+          `correct ip for ${details.url}`
+        );
+      }
+      if (expected.headers && expected.headers.response) {
+        checkHeaders("response", expected, details);
+      }
+    },
+    onErrorOccurred(expected, details, result) {
+      if (expected.error) {
+        if (Array.isArray(expected.error)) {
+          browser.test.assertTrue(
+            expected.error.includes(details.error),
+            "expected error message received in onErrorOccurred"
+          );
+        } else {
+          browser.test.assertEq(
+            expected.error,
+            details.error,
+            "expected error message received in onErrorOccurred"
+          );
+        }
+      }
+    },
+  };
+
+  function getListener(name) {
+    return details => {
+      let result = {};
+      browser.test.log(`${name} ${details.requestId} ${details.url}`);
+      let expected = getExpected(details);
+      if (!expected) {
+        return result;
+      }
+      let expectedEvent = expected.events[0] == name;
+      if (expectedEvent) {
+        expected.events.shift();
+      } else {
+        // e10s vs. non-e10s errors can end with either onCompleted or onErrorOccurred
+        expectedEvent = expected.optional_events.includes(name);
+      }
+      browser.test.assertTrue(expectedEvent, `received ${name}`);
+      browser.test.assertEq(
+        expected.type,
+        details.type,
+        "resource type is correct"
+      );
+      browser.test.assertEq(
+        expected.origin || defaultOrigin,
+        details.originUrl,
+        "origin is correct"
+      );
+
+      if (name != "onBeforeRequest") {
+        // On events after onBeforeRequest, check the previous values.
+        browser.test.assertEq(
+          expected.test.requestId,
+          details.requestId,
+          "correct requestId"
+        );
+        browser.test.assertEq(
+          expected.test.tabId,
+          details.tabId,
+          "correct tabId"
+        );
+      }
+      try {
+        listeners[name](expected, details, result);
+      } catch (e) {
+        browser.test.fail(`unexpected webrequest failure ${name} ${e}`);
+      }
+
+      if (expected.cancel && expected.cancel == name) {
+        browser.test.log(`${name} cancel request`);
+        browser.test.sendMessage("cancelled");
+        result.cancel = true;
+      }
+      // If we've used up all the events for this test, resolve the promise.
+      // If something wrong happens and more events come through, there will be
+      // failures.
+      if (expected.events.length <= 0) {
+        expected.test.resolve();
+      }
+      return result;
+    };
+  }
+
+  for (let [name, args] of Object.entries(events)) {
+    browser.test.log(`adding listener for ${name}`);
+    try {
+      browser.webRequest[name].addListener(getListener(name), ...args);
+    } catch (e) {
+      browser.test.assertTrue(
+        /\brequestBody\b/.test(e.message),
+        "Request body is unsupported"
+      );
+
+      // RequestBody is disabled in release builds.
+      if (!/\brequestBody\b/.test(e.message)) {
+        throw e;
+      }
+
+      args.splice(args.indexOf("requestBody"), 1);
+      browser.webRequest[name].addListener(getListener(name), ...args);
+    }
+  }
+}
+
+/* exported makeExtension */
+
+function makeExtension(events = commonEvents) {
+  return ExtensionTestUtils.loadExtension({
+    manifest: {
+      permissions: ["webRequest", "webRequestBlocking", "<all_urls>"],
+    },
+    background: `(${background})(${JSON.stringify(events)})`,
+  });
+}
+
+/* exported addStylesheet */
+
+function addStylesheet(file) {
+  let link = document.createElement("link");
+  link.setAttribute("rel", "stylesheet");
+  link.setAttribute("href", file);
+  document.body.appendChild(link);
+}
+
+/* exported addLink */
+
+function addLink(file) {
+  let a = document.createElement("a");
+  a.setAttribute("href", file);
+  a.setAttribute("target", "_blank");
+  a.setAttribute("rel", "opener");
+  document.body.appendChild(a);
+  return a;
+}
+
+/* exported addImage */
+
+function addImage(file) {
+  let img = document.createElement("img");
+  img.setAttribute("src", file);
+  document.body.appendChild(img);
+}
+
+/* exported addScript */
+
+function addScript(file) {
+  let script = document.createElement("script");
+  script.setAttribute("type", "text/javascript");
+  script.setAttribute("src", file);
+  document.getElementsByTagName("head").item(0).appendChild(script);
+}
+
+/* exported addFrame */
+
+function addFrame(file) {
+  let frame = document.createElement("iframe");
+  frame.setAttribute("width", "200");
+  frame.setAttribute("height", "200");
+  frame.setAttribute("src", file);
+  document.body.appendChild(frame);
+}
diff --git a/toolkit/components/extensions/test/mochitest/hsts.sjs b/toolkit/components/extensions/test/mochitest/hsts.sjs
new file mode 100644
index 0000000000..52b9dd340b
--- /dev/null
+++ b/toolkit/components/extensions/test/mochitest/hsts.sjs
@@ -0,0 +1,10 @@
+"use strict";
+
+function handleRequest(request, response) {
+  let page = "<!DOCTYPE html><html><body><p>HSTS page</p></body></html>";
+  response.setStatusLine(request.httpVersion, "200", "OK");
+  response.setHeader("Strict-Transport-Security", "max-age=60");
+  response.setHeader("Content-Type", "text/html", false);
+  response.setHeader("Content-Length", page.length + "", false);
+  response.write(page);
+}
diff --git a/toolkit/components/extensions/test/mochitest/mochitest-common.ini b/toolkit/components/extensions/test/mochitest/mochitest-common.ini
new file mode 100644
index 0000000000..83d4bdc41b
--- /dev/null
+++ b/toolkit/components/extensions/test/mochitest/mochitest-common.ini
@@ -0,0 +1,350 @@
+[DEFAULT]
+tags = condprof
+support-files =
+  chrome_cleanup_script.js
+  file_WebNavigation_page1.html
+  file_WebNavigation_page2.html
+  file_WebNavigation_page3.html
+  file_WebRequest_page3.html
+  file_contains_img.html
+  file_contains_iframe.html
+  file_green.html
+  file_green_blue.html
+  file_contentscript_activeTab.html
+  file_contentscript_activeTab2.html
+  file_contentscript_iframe.html
+  file_image_bad.png
+  file_image_good.png
+  file_image_great.png
+  file_image_redirect.png
+  file_indexedDB.html
+  file_mixed.html
+  file_remote_frame.html
+  file_sample.html
+  file_sample.txt
+  file_sample.txt^headers^
+  file_script_bad.js
+  file_script_good.js
+  file_script_redirect.js
+  file_script_xhr.js
+  file_serviceWorker.html
+  file_simple_iframe_worker.html
+  file_simple_sandboxed_frame.html
+  file_simple_sandboxed_subframe.html
+  file_simple_xhr.html
+  file_simple_xhr_frame.html
+  file_simple_xhr_frame2.html
+  file_simple_sharedworker.js
+  file_simple_webrequest_worker.html
+  file_simple_worker.js
+  file_slowed_document.sjs
+  file_streamfilter.txt
+  file_style_bad.css
+  file_style_good.css
+  file_style_redirect.css
+  file_third_party.html
+  file_to_drawWindow.html
+  file_webNavigation_clientRedirect.html
+  file_webNavigation_clientRedirect_httpHeaders.html
+  file_webNavigation_clientRedirect_httpHeaders.html^headers^
+  file_webNavigation_frameClientRedirect.html
+  file_webNavigation_frameRedirect.html
+  file_webNavigation_manualSubframe.html
+  file_webNavigation_manualSubframe_page1.html
+  file_webNavigation_manualSubframe_page2.html
+  file_with_about_blank.html
+  file_with_subframes_and_embed.html
+  file_with_xorigin_frame.html
+  head.js
+  head_cookies.js
+  head_notifications.js
+  head_unlimitedStorage.js
+  head_webrequest.js
+  hsts.sjs
+  mochitest_console.js
+  oauth.html
+  redirect_auto.sjs
+  redirection.sjs
+  return_headers.sjs
+  serviceWorker.js
+  slow_response.sjs
+  webrequest_worker.js
+  !/dom/tests/mochitest/geolocation/network_geolocation.sjs
+  !/toolkit/components/passwordmgr/test/authenticate.sjs
+  file_redirect_data_uri.html
+  file_redirect_cors_bypass.html
+  file_tabs_permission_page1.html
+  file_tabs_permission_page2.html
+prefs =
+  security.mixed_content.upgrade_display_content=false
+  browser.chrome.guess_favicon=true
+
+[test_check_startupcache.html]
+[test_ext_action.html]
+[test_ext_activityLog.html]
+skip-if =
+  os == 'android'
+  tsan  # Times out on TSan, bug 1612707
+  xorigin  # Inconsistent pass/fail in opt and debug
+  http3
+[test_ext_async_clipboard.html]
+skip-if = toolkit == 'android' || tsan # near-permafail after landing bug 1270059: Bug 1523131. tsan: bug 1612707
+[test_ext_background_canvas.html]
+[test_ext_background_page.html]
+skip-if = (toolkit == 'android') # android doesn't have devtools
+[test_ext_background_page_dpi.html]
+[test_ext_browserAction_openPopup.html]
+skip-if =
+  http3
+[test_ext_browserAction_openPopup_incognito_window.html]
+skip-if = os == "android" # cannot open private windows - bug 1372178
+[test_ext_browserAction_openPopup_windowId.html]
+skip-if = os == "android" # only the current window is supported - bug 1795956
+[test_ext_browserAction_openPopup_without_pref.html]
+[test_ext_browsingData_indexedDB.html]
+skip-if =
+  http3
+[test_ext_browsingData_localStorage.html]
+skip-if =
+  http3
+[test_ext_browsingData_pluginData.html]
+[test_ext_browsingData_serviceWorkers.html]
+skip-if =
+  condprof  #  "Wait for 2 service workers to be registered - timed out after 50 tries."
+  http3
+[test_ext_browsingData_settings.html]
+[test_ext_canvas_resistFingerprinting.html]
+skip-if =
+  http3
+[test_ext_clipboard.html]
+skip-if =
+  os == 'android'
+  http3
+[test_ext_clipboard_image.html]
+skip-if = headless # Bug 1405872
+[test_ext_contentscript_about_blank.html]
+skip-if =
+  os == 'android' # bug 1369440
+  condprof  #: "exactly 7 more scripts ran - got 11, expected 10"
+  http3
+[test_ext_contentscript_activeTab.html]
+skip-if =
+  http3
+[test_ext_contentscript_cache.html]
+skip-if = (os == 'linux' && debug) || (toolkit == 'android' && debug) # bug 1348241
+fail-if = xorigin # TypeError: can't access property "staticScripts", ext is undefined - Should not throw any errors
+[test_ext_contentscript_canvas.html]
+skip-if = (os == 'android') || (verify && debug && (os == 'linux')) # Bug 1617062
+[test_ext_contentscript_devtools_metadata.html]
+skip-if =
+  http3
+[test_ext_contentscript_fission_frame.html]
+skip-if =
+  http3
+[test_ext_contentscript_getFrameId.html]
+[test_ext_contentscript_incognito.html]
+skip-if =
+  os == 'android' # Android does not support multiple windows.
+  http3
+[test_ext_contentscript_permission.html]
+skip-if = tsan # Times out on TSan, bug 1612707
+[test_ext_cookies.html]
+skip-if =
+  os == 'android' || tsan # Times out on TSan intermittently, bug 1615184; not supported on Android yet
+  condprof  #: "one tabId returned for store - Expected: 1, Actual: 3"
+  http3
+[test_ext_cookies_containers.html]
+[test_ext_cookies_expiry.html]
+[test_ext_cookies_first_party.html]
+[test_ext_cookies_incognito.html]
+skip-if = os == 'android' # Bug 1513544 Android does not support multiple windows.
+[test_ext_cookies_permissions_bad.html]
+[test_ext_cookies_permissions_good.html]
+[test_ext_dnr_other_extensions.html]
+[test_ext_dnr_tabIds.html]
+[test_ext_dnr_upgradeScheme.html]
+skip-if =
+  http3
+[test_ext_downloads_download.html]
+[test_ext_embeddedimg_iframe_frameAncestors.html]
+skip-if =
+  http3
+[test_ext_exclude_include_globs.html]
+skip-if =
+  http3
+[test_ext_extension_iframe_messaging.html]
+skip-if =
+  http3
+[test_ext_external_messaging.html]
+[test_ext_generate.html]
+[test_ext_geolocation.html]
+skip-if = os == 'android' # Android support Bug 1336194
+[test_ext_identity.html]
+skip-if = 
+  win11_2009 && !debug && socketprocess_networking  # Bug 1777016
+  os == 'android' || tsan # unsupported. tsan: bug 1612707
+[test_ext_idle.html]
+skip-if = tsan # Times out on TSan, bug 1612707
+[test_ext_inIncognitoContext_window.html]
+skip-if = os == 'android' # Android does not support multiple windows.
+[test_ext_listener_proxies.html]
+[test_ext_new_tab_processType.html]
+skip-if =
+  verify && debug && (os == 'linux' || os == 'mac')
+  condprof  #: Page URL should match - got "https://example.com/tests/toolkit/components/extensions/test/mochitest/file_serviceWorker.html", expected "https://example.com/"
+  http3
+[test_ext_notifications.html]
+skip-if = os == 'android' # Not supported on Android yet
+[test_ext_optional_permissions.html]
+[test_ext_protocolHandlers.html]
+skip-if = (toolkit == 'android') # bug 1342577
+[test_ext_redirect_jar.html]
+skip-if = os == 'win' && (debug || asan) # Bug 1563440
+[test_ext_request_urlClassification.html]
+skip-if =
+  os == 'android' # Bug 1615427
+  http3
+[test_ext_runtime_connect.html]
+skip-if =
+  http3
+[test_ext_runtime_connect_iframe.html]
+[test_ext_runtime_connect_twoway.html]
+skip-if =
+  http3
+[test_ext_runtime_connect2.html]
+skip-if =
+  http3
+[test_ext_runtime_disconnect.html]
+skip-if =
+  http3
+[test_ext_script_filenames.html]
+[test_ext_scripting_contentScripts.html]
+skip-if =
+  http3
+[test_ext_scripting_executeScript.html]
+skip-if =
+  http3
+[test_ext_scripting_executeScript_activeTab.html]
+skip-if =
+  http3
+[test_ext_scripting_executeScript_injectImmediately.html]
+skip-if =
+  http3
+[test_ext_scripting_insertCSS.html]
+skip-if =
+  http3
+[test_ext_scripting_permissions.html]
+skip-if =
+  http3
+[test_ext_scripting_removeCSS.html]
+skip-if =
+  http3
+[test_ext_sendmessage_doublereply.html]
+skip-if =
+  http3
+[test_ext_sendmessage_frameId.html]
+[test_ext_sendmessage_no_receiver.html]
+skip-if =
+  http3
+[test_ext_sendmessage_reply.html]
+skip-if =
+  http3
+[test_ext_sendmessage_reply2.html]
+skip-if =
+  os == 'android'
+  http3
+[test_ext_storage_manager_capabilities.html]
+skip-if =
+  xorigin # JavaScript Error: "SecurityError: Permission denied to access property "wrappedJSObject" on cross-origin object" {file: "https://example.com/tests/SimpleTest/TestRunner.js" line: 157}
+  http3
+scheme=https
+[test_ext_storage_smoke_test.html]
+[test_ext_streamfilter_multiple.html]
+skip-if =
+  !debug # Bug 1628642
+  os == 'linux' # Bug 1628642
+[test_ext_streamfilter_processswitch.html]
+skip-if =
+  http3
+[test_ext_subframes_privileges.html]
+skip-if =
+  os == 'android' || verify # bug 1489771
+  http3
+[test_ext_tabs_captureTab.html]
+skip-if =
+  http3
+[test_ext_tabs_executeScript_good.html]
+skip-if =
+  http3
+[test_ext_tabs_create_cookieStoreId.html]
+[test_ext_tabs_query_popup.html]
+[test_ext_tabs_permissions.html]
+skip-if =
+  http3
+[test_ext_tabs_sendMessage.html]
+skip-if =
+  http3
+[test_ext_test.html]
+skip-if =
+  http3
+[test_ext_unlimitedStorage.html]
+skip-if = os == 'android'
+[test_ext_web_accessible_resources.html]
+skip-if = (os == 'android' && debug) || (os  == "linux" && bits == 64) # bug 1397615, bug 1618231
+[test_ext_web_accessible_incognito.html]
+skip-if = (os == 'android') # bug 1397615, bug 1513544
+[test_ext_webnavigation.html]
+skip-if =
+  (os == 'android' && debug) # bug 1397615
+  http3
+[test_ext_webnavigation_filters.html]
+skip-if =
+  (os == 'android' && debug) || (verify && (os == 'linux' || os == 'mac')) # bug 1397615
+  http3
+[test_ext_webnavigation_incognito.html]
+skip-if =
+  os == 'android' # bug 1513544
+  http3
+[test_ext_webrequest_and_proxy_filter.html]
+skip-if =
+  http3
+[test_ext_webrequest_auth.html]
+skip-if =
+  os == 'android'
+  http3
+[test_ext_webrequest_background_events.html]
+[test_ext_webrequest_basic.html]
+skip-if =
+  os == 'android' && debug  # bug 1397615
+  tsan  # bug 1612707
+  xorigin  # JavaScript Error: "SecurityError: Permission denied to access property "wrappedJSObject" on cross-origin object" {file: "http://mochi.false-test:8888/tests/SimpleTest/TestRunner.js" line: 157}]
+  os == "linux" && bits == 64 && !debug && asan # Bug 1633189
+  http3
+[test_ext_webrequest_errors.html]
+skip-if =
+  tsan
+  http3
+[test_ext_webrequest_filter.html]
+skip-if =
+ os == 'android' && debug || tsan # bug 1452348. tsan: bug 1612707
+ os == 'linux' && bits == 64 && !debug && xorigin # Bug 1756023
+[test_ext_webrequest_frameId.html]
+[test_ext_webrequest_getSecurityInfo.html]
+skip-if =
+  http3
+[test_ext_webrequest_hsts.html]
+https_first_disabled = true
+skip-if =
+  http3
+[test_ext_webrequest_upgrade.html]
+https_first_disabled = true
+[test_ext_webrequest_upload.html]
+skip-if = os == 'android' # Currently fails in emulator tests
+[test_ext_webrequest_redirect_bypass_cors.html]
+[test_ext_webrequest_redirect_data_uri.html]
+[test_ext_webrequest_worker.html]
+[test_ext_window_postMessage.html]
+skip-if =
+  http3
+# test_startup_canary.html is at the bottom to minimize the time spent waiting in the test.
+[test_startup_canary.html]
diff --git a/toolkit/components/extensions/test/mochitest/mochitest-remote.ini b/toolkit/components/extensions/test/mochitest/mochitest-remote.ini
new file mode 100644
index 0000000000..0a66b11755
--- /dev/null
+++ b/toolkit/components/extensions/test/mochitest/mochitest-remote.ini
@@ -0,0 +1,11 @@
+[DEFAULT]
+tags = webextensions remote-webextensions
+skip-if = os == 'android' # Bug 1620091: disable on android until extension process is done
+prefs =
+  extensions.webextensions.remote=true
+  # We don't want to reset this at the end of the test, so that we don't have
+  # to spawn a new extension child process for each test unit.
+  dom.ipc.keepProcessesAlive.extension=1
+
+[test_verify_remote_mode.html]
+[include:mochitest-common.ini]
diff --git a/toolkit/components/extensions/test/mochitest/mochitest-serviceworker.ini b/toolkit/components/extensions/test/mochitest/mochitest-serviceworker.ini
new file mode 100644
index 0000000000..4468349d84
--- /dev/null
+++ b/toolkit/components/extensions/test/mochitest/mochitest-serviceworker.ini
@@ -0,0 +1,28 @@
+[DEFAULT]
+tags = webextensions sw-webextensions condprof
+skip-if =
+  !e10s             # Thunderbird does still run in non e10s mode (and so also with in-process-webextensions mode)
+  (os == 'android') # Bug 1620091: disable on android until extension process is done
+  http3
+
+prefs =
+  extensions.webextensions.remote=true
+  # We don't want to reset this at the end of the test, so that we don't have
+  # to spawn a new extension child process for each test unit.
+  dom.ipc.keepProcessesAlive.extension=1
+  extensions.backgroundServiceWorker.enabled=true
+  extensions.backgroundServiceWorker.forceInTestExtension=true
+
+dupe-manifest = true
+
+# `test_verify_sw_mode.html` should be the first one, even if it breaks the
+# alphabetical order.
+[test_verify_sw_mode.html]
+[test_ext_scripting_contentScripts.html]
+[test_ext_scripting_executeScript.html]
+skip-if = true # Bug 1748315 - Add WebIDL bindings for `scripting.executeScript()`
+[test_ext_scripting_insertCSS.html]
+skip-if = true # Bug 1748318 - Add WebIDL bindings for `tabs`
+[test_ext_scripting_removeCSS.html]
+skip-if = true # Bug 1748318 - Add WebIDL bindings for `tabs`
+[test_ext_test.html]
diff --git a/toolkit/components/extensions/test/mochitest/mochitest.ini b/toolkit/components/extensions/test/mochitest/mochitest.ini
new file mode 100644
index 0000000000..f2f6117726
--- /dev/null
+++ b/toolkit/components/extensions/test/mochitest/mochitest.ini
@@ -0,0 +1,13 @@
+[DEFAULT]
+tags = webextensions in-process-webextensions
+prefs =
+    extensions.webextensions.remote=false
+    javascript.options.asyncstack_capture_debuggee_only=false
+dupe-manifest = true
+
+[test_verify_non_remote_mode.html]
+[test_ext_storage_cleanup.html]
+# Bug 1426514 storage_cleanup: clearing localStorage fails with oop
+
+[include:mochitest-common.ini]
+skip-if = os == 'win' # Windows WebExtensions always run OOP
diff --git a/toolkit/components/extensions/test/mochitest/mochitest_console.js b/toolkit/components/extensions/test/mochitest/mochitest_console.js
new file mode 100644
index 0000000000..582e12b48f
--- /dev/null
+++ b/toolkit/components/extensions/test/mochitest/mochitest_console.js
@@ -0,0 +1,54 @@
+/* eslint-env mozilla/chrome-script */
+
+"use strict";
+
+const { addMessageListener, sendAsyncMessage } = this;
+
+// Much of the console monitoring code is copied from TestUtils but simplified
+// to our needs.
+function monitorConsole(msgs) {
+  function msgMatches(msg, pat) {
+    for (let k in pat) {
+      if (!(k in msg)) {
+        return false;
+      }
+      if (pat[k] instanceof RegExp && typeof msg[k] === "string") {
+        if (!pat[k].test(msg[k])) {
+          return false;
+        }
+      } else if (msg[k] !== pat[k]) {
+        return false;
+      }
+    }
+    return true;
+  }
+
+  let counter = 0;
+  function listener(msg) {
+    if (msgMatches(msg, msgs[counter])) {
+      counter++;
+    }
+  }
+  addMessageListener("waitForConsole", () => {
+    sendAsyncMessage("consoleDone", {
+      ok: counter >= msgs.length,
+      message: `monitorConsole | messages left expected at least ${msgs.length} got ${counter}`,
+    });
+    Services.console.unregisterListener(listener);
+  });
+
+  Services.console.registerListener(listener);
+}
+
+addMessageListener("consoleStart", messages => {
+  for (let msg of messages) {
+    // Message might be a RegExp object from a different compartment, but
+    // instanceof RegExp will fail.  If we have an object, lets just make
+    // sure.
+    let message = msg.message;
+    if (typeof message == "object" && !(message instanceof RegExp)) {
+      msg.message = new RegExp(message);
+    }
+  }
+  monitorConsole(messages);
+});
diff --git a/toolkit/components/extensions/test/mochitest/oauth.html b/toolkit/components/extensions/test/mochitest/oauth.html
new file mode 100644
index 0000000000..8b9b1d65ec
--- /dev/null
+++ b/toolkit/components/extensions/test/mochitest/oauth.html
@@ -0,0 +1,26 @@
+<!DOCTYPE html>
+<html>
+<head>
+  <script>
+  "use strict";
+
+  onload = () => {
+    let url = new URL(location);
+    if (url.searchParams.get("post")) {
+      let server_redirect = `${url.searchParams.get("server_uri")}?redirect_uri=${encodeURIComponent(url.searchParams.get("redirect_uri"))}`;
+      let form = document.forms.testform;
+      form.setAttribute("action", server_redirect);
+      form.submit();
+    } else {
+      let end = new URL(url.searchParams.get("redirect_uri"));
+      end.searchParams.set("access_token", "here ya go");
+      location.href = end.href;
+    }
+  };
+  </script>
+</head>
+<body>
+  <form name="testform" action="" method="POST">
+  </form>
+</body>
+</html>
diff --git a/toolkit/components/extensions/test/mochitest/redirect_auto.sjs b/toolkit/components/extensions/test/mochitest/redirect_auto.sjs
new file mode 100644
index 0000000000..bf7af2556b
--- /dev/null
+++ b/toolkit/components/extensions/test/mochitest/redirect_auto.sjs
@@ -0,0 +1,24 @@
+/* Any copyright is dedicated to the Public Domain.
+ * http://creativecommons.org/publicdomain/zero/1.0/
+ */
+"use strict";
+Cu.importGlobalProperties(["URLSearchParams", "URL"]);
+
+function handleRequest(request, response) {
+  let params = new URLSearchParams(request.queryString);
+  if (params.has("no_redirect")) {
+    response.setStatusLine(request.httpVersion, 200, "OK");
+    response.write("ok");
+  } else {
+    if (request.method == "POST") {
+      response.setStatusLine(request.httpVersion, 303, "Redirected");
+    } else {
+      response.setStatusLine(request.httpVersion, 302, "Moved Temporarily");
+    }
+    let url = new URL(
+      params.get("redirect_uri") || params.get("default_redirect")
+    );
+    url.searchParams.set("access_token", "here ya go");
+    response.setHeader("Location", url.href);
+  }
+}
diff --git a/toolkit/components/extensions/test/mochitest/redirection.sjs b/toolkit/components/extensions/test/mochitest/redirection.sjs
new file mode 100644
index 0000000000..873a3d41ba
--- /dev/null
+++ b/toolkit/components/extensions/test/mochitest/redirection.sjs
@@ -0,0 +1,6 @@
+"use strict";
+
+function handleRequest(request, response) {
+  response.setStatusLine(request.httpVersion, 302);
+  response.setHeader("Location", "./dummy_page.html");
+}
diff --git a/toolkit/components/extensions/test/mochitest/return_headers.sjs b/toolkit/components/extensions/test/mochitest/return_headers.sjs
new file mode 100644
index 0000000000..46beab8185
--- /dev/null
+++ b/toolkit/components/extensions/test/mochitest/return_headers.sjs
@@ -0,0 +1,19 @@
+/* -*- Mode: indent-tabs-mode: nil; js-indent-level: 2 -*- */
+/* vim: set ft=javascript sts=2 sw=2 et tw=80: */
+"use strict";
+
+/* exported handleRequest */
+
+function handleRequest(request, response) {
+  response.setHeader("Content-Type", "text/plain", false);
+
+  let headers = {};
+  // Why on earth is this a nsISimpleEnumerator...
+  let enumerator = request.headers;
+  while (enumerator.hasMoreElements()) {
+    let header = enumerator.getNext().data;
+    headers[header.toLowerCase()] = request.getHeader(header);
+  }
+
+  response.write(JSON.stringify(headers));
+}
diff --git a/toolkit/components/extensions/test/mochitest/serviceWorker.js b/toolkit/components/extensions/test/mochitest/serviceWorker.js
new file mode 100644
index 0000000000..e69de29bb2
--- /dev/null
+++ b/toolkit/components/extensions/test/mochitest/serviceWorker.js
diff --git a/toolkit/components/extensions/test/mochitest/slow_response.sjs b/toolkit/components/extensions/test/mochitest/slow_response.sjs
new file mode 100644
index 0000000000..d39c4c0bf0
--- /dev/null
+++ b/toolkit/components/extensions/test/mochitest/slow_response.sjs
@@ -0,0 +1,60 @@
+/* -*- Mode: indent-tabs-mode: nil; js-indent-level: 2 -*- */
+/* vim: set sts=2 sw=2 et tw=80 ft=javascript: */
+"use strict";
+
+/* eslint-disable no-unused-vars */
+
+let { AppConstants } = ChromeUtils.importESModule(
+  "resource://gre/modules/AppConstants.sys.mjs"
+);
+
+const DELAY = AppConstants.DEBUG ? 4000 : 800;
+
+let nsTimer = Components.Constructor(
+  "@mozilla.org/timer;1",
+  "nsITimer",
+  "initWithCallback"
+);
+
+let timer;
+function delay() {
+  return new Promise(resolve => {
+    timer = nsTimer(resolve, DELAY, Ci.nsITimer.TYPE_ONE_SHOT);
+  });
+}
+
+const PARTS = [
+  `<!DOCTYPE html>
+    <html lang="en">
+    <head>
+      <meta charset="UTF-8">
+      <title></title>
+    </head>
+    <body>`,
+  "Lorem ipsum dolor sit amet, <br>",
+  "consectetur adipiscing elit, <br>",
+  "sed do eiusmod tempor incididunt ut labore et dolore magna aliqua. <br>",
+  "Ut enim ad minim veniam, quis nostrud exercitation ullamco laboris nisi ut aliquip ex ea commodo consequat. <br>",
+  "Duis aute irure dolor in reprehenderit in voluptate velit esse cillum dolore eu fugiat nulla pariatur. <br>",
+  "Excepteur sint occaecat cupidatat non proident, <br>",
+  "sunt in culpa qui officia deserunt mollit anim id est laborum.<br>",
+  `
+    </body>
+    </html>`,
+];
+
+async function handleRequest(request, response) {
+  response.processAsync();
+
+  response.setHeader("Content-Type", "text/html", false);
+  response.setHeader("Cache-Control", "no-cache", false);
+
+  await delay();
+
+  for (let part of PARTS) {
+    response.write(`${part}\n`);
+    await delay();
+  }
+
+  response.finish();
+}
diff --git a/toolkit/components/extensions/test/mochitest/test_check_startupcache.html b/toolkit/components/extensions/test/mochitest/test_check_startupcache.html
new file mode 100644
index 0000000000..01d361ca5e
--- /dev/null
+++ b/toolkit/components/extensions/test/mochitest/test_check_startupcache.html
@@ -0,0 +1,61 @@
+<!DOCTYPE HTML>
+<html>
+<head>
+  <title>Check StartupCache</title>
+  <meta charset="utf-8">
+  <script src="/tests/SimpleTest/SimpleTest.js"></script>
+  <script type="text/javascript" src="head.js"></script>
+  <link rel="stylesheet" type="text/css" href="/tests/SimpleTest/test.css"/>
+</head>
+<body>
+
+<script type="text/javascript">
+"use strict";
+
+add_task(async function check_ExtensionParent_StartupCache_is_non_empty() {
+  // This test aims to verify that the StartupCache of extensions is populated.
+  // Ideally, we would load an extension, restart the browser and confirm the
+  // existence of the StartupCache. That is not possible in a mochitest.
+  // So we will just read the contents of the StartupCache and verify that it
+  // populated and assume that it carries over to the next startup.
+  // The latter is checked in test_startup_canary.html
+
+  const { WebExtensionPolicy } = SpecialPowers.Cu.getGlobalForObject(SpecialPowers.Services);
+  // The Mochikit extension is part of the mochitests framework, so the fact
+  // that this test runs implies that the extension should have been started.
+  ok(
+    WebExtensionPolicy.getByID("mochikit@mozilla.org"),
+    "This test expects the Mochikit extension to be running"
+  );
+
+  let chromeScript = loadChromeScript(() => {
+    const {
+      ExtensionParent,
+    } = ChromeUtils.import("resource://gre/modules/ExtensionParent.jsm");
+    const { StartupCache } = ExtensionParent;
+    this.sendAsyncMessage("StartupCache_data", StartupCache._data);
+  });
+
+  let map = await chromeScript.promiseOneMessage("StartupCache_data");
+  chromeScript.destroy();
+
+  // "manifests" is populated by Extension's parseManifest in Extension.jsm.
+  const keys = ["manifests", "mochikit@mozilla.org", "2.0", "en-US"];
+  for (let key of keys) {
+    map = map.get(key);
+    ok(map, `StartupCache data map contains ${key}`);
+  }
+
+  // At this point `map` is expected to be the return value of
+  // ExtensionData's parseManifest.
+
+  is(
+    map?.manifest?.applications?.gecko?.id,
+    "mochikit@mozilla.org",
+    "StartupCache.manifests contains a parsed manifest"
+  );
+});
+</script>
+
+</body>
+</html>
diff --git a/toolkit/components/extensions/test/mochitest/test_chrome_ext_contentscript_data_uri.html b/toolkit/components/extensions/test/mochitest/test_chrome_ext_contentscript_data_uri.html
new file mode 100644
index 0000000000..42950c50ec
--- /dev/null
+++ b/toolkit/components/extensions/test/mochitest/test_chrome_ext_contentscript_data_uri.html
@@ -0,0 +1,104 @@
+<!DOCTYPE html>
+<html>
+<head>
+  <title>Test content script matching a data: URI</title>
+  <script src="chrome://mochikit/content/tests/SimpleTest/SimpleTest.js"></script>
+  <script src="chrome://mochikit/content/tests/SimpleTest/ExtensionTestUtils.js"></script>
+  <script src="head.js"></script>
+  <link rel="stylesheet" href="chrome://mochikit/contents/tests/SimpleTest/test.css"/>
+</head>
+<body>
+
+<script>
+"use strict";
+
+add_task(async function test_contentscript_data_uri() {
+  const target = ExtensionTestUtils.loadExtension({
+    files: {
+      "page.html": `<!DOCTYPE html>
+        <meta charset="utf-8">
+        <iframe id="inherited" src="data:text/html;charset=utf-8,inherited"></iframe>
+      `,
+    },
+    background() {
+      browser.test.sendMessage("page", browser.runtime.getURL("page.html"));
+    },
+  });
+
+  const scripts = ExtensionTestUtils.loadExtension({
+    manifest: {
+      permissions: ["webNavigation"],
+      content_scripts: [{
+        all_frames: true,
+        matches: ["<all_urls>"],
+        run_at: "document_start",
+        css: ["all_urls.css"],
+        js: ["all_urls.js"],
+      }],
+    },
+    files: {
+      "all_urls.css": `
+        body { background: yellow; }
+      `,
+      "all_urls.js": function() {
+        document.body.style.color = "red";
+        browser.test.assertTrue(location.protocol !== "data:",
+                                `Matched document not a data URI: ${location.href}`);
+      },
+    },
+    background() {
+      browser.webNavigation.onCompleted.addListener(({url, frameId}) => {
+        browser.test.log(`Document loading complete: ${url}`);
+        if (frameId === 0) {
+          browser.test.sendMessage("tab-ready", url);
+        }
+      });
+    },
+  });
+
+  await target.startup();
+  await scripts.startup();
+
+  // Test extension page with a data: iframe.
+  const page = await target.awaitMessage("page");
+
+  // Hold on to the tab by the browser, as extension loads are COOP loads, and
+  // will break WindowProxy references.
+  let win = window.open();
+  const browserFrame = win.browsingContext.embedderElement;
+  win.location.href = page;
+
+  await scripts.awaitMessage("tab-ready");
+  win = browserFrame.contentWindow;
+  is(win.location.href, page, "Extension page loaded into a tab");
+  is(win.document.readyState, "complete", "Page finished loading");
+
+  const iframe = win.document.getElementById("inherited").contentWindow;
+  is(iframe.document.readyState, "complete", "iframe finished loading");
+
+  const style1 = iframe.getComputedStyle(iframe.document.body);
+  is(style1.color, "rgb(0, 0, 0)", "iframe text color is unmodified");
+  is(style1.backgroundColor, "rgba(0, 0, 0, 0)", "iframe background unmodified");
+
+  // Test extension tab navigated to a data: URI.
+  const data = "data:text/html;charset=utf-8,also-inherits";
+  win.location.href = data;
+
+  await scripts.awaitMessage("tab-ready");
+  win = browserFrame.contentWindow;
+  is(win.location.href, data, "Extension tab navigated to a data: URI");
+  is(win.document.readyState, "complete", "Tab finished loading");
+
+  const style2 = win.getComputedStyle(win.document.body);
+  is(style2.color, "rgb(0, 0, 0)", "Tab text color is unmodified");
+  is(style2.backgroundColor, "rgba(0, 0, 0, 0)", "Tab background unmodified");
+
+  win.close();
+  await target.unload();
+  await scripts.unload();
+});
+
+</script>
+
+</body>
+</html>
diff --git a/toolkit/components/extensions/test/mochitest/test_chrome_ext_contentscript_telemetry.html b/toolkit/components/extensions/test/mochitest/test_chrome_ext_contentscript_telemetry.html
new file mode 100644
index 0000000000..224e806288
--- /dev/null
+++ b/toolkit/components/extensions/test/mochitest/test_chrome_ext_contentscript_telemetry.html
@@ -0,0 +1,68 @@
+<!DOCTYPE html>
+<html>
+<head>
+  <title>Test for telemetry for content script injection</title>
+  <script src="chrome://mochikit/content/tests/SimpleTest/SimpleTest.js"></script>
+  <script src="chrome://mochikit/content/tests/SimpleTest/ExtensionTestUtils.js"></script>
+  <script src="head.js"></script>
+  <link rel="stylesheet" href="chrome://mochikit/contents/tests/SimpleTest/test.css"/>
+</head>
+<body>
+
+<script>
+"use strict";
+
+const HISTOGRAM = "WEBEXT_CONTENT_SCRIPT_INJECTION_MS";
+
+add_task(async function test_contentscript_telemetry() {
+  // Turn on telemetry and reset it to the previous state once the test is completed.
+  const telemetryCanRecordBase = SpecialPowers.Services.telemetry.canRecordBase;
+  SpecialPowers.Services.telemetry.canRecordBase = true;
+  SimpleTest.registerCleanupFunction(() => {
+    SpecialPowers.Services.telemetry.canRecordBase = telemetryCanRecordBase;
+  });
+
+  function background() {
+    browser.test.onMessage.addListener(() => {
+      browser.tabs.executeScript({code: 'browser.test.sendMessage("content-script-run");'});
+    });
+  }
+
+  let extensionData = {
+    manifest: {
+      permissions: ["<all_urls>"],
+    },
+    background,
+  };
+
+  let tab = await AppTestDelegate.openNewForegroundTab(
+    window,
+    "https://example.com",
+    true
+  );
+
+  let extension = ExtensionTestUtils.loadExtension(extensionData);
+
+  let histogram = SpecialPowers.Services.telemetry.getHistogramById(HISTOGRAM);
+  histogram.clear();
+  is(histogram.snapshot().sum, 0,
+     `No data recorded for histogram: ${HISTOGRAM}.`);
+
+  await extension.startup();
+  is(histogram.snapshot().sum, 0,
+     `No data recorded for histogram after startup: ${HISTOGRAM}.`);
+
+  extension.sendMessage();
+  await extension.awaitMessage("content-script-run");
+
+  let histogramSum = histogram.snapshot().sum;
+  ok(histogramSum > 0,
+     `Data recorded for first extension for histogram: ${HISTOGRAM}.`);
+
+  await AppTestDelegate.removeTab(window, tab);
+  await extension.unload();
+});
+</script>
+
+</body>
+</html>
diff --git a/toolkit/components/extensions/test/mochitest/test_chrome_ext_contentscript_unrecognizedprop_warning.html b/toolkit/components/extensions/test/mochitest/test_chrome_ext_contentscript_unrecognizedprop_warning.html
new file mode 100644
index 0000000000..40403dea2b
--- /dev/null
+++ b/toolkit/components/extensions/test/mochitest/test_chrome_ext_contentscript_unrecognizedprop_warning.html
@@ -0,0 +1,80 @@
+<!DOCTYPE HTML>
+<html>
+<head>
+  <title>Test for content script unrecognized property on manifest</title>
+  <script src="chrome://mochikit/content/tests/SimpleTest/SimpleTest.js"></script>
+  <script src="chrome://mochikit/content/tests/SimpleTest/ExtensionTestUtils.js"></script>
+  <script type="text/javascript" src="head.js"></script>
+  <link rel="stylesheet" href="chrome://mochikit/content/tests/SimpleTest/test.css"/>
+</head>
+<body>
+
+<script type="text/javascript">
+"use strict";
+
+const BASE = "http://mochi.test:8888/chrome/toolkit/components/extensions/test/mochitest";
+
+add_task(async function test_contentscript() {
+  function background() {
+    browser.runtime.onMessage.addListener(async (msg) => {
+      if (msg == "loaded") {
+        // NOTE: we're removing the tab from here because doing a win.close()
+        // from the chrome test code is raising a "TypeError: can't access
+        // dead object" exception.
+        let tabs = await browser.tabs.query({active: true, currentWindow: true});
+        await browser.tabs.remove(tabs[0].id);
+
+        browser.test.notifyPass("content-script-loaded");
+      }
+    });
+  }
+
+  function contentScript() {
+    chrome.runtime.sendMessage("loaded");
+  }
+
+  let extensionData = {
+    manifest: {
+      content_scripts: [
+        {
+          "matches": ["http://mochi.test/*/file_sample.html"],
+          "js": ["content_script.js"],
+          "run_at": "document_idle",
+          "unrecognized_property": "with-a-random-value",
+        },
+      ],
+    },
+    background,
+
+    files: {
+      "content_script.js": contentScript,
+    },
+  };
+
+  let extension = ExtensionTestUtils.loadExtension(extensionData);
+
+  SimpleTest.waitForExplicitFinish();
+  let waitForConsole = new Promise(resolve => {
+    SimpleTest.monitorConsole(resolve, [{
+      message: /Reading manifest: Warning processing content_scripts.*.unrecognized_property: An unexpected property was found/,
+    }]);
+  });
+
+  ExtensionTestUtils.failOnSchemaWarnings(false);
+  await extension.startup();
+  ExtensionTestUtils.failOnSchemaWarnings(true);
+
+  window.open(`${BASE}/file_sample.html`);
+
+  await Promise.all([extension.awaitFinish("content-script-loaded")]);
+  info("test page loaded");
+
+  await extension.unload();
+
+  SimpleTest.endMonitorConsole();
+  await waitForConsole;
+});
+</script>
+
+</body>
+</html>
diff --git a/toolkit/components/extensions/test/mochitest/test_chrome_ext_downloads_open.html b/toolkit/components/extensions/test/mochitest/test_chrome_ext_downloads_open.html
new file mode 100644
index 0000000000..530937c1ac
--- /dev/null
+++ b/toolkit/components/extensions/test/mochitest/test_chrome_ext_downloads_open.html
@@ -0,0 +1,114 @@
+<!DOCTYPE HTML>
+<html>
+<head>
+  <title>Test for permissions</title>
+  <script src="chrome://mochikit/content/tests/SimpleTest/SimpleTest.js"></script>
+  <script src="chrome://mochikit/content/tests/SimpleTest/EventUtils.js"></script>
+  <script src="chrome://mochikit/content/tests/SimpleTest/ExtensionTestUtils.js"></script>
+  <link rel="stylesheet" href="chrome://mochikit/content/tests/SimpleTest/test.css"/>
+</head>
+<body>
+
+<script type="text/javascript">
+"use strict";
+
+add_task(async function test_downloads_open_permission() {
+  function backgroundScript() {
+    browser.test.assertEq(browser.downloads.open, undefined,
+                          "`downloads.open` permission is required.");
+    browser.test.notifyPass("downloads tests");
+  }
+
+  let extensionData = {
+    background: backgroundScript,
+    manifest: {
+      permissions: ["downloads"],
+    },
+  };
+
+  let extension = ExtensionTestUtils.loadExtension(extensionData);
+  await extension.startup();
+  await extension.awaitFinish("downloads tests");
+  await extension.unload();
+});
+
+add_task(async function test_downloads_open_requires_user_interaction() {
+  async function backgroundScript() {
+    await browser.test.assertRejects(
+      browser.downloads.open(10),
+      "downloads.open may only be called from a user input handler",
+      "The error is informative.");
+
+    browser.test.notifyPass("downloads tests");
+  }
+
+  let extensionData = {
+    background: backgroundScript,
+    manifest: {
+      permissions: ["downloads", "downloads.open"],
+    },
+  };
+
+  let extension = ExtensionTestUtils.loadExtension(extensionData);
+  await extension.startup();
+  await extension.awaitFinish("downloads tests");
+  await extension.unload();
+});
+
+add_task(async function downloads_open_invalid_id() {
+  async function pageScript() {
+    window.addEventListener("keypress", async function handler() {
+      try {
+        await browser.downloads.open(10);
+        browser.test.sendMessage("download-open.result", {success: true});
+      } catch (e) {
+        browser.test.sendMessage("download-open.result", {
+          success: false,
+          error: e.message,
+        });
+      }
+      window.removeEventListener("keypress", handler);
+    });
+
+    browser.test.sendMessage("page-ready");
+  }
+
+  let extensionData = {
+    background() {
+      browser.test.sendMessage("ready", browser.runtime.getURL("page.html"));
+    },
+    files: {
+      "foo.txt": "It's the file called foo.txt.",
+      "page.html": `<html><head>
+        <script src="page.js"><\/script>
+      </head></html>`,
+      "page.js": pageScript,
+    },
+    manifest: {
+      permissions: ["downloads", "downloads.open"],
+    },
+  };
+
+  let extension = ExtensionTestUtils.loadExtension(extensionData);
+  await extension.startup();
+
+  let url = await extension.awaitMessage("ready");
+  let win = window.open();
+  let browserFrame = win.browsingContext.embedderElement;
+  win.location.href = url;
+  await extension.awaitMessage("page-ready");
+
+  synthesizeKey("a", {}, browserFrame.contentWindow);
+  let result = await extension.awaitMessage("download-open.result");
+
+  is(result.success, false, "Opening download fails.");
+  is(result.error, "Invalid download id 10", "The error is informative.");
+
+
+  await extension.unload();
+});
+
+</script>
+
+</body>
+</html>
diff --git a/toolkit/components/extensions/test/mochitest/test_chrome_ext_downloads_saveAs.html b/toolkit/components/extensions/test/mochitest/test_chrome_ext_downloads_saveAs.html
new file mode 100644
index 0000000000..64cfcfd289
--- /dev/null
+++ b/toolkit/components/extensions/test/mochitest/test_chrome_ext_downloads_saveAs.html
@@ -0,0 +1,257 @@
+<!doctype html>
+<html>
+<head>
+  <title>Test downloads.download() saveAs option</title>
+  <script src="chrome://mochikit/content/tests/SimpleTest/SimpleTest.js"></script>
+  <script src="chrome://mochikit/content/tests/SimpleTest/ExtensionTestUtils.js"></script>
+  <script src="head.js"></script>
+  <link rel="stylesheet" href="chrome://mochikit/content/tests/SimpleTest/test.css"/>
+</head>
+<body>
+
+<script type="text/javascript">
+"use strict";
+
+const {FileUtils} = ChromeUtils.import("resource://gre/modules/FileUtils.jsm");
+
+const PROMPTLESS_DOWNLOAD_PREF = "browser.download.useDownloadDir";
+
+const DOWNLOAD_FILENAME = "file_download.nonext.txt";
+const DEFAULT_SUBDIR = "subdir";
+
+// We need to be able to distinguish files downloaded by the file picker from
+// files downloaded without it.
+let pickerDir;
+let pbPickerDir; // for incognito downloads
+let defaultDir;
+
+add_task(async function setup() {
+  // Reset DownloadLastDir preferences in case other tests set them.
+  SpecialPowers.Services.obs.notifyObservers(
+    null,
+    "browser:purge-session-history"
+  );
+
+  // Set up temporary directories.
+  let downloadDir = FileUtils.getDir("TmpD", ["downloads"]);
+  pickerDir = downloadDir.clone();
+  pickerDir.createUnique(Ci.nsIFile.DIRECTORY_TYPE, FileUtils.PERMS_DIRECTORY);
+  info(`Using file picker download directory ${pickerDir.path}`);
+  pbPickerDir = downloadDir.clone();
+  pbPickerDir.createUnique(Ci.nsIFile.DIRECTORY_TYPE, FileUtils.PERMS_DIRECTORY);
+  info(`Using private browsing file picker download directory ${pbPickerDir.path}`);
+  defaultDir = downloadDir.clone();
+  defaultDir.createUnique(Ci.nsIFile.DIRECTORY_TYPE, FileUtils.PERMS_DIRECTORY);
+  info(`Using default download directory ${defaultDir.path}`);
+  let subDir = defaultDir.clone();
+  subDir.append(DEFAULT_SUBDIR);
+  subDir.create(Ci.nsIFile.DIRECTORY_TYPE, FileUtils.PERMS_DIRECTORY);
+
+  isnot(pickerDir.path, defaultDir.path,
+        "Should be able to distinguish between files saved with or without the file picker");
+  isnot(pickerDir.path, pbPickerDir.path,
+        "Should be able to distinguish between files saved in and out of private browsing mode");
+
+  await SpecialPowers.pushPrefEnv({"set": [
+    ["browser.download.folderList", 2],
+    ["browser.download.dir", defaultDir.path],
+  ]});
+
+  SimpleTest.registerCleanupFunction(async () => {
+    await SpecialPowers.popPrefEnv();
+    pickerDir.remove(true);
+    pbPickerDir.remove(true);
+    defaultDir.remove(true); // This also removes DEFAULT_SUBDIR.
+  });
+});
+
+add_task(async function test_downloads_saveAs() {
+  const pickerFile = pickerDir.clone();
+  pickerFile.append(DOWNLOAD_FILENAME);
+
+  const pbPickerFile = pbPickerDir.clone();
+  pbPickerFile.append(DOWNLOAD_FILENAME);
+
+  const defaultFile = defaultDir.clone();
+  defaultFile.append(DOWNLOAD_FILENAME);
+
+  const {MockFilePicker} = SpecialPowers;
+  MockFilePicker.init(window);
+
+  function mockFilePickerCallback(expectedStartingDir, pickedFile) {
+    return fp => {
+      // Assert that the downloads API correctly sets the starting directory.
+      ok(fp.displayDirectory.equals(expectedStartingDir), "Got the expected FilePicker displayDirectory");
+
+      // Assert that the downloads API configures both default properties.
+      is(fp.defaultString, DOWNLOAD_FILENAME, "Got the expected FilePicker defaultString");
+      is(fp.defaultExtension, "txt", "Got the expected FilePicker defaultExtension");
+
+      MockFilePicker.setFiles([pickedFile]);
+    };
+  }
+
+  function background() {
+    const url = URL.createObjectURL(new Blob(["file content"]));
+    browser.test.onMessage.addListener(async (filename, saveAs, isPrivate) => {
+      try {
+        let options = {
+          url,
+          filename,
+          incognito: isPrivate,
+        };
+        // Only define the saveAs option if the argument was actually set
+        if (saveAs !== undefined) {
+          options.saveAs = saveAs;
+        }
+        let id = await browser.downloads.download(options);
+        browser.downloads.onChanged.addListener(delta => {
+          if (delta.id == id && delta.state.current === "complete") {
+            browser.test.sendMessage("done", {ok: true, id});
+          }
+        });
+      } catch ({message}) {
+        browser.test.sendMessage("done", {ok: false, message});
+      }
+    });
+    browser.test.sendMessage("ready");
+  }
+
+  const manifest = {
+    background,
+    incognitoOverride: "spanning",
+    manifest: {permissions: ["downloads"]},
+  };
+  const extension = ExtensionTestUtils.loadExtension(manifest);
+
+  await extension.startup();
+  await extension.awaitMessage("ready");
+
+  // options should have the following properties:
+  //   saveAs (Boolean or undefined)
+  //   isPrivate (Boolean)
+  //   fileName (string)
+  //   expectedStartingDir (nsIFile)
+  //   destinationFile (nsIFile)
+  async function testExpectFilePicker(options) {
+    ok(!options.destinationFile.exists(), "the file should have been cleaned up properly previously");
+
+    MockFilePicker.showCallback = mockFilePickerCallback(
+      options.expectedStartingDir,
+      options.destinationFile
+    );
+    MockFilePicker.returnValue = MockFilePicker.returnOK;
+
+    extension.sendMessage(options.fileName, options.saveAs, options.isPrivate);
+    let result = await extension.awaitMessage("done");
+    ok(result.ok, `downloads.download() works with saveAs=${options.saveAs}`);
+
+    ok(options.destinationFile.exists(), "the file exists.");
+    is(options.destinationFile.fileSize, 12, "downloaded file is the correct size");
+    options.destinationFile.remove(false);
+    MockFilePicker.reset();
+
+    // Test the user canceling the save dialog.
+    MockFilePicker.returnValue = MockFilePicker.returnCancel;
+
+    extension.sendMessage(options.fileName, options.saveAs, options.isPrivate);
+    result = await extension.awaitMessage("done");
+
+    ok(!result.ok, "download rejected if the user cancels the dialog");
+    is(result.message, "Download canceled by the user", "with the correct message");
+    ok(!options.destinationFile.exists(), "file was not downloaded");
+    MockFilePicker.reset();
+  }
+
+  async function testNoFilePicker(saveAs) {
+    ok(!defaultFile.exists(), "the file should have been cleaned up properly previously");
+
+    extension.sendMessage(DOWNLOAD_FILENAME, saveAs, false);
+    let result = await extension.awaitMessage("done");
+    ok(result.ok, `downloads.download() works with saveAs=${saveAs}`);
+
+    ok(defaultFile.exists(), "the file exists.");
+    is(defaultFile.fileSize, 12, "downloaded file is the correct size");
+    defaultFile.remove(false);
+  }
+
+  info("Testing that saveAs=true uses the file picker as expected");
+  let expectedStartingDir = defaultDir;
+  let fpOptions = {
+    saveAs: true,
+    isPrivate: false,
+    fileName: DOWNLOAD_FILENAME,
+    expectedStartingDir: expectedStartingDir,
+    destinationFile: pickerFile,
+  };
+  await testExpectFilePicker(fpOptions);
+
+  info("Testing that saveas=true reuses last file picker directory");
+  fpOptions.expectedStartingDir = pickerDir;
+  await testExpectFilePicker(fpOptions);
+
+  info("Testing that saveAs=true in PB reuses last directory");
+  let nonPBStartingDir = fpOptions.expectedStartingDir;
+  fpOptions.isPrivate = true;
+  fpOptions.destinationFile = pbPickerFile;
+  await testExpectFilePicker(fpOptions);
+
+  info("Testing that saveAs=true in PB uses a separate last directory");
+  fpOptions.expectedStartingDir = pbPickerDir;
+  await testExpectFilePicker(fpOptions);
+
+  info("Testing that saveAs=true in Permanent PB mode ignores the incognito option");
+  await SpecialPowers.pushPrefEnv({
+    set: [["browser.privatebrowsing.autostart", true]],
+  });
+  fpOptions.isPrivate = false;
+  fpOptions.expectedStartingDir = pbPickerDir;
+  await testExpectFilePicker(fpOptions);
+
+  info("Testing that saveas=true reuses the non-PB last directory after private download");
+  await SpecialPowers.popPrefEnv();
+  fpOptions.isPrivate = false;
+  fpOptions.expectedStartingDir = nonPBStartingDir;
+  fpOptions.destinationFile = pickerFile;
+  await testExpectFilePicker(fpOptions);
+
+  info("Testing that saveAs=true does not reuse last directory when filename contains a path separator");
+  fpOptions.fileName = DEFAULT_SUBDIR + "/" + DOWNLOAD_FILENAME;
+  let destinationFile = defaultDir.clone();
+  destinationFile.append(DEFAULT_SUBDIR);
+  fpOptions.expectedStartingDir = destinationFile.clone();
+  destinationFile.append(DOWNLOAD_FILENAME);
+  fpOptions.destinationFile = destinationFile;
+  await testExpectFilePicker(fpOptions);
+
+  info("Testing that saveAs=false does not use the file picker");
+  fpOptions.saveAs = false;
+  await testNoFilePicker(fpOptions.saveAs);
+
+  // When saveAs is not set, the behavior should be determined by the Firefox
+  // pref that normally determines whether the "Save As" prompt should be
+  // displayed.
+  info(`Testing that the file picker is used when saveAs is not specified ` +
+       `but ${PROMPTLESS_DOWNLOAD_PREF} is disabled`);
+  fpOptions.saveAs = undefined;
+  await SpecialPowers.pushPrefEnv({"set": [
+    [PROMPTLESS_DOWNLOAD_PREF, false],
+  ]});
+  await testExpectFilePicker(fpOptions);
+
+  info(`Testing that the file picker is NOT used when saveAs is not ` +
+       `specified but ${PROMPTLESS_DOWNLOAD_PREF} is enabled`);
+  await SpecialPowers.popPrefEnv();
+  await SpecialPowers.pushPrefEnv({"set": [
+    [PROMPTLESS_DOWNLOAD_PREF, true],
+  ]});
+  await testNoFilePicker(fpOptions.saveAs);
+
+  await extension.unload();
+  MockFilePicker.cleanup();
+});
+
+</script>
+
+</body>
+</html>
diff --git a/toolkit/components/extensions/test/mochitest/test_chrome_ext_downloads_uniquify.html b/toolkit/components/extensions/test/mochitest/test_chrome_ext_downloads_uniquify.html
new file mode 100644
index 0000000000..b5fedee7ec
--- /dev/null
+++ b/toolkit/components/extensions/test/mochitest/test_chrome_ext_downloads_uniquify.html
@@ -0,0 +1,116 @@
+<!doctype html>
+<html>
+<head>
+  <title>Test downloads.download() uniquify option</title>
+  <script src="chrome://mochikit/content/tests/SimpleTest/SimpleTest.js"></script>
+  <script src="chrome://mochikit/content/tests/SimpleTest/ExtensionTestUtils.js"></script>
+  <script src="head.js"></script>
+  <link rel="stylesheet" href="chrome://mochikit/content/tests/SimpleTest/test.css"/>
+</head>
+<body>
+
+<script type="text/javascript">
+"use strict";
+
+const {FileUtils} = ChromeUtils.import("resource://gre/modules/FileUtils.jsm");
+
+let directory;
+
+add_task(async function setup() {
+  directory = FileUtils.getDir("TmpD", ["downloads"]);
+  directory.createUnique(Ci.nsIFile.DIRECTORY_TYPE, FileUtils.PERMS_DIRECTORY);
+  info(`Using download directory ${directory.path}`);
+
+  await SpecialPowers.pushPrefEnv({"set": [
+    ["browser.download.folderList", 2],
+    ["browser.download.dir", directory.path],
+  ]});
+
+  SimpleTest.registerCleanupFunction(async () => {
+    await SpecialPowers.popPrefEnv();
+    directory.remove(true);
+  });
+});
+
+add_task(async function test_downloads_uniquify() {
+  const file = directory.clone();
+  file.append("file_download.txt");
+
+  const unique = directory.clone();
+  unique.append("file_download(1).txt");
+
+  const {MockFilePicker} = SpecialPowers;
+  MockFilePicker.init(window);
+  MockFilePicker.returnValue = MockFilePicker.returnOK;
+
+  MockFilePicker.showCallback = fp => {
+    let file = directory.clone();
+    file.append(fp.defaultString);
+    MockFilePicker.setFiles([file]);
+  };
+
+  function background() {
+    const url = URL.createObjectURL(new Blob(["file content"]));
+    browser.test.onMessage.addListener(async (filename, saveAs) => {
+      try {
+        let id = await browser.downloads.download({
+          url,
+          filename,
+          saveAs,
+          conflictAction: "uniquify",
+        });
+        browser.downloads.onChanged.addListener(delta => {
+          if (delta.id == id && delta.state.current === "complete") {
+            browser.test.sendMessage("done", {ok: true, id});
+          }
+        });
+      } catch ({message}) {
+        browser.test.sendMessage("done", {ok: false, message});
+      }
+    });
+    browser.test.sendMessage("ready");
+  }
+
+  const manifest = {background, manifest: {permissions: ["downloads"]}};
+  const extension = ExtensionTestUtils.loadExtension(manifest);
+
+  await extension.startup();
+  await extension.awaitMessage("ready");
+
+  async function testUniquify(saveAs) {
+    info(`Testing conflictAction:"uniquify" with saveAs=${saveAs}`);
+
+    ok(!file.exists(), "downloaded file should have been cleaned up before test ran");
+    ok(!unique.exists(), "uniquified file should have been cleaned up before test ran");
+
+    // Test download without uniquify and create a conflicting file so we can
+    // test with uniquify.
+    extension.sendMessage("file_download.txt", saveAs);
+    let result = await extension.awaitMessage("done");
+    ok(result.ok, "downloads.download() works with saveAs");
+
+    ok(file.exists(), "the file exists.");
+    is(file.fileSize, 12, "downloaded file is the correct size");
+
+    // Now that a conflicting file exists, test the uniquify behavior
+    extension.sendMessage("file_download.txt", saveAs);
+    result = await extension.awaitMessage("done");
+    ok(result.ok, "downloads.download() works with saveAs and uniquify");
+
+    ok(unique.exists(), "the file exists.");
+    is(unique.fileSize, 12, "downloaded file is the correct size");
+
+    file.remove(false);
+    unique.remove(false);
+  }
+  await testUniquify(true);
+  await testUniquify(false);
+
+  await extension.unload();
+  MockFilePicker.cleanup();
+});
+
+</script>
+
+</body>
+</html>
diff --git a/toolkit/components/extensions/test/mochitest/test_chrome_ext_permissions.html b/toolkit/components/extensions/test/mochitest/test_chrome_ext_permissions.html
new file mode 100644
index 0000000000..65bf0a50d0
--- /dev/null
+++ b/toolkit/components/extensions/test/mochitest/test_chrome_ext_permissions.html
@@ -0,0 +1,172 @@
+<!DOCTYPE HTML>
+<html>
+<head>
+  <title>Test for permissions</title>
+  <script src="chrome://mochikit/content/tests/SimpleTest/SimpleTest.js"></script>
+  <script src="chrome://mochikit/content/tests/SimpleTest/EventUtils.js"></script>
+  <script src="chrome://mochikit/content/tests/SimpleTest/ExtensionTestUtils.js"></script>
+  <link rel="stylesheet" href="chrome://mochikit/content/tests/SimpleTest/test.css"/>
+</head>
+<body>
+
+<script type="text/javascript">
+"use strict";
+
+function makeTest(manifestPermissions, optionalPermissions, checkFetch = true) {
+  return async function() {
+    function pageScript() {
+      /* global PERMISSIONS */
+      browser.test.onMessage.addListener(async msg => {
+        if (msg == "set-cookie") {
+          try {
+            await browser.cookies.set({
+              url: "http://example.com/",
+              name: "COOKIE",
+              value: "NOM NOM",
+            });
+            browser.test.sendMessage("set-cookie.result", {success: true});
+          } catch (err) {
+            dump(`set cookie failed with ${err.message}\n`);
+            browser.test.sendMessage("set-cookie.result",
+                                     {success: false, message: err.message});
+          }
+        } else if (msg == "remove") {
+          browser.permissions.remove(PERMISSIONS).then(result => {
+            browser.test.sendMessage("remove.result", result);
+          });
+        } else if (msg == "request") {
+          browser.test.withHandlingUserInput(() => {
+            browser.permissions.request(PERMISSIONS).then(result => {
+              browser.test.sendMessage("request.result", result);
+            });
+          });
+        }
+      });
+
+      browser.test.sendMessage("page-ready");
+    }
+
+    let extension = ExtensionTestUtils.loadExtension({
+      background() {
+        browser.test.sendMessage("ready", browser.runtime.getURL("page.html"));
+      },
+
+      manifest: {
+        permissions: manifestPermissions,
+        optional_permissions: [...(optionalPermissions.permissions || []),
+                               ...(optionalPermissions.origins || [])],
+
+        content_scripts: [{
+          matches: ["http://mochi.test/*/file_sample.html"],
+          js: ["content_script.js"],
+        }],
+      },
+
+      files: {
+        "content_script.js": async () => {
+          let url = new URL(window.location.pathname, "http://example.com/");
+          fetch(url, {}).then(response => {
+            browser.test.sendMessage("fetch.result", response.ok);
+          }).catch(err => {
+            browser.test.sendMessage("fetch.result", false);
+          });
+        },
+
+        "page.html": `<html><head>
+          <script src="page.js"><\/script>
+        </head></html>`,
+
+        "page.js": `const PERMISSIONS = ${JSON.stringify(optionalPermissions)}; (${pageScript})();`,
+      },
+    });
+
+    await extension.startup();
+
+    function call(method) {
+      extension.sendMessage(method);
+      return extension.awaitMessage(`${method}.result`);
+    }
+
+    let base = window.location.href.replace(/^chrome:\/\/mochitests\/content/,
+                                            "http://mochi.test:8888");
+    let file = new URL("file_sample.html", base);
+
+    async function testContentScript() {
+      let win = window.open(file);
+      let result = await extension.awaitMessage("fetch.result");
+      win.close();
+      return result;
+    }
+
+    let url = await extension.awaitMessage("ready");
+    let win = window.open();
+    win.location.href = url;
+    await extension.awaitMessage("page-ready");
+
+    // Using the cookies API from an extension page should fail
+    let result = await call("set-cookie");
+    is(result.success, false, "setting cookie failed");
+    if (manifestPermissions.includes("cookies")) {
+      ok(/^Permission denied/.test(result.message),
+         "setting cookie failed with an appropriate error due to missing host permission");
+    } else {
+      ok(/browser\.cookies is undefined/.test(result.message),
+         "setting cookie failed since cookies API is not present");
+    }
+
+    // Making a cross-origin request from a content script should fail
+    if (checkFetch) {
+      result = await testContentScript();
+      is(result, false, "fetch() failed from content script due to lack of host permission");
+    }
+
+    result = await call("request");
+    is(result, true, "permissions.request() succeeded");
+
+    // Using the cookies API from an extension page should succeed
+    result = await call("set-cookie");
+    is(result.success, true, "setting cookie succeeded");
+
+    // Making a cross-origin request from a content script should succeed
+    if (checkFetch) {
+      result = await testContentScript();
+      is(result, true, "fetch() succeeded from content script due to lack of host permission");
+    }
+
+    // Now revoke our permissions
+    result = await call("remove");
+
+    // The cookies API should once again fail
+    result = await call("set-cookie");
+    is(result.success, false, "setting cookie failed");
+
+    // As should the cross-origin request from a content script
+    if (checkFetch) {
+      result = await testContentScript();
+      is(result, false, "fetch() failed from content script due to lack of host permission");
+    }
+
+    await extension.unload();
+  };
+}
+
+add_task(function setup() {
+  // Don't bother with prompts in this test.
+  return SpecialPowers.pushPrefEnv({
+    set: [["extensions.webextOptionalPermissionPrompts", false]],
+  });
+});
+
+const ORIGIN = "*://example.com/";
+add_task(makeTest([], {
+  permissions: ["cookies"],
+  origins: [ORIGIN],
+}));
+
+add_task(makeTest(["cookies"], {origins: [ORIGIN]}));
+add_task(makeTest([ORIGIN], {permissions: ["cookies"]}, false));
+
+</script>
+
+</body>
+</html>
diff --git a/toolkit/components/extensions/test/mochitest/test_chrome_ext_svg_context_fill.html b/toolkit/components/extensions/test/mochitest/test_chrome_ext_svg_context_fill.html
new file mode 100644
index 0000000000..3b022be5ec
--- /dev/null
+++ b/toolkit/components/extensions/test/mochitest/test_chrome_ext_svg_context_fill.html
@@ -0,0 +1,204 @@
+<!DOCTYPE HTML>
+<html>
+<head>
+  <title>Test for permissions</title>
+  <script src="chrome://mochikit/content/tests/SimpleTest/SimpleTest.js"></script>
+  <script src="chrome://mochikit/content/tests/SimpleTest/EventUtils.js"></script>
+  <script src="chrome://mochikit/content/tests/SimpleTest/ExtensionTestUtils.js"></script>
+  <link rel="stylesheet" href="chrome://mochikit/content/tests/SimpleTest/test.css"/>
+</head>
+<body>
+  <style>
+    img {
+      -moz-context-properties: fill;
+      fill: green;
+    }
+
+    img, div.ref {
+      width: 100px;
+      height: 100px;
+    }
+
+    div#green {
+      background: green;
+    }
+
+    div#red {
+      background: red;
+    }
+  </style>
+  <h3>Testing on: <span id="test-params"></span></h3>
+  <table>
+   <thead>
+     <tr>
+       <th>webext image</th>
+       <th>allowed ref</th>
+       <th>disallowed ref</th>
+    </tr>
+   </thead>
+   <tbody>
+     <tr>
+       <td>
+         <img id="actual">
+       </td>
+       <td>
+         <div id="green" class="ref"></div>
+       </td>
+       <td>
+         <div id="red" class="ref"></div>
+       </td>
+     </tr>
+   </tbody>
+  </table>
+
+<script type="text/javascript">
+"use strict";
+
+const { TestUtils } = SpecialPowers.ChromeUtils.import(
+  "resource://testing-common/TestUtils.jsm"
+);
+
+function screenshotPage(win, elementSelector) {
+  const el = win.document.querySelector(elementSelector);
+  return TestUtils.screenshotArea(el, win);
+}
+
+async function test_moz_extension_svg_context_fill({
+  addonId,
+  isPrivileged,
+  expectAllowed,
+}) {
+  // Include current test params in the rendered html page (to be included in failure
+  // screenshots).
+  document.querySelector("#test-params").textContent = JSON.stringify({
+    addonId,
+    isPrivileged,
+    expectAllowed,
+  });
+
+  let extDefinition = {
+    manifest: {
+      browser_specific_settings: { gecko: { id: addonId } },
+    },
+    background() {
+      browser.test.sendMessage("svg-url", browser.runtime.getURL("context-fill-fallback-red.svg"));
+    },
+    files: {
+      "context-fill-fallback-red.svg": `
+        <svg xmlns="http://www.w3.org/2000/svg" version="1.1"
+             xmlns:xlink="http://www.w3.org/1999/xlink">
+          <rect height="100%" width="100%" fill="context-fill red" />
+        </svg>
+      `,
+    },
+  }
+
+  if (isPrivileged) {
+    // isPrivileged is unused when useAddonManager is set (see ExtensionTestCommon.generate),
+    // the internal permission being tested is only added when the extension has a startupReason
+    // related to new installations and upgrades/downgrades and so the `startupReason` is set here
+    // to be able to mock the startupReason expected when useAddonManager can't be used.
+    extDefinition = {
+      ...extDefinition,
+      isPrivileged,
+      startupReason: "ADDON_INSTALL",
+    };
+  } else {
+    // useAddonManager temporary is instead used to explicitly test the other cases when the extension
+    // is not expected to be privileged.
+    extDefinition = {
+      ...extDefinition,
+      useAddonManager: "temporary",
+    };
+  }
+
+  const extension = ExtensionTestUtils.loadExtension(extDefinition);
+
+  await extension.startup();
+
+  // Set the extension url on the img element part of the
+  // comparison table defined in the html part of this test file.
+  const svgURL = await extension.awaitMessage("svg-url");
+  document.querySelector("#actual").src = svgURL;
+
+  let screenshots;
+
+  // Wait until the svg context fill has been applied
+  // (unfortunately waiting for a document reflow does
+  // not seem to be enough).
+  const expectedColor = expectAllowed ? "green" : "red";
+  await TestUtils.waitForCondition(
+    async () => {
+      const result = await screenshotPage(window, "#actual");
+      const reference = await screenshotPage(window, `#${expectedColor}`);
+      screenshots = {result, reference};
+      return result == reference;
+    },
+    `Context-fill should be ${
+      expectAllowed ? "allowed" : "disallowed"
+    } (resulting in ${expectedColor}) on "${addonId}" extension`
+  );
+
+  // At least an assertion is required to prevent the test from
+  // failing.
+  is(
+    screenshots.result,
+    screenshots.reference,
+    "svg context-fill test completed, result does match reference"
+  );
+
+  await extension.unload();
+}
+
+// This test file verify that the non-standard svg context-fill feature is allowed
+// on extensions svg files coming from Mozilla-owned extensions.
+//
+// NOTE: line extension permission to use context fill is tested in test_recommendations.js
+
+add_task(async function test_allowed_on_privileged_ext() {
+  await test_moz_extension_svg_context_fill({
+    addonId: "privileged-addon@mochi.test",
+    isPrivileged: true,
+    expectAllowed: true,
+  });
+});
+
+add_task(async function test_disallowed_on_non_privileged_ext() {
+  await test_moz_extension_svg_context_fill({
+    addonId: "non-privileged-arbitrary-addon-id@mochi.test",
+    isPrivileged: false,
+    expectAllowed: false,
+  });
+});
+
+add_task(async function test_allowed_on_privileged_ext_with_mozilla_id() {
+  await test_moz_extension_svg_context_fill({
+    addonId: "privileged-addon@mozilla.org",
+    isPrivileged: true,
+    expectAllowed: true,
+  });
+
+  await test_moz_extension_svg_context_fill({
+    addonId: "privileged-addon@mozilla.com",
+    isPrivileged: true,
+    expectAllowed: true,
+  });
+});
+
+add_task(async function test_allowed_on_non_privileged_ext_with_mozilla_id() {
+  await test_moz_extension_svg_context_fill({
+    addonId: "non-privileged-addon@mozilla.org",
+    isPrivileged: false,
+    expectAllowed: true,
+  });
+
+  await test_moz_extension_svg_context_fill({
+    addonId: "non-privileged-addon@mozilla.com",
+    isPrivileged: false,
+    expectAllowed: true,
+  });
+});
+</script>
+
+</body>
+</html>
diff --git a/toolkit/components/extensions/test/mochitest/test_chrome_ext_trackingprotection.html b/toolkit/components/extensions/test/mochitest/test_chrome_ext_trackingprotection.html
new file mode 100644
index 0000000000..580ea5e793
--- /dev/null
+++ b/toolkit/components/extensions/test/mochitest/test_chrome_ext_trackingprotection.html
@@ -0,0 +1,98 @@
+<!DOCTYPE HTML>
+<html>
+<head>
+  <title>Test for simple WebExtension</title>
+  <script src="chrome://mochikit/content/tests/SimpleTest/SimpleTest.js"></script>
+  <script src="chrome://mochikit/content/tests/SimpleTest/ExtensionTestUtils.js"></script>
+  <script type="text/javascript" src="head.js"></script>
+  <link rel="stylesheet" type="text/css" href="chrome://mochikit/content/tests/SimpleTest/test.css"/>
+</head>
+<body>
+
+<script type="text/javascript">
+"use strict";
+
+var {UrlClassifierTestUtils} = ChromeUtils.import("resource://testing-common/UrlClassifierTestUtils.jsm");
+
+function tp_background(expectFail = true) {
+  fetch("https://tracking.example.com/example.txt").then(() => {
+    browser.test.assertTrue(!expectFail, "fetch received");
+    browser.test.sendMessage("done");
+  }, () => {
+    browser.test.assertTrue(expectFail, "fetch failure");
+    browser.test.sendMessage("done");
+  });
+}
+
+async function test_permission(permissions, expectFail) {
+  let extension = ExtensionTestUtils.loadExtension({
+    manifest: {
+      permissions,
+    },
+    background: `(${tp_background})(${expectFail})`,
+  });
+
+  await extension.startup();
+  await extension.awaitMessage("done");
+  await extension.unload();
+}
+
+add_task(async function setup() {
+  await UrlClassifierTestUtils.addTestTrackers();
+  await SpecialPowers.pushPrefEnv({
+    set: [["privacy.trackingprotection.enabled", true]],
+  });
+});
+
+// Fetch would be blocked with these tests
+add_task(async function() { await test_permission([], true); });
+add_task(async function() { await test_permission(["http://*/"], true); });
+add_task(async function() { await test_permission(["http://*.example.com/"], true); });
+add_task(async function() { await test_permission(["http://localhost/*"], true); });
+// Fetch will not be blocked if the extension has host permissions.
+add_task(async function() { await test_permission(["<all_urls>"], false); });
+add_task(async function() { await test_permission(["*://tracking.example.com/*"], false); });
+
+add_task(async function test_contentscript() {
+  function contentScript() {
+    fetch("https://tracking.example.com/example.txt").then(() => {
+      browser.test.notifyPass("fetch received");
+    }, () => {
+      browser.test.notifyFail("fetch failure");
+    });
+  }
+
+  let extensionData = {
+    manifest: {
+      permissions: ["*://tracking.example.com/*"],
+      content_scripts: [
+        {
+          "matches": ["http://mochi.test/*/file_sample.html"],
+          "js": ["content_script.js"],
+          "run_at": "document_start",
+        },
+      ],
+    },
+
+    files: {
+      "content_script.js": contentScript,
+    },
+  };
+  const url = "http://mochi.test:8888/chrome/toolkit/components/extensions/test/mochitest/file_sample.html";
+
+  let extension = ExtensionTestUtils.loadExtension(extensionData);
+
+  await extension.startup();
+  let win = window.open(url);
+  await extension.awaitFinish();
+  win.close();
+  await extension.unload();
+});
+
+add_task(async function teardown() {
+  UrlClassifierTestUtils.cleanupTestTrackers();
+});
+</script>
+
+</body>
+</html>
diff --git a/toolkit/components/extensions/test/mochitest/test_chrome_ext_webnavigation_resolved_urls.html b/toolkit/components/extensions/test/mochitest/test_chrome_ext_webnavigation_resolved_urls.html
new file mode 100644
index 0000000000..7e876694a0
--- /dev/null
+++ b/toolkit/components/extensions/test/mochitest/test_chrome_ext_webnavigation_resolved_urls.html
@@ -0,0 +1,81 @@
+<!DOCTYPE HTML>
+<html>
+<head>
+  <title>Test for simple WebExtension</title>
+  <script src="chrome://mochikit/content/tests/SimpleTest/SimpleTest.js"></script>
+  <script src="chrome://mochikit/content/tests/SimpleTest/ExtensionTestUtils.js"></script>
+  <script type="text/javascript" src="head.js"></script>
+  <link rel="stylesheet" href="chrome://mochikit/content/tests/SimpleTest/test.css"/>
+</head>
+<body>
+
+<script type="text/javascript">
+"use strict";
+
+add_task(async function webnav_unresolved_uri_on_expected_URI_scheme() {
+  function background() {
+    let checkURLs;
+
+    browser.webNavigation.onCompleted.addListener(async msg => {
+      if (checkURLs.length) {
+        let expectedURL = checkURLs.shift();
+        browser.test.assertEq(expectedURL, msg.url, "Got the expected URL");
+        await browser.tabs.remove(msg.tabId);
+        browser.test.sendMessage("next");
+      }
+    });
+
+    browser.test.onMessage.addListener((name, urls) => {
+      if (name == "checkURLs") {
+        checkURLs = urls;
+      }
+    });
+
+    browser.test.sendMessage("ready", browser.runtime.getURL("/tab.html"));
+  }
+
+  let extensionData = {
+    manifest: {
+      permissions: [
+        "webNavigation",
+      ],
+    },
+    background,
+    files: {
+      "tab.html": `<!DOCTYPE html>
+        <html>
+          <head>
+           <meta charset="utf-8">
+          </head>
+        </html>
+      `,
+    },
+  };
+
+  let extension = ExtensionTestUtils.loadExtension(extensionData);
+
+  await extension.startup();
+
+  let checkURLs = [
+    "resource://gre/modules/XPCOMUtils.sys.mjs",
+    "chrome://mochikit/content/tests/SimpleTest/SimpleTest.js",
+    "about:mozilla",
+  ];
+
+  let tabURL = await extension.awaitMessage("ready");
+  checkURLs.push(tabURL);
+
+  extension.sendMessage("checkURLs", checkURLs);
+
+  for (let url of checkURLs) {
+    window.open(url);
+    await extension.awaitMessage("next");
+  }
+
+  await extension.unload();
+});
+
+</script>
+
+</body>
+</html>
diff --git a/toolkit/components/extensions/test/mochitest/test_chrome_ext_webrequest_background_events.html b/toolkit/components/extensions/test/mochitest/test_chrome_ext_webrequest_background_events.html
new file mode 100644
index 0000000000..a9dfb0a902
--- /dev/null
+++ b/toolkit/components/extensions/test/mochitest/test_chrome_ext_webrequest_background_events.html
@@ -0,0 +1,94 @@
+<!DOCTYPE HTML>
+<html>
+<head>
+  <title>Test for simple WebExtension</title>
+  <script src="chrome://mochikit/content/tests/SimpleTest/SimpleTest.js"></script>
+  <script src="chrome://mochikit/content/tests/SimpleTest/ExtensionTestUtils.js"></script>
+  <script type="text/javascript" src="head.js"></script>
+  <link rel="stylesheet" type="text/css" href="chrome://mochikit/content/tests/SimpleTest/test.css"/>
+</head>
+<body>
+
+<script type="text/javascript">
+"use strict";
+
+const {webrequest_test} = ChromeUtils.import(SimpleTest.getTestFileURL("webrequest_test.jsm"));
+let {testFetch, testXHR} = webrequest_test;
+
+// Here we test that any requests originating from a system principal are not
+// accessible through WebRequest.  text_ext_webrequest_background_events tests
+// non-system principal requests.
+
+let testExtension = {
+  manifest: {
+    permissions: [
+      "webRequest",
+      "<all_urls>",
+    ],
+  },
+  background() {
+    let eventNames = [
+      "onBeforeRequest",
+      "onBeforeSendHeaders",
+      "onSendHeaders",
+      "onHeadersReceived",
+      "onResponseStarted",
+      "onCompleted",
+    ];
+
+    function listener(name, details) {
+      // If we get anything, we failed.  Removing the system principal check
+      // in ext-webrequest triggers this failure.
+      browser.test.fail(`received ${name}`);
+    }
+
+    for (let name of eventNames) {
+      browser.webRequest[name].addListener(
+        listener.bind(null, name),
+        {urls: ["https://example.com/*"]}
+      );
+    }
+  },
+};
+
+add_task(async function test_webRequest_chromeworker_events() {
+  let extension = ExtensionTestUtils.loadExtension(testExtension);
+  await extension.startup();
+  await new Promise(resolve => {
+    let worker = new ChromeWorker("webrequest_chromeworker.js");
+    worker.onmessage = event => {
+      ok("chrome worker fetch finished");
+      resolve();
+    };
+    worker.postMessage("go");
+  });
+  await extension.unload();
+});
+
+add_task(async function test_webRequest_chromepage_events() {
+  let extension = ExtensionTestUtils.loadExtension(testExtension);
+  await extension.startup();
+  await new Promise(resolve => {
+    fetch("https://example.com/example.txt").then(() => {
+      ok("test page loaded");
+      resolve();
+    });
+  });
+  await extension.unload();
+});
+
+add_task(async function test_webRequest_jsm_events() {
+  let extension = ExtensionTestUtils.loadExtension(testExtension);
+  await extension.startup();
+  await testFetch("https://example.com/example.txt").then(() => {
+    ok("fetch page loaded");
+  });
+  await testXHR("https://example.com/example.txt").then(() => {
+    ok("xhr page loaded");
+  });
+  await extension.unload();
+});
+</script>
+
+</body>
+</html>
diff --git a/toolkit/components/extensions/test/mochitest/test_chrome_ext_webrequest_host_permissions.html b/toolkit/components/extensions/test/mochitest/test_chrome_ext_webrequest_host_permissions.html
new file mode 100644
index 0000000000..19c812f59f
--- /dev/null
+++ b/toolkit/components/extensions/test/mochitest/test_chrome_ext_webrequest_host_permissions.html
@@ -0,0 +1,89 @@
+<!doctype html>
+<html>
+<head>
+  <title>Test webRequest checks host permissions</title>
+  <script src="chrome://mochikit/content/tests/SimpleTest/SimpleTest.js"></script>
+  <script src="chrome://mochikit/content/tests/SimpleTest/ExtensionTestUtils.js"></script>
+  <script src="head.js"></script>
+  <link rel="stylesheet" href="chrome://mochikit/content/tests/SimpleTest/test.css"/>
+</head>
+<body>
+
+
+<script type="text/javascript">
+"use strict";
+
+add_task(async function test_webRequest_host_permissions() {
+  function background() {
+    function png(details) {
+      browser.test.sendMessage("png", details.url);
+    }
+    browser.webRequest.onBeforeRequest.addListener(png, {urls: ["*://*/*.png"]});
+    browser.test.sendMessage("ready");
+  }
+
+  const all = ExtensionTestUtils.loadExtension({background, manifest: {permissions: ["webRequest", "<all_urls>"]}});
+  const example = ExtensionTestUtils.loadExtension({background, manifest: {permissions: ["webRequest", "https://example.com/"]}});
+  const mochi_test = ExtensionTestUtils.loadExtension({background, manifest: {permissions: ["webRequest", "http://mochi.test/"]}});
+
+  await all.startup();
+  await example.startup();
+  await mochi_test.startup();
+
+  await all.awaitMessage("ready");
+  await example.awaitMessage("ready");
+  await mochi_test.awaitMessage("ready");
+
+  const win1 = window.open("https://example.com/chrome/toolkit/components/extensions/test/mochitest/file_with_images.html");
+  let urls = [await all.awaitMessage("png"),
+              await all.awaitMessage("png")];
+  ok(urls.some(url => url.endsWith("good.png")), "<all_urls> permission gets to see good.png");
+  ok((await example.awaitMessage("png")).endsWith("good.png"), "example permission sees same-origin example.com image");
+  ok(urls.some(url => url.endsWith("great.png")), "<all_urls> permission also sees great.png");
+
+  // Clear the in-memory image cache, it can prevent listeners from receiving events.
+  const imgTools = SpecialPowers.Cc["@mozilla.org/image/tools;1"].getService(SpecialPowers.Ci.imgITools);
+  imgTools.getImgCacheForDocument(win1.document).clearCache(false);
+  win1.close();
+
+  const win2 = window.open("http://mochi.test:8888/chrome/toolkit/components/extensions/test/mochitest/file_with_images.html");
+  urls = [await all.awaitMessage("png"),
+          await all.awaitMessage("png")];
+  ok(urls.some(url => url.endsWith("good.png")), "<all_urls> permission gets to see good.png");
+  ok((await mochi_test.awaitMessage("png")).endsWith("great.png"), "mochi.test permission sees same-origin mochi.test image");
+  ok(urls.some(url => url.endsWith("great.png")), "<all_urls> permission also sees great.png");
+  win2.close();
+
+  await all.unload();
+  await example.unload();
+  await mochi_test.unload();
+});
+
+add_task(async function test_webRequest_filter_permissions_warning() {
+  const manifest = {
+    permissions: ["webRequest", "http://example.com/"],
+  };
+
+  async function background() {
+    await browser.webRequest.onBeforeRequest.addListener(() => {}, {urls: ["http://example.org/"]});
+    browser.test.notifyPass();
+  }
+
+  const extension = ExtensionTestUtils.loadExtension({manifest, background});
+
+  const warning = new Promise(resolve => {
+    SimpleTest.monitorConsole(resolve, [{message: /filter doesn't overlap with host permissions/}]);
+  });
+
+  await extension.startup();
+  await extension.awaitFinish();
+
+  SimpleTest.endMonitorConsole();
+  await warning;
+
+  await extension.unload();
+});
+
+</script>
+</body>
+</html>
diff --git a/toolkit/components/extensions/test/mochitest/test_chrome_ext_webrequest_mozextension.html b/toolkit/components/extensions/test/mochitest/test_chrome_ext_webrequest_mozextension.html
new file mode 100644
index 0000000000..6a41b9cf08
--- /dev/null
+++ b/toolkit/components/extensions/test/mochitest/test_chrome_ext_webrequest_mozextension.html
@@ -0,0 +1,193 @@
+<!DOCTYPE HTML>
+<html>
+<head>
+  <title>Test moz-extension protocol use</title>
+  <script src="chrome://mochikit/content/tests/SimpleTest/SimpleTest.js"></script>
+  <script src="chrome://mochikit/content/tests/SimpleTest/ExtensionTestUtils.js"></script>
+  <script type="text/javascript" src="head.js"></script>
+  <link rel="stylesheet" type="text/css" href="chrome://mochikit/content/tests/SimpleTest/test.css"/>
+</head>
+<body>
+
+<script type="text/javascript">
+"use strict";
+
+let peakAchu;
+add_task(async function setup() {
+  peakAchu = ExtensionTestUtils.loadExtension({
+    manifest: {
+      permissions: [
+        "webRequest",
+        "<all_urls>",
+      ],
+    },
+    background() {
+      // ID for the extension in the tests.  Try to observe it to ensure we cannot.
+      browser.webRequest.onBeforeRequest.addListener(details => {
+        browser.test.notifyFail(`PeakAchu onBeforeRequest ${details.url}`);
+      }, {urls: ["<all_urls>", "moz-extension://*/*"]});
+
+      browser.test.onMessage.addListener((msg, extensionUrl) => {
+        browser.test.log(`spying for ${extensionUrl}`);
+        browser.webRequest.onBeforeRequest.addListener(details => {
+          browser.test.notifyFail(`PeakAchu onBeforeRequest ${details.url}`);
+        }, {urls: [extensionUrl]});
+      });
+    },
+  });
+  await peakAchu.startup();
+});
+
+add_task(async function test_webRequest_no_mozextension_permission() {
+  let extension = ExtensionTestUtils.loadExtension({
+    manifest: {
+      permissions: [
+        "webRequest",
+        "tabs",
+        "moz-extension://c9e007e0-e518-ed4c-8202-83849981dd21/*",
+        "moz-extension://*/*",
+      ],
+    },
+    background() {
+      browser.test.notifyPass("loaded");
+    },
+  });
+
+  let messages = [
+    {message: /processing permissions\.2: Value "moz-extension:\/\/c9e007e0-e518-ed4c-8202-83849981dd21\/\*"/},
+    {message: /processing permissions\.3: Value "moz-extension:\/\/\*\/\*"/},
+  ];
+
+  let waitForConsole = new Promise(resolve => {
+    SimpleTest.monitorConsole(resolve, messages);
+  });
+
+  await extension.startup();
+  await extension.awaitFinish("loaded");
+  await extension.unload();
+
+  SimpleTest.endMonitorConsole();
+  await waitForConsole;
+});
+
+add_task(async function test_webRequest_mozextension_fetch() {
+  function background() {
+    let page = browser.runtime.getURL("fetched.html");
+    browser.webRequest.onBeforeRequest.addListener(details => {
+      browser.test.assertEq(details.url, page, "got correct url in onBeforeRequest");
+      browser.test.sendMessage("request-started");
+    }, {urls: [browser.runtime.getURL("*")]}, ["blocking"]);
+    browser.webRequest.onCompleted.addListener(details => {
+      browser.test.assertEq(details.url, page, "got correct url in onCompleted");
+      browser.test.sendMessage("request-complete");
+    }, {urls: [browser.runtime.getURL("*")]});
+
+    browser.test.onMessage.addListener((msg, data) => {
+      fetch(page).then(() => {
+        browser.test.notifyPass("fetch success");
+        browser.test.sendMessage("done");
+      }, () => {
+        browser.test.fail("fetch failed");
+        browser.test.sendMessage("done");
+      });
+    });
+    browser.test.sendMessage("extensionUrl", browser.runtime.getURL("*"));
+  }
+
+  // Use webrequest to monitor moz-extension:// requests
+  let extension = ExtensionTestUtils.loadExtension({
+    manifest: {
+      permissions: [
+        "webRequest",
+        "webRequestBlocking",
+        "tabs",
+        "<all_urls>",
+      ],
+    },
+    files: {
+      "fetched.html": `
+        <!DOCTYPE html>
+        <html>
+          <head>
+            <meta charset="utf-8">
+          </head>
+          <body>
+            <h1>moz-extension file</h1>
+          </body>
+        </html>
+      `.trim(),
+    },
+    background,
+  });
+
+  await extension.startup();
+  // send the url for this extension to the monitoring extension
+  peakAchu.sendMessage("extensionUrl", await extension.awaitMessage("extensionUrl"));
+
+  extension.sendMessage("testFetch");
+  await extension.awaitMessage("request-started");
+  await extension.awaitMessage("request-complete");
+  await extension.awaitMessage("done");
+
+  await extension.unload();
+});
+
+add_task(async function test_webRequest_mozextension_tab_query() {
+  function background() {
+    browser.test.sendMessage("extensionUrl", browser.runtime.getURL("*"));
+    let page = browser.runtime.getURL("tab.html");
+
+    async function onUpdated(tabId, tabInfo, tab) {
+      if (tabInfo.status !== "complete") {
+        return;
+      }
+      browser.test.log(`tab created ${tabId} ${JSON.stringify(tabInfo)} ${tab.url}`);
+      let tabs = await browser.tabs.query({url: browser.runtime.getURL("*")});
+      browser.test.assertEq(1, tabs.length, "got one tab");
+      browser.test.assertEq(tabs.length && tabs[0].id, tab.id, "got the correct tab");
+      browser.test.assertEq(tabs.length && tabs[0].url, page, "got correct url in tab");
+      browser.tabs.remove(tabId);
+      browser.tabs.onUpdated.removeListener(onUpdated);
+      browser.test.sendMessage("tabs-done");
+    }
+    browser.tabs.onUpdated.addListener(onUpdated);
+    browser.tabs.create({url: page});
+  }
+
+  let extension = ExtensionTestUtils.loadExtension({
+    manifest: {
+      permissions: [
+        "webRequest",
+        "tabs",
+        "<all_urls>",
+      ],
+    },
+    files: {
+      "tab.html": `
+        <!DOCTYPE html>
+        <html>
+          <head>
+            <meta charset="utf-8">
+          </head>
+          <body>
+            <h1>moz-extension file</h1>
+          </body>
+        </html>
+      `.trim(),
+    },
+    background,
+  });
+
+  await extension.startup();
+  peakAchu.sendMessage("extensionUrl", await extension.awaitMessage("extensionUrl"));
+  await extension.awaitMessage("tabs-done");
+  await extension.unload();
+});
+
+add_task(async function teardown() {
+  await peakAchu.unload();
+});
+</script>
+
+</body>
+</html>
diff --git a/toolkit/components/extensions/test/mochitest/test_chrome_native_messaging_paths.html b/toolkit/components/extensions/test/mochitest/test_chrome_native_messaging_paths.html
new file mode 100644
index 0000000000..c29b6286d9
--- /dev/null
+++ b/toolkit/components/extensions/test/mochitest/test_chrome_native_messaging_paths.html
@@ -0,0 +1,58 @@
+<!DOCTYPE HTML>
+<html>
+<head>
+  <title>WebExtension test</title>
+  <script src="chrome://mochikit/content/tests/SimpleTest/SimpleTest.js"></script>
+  <script src="chrome://mochikit/content/tests/SimpleTest/ExtensionTestUtils.js"></script>
+  <script type="text/javascript" src="head.js"></script>
+  <link rel="stylesheet" href="chrome://mochikit/content/tests/SimpleTest/test.css"/>
+</head>
+<body>
+
+<script type="text/javascript">
+"use strict";
+
+// Test that the default paths searched for native host manifests
+// are the ones we expect.
+add_task(async function test_default_paths() {
+  let expectUser, expectGlobal;
+  switch (AppConstants.platform) {
+    case "macosx": {
+      expectUser = PathUtils.joinRelative(
+        Services.dirsvc.get("Home", Ci.nsIFile).path,
+        "Library/Application Support/Mozilla"
+      );
+      expectGlobal = "/Library/Application Support/Mozilla";
+
+      break;
+    }
+
+    case "linux": {
+      expectUser = PathUtils.join(
+        Services.dirsvc.get("Home", Ci.nsIFile).path,
+        ".mozilla"
+      );
+
+      const libdir = AppConstants.HAVE_USR_LIB64_DIR ? "lib64" : "lib";
+      expectGlobal = PathUtils.join("/usr", libdir, "mozilla");
+      break;
+    }
+
+    default:
+      // Fixed filesystem paths are only defined for MacOS and Linux,
+      // there's nothing to test on other platforms.
+      ok(false, `This test does not apply on ${AppConstants.platform}`);
+      break;
+  }
+
+  let userDir = Services.dirsvc.get("XREUserNativeManifests", Ci.nsIFile).path;
+  is(userDir, expectUser, "user-specific native messaging directory is correct");
+
+  let globalDir = Services.dirsvc.get("XRESysNativeManifests", Ci.nsIFile).path;
+  is(globalDir, expectGlobal, "system-wide native messaing directory is correct");
+});
+
+</script>
+
+</body>
+</html>
diff --git a/toolkit/components/extensions/test/mochitest/test_ext_action.html b/toolkit/components/extensions/test/mochitest/test_ext_action.html
new file mode 100644
index 0000000000..1899475723
--- /dev/null
+++ b/toolkit/components/extensions/test/mochitest/test_ext_action.html
@@ -0,0 +1,51 @@
+<!DOCTYPE HTML>
+<html>
+<head>
+  <meta charset="utf-8">
+  <title>Action with MV3</title>
+  <script type="text/javascript" src="/tests/SimpleTest/SimpleTest.js"></script>
+  <script type="text/javascript" src="/tests/SimpleTest/ExtensionTestUtils.js"></script>
+  <script type="text/javascript" src="head.js"></script>
+  <link rel="stylesheet" type="text/css" href="/tests/SimpleTest/test.css">
+</head>
+<body>
+
+<script type="text/javascript">
+"use strict";
+
+
+add_task(async function setup() {
+  await SpecialPowers.pushPrefEnv({
+    set: [["extensions.manifestV3.enabled", true]],
+  });
+});
+
+add_task(async function test_action_onClicked() {
+  const extension = ExtensionTestUtils.loadExtension({
+    manifest: {
+      manifest_version: 3,
+      action: {},
+    },
+    background() {
+      browser.action.onClicked.addListener(async () => {
+        browser.test.notifyPass("action-clicked");
+      });
+
+      browser.test.sendMessage("background-ready");
+    },
+  });
+
+  await extension.startup();
+  await extension.awaitMessage("background-ready");
+
+  await AppTestDelegate.clickBrowserAction(window, extension);
+  await extension.awaitFinish("action-clicked");
+  await AppTestDelegate.closeBrowserAction(window, extension);
+
+  await extension.unload();
+});
+
+</script>
+
+</body>
+</html>
diff --git a/toolkit/components/extensions/test/mochitest/test_ext_activityLog.html b/toolkit/components/extensions/test/mochitest/test_ext_activityLog.html
new file mode 100644
index 0000000000..c426913373
--- /dev/null
+++ b/toolkit/components/extensions/test/mochitest/test_ext_activityLog.html
@@ -0,0 +1,390 @@
+<!DOCTYPE HTML>
+<html>
+<head>
+  <title>WebExtension activityLog test</title>
+  <script src="/tests/SimpleTest/SimpleTest.js"></script>
+  <script src="/tests/SimpleTest/ExtensionTestUtils.js"></script>
+  <script type="text/javascript" src="head.js"></script>
+  <link rel="stylesheet" type="text/css" href="/tests/SimpleTest/test.css"/>
+</head>
+<body>
+
+<script type="text/javascript">
+"use strict";
+
+add_task(async function test_api() {
+  let URL =
+    "http://mochi.test:8888/tests/toolkit/components/extensions/test/mochitest/file_sample.html";
+
+  // Test that an unspecified extension is not logged by the watcher extension.
+  let unlogged = ExtensionTestUtils.loadExtension({
+    isPrivileged: true,
+    manifest: {
+      browser_specific_settings: { gecko: { id: "unlogged@tests.mozilla.org" } },
+      permissions: ["webRequest", "webRequestBlocking", "<all_urls>"],
+    },
+    background() {
+      // This privileged test extension should not affect the webRequest
+      // data received by non-privileged extensions (See Bug 1576272).
+      browser.webRequest.onBeforeRequest.addListener(
+        details => {
+          return { cancel: false };
+        },
+        { urls: ["http://mochi.test/*/file_sample.html"] },
+        ["blocking"]
+      );
+    },
+  });
+  await unlogged.startup();
+
+  let extension = ExtensionTestUtils.loadExtension({
+    manifest: {
+      browser_specific_settings: { gecko: { id: "watched@tests.mozilla.org" } },
+      permissions: [
+        "tabs",
+        "tabHide",
+        "storage",
+        "webRequest",
+        "webRequestBlocking",
+        "<all_urls>",
+      ],
+      content_scripts: [
+        {
+          matches: ["http://mochi.test/*/file_sample.html"],
+          js: ["content_script.js"],
+          run_at: "document_idle",
+        },
+      ],
+    },
+    files: {
+      "content_script.js": () => {
+        browser.test.sendMessage("content_script");
+      },
+      "registered_script.js": () => {
+        browser.test.sendMessage("registered_script");
+      },
+    },
+    async background() {
+      let listen = () => {};
+      async function runTest() {
+        // Test activity for a child function call.
+        browser.test.assertEq(
+          undefined,
+          browser.activityLog,
+          "activityLog requires permission"
+        );
+
+        // Test a child event manager.
+        browser.storage.onChanged.addListener(listen);
+        browser.storage.onChanged.removeListener(listen);
+
+        // Test a parent event manager.
+        let webRequestListener = details => {
+          browser.webRequest.onBeforeRequest.removeListener(webRequestListener);
+          return { cancel: false };
+        };
+        browser.webRequest.onBeforeRequest.addListener(
+          webRequestListener,
+          { urls: ["http://mochi.test/*/file_sample.html"] },
+          ["blocking"]
+        );
+
+        // A manifest based content script is already
+        // registered, we do a dynamic registration here.
+        await browser.contentScripts.register({
+          js: [{ file: "registered_script.js" }],
+          matches: ["http://mochi.test/*/file_sample.html"],
+          runAt: "document_start",
+        });
+        browser.test.sendMessage("ready");
+      }
+      browser.test.onMessage.addListener((msg, data) => {
+        // Logging has started here so this listener is logged, but the
+        // call adding it was not.  We do an additional onMessage.addListener
+        // call in the test function to validate child based event managers.
+        if (msg == "runtest") {
+          browser.test.assertTrue(true, msg);
+          runTest();
+        }
+        if (msg == "hideTab") {
+          browser.tabs.hide(data);
+        }
+      });
+      browser.test.sendMessage("url", browser.runtime.getURL(""));
+    },
+  });
+
+  async function backgroundScript(expectedUrl, extensionUrl) {
+    let expecting = [
+      // Test child-only api_call.
+      {
+        type: "api_call",
+        name: "test.assertTrue",
+        data: { args: [true, "runtest"] },
+      },
+
+      // Test child-only api_call.
+      {
+        type: "api_call",
+        name: "test.assertEq",
+        data: {
+          args: [undefined, undefined, "activityLog requires permission"],
+        },
+      },
+      // Test child addListener calls.
+      {
+        type: "api_call",
+        name: "storage.onChanged.addListener",
+        data: {
+          args: [],
+        },
+      },
+      {
+        type: "api_call",
+        name: "storage.onChanged.removeListener",
+        data: {
+          args: [],
+        },
+      },
+      // Test parent addListener calls.
+      {
+        type: "api_call",
+        name: "webRequest.onBeforeRequest.addListener",
+        data: {
+          args: [
+            {
+              incognito: null,
+              tabId: null,
+              types: null,
+              urls: ["http://mochi.test/*/file_sample.html"],
+              windowId: null,
+            },
+            ["blocking"],
+          ],
+        },
+      },
+      // Test an api that makes use of callParentAsyncFunction.
+      {
+        type: "api_call",
+        name: "contentScripts.register",
+        data: {
+          args: [
+            {
+              allFrames: null,
+              css: null,
+              excludeGlobs: null,
+              excludeMatches: null,
+              includeGlobs: null,
+              js: [
+                {
+                  file: `${extensionUrl}registered_script.js`,
+                },
+              ],
+              matchAboutBlank: null,
+              matches: ["http://mochi.test/*/file_sample.html"],
+              runAt: "document_start",
+            },
+          ],
+        },
+      },
+      // Test child api_event calls.
+      {
+        type: "api_event",
+        name: "test.onMessage",
+        data: { args: ["runtest"] },
+      },
+      {
+        type: "api_call",
+        name: "test.sendMessage",
+        data: { args: ["ready"] },
+      },
+      // Test parent api_event calls.
+      {
+        type: "api_call",
+        name: "webRequest.onBeforeRequest.removeListener",
+        data: {
+          args: [],
+        },
+      },
+      {
+        type: "api_event",
+        name: "webRequest.onBeforeRequest",
+        data: {
+          args: [
+            {
+              url: expectedUrl,
+              method: "GET",
+              type: "main_frame",
+              frameId: 0,
+              parentFrameId: -1,
+              incognito: false,
+              thirdParty: false,
+              ip: null,
+              frameAncestors: [],
+              urlClassification: { firstParty: [], thirdParty: [] },
+              requestSize: 0,
+              responseSize: 0,
+            },
+          ],
+          result: {
+            cancel: false,
+          },
+        },
+      },
+      // Test manifest based content script.
+      {
+        type: "content_script",
+        name: "content_script.js",
+        data: { url: expectedUrl, tabId: 1 },
+      },
+      // registered script test
+      {
+        type: "content_script",
+        name: `${extensionUrl}registered_script.js`,
+        data: { url: expectedUrl, tabId: 1 },
+      },
+      {
+        type: "api_call",
+        name: "test.sendMessage",
+        data: { args: ["registered_script"], tabId: 1 },
+      },
+      {
+        type: "api_call",
+        name: "test.sendMessage",
+        data: { args: ["content_script"], tabId: 1 },
+      },
+      // Child api call
+      {
+        type: "api_call",
+        name: "tabs.hide",
+        data: { args: ["__TAB_ID"] },
+      },
+      {
+        type: "api_event",
+        name: "test.onMessage",
+        data: { args: ["hideTab", "__TAB_ID"] },
+      },
+    ];
+    browser.test.assertTrue(browser.activityLog, "activityLog is privileged");
+
+    // Slightly less than a normal deep equal, we want to know that the values
+    // in our expected data are the same in the actual data, but we don't care
+    // if actual data has additional data or if data is in the same order in objects.
+    // This allows us to ignore keys that may be variable, or that are set in
+    // the api with an undefined value.
+    function deepEquivalent(a, b) {
+      if (a === b) {
+        return true;
+      }
+      if (
+        typeof a != "object" ||
+        typeof b != "object" ||
+        a === null ||
+        b === null
+      ) {
+        return false;
+      }
+      for (let k in a) {
+        if (!deepEquivalent(a[k], b[k])) {
+          return false;
+        }
+      }
+      return true;
+    }
+
+    let tab;
+    let handler = async details => {
+      browser.test.log(`onExtensionActivity ${JSON.stringify(details)}`);
+      let test = expecting.shift();
+      if (!test) {
+        browser.test.notifyFail(`no test for ${details.name}`);
+      }
+
+      // On multiple runs, tabId will be different.  Set the current
+      // tabId where we need it.
+      if (test.data.tabId !== undefined) {
+        test.data.tabId = tab.id;
+      }
+      if (test.data.args !== undefined) {
+        test.data.args = test.data.args.map(value =>
+          value === "__TAB_ID" ? tab.id : value
+        );
+      }
+
+      browser.test.assertEq(test.type, details.type, "type matches");
+      if (test.type == "content_script") {
+        browser.test.assertTrue(
+          details.name.includes(test.name),
+          "content script name matches"
+        );
+      } else {
+        browser.test.assertEq(test.name, details.name, "name matches");
+      }
+
+      browser.test.assertTrue(
+        deepEquivalent(test.data, details.data),
+        `expected ${JSON.stringify(
+          test.data
+        )} included in actual ${JSON.stringify(details.data)}`
+      );
+      if (!expecting.length) {
+        await browser.tabs.remove(tab.id);
+        browser.test.notifyPass("activity");
+      }
+    };
+    browser.activityLog.onExtensionActivity.addListener(
+      handler,
+      "watched@tests.mozilla.org"
+    );
+
+    browser.test.onMessage.addListener(async msg => {
+      if (msg === "opentab") {
+        tab = await browser.tabs.create({ url: expectedUrl });
+        browser.test.sendMessage("tabid", tab.id);
+      }
+      if (msg === "done") {
+        browser.activityLog.onExtensionActivity.removeListener(
+          handler,
+          "watched@tests.mozilla.org"
+        );
+      }
+    });
+  }
+
+  await extension.startup();
+  let extensionUrl = await extension.awaitMessage("url");
+
+  let logger = ExtensionTestUtils.loadExtension({
+    isPrivileged: true,
+    manifest: {
+      browser_specific_settings: { gecko: { id: "watcher@tests.mozilla.org" } },
+      permissions: ["activityLog"],
+    },
+    background: `(${backgroundScript})("${URL}", "${extensionUrl}")`,
+  });
+  await logger.startup();
+  extension.sendMessage("runtest");
+  await extension.awaitMessage("ready");
+  logger.sendMessage("opentab");
+  let id = await logger.awaitMessage("tabid");
+
+  await Promise.all([
+    extension.awaitMessage("content_script"),
+    extension.awaitMessage("registered_script"),
+  ]);
+
+  extension.sendMessage("hideTab", id);
+  await logger.awaitFinish("activity");
+
+  // Stop watching because we get extra calls on extension shutdown
+  // such as listener removal.
+  logger.sendMessage("done");
+
+  await extension.unload();
+  await unlogged.unload();
+  await logger.unload();
+});
+</script>
+
+</body>
+</html>
diff --git a/toolkit/components/extensions/test/mochitest/test_ext_all_apis.js b/toolkit/components/extensions/test/mochitest/test_ext_all_apis.js
new file mode 100644
index 0000000000..4c82a4575c
--- /dev/null
+++ b/toolkit/components/extensions/test/mochitest/test_ext_all_apis.js
@@ -0,0 +1,245 @@
+/* -*- Mode: indent-tabs-mode: nil; js-indent-level: 2 -*- */
+/* vim: set sts=2 sw=2 et tw=80: */
+"use strict";
+
+// Tests whether not too many APIs are visible by default.
+// This file is used by test_ext_all_apis.html in browser/ and mobile/android/,
+// which may modify the following variables to add or remove expected APIs.
+/* globals expectedContentApisTargetSpecific */
+/* globals expectedBackgroundApisTargetSpecific */
+
+// Generates a list of expectations.
+function generateExpectations(list) {
+  return list
+    .reduce((allApis, path) => {
+      return allApis.concat(`browser.${path}`, `chrome.${path}`);
+    }, [])
+    .sort();
+}
+
+let expectedCommonApis = [
+  "extension.getURL",
+  "extension.inIncognitoContext",
+  "extension.lastError",
+  "i18n.detectLanguage",
+  "i18n.getAcceptLanguages",
+  "i18n.getMessage",
+  "i18n.getUILanguage",
+  "runtime.OnInstalledReason",
+  "runtime.OnRestartRequiredReason",
+  "runtime.PlatformArch",
+  "runtime.PlatformOs",
+  "runtime.RequestUpdateCheckStatus",
+  "runtime.getManifest",
+  "runtime.connect",
+  "runtime.getFrameId",
+  "runtime.getURL",
+  "runtime.id",
+  "runtime.lastError",
+  "runtime.onConnect",
+  "runtime.onMessage",
+  "runtime.sendMessage",
+  // browser.test is only available in xpcshell or when
+  // Cu.isInAutomation is true.
+  "test.assertDeepEq",
+  "test.assertEq",
+  "test.assertFalse",
+  "test.assertRejects",
+  "test.assertThrows",
+  "test.assertTrue",
+  "test.fail",
+  "test.log",
+  "test.notifyFail",
+  "test.notifyPass",
+  "test.onMessage",
+  "test.sendMessage",
+  "test.succeed",
+  "test.withHandlingUserInput",
+];
+
+let expectedContentApis = [
+  ...expectedCommonApis,
+  ...expectedContentApisTargetSpecific,
+];
+
+let expectedBackgroundApis = [
+  ...expectedCommonApis,
+  ...expectedBackgroundApisTargetSpecific,
+  "contentScripts.register",
+  "experiments.APIChildScope",
+  "experiments.APIEvent",
+  "experiments.APIParentScope",
+  "extension.ViewType",
+  "extension.getBackgroundPage",
+  "extension.getViews",
+  "extension.isAllowedFileSchemeAccess",
+  "extension.isAllowedIncognitoAccess",
+  // Note: extensionTypes is not visible in Chrome.
+  "extensionTypes.CSSOrigin",
+  "extensionTypes.ImageFormat",
+  "extensionTypes.RunAt",
+  "management.ExtensionDisabledReason",
+  "management.ExtensionInstallType",
+  "management.ExtensionType",
+  "management.getSelf",
+  "management.uninstallSelf",
+  "permissions.getAll",
+  "permissions.contains",
+  "permissions.request",
+  "permissions.remove",
+  "permissions.onAdded",
+  "permissions.onRemoved",
+  "runtime.getBackgroundPage",
+  "runtime.getBrowserInfo",
+  "runtime.getPlatformInfo",
+  "runtime.onConnectExternal",
+  "runtime.onInstalled",
+  "runtime.onMessageExternal",
+  "runtime.onStartup",
+  "runtime.onSuspend",
+  "runtime.onSuspendCanceled",
+  "runtime.onUpdateAvailable",
+  "runtime.openOptionsPage",
+  "runtime.reload",
+  "runtime.setUninstallURL",
+  "theme.getCurrent",
+  "theme.onUpdated",
+  "types.LevelOfControl",
+  "types.SettingScope",
+];
+
+// APIs that are exposed to MV2 by default, but not to MV3.
+const mv2onlyBackgroundApis = new Set([
+  "extension.getURL",
+  "extension.lastError",
+  "contentScripts.register",
+  "tabs.executeScript",
+  "tabs.insertCSS",
+  "tabs.removeCSS",
+]);
+let expectedBackgroundApisMV3 = expectedBackgroundApis.filter(
+  path => !mv2onlyBackgroundApis.has(path)
+);
+
+function sendAllApis() {
+  function isEvent(key, val) {
+    if (!/^on[A-Z]/.test(key)) {
+      return false;
+    }
+    let eventKeys = [];
+    for (let prop in val) {
+      eventKeys.push(prop);
+    }
+    eventKeys = eventKeys.sort().join();
+    return eventKeys === "addListener,hasListener,removeListener";
+  }
+  // Some items are removed from the namespaces in the lazy getters after the first get.  This
+  // in one case, the events namespace, leaves a namespace that is empty.  Make sure we don't
+  // consider those as a part of our testing.
+  function isEmptyObject(val) {
+    return val !== null && typeof val == "object" && !Object.keys(val).length;
+  }
+  function mayRecurse(key, val) {
+    if (Object.keys(val).filter(k => !/^[A-Z\-0-9_]+$/.test(k)).length === 0) {
+      // Don't recurse on constants and empty objects.
+      return false;
+    }
+    return !isEvent(key, val);
+  }
+
+  let results = [];
+  function diveDeeper(path, obj) {
+    for (const [key, val] of Object.entries(obj)) {
+      if (typeof val == "object" && val !== null && mayRecurse(key, val)) {
+        diveDeeper(`${path}.${key}`, val);
+      } else if (val !== undefined && !isEmptyObject(val)) {
+        results.push(`${path}.${key}`);
+      }
+    }
+  }
+  diveDeeper("browser", browser);
+  diveDeeper("chrome", chrome);
+  browser.test.sendMessage("allApis", results.sort());
+  browser.test.sendMessage("namespaces", browser === chrome);
+}
+
+add_task(async function setup() {
+  // This test enumerates all APIs and may access a deprecated API. Just log a
+  // warning instead of throwing.
+  await ExtensionTestUtils.failOnSchemaWarnings(false);
+});
+
+add_task(async function test_enumerate_content_script_apis() {
+  let extensionData = {
+    manifest: {
+      content_scripts: [
+        {
+          matches: ["http://mochi.test/*/file_sample.html"],
+          js: ["contentscript.js"],
+          run_at: "document_start",
+        },
+      ],
+    },
+    files: {
+      "contentscript.js": sendAllApis,
+    },
+  };
+  let extension = ExtensionTestUtils.loadExtension(extensionData);
+  await extension.startup();
+
+  let win = window.open("file_sample.html");
+  let actualApis = await extension.awaitMessage("allApis");
+  win.close();
+  let expectedApis = generateExpectations(expectedContentApis);
+  isDeeply(actualApis, expectedApis, "content script APIs");
+
+  let sameness = await extension.awaitMessage("namespaces");
+  ok(sameness, "namespaces are same object");
+
+  await extension.unload();
+});
+
+add_task(async function test_enumerate_background_script_apis() {
+  let extensionData = {
+    background: sendAllApis,
+  };
+  let extension = ExtensionTestUtils.loadExtension(extensionData);
+  await extension.startup();
+
+  let actualApis = await extension.awaitMessage("allApis");
+  let expectedApis = generateExpectations(expectedBackgroundApis);
+  isDeeply(actualApis, expectedApis, "background script APIs");
+
+  let sameness = await extension.awaitMessage("namespaces");
+  ok(!sameness, "namespaces are different objects");
+
+  await extension.unload();
+});
+
+add_task(async function test_enumerate_background_script_apis_mv3() {
+  await SpecialPowers.pushPrefEnv({
+    set: [["extensions.manifestV3.enabled", true]],
+  });
+  let extensionData = {
+    background: sendAllApis,
+    manifest: {
+      manifest_version: 3,
+
+      // Features that expose APIs in MV2, but should not do anything with MV3.
+      browser_action: {},
+      user_scripts: {},
+    },
+  };
+  let extension = ExtensionTestUtils.loadExtension(extensionData);
+  await extension.startup();
+
+  let actualApis = await extension.awaitMessage("allApis");
+  let expectedApis = generateExpectations(expectedBackgroundApisMV3);
+  isDeeply(actualApis, expectedApis, "background script APIs in MV3");
+
+  let sameness = await extension.awaitMessage("namespaces");
+  ok(sameness, "namespaces are same object");
+
+  await extension.unload();
+  await SpecialPowers.popPrefEnv();
+});
diff --git a/toolkit/components/extensions/test/mochitest/test_ext_async_clipboard.html b/toolkit/components/extensions/test/mochitest/test_ext_async_clipboard.html
new file mode 100644
index 0000000000..458dc65d99
--- /dev/null
+++ b/toolkit/components/extensions/test/mochitest/test_ext_async_clipboard.html
@@ -0,0 +1,401 @@
+<!DOCTYPE HTML>
+<html>
+<head>
+  <title>Async Clipboard permissions tests</title>
+  <script src="/tests/SimpleTest/SimpleTest.js"></script>
+  <script src="/tests/SimpleTest/ExtensionTestUtils.js"></script>
+  <script src="head.js"></script>
+  <link rel="stylesheet" href="/tests/SimpleTest/test.css">
+</head>
+<body>
+
+<script>
+"use strict";
+
+// Bug 1479956 - On android-debug verify this test times out
+SimpleTest.requestLongerTimeout(2);
+
+/* globals ClipboardItem, clipboardWriteText, clipboardWrite, clipboardReadText, clipboardRead */
+function shared() {
+  this.clipboardWriteText = function(txt) {
+    return navigator.clipboard.writeText(txt);
+  };
+
+  this.clipboardWrite = function(items) {
+    return navigator.clipboard.write(items);
+  };
+
+  this.clipboardReadText = function() {
+    return navigator.clipboard.readText();
+  };
+
+  this.clipboardRead = function() {
+    return navigator.clipboard.read();
+  };
+}
+
+/**
+ * Clear the clipboard.
+ *
+ * This is needed because Services.clipboard.emptyClipboard() does not clear the actual system clipboard.
+ */
+function clearClipboard() {
+  if (AppConstants.platform == "android") {
+    // On android, this clears the actual system clipboard
+    SpecialPowers.Services.clipboard.emptyClipboard(SpecialPowers.Services.clipboard.kGlobalClipboard);
+    return;
+  }
+  // Need to do this hack on other platforms to clear the actual system clipboard
+  let transf = SpecialPowers.Cc["@mozilla.org/widget/transferable;1"]
+    .createInstance(SpecialPowers.Ci.nsITransferable);
+  transf.init(null);
+  // Empty transferables may cause crashes, so just add an unknown type.
+  const TYPE = "text/x-moz-place-empty";
+  transf.addDataFlavor(TYPE);
+  transf.setTransferData(TYPE, {});
+  SpecialPowers.Services.clipboard.setData(transf, null, SpecialPowers.Services.clipboard.kGlobalClipboard);
+}
+
+add_task(async function setup() {
+  await SpecialPowers.pushPrefEnv({"set": [
+    ["dom.events.asyncClipboard.clipboardItem", true],
+  ]});
+});
+
+// Test that without enough permissions, we are NOT allowed to use writeText, write, read or readText in background script
+add_task(async function test_background_async_clipboard_no_permissions() {
+  function backgroundScript() {
+    const item = new ClipboardItem({
+      "text/plain": new Blob(["HI"], {type: "text/plain"})
+    });
+    browser.test.assertRejects(
+      clipboardRead(),
+      (err) => err === undefined,
+      "Read should be denied without permission"
+    );
+    browser.test.assertRejects(
+      clipboardWrite([item]),
+      "Clipboard write was blocked due to lack of user activation.",
+      "Write should be denied without permission"
+    );
+    browser.test.assertRejects(
+      clipboardWriteText("blabla"),
+      "Clipboard write was blocked due to lack of user activation.",
+      "WriteText should be denied without permission"
+    );
+    browser.test.assertRejects(
+      clipboardReadText(),
+      (err) => err === undefined,
+      "ReadText should be denied without permission"
+    );
+    browser.test.sendMessage("ready");
+  }
+  let extensionData = {
+    background: [shared, backgroundScript],
+  };
+  let extension = ExtensionTestUtils.loadExtension(extensionData);
+  await extension.startup();
+  await extension.awaitMessage("ready");
+  await extension.unload();
+});
+
+// Test that without enough permissions, we are NOT allowed to use writeText, write, read or readText in content script
+add_task(async function test_contentscript_async_clipboard_no_permission() {
+  function contentScript() {
+    const item = new ClipboardItem({
+      "text/plain": new Blob(["HI"], {type: "text/plain"})
+    });
+    browser.test.assertRejects(
+      clipboardRead(),
+      (err) => err === undefined,
+      "Read should be denied without permission"
+    );
+    browser.test.assertRejects(
+      clipboardWrite([item]),
+      "Clipboard write was blocked due to lack of user activation.",
+      "Write should be denied without permission"
+    );
+    browser.test.assertRejects(
+      clipboardWriteText("blabla"),
+      "Clipboard write was blocked due to lack of user activation.",
+      "WriteText should be denied without permission"
+    );
+    browser.test.assertRejects(
+      clipboardReadText(),
+      (err) => err === undefined,
+      "ReadText should be denied without permission"
+    );
+    browser.test.sendMessage("ready");
+  }
+  let extensionData = {
+    manifest: {
+      content_scripts: [{
+        js: ["shared.js", "contentscript.js"],
+        matches: ["https://example.com/*/file_sample.html"],
+      }],
+    },
+    files: {
+      "shared.js": shared,
+      "contentscript.js": contentScript,
+    },
+  };
+  let extension = ExtensionTestUtils.loadExtension(extensionData);
+  await extension.startup();
+  let win = window.open("https://example.com/tests/toolkit/components/extensions/test/mochitest/file_sample.html");
+  await extension.awaitMessage("ready");
+  win.close();
+  await extension.unload();
+});
+
+// Test that with enough permissions, we are allowed to use writeText  in content script
+add_task(async function test_contentscript_clipboard_permission_writetext() {
+  function contentScript() {
+    let str = "HI";
+    clipboardWriteText(str).then(function() {
+      // nothing here
+      browser.test.sendMessage("ready");
+    }, function(err) {
+      browser.test.fail("WriteText promise rejected");
+      browser.test.sendMessage("ready");
+    }); // clipboardWriteText
+  }
+  let extensionData = {
+    manifest: {
+      content_scripts: [{
+        js: ["shared.js", "contentscript.js"],
+        matches: ["https://example.com/*/file_sample.html"],
+      }],
+      permissions: [
+        "clipboardWrite",
+        "clipboardRead",
+      ],
+    },
+    files: {
+      "shared.js": shared,
+      "contentscript.js": contentScript,
+    },
+  };
+  let extension = ExtensionTestUtils.loadExtension(extensionData);
+  await extension.startup();
+  let win = window.open("https://example.com/tests/toolkit/components/extensions/test/mochitest/file_sample.html");
+  await extension.awaitMessage("ready");
+  const actual = SpecialPowers.getClipboardData("text/plain");
+  is(actual, "HI", "right string copied by write");
+  win.close();
+  await extension.unload();
+});
+
+// Test that with enough permissions, we are allowed to use readText in content script
+add_task(async function test_contentscript_clipboard_permission_readtext() {
+  function contentScript() {
+    let str = "HI";
+    clipboardReadText().then(function(strData) {
+      if (strData == str) {
+        browser.test.succeed("Successfully read from clipboard");
+      } else {
+        browser.test.fail("ReadText read the wrong thing from clipboard:" + strData);
+      }
+      browser.test.sendMessage("ready");
+    }, function(err) {
+      browser.test.fail("ReadText promise rejected");
+      browser.test.sendMessage("ready");
+    }); // clipboardReadText
+  }
+  let extensionData = {
+    manifest: {
+      content_scripts: [{
+        js: ["shared.js", "contentscript.js"],
+        matches: ["https://example.com/*/file_sample.html"],
+      }],
+      permissions: [
+        "clipboardWrite",
+        "clipboardRead",
+      ],
+    },
+    files: {
+      "shared.js": shared,
+      "contentscript.js": contentScript,
+    },
+  };
+  await SimpleTest.promiseClipboardChange("HI", () => {
+    SpecialPowers.clipboardCopyString("HI");
+  }, "text/plain");
+  let extension = ExtensionTestUtils.loadExtension(extensionData);
+  await extension.startup();
+  let win = window.open("https://example.com/tests/toolkit/components/extensions/test/mochitest/file_sample.html");
+  await extension.awaitMessage("ready");
+  win.close();
+  await extension.unload();
+});
+
+// Test that with enough permissions, we are allowed to use write in content script
+add_task(async function test_contentscript_clipboard_permission_write() {
+  function contentScript() {
+    const item = new ClipboardItem({
+      "text/plain": new Blob(["HI"], {type: "text/plain"})
+    });
+    clipboardWrite([item]).then(function() {
+      // nothing here
+      browser.test.sendMessage("ready");
+    }, function(err) { // clipboardWrite promise error function
+      browser.test.fail("Write promise rejected");
+      browser.test.sendMessage("ready");
+    }); // clipboard write
+  }
+  let extensionData = {
+    manifest: {
+      content_scripts: [{
+        js: ["shared.js", "contentscript.js"],
+        matches: ["https://example.com/*/file_sample.html"],
+      }],
+      permissions: [
+        "clipboardWrite",
+        "clipboardRead",
+      ],
+    },
+    files: {
+      "shared.js": shared,
+      "contentscript.js": contentScript,
+    },
+  };
+  let extension = ExtensionTestUtils.loadExtension(extensionData);
+  await extension.startup();
+  let win = window.open("https://example.com/tests/toolkit/components/extensions/test/mochitest/file_sample.html");
+  await extension.awaitMessage("ready");
+  const actual = SpecialPowers.getClipboardData("text/plain");
+  is(actual, "HI", "right string copied by write");
+  win.close();
+  await extension.unload();
+});
+
+// Test that with enough permissions, we are allowed to use read in content script
+add_task(async function test_contentscript_clipboard_permission_read() {
+  function contentScript() {
+    clipboardRead().then(async function(items) {
+      let blob = await items[0].getType("text/plain");
+      let s = await blob.text();
+      if (s == "HELLO") {
+        browser.test.succeed("Read promise successfully read the right thing");
+      } else {
+        browser.test.fail("Read read the wrong string from clipboard:" + s);
+      }
+      browser.test.sendMessage("ready");
+    }, function(err) { // clipboardRead promise error function
+      browser.test.fail("Read promise rejected");
+      browser.test.sendMessage("ready");
+    }); // clipboard read
+  }
+  let extensionData = {
+    manifest: {
+      content_scripts: [{
+        js: ["shared.js", "contentscript.js"],
+        matches: ["https://example.com/*/file_sample.html"],
+      }],
+      permissions: [
+        "clipboardWrite",
+        "clipboardRead",
+      ],
+    },
+    files: {
+      "shared.js": shared,
+      "contentscript.js": contentScript,
+    },
+  };
+  await SimpleTest.promiseClipboardChange("HELLO", () => {
+    SpecialPowers.clipboardCopyString("HELLO");
+  }, "text/plain");
+  let extension = ExtensionTestUtils.loadExtension(extensionData);
+  await extension.startup();
+  let win = window.open("https://example.com/tests/toolkit/components/extensions/test/mochitest/file_sample.html");
+  await extension.awaitMessage("ready");
+  win.close();
+  await extension.unload();
+});
+
+// Test that performing readText(...) when the clipboard is empty returns an empty string
+add_task(async function test_contentscript_clipboard_nocontents_readtext() {
+  function contentScript() {
+    clipboardReadText().then(function(strData) {
+      if (strData == "") {
+        browser.test.succeed("ReadText successfully read correct thing from an empty clipboard");
+      } else {
+        browser.test.fail("ReadText should have read an empty string, but read:" + strData);
+      }
+      browser.test.sendMessage("ready");
+    }, function(err) {
+      browser.test.fail("ReadText promise rejected: " + err);
+      browser.test.sendMessage("ready");
+    });
+  }
+  let extensionData = {
+    manifest: {
+      content_scripts: [{
+        js: ["shared.js", "contentscript.js"],
+        matches: ["https://example.com/*/file_sample.html"],
+      }],
+      permissions: [
+        "clipboardRead",
+      ],
+    },
+    files: {
+      "shared.js": shared,
+      "contentscript.js": contentScript,
+    },
+  };
+
+  await SimpleTest.promiseClipboardChange("", () => {
+    clearClipboard();
+  }, "text/x-moz-place-empty");
+  let extension = ExtensionTestUtils.loadExtension(extensionData);
+  await extension.startup();
+  let win = window.open("https://example.com/tests/toolkit/components/extensions/test/mochitest/file_sample.html");
+  await extension.awaitMessage("ready");
+  win.close();
+  await extension.unload();
+});
+
+// Test that performing read(...) when the clipboard is empty returns an empty ClipboardItem
+add_task(async function test_contentscript_clipboard_nocontents_read() {
+  function contentScript() {
+    clipboardRead().then(function(items) {
+      if (items[0].types.length) {
+        browser.test.fail("Read read the wrong thing from clipboard, " +
+          "ClipboardItem has this many entries: " + items[0].types.length);
+      } else {
+        browser.test.succeed("Read promise successfully resolved");
+      }
+      browser.test.sendMessage("ready");
+    }, function(err) {
+      browser.test.fail("Read promise rejected: " + err);
+      browser.test.sendMessage("ready");
+    });
+  }
+  let extensionData = {
+    manifest: {
+      content_scripts: [{
+        js: ["shared.js", "contentscript.js"],
+        matches: ["https://example.com/*/file_sample.html"],
+      }],
+      permissions: [
+        "clipboardRead",
+      ],
+    },
+    files: {
+      "shared.js": shared,
+      "contentscript.js": contentScript,
+    },
+  };
+
+  await SimpleTest.promiseClipboardChange("", () => {
+    clearClipboard();
+  }, "text/x-moz-place-empty");
+  let extension = ExtensionTestUtils.loadExtension(extensionData);
+  await extension.startup();
+  let win = window.open("https://example.com/tests/toolkit/components/extensions/test/mochitest/file_sample.html");
+  await extension.awaitMessage("ready");
+  win.close();
+  await extension.unload();
+});
+</script>
+</body>
+</html>
diff --git a/toolkit/components/extensions/test/mochitest/test_ext_background_canvas.html b/toolkit/components/extensions/test/mochitest/test_ext_background_canvas.html
new file mode 100644
index 0000000000..e7745f08c5
--- /dev/null
+++ b/toolkit/components/extensions/test/mochitest/test_ext_background_canvas.html
@@ -0,0 +1,42 @@
+<!DOCTYPE HTML>
+<html>
+<head>
+  <title>Test for background page canvas rendering</title>
+  <script src="/tests/SimpleTest/SimpleTest.js"></script>
+  <script src="/tests/SimpleTest/ExtensionTestUtils.js"></script>
+  <script type="text/javascript" src="head.js"></script>
+  <link rel="stylesheet" type="text/css" href="/tests/SimpleTest/test.css"/>
+</head>
+<body>
+
+<script type="text/javascript">
+"use strict";
+
+add_task(async function test_background_canvas() {
+  function background() {
+    try {
+      let canvas = document.createElement("canvas");
+
+      let context = canvas.getContext("2d");
+
+      // This ensures that we have a working PresShell, and can successfully
+      // calculate font metrics.
+      context.font = "8pt fixed";
+
+      browser.test.notifyPass("background-canvas");
+    } catch (e) {
+      browser.test.fail(`Error: ${e} :: ${e.stack}`);
+      browser.test.notifyFail("background-canvas");
+    }
+  }
+
+  let extension = ExtensionTestUtils.loadExtension({ background });
+
+  await extension.startup();
+  await extension.awaitFinish("background-canvas");
+  await extension.unload();
+});
+</script>
+
+</body>
+</html>
diff --git a/toolkit/components/extensions/test/mochitest/test_ext_background_page.html b/toolkit/components/extensions/test/mochitest/test_ext_background_page.html
new file mode 100644
index 0000000000..2f4fe3b96c
--- /dev/null
+++ b/toolkit/components/extensions/test/mochitest/test_ext_background_page.html
@@ -0,0 +1,84 @@
+<!DOCTYPE HTML>
+<html>
+  <head>
+    <title>WebExtension test</title>
+    <meta charset="utf-8">
+    <script src="/tests/SimpleTest/SimpleTest.js"></script>
+    <script src="/tests/SimpleTest/ExtensionTestUtils.js"></script>
+    <script src="head.js" type="text/javascript"></script>
+    <link href="/tests/SimpleTest/test.css" rel="stylesheet"/>
+  </head>
+  <body>
+
+    <script type="text/javascript">
+      "use strict";
+
+      /* eslint-disable mozilla/balanced-listeners */
+
+      add_task(async function testAlertNotShownInBackgroundWindow() {
+        let extension = ExtensionTestUtils.loadExtension({
+          background: function () {
+            alert("I am an alert in the background.");
+
+            browser.test.notifyPass("alertCalled");
+          }
+        });
+
+        let consoleOpened = loadChromeScript(() => {
+          const {sendAsyncMessage, assert} = this;
+          assert.ok(!Services.wm.getEnumerator("alert:alert").hasMoreElements(), "Alerts should not be present at the start of the test.");
+
+          Services.obs.addObserver(function observer() {
+            sendAsyncMessage("web-console-created");
+            Services.obs.removeObserver(observer, "web-console-created");
+          }, "web-console-created");
+        });
+        let opened = consoleOpened.promiseOneMessage("web-console-created");
+
+        consoleMonitor.start([
+          {
+            message: /alert\(\) is not supported in background windows/
+          }, {
+            message: /I am an alert in the background/
+          }
+        ]);
+
+        await extension.startup();
+        await extension.awaitFinish("alertCalled");
+
+        let chromeScript = loadChromeScript(async () => {
+          const {assert} = this;
+          assert.ok(!Services.wm.getEnumerator("alert:alert").hasMoreElements(), "Alerts should not be present after calling alert().");
+        });
+        chromeScript.destroy();
+
+        await consoleMonitor.finished();
+
+        await opened;
+        consoleOpened.destroy();
+
+        chromeScript = loadChromeScript(async () => {
+          const {sendAsyncMessage} = this;
+          let {require} = ChromeUtils.importESModule("resource://devtools/shared/loader/Loader.sys.mjs");
+          require("devtools/client/framework/devtools-browser");
+          let {BrowserConsoleManager} = require("devtools/client/webconsole/browser-console-manager");
+
+          // And then double check that we have an actual browser console.
+          let haveConsole = !!BrowserConsoleManager.getBrowserConsole();
+
+          if (haveConsole) {
+            await BrowserConsoleManager.toggleBrowserConsole();
+          }
+          sendAsyncMessage("done", haveConsole);
+        });
+
+        let consoleShown = await chromeScript.promiseOneMessage("done");
+        ok(consoleShown, "console was shown");
+        chromeScript.destroy();
+
+        await extension.unload();
+      });
+    </script>
+
+  </body>
+</html>
diff --git a/toolkit/components/extensions/test/mochitest/test_ext_background_page_dpi.html b/toolkit/components/extensions/test/mochitest/test_ext_background_page_dpi.html
new file mode 100644
index 0000000000..40772402b1
--- /dev/null
+++ b/toolkit/components/extensions/test/mochitest/test_ext_background_page_dpi.html
@@ -0,0 +1,46 @@
+<!DOCTYPE HTML>
+<meta charset="utf-8">
+<title>DPI of background page</title>
+<script src="/tests/SimpleTest/SimpleTest.js"></script>
+<script src="/tests/SimpleTest/ExtensionTestUtils.js"></script>
+<script src="head.js"></script>
+<link rel="stylesheet" href="/tests/SimpleTest/test.css">
+<script>
+"use strict";
+
+async function testDPIMatches(description) {
+  let extension = ExtensionTestUtils.loadExtension({
+    background: function() {
+      browser.test.sendMessage("dpi", window.devicePixelRatio);
+    },
+  });
+  await extension.startup();
+  let dpi = await extension.awaitMessage("dpi");
+  await extension.unload();
+
+  // This assumes that the window is loaded in a device DPI.
+  is(
+    dpi,
+    window.devicePixelRatio,
+    `DPI in a background page should match DPI in primary chrome page ${description}`
+  );
+}
+
+add_task(async function test_dpi_simple() {
+  await testDPIMatches("by default");
+});
+
+add_task(async function test_dpi_devPixelsPerPx() {
+  await SpecialPowers.pushPrefEnv({
+    set: [["layout.css.devPixelsPerPx", 1.5]],
+  });
+  await testDPIMatches("with devPixelsPerPx");
+  await SpecialPowers.popPrefEnv();
+});
+
+add_task(async function test_dpi_os_zoom() {
+  await SpecialPowers.pushPrefEnv({ set: [["ui.textScaleFactor", 200]] });
+  await testDPIMatches("with OS zoom");
+  await SpecialPowers.popPrefEnv();
+});
+</script>
diff --git a/toolkit/components/extensions/test/mochitest/test_ext_browserAction_openPopup.html b/toolkit/components/extensions/test/mochitest/test_ext_browserAction_openPopup.html
new file mode 100644
index 0000000000..0d038da897
--- /dev/null
+++ b/toolkit/components/extensions/test/mochitest/test_ext_browserAction_openPopup.html
@@ -0,0 +1,183 @@
+<!DOCTYPE HTML>
+<html>
+<head>
+  <title>action.openPopup Test</title>
+  <script type="text/javascript" src="/tests/SimpleTest/SimpleTest.js"></script>
+  <script type="text/javascript" src="/tests/SimpleTest/ExtensionTestUtils.js"></script>
+  <script type="text/javascript" src="head.js"></script>
+  <link rel="stylesheet" href="/tests/SimpleTest/test.css"/>
+</head>
+<body>
+
+<script type="text/javascript">
+"use strict";
+
+let extensionData = {
+  manifest: {
+    browser_specific_settings: {
+      gecko: {
+        id: "open-popup@tests.mozilla.org",
+      }
+    },
+    browser_action: {
+      default_popup: "popup.html",
+    },
+    permissions: ["activeTab"]
+  },
+
+  useAddonManager: "android-only",
+};
+
+add_task(async function setup() {
+  await SpecialPowers.pushPrefEnv({
+    "set": [
+      ["extensions.openPopupWithoutUserGesture.enabled", true],
+    ],
+  });
+});
+
+async function testActiveTabPermissions(withHandlingUserInput) {
+  const background = async function(withHandlingUserInput) {
+    let tabPromise;
+    let tabLoadedPromise = new Promise(resolve => {
+      // Wait for the tab to actually finish loading (bug 1589734)
+      browser.tabs.onUpdated.addListener(async (id, { status }) => {
+        if (id === (await tabPromise).id && status === "complete") {
+          resolve();
+        }
+      });
+    });
+    tabPromise = browser.tabs.create({ url: "https://www.example.com" });
+    tabLoadedPromise.then(() => {
+      // Once the popup opens, check if we have activeTab permission
+      browser.runtime.onMessage.addListener(async msg => {
+        if (msg === "popup-open") {
+          let tabs = await browser.tabs.query({});
+
+          browser.test.assertEq(
+            withHandlingUserInput ? 1 : 0,
+            tabs.filter((t) => typeof t.url !== "undefined").length,
+            "active tab permission only granted with user input"
+          );
+
+          await browser.tabs.remove((await tabPromise).id);
+          browser.test.sendMessage("activeTabsChecked");
+        }
+      });
+
+      if (withHandlingUserInput) {
+        browser.test.withHandlingUserInput(() => {
+          browser.browserAction.openPopup();
+        });
+      } else {
+        browser.browserAction.openPopup();
+      }
+    })
+  };
+
+  let extension = ExtensionTestUtils.loadExtension({
+    ...extensionData,
+
+    background: `(${background})(${withHandlingUserInput})`,
+
+    files: {
+      "popup.html": `<!DOCTYPE html><meta charset="utf-8"><script src="popup.js"><\/script>`,
+      async "popup.js"() {
+        browser.runtime.sendMessage("popup-open");
+      },
+    },
+  });
+
+  await extension.startup();
+  await extension.awaitMessage("activeTabsChecked");
+  await extension.unload();
+}
+
+add_task(async function test_browserAction_openPopup_activeTab() {
+  await testActiveTabPermissions(true);
+});
+
+add_task(async function test_browserAction_openPopup_non_activeTab() {
+  await testActiveTabPermissions(false);
+});
+
+add_task(async function test_browserAction_openPopup_invalid_states() {
+  let extension = ExtensionTestUtils.loadExtension({
+    ...extensionData,
+
+    background: async function() {
+      await browser.browserAction.setPopup({ popup: "" })
+      await browser.test.assertRejects(
+        browser.browserAction.openPopup(),
+        "No popup URL is set",
+        "Should throw when no URL is set"
+      );
+
+      await browser.browserAction.disable()
+      await browser.test.assertRejects(
+        browser.browserAction.openPopup(),
+        "Popup is disabled",
+        "Should throw when disabled"
+      );
+
+      browser.test.notifyPass("invalidStates");
+    },
+  });
+
+  await extension.startup();
+  await extension.awaitFinish("invalidStates");
+  await extension.unload();
+});
+
+add_task(async function test_browserAction_openPopup_no_click_event() {
+  let extension = ExtensionTestUtils.loadExtension({
+    ...extensionData,
+
+    background: async function() {
+      let clicks = 0;
+
+      browser.browserAction.onClicked.addListener(() => {
+        clicks++;
+      });
+
+      // Test with popup set
+      await browser.browserAction.openPopup();
+      browser.test.sendMessage("close-popup");
+
+      browser.test.onMessage.addListener(async (msg) => {
+        if (msg === "popup-closed") {
+          // Test without popup
+          await browser.browserAction.setPopup({ popup: "" });
+
+          await browser.test.assertRejects(
+            browser.browserAction.openPopup(),
+            "No popup URL is set",
+            "Should throw when no URL is set"
+          );
+
+          // We expect the last call to be a no-op, so there isn't really anything
+          // to wait on. Instead, check that no clicks are registered after waiting
+          // for a sufficient amount of time.
+          // eslint-disable-next-line mozilla/no-arbitrary-setTimeout
+          setTimeout(() => {
+            browser.test.assertEq(0, clicks, "onClicked should not be called");
+            browser.test.notifyPass("noClick");
+          }, 1000);
+        }
+      });
+    },
+  });
+
+  extension.onMessage("close-popup", async () => {
+    await AppTestDelegate.closeBrowserAction(window, extension);
+    extension.sendMessage("popup-closed");
+  });
+
+  await extension.startup();
+  await extension.awaitFinish("noClick");
+  await extension.unload();
+});
+</script>
+
+</body>
+</html>
diff --git a/toolkit/components/extensions/test/mochitest/test_ext_browserAction_openPopup_incognito_window.html b/toolkit/components/extensions/test/mochitest/test_ext_browserAction_openPopup_incognito_window.html
new file mode 100644
index 0000000000..8036d97398
--- /dev/null
+++ b/toolkit/components/extensions/test/mochitest/test_ext_browserAction_openPopup_incognito_window.html
@@ -0,0 +1,151 @@
+<!DOCTYPE HTML>
+<html>
+<head>
+  <title>action.openPopup Incognito Test</title>
+  <script type="text/javascript" src="/tests/SimpleTest/SimpleTest.js"></script>
+  <script type="text/javascript" src="/tests/SimpleTest/ExtensionTestUtils.js"></script>
+  <script type="text/javascript" src="head.js"></script>
+  <link rel="stylesheet" href="/tests/SimpleTest/test.css"/>
+</head>
+<body>
+
+<script type="text/javascript">
+"use strict";
+
+let extensionData = {
+  manifest: {
+    browser_specific_settings: {
+      gecko: {
+        id: "open-popup@tests.mozilla.org",
+      }
+    },
+    browser_action: {
+      default_popup: "popup.html",
+    },
+    permissions: ["activeTab"]
+  },
+
+  useAddonManager: "android-only",
+};
+
+add_task(async function setup() {
+  await SpecialPowers.pushPrefEnv({
+    "set": [
+      ["extensions.openPopupWithoutUserGesture.enabled", true],
+    ],
+  });
+});
+
+async function getIncognitoWindow() {
+  // Since events will be limited based on incognito, we need a
+  // spanning extension to get the tab id so we can test access failure.
+
+  let windowWatcher = ExtensionTestUtils.loadExtension({
+    manifest: {
+      permissions: ["tabs"],
+    },
+    background: function() {
+      browser.windows.create({ incognito: true }).then(({ id: windowId }) => {
+        browser.test.onMessage.addListener(async data => {
+          if (data === "close") {
+            await browser.windows.remove(windowId);
+            browser.test.sendMessage("window-closed");
+          }
+        });
+
+        browser.test.sendMessage("window-id", windowId);
+      });
+    },
+    incognitoOverride: "spanning",
+  });
+
+  await windowWatcher.startup();
+  let windowId = await windowWatcher.awaitMessage("window-id");
+
+  return {
+    windowId,
+    close: async () => {
+      windowWatcher.sendMessage("close");
+      await windowWatcher.awaitMessage("window-closed");
+      await windowWatcher.unload();
+    },
+  };
+}
+
+async function testWithIncognitoOverride(incognitoOverride) {
+  let extension = ExtensionTestUtils.loadExtension({
+    ...extensionData,
+
+    incognitoOverride,
+
+    background: async function() {
+      browser.test.onMessage.addListener(async ({ windowId, incognitoOverride }) => {
+        const openPromise = browser.browserAction.openPopup({ windowId });
+
+        if (incognitoOverride === "not_allowed") {
+          await browser.test.assertRejects(
+            openPromise,
+            /Invalid window ID/,
+            "Should prevent open popup call for incognito window"
+          );
+        } else {
+          try {
+            browser.test.assertEq(await openPromise, undefined, "openPopup resolved");
+          } catch (e) {
+            browser.test.fail(`Unexpected error: ${e}`);
+          }
+        }
+
+        browser.test.sendMessage("incognitoWindow");
+      });
+    },
+
+    files: {
+      "popup.html": `<!DOCTYPE html><meta charset="utf-8"><script src="popup.js"><\/script>`,
+      "popup.js"() {
+        browser.test.sendMessage("popup");
+      },
+    },
+  });
+
+  await extension.startup();
+
+  let incognitoWindow = await getIncognitoWindow();
+  await extension.sendMessage({ windowId: incognitoWindow.windowId, incognitoOverride });
+
+  await extension.awaitMessage("incognitoWindow");
+
+  // Wait for the popup to open - bug 1800100
+  if (incognitoOverride === "spanning") {
+    await extension.awaitMessage("popup");
+  }
+
+  await extension.unload();
+
+  await incognitoWindow.close();
+}
+
+add_task(async function test_browserAction_openPopup_incognito_window_spanning() {
+  if (AppConstants.platform == "android") {
+    // TODO bug 1372178: Cannot open private windows from an extension.
+    todo(false, "Cannot open private windows on Android");
+    return;
+  }
+
+  await testWithIncognitoOverride("spanning");
+});
+
+add_task(async function test_browserAction_openPopup_incognito_window_not_allowed() {
+  if (AppConstants.platform == "android") {
+    // TODO bug 1372178: Cannot open private windows from an extension.
+    todo(false, "Cannot open private windows on Android");
+    return;
+  }
+
+
+  await testWithIncognitoOverride("not_allowed");
+});
+</script>
+
+</body>
+</html>
diff --git a/toolkit/components/extensions/test/mochitest/test_ext_browserAction_openPopup_windowId.html b/toolkit/components/extensions/test/mochitest/test_ext_browserAction_openPopup_windowId.html
new file mode 100644
index 0000000000..c528028901
--- /dev/null
+++ b/toolkit/components/extensions/test/mochitest/test_ext_browserAction_openPopup_windowId.html
@@ -0,0 +1,162 @@
+<!DOCTYPE HTML>
+<html>
+<head>
+  <title>action.openPopup Window ID Test</title>
+  <script type="text/javascript" src="/tests/SimpleTest/SimpleTest.js"></script>
+  <script type="text/javascript" src="/tests/SimpleTest/ExtensionTestUtils.js"></script>
+  <script type="text/javascript" src="head.js"></script>
+  <link rel="stylesheet" href="/tests/SimpleTest/test.css"/>
+</head>
+<body>
+
+<script type="text/javascript">
+"use strict";
+
+let extensionData = {
+  manifest: {
+    browser_specific_settings: {
+      gecko: {
+        id: "open-popup@tests.mozilla.org",
+      }
+    },
+    browser_action: {
+      default_popup: "popup.html",
+      default_area: "navbar",
+    },
+    permissions: ["activeTab"]
+  },
+
+  useAddonManager: "android-only",
+};
+
+add_task(async function setup() {
+  await SpecialPowers.pushPrefEnv({
+    "set": [
+      ["extensions.openPopupWithoutUserGesture.enabled", true],
+    ],
+  });
+});
+
+async function testWithWindowState(state) {
+  const background = async function(state) {
+    const originalWindow = await browser.windows.getCurrent();
+
+    let newWindowPromise;
+    const tabLoadedPromise = new Promise(resolve => {
+      browser.tabs.onUpdated.addListener(async (id, { status }, tab) => {
+        if (tab.windowId === (await newWindowPromise).id && status === "complete") {
+          resolve();
+        }
+      });
+    });
+
+    newWindowPromise = browser.windows.create({ url: "tab.html" });
+
+    browser.test.onMessage.addListener(async (msg) => {
+      if (msg === "close-window") {
+        await browser.windows.remove((await newWindowPromise).id);
+        browser.test.sendMessage("window-closed");
+      }
+    });
+
+    tabLoadedPromise.then(async () => {
+      const windowId = (await newWindowPromise).id;
+
+      switch (state) {
+        case "inactive":
+          const focusChangePromise = new Promise(resolve => {
+            browser.windows.onFocusChanged.addListener((focusedWindowId) => {
+              if (focusedWindowId === originalWindow.id) {
+                resolve();
+              }
+            })
+          });
+          await browser.windows.update(originalWindow.id, { focused: true });
+          await focusChangePromise;
+          break;
+        case "minimized":
+          await browser.windows.update(windowId, { state: "minimized" });
+          break;
+        default:
+          throw new Error(`Invalid state: ${state}`);
+      }
+
+      await browser.browserAction.openPopup({ windowId });
+    });
+  };
+
+  let extension = ExtensionTestUtils.loadExtension({
+    ...extensionData,
+
+    background: `(${background})(${JSON.stringify(state)})`,
+
+    files: {
+      "tab.html": "<!DOCTYPE html>",
+      "popup.html": `<!DOCTYPE html><meta charset="utf-8"><script src="popup.js"><\/script>`,
+      "popup.js"() {
+        // Small timeout to ensure the popup doesn't immediately close, which can
+        // happen when focus moves between windows
+        // eslint-disable-next-line mozilla/no-arbitrary-setTimeout
+        setTimeout(async () => {
+          let windows = await browser.windows.getAll();
+          let highestWindowIdIsFocused = Math.max(...windows.map((w) => w.id))
+            === windows.find((w) => w.focused).id;
+
+          browser.test.assertEq(true, highestWindowIdIsFocused, "new window is focused");
+
+          await browser.test.sendMessage("popup-open");
+
+          // Bug 1800100: Window leaks if not explicitly closed
+          window.close();
+        }, 1000);
+      },
+    },
+  });
+
+  await extension.startup();
+  await extension.awaitMessage("popup-open");
+  await extension.sendMessage("close-window");
+  await extension.awaitMessage("window-closed");
+  await extension.unload();
+}
+
+add_task(async function test_browserAction_openPopup_window_inactive() {
+  if (AppConstants.platform == "linux") {
+    // TODO bug 1798334: Currently unreliable on linux
+    todo(false, "Unreliable on linux");
+    return;
+  }
+  await testWithWindowState("inactive");
+});
+
+add_task(async function test_browserAction_openPopup_window_minimized() {
+  if (AppConstants.platform == "linux") {
+    // TODO bug 1798334: Currently unreliable on linux
+    todo(false, "Unreliable on linux");
+    return;
+  }
+  await testWithWindowState("minimized");
+});
+
+add_task(async function test_browserAction_openPopup_invalid_window() {
+  let extension = ExtensionTestUtils.loadExtension({
+    ...extensionData,
+
+    background: async function() {
+      await browser.test.assertRejects(
+        browser.browserAction.openPopup({ windowId: Number.MAX_SAFE_INTEGER }),
+        /Invalid window ID/,
+        "Should throw for invalid window ID"
+      );
+      browser.test.notifyPass("invalidWindow");
+    },
+  });
+
+  await extension.startup();
+  await extension.awaitFinish("invalidWindow");
+  await extension.unload();
+});
+</script>
+
+</body>
+</html>
diff --git a/toolkit/components/extensions/test/mochitest/test_ext_browserAction_openPopup_without_pref.html b/toolkit/components/extensions/test/mochitest/test_ext_browserAction_openPopup_without_pref.html
new file mode 100644
index 0000000000..aa7285d5f5
--- /dev/null
+++ b/toolkit/components/extensions/test/mochitest/test_ext_browserAction_openPopup_without_pref.html
@@ -0,0 +1,58 @@
+<!DOCTYPE HTML>
+<html>
+<head>
+  <title>action.openPopup Preference Test</title>
+  <script type="text/javascript" src="/tests/SimpleTest/SimpleTest.js"></script>
+  <script type="text/javascript" src="/tests/SimpleTest/ExtensionTestUtils.js"></script>
+  <script type="text/javascript" src="head.js"></script>
+  <link rel="stylesheet" href="/tests/SimpleTest/test.css"/>
+</head>
+<body>
+
+<script type="text/javascript">
+"use strict";
+
+let extensionData = {
+  manifest: {
+    browser_specific_settings: {
+      gecko: {
+        id: "open-popup@tests.mozilla.org",
+      }
+    },
+    browser_action: {
+      default_popup: "popup.html",
+    }
+  },
+
+  useAddonManager: "android-only",
+};
+
+add_task(async function test_browserAction_openPopup_without_pref() {
+  await SpecialPowers.pushPrefEnv({
+    "set": [
+      ["extensions.openPopupWithoutUserGesture.enabled", false],
+    ],
+  });
+
+  let extension = ExtensionTestUtils.loadExtension({
+    ...extensionData,
+
+    background: async function() {
+      await browser.test.assertRejects(
+        browser.browserAction.openPopup(),
+        "openPopup requires a user gesture",
+        "Should throw when preference is unset"
+      );
+
+      browser.test.notifyPass("withoutPref");
+    },
+  });
+
+  await extension.startup();
+  await extension.awaitFinish("withoutPref");
+  await extension.unload();
+});
+</script>
+
+</body>
+</html>
diff --git a/toolkit/components/extensions/test/mochitest/test_ext_browsingData_indexedDB.html b/toolkit/components/extensions/test/mochitest/test_ext_browsingData_indexedDB.html
new file mode 100644
index 0000000000..f8ea41ddab
--- /dev/null
+++ b/toolkit/components/extensions/test/mochitest/test_ext_browsingData_indexedDB.html
@@ -0,0 +1,159 @@
+<!-- Any copyright is dedicated to the Public Domain.
+   - http://creativecommons.org/publicdomain/zero/1.0/ -->
+<!DOCTYPE HTML>
+<html>
+<head>
+  <title>Test browsingData.remove indexedDB</title>
+  <script src="/tests/SimpleTest/SimpleTest.js"></script>
+  <script src="/tests/SimpleTest/ExtensionTestUtils.js"></script>
+  <script src="head.js"></script>
+  <link rel="stylesheet" type="text/css" href="/tests/SimpleTest/test.css" />
+</head>
+<body>
+
+<script type="text/javascript">
+"use strict";
+
+add_task(async function testIndexedDB() {
+  await SpecialPowers.pushPrefEnv({
+    set: [["privacy.userContext.enabled", true]],
+  });
+
+  async function background() {
+    const PAGE =
+      "/tests/toolkit/components/extensions/test/mochitest/file_indexedDB.html";
+
+    let tabs = [];
+
+    browser.test.onMessage.addListener(async msg => {
+      if (msg == "cleanup") {
+        await Promise.all(tabs.map(tabId => browser.tabs.remove(tabId)));
+        browser.test.sendMessage("done");
+        return;
+      }
+
+      await browser.browsingData.remove(msg, { indexedDB: true });
+      browser.test.sendMessage("indexedDBRemoved");
+    });
+
+    // Create two tabs.
+    let tab = await browser.tabs.create({ url: `https://example.org${PAGE}` });
+    tabs.push(tab.id);
+
+    tab = await browser.tabs.create({ url: `https://example.com${PAGE}` });
+    tabs.push(tab.id);
+
+    // Create tab with cookieStoreId "firefox-container-1"
+    tab = await browser.tabs.create({ url: `https://example.net${PAGE}`, cookieStoreId: 'firefox-container-1' });
+    tabs.push(tab.id);
+  }
+
+  function contentScript() {
+    // eslint-disable-next-line mozilla/balanced-listeners
+    window.addEventListener(
+      "message",
+      msg => {
+        browser.test.sendMessage("indexedDBCreated");
+      },
+      true
+    );
+  }
+
+  let extension = ExtensionTestUtils.loadExtension({
+    background,
+    manifest: {
+      permissions: ["browsingData", "tabs", "cookies"],
+      content_scripts: [
+        {
+          matches: [
+            "https://example.org/*/file_indexedDB.html",
+            "https://example.com/*/file_indexedDB.html",
+            "https://example.net/*/file_indexedDB.html",
+          ],
+          js: ["script.js"],
+          run_at: "document_start",
+        },
+      ],
+    },
+    files: {
+      "script.js": contentScript,
+    },
+  });
+
+  await extension.startup();
+
+  await extension.awaitMessage("indexedDBCreated");
+  await extension.awaitMessage("indexedDBCreated");
+  await extension.awaitMessage("indexedDBCreated");
+
+  function getUsage() {
+    return new Promise(resolve => {
+      let qms = SpecialPowers.Services.qms;
+      let cb = SpecialPowers.wrapCallback(request => resolve(request.result));
+      qms.getUsage(cb);
+    });
+  }
+
+  async function getOrigins() {
+    let origins = [];
+    let result = await getUsage();
+    for (let i = 0; i < result.length; ++i) {
+      if (result[i].usage === 0) {
+        continue;
+      }
+      if (
+        result[i].origin.startsWith("https://example.org") ||
+        result[i].origin.startsWith("https://example.com") ||
+        result[i].origin.startsWith("https://example.net")
+      ) {
+        origins.push(result[i].origin);
+      }
+    }
+    return origins.sort();
+  }
+
+  let origins = await getOrigins();
+  is(origins.length, 3, "IndexedDB databases have been populated.");
+
+  // Deleting private browsing mode data is silently ignored.
+  extension.sendMessage({ cookieStoreId: "firefox-private" });
+  await extension.awaitMessage("indexedDBRemoved");
+
+  origins = await getOrigins();
+  is(origins.length, 3, "All indexedDB remains after clearing firefox-private");
+
+  // Delete by hostname
+  extension.sendMessage({ hostnames: ["example.com"] });
+  await extension.awaitMessage("indexedDBRemoved");
+
+  origins = await getOrigins();
+  is(origins.length, 2, "IndexedDB data only for only two domains left");
+  ok(origins[0].startsWith("https://example.net"), "example.net not deleted");
+  ok(origins[1].startsWith("https://example.org"), "example.org not deleted");
+
+  // TODO: Bug 1643740
+  if (AppConstants.platform != "android") {
+    // Delete by cookieStoreId
+    extension.sendMessage({ cookieStoreId: "firefox-container-1" });
+    await extension.awaitMessage("indexedDBRemoved");
+
+    origins = await getOrigins();
+    is(origins.length, 1, "IndexedDB data only for only one domain");
+    ok(origins[0].startsWith("https://example.org"), "example.org not deleted");
+  }
+
+  // Delete all
+  extension.sendMessage({});
+  await extension.awaitMessage("indexedDBRemoved");
+
+  origins = await getOrigins();
+  is(origins.length, 0, "All IndexedDB data has been removed.");
+
+  await extension.sendMessage("cleanup");
+  await extension.awaitMessage("done");
+
+  await extension.unload();
+});
+</script>
+</body>
+</html>
diff --git a/toolkit/components/extensions/test/mochitest/test_ext_browsingData_localStorage.html b/toolkit/components/extensions/test/mochitest/test_ext_browsingData_localStorage.html
new file mode 100644
index 0000000000..0b61ce341f
--- /dev/null
+++ b/toolkit/components/extensions/test/mochitest/test_ext_browsingData_localStorage.html
@@ -0,0 +1,323 @@
+<!-- Any copyright is dedicated to the Public Domain.
+   - http://creativecommons.org/publicdomain/zero/1.0/ -->
+<!DOCTYPE HTML>
+<html>
+<head>
+  <title>Test browsingData.remove indexedDB</title>
+  <script src="/tests/SimpleTest/SimpleTest.js"></script>
+  <script src="/tests/SimpleTest/ExtensionTestUtils.js"></script>
+  <script src="head.js"></script>
+  <link rel="stylesheet" type="text/css" href="/tests/SimpleTest/test.css" />
+</head>
+<body>
+
+<script type="text/javascript">
+"use strict";
+
+add_task(async function setup() {
+  // make sure userContext is enabled.
+  return SpecialPowers.pushPrefEnv({
+    set: [["privacy.userContext.enabled", true]],
+  });
+});
+
+add_task(async function testLocalStorage() {
+  async function background() {
+    function waitForTabs() {
+      return new Promise(resolve => {
+        let tabs = {};
+
+        let listener = async (msg, { tab }) => {
+          if (msg !== "content-script-ready") {
+            return;
+          }
+
+          tabs[tab.url] = tab;
+          if (Object.keys(tabs).length == 3) {
+            browser.runtime.onMessage.removeListener(listener);
+            resolve(tabs);
+          }
+        };
+        browser.runtime.onMessage.addListener(listener);
+      });
+    }
+
+    function sendMessageToTabs(tabs, message) {
+      return Promise.all(
+        Object.values(tabs).map(tab => {
+          return browser.tabs.sendMessage(tab.id, message);
+        })
+      );
+    }
+
+    let tabs = await waitForTabs();
+
+    browser.test.assertRejects(
+      browser.browsingData.removeLocalStorage({ since: Date.now() }),
+      "Firefox does not support clearing localStorage with 'since'.",
+      "Expected error received when using unimplemented parameter 'since'."
+    );
+
+    await sendMessageToTabs(tabs, "resetLocalStorage");
+    await browser.browsingData.removeLocalStorage({
+      hostnames: ["example.com"],
+    });
+    await browser.tabs.sendMessage(tabs["https://example.com/"].id, "checkLocalStorageCleared");
+    await browser.tabs.sendMessage(tabs["https://example.net/"].id, "checkLocalStorageSet");
+
+    if (
+      SpecialPowers.Services.domStorageManager.nextGenLocalStorageEnabled ===
+      false
+    ) {
+      // This assertion fails when localStorage is using the legacy
+      // implementation (See Bug 1595431).
+      browser.test.log("Skipped assertion on nextGenLocalStorageEnabled=false");
+    } else {
+      await browser.tabs.sendMessage(tabs["https://test1.example.com/"].id, "checkLocalStorageSet");
+    }
+
+    await sendMessageToTabs(tabs, "resetLocalStorage");
+    await sendMessageToTabs(tabs, "checkLocalStorageSet");
+    await browser.browsingData.removeLocalStorage({});
+    await sendMessageToTabs(tabs, "checkLocalStorageCleared");
+
+    await sendMessageToTabs(tabs, "resetLocalStorage");
+    await sendMessageToTabs(tabs, "checkLocalStorageSet");
+    await browser.browsingData.remove({}, { localStorage: true });
+    await sendMessageToTabs(tabs, "checkLocalStorageCleared");
+
+    // Can only delete cookieStoreId with LSNG enabled.
+    if (SpecialPowers.Services.domStorageManager.nextGenLocalStorageEnabled) {
+      await sendMessageToTabs(tabs, "resetLocalStorage");
+      await sendMessageToTabs(tabs, "checkLocalStorageSet");
+      await browser.browsingData.removeLocalStorage({
+        cookieStoreId: "firefox-container-1",
+      });
+      await browser.tabs.sendMessage(tabs["https://example.com/"].id, "checkLocalStorageSet");
+      await browser.tabs.sendMessage(tabs["https://example.net/"].id, "checkLocalStorageSet");
+
+      // TODO: containers support is lacking on GeckoView (Bug 1643740)
+      if (!navigator.userAgent.includes("Android")) {
+        await browser.tabs.sendMessage(tabs["https://test1.example.com/"].id, "checkLocalStorageCleared");
+      }
+
+      await sendMessageToTabs(tabs, "resetLocalStorage");
+      await sendMessageToTabs(tabs, "checkLocalStorageSet");
+      // Hostname doesn't match, so nothing cleared.
+      await browser.browsingData.removeLocalStorage({
+        cookieStoreId: "firefox-container-1",
+        hostnames: ["example.net"],
+      });
+      await sendMessageToTabs(tabs, "checkLocalStorageSet");
+
+      await sendMessageToTabs(tabs, "resetLocalStorage");
+      await sendMessageToTabs(tabs, "checkLocalStorageSet");
+      // Deleting private browsing mode data is silently ignored.
+      await browser.browsingData.removeLocalStorage({
+        cookieStoreId: "firefox-private",
+      });
+      await sendMessageToTabs(tabs, "checkLocalStorageSet");
+    } else {
+      await browser.test.assertRejects(
+        browser.browsingData.removeLocalStorage({
+          cookieStoreId: "firefox-container-1",
+        }),
+        "Firefox does not support clearing localStorage with 'cookieStoreId'.",
+        "removeLocalStorage with cookieStoreId requires LSNG"
+      );
+    }
+
+    // Cleanup (checkLocalStorageCleared creates empty LS databases).
+    await browser.browsingData.removeLocalStorage({});
+
+    browser.test.notifyPass("done");
+  }
+
+  function contentScript() {
+    browser.runtime.onMessage.addListener(msg => {
+      if (msg === "resetLocalStorage") {
+        localStorage.clear();
+        localStorage.setItem("test", "test");
+      } else if (msg === "checkLocalStorageSet") {
+        browser.test.assertEq(
+          "test",
+          localStorage.getItem("test"),
+          `checkLocalStorageSet: ${location.href}`
+        );
+      } else if (msg === "checkLocalStorageCleared") {
+        browser.test.assertEq(
+          null,
+          localStorage.getItem("test"),
+          `checkLocalStorageCleared: ${location.href}`
+        );
+      }
+    });
+    browser.runtime.sendMessage("content-script-ready");
+  }
+
+  // This extension is responsible for opening tabs with a specified
+  // cookieStoreId, we use a separate extension to make sure that browsingData
+  // works without the cookies permission.
+  let openTabsExtension = ExtensionTestUtils.loadExtension({
+    useAddonManager: "permanent",
+    manifest: {
+      name: "Open tabs",
+      browser_specific_settings: { gecko: { id: "open-tabs@tests.mozilla.org" }, },
+      permissions: ["cookies"],
+    },
+    async background() {
+      const TABS = [
+        { url: "https://example.com" },
+        { url: "https://example.net" },
+        {
+          url: "https://test1.example.com",
+          cookieStoreId: 'firefox-container-1',
+        },
+      ];
+
+      function awaitLoad(tabId) {
+        return new Promise(resolve => {
+          browser.tabs.onUpdated.addListener(function listener(tabId_, changed, tab) {
+            if (tabId == tabId_ && changed.status == "complete") {
+              browser.tabs.onUpdated.removeListener(listener);
+              resolve();
+            }
+          });
+        });
+      }
+
+      let tabs = [];
+      let loaded = [];
+      for (let options of TABS) {
+        let tab = await browser.tabs.create(options);
+        loaded.push(awaitLoad(tab.id));
+        tabs.push(tab);
+      }
+
+      await Promise.all(loaded);
+
+      browser.test.onMessage.addListener(async msg => {
+        if (msg === "cleanup") {
+          const tabIds = tabs.map(tab => tab.id);
+          let removedTabs = 0;
+          browser.tabs.onRemoved.addListener(tabId => {
+            browser.test.log(`Removing tab ${tabId}.`);
+            if (tabIds.includes(tabId)) {
+              removedTabs++;
+              if (removedTabs == tabIds.length) {
+                browser.test.sendMessage("done");
+              }
+            }
+          });
+          await browser.tabs.remove(tabIds);
+        }
+      });
+    }
+  });
+
+  let extension = ExtensionTestUtils.loadExtension({
+    useAddonManager: "permanent",
+    background,
+    manifest: {
+      name: "Test Extension",
+      browser_specific_settings: { gecko: { id: "localStorage@tests.mozilla.org" } },
+      permissions: ["browsingData", "tabs"],
+      content_scripts: [
+        {
+          matches: [
+            "https://example.com/",
+            "https://example.net/",
+            "https://test1.example.com/",
+          ],
+          js: ["content-script.js"],
+          run_at: "document_end",
+        },
+      ],
+    },
+    files: {
+      "content-script.js": contentScript,
+    },
+  });
+
+  await openTabsExtension.startup();
+
+  await extension.startup();
+  await extension.awaitFinish("done");
+  await extension.unload();
+
+  await openTabsExtension.sendMessage("cleanup");
+  await openTabsExtension.awaitMessage("done");
+  await openTabsExtension.unload();
+});
+
+// Verify that browsingData.removeLocalStorage doesn't break on data stored
+// in about:newtab or file principals.
+add_task(async function test_browserData_on_aboutnewtab_and_file_data() {
+  let extension = ExtensionTestUtils.loadExtension({
+    useAddonManager: "permanent",
+    async background() {
+      await browser.browsingData.removeLocalStorage({}).catch(err => {
+        browser.test.fail(`${err} :: ${err.stack}`);
+      });
+      browser.test.sendMessage("done");
+    },
+    manifest: {
+      browser_specific_settings: { gecko: { id: "indexed-db-file@test.mozilla.org" } },
+      permissions: ["browsingData"],
+    },
+  });
+
+  await new Promise(resolve => {
+    const chromeScript = SpecialPowers.loadChromeScript(async () => {
+      /* eslint-env mozilla/chrome-script */
+      const { SiteDataTestUtils } = ChromeUtils.import(
+        "resource://testing-common/SiteDataTestUtils.jsm"
+      );
+      await SiteDataTestUtils.addToIndexedDB("about:newtab");
+      await SiteDataTestUtils.addToIndexedDB("file:///fake/file");
+      sendAsyncMessage("done");
+    });
+
+    chromeScript.addMessageListener("done", () => {
+      chromeScript.destroy();
+      resolve();
+    });
+  });
+
+  await extension.startup();
+  await extension.awaitMessage("done");
+  await extension.unload();
+});
+
+add_task(async function test_browserData_should_not_remove_extension_data() {
+  if (SpecialPowers.getBoolPref("dom.storage.enable_unsupported_legacy_implementation")) {
+    // When LSNG isn't enabled, the browsingData API does still clear
+    // all the extensions localStorage if called without a list of specific
+    // origins to clear.
+    info("Test skipped because LSNG is currently disabled");
+    return;
+  }
+
+  let extension = ExtensionTestUtils.loadExtension({
+    useAddonManager: "permanent",
+    async background() {
+      window.localStorage.setItem("key", "value");
+      await browser.browsingData.removeLocalStorage({}).catch(err => {
+        browser.test.fail(`${err} :: ${err.stack}`);
+      });
+      browser.test.sendMessage("done", window.localStorage.getItem("key"));
+    },
+    manifest: {
+      browser_specific_settings: { gecko: { id: "extension-data@tests.mozilla.org" } },
+      permissions: ["browsingData"],
+    },
+  });
+
+  await extension.startup();
+  const lsValue = await extension.awaitMessage("done");
+  is(lsValue, "value", "Got the expected localStorage data");
+  await extension.unload();
+});
+</script>
+</body>
+</html>
diff --git a/toolkit/components/extensions/test/mochitest/test_ext_browsingData_pluginData.html b/toolkit/components/extensions/test/mochitest/test_ext_browsingData_pluginData.html
new file mode 100644
index 0000000000..bf4bd8fe80
--- /dev/null
+++ b/toolkit/components/extensions/test/mochitest/test_ext_browsingData_pluginData.html
@@ -0,0 +1,69 @@
+<!-- Any copyright is dedicated to the Public Domain.
+   - http://creativecommons.org/publicdomain/zero/1.0/ -->
+<!DOCTYPE HTML>
+<html>
+<head>
+  <title>Test browsingData.remove indexedDB</title>
+  <script src="/tests/SimpleTest/SimpleTest.js"></script>
+  <script src="/tests/SimpleTest/ExtensionTestUtils.js"></script>
+  <script src="head.js"></script>
+  <link rel="stylesheet" type="text/css" href="/tests/SimpleTest/test.css" />
+</head>
+<body>
+
+<script type="text/javascript">
+"use strict";
+
+// NB: Since plugins are disabled, there is never any data to clear.
+// We are really testing that these operations are no-ops.
+
+add_task(async function testPluginData() {
+  async function background() {
+    const REFERENCE_DATE = Date.now();
+    const TEST_CASES = [
+      // Clear plugin data with no since value.
+      {},
+      // Clear pluginData with recent since value.
+      { since: REFERENCE_DATE - 20000 },
+      // Clear pluginData with old since value.
+      { since: REFERENCE_DATE - 1000000 },
+      // Clear pluginData for specific hosts.
+      { hostnames: ["bar.com", "baz.com"] },
+      // Clear pluginData for no hosts.
+      { hostnames: [] },
+    ];
+
+    for (let method of ["removePluginData", "remove"]) {
+      for (let options of TEST_CASES) {
+        browser.test.log(`Testing ${method} with ${JSON.stringify(options)}`);
+        if (method == "removePluginData") {
+          await browser.browsingData.removePluginData(options);
+        } else {
+          await browser.browsingData.remove(options, { pluginData: true });
+        }
+      }
+    }
+
+    browser.test.sendMessage("done");
+  }
+
+  let extension = ExtensionTestUtils.loadExtension({
+    background,
+    manifest: {
+      permissions: ["tabs", "browsingData"],
+    },
+  });
+
+  await extension.startup();
+  await extension.awaitMessage("done");
+
+  // This test has no assertions because it's only meant to check that we don't
+  // throw when calling removePluginData and remove with pluginData: true.
+  ok(true, "dummy check");
+
+  await extension.unload();
+});
+</script>
+
+</body>
+</html>
diff --git a/toolkit/components/extensions/test/mochitest/test_ext_browsingData_serviceWorkers.html b/toolkit/components/extensions/test/mochitest/test_ext_browsingData_serviceWorkers.html
new file mode 100644
index 0000000000..900546f32c
--- /dev/null
+++ b/toolkit/components/extensions/test/mochitest/test_ext_browsingData_serviceWorkers.html
@@ -0,0 +1,141 @@
+<!-- Any copyright is dedicated to the Public Domain.
+   - http://creativecommons.org/publicdomain/zero/1.0/ -->
+<!DOCTYPE HTML>
+<html>
+<head>
+  <title>Test browsingData.remove indexedDB</title>
+  <script src="/tests/SimpleTest/SimpleTest.js"></script>
+  <script src="/tests/SimpleTest/ExtensionTestUtils.js"></script>
+  <script src="head.js"></script>
+  <link rel="stylesheet" type="text/css" href="/tests/SimpleTest/test.css" />
+</head>
+<body>
+
+<script type="text/javascript">
+"use strict";
+
+const { TestUtils } = SpecialPowers.ChromeUtils.import(
+  "resource://testing-common/TestUtils.jsm"
+);
+
+add_task(async function setup() {
+  await SpecialPowers.pushPrefEnv({
+    set: [
+      ["dom.serviceWorkers.exemptFromPerDomainMax", true],
+      ["dom.serviceWorkers.enabled", true],
+      ["dom.serviceWorkers.testing.enabled", true],
+    ],
+  });
+});
+
+add_task(async function testServiceWorkers() {
+  async function background() {
+    const PAGE =
+      "/tests/toolkit/components/extensions/test/mochitest/file_serviceWorker.html";
+
+    browser.runtime.onMessage.addListener(msg => {
+      browser.test.sendMessage("serviceWorkerRegistered");
+    });
+
+    let tabs = [];
+
+    browser.test.onMessage.addListener(async msg => {
+      if (msg == "cleanup") {
+        await browser.tabs.remove(tabs.map(tab => tab.id));
+        browser.test.sendMessage("done");
+        return;
+      }
+
+      await browser.browsingData.remove(
+        { hostnames: msg.hostnames },
+        { serviceWorkers: true }
+      );
+      browser.test.sendMessage("serviceWorkersRemoved");
+    });
+
+    // Create two serviceWorkers.
+    let tab = await browser.tabs.create({ url: `http://mochi.test:8888${PAGE}` });
+    tabs.push(tab);
+
+    tab = await browser.tabs.create({ url: `https://example.com${PAGE}` });
+    tabs.push(tab);
+  }
+
+  function contentScript() {
+    // eslint-disable-next-line mozilla/balanced-listeners
+    window.addEventListener(
+      "message",
+      msg => {
+        if (msg.data == "serviceWorkerRegistered") {
+          browser.runtime.sendMessage("serviceWorkerRegistered");
+        }
+      },
+      true
+    );
+  }
+
+  let extension = ExtensionTestUtils.loadExtension({
+    background,
+    manifest: {
+      permissions: ["browsingData", "tabs"],
+      content_scripts: [
+        {
+          matches: [
+            "http://mochi.test/*/file_serviceWorker.html",
+            "https://example.com/*/file_serviceWorker.html",
+          ],
+          js: ["script.js"],
+          run_at: "document_start",
+        },
+      ],
+    },
+    files: {
+      "script.js": contentScript,
+    },
+  });
+
+  await extension.startup();
+  await extension.awaitMessage("serviceWorkerRegistered");
+  await extension.awaitMessage("serviceWorkerRegistered");
+
+  // Even though we await the registrations by waiting for the messages,
+  // sometimes the serviceWorkers are still not registered at this point.
+  async function getRegistrations(count) {
+    await TestUtils.waitForCondition(
+      async () => (await SpecialPowers.registeredServiceWorkers()).length === count,
+      `Wait for ${count} service workers to be registered`
+    );
+    return SpecialPowers.registeredServiceWorkers();
+  }
+
+  let serviceWorkers = await getRegistrations(2);
+  is(serviceWorkers.length, 2, "ServiceWorkers have been registered.");
+
+  extension.sendMessage({ hostnames: ["example.com"] });
+  await extension.awaitMessage("serviceWorkersRemoved");
+
+  serviceWorkers = await getRegistrations(1);
+  is(
+    serviceWorkers.length,
+    1,
+    "ServiceWorkers for example.com have been removed."
+  );
+
+  let { scriptSpec } = serviceWorkers[0];
+  dump(`Service worker spec: ${scriptSpec}`);
+  ok(scriptSpec.startsWith("http://mochi.test:8888/"),
+     "ServiceWorkers for example.com have been removed.");
+
+  extension.sendMessage({});
+  await extension.awaitMessage("serviceWorkersRemoved");
+
+  serviceWorkers = await getRegistrations(0);
+  is(serviceWorkers.length, 0, "All ServiceWorkers have been removed.");
+
+  extension.sendMessage("cleanup");
+  await extension.awaitMessage("done");
+  await extension.unload();
+});
+</script>
+</body>
+</html>
diff --git a/toolkit/components/extensions/test/mochitest/test_ext_browsingData_settings.html b/toolkit/components/extensions/test/mochitest/test_ext_browsingData_settings.html
new file mode 100644
index 0000000000..11c690e5bf
--- /dev/null
+++ b/toolkit/components/extensions/test/mochitest/test_ext_browsingData_settings.html
@@ -0,0 +1,65 @@
+<!-- Any copyright is dedicated to the Public Domain.
+   - http://creativecommons.org/publicdomain/zero/1.0/ -->
+<!DOCTYPE HTML>
+<html>
+<head>
+  <title>Test browsingData.settings</title>
+  <script src="/tests/SimpleTest/SimpleTest.js"></script>
+  <script src="/tests/SimpleTest/ExtensionTestUtils.js"></script>
+  <script src="head.js"></script>
+  <link rel="stylesheet" type="text/css" href="/tests/SimpleTest/test.css" />
+</head>
+<body>
+
+<script type="text/javascript">
+"use strict";
+
+const SETTINGS_LIST = [
+  "cache",
+  "cookies",
+  "history",
+  "formData",
+  "downloads",
+].sort();
+
+add_task(async function testSettings() {
+  async function background() {
+    browser.browsingData.settings().then(settings => {
+      browser.test.sendMessage("settings", settings);
+    });
+  }
+
+  let extension = ExtensionTestUtils.loadExtension({
+    background,
+    manifest: {
+      permissions: ["browsingData"],
+    },
+  });
+
+  await extension.startup();
+  let settings = await extension.awaitMessage("settings");
+
+  // Verify that we get the keys back we expect.
+  isDeeply(
+    Object.entries(settings.dataToRemove)
+      .filter(([key, value]) => value)
+      .map(([key, value]) => key)
+      .sort(),
+    SETTINGS_LIST,
+    "dataToRemove contains expected properties."
+  );
+  isDeeply(
+    Object.entries(settings.dataRemovalPermitted)
+      .filter(([key, value]) => value)
+      .map(([key, value]) => key)
+      .sort(),
+    SETTINGS_LIST,
+    "dataToRemove contains expected properties."
+  );
+  is("since" in settings.options, true, "options contains |since|");
+
+  await extension.unload();
+});
+</script>
+</body>
+</html>
diff --git a/toolkit/components/extensions/test/mochitest/test_ext_canvas_resistFingerprinting.html b/toolkit/components/extensions/test/mochitest/test_ext_canvas_resistFingerprinting.html
new file mode 100644
index 0000000000..7116d03235
--- /dev/null
+++ b/toolkit/components/extensions/test/mochitest/test_ext_canvas_resistFingerprinting.html
@@ -0,0 +1,64 @@
+<!DOCTYPE HTML>
+<html>
+<head>
+  <title>WebExtension test</title>
+  <script src="/tests/SimpleTest/SimpleTest.js"></script>
+  <script src="/tests/SimpleTest/ExtensionTestUtils.js"></script>
+  <script type="text/javascript" src="head.js"></script>
+  <script type="text/javascript" src="head_cookies.js"></script>
+  <link rel="stylesheet" type="text/css" href="/tests/SimpleTest/test.css"/>
+</head>
+<body>
+
+<script type="text/javascript">
+"use strict";
+
+add_task(async function setup() {
+  await SpecialPowers.pushPrefEnv({
+    set: [["privacy.resistFingerprinting", true]],
+  });
+});
+
+add_task(async function test_contentscript() {
+  function contentScript() {
+    let canvas = document.createElement("canvas");
+    canvas.width = canvas.height = "100";
+
+    let ctx = canvas.getContext("2d");
+    ctx.fillStyle = "green";
+    ctx.fillRect(0, 0, 100, 100);
+    let data = ctx.getImageData(0, 0, 100, 100);
+
+    browser.test.sendMessage("data-color", data.data[1]);
+  }
+
+  let extensionData = {
+    manifest: {
+      content_scripts: [
+        {
+          "matches": ["http://mochi.test/*/file_sample.html"],
+          "js": ["content_script.js"],
+          "run_at": "document_start",
+        },
+      ],
+    },
+
+    files: {
+      "content_script.js": contentScript,
+    },
+  };
+  const url = "http://mochi.test:8888/chrome/toolkit/components/extensions/test/mochitest/file_sample.html";
+
+  let extension = ExtensionTestUtils.loadExtension(extensionData);
+
+  await extension.startup();
+  let win = window.open(url);
+  let color = await extension.awaitMessage("data-color");
+  is(color, 128, "Got correct pixel data for green");
+  win.close();
+  await extension.unload();
+});
+</script>
+
+</body>
+</html>
diff --git a/toolkit/components/extensions/test/mochitest/test_ext_clipboard.html b/toolkit/components/extensions/test/mochitest/test_ext_clipboard.html
new file mode 100644
index 0000000000..77ac767391
--- /dev/null
+++ b/toolkit/components/extensions/test/mochitest/test_ext_clipboard.html
@@ -0,0 +1,210 @@
+<!DOCTYPE HTML>
+<html>
+<head>
+  <title>Clipboard permissions tests</title>
+  <script src="/tests/SimpleTest/SimpleTest.js"></script>
+  <script src="/tests/SimpleTest/ExtensionTestUtils.js"></script>
+  <script src="head.js"></script>
+  <link rel="stylesheet" href="/tests/SimpleTest/test.css">
+</head>
+<body>
+
+<script>
+"use strict";
+
+/* globals doCopy, doPaste */
+function shared() {
+  let field = document.createElement("textarea");
+  document.body.appendChild(field);
+  field.contentEditable = true;
+
+  this.doCopy = function(txt) {
+    field.value = txt;
+    field.select();
+    return document.execCommand("copy");
+  };
+
+  this.doPaste = function() {
+    field.select();
+    return document.execCommand("paste") && field.value;
+  };
+}
+
+add_task(async function test_background_clipboard_permissions() {
+  function backgroundScript() {
+    browser.test.assertEq(false, doCopy("whatever"),
+                          "copy should be denied without permission");
+    browser.test.assertEq(false, doPaste(),
+                          "paste should be denied without permission");
+    browser.test.sendMessage("ready");
+  }
+  let extensionData = {
+    background: [shared, backgroundScript],
+  };
+  let extension = ExtensionTestUtils.loadExtension(extensionData);
+  await extension.startup();
+
+  await extension.awaitMessage("ready");
+
+  await extension.unload();
+});
+
+add_task(async function test_background_clipboard_copy() {
+  function backgroundScript() {
+    browser.test.onMessage.addListener(txt => {
+      browser.test.assertEq(true, doCopy(txt),
+        "copy should be allowed with permission");
+    });
+    browser.test.sendMessage("ready");
+  }
+  let extensionData = {
+    background: `(${shared})();(${backgroundScript})();`,
+    manifest: {
+      permissions: [
+        "clipboardWrite",
+      ],
+    },
+  };
+  let extension = ExtensionTestUtils.loadExtension(extensionData);
+  await extension.startup();
+  await extension.awaitMessage("ready");
+
+  const DUMMY_STR = "dummy string to copy";
+  await new Promise(resolve => {
+    SimpleTest.waitForClipboard(DUMMY_STR, () => {
+      extension.sendMessage(DUMMY_STR);
+    }, resolve, resolve);
+  });
+
+  await extension.unload();
+});
+
+add_task(async function test_contentscript_clipboard_permissions() {
+  function contentScript() {
+    browser.test.assertEq(false, doCopy("whatever"),
+                          "copy should be denied without permission");
+    browser.test.assertEq(false, doPaste(),
+                          "paste should be denied without permission");
+    browser.test.sendMessage("ready");
+  }
+  let extensionData = {
+    manifest: {
+      content_scripts: [{
+        js: ["shared.js", "contentscript.js"],
+        matches: ["http://mochi.test/*/file_sample.html"],
+      }],
+    },
+    files: {
+      "shared.js": shared,
+      "contentscript.js": contentScript,
+    },
+  };
+  let extension = ExtensionTestUtils.loadExtension(extensionData);
+  await extension.startup();
+
+  let win = window.open("file_sample.html");
+  await extension.awaitMessage("ready");
+  win.close();
+
+  await extension.unload();
+});
+
+add_task(async function test_contentscript_clipboard_copy() {
+  function contentScript() {
+    browser.test.onMessage.addListener(txt => {
+      browser.test.assertEq(true, doCopy(txt),
+                            "copy should be allowed with permission");
+    });
+    browser.test.sendMessage("ready");
+  }
+  let extensionData = {
+    manifest: {
+      content_scripts: [{
+        js: ["shared.js", "contentscript.js"],
+        matches: ["http://mochi.test/*/file_sample.html"],
+      }],
+      permissions: [
+        "clipboardWrite",
+      ],
+    },
+    files: {
+      "shared.js": shared,
+      "contentscript.js": contentScript,
+    },
+  };
+  let extension = ExtensionTestUtils.loadExtension(extensionData);
+  await extension.startup();
+
+  let win = window.open("file_sample.html");
+  await extension.awaitMessage("ready");
+
+  const DUMMY_STR = "dummy string to copy in content script";
+  await new Promise(resolve => {
+    SimpleTest.waitForClipboard(DUMMY_STR, () => {
+      extension.sendMessage(DUMMY_STR);
+    }, resolve, resolve);
+  });
+
+  win.close();
+
+  await extension.unload();
+});
+
+add_task(async function test_contentscript_clipboard_paste() {
+  const extension = ExtensionTestUtils.loadExtension({
+    manifest: {
+      permissions: [
+        "clipboardRead",
+      ],
+      content_scripts: [{
+        matches: ["http://mochi.test/*/file_sample.html"],
+        js: ["shared.js", "content_script.js"],
+      }],
+    },
+    files: {
+      "shared.js": shared,
+      "content_script.js": () => {
+        browser.test.sendMessage("paste", doPaste());
+      },
+    },
+  });
+
+  const STRANGE = "A Strange Thing";
+  SpecialPowers.clipboardCopyString(STRANGE);
+
+  await extension.startup();
+  const win = window.open("file_sample.html");
+
+  const paste = await extension.awaitMessage("paste");
+  is(paste, STRANGE, "the correct string was pasted");
+
+  win.close();
+  await extension.unload();
+});
+
+add_task(async function test_background_clipboard_paste() {
+  function background() {
+    browser.test.sendMessage("paste", doPaste());
+  }
+
+  const extension = ExtensionTestUtils.loadExtension({
+    manifest: {
+      permissions: ["clipboardRead"],
+    },
+    background: [shared, background],
+  });
+
+  const STRANGE = "Stranger Things";
+  SpecialPowers.clipboardCopyString(STRANGE);
+
+  await extension.startup();
+
+  const paste = await extension.awaitMessage("paste");
+  is(paste, STRANGE, "the correct string was pasted");
+
+  await extension.unload();
+});
+
+</script>
+</body>
+</html>
diff --git a/toolkit/components/extensions/test/mochitest/test_ext_clipboard_image.html b/toolkit/components/extensions/test/mochitest/test_ext_clipboard_image.html
new file mode 100644
index 0000000000..b5d5f6764a
--- /dev/null
+++ b/toolkit/components/extensions/test/mochitest/test_ext_clipboard_image.html
@@ -0,0 +1,262 @@
+<!DOCTYPE HTML>
+<html>
+<head>
+  <title>Clipboard permissions tests</title>
+  <script src="/tests/SimpleTest/SimpleTest.js"></script>
+  <script src="/tests/SimpleTest/ExtensionTestUtils.js"></script>
+  <script src="head.js"></script>
+  <link rel="stylesheet" href="/tests/SimpleTest/test.css">
+</head>
+<body>
+
+<script>
+"use strict";
+/**
+ * This cannot be a xpcshell test, because:
+ * - On Android, copyString of nsIClipboardHelper segfaults because
+ *   widget/android/nsClipboard.cpp calls java::Clipboard::SetText, which is
+ *   unavailable in xpcshell.
+ * - On Windows, the clipboard is unavailable to xpcshell.
+ */
+
+function resetClipboard() {
+  SpecialPowers.clipboardCopyString(
+    "This is the default value of the clipboard in the test.");
+}
+
+async function checkClipboardHasTestImage(imageType) {
+  async function backgroundScript(imageType) {
+    async function verifyImage(img) {
+      // Checks whether the image is a 1x1 red image.
+      browser.test.assertEq(1, img.naturalWidth, "image width should match");
+      browser.test.assertEq(1, img.naturalHeight, "image height should match");
+
+      let canvas = document.createElement("canvas");
+      canvas.width = 1;
+      canvas.height = 1;
+      let ctx = canvas.getContext("2d");
+      ctx.drawImage(img, 0, 0); // Draw without scaling.
+      let [r, g, b, a] = ctx.getImageData(0, 0, 1, 1).data;
+      let expectedColor;
+      if (imageType === "png") {
+        expectedColor = [255, 0, 0];
+      } else if (imageType === "jpeg") {
+        expectedColor = [254, 0, 0];
+      }
+      let {os} = await browser.runtime.getPlatformInfo();
+      if (os === "mac") {
+        // Due to https://bugzil.la/1396587, the pasted image differs from the
+        // original/expected image.
+        // Once that bug is fixed, this whole macOS-only branch can be removed.
+        if (imageType === "png") {
+          expectedColor = [255, 38, 0];
+        } else if (imageType === "jpeg") {
+          expectedColor = [255, 38, 0];
+        }
+      }
+      browser.test.assertEq(expectedColor[0], r, "pixel should be red");
+      browser.test.assertEq(expectedColor[1], g, "pixel should not contain green");
+      browser.test.assertEq(expectedColor[2], b, "pixel should not contain blue");
+      browser.test.assertEq(255, a, "pixel should be opaque");
+    }
+
+    let editable = document.body;
+    editable.contentEditable = true;
+    let file;
+    await new Promise(resolve => {
+      document.addEventListener("paste", function(event) {
+        browser.test.assertEq(1, event.clipboardData.types.length, "expected one type");
+        browser.test.assertEq("Files", event.clipboardData.types[0], "expected type");
+        browser.test.assertEq(1, event.clipboardData.files.length, "expected one file");
+
+        // After returning from the paste event, event.clipboardData is cleaned, so we
+        // have to store the file in a separate variable.
+        file = event.clipboardData.files[0];
+        resolve();
+      }, {once: true});
+
+      document.execCommand("paste"); // requires clipboardWrite permission.
+    });
+
+    // When image data is copied, its first frame is decoded and exported to the
+    // clipboard. The pasted result is always an unanimated PNG file, regardless
+    // of the input.
+    browser.test.assertEq("image/png", file.type, "expected file.type");
+
+    // event.files[0] should be an accurate representation of the input image.
+    {
+      let img = new Image();
+      await new Promise((resolve, reject) => {
+        img.onload = resolve;
+        img.onerror = () => reject(new Error(`Failed to load image ${img.src} of size ${file.size}`));
+        img.src = URL.createObjectURL(file);
+      });
+
+      await verifyImage(img);
+    }
+
+    // This confirms that an image was put on the clipboard.
+    // In contrast, when document.execCommand('copy') + clipboardData.setData
+    // is used, then the 'paste' event will also have the image data (as tested
+    // above), but the contentEditable area will be empty.
+    {
+      let imgs = editable.querySelectorAll("img");
+      browser.test.assertEq(1, imgs.length, "should have pasted one image");
+      await verifyImage(imgs[0]);
+    }
+    browser.test.sendMessage("tested image on clipboard");
+  }
+
+  let extension = ExtensionTestUtils.loadExtension({
+    background: `(${backgroundScript})("${imageType}");`,
+    manifest: {
+      permissions: ["clipboardRead"],
+    },
+  });
+  await extension.startup();
+  await extension.awaitMessage("tested image on clipboard");
+  await extension.unload();
+}
+
+add_task(async function test_without_clipboard_permission() {
+  let extension = ExtensionTestUtils.loadExtension({
+    background() {
+      browser.test.assertEq(undefined, browser.clipboard,
+                            "clipboard API requires the clipboardWrite permission.");
+      browser.test.notifyPass();
+    },
+    manifest: {
+      permissions: ["clipboardRead"],
+    },
+  });
+  await extension.startup();
+  await extension.awaitFinish();
+  await extension.unload();
+});
+
+add_task(async function test_copy_png() {
+  if (AppConstants.platform === "android") {
+    return; // Android does not support images on the clipboard.
+  }
+  let extension = ExtensionTestUtils.loadExtension({
+    async background() {
+      // A 1x1 red PNG image.
+      let b64data = "iVBORw0KGgoAAAANSUhEUgAAAAEAAAABAQMAAAAl21bKAAAABlBMVEX/AAD///9BHTQRAAAACXBIWXMAAA7EAAAOxAGVKw4bAAAACklEQVQImWNgAAAAAgAB9HFkpgAAAABJRU5ErkJggg==";
+      let imageData = Uint8Array.from(atob(b64data), c => c.charCodeAt(0)).buffer;
+      await browser.clipboard.setImageData(imageData, "png");
+      browser.test.sendMessage("Called setImageData with PNG");
+    },
+    manifest: {
+      permissions: ["clipboardWrite"],
+    },
+  });
+
+  resetClipboard();
+
+  await extension.startup();
+  await extension.awaitMessage("Called setImageData with PNG");
+  await extension.unload();
+
+  await checkClipboardHasTestImage("png");
+});
+
+add_task(async function test_copy_jpeg() {
+  if (AppConstants.platform === "android") {
+    return; // Android does not support images on the clipboard.
+  }
+  let extension = ExtensionTestUtils.loadExtension({
+    async background() {
+      // A 1x1 red JPEG image, created using: convert xc:red red.jpg.
+      // JPEG is lossy, and the red pixel value is actually #FE0000 instead of
+      // #FF0000 (also seen using: convert red.jpg text:-).
+      let b64data = "/9j/4AAQSkZJRgABAQAAAQABAAD/2wBDAAMCAgICAgMCAgIDAwMDBAYEBAQEBAgGBgUGCQgKCgkICQkKDA8MCgsOCwkJDRENDg8QEBEQCgwSExIQEw8QEBD/2wBDAQMDAwQDBAgEBAgQCwkLEBAQEBAQEBAQEBAQEBAQEBAQEBAQEBAQEBAQEBAQEBAQEBAQEBAQEBAQEBAQEBAQEBD/wAARCAABAAEDAREAAhEBAxEB/8QAFAABAAAAAAAAAAAAAAAAAAAACP/EABQQAQAAAAAAAAAAAAAAAAAAAAD/xAAVAQEBAAAAAAAAAAAAAAAAAAAHCf/EABQRAQAAAAAAAAAAAAAAAAAAAAD/2gAMAwEAAhEDEQA/ADoDFU3/2Q==";
+      let imageData = Uint8Array.from(atob(b64data), c => c.charCodeAt(0)).buffer;
+      await browser.clipboard.setImageData(imageData, "jpeg");
+      browser.test.sendMessage("Called setImageData with JPEG");
+    },
+    manifest: {
+      permissions: ["clipboardWrite"],
+    },
+  });
+
+  resetClipboard();
+
+  await extension.startup();
+  await extension.awaitMessage("Called setImageData with JPEG");
+  await extension.unload();
+
+  await checkClipboardHasTestImage("jpeg");
+});
+
+add_task(async function test_copy_invalid_image() {
+  if (AppConstants.platform === "android") {
+    // Android does not support images on the clipboard.
+    return;
+  }
+  let extension = ExtensionTestUtils.loadExtension({
+    async background() {
+      // This is a PNG image.
+      let b64data = "iVBORw0KGgoAAAANSUhEUgAAAAEAAAABAQMAAAAl21bKAAAABlBMVEX/AAD///9BHTQRAAAACXBIWXMAAA7EAAAOxAGVKw4bAAAACklEQVQImWNgAAAAAgAB9HFkpgAAAABJRU5ErkJggg==";
+      let pngImageData = Uint8Array.from(atob(b64data), c => c.charCodeAt(0)).buffer;
+      await browser.test.assertRejects(
+        browser.clipboard.setImageData(pngImageData, "jpeg"),
+        "Data is not a valid jpeg image",
+        "Image data that is not valid for the given type should be rejected.");
+      browser.test.sendMessage("finished invalid image");
+    },
+    manifest: {
+      permissions: ["clipboardWrite"],
+    },
+  });
+
+  await extension.startup();
+  await extension.awaitMessage("finished invalid image");
+  await extension.unload();
+});
+
+add_task(async function test_copy_invalid_image_type() {
+  let extension = ExtensionTestUtils.loadExtension({
+    async background() {
+      // setImageData expects "png" or "jpeg", but we pass "image/png" here.
+      browser.test.assertThrows(
+        () => { browser.clipboard.setImageData(new ArrayBuffer(0), "image/png"); },
+        "Type error for parameter imageType (Invalid enumeration value \"image/png\") for clipboard.setImageData.",
+        "An invalid type for setImageData should be rejected.");
+      browser.test.sendMessage("finished invalid type");
+    },
+    manifest: {
+      permissions: ["clipboardWrite"],
+    },
+  });
+
+  await extension.startup();
+  await extension.awaitMessage("finished invalid type");
+  await extension.unload();
+});
+
+if (AppConstants.platform === "android") {
+  add_task(async function test_setImageData_unsupported_on_android() {
+    let extension = ExtensionTestUtils.loadExtension({
+      async background() {
+        // Android does not support images on the clipboard,
+        // so it should not try to decode an image but fail immediately.
+        await browser.test.assertRejects(
+          browser.clipboard.setImageData(new ArrayBuffer(0), "png"),
+          "Writing images to the clipboard is not supported on Android",
+          "Should get an error when setImageData is called on Android.");
+        browser.test.sendMessage("finished unsupported setImageData");
+      },
+      manifest: {
+        permissions: ["clipboardWrite"],
+      },
+    });
+
+    await extension.startup();
+    await extension.awaitMessage("finished unsupported setImageData");
+    await extension.unload();
+  });
+}
+
+</script>
+</body>
+</html>
diff --git a/toolkit/components/extensions/test/mochitest/test_ext_contentscript_about_blank.html b/toolkit/components/extensions/test/mochitest/test_ext_contentscript_about_blank.html
new file mode 100644
index 0000000000..127305715f
--- /dev/null
+++ b/toolkit/components/extensions/test/mochitest/test_ext_contentscript_about_blank.html
@@ -0,0 +1,116 @@
+<!doctype html>
+<html>
+<head>
+  <title>Test content script match_about_blank option</title>
+  <script src="/tests/SimpleTest/SimpleTest.js"></script>
+  <script src="/tests/SimpleTest/ExtensionTestUtils.js"></script>
+  <link rel="stylesheet" type="text/css" href="/tests/SimpleTest/test.css"/>
+</head>
+<body>
+
+<script type="text/javascript">
+"use strict";
+
+add_task(async function test_contentscript_about_blank() {
+  const manifest = {
+    content_scripts: [
+      {
+        match_about_blank: true,
+        matches: ["http://mochi.test/*/file_with_about_blank.html", "https://example.com/*"],
+        all_frames: true,
+        css: ["all.css"],
+        js: ["all.js"],
+      }, {
+        matches: ["http://mochi.test/*/file_with_about_blank.html"],
+        css: ["mochi_without.css"],
+        js: ["mochi_without.js"],
+        all_frames: true,
+      }, {
+        match_about_blank: true,
+        matches: ["http://mochi.test/*/file_with_about_blank.html"],
+        css: ["mochi_with.css"],
+        js: ["mochi_with.js"],
+        all_frames: true,
+      },
+    ],
+  };
+
+  const files = {
+    "all.js": function() {
+      browser.runtime.sendMessage("all");
+    },
+    "all.css": `
+      body { color: red; }
+    `,
+    "mochi_without.js": function() {
+      browser.runtime.sendMessage("mochi_without");
+    },
+    "mochi_without.css": `
+      body { background: yellow; }
+    `,
+    "mochi_with.js": function() {
+      browser.runtime.sendMessage("mochi_with");
+    },
+    "mochi_with.css": `
+      body { text-align: right; }
+    `,
+  };
+
+  function background() {
+    browser.runtime.onMessage.addListener((script, {url}) => {
+      const kind = url.startsWith("about:") ? url : "top";
+      browser.test.sendMessage("script", [script, kind, url]);
+      browser.test.sendMessage(`${script}:${kind}`);
+    });
+  }
+
+  const PATH = "tests/toolkit/components/extensions/test/mochitest/file_with_about_blank.html";
+  const extension = ExtensionTestUtils.loadExtension({manifest, files, background});
+  await extension.startup();
+
+  let count = 0;
+  extension.onMessage("script", script => {
+    info(`script ran: ${script}`);
+    count++;
+  });
+
+  let win = window.open("https://example.com/" + PATH);
+  await Promise.all([
+    extension.awaitMessage("all:top"),
+    extension.awaitMessage("all:about:blank"),
+    extension.awaitMessage("all:about:srcdoc"),
+  ]);
+  is(count, 3, "exactly 3 scripts ran");
+  win.close();
+
+  win = window.open("http://mochi.test:8888/" + PATH);
+  await Promise.all([
+    extension.awaitMessage("all:top"),
+    extension.awaitMessage("all:about:blank"),
+    extension.awaitMessage("all:about:srcdoc"),
+    extension.awaitMessage("mochi_without:top"),
+    extension.awaitMessage("mochi_with:top"),
+    extension.awaitMessage("mochi_with:about:blank"),
+    extension.awaitMessage("mochi_with:about:srcdoc"),
+  ]);
+
+  let style = win.getComputedStyle(win.document.body);
+  is(style.color, "rgb(255, 0, 0)", "top window text color is red");
+  is(style.backgroundColor, "rgb(255, 255, 0)", "top window background is yellow");
+  is(style.textAlign, "right", "top window text is right-aligned");
+
+  let a_b = win.document.getElementById("a_b");
+  style = a_b.contentWindow.getComputedStyle(a_b.contentDocument.body);
+  is(style.color, "rgb(255, 0, 0)", "about:blank iframe text color is red");
+  is(style.backgroundColor, "rgba(0, 0, 0, 0)", "about:blank iframe background is transparent");
+  is(style.textAlign, "right", "about:blank text is right-aligned");
+
+  is(count, 10, "exactly 7 more scripts ran");
+  win.close();
+
+  await extension.unload();
+});
+</script>
+
+</body>
+</html>
diff --git a/toolkit/components/extensions/test/mochitest/test_ext_contentscript_activeTab.html b/toolkit/components/extensions/test/mochitest/test_ext_contentscript_activeTab.html
new file mode 100644
index 0000000000..96091fd959
--- /dev/null
+++ b/toolkit/components/extensions/test/mochitest/test_ext_contentscript_activeTab.html
@@ -0,0 +1,711 @@
+<!DOCTYPE HTML>
+<html>
+<head>
+  <title>Test for content script</title>
+  <script type="text/javascript" src="/tests/SimpleTest/SimpleTest.js"></script>
+  <script type="text/javascript" src="/tests/SimpleTest/ExtensionTestUtils.js"></script>
+  <script type="text/javascript" src="head.js"></script>
+  <link rel="stylesheet" type="text/css" href="/tests/SimpleTest/test.css"/>
+</head>
+<body>
+
+<script type="text/javascript">
+"use strict";
+
+add_task(async function setup() {
+  await SpecialPowers.pushPrefEnv({
+    set: [["extensions.manifestV3.enabled", true]],
+  });
+});
+
+// Create a test extension with the provided function as the background
+// script.  The background script will have a few helpful functions
+// available.
+/* global awaitLoad, gatherFrameSources */
+function makeExtension({
+  background,
+  useScriptingAPI = false,
+  manifest_version = 2,
+  host_permissions,
+}) {
+  // Wait for a webNavigation.onCompleted event where the details for the
+  // loaded page match the attributes of `filter`.
+  function awaitLoad(filter) {
+    return new Promise(resolve => {
+      const listener = details => {
+        if (Object.keys(filter).every(key => details[key] === filter[key])) {
+          browser.webNavigation.onCompleted.removeListener(listener);
+          resolve();
+        }
+      };
+      browser.webNavigation.onCompleted.addListener(listener);
+    });
+  }
+
+  // Return a string with a (sorted) list of the source of all frames
+  // in the given tab into which this extension can inject scripts
+  // (ie all frames for which it has the activeTab permission).
+  // Source is the hostname for frames in http sources, or the full
+  // location href in other documents (eg about: pages)
+  const gatherFrameSources = useScriptingAPI ?
+    async function gatherFrameSources(tabid) {
+      let results = await browser.scripting.executeScript({
+        target: { tabId: tabid, allFrames: true },
+        func: () => window.location.hostname || window.location.href,
+      });
+      // Adjust `result` so that it looks like the one returned by
+      // `tabs.executeScript()`.
+      let result = results.map(res => res.result);
+
+      return String(result.sort());
+    } : async function gatherFrameSources(tabid) {
+      let result = await browser.tabs.executeScript(tabid, {
+        allFrames: true,
+        matchAboutBlank: true,
+        code: "window.location.hostname || window.location.href;",
+      });
+
+      return String(result.sort());
+    };
+
+  const permissions = ["webNavigation"];
+  if (useScriptingAPI) {
+    permissions.push("scripting");
+  }
+
+  // When host_permissions is passed, test "automatic activeTab" for ungranted
+  // host_permissions in mv3, else test with the normal activeTab permission.
+  if (!host_permissions) {
+    permissions.push("activeTab");
+  }
+
+  return ExtensionTestUtils.loadExtension({
+    manifest: {
+      manifest_version,
+      permissions,
+      host_permissions,
+    },
+    background: [
+      `const useScriptingAPI = ${useScriptingAPI};`,
+      `const manifest_version = ${manifest_version};`,
+      `${awaitLoad}`,
+      `${gatherFrameSources}`,
+      `${ExtensionTestCommon.serializeScript(background)}`,
+    ].join("\n")
+  });
+}
+
+// Helper function to verify that executeScript() fails without the activeTab
+// permission (or any specific origin permissions).
+const verifyNoActiveTab = async ({ useScriptingAPI, manifest_version, host_permissions }) => {
+  let extension = makeExtension({
+    async background() {
+      const URL = "http://mochi.test:8888/tests/toolkit/components/extensions/test/mochitest/file_contentscript_activeTab.html";
+
+      let [tab] = await Promise.all([
+        browser.tabs.create({url: URL}),
+        awaitLoad({frameId: 0}),
+      ]);
+
+      await browser.test.assertRejects(
+        gatherFrameSources(tab.id),
+        /^Missing host permission/,
+        "executeScript should fail without activeTab permission"
+      );
+
+      await browser.tabs.remove(tab.id);
+
+      browser.test.notifyPass("no-active-tab");
+    },
+    useScriptingAPI,
+    manifest_version,
+    host_permissions,
+  });
+
+  await extension.startup();
+  await extension.awaitFinish("no-active-tab");
+  await extension.unload();
+};
+
+add_task(async function test_no_activeTab_tabs() {
+  await verifyNoActiveTab({ useScriptingAPI: false });
+});
+
+add_task(async function test_no_activeTab_scripting() {
+  await verifyNoActiveTab({ useScriptingAPI: true });
+});
+
+add_task(async function test_no_activeTab_scripting_mv3() {
+  await verifyNoActiveTab({
+    useScriptingAPI: true,
+    manifest_version: 3,
+    host_permissions: null,
+  });
+});
+
+add_task(async function test_no_activeTab_scripting_mv3_autoActiveTab() {
+  await verifyNoActiveTab({
+    useScriptingAPI: true,
+    manifest_version: 3,
+    host_permissions: ["http://mochi.test/"],
+  });
+});
+
+// Test helper to verify that dynamically created iframes do not get the
+// activeTab permission.
+const verifyDynamicFrames = async ({ useScriptingAPI, manifest_version, host_permissions }) => {
+  let extension = makeExtension({
+    async background() {
+      const BASE_HOST = "www.example.com";
+
+      let [tab] = await Promise.all([
+        browser.tabs.create({url: `https://${BASE_HOST}/`}),
+        awaitLoad({frameId: 0}),
+      ]);
+
+      function inject() {
+        let nframes = 4;
+        function frameLoaded() {
+          nframes--;
+          if (nframes == 0) {
+            browser.runtime.sendMessage("frames-loaded");
+          }
+        }
+
+        let frame = document.createElement("iframe");
+        frame.addEventListener("load", frameLoaded, {once: true});
+        document.body.appendChild(frame);
+
+        let div = document.createElement("div");
+        div.innerHTML = "<iframe src='https://test1.example.com/'></iframe>";
+        let framelist = div.getElementsByTagName("iframe");
+        browser.test.assertEq(1, framelist.length, "Found 1 frame inside div");
+        framelist[0].addEventListener("load", frameLoaded, {once: true});
+        document.body.appendChild(div);
+
+        let div2 = document.createElement("div");
+        div2.innerHTML = "<iframe srcdoc=\"<iframe src='https://test2.example.com/'&gt;</iframe&gt;\"></iframe>";
+        framelist = div2.getElementsByTagName("iframe");
+        browser.test.assertEq(1, framelist.length, "Found 1 frame inside div");
+        framelist[0].addEventListener("load", frameLoaded, {once: true});
+        document.body.appendChild(div2);
+
+        const URL = "https://www.example.com/tests/toolkit/components/extensions/test/mochitest/file_contentscript_iframe.html";
+
+        let xhr = new XMLHttpRequest();
+        xhr.open("GET", URL);
+        xhr.responseType = "document";
+        xhr.overrideMimeType("text/html");
+
+        xhr.addEventListener("load", () => {
+          if (xhr.readyState != 4) {
+            return;
+          }
+          if (xhr.status != 200) {
+            browser.runtime.sendMessage("error");
+          }
+
+          let frame = xhr.response.getElementById("frame");
+          browser.test.assertTrue(frame, "Found frame in response document");
+          frame.addEventListener("load", frameLoaded, {once: true});
+          document.body.appendChild(frame);
+        }, {once: true});
+        xhr.addEventListener("error", () => {
+          browser.runtime.sendMessage("error");
+        }, {once: true});
+        xhr.send();
+      }
+
+      browser.test.onMessage.addListener(async msg => {
+        if (msg !== "go") {
+          browser.test.fail(`unexpected message received: ${msg}`);
+          return;
+        }
+
+        let loadedPromise = new Promise((resolve, reject) => {
+          let listener = msg => {
+            let unlisten = () => browser.runtime.onMessage.removeListener(listener);
+            if (msg == "frames-loaded") {
+              unlisten();
+              resolve();
+            } else if (msg == "error") {
+              unlisten();
+              reject();
+            }
+          };
+          browser.runtime.onMessage.addListener(listener);
+        });
+
+        if (useScriptingAPI) {
+          await browser.scripting.executeScript({
+            target: { tabId: tab.id },
+            func: inject,
+          });
+        } else {
+          await browser.tabs.executeScript(tab.id, {
+            code: `(${inject})();`,
+          });
+        }
+
+        await loadedPromise;
+
+        let result = await gatherFrameSources(tab.id);
+
+        if (manifest_version < 3) {
+          browser.test.assertEq(
+            String([BASE_HOST]),
+            result,
+            "Script is not injected into dynamically created frames"
+          );
+        } else {
+          browser.test.assertEq(
+            String(["about:blank", "about:srcdoc", BASE_HOST]),
+            result,
+            `Script injected only into (same origin) about:blank-ish dynamically created frames`
+          );
+        }
+
+        await browser.tabs.remove(tab.id);
+
+        browser.test.notifyPass("dynamic-frames");
+      });
+
+      browser.test.sendMessage("ready", tab.id);
+    },
+    useScriptingAPI,
+    manifest_version,
+    host_permissions,
+  });
+
+  await extension.startup();
+
+  let tabId = await extension.awaitMessage("ready");
+  extension.grantActiveTab(tabId);
+
+  extension.sendMessage("go");
+  await extension.awaitFinish("dynamic-frames");
+
+  await extension.unload();
+};
+
+add_task(async function test_dynamic_frames_tabs() {
+  await verifyDynamicFrames({ useScriptingAPI: false });
+});
+
+add_task(async function test_dynamic_frames_scripting() {
+  await verifyDynamicFrames({ useScriptingAPI: true });
+});
+
+add_task(async function test_dynamic_frames_scripting_mv3() {
+  await verifyDynamicFrames({
+    useScriptingAPI: true,
+    manifest_version: 3,
+    host_permissions: null,
+  });
+});
+
+add_task(async function test_dynamic_frames_scripting_mv3_autoActiveTab() {
+  await verifyDynamicFrames({
+    useScriptingAPI: true,
+    manifest_version: 3,
+    host_permissions: ["https://www.example.com/"],
+  });
+});
+
+// Test helper to verify that an iframe created from an <iframe srcdoc> gets
+// the activeTab permission.
+const verifySrcdoc = async ({ useScriptingAPI, manifest_version, host_permissions }) => {
+  let extension = makeExtension({
+    async background() {
+      const URL = "http://mochi.test:8888/tests/toolkit/components/extensions/test/mochitest/file_contentscript_activeTab2.html";
+      const OUTER_SOURCE = "about:srcdoc";
+      const PAGE_SOURCE = "mochi.test";
+      const FRAME_SOURCE = "test1.example.com";
+
+      let [tab] = await Promise.all([
+        browser.tabs.create({url: URL}),
+        awaitLoad({frameId: 0}),
+      ]);
+
+      browser.test.onMessage.addListener(async msg => {
+        if (msg !== "go") {
+          browser.test.fail(`unexpected message received: ${msg}`);
+          return;
+        }
+
+        let result = await gatherFrameSources(tab.id);
+
+        if (manifest_version < 3) {
+          browser.test.assertEq(
+            String([OUTER_SOURCE, PAGE_SOURCE, FRAME_SOURCE]),
+            result,
+            "Script is injected into frame created from <iframe srcdoc>"
+          );
+        } else {
+          browser.test.assertEq(
+            String([OUTER_SOURCE, PAGE_SOURCE]),
+            result,
+            "Script is not injected into cross-origin frame created from <iframe srcdoc>"
+          );
+        }
+
+        await browser.tabs.remove(tab.id);
+
+        browser.test.notifyPass("srcdoc");
+      });
+
+      browser.test.sendMessage("ready", tab.id);
+    },
+    useScriptingAPI,
+    manifest_version,
+    host_permissions,
+  });
+
+  await extension.startup();
+
+  let tabId = await extension.awaitMessage("ready");
+  extension.grantActiveTab(tabId);
+
+  extension.sendMessage("go");
+  await extension.awaitFinish("srcdoc");
+
+  await extension.unload();
+};
+
+add_task(async function test_srcdoc_tabs() {
+  await verifySrcdoc({ useScriptingAPI: false });
+});
+
+add_task(async function test_srcdoc_scripting() {
+  await verifySrcdoc({ useScriptingAPI: true });
+});
+
+add_task(async function test_srcdoc_scripting_mv3() {
+  await verifySrcdoc({
+    useScriptingAPI: true,
+    manifest_version: 3,
+    host_permissions: null,
+  });
+});
+
+add_task(async function test_srcdoc_scripting_mv3_autoActiveTab() {
+  await verifySrcdoc({
+    useScriptingAPI: true,
+    manifest_version: 3,
+    host_permissions: ["http://mochi.test/"],
+  });
+});
+
+// Test helper to verify that navigating frames by setting the src attribute
+// from the parent page revokes the activeTab permission.
+const verifyNavigateBySrc = async ({ useScriptingAPI, manifest_version, host_permissions }) => {
+  let extension = makeExtension({
+    async background() {
+      const URL = "http://mochi.test:8888/tests/toolkit/components/extensions/test/mochitest/file_contentscript_activeTab.html";
+      const PAGE_SOURCE = "mochi.test";
+      const EMPTY_SOURCE = "about:blank";
+      const FRAME_SOURCE = "test1.example.com";
+
+      let [tab] = await Promise.all([
+        browser.tabs.create({url: URL}),
+        awaitLoad({frameId: 0}),
+      ]);
+
+      browser.test.onMessage.addListener(async msg => {
+        if (msg !== "go") {
+          browser.test.fail(`unexpected message received: ${msg}`);
+          return;
+        }
+
+        let result = await gatherFrameSources(tab.id);
+        if (manifest_version < 3) {
+          browser.test.assertEq(
+            String([EMPTY_SOURCE, PAGE_SOURCE, FRAME_SOURCE]),
+            result,
+            "In original page, script is injected into base page and original frames"
+          );
+        } else {
+          browser.test.assertEq(
+            String([EMPTY_SOURCE, PAGE_SOURCE]),
+            result,
+            "In original page, script is injected into same-origin frames"
+          );
+        }
+
+        let loadedPromise = awaitLoad({tabId: tab.id});
+
+        let func = () => {
+          document.getElementById('emptyframe').src = 'http://test2.example.com/';
+        };
+
+        if (useScriptingAPI) {
+          await browser.scripting.executeScript({
+            target: { tabId: tab.id },
+            func,
+          });
+        } else {
+          await browser.tabs.executeScript(tab.id, { code: `(${func})();` });
+        }
+
+        await loadedPromise;
+
+
+        result = await gatherFrameSources(tab.id);
+        if (manifest_version < 3) {
+          browser.test.assertEq(
+            String([PAGE_SOURCE, FRAME_SOURCE]),
+            result,
+            "Script is not injected into initially empty frame after navigation"
+          );
+        } else {
+          browser.test.assertEq(
+            String([PAGE_SOURCE]),
+            result,
+            "Script is not injected into initially empty frame after navigation"
+          );
+        }
+
+        loadedPromise = awaitLoad({tabId: tab.id});
+
+        func = () => {
+          document.getElementById('regularframe').src = 'http://mochi.test:8888/';
+        };
+
+        if (useScriptingAPI) {
+          await browser.scripting.executeScript({
+            target: { tabId: tab.id },
+            func,
+          });
+        } else {
+          await browser.tabs.executeScript(tab.id, { code: `(${func})();` });
+        }
+
+        await loadedPromise;
+
+        result = await gatherFrameSources(tab.id);
+
+        if (manifest_version < 3) {
+          browser.test.assertEq(
+            String([PAGE_SOURCE]),
+            result,
+            "Script is not injected into regular frame after navigation"
+          );
+        } else {
+          browser.test.assertEq(
+            String([PAGE_SOURCE, PAGE_SOURCE]),
+            result,
+            "Script injected into frame after navigating to same-origin"
+          );
+        }
+
+        await browser.tabs.remove(tab.id);
+        browser.test.notifyPass("test-scripts");
+      });
+
+      browser.test.sendMessage("ready", tab.id);
+    },
+    useScriptingAPI,
+    manifest_version,
+    host_permissions,
+  });
+
+  await extension.startup();
+
+  let tabId = await extension.awaitMessage("ready");
+  extension.grantActiveTab(tabId);
+
+  extension.sendMessage("go");
+  await extension.awaitFinish("test-scripts");
+
+  await extension.unload();
+};
+
+add_task(async function test_navigate_by_src_tabs() {
+  await verifyNavigateBySrc({ useScriptingAPI: false });
+});
+
+add_task(async function test_navigate_by_src_scripting() {
+  await verifyNavigateBySrc({ useScriptingAPI: true });
+});
+
+add_task(async function test_navigate_by_src_scripting_mv3() {
+  await verifyNavigateBySrc({
+    useScriptingAPI: true,
+    manifest_version: 3,
+    host_permissions: null,
+  });
+});
+
+add_task(async function test_navigate_by_src_scripting_mv3_autoActiveTab() {
+  await verifyNavigateBySrc({
+    useScriptingAPI: true,
+    manifest_version: 3,
+    host_permissions: ["http://mochi.test/"],
+  });
+});
+
+// Test helper to verify that navigating frames by setting window.location from
+// inside the frame revokes the activeTab permission.
+const verifyNavigateByWindowLocation = async ({ useScriptingAPI, manifest_version, host_permissions }) => {
+  let extension = makeExtension({
+    async background() {
+      const URL = "http://mochi.test:8888/tests/toolkit/components/extensions/test/mochitest/file_contentscript_activeTab.html";
+      const PAGE_SOURCE = "mochi.test";
+      const EMPTY_SOURCE = "about:blank";
+      const FRAME_SOURCE = "test1.example.com";
+
+      let [tab] = await Promise.all([
+        browser.tabs.create({url: URL}),
+        awaitLoad({frameId: 0}),
+      ]);
+
+      browser.test.onMessage.addListener(async msg => {
+        if (msg !== "go") {
+          browser.test.fail(`unexpected message received: ${msg}`);
+          return;
+        }
+
+        let result = await gatherFrameSources(tab.id);
+
+        if (manifest_version < 3) {
+          browser.test.assertEq(
+            String([EMPTY_SOURCE, PAGE_SOURCE, FRAME_SOURCE]),
+            result,
+            "Script initially injected into all frames"
+          );
+        } else {
+          browser.test.assertEq(
+            String([EMPTY_SOURCE, PAGE_SOURCE]),
+            result,
+            "Script initially injected into all same-origin frames"
+          );
+        }
+
+        let nframes = 0;
+        let frames = await browser.webNavigation.getAllFrames({tabId: tab.id});
+        for (let frame of frames) {
+          if (frame.parentFrameId == -1) {
+            continue;
+          }
+
+          if (manifest_version >= 3 && frame.url.includes(FRAME_SOURCE)) {
+            // In MV3, can't access cross-origin iframes from the start.
+
+            let invalidPromise = browser.scripting.executeScript({
+              target: { tabId: tab.id, frameIds: [frame.frameId] },
+              func: () => window.location.hostname,
+            });
+            await browser.test.assertRejects(
+              invalidPromise,
+              /^Missing host permission for the tab or frames/,
+              "executeScript should fail on cross-origin frame"
+            );
+
+            continue;
+          }
+
+          let loadPromise = awaitLoad({
+            tabId: tab.id,
+            frameId: frame.frameId,
+          });
+
+          let func = () => {
+            window.location.href = 'https://test2.example.com/';
+          };
+
+          if (useScriptingAPI) {
+            await browser.scripting.executeScript({
+              target: { tabId: tab.id, frameIds: [frame.frameId] },
+              func,
+            });
+          } else {
+            await browser.tabs.executeScript(tab.id, {
+              frameId: frame.frameId,
+              matchAboutBlank: true,
+              code: `(${func})();`,
+            });
+          }
+
+          await loadPromise;
+
+          let executePromise;
+          func = () => window.location.hostname;
+
+          if (useScriptingAPI) {
+            executePromise = browser.scripting.executeScript({
+              target: { tabId: tab.id, frameIds: [frame.frameId] },
+              func,
+            });
+          } else {
+            executePromise = browser.tabs.executeScript(tab.id, {
+              frameId: frame.frameId,
+              matchAboutBlank: true,
+              code: `(${func})();`,
+            });
+          }
+
+          await browser.test.assertRejects(
+            executePromise,
+            /^Missing host permission for the tab or frames/,
+            "executeScript should have failed on navigated frame"
+          );
+
+          nframes++;
+        }
+
+        if (manifest_version < 3) {
+          browser.test.assertEq(2, nframes, "Found 2 frames");
+        } else {
+          browser.test.assertEq(1, nframes, "Found 1 frame");
+        }
+
+        await browser.tabs.remove(tab.id);
+        browser.test.notifyPass("scripted-navigation");
+      });
+
+      browser.test.sendMessage("ready", tab.id);
+    },
+    useScriptingAPI,
+    manifest_version,
+    host_permissions,
+  });
+
+  await extension.startup();
+
+  let tabId = await extension.awaitMessage("ready");
+  extension.grantActiveTab(tabId);
+
+  extension.sendMessage("go");
+  await extension.awaitFinish("scripted-navigation");
+
+  await extension.unload();
+};
+
+add_task(async function test_navigate_by_window_location_tabs() {
+  await verifyNavigateByWindowLocation({ useScriptingAPI: false });
+});
+
+add_task(async function test_navigate_by_window_location_scripting() {
+  await verifyNavigateByWindowLocation({ useScriptingAPI: true });
+});
+
+add_task(async function test_navigate_by_window_location_scripting_mv3() {
+  await verifyNavigateByWindowLocation({
+    useScriptingAPI: true,
+    manifest_version: 3,
+    host_permissions: null,
+   });
+});
+
+add_task(async function test_navigate_by_window_location_scripting_mv3_autoActiveTab() {
+  await verifyNavigateByWindowLocation({
+    useScriptingAPI: true,
+    manifest_version: 3,
+    host_permissions: ["http://mochi.test/"],
+   });
+});
+
+</script>
+
+</body>
+</html>
diff --git a/toolkit/components/extensions/test/mochitest/test_ext_contentscript_cache.html b/toolkit/components/extensions/test/mochitest/test_ext_contentscript_cache.html
new file mode 100644
index 0000000000..6e2420e1c5
--- /dev/null
+++ b/toolkit/components/extensions/test/mochitest/test_ext_contentscript_cache.html
@@ -0,0 +1,117 @@
+<!DOCTYPE HTML>
+<html>
+<head>
+  <title>Test for content script caching</title>
+  <script src="/tests/SimpleTest/SimpleTest.js"></script>
+  <script src="/tests/SimpleTest/ExtensionTestUtils.js"></script>
+  <script type="text/javascript" src="head.js"></script>
+  <link rel="stylesheet" type="text/css" href="/tests/SimpleTest/test.css"/>
+</head>
+<body>
+
+<script type="text/javascript">
+"use strict";
+
+// This file defines content scripts.
+
+const BASE = "http://mochi.test:8888/tests/toolkit/components/extensions/test/mochitest";
+
+add_task(async function test_contentscript_cache() {
+  let extension = ExtensionTestUtils.loadExtension({
+    manifest: {
+      content_scripts: [{
+        "matches": ["http://mochi.test/*/file_sample.html"],
+        "js": ["content_script.js"],
+        "run_at": "document_start",
+      }],
+
+      permissions: ["<all_urls>", "tabs"],
+    },
+
+    async background() {
+      // Force our extension instance to be initialized for the current content process.
+      await browser.tabs.insertCSS({code: ""});
+
+      browser.test.sendMessage("origin", location.origin);
+    },
+
+    files: {
+      "content_script.js": function() {
+        browser.test.sendMessage("content-script-loaded");
+      },
+    },
+  });
+
+  await extension.startup();
+
+  let origin = await extension.awaitMessage("origin");
+  let scriptUrl = `${origin}/content_script.js`;
+
+  const { ExtensionProcessScript } = SpecialPowers.ChromeUtils.import(
+    "resource://gre/modules/ExtensionProcessScript.jsm"
+  );
+  let ext = ExtensionProcessScript.getExtensionChild(extension.id);
+
+  ext.staticScripts.expiryTimeout = 3000;
+  is(ext.staticScripts.size, 0, "Should have no cached scripts");
+
+  let win = window.open(`${BASE}/file_sample.html`);
+  await extension.awaitMessage("content-script-loaded");
+
+  if (AppConstants.platform !== "android") {
+    is(ext.staticScripts.size, 1, "Should have one cached script");
+    ok(ext.staticScripts.has(scriptUrl), "Script cache should contain script URL");
+  }
+
+  let chromeScript, chromeScriptDone;
+  let { appinfo } = SpecialPowers.Services;
+  if (appinfo.processType === appinfo.PROCESS_TYPE_CONTENT) {
+    /* globals addMessageListener, assert */
+    chromeScript = SpecialPowers.loadChromeScript(() => {
+      /* eslint-env mozilla/chrome-script */
+      addMessageListener("check-script-cache", extensionId => {
+        const { ExtensionProcessScript } = ChromeUtils.import(
+          "resource://gre/modules/ExtensionProcessScript.jsm"
+        );
+        let ext = ExtensionProcessScript.getExtensionChild(extensionId);
+
+        if (ext && ext.staticScripts) {
+          assert.equal(ext.staticScripts.size, 0, "Should have no cached scripts in the parent process");
+        }
+
+        sendAsyncMessage("done");
+      });
+    });
+    chromeScript.sendAsyncMessage("check-script-cache", extension.id);
+    chromeScriptDone = chromeScript.promiseOneMessage("done");
+  }
+
+  SimpleTest.requestFlakyTimeout("Required to test expiry timeout");
+  await new Promise(resolve => setTimeout(resolve, 3000));
+  is(ext.staticScripts.size, 0, "Should have no cached scripts");
+
+  if (chromeScript) {
+    await chromeScriptDone;
+    chromeScript.destroy();
+  }
+
+  win.close();
+
+  win = window.open(`${BASE}/file_sample.html`);
+  await extension.awaitMessage("content-script-loaded");
+
+  is(ext.staticScripts.size, 1, "Should have one cached script");
+  ok(ext.staticScripts.has(scriptUrl));
+
+  SpecialPowers.Services.obs.notifyObservers(null, "memory-pressure", "heap-minimize");
+
+  is(ext.staticScripts.size, 0, "Should have no cached scripts after heap-minimize");
+
+  win.close();
+
+  await extension.unload();
+});
+</script>
+
+</body>
+</html>
diff --git a/toolkit/components/extensions/test/mochitest/test_ext_contentscript_canvas.html b/toolkit/components/extensions/test/mochitest/test_ext_contentscript_canvas.html
new file mode 100644
index 0000000000..8659d8c409
--- /dev/null
+++ b/toolkit/components/extensions/test/mochitest/test_ext_contentscript_canvas.html
@@ -0,0 +1,134 @@
+<!doctype html>
+<html>
+<head>
+  <title>Test content script access to canvas drawWindow()</title>
+  <script src="/tests/SimpleTest/SimpleTest.js"></script>
+  <script src="/tests/SimpleTest/ExtensionTestUtils.js"></script>
+  <script src="head.js"></script>
+  <link rel="stylesheet" type="text/css" href="/tests/SimpleTest/test.css"/>
+</head>
+<script>
+"use strict";
+
+add_task(async function test_drawWindow() {
+  const permissions = [
+    "<all_urls>",
+  ];
+
+  const content_scripts = [{
+    matches: ["https://example.org/*"],
+    js: ["content_script.js"],
+  }];
+
+  const files = {
+    "content_script.js": () => {
+      const canvas = document.createElement("canvas");
+      const ctx = canvas.getContext("2d");
+      try {
+        ctx.drawWindow(window, 0, 0, 10, 10, "red");
+        const {data} = ctx.getImageData(0, 0, 10, 10);
+        browser.test.sendMessage("success", data.slice(0, 3).join());
+      } catch (e) {
+        browser.test.sendMessage("error", e.message);
+      }
+    },
+  };
+
+  const first = ExtensionTestUtils.loadExtension({
+    manifest: {
+      permissions,
+      content_scripts
+    },
+    files
+  });
+  const second = ExtensionTestUtils.loadExtension({
+    manifest: {
+      content_scripts
+    },
+    files
+  });
+
+  consoleMonitor.start([{ message: /Use of drawWindow [\w\s]+ is deprecated. Use tabs.captureTab/ }]);
+
+  await first.startup();
+  await second.startup();
+
+  const win = window.open("https://example.org/tests/toolkit/components/extensions/test/mochitest/file_to_drawWindow.html");
+
+  const colour = await first.awaitMessage("success");
+  is(colour, "255,255,153", "drawWindow() call was successful: #ff9 == rgb(255,255,153)");
+
+  const error = await second.awaitMessage("error");
+  is(error, "ctx.drawWindow is not a function", "drawWindow() method not awailable without permission");
+
+  win.close();
+  await first.unload();
+  await second.unload();
+  await consoleMonitor.finished();
+});
+
+add_task(async function test_tainted_canvas() {
+  const permissions = [
+    "<all_urls>",
+  ];
+
+  const content_scripts = [{
+    matches: ["https://example.org/*"],
+    js: ["content_script.js"],
+  }];
+
+  const files = {
+    "content_script.js": () => {
+      const canvas = document.createElement("canvas");
+      const ctx = canvas.getContext("2d");
+      const img = new Image();
+
+      img.onload = function() {
+        ctx.drawImage(img, 0, 0);
+        try {
+          const png = canvas.toDataURL();
+          const {data} = ctx.getImageData(0, 0, 10, 10);
+          browser.test.sendMessage("success", {png, colour: data.slice(0, 4).join()});
+        } catch (e) {
+          browser.test.log(`Exception: ${e.message}`);
+          browser.test.sendMessage("error", e.message);
+        }
+      };
+
+      // Cross-origin image from example.com.
+      img.src = "https://example.com/tests/toolkit/components/extensions/test/mochitest/file_image_good.png";
+    },
+  };
+
+  const first = ExtensionTestUtils.loadExtension({
+    manifest: {
+      permissions,
+      content_scripts
+    },
+    files
+  });
+  const second = ExtensionTestUtils.loadExtension({
+    manifest: {
+      content_scripts
+    },
+    files
+  });
+
+  await first.startup();
+  await second.startup();
+
+  const win = window.open("https://example.org/tests/toolkit/components/extensions/test/mochitest/file_to_drawWindow.html");
+
+  const {png, colour} = await first.awaitMessage("success");
+  ok(png.startsWith("data:image/png;base64,"), "toDataURL() call was successful.");
+  is(colour, "0,0,0,0", "getImageData() returned the correct colour (transparent).");
+
+  const error = await second.awaitMessage("error");
+  is(error, "The operation is insecure.", "toDataURL() throws without permission.");
+
+  win.close();
+  await first.unload();
+  await second.unload();
+});
+
+</script>
diff --git a/toolkit/components/extensions/test/mochitest/test_ext_contentscript_devtools_metadata.html b/toolkit/components/extensions/test/mochitest/test_ext_contentscript_devtools_metadata.html
new file mode 100644
index 0000000000..d7030258b3
--- /dev/null
+++ b/toolkit/components/extensions/test/mochitest/test_ext_contentscript_devtools_metadata.html
@@ -0,0 +1,77 @@
+<!DOCTYPE HTML>
+<html>
+<head>
+  <title>Test for Sandbox metadata on WebExtensions ContentScripts</title>
+  <script src="/tests/SimpleTest/SimpleTest.js"></script>
+  <script src="/tests/SimpleTest/ExtensionTestUtils.js"></script>
+  <script type="text/javascript" src="head.js"></script>
+  <link rel="stylesheet" type="text/css" href="/tests/SimpleTest/test.css"/>
+</head>
+<body>
+
+<script type="text/javascript">
+"use strict";
+
+add_task(async function test_contentscript_devtools_sandbox_metadata() {
+  function contentScript() {
+    browser.runtime.sendMessage("contentScript.executed");
+  }
+
+  function background() {
+    browser.runtime.onMessage.addListener((msg) => {
+      if (msg == "contentScript.executed") {
+        browser.test.notifyPass("contentScript.executed");
+      }
+    });
+  }
+
+  let extensionData = {
+    manifest: {
+      content_scripts: [
+        {
+          "matches": ["http://mochi.test/*/file_sample.html"],
+          "js": ["content_script.js"],
+          "run_at": "document_idle",
+        },
+      ],
+    },
+
+    background,
+    files: {
+      "content_script.js": contentScript,
+    },
+  };
+
+  let extension = ExtensionTestUtils.loadExtension(extensionData);
+
+  await extension.startup();
+
+  let win = window.open("file_sample.html");
+
+  let innerWindowID = SpecialPowers.wrap(win).windowGlobalChild.innerWindowId;
+
+  await extension.awaitFinish("contentScript.executed");
+
+  const { ExtensionContent } = SpecialPowers.ChromeUtils.import(
+    "resource://gre/modules/ExtensionContent.jsm"
+  );
+
+  let res = ExtensionContent.getContentScriptGlobals(win);
+  is(res.length, 1, "Got the expected array of globals");
+  let metadata = SpecialPowers.Cu.getSandboxMetadata(res[0]) || {};
+
+  is(metadata.addonId, extension.id, "Got the expected addonId");
+  is(metadata["inner-window-id"], innerWindowID, "Got the expected inner-window-id");
+
+  await extension.unload();
+  info("extension unloaded");
+
+  res = ExtensionContent.getContentScriptGlobals(win);
+  is(res.length, 0, "No content scripts globals found once the extension is unloaded");
+
+  win.close();
+});
+</script>
+
+</body>
+</html>
diff --git a/toolkit/components/extensions/test/mochitest/test_ext_contentscript_fission_frame.html b/toolkit/components/extensions/test/mochitest/test_ext_contentscript_fission_frame.html
new file mode 100644
index 0000000000..6e03c3e9cd
--- /dev/null
+++ b/toolkit/components/extensions/test/mochitest/test_ext_contentscript_fission_frame.html
@@ -0,0 +1,109 @@
+<!doctype html>
+<head>
+  <title>Test content script in cross-origin frame</title>
+  <script src="/tests/SimpleTest/SimpleTest.js"></script>
+  <script src="/tests/SimpleTest/ExtensionTestUtils.js"></script>
+  <script src="head.js"></script>
+  <link rel="stylesheet" href="/tests/SimpleTest/test.css"/>
+</head>
+<script>
+"use strict";
+
+add_task(async function test_content_script_cross_origin_frame() {
+
+  const extensionData = {
+    manifest: {
+      content_scripts: [{
+        matches: ["https://example.net/*/file_sample.html"],
+        all_frames: true,
+        js: ["cs.js"],
+      }],
+      permissions: ["https://example.net/"],
+    },
+
+    background() {
+      browser.runtime.onConnect.addListener(port => {
+        port.onMessage.addListener(async num => {
+          let { tab, url, frameId } = port.sender;
+
+          browser.test.assertTrue(frameId > 0, "sender frameId is ok");
+          browser.test.assertTrue(url.endsWith("file_sample.html"), "url is ok");
+
+          let shared = await browser.tabs.executeScript(tab.id, {
+            allFrames: true,
+            code: `window.sharedVal`,
+          });
+          browser.test.assertEq(shared[0], 357, "CS runs in a shared Sandbox");
+
+          let code = "does.not.exist";
+          await browser.test.assertRejects(
+            browser.tabs.executeScript(tab.id, { allFrames: true, code }),
+            /does is not defined/,
+            "Got the expected rejection from tabs.executeScript"
+          );
+
+          code = "() => {}";
+          await browser.test.assertRejects(
+            browser.tabs.executeScript(tab.id, { allFrames: true, code }),
+            /Script .* result is non-structured-clonable data/,
+            "Got the expected rejection from tabs.executeScript"
+          );
+
+          let result = await browser.tabs.sendMessage(tab.id, num);
+          port.postMessage(result);
+          port.disconnect();
+        });
+      });
+    },
+
+    files: {
+      "cs.js"() {
+        let text = document.getElementById("test").textContent;
+        browser.test.assertEq(text, "Sample text", "CS can access page DOM");
+
+        let manifest = browser.runtime.getManifest();
+        browser.test.assertEq(manifest.version, "1.0");
+        browser.test.assertEq(manifest.name, "Generated extension");
+
+        browser.runtime.onMessage.addListener(async num => {
+          browser.test.log("content script received tabs.sendMessage");
+          return num * 3;
+        })
+
+        let response;
+        window.sharedVal = 357;
+
+        let port = browser.runtime.connect();
+        port.onMessage.addListener(num => {
+          response = num;
+        });
+        port.onDisconnect.addListener(() => {
+          browser.test.assertEq(response, 21, "Got correct response");
+          browser.test.notifyPass();
+        });
+        port.postMessage(7);
+      },
+    },
+  };
+
+  info("Load first extension");
+  let ext1 = ExtensionTestUtils.loadExtension(extensionData);
+  await ext1.startup();
+
+  info("Load a page, test content scripts in new frame with extension loaded");
+  let base = "https://example.org/tests/toolkit/components/extensions/test";
+  let win = window.open(`${base}/mochitest/file_with_xorigin_frame.html`);
+
+  await ext1.awaitFinish();
+  await ext1.unload();
+
+  info("Load second extension, test content scripts in existing frame");
+  let ext2 = ExtensionTestUtils.loadExtension(extensionData);
+  await ext2.startup();
+  await ext2.awaitFinish();
+
+  win.close();
+  await ext2.unload();
+});
+
+</script>
diff --git a/toolkit/components/extensions/test/mochitest/test_ext_contentscript_getFrameId.html b/toolkit/components/extensions/test/mochitest/test_ext_contentscript_getFrameId.html
new file mode 100644
index 0000000000..d679634030
--- /dev/null
+++ b/toolkit/components/extensions/test/mochitest/test_ext_contentscript_getFrameId.html
@@ -0,0 +1,189 @@
+<!doctype html>
+<head>
+  <title>Test content script runtime.getFrameId</title>
+  <script src="/tests/SimpleTest/SimpleTest.js"></script>
+  <script src="/tests/SimpleTest/ExtensionTestUtils.js"></script>
+  <script src="head.js"></script>
+  <link rel="stylesheet" href="/tests/SimpleTest/test.css"/>
+</head>
+<script>
+"use strict";
+
+add_task(async function test_runtime_getFrameId_invalid() {
+  let extension = ExtensionTestUtils.loadExtension({
+    async background() {
+      let proxy = new Proxy(window, {});
+      let proto = Object.create(window);
+
+      class FakeFrame extends HTMLIFrameElement {
+        constructor() {
+          super();
+          console.log("FakeFrame ctor");  // eslint-disable-line
+        }
+      }
+      customElements.define('fake-frame', FakeFrame, { extends: 'iframe' });
+      let custom = document.createElement("fake-frame");
+
+      let invalid = [null, 13, "blah", document.body, proxy, proto, custom];
+
+      for (let value of invalid) {
+        browser.test.assertThrows(
+          () => browser.runtime.getFrameId(value),
+          /Invalid argument/,
+          "Correct exception thrown."
+        );
+      }
+
+      let detached = document.createElement("iframe");
+      let id = browser.runtime.getFrameId(detached);
+      browser.test.assertEq(id, -1, "Detached iframe has no frameId.");
+
+      browser.test.sendMessage("done");
+    },
+  });
+
+  await extension.startup();
+  await extension.awaitMessage("done");
+  await extension.unload();
+});
+
+add_task(async function test_contentscript_runtime_getFrameId() {
+  let extension = ExtensionTestUtils.loadExtension({
+    manifest: {
+      permissions: ["webNavigation", "tabs"],
+      host_permissions: ["https://example.org/"],
+    },
+
+    files: {
+      "cs.js"() {
+        browser.test.log(`Content script loaded on: ${location.href}`);
+        let parents = {};
+
+        // Recursivelly walk descendant frames and get parent frameIds.
+        function visit(win) {
+          let frameId = browser.runtime.getFrameId(win);
+          let parentId = browser.runtime.getFrameId(win.parent);
+          parents[frameId] = (win.parent != win) ? parentId : -1;
+
+          try {
+            let frameEl = browser.runtime.getFrameId(win.frameElement);
+            browser.test.assertEq(frameId, frameEl, "frameElement id correct");
+          } catch (e) {
+            // Can't access a cross-origin .frameElement.
+          }
+
+          for (let i = 0; i < win.frames.length; i++) {
+            visit(win.frames[i]);
+          }
+        }
+        visit(window);
+
+        // Add the <embed> frame if it exists.
+        let embed = document.querySelector("embed");
+        if (embed) {
+          let id = browser.runtime.getFrameId(embed);
+          parents[id] = 0;
+        }
+
+        // Add the <object> frame if it exists.
+        let object = document.querySelector("object");
+        if (object) {
+          let id = browser.runtime.getFrameId(object);
+          parents[id] = 0;
+        }
+
+        browser.test.log(`Parents tree: ${JSON.stringify(parents)}`);
+        return parents;
+      },
+
+      async "closedPopup.js"() {
+        let popup = window.open("https://example.org/?popup");
+        popup.close();
+        for (let i = 0; i < 100; i++) {
+          await new Promise(r => setTimeout(r, 50));
+          try {
+            popup.blur();
+          } catch(e) {
+            if (e.message === "can't access dead object") {
+              browser.test.assertThrows(
+                () => browser.runtime.getFrameId(popup),
+                /An exception was thrown/,
+                "Passing a dead object throws."
+              );
+              browser.test.sendMessage("done");
+              return;
+            }
+          }
+        }
+        browser.test.fail("Timed out while waiting for popup to close.");
+      },
+      "closedPopup.html": `
+        <!doctype html>
+        <meta charset="utf-8">
+        <script src="closedPopup.js"><\/script>
+      `,
+    },
+
+    async background() {
+      let base = "https://example.org/tests/toolkit/components/extensions/test/mochitest";
+      let files = {
+        "file_contains_iframe.html": 2,
+        "file_WebNavigation_page1.html": 2,
+        "file_with_xorigin_frame.html": 2,
+        // Contains all of the above.
+        "file_with_subframes_and_embed.html": 9,
+      };
+
+      for (let [file, count] of Object.entries(files)) {
+        let tab;
+        let completed = new Promise(resolve => {
+          browser.webNavigation.onCompleted.addListener(function cb(details) {
+            browser.test.log(`onCompleted: ${JSON.stringify(details)}`);
+
+            if (details.tabId === tab?.id && details.frameId === 0) {
+              browser.webNavigation.onCompleted.removeListener(cb);
+              resolve();
+            }
+          });
+        });
+
+        browser.test.log(`Load a test page: ${file}`);
+        tab = await browser.tabs.create({ url: `${base}/${file}` });
+        await completed;
+
+        let [parents] = await browser.tabs.executeScript(tab.id, {
+          file: "cs.js"
+        });
+
+        let all = await browser.webNavigation.getAllFrames({ tabId: tab.id });
+        browser.test.log(`getAllFrames: ${JSON.stringify(all)}`);
+
+        browser.test.assertEq(all.length, count, "All frames accounted for.");
+
+        browser.test.assertEq(
+          Object.keys(parents).length,
+          count,
+          "All frames accounted for from content script."
+        );
+
+        for (let frame of all) {
+          browser.test.assertEq(
+            frame.parentFrameId,
+            parents[frame.frameId],
+            "Correct frame ancestor info."
+          );
+        }
+
+        await browser.tabs.remove(tab.id);
+      }
+
+      browser.tabs.create({ url: browser.runtime.getURL("closedPopup.html" )});
+    },
+  });
+
+  await extension.startup();
+  await extension.awaitMessage("done");
+  await extension.unload();
+});
+
+</script>
diff --git a/toolkit/components/extensions/test/mochitest/test_ext_contentscript_incognito.html b/toolkit/components/extensions/test/mochitest/test_ext_contentscript_incognito.html
new file mode 100644
index 0000000000..de2a2571a9
--- /dev/null
+++ b/toolkit/components/extensions/test/mochitest/test_ext_contentscript_incognito.html
@@ -0,0 +1,101 @@
+<!DOCTYPE HTML>
+<html>
+<head>
+  <title>Test for content script private browsing ID</title>
+  <script src="/tests/SimpleTest/SimpleTest.js"></script>
+  <script src="/tests/SimpleTest/ChromeTask.js"></script>
+  <script src="/tests/SimpleTest/ExtensionTestUtils.js"></script>
+  <script type="text/javascript" src="head.js"></script>
+  <link rel="stylesheet" type="text/css" href="/tests/SimpleTest/test.css"/>
+</head>
+<body>
+
+<script type="text/javascript">
+"use strict";
+
+async function test_contentscript_incognito() {
+  let extension = ExtensionTestUtils.loadExtension({
+    incognitoOverride: "spanning",
+    manifest: {
+      content_scripts: [
+        {
+          "matches": ["http://mochi.test/*/file_sample.html"],
+          "js": ["content_script.js"],
+        },
+      ],
+    },
+
+    background() {
+      let windowId;
+
+      browser.test.onMessage.addListener(([msg, url]) => {
+        if (msg === "open-window") {
+          browser.windows.create({url, incognito: true}).then(window => {
+            windowId = window.id;
+          });
+        } else if (msg === "close-window") {
+          browser.windows.remove(windowId).then(() => {
+            browser.test.sendMessage("done");
+          });
+        }
+      });
+    },
+
+    files: {
+      "content_script.js": async () => {
+        const COOKIE = "foo=florgheralzps";
+        document.cookie = COOKIE;
+
+        let url = new URL("return_headers.sjs", location.href);
+
+        let responses = [
+          new Promise(resolve => {
+            let xhr = new XMLHttpRequest();
+            xhr.open("GET", url);
+            xhr.onload = () => resolve(JSON.parse(xhr.responseText));
+            xhr.send();
+          }),
+
+          fetch(url, {credentials: "include"}).then(body => body.json()),
+        ];
+
+        try {
+          for (let response of await Promise.all(responses)) {
+            browser.test.assertEq(COOKIE, response.cookie, "Got expected cookie header");
+          }
+          browser.test.notifyPass("cookies");
+        } catch (e) {
+          browser.test.fail(`Error: ${e}`);
+          browser.test.notifyFail("cookies");
+        }
+      },
+    },
+  });
+
+  await extension.startup();
+
+  extension.sendMessage(["open-window", SimpleTest.getTestFileURL("file_sample.html")]);
+
+  await extension.awaitFinish("cookies");
+
+  extension.sendMessage(["close-window"]);
+  await extension.awaitMessage("done");
+
+  await extension.unload();
+}
+
+add_task(async function() {
+  await test_contentscript_incognito();
+});
+
+add_task(async function() {
+  await SpecialPowers.pushPrefEnv({set: [
+    ["network.cookie.cookieBehavior", 3],
+  ]});
+  await test_contentscript_incognito();
+});
+
+</script>
+
+</body>
+</html>
diff --git a/toolkit/components/extensions/test/mochitest/test_ext_contentscript_permission.html b/toolkit/components/extensions/test/mochitest/test_ext_contentscript_permission.html
new file mode 100644
index 0000000000..8ab4b1fb28
--- /dev/null
+++ b/toolkit/components/extensions/test/mochitest/test_ext_contentscript_permission.html
@@ -0,0 +1,59 @@
+<!DOCTYPE HTML>
+<html>
+<head>
+  <title>Test for content script</title>
+  <script src="/tests/SimpleTest/SimpleTest.js"></script>
+  <script src="/tests/SimpleTest/ExtensionTestUtils.js"></script>
+  <script type="text/javascript" src="head.js"></script>
+  <link rel="stylesheet" type="text/css" href="/tests/SimpleTest/test.css"/>
+</head>
+<body>
+
+<script type="text/javascript">
+"use strict";
+
+add_task(async function test_contentscript() {
+  function background() {
+    browser.test.onMessage.addListener(async url => {
+      let tab = await browser.tabs.create({url});
+
+      let executed = true;
+      try {
+        await browser.tabs.executeScript(tab.id, {code: "true;"});
+      } catch (e) {
+        executed = false;
+      }
+
+      await browser.tabs.remove([tab.id]);
+      browser.test.sendMessage("executed", executed);
+    });
+  }
+
+  let extensionData = {
+    manifest: {
+      permissions: ["<all_urls>"],
+    },
+    background,
+  };
+
+  let extension = ExtensionTestUtils.loadExtension(extensionData);
+  await extension.startup();
+
+  extension.sendMessage("https://example.com");
+  let result = await extension.awaitMessage("executed");
+  is(result, true, "Content script can be run in a page without mozAddonManager");
+
+  await SpecialPowers.pushPrefEnv({
+    set: [["extensions.webapi.testing", true]],
+  });
+
+  extension.sendMessage("https://example.com");
+  result = await extension.awaitMessage("executed");
+  is(result, false, "Content script cannot be run in a page with mozAddonManager");
+
+  await extension.unload();
+});
+</script>
+
+</body>
+</html>
diff --git a/toolkit/components/extensions/test/mochitest/test_ext_cookies.html b/toolkit/components/extensions/test/mochitest/test_ext_cookies.html
new file mode 100644
index 0000000000..cdec628975
--- /dev/null
+++ b/toolkit/components/extensions/test/mochitest/test_ext_cookies.html
@@ -0,0 +1,367 @@
+<!DOCTYPE HTML>
+<html>
+<head>
+  <title>WebExtension test</title>
+  <script src="/tests/SimpleTest/SimpleTest.js"></script>
+  <script src="/tests/SimpleTest/ExtensionTestUtils.js"></script>
+  <script type="text/javascript" src="head.js"></script>
+  <link rel="stylesheet" type="text/css" href="/tests/SimpleTest/test.css"/>
+</head>
+<body>
+
+<script type="text/javascript">
+"use strict";
+
+add_task(async function test_cookies() {
+  await SpecialPowers.pushPrefEnv({set: [
+    ["dom.security.https_first_pbm", false],
+    ["dom.security.https_first", false],
+  ]});
+
+  async function background() {
+    function assertExpected(expected, cookie) {
+      for (let key of Object.keys(cookie)) {
+        browser.test.assertTrue(key in expected, `found property ${key}`);
+        browser.test.assertEq(expected[key], cookie[key], `property value for ${key} is correct`);
+      }
+      browser.test.assertEq(Object.keys(expected).length, Object.keys(cookie).length, "all expected properties found");
+    }
+
+    async function getDocumentCookie(tabId) {
+      let results = await browser.tabs.executeScript(tabId, {
+        code: "document.cookie",
+      });
+      browser.test.assertEq(1, results.length, "executeScript returns one result");
+      return results[0];
+    }
+
+    async function testIpCookie(ipAddress, setHostOnly) {
+      const IP_TEST_HOST = ipAddress;
+      const IP_TEST_URL = `http://${IP_TEST_HOST}/`;
+      const IP_THE_FUTURE = Date.now() + 5 * 60;
+      const IP_STORE_ID = "firefox-default";
+
+      let expectedCookie = {
+        name: "name1",
+        value: "value1",
+        domain: IP_TEST_HOST,
+        hostOnly: true,
+        path: "/",
+        secure: false,
+        httpOnly: false,
+        sameSite: "no_restriction",
+        session: false,
+        expirationDate: IP_THE_FUTURE,
+        storeId: IP_STORE_ID,
+        firstPartyDomain: "",
+        partitionKey: null,
+      };
+
+      await browser.browsingData.removeCookies({});
+      let ip_cookie = await browser.cookies.set({
+        url: IP_TEST_URL,
+        domain: setHostOnly ? ipAddress : undefined,
+        name: "name1",
+        value: "value1",
+        expirationDate: IP_THE_FUTURE,
+      });
+      assertExpected(expectedCookie, ip_cookie);
+
+      let ip_cookies = await browser.cookies.getAll({name: "name1"});
+      browser.test.assertEq(1, ip_cookies.length, "ip cookie can be added");
+      assertExpected(expectedCookie, ip_cookies[0]);
+
+      ip_cookies = await browser.cookies.getAll({domain: IP_TEST_HOST, name: "name1"});
+      browser.test.assertEq(1, ip_cookies.length, "can get ip cookie by host");
+      assertExpected(expectedCookie, ip_cookies[0]);
+
+      let ip_details = await browser.cookies.remove({url: IP_TEST_URL, name: "name1"});
+      assertExpected({url: IP_TEST_URL, name: "name1", storeId: IP_STORE_ID, firstPartyDomain: "", partitionKey: null}, ip_details);
+
+      ip_cookies = await browser.cookies.getAll({name: "name1"});
+      browser.test.assertEq(0, ip_cookies.length, "ip cookie can be removed");
+    }
+
+    async function openPrivateWindowAndTab(TEST_URL) {
+      // Add some random suffix to make sure that we select the right tab.
+      const PRIVATE_TEST_URL = TEST_URL + "?random" + Math.random();
+
+      let tabReadyPromise = new Promise((resolve) => {
+        browser.webNavigation.onDOMContentLoaded.addListener(function listener({tabId}) {
+          browser.webNavigation.onDOMContentLoaded.removeListener(listener);
+          resolve(tabId);
+        }, {
+          url: [{
+            urlPrefix: PRIVATE_TEST_URL,
+          }],
+        });
+      });
+      // This tab is opened for two purposes:
+      // 1. To allow tests to run content scripts in the context of a tab,
+      //    for fetching the value of document.cookie.
+      // 2. TODO Bug 1309637 To work around cookies in incognito windows,
+      //    based on the analysis in comment 8.
+      let {id: windowId} = await browser.windows.create({
+        incognito: true,
+        url: PRIVATE_TEST_URL,
+      });
+      let tabId = await tabReadyPromise;
+      return {windowId, tabId};
+    }
+
+    function changePort(href, port) {
+      let url = new URL(href);
+      url.port = port;
+      return url.href;
+    }
+
+    await testIpCookie("[2a03:4000:6:310e:216:3eff:fe53:99b]", false);
+    await testIpCookie("[2a03:4000:6:310e:216:3eff:fe53:99b]", true);
+    await testIpCookie("192.168.1.1", false);
+    await testIpCookie("192.168.1.1", true);
+
+    const TEST_URL = "http://example.org/";
+    const TEST_SECURE_URL = "https://example.org/";
+    const THE_FUTURE = Date.now() + 5 * 60;
+    const TEST_PATH = "set_path";
+    const TEST_URL_WITH_PATH = TEST_URL + TEST_PATH;
+    const TEST_COOKIE_PATH = `/${TEST_PATH}`;
+    const STORE_ID = "firefox-default";
+    const PRIVATE_STORE_ID = "firefox-private";
+
+    let expected = {
+      name: "name1",
+      value: "value1",
+      domain: "example.org",
+      hostOnly: true,
+      path: "/",
+      secure: false,
+      httpOnly: false,
+      sameSite: "no_restriction",
+      session: false,
+      expirationDate: THE_FUTURE,
+      storeId: STORE_ID,
+      firstPartyDomain: "",
+      partitionKey: null,
+    };
+
+    // Remove all cookies before starting the test.
+    await browser.browsingData.removeCookies({});
+
+    let cookie = await browser.cookies.set({url: TEST_URL, name: "name1", value: "value1", expirationDate: THE_FUTURE});
+    assertExpected(expected, cookie);
+
+    cookie = await browser.cookies.get({url: TEST_URL, name: "name1"});
+    assertExpected(expected, cookie);
+
+    let cookies = await browser.cookies.getAll({name: "name1"});
+    browser.test.assertEq(1, cookies.length, "one cookie found for matching name");
+    assertExpected(expected, cookies[0]);
+
+    cookies = await browser.cookies.getAll({domain: "example.org"});
+    browser.test.assertEq(1, cookies.length, "one cookie found for matching domain");
+    assertExpected(expected, cookies[0]);
+
+    cookies = await browser.cookies.getAll({domain: "example.net"});
+    browser.test.assertEq(0, cookies.length, "no cookies found for non-matching domain");
+
+    cookies = await browser.cookies.getAll({secure: false});
+    browser.test.assertEq(1, cookies.length, "one non-secure cookie found");
+    assertExpected(expected, cookies[0]);
+
+    cookies = await browser.cookies.getAll({secure: true});
+    browser.test.assertEq(0, cookies.length, "no secure cookies found");
+
+    cookies = await browser.cookies.getAll({storeId: STORE_ID});
+    browser.test.assertEq(1, cookies.length, "one cookie found for valid storeId");
+    assertExpected(expected, cookies[0]);
+
+    cookies = await browser.cookies.getAll({storeId: "invalid_id"});
+    browser.test.assertEq(0, cookies.length, "no cookies found for invalid storeId");
+
+    let details = await browser.cookies.remove({url: TEST_URL, name: "name1"});
+    assertExpected({url: TEST_URL, name: "name1", storeId: STORE_ID, firstPartyDomain: "", partitionKey: null}, details);
+
+    cookie = await browser.cookies.get({url: TEST_URL, name: "name1"});
+    browser.test.assertEq(null, cookie, "removed cookie not found");
+
+    // Ports in cookie URLs should be ignored. Every API call uses a different port number for better coverage.
+    cookie = await browser.cookies.set({url: changePort(TEST_URL, 1234), name: "name1", value: "value1", expirationDate: THE_FUTURE});
+    assertExpected(expected, cookie);
+
+    cookie = await browser.cookies.get({url: changePort(TEST_URL, 65535), name: "name1"});
+    assertExpected(expected, cookie);
+
+    cookies = await browser.cookies.getAll({url: TEST_URL});
+    browser.test.assertEq(cookies.length, 1, "Found cookie using getAll without port");
+    assertExpected(expected, cookies[0]);
+
+    cookies = await browser.cookies.getAll({url: changePort(TEST_URL, 1)});
+    browser.test.assertEq(cookies.length, 1, "Found cookie using getAll with port");
+    assertExpected(expected, cookies[0]);
+
+    // .remove should return the URL of the API call, so the port is included in the return value.
+    const TEST_URL_TO_REMOVE = changePort(TEST_URL, 1023);
+    details = await browser.cookies.remove({url: TEST_URL_TO_REMOVE, name: "name1"});
+    assertExpected({url: TEST_URL_TO_REMOVE, name: "name1", storeId: STORE_ID, firstPartyDomain: "", partitionKey: null}, details);
+
+    cookie = await browser.cookies.get({url: TEST_URL, name: "name1"});
+    browser.test.assertEq(null, cookie, "removed cookie not found");
+
+    let stores = await browser.cookies.getAllCookieStores();
+    browser.test.assertEq(1, stores.length, "expected number of stores returned");
+    browser.test.assertEq(STORE_ID, stores[0].id, "expected store id returned");
+    browser.test.assertEq(1, stores[0].tabIds.length, "one tabId returned for store");
+    browser.test.assertEq("number", typeof stores[0].tabIds[0], "tabId is a number");
+
+    // TODO bug 1372178: Opening private windows/tabs is not supported on Android
+    if (browser.windows) {
+      let {windowId} = await openPrivateWindowAndTab(TEST_URL);
+      let stores = await browser.cookies.getAllCookieStores();
+
+      browser.test.assertEq(2, stores.length, "expected number of stores returned");
+      browser.test.assertEq(STORE_ID, stores[0].id, "expected store id returned");
+      browser.test.assertEq(1, stores[0].tabIds.length, "one tab returned for store");
+      browser.test.assertEq(PRIVATE_STORE_ID, stores[1].id, "expected private store id returned");
+      browser.test.assertEq(1, stores[0].tabIds.length, "one tab returned for private store");
+
+      await browser.windows.remove(windowId);
+    }
+
+    cookie = await browser.cookies.set({url: TEST_URL, name: "name2", domain: ".example.org", expirationDate: THE_FUTURE});
+    browser.test.assertEq(false, cookie.hostOnly, "cookie is not a hostOnly cookie");
+
+    details = await browser.cookies.remove({url: TEST_URL, name: "name2"});
+    assertExpected({url: TEST_URL, name: "name2", storeId: STORE_ID, firstPartyDomain: "", partitionKey: null}, details);
+
+    // Create a session cookie.
+    cookie = await browser.cookies.set({url: TEST_URL, name: "name1", value: "value1"});
+    browser.test.assertEq(true, cookie.session, "session cookie set");
+
+    cookie = await browser.cookies.get({url: TEST_URL, name: "name1"});
+    browser.test.assertEq(true, cookie.session, "got session cookie");
+
+    cookies = await browser.cookies.getAll({session: true});
+    browser.test.assertEq(1, cookies.length, "one session cookie found");
+    browser.test.assertEq(true, cookies[0].session, "found session cookie");
+
+    cookies = await browser.cookies.getAll({session: false});
+    browser.test.assertEq(0, cookies.length, "no non-session cookies found");
+
+    details = await browser.cookies.remove({url: TEST_URL, name: "name1"});
+    assertExpected({url: TEST_URL, name: "name1", storeId: STORE_ID, firstPartyDomain: "", partitionKey: null}, details);
+
+    cookie = await browser.cookies.get({url: TEST_URL, name: "name1"});
+    browser.test.assertEq(null, cookie, "removed cookie not found");
+
+    cookie = await browser.cookies.set({url: TEST_SECURE_URL, name: "name1", value: "value1", secure: true});
+    browser.test.assertEq(true, cookie.secure, "secure cookie set");
+
+    cookie = await browser.cookies.get({url: TEST_SECURE_URL, name: "name1"});
+    browser.test.assertEq(true, cookie.session, "got secure cookie");
+
+    cookies = await browser.cookies.getAll({secure: true});
+    browser.test.assertEq(1, cookies.length, "one secure cookie found");
+    browser.test.assertEq(true, cookies[0].secure, "found secure cookie");
+
+    cookies = await browser.cookies.getAll({secure: false});
+    browser.test.assertEq(0, cookies.length, "no non-secure cookies found");
+
+    details = await browser.cookies.remove({url: TEST_SECURE_URL, name: "name1"});
+    assertExpected({url: TEST_SECURE_URL, name: "name1", storeId: STORE_ID, firstPartyDomain: "", partitionKey: null}, details);
+
+    cookie = await browser.cookies.get({url: TEST_SECURE_URL, name: "name1"});
+    browser.test.assertEq(null, cookie, "removed cookie not found");
+
+    cookie = await browser.cookies.set({url: TEST_URL_WITH_PATH, path: TEST_COOKIE_PATH, name: "name1", value: "value1", expirationDate: THE_FUTURE});
+    browser.test.assertEq(TEST_COOKIE_PATH, cookie.path, "created cookie with path");
+
+    cookie = await browser.cookies.get({url: TEST_URL_WITH_PATH, name: "name1"});
+    browser.test.assertEq(TEST_COOKIE_PATH, cookie.path, "got cookie with path");
+
+    cookies = await browser.cookies.getAll({path: TEST_COOKIE_PATH});
+    browser.test.assertEq(1, cookies.length, "one cookie with path found");
+    browser.test.assertEq(TEST_COOKIE_PATH, cookies[0].path, "found cookie with path");
+
+    cookie = await browser.cookies.get({url: TEST_URL + "invalid_path", name: "name1"});
+    browser.test.assertEq(null, cookie, "get with invalid path returns null");
+
+    cookies = await browser.cookies.getAll({path: "/invalid_path"});
+    browser.test.assertEq(0, cookies.length, "getAll with invalid path returns 0 cookies");
+
+    details = await browser.cookies.remove({url: TEST_URL_WITH_PATH, name: "name1"});
+    assertExpected({url: TEST_URL_WITH_PATH, name: "name1", storeId: STORE_ID, firstPartyDomain: "", partitionKey: null}, details);
+
+    cookie = await browser.cookies.set({url: TEST_URL, name: "name1", value: "value1", httpOnly: true});
+    browser.test.assertEq(true, cookie.httpOnly, "httpOnly cookie set");
+
+    cookie = await browser.cookies.set({url: TEST_URL, name: "name1", value: "value1", httpOnly: false});
+    browser.test.assertEq(false, cookie.httpOnly, "non-httpOnly cookie set");
+
+    details = await browser.cookies.remove({url: TEST_URL, name: "name1"});
+    assertExpected({url: TEST_URL, name: "name1", storeId: STORE_ID, firstPartyDomain: "", partitionKey: null}, details);
+
+    cookie = await browser.cookies.set({url: TEST_URL});
+    browser.test.assertEq("", cookie.name, "default name set");
+    browser.test.assertEq("", cookie.value, "default value set");
+    browser.test.assertEq(true, cookie.session, "no expiry date created session cookie");
+
+    // TODO bug 1372178: Opening private windows/tabs is not supported on Android
+    if (browser.windows) {
+      let {tabId, windowId} = await openPrivateWindowAndTab(TEST_URL);
+
+      browser.test.assertEq("", await getDocumentCookie(tabId), "initially no cookie");
+
+      let cookie = await browser.cookies.set({url: TEST_URL, name: "store", value: "private", expirationDate: THE_FUTURE, storeId: PRIVATE_STORE_ID});
+      browser.test.assertEq("private", cookie.value, "set the private cookie");
+
+      cookie = await browser.cookies.set({url: TEST_URL, name: "store", value: "default", expirationDate: THE_FUTURE, storeId: STORE_ID});
+      browser.test.assertEq("default", cookie.value, "set the default cookie");
+
+      cookie = await browser.cookies.get({url: TEST_URL, name: "store", storeId: PRIVATE_STORE_ID});
+      browser.test.assertEq("private", cookie.value, "get the private cookie");
+      browser.test.assertEq(PRIVATE_STORE_ID, cookie.storeId, "get the private cookie storeId");
+
+      cookie = await browser.cookies.get({url: TEST_URL, name: "store", storeId: STORE_ID});
+      browser.test.assertEq("default", cookie.value, "get the default cookie");
+      browser.test.assertEq(STORE_ID, cookie.storeId, "get the default cookie storeId");
+
+      browser.test.assertEq("store=private", await getDocumentCookie(tabId), "private document.cookie should be set");
+
+      let details = await browser.cookies.remove({url: TEST_URL, name: "store", storeId: STORE_ID});
+      assertExpected({url: TEST_URL, name: "store", storeId: STORE_ID, firstPartyDomain: "", partitionKey: null}, details);
+
+      cookie = await browser.cookies.get({url: TEST_URL, name: "store", storeId: STORE_ID});
+      browser.test.assertEq(null, cookie, "deleted the default cookie");
+
+      details = await browser.cookies.remove({url: TEST_URL, name: "store", storeId: PRIVATE_STORE_ID});
+      assertExpected({url: TEST_URL, name: "store", storeId: PRIVATE_STORE_ID, firstPartyDomain: "", partitionKey: null}, details);
+
+      cookie = await browser.cookies.get({url: TEST_URL, name: "store", storeId: PRIVATE_STORE_ID});
+      browser.test.assertEq(null, cookie, "deleted the private cookie");
+
+      browser.test.assertEq("", await getDocumentCookie(tabId), "private document.cookie should be removed");
+
+      await browser.windows.remove(windowId);
+    }
+
+    browser.test.notifyPass("cookies");
+  }
+
+  let extension = ExtensionTestUtils.loadExtension({
+    incognitoOverride: "spanning",
+    background,
+    manifest: {
+      permissions: ["cookies", "*://example.org/", "*://[2a03:4000:6:310e:216:3eff:fe53:99b]/", "*://192.168.1.1/", "webNavigation", "browsingData"],
+    },
+  });
+
+  await extension.startup();
+  await extension.awaitFinish("cookies");
+  await extension.unload();
+});
+
+</script>
+
+</body>
+</html>
diff --git a/toolkit/components/extensions/test/mochitest/test_ext_cookies_containers.html b/toolkit/components/extensions/test/mochitest/test_ext_cookies_containers.html
new file mode 100644
index 0000000000..d4bbd61177
--- /dev/null
+++ b/toolkit/components/extensions/test/mochitest/test_ext_cookies_containers.html
@@ -0,0 +1,98 @@
+<!DOCTYPE HTML>
+<html>
+<head>
+  <title>WebExtension test</title>
+  <meta charset="utf-8">
+  <script src="/tests/SimpleTest/SimpleTest.js"></script>
+  <script src="/tests/SimpleTest/ExtensionTestUtils.js"></script>
+  <script type="text/javascript" src="head.js"></script>
+  <link rel="stylesheet" type="text/css" href="/tests/SimpleTest/test.css"/>
+</head>
+<body>
+
+<script type="text/javascript">
+"use strict";
+
+add_task(async function setup() {
+  // make sure userContext is enabled.
+  await SpecialPowers.pushPrefEnv({"set": [
+    ["privacy.userContext.enabled", true],
+  ]});
+});
+
+add_task(async function test_cookie_containers() {
+  async function background() {
+    // Sometimes there is a cookie without name/value when running tests.
+    let cookiesAtStart = await browser.cookies.getAll({storeId: "firefox-default"});
+
+    function assertExpected(expected, cookie) {
+      for (let key of Object.keys(cookie)) {
+        browser.test.assertTrue(key in expected, `found property ${key}`);
+        browser.test.assertEq(expected[key], cookie[key], `property value for ${key} is correct`);
+      }
+      browser.test.assertEq(Object.keys(expected).length, Object.keys(cookie).length, "all expected properties found");
+    }
+
+    const TEST_URL = "http://example.org/";
+    const THE_FUTURE = Date.now() + 5 * 60;
+
+    let expected = {
+      name: "name1",
+      value: "value1",
+      domain: "example.org",
+      hostOnly: true,
+      path: "/",
+      secure: false,
+      httpOnly: false,
+      sameSite: "no_restriction",
+      session: false,
+      expirationDate: THE_FUTURE,
+      storeId: "firefox-container-1",
+      firstPartyDomain: "",
+      partitionKey: null,
+    };
+
+    let cookie = await browser.cookies.set({
+      url: TEST_URL, name: "name1", value: "value1",
+      expirationDate: THE_FUTURE, storeId: "firefox-container-1",
+    });
+    browser.test.assertEq("firefox-container-1", cookie.storeId, "the cookie has the correct storeId");
+
+    cookie = await browser.cookies.get({url: TEST_URL, name: "name1"});
+    browser.test.assertEq(null, cookie, "get() without storeId returns null");
+
+    cookie = await browser.cookies.get({url: TEST_URL, name: "name1", storeId: "firefox-container-1"});
+    assertExpected(expected, cookie);
+
+    let cookies = await browser.cookies.getAll({storeId: "firefox-default"});
+    browser.test.assertEq(0, cookiesAtStart.length - cookies.length, "getAll() with default storeId hasn't added cookies");
+
+    cookies = await browser.cookies.getAll({storeId: "firefox-container-1"});
+    browser.test.assertEq(1, cookies.length, "one cookie found for matching domain");
+    assertExpected(expected, cookies[0]);
+
+    let details = await browser.cookies.remove({url: TEST_URL, name: "name1", storeId: "firefox-container-1"});
+    assertExpected({url: TEST_URL, name: "name1", storeId: "firefox-container-1", firstPartyDomain: "", partitionKey: null}, details);
+
+    cookie = await browser.cookies.get({url: TEST_URL, name: "name1", storeId: "firefox-container-1"});
+    browser.test.assertEq(null, cookie, "removed cookie not found");
+
+    browser.test.notifyPass("cookies");
+  }
+
+  let extension = ExtensionTestUtils.loadExtension({
+    background,
+    manifest: {
+      permissions: ["cookies", "*://example.org/"],
+    },
+  });
+
+  await extension.startup();
+  await extension.awaitFinish("cookies");
+  await extension.unload();
+});
+
+</script>
+
+</body>
+</html>
diff --git a/toolkit/components/extensions/test/mochitest/test_ext_cookies_expiry.html b/toolkit/components/extensions/test/mochitest/test_ext_cookies_expiry.html
new file mode 100644
index 0000000000..fa118f5271
--- /dev/null
+++ b/toolkit/components/extensions/test/mochitest/test_ext_cookies_expiry.html
@@ -0,0 +1,72 @@
+<!DOCTYPE HTML>
+<html>
+<head>
+  <title>WebExtension cookies test</title>
+  <meta charset="utf-8">
+  <script src="/tests/SimpleTest/SimpleTest.js"></script>
+  <script src="/tests/SimpleTest/ExtensionTestUtils.js"></script>
+  <script type="text/javascript" src="head.js"></script>
+  <link rel="stylesheet" type="text/css" href="/tests/SimpleTest/test.css"/>
+</head>
+<body>
+
+<script type="text/javascript">
+"use strict";
+
+add_task(async function test_cookies_expiry() {
+  function background() {
+    let expectedEvents = [];
+
+    browser.cookies.onChanged.addListener(event => {
+      expectedEvents.push(`${event.removed}:${event.cause}`);
+      if (expectedEvents.length === 1) {
+        browser.test.assertEq("true:expired", expectedEvents[0], "expired cookie removed");
+        browser.test.assertEq("first", event.cookie.name, "expired cookie has the expected name");
+        browser.test.assertEq("one", event.cookie.value, "expired cookie has the expected value");
+      } else {
+        browser.test.assertEq("false:explicit", expectedEvents[1], "new cookie added");
+        browser.test.assertEq("first", event.cookie.name, "new cookie has the expected name");
+        browser.test.assertEq("one-again", event.cookie.value, "new cookie has the expected value");
+        browser.test.notifyPass("cookie-expiry");
+      }
+    });
+
+    setTimeout(() => {
+      browser.test.sendMessage("change-cookies");
+    }, 1000);
+  }
+
+  let extension = ExtensionTestUtils.loadExtension({
+    manifest: {
+      "permissions": ["http://example.com/", "cookies"],
+    },
+    background,
+  });
+
+  let chromeScript = loadChromeScript(() => {
+    const {sendAsyncMessage} = this;
+    Services.cookies.add(".example.com", "/", "first", "one", false, false, false, Date.now() / 1000 + 1, {}, Ci.nsICookie.SAMESITE_NONE, Ci.nsICookie.SCHEME_HTTP);
+    sendAsyncMessage("done");
+  });
+  await chromeScript.promiseOneMessage("done");
+  chromeScript.destroy();
+
+  await extension.startup();
+  await extension.awaitMessage("change-cookies");
+
+  chromeScript = loadChromeScript(() => {
+    const {sendAsyncMessage} = this;
+    Services.cookies.add(".example.com", "/", "first", "one-again", false, false, false, Date.now() / 1000 + 10, {}, Ci.nsICookie.SAMESITE_NONE, Ci.nsICookie.SCHEME_HTTP);
+    sendAsyncMessage("done");
+  });
+  await chromeScript.promiseOneMessage("done");
+  chromeScript.destroy();
+
+  await extension.awaitFinish("cookie-expiry");
+  await extension.unload();
+});
+
+</script>
+
+</body>
+</html>
diff --git a/toolkit/components/extensions/test/mochitest/test_ext_cookies_first_party.html b/toolkit/components/extensions/test/mochitest/test_ext_cookies_first_party.html
new file mode 100644
index 0000000000..7e33f4731d
--- /dev/null
+++ b/toolkit/components/extensions/test/mochitest/test_ext_cookies_first_party.html
@@ -0,0 +1,316 @@
+<!DOCTYPE html>
+<meta charset="utf-8">
+<script src="/tests/SimpleTest/SimpleTest.js"></script>
+<script src="/tests/SimpleTest/ExtensionTestUtils.js"></script>
+<script src="head.js"></script>
+<script>
+"use strict";
+
+async function background() {
+  const url = "http://ext-cookie-first-party.mochi.test/";
+  const firstPartyDomain = "ext-cookie-first-party.mochi.test";
+  // A first party domain with invalid characters for the file system, which just happens to be a IPv6 address.
+  const firstPartyDomainInvalidChars = "[2606:4700:4700::1111]";
+  const expectedError = "First-Party Isolation is enabled, but the required 'firstPartyDomain' attribute was not set.";
+
+  const assertExpectedCookies = (expected, cookies, message) => {
+    let matches = (cookie, expected) => {
+      if (!cookie || !expected) {
+        return cookie === expected; // true if both are null.
+      }
+      for (let key of Object.keys(expected)) {
+        if (cookie[key] !== expected[key]) {
+          return false;
+        }
+      }
+      return true;
+    };
+    browser.test.assertEq(expected.length, cookies.length, `Got expected number of cookies - ${message}`);
+    if (cookies.length !== expected.length) {
+      return;
+    }
+    for (let expect of expected) {
+      let foundCookies = cookies.filter(cookie => matches(cookie, expect));
+      browser.test.assertEq(1, foundCookies.length,
+                            `Expected cookie ${JSON.stringify(expect)} found - ${message}`);
+    }
+  };
+
+  // Test when FPI is disabled.
+  const test_fpi_disabled = async () => {
+    let cookie, cookies;
+
+    // set
+    cookie = await browser.cookies.set({url, name: "foo1", value: "bar1"});
+    assertExpectedCookies([
+      {name: "foo1", value: "bar1", firstPartyDomain: ""},
+    ], [cookie], "set: FPI off, w/ empty firstPartyDomain, non-FP cookie");
+    cookie = await browser.cookies.set({url, name: "foo2", value: "bar2", firstPartyDomain});
+    assertExpectedCookies([
+      {name: "foo2", value: "bar2", firstPartyDomain},
+    ], [cookie], "set: FPI off, w/ firstPartyDomain, FP cookie");
+
+    // get
+    // When FPI is disabled, missing key/null/undefined is equivalent to "".
+    cookie = await browser.cookies.get({url, name: "foo1"});
+    assertExpectedCookies([
+      {name: "foo1", value: "bar1", firstPartyDomain: ""},
+    ], [cookie], "get: FPI off, w/o firstPartyDomain, non-FP cookie");
+    cookie = await browser.cookies.get({url, name: "foo1", firstPartyDomain: ""});
+    assertExpectedCookies([
+      {name: "foo1", value: "bar1", firstPartyDomain: ""},
+    ], [cookie], "get: FPI off, w/ empty firstPartyDomain, non-FP cookie");
+    cookie = await browser.cookies.get({url, name: "foo1", firstPartyDomain: null});
+    assertExpectedCookies([
+      {name: "foo1", value: "bar1", firstPartyDomain: ""},
+    ], [cookie], "get: FPI off, w/ null firstPartyDomain, non-FP cookie");
+    cookie = await browser.cookies.get({url, name: "foo1", firstPartyDomain: undefined});
+    assertExpectedCookies([
+      {name: "foo1", value: "bar1", firstPartyDomain: ""},
+    ], [cookie], "get: FPI off, w/ undefined firstPartyDomain, non-FP cookie");
+
+    cookie = await browser.cookies.get({url, name: "foo2", firstPartyDomain});
+    assertExpectedCookies([
+      {name: "foo2", value: "bar2", firstPartyDomain},
+    ], [cookie], "get: FPI off, w/ firstPartyDomain, FP cookie");
+    // There is no match for non-FP cookies with name "foo2".
+    cookie = await browser.cookies.get({url, name: "foo2"});
+    assertExpectedCookies([null], [cookie], "get: FPI off, w/o firstPartyDomain, no cookie");
+    cookie = await browser.cookies.get({url, name: "foo2", firstPartyDomain: ""});
+    assertExpectedCookies([null], [cookie], "get: FPI off, w/ empty firstPartyDomain, no cookie");
+    cookie = await browser.cookies.get({url, name: "foo2", firstPartyDomain: null});
+    assertExpectedCookies([null], [cookie], "get: FPI off, w/ null firstPartyDomain, no cookie");
+    cookie = await browser.cookies.get({url, name: "foo2", firstPartyDomain: undefined});
+    assertExpectedCookies([null], [cookie], "get: FPI off, w/ undefined firstPartyDomain, no cookie");
+
+    // getAll
+    for (let extra of [{}, {url}, {domain: firstPartyDomain}]) {
+      const prefix = `getAll(${JSON.stringify(extra)})`;
+      cookies = await browser.cookies.getAll({...extra});
+      assertExpectedCookies([
+        {name: "foo1", value: "bar1", firstPartyDomain: ""},
+      ], cookies, `${prefix}: FPI off, w/o firstPartyDomain, non-FP cookies`);
+      cookies = await browser.cookies.getAll({...extra, firstPartyDomain: ""});
+      assertExpectedCookies([
+        {name: "foo1", value: "bar1", firstPartyDomain: ""},
+      ], cookies, `${prefix}: FPI off, w/ empty firstPartyDomain, non-FP cookies`);
+      cookies = await browser.cookies.getAll({...extra, firstPartyDomain: null});
+      assertExpectedCookies([
+        {name: "foo1", value: "bar1", firstPartyDomain: ""},
+        {name: "foo2", value: "bar2", firstPartyDomain},
+      ], cookies, `${prefix}: FPI off, w/ null firstPartyDomain, all cookies`);
+      cookies = await browser.cookies.getAll({...extra, firstPartyDomain: undefined});
+      assertExpectedCookies([
+        {name: "foo1", value: "bar1", firstPartyDomain: ""},
+        {name: "foo2", value: "bar2", firstPartyDomain},
+      ], cookies, `${prefix}: FPI off, w/ undefined firstPartyDomain, all cookies`);
+      cookies = await browser.cookies.getAll({...extra, firstPartyDomain});
+      assertExpectedCookies([
+        {name: "foo2", value: "bar2", firstPartyDomain},
+      ], cookies, `${prefix}: FPI off, w/ firstPartyDomain, FP cookies`);
+    }
+
+    // remove
+    cookie = await browser.cookies.remove({url, name: "foo1"});
+    assertExpectedCookies([
+      {url, name: "foo1", firstPartyDomain: ""},
+    ], [cookie], "remove: FPI off, w/ empty firstPartyDomain, non-FP cookie");
+    cookie = await browser.cookies.remove({url, name: "foo2", firstPartyDomain});
+    assertExpectedCookies([
+      {url, name: "foo2", firstPartyDomain},
+    ], [cookie], "remove: FPI off, w/ firstPartyDomain, FP cookie");
+
+    // Test if FP cookies set when FPI off can be accessed when FPI on.
+    await browser.cookies.set({url, name: "foo1", value: "bar1"});
+    await browser.cookies.set({url, name: "foo2", value: "bar2", firstPartyDomain});
+
+    browser.test.sendMessage("test_fpi_disabled");
+  };
+
+  // Test when FPI is enabled.
+  const test_fpi_enabled = async () => {
+    let cookie, cookies;
+
+    // set
+    await browser.test.assertRejects(
+      browser.cookies.set({url, name: "foo3", value: "bar3"}),
+      expectedError,
+      "set: FPI on, w/o firstPartyDomain, rejection");
+    cookie = await browser.cookies.set({url, name: "foo4", value: "bar4", firstPartyDomain});
+    assertExpectedCookies([
+      {name: "foo4", value: "bar4", firstPartyDomain},
+    ], [cookie], "set: FPI on, w/ firstPartyDomain, FP cookie");
+
+    // get
+    await browser.test.assertRejects(
+      browser.cookies.get({url, name: "foo3"}),
+      expectedError,
+      "get: FPI on, w/o firstPartyDomain, rejection");
+    await browser.test.assertRejects(
+      browser.cookies.get({url, name: "foo3", firstPartyDomain: null}),
+      expectedError,
+      "get: FPI on, w/ null firstPartyDomain, rejection");
+    await browser.test.assertRejects(
+      browser.cookies.get({url, name: "foo3", firstPartyDomain: undefined}),
+      expectedError,
+      "get: FPI on, w/ undefined firstPartyDomain, rejection");
+    cookie = await browser.cookies.get({url, name: "foo1", firstPartyDomain: ""});
+    assertExpectedCookies([
+      {name: "foo1", value: "bar1", firstPartyDomain: ""},
+    ], [cookie], "get: FPI on, w/ empty firstPartyDomain, non-FP cookie");
+    cookie = await browser.cookies.get({url, name: "foo4", firstPartyDomain});
+    assertExpectedCookies([
+      {name: "foo4", value: "bar4", firstPartyDomain},
+    ], [cookie], "get: FPI on, w/ firstPartyDomain, FP cookie");
+    cookie = await browser.cookies.get({url, name: "foo2", firstPartyDomain});
+    assertExpectedCookies([
+      {name: "foo2", value: "bar2", firstPartyDomain},
+    ], [cookie], "get: FPI on, w/ firstPartyDomain, FP cookie (set when FPI off)");
+
+    // getAll
+    for (let extra of [{}, {url}, {domain: firstPartyDomain}]) {
+      const prefix = `getAll(${JSON.stringify(extra)})`;
+      await browser.test.assertRejects(
+        browser.cookies.getAll({...extra}),
+        expectedError,
+        `${prefix}: FPI on, w/o firstPartyDomain, rejection`);
+      cookies = await browser.cookies.getAll({...extra, firstPartyDomain: ""});
+      assertExpectedCookies([
+        {name: "foo1", value: "bar1", firstPartyDomain: ""},
+      ], cookies, `${prefix}: FPI on, w/ empty firstPartyDomain, non-FP cookies`);
+      cookies = await browser.cookies.getAll({...extra, firstPartyDomain: null});
+      assertExpectedCookies([
+        {name: "foo1", value: "bar1", firstPartyDomain: ""},
+        {name: "foo2", value: "bar2", firstPartyDomain},
+        {name: "foo4", value: "bar4", firstPartyDomain},
+      ], cookies, `${prefix}: FPI on, w/ null firstPartyDomain, all cookies`);
+      cookies = await browser.cookies.getAll({...extra, firstPartyDomain: undefined});
+      assertExpectedCookies([
+        {name: "foo1", value: "bar1", firstPartyDomain: ""},
+        {name: "foo2", value: "bar2", firstPartyDomain},
+        {name: "foo4", value: "bar4", firstPartyDomain},
+      ], cookies, `${prefix}: FPI on, w/ undefined firstPartyDomain, all cookies`);
+      cookies = await browser.cookies.getAll({...extra, firstPartyDomain});
+      assertExpectedCookies([
+        {name: "foo2", value: "bar2", firstPartyDomain},
+        {name: "foo4", value: "bar4", firstPartyDomain},
+      ], cookies, `${prefix}: FPI on, w/ firstPartyDomain, FP cookies`);
+    }
+
+    // remove
+    await browser.test.assertRejects(
+      browser.cookies.remove({url, name: "foo3"}),
+      expectedError,
+      "remove: FPI on, w/o firstPartyDomain, rejection");
+    cookie = await browser.cookies.remove({url, name: "foo4", firstPartyDomain});
+    assertExpectedCookies([
+      {url, name: "foo4", firstPartyDomain},
+    ], [cookie], "remove: FPI on, w/ firstPartyDomain, FP cookie");
+    cookie = await browser.cookies.remove({url, name: "foo2", firstPartyDomain});
+    assertExpectedCookies([
+      {url, name: "foo2", firstPartyDomain},
+    ], [cookie], "remove: FPI on, w/ firstPartyDomain, FP cookie (set when FPI off)");
+
+    // Test if FP cookies set when FPI on can be accessed when FPI off.
+    await browser.cookies.set({url, name: "foo4", value: "bar4", firstPartyDomain});
+
+    browser.test.sendMessage("test_fpi_enabled");
+  };
+
+  // Test FPI with a first party domain with invalid characters for
+  // the file system.
+  const test_fpi_with_invalid_characters = async () => {
+    let cookie;
+
+    // Test setting a cookie with a first party domain with invalid characters
+    // for the file system.
+    cookie = await browser.cookies.set({url, name: "foo5", value: "bar5",
+                                        firstPartyDomain: firstPartyDomainInvalidChars});
+    assertExpectedCookies([
+      {name: "foo5", value: "bar5", firstPartyDomain: firstPartyDomainInvalidChars},
+    ], [cookie], "set: FPI on, w/ firstPartyDomain with invalid characters, FP cookie");
+
+    // Test getting a cookie with a first party domain with invalid characters
+    // for the file system.
+    cookie = await browser.cookies.get({url, name: "foo5",
+                                        firstPartyDomain: firstPartyDomainInvalidChars});
+    assertExpectedCookies([
+      {name: "foo5", value: "bar5", firstPartyDomain: firstPartyDomainInvalidChars},
+    ], [cookie], "get: FPI on, w/ firstPartyDomain with invalid characters, FP cookie");
+
+    // Test removing a cookie with a first party domain with invalid characters
+    // for the file system.
+    cookie = await browser.cookies.remove({url, name: "foo5",
+                                           firstPartyDomain: firstPartyDomainInvalidChars});
+    assertExpectedCookies([
+      {url, name: "foo5", firstPartyDomain: firstPartyDomainInvalidChars},
+    ], [cookie], "remove: FPI on, w/ firstPartyDomain with invalid characters, FP cookie");
+
+    browser.test.sendMessage("test_fpi_with_invalid_characters");
+  };
+
+  // Test when FPI is disabled again, accessing FP cookies set when FPI is enabled.
+  const test_fpd_cookies_on_fpi_disabled = async () => {
+    let cookie, cookies;
+    cookie = await browser.cookies.get({url, name: "foo4", firstPartyDomain});
+    assertExpectedCookies([
+      {name: "foo4", value: "bar4", firstPartyDomain},
+    ], [cookie], "get: FPI off, w/ firstPartyDomain, FP cookie (set when FPI on)");
+    cookie = await browser.cookies.remove({url, name: "foo4", firstPartyDomain});
+    assertExpectedCookies([
+      {url, name: "foo4", firstPartyDomain},
+    ], [cookie], "remove: FPI off, w/ firstPartyDomain, FP cookie (set when FPI on)");
+
+    // Clean up.
+    await browser.cookies.remove({url, name: "foo1"});
+
+    cookies = await browser.cookies.getAll({firstPartyDomain: null});
+    assertExpectedCookies([], cookies, "Test is finishing, all cookies removed");
+
+    browser.test.sendMessage("test_fpd_cookies_on_fpi_disabled");
+  };
+
+  browser.test.onMessage.addListener((message) => {
+    switch (message) {
+      case "test_fpi_disabled": return test_fpi_disabled();
+      case "test_fpi_enabled": return test_fpi_enabled();
+      case "test_fpi_with_invalid_characters": return test_fpi_with_invalid_characters();
+      case "test_fpd_cookies_on_fpi_disabled": return test_fpd_cookies_on_fpi_disabled();
+      default: return browser.test.notifyFail("unknown-message");
+    }
+  });
+}
+
+function enableFirstPartyIsolation() {
+  return SpecialPowers.pushPrefEnv({
+    set: [
+      ["privacy.firstparty.isolate", true],
+    ],
+  });
+}
+
+function disableFirstPartyIsolation() {
+  return SpecialPowers.popPrefEnv();
+}
+
+add_task(async () => {
+  let extension = ExtensionTestUtils.loadExtension({
+    background,
+    manifest: {
+      permissions: ["cookies", "*://ext-cookie-first-party.mochi.test/"],
+    },
+  });
+  await extension.startup();
+  extension.sendMessage("test_fpi_disabled");
+  await extension.awaitMessage("test_fpi_disabled");
+  await enableFirstPartyIsolation();
+  extension.sendMessage("test_fpi_enabled");
+  await extension.awaitMessage("test_fpi_enabled");
+  extension.sendMessage("test_fpi_with_invalid_characters");
+  await extension.awaitMessage("test_fpi_with_invalid_characters");
+  await disableFirstPartyIsolation();
+  extension.sendMessage("test_fpd_cookies_on_fpi_disabled");
+  await extension.awaitMessage("test_fpd_cookies_on_fpi_disabled");
+  await extension.unload();
+});
+</script>
diff --git a/toolkit/components/extensions/test/mochitest/test_ext_cookies_incognito.html b/toolkit/components/extensions/test/mochitest/test_ext_cookies_incognito.html
new file mode 100644
index 0000000000..b33ceecf06
--- /dev/null
+++ b/toolkit/components/extensions/test/mochitest/test_ext_cookies_incognito.html
@@ -0,0 +1,107 @@
+<!DOCTYPE HTML>
+<html>
+<head>
+  <title>WebExtension test</title>
+  <meta charset="utf-8">
+  <script src="/tests/SimpleTest/SimpleTest.js"></script>
+  <script src="/tests/SimpleTest/ExtensionTestUtils.js"></script>
+  <script type="text/javascript" src="head.js"></script>
+  <link rel="stylesheet" type="text/css" href="/tests/SimpleTest/test.css"/>
+</head>
+<body>
+
+<script type="text/javascript">
+"use strict";
+
+add_task(async function test_cookies_incognito_not_allowed() {
+  let privateExtension = ExtensionTestUtils.loadExtension({
+    incognitoOverride: "spanning",
+    async background() {
+      let window = await browser.windows.create({incognito: true});
+      browser.test.onMessage.addListener(async () => {
+        await browser.windows.remove(window.id);
+        browser.test.sendMessage("done");
+      });
+      browser.test.sendMessage("ready");
+    },
+    manifest: {
+      permissions: ["cookies", "*://example.org/"],
+    },
+  });
+  await privateExtension.startup();
+  await privateExtension.awaitMessage("ready");
+
+  async function background() {
+    const storeId = "firefox-private";
+    const url = "http://example.org/";
+
+    // Getting the wrong storeId will fail, otherwise we should finish the test fine.
+    browser.cookies.onChanged.addListener(changeInfo => {
+      let {cookie} = changeInfo;
+      browser.test.assertTrue(cookie.storeId != storeId, "cookie store is correct");
+    });
+
+    browser.test.onMessage.addListener(async () => {
+      let stores = await browser.cookies.getAllCookieStores();
+      let store = stores.find(s => s.incognito);
+      browser.test.assertTrue(!store, "incognito cookie store should not be available");
+      browser.test.notifyPass("cookies");
+    });
+
+    await browser.test.assertRejects(
+      browser.cookies.set({url, name: "test", storeId}),
+      /Extension disallowed access/,
+      "API should reject setting cookie");
+    await browser.test.assertRejects(
+      browser.cookies.get({url, name: "test", storeId}),
+      /Extension disallowed access/,
+      "API should reject getting cookie");
+    await browser.test.assertRejects(
+      browser.cookies.getAll({url, storeId}),
+      /Extension disallowed access/,
+      "API should reject getting cookie");
+    await browser.test.assertRejects(
+      browser.cookies.remove({url, name: "test", storeId}),
+      /Extension disallowed access/,
+      "API should reject getting cookie");
+    await browser.test.assertRejects(
+      browser.cookies.getAll({url, storeId}),
+      /Extension disallowed access/,
+      "API should reject getting cookie");
+
+    browser.test.sendMessage("set-cookies");
+  }
+
+  let extension = ExtensionTestUtils.loadExtension({
+    background,
+    manifest: {
+      permissions: ["cookies", "*://example.org/"],
+    },
+  });
+
+  await extension.startup();
+  await extension.awaitMessage("set-cookies");
+
+  let chromeScript = SpecialPowers.loadChromeScript(() => {
+    /* eslint-env mozilla/chrome-script */
+    Services.cookies.add("example.org", "/", "public", `foo${Math.random()}`,
+                         false, false, false, Number.MAX_SAFE_INTEGER, {},
+                         Ci.nsICookie.SAMESITE_NONE);
+    Services.cookies.add("example.org", "/", "private", `foo${Math.random()}`,
+                         false, false, false, Number.MAX_SAFE_INTEGER, {privateBrowsingId: 1},
+                         Ci.nsICookie.SAMESITE_NONE);
+  });
+  extension.sendMessage("test-cookie-store");
+  await extension.awaitFinish("cookies");
+
+  await extension.unload();
+  privateExtension.sendMessage("close");
+  await privateExtension.awaitMessage("done");
+  await privateExtension.unload();
+  chromeScript.destroy();
+});
+
+</script>
+
+</body>
+</html>
diff --git a/toolkit/components/extensions/test/mochitest/test_ext_cookies_permissions_bad.html b/toolkit/components/extensions/test/mochitest/test_ext_cookies_permissions_bad.html
new file mode 100644
index 0000000000..0bd2852075
--- /dev/null
+++ b/toolkit/components/extensions/test/mochitest/test_ext_cookies_permissions_bad.html
@@ -0,0 +1,115 @@
+<!DOCTYPE HTML>
+<html>
+<head>
+  <title>WebExtension test</title>
+  <script src="/tests/SimpleTest/SimpleTest.js"></script>
+  <script src="/tests/SimpleTest/ExtensionTestUtils.js"></script>
+  <script type="text/javascript" src="head.js"></script>
+  <script type="text/javascript" src="head_cookies.js"></script>
+  <link rel="stylesheet" type="text/css" href="/tests/SimpleTest/test.css"/>
+</head>
+<body>
+
+<script type="text/javascript">
+"use strict";
+
+add_task(async function init() {
+  // We need to trigger a cookie eviction in order to test our batch delete
+  // observer.
+
+  // Set quotaPerHost to maxPerHost - 1, so there is only one cookie
+  // will be evicted everytime.
+  SpecialPowers.setIntPref("network.cookie.quotaPerHost", 2);
+  SpecialPowers.setIntPref("network.cookie.maxPerHost", 3);
+  SimpleTest.registerCleanupFunction(() => {
+    SpecialPowers.clearUserPref("network.cookie.quotaPerHost");
+    SpecialPowers.clearUserPref("network.cookie.maxPerHost");
+  });
+});
+
+add_task(async function test_bad_cookie_permissions() {
+  info("Test non-matching, non-secure domain with non-secure cookie");
+  await testCookies({
+    permissions: ["http://example.com/", "cookies"],
+    url: "http://example.net/",
+    domain: "example.net",
+    secure: false,
+    shouldPass: false,
+    shouldWrite: false,
+  });
+
+  info("Test non-matching, secure domain with non-secure cookie");
+  await testCookies({
+    permissions: ["https://example.com/", "cookies"],
+    url: "https://example.net/",
+    domain: "example.net",
+    secure: false,
+    shouldPass: false,
+    shouldWrite: false,
+  });
+
+  info("Test non-matching, secure domain with secure cookie");
+  await testCookies({
+    permissions: ["https://example.com/", "cookies"],
+    url: "https://example.net/",
+    domain: "example.net",
+    secure: false,
+    shouldPass: false,
+    shouldWrite: false,
+  });
+
+  info("Test matching subdomain with superdomain privileges, secure cookie (http)");
+  await testCookies({
+    permissions: ["http://foo.bar.example.com/", "cookies"],
+    url: "http://foo.bar.example.com/",
+    domain: ".example.com",
+    secure: true,
+    shouldPass: false,
+    shouldWrite: true,
+  });
+
+  info("Test matching, non-secure domain with secure cookie");
+  await testCookies({
+    permissions: ["http://example.com/", "cookies"],
+    url: "http://example.com/",
+    domain: "example.com",
+    secure: true,
+    shouldPass: false,
+    shouldWrite: true,
+  });
+
+  info("Test matching, non-secure host, secure URL");
+  await testCookies({
+    permissions: ["http://example.com/", "cookies"],
+    url: "https://example.com/",
+    domain: "example.com",
+    secure: true,
+    shouldPass: false,
+    shouldWrite: false,
+  });
+
+  info("Test non-matching domain");
+  await testCookies({
+    permissions: ["http://example.com/", "cookies"],
+    url: "http://example.com/",
+    domain: "example.net",
+    secure: false,
+    shouldPass: false,
+    shouldWrite: false,
+  });
+
+  info("Test invalid scheme");
+  await testCookies({
+    permissions: ["ftp://example.com/", "cookies"],
+    url: "ftp://example.com/",
+    domain: "example.com",
+    secure: false,
+    shouldPass: false,
+    shouldWrite: false,
+  });
+});
+
+</script>
+
+</body>
+</html>
diff --git a/toolkit/components/extensions/test/mochitest/test_ext_cookies_permissions_good.html b/toolkit/components/extensions/test/mochitest/test_ext_cookies_permissions_good.html
new file mode 100644
index 0000000000..bd76f2b9c0
--- /dev/null
+++ b/toolkit/components/extensions/test/mochitest/test_ext_cookies_permissions_good.html
@@ -0,0 +1,89 @@
+<!DOCTYPE HTML>
+<html>
+<head>
+  <title>WebExtension test</title>
+  <script src="/tests/SimpleTest/SimpleTest.js"></script>
+  <script src="/tests/SimpleTest/ExtensionTestUtils.js"></script>
+  <script type="text/javascript" src="head.js"></script>
+  <script type="text/javascript" src="head_cookies.js"></script>
+  <link rel="stylesheet" type="text/css" href="/tests/SimpleTest/test.css"/>
+</head>
+<body>
+
+<script type="text/javascript">
+"use strict";
+
+add_task(async function init() {
+  // We need to trigger a cookie eviction in order to test our batch delete
+  // observer.
+
+  // Set quotaPerHost to maxPerHost - 1, so there is only one cookie
+  // will be evicted everytime.
+  SpecialPowers.setIntPref("network.cookie.quotaPerHost", 2);
+  SpecialPowers.setIntPref("network.cookie.maxPerHost", 3);
+  SimpleTest.registerCleanupFunction(() => {
+    SpecialPowers.clearUserPref("network.cookie.quotaPerHost");
+    SpecialPowers.clearUserPref("network.cookie.maxPerHost");
+  });
+});
+
+add_task(async function test_good_cookie_permissions() {
+  info("Test matching, non-secure domain with non-secure cookie");
+  await testCookies({
+    permissions: ["http://example.com/", "cookies"],
+    url: "http://example.com/",
+    domain: "example.com",
+    secure: false,
+    shouldPass: true,
+  });
+
+  info("Test matching, secure domain with non-secure cookie");
+  await testCookies({
+    permissions: ["https://example.com/", "cookies"],
+    url: "https://example.com/",
+    domain: "example.com",
+    secure: false,
+    shouldPass: true,
+  });
+
+  info("Test matching, secure domain with secure cookie");
+  await testCookies({
+    permissions: ["https://example.com/", "cookies"],
+    url: "https://example.com/",
+    domain: "example.com",
+    secure: true,
+    shouldPass: true,
+  });
+
+  info("Test matching subdomain with superdomain privileges, secure cookie (https)");
+  await testCookies({
+    permissions: ["https://foo.bar.example.com/", "cookies"],
+    url: "https://foo.bar.example.com/",
+    domain: ".example.com",
+    secure: true,
+    shouldPass: true,
+  });
+
+  info("Test matching subdomain with superdomain privileges, non-secure cookie (https)");
+  await testCookies({
+    permissions: ["https://foo.bar.example.com/", "cookies"],
+    url: "https://foo.bar.example.com/",
+    domain: ".example.com",
+    secure: false,
+    shouldPass: true,
+  });
+
+  info("Test matching subdomain with superdomain privileges, non-secure cookie  (http)");
+  await testCookies({
+    permissions: ["http://foo.bar.example.com/", "cookies"],
+    url: "http://foo.bar.example.com/",
+    domain: ".example.com",
+    secure: false,
+    shouldPass: true,
+  });
+});
+
+</script>
+
+</body>
+</html>
diff --git a/toolkit/components/extensions/test/mochitest/test_ext_dnr_other_extensions.html b/toolkit/components/extensions/test/mochitest/test_ext_dnr_other_extensions.html
new file mode 100644
index 0000000000..d3074b3dec
--- /dev/null
+++ b/toolkit/components/extensions/test/mochitest/test_ext_dnr_other_extensions.html
@@ -0,0 +1,113 @@
+<!DOCTYPE HTML>
+<html>
+<head>
+  <meta charset="utf-8">
+  <title>DNR and tabs.create from other extension</title>
+  <script type="text/javascript" src="/tests/SimpleTest/SimpleTest.js"></script>
+  <script type="text/javascript" src="/tests/SimpleTest/ExtensionTestUtils.js"></script>
+  <script type="text/javascript" src="head.js"></script>
+  <link rel="stylesheet" type="text/css" href="/tests/SimpleTest/test.css">
+</head>
+<body>
+<script>
+"use strict";
+
+
+// While most DNR tests are xpcshell tests, this one is a mochitest because the
+// tabs.create API does not work in a xpcshell test.
+
+add_setup(async () => {
+  await SpecialPowers.pushPrefEnv({
+    set: [
+      ["extensions.manifestV3.enabled", true],
+      ["extensions.dnr.enabled", true],
+    ],
+  });
+});
+
+
+add_task(async function tabs_create_can_be_redirected_by_other_dnr_extension() {
+  let dnrExtension = ExtensionTestUtils.loadExtension({
+    manifest: {
+      permissions: ["declarativeNetRequestWithHostAccess"],
+      // redirect action requires host permissions:
+      host_permissions: ["*://example.com/*"],
+    },
+    async background() {
+      await browser.declarativeNetRequest.updateSessionRules({
+        addRules: [
+          {
+            id: 1,
+            condition: {
+              resourceTypes: ["main_frame"],
+              urlFilter: "?dnr_redir_me_pls",
+            },
+            action: {
+              type: "redirect",
+              redirect: {
+                transform: {
+                  query: "?dnr_redir_target"
+                },
+              },
+            },
+          },
+        ],
+      });
+      browser.test.sendMessage("dnr_registered");
+    },
+  });
+  await dnrExtension.startup();
+  await dnrExtension.awaitMessage("dnr_registered");
+
+  let extension = ExtensionTestUtils.loadExtension({
+    manifest: {
+      permissions: ["webNavigation"],
+    },
+    async background() {
+      async function createTabAndGetFinalUrl(url) {
+        let navigationDonePromise = new Promise(resolve => {
+          browser.webNavigation.onDOMContentLoaded.addListener(
+            function listener(details) {
+              browser.webNavigation.onDOMContentLoaded.removeListener(listener);
+              resolve(details);
+            },
+            // All input URLs and redirection targets match this URL filter:
+            { url: [{ queryPrefix: "dnr_redir_" }] }
+          );
+        });
+        const tab = await browser.tabs.create({ url });
+        browser.test.log(`Waiting for navigation done, starting from ${url}`);
+        const result = await navigationDonePromise;
+        browser.test.assertEq(
+          tab.id,
+          result.tabId,
+          `Observed load completion for navigation tab with initial URL ${url}`
+        );
+        await browser.tabs.remove(tab.id);
+        return result.url;
+      }
+
+      browser.test.assertEq(
+        "https://example.com/?dnr_redir_target",
+        await createTabAndGetFinalUrl("https://example.com/?dnr_redir_me_pls"),
+        "DNR rule from other extension should have redirected the navigation"
+      );
+
+      browser.test.assertEq(
+        "https://example.org/?dnr_redir_me_pls",
+        await createTabAndGetFinalUrl("https://example.org/?dnr_redir_me_pls"),
+        "DNR redirect ignored for URLs without host permission"
+      );
+      browser.test.sendMessage("done");
+    }
+  });
+  await extension.startup();
+  await extension.awaitMessage("done");
+
+  await dnrExtension.unload();
+  await extension.unload();
+});
+
+</script>
+</body>
+</html>
diff --git a/toolkit/components/extensions/test/mochitest/test_ext_dnr_tabIds.html b/toolkit/components/extensions/test/mochitest/test_ext_dnr_tabIds.html
new file mode 100644
index 0000000000..0278a8ccc8
--- /dev/null
+++ b/toolkit/components/extensions/test/mochitest/test_ext_dnr_tabIds.html
@@ -0,0 +1,137 @@
+<!DOCTYPE HTML>
+<html>
+<head>
+  <meta charset="utf-8">
+  <title>DNR with tabIds condition</title>
+  <script type="text/javascript" src="/tests/SimpleTest/SimpleTest.js"></script>
+  <script type="text/javascript" src="/tests/SimpleTest/ExtensionTestUtils.js"></script>
+  <script type="text/javascript" src="head.js"></script>
+  <link rel="stylesheet" type="text/css" href="/tests/SimpleTest/test.css">
+</head>
+<body>
+<script>
+"use strict";
+
+// While most DNR tests are xpcshell tests, this one is a mochitest because it
+// is not possible to create a tab and get a tabId in a xpcshell test.
+
+// toolkit/components/extensions/test/xpcshell/test_ext_dnr_tabIds.js does
+// exist, as an isolated xpcshell is needed to verify that the internals are
+// working as expected. A mochitest is not a good fit for that because it has
+// built-in add-ons that may affect the observed behavior.
+
+add_setup(async () => {
+  await SpecialPowers.pushPrefEnv({
+    set: [
+      ["extensions.manifestV3.enabled", true],
+      ["extensions.dnr.enabled", true],
+    ],
+  });
+});
+
+add_task(async function match_by_tabIds() {
+  let extension = ExtensionTestUtils.loadExtension({
+    async background() {
+      async function createTabAndPort() {
+        let portPromise = new Promise(resolve => {
+          browser.runtime.onConnect.addListener(function listener(port) {
+            browser.runtime.onConnect.removeListener(listener);
+            browser.test.assertEq("port_from_tab", port.name, "Got port");
+            resolve(port);
+          });
+        });
+        const tab = await browser.tabs.create({ url: "tab.html" });
+        const port = await portPromise;
+        browser.test.assertEq(tab.id, port.sender.tab.id, "Got port from tab");
+        browser.test.assertTrue(tab.id > 0, `tabId must be valid: ${tab.id}`);
+        tab.port = port;
+        return tab;
+      }
+      async function getFinalUrlForFetchInTab(tabWithPort, url) {
+        const port = tabWithPort.port; // from createTabAndPort.
+        return new Promise(resolve => {
+          port.onMessage.addListener(function listener(responseUrl) {
+            port.onMessage.removeListener(listener);
+            resolve(responseUrl);
+          });
+          port.postMessage(url);
+        });
+      }
+      let tab1 = await createTabAndPort();
+      let tab2 = await createTabAndPort();
+
+      const URL_PREFIX = "https://example.com/tests/toolkit/components/extensions/test/mochitest/file_sample.txt";
+
+      function makeRedirect(id, condition, url) {
+        return {
+          id,
+          // The test sends a request to example.net and expects a redirect to
+          // URL_PREFIX (example.com).
+          condition: { requestDomains: ["example.net"], ...condition },
+          action: { type: "redirect", redirect: { url }},
+        };
+      }
+      await browser.declarativeNetRequest.updateSessionRules({
+        addRules: [
+          makeRedirect(1, { tabIds: [-1] }, `${URL_PREFIX}?tabId/-1`),
+          makeRedirect(2, { tabIds: [tab1.id] }, `${URL_PREFIX}?tabId/tab1`),
+          makeRedirect(
+            3,
+            { excludedTabIds: [-1, tab1.id] },
+            `${URL_PREFIX}?tabId/not-1,not-tab1`
+          ),
+        ],
+      });
+
+      browser.test.assertEq(
+        `${URL_PREFIX}?tabId/-1`,
+        (await fetch("https://example.net/?pre-redirect-bg")).url,
+        "Request from background should match tabIds: [-1]"
+      );
+      browser.test.assertEq(
+        `${URL_PREFIX}?tabId/tab1`,
+        await getFinalUrlForFetchInTab(tab1, "https://example.net/?pre-tab1"),
+        "Request from tab1 should match tabIds: [tab1]"
+      );
+      browser.test.assertEq(
+        `${URL_PREFIX}?tabId/not-1,not-tab1`,
+        await getFinalUrlForFetchInTab(tab2, "https://example.net/?pre-tab2"),
+        "Request from tab2 should match excludedTabIds: [-1, tab1]"
+      );
+
+      await browser.tabs.remove(tab1.id);
+      await browser.tabs.remove(tab2.id);
+
+      browser.test.sendMessage("done");
+    },
+    temporarilyInstalled: true, // Needed for granted_host_permissions
+    manifest: {
+      manifest_version: 3,
+      host_permissions: ["*://example.com/*", "*://example.net/*"],
+      permissions: ["declarativeNetRequest"],
+      granted_host_permissions: true,
+    },
+    files: {
+      "tab.html": `<!DOCTYPE html><script src="tab.js"><\/script>`,
+      "tab.js": () => {
+        let port = browser.runtime.connect({ name: "port_from_tab" });
+        port.onMessage.addListener(async url => {
+          try {
+            let res = await fetch(url);
+            port.postMessage(res.url);
+          } catch (e) {
+            port.postMessage(e.message);
+          }
+        });
+      },
+    },
+  });
+  await extension.startup();
+  await extension.awaitMessage("done");
+
+  await extension.unload();
+});
+
+</script>
+</body>
+</html>
diff --git a/toolkit/components/extensions/test/mochitest/test_ext_dnr_upgradeScheme.html b/toolkit/components/extensions/test/mochitest/test_ext_dnr_upgradeScheme.html
new file mode 100644
index 0000000000..43bc8a5a00
--- /dev/null
+++ b/toolkit/components/extensions/test/mochitest/test_ext_dnr_upgradeScheme.html
@@ -0,0 +1,137 @@
+<!DOCTYPE HTML>
+<html>
+<head>
+  <meta charset="utf-8">
+  <title>DNR with upgradeScheme action</title>
+  <script type="text/javascript" src="/tests/SimpleTest/SimpleTest.js"></script>
+  <script type="text/javascript" src="/tests/SimpleTest/ExtensionTestUtils.js"></script>
+  <script type="text/javascript" src="head.js"></script>
+  <link rel="stylesheet" type="text/css" href="/tests/SimpleTest/test.css">
+</head>
+<body>
+<script>
+"use strict";
+
+// This test is not a xpcshell test, because we want to test upgrades to https,
+// and HttpServer helper does not support https (bug 1742061).
+
+add_setup(async () => {
+  await SpecialPowers.pushPrefEnv({
+    set: [
+      ["extensions.manifestV3.enabled", true],
+      ["extensions.dnr.enabled", true],
+      ["extensions.dnr.match_requests_from_other_extensions", true],
+    ],
+  });
+});
+
+// Tests that the upgradeScheme action works as expected:
+// - http should be upgraded to https
+// - after the https upgrade the request should happen instead of being stuck
+//   in a upgrade redirect loop.
+add_task(async function upgradeScheme_with_dnr() {
+  let extension = ExtensionTestUtils.loadExtension({
+    async background() {
+      await browser.declarativeNetRequest.updateSessionRules({
+        addRules: [{ id: 1, condition: { requestDomains: ["example.com"] }, action: { type: "upgradeScheme" } }],
+      });
+
+      let sanityCheckResponse = await fetch(
+        // eslint-disable-next-line @microsoft/sdl/no-insecure-url
+        "http://example.net/tests/toolkit/components/extensions/test/mochitest/file_sample.txt"
+      );
+      browser.test.assertEq(
+        // eslint-disable-next-line @microsoft/sdl/no-insecure-url
+        "http://example.net/tests/toolkit/components/extensions/test/mochitest/file_sample.txt",
+        sanityCheckResponse.url,
+        "non-matching request should not be upgraded"
+      );
+
+      let res = await fetch(
+        // eslint-disable-next-line @microsoft/sdl/no-insecure-url
+        "http://example.com/tests/toolkit/components/extensions/test/mochitest/file_sample.txt"
+      );
+      browser.test.assertEq(
+        "https://example.com/tests/toolkit/components/extensions/test/mochitest/file_sample.txt",
+        res.url,
+        "upgradeScheme should have upgraded to https"
+      );
+      // Server adds "Access-Control-Allow-Origin: *" to file_sample.txt, so
+      // we should be able to read the response despite no host_permissions.
+      browser.test.assertEq("Sample", await res.text(), "read body with CORS");
+
+      browser.test.sendMessage("dnr_registered");
+    },
+    manifest: {
+      manifest_version: 3,
+      // Note: host_permissions missing. upgradeScheme should not need it.
+      permissions: ["declarativeNetRequest"],
+    },
+    allowInsecureRequests: true,
+  });
+  await extension.startup();
+  await extension.awaitMessage("dnr_registered");
+
+  // The request made by otherExtension is affected by the DNR rule from the
+  // extension because extensions.dnr.match_requests_from_other_extensions was
+  // set to true. A realistic alternative would have been to trigger the fetch
+  // requests from a content page instead of the extension.
+  let otherExtension = ExtensionTestUtils.loadExtension({
+    async background() {
+      let firstRequestPromise = new Promise(resolve => {
+        let count = 0;
+        browser.webRequest.onBeforeRequest.addListener(
+          ({ url }) => {
+            ++count;
+            browser.test.assertTrue(
+              count <= 2,
+              `Expected at most two requests; got ${count} to ${url}`
+            );
+            resolve(url);
+          },
+          { urls: ["*://example.com/?test_dnr_upgradeScheme"] }
+        );
+      });
+      // Round-trip through ext-webRequest.js implementation to ensure that the
+      // listener has been registered (workaround for bug 1300234).
+      await browser.webRequest.handlerBehaviorChanged();
+
+      // eslint-disable-next-line @microsoft/sdl/no-insecure-url
+      const insecureInitialUrl = "http://example.com/?test_dnr_upgradeScheme";
+      browser.test.log(`Requesting insecure URL: ${insecureInitialUrl}`);
+
+      let req = await fetch(insecureInitialUrl);
+      browser.test.assertEq(
+        "https://example.com/?test_dnr_upgradeScheme",
+        req.url,
+        "upgradeScheme action upgraded http to https"
+      );
+      browser.test.assertEq(200, req.status, "Correct HTTP status");
+
+      await req.text(); // Verify that the body can be read, just in case.
+
+      // Sanity check that the test did not pass trivially due to an automatic
+      // https upgrade of the extension / test environment.
+      browser.test.assertEq(
+        insecureInitialUrl,
+        await firstRequestPromise,
+        "Initial URL should be http"
+      );
+
+      browser.test.sendMessage("tested_dnr_upgradeScheme");
+    },
+    manifest: {
+      host_permissions: ["*://example.com/*"],
+      permissions: ["webRequest"],
+    },
+  });
+  await otherExtension.startup();
+  await otherExtension.awaitMessage("tested_dnr_upgradeScheme");
+  await otherExtension.unload();
+
+  await extension.unload();
+});
+
+</script>
+</body>
+</html>
diff --git a/toolkit/components/extensions/test/mochitest/test_ext_downloads_download.html b/toolkit/components/extensions/test/mochitest/test_ext_downloads_download.html
new file mode 100644
index 0000000000..23058c35ec
--- /dev/null
+++ b/toolkit/components/extensions/test/mochitest/test_ext_downloads_download.html
@@ -0,0 +1,94 @@
+<!DOCTYPE HTML>
+<html>
+<head>
+  <meta charset="utf-8">
+  <title>Downloads Test</title>
+  <script type="text/javascript" src="/tests/SimpleTest/SimpleTest.js"></script>
+  <script type="text/javascript" src="/tests/SimpleTest/ExtensionTestUtils.js"></script>
+  <script type="text/javascript" src="head.js"></script>
+  <link rel="stylesheet" href="/tests/SimpleTest/test.css"/>
+</head>
+<body>
+
+<script type="text/javascript">
+"use strict";
+
+async function background() {
+  const url = "http://mochi.test:8888/tests/mobile/android/components/extensions/test/mochitest/context_tabs_onUpdated_page.html";
+
+  browser.test.assertThrows(
+    () => browser.downloads.download(),
+    /Incorrect argument types for downloads.download/,
+    "Should fail without options"
+  );
+
+  browser.test.assertThrows(
+    () => browser.downloads.download({url: "invalid url"}),
+    /invalid url is not a valid URL/,
+    "Should fail on invalid URL"
+  );
+
+  browser.test.assertThrows(
+    () => browser.downloads.download({}),
+    /Property "url" is required/,
+    "Should fail with no URL"
+  );
+
+  browser.test.assertThrows(
+    () => browser.downloads.download({url, method: "DELETE"}),
+    /Invalid enumeration value "DELETE"/,
+    "Should fail with invalid method"
+  );
+
+  await browser.test.assertRejects(
+    browser.downloads.download({url, headers: [{name: "Host", value: "Banana"}]}),
+    /Forbidden request header name/,
+    "Should fail with a forbidden header"
+  );
+
+  const absoluteFilename = SpecialPowers.Services.appinfo.OS === "WINNT"
+    ? "C:\\tmp\\file.gif"
+    : "/tmp/file.gif";
+
+  await browser.test.assertRejects(
+    browser.downloads.download({url, filename: absoluteFilename}),
+    /filename must not be an absolute path/,
+    "Should fail with an absolute file path"
+  );
+
+  await browser.test.assertRejects(
+    browser.downloads.download({url, filename: ""}),
+    /filename must not be empty/,
+    "Should fail with an empty file path"
+  );
+
+  await browser.test.assertRejects(
+    browser.downloads.download({url, filename: "file."}),
+    /filename must not contain illegal characters/,
+    "Should fail with a dot in the filename"
+  );
+
+  await browser.test.assertRejects(
+    browser.downloads.download({url, filename: "../file.gif"}),
+    /filename must not contain back-references/,
+    "Should fail with a file path that contains back-references"
+  );
+
+  browser.test.notifyPass("download.done");
+}
+
+add_task(async function test_invalid_download_parameters() {
+  const extension = ExtensionTestUtils.loadExtension({
+    manifest: {permissions: ["downloads"]},
+    background,
+  });
+  await extension.startup();
+
+  await extension.awaitFinish("download.done");
+
+  await extension.unload();
+});
+</script>
+
+</body>
+</html>
diff --git a/toolkit/components/extensions/test/mochitest/test_ext_embeddedimg_iframe_frameAncestors.html b/toolkit/components/extensions/test/mochitest/test_ext_embeddedimg_iframe_frameAncestors.html
new file mode 100644
index 0000000000..d6702da4d3
--- /dev/null
+++ b/toolkit/components/extensions/test/mochitest/test_ext_embeddedimg_iframe_frameAncestors.html
@@ -0,0 +1,94 @@
+<!DOCTYPE html>
+<html>
+<head>
+  <title>Test checking webRequest.onBeforeRequest details object</title>
+  <script src="/tests/SimpleTest/SimpleTest.js"></script>
+  <script src="/tests/SimpleTest/EventUtils.js"></script>
+  <script src="/tests/SimpleTest/ExtensionTestUtils.js"></script>
+  <link rel="stylesheet" type="text/css" href="/tests/SimpleTest/test.css"/>
+</head>
+<body>
+
+<script type="text/javascript">
+"use strict";
+
+let expected = {
+  "file_contains_iframe.html": {
+    type: "main_frame",
+    frameAncestor_length: 0,
+  },
+  "file_contains_img.html": {
+    type: "sub_frame",
+    frameAncestor_length: 1,
+  },
+  "file_image_good.png": {
+    type: "image",
+    frameAncestor_length: 1,
+  }
+};
+
+function checkDetails(details) {
+  let url = new URL(details.url);
+  let filename = url.pathname.split("/").pop();
+  ok(expected.hasOwnProperty(filename), `Should be expecting a request for ${filename}`);
+  let expect = expected[filename];
+  is(expect.type, details.type, `${details.type} type matches`);
+  is(expect.frameAncestor_length, details.frameAncestors.length, "incorrect frameAncestors length");
+  if (filename == "file_contains_img.html") {
+    is(details.frameAncestors[0].frameId, details.parentFrameId,
+    "frameAncestors[0] should match parentFrameId");
+    expected["file_image_good.png"].frameId = details.frameId;
+  } else if (filename == "file_image_good.png") {
+    is(details.frameAncestors[0].frameId, details.parentFrameId,
+       "frameAncestors[0] should match parentFrameId");
+    is(details.frameId, expect.frameId,
+       "frameId for image and iframe should match");
+  }
+}
+
+add_task(async () => {
+  // Clear the image cache, since it gets in the way otherwise.
+  let imgTools = SpecialPowers.Cc["@mozilla.org/image/tools;1"].getService(SpecialPowers.Ci.imgITools);
+  let cache = imgTools.getImgCacheForDocument(document);
+  cache.clearCache(false);
+  await SpecialPowers.spawnChrome([], async () => {
+    Services.cache2.clear();
+  });
+
+  const extension = ExtensionTestUtils.loadExtension({
+    manifest: {
+      permissions: ["webRequest", "<all_urls>"],
+    },
+    background() {
+      browser.webRequest.onBeforeRequest.addListener(
+        details => {
+          browser.test.sendMessage("onBeforeRequest", details);
+        },
+        {
+          urls: [
+          "http://example.org/*/file_contains_img.html",
+          "http://mochi.test/*/file_contains_iframe.html",
+          "*://*/*.png",
+          ],
+        }
+      );
+    },
+  });
+
+  await extension.startup();
+  const FILE_URL = "http://mochi.test:8888/tests/toolkit/components/extensions/test/mochitest/file_contains_iframe.html";
+  let win = window.open(FILE_URL);
+  await new Promise(resolve => win.addEventListener("load", () => resolve(), {once: true}));
+
+  for (let i = 0; i < Object.keys(expected).length; i++) {
+    checkDetails(await extension.awaitMessage("onBeforeRequest"));
+  }
+
+  win.close();
+  await extension.unload();
+});
+
+</script>
+
+</body>
+</html>
diff --git a/toolkit/components/extensions/test/mochitest/test_ext_exclude_include_globs.html b/toolkit/components/extensions/test/mochitest/test_ext_exclude_include_globs.html
new file mode 100644
index 0000000000..f87b5620d6
--- /dev/null
+++ b/toolkit/components/extensions/test/mochitest/test_ext_exclude_include_globs.html
@@ -0,0 +1,91 @@
+<!DOCTYPE HTML>
+<html>
+<head>
+  <title>Test for content script</title>
+  <script src="/tests/SimpleTest/SimpleTest.js"></script>
+  <script src="/tests/SimpleTest/ExtensionTestUtils.js"></script>
+  <script type="text/javascript" src="head.js"></script>
+  <link rel="stylesheet" type="text/css" href="/tests/SimpleTest/test.css"/>
+</head>
+<body>
+
+<script type="text/javascript">
+"use strict";
+
+add_task(async function test_contentscript() {
+  function background() {
+    browser.runtime.onMessage.addListener(([script], sender) => {
+      browser.test.sendMessage("run", {script});
+      browser.test.sendMessage("run-" + script);
+    });
+    browser.test.sendMessage("running");
+  }
+
+  function contentScriptAll() {
+    browser.runtime.sendMessage(["all"]);
+  }
+  function contentScriptIncludesTest1() {
+    browser.runtime.sendMessage(["includes-test1"]);
+  }
+  function contentScriptExcludesTest1() {
+    browser.runtime.sendMessage(["excludes-test1"]);
+  }
+
+  let extensionData = {
+    manifest: {
+      content_scripts: [
+        {
+          "matches": ["https://example.org/", "https://*.example.org/"],
+          "exclude_globs": [],
+          "include_globs": ["*"],
+          "js": ["content_script_all.js"],
+        },
+        {
+          "matches": ["https://example.org/", "https://*.example.org/"],
+          "include_globs": ["*test1*"],
+          "js": ["content_script_includes_test1.js"],
+        },
+        {
+          "matches": ["https://example.org/", "https://*.example.org/"],
+          "exclude_globs": ["*test1*"],
+          "js": ["content_script_excludes_test1.js"],
+        },
+      ],
+    },
+    background,
+
+    files: {
+      "content_script_all.js": contentScriptAll,
+      "content_script_includes_test1.js": contentScriptIncludesTest1,
+      "content_script_excludes_test1.js": contentScriptExcludesTest1,
+    },
+
+  };
+
+  let extension = ExtensionTestUtils.loadExtension(extensionData);
+
+  let ran = 0;
+  extension.onMessage("run", ({script}) => {
+    ran++;
+  });
+
+  await Promise.all([extension.startup(), extension.awaitMessage("running")]);
+  info("extension loaded");
+
+  let win = window.open("https://example.org/");
+  await Promise.all([extension.awaitMessage("run-all"), extension.awaitMessage("run-excludes-test1")]);
+  win.close();
+  is(ran, 2);
+
+  win = window.open("https://test1.example.org/");
+  await Promise.all([extension.awaitMessage("run-all"), extension.awaitMessage("run-includes-test1")]);
+  win.close();
+  is(ran, 4);
+
+  await extension.unload();
+  info("extension unloaded");
+});
+</script>
+
+</body>
+</html>
diff --git a/toolkit/components/extensions/test/mochitest/test_ext_extension_iframe_messaging.html b/toolkit/components/extensions/test/mochitest/test_ext_extension_iframe_messaging.html
new file mode 100644
index 0000000000..403782ab7d
--- /dev/null
+++ b/toolkit/components/extensions/test/mochitest/test_ext_extension_iframe_messaging.html
@@ -0,0 +1,124 @@
+<!DOCTYPE html>
+<html>
+<head>
+  <title>Test moz-extension iframe messaging</title>
+  <meta charset="utf-8">
+  <script src="/tests/SimpleTest/SimpleTest.js"></script>
+  <script src="/tests/SimpleTest/ExtensionTestUtils.js"></script>
+  <script type="text/javascript" src="head.js"></script>
+  <link rel="stylesheet" type="text/css" href="/tests/SimpleTest/test.css">
+</head>
+<body>
+<script>
+"use strict";
+
+add_task(async function test_moz_extension_iframe_messaging() {
+  await SpecialPowers.pushPrefEnv({
+    set: [
+      ["extensions.content_web_accessible.enabled", true],
+    ],
+  });
+
+  let extension = ExtensionTestUtils.loadExtension({
+    manifest: {
+      content_scripts: [{
+        js: ["cs.js"],
+        matches: ["http://mochi.test/*/file_sample.html"],
+      }],
+      web_accessible_resources: ["iframe.html"],
+      permissions: ["tabs"],
+    },
+    files: {
+      "cs.js"() {
+        let iframe = document.createElement("iframe");
+        iframe.src = browser.runtime.getURL("iframe.html");
+        document.body.append(iframe);
+      },
+
+      "iframe.html": `<!doctype html><script src=iframe.js><\/script>`,
+      async "iframe.js"() {
+        browser.runtime.onMessage.addListener(async msg => {
+          browser.test.assertEq(msg, "from-background", "Correct message.");
+          return "iframe-response";
+        });
+
+        browser.runtime.onConnect.addListener(async port => {
+          port.postMessage("port-message");
+        });
+
+        await browser.test.assertRejects(
+          browser.runtime.sendMessage("from-iframe"),
+          "Could not establish connection. Receiving end does not exist.",
+          "No onMessage listener in the background."
+        );
+
+        await new Promise(resolve => {
+          let port = browser.runtime.connect();
+          port.onDisconnect.addListener(() => {
+            browser.test.assertEq(
+              port.error.message,
+              "Could not establish connection. Receiving end does not exist.",
+              "No onConnect listener in the background."
+            );
+            resolve();
+          })
+        });
+
+        // TODO: If/when the tabs API is available from extension iframes, test
+        // that it won't send a message to itself via browser.tabs.sendMessage()
+        browser.test.assertEq(browser.tabs, undefined, "No tabs API");
+
+        browser.test.sendMessage("iframe-done");
+      },
+    },
+    background() {
+      browser.test.onMessage.addListener(async msg => {
+
+        await browser.test.assertRejects(
+          browser.runtime.sendMessage("from-background"),
+          "Could not establish connection. Receiving end does not exist.",
+          "No onMessage listener in another extension page."
+        );
+
+        await new Promise(resolve => {
+          let port = browser.runtime.connect();
+          port.onDisconnect.addListener(() => {
+            browser.test.assertEq(
+              port.error.message,
+              "Could not establish connection. Receiving end does not exist.",
+              "No onConnect listener in another extension page."
+            );
+            resolve();
+          })
+        });
+
+        let [tab] = await browser.tabs.query({
+          url: "http://mochi.test/*/file_sample.html",
+        });
+        let res = await browser.tabs.sendMessage(tab.id, "from-background");
+        browser.test.assertEq(res, "iframe-response", "Correct response.");
+
+        let port = browser.tabs.connect(tab.id);
+        port.onMessage.addListener(msg => {
+          browser.test.assertEq(msg, "port-message", "Correct port message.");
+          browser.test.notifyPass("done");
+        });
+      })
+    }
+  });
+
+  await extension.startup();
+
+  let win = window.open("file_sample.html");
+  await extension.awaitMessage("iframe-done");
+
+  extension.sendMessage("run-background");
+  await extension.awaitFinish("done");
+  win.close();
+
+  await extension.unload();
+});
+
+</script>
+</body>
+</html>
diff --git a/toolkit/components/extensions/test/mochitest/test_ext_external_messaging.html b/toolkit/components/extensions/test/mochitest/test_ext_external_messaging.html
new file mode 100644
index 0000000000..639cacef28
--- /dev/null
+++ b/toolkit/components/extensions/test/mochitest/test_ext_external_messaging.html
@@ -0,0 +1,110 @@
+<!DOCTYPE HTML>
+<html>
+<head>
+  <title>WebExtension external messaging</title>
+  <script src="/tests/SimpleTest/SimpleTest.js"></script>
+  <script src="/tests/SimpleTest/ExtensionTestUtils.js"></script>
+  <script type="text/javascript" src="head.js"></script>
+  <link rel="stylesheet" type="text/css" href="/tests/SimpleTest/test.css"/>
+</head>
+<body>
+
+<script type="text/javascript">
+"use strict";
+
+function backgroundScript(id, otherId) {
+  browser.runtime.onMessage.addListener((msg, sender) => {
+    browser.test.fail(`Got unexpected message: ${uneval(msg)} ${uneval(sender)}`);
+  });
+
+  browser.runtime.onConnect.addListener(port => {
+    browser.test.fail(`Got unexpected connection: ${uneval(port.sender)}`);
+  });
+
+  browser.runtime.onMessageExternal.addListener((msg, sender) => {
+    browser.test.assertEq(otherId, sender.id, `${id}: Got expected external sender ID`);
+    browser.test.assertEq(`helo-${id}`, msg, "Got expected message");
+
+    browser.test.sendMessage("onMessage-done");
+
+    return Promise.resolve(`ehlo-${otherId}`);
+  });
+
+  browser.runtime.onConnectExternal.addListener(port => {
+    browser.test.assertEq(otherId, port.sender.id, `${id}: Got expected external connecter ID`);
+
+    port.onMessage.addListener(msg => {
+      browser.test.assertEq(`helo-${id}`, msg, "Got expected port message");
+
+      port.postMessage(`ehlo-${otherId}`);
+
+      browser.test.sendMessage("onConnect-done");
+    });
+  });
+
+  browser.test.onMessage.addListener(msg => {
+    if (msg === "go") {
+      browser.runtime.sendMessage(otherId, `helo-${otherId}`).then(result => {
+        browser.test.assertEq(`ehlo-${id}`, result, "Got expected reply");
+        browser.test.sendMessage("sendMessage-done");
+      });
+
+      let port = browser.runtime.connect(otherId);
+      port.postMessage(`helo-${otherId}`);
+
+      port.onMessage.addListener(msg => {
+        port.disconnect();
+
+        browser.test.assertEq(msg, `ehlo-${id}`, "Got expected port reply");
+        browser.test.sendMessage("connect-done");
+      });
+    }
+  });
+}
+
+function makeExtension(id, otherId) {
+  let args = `${JSON.stringify(id)}, ${JSON.stringify(otherId)}`;
+
+  let extensionData = {
+    background: `(${backgroundScript})(${args})`,
+    manifest: {
+      browser_specific_settings: {gecko: {id}},
+    },
+  };
+
+  return ExtensionTestUtils.loadExtension(extensionData);
+}
+
+add_task(async function test_contentscript() {
+  const ID1 = "foo-message@mochitest.mozilla.org";
+  const ID2 = "bar-message@mochitest.mozilla.org";
+
+  let extension1 = makeExtension(ID1, ID2);
+  let extension2 = makeExtension(ID2, ID1);
+
+  await Promise.all([extension1.startup(), extension2.startup()]);
+
+  extension1.sendMessage("go");
+  extension2.sendMessage("go");
+
+  await Promise.all([
+    extension1.awaitMessage("sendMessage-done"),
+    extension2.awaitMessage("sendMessage-done"),
+
+    extension1.awaitMessage("onMessage-done"),
+    extension2.awaitMessage("onMessage-done"),
+
+    extension1.awaitMessage("connect-done"),
+    extension2.awaitMessage("connect-done"),
+
+    extension1.awaitMessage("onConnect-done"),
+    extension2.awaitMessage("onConnect-done"),
+  ]);
+
+  await extension1.unload();
+  await extension2.unload();
+});
+</script>
+
+</body>
+</html>
diff --git a/toolkit/components/extensions/test/mochitest/test_ext_generate.html b/toolkit/components/extensions/test/mochitest/test_ext_generate.html
new file mode 100644
index 0000000000..ba88d16ca3
--- /dev/null
+++ b/toolkit/components/extensions/test/mochitest/test_ext_generate.html
@@ -0,0 +1,48 @@
+<!DOCTYPE HTML>
+<html>
+<head>
+  <title>Test for generating WebExtensions</title>
+  <script src="/tests/SimpleTest/SimpleTest.js"></script>
+  <script src="/tests/SimpleTest/ExtensionTestUtils.js"></script>
+  <script type="text/javascript" src="head.js"></script>
+  <link rel="stylesheet" type="text/css" href="/tests/SimpleTest/test.css"/>
+</head>
+<body>
+
+<script type="text/javascript">
+"use strict";
+
+function background() {
+  browser.test.log("running background script");
+
+  browser.test.onMessage.addListener((x, y) => {
+    browser.test.assertEq(x, 10, "x is 10");
+    browser.test.assertEq(y, 20, "y is 20");
+
+    browser.test.notifyPass("background test passed");
+  });
+
+  browser.test.sendMessage("running", 1);
+}
+
+let extensionData = {
+  background,
+};
+
+add_task(async function test_background() {
+  let extension = ExtensionTestUtils.loadExtension(extensionData);
+  info("load complete");
+  let [, x] = await Promise.all([extension.startup(), extension.awaitMessage("running")]);
+  is(x, 1, "got correct value from extension");
+  info("startup complete");
+  extension.sendMessage(10, 20);
+  await extension.awaitFinish();
+  info("test complete");
+  await extension.unload();
+  info("extension unloaded successfully");
+});
+
+</script>
+
+</body>
+</html>
diff --git a/toolkit/components/extensions/test/mochitest/test_ext_geolocation.html b/toolkit/components/extensions/test/mochitest/test_ext_geolocation.html
new file mode 100644
index 0000000000..9f326372bb
--- /dev/null
+++ b/toolkit/components/extensions/test/mochitest/test_ext_geolocation.html
@@ -0,0 +1,86 @@
+<!DOCTYPE HTML>
+
+<html>
+<head>
+<meta charset="utf-8">
+  <script src="/tests/SimpleTest/SimpleTest.js"></script>
+  <script src="/tests/SimpleTest/ExtensionTestUtils.js"></script>
+  <script type="text/javascript" src="head.js"></script>
+  <link rel="stylesheet" type="text/css" href="/tests/SimpleTest/test.css"/>
+<script>
+"use strict";
+
+add_task(async function test_geolocation_nopermission() {
+  let GEO_URL = "http://mochi.test:8888/tests/dom/tests/mochitest/geolocation/network_geolocation.sjs";
+  await SpecialPowers.pushPrefEnv({"set": [["geo.provider.network.url", GEO_URL]]});
+});
+
+add_task(async function test_geolocation() {
+  let extension = ExtensionTestUtils.loadExtension({
+    manifest: {
+      permissions: [
+        "geolocation",
+      ],
+    },
+    background() {
+      navigator.geolocation.getCurrentPosition(() => {
+        browser.test.notifyPass("success geolocation call");
+      }, (error) => {
+        browser.test.notifyFail(`geolocation call ${error}`);
+      });
+    },
+  });
+
+  await extension.startup();
+  await extension.awaitFinish();
+  await extension.unload();
+});
+
+add_task(async function test_geolocation_nopermission() {
+  let extension = ExtensionTestUtils.loadExtension({
+    background() {
+      navigator.geolocation.getCurrentPosition(() => {
+        browser.test.notifyFail("success geolocation call");
+      }, (error) => {
+        browser.test.notifyPass(`geolocation call ${error}`);
+      });
+    },
+  });
+
+  await extension.startup();
+  await extension.awaitFinish();
+  await extension.unload();
+});
+
+add_task(async function test_geolocation_prompt() {
+  let extension = ExtensionTestUtils.loadExtension({
+    background() {
+      browser.tabs.create({url: "tab.html"});
+    },
+    files: {
+      "tab.html": `<html><head>
+        <meta charset="utf-8">
+        <script src="tab.js"><\/script>
+      </head></html>`,
+      "tab.js": () => {
+        navigator.geolocation.getCurrentPosition(() => {
+          browser.test.notifyPass("success geolocation call");
+        }, (error) => {
+          browser.test.notifyFail(`geolocation call ${error}`);
+        });
+      },
+    },
+  });
+
+  // Bypass the actual prompt, but the prompt result is to allow access.
+  await SpecialPowers.pushPrefEnv({"set": [["geo.prompt.testing", true], ["geo.prompt.testing.allow", true]]});
+  await extension.startup();
+  await extension.awaitFinish();
+  await extension.unload();
+});
+</script>
+</head>
+<body>
+
+</body>
+</html>
diff --git a/toolkit/components/extensions/test/mochitest/test_ext_identity.html b/toolkit/components/extensions/test/mochitest/test_ext_identity.html
new file mode 100644
index 0000000000..7aa590ec22
--- /dev/null
+++ b/toolkit/components/extensions/test/mochitest/test_ext_identity.html
@@ -0,0 +1,390 @@
+<!DOCTYPE HTML>
+<html>
+<head>
+  <title>Test for WebExtension Identity</title>
+  <script src="/tests/SimpleTest/SimpleTest.js"></script>
+  <script src="/tests/SimpleTest/ExtensionTestUtils.js"></script>
+  <script src="head.js"></script>
+  <link rel="stylesheet" href="/tests/SimpleTest/test.css">
+</head>
+<body>
+
+<script type="text/javascript">
+"use strict";
+
+add_task(async function setup() {
+  await SpecialPowers.pushPrefEnv({
+    set: [
+      ["extensions.webextensions.identity.redirectDomain", "example.com"],
+      // Disable the network cache first-party partition during this
+      // test (TODO: look more closely to how that is affecting the intermittency
+      // of this test on MacOS, see Bug 1626482).
+      ["privacy.partition.network_state", false],
+    ],
+  });
+});
+
+add_task(async function test_noPermission() {
+  let extension = ExtensionTestUtils.loadExtension({
+    background() {
+      browser.test.assertEq(
+        undefined,
+        browser.identity,
+        "No identity api without permission"
+      );
+      browser.test.sendMessage("done");
+    },
+  });
+
+  await extension.startup();
+  await extension.awaitMessage("done");
+  await extension.unload();
+});
+
+add_task(async function test_getRedirectURL() {
+  let extension = ExtensionTestUtils.loadExtension({
+    manifest: {
+      browser_specific_settings: {
+        gecko: {
+          id: "identity@mozilla.org",
+        },
+      },
+      permissions: ["identity", "https://example.com/"],
+    },
+    async background() {
+      let redirect_base =
+        "https://35b64b676900f491c00e7f618d43f7040e88422e.example.com/";
+      await browser.test.assertEq(
+        redirect_base,
+        browser.identity.getRedirectURL(),
+        "redirect url ok"
+      );
+      await browser.test.assertEq(
+        redirect_base,
+        browser.identity.getRedirectURL(""),
+        "redirect url ok"
+      );
+      await browser.test.assertEq(
+        redirect_base + "foobar",
+        browser.identity.getRedirectURL("foobar"),
+        "redirect url ok"
+      );
+      await browser.test.assertEq(
+        redirect_base + "callback",
+        browser.identity.getRedirectURL("/callback"),
+        "redirect url ok"
+      );
+      browser.test.sendMessage("done");
+    },
+  });
+
+  await extension.startup();
+  await extension.awaitMessage("done");
+  await extension.unload();
+});
+
+add_task(async function test_badAuthURI() {
+  let extension = ExtensionTestUtils.loadExtension({
+    manifest: {
+      permissions: ["identity", "https://example.com/"],
+    },
+    async background() {
+      for (let url of [
+        "foobar",
+        "about:addons",
+        "about:blank",
+        "ftp://example.com/test",
+      ]) {
+        await browser.test.assertThrows(
+          () => {
+            browser.identity.launchWebAuthFlow({ interactive: true, url });
+          },
+          /Type error for parameter details/,
+          "details.url is invalid"
+        );
+      }
+
+      browser.test.sendMessage("done");
+    },
+  });
+
+  await extension.startup();
+  await extension.awaitMessage("done");
+  await extension.unload();
+});
+
+add_task(async function test_badRequestURI() {
+  let extension = ExtensionTestUtils.loadExtension({
+    manifest: {
+      permissions: ["identity", "https://example.com/"],
+    },
+    async background() {
+      let base_uri =
+        "https://example.com/tests/toolkit/components/extensions/test/mochitest/";
+      let url = `${base_uri}?redirect_uri=badrobot}`;
+      await browser.test.assertRejects(
+        browser.identity.launchWebAuthFlow({ interactive: true, url }),
+        "redirect_uri is invalid",
+        "invalid redirect url"
+      );
+      url = `${base_uri}?redirect_uri=https://somesite.com`;
+      await browser.test.assertRejects(
+        browser.identity.launchWebAuthFlow({ interactive: true, url }),
+        "redirect_uri not allowed",
+        "invalid redirect url"
+      );
+      browser.test.sendMessage("done");
+    },
+  });
+
+  await extension.startup();
+  await extension.awaitMessage("done");
+  await extension.unload();
+});
+
+add_task(async function background_launchWebAuthFlow_requires_interaction() {
+  let extension = ExtensionTestUtils.loadExtension({
+    manifest: {
+      permissions: ["identity", "https://example.com/"],
+    },
+    async background() {
+      let base_uri =
+        "https://example.com/tests/toolkit/components/extensions/test/mochitest/";
+      let url = `${base_uri}?redirect_uri=${browser.identity.getRedirectURL(
+        "redirect"
+      )}`;
+      await browser.test.assertRejects(
+        browser.identity.launchWebAuthFlow({ interactive: false, url }),
+        "Requires user interaction",
+        "Rejects on required user interaction"
+      );
+      browser.test.sendMessage("done");
+    },
+  });
+
+  await extension.startup();
+  await extension.awaitMessage("done");
+  await extension.unload();
+});
+
+function background_launchWebAuthFlow({
+  interactive = false,
+  path = "redirect_auto.sjs",
+  params = {},
+  redirect = true,
+  useRedirectUri = true,
+} = {}) {
+  let uri_path = useRedirectUri ? "identity_cb" : "";
+  let expected_redirect = `https://35b64b676900f491c00e7f618d43f7040e88422e.example.com/${uri_path}`;
+  let base_uri =
+    "https://example.com/tests/toolkit/components/extensions/test/mochitest/";
+  let redirect_uri = browser.identity.getRedirectURL(
+    useRedirectUri ? uri_path : undefined
+  );
+  browser.test.assertEq(
+    expected_redirect,
+    redirect_uri,
+    "expected redirect uri matches hash"
+  );
+  let url = `${base_uri}${path}`;
+  if (useRedirectUri) {
+    params.redirect_uri = redirect_uri;
+  } else {
+    // We kind of fake it with the redirect url that would normally be configured
+    // in the oauth service.  This does still test that the identity service falls back
+    // to the extensions redirect url.
+    params.default_redirect = expected_redirect;
+  }
+  if (!redirect) {
+    params.no_redirect = 1;
+  }
+  let query = [];
+  for (let [param, value] of Object.entries(params)) {
+    query.push(`${param}=${encodeURIComponent(value)}`);
+  }
+  url = `${url}?${query.join("&")}`;
+
+  // Ensure we do not start the actual request for the redirect url.  In the case
+  // of a 303 POST redirect we are getting a request started.
+  let watchRedirectRequest = () => {};
+  if (params.post !== 303) {
+    watchRedirectRequest = details => {
+      if (details.url.startsWith(expected_redirect)) {
+        browser.test.fail(`onBeforeRequest called for redirect url: ${JSON.stringify(details)}`);
+      }
+    };
+
+    browser.webRequest.onBeforeRequest.addListener(
+      watchRedirectRequest,
+      {
+        urls: [
+          "https://35b64b676900f491c00e7f618d43f7040e88422e.example.com/*",
+        ],
+      }
+    );
+  }
+
+  browser.identity
+    .launchWebAuthFlow({ interactive, url })
+    .then(redirectURL => {
+      browser.test.assertTrue(
+        redirectURL.startsWith(redirect_uri),
+        `correct redirect url ${redirectURL}`
+      );
+      if (redirect) {
+        let url = new URL(redirectURL);
+        browser.test.assertEq(
+          "here ya go",
+          url.searchParams.get("access_token"),
+          "Handled auto redirection"
+        );
+      }
+    })
+    .catch(error => {
+      if (redirect) {
+        browser.test.fail(error.message);
+      } else {
+        browser.test.assertEq(
+          "Requires user interaction",
+          error.message,
+          "Auth page loaded, interaction required."
+        );
+      }
+    }).then(() => {
+      browser.webRequest.onBeforeRequest.removeListener(watchRedirectRequest);
+      browser.test.sendMessage("done");
+    });
+}
+
+// Tests the situation where the oauth provider has already granted access and
+// simply redirects the oauth client to provide the access key or code.
+add_task(async function test_autoRedirect() {
+  let extension = ExtensionTestUtils.loadExtension({
+    manifest: {
+      browser_specific_settings: {
+        gecko: {
+          id: "identity@mozilla.org",
+        },
+      },
+      permissions: ["webRequest", "identity", "https://*.example.com/*"],
+    },
+    background: `(${background_launchWebAuthFlow})()`,
+  });
+
+  await extension.startup();
+  await extension.awaitMessage("done");
+  await extension.unload();
+});
+
+add_task(async function test_autoRedirect_noRedirectURI() {
+  let extension = ExtensionTestUtils.loadExtension({
+    manifest: {
+      browser_specific_settings: {
+        gecko: {
+          id: "identity@mozilla.org",
+        },
+      },
+      permissions: ["webRequest", "identity", "https://*.example.com/*"],
+    },
+    background: `(${background_launchWebAuthFlow})({useRedirectUri: false})`,
+  });
+
+  await extension.startup();
+  await extension.awaitMessage("done");
+  await extension.unload();
+});
+
+// Tests the situation where the oauth provider has not granted access and interactive=false
+add_task(async function test_noRedirect() {
+  let extension = ExtensionTestUtils.loadExtension({
+    manifest: {
+      browser_specific_settings: {
+        gecko: {
+          id: "identity@mozilla.org",
+        },
+      },
+      permissions: ["webRequest", "identity", "https://*.example.com/*"],
+    },
+    background: `(${background_launchWebAuthFlow})({redirect: false})`,
+  });
+
+  await extension.startup();
+  await extension.awaitMessage("done");
+  await extension.unload();
+});
+
+// Tests the situation where the oauth provider must show a window where
+// presumably the user interacts, then the redirect occurs and access key or
+// code is provided.  We bypass any real interaction, but want the window to
+// open and result in a redirect.
+add_task(async function test_interaction() {
+  let extension = ExtensionTestUtils.loadExtension({
+    manifest: {
+      browser_specific_settings: {
+        gecko: {
+          id: "identity@mozilla.org",
+        },
+      },
+      permissions: ["webRequest", "identity", "https://*.example.com/*"],
+    },
+    background: `(${background_launchWebAuthFlow})({interactive: true, path: "oauth.html"})`,
+  });
+
+  await extension.startup();
+  await extension.awaitMessage("done");
+  await extension.unload();
+});
+
+// Tests the situation where the oauth provider redirects with a 303.
+add_task(async function test_auto303Redirect() {
+  let extension = ExtensionTestUtils.loadExtension({
+    manifest: {
+      browser_specific_settings: {
+        gecko: {
+          id: "identity@mozilla.org",
+        },
+      },
+      permissions: ["webRequest", "identity", "https://*.example.com/*"],
+    },
+    background: `(${background_launchWebAuthFlow})({interactive: true, path: "oauth.html", params: {post: 303, server_uri: "redirect_auto.sjs"}})`,
+  });
+
+  await extension.startup();
+  await extension.awaitMessage("done");
+  await extension.unload();
+});
+
+add_task(async function test_loopbackRedirectURI() {
+  let extension = ExtensionTestUtils.loadExtension({
+    manifest: {
+      browser_specific_settings: {
+        gecko: {
+          id: "identity@mozilla.org",
+        },
+      },
+      permissions: ["identity"],
+    },
+    async background() {
+      let redirectURL = "http://127.0.0.1/mozoauth2/35b64b676900f491c00e7f618d43f7040e88422e";
+      let actualRedirect = await browser.identity.launchWebAuthFlow({
+        interactive: true,
+        url: `https://example.com/tests/toolkit/components/extensions/test/mochitest/oauth.html?redirect_uri=${encodeURIComponent(redirectURL)}`
+      }).catch(error => {
+        browser.test.fail(error.message)
+      });
+      browser.test.assertTrue(
+        actualRedirect.startsWith(redirectURL),
+        "Expected redirect url to be loopback address"
+      )
+      browser.test.sendMessage("done");
+    },
+  });
+
+  await extension.startup();
+  await extension.awaitMessage("done");
+  await extension.unload();
+});
+</script>
+
+</body>
+</html>
diff --git a/toolkit/components/extensions/test/mochitest/test_ext_idle.html b/toolkit/components/extensions/test/mochitest/test_ext_idle.html
new file mode 100644
index 0000000000..381687ee38
--- /dev/null
+++ b/toolkit/components/extensions/test/mochitest/test_ext_idle.html
@@ -0,0 +1,68 @@
+<!DOCTYPE HTML>
+<html>
+<head>
+  <title>WebExtension test</title>
+  <script src="/tests/SimpleTest/SimpleTest.js"></script>
+  <script src="/tests/SimpleTest/ExtensionTestUtils.js"></script>
+  <script type="text/javascript" src="head.js"></script>
+  <link rel="stylesheet" href="/tests/SimpleTest/test.css"/>
+</head>
+<body>
+
+<script type="text/javascript">
+"use strict";
+
+add_task(async function testWithRealIdleService() {
+  function background() {
+    browser.test.onMessage.addListener(async (msg, ...args) => {
+      let detectionInterval = args[0];
+      if (msg == "addListener") {
+        let status = await browser.idle.queryState(detectionInterval);
+        browser.test.assertEq("active", status, "Idle status is active");
+        browser.idle.setDetectionInterval(detectionInterval);
+        browser.idle.onStateChanged.addListener(newState => {
+          browser.test.assertEq("idle", newState, "listener fired with the expected state");
+          browser.test.sendMessage("listenerFired");
+        });
+        browser.test.sendMessage("listenerAdded");
+      } else if (msg == "checkState") {
+        let status = await browser.idle.queryState(detectionInterval);
+        browser.test.assertEq("idle", status, "Idle status is idle");
+        browser.test.notifyPass("idle");
+      }
+    });
+  }
+
+  let extension = ExtensionTestUtils.loadExtension({
+    background,
+    manifest: {
+      permissions: ["idle"],
+    },
+  });
+
+  await extension.startup();
+
+  let chromeScript = loadChromeScript(() => {
+    const {sendAsyncMessage} = this;
+    const idleService = Cc["@mozilla.org/widget/useridleservice;1"].getService(Ci.nsIUserIdleService);
+    let idleTime = idleService.idleTime;
+    sendAsyncMessage("detectionInterval", Math.max(Math.ceil(idleTime / 1000) + 10, 15));
+  });
+  let detectionInterval = await chromeScript.promiseOneMessage("detectionInterval");
+  chromeScript.destroy();
+
+  info(`Setting interval to ${detectionInterval}`);
+  extension.sendMessage("addListener", detectionInterval);
+  await extension.awaitMessage("listenerAdded");
+  info("Listener added");
+  await extension.awaitMessage("listenerFired");
+  info("Listener fired");
+  extension.sendMessage("checkState", detectionInterval);
+  await extension.awaitFinish("idle");
+  await extension.unload();
+});
+
+</script>
+
+</body>
+</html>
diff --git a/toolkit/components/extensions/test/mochitest/test_ext_inIncognitoContext_window.html b/toolkit/components/extensions/test/mochitest/test_ext_inIncognitoContext_window.html
new file mode 100644
index 0000000000..5b36902581
--- /dev/null
+++ b/toolkit/components/extensions/test/mochitest/test_ext_inIncognitoContext_window.html
@@ -0,0 +1,49 @@
+<!DOCTYPE HTML>
+<html>
+<head>
+  <title>WebExtension test</title>
+  <script src="/tests/SimpleTest/SimpleTest.js"></script>
+  <script src="/tests/SimpleTest/ExtensionTestUtils.js"></script>
+  <script type="text/javascript" src="head.js"></script>
+  <link rel="stylesheet" type="text/css" href="/tests/SimpleTest/test.css"/>
+</head>
+<body>
+
+<script type="text/javascript">
+"use strict";
+
+add_task(async function test_in_incognito_context_true() {
+  function background() {
+    browser.runtime.onMessage.addListener(msg => {
+      browser.test.assertEq(true, msg, "inIncognitoContext is true");
+      browser.test.notifyPass("inIncognitoContext");
+    });
+
+    browser.windows.create({url: browser.runtime.getURL("/tab.html"), incognito: true});
+  }
+
+  function tabScript() {
+    browser.runtime.sendMessage(browser.extension.inIncognitoContext);
+  }
+
+  let extension = ExtensionTestUtils.loadExtension({
+    background,
+    files: {
+      "tab.js": tabScript,
+      "tab.html": `<!DOCTYPE html><html><head>
+        <meta charset="utf-8">
+        <script src="tab.js"><\/script>
+      </head></html>`,
+    },
+    incognitoOverride: "spanning",
+  });
+
+  await extension.startup();
+  await extension.awaitFinish("inIncognitoContext");
+  await extension.unload();
+});
+
+</script>
+
+</body>
+</html>
diff --git a/toolkit/components/extensions/test/mochitest/test_ext_listener_proxies.html b/toolkit/components/extensions/test/mochitest/test_ext_listener_proxies.html
new file mode 100644
index 0000000000..cc161f735f
--- /dev/null
+++ b/toolkit/components/extensions/test/mochitest/test_ext_listener_proxies.html
@@ -0,0 +1,62 @@
+<!DOCTYPE HTML>
+<html>
+<head>
+  <title>Test for content script</title>
+  <script src="/tests/SimpleTest/SimpleTest.js"></script>
+  <script src="/tests/SimpleTest/ExtensionTestUtils.js"></script>
+  <script type="text/javascript" src="head.js"></script>
+  <link rel="stylesheet" type="text/css" href="/tests/SimpleTest/test.css"/>
+</head>
+<body>
+
+<script type="text/javascript">
+"use strict";
+
+add_task(async function test_listener_proxies() {
+  let extension = ExtensionTestUtils.loadExtension({
+    useAddonManager: "temporary",
+
+    manifest: {
+      "permissions": ["storage"],
+    },
+
+    async background() {
+      // Test that adding multiple listeners for the same event works as
+      // expected.
+
+      let awaitChanged = () => new Promise(resolve => {
+        browser.storage.onChanged.addListener(function listener() {
+          browser.storage.onChanged.removeListener(listener);
+          resolve();
+        });
+      });
+
+      let promises = [
+        awaitChanged(),
+        awaitChanged(),
+      ];
+
+      function removedListener() {}
+      browser.storage.onChanged.addListener(removedListener);
+      browser.storage.onChanged.removeListener(removedListener);
+
+      promises.push(awaitChanged(), awaitChanged());
+
+      browser.storage.local.set({foo: "bar"});
+
+      await Promise.all(promises);
+
+      browser.test.notifyPass("onchanged-listeners");
+    },
+  });
+
+  await extension.startup();
+
+  await extension.awaitFinish("onchanged-listeners");
+
+  await extension.unload();
+});
+</script>
+
+</body>
+</html>
diff --git a/toolkit/components/extensions/test/mochitest/test_ext_new_tab_processType.html b/toolkit/components/extensions/test/mochitest/test_ext_new_tab_processType.html
new file mode 100644
index 0000000000..2c5ae1c0ba
--- /dev/null
+++ b/toolkit/components/extensions/test/mochitest/test_ext_new_tab_processType.html
@@ -0,0 +1,168 @@
+<!DOCTYPE html>
+<html>
+<head>
+  <title>Test for opening links in new tabs from extension frames</title>
+  <script src="/tests/SimpleTest/SimpleTest.js"></script>
+  <script src="/tests/SimpleTest/EventUtils.js"></script>
+  <script src="/tests/SimpleTest/ExtensionTestUtils.js"></script>
+  <link rel="stylesheet" type="text/css" href="/tests/SimpleTest/test.css"/>
+</head>
+<body>
+
+<script type="text/javascript">
+"use strict";
+
+function promiseObserved(topic, check) {
+  return new Promise(resolve => {
+    let obs = SpecialPowers.Services.obs;
+
+    function observer(subject, topic, data) {
+      subject = SpecialPowers.wrap(subject);
+      if (check(subject, data)) {
+        obs.removeObserver(observer, topic);
+        resolve({subject, data});
+      }
+    }
+    obs.addObserver(observer, topic);
+  });
+}
+
+add_task(async function test_target_blank_link_no_opener_from_privileged() {
+  const linkURL = "https://example.com/";
+
+  function extension_tab() {
+    document.getElementById("link").click();
+  }
+
+  function content_script() {
+    browser.runtime.sendMessage("content_page_loaded");
+  }
+
+  let extension = ExtensionTestUtils.loadExtension({
+    manifest: {
+      content_scripts: [{
+        js: ["content_script.js"],
+        matches: ["https://example.com/*"],
+        run_at: "document_idle",
+      }],
+      permissions: ["tabs"],
+    },
+    files: {
+      "page.html": `<!DOCTYPE html>
+        <html>
+          <head><meta charset="utf-8"></html>
+          <body>
+            <a href="${linkURL}" target="_blank" id="link">link</a>
+            <script src="extension_tab.js"><\/script>
+          </body>
+        </html>`,
+      "extension_tab.js": extension_tab,
+      "content_script.js": content_script,
+    },
+    async background() {
+      let pageTab;
+      browser.test.onMessage.addListener(async (msg) => {
+        if (msg !== "close_tab") {
+          browser.test.fail("Unexpected test message: " + msg);
+          return;
+        }
+        if (!pageTab) {
+          browser.test.fail("Unexpected close-tab test message received when there is no pageTab");
+          return;
+        }
+        await browser.tabs.remove(pageTab.id);
+        browser.test.sendMessage("close_tab_done");
+      });
+      browser.runtime.onMessage.addListener(async (msg, sender) => {
+        if (sender.tab) {
+          await browser.tabs.remove(sender.tab.id);
+          browser.test.sendMessage(msg, sender.tab.url);
+        }
+      });
+      pageTab = await browser.tabs.create({ url: browser.runtime.getURL("page.html") });
+      browser.test.sendMessage("tab_created");
+    },
+  });
+
+  await extension.startup();
+
+  await extension.awaitMessage("tab_created");
+
+  // Make sure page is loaded correctly
+  const url = await extension.awaitMessage("content_page_loaded");
+  is(url, linkURL, "Page URL should match");
+
+  // Clean up opened tab.
+  extension.sendMessage("close_tab");
+  await extension.awaitMessage("close_tab_done");
+
+  await extension.unload();
+});
+
+add_task(async function test_target_blank_link() {
+  const linkURL = "http://mochi.test:8888/tests/toolkit/";
+
+  let extension = ExtensionTestUtils.loadExtension({
+    manifest: {
+      content_security_policy: "script-src 'self' 'unsafe-eval'; object-src 'self';",
+
+      web_accessible_resources: ["iframe.html"],
+    },
+    files: {
+      "iframe.html": `<!DOCTYPE html>
+        <html>
+          <head><meta charset="utf-8"></html>
+          <body>
+            <a href="${linkURL}" target="_blank" id="link" rel="opener">link</a>
+          </body>
+        </html>`,
+    },
+    background() {
+      browser.test.sendMessage("frame_url", browser.runtime.getURL("iframe.html"));
+    },
+  });
+
+  await extension.startup();
+
+  let url = await extension.awaitMessage("frame_url");
+
+  let iframe = document.createElement("iframe");
+  iframe.src = url;
+  document.body.appendChild(iframe);
+  await new Promise(resolve => iframe.addEventListener("load", () => setTimeout(resolve, 0), {once: true}));
+
+  let win = SpecialPowers.wrap(iframe).contentWindow;
+
+  {
+    // Flush layout so that synthesizeMouseAtCenter on a cross-origin iframe
+    // works as expected.
+    document.body.getBoundingClientRect();
+
+    let promise = promiseObserved("document-element-inserted", doc => doc.documentURI === linkURL);
+
+    await SpecialPowers.spawn(iframe, [], async () => {
+      this.content.document.getElementById("link").click();
+    });
+
+    let {subject: doc} = await promise;
+    info("Link opened");
+    doc.defaultView.close();
+    info("Window closed");
+  }
+
+  {
+    let promise = promiseObserved("document-element-inserted", doc => doc.documentURI === linkURL);
+
+    let res = win.eval(`window.open("${linkURL}")`);
+    let {subject: doc} = await promise;
+    is(SpecialPowers.unwrap(res), SpecialPowers.unwrap(doc.defaultView), "window.open worked as expected");
+
+    doc.defaultView.close();
+  }
+
+  await extension.unload();
+});
+</script>
+
+</body>
+</html>
diff --git a/toolkit/components/extensions/test/mochitest/test_ext_notifications.html b/toolkit/components/extensions/test/mochitest/test_ext_notifications.html
new file mode 100644
index 0000000000..7a91320373
--- /dev/null
+++ b/toolkit/components/extensions/test/mochitest/test_ext_notifications.html
@@ -0,0 +1,340 @@
+<!DOCTYPE HTML>
+<html>
+<head>
+  <title>Test for notifications</title>
+  <script src="/tests/SimpleTest/SimpleTest.js"></script>
+  <script src="/tests/SimpleTest/ExtensionTestUtils.js"></script>
+  <script type="text/javascript" src="head_notifications.js"></script>
+  <link rel="stylesheet" type="text/css" href="/tests/SimpleTest/test.css"/>
+</head>
+<body>
+
+<script type="text/javascript">
+"use strict";
+
+// A 1x1 PNG image.
+// Source: https://commons.wikimedia.org/wiki/File:1x1.png (Public Domain)
+let image = atob("iVBORw0KGgoAAAANSUhEUgAAAAEAAAABAQMAAAAl21bKAAAAA1BMVEUAA" +
+                 "ACnej3aAAAAAXRSTlMAQObYZgAAAApJREFUCNdjYAAAAAIAAeIhvDMAAAAASUVORK5CYII=");
+const IMAGE_ARRAYBUFFER = Uint8Array.from(image, byte => byte.charCodeAt(0)).buffer;
+
+add_task(async function setup_mock_alert_service() {
+  await MockAlertsService.register();
+});
+
+add_task(async function test_notification() {
+  async function background() {
+    let opts = {
+      type: "basic",
+      title: "Testing Notification",
+      message: "Carry on",
+    };
+
+    let id = await browser.notifications.create(opts);
+
+    browser.test.sendMessage("running", id);
+    browser.test.notifyPass("background test passed");
+  }
+
+  let extension = ExtensionTestUtils.loadExtension({
+    manifest: {
+      permissions: ["notifications"],
+    },
+    background,
+  });
+  await extension.startup();
+  let x = await extension.awaitMessage("running");
+  is(x, "0", "got correct id from notifications.create");
+  await extension.awaitFinish();
+  await extension.unload();
+});
+
+add_task(async function test_notification_events() {
+  async function background() {
+    let opts = {
+      type: "basic",
+      title: "Testing Notification",
+      message: "Carry on",
+    };
+
+    let createdId = "98";
+
+    // Test an ignored listener.
+    browser.notifications.onButtonClicked.addListener(function() {});
+
+    // We cannot test onClicked listener without a mock
+    // but we can attempt to add a listener.
+    browser.notifications.onClicked.addListener(async function(id) {
+      browser.test.assertEq(createdId, id, "onClicked has the expected ID");
+      browser.test.sendMessage("notification-event", "clicked");
+    });
+
+    browser.notifications.onShown.addListener(async function listener(id) {
+      browser.test.assertEq(createdId, id, "onShown has the expected ID");
+      browser.test.sendMessage("notification-event", "shown");
+    });
+
+    browser.test.onMessage.addListener(async function(msg, expectedCount) {
+      if (msg === "create-again") {
+        let newId = await browser.notifications.create(createdId, opts);
+        browser.test.assertEq(createdId, newId, "create returned the expected id.");
+        browser.test.sendMessage("notification-created-twice");
+      } else if (msg === "check-count") {
+        let notifications = await browser.notifications.getAll();
+        let ids = Object.keys(notifications);
+        browser.test.assertEq(expectedCount, ids.length, `getAll() = ${ids}`);
+        browser.test.sendMessage("check-count-result");
+      }
+    });
+
+    // Test onClosed listener.
+    browser.notifications.onClosed.addListener(function listener(id) {
+      browser.test.assertEq(createdId, id, "onClosed received the expected id.");
+      browser.test.sendMessage("notification-event", "closed");
+    });
+
+    await browser.notifications.create(createdId, opts);
+
+    browser.test.sendMessage("notification-created-once");
+  }
+
+  let extension = ExtensionTestUtils.loadExtension({
+    manifest: {
+      permissions: ["notifications"],
+    },
+    background,
+  });
+
+  await extension.startup();
+
+  async function waitForNotificationEvent(name) {
+    info(`Waiting for notification event: ${name}`);
+    is(name, await extension.awaitMessage("notification-event"),
+       "Expected notification event");
+  }
+  async function checkNotificationCount(expectedCount) {
+    extension.sendMessage("check-count", expectedCount);
+    await extension.awaitMessage("check-count-result");
+  }
+
+  await extension.awaitMessage("notification-created-once");
+  await waitForNotificationEvent("shown");
+  await checkNotificationCount(1);
+
+  // On most platforms, clicking the notification closes it.
+  // But on macOS, the notification can repeatedly be clicked without closing.
+  await MockAlertsService.clickNotificationsWithoutClose();
+  await waitForNotificationEvent("clicked");
+  await checkNotificationCount(1);
+  await MockAlertsService.clickNotificationsWithoutClose();
+  await waitForNotificationEvent("clicked");
+  await checkNotificationCount(1);
+  await MockAlertsService.clickNotifications();
+  await waitForNotificationEvent("clicked");
+  await waitForNotificationEvent("closed");
+  await checkNotificationCount(0);
+
+  extension.sendMessage("create-again");
+  await extension.awaitMessage("notification-created-twice");
+  await waitForNotificationEvent("shown");
+  await checkNotificationCount(1);
+
+  await MockAlertsService.closeNotifications();
+  await waitForNotificationEvent("closed");
+  await checkNotificationCount(0);
+
+  await extension.unload();
+});
+
+add_task(async function test_notification_clear() {
+  function background() {
+    let opts = {
+      type: "basic",
+      title: "Testing Notification",
+      message: "Carry on",
+    };
+
+    let createdId = "99";
+
+    browser.notifications.onShown.addListener(async id => {
+      browser.test.assertEq(createdId, id, "onShown received the expected id.");
+      let wasCleared = await browser.notifications.clear(id);
+      browser.test.assertTrue(wasCleared, "notifications.clear returned true.");
+    });
+
+    browser.notifications.onClosed.addListener(id => {
+      browser.test.assertEq(createdId, id, "onClosed received the expected id.");
+      browser.test.notifyPass("background test passed");
+    });
+
+    browser.notifications.create(createdId, opts);
+  }
+
+  let extension = ExtensionTestUtils.loadExtension({
+    manifest: {
+      permissions: ["notifications"],
+    },
+    background,
+  });
+
+  await extension.startup();
+  await extension.awaitFinish();
+  await extension.unload();
+});
+
+add_task(async function test_notifications_empty_getAll() {
+  async function background() {
+    let notifications = await browser.notifications.getAll();
+
+    browser.test.assertEq("object", typeof notifications, "getAll() returned an object");
+    browser.test.assertEq(0, Object.keys(notifications).length, "the object has no properties");
+    browser.test.notifyPass("getAll empty");
+  }
+
+  let extension = ExtensionTestUtils.loadExtension({
+    manifest: {
+      permissions: ["notifications"],
+    },
+    background,
+  });
+  await extension.startup();
+  await extension.awaitFinish("getAll empty");
+  await extension.unload();
+});
+
+add_task(async function test_notifications_populated_getAll() {
+  async function background() {
+    let opts = {
+      type: "basic",
+      iconUrl: "a.png",
+      title: "Testing Notification",
+      message: "Carry on",
+    };
+
+    await browser.notifications.create("p1", opts);
+    await browser.notifications.create("p2", opts);
+    let notifications = await browser.notifications.getAll();
+
+    browser.test.assertEq("object", typeof notifications, "getAll() returned an object");
+    browser.test.assertEq(2, Object.keys(notifications).length, "the object has 2 properties");
+
+    for (let notificationId of ["p1", "p2"]) {
+      for (let key of Object.keys(opts)) {
+        browser.test.assertEq(
+          opts[key],
+          notifications[notificationId][key],
+          `the notification has the expected value for option: ${key}`
+        );
+      }
+    }
+
+    browser.test.notifyPass("getAll populated");
+  }
+
+  let extension = ExtensionTestUtils.loadExtension({
+    manifest: {
+      permissions: ["notifications"],
+    },
+    background,
+    files: {
+      "a.png": IMAGE_ARRAYBUFFER,
+    },
+  });
+  await extension.startup();
+  await extension.awaitFinish("getAll populated");
+  await extension.unload();
+});
+
+add_task(async function test_buttons_unsupported() {
+  function background() {
+    let opts = {
+      type: "basic",
+      title: "Testing Notification",
+      message: "Carry on",
+      buttons: [{title: "Button title"}],
+    };
+
+    let exception = {};
+    try {
+      browser.notifications.create(opts);
+    } catch (e) {
+      exception = e;
+    }
+
+    browser.test.assertTrue(
+      String(exception).includes('Property "buttons" is unsupported by Firefox'),
+      "notifications.create with buttons option threw an expected exception"
+    );
+    browser.test.notifyPass("buttons-unsupported");
+  }
+
+  let extension = ExtensionTestUtils.loadExtension({
+    manifest: {
+      permissions: ["notifications"],
+    },
+    background,
+  });
+  await extension.startup();
+  await extension.awaitFinish("buttons-unsupported");
+  await extension.unload();
+});
+
+add_task(async function test_notifications_different_contexts() {
+  async function background() {
+    let opts = {
+      type: "basic",
+      title: "Testing Notification",
+      message: "Carry on",
+    };
+
+    let id = await browser.notifications.create(opts);
+
+    browser.runtime.onMessage.addListener(async (message, sender) => {
+      await browser.tabs.remove(sender.tab.id);
+
+      // We should be able to clear the notification after creating and
+      // destroying the tab.html page.
+      let wasCleared = await browser.notifications.clear(id);
+      browser.test.assertTrue(wasCleared, "The notification was cleared.");
+      browser.test.notifyPass("notifications");
+    });
+
+    browser.tabs.create({url: browser.runtime.getURL("/tab.html")});
+  }
+
+  async function tabScript() {
+    // We should be able to see the notification created in the background page
+    // in this page.
+    let notifications = await browser.notifications.getAll();
+    browser.test.assertEq(1, Object.keys(notifications).length,
+                          "One notification found.");
+    browser.runtime.sendMessage("continue-test");
+  }
+
+  let extension = ExtensionTestUtils.loadExtension({
+    manifest: {
+      permissions: ["notifications"],
+    },
+    background,
+    files: {
+      "tab.js": tabScript,
+      "tab.html": `<!DOCTYPE html><html><head>
+        <meta charset="utf-8">
+        <script src="tab.js"><\/script>
+      </head></html>`,
+    },
+  });
+
+  await extension.startup();
+  await extension.awaitFinish("notifications");
+  await extension.unload();
+});
+
+add_task(async function teardown_mock_alert_service() {
+  await MockAlertsService.unregister();
+});
+
+</script>
+
+</body>
+</html>
diff --git a/toolkit/components/extensions/test/mochitest/test_ext_optional_permissions.html b/toolkit/components/extensions/test/mochitest/test_ext_optional_permissions.html
new file mode 100644
index 0000000000..659a55f5c9
--- /dev/null
+++ b/toolkit/components/extensions/test/mochitest/test_ext_optional_permissions.html
@@ -0,0 +1,98 @@
+<!DOCTYPE HTML>
+<html>
+<head>
+  <meta charset="utf-8">
+  <title>optional permissions and preloaded processes</title>
+  <script type="text/javascript" src="/tests/SimpleTest/SimpleTest.js"></script>
+  <script type="text/javascript" src="/tests/SimpleTest/ExtensionTestUtils.js"></script>
+  <script type="text/javascript" src="head.js"></script>
+  <link rel="stylesheet" href="/tests/SimpleTest/test.css"/>
+</head>
+<body>
+
+<script type="text/javascript">
+"use strict";
+
+add_task(async function setup() {
+  await SpecialPowers.pushPrefEnv({
+    set: [["extensions.webextOptionalPermissionPrompts", false]],
+  });
+});
+
+// This test case verifies that newly granted optional permissions are
+// propagated to all processes, especially preloaded processes.
+add_task(async function test_optional_permissions_should_be_propagated() {
+  let anOptionalPermission = "*://example.org/*";
+
+  let extension = ExtensionTestUtils.loadExtension({
+    manifest: {
+      permissions: [
+        "scripting",
+        "*://example.com/*",
+      ],
+      optional_permissions: [anOptionalPermission],
+    },
+    async background() {
+      browser.test.onMessage.addListener(async (msg, value) => {
+        browser.test.assertEq("grant-permission", msg, "expected message");
+
+        let granted = await new Promise(resolve => {
+          browser.test.withHandlingUserInput(() => {
+            resolve(browser.permissions.request(value));
+          });
+        });
+        browser.test.assertTrue(granted, "permission request succeeded");
+        browser.test.sendMessage("permission-granted");
+      });
+
+      await browser.scripting.registerContentScripts([
+        {
+          id: "script",
+          js: ["script.js"],
+          matches: ["*://example.com/*", "*://example.org/*"],
+          persistAcrossSessions: false,
+        },
+      ]);
+
+      browser.test.sendMessage("background-ready");
+    },
+    files: {
+      "script.js": () => {
+        browser.test.sendMessage("script-ran", window.location.host);
+      },
+    },
+  });
+
+  await extension.startup();
+  await extension.awaitMessage("background-ready");
+
+  let tab = await AppTestDelegate.openNewForegroundTab(
+    window,
+    "http://example.com/",
+    true
+  );
+  let host = await extension.awaitMessage("script-ran");
+  is(host, "example.com", "expected host: example.com");
+  await AppTestDelegate.removeTab(window, tab);
+
+  extension.sendMessage("grant-permission", {
+    origins: ["*://example.org/*"],
+  });
+  await extension.awaitMessage("permission-granted");
+
+  tab = await AppTestDelegate.openNewForegroundTab(
+    window,
+    "https://example.org/",
+    true
+  );
+  host = await extension.awaitMessage("script-ran");
+  is(host, "example.org", "expected host: example.org");
+  await AppTestDelegate.removeTab(window, tab);
+
+  await extension.unload();
+});
+
+</script>
+
+</body>
+</html>
diff --git a/toolkit/components/extensions/test/mochitest/test_ext_protocolHandlers.html b/toolkit/components/extensions/test/mochitest/test_ext_protocolHandlers.html
new file mode 100644
index 0000000000..41db82eff7
--- /dev/null
+++ b/toolkit/components/extensions/test/mochitest/test_ext_protocolHandlers.html
@@ -0,0 +1,580 @@
+<!DOCTYPE HTML>
+<html>
+<head>
+  <meta charset="utf-8">
+  <title>Test for protocol handlers</title>
+  <script src="/tests/SimpleTest/SimpleTest.js"></script>
+  <script src="/tests/SimpleTest/ExtensionTestUtils.js"></script>
+  <script type="text/javascript" src="head.js"></script>
+  <link rel="stylesheet" type="text/css" href="/tests/SimpleTest/test.css"/>
+</head>
+<body>
+
+<script type="text/javascript">
+"use strict";
+
+/* eslint-disable mozilla/balanced-listeners */
+
+function protocolChromeScript() {
+  const PROTOCOL_HANDLER_OPEN_PERM_KEY = "open-protocol-handler";
+  const PERMISSION_KEY_DELIMITER = "^";
+
+  /* eslint-env mozilla/chrome-script */
+  addMessageListener("setup", ({ protocol, principalOrigins }) => {
+    let data = {};
+    const protoSvc = Cc[
+      "@mozilla.org/uriloader/external-protocol-service;1"
+    ].getService(Ci.nsIExternalProtocolService);
+    let protoInfo = protoSvc.getProtocolHandlerInfo(protocol);
+    data.preferredAction = protoInfo.preferredAction == protoInfo.useHelperApp;
+
+    let handlers = protoInfo.possibleApplicationHandlers;
+    data.handlers = handlers.length;
+
+    let handler = handlers.queryElementAt(0, Ci.nsIHandlerApp);
+    data.isWebHandler = handler instanceof Ci.nsIWebHandlerApp;
+    data.uriTemplate = handler.uriTemplate;
+
+    // ext+ protocols should be set as default when there is only one
+    data.preferredApplicationHandler =
+      protoInfo.preferredApplicationHandler == handler;
+    data.alwaysAskBeforeHandling = protoInfo.alwaysAskBeforeHandling;
+    const handlerSvc = Cc[
+      "@mozilla.org/uriloader/handler-service;1"
+    ].getService(Ci.nsIHandlerService);
+    handlerSvc.store(protoInfo);
+
+    for (let origin of principalOrigins) {
+      let principal = Services.scriptSecurityManager.createContentPrincipal(
+        Services.io.newURI(origin),
+        {}
+      );
+      let pbPrincipal = Services.scriptSecurityManager.createContentPrincipal(
+        Services.io.newURI(origin),
+        {
+          privateBrowsingId: 1,
+        }
+      );
+      let permKey =
+        PROTOCOL_HANDLER_OPEN_PERM_KEY + PERMISSION_KEY_DELIMITER + protocol;
+      Services.perms.addFromPrincipal(
+        principal,
+        permKey,
+        Services.perms.ALLOW_ACTION,
+        Services.perms.EXPIRE_NEVER
+      );
+      Services.perms.addFromPrincipal(
+        pbPrincipal,
+        permKey,
+        Services.perms.ALLOW_ACTION,
+        Services.perms.EXPIRE_NEVER
+      );
+    }
+
+    sendAsyncMessage("handlerData", data);
+  });
+  addMessageListener("setPreferredAction", data => {
+    let { protocol, template } = data;
+    const protoSvc = Cc[
+      "@mozilla.org/uriloader/external-protocol-service;1"
+    ].getService(Ci.nsIExternalProtocolService);
+    let protoInfo = protoSvc.getProtocolHandlerInfo(protocol);
+
+    for (let handler of protoInfo.possibleApplicationHandlers.enumerate()) {
+      if (handler.uriTemplate.startsWith(template)) {
+        protoInfo.preferredApplicationHandler = handler;
+        protoInfo.preferredAction = protoInfo.useHelperApp;
+        protoInfo.alwaysAskBeforeHandling = false;
+      }
+    }
+    const handlerSvc = Cc[
+      "@mozilla.org/uriloader/handler-service;1"
+    ].getService(Ci.nsIHandlerService);
+    handlerSvc.store(protoInfo);
+    sendAsyncMessage("set");
+  });
+}
+
+add_task(async function test_protocolHandler() {
+  let extensionData = {
+    manifest: {
+      protocol_handlers: [
+        {
+          protocol: "ext+foo",
+          name: "a foo protocol handler",
+          uriTemplate: "foo.html?val=%s",
+        },
+      ],
+    },
+
+    background() {
+      browser.test.onMessage.addListener(async (msg, arg) => {
+        if (msg == "open") {
+          let tab = await browser.tabs.create({ url: arg });
+          browser.test.sendMessage("opened", tab.id);
+        } else if (msg == "close") {
+          await browser.tabs.remove(arg);
+          browser.test.sendMessage("closed");
+        }
+      });
+      browser.test.sendMessage("test-url", browser.runtime.getURL("foo.html"));
+    },
+
+    files: {
+      "foo.js": function() {
+        browser.test.sendMessage("test-query", location.search);
+        browser.tabs.getCurrent().then(tab => browser.test.sendMessage("test-tab", tab.id));
+      },
+      "foo.html": `<!DOCTYPE html>
+        <html>
+          <head>
+            <meta charset="utf-8">
+            <script src="foo.js"><\/script>
+          </head>
+        </html>`,
+    },
+  };
+
+  let pb_extension = ExtensionTestUtils.loadExtension({
+    background() {
+      browser.test.onMessage.addListener(async (msg, arg) => {
+        if (msg == "open") {
+          let win = await browser.windows.create({ url: arg, incognito: true });
+          browser.test.sendMessage("opened", {
+            windowId: win.id,
+            tabId: win.tabs[0].id,
+          });
+        } else if (msg == "nav") {
+          await browser.tabs.update(arg.tabId, { url: arg.url });
+          browser.test.sendMessage("navigated");
+        } else if (msg == "close") {
+          await browser.windows.remove(arg);
+          browser.test.sendMessage("closed");
+        }
+      });
+    },
+    incognitoOverride: "spanning",
+  });
+  await pb_extension.startup();
+
+  let extension = ExtensionTestUtils.loadExtension(extensionData);
+  await extension.startup();
+  let handlerUrl = await extension.awaitMessage("test-url");
+
+  // Ensure that the protocol handler is configured, and set it as default to
+  // bypass the dialog.
+  let chromeScript = SpecialPowers.loadChromeScript(protocolChromeScript);
+
+  let msg = chromeScript.promiseOneMessage("handlerData");
+  chromeScript.sendAsyncMessage("setup", {
+    protocol: "ext+foo",
+    principalOrigins: [
+      `moz-extension://${extension.uuid}/`,
+      `moz-extension://${pb_extension.uuid}/`,
+    ],
+  });
+  let data = await msg;
+  ok(
+    data.preferredAction,
+    "using a helper application is the preferred action"
+  );
+  ok(data.preferredApplicationHandler, "handler was set as default handler");
+  is(data.handlers, 1, "one handler is set");
+  ok(!data.alwaysAskBeforeHandling, "will not show dialog");
+  ok(data.isWebHandler, "the handler is a web handler");
+  is(data.uriTemplate, `${handlerUrl}?val=%s`, "correct url template");
+  chromeScript.destroy();
+
+  extension.sendMessage("open", "ext+foo:test");
+  let id = await extension.awaitMessage("opened");
+
+  let query = await extension.awaitMessage("test-query");
+  is(query, "?val=ext%2Bfoo%3Atest", "test query ok");
+  is(id, await extension.awaitMessage("test-tab"), "id should match opened tab");
+
+  extension.sendMessage("close", id);
+  await extension.awaitMessage("closed");
+
+  // Test that handling a URL from the commandline works.
+  chromeScript = SpecialPowers.loadChromeScript(() => {
+    /* eslint-env mozilla/chrome-script */
+    let cmdLineHandler = Cc["@mozilla.org/browser/final-clh;1"].getService(
+      Ci.nsICommandLineHandler
+    );
+    let fakeCmdLine = Cu.createCommandLine(
+      ["-url", "ext+foo:cmdline"],
+      null,
+      Ci.nsICommandLine.STATE_REMOTE_EXPLICIT
+    );
+    cmdLineHandler.handle(fakeCmdLine);
+  });
+  query = await extension.awaitMessage("test-query");
+  is(query, "?val=ext%2Bfoo%3Acmdline", "cmdline query ok");
+  id = await extension.awaitMessage("test-tab");
+  extension.sendMessage("close", id);
+  await extension.awaitMessage("closed");
+  chromeScript.destroy();
+
+  // Test the protocol in a private window, watch for the
+  // console error.
+  consoleMonitor.start([{ message: /NS_ERROR_FILE_NOT_FOUND/ }]);
+
+  // Expect the chooser window to be open, close it.
+  chromeScript = SpecialPowers.loadChromeScript(async () => {
+    /* eslint-env mozilla/chrome-script */
+    const CONTENT_HANDLING_URL =
+      "chrome://mozapps/content/handling/appChooser.xhtml";
+    const { BrowserTestUtils } = ChromeUtils.import(
+      "resource://testing-common/BrowserTestUtils.jsm"
+    );
+
+    let windowOpen = BrowserTestUtils.domWindowOpenedAndLoaded();
+
+    sendAsyncMessage("listenWindow");
+
+    let window = await windowOpen;
+    let gBrowser = window.gBrowser;
+    let tabDialogBox = gBrowser.getTabDialogBox(gBrowser.selectedBrowser);
+    let dialogStack = tabDialogBox.getTabDialogManager()._dialogStack;
+
+    let checkFn = dialogEvent =>
+      dialogEvent.detail.dialog?._openedURL == CONTENT_HANDLING_URL;
+
+    let eventPromise = BrowserTestUtils.waitForEvent(
+      dialogStack,
+      "dialogopen",
+      true,
+      checkFn
+    );
+
+    sendAsyncMessage("listenDialog");
+
+    let event = await eventPromise;
+
+    let { dialog } = event.detail;
+
+    let entry = dialog._frame.contentDocument.getElementById("items")
+      .firstChild;
+    sendAsyncMessage("handling", {
+      name: entry.getAttribute("name"),
+      disabled: entry.disabled,
+    });
+
+    dialog.close();
+  });
+
+  // Wait for the chrome script to attach window listener
+  await chromeScript.promiseOneMessage("listenWindow");
+
+  let listenDialog = chromeScript.promiseOneMessage("listenDialog");
+  let windowOpen = pb_extension.awaitMessage("opened");
+
+  pb_extension.sendMessage("open", "ext+foo:test");
+
+  // Wait for chrome script to attach dialog listener
+  await listenDialog;
+  let { tabId, windowId } = await windowOpen;
+
+  let testData = chromeScript.promiseOneMessage("handling");
+  let navPromise = pb_extension.awaitMessage("navigated");
+  pb_extension.sendMessage("nav", { url: "ext+foo:test", tabId });
+  await navPromise;
+  await consoleMonitor.finished();
+  let entry = await testData;
+
+  is(entry.name, "a foo protocol handler", "entry is correct");
+  ok(entry.disabled, "handler is disabled");
+
+  let promiseClosed = pb_extension.awaitMessage("closed");
+  pb_extension.sendMessage("close", windowId);
+  await promiseClosed;
+  await pb_extension.unload();
+
+  // Shutdown the addon, then ensure the protocol was removed.
+  await extension.unload();
+  chromeScript = SpecialPowers.loadChromeScript(() => {
+    /* eslint-env mozilla/chrome-script */
+    addMessageListener("setup", () => {
+      const protoSvc = Cc[
+        "@mozilla.org/uriloader/external-protocol-service;1"
+      ].getService(Ci.nsIExternalProtocolService);
+      let protoInfo = protoSvc.getProtocolHandlerInfo("ext+foo");
+      sendAsyncMessage(
+        "preferredApplicationHandler",
+        !protoInfo.preferredApplicationHandler
+      );
+      let handlers = protoInfo.possibleApplicationHandlers;
+
+      sendAsyncMessage("handlerData", {
+        preferredApplicationHandler: !protoInfo.preferredApplicationHandler,
+        handlers: handlers.length,
+      });
+    });
+  });
+
+  msg = chromeScript.promiseOneMessage("handlerData");
+  chromeScript.sendAsyncMessage("setup");
+  data = await msg;
+  ok(data.preferredApplicationHandler, "no preferred handler is set");
+  is(data.handlers, 0, "no handler is set");
+  chromeScript.destroy();
+});
+
+add_task(async function test_protocolHandler_two() {
+  let extensionData = {
+    manifest: {
+      protocol_handlers: [
+        {
+          protocol: "ext+foo",
+          name: "a foo protocol handler",
+          uriTemplate: "foo.html?val=%s",
+        },
+        {
+          protocol: "ext+foo",
+          name: "another foo protocol handler",
+          uriTemplate: "foo2.html?val=%s",
+        },
+      ],
+    },
+  };
+
+  let extension = ExtensionTestUtils.loadExtension(extensionData);
+  await extension.startup();
+
+  // Ensure that the protocol handler is configured, and set it as default,
+  // but because there are two handlers, the dialog is not bypassed.  We
+  // don't test the actual dialog ui, it's been here forever and works based
+  // on the alwaysAskBeforeHandling value.
+  let chromeScript = SpecialPowers.loadChromeScript(protocolChromeScript);
+
+  let msg = chromeScript.promiseOneMessage("handlerData");
+  chromeScript.sendAsyncMessage("setup", {
+    protocol: "ext+foo",
+    principalOrigins: [],
+  });
+  let data = await msg;
+  ok(
+    data.preferredAction,
+    "using a helper application is the preferred action"
+  );
+  ok(data.preferredApplicationHandler, "preferred handler is set");
+  is(data.handlers, 2, "two handlers are set");
+  ok(data.alwaysAskBeforeHandling, "will show dialog");
+  ok(data.isWebHandler, "the handler is a web handler");
+  chromeScript.destroy();
+  await extension.unload();
+});
+
+add_task(async function test_protocolHandler_https_target() {
+  let extensionData = {
+    manifest: {
+      protocol_handlers: [
+        {
+          protocol: "ext+foo",
+          name: "http target",
+          uriTemplate: "https://example.com/foo.html?val=%s",
+        },
+      ],
+    },
+  };
+
+  let extension = ExtensionTestUtils.loadExtension(extensionData);
+  await extension.startup();
+  ok(true, "https uriTemplate target works");
+  await extension.unload();
+});
+
+add_task(async function test_protocolHandler_http_target() {
+  let extensionData = {
+    manifest: {
+      protocol_handlers: [
+        {
+          protocol: "ext+foo",
+          name: "http target",
+          uriTemplate: "http://example.com/foo.html?val=%s",
+        },
+      ],
+    },
+  };
+
+  let extension = ExtensionTestUtils.loadExtension(extensionData);
+  await extension.startup();
+  ok(true, "http uriTemplate target works");
+  await extension.unload();
+});
+
+add_task(async function test_protocolHandler_restricted_protocol() {
+  let extensionData = {
+    manifest: {
+      protocol_handlers: [
+        {
+          protocol: "http",
+          name: "take over the http protocol",
+          uriTemplate: "http.html?val=%s",
+        },
+      ],
+    },
+  };
+
+  consoleMonitor.start([
+    { message: /processing protocol_handlers\.0\.protocol/ },
+  ]);
+
+  let extension = ExtensionTestUtils.loadExtension(extensionData);
+  await Assert.rejects(
+    extension.startup(),
+    /startup failed/,
+    "unable to register restricted handler protocol"
+  );
+
+  await consoleMonitor.finished();
+});
+
+add_task(async function test_protocolHandler_restricted_uriTemplate() {
+  let extensionData = {
+    manifest: {
+      protocol_handlers: [
+        {
+          protocol: "ext+foo",
+          name: "take over the http protocol",
+          uriTemplate: "ftp://example.com/file.txt",
+        },
+      ],
+    },
+  };
+
+  consoleMonitor.start([
+    { message: /processing protocol_handlers\.0\.uriTemplate/ },
+  ]);
+
+  let extension = ExtensionTestUtils.loadExtension(extensionData);
+  await Assert.rejects(
+    extension.startup(),
+    /startup failed/,
+    "unable to register restricted handler uriTemplate"
+  );
+
+  await consoleMonitor.finished();
+});
+
+add_task(async function test_protocolHandler_duplicate() {
+  let extensionData = {
+    manifest: {
+      protocol_handlers: [
+        {
+          protocol: "ext+foo",
+          name: "foo protocol",
+          uriTemplate: "foo.html?val=%s",
+        },
+        {
+          protocol: "ext+foo",
+          name: "foo protocol",
+          uriTemplate: "foo.html?val=%s",
+        },
+      ],
+    },
+  };
+
+  let extension = ExtensionTestUtils.loadExtension(extensionData);
+  await extension.startup();
+
+  // Get the count of handlers installed.
+  let chromeScript = SpecialPowers.loadChromeScript(() => {
+    /* eslint-env mozilla/chrome-script */
+    addMessageListener("setup", () => {
+      const protoSvc = Cc[
+        "@mozilla.org/uriloader/external-protocol-service;1"
+      ].getService(Ci.nsIExternalProtocolService);
+      let protoInfo = protoSvc.getProtocolHandlerInfo("ext+foo");
+      let handlers = protoInfo.possibleApplicationHandlers;
+      sendAsyncMessage("handlerData", handlers.length);
+    });
+  });
+
+  let msg = chromeScript.promiseOneMessage("handlerData");
+  chromeScript.sendAsyncMessage("setup");
+  let data = await msg;
+  is(data, 1, "cannot re-register the same handler config");
+  chromeScript.destroy();
+  await extension.unload();
+});
+
+// Test that a protocol handler will work if ftp is enabled
+add_task(async function test_ftp_protocolHandler() {
+  await SpecialPowers.pushPrefEnv({
+    set: [
+      // Disabling the external protocol permission prompt. We don't need it
+      // for this test.
+      ["security.external_protocol_requires_permission", false],
+    ],
+  });
+  let extensionData = {
+    manifest: {
+      protocol_handlers: [
+        {
+          protocol: "ftp",
+          name: "an ftp protocol handler",
+          uriTemplate: "ftp.html?val=%s",
+        },
+      ],
+    },
+
+    async background() {
+      let url = "ftp://example.com/file.txt";
+      browser.test.onMessage.addListener(async () => {
+        await browser.tabs.create({ url });
+      });
+    },
+
+    files: {
+      "ftp.js": function() {
+        browser.test.sendMessage("test-query", location.search);
+      },
+      "ftp.html": `<!DOCTYPE html>
+        <html>
+          <head>
+            <meta charset="utf-8">
+            <script src="ftp.js"><\/script>
+          </head>
+        </html>`,
+    },
+  };
+  let extension = ExtensionTestUtils.loadExtension(extensionData);
+  await extension.startup();
+  const handlerUrl = `moz-extension://${extension.uuid}/ftp.html`;
+
+  let chromeScript = SpecialPowers.loadChromeScript(protocolChromeScript);
+
+  // Set the preferredAction to this extension as ftp will default to system.  If
+  // we didn't bypass the dialog for this test, the user would get asked in this case.
+  let msg = chromeScript.promiseOneMessage("set");
+  chromeScript.sendAsyncMessage("setPreferredAction", {
+    protocol: "ftp",
+    template: handlerUrl,
+  });
+  await msg;
+
+  msg = chromeScript.promiseOneMessage("handlerData");
+  chromeScript.sendAsyncMessage("setup", { protocol: "ftp", principalOrigins: [] });
+  let data = await msg;
+  ok(
+    data.preferredAction,
+    "using a helper application is the preferred action"
+  );
+  ok(data.preferredApplicationHandler, "handler was set as default handler");
+  is(data.handlers, 1, "one handler is set");
+  ok(!data.alwaysAskBeforeHandling, "will not show dialog");
+  ok(data.isWebHandler, "the handler is a web handler");
+  is(data.uriTemplate, `${handlerUrl}?val=%s`, "correct url template");
+
+  chromeScript.destroy();
+
+  extension.sendMessage("run");
+  let query = await extension.awaitMessage("test-query");
+  is(query, "?val=ftp%3A%2F%2Fexample.com%2Ffile.txt", "test query ok");
+  await extension.unload();
+});
+</script>
+
+</body>
+</html>
diff --git a/toolkit/components/extensions/test/mochitest/test_ext_redirect_jar.html b/toolkit/components/extensions/test/mochitest/test_ext_redirect_jar.html
new file mode 100644
index 0000000000..18ff14a6de
--- /dev/null
+++ b/toolkit/components/extensions/test/mochitest/test_ext_redirect_jar.html
@@ -0,0 +1,92 @@
+<!DOCTYPE HTML>
+
+<html>
+<head>
+<meta charset="utf-8">
+  <script src="/tests/SimpleTest/SimpleTest.js"></script>
+  <script src="/tests/SimpleTest/ExtensionTestUtils.js"></script>
+  <script type="text/javascript" src="head.js"></script>
+  <link rel="stylesheet" type="text/css" href="/tests/SimpleTest/test.css"/>
+</head>
+<body>
+
+<script>
+"use strict";
+
+function getExtension() {
+  return ExtensionTestUtils.loadExtension({
+    manifest: {
+      "browser_specific_settings": {
+        "gecko": {
+          "id": "redirect-to-jar@mochi.test",
+        },
+      },
+      "permissions": [
+        "webRequest",
+        "webRequestBlocking",
+        "<all_urls>",
+      ],
+      "web_accessible_resources": [
+        "finished.html",
+      ],
+    },
+    useAddonManager: "temporary",
+    files: {
+      "finished.html": `
+        <!DOCTYPE html>
+        <html>
+          <head>
+            <meta charset="utf-8">
+          </head>
+          <body>
+            <h1>redirected!</h1>
+          </body>
+        </html>
+      `,
+    },
+    background: async () => {
+      let redirectUrl = browser.runtime.getURL("finished.html");
+      browser.webRequest.onBeforeRequest.addListener(details => {
+        return {redirectUrl};
+      }, {urls: ["*://*/intercept*"]}, ["blocking"]);
+
+      let code = `new Promise(resolve => {
+            var s = document.createElement('iframe');
+            s.src = "/intercept?r=" + Math.random();
+            s.onload = async () => {
+                let url = await window.wrappedJSObject.SpecialPowers.spawn(s, [], () => content.location.href );
+              resolve(['loaded', url]);
+            }
+            s.onerror = () => resolve(['error']);
+            document.documentElement.appendChild(s);
+          });`;
+
+      async function testSubFrameResource(tabId, code) {
+        let [result] = await browser.tabs.executeScript(tabId, { code });
+        return result;
+      }
+
+      let tab = await browser.tabs.create({url: "http://mochi.test:8888/tests/toolkit/components/extensions/test/mochitest/file_sample.html"});
+      let result = await testSubFrameResource(tab.id, code);
+      browser.test.assertEq("loaded", result[0], "frame 1 loaded");
+      browser.test.assertEq(redirectUrl, result[1], "frame 1 redirected");
+      // If jar caching breaks redirects, this next test will fail (See Bug 1390346).
+      result = await testSubFrameResource(tab.id, code);
+      browser.test.assertEq("loaded", result[0], "frame 2 loaded");
+      browser.test.assertEq(redirectUrl, result[1], "frame 2 redirected");
+      await browser.tabs.remove(tab.id);
+      browser.test.sendMessage("requestsCompleted");
+    },
+  });
+}
+
+add_task(async function test_redirect_to_jar() {
+  let extension = getExtension();
+  await extension.startup();
+  await extension.awaitMessage("requestsCompleted");
+  await extension.unload();
+});
+
+</script>
+</body>
+</html>
diff --git a/toolkit/components/extensions/test/mochitest/test_ext_request_urlClassification.html b/toolkit/components/extensions/test/mochitest/test_ext_request_urlClassification.html
new file mode 100644
index 0000000000..a5c7024a83
--- /dev/null
+++ b/toolkit/components/extensions/test/mochitest/test_ext_request_urlClassification.html
@@ -0,0 +1,130 @@
+<!DOCTYPE HTML>
+<html>
+<head>
+  <title>Test for WebRequest urlClassification</title>
+  <script src="/tests/SimpleTest/SimpleTest.js"></script>
+  <script src="/tests/SimpleTest/ExtensionTestUtils.js"></script>
+  <script type="text/javascript" src="head.js"></script>
+  <link rel="stylesheet" type="text/css" href="/tests/SimpleTest/test.css"/>
+</head>
+<body>
+
+<script type="text/javascript">
+"use strict";
+
+add_task(async function setup() {
+  await SpecialPowers.pushPrefEnv({
+    set: [["privacy.trackingprotection.enabled", true]],
+  });
+
+  let chromeScript = SpecialPowers.loadChromeScript(async _ => {
+    /* eslint-env mozilla/chrome-script */
+    const {UrlClassifierTestUtils} = ChromeUtils.import("resource://testing-common/UrlClassifierTestUtils.jsm");
+    await UrlClassifierTestUtils.addTestTrackers();
+    sendAsyncMessage("trackersLoaded");
+  });
+  await chromeScript.promiseOneMessage("trackersLoaded");
+  chromeScript.destroy();
+});
+
+add_task(async function test_urlClassification() {
+  await SpecialPowers.pushPrefEnv({
+    set: [["dom.security.https_first", false]],
+  });
+  let extension = ExtensionTestUtils.loadExtension({
+    manifest: {
+      permissions: ["webRequest", "webRequestBlocking", "proxy", "<all_urls>"],
+    },
+    background() {
+      let expected = {
+        "http://tracking.example.org/": {first: "tracking", thirdParty: false, },
+        "http://mochi.test:8888/tests/toolkit/components/extensions/test/mochitest/file_third_party.html?domain=tracking.example.org": { thirdParty: false, },
+        "http://tracking.example.org/tests/toolkit/components/extensions/test/mochitest/file_image_bad.png": {third: "tracking", thirdParty: true, },
+        "http://mochi.test:8888/tests/toolkit/components/extensions/test/mochitest/file_third_party.html?domain=example.net": { thirdParty: false, },
+        "http://example.net/tests/toolkit/components/extensions/test/mochitest/file_image_bad.png": { thirdParty: true, },
+      };
+      function testRequest(details) {
+        let expect = expected[details.url];
+        if (expect) {
+          if (expect.first) {
+            browser.test.assertTrue(details.urlClassification.firstParty.includes("tracking"), "tracking firstParty");
+          } else {
+            browser.test.assertEq(details.urlClassification.firstParty.length, 0, "not tracking firstParty");
+          }
+          if (expect.third) {
+            browser.test.assertTrue(details.urlClassification.thirdParty.includes("tracking"), "tracking thirdParty");
+          } else {
+            browser.test.assertEq(details.urlClassification.thirdParty.length, 0, "not tracking thirdParty");
+          }
+
+          browser.test.assertEq(details.thirdParty, expect.thirdParty, "3rd party flag matches");
+          return true;
+        }
+        return false;
+      }
+
+      browser.proxy.onRequest.addListener(details => {
+        browser.test.log(`proxy.onRequest ${JSON.stringify(details)}`);
+        testRequest(details);
+      }, {urls: ["http://mochi.test/tests/*", "http://tracking.example.org/*", "http://example.net/*"]});
+      browser.webRequest.onBeforeRequest.addListener(async (details) => {
+        browser.test.log(`webRequest.onBeforeRequest ${JSON.stringify(details)}`);
+        testRequest(details);
+      }, {urls: ["http://mochi.test/tests/*", "http://tracking.example.org/*", "http://example.net/*"]}, ["blocking"]);
+      browser.webRequest.onCompleted.addListener(async (details) => {
+        browser.test.log(`webRequest.onCompleted ${JSON.stringify(details)}`);
+        if (testRequest(details)) {
+          browser.test.sendMessage("classification", details.url);
+        }
+      }, {urls: ["http://mochi.test/tests/*", "http://tracking.example.org/*", "http://example.net/*"]});
+    },
+  });
+  await extension.startup();
+
+  // Test first party tracking classification.
+  let url = "http://tracking.example.org/";
+  let win = window.open(url);
+  is(await extension.awaitMessage("classification"), url, "request completed");
+  win.close();
+
+  // Test third party tracking classification, expecting two results.
+  url = "http://mochi.test:8888/tests/toolkit/components/extensions/test/mochitest/file_third_party.html?domain=tracking.example.org";
+  win = window.open(url);
+  is(await extension.awaitMessage("classification"), url);
+  is(await extension.awaitMessage("classification"),
+     "http://tracking.example.org/tests/toolkit/components/extensions/test/mochitest/file_image_bad.png",
+     "request completed");
+  win.close();
+
+  // Test third party tracking classification, expecting two results.
+  url = "http://mochi.test:8888/tests/toolkit/components/extensions/test/mochitest/file_third_party.html?domain=example.net";
+  win = window.open(url);
+  is(await extension.awaitMessage("classification"), url);
+  is(await extension.awaitMessage("classification"),
+     "http://example.net/tests/toolkit/components/extensions/test/mochitest/file_image_bad.png",
+     "request completed");
+  win.close();
+
+  await extension.unload();
+});
+
+add_task(async function teardown() {
+  let chromeScript = SpecialPowers.loadChromeScript(async _ => {
+    /* eslint-env mozilla/chrome-script */
+    // Cleanup cache
+    await new Promise(resolve => {
+      Services.clearData.deleteData(Ci.nsIClearDataService.CLEAR_ALL, value => resolve());
+    });
+
+    const {UrlClassifierTestUtils} = ChromeUtils.import("resource://testing-common/UrlClassifierTestUtils.jsm");
+    await UrlClassifierTestUtils.cleanupTestTrackers();
+    sendAsyncMessage("trackersUnloaded");
+  });
+  await chromeScript.promiseOneMessage("trackersUnloaded");
+  chromeScript.destroy();
+});
+
+</script>
+
+</body>
+</html>
diff --git a/toolkit/components/extensions/test/mochitest/test_ext_runtime_connect.html b/toolkit/components/extensions/test/mochitest/test_ext_runtime_connect.html
new file mode 100644
index 0000000000..85f98d5034
--- /dev/null
+++ b/toolkit/components/extensions/test/mochitest/test_ext_runtime_connect.html
@@ -0,0 +1,83 @@
+<!DOCTYPE HTML>
+<html>
+<head>
+  <title>WebExtension test</title>
+  <script src="/tests/SimpleTest/SimpleTest.js"></script>
+  <script src="/tests/SimpleTest/ExtensionTestUtils.js"></script>
+  <script type="text/javascript" src="head.js"></script>
+  <link rel="stylesheet" type="text/css" href="/tests/SimpleTest/test.css"/>
+</head>
+<body>
+
+<script type="text/javascript">
+"use strict";
+
+function background() {
+  browser.runtime.onConnect.addListener(port => {
+    browser.test.assertEq(port.name, "ernie", "port name correct");
+    browser.test.assertTrue(port.sender.url.endsWith("file_sample.html"), "URL correct");
+    browser.test.assertTrue(port.sender.tab.url.endsWith("file_sample.html"), "tab URL correct");
+    browser.test.assertEq(port.sender.frameId, 0, "frameId of top frame");
+
+    let expected = "message 1";
+    port.onMessage.addListener(msg => {
+      browser.test.assertEq(msg, expected, "message is expected");
+      if (expected == "message 1") {
+        port.postMessage("message 2");
+        expected = "message 3";
+      } else if (expected == "message 3") {
+        expected = "disconnect";
+        browser.test.notifyPass("runtime.connect");
+      }
+    });
+    port.onDisconnect.addListener(() => {
+      browser.test.assertEq(null, port.error, "No error because port is closed by disconnect() at other end");
+      browser.test.assertEq(expected, "disconnect", "got disconnection at right time");
+    });
+  });
+}
+
+function contentScript() {
+  let port = browser.runtime.connect({name: "ernie"});
+  port.postMessage("message 1");
+  port.onMessage.addListener(msg => {
+    if (msg == "message 2") {
+      port.postMessage("message 3");
+      port.disconnect();
+    }
+  });
+}
+
+let extensionData = {
+  background,
+  manifest: {
+    "permissions": ["tabs"],
+    "content_scripts": [{
+      "matches": ["http://mochi.test/*/file_sample.html"],
+      "js": ["content_script.js"],
+      "run_at": "document_start",
+    }],
+  },
+
+  files: {
+    "content_script.js": contentScript,
+  },
+};
+
+add_task(async function test_contentscript() {
+  let extension = ExtensionTestUtils.loadExtension(extensionData);
+  await extension.startup();
+
+  let win = window.open("file_sample.html");
+
+  await Promise.all([waitForLoad(win), extension.awaitFinish("runtime.connect")]);
+
+  win.close();
+
+  await extension.unload();
+  info("extension unloaded");
+});
+</script>
+
+</body>
+</html>
diff --git a/toolkit/components/extensions/test/mochitest/test_ext_runtime_connect2.html b/toolkit/components/extensions/test/mochitest/test_ext_runtime_connect2.html
new file mode 100644
index 0000000000..13b9029c48
--- /dev/null
+++ b/toolkit/components/extensions/test/mochitest/test_ext_runtime_connect2.html
@@ -0,0 +1,102 @@
+<!DOCTYPE HTML>
+<html>
+<head>
+  <title>WebExtension test</title>
+  <script src="/tests/SimpleTest/SimpleTest.js"></script>
+  <script src="/tests/SimpleTest/ExtensionTestUtils.js"></script>
+  <script type="text/javascript" src="head.js"></script>
+  <link rel="stylesheet" type="text/css" href="/tests/SimpleTest/test.css"/>
+</head>
+<body>
+
+<script type="text/javascript">
+"use strict";
+
+function backgroundScript(token) {
+  browser.runtime.onMessage.addListener(msg => {
+    browser.test.assertEq(msg, "done");
+    browser.test.notifyPass("sendmessage_reply");
+  });
+
+  browser.runtime.onConnect.addListener(port => {
+    browser.test.assertTrue(port.sender.url.endsWith("file_sample.html"), "sender url correct");
+    browser.test.assertTrue(port.sender.tab.url.endsWith("file_sample.html"), "sender url correct");
+
+    let tabId = port.sender.tab.id;
+    browser.tabs.connect(tabId, {name: token});
+
+    browser.test.assertEq(port.name, token, "token matches");
+    port.postMessage(token + "-done");
+  });
+
+  browser.test.sendMessage("background-ready");
+}
+
+function contentScript(token) {
+  let gotTabMessage = false;
+  let badTabMessage = false;
+  browser.runtime.onConnect.addListener(port => {
+    if (port.name == token) {
+      gotTabMessage = true;
+    } else {
+      badTabMessage = true;
+    }
+    port.disconnect();
+  });
+
+  let port = browser.runtime.connect(null, {name: token});
+  port.onMessage.addListener(function(msg) {
+    if (msg != token + "-done" || !gotTabMessage || badTabMessage) {
+      return; // test failed
+    }
+
+    // FIXME: Removing this line causes the test to fail:
+    // resource://gre/modules/ExtensionUtils.jsm, line 651: NS_ERROR_NOT_INITIALIZED
+    port.disconnect();
+    browser.runtime.sendMessage("done");
+  });
+}
+
+function makeExtension() {
+  let token = Math.random();
+  let extensionData = {
+    background: `(${backgroundScript})("${token}")`,
+    manifest: {
+      "permissions": ["tabs"],
+      "content_scripts": [{
+        "matches": ["http://mochi.test/*/file_sample.html"],
+        "js": ["content_script.js"],
+        "run_at": "document_idle",
+      }],
+    },
+
+    files: {
+      "content_script.js": `(${contentScript})("${token}")`,
+    },
+  };
+  return extensionData;
+}
+
+add_task(async function test_contentscript() {
+  let extension1 = ExtensionTestUtils.loadExtension(makeExtension());
+  let extension2 = ExtensionTestUtils.loadExtension(makeExtension());
+  await Promise.all([extension1.startup(), extension2.startup()]);
+
+  await extension1.awaitMessage("background-ready");
+  await extension2.awaitMessage("background-ready");
+
+  let win = window.open("file_sample.html");
+
+  await Promise.all([waitForLoad(win),
+                     extension1.awaitFinish("sendmessage_reply"),
+                     extension2.awaitFinish("sendmessage_reply")]);
+
+  win.close();
+
+  await extension1.unload();
+  await extension2.unload();
+});
+</script>
+
+</body>
+</html>
diff --git a/toolkit/components/extensions/test/mochitest/test_ext_runtime_connect_iframe.html b/toolkit/components/extensions/test/mochitest/test_ext_runtime_connect_iframe.html
new file mode 100644
index 0000000000..9c64635063
--- /dev/null
+++ b/toolkit/components/extensions/test/mochitest/test_ext_runtime_connect_iframe.html
@@ -0,0 +1,136 @@
+<!DOCTYPE HTML>
+<html>
+<head>
+  <title>WebExtension test</title>
+  <script src="/tests/SimpleTest/SimpleTest.js"></script>
+  <script src="/tests/SimpleTest/ExtensionTestUtils.js"></script>
+  <script type="text/javascript" src="head.js"></script>
+  <link rel="stylesheet" type="text/css" href="/tests/SimpleTest/test.css"/>
+</head>
+<body>
+
+<script type="text/javascript">
+"use strict";
+
+// The purpose of this test is to verify that the port.sender properties are
+// not set for messages from iframes in background scripts. This is the toolkit
+// version of the browser_ext_contentscript_nontab_connect.js test, and exists
+// to provide test coverage for non-toolkit builds (e.g. Android).
+//
+// This used to be a xpcshell test (from bug 1488105), but became a mochitest
+// because port.sender.tab and port.sender.frameId do not represent the real
+// values in xpcshell tests.
+// Specifically, ProxyMessenger.prototype.getSender uses the tabTracker, which
+// expects real tabs instead of browsers from the ContentPage API in xpcshell
+// tests.
+add_task(async function connect_from_background_frame() {
+  if (!SpecialPowers.getBoolPref("extensions.webextensions.remote", true)) {
+    info("Cannot load remote content in parent process; skipping test task");
+    return;
+  }
+  async function background() {
+    const FRAME_URL = "https://example.com/tests/toolkit/components/extensions/test/mochitest/file_sample.html";
+    browser.runtime.onConnect.addListener(port => {
+      // The next two assertions are the reason for this being a mochitest
+      // instead of a xpcshell test.
+      browser.test.assertEq(port.sender.tab, undefined, "Sender is not a tab");
+      browser.test.assertEq(port.sender.frameId, undefined, "frameId unset");
+      browser.test.assertEq(port.sender.url, FRAME_URL, "Expected sender URL");
+      port.onMessage.addListener(msg => {
+        browser.test.assertEq("pong", msg, "Reply from content script");
+        port.disconnect();
+      });
+      port.postMessage("ping");
+    });
+
+    await browser.contentScripts.register({
+      matches: [FRAME_URL],
+      js: [{ file: "contentscript.js" }],
+      allFrames: true,
+    });
+
+    let f = document.createElement("iframe");
+    f.src = FRAME_URL;
+    document.body.appendChild(f);
+  }
+
+  function contentScript() {
+    browser.test.log(`Running content script at ${document.URL}`);
+
+    let port = browser.runtime.connect();
+    port.onMessage.addListener(msg => {
+      browser.test.assertEq("ping", msg, "Expected message to content script");
+      port.postMessage("pong");
+    });
+    port.onDisconnect.addListener(() => {
+      browser.test.sendMessage("disconnected_in_content_script");
+    });
+  }
+
+  let extension = ExtensionTestUtils.loadExtension({
+    manifest: {
+      permissions: ["https://example.com/*"],
+    },
+    files: {
+      "contentscript.js": contentScript,
+    },
+    background,
+  });
+  await extension.startup();
+  await extension.awaitMessage("disconnected_in_content_script");
+  await extension.unload();
+});
+
+// The test_ext_contentscript_fission_frame.html test already checks the
+// behavior of onConnect in cross-origin frames, so here we just limit the test
+// to checking that the port.sender properties are sensible.
+add_task(async function connect_from_content_script_in_frame() {
+  async function background() {
+    const TAB_URL = "https://example.org/tests/toolkit/components/extensions/test/mochitest/file_contains_iframe.html";
+    const FRAME_URL = "https://example.org/tests/toolkit/components/extensions/test/mochitest/file_contains_img.html";
+    let createdTab;
+    browser.runtime.onConnect.addListener(port => {
+      // The next two assertions are the reason for this being a mochitest
+      // instead of a xpcshell test.
+      browser.test.assertEq(port.sender.tab.url, TAB_URL, "Sender is the tab");
+      browser.test.assertTrue(port.sender.frameId > 0, "frameId is set");
+      browser.test.assertEq(port.sender.url, FRAME_URL, "Expected sender URL");
+
+      browser.test.assertEq(createdTab.id, port.sender.tab.id, "Tab to close");
+      browser.tabs.remove(port.sender.tab.id).then(() => {
+        browser.test.sendMessage("tab_port_checked_and_tab_closed");
+      });
+    });
+
+    await browser.contentScripts.register({
+      matches: [FRAME_URL],
+      js: [{ file: "contentscript.js" }],
+      allFrames: true,
+    });
+
+    createdTab = await browser.tabs.create({ url: TAB_URL });
+  }
+
+  function contentScript() {
+    browser.test.log(`Running content script at ${document.URL}`);
+
+    browser.runtime.connect();
+  }
+
+  let extension = ExtensionTestUtils.loadExtension({
+    manifest: {
+      permissions: ["https://example.org/*"],
+    },
+    files: {
+      "contentscript.js": contentScript,
+    },
+    background,
+  });
+  await extension.startup();
+  await extension.awaitMessage("tab_port_checked_and_tab_closed");
+  await extension.unload();
+});
+</script>
+
+</body>
+</html>
diff --git a/toolkit/components/extensions/test/mochitest/test_ext_runtime_connect_twoway.html b/toolkit/components/extensions/test/mochitest/test_ext_runtime_connect_twoway.html
new file mode 100644
index 0000000000..b671cba23d
--- /dev/null
+++ b/toolkit/components/extensions/test/mochitest/test_ext_runtime_connect_twoway.html
@@ -0,0 +1,126 @@
+<!DOCTYPE HTML>
+<html>
+<head>
+  <title>WebExtension test</title>
+  <script src="/tests/SimpleTest/SimpleTest.js"></script>
+  <script src="/tests/SimpleTest/ExtensionTestUtils.js"></script>
+  <script type="text/javascript" src="head.js"></script>
+  <link rel="stylesheet" type="text/css" href="/tests/SimpleTest/test.css">
+</head>
+<body>
+
+<script>
+"use strict";
+
+add_task(async function test_connect_bidirectionally_and_postMessage() {
+  function background() {
+    let onConnectCount = 0;
+    browser.runtime.onConnect.addListener(port => {
+      // 3. onConnect by connect() from CS.
+      browser.test.assertEq("from-cs", port.name);
+      browser.test.assertEq(1, ++onConnectCount,
+                            "BG onConnect should be called once");
+
+      let tabId = port.sender.tab.id;
+      browser.test.assertTrue(tabId, "content script must have a tab ID");
+
+      let port2;
+      let postMessageCount1 = 0;
+      port.onMessage.addListener(msg => {
+        // 11. port.onMessage by port.postMessage in CS.
+        browser.test.assertEq("from CS to port", msg);
+        browser.test.assertEq(1, ++postMessageCount1,
+                              "BG port.onMessage should be called once");
+
+        // 12. should trigger port2.onMessage in CS.
+        port2.postMessage("from BG to port2");
+      });
+
+      // 4. Should trigger onConnect in CS.
+      port2 = browser.tabs.connect(tabId, {name: "from-bg"});
+      let postMessageCount2 = 0;
+      port2.onMessage.addListener(msg => {
+        // 7. onMessage by port2.postMessage in CS.
+        browser.test.assertEq("from CS to port2", msg);
+        browser.test.assertEq(1, ++postMessageCount2,
+                              "BG port2.onMessage should be called once");
+
+        // 8. Should trigger port.onMessage in CS.
+        port.postMessage("from BG to port");
+      });
+    });
+
+    // 1. Notify test runner to create a new tab.
+    browser.test.sendMessage("ready");
+  }
+
+  function contentScript() {
+    let onConnectCount = 0;
+    let port;
+    browser.runtime.onConnect.addListener(port2 => {
+      // 5. onConnect by connect() from BG.
+      browser.test.assertEq("from-bg", port2.name);
+      browser.test.assertEq(1, ++onConnectCount,
+                            "CS onConnect should be called once");
+
+      let postMessageCount2 = 0;
+      port2.onMessage.addListener(msg => {
+        // 12. port2.onMessage by port2.postMessage in BG.
+        browser.test.assertEq("from BG to port2", msg);
+        browser.test.assertEq(1, ++postMessageCount2,
+                              "CS port2.onMessage should be called once");
+
+        // TODO(robwu): Do not explicitly disconnect, it should not be a problem
+        // if we keep the ports open. However, not closing the ports causes the
+        // test to fail with NS_ERROR_NOT_INITIALIZED in ExtensionUtils.jsm, in
+        // Port.prototype.disconnect (nsIMessageSender.sendAsyncMessage).
+        port.disconnect();
+        port2.disconnect();
+        browser.test.notifyPass("ping pong done");
+      });
+      // 6. should trigger port2.onMessage in BG.
+      port2.postMessage("from CS to port2");
+    });
+
+    // 2. should trigger onConnect in BG.
+    port = browser.runtime.connect({name: "from-cs"});
+    let postMessageCount1 = 0;
+    port.onMessage.addListener(msg => {
+      // 9. onMessage by port.postMessage in BG.
+      browser.test.assertEq("from BG to port", msg);
+      browser.test.assertEq(1, ++postMessageCount1,
+                            "CS port.onMessage should be called once");
+
+      // 10. should trigger port.onMessage in BG.
+      port.postMessage("from CS to port");
+    });
+  }
+
+  let extensionData = {
+    background,
+    manifest: {
+      content_scripts: [{
+        js: ["contentscript.js"],
+        matches: ["http://mochi.test/*/file_sample.html"],
+      }],
+    },
+    files: {
+      "contentscript.js": contentScript,
+    },
+  };
+
+  let extension = ExtensionTestUtils.loadExtension(extensionData);
+  await extension.startup();
+  info("extension loaded");
+
+  await extension.awaitMessage("ready");
+
+  let win = window.open("file_sample.html");
+  await extension.awaitFinish("ping pong done");
+  win.close();
+
+  await extension.unload();
+  info("extension unloaded");
+});
+</script>
+</body>
diff --git a/toolkit/components/extensions/test/mochitest/test_ext_runtime_disconnect.html b/toolkit/components/extensions/test/mochitest/test_ext_runtime_disconnect.html
new file mode 100644
index 0000000000..f18190bf8b
--- /dev/null
+++ b/toolkit/components/extensions/test/mochitest/test_ext_runtime_disconnect.html
@@ -0,0 +1,77 @@
+<!DOCTYPE HTML>
+<html>
+<head>
+  <title>WebExtension test</title>
+  <script src="/tests/SimpleTest/SimpleTest.js"></script>
+  <script src="/tests/SimpleTest/ExtensionTestUtils.js"></script>
+  <script type="text/javascript" src="head.js"></script>
+  <link rel="stylesheet" type="text/css" href="/tests/SimpleTest/test.css"/>
+</head>
+<body>
+
+<script type="text/javascript">
+"use strict";
+
+function background() {
+  browser.runtime.onConnect.addListener(port => {
+    browser.test.assertEq(port.name, "ernie", "port name correct");
+    port.onDisconnect.addListener(() => {
+      browser.test.assertEq(null, port.error, "The port is implicitly closed without errors when the other context unloads");
+      // Closing an already-disconnected port is a no-op.
+      port.disconnect();
+      port.disconnect();
+      browser.test.sendMessage("disconnected");
+    });
+    browser.test.sendMessage("connected");
+  });
+}
+
+function contentScript() {
+  browser.runtime.connect({name: "ernie"});
+}
+
+let extensionData = {
+  background,
+  manifest: {
+    "permissions": ["tabs"],
+    "content_scripts": [{
+      "matches": ["http://mochi.test/*/file_sample.html"],
+      "js": ["content_script.js"],
+      "run_at": "document_idle",
+    }],
+  },
+
+  files: {
+    "content_script.js": contentScript,
+  },
+};
+
+add_task(async function test_contentscript() {
+  let extension = ExtensionTestUtils.loadExtension(extensionData);
+  await extension.startup();
+
+  let win = window.open("file_sample.html");
+  await Promise.all([waitForLoad(win), extension.awaitMessage("connected")]);
+  win.close();
+  await extension.awaitMessage("disconnected");
+
+  info("win.close() succeeded");
+
+  win = window.open("file_sample.html");
+  await Promise.all([waitForLoad(win), extension.awaitMessage("connected")]);
+
+  // Add an "unload" listener so that we don't put the window in the
+  // bfcache. This way it gets destroyed immediately upon navigation.
+  win.addEventListener("unload", function() {}); // eslint-disable-line mozilla/balanced-listeners
+
+  win.location = "http://example.com";
+  await extension.awaitMessage("disconnected");
+  win.close();
+
+  await extension.unload();
+  info("extension unloaded");
+});
+</script>
+
+</body>
+</html>
diff --git a/toolkit/components/extensions/test/mochitest/test_ext_script_filenames.html b/toolkit/components/extensions/test/mochitest/test_ext_script_filenames.html
new file mode 100644
index 0000000000..de0993c33d
--- /dev/null
+++ b/toolkit/components/extensions/test/mochitest/test_ext_script_filenames.html
@@ -0,0 +1,62 @@
+<!DOCTYPE HTML>
+<html>
+<head>
+  <title>Script Filenames Test</title>
+  <script type="text/javascript" src="/tests/SimpleTest/SimpleTest.js"></script>
+  <script type="text/javascript" src="/tests/SimpleTest/ExtensionTestUtils.js"></script>
+  <script type="text/javascript" src="head.js"></script>
+  <link rel="stylesheet" href="/tests/SimpleTest/test.css"/>
+</head>
+<body>
+
+<script type="text/javascript">
+"use strict";
+
+add_task(async function test_tabs_executeScript() {
+  let validFileName = "script.js";
+  let invalidFileName = "script.xyz";
+
+  async function background() {
+    await browser.tabs.executeScript({ file: "script.js" });
+
+    await browser.test.assertRejects(
+      browser.tabs.executeScript({ file: "script.xyz" }),
+      Error,
+      "invalid filename does not execute"
+    );
+    browser.test.notifyPass("execute-script");
+  }
+
+  let extension = ExtensionTestUtils.loadExtension({
+    manifest: {
+      permissions: ["<all_urls>"],
+    },
+
+    background,
+
+    files: {
+      [validFileName]: function contentScript1() {
+        browser.test.sendMessage("content-script-loaded");
+      },
+      [invalidFileName]: function contentScript2() {
+        browser.test.fail("this script should not be loaded");
+      },
+    },
+  });
+
+  let tab = await AppTestDelegate.openNewForegroundTab(
+    window,
+    "http://mochi.test:8888/",
+    true
+  );
+  await extension.startup();
+
+  await extension.awaitMessage("content-script-loaded");
+  await extension.awaitFinish("execute-script");
+
+  await extension.unload();
+  await AppTestDelegate.removeTab(window, tab);
+});
+</script>
+</body>
+</html>
diff --git a/toolkit/components/extensions/test/mochitest/test_ext_scripting_contentScripts.html b/toolkit/components/extensions/test/mochitest/test_ext_scripting_contentScripts.html
new file mode 100644
index 0000000000..c8457b6d36
--- /dev/null
+++ b/toolkit/components/extensions/test/mochitest/test_ext_scripting_contentScripts.html
@@ -0,0 +1,1532 @@
+<!DOCTYPE HTML>
+<html>
+<head>
+  <meta charset="utf-8">
+  <title>Tests scripting.*ContentScripts()</title>
+  <script type="text/javascript" src="/tests/SimpleTest/SimpleTest.js"></script>
+  <script type="text/javascript" src="/tests/SimpleTest/ExtensionTestUtils.js"></script>
+  <script type="text/javascript" src="head.js"></script>
+  <link rel="stylesheet" href="/tests/SimpleTest/test.css"/>
+</head>
+<body>
+
+<script type="text/javascript">
+
+"use strict";
+
+const MOCHITEST_HOST_PERMISSIONS = [
+  "*://mochi.test/",
+  "*://mochi.xorigin-test/",
+  "*://test1.example.com/",
+];
+
+const makeExtension = ({ manifest: manifestProps, ...otherProps }) => {
+  return ExtensionTestUtils.loadExtension({
+    manifest: {
+      manifest_version: 3,
+      permissions: ["scripting"],
+      host_permissions: [
+        ...MOCHITEST_HOST_PERMISSIONS,
+        // Used in `file_contains_iframe.html`
+        "*://example.org/",
+      ],
+      granted_host_permissions: true,
+      ...manifestProps,
+    },
+    useAddonManager: "temporary",
+    ...otherProps,
+  });
+};
+
+add_task(async function setup() {
+  await SpecialPowers.pushPrefEnv({
+    set: [["extensions.manifestV3.enabled", true]],
+  });
+});
+
+add_task(async function test_validate_registerContentScripts_params() {
+  let extension = makeExtension({
+    async background() {
+      const TEST_CASES = [
+        {
+          title: "no js and no css",
+          params: [
+            {
+              id: "script",
+              matches: ["*://mochi.test/*"],
+              persistAcrossSessions: false,
+            },
+          ],
+          expectedError: "At least one js or css must be specified.",
+        },
+        {
+          title: "empty js",
+          params: [
+            {
+              id: "script",
+              js: [],
+              matches: ["*://mochi.test/*"],
+              persistAcrossSessions: false,
+            },
+          ],
+          expectedError: "At least one js or css must be specified.",
+        },
+        {
+          title: "empty css",
+          params: [
+            {
+              id: "script",
+              css: [],
+              matches: ["*://mochi.test/*"],
+              persistAcrossSessions: false,
+            },
+          ],
+          expectedError: "At least one js or css must be specified.",
+        },
+        {
+          title: "no matches",
+          params: [
+            {
+              id: "script",
+              js: ["script.js"],
+              persistAcrossSessions: false,
+            },
+          ],
+          expectedError: "matches must be specified.",
+        },
+        {
+          title: "empty matches",
+          params: [
+            {
+              id: "script",
+              js: ["script.js"],
+              matches: [],
+              persistAcrossSessions: false,
+            },
+          ],
+          expectedError: "matches must be specified.",
+        },
+        {
+          title: "one empty match",
+          params: [
+            {
+              id: "script",
+              js: ["script.js"],
+              matches: [""],
+              persistAcrossSessions: false,
+            },
+          ],
+          expectedError: "Invalid url pattern: ",
+        },
+        {
+          title: "invalid match",
+          params: [
+            {
+              id: "script",
+              js: ["script.js"],
+              matches: ["not-a-pattern"],
+              persistAcrossSessions: false,
+            },
+          ],
+          expectedError: "Invalid url pattern: not-a-pattern",
+        },
+        {
+          title: "invalid match and valid match",
+          params: [
+            {
+              id: "script",
+              js: ["script.js"],
+              matches: ["*://mochi.test/*", "not-a-pattern"],
+              persistAcrossSessions: false,
+            },
+          ],
+          expectedError: "Invalid url pattern: not-a-pattern",
+        },
+        {
+          title: "one empty value in excludeMatches",
+          params: [
+            {
+              id: "script",
+              js: ["script.js"],
+              matches: ["*://mochi.test/*"],
+              excludeMatches: [""],
+              persistAcrossSessions: false,
+            },
+          ],
+          expectedError: "Invalid url pattern: ",
+        },
+        {
+          title: "invalid value in excludeMatches",
+          params: [
+            {
+              id: "script",
+              js: ["script.js"],
+              matches: ["*://mochi.test/*"],
+              excludeMatches: ["not-a-pattern"],
+              persistAcrossSessions: false,
+            },
+          ],
+          expectedError: "Invalid url pattern: not-a-pattern",
+        },
+        {
+          title: "duplicate IDs",
+          params: [
+            {
+              id: "script-1",
+              js: ["script.js"],
+              matches: ["*://mochi.test/*"],
+              persistAcrossSessions: false,
+            },
+            {
+              id: "script-1",
+              js: ["script.js"],
+              matches: ["*://mochi.test/*"],
+              persistAcrossSessions: false,
+            },
+          ],
+          expectedError: `Script ID "script-1" found more than once in 'scripts' array.`,
+        },
+        {
+          title: "empty id",
+          params: [
+            {
+              id: "",
+              js: ["script.js"],
+              matches: ["*://mochi.test/*"],
+              persistAcrossSessions: false,
+            },
+          ],
+          expectedError: "Invalid content script id.",
+        },
+        {
+          title: "id starting with _",
+          params: [
+            {
+              id: "_foo",
+              js: ["script.js"],
+              matches: ["*://mochi.test/*"],
+              persistAcrossSessions: false,
+            },
+          ],
+          expectedError: "Invalid content script id.",
+        },
+      ];
+
+      for (const { title, params, expectedError } of TEST_CASES) {
+        await browser.test.assertRejects(
+          browser.scripting.registerContentScripts(params),
+          expectedError,
+          `${title} - got expected error`
+        );
+      }
+
+      let scripts = await browser.scripting.getRegisteredContentScripts();
+      browser.test.assertEq(0, scripts.length, "expected no registered script");
+
+      browser.test.notifyPass("test-finished");
+    },
+    files: {
+      "script.js": "",
+    },
+  });
+
+  await extension.startup();
+  await extension.awaitFinish("test-finished");
+  await extension.unload();
+});
+
+add_task(async function test_registerContentScripts_with_already_registered_id() {
+  let extension = makeExtension({
+    async background() {
+      const script = {
+        id: "script-1",
+        js: ["script.js"],
+        matches: ["*://test1.example.com/*"],
+        persistAcrossSessions: false,
+      };
+
+      await browser.scripting.registerContentScripts([script]);
+
+      let scripts = await browser.scripting.getRegisteredContentScripts();
+      browser.test.assertEq(1, scripts.length, "expected 1 registered script");
+
+      await browser.test.assertRejects(
+        browser.scripting.registerContentScripts([script]),
+        `Content script with id "${script.id}" is already registered.`,
+        "got expected error"
+      );
+
+      scripts = await browser.scripting.getRegisteredContentScripts();
+      browser.test.assertEq(1, scripts.length, "expected 1 registered script");
+
+      browser.test.notifyPass("test-finished");
+    },
+    files: {
+      "script.js": "",
+    },
+  });
+
+  await extension.startup();
+  await extension.awaitFinish("test-finished");
+  await extension.unload();
+});
+
+add_task(async function test_validate_getRegisteredContentScripts_params() {
+  let extension = makeExtension({
+    async background() {
+      let scripts = await browser.scripting.getRegisteredContentScripts();
+      browser.test.assertEq(0, scripts.length, "expected no registered scripts");
+
+      scripts = await browser.scripting.getRegisteredContentScripts({
+        ids: ["non-existent-id"]
+      });
+      browser.test.assertEq(0, scripts.length, "expected no registered scripts");
+
+      browser.test.log("test call with undefined filter and a chrome-compatible callback");
+      scripts = await new Promise(resolve => {
+        browser.scripting.getRegisteredContentScripts(undefined, resolve);
+      });
+      browser.test.assertEq(0, scripts.length, "expected no registered scripts");
+
+      browser.test.log("test call with only the chrome-compatible callback");
+      scripts = await new Promise(resolve => {
+        browser.scripting.getRegisteredContentScripts(resolve);
+      });
+      browser.test.assertEq(0, scripts.length, "expected no registered scripts");
+
+      browser.test.notifyPass("test-finished");
+    },
+  });
+
+  await extension.startup();
+  await extension.awaitFinish("test-finished");
+  await extension.unload();
+});
+
+add_task(async function test_getRegisteredContentScripts() {
+  let extension = makeExtension({
+    async background() {
+      let scripts = await browser.scripting.getRegisteredContentScripts();
+      browser.test.assertEq(0, scripts.length, "expected no registered scripts");
+
+      const aScript = {
+        id: "a-script",
+        js: ["script.js"],
+        matches: ["<all_urls>"],
+        persistAcrossSessions: false,
+      };
+
+      await browser.scripting.registerContentScripts([aScript]);
+
+      scripts = await browser.scripting.getRegisteredContentScripts();
+      browser.test.assertEq(1, scripts.length, "expected 1 registered script");
+      browser.test.assertEq(aScript.id, scripts[0].id, "expected correct id");
+
+      // This should return no registered scripts.
+      scripts = await browser.scripting.getRegisteredContentScripts({ ids: [] });
+      browser.test.assertEq(0, scripts.length, "expected 0 registered script");
+
+      // Verify that invalid IDs are omitted but valid IDs are used to return
+      // registered scripts.
+      scripts = await browser.scripting.getRegisteredContentScripts({
+        ids: ["non-existent-id", aScript.id]
+      });
+      browser.test.assertEq(1, scripts.length, "expected 1 registered script");
+      browser.test.assertEq(aScript.id, scripts[0].id, "expected correct id");
+
+      browser.test.notifyPass("test-finished");
+    },
+    files: {
+      "script.js": "",
+    },
+  });
+
+  await extension.startup();
+  await extension.awaitFinish("test-finished");
+  await extension.unload();
+});
+
+add_task(async function test_registerContentScripts_js() {
+  let extension = makeExtension({
+    async background() {
+      const TEST_CASES = [
+        // This should have no effect but it should not throw.
+        {
+          title: "no script",
+          params: [],
+        },
+        {
+          title: "one script",
+          params: [
+            {
+              id: "script-1",
+              js: ["script-1.js"],
+              matches: ["*://test1.example.com/*"],
+              persistAcrossSessions: false,
+            }
+          ],
+        },
+        {
+          title: "one script in all frames",
+          params: [
+            {
+              id: "script-2",
+              js: ["script-2.js"],
+              matches: [
+                "*://test1.example.com/*",
+                "*://example.org/*",
+              ],
+              allFrames: true,
+              persistAcrossSessions: false,
+            }
+          ],
+        },
+        {
+          title: "one script in all frames with excludeMatches set",
+          params: [
+            {
+              id: "script-3",
+              js: ["script-3.js"],
+              matches: [
+                "*://test1.example.com/*",
+                "*://example.org/*",
+              ],
+              allFrames: true,
+              excludeMatches: ["*://test1.example.com/*"],
+              persistAcrossSessions: false,
+            }
+          ],
+        },
+        {
+          title: "one script, two js paths",
+          params: [
+            {
+              id: "script-4",
+              js: ["script-4-1.js", "script-4-2.js"],
+              matches: ["*://test1.example.com/*"],
+              persistAcrossSessions: false,
+            }
+          ],
+        },
+        {
+          title: "empty excludeMatches",
+          params: [
+            {
+              id: "script-5",
+              // This path should be normalized.
+              js: ["/script-5.js"],
+              matches: ["*://test1.example.com/*"],
+              excludeMatches: [],
+              persistAcrossSessions: false,
+            }
+          ],
+        },
+      ];
+
+      let scripts = await browser.scripting.getRegisteredContentScripts();
+      browser.test.assertEq(0, scripts.length, "expected no registered script");
+
+      for (const { title, params } of TEST_CASES) {
+        const res = await browser.scripting.registerContentScripts(params);
+        browser.test.assertEq(
+          undefined,
+          res,
+          `${title} - expected no result`
+        );
+
+        const script = await browser.scripting.getRegisteredContentScripts({
+          ids: params.map(param => param.id)
+        });
+        browser.test.assertEq(
+          params.length,
+          script.length,
+          `${title} - got the expected number of registered scripts`
+        );
+      }
+
+      scripts = await browser.scripting.getRegisteredContentScripts();
+      browser.test.assertEq(
+        // A test case declared above does not contain any script to register.
+        TEST_CASES.length - 1,
+        scripts.length,
+        "got the expected number of registered scripts"
+      );
+      browser.test.assertEq(
+        JSON.stringify([
+          {
+            id: "script-1",
+            allFrames: false,
+            matches: ["*://test1.example.com/*"],
+            runAt: "document_idle",
+            persistAcrossSessions: false,
+            js: ["script-1.js"],
+          },
+          {
+            id: "script-2",
+            allFrames: true,
+            matches: [
+              "*://test1.example.com/*",
+              "*://example.org/*",
+            ],
+            runAt: "document_idle",
+            persistAcrossSessions: false,
+            js: ["script-2.js"],
+          },
+          {
+            id: "script-3",
+            allFrames: true,
+            matches: [
+              "*://test1.example.com/*",
+              "*://example.org/*",
+            ],
+            runAt: "document_idle",
+            persistAcrossSessions: false,
+            excludeMatches: ["*://test1.example.com/*"],
+            js: ["script-3.js"],
+          },
+          {
+            id: "script-4",
+            allFrames: false,
+            matches: ["*://test1.example.com/*"],
+            runAt: "document_idle",
+            persistAcrossSessions: false,
+            js: ["script-4-1.js", "script-4-2.js"],
+          },
+          {
+            id: "script-5",
+            allFrames: false,
+            matches: ["*://test1.example.com/*"],
+            runAt: "document_idle",
+            persistAcrossSessions: false,
+            js: ["script-5.js"],
+          },
+        ]),
+        JSON.stringify(scripts),
+        "got expected scripts"
+      );
+
+      browser.test.sendMessage("background-ready");
+    },
+    files: {
+      "script-1.js": () => {
+        browser.test.sendMessage(
+          "script-ran",
+          { file: "script-1.js", value: document.title }
+        );
+      },
+      "script-2.js": () => {
+        browser.test.sendMessage(
+          "script-ran",
+          { file: "script-2.js", value: document.title }
+        );
+      },
+      "script-3.js": () => {
+        browser.test.sendMessage(
+          "script-ran",
+          { file: "script-3.js", value: document.title }
+        );
+      },
+      "script-4-1.js": () => {
+        // We inject this script (first) as well as the one defined right
+        // after. The order should be respected, which is why we define a
+        // property here and check it in the second script.
+        window.SCRIPT_4_INJECTED = "SCRIPT_4_INJECTED";
+      },
+      "script-4-2.js": () => {
+        browser.test.sendMessage(
+          "script-ran",
+          { file: "script-4-2.js", value: window.SCRIPT_4_INJECTED }
+        );
+        delete window.SCRIPT_4_INJECTED;
+      },
+      "script-5.js": () => {
+        browser.test.sendMessage(
+          "script-ran",
+          { file: "script-5.js", value: document.title }
+        );
+      },
+    },
+  });
+
+  let scriptsRan = 0;
+  let results = [];
+  let completePromise = new Promise(resolve => {
+    extension.onMessage("script-ran", result => {
+      results.push(result);
+      scriptsRan++;
+
+      // The value below should be updated when TEST_CASES above is changed.
+      if (scriptsRan === 6) {
+        resolve();
+      }
+    });
+  });
+
+  await extension.startup();
+  await extension.awaitMessage("background-ready");
+
+  // Load a page that will trigger the content scripts previously registered.
+  let tab = await AppTestDelegate.openNewForegroundTab(
+    window,
+    "https://test1.example.com/tests/toolkit/components/extensions/test/mochitest/file_contains_iframe.html",
+    true
+  );
+
+  // Wait for all content scripts to be executed.
+  await completePromise;
+
+  // Verify that the scripts have been executed correctly. We sort the results
+  // to compare them against expected values.
+  results.sort((a, b) => {
+    return a.file.localeCompare(b.file) || a.value.localeCompare(b.value);
+  });
+  ok(
+    JSON.stringify([
+      { file: "script-1.js", value: "file contains iframe" },
+      // script-2.js should be injected in two frames
+      { file: "script-2.js", value: "file contains iframe" },
+      { file: "script-2.js", value: "file contains img" },
+      { file: "script-3.js", value: "file contains img" },
+      // script-4-1.js will add a prop to the `window` object, which should be
+      // read by `script-4-2.js`.
+      { file: "script-4-2.js", value: "SCRIPT_4_INJECTED" },
+      { file: "script-5.js", value: "file contains iframe" },
+    ]) === JSON.stringify(results),
+    "got expected script results" + JSON.stringify(results)
+  );
+
+  await AppTestDelegate.removeTab(window, tab);
+  await extension.unload();
+});
+
+add_task(async function test_registerContentScripts_are_not_unregistered() {
+  let extension = makeExtension({
+    files: {
+      "background.html": `<!DOCTYPE html>
+        <html>
+          <head><meta charset="utf-8"></head>
+          <body>
+            <script src="background.js"><\/script>
+          </body>
+        </html>
+      `,
+      "background.js": async () => {
+        await browser.scripting.registerContentScripts([
+          {
+            id: "a-script",
+            js: ["script.js"],
+            matches: ["*://test1.example.com/*"],
+            persistAcrossSessions: false,
+          },
+        ]);
+
+        browser.test.sendMessage("background-executed");
+      },
+      "script.js": () => {
+        browser.test.sendMessage("script-executed");
+      },
+    },
+  });
+
+  await extension.startup();
+
+  // Load the background page that registers a content script.
+  let tab = await AppTestDelegate.openNewForegroundTab(
+    window,
+    `moz-extension://${extension.uuid}/background.html`,
+    true
+  );
+  await extension.awaitMessage("background-executed");
+  await AppTestDelegate.removeTab(window, tab);
+
+  // Load a page that will trigger the content scripts previously registered.
+  tab = await AppTestDelegate.openNewForegroundTab(
+    window,
+    "https://test1.example.com/tests/toolkit/components/extensions/test/mochitest/file_contains_iframe.html",
+    true
+  );
+
+  await extension.awaitMessage("script-executed");
+
+  await AppTestDelegate.removeTab(window, tab);
+  await extension.unload();
+});
+
+add_task(async function test_scripts_dont_run_after_shutdown() {
+  let extension = makeExtension({
+    async background() {
+      await browser.scripting.registerContentScripts([
+        {
+          id: "script-that-should-not-run",
+          js: ["script.js"],
+          matches: ["*://test1.example.com/*"],
+          persistAcrossSessions: false,
+        },
+      ]);
+
+      browser.test.sendMessage("background-ready");
+    },
+    files: {
+      "script.js": () => {
+        browser.test.fail("this script should not be executed.");
+      },
+    },
+  });
+  // We use a second extension to wait enough time to confirm that the script
+  // registered in the previous extension has not been executed at all, in case
+  // the tab closes before the scheduled content script has had a chance to
+  // run.
+  let anotherExtension = makeExtension({
+    async background() {
+      await browser.scripting.registerContentScripts([
+        {
+          id: "this-script-should-run",
+          js: ["script.js"],
+          matches: ["*://test1.example.com/*"],
+          persistAcrossSessions: false,
+        },
+      ]);
+
+      browser.test.sendMessage("background-ready");
+    },
+    files: {
+      "script.js": () => {
+        browser.test.sendMessage("script-ran");
+      },
+    },
+  });
+
+  await extension.startup();
+  await extension.awaitMessage("background-ready");
+
+  await anotherExtension.startup();
+  await anotherExtension.awaitMessage("background-ready");
+
+  await extension.unload();
+
+  let tab = await AppTestDelegate.openNewForegroundTab(
+    window,
+    "https://test1.example.com/tests/toolkit/components/extensions/test/mochitest/file_contains_iframe.html",
+    true
+  );
+  await anotherExtension.awaitMessage("script-ran");
+  await AppTestDelegate.removeTab(window, tab);
+
+  await anotherExtension.unload();
+});
+
+add_task(async function test_registerContentScripts_with_wrong_matches() {
+  let extension = makeExtension({
+    async background() {
+      // Register a content script that should not be injected in this test
+      // case because the `matches` values don't match the host permissions.
+      await browser.scripting.registerContentScripts([
+        {
+          id: "script-that-should-not-run",
+          js: ["script.js"],
+          matches: ["*://mozilla.org/*"],
+          persistAcrossSessions: false,
+        },
+      ]);
+
+      browser.test.sendMessage("background-ready");
+    },
+    files: {
+      "script.js": () => {
+        browser.test.fail("this script should not be executed.");
+      },
+    },
+  });
+  // We use a second extension to wait enough time to confirm that the script
+  // registered in the previous extension has not been executed at all, in case
+  // the tab closes before the scheduled content script has had a chance to
+  // run.
+  let anotherExtension = makeExtension({
+    async background() {
+      await browser.scripting.registerContentScripts([
+        {
+          id: "this-script-should-run",
+          js: ["script.js"],
+          matches: ["*://test1.example.com/*"],
+          persistAcrossSessions: false,
+        },
+      ]);
+
+      browser.test.sendMessage("background-ready");
+    },
+    files: {
+      "script.js": () => {
+        browser.test.sendMessage("script-ran");
+      },
+    },
+  });
+
+  await extension.startup();
+  await extension.awaitMessage("background-ready");
+
+  await anotherExtension.startup();
+  await anotherExtension.awaitMessage("background-ready");
+
+  let tab = await AppTestDelegate.openNewForegroundTab(
+    window,
+    "https://test1.example.com/tests/toolkit/components/extensions/test/mochitest/file_contains_iframe.html",
+    true
+  );
+  await anotherExtension.awaitMessage("script-ran");
+
+  await extension.unload();
+  await anotherExtension.unload();
+
+  // We remove the tab after having unloaded the extensions to avoid failures
+  // on Windows, see: Bug 1761550.
+  await AppTestDelegate.removeTab(window, tab);
+});
+
+add_task(async function test_registerContentScripts_twice_with_same_id() {
+  let extension = makeExtension({
+    async background() {
+      const script = {
+        id: "script-that-should-not-run",
+        js: ["script.js"],
+        matches: ["*://test1.example.com/*"],
+        persistAcrossSessions: false,
+      };
+
+      const results = await Promise.allSettled([
+        browser.scripting.registerContentScripts([script]),
+        browser.scripting.registerContentScripts([script]),
+      ]);
+
+      browser.test.assertEq(2, results.length, "got expected length");
+      browser.test.assertEq(
+        "fulfilled",
+        results[0].status,
+        "expected fulfilled promise"
+      );
+      browser.test.assertEq(
+        "rejected",
+        results[1].status,
+        "expected rejected promise"
+      );
+      browser.test.assertEq(
+        `Content script with id "script-that-should-not-run" is already registered.`,
+        results[1].reason.message,
+        "expected reason"
+      );
+
+      let scripts = await browser.scripting.getRegisteredContentScripts();
+      browser.test.assertEq(1, scripts.length, "expected 1 registered script");
+
+      browser.test.sendMessage("background-done");
+    },
+    files: {
+      "script.js": "",
+    },
+  });
+
+  await extension.startup();
+  await extension.awaitMessage("background-done");
+  await extension.unload();
+});
+
+add_task(async function test_getRegisteredContentScripts_during_a_registration() {
+  let extension = makeExtension({
+    async background() {
+      browser.scripting.registerContentScripts([
+        {
+          id: "a-script",
+          js: ["script.js"],
+          matches: ["*://test1.example.com/*"],
+          persistAcrossSessions: false,
+        },
+      ]);
+
+      const scripts = await browser.scripting.getRegisteredContentScripts();
+      browser.test.assertEq(
+        JSON.stringify([
+          {
+            id: "a-script",
+            allFrames: false,
+            matches: ["*://test1.example.com/*"],
+            runAt: "document_idle",
+            persistAcrossSessions: false,
+            js: ["script.js"],
+          },
+        ]),
+        JSON.stringify(scripts),
+        "expected 1 registered script"
+      );
+
+      browser.test.sendMessage("background-done");
+    },
+    files: {
+      "script.js": "",
+    },
+  });
+
+  await extension.startup();
+  await extension.awaitMessage("background-done");
+  await extension.unload();
+});
+
+add_task(async function test_validate_unregisterContentScripts_params() {
+  let extension = makeExtension({
+    async background() {
+      const TEST_CASES = [
+        {
+          title: "unknown id",
+          params: {
+            ids: ["non-existent-id"],
+          },
+          expectedError: `Content script with id "non-existent-id" does not exist.`
+        },
+        {
+          title: "invalid id",
+          params: {
+            ids: ["_invalid-id"],
+          },
+          expectedError: "Invalid content script id.",
+        },
+      ];
+
+      for (const { title, params, expectedError } of TEST_CASES) {
+        await browser.test.assertRejects(
+          browser.scripting.unregisterContentScripts(params),
+          expectedError,
+          `${title} - got expected error`
+        );
+      }
+
+      let scripts = await browser.scripting.getRegisteredContentScripts();
+      browser.test.assertEq(0, scripts.length, "expected no script");
+
+      browser.test.sendMessage("background-done");
+    },
+  });
+
+  await extension.startup();
+  await extension.awaitMessage("background-done");
+  await extension.unload();
+});
+
+add_task(async function test_unregisterContentScripts_with_chrome_compatible_callback() {
+  let extension = makeExtension({
+    async background() {
+      let scripts = await browser.scripting.getRegisteredContentScripts();
+      browser.test.assertEq(0, scripts.length, "expected no script");
+
+      // Register a script that we can unregister after.
+      await browser.scripting.registerContentScripts([
+        {
+          id: "script-1",
+          js: ["script.js"],
+          matches: ["*://test1.example.com/*"],
+          persistAcrossSessions: false,
+        },
+      ]);
+      scripts = await browser.scripting.getRegisteredContentScripts();
+      browser.test.assertEq(1, scripts.length, "expected 1 registered script");
+
+      browser.test.log("test call with undefined filter and a chrome-compatible callback");
+      await new Promise(resolve => {
+        browser.scripting.unregisterContentScripts(undefined, resolve);
+      });
+
+      scripts = await browser.scripting.getRegisteredContentScripts();
+      browser.test.assertEq(0, scripts.length, "expected no registered scripts");
+
+      // Re-register a script that we can unregister after.
+      await browser.scripting.registerContentScripts([
+        {
+          id: "script-1",
+          js: ["script.js"],
+          matches: ["*://test1.example.com/*"],
+          persistAcrossSessions: false,
+        },
+      ]);
+
+      browser.test.log("test call with only the chrome-compatible callback");
+      await new Promise(resolve => {
+        browser.scripting.unregisterContentScripts(resolve);
+      });
+
+      scripts = await browser.scripting.getRegisteredContentScripts();
+      browser.test.assertEq(0, scripts.length, "expected no registered scripts");
+
+      browser.test.sendMessage("background-done");
+    },
+    files: {
+      "script.js": "",
+    },
+  });
+
+  await extension.startup();
+  await extension.awaitMessage("background-done");
+  await extension.unload();
+});
+
+add_task(async function test_unregisterContentScripts() {
+  let extension = makeExtension({
+    async background() {
+      const script1 = {
+        id: "script-1",
+        js: ["script.js"],
+        matches: ["*://test1.example.com/*"],
+        persistAcrossSessions: false,
+      };
+      const script2 = {
+        id: "script-2",
+        js: ["script.js"],
+        matches: ["*://test1.example.com/*"],
+        persistAcrossSessions: false,
+      }
+      const script3 = {
+        id: "script-3",
+        js: ["script.js"],
+        matches: ["*://test1.example.com/*"],
+        persistAcrossSessions: false,
+      }
+
+      let res = await browser.scripting.registerContentScripts([
+        script1,
+        script2,
+        script3,
+      ]);
+      browser.test.assertEq(undefined, res, "expected no result");
+
+      let scripts = await browser.scripting.getRegisteredContentScripts();
+      browser.test.assertEq(3, scripts.length, "expected 3 scripts");
+      browser.test.assertEq(script1.id, scripts[0].id, "expected correct id");
+      browser.test.assertEq(script2.id, scripts[1].id, "expected correct id");
+      browser.test.assertEq(script3.id, scripts[2].id, "expected correct id");
+
+      // No unregistration when unknown IDs are passed along with valid IDs.
+      await browser.test.assertRejects(
+        browser.scripting.unregisterContentScripts({
+          ids: [script2.id, "non-existent-id"],
+        }),
+        `Content script with id "non-existent-id" does not exist.`
+      );
+
+      scripts = await browser.scripting.getRegisteredContentScripts();
+      browser.test.assertEq(3, scripts.length, "expected 3 scripts");
+
+      // Unregister 1 script.
+      res = await browser.scripting.unregisterContentScripts({
+        ids: [script2.id]
+      });
+      browser.test.assertEq(undefined, res, "expected no result");
+
+      scripts = await browser.scripting.getRegisteredContentScripts();
+      browser.test.assertEq(2, scripts.length, "expected 2 scripts");
+      browser.test.assertEq(script1.id, scripts[0].id, "expected correct id");
+      browser.test.assertEq(script3.id, scripts[1].id, "expected correct id");
+
+      // This should unregister all the remaining registered scripts.
+      res = await browser.scripting.unregisterContentScripts();
+      browser.test.assertEq(undefined, res, "expected no result");
+
+      scripts = await browser.scripting.getRegisteredContentScripts();
+      browser.test.assertEq(0, scripts.length, "expected no script");
+
+      browser.test.sendMessage("background-done");
+    },
+    files: {
+      "script.js": "",
+    },
+  });
+
+  await extension.startup();
+  await extension.awaitMessage("background-done");
+  await extension.unload();
+});
+
+add_task(async function test_unregisterContentScripts_twice_with_same_id() {
+  let extension = makeExtension({
+    async background() {
+      const script = {
+        id: "script-to-unregister",
+        js: ["script.js"],
+        matches: ["*://test1.example.com/*"],
+        persistAcrossSessions: false,
+      };
+
+      await browser.scripting.registerContentScripts([script]);
+
+      let scripts = await browser.scripting.getRegisteredContentScripts();
+      browser.test.assertEq(1, scripts.length, "expected 1 registered script");
+
+      const results = await Promise.allSettled([
+        browser.scripting.unregisterContentScripts({ ids: [script.id] }),
+        browser.scripting.unregisterContentScripts({ ids: [script.id] }),
+      ]);
+
+      browser.test.assertEq(2, results.length, "got expected length");
+      browser.test.assertEq(
+        "fulfilled",
+        results[0].status,
+        "expected fulfilled promise"
+      );
+      browser.test.assertEq(
+        "rejected",
+        results[1].status,
+        "expected rejected promise"
+      );
+      browser.test.assertEq(
+        `Content script with id "script-to-unregister" does not exist.`,
+        results[1].reason.message,
+        "expected reason"
+      );
+
+      scripts = await browser.scripting.getRegisteredContentScripts();
+      browser.test.assertEq(0, scripts.length, "expected 0 registered script");
+
+      browser.test.sendMessage("background-done");
+    },
+    files: {
+      "script.js": "",
+    },
+  });
+
+  await extension.startup();
+  await extension.awaitMessage("background-done");
+  await extension.unload();
+});
+
+add_task(async function test_validate_updateContentScripts_params() {
+  let extension = makeExtension({
+    async background() {
+      const script = {
+        id: "registered-script",
+        js: ["script-1.js"],
+        matches: ["*://test1.example.com/*"],
+        persistAcrossSessions: false,
+      };
+
+      const TEST_CASES = [
+        {
+          title: "invalid script ID",
+          params: [
+            {
+              id: "_invalid-id",
+            },
+          ],
+          expectedError: 'Invalid content script id.',
+        },
+        {
+          title: "empty script ID",
+          params: [
+            {
+              id: "",
+            },
+          ],
+          expectedError: 'Invalid content script id.',
+        },
+        {
+          title: "unknown script ID",
+          params: [
+            {
+              id: "unknown-id",
+            },
+          ],
+          expectedError: 'Content script with id "unknown-id" does not exist.',
+        },
+        {
+          title: "duplicate valid script IDs",
+          params: [
+            {
+              id: script.id,
+            },
+            {
+              id: script.id,
+            },
+          ],
+          expectedError: `Script ID "${script.id}" found more than once in 'scripts' array.`,
+        },
+        {
+          title: "empty matches",
+          params: [
+            {
+              id: script.id,
+              matches: [],
+            },
+          ],
+          expectedError: "matches must be specified.",
+        },
+        {
+          title: "one empty match",
+          params: [
+            {
+              id: script.id,
+              matches: [""],
+            },
+          ],
+          expectedError: "Invalid url pattern: ",
+        },
+        {
+          title: "invalid match",
+          params: [
+            {
+              id: script.id,
+              matches: ["not-a-pattern"],
+            },
+          ],
+          expectedError: "Invalid url pattern: not-a-pattern",
+        },
+        {
+          title: "invalid match and valid match",
+          params: [
+            {
+              id: script.id,
+              matches: ["*://mochi.test/*", "not-a-pattern"],
+            },
+          ],
+          expectedError: "Invalid url pattern: not-a-pattern",
+        },
+        {
+          title: "one empty value in excludeMatches",
+          params: [
+            {
+              id: script.id,
+              excludeMatches: [""],
+            },
+          ],
+          expectedError: "Invalid url pattern: ",
+        },
+        {
+          title: "invalid value in excludeMatches",
+          params: [
+            {
+              id: script.id,
+              excludeMatches: ["not-a-pattern"],
+            },
+          ],
+          expectedError: "Invalid url pattern: not-a-pattern",
+        },
+        {
+          title: "empty js",
+          params: [
+            {
+              id: script.id,
+              js: [],
+            },
+          ],
+          expectedError: "At least one js or css must be specified.",
+        },
+        {
+          title: "empty js and css",
+          params: [
+            {
+              id: script.id,
+              js: [],
+              css: [],
+            },
+          ],
+          expectedError: "At least one js or css must be specified.",
+        },
+      ];
+
+      // Register a valid script so that we can verify update params beyond
+      // script IDs.
+      await browser.scripting.registerContentScripts([script]);
+
+      for (const { title, params, expectedError } of TEST_CASES) {
+        await browser.test.assertRejects(
+          browser.scripting.updateContentScripts(params),
+          expectedError,
+          `${title} - got expected error`
+        );
+      }
+
+      let scripts = await browser.scripting.getRegisteredContentScripts();
+      browser.test.assertEq(1, scripts.length, "expected 1 registered script");
+      browser.test.assertEq(
+        JSON.stringify([
+          {
+            id: script.id,
+            allFrames: false,
+            matches: script.matches,
+            runAt: "document_idle",
+            persistAcrossSessions: false,
+            js: script.js,
+          },
+        ]),
+        JSON.stringify(scripts),
+        "expected script to not have been modified"
+      );
+
+      browser.test.sendMessage("background-done");
+    },
+  });
+
+  await extension.startup();
+  await extension.awaitMessage("background-done");
+  await extension.unload();
+});
+
+add_task(async function test_updateContentScripts() {
+  let extension = makeExtension({
+    async background() {
+      const SCRIPT_ID = "script-to-update";
+
+      await browser.scripting.registerContentScripts([
+        {
+          id: SCRIPT_ID,
+          js: ["script-1.js"],
+          matches: ["*://test1.example.com/*"],
+          persistAcrossSessions: false,
+        },
+      ]);
+
+      browser.test.onMessage.addListener(async (msg, params) => {
+        switch (msg) {
+          case "updateContentScripts": {
+            const {
+              title,
+              updateContentScriptsParams,
+              expectedRegisteredContentScript
+            } = params;
+
+            let result = await browser.scripting.updateContentScripts([
+              updateContentScriptsParams,
+            ]);
+            browser.test.assertEq(
+              undefined,
+              result,
+              `${title} - expected no return value`
+            );
+
+            let scripts = await browser.scripting.getRegisteredContentScripts();
+            browser.test.assertEq(
+              JSON.stringify([expectedRegisteredContentScript]),
+              JSON.stringify(scripts),
+              `${title} - expected registered script`
+            );
+
+            browser.test.sendMessage(`${msg}-done`);
+            break;
+          }
+
+          default:
+            browser.test.fail(`invalid message received: ${msg}`);
+        }
+      });
+
+      browser.test.sendMessage("background-ready");
+    },
+    files: {
+      "script-1.js": () => {
+        browser.test.sendMessage(
+          `script-1 executed in ${location.pathname.split("/").pop()}`
+        );
+      },
+      "script-2.js": () => {
+        browser.test.sendMessage(
+          `script-2 executed in ${location.pathname.split("/").pop()}`
+        );
+      },
+      "script-3.js": () => {
+        browser.test.sendMessage(
+          `script-3 executed in ${location.pathname.split("/").pop()}`
+        );
+      },
+      "script-4.js": () => {
+        browser.test.sendMessage(
+          `script-4 executed in ${location.pathname.split("/").pop()}`
+        );
+      },
+      "style.css": "body { background-color: rgb(0, 255, 0); }",
+      "script-check-style.js": () => {
+        browser.test.assertEq(
+          "rgb(0, 255, 0)",
+          getComputedStyle(document.querySelector('body')).backgroundColor,
+          "expected background color"
+        );
+        browser.test.sendMessage(
+          `script-check-style executed in ${location.pathname.split("/").pop()}`
+        );
+      },
+    },
+  });
+
+  const SCRIPT_ID = "script-to-update";
+  const TEST_PAGE = "https://test1.example.com/tests/toolkit/components/extensions/test/mochitest/file_contains_iframe.html";
+
+  const runTestCase = async ({
+    title,
+      updateContentScriptsParams,
+      expectedRegisteredContentScript,
+      expectedMessages
+  }) => {
+    // Register content script and verify results.
+    extension.sendMessage("updateContentScripts", {
+      title,
+      updateContentScriptsParams,
+      expectedRegisteredContentScript,
+    });
+    await extension.awaitMessage("updateContentScripts-done");
+
+    let tab = await AppTestDelegate.openNewForegroundTab(
+      window,
+      TEST_PAGE,
+      true
+    );
+
+    await Promise.all(expectedMessages.map(msg => extension.awaitMessage(msg)));
+
+    await AppTestDelegate.removeTab(window, tab);
+  };
+
+  await extension.startup();
+  await extension.awaitMessage("background-ready");
+
+  // Load a page that will trigger the content script initially registered.
+  let tab = await AppTestDelegate.openNewForegroundTab(window, TEST_PAGE, true);
+  await extension.awaitMessage("script-1 executed in file_contains_iframe.html");
+  await AppTestDelegate.removeTab(window, tab);
+
+  // Now, let's update this content script a few times.
+  await runTestCase({
+    title: "update ID only",
+    updateContentScriptsParams: {
+      id: SCRIPT_ID,
+    },
+    expectedRegisteredContentScript: {
+      id: SCRIPT_ID,
+      allFrames: false,
+      matches: ["*://test1.example.com/*"],
+      runAt: "document_idle",
+      persistAcrossSessions: false,
+      js: ["script-1.js"],
+    },
+    expectedMessages: ["script-1 executed in file_contains_iframe.html"],
+  });
+
+  await runTestCase({
+    title: "update js",
+    updateContentScriptsParams: {
+      id: SCRIPT_ID,
+      js: ["script-2.js"],
+    },
+    expectedRegisteredContentScript: {
+      id: SCRIPT_ID,
+      allFrames: false,
+      matches: ["*://test1.example.com/*"],
+      runAt: "document_idle",
+      persistAcrossSessions: false,
+      js: ["script-2.js"],
+    },
+    expectedMessages: ["script-2 executed in file_contains_iframe.html"],
+  });
+
+  await runTestCase({
+    title: "update allFrames and matches",
+    updateContentScriptsParams: {
+      id: SCRIPT_ID,
+      matches: [
+        "*://test1.example.com/*",
+        "*://example.org/*",
+      ],
+      allFrames: true,
+    },
+    expectedRegisteredContentScript: {
+      id: SCRIPT_ID,
+      allFrames: true,
+      matches: [
+        "*://test1.example.com/*",
+        "*://example.org/*",
+      ],
+      runAt: "document_idle",
+      persistAcrossSessions: false,
+      js: ["script-2.js"],
+    },
+    expectedMessages: [
+      "script-2 executed in file_contains_iframe.html",
+      "script-2 executed in file_contains_img.html",
+    ],
+  });
+
+  await runTestCase({
+    title: "update excludeMatches and js",
+    updateContentScriptsParams: {
+      id: SCRIPT_ID,
+      js: ["script-3.js"],
+      excludeMatches: ["*://test1.example.com/*"],
+      allFrames: true,
+    },
+    expectedRegisteredContentScript: {
+      id: SCRIPT_ID,
+      allFrames: true,
+      matches: [
+        "*://test1.example.com/*",
+        "*://example.org/*",
+      ],
+      runAt: "document_idle",
+      persistAcrossSessions: false,
+      excludeMatches: ["*://test1.example.com/*"],
+      js: ["script-3.js"],
+    },
+    expectedMessages: [
+      "script-3 executed in file_contains_img.html",
+    ],
+  });
+
+  await runTestCase({
+    title: "update allFrames, excludeMatches, js and runAt",
+    updateContentScriptsParams: {
+      id: SCRIPT_ID,
+      allFrames: false,
+      excludeMatches: [],
+      js: ["script-4.js"],
+      runAt: "document_start",
+    },
+    expectedRegisteredContentScript: {
+      id: SCRIPT_ID,
+      allFrames: false,
+      matches: [
+        "*://test1.example.com/*",
+        "*://example.org/*",
+      ],
+      runAt: "document_start",
+      persistAcrossSessions: false,
+      js: ["script-4.js"],
+    },
+    expectedMessages: [
+      "script-4 executed in file_contains_iframe.html",
+    ],
+  });
+
+  await runTestCase({
+    title: "update allFrames, css, js and runAt",
+    updateContentScriptsParams: {
+      id: SCRIPT_ID,
+      allFrames: true,
+      css: ["style.css"],
+      js: ["script-check-style.js"],
+      runAt: "document_idle",
+    },
+    expectedRegisteredContentScript: {
+      id: SCRIPT_ID,
+      allFrames: true,
+      matches: [
+        "*://test1.example.com/*",
+        "*://example.org/*",
+      ],
+      runAt: "document_idle",
+      persistAcrossSessions: false,
+      css: ["style.css"],
+      js: ["script-check-style.js"],
+    },
+    expectedMessages: [
+      "script-check-style executed in file_contains_iframe.html",
+      "script-check-style executed in file_contains_img.html",
+    ],
+  });
+
+  await extension.unload();
+});
+
+</script>
+
+</body>
+</html>
diff --git a/toolkit/components/extensions/test/mochitest/test_ext_scripting_executeScript.html b/toolkit/components/extensions/test/mochitest/test_ext_scripting_executeScript.html
new file mode 100644
index 0000000000..a2d741606f
--- /dev/null
+++ b/toolkit/components/extensions/test/mochitest/test_ext_scripting_executeScript.html
@@ -0,0 +1,1479 @@
+<!DOCTYPE HTML>
+<html>
+<head>
+  <meta charset="utf-8">
+  <title>Tests scripting.executeScript()</title>
+  <script type="text/javascript" src="/tests/SimpleTest/SimpleTest.js"></script>
+  <script type="text/javascript" src="/tests/SimpleTest/ExtensionTestUtils.js"></script>
+  <script type="text/javascript" src="head.js"></script>
+  <link rel="stylesheet" href="/tests/SimpleTest/test.css"/>
+</head>
+<body>
+
+<iframe src="https://example.com/tests/toolkit/components/extensions/test/mochitest/file_sample.html"></iframe>
+
+<script type="text/javascript">
+
+"use strict";
+
+const MOCHITEST_HOST_PERMISSIONS = [
+  "*://mochi.test/",
+  "*://mochi.xorigin-test/",
+  "*://test1.example.com/",
+];
+
+const makeExtension = ({ manifest: manifestProps, ...otherProps }) => {
+  return ExtensionTestUtils.loadExtension({
+    manifest: {
+      manifest_version: 3,
+      permissions: ["scripting"],
+      host_permissions: [
+        ...MOCHITEST_HOST_PERMISSIONS,
+        "https://example.com/",
+        // Used in `file_contains_iframe.html`
+        "https://example.org/",
+      ],
+      granted_host_permissions: true,
+      ...manifestProps,
+    },
+    useAddonManager: "temporary",
+    ...otherProps,
+  });
+};
+
+add_task(async function setup() {
+  await SpecialPowers.pushPrefEnv({
+    set: [["extensions.manifestV3.enabled", true]],
+  });
+});
+
+add_task(async function test_executeScript_params_validation() {
+  let extension = makeExtension({
+    async background() {
+      const tabs = await browser.tabs.query({ active: true });
+      const tabId = tabs[0].id;
+
+      const TEST_CASES = [
+        {
+          title: "no files and no func",
+          executeScriptParams: {},
+          expectedError: /Exactly one of files and func must be specified/,
+        },
+        {
+          title: "both files and func are passed",
+          executeScriptParams: { files: ["script.js"], func() {} },
+          expectedError: /Exactly one of files and func must be specified/,
+        },
+        {
+          title: "non-empty args is passed with files",
+          executeScriptParams: { files: ["script.js"], args: [123] },
+          expectedError: /'args' may not be used with file injections/,
+        },
+        {
+          title: "empty args is passed with files",
+          executeScriptParams: { files: ["script.js"], args: [] },
+          expectedError: /'args' may not be used with file injections/,
+        },
+        {
+          title: "unserializable argument",
+          executeScriptParams: { func() {}, args: [window] },
+          expectedError: /Unserializable arguments/,
+        },
+        {
+          title: "both allFrames and frameIds are passed",
+          executeScriptParams: {
+            target: {
+              tabId,
+              allFrames: true,
+              frameIds: [1, 2, 3],
+            },
+            files: ["script.js"],
+          },
+          expectedError: /Cannot specify both 'allFrames' and 'frameIds'/,
+        },
+        {
+          title: "invalid IDs in frameIds",
+          executeScriptParams: {
+            target: { tabId, frameIds: [0, 1, 2] },
+            func: () => {},
+          },
+          expectedError: "Invalid frame IDs: [1, 2].",
+        },
+        {
+          title: "throw non-structurally cloneable data in all frames",
+          executeScriptParams: {
+            target: {
+              tabId,
+              allFrames: true,
+            },
+            func: () => {
+              throw window;
+            },
+          },
+          expectedError: /Script '<anonymous code>' result is non-structured-clonable data/,
+        },
+      ];
+
+      for (const { title, executeScriptParams, expectedError } of TEST_CASES) {
+        await browser.test.assertRejects(
+          browser.scripting.executeScript({
+            target: { tabId: tabs[0].id },
+            ...executeScriptParams,
+          }),
+          expectedError,
+          `expected error when: ${title}`
+        );
+      }
+
+      browser.test.notifyPass("execute-script");
+    },
+  });
+
+  await extension.startup();
+  await extension.awaitFinish("execute-script");
+  await extension.unload();
+});
+
+add_task(async function test_executeScript_main_world() {
+  let extension = makeExtension({
+    async background() {
+      browser.test.assertThrows(
+        () => {
+          browser.scripting.executeScript({
+            target: { tabId: 123 },
+            func: () => {},
+            world: "MAIN",
+          });
+        },
+        /world: Invalid enumeration value "MAIN"/,
+        "expected 'MAIN' world to not be supported yet"
+      );
+
+      browser.test.notifyPass("background-done");
+    },
+  });
+
+  await extension.startup();
+  await extension.awaitFinish("background-done");
+  await extension.unload();
+});
+
+add_task(async function test_executeScript_isolated_world() {
+  let extension = makeExtension({
+    manifest: {
+      browser_specific_settings: {
+        gecko: { id: "@isolated-addon-id" },
+      },
+    },
+    async background() {
+      const tabs = await browser.tabs.query({ active: true });
+      browser.test.assertEq(1, tabs.length, "expected 1 tab");
+
+      let results = await browser.scripting.executeScript({
+        target: { tabId: tabs[0].id },
+        func: () => {
+          globalThis.defaultWorldVar = browser.runtime.id;
+          return "default world";
+        },
+      });
+
+      browser.test.assertEq(
+        1,
+        results.length,
+        "got expected number of results"
+      );
+      browser.test.assertEq(
+        "default world",
+        results[0].result,
+        "got expected return value"
+      );
+
+      results = await browser.scripting.executeScript({
+        target: { tabId: tabs[0].id },
+        func: () => {
+          return `isolated: ${browser.runtime.id}; existing default var: ${typeof defaultWorldVar}`;
+        },
+        world: "ISOLATED",
+      });
+
+      browser.test.assertEq(
+        1,
+        results.length,
+        "got expected number of results"
+      );
+      browser.test.assertEq(
+        "isolated: @isolated-addon-id; existing default var: string",
+        results[0].result,
+        "got expected return value"
+      );
+
+      browser.test.notifyPass("execute-script");
+    },
+  });
+
+  let tab = await AppTestDelegate.openNewForegroundTab(
+    window,
+    "https://test1.example.com/tests/toolkit/components/extensions/test/mochitest/file_sample.html",
+    true
+  );
+
+  await extension.startup();
+  await extension.awaitFinish("execute-script");
+  await extension.unload();
+
+  await AppTestDelegate.removeTab(window, tab);
+});
+
+add_task(async function test_execution_world_constants() {
+  let extension = makeExtension({
+    async background() {
+      browser.test.assertTrue(
+        !!browser.scripting.ExecutionWorld,
+        "expected scripting.ExecutionWorld to be defined"
+      );
+      browser.test.assertEq(
+        1,
+        Object.keys(browser.scripting.ExecutionWorld).length,
+        "expected 1 ExecutionWorld constant"
+      );
+      browser.test.assertEq(
+        "ISOLATED",
+        browser.scripting.ExecutionWorld.ISOLATED,
+        "expected ISOLATED constant to be defined"
+      );
+      // TODO: Bug 1736575 - Add support for other execution worlds like MAIN.
+      browser.test.assertEq(
+        undefined,
+        browser.scripting.ExecutionWorld.MAIN,
+        "expected MAIN constant to be undefined"
+      );
+
+      browser.test.notifyPass("background-done");
+    },
+  });
+
+  await extension.startup();
+  await extension.awaitFinish("background-done");
+  await extension.unload();
+});
+
+add_task(async function test_executeScript_with_wrong_host_permissions() {
+  let extension = makeExtension({
+    manifest: {
+      host_permissions: [],
+    },
+    async background() {
+      const tabs = await browser.tabs.query({ active: true });
+
+      browser.test.assertEq(1, tabs.length, "expected 1 tab");
+
+      await browser.test.assertRejects(
+        browser.scripting.executeScript({
+          target: { tabId: tabs[0].id },
+          func: () => {
+            browser.test.fail("Unexpected execution");
+          },
+        }),
+        "Missing host permission for the tab",
+        "expected host permission error"
+      );
+
+      browser.test.notifyPass("execute-script");
+    },
+  });
+
+  await extension.startup();
+  await extension.awaitFinish("execute-script");
+  await extension.unload();
+});
+
+add_task(async function test_executeScript_with_invalid_tabId() {
+  let extension = makeExtension({
+    async background() {
+      // This tab ID should not exist.
+      const tabId = 123456789;
+
+      await browser.test.assertRejects(
+        browser.scripting.executeScript({
+          target: { tabId },
+          func: () => {
+            browser.test.fail("Unexpected execution");
+          },
+        }),
+        `Invalid tab ID: ${tabId}`
+      );
+
+      browser.test.notifyPass("execute-script");
+    },
+  });
+
+  await extension.startup();
+  await extension.awaitFinish("execute-script");
+  await extension.unload();
+});
+
+add_task(async function test_executeScript_with_func() {
+  let extension = makeExtension({
+    async background() {
+      const getTitle = () => {
+        return document.title;
+      };
+
+      const tabs = await browser.tabs.query({ active: true });
+
+      browser.test.assertEq(1, tabs.length, "expected 1 tab");
+
+      const results = await browser.scripting.executeScript({
+        target: { tabId: tabs[0].id },
+        func: getTitle,
+      });
+
+      browser.test.assertEq(
+        1,
+        results.length,
+        "got expected number of results"
+      );
+      browser.test.assertEq(
+        "file sample",
+        results[0].result,
+        "got the expected title"
+      );
+      browser.test.assertEq(0, results[0].frameId, "got the expected frameId");
+
+      browser.test.notifyPass("execute-script");
+    },
+  });
+
+  let tab = await AppTestDelegate.openNewForegroundTab(
+    window,
+    "https://test1.example.com/tests/toolkit/components/extensions/test/mochitest/file_sample.html",
+    true
+  );
+
+  await extension.startup();
+  await extension.awaitFinish("execute-script");
+  await extension.unload();
+
+  await AppTestDelegate.removeTab(window, tab);
+});
+
+add_task(async function test_executeScript_with_func_and_args() {
+  let extension = makeExtension({
+    async background() {
+      const formatArgs = (a, b, c) => {
+        return `received ${a}, ${b} and ${c}`;
+      };
+
+      const tabs = await browser.tabs.query({ active: true });
+
+      browser.test.assertEq(1, tabs.length, "expected 1 tab");
+
+      const results = await browser.scripting.executeScript({
+        target: { tabId: tabs[0].id },
+        func: formatArgs,
+        args: [true, undefined, "str"],
+      });
+
+      browser.test.assertEq(
+        1,
+        results.length,
+        "got expected number of results"
+      );
+      browser.test.assertEq(
+        // undefined is converted to null when json-stringified in an array.
+        "received true, null and str",
+        results[0].result,
+        "got the expected return value"
+      );
+      browser.test.assertEq(0, results[0].frameId, "got the expected frameId");
+
+      browser.test.notifyPass("execute-script");
+    },
+  });
+
+  await extension.startup();
+  await extension.awaitFinish("execute-script");
+  await extension.unload();
+});
+
+add_task(async function test_executeScript_returns_nothing() {
+  let extension = makeExtension({
+    async background() {
+      const tabs = await browser.tabs.query({ active: true });
+
+      browser.test.assertEq(1, tabs.length, "expected 1 tab");
+
+      const results = await browser.scripting.executeScript({
+        target: { tabId: tabs[0].id },
+        func: () => {},
+      });
+
+      browser.test.assertEq(
+        1,
+        results.length,
+        "got expected number of results"
+      );
+      browser.test.assertEq(
+        undefined,
+        results[0].result,
+        "got expected undefined result"
+      );
+      browser.test.assertEq(0, results[0].frameId, "got the expected frameId");
+
+      browser.test.notifyPass("execute-script");
+    },
+  });
+
+  await extension.startup();
+  await extension.awaitFinish("execute-script");
+  await extension.unload();
+});
+
+add_task(async function test_executeScript_returns_null() {
+  let extension = makeExtension({
+    async background() {
+      const tabs = await browser.tabs.query({ active: true });
+
+      browser.test.assertEq(1, tabs.length, "expected 1 tab");
+
+      const results = await browser.scripting.executeScript({
+        target: { tabId: tabs[0].id },
+        func: () => {
+          return null;
+        },
+      });
+
+      browser.test.assertEq(
+        1,
+        results.length,
+        "got expected number of results"
+      );
+      browser.test.assertEq(
+        null,
+        results[0].result,
+        "got expected null result"
+      );
+      browser.test.assertEq(0, results[0].frameId, "got the expected frameId");
+
+      browser.test.notifyPass("execute-script");
+    },
+  });
+
+  await extension.startup();
+  await extension.awaitFinish("execute-script");
+  await extension.unload();
+});
+
+add_task(async function test_executeScript_with_error_in_func() {
+  let extension = makeExtension({
+    async background() {
+      const tabs = await browser.tabs.query({ active: true });
+
+      browser.test.assertEq(1, tabs.length, "expected 1 tab");
+
+      const results = await browser.scripting.executeScript({
+        target: { tabId: tabs[0].id },
+        func: () => {
+          throw new Error(`Thrown at ${location.pathname.split("/").pop()}`);
+        },
+      });
+
+      browser.test.assertEq(
+        1,
+        results.length,
+        "got expected number of results"
+      );
+      browser.test.assertEq(0, results[0].frameId, "got the expected frameId");
+      browser.test.assertEq(
+        "Thrown at file_sample.html",
+        results[0].error.message,
+        "got the expected error message"
+      );
+
+      browser.test.notifyPass("execute-script");
+    },
+  });
+
+  let tab = await AppTestDelegate.openNewForegroundTab(
+    window,
+    "https://test1.example.com/tests/toolkit/components/extensions/test/mochitest/file_sample.html",
+    true
+  );
+
+  await extension.startup();
+  await extension.awaitFinish("execute-script");
+  await extension.unload();
+
+  await AppTestDelegate.removeTab(window, tab);
+});
+
+add_task(async function test_executeScript_with_a_file() {
+  let extension = makeExtension({
+    async background() {
+      const tabs = await browser.tabs.query({ active: true });
+
+      browser.test.assertEq(1, tabs.length, "expected 1 tab");
+
+      const results = await browser.scripting.executeScript({
+        target: { tabId: tabs[0].id },
+        files: ["script.js"],
+      });
+
+      browser.test.assertEq(
+        1,
+        results.length,
+        "got expected number of results"
+      );
+      browser.test.assertEq(
+        "value from script.js",
+        results[0].result,
+        "got the expected result"
+      );
+      browser.test.assertEq(0, results[0].frameId, "got the expected frameId");
+
+      browser.test.notifyPass("execute-script");
+    },
+    files: {
+      "script.js": function() {
+        return "value from script.js";
+      },
+    },
+  });
+
+  await extension.startup();
+  await extension.awaitFinish("execute-script");
+  await extension.unload();
+});
+
+add_task(async function test_executeScript_in_one_frame() {
+  let extension = makeExtension({
+    manifest: {
+      permissions: ["scripting", "webNavigation"],
+    },
+    async background() {
+      const tabs = await browser.tabs.query({ active: true });
+      browser.test.assertEq(1, tabs.length, "expected 1 tab");
+
+      const tabId = tabs[0].id;
+      const frames = await browser.webNavigation.getAllFrames({ tabId });
+      // 1. Top-level frame with the MochiTest runner
+      // 2. Frame for this file
+      // 3. Frame that loads `file_sample.html` at the top of this file
+      browser.test.assertEq(3, frames.length, "expected 3 frames");
+
+      const fileSampleFrameId = frames[2].frameId;
+      browser.test.assertTrue(
+        frames[2].url.includes("file_sample.html"),
+        "expected frame URL"
+      );
+
+      const TEST_CASES = [
+        {
+          title: "with a file and a frame ID",
+          params: {
+            target: { tabId, frameIds: [fileSampleFrameId] },
+            files: ["script.js"],
+          },
+          expectedResults: [
+            {
+              frameId: fileSampleFrameId,
+              result: "Sample text",
+            },
+          ],
+        },
+        {
+          title: "with no frame ID",
+          params: {
+            target: { tabId },
+            func: () => {
+              return 123;
+            },
+          },
+          expectedResults: [{ frameId: 0, result: 123 }],
+        },
+      ];
+
+      for (const { title, params, expectedResults } of TEST_CASES) {
+        const results = await browser.scripting.executeScript(params);
+
+        browser.test.assertEq(
+          expectedResults.length,
+          results.length,
+          `${title} - got expected number of results`
+        );
+        expectedResults.forEach(({ frameId, result }, index) => {
+          browser.test.assertEq(
+            result,
+            results[index].result,
+            `${title} - got the expected results[${index}].result`
+          );
+          browser.test.assertEq(
+            frameId,
+            results[index].frameId,
+            `${title} - got the expected results[${index}].frameId`
+          );
+        });
+      }
+
+      browser.test.notifyPass("execute-script");
+    },
+    files: {
+      "script.js": function() {
+        return document.getElementById("test").textContent;
+      },
+    },
+  });
+
+  await extension.startup();
+  await extension.awaitFinish("execute-script");
+  await extension.unload();
+});
+
+add_task(async function test_executeScript_in_multiple_frameIds() {
+  let extension = makeExtension({
+    manifest: {
+      permissions: ["scripting", "webNavigation"],
+    },
+    async background() {
+      const tabs = await browser.tabs.query({ active: true });
+      browser.test.assertEq(1, tabs.length, "expected 1 tab");
+
+      const tabId = tabs[0].id;
+      const frames = await browser.webNavigation.getAllFrames({ tabId });
+      // 1. Top-level frame that loads `file_contains_iframe.html`
+      // 2. Frame that loads `file_contains_img.html`
+      browser.test.assertEq(2, frames.length, "expected 2 frames");
+
+      const frameIds = frames.map(frame => frame.frameId);
+
+      const getTitle = () => {
+        return document.title;
+      };
+
+      const TEST_CASES = [
+        {
+          title: "multiple frame IDs",
+          params: {
+            target: { tabId, frameIds },
+            func: getTitle,
+          },
+          expectedResults: [
+            {
+              frameId: frameIds[0],
+              result: "file contains iframe",
+            },
+            {
+              frameId: frameIds[1],
+              result: "file contains img",
+            },
+          ],
+        },
+        {
+          title: "empty list of frame IDs",
+          params: {
+            target: { tabId, frameIds: [] },
+            func: getTitle,
+          },
+          expectedResults: [],
+        },
+      ];
+
+      for (const { title, params, expectedResults } of TEST_CASES) {
+        const results = await browser.scripting.executeScript(params);
+
+        browser.test.assertEq(
+          expectedResults.length,
+          results.length,
+          `${title} - got expected number of results`
+        );
+        // Sort injection results by frameId to always assert the results in
+        // the same order.
+        results.sort((a, b) => a.frameId - b.frameId);
+
+        browser.test.assertEq(
+          JSON.stringify(expectedResults),
+          JSON.stringify(results),
+          `${title} - got expected results`
+        );
+      }
+
+      browser.test.notifyPass("execute-script");
+    },
+  });
+
+  let tab = await AppTestDelegate.openNewForegroundTab(
+    window,
+    "https://test1.example.com/tests/toolkit/components/extensions/test/mochitest/file_contains_iframe.html",
+    true
+  );
+
+  await extension.startup();
+  await extension.awaitFinish("execute-script");
+  await extension.unload();
+
+  await AppTestDelegate.removeTab(window, tab);
+});
+
+add_task(async function test_executeScript_with_errors_in_multiple_frameIds() {
+  let extension = makeExtension({
+    manifest: {
+      permissions: ["scripting", "webNavigation"],
+    },
+    async background() {
+      const tabs = await browser.tabs.query({ active: true });
+      browser.test.assertEq(1, tabs.length, "expected 1 tab");
+
+      const tabId = tabs[0].id;
+      const frames = await browser.webNavigation.getAllFrames({ tabId });
+      // 1. Top-level frame that loads `file_contains_iframe.html`
+      // 2. Frame that loads `file_contains_img.html`
+      browser.test.assertEq(2, frames.length, "expected 2 frames");
+
+      const frameIds = frames.map(frame => frame.frameId);
+
+      const results = await browser.scripting.executeScript({
+        target: { tabId, frameIds },
+        func: () => {
+          throw new Error(`Thrown at ${location.pathname.split("/").pop()}`);
+        },
+      });
+
+      browser.test.assertEq(
+        2,
+        results.length,
+        "got expected number of results"
+      );
+      browser.test.assertEq(
+        "Thrown at file_contains_iframe.html",
+        results[0].error.message,
+        "got expected error message in results[0]"
+      );
+      browser.test.assertEq(
+        "Thrown at file_contains_img.html",
+        results[1].error.message,
+        "got expected error message in results[1]"
+      );
+
+      browser.test.notifyPass("execute-script");
+    },
+  });
+
+  let tab = await AppTestDelegate.openNewForegroundTab(
+    window,
+    "https://test1.example.com/tests/toolkit/components/extensions/test/mochitest/file_contains_iframe.html",
+    true
+  );
+
+  await extension.startup();
+  await extension.awaitFinish("execute-script");
+  await extension.unload();
+
+  await AppTestDelegate.removeTab(window, tab);
+});
+
+add_task(async function test_executeScript_with_frameId_and_wrong_host_permission() {
+  let extension = makeExtension({
+    manifest: {
+      host_permissions: MOCHITEST_HOST_PERMISSIONS,
+      permissions: ["scripting", "webNavigation"],
+    },
+    async background() {
+      const tabs = await browser.tabs.query({ active: true });
+      browser.test.assertEq(1, tabs.length, "expected 1 tab");
+
+      const tabId = tabs[0].id;
+      const frames = await browser.webNavigation.getAllFrames({ tabId });
+      // 1. Top-level frame with the MochiTest runner
+      // 2. Frame for this file
+      // 3. Frame that loads `file_sample.html` at the top of this file
+      browser.test.assertEq(3, frames.length, "expected 3 frames");
+
+      const frameIds = frames.map(frame => frame.frameId);
+
+      await browser.test.assertRejects(
+        browser.scripting.executeScript({
+          target: { tabId, frameIds: [frameIds[2]] },
+          func: () => {
+            browser.test.fail("Unexpected execution");
+          },
+        }),
+        "Missing host permission for the tab or frames",
+        "got the expected error message"
+      );
+
+      browser.test.notifyPass("execute-script");
+    },
+  });
+
+  await extension.startup();
+  await extension.awaitFinish("execute-script");
+  await extension.unload();
+});
+
+add_task(async function test_executeScript_with_multiple_frameIds_and_wrong_host_permissions() {
+  let extension = makeExtension({
+    manifest: {
+      host_permissions: MOCHITEST_HOST_PERMISSIONS,
+      permissions: ["scripting", "webNavigation"],
+    },
+    async background() {
+      const tabs = await browser.tabs.query({ active: true });
+      browser.test.assertEq(1, tabs.length, "expected 1 tab");
+
+      const tabId = tabs[0].id;
+      const frames = await browser.webNavigation.getAllFrames({ tabId });
+      // 1. Top-level frame with the MochiTest runner
+      // 2. Frame for this file
+      // 3. Frame that loads `file_sample.html` at the top of this file
+      browser.test.assertEq(3, frames.length, "expected 3 frames");
+
+      const frameIds = frames.map(frame => frame.frameId);
+
+      const results = await browser.scripting.executeScript({
+        target: { tabId, frameIds },
+        func: () => {},
+      });
+
+      // We get 2 results because we cannot inject into the 3rd frame.
+      browser.test.assertEq(
+        2,
+        results.length,
+        "got expected number of results"
+      );
+      browser.test.assertTrue(
+        typeof results[0].error === "undefined",
+        "expected no error in results[0]"
+      );
+      browser.test.assertTrue(
+        typeof results[1].error === "undefined",
+        "expected no error in results[1]"
+      );
+
+      browser.test.notifyPass("execute-script");
+    },
+  });
+
+  await extension.startup();
+  await extension.awaitFinish("execute-script");
+  await extension.unload();
+});
+
+add_task(async function test_executeScript_with_iframe_srcdoc_and_aboutblank() {
+  let iframe = document.createElement("iframe");
+  iframe.srcdoc = `<!DOCTYPE html>
+    <html>
+      <head><title>iframe with srcdoc</title></head>
+    </html>`;
+  await new Promise(resolve => {
+    iframe.onload = resolve;
+    document.body.appendChild(iframe);
+  });
+
+  let iframeAboutBlank = document.createElement("iframe");
+  iframeAboutBlank.src = "about:blank";
+  await new Promise(resolve => {
+    iframeAboutBlank.onload = resolve;
+    document.body.appendChild(iframeAboutBlank);
+  });
+
+  let extension = makeExtension({
+    manifest: {
+      permissions: ["scripting", "webNavigation"],
+    },
+    async background() {
+      const tabs = await browser.tabs.query({ active: true });
+      browser.test.assertEq(1, tabs.length, "expected 1 tab");
+
+      const tabId = tabs[0].id;
+      const frames = await browser.webNavigation.getAllFrames({ tabId });
+      // 1. Top-level frame with the MochiTest runner
+      // 2. Frame for this file
+      // 3. Frame that loads `file_sample.html` at the top of this file
+      // 4. Frame that loads the `srcdoc`
+      // 5. Frame for `about:blank`
+      browser.test.assertEq(5, frames.length, "expected 5 frames");
+
+      const frameIds = frames.map(frame => frame.frameId);
+
+      const TEST_CASES = [
+        {
+          title: "with frameIds for all frames",
+          params: {
+            target: { tabId, frameIds },
+          },
+          expectedResults: {
+            count: 5,
+            entriesAtIndex: {
+              3: {
+                frameId: frameIds[3],
+                result: "iframe with srcdoc",
+              },
+              4: {
+                frameId: frameIds[4],
+                result: "about:blank",
+              },
+            },
+          },
+        },
+        {
+          title: "with allFrames: true",
+          params: {
+            target: { tabId, allFrames: true },
+          },
+          expectedResults: {
+            count: 5,
+            entriesAtIndex: {
+              3: {
+                frameId: frameIds[3],
+                result: "iframe with srcdoc",
+              },
+              4: {
+                frameId: frameIds[4],
+                result: "about:blank",
+              },
+            },
+          },
+        },
+        {
+          title: "with a single frame specified",
+          params: {
+            target: { tabId, frameIds: [frameIds[3]] },
+          },
+          expectedResults: {
+            count: 1,
+            entriesAtIndex: {
+              0: {
+                frameId: frameIds[3],
+                result: "iframe with srcdoc",
+              },
+            },
+          },
+        },
+      ];
+
+      for (const { title, params, expectedResults } of TEST_CASES) {
+        const results = await browser.scripting.executeScript({
+          ...params,
+          func: () => {
+            return document.title || document.URL;
+          },
+        });
+        // Sort injection results by frameId to always assert the results in
+        // the same order.
+        results.sort((a, b) => a.frameId - b.frameId);
+
+        browser.test.assertEq(
+          expectedResults.count,
+          results.length,
+          `${title} - got the expected number of results`
+        );
+        Object.keys(expectedResults.entriesAtIndex).forEach(index => {
+          browser.test.assertEq(
+            JSON.stringify(expectedResults.entriesAtIndex[index]),
+            JSON.stringify(results[index]),
+            `${title} - got expected results[${index}]`
+          );
+        });
+      }
+
+      browser.test.notifyPass("execute-script");
+    },
+  });
+
+  await extension.startup();
+  await extension.awaitFinish("execute-script");
+  await extension.unload();
+
+  iframe.remove();
+  iframeAboutBlank.remove();
+});
+
+add_task(async function test_executeScript_with_multiple_files() {
+  let extension = makeExtension({
+    async background() {
+      const tabs = await browser.tabs.query({ active: true });
+
+      browser.test.assertEq(1, tabs.length, "expected 1 tab");
+
+      const results = await browser.scripting.executeScript({
+        target: { tabId: tabs[0].id },
+        files: ["1.js", "2.js"],
+      });
+
+      browser.test.assertEq(
+        1,
+        results.length,
+        "got expected number of results"
+      );
+      browser.test.assertEq(
+        "value from 2.js",
+        results[0].result,
+        "got the expected result"
+      );
+      browser.test.assertEq(0, results[0].frameId, "got the expected frameId");
+
+      browser.test.notifyPass("execute-script");
+    },
+    files: {
+      "1.js": function() {
+        return "value from 1.js";
+      },
+      "2.js": function() {
+        return "value from 2.js";
+      },
+    },
+  });
+
+  await extension.startup();
+  await extension.awaitFinish("execute-script");
+  await extension.unload();
+});
+
+add_task(async function test_executeScript_with_multiple_files_and_an_error() {
+  let tab = await AppTestDelegate.openNewForegroundTab(
+    window,
+    "https://test1.example.com/tests/toolkit/components/extensions/test/mochitest/file_contains_iframe.html",
+    true
+  );
+
+  let extension = makeExtension({
+    async background() {
+      const tabs = await browser.tabs.query({ active: true });
+
+      browser.test.assertEq(1, tabs.length, "expected 1 tab");
+
+      const results = await browser.scripting.executeScript({
+        target: { tabId: tabs[0].id },
+        files: ["1.js", "2.js"],
+      });
+
+      browser.test.assertEq(
+        1,
+        results.length,
+        "got expected number of results"
+      );
+      browser.test.assertEq(0, results[0].frameId, "got the expected frameId");
+      browser.test.assertEq(
+        "Thrown at file_contains_iframe.html",
+        results[0].error.message,
+        "got the expected error message"
+      );
+
+      browser.test.notifyPass("execute-script");
+    },
+    files: {
+      "1.js": function() {
+        throw new Error(`Thrown at ${location.pathname.split("/").pop()}`);
+      },
+      "2.js": function() {
+        return "value from 2.js";
+      },
+    },
+  });
+
+  await extension.startup();
+  await extension.awaitFinish("execute-script");
+  await extension.unload();
+
+  await AppTestDelegate.removeTab(window, tab);
+});
+
+add_task(async function test_executeScript_with_file_not_in_extension() {
+  let tab = await AppTestDelegate.openNewForegroundTab(
+    window,
+    "https://test1.example.com/tests/toolkit/components/extensions/test/mochitest/file_contains_iframe.html",
+    true
+  );
+
+  let extension = makeExtension({
+    async background() {
+      const tabs = await browser.tabs.query({ active: true });
+
+      browser.test.assertEq(1, tabs.length, "expected 1 tab");
+
+      await browser.test.assertRejects(
+        browser.scripting.executeScript({
+          target: { tabId: tabs[0].id },
+          files: ["https://example.com/script.js"],
+        }),
+        /Files to be injected must be within the extension/,
+        "got the expected error message"
+      );
+
+      browser.test.notifyPass("execute-script");
+    },
+  });
+
+  await extension.startup();
+  await extension.awaitFinish("execute-script");
+  await extension.unload();
+
+  await AppTestDelegate.removeTab(window, tab);
+});
+
+add_task(async function test_executeScript_allFrames() {
+  let extension = makeExtension({
+    manifest: {
+      permissions: ["scripting", "webNavigation"],
+    },
+    async background() {
+      const tabs = await browser.tabs.query({ active: true });
+      browser.test.assertEq(1, tabs.length, "expected 1 tab");
+
+      const tabId = tabs[0].id;
+      const frames = await browser.webNavigation.getAllFrames({ tabId });
+      // 1. Top-level frame that loads `file_contains_iframe.html`
+      // 2. Frame that loads `file_contains_img.html`
+      browser.test.assertEq(2, frames.length, "expected 2 frames");
+      const frameIds = frames.map(frame => frame.frameId);
+
+      const getTitle = () => {
+        return document.title;
+      };
+
+      const TEST_CASES = [
+        {
+          title: "allFrames set to true",
+          scriptingParams: {
+            target: { tabId, allFrames: true },
+            func: getTitle,
+          },
+          expectedResults: [
+            {
+              frameId: frameIds[0],
+              result: "file contains iframe",
+            },
+            {
+              frameId: frameIds[1],
+              result: "file contains img",
+            },
+          ],
+        },
+        {
+          title: "allFrames set to false",
+          scriptingParams: {
+            target: { tabId, allFrames: false },
+            func: getTitle,
+          },
+          expectedResults: [
+            {
+              frameId: frameIds[0],
+              result: "file contains iframe",
+            },
+          ],
+        },
+      ];
+
+      for (const { title, scriptingParams, expectedResults } of TEST_CASES) {
+        const results = await browser.scripting.executeScript(scriptingParams);
+        // Sort injection results by frameId to always assert the results in
+        // the same order.
+        results.sort((a, b) => a.frameId - b.frameId);
+
+        browser.test.assertDeepEq(
+          expectedResults,
+          results,
+          `${title} - got expected results`
+        );
+
+        // Make sure the `error` prop is never set.
+        for (const result of results) {
+          browser.test.assertFalse(
+            "error" in result,
+            `${title} - expected error property to be unset`
+          );
+        }
+      }
+
+      browser.test.notifyPass("execute-script");
+    },
+  });
+
+  let tab = await AppTestDelegate.openNewForegroundTab(
+    window,
+    "https://test1.example.com/tests/toolkit/components/extensions/test/mochitest/file_contains_iframe.html",
+    true
+  );
+
+  await extension.startup();
+  await extension.awaitFinish("execute-script");
+  await extension.unload();
+
+  await AppTestDelegate.removeTab(window, tab);
+});
+
+add_task(async function test_executeScript_runtime_errors() {
+  let extension = makeExtension({
+    manifest: {
+      permissions: ["scripting", "webNavigation"],
+    },
+    async background() {
+      const tabs = await browser.tabs.query({ active: true });
+      browser.test.assertEq(1, tabs.length, "expected 1 tab");
+
+      const tabId = tabs[0].id;
+      const frames = await browser.webNavigation.getAllFrames({ tabId });
+      // 1. Top-level frame that loads `file_contains_iframe.html`
+      // 2. Frame that loads `file_contains_img.html`
+      browser.test.assertEq(2, frames.length, "expected 2 frames");
+
+      const TEST_CASES = [
+        {
+          title: "reference error",
+          scriptingParams: {
+            target: { tabId },
+            func: () => {
+              // We do not define `e` on purpose.
+              // eslint-disable-next-line no-undef
+              return String(e);
+            },
+          },
+          expectedErrors: [
+            { type: "Error", stringRepr: "ReferenceError: e is not defined" },
+          ],
+        },
+        {
+          title: "eval error",
+          scriptingParams: {
+            target: { tabId },
+            func: () => {
+              // We use `eval()` on purpose.
+              // eslint-disable-next-line no-eval
+              eval("");
+            },
+          },
+          expectedErrors: [
+            { type: "Error", stringRepr: "EvalError: call to eval() blocked by CSP" },
+          ],
+        },
+        {
+          title: "errors thrown in allFrames",
+          scriptingParams: {
+            target: { tabId, allFrames: true },
+            func: () => {
+              throw new Error(`Thrown at ${location.pathname.split("/").pop()}`);
+            },
+          },
+          expectedErrors: [
+            { type: "Error", stringRepr: "Error: Thrown at file_contains_iframe.html" },
+            { type: "Error", stringRepr: "Error: Thrown at file_contains_img.html" },
+          ],
+        },
+        {
+          title: "custom error",
+          scriptingParams: {
+            target: { tabId },
+            func: () => {
+              class CustomError extends Error {
+                constructor(message) {
+                  super(message);
+
+                  this.name = 'CustomError';
+                }
+              }
+
+              throw new CustomError("a custom error message");
+            },
+          },
+          // See Bug 1556604 for why a custom (derived) error looks like a
+          // normal error object after cloning.
+          expectedErrors: [
+            { type: "Error", stringRepr: "Error: a custom error message" },
+          ],
+        },
+        {
+          title: "promise rejection with a string value",
+          scriptingParams: {
+            target: { tabId },
+            func: () => {
+              // eslint-disable-next-line no-throw-literal
+              throw 'an error message';
+            },
+          },
+          expectedErrors: [
+            { type: "String", stringRepr: "an error message" },
+          ],
+        },
+        {
+          title: "promise rejection with an error",
+          scriptingParams: {
+            target: { tabId },
+            func: () => {
+              throw new Error('ooops');
+            },
+          },
+          expectedErrors: [
+            { type: "Error", stringRepr: "Error: ooops" },
+          ],
+        },
+        {
+          title: "promise rejection with null",
+          scriptingParams: {
+            target: { tabId },
+            func: () => {
+              throw null; // eslint-disable-line no-throw-literal
+            },
+          },
+          expectedErrors: [
+            // This means we would receive `error: null`.
+            { type: "Null", stringRepr: "null" },
+          ],
+        },
+        {
+          title: "promise rejection with undefined",
+          scriptingParams: {
+            target: { tabId },
+            func: () => {
+              return new Promise((resolve, reject) => {
+                reject(undefined);
+              });
+            },
+          },
+          expectedErrors: [
+            // This means we would receive `error: undefined`.
+            { type: "Undefined", stringRepr: "undefined" },
+          ],
+        },
+        {
+          title: "promise rejection with empty string",
+          scriptingParams: {
+            target: { tabId },
+            func: () => {
+              throw ""; // eslint-disable-line no-throw-literal
+            },
+          },
+          expectedErrors: [
+            { type: "String", stringRepr: "" },
+          ],
+        },
+        {
+          title: "promise rejection with zero",
+          scriptingParams: {
+            target: { tabId },
+            func: () => {
+              throw 0; // eslint-disable-line no-throw-literal
+            },
+          },
+          expectedErrors: [
+            { type: "Number", stringRepr: "0" },
+          ],
+        },
+        {
+          title: "promise rejection with false",
+          scriptingParams: {
+            target: { tabId },
+            func: () => {
+              throw false; // eslint-disable-line no-throw-literal
+            },
+          },
+          expectedErrors: [
+            { type: "Boolean", stringRepr: "false" },
+          ],
+        },
+      ];
+
+      for (const { title, scriptingParams, expectedErrors } of TEST_CASES) {
+        const results = await browser.scripting.executeScript(scriptingParams);
+        // Sort injection results by frameId to always assert the results in
+        // the same order.
+        results.sort((a, b) => a.frameId - b.frameId);
+
+        browser.test.assertEq(
+          expectedErrors.length,
+          results.length,
+          `expected ${expectedErrors.length} results`
+        );
+
+        for (const [i, { type, stringRepr }] of expectedErrors.entries()) {
+          browser.test.assertTrue(
+            "error" in results[i],
+            `${title} - expected error property to be set`
+          );
+          browser.test.assertFalse(
+            "result" in results[i],
+            `${title} - expected result property to be unset`
+          );
+
+          const { frameId, error } = results[i];
+
+          browser.test.assertEq(
+            `[object ${type}]`,
+            Object.prototype.toString.call(error),
+            `${title} - expected instance of ${type} - ${frameId}`
+          );
+          browser.test.assertEq(
+            stringRepr,
+            String(error),
+            `${title} - got expected errors - ${frameId}`
+          );
+        }
+      }
+
+      browser.test.notifyPass("execute-script");
+    },
+  });
+
+  let tab = await AppTestDelegate.openNewForegroundTab(
+    window,
+    "https://test1.example.com/tests/toolkit/components/extensions/test/mochitest/file_contains_iframe.html",
+    true
+  );
+
+  await extension.startup();
+  await extension.awaitFinish("execute-script");
+  await extension.unload();
+
+  await AppTestDelegate.removeTab(window, tab);
+});
+
+add_task(
+  async function test_executeScript_with_allFrames_and_wrong_host_permissions() {
+    let extension = makeExtension({
+      manifest: {
+        host_permissions: MOCHITEST_HOST_PERMISSIONS,
+        permissions: ["scripting", "webNavigation"],
+      },
+      async background() {
+        const tabs = await browser.tabs.query({ active: true });
+        browser.test.assertEq(1, tabs.length, "expected 1 tab");
+
+        const tabId = tabs[0].id;
+        const frames = await browser.webNavigation.getAllFrames({ tabId });
+        // 1. Top-level frame with the MochiTest runner
+        // 2. Frame for this file
+        // 3. Frame that loads `file_sample.html` at the top of this file
+        browser.test.assertEq(3, frames.length, "expected 3 frames");
+
+        const results = await browser.scripting.executeScript({
+          target: { tabId, allFrames: true },
+          func: () => {},
+        });
+
+        browser.test.assertEq(
+          2,
+          results.length,
+          "got expected number of results"
+        );
+        browser.test.assertTrue(
+          typeof results[0].error === "undefined",
+          "expected no error in results[0]"
+        );
+        browser.test.assertTrue(
+          typeof results[1].error === "undefined",
+          "expected no error in results[1]"
+        );
+
+        browser.test.notifyPass("execute-script");
+      },
+    });
+
+    await extension.startup();
+    await extension.awaitFinish("execute-script");
+    await extension.unload();
+  }
+);
+
+</script>
+
+</body>
+</html>
diff --git a/toolkit/components/extensions/test/mochitest/test_ext_scripting_executeScript_activeTab.html b/toolkit/components/extensions/test/mochitest/test_ext_scripting_executeScript_activeTab.html
new file mode 100644
index 0000000000..5eb2193409
--- /dev/null
+++ b/toolkit/components/extensions/test/mochitest/test_ext_scripting_executeScript_activeTab.html
@@ -0,0 +1,144 @@
+<!DOCTYPE HTML>
+<html>
+<head>
+  <meta charset="utf-8">
+  <title>Tests scripting.executeScript() and activeTab</title>
+  <script type="text/javascript" src="/tests/SimpleTest/SimpleTest.js"></script>
+  <script type="text/javascript" src="/tests/SimpleTest/ExtensionTestUtils.js"></script>
+  <script type="text/javascript" src="head.js"></script>
+  <link rel="stylesheet" href="/tests/SimpleTest/test.css"/>
+</head>
+<body>
+
+<script type="text/javascript">
+
+"use strict";
+
+const makeExtension = ({ manifest: manifestProps, ...otherProps }) => {
+  return ExtensionTestUtils.loadExtension({
+    manifest: {
+      manifest_version: 3,
+      action: {},
+      ...manifestProps,
+    },
+    ...otherProps,
+  });
+};
+
+add_task(async function setup() {
+  await SpecialPowers.pushPrefEnv({
+    set: [["extensions.manifestV3.enabled", true]],
+  });
+});
+
+async function verifyExecuteScriptActiveTab(permissions, host_permissions) {
+  let extension = makeExtension({
+    manifest: {
+      permissions: ["scripting", ...permissions],
+      host_permissions,
+    },
+    background() {
+      browser.action.onClicked.addListener(async tab => {
+        const results = await browser.scripting.executeScript({
+          target: { tabId: tab.id },
+          func: () => document.title,
+        });
+
+        browser.test.assertEq(
+          1,
+          results.length,
+          "got expected number of results"
+        );
+        browser.test.assertEq(
+          "file sample",
+          results[0].result,
+          "got the expected title"
+        );
+        browser.test.assertEq(
+          0,
+          results[0].frameId,
+          "got the expected frameId"
+        );
+
+        browser.test.sendMessage("execute-script");
+      });
+
+      browser.test.onMessage.addListener(async msg => {
+        switch (msg) {
+          case "reload-and-execute":
+            const tabs = await browser.tabs.query({ active: true });
+            const tabId = tabs[0].id;
+
+            let promiseTabLoad = new Promise(resolve => {
+              browser.tabs.onUpdated.addListener(function listener(updatedTabId, changeInfo) {
+                browser.test.assertEq(tabId, updatedTabId, "got expected tabId");
+
+                if (tabId === updatedTabId && changeInfo.status === "complete") {
+                  browser.tabs.onUpdated.removeListener(listener);
+                  resolve();
+                }
+              });
+            });
+
+            await browser.tabs.reload();
+            await promiseTabLoad;
+
+            await browser.test.assertRejects(
+              browser.scripting.executeScript({
+                target: { tabId },
+                func: () => {
+                  browser.test.fail("Unexpected execution");
+                },
+              }),
+              "Missing host permission for the tab",
+              "expected host permission error"
+            );
+
+            browser.test.sendMessage("execute-script-after-reload");
+
+            break;
+          default:
+            browser.test.fail(`invalid message received: ${msg}`);
+        }
+      });
+
+      browser.test.sendMessage("background-ready");
+    },
+  });
+
+  let tab = await AppTestDelegate.openNewForegroundTab(
+    window,
+    "https://test1.example.com/tests/toolkit/components/extensions/test/mochitest/file_sample.html",
+    true
+  );
+
+  await extension.startup();
+  await extension.awaitMessage("background-ready");
+
+  await AppTestDelegate.clickBrowserAction(window, extension);
+  await extension.awaitMessage("execute-script");
+  await AppTestDelegate.closeBrowserAction(window, extension);
+
+  extension.sendMessage("reload-and-execute");
+  await extension.awaitMessage("execute-script-after-reload");
+
+  await extension.unload();
+
+  await AppTestDelegate.removeTab(window, tab);
+}
+
+// Test executeScript works with the standard activeTab permission.
+add_task(async function test_executeScript_activeTab_permission() {
+  await verifyExecuteScriptActiveTab(["activeTab"], []);
+});
+
+// Test executeScript works with automatic activeTab granted from optional
+// host permissions.
+add_task(async function test_executeScript_activeTab_automatic_originControls() {
+  await verifyExecuteScriptActiveTab([], ["*://test1.example.com/*"]);
+});
+
+</script>
+
+</body>
+</html>
diff --git a/toolkit/components/extensions/test/mochitest/test_ext_scripting_executeScript_injectImmediately.html b/toolkit/components/extensions/test/mochitest/test_ext_scripting_executeScript_injectImmediately.html
new file mode 100644
index 0000000000..9d05925adc
--- /dev/null
+++ b/toolkit/components/extensions/test/mochitest/test_ext_scripting_executeScript_injectImmediately.html
@@ -0,0 +1,215 @@
+<!DOCTYPE HTML>
+  <html>
+<head>
+  <meta charset="utf-8">
+  <title>Tests scripting.executeScript() and injectImmediately</title>
+  <script type="text/javascript" src="/tests/SimpleTest/SimpleTest.js"></script>
+  <script type="text/javascript" src="/tests/SimpleTest/ExtensionTestUtils.js"></script>
+  <script type="text/javascript" src="head.js"></script>
+  <link rel="stylesheet" href="/tests/SimpleTest/test.css"/>
+</head>
+<body>
+
+<script type="text/javascript">
+
+"use strict";
+
+const MOCHITEST_HOST_PERMISSIONS = [
+  "*://mochi.test/",
+  "*://mochi.xorigin-test/",
+  "*://test1.example.com/",
+];
+
+const makeExtension = ({ manifest: manifestProps, ...otherProps }) => {
+  return ExtensionTestUtils.loadExtension({
+    manifest: {
+      manifest_version: 3,
+      permissions: ["scripting"],
+      host_permissions: [
+        ...MOCHITEST_HOST_PERMISSIONS,
+        // Used in `file_contains_iframe.html`
+        "https://example.org/",
+      ],
+      granted_host_permissions: true,
+      ...manifestProps,
+    },
+    useAddonManager: "temporary",
+    ...otherProps,
+  });
+};
+
+add_task(async function setup() {
+  await SpecialPowers.pushPrefEnv({
+    set: [["extensions.manifestV3.enabled", true]],
+  });
+});
+
+add_task(async function test_executeScript_injectImmediately() {
+  let extension = makeExtension({
+    async background() {
+      const tabs = await browser.tabs.query({ active: true });
+      const tabId = tabs[0].id;
+
+      let onUpdatedPromise = (tabId, url, status) => {
+        return new Promise(resolve => {
+          browser.tabs.onUpdated.addListener(function listener(_, changed, tab) {
+            if (tabId == tab.id && changed.status == status && tab.url == url) {
+              browser.tabs.onUpdated.removeListener(listener);
+              resolve();
+            }
+          });
+        });
+      };
+
+      const url = [
+        "https://test1.example.com/tests/toolkit/components/extensions/test/mochitest/",
+        `file_slowed_document.sjs?with-iframe&r=${Math.random()}`,
+      ].join("");
+      const loadingPromise = onUpdatedPromise(tabId, url, "loading");
+      const completePromise = onUpdatedPromise(tabId, url, "complete");
+
+      await browser.tabs.update(tabId, { url });
+      await loadingPromise;
+
+      const func = () => {
+        window.counter = (window.counter || 0) + 1;
+
+        return window.counter;
+      };
+
+      let results = await Promise.all([
+        // counter = 1
+        browser.scripting.executeScript({
+          target: { tabId },
+          func,
+          injectImmediately: true,
+        }),
+        // counter = 3
+        browser.scripting.executeScript({
+          target: { tabId },
+          func,
+          injectImmediately: false,
+        }),
+        // counter = 4
+        browser.scripting.executeScript({
+          target: { tabId },
+          func,
+          // `injectImmediately` is `false` by default
+        }),
+        // counter = 2
+        browser.scripting.executeScript({
+          target: { tabId },
+          func,
+          injectImmediately: true,
+        }),
+        // counter = 5
+        browser.scripting.executeScript({
+          target: { tabId },
+          func,
+          injectImmediately: false,
+        }),
+      ]);
+      browser.test.assertEq(
+        5,
+        results.length,
+        "got expected number of results"
+      );
+      browser.test.assertEq(
+        "1 3 4 2 5",
+        results.map(res => res[0].result).join(" "),
+        `got expected results: ${JSON.stringify(results)}`
+      );
+
+      await completePromise;
+
+      browser.test.notifyPass("execute-script");
+    },
+  });
+
+
+  let tab = await AppTestDelegate.openNewForegroundTab(
+    window,
+    "https://test1.example.com/",
+    true
+  );
+
+  await extension.startup();
+  await extension.awaitFinish("execute-script");
+  await extension.unload();
+
+  await AppTestDelegate.removeTab(window, tab);
+});
+
+add_task(async function test_executeScript_injectImmediately_after_document_idle() {
+  let extension = makeExtension({
+    async background() {
+      const tabs = await browser.tabs.query({ active: true });
+      browser.test.assertEq(1, tabs.length, "expected 1 tab");
+
+      const tabId = tabs[0].id;
+
+      const func = () => {
+        window.counter = (window.counter || 0) + 1;
+
+        return window.counter;
+      };
+
+      let results = await Promise.all([
+        browser.scripting.executeScript({
+          target: { tabId },
+          func,
+          injectImmediately: true,
+        }),
+        browser.scripting.executeScript({
+          target: { tabId },
+          func,
+          injectImmediately: false,
+        }),
+        browser.scripting.executeScript({
+          target: { tabId },
+          func,
+          // `injectImmediately` is `false` by default
+        }),
+        browser.scripting.executeScript({
+          target: { tabId },
+          func,
+          injectImmediately: true,
+        }),
+        browser.scripting.executeScript({
+          target: { tabId },
+          func,
+          injectImmediately: false,
+        }),
+      ]);
+      browser.test.assertEq(
+        5,
+        results.length,
+        "got expected number of results"
+      );
+      browser.test.assertEq(
+        "1 2 3 4 5",
+        results.map(res => res[0].result).join(" "),
+        `got expected results: ${JSON.stringify(results)}`
+      );
+
+      browser.test.notifyPass("execute-script");
+    },
+  });
+
+  let tab = await AppTestDelegate.openNewForegroundTab(
+    window,
+    "https://test1.example.com/tests/toolkit/components/extensions/test/mochitest/file_contains_iframe.html",
+    true
+  );
+
+  await extension.startup();
+  await extension.awaitFinish("execute-script");
+  await extension.unload();
+
+  await AppTestDelegate.removeTab(window, tab);
+});
+
+</script>
+
+</body>
+</html>
diff --git a/toolkit/components/extensions/test/mochitest/test_ext_scripting_insertCSS.html b/toolkit/components/extensions/test/mochitest/test_ext_scripting_insertCSS.html
new file mode 100644
index 0000000000..3e2cef8721
--- /dev/null
+++ b/toolkit/components/extensions/test/mochitest/test_ext_scripting_insertCSS.html
@@ -0,0 +1,395 @@
+<!DOCTYPE HTML>
+<html>
+<head>
+  <meta charset="utf-8">
+  <title>Tests scripting.insertCSS()</title>
+  <script type="text/javascript" src="/tests/SimpleTest/SimpleTest.js"></script>
+  <script type="text/javascript" src="/tests/SimpleTest/ExtensionTestUtils.js"></script>
+  <script type="text/javascript" src="head.js"></script>
+  <link rel="stylesheet" href="/tests/SimpleTest/test.css"/>
+</head>
+<body>
+
+<script type="text/javascript">
+"use strict";
+
+const MOCHITEST_HOST_PERMISSIONS = [
+  "*://mochi.test/",
+  "*://mochi.xorigin-test/",
+  "*://test1.example.com/",
+];
+
+const makeExtension = ({ manifest: manifestProps, ...otherProps }) => {
+  return ExtensionTestUtils.loadExtension({
+    manifest: {
+      manifest_version: 3,
+      permissions: ["scripting"],
+      host_permissions: [
+        ...MOCHITEST_HOST_PERMISSIONS,
+        // Used in `file_contains_iframe.html`
+        "https://example.org/",
+      ],
+      granted_host_permissions: true,
+      ...manifestProps,
+    },
+    useAddonManager: "temporary",
+    ...otherProps,
+  });
+};
+
+add_task(async function setup() {
+  await SpecialPowers.pushPrefEnv({
+    set: [["extensions.manifestV3.enabled", true]],
+  });
+});
+
+add_task(async function test_insertCSS_and_removeCSS_params_validation() {
+  let extension = makeExtension({
+    async background() {
+      const tabs = await browser.tabs.query({ active: true });
+
+      const TEST_CASES = [
+        {
+          title: "no files and no css",
+          cssParams: {},
+          expectedError: "Exactly one of files and css must be specified.",
+        },
+        {
+          title: "both files and css are passed",
+          cssParams: {
+            files: ["styles.css"],
+            css: "* { background: rgb(1, 1, 1) }",
+          },
+          expectedError: "Exactly one of files and css must be specified.",
+        },
+        {
+          title: "both allFrames and frameIds are passed",
+          cssParams: {
+            target: {
+              tabId: tabs[0].id,
+              allFrames: true,
+              frameIds: [1, 2, 3],
+            },
+            files: ["styles.css"],
+          },
+          expectedError: "Cannot specify both 'allFrames' and 'frameIds'.",
+        },
+        {
+          title: "empty css string with a file",
+          cssParams: {
+            css: "",
+            files: ["styles.css"],
+          },
+          expectedError: "Exactly one of files and css must be specified.",
+        },
+      ];
+
+      for (const { title, cssParams, expectedError } of TEST_CASES) {
+        await browser.test.assertRejects(
+          browser.scripting.insertCSS({
+            target: { tabId: tabs[0].id },
+            ...cssParams,
+          }),
+          expectedError,
+          `${title} - expected error for insertCSS()`
+        );
+
+        await browser.test.assertRejects(
+          browser.scripting.removeCSS({
+            target: { tabId: tabs[0].id },
+            ...cssParams,
+          }),
+          expectedError,
+          `${title} - expected error for removeCSS()`
+        );
+      }
+
+      browser.test.notifyPass("checks-done");
+    },
+  });
+
+  await extension.startup();
+  await extension.awaitFinish("checks-done");
+  await extension.unload();
+});
+
+add_task(async function test_insertCSS_with_invalid_tabId() {
+  let extension = makeExtension({
+    async background() {
+      // This tab ID should not exist.
+      const tabId = 123456789;
+
+      await browser.test.assertRejects(
+        browser.scripting.insertCSS({
+          target: { tabId },
+          css: "* { background: rgb(1, 1, 1) }",
+        }),
+        `Invalid tab ID: ${tabId}`
+      );
+
+      browser.test.notifyPass("insert-css");
+    },
+  });
+
+  await extension.startup();
+  await extension.awaitFinish("insert-css");
+  await extension.unload();
+});
+
+add_task(async function test_insertCSS_with_wrong_host_permissions() {
+  let extension = makeExtension({
+    manifest: {
+      host_permissions: [],
+    },
+    async background() {
+      const tabs = await browser.tabs.query({ active: true });
+
+      browser.test.assertEq(1, tabs.length, "expected 1 tab");
+
+      browser.test.assertRejects(
+        browser.scripting.insertCSS({
+          target: { tabId: tabs[0].id },
+          css: "* { background: rgb(1, 1, 1) }",
+        }),
+        /Missing host permission for the tab/,
+        "expected host permission error"
+      );
+
+      browser.test.notifyPass("insert-css");
+    },
+  });
+
+  await extension.startup();
+  await extension.awaitFinish("insert-css");
+  await extension.unload();
+});
+
+add_task(async function test_insertCSS_and_removeCSS() {
+  let extension = makeExtension({
+    manifest: {
+      permissions: ["scripting", "webNavigation"],
+    },
+    async background() {
+      const tabs = await browser.tabs.query({ active: true });
+      browser.test.assertEq(1, tabs.length, "expected 1 tab");
+
+      const tabId = tabs[0].id;
+
+      const frames = await browser.webNavigation.getAllFrames({ tabId });
+      // 1. Top-level frame that loads `file_contains_iframe.html`
+      // 2. Frame that loads `file_contains_img.html`
+      browser.test.assertEq(2, frames.length, "expected 2 frames");
+      const frameIds = frames.map(frame => frame.frameId);
+
+      const cssColor1 = "rgb(1, 1, 1)";
+      const cssColor2 = "rgb(2, 2, 2)";
+      const cssColorInFile1 = "rgb(3, 3, 3)";
+      const defaultColor = "rgba(0, 0, 0, 0)";
+
+      const TEST_CASES = [
+        {
+          title: "with css prop",
+          elementId: "div-1",
+          cssParams: [
+            {
+              target: { tabId },
+              css: `#div-1 { background: ${cssColor1} }`,
+            },
+          ],
+          expectedResults: [cssColor1, defaultColor],
+        },
+        {
+          title: "with a file",
+          elementId: "div-2",
+          cssParams: [
+            {
+              target: { tabId },
+              files: ["file1.css"],
+            },
+          ],
+          expectedResults: [cssColorInFile1, defaultColor],
+        },
+        {
+          title: "css prop in a single frame",
+          elementId: "div-3",
+          cssParams: [
+            {
+              target: { tabId, frameIds: [frameIds[0]] },
+              css: `#div-3 { background: ${cssColor2} }`,
+            },
+          ],
+          expectedResults: [cssColor2, defaultColor],
+        },
+        {
+          title: "css prop in multiple frames",
+          elementId: "div-4",
+          cssParams: [
+            {
+              target: { tabId, frameIds },
+              css: `#div-4 { background: ${cssColor1} }`,
+            },
+          ],
+          expectedResults: [cssColor1, cssColor1],
+        },
+        {
+          title: "allFrames is true",
+          elementId: "div-5",
+          cssParams: [
+            {
+              target: { tabId, allFrames: true },
+              css: `#div-5 { background: ${defaultColor} }`,
+            },
+          ],
+          expectedResults: [defaultColor, defaultColor],
+        },
+        {
+          title: "origin: 'AUTHOR'",
+          elementId: "div-6",
+          cssParams: [
+            {
+              target: { tabId },
+              css: `#div-6 { background: ${cssColor1} }`,
+              origin: "AUTHOR",
+            },
+            {
+              target: { tabId },
+              css: `#div-6 { background: ${cssColor2} }`,
+              origin: "AUTHOR",
+            },
+          ],
+          expectedResults: [cssColor2, defaultColor],
+        },
+        {
+          title: "origin: 'USER'",
+          elementId: "div-7",
+          cssParams: [
+            {
+              target: { tabId },
+              css: `#div-7 { background: ${cssColor1} !important }`,
+              origin: "USER",
+            },
+            {
+              target: { tabId },
+              css: `#div-7 { background: ${cssColor2} !important }`,
+              origin: "AUTHOR",
+            },
+          ],
+          // User has higher importance.
+          expectedResults: [cssColor1, defaultColor],
+        },
+        {
+          title: "empty css string",
+          elementId: "div-8",
+          cssParams: [
+            {
+              target: { tabId },
+              css: "",
+            },
+          ],
+          expectedResults: [defaultColor, defaultColor],
+        },
+        {
+          title: "allFrames is false",
+          elementId: "div-9",
+          cssParams: [
+            {
+              target: { tabId, allFrames: false },
+              css: `#div-9 { background: ${cssColor1} }`,
+            },
+          ],
+          expectedResults: [cssColor1, defaultColor],
+        },
+      ];
+
+      const getBackgroundColor = elementId => {
+        return window.getComputedStyle(document.getElementById(elementId))
+          .backgroundColor;
+      };
+
+      for (const {
+        title,
+        elementId,
+        cssParams,
+        expectedResults,
+      } of TEST_CASES) {
+        // Create a unique element for the current test case.
+        await browser.scripting.executeScript({
+          target: { tabId, allFrames: true },
+          func: elementId => {
+            const element = document.createElement("div");
+            element.setAttribute("id", elementId);
+            document.body.appendChild(element);
+          },
+          args: [elementId],
+        });
+
+        for (const params of cssParams) {
+          const result = await browser.scripting.insertCSS(params);
+          // `insertCSS()` should not resolve to a value.
+          browser.test.assertEq(undefined, result, "got expected empty result");
+        }
+
+        let results = await browser.scripting.executeScript({
+          target: { tabId, allFrames: true },
+          func: getBackgroundColor,
+          args: [elementId],
+        });
+        results.sort((a, b) => a.frameId - b.frameId);
+
+        browser.test.assertEq(
+          expectedResults.length,
+          results.length,
+          `${title} - got the expected number of results`
+        );
+        results.forEach((result, index) => {
+          browser.test.assertEq(
+            expectedResults[index],
+            result.result,
+            `${title} - got expected result (index=${index}): ${title}`
+          );
+        });
+
+        results = await Promise.all(
+          cssParams.map(params => browser.scripting.removeCSS(params))
+        );
+        // `removeCSS()` should not resolve to a value.
+        results.forEach(result => {
+          browser.test.assertEq(undefined, result, "got expected empty result");
+        });
+
+        results = await browser.scripting.executeScript({
+          target: { tabId, allFrames: true },
+          func: getBackgroundColor,
+          args: [elementId],
+        });
+
+        browser.test.assertTrue(
+          results.every(({ result }) => result === defaultColor),
+          "got expected default color in all frames"
+        );
+      }
+
+      browser.test.notifyPass("insert-and-remove-css");
+    },
+    files: {
+      "file1.css": "#div-2 { background: rgb(3, 3, 3) }",
+    },
+  });
+
+  let tab = await AppTestDelegate.openNewForegroundTab(
+    window,
+    "https://test1.example.com/tests/toolkit/components/extensions/test/mochitest/file_contains_iframe.html",
+    true
+  );
+
+  await extension.startup();
+  await extension.awaitFinish("insert-and-remove-css");
+  await extension.unload();
+
+  await AppTestDelegate.removeTab(window, tab);
+});
+
+</script>
+
+</body>
+</html>
diff --git a/toolkit/components/extensions/test/mochitest/test_ext_scripting_permissions.html b/toolkit/components/extensions/test/mochitest/test_ext_scripting_permissions.html
new file mode 100644
index 0000000000..e3e6552290
--- /dev/null
+++ b/toolkit/components/extensions/test/mochitest/test_ext_scripting_permissions.html
@@ -0,0 +1,149 @@
+<!DOCTYPE HTML>
+<html>
+<head>
+  <meta charset="utf-8">
+  <title>Tests scripting APIs and permissions</title>
+  <script type="text/javascript" src="/tests/SimpleTest/SimpleTest.js"></script>
+  <script type="text/javascript" src="/tests/SimpleTest/ExtensionTestUtils.js"></script>
+  <script type="text/javascript" src="head.js"></script>
+  <link rel="stylesheet" href="/tests/SimpleTest/test.css"/>
+</head>
+<body>
+
+<script type="text/javascript">
+
+"use strict";
+
+const verifyRegisterContentScripts = async ({ manifest_version }) => {
+  let extension = ExtensionTestUtils.loadExtension({
+    manifest: {
+      manifest_version,
+      permissions: ["scripting"],
+      host_permissions: ["*://example.com/*"],
+      optional_permissions: ["*://example.org/*"],
+
+    },
+    async background() {
+      browser.test.onMessage.addListener(async (msg, value) => {
+        switch (msg) {
+          case "grant-permission":
+            let granted = await new Promise(resolve => {
+              browser.test.withHandlingUserInput(() => {
+                resolve(browser.permissions.request(value));
+              });
+            });
+            browser.test.assertTrue(granted, "permission request succeeded");
+            browser.test.sendMessage("permission-granted");
+            break;
+
+          default:
+            browser.test.fail(`invalid message received: ${msg}`);
+        }
+      });
+
+      await browser.scripting.registerContentScripts([
+        {
+          id: "script",
+          js: ["script.js"],
+          matches: [
+            "*://example.com/*",
+            "*://example.net/*",
+            "*://example.org/*",
+          ],
+          persistAcrossSessions: false,
+        },
+      ]);
+
+      browser.test.sendMessage("background-ready");
+    },
+    files: {
+      "script.js": () => {
+        browser.test.sendMessage(
+          "script-ran",
+          window.location.host + window.location.search
+        );
+      },
+    },
+  });
+
+  await extension.startup();
+  await extension.awaitMessage("background-ready");
+
+  if (manifest_version > 2) {
+    extension.sendMessage("grant-permission", {
+      origins: ["*://example.com/*"],
+    });
+    await extension.awaitMessage("permission-granted");
+  }
+
+  // `example.net` is not declared in the list of `permissions`.
+  let tabExampleNet = await AppTestDelegate.openNewForegroundTab(
+    window,
+    "https://example.net/",
+    true
+  );
+  // `example.org` is listed in `optional_permissions`.
+  let tabExampleOrg = await AppTestDelegate.openNewForegroundTab(
+    window,
+    "https://example.org/",
+    true
+  );
+  // `example.com` is listed in `permissions`.
+  let tabExampleCom = await AppTestDelegate.openNewForegroundTab(
+    window,
+    "https://example.com/",
+    true
+  );
+
+  let value = await extension.awaitMessage("script-ran");
+  ok(
+    value === "example.com",
+    `expected: example.com, received: ${value}`
+  );
+
+  extension.sendMessage("grant-permission", {
+    origins: ["*://example.org/*"],
+  });
+  await extension.awaitMessage("permission-granted");
+
+  let tabExampleOrg2 = await AppTestDelegate.openNewForegroundTab(
+    window,
+    "https://example.org/?2",
+    true
+  );
+
+  value = await extension.awaitMessage("script-ran");
+  ok(
+    value === "example.org?2",
+    `expected: example.org?2, received: ${value}`
+  );
+
+  await AppTestDelegate.removeTab(window, tabExampleNet);
+  await AppTestDelegate.removeTab(window, tabExampleOrg);
+  await AppTestDelegate.removeTab(window, tabExampleCom);
+  await AppTestDelegate.removeTab(window, tabExampleOrg2);
+
+  await extension.unload();
+};
+
+add_task(async function setup() {
+  await SpecialPowers.pushPrefEnv({
+    set: [
+      ["extensions.manifestV3.enabled", true],
+      ["extensions.webextOptionalPermissionPrompts", false],
+    ],
+  });
+});
+
+add_task(async function test_scripting_registerContentScripts_mv2() {
+  await verifyRegisterContentScripts({ manifest_version: 2 });
+});
+
+add_task(async function test_scripting_registerContentScripts_mv3() {
+  await verifyRegisterContentScripts({ manifest_version: 3 });
+});
+
+</script>
+
+</body>
+</html>
diff --git a/toolkit/components/extensions/test/mochitest/test_ext_scripting_removeCSS.html b/toolkit/components/extensions/test/mochitest/test_ext_scripting_removeCSS.html
new file mode 100644
index 0000000000..3036e49761
--- /dev/null
+++ b/toolkit/components/extensions/test/mochitest/test_ext_scripting_removeCSS.html
@@ -0,0 +1,135 @@
+<!DOCTYPE HTML>
+<html>
+<head>
+  <meta charset="utf-8">
+  <title>Tests scripting.removeCSS()</title>
+  <script type="text/javascript" src="/tests/SimpleTest/SimpleTest.js"></script>
+  <script type="text/javascript" src="/tests/SimpleTest/ExtensionTestUtils.js"></script>
+  <script type="text/javascript" src="head.js"></script>
+  <link rel="stylesheet" href="/tests/SimpleTest/test.css"/>
+</head>
+<body>
+
+<script type="text/javascript">
+"use strict";
+
+const MOCHITEST_HOST_PERMISSIONS = [
+  "*://mochi.test/",
+  "*://mochi.xorigin-test/",
+  "*://test1.example.com/",
+];
+
+const makeExtension = ({ manifest: manifestProps, ...otherProps }) => {
+  return ExtensionTestUtils.loadExtension({
+    manifest: {
+      manifest_version: 3,
+      permissions: ["scripting"],
+      host_permissions: [...MOCHITEST_HOST_PERMISSIONS],
+      granted_host_permissions: true,
+      ...manifestProps,
+    },
+    useAddonManager: "temporary",
+    ...otherProps,
+  });
+};
+
+add_task(async function setup() {
+  await SpecialPowers.pushPrefEnv({
+    set: [["extensions.manifestV3.enabled", true]],
+  });
+});
+
+add_task(async function test_removeCSS_with_invalid_tabId() {
+  let extension = makeExtension({
+    async background() {
+      // This tab ID should not exist.
+      const tabId = 123456789;
+
+      await browser.test.assertRejects(
+        browser.scripting.removeCSS({
+          target: { tabId },
+          css: "* { background: rgb(42, 42, 42) }",
+        }),
+        `Invalid tab ID: ${tabId}`
+      );
+
+      browser.test.notifyPass("remove-css");
+    },
+  });
+
+  await extension.startup();
+  await extension.awaitFinish("remove-css");
+  await extension.unload();
+});
+
+add_task(async function test_removeCSS_without_insertCSS_called_before() {
+  let extension = makeExtension({
+    async background() {
+      const tabs = await browser.tabs.query({ active: true });
+      browser.test.assertEq(1, tabs.length, "expected 1 tab");
+
+      browser.scripting
+        .removeCSS({
+          target: { tabId: tabs[0].id },
+          css: "* { background: rgb(42, 42, 42) }",
+        })
+        .then(() => {
+          browser.test.notifyPass("remove-css");
+        })
+        .catch(() => {
+          browser.test.notifyFail("remove-css");
+        });
+    },
+  });
+
+  await extension.startup();
+  await extension.awaitFinish("remove-css");
+  await extension.unload();
+});
+
+add_task(async function test_removeCSS_with_origin_mismatch() {
+  let extension = makeExtension({
+    async background() {
+      const tabs = await browser.tabs.query({ active: true });
+      browser.test.assertEq(1, tabs.length, "expected 1 tab");
+
+      const cssColor = "rgb(42, 42, 42)";
+      const cssParams = {
+        target: { tabId: tabs[0].id },
+        css: `* { background: ${cssColor} !important }`,
+      };
+
+      await browser.scripting.insertCSS({ ...cssParams, origin: "AUTHOR" });
+
+      let results = await browser.scripting.executeScript({
+        target: { tabId: tabs[0].id },
+        func: () => {
+          return window.getComputedStyle(document.body).backgroundColor;
+        },
+      });
+
+      browser.test.assertEq(cssColor, results[0].result, "got expected color");
+
+      // Here, we pass a different origin, which should result in no CSS
+      // removal.
+      await browser.scripting.removeCSS({ ...cssParams, origin: "USER" });
+
+      browser.test.assertEq(
+        cssColor,
+        results[0].result,
+        "got expected color after removeCSS"
+      );
+
+      browser.test.notifyPass("remove-css");
+    },
+  });
+
+  await extension.startup();
+  await extension.awaitFinish("remove-css");
+  await extension.unload();
+});
+
+</script>
+
+</body>
+</html>
diff --git a/toolkit/components/extensions/test/mochitest/test_ext_sendmessage_doublereply.html b/toolkit/components/extensions/test/mochitest/test_ext_sendmessage_doublereply.html
new file mode 100644
index 0000000000..ffdbc90efb
--- /dev/null
+++ b/toolkit/components/extensions/test/mochitest/test_ext_sendmessage_doublereply.html
@@ -0,0 +1,100 @@
+<!DOCTYPE HTML>
+<html>
+<head>
+  <title>WebExtension test</title>
+  <script src="/tests/SimpleTest/SimpleTest.js"></script>
+  <script src="/tests/SimpleTest/ExtensionTestUtils.js"></script>
+  <script type="text/javascript" src="head.js"></script>
+  <link rel="stylesheet" type="text/css" href="/tests/SimpleTest/test.css"/>
+</head>
+<body>
+
+<script type="text/javascript">
+"use strict";
+
+function background() {
+  // Add two listeners that both send replies. We're supposed to ignore all but one
+  // of them. Which one is chosen is non-deterministic.
+
+  browser.runtime.onMessage.addListener((msg, sender, sendReply) => {
+    browser.test.assertTrue(sender.tab.url.endsWith("file_sample.html"), "sender url correct");
+
+    if (msg == "getreply") {
+      sendReply("reply1");
+    }
+  });
+
+  browser.runtime.onMessage.addListener((msg, sender, sendReply) => {
+    browser.test.assertTrue(sender.tab.url.endsWith("file_sample.html"), "sender url correct");
+
+    if (msg == "getreply") {
+      sendReply("reply2");
+    }
+  });
+
+  function sleep(callback, n = 10) {
+    if (n == 0) {
+      callback();
+    } else {
+      setTimeout(function() { sleep(callback, n - 1); }, 0);
+    }
+  }
+
+  let done_count = 0;
+  browser.runtime.onMessage.addListener((msg, sender, sendReply) => {
+    browser.test.assertTrue(sender.tab.url.endsWith("file_sample.html"), "sender url correct");
+
+    if (msg == "done") {
+      done_count++;
+      browser.test.assertEq(done_count, 1, "got exactly one reply");
+
+      // Go through the event loop a few times to make sure we don't get multiple replies.
+      sleep(function() {
+        browser.test.notifyPass("sendmessage_doublereply");
+      });
+    }
+  });
+}
+
+function contentScript() {
+  browser.runtime.sendMessage("getreply", function(resp) {
+    if (resp != "reply1" && resp != "reply2") {
+      return; // test failed
+    }
+    browser.runtime.sendMessage("done");
+  });
+}
+
+let extensionData = {
+  background,
+  manifest: {
+    "permissions": ["tabs"],
+    "content_scripts": [{
+      "matches": ["http://mochi.test/*/file_sample.html"],
+      "js": ["content_script.js"],
+      "run_at": "document_start",
+    }],
+  },
+
+  files: {
+    "content_script.js": contentScript,
+  },
+};
+
+add_task(async function test_contentscript() {
+  let extension = ExtensionTestUtils.loadExtension(extensionData);
+  await extension.startup();
+
+  let win = window.open("file_sample.html");
+
+  await Promise.all([waitForLoad(win), extension.awaitFinish("sendmessage_doublereply")]);
+
+  win.close();
+
+  await extension.unload();
+  info("extension unloaded");
+});
+</script>
+
+</body>
+</html>
diff --git a/toolkit/components/extensions/test/mochitest/test_ext_sendmessage_frameId.html b/toolkit/components/extensions/test/mochitest/test_ext_sendmessage_frameId.html
new file mode 100644
index 0000000000..6b42073031
--- /dev/null
+++ b/toolkit/components/extensions/test/mochitest/test_ext_sendmessage_frameId.html
@@ -0,0 +1,45 @@
+<!doctype html>
+<head>
+  <title>Test sendMessage frameId</title>
+  <script src="/tests/SimpleTest/SimpleTest.js"></script>
+  <script src="/tests/SimpleTest/ExtensionTestUtils.js"></script>
+  <script src="head.js"></script>
+  <link rel="stylesheet" href="/tests/SimpleTest/test.css"/>
+</head>
+<script>
+"use strict";
+
+add_task(async function test_sendMessage_frameId() {
+  const html = `<!doctype html><meta charset="utf-8"><script src="script.js"><\/script>`;
+
+  const extension = ExtensionTestUtils.loadExtension({
+    background() {
+      browser.runtime.onMessage.addListener((msg, sender) => {
+        browser.test.sendMessage(msg, sender);
+      });
+      browser.tabs.create({url: "tab.html"});
+    },
+    files: {
+      "iframe.html": html,
+      "tab.html": `${html}<iframe src="iframe.html"></iframe>`,
+      "script.js": () => {
+        browser.runtime.sendMessage(window.top === window ? "tab" : "iframe");
+      },
+    },
+  });
+
+  await extension.startup();
+
+  const tab = await extension.awaitMessage("tab");
+  ok(tab.url.endsWith("tab.html"), "Got the message from the tab");
+  is(tab.frameId, 0, "And sender.frameId is zero");
+
+  const iframe = await extension.awaitMessage("iframe");
+  ok(iframe.url.endsWith("iframe.html"), "Got the message from the iframe");
+  is(typeof iframe.frameId, "number", "With sender.frameId of type number");
+  ok(iframe.frameId > 0, "And sender.frameId greater than zero");
+
+  await extension.unload();
+});
+
+</script>
diff --git a/toolkit/components/extensions/test/mochitest/test_ext_sendmessage_no_receiver.html b/toolkit/components/extensions/test/mochitest/test_ext_sendmessage_no_receiver.html
new file mode 100644
index 0000000000..a18b003e48
--- /dev/null
+++ b/toolkit/components/extensions/test/mochitest/test_ext_sendmessage_no_receiver.html
@@ -0,0 +1,115 @@
+<!DOCTYPE html>
+<html>
+<head>
+  <title>WebExtension test</title>
+  <meta charset="utf-8">
+  <script src="/tests/SimpleTest/SimpleTest.js"></script>
+  <script src="/tests/SimpleTest/ExtensionTestUtils.js"></script>
+  <script type="text/javascript" src="head.js"></script>
+  <link rel="stylesheet" type="text/css" href="/tests/SimpleTest/test.css">
+</head>
+<body>
+<script>
+"use strict";
+
+async function testFn(expectPromise) {
+  browser.test.assertEq(null, chrome.runtime.lastError, "no lastError before call");
+  let retval = chrome.runtime.sendMessage("msg");
+  browser.test.assertEq(null, chrome.runtime.lastError, "no lastError after call");
+  if (expectPromise) {
+    browser.test.assertTrue(retval instanceof Promise, "chrome.runtime.sendMessage should return a promise");
+  } else {
+    browser.test.assertEq(undefined, retval, "return value of chrome.runtime.sendMessage with callback");
+  }
+
+  let isAsyncCall = false;
+  retval = chrome.runtime.sendMessage("msg", reply => {
+    browser.test.assertEq(undefined, reply, "no reply");
+    browser.test.assertTrue(isAsyncCall, "chrome.runtime.sendMessage's callback must be called asynchronously");
+    browser.test.assertEq(undefined, retval, "return value of chrome.runtime.sendMessage with callback");
+    browser.test.assertEq("Could not establish connection. Receiving end does not exist.", chrome.runtime.lastError.message);
+    browser.test.sendMessage("finished", retval);
+  });
+  isAsyncCall = true;
+}
+
+add_task(async function test_content_script_sendMessage_without_listener() {
+  async function contentScript() {
+    await browser.test.assertRejects(
+      browser.runtime.sendMessage("msg"),
+      "Could not establish connection. Receiving end does not exist.");
+
+    browser.test.notifyPass("sendMessage callback was invoked");
+  }
+
+  let extension = ExtensionTestUtils.loadExtension({
+    manifest: {
+      content_scripts: [{
+        js: ["contentscript.js"],
+        matches: ["http://mochi.test/*/file_sample.html"],
+      }],
+    },
+    files: {
+      "contentscript.js": contentScript,
+    },
+  });
+
+  await extension.startup();
+
+  let win = window.open("file_sample.html");
+  await extension.awaitFinish("sendMessage callback was invoked");
+  win.close();
+
+  await extension.unload();
+});
+
+add_task(async function test_content_script_chrome_sendMessage_without_listener() {
+  let extension = ExtensionTestUtils.loadExtension({
+    manifest: {
+      manifest_version: 2,
+      content_scripts: [{
+        js: ["contentscript.js"],
+        matches: ["http://mochi.test/*/file_sample.html"],
+      }],
+    },
+    // In MV2, chrome namespace in content scripts do get promises, however in background pages they do not.
+    background: `(${testFn})(false)`,
+    files: {
+      "contentscript.js": `(${testFn})(true)`,
+    },
+  });
+
+  await extension.startup();
+  await extension.awaitMessage("finished");
+
+  let win = window.open("file_sample.html");
+  await extension.awaitMessage("finished");
+  win.close();
+
+  await extension.unload();
+});
+
+add_task(async function test_chrome_sendMessage_without_listener_v3() {
+  await SpecialPowers.pushPrefEnv({
+    set: [["extensions.manifestV3.enabled", true]],
+  });
+
+  // We only test the background here because content script behavior
+  // is independant of the manifest version.
+  let extension = ExtensionTestUtils.loadExtension({
+    manifest: {
+      manifest_version: 3,
+    },
+    background: `(${testFn})(true)`,
+  });
+
+  await extension.startup();
+
+  await extension.awaitMessage("finished");
+
+  await extension.unload();
+  await SpecialPowers.popPrefEnv();
+});
+</script>
+</body>
+</html>
diff --git a/toolkit/components/extensions/test/mochitest/test_ext_sendmessage_reply.html b/toolkit/components/extensions/test/mochitest/test_ext_sendmessage_reply.html
new file mode 100644
index 0000000000..a7f6314efd
--- /dev/null
+++ b/toolkit/components/extensions/test/mochitest/test_ext_sendmessage_reply.html
@@ -0,0 +1,78 @@
+<!DOCTYPE HTML>
+<html>
+<head>
+  <title>WebExtension test</title>
+  <script src="/tests/SimpleTest/SimpleTest.js"></script>
+  <script src="/tests/SimpleTest/ExtensionTestUtils.js"></script>
+  <script type="text/javascript" src="head.js"></script>
+  <link rel="stylesheet" type="text/css" href="/tests/SimpleTest/test.css"/>
+</head>
+<body>
+
+<script type="text/javascript">
+"use strict";
+
+function background() {
+  browser.runtime.onMessage.addListener((msg, sender, sendReply) => {
+    browser.test.assertTrue(sender.tab.url.endsWith("file_sample.html"), "sender url correct");
+
+    if (msg == 0) {
+      sendReply("reply1");
+    } else if (msg == 1) {
+      window.setTimeout(function() {
+        sendReply("reply2");
+      }, 0);
+      return true;
+    } else if (msg == 2) {
+      browser.test.notifyPass("sendmessage_reply");
+    }
+  });
+}
+
+function contentScript() {
+  browser.runtime.sendMessage(0, function(resp1) {
+    if (resp1 != "reply1") {
+      return; // test failed
+    }
+    browser.runtime.sendMessage(1, function(resp2) {
+      if (resp2 != "reply2") {
+        return; // test failed
+      }
+      browser.runtime.sendMessage(2);
+    });
+  });
+}
+
+let extensionData = {
+  background,
+  manifest: {
+    "permissions": ["tabs"],
+    "content_scripts": [{
+      "matches": ["http://mochi.test/*/file_sample.html"],
+      "js": ["content_script.js"],
+      "run_at": "document_idle",
+    }],
+  },
+
+  files: {
+    "content_script.js": contentScript,
+  },
+};
+
+add_task(async function test_contentscript() {
+  let extension = ExtensionTestUtils.loadExtension(extensionData);
+  await extension.startup();
+
+  let win = window.open("file_sample.html");
+
+  await Promise.all([waitForLoad(win), extension.awaitFinish("sendmessage_reply")]);
+
+  win.close();
+
+  await extension.unload();
+  info("extension unloaded");
+});
+</script>
+
+</body>
+</html>
diff --git a/toolkit/components/extensions/test/mochitest/test_ext_sendmessage_reply2.html b/toolkit/components/extensions/test/mochitest/test_ext_sendmessage_reply2.html
new file mode 100644
index 0000000000..8cce833b49
--- /dev/null
+++ b/toolkit/components/extensions/test/mochitest/test_ext_sendmessage_reply2.html
@@ -0,0 +1,202 @@
+<!DOCTYPE HTML>
+<html>
+<head>
+  <title>WebExtension test</title>
+  <script src="/tests/SimpleTest/SimpleTest.js"></script>
+  <script src="/tests/SimpleTest/ExtensionTestUtils.js"></script>
+  <script type="text/javascript" src="head.js"></script>
+  <link rel="stylesheet" type="text/css" href="/tests/SimpleTest/test.css"/>
+</head>
+<body>
+
+<script type="text/javascript">
+"use strict";
+
+function backgroundScript(token, id, otherId) {
+  browser.runtime.onMessage.addListener((msg, sender, sendReply) => {
+    browser.test.assertEq(id, sender.id, `${id}: Got expected sender ID`);
+
+    if (msg === `content-${token}`) {
+      browser.test.assertTrue(sender.tab.url.endsWith("file_sample.html"),
+                              `${id}: sender url correct`);
+
+      let tabId = sender.tab.id;
+      browser.tabs.sendMessage(tabId, `${token}-contentMessage`);
+
+      sendReply(`${token}-done`);
+    } else if (msg === `tab-${token}`) {
+      browser.runtime.sendMessage(otherId, `${otherId}-tabMessage`);
+      browser.runtime.sendMessage(`${token}-tabMessage`);
+
+      sendReply(`${token}-done`);
+    } else {
+      browser.test.fail(`${id}: Unexpected runtime message received: ${msg} ${uneval(sender)}`);
+    }
+  });
+
+  browser.runtime.onMessageExternal.addListener((msg, sender, sendReply) => {
+    browser.test.assertEq(otherId, sender.id, `${id}: Got expected external sender ID`);
+
+    if (msg === `content-${id}`) {
+      browser.test.assertTrue(sender.tab.url.endsWith("file_sample.html"),
+                              `${id}: external sender url correct`);
+
+      sendReply(`${otherId}-done`);
+    } else if (msg === `tab-${id}`) {
+      sendReply(`${otherId}-done`);
+    } else if (msg !== `${id}-tabMessage`) {
+      browser.test.fail(`${id}: Unexpected runtime external message received: ${msg} ${uneval(sender)}`);
+    }
+  });
+
+  browser.tabs.create({url: "tab.html"});
+}
+
+function contentScript(token, id, otherId) {
+  let gotContentMessage = false;
+  browser.runtime.onMessage.addListener((msg, sender, sendReply) => {
+    browser.test.assertEq(id, sender.id, `${id}: Got expected sender ID`);
+
+    browser.test.assertEq(`${token}-contentMessage`, msg,
+                          `${id}: Correct content script message`);
+    if (msg === `${token}-contentMessage`) {
+      gotContentMessage = true;
+    }
+  });
+
+  Promise.all([
+    browser.runtime.sendMessage(otherId, `content-${otherId}`).then(resp => {
+      browser.test.assertEq(`${id}-done`, resp, `${id}: Correct content script external response token`);
+    }),
+
+    browser.runtime.sendMessage(`content-${token}`).then(resp => {
+      browser.test.assertEq(`${token}-done`, resp, `${id}: Correct content script response token`);
+    }).catch(e => {
+      browser.test.fail(`content-${token} rejected with ${e.message}`);
+    }),
+  ]).then(() => {
+    browser.test.assertTrue(gotContentMessage, `${id}: Got content script message`);
+
+    browser.test.sendMessage("content-script-done");
+  });
+}
+
+async function tabScript(token, id, otherId) {
+  let gotTabMessage = false;
+  browser.runtime.onMessage.addListener((msg, sender, sendReply) => {
+    browser.test.assertEq(id, sender.id, `${id}: Got expected sender ID`);
+
+    if (String(msg).startsWith("content-")) {
+      return;
+    }
+
+    browser.test.assertEq(`${token}-tabMessage`, msg,
+                          `${id}: Correct tab script message`);
+    if (msg === `${token}-tabMessage`) {
+      gotTabMessage = true;
+    }
+  });
+
+  browser.test.sendMessage("tab-script-loaded");
+
+  await new Promise(resolve => {
+    const listener = (msg) => {
+      if (msg !== "run-tab-script") {
+        return;
+      }
+      browser.test.onMessage.removeListener(listener);
+      resolve();
+    };
+    browser.test.onMessage.addListener(listener);
+  });
+
+  Promise.all([
+    browser.runtime.sendMessage(otherId, `tab-${otherId}`).then(resp => {
+      browser.test.assertEq(`${id}-done`, resp, `${id}: Correct tab script external response token`);
+    }),
+
+    browser.runtime.sendMessage(`tab-${token}`).then(resp => {
+      browser.test.assertEq(`${token}-done`, resp, `${id}: Correct tab script response token`);
+    }),
+  ]).then(() => {
+    browser.test.assertTrue(gotTabMessage, `${id}: Got tab script message`);
+
+    window.close();
+
+    browser.test.sendMessage("tab-script-done");
+  });
+}
+
+function makeExtension(id, otherId) {
+  let token = Math.random();
+
+  let args = `${token}, ${JSON.stringify(id)}, ${JSON.stringify(otherId)}`;
+
+  let extensionData = {
+    background: `(${backgroundScript})(${args})`,
+    manifest: {
+      "browser_specific_settings": {"gecko": {id}},
+
+      "permissions": ["tabs"],
+
+      "content_scripts": [{
+        "matches": ["http://mochi.test/*/file_sample.html"],
+        "js": ["content_script.js"],
+        "run_at": "document_start",
+      }],
+    },
+
+    files: {
+      "tab.html": `<!DOCTYPE html>
+        <html>
+          <head>
+            <meta charset="utf-8">
+            <script src="tab.js"><\/script>
+          </head>
+        </html>`,
+
+      "tab.js": `(${tabScript})(${args})`,
+
+      "content_script.js": `(${contentScript})(${args})`,
+    },
+  };
+  return extensionData;
+}
+
+add_task(async function test_contentscript() {
+  const ID1 = "sendmessage1@mochitest.mozilla.org";
+  const ID2 = "sendmessage2@mochitest.mozilla.org";
+
+  let extension1 = ExtensionTestUtils.loadExtension(makeExtension(ID1, ID2));
+  let extension2 = ExtensionTestUtils.loadExtension(makeExtension(ID2, ID1));
+
+  await Promise.all([
+    extension1.startup(),
+    extension2.startup(),
+    extension1.awaitMessage("tab-script-loaded"),
+    extension2.awaitMessage("tab-script-loaded"),
+  ]);
+
+  extension1.sendMessage("run-tab-script");
+  extension2.sendMessage("run-tab-script");
+
+  let win = window.open("file_sample.html");
+
+  await waitForLoad(win);
+
+  await Promise.all([
+    extension1.awaitMessage("content-script-done"),
+    extension2.awaitMessage("content-script-done"),
+    extension1.awaitMessage("tab-script-done"),
+    extension2.awaitMessage("tab-script-done"),
+  ]);
+
+  win.close();
+
+  await extension1.unload();
+  await extension2.unload();
+});
+</script>
+
+</body>
+</html>
diff --git a/toolkit/components/extensions/test/mochitest/test_ext_storage_cleanup.html b/toolkit/components/extensions/test/mochitest/test_ext_storage_cleanup.html
new file mode 100644
index 0000000000..71ef3a2214
--- /dev/null
+++ b/toolkit/components/extensions/test/mochitest/test_ext_storage_cleanup.html
@@ -0,0 +1,277 @@
+<!DOCTYPE HTML>
+<html>
+<head>
+  <title>WebExtension test</title>
+  <script src="/tests/SimpleTest/SimpleTest.js"></script>
+  <script src="/tests/SimpleTest/ExtensionTestUtils.js"></script>
+  <script type="text/javascript" src="head.js"></script>
+  <link rel="stylesheet" type="text/css" href="/tests/SimpleTest/test.css"/>
+</head>
+<body>
+
+<script type="text/javascript">
+"use strict";
+
+const { ExtensionStorageIDB } = SpecialPowers.ChromeUtils.import(
+  "resource://gre/modules/ExtensionStorageIDB.jsm"
+);
+
+const storageTestHelpers = {
+  storageLocal: {
+    async writeData() {
+      await browser.storage.local.set({hello: "world"});
+      browser.test.sendMessage("finished");
+    },
+
+    async readData() {
+      const matchBrowserStorage = await browser.storage.local.get("hello").then(result => {
+        return (Object.keys(result).length == 1 && result.hello == "world");
+      });
+
+      browser.test.sendMessage("results", {matchBrowserStorage});
+    },
+
+    assertResults({results, keepOnUninstall}) {
+      if (keepOnUninstall) {
+        is(results.matchBrowserStorage, true, "browser.storage.local data is still present");
+      } else {
+        is(results.matchBrowserStorage, false, "browser.storage.local data was cleared");
+      }
+    },
+  },
+  storageSync: {
+    async writeData() {
+      await browser.storage.sync.set({hello: "world"});
+      browser.test.sendMessage("finished");
+    },
+
+    async readData() {
+      const matchBrowserStorage = await browser.storage.sync.get("hello").then(result => {
+        return (Object.keys(result).length == 1 && result.hello == "world");
+      });
+
+      browser.test.sendMessage("results", {matchBrowserStorage});
+    },
+
+    assertResults({results, keepOnUninstall}) {
+      if (keepOnUninstall) {
+        is(results.matchBrowserStorage, true, "browser.storage.sync data is still present");
+      } else {
+        is(results.matchBrowserStorage, false, "browser.storage.sync data was cleared");
+      }
+    },
+  },
+  webAPIs: {
+    async readData() {
+      let matchLocalStorage = (localStorage.getItem("hello") == "world");
+
+      let idbPromise = new Promise((resolve, reject) => {
+        let req = indexedDB.open("test");
+        req.onerror = e => {
+          reject(new Error(`indexedDB open failed with ${e.errorCode}`));
+        };
+
+        req.onupgradeneeded = e => {
+          // no database, data is not present
+          resolve(false);
+        };
+
+        req.onsuccess = e => {
+          let db = e.target.result;
+          let transaction = db.transaction("store", "readwrite");
+          let addreq = transaction.objectStore("store").get("hello");
+          addreq.onerror = addreqError => {
+            reject(new Error(`read from indexedDB failed with ${addreqError.errorCode}`));
+          };
+          addreq.onsuccess = () => {
+            let match = (addreq.result.value == "world");
+            resolve(match);
+          };
+        };
+      });
+
+      await idbPromise.then(matchIDB => {
+        let result = {matchLocalStorage, matchIDB};
+        browser.test.sendMessage("results", result);
+      });
+    },
+
+    async writeData() {
+      localStorage.setItem("hello", "world");
+
+      let idbPromise = new Promise((resolve, reject) => {
+        let req = indexedDB.open("test");
+        req.onerror = e => {
+          reject(new Error(`indexedDB open failed with ${e.errorCode}`));
+        };
+
+        req.onupgradeneeded = e => {
+          let db = e.target.result;
+          db.createObjectStore("store", {keyPath: "name"});
+        };
+
+        req.onsuccess = e => {
+          let db = e.target.result;
+          let transaction = db.transaction("store", "readwrite");
+          let addreq = transaction.objectStore("store")
+                                  .add({name: "hello", value: "world"});
+          addreq.onerror = addreqError => {
+            reject(new Error(`add to indexedDB failed with ${addreqError.errorCode}`));
+          };
+          addreq.onsuccess = () => {
+            resolve();
+          };
+        };
+      });
+
+      await idbPromise.then(() => {
+        browser.test.sendMessage("finished");
+      });
+    },
+
+    assertResults({results, keepOnUninstall}) {
+      if (keepOnUninstall) {
+        is(results.matchLocalStorage, true, "localStorage data is still present");
+        is(results.matchIDB, true, "indexedDB data is still present");
+      } else {
+        is(results.matchLocalStorage, false, "localStorage data was cleared");
+        is(results.matchIDB, false, "indexedDB data was cleared");
+      }
+    },
+  },
+};
+
+async function test_uninstall({extensionId, writeData, readData, assertResults}) {
+  // Set the pref to prevent cleaning up storage on uninstall in a separate prefEnv
+  // so we can pop it below, leaving flags set in the previous prefEnvs unmodified.
+  await SpecialPowers.pushPrefEnv({
+    set: [["extensions.webextensions.keepStorageOnUninstall", true]],
+  });
+
+  let extension = ExtensionTestUtils.loadExtension({
+    background: writeData,
+    manifest: {
+      browser_specific_settings: {gecko: {id: extensionId}},
+      permissions: ["storage"],
+    },
+    useAddonManager: "temporary",
+  });
+
+  await extension.startup();
+  await extension.awaitMessage("finished");
+  await extension.unload();
+
+  // Check that we can still see data we wrote to storage but clear the
+  // "leave storage" flag so our storaged gets cleared on the next uninstall.
+  // This effectively tests the keepUuidOnUninstall logic, which ensures
+  // that when we read storage again and check that it is cleared, that
+  // it is actually a meaningful test!
+  await SpecialPowers.popPrefEnv();
+
+  extension = ExtensionTestUtils.loadExtension({
+    background: readData,
+    manifest: {
+      browser_specific_settings: {gecko: {id: extensionId}},
+      permissions: ["storage"],
+    },
+    useAddonManager: "temporary",
+  });
+
+  await extension.startup();
+  let results = await extension.awaitMessage("results");
+
+  assertResults({results, keepOnUninstall: true});
+
+  await extension.unload();
+
+  // Read again.  This time, our data should be gone.
+  extension = ExtensionTestUtils.loadExtension({
+    background: readData,
+    manifest: {
+      browser_specific_settings: {gecko: {id: extensionId}},
+      permissions: ["storage"],
+    },
+    useAddonManager: "temporary",
+  });
+
+  await extension.startup();
+  results = await extension.awaitMessage("results");
+
+  assertResults({results, keepOnUninstall: false});
+
+  await extension.unload();
+}
+
+
+add_task(async function test_setup_keep_uuid_on_uninstall() {
+  // Use a test-only pref to leave the addonid->uuid mapping around after
+  // uninstall so that we can re-attach to the same storage (this prefEnv
+  // is kept for this entire file and cleared automatically once all the
+  // tests in this file have been executed).
+  await SpecialPowers.pushPrefEnv({
+    set: [["extensions.webextensions.keepUuidOnUninstall", true]],
+  });
+});
+
+// Test extension indexedDB and localStorage storages get cleaned up when the
+// extension is uninstalled.
+add_task(async function test_uninstall_with_webapi_storages() {
+  await test_uninstall({
+    extensionId: "storage.cleanup-WebAPIStorages@tests.mozilla.org",
+    ...(storageTestHelpers.webAPIs),
+  });
+});
+
+// Test browser.storage.local with JSONFile backend gets cleaned up when the
+// extension is uninstalled.
+add_task(async function test_uninistall_with_storage_local_file_backend() {
+  await SpecialPowers.pushPrefEnv({
+    set: [[ExtensionStorageIDB.BACKEND_ENABLED_PREF, false]],
+  });
+
+  await test_uninstall({
+    extensionId: "storage.cleanup-JSONFileBackend@tests.mozilla.org",
+    ...(storageTestHelpers.storageLocal),
+  });
+
+  await SpecialPowers.popPrefEnv();
+});
+
+// Repeat the cleanup test when the storage.local IndexedDB backend is enabled.
+add_task(async function test_uninistall_with_storage_local_idb_backend() {
+  await SpecialPowers.pushPrefEnv({
+    set: [[ExtensionStorageIDB.BACKEND_ENABLED_PREF, true]],
+  });
+
+  await test_uninstall({
+    extensionId: "storage.cleanup-IDBBackend@tests.mozilla.org",
+    ...(storageTestHelpers.storageLocal),
+  });
+
+  await SpecialPowers.popPrefEnv();
+});
+
+// Legacy storage.sync backend is still being used on GeckoView builds.
+const storageSyncOldKintoBackend = SpecialPowers.Services.prefs.getBoolPref(
+  "webextensions.storage.sync.kinto",
+  false
+);
+
+// Verify browser.storage.sync rust backend is also cleared on uninstall.
+async function test_uninistall_with_storage_sync() {
+  await test_uninstall({
+    extensionId: "storage.cleanup-sync@tests.mozilla.org",
+    ...(storageTestHelpers.storageSync),
+  });
+}
+
+// NOTE: ideally we would be using a skip_if option on the add_task call,
+// but we don't support that in the add_task defined in mochitest-plain.
+if (!storageSyncOldKintoBackend) {
+  add_task(test_uninistall_with_storage_sync);
+}
+
+</script>
+
+</body>
+</html>
diff --git a/toolkit/components/extensions/test/mochitest/test_ext_storage_manager_capabilities.html b/toolkit/components/extensions/test/mochitest/test_ext_storage_manager_capabilities.html
new file mode 100644
index 0000000000..135d2b9589
--- /dev/null
+++ b/toolkit/components/extensions/test/mochitest/test_ext_storage_manager_capabilities.html
@@ -0,0 +1,130 @@
+<!DOCTYPE HTML>
+<html>
+<head>
+  <title>Test Storage API </title>
+  <script src="/tests/SimpleTest/SimpleTest.js"></script>
+  <script src="/tests/SimpleTest/ExtensionTestUtils.js"></script>
+  <script type="text/javascript" src="head.js"></script>
+  <link rel="stylesheet" type="text/css" href="/tests/SimpleTest/test.css"/>
+</head>
+<body>
+
+<script type="text/javascript">
+"use strict";
+
+add_task(async function setup() {
+  await SpecialPowers.pushPrefEnv({
+    "set": [
+      ["dom.storageManager.enabled", true],
+      ["dom.storageManager.prompt.testing", true],
+      ["dom.storageManager.prompt.testing.allow", true],
+    ],
+  });
+});
+
+add_task(async function test_backgroundScript() {
+  function background() {
+    browser.test.assertTrue(navigator.storage !== undefined, "Has storage api interface");
+
+    // Test estimate.
+    browser.test.assertTrue("estimate" in navigator.storage, "Has estimate function");
+    browser.test.assertEq("function", typeof navigator.storage.estimate, "estimate is function");
+    browser.test.assertTrue(navigator.storage.estimate() instanceof Promise, "estimate returns a promise");
+
+    return browser.test.notifyPass("navigation_storage_api.done");
+  }
+
+  let extension = ExtensionTestUtils.loadExtension({
+    background,
+  });
+
+  await extension.startup();
+  await extension.awaitFinish("navigation_storage_api.done");
+  await extension.unload();
+});
+
+add_task(async function test_contentScript() {
+  await SpecialPowers.pushPrefEnv({
+    set: [["dom.security.https_first", false]],
+  });
+
+  function contentScript() {
+    // Should not access storage api in non-secure context.
+    browser.test.assertEq(undefined, navigator.storage,
+                          "A page from the unsecure http protocol " +
+                          "doesn't have access to the navigator.storage API");
+
+    return browser.test.notifyPass("navigation_storage_api.done");
+  }
+
+  let extension = ExtensionTestUtils.loadExtension({
+    manifest: {
+      content_scripts: [{
+        "matches": ["http://example.com/*/file_sample.html"],
+        "js": ["content_script.js"],
+      }],
+    },
+
+    files: {
+      "content_script.js":  `(${contentScript})()`,
+    },
+  });
+
+  await extension.startup();
+
+  // Open an explicit URL for testing Storage API in an insecure context.
+  let win = window.open("http://example.com/tests/toolkit/components/extensions/test/mochitest/file_sample.html");
+
+  await extension.awaitFinish("navigation_storage_api.done");
+
+  await extension.unload();
+  win.close();
+});
+
+add_task(async function test_contentScriptSecure() {
+  function contentScript() {
+    browser.test.assertTrue(navigator.storage !== undefined, "Has storage api interface");
+
+    // Test estimate.
+    browser.test.assertTrue("estimate" in navigator.storage, "Has estimate function");
+    browser.test.assertEq("function", typeof navigator.storage.estimate, "estimate is function");
+
+    // The promise that estimate function returns belongs to the content page,
+    // but the Promise constructor belongs to the content script sandbox.
+    // Check window.Promise here.
+    browser.test.assertTrue(navigator.storage.estimate() instanceof window.Promise, "estimate returns a promise");
+
+    return browser.test.notifyPass("navigation_storage_api.done");
+  }
+
+  let extension = ExtensionTestUtils.loadExtension({
+    manifest: {
+      content_scripts: [{
+        "matches": ["https://example.com/*/file_sample.html"],
+        "js": ["content_script.js"],
+      }],
+    },
+
+    files: {
+      "content_script.js":  `(${contentScript})()`,
+    },
+  });
+
+  await extension.startup();
+
+  // Open an explicit URL for testing Storage API in a secure context.
+  let win = window.open("file_sample.html");
+
+  await extension.awaitFinish("navigation_storage_api.done");
+
+  await extension.unload();
+  win.close();
+});
+
+add_task(async function cleanup() {
+  await SpecialPowers.popPrefEnv();
+});
+</script>
+
+</body>
+</html>
diff --git a/toolkit/components/extensions/test/mochitest/test_ext_storage_smoke_test.html b/toolkit/components/extensions/test/mochitest/test_ext_storage_smoke_test.html
new file mode 100644
index 0000000000..e68caa7e55
--- /dev/null
+++ b/toolkit/components/extensions/test/mochitest/test_ext_storage_smoke_test.html
@@ -0,0 +1,108 @@
+<!DOCTYPE HTML>
+<html>
+<head>
+  <title>WebExtension test</title>
+  <meta charset="utf-8">
+  <script src="/tests/SimpleTest/SimpleTest.js"></script>
+  <script src="/tests/SimpleTest/ExtensionTestUtils.js"></script>
+  <script type="text/javascript" src="head.js"></script>
+  <link rel="stylesheet" type="text/css" href="/tests/SimpleTest/test.css"/>
+</head>
+<body>
+
+<script type="text/javascript">
+"use strict";
+
+// The purpose of this test is making sure that the implementation enabled by
+// default for the storage.local and storage.sync APIs does work across all
+// platforms/builds/apps
+add_task(async function test_storage_smoke_test() {
+  let extension = ExtensionTestUtils.loadExtension({
+    async background() {
+      for (let storageArea of ["sync", "local"]) {
+        let storage = browser.storage[storageArea];
+
+        browser.test.assertTrue(!!storage, `StorageArea ${storageArea} is present.`)
+
+        let data = await storage.get();
+        browser.test.assertEq(0, Object.keys(data).length,
+            `Storage starts out empty for ${storageArea}`);
+
+        data = await storage.get("test");
+        browser.test.assertEq(0, Object.keys(data).length,
+            `Can read non-existent keys for ${storageArea}`);
+
+        await storage.set({
+          "test1": "test-value1",
+          "test2": "test-value2",
+          "test3": "test-value3"
+        });
+
+        browser.test.assertEq(
+            "test-value1",
+            (await storage.get("test1")).test1,
+            `Can set and read back single values for ${storageArea}`);
+
+        browser.test.assertEq(
+            "test-value2",
+            (await storage.get("test2")).test2,
+            `Can set and read back single values for ${storageArea}`);
+
+        data = await storage.get();
+        browser.test.assertEq(3, Object.keys(data).length,
+            `Can set and read back all values for ${storageArea}`);
+        browser.test.assertEq("test-value1", data.test1,
+            `Can set and read back all values for ${storageArea}`);
+        browser.test.assertEq("test-value2", data.test2,
+            `Can set and read back all values for ${storageArea}`);
+        browser.test.assertEq("test-value3", data.test3,
+            `Can set and read back all values for ${storageArea}`);
+
+        data = await storage.get(["test1", "test2"]);
+        browser.test.assertEq(2, Object.keys(data).length,
+            `Can set and read back array of values for ${storageArea}`);
+        browser.test.assertEq("test-value1", data.test1,
+            `Can set and read back array of values for ${storageArea}`);
+        browser.test.assertEq("test-value2", data.test2,
+            `Can set and read back array of values for ${storageArea}`);
+
+        await storage.remove("test1");
+        data = await storage.get(["test1", "test2"]);
+        browser.test.assertEq(1, Object.keys(data).length,
+            `Data can be removed for ${storageArea}`);
+        browser.test.assertEq("test-value2", data.test2,
+            `Data can be removed for ${storageArea}`);
+
+        data = await storage.get({
+          test1: 1,
+          test2: 2,
+        });
+        browser.test.assertEq(2, Object.keys(data).length,
+            `Expected a key-value pair for every property for ${storageArea}`);
+        browser.test.assertEq(1, data.test1,
+            `Use default value if key was deleted for ${storageArea}`);
+        browser.test.assertEq("test-value2", data.test2,
+            `Use stored value if found for ${storageArea}`);
+
+        await storage.clear();
+        data = await storage.get();
+        browser.test.assertEq(0, Object.keys(data).length,
+            `Data is empty after clear for ${storageArea}`);
+      }
+
+      browser.test.sendMessage("done");
+    },
+    manifest: {
+      permissions: ["storage"],
+    },
+  });
+
+  await extension.startup();
+  await extension.awaitMessage("done");
+  await extension.unload();
+});
+
+</script>
+
+</body>
+</html>
diff --git a/toolkit/components/extensions/test/mochitest/test_ext_streamfilter_multiple.html b/toolkit/components/extensions/test/mochitest/test_ext_streamfilter_multiple.html
new file mode 100644
index 0000000000..d1bfbd824b
--- /dev/null
+++ b/toolkit/components/extensions/test/mochitest/test_ext_streamfilter_multiple.html
@@ -0,0 +1,91 @@
+<!DOCTYPE html>
+<html>
+<head>
+  <title>Test for multiple extensions trying to filterResponseData on the same request</title>
+  <script src="/tests/SimpleTest/SimpleTest.js"></script>
+  <script src="/tests/SimpleTest/EventUtils.js"></script>
+  <script src="/tests/SimpleTest/ExtensionTestUtils.js"></script>
+  <link rel="stylesheet" type="text/css" href="/tests/SimpleTest/test.css"/>
+</head>
+<body>
+
+<script type="text/javascript">
+"use strict";
+
+const TEST_URL =
+  "http://example.org/tests/toolkit/components/extensions/test/mochitest/file_streamfilter.txt";
+
+add_task(async () => {
+  const firstExtension = ExtensionTestUtils.loadExtension({
+    manifest: {
+      permissions: ["webRequest", "webRequestBlocking", "<all_urls>"],
+    },
+
+    background() {
+      browser.webRequest.onBeforeRequest.addListener(
+        ({ requestId }) => {
+          const filter = browser.webRequest.filterResponseData(requestId);
+          filter.ondata = event => {
+            filter.write(new TextEncoder().encode("Start "));
+            filter.write(event.data);
+            filter.disconnect();
+          };
+        },
+        {
+          urls: [
+            "http://example.org/*/file_streamfilter.txt",
+          ],
+        },
+        ["blocking"]
+      );
+    },
+  });
+
+  const secondExtension = ExtensionTestUtils.loadExtension({
+    manifest: {
+      permissions: ["webRequest", "webRequestBlocking", "<all_urls>"],
+    },
+
+    background() {
+      browser.webRequest.onBeforeRequest.addListener(
+        ({ requestId }) => {
+          const filter = browser.webRequest.filterResponseData(requestId);
+          filter.ondata = event => {
+            filter.write(event.data);
+          };
+          filter.onstop = event => {
+            filter.write(new TextEncoder().encode(" End"));
+            filter.close();
+          };
+        },
+        {
+          urls: [
+            "http://example.org/tests/toolkit/components/extensions/test/mochitest/file_streamfilter.txt",
+          ],
+        },
+        ["blocking"]
+      );
+    },
+  });
+
+  await firstExtension.startup();
+  await secondExtension.startup();
+
+  let iframe = document.createElement("iframe");
+  iframe.src = TEST_URL;
+  document.body.appendChild(iframe);
+  await new Promise(resolve => iframe.addEventListener("load", () => resolve(), {once: true}));
+
+  let content = await SpecialPowers.spawn(iframe, [], async () => {
+    return this.content.document.body.textContent;
+  });
+  SimpleTest.is(content, "Start Middle\n End", "Correctly intercepted page content");
+
+  await firstExtension.unload();
+  await secondExtension.unload();
+});
+
+</script>
+
+</body>
+</html>
diff --git a/toolkit/components/extensions/test/mochitest/test_ext_streamfilter_processswitch.html b/toolkit/components/extensions/test/mochitest/test_ext_streamfilter_processswitch.html
new file mode 100644
index 0000000000..049178cad0
--- /dev/null
+++ b/toolkit/components/extensions/test/mochitest/test_ext_streamfilter_processswitch.html
@@ -0,0 +1,76 @@
+<!DOCTYPE html>
+<html>
+<head>
+  <title>Test for using filterResponseData to intercept a cross-origin navigation that will involve a process switch with fission</title>
+  <script src="/tests/SimpleTest/SimpleTest.js"></script>
+  <script src="/tests/SimpleTest/EventUtils.js"></script>
+  <script src="/tests/SimpleTest/ExtensionTestUtils.js"></script>
+  <link rel="stylesheet" type="text/css" href="/tests/SimpleTest/test.css"/>
+</head>
+<body>
+
+<script type="text/javascript">
+"use strict";
+
+const TEST_HOST = "http://example.com/";
+const CROSS_ORIGIN_HOST = "http://example.org/";
+const TEST_PATH =
+  "tests/toolkit/components/extensions/test/mochitest/file_streamfilter.txt";
+
+const TEST_URL = TEST_HOST + TEST_PATH;
+const CROSS_ORIGIN_URL = CROSS_ORIGIN_HOST + TEST_PATH;
+
+add_task(async () => {
+  const extension = ExtensionTestUtils.loadExtension({
+    manifest: {
+      permissions: ["webRequest", "webRequestBlocking", "<all_urls>"],
+    },
+
+    background() {
+      browser.webRequest.onBeforeRequest.addListener(
+        ({ requestId }) => {
+          const filter = browser.webRequest.filterResponseData(requestId);
+          filter.onerror = () => browser.test.fail(
+            `Unexpected filterResponseData error: ${filter.error}`
+          );
+          filter.ondata = event => {
+            filter.write(event.data);
+          };
+          filter.onstop = event => {
+            filter.write(new TextEncoder().encode(" End"));
+            filter.close();
+          };
+        },
+        {
+          urls: [
+            "http://example.org/*/file_streamfilter.txt",
+          ],
+        },
+        ["blocking"]
+      );
+    },
+  });
+
+  await extension.startup();
+
+  let iframe = document.createElement("iframe");
+  iframe.src = TEST_URL;
+  document.body.appendChild(iframe);
+  await new Promise(resolve => iframe.addEventListener("load", () => resolve(), {once: true}));
+
+
+  iframe.src = CROSS_ORIGIN_URL;
+  await new Promise(resolve => iframe.addEventListener("load", () => resolve(), {once: true}));
+
+  let content = await SpecialPowers.spawn(iframe, [], async () => {
+    return this.content.document.body.textContent;
+  });
+  SimpleTest.is(content, "Middle\n End", "Correctly intercepted page content");
+
+  await extension.unload();
+});
+
+</script>
+
+</body>
+</html>
diff --git a/toolkit/components/extensions/test/mochitest/test_ext_subframes_privileges.html b/toolkit/components/extensions/test/mochitest/test_ext_subframes_privileges.html
new file mode 100644
index 0000000000..fd034f0b65
--- /dev/null
+++ b/toolkit/components/extensions/test/mochitest/test_ext_subframes_privileges.html
@@ -0,0 +1,340 @@
+<!DOCTYPE HTML>
+<html>
+<head>
+  <meta charset="utf-8">
+  <title>WebExtension test</title>
+  <script src="/tests/SimpleTest/SimpleTest.js"></script>
+  <script src="/tests/SimpleTest/ExtensionTestUtils.js"></script>
+  <script type="text/javascript" src="head.js"></script>
+  <link rel="stylesheet" type="text/css" href="/tests/SimpleTest/test.css"/>
+</head>
+<body>
+
+<script type="text/javascript">
+"use strict";
+/* eslint-disable mozilla/balanced-listeners */
+
+add_task(async function test_webext_tab_subframe_privileges() {
+  function background() {
+    browser.runtime.onMessage.addListener(async ({msg, success, tabId, error}) => {
+      if (msg == "webext-tab-subframe-privileges") {
+        if (success) {
+          await browser.tabs.remove(tabId);
+
+          browser.test.notifyPass(msg);
+        } else {
+          browser.test.log(`Got an unexpected error: ${error}`);
+
+          let tabs = await browser.tabs.query({active: true});
+          await browser.tabs.remove(tabs[0].id);
+
+          browser.test.notifyFail(msg);
+        }
+      }
+    });
+    browser.tabs.create({url: browser.runtime.getURL("/tab.html")});
+  }
+
+  async function tabSubframeScript() {
+    browser.test.assertTrue(browser.tabs != undefined,
+                            "Subframe of a privileged page has access to privileged APIs");
+    if (browser.tabs) {
+      try {
+        let tab = await browser.tabs.getCurrent();
+        browser.runtime.sendMessage({
+          msg: "webext-tab-subframe-privileges",
+          success: true,
+          tabId: tab.id,
+        });
+      } catch (e) {
+        browser.runtime.sendMessage({msg: "webext-tab-subframe-privileges", success: false, error: `${e}`});
+      }
+    } else {
+      browser.runtime.sendMessage({
+        msg: "webext-tab-subframe-privileges",
+        success: false,
+        error: `Privileged APIs missing in WebExtension tab sub-frame`,
+      });
+    }
+  }
+
+  let extensionData = {
+    background,
+    files: {
+      "tab.html": `<!DOCTYPE>
+          <head>
+            <meta charset="utf-8">
+          </head>
+          <body>
+            <iframe src="tab-subframe.html"></iframe>
+          </body>
+        </html>`,
+      "tab-subframe.html": `<!DOCTYPE>
+          <head>
+            <meta charset="utf-8">
+            <script src="tab-subframe.js"><\/script>
+          </head>
+        </html>`,
+      "tab-subframe.js": tabSubframeScript,
+    },
+  };
+  let extension = ExtensionTestUtils.loadExtension(extensionData);
+
+  await extension.startup();
+
+  await extension.awaitFinish("webext-tab-subframe-privileges");
+  await extension.unload();
+});
+
+add_task(async function test_webext_background_subframe_privileges() {
+  function backgroundSubframeScript() {
+    browser.test.assertTrue(browser.tabs != undefined,
+                            "Subframe of a background page has access to privileged APIs");
+    browser.test.notifyPass("webext-background-subframe-privileges");
+  }
+
+  let extensionData = {
+    manifest: {
+      background: {
+        page: "background.html",
+      },
+    },
+    files: {
+      "background.html": `<!DOCTYPE>
+         <head>
+           <meta charset="utf-8">
+         </head>
+         <body>
+           <iframe src="background-subframe.html"></iframe>
+         </body>
+       </html>`,
+      "background-subframe.html": `<!DOCTYPE>
+         <head>
+           <meta charset="utf-8">
+           <script src="background-subframe.js"><\/script>
+         </head>
+       </html>`,
+      "background-subframe.js": backgroundSubframeScript,
+    },
+  };
+  let extension = ExtensionTestUtils.loadExtension(extensionData);
+
+  await extension.startup();
+
+  await extension.awaitFinish("webext-background-subframe-privileges");
+  await extension.unload();
+});
+
+add_task(async function test_webext_contentscript_iframe_subframe_privileges() {
+  function background() {
+    browser.runtime.onMessage.addListener(({name, hasTabsAPI, hasStorageAPI}) => {
+      if (name == "contentscript-iframe-loaded") {
+        browser.test.assertFalse(hasTabsAPI,
+                                 "Subframe of a content script privileged iframes has no access to privileged APIs");
+        browser.test.assertTrue(hasStorageAPI,
+                                "Subframe of a content script privileged iframes has access to content script APIs");
+
+        browser.test.notifyPass("webext-contentscript-subframe-privileges");
+      }
+    });
+  }
+
+  function subframeScript() {
+    browser.runtime.sendMessage({
+      name: "contentscript-iframe-loaded",
+      hasTabsAPI: browser.tabs != undefined,
+      hasStorageAPI: browser.storage != undefined,
+    });
+  }
+
+  function contentScript() {
+    let iframe = document.createElement("iframe");
+    iframe.setAttribute("src", browser.runtime.getURL("/contentscript-iframe.html"));
+    document.body.appendChild(iframe);
+  }
+
+  let extensionData = {
+    background,
+    manifest: {
+      "permissions": ["storage"],
+      "content_scripts": [{
+        "matches": ["https://example.com/*"],
+        "js": ["contentscript.js"],
+      }],
+      web_accessible_resources: [
+        "contentscript-iframe.html",
+      ],
+    },
+    files: {
+      "contentscript.js": contentScript,
+      "contentscript-iframe.html": `<!DOCTYPE>
+         <head>
+           <meta charset="utf-8">
+         </head>
+         <body>
+           <iframe src="contentscript-iframe-subframe.html"></iframe>
+         </body>
+       </html>`,
+      "contentscript-iframe-subframe.html": `<!DOCTYPE>
+         <head>
+           <meta charset="utf-8">
+           <script src="contentscript-iframe-subframe.js"><\/script>
+         </head>
+       </html>`,
+      "contentscript-iframe-subframe.js": subframeScript,
+    },
+  };
+  let extension = ExtensionTestUtils.loadExtension(extensionData);
+
+  await extension.startup();
+
+  let win = window.open("https://example.com");
+
+  await extension.awaitFinish("webext-contentscript-subframe-privileges");
+
+  win.close();
+
+  await extension.unload();
+});
+
+add_task(async function test_webext_background_remote_subframe_privileges() {
+  function backgroundSubframeScript() {
+    window.addEventListener("message", evt => {
+      browser.test.assertEq("http://mochi.test:8888", evt.origin, "postmessage origin ok");
+      browser.test.assertFalse(evt.data.tabs, "remote frame cannot access webextension APIs");
+      browser.test.assertEq("cookie=monster", evt.data.cookie, "Expected cookie value");
+      browser.test.notifyPass("webext-background-subframe-privileges");
+    }, {once: true});
+    browser.cookies.set({url: "http://mochi.test:8888", name: "cookie", "value": "monster"});
+  }
+
+  let extensionData = {
+    manifest: {
+      permissions: ["cookies", "*://mochi.test/*", "tabs"],
+      background: {
+        page: "background.html",
+      },
+    },
+    files: {
+      "background.html": `<!DOCTYPE>
+         <head>
+           <meta charset="utf-8">
+           <script src="background-subframe.js"><\/script>
+         </head>
+         <body>
+           <iframe src='${SimpleTest.getTestFileURL("file_remote_frame.html")}'></iframe>
+         </body>
+       </html>`,
+      "background-subframe.js": backgroundSubframeScript,
+    },
+  };
+  // Need remote webextensions to be able to load remote content from a background page.
+  if (!SpecialPowers.getBoolPref("extensions.webextensions.remote", true)) {
+    return;
+  }
+  let extension = ExtensionTestUtils.loadExtension(extensionData);
+
+  await extension.startup();
+
+  await extension.awaitFinish("webext-background-subframe-privileges");
+  await extension.unload();
+});
+
+// Test a moz-extension:// iframe inside a content iframe in an extension page.
+add_task(async function test_sub_subframe_conduit_verified_env() {
+  let manifest = {
+    content_scripts: [{
+      matches: ["http://mochi.test/*/file_sample.html"],
+      all_frames: true,
+      js: ["cs.js"],
+    }],
+    background: {
+      page: "background.html",
+    },
+    web_accessible_resources: ["iframe.html"],
+  };
+
+  let files = {
+    "iframe.html": `<!DOCTYPE html><meta charset=utf-8> iframe`,
+    "cs.js"() {
+      // A compromised content sandbox shouldn't be able to trick the parent
+      // process into giving it extension privileges by sending false metadata.
+      async function faker(extensionId, envType) {
+        try {
+          let id = envType + "-xyz1234";
+          let wgc = this.content.windowGlobalChild;
+
+          let conduit = wgc.getActor("Conduits").openConduit({}, {
+            id,
+            envType,
+            extensionId,
+            query: ["CreateProxyContext"],
+          });
+
+          return await conduit.queryCreateProxyContext({
+            childId: id,
+            extensionId,
+            envType: "addon_parent",
+            url: this.content.location.href,
+            viewType: "tab",
+          });
+        } catch (e) {
+          return e.message;
+        }
+      }
+
+      let iframe = document.createElement("iframe");
+      iframe.src = browser.runtime.getURL("iframe.html");
+
+      iframe.onload = async () => {
+        for (let envType of ["content_child", "addon_child"]) {
+          let msg = await this.wrappedJSObject.SpecialPowers.spawn(
+              iframe, [browser.runtime.id, envType], faker);
+          browser.test.sendMessage(envType, msg);
+        }
+      };
+      document.body.appendChild(iframe);
+    },
+    "background.html": `<!DOCTYPE html>
+      <meta charset=utf-8>
+      <iframe src="${SimpleTest.getTestFileURL("file_sample.html")}">
+      </iframe>
+      page
+    `,
+  };
+
+  async function expectErrors(ext, log) {
+    let err = await ext.awaitMessage("content_child");
+    is(err, "Bad sender context envType: content_child");
+
+    err = await ext.awaitMessage("addon_child");
+    is(err, "Unknown sender or wrong actor for recvCreateProxyContext");
+  }
+
+  let remote = SpecialPowers.getBoolPref("extensions.webextensions.remote");
+
+  let badProcess = { message: /Bad {[\w-]+} process: web/ };
+  let badPrincipal = { message: /Bad {[\w-]+} principal: http/ };
+  consoleMonitor.start(remote ? [badPrincipal, badProcess] : [badProcess]);
+
+  let extension = ExtensionTestUtils.loadExtension({ manifest, files });
+  await extension.startup();
+
+  if (remote) {
+    info("Need OOP to spoof from a web iframe inside background page.");
+    await expectErrors(extension);
+  }
+
+  info("Try spoofing from the web process.");
+  let win = window.open("./file_sample.html");
+  await expectErrors(extension);
+  win.close();
+
+  await extension.unload();
+  await consoleMonitor.finished();
+  info("Conduit creation logged correct exception(s).");
+});
+
+</script>
+</body>
+</html>
diff --git a/toolkit/components/extensions/test/mochitest/test_ext_tabs_captureTab.html b/toolkit/components/extensions/test/mochitest/test_ext_tabs_captureTab.html
new file mode 100644
index 0000000000..ab06a965ed
--- /dev/null
+++ b/toolkit/components/extensions/test/mochitest/test_ext_tabs_captureTab.html
@@ -0,0 +1,324 @@
+<!DOCTYPE HTML>
+<html>
+<head>
+  <meta charset="utf-8">
+  <title>Tests tabs.captureTab and tabs.captureVisibleTab</title>
+  <script type="text/javascript" src="/tests/SimpleTest/SimpleTest.js"></script>
+  <script type="text/javascript" src="/tests/SimpleTest/ExtensionTestUtils.js"></script>
+  <script type="text/javascript" src="head.js"></script>
+  <link rel="stylesheet" href="/tests/SimpleTest/test.css"/>
+</head>
+<body>
+<script type="text/javascript">
+"use strict";
+
+async function runTest({ html, fullZoom, coords, rect, scale }) {
+  let url = `data:text/html,${encodeURIComponent(html)}#scroll`;
+
+  async function background({ coords, rect, scale, method, fullZoom }) {
+    try {
+      // Wait for the page to load
+      await new Promise(resolve => {
+        browser.webNavigation.onCompleted.addListener(
+          () => resolve(),
+          {url: [{schemes: ["data"]}]});
+      });
+
+      let [tab] = await browser.tabs.query({
+        currentWindow: true,
+        active: true,
+      });
+
+      // TODO: Bug 1665429 - on mobile we ignore zoom for now
+      if (browser.tabs.setZoom) {
+        await browser.tabs.setZoom(tab.id, fullZoom ?? 1);
+      }
+
+      let id = method === "captureVisibleTab" ? tab.windowId : tab.id;
+
+      let [jpeg, png, ...pngs] = await Promise.all([
+        browser.tabs[method](id, { format: "jpeg", quality: 95, rect, scale }),
+        browser.tabs[method](id, { format: "png", quality: 95, rect, scale }),
+        browser.tabs[method](id, { quality: 95, rect, scale }),
+        browser.tabs[method](id, { rect, scale }),
+      ]);
+
+      browser.test.assertTrue(
+        pngs.every(url => url == png),
+        "All PNGs are identical"
+      );
+
+      browser.test.assertTrue(
+        jpeg.startsWith("data:image/jpeg;base64,"),
+        "jpeg is JPEG"
+      );
+      browser.test.assertTrue(
+        png.startsWith("data:image/png;base64,"),
+        "png is PNG"
+      );
+
+      let promises = [jpeg, png].map(
+        url =>
+          new Promise(resolve => {
+            let img = new Image();
+            img.src = url;
+            img.onload = () => resolve(img);
+          })
+      );
+
+      let width = (rect?.width ?? tab.width) * (scale ?? devicePixelRatio);
+      let height = (rect?.height ?? tab.height) * (scale ?? devicePixelRatio);
+
+      [jpeg, png] = await Promise.all(promises);
+      let images = { jpeg, png };
+      for (let format of Object.keys(images)) {
+        let img = images[format];
+
+        // WGP.drawSnapshot() deals in int coordinates, and rounds down.
+        browser.test.assertTrue(
+          Math.abs(width - img.width) <= 1,
+          `${format} ok image width: ${img.width}, expected: ${width}`
+        );
+        browser.test.assertTrue(
+          Math.abs(height - img.height) <= 1,
+          `${format} ok image height ${img.height}, expected: ${height}`
+        );
+
+        let canvas = document.createElement("canvas");
+        canvas.width = img.width;
+        canvas.height = img.height;
+        canvas.mozOpaque = true;
+
+        let ctx = canvas.getContext("2d");
+        ctx.drawImage(img, 0, 0);
+
+        for (let { x, y, color } of coords) {
+          x = (x + img.width) % img.width;
+          y = (y + img.height) % img.height;
+          let imageData = ctx.getImageData(x, y, 1, 1).data;
+
+          if (format == "png") {
+            browser.test.assertEq(
+              `rgba(${color},255)`,
+              `rgba(${[...imageData]})`,
+              `${format} image color is correct at (${x}, ${y})`
+            );
+          } else {
+            // Allow for some deviation in JPEG version due to lossy compression.
+            const SLOP = 3;
+
+            browser.test.log(
+              `Testing ${format} image color at (${x}, ${y}), have rgba(${[
+                ...imageData,
+              ]}), expecting approx. rgba(${color},255)`
+            );
+
+            browser.test.assertTrue(
+              Math.abs(color[0] - imageData[0]) <= SLOP,
+              `${format} image color.red is correct at (${x}, ${y})`
+            );
+            browser.test.assertTrue(
+              Math.abs(color[1] - imageData[1]) <= SLOP,
+              `${format} image color.green is correct at (${x}, ${y})`
+            );
+            browser.test.assertTrue(
+              Math.abs(color[2] - imageData[2]) <= SLOP,
+              `${format} image color.blue is correct at (${x}, ${y})`
+            );
+            browser.test.assertEq(
+              255,
+              imageData[3],
+              `${format} image color.alpha is correct at (${x}, ${y})`
+            );
+          }
+        }
+      }
+
+      browser.test.notifyPass("captureTab");
+    } catch (e) {
+      browser.test.fail(`Error: ${e} :: ${e.stack}`);
+      browser.test.notifyFail("captureTab");
+    }
+  }
+
+  for (let method of ["captureTab", "captureVisibleTab"]) {
+    let options = { coords, rect, scale, method, fullZoom };
+    info(`Testing configuration: ${JSON.stringify(options)}`);
+
+    let extension = ExtensionTestUtils.loadExtension({
+      manifest: {
+        permissions: ["<all_urls>", "webNavigation"],
+      },
+
+      background: `(${background})(${JSON.stringify(options)})`,
+    });
+
+    await extension.startup();
+
+    let testWindow = window.open(url);
+    await extension.awaitFinish("captureTab");
+
+    testWindow.close();
+    await extension.unload();
+  }
+}
+
+async function testEdgeToEdge({ color, fullZoom }) {
+  let neutral = [0xaa, 0xaa, 0xaa];
+
+  let html = `
+    <!DOCTYPE html>
+    <html lang="en">
+    <head>
+      <meta charset="UTF-8">
+      <meta name="viewport" content="width=device-width, initial-scale=1">
+    </head>
+    <body style="background-color: rgb(${color})">
+      <!-- Fill most of the image with a neutral color to test edge-to-edge scaling. -->
+      <div style="position: absolute;
+                  left: 2px;
+                  right: 2px;
+                  top: 2px;
+                  bottom: 2px;
+                  background: rgb(${neutral});"></div>
+    </body>
+    </html>
+  `;
+
+  // Check the colors of the first and last pixels of the image, to make
+  // sure we capture the entire frame, and scale it correctly.
+  let coords = [
+    { x: 0, y: 0, color },
+    { x: -1, y: -1, color },
+    { x: 300, y: 200, color: neutral },
+  ];
+
+  info(`Test edge to edge color ${color} at fullZoom=${fullZoom}`);
+  await runTest({ html, fullZoom, coords });
+}
+
+add_task(async function testCaptureEdgeToEdge() {
+  await testEdgeToEdge({ color: [0, 0, 0], fullZoom: 1 });
+  await testEdgeToEdge({ color: [0, 0, 0], fullZoom: 2 });
+  await testEdgeToEdge({ color: [0, 0, 0], fullZoom: 0.5 });
+  await testEdgeToEdge({ color: [255, 255, 255], fullZoom: 1 });
+});
+
+const tallDoc = `<!DOCTYPE html>
+  <meta charset=utf-8>
+  <meta name="viewport" content="width=device-width, initial-scale=1">
+  <div style="background: yellow; width: 50%; height: 500px;"></div>
+  <div id=scroll style="background: red; width: 25%; height: 5000px;"></div>
+  Opened with the #scroll fragment, scrolls the div ^ into view.
+`;
+
+// Test currently visible viewport is captured if scrolling is involved.
+add_task(async function testScrolledViewport() {
+  await runTest({
+    html: tallDoc,
+    coords: [
+      { x: 50, y: 50, color: [255, 0, 0] },
+      { x: 50, y: -50, color: [255, 0, 0] },
+      { x: -50, y: -50, color: [255, 255, 255] },
+    ],
+  });
+});
+
+// Test rect and scale options.
+add_task(async function testRectAndScale() {
+  await runTest({
+    html: tallDoc,
+    rect: { x: 50, y: 50, width: 10, height: 1000 },
+    scale: 4,
+    coords: [
+      { x: 0, y: 0, color: [255, 255, 0] },
+      { x: -1, y: 0, color: [255, 255, 0] },
+      { x: 0, y: -1, color: [255, 0, 0] },
+      { x: -1, y: -1, color: [255, 0, 0] },
+    ],
+  });
+});
+
+// Test OOP iframes are captured, for Fission compatibility.
+add_task(async function testOOPiframe() {
+  await runTest({
+    html: `<!DOCTYPE html>
+      <meta charset=utf-8>
+      <meta name="viewport" content="width=device-width, initial-scale=1">
+      <iframe src="http://example.net/tests/toolkit/components/extensions/test/mochitest/file_green.html"></iframe>
+    `,
+    coords: [
+      { x: 50, y: 50, color: [0, 255, 0] },
+      { x: 50, y: -50, color: [255, 255, 255] },
+      { x: -50, y: 50, color: [255, 255, 255] },
+    ],
+  });
+});
+
+add_task(async function testOOPiframeScale() {
+  let scale = 2;
+  await runTest({
+    html: `<!DOCTYPE html>
+      <meta charset=utf-8>
+      <meta name="viewport" content="width=device-width, initial-scale=1">
+      <style>
+        body {
+          background: yellow;
+          margin: 0;
+        }
+      </style>
+      <iframe frameborder="0" style="width: 300px; height: 300px" src="http://example.net/tests/toolkit/components/extensions/test/mochitest/file_green_blue.html"></iframe>
+    `,
+    coords: [
+      { x: 20 * scale, y: 20 * scale, color: [0, 255, 0] },
+      { x: 200 * scale, y: 20 * scale, color: [0, 0, 255] },
+      { x: 20 * scale, y: 200 * scale, color: [0, 0, 255] },
+    ],
+    scale,
+  });
+});
+
+add_task(async function testCaptureTabPermissions() {
+  let extension = ExtensionTestUtils.loadExtension({
+    manifest: {
+      permissions: ["tabs"],
+    },
+
+    background() {
+      browser.test.assertEq(
+        undefined,
+        browser.tabs.captureTab,
+        'Extension without "<all_urls>" permission should not have access to captureTab'
+      );
+      browser.test.notifyPass("captureTabPermissions");
+    },
+  });
+
+  await extension.startup();
+  await extension.awaitFinish("captureTabPermissions");
+  await extension.unload();
+});
+
+add_task(async function testCaptureVisibleTabPermissions() {
+  let extension = ExtensionTestUtils.loadExtension({
+    manifest: {
+      permissions: ["tabs"],
+    },
+
+    background() {
+      browser.test.assertEq(
+        undefined,
+        browser.tabs.captureVisibleTab,
+        'Extension without "<all_urls>" permission should not have access to captureVisibleTab'
+      );
+      browser.test.notifyPass("captureVisibleTabPermissions");
+    },
+  });
+
+  await extension.startup();
+  await extension.awaitFinish("captureVisibleTabPermissions");
+  await extension.unload();
+});
+</script>
+</body>
+</html>
diff --git a/toolkit/components/extensions/test/mochitest/test_ext_tabs_create_cookieStoreId.html b/toolkit/components/extensions/test/mochitest/test_ext_tabs_create_cookieStoreId.html
new file mode 100644
index 0000000000..331faca016
--- /dev/null
+++ b/toolkit/components/extensions/test/mochitest/test_ext_tabs_create_cookieStoreId.html
@@ -0,0 +1,210 @@
+<!DOCTYPE html>
+<html lang="en">
+<head>
+  <title>Test tabs.create(cookieStoreId)</title>
+  <script src="/tests/SimpleTest/SimpleTest.js"></script>
+  <script src="/tests/SimpleTest/ExtensionTestUtils.js"></script>
+  <script type="text/javascript" src="head.js"></script>
+  <link rel="stylesheet" type="text/css" href="/tests/SimpleTest/test.css"/>
+</head>
+<body>
+<script type="text/javascript">
+"use strict";
+
+add_task(async function no_cookies_permission() {
+  await SpecialPowers.pushPrefEnv({
+    set: [["privacy.userContext.enabled", true]],
+  });
+
+  let extension = ExtensionTestUtils.loadExtension({
+    async background() {
+      await browser.test.assertRejects(
+        browser.tabs.create({ cookieStoreId: "firefox-container-1" }),
+        /No permission for cookieStoreId/,
+        "cookieStoreId requires cookies permission"
+      );
+      browser.test.sendMessage("done");
+    },
+  });
+
+  await extension.startup();
+  await extension.awaitMessage("done");
+  await extension.unload();
+  await SpecialPowers.popPrefEnv();
+});
+
+add_task(async function invalid_cookieStoreId() {
+  await SpecialPowers.pushPrefEnv({
+    set: [["privacy.userContext.enabled", true]],
+  });
+
+  let extension = ExtensionTestUtils.loadExtension({
+    manifest: {
+      permissions: ["tabs", "cookies"],
+    },
+    async background() {
+      await browser.test.assertRejects(
+        browser.tabs.create({ cookieStoreId: "not-firefox-container-1" }),
+        /Illegal cookieStoreId/,
+        "cookieStoreId must be valid"
+      );
+
+      await browser.test.assertRejects(
+        browser.tabs.create({ cookieStoreId: "firefox-private" }),
+        /Illegal to set private cookieStoreId in a non-private window/,
+        "cookieStoreId cannot be private in a non-private window"
+      );
+
+      browser.test.sendMessage("done");
+    },
+  });
+
+  await extension.startup();
+  await extension.awaitMessage("done");
+  await extension.unload();
+  await SpecialPowers.popPrefEnv();
+});
+
+add_task(async function perma_private_browsing_mode() {
+  await SpecialPowers.pushPrefEnv({
+    set: [["browser.privatebrowsing.autostart", true]],
+  });
+
+  let extension = ExtensionTestUtils.loadExtension({
+    incognitoOverride: "spanning",
+    manifest: {
+      permissions: ["tabs", "cookies"],
+    },
+    async background() {
+      await browser.test.assertRejects(
+        browser.tabs.create({ cookieStoreId: "firefox-container-1" }),
+        /Contextual identities are unavailable in permanent private browsing mode/,
+        "cookieStoreId cannot be a container tab ID in perma-private browsing mode"
+      );
+
+      browser.test.sendMessage("done");
+    },
+  });
+  await extension.startup();
+  await extension.awaitMessage("done");
+  await extension.unload();
+  await SpecialPowers.popPrefEnv();
+});
+
+add_task(async function userContext_disabled() {
+  await SpecialPowers.pushPrefEnv({
+    set: [["privacy.userContext.enabled", false]],
+  });
+  let extension = ExtensionTestUtils.loadExtension({
+    manifest: {
+      permissions: ["tabs", "cookies"],
+    },
+    async background() {
+      await browser.test.assertRejects(
+        browser.tabs.create({ cookieStoreId: "firefox-container-1" }),
+        /Contextual identities are currently disabled/,
+        "cookieStoreId cannot be a container tab ID when contextual identities are disabled"
+      );
+      browser.test.sendMessage("done");
+    },
+  });
+  await extension.startup();
+  await extension.awaitMessage("done");
+  await extension.unload();
+  await SpecialPowers.popPrefEnv();
+});
+
+add_task(async function valid_cookieStoreId() {
+  await SpecialPowers.pushPrefEnv({
+    set: [["privacy.userContext.enabled", true]],
+  });
+
+  const testCases = [
+    {
+      description: "no explicit URL",
+      createProperties: {
+        cookieStoreId: "firefox-container-1",
+      },
+      expectedCookieStoreId: "firefox-container-1",
+    },
+    {
+      description: "pass explicit url",
+      createProperties: {
+        url: "about:blank",
+        cookieStoreId: "firefox-container-1",
+      },
+      expectedCookieStoreId: "firefox-container-1",
+    },{
+      description: "pass explicit not-blank url",
+      createProperties: {
+        url: "https://example.com/",
+        cookieStoreId: "firefox-container-1",
+      },
+      expectedCookieStoreId: "firefox-container-1",
+    },{
+      description: "pass extension page url",
+      createProperties: {
+        url: "blank.html",
+        cookieStoreId: "firefox-container-1",
+      },
+      expectedCookieStoreId: "firefox-container-1",
+    }
+  ];
+
+  async function background(testCases) {
+    for (let { createProperties, expectedCookieStoreId } of testCases) {
+      const { url } = createProperties;
+      const updatedPromise = new Promise(resolve => {
+        const onUpdated = (changedTabId, changed) => {
+          // Loading an extension page causes two `about:blank` messages
+          // because of the process switch
+          if (changed.url && (url == "about:blank" || changed.url != "about:blank")) {
+            browser.tabs.onUpdated.removeListener(onUpdated);
+            resolve({tabId: changedTabId, url: changed.url});
+          }
+        };
+        browser.tabs.onUpdated.addListener(onUpdated);
+      });
+
+      const tab = await browser.tabs.create(createProperties);
+      browser.test.assertEq(
+        expectedCookieStoreId,
+        tab.cookieStoreId,
+        "Expected cookieStoreId for container tab"
+      );
+
+      if (url && url !== "about:blank") {
+        // Make sure tab can load successfully
+        const updated = await updatedPromise;
+        browser.test.assertEq(tab.id, updated.tabId, `Expected value for tab.id`);
+        if (updated.url.startsWith("moz-extension")) {
+          browser.test.assertEq(browser.runtime.getURL(url), updated.url,
+            `Expected value for extension page url`);
+        } else {
+          browser.test.assertEq(url, updated.url, `Expected value for tab.url`);
+        }
+      }
+
+      await browser.tabs.remove(tab.id);
+    }
+    browser.test.sendMessage("done");
+  }
+
+  let extension = ExtensionTestUtils.loadExtension({
+    manifest: {
+      permissions: ["tabs", "cookies"],
+    },
+    files: {
+      "blank.html": `<html><head><meta charset="utf-8"></head></html>`,
+    },
+    background: `(${background})(${JSON.stringify(testCases)})`,
+  });
+
+  await extension.startup();
+  await extension.awaitMessage("done");
+  await extension.unload();
+  await SpecialPowers.popPrefEnv();
+});
+</script>
+</body>
+</html>
diff --git a/toolkit/components/extensions/test/mochitest/test_ext_tabs_executeScript_good.html b/toolkit/components/extensions/test/mochitest/test_ext_tabs_executeScript_good.html
new file mode 100644
index 0000000000..ab3b9de5a3
--- /dev/null
+++ b/toolkit/components/extensions/test/mochitest/test_ext_tabs_executeScript_good.html
@@ -0,0 +1,162 @@
+<!DOCTYPE HTML>
+<html>
+<head>
+  <title>Tabs executeScript Test</title>
+  <script type="text/javascript" src="/tests/SimpleTest/SimpleTest.js"></script>
+  <script type="text/javascript" src="/tests/SimpleTest/ExtensionTestUtils.js"></script>
+  <script type="text/javascript" src="head.js"></script>
+  <link rel="stylesheet" href="/tests/SimpleTest/test.css"/>
+</head>
+<body>
+
+<script type="text/javascript">
+"use strict";
+
+async function testHasPermission(params) {
+  let contentSetup = params.contentSetup || (() => Promise.resolve());
+
+  async function background(contentSetup) {
+    browser.runtime.onMessage.addListener((msg, sender) => {
+      browser.test.assertEq(msg, "script ran", "script ran");
+      browser.test.notifyPass("executeScript");
+    });
+
+    browser.test.onMessage.addListener(msg => {
+      browser.test.assertEq(msg, "execute-script");
+
+      browser.tabs.executeScript({
+        file: "script.js",
+      });
+    });
+
+    await contentSetup();
+
+    browser.test.sendMessage("ready");
+  }
+
+  let extension = ExtensionTestUtils.loadExtension({
+    manifest: params.manifest,
+
+    background: `(${background})(${contentSetup})`,
+
+    files: {
+      "panel.html": `<!DOCTYPE html>
+        <html>
+          <head><meta charset="utf-8"></head>
+          <body>
+          </body>
+        </html>`,
+      "script.js": function() {
+        browser.runtime.sendMessage("script ran");
+      },
+    },
+  });
+
+  await extension.startup();
+  await extension.awaitMessage("ready");
+
+  if (params.setup) {
+    await params.setup(extension);
+  }
+
+  extension.sendMessage("execute-script");
+
+  await extension.awaitFinish("executeScript");
+
+  if (params.tearDown) {
+    await params.tearDown(extension);
+  }
+
+  await extension.unload();
+}
+
+add_task(async function testGoodPermissions() {
+  let tab = await AppTestDelegate.openNewForegroundTab(
+    window,
+    "http://mochi.test:8888/",
+    true
+  );
+
+  info("Test explicit host permission");
+  await testHasPermission({
+    manifest: { permissions: ["http://mochi.test/"] },
+  });
+
+  info("Test explicit host subdomain permission");
+  await testHasPermission({
+    manifest: { permissions: ["http://*.mochi.test/"] },
+  });
+
+  info("Test explicit <all_urls> permission");
+  await testHasPermission({
+    manifest: { permissions: ["<all_urls>"] },
+  });
+
+  info("Test activeTab permission with a browser action click");
+  await testHasPermission({
+    manifest: {
+      permissions: ["activeTab"],
+      browser_action: {},
+    },
+    contentSetup: function() {
+      browser.browserAction.onClicked.addListener(() => {
+        browser.test.log("Clicked.");
+      });
+      return Promise.resolve();
+    },
+    setup: extension => AppTestDelegate.clickBrowserAction(window, extension),
+    tearDown: extension => AppTestDelegate.closeBrowserAction(window, extension),
+  });
+
+  info("Test activeTab permission with a page action click");
+  await testHasPermission({
+    manifest: {
+      permissions: ["activeTab"],
+      page_action: {},
+    },
+    contentSetup: async () => {
+      let [tab] = await browser.tabs.query({
+        active: true,
+        currentWindow: true,
+      });
+      await browser.pageAction.show(tab.id);
+    },
+    setup: extension => AppTestDelegate.clickPageAction(window, extension),
+    tearDown: extension => AppTestDelegate.closePageAction(window, extension),
+  });
+
+  info("Test activeTab permission with a browser action w/popup click");
+  await testHasPermission({
+    manifest: {
+      permissions: ["activeTab"],
+      browser_action: { default_popup: "panel.html" },
+    },
+    setup: async extension => {
+      await AppTestDelegate.clickBrowserAction(window, extension);
+      return AppTestDelegate.awaitExtensionPanel(window, extension);
+    },
+    tearDown: extension => AppTestDelegate.closeBrowserAction(window, extension),
+  });
+
+  info("Test activeTab permission with a page action w/popup click");
+  await testHasPermission({
+    manifest: {
+      permissions: ["activeTab"],
+      page_action: { default_popup: "panel.html" },
+    },
+    contentSetup: async () => {
+      let [tab] = await browser.tabs.query({
+        active: true,
+        currentWindow: true,
+      });
+      await browser.pageAction.show(tab.id);
+    },
+    setup: extension => AppTestDelegate.clickPageAction(window, extension),
+    tearDown: extension => AppTestDelegate.closePageAction(window, extension),
+  });
+
+  await AppTestDelegate.removeTab(window, tab);
+});
+</script>
+</body>
+</html>
diff --git a/toolkit/components/extensions/test/mochitest/test_ext_tabs_permissions.html b/toolkit/components/extensions/test/mochitest/test_ext_tabs_permissions.html
new file mode 100644
index 0000000000..217139f12b
--- /dev/null
+++ b/toolkit/components/extensions/test/mochitest/test_ext_tabs_permissions.html
@@ -0,0 +1,752 @@
+<!DOCTYPE HTML>
+<html>
+<head>
+  <title>Tabs permissions test</title>
+  <script type="text/javascript" src="/tests/SimpleTest/SimpleTest.js"></script>
+  <script type="text/javascript" src="/tests/SimpleTest/ExtensionTestUtils.js"></script>
+  <script type="text/javascript" src="head.js"></script>
+  <link rel="stylesheet" href="/tests/SimpleTest/test.css"/>
+</head>
+<body>
+
+<script type="text/javascript">
+"use strict";
+
+const URL1 =
+  "https://www.example.com/tests/toolkit/components/extensions/test/mochitest/file_tabs_permission_page1.html";
+const URL2 =
+  "https://example.net/tests/toolkit/components/extensions/test/mochitest/file_tabs_permission_page2.html";
+
+const helperExtensionDef = {
+  manifest: {
+    permissions: ["webNavigation", "<all_urls>"],
+  },
+
+  async background() {
+    browser.test.onMessage.addListener(async message => {
+      switch (message.subject) {
+        case "createTab": {
+          const tabLoaded = new Promise(resolve => {
+            browser.webNavigation.onCompleted.addListener(function listener(
+              details
+            ) {
+              if (details.url === message.data.url) {
+                browser.webNavigation.onCompleted.removeListener(listener);
+                resolve();
+              }
+            });
+          });
+
+          const tab = await browser.tabs.create({ url: message.data.url });
+          await tabLoaded;
+          browser.test.sendMessage("tabCreated", tab.id);
+          break;
+        }
+
+        case "changeTabURL": {
+          const tabLoaded = new Promise(resolve => {
+            browser.webNavigation.onCompleted.addListener(function listener(
+              details
+            ) {
+              if (details.url === message.data.url) {
+                browser.webNavigation.onCompleted.removeListener(listener);
+                resolve();
+              }
+            });
+          });
+
+          await browser.tabs.update(message.data.tabId, {
+            url: message.data.url,
+          });
+          await tabLoaded;
+          browser.test.sendMessage("tabURLChanged", message.data.tabId);
+          break;
+        }
+
+        case "changeTabHashAndTitle": {
+          const tabChanged = new Promise(resolve => {
+            let hasURLChangeInfo = false,
+              hasTitleChangeInfo = false;
+            browser.tabs.onUpdated.addListener(function listener(
+              tabId,
+              changeInfo,
+              tab
+            ) {
+              if (changeInfo.url?.endsWith(message.data.urlHash)) {
+                hasURLChangeInfo = true;
+              }
+              if (changeInfo.title === message.data.title) {
+                hasTitleChangeInfo = true;
+              }
+              if (hasURLChangeInfo && hasTitleChangeInfo) {
+                browser.tabs.onUpdated.removeListener(listener);
+                resolve();
+              }
+            });
+          });
+
+          await browser.tabs.executeScript(message.data.tabId, {
+            code: `
+              document.location.hash = ${JSON.stringify(message.data.urlHash)};
+              document.title = ${JSON.stringify(message.data.title)};
+            `,
+          });
+          await tabChanged;
+          browser.test.sendMessage("tabHashAndTitleChanged");
+          break;
+        }
+
+        case "removeTab": {
+          await browser.tabs.remove(message.data.tabId);
+          browser.test.sendMessage("tabRemoved");
+          break;
+        }
+
+        default:
+          browser.test.fail(`Received unexpected message: ${message}`);
+      }
+    });
+  },
+};
+
+/*
+ * Test tabs.query function
+ * Check if the correct tabs are queried by url or title based on the granted permissions
+ */
+async function test_query(testCases, permissions) {
+  const helperExtension = ExtensionTestUtils.loadExtension(helperExtensionDef);
+
+  const extension = ExtensionTestUtils.loadExtension({
+    manifest: {
+      permissions,
+    },
+
+    async background() {
+      // wait for start message
+      const [testCases, tabIdFromURL1, tabIdFromURL2] = await new Promise(
+        resolve => {
+          browser.test.onMessage.addListener(message => resolve(message));
+        }
+      );
+
+      for (const testCase of testCases) {
+        const query = testCase.query;
+        const matchingTabs = testCase.matchingTabs;
+
+        let tabQuery = await browser.tabs.query(query);
+        // ignore other tabs in the window
+        tabQuery = tabQuery.filter(tab => {
+          return tab.id === tabIdFromURL1 || tab.id === tabIdFromURL2;
+        });
+
+        browser.test.assertEq(matchingTabs, tabQuery.length, `Tabs queried`);
+      }
+      // send end message
+      browser.test.notifyPass("tabs.query");
+    },
+  });
+
+  await helperExtension.startup();
+  await extension.startup();
+
+  helperExtension.sendMessage({
+    subject: "createTab",
+    data: { url: URL1 },
+  });
+  const tabIdFromURL1 = await helperExtension.awaitMessage("tabCreated");
+
+  helperExtension.sendMessage({
+    subject: "createTab",
+    data: { url: URL2 },
+  });
+  const tabIdFromURL2 = await helperExtension.awaitMessage("tabCreated");
+
+  if (permissions.includes("activeTab")) {
+    extension.grantActiveTab(tabIdFromURL2);
+  }
+
+  extension.sendMessage([testCases, tabIdFromURL1, tabIdFromURL2]);
+  await extension.awaitFinish("tabs.query");
+
+  helperExtension.sendMessage({
+    subject: "removeTab",
+    data: { tabId: tabIdFromURL1 },
+  });
+  await helperExtension.awaitMessage("tabRemoved");
+
+  helperExtension.sendMessage({
+    subject: "removeTab",
+    data: { tabId: tabIdFromURL2 },
+  });
+  await helperExtension.awaitMessage("tabRemoved");
+
+  await extension.unload();
+  await helperExtension.unload();
+}
+
+// https://www.example.com host permission
+add_task(function query_with_host_permission_url1() {
+  return test_query(
+    [
+      {
+        query: { url: "*://www.example.com/*" },
+        matchingTabs: 1,
+      },
+      {
+        query: { url: "<all_urls>" },
+        matchingTabs: 1,
+      },
+      {
+        query: { url: ["*://www.example.com/*", "*://example.net/*"] },
+        matchingTabs: 1,
+      },
+      {
+        query: { title: "The Title" },
+        matchingTabs: 1,
+      },
+      {
+        query: { title: "Another Title" },
+        matchingTabs: 0,
+      },
+      {
+        query: {},
+        matchingTabs: 2,
+      },
+    ],
+    ["*://www.example.com/*"]
+  );
+});
+
+// https://example.net host permission
+add_task(function query_with_host_permission_url2() {
+  return test_query(
+    [
+      {
+        query: { url: "*://www.example.com/*" },
+        matchingTabs: 0,
+      },
+      {
+        query: { url: "<all_urls>" },
+        matchingTabs: 1,
+      },
+      {
+        query: { url: ["*://www.example.com/*", "*://example.net/*"] },
+        matchingTabs: 1,
+      },
+      {
+        query: { title: "The Title" },
+        matchingTabs: 0,
+      },
+      {
+        query: { title: "Another Title" },
+        matchingTabs: 1,
+      },
+      {
+        query: {},
+        matchingTabs: 2,
+      },
+    ],
+    ["*://example.net/*"]
+  );
+});
+
+// <all_urls> permission
+add_task(function query_with_host_permission_all_urls() {
+  return test_query(
+    [
+      {
+        query: { url: "*://www.example.com/*" },
+        matchingTabs: 1,
+      },
+      {
+        query: { url: "<all_urls>" },
+        matchingTabs: 2,
+      },
+      {
+        query: { url: ["*://www.example.com/*", "*://example.net/*"] },
+        matchingTabs: 2,
+      },
+      {
+        query: { title: "The Title" },
+        matchingTabs: 1,
+      },
+      {
+        query: { title: "Another Title" },
+        matchingTabs: 1,
+      },
+      {
+        query: {},
+        matchingTabs: 2,
+      },
+    ],
+    ["<all_urls>"]
+  );
+});
+
+// tabs permission
+add_task(function query_with_tabs_permission() {
+  return test_query(
+    [
+      {
+        query: { url: "*://www.example.com/*" },
+        matchingTabs: 1,
+      },
+      {
+        query: { url: "<all_urls>" },
+        matchingTabs: 2,
+      },
+      {
+        query: { url: ["*://www.example.com/*", "*://example.net/*"] },
+        matchingTabs: 2,
+      },
+      {
+        query: { title: "The Title" },
+        matchingTabs: 1,
+      },
+      {
+        query: { title: "Another Title" },
+        matchingTabs: 1,
+      },
+      {
+        query: {},
+        matchingTabs: 2,
+      },
+    ],
+    ["tabs"]
+  );
+});
+
+// activeTab permission
+add_task(function query_with_activeTab_permission() {
+  return test_query(
+    [
+      {
+        query: { url: "*://www.example.com/*" },
+        matchingTabs: 0,
+      },
+      {
+        query: { url: "<all_urls>" },
+        matchingTabs: 1,
+      },
+      {
+        query: { url: ["*://www.example.com/*", "*://example.net/*"] },
+        matchingTabs: 1,
+      },
+      {
+        query: { title: "The Title" },
+        matchingTabs: 0,
+      },
+      {
+        query: { title: "Another Title" },
+        matchingTabs: 1,
+      },
+      {
+        query: {},
+        matchingTabs: 2,
+      },
+    ],
+    ["activeTab"]
+  );
+});
+// no permission
+add_task(function query_without_permission() {
+  return test_query(
+    [
+      {
+        query: { url: "*://www.example.com/*" },
+        matchingTabs: 0,
+      },
+      {
+        query: { url: "<all_urls>" },
+        matchingTabs: 0,
+      },
+      {
+        query: { url: ["*://www.example.com/*", "*://example.net/*"] },
+        matchingTabs: 0,
+      },
+      {
+        query: { title: "The Title" },
+        matchingTabs: 0,
+      },
+      {
+        query: { title: "Another Title" },
+        matchingTabs: 0,
+      },
+      {
+        query: {},
+        matchingTabs: 2,
+      },
+    ],
+    []
+  );
+});
+
+/*
+ * Test tabs.onUpdate and tabs.get function
+ * Check if the changeInfo or tab object contains the restricted properties
+ * url and title only when the right permissions are granted
+ * The tab is updated without causing navigation in order to also test activeTab permission
+ */
+async function test_restricted_properties(
+  permissions,
+  hasRestrictedProperties
+) {
+  const helperExtension = ExtensionTestUtils.loadExtension(helperExtensionDef);
+
+  const extension = ExtensionTestUtils.loadExtension({
+    manifest: {
+      permissions,
+    },
+
+    async background() {
+      // wait for test start signal and data
+      const [
+        hasRestrictedProperties,
+        tabId,
+        urlHash,
+        title,
+      ] = await new Promise(resolve => {
+        browser.test.onMessage.addListener(message => {
+          resolve(message);
+        });
+      });
+
+      let hasURLChangeInfo = false,
+        hasTitleChangeInfo = false;
+      function onUpdateListener(tabId, changeInfo, tab) {
+        if (changeInfo.url?.endsWith(urlHash)) {
+          hasURLChangeInfo = true;
+        }
+        if (changeInfo.title === title) {
+          hasTitleChangeInfo = true;
+        }
+      }
+      browser.tabs.onUpdated.addListener(onUpdateListener);
+
+      // wait for test evaluation signal and data
+      await new Promise(resolve => {
+        browser.test.onMessage.addListener(message => {
+          if (message === "collectTestResults") {
+            resolve(message);
+          }
+        });
+        browser.test.sendMessage("waitingForTabPropertyChanges");
+      });
+
+      // check onUpdate changeInfo
+      browser.test.assertEq(
+        hasRestrictedProperties,
+        hasURLChangeInfo,
+        `Has changeInfo property "url"`
+      );
+      browser.test.assertEq(
+        hasRestrictedProperties,
+        hasTitleChangeInfo,
+        `Has changeInfo property "title"`
+      );
+      // check tab properties
+      const tabGet = await browser.tabs.get(tabId);
+      browser.test.assertEq(
+        hasRestrictedProperties,
+        !!tabGet.url?.endsWith(urlHash),
+        `Has tab property "url"`
+      );
+      browser.test.assertEq(
+        hasRestrictedProperties,
+        tabGet.title === title,
+        `Has tab property "title"`
+      );
+      // send end message
+      browser.test.notifyPass("tabs.restricted_properties");
+    },
+  });
+
+  const urlHash = "#ChangedURL";
+  const title = "Changed Title";
+
+  await helperExtension.startup();
+  await extension.startup();
+
+  helperExtension.sendMessage({
+    subject: "createTab",
+    data: { url: URL1 },
+  });
+  const tabId = await helperExtension.awaitMessage("tabCreated");
+
+  if (permissions.includes("activeTab")) {
+    extension.grantActiveTab(tabId);
+  }
+  // send test start signal and data
+  extension.sendMessage([hasRestrictedProperties, tabId, urlHash, title]);
+  await extension.awaitMessage("waitingForTabPropertyChanges");
+
+  helperExtension.sendMessage({
+    subject: "changeTabHashAndTitle",
+    data: {
+      tabId,
+      urlHash,
+      title,
+    },
+  });
+  await helperExtension.awaitMessage("tabHashAndTitleChanged");
+
+  // send end signal and evaluate results
+  extension.sendMessage("collectTestResults");
+  await extension.awaitFinish("tabs.restricted_properties");
+
+  helperExtension.sendMessage({
+    subject: "removeTab",
+    data: { tabId },
+  });
+  await helperExtension.awaitMessage("tabRemoved");
+
+  await extension.unload();
+  await helperExtension.unload();
+}
+
+// https://www.example.com host permission
+add_task(function has_restricted_properties_with_host_permission_url1() {
+  return test_restricted_properties(["*://www.example.com/*"], true);
+});
+// https://example.net host permission
+add_task(function has_restricted_properties_with_host_permission_url2() {
+  return test_restricted_properties(["*://example.net/*"], false);
+});
+// <all_urls> permission
+add_task(function has_restricted_properties_with_host_permission_all_urls() {
+  return test_restricted_properties(["<all_urls>"], true);
+});
+// tabs permission
+add_task(function has_restricted_properties_with_tabs_permission() {
+  return test_restricted_properties(["tabs"], true);
+});
+// activeTab permission
+add_task(function has_restricted_properties_with_activeTab_permission() {
+  return test_restricted_properties(["activeTab"], true);
+}).skip(); // TODO bug 1686080: support changeInfo.url with activeTab
+// no permission
+add_task(function has_restricted_properties_without_permission() {
+  return test_restricted_properties([], false);
+});
+
+
+/*
+ * Test tabs.onUpdate filter functionality
+ * Check if the restricted filter properties only work if the
+ * right permissions are granted
+ */
+async function test_onUpdateFilter(testCases, permissions) {
+  // Filters for onUpdated are not supported on Android.
+  if (AppConstants.platform === "android") {
+    return;
+  }
+
+  const helperExtension = ExtensionTestUtils.loadExtension(helperExtensionDef);
+
+  const extension = ExtensionTestUtils.loadExtension({
+    manifest: {
+      permissions,
+    },
+
+    async background() {
+      let listenerGotCalled = false;
+      function onUpdateListener(tabId, changeInfo, tab) {
+        listenerGotCalled = true;
+      }
+
+      browser.test.onMessage.addListener(async message => {
+        switch (message.subject) {
+          case "setup": {
+            browser.tabs.onUpdated.addListener(
+              onUpdateListener,
+              message.data.filter
+            );
+            browser.test.sendMessage("done");
+            break;
+          }
+
+          case "collectTestResults": {
+            browser.test.assertEq(
+              message.data.expectEvent,
+              listenerGotCalled,
+              `Update listener called`
+            );
+            browser.tabs.onUpdated.removeListener(onUpdateListener);
+            listenerGotCalled = false;
+            browser.test.sendMessage("done");
+            break;
+          }
+
+          default:
+            browser.test.fail(`Received unexpected message: ${message}`);
+        }
+      });
+    },
+  });
+
+  await helperExtension.startup();
+  await extension.startup();
+
+  for (const testCase of testCases) {
+    helperExtension.sendMessage({
+      subject: "createTab",
+      data: { url: URL1 },
+    });
+    const tabId = await helperExtension.awaitMessage("tabCreated");
+
+    extension.sendMessage({
+      subject: "setup",
+      data: {
+        filter: testCase.filter,
+      },
+    });
+    await extension.awaitMessage("done");
+
+    helperExtension.sendMessage({
+      subject: "changeTabURL",
+      data: {
+        tabId,
+        url: URL2,
+      },
+    });
+    await helperExtension.awaitMessage("tabURLChanged");
+
+    extension.sendMessage({
+      subject: "collectTestResults",
+      data: {
+        expectEvent: testCase.expectEvent,
+      },
+    });
+    await extension.awaitMessage("done");
+
+    helperExtension.sendMessage({
+      subject: "removeTab",
+      data: { tabId },
+    });
+    await helperExtension.awaitMessage("tabRemoved");
+  }
+
+  await extension.unload();
+  await helperExtension.unload();
+}
+
+// https://mozilla.org host permission
+add_task(function onUpdateFilter_with_host_permission_url3() {
+  return test_onUpdateFilter(
+    [
+      {
+        filter: { urls: ["*://mozilla.org/*"] },
+        expectEvent: false,
+      },
+      {
+        filter: { urls: ["<all_urls>"] },
+        expectEvent: false,
+      },
+      {
+        filter: { urls: ["*://mozilla.org/*", "*://example.net/*"] },
+        expectEvent: false,
+      },
+      {
+        filter: { properties: ["title"] },
+        expectEvent: false,
+      },
+      {
+        filter: {},
+        expectEvent: true,
+      },
+    ],
+    ["*://mozilla.org/*"]
+  );
+});
+
+// https://example.net host permission
+add_task(function onUpdateFilter_with_host_permission_url2() {
+  return test_onUpdateFilter(
+    [
+      {
+        filter: { urls: ["*://mozilla.org/*"] },
+        expectEvent: false,
+      },
+      {
+        filter: { urls: ["<all_urls>"] },
+        expectEvent: true,
+      },
+      {
+        filter: { urls: ["*://mozilla.org/*", "*://example.net/*"] },
+        expectEvent: true,
+      },
+      {
+        filter: { properties: ["title"] },
+        expectEvent: true,
+      },
+      {
+        filter: {},
+        expectEvent: true,
+      },
+    ],
+    ["*://example.net/*"]
+  );
+});
+
+// <all_urls> permission
+add_task(function onUpdateFilter_with_host_permission_all_urls() {
+  return test_onUpdateFilter(
+    [
+      {
+        filter: { urls: ["*://mozilla.org/*"] },
+        expectEvent: false,
+      },
+      {
+        filter: { urls: ["<all_urls>"] },
+        expectEvent: true,
+      },
+      {
+        filter: { urls: ["*://mozilla.org/*", "*://example.net/*"] },
+        expectEvent: true,
+      },
+      {
+        filter: { properties: ["title"] },
+        expectEvent: true,
+      },
+      {
+        filter: {},
+        expectEvent: true,
+      },
+    ],
+    ["<all_urls>"]
+  );
+});
+
+// tabs permission
+add_task(function onUpdateFilter_with_tabs_permission() {
+  return test_onUpdateFilter(
+    [
+      {
+        filter: { urls: ["*://mozilla.org/*"] },
+        expectEvent: false,
+      },
+      {
+        filter: { urls: ["<all_urls>"] },
+        expectEvent: true,
+      },
+      {
+        filter: { urls: ["*://mozilla.org/*", "*://example.net/*"] },
+        expectEvent: true,
+      },
+      {
+        filter: { properties: ["title"] },
+        expectEvent: true,
+      },
+      {
+        filter: {},
+        expectEvent: true,
+      },
+    ],
+    ["tabs"]
+  );
+});
+
+</script>
+
+</body>
+</html>
diff --git a/toolkit/components/extensions/test/mochitest/test_ext_tabs_query_popup.html b/toolkit/components/extensions/test/mochitest/test_ext_tabs_query_popup.html
new file mode 100644
index 0000000000..80b6def0ab
--- /dev/null
+++ b/toolkit/components/extensions/test/mochitest/test_ext_tabs_query_popup.html
@@ -0,0 +1,102 @@
+<!DOCTYPE HTML>
+<html>
+<head>
+  <title>Tabs create Test</title>
+  <script type="text/javascript" src="/tests/SimpleTest/SimpleTest.js"></script>
+  <script type="text/javascript" src="/tests/SimpleTest/ExtensionTestUtils.js"></script>
+  <script type="text/javascript" src="head.js"></script>
+  <link rel="stylesheet" href="/tests/SimpleTest/test.css"/>
+</head>
+<body>
+
+<script type="text/javascript">
+"use strict";
+
+add_setup(async () => {
+  // TODO bug 1799344: remove this when the pref is true by default.
+  await SpecialPowers.pushPrefEnv({
+    "set": [
+      ["extensions.openPopupWithoutUserGesture.enabled", true],
+    ],
+  });
+});
+
+async function test_query(query) {
+  let extension = ExtensionTestUtils.loadExtension({
+    manifest: {
+      browser_specific_settings: {
+        gecko: {
+          id: "current-window@tests.mozilla.org",
+        }
+      },
+      permissions: ["tabs"],
+      browser_action: {
+        default_popup: "popup.html",
+      },
+    },
+
+    useAddonManager: "permanent",
+
+    background: async function() {
+      let query = await new Promise(resolve => {
+        browser.test.onMessage.addListener(message => {
+          resolve(message);
+        });
+      });
+      let tab = await browser.tabs.create({ url: "http://www.example.com", active: true });
+      browser.runtime.onMessage.addListener(message => {
+        if (message === "popup-loaded") {
+          browser.runtime.sendMessage({ tab, query });
+        }
+      });
+      browser.browserAction.openPopup();
+    },
+
+    files: {
+      "popup.html": `<!DOCTYPE html><meta charset="utf-8"><script src="popup.js"><\/script>`,
+      "popup.js"() {
+        browser.runtime.onMessage.addListener(async function({ tab, query }) {
+          let tabs = await browser.tabs.query(query);
+          browser.test.assertEq(tabs.length, 1, `Got one tab`);
+          browser.test.assertEq(tabs[0].id, tab.id, "The tab is the right one");
+
+          // Create a new tab and verify that we still see the right result
+          let newTab = await browser.tabs.create({ url: "http://www.example.com", active: true });
+          tabs = await browser.tabs.query(query);
+          browser.test.assertEq(tabs.length, 1, `Got one tab`);
+          browser.test.assertEq(tabs[0].id, newTab.id, "Got the newly-created tab");
+
+          await browser.tabs.remove(newTab.id);
+
+          // Remove the tab and verify that we see the old tab
+          tabs = await browser.tabs.query(query);
+          browser.test.assertEq(tabs.length, 1, `Got one tab`);
+          browser.test.assertEq(tabs[0].id, tab.id, "Got the tab that was active before");
+
+          // Cleanup
+          await browser.tabs.remove(tab.id);
+
+          browser.test.notifyPass("tabs.query");
+        });
+        browser.runtime.sendMessage("popup-loaded");
+      },
+    },
+  });
+
+  await extension.startup();
+  extension.sendMessage(query);
+  await extension.awaitFinish("tabs.query");
+  await extension.unload();
+}
+
+add_task(function test_query_currentWindow_from_popup() {
+  return test_query({ currentWindow: true, active: true });
+});
+
+add_task(function test_query_lastActiveWindow_from_popup() {
+  return test_query({ lastFocusedWindow: true, active: true });
+});
+</script>
+
+</body>
+</html>
diff --git a/toolkit/components/extensions/test/mochitest/test_ext_tabs_sendMessage.html b/toolkit/components/extensions/test/mochitest/test_ext_tabs_sendMessage.html
new file mode 100644
index 0000000000..4b230c258c
--- /dev/null
+++ b/toolkit/components/extensions/test/mochitest/test_ext_tabs_sendMessage.html
@@ -0,0 +1,152 @@
+<!DOCTYPE HTML>
+<html>
+<head>
+  <title>Test tabs.sendMessage</title>
+  <script src="/tests/SimpleTest/SimpleTest.js"></script>
+  <script src="/tests/SimpleTest/ExtensionTestUtils.js"></script>
+  <script type="text/javascript" src="head.js"></script>
+  <link rel="stylesheet" type="text/css" href="/tests/SimpleTest/test.css"/>
+</head>
+<body>
+<script>
+"use strict";
+
+add_task(async function test_tabs_sendMessage_to_extension_page_frame() {
+  let extension = ExtensionTestUtils.loadExtension({
+    manifest: {
+      content_scripts: [{
+        matches: ["http://mochi.test/*/file_sample.html?tabs.sendMessage"],
+        js: ["cs.js"],
+      }],
+      web_accessible_resources: ["page.html", "page.js"],
+    },
+
+    async background() {
+      let tab;
+
+      browser.runtime.onMessage.addListener(async (msg, sender) => {
+        browser.test.assertEq(msg, "page-script-ready");
+        browser.test.assertEq(sender.url, browser.runtime.getURL("page.html"));
+
+        let tabId = sender.tab.id;
+        let response = await browser.tabs.sendMessage(tabId, "tab-sendMessage");
+
+        switch (response) {
+          case "extension-tab":
+            browser.test.assertEq(tab.id, tabId, "Extension tab responded");
+            browser.test.assertEq(sender.frameId, 0, "Response from top level");
+            await browser.tabs.remove(tab.id);
+            browser.test.sendMessage("extension-tab-responded");
+            break;
+
+          case "extension-frame":
+            browser.test.assertTrue(sender.frameId > 0, "Response from iframe");
+            browser.test.sendMessage("extension-frame-responded");
+            break;
+
+          default:
+            browser.test.fail("Unexpected response: " + response);
+        }
+      });
+
+      tab = await browser.tabs.create({ url: "page.html" });
+    },
+
+    files: {
+      "cs.js"() {
+        let iframe = document.createElement("iframe");
+        iframe.src = browser.runtime.getURL("page.html");
+        document.body.append(iframe);
+        browser.test.sendMessage("content-script-done");
+      },
+
+      "page.html": `<!DOCTYPE html>
+        <meta charset=utf-8>
+        <script src=page.js><\/script>
+        Extension page`,
+
+      "page.js"() {
+        browser.runtime.onMessage.addListener(async msg => {
+          browser.test.assertEq(msg, "tab-sendMessage");
+          return window.parent === window ? "extension-tab" : "extension-frame";
+        });
+        browser.runtime.sendMessage("page-script-ready");
+      },
+    }
+  });
+
+  await extension.startup();
+  await extension.awaitMessage("extension-tab-responded");
+
+  let win = window.open("file_sample.html?tabs.sendMessage");
+  await extension.awaitMessage("content-script-done");
+  await extension.awaitMessage("extension-frame-responded");
+  win.close();
+
+  await extension.unload();
+});
+
+add_task(async function test_tabs_sendMessage_using_frameId() {
+  let extension = ExtensionTestUtils.loadExtension({
+    manifest: {
+      content_scripts: [
+        {
+          matches: ["http://mochi.test/*/file_contains_iframe.html"],
+          run_at: "document_start",
+          js: ["cs_top.js"],
+        },
+        {
+          matches: ["http://example.org/*/file_contains_img.html"],
+          js: ["cs_iframe.js"],
+          all_frames: true,
+        },
+      ],
+    },
+
+    background() {
+      browser.runtime.onMessage.addListener(async (msg, sender) => {
+        let { tab, frameId } = sender;
+        browser.test.assertEq(msg, "cs_iframe_ready", "Iframe cs ready.");
+        browser.test.assertTrue(frameId > 0, "Not from the top frame.");
+
+        let response = await browser.tabs.sendMessage(tab.id, "msg");
+        browser.test.assertEq(response, "cs_top", "Top cs responded first.");
+
+        response = await browser.tabs.sendMessage(tab.id, "msg", { frameId });
+        browser.test.assertEq(response, "cs_iframe", "Iframe cs reponded.");
+
+        browser.test.sendMessage("done");
+      });
+      browser.test.sendMessage("ready");
+    },
+
+    files: {
+      "cs_top.js"() {
+        browser.test.log("Top content script loaded.")
+        browser.runtime.onMessage.addListener(async () => "cs_top");
+      },
+      "cs_iframe.js"() {
+        browser.test.log("Iframe content script loaded.")
+        browser.runtime.onMessage.addListener((msg, sender, sendResponse) => {
+          browser.test.log("Iframe content script received message.")
+          setTimeout(() => sendResponse("cs_iframe"), 100);
+          return true;
+        });
+        browser.runtime.sendMessage("cs_iframe_ready");
+      },
+    },
+  });
+
+  await extension.startup();
+  await extension.awaitMessage("ready");
+
+  let win = window.open("file_contains_iframe.html");
+  await extension.awaitMessage("done");
+  win.close();
+
+  await extension.unload();
+});
+
+</script>
+</body>
+</html>
diff --git a/toolkit/components/extensions/test/mochitest/test_ext_test.html b/toolkit/components/extensions/test/mochitest/test_ext_test.html
new file mode 100644
index 0000000000..bf68786465
--- /dev/null
+++ b/toolkit/components/extensions/test/mochitest/test_ext_test.html
@@ -0,0 +1,341 @@
+<!DOCTYPE HTML>
+<html>
+<head>
+  <title>Testing test</title>
+  <script src="/tests/SimpleTest/SimpleTest.js"></script>
+  <script src="/tests/SimpleTest/ExtensionTestUtils.js"></script>
+  <script type="text/javascript" src="head.js"></script>
+  <link rel="stylesheet" type="text/css" href="/tests/SimpleTest/test.css">
+</head>
+<body>
+
+<script>
+"use strict";
+
+function loadExtensionAndInterceptTest(extensionData) {
+  let results = [];
+  let testResolve;
+  let testDone = new Promise(resolve => { testResolve = resolve; });
+  let handler = {
+    testResult(...result) {
+      result.pop();
+      results.push(result);
+      SimpleTest.info(`Received test result: ${JSON.stringify(result)}`);
+    },
+
+    testMessage(msg, ...args) {
+      results.push(["test-message", msg, ...args]);
+      SimpleTest.info(`Received message: ${msg} ${JSON.stringify(args)}`);
+      if (msg === "This is the last browser.test call") {
+        testResolve();
+      }
+    },
+  };
+  let extension = SpecialPowers.loadExtension(extensionData, handler);
+  SimpleTest.registerCleanupFunction(() => {
+    if (extension.state == "pending" || extension.state == "running") {
+      SimpleTest.ok(false, "Extension left running at test shutdown");
+      return extension.unload();
+    } else if (extension.state == "unloading") {
+      SimpleTest.ok(false, "Extension not fully unloaded at test shutdown");
+    }
+  });
+  extension.awaitResults = () => testDone.then(() => results);
+  return extension;
+}
+
+// NOTE: This test does not verify the behavior expected by calling the browser.test API methods.
+//
+// On the contrary it tests what messages ext-test.js sends to the parent process as a result of
+// processing different kind of parameters (e.g. how a dom element or a JS object with a custom
+// toString method are being serialized into strings).
+//
+// All browser.test calls results are intercepted by the test itself, see verifyTestResults for
+// the expectations of each browser.test call.
+function testScript() {
+  browser.test.notifyPass("dot notifyPass");
+  browser.test.notifyFail("dot notifyFail");
+  browser.test.log("dot log");
+  browser.test.fail("dot fail");
+  browser.test.succeed("dot succeed");
+  browser.test.assertTrue(true);
+  browser.test.assertFalse(false);
+  browser.test.assertEq("", "");
+
+  let obj = {};
+  let arr = [];
+  browser.test.assertTrue(obj, "Object truthy");
+  browser.test.assertTrue(arr, "Array truthy");
+  browser.test.assertTrue(true, "True truthy");
+  browser.test.assertTrue(false, "False truthy");
+  browser.test.assertTrue(null, "Null truthy");
+  browser.test.assertTrue(undefined, "Void truthy");
+
+  browser.test.assertFalse(obj, "Object falsey");
+  browser.test.assertFalse(arr, "Array falsey");
+  browser.test.assertFalse(true, "True falsey");
+  browser.test.assertFalse(false, "False falsey");
+  browser.test.assertFalse(null, "Null falsey");
+  browser.test.assertFalse(undefined, "Void falsey");
+
+  browser.test.assertEq(obj, obj, "Object equality");
+  browser.test.assertEq(arr, arr, "Array equality");
+  browser.test.assertEq(null, null, "Null equality");
+  browser.test.assertEq(undefined, undefined, "Void equality");
+
+  browser.test.assertEq({}, {}, "Object reference inequality");
+  browser.test.assertEq([], [], "Array reference inequality");
+  browser.test.assertEq(true, 1, "strict: true and 1 inequality");
+  browser.test.assertEq("1", 1, "strict: '1' and 1 inequality");
+  browser.test.assertEq(null, undefined, "Null and void inequality");
+
+  browser.test.assertDeepEq({a: 1, b: 1}, {b: 1, a: 1}, "Object deep eq");
+  browser.test.assertDeepEq([[2], [1]], [[2], [1]], "Array deep eq");
+  browser.test.assertDeepEq(true, 1, "strict: true and 1 deep ineq");
+  browser.test.assertDeepEq("1", 1, "strict: '1' and 1 deep ineq");
+  // Key with undefined value should be different from object without key:
+  browser.test.assertDeepEq(null, undefined, "Null and void deep ineq");
+  browser.test.assertDeepEq({c: undefined}, {c: null}, "void+null deep ineq");
+  browser.test.assertDeepEq({a: undefined, b: 1}, {b: 1}, "void/- deep ineq");
+
+  browser.test.assertDeepEq(NaN, NaN, "NaN deep eq");
+  browser.test.assertDeepEq(NaN, null, "NaN+null deep ineq");
+  browser.test.assertDeepEq(Infinity, Infinity, "Infinity deep eq");
+  browser.test.assertDeepEq(Infinity, null, "Infinity+null deep ineq");
+
+  obj = {
+    toString() {
+      return "Dynamic toString";
+    },
+  };
+  browser.test.assertEq(obj, obj, "obj with dynamic toString()");
+
+  browser.test.assertThrows(
+    () => { throw new Error("dummy"); },
+    /dummy2/,
+    "intentional failure"
+  );
+  browser.test.assertThrows(
+    () => { throw new Error("dummy2"); },
+    /dummy3/
+  );
+  browser.test.assertThrows(
+    () => {},
+    /dummy/
+  );
+
+  // The WebIDL version of assertDeepEq structurally clones before sending the
+  // params to the main thread. This check verifies that the behavior is
+  // consistent between the WebIDL and Schemas.jsm-generated API bindings.
+  browser.test.assertThrows(
+    () => browser.test.assertDeepEq(obj, obj, "obj with func"),
+    /An unexpected error occurred/,
+    "assertDeepEq obj with function throws"
+  );
+  browser.test.assertThrows(
+    () => browser.test.assertDeepEq(() => {}, () => {}, "func to assertDeepEq"),
+    /An unexpected error occurred/,
+    "assertDeepEq with function throws"
+  );
+  browser.test.assertThrows(
+    () => browser.test.assertDeepEq(/./, /./, "regexp"),
+    /Unsupported obj type: RegExp/,
+    "assertDeepEq with RegExp throws"
+  );
+
+  // Set of additional tests to only run on background page and content script
+  // (but skip on background service worker).
+  if (self === self.window) {
+    let dom = document.createElement("body");
+    browser.test.assertTrue(dom, "Element truthy");
+    browser.test.assertTrue(false, document.createElement("html"));
+    browser.test.assertFalse(dom, "Element falsey");
+    browser.test.assertFalse(true, document.createElement("head"));
+    browser.test.assertEq(dom, dom, "Element equality");
+    browser.test.assertEq(dom, document.createElement("body"), "Element inequality");
+    browser.test.assertEq(true, false, document.createElement("div"));
+  }
+
+  browser.test.sendMessage("Ran test at", location.protocol);
+  browser.test.sendMessage("This is the last browser.test call");
+}
+
+function verifyTestResults(results, shortName, expectedProtocol, useServiceWorker) {
+  let expectations = [
+    ["test-done", true, "dot notifyPass"],
+    ["test-done", false, "dot notifyFail"],
+    ["test-log", true, "dot log"],
+    ["test-result", false, "dot fail"],
+    ["test-result", true, "dot succeed"],
+    ["test-result", true, "undefined"],
+    ["test-result", true, "undefined"],
+    ["test-eq", true, "undefined", "", ""],
+
+    ["test-result", true, "Object truthy"],
+    ["test-result", true, "Array truthy"],
+    ["test-result", true, "True truthy"],
+    ["test-result", false, "False truthy"],
+    ["test-result", false, "Null truthy"],
+    ["test-result", false, "Void truthy"],
+
+    ["test-result", false, "Object falsey"],
+    ["test-result", false, "Array falsey"],
+    ["test-result", false, "True falsey"],
+    ["test-result", true, "False falsey"],
+    ["test-result", true, "Null falsey"],
+    ["test-result", true, "Void falsey"],
+
+    ["test-eq", true, "Object equality", "[object Object]", "[object Object]"],
+    ["test-eq", true, "Array equality", "", ""],
+    ["test-eq", true, "Null equality", "null", "null"],
+    ["test-eq", true, "Void equality", "undefined", "undefined"],
+
+    ["test-eq", false, "Object reference inequality", "[object Object]", "[object Object] (different)"],
+    ["test-eq", false, "Array reference inequality", "", " (different)"],
+    ["test-eq", false, "strict: true and 1 inequality", "true", "1"],
+    ["test-eq", false, "strict: '1' and 1 inequality", "1", "1 (different)"],
+    ["test-eq", false, "Null and void inequality", "null", "undefined"],
+
+    ["test-eq", true, "Object deep eq", `{"a":1,"b":1}`, `{"b":1,"a":1}`],
+    ["test-eq", true, "Array deep eq", "[[2],[1]]", "[[2],[1]]"],
+    ["test-eq", false, "strict: true and 1 deep ineq", "true", "1"],
+    ["test-eq", false, "strict: '1' and 1 deep ineq", `"1"`, "1"],
+    ["test-eq", false, "Null and void deep ineq", "null", "undefined"],
+    ["test-eq", false, "void+null deep ineq", `{"c":"undefined"}`, `{"c":null}`],
+    ["test-eq", false, "void/- deep ineq", `{"a":"undefined","b":1}`, `{"b":1}`],
+
+    ["test-eq", true, "NaN deep eq", `NaN`, `NaN`],
+    ["test-eq", false, "NaN+null deep ineq", `NaN`, `null`],
+    ["test-eq", true, "Infinity deep eq", `Infinity`, `Infinity`],
+    ["test-eq", false, "Infinity+null deep ineq", `Infinity`, `null`],
+
+    [
+      "test-eq",
+      true,
+      "obj with dynamic toString()",
+      // - Privileged JS API Bindings: the ext-test.js module will get a XrayWrapper and so when
+      //   the object is being stringified the custom `toString()` method will not be called and
+      //   "[object Object]" is the value we expect.
+      // - WebIDL API Bindngs: the parameter is being serialized into a string on the worker thread,
+      //   the object is stringified using the worker principal and so there is no XrayWrapper
+      //   involved and the value expected is the value returned by the custom toString method the.
+      //   object does provide.
+      useServiceWorker ? "Dynamic toString" : "[object Object]",
+      useServiceWorker ? "Dynamic toString" : "[object Object]",
+    ],
+
+    [
+      "test-result", false,
+      "Function threw, expecting error to match '/dummy2/', got \'Error: dummy\': intentional failure"
+    ],
+    [
+      "test-result", false,
+      "Function threw, expecting error to match '/dummy3/', got \'Error: dummy2\'"
+    ],
+    [
+      "test-result", false,
+      "Function did not throw, expected error '/dummy/'"
+    ],
+    [
+      "test-result", true,
+      "Function threw, expecting error to match '/An unexpected error occurred/', got 'Error: An unexpected error occurred': assertDeepEq obj with function throws",
+    ],
+    [
+      "test-result", true,
+      "Function threw, expecting error to match '/An unexpected error occurred/', got 'Error: An unexpected error occurred': assertDeepEq with function throws",
+    ],
+    [
+      "test-result", true,
+      "Function threw, expecting error to match '/Unsupported obj type: RegExp/', got 'Error: Unsupported obj type: RegExp': assertDeepEq with RegExp throws",
+    ],
+  ];
+
+  if (!useServiceWorker) {
+    expectations.push(...[
+      ["test-result", true, "Element truthy"],
+      ["test-result", false, "[object HTMLHtmlElement]"],
+      ["test-result", false, "Element falsey"],
+      ["test-result", false, "[object HTMLHeadElement]"],
+      ["test-eq", true, "Element equality", "[object HTMLBodyElement]", "[object HTMLBodyElement]"],
+      ["test-eq", false, "Element inequality", "[object HTMLBodyElement]", "[object HTMLBodyElement] (different)"],
+      ["test-eq", false, "[object HTMLDivElement]", "true", "false"],
+    ]);
+  }
+
+  expectations.push(...[
+    ["test-message", "Ran test at", expectedProtocol],
+    ["test-message", "This is the last browser.test call"],
+  ]);
+
+  expectations.forEach((expectation, i) => {
+    let msg = expectation.slice(2).join(" - ");
+    isDeeply(results[i], expectation, `${shortName} (${msg})`);
+  });
+  is(results[expectations.length], undefined, "No more results");
+}
+
+add_task(async function test_test_in_background() {
+  let extensionData = {
+    background: `(${testScript})()`,
+    // This test case should never run the background script in a worker,
+    // even if this test file is running when "extensions.backgroundServiceWorker.forceInTest"
+    // pref is true
+    useServiceWorker: false,
+  };
+
+  let extension = loadExtensionAndInterceptTest(extensionData);
+  await extension.startup();
+  let results = await extension.awaitResults();
+  verifyTestResults(results, "background page", "moz-extension:", false);
+  await extension.unload();
+});
+
+add_task(async function test_test_in_background_service_worker() {
+  if (!ExtensionTestUtils.isInBackgroundServiceWorkerTests()) {
+    is(
+      ExtensionTestUtils.getBackgroundServiceWorkerEnabled(),
+      false,
+      "This test should only be skipped with background service worker disabled"
+    )
+    info("Test intentionally skipped on 'extensions.backgroundServiceWorker.enabled=false'");
+    return;
+  }
+
+  let extensionData = {
+    background: `(${testScript})()`,
+    // This test case should always run the background script in a worker,
+    // or be skipped if the background service worker is disabled by prefs.
+    useServiceWorker: true,
+  };
+
+  let extension = loadExtensionAndInterceptTest(extensionData);
+  await extension.startup();
+  let results = await extension.awaitResults();
+  verifyTestResults(results, "background service worker", "moz-extension:", true);
+  await extension.unload();
+});
+
+add_task(async function test_test_in_content_script() {
+  let extensionData = {
+    manifest: {
+      content_scripts: [{
+        matches: ["http://mochi.test/*/file_sample.html"],
+        js: ["contentscript.js"],
+      }],
+    },
+    files: {
+      "contentscript.js": `(${testScript})()`,
+    },
+  };
+
+  let extension = loadExtensionAndInterceptTest(extensionData);
+  await extension.startup();
+  let win = window.open("file_sample.html");
+  let results = await extension.awaitResults();
+  win.close();
+  verifyTestResults(results, "content script", "http:", false);
+  await extension.unload();
+});
+</script>
+</body>
+</html>
diff --git a/toolkit/components/extensions/test/mochitest/test_ext_unlimitedStorage.html b/toolkit/components/extensions/test/mochitest/test_ext_unlimitedStorage.html
new file mode 100644
index 0000000000..db0f512ac3
--- /dev/null
+++ b/toolkit/components/extensions/test/mochitest/test_ext_unlimitedStorage.html
@@ -0,0 +1,138 @@
+<!DOCTYPE HTML>
+<html>
+<head>
+  <title>Test for simple WebExtension</title>
+  <meta charset="utf-8">
+  <script src="/tests/SimpleTest/SimpleTest.js"></script>
+  <script src="/tests/SimpleTest/ExtensionTestUtils.js"></script>
+  <script src="/tests/SimpleTest/EventUtils.js"></script>
+  <script type="text/javascript" src="head.js"></script>
+  <script type="text/javascript" src="head_unlimitedStorage.js"></script>
+  <link rel="stylesheet" type="text/css" href="/tests/SimpleTest/test.css"/>
+</head>
+<body>
+
+<script type="text/javascript">
+
+"use strict";
+
+async function test_background_storagePersist(EXTENSION_ID) {
+  await SpecialPowers.pushPrefEnv({
+    "set": [
+      ["dom.storageManager.enabled", true],
+      ["dom.storageManager.prompt.testing", false],
+      ["dom.storageManager.prompt.testing.allow", false],
+    ],
+  });
+
+  const extension = ExtensionTestUtils.loadExtension({
+    useAddonManager: "permanent",
+
+    manifest: {
+      permissions: ["storage", "unlimitedStorage"],
+      browser_specific_settings: {
+        gecko: {
+          id: EXTENSION_ID,
+        },
+      },
+    },
+
+    background: async function() {
+      const PROMISE_RACE_TIMEOUT = 8000;
+
+      browser.test.sendMessage("extension-uuid", window.location.host);
+
+      await browser.storage.local.set({testkey: "testvalue"});
+      await browser.test.sendMessage("storage-local-called");
+
+      const requestStoragePersist = async () => {
+        const persistAllowed = await navigator.storage.persist();
+        if (!persistAllowed) {
+          throw new Error("navigator.storage.persist() has been denied");
+        }
+      };
+
+      await Promise.race([
+        requestStoragePersist(),
+        new Promise((resolve, reject) => {
+          setTimeout(() => {
+            reject(new Error("Timeout opening persistent db from background page"));
+          }, PROMISE_RACE_TIMEOUT);
+        }),
+      ]).then(
+        () => {
+          browser.test.notifyPass("indexeddb-storagePersistent-unlimitedStorage-done");
+        },
+        (error) => {
+          browser.test.fail(`error while testing persistent IndexedDB storage: ${error}`);
+          browser.test.notifyFail("indexeddb-storagePersistent-unlimitedStorage-done");
+        }
+      );
+    },
+  });
+
+  await extension.startup();
+
+  const uuid = await extension.awaitMessage("extension-uuid");
+
+  await extension.awaitMessage("storage-local-called");
+
+  let chromeScript = SpecialPowers.loadChromeScript(function test_country_data() {
+    /* eslint-env mozilla/chrome-script */
+    const {addMessageListener, sendAsyncMessage} = this;
+
+    addMessageListener("getPersistedStatus", (uuid) => {
+      const {
+        ExtensionStorageIDB,
+      } = ChromeUtils.import("resource://gre/modules/ExtensionStorageIDB.jsm");
+
+      const {WebExtensionPolicy} = Cu.getGlobalForObject(ExtensionStorageIDB);
+      const policy = WebExtensionPolicy.getByHostname(uuid);
+      const storagePrincipal = ExtensionStorageIDB.getStoragePrincipal(policy.extension);
+      const request = Services.qms.persisted(storagePrincipal);
+      request.callback = () => {
+        // request.result will be undeinfed if the request failed (request.resultCode !== Cr.NS_OK).
+        sendAsyncMessage("gotPersistedStatus", request.result);
+      };
+    });
+  });
+
+  const persistedPromise = chromeScript.promiseOneMessage("gotPersistedStatus");
+  chromeScript.sendAsyncMessage("getPersistedStatus", uuid);
+  is(await persistedPromise, true, "Got the expected persist status for the storagePrincipal");
+
+  await extension.awaitFinish("indexeddb-storagePersistent-unlimitedStorage-done");
+  await extension.unload();
+
+  checkSitePermissions(uuid, Services.perms.UNKNOWN_ACTION, "has been cleared");
+}
+
+add_task(async function test_unlimitedStorage() {
+  const EXTENSION_ID = "test-storagePersist@mozilla";
+  await SpecialPowers.pushPrefEnv({
+    "set": [
+      ["extensions.webextensions.ExtensionStorageIDB.enabled", true],
+    ],
+  });
+
+  // Verify persist mode enabled when the storage.local IDB database is opened from
+  // the main process (from parent/ext-storage.js).
+  info("Test unlimitedStorage on an extension migrating to the IndexedDB storage.local backend)");
+  await test_background_storagePersist(EXTENSION_ID);
+
+  await SpecialPowers.pushPrefEnv({
+    "set": [
+      [`extensions.webextensions.ExtensionStorageIDB.migrated.` + EXTENSION_ID, true],
+    ],
+  });
+
+  // Verify persist mode enabled when the storage.local IDB database is opened from
+  // the child process (from child/ext-storage.js).
+  info("Test unlimitedStorage on an extension migrated to the IndexedDB storage.local backend");
+  await test_background_storagePersist(EXTENSION_ID);
+});
+
+</script>
+
+</body>
+</html>
diff --git a/toolkit/components/extensions/test/mochitest/test_ext_web_accessible_incognito.html b/toolkit/components/extensions/test/mochitest/test_ext_web_accessible_incognito.html
new file mode 100644
index 0000000000..d1c41d2030
--- /dev/null
+++ b/toolkit/components/extensions/test/mochitest/test_ext_web_accessible_incognito.html
@@ -0,0 +1,170 @@
+<!DOCTYPE HTML>
+<html>
+<head>
+  <title>Test the web_accessible_resources incognito</title>
+  <script src="/tests/SimpleTest/SimpleTest.js"></script>
+  <script src="/tests/SimpleTest/ExtensionTestUtils.js"></script>
+  <script type="text/javascript" src="head.js"></script>
+  <link rel="stylesheet" type="text/css" href="/tests/SimpleTest/test.css"/>
+</head>
+<body>
+
+<script type="text/javascript">
+"use strict";
+
+let image = atob("iVBORw0KGgoAAAANSUhEUgAAAAEAAAABAQMAAAAl21bKAAAAA1BMVEUAA" +
+                 "ACnej3aAAAAAXRSTlMAQObYZgAAAApJREFUCNdjYAAAAAIAAeIhvDMAAAAASUVORK5CYII=");
+const IMAGE_ARRAYBUFFER = Uint8Array.from(image, byte => byte.charCodeAt(0)).buffer;
+
+async function testImageLoading(src, expectedAction) {
+  let imageLoadingPromise = new Promise((resolve, reject) => {
+    let cleanupListeners;
+    let testImage = new window.Image();
+    // Set the src via wrappedJSObject so the load is triggered with the
+    // content page's principal rather than ours.
+    testImage.wrappedJSObject.setAttribute("src", src);
+
+    let loadListener = () => {
+      cleanupListeners();
+      resolve(expectedAction === "loaded");
+    };
+
+    let errorListener = (event) => {
+      cleanupListeners();
+      resolve(expectedAction === "blocked");
+      browser.test.log(`+++ image loading ${event.error}`);
+    };
+
+    cleanupListeners = () => {
+      testImage.removeEventListener("load", loadListener);
+      testImage.removeEventListener("error", errorListener);
+    };
+
+    testImage.addEventListener("load", loadListener);
+    testImage.addEventListener("error", errorListener);
+  });
+
+  let success = await imageLoadingPromise;
+  browser.runtime.sendMessage({name: "image-loading", expectedAction, success});
+}
+
+function testScript() {
+  window.postMessage("test-script-loaded", "*");
+}
+
+add_task(async function test_web_accessible_resources_incognito() {
+  // This extension will not have access to private browsing so its
+  // accessible resources should not be able to load in them.
+  let extension = ExtensionTestUtils.loadExtension({
+    manifest: {
+      "web_accessible_resources": [
+        "image.png",
+        "test_script.js",
+        "accessible.html",
+      ],
+    },
+    background() {
+      browser.test.sendMessage("url", browser.runtime.getURL(""));
+    },
+    files: {
+      "image.png": IMAGE_ARRAYBUFFER,
+      "test_script.js": testScript,
+      "accessible.html": `<html><head>
+        <meta charset="utf-8">
+      </head></html>`,
+    },
+  });
+
+  await extension.startup();
+  let baseUrl = await extension.awaitMessage("url");
+
+  async function content() {
+    let baseUrl = await browser.runtime.sendMessage({name: "get-url"});
+    testImageLoading(`${baseUrl}image.png`, "loaded");
+
+    let testScriptElement = document.createElement("script");
+    // Set the src via wrappedJSObject so the load is triggered with the
+    // content page's principal rather than ours.
+    testScriptElement.wrappedJSObject.setAttribute("src", `${baseUrl}test_script.js`);
+    document.head.appendChild(testScriptElement);
+
+    let iframe = document.createElement("iframe");
+    // Set the src via wrappedJSObject so the load is triggered with the
+    // content page's principal rather than ours.
+    iframe.wrappedJSObject.setAttribute("src", `${baseUrl}accessible.html`);
+    document.body.appendChild(iframe);
+
+    // eslint-disable-next-line mozilla/balanced-listeners
+    window.addEventListener("message", event => {
+      browser.runtime.sendMessage({"name": event.data});
+    });
+  }
+
+  let pb_extension = ExtensionTestUtils.loadExtension({
+    incognitoOverride: "spanning",
+    manifest: {
+      permissions: ["tabs"],
+      content_scripts: [{
+        "matches": ["*://example.com/*/file_sample.html"],
+        "run_at": "document_end",
+        "js": ["content_script_helper.js", "content_script.js"],
+      }],
+    },
+    files: {
+      "content_script_helper.js": `${testImageLoading}`,
+      "content_script.js": content,
+    },
+    background() {
+      let url = "http://example.com/tests/toolkit/components/extensions/test/mochitest/file_sample.html";
+      let baseUrl;
+      let window;
+
+      browser.runtime.onMessage.addListener(async msg => {
+        switch (msg.name) {
+          case "image-loading":
+            browser.test.assertFalse(msg.success, `Image was ${msg.expectedAction}`);
+            browser.test.sendMessage(`image-${msg.expectedAction}`);
+            break;
+          case "get-url":
+            return baseUrl;
+          default:
+            browser.test.fail(`unexepected message ${msg.name}`);
+        }
+      });
+
+      browser.test.onMessage.addListener(async (msg, data) => {
+        if (msg == "start") {
+          baseUrl = data;
+          window = await browser.windows.create({url, incognito: true});
+        }
+        if (msg == "close") {
+          browser.windows.remove(window.id);
+        }
+      });
+    },
+  });
+  await pb_extension.startup();
+
+  consoleMonitor.start([
+    {message: /may not load or link to.*image.png/},
+    {message: /may not load or link to.*test_script.js/},
+    {message: /\<script\> source URI is not allowed in this document/},
+    {message: /may not load or link to.*accessible.html/},
+  ]);
+
+  pb_extension.sendMessage("start", baseUrl);
+
+  await pb_extension.awaitMessage("image-loaded");
+
+  pb_extension.sendMessage("close");
+
+  await extension.unload();
+  await pb_extension.unload();
+
+  await consoleMonitor.finished();
+});
+
+</script>
+
+</body>
+</html>
diff --git a/toolkit/components/extensions/test/mochitest/test_ext_web_accessible_resources.html b/toolkit/components/extensions/test/mochitest/test_ext_web_accessible_resources.html
new file mode 100644
index 0000000000..c13e40e265
--- /dev/null
+++ b/toolkit/components/extensions/test/mochitest/test_ext_web_accessible_resources.html
@@ -0,0 +1,567 @@
+<!DOCTYPE HTML>
+<html>
+<head>
+  <title>Test the web_accessible_resources manifest directive</title>
+  <script src="/tests/SimpleTest/SimpleTest.js"></script>
+  <script src="/tests/SimpleTest/ExtensionTestUtils.js"></script>
+  <script type="text/javascript" src="head.js"></script>
+  <link rel="stylesheet" type="text/css" href="/tests/SimpleTest/test.css"/>
+</head>
+<body>
+
+<script type="text/javascript">
+"use strict";
+
+// add_setup not available in mochitest
+add_task(async function setup() {
+  await SpecialPowers.pushPrefEnv({set: [["extensions.manifestV3.enabled", true]]});
+})
+
+let image = atob(
+  "iVBORw0KGgoAAAANSUhEUgAAAAEAAAABAQMAAAAl21bKAAAAA1BMVEUAA" +
+    "ACnej3aAAAAAXRSTlMAQObYZgAAAApJREFUCNdjYAAAAAIAAeIhvDMAAAAASUVORK5CYII="
+);
+const IMAGE_ARRAYBUFFER = Uint8Array.from(image, byte => byte.charCodeAt(0))
+  .buffer;
+
+const ANDROID = navigator.userAgent.includes("Android");
+
+async function testImageLoading(src, expectedAction) {
+  let imageLoadingPromise = new Promise((resolve, reject) => {
+    let cleanupListeners;
+    let testImage = document.createElement("img");
+    // Set the src via wrappedJSObject so the load is triggered with the
+    // content page's principal rather than ours.
+    testImage.wrappedJSObject.setAttribute("src", src);
+
+    let loadListener = () => {
+      cleanupListeners();
+      resolve(expectedAction === "loaded");
+    };
+
+    let errorListener = () => {
+      cleanupListeners();
+      resolve(expectedAction === "blocked");
+    };
+
+    cleanupListeners = () => {
+      testImage.removeEventListener("load", loadListener);
+      testImage.removeEventListener("error", errorListener);
+    };
+
+    testImage.addEventListener("load", loadListener);
+    testImage.addEventListener("error", errorListener);
+
+    document.body.appendChild(testImage);
+  });
+
+  let success = await imageLoadingPromise;
+  browser.runtime.sendMessage({
+    name: "image-loading",
+    expectedAction,
+    success,
+  });
+}
+
+async function _test_web_accessible_resources({
+  manifest,
+  expectShouldLoadByDefault = true,
+  usePagePrincipal = false,
+}) {
+  function background(shouldLoad, usePagePrincipal) {
+    let gotURL;
+    let tabId;
+    let expectBrowserAPI;
+
+    function loadFrame(url, sandbox = null, srcdoc = false) {
+      return new Promise(resolve => {
+        browser.tabs.sendMessage(
+          tabId,
+          ["load-iframe", url, sandbox, srcdoc, usePagePrincipal],
+          reply => {
+            resolve(reply);
+          }
+        );
+      });
+    }
+
+    // shouldLoad will be true unless we expect all attempts to fail.
+    let urls = [
+      // { url, shouldLoad, sandbox, srcdoc }
+      {
+        url: browser.runtime.getURL("accessible.html"),
+        shouldLoad,
+      },
+      {
+        url: browser.runtime.getURL("accessible.html") + "?foo=bar",
+        shouldLoad,
+      },
+      {
+        url: browser.runtime.getURL("accessible.html") + "#!foo=bar",
+        shouldLoad,
+      },
+      {
+        url: browser.runtime.getURL("accessible.html"),
+        shouldLoad,
+        sandbox: "allow-scripts",
+      },
+      {
+        url: browser.runtime.getURL("accessible.html"),
+        shouldLoad,
+        sandbox: "allow-same-origin allow-scripts",
+      },
+      {
+        url: browser.runtime.getURL("accessible.html"),
+        shouldLoad,
+        sandbox: "allow-scripts",
+        srcdoc: true,
+      },
+      {
+        url: browser.runtime.getURL("inaccessible.html"),
+        shouldLoad: false,
+      },
+      {
+        url: browser.runtime.getURL("inaccessible.html"),
+        shouldLoad: false,
+        sandbox: "allow-same-origin allow-scripts",
+      },
+      {
+        url: browser.runtime.getURL("inaccessible.html"),
+        shouldLoad: false,
+        sandbox: "allow-same-origin allow-scripts",
+        srcdoc: true,
+      },
+      {
+        url: browser.runtime.getURL("wild1.html"),
+        shouldLoad,
+      },
+      {
+        url: browser.runtime.getURL("wild2.htm"),
+        shouldLoad: false,
+      },
+    ];
+
+    async function runTests() {
+      for (let { url, shouldLoad, sandbox, srcdoc } of urls) {
+        // Sandboxed pages with an opaque origin do not get browser api.
+        expectBrowserAPI = !sandbox || sandbox.includes("allow-same-origin");
+        let success = await loadFrame(url, sandbox, srcdoc);
+
+        browser.test.assertEq(shouldLoad, success, "Load was successful");
+        if (shouldLoad && !srcdoc) {
+          browser.test.assertEq(url, gotURL, "Got expected url");
+        } else {
+          browser.test.assertEq(undefined, gotURL, "Got no url");
+        }
+        gotURL = undefined;
+      }
+
+      browser.test.notifyPass("web-accessible-resources");
+    }
+
+    browser.runtime.onMessage.addListener(
+      ([msg, url, hasBrowserAPI], sender) => {
+        if (msg == "content-script-ready") {
+          tabId = sender.tab.id;
+          runTests();
+        } else if (msg == "page-script") {
+          browser.test.assertEq(
+            undefined,
+            gotURL,
+            "Should have gotten only one message"
+          );
+          browser.test.assertEq("string", typeof url, "URL should be a string");
+          browser.test.assertEq(
+            expectBrowserAPI,
+            hasBrowserAPI,
+            "has access to browser api"
+          );
+          gotURL = url;
+        }
+      }
+    );
+
+    browser.test.sendMessage("ready");
+  }
+
+  function contentScript() {
+    window.addEventListener("message", event => {
+      // bounce the postmessage to the background script
+      if (event.data[0] == "page-script") {
+        browser.runtime.sendMessage(event.data);
+      }
+    });
+
+    browser.runtime.onMessage.addListener(
+      ([msg, url, sandboxed, srcdoc, usePagePrincipal], sender, respond) => {
+        if (msg == "load-iframe") {
+          // construct the frame using srcdoc if requested.
+          if (srcdoc) {
+            sandboxed = sandboxed !== null ? `sandbox="${sandboxed}"` : "";
+            let frameSrc = `<iframe ${sandboxed} src="${url}" onload="parent.postMessage(true, '*')" onerror="parent.postMessage(false, '*')">`;
+            let frame = document.createElement("iframe");
+            frame.setAttribute("srcdoc", frameSrc);
+            window.addEventListener("message", function listener(event) {
+              if (event.source === frame.contentWindow) {
+                window.removeEventListener("message", listener);
+                respond(event.data);
+              }
+            });
+            document.body.appendChild(frame);
+            return true;
+          }
+
+          let iframe = document.createElement("iframe");
+          if (sandboxed !== null) {
+            iframe.setAttribute("sandbox", sandboxed);
+          }
+
+          if (usePagePrincipal) {
+            // Test using the page principal
+            iframe.wrappedJSObject.src = url;
+          } else {
+            // Test using the expanded principal
+            iframe.src = url;
+          }
+          iframe.addEventListener("load", () => {
+            respond(true);
+          });
+          iframe.addEventListener("error", () => {
+            respond(false);
+          });
+          document.body.appendChild(iframe);
+          return true;
+        }
+      }
+    );
+    browser.runtime.sendMessage(["content-script-ready"]);
+  }
+
+  let extension = ExtensionTestUtils.loadExtension({
+    useAddonManager: "temporary",
+    manifest: {
+      content_scripts: [
+        {
+          matches: ["https://example.com/"],
+          js: ["content_script.js"],
+          run_at: "document_idle",
+        },
+      ],
+      ...manifest,
+    },
+
+    background: `(${background})(${expectShouldLoadByDefault}, ${usePagePrincipal})`,
+
+    files: {
+      "content_script.js": contentScript,
+
+      "accessible.html": `<!DOCTYPE html><html><head>
+        <meta charset="utf-8">
+        <script src="pagescript.js"><\/script>
+      </head></html>`,
+
+      "inaccessible.html": `<!DOCTYPE html><html><head>
+        <meta charset="utf-8">
+        <script src="pagescript.js"><\/script>
+      </head></html>`,
+
+      "wild1.html": `<!DOCTYPE html><html><head>
+        <meta charset="utf-8">
+        <script src="pagescript.js"><\/script>
+      </head></html>`,
+
+      "wild2.htm": `<!DOCTYPE html><html><head>
+        <meta charset="utf-8">
+        <script src="pagescript.js"><\/script>
+      </head></html>`,
+
+      "pagescript.js":
+        // We postmessage so we can determine when browser is not available
+        'window.parent.postMessage(["page-script", location.href, typeof browser !== "undefined"], "*");',
+    },
+  });
+
+  await extension.startup();
+
+  await extension.awaitMessage("ready");
+
+  let win = window.open("https://example.com/");
+
+  await extension.awaitFinish("web-accessible-resources");
+
+  win.close();
+
+  await extension.unload();
+};
+
+add_task(async function test_web_accessible_resources_v2() {
+  await SpecialPowers.pushPrefEnv({set: [["extensions.content_web_accessible.enabled", true]]});
+  consoleMonitor.start([
+    {message: /Content at https:\/\/example.com\/ may not load or link to.*inaccessible.html/},
+  ]);
+  await _test_web_accessible_resources({
+    manifest: {
+      manifest_version: 2,
+      web_accessible_resources: ["/accessible.html", "wild*.html"],
+    }
+  });
+  await consoleMonitor.finished();
+  await SpecialPowers.popPrefEnv();
+});
+
+// Same test as above, but using only the content principal
+add_task(async function test_web_accessible_resources_v2_content() {
+  await SpecialPowers.pushPrefEnv({set: [["extensions.content_web_accessible.enabled", true]]});
+  consoleMonitor.start([
+    {message: /Content at https:\/\/example.com\/ may not load or link to.*inaccessible.html/},
+  ]);
+  await _test_web_accessible_resources({
+    manifest: {
+      manifest_version: 2,
+      web_accessible_resources: ["/accessible.html", "wild*.html"],
+    },
+    usePagePrincipal: true,
+  });
+  await consoleMonitor.finished();
+  await SpecialPowers.popPrefEnv();
+});
+
+add_task(async function test_web_accessible_resources_v3() {
+  // MV3 always requires this, pref off to ensure it works.
+  await SpecialPowers.pushPrefEnv({set: [["extensions.content_web_accessible.enabled", false]]});
+  consoleMonitor.start([
+    {message: /Content at https:\/\/example.com\/ may not load or link to.*inaccessible.html/},
+  ]);
+  await _test_web_accessible_resources({
+    manifest: {
+      manifest_version: 3,
+      web_accessible_resources: [
+        {
+          resources: ["/accessible.html", "wild*.html"],
+          matches: ["*://example.com/*"]
+        },
+      ],
+      host_permissions: ["*://example.com/*"],
+      granted_host_permissions: true,
+    }
+  });
+  await consoleMonitor.finished();
+  await SpecialPowers.popPrefEnv();
+});
+
+add_task(async function test_web_accessible_resources_v3_by_id() {
+  consoleMonitor.start([
+    {message: /Content at https:\/\/example.com\/ may not load or link to.*accessible.html/},
+    {message: /Content at https:\/\/example.com\/ may not load or link to.*inaccessible.html/},
+  ]);
+  await _test_web_accessible_resources({
+    manifest: {
+      manifest_version: 3,
+      browser_specific_settings: {
+        gecko: {
+          id: "extension_wac@mochitest",
+        },
+      },
+      web_accessible_resources: [
+        {
+          resources: ["/accessible.html", "wild*.html"],
+          extension_ids: ["extension_wac@mochitest"]
+        },
+      ],
+      host_permissions: ["*://example.com/*"],
+      // Work-around for bug 1766752 to allow content_scripts to run:
+      granted_host_permissions: true,
+    },
+    expectShouldLoadByDefault: false,
+  });
+  await consoleMonitor.finished();
+});
+
+add_task(async function test_web_accessible_resources_mixed_content() {
+  function background() {
+    browser.runtime.onMessage.addListener(msg => {
+      if (msg.name === "image-loading") {
+        browser.test.assertTrue(msg.success, `Image was ${msg.expectedAction}`);
+        browser.test.sendMessage(`image-${msg.expectedAction}`);
+      } else {
+        browser.test.sendMessage(msg);
+        if (msg === "accessible-script-loaded") {
+          browser.test.notifyPass("mixed-test");
+        }
+      }
+    });
+
+    browser.test.sendMessage("background-ready");
+  }
+
+  async function content() {
+    await testImageLoading(
+      "http://example.com/tests/toolkit/components/extensions/test/mochitest/file_image_bad.png",
+      "blocked"
+    );
+    await testImageLoading(browser.runtime.getURL("image.png"), "loaded");
+
+    let testScriptElement = document.createElement("script");
+    // Set the src via wrappedJSObject so the load is triggered with the
+    // content page's principal rather than ours.
+    testScriptElement.wrappedJSObject.setAttribute(
+      "src",
+      browser.runtime.getURL("test_script.js")
+    );
+    document.head.appendChild(testScriptElement);
+
+    window.addEventListener("message", event => {
+      browser.runtime.sendMessage(event.data);
+    });
+  }
+
+  function testScript() {
+    window.postMessage("accessible-script-loaded", "*");
+  }
+
+  let extension = ExtensionTestUtils.loadExtension({
+    manifest: {
+      content_scripts: [
+        {
+          matches: ["https://example.com/*/file_mixed.html"],
+          run_at: "document_end",
+          js: ["content_script_helper.js", "content_script.js"],
+        },
+      ],
+      web_accessible_resources: ["image.png", "test_script.js"],
+    },
+    background,
+    files: {
+      "content_script_helper.js": `${testImageLoading}`,
+      "content_script.js": content,
+      "test_script.js": testScript,
+      "image.png": IMAGE_ARRAYBUFFER,
+    },
+  });
+
+  await SpecialPowers.pushPrefEnv({set: [
+    ["security.mixed_content.upgrade_display_content", false],
+    ["security.mixed_content.block_display_content", true],
+  ]});
+
+  await Promise.all([
+    extension.startup(),
+    extension.awaitMessage("background-ready"),
+  ]);
+
+  let win = window.open(
+    "https://example.com/tests/toolkit/components/extensions/test/mochitest/file_mixed.html"
+  );
+
+  await Promise.all([
+    extension.awaitMessage("image-blocked"),
+    extension.awaitMessage("image-loaded"),
+    extension.awaitMessage("accessible-script-loaded"),
+  ]);
+  await extension.awaitFinish("mixed-test");
+  win.close();
+
+  await extension.unload();
+  await SpecialPowers.popPrefEnv();
+});
+
+// test that MV2 extensions continue to open other MV2 extension pages
+// when they are not listed in web_accessible_resources.  This test also
+// covers mobile/android tab creation.
+add_task(async function test_web_accessible_resources_extensions_MV2() {
+  function background() {
+    let newtab;
+    let win;
+    let expectUrl;
+    browser.tabs.onUpdated.addListener(async (tabId, changeInfo, tab) => {
+      if (!expectUrl || tab.url != expectUrl || changeInfo.status !== "complete") {
+        return;
+      }
+      expectUrl = undefined;
+      browser.test.log(`onUpdated ${JSON.stringify(changeInfo)} ${tab.url}`);
+      browser.test.sendMessage("onUpdated", tab.url);
+    });
+    browser.test.onMessage.addListener(async (msg, url) => {
+      browser.test.log(`onMessage ${msg} ${url}`);
+      expectUrl = url;
+      if (msg == "create") {
+        newtab = await browser.tabs.create({ url });
+        browser.test.assertTrue(
+          newtab.id !== browser.tabs.TAB_ID_NONE,
+          "New tab was created."
+        );
+      } else if (msg == "update") {
+        await browser.tabs.update(newtab.id, { url });
+      } else if (msg == "remove") {
+        await browser.tabs.remove(newtab.id);
+        newtab = null;
+        browser.test.sendMessage("completed");
+      } else if (msg == "open-window") {
+        win = await browser.windows.create({ url });
+      } else if (msg == "close-window") {
+        await browser.windows.remove(win.id);
+        browser.test.sendMessage("completed");
+        win = null;
+      }
+    });
+  }
+
+  let extension = ExtensionTestUtils.loadExtension({
+    manifest: {
+      browser_specific_settings: { gecko: { id: "this-mv2@mochitest" } },
+    },
+    background,
+    files: {
+      "page.html": `<!DOCTYPE html><html><head>
+          <meta charset="utf-8">
+        </head></html>`,
+    },
+  });
+
+  async function testTabsAction(ext, action, url) {
+    ext.sendMessage(action, url);
+    is(await ext.awaitMessage("onUpdated"), url, "extension url was loaded");
+  }
+
+  await extension.startup();
+  let extensionUrl = `moz-extension://${extension.uuid}/page.html`;
+
+  // Test opening its own pages
+  await testTabsAction(extension, "create", `${extensionUrl}?q=1`);
+  await testTabsAction(extension, "update", `${extensionUrl}?q=2`);
+  extension.sendMessage("remove");
+  await extension.awaitMessage("completed");
+  if (!ANDROID) {
+    await testTabsAction(extension, "open-window", `${extensionUrl}?q=3`);
+    extension.sendMessage("close-window");
+    await extension.awaitMessage("completed");
+  }
+
+  // Extension used to open the homepage in a new window.
+  let other = ExtensionTestUtils.loadExtension({
+    manifest: {
+      permissions: ["tabs", "<all_urls>"],
+    },
+    background,
+  });
+  await other.startup();
+
+  // Test opening another extensions pages
+  await testTabsAction(other, "create", `${extensionUrl}?q=4`);
+  await testTabsAction(other, "update", `${extensionUrl}?q=5`);
+  other.sendMessage("remove");
+  await other.awaitMessage("completed");
+  if (!ANDROID) {
+    await testTabsAction(other, "open-window", `${extensionUrl}?q=6`);
+    other.sendMessage("close-window");
+    await other.awaitMessage("completed");
+  }
+
+  await extension.unload();
+  await other.unload();
+});
+
+</script>
+
+</body>
+</html>
diff --git a/toolkit/components/extensions/test/mochitest/test_ext_webnavigation.html b/toolkit/components/extensions/test/mochitest/test_ext_webnavigation.html
new file mode 100644
index 0000000000..12c90f8350
--- /dev/null
+++ b/toolkit/components/extensions/test/mochitest/test_ext_webnavigation.html
@@ -0,0 +1,610 @@
+<!DOCTYPE HTML>
+<html>
+<head>
+  <title>Test for simple WebExtension</title>
+  <script src="/tests/SimpleTest/SimpleTest.js"></script>
+  <script src="/tests/SimpleTest/ExtensionTestUtils.js"></script>
+  <script src="/tests/SimpleTest/EventUtils.js"></script>
+  <script type="text/javascript" src="head.js"></script>
+  <link rel="stylesheet" type="text/css" href="/tests/SimpleTest/test.css"/>
+</head>
+<body>
+
+<script type="text/javascript">
+"use strict";
+
+if (AppConstants.platform === "android") {
+  SimpleTest.requestLongerTimeout(3);
+}
+
+/* globals sendMouseEvent */
+
+function backgroundScript() {
+  const BASE = "http://mochi.test:8888/tests/toolkit/components/extensions/test/mochitest";
+  const URL = BASE + "/file_WebNavigation_page1.html";
+
+  const EVENTS = [
+    "onTabReplaced",
+    "onBeforeNavigate",
+    "onCommitted",
+    "onDOMContentLoaded",
+    "onCompleted",
+    "onErrorOccurred",
+    "onReferenceFragmentUpdated",
+    "onHistoryStateUpdated",
+  ];
+
+  let expectedTabId = -1;
+
+  function gotEvent(event, details) {
+    if (!details.url.startsWith(BASE)) {
+      return;
+    }
+    browser.test.log(`Got ${event} ${details.url} ${details.frameId} ${details.parentFrameId}`);
+
+    if (expectedTabId == -1) {
+      browser.test.assertTrue(details.tabId !== undefined, "tab ID defined");
+      expectedTabId = details.tabId;
+    }
+
+    browser.test.assertEq(details.tabId, expectedTabId, "correct tab");
+
+    browser.test.sendMessage("received", {url: details.url, event});
+
+    if (details.url == URL) {
+      browser.test.assertEq(0, details.frameId, "root frame ID correct");
+      browser.test.assertEq(-1, details.parentFrameId, "root parent frame ID correct");
+    } else {
+      browser.test.assertEq(0, details.parentFrameId, "parent frame ID correct");
+      browser.test.assertTrue(details.frameId != 0, "frame ID probably okay");
+    }
+
+    browser.test.assertTrue(details.frameId !== undefined, "frameId != undefined");
+    browser.test.assertTrue(details.parentFrameId !== undefined, "parentFrameId != undefined");
+  }
+
+  let listeners = {};
+  for (let event of EVENTS) {
+    listeners[event] = gotEvent.bind(null, event);
+    browser.webNavigation[event].addListener(listeners[event]);
+  }
+
+  browser.test.sendMessage("ready");
+}
+
+const BASE = "http://mochi.test:8888/tests/toolkit/components/extensions/test/mochitest";
+const URL = BASE + "/file_WebNavigation_page1.html";
+const FORM_URL = URL + "?";
+const FRAME = BASE + "/file_WebNavigation_page2.html";
+const FRAME2 = BASE + "/file_WebNavigation_page3.html";
+const FRAME_PUSHSTATE = BASE + "/file_WebNavigation_page3_pushState.html";
+const REDIRECT = BASE + "/redirection.sjs";
+const REDIRECTED = BASE + "/dummy_page.html";
+const CLIENT_REDIRECT = BASE + "/file_webNavigation_clientRedirect.html";
+const CLIENT_REDIRECT_HTTPHEADER = BASE + "/file_webNavigation_clientRedirect_httpHeaders.html";
+const FRAME_CLIENT_REDIRECT = BASE + "/file_webNavigation_frameClientRedirect.html";
+const FRAME_REDIRECT = BASE + "/file_webNavigation_frameRedirect.html";
+const FRAME_MANUAL = BASE + "/file_webNavigation_manualSubframe.html";
+const FRAME_MANUAL_PAGE1 = BASE + "/file_webNavigation_manualSubframe_page1.html";
+const FRAME_MANUAL_PAGE2 = BASE + "/file_webNavigation_manualSubframe_page2.html";
+const INVALID_PAGE = "https://invalid.localhost/";
+
+const REQUIRED = [
+  "onBeforeNavigate",
+  "onCommitted",
+  "onDOMContentLoaded",
+  "onCompleted",
+];
+
+var received = [];
+var completedResolve;
+var waitingURL, waitingEvent;
+
+function loadAndWait(win, event, url, script) {
+  received = [];
+  waitingEvent = event;
+  waitingURL = url;
+  dump(`RUN ${script}\n`);
+  script();
+  return new Promise(resolve => { completedResolve = resolve; });
+}
+
+add_task(async function webnav_transitions_props() {
+  function backgroundScriptTransitions() {
+    const EVENTS = [
+      "onCommitted",
+      "onHistoryStateUpdated",
+      "onReferenceFragmentUpdated",
+      "onCompleted",
+    ];
+
+    function gotEvent(event, details) {
+      browser.test.log(`Got ${event} ${details.url} ${details.transitionType} ${details.transitionQualifiers && JSON.stringify(details.transitionQualifiers)}`);
+
+      browser.test.sendMessage("received", {url: details.url, details, event});
+    }
+
+    let listeners = {};
+    for (let event of EVENTS) {
+      listeners[event] = gotEvent.bind(null, event);
+      browser.webNavigation[event].addListener(listeners[event]);
+    }
+
+    browser.test.sendMessage("ready");
+  }
+
+  let extensionData = {
+    manifest: {
+      permissions: [
+        "webNavigation",
+      ],
+    },
+    background: backgroundScriptTransitions,
+  };
+
+  let extension = ExtensionTestUtils.loadExtension(extensionData);
+
+  extension.onMessage("received", ({url, event, details}) => {
+    received.push({url, event, details});
+
+    if (event == waitingEvent && url == waitingURL) {
+      completedResolve();
+    }
+  });
+
+  await Promise.all([extension.startup(), extension.awaitMessage("ready")]);
+  info("webnavigation extension loaded");
+
+  let win = window.open();
+
+  await loadAndWait(win, "onCompleted", URL, () => { win.location = URL; });
+
+  // transitionType: reload
+  received = [];
+  await loadAndWait(win, "onCompleted", URL, () => { win.location.reload(); });
+
+  let found = received.find((data) => (data.event == "onCommitted" && data.url == URL));
+
+  ok(found, "Got the onCommitted event");
+
+  if (found) {
+    is(found.details.transitionType, "reload",
+       "Got the expected 'reload' transitionType in the OnCommitted event");
+    ok(Array.isArray(found.details.transitionQualifiers),
+       "transitionQualifiers found in the OnCommitted events");
+  }
+
+  // transitionType: auto_subframe
+  found = received.find((data) => (data.event == "onCommitted" && data.url == FRAME));
+
+  ok(found, "Got the sub-frame onCommitted event");
+
+  if (found) {
+    is(found.details.transitionType, "auto_subframe",
+       "Got the expected 'auto_subframe' transitionType in the OnCommitted event");
+    ok(Array.isArray(found.details.transitionQualifiers),
+       "transitionQualifiers found in the OnCommitted events");
+  }
+
+  // transitionType: form_submit
+  received = [];
+  await loadAndWait(win, "onCompleted", FORM_URL, () => {
+    win.document.querySelector("form").submit();
+  });
+
+  found = received.find((data) => (data.event == "onCommitted" && data.url == FORM_URL));
+
+  ok(found, "Got the onCommitted event");
+
+  if (found) {
+    is(found.details.transitionType, "form_submit",
+       "Got the expected 'form_submit' transitionType in the OnCommitted event");
+    ok(Array.isArray(found.details.transitionQualifiers),
+       "transitionQualifiers found in the OnCommitted events");
+  }
+
+  // transitionQualifier: server_redirect
+  received = [];
+  await loadAndWait(win, "onCompleted", REDIRECTED, () => { win.location = REDIRECT; });
+
+  found = received.find((data) => (data.event == "onCommitted" && data.url == REDIRECTED));
+
+  ok(found, "Got the onCommitted event");
+
+  if (found) {
+    is(found.details.transitionType, "link",
+       "Got the expected 'link' transitionType in the OnCommitted event");
+    ok(Array.isArray(found.details.transitionQualifiers) &&
+       found.details.transitionQualifiers.find((q) => q == "server_redirect"),
+       "Got the expected 'server_redirect' transitionQualifiers in the OnCommitted events");
+  }
+
+  // transitionQualifier: forward_back
+  received = [];
+  await loadAndWait(win, "onCompleted", FORM_URL, () => { win.history.back(); });
+
+  found = received.find((data) => (data.event == "onCommitted" && data.url == FORM_URL));
+
+  ok(found, "Got the onCommitted event");
+
+  if (found) {
+    is(found.details.transitionType, "link",
+       "Got the expected 'link' transitionType in the OnCommitted event");
+    ok(Array.isArray(found.details.transitionQualifiers) &&
+       found.details.transitionQualifiers.find((q) => q == "forward_back"),
+       "Got the expected 'forward_back' transitionQualifiers in the OnCommitted events");
+  }
+
+  // transitionQualifier: client_redirect
+  // (from meta http-equiv tag)
+  received = [];
+  await loadAndWait(win, "onCompleted", REDIRECTED, () => {
+    win.location = CLIENT_REDIRECT;
+  });
+
+  found = received.find((data) => (data.event == "onCommitted" && data.url == REDIRECTED));
+
+  ok(found, "Got the onCommitted event");
+
+  if (found) {
+    is(found.details.transitionType, "link",
+       "Got the expected 'link' transitionType in the OnCommitted event");
+    ok(Array.isArray(found.details.transitionQualifiers) &&
+       found.details.transitionQualifiers.find((q) => q == "client_redirect"),
+       "Got the expected 'client_redirect' transitionQualifiers in the OnCommitted events");
+  }
+
+  // transitionQualifier: client_redirect
+  // (from http headers)
+  received = [];
+  await loadAndWait(win, "onCompleted", REDIRECTED, () => {
+    win.location = CLIENT_REDIRECT_HTTPHEADER;
+  });
+
+  found = received.find((data) => (data.event == "onCommitted" && data.url == REDIRECTED));
+
+  ok(found, "Got the onCommitted event");
+
+  if (found) {
+    is(found.details.transitionType, "link",
+       "Got the expected 'link' transitionType in the OnCommitted event");
+    ok(Array.isArray(found.details.transitionQualifiers) &&
+       found.details.transitionQualifiers.find((q) => q == "client_redirect"),
+       "Got the expected 'client_redirect' transitionQualifiers in the OnCommitted events");
+  }
+
+  // transitionQualifier: client_redirect (sub-frame)
+  // (from meta http-equiv tag)
+  received = [];
+  await loadAndWait(win, "onCompleted", REDIRECTED, () => {
+    win.location = FRAME_CLIENT_REDIRECT;
+  });
+
+  found = received.find((data) => (data.event == "onCommitted" && data.url == REDIRECTED));
+
+  ok(found, "Got the onCommitted event");
+
+  if (found) {
+    is(found.details.transitionType, "auto_subframe",
+       "Got the expected 'auto_subframe' transitionType in the OnCommitted event");
+    ok(Array.isArray(found.details.transitionQualifiers) &&
+       found.details.transitionQualifiers.find((q) => q == "client_redirect"),
+       "Got the expected 'client_redirect' transitionQualifiers in the OnCommitted events");
+  }
+
+  // transitionQualifier: server_redirect (sub-frame)
+  received = [];
+  await loadAndWait(win, "onCompleted", REDIRECTED, () => { win.location = FRAME_REDIRECT; });
+
+  found = received.find((data) => (data.event == "onCommitted" && data.url == REDIRECT));
+
+  ok(found, "Got the onCommitted event");
+
+  if (found) {
+    is(found.details.transitionType, "auto_subframe",
+       "Got the expected 'auto_subframe' transitionType in the OnCommitted event");
+    // TODO BUG 1264936: currently the server_redirect is not detected in sub-frames
+    // once we fix it we can test it here:
+    //
+    // ok(Array.isArray(found.details.transitionQualifiers) &&
+    //    found.details.transitionQualifiers.find((q) => q == "server_redirect"),
+    //    "Got the expected 'server_redirect' transitionQualifiers in the OnCommitted events");
+  }
+
+  // transitionType: manual_subframe
+  received = [];
+  await loadAndWait(win, "onCompleted", FRAME_MANUAL, () => { win.location = FRAME_MANUAL; });
+  found = received.find((data) => (data.event == "onCommitted" &&
+                                   data.url == FRAME_MANUAL_PAGE1));
+
+  ok(found, "Got the onCommitted event");
+
+  if (found) {
+    is(found.details.transitionType, "auto_subframe",
+       "Got the expected 'auto_subframe' transitionType in the OnCommitted event");
+  }
+
+  received = [];
+  await loadAndWait(win, "onCompleted", FRAME_MANUAL_PAGE2, () => {
+    let el = win.document.querySelector("iframe")
+                .contentDocument.querySelector("a");
+    sendMouseEvent({type: "click"}, el, win);
+  });
+
+  found = received.find((data) => (data.event == "onCommitted" &&
+                                   data.url == FRAME_MANUAL_PAGE2));
+
+  ok(found, "Got the onCommitted event");
+
+  if (found) {
+    if (AppConstants.MOZ_BUILD_APP === "browser") {
+      is(found.details.transitionType, "manual_subframe",
+         "Got the expected 'manual_subframe' transitionType in the OnCommitted event");
+    } else {
+      is(found.details.transitionType, "auto_subframe",
+         "Got the expected 'manual_subframe' transitionType in the OnCommitted event");
+    }
+  }
+
+  // Test transitions properties on onHistoryStateUpdated events.
+
+  received = [];
+  await loadAndWait(win, "onCompleted", FRAME2, () => { win.location = FRAME2; });
+
+  received = [];
+  await loadAndWait(win, "onHistoryStateUpdated", `${FRAME2}/pushState`, () => {
+    win.history.pushState({}, "History PushState", `${FRAME2}/pushState`);
+  });
+
+  found = received.find((data) => (data.event == "onHistoryStateUpdated" &&
+                                   data.url == `${FRAME2}/pushState`));
+
+  ok(found, "Got the onHistoryStateUpdated event");
+
+  if (found) {
+    is(typeof found.details.transitionType, "string",
+       "Got transitionType in the onHistoryStateUpdated event");
+    ok(Array.isArray(found.details.transitionQualifiers),
+       "Got transitionQualifiers in the onHistoryStateUpdated event");
+  }
+
+  // Test transitions properties on onReferenceFragmentUpdated events.
+
+  received = [];
+  await loadAndWait(win, "onReferenceFragmentUpdated", `${FRAME2}/pushState#ref2`, () => {
+    win.history.pushState({}, "ReferenceFragment Update", `${FRAME2}/pushState#ref2`);
+  });
+
+  found = received.find((data) => (data.event == "onReferenceFragmentUpdated" &&
+                                   data.url == `${FRAME2}/pushState#ref2`));
+
+  ok(found, "Got the onReferenceFragmentUpdated event");
+
+  if (found) {
+    is(typeof found.details.transitionType, "string",
+       "Got transitionType in the onReferenceFragmentUpdated event");
+    ok(Array.isArray(found.details.transitionQualifiers),
+       "Got transitionQualifiers in the onReferenceFragmentUpdated event");
+  }
+
+  // cleanup phase
+  win.close();
+
+  await extension.unload();
+  info("webnavigation extension unloaded");
+});
+
+add_task(async function webnav_ordering() {
+  let extensionData = {
+    manifest: {
+      permissions: [
+        "webNavigation",
+      ],
+    },
+    background: backgroundScript,
+  };
+
+  let extension = ExtensionTestUtils.loadExtension(extensionData);
+
+  extension.onMessage("received", ({url, event}) => {
+    received.push({url, event});
+
+    if (event == waitingEvent && url == waitingURL) {
+      completedResolve();
+    }
+  });
+
+  await extension.startup();
+  await extension.awaitMessage("ready");
+  info("webnavigation extension loaded");
+
+  let win = window.open();
+
+  await loadAndWait(win, "onCompleted", URL, () => { win.location = URL; });
+
+  function checkRequired(url) {
+    for (let event of REQUIRED) {
+      let found = false;
+      for (let r of received) {
+        if (r.url == url && r.event == event) {
+          found = true;
+        }
+      }
+      ok(found, `Received event ${event} from ${url}`);
+    }
+  }
+
+  checkRequired(URL);
+  checkRequired(FRAME);
+
+  function checkBefore(action1, action2) {
+    function find(action) {
+      for (let i = 0; i < received.length; i++) {
+        if (received[i].url == action.url && received[i].event == action.event) {
+          return i;
+        }
+      }
+      return -1;
+    }
+
+    let index1 = find(action1);
+    let index2 = find(action2);
+    ok(index1 != -1, `Action ${JSON.stringify(action1)} happened`);
+    ok(index2 != -1, `Action ${JSON.stringify(action2)} happened`);
+    ok(index1 < index2, `Action ${JSON.stringify(action1)} happened before ${JSON.stringify(action2)}`);
+  }
+
+  // As required in the webNavigation API documentation:
+  // If a navigating frame contains subframes, its onCommitted is fired before any
+  // of its children's onBeforeNavigate; while onCompleted is fired after
+  // all of its children's onCompleted.
+  checkBefore({url: URL, event: "onCommitted"}, {url: FRAME, event: "onBeforeNavigate"});
+  checkBefore({url: FRAME, event: "onCompleted"}, {url: URL, event: "onCompleted"});
+
+  // As required in the webNAvigation API documentation, check the event sequence:
+  // onBeforeNavigate -> onCommitted -> onDOMContentLoaded -> onCompleted
+  let expectedEventSequence = [
+    "onBeforeNavigate", "onCommitted", "onDOMContentLoaded", "onCompleted",
+  ];
+
+  for (let i = 1; i < expectedEventSequence.length; i++) {
+    let after = expectedEventSequence[i];
+    let before = expectedEventSequence[i - 1];
+    checkBefore({url: URL, event: before}, {url: URL, event: after});
+    checkBefore({url: FRAME, event: before}, {url: FRAME, event: after});
+  }
+
+  await loadAndWait(win, "onCompleted", FRAME2, () => { win.frames[0].location = FRAME2; });
+
+  checkRequired(FRAME2);
+
+  let navigationSequence = [
+    {
+      action: () => { win.frames[0].document.getElementById("elt").click(); },
+      waitURL: `${FRAME2}#ref`,
+      expectedEvent: "onReferenceFragmentUpdated",
+      description: "clicked an anchor link",
+    },
+    {
+      action: () => { win.frames[0].history.pushState({}, "History PushState", `${FRAME2}#ref2`); },
+      waitURL: `${FRAME2}#ref2`,
+      expectedEvent: "onReferenceFragmentUpdated",
+      description: "history.pushState, same pathname, different hash",
+    },
+    {
+      action: () => { win.frames[0].history.pushState({}, "History PushState", `${FRAME2}#ref2`); },
+      waitURL: `${FRAME2}#ref2`,
+      expectedEvent: "onHistoryStateUpdated",
+      description: "history.pushState, same pathname, same hash",
+    },
+    {
+      action: () => {
+        win.frames[0].history.pushState({}, "History PushState", `${FRAME2}?query_param1=value#ref2`);
+      },
+      waitURL: `${FRAME2}?query_param1=value#ref2`,
+      expectedEvent: "onHistoryStateUpdated",
+      description: "history.pushState, same pathname, same hash, different query params",
+    },
+    {
+      action: () => {
+        win.frames[0].history.pushState({}, "History PushState", `${FRAME2}?query_param2=value#ref3`);
+      },
+      waitURL: `${FRAME2}?query_param2=value#ref3`,
+      expectedEvent: "onHistoryStateUpdated",
+      description: "history.pushState, same pathname, different hash, different query params",
+    },
+    {
+      action: () => { win.frames[0].history.pushState(null, "History PushState", FRAME_PUSHSTATE); },
+      waitURL: FRAME_PUSHSTATE,
+      expectedEvent: "onHistoryStateUpdated",
+      description: "history.pushState, different pathname",
+    },
+  ];
+
+  for (let navigation of navigationSequence) {
+    let {expectedEvent, waitURL, action, description} = navigation;
+    info(`Waiting ${expectedEvent} from ${waitURL} - ${description}`);
+    await loadAndWait(win, expectedEvent, waitURL, action);
+    info(`Received ${expectedEvent} from ${waitURL} - ${description}`);
+  }
+
+  for (let i = navigationSequence.length - 1; i > 0; i--) {
+    let {waitURL: fromURL, expectedEvent} = navigationSequence[i];
+    let {waitURL} = navigationSequence[i - 1];
+    info(`Waiting ${expectedEvent} from ${waitURL} - history.back() from ${fromURL} to ${waitURL}`);
+    await loadAndWait(win, expectedEvent, waitURL, () => { win.frames[0].history.back(); });
+    info(`Received ${expectedEvent} from ${waitURL} - history.back() from ${fromURL} to ${waitURL}`);
+  }
+
+  for (let i = 0; i < navigationSequence.length - 1; i++) {
+    let {waitURL: fromURL} = navigationSequence[i];
+    let {waitURL, expectedEvent} = navigationSequence[i + 1];
+    info(`Waiting ${expectedEvent} from ${waitURL} - history.forward() from ${fromURL} to ${waitURL}`);
+    await loadAndWait(win, expectedEvent, waitURL, () => { win.frames[0].history.forward(); });
+    info(`Received ${expectedEvent} from ${waitURL} - history.forward() from ${fromURL} to ${waitURL}`);
+  }
+
+  win.close();
+
+  await extension.unload();
+  info("webnavigation extension unloaded");
+});
+
+add_task(async function webnav_error_event() {
+  function backgroundScriptErrorEvent() {
+    browser.webNavigation.onErrorOccurred.addListener((details) => {
+      browser.test.log(`Got onErrorOccurred ${details.url} ${details.error}`);
+
+      browser.test.sendMessage("received", {url: details.url, details, event: "onErrorOccurred"});
+    });
+
+    browser.test.sendMessage("ready");
+  }
+
+  let extensionData = {
+    manifest: {
+      permissions: [
+        "webNavigation",
+      ],
+    },
+    background: backgroundScriptErrorEvent,
+  };
+
+  let extension = ExtensionTestUtils.loadExtension(extensionData);
+
+  extension.onMessage("received", ({url, event, details}) => {
+    received.push({url, event, details});
+
+    if (event == waitingEvent && url == waitingURL) {
+      completedResolve();
+    }
+  });
+
+  await Promise.all([extension.startup(), extension.awaitMessage("ready")]);
+  info("webnavigation extension loaded");
+
+  let win = window.open();
+
+  received = [];
+  await loadAndWait(win, "onErrorOccurred", INVALID_PAGE, () => { win.location = INVALID_PAGE; });
+
+  let found = received.find((data) => (data.event == "onErrorOccurred" &&
+                                   data.url == INVALID_PAGE));
+
+  ok(found, "Got the onErrorOccurred event");
+
+  if (found) {
+    ok(found.details.error.match(/Error code [0-9]+/),
+       "Got the expected error string in the onErrorOccurred event");
+  }
+
+  // cleanup phase
+  win.close();
+
+  await extension.unload();
+  info("webnavigation extension unloaded");
+});
+</script>
+
+</body>
+</html>
diff --git a/toolkit/components/extensions/test/mochitest/test_ext_webnavigation_filters.html b/toolkit/components/extensions/test/mochitest/test_ext_webnavigation_filters.html
new file mode 100644
index 0000000000..19cb6539d7
--- /dev/null
+++ b/toolkit/components/extensions/test/mochitest/test_ext_webnavigation_filters.html
@@ -0,0 +1,313 @@
+<!DOCTYPE HTML>
+<html>
+<head>
+  <title>Test for simple WebExtension</title>
+  <script src="/tests/SimpleTest/SimpleTest.js"></script>
+  <script src="/tests/SimpleTest/ExtensionTestUtils.js"></script>
+  <script type="text/javascript" src="head.js"></script>
+  <link rel="stylesheet" type="text/css" href="/tests/SimpleTest/test.css"/>
+</head>
+<body>
+
+<script type="text/javascript">
+"use strict";
+
+add_task(async function test_webnav_unresolved_uri_on_expected_URI_scheme() {
+  function background() {
+    let listeners = [];
+
+    function cleanupTestListeners() {
+      browser.test.log(`Cleanup previous test event listeners`);
+      for (let {event, listener} of listeners.splice(0)) {
+        browser.webNavigation[event].removeListener(listener);
+      }
+    }
+
+    function createTestListener(event, fail, urlFilter) {
+      return new Promise(resolve => {
+        function listener(details) {
+          let log = JSON.stringify({url: details.url, urlFilter});
+          if (fail) {
+            browser.test.fail(`Got an unexpected ${event} on the failure listener: ${log}`);
+          } else {
+            browser.test.succeed(`Got the expected ${event} on the success listener: ${log}`);
+          }
+
+          resolve();
+        }
+
+        browser.webNavigation[event].addListener(listener, {url: urlFilter});
+        listeners.push({event, listener});
+      });
+    }
+
+    browser.test.onMessage.addListener((msg, events, data) => {
+      if (msg !== "test-filters") {
+        return;
+      }
+
+      let promises = [];
+
+      for (let {okFilter, failFilter} of data.filters) {
+        for (let event of events) {
+          promises.push(
+            Promise.race([
+              createTestListener(event, false, okFilter),
+              createTestListener(event, true, failFilter),
+            ]));
+        }
+      }
+
+      Promise.all(promises).catch(e => {
+        browser.test.fail(`Error: ${e} :: ${e.stack}`);
+      }).then(() => {
+        cleanupTestListeners();
+        browser.test.sendMessage("test-filter-next");
+      });
+
+      browser.test.sendMessage("test-filter-ready");
+    });
+  }
+
+  let extensionData = {
+    manifest: {
+      permissions: [
+        "webNavigation",
+      ],
+    },
+    background,
+  };
+
+  let extension = ExtensionTestUtils.loadExtension(extensionData);
+
+  await extension.startup();
+
+  let win = window.open();
+
+  let testFilterScenarios = [
+    {
+      url: "https://example.net/browser",
+      filters: [
+        // schemes
+        {
+          okFilter: [{schemes: ["https"]}],
+          failFilter: [{schemes: ["http"]}],
+        },
+        // ports
+        {
+          okFilter: [{ports: [80, 22, 443]}],
+          failFilter: [{ports: [81, 82, 83]}],
+        },
+        {
+          okFilter: [{ports: [22, 443, [10, 80]]}],
+          failFilter: [{ports: [22, 23, [81, 100]]}],
+        },
+        // multiple criteria in a single filter:
+        // if one of the criteria is not verified, the event should not be received.
+        {
+          okFilter: [{schemes: ["https"], ports: [80, 22, 443]}],
+          failFilter: [{schemes: ["https"], ports: [81, 82, 83]}],
+        },
+        {
+          okFilter: [{hostEquals: "example.net", ports: [80, 22, 443]}],
+          failFilter: [{hostEquals: "example.org", ports: [80, 22, 443]}],
+        },
+        // multiple urlFilters on the same listener
+        // if at least one of the criteria is verified, the event should be received.
+        {
+          okFilter: [{schemes: ["http"]}, {ports: [80, 22, 443]}],
+          failFilter: [{schemes: ["http"]}, {ports: [81, 82, 83]}],
+        },
+      ],
+    },
+    {
+      url: "https://example.net/browser?param=1#ref",
+      filters: [
+        // host: Equals, Contains, Prefix, Suffix
+        {
+          okFilter: [{hostEquals: "example.net"}],
+          failFilter: [{hostEquals: "example.com"}],
+        },
+        {
+          okFilter: [{hostContains: ".example"}],
+          failFilter: [{hostContains: ".www"}],
+        },
+        {
+          okFilter: [{hostPrefix: "example"}],
+          failFilter: [{hostPrefix: "www"}],
+        },
+        {
+          okFilter: [{hostSuffix: "net"}],
+          failFilter: [{hostSuffix: "com"}],
+        },
+        // path: Equals, Contains, Prefix, Suffix
+        {
+          okFilter: [{pathEquals: "/browser"}],
+          failFilter: [{pathEquals: "/"}],
+        },
+        {
+          okFilter: [{pathContains: "brow"}],
+          failFilter: [{pathContains: "tool"}],
+        },
+        {
+          okFilter: [{pathPrefix: "/bro"}],
+          failFilter: [{pathPrefix: "/tool"}],
+        },
+        {
+          okFilter: [{pathSuffix: "wser"}],
+          failFilter: [{pathSuffix: "kit"}],
+        },
+        // query: Equals, Contains, Prefix, Suffix
+        {
+          okFilter: [{queryEquals: "param=1"}],
+          failFilter: [{queryEquals: "wrongparam=2"}],
+        },
+        {
+          okFilter: [{queryContains: "param"}],
+          failFilter: [{queryContains: "wrongparam"}],
+        },
+        {
+          okFilter: [{queryPrefix: "param="}],
+          failFilter: [{queryPrefix: "wrong"}],
+        },
+        {
+          okFilter: [{querySuffix: "=1"}],
+          failFilter: [{querySuffix: "=2"}],
+        },
+        // urlMatches, originAndPathMatches
+        {
+          okFilter: [{urlMatches: "example.net/.*\?param=1"}],
+          failFilter: [{urlMatches: "example.net/.*\?wrongparam=2"}],
+        },
+        {
+          okFilter: [{originAndPathMatches: "example.net\/browser"}],
+          failFilter: [{originAndPathMatches: "example.net/.*\?param=1"}],
+        },
+      ],
+    },
+  ];
+
+  info("WebNavigation event filters test scenarios starting...");
+
+  const EVENTS = [
+    "onBeforeNavigate",
+    "onCommitted",
+    "onDOMContentLoaded",
+    "onCompleted",
+  ];
+
+  for (let data of testFilterScenarios) {
+    info(`Prepare the new test scenario: ${JSON.stringify(data)}`);
+
+    win.location = "about:blank";
+
+    // Wait for the about:blank load to finish before continuing, in case this
+    // load is causing a process switch back into our process.
+    await SimpleTest.promiseWaitForCondition(() => {
+      try {
+        return win.location.href == "about:blank" &&
+          win.document.readyState == "complete";
+      } catch (e) {
+        return false;
+      }
+    });
+
+    extension.sendMessage("test-filters", EVENTS, data);
+    await extension.awaitMessage("test-filter-ready");
+
+    info(`Loading the test url: ${data.url}`);
+    win.location = data.url;
+
+    await extension.awaitMessage("test-filter-next");
+
+    info("Test scenario completed. Moving to the next test scenario.");
+  }
+
+  info("WebNavigation event filters test onReferenceFragmentUpdated scenario starting...");
+
+  const BASE = "http://mochi.test:8888/tests/toolkit/components/extensions/test/mochitest";
+  let url = BASE + "/file_WebNavigation_page3.html";
+
+  let okFilter = [{urlContains: "_page3.html"}];
+  let failFilter = [{ports: [444]}];
+  let data = {filters: [{okFilter, failFilter}]};
+  let event = "onCompleted";
+
+  info(`Loading the initial test url: ${url}`);
+  extension.sendMessage("test-filters", [event], data);
+
+  await extension.awaitMessage("test-filter-ready");
+  win.location = url;
+  await extension.awaitMessage("test-filter-next");
+
+  event = "onReferenceFragmentUpdated";
+  extension.sendMessage("test-filters", [event], data);
+
+  await extension.awaitMessage("test-filter-ready");
+  win.location = url + "#ref1";
+  await extension.awaitMessage("test-filter-next");
+
+  info("WebNavigation event filters test onHistoryStateUpdated scenario starting...");
+
+  event = "onHistoryStateUpdated";
+  extension.sendMessage("test-filters", [event], data);
+  await extension.awaitMessage("test-filter-ready");
+
+  win.history.pushState({}, "", BASE + "/pushState_page3.html");
+  await extension.awaitMessage("test-filter-next");
+
+  // TODO: add additional specific tests for the other webNavigation events:
+  // onErrorOccurred (and onCreatedNavigationTarget on supported)
+
+  info("WebNavigation event filters test scenarios completed.");
+
+  await extension.unload();
+
+  win.close();
+});
+
+add_task(async function test_webnav_empty_filter_validation_error() {
+  function background() {
+    let catchedException;
+
+    try {
+      browser.webNavigation.onCompleted.addListener(
+        // Empty callback (not really used)
+        () => {},
+        // Empty filter (which should raise a validation error exception).
+        {url: []}
+      );
+    } catch (e) {
+      catchedException = e;
+      browser.test.log(`Got an exception`);
+    }
+
+    if (catchedException &&
+        catchedException.message.includes("Type error for parameter filters") &&
+        catchedException.message.includes("Array requires at least 1 items; you have 0")) {
+      browser.test.notifyPass("webNav.emptyFilterValidationError");
+    } else {
+      browser.test.notifyFail("webNav.emptyFilterValidationError");
+    }
+  }
+
+  let extension = ExtensionTestUtils.loadExtension({
+    manifest: {
+      permissions: [
+        "webNavigation",
+      ],
+    },
+    background,
+  });
+
+  await extension.startup();
+
+  await extension.awaitFinish("webNav.emptyFilterValidationError");
+
+  await extension.unload();
+});
+
+</script>
+
+</body>
+</html>
diff --git a/toolkit/components/extensions/test/mochitest/test_ext_webnavigation_incognito.html b/toolkit/components/extensions/test/mochitest/test_ext_webnavigation_incognito.html
new file mode 100644
index 0000000000..45147365ee
--- /dev/null
+++ b/toolkit/components/extensions/test/mochitest/test_ext_webnavigation_incognito.html
@@ -0,0 +1,105 @@
+<!DOCTYPE HTML>
+<html>
+<head>
+  <title>Test for simple WebExtension</title>
+  <meta charset="utf-8">
+  <script src="/tests/SimpleTest/SimpleTest.js"></script>
+  <script src="/tests/SimpleTest/ExtensionTestUtils.js"></script>
+  <script src="/tests/SimpleTest/EventUtils.js"></script>
+  <script type="text/javascript" src="head.js"></script>
+  <link rel="stylesheet" type="text/css" href="/tests/SimpleTest/test.css"/>
+</head>
+<body>
+
+<script type="text/javascript">
+"use strict";
+
+add_task(async function webnav_test_incognito() {
+  // Monitor will fail if it gets any event.
+  let monitor = ExtensionTestUtils.loadExtension({
+    manifest: {
+      "permissions": ["webNavigation", "*://mochi.test/*"],
+    },
+    background() {
+      const EVENTS = [
+        "onTabReplaced",
+        "onBeforeNavigate",
+        "onCommitted",
+        "onDOMContentLoaded",
+        "onCompleted",
+        "onErrorOccurred",
+        "onReferenceFragmentUpdated",
+        "onHistoryStateUpdated",
+      ];
+
+      function onEvent(event, details) {
+        browser.test.fail(`not_allowed - Got ${event} ${details.url} ${details.frameId} ${details.parentFrameId}`);
+      }
+
+      let listeners = {};
+      for (let event of EVENTS) {
+        listeners[event] = onEvent.bind(null, event);
+        browser.webNavigation[event].addListener(listeners[event]);
+      }
+
+      browser.test.onMessage.addListener(async (message, tabId) => {
+        // try to access the private window
+        await browser.test.assertRejects(browser.webNavigation.getAllFrames({tabId}),
+                                         /Invalid tab ID/,
+                                         "should not be able to get incognito frames");
+        await browser.test.assertRejects(browser.webNavigation.getFrame({tabId, frameId: 0}),
+                                         /Invalid tab ID/,
+                                         "should not be able to get incognito frames");
+        browser.test.notifyPass("completed");
+      });
+    },
+  });
+
+  // extension loads a private window and waits for the onCompleted event.
+  let extension = ExtensionTestUtils.loadExtension({
+    incognitoOverride: "spanning",
+    manifest: {
+      permissions: ["tabs", "webNavigation", "*://mochi.test/*"],
+    },
+    async background() {
+      const BASE = "http://mochi.test:8888/tests/toolkit/components/extensions/test/mochitest";
+      const url = BASE + "/file_WebNavigation_page1.html";
+      let window;
+
+      browser.webNavigation.onCompleted.addListener(async (details) => {
+        if (details.url !== url) {
+          return;
+        }
+        browser.test.log(`spanning - Got onCompleted ${details.url} ${details.frameId} ${details.parentFrameId}`);
+        browser.test.sendMessage("completed");
+      });
+      browser.test.onMessage.addListener(async () => {
+        await browser.windows.remove(window.id);
+        browser.test.notifyPass("done");
+      });
+      window = await browser.windows.create({url, incognito: true});
+      let tabs = await browser.tabs.query({active: true, windowId: window.id});
+      browser.test.sendMessage("tabId", tabs[0].id);
+    },
+  });
+
+  await monitor.startup();
+  await extension.startup();
+
+  await extension.awaitMessage("completed");
+  let tabId = await extension.awaitMessage("tabId");
+
+  await monitor.sendMessage("tab", tabId);
+  await monitor.awaitFinish("completed");
+
+  await extension.sendMessage("close");
+  await extension.awaitFinish("done");
+
+  await extension.unload();
+  await monitor.unload();
+});
+
+</script>
+
+</body>
+</html>
diff --git a/toolkit/components/extensions/test/mochitest/test_ext_webrequest_and_proxy_filter.html b/toolkit/components/extensions/test/mochitest/test_ext_webrequest_and_proxy_filter.html
new file mode 100644
index 0000000000..b28cbb7635
--- /dev/null
+++ b/toolkit/components/extensions/test/mochitest/test_ext_webrequest_and_proxy_filter.html
@@ -0,0 +1,131 @@
+<!DOCTYPE HTML>
+
+<html>
+<head>
+<meta charset="utf-8">
+  <script src="/tests/SimpleTest/SimpleTest.js"></script>
+  <script src="/tests/SimpleTest/ExtensionTestUtils.js"></script>
+  <script type="text/javascript" src="head.js"></script>
+  <link rel="stylesheet" type="text/css" href="/tests/SimpleTest/test.css">
+<script>
+"use strict";
+
+// Check that the windowId and tabId filter work as expected in the webRequest
+// and proxy API:
+// - A non-matching windowId / tabId listener won't trigger events.
+// - A matching tabId from a tab triggers the event.
+// - A matching windowId from a tab triggers the event.
+//   (unlike test_ext_webrequest_filter.html, this also works on Android)
+// - Requests from background pages can be matched with windowId and tabId -1.
+add_task(async function test_filter_tabId_and_windowId() {
+  async function tabScript() {
+    let pendingExpectations = new Set();
+    // Helper to detect completion of expected requests.
+    function watchExpected(filter, desc) {
+      desc += ` - ${JSON.stringify(filter)}`;
+      const DESC_PROXY = `${desc} (proxy)`;
+      const DESC_WEBREQUEST = `${desc} (webRequest)`;
+      pendingExpectations.add(DESC_PROXY);
+      pendingExpectations.add(DESC_WEBREQUEST);
+      browser.proxy.onRequest.addListener(() => {
+        pendingExpectations.delete(DESC_PROXY);
+      }, filter);
+      browser.webRequest.onBeforeRequest.addListener(
+        () => {
+          pendingExpectations.delete(DESC_WEBREQUEST);
+        },
+        filter,
+        ["blocking"]
+      );
+    }
+
+    // Helper to detect unexpected requests.
+    function watchUnexpected(filter, desc) {
+      desc += ` - ${JSON.stringify(filter)}`;
+      browser.proxy.onRequest.addListener(() => {
+        browser.test.fail(`${desc} - unexpected proxy event`);
+      }, filter);
+      browser.webRequest.onBeforeRequest.addListener(() => {
+        browser.test.fail(`${desc} - unexpected webRequest event`);
+      }, filter);
+    }
+
+    function registerExpectations(url, windowId, tabId) {
+      const urls = [url];
+      watchUnexpected({ urls, windowId: 0 }, "non-matching windowId");
+      watchUnexpected({ urls, tabId: 0 }, "non-matching tabId");
+
+      watchExpected({ urls, windowId }, "windowId matches");
+      watchExpected({ urls, tabId }, "tabId matches");
+    }
+
+    try {
+      let { windowId, tabId } = await browser.runtime.sendMessage("getIds");
+      browser.test.log(`Dummy tab has: tabId=${tabId} windowId=${windowId}`);
+      registerExpectations("http://example.com/?tab", windowId, tabId);
+      registerExpectations("http://example.com/?bg", -1, -1);
+
+      // Call an API method implemented in the parent process to ensure that
+      // the listeners have been registered (workaround for bug 1300234).
+      // There is a .catch() at the end because the call is rejected on Android.
+      await browser.proxy.settings.get({}).catch(() => {});
+
+      browser.test.log("Triggering request from background page.");
+      await browser.runtime.sendMessage("triggerBackgroundRequest");
+
+      browser.test.log("Triggering request from tab.");
+      await fetch("http://example.com/?tab");
+
+      browser.test.assertEq(0, pendingExpectations.size, "got all events");
+      for (let description of pendingExpectations) {
+        browser.test.fail(`Event not observed: ${description}`);
+      }
+    } catch (e) {
+      browser.test.fail(`Unexpected test failure: ${e} :: ${e.stack}`);
+    }
+    browser.runtime.sendMessage("testCompleted");
+  }
+
+  function background() {
+    browser.runtime.onMessage.addListener(async (msg, sender) => {
+      if (msg === "getIds") {
+        return { windowId: sender.tab.windowId, tabId: sender.tab.id };
+      }
+      if (msg === "triggerBackgroundRequest") {
+        await fetch("http://example.com/?bg");
+      }
+      if (msg === "testCompleted") {
+        await browser.tabs.remove(sender.tab.id);
+        browser.test.sendMessage("testCompleted");
+      }
+    });
+    browser.tabs.create({
+      url: browser.runtime.getURL("tab.html"),
+    });
+  }
+
+  let extension = ExtensionTestUtils.loadExtension({
+    manifest: {
+      permissions: [
+        "proxy",
+        "webRequest",
+        "webRequestBlocking",
+        "http://example.com/*",
+      ],
+    },
+    background,
+    files: {
+      "tab.html": `<!DOCTYPE html><script src="tab.js"><\/script>`,
+      "tab.js": tabScript,
+    },
+  });
+  await extension.startup();
+
+  await extension.awaitMessage("testCompleted");
+  await extension.unload();
+});
+</script>
+</head>
+<body>
+</body>
+</html>
diff --git a/toolkit/components/extensions/test/mochitest/test_ext_webrequest_auth.html b/toolkit/components/extensions/test/mochitest/test_ext_webrequest_auth.html
new file mode 100644
index 0000000000..f260f040a1
--- /dev/null
+++ b/toolkit/components/extensions/test/mochitest/test_ext_webrequest_auth.html
@@ -0,0 +1,181 @@
+<!DOCTYPE HTML>
+
+<html>
+<head>
+<meta charset="utf-8">
+  <script src="/tests/SimpleTest/SimpleTest.js"></script>
+  <script src="/tests/SimpleTest/ExtensionTestUtils.js"></script>
+  <script type="text/javascript" src="head_webrequest.js"></script>
+  <script type="text/javascript" src="head.js"></script>
+  <link rel="stylesheet" type="text/css" href="/tests/SimpleTest/test.css"/>
+<script>
+"use strict";
+
+// This file defines content scripts.
+
+let baseUrl = "http://mochi.test:8888/tests/toolkit/components/passwordmgr/test/mochitest/authenticate.sjs";
+function testXHR(url) {
+  return new Promise((resolve, reject) => {
+    let xhr = new XMLHttpRequest();
+    xhr.open("GET", url);
+    xhr.onload = resolve;
+    xhr.onabort = reject;
+    xhr.onerror = reject;
+    xhr.send();
+  });
+}
+
+function getAuthHandler(result, blocking = true) {
+  function background(result) {
+    browser.webRequest.onAuthRequired.addListener((details) => {
+      browser.test.succeed(`authHandler.onAuthRequired called with ${details.requestId} ${details.url} result ${JSON.stringify(result)}`);
+      browser.test.sendMessage("onAuthRequired");
+      return result;
+    }, {urls: ["*://mochi.test/*"]}, ["blocking"]);
+    browser.webRequest.onCompleted.addListener((details) => {
+      browser.test.succeed(`authHandler.onCompleted called with ${details.requestId} ${details.url}`);
+      browser.test.sendMessage("onCompleted");
+    }, {urls: ["*://mochi.test/*"]});
+    browser.webRequest.onErrorOccurred.addListener((details) => {
+      browser.test.succeed(`authHandler.onErrorOccurred called with ${details.requestId} ${details.url}`);
+      browser.test.sendMessage("onErrorOccurred");
+    }, {urls: ["*://mochi.test/*"]});
+  }
+
+  let permissions = [
+    "webRequest",
+    "*://mochi.test/*",
+  ];
+  if (blocking) {
+    permissions.push("webRequestBlocking");
+  }
+  return ExtensionTestUtils.loadExtension({
+    manifest: {
+      permissions,
+    },
+    background: `(${background})(${JSON.stringify(result)})`,
+  });
+}
+
+add_task(async function test_webRequest_auth_nonblocking_forwardAuthProvider() {
+  // The chrome script sets up a default auth handler on the channel, the
+  // extension does not return anything in the authRequred call.  We should
+  // get the call in the extension first, then in the chrome code where we
+  // cancel the request to avoid dealing with the prompt dialog here.  The test
+  // is to ensure that WebRequest calls the previous notificationCallbacks
+  // if the authorization is not handled by the onAuthRequired handler.
+
+  let chromeScript = SpecialPowers.loadChromeScript(() => {
+    /* eslint-env mozilla/chrome-script */
+    let observer = channel => {
+      if (!(channel instanceof Ci.nsIHttpChannel && channel.URI.host === "mochi.test" &&
+            channel.URI.spec.includes("authenticate.sjs"))) {
+        return;
+      }
+      Services.obs.removeObserver(observer, "http-on-modify-request");
+      channel.notificationCallbacks = {
+        QueryInterface: ChromeUtils.generateQI(["nsIInterfaceRequestor",
+                                                "nsIAuthPromptProvider",
+                                                "nsIAuthPrompt2"]),
+        getInterface: ChromeUtils.generateQI(["nsIAuthPromptProvider",
+                                              "nsIAuthPrompt2"]),
+        promptAuth(channel, level, authInfo) {
+          throw Components.Exception("", Cr.NS_ERROR_NO_INTERFACE);
+        },
+        getAuthPrompt(reason, iid) {
+          return this;
+        },
+        asyncPromptAuth(channel, callback, context, level, authInfo) {
+          // We just cancel here, we're only ensuring that non-webrequest
+          // notificationcallbacks get called if webrequest doesn't handle it.
+          Promise.resolve().then(() => {
+            callback.onAuthCancelled(context, false);
+            channel.cancel(Cr.NS_BINDING_ABORTED);
+            sendAsyncMessage("callback-complete");
+          });
+        },
+      };
+    };
+    Services.obs.addObserver(observer, "http-on-modify-request");
+    sendAsyncMessage("chrome-ready");
+  });
+  await chromeScript.promiseOneMessage("chrome-ready");
+  let callbackComplete = chromeScript.promiseOneMessage("callback-complete");
+
+  let handlingExt = getAuthHandler();
+  await handlingExt.startup();
+
+  await Assert.rejects(testXHR(`${baseUrl}?realm=auth_nonblocking_forwardAuth&user=auth_nonblocking_forwardAuth&pass=auth_nonblocking_forwardAuth`),
+                       ProgressEvent,
+                       "caught rejected xhr");
+
+  await callbackComplete;
+  await handlingExt.awaitMessage("onAuthRequired");
+  // We expect onErrorOccurred because the "default" authprompt above cancelled
+  // the auth request to avoid a dialog.
+  await handlingExt.awaitMessage("onErrorOccurred");
+  await handlingExt.unload();
+  chromeScript.destroy();
+});
+
+add_task(async function test_webRequest_auth_nonblocking_forwardAuthPrompt2() {
+  // The chrome script sets up a default auth handler on the channel, the
+  // extension does not return anything in the authRequred call.  We should
+  // get the call in the extension first, then in the chrome code where we
+  // cancel the request to avoid dealing with the prompt dialog here.  The test
+  // is to ensure that WebRequest calls the previous notificationCallbacks
+  // if the authorization is not handled by the onAuthRequired handler.
+
+  let chromeScript = SpecialPowers.loadChromeScript(() => {
+    /* eslint-env mozilla/chrome-script */
+    let observer = channel => {
+      if (!(channel instanceof Ci.nsIHttpChannel && channel.URI.host === "mochi.test" &&
+            channel.URI.spec.includes("authenticate.sjs"))) {
+        return;
+      }
+      Services.obs.removeObserver(observer, "http-on-modify-request");
+      channel.notificationCallbacks = {
+        QueryInterface: ChromeUtils.generateQI(["nsIInterfaceRequestor",
+                                                "nsIAuthPrompt2"]),
+        getInterface: ChromeUtils.generateQI(["nsIAuthPrompt2"]),
+        promptAuth(request, level, authInfo) {
+          throw Components.Exception("", Cr.NS_ERROR_NO_INTERFACE);
+        },
+        asyncPromptAuth(request, callback, context, level, authInfo) {
+          // We just cancel here, we're only ensuring that non-webrequest
+          // notificationcallbacks get called if webrequest doesn't handle it.
+          Promise.resolve().then(() => {
+            request.cancel(Cr.NS_BINDING_ABORTED);
+            sendAsyncMessage("callback-complete");
+          });
+        },
+      };
+    };
+    Services.obs.addObserver(observer, "http-on-modify-request");
+    sendAsyncMessage("chrome-ready");
+  });
+  await chromeScript.promiseOneMessage("chrome-ready");
+  let callbackComplete = chromeScript.promiseOneMessage("callback-complete");
+
+  let handlingExt = getAuthHandler();
+  await handlingExt.startup();
+
+  await Assert.rejects(testXHR(`${baseUrl}?realm=auth_nonblocking_forwardAuthPromptProvider&user=auth_nonblocking_forwardAuth&pass=auth_nonblocking_forwardAuth`),
+                       ProgressEvent,
+                       "caught rejected xhr");
+
+  await callbackComplete;
+  await handlingExt.awaitMessage("onAuthRequired");
+  // We expect onErrorOccurred because the "default" authprompt above cancelled
+  // the auth request to avoid a dialog.
+  await handlingExt.awaitMessage("onErrorOccurred");
+  await handlingExt.unload();
+  chromeScript.destroy();
+});
+</script>
+</head>
+<body>
+<div id="test">Authorization Test</div>
+
+</body>
+</html>
diff --git a/toolkit/components/extensions/test/mochitest/test_ext_webrequest_background_events.html b/toolkit/components/extensions/test/mochitest/test_ext_webrequest_background_events.html
new file mode 100644
index 0000000000..86cec62fb4
--- /dev/null
+++ b/toolkit/components/extensions/test/mochitest/test_ext_webrequest_background_events.html
@@ -0,0 +1,120 @@
+<!DOCTYPE HTML>
+<html>
+<head>
+  <title>Test for simple WebExtension</title>
+  <script src="/tests/SimpleTest/SimpleTest.js"></script>
+  <script src="/tests/SimpleTest/ExtensionTestUtils.js"></script>
+  <script type="text/javascript" src="head.js"></script>
+  <link rel="stylesheet" type="text/css" href="/tests/SimpleTest/test.css"/>
+</head>
+<body>
+
+<script type="text/javascript">
+"use strict";
+
+add_task(async function test_webRequest_serviceworker_events() {
+  await SpecialPowers.pushPrefEnv({
+    set: [["dom.serviceWorkers.testing.enabled", true]],
+  });
+
+  let extension = ExtensionTestUtils.loadExtension({
+    manifest: {
+      permissions: [
+        "webRequest",
+        "<all_urls>",
+      ],
+    },
+    background() {
+      let eventNames = new Set([
+        "onBeforeRequest",
+        "onBeforeSendHeaders",
+        "onSendHeaders",
+        "onHeadersReceived",
+        "onResponseStarted",
+        "onCompleted",
+        "onErrorOccurred",
+      ]);
+
+      function listener(name, details) {
+        browser.test.assertTrue(eventNames.has(name), `received ${name}`);
+        eventNames.delete(name);
+        if (name == "onCompleted") {
+          eventNames.delete("onErrorOccurred");
+        } else if (name == "onErrorOccurred") {
+          eventNames.delete("onCompleted");
+        }
+        if (eventNames.size == 0) {
+          browser.test.sendMessage("done");
+        }
+      }
+
+      for (let name of eventNames) {
+        browser.webRequest[name].addListener(
+          listener.bind(null, name),
+          {urls: ["https://example.com/*"]}
+        );
+      }
+    },
+  });
+
+  await extension.startup();
+  let registration = await navigator.serviceWorker.register("webrequest_worker.js", {scope: "."});
+  await waitForState(registration.installing, "activated");
+  await extension.awaitMessage("done");
+  await registration.unregister();
+  await extension.unload();
+});
+
+add_task(async function test_webRequest_background_events() {
+  let extension = ExtensionTestUtils.loadExtension({
+    manifest: {
+      permissions: [
+        "webRequest",
+        "<all_urls>",
+      ],
+    },
+    background() {
+      let eventNames = new Set([
+        "onBeforeRequest",
+        "onBeforeSendHeaders",
+        "onSendHeaders",
+        "onHeadersReceived",
+        "onResponseStarted",
+        "onCompleted",
+      ]);
+
+      function listener(name, details) {
+        browser.test.assertTrue(eventNames.has(name), `received ${name}`);
+        eventNames.delete(name);
+
+        if (eventNames.size === 0) {
+          browser.test.assertEq("xmlhttprequest", details.type, "correct type for fetch [see bug 1366710]");
+          browser.test.assertEq(0, eventNames.size, "messages received");
+          browser.test.sendMessage("done");
+        }
+      }
+
+      for (let name of eventNames) {
+        browser.webRequest[name].addListener(
+          listener.bind(null, name),
+          {urls: ["https://example.com/*"]}
+        );
+      }
+
+      fetch("https://example.com/example.txt").then(() => {
+        browser.test.succeed("Fetch succeeded.");
+      }, () => {
+        browser.test.fail("fetch received");
+        browser.test.sendMessage("done");
+      });
+    },
+  });
+
+  await extension.startup();
+  await extension.awaitMessage("done");
+  await extension.unload();
+});
+</script>
+
+</body>
+</html>
diff --git a/toolkit/components/extensions/test/mochitest/test_ext_webrequest_basic.html b/toolkit/components/extensions/test/mochitest/test_ext_webrequest_basic.html
new file mode 100644
index 0000000000..9d57d55681
--- /dev/null
+++ b/toolkit/components/extensions/test/mochitest/test_ext_webrequest_basic.html
@@ -0,0 +1,445 @@
+<!DOCTYPE HTML>
+
+<html>
+<head>
+<meta charset="utf-8">
+  <script src="/tests/SimpleTest/SimpleTest.js"></script>
+  <script src="/tests/SimpleTest/ExtensionTestUtils.js"></script>
+  <script type="text/javascript" src="head_webrequest.js"></script>
+  <script type="text/javascript" src="head.js"></script>
+  <link rel="stylesheet" type="text/css" href="/tests/SimpleTest/test.css"/>
+<script>
+"use strict";
+
+const expectedBaseProps = {
+  // On Desktop builds, if "browse.chrome.guess_favicon" is set to true,
+  // a favicon requests may be triggered at a random time while the test
+  // cases are running, we include it the ignore list by default to prevent
+  // intermittent failures (e.g. see Bug 1733781 and Bug 1633189).
+  ignore: ["favicon.ico"],
+};
+
+function promiseWindowEvent(name, accept) {
+  return new Promise(resolve => {
+    window.addEventListener(name, function listener(event) {
+      if (event.data !== accept) {
+        return;
+      }
+      window.removeEventListener(name, listener);
+      resolve(event);
+    });
+  });
+}
+
+if (AppConstants.platform === "android") {
+  SimpleTest.requestLongerTimeout(3);
+}
+
+let extension;
+add_task(async function setup() {
+  // Clear the image cache, since it gets in the way otherwise.
+  let imgTools = SpecialPowers.Cc["@mozilla.org/image/tools;1"].getService(SpecialPowers.Ci.imgITools);
+  let cache = imgTools.getImgCacheForDocument(document);
+  cache.clearCache(false);
+  await SpecialPowers.spawnChrome([], async () => {
+    Services.cache2.clear();
+  });
+
+  await SpecialPowers.pushPrefEnv({
+    set: [["network.http.rcwn.enabled", false]],
+  });
+
+  extension = makeExtension();
+  await extension.startup();
+});
+
+// expect is a set of test values used by the background script.
+//
+// type: type of request action
+// events: optional, If defined only the events listed are expected for the
+//                   request. If undefined, all events except onErrorOccurred
+//                   and onBeforeRedirect are expected.  Must be in order received.
+// redirect: url to redirect to during onBeforeSendHeaders
+// status: number    expected status during onHeadersReceived, 200 default
+// cancel: event in which we return cancel=true.  cancelled message is sent.
+// cached: expected fromCache value, default is false, checked in onCompletion
+// headers: request or response headers to modify
+// origin: The expected originUrl, a default origin can be passed for all files
+
+add_task(async function test_webRequest_links() {
+  let expect = {
+    "file_style_bad.css": {
+      type: "stylesheet",
+      events: ["onBeforeRequest", "onErrorOccurred"],
+      cancel: "onBeforeRequest",
+    },
+    "file_style_redirect.css": {
+      type: "stylesheet",
+      events: ["onBeforeRequest", "onBeforeSendHeaders", "onBeforeRedirect"],
+      optional_events: ["onHeadersReceived"],
+      redirect: "file_style_good.css",
+    },
+    "file_style_good.css": {
+      type: "stylesheet",
+    },
+  };
+  extension.sendMessage("set-expected", {expect, origin: location.href});
+  await extension.awaitMessage("continue");
+  addStylesheet("file_style_bad.css");
+  await extension.awaitMessage("cancelled");
+  // we redirect to style_good which completes the test
+  addStylesheet(`file_style_redirect.css?nocache=${Math.random()}`);
+  await extension.awaitMessage("done");
+});
+
+add_task(async function test_webRequest_images() {
+  let expect = {
+    "file_image_bad.png": {
+      type: "image",
+      events: ["onBeforeRequest", "onErrorOccurred"],
+      cancel: "onBeforeRequest",
+    },
+    "file_image_redirect.png": {
+      type: "image",
+      events: ["onBeforeRequest", "onBeforeSendHeaders", "onBeforeRedirect"],
+      optional_events: ["onHeadersReceived"],
+      redirect: "file_image_good.png",
+    },
+    "file_image_good.png": {
+      type: "image",
+    },
+  };
+  extension.sendMessage("set-expected", {expect, origin: location.href});
+  await extension.awaitMessage("continue");
+  addImage("file_image_bad.png");
+  await extension.awaitMessage("cancelled");
+  // we redirect to image_good which completes the test
+  addImage("file_image_redirect.png");
+  await extension.awaitMessage("done");
+});
+
+add_task(async function test_webRequest_scripts() {
+  let expect = {
+    "file_script_bad.js": {
+      type: "script",
+      events: ["onBeforeRequest", "onErrorOccurred"],
+      cancel: "onBeforeRequest",
+    },
+    "file_script_redirect.js": {
+      type: "script",
+      events: ["onBeforeRequest", "onBeforeSendHeaders", "onBeforeRedirect"],
+      optional_events: ["onHeadersReceived"],
+      redirect: "file_script_good.js",
+    },
+    "file_script_good.js": {
+      type: "script",
+    },
+  };
+  extension.sendMessage("set-expected", {expect, origin: location.href});
+  await extension.awaitMessage("continue");
+  let message = promiseWindowEvent("message", "test1");
+  addScript("file_script_bad.js");
+  await extension.awaitMessage("cancelled");
+  // we redirect to script_good which completes the test
+  addScript("file_script_redirect.js?q=test1");
+  await extension.awaitMessage("done");
+
+  is((await message).data, "test1", "good script ran");
+});
+
+add_task(async function test_webRequest_xhr_get() {
+  let expect = {
+    "file_script_xhr.js": {
+      type: "script",
+    },
+    "xhr_resource": {
+      status: 404,
+      type: "xmlhttprequest",
+    },
+  };
+  extension.sendMessage("set-expected", {expect, origin: location.href});
+  await extension.awaitMessage("continue");
+  addScript("file_script_xhr.js");
+  await extension.awaitMessage("done");
+});
+
+add_task(async function test_webRequest_nonexistent() {
+  let expect = {
+    "nonexistent_script_url.js": {
+      status: 404,
+      type: "script",
+    },
+  };
+  extension.sendMessage("set-expected", {expect, origin: location.href});
+  await extension.awaitMessage("continue");
+  addScript("nonexistent_script_url.js");
+  await extension.awaitMessage("done");
+});
+
+add_task(async function test_webRequest_checkCached() {
+  let expect = {
+    "file_image_good.png": {
+      type: "image",
+      cached: true,
+    },
+    "file_script_good.js": {
+      type: "script",
+      cached: true,
+    },
+    "file_style_good.css": {
+      type: "stylesheet",
+      cached: false,
+    },
+    "nonexistent_script_url.js": {
+      status: 404,
+      type: "script",
+      cached: false,
+    },
+  };
+  extension.sendMessage("set-expected", {expect, origin: location.href});
+  await extension.awaitMessage("continue");
+  let message = promiseWindowEvent("message", "test1");
+
+  addImage("file_image_good.png");
+  addScript("file_script_good.js?q=test1");
+
+  is((await message).data, "test1", "good script ran");
+
+  addStylesheet(`file_style_good.css?nocache=${Math.random()}`);
+  addScript("nonexistent_script_url.js");
+  await extension.awaitMessage("done");
+});
+
+add_task(async function test_webRequest_headers() {
+  let expect = {
+    "file_script_nonexistent.js": {
+      type: "script",
+      status: 404,
+      headers: {
+        request: {
+          add: {
+            "X-WebRequest-request": "text",
+            "X-WebRequest-request-binary": "binary",
+          },
+          modify: {
+            "user-agent": "WebRequest",
+          },
+          remove: [
+            "referer",
+          ],
+        },
+        response: {
+          add: {
+            "X-WebRequest-response": "text",
+            "X-WebRequest-response-binary": "binary",
+          },
+          modify: {
+            "server": "WebRequest",
+            "content-type": "text/html; charset=utf-8",
+          },
+          remove: [
+            "connection",
+          ],
+        },
+      },
+      completion: "onCompleted",
+    },
+  };
+  extension.sendMessage("set-expected", {expect, origin: location.href});
+  await extension.awaitMessage("continue");
+  addScript("file_script_nonexistent.js");
+  await extension.awaitMessage("done");
+});
+
+add_task(async function test_webRequest_tabId() {
+  function background() {
+    let tab;
+    browser.tabs.onCreated.addListener(newTab => {
+      tab = newTab;
+    });
+
+    browser.test.onMessage.addListener(msg => {
+      if (msg === "close-tab") {
+        browser.tabs.remove(tab.id);
+        browser.test.sendMessage("tab-closed");
+      }
+    });
+  }
+
+  let tabExt = ExtensionTestUtils.loadExtension({
+    manifest: {
+      permissions: [
+        "tabs",
+      ],
+    },
+    background,
+  });
+  await tabExt.startup();
+
+  let linkUrl = `file_WebRequest_page3.html?trigger=a&nocache=${Math.random()}`;
+  let expect = {
+    "file_WebRequest_page3.html": {
+      type: "main_frame",
+    },
+  };
+
+  extension.sendMessage("set-expected", {
+    ...expectedBaseProps,
+    expect,
+    origin: location.href,
+  });
+  await extension.awaitMessage("continue");
+  let a = addLink(linkUrl);
+  a.click();
+  await extension.awaitMessage("done");
+
+  let closed = tabExt.awaitMessage("tab-closed");
+  tabExt.sendMessage("close-tab");
+  await closed;
+
+  await tabExt.unload();
+});
+
+add_task(async function test_webRequest_tabId_browser() {
+  async function background(url) {
+    let tabId;
+    browser.test.onMessage.addListener(async (msg, expected) => {
+      if (msg == "create") {
+        let tab = await browser.tabs.create({url});
+        tabId = tab.id;
+        return;
+      }
+      if (msg == "done") {
+        await browser.tabs.remove(tabId);
+        browser.test.sendMessage("done");
+      }
+    });
+    browser.test.sendMessage("origin", browser.runtime.getURL("/"));
+  }
+
+  let pageUrl = `${SimpleTest.getTestFileURL("file_sample.html")}?nocache=${Math.random()}`;
+  let tabExt = ExtensionTestUtils.loadExtension({
+    manifest: {
+      permissions: [
+        "tabs",
+      ],
+    },
+    background: `(${background})('${pageUrl}')`,
+  });
+
+  let expect = {
+    "file_sample.html": {
+      type: "main_frame",
+    },
+  };
+
+  await tabExt.startup();
+  let origin = await tabExt.awaitMessage("origin");
+
+  // expecting origin == extension baseUrl
+  extension.sendMessage("set-expected", {
+    ...expectedBaseProps,
+    expect,
+    origin,
+  });
+  await extension.awaitMessage("continue");
+
+  // open a tab from an extension principal
+  tabExt.sendMessage("create");
+  await extension.awaitMessage("done");
+  tabExt.sendMessage("done");
+  await tabExt.awaitMessage("done");
+  await tabExt.unload();
+});
+
+add_task(async function test_webRequest_frames() {
+  let expect = {
+    "redirection.sjs": {
+      status: 302,
+      type: "sub_frame",
+      events: ["onBeforeRequest", "onBeforeSendHeaders", "onSendHeaders", "onHeadersReceived", "onBeforeRedirect"],
+    },
+    "dummy_page.html": {
+      type: "sub_frame",
+      status: 404,
+    },
+    "badrobot": {
+      type: "sub_frame",
+      status: 404,
+      events: ["onBeforeRequest", "onBeforeSendHeaders", "onSendHeaders", "onErrorOccurred"],
+      // When an url's hostname fails to be resolved, an NS_ERROR_NET_ON_RESOLVED/RESOLVING
+      // onError event may be fired right before the NS_ERROR_UNKNOWN_HOST
+      // (See Bug 1516862 for a rationale).
+      optional_events: ["onErrorOccurred"],
+      error: ["NS_ERROR_UNKNOWN_HOST", "NS_ERROR_NET_ON_RESOLVED", "NS_ERROR_NET_ON_RESOLVING"],
+    },
+  };
+  extension.sendMessage("set-expected", {
+    ...expectedBaseProps,
+    expect,
+    origin: location.href
+  });
+  await extension.awaitMessage("continue");
+  addFrame("redirection.sjs");
+  addFrame("https://nonresolvablehostname.invalid/badrobot");
+  await extension.awaitMessage("done");
+});
+
+add_task(async function teardown() {
+  await extension.unload();
+});
+
+add_task(async function test_case_preserving() {
+  const manifest = {
+    permissions: [
+      "webRequest",
+      "webRequestBlocking",
+      "http://mochi.test/",
+    ],
+  };
+
+  async function background() {
+    // This is testing if header names preserve case,
+    // so the case-sensitive comparison is on purpose.
+    function ua({url, requestHeaders}) {
+      if (url.endsWith("?blind-add")) {
+        requestHeaders.push({name: "user-agent", value: "Blind/Add"});
+        return {requestHeaders};
+      }
+      for (const header of requestHeaders) {
+        if (header.name === "User-Agent") {
+          header.value = "Case/Sensitive";
+        }
+      }
+      return {requestHeaders};
+    }
+
+    await browser.webRequest.onBeforeSendHeaders.addListener(ua, {urls: ["<all_urls>"]}, ["blocking", "requestHeaders"]);
+    browser.test.sendMessage("ready");
+  }
+
+  const extension = ExtensionTestUtils.loadExtension({manifest, background});
+
+  await extension.startup();
+  await extension.awaitMessage("ready");
+
+  const response1 = await fetch(SimpleTest.getTestFileURL("return_headers.sjs"));
+  const headers1 = JSON.parse(await response1.text());
+
+  is(headers1["user-agent"], "Case/Sensitive", "User-Agent header matched and changed.");
+
+  const response2 = await fetch(SimpleTest.getTestFileURL("return_headers.sjs?blind-add"));
+  const headers2 = JSON.parse(await response2.text());
+
+  is(headers2["user-agent"], "Blind/Add", "User-Agent header blindly added.");
+
+  await extension.unload();
+});
+
+</script>
+</head>
+<body>
+<div id="test">Sample text</div>
+
+</body>
+</html>
diff --git a/toolkit/components/extensions/test/mochitest/test_ext_webrequest_errors.html b/toolkit/components/extensions/test/mochitest/test_ext_webrequest_errors.html
new file mode 100644
index 0000000000..cbfc5c17e7
--- /dev/null
+++ b/toolkit/components/extensions/test/mochitest/test_ext_webrequest_errors.html
@@ -0,0 +1,59 @@
+<!DOCTYPE HTML>
+<html>
+<head>
+  <title>Test for WebRequest errors</title>
+  <script src="/tests/SimpleTest/SimpleTest.js"></script>
+  <script src="/tests/SimpleTest/ExtensionTestUtils.js"></script>
+  <script type="text/javascript" src="head.js"></script>
+  <link rel="stylesheet" type="text/css" href="/tests/SimpleTest/test.css"/>
+</head>
+<body>
+<script type="text/javascript">
+"use strict";
+
+async function test_connection_refused(url, expectedError) {
+  async function background(url, expectedError) {
+    browser.test.log(`background url is ${url}`);
+    browser.webRequest.onErrorOccurred.addListener(details => {
+      if (details.url != url) {
+        return;
+      }
+      browser.test.assertTrue(details.error.startsWith(expectedError), "error correct");
+      browser.test.sendMessage("onErrorOccurred");
+    }, {urls: ["<all_urls>"]});
+
+    let tabId;
+    browser.test.onMessage.addListener(async (msg, expected) => {
+      await browser.tabs.remove(tabId);
+      browser.test.sendMessage("done");
+    });
+
+    let tab = await browser.tabs.create({url});
+    tabId = tab.id;
+  }
+
+  let extensionData = {
+    manifest: {
+      permissions: ["webRequest", "tabs", "*://badchain.include-subdomains.pinning.example.com/*"],
+    },
+    background: `(${background})("${url}", "${expectedError}")`,
+  };
+
+  let extension = ExtensionTestUtils.loadExtension(extensionData);
+  await extension.startup();
+
+  await extension.awaitMessage("onErrorOccurred");
+  extension.sendMessage("close-tab");
+  await extension.awaitMessage("done");
+
+  await extension.unload();
+}
+
+add_task(function test_bad_cert() {
+  return test_connection_refused("https://badchain.include-subdomains.pinning.example.com/", "Unable to communicate securely with peer");
+});
+
+</script>
+
+</body>
+</html>
diff --git a/toolkit/components/extensions/test/mochitest/test_ext_webrequest_filter.html b/toolkit/components/extensions/test/mochitest/test_ext_webrequest_filter.html
new file mode 100644
index 0000000000..5ccbf761ec
--- /dev/null
+++ b/toolkit/components/extensions/test/mochitest/test_ext_webrequest_filter.html
@@ -0,0 +1,226 @@
+<!DOCTYPE HTML>
+
+<html>
+<head>
+<meta charset="utf-8">
+  <script src="/tests/SimpleTest/SimpleTest.js"></script>
+  <script src="/tests/SimpleTest/ExtensionTestUtils.js"></script>
+  <script type="text/javascript" src="head.js"></script>
+  <script type="text/javascript" src="head_webrequest.js"></script>
+  <link rel="stylesheet" type="text/css" href="/tests/SimpleTest/test.css"/>
+<script>
+"use strict";
+
+if (AppConstants.platform === "android") {
+  SimpleTest.requestLongerTimeout(6);
+}
+
+let windowData, testWindow;
+
+add_task(async function setup() {
+  await SpecialPowers.spawnChrome([], async () => {
+    Services.cache2.clear();
+  });
+
+  testWindow = window.open("about:blank", "_blank", "width=100,height=100");
+  await waitForLoad(testWindow);
+
+  // Fetch the windowId and tabId we need to filter with WebRequest.
+  let extension = ExtensionTestUtils.loadExtension({
+    manifest: {
+      permissions: [
+        "tabs",
+      ],
+    },
+    background() {
+      browser.tabs.query({currentWindow: true}).then(tabs => {
+        let tab = tabs.find(tab => tab.active);
+        let {windowId} = tab;
+
+        browser.test.log(`current window ${windowId} tabs: ${JSON.stringify(tabs.map(tab => [tab.id, tab.url]))}`);
+        browser.test.sendMessage("windowData", {windowId, tabId: tab.id});
+      });
+    },
+  });
+  await extension.startup();
+  windowData = await extension.awaitMessage("windowData");
+  info(`window is ${JSON.stringify(windowData)}`);
+  await extension.unload();
+});
+
+add_task(async function test_webRequest_filter_window() {
+  if (AppConstants.MOZ_BUILD_APP !== "browser") {
+    // Android does not support multiple windows.
+    return;
+  }
+
+  await SpecialPowers.pushPrefEnv({
+    set: [["dom.serviceWorkers.testing.enabled", true],
+          ["network.http.rcwn.enabled", false]],
+  });
+
+  let events = {
+    "onBeforeRequest":     [{urls: ["<all_urls>"], windowId: windowData.windowId}],
+    "onBeforeSendHeaders": [{urls: ["<all_urls>"], windowId: windowData.windowId}, ["requestHeaders"]],
+    "onSendHeaders":       [{urls: ["<all_urls>"], windowId: windowData.windowId}, ["requestHeaders"]],
+    "onBeforeRedirect":    [{urls: ["<all_urls>"], windowId: windowData.windowId}],
+    "onHeadersReceived":   [{urls: ["<all_urls>"], windowId: windowData.windowId}, ["responseHeaders"]],
+    "onResponseStarted":   [{urls: ["<all_urls>"], windowId: windowData.windowId}],
+    "onCompleted":         [{urls: ["<all_urls>"], windowId: windowData.windowId}, ["responseHeaders"]],
+    "onErrorOccurred":     [{urls: ["<all_urls>"], windowId: windowData.windowId}],
+  };
+  let expect = {
+    "file_image_bad.png": {
+      optional_events: ["onBeforeRedirect", "onBeforeRequest", "onBeforeSendHeaders", "onSendHeaders"],
+      type: "main_frame",
+    },
+  };
+
+  if (AppConstants.platform != "android") {
+    expect["favicon.ico"] = {
+      // These events only happen in non-e10s. See bug 1472156.
+      optional_events: ["onBeforeRedirect", "onBeforeRequest", "onBeforeSendHeaders", "onSendHeaders"],
+      type: "image",
+      origin: SimpleTest.getTestFileURL("file_image_bad.png"),
+    };
+  }
+
+  let extension = makeExtension(events);
+  await extension.startup();
+  extension.sendMessage("set-expected", {expect, origin: location.href});
+  await extension.awaitMessage("continue");
+
+  // We should not get events for a new window load.
+  let newWindow = window.open("file_image_good.png", "_blank", "width=100,height=100");
+  await waitForLoad(newWindow);
+  newWindow.close();
+
+  // We should not get background events.
+  let registration = await navigator.serviceWorker.register("webrequest_worker.js?test0", {scope: "."});
+  await waitForState(registration.installing, "activated");
+
+  // We should get events for the reload.
+  testWindow.location = "file_image_bad.png";
+  await extension.awaitMessage("done");
+
+  testWindow.location = "about:blank";
+  await registration.unregister();
+  await extension.unload();
+});
+
+add_task(async function test_webRequest_filter_tab() {
+  await SpecialPowers.pushPrefEnv({
+    set: [["dom.serviceWorkers.testing.enabled", true]],
+  });
+
+  let img = `file_image_good.png?r=${Math.random()}`;
+
+  let events = {
+    "onBeforeRequest":     [{urls: ["<all_urls>"], tabId: windowData.tabId}],
+    "onBeforeSendHeaders": [{urls: ["<all_urls>"], tabId: windowData.tabId}, ["requestHeaders"]],
+    "onSendHeaders":       [{urls: ["<all_urls>"], tabId: windowData.tabId}, ["requestHeaders"]],
+    "onBeforeRedirect":    [{urls: ["<all_urls>"], tabId: windowData.tabId}],
+    "onHeadersReceived":   [{urls: ["<all_urls>"], tabId: windowData.tabId}, ["responseHeaders"]],
+    "onResponseStarted":   [{urls: ["<all_urls>"], tabId: windowData.tabId}],
+    "onCompleted":         [{urls: ["<all_urls>"], tabId: windowData.tabId}, ["responseHeaders"]],
+    "onErrorOccurred":     [{urls: ["<all_urls>"], tabId: windowData.tabId}],
+  };
+  let expect = {
+    "file_image_good.png": {
+      // These events only happen in non-e10s. See bug 1472156.
+      optional_events: ["onBeforeRedirect", "onBeforeRequest", "onBeforeSendHeaders", "onSendHeaders"],
+      type: "main_frame",
+      // cached: AppConstants.MOZ_BUILD_APP === "browser",
+    },
+  };
+
+  if (AppConstants.platform != "android") {
+    // A favicon request may be initiated, and complete or be aborted.
+    expect["favicon.ico"] = {
+      optional_events: ["onBeforeRedirect", "onBeforeRequest", "onBeforeSendHeaders", "onSendHeaders", "onHeadersReceived", "onResponseStarted", "onCompleted", "onErrorOccurred"],
+      type: "image",
+      origin: SimpleTest.getTestFileURL(img),
+    };
+  }
+
+  let extension = makeExtension(events);
+  await extension.startup();
+  extension.sendMessage("set-expected", {expect, origin: location.href});
+  await extension.awaitMessage("continue");
+
+  if (AppConstants.MOZ_BUILD_APP === "browser") {
+    // We should not get events for a new window load.
+    let newWindow = window.open(img, "_blank", "width=100,height=100");
+    await waitForLoad(newWindow);
+    newWindow.close();
+  }
+
+  // We should not get background events.
+  let registration = await navigator.serviceWorker.register("webrequest_worker.js?test1", {scope: "."});
+  await waitForState(registration.installing, "activated");
+
+  // We should get events for the reload.
+  testWindow.location = img;
+  await extension.awaitMessage("done");
+
+  testWindow.location = "about:blank";
+  await registration.unregister();
+  await extension.unload();
+});
+
+
+add_task(async function test_webRequest_filter_background() {
+  await SpecialPowers.pushPrefEnv({
+    set: [["dom.serviceWorkers.testing.enabled", true]],
+  });
+
+  let events = {
+    "onBeforeRequest":     [{urls: ["<all_urls>"], tabId: -1}],
+    "onBeforeSendHeaders": [{urls: ["<all_urls>"], tabId: -1}, ["requestHeaders"]],
+    "onSendHeaders":       [{urls: ["<all_urls>"], tabId: -1}, ["requestHeaders"]],
+    "onBeforeRedirect":    [{urls: ["<all_urls>"], tabId: -1}],
+    "onHeadersReceived":   [{urls: ["<all_urls>"], tabId: -1}, ["responseHeaders"]],
+    "onResponseStarted":   [{urls: ["<all_urls>"], tabId: -1}],
+    "onCompleted":         [{urls: ["<all_urls>"], tabId: -1}, ["responseHeaders"]],
+    "onErrorOccurred":     [{urls: ["<all_urls>"], tabId: -1}],
+  };
+  let expect = {
+    "webrequest_worker.js": {
+      type: "script",
+    },
+    "example.txt": {
+      status: 404,
+      events: ["onBeforeRequest", "onBeforeSendHeaders", "onSendHeaders", "onHeadersReceived", "onResponseStarted"],
+      optional_events: ["onCompleted", "onErrorOccurred"],
+      type: "xmlhttprequest",
+      origin: SimpleTest.getTestFileURL("webrequest_worker.js?test2"),
+    },
+  };
+
+  let extension = makeExtension(events);
+  await extension.startup();
+  extension.sendMessage("set-expected", {expect, origin: location.href});
+  await extension.awaitMessage("continue");
+
+  // We should not get events for a window.
+  testWindow.location = "file_image_bad.png";
+
+  // We should get events for the background page.
+  let registration = await navigator.serviceWorker.register(SimpleTest.getTestFileURL("webrequest_worker.js?test2"), {scope: "."});
+  await waitForState(registration.installing, "activated");
+  await extension.awaitMessage("done");
+  testWindow.location = "about:blank";
+  await registration.unregister();
+
+  await extension.unload();
+});
+
+add_task(async function teardown() {
+  testWindow.close();
+});
+</script>
+</head>
+<body>
+
+</body>
+</html>
diff --git a/toolkit/components/extensions/test/mochitest/test_ext_webrequest_frameId.html b/toolkit/components/extensions/test/mochitest/test_ext_webrequest_frameId.html
new file mode 100644
index 0000000000..76a13be1af
--- /dev/null
+++ b/toolkit/components/extensions/test/mochitest/test_ext_webrequest_frameId.html
@@ -0,0 +1,213 @@
+<!DOCTYPE HTML>
+
+<html>
+<head>
+<meta charset="utf-8">
+  <script src="/tests/SimpleTest/SimpleTest.js"></script>
+  <script src="/tests/SimpleTest/ExtensionTestUtils.js"></script>
+  <script type="text/javascript" src="head_webrequest.js"></script>
+  <script type="text/javascript" src="head.js"></script>
+  <link rel="stylesheet" type="text/css" href="/tests/SimpleTest/test.css"/>
+<script>
+"use strict";
+
+let extensionData = {
+  manifest: {
+    permissions: ["webRequest", "webRequestBlocking", "<all_urls>", "tabs"],
+  },
+  background() {
+    browser.webRequest.onBeforeRequest.addListener(details => {
+      if (details.url.endsWith("/favicon.ico")) {
+        // We don't care about favicon.ico in this test. It is hard to control
+        // whether the request happens.
+        browser.test.log(`Ignoring favicon request: ${details.url}`);
+        return;
+      }
+      browser.test.sendMessage("onBeforeRequest", details);
+    }, {urls: ["<all_urls>"]}, ["blocking"]);
+
+    let tab;
+    browser.tabs.onCreated.addListener(newTab => {
+      browser.test.sendMessage("tab-created");
+      tab = newTab;
+    });
+
+    browser.test.onMessage.addListener(msg => {
+      if (msg === "close-tab") {
+        browser.tabs.remove(tab.id);
+        browser.test.sendMessage("tab-closed");
+      }
+    });
+  },
+};
+
+let expected = {
+  "file_simple_xhr.html": {
+    type: "main_frame",
+    toplevel: true,
+  },
+  "file_image_good.png": {
+    type: "image",
+    toplevel: true,
+    origin: "file_simple_xhr.html",
+  },
+  "example.txt": {
+    type: "xmlhttprequest",
+    toplevel: true,
+    origin: "file_simple_xhr.html",
+  },
+  // sub frames will have the origin and first ancestor is the
+  // parent document
+  "file_simple_xhr_frame.html": {
+    type: "sub_frame",
+    toplevelParent: true,
+    origin: "file_simple_xhr.html",
+    parent: "file_simple_xhr.html",
+  },
+  // a resource in a sub frame will have origin of the subframe,
+  // but the ancestor chain starts with the parent document
+  "xhr_resource": {
+    type: "xmlhttprequest",
+    origin: "file_simple_xhr_frame.html",
+    parent: "file_simple_xhr.html",
+  },
+  "file_image_bad.png": {
+    type: "image",
+    depth: 2,
+    origin: "file_simple_xhr_frame.html",
+    parent: "file_simple_xhr.html",
+  },
+  "file_simple_xhr_frame2.html": {
+    type: "sub_frame",
+    depth: 2,
+    origin: "file_simple_xhr_frame.html",
+    parent: "file_simple_xhr_frame.html",
+  },
+  "file_image_redirect.png": {
+    type: "image",
+    depth: 2,
+    origin: "file_simple_xhr_frame2.html",
+    parent: "file_simple_xhr_frame.html",
+  },
+  "xhr_resource_2": {
+    type: "xmlhttprequest",
+    depth: 2,
+    origin: "file_simple_xhr_frame2.html",
+    parent: "file_simple_xhr_frame.html",
+  },
+  // This is loaded in a sandbox iframe.  originUrl is not available for that,
+  // and requests within a sandboxed iframe will additionally have an empty
+  // url on their immediate parent/ancestor.
+  "file_simple_sandboxed_frame.html": {
+    type: "sub_frame",
+    depth: 3,
+    parent: "file_simple_xhr_frame2.html",
+  },
+  "xhr_sandboxed": {
+    type: "xmlhttprequest",
+    sandboxed: true,
+    depth: 3,
+    parent: "",
+  },
+  "file_image_great.png": {
+    type: "image",
+    sandboxed: true,
+    depth: 3,
+    parent: "",
+  },
+  "file_simple_sandboxed_subframe.html": {
+    type: "sub_frame",
+    depth: 4,
+    parent: "",
+  },
+};
+
+function checkDetails(details) {
+  let url = new URL(details.url);
+  let filename = url.pathname.split("/").pop();
+  ok(filename in expected, `Should be expecting a request for ${filename}`);
+  let expect = expected[filename];
+  is(expect.type, details.type, `${details.type} type matches`);
+  if (details.parentFrameId == -1) {
+    is(details.frameAncestors.length, 0, "no ancestors for main_frame requests");
+  } else if (details.parentFrameId == 0) {
+    is(details.frameAncestors.length, 1, "one ancestors for sub_frame requests");
+  } else {
+    ok(details.frameAncestors.length > 1, "have multiple ancestors for deep subframe requests");
+    is(details.frameAncestors.length, expect.depth, "have multiple ancestors for deep subframe requests");
+  }
+  if (details.parentFrameId > -1) {
+    ok(!expect.origin || details.originUrl.includes(expect.origin), "origin url is correct");
+    is(details.frameAncestors[0].frameId, details.parentFrameId, "first ancestor matches request.parentFrameId");
+    ok(details.frameAncestors[0].url.includes(expect.parent), "ancestor parent page correct");
+    is(details.frameAncestors[details.frameAncestors.length - 1].frameId, 0, "last ancestor is always zero");
+    // All our tests should be somewhere within the frame that we set topframe in the query string.  That
+    // frame will always be the last ancestor.
+    ok(details.frameAncestors[details.frameAncestors.length - 1].url.includes("topframe=true"), "last ancestor is always topframe");
+  }
+  if (expect.toplevel) {
+    is(details.frameId, 0, "expect load at top level");
+    is(details.parentFrameId, -1, "expect top level frame to have no parent");
+  } else if (details.type == "sub_frame") {
+    ok(details.frameId > 0, "expect sub_frame to load into a new frame");
+    if (expect.toplevelParent) {
+      is(details.parentFrameId, 0, "expect sub_frame to have top level parent");
+      is(details.frameAncestors.length, 1, "one ancestor for top sub_frame request");
+    } else {
+      ok(details.parentFrameId > 0, "expect sub_frame to have parent");
+      ok(details.frameAncestors.length > 1, "sub_frame has ancestors");
+    }
+    expect.subframeId = details.frameId;
+    expect.parentId = details.parentFrameId;
+  } else if (expect.sandboxed) {
+    is(details.documentUrl, undefined, "null principal documentUrl for sandboxed request");
+  } else {
+    // get the parent frame.
+    let purl = new URL(details.documentUrl);
+    let pfilename = purl.pathname.split("/").pop();
+    let parent = expected[pfilename];
+    is(details.frameId, parent.subframeId, "expect load in subframe");
+    is(details.parentFrameId, parent.parentId, "expect subframe parent");
+  }
+  return filename;
+}
+
+add_task(async function test_webRequest_main_frame() {
+  // Clear the image cache, since it gets in the way otherwise.
+  let imgTools = SpecialPowers.Cc["@mozilla.org/image/tools;1"].getService(SpecialPowers.Ci.imgITools);
+  let cache = imgTools.getImgCacheForDocument(document);
+  cache.clearCache(false);
+  await SpecialPowers.spawnChrome([], async () => {
+    Services.cache2.clear();
+  });
+
+  let extension = ExtensionTestUtils.loadExtension(extensionData);
+  await extension.startup();
+
+  let a = addLink(`file_simple_xhr.html?topframe=true&nocache=${Math.random()}`);
+  a.click();
+
+  let remaining = new Set(Object.keys(expected));
+  let totalExpectedCount = remaining.size;
+  for (let i = 0; i < totalExpectedCount; i++) {
+    info(`Waiting for request ${i + 1} out of ${totalExpectedCount}`);
+    info(`Expecting one of: ${Array.from(remaining)}`);
+    let details = await extension.awaitMessage("onBeforeRequest");
+    info(`Checking details for request ${i}: ${JSON.stringify(details)}`);
+    let filename = checkDetails(details);
+    ok(remaining.delete(filename), `Got only one request for ${filename}`);
+  }
+
+  await extension.awaitMessage("tab-created");
+  extension.sendMessage("close-tab");
+  await extension.awaitMessage("tab-closed");
+
+  await extension.unload();
+});
+</script>
+</head>
+<body>
+<div id="test">Sample text</div>
+
+</body>
+</html>
diff --git a/toolkit/components/extensions/test/mochitest/test_ext_webrequest_getSecurityInfo.html b/toolkit/components/extensions/test/mochitest/test_ext_webrequest_getSecurityInfo.html
new file mode 100644
index 0000000000..5628109483
--- /dev/null
+++ b/toolkit/components/extensions/test/mochitest/test_ext_webrequest_getSecurityInfo.html
@@ -0,0 +1,98 @@
+<!DOCTYPE HTML>
+<html>
+<head>
+  <meta charset="utf-8">
+  <title>browser.webRequest.getSecurityInfo()</title>
+  <script src="/tests/SimpleTest/SimpleTest.js"></script>
+  <script src="/tests/SimpleTest/ExtensionTestUtils.js"></script>
+  <link rel="stylesheet" href="/tests/SimpleTest/test.css"/>
+</head>
+<body>
+
+<script>
+"use strict";
+
+add_task(async function test_getSecurityInfo() {
+  const extension = ExtensionTestUtils.loadExtension({
+    manifest: {
+      permissions: [
+        "webRequest",
+        "webRequestBlocking",
+        "<all_urls>"
+      ],
+    },
+    async background() {
+      const url = "https://example.org/tests/toolkit/components/extensions/test/mochitest/file_sample.html";
+
+      let tab;
+      browser.webRequest.onHeadersReceived.addListener(async details => {
+        const securityInfo = await browser.webRequest.getSecurityInfo(
+          details.requestId,
+          {}
+        );
+
+        // Some properties have dynamic values so let's take them out of the
+        // `securityInfo` object before asserting all the other props with deep
+        // equality.
+        const {
+          cipherSuite,
+          secretKeyLength,
+          keaGroupName,
+          signatureSchemeName,
+          protocolVersion,
+          certificates,
+          ...otherProps
+        } = securityInfo;
+
+        browser.test.assertTrue(cipherSuite.length, "expected cipher suite");
+        browser.test.assertTrue(
+          Number.isInteger(secretKeyLength),
+          "expected secret key length"
+        );
+        browser.test.assertTrue(
+          keaGroupName.length,
+          "expected kea group name"
+        );
+        browser.test.assertTrue(
+          signatureSchemeName.length,
+          "expected signature scheme name"
+        );
+        browser.test.assertTrue(
+          protocolVersion.length,
+          "expected protocol version"
+        );
+        browser.test.assertTrue(
+          Array.isArray(certificates),
+          "expected an array of certificates"
+        );
+
+        browser.test.assertDeepEq({
+          state: "secure",
+          isExtendedValidation: false,
+          certificateTransparencyStatus: "not_applicable",
+          hsts: false,
+          hpkp: false,
+          usedEch: false,
+          usedDelegatedCredentials: false,
+          usedOcsp: false,
+          usedPrivateDns: false,
+        }, otherProps, "expected security info");
+
+        await browser.tabs.remove(tab.id);
+        browser.test.notifyPass("success");
+      }, { urls: [url] } , ["blocking"]);
+
+      tab = await browser.tabs.create({ url });
+    },
+  });
+  await extension.startup();
+
+  await extension.awaitFinish("success");
+
+  await extension.unload();
+});
+
+</script>
+
+</body>
+</html>
diff --git a/toolkit/components/extensions/test/mochitest/test_ext_webrequest_hsts.html b/toolkit/components/extensions/test/mochitest/test_ext_webrequest_hsts.html
new file mode 100644
index 0000000000..e66b5c471a
--- /dev/null
+++ b/toolkit/components/extensions/test/mochitest/test_ext_webrequest_hsts.html
@@ -0,0 +1,252 @@
+<!DOCTYPE HTML>
+
+<html>
+<head>
+<meta charset="utf-8">
+  <script src="/tests/SimpleTest/SimpleTest.js"></script>
+  <script src="/tests/SimpleTest/ExtensionTestUtils.js"></script>
+  <script type="text/javascript" src="head.js"></script>
+  <script type="text/javascript" src="head_webrequest.js"></script>
+  <link rel="stylesheet" type="text/css" href="/tests/SimpleTest/test.css"/>
+<script>
+"use strict";
+
+function getExtension() {
+  async function background() {
+    let expect;
+    let urls = ["*://*.example.org/tests/*"];
+    browser.webRequest.onBeforeRequest.addListener(details => {
+      browser.test.assertEq(expect.shift(), "onBeforeRequest");
+    }, {urls}, ["blocking"]);
+    browser.webRequest.onBeforeSendHeaders.addListener(details => {
+      browser.test.assertEq(expect.shift(), "onBeforeSendHeaders");
+    }, {urls}, ["blocking", "requestHeaders"]);
+    browser.webRequest.onSendHeaders.addListener(details => {
+      browser.test.assertEq(expect.shift(), "onSendHeaders");
+    }, {urls}, ["requestHeaders"]);
+
+    async function testSecurityInfo(securityInfo, options) {
+      if (options.certificateChain) {
+        // Some of the tests here only produce a single cert in the chain.
+        browser.test.assertTrue(securityInfo.certificates.length >= 1, "have certificate chain");
+      } else {
+        browser.test.assertTrue(securityInfo.certificates.length == 1, "no certificate chain");
+      }
+      let cert = securityInfo.certificates[0];
+      let now = Date.now();
+      browser.test.assertTrue(Number.isInteger(cert.validity.start), "cert start is integer");
+      browser.test.assertTrue(Number.isInteger(cert.validity.end), "cert end is integer");
+      browser.test.assertTrue(cert.validity.start < now, "cert start validity is correct");
+      browser.test.assertTrue(now < cert.validity.end, "cert end validity is correct");
+      if (options.rawDER) {
+        for (let cert of securityInfo.certificates) {
+          browser.test.assertTrue(!!cert.rawDER.length, "have rawDER");
+        }
+      }
+    }
+
+    function stripQuery(url) {
+      // In this whole test we are not interested in the query part of the URL.
+      // Most tests include a cache buster (bustcache) param in the URL.
+      return url.split("?")[0];
+    }
+
+    browser.webRequest.onHeadersReceived.addListener(async (details) => {
+      browser.test.assertEq(expect.shift(), "onHeadersReceived");
+
+      // We expect all requests to have been upgraded at this point.
+      browser.test.assertTrue(details.url.startsWith("https"), "connection is https");
+      let securityInfo = await browser.webRequest.getSecurityInfo(details.requestId, {});
+      browser.test.assertTrue(securityInfo && securityInfo.state == "secure",
+                              "security info reflects https");
+      await testSecurityInfo(securityInfo, {});
+      securityInfo = await browser.webRequest.getSecurityInfo(details.requestId, {certificateChain: true});
+      await testSecurityInfo(securityInfo, {certificateChain: true});
+      securityInfo = await browser.webRequest.getSecurityInfo(details.requestId, {rawDER: true});
+      await testSecurityInfo(securityInfo, {rawDER: true});
+      securityInfo = await browser.webRequest.getSecurityInfo(details.requestId, {certificateChain: true, rawDER: true});
+      await testSecurityInfo(securityInfo, {certificateChain: true, rawDER: true});
+
+      browser.test.sendMessage("hsts", securityInfo.hsts);
+      let headers = details.responseHeaders || [];
+      for (let header of headers) {
+        if (header.name.toLowerCase() === "strict-transport-security") {
+          return;
+        }
+      }
+      if (details.url.includes("addHsts")) {
+        headers.push({
+          name: "Strict-Transport-Security",
+          value: "max-age=31536000000",
+        });
+      }
+      return {responseHeaders: headers};
+    }, {urls}, ["blocking", "responseHeaders"]);
+    browser.webRequest.onBeforeRedirect.addListener(details => {
+      browser.test.assertEq(expect.shift(), "onBeforeRedirect");
+    }, {urls});
+    browser.webRequest.onResponseStarted.addListener(details => {
+      browser.test.assertEq(expect.shift(), "onResponseStarted");
+    }, {urls});
+    browser.webRequest.onCompleted.addListener(details => {
+      browser.test.assertEq(expect.shift(), "onCompleted");
+      browser.test.sendMessage("onCompleted", stripQuery(details.url));
+    }, {urls});
+    browser.webRequest.onErrorOccurred.addListener(details => {
+      browser.test.notifyFail(`onErrorOccurred ${JSON.stringify(details)}`);
+    }, {urls});
+
+    async function onUpdated(tabId, tabInfo, tab) {
+      if (tabInfo.status !== "complete" || tab.url === "about:blank") {
+        return;
+      }
+      browser.tabs.remove(tabId);
+      browser.tabs.onUpdated.removeListener(onUpdated);
+      browser.test.sendMessage("tabs-done", stripQuery(tab.url));
+    }
+    browser.test.onMessage.addListener((url, expected) => {
+      expect = expected;
+      browser.tabs.onUpdated.addListener(onUpdated);
+      browser.tabs.create({url});
+    });
+  }
+
+  let manifest = {
+    "permissions": [
+      "tabs",
+      "webRequest",
+      "webRequestBlocking",
+      "<all_urls>",
+    ],
+  };
+  return ExtensionTestUtils.loadExtension({
+    manifest,
+    background,
+  });
+}
+
+add_setup(async () => {
+  // In bug 1605515, we repeatedly saw a missing onHeadersReceived event,
+  // possibly related to bug 1595610. As a workaround, clear the cache.
+  await SpecialPowers.spawnChrome([], async () => {
+    Services.cache2.clear();
+    await new Promise(resolve => {
+      Services.clearData.deleteData(Ci.nsIClearDataService.CLEAR_HSTS, resolve);
+    });
+  });
+});
+
+// This test makes a request against a server that redirects with a 302.
+add_task(async function test_hsts_request() {
+  const testPath = "example.org/tests/toolkit/components/extensions/test/mochitest";
+
+  let extension = getExtension();
+  await extension.startup();
+
+  // simple redirect
+  let sample = "https://example.org/tests/toolkit/components/extensions/test/mochitest/file_sample.html";
+  extension.sendMessage(
+    `https://${testPath}/redirect_auto.sjs?redirect_uri=${sample}?bustcache1=${Math.random()}`,
+    ["onBeforeRequest", "onBeforeSendHeaders", "onSendHeaders",
+     "onHeadersReceived", "onBeforeRedirect", "onBeforeRequest",
+     "onBeforeSendHeaders", "onSendHeaders", "onHeadersReceived",
+     "onResponseStarted", "onCompleted"]);
+  is(await extension.awaitMessage("hsts"), false, "First request to this host, not receiving a hsts header");
+  is(await extension.awaitMessage("hsts"), false, "second (redirected) reqiest to the same host, still no knowledge about the hosts hsts preference");
+  // Note: stripQuery strips query string added by redirect_auto.
+  is(await extension.awaitMessage("tabs-done"), sample, "redirection ok");
+  is(await extension.awaitMessage("onCompleted"), sample, "redirection ok");
+
+  // priming hsts
+  extension.sendMessage(
+    `https://${testPath}/hsts.sjs`,
+    ["onBeforeRequest", "onBeforeSendHeaders", "onSendHeaders",
+     "onHeadersReceived", "onResponseStarted", "onCompleted"]);
+  is(await extension.awaitMessage("hsts"), false, "First request to this host, receiving hsts header and saving the hosts STS preference for the next request");
+  is(await extension.awaitMessage("tabs-done"),
+     "https://example.org/tests/toolkit/components/extensions/test/mochitest/hsts.sjs",
+     "hsts primed");
+  is(await extension.awaitMessage("onCompleted"),
+     "https://example.org/tests/toolkit/components/extensions/test/mochitest/hsts.sjs");
+
+  // test upgrade
+  extension.sendMessage(
+    `http://${testPath}/hsts.sjs`,
+    ["onBeforeRequest", "onBeforeRedirect", "onBeforeRequest",
+     "onBeforeSendHeaders", "onSendHeaders", "onHeadersReceived",
+     "onResponseStarted", "onCompleted"]);
+  is(await extension.awaitMessage("hsts"), true, "second (redirected) reqiest to the same host, we know about the hsts status of the host this time");
+  is(await extension.awaitMessage("tabs-done"),
+     "https://example.org/tests/toolkit/components/extensions/test/mochitest/hsts.sjs",
+     "hsts upgraded");
+  is(await extension.awaitMessage("onCompleted"),
+     "https://example.org/tests/toolkit/components/extensions/test/mochitest/hsts.sjs");
+
+  await extension.unload();
+});
+
+// This test makes a priming request and adds the STS header, then tests the upgrade.
+add_task(async function test_hsts_header() {
+  const testPath = "test1.example.org/tests/toolkit/components/extensions/test/mochitest";
+
+  let extension = getExtension();
+  await extension.startup();
+
+  // priming hsts, this time there is no STS header, onHeadersReceived adds it.
+  let completed = extension.awaitMessage("onCompleted");
+  let tabdone = extension.awaitMessage("tabs-done");
+  extension.sendMessage(
+    `https://${testPath}/file_sample.html?bustcache2=${Math.random()}&addHsts=true`,
+    ["onBeforeRequest", "onBeforeSendHeaders", "onSendHeaders",
+     "onHeadersReceived", "onResponseStarted", "onCompleted"]);
+  is(await extension.awaitMessage("hsts"), false, "First reqeuest to this host, we don't know about the hosts STS setting yet");
+  is(await tabdone, `https://${testPath}/file_sample.html`, "priming request done");
+  is(await completed, `https://${testPath}/file_sample.html`, "priming request done");
+
+  // test upgrade from http to https due to onHeadersReceived adding STS header
+  completed = extension.awaitMessage("onCompleted");
+  tabdone = extension.awaitMessage("tabs-done");
+  extension.sendMessage(
+    `http://${testPath}/file_sample.html?bustcache3=${Math.random()}`,
+    ["onBeforeRequest", "onBeforeRedirect", "onBeforeRequest",
+     "onBeforeSendHeaders", "onSendHeaders", "onHeadersReceived",
+     "onResponseStarted", "onCompleted"]);
+  is(await extension.awaitMessage("hsts"), true, "We have received an hsts header last request via oneadersReceived");
+  is(await tabdone, `https://${testPath}/file_sample.html`, "hsts upgraded");
+  is(await completed, `https://${testPath}/file_sample.html`, "request upgraded");
+
+  await extension.unload();
+});
+
+add_task(async function test_nonBlocking_securityInfo() {
+  let extension = ExtensionTestUtils.loadExtension({
+    manifest: {
+      "permissions": [
+        "webRequest",
+        "<all_urls>",
+      ],
+    },
+    async background() {
+      let tab;
+      browser.webRequest.onHeadersReceived.addListener(async (details) => {
+        let securityInfo = await browser.webRequest.getSecurityInfo(details.requestId, {});
+        browser.test.assertTrue(!securityInfo, "securityInfo undefined on http request");
+        browser.tabs.remove(tab.id);
+        browser.test.notifyPass("success");
+      }, {urls: ["<all_urls>"], types: ["main_frame"]});
+      tab = await browser.tabs.create({
+        url: `https://example.org/tests/toolkit/components/extensions/test/mochitest/file_sample.html?bustcache4=${Math.random()}`,
+      });
+    },
+  });
+  await extension.startup();
+
+  await extension.awaitFinish("success");
+  await extension.unload();
+});
+</script>
+</head>
+<body>
+
+</body>
+</html>
diff --git a/toolkit/components/extensions/test/mochitest/test_ext_webrequest_redirect_bypass_cors.html b/toolkit/components/extensions/test/mochitest/test_ext_webrequest_redirect_bypass_cors.html
new file mode 100644
index 0000000000..87dbbd6598
--- /dev/null
+++ b/toolkit/components/extensions/test/mochitest/test_ext_webrequest_redirect_bypass_cors.html
@@ -0,0 +1,75 @@
+<!DOCTYPE HTML>
+<html>
+<head>
+  <title>Bug 1450965: Skip Cors Check for Early WebExtention Redirects </title>
+  <script src="/tests/SimpleTest/SimpleTest.js"></script>
+  <script src="/tests/SimpleTest/ExtensionTestUtils.js"></script>
+  <script type="text/javascript" src="head.js"></script>
+  <link rel="stylesheet" type="text/css" href="/tests/SimpleTest/test.css"/>
+</head>
+<body>
+
+<script type="text/javascript">
+"use strict";
+
+/* Description of the test:
+ * We try to Check if a WebExtention can redirect a request and bypass CORS
+ * We're redirecting a fetch request in onBeforeRequest
+ * which should not be blocked, even though we do not have
+ * the CORS information yet.
+ */
+
+const WIN_URL =
+  "http://mochi.test:8888/tests/toolkit/components/extensions/test/mochitest/file_redirect_cors_bypass.html";
+
+
+add_task(async function test_webRequest_redirect_cors_bypass() {
+  // disable third-party storage isolation so the test works as expected
+  await SpecialPowers.pushPrefEnv({
+    set: [["privacy.partition.always_partition_third_party_non_cookie_storage", false]],
+  });
+
+  let extension = ExtensionTestUtils.loadExtension({
+    manifest: {
+      permissions: [
+        "webRequest",
+        "webRequestBlocking",
+        "<all_urls>",
+      ],
+    },
+    background() {
+      browser.webRequest.onBeforeRequest.addListener((details) => {
+        if (details.url.includes("file_cors_blocked.txt")) {
+          // File_cors_blocked does not need to exist, because we're redirecting anyway.
+          const testPath = "example.org/tests/toolkit/components/extensions/test/mochitest";
+          let redirectUrl = `https://${testPath}/file_sample.txt`;
+
+          // If the WebExtion cant bypass CORS, the fetch will throw a CORS-Exception
+          // because we do not have the CORS header yet for 'file-cors-blocked.txt'
+          return {redirectUrl};
+        }
+      }, {urls: ["<all_urls>"]}, ["blocking"]);
+    },
+
+  });
+
+  await extension.startup();
+  let win = window.open(WIN_URL);
+  // Creating a message channel to the new tab.
+  const channel = new BroadcastChannel("test_bus");
+  await new Promise((resolve, reject) => {
+    channel.onmessage = async function(fetch_result) {
+      // Fetch result data will either be the text content of file_sample.txt -> 'Sample'
+      // or a network-Error.
+      // In case it's 'Sample' the redirect did happen correctly.
+      ok(fetch_result.data == "Sample", "Cors was Bypassed");
+      win.close();
+      await extension.unload();
+      resolve();
+    };
+  });
+});
+
+</script>
+</body>
+</html>
diff --git a/toolkit/components/extensions/test/mochitest/test_ext_webrequest_redirect_data_uri.html b/toolkit/components/extensions/test/mochitest/test_ext_webrequest_redirect_data_uri.html
new file mode 100644
index 0000000000..5d58549c46
--- /dev/null
+++ b/toolkit/components/extensions/test/mochitest/test_ext_webrequest_redirect_data_uri.html
@@ -0,0 +1,83 @@
+<!DOCTYPE HTML>
+<html>
+<head>
+  <title>Bug 1434357: Allow Web Request API to redirect to data: URI</title>
+  <script src="/tests/SimpleTest/SimpleTest.js"></script>
+  <script src="/tests/SimpleTest/ExtensionTestUtils.js"></script>
+  <script type="text/javascript" src="head.js"></script>
+  <link rel="stylesheet" type="text/css" href="/tests/SimpleTest/test.css"/>
+</head>
+<body>
+
+<script type="text/javascript">
+"use strict";
+
+/* Description of the test:
+ * We load a *.js file which gets redirected to a data: URI.
+ * Since there is no good way to communicate loaded data: URI scripts
+ * we use updating a divContainer as a detour to verify the data: URI
+ * script has loaded.
+ */
+
+const WIN_URL =
+  "http://mochi.test:8888/tests/toolkit/components/extensions/test/mochitest/file_redirect_data_uri.html";
+
+add_task(async function test_webRequest_redirect_data_uri() {
+  let extension = ExtensionTestUtils.loadExtension({
+    manifest: {
+      permissions: [
+        "webRequest",
+        "webRequestBlocking",
+        "*://mochi.test/tests/*",
+      ],
+      content_scripts: [{
+        matches: ["*://mochi.test/tests/*/file_redirect_data_uri.html"],
+        run_at: "document_end",
+        js: ["content_script.js"],
+        "all_frames": true,
+      }],
+    },
+
+    background() {
+      browser.webRequest.onBeforeRequest.addListener((details) => {
+        if (details.url.includes("dummy_non_existend_file.js")) {
+          let redirectUrl =
+            "data:text/javascript,document.getElementById('testdiv').textContent='loaded'";
+          return {redirectUrl};
+        }
+      }, {urls: ["*://mochi.test/tests/*"]}, ["blocking"]);
+    },
+
+    files: {
+      "content_script.js": function() {
+        let scriptEl = document.createElement("script");
+        // please note that dummy_non_existend_file.js file does not really need
+        // to exist because we redirect the load within onBeforeRequest().
+        scriptEl.src = "dummy_non_existend_file.js";
+        document.body.appendChild(scriptEl);
+
+        scriptEl.onload = function() {
+          let divContent = document.getElementById("testdiv").textContent;
+          browser.test.assertEq(divContent, "loaded",
+                                "redirect to data: URI allowed");
+          browser.test.sendMessage("finished");
+        };
+        scriptEl.onerror = function() {
+          browser.test.fail("script load failure");
+          browser.test.sendMessage("finished");
+        };
+      },
+    },
+  });
+
+  await extension.startup();
+  let win = window.open(WIN_URL);
+  await extension.awaitMessage("finished");
+  win.close();
+  await extension.unload();
+});
+
+</script>
+
+</body>
+</html>
diff --git a/toolkit/components/extensions/test/mochitest/test_ext_webrequest_upgrade.html b/toolkit/components/extensions/test/mochitest/test_ext_webrequest_upgrade.html
new file mode 100644
index 0000000000..f086d29d02
--- /dev/null
+++ b/toolkit/components/extensions/test/mochitest/test_ext_webrequest_upgrade.html
@@ -0,0 +1,139 @@
+<!DOCTYPE HTML>
+<html>
+<head>
+  <title>Test for simple WebExtension</title>
+  <script src="/tests/SimpleTest/SimpleTest.js"></script>
+  <script src="/tests/SimpleTest/ExtensionTestUtils.js"></script>
+  <script type="text/javascript" src="head.js"></script>
+  <link rel="stylesheet" type="text/css" href="/tests/SimpleTest/test.css"/>
+</head>
+<body>
+
+<script type="text/javascript">
+"use strict";
+
+add_task(async function test_webRequest_upgrade() {
+  let extension = ExtensionTestUtils.loadExtension({
+    manifest: {
+      permissions: [
+        "webRequest",
+        "webRequestBlocking",
+        "*://mochi.test/tests/*",
+      ],
+    },
+    background() {
+      browser.webRequest.onSendHeaders.addListener((details) => {
+        // At this point, the request should have been upgraded.
+        browser.test.assertTrue(details.url.startsWith("https:"), "request is upgraded");
+        browser.test.assertTrue(details.url.includes("file_sample"), "redirect after upgrade worked");
+        // Note: although not significant for the test assertions, note that
+        // the requested file won't load - https://mochi.test:8888/ does not
+        // resolve to anything on the test server.
+        browser.test.sendMessage("finished");
+      }, {urls: ["*://mochi.test/tests/*"]});
+
+      browser.webRequest.onBeforeRequest.addListener((details) => {
+        browser.test.log(`onBeforeRequest ${details.requestId} ${details.url}`);
+        let url = new URL(details.url);
+        if (url.protocol == "http:") {
+          return {upgradeToSecure: true};
+        }
+        // After the channel is initially upgraded, we get another onBeforeRequest
+        // call.  Here we can redirect again to a new url.
+        if (details.url.includes("file_mixed.html")) {
+          let redirectUrl = new URL("file_sample.html", details.url).href;
+          return {redirectUrl};
+        }
+      }, {urls: ["*://mochi.test/tests/*"]}, ["blocking"]);
+    },
+  });
+
+  await extension.startup();
+  let win = window.open("http://mochi.test:8888/tests/toolkit/components/extensions/test/mochitest/file_mixed.html");
+  await extension.awaitMessage("finished");
+  win.close();
+  await extension.unload();
+});
+
+add_task(async function test_webRequest_redirect_wins() {
+  let extension = ExtensionTestUtils.loadExtension({
+    manifest: {
+      permissions: [
+        "webRequest",
+        "webRequestBlocking",
+        "*://mochi.test/tests/*",
+      ],
+    },
+    background() {
+      browser.webRequest.onSendHeaders.addListener((details) => {
+        // At this point, the request should have been redirected instead of upgraded.
+        browser.test.assertTrue(details.url.includes("file_sample"), "request was redirected");
+        browser.test.sendMessage("finished");
+      }, {urls: ["*://mochi.test/tests/*"]});
+
+      browser.webRequest.onBeforeRequest.addListener((details) => {
+        if (details.url.includes("file_mixed.html")) {
+          let redirectUrl = new URL("file_sample.html", details.url).href;
+          return {upgradeToSecure: true, redirectUrl};
+        }
+      }, {urls: ["*://mochi.test/tests/*"]}, ["blocking"]);
+    },
+  });
+
+  await extension.startup();
+  let win = window.open("http://mochi.test:8888/tests/toolkit/components/extensions/test/mochitest/file_mixed.html");
+  await extension.awaitMessage("finished");
+  win.close();
+  await extension.unload();
+});
+
+// Test that there is no infinite redirect loop when upgradeToSecure is used on
+// https. This test checks that the redirect chain is: http -> https -> done.
+add_task(async function upgradeToSecure_for_https_is_noop() {
+  let extension = ExtensionTestUtils.loadExtension({
+    manifest: {
+      permissions: [
+        "webRequest",
+        "webRequestBlocking",
+        "*://example.com/tests/*",
+      ],
+    },
+    background() {
+      let count = 0;
+      browser.webRequest.onBeforeRequest.addListener(
+        details => {
+          browser.test.log(`onBeforeRequest ${details.requestId} ${details.url}`);
+          ++count;
+          if (details.url.startsWith("http:")) {
+            browser.test.assertEq(1, count, "Initial request is http:");
+          } else {
+            browser.test.assertEq(2, count, "Second request is https:");
+          }
+          return {upgradeToSecure: true};
+        },
+        { urls: ["*://example.com/tests/*file_sample.html"] },
+        ["blocking"]
+      );
+      browser.webRequest.onCompleted.addListener(
+        details => {
+          browser.test.log(`onCompleted ${details.requestId} ${details.url}`);
+          browser.test.assertTrue(details.url.startsWith("https"), "is https");
+          browser.test.assertEq(2, count, "Seen two requests (http + https)");
+          browser.test.sendMessage("finished");
+        },
+        { urls: ["*://example.com/tests/*file_sample.html"] },
+      );
+    },
+  });
+
+  await extension.startup();
+  // eslint-disable-next-line @microsoft/sdl/no-insecure-url
+  let win = window.open("http://example.com/tests/toolkit/components/extensions/test/mochitest/file_sample.html");
+  await extension.awaitMessage("finished");
+  win.close();
+  await extension.unload();
+});
+</script>
+
+</body>
+</html>
diff --git a/toolkit/components/extensions/test/mochitest/test_ext_webrequest_upload.html b/toolkit/components/extensions/test/mochitest/test_ext_webrequest_upload.html
new file mode 100644
index 0000000000..30ecb0aa78
--- /dev/null
+++ b/toolkit/components/extensions/test/mochitest/test_ext_webrequest_upload.html
@@ -0,0 +1,265 @@
+<!DOCTYPE HTML>
+
+<html>
+<head>
+<meta charset="utf-8">
+  <script src="/tests/SimpleTest/SimpleTest.js"></script>
+  <script src="/tests/SimpleTest/ExtensionTestUtils.js"></script>
+  <script type="text/javascript" src="head.js"></script>
+  <link rel="stylesheet" type="text/css" href="/tests/SimpleTest/test.css"/>
+</head>
+<body>
+
+<form method="post"
+  action="file_WebRequest_page3.html?trigger=form"
+  target="_blank"
+  enctype="multipart/form-data"
+  >
+<input type="text" name="&quot;special&quot; &#x0D;&#x0A; ch�rs" value="sp�cial">
+<input type="file" name="testFile">
+<input type="file" name="emptyFile">
+<input type="text" name="textInput1" value="value1">
+</form>
+
+<form method="post"
+  action="file_WebRequest_page3.html?trigger=form"
+  target="_blank"
+  enctype="multipart/form-data"
+  >
+<input type="text" name="textInput2" value="value2">
+<input type="file" name="testFile">
+<input type="file" name="emptyFile">
+</form>
+
+</form>
+<form method="post"
+  action="file_WebRequest_page3.html?trigger=form"
+  target="_blank"
+  >
+<input type="text" name="textInput" value="value1">
+<input type="text" name="textInput" value="value2">
+</form>
+<script>
+"use strict";
+
+let files, testFile, blob, file, uploads;
+add_task(async function test_setup() {
+  files = await new Promise(resolve => {
+    SpecialPowers.createFiles([{name: "testFile.pdf", data: "Not really a PDF file :)", "type": "application/x-pdf"}], (result) => {
+      resolve(result);
+    });
+  });
+  testFile = files[0];
+  blob = {
+    name: "blobAsFile",
+    content: new Blob(["A blob sent as a file"], {type: "text/csv"}),
+    fileName: "blobAsFile.csv",
+  };
+  file = {
+    name: "testFile",
+    fileName: testFile.name,
+  };
+  uploads = {
+    [blob.name]: blob,
+    [file.name]: file,
+    "emptyFile": {fileName: ""}
+  };
+});
+
+function background() {
+  const FILTERS = {urls: ["<all_urls>"]};
+
+  function onUpload(details) {
+    let url = new URL(details.url);
+    let upload = url.searchParams.get("upload");
+    if (!upload) {
+      return;
+    }
+
+    let requestBody = details.requestBody;
+    browser.test.log(`onBeforeRequest upload: ${details.url} ${JSON.stringify(details.requestBody)}`);
+    browser.test.assertTrue(!!requestBody, `Intercepted upload ${details.url} #${details.requestId} ${upload} have a requestBody`);
+    if (!requestBody) {
+      return;
+    }
+    let byteLength = parseInt(upload, 10);
+    if (byteLength) {
+      browser.test.assertTrue(!!requestBody.raw, `Binary upload ${details.url} #${details.requestId} ${upload} have a raw attribute`);
+      browser.test.assertEq(byteLength, requestBody.raw && requestBody.raw.map(r => r.bytes ? r.bytes.byteLength : 0).reduce((a, b) => a + b), `Binary upload size matches`);
+      return;
+    }
+    if ("raw" in requestBody) {
+      browser.test.assertEq(upload, JSON.stringify(requestBody.raw).replace(/(\bfile: ")[^"]+/, "$1<file>"), `Upload ${details.url} #${details.requestId} matches raw data`);
+    } else {
+      browser.test.assertEq(upload, JSON.stringify(requestBody.formData), `Upload ${details.url} #${details.requestId} matches form data.`);
+    }
+  }
+
+  browser.webRequest.onCompleted.addListener(
+    details => {
+      browser.test.log(`onCompleted ${details.requestId} ${details.url}`);
+      // See bug 1471387
+      if (details.url.endsWith("/favicon.ico") || details.originUrl == "about:newtab") {
+        return;
+      }
+
+      browser.test.sendMessage("done");
+    },
+    FILTERS);
+
+  let onBeforeRequest = details => {
+    browser.test.log(`${name} ${details.requestId} ${details.url}`);
+    // See bug 1471387
+    if (details.url.endsWith("/favicon.ico") || details.originUrl == "about:newtab") {
+      return;
+    }
+
+    onUpload(details);
+  };
+
+  browser.webRequest.onBeforeRequest.addListener(
+    onBeforeRequest, FILTERS, ["requestBody"]);
+
+  let tab;
+  browser.tabs.onCreated.addListener(newTab => {
+    tab = newTab;
+  });
+
+  browser.test.onMessage.addListener(msg => {
+    if (msg === "close-tab") {
+      browser.tabs.remove(tab.id);
+      browser.test.sendMessage("tab-closed");
+    }
+  });
+}
+
+add_task(async function test_xhr_forms() {
+  let extension = ExtensionTestUtils.loadExtension({
+    manifest: {
+      permissions: [
+        "tabs",
+        "webRequest",
+        "webRequestBlocking",
+        "<all_urls>",
+      ],
+    },
+    background,
+  });
+
+  await extension.startup();
+
+  async function doneAndTabClosed() {
+    await extension.awaitMessage("done");
+    let closed = extension.awaitMessage("tab-closed");
+    extension.sendMessage("close-tab");
+    await closed;
+  }
+
+  for (let form of document.forms) {
+    if (file.name in form.elements) {
+      SpecialPowers.wrap(form.elements[file.name]).mozSetFileArray(files);
+    }
+    let action = new URL(form.action);
+    let formData = new FormData(form);
+    let webRequestFD = {};
+
+    let updateActionURL = () => {
+      for (let name of formData.keys()) {
+        webRequestFD[name] = name in uploads ? [uploads[name].fileName] : formData.getAll(name);
+      }
+      action.searchParams.set("upload", JSON.stringify(webRequestFD));
+      action.searchParams.set("enctype", form.enctype);
+    };
+
+    updateActionURL();
+
+    form.action = action;
+    form.submit();
+    await doneAndTabClosed();
+
+    if (form.enctype !== "multipart/form-data") {
+      continue;
+    }
+
+    let post = (data) => {
+      let xhr = new XMLHttpRequest();
+      action.searchParams.set("xhr", "1");
+      xhr.open("POST", action.href);
+      xhr.send(data);
+      action.searchParams.delete("xhr");
+      return doneAndTabClosed();
+    };
+
+    formData.append(blob.name, blob.content, blob.fileName);
+    formData.append("formDataField", "some value");
+    updateActionURL();
+    await post(formData);
+
+    action.searchParams.set("upload", JSON.stringify([{file: "<file>"}]));
+    await post(testFile);
+
+    action.searchParams.set("upload", `${blob.content.size} bytes`);
+    await post(blob.content);
+
+    let byteLength = 16;
+    action.searchParams.set("upload", `${byteLength} bytes`);
+    await post(new ArrayBuffer(byteLength));
+  }
+
+  // Testing the decoding of percent escapes even in cases where the
+  // multipart/form-data serializer won't emit them.
+  {
+    let boundary = "-".repeat(27);
+    for (let i = 0; i < 3; i++) {
+      const randomNumber = Math.floor(Math.random() * (2 ** 32));
+      boundary += String(randomNumber);
+    }
+
+    const formPayload = [
+      `--${boundary}`,
+      'Content-Disposition: form-data; name="percent escapes other than%20quotes and newlines"',
+      "",
+      "",
+      `--${boundary}`,
+      'Content-Disposition: form-data; name="valid UTF-8: %F0%9F%92%A9"',
+      "",
+      "",
+      `--${boundary}`,
+      'Content-Disposition: form-data; name="broken UTF-8: %F0%9F %92%A9"',
+      "",
+      "",
+      `--${boundary}`,
+      'Content-Disposition: form-data; name="percent escapes aren\'t decoded in filenames"; filename="%0D%0A%22"',
+      "Content-Type: application/octet-stream",
+      "",
+      "",
+      `--${boundary}--`,
+      ""
+    ].join("\r\n");
+
+    const action = new URL("file_WebRequest_page3.html?trigger=form", document.location.href);
+    action.searchParams.set("xhr", "1");
+    action.searchParams.set("upload", JSON.stringify({
+      "percent escapes other than quotes and newlines": [""],
+      "valid UTF-8: 💩": [""],
+      "broken UTF-8: � ��": [""],
+      "percent escapes aren't decoded in filenames": ["%0D%0A%22"]
+    }));
+    action.searchParams.set("enctype", "multipart/form-data");
+
+    await fetch(
+      action.href,
+      {
+        method: "POST",
+        headers: {"Content-Type": `multipart/form-data; boundary=${boundary}`},
+        body: formPayload
+      },
+    );
+    await doneAndTabClosed();
+  }
+
+  await extension.unload();
+});
+</script>
+</body>
+</html>
diff --git a/toolkit/components/extensions/test/mochitest/test_ext_webrequest_worker.html b/toolkit/components/extensions/test/mochitest/test_ext_webrequest_worker.html
new file mode 100644
index 0000000000..9fc3e00f01
--- /dev/null
+++ b/toolkit/components/extensions/test/mochitest/test_ext_webrequest_worker.html
@@ -0,0 +1,192 @@
+<!DOCTYPE HTML>
+
+<html>
+<head>
+<meta charset="utf-8">
+  <script src="/tests/SimpleTest/SimpleTest.js"></script>
+  <script src="/tests/SimpleTest/ExtensionTestUtils.js"></script>
+  <script type="text/javascript" src="head_webrequest.js"></script>
+  <script type="text/javascript" src="head.js"></script>
+  <link rel="stylesheet" type="text/css" href="/tests/SimpleTest/test.css"/>
+<script>
+"use strict";
+
+let tabId;
+
+let extensionData = {
+  manifest: {
+    permissions: ["webRequest", "webRequestBlocking", "<all_urls>", "tabs"],
+  },
+  background() {
+    browser.webRequest.onBeforeRequest.addListener(details => {
+      if (details.url.endsWith("/favicon.ico")) {
+        // We don't care about favicon.ico in this test. It is hard to control
+        // whether the request happens.
+        browser.test.log(`Ignoring favicon request: ${details.url}`);
+        return;
+      }
+      browser.test.sendMessage("onBeforeRequest", details);
+    }, {urls: ["<all_urls>"]}, ["blocking"]);
+
+    let tab;
+    browser.tabs.onCreated.addListener(newTab => {
+      tab = newTab;
+      browser.test.sendMessage("tab-created", tab.id);
+    });
+
+    browser.test.onMessage.addListener(async (msg) => {
+      if (msg === "close-tab") {
+        await browser.tabs.remove(tab.id);
+        browser.test.sendMessage("tab-closed");
+      }
+    });
+  },
+};
+
+let expected = {
+  "file_simple_webrequest_worker.html?topframe=true": {
+    type: "main_frame",
+    toplevel: true,
+    origin: "test_ext_webrequest_worker.html",
+    tabId: true,
+    parentFrameId: -1,
+  },
+  "file_simple_iframe_worker.html": {
+    type: "sub_frame",
+    toplevel: false,
+    origin: "file_simple_webrequest_worker.html?topframe=true",
+    tabId: true,
+    parentFrameId: 0,
+  },
+  "file_simple_toplevel.txt": {
+    type: "xmlhttprequest",
+    toplevel: true,
+    origin: "file_simple_webrequest_worker.html?topframe=true",
+    tabId: true,
+    parentFrameId: -1,
+  },
+  "file_simple_iframe.txt": {
+    type: "xmlhttprequest",
+    toplevel: false,
+    origin: "file_simple_iframe_worker.html",
+    tabId: true,
+    parentFrameId: 0,
+  },
+  "file_simple_worker.txt": {
+    type: "xmlhttprequest",
+    toplevel: true,
+    origin: "file_simple_worker.js",
+    tabId: true,
+    parentFrameId: -1,
+  },
+  "file_simple_iframe_worker.txt": {
+    type: "xmlhttprequest",
+    toplevel: false,
+    origin: "file_simple_worker.js?iniframe=true",
+    tabId: true,
+    parentFrameId: 0,
+  },
+  "file_simple_sharedworker.txt": {
+    type: "xmlhttprequest",
+    toplevel: undefined,
+    origin: "file_simple_sharedworker.js",
+    tabId: false,
+    parentFrameId: -1,
+  },
+  "file_simple_iframe_sharedworker.txt": {
+    type: "xmlhttprequest",
+    toplevel: undefined,
+    origin: "file_simple_sharedworker.js?iniframe=true",
+    tabId: false,
+    parentFrameId: -1,
+  },
+  "file_simple_worker.js": {
+    type: "script",
+    toplevel: true,
+    origin: "file_simple_webrequest_worker.html?topframe=true",
+    tabId: true,
+    parentFrameId: -1,
+  },
+  "file_simple_sharedworker.js": {
+    type: "script",
+    toplevel: undefined,
+    origin: "file_simple_webrequest_worker.html?topframe=true",
+    tabId: false,
+    parentFrameId: -1,
+  },
+  "file_simple_worker.js?iniframe=true": {
+    type: "script",
+    toplevel: false,
+    origin: "file_simple_iframe_worker.html",
+    tabId: true,
+    parentFrameId: 0,
+  },
+  "file_simple_sharedworker.js?iniframe=true": {
+    type: "script",
+    toplevel: undefined,
+    origin: "file_simple_iframe_worker.html",
+    tabId: false,
+    parentFrameId: -1,
+  },
+
+
+};
+
+function checkDetails(details) {
+  let filename = details.url.split("/").pop();
+  ok(filename in expected, `Should be expecting a request for ${filename}`);
+  let expect = expected[filename];
+  is(expect.type, details.type, `${details.type} type matches`);
+  const originUrlSuffix = details.originUrl?.split("/").pop();
+  ok(expect.origin === originUrlSuffix || originUrlSuffix.startsWith(expect.origin), `origin url is correct`);
+  is(details.parentFrameId, expect.parentFrameId, "parentFrameId matches");
+  is(expect.tabId ? tabId : -1, details.tabId, "tabId matches");
+  // TODO: When expect.toplevel is "undefined", the details.frameId is supposed
+  // to be -1.
+  // details in https://phabricator.services.mozilla.com/D182705#inline-1030548.
+  if (expect.toplevel === undefined || expect.toplevel) {
+    is(details.frameId, 0, "expect zero frameId");
+  } else {
+    ok(details.frameId > 0, "expect non-zero frameId");
+  }
+  return filename;
+}
+
+add_task(async function test_webRequest_worker() {
+  await SpecialPowers.spawnChrome([], async () => {
+    Services.cache2.clear();
+  });
+
+  let extension = ExtensionTestUtils.loadExtension(extensionData);
+  await extension.startup();
+
+  let a = addLink(`file_simple_webrequest_worker.html?topframe=true`);
+  a.click();
+  tabId = await extension.awaitMessage("tab-created");
+  info(`Get created tab(${tabId}`);
+
+  let remaining = new Set(Object.keys(expected));
+  let totalExpectedCount = remaining.size;
+  let currentExpectedCount = 0;
+  while (remaining.size !== 0) {
+    info(`Waiting for request ${currentExpectedCount + 1} out of ${totalExpectedCount}`);
+    info(`Expecting one of: ${Array.from(remaining)}`);
+    let details = await extension.awaitMessage("onBeforeRequest");
+    info(`Checking details for request: ${JSON.stringify(details)}`);
+    let filename = checkDetails(details);
+    ok(remaining.delete(filename), `Got only one request for ${filename}`);
+    currentExpectedCount = currentExpectedCount + 1;
+  }
+
+  extension.sendMessage("close-tab");
+  await extension.awaitMessage("tab-closed");
+  await extension.unload();
+});
+
+</script>
+</head>
+<body>
+<div id="test">Sample text</div>
+
+</body>
+</html>
diff --git a/toolkit/components/extensions/test/mochitest/test_ext_window_postMessage.html b/toolkit/components/extensions/test/mochitest/test_ext_window_postMessage.html
new file mode 100644
index 0000000000..53b19d0ead
--- /dev/null
+++ b/toolkit/components/extensions/test/mochitest/test_ext_window_postMessage.html
@@ -0,0 +1,104 @@
+<!DOCTYPE HTML>
+<html>
+<head>
+  <title>Test for content script</title>
+  <script src="/tests/SimpleTest/SimpleTest.js"></script>
+  <script src="/tests/SimpleTest/ExtensionTestUtils.js"></script>
+  <script type="text/javascript" src="head.js"></script>
+  <link rel="stylesheet" type="text/css" href="/tests/SimpleTest/test.css"/>
+</head>
+<body>
+
+<script type="text/javascript">
+"use strict";
+
+/* eslint-disable mozilla/balanced-listeners */
+
+add_task(async function test_postMessage() {
+  let extensionData = {
+    manifest: {
+      content_scripts: [
+        {
+          "matches": ["http://mochi.test/*/file_sample.html"],
+          "js": ["content_script.js"],
+          "run_at": "document_start",
+          "all_frames": true,
+        },
+      ],
+
+      web_accessible_resources: ["iframe.html"],
+    },
+
+    background() {
+      browser.test.sendMessage("iframe-url", browser.runtime.getURL("iframe.html"));
+    },
+
+    files: {
+      "content_script.js": function() {
+        window.addEventListener("message", event => {
+          if (event.data == "ping") {
+            event.source.postMessage({pong: location.href},
+                                     event.origin);
+          }
+        });
+      },
+
+      "iframe.html": `<!DOCTYPE html>
+        <html>
+          <head>
+            <meta charset="utf-8">
+            <script src="content_script.js"><\/script>
+          </head>
+        </html>`,
+    },
+  };
+
+  let createIframe = url => {
+    let iframe = document.createElement("iframe");
+    return new Promise(resolve => {
+      iframe.src = url;
+      iframe.onload = resolve;
+      document.body.appendChild(iframe);
+    }).then(() => {
+      return iframe;
+    });
+  };
+
+  let awaitMessage = () => {
+    return new Promise(resolve => {
+      let listener = event => {
+        if (event.data.pong) {
+          window.removeEventListener("message", listener);
+          resolve(event.data);
+        }
+      };
+      window.addEventListener("message", listener);
+    });
+  };
+
+  let extension = ExtensionTestUtils.loadExtension(extensionData);
+  await extension.startup();
+
+  let iframeURL = await extension.awaitMessage("iframe-url");
+  let testURL = SimpleTest.getTestFileURL("file_sample.html");
+
+  for (let url of [iframeURL, testURL]) {
+    info(`Testing URL ${url}`);
+
+    let iframe = await createIframe(url);
+
+    iframe.contentWindow.postMessage(
+      "ping", url);
+
+    let pong = await awaitMessage();
+    is(pong.pong, url, "Got expected pong");
+
+    iframe.remove();
+  }
+
+  await extension.unload();
+});
+</script>
+
+</body>
+</html>
diff --git a/toolkit/components/extensions/test/mochitest/test_startup_canary.html b/toolkit/components/extensions/test/mochitest/test_startup_canary.html
new file mode 100644
index 0000000000..1f705940c2
--- /dev/null
+++ b/toolkit/components/extensions/test/mochitest/test_startup_canary.html
@@ -0,0 +1,76 @@
+<!DOCTYPE HTML>
+<html>
+<head>
+  <title>Check StartupCache</title>
+  <meta charset="utf-8">
+  <script src="/tests/SimpleTest/SimpleTest.js"></script>
+  <script type="text/javascript" src="head.js"></script>
+  <link rel="stylesheet" type="text/css" href="/tests/SimpleTest/test.css"/>
+</head>
+<body>
+
+<script type="text/javascript">
+"use strict";
+
+// The startup canary file is removed sometime after the startup, with a delay,
+// e.g. 30 seconds on desktop:
+// https://searchfox.org/mozilla-central/rev/aa46c2dcccbc6fd4265edca05d3d00cccdfc97b9/browser/components/BrowserGlue.jsm#2486-2490
+// e.g. up to 15 seconds (as an idle timeout) on Android:
+// https://searchfox.org/mozilla-central/rev/aa46c2dcccbc6fd4265edca05d3d00cccdfc97b9/mobile/android/chrome/geckoview/geckoview.js#510
+//
+// This test completes quickly if run sequentially after the many tests in this
+// directory. Otherwise the test may wait for up to MAX_DELAY_SEC seconds.
+const MAX_DELAY_SEC = 30;
+SimpleTest.requestFlakyTimeout("trackStartupCrashEnd() is called with a delay");
+
+// This test is not extension-specific, but placed in the extensions/ directory
+// because it complements the test_check_startupcache.html test, and because
+// the directory has many other tests, to minimize the amount of time wasted on
+// waiting.
+
+add_task(async function check_startup_canary() {
+  // The ".startup-incomplete" file is created at the startup, and supposedly
+  // cleared "soon" after startup (when the application knows that the startup
+  // succeeded without crash). Bug 1624724 and bug 1728461 show that this has
+  // not always been the case, so this regression test verifies that the file
+  // is actually non-existent when this test start, see
+  // https://bugzilla.mozilla.org/show_bug.cgi?id=1728461#c12
+
+  // This test is opened as a web page in the browser, so that should have been
+  // a point where the startup should have been considered done.
+
+  async function canaryExists() {
+    let chromeScript = loadChromeScript(async () => {
+      // This file is called FILE_STARTUP_INCOMPLETE in nsAppRunner.cpp and
+      // referenced via mozilla::startup::GetIncompleteStartupFile:
+      let file = Services.dirsvc.get("ProfLD", Ci.nsIFile);
+      file.append(".startup-incomplete");
+      this.sendAsyncMessage("canary_exists", file.exists());
+    });
+    let exists = await chromeScript.promiseOneMessage("canary_exists");
+    chromeScript.destroy();
+    return exists;
+  }
+
+  info("Checking if startup canary exists");
+  let i = 0;
+  while (await canaryExists()) {
+      if (i++ > MAX_DELAY_SEC) {
+      info("Canary still exists, giving up on waiting");
+      break;
+    }
+    info(`Startup canary exists, will retry ${i} / ${MAX_DELAY_SEC}.`);
+    await new Promise(resolve => setTimeout(resolve, 1000));
+  }
+
+  is(
+    await canaryExists(),
+    false,
+    "Startup canary should have been removed after early startup"
+  );
+});
+
+</script>
+
+</body>
+</html>
diff --git a/toolkit/components/extensions/test/mochitest/test_verify_non_remote_mode.html b/toolkit/components/extensions/test/mochitest/test_verify_non_remote_mode.html
new file mode 100644
index 0000000000..3713243c1b
--- /dev/null
+++ b/toolkit/components/extensions/test/mochitest/test_verify_non_remote_mode.html
@@ -0,0 +1,32 @@
+<!DOCTYPE HTML>
+<html>
+<head>
+  <title>Verify non-remote mode</title>
+  <meta charset="utf-8">
+  <script src="/tests/SimpleTest/SimpleTest.js"></script>
+  <script src="/tests/SimpleTest/ExtensionTestUtils.js"></script>
+  <script type="text/javascript" src="head.js"></script>
+  <link rel="stylesheet" type="text/css" href="/tests/SimpleTest/test.css"/>
+</head>
+<body>
+
+<script type="text/javascript">
+"use strict";
+add_task(async function verify_extensions_in_parent_process() {
+  // This test ensures we are running with the proper settings.
+  const { WebExtensionPolicy } = SpecialPowers.Cu.getGlobalForObject(SpecialPowers.Services);
+  SimpleTest.ok(!WebExtensionPolicy.useRemoteWebExtensions, "extensions running in-process");
+
+  let chromeScript = SpecialPowers.loadChromeScript(() => {
+    /* eslint-env mozilla/chrome-script */
+    const { WebExtensionPolicy } = Cu.getGlobalForObject(Services);
+    Assert.ok(WebExtensionPolicy.isExtensionProcess, "parent is extension process");
+    this.sendAsyncMessage("checks_done");
+  });
+  await chromeScript.promiseOneMessage("checks_done");
+  chromeScript.destroy();
+});
+</script>
+
+</body>
+</html>
diff --git a/toolkit/components/extensions/test/mochitest/test_verify_remote_mode.html b/toolkit/components/extensions/test/mochitest/test_verify_remote_mode.html
new file mode 100644
index 0000000000..2be0e19179
--- /dev/null
+++ b/toolkit/components/extensions/test/mochitest/test_verify_remote_mode.html
@@ -0,0 +1,22 @@
+<!DOCTYPE HTML>
+<html>
+<head>
+  <title>Verify remote mode</title>
+  <meta charset="utf-8">
+  <script src="/tests/SimpleTest/SimpleTest.js"></script>
+  <script src="/tests/SimpleTest/ExtensionTestUtils.js"></script>
+  <script type="text/javascript" src="head.js"></script>
+  <link rel="stylesheet" type="text/css" href="/tests/SimpleTest/test.css"/>
+</head>
+<body>
+
+<script type="text/javascript">
+  "use strict";
+  // This test ensures we are running with the proper settings.
+  const {WebExtensionPolicy} = SpecialPowers.Cu.getGlobalForObject(SpecialPowers.Services);
+  SimpleTest.ok(WebExtensionPolicy.useRemoteWebExtensions, "extensions running remote");
+  SimpleTest.ok(!WebExtensionPolicy.isExtensionProcess, "testing from remote process");
+</script>
+
+</body>
+</html>
diff --git a/toolkit/components/extensions/test/mochitest/test_verify_sw_mode.html b/toolkit/components/extensions/test/mochitest/test_verify_sw_mode.html
new file mode 100644
index 0000000000..5aea44b62b
--- /dev/null
+++ b/toolkit/components/extensions/test/mochitest/test_verify_sw_mode.html
@@ -0,0 +1,24 @@
+<!DOCTYPE HTML>
+<html>
+<head>
+  <title>Verify WebExtension background service worker mode</title>
+  <meta charset="utf-8">
+  <script src="/tests/SimpleTest/SimpleTest.js"></script>
+  <script src="/tests/SimpleTest/ExtensionTestUtils.js"></script>
+  <script type="text/javascript" src="head.js"></script>
+  <link rel="stylesheet" type="text/css" href="/tests/SimpleTest/test.css"/>
+</head>
+<body>
+
+<script type="text/javascript">
+  "use strict";
+  // This test ensures we are running with the proper settings.
+  const {WebExtensionPolicy} = SpecialPowers.Cu.getGlobalForObject(SpecialPowers.Services);
+  SimpleTest.ok(WebExtensionPolicy.useRemoteWebExtensions, "extensions running remote");
+  SimpleTest.ok(!WebExtensionPolicy.isExtensionProcess, "testing from remote process");
+  SimpleTest.ok(WebExtensionPolicy.backgroundServiceWorkerEnabled, "extensions background service worker enabled");
+  SimpleTest.ok(AppConstants.MOZ_WEBEXT_WEBIDL_ENABLED, "extensions API webidl bindings enabled");
+</script>
+
+</body>
+</html>
diff --git a/toolkit/components/extensions/test/mochitest/webrequest_chromeworker.js b/toolkit/components/extensions/test/mochitest/webrequest_chromeworker.js
new file mode 100644
index 0000000000..14d3ad2bab
--- /dev/null
+++ b/toolkit/components/extensions/test/mochitest/webrequest_chromeworker.js
@@ -0,0 +1,9 @@
+"use strict";
+
+/* eslint-env worker */
+
+onmessage = function (event) {
+  fetch("https://example.com/example.txt").then(() => {
+    postMessage("Done!");
+  });
+};
diff --git a/toolkit/components/extensions/test/mochitest/webrequest_test.sys.mjs b/toolkit/components/extensions/test/mochitest/webrequest_test.sys.mjs
new file mode 100644
index 0000000000..33554f3023
--- /dev/null
+++ b/toolkit/components/extensions/test/mochitest/webrequest_test.sys.mjs
@@ -0,0 +1,16 @@
+export var webrequest_test = {
+  testFetch(url) {
+    return fetch(url);
+  },
+
+  testXHR(url) {
+    return new Promise(resolve => {
+      let xhr = new XMLHttpRequest();
+      xhr.open("HEAD", url);
+      xhr.onload = () => {
+        resolve();
+      };
+      xhr.send();
+    });
+  },
+};
diff --git a/toolkit/components/extensions/test/mochitest/webrequest_worker.js b/toolkit/components/extensions/test/mochitest/webrequest_worker.js
new file mode 100644
index 0000000000..dcffd08578
--- /dev/null
+++ b/toolkit/components/extensions/test/mochitest/webrequest_worker.js
@@ -0,0 +1,3 @@
+"use strict";
+
+fetch("https://example.com/example.txt");
diff --git a/toolkit/components/extensions/test/xpcshell/.eslintrc.js b/toolkit/components/extensions/test/xpcshell/.eslintrc.js
new file mode 100644
index 0000000000..60d784b53c
--- /dev/null
+++ b/toolkit/components/extensions/test/xpcshell/.eslintrc.js
@@ -0,0 +1,13 @@
+"use strict";
+
+module.exports = {
+  env: {
+    // The tests in this folder are testing based on WebExtensions, so lets
+    // just define the webextensions environment here.
+    webextensions: true,
+    // Many parts of WebExtensions test definitions (e.g. content scripts) also
+    // interact with the browser environment, so define that here as we don't
+    // have an easy way to handle per-function/scope usage yet.
+    browser: true,
+  },
+};
diff --git a/toolkit/components/extensions/test/xpcshell/data/TestWorkerWatcherChild.sys.mjs b/toolkit/components/extensions/test/xpcshell/data/TestWorkerWatcherChild.sys.mjs
new file mode 100644
index 0000000000..907631dec1
--- /dev/null
+++ b/toolkit/components/extensions/test/xpcshell/data/TestWorkerWatcherChild.sys.mjs
@@ -0,0 +1,62 @@
+import { XPCOMUtils } from "resource://gre/modules/XPCOMUtils.sys.mjs";
+
+const lazy = {};
+
+XPCOMUtils.defineLazyServiceGetter(
+  lazy,
+  "wdm",
+  "@mozilla.org/dom/workers/workerdebuggermanager;1",
+  "nsIWorkerDebuggerManager"
+);
+
+export class TestWorkerWatcherChild extends JSProcessActorChild {
+  async receiveMessage(msg) {
+    switch (msg.name) {
+      case "Test:StartWatchingWorkers":
+        this.startWatchingWorkers();
+        break;
+      case "Test:StopWatchingWorkers":
+        this.stopWatchingWorkers();
+        break;
+      default:
+        // Ensure the test case will fail if this JSProcessActorChild does receive
+        // unexpected messages.
+        return Promise.reject(
+          new Error(`Unexpected message received: ${msg.name}`)
+        );
+    }
+  }
+
+  startWatchingWorkers() {
+    if (!this._workerDebuggerListener) {
+      const actor = this;
+      this._workerDebuggerListener = {
+        onRegister(dbg) {
+          actor.sendAsyncMessage("Test:WorkerSpawned", {
+            workerType: dbg.type,
+            workerUrl: dbg.url,
+          });
+        },
+        onUnregister(dbg) {
+          actor.sendAsyncMessage("Test:WorkerTerminated", {
+            workerType: dbg.type,
+            workerUrl: dbg.url,
+          });
+        },
+      };
+
+      lazy.wdm.addListener(this._workerDebuggerListener);
+    }
+  }
+
+  stopWatchingWorkers() {
+    if (this._workerDebuggerListener) {
+      lazy.wdm.removeListener(this._workerDebuggerListener);
+      this._workerDebuggerListener = null;
+    }
+  }
+
+  willDestroy() {
+    this.stopWatchingWorkers();
+  }
+}
diff --git a/toolkit/components/extensions/test/xpcshell/data/TestWorkerWatcherParent.sys.mjs b/toolkit/components/extensions/test/xpcshell/data/TestWorkerWatcherParent.sys.mjs
new file mode 100644
index 0000000000..a9d919f1ed
--- /dev/null
+++ b/toolkit/components/extensions/test/xpcshell/data/TestWorkerWatcherParent.sys.mjs
@@ -0,0 +1,20 @@
+export class TestWorkerWatcherParent extends JSProcessActorParent {
+  constructor() {
+    super();
+    // This is set by the test helper that does use these process actors.
+    this.eventEmitter = null;
+  }
+
+  receiveMessage(msg) {
+    switch (msg.name) {
+      case "Test:WorkerSpawned":
+        this.eventEmitter?.emit("worker-spawned", msg.data);
+        break;
+      case "Test:WorkerTerminated":
+        this.eventEmitter?.emit("worker-terminated", msg.data);
+        break;
+      default:
+        throw new Error(`Unexpected message received: ${msg.name}`);
+    }
+  }
+}
diff --git a/toolkit/components/extensions/test/xpcshell/data/dummy_page.html b/toolkit/components/extensions/test/xpcshell/data/dummy_page.html
new file mode 100644
index 0000000000..c1c9a4e043
--- /dev/null
+++ b/toolkit/components/extensions/test/xpcshell/data/dummy_page.html
@@ -0,0 +1,7 @@
+<!DOCTYPE html>
+
+<html>
+<body>
+<p>Page</p>
+</body>
+</html>
diff --git a/toolkit/components/extensions/test/xpcshell/data/empty_file_download.txt b/toolkit/components/extensions/test/xpcshell/data/empty_file_download.txt
new file mode 100644
index 0000000000..e69de29bb2
--- /dev/null
+++ b/toolkit/components/extensions/test/xpcshell/data/empty_file_download.txt
diff --git a/toolkit/components/extensions/test/xpcshell/data/file   download.txt b/toolkit/components/extensions/test/xpcshell/data/file   download.txt
new file mode 100644
index 0000000000..6293c7af79
--- /dev/null
+++ b/toolkit/components/extensions/test/xpcshell/data/file   download.txt
@@ -0,0 +1 @@
+This is a sample file used in download tests.
diff --git a/toolkit/components/extensions/test/xpcshell/data/file_WebRequest_page2.html b/toolkit/components/extensions/test/xpcshell/data/file_WebRequest_page2.html
new file mode 100644
index 0000000000..b2cf48f9e1
--- /dev/null
+++ b/toolkit/components/extensions/test/xpcshell/data/file_WebRequest_page2.html
@@ -0,0 +1,25 @@
+<!DOCTYPE HTML>
+
+<html>
+<head>
+<meta charset="utf-8">
+<link rel="stylesheet" href="file_style_good.css">
+<link rel="stylesheet" href="file_style_bad.css">
+<link rel="stylesheet" href="file_style_redirect.css">
+</head>
+<body>
+
+<div class="test">Sample text</div>
+
+<img id="img_good" src="file_image_good.png">
+<img id="img_bad" src="file_image_bad.png">
+<img id="img_redirect" src="file_image_redirect.png">
+
+<script src="file_script_good.js"></script>
+<script src="file_script_bad.js"></script>
+<script src="file_script_redirect.js"></script>
+
+<script src="nonexistent_script_url.js"></script>
+
+</body>
+</html>
diff --git a/toolkit/components/extensions/test/xpcshell/data/file_WebRequest_permission_original.html b/toolkit/components/extensions/test/xpcshell/data/file_WebRequest_permission_original.html
new file mode 100644
index 0000000000..f6b5142c4d
--- /dev/null
+++ b/toolkit/components/extensions/test/xpcshell/data/file_WebRequest_permission_original.html
@@ -0,0 +1,19 @@
+<!DOCTYPE HTML>
+
+<html>
+<head>
+<meta charset="utf-8">
+</head>
+<body>
+
+<script src="http://example.org/data/file_WebRequest_permission_original.js"></script>
+<script>
+"use strict";
+
+window.parent.postMessage({
+  page: "original",
+  script: window.testScript,
+}, "*");
+</script>
+</body>
+</html>
diff --git a/toolkit/components/extensions/test/xpcshell/data/file_WebRequest_permission_original.js b/toolkit/components/extensions/test/xpcshell/data/file_WebRequest_permission_original.js
new file mode 100644
index 0000000000..2981108b64
--- /dev/null
+++ b/toolkit/components/extensions/test/xpcshell/data/file_WebRequest_permission_original.js
@@ -0,0 +1,2 @@
+"use strict";
+window.testScript = "original";
diff --git a/toolkit/components/extensions/test/xpcshell/data/file_WebRequest_permission_redirected.html b/toolkit/components/extensions/test/xpcshell/data/file_WebRequest_permission_redirected.html
new file mode 100644
index 0000000000..0979593f7b
--- /dev/null
+++ b/toolkit/components/extensions/test/xpcshell/data/file_WebRequest_permission_redirected.html
@@ -0,0 +1,19 @@
+<!DOCTYPE HTML>
+
+<html>
+<head>
+<meta charset="utf-8">
+</head>
+<body>
+
+<script src="http://example.org/data/file_WebRequest_permission_original.js"></script>
+<script>
+"use strict";
+
+window.parent.postMessage({
+  page: "redirected",
+  script: window.testScript,
+}, "*");
+</script>
+</body>
+</html>
diff --git a/toolkit/components/extensions/test/xpcshell/data/file_WebRequest_permission_redirected.js b/toolkit/components/extensions/test/xpcshell/data/file_WebRequest_permission_redirected.js
new file mode 100644
index 0000000000..06fd42aa40
--- /dev/null
+++ b/toolkit/components/extensions/test/xpcshell/data/file_WebRequest_permission_redirected.js
@@ -0,0 +1,2 @@
+"use strict";
+window.testScript = "redirected";
diff --git a/toolkit/components/extensions/test/xpcshell/data/file_content_script_errors.html b/toolkit/components/extensions/test/xpcshell/data/file_content_script_errors.html
new file mode 100644
index 0000000000..da1d1c32bc
--- /dev/null
+++ b/toolkit/components/extensions/test/xpcshell/data/file_content_script_errors.html
@@ -0,0 +1,7 @@
+<!DOCTYPE html>
+<html>
+  <head>
+    <meta charset="utf-8">
+  </head>
+  <body>Content script errors</body>
+</html>
diff --git a/toolkit/components/extensions/test/xpcshell/data/file_csp.html b/toolkit/components/extensions/test/xpcshell/data/file_csp.html
new file mode 100644
index 0000000000..9f5cf92f5a
--- /dev/null
+++ b/toolkit/components/extensions/test/xpcshell/data/file_csp.html
@@ -0,0 +1,14 @@
+<!DOCTYPE HTML>
+
+<html>
+<head>
+<meta charset="utf-8">
+</head>
+<body>
+
+<div id="test">Sample text</div>
+<img id="bad-image" src="http://example.org/data/file_image_bad.png">
+<script id="bad-script" src="http://example.org/data/file_script_bad.js"></script>
+
+</body>
+</html>
diff --git a/toolkit/components/extensions/test/xpcshell/data/file_csp.html^headers^ b/toolkit/components/extensions/test/xpcshell/data/file_csp.html^headers^
new file mode 100644
index 0000000000..4c6fa3c26a
--- /dev/null
+++ b/toolkit/components/extensions/test/xpcshell/data/file_csp.html^headers^
@@ -0,0 +1 @@
+Content-Security-Policy: default-src 'self'
diff --git a/toolkit/components/extensions/test/xpcshell/data/file_do_load_script_subresource.html b/toolkit/components/extensions/test/xpcshell/data/file_do_load_script_subresource.html
new file mode 100644
index 0000000000..c74dec5f5a
--- /dev/null
+++ b/toolkit/components/extensions/test/xpcshell/data/file_do_load_script_subresource.html
@@ -0,0 +1,9 @@
+<!DOCTYPE HTML>
+<html>
+<head>
+<meta charset="utf-8">
+</head>
+<body>
+<script src="http://example.net/intercept_by_webRequest.js"></script>
+</body>
+</html>
diff --git a/toolkit/components/extensions/test/xpcshell/data/file_document_open.html b/toolkit/components/extensions/test/xpcshell/data/file_document_open.html
new file mode 100644
index 0000000000..dae5e90667
--- /dev/null
+++ b/toolkit/components/extensions/test/xpcshell/data/file_document_open.html
@@ -0,0 +1,21 @@
+<!DOCTYPE HTML>
+<html>
+<head>
+<meta charset="utf-8">
+</head>
+<body>
+
+  <iframe id="iframe"></iframe>
+
+  <script type="text/javascript">
+    "use strict";
+    addEventListener("load", () => {
+      let iframe = document.getElementById("iframe");
+      let doc = iframe.contentDocument;
+      doc.open("text/html");
+      doc.write("Hello.");
+      doc.close();
+    }, {once: true});
+  </script>
+</body>
+</html>
diff --git a/toolkit/components/extensions/test/xpcshell/data/file_document_write.html b/toolkit/components/extensions/test/xpcshell/data/file_document_write.html
new file mode 100644
index 0000000000..f8369ae574
--- /dev/null
+++ b/toolkit/components/extensions/test/xpcshell/data/file_document_write.html
@@ -0,0 +1,36 @@
+<!DOCTYPE HTML>
+<html>
+<head>
+<meta charset="utf-8">
+</head>
+<body>
+  <iframe id="iframe"></iframe>
+
+  <script type="text/javascript">
+    "use strict";
+    addEventListener("load", () => {
+      // Send a heap-minimize observer notification so our script cache is
+      // cleared, and our content script isn't available for synchronous
+      // insertion.
+      window.dispatchEvent(new CustomEvent("MozHeapMinimize"));
+
+      let iframe = document.getElementById("iframe");
+      let doc = iframe.contentDocument;
+      let win = iframe.contentWindow;
+      doc.open("text/html");
+      // We need to do two writes here. The first creates the document element,
+      // which normally triggers parser blocking. The second triggers the
+      // creation of the element we're about to query for, which would normally
+      // happen asynchronously if the parser were blocked.
+      doc.write("<div id=meh>");
+      doc.write("<div id=beer></div>");
+
+      let elem = doc.getElementById("beer");
+      top.postMessage(elem instanceof win.HTMLDivElement ? "ok" : "fail",
+                      "*");
+
+      doc.close();
+    }, {once: true});
+  </script>
+</body>
+</html>
diff --git a/toolkit/components/extensions/test/xpcshell/data/file_download.html b/toolkit/components/extensions/test/xpcshell/data/file_download.html
new file mode 100644
index 0000000000..d970c63259
--- /dev/null
+++ b/toolkit/components/extensions/test/xpcshell/data/file_download.html
@@ -0,0 +1,12 @@
+<!DOCTYPE HTML>
+
+<html>
+<head>
+<meta charset="utf-8">
+</head>
+<body>
+
+<div>Download HTML File</div>
+
+</body>
+</html>
diff --git a/toolkit/components/extensions/test/xpcshell/data/file_download.txt b/toolkit/components/extensions/test/xpcshell/data/file_download.txt
new file mode 100644
index 0000000000..6293c7af79
--- /dev/null
+++ b/toolkit/components/extensions/test/xpcshell/data/file_download.txt
@@ -0,0 +1 @@
+This is a sample file used in download tests.
diff --git a/toolkit/components/extensions/test/xpcshell/data/file_iframe.html b/toolkit/components/extensions/test/xpcshell/data/file_iframe.html
new file mode 100644
index 0000000000..0cd68be586
--- /dev/null
+++ b/toolkit/components/extensions/test/xpcshell/data/file_iframe.html
@@ -0,0 +1,9 @@
+<!DOCTYPE html>
+<html lang="en">
+<head>
+  <meta charset="UTF-8">
+  <title>Iframe document</title>
+</head>
+<body>
+</body>
+</html>
diff --git a/toolkit/components/extensions/test/xpcshell/data/file_image_bad.png b/toolkit/components/extensions/test/xpcshell/data/file_image_bad.png
new file mode 100644
index 0000000000..4c3be50847
--- /dev/null
+++ b/toolkit/components/extensions/test/xpcshell/data/file_image_bad.png
diff --git a/toolkit/components/extensions/test/xpcshell/data/file_image_good.png b/toolkit/components/extensions/test/xpcshell/data/file_image_good.png
new file mode 100644
index 0000000000..769c636340
--- /dev/null
+++ b/toolkit/components/extensions/test/xpcshell/data/file_image_good.png
diff --git a/toolkit/components/extensions/test/xpcshell/data/file_image_redirect.png b/toolkit/components/extensions/test/xpcshell/data/file_image_redirect.png
new file mode 100644
index 0000000000..4c3be50847
--- /dev/null
+++ b/toolkit/components/extensions/test/xpcshell/data/file_image_redirect.png
diff --git a/toolkit/components/extensions/test/xpcshell/data/file_page_xhr.html b/toolkit/components/extensions/test/xpcshell/data/file_page_xhr.html
new file mode 100644
index 0000000000..387b5285f5
--- /dev/null
+++ b/toolkit/components/extensions/test/xpcshell/data/file_page_xhr.html
@@ -0,0 +1,34 @@
+<!DOCTYPE html>
+<html>
+<head>
+<meta charset="utf-8">
+</head>
+<body>
+
+<script>
+"use strict";
+
+addEventListener("message", async function(event) {
+  const url = new URL("/return_headers.sjs", location).href;
+
+  const webpageFetchResult = await fetch(url).then(res => res.json());
+  const webpageXhrResult = await new Promise(resolve => {
+    const req = new XMLHttpRequest();
+    req.open("GET", url);
+    req.addEventListener("load", () => resolve(JSON.parse(req.responseText)),
+                         {once: true});
+    req.addEventListener("error", () => resolve({error: "webpage xhr failed to complete"}),
+                         {once: true});
+    req.send();
+  });
+
+  postMessage({
+    type: "testPageGlobals",
+    webpageFetchResult,
+    webpageXhrResult,
+  }, "*");
+}, {once: true});
+</script>
+
+</body>
+</html>
diff --git a/toolkit/components/extensions/test/xpcshell/data/file_permission_xhr.html b/toolkit/components/extensions/test/xpcshell/data/file_permission_xhr.html
new file mode 100644
index 0000000000..6f1bb4648b
--- /dev/null
+++ b/toolkit/components/extensions/test/xpcshell/data/file_permission_xhr.html
@@ -0,0 +1,61 @@
+<!DOCTYPE HTML>
+
+<html>
+<head>
+<meta charset="utf-8">
+</head>
+<body>
+
+<script>
+"use strict";
+
+/* globals privilegedFetch, privilegedXHR */
+/* eslint-disable mozilla/balanced-listeners */
+
+addEventListener("message", function rcv(event) {
+  removeEventListener("message", rcv, false);
+
+  function assertTrue(condition, description) {
+    postMessage({msg: "assertTrue", condition, description}, "*");
+  }
+
+  function assertThrows(func, expectedError, msg) {
+    try {
+      func();
+    } catch (e) {
+      assertTrue(expectedError.test(e), msg + ": threw " + e);
+      return;
+    }
+
+    assertTrue(false, "Function did not throw, " +
+                      "expected error should have matched " + expectedError);
+  }
+
+  function passListener() {
+    assertTrue(true, "Content XHR has no elevated privileges");
+    postMessage({"msg": "finish"}, "*");
+  }
+
+  function failListener() {
+    assertTrue(false, "Content XHR has no elevated privileges");
+    postMessage({"msg": "finish"}, "*");
+  }
+
+  assertThrows(function() { new privilegedXHR(); },
+               /Permission denied to access object/,
+               "Content should not be allowed to construct a privileged XHR constructor");
+
+  assertThrows(function() { new privilegedFetch(); },
+               / is not a constructor/,
+               "Content should not be allowed to construct a privileged fetch() constructor");
+
+  let req = new XMLHttpRequest();
+  req.addEventListener("load", failListener);
+  req.addEventListener("error", passListener);
+  req.open("GET", "http://example.org/example.txt");
+  req.send();
+}, false);
+</script>
+
+</body>
+</html>
diff --git a/toolkit/components/extensions/test/xpcshell/data/file_privilege_escalation.html b/toolkit/components/extensions/test/xpcshell/data/file_privilege_escalation.html
new file mode 100644
index 0000000000..258f7058d9
--- /dev/null
+++ b/toolkit/components/extensions/test/xpcshell/data/file_privilege_escalation.html
@@ -0,0 +1,13 @@
+<!DOCTYPE HTML>
+
+<html>
+<head>
+<meta charset="utf-8">
+</head>
+<body>
+  <script type="text/javascript">
+    "use strict";
+    throw new Error(`WebExt Privilege Escalation: typeof(browser) = ${typeof(browser)}`);
+  </script>
+</body>
+</html>
diff --git a/toolkit/components/extensions/test/xpcshell/data/file_sample.html b/toolkit/components/extensions/test/xpcshell/data/file_sample.html
new file mode 100644
index 0000000000..a20e49a1f0
--- /dev/null
+++ b/toolkit/components/extensions/test/xpcshell/data/file_sample.html
@@ -0,0 +1,12 @@
+<!DOCTYPE HTML>
+
+<html>
+<head>
+<meta charset="utf-8">
+</head>
+<body>
+
+<div id="test">Sample text</div>
+
+</body>
+</html>
diff --git a/toolkit/components/extensions/test/xpcshell/data/file_sample_registered_styles.html b/toolkit/components/extensions/test/xpcshell/data/file_sample_registered_styles.html
new file mode 100644
index 0000000000..9f5c5d5a6a
--- /dev/null
+++ b/toolkit/components/extensions/test/xpcshell/data/file_sample_registered_styles.html
@@ -0,0 +1,13 @@
+<!DOCTYPE HTML>
+
+<html>
+<head>
+<meta charset="utf-8">
+</head>
+<body>
+
+<div id="registered-extension-url-style">Registered Extension URL style</div>
+<div id="registered-extension-text-style">Registered Extension Text style</div>
+
+</body>
+</html>
diff --git a/toolkit/components/extensions/test/xpcshell/data/file_script.html b/toolkit/components/extensions/test/xpcshell/data/file_script.html
new file mode 100644
index 0000000000..8d192b7d8e
--- /dev/null
+++ b/toolkit/components/extensions/test/xpcshell/data/file_script.html
@@ -0,0 +1,14 @@
+<!DOCTYPE HTML>
+
+<html>
+<head>
+<meta charset="utf-8">
+<script type="application/javascript" src="file_script_good.js"></script>
+<script type="application/javascript" src="file_script_bad.js"></script>
+</head>
+<body>
+
+<div id="test">Sample text</div>
+
+</body>
+</html>
diff --git a/toolkit/components/extensions/test/xpcshell/data/file_script_bad.js b/toolkit/components/extensions/test/xpcshell/data/file_script_bad.js
new file mode 100644
index 0000000000..ff4572865b
--- /dev/null
+++ b/toolkit/components/extensions/test/xpcshell/data/file_script_bad.js
@@ -0,0 +1,12 @@
+"use strict";
+
+window.failure = true;
+window.addEventListener(
+  "load",
+  () => {
+    let el = document.createElement("div");
+    el.setAttribute("id", "bad");
+    document.body.appendChild(el);
+  },
+  { once: true }
+);
diff --git a/toolkit/components/extensions/test/xpcshell/data/file_script_good.js b/toolkit/components/extensions/test/xpcshell/data/file_script_good.js
new file mode 100644
index 0000000000..bf47fb36d2
--- /dev/null
+++ b/toolkit/components/extensions/test/xpcshell/data/file_script_good.js
@@ -0,0 +1,12 @@
+"use strict";
+
+window.success = window.success ? window.success + 1 : 1;
+window.addEventListener(
+  "load",
+  () => {
+    let el = document.createElement("div");
+    el.setAttribute("id", "good");
+    document.body.appendChild(el);
+  },
+  { once: true }
+);
diff --git a/toolkit/components/extensions/test/xpcshell/data/file_script_redirect.js b/toolkit/components/extensions/test/xpcshell/data/file_script_redirect.js
new file mode 100644
index 0000000000..c425122c71
--- /dev/null
+++ b/toolkit/components/extensions/test/xpcshell/data/file_script_redirect.js
@@ -0,0 +1,3 @@
+"use strict";
+
+window.failure = true;
diff --git a/toolkit/components/extensions/test/xpcshell/data/file_script_xhr.js b/toolkit/components/extensions/test/xpcshell/data/file_script_xhr.js
new file mode 100644
index 0000000000..24a26cb8d1
--- /dev/null
+++ b/toolkit/components/extensions/test/xpcshell/data/file_script_xhr.js
@@ -0,0 +1,9 @@
+"use strict";
+
+var request = new XMLHttpRequest();
+request.open(
+  "get",
+  "http://example.com/browser/toolkit/modules/tests/browser/xhr_resource",
+  false
+);
+request.send();
diff --git a/toolkit/components/extensions/test/xpcshell/data/file_shadowdom.html b/toolkit/components/extensions/test/xpcshell/data/file_shadowdom.html
new file mode 100644
index 0000000000..c4e7db14e7
--- /dev/null
+++ b/toolkit/components/extensions/test/xpcshell/data/file_shadowdom.html
@@ -0,0 +1,13 @@
+<!DOCTYPE HTML>
+<html>
+<head>
+<meta charset="utf-8">
+</head>
+<body>
+<div id="host">host</div>
+<script>
+  "use strict";
+  document.getElementById("host").attachShadow({mode: "closed"});
+</script>
+</body>
+</html>
diff --git a/toolkit/components/extensions/test/xpcshell/data/file_style_bad.css b/toolkit/components/extensions/test/xpcshell/data/file_style_bad.css
new file mode 100644
index 0000000000..8dbc8dc7a4
--- /dev/null
+++ b/toolkit/components/extensions/test/xpcshell/data/file_style_bad.css
@@ -0,0 +1,3 @@
+#test {
+  color: green !important;
+}
diff --git a/toolkit/components/extensions/test/xpcshell/data/file_style_good.css b/toolkit/components/extensions/test/xpcshell/data/file_style_good.css
new file mode 100644
index 0000000000..46f9774b5f
--- /dev/null
+++ b/toolkit/components/extensions/test/xpcshell/data/file_style_good.css
@@ -0,0 +1,3 @@
+#test {
+  color: red;
+}
diff --git a/toolkit/components/extensions/test/xpcshell/data/file_style_redirect.css b/toolkit/components/extensions/test/xpcshell/data/file_style_redirect.css
new file mode 100644
index 0000000000..8dbc8dc7a4
--- /dev/null
+++ b/toolkit/components/extensions/test/xpcshell/data/file_style_redirect.css
@@ -0,0 +1,3 @@
+#test {
+  color: green !important;
+}
diff --git a/toolkit/components/extensions/test/xpcshell/data/file_stylesheet_cache.css b/toolkit/components/extensions/test/xpcshell/data/file_stylesheet_cache.css
new file mode 100644
index 0000000000..6a9140d97e
--- /dev/null
+++ b/toolkit/components/extensions/test/xpcshell/data/file_stylesheet_cache.css
@@ -0,0 +1 @@
+:root { color: green; }
diff --git a/toolkit/components/extensions/test/xpcshell/data/file_stylesheet_cache.html b/toolkit/components/extensions/test/xpcshell/data/file_stylesheet_cache.html
new file mode 100644
index 0000000000..6d6d187a27
--- /dev/null
+++ b/toolkit/components/extensions/test/xpcshell/data/file_stylesheet_cache.html
@@ -0,0 +1,3 @@
+<!doctype html>
+<meta charset=utf-8>
+<link rel=stylesheet href=file_stylesheet_cache.css>
diff --git a/toolkit/components/extensions/test/xpcshell/data/file_stylesheet_cache_2.html b/toolkit/components/extensions/test/xpcshell/data/file_stylesheet_cache_2.html
new file mode 100644
index 0000000000..07a4324c44
--- /dev/null
+++ b/toolkit/components/extensions/test/xpcshell/data/file_stylesheet_cache_2.html
@@ -0,0 +1,19 @@
+<!doctype html>
+<meta charset=utf-8>
+<!-- The first one should hit the cache, the second one should not. -->
+<link rel=stylesheet href=file_stylesheet_cache.css>
+<script>
+  "use strict";
+  // This script guarantees that the load of the above stylesheet has happened
+  // by now.
+  //
+  // Now we can go ahead and load the other one programmatically. It's
+  // important that we don't just throw a <link> in the markup below to
+  // guarantee
+  // that the load happens afterwards (that is, to cheat the parser's speculative
+  // load mechanism).
+  const link = document.createElement("link");
+  link.rel = "stylesheet";
+  link.href = "file_stylesheet_cache.css?2";
+  document.head.appendChild(link);
+</script>
diff --git a/toolkit/components/extensions/test/xpcshell/data/file_toplevel.html b/toolkit/components/extensions/test/xpcshell/data/file_toplevel.html
new file mode 100644
index 0000000000..d93813d0f5
--- /dev/null
+++ b/toolkit/components/extensions/test/xpcshell/data/file_toplevel.html
@@ -0,0 +1,12 @@
+<!DOCTYPE html>
+<html lang="en">
+<head>
+  <meta charset="UTF-8">
+  <title>Top-level frame document</title>
+</head>
+<body>
+  <iframe src="file_iframe.html"></iframe>
+  <iframe src="about:blank"></iframe>
+  <iframe srcdoc="Iframe srcdoc"></iframe>
+</body>
+</html>
diff --git a/toolkit/components/extensions/test/xpcshell/data/file_with_iframe.html b/toolkit/components/extensions/test/xpcshell/data/file_with_iframe.html
new file mode 100644
index 0000000000..705350d55c
--- /dev/null
+++ b/toolkit/components/extensions/test/xpcshell/data/file_with_iframe.html
@@ -0,0 +1,11 @@
+<!DOCTYPE html>
+<html lang="en">
+  <head>
+    <meta charset="UTF-8">
+    <title>file with iframe</title>
+  </head>
+  <body>
+    <div id="test"></div>
+    <iframe src="./file_sample.html"></iframe>
+  </body>
+</html>
diff --git a/toolkit/components/extensions/test/xpcshell/data/file_with_xorigin_frame.html b/toolkit/components/extensions/test/xpcshell/data/file_with_xorigin_frame.html
new file mode 100644
index 0000000000..199c2ce4d4
--- /dev/null
+++ b/toolkit/components/extensions/test/xpcshell/data/file_with_xorigin_frame.html
@@ -0,0 +1,10 @@
+<!DOCTYPE html>
+<html lang="en">
+<head>
+  <meta charset="UTF-8">
+  <title>Document with example.org frame</title>
+</head>
+<body>
+  <iframe src="http://example.org/data/file_iframe.html"></iframe>
+</body>
+</html>
diff --git a/toolkit/components/extensions/test/xpcshell/data/lorem.html.gz b/toolkit/components/extensions/test/xpcshell/data/lorem.html.gz
new file mode 100644
index 0000000000..9eb8d73d50
--- /dev/null
+++ b/toolkit/components/extensions/test/xpcshell/data/lorem.html.gz
diff --git a/toolkit/components/extensions/test/xpcshell/data/pixel_green.gif b/toolkit/components/extensions/test/xpcshell/data/pixel_green.gif
new file mode 100644
index 0000000000..baf8166dae
--- /dev/null
+++ b/toolkit/components/extensions/test/xpcshell/data/pixel_green.gif
diff --git a/toolkit/components/extensions/test/xpcshell/data/pixel_red.gif b/toolkit/components/extensions/test/xpcshell/data/pixel_red.gif
new file mode 100644
index 0000000000..48f97f74bd
--- /dev/null
+++ b/toolkit/components/extensions/test/xpcshell/data/pixel_red.gif
diff --git a/toolkit/components/extensions/test/xpcshell/head.js b/toolkit/components/extensions/test/xpcshell/head.js
new file mode 100644
index 0000000000..10be62a7e2
--- /dev/null
+++ b/toolkit/components/extensions/test/xpcshell/head.js
@@ -0,0 +1,354 @@
+"use strict";
+/* exported createHttpServer, cleanupDir, clearCache, optionalPermissionsPromptHandler, promiseConsoleOutput,
+            promiseQuotaManagerServiceReset, promiseQuotaManagerServiceClear,
+            runWithPrefs, testEnv, withHandlingUserInput, resetHandlingUserInput,
+            assertPersistentListeners, promiseExtensionEvent, assertHasPersistedScriptsCachedFlag,
+            assertIsPersistedScriptsCachedFlag
+*/
+
+var { AppConstants } = ChromeUtils.importESModule(
+  "resource://gre/modules/AppConstants.sys.mjs"
+);
+var { XPCOMUtils } = ChromeUtils.importESModule(
+  "resource://gre/modules/XPCOMUtils.sys.mjs"
+);
+var {
+  clearInterval,
+  clearTimeout,
+  setInterval,
+  setIntervalWithTarget,
+  setTimeout,
+  setTimeoutWithTarget,
+} = ChromeUtils.importESModule("resource://gre/modules/Timer.sys.mjs");
+var { AddonTestUtils, MockAsyncShutdown } = ChromeUtils.importESModule(
+  "resource://testing-common/AddonTestUtils.sys.mjs"
+);
+
+ChromeUtils.defineESModuleGetters(this, {
+  ContentTask: "resource://testing-common/ContentTask.sys.mjs",
+  Extension: "resource://gre/modules/Extension.sys.mjs",
+  ExtensionData: "resource://gre/modules/Extension.sys.mjs",
+  ExtensionParent: "resource://gre/modules/ExtensionParent.sys.mjs",
+  ExtensionTestUtils:
+    "resource://testing-common/ExtensionXPCShellUtils.sys.mjs",
+  FileUtils: "resource://gre/modules/FileUtils.sys.mjs",
+  MessageChannel: "resource://testing-common/MessageChannel.sys.mjs",
+  PromiseTestUtils: "resource://testing-common/PromiseTestUtils.sys.mjs",
+  Schemas: "resource://gre/modules/Schemas.sys.mjs",
+});
+
+XPCOMUtils.defineLazyModuleGetters(this, {
+  NetUtil: "resource://gre/modules/NetUtil.jsm",
+});
+
+PromiseTestUtils.allowMatchingRejectionsGlobally(
+  /Message manager disconnected/
+);
+
+// Persistent Listener test functionality
+const { assertPersistentListeners } = ExtensionTestUtils.testAssertions;
+
+// https_first automatically upgrades http to https, but the tests are not
+// designed to expect that. And it is not easy to change that because
+// nsHttpServer does not support https (bug 1742061). So disable https_first.
+Services.prefs.setBoolPref("dom.security.https_first", false);
+
+// These values may be changed in later head files and tested in check_remote
+// below.
+Services.prefs.setBoolPref("browser.tabs.remote.autostart", false);
+Services.prefs.setBoolPref("extensions.webextensions.remote", false);
+const testEnv = {
+  expectRemote: false,
+};
+
+add_setup(function check_remote() {
+  Assert.equal(
+    WebExtensionPolicy.useRemoteWebExtensions,
+    testEnv.expectRemote,
+    "useRemoteWebExtensions matches"
+  );
+  Assert.equal(
+    WebExtensionPolicy.isExtensionProcess,
+    !testEnv.expectRemote,
+    "testing from extension process"
+  );
+});
+
+ExtensionTestUtils.init(this);
+
+var createHttpServer = (...args) => {
+  AddonTestUtils.maybeInit(this);
+  return AddonTestUtils.createHttpServer(...args);
+};
+
+if (AppConstants.platform === "android") {
+  Services.io.offline = true;
+}
+
+/**
+ * Clears the HTTP and content image caches.
+ */
+function clearCache() {
+  Services.cache2.clear();
+
+  let imageCache = Cc["@mozilla.org/image/tools;1"]
+    .getService(Ci.imgITools)
+    .getImgCacheForDocument(null);
+  imageCache.clearCache(false);
+}
+
+var promiseConsoleOutput = async function (task) {
+  const DONE = `=== console listener ${Math.random()} done ===`;
+
+  let listener;
+  let messages = [];
+  let awaitListener = new Promise(resolve => {
+    listener = msg => {
+      if (msg == DONE) {
+        resolve();
+      } else {
+        void (msg instanceof Ci.nsIConsoleMessage);
+        void (msg instanceof Ci.nsIScriptError);
+        messages.push(msg);
+      }
+    };
+  });
+
+  Services.console.registerListener(listener);
+  try {
+    let result = await task();
+
+    Services.console.logStringMessage(DONE);
+    await awaitListener;
+
+    return { messages, result };
+  } finally {
+    Services.console.unregisterListener(listener);
+  }
+};
+
+// Attempt to remove a directory.  If the Windows OS is still using the
+// file sometimes remove() will fail.  So try repeatedly until we can
+// remove it or we give up.
+function cleanupDir(dir) {
+  let count = 0;
+  return new Promise((resolve, reject) => {
+    function tryToRemoveDir() {
+      count += 1;
+      try {
+        dir.remove(true);
+      } catch (e) {
+        // ignore
+      }
+      if (!dir.exists()) {
+        return resolve();
+      }
+      if (count >= 25) {
+        return reject(`Failed to cleanup directory: ${dir}`);
+      }
+      setTimeout(tryToRemoveDir, 100);
+    }
+    tryToRemoveDir();
+  });
+}
+
+// Run a test with the specified preferences and then restores their initial values
+// right after the test function run (whether it passes or fails).
+async function runWithPrefs(prefsToSet, testFn) {
+  const setPrefs = prefs => {
+    for (let [pref, value] of prefs) {
+      if (value === undefined) {
+        // Clear any pref that didn't have a user value.
+        info(`Clearing pref "${pref}"`);
+        Services.prefs.clearUserPref(pref);
+        continue;
+      }
+
+      info(`Setting pref "${pref}": ${value}`);
+      switch (typeof value) {
+        case "boolean":
+          Services.prefs.setBoolPref(pref, value);
+          break;
+        case "number":
+          Services.prefs.setIntPref(pref, value);
+          break;
+        case "string":
+          Services.prefs.setStringPref(pref, value);
+          break;
+        default:
+          throw new Error("runWithPrefs doesn't support this pref type yet");
+      }
+    }
+  };
+
+  const getPrefs = prefs => {
+    return prefs.map(([pref, value]) => {
+      info(`Getting initial pref value for "${pref}"`);
+      if (!Services.prefs.prefHasUserValue(pref)) {
+        // Check if the pref doesn't have a user value.
+        return [pref, undefined];
+      }
+      switch (typeof value) {
+        case "boolean":
+          return [pref, Services.prefs.getBoolPref(pref)];
+        case "number":
+          return [pref, Services.prefs.getIntPref(pref)];
+        case "string":
+          return [pref, Services.prefs.getStringPref(pref)];
+        default:
+          throw new Error("runWithPrefs doesn't support this pref type yet");
+      }
+    });
+  };
+
+  let initialPrefsValues = [];
+
+  try {
+    initialPrefsValues = getPrefs(prefsToSet);
+
+    setPrefs(prefsToSet);
+
+    await testFn();
+  } finally {
+    info("Restoring initial preferences values on exit");
+    setPrefs(initialPrefsValues);
+  }
+}
+
+// "Handling User Input" test helpers.
+
+let extensionHandlers = new WeakSet();
+
+function handlingUserInputFrameScript() {
+  /* globals content */
+  // eslint-disable-next-line no-shadow
+  const { MessageChannel } = ChromeUtils.importESModule(
+    "resource://testing-common/MessageChannel.sys.mjs"
+  );
+
+  let handle;
+  MessageChannel.addListener(this, "ExtensionTest:HandleUserInput", {
+    receiveMessage({ name, data }) {
+      if (data) {
+        handle = content.windowUtils.setHandlingUserInput(true);
+      } else if (handle) {
+        handle.destruct();
+        handle = null;
+      }
+    },
+  });
+}
+
+// If you use withHandlingUserInput then restart the addon manager,
+// you need to reset this before using withHandlingUserInput again.
+function resetHandlingUserInput() {
+  extensionHandlers = new WeakSet();
+}
+
+async function withHandlingUserInput(extension, fn) {
+  let { messageManager } = extension.extension.groupFrameLoader;
+
+  if (!extensionHandlers.has(extension)) {
+    messageManager.loadFrameScript(
+      `data:,(${encodeURI(handlingUserInputFrameScript)}).call(this)`,
+      false,
+      true
+    );
+    extensionHandlers.add(extension);
+  }
+
+  await MessageChannel.sendMessage(
+    messageManager,
+    "ExtensionTest:HandleUserInput",
+    true
+  );
+  await fn();
+  await MessageChannel.sendMessage(
+    messageManager,
+    "ExtensionTest:HandleUserInput",
+    false
+  );
+}
+
+// QuotaManagerService test helpers.
+
+function promiseQuotaManagerServiceReset() {
+  info("Calling QuotaManagerService.reset to enforce new test storage limits");
+  return new Promise(resolve => {
+    Services.qms.reset().callback = resolve;
+  });
+}
+
+function promiseQuotaManagerServiceClear() {
+  info(
+    "Calling QuotaManagerService.clear to empty the test data and refresh test storage limits"
+  );
+  return new Promise(resolve => {
+    Services.qms.clear().callback = resolve;
+  });
+}
+
+// Optional Permission prompt handling
+const optionalPermissionsPromptHandler = {
+  sawPrompt: false,
+  acceptPrompt: false,
+
+  init() {
+    Services.prefs.setBoolPref(
+      "extensions.webextOptionalPermissionPrompts",
+      true
+    );
+    Services.obs.addObserver(this, "webextension-optional-permission-prompt");
+    registerCleanupFunction(() => {
+      Services.obs.removeObserver(
+        this,
+        "webextension-optional-permission-prompt"
+      );
+      Services.prefs.clearUserPref(
+        "extensions.webextOptionalPermissionPrompts"
+      );
+    });
+  },
+
+  observe(subject, topic, data) {
+    if (topic == "webextension-optional-permission-prompt") {
+      this.sawPrompt = true;
+      let { resolve } = subject.wrappedJSObject;
+      resolve(this.acceptPrompt);
+    }
+  },
+};
+
+function promiseExtensionEvent(wrapper, event) {
+  return new Promise(resolve => {
+    wrapper.extension.once(event, (...args) => resolve(args));
+  });
+}
+
+async function assertHasPersistedScriptsCachedFlag(ext) {
+  const { StartupCache } = ExtensionParent;
+  const allCachedGeneral = StartupCache._data.get("general");
+  equal(
+    allCachedGeneral
+      .get(ext.id)
+      ?.get(ext.version)
+      ?.get("scripting")
+      ?.has("hasPersistedScripts"),
+    true,
+    "Expect the StartupCache to include hasPersistedScripts flag"
+  );
+}
+
+async function assertIsPersistentScriptsCachedFlag(ext, expectedValue) {
+  const { StartupCache } = ExtensionParent;
+  const allCachedGeneral = StartupCache._data.get("general");
+  equal(
+    allCachedGeneral
+      .get(ext.id)
+      ?.get(ext.version)
+      ?.get("scripting")
+      ?.get("hasPersistedScripts"),
+    expectedValue,
+    "Expected cached value set on hasPersistedScripts flag"
+  );
+}
diff --git a/toolkit/components/extensions/test/xpcshell/head_dnr.js b/toolkit/components/extensions/test/xpcshell/head_dnr.js
new file mode 100644
index 0000000000..0c65869722
--- /dev/null
+++ b/toolkit/components/extensions/test/xpcshell/head_dnr.js
@@ -0,0 +1,203 @@
+/* Any copyright is dedicated to the Public Domain.
+ * http://creativecommons.org/publicdomain/zero/1.0/ */
+
+"use strict";
+
+/* exported assertDNRStoreData, getDNRRule, getSchemaNormalizedRule, getSchemaNormalizedRules
+ */
+
+ChromeUtils.defineESModuleGetters(this, {
+  Schemas: "resource://gre/modules/Schemas.sys.mjs",
+});
+
+function getDNRRule({
+  id = 1,
+  priority = 1,
+  action = {},
+  condition = {},
+} = {}) {
+  return {
+    id,
+    priority,
+    action: {
+      type: "block",
+      ...action,
+    },
+    condition: {
+      ...condition,
+    },
+  };
+}
+
+const getSchemaNormalizedRule = (extensionTestWrapper, value) => {
+  const { extension } = extensionTestWrapper;
+  const validationContext = {
+    url: extension.baseURI.spec,
+    principal: extension.principal,
+    logError: err => {
+      // We don't expect this test helper function to be called on invalid rules,
+      // and so we trigger an explicit test failure if we ever hit any.
+      Assert.ok(
+        false,
+        `Unexpected logError on normalizing DNR rule ${JSON.stringify(
+          value
+        )} - ${err}`
+      );
+    },
+    preprocessors: {},
+    manifestVersion: extension.manifestVersion,
+  };
+
+  return Schemas.normalize(
+    value,
+    "declarativeNetRequest.Rule",
+    validationContext
+  );
+};
+
+const getSchemaNormalizedRules = (extensionTestWrapper, rules) => {
+  return rules.map(rule => {
+    const normalized = getSchemaNormalizedRule(extensionTestWrapper, rule);
+    if (normalized.error) {
+      throw new Error(
+        `Unexpected DNR Rule normalization error: ${normalized.error}`
+      );
+    }
+    return normalized.value;
+  });
+};
+
+const assertDNRStoreData = async (
+  dnrStore,
+  extensionTestWrapper,
+  expectedRulesets,
+  { assertIndividualRules = true } = {}
+) => {
+  const extUUID = extensionTestWrapper.uuid;
+  const rule_resources =
+    extensionTestWrapper.extension.manifest.declarative_net_request
+      ?.rule_resources;
+  const expectedRulesetIds = Array.from(Object.keys(expectedRulesets));
+  const expectedRulesetIndexesMap = expectedRulesetIds.reduce((acc, rsId) => {
+    acc.set(
+      rsId,
+      rule_resources.findIndex(rr => rr.id === rsId)
+    );
+    return acc;
+  }, new Map());
+
+  ok(
+    dnrStore._dataPromises.has(extUUID),
+    "Got promise for the test extension DNR data being loaded"
+  );
+
+  await dnrStore._dataPromises.get(extUUID);
+
+  ok(dnrStore._data.has(extUUID), "Got data for the test extension");
+
+  const dnrExtData = dnrStore._data.get(extUUID);
+  Assert.deepEqual(
+    {
+      schemaVersion: dnrExtData.schemaVersion,
+      extVersion: dnrExtData.extVersion,
+    },
+    {
+      schemaVersion: dnrExtData.constructor.VERSION,
+      extVersion: extensionTestWrapper.extension.version,
+    },
+    "Got the expected data schema version and extension version in the store data"
+  );
+  Assert.deepEqual(
+    Array.from(dnrExtData.staticRulesets.keys()),
+    expectedRulesetIds,
+    "Got the enabled rulesets in the stored data staticRulesets Map"
+  );
+
+  for (const rulesetId of expectedRulesetIds) {
+    const expectedRulesetIdx = expectedRulesetIndexesMap.get(rulesetId);
+    const expectedRulesetRules = getSchemaNormalizedRules(
+      extensionTestWrapper,
+      expectedRulesets[rulesetId]
+    );
+    const actualData = dnrExtData.staticRulesets.get(rulesetId);
+    equal(
+      actualData.idx,
+      expectedRulesetIdx,
+      `Got the expected ruleset index for ruleset id ${rulesetId}`
+    );
+
+    // Asserting an entire array of rules all at once will produce
+    // a big enough output to don't be immediately useful to investigate
+    // failures, asserting each rule individually would produce more
+    // readable assertion failure logs.
+    const assertRuleAtIdx = ruleIdx => {
+      const actualRule = actualData.rules[ruleIdx];
+      const expectedRule = expectedRulesetRules[ruleIdx];
+      Assert.deepEqual(
+        actualRule,
+        expectedRule,
+        `Got the expected rule at index ${ruleIdx} for ruleset id "${rulesetId}"`
+      );
+      Assert.equal(
+        actualRule.constructor.name,
+        "Rule",
+        `Expect rule at index ${ruleIdx} to be an instance of the Rule class`
+      );
+      if (expectedRule.condition.regexFilter) {
+        const compiledRegexFilter =
+          actualData.rules[ruleIdx].condition.getCompiledRegexFilter();
+        Assert.equal(
+          compiledRegexFilter?.constructor.name,
+          "RegExp",
+          `Expect rule ${ruleIdx} condition.getCompiledRegexFilter() to return a compiled regexp filter`
+        );
+        Assert.equal(
+          compiledRegexFilter?.source,
+          new RegExp(expectedRule.condition.regexFilter).source,
+          `Expect rule ${ruleIdx} condition's compiled RegExp source to match the regexFilter string`
+        );
+        Assert.equal(
+          compiledRegexFilter?.ignoreCase,
+          !expectedRule.condition.isUrlFilterCaseSensitive,
+          `Expect rule ${ruleIdx} conditions's compiled RegExp ignoreCase to be set based on condition.isUrlFilterCaseSensitive`
+        );
+      }
+    };
+
+    // Some tests may be using a big enough number of rules that
+    // the assertiongs would be producing a huge amount of log spam,
+    // and so for those tests we only explicitly assert the first
+    // and last rule and that the total amount of rules matches the
+    // expected number of rules (there are still other tests explicitly
+    // asserting all loaded rules).
+    if (assertIndividualRules) {
+      info(`Verify each individual rule loaded for ruleset id "${rulesetId}"`);
+      for (let ruleIdx = 0; ruleIdx < expectedRulesetRules.length; ruleIdx++) {
+        assertRuleAtIdx(ruleIdx);
+      }
+    } else if (expectedRulesetRules.length) {
+      // NOTE: Only asserting the first and last rule also helps to speed up
+      // the test is some slower builds when the number of expected rules is
+      // big enough (e.g. the test task verifying the enforced rule count limits
+      // was timing out in tsan build because asserting all indidual rules was
+      // taking long enough and the event page was being suspended on the idle
+      // timeout by the time we did run all these assertion and proceeding with
+      // the rest of the test task assertions), we still confirm that the total
+      // number of expected vs actual rules also matches right after these
+      // assertions.
+      info(
+        `Verify the first and last rules loaded for ruleset id "${rulesetId}"`
+      );
+      const lastExpectedRuleIdx = expectedRulesetRules.length - 1;
+      for (const ruleIdx of [0, lastExpectedRuleIdx]) {
+        assertRuleAtIdx(ruleIdx);
+      }
+    }
+
+    equal(
+      actualData.rules.length,
+      expectedRulesetRules.length,
+      `Got the expected number of rules loaded for ruleset id "${rulesetId}"`
+    );
+  }
+};
diff --git a/toolkit/components/extensions/test/xpcshell/head_e10s.js b/toolkit/components/extensions/test/xpcshell/head_e10s.js
new file mode 100644
index 0000000000..196afae7c9
--- /dev/null
+++ b/toolkit/components/extensions/test/xpcshell/head_e10s.js
@@ -0,0 +1,8 @@
+"use strict";
+
+/* globals ExtensionTestUtils */
+
+// xpcshell disables e10s by default. Turn it on.
+Services.prefs.setBoolPref("browser.tabs.remote.autostart", true);
+
+ExtensionTestUtils.remoteContentScripts = true;
diff --git a/toolkit/components/extensions/test/xpcshell/head_legacy_ep.js b/toolkit/components/extensions/test/xpcshell/head_legacy_ep.js
new file mode 100644
index 0000000000..8bb39c0452
--- /dev/null
+++ b/toolkit/components/extensions/test/xpcshell/head_legacy_ep.js
@@ -0,0 +1,13 @@
+"use strict";
+
+// Bug 1646182: Test the legacy ExtensionPermission backend until we fully
+// migrate to rkv
+
+{
+  const { ExtensionPermissions } = ChromeUtils.importESModule(
+    "resource://gre/modules/ExtensionPermissions.sys.mjs"
+  );
+
+  ExtensionPermissions._useLegacyStorageBackend = true;
+  ExtensionPermissions._uninit();
+}
diff --git a/toolkit/components/extensions/test/xpcshell/head_native_messaging.js b/toolkit/components/extensions/test/xpcshell/head_native_messaging.js
new file mode 100644
index 0000000000..32b6948033
--- /dev/null
+++ b/toolkit/components/extensions/test/xpcshell/head_native_messaging.js
@@ -0,0 +1,152 @@
+/* -*- Mode: indent-tabs-mode: nil; js-indent-level: 2 -*- */
+/* vim: set sts=2 sw=2 et tw=80: */
+"use strict";
+
+/* globals AppConstants, FileUtils */
+/* exported getSubprocessCount, setupHosts, waitForSubprocessExit */
+
+ChromeUtils.defineESModuleGetters(this, {
+  MockRegistry: "resource://testing-common/MockRegistry.sys.mjs",
+});
+if (AppConstants.platform == "win") {
+  ChromeUtils.defineESModuleGetters(this, {
+    SubprocessImpl: "resource://gre/modules/subprocess/subprocess_win.sys.mjs",
+  });
+} else {
+  ChromeUtils.defineESModuleGetters(this, {
+    SubprocessImpl: "resource://gre/modules/subprocess/subprocess_unix.sys.mjs",
+  });
+}
+
+const { Subprocess } = ChromeUtils.importESModule(
+  "resource://gre/modules/Subprocess.sys.mjs"
+);
+
+// It's important that we use a space in this directory name to make sure we
+// correctly handle executing batch files with spaces in their path.
+let tmpDir = FileUtils.getDir("TmpD", ["Native Messaging"]);
+tmpDir.createUnique(Ci.nsIFile.DIRECTORY_TYPE, FileUtils.PERMS_DIRECTORY);
+
+const TYPE_SLUG =
+  AppConstants.platform === "linux"
+    ? "native-messaging-hosts"
+    : "NativeMessagingHosts";
+
+add_setup(async function setup() {
+  await IOUtils.makeDirectory(PathUtils.join(tmpDir.path, TYPE_SLUG));
+});
+
+registerCleanupFunction(async () => {
+  await IOUtils.remove(tmpDir.path, { recursive: true });
+});
+
+function getPath(filename) {
+  return PathUtils.join(tmpDir.path, TYPE_SLUG, filename);
+}
+
+const ID = "native@tests.mozilla.org";
+
+async function setupHosts(scripts) {
+  const pythonPath = await Subprocess.pathSearch(Services.env.get("PYTHON"));
+
+  async function writeManifest(script, scriptPath, path) {
+    let body = `#!${pythonPath} -u\n${script.script}`;
+
+    await IOUtils.writeUTF8(scriptPath, body);
+    await IOUtils.setPermissions(scriptPath, 0o755);
+
+    let manifest = {
+      name: script.name,
+      description: script.description,
+      path,
+      type: "stdio",
+      allowed_extensions: [ID],
+    };
+
+    // Optionally, allow the test to change the manifest before writing.
+    script._hookModifyManifest?.(manifest);
+
+    let manifestPath = getPath(`${script.name}.json`);
+    await IOUtils.writeJSON(manifestPath, manifest);
+
+    return manifestPath;
+  }
+
+  switch (AppConstants.platform) {
+    case "macosx":
+    case "linux":
+      let dirProvider = {
+        getFile(property) {
+          if (property == "XREUserNativeManifests") {
+            return tmpDir.clone();
+          } else if (property == "XRESysNativeManifests") {
+            return tmpDir.clone();
+          }
+          return null;
+        },
+      };
+
+      Services.dirsvc.registerProvider(dirProvider);
+      registerCleanupFunction(() => {
+        Services.dirsvc.unregisterProvider(dirProvider);
+      });
+
+      for (let script of scripts) {
+        let path = getPath(`${script.name}.py`);
+
+        await writeManifest(script, path, path);
+      }
+      break;
+
+    case "win":
+      const REGKEY = String.raw`Software\Mozilla\NativeMessagingHosts`;
+
+      let registry = new MockRegistry();
+      registerCleanupFunction(() => {
+        registry.shutdown();
+      });
+
+      for (let script of scripts) {
+        let { scriptExtension = "bat" } = script;
+
+        // It's important that we use a space in this filename. See directory
+        // name comment above.
+        let batPath = getPath(`batch ${script.name}.${scriptExtension}`);
+        let scriptPath = getPath(`${script.name}.py`);
+
+        let batBody = `@ECHO OFF\n${pythonPath} -u "${scriptPath}" %*\n`;
+        await IOUtils.writeUTF8(batPath, batBody);
+
+        let manifestPath = await writeManifest(script, scriptPath, batPath);
+
+        registry.setValue(
+          Ci.nsIWindowsRegKey.ROOT_KEY_CURRENT_USER,
+          `${REGKEY}\\${script.name}`,
+          "",
+          manifestPath
+        );
+      }
+      break;
+
+    default:
+      ok(
+        false,
+        `Native messaging is not supported on ${AppConstants.platform}`
+      );
+  }
+}
+
+function getSubprocessCount() {
+  return SubprocessImpl.Process.getWorker()
+    .call("getProcesses", [])
+    .then(result => result.size);
+}
+function waitForSubprocessExit() {
+  return SubprocessImpl.Process.getWorker()
+    .call("waitForNoProcesses", [])
+    .then(() => {
+      // Return to the main event loop to give IO handlers enough time to consume
+      // their remaining buffered input.
+      return new Promise(resolve => setTimeout(resolve, 0));
+    });
+}
diff --git a/toolkit/components/extensions/test/xpcshell/head_remote.js b/toolkit/components/extensions/test/xpcshell/head_remote.js
new file mode 100644
index 0000000000..f9c31144c9
--- /dev/null
+++ b/toolkit/components/extensions/test/xpcshell/head_remote.js
@@ -0,0 +1,7 @@
+"use strict";
+
+Services.prefs.setBoolPref("extensions.webextensions.remote", true);
+Services.prefs.setIntPref("dom.ipc.keepProcessesAlive.extension", 1);
+
+/* globals testEnv */
+testEnv.expectRemote = true; // tested in head_test.js
diff --git a/toolkit/components/extensions/test/xpcshell/head_schemas.js b/toolkit/components/extensions/test/xpcshell/head_schemas.js
new file mode 100644
index 0000000000..94af4a631a
--- /dev/null
+++ b/toolkit/components/extensions/test/xpcshell/head_schemas.js
@@ -0,0 +1,129 @@
+"use strict";
+
+/* exported Schemas, LocalAPIImplementation, SchemaAPIInterface, getContextWrapper */
+
+const { Schemas } = ChromeUtils.importESModule(
+  "resource://gre/modules/Schemas.sys.mjs"
+);
+
+const { ExtensionCommon } = ChromeUtils.importESModule(
+  "resource://gre/modules/ExtensionCommon.sys.mjs"
+);
+
+let { LocalAPIImplementation, SchemaAPIInterface } = ExtensionCommon;
+
+const contextCloneScope = this;
+
+class TallyingAPIImplementation extends SchemaAPIInterface {
+  constructor(context, namespace, name) {
+    super();
+    this.namespace = namespace;
+    this.name = name;
+    this.context = context;
+  }
+
+  callFunction(args) {
+    this.context.tally("call", this.namespace, this.name, args);
+    if (this.name === "sub_foo") {
+      return 13;
+    }
+  }
+
+  callFunctionNoReturn(args) {
+    this.context.tally("call", this.namespace, this.name, args);
+  }
+
+  getProperty() {
+    this.context.tally("get", this.namespace, this.name);
+  }
+
+  setProperty(value) {
+    this.context.tally("set", this.namespace, this.name, value);
+  }
+
+  addListener(listener, args) {
+    this.context.tally("addListener", this.namespace, this.name, [
+      listener,
+      args,
+    ]);
+  }
+
+  removeListener(listener) {
+    this.context.tally("removeListener", this.namespace, this.name, [listener]);
+  }
+
+  hasListener(listener) {
+    this.context.tally("hasListener", this.namespace, this.name, [listener]);
+  }
+}
+
+function getContextWrapper(manifestVersion = 2) {
+  return {
+    url: "moz-extension://b66e3509-cdb3-44f6-8eb8-c8b39b3a1d27/",
+
+    cloneScope: contextCloneScope,
+
+    manifestVersion,
+
+    permissions: new Set(),
+    tallied: null,
+    talliedErrors: [],
+
+    tally(kind, ns, name, args) {
+      this.tallied = [kind, ns, name, args];
+    },
+
+    verify(...args) {
+      Assert.equal(JSON.stringify(this.tallied), JSON.stringify(args));
+      this.tallied = null;
+    },
+
+    checkErrors(errors) {
+      let { talliedErrors } = this;
+      Assert.equal(
+        talliedErrors.length,
+        errors.length,
+        "Got expected number of errors"
+      );
+      for (let [i, error] of errors.entries()) {
+        Assert.ok(
+          i in talliedErrors && String(talliedErrors[i]).includes(error),
+          `${JSON.stringify(error)} is a substring of error ${JSON.stringify(
+            talliedErrors[i]
+          )}`
+        );
+      }
+
+      talliedErrors.length = 0;
+    },
+
+    checkLoadURL(url) {
+      return !url.startsWith("chrome:");
+    },
+
+    preprocessors: {
+      localize(value, context) {
+        return value.replace(
+          /__MSG_(.*?)__/g,
+          (m0, m1) => `${m1.toUpperCase()}`
+        );
+      },
+    },
+
+    logError(message) {
+      this.talliedErrors.push(message);
+    },
+
+    hasPermission(permission) {
+      return this.permissions.has(permission);
+    },
+
+    shouldInject(ns, name, allowedContexts) {
+      return name != "do-not-inject";
+    },
+
+    getImplementation(namespace, name) {
+      return new TallyingAPIImplementation(this, namespace, name);
+    },
+  };
+}
diff --git a/toolkit/components/extensions/test/xpcshell/head_service_worker.js b/toolkit/components/extensions/test/xpcshell/head_service_worker.js
new file mode 100644
index 0000000000..f83250f84c
--- /dev/null
+++ b/toolkit/components/extensions/test/xpcshell/head_service_worker.js
@@ -0,0 +1,158 @@
+/* -*- Mode: indent-tabs-mode: nil; js-indent-level: 2 -*- */
+/* vim: set sts=2 sw=2 et tw=80: */
+"use strict";
+
+/* exported TestWorkerWatcher */
+
+ChromeUtils.defineESModuleGetters(this, {
+  ExtensionCommon: "resource://gre/modules/ExtensionCommon.sys.mjs",
+});
+
+// Ensure that the profile-after-change message has been notified,
+// so that ServiceWokerRegistrar is going to be initialized,
+// otherwise tests using a background service worker will fail.
+// in debug builds because of an assertion failure triggered
+// by ServiceWorkerRegistrar.cpp (due to not being initialized
+// automatically on startup as in a real Firefox instance).
+Services.obs.notifyObservers(
+  null,
+  "profile-after-change",
+  "force-serviceworkerrestart-init"
+);
+
+// A test utility class used in the test case to watch for a given extension
+// service worker being spawned and terminated (using the same kind of Firefox DevTools
+// internals that about:debugging is using to watch the workers activity).
+//
+// NOTE: this helper class does also depends from the two jsm files where the
+// Parent and Child TestWorkerWatcher actor is defined:
+//
+// - data/TestWorkerWatcherParent.jsm
+// - data/TestWorkerWatcherChild.jsm
+class TestWorkerWatcher extends ExtensionCommon.EventEmitter {
+  JS_ACTOR_NAME = "TestWorkerWatcher";
+
+  constructor(dataRelPath = "./data") {
+    super();
+    this.dataRelPath = dataRelPath;
+    this.extensionProcess = null;
+    this.extensionProcessActor = null;
+    this.registerProcessActor();
+    this.getAndWatchExtensionProcess();
+    // Observer child process creation and shutdown if the extension
+    // are meant to run in a child process.
+    Services.obs.addObserver(this, "ipc:content-created");
+    Services.obs.addObserver(this, "ipc:content-shutdown");
+  }
+
+  async destroy() {
+    await this.stopWatchingWorkers();
+    ChromeUtils.unregisterProcessActor(this.JS_ACTOR_NAME);
+  }
+
+  get swm() {
+    return Cc["@mozilla.org/serviceworkers/manager;1"].getService(
+      Ci.nsIServiceWorkerManager
+    );
+  }
+
+  getRegistration(extension) {
+    return this.swm.getRegistrationByPrincipal(
+      extension.extension.principal,
+      extension.extension.principal.spec
+    );
+  }
+
+  watchExtensionServiceWorker(extension) {
+    // These events are emitted by TestWatchExtensionWorkersParent.
+    const promiseWorkerSpawned = this.waitForEvent("worker-spawned", extension);
+    const promiseWorkerTerminated = this.waitForEvent(
+      "worker-terminated",
+      extension
+    );
+
+    // Terminate the worker sooner by settng the idle_timeout to 0,
+    // then clear the pref as soon as the worker has been terminated.
+    const terminate = () => {
+      promiseWorkerTerminated.then(() => {
+        Services.prefs.clearUserPref("dom.serviceWorkers.idle_timeout");
+      });
+      Services.prefs.setIntPref("dom.serviceWorkers.idle_timeout", 0);
+      const swReg = this.getRegistration(extension);
+      // If the active worker is already active, we have to make sure the new value
+      // set on the idle_timeout pref is picked up by ServiceWorkerPrivate::ResetIdleTimeout.
+      swReg.activeWorker?.attachDebugger();
+      swReg.activeWorker?.detachDebugger();
+      return promiseWorkerTerminated;
+    };
+
+    return {
+      promiseWorkerSpawned,
+      promiseWorkerTerminated,
+      terminate,
+    };
+  }
+
+  // Methods only used internally.
+
+  waitForEvent(event, extension) {
+    return new Promise(resolve => {
+      const listener = (_eventName, data) => {
+        if (!data.workerUrl.startsWith(extension.extension?.principal.spec)) {
+          return;
+        }
+        this.off(event, listener);
+        resolve(data);
+      };
+
+      this.on(event, listener);
+    });
+  }
+
+  registerProcessActor() {
+    const { JS_ACTOR_NAME } = this;
+    ChromeUtils.registerProcessActor(JS_ACTOR_NAME, {
+      parent: {
+        moduleURI: `resource://testing-common/${JS_ACTOR_NAME}Parent.jsm`,
+      },
+      child: {
+        moduleURI: `resource://testing-common/${JS_ACTOR_NAME}Child.jsm`,
+      },
+    });
+  }
+
+  startWatchingWorkers() {
+    if (!this.extensionProcessActor) {
+      return;
+    }
+    this.extensionProcessActor.eventEmitter = this;
+    return this.extensionProcessActor.sendQuery("Test:StartWatchingWorkers");
+  }
+
+  stopWatchingWorkers() {
+    if (!this.extensionProcessActor) {
+      return;
+    }
+    this.extensionProcessActor.eventEmitter = null;
+    return this.extensionProcessActor.sendQuery("Test:StopWatchingWorkers");
+  }
+
+  getAndWatchExtensionProcess() {
+    const extensionProcess = ChromeUtils.getAllDOMProcesses().find(p => {
+      return p.remoteType === "extension";
+    });
+    if (extensionProcess !== this.extensionProcess) {
+      this.extensionProcess = extensionProcess;
+      this.extensionProcessActor = extensionProcess
+        ? extensionProcess.getActor(this.JS_ACTOR_NAME)
+        : null;
+      this.startWatchingWorkers();
+    }
+  }
+
+  observe(subject, topic, childIDString) {
+    // Keep the watched process and related test child process actor updated
+    // when a process is created or destroyed.
+    this.getAndWatchExtensionProcess();
+  }
+}
diff --git a/toolkit/components/extensions/test/xpcshell/head_storage.js b/toolkit/components/extensions/test/xpcshell/head_storage.js
new file mode 100644
index 0000000000..139c84bf8d
--- /dev/null
+++ b/toolkit/components/extensions/test/xpcshell/head_storage.js
@@ -0,0 +1,1400 @@
+/* -*- Mode: indent-tabs-mode: nil; js-indent-level: 2 -*- */
+/* vim: set sts=2 sw=2 et tw=80: */
+"use strict";
+
+/* import-globals-from head.js */
+
+const STORAGE_SYNC_PREF = "webextensions.storage.sync.enabled";
+
+// Test implementations and utility functions that are used against multiple
+// storage areas (eg, a test which is run against browser.storage.local and
+// browser.storage.sync, or a test against browser.storage.sync but needs to
+// be run against both the kinto and rust implementations.)
+
+/**
+ * Utility function to ensure that all supported APIs for getting are
+ * tested.
+ *
+ * @param {string} areaName
+ *        either "local" or "sync" according to what we want to test
+ * @param {string} prop
+ *        "key" to look up using the storage API
+ * @param {object} value
+ *        "value" to compare against
+ */
+async function checkGetImpl(areaName, prop, value) {
+  let storage = browser.storage[areaName];
+
+  let data = await storage.get();
+  browser.test.assertEq(
+    value,
+    data[prop],
+    `unspecified getter worked for ${prop} in ${areaName}`
+  );
+
+  data = await storage.get(null);
+  browser.test.assertEq(
+    value,
+    data[prop],
+    `null getter worked for ${prop} in ${areaName}`
+  );
+
+  data = await storage.get(prop);
+  browser.test.assertEq(
+    value,
+    data[prop],
+    `string getter worked for ${prop} in ${areaName}`
+  );
+  browser.test.assertEq(
+    Object.keys(data).length,
+    1,
+    `string getter should return an object with a single property`
+  );
+
+  data = await storage.get([prop]);
+  browser.test.assertEq(
+    value,
+    data[prop],
+    `array getter worked for ${prop} in ${areaName}`
+  );
+  browser.test.assertEq(
+    Object.keys(data).length,
+    1,
+    `array getter with a single key should return an object with a single property`
+  );
+
+  data = await storage.get({ [prop]: undefined });
+  browser.test.assertEq(
+    value,
+    data[prop],
+    `object getter worked for ${prop} in ${areaName}`
+  );
+  browser.test.assertEq(
+    Object.keys(data).length,
+    1,
+    `object getter with a single key should return an object with a single property`
+  );
+}
+
+function test_config_flag_needed() {
+  async function testFn() {
+    function background() {
+      let promises = [];
+      let apiTests = [
+        { method: "get", args: ["foo"] },
+        { method: "set", args: [{ foo: "bar" }] },
+        { method: "remove", args: ["foo"] },
+        { method: "clear", args: [] },
+      ];
+      apiTests.forEach(testDef => {
+        promises.push(
+          browser.test.assertRejects(
+            browser.storage.sync[testDef.method](...testDef.args),
+            "Please set webextensions.storage.sync.enabled to true in about:config",
+            `storage.sync.${testDef.method} is behind a flag`
+          )
+        );
+      });
+
+      Promise.all(promises).then(() => browser.test.notifyPass("flag needed"));
+    }
+
+    ok(
+      !Services.prefs.getBoolPref(STORAGE_SYNC_PREF, false),
+      "The `${STORAGE_SYNC_PREF}` should be set to false"
+    );
+
+    let extension = ExtensionTestUtils.loadExtension({
+      manifest: {
+        permissions: ["storage"],
+      },
+      background,
+    });
+
+    await extension.startup();
+    await extension.awaitFinish("flag needed");
+    await extension.unload();
+  }
+
+  return runWithPrefs([[STORAGE_SYNC_PREF, false]], testFn);
+}
+
+async function test_storage_after_reload(areaName, { expectPersistency }) {
+  // Just some random extension ID that we can re-use
+  const extensionId = "my-extension-id@1";
+
+  function loadExtension() {
+    async function background(areaName) {
+      browser.test.sendMessage(
+        "initialItems",
+        await browser.storage[areaName].get(null)
+      );
+      await browser.storage[areaName].set({ a: "b" });
+      browser.test.notifyPass("set-works");
+    }
+
+    return ExtensionTestUtils.loadExtension({
+      manifest: {
+        browser_specific_settings: { gecko: { id: extensionId } },
+        permissions: ["storage"],
+      },
+      background: `(${background})("${areaName}")`,
+    });
+  }
+
+  let extension1 = loadExtension();
+  await extension1.startup();
+
+  Assert.deepEqual(
+    await extension1.awaitMessage("initialItems"),
+    {},
+    "No stored items at first"
+  );
+
+  await extension1.awaitFinish("set-works");
+  await extension1.unload();
+
+  let extension2 = loadExtension();
+  await extension2.startup();
+
+  Assert.deepEqual(
+    await extension2.awaitMessage("initialItems"),
+    expectPersistency ? { a: "b" } : {},
+    `Expect ${areaName} stored items ${
+      expectPersistency ? "to" : "not"
+    } be available after restart`
+  );
+
+  await extension2.awaitFinish("set-works");
+  await extension2.unload();
+}
+
+function test_sync_reloading_extensions_works() {
+  return runWithPrefs([[STORAGE_SYNC_PREF, true]], async () => {
+    ok(
+      Services.prefs.getBoolPref(STORAGE_SYNC_PREF, false),
+      "The `${STORAGE_SYNC_PREF}` should be set to true"
+    );
+
+    await test_storage_after_reload("sync", { expectPersistency: true });
+  });
+}
+
+async function test_background_page_storage(testAreaName) {
+  async function backgroundScript(checkGet) {
+    let globalChanges, gResolve;
+    function clearGlobalChanges() {
+      globalChanges = new Promise(resolve => {
+        gResolve = resolve;
+      });
+    }
+    clearGlobalChanges();
+    let expectedAreaName;
+
+    browser.storage.onChanged.addListener((changes, areaName) => {
+      browser.test.assertEq(
+        expectedAreaName,
+        areaName,
+        "Expected area name received by listener"
+      );
+      gResolve(changes);
+    });
+
+    async function checkChanges(areaName, changes, message) {
+      function checkSub(obj1, obj2) {
+        for (let prop in obj1) {
+          browser.test.assertTrue(
+            obj1[prop] !== undefined,
+            `checkChanges ${areaName} ${prop} is missing (${message})`
+          );
+          browser.test.assertTrue(
+            obj2[prop] !== undefined,
+            `checkChanges ${areaName} ${prop} is missing (${message})`
+          );
+          browser.test.assertEq(
+            obj1[prop].oldValue,
+            obj2[prop].oldValue,
+            `checkChanges ${areaName} ${prop} old (${message})`
+          );
+          browser.test.assertEq(
+            obj1[prop].newValue,
+            obj2[prop].newValue,
+            `checkChanges ${areaName} ${prop} new (${message})`
+          );
+        }
+      }
+
+      const recentChanges = await globalChanges;
+      checkSub(changes, recentChanges);
+      checkSub(recentChanges, changes);
+      clearGlobalChanges();
+    }
+
+    // Regression test for https://bugzilla.mozilla.org/show_bug.cgi?id=1645598
+    async function testNonExistingKeys(storage, storageAreaDesc) {
+      let data = await storage.get({ test6: 6 });
+      browser.test.assertEq(
+        `{"test6":6}`,
+        JSON.stringify(data),
+        `Use default value when not stored for ${storageAreaDesc}`
+      );
+
+      data = await storage.get({ test6: null });
+      browser.test.assertEq(
+        `{"test6":null}`,
+        JSON.stringify(data),
+        `Use default value, even if null for ${storageAreaDesc}`
+      );
+
+      data = await storage.get("test6");
+      browser.test.assertEq(
+        `{}`,
+        JSON.stringify(data),
+        `Empty result if key is not found for ${storageAreaDesc}`
+      );
+
+      data = await storage.get(["test6", "test7"]);
+      browser.test.assertEq(
+        `{}`,
+        JSON.stringify(data),
+        `Empty result if list of keys is not found for ${storageAreaDesc}`
+      );
+    }
+
+    async function testFalseyValues(areaName) {
+      let storage = browser.storage[areaName];
+      const dataInitial = {
+        "test-falsey-value-bool": false,
+        "test-falsey-value-string": "",
+        "test-falsey-value-number": 0,
+      };
+      const dataUpdate = {
+        "test-falsey-value-bool": true,
+        "test-falsey-value-string": "non-empty-string",
+        "test-falsey-value-number": 10,
+      };
+
+      // Compute the expected changes.
+      const onSetInitial = {
+        "test-falsey-value-bool": { newValue: false },
+        "test-falsey-value-string": { newValue: "" },
+        "test-falsey-value-number": { newValue: 0 },
+      };
+      const onRemovedFalsey = {
+        "test-falsey-value-bool": { oldValue: false },
+        "test-falsey-value-string": { oldValue: "" },
+        "test-falsey-value-number": { oldValue: 0 },
+      };
+      const onUpdatedFalsey = {
+        "test-falsey-value-bool": { newValue: true, oldValue: false },
+        "test-falsey-value-string": {
+          newValue: "non-empty-string",
+          oldValue: "",
+        },
+        "test-falsey-value-number": { newValue: 10, oldValue: 0 },
+      };
+      const keys = Object.keys(dataInitial);
+
+      // Test on removing falsey values.
+      await storage.set(dataInitial);
+      await checkChanges(areaName, onSetInitial, "set falsey values");
+      await storage.remove(keys);
+      await checkChanges(areaName, onRemovedFalsey, "remove falsey value");
+
+      // Test on updating falsey values.
+      await storage.set(dataInitial);
+      await checkChanges(areaName, onSetInitial, "set falsey values");
+      await storage.set(dataUpdate);
+      await checkChanges(areaName, onUpdatedFalsey, "set non-falsey values");
+
+      // Clear the storage state.
+      await testNonExistingKeys(storage, `${areaName} before clearing`);
+      await storage.clear();
+      await testNonExistingKeys(storage, `${areaName} after clearing`);
+      await globalChanges;
+      clearGlobalChanges();
+    }
+
+    function CustomObj() {
+      this.testKey1 = "testValue1";
+    }
+
+    CustomObj.prototype.toString = function () {
+      return '{"testKey2":"testValue2"}';
+    };
+
+    CustomObj.prototype.toJSON = function customObjToJSON() {
+      return { testKey1: "testValue3" };
+    };
+
+    /* eslint-disable dot-notation */
+    async function runTests(areaName) {
+      expectedAreaName = areaName;
+      let storage = browser.storage[areaName];
+      // Set some data and then test getters.
+      try {
+        await storage.set({ "test-prop1": "value1", "test-prop2": "value2" });
+        await checkChanges(
+          areaName,
+          {
+            "test-prop1": { newValue: "value1" },
+            "test-prop2": { newValue: "value2" },
+          },
+          "set (a)"
+        );
+
+        await checkGet(areaName, "test-prop1", "value1");
+        await checkGet(areaName, "test-prop2", "value2");
+
+        let data = await storage.get({
+          "test-prop1": undefined,
+          "test-prop2": undefined,
+          other: "default",
+        });
+        browser.test.assertEq(
+          "value1",
+          data["test-prop1"],
+          "prop1 correct (a)"
+        );
+        browser.test.assertEq(
+          "value2",
+          data["test-prop2"],
+          "prop2 correct (a)"
+        );
+        browser.test.assertEq("default", data["other"], "other correct");
+
+        data = await storage.get(["test-prop1", "test-prop2", "other"]);
+        browser.test.assertEq(
+          "value1",
+          data["test-prop1"],
+          "prop1 correct (b)"
+        );
+        browser.test.assertEq(
+          "value2",
+          data["test-prop2"],
+          "prop2 correct (b)"
+        );
+        browser.test.assertFalse("other" in data, "other correct");
+
+        // Remove data in various ways.
+        await storage.remove("test-prop1");
+        await checkChanges(
+          areaName,
+          { "test-prop1": { oldValue: "value1" } },
+          "remove string"
+        );
+
+        data = await storage.get(["test-prop1", "test-prop2"]);
+        browser.test.assertFalse(
+          "test-prop1" in data,
+          "prop1 absent (remove string)"
+        );
+        browser.test.assertTrue(
+          "test-prop2" in data,
+          "prop2 present (remove string)"
+        );
+
+        await storage.set({ "test-prop1": "value1" });
+        await checkChanges(
+          areaName,
+          { "test-prop1": { newValue: "value1" } },
+          "set (c)"
+        );
+
+        data = await storage.get(["test-prop1", "test-prop2"]);
+        browser.test.assertEq(
+          data["test-prop1"],
+          "value1",
+          "prop1 correct (c)"
+        );
+        browser.test.assertEq(
+          data["test-prop2"],
+          "value2",
+          "prop2 correct (c)"
+        );
+
+        await storage.remove(["test-prop1", "test-prop2"]);
+        await checkChanges(
+          areaName,
+          {
+            "test-prop1": { oldValue: "value1" },
+            "test-prop2": { oldValue: "value2" },
+          },
+          "remove array"
+        );
+
+        data = await storage.get(["test-prop1", "test-prop2"]);
+        browser.test.assertFalse(
+          "test-prop1" in data,
+          "prop1 absent (remove array)"
+        );
+        browser.test.assertFalse(
+          "test-prop2" in data,
+          "prop2 absent (remove array)"
+        );
+
+        await testFalseyValues(areaName);
+
+        // test storage.clear
+        await storage.set({ "test-prop1": "value1", "test-prop2": "value2" });
+        // Make sure that set() handler happened before we clear the
+        // promise again.
+        await globalChanges;
+
+        clearGlobalChanges();
+        await storage.clear();
+
+        await checkChanges(
+          areaName,
+          {
+            "test-prop1": { oldValue: "value1" },
+            "test-prop2": { oldValue: "value2" },
+          },
+          "clear"
+        );
+        data = await storage.get(["test-prop1", "test-prop2"]);
+        browser.test.assertFalse("test-prop1" in data, "prop1 absent (clear)");
+        browser.test.assertFalse("test-prop2" in data, "prop2 absent (clear)");
+
+        // Make sure we can store complex JSON data.
+        // known previous values
+        await storage.set({ "test-prop1": "value1", "test-prop2": "value2" });
+
+        // Make sure the set() handler landed.
+        await globalChanges;
+
+        let date = new Date(0);
+
+        clearGlobalChanges();
+        await storage.set({
+          "test-prop1": {
+            str: "hello",
+            bool: true,
+            null: null,
+            undef: undefined,
+            obj: {},
+            nestedObj: {
+              testKey: {},
+            },
+            intKeyObj: {
+              4: "testValue1",
+              3: "testValue2",
+              99: "testValue3",
+            },
+            floatKeyObj: {
+              1.4: "testValue1",
+              5.5: "testValue2",
+            },
+            customObj: new CustomObj(),
+            arr: [1, 2],
+            nestedArr: [1, [2, 3]],
+            date,
+            regexp: /regexp/,
+          },
+        });
+
+        await browser.test.assertRejects(
+          storage.set({
+            window,
+          }),
+          /DataCloneError|cyclic object value/
+        );
+
+        await browser.test.assertRejects(
+          storage.set({ "test-prop2": function func() {} }),
+          /DataCloneError/
+        );
+
+        const recentChanges = await globalChanges;
+
+        browser.test.assertEq(
+          "value1",
+          recentChanges["test-prop1"].oldValue,
+          "oldValue correct"
+        );
+        browser.test.assertEq(
+          "object",
+          typeof recentChanges["test-prop1"].newValue,
+          "newValue is obj"
+        );
+        clearGlobalChanges();
+
+        data = await storage.get({
+          "test-prop1": undefined,
+          "test-prop2": undefined,
+        });
+        let obj = data["test-prop1"];
+
+        browser.test.assertEq(
+          "object",
+          typeof obj.customObj,
+          "custom object part correct"
+        );
+        browser.test.assertEq(
+          1,
+          Object.keys(obj.customObj).length,
+          "customObj keys correct"
+        );
+
+        if (areaName === "local" || areaName === "session") {
+          browser.test.assertEq(
+            String(date),
+            String(obj.date),
+            "date part correct"
+          );
+          browser.test.assertEq(
+            "/regexp/",
+            obj.regexp.toString(),
+            "regexp part correct"
+          );
+          // storage.local and .session don't use toJSON().
+          browser.test.assertEq(
+            "testValue1",
+            obj.customObj.testKey1,
+            "customObj keys correct"
+          );
+        } else {
+          browser.test.assertEq(
+            "1970-01-01T00:00:00.000Z",
+            String(obj.date),
+            "date part correct"
+          );
+
+          browser.test.assertEq(
+            "object",
+            typeof obj.regexp,
+            "regexp part is an object"
+          );
+          browser.test.assertEq(
+            0,
+            Object.keys(obj.regexp).length,
+            "regexp part is an empty object"
+          );
+          // storage.sync does call toJSON
+          browser.test.assertEq(
+            "testValue3",
+            obj.customObj.testKey1,
+            "customObj keys correct"
+          );
+        }
+
+        browser.test.assertEq("hello", obj.str, "string part correct");
+        browser.test.assertEq(true, obj.bool, "bool part correct");
+        browser.test.assertEq(null, obj.null, "null part correct");
+        browser.test.assertEq(undefined, obj.undef, "undefined part correct");
+        browser.test.assertEq(undefined, obj.window, "window part correct");
+        browser.test.assertEq("object", typeof obj.obj, "object part correct");
+        browser.test.assertEq(
+          "object",
+          typeof obj.nestedObj,
+          "nested object part correct"
+        );
+        browser.test.assertEq(
+          "object",
+          typeof obj.nestedObj.testKey,
+          "nestedObj.testKey part correct"
+        );
+        browser.test.assertEq(
+          "object",
+          typeof obj.intKeyObj,
+          "int key object part correct"
+        );
+        browser.test.assertEq(
+          "testValue1",
+          obj.intKeyObj[4],
+          "intKeyObj[4] part correct"
+        );
+        browser.test.assertEq(
+          "testValue2",
+          obj.intKeyObj[3],
+          "intKeyObj[3] part correct"
+        );
+        browser.test.assertEq(
+          "testValue3",
+          obj.intKeyObj[99],
+          "intKeyObj[99] part correct"
+        );
+        browser.test.assertEq(
+          "object",
+          typeof obj.floatKeyObj,
+          "float key object part correct"
+        );
+        browser.test.assertEq(
+          "testValue1",
+          obj.floatKeyObj[1.4],
+          "floatKeyObj[1.4] part correct"
+        );
+        browser.test.assertEq(
+          "testValue2",
+          obj.floatKeyObj[5.5],
+          "floatKeyObj[5.5] part correct"
+        );
+
+        browser.test.assertTrue(Array.isArray(obj.arr), "array part present");
+        browser.test.assertEq(1, obj.arr[0], "arr[0] part correct");
+        browser.test.assertEq(2, obj.arr[1], "arr[1] part correct");
+        browser.test.assertEq(2, obj.arr.length, "arr.length part correct");
+        browser.test.assertTrue(
+          Array.isArray(obj.nestedArr),
+          "nested array part present"
+        );
+        browser.test.assertEq(
+          2,
+          obj.nestedArr.length,
+          "nestedArr.length part correct"
+        );
+        browser.test.assertEq(1, obj.nestedArr[0], "nestedArr[0] part correct");
+        browser.test.assertTrue(
+          Array.isArray(obj.nestedArr[1]),
+          "nestedArr[1] part present"
+        );
+        browser.test.assertEq(
+          2,
+          obj.nestedArr[1].length,
+          "nestedArr[1].length part correct"
+        );
+        browser.test.assertEq(
+          2,
+          obj.nestedArr[1][0],
+          "nestedArr[1][0] part correct"
+        );
+        browser.test.assertEq(
+          3,
+          obj.nestedArr[1][1],
+          "nestedArr[1][1] part correct"
+        );
+      } catch (e) {
+        browser.test.fail(`Error: ${e} :: ${e.stack}`);
+        browser.test.notifyFail("storage");
+      }
+    }
+
+    browser.test.onMessage.addListener(msg => {
+      let promise;
+      if (msg === "test-local") {
+        promise = runTests("local");
+      } else if (msg === "test-sync") {
+        promise = runTests("sync");
+      } else if (msg === "test-session") {
+        promise = runTests("session");
+      }
+      promise.then(() => browser.test.sendMessage("test-finished"));
+    });
+
+    browser.test.sendMessage("ready");
+  }
+
+  let extensionData = {
+    background: `(${backgroundScript})(${checkGetImpl})`,
+    manifest: {
+      permissions: ["storage"],
+    },
+  };
+
+  let extension = ExtensionTestUtils.loadExtension(extensionData);
+  await extension.startup();
+  await extension.awaitMessage("ready");
+
+  extension.sendMessage(`test-${testAreaName}`);
+  await extension.awaitMessage("test-finished");
+
+  await extension.unload();
+}
+
+function test_storage_sync_requires_real_id() {
+  async function testFn() {
+    async function background() {
+      const EXCEPTION_MESSAGE =
+        "The storage API will not work with a temporary addon ID. " +
+        "Please add an explicit addon ID to your manifest. " +
+        "For more information see https://mzl.la/3lPk1aE.";
+
+      await browser.test.assertRejects(
+        browser.storage.sync.set({ foo: "bar" }),
+        EXCEPTION_MESSAGE
+      );
+
+      browser.test.notifyPass("exception correct");
+    }
+
+    let extensionData = {
+      background,
+      manifest: {
+        permissions: ["storage"],
+      },
+      useAddonManager: "temporary",
+    };
+
+    let extension = ExtensionTestUtils.loadExtension(extensionData);
+    await extension.startup();
+    await extension.awaitFinish("exception correct");
+
+    await extension.unload();
+  }
+
+  return runWithPrefs([[STORAGE_SYNC_PREF, true]], testFn);
+}
+
+// Test for storage areas which don't support getBytesInUse() nor QUOTA
+// constants.
+async function check_storage_area_no_bytes_in_use(area) {
+  let impl = browser.storage[area];
+
+  browser.test.assertEq(
+    typeof impl.getBytesInUse,
+    "undefined",
+    "getBytesInUse API method should not be available"
+  );
+  browser.test.sendMessage("test-complete");
+}
+
+async function test_background_storage_area_no_bytes_in_use(area) {
+  const EXT_ID = "test-gbiu@mozilla.org";
+
+  const extensionDef = {
+    manifest: {
+      permissions: ["storage"],
+      browser_specific_settings: { gecko: { id: EXT_ID } },
+    },
+    background: `(${check_storage_area_no_bytes_in_use})("${area}")`,
+  };
+
+  const extension = ExtensionTestUtils.loadExtension(extensionDef);
+
+  await extension.startup();
+  await extension.awaitMessage("test-complete");
+  await extension.unload();
+}
+
+async function test_contentscript_storage_area_no_bytes_in_use(area) {
+  let contentPage = await ExtensionTestUtils.loadContentPage(
+    "http://example.com/data/file_sample.html"
+  );
+
+  function contentScript(checkImpl) {
+    browser.test.onMessage.addListener(msg => {
+      if (msg === "test-local") {
+        checkImpl("local");
+      } else if (msg === "test-sync") {
+        checkImpl("sync");
+      } else if (msg === "test-session") {
+        checkImpl("session");
+      } else {
+        browser.test.fail(`Unexpected test message received: ${msg}`);
+        browser.test.sendMessage("test-complete");
+      }
+    });
+    browser.test.sendMessage("ready");
+  }
+
+  let extensionData = {
+    manifest: {
+      content_scripts: [
+        {
+          matches: ["http://example.com/data/file_sample.html"],
+          js: ["content_script.js"],
+          run_at: "document_idle",
+        },
+      ],
+
+      permissions: ["storage"],
+    },
+
+    files: {
+      "content_script.js": `(${contentScript})(${check_storage_area_no_bytes_in_use})`,
+    },
+  };
+
+  let extension = ExtensionTestUtils.loadExtension(extensionData);
+  await extension.startup();
+  await extension.awaitMessage("ready");
+
+  extension.sendMessage(`test-${area}`);
+  await extension.awaitMessage("test-complete");
+
+  await extension.unload();
+  await contentPage.close();
+}
+
+// Test for storage areas which do support getBytesInUse() (but which may or may
+// not support enforcement of the quota)
+async function check_storage_area_with_bytes_in_use(area, expectQuota) {
+  let impl = browser.storage[area];
+
+  // QUOTA_* constants aren't currently exposed - see bug 1396810.
+  // However, the quotas are still enforced, so test them here.
+  // (Note that an implication of this is that we can't test area other than
+  // 'sync', because its limits are different - so for completeness...)
+  browser.test.assertEq(
+    area,
+    "sync",
+    "Running test on storage.sync API as expected"
+  );
+  const QUOTA_BYTES_PER_ITEM = 8192;
+  const MAX_ITEMS = 512;
+
+  // bytes is counted as "length of key as a string, length of value as
+  // JSON" - ie, quotes not counted in the key, but are in the value.
+  let value = "x".repeat(QUOTA_BYTES_PER_ITEM - 3);
+
+  await impl.set({ x: value }); // Shouldn't reject on either kinto or rust-based storage.sync.
+  browser.test.assertEq(await impl.getBytesInUse(null), QUOTA_BYTES_PER_ITEM);
+  // kinto does implement getBytesInUse() but doesn't enforce a quota.
+  if (expectQuota) {
+    await browser.test.assertRejects(
+      impl.set({ x: value + "x" }),
+      /QuotaExceededError/,
+      "Got a rejection with the expected error message"
+    );
+    // MAX_ITEMS
+    await impl.clear();
+    let ob = {};
+    for (let i = 0; i < MAX_ITEMS; i++) {
+      ob[`key-${i}`] = "x";
+    }
+    await impl.set(ob); // should work.
+    await browser.test.assertRejects(
+      impl.set({ straw: "camel's back" }), // exceeds MAX_ITEMS
+      /QuotaExceededError/,
+      "Got a rejection with the expected error message"
+    );
+    // QUOTA_BYTES is being already tested for the underlying StorageSyncService
+    // so we don't duplicate those tests here.
+  } else {
+    // Exceeding quota should work on the previous kinto-based storage.sync implementation
+    await impl.set({ x: value + "x" }); // exceeds quota but should work.
+    browser.test.assertEq(
+      await impl.getBytesInUse(null),
+      QUOTA_BYTES_PER_ITEM + 1,
+      "Got the expected result from getBytesInUse"
+    );
+  }
+  browser.test.sendMessage("test-complete");
+}
+
+async function test_background_storage_area_with_bytes_in_use(
+  area,
+  expectQuota
+) {
+  const EXT_ID = "test-gbiu@mozilla.org";
+
+  const extensionDef = {
+    manifest: {
+      permissions: ["storage"],
+      browser_specific_settings: { gecko: { id: EXT_ID } },
+    },
+    background: `(${check_storage_area_with_bytes_in_use})("${area}", ${expectQuota})`,
+  };
+
+  const extension = ExtensionTestUtils.loadExtension(extensionDef);
+
+  await extension.startup();
+  await extension.awaitMessage("test-complete");
+  await extension.unload();
+}
+
+async function test_contentscript_storage_area_with_bytes_in_use(
+  area,
+  expectQuota
+) {
+  let contentPage = await ExtensionTestUtils.loadContentPage(
+    "http://example.com/data/file_sample.html"
+  );
+
+  function contentScript(checkImpl) {
+    browser.test.onMessage.addListener(([area, expectQuota]) => {
+      if (
+        !["local", "sync"].includes(area) ||
+        typeof expectQuota !== "boolean"
+      ) {
+        browser.test.fail(`Unexpected test message: [${area}, ${expectQuota}]`);
+        // Let the test to fail immediately instead of wait for a timeout failure.
+        browser.test.sendMessage("test-complete");
+        return;
+      }
+      checkImpl(area, expectQuota);
+    });
+    browser.test.sendMessage("ready");
+  }
+
+  let extensionData = {
+    manifest: {
+      content_scripts: [
+        {
+          matches: ["http://example.com/data/file_sample.html"],
+          js: ["content_script.js"],
+          run_at: "document_idle",
+        },
+      ],
+
+      permissions: ["storage"],
+    },
+
+    files: {
+      "content_script.js": `(${contentScript})(${check_storage_area_with_bytes_in_use})`,
+    },
+  };
+
+  let extension = ExtensionTestUtils.loadExtension(extensionData);
+  await extension.startup();
+  await extension.awaitMessage("ready");
+
+  extension.sendMessage([area, expectQuota]);
+  await extension.awaitMessage("test-complete");
+
+  await extension.unload();
+  await contentPage.close();
+}
+
+// A couple of common tests for checking content scripts.
+async function testStorageContentScript(checkGet) {
+  let globalChanges, gResolve;
+  function clearGlobalChanges() {
+    globalChanges = new Promise(resolve => {
+      gResolve = resolve;
+    });
+  }
+  clearGlobalChanges();
+  let expectedAreaName;
+
+  browser.storage.onChanged.addListener((changes, areaName) => {
+    browser.test.assertEq(
+      expectedAreaName,
+      areaName,
+      "Expected area name received by listener"
+    );
+    gResolve(changes);
+  });
+
+  async function checkChanges(areaName, changes, message) {
+    function checkSub(obj1, obj2) {
+      for (let prop in obj1) {
+        browser.test.assertTrue(
+          obj1[prop] !== undefined,
+          `checkChanges ${areaName} ${prop} is missing (${message})`
+        );
+        browser.test.assertTrue(
+          obj2[prop] !== undefined,
+          `checkChanges ${areaName} ${prop} is missing (${message})`
+        );
+        browser.test.assertEq(
+          obj1[prop].oldValue,
+          obj2[prop].oldValue,
+          `checkChanges ${areaName} ${prop} old (${message})`
+        );
+        browser.test.assertEq(
+          obj1[prop].newValue,
+          obj2[prop].newValue,
+          `checkChanges ${areaName} ${prop} new (${message})`
+        );
+      }
+    }
+
+    const recentChanges = await globalChanges;
+    checkSub(changes, recentChanges);
+    checkSub(recentChanges, changes);
+    clearGlobalChanges();
+  }
+
+  /* eslint-disable dot-notation */
+  async function runTests(areaName) {
+    expectedAreaName = areaName;
+    let storage = browser.storage[areaName];
+    // Set some data and then test getters.
+    try {
+      await storage.set({ "test-prop1": "value1", "test-prop2": "value2" });
+      await checkChanges(
+        areaName,
+        {
+          "test-prop1": { newValue: "value1" },
+          "test-prop2": { newValue: "value2" },
+        },
+        "set (a)"
+      );
+
+      await checkGet(areaName, "test-prop1", "value1");
+      await checkGet(areaName, "test-prop2", "value2");
+
+      let data = await storage.get({
+        "test-prop1": undefined,
+        "test-prop2": undefined,
+        other: "default",
+      });
+      browser.test.assertEq("value1", data["test-prop1"], "prop1 correct (a)");
+      browser.test.assertEq("value2", data["test-prop2"], "prop2 correct (a)");
+      browser.test.assertEq("default", data["other"], "other correct");
+
+      data = await storage.get(["test-prop1", "test-prop2", "other"]);
+      browser.test.assertEq("value1", data["test-prop1"], "prop1 correct (b)");
+      browser.test.assertEq("value2", data["test-prop2"], "prop2 correct (b)");
+      browser.test.assertFalse("other" in data, "other correct");
+
+      // Remove data in various ways.
+      await storage.remove("test-prop1");
+      await checkChanges(
+        areaName,
+        { "test-prop1": { oldValue: "value1" } },
+        "remove string"
+      );
+
+      data = await storage.get(["test-prop1", "test-prop2"]);
+      browser.test.assertFalse(
+        "test-prop1" in data,
+        "prop1 absent (remove string)"
+      );
+      browser.test.assertTrue(
+        "test-prop2" in data,
+        "prop2 present (remove string)"
+      );
+
+      await storage.set({ "test-prop1": "value1" });
+      await checkChanges(
+        areaName,
+        { "test-prop1": { newValue: "value1" } },
+        "set (c)"
+      );
+
+      data = await storage.get(["test-prop1", "test-prop2"]);
+      browser.test.assertEq(data["test-prop1"], "value1", "prop1 correct (c)");
+      browser.test.assertEq(data["test-prop2"], "value2", "prop2 correct (c)");
+
+      await storage.remove(["test-prop1", "test-prop2"]);
+      await checkChanges(
+        areaName,
+        {
+          "test-prop1": { oldValue: "value1" },
+          "test-prop2": { oldValue: "value2" },
+        },
+        "remove array"
+      );
+
+      data = await storage.get(["test-prop1", "test-prop2"]);
+      browser.test.assertFalse(
+        "test-prop1" in data,
+        "prop1 absent (remove array)"
+      );
+      browser.test.assertFalse(
+        "test-prop2" in data,
+        "prop2 absent (remove array)"
+      );
+
+      // test storage.clear
+      await storage.set({ "test-prop1": "value1", "test-prop2": "value2" });
+      // Make sure that set() handler happened before we clear the
+      // promise again.
+      await globalChanges;
+
+      clearGlobalChanges();
+      await storage.clear();
+
+      await checkChanges(
+        areaName,
+        {
+          "test-prop1": { oldValue: "value1" },
+          "test-prop2": { oldValue: "value2" },
+        },
+        "clear"
+      );
+      data = await storage.get(["test-prop1", "test-prop2"]);
+      browser.test.assertFalse("test-prop1" in data, "prop1 absent (clear)");
+      browser.test.assertFalse("test-prop2" in data, "prop2 absent (clear)");
+
+      // Make sure we can store complex JSON data.
+      // known previous values
+      await storage.set({ "test-prop1": "value1", "test-prop2": "value2" });
+
+      // Make sure the set() handler landed.
+      await globalChanges;
+
+      let date = new Date(0);
+
+      clearGlobalChanges();
+      await storage.set({
+        "test-prop1": {
+          str: "hello",
+          bool: true,
+          null: null,
+          undef: undefined,
+          obj: {},
+          arr: [1, 2],
+          date: new Date(0),
+          regexp: /regexp/,
+        },
+      });
+
+      await browser.test.assertRejects(
+        storage.set({
+          window,
+        }),
+        /DataCloneError|cyclic object value/
+      );
+
+      await browser.test.assertRejects(
+        storage.set({ "test-prop2": function func() {} }),
+        /DataCloneError/
+      );
+
+      const recentChanges = await globalChanges;
+
+      browser.test.assertEq(
+        "value1",
+        recentChanges["test-prop1"].oldValue,
+        "oldValue correct"
+      );
+      browser.test.assertEq(
+        "object",
+        typeof recentChanges["test-prop1"].newValue,
+        "newValue is obj"
+      );
+      clearGlobalChanges();
+
+      data = await storage.get({
+        "test-prop1": undefined,
+        "test-prop2": undefined,
+      });
+      let obj = data["test-prop1"];
+
+      if (areaName === "local") {
+        browser.test.assertEq(
+          String(date),
+          String(obj.date),
+          "date part correct"
+        );
+        browser.test.assertEq(
+          "/regexp/",
+          obj.regexp.toString(),
+          "regexp part correct"
+        );
+      } else {
+        browser.test.assertEq(
+          "1970-01-01T00:00:00.000Z",
+          String(obj.date),
+          "date part correct"
+        );
+
+        browser.test.assertEq(
+          "object",
+          typeof obj.regexp,
+          "regexp part is an object"
+        );
+        browser.test.assertEq(
+          0,
+          Object.keys(obj.regexp).length,
+          "regexp part is an empty object"
+        );
+      }
+
+      browser.test.assertEq("hello", obj.str, "string part correct");
+      browser.test.assertEq(true, obj.bool, "bool part correct");
+      browser.test.assertEq(null, obj.null, "null part correct");
+      browser.test.assertEq(undefined, obj.undef, "undefined part correct");
+      browser.test.assertEq(undefined, obj.window, "window part correct");
+      browser.test.assertEq("object", typeof obj.obj, "object part correct");
+      browser.test.assertTrue(Array.isArray(obj.arr), "array part present");
+      browser.test.assertEq(1, obj.arr[0], "arr[0] part correct");
+      browser.test.assertEq(2, obj.arr[1], "arr[1] part correct");
+      browser.test.assertEq(2, obj.arr.length, "arr.length part correct");
+    } catch (e) {
+      browser.test.fail(`Error: ${e} :: ${e.stack}`);
+      browser.test.notifyFail("storage");
+    }
+  }
+
+  browser.test.onMessage.addListener(msg => {
+    let promise;
+    if (msg === "test-local") {
+      promise = runTests("local");
+    } else if (msg === "test-sync") {
+      promise = runTests("sync");
+    } else if (msg === "test-session") {
+      promise = runTests("session");
+    }
+    promise.then(() => browser.test.sendMessage("test-finished"));
+  });
+
+  browser.test.sendMessage("ready");
+}
+
+async function test_contentscript_storage(storageType) {
+  let contentPage = await ExtensionTestUtils.loadContentPage(
+    "http://example.com/data/file_sample.html"
+  );
+
+  let extensionData = {
+    manifest: {
+      content_scripts: [
+        {
+          matches: ["http://example.com/data/file_sample.html"],
+          js: ["content_script.js"],
+          run_at: "document_idle",
+        },
+      ],
+
+      permissions: ["storage"],
+    },
+
+    files: {
+      "content_script.js": `(${testStorageContentScript})(${checkGetImpl})`,
+    },
+  };
+
+  let extension = ExtensionTestUtils.loadExtension(extensionData);
+  await extension.startup();
+  await extension.awaitMessage("ready");
+
+  extension.sendMessage(`test-${storageType}`);
+  await extension.awaitMessage("test-finished");
+
+  await extension.unload();
+  await contentPage.close();
+}
+
+async function test_storage_empty_events(areaName) {
+  async function background(areaName) {
+    let eventCount = 0;
+
+    browser.storage[areaName].onChanged.addListener(changes => {
+      browser.test.sendMessage("onChanged", [++eventCount, changes]);
+    });
+
+    browser.test.onMessage.addListener(async (method, arg) => {
+      let result = await browser.storage[areaName][method](arg);
+      browser.test.sendMessage("result", result);
+    });
+
+    browser.test.sendMessage("ready");
+  }
+
+  let extension = ExtensionTestUtils.loadExtension({
+    manifest: { permissions: ["storage"] },
+    background: `(${background})("${areaName}")`,
+  });
+
+  await extension.startup();
+  await extension.awaitMessage("ready");
+
+  async function callStorageMethod(method, arg) {
+    info(`call storage.${areaName}.${method}(${JSON.stringify(arg) ?? ""})`);
+    extension.sendMessage(method, arg);
+    await extension.awaitMessage("result");
+  }
+
+  async function expectEvent(expectCount, expectChanges) {
+    equal(
+      JSON.stringify([expectCount, expectChanges]),
+      JSON.stringify(await extension.awaitMessage("onChanged")),
+      "Correct onChanged events count and data in the last changes notified."
+    );
+  }
+
+  await callStorageMethod("set", { alpha: 1 });
+  await expectEvent(1, { alpha: { newValue: 1 } });
+
+  await callStorageMethod("set", {});
+  // Setting nothing doesn't trigger onChanged event.
+
+  await callStorageMethod("set", { beta: 12 });
+  await expectEvent(2, { beta: { newValue: 12 } });
+
+  await callStorageMethod("remove", "alpha");
+  await expectEvent(3, { alpha: { oldValue: 1 } });
+
+  await callStorageMethod("remove", "alpha");
+  // Trying to remove alpha again doesn't trigger onChanged.
+
+  await callStorageMethod("clear");
+  await expectEvent(4, { beta: { oldValue: 12 } });
+
+  await callStorageMethod("clear");
+  // Clear again wothout onChanged. Test will fail on unexpected event/message.
+
+  await extension.unload();
+}
+
+async function test_storage_change_event_page(areaName) {
+  async function testOnChanged(targetIsStorageArea) {
+    function backgroundTestStorageTopNamespace(areaName) {
+      browser.storage.onChanged.addListener((changes, area) => {
+        browser.test.assertEq(area, areaName, "Expected areaName");
+        browser.test.assertEq(
+          JSON.stringify(changes),
+          `{"storageKey":{"newValue":"newStorageValue"}}`,
+          "Expected changes"
+        );
+        browser.test.sendMessage("onChanged_was_fired");
+      });
+    }
+    function backgroundTestStorageAreaNamespace(areaName) {
+      browser.storage[areaName].onChanged.addListener((changes, ...args) => {
+        browser.test.assertEq(args.length, 0, "no more args after changes");
+        browser.test.assertEq(
+          JSON.stringify(changes),
+          `{"storageKey":{"newValue":"newStorageValue"}}`,
+          `Expected changes via ${areaName}.onChanged event`
+        );
+        browser.test.sendMessage("onChanged_was_fired");
+      });
+    }
+    let background, onChangedName;
+    if (targetIsStorageArea) {
+      // Test storage.local.onChanged / storage.sync.onChanged.
+      background = backgroundTestStorageAreaNamespace;
+      onChangedName = `${areaName}.onChanged`;
+    } else {
+      background = backgroundTestStorageTopNamespace;
+      onChangedName = "onChanged";
+    }
+    let extension = ExtensionTestUtils.loadExtension({
+      manifest: {
+        permissions: ["storage"],
+        background: { persistent: false },
+      },
+      background: `(${background})("${areaName}")`,
+      files: {
+        "trigger-change.html": `
+          <!DOCTYPE html><meta charset="utf-8">
+          <script src="trigger-change.js"></script>
+        `,
+        "trigger-change.js": async () => {
+          let areaName = location.search.slice(1);
+          await browser.storage[areaName].set({
+            storageKey: "newStorageValue",
+          });
+          browser.test.sendMessage("tried_to_trigger_change");
+        },
+      },
+    });
+    await extension.startup();
+    assertPersistentListeners(extension, "storage", onChangedName, {
+      primed: false,
+    });
+
+    await extension.terminateBackground();
+    assertPersistentListeners(extension, "storage", onChangedName, {
+      primed: true,
+    });
+
+    // Now trigger the event
+    let contentPage = await ExtensionTestUtils.loadContentPage(
+      `moz-extension://${extension.uuid}/trigger-change.html?${areaName}`
+    );
+    await extension.awaitMessage("tried_to_trigger_change");
+    await contentPage.close();
+    await extension.awaitMessage("onChanged_was_fired");
+
+    assertPersistentListeners(extension, "storage", onChangedName, {
+      primed: false,
+    });
+    await extension.unload();
+  }
+
+  async function testFn() {
+    // Test browser.storage.onChanged.addListener
+    await testOnChanged(/* targetIsStorageArea */ false);
+    // Test browser.storage.local.onChanged.addListener
+    // and browser.storage.sync.onChanged.addListener, depending on areaName.
+    await testOnChanged(/* targetIsStorageArea */ true);
+  }
+
+  return runWithPrefs([["extensions.eventPages.enabled", true]], testFn);
+}
diff --git a/toolkit/components/extensions/test/xpcshell/head_sync.js b/toolkit/components/extensions/test/xpcshell/head_sync.js
new file mode 100644
index 0000000000..7c88e23a86
--- /dev/null
+++ b/toolkit/components/extensions/test/xpcshell/head_sync.js
@@ -0,0 +1,66 @@
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+"use strict";
+
+/* exported withSyncContext */
+
+const { ExtensionCommon } = ChromeUtils.importESModule(
+  "resource://gre/modules/ExtensionCommon.sys.mjs"
+);
+
+class KintoExtContext extends ExtensionCommon.BaseContext {
+  constructor(principal) {
+    let fakeExtension = { id: "test@web.extension", manifestVersion: 2 };
+    super("addon_parent", fakeExtension);
+    Object.defineProperty(this, "principal", {
+      value: principal,
+      configurable: true,
+    });
+    this.sandbox = Cu.Sandbox(principal, { wantXrays: false });
+  }
+
+  get cloneScope() {
+    return this.sandbox;
+  }
+}
+
+/**
+ * Call the given function with a newly-constructed context.
+ * Unload the context on the way out.
+ *
+ * @param {Function} f    the function to call
+ */
+async function withContext(f) {
+  const ssm = Services.scriptSecurityManager;
+  const PRINCIPAL1 = ssm.createContentPrincipalFromOrigin(
+    "http://www.example.org"
+  );
+  const context = new KintoExtContext(PRINCIPAL1);
+  try {
+    await f(context);
+  } finally {
+    await context.unload();
+  }
+}
+
+/**
+ * Like withContext(), but also turn on the "storage.sync" pref for
+ * the duration of the function.
+ * Calls to this function can be replaced with calls to withContext
+ * once the pref becomes on by default.
+ *
+ * @param {Function} f    the function to call
+ */
+async function withSyncContext(f) {
+  const STORAGE_SYNC_PREF = "webextensions.storage.sync.enabled";
+  let prefs = Services.prefs;
+
+  try {
+    prefs.setBoolPref(STORAGE_SYNC_PREF, true);
+    await withContext(f);
+  } finally {
+    prefs.clearUserPref(STORAGE_SYNC_PREF);
+  }
+}
diff --git a/toolkit/components/extensions/test/xpcshell/head_telemetry.js b/toolkit/components/extensions/test/xpcshell/head_telemetry.js
new file mode 100644
index 0000000000..b3aa5e84a8
--- /dev/null
+++ b/toolkit/components/extensions/test/xpcshell/head_telemetry.js
@@ -0,0 +1,435 @@
+/* -*- Mode: indent-tabs-mode: nil; js-indent-level: 2 -*- */
+/* vim: set sts=2 sw=2 et tw=80: */
+"use strict";
+
+/* exported IS_ANDROID_BUILD, IS_OOP, valueSum, clearHistograms, getSnapshots, promiseTelemetryRecorded,
+            assertDNRTelemetryMetricsDefined, assertDNRTelemetryMetricsNoSamples, assertDNRTelemetryMetricsGetValueEq,
+            assertDNRTelemetryMetricsSamplesCount, resetTelemetryData, setupTelemetryForTests */
+
+ChromeUtils.defineESModuleGetters(this, {
+  ContentTaskUtils: "resource://testing-common/ContentTaskUtils.sys.mjs",
+});
+
+// Allows to run xpcshell telemetry test also on products (e.g. Thunderbird) where
+// that telemetry wouldn't be actually collected in practice (but to be sure
+// that it will work on those products as well by just adding the product in
+// the telemetry metric definitions if it turns out we want to).
+Services.prefs.setBoolPref(
+  "toolkit.telemetry.testing.overrideProductsCheck",
+  true
+);
+
+const IS_OOP = Services.prefs.getBoolPref("extensions.webextensions.remote");
+
+// Initializing and asserting the expected telemetry is currently conditioned
+// on this const.
+// TODO(Bug 1752139) remove this along with initializing and asserting the expected
+// telemetry also for android build, once `Services.fog.testResetFOG()` is implemented
+// for Android builds.
+const IS_ANDROID_BUILD = AppConstants.platform === "android";
+
+const WEBEXT_EVENTPAGE_RUNNING_TIME_MS = "WEBEXT_EVENTPAGE_RUNNING_TIME_MS";
+const WEBEXT_EVENTPAGE_RUNNING_TIME_MS_BY_ADDONID =
+  "WEBEXT_EVENTPAGE_RUNNING_TIME_MS_BY_ADDONID";
+const WEBEXT_EVENTPAGE_IDLE_RESULT_COUNT = "WEBEXT_EVENTPAGE_IDLE_RESULT_COUNT";
+const WEBEXT_EVENTPAGE_IDLE_RESULT_COUNT_BY_ADDONID =
+  "WEBEXT_EVENTPAGE_IDLE_RESULT_COUNT_BY_ADDONID";
+
+// Keep this in sync with the order in Histograms.json for "WEBEXT_EVENTPAGE_IDLE_RESULT_COUNT":
+// the position of the category string determines the index of the values collected in the categorial
+// histogram and so the existing labels should be kept in the exact same order and any new category
+// to be added in the future should be appended to the existing ones.
+const HISTOGRAM_EVENTPAGE_IDLE_RESULT_CATEGORIES = [
+  "suspend",
+  "reset_other",
+  "reset_event",
+  "reset_listeners",
+  "reset_nativeapp",
+  "reset_streamfilter",
+];
+
+function valueSum(arr) {
+  return Object.values(arr).reduce((a, b) => a + b, 0);
+}
+
+function clearHistograms() {
+  Services.telemetry.getSnapshotForHistograms("main", true /* clear */);
+  Services.telemetry.getSnapshotForKeyedHistograms("main", true /* clear */);
+}
+
+function clearScalars() {
+  Services.telemetry.getSnapshotForScalars("main", true /* clear */);
+  Services.telemetry.getSnapshotForKeyedScalars("main", true /* clear */);
+}
+
+function getSnapshots(process) {
+  return Services.telemetry.getSnapshotForHistograms("main", false /* clear */)[
+    process
+  ];
+}
+
+function getKeyedSnapshots(process) {
+  return Services.telemetry.getSnapshotForKeyedHistograms(
+    "main",
+    false /* clear */
+  )[process];
+}
+
+// TODO Bug 1357509: There is no good way to make sure that the parent received
+// the histogram entries from the extension and content processes.  Let's stick
+// to the ugly, spinning the event loop until we have a good approach.
+function promiseTelemetryRecorded(id, process, expectedCount) {
+  let condition = () => {
+    let snapshot = Services.telemetry.getSnapshotForHistograms(
+      "main",
+      false /* clear */
+    )[process][id];
+    return snapshot && valueSum(snapshot.values) >= expectedCount;
+  };
+  return ContentTaskUtils.waitForCondition(condition);
+}
+
+function promiseKeyedTelemetryRecorded(
+  id,
+  process,
+  expectedKey,
+  expectedCount
+) {
+  let condition = () => {
+    let snapshot = Services.telemetry.getSnapshotForKeyedHistograms(
+      "main",
+      false /* clear */
+    )[process][id];
+    return (
+      snapshot &&
+      snapshot[expectedKey] &&
+      valueSum(snapshot[expectedKey].values) >= expectedCount
+    );
+  };
+  return ContentTaskUtils.waitForCondition(condition);
+}
+
+function assertHistogramSnapshot(
+  histogramId,
+  { keyed, processSnapshot, expectedValue },
+  msg
+) {
+  let histogram;
+
+  if (keyed) {
+    histogram = Services.telemetry.getKeyedHistogramById(histogramId);
+  } else {
+    histogram = Services.telemetry.getHistogramById(histogramId);
+  }
+
+  let res = processSnapshot(histogram.snapshot());
+  Assert.deepEqual(res, expectedValue, msg);
+  return res;
+}
+
+function assertHistogramEmpty(histogramId) {
+  assertHistogramSnapshot(
+    histogramId,
+    {
+      processSnapshot: snapshot => snapshot.sum,
+      expectedValue: 0,
+    },
+    `No data recorded for histogram: ${histogramId}.`
+  );
+}
+
+function assertKeyedHistogramEmpty(histogramId) {
+  assertHistogramSnapshot(
+    histogramId,
+    {
+      keyed: true,
+      processSnapshot: snapshot => Object.keys(snapshot).length,
+      expectedValue: 0,
+    },
+    `No data recorded for histogram: ${histogramId}.`
+  );
+}
+
+function assertHistogramCategoryNotEmpty(
+  histogramId,
+  { category, categories, keyed, key },
+  msg
+) {
+  let message = msg;
+
+  if (!msg) {
+    message = `Data recorded for histogram: ${histogramId}, category "${category}"`;
+    if (keyed) {
+      message += `, key "${key}"`;
+    }
+  }
+
+  assertHistogramSnapshot(
+    histogramId,
+    {
+      keyed,
+      processSnapshot: snapshot => {
+        const categoryIndex = categories.indexOf(category);
+        if (keyed) {
+          return {
+            [key]: snapshot[key]
+              ? snapshot[key].values[categoryIndex] > 0
+              : null,
+          };
+        }
+        return snapshot.values[categoryIndex] > 0;
+      },
+      expectedValue: keyed ? { [key]: true } : true,
+    },
+    message
+  );
+}
+
+function setupTelemetryForTests() {
+  // FOG needs a profile directory to put its data in.
+  do_get_profile();
+  // FOG needs to be initialized in order for data to flow.
+  Services.fog.initializeFOG();
+}
+
+function resetTelemetryData() {
+  if (IS_ANDROID_BUILD) {
+    info("Skip testResetFOG on android builds");
+    return;
+  }
+  Services.fog.testResetFOG();
+
+  // Clear histograms data recorded in the unified telemetry
+  // (needed to make sure we can keep asserting that the same
+  // amount of samples collected by Glean should also be found
+  // in the related mirrored unified telemetry probe after we
+  // have reset Glean metrics data using testResetFOG).
+  clearHistograms();
+  clearScalars();
+}
+
+function assertDNRTelemetryMetricsDefined(metrics) {
+  const metricsNotFound = metrics.filter(metricDetails => {
+    const { metric, label } = metricDetails;
+    if (!Glean.extensionsApisDnr[metric]) {
+      return true;
+    }
+    if (label) {
+      return !Glean.extensionsApisDnr[metric][label];
+    }
+    return false;
+  });
+  Assert.deepEqual(
+    metricsNotFound,
+    [],
+    `All expected extensionsApisDnr Glean metrics should be found`
+  );
+}
+
+function assertDNRTelemetryMirrored({
+  gleanMetric,
+  gleanLabel,
+  unifiedName,
+  unifiedType,
+}) {
+  assertDNRTelemetryMetricsDefined([
+    { metric: gleanMetric, label: gleanLabel },
+  ]);
+  const gleanData = gleanLabel
+    ? Glean.extensionsApisDnr[gleanMetric][gleanLabel].testGetValue()
+    : Glean.extensionsApisDnr[gleanMetric].testGetValue();
+
+  if (!unifiedName) {
+    Assert.ok(
+      false,
+      `Unexpected missing unifiedName parameter on call to assertDNRTelemetryMirrored`
+    );
+    return;
+  }
+
+  let unifiedData;
+
+  switch (unifiedType) {
+    case "histogram": {
+      let found = false;
+      try {
+        const histogram = Services.telemetry.getHistogramById(unifiedName);
+        found = !!histogram;
+      } catch (err) {
+        Cu.reportError(err);
+      }
+      Assert.ok(found, `Expect an histogram named ${unifiedName} to be found`);
+      unifiedData = Services.telemetry.getSnapshotForHistograms("main", false)
+        .parent[unifiedName];
+      break;
+    }
+    case "keyedScalar": {
+      const snapshot = Services.telemetry.getSnapshotForKeyedScalars(
+        "main",
+        false
+      );
+      if (unifiedName in (snapshot?.parent || {})) {
+        unifiedData = snapshot.parent[unifiedName][gleanLabel];
+      }
+      break;
+    }
+    case "scalar": {
+      const snapshot = Services.telemetry.getSnapshotForScalars("main", false);
+      if (unifiedName in (snapshot?.parent || {})) {
+        unifiedData = snapshot.parent[unifiedName];
+      }
+      break;
+    }
+    default:
+      Assert.ok(
+        false,
+        `Unexpected unifiedType ${unifiedType} on call to assertDNRTelemetryMirrored`
+      );
+      return;
+  }
+
+  if (gleanData == undefined) {
+    Assert.deepEqual(
+      unifiedData,
+      undefined,
+      `Expect mirrored unified telemetry ${unifiedType} ${unifiedName} has no samples as Glean ${gleanMetric}`
+    );
+  } else {
+    switch (unifiedType) {
+      case "histogram": {
+        Assert.deepEqual(
+          valueSum(unifiedData.values),
+          valueSum(gleanData.values),
+          `Expect mirrored unified telemetry ${unifiedType} ${unifiedName} has samples mirrored from Glean ${gleanMetric}`
+        );
+        break;
+      }
+      case "scalar":
+      case "keyedScalar": {
+        Assert.deepEqual(
+          unifiedData,
+          gleanData,
+          `Expect mirrored unified telemetry ${unifiedType} ${unifiedName} has samples mirrored from Glean ${gleanMetric}`
+        );
+        break;
+      }
+    }
+  }
+}
+
+function assertDNRTelemetryMetricsNoSamples(metrics, msg) {
+  assertDNRTelemetryMetricsDefined(metrics);
+  for (const metricDetails of metrics) {
+    const { metric, label } = metricDetails;
+    if (IS_ANDROID_BUILD) {
+      info(
+        `Skip assertions on collected samples for extensionsApisDnr.${metric} on android builds (${msg})`
+      );
+      return;
+    }
+    const gleanData = label
+      ? Glean.extensionsApisDnr[metric][label].testGetValue()
+      : Glean.extensionsApisDnr[metric].testGetValue();
+    Assert.deepEqual(
+      gleanData,
+      undefined,
+      `Expect no sample for Glean metric extensionApisDnr.${metric} (${msg}): ${gleanData}`
+    );
+
+    if (metricDetails.mirroredName) {
+      const { mirroredName, mirroredType } = metricDetails;
+      assertDNRTelemetryMirrored({
+        gleanMetric: metric,
+        gleanLabel: label,
+        unifiedName: mirroredName,
+        unifiedType: mirroredType,
+      });
+    }
+  }
+}
+
+function assertDNRTelemetryMetricsGetValueEq(metrics, msg) {
+  assertDNRTelemetryMetricsDefined(metrics);
+  for (const metricDetails of metrics) {
+    const { metric, label, expectedGetValue } = metricDetails;
+    if (IS_ANDROID_BUILD) {
+      info(
+        `Skip assertions on collected samples for extensionsApisDnr.${metric} on android builds`
+      );
+      return;
+    }
+    const gleanData = label
+      ? Glean.extensionsApisDnr[metric][label].testGetValue()
+      : Glean.extensionsApisDnr[metric].testGetValue();
+    Assert.deepEqual(
+      gleanData,
+      expectedGetValue,
+      `Got expected value set on Glean metric extensionApisDnr.${metric}${
+        label ? `.${label}` : ""
+      } (${msg})`
+    );
+
+    if (metricDetails.mirroredName) {
+      const { mirroredName, mirroredType } = metricDetails;
+      assertDNRTelemetryMirrored({
+        gleanMetric: metric,
+        gleanLabel: label,
+        unifiedName: mirroredName,
+        unifiedType: mirroredType,
+      });
+    }
+  }
+}
+
+function assertDNRTelemetryMetricsSamplesCount(metrics, msg) {
+  assertDNRTelemetryMetricsDefined(metrics);
+
+  // This assertion helpers doesn't currently handle labeled metrics,
+  // raise an explicit error to catch if one is included by mistake.
+  const labeledMetricsFound = metrics.filter(metric => !!metric.label);
+  if (labeledMetricsFound.length) {
+    throw new Error(
+      `Unexpected labeled metrics in call to assertDNRTelemetryMetricsSamplesCount: ${labeledMetricsFound}`
+    );
+  }
+
+  for (const metricDetails of metrics) {
+    const { metric, expectedSamplesCount } = metricDetails;
+    if (IS_ANDROID_BUILD) {
+      info(
+        `Skip assertions on collected samples for extensionsApisDnr.${metric} on android builds`
+      );
+      return;
+    }
+    const gleanData = Glean.extensionsApisDnr[metric].testGetValue();
+    Assert.notEqual(
+      gleanData,
+      undefined,
+      `Got some sample for Glean metric extensionApisDnr.${metric}: ${
+        gleanData && JSON.stringify(gleanData)
+      }`
+    );
+    Assert.equal(
+      valueSum(gleanData.values),
+      expectedSamplesCount,
+      `Got the expected number of samples for Glean metric extensionsApisDnr.${metric} (${msg})`
+    );
+    // Make sure we are accumulating meaningfull values in the sample,
+    // if we do have samples for the bucket "0" it likely means we have
+    // not been collecting the value correctly (e.g. typo in the property
+    // name being collected).
+    Assert.ok(
+      !gleanData.values["0"],
+      `No sample for Glean metric extensionsApisDnr.${metric} should be collected for the bucket "0"`
+    );
+
+    if (metricDetails.mirroredName) {
+      const { mirroredName, mirroredType } = metricDetails;
+      assertDNRTelemetryMirrored({
+        gleanMetric: metric,
+        unifiedName: mirroredName,
+        unifiedType: mirroredType,
+      });
+    }
+  }
+}
diff --git a/toolkit/components/extensions/test/xpcshell/native_messaging.ini b/toolkit/components/extensions/test/xpcshell/native_messaging.ini
new file mode 100644
index 0000000000..06702670bc
--- /dev/null
+++ b/toolkit/components/extensions/test/xpcshell/native_messaging.ini
@@ -0,0 +1,19 @@
+[DEFAULT]
+head = head.js head_e10s.js head_native_messaging.js head_telemetry.js
+tail =
+firefox-appdir = browser
+skip-if = appname == "thunderbird" || os == "android"
+subprocess = true
+support-files =
+  data/**
+tags = webextensions
+
+[test_ext_native_messaging.js]
+skip-if =
+  (os == "win" && processor == "aarch64") # bug 1530841
+  apple_silicon # bug 1729540
+run-sequentially = very high failure rate in parallel
+[test_ext_native_messaging_perf.js]
+skip-if = tsan # Unreasonably slow, bug 1612707
+  os == "win" && os_version == "6.1" # Skip on Azure - frequent failure
+[test_ext_native_messaging_unresponsive.js]
diff --git a/toolkit/components/extensions/test/xpcshell/test_ExtensionShortcutKeyMap.js b/toolkit/components/extensions/test/xpcshell/test_ExtensionShortcutKeyMap.js
new file mode 100644
index 0000000000..8e48684095
--- /dev/null
+++ b/toolkit/components/extensions/test/xpcshell/test_ExtensionShortcutKeyMap.js
@@ -0,0 +1,141 @@
+/* -*- Mode: indent-tabs-mode: nil; js-indent-level: 2 -*- */
+/* vim: set sts=2 sw=2 et tw=80: */
+"use strict";
+
+const { ExtensionShortcutKeyMap } = ChromeUtils.importESModule(
+  "resource://gre/modules/ExtensionShortcuts.sys.mjs"
+);
+
+add_task(function test_ExtensionShortcutKeymap() {
+  const shortcutsMap = new ExtensionShortcutKeyMap();
+
+  shortcutsMap.recordShortcut("Ctrl+Shift+1", "Addon1", "Command1");
+  shortcutsMap.recordShortcut("Ctrl+Shift+1", "Addon2", "Command2");
+  shortcutsMap.recordShortcut("Ctrl+Alt+2", "Addon2", "Command3");
+  // Empty shortcut not expected to be recorded, just ignored.
+  shortcutsMap.recordShortcut("", "Addon3", "Command4");
+
+  Assert.equal(
+    shortcutsMap.size,
+    2,
+    "Got the expected number of shortcut entries"
+  );
+  Assert.deepEqual(
+    {
+      shortcutWithTwoExtensions: shortcutsMap.getFirstAddonName("Ctrl+Shift+1"),
+      shortcutWithOnlyOneExtension:
+        shortcutsMap.getFirstAddonName("Ctrl+Alt+2"),
+      shortcutWithNoExtension: shortcutsMap.getFirstAddonName(""),
+    },
+    {
+      shortcutWithTwoExtensions: "Addon1",
+      shortcutWithOnlyOneExtension: "Addon2",
+      shortcutWithNoExtension: null,
+    },
+    "Got the expected results from getFirstAddonName calls"
+  );
+
+  Assert.deepEqual(
+    {
+      shortcutWithTwoExtensions: shortcutsMap.has("Ctrl+Shift+1"),
+      shortcutWithOnlyOneExtension: shortcutsMap.has("Ctrl+Alt+2"),
+      shortcutWithNoExtension: shortcutsMap.has(""),
+    },
+    {
+      shortcutWithTwoExtensions: true,
+      shortcutWithOnlyOneExtension: true,
+      shortcutWithNoExtension: false,
+    },
+    "Got the expected results from `has` calls"
+  );
+
+  shortcutsMap.removeShortcut("Ctrl+Shift+1", "Addon1", "Command1");
+  Assert.equal(
+    shortcutsMap.has("Ctrl+Shift+1"),
+    true,
+    "Expect shortcut to already exist after removing one duplicate"
+  );
+  Assert.equal(
+    shortcutsMap.getFirstAddonName("Ctrl+Shift+1"),
+    "Addon2",
+    "Expect getFirstAddonName to return the remaining addon name"
+  );
+
+  shortcutsMap.removeShortcut("Ctrl+Shift+1", "Addon2", "Command2");
+  Assert.equal(
+    shortcutsMap.has("Ctrl+Shift+1"),
+    false,
+    "Expect shortcut to not exist anymore after removing last entry"
+  );
+  Assert.equal(shortcutsMap.size, 1, "Got only one shortcut as expected");
+
+  shortcutsMap.clear();
+  Assert.equal(
+    shortcutsMap.size,
+    0,
+    "Got no shortcut as expected after clearing the map"
+  );
+});
+
+// This test verify that ExtensionShortcutKeyMap does catch duplicated
+// shortcut when the two modifiers strings are associated to the same
+// key (in particular on macOS where Ctrl and Command keys are both translated
+// in the same modifier in the keyboard shortcuts).
+add_task(function test_PlatformShortcutString() {
+  const shortcutsMap = new ExtensionShortcutKeyMap();
+
+  // Make the class instance behave like it would while running on macOS.
+  // (this is just for unit testing purpose, there is a separate integration
+  // test exercising this behavior in a real "Manage Extension Shortcut"
+  // about:addons view and only running on macOS, skipped on other platforms).
+  shortcutsMap._os = "mac";
+
+  shortcutsMap.recordShortcut("Ctrl+Shift+1", "Addon1", "MacCommand1");
+
+  Assert.deepEqual(
+    {
+      hasWithCtrl: shortcutsMap.has("Ctrl+Shift+1"),
+      hasWithCommand: shortcutsMap.has("Command+Shift+1"),
+    },
+    {
+      hasWithCtrl: true,
+      hasWithCommand: true,
+    },
+    "Got the expected results from `has` calls"
+  );
+
+  Assert.deepEqual(
+    {
+      nameWithCtrl: shortcutsMap.getFirstAddonName("Ctrl+Shift+1"),
+      nameWithCommand: shortcutsMap.getFirstAddonName("Command+Shift+1"),
+    },
+    {
+      nameWithCtrl: "Addon1",
+      nameWithCommand: "Addon1",
+    },
+    "Got the expected results from `getFirstAddonName` calls"
+  );
+
+  // Add a duplicate shortcut using Command instead of Ctrl and
+  // verify the expected behaviors.
+  shortcutsMap.recordShortcut("Command+Shift+1", "Addon2", "MacCommand2");
+  Assert.equal(shortcutsMap.size, 1, "Got still one shortcut as expected");
+  shortcutsMap.removeShortcut("Ctrl+Shift+1", "Addon1", "MacCommand1");
+  Assert.equal(shortcutsMap.size, 1, "Got still one shortcut as expected");
+  Assert.deepEqual(
+    {
+      nameWithCtrl: shortcutsMap.getFirstAddonName("Ctrl+Shift+1"),
+      nameWithCommand: shortcutsMap.getFirstAddonName("Command+Shift+1"),
+    },
+    {
+      nameWithCtrl: "Addon2",
+      nameWithCommand: "Addon2",
+    },
+    "Got the expected results from `getFirstAddonName` calls"
+  );
+
+  // Remove the entry added with a shortcut using "Command" by using the
+  // equivalent shortcut using Ctrl.
+  shortcutsMap.removeShortcut("Ctrl+Shift+1", "Addon2", "MacCommand2");
+  Assert.equal(shortcutsMap.size, 0, "Got no shortcut as expected");
+});
diff --git a/toolkit/components/extensions/test/xpcshell/test_ExtensionStorageSync_migration_kinto.js b/toolkit/components/extensions/test/xpcshell/test_ExtensionStorageSync_migration_kinto.js
new file mode 100644
index 0000000000..7cde68ee98
--- /dev/null
+++ b/toolkit/components/extensions/test/xpcshell/test_ExtensionStorageSync_migration_kinto.js
@@ -0,0 +1,86 @@
+/* -*- Mode: indent-tabs-mode: nil; js-indent-level: 2 -*- */
+/* vim: set sts=2 sw=2 et tw=80: */
+"use strict";
+
+// Import the rust-based and kinto-based implementations
+const { extensionStorageSync: rustImpl } = ChromeUtils.importESModule(
+  "resource://gre/modules/ExtensionStorageSync.sys.mjs"
+);
+const { extensionStorageSyncKinto: kintoImpl } = ChromeUtils.importESModule(
+  "resource://gre/modules/ExtensionStorageSyncKinto.sys.mjs"
+);
+
+Services.prefs.setBoolPref("webextensions.storage.sync.kinto", false);
+
+add_task(async function test_sync_migration() {
+  // There's no good reason to perform this test via test extensions - we just
+  // call the underlying APIs directly.
+
+  // Set some stuff using the kinto-based impl.
+  let e1 = { id: "test@mozilla.com" };
+  let c1 = { extension: e1, callOnClose() {} };
+  await kintoImpl.set(e1, { foo: "bar" }, c1);
+
+  let e2 = { id: "test-2@mozilla.com" };
+  let c2 = { extension: e2, callOnClose() {} };
+  await kintoImpl.set(e2, { second: "2nd" }, c2);
+
+  let e3 = { id: "test-3@mozilla.com" };
+  let c3 = { extension: e3, callOnClose() {} };
+
+  // And all the data should be magically migrated.
+  Assert.deepEqual(await rustImpl.get(e1, "foo", c1), { foo: "bar" });
+  Assert.deepEqual(await rustImpl.get(e2, null, c2), { second: "2nd" });
+
+  // Sanity check we really are doing what we think we are - set a value in our
+  // new one, it should not be reflected by kinto.
+  await rustImpl.set(e3, { third: "3rd" }, c3);
+  Assert.deepEqual(await rustImpl.get(e3, null, c3), { third: "3rd" });
+  Assert.deepEqual(await kintoImpl.get(e3, null, c3), {});
+  // cleanup.
+  await kintoImpl.clear(e1, c1);
+  await kintoImpl.clear(e2, c2);
+  await kintoImpl.clear(e3, c3);
+  await rustImpl.clear(e1, c1);
+  await rustImpl.clear(e2, c2);
+  await rustImpl.clear(e3, c3);
+});
+
+// It would be great to have failure tests, but that seems impossible to have
+// in automated tests given the conditions under which we migrate - it would
+// basically require us to arrange for zero free disk space or to somehow
+// arrange for sqlite to see an io error. Specially crafted "corrupt"
+// sqlite files doesn't help because that file must not exist for us to even
+// attempt migration.
+//
+// But - what we can test is that if .migratedOk on the new impl ever goes to
+// false we delegate correctly.
+add_task(async function test_sync_migration_delgates() {
+  let e1 = { id: "test@mozilla.com" };
+  let c1 = { extension: e1, callOnClose() {} };
+  await kintoImpl.set(e1, { foo: "bar" }, c1);
+
+  // We think migration went OK - `get` shouldn't see kinto.
+  Assert.deepEqual(rustImpl.get(e1, null, c1), {});
+
+  info(
+    "Setting migration failure flag to ensure we delegate to kinto implementation"
+  );
+  rustImpl.migrationOk = false;
+  // get should now be seeing kinto.
+  Assert.deepEqual(await rustImpl.get(e1, null, c1), { foo: "bar" });
+  // check everything else delegates.
+
+  await rustImpl.set(e1, { foo: "foo" }, c1);
+  Assert.deepEqual(await kintoImpl.get(e1, null, c1), { foo: "foo" });
+
+  Assert.equal(await rustImpl.getBytesInUse(e1, null, c1), 8);
+
+  await rustImpl.remove(e1, "foo", c1);
+  Assert.deepEqual(await kintoImpl.get(e1, null, c1), {});
+
+  await rustImpl.set(e1, { foo: "foo" }, c1);
+  Assert.deepEqual(await kintoImpl.get(e1, null, c1), { foo: "foo" });
+  await rustImpl.clear(e1, c1);
+  Assert.deepEqual(await kintoImpl.get(e1, null, c1), {});
+});
diff --git a/toolkit/components/extensions/test/xpcshell/test_MatchPattern.js b/toolkit/components/extensions/test/xpcshell/test_MatchPattern.js
new file mode 100644
index 0000000000..1a57d0870e
--- /dev/null
+++ b/toolkit/components/extensions/test/xpcshell/test_MatchPattern.js
@@ -0,0 +1,602 @@
+/* -*- Mode: indent-tabs-mode: nil; js-indent-level: 2 -*- */
+/* vim: set sts=2 sw=2 et tw=80: */
+"use strict";
+
+add_task(async function test_MatchPattern_matches() {
+  function test(url, pattern, normalized = pattern, options = {}, explicit) {
+    let uri = Services.io.newURI(url);
+
+    pattern = Array.prototype.concat.call(pattern);
+    normalized = Array.prototype.concat.call(normalized);
+
+    let patterns = pattern.map(pat => new MatchPattern(pat, options));
+
+    let set = new MatchPatternSet(pattern, options);
+    let set2 = new MatchPatternSet(patterns, options);
+
+    deepEqual(
+      set2.patterns,
+      patterns,
+      "Patterns in set should equal the input patterns"
+    );
+
+    equal(
+      set.matches(uri, explicit),
+      set2.matches(uri, explicit),
+      "Single pattern and pattern set should return the same match"
+    );
+
+    for (let [i, pat] of patterns.entries()) {
+      equal(
+        pat.pattern,
+        normalized[i],
+        "Pattern property should contain correct normalized pattern value"
+      );
+    }
+
+    if (patterns.length == 1) {
+      equal(
+        patterns[0].matches(uri, explicit),
+        set.matches(uri, explicit),
+        "Single pattern and string set should return the same match"
+      );
+    }
+
+    return set.matches(uri, explicit);
+  }
+
+  function pass({ url, pattern, normalized, options, explicit }) {
+    ok(
+      test(url, pattern, normalized, options, explicit),
+      `Expected match: ${JSON.stringify(pattern)}, ${url}`
+    );
+  }
+
+  function fail({ url, pattern, normalized, options, explicit }) {
+    ok(
+      !test(url, pattern, normalized, options, explicit),
+      `Expected no match: ${JSON.stringify(pattern)}, ${url}`
+    );
+  }
+
+  function invalid({ pattern }) {
+    Assert.throws(
+      () => new MatchPattern(pattern),
+      /.*/,
+      `Invalid pattern '${pattern}' should throw`
+    );
+    Assert.throws(
+      () => new MatchPatternSet([pattern]),
+      /.*/,
+      `Invalid pattern '${pattern}' should throw`
+    );
+  }
+
+  // Invalid pattern.
+  invalid({ pattern: "" });
+
+  // Pattern must include trailing slash.
+  invalid({ pattern: "http://mozilla.org" });
+
+  // Protocol not allowed.
+  invalid({ pattern: "gopher://wuarchive.wustl.edu/" });
+
+  pass({ url: "http://mozilla.org", pattern: "http://mozilla.org/" });
+  pass({ url: "http://mozilla.org/", pattern: "http://mozilla.org/" });
+
+  pass({ url: "http://mozilla.org/", pattern: "*://mozilla.org/" });
+  pass({ url: "https://mozilla.org/", pattern: "*://mozilla.org/" });
+  fail({ url: "file://mozilla.org/", pattern: "*://mozilla.org/" });
+  fail({ url: "ftp://mozilla.org/", pattern: "*://mozilla.org/" });
+
+  fail({ url: "http://mozilla.com", pattern: "http://*mozilla.com*/" });
+  fail({ url: "http://mozilla.com", pattern: "http://mozilla.*/" });
+  invalid({ pattern: "http:/mozilla.com/" });
+
+  pass({ url: "http://google.com", pattern: "http://*.google.com/" });
+  pass({ url: "http://docs.google.com", pattern: "http://*.google.com/" });
+
+  pass({ url: "http://mozilla.org:8080", pattern: "http://mozilla.org/" });
+  pass({ url: "http://mozilla.org:8080", pattern: "*://mozilla.org/" });
+  fail({ url: "http://mozilla.org:8080", pattern: "http://mozilla.org:8080/" });
+
+  // Now try with * in the path.
+  pass({ url: "http://mozilla.org", pattern: "http://mozilla.org/*" });
+  pass({ url: "http://mozilla.org/", pattern: "http://mozilla.org/*" });
+
+  pass({ url: "http://mozilla.org/", pattern: "*://mozilla.org/*" });
+  pass({ url: "https://mozilla.org/", pattern: "*://mozilla.org/*" });
+  fail({ url: "file://mozilla.org/", pattern: "*://mozilla.org/*" });
+  fail({ url: "http://mozilla.com", pattern: "http://mozilla.*/*" });
+
+  pass({ url: "http://google.com", pattern: "http://*.google.com/*" });
+  pass({ url: "http://docs.google.com", pattern: "http://*.google.com/*" });
+
+  // Check path stuff.
+  fail({ url: "http://mozilla.com/abc/def", pattern: "http://mozilla.com/" });
+  pass({ url: "http://mozilla.com/abc/def", pattern: "http://mozilla.com/*" });
+  pass({
+    url: "http://mozilla.com/abc/def",
+    pattern: "http://mozilla.com/a*f",
+  });
+  pass({ url: "http://mozilla.com/abc/def", pattern: "http://mozilla.com/a*" });
+  pass({ url: "http://mozilla.com/abc/def", pattern: "http://mozilla.com/*f" });
+  fail({ url: "http://mozilla.com/abc/def", pattern: "http://mozilla.com/*e" });
+  fail({ url: "http://mozilla.com/abc/def", pattern: "http://mozilla.com/*c" });
+
+  invalid({ pattern: "http:///a.html" });
+  pass({ url: "file:///foo", pattern: "file:///foo*" });
+  pass({ url: "file:///foo/bar.html", pattern: "file:///foo*" });
+
+  pass({ url: "http://mozilla.org/a", pattern: "<all_urls>" });
+  pass({ url: "https://mozilla.org/a", pattern: "<all_urls>" });
+  pass({ url: "ftp://mozilla.org/a", pattern: "<all_urls>" });
+  pass({ url: "file:///a", pattern: "<all_urls>" });
+  fail({ url: "gopher://wuarchive.wustl.edu/a", pattern: "<all_urls>" });
+
+  // Multiple patterns.
+  pass({ url: "http://mozilla.org", pattern: ["http://mozilla.org/"] });
+  pass({
+    url: "http://mozilla.org",
+    pattern: ["http://mozilla.org/", "http://mozilla.com/"],
+  });
+  pass({
+    url: "http://mozilla.com",
+    pattern: ["http://mozilla.org/", "http://mozilla.com/"],
+  });
+  fail({
+    url: "http://mozilla.biz",
+    pattern: ["http://mozilla.org/", "http://mozilla.com/"],
+  });
+
+  // Match url with fragments.
+  pass({
+    url: "http://mozilla.org/base#some-fragment",
+    pattern: "http://mozilla.org/base",
+  });
+
+  // Match data:-URLs.
+  pass({ url: "data:text/plain,foo", pattern: ["data:text/plain,foo"] });
+  pass({ url: "data:text/plain,foo", pattern: ["data:text/plain,*"] });
+  pass({
+    url: "data:text/plain;charset=utf-8,foo",
+    pattern: ["data:text/plain;charset=utf-8,foo"],
+  });
+  fail({
+    url: "data:text/plain,foo",
+    pattern: ["data:text/plain;charset=utf-8,foo"],
+  });
+  fail({
+    url: "data:text/plain;charset=utf-8,foo",
+    pattern: ["data:text/plain,foo"],
+  });
+
+  // Privileged matchers:
+  invalid({ pattern: "about:foo" });
+  invalid({ pattern: "resource://foo/*" });
+
+  pass({
+    url: "about:foo",
+    pattern: ["about:foo", "about:foo*"],
+    options: { restrictSchemes: false },
+  });
+  pass({
+    url: "about:foo",
+    pattern: ["about:foo*"],
+    options: { restrictSchemes: false },
+  });
+  pass({
+    url: "about:foobar",
+    pattern: ["about:foo*"],
+    options: { restrictSchemes: false },
+  });
+
+  pass({
+    url: "resource://foo/bar",
+    pattern: ["resource://foo/bar"],
+    options: { restrictSchemes: false },
+  });
+  fail({
+    url: "resource://fog/bar",
+    pattern: ["resource://foo/bar"],
+    options: { restrictSchemes: false },
+  });
+  fail({
+    url: "about:foo",
+    pattern: ["about:meh"],
+    options: { restrictSchemes: false },
+  });
+
+  // Matchers for schemes without host should ignore ignorePath.
+  pass({
+    url: "about:reader?http://e.com/",
+    pattern: ["about:reader*"],
+    options: { ignorePath: true, restrictSchemes: false },
+  });
+  pass({ url: "data:,", pattern: ["data:,*"], options: { ignorePath: true } });
+
+  // Matchers for schems without host should still match even if the explicit (host) flag is set.
+  pass({
+    url: "about:reader?explicit",
+    pattern: ["about:reader*"],
+    options: { restrictSchemes: false },
+    explicit: true,
+  });
+  pass({
+    url: "about:reader?explicit",
+    pattern: ["about:reader?explicit"],
+    options: { restrictSchemes: false },
+    explicit: true,
+  });
+  pass({ url: "data:,explicit", pattern: ["data:,explicit"], explicit: true });
+  pass({ url: "data:,explicit", pattern: ["data:,*"], explicit: true });
+
+  // Matchers without "//" separator in the pattern.
+  pass({ url: "data:text/plain;charset=utf-8,foo", pattern: ["data:*"] });
+  pass({
+    url: "about:blank",
+    pattern: ["about:*"],
+    options: { restrictSchemes: false },
+  });
+  pass({
+    url: "view-source:https://example.com",
+    pattern: ["view-source:*"],
+    options: { restrictSchemes: false },
+  });
+  invalid({ pattern: ["chrome:*"], options: { restrictSchemes: false } });
+  invalid({ pattern: "http:*" });
+
+  // Matchers for unrecognized schemes.
+  invalid({ pattern: "unknown-scheme:*" });
+  pass({
+    url: "unknown-scheme:foo",
+    pattern: ["unknown-scheme:foo"],
+    options: { restrictSchemes: false },
+  });
+  pass({
+    url: "unknown-scheme:foo",
+    pattern: ["unknown-scheme:*"],
+    options: { restrictSchemes: false },
+  });
+  pass({
+    url: "unknown-scheme://foo",
+    pattern: ["unknown-scheme://foo"],
+    options: { restrictSchemes: false },
+  });
+  pass({
+    url: "unknown-scheme://foo",
+    pattern: ["unknown-scheme://*"],
+    options: { restrictSchemes: false },
+  });
+  pass({
+    url: "unknown-scheme://foo",
+    pattern: ["unknown-scheme:*"],
+    options: { restrictSchemes: false },
+  });
+  fail({
+    url: "unknown-scheme://foo",
+    pattern: ["unknown-scheme:foo"],
+    options: { restrictSchemes: false },
+  });
+  fail({
+    url: "unknown-scheme:foo",
+    pattern: ["unknown-scheme://foo"],
+    options: { restrictSchemes: false },
+  });
+  fail({
+    url: "unknown-scheme:foo",
+    pattern: ["unknown-scheme://*"],
+    options: { restrictSchemes: false },
+  });
+
+  // Matchers for IPv6
+  pass({ url: "http://[::1]/", pattern: ["http://[::1]/"] });
+  pass({
+    url: "http://[2a03:4000:6:310e:216:3eff:fe53:99b]/",
+    pattern: ["http://[2a03:4000:6:310e:216:3eff:fe53:99b]/"],
+  });
+  fail({
+    url: "http://[2:4:6:3:2:3:f:b]/",
+    pattern: ["http://[2a03:4000:6:310e:216:3eff:fe53:99b]/"],
+  });
+
+  // Before fixing Bug 1529230, the only way to match a specific IPv6 url is by droping the brackets in pattern,
+  // thus we keep this pattern valid for the sake of backward compatibility
+  pass({ url: "http://[::1]/", pattern: ["http://::1/"] });
+  pass({
+    url: "http://[2a03:4000:6:310e:216:3eff:fe53:99b]/",
+    pattern: ["http://2a03:4000:6:310e:216:3eff:fe53:99b/"],
+  });
+});
+
+add_task(async function test_MatchPattern_overlaps() {
+  function test(filter, hosts, optional) {
+    filter = Array.prototype.concat.call(filter);
+    hosts = Array.prototype.concat.call(hosts);
+    optional = Array.prototype.concat.call(optional);
+
+    const set = new MatchPatternSet([...hosts, ...optional]);
+    const pat = new MatchPatternSet(filter);
+    return set.overlapsAll(pat);
+  }
+
+  function pass({ filter = [], hosts = [], optional = [] }) {
+    ok(
+      test(filter, hosts, optional),
+      `Expected overlap: ${filter}, ${hosts} (${optional})`
+    );
+  }
+
+  function fail({ filter = [], hosts = [], optional = [] }) {
+    ok(
+      !test(filter, hosts, optional),
+      `Expected no overlap: ${filter}, ${hosts} (${optional})`
+    );
+  }
+
+  // Direct comparison.
+  pass({ hosts: "http://ab.cd/", filter: "http://ab.cd/" });
+  fail({ hosts: "http://ab.cd/", filter: "ftp://ab.cd/" });
+
+  // Wildcard protocol.
+  pass({ hosts: "*://ab.cd/", filter: "https://ab.cd/" });
+  fail({ hosts: "*://ab.cd/", filter: "ftp://ab.cd/" });
+
+  // Wildcard subdomain.
+  pass({ hosts: "http://*.ab.cd/", filter: "http://ab.cd/" });
+  pass({ hosts: "http://*.ab.cd/", filter: "http://www.ab.cd/" });
+  fail({ hosts: "http://*.ab.cd/", filter: "http://ab.cd.ef/" });
+  fail({ hosts: "http://*.ab.cd/", filter: "http://www.cd/" });
+
+  // Wildcard subsumed.
+  pass({ hosts: "http://*.ab.cd/", filter: "http://*.cd/" });
+  fail({ hosts: "http://*.cd/", filter: "http://*.xy/" });
+
+  // Subdomain vs substring.
+  fail({ hosts: "http://*.ab.cd/", filter: "http://fake-ab.cd/" });
+  fail({ hosts: "http://*.ab.cd/", filter: "http://*.fake-ab.cd/" });
+
+  // Wildcard domain.
+  pass({ hosts: "http://*/", filter: "http://ab.cd/" });
+  fail({ hosts: "http://*/", filter: "https://ab.cd/" });
+
+  // Wildcard wildcards.
+  pass({ hosts: "<all_urls>", filter: "ftp://ab.cd/" });
+  fail({ hosts: "<all_urls>" });
+
+  // Multiple hosts.
+  pass({ hosts: ["http://ab.cd/"], filter: ["http://ab.cd/"] });
+  pass({ hosts: ["http://ab.cd/", "http://ab.xy/"], filter: "http://ab.cd/" });
+  pass({ hosts: ["http://ab.cd/", "http://ab.xy/"], filter: "http://ab.xy/" });
+  fail({ hosts: ["http://ab.cd/", "http://ab.xy/"], filter: "http://ab.zz/" });
+
+  // Multiple Multiples.
+  pass({
+    hosts: ["http://*.ab.cd/"],
+    filter: ["http://ab.cd/", "http://www.ab.cd/"],
+  });
+  pass({
+    hosts: ["http://ab.cd/", "http://ab.xy/"],
+    filter: ["http://ab.cd/", "http://ab.xy/"],
+  });
+  fail({
+    hosts: ["http://ab.cd/", "http://ab.xy/"],
+    filter: ["http://ab.cd/", "http://ab.zz/"],
+  });
+
+  // Optional.
+  pass({ hosts: [], optional: "http://ab.cd/", filter: "http://ab.cd/" });
+  pass({
+    hosts: "http://ab.cd/",
+    optional: "http://ab.xy/",
+    filter: ["http://ab.cd/", "http://ab.xy/"],
+  });
+  fail({
+    hosts: "http://ab.cd/",
+    optional: "https://ab.xy/",
+    filter: "http://ab.xy/",
+  });
+});
+
+add_task(async function test_MatchGlob() {
+  function test(url, pattern) {
+    let m = new MatchGlob(pattern[0]);
+    return m.matches(Services.io.newURI(url).spec);
+  }
+
+  function pass({ url, pattern }) {
+    ok(
+      test(url, pattern),
+      `Expected match: ${JSON.stringify(pattern)}, ${url}`
+    );
+  }
+
+  function fail({ url, pattern }) {
+    ok(
+      !test(url, pattern),
+      `Expected no match: ${JSON.stringify(pattern)}, ${url}`
+    );
+  }
+
+  let moz = "http://mozilla.org";
+
+  pass({ url: moz, pattern: ["*"] });
+  pass({ url: moz, pattern: ["http://*"] });
+  pass({ url: moz, pattern: ["*mozilla*"] });
+  // pass({url: moz, pattern: ["*example*", "*mozilla*"]});
+
+  pass({ url: moz, pattern: ["*://*"] });
+  pass({ url: "https://mozilla.org", pattern: ["*://*"] });
+
+  // Documentation example
+  pass({
+    url: "http://www.example.com/foo/bar",
+    pattern: ["http://???.example.com/foo/*"],
+  });
+  pass({
+    url: "http://the.example.com/foo/",
+    pattern: ["http://???.example.com/foo/*"],
+  });
+  fail({
+    url: "http://my.example.com/foo/bar",
+    pattern: ["http://???.example.com/foo/*"],
+  });
+  fail({
+    url: "http://example.com/foo/",
+    pattern: ["http://???.example.com/foo/*"],
+  });
+  fail({
+    url: "http://www.example.com/foo",
+    pattern: ["http://???.example.com/foo/*"],
+  });
+
+  // Matches path
+  let path = moz + "/abc/def";
+  pass({ url: path, pattern: ["*def"] });
+  pass({ url: path, pattern: ["*c/d*"] });
+  pass({ url: path, pattern: ["*org/abc*"] });
+  fail({ url: path + "/", pattern: ["*def"] });
+
+  // Trailing slash
+  pass({ url: moz, pattern: ["*.org/"] });
+  fail({ url: moz, pattern: ["*.org"] });
+
+  // Wrong TLD
+  fail({ url: moz, pattern: ["*oz*.com/"] });
+  // Case sensitive
+  fail({ url: moz, pattern: ["*.ORG/"] });
+});
+
+add_task(async function test_MatchGlob_redundant_wildcards_backtracking() {
+  const slow_build =
+    AppConstants.DEBUG || AppConstants.TSAN || AppConstants.ASAN;
+  const first_limit = slow_build ? 200 : 20;
+  {
+    // Bug 1570868 - repeated * in tabs.query glob causes too much backtracking.
+    let title = `Monster${"*".repeat(99)}Mash`;
+
+    // The first run could take longer than subsequent runs, as the DFA is lazily created.
+    let first_start = Date.now();
+    let glob = new MatchGlob(title);
+    let first_matches = glob.matches(title);
+    let first_duration = Date.now() - first_start;
+    ok(first_matches, `Expected match: ${title}, ${title}`);
+    ok(
+      first_duration < first_limit,
+      `First matching duration: ${first_duration}ms (limit: ${first_limit}ms)`
+    );
+
+    let start = Date.now();
+    let matches = glob.matches(title);
+    let duration = Date.now() - start;
+
+    ok(matches, `Expected match: ${title}, ${title}`);
+    ok(duration < 10, `Matching duration: ${duration}ms`);
+  }
+  {
+    // Similarly with any continuous combination of ?**???****? wildcards.
+    let title = `Monster${"?*".repeat(99)}Mash`;
+
+    // The first run could take longer than subsequent runs, as the DFA is lazily created.
+    let first_start = Date.now();
+    let glob = new MatchGlob(title);
+    let first_matches = glob.matches(title);
+    let first_duration = Date.now() - first_start;
+    ok(first_matches, `Expected match: ${title}, ${title}`);
+    ok(
+      first_duration < first_limit,
+      `First matching duration: ${first_duration}ms (limit: ${first_limit}ms)`
+    );
+
+    let start = Date.now();
+    let matches = glob.matches(title);
+    let duration = Date.now() - start;
+
+    ok(matches, `Expected match: ${title}, ${title}`);
+    ok(duration < 10, `Matching duration: ${duration}ms`);
+  }
+});
+
+add_task(async function test_MatchPattern_subsumes() {
+  function test(oldPat, newPat) {
+    let m = new MatchPatternSet(oldPat);
+    return m.subsumes(new MatchPattern(newPat));
+  }
+
+  function pass({ oldPat, newPat }) {
+    ok(test(oldPat, newPat), `${JSON.stringify(oldPat)} subsumes "${newPat}"`);
+  }
+
+  function fail({ oldPat, newPat }) {
+    ok(
+      !test(oldPat, newPat),
+      `${JSON.stringify(oldPat)} doesn't subsume "${newPat}"`
+    );
+  }
+
+  pass({ oldPat: ["<all_urls>"], newPat: "*://*/*" });
+  pass({ oldPat: ["<all_urls>"], newPat: "http://*/*" });
+  pass({ oldPat: ["<all_urls>"], newPat: "http://*.example.com/*" });
+
+  pass({ oldPat: ["*://*/*"], newPat: "http://*/*" });
+  pass({ oldPat: ["*://*/*"], newPat: "wss://*/*" });
+  pass({ oldPat: ["*://*/*"], newPat: "http://*.example.com/*" });
+
+  pass({ oldPat: ["*://*.example.com/*"], newPat: "http://*.example.com/*" });
+  pass({ oldPat: ["*://*.example.com/*"], newPat: "*://sub.example.com/*" });
+
+  pass({ oldPat: ["https://*/*"], newPat: "https://*.example.com/*" });
+  pass({
+    oldPat: ["http://*.example.com/*"],
+    newPat: "http://subdomain.example.com/*",
+  });
+  pass({
+    oldPat: ["http://*.sub.example.com/*"],
+    newPat: "http://sub.example.com/*",
+  });
+  pass({
+    oldPat: ["http://*.sub.example.com/*"],
+    newPat: "http://sec.sub.example.com/*",
+  });
+  pass({
+    oldPat: ["http://www.example.com/*"],
+    newPat: "http://www.example.com/path/*",
+  });
+  pass({
+    oldPat: ["http://www.example.com/path/*"],
+    newPat: "http://www.example.com/*",
+  });
+
+  fail({ oldPat: ["*://*/*"], newPat: "<all_urls>" });
+  fail({ oldPat: ["*://*/*"], newPat: "ftp://*/*" });
+  fail({ oldPat: ["*://*/*"], newPat: "file://*/*" });
+
+  fail({ oldPat: ["http://example.com/*"], newPat: "*://example.com/*" });
+  fail({ oldPat: ["http://example.com/*"], newPat: "https://example.com/*" });
+  fail({
+    oldPat: ["http://example.com/*"],
+    newPat: "http://otherexample.com/*",
+  });
+  fail({ oldPat: ["http://example.com/*"], newPat: "http://*.example.com/*" });
+  fail({
+    oldPat: ["http://example.com/*"],
+    newPat: "http://subdomain.example.com/*",
+  });
+
+  fail({
+    oldPat: ["http://subdomain.example.com/*"],
+    newPat: "http://example.com/*",
+  });
+  fail({
+    oldPat: ["http://subdomain.example.com/*"],
+    newPat: "http://*.example.com/*",
+  });
+  fail({
+    oldPat: ["http://sub.example.com/*"],
+    newPat: "http://*.sub.example.com/*",
+  });
+
+  fail({ oldPat: ["ws://example.com/*"], newPat: "wss://example.com/*" });
+  fail({ oldPat: ["http://example.com/*"], newPat: "ws://example.com/*" });
+  fail({ oldPat: ["https://example.com/*"], newPat: "wss://example.com/*" });
+});
diff --git a/toolkit/components/extensions/test/xpcshell/test_QuarantinedDomains.js b/toolkit/components/extensions/test/xpcshell/test_QuarantinedDomains.js
new file mode 100644
index 0000000000..e7f223f072
--- /dev/null
+++ b/toolkit/components/extensions/test/xpcshell/test_QuarantinedDomains.js
@@ -0,0 +1,217 @@
+"use strict";
+
+AddonTestUtils.init(this);
+AddonTestUtils.createAppInfo(
+  "xpcshell@tests.mozilla.org",
+  "XPCShell",
+  "1",
+  "43"
+);
+
+const ADDONS_RESTRICTED_DOMAINS_PREF =
+  "extensions.webextensions.addons-restricted-domains@mozilla.com.disabled";
+
+const DOMAINS = [
+  "addons-dev.allizom.org",
+  "mixed.badssl.com",
+  "careers.mozilla.com",
+  "developer.mozilla.org",
+  "test.example.com",
+];
+
+const CAN_ACCESS_ALL = DOMAINS.reduce((map, domain) => {
+  return { ...map, [domain]: true };
+}, {});
+
+function makePolicy(options) {
+  return new WebExtensionPolicy({
+    baseURL: "file:///foo/",
+    localizeCallback: str => str,
+    allowedOrigins: new MatchPatternSet(["<all_urls>"], { ignorePath: true }),
+    mozExtensionHostname: Services.uuid.generateUUID().toString().slice(1, -1),
+    ...options,
+  });
+}
+
+function makeCS(policy) {
+  return new WebExtensionContentScript(policy, {
+    matches: new MatchPatternSet(["<all_urls>"]),
+  });
+}
+
+function expectQuarantined(expectedDomains) {
+  for (let domain of DOMAINS) {
+    let uri = Services.io.newURI(`https://${domain}/`);
+    let quarantined = expectedDomains.includes(domain);
+
+    equal(
+      quarantined,
+      WebExtensionPolicy.isQuarantinedURI(uri),
+      `Expect ${uri.spec} to ${quarantined ? "" : "not"} be quarantined.`
+    );
+  }
+}
+
+function expectAccess(policy, cs, expected) {
+  for (let domain of DOMAINS) {
+    let uri = Services.io.newURI(`https://${domain}/`);
+    let access = expected[domain];
+    let match = access;
+
+    equal(
+      access,
+      !policy.quarantinedFromURI(uri),
+      `${policy.id} is ${access ? "not" : ""} quarantined from ${uri.spec}.`
+    );
+    equal(
+      access,
+      policy.canAccessURI(uri),
+      `Expect ${policy.id} ${access ? "can" : "can't"} access ${uri.spec}.`
+    );
+
+    equal(
+      match,
+      cs.matchesURI(uri),
+      `Expect ${cs.extension.id} to ${match ? "" : "not"} match ${uri.spec}.`
+    );
+  }
+}
+
+function expectHost(desc, host, quarantined) {
+  let uri = Services.io.newURI(`https://${host}/`);
+  equal(
+    quarantined,
+    WebExtensionPolicy.isQuarantinedURI(uri),
+    `Expect ${desc} "${host}" to ${quarantined ? "" : "not"} be quarantined.`
+  );
+}
+
+function makePolicies() {
+  const plain = makePolicy({ id: "plain@test" });
+  const system = makePolicy({ id: "system@test", isPrivileged: true });
+  const exempt = makePolicy({ id: "exempt@test", ignoreQuarantine: true });
+
+  return { plain, system, exempt };
+}
+
+function makeContentScripts(policies) {
+  return policies.map(makeCS);
+}
+
+add_task(async function test_QuarantinedDomains() {
+  const { plain, system, exempt } = makePolicies();
+  const [plainCS, systemCS, exemptCS] = makeContentScripts([
+    plain,
+    system,
+    exempt,
+  ]);
+
+  info("Initial pref state is an empty list.");
+  expectQuarantined([]);
+
+  expectAccess(plain, plainCS, CAN_ACCESS_ALL);
+  expectAccess(system, systemCS, CAN_ACCESS_ALL);
+  expectAccess(exempt, exemptCS, CAN_ACCESS_ALL);
+
+  info("Default test domain list.");
+  Services.prefs.setStringPref(
+    "extensions.quarantinedDomains.list",
+    "addons-dev.allizom.org,mixed.badssl.com,test.example.com"
+  );
+
+  expectQuarantined([
+    "addons-dev.allizom.org",
+    "mixed.badssl.com",
+    "test.example.com",
+  ]);
+
+  expectAccess(plain, plainCS, {
+    "addons-dev.allizom.org": false,
+    "mixed.badssl.com": false,
+    "careers.mozilla.com": true,
+    "developer.mozilla.org": true,
+    "test.example.com": false,
+  });
+
+  expectAccess(system, systemCS, CAN_ACCESS_ALL);
+  expectAccess(exempt, exemptCS, CAN_ACCESS_ALL);
+
+  info("Disable the Quarantined Domains feature.");
+  Services.prefs.setBoolPref("extensions.quarantinedDomains.enabled", false);
+  expectQuarantined([]);
+
+  expectAccess(plain, plainCS, CAN_ACCESS_ALL);
+  expectAccess(system, systemCS, CAN_ACCESS_ALL);
+  expectAccess(exempt, exemptCS, CAN_ACCESS_ALL);
+
+  info(
+    "Enable again, drop addons-dev.allizom.org and add developer.mozilla.org to the pref."
+  );
+  Services.prefs.setBoolPref("extensions.quarantinedDomains.enabled", true);
+
+  Services.prefs.setStringPref(
+    "extensions.quarantinedDomains.list",
+    "mixed.badssl.com,developer.mozilla.org,test.example.com"
+  );
+  expectQuarantined([
+    "mixed.badssl.com",
+    "developer.mozilla.org",
+    "test.example.com",
+  ]);
+
+  expectAccess(plain, plainCS, {
+    "addons-dev.allizom.org": true,
+    "mixed.badssl.com": false,
+    "careers.mozilla.com": true,
+    "developer.mozilla.org": false,
+    "test.example.com": false,
+  });
+
+  expectAccess(system, systemCS, CAN_ACCESS_ALL);
+  expectAccess(exempt, exemptCS, CAN_ACCESS_ALL);
+
+  expectHost("host with a port", "test.example.com:1025", true);
+
+  expectHost("FQDN", "test.example.com.", false);
+  expectHost("subdomain", "subdomain.test.example.com", false);
+  expectHost("domain with prefix", "pretest.example.com", false);
+  expectHost("domain with suffix", "test.example.comsuf", false);
+});
+
+// Make sure we honor the system add-on pref.
+add_task(
+  {
+    pref_set: [
+      [ADDONS_RESTRICTED_DOMAINS_PREF, true],
+      [
+        "extensions.quarantinedDomains.list",
+        "addons-dev.allizom.org,mixed.badssl.com,test.example.com",
+      ],
+    ],
+  },
+  async function test_QuarantinedDomains_with_system_addon_disabled() {
+    await AddonTestUtils.promiseRestartManager();
+
+    const { plain, system, exempt } = makePolicies();
+    const [plainCS, systemCS, exemptCS] = makeContentScripts([
+      plain,
+      system,
+      exempt,
+    ]);
+
+    expectQuarantined([]);
+    expectAccess(plain, plainCS, CAN_ACCESS_ALL);
+    expectAccess(system, systemCS, CAN_ACCESS_ALL);
+    expectAccess(exempt, exemptCS, CAN_ACCESS_ALL);
+
+    // When the user changes this pref to re-enable the system add-on...
+    Services.prefs.setBoolPref(ADDONS_RESTRICTED_DOMAINS_PREF, false);
+    // ...after a AOM restart...
+    await AddonTestUtils.promiseRestartManager();
+    // ...we expect no change.
+    expectQuarantined([]);
+    expectAccess(plain, plainCS, CAN_ACCESS_ALL);
+    expectAccess(system, systemCS, CAN_ACCESS_ALL);
+    expectAccess(exempt, exemptCS, CAN_ACCESS_ALL);
+  }
+);
diff --git a/toolkit/components/extensions/test/xpcshell/test_StorageSyncService.js b/toolkit/components/extensions/test/xpcshell/test_StorageSyncService.js
new file mode 100644
index 0000000000..ef55ed37e8
--- /dev/null
+++ b/toolkit/components/extensions/test/xpcshell/test_StorageSyncService.js
@@ -0,0 +1,274 @@
+/* Any copyright is dedicated to the Public Domain.
+ * http://creativecommons.org/publicdomain/zero/1.0/ */
+
+"use strict";
+
+const NS_ERROR_DOM_QUOTA_EXCEEDED_ERR = 0x80530016;
+
+XPCOMUtils.defineLazyServiceGetter(
+  this,
+  "StorageSyncService",
+  "@mozilla.org/extensions/storage/sync;1",
+  "nsIInterfaceRequestor"
+);
+
+function promisify(func, ...params) {
+  return new Promise((resolve, reject) => {
+    let changes = [];
+    func(...params, {
+      QueryInterface: ChromeUtils.generateQI([
+        "mozIExtensionStorageListener",
+        "mozIExtensionStorageCallback",
+        "mozIBridgedSyncEngineCallback",
+        "mozIBridgedSyncEngineApplyCallback",
+      ]),
+      onChanged(extId, json) {
+        changes.push({ extId, changes: JSON.parse(json) });
+      },
+      handleSuccess(value) {
+        resolve({
+          changes,
+          value: typeof value == "string" ? JSON.parse(value) : value,
+        });
+      },
+      handleError(code, message) {
+        reject(Components.Exception(message, code));
+      },
+    });
+  });
+}
+
+add_task(async function setup_storage_sync() {
+  // So that we can write to the profile directory.
+  do_get_profile();
+});
+
+add_task(async function test_storage_sync_service() {
+  const service = StorageSyncService.getInterface(Ci.mozIExtensionStorageArea);
+  {
+    let { changes, value } = await promisify(
+      service.set,
+      "ext-1",
+      JSON.stringify({
+        hi: "hello! 💖",
+        bye: "adiós",
+      })
+    );
+    deepEqual(
+      changes,
+      [
+        {
+          extId: "ext-1",
+          changes: {
+            hi: {
+              newValue: "hello! 💖",
+            },
+            bye: {
+              newValue: "adiós",
+            },
+          },
+        },
+      ],
+      "`set` should notify listeners about changes"
+    );
+    ok(!value, "`set` should not return a value");
+  }
+
+  {
+    let { changes, value } = await promisify(
+      service.get,
+      "ext-1",
+      JSON.stringify(["hi"])
+    );
+    deepEqual(changes, [], "`get` should not notify listeners");
+    deepEqual(
+      value,
+      {
+        hi: "hello! 💖",
+      },
+      "`get` with key should return value"
+    );
+
+    let { value: allValues } = await promisify(service.get, "ext-1", "null");
+    deepEqual(
+      allValues,
+      {
+        hi: "hello! 💖",
+        bye: "adiós",
+      },
+      "`get` without a key should return all values"
+    );
+  }
+
+  {
+    await promisify(
+      service.set,
+      "ext-2",
+      JSON.stringify({
+        hi: "hola! 👋",
+      })
+    );
+    await promisify(service.clear, "ext-1");
+    let { value: allValues } = await promisify(service.get, "ext-1", "null");
+    deepEqual(allValues, {}, "clear removed ext-1");
+
+    let { value: allValues2 } = await promisify(service.get, "ext-2", "null");
+    deepEqual(allValues2, { hi: "hola! 👋" }, "clear didn't remove ext-2");
+    // We need to clear data for ext-2 too, so later tests don't fail due to
+    // this data.
+    await promisify(service.clear, "ext-2");
+  }
+});
+
+add_task(async function test_storage_sync_bridged_engine() {
+  const area = StorageSyncService.getInterface(Ci.mozIExtensionStorageArea);
+  const engine = StorageSyncService.getInterface(Ci.mozIBridgedSyncEngine);
+
+  info("Add some local items");
+  await promisify(area.set, "ext-1", JSON.stringify({ a: "abc" }));
+  await promisify(area.set, "ext-2", JSON.stringify({ b: "xyz" }));
+
+  info("Start a sync");
+  await promisify(engine.syncStarted);
+
+  info("Store some incoming synced items");
+  let incomingEnvelopesAsJSON = [
+    {
+      id: "guidAAA",
+      modified: 0.1,
+      payload: JSON.stringify({
+        extId: "ext-2",
+        data: JSON.stringify({
+          c: 1234,
+        }),
+      }),
+    },
+    {
+      id: "guidBBB",
+      modified: 0.1,
+      payload: JSON.stringify({
+        extId: "ext-3",
+        data: JSON.stringify({
+          d: "new! ✨",
+        }),
+      }),
+    },
+  ].map(e => JSON.stringify(e));
+  await promisify(area.storeIncoming, incomingEnvelopesAsJSON);
+
+  info("Merge");
+  // Three levels of JSON wrapping: each outgoing envelope, the cleartext in
+  // each envelope, and the extension storage data in each cleartext payload.
+  let { value: outgoingEnvelopesAsJSON } = await promisify(area.apply);
+  let outgoingEnvelopes = outgoingEnvelopesAsJSON.map(json => JSON.parse(json));
+  let parsedCleartexts = outgoingEnvelopes.map(e => JSON.parse(e.payload));
+  let parsedData = parsedCleartexts.map(c => JSON.parse(c.data));
+
+  let { changes } = await promisify(
+    area.QueryInterface(Ci.mozISyncedExtensionStorageArea)
+      .fetchPendingSyncChanges
+  );
+  deepEqual(
+    changes,
+    [
+      {
+        extId: "ext-2",
+        changes: {
+          c: { newValue: 1234 },
+        },
+      },
+      {
+        extId: "ext-3",
+        changes: {
+          d: { newValue: "new! ✨" },
+        },
+      },
+    ],
+    "Should return pending synced changes for observers"
+  );
+
+  // ext-1 doesn't exist remotely yet, so the Rust sync layer will generate
+  // a GUID for it. We don't know what it is, so we find it by the extension
+  // ID.
+  let ext1Index = parsedCleartexts.findIndex(c => c.extId == "ext-1");
+  greater(ext1Index, -1, "Should find envelope for ext-1");
+  let ext1Guid = outgoingEnvelopes[ext1Index].id;
+
+  // ext-2 has a remote GUID that we set in the test above.
+  let ext2Index = outgoingEnvelopes.findIndex(c => c.id == "guidAAA");
+  greater(ext2Index, -1, "Should find envelope for ext-2");
+
+  equal(outgoingEnvelopes.length, 2, "Should upload ext-1 and ext-2");
+  deepEqual(
+    parsedData[ext1Index],
+    {
+      a: "abc",
+    },
+    "Should upload new data for ext-1"
+  );
+  deepEqual(
+    parsedData[ext2Index],
+    {
+      b: "xyz",
+      c: 1234,
+    },
+    "Should merge local and remote data for ext-2"
+  );
+
+  info("Mark all extensions as uploaded");
+  await promisify(engine.setUploaded, 0, [ext1Guid, "guidAAA"]);
+
+  info("Finish sync");
+  await promisify(engine.syncFinished);
+
+  // Try fetching values for the remote-only extension we just synced.
+  let { value: ext3Value } = await promisify(area.get, "ext-3", "null");
+  deepEqual(
+    ext3Value,
+    {
+      d: "new! ✨",
+    },
+    "Should return new keys for ext-3"
+  );
+
+  info("Try applying a second time");
+  let secondApply = await promisify(area.apply);
+  deepEqual(secondApply.value, {}, "Shouldn't merge anything on second apply");
+
+  info("Wipe all items");
+  await promisify(engine.wipe);
+
+  for (let extId of ["ext-1", "ext-2", "ext-3"]) {
+    // `get` always returns an object, even if there are no keys for the
+    // extension ID.
+    let { value } = await promisify(area.get, extId, "null");
+    deepEqual(value, {}, `Wipe should remove all values for ${extId}`);
+  }
+});
+
+add_task(async function test_storage_sync_quota() {
+  const service = StorageSyncService.getInterface(Ci.mozIExtensionStorageArea);
+  const engine = StorageSyncService.getInterface(Ci.mozIBridgedSyncEngine);
+  await promisify(engine.wipe);
+  await promisify(service.set, "ext-1", JSON.stringify({ x: "hi" }));
+  await promisify(service.set, "ext-1", JSON.stringify({ longer: "value" }));
+
+  let { value: v1 } = await promisify(service.getBytesInUse, "ext-1", '"x"');
+  Assert.equal(v1, 5); // key len without quotes, value len with quotes.
+  let { value: v2 } = await promisify(service.getBytesInUse, "ext-1", "null");
+  // 5 from 'x', plus 'longer' (6 for key, 7 for value = 13) = 18.
+  Assert.equal(v2, 18);
+
+  // Now set something greater than our quota.
+  await Assert.rejects(
+    promisify(
+      service.set,
+      "ext-1",
+      JSON.stringify({
+        big: "x".repeat(Ci.mozIExtensionStorageArea.SYNC_QUOTA_BYTES),
+      })
+    ),
+    ex => ex.result == NS_ERROR_DOM_QUOTA_EXCEEDED_ERR,
+    "should reject with NS_ERROR_DOM_QUOTA_EXCEEDED_ERR"
+  );
+});
diff --git a/toolkit/components/extensions/test/xpcshell/test_WebExtensionContentScript.js b/toolkit/components/extensions/test/xpcshell/test_WebExtensionContentScript.js
new file mode 100644
index 0000000000..fe05893f84
--- /dev/null
+++ b/toolkit/components/extensions/test/xpcshell/test_WebExtensionContentScript.js
@@ -0,0 +1,323 @@
+/* -*- Mode: indent-tabs-mode: nil; js-indent-level: 2 -*- */
+/* vim: set sts=2 sw=2 et tw=80: */
+"use strict";
+
+const { newURI } = Services.io;
+
+const server = createHttpServer({ hosts: ["example.com"] });
+server.registerDirectory("/data/", do_get_file("data"));
+
+async function test_url_matching({
+  manifestVersion = 2,
+  allowedOrigins = [],
+  checkPermissions,
+  expectMatches,
+}) {
+  let policy = new WebExtensionPolicy({
+    id: "foo@bar.baz",
+    mozExtensionHostname: "88fb51cd-159f-4859-83db-7065485bc9b2",
+    baseURL: "file:///foo",
+
+    manifestVersion,
+    allowedOrigins: new MatchPatternSet(allowedOrigins),
+    localizeCallback() {},
+  });
+
+  let contentScript = new WebExtensionContentScript(policy, {
+    checkPermissions,
+
+    matches: new MatchPatternSet(["http://*.foo.com/bar", "*://bar.com/baz/*"]),
+
+    excludeMatches: new MatchPatternSet(["*://bar.com/baz/quux"]),
+
+    includeGlobs: ["*flerg*", "*.com/bar", "*/quux"].map(
+      glob => new MatchGlob(glob)
+    ),
+
+    excludeGlobs: ["*glorg*"].map(glob => new MatchGlob(glob)),
+  });
+
+  equal(
+    expectMatches,
+    contentScript.matchesURI(newURI("http://www.foo.com/bar")),
+    `Simple matches include should ${expectMatches ? "" : "not "} match.`
+  );
+
+  equal(
+    expectMatches,
+    contentScript.matchesURI(newURI("https://bar.com/baz/xflergx")),
+    `Simple matches include should ${expectMatches ? "" : "not "} match.`
+  );
+
+  ok(
+    !contentScript.matchesURI(newURI("https://bar.com/baz/xx")),
+    "Failed includeGlobs match pattern should not match"
+  );
+
+  ok(
+    !contentScript.matchesURI(newURI("https://bar.com/baz/quux")),
+    "Excluded match pattern should not match"
+  );
+
+  ok(
+    !contentScript.matchesURI(newURI("https://bar.com/baz/xflergxglorgx")),
+    "Excluded match glob should not match"
+  );
+}
+
+add_task(function test_WebExtensionContentScript_urls_mv2() {
+  return test_url_matching({ manifestVersion: 2, expectMatches: true });
+});
+
+add_task(function test_WebExtensionContentScript_urls_mv2_checkPermissions() {
+  return test_url_matching({
+    manifestVersion: 2,
+    checkPermissions: true,
+    expectMatches: false,
+  });
+});
+
+add_task(function test_WebExtensionContentScript_urls_mv2_with_permissions() {
+  return test_url_matching({
+    manifestVersion: 2,
+    checkPermissions: true,
+    allowedOrigins: ["<all_urls>"],
+    expectMatches: true,
+  });
+});
+
+add_task(function test_WebExtensionContentScript_urls_mv3() {
+  // checkPermissions ignored here because it's forced for MV3.
+  return test_url_matching({
+    manifestVersion: 3,
+    checkPermissions: false,
+    expectMatches: false,
+  });
+});
+
+add_task(function test_WebExtensionContentScript_mv3_all_urls() {
+  return test_url_matching({
+    manifestVersion: 3,
+    allowedOrigins: ["<all_urls>"],
+    expectMatches: true,
+  });
+});
+
+add_task(function test_WebExtensionContentScript_mv3_wildcards() {
+  return test_url_matching({
+    manifestVersion: 3,
+    allowedOrigins: ["*://*.foo.com/*", "*://*.bar.com/*"],
+    expectMatches: true,
+  });
+});
+
+add_task(function test_WebExtensionContentScript_mv3_specific() {
+  return test_url_matching({
+    manifestVersion: 3,
+    allowedOrigins: ["http://www.foo.com/*", "https://bar.com/*"],
+    expectMatches: true,
+  });
+});
+
+add_task(function test_WebExtensionContentScript_restricted() {
+  let tests = [
+    {
+      manifestVersion: 2,
+      permissions: [],
+      expect: false,
+    },
+    {
+      manifestVersion: 2,
+      permissions: ["mozillaAddons"],
+      expect: true,
+    },
+    {
+      manifestVersion: 3,
+      permissions: [],
+      expect: false,
+    },
+    {
+      manifestVersion: 3,
+      permissions: ["mozillaAddons"],
+      expect: true,
+    },
+  ];
+
+  for (let { manifestVersion, permissions, expect } of tests) {
+    let policy = new WebExtensionPolicy({
+      id: "foo@bar.baz",
+      mozExtensionHostname: "88fb51cd-159f-4859-83db-7065485bc9b2",
+      baseURL: "file:///foo",
+
+      manifestVersion,
+      permissions,
+      allowedOrigins: new MatchPatternSet(["<all_urls>"]),
+      localizeCallback() {},
+    });
+    let contentScript = new WebExtensionContentScript(policy, {
+      checkPermissions: true,
+      matches: new MatchPatternSet(["<all_urls>"]),
+    });
+
+    // AMO is on the extensions.webextensions.restrictedDomains list.
+    equal(
+      expect,
+      contentScript.matchesURI(newURI("https://addons.mozilla.org/foo")),
+      `Expect extension with [${permissions}] to ${expect ? "" : "not"} match`
+    );
+  }
+});
+
+async function test_frame_matching(meta) {
+  if (AppConstants.platform == "linux") {
+    // The windowless browser currently does not load correctly on Linux on
+    // infra.
+    return;
+  }
+
+  let baseURL = `http://example.com/data`;
+  let urls = {
+    topLevel: `${baseURL}/file_toplevel.html`,
+    iframe: `${baseURL}/file_iframe.html`,
+    srcdoc: "about:srcdoc",
+    aboutBlank: "about:blank",
+  };
+
+  let contentPage = await ExtensionTestUtils.loadContentPage(urls.topLevel);
+
+  let tests = [
+    {
+      matches: ["http://example.com/data/*"],
+      contentScript: {},
+      topLevel: true,
+      iframe: false,
+      aboutBlank: false,
+      srcdoc: false,
+    },
+
+    {
+      matches: ["http://example.com/data/*"],
+      contentScript: {
+        frameID: 0,
+      },
+      topLevel: true,
+      iframe: false,
+      aboutBlank: false,
+      srcdoc: false,
+    },
+
+    {
+      matches: ["http://example.com/data/*"],
+      contentScript: {
+        allFrames: true,
+      },
+      topLevel: true,
+      iframe: true,
+      aboutBlank: false,
+      srcdoc: false,
+    },
+
+    {
+      matches: ["http://example.com/data/*"],
+      contentScript: {
+        allFrames: true,
+        matchAboutBlank: true,
+      },
+      topLevel: true,
+      iframe: true,
+      aboutBlank: true,
+      srcdoc: true,
+    },
+
+    {
+      matches: ["http://foo.com/data/*"],
+      contentScript: {
+        allFrames: true,
+        matchAboutBlank: true,
+      },
+      topLevel: false,
+      iframe: false,
+      aboutBlank: false,
+      srcdoc: false,
+    },
+  ];
+
+  // matchesWindowGlobal tests against content frames
+  await contentPage.spawn([{ tests, urls, meta }], args => {
+    let { manifestVersion = 2, allowedOrigins = [], expectMatches } = args.meta;
+
+    this.windows = new Map();
+    this.windows.set(this.content.location.href, this.content);
+    for (let c of Array.from(this.content.frames)) {
+      this.windows.set(c.location.href, c);
+    }
+    const { MatchPatternSet, WebExtensionContentScript, WebExtensionPolicy } =
+      Cu.getGlobalForObject(Services);
+    this.policy = new WebExtensionPolicy({
+      id: "foo@bar.baz",
+      mozExtensionHostname: "88fb51cd-159f-4859-83db-7065485bc9b2",
+      baseURL: "file:///foo",
+
+      manifestVersion,
+      allowedOrigins: new MatchPatternSet(allowedOrigins),
+      localizeCallback() {},
+    });
+
+    let tests = args.tests.map(t => {
+      t.contentScript.matches = new MatchPatternSet(t.matches);
+      t.script = new WebExtensionContentScript(this.policy, t.contentScript);
+      return t;
+    });
+    for (let [i, test] of tests.entries()) {
+      for (let [frame, url] of Object.entries(args.urls)) {
+        let should = test[frame] ? "should" : "should not";
+        let wgc = this.windows.get(url).windowGlobalChild;
+        Assert.equal(
+          test.script.matchesWindowGlobal(wgc),
+          test[frame] && expectMatches,
+          `Script ${i} ${should} match the ${frame} frame`
+        );
+      }
+    }
+  });
+
+  await contentPage.close();
+}
+
+add_task(function test_WebExtensionContentScript_frames_mv2() {
+  return test_frame_matching({
+    manifestVersion: 2,
+    expectMatches: true,
+  });
+});
+
+add_task(function test_WebExtensionContentScript_frames_mv3() {
+  return test_frame_matching({
+    manifestVersion: 3,
+    expectMatches: false,
+  });
+});
+
+add_task(function test_WebExtensionContentScript_frames_mv3_all_urls() {
+  return test_frame_matching({
+    manifestVersion: 3,
+    allowedOrigins: ["<all_urls>"],
+    expectMatches: true,
+  });
+});
+
+add_task(function test_WebExtensionContentScript_frames_mv3_wildcards() {
+  return test_frame_matching({
+    manifestVersion: 3,
+    allowedOrigins: ["*://*.example.com/*"],
+    expectMatches: true,
+  });
+});
+
+add_task(function test_WebExtensionContentScript_frames_mv3_specific() {
+  return test_frame_matching({
+    manifestVersion: 3,
+    allowedOrigins: ["http://example.com/*"],
+    expectMatches: true,
+  });
+});
diff --git a/toolkit/components/extensions/test/xpcshell/test_WebExtensionPolicy.js b/toolkit/components/extensions/test/xpcshell/test_WebExtensionPolicy.js
new file mode 100644
index 0000000000..ff2cc3c2ac
--- /dev/null
+++ b/toolkit/components/extensions/test/xpcshell/test_WebExtensionPolicy.js
@@ -0,0 +1,620 @@
+/* -*- Mode: indent-tabs-mode: nil; js-indent-level: 2 -*- */
+/* vim: set sts=2 sw=2 et tw=80: */
+"use strict";
+
+const { newURI } = Services.io;
+
+add_task(async function test_WebExtensionPolicy() {
+  const id = "foo@bar.baz";
+  const uuid = "ca9d3f23-125c-4b24-abfc-1ca2692b0610";
+
+  const baseURL = "file:///foo/";
+  const mozExtURL = `moz-extension://${uuid}/`;
+  const mozExtURI = newURI(mozExtURL);
+
+  let policy = new WebExtensionPolicy({
+    id,
+    mozExtensionHostname: uuid,
+    baseURL,
+
+    localizeCallback(str) {
+      return `<${str}>`;
+    },
+
+    allowedOrigins: new MatchPatternSet(["http://foo.bar/", "*://*.baz/"], {
+      ignorePath: true,
+    }),
+    permissions: ["<all_urls>"],
+    webAccessibleResources: [
+      {
+        resources: ["/foo/*", "/bar.baz"].map(glob => new MatchGlob(glob)),
+      },
+    ],
+  });
+
+  equal(policy.active, false, "Active attribute should initially be false");
+
+  // GetURL
+
+  equal(
+    policy.getURL(),
+    mozExtURL,
+    "getURL() should return the correct root URL"
+  );
+  equal(
+    policy.getURL("path/foo.html"),
+    `${mozExtURL}path/foo.html`,
+    "getURL(path) should return the correct URL"
+  );
+
+  // Permissions
+
+  deepEqual(
+    policy.permissions,
+    ["<all_urls>"],
+    "Initial permissions should be correct"
+  );
+
+  ok(
+    policy.hasPermission("<all_urls>"),
+    "hasPermission should match existing permission"
+  );
+  ok(
+    !policy.hasPermission("history"),
+    "hasPermission should not match nonexistent permission"
+  );
+
+  Assert.throws(
+    () => {
+      policy.permissions[0] = "foo";
+    },
+    TypeError,
+    "Permissions array should be frozen"
+  );
+
+  policy.permissions = ["history"];
+  deepEqual(
+    policy.permissions,
+    ["history"],
+    "Permissions should be updateable as a set"
+  );
+
+  ok(
+    policy.hasPermission("history"),
+    "hasPermission should match existing permission"
+  );
+  ok(
+    !policy.hasPermission("<all_urls>"),
+    "hasPermission should not match nonexistent permission"
+  );
+
+  // Origins
+
+  ok(
+    policy.canAccessURI(newURI("http://foo.bar/quux")),
+    "Should be able to access permitted URI"
+  );
+  ok(
+    policy.canAccessURI(newURI("https://x.baz/foo")),
+    "Should be able to access permitted URI"
+  );
+
+  ok(
+    !policy.canAccessURI(newURI("https://foo.bar/quux")),
+    "Should not be able to access non-permitted URI"
+  );
+
+  policy.allowedOrigins = new MatchPatternSet(["https://foo.bar/"], {
+    ignorePath: true,
+  });
+
+  ok(
+    policy.canAccessURI(newURI("https://foo.bar/quux")),
+    "Should be able to access updated permitted URI"
+  );
+  ok(
+    !policy.canAccessURI(newURI("https://x.baz/foo")),
+    "Should not be able to access removed permitted URI"
+  );
+
+  // Web-accessible resources
+
+  ok(
+    policy.isWebAccessiblePath("/foo/bar"),
+    "Web-accessible glob should be web-accessible"
+  );
+  ok(
+    policy.isWebAccessiblePath("/bar.baz"),
+    "Web-accessible path should be web-accessible"
+  );
+  ok(
+    !policy.isWebAccessiblePath("/bar.baz/quux"),
+    "Non-web-accessible path should not be web-accessible"
+  );
+
+  ok(
+    policy.sourceMayAccessPath(mozExtURI, "/bar.baz"),
+    "Web-accessible path should be web-accessible to self"
+  );
+
+  // Localization
+
+  equal(
+    policy.localize("foo"),
+    "<foo>",
+    "Localization callback should work as expected"
+  );
+
+  // Protocol and lookups.
+
+  let proto = Services.io
+    .getProtocolHandler("moz-extension", uuid)
+    .QueryInterface(Ci.nsISubstitutingProtocolHandler);
+
+  deepEqual(
+    WebExtensionPolicy.getActiveExtensions(),
+    [],
+    "Should have no active extensions"
+  );
+  equal(
+    WebExtensionPolicy.getByID(id),
+    null,
+    "ID lookup should not return extension when not active"
+  );
+  equal(
+    WebExtensionPolicy.getByHostname(uuid),
+    null,
+    "Hostname lookup should not return extension when not active"
+  );
+  Assert.throws(
+    () => proto.resolveURI(mozExtURI),
+    /NS_ERROR_NOT_AVAILABLE/,
+    "URL should not resolve when not active"
+  );
+
+  policy.active = true;
+  equal(policy.active, true, "Active attribute should be updated");
+
+  let exts = WebExtensionPolicy.getActiveExtensions();
+  equal(exts.length, 1, "Should have one active extension");
+  equal(exts[0], policy, "Should have the correct active extension");
+
+  equal(
+    WebExtensionPolicy.getByID(id),
+    policy,
+    "ID lookup should return extension when active"
+  );
+  equal(
+    WebExtensionPolicy.getByHostname(uuid),
+    policy,
+    "Hostname lookup should return extension when active"
+  );
+
+  equal(
+    proto.resolveURI(mozExtURI),
+    baseURL,
+    "URL should resolve correctly while active"
+  );
+
+  policy.active = false;
+  equal(policy.active, false, "Active attribute should be updated");
+
+  deepEqual(
+    WebExtensionPolicy.getActiveExtensions(),
+    [],
+    "Should have no active extensions"
+  );
+  equal(
+    WebExtensionPolicy.getByID(id),
+    null,
+    "ID lookup should not return extension when not active"
+  );
+  equal(
+    WebExtensionPolicy.getByHostname(uuid),
+    null,
+    "Hostname lookup should not return extension when not active"
+  );
+  Assert.throws(
+    () => proto.resolveURI(mozExtURI),
+    /NS_ERROR_NOT_AVAILABLE/,
+    "URL should not resolve when not active"
+  );
+
+  // Conflicting policies.
+
+  // This asserts in debug builds, so only test in non-debug builds.
+  if (!AppConstants.DEBUG) {
+    policy.active = true;
+
+    let attrs = [
+      { id, uuid },
+      { id, uuid: "d916886c-cfdf-482e-b7b1-d7f5b0facfa5" },
+      { id: "foo@quux", uuid },
+    ];
+
+    // eslint-disable-next-line no-shadow
+    for (let { id, uuid } of attrs) {
+      let policy2 = new WebExtensionPolicy({
+        id,
+        mozExtensionHostname: uuid,
+        baseURL: "file://bar/",
+
+        localizeCallback() {},
+
+        allowedOrigins: new MatchPatternSet([]),
+      });
+
+      Assert.throws(
+        () => {
+          policy2.active = true;
+        },
+        /NS_ERROR_UNEXPECTED/,
+        `Should not be able to activate conflicting policy: ${id} ${uuid}`
+      );
+    }
+
+    policy.active = false;
+  }
+});
+
+// mozExtensionHostname is normalized to lower case when using
+// policy.getURL whereas using policy.getByHostname does
+// not.  Tests below will fail without case insensitive
+// comparisons in ExtensionPolicyService
+add_task(async function test_WebExtensionPolicy_case_sensitivity() {
+  const id = "policy-case@mochitest";
+  const uuid = "BAD93A23-125C-4B24-ABFC-1CA2692B0610";
+
+  const baseURL = "file:///foo/";
+  const mozExtURL = `moz-extension://${uuid}/`;
+  const mozExtURI = newURI(mozExtURL);
+
+  let policy = new WebExtensionPolicy({
+    id: id,
+    mozExtensionHostname: uuid,
+    baseURL,
+    localizeCallback() {},
+    allowedOrigins: new MatchPatternSet([]),
+    permissions: ["<all_urls>"],
+  });
+  policy.active = true;
+
+  equal(
+    WebExtensionPolicy.getByHostname(uuid)?.mozExtensionHostname,
+    policy.mozExtensionHostname,
+    "Hostname lookup should match policy"
+  );
+
+  equal(
+    WebExtensionPolicy.getByHostname(uuid.toLowerCase())?.mozExtensionHostname,
+    policy.mozExtensionHostname,
+    "Hostname lookup should match policy"
+  );
+
+  equal(policy.getURL(), mozExtURI.spec, "Urls should match policy");
+  ok(
+    policy.sourceMayAccessPath(mozExtURI, "/bar.baz"),
+    "Extension path should be accessible to self"
+  );
+
+  policy.active = false;
+});
+
+add_task(async function test_WebExtensionPolicy_V3() {
+  const id = "foo@bar.baz";
+  const uuid = "ca9d3f23-125c-4b24-abfc-1ca2692b0610";
+  const id2 = "foo-2@bar.baz";
+  const uuid2 = "89383c45-7db4-4999-83f7-f4cc246372cd";
+  const id3 = "foo-3@bar.baz";
+  const uuid3 = "56652231-D7E2-45D1-BDBD-BD3BFF80927E";
+
+  const baseURL = "file:///foo/";
+  const mozExtURL = `moz-extension://${uuid}/`;
+  const mozExtURI = newURI(mozExtURL);
+  const fooSite = newURI("http://foo.bar/");
+  const exampleSite = newURI("https://example.com/");
+
+  let policy = new WebExtensionPolicy({
+    id,
+    mozExtensionHostname: uuid,
+    baseURL,
+    manifestVersion: 3,
+
+    localizeCallback(str) {
+      return `<${str}>`;
+    },
+
+    allowedOrigins: new MatchPatternSet(["http://foo.bar/", "*://*.baz/"], {
+      ignorePath: true,
+    }),
+    permissions: ["<all_urls>"],
+    webAccessibleResources: [
+      {
+        resources: ["/foo/*", "/bar.baz"].map(glob => new MatchGlob(glob)),
+        matches: ["http://foo.bar/"],
+        extension_ids: [id3],
+      },
+      {
+        resources: ["/foo.bar.baz"].map(glob => new MatchGlob(glob)),
+        extension_ids: ["*"],
+      },
+    ],
+  });
+  policy.active = true;
+  equal(
+    WebExtensionPolicy.getByHostname(uuid),
+    policy,
+    "Hostname lookup should match policy"
+  );
+
+  let policy2 = new WebExtensionPolicy({
+    id: id2,
+    mozExtensionHostname: uuid2,
+    baseURL,
+    localizeCallback() {},
+    allowedOrigins: new MatchPatternSet([]),
+    permissions: ["<all_urls>"],
+  });
+  policy2.active = true;
+  equal(
+    WebExtensionPolicy.getByHostname(uuid2),
+    policy2,
+    "Hostname lookup should match policy"
+  );
+
+  let policy3 = new WebExtensionPolicy({
+    id: id3,
+    mozExtensionHostname: uuid3,
+    baseURL,
+    localizeCallback() {},
+    allowedOrigins: new MatchPatternSet([]),
+    permissions: ["<all_urls>"],
+  });
+  policy3.active = true;
+  equal(
+    WebExtensionPolicy.getByHostname(uuid3),
+    policy3,
+    "Hostname lookup should match policy"
+  );
+
+  ok(
+    policy.isWebAccessiblePath("/bar.baz"),
+    "Web-accessible path should be web-accessible"
+  );
+  ok(
+    !policy.isWebAccessiblePath("/bar.baz/quux"),
+    "Non-web-accessible path should not be web-accessible"
+  );
+  // Extension can always access itself
+  ok(
+    policy.sourceMayAccessPath(mozExtURI, "/bar.baz"),
+    "Web-accessible path should be accessible to self"
+  );
+  ok(
+    policy.sourceMayAccessPath(mozExtURI, "/foo.bar.baz"),
+    "Web-accessible path should be accessible to self"
+  );
+
+  ok(
+    !policy.sourceMayAccessPath(newURI(`https://${uuid}/`), "/bar.baz"),
+    "Web-accessible path should not be accessible due to scheme mismatch"
+  );
+
+  // non-matching site cannot access url
+  ok(
+    policy.sourceMayAccessPath(fooSite, "/bar.baz"),
+    "Web-accessible path should be accessible to foo.bar site"
+  );
+  ok(
+    !policy.sourceMayAccessPath(fooSite, "/foo.bar.baz"),
+    "Web-accessible path should not be accessible to foo.bar site"
+  );
+
+  // non-matching site cannot access url
+  ok(
+    !policy.sourceMayAccessPath(exampleSite, "/bar.baz"),
+    "Web-accessible path should not be accessible to example.com"
+  );
+  ok(
+    !policy.sourceMayAccessPath(exampleSite, "/foo.bar.baz"),
+    "Web-accessible path should not be accessible to example.com"
+  );
+
+  let extURI = newURI(policy2.getURL(""));
+  ok(
+    !policy.sourceMayAccessPath(extURI, "/bar.baz"),
+    "Web-accessible path should not be accessible to other extension"
+  );
+  ok(
+    policy.sourceMayAccessPath(extURI, "/foo.bar.baz"),
+    "Web-accessible path should be accessible to other extension"
+  );
+
+  extURI = newURI(policy3.getURL(""));
+  ok(
+    policy.sourceMayAccessPath(extURI, "/bar.baz"),
+    "Web-accessible path should be accessible to other extension"
+  );
+  ok(
+    policy.sourceMayAccessPath(extURI, "/foo.bar.baz"),
+    "Web-accessible path should be accessible to other extension"
+  );
+
+  policy.active = false;
+  policy2.active = false;
+  policy3.active = false;
+});
+
+add_task(async function test_WebExtensionPolicy_registerContentScripts() {
+  const id = "foo@bar.baz";
+  const uuid = "77a7b9d3-e73c-4cf3-97fb-1824868fe00f";
+
+  const id2 = "foo-2@bar.baz";
+  const uuid2 = "89383c45-7db4-4999-83f7-f4cc246372cd";
+
+  const baseURL = "file:///foo/";
+
+  const mozExtURL = `moz-extension://${uuid}/`;
+  const mozExtURL2 = `moz-extension://${uuid2}/`;
+
+  let policy = new WebExtensionPolicy({
+    id,
+    mozExtensionHostname: uuid,
+    baseURL,
+    localizeCallback() {},
+    allowedOrigins: new MatchPatternSet([]),
+    permissions: ["<all_urls>"],
+  });
+
+  let policy2 = new WebExtensionPolicy({
+    id: id2,
+    mozExtensionHostname: uuid2,
+    baseURL,
+    localizeCallback() {},
+    allowedOrigins: new MatchPatternSet([]),
+    permissions: ["<all_urls>"],
+  });
+
+  let script1 = new WebExtensionContentScript(policy, {
+    run_at: "document_end",
+    js: [`${mozExtURL}/registered-content-script.js`],
+    matches: new MatchPatternSet(["http://localhost/data/*"]),
+  });
+
+  let script2 = new WebExtensionContentScript(policy, {
+    run_at: "document_end",
+    css: [`${mozExtURL}/registered-content-style.css`],
+    matches: new MatchPatternSet(["http://localhost/data/*"]),
+  });
+
+  let script3 = new WebExtensionContentScript(policy2, {
+    run_at: "document_end",
+    css: [`${mozExtURL2}/registered-content-style.css`],
+    matches: new MatchPatternSet(["http://localhost/data/*"]),
+  });
+
+  deepEqual(
+    policy.contentScripts,
+    [],
+    "The policy contentScripts is initially empty"
+  );
+
+  policy.registerContentScript(script1);
+
+  deepEqual(
+    policy.contentScripts,
+    [script1],
+    "script1 has been added to the policy contentScripts"
+  );
+
+  Assert.throws(
+    () => policy.registerContentScript(script1),
+    e => e.result == Cr.NS_ERROR_ILLEGAL_VALUE,
+    "Got the expected NS_ERROR_ILLEGAL_VALUE when trying to register a script more than once"
+  );
+
+  Assert.throws(
+    () => policy.registerContentScript(script3),
+    e => e.result == Cr.NS_ERROR_ILLEGAL_VALUE,
+    "Got the expected NS_ERROR_ILLEGAL_VALUE when trying to register a script related to " +
+      "a different extension"
+  );
+
+  Assert.throws(
+    () => policy.unregisterContentScript(script3),
+    e => e.result == Cr.NS_ERROR_ILLEGAL_VALUE,
+    "Got the expected NS_ERROR_ILLEGAL_VALUE when trying to unregister a script related to " +
+      "a different extension"
+  );
+
+  deepEqual(
+    policy.contentScripts,
+    [script1],
+    "script1 has not been added twice"
+  );
+
+  policy.registerContentScript(script2);
+
+  deepEqual(
+    policy.contentScripts,
+    [script1, script2],
+    "script2 has the last item of the policy contentScripts array"
+  );
+
+  policy.unregisterContentScript(script1);
+
+  deepEqual(
+    policy.contentScripts,
+    [script2],
+    "script1 has been removed from the policy contentscripts"
+  );
+
+  Assert.throws(
+    () => policy.unregisterContentScript(script1),
+    e => e.result == Cr.NS_ERROR_ILLEGAL_VALUE,
+    "Got the expected NS_ERROR_ILLEGAL_VALUE when trying to unregister a script more than once"
+  );
+
+  deepEqual(
+    policy.contentScripts,
+    [script2],
+    "the policy contentscripts is unmodified when unregistering an unknown contentScript"
+  );
+
+  policy.unregisterContentScript(script2);
+
+  deepEqual(
+    policy.contentScripts,
+    [],
+    "script2 has been removed from the policy contentScripts"
+  );
+});
+
+add_task(async function test_WebExtensionPolicy_static_themes_resources() {
+  const uuid = "0e7ae607-b5b3-4204-9838-c2138c14bc3c";
+  const mozExtURL = `moz-extension://${uuid}/`;
+  const mozExtURI = newURI(mozExtURL);
+
+  let policy = new WebExtensionPolicy({
+    id: "test-extension@mochitest",
+    mozExtensionHostname: uuid,
+    baseURL: "file:///foo/foo/",
+    localizeCallback() {},
+    allowedOrigins: new MatchPatternSet([]),
+    permissions: [],
+  });
+  policy.active = true;
+
+  let staticThemePolicy = new WebExtensionPolicy({
+    id: "statictheme@bar.baz",
+    mozExtensionHostname: "164d05dc-b45b-4731-aefc-7c1691bae9a4",
+    baseURL: "file:///static_theme/",
+    type: "theme",
+    allowedOrigins: new MatchPatternSet([]),
+    localizeCallback() {},
+  });
+
+  staticThemePolicy.active = true;
+
+  ok(
+    staticThemePolicy.sourceMayAccessPath(mozExtURI, "/someresource.ext"),
+    "Active extensions should be allowed to access the static themes resources"
+  );
+
+  policy.active = false;
+
+  ok(
+    !staticThemePolicy.sourceMayAccessPath(mozExtURI, "/someresource.ext"),
+    "Disabled extensions should be disallowed the static themes resources"
+  );
+
+  ok(
+    !staticThemePolicy.sourceMayAccessPath(
+      Services.io.newURI("http://example.com"),
+      "/someresource.ext"
+    ),
+    "Web content should be disallowed the static themes resources"
+  );
+
+  staticThemePolicy.active = false;
+});
diff --git a/toolkit/components/extensions/test/xpcshell/test_change_remote_mode.js b/toolkit/components/extensions/test/xpcshell/test_change_remote_mode.js
new file mode 100644
index 0000000000..a6d22e8703
--- /dev/null
+++ b/toolkit/components/extensions/test/xpcshell/test_change_remote_mode.js
@@ -0,0 +1,20 @@
+/* -*- Mode: indent-tabs-mode: nil; js-indent-level: 2 -*- */
+/* vim: set sts=2 sw=2 et tw=80: */
+"use strict";
+
+add_task(async function change_remote() {
+  let remote = Services.prefs.getBoolPref("extensions.webextensions.remote");
+  Assert.equal(
+    WebExtensionPolicy.useRemoteWebExtensions,
+    remote,
+    "value of useRemoteWebExtensions matches the pref"
+  );
+
+  Services.prefs.setBoolPref("extensions.webextensions.remote", !remote);
+
+  Assert.equal(
+    WebExtensionPolicy.useRemoteWebExtensions,
+    remote,
+    "value of useRemoteWebExtensions is still the same after changing the pref"
+  );
+});
diff --git a/toolkit/components/extensions/test/xpcshell/test_csp_custom_policies.js b/toolkit/components/extensions/test/xpcshell/test_csp_custom_policies.js
new file mode 100644
index 0000000000..c860d73cc8
--- /dev/null
+++ b/toolkit/components/extensions/test/xpcshell/test_csp_custom_policies.js
@@ -0,0 +1,303 @@
+/* -*- Mode: indent-tabs-mode: nil; js-indent-level: 2 -*- */
+/* vim: set sts=2 sw=2 et tw=80: */
+"use strict";
+
+const { Preferences } = ChromeUtils.importESModule(
+  "resource://gre/modules/Preferences.sys.mjs"
+);
+
+const ADDON_ID = "test@web.extension";
+
+const aps = Cc["@mozilla.org/addons/policy-service;1"].getService(
+  Ci.nsIAddonPolicyService
+);
+
+const v2_csp = Preferences.get(
+  "extensions.webextensions.base-content-security-policy"
+);
+const v3_csp = Preferences.get(
+  "extensions.webextensions.base-content-security-policy.v3"
+);
+
+add_task(async function test_invalid_addon_csp() {
+  await Assert.throws(
+    () => aps.getBaseCSP("invalid@missing"),
+    /NS_ERROR_ILLEGAL_VALUE/,
+    "no base csp for non-existent addon"
+  );
+  await Assert.throws(
+    () => aps.getExtensionPageCSP("invalid@missing"),
+    /NS_ERROR_ILLEGAL_VALUE/,
+    "no extension page csp for non-existent addon"
+  );
+});
+
+add_task(async function test_policy_csp() {
+  equal(
+    aps.defaultCSP,
+    Preferences.get("extensions.webextensions.default-content-security-policy"),
+    "Expected default CSP value"
+  );
+
+  const CUSTOM_POLICY = "script-src: 'self' https://xpcshell.test.custom.csp";
+
+  let tests = [
+    {
+      name: "manifest version 2, no custom policy",
+      policyData: {},
+      expectedPolicy: aps.defaultCSP,
+    },
+    {
+      name: "manifest version 2, no custom policy",
+      policyData: {
+        manifestVersion: 2,
+      },
+      expectedPolicy: aps.defaultCSP,
+    },
+    {
+      name: "version 2 custom extension policy",
+      policyData: {
+        extensionPageCSP: CUSTOM_POLICY,
+      },
+      expectedPolicy: CUSTOM_POLICY,
+    },
+    {
+      name: "manifest version 2 set, custom extension policy",
+      policyData: {
+        manifestVersion: 2,
+        extensionPageCSP: CUSTOM_POLICY,
+      },
+      expectedPolicy: CUSTOM_POLICY,
+    },
+    {
+      name: "manifest version 3, no custom policy",
+      policyData: {
+        manifestVersion: 3,
+      },
+      expectedPolicy: aps.defaultCSPV3,
+    },
+    {
+      name: "manifest 3 version set, custom extensionPage policy",
+      policyData: {
+        manifestVersion: 3,
+        extensionPageCSP: CUSTOM_POLICY,
+      },
+      expectedPolicy: CUSTOM_POLICY,
+    },
+  ];
+
+  let policy = null;
+
+  function setExtensionCSP({ manifestVersion, extensionPageCSP }) {
+    if (policy) {
+      policy.active = false;
+    }
+
+    policy = new WebExtensionPolicy({
+      id: ADDON_ID,
+      mozExtensionHostname: ADDON_ID,
+      baseURL: "file:///",
+
+      allowedOrigins: new MatchPatternSet([]),
+      localizeCallback() {},
+
+      manifestVersion,
+      extensionPageCSP,
+    });
+
+    policy.active = true;
+  }
+
+  for (let test of tests) {
+    info(test.name);
+    setExtensionCSP(test.policyData);
+    equal(
+      aps.getBaseCSP(ADDON_ID),
+      test.policyData.manifestVersion == 3 ? v3_csp : v2_csp,
+      "baseCSP is correct"
+    );
+    equal(
+      aps.getExtensionPageCSP(ADDON_ID),
+      test.expectedPolicy,
+      "extensionPageCSP is correct"
+    );
+  }
+});
+
+add_task(async function test_extension_csp() {
+  Services.prefs.setBoolPref("extensions.manifestV3.enabled", true);
+
+  ExtensionTestUtils.failOnSchemaWarnings(false);
+
+  let extension_pages = "script-src 'self'; img-src 'none'";
+
+  let tests = [
+    {
+      name: "manifest_v2 invalid csp results in default csp used",
+      manifest: {
+        content_security_policy: `script-src 'none'`,
+      },
+      expectedPolicy: aps.defaultCSP,
+    },
+    {
+      name: "manifest_v2 allows https protocol",
+      manifest: {
+        manifest_version: 2,
+        content_security_policy: `script-src 'self' https://example.com`,
+      },
+      expectedPolicy: `script-src 'self' https://example.com`,
+    },
+    {
+      name: "manifest_v2 allows unsafe-eval",
+      manifest: {
+        manifest_version: 2,
+        content_security_policy: `script-src 'self' 'unsafe-eval'`,
+      },
+      expectedPolicy: `script-src 'self' 'unsafe-eval'`,
+    },
+    {
+      name: "manifest_v2 allows wasm-unsafe-eval",
+      manifest: {
+        manifest_version: 2,
+        content_security_policy: `script-src 'self' 'wasm-unsafe-eval'`,
+      },
+      expectedPolicy: `script-src 'self' 'wasm-unsafe-eval'`,
+    },
+    {
+      // object-src used to require local sources, but now we accept anything.
+      name: "manifest_v2 allows object-src, with non-local sources",
+      manifest: {
+        manifest_version: 2,
+        content_security_policy: `script-src 'self'; object-src https:'`,
+      },
+      expectedPolicy: `script-src 'self'; object-src https:'`,
+    },
+    {
+      name: "manifest_v3 invalid csp results in default csp used",
+      manifest: {
+        manifest_version: 3,
+        content_security_policy: {
+          extension_pages: `script-src 'none'`,
+        },
+      },
+      expectedPolicy: aps.defaultCSPV3,
+    },
+    {
+      name: "manifest_v3 forbidden protocol results in default csp used",
+      manifest: {
+        manifest_version: 3,
+        content_security_policy: {
+          extension_pages: `script-src 'self' https://*`,
+        },
+      },
+      expectedPolicy: aps.defaultCSPV3,
+    },
+    {
+      name: "manifest_v3 forbidden eval results in default csp used",
+      manifest: {
+        manifest_version: 3,
+        content_security_policy: {
+          extension_pages: `script-src 'self' 'unsafe-eval'`,
+        },
+      },
+      expectedPolicy: aps.defaultCSPV3,
+    },
+    {
+      name: "manifest_v3 disallows localhost",
+      manifest: {
+        manifest_version: 3,
+        content_security_policy: {
+          extension_pages: `script-src 'self' https://localhost`,
+        },
+      },
+      expectedPolicy: aps.defaultCSPV3,
+    },
+    {
+      name: "manifest_v3 disallows 127.0.0.1",
+      manifest: {
+        manifest_version: 3,
+        content_security_policy: {
+          extension_pages: `script-src 'self' https://127.0.0.1`,
+        },
+      },
+      expectedPolicy: aps.defaultCSPV3,
+    },
+    {
+      name: "manifest_v3 allows wasm-unsafe-eval",
+      manifest: {
+        manifest_version: 3,
+        content_security_policy: {
+          extension_pages: `script-src 'self' 'wasm-unsafe-eval'`,
+        },
+      },
+      expectedPolicy: `script-src 'self' 'wasm-unsafe-eval'`,
+    },
+    {
+      // object-src used to require local sources, but now we accept anything.
+      name: "manifest_v3 allows object-src, with non-local sources",
+      manifest: {
+        manifest_version: 3,
+        content_security_policy: {
+          extension_pages: `script-src 'self'; object-src https:'`,
+        },
+      },
+      expectedPolicy: `script-src 'self'; object-src https:'`,
+    },
+    {
+      name: "manifest_v2 csp",
+      manifest: {
+        manifest_version: 2,
+        content_security_policy: extension_pages,
+      },
+      expectedPolicy: extension_pages,
+    },
+    {
+      name: "manifest_v2 with no csp, expect default",
+      manifest: {
+        manifest_version: 2,
+      },
+      expectedPolicy: aps.defaultCSP,
+    },
+    {
+      name: "manifest_v3 used with no csp, expect default",
+      manifest: {
+        manifest_version: 3,
+      },
+      expectedPolicy: aps.defaultCSPV3,
+    },
+    {
+      name: "manifest_v3 syntax used",
+      manifest: {
+        manifest_version: 3,
+        content_security_policy: {
+          extension_pages,
+        },
+      },
+      expectedPolicy: extension_pages,
+    },
+  ];
+
+  for (let test of tests) {
+    info(test.name);
+    let extension = ExtensionTestUtils.loadExtension({
+      manifest: test.manifest,
+    });
+    await extension.startup();
+    let policy = WebExtensionPolicy.getByID(extension.id);
+    equal(
+      policy.baseCSP,
+      test.manifest.manifest_version == 3 ? v3_csp : v2_csp,
+      "baseCSP is correct"
+    );
+    equal(
+      policy.extensionPageCSP,
+      test.expectedPolicy,
+      "extensionPageCSP is correct."
+    );
+    await extension.unload();
+  }
+
+  ExtensionTestUtils.failOnSchemaWarnings(true);
+
+  Services.prefs.clearUserPref("extensions.manifestV3.enabled");
+});
diff --git a/toolkit/components/extensions/test/xpcshell/test_csp_validator.js b/toolkit/components/extensions/test/xpcshell/test_csp_validator.js
new file mode 100644
index 0000000000..12ba3f93e9
--- /dev/null
+++ b/toolkit/components/extensions/test/xpcshell/test_csp_validator.js
@@ -0,0 +1,322 @@
+/* -*- Mode: indent-tabs-mode: nil; js-indent-level: 2 -*- */
+/* vim: set sts=2 sw=2 et tw=80: */
+"use strict";
+
+const cps = Cc["@mozilla.org/addons/content-policy;1"].getService(
+  Ci.nsIAddonContentPolicy
+);
+
+add_task(async function test_csp_validator_flags() {
+  let checkPolicy = (policy, flags, expectedResult, message = null) => {
+    info(`Checking policy: ${policy}`);
+
+    let result = cps.validateAddonCSP(policy, flags);
+    equal(result, expectedResult);
+  };
+
+  let flags = Ci.nsIAddonContentPolicy;
+
+  checkPolicy(
+    "default-src 'self'; script-src 'self' http://localhost",
+    0,
+    "\u2018script-src\u2019 directive contains a forbidden http: protocol source",
+    "localhost disallowed"
+  );
+  checkPolicy(
+    "default-src 'self'; script-src 'self' http://localhost",
+    flags.CSP_ALLOW_LOCALHOST,
+    null,
+    "localhost allowed"
+  );
+
+  checkPolicy(
+    "default-src 'self'; script-src 'self' 'unsafe-eval'",
+    0,
+    "\u2018script-src\u2019 directive contains a forbidden 'unsafe-eval' keyword",
+    "eval disallowed"
+  );
+  checkPolicy(
+    "default-src 'self'; script-src 'self' 'unsafe-eval'",
+    flags.CSP_ALLOW_EVAL,
+    null,
+    "eval allowed"
+  );
+
+  checkPolicy(
+    "default-src 'self'; script-src 'self' 'wasm-unsafe-eval'",
+    0,
+    "\u2018script-src\u2019 directive contains a forbidden 'wasm-unsafe-eval' keyword",
+    "wasm disallowed"
+  );
+  checkPolicy(
+    "default-src 'self'; script-src 'self' 'wasm-unsafe-eval'",
+    flags.CSP_ALLOW_WASM,
+    null,
+    "wasm allowed"
+  );
+  checkPolicy(
+    "default-src 'self'; script-src 'self' 'unsafe-eval' 'wasm-unsafe-eval'",
+    flags.CSP_ALLOW_EVAL,
+    null,
+    "wasm and eval allowed"
+  );
+
+  checkPolicy(
+    "default-src 'self'; script-src 'self' https://example.com",
+    0,
+    "\u2018script-src\u2019 directive contains a forbidden https: protocol source",
+    "remote disallowed"
+  );
+  checkPolicy(
+    "default-src 'self'; script-src 'self' https://example.com",
+    flags.CSP_ALLOW_REMOTE,
+    null,
+    "remote allowed"
+  );
+});
+
+add_task(async function test_csp_validator() {
+  let checkPolicy = (policy, expectedResult, message = null) => {
+    info(`Checking policy: ${policy}`);
+
+    let result = cps.validateAddonCSP(
+      policy,
+      Ci.nsIAddonContentPolicy.CSP_ALLOW_ANY
+    );
+    equal(result, expectedResult);
+  };
+
+  checkPolicy("script-src 'self';", null);
+
+  // In the past, object-src was required to be secure and defaulted to 'self'.
+  // But that is no longer required (see bug 1766881).
+  checkPolicy("script-src 'self'; object-src 'self';", null);
+  checkPolicy("script-src 'self'; object-src https:;", null);
+
+  let hash =
+    "'sha256-NjZhMDQ1YjQ1MjEwMmM1OWQ4NDBlYzA5N2Q1OWQ5NDY3ZTEzYTNmMzRmNjQ5NGU1MzlmZmQzMmMxYmIzNWYxOCAgLQo='";
+
+  checkPolicy(
+    `script-src 'self' https://com https://*.example.com moz-extension://09abcdef blob: filesystem: ${hash} 'unsafe-eval'; ` +
+      `object-src 'self' https://com https://*.example.com moz-extension://09abcdef blob: filesystem: ${hash}`,
+    null
+  );
+
+  checkPolicy(
+    "",
+    "Policy is missing a required \u2018script-src\u2019 directive"
+  );
+
+  checkPolicy(
+    "object-src 'none';",
+    "Policy is missing a required \u2018script-src\u2019 directive"
+  );
+
+  checkPolicy(
+    "default-src 'self' http:",
+    "Policy is missing a required \u2018script-src\u2019 directive",
+    "A strict default-src is required as a fallback if script-src is missing"
+  );
+
+  checkPolicy(
+    "default-src 'self' http:; script-src 'self'",
+    null,
+    "A valid script-src removes the need for a strict default-src fallback"
+  );
+
+  checkPolicy(
+    "default-src 'self'",
+    null,
+    "A valid default-src should count as a valid script-src"
+  );
+
+  checkPolicy(
+    "default-src 'self'; script-src 'self'",
+    null,
+    "A valid default-src should count as a valid script-src"
+  );
+
+  checkPolicy(
+    "default-src 'self'; script-src http://example.com",
+    "\u2018script-src\u2019 directive contains a forbidden http: protocol source",
+    "A valid default-src should not allow an invalid script-src directive"
+  );
+
+  checkPolicy(
+    "script-src 'none'",
+    "\u2018script-src\u2019 must include the source 'self'"
+  );
+
+  checkPolicy(
+    "script-src 'self' 'unsafe-inline'",
+    "\u2018script-src\u2019 directive contains a forbidden 'unsafe-inline' keyword"
+  );
+
+  // Localhost is always valid
+  for (let src of [
+    "http://localhost",
+    "https://localhost",
+    "http://127.0.0.1",
+    "https://127.0.0.1",
+  ]) {
+    checkPolicy(`script-src 'self' ${src};`, null);
+  }
+
+  let directives = ["script-src", "worker-src"];
+
+  for (let [directive, other] of [directives, directives.slice().reverse()]) {
+    for (let src of ["https://*", "https://*.blogspot.com", "https://*"]) {
+      checkPolicy(
+        `${directive} 'self' ${src}; ${other} 'self';`,
+        `https: wildcard sources in \u2018${directive}\u2019 directives must include at least one non-generic sub-domain (e.g., *.example.com rather than *.com)`
+      );
+    }
+
+    for (let protocol of ["http", "https"]) {
+      checkPolicy(
+        `${directive} 'self' ${protocol}:; ${other} 'self';`,
+        `${protocol}: protocol requires a host in \u2018${directive}\u2019 directives`
+      );
+    }
+
+    checkPolicy(
+      `${directive} 'self' http://example.com; ${other} 'self';`,
+      `\u2018${directive}\u2019 directive contains a forbidden http: protocol source`
+    );
+
+    for (let protocol of ["ftp", "meh"]) {
+      checkPolicy(
+        `${directive} 'self' ${protocol}:; ${other} 'self';`,
+        `\u2018${directive}\u2019 directive contains a forbidden ${protocol}: protocol source`
+      );
+    }
+
+    checkPolicy(
+      `${directive} 'self' 'nonce-01234'; ${other} 'self';`,
+      `\u2018${directive}\u2019 directive contains a forbidden 'nonce-*' keyword`
+    );
+  }
+});
+
+add_task(async function test_csp_validator_extension_pages() {
+  let checkPolicy = (policy, expectedResult, message = null) => {
+    info(`Checking policy: ${policy}`);
+
+    // While Schemas.jsm uses Ci.nsIAddonContentPolicy.CSP_ALLOW_WASM, we don't
+    // pass that here because we are only verifying that remote scripts are
+    // blocked here.
+    let result = cps.validateAddonCSP(policy, 0);
+    equal(result, expectedResult);
+  };
+
+  checkPolicy("script-src 'self';", null);
+  checkPolicy("script-src 'self'; worker-src 'none'", null);
+  checkPolicy("script-src 'self'; worker-src 'self'", null);
+
+  // In the past, object-src was required to be secure and defaulted to 'self'.
+  // But that is no longer required (see bug 1766881).
+  checkPolicy("script-src 'self'; object-src 'self';", null);
+  checkPolicy("script-src 'self'; object-src https:;", null);
+
+  let hash =
+    "'sha256-NjZhMDQ1YjQ1MjEwMmM1OWQ4NDBlYzA5N2Q1OWQ5NDY3ZTEzYTNmMzRmNjQ5NGU1MzlmZmQzMmMxYmIzNWYxOCAgLQo='";
+
+  checkPolicy(
+    `script-src 'self' moz-extension://09abcdef blob: filesystem: ${hash}; `,
+    null
+  );
+
+  for (let policy of ["", "script-src-elem 'none';", "worker-src 'none';"]) {
+    checkPolicy(
+      policy,
+      "Policy is missing a required \u2018script-src\u2019 directive"
+    );
+  }
+
+  checkPolicy(
+    "default-src 'self' http:; script-src 'self'",
+    null,
+    "A valid script-src removes the need for a strict default-src fallback"
+  );
+
+  checkPolicy(
+    "default-src 'self'",
+    null,
+    "A valid default-src should count as a valid script-src"
+  );
+
+  for (let directive of ["script-src", "worker-src"]) {
+    checkPolicy(
+      `default-src 'self'; ${directive} 'self'`,
+      null,
+      `A valid default-src should count as a valid ${directive}`
+    );
+    checkPolicy(
+      `default-src 'self'; ${directive} http://example.com`,
+      `\u2018${directive}\u2019 directive contains a forbidden http: protocol source`,
+      `A valid default-src should not allow an invalid ${directive} directive`
+    );
+  }
+
+  checkPolicy(
+    "script-src 'none'",
+    "\u2018script-src\u2019 must include the source 'self'"
+  );
+
+  checkPolicy(
+    "script-src 'self' 'unsafe-inline';",
+    "\u2018script-src\u2019 directive contains a forbidden 'unsafe-inline' keyword"
+  );
+
+  checkPolicy(
+    "script-src 'self' 'unsafe-eval';",
+    "\u2018script-src\u2019 directive contains a forbidden 'unsafe-eval' keyword"
+  );
+
+  // Localhost is invalid
+  for (let src of [
+    "http://localhost",
+    "https://localhost",
+    "http://127.0.0.1",
+    "https://127.0.0.1",
+  ]) {
+    const protocol = src.split(":")[0];
+    checkPolicy(
+      `script-src 'self' ${src};`,
+      `\u2018script-src\u2019 directive contains a forbidden ${protocol}: protocol source`
+    );
+  }
+
+  let directives = ["script-src", "worker-src"];
+
+  for (let [directive, other] of [directives, directives.slice().reverse()]) {
+    for (let protocol of ["http", "https"]) {
+      checkPolicy(
+        `${directive} 'self' ${protocol}:; ${other} 'self';`,
+        `${protocol}: protocol requires a host in \u2018${directive}\u2019 directives`
+      );
+    }
+
+    checkPolicy(
+      `${directive} 'self' https://example.com; ${other} 'self';`,
+      `\u2018${directive}\u2019 directive contains a forbidden https: protocol source`
+    );
+
+    checkPolicy(
+      `${directive} 'self' http://example.com; ${other} 'self';`,
+      `\u2018${directive}\u2019 directive contains a forbidden http: protocol source`
+    );
+
+    for (let protocol of ["ftp", "meh"]) {
+      checkPolicy(
+        `${directive} 'self' ${protocol}:; ${other} 'self';`,
+        `\u2018${directive}\u2019 directive contains a forbidden ${protocol}: protocol source`
+      );
+    }
+
+    checkPolicy(
+      `${directive} 'self' 'nonce-01234'; ${other} 'self';`,
+      `\u2018${directive}\u2019 directive contains a forbidden 'nonce-*' keyword`
+    );
+  }
+});
diff --git a/toolkit/components/extensions/test/xpcshell/test_ext_MessageManagerProxy.js b/toolkit/components/extensions/test/xpcshell/test_ext_MessageManagerProxy.js
new file mode 100644
index 0000000000..988da4f405
--- /dev/null
+++ b/toolkit/components/extensions/test/xpcshell/test_ext_MessageManagerProxy.js
@@ -0,0 +1,80 @@
+/* -*- Mode: indent-tabs-mode: nil; js-indent-level: 2 -*- */
+/* vim: set sts=2 sw=2 et tw=80: */
+"use strict";
+
+const { MessageManagerProxy } = ChromeUtils.importESModule(
+  "resource://gre/modules/MessageManagerProxy.sys.mjs"
+);
+const { PromiseUtils } = ChromeUtils.importESModule(
+  "resource://gre/modules/PromiseUtils.sys.mjs"
+);
+
+class TestMessageManagerProxy extends MessageManagerProxy {
+  constructor(contentPage, identifier) {
+    super(contentPage.browser);
+    this.identifier = identifier;
+    this.contentPage = contentPage;
+    this.deferred = null;
+  }
+
+  // Registers message listeners. Call dispose() once you've finished.
+  async setupPingPongListeners() {
+    await this.contentPage.loadFrameScript(`() => {
+      this.addMessageListener("test:MessageManagerProxy:Ping", ({data}) => {
+        this.sendAsyncMessage("test:MessageManagerProxy:Pong", "${this.identifier}:" + data);
+      });
+    }`);
+
+    // Register the listener here instead of during testPingPong, to make sure
+    // that the listener is correctly registered during the whole test.
+    this.addMessageListener("test:MessageManagerProxy:Pong", event => {
+      ok(
+        this.deferred,
+        `[${this.identifier}] expected to be waiting for ping-pong`
+      );
+      this.deferred.resolve(event.data);
+      this.deferred = null;
+    });
+  }
+
+  async testPingPong(description) {
+    equal(this.deferred, null, "should not be waiting for a message");
+    this.deferred = PromiseUtils.defer();
+    this.sendAsyncMessage("test:MessageManagerProxy:Ping", description);
+    let result = await this.deferred.promise;
+    equal(result, `${this.identifier}:${description}`, "Expected ping-pong");
+  }
+}
+
+// Tests that MessageManagerProxy continues to proxy messages after docshells
+// have been swapped.
+add_task(async function test_message_after_swapdocshells() {
+  let page1 = await ExtensionTestUtils.loadContentPage("about:blank");
+  let page2 = await ExtensionTestUtils.loadContentPage("about:blank");
+
+  let testProxyOne = new TestMessageManagerProxy(page1, "page1");
+  let testProxyTwo = new TestMessageManagerProxy(page2, "page2");
+
+  await testProxyOne.setupPingPongListeners();
+  await testProxyTwo.setupPingPongListeners();
+
+  await testProxyOne.testPingPong("after setup (to 1)");
+  await testProxyTwo.testPingPong("after setup (to 2)");
+
+  page1.browser.swapDocShells(page2.browser);
+
+  await testProxyOne.testPingPong("after docshell swap (to 1)");
+  await testProxyTwo.testPingPong("after docshell swap (to 2)");
+
+  // Swap again to verify that listeners are repeatedly moved when needed.
+  page1.browser.swapDocShells(page2.browser);
+
+  await testProxyOne.testPingPong("after another docshell swap (to 1)");
+  await testProxyTwo.testPingPong("after another docshell swap (to 2)");
+
+  // Verify that dispose() works regardless of the browser's validity.
+  await testProxyOne.dispose();
+  await page1.close();
+  await page2.close();
+  await testProxyTwo.dispose();
+});
diff --git a/toolkit/components/extensions/test/xpcshell/test_ext_activityLog.js b/toolkit/components/extensions/test/xpcshell/test_ext_activityLog.js
new file mode 100644
index 0000000000..00173f3a4d
--- /dev/null
+++ b/toolkit/components/extensions/test/xpcshell/test_ext_activityLog.js
@@ -0,0 +1,78 @@
+"use strict";
+
+AddonTestUtils.init(this);
+AddonTestUtils.overrideCertDB();
+AddonTestUtils.usePrivilegedSignatures = false;
+AddonTestUtils.createAppInfo(
+  "xpcshell@tests.mozilla.org",
+  "XPCShell",
+  "1",
+  "42"
+);
+
+add_setup(async () => {
+  await AddonTestUtils.promiseStartupManager();
+});
+
+// This test should produce a warning, but still startup
+add_task(async function test_api_restricted() {
+  let extension = ExtensionTestUtils.loadExtension({
+    manifest: {
+      browser_specific_settings: {
+        gecko: { id: "activityLog-permission@tests.mozilla.org" },
+      },
+      permissions: ["activityLog"],
+    },
+    async background() {
+      browser.test.assertEq(
+        undefined,
+        browser.activityLog,
+        "activityLog is privileged"
+      );
+    },
+    useAddonManager: "permanent",
+  });
+  await extension.startup();
+  await extension.unload();
+});
+
+// This test should produce a error and not startup
+add_task(
+  {
+    // Some builds (e.g. thunderbird) have experiments enabled by default.
+    pref_set: [["extensions.experiments.enabled", false]],
+  },
+  async function test_api_restricted_temporary_without_privilege() {
+    let extension = ExtensionTestUtils.loadExtension({
+      temporarilyInstalled: true,
+      isPrivileged: false,
+      manifest: {
+        browser_specific_settings: {
+          gecko: { id: "activityLog-permission@tests.mozilla.org" },
+        },
+        permissions: ["activityLog"],
+      },
+    });
+    ExtensionTestUtils.failOnSchemaWarnings(false);
+    let { messages } = await promiseConsoleOutput(async () => {
+      await Assert.rejects(
+        extension.startup(),
+        /Using the privileged permission/,
+        "Startup failed with privileged permission"
+      );
+    });
+    ExtensionTestUtils.failOnSchemaWarnings(true);
+    AddonTestUtils.checkMessages(
+      messages,
+      {
+        expected: [
+          {
+            message:
+              /Using the privileged permission 'activityLog' requires a privileged add-on/,
+          },
+        ],
+      },
+      true
+    );
+  }
+);
diff --git a/toolkit/components/extensions/test/xpcshell/test_ext_adoption_with_private_field_xrays.js b/toolkit/components/extensions/test/xpcshell/test_ext_adoption_with_private_field_xrays.js
new file mode 100644
index 0000000000..2d8b02bcd9
--- /dev/null
+++ b/toolkit/components/extensions/test/xpcshell/test_ext_adoption_with_private_field_xrays.js
@@ -0,0 +1,160 @@
+"use strict";
+
+// ExtensionContent.jsm needs to know when it's running from xpcshell,
+// to use the right timeout for content scripts executed at document_idle.
+ExtensionTestUtils.mockAppInfo();
+const server = createHttpServer();
+server.registerDirectory("/data/", do_get_file("data"));
+
+const BASE_URL = `http://localhost:${server.identity.primaryPort}/data`;
+
+add_task(async function test_contentscript_private_field_xrays() {
+  async function contentScript() {
+    let node = window.document.createElement("div");
+
+    class Base {
+      constructor(o) {
+        return o;
+      }
+    }
+
+    class A extends Base {
+      #x = 5;
+      static gx(o) {
+        return o.#x;
+      }
+      static sx(o, v) {
+        o.#x = v;
+      }
+    }
+
+    browser.test.log(A.toString());
+
+    // Stamp node with A's private field.
+    new A(node);
+
+    browser.test.log("stamped");
+
+    browser.test.assertEq(
+      A.gx(node),
+      5,
+      "We should be able to see our expando private field"
+    );
+    browser.test.log("Read");
+    browser.test.assertThrows(
+      () => A.gx(node.wrappedJSObject),
+      /can't access private field or method/,
+      "Underlying object should not have our private field"
+    );
+
+    browser.test.log("threw");
+    window.frames[0].document.adoptNode(node);
+    browser.test.log("adopted");
+    browser.test.assertEq(
+      A.gx(node),
+      5,
+      "Adoption should not change expando private field"
+    );
+    browser.test.log("read");
+    browser.test.assertThrows(
+      () => A.gx(node.wrappedJSObject),
+      /can't access private field or method/,
+      "Adoption should really not change expandos private fields"
+    );
+    browser.test.log("threw2");
+
+    // Repeat but now with an object that has a reference from the
+    // window it's being cloned into.
+    node = window.document.createElement("div");
+    // Stamp node with A's private field.
+    new A(node);
+    A.sx(node, 6);
+
+    browser.test.assertEq(
+      A.gx(node),
+      6,
+      "We should be able to see our expando (2)"
+    );
+    browser.test.assertThrows(
+      () => A.gx(node.wrappedJSObject),
+      /can't access private field or method/,
+      "Underlying object should not have exxpando. (2)"
+    );
+
+    window.frames[0].wrappedJSObject.incoming = node.wrappedJSObject;
+    window.frames[0].document.adoptNode(node);
+
+    browser.test.assertEq(
+      A.gx(node),
+      6,
+      "We should be able to see our expando (3)"
+    );
+    browser.test.assertThrows(
+      () => A.gx(node.wrappedJSObject),
+      /can't access private field or method/,
+      "Underlying object should not have exxpando. (3)"
+    );
+
+    // Repeat once more, now with an expando that refers to the object itself
+    node = window.document.createElement("div");
+    new A(node);
+    A.sx(node, node);
+
+    browser.test.assertEq(
+      A.gx(node),
+      node,
+      "We should be able to see our self-referential expando (4)"
+    );
+    browser.test.assertThrows(
+      () => A.gx(node.wrappedJSObject),
+      /can't access private field or method/,
+      "Underlying object should not have exxpando. (4)"
+    );
+
+    window.frames[0].document.adoptNode(node);
+
+    browser.test.assertEq(
+      A.gx(node),
+      node,
+      "Adoption should not change our self-referential expando (4)"
+    );
+    browser.test.assertThrows(
+      () => A.gx(node.wrappedJSObject),
+      /can't access private field or method/,
+      "Adoption should not change underlying object. (4)"
+    );
+
+    // And test what happens if we now set document.domain and cause
+    // wrapper remapping.
+    let doc = window.frames[0].document;
+    // eslint-disable-next-line no-self-assign
+    doc.domain = doc.domain;
+
+    browser.test.notifyPass("privateFieldXRayAdoption");
+  }
+
+  let extension = ExtensionTestUtils.loadExtension({
+    manifest: {
+      content_scripts: [
+        {
+          matches: ["http://*/*/file_toplevel.html"],
+          js: ["content_script.js"],
+        },
+      ],
+    },
+
+    files: {
+      "content_script.js": contentScript,
+    },
+  });
+
+  await extension.startup();
+  let contentPage = await ExtensionTestUtils.loadContentPage(
+    `${BASE_URL}/file_toplevel.html`
+  );
+
+  await extension.awaitFinish("privateFieldXRayAdoption");
+
+  await contentPage.close();
+  await extension.unload();
+});
diff --git a/toolkit/components/extensions/test/xpcshell/test_ext_adoption_with_xrays.js b/toolkit/components/extensions/test/xpcshell/test_ext_adoption_with_xrays.js
new file mode 100644
index 0000000000..9655c157d1
--- /dev/null
+++ b/toolkit/components/extensions/test/xpcshell/test_ext_adoption_with_xrays.js
@@ -0,0 +1,129 @@
+"use strict";
+
+// ExtensionContent.jsm needs to know when it's running from xpcshell,
+// to use the right timeout for content scripts executed at document_idle.
+ExtensionTestUtils.mockAppInfo();
+const server = createHttpServer();
+server.registerDirectory("/data/", do_get_file("data"));
+
+const BASE_URL = `http://localhost:${server.identity.primaryPort}/data`;
+
+add_task(async function test_contentscript_xrays() {
+  async function contentScript() {
+    let node = window.document.createElement("div");
+    node.expando = 5;
+
+    browser.test.assertEq(
+      node.expando,
+      5,
+      "We should be able to see our expando"
+    );
+    browser.test.assertEq(
+      node.wrappedJSObject.expando,
+      undefined,
+      "Underlying object should not have our expando"
+    );
+
+    window.frames[0].document.adoptNode(node);
+    browser.test.assertEq(
+      node.expando,
+      5,
+      "Adoption should not change expandos"
+    );
+    browser.test.assertEq(
+      node.wrappedJSObject.expando,
+      undefined,
+      "Adoption should really not change expandos"
+    );
+
+    // Repeat but now with an object that has a reference from the
+    // window it's being cloned into.
+    node = window.document.createElement("div");
+    node.expando = 6;
+
+    browser.test.assertEq(
+      node.expando,
+      6,
+      "We should be able to see our expando (2)"
+    );
+    browser.test.assertEq(
+      node.wrappedJSObject.expando,
+      undefined,
+      "Underlying object should not have our expando (2)"
+    );
+
+    window.frames[0].wrappedJSObject.incoming = node.wrappedJSObject;
+
+    window.frames[0].document.adoptNode(node);
+    browser.test.assertEq(
+      node.expando,
+      6,
+      "Adoption should not change expandos (2)"
+    );
+    browser.test.assertEq(
+      node.wrappedJSObject.expando,
+      undefined,
+      "Adoption should really not change expandos (2)"
+    );
+
+    // Repeat once more, now with an expando that refers to the object itself.
+    node = window.document.createElement("div");
+    node.expando = node;
+
+    browser.test.assertEq(
+      node.expando,
+      node,
+      "We should be able to see our self-referential expando (3)"
+    );
+    browser.test.assertEq(
+      node.wrappedJSObject.expando,
+      undefined,
+      "Underlying object should not have our self-referential expando (3)"
+    );
+
+    window.frames[0].document.adoptNode(node);
+    browser.test.assertEq(
+      node.expando,
+      node,
+      "Adoption should not change self-referential expando (3)"
+    );
+    browser.test.assertEq(
+      node.wrappedJSObject.expando,
+      undefined,
+      "Adoption should really not change self-referential expando (3)"
+    );
+
+    // And test what happens if we now set document.domain and cause
+    // wrapper remapping.
+    let doc = window.frames[0].document;
+    // eslint-disable-next-line no-self-assign
+    doc.domain = doc.domain;
+
+    browser.test.notifyPass("contentScriptAdoptionWithXrays");
+  }
+
+  let extension = ExtensionTestUtils.loadExtension({
+    manifest: {
+      content_scripts: [
+        {
+          matches: ["http://*/*/file_toplevel.html"],
+          js: ["content_script.js"],
+        },
+      ],
+    },
+
+    files: {
+      "content_script.js": contentScript,
+    },
+  });
+
+  await extension.startup();
+  let contentPage = await ExtensionTestUtils.loadContentPage(
+    `${BASE_URL}/file_toplevel.html`
+  );
+
+  await extension.awaitFinish("contentScriptAdoptionWithXrays");
+
+  await contentPage.close();
+  await extension.unload();
+});
diff --git a/toolkit/components/extensions/test/xpcshell/test_ext_alarms.js b/toolkit/components/extensions/test/xpcshell/test_ext_alarms.js
new file mode 100644
index 0000000000..892a82e2e3
--- /dev/null
+++ b/toolkit/components/extensions/test/xpcshell/test_ext_alarms.js
@@ -0,0 +1,346 @@
+/* -*- Mode: indent-tabs-mode: nil; js-indent-level: 2 -*- */
+/* vim: set sts=2 sw=2 et tw=80: */
+/* eslint-disable mozilla/no-arbitrary-setTimeout */
+"use strict";
+
+AddonTestUtils.init(this);
+AddonTestUtils.overrideCertDB();
+AddonTestUtils.createAppInfo(
+  "xpcshell@tests.mozilla.org",
+  "XPCShell",
+  "1",
+  "43"
+);
+
+add_task(
+  {
+    // TODO(Bug 1725478): remove the skip if once webidl API bindings will be hidden based on permissions.
+    skip_if: () => ExtensionTestUtils.isInBackgroundServiceWorkerTests(),
+  },
+  async function test_alarm_without_permissions() {
+    function backgroundScript() {
+      browser.test.assertTrue(
+        !browser.alarms,
+        "alarm API is not available when the alarm permission is not required"
+      );
+      browser.test.notifyPass("alarms_permission");
+    }
+
+    let extension = ExtensionTestUtils.loadExtension({
+      background: `(${backgroundScript})()`,
+      manifest: {
+        permissions: [],
+      },
+    });
+
+    await extension.startup();
+    await extension.awaitFinish("alarms_permission");
+    await extension.unload();
+  }
+);
+
+add_task(async function test_alarm_clear_non_matching_name() {
+  async function backgroundScript() {
+    let ALARM_NAME = "test_ext_alarms";
+
+    browser.alarms.create(ALARM_NAME, { when: Date.now() + 2000000 });
+
+    let wasCleared = await browser.alarms.clear(ALARM_NAME + "1");
+    browser.test.assertFalse(wasCleared, "alarm was not cleared");
+
+    let alarms = await browser.alarms.getAll();
+    browser.test.assertEq(1, alarms.length, "alarm was not removed");
+    browser.test.notifyPass("alarm-clear");
+  }
+
+  let extension = ExtensionTestUtils.loadExtension({
+    background: `(${backgroundScript})()`,
+    manifest: {
+      permissions: ["alarms"],
+    },
+  });
+
+  await extension.startup();
+  await extension.awaitFinish("alarm-clear");
+  await extension.unload();
+});
+
+add_task(async function test_alarm_get_and_clear_single_argument() {
+  async function backgroundScript() {
+    browser.alarms.create({ when: Date.now() + 2000000 });
+
+    let alarm = await browser.alarms.get();
+    browser.test.assertEq("", alarm.name, "expected alarm returned");
+
+    let wasCleared = await browser.alarms.clear();
+    browser.test.assertTrue(wasCleared, "alarm was cleared");
+
+    let alarms = await browser.alarms.getAll();
+    browser.test.assertEq(0, alarms.length, "alarm was removed");
+
+    browser.test.notifyPass("alarm-single-arg");
+  }
+
+  let extension = ExtensionTestUtils.loadExtension({
+    background: `(${backgroundScript})()`,
+    manifest: {
+      permissions: ["alarms"],
+    },
+  });
+
+  await extension.startup();
+  await extension.awaitFinish("alarm-single-arg");
+  await extension.unload();
+});
+
+// This test case covers the behavior of browser.alarms.create when the
+// first optional argument (the alarm name) is passed explicitly as null
+// or undefined instead of being omitted.
+add_task(async function test_alarm_name_arg_null_or_undefined() {
+  async function backgroundScript(alarmName) {
+    browser.alarms.create(alarmName, { when: Date.now() + 2000000 });
+
+    let alarm = await browser.alarms.get();
+    browser.test.assertTrue(alarm, "got an alarm");
+    browser.test.assertEq("", alarm.name, "expected alarm returned");
+
+    let wasCleared = await browser.alarms.clear();
+    browser.test.assertTrue(wasCleared, "alarm was cleared");
+
+    let alarms = await browser.alarms.getAll();
+    browser.test.assertEq(0, alarms.length, "alarm was removed");
+
+    browser.test.notifyPass("alarm-test-done");
+  }
+
+  for (const alarmName of [null, undefined]) {
+    info(`Test alarm.create with alarm name ${alarmName}`);
+    let extension = ExtensionTestUtils.loadExtension({
+      background: `(${backgroundScript})(${alarmName})`,
+      manifest: {
+        permissions: ["alarms"],
+      },
+    });
+    await extension.startup();
+    await extension.awaitFinish("alarm-test-done");
+    await extension.unload();
+  }
+});
+
+add_task(async function test_get_get_all_clear_all_alarms() {
+  async function backgroundScript() {
+    const ALARM_NAME = "test_alarm";
+
+    let suffixes = [0, 1, 2];
+
+    for (let suffix of suffixes) {
+      browser.alarms.create(ALARM_NAME + suffix, {
+        when: Date.now() + (suffix + 1) * 10000,
+      });
+    }
+
+    let alarms = await browser.alarms.getAll();
+    browser.test.assertEq(
+      suffixes.length,
+      alarms.length,
+      "expected number of alarms were found"
+    );
+    alarms.forEach((alarm, index) => {
+      browser.test.assertEq(
+        ALARM_NAME + index,
+        alarm.name,
+        "alarm has the expected name"
+      );
+    });
+
+    for (let suffix of suffixes) {
+      let alarm = await browser.alarms.get(ALARM_NAME + suffix);
+      browser.test.assertEq(
+        ALARM_NAME + suffix,
+        alarm.name,
+        "alarm has the expected name"
+      );
+      browser.test.sendMessage(`get-${suffix}`);
+    }
+
+    let wasCleared = await browser.alarms.clear(ALARM_NAME + suffixes[0]);
+    browser.test.assertTrue(wasCleared, "alarm was cleared");
+
+    alarms = await browser.alarms.getAll();
+    browser.test.assertEq(2, alarms.length, "alarm was removed");
+
+    let alarm = await browser.alarms.get(ALARM_NAME + suffixes[0]);
+    browser.test.assertEq(undefined, alarm, "non-existent alarm is undefined");
+    browser.test.sendMessage(`get-invalid`);
+
+    wasCleared = await browser.alarms.clearAll();
+    browser.test.assertTrue(wasCleared, "alarms were cleared");
+
+    alarms = await browser.alarms.getAll();
+    browser.test.assertEq(0, alarms.length, "no alarms exist");
+    browser.test.sendMessage("clearAll");
+    browser.test.sendMessage("clear");
+    browser.test.sendMessage("getAll");
+  }
+
+  let extension = ExtensionTestUtils.loadExtension({
+    background: `(${backgroundScript})()`,
+    manifest: {
+      permissions: ["alarms"],
+    },
+  });
+
+  await Promise.all([
+    extension.startup(),
+    extension.awaitMessage("getAll"),
+    extension.awaitMessage("get-0"),
+    extension.awaitMessage("get-1"),
+    extension.awaitMessage("get-2"),
+    extension.awaitMessage("clear"),
+    extension.awaitMessage("get-invalid"),
+    extension.awaitMessage("clearAll"),
+  ]);
+  await extension.unload();
+});
+
+function getAlarmExtension(alarmCreateOptions, extOpts = {}) {
+  info(
+    `Test alarms.create fires with options: ${JSON.stringify(
+      alarmCreateOptions
+    )}`
+  );
+
+  function backgroundScript(createOptions) {
+    let ALARM_NAME = "test_ext_alarms";
+    let timer;
+
+    browser.alarms.onAlarm.addListener(alarm => {
+      browser.test.assertEq(
+        ALARM_NAME,
+        alarm.name,
+        "alarm has the expected name"
+      );
+      clearTimeout(timer);
+      browser.test.sendMessage("alarms-create-with-options");
+    });
+
+    browser.alarms.create(ALARM_NAME, createOptions);
+
+    timer = setTimeout(async () => {
+      browser.test.fail("alarm fired within expected time");
+      let wasCleared = await browser.alarms.clear(ALARM_NAME);
+      browser.test.assertTrue(wasCleared, "alarm was cleared");
+      browser.test.sendMessage("alarms-create-with-options");
+    }, 10000);
+  }
+
+  let { persistent, useAddonManager } = extOpts;
+  return ExtensionTestUtils.loadExtension({
+    useAddonManager,
+    // Pass the alarms.create options to the background page.
+    background: `(${backgroundScript})(${JSON.stringify(alarmCreateOptions)})`,
+    manifest: {
+      permissions: ["alarms"],
+      background: { persistent },
+    },
+  });
+}
+
+async function test_alarm_fires_with_options(alarmCreateOptions) {
+  let extension = getAlarmExtension(alarmCreateOptions);
+
+  await extension.startup();
+  await extension.awaitMessage("alarms-create-with-options");
+
+  // Defer unloading the extension so the asynchronous event listener
+  // reply finishes.
+  await new Promise(resolve => setTimeout(resolve, 0));
+  await extension.unload();
+}
+
+add_task(async function test_alarm_fires() {
+  Services.prefs.setBoolPref(
+    "privacy.resistFingerprinting.reduceTimerPrecision.jitter",
+    false
+  );
+
+  await test_alarm_fires_with_options({ delayInMinutes: 0.01 });
+  await test_alarm_fires_with_options({ when: Date.now() + 1000 });
+  await test_alarm_fires_with_options({ delayInMinutes: -10 });
+  await test_alarm_fires_with_options({ when: Date.now() - 1000 });
+
+  Services.prefs.clearUserPref(
+    "privacy.resistFingerprinting.reduceTimerPrecision.jitter"
+  );
+});
+
+function trackEvents(wrapper) {
+  let events = new Map();
+  for (let event of ["background-script-event", "start-background-script"]) {
+    events.set(event, false);
+    wrapper.extension.once(event, () => events.set(event, true));
+  }
+  return events;
+}
+
+add_task(
+  {
+    // TODO(Bug 1748665): remove the skip once background service worker is also
+    // woken up by persistent listeners.
+    skip_if: () => ExtensionTestUtils.isInBackgroundServiceWorkerTests(),
+    pref_set: [
+      ["privacy.resistFingerprinting.reduceTimerPrecision.jitter", false],
+      ["extensions.eventPages.enabled", true],
+    ],
+  },
+  async function test_alarm_persists() {
+    await AddonTestUtils.promiseStartupManager();
+
+    let extension = getAlarmExtension(
+      { periodInMinutes: 0.01 },
+      { useAddonManager: "permanent", persistent: false }
+    );
+    info(`wait startup`);
+    await extension.startup();
+    assertPersistentListeners(extension, "alarms", "onAlarm", {
+      primed: false,
+    });
+    info(`wait first alarm`);
+    await extension.awaitMessage("alarms-create-with-options");
+
+    await extension.terminateBackground({ disableResetIdleForTest: true });
+    ok(
+      !extension.extension.backgroundContext,
+      "Background Extension context should have been destroyed"
+    );
+
+    assertPersistentListeners(extension, "alarms", "onAlarm", {
+      primed: true,
+    });
+
+    // Test an early startup event
+    let events = trackEvents(extension);
+    ok(
+      !events.get("background-script-event"),
+      "Should not have received a background script event"
+    );
+    ok(
+      !events.get("start-background-script"),
+      "Background script should not be started"
+    );
+
+    info("waiting for alarm to wake background");
+    await extension.awaitMessage("alarms-create-with-options");
+    ok(
+      events.get("background-script-event"),
+      "Should have received a background script event"
+    );
+    ok(
+      events.get("start-background-script"),
+      "Background script should be started"
+    );
+
+    await extension.unload();
+    await AddonTestUtils.promiseShutdownManager();
+  }
+);
diff --git a/toolkit/components/extensions/test/xpcshell/test_ext_alarms_does_not_fire.js b/toolkit/components/extensions/test/xpcshell/test_ext_alarms_does_not_fire.js
new file mode 100644
index 0000000000..fe385004ba
--- /dev/null
+++ b/toolkit/components/extensions/test/xpcshell/test_ext_alarms_does_not_fire.js
@@ -0,0 +1,34 @@
+/* -*- Mode: indent-tabs-mode: nil; js-indent-level: 2 -*- */
+/* vim: set sts=2 sw=2 et tw=80: */
+/* eslint-disable mozilla/no-arbitrary-setTimeout */
+"use strict";
+
+add_task(async function test_cleared_alarm_does_not_fire() {
+  async function backgroundScript() {
+    let ALARM_NAME = "test_ext_alarms";
+
+    browser.alarms.onAlarm.addListener(alarm => {
+      browser.test.fail("cleared alarm does not fire");
+      browser.test.notifyFail("alarm-cleared");
+    });
+    browser.alarms.create(ALARM_NAME, { when: Date.now() + 1000 });
+
+    let wasCleared = await browser.alarms.clear(ALARM_NAME);
+    browser.test.assertTrue(wasCleared, "alarm was cleared");
+
+    await new Promise(resolve => setTimeout(resolve, 2000));
+
+    browser.test.notifyPass("alarm-cleared");
+  }
+
+  let extension = ExtensionTestUtils.loadExtension({
+    background: `(${backgroundScript})()`,
+    manifest: {
+      permissions: ["alarms"],
+    },
+  });
+
+  await extension.startup();
+  await extension.awaitFinish("alarm-cleared");
+  await extension.unload();
+});
diff --git a/toolkit/components/extensions/test/xpcshell/test_ext_alarms_periodic.js b/toolkit/components/extensions/test/xpcshell/test_ext_alarms_periodic.js
new file mode 100644
index 0000000000..b78d6da649
--- /dev/null
+++ b/toolkit/components/extensions/test/xpcshell/test_ext_alarms_periodic.js
@@ -0,0 +1,50 @@
+/* -*- Mode: indent-tabs-mode: nil; js-indent-level: 2 -*- */
+/* vim: set sts=2 sw=2 et tw=80: */
+/* eslint-disable mozilla/no-arbitrary-setTimeout */
+"use strict";
+
+add_task(async function test_periodic_alarm_fires() {
+  function backgroundScript() {
+    const ALARM_NAME = "test_ext_alarms";
+    let count = 0;
+    let timer;
+
+    browser.alarms.onAlarm.addListener(alarm => {
+      browser.test.assertEq(
+        alarm.name,
+        ALARM_NAME,
+        "alarm has the expected name"
+      );
+      if (count++ === 3) {
+        clearTimeout(timer);
+        browser.alarms.clear(ALARM_NAME).then(wasCleared => {
+          browser.test.assertTrue(wasCleared, "alarm was cleared");
+
+          browser.test.notifyPass("alarm-periodic");
+        });
+      }
+    });
+
+    browser.alarms.create(ALARM_NAME, { periodInMinutes: 0.02 });
+
+    timer = setTimeout(async () => {
+      browser.test.fail("alarm fired expected number of times");
+
+      let wasCleared = await browser.alarms.clear(ALARM_NAME);
+      browser.test.assertTrue(wasCleared, "alarm was cleared");
+
+      browser.test.notifyFail("alarm-periodic");
+    }, 30000);
+  }
+
+  let extension = ExtensionTestUtils.loadExtension({
+    background: `(${backgroundScript})()`,
+    manifest: {
+      permissions: ["alarms"],
+    },
+  });
+
+  await extension.startup();
+  await extension.awaitFinish("alarm-periodic");
+  await extension.unload();
+});
diff --git a/toolkit/components/extensions/test/xpcshell/test_ext_alarms_replaces.js b/toolkit/components/extensions/test/xpcshell/test_ext_alarms_replaces.js
new file mode 100644
index 0000000000..0d7597fa5a
--- /dev/null
+++ b/toolkit/components/extensions/test/xpcshell/test_ext_alarms_replaces.js
@@ -0,0 +1,56 @@
+/* -*- Mode: indent-tabs-mode: nil; js-indent-level: 2 -*- */
+/* vim: set sts=2 sw=2 et tw=80: */
+"use strict";
+
+add_task(async function test_duplicate_alarm_name_replaces_alarm() {
+  function backgroundScript() {
+    let count = 0;
+
+    browser.alarms.onAlarm.addListener(async alarm => {
+      browser.test.assertEq(
+        "replaced alarm",
+        alarm.name,
+        "Expected last alarm"
+      );
+      browser.test.assertEq(
+        0,
+        count++,
+        "duplicate named alarm replaced existing alarm"
+      );
+      let results = await browser.alarms.getAll();
+
+      // "replaced alarm" is expected to be replaced with a non-repeating
+      // alarm, so it should not appear in the list of alarms.
+      browser.test.assertEq(1, results.length, "exactly one alarms exists");
+      browser.test.assertEq(
+        "unrelated alarm",
+        results[0].name,
+        "remaining alarm has the expected name"
+      );
+
+      browser.test.notifyPass("alarm-duplicate");
+    });
+
+    // Alarm that is so far in the future that it is never triggered.
+    browser.alarms.create("unrelated alarm", { delayInMinutes: 60 });
+    // Alarm that repeats.
+    browser.alarms.create("replaced alarm", {
+      delayInMinutes: 1 / 60,
+      periodInMinutes: 1 / 60,
+    });
+    // Before the repeating alarm is triggered, it is immediately replaced with
+    // a non-repeating alarm.
+    browser.alarms.create("replaced alarm", { delayInMinutes: 3 / 60 });
+  }
+
+  let extension = ExtensionTestUtils.loadExtension({
+    background: `(${backgroundScript})()`,
+    manifest: {
+      permissions: ["alarms"],
+    },
+  });
+
+  await extension.startup();
+  await extension.awaitFinish("alarm-duplicate");
+  await extension.unload();
+});
diff --git a/toolkit/components/extensions/test/xpcshell/test_ext_api_events_listener_calls_exceptions.js b/toolkit/components/extensions/test/xpcshell/test_ext_api_events_listener_calls_exceptions.js
new file mode 100644
index 0000000000..44ff592d83
--- /dev/null
+++ b/toolkit/components/extensions/test/xpcshell/test_ext_api_events_listener_calls_exceptions.js
@@ -0,0 +1,369 @@
+/* Any copyright is dedicated to the Public Domain.
+ * http://creativecommons.org/publicdomain/zero/1.0/ */
+
+"use strict";
+
+const { ExtensionStorageIDB } = ChromeUtils.importESModule(
+  "resource://gre/modules/ExtensionStorageIDB.sys.mjs"
+);
+
+// Detect if the current build is still using the legacy storage.sync Kinto-based backend
+// (currently only GeckoView builds does have that still enabled).
+//
+// TODO(Bug 1625257): remove this once the rust-based storage.sync backend has been enabled
+// also on GeckoView build and the legacy Kinto-based backend has been ripped off.
+const storageSyncKintoEnabled = Services.prefs.getBoolPref(
+  "webextensions.storage.sync.kinto"
+);
+
+const server = createHttpServer({ hosts: ["example.com"] });
+server.registerDirectory("/data/", do_get_file("data"));
+server.registerPathHandler("/test-page.html", (req, res) => {
+  res.setHeader("Content-Type", "text/html", false);
+  res.write(`<!DOCTYPE html>
+    <html><body><script>
+      window.onerror = (evt) => {
+        browser.test.log("webpage page got error event, error property set to: " + String(evt.error) + "::" +
+                         evt.error?.stack + "\\n");
+        window.postMessage(
+          {
+            message: evt.message,
+            sourceName: evt.filename,
+            lineNumber: evt.lineno,
+            columnNumber: evt.colno,
+            errorIsDefined: !!evt.error,
+          },
+          "*"
+        );
+      };
+      window.errorListenerReady = true;
+    </script></body></html>
+  `);
+});
+
+add_task(async function test_api_listener_call_exception() {
+  const extension = ExtensionTestUtils.loadExtension({
+    manifest: {
+      permissions: [
+        "storage",
+        "webRequest",
+        "webRequestBlocking",
+        "http://example.com/*",
+      ],
+      content_scripts: [
+        {
+          js: ["contentscript.js"],
+          matches: ["http://example.com/test-page.html"],
+          run_at: "document_start",
+        },
+      ],
+    },
+    files: {
+      "contentscript.js": () => {
+        window.onload = () => {
+          browser.test.assertEq(
+            window.wrappedJSObject.errorListenerReady,
+            true,
+            "Got an onerror listener on the content page side"
+          );
+          browser.test.sendMessage("contentscript-attached");
+        };
+        // eslint-disable-next-line mozilla/balanced-listeners
+        window.addEventListener("message", evt => {
+          browser.test.fail(
+            `Webpage got notified on an exception raised from the content script: ${JSON.stringify(
+              evt.data
+            )}`
+          );
+        });
+        // eslint-disable-next-line mozilla/balanced-listeners
+        window.addEventListener("error", evt => {
+          const errorDetails = {
+            message: evt.message,
+            sourceName: evt.filename,
+            lineNumber: evt.lineno,
+            columnNumber: evt.colno,
+            errorIsDefined: !!evt.error,
+          };
+          browser.test.fail(
+            `Webpage got notified on an exception raised from the content script: ${JSON.stringify(
+              errorDetails
+            )}`
+          );
+        });
+        const throwAnError = () => {
+          throw new Error("test-contentscript-error");
+        };
+        browser.storage.sync.onChanged.addListener(() => {
+          throwAnError();
+        });
+
+        browser.storage.local.onChanged.addListener(() => {
+          throw undefined; // eslint-disable-line no-throw-literal
+        });
+      },
+      "extpage.html": `<!DOCTYPE html><script src="extpage.js"></script>`,
+      "extpage.js": () => {
+        // eslint-disable-next-line mozilla/balanced-listeners
+        window.addEventListener("error", evt => {
+          browser.test.log(
+            `Extension page got error event, error property set to: ${evt.error} :: ${evt.error?.stack}\n`
+          );
+          const errorDetails = {
+            message: evt.message,
+            sourceName: evt.filename,
+            lineNumber: evt.lineno,
+            columnNumber: evt.colno,
+            errorIsDefined: !!evt.error,
+          };
+
+          // Theoretically the exception thrown by a listener registered
+          // from an extension webpage should be emitting an error event
+          // (e.g. like for a DOM Event listener in a similar scenario),
+          // but we never emitted it and so it would be better to only emit
+          // it after have explicitly accepted the slightly change in behavior.
+          browser.test.log(
+            `extension page got notified on an exception raised from the API event listener: ${JSON.stringify(
+              errorDetails
+            )}`
+          );
+        });
+        browser.webRequest.onBeforeRequest.addListener(
+          () => {
+            throw new Error(`Mock webRequest listener exception`);
+          },
+          { urls: ["http://example.com/data/*"] },
+          ["blocking"]
+        );
+
+        // An object with a custom getter for the `message` property and a custom
+        // toString method, both are triggering a test failure to make sure we do
+        // catch with a failure if we are running the extension code as a side effect
+        // of logging the error to the console service.
+        const nonError = {
+          get message() {
+            browser.test.fail(`Unexpected extension code executed`);
+          },
+
+          toString() {
+            browser.test.fail(`Unexpected extension code executed`);
+          },
+        };
+        browser.storage.sync.onChanged.addListener(() => {
+          throw nonError;
+        });
+
+        // Throwing undefined or null is also allowed and so we cover that here as well
+        // to confirm we are not making any assumption about the value being raised to
+        // be always defined.
+        browser.storage.local.onChanged.addListener(() => {
+          throw undefined; // eslint-disable-line no-throw-literal
+        });
+      },
+    },
+  });
+
+  await extension.startup();
+
+  const page = await ExtensionTestUtils.loadContentPage(
+    extension.extension.baseURI.resolve("extpage.html"),
+    { extension }
+  );
+
+  // Prepare to collect the error reported for the exception being triggered
+  // by the test itself.
+  const prepareWaitForConsoleMessage = () => {
+    this.content.waitForConsoleMessage = new Promise(resolve => {
+      const currInnerWindowID = this.content.windowGlobalChild?.innerWindowId;
+      const consoleListener = {
+        QueryInterface: ChromeUtils.generateQI(["nsIConsoleListener"]),
+        observe: message => {
+          if (
+            message instanceof Ci.nsIScriptError &&
+            message.innerWindowID === currInnerWindowID
+          ) {
+            resolve({
+              message: message.message,
+              category: message.category,
+              sourceName: message.sourceName,
+              hasStack: !!message.stack,
+            });
+            Services.console.unregisterListener(consoleListener);
+          }
+        },
+      };
+      Services.console.registerListener(consoleListener);
+    });
+  };
+
+  const notifyStorageSyncListener = extensionTestWrapper => {
+    // The notifyListeners method from ExtensionStorageSyncKinto does use
+    // the Extension class instance as the key for the storage.sync listeners
+    // map, whereas ExtensionStorageSync does use the extension id instead.
+    //
+    // TODO(Bug 1625257): remove this once the rust-based storage.sync backend has been enabled
+    // also on GeckoView build and the legacy Kinto-based backend has been ripped off.
+    let listenersMapKey = storageSyncKintoEnabled
+      ? extensionTestWrapper.extension
+      : extensionTestWrapper.id;
+    ok(
+      ExtensionParent.apiManager.global.extensionStorageSync.listeners.has(
+        listenersMapKey
+      ),
+      "Got a storage.sync onChanged listener for the test extension"
+    );
+    ExtensionParent.apiManager.global.extensionStorageSync.notifyListeners(
+      listenersMapKey,
+      {}
+    );
+  };
+
+  // Retrieve the message collected from the previously created promise.
+  const asyncAssertConsoleMessage = async ({
+    targetPage,
+    expectedErrorRegExp,
+    expectedSourceName,
+    shouldIncludeStack,
+  }) => {
+    const { message, category, sourceName, hasStack } = await targetPage.spawn(
+      [],
+      () => this.content.waitForConsoleMessage
+    );
+
+    ok(
+      expectedErrorRegExp.test(message),
+      `Got the expected error message: ${message}`
+    );
+
+    Assert.deepEqual(
+      { category, sourceName, hasStack },
+      {
+        category: "content javascript",
+        sourceName: expectedSourceName,
+        hasStack: shouldIncludeStack,
+      },
+      "Expected category and sourceName are set on the nsIScriptError"
+    );
+  };
+
+  {
+    info("Test exception raised by webRequest listener");
+    const expectedErrorRegExp = new RegExp(
+      `Error: Mock webRequest listener exception`
+    );
+    const expectedSourceName =
+      extension.extension.baseURI.resolve("extpage.js");
+    await page.spawn([], prepareWaitForConsoleMessage);
+    await ExtensionTestUtils.fetch(
+      "http://example.com",
+      "http://example.com/data/file_sample.html"
+    );
+    await asyncAssertConsoleMessage({
+      targetPage: page,
+      expectedErrorRegExp,
+      expectedSourceName,
+      // TODO(Bug 1810582): this should be expected to be true.
+      shouldIncludeStack: false,
+    });
+  }
+
+  {
+    info("Test exception raised by storage.sync listener");
+    // The listener has throw an object that isn't an Error instance and
+    // it also has a getter for the message property, we expect it to be
+    // logged using the string returned by the native toString method.
+    const expectedErrorRegExp = new RegExp(
+      `uncaught exception: \\[object Object\\]`
+    );
+    // TODO(Bug 1810582): this should be expected to be the script url
+    // where the exception has been originated from.
+    const expectedSourceName =
+      extension.extension.baseURI.resolve("extpage.html");
+
+    await page.spawn([], prepareWaitForConsoleMessage);
+    notifyStorageSyncListener(extension);
+    await asyncAssertConsoleMessage({
+      targetPage: page,
+      expectedErrorRegExp,
+      expectedSourceName,
+      // TODO(Bug 1810582): this should be expected to be true.
+      shouldIncludeStack: false,
+    });
+  }
+
+  {
+    info("Test exception raised by storage.local listener");
+    // The listener has throw an object that isn't an Error instance and
+    // it also has a getter for the message property, we expect it to be
+    // logged using the string returned by the native toString method.
+    const expectedErrorRegExp = new RegExp(`uncaught exception: undefined`);
+    // TODO(Bug 1810582): this should be expected to be the script url
+    // where the exception has been originated from.
+    const expectedSourceName =
+      extension.extension.baseURI.resolve("extpage.html");
+    await page.spawn([], prepareWaitForConsoleMessage);
+    ExtensionStorageIDB.notifyListeners(extension.id, {});
+    await asyncAssertConsoleMessage({
+      targetPage: page,
+      expectedErrorRegExp,
+      expectedSourceName,
+      // TODO(Bug 1810582): this should be expected to be true.
+      shouldIncludeStack: false,
+    });
+  }
+
+  await page.close();
+
+  info("Test content script API event listeners exception");
+
+  const contentPage = await ExtensionTestUtils.loadContentPage(
+    "http://example.com/test-page.html"
+  );
+
+  await extension.awaitMessage("contentscript-attached");
+
+  {
+    info("Test exception raised by content script storage.sync listener");
+    // The listener has throw an object that isn't an Error instance and
+    // it also has a getter for the message property, we expect it to be
+    // logged using the string returned by the native toString method.
+    const expectedErrorRegExp = new RegExp(`Error: test-contentscript-error`);
+    const expectedSourceName =
+      extension.extension.baseURI.resolve("contentscript.js");
+
+    await contentPage.spawn([], prepareWaitForConsoleMessage);
+    notifyStorageSyncListener(extension);
+    await asyncAssertConsoleMessage({
+      targetPage: contentPage,
+      expectedErrorRegExp,
+      expectedSourceName,
+      // TODO(Bug 1810582): this should be expected to be true.
+      shouldIncludeStack: false,
+    });
+  }
+
+  {
+    info("Test exception raised by content script storage.local listener");
+    // The listener has throw an object that isn't an Error instance and
+    // it also has a getter for the message property, we expect it to be
+    // logged using the string returned by the native toString method.
+    const expectedErrorRegExp = new RegExp(`uncaught exception: undefined`);
+    // TODO(Bug 1810582): this should be expected to be the script url
+    // where the exception has been originated from.
+    const expectedSourceName = extension.extension.baseURI.resolve("/");
+
+    await contentPage.spawn([], prepareWaitForConsoleMessage);
+    ExtensionStorageIDB.notifyListeners(extension.id, {});
+    await asyncAssertConsoleMessage({
+      targetPage: contentPage,
+      expectedErrorRegExp,
+      expectedSourceName,
+      // TODO(Bug 1810582): this should be expected to be true.
+      shouldIncludeStack: false,
+    });
+  }
+
+  await contentPage.close();
+
+  await extension.unload();
+});
diff --git a/toolkit/components/extensions/test/xpcshell/test_ext_api_permissions.js b/toolkit/components/extensions/test/xpcshell/test_ext_api_permissions.js
new file mode 100644
index 0000000000..8083f5c920
--- /dev/null
+++ b/toolkit/components/extensions/test/xpcshell/test_ext_api_permissions.js
@@ -0,0 +1,75 @@
+/* -*- Mode: indent-tabs-mode: nil; js-indent-level: 2 -*- */
+/* vim: set sts=2 sw=2 et tw=80: */
+"use strict";
+
+const { Management } = ChromeUtils.importESModule(
+  "resource://gre/modules/Extension.sys.mjs"
+);
+function getNextContext() {
+  return new Promise(resolve => {
+    Management.on("proxy-context-load", function listener(type, context) {
+      Management.off("proxy-context-load", listener);
+      resolve(context);
+    });
+  });
+}
+
+add_task(async function test_storage_api_without_permissions() {
+  let extension = ExtensionTestUtils.loadExtension({
+    background() {
+      // Force API initialization.
+      try {
+        browser.storage.onChanged.addListener(() => {});
+      } catch (e) {
+        // Ignore.
+      }
+    },
+
+    manifest: {
+      permissions: [],
+    },
+  });
+
+  let contextPromise = getNextContext();
+  await extension.startup();
+
+  let context = await contextPromise;
+
+  // Force API initialization.
+  void context.apiObj;
+
+  ok(
+    !("storage" in context.apiObj),
+    "The storage API should not be initialized"
+  );
+
+  await extension.unload();
+});
+
+add_task(async function test_storage_api_with_permissions() {
+  let extension = ExtensionTestUtils.loadExtension({
+    background() {
+      browser.storage.onChanged.addListener(() => {});
+    },
+
+    manifest: {
+      permissions: ["storage"],
+    },
+  });
+
+  let contextPromise = getNextContext();
+  await extension.startup();
+
+  let context = await contextPromise;
+
+  // Force API initialization.
+  void context.apiObj;
+
+  equal(
+    typeof context.apiObj.storage,
+    "object",
+    "The storage API should be initialized"
+  );
+
+  await extension.unload();
+});
diff --git a/toolkit/components/extensions/test/xpcshell/test_ext_asyncAPICall_isHandlingUserInput.js b/toolkit/components/extensions/test/xpcshell/test_ext_asyncAPICall_isHandlingUserInput.js
new file mode 100644
index 0000000000..73593b7e81
--- /dev/null
+++ b/toolkit/components/extensions/test/xpcshell/test_ext_asyncAPICall_isHandlingUserInput.js
@@ -0,0 +1,149 @@
+/* Any copyright is dedicated to the Public Domain.
+ * http://creativecommons.org/publicdomain/zero/1.0/ */
+
+"use strict";
+
+const { ExtensionAPI } = ExtensionCommon;
+
+const API_CLASS = class extends ExtensionAPI {
+  getAPI(context) {
+    return {
+      testMockAPI: {
+        async anAsyncAPIMethod(...args) {
+          const callContextDataBeforeAwait = context.callContextData;
+          await Promise.resolve();
+          const callContextDataAfterAwait = context.callContextData;
+          return {
+            args,
+            callContextDataBeforeAwait,
+            callContextDataAfterAwait,
+          };
+        },
+      },
+    };
+  }
+};
+
+const API_SCRIPT = `
+  this.testMockAPI = ${API_CLASS.toString()};
+`;
+
+const API_SCHEMA = [
+  {
+    namespace: "testMockAPI",
+    functions: [
+      {
+        name: "anAsyncAPIMethod",
+        type: "function",
+        async: true,
+        parameters: [
+          {
+            name: "param1",
+            type: "object",
+            additionalProperties: {
+              type: "string",
+            },
+          },
+          {
+            name: "param2",
+            type: "string",
+          },
+        ],
+      },
+    ],
+  },
+];
+
+const MODULE_INFO = {
+  testMockAPI: {
+    schema: `data:,${JSON.stringify(API_SCHEMA)}`,
+    scopes: ["addon_parent"],
+    paths: [["testMockAPI"]],
+    url: URL.createObjectURL(new Blob([API_SCRIPT])),
+  },
+};
+
+add_setup(async function () {
+  // The blob:-URL registered above in MODULE_INFO gets loaded at
+  // https://searchfox.org/mozilla-central/rev/0fec57c05d3996cc00c55a66f20dd5793a9bfb5d/toolkit/components/extensions/ExtensionCommon.jsm#1649
+  Services.prefs.setBoolPref(
+    "security.allow_parent_unrestricted_js_loads",
+    true
+  );
+  registerCleanupFunction(() => {
+    Services.prefs.clearUserPref("security.allow_parent_unrestricted_js_loads");
+  });
+
+  ExtensionParent.apiManager.registerModules(MODULE_INFO);
+});
+
+add_task(
+  async function test_propagated_isHandlingUserInput_on_async_api_methods_calls() {
+    const extension = ExtensionTestUtils.loadExtension({
+      manifest: {
+        browser_specific_settings: { gecko: { id: "@test-ext" } },
+      },
+      background() {
+        browser.test.onMessage.addListener(async (msg, args) => {
+          if (msg !== "async-method-call") {
+            browser.test.fail(`Unexpected test message: ${msg}`);
+            return;
+          }
+
+          try {
+            let result = await browser.testMockAPI.anAsyncAPIMethod(...args);
+            browser.test.sendMessage("async-method-call:result", result);
+          } catch (err) {
+            browser.test.sendMessage("async-method-call:error", err.message);
+          }
+        });
+      },
+    });
+
+    await extension.startup();
+
+    const callArgs = [{ param1: "param1" }, "param2"];
+
+    info("Test API method called without handling user input");
+
+    extension.sendMessage("async-method-call", callArgs);
+    const result = await extension.awaitMessage("async-method-call:result");
+    Assert.deepEqual(
+      result?.args,
+      callArgs,
+      "Got the expected parameters when called without handling user input"
+    );
+    Assert.deepEqual(
+      result?.callContextDataBeforeAwait,
+      { isHandlingUserInput: false },
+      "Got the expected callContextData before awaiting on a promise"
+    );
+    Assert.deepEqual(
+      result?.callContextDataAfterAwait,
+      null,
+      "context.callContextData should have been nullified after awaiting on a promise"
+    );
+
+    await withHandlingUserInput(extension, async () => {
+      extension.sendMessage("async-method-call", callArgs);
+      const result = await extension.awaitMessage("async-method-call:result");
+      Assert.deepEqual(
+        result?.args,
+        callArgs,
+        "Got the expected parameters when called while handling user input"
+      );
+      Assert.deepEqual(
+        result?.callContextDataBeforeAwait,
+        { isHandlingUserInput: true },
+        "Got the expected callContextData before awaiting on a promise"
+      );
+      Assert.deepEqual(
+        result?.callContextDataAfterAwait,
+        null,
+        "context.callContextData should have been nullified after awaiting on a promise"
+      );
+    });
+
+    await extension.unload();
+  }
+);
diff --git a/toolkit/components/extensions/test/xpcshell/test_ext_background_api_injection.js b/toolkit/components/extensions/test/xpcshell/test_ext_background_api_injection.js
new file mode 100644
index 0000000000..a603b03a29
--- /dev/null
+++ b/toolkit/components/extensions/test/xpcshell/test_ext_background_api_injection.js
@@ -0,0 +1,35 @@
+"use strict";
+
+const server = createHttpServer({ hosts: ["example.com"] });
+server.registerDirectory("/data/", do_get_file("data"));
+
+add_task(async function testBackgroundWindow() {
+  let extension = ExtensionTestUtils.loadExtension({
+    background() {
+      browser.test.log("background script executed");
+      window.location =
+        "http://example.com/data/file_privilege_escalation.html";
+    },
+  });
+
+  let awaitConsole = new Promise(resolve => {
+    Services.console.registerListener(function listener(message) {
+      if (/WebExt Privilege Escalation/.test(message.message)) {
+        Services.console.unregisterListener(listener);
+        resolve(message);
+      }
+    });
+  });
+
+  await extension.startup();
+
+  let message = await awaitConsole;
+  ok(
+    message.message.includes(
+      "WebExt Privilege Escalation: typeof(browser) = undefined"
+    ),
+    "Document does not have `browser` APIs."
+  );
+
+  await extension.unload();
+});
diff --git a/toolkit/components/extensions/test/xpcshell/test_ext_background_early_shutdown.js b/toolkit/components/extensions/test/xpcshell/test_ext_background_early_shutdown.js
new file mode 100644
index 0000000000..7f27348a1d
--- /dev/null
+++ b/toolkit/components/extensions/test/xpcshell/test_ext_background_early_shutdown.js
@@ -0,0 +1,187 @@
+/* -*- Mode: indent-tabs-mode: nil; js-indent-level: 2 -*- */
+/* vim: set sts=2 sw=2 et tw=80: */
+"use strict";
+
+const { BrowserTestUtils } = ChromeUtils.importESModule(
+  "resource://testing-common/BrowserTestUtils.sys.mjs"
+);
+
+AddonTestUtils.init(this);
+AddonTestUtils.overrideCertDB();
+AddonTestUtils.createAppInfo(
+  "xpcshell@tests.mozilla.org",
+  "XPCShell",
+  "1",
+  "43"
+);
+
+let { promiseRestartManager, promiseShutdownManager, promiseStartupManager } =
+  AddonTestUtils;
+
+const { Management } = ChromeUtils.importESModule(
+  "resource://gre/modules/Extension.sys.mjs"
+);
+
+// Crashes a <browser>'s remote process.
+// Based on BrowserTestUtils.crashFrame.
+function crashFrame(browser) {
+  if (!browser.isRemoteBrowser) {
+    // The browser should be remote, or the test runner would be killed.
+    throw new Error("<browser> must be remote");
+  }
+
+  // Trigger crash by sending a message to BrowserTestUtils actor.
+  BrowserTestUtils.sendAsyncMessage(
+    browser.browsingContext,
+    "BrowserTestUtils:CrashFrame",
+    {}
+  );
+}
+
+// Verifies that a delayed background page is not loaded when an extension is
+// shut down during startup.
+add_task(async function test_unload_extension_before_background_page_startup() {
+  await promiseStartupManager();
+
+  let extension = ExtensionTestUtils.loadExtension({
+    useAddonManager: "permanent",
+    background() {
+      browser.test.sendMessage("background_startup_observed");
+    },
+  });
+
+  // Delayed startup are only enabled for browser (re)starts, so we need to
+  // install the extension first, and then unload it.
+
+  await extension.startup();
+  await extension.awaitMessage("background_startup_observed");
+
+  // Now the actual test: Unloading an extension before the startup has
+  // finished should interrupt the start-up and abort pending delayed loads.
+  info("Starting extension whose startup will be interrupted");
+  await promiseRestartManager({ earlyStartup: false });
+  await extension.awaitStartup();
+
+  let extensionBrowserInsertions = 0;
+  let onExtensionBrowserInserted = () => ++extensionBrowserInsertions;
+  Management.on("extension-browser-inserted", onExtensionBrowserInserted);
+
+  info("Unloading extension before the delayed background page starts loading");
+  await extension.addon.disable();
+
+  // Re-enable the add-on to let enough time pass to load a whole background
+  // page. If at the end of this the original background page hasn't loaded,
+  // we can consider the test successful.
+  await extension.addon.enable();
+
+  // Trigger the notification that would load a background page.
+  info("Forcing pending delayed background page to load");
+  AddonTestUtils.notifyLateStartup();
+
+  // This is the expected message from the re-enabled add-on.
+  await extension.awaitMessage("background_startup_observed");
+  await extension.unload();
+
+  await promiseShutdownManager();
+
+  Management.off("extension-browser-inserted", onExtensionBrowserInserted);
+  Assert.equal(
+    extensionBrowserInsertions,
+    1,
+    "Extension browser should have been inserted only once"
+  );
+});
+
+// Verifies that the "build" method of BackgroundPage in ext-backgroundPage.js
+// does not deadlock when startup is interrupted by extension shutdown.
+add_task(async function test_unload_extension_during_background_page_startup() {
+  await promiseStartupManager();
+
+  let extension = ExtensionTestUtils.loadExtension({
+    useAddonManager: "permanent",
+    background() {
+      browser.test.sendMessage("background_starting");
+    },
+  });
+
+  // Delayed startup are only enabled for browser (re)starts, so we need to
+  // install the extension first, and then reload it.
+  await extension.startup();
+  await extension.awaitMessage("background_starting");
+
+  await promiseRestartManager({ lateStartup: false });
+  await extension.awaitStartup();
+
+  let bgStartupPromise = new Promise(resolve => {
+    function onBackgroundPageDone(eventName) {
+      extension.extension.off(
+        "background-script-started",
+        onBackgroundPageDone
+      );
+      extension.extension.off(
+        "background-script-aborted",
+        onBackgroundPageDone
+      );
+
+      if (eventName === "background-script-aborted") {
+        info("Background script startup was interrupted");
+        resolve("bg_aborted");
+      } else {
+        info("Background script startup finished normally");
+        resolve("bg_fully_loaded");
+      }
+    }
+    extension.extension.on("background-script-started", onBackgroundPageDone);
+    extension.extension.on("background-script-aborted", onBackgroundPageDone);
+  });
+
+  let bgStartingPromise = new Promise(resolve => {
+    let backgroundLoadCount = 0;
+    let backgroundPageUrl = extension.extension.baseURI.resolve(
+      "_generated_background_page.html"
+    );
+
+    // Prevent the background page from actually loading.
+    Management.once("extension-browser-inserted", (eventName, browser) => {
+      // Intercept background page load.
+      let browserFixupAndLoadURIString = browser.fixupAndLoadURIString;
+      browser.fixupAndLoadURIString = function () {
+        Assert.equal(++backgroundLoadCount, 1, "loadURI should be called once");
+        Assert.equal(
+          arguments[0],
+          backgroundPageUrl,
+          "Expected background page"
+        );
+        // Reset to "about:blank" to not load the actual background page.
+        arguments[0] = "about:blank";
+        browserFixupAndLoadURIString.apply(this, arguments);
+
+        // And force the extension process to crash.
+        if (browser.isRemote) {
+          crashFrame(browser);
+        } else {
+          // If extensions are not running in out-of-process mode, then the
+          // non-remote process should not be killed (or the test runner dies).
+          // Remove <browser> instead, to simulate the immediate disconnection
+          // of the message manager (that would happen if the process crashed).
+          browser.remove();
+        }
+        resolve();
+      };
+    });
+  });
+
+  // Force background page to initialize.
+  AddonTestUtils.notifyLateStartup();
+  await bgStartingPromise;
+
+  await extension.unload();
+  await promiseShutdownManager();
+
+  // This part is the regression test for bug 1501375. It verifies that the
+  // background building completes eventually.
+  // If it does not, then the next line will cause a timeout.
+  info("Waiting for background builder to finish");
+  let bgLoadState = await bgStartupPromise;
+  Assert.equal(bgLoadState, "bg_aborted", "Startup should be interrupted");
+});
diff --git a/toolkit/components/extensions/test/xpcshell/test_ext_background_generated_load_events.js b/toolkit/components/extensions/test/xpcshell/test_ext_background_generated_load_events.js
new file mode 100644
index 0000000000..cac574b8ca
--- /dev/null
+++ b/toolkit/components/extensions/test/xpcshell/test_ext_background_generated_load_events.js
@@ -0,0 +1,23 @@
+/* -*- Mode: indent-tabs-mode: nil; js-indent-level: 2 -*- */
+/* vim: set sts=2 sw=2 et tw=80: */
+"use strict";
+
+/* eslint-disable mozilla/balanced-listeners */
+
+add_task(async function test_DOMContentLoaded_in_generated_background_page() {
+  let extension = ExtensionTestUtils.loadExtension({
+    background() {
+      function reportListener(event) {
+        browser.test.sendMessage("eventname", event.type);
+      }
+      document.addEventListener("DOMContentLoaded", reportListener);
+      window.addEventListener("load", reportListener);
+    },
+  });
+
+  await extension.startup();
+  equal("DOMContentLoaded", await extension.awaitMessage("eventname"));
+  equal("load", await extension.awaitMessage("eventname"));
+
+  await extension.unload();
+});
diff --git a/toolkit/components/extensions/test/xpcshell/test_ext_background_generated_reload.js b/toolkit/components/extensions/test/xpcshell/test_ext_background_generated_reload.js
new file mode 100644
index 0000000000..a22db9d582
--- /dev/null
+++ b/toolkit/components/extensions/test/xpcshell/test_ext_background_generated_reload.js
@@ -0,0 +1,24 @@
+/* -*- Mode: indent-tabs-mode: nil; js-indent-level: 2 -*- */
+/* vim: set sts=2 sw=2 et tw=80: */
+"use strict";
+
+add_task(async function test_reload_generated_background_page() {
+  let extension = ExtensionTestUtils.loadExtension({
+    background() {
+      if (location.hash !== "#firstrun") {
+        browser.test.sendMessage("first run");
+        location.hash = "#firstrun";
+        browser.test.assertEq("#firstrun", location.hash);
+        location.reload();
+      } else {
+        browser.test.notifyPass("second run");
+      }
+    },
+  });
+
+  await extension.startup();
+  await extension.awaitMessage("first run");
+  await extension.awaitFinish("second run");
+
+  await extension.unload();
+});
diff --git a/toolkit/components/extensions/test/xpcshell/test_ext_background_global_history.js b/toolkit/components/extensions/test/xpcshell/test_ext_background_global_history.js
new file mode 100644
index 0000000000..19a918eff9
--- /dev/null
+++ b/toolkit/components/extensions/test/xpcshell/test_ext_background_global_history.js
@@ -0,0 +1,24 @@
+/* -*- Mode: indent-tabs-mode: nil; js-indent-level: 2 -*- */
+/* vim: set sts=2 sw=2 et tw=80: */
+"use strict";
+
+const { PlacesTestUtils } = ChromeUtils.importESModule(
+  "resource://testing-common/PlacesTestUtils.sys.mjs"
+);
+
+add_task(async function test_global_history() {
+  let extension = ExtensionTestUtils.loadExtension({
+    background() {
+      browser.test.sendMessage("background-loaded", location.href);
+    },
+  });
+
+  await extension.startup();
+
+  let backgroundURL = await extension.awaitMessage("background-loaded");
+
+  await extension.unload();
+
+  let exists = await PlacesTestUtils.isPageInDB(backgroundURL);
+  ok(!exists, "Background URL should not be in history database");
+});
diff --git a/toolkit/components/extensions/test/xpcshell/test_ext_background_private_browsing.js b/toolkit/components/extensions/test/xpcshell/test_ext_background_private_browsing.js
new file mode 100644
index 0000000000..9ce80f3fda
--- /dev/null
+++ b/toolkit/components/extensions/test/xpcshell/test_ext_background_private_browsing.js
@@ -0,0 +1,44 @@
+/* -*- Mode: indent-tabs-mode: nil; js-indent-level: 2 -*- */
+/* vim: set sts=2 sw=2 et tw=80: */
+"use strict";
+
+add_task(async function test_background_incognito() {
+  info(
+    "Test background page incognito value with permanent private browsing enabled"
+  );
+
+  Services.prefs.setBoolPref("browser.privatebrowsing.autostart", true);
+  registerCleanupFunction(() => {
+    Services.prefs.clearUserPref("browser.privatebrowsing.autostart");
+  });
+
+  let extension = ExtensionTestUtils.loadExtension({
+    incognitoOverride: "spanning",
+    async background() {
+      browser.test.assertEq(
+        window,
+        browser.extension.getBackgroundPage(),
+        "Caller should be able to access itself as a background page"
+      );
+      browser.test.assertEq(
+        window,
+        await browser.runtime.getBackgroundPage(),
+        "Caller should be able to access itself as a background page"
+      );
+
+      browser.test.assertEq(
+        browser.extension.inIncognitoContext,
+        true,
+        "inIncognitoContext is true for permanent private browsing"
+      );
+
+      browser.test.notifyPass("incognito");
+    },
+  });
+
+  await extension.startup();
+
+  await extension.awaitFinish("incognito");
+
+  await extension.unload();
+});
diff --git a/toolkit/components/extensions/test/xpcshell/test_ext_background_runtime_connect_params.js b/toolkit/components/extensions/test/xpcshell/test_ext_background_runtime_connect_params.js
new file mode 100644
index 0000000000..aa0976434b
--- /dev/null
+++ b/toolkit/components/extensions/test/xpcshell/test_ext_background_runtime_connect_params.js
@@ -0,0 +1,88 @@
+/* -*- Mode: indent-tabs-mode: nil; js-indent-level: 2 -*- */
+/* vim: set sts=2 sw=2 et tw=80: */
+"use strict";
+
+function backgroundScript() {
+  let received_ports_number = 0;
+
+  const expected_received_ports_number = 1;
+
+  function countReceivedPorts(port) {
+    received_ports_number++;
+
+    if (port.name == "check-results") {
+      browser.runtime.onConnect.removeListener(countReceivedPorts);
+
+      browser.test.assertEq(
+        expected_received_ports_number,
+        received_ports_number,
+        "invalid connect should not create a port"
+      );
+
+      browser.test.notifyPass("runtime.connect invalid params");
+    }
+  }
+
+  browser.runtime.onConnect.addListener(countReceivedPorts);
+
+  let childFrame = document.createElement("iframe");
+  childFrame.src = "extensionpage.html";
+  document.body.appendChild(childFrame);
+}
+
+function senderScript() {
+  let detected_invalid_connect_params = 0;
+
+  const invalid_connect_params = [
+    // too many params
+    [
+      "fake-extensions-id",
+      { name: "fake-conn-name" },
+      "unexpected third params",
+    ],
+    // invalid params format
+    [{}, {}],
+    ["fake-extensions-id", "invalid-connect-info-format"],
+  ];
+  const expected_detected_invalid_connect_params =
+    invalid_connect_params.length;
+
+  function assertInvalidConnectParamsException(params) {
+    try {
+      browser.runtime.connect(...params);
+    } catch (e) {
+      detected_invalid_connect_params++;
+      browser.test.assertTrue(
+        e.toString().includes("Incorrect argument types for runtime.connect."),
+        "exception message is correct"
+      );
+    }
+  }
+  for (let params of invalid_connect_params) {
+    assertInvalidConnectParamsException(params);
+  }
+  browser.test.assertEq(
+    expected_detected_invalid_connect_params,
+    detected_invalid_connect_params,
+    "all invalid runtime.connect params detected"
+  );
+
+  browser.runtime.connect(browser.runtime.id, { name: "check-results" });
+}
+
+let extensionData = {
+  background: backgroundScript,
+  files: {
+    "senderScript.js": senderScript,
+    "extensionpage.html": `<!DOCTYPE html><meta charset="utf-8"><script src="senderScript.js"></script>`,
+  },
+};
+
+add_task(async function test_backgroundRuntimeConnectParams() {
+  let extension = ExtensionTestUtils.loadExtension(extensionData);
+  await extension.startup();
+
+  await extension.awaitFinish("runtime.connect invalid params");
+
+  await extension.unload();
+});
diff --git a/toolkit/components/extensions/test/xpcshell/test_ext_background_service_worker.js b/toolkit/components/extensions/test/xpcshell/test_ext_background_service_worker.js
new file mode 100644
index 0000000000..2efbc52739
--- /dev/null
+++ b/toolkit/components/extensions/test/xpcshell/test_ext_background_service_worker.js
@@ -0,0 +1,321 @@
+/* -*- Mode: indent-tabs-mode: nil; js-indent-level: 2 -*- */
+/* vim: set sts=2 sw=2 et tw=80: */
+"use strict";
+
+const { TestUtils } = ChromeUtils.importESModule(
+  "resource://testing-common/TestUtils.sys.mjs"
+);
+
+ChromeUtils.defineESModuleGetters(this, {
+  AddonManager: "resource://gre/modules/AddonManager.sys.mjs",
+});
+
+AddonTestUtils.init(this);
+AddonTestUtils.createAppInfo(
+  "xpcshell@tests.mozilla.org",
+  "XPCShell",
+  "1",
+  "42"
+);
+AddonTestUtils.overrideCertDB();
+
+add_task(async function setup() {
+  ok(
+    WebExtensionPolicy.useRemoteWebExtensions,
+    "Expect remote-webextensions mode enabled"
+  );
+  ok(
+    WebExtensionPolicy.backgroundServiceWorkerEnabled,
+    "Expect remote-webextensions mode enabled"
+  );
+
+  await AddonTestUtils.promiseStartupManager();
+
+  Services.prefs.setBoolPref("dom.serviceWorkers.testing.enabled", true);
+
+  registerCleanupFunction(() => {
+    Services.prefs.clearUserPref("dom.serviceWorkers.testing.enabled");
+    Services.prefs.clearUserPref("dom.serviceWorkers.idle_timeout");
+  });
+});
+
+add_task(
+  async function test_fail_spawn_extension_worker_for_disabled_extension() {
+    const extension = ExtensionTestUtils.loadExtension({
+      useAddonManager: "temporary",
+      manifest: {
+        version: "1.0",
+        background: {
+          service_worker: "sw.js",
+        },
+        browser_specific_settings: { gecko: { id: "test-bg-sw@mochi.test" } },
+      },
+      files: {
+        "page.html": "<!DOCTYPE html><body></body>",
+        "sw.js": "dump('Background ServiceWorker - executed\\n');",
+      },
+    });
+
+    const testWorkerWatcher = new TestWorkerWatcher();
+    let watcher = await testWorkerWatcher.watchExtensionServiceWorker(
+      extension
+    );
+
+    await extension.startup();
+
+    info("Wait for the background service worker to be spawned");
+
+    ok(
+      await watcher.promiseWorkerSpawned,
+      "The extension service worker has been spawned as expected"
+    );
+
+    info("Wait for the background service worker to be terminated");
+    ok(
+      await watcher.terminate(),
+      "The extension service worker has been terminated as expected"
+    );
+
+    const swReg = testWorkerWatcher.getRegistration(extension);
+    ok(swReg, "Got a service worker registration");
+    ok(swReg?.activeWorker, "Got an active worker");
+
+    info("Spawn the active worker by attaching the debugger");
+
+    watcher = await testWorkerWatcher.watchExtensionServiceWorker(extension);
+
+    swReg.activeWorker.attachDebugger();
+    info(
+      "Wait for the background service worker to be spawned after attaching the debugger"
+    );
+    ok(
+      await watcher.promiseWorkerSpawned,
+      "The extension service worker has been spawned as expected"
+    );
+
+    swReg.activeWorker.detachDebugger();
+    info(
+      "Wait for the background service worker to be terminated after detaching the debugger"
+    );
+    ok(
+      await watcher.terminate(),
+      "The extension service worker has been terminated as expected"
+    );
+
+    info(
+      "Disabling the addon policy, and then double-check that the worker can't be spawned"
+    );
+    const policy = WebExtensionPolicy.getByID(extension.id);
+    policy.active = false;
+
+    await Assert.throws(
+      () => swReg.activeWorker.attachDebugger(),
+      /InvalidStateError/,
+      "Got the expected extension when trying to spawn a worker for a disabled addon"
+    );
+
+    info(
+      "Enabling the addon policy and double-check the worker is spawned successfully"
+    );
+    policy.active = true;
+
+    watcher = await testWorkerWatcher.watchExtensionServiceWorker(extension);
+
+    swReg.activeWorker.attachDebugger();
+    info(
+      "Wait for the background service worker to be spawned after attaching the debugger"
+    );
+    ok(
+      await watcher.promiseWorkerSpawned,
+      "The extension service worker has been spawned as expected"
+    );
+
+    swReg.activeWorker.detachDebugger();
+    info(
+      "Wait for the background service worker to be terminated after detaching the debugger"
+    );
+    ok(
+      await watcher.terminate(),
+      "The extension service worker has been terminated as expected"
+    );
+
+    await testWorkerWatcher.destroy();
+    await extension.unload();
+  }
+);
+
+add_task(async function test_serviceworker_lifecycle_events() {
+  async function assertLifecycleEvents({ extension, expected, message }) {
+    const getLifecycleEvents = async () => {
+      const { active } = await this.content.navigator.serviceWorker.ready;
+      const { port1, port2 } = new content.MessageChannel();
+
+      return new Promise(resolve => {
+        port1.onmessage = msg => resolve(msg.data.lifecycleEvents);
+        active.postMessage("test", [port2]);
+      });
+    };
+    const page = await ExtensionTestUtils.loadContentPage(
+      extension.extension.baseURI.resolve("page.html"),
+      { extension }
+    );
+    Assert.deepEqual(
+      await page.spawn([], getLifecycleEvents),
+      expected,
+      `Got the expected lifecycle events on ${message}`
+    );
+    await page.close();
+  }
+
+  const swm = Cc["@mozilla.org/serviceworkers/manager;1"].getService(
+    Ci.nsIServiceWorkerManager
+  );
+
+  const extension = ExtensionTestUtils.loadExtension({
+    useAddonManager: "permanent",
+    manifest: {
+      version: "1.0",
+      background: {
+        service_worker: "sw.js",
+      },
+      browser_specific_settings: { gecko: { id: "test-bg-sw@mochi.test" } },
+    },
+    files: {
+      "page.html": "<!DOCTYPE html><body></body>",
+      "sw.js": `
+        dump('Background ServiceWorker - executed\\n');
+
+        const lifecycleEvents = [];
+        self.oninstall = () => {
+          dump('Background ServiceWorker - oninstall\\n');
+          lifecycleEvents.push("install");
+        };
+        self.onactivate = () => {
+          dump('Background ServiceWorker - onactivate\\n');
+          lifecycleEvents.push("activate");
+        };
+        self.onmessage = (evt) => {
+          dump('Background ServiceWorker - onmessage\\n');
+          evt.ports[0].postMessage({ lifecycleEvents });
+          dump('Background ServiceWorker - postMessage\\n');
+        };
+      `,
+    },
+  });
+
+  const testWorkerWatcher = new TestWorkerWatcher();
+  let watcher = await testWorkerWatcher.watchExtensionServiceWorker(extension);
+
+  await extension.startup();
+
+  await assertLifecycleEvents({
+    extension,
+    expected: ["install", "activate"],
+    message: "initial worker registration",
+  });
+
+  const file = Services.dirsvc.get("ProfD", Ci.nsIFile);
+  file.append("serviceworker.txt");
+  await TestUtils.waitForCondition(
+    () => file.exists(),
+    "Wait for service worker registrations to have been dumped on disk"
+  );
+
+  const managerShutdownCompleted = AddonTestUtils.promiseShutdownManager();
+
+  const firstSwReg = swm.getRegistrationByPrincipal(
+    extension.extension.principal,
+    extension.extension.principal.spec
+  );
+  // Force the worker shutdown (in normal condition the worker would have been
+  // terminated as part of the entire application shutting down).
+  firstSwReg.forceShutdown();
+
+  info(
+    "Wait for the background service worker to be terminated while the app is shutting down"
+  );
+  ok(
+    await watcher.promiseWorkerTerminated,
+    "The extension service worker has been terminated as expected"
+  );
+  await managerShutdownCompleted;
+
+  Assert.equal(
+    firstSwReg,
+    swm.getRegistrationByPrincipal(
+      extension.extension.principal,
+      extension.extension.principal.spec
+    ),
+    "Expect the service worker to not be unregistered on application shutdown"
+  );
+
+  info("Restart AddonManager (mocking Browser instance restart)");
+  // Start the addon manager with `earlyStartup: false` to keep the background service worker
+  // from being started right away:
+  //
+  // - the call to `swm.reloadRegistrationForTest()` that follows is making sure that
+  //   the previously registered service worker is in the same state it would be when
+  //   the entire browser is restarted.
+  //
+  // - if the background service worker is being spawned again by the time we call
+  //   `swm.reloadRegistrationForTest()`, ServiceWorkerUpdateJob would fail and trigger
+  //   an `mState == State::Started` diagnostic assertion from ServiceWorkerJob::Finish
+  //   and the xpcshell test will fail for the crash triggered by the assertion.
+  await AddonTestUtils.promiseStartupManager({ lateStartup: false });
+  await extension.awaitStartup();
+
+  info(
+    "Force reload ServiceWorkerManager registrations (mocking a Browser instance restart)"
+  );
+  swm.reloadRegistrationsForTest();
+
+  info(
+    "trigger delayed call to nsIServiceWorkerManager.registerForAddonPrincipal"
+  );
+  // complete the startup notifications, then start the background
+  AddonTestUtils.notifyLateStartup();
+  extension.extension.emit("start-background-script");
+
+  info("Force activate the extension worker");
+  const newSwReg = swm.getRegistrationByPrincipal(
+    extension.extension.principal,
+    extension.extension.principal.spec
+  );
+
+  Assert.notEqual(
+    newSwReg,
+    firstSwReg,
+    "Expect the service worker registration to have been recreated"
+  );
+
+  await assertLifecycleEvents({
+    extension,
+    expected: [],
+    message: "on previous registration loaded",
+  });
+
+  const { principal } = extension.extension;
+  const addon = await AddonManager.getAddonByID(extension.id);
+  await addon.disable();
+
+  ok(
+    await watcher.promiseWorkerTerminated,
+    "The extension service worker has been terminated as expected"
+  );
+
+  Assert.throws(
+    () => swm.getRegistrationByPrincipal(principal, principal.spec),
+    /NS_ERROR_FAILURE/,
+    "Expect the service worker to have been unregistered on addon disabled"
+  );
+
+  await addon.enable();
+  await assertLifecycleEvents({
+    extension,
+    expected: ["install", "activate"],
+    message: "on disabled addon re-enabled",
+  });
+
+  await testWorkerWatcher.destroy();
+  await extension.unload();
+});
diff --git a/toolkit/components/extensions/test/xpcshell/test_ext_background_sub_windows.js b/toolkit/components/extensions/test/xpcshell/test_ext_background_sub_windows.js
new file mode 100644
index 0000000000..1c3180b1b6
--- /dev/null
+++ b/toolkit/components/extensions/test/xpcshell/test_ext_background_sub_windows.js
@@ -0,0 +1,46 @@
+/* -*- Mode: indent-tabs-mode: nil; js-indent-level: 2 -*- */
+/* vim: set sts=2 sw=2 et tw=80: */
+"use strict";
+
+add_task(async function testBackgroundWindow() {
+  let extension = ExtensionTestUtils.loadExtension({
+    background() {
+      browser.test.log("background script executed");
+
+      browser.test.sendMessage("background-script-load");
+
+      let img = document.createElement("img");
+      img.src =
+        "data:image/gif;base64,R0lGODlhAQABAIAAAAAAAP///yH5BAEAAAAALAAAAAABAAEAAAIBRAA7";
+      document.body.appendChild(img);
+
+      img.onload = () => {
+        browser.test.log("image loaded");
+
+        let iframe = document.createElement("iframe");
+        iframe.src = "about:blank?1";
+
+        iframe.onload = () => {
+          browser.test.log("iframe loaded");
+          setTimeout(() => {
+            browser.test.notifyPass("background sub-window test done");
+          }, 0);
+        };
+        document.body.appendChild(iframe);
+      };
+    },
+  });
+
+  let loadCount = 0;
+  extension.onMessage("background-script-load", () => {
+    loadCount++;
+  });
+
+  await extension.startup();
+
+  await extension.awaitFinish("background sub-window test done");
+
+  equal(loadCount, 1, "background script loaded only once");
+
+  await extension.unload();
+});
diff --git a/toolkit/components/extensions/test/xpcshell/test_ext_background_teardown.js b/toolkit/components/extensions/test/xpcshell/test_ext_background_teardown.js
new file mode 100644
index 0000000000..243bc27867
--- /dev/null
+++ b/toolkit/components/extensions/test/xpcshell/test_ext_background_teardown.js
@@ -0,0 +1,98 @@
+"use strict";
+
+add_task(async function test_background_reload_and_unload() {
+  let events = [];
+  {
+    const { Management } = ChromeUtils.importESModule(
+      "resource://gre/modules/Extension.sys.mjs"
+    );
+    let record = (type, extensionContext) => {
+      let eventType = type == "proxy-context-load" ? "load" : "unload";
+      let url = extensionContext.uri.spec;
+      let extensionId = extensionContext.extension.id;
+      events.push({ eventType, url, extensionId });
+    };
+
+    Management.on("proxy-context-load", record);
+    Management.on("proxy-context-unload", record);
+    registerCleanupFunction(() => {
+      Management.off("proxy-context-load", record);
+      Management.off("proxy-context-unload", record);
+    });
+  }
+
+  let extension = ExtensionTestUtils.loadExtension({
+    background() {
+      browser.test.onMessage.addListener(msg => {
+        browser.test.assertEq("reload-background", msg);
+        location.reload();
+      });
+      browser.test.sendMessage("background-url", location.href);
+    },
+  });
+
+  await extension.startup();
+  let backgroundUrl = await extension.awaitMessage("background-url");
+
+  let contextEvents = events.splice(0);
+  equal(
+    contextEvents.length,
+    1,
+    "ExtensionContext state change after loading an extension"
+  );
+  equal(contextEvents[0].eventType, "load");
+  equal(
+    contextEvents[0].url,
+    backgroundUrl,
+    "The ExtensionContext should be the background page"
+  );
+
+  extension.sendMessage("reload-background");
+  await extension.awaitMessage("background-url");
+
+  contextEvents = events.splice(0);
+  equal(
+    contextEvents.length,
+    2,
+    "ExtensionContext state changes after reloading the background page"
+  );
+  equal(
+    contextEvents[0].eventType,
+    "unload",
+    "Unload ExtensionContext of background page"
+  );
+  equal(
+    contextEvents[0].url,
+    backgroundUrl,
+    "ExtensionContext URL = background"
+  );
+  equal(
+    contextEvents[1].eventType,
+    "load",
+    "Create new ExtensionContext for background page"
+  );
+  equal(
+    contextEvents[1].url,
+    backgroundUrl,
+    "ExtensionContext URL = background"
+  );
+
+  await extension.unload();
+
+  contextEvents = events.splice(0);
+  equal(
+    contextEvents.length,
+    1,
+    "ExtensionContext state change after unloading the extension"
+  );
+  equal(
+    contextEvents[0].eventType,
+    "unload",
+    "Unload ExtensionContext for background page after extension unloads"
+  );
+  equal(
+    contextEvents[0].url,
+    backgroundUrl,
+    "ExtensionContext URL = background"
+  );
+});
diff --git a/toolkit/components/extensions/test/xpcshell/test_ext_background_telemetry.js b/toolkit/components/extensions/test/xpcshell/test_ext_background_telemetry.js
new file mode 100644
index 0000000000..1c018005c4
--- /dev/null
+++ b/toolkit/components/extensions/test/xpcshell/test_ext_background_telemetry.js
@@ -0,0 +1,98 @@
+/* -*- Mode: indent-tabs-mode: nil; js-indent-level: 2 -*- */
+/* vim: set sts=2 sw=2 et tw=80: */
+"use strict";
+
+const HISTOGRAM = "WEBEXT_BACKGROUND_PAGE_LOAD_MS";
+const HISTOGRAM_KEYED = "WEBEXT_BACKGROUND_PAGE_LOAD_MS_BY_ADDONID";
+
+add_task(async function test_telemetry() {
+  let extension1 = ExtensionTestUtils.loadExtension({
+    background() {
+      browser.test.sendMessage("loaded");
+    },
+  });
+
+  let extension2 = ExtensionTestUtils.loadExtension({
+    background() {
+      browser.test.sendMessage("loaded");
+    },
+  });
+
+  clearHistograms();
+
+  assertHistogramEmpty(HISTOGRAM);
+  assertKeyedHistogramEmpty(HISTOGRAM_KEYED);
+
+  await extension1.startup();
+  await extension1.awaitMessage("loaded");
+
+  const processSnapshot = snapshot => {
+    return snapshot.sum > 0;
+  };
+
+  const processKeyedSnapshot = snapshot => {
+    let res = {};
+    for (let key of Object.keys(snapshot)) {
+      res[key] = snapshot[key].sum > 0;
+    }
+    return res;
+  };
+
+  assertHistogramSnapshot(
+    HISTOGRAM,
+    { processSnapshot, expectedValue: true },
+    `Data recorded for first extension for histogram: ${HISTOGRAM}.`
+  );
+
+  assertHistogramSnapshot(
+    HISTOGRAM_KEYED,
+    {
+      keyed: true,
+      processSnapshot: processKeyedSnapshot,
+      expectedValue: {
+        [extension1.extension.id]: true,
+      },
+    },
+    `Data recorded for first extension for histogram ${HISTOGRAM_KEYED}`
+  );
+
+  let histogram = Services.telemetry.getHistogramById(HISTOGRAM);
+  let histogramKeyed =
+    Services.telemetry.getKeyedHistogramById(HISTOGRAM_KEYED);
+  let histogramSum = histogram.snapshot().sum;
+  let histogramSumExt1 = histogramKeyed.snapshot()[extension1.extension.id].sum;
+
+  await extension2.startup();
+  await extension2.awaitMessage("loaded");
+
+  assertHistogramSnapshot(
+    HISTOGRAM,
+    {
+      processSnapshot: snapshot => snapshot.sum > histogramSum,
+      expectedValue: true,
+    },
+    `Data recorded for second extension for histogram: ${HISTOGRAM}.`
+  );
+
+  assertHistogramSnapshot(
+    HISTOGRAM_KEYED,
+    {
+      keyed: true,
+      processSnapshot: processKeyedSnapshot,
+      expectedValue: {
+        [extension1.extension.id]: true,
+        [extension2.extension.id]: true,
+      },
+    },
+    `Data recorded for second extension for histogram ${HISTOGRAM_KEYED}`
+  );
+
+  equal(
+    histogramKeyed.snapshot()[extension1.extension.id].sum,
+    histogramSumExt1,
+    `Data recorder for first extension is unchanged on the keyed histogram ${HISTOGRAM_KEYED}`
+  );
+
+  await extension1.unload();
+  await extension2.unload();
+});
diff --git a/toolkit/components/extensions/test/xpcshell/test_ext_background_type_module.js b/toolkit/components/extensions/test/xpcshell/test_ext_background_type_module.js
new file mode 100644
index 0000000000..74512e1e41
--- /dev/null
+++ b/toolkit/components/extensions/test/xpcshell/test_ext_background_type_module.js
@@ -0,0 +1,133 @@
+/* Any copyright is dedicated to the Public Domain.
+ * http://creativecommons.org/publicdomain/zero/1.0/ */
+
+"use strict";
+
+async function assertBackgroundScriptTypes(
+  extensionTestWrapper,
+  expectedScriptTypesMap
+) {
+  const { baseURI } = extensionTestWrapper.extension;
+  let expectedMapWithResolvedURLs = Object.keys(expectedScriptTypesMap).reduce(
+    (result, scriptPath) => {
+      result[baseURI.resolve(scriptPath)] = expectedScriptTypesMap[scriptPath];
+      return result;
+    },
+    {}
+  );
+  const page = await ExtensionTestUtils.loadContentPage(
+    baseURI.resolve("_generated_background_page.html")
+  );
+  const scriptTypesMap = await page.spawn([], () => {
+    const scripts = Array.from(
+      this.content.document.querySelectorAll("script")
+    );
+    return scripts.reduce((result, script) => {
+      result[script.getAttribute("src")] = script.getAttribute("type");
+      return result;
+    }, {});
+  });
+  await page.close();
+  Assert.deepEqual(
+    scriptTypesMap,
+    expectedMapWithResolvedURLs,
+    "Got the expected script type from the generated background page"
+  );
+}
+
+async function testBackgroundScriptClassic({ manifestTypeClassicSet }) {
+  const extension = ExtensionTestUtils.loadExtension({
+    manifest: {
+      background: {
+        scripts: ["anotherScript.js", "main.js"],
+        type: manifestTypeClassicSet ? "classic" : undefined,
+      },
+    },
+    files: {
+      "main.js": ``,
+      "anotherScript.js": ``,
+    },
+  });
+
+  await extension.startup();
+  await assertBackgroundScriptTypes(extension, {
+    "main.js": "text/javascript",
+    "anotherScript.js": "text/javascript",
+  });
+  await extension.unload();
+}
+
+add_task(async function test_background_scripts_type_default() {
+  await testBackgroundScriptClassic({ manifestTypeClassicSet: false });
+});
+
+add_task(async function test_background_scripts_type_classic() {
+  await testBackgroundScriptClassic({ manifestTypeClassicSet: true });
+});
+
+add_task(async function test_background_scripts_type_module() {
+  const extension = ExtensionTestUtils.loadExtension({
+    manifest: {
+      background: {
+        scripts: ["anotherModule.js", "mainModule.js"],
+        type: "module",
+      },
+    },
+    files: {
+      "mainModule.js": `
+        import { initBackground } from "/importedModule.js";
+        browser.test.log("mainModule.js - ESM module executing");
+        initBackground();
+      `,
+      "importedModule.js": `
+        export function initBackground() {
+          browser.test.onMessage.addListener((msg) => {
+            browser.test.log("importedModule.js - test message received");
+            browser.test.sendMessage("esm-module-reply", msg);
+          });
+          browser.test.log("importedModule.js - initBackground executed");
+        }
+        browser.test.log("importedModule.js - ESM module loaded");
+      `,
+      "anotherModule.js": `
+        browser.test.log("anotherModule.js - ESM module loaded");
+      `,
+    },
+  });
+
+  await extension.startup();
+  await extension.sendMessage("test-event-value");
+  equal(
+    await extension.awaitMessage("esm-module-reply"),
+    "test-event-value",
+    "Got the expected event from the ESM module loaded from the background script"
+  );
+  await assertBackgroundScriptTypes(extension, {
+    "mainModule.js": "module",
+    "anotherModule.js": "module",
+  });
+  await extension.unload();
+});
+
+add_task(async function test_background_scripts_type_invalid() {
+  const extension = ExtensionTestUtils.loadExtension({
+    manifest: {
+      background: {
+        scripts: ["anotherScript.js", "main.js"],
+        type: "invalid",
+      },
+    },
+    files: {
+      "main.js": ``,
+      "anotherScript.js": ``,
+    },
+  });
+
+  ExtensionTestUtils.failOnSchemaWarnings(false);
+  await Assert.rejects(
+    extension.startup(),
+    /Error processing background: .* \.type must be one of/,
+    "Expected install to fail"
+  );
+  ExtensionTestUtils.failOnSchemaWarnings(true);
+});
diff --git a/toolkit/components/extensions/test/xpcshell/test_ext_background_window_properties.js b/toolkit/components/extensions/test/xpcshell/test_ext_background_window_properties.js
new file mode 100644
index 0000000000..fb2ca27482
--- /dev/null
+++ b/toolkit/components/extensions/test/xpcshell/test_ext_background_window_properties.js
@@ -0,0 +1,41 @@
+/* -*- Mode: indent-tabs-mode: nil; js-indent-level: 2 -*- */
+/* vim: set sts=2 sw=2 et tw=80: */
+"use strict";
+
+add_task(async function testBackgroundWindowProperties() {
+  let extension = ExtensionTestUtils.loadExtension({
+    background() {
+      let expectedValues = {
+        screenX: 0,
+        screenY: 0,
+        outerWidth: 0,
+        outerHeight: 0,
+      };
+
+      for (let k in window) {
+        try {
+          if (k in expectedValues) {
+            browser.test.assertEq(
+              expectedValues[k],
+              window[k],
+              `should return the expected value for window property: ${k}`
+            );
+          } else {
+            void window[k];
+          }
+        } catch (e) {
+          browser.test.assertEq(
+            null,
+            e,
+            `unexpected exception accessing window property: ${k}`
+          );
+        }
+      }
+
+      browser.test.notifyPass("background.testWindowProperties.done");
+    },
+  });
+  await extension.startup();
+  await extension.awaitFinish("background.testWindowProperties.done");
+  await extension.unload();
+});
diff --git a/toolkit/components/extensions/test/xpcshell/test_ext_brokenlinks.js b/toolkit/components/extensions/test/xpcshell/test_ext_brokenlinks.js
new file mode 100644
index 0000000000..c066147268
--- /dev/null
+++ b/toolkit/components/extensions/test/xpcshell/test_ext_brokenlinks.js
@@ -0,0 +1,54 @@
+/* -*- Mode: indent-tabs-mode: nil; js-indent-level: 2 -*- */
+/* vim: set sts=2 sw=2 et tw=80: */
+"use strict";
+
+/*
+ * This test extension has a background script 'missing.js' that is missing
+ * from the XPI. Such an extension should install/uninstall cleanly without
+ * causing timeouts.
+ */
+add_task(async function testXPIMissingBackGroundScript() {
+  let extension = ExtensionTestUtils.loadExtension({
+    manifest: {
+      background: {
+        scripts: ["missing.js"],
+      },
+    },
+  });
+
+  await extension.startup();
+  await extension.unload();
+  ok(true, "load/unload completed without timing out");
+});
+
+/*
+ * This test extension includes a page with a missing script. The
+ * extension should install/uninstall cleanly without causing hangs.
+ */
+add_task(async function testXPIMissingPageScript() {
+  async function pageScript() {
+    browser.test.sendMessage("pageReady");
+  }
+
+  let extension = ExtensionTestUtils.loadExtension({
+    background() {
+      browser.test.sendMessage("ready", browser.runtime.getURL("page.html"));
+    },
+    files: {
+      "page.html": `<html><head>
+                    <script src="missing.js"></script>
+                    <script src="page.js"></script>
+                    </head></html>`,
+      "page.js": pageScript,
+    },
+  });
+
+  await extension.startup();
+  let url = await extension.awaitMessage("ready");
+  let contentPage = await ExtensionTestUtils.loadContentPage(url);
+  await extension.awaitMessage("pageReady");
+  await extension.unload();
+  await contentPage.close();
+
+  ok(true, "load/unload completed without timing out");
+});
diff --git a/toolkit/components/extensions/test/xpcshell/test_ext_browserSettings.js b/toolkit/components/extensions/test/xpcshell/test_ext_browserSettings.js
new file mode 100644
index 0000000000..f1f681b240
--- /dev/null
+++ b/toolkit/components/extensions/test/xpcshell/test_ext_browserSettings.js
@@ -0,0 +1,528 @@
+/* -*- Mode: indent-tabs-mode: nil; js-indent-level: 2 -*- */
+/* vim: set sts=2 sw=2 et tw=80: */
+"use strict";
+
+ChromeUtils.defineESModuleGetters(this, {
+  AddonManager: "resource://gre/modules/AddonManager.sys.mjs",
+  Preferences: "resource://gre/modules/Preferences.sys.mjs",
+});
+
+// The test extension uses an insecure update url.
+Services.prefs.setBoolPref("extensions.checkUpdateSecurity", false);
+
+const SETTINGS_ID = "test_settings_staged_restart_webext@tests.mozilla.org";
+
+const { createAppInfo, promiseShutdownManager, promiseStartupManager } =
+  AddonTestUtils;
+
+AddonTestUtils.init(this);
+AddonTestUtils.overrideCertDB();
+
+createAppInfo("xpcshell@tests.mozilla.org", "XPCShell", "42", "42");
+
+add_task(async function test_browser_settings() {
+  const PERM_DENY_ACTION = Services.perms.DENY_ACTION;
+  const PERM_UNKNOWN_ACTION = Services.perms.UNKNOWN_ACTION;
+
+  // Create an object to hold the values to which we will initialize the prefs.
+  const PREFS = {
+    "browser.cache.disk.enable": true,
+    "browser.cache.memory.enable": true,
+    "dom.popup_allowed_events": Preferences.get("dom.popup_allowed_events"),
+    "image.animation_mode": "none",
+    "permissions.default.desktop-notification": PERM_UNKNOWN_ACTION,
+    "ui.context_menus.after_mouseup": false,
+    "browser.tabs.closeTabByDblclick": false,
+    "browser.tabs.loadBookmarksInTabs": false,
+    "browser.search.openintab": false,
+    "browser.tabs.insertRelatedAfterCurrent": true,
+    "browser.tabs.insertAfterCurrent": false,
+    "browser.display.document_color_use": 1,
+    "layout.css.prefers-color-scheme.content-override": 2,
+    "browser.display.use_document_fonts": 1,
+    "browser.zoom.full": true,
+    "browser.zoom.siteSpecific": true,
+  };
+
+  async function background() {
+    let listeners = new Set([]);
+    browser.test.onMessage.addListener(async (msg, apiName, value) => {
+      let apiObj = browser.browserSettings;
+      let apiNameSplit = apiName.split(".");
+      for (let apiPart of apiNameSplit) {
+        apiObj = apiObj[apiPart];
+      }
+      if (msg == "get") {
+        browser.test.sendMessage("settingData", await apiObj.get({}));
+        return;
+      }
+
+      // set and setNoOp
+
+      // Don't add more than one listner per apiName.  We leave the
+      // listener to ensure we do not get more calls than we expect.
+      if (!listeners.has(apiName)) {
+        apiObj.onChange.addListener(details => {
+          browser.test.sendMessage("onChange", {
+            details,
+            setting: apiName,
+          });
+        });
+        listeners.add(apiName);
+      }
+      let result = await apiObj.set({ value });
+      if (msg === "set") {
+        browser.test.assertTrue(result, "set returns true.");
+        browser.test.sendMessage("settingData", await apiObj.get({}));
+      } else {
+        browser.test.assertFalse(result, "set returns false for a no-op.");
+        browser.test.sendMessage("no-op set");
+      }
+    });
+  }
+
+  // Set prefs to our initial values.
+  for (let pref in PREFS) {
+    Preferences.set(pref, PREFS[pref]);
+  }
+
+  registerCleanupFunction(() => {
+    // Reset the prefs.
+    for (let pref in PREFS) {
+      Preferences.reset(pref);
+    }
+  });
+
+  let extension = ExtensionTestUtils.loadExtension({
+    background,
+    manifest: {
+      permissions: ["browserSettings"],
+    },
+    useAddonManager: "temporary",
+  });
+
+  await promiseStartupManager();
+  await extension.startup();
+
+  async function testSetting(setting, value, expected, expectedValue = value) {
+    extension.sendMessage("set", setting, value);
+    let data = await extension.awaitMessage("settingData");
+    let dataChange = await extension.awaitMessage("onChange");
+    equal(setting, dataChange.setting, "onChange fired");
+    equal(
+      data.value,
+      dataChange.details.value,
+      "onChange fired with correct value"
+    );
+    deepEqual(
+      data.value,
+      expectedValue,
+      `The ${setting} setting has the expected value.`
+    );
+    equal(
+      data.levelOfControl,
+      "controlled_by_this_extension",
+      `The ${setting} setting has the expected levelOfControl.`
+    );
+    for (let pref in expected) {
+      equal(
+        Preferences.get(pref),
+        expected[pref],
+        `${pref} set correctly for ${value}`
+      );
+    }
+  }
+
+  async function testNoOpSetting(setting, value, expected) {
+    extension.sendMessage("setNoOp", setting, value);
+    await extension.awaitMessage("no-op set");
+    for (let pref in expected) {
+      equal(
+        Preferences.get(pref),
+        expected[pref],
+        `${pref} set correctly for ${value}`
+      );
+    }
+  }
+
+  await testSetting("cacheEnabled", false, {
+    "browser.cache.disk.enable": false,
+    "browser.cache.memory.enable": false,
+  });
+  await testSetting("cacheEnabled", true, {
+    "browser.cache.disk.enable": true,
+    "browser.cache.memory.enable": true,
+  });
+
+  await testSetting("allowPopupsForUserEvents", false, {
+    "dom.popup_allowed_events": "",
+  });
+  await testSetting("allowPopupsForUserEvents", true, {
+    "dom.popup_allowed_events": PREFS["dom.popup_allowed_events"],
+  });
+
+  for (let value of ["normal", "none", "once"]) {
+    await testSetting("imageAnimationBehavior", value, {
+      "image.animation_mode": value,
+    });
+  }
+
+  await testSetting("webNotificationsDisabled", true, {
+    "permissions.default.desktop-notification": PERM_DENY_ACTION,
+  });
+  await testSetting("webNotificationsDisabled", false, {
+    // This pref is not defaulted on Android.
+    "permissions.default.desktop-notification":
+      AppConstants.MOZ_BUILD_APP !== "browser"
+        ? undefined
+        : PERM_UNKNOWN_ACTION,
+  });
+
+  // This setting is a no-op on Android.
+  if (AppConstants.platform === "android") {
+    await testNoOpSetting("contextMenuShowEvent", "mouseup", {
+      "ui.context_menus.after_mouseup": false,
+    });
+  } else {
+    await testSetting("contextMenuShowEvent", "mouseup", {
+      "ui.context_menus.after_mouseup": true,
+    });
+  }
+
+  // "mousedown" is also a no-op on Windows.
+  if (["android", "win"].includes(AppConstants.platform)) {
+    await testNoOpSetting("contextMenuShowEvent", "mousedown", {
+      "ui.context_menus.after_mouseup": AppConstants.platform === "win",
+    });
+  } else {
+    await testSetting("contextMenuShowEvent", "mousedown", {
+      "ui.context_menus.after_mouseup": false,
+    });
+  }
+
+  if (AppConstants.platform !== "android") {
+    await testSetting("closeTabsByDoubleClick", true, {
+      "browser.tabs.closeTabByDblclick": true,
+    });
+    await testSetting("closeTabsByDoubleClick", false, {
+      "browser.tabs.closeTabByDblclick": false,
+    });
+  }
+
+  extension.sendMessage("get", "ftpProtocolEnabled");
+  let data = await extension.awaitMessage("settingData");
+  equal(data.value, false);
+  equal(
+    data.levelOfControl,
+    "not_controllable",
+    `ftpProtocolEnabled is not controllable.`
+  );
+
+  await testSetting("newTabPosition", "afterCurrent", {
+    "browser.tabs.insertRelatedAfterCurrent": false,
+    "browser.tabs.insertAfterCurrent": true,
+  });
+  await testSetting("newTabPosition", "atEnd", {
+    "browser.tabs.insertRelatedAfterCurrent": false,
+    "browser.tabs.insertAfterCurrent": false,
+  });
+  await testSetting("newTabPosition", "relatedAfterCurrent", {
+    "browser.tabs.insertRelatedAfterCurrent": true,
+    "browser.tabs.insertAfterCurrent": false,
+  });
+
+  await testSetting("openBookmarksInNewTabs", true, {
+    "browser.tabs.loadBookmarksInTabs": true,
+  });
+  await testSetting("openBookmarksInNewTabs", false, {
+    "browser.tabs.loadBookmarksInTabs": false,
+  });
+
+  await testSetting("openSearchResultsInNewTabs", true, {
+    "browser.search.openintab": true,
+  });
+  await testSetting("openSearchResultsInNewTabs", false, {
+    "browser.search.openintab": false,
+  });
+
+  await testSetting("openUrlbarResultsInNewTabs", true, {
+    "browser.urlbar.openintab": true,
+  });
+  await testSetting("openUrlbarResultsInNewTabs", false, {
+    "browser.urlbar.openintab": false,
+  });
+
+  await testSetting("overrideDocumentColors", "high-contrast-only", {
+    "browser.display.document_color_use": 0,
+  });
+  await testSetting("overrideDocumentColors", "never", {
+    "browser.display.document_color_use": 1,
+  });
+  await testSetting("overrideDocumentColors", "always", {
+    "browser.display.document_color_use": 2,
+  });
+
+  await testSetting("overrideContentColorScheme", "dark", {
+    "layout.css.prefers-color-scheme.content-override": 0,
+  });
+  await testSetting("overrideContentColorScheme", "light", {
+    "layout.css.prefers-color-scheme.content-override": 1,
+  });
+  await testSetting("overrideContentColorScheme", "auto", {
+    "layout.css.prefers-color-scheme.content-override": 2,
+  });
+
+  await testSetting("useDocumentFonts", false, {
+    "browser.display.use_document_fonts": 0,
+  });
+  await testSetting("useDocumentFonts", true, {
+    "browser.display.use_document_fonts": 1,
+  });
+
+  await testSetting("zoomFullPage", true, {
+    "browser.zoom.full": true,
+  });
+  await testSetting("zoomFullPage", false, {
+    "browser.zoom.full": false,
+  });
+
+  await testSetting("zoomSiteSpecific", true, {
+    "browser.zoom.siteSpecific": true,
+  });
+  await testSetting("zoomSiteSpecific", false, {
+    "browser.zoom.siteSpecific": false,
+  });
+
+  await testSetting("colorManagement.mode", "off", {
+    "gfx.color_management.mode": 0,
+  });
+  await testSetting("colorManagement.mode", "full", {
+    "gfx.color_management.mode": 1,
+  });
+  await testSetting("colorManagement.mode", "tagged_only", {
+    "gfx.color_management.mode": 2,
+  });
+
+  await testSetting("colorManagement.useNativeSRGB", false, {
+    "gfx.color_management.native_srgb": false,
+  });
+  await testSetting("colorManagement.useNativeSRGB", true, {
+    "gfx.color_management.native_srgb": true,
+  });
+
+  await testSetting("colorManagement.useWebRenderCompositor", false, {
+    "gfx.webrender.compositor": false,
+  });
+  await testSetting("colorManagement.useWebRenderCompositor", true, {
+    "gfx.webrender.compositor": true,
+  });
+
+  await extension.unload();
+  await promiseShutdownManager();
+});
+
+add_task(async function test_bad_value() {
+  async function background() {
+    await browser.test.assertRejects(
+      browser.browserSettings.contextMenuShowEvent.set({ value: "bad" }),
+      /bad is not a valid value for contextMenuShowEvent/,
+      "contextMenuShowEvent.set rejects with an invalid value."
+    );
+
+    await browser.test.assertRejects(
+      browser.browserSettings.overrideDocumentColors.set({ value: 2 }),
+      /2 is not a valid value for overrideDocumentColors/,
+      "overrideDocumentColors.set rejects with an invalid value."
+    );
+
+    await browser.test.assertRejects(
+      browser.browserSettings.overrideDocumentColors.set({ value: "bad" }),
+      /bad is not a valid value for overrideDocumentColors/,
+      "overrideDocumentColors.set rejects with an invalid value."
+    );
+
+    await browser.test.assertRejects(
+      browser.browserSettings.overrideContentColorScheme.set({ value: 0 }),
+      /0 is not a valid value for overrideContentColorScheme/,
+      "overrideContentColorScheme.set rejects with an invalid value."
+    );
+
+    await browser.test.assertRejects(
+      browser.browserSettings.overrideContentColorScheme.set({ value: "bad" }),
+      /bad is not a valid value for overrideContentColorScheme/,
+      "overrideContentColorScheme.set rejects with an invalid value."
+    );
+
+    await browser.test.assertRejects(
+      browser.browserSettings.zoomFullPage.set({ value: 0 }),
+      /0 is not a valid value for zoomFullPage/,
+      "zoomFullPage.set rejects with an invalid value."
+    );
+
+    await browser.test.assertRejects(
+      browser.browserSettings.zoomFullPage.set({ value: "bad" }),
+      /bad is not a valid value for zoomFullPage/,
+      "zoomFullPage.set rejects with an invalid value."
+    );
+
+    await browser.test.assertRejects(
+      browser.browserSettings.zoomSiteSpecific.set({ value: 0 }),
+      /0 is not a valid value for zoomSiteSpecific/,
+      "zoomSiteSpecific.set rejects with an invalid value."
+    );
+
+    await browser.test.assertRejects(
+      browser.browserSettings.zoomSiteSpecific.set({ value: "bad" }),
+      /bad is not a valid value for zoomSiteSpecific/,
+      "zoomSiteSpecific.set rejects with an invalid value."
+    );
+
+    browser.test.sendMessage("done");
+  }
+
+  let extension = ExtensionTestUtils.loadExtension({
+    background,
+    manifest: {
+      permissions: ["browserSettings"],
+    },
+  });
+
+  await extension.startup();
+  await extension.awaitMessage("done");
+  await extension.unload();
+});
+
+add_task(async function test_bad_value_android() {
+  if (AppConstants.platform !== "android") {
+    return;
+  }
+
+  async function background() {
+    await browser.test.assertRejects(
+      browser.browserSettings.closeTabsByDoubleClick.set({ value: true }),
+      /android is not a supported platform for the closeTabsByDoubleClick setting/,
+      "closeTabsByDoubleClick.set rejects on Android."
+    );
+
+    await browser.test.assertRejects(
+      browser.browserSettings.closeTabsByDoubleClick.get({}),
+      /android is not a supported platform for the closeTabsByDoubleClick setting/,
+      "closeTabsByDoubleClick.get rejects on Android."
+    );
+
+    await browser.test.assertRejects(
+      browser.browserSettings.closeTabsByDoubleClick.clear({}),
+      /android is not a supported platform for the closeTabsByDoubleClick setting/,
+      "closeTabsByDoubleClick.clear rejects on Android."
+    );
+
+    browser.test.sendMessage("done");
+  }
+
+  let extension = ExtensionTestUtils.loadExtension({
+    background,
+    manifest: {
+      permissions: ["browserSettings"],
+    },
+  });
+
+  await extension.startup();
+  await extension.awaitMessage("done");
+  await extension.unload();
+});
+
+// Verifies settings remain after a staged update on restart.
+add_task(async function delay_updates_settings_after_restart() {
+  let server = AddonTestUtils.createHttpServer({ hosts: ["example.com"] });
+  AddonTestUtils.registerJSON(server, "/test_update.json", {
+    addons: {
+      "test_settings_staged_restart_webext@tests.mozilla.org": {
+        updates: [
+          {
+            version: "2.0",
+            update_link:
+              "http://example.com/addons/test_settings_staged_restart_v2.xpi",
+          },
+        ],
+      },
+    },
+  });
+  const update_xpi = AddonTestUtils.createTempXPIFile({
+    "manifest.json": {
+      manifest_version: 2,
+      name: "Delay Upgrade",
+      version: "2.0",
+      browser_specific_settings: {
+        gecko: { id: SETTINGS_ID },
+      },
+      permissions: ["browserSettings"],
+    },
+  });
+  server.registerFile(
+    `/addons/test_settings_staged_restart_v2.xpi`,
+    update_xpi
+  );
+
+  await AddonTestUtils.promiseStartupManager();
+
+  let extension = ExtensionTestUtils.loadExtension({
+    useAddonManager: "permanent",
+    manifest: {
+      version: "1.0",
+      browser_specific_settings: {
+        gecko: {
+          id: SETTINGS_ID,
+          update_url: `http://example.com/test_update.json`,
+        },
+      },
+      permissions: ["browserSettings"],
+    },
+    background() {
+      browser.runtime.onUpdateAvailable.addListener(async details => {
+        if (details) {
+          await browser.browserSettings.webNotificationsDisabled.set({
+            value: true,
+          });
+          if (details.version) {
+            // This should be the version of the pending update.
+            browser.test.assertEq("2.0", details.version, "correct version");
+            browser.test.notifyPass("delay");
+          }
+        } else {
+          browser.test.fail("no details object passed");
+        }
+      });
+      browser.test.sendMessage("ready");
+    },
+  });
+
+  await Promise.all([extension.startup(), extension.awaitMessage("ready")]);
+
+  let prefname = "permissions.default.desktop-notification";
+  let val = Services.prefs.getIntPref(prefname);
+  Assert.notEqual(val, 2, "webNotificationsDisabled pref not set");
+
+  let update = await AddonTestUtils.promiseFindAddonUpdates(extension.addon);
+  let install = update.updateAvailable;
+  Assert.ok(install, `install is available ${update.error}`);
+
+  await AddonTestUtils.promiseCompleteAllInstalls([install]);
+
+  Assert.equal(install.state, AddonManager.STATE_POSTPONED);
+  await extension.awaitFinish("delay");
+
+  // restarting allows upgrade to proceed
+  await AddonTestUtils.promiseRestartManager();
+
+  await extension.awaitStartup();
+
+  // If an update is not handled correctly we would fail here.  Bug 1639705.
+  val = Services.prefs.getIntPref(prefname);
+  Assert.equal(val, 2, "webNotificationsDisabled pref set");
+
+  await extension.unload();
+  await AddonTestUtils.promiseShutdownManager();
+
+  val = Services.prefs.getIntPref(prefname);
+  Assert.notEqual(val, 2, "webNotificationsDisabled pref not set");
+});
diff --git a/toolkit/components/extensions/test/xpcshell/test_ext_browserSettings_homepage.js b/toolkit/components/extensions/test/xpcshell/test_ext_browserSettings_homepage.js
new file mode 100644
index 0000000000..8d1d16c743
--- /dev/null
+++ b/toolkit/components/extensions/test/xpcshell/test_ext_browserSettings_homepage.js
@@ -0,0 +1,36 @@
+/* -*- Mode: indent-tabs-mode: nil; js-indent-level: 2 -*- */
+/* vim: set sts=2 sw=2 et tw=80: */
+"use strict";
+
+add_task(async function test_homepage_get_without_set() {
+  async function background() {
+    let homepage = await browser.browserSettings.homepageOverride.get({});
+    browser.test.sendMessage("homepage", homepage);
+  }
+
+  let extension = ExtensionTestUtils.loadExtension({
+    background,
+    manifest: {
+      permissions: ["browserSettings"],
+    },
+  });
+
+  let defaultHomepage = Services.prefs.getStringPref(
+    "browser.startup.homepage"
+  );
+
+  await extension.startup();
+  let homepage = await extension.awaitMessage("homepage");
+  equal(
+    homepage.value,
+    defaultHomepage,
+    "The homepageOverride setting has the expected value."
+  );
+  equal(
+    homepage.levelOfControl,
+    "not_controllable",
+    "The homepageOverride setting has the expected levelOfControl."
+  );
+
+  await extension.unload();
+});
diff --git a/toolkit/components/extensions/test/xpcshell/test_ext_browser_style_deprecation.js b/toolkit/components/extensions/test/xpcshell/test_ext_browser_style_deprecation.js
new file mode 100644
index 0000000000..2046242865
--- /dev/null
+++ b/toolkit/components/extensions/test/xpcshell/test_ext_browser_style_deprecation.js
@@ -0,0 +1,335 @@
+"use strict";
+
+AddonTestUtils.init(this);
+// This test expects and checks deprecation warnings.
+ExtensionTestUtils.failOnSchemaWarnings(false);
+
+const PREF_SUPPORTED = "extensions.browser_style_mv3.supported";
+const PREF_SAME_AS_MV2 = "extensions.browser_style_mv3.same_as_mv2";
+
+// Set the prefs to the defaults at the end of the deprecation process.
+// TODO bug 1830711: remove these two lines.
+Services.prefs.setBoolPref(PREF_SUPPORTED, false);
+Services.prefs.setBoolPref(PREF_SAME_AS_MV2, false);
+
+function checkBrowserStyleInManifestKey(extension, key, expected) {
+  let actual = extension.extension.manifest[key].browser_style;
+  Assert.strictEqual(actual, expected, `Expected browser_style of "${key}"`);
+}
+
+const BROWSER_STYLE_MV2_DEFAULTS = "BROWSER_STYLE_MV2_DEFAULTS";
+async function checkBrowserStyle({
+  manifest_version = 3,
+  browser_style_in_manifest = null,
+  expected_browser_style,
+  expected_warnings,
+}) {
+  const actionKey = manifest_version === 2 ? "browser_action" : "action";
+  // sidebar_action is implemented in browser/ and therefore only available to
+  // Firefox desktop and not other toolkit apps such as Firefox for Android,
+  // Thunderbird, etc.
+  const IS_SIDEBAR_SUPPORTED = AppConstants.MOZ_BUILD_APP === "browser";
+  const extension = ExtensionTestUtils.loadExtension({
+    manifest: {
+      manifest_version,
+      options_ui: {
+        page: "options.html",
+        browser_style: browser_style_in_manifest,
+      },
+      [actionKey]: {
+        browser_style: browser_style_in_manifest,
+      },
+      page_action: {
+        browser_style: browser_style_in_manifest,
+      },
+      sidebar_action: {
+        default_panel: "sidebar.html",
+        browser_style: browser_style_in_manifest,
+      },
+    },
+  });
+  await extension.startup();
+  if (expected_browser_style === BROWSER_STYLE_MV2_DEFAULTS) {
+    checkBrowserStyleInManifestKey(extension, "options_ui", true);
+    checkBrowserStyleInManifestKey(extension, actionKey, false);
+    checkBrowserStyleInManifestKey(extension, "page_action", false);
+    if (IS_SIDEBAR_SUPPORTED) {
+      checkBrowserStyleInManifestKey(extension, "sidebar_action", true);
+    }
+  } else {
+    let value = expected_browser_style;
+    checkBrowserStyleInManifestKey(extension, "options_ui", value);
+    checkBrowserStyleInManifestKey(extension, actionKey, value);
+    checkBrowserStyleInManifestKey(extension, "page_action", value);
+    if (IS_SIDEBAR_SUPPORTED) {
+      checkBrowserStyleInManifestKey(extension, "sidebar_action", value);
+    }
+  }
+  if (!IS_SIDEBAR_SUPPORTED) {
+    expected_warnings = expected_warnings.filter(
+      msg => !msg.includes("sidebar_action")
+    );
+    expected_warnings.unshift(
+      `Reading manifest: Warning processing sidebar_action: An unexpected property was found in the WebExtension manifest.`
+    );
+  }
+  const warnings = extension.extension.warnings;
+  await extension.unload();
+  Assert.deepEqual(
+    warnings,
+    expected_warnings,
+    `Got expected warnings for MV${manifest_version} extension with browser_style:${browser_style_in_manifest}.`
+  );
+}
+
+async function checkBrowserStyleWithOpenInTabTrue({
+  manifest_version = 3,
+  browser_style_in_manifest = null,
+  expected_browser_style,
+}) {
+  info(
+    `Testing options_ui.open_in_tab=true + browser_style=${browser_style_in_manifest} for MV${manifest_version} extension`
+  );
+  let extension = ExtensionTestUtils.loadExtension({
+    manifest: {
+      manifest_version,
+      options_ui: {
+        page: "options.html",
+        browser_style: browser_style_in_manifest,
+        open_in_tab: true,
+      },
+    },
+  });
+  await extension.startup();
+  checkBrowserStyleInManifestKey(
+    extension,
+    "options_ui",
+    expected_browser_style
+  );
+  const warnings = extension.extension.warnings;
+  await extension.unload();
+  Assert.deepEqual(
+    warnings,
+    [],
+    "Expected no warnings on extension with options_ui.open_in_tab true"
+  );
+}
+
+async function repeatTestIndependentOfPref_browser_style_same_as_mv2(testFn) {
+  for (let same_as_mv2 of [true, false]) {
+    await runWithPrefs([[PREF_SAME_AS_MV2, same_as_mv2]], testFn);
+  }
+}
+async function repeatTestIndependentOf_browser_style_deprecation_prefs(testFn) {
+  for (let supported of [true, false]) {
+    for (let same_as_mv2 of [true, false]) {
+      await runWithPrefs(
+        [
+          [PREF_SUPPORTED, supported],
+          [PREF_SAME_AS_MV2, same_as_mv2],
+        ],
+        testFn
+      );
+    }
+  }
+}
+
+add_task(async function browser_style_never_deprecated_in_MV2() {
+  async function check_browser_style_never_deprecated_in_MV2() {
+    await checkBrowserStyle({
+      manifest_version: 2,
+      browser_style_in_manifest: true,
+      expected_browser_style: true,
+      expected_warnings: [],
+    });
+    await checkBrowserStyle({
+      manifest_version: 2,
+      browser_style_in_manifest: false,
+      expected_browser_style: false,
+      expected_warnings: [],
+    });
+    await checkBrowserStyle({
+      manifest_version: 2,
+      browser_style_in_manifest: null,
+      expected_browser_style: "BROWSER_STYLE_MV2_DEFAULTS",
+      expected_warnings: [],
+    });
+
+    // When open_in_tab is true, browser_style is not used and its value does
+    // not matter. Since we want the parsed value to be false in MV3, and the
+    // implementation is simpler if consistently applied to MV2, browser_style
+    // is false when open_in_tab is true (even if browser_style:true is set).
+    await checkBrowserStyleWithOpenInTabTrue({
+      manifest_version: 2,
+      browser_style_in_manifest: null,
+      expected_browser_style: false,
+    });
+    await checkBrowserStyleWithOpenInTabTrue({
+      manifest_version: 2,
+      browser_style_in_manifest: true,
+      expected_browser_style: false,
+    });
+  }
+  // Regardless of all potential test configurations, browser_style is never
+  // deprecated in MV2.
+  await repeatTestIndependentOf_browser_style_deprecation_prefs(
+    check_browser_style_never_deprecated_in_MV2
+  );
+});
+
+add_task(async function open_in_tab_implies_browser_style_false_MV3() {
+  // Regardless of all potential test configurations, when
+  // options_ui.open_in_tab is true, options_ui.browser_style should be false,
+  // because it being true would print deprecation warnings in MV3, and
+  // browser_style:true does not have any effect when open_in_tab is true.
+  await repeatTestIndependentOf_browser_style_deprecation_prefs(async () => {
+    await checkBrowserStyleWithOpenInTabTrue({
+      manifest_version: 3,
+      browser_style_in_manifest: null,
+      expected_browser_style: false,
+    });
+    await checkBrowserStyleWithOpenInTabTrue({
+      manifest_version: 3,
+      browser_style_in_manifest: true,
+      expected_browser_style: false,
+    });
+  });
+});
+
+// Disable browser_style:true - bug 1830711.
+add_task(async function unsupported_and_browser_style_true() {
+  await checkBrowserStyle({
+    manifest_version: 3,
+    browser_style_in_manifest: true,
+    expected_browser_style: false,
+    expected_warnings: [
+      // TODO bug 1830712: Update warnings when max_manifest_version:2 is used.
+      `Reading manifest: Warning processing options_ui.browser_style: "browser_style:true" is no longer supported in Manifest Version 3.`,
+      `Reading manifest: Warning processing action.browser_style: "browser_style:true" is no longer supported in Manifest Version 3.`,
+      `Reading manifest: Warning processing page_action.browser_style: "browser_style:true" is no longer supported in Manifest Version 3.`,
+      `Reading manifest: Warning processing sidebar_action.browser_style: "browser_style:true" is no longer supported in Manifest Version 3.`,
+    ],
+  });
+});
+
+add_task(async function unsupported_and_browser_style_false() {
+  await checkBrowserStyle({
+    manifest_version: 3,
+    browser_style_in_manifest: false,
+    expected_browser_style: false,
+    // TODO bug 1830712: Add warnings when max_manifest_version:2 is used.
+    expected_warnings: [],
+  });
+});
+
+add_task(async function unsupported_and_browser_style_default() {
+  await checkBrowserStyle({
+    manifest_version: 3,
+    browser_style_in_manifest: null,
+    expected_browser_style: false,
+    expected_warnings: [],
+  });
+});
+
+add_task(
+  { pref_set: [[PREF_SUPPORTED, true]] },
+  async function supported_with_browser_style_true() {
+    await repeatTestIndependentOfPref_browser_style_same_as_mv2(async () => {
+      await checkBrowserStyle({
+        manifest_version: 3,
+        browser_style_in_manifest: true,
+        expected_browser_style: true,
+        expected_warnings: [
+          `Reading manifest: Warning processing options_ui.browser_style: "browser_style:true" has been deprecated in Manifest Version 3 and will be unsupported in the near future.`,
+          `Reading manifest: Warning processing action.browser_style: "browser_style:true" has been deprecated in Manifest Version 3 and will be unsupported in the near future.`,
+          `Reading manifest: Warning processing page_action.browser_style: "browser_style:true" has been deprecated in Manifest Version 3 and will be unsupported in the near future.`,
+          `Reading manifest: Warning processing sidebar_action.browser_style: "browser_style:true" has been deprecated in Manifest Version 3 and will be unsupported in the near future.`,
+        ],
+      });
+    });
+  }
+);
+
+add_task(
+  { pref_set: [[PREF_SUPPORTED, true]] },
+  async function supported_with_browser_style_false() {
+    await repeatTestIndependentOfPref_browser_style_same_as_mv2(async () => {
+      await checkBrowserStyle({
+        manifest_version: 3,
+        browser_style_in_manifest: false,
+        expected_browser_style: false,
+        expected_warnings: [],
+      });
+    });
+  }
+);
+
+// Initial prefs - warn only - https://bugzilla.mozilla.org/show_bug.cgi?id=1827910#c1
+add_task(
+  {
+    pref_set: [
+      [PREF_SUPPORTED, true],
+      [PREF_SAME_AS_MV2, true],
+    ],
+  },
+  async function supported_with_mv2_defaults() {
+    const makeWarning = manifestKey =>
+      `Reading manifest: Warning processing ${manifestKey}.browser_style: "browser_style:true" has been deprecated in Manifest Version 3 and will be unsupported in the near future. While "${manifestKey}.browser_style" was not explicitly specified in manifest.json, its default value was true. Its default will change to false in Manifest Version 3 starting from Firefox 115.`;
+    await checkBrowserStyle({
+      manifest_version: 3,
+      browser_style_in_manifest: null,
+      expected_browser_style: "BROWSER_STYLE_MV2_DEFAULTS",
+      expected_warnings: [
+        makeWarning("options_ui"),
+        makeWarning("sidebar_action"),
+      ],
+    });
+  }
+);
+
+// Deprecation + change defaults - bug 1830710.
+add_task(
+  {
+    pref_set: [
+      [PREF_SUPPORTED, true],
+      [PREF_SAME_AS_MV2, false],
+    ],
+  },
+  async function supported_with_browser_style_default_false() {
+    const makeWarning = manifestKey =>
+      `Reading manifest: Warning processing ${manifestKey}.browser_style: "browser_style:true" has been deprecated in Manifest Version 3 and will be unsupported in the near future. While "${manifestKey}.browser_style" was not explicitly specified in manifest.json, its default value was true. The default value of "${manifestKey}.browser_style" has changed from true to false in Manifest Version 3.`;
+    await checkBrowserStyle({
+      manifest_version: 3,
+      browser_style_in_manifest: null,
+      expected_browser_style: false,
+      expected_warnings: [
+        makeWarning("options_ui"),
+        makeWarning("sidebar_action"),
+      ],
+    });
+  }
+);
+
+// While we are not planning to set this pref combination, users can do so if
+// they desire.
+add_task(
+  {
+    pref_set: [
+      [PREF_SUPPORTED, false],
+      [PREF_SAME_AS_MV2, true],
+    ],
+  },
+  async function unsupported_with_mv2_defaults() {
+    const makeWarning = manifestKey =>
+      `Reading manifest: Warning processing ${manifestKey}.browser_style: "browser_style:true" is no longer supported in Manifest Version 3. While "${manifestKey}.browser_style" was not explicitly specified in manifest.json, its default value was true. Its default will change to false in Manifest Version 3 starting from Firefox 115.`;
+    await checkBrowserStyle({
+      manifest_version: 3,
+      browser_style_in_manifest: null,
+      expected_browser_style: false,
+      expected_warnings: [
+        makeWarning("options_ui"),
+        makeWarning("sidebar_action"),
+      ],
+    });
+  }
+);
diff --git a/toolkit/components/extensions/test/xpcshell/test_ext_browsingData.js b/toolkit/components/extensions/test/xpcshell/test_ext_browsingData.js
new file mode 100644
index 0000000000..1df5e60478
--- /dev/null
+++ b/toolkit/components/extensions/test/xpcshell/test_ext_browsingData.js
@@ -0,0 +1,48 @@
+/* -*- Mode: indent-tabs-mode: nil; js-indent-level: 2 -*- */
+/* vim: set sts=2 sw=2 et tw=80: */
+"use strict";
+
+add_task(async function testInvalidArguments() {
+  async function background() {
+    const UNSUPPORTED_DATA_TYPES = ["appcache", "fileSystems", "webSQL"];
+
+    await browser.test.assertRejects(
+      browser.browsingData.remove(
+        { originTypes: { protectedWeb: true } },
+        { cookies: true }
+      ),
+      "Firefox does not support protectedWeb or extension as originTypes.",
+      "Expected error received when using protectedWeb originType."
+    );
+
+    await browser.test.assertRejects(
+      browser.browsingData.removeCookies({ originTypes: { extension: true } }),
+      "Firefox does not support protectedWeb or extension as originTypes.",
+      "Expected error received when using extension originType."
+    );
+
+    for (let dataType of UNSUPPORTED_DATA_TYPES) {
+      let dataTypes = {};
+      dataTypes[dataType] = true;
+      browser.test.assertThrows(
+        () => browser.browsingData.remove({}, dataTypes),
+        /Type error for parameter dataToRemove/,
+        `Expected error received when using ${dataType} dataType.`
+      );
+    }
+
+    browser.test.notifyPass("invalidArguments");
+  }
+
+  let extensionData = {
+    background: background,
+    manifest: {
+      permissions: ["browsingData"],
+    },
+  };
+
+  let extension = ExtensionTestUtils.loadExtension(extensionData);
+  await extension.startup();
+  await extension.awaitFinish("invalidArguments");
+  await extension.unload();
+});
diff --git a/toolkit/components/extensions/test/xpcshell/test_ext_browsingData_cookies_cache.js b/toolkit/components/extensions/test/xpcshell/test_ext_browsingData_cookies_cache.js
new file mode 100644
index 0000000000..577d727a49
--- /dev/null
+++ b/toolkit/components/extensions/test/xpcshell/test_ext_browsingData_cookies_cache.js
@@ -0,0 +1,456 @@
+/* -*- Mode: indent-tabs-mode: nil; js-indent-level: 2 -*- */
+/* vim: set sts=2 sw=2 et tw=80: */
+/* eslint-disable mozilla/no-arbitrary-setTimeout */
+"use strict";
+
+const { SiteDataTestUtils } = ChromeUtils.importESModule(
+  "resource://testing-common/SiteDataTestUtils.sys.mjs"
+);
+
+const COOKIE = {
+  host: "example.com",
+  name: "test_cookie",
+  path: "/",
+};
+const COOKIE_NET = {
+  host: "example.net",
+  name: "test_cookie",
+  path: "/",
+};
+const COOKIE_ORG = {
+  host: "example.org",
+  name: "test_cookie",
+  path: "/",
+};
+let since, oldCookie;
+
+function addCookie(cookie) {
+  Services.cookies.add(
+    cookie.host,
+    cookie.path,
+    cookie.name,
+    "test",
+    false,
+    false,
+    false,
+    Date.now() / 1000 + 10000,
+    {},
+    Ci.nsICookie.SAMESITE_NONE,
+    Ci.nsICookie.SCHEME_HTTPS
+  );
+  ok(
+    Services.cookies.cookieExists(cookie.host, cookie.path, cookie.name, {}),
+    `Cookie ${cookie.name} was created.`
+  );
+}
+
+async function setUpCookies() {
+  Services.cookies.removeAll();
+
+  // Add a cookie which will end up with an older creationTime.
+  oldCookie = Object.assign({}, COOKIE, { name: Date.now() });
+  addCookie(oldCookie);
+  await new Promise(resolve => setTimeout(resolve, 10));
+  since = Date.now();
+  await new Promise(resolve => setTimeout(resolve, 10));
+
+  // Add a cookie which will end up with a more recent creationTime.
+  addCookie(COOKIE);
+
+  // Add cookies for different domains.
+  addCookie(COOKIE_NET);
+  addCookie(COOKIE_ORG);
+}
+
+async function setUpCache() {
+  Services.cache2.clear();
+
+  // Add cache entries for different domains.
+  for (const domain of ["example.net", "example.org", "example.com"]) {
+    await SiteDataTestUtils.addCacheEntry(`http://${domain}/`, "disk");
+    await SiteDataTestUtils.addCacheEntry(`http://${domain}/`, "memory");
+  }
+}
+
+function hasCacheEntry(domain) {
+  const disk = SiteDataTestUtils.hasCacheEntry(`http://${domain}/`, "disk");
+  const memory = SiteDataTestUtils.hasCacheEntry(`http://${domain}/`, "memory");
+
+  equal(
+    disk,
+    memory,
+    `For ${domain} either either both or neither caches need to exists.`
+  );
+  return disk;
+}
+
+add_task(async function testCache() {
+  function background() {
+    browser.test.onMessage.addListener(async msg => {
+      if (msg == "removeCache") {
+        await browser.browsingData.removeCache({});
+      } else {
+        await browser.browsingData.remove({}, { cache: true });
+      }
+      browser.test.sendMessage("cacheRemoved");
+    });
+  }
+
+  let extension = ExtensionTestUtils.loadExtension({
+    background,
+    manifest: {
+      permissions: ["browsingData"],
+    },
+  });
+
+  async function testRemovalMethod(method) {
+    await setUpCache();
+
+    extension.sendMessage(method);
+    await extension.awaitMessage("cacheRemoved");
+
+    ok(!hasCacheEntry("example.net"), "example.net cache was removed");
+    ok(!hasCacheEntry("example.org"), "example.org cache was removed");
+    ok(!hasCacheEntry("example.com"), "example.com cache was removed");
+  }
+
+  await extension.startup();
+
+  await testRemovalMethod("removeCache");
+  await testRemovalMethod("remove");
+
+  await extension.unload();
+});
+
+add_task(async function testCookies() {
+  // Above in setUpCookies we create an 'old' cookies, wait 10ms, then log a timestamp.
+  // Here we ask the browser to delete all cookies after the timestamp, with the intention
+  // that the 'old' cookie is not removed. The issue arises when the timer precision is
+  // low enough such that the timestamp that gets logged is the same as the 'old' cookie.
+  // We hardcode a precision value to ensure that there is time between the 'old' cookie
+  // and the timestamp generation.
+  Services.prefs.setBoolPref("privacy.reduceTimerPrecision", true);
+  Services.prefs.setIntPref(
+    "privacy.resistFingerprinting.reduceTimerPrecision.microseconds",
+    2000
+  );
+
+  registerCleanupFunction(function () {
+    Services.prefs.clearUserPref("privacy.reduceTimerPrecision");
+    Services.prefs.clearUserPref(
+      "privacy.resistFingerprinting.reduceTimerPrecision.microseconds"
+    );
+  });
+
+  function background() {
+    browser.test.onMessage.addListener(async (msg, options) => {
+      if (msg == "removeCookies") {
+        await browser.browsingData.removeCookies(options);
+      } else {
+        await browser.browsingData.remove(options, { cookies: true });
+      }
+      browser.test.sendMessage("cookiesRemoved");
+    });
+  }
+
+  let extension = ExtensionTestUtils.loadExtension({
+    background,
+    manifest: {
+      permissions: ["browsingData"],
+    },
+  });
+
+  async function testRemovalMethod(method) {
+    // Clear cookies with a recent since value.
+    await setUpCookies();
+    extension.sendMessage(method, { since });
+    await extension.awaitMessage("cookiesRemoved");
+
+    ok(
+      Services.cookies.cookieExists(
+        oldCookie.host,
+        oldCookie.path,
+        oldCookie.name,
+        {}
+      ),
+      "Old cookie was not removed."
+    );
+    ok(
+      !Services.cookies.cookieExists(COOKIE.host, COOKIE.path, COOKIE.name, {}),
+      "Recent cookie was removed."
+    );
+
+    // Clear cookies with an old since value.
+    await setUpCookies();
+    addCookie(COOKIE);
+    extension.sendMessage(method, { since: since - 100000 });
+    await extension.awaitMessage("cookiesRemoved");
+
+    ok(
+      !Services.cookies.cookieExists(
+        oldCookie.host,
+        oldCookie.path,
+        oldCookie.name,
+        {}
+      ),
+      "Old cookie was removed."
+    );
+    ok(
+      !Services.cookies.cookieExists(COOKIE.host, COOKIE.path, COOKIE.name, {}),
+      "Recent cookie was removed."
+    );
+
+    // Clear cookies with no since value and valid originTypes.
+    await setUpCookies();
+    extension.sendMessage(method, {
+      originTypes: { unprotectedWeb: true, protectedWeb: false },
+    });
+    await extension.awaitMessage("cookiesRemoved");
+
+    ok(
+      !Services.cookies.cookieExists(COOKIE.host, COOKIE.path, COOKIE.name, {}),
+      `Cookie ${COOKIE.name}  was removed.`
+    );
+    ok(
+      !Services.cookies.cookieExists(
+        oldCookie.host,
+        oldCookie.path,
+        oldCookie.name,
+        {}
+      ),
+      `Cookie ${oldCookie.name}  was removed.`
+    );
+  }
+
+  await extension.startup();
+
+  await testRemovalMethod("removeCookies");
+  await testRemovalMethod("remove");
+
+  await extension.unload();
+});
+
+add_task(async function testCacheAndCookies() {
+  function background() {
+    browser.test.onMessage.addListener(async options => {
+      await browser.browsingData.remove(options, {
+        cache: true,
+        cookies: true,
+      });
+      browser.test.sendMessage("cacheAndCookiesRemoved");
+    });
+  }
+
+  let extension = ExtensionTestUtils.loadExtension({
+    background,
+    manifest: {
+      permissions: ["browsingData"],
+    },
+  });
+
+  await extension.startup();
+
+  // Clear cache and cookies with a recent since value.
+  await setUpCookies();
+  await setUpCache();
+  extension.sendMessage({ since });
+  await extension.awaitMessage("cacheAndCookiesRemoved");
+
+  ok(
+    Services.cookies.cookieExists(
+      oldCookie.host,
+      oldCookie.path,
+      oldCookie.name,
+      {}
+    ),
+    "Old cookie was not removed."
+  );
+  ok(
+    !Services.cookies.cookieExists(COOKIE.host, COOKIE.path, COOKIE.name, {}),
+    "Recent cookie was removed."
+  );
+
+  // Cache does not support |since| and deletes everything!
+  ok(!hasCacheEntry("example.net"), "example.net cache was removed");
+  ok(!hasCacheEntry("example.org"), "example.org cache was removed");
+  ok(!hasCacheEntry("example.com"), "example.com cache was removed");
+
+  // Clear cache and cookies with an old since value.
+  await setUpCookies();
+  await setUpCache();
+  extension.sendMessage({ since: since - 100000 });
+  await extension.awaitMessage("cacheAndCookiesRemoved");
+
+  // Cache does not support |since| and deletes everything!
+  ok(!hasCacheEntry("example.net"), "example.net cache was removed");
+  ok(!hasCacheEntry("example.org"), "example.org cache was removed");
+  ok(!hasCacheEntry("example.com"), "example.com cache was removed");
+
+  ok(
+    !Services.cookies.cookieExists(
+      oldCookie.host,
+      oldCookie.path,
+      oldCookie.name,
+      {}
+    ),
+    "Old cookie was removed."
+  );
+  ok(
+    !Services.cookies.cookieExists(COOKIE.host, COOKIE.path, COOKIE.name, {}),
+    "Recent cookie was removed."
+  );
+
+  // Clear cache and cookies with hostnames value.
+  await setUpCookies();
+  await setUpCache();
+  extension.sendMessage({
+    hostnames: ["example.net", "example.org", "unknown.com"],
+  });
+  await extension.awaitMessage("cacheAndCookiesRemoved");
+
+  ok(
+    Services.cookies.cookieExists(COOKIE.host, COOKIE.path, COOKIE.name, {}),
+    `Cookie ${COOKIE.name}  was not removed.`
+  );
+  ok(
+    !Services.cookies.cookieExists(
+      COOKIE_NET.host,
+      COOKIE_NET.path,
+      COOKIE_NET.name,
+      {}
+    ),
+    `Cookie ${COOKIE_NET.name}  was removed.`
+  );
+  ok(
+    !Services.cookies.cookieExists(
+      COOKIE_ORG.host,
+      COOKIE_ORG.path,
+      COOKIE_ORG.name,
+      {}
+    ),
+    `Cookie ${COOKIE_ORG.name}  was removed.`
+  );
+
+  ok(!hasCacheEntry("example.net"), "example.net cache was removed");
+  ok(!hasCacheEntry("example.org"), "example.org cache was removed");
+  ok(hasCacheEntry("example.com"), "example.com cache was not removed");
+
+  // Clear cache and cookies with (empty) hostnames value.
+  await setUpCookies();
+  await setUpCache();
+  extension.sendMessage({ hostnames: [] });
+  await extension.awaitMessage("cacheAndCookiesRemoved");
+
+  ok(
+    Services.cookies.cookieExists(COOKIE.host, COOKIE.path, COOKIE.name, {}),
+    `Cookie ${COOKIE.name}  was not removed.`
+  );
+  ok(
+    Services.cookies.cookieExists(
+      COOKIE_NET.host,
+      COOKIE_NET.path,
+      COOKIE_NET.name,
+      {}
+    ),
+    `Cookie ${COOKIE_NET.name}  was not removed.`
+  );
+  ok(
+    Services.cookies.cookieExists(
+      COOKIE_ORG.host,
+      COOKIE_ORG.path,
+      COOKIE_ORG.name,
+      {}
+    ),
+    `Cookie ${COOKIE_ORG.name}  was not removed.`
+  );
+
+  ok(hasCacheEntry("example.net"), "example.net cache was not removed");
+  ok(hasCacheEntry("example.org"), "example.org cache was not removed");
+  ok(hasCacheEntry("example.com"), "example.com cache was not removed");
+
+  // Clear cache and cookies with both hostnames and since values.
+  await setUpCache();
+  await setUpCookies();
+  extension.sendMessage({ hostnames: ["example.com"], since });
+  await extension.awaitMessage("cacheAndCookiesRemoved");
+
+  ok(
+    Services.cookies.cookieExists(
+      oldCookie.host,
+      oldCookie.path,
+      oldCookie.name,
+      {}
+    ),
+    "Old cookie was not removed."
+  );
+  ok(
+    !Services.cookies.cookieExists(COOKIE.host, COOKIE.path, COOKIE.name, {}),
+    "Recent cookie was removed."
+  );
+  ok(
+    Services.cookies.cookieExists(
+      COOKIE_NET.host,
+      COOKIE_NET.path,
+      COOKIE_NET.name,
+      {}
+    ),
+    "Cookie with different hostname was not removed"
+  );
+  ok(
+    Services.cookies.cookieExists(
+      COOKIE_ORG.host,
+      COOKIE_ORG.path,
+      COOKIE_ORG.name,
+      {}
+    ),
+    "Cookie with different hostname was not removed"
+  );
+
+  ok(hasCacheEntry("example.net"), "example.net cache was not removed");
+  ok(hasCacheEntry("example.org"), "example.org cache was not removed");
+  ok(!hasCacheEntry("example.com"), "example.com cache was removed");
+
+  // Clear cache and cookies with no since or hostnames value.
+  await setUpCache();
+  await setUpCookies();
+  extension.sendMessage({});
+  await extension.awaitMessage("cacheAndCookiesRemoved");
+
+  ok(
+    !Services.cookies.cookieExists(COOKIE.host, COOKIE.path, COOKIE.name, {}),
+    `Cookie ${COOKIE.name}  was removed.`
+  );
+  ok(
+    !Services.cookies.cookieExists(
+      oldCookie.host,
+      oldCookie.path,
+      oldCookie.name,
+      {}
+    ),
+    `Cookie ${oldCookie.name}  was removed.`
+  );
+  ok(
+    !Services.cookies.cookieExists(
+      COOKIE_NET.host,
+      COOKIE_NET.path,
+      COOKIE_NET.name,
+      {}
+    ),
+    `Cookie ${COOKIE_NET.name}  was removed.`
+  );
+  ok(
+    !Services.cookies.cookieExists(
+      COOKIE_ORG.host,
+      COOKIE_ORG.path,
+      COOKIE_ORG.name,
+      {}
+    ),
+    `Cookie ${COOKIE_ORG.name}  was removed.`
+  );
+
+  ok(!hasCacheEntry("example.net"), "example.net cache was removed");
+  ok(!hasCacheEntry("example.org"), "example.org cache was removed");
+  ok(!hasCacheEntry("example.com"), "example.com cache was removed");
+
+  await extension.unload();
+});
diff --git a/toolkit/components/extensions/test/xpcshell/test_ext_browsingData_cookies_cookieStoreId.js b/toolkit/components/extensions/test/xpcshell/test_ext_browsingData_cookies_cookieStoreId.js
new file mode 100644
index 0000000000..d3d066efd2
--- /dev/null
+++ b/toolkit/components/extensions/test/xpcshell/test_ext_browsingData_cookies_cookieStoreId.js
@@ -0,0 +1,192 @@
+/* -*- Mode: indent-tabs-mode: nil; js-indent-level: 2 -*- */
+/* vim: set sts=2 sw=2 et tw=80: */
+/* eslint-disable mozilla/no-arbitrary-setTimeout */
+"use strict";
+
+// "Normal" cookie
+const COOKIE_NORMAL = {
+  host: "example.com",
+  name: "test_cookie",
+  path: "/",
+  originAttributes: {},
+};
+// Private browsing cookie
+const COOKIE_PRIVATE = {
+  host: "example.net",
+  name: "test_cookie",
+  path: "/",
+  originAttributes: {
+    privateBrowsingId: 1,
+  },
+};
+// "firefox-container-1" cookie
+const COOKIE_CONTAINER = {
+  host: "example.org",
+  name: "test_cookie",
+  path: "/",
+  originAttributes: {
+    userContextId: 1,
+  },
+};
+
+function cookieExists(cookie) {
+  return Services.cookies.cookieExists(
+    cookie.host,
+    cookie.path,
+    cookie.name,
+    cookie.originAttributes
+  );
+}
+
+function addCookie(cookie) {
+  const THE_FUTURE = Date.now() + 5 * 60;
+
+  Services.cookies.add(
+    cookie.host,
+    cookie.path,
+    cookie.name,
+    "test",
+    false,
+    false,
+    false,
+    THE_FUTURE,
+    cookie.originAttributes,
+    Ci.nsICookie.SAMESITE_NONE,
+    Ci.nsICookie.SCHEME_HTTPS
+  );
+
+  ok(cookieExists(cookie), `Cookie ${cookie.name} was created.`);
+}
+
+async function setUpCookies() {
+  Services.cookies.removeAll();
+
+  addCookie(COOKIE_NORMAL);
+  addCookie(COOKIE_PRIVATE);
+  addCookie(COOKIE_CONTAINER);
+}
+
+add_task(async function testCookies() {
+  Services.prefs.setBoolPref("privacy.userContext.enabled", true);
+
+  function background() {
+    browser.test.onMessage.addListener(async (msg, options) => {
+      if (msg == "removeCookies") {
+        await browser.browsingData.removeCookies(options);
+      } else {
+        await browser.browsingData.remove(options, { cookies: true });
+      }
+      browser.test.sendMessage("cookiesRemoved");
+    });
+  }
+
+  let extension = ExtensionTestUtils.loadExtension({
+    background,
+    manifest: {
+      permissions: ["browsingData"],
+    },
+  });
+
+  async function testRemovalMethod(method) {
+    // Clear only "normal"/default cookies.
+    await setUpCookies();
+
+    extension.sendMessage(method, { cookieStoreId: "firefox-default" });
+    await extension.awaitMessage("cookiesRemoved");
+
+    ok(!cookieExists(COOKIE_NORMAL), "Normal cookie was removed");
+    ok(cookieExists(COOKIE_PRIVATE), "Private cookie was not removed");
+    ok(cookieExists(COOKIE_CONTAINER), "Container cookie was not removed");
+
+    // Clear container cookie
+    await setUpCookies();
+
+    extension.sendMessage(method, { cookieStoreId: "firefox-container-1" });
+    await extension.awaitMessage("cookiesRemoved");
+
+    ok(cookieExists(COOKIE_NORMAL), "Normal cookie was not removed");
+    ok(cookieExists(COOKIE_PRIVATE), "Private cookie was not removed");
+    ok(!cookieExists(COOKIE_CONTAINER), "Container cookie was removed");
+
+    // Clear private cookie
+    await setUpCookies();
+
+    extension.sendMessage(method, { cookieStoreId: "firefox-private" });
+    await extension.awaitMessage("cookiesRemoved");
+
+    ok(cookieExists(COOKIE_NORMAL), "Normal cookie was not removed");
+    ok(!cookieExists(COOKIE_PRIVATE), "Private cookie was removed");
+    ok(cookieExists(COOKIE_CONTAINER), "Container cookie was not removed");
+
+    // Clear container cookie with correct hostname
+    await setUpCookies();
+
+    extension.sendMessage(method, {
+      cookieStoreId: "firefox-container-1",
+      hostnames: ["example.org"],
+    });
+    await extension.awaitMessage("cookiesRemoved");
+
+    ok(cookieExists(COOKIE_NORMAL), "Normal cookie was not removed");
+    ok(cookieExists(COOKIE_PRIVATE), "Private cookie was not removed");
+    ok(!cookieExists(COOKIE_CONTAINER), "Container cookie was removed");
+
+    // Clear container cookie with incorrect hostname; nothing is removed
+    await setUpCookies();
+
+    extension.sendMessage(method, {
+      cookieStoreId: "firefox-container-1",
+      hostnames: ["example.com"],
+    });
+    await extension.awaitMessage("cookiesRemoved");
+
+    ok(cookieExists(COOKIE_NORMAL), "Normal cookie was not removed");
+    ok(cookieExists(COOKIE_PRIVATE), "Private cookie was not removed");
+    ok(cookieExists(COOKIE_CONTAINER), "Container cookie was not removed");
+
+    // Clear private cookie with correct hostname
+    await setUpCookies();
+
+    extension.sendMessage(method, {
+      cookieStoreId: "firefox-private",
+      hostnames: ["example.net"],
+    });
+    await extension.awaitMessage("cookiesRemoved");
+
+    ok(cookieExists(COOKIE_NORMAL), "Normal cookie was not removed");
+    ok(!cookieExists(COOKIE_PRIVATE), "Private cookie was removed");
+    ok(cookieExists(COOKIE_CONTAINER), "Container cookie was not removed");
+
+    // Clear private cookie with incorrect hostname; nothing is removed
+    await setUpCookies();
+
+    extension.sendMessage(method, {
+      cookieStoreId: "firefox-private",
+      hostnames: ["example.com"],
+    });
+    await extension.awaitMessage("cookiesRemoved");
+
+    ok(cookieExists(COOKIE_NORMAL), "Normal cookie was not removed");
+    ok(cookieExists(COOKIE_PRIVATE), "Private cookie was not removed");
+    ok(cookieExists(COOKIE_CONTAINER), "Container cookie was not removed");
+
+    // Clear private cookie by hostname
+    await setUpCookies();
+
+    extension.sendMessage(method, {
+      hostnames: ["example.net"],
+    });
+    await extension.awaitMessage("cookiesRemoved");
+
+    ok(cookieExists(COOKIE_NORMAL), "Normal cookie was not removed");
+    ok(!cookieExists(COOKIE_PRIVATE), "Private cookie was removed");
+    ok(cookieExists(COOKIE_CONTAINER), "Container cookie was not removed");
+  }
+
+  await extension.startup();
+
+  await testRemovalMethod("removeCookies");
+  await testRemovalMethod("remove");
+
+  await extension.unload();
+});
diff --git a/toolkit/components/extensions/test/xpcshell/test_ext_cache_api.js b/toolkit/components/extensions/test/xpcshell/test_ext_cache_api.js
new file mode 100644
index 0000000000..ee00f4de83
--- /dev/null
+++ b/toolkit/components/extensions/test/xpcshell/test_ext_cache_api.js
@@ -0,0 +1,303 @@
+/* -*- Mode: indent-tabs-mode: nil; js-indent-level: 2 -*- */
+/* vim: set sts=2 sw=2 et tw=80: */
+
+"use strict";
+
+AddonTestUtils.init(this);
+AddonTestUtils.createAppInfo(
+  "xpcshell@tests.mozilla.org",
+  "XPCShell",
+  "1",
+  "42"
+);
+
+const server = createHttpServer({
+  hosts: ["example.com", "anotherdomain.com"],
+});
+server.registerPathHandler("/dummy", (request, response) => {
+  response.setStatusLine(request.httpVersion, 200, "OK");
+  response.setHeader("Content-Type", "text/html", false);
+  response.write("test_ext_cache_api.js");
+});
+
+add_task(async function test_cache_api_http_resource_allowed() {
+  async function background() {
+    try {
+      const BASE_URL = `http://example.com/dummy`;
+
+      const cache = await window.caches.open("test-cache-api");
+      browser.test.assertTrue(
+        await window.caches.has("test-cache-api"),
+        "CacheStorage.has should resolve to true"
+      );
+
+      // Test that adding and requesting cached http urls
+      // works as well.
+      await cache.add(BASE_URL);
+      browser.test.assertEq(
+        "test_ext_cache_api.js",
+        await cache.match(BASE_URL).then(res => res.text()),
+        "Got the expected content from the cached http url"
+      );
+
+      // Test that the http urls that the cache API is allowed
+      // to fetch and cache are limited by the host permissions
+      // associated to the extensions (same as when the extension
+      // for fetch from those urls using fetch or XHR).
+      await browser.test.assertRejects(
+        cache.add(`http://anotherdomain.com/dummy`),
+        "NetworkError when attempting to fetch resource.",
+        "Got the expected rejection of requesting an http not allowed by host permissions"
+      );
+
+      // Test that deleting the cache storage works as expected.
+      browser.test.assertTrue(
+        await window.caches.delete("test-cache-api"),
+        "Cache deleted successfully"
+      );
+      browser.test.assertTrue(
+        !(await window.caches.has("test-cache-api")),
+        "CacheStorage.has should resolve to false"
+      );
+    } catch (err) {
+      browser.test.fail(`Unexpected error on using Cache API: ${err}`);
+      throw err;
+    } finally {
+      browser.test.sendMessage("test-cache-api-allowed");
+    }
+  }
+
+  // Verify that Cache API support for http urls is available
+  // regardless of extensions.backgroundServiceWorker.enabled pref.
+  const extension = ExtensionTestUtils.loadExtension({
+    manifest: { permissions: ["http://example.com/*"] },
+    background,
+  });
+
+  await extension.startup();
+
+  await extension.awaitMessage("test-cache-api-allowed");
+  await extension.unload();
+});
+
+// This test is similar to `test_cache_api_http_resource_allowed` but it does
+// exercise the Cache API from a moz-extension shared worker.
+// We expect the cache API calls to be successfull when it is being used to
+// cache an HTTP url that is allowed for the extensions based on its host
+// permission, but to fail if the extension doesn't have the required host
+// permission to fetch data from that url.
+add_task(async function test_cache_api_from_ext_shared_worker() {
+  if (!WebExtensionPolicy.useRemoteWebExtensions) {
+    // Ensure RemoteWorkerService has been initialized in the main
+    // process.
+    Services.obs.notifyObservers(null, "profile-after-change");
+  }
+
+  const background = async function () {
+    const BASE_URL_OK = `http://example.com/dummy`;
+    const BASE_URL_KO = `http://anotherdomain.com/dummy`;
+    const worker = new SharedWorker("worker.js");
+    const { data: resultOK } = await new Promise(resolve => {
+      worker.port.onmessage = resolve;
+      worker.port.postMessage(["worker-cacheapi-test-allowed", BASE_URL_OK]);
+    });
+    browser.test.log(
+      `Got result from extension worker for allowed host url: ${JSON.stringify(
+        resultOK
+      )}`
+    );
+    const { data: resultKO } = await new Promise(resolve => {
+      worker.port.onmessage = resolve;
+      worker.port.postMessage(["worker-cacheapi-test-disallowed", BASE_URL_KO]);
+    });
+    browser.test.log(
+      `Got result from extension worker for disallowed host url: ${JSON.stringify(
+        resultKO
+      )}`
+    );
+
+    browser.test.assertTrue(
+      await window.caches.has("test-cache-api"),
+      "CacheStorage.has should resolve to true"
+    );
+    const cache = await window.caches.open("test-cache-api");
+    browser.test.assertEq(
+      "test_ext_cache_api.js",
+      await cache.match(BASE_URL_OK).then(res => res.text()),
+      "Got the expected content from the cached http url"
+    );
+    browser.test.assertEq(
+      true,
+      await cache.match(BASE_URL_KO).then(res => res == undefined),
+      "Got no match for the http url that isn't allowed by host permissions"
+    );
+
+    browser.test.sendMessage("test-cacheapi-sharedworker:done", {
+      expectAllowed: resultOK,
+      expectDisallowed: resultKO,
+    });
+  };
+
+  const extension = ExtensionTestUtils.loadExtension({
+    background,
+    manifest: { permissions: ["http://example.com/*"] },
+    files: {
+      "worker.js": function () {
+        self.onconnect = evt => {
+          const port = evt.ports[0];
+          port.onmessage = async evt => {
+            let result = {};
+            let message;
+            try {
+              const [msg, BASE_URL] = evt.data;
+              message = msg;
+              const cache = await self.caches.open("test-cache-api");
+              await cache.add(BASE_URL);
+              result.success = true;
+            } catch (err) {
+              result.error = err.message;
+              throw err;
+            } finally {
+              port.postMessage([`${message}:result`, result]);
+            }
+          };
+        };
+      },
+    },
+  });
+
+  await extension.startup();
+  const { expectAllowed, expectDisallowed } = await extension.awaitMessage(
+    "test-cacheapi-sharedworker:done"
+  );
+  // Increase the chance to have the error message related to an unexpected
+  // failure to be explicitly mention in the failure message.
+  Assert.deepEqual(
+    expectAllowed,
+    ["worker-cacheapi-test-allowed:result", { success: true }],
+    "Expect worker result to be successfull with the required host permission"
+  );
+  Assert.deepEqual(
+    expectDisallowed,
+    [
+      "worker-cacheapi-test-disallowed:result",
+      { error: "NetworkError when attempting to fetch resource." },
+    ],
+    "Expect worker result to be unsuccessfull without the required host permission"
+  );
+
+  await extension.unload();
+});
+
+add_task(async function test_cache_storage_evicted_on_addon_uninstalled() {
+  async function background() {
+    try {
+      const BASE_URL = `http://example.com/dummy`;
+
+      const cache = await window.caches.open("test-cache-api");
+      browser.test.assertTrue(
+        await window.caches.has("test-cache-api"),
+        "CacheStorage.has should resolve to true"
+      );
+
+      // Test that adding and requesting cached http urls
+      // works as well.
+      await cache.add(BASE_URL);
+      browser.test.assertEq(
+        "test_ext_cache_api.js",
+        await cache.match(BASE_URL).then(res => res.text()),
+        "Got the expected content from the cached http url"
+      );
+    } catch (err) {
+      browser.test.fail(`Unexpected error on using Cache API: ${err}`);
+      throw err;
+    } finally {
+      browser.test.sendMessage("cache-storage-created");
+    }
+  }
+
+  const extension = ExtensionTestUtils.loadExtension({
+    manifest: { permissions: ["http://example.com/*"] },
+    background,
+    // Necessary to be sure the expected extension stored data cleanup callback
+    // will be called when the extension is uninstalled from an AddonManager
+    // perspective.
+    useAddonManager: "temporary",
+  });
+
+  await AddonTestUtils.promiseStartupManager();
+  await extension.startup();
+  await extension.awaitMessage("cache-storage-created");
+
+  const extURL = `moz-extension://${extension.extension.uuid}`;
+  const extPrincipal = Services.scriptSecurityManager.createContentPrincipal(
+    Services.io.newURI(extURL),
+    {}
+  );
+  let extCacheStorage = new CacheStorage("content", extPrincipal);
+
+  ok(
+    await extCacheStorage.has("test-cache-api"),
+    "Got the expected extension cache storage"
+  );
+
+  await extension.unload();
+
+  ok(
+    !(await extCacheStorage.has("test-cache-api")),
+    "The extension cache storage data should have been evicted on addon uninstall"
+  );
+});
+
+add_task(
+  {
+    // Pref used to allow to use the Cache WebAPI related to a page loaded from http
+    // (otherwise Gecko will throw a SecurityError when trying to access the webpage
+    // cache storage from the content script, unless the webpage is loaded from https).
+    pref_set: [["dom.caches.testing.enabled", true]],
+  },
+  async function test_cache_put_from_contentscript() {
+    const extension = ExtensionTestUtils.loadExtension({
+      manifest: {
+        content_scripts: [
+          {
+            matches: ["http://example.com/*"],
+            js: ["content.js"],
+          },
+        ],
+      },
+      files: {
+        "content.js": async function () {
+          const cache = await caches.open("test-cachestorage");
+          const request = "http://example.com";
+          const response = await fetch(request);
+          await cache.put(request, response).catch(err => {
+            browser.test.sendMessage("cache-put-error", {
+              name: err.name,
+              message: err.message,
+            });
+          });
+        },
+      },
+    });
+
+    await extension.startup();
+
+    const page = await ExtensionTestUtils.loadContentPage("http://example.com");
+    const actualError = await extension.awaitMessage("cache-put-error");
+    equal(
+      actualError.name,
+      "SecurityError",
+      "Got a security error from cache.put call as expected"
+    );
+    ok(
+      /Disallowed on WebExtension ContentScript Request/.test(
+        actualError.message
+      ),
+      `Got the expected error message: ${actualError.message}`
+    );
+
+    await page.close();
+    await extension.unload();
+  }
+);
diff --git a/toolkit/components/extensions/test/xpcshell/test_ext_captivePortal.js b/toolkit/components/extensions/test/xpcshell/test_ext_captivePortal.js
new file mode 100644
index 0000000000..dfb5c4c415
--- /dev/null
+++ b/toolkit/components/extensions/test/xpcshell/test_ext_captivePortal.js
@@ -0,0 +1,202 @@
+"use strict";
+
+Services.prefs.setBoolPref(
+  "extensions.webextensions.background-delayed-startup",
+  true
+);
+
+AddonTestUtils.init(this);
+AddonTestUtils.overrideCertDB();
+AddonTestUtils.createAppInfo(
+  "xpcshell@tests.mozilla.org",
+  "XPCShell",
+  "1",
+  "43"
+);
+
+/**
+ * This duplicates the test from netwerk/test/unit/test_captive_portal_service.js
+ * however using an extension to gather the captive portal information.
+ */
+
+const PREF_CAPTIVE_ENABLED = "network.captive-portal-service.enabled";
+const PREF_CAPTIVE_TESTMODE = "network.captive-portal-service.testMode";
+const PREF_CAPTIVE_MINTIME = "network.captive-portal-service.minInterval";
+const PREF_CAPTIVE_ENDPOINT = "captivedetect.canonicalURL";
+const PREF_DNS_NATIVE_IS_LOCALHOST = "network.dns.native-is-localhost";
+
+const SUCCESS_STRING =
+  '<meta http-equiv="refresh" content="0;url=https://support.mozilla.org/kb/captive-portal"/>';
+let cpResponse = SUCCESS_STRING;
+
+const httpserver = createHttpServer();
+httpserver.registerPathHandler("/captive.txt", (request, response) => {
+  response.setStatusLine(request.httpVersion, 200, "OK");
+  response.setHeader("Content-Type", "text/plain");
+  response.write(cpResponse);
+});
+
+registerCleanupFunction(() => {
+  Services.prefs.clearUserPref(PREF_CAPTIVE_ENABLED);
+  Services.prefs.clearUserPref(PREF_CAPTIVE_TESTMODE);
+  Services.prefs.clearUserPref(PREF_CAPTIVE_ENDPOINT);
+  Services.prefs.clearUserPref(PREF_CAPTIVE_MINTIME);
+  Services.prefs.clearUserPref(PREF_DNS_NATIVE_IS_LOCALHOST);
+});
+
+add_task(async function setup() {
+  Services.prefs.setCharPref(
+    PREF_CAPTIVE_ENDPOINT,
+    `http://localhost:${httpserver.identity.primaryPort}/captive.txt`
+  );
+  Services.prefs.setBoolPref(PREF_CAPTIVE_TESTMODE, true);
+  Services.prefs.setIntPref(PREF_CAPTIVE_MINTIME, 0);
+  Services.prefs.setBoolPref(PREF_DNS_NATIVE_IS_LOCALHOST, true);
+
+  Services.prefs.setBoolPref("extensions.eventPages.enabled", true);
+  await AddonTestUtils.promiseStartupManager();
+});
+
+add_task(async function test_captivePortal_basic() {
+  let cps = Cc["@mozilla.org/network/captive-portal-service;1"].getService(
+    Ci.nsICaptivePortalService
+  );
+
+  let extension = ExtensionTestUtils.loadExtension({
+    useAddonManager: "permanent",
+    manifest: {
+      permissions: ["captivePortal"],
+      background: { persistent: false },
+    },
+    isPrivileged: true,
+    async background() {
+      browser.captivePortal.onConnectivityAvailable.addListener(details => {
+        browser.test.log(
+          `onConnectivityAvailable received ${JSON.stringify(details)}`
+        );
+        browser.test.sendMessage("connectivity", details);
+      });
+
+      browser.captivePortal.onStateChanged.addListener(details => {
+        browser.test.log(`onStateChanged received ${JSON.stringify(details)}`);
+        browser.test.sendMessage("state", details);
+      });
+
+      browser.captivePortal.canonicalURL.onChange.addListener(details => {
+        browser.test.sendMessage("url", details);
+      });
+
+      browser.test.onMessage.addListener(async msg => {
+        if (msg == "getstate") {
+          browser.test.sendMessage(
+            "getstate",
+            await browser.captivePortal.getState()
+          );
+        }
+      });
+    },
+  });
+  await extension.startup();
+
+  extension.sendMessage("getstate");
+  let details = await extension.awaitMessage("getstate");
+  equal(details, "unknown", "initial state");
+
+  // The captive portal service is started by nsIOService when the pref becomes true, so we
+  // toggle the pref.  We cannot set to false before the extension loads above.
+  Services.prefs.setBoolPref(PREF_CAPTIVE_ENABLED, false);
+  Services.prefs.setBoolPref(PREF_CAPTIVE_ENABLED, true);
+
+  details = await extension.awaitMessage("connectivity");
+  equal(details.status, "clear", "initial connectivity");
+  extension.sendMessage("getstate");
+  details = await extension.awaitMessage("getstate");
+  equal(details, "not_captive", "initial state");
+
+  info("REFRESH to other");
+  cpResponse = "other";
+  cps.recheckCaptivePortal();
+  details = await extension.awaitMessage("state");
+  equal(details.state, "locked_portal", "state in portal");
+
+  info("REFRESH to success");
+  cpResponse = SUCCESS_STRING;
+  cps.recheckCaptivePortal();
+  details = await extension.awaitMessage("connectivity");
+  equal(details.status, "captive", "final connectivity");
+
+  details = await extension.awaitMessage("state");
+  equal(details.state, "unlocked_portal", "state after unlocking portal");
+
+  assertPersistentListeners(
+    extension,
+    "captivePortal",
+    "onConnectivityAvailable",
+    {
+      primed: false,
+    }
+  );
+
+  assertPersistentListeners(extension, "captivePortal", "onStateChanged", {
+    primed: false,
+  });
+
+  assertPersistentListeners(extension, "captivePortal", "captiveURL.onChange", {
+    primed: false,
+  });
+
+  info("Test event page terminate/waken");
+
+  await extension.terminateBackground({ disableResetIdleForTest: true });
+  ok(
+    !extension.extension.backgroundContext,
+    "Background Extension context should have been destroyed"
+  );
+
+  assertPersistentListeners(extension, "captivePortal", "onStateChanged", {
+    primed: true,
+  });
+  assertPersistentListeners(
+    extension,
+    "captivePortal",
+    "onConnectivityAvailable",
+    {
+      primed: true,
+    }
+  );
+
+  assertPersistentListeners(extension, "captivePortal", "captiveURL.onChange", {
+    primed: true,
+  });
+
+  info("REFRESH 2nd pass to other");
+  cpResponse = "other";
+  cps.recheckCaptivePortal();
+  details = await extension.awaitMessage("state");
+  equal(details.state, "locked_portal", "state in portal");
+
+  info("Test event page terminate/waken with settings");
+
+  await extension.terminateBackground({ disableResetIdleForTest: true });
+  ok(
+    !extension.extension.backgroundContext,
+    "Background Extension context should have been destroyed"
+  );
+
+  assertPersistentListeners(extension, "captivePortal", "captiveURL.onChange", {
+    primed: true,
+  });
+
+  Services.prefs.setStringPref(
+    "captivedetect.canonicalURL",
+    "http://example.com"
+  );
+  let url = await extension.awaitMessage("url");
+  equal(
+    url.value,
+    "http://example.com",
+    "The canonicalURL setting has the expected value."
+  );
+
+  await extension.unload();
+});
diff --git a/toolkit/components/extensions/test/xpcshell/test_ext_captivePortal_url.js b/toolkit/components/extensions/test/xpcshell/test_ext_captivePortal_url.js
new file mode 100644
index 0000000000..7bd83b0572
--- /dev/null
+++ b/toolkit/components/extensions/test/xpcshell/test_ext_captivePortal_url.js
@@ -0,0 +1,53 @@
+/* -*- Mode: indent-tabs-mode: nil; js-indent-level: 2 -*- */
+/* vim: set sts=2 sw=2 et tw=80: */
+"use strict";
+
+add_task(async function test_url_get_without_set() {
+  async function background() {
+    browser.captivePortal.canonicalURL.onChange.addListener(details => {
+      browser.test.sendMessage("url", details);
+    });
+    let url = await browser.captivePortal.canonicalURL.get({});
+    browser.test.sendMessage("url", url);
+  }
+
+  let extension = ExtensionTestUtils.loadExtension({
+    background,
+    manifest: {
+      permissions: ["captivePortal"],
+    },
+  });
+
+  let defaultURL = Services.prefs.getStringPref("captivedetect.canonicalURL");
+
+  await extension.startup();
+  let url = await extension.awaitMessage("url");
+  equal(
+    url.value,
+    defaultURL,
+    "The canonicalURL setting has the expected value."
+  );
+  equal(
+    url.levelOfControl,
+    "not_controllable",
+    "The canonicalURL setting has the expected levelOfControl."
+  );
+
+  Services.prefs.setStringPref(
+    "captivedetect.canonicalURL",
+    "http://example.com"
+  );
+  url = await extension.awaitMessage("url");
+  equal(
+    url.value,
+    "http://example.com",
+    "The canonicalURL setting has the expected value."
+  );
+  equal(
+    url.levelOfControl,
+    "not_controllable",
+    "The canonicalURL setting has the expected levelOfControl."
+  );
+
+  await extension.unload();
+});
diff --git a/toolkit/components/extensions/test/xpcshell/test_ext_clear_cached_resources.js b/toolkit/components/extensions/test/xpcshell/test_ext_clear_cached_resources.js
new file mode 100644
index 0000000000..e4f9f1d40b
--- /dev/null
+++ b/toolkit/components/extensions/test/xpcshell/test_ext_clear_cached_resources.js
@@ -0,0 +1,417 @@
+/* -*- Mode: indent-tabs-mode: nil; js-indent-level: 2 -*- */
+/* vim: set sts=2 sw=2 et tw=80: */
+
+"use strict";
+
+Services.prefs.setBoolPref("extensions.blocklist.enabled", false);
+
+AddonTestUtils.init(this);
+AddonTestUtils.overrideCertDB();
+AddonTestUtils.createAppInfo(
+  "xpcshell@tests.mozilla.org",
+  "XPCShell",
+  "1",
+  "43"
+);
+
+const { AddonManager } = ChromeUtils.importESModule(
+  "resource://gre/modules/AddonManager.sys.mjs"
+);
+
+const LEAVE_UUID_PREF = "extensions.webextensions.keepUuidOnUninstall";
+
+const BASE64_R_PIXEL =
+  "iVBORw0KGgoAAAANSUhEUgAAAAEAAAABCAYAAAAfFcSJAAAADUlEQVQIW2P4z8DwHwAFAAH/F1FwBgAAAABJRU5ErkJggg==";
+const BASE64_G_PIXEL =
+  "iVBORw0KGgoAAAANSUhEUgAAAAEAAAABCAYAAAAfFcSJAAAADUlEQVQIW2Ng+M/wHwAEAQH/7yMK/gAAAABJRU5ErkJggg==";
+const BASE64_B_PIXEL =
+  "iVBORw0KGgoAAAANSUhEUgAAAAEAAAABCAYAAAAfFcSJAAAADUlEQVQIW2NgYPj/HwADAgH/eL9GtQAAAABJRU5ErkJggg==";
+
+const toArrayBuffer = b64data =>
+  Uint8Array.from(atob(b64data), c => c.charCodeAt(0));
+const IMAGE_RED = toArrayBuffer(BASE64_R_PIXEL).buffer;
+const IMAGE_GREEN = toArrayBuffer(BASE64_G_PIXEL).buffer;
+const IMAGE_BLUE = toArrayBuffer(BASE64_B_PIXEL).buffer;
+
+const RGB_RED = "rgb(255, 0, 0)";
+const RGB_GREEN = "rgb(0, 255, 0)";
+const RGB_BLUE = "rgb(0, 0, 255)";
+
+const CSS_RED_BG = `body { background-color: ${RGB_RED}; }`;
+const CSS_GREEN_BG = `body { background-color: ${RGB_GREEN}; }`;
+const CSS_BLUE_BG = `body { background-color: ${RGB_BLUE}; }`;
+
+const ADDON_ID = "test-cached-resources@test";
+
+const manifest = {
+  version: "1",
+  browser_specific_settings: { gecko: { id: ADDON_ID } },
+};
+
+const files = {
+  "extpage.html": `<!DOCTYPE html>
+     <html>
+       <head>
+         <link rel="stylesheet" href="extpage.css">
+       </head>
+       <body>
+         <img id="test-image" src="image.png">
+       </body>
+     </html>
+  `,
+  "other_extpage.html": `<!DOCTYPE html>
+     <html>
+       <body>
+       </body>
+     </html>
+  `,
+  "extpage.css": CSS_RED_BG,
+  "image.png": IMAGE_RED,
+};
+
+const getBackgroundColor = () => {
+  return this.content.getComputedStyle(this.content.document.body)
+    .backgroundColor;
+};
+
+const hasCachedImage = imgUrl => {
+  const { document } = this.content;
+
+  const imageCache = Cc["@mozilla.org/image/tools;1"]
+    .getService(Ci.imgITools)
+    .getImgCacheForDocument(document);
+
+  const imgCacheProps = imageCache.findEntryProperties(
+    Services.io.newURI(imgUrl),
+    document
+  );
+
+  // return true if the image was in the cache.
+  return !!imgCacheProps;
+};
+
+const getImageColor = () => {
+  const { document } = this.content;
+  const img = document.querySelector("img#test-image");
+  const canvas = document.createElement("canvas");
+  canvas.width = 1;
+  canvas.height = 1;
+  const ctx = canvas.getContext("2d");
+  ctx.drawImage(img, 0, 0); // Draw without scaling.
+  const [r, g, b, a] = ctx.getImageData(0, 0, 1, 1).data;
+  if (a < 1) {
+    return `rgba(${r}, ${g}, ${b}, ${a})`;
+  }
+  return `rgb(${r}, ${g}, ${b})`;
+};
+
+async function assertBackgroundColor(page, color, message) {
+  equal(
+    await page.spawn([], getBackgroundColor),
+    color,
+    `Got the expected ${message}`
+  );
+}
+
+async function assertImageColor(page, color, message) {
+  equal(await page.spawn([], getImageColor), color, message);
+}
+
+async function assertImageCached(page, imageUrl, message) {
+  ok(await page.spawn([imageUrl], hasCachedImage), message);
+}
+
+// This test verifies that cached css are cleared across addon upgrades and downgrades
+// for permanently installed addon (See Bug 1746841).
+add_task(async function test_cached_resources_cleared_across_addon_updates() {
+  await AddonTestUtils.promiseStartupManager();
+
+  const extension = ExtensionTestUtils.loadExtension({
+    useAddonManager: "permanent",
+    manifest,
+    files,
+  });
+
+  await extension.startup();
+  equal(
+    extension.version,
+    "1",
+    "Got the expected version for the initial extension"
+  );
+
+  const url = extension.extension.baseURI.resolve("extpage.html");
+  let page = await ExtensionTestUtils.loadContentPage(url);
+  await assertBackgroundColor(
+    page,
+    RGB_RED,
+    "background color (initial extension version)"
+  );
+  await assertImageColor(page, RGB_RED, "image (initial extension version)");
+
+  info("Verify extension page css and image after addon upgrade");
+
+  await extension.upgrade({
+    useAddonManager: "permanent",
+    manifest: {
+      ...manifest,
+      version: "2",
+    },
+    files: {
+      ...files,
+      "extpage.css": CSS_GREEN_BG,
+      "image.png": IMAGE_GREEN,
+    },
+  });
+  equal(
+    extension.version,
+    "2",
+    "Got the expected version for the upgraded extension"
+  );
+
+  await page.loadURL(url);
+
+  await assertBackgroundColor(
+    page,
+    RGB_GREEN,
+    "background color (upgraded extension version)"
+  );
+  await assertImageColor(page, RGB_GREEN, "image (upgraded extension version)");
+
+  info("Verify extension page css and image after addon downgrade");
+
+  await extension.upgrade({
+    useAddonManager: "permanent",
+    manifest,
+    files,
+  });
+  equal(
+    extension.version,
+    "1",
+    "Got the expected version for the downgraded extension"
+  );
+
+  await page.loadURL(url);
+
+  await assertBackgroundColor(
+    page,
+    RGB_RED,
+    "background color (downgraded extension version)"
+  );
+  await assertImageColor(
+    page,
+    RGB_RED,
+    "image color (downgraded extension version)"
+  );
+
+  await page.close();
+  await extension.unload();
+  await AddonTestUtils.promiseShutdownManager();
+});
+
+// This test verifies that cached css are cleared if we are installing a new
+// extension and we did not clear the cache for a previous one with the same uuid
+// when it was uninstalled (See Bug 1746841).
+add_task(async function test_cached_resources_cleared_on_addon_install() {
+  // Make sure the test addon installed without an AddonManager addon wrapper
+  // and the ones installed right after that using the AddonManager will share
+  // the same uuid (and so also the same moz-extension resource urls).
+  Services.prefs.setBoolPref(LEAVE_UUID_PREF, true);
+  registerCleanupFunction(() => Services.prefs.clearUserPref(LEAVE_UUID_PREF));
+
+  await AddonTestUtils.promiseStartupManager();
+
+  const nonAOMExtension = ExtensionTestUtils.loadExtension({
+    manifest,
+    files: {
+      ...files,
+      // Override css with a different color from the one expected
+      // later in this test case.
+      "extpage.css": CSS_BLUE_BG,
+      "image.png": IMAGE_BLUE,
+    },
+  });
+
+  await nonAOMExtension.startup();
+  equal(
+    await AddonManager.getAddonByID(ADDON_ID),
+    null,
+    "No AOM addon wrapper found as expected"
+  );
+  let url = nonAOMExtension.extension.baseURI.resolve("extpage.html");
+  let page = await ExtensionTestUtils.loadContentPage(url);
+  await assertBackgroundColor(
+    page,
+    RGB_BLUE,
+    "background color (addon installed without uninstall observer)"
+  );
+  await assertImageColor(
+    page,
+    RGB_BLUE,
+    "image (addon uninstalled without clearing cache)"
+  );
+
+  // NOTE: unloading a test extension that does not have an AddonManager addon wrapper
+  // does not trigger the uninstall observer, and this is what this test needs to make
+  // sure that if the cached resources were not cleared on uninstall, then we will still
+  // clear it when a newly installed addon is installed even if the two extensions
+  // are sharing the same addon uuid (and so also the same moz-extension resource urls).
+  await nonAOMExtension.unload();
+
+  const extension = ExtensionTestUtils.loadExtension({
+    useAddonManager: "permanent",
+    manifest,
+    files,
+  });
+
+  await extension.startup();
+  await page.loadURL(url);
+
+  await assertBackgroundColor(
+    page,
+    RGB_RED,
+    "background color (newly installed addon, same addon id)"
+  );
+  await assertImageColor(
+    page,
+    RGB_RED,
+    "image (newly installed addon, same addon id)"
+  );
+
+  await page.close();
+  await extension.unload();
+  await AddonTestUtils.promiseShutdownManager();
+});
+
+// This test verifies that reloading a temporarily installed addon after
+// changing a css file cached in a previous run clears the previously
+// cached css and uses the new one changed on disk (See Bug 1746841).
+add_task(
+  async function test_cached_resources_cleared_on_temporary_addon_reload() {
+    await AddonTestUtils.promiseStartupManager();
+
+    const xpi = AddonTestUtils.createTempWebExtensionFile({
+      manifest,
+      files,
+    });
+
+    // This temporary directory is going to be removed from the
+    // cleanup function, but also make it unique as we do for the
+    // other temporary files (e.g. like getTemporaryFile as defined
+    // in XPInstall.jsm).
+    const random = Math.round(Math.random() * 36 ** 3).toString(36);
+    const tmpDirName = `xpcshelltest_unpacked_addons_${random}`;
+    let tmpExtPath = FileUtils.getDir("TmpD", [tmpDirName], true);
+    registerCleanupFunction(() => {
+      tmpExtPath.remove(true);
+    });
+
+    // Unpacking the xpi file into the temporary directory.
+    const extDir = await AddonTestUtils.manuallyInstall(
+      xpi,
+      tmpExtPath,
+      null,
+      /* unpacked */ true
+    );
+
+    let extension = ExtensionTestUtils.expectExtension(ADDON_ID);
+    await AddonManager.installTemporaryAddon(extDir);
+    await extension.awaitStartup();
+
+    equal(
+      extension.version,
+      "1",
+      "Got the expected version for the initial extension"
+    );
+
+    const url = extension.extension.baseURI.resolve("extpage.html");
+    let page = await ExtensionTestUtils.loadContentPage(url);
+    await assertBackgroundColor(
+      page,
+      RGB_RED,
+      "background color (initial extension version)"
+    );
+    await assertImageColor(page, RGB_RED, "image (initial extension version)");
+
+    info("Verify updated extension page css and image after addon reload");
+
+    const targetCSSFile = extDir.clone();
+    targetCSSFile.append("extpage.css");
+    ok(
+      targetCSSFile.exists(),
+      `Found the ${targetCSSFile.path} target file on disk`
+    );
+    await IOUtils.writeUTF8(targetCSSFile.path, CSS_GREEN_BG);
+
+    const targetPNGFile = extDir.clone();
+    targetPNGFile.append("image.png");
+    ok(
+      targetPNGFile.exists(),
+      `Found the ${targetPNGFile.path} target file on disk`
+    );
+    await IOUtils.write(targetPNGFile.path, toArrayBuffer(BASE64_G_PIXEL));
+
+    const addon = await AddonManager.getAddonByID(ADDON_ID);
+    ok(addon, "Got an AddonWrapper for the test extension");
+    await addon.reload();
+
+    await page.loadURL(url);
+
+    await assertBackgroundColor(
+      page,
+      RGB_GREEN,
+      "background (updated files on disk)"
+    );
+    await assertImageColor(page, RGB_GREEN, "image (updated files on disk)");
+
+    await page.close();
+    await addon.uninstall();
+    await AddonTestUtils.promiseShutdownManager();
+  }
+);
+
+// This test verifies that cached images are not cleared between
+// permanently installed addon reloads.
+add_task(async function test_cached_image_kept_on_permanent_addon_restarts() {
+  await AddonTestUtils.promiseStartupManager();
+  const extension = ExtensionTestUtils.loadExtension({
+    useAddonManager: "permanent",
+    manifest,
+    files,
+  });
+
+  await extension.startup();
+
+  equal(
+    extension.version,
+    "1",
+    "Got the expected version for the initial extension"
+  );
+
+  const imageUrl = extension.extension.baseURI.resolve("image.png");
+  const url = extension.extension.baseURI.resolve("extpage.html");
+
+  let page = await ExtensionTestUtils.loadContentPage(url);
+  await assertBackgroundColor(
+    page,
+    RGB_RED,
+    "background color (first startup)"
+  );
+  await assertImageColor(page, RGB_RED, "image (first startup)");
+  await assertImageCached(page, imageUrl, "image cached (first startup)");
+
+  info("Reload the AddonManager to simulate browser restart");
+  extension.setRestarting();
+  await AddonTestUtils.promiseRestartManager();
+  await extension.awaitStartup();
+
+  await page.loadURL(extension.extension.baseURI.resolve("other_extpage.html"));
+  await assertImageCached(
+    page,
+    imageUrl,
+    "image still cached after AddonManager restart"
+  );
+
+  await page.close();
+  await extension.unload();
+  await AddonTestUtils.promiseShutdownManager();
+});
diff --git a/toolkit/components/extensions/test/xpcshell/test_ext_contentScripts_register.js b/toolkit/components/extensions/test/xpcshell/test_ext_contentScripts_register.js
new file mode 100644
index 0000000000..c92ed11022
--- /dev/null
+++ b/toolkit/components/extensions/test/xpcshell/test_ext_contentScripts_register.js
@@ -0,0 +1,808 @@
+"use strict";
+
+const { createAppInfo } = AddonTestUtils;
+
+AddonTestUtils.init(this);
+
+createAppInfo("xpcshell@tests.mozilla.org", "XPCShell", "1", "49");
+
+const server = createHttpServer();
+server.registerDirectory("/data/", do_get_file("data"));
+
+const BASE_URL = `http://localhost:${server.identity.primaryPort}/data`;
+
+function check_applied_styles() {
+  const urlElStyle = getComputedStyle(
+    document.querySelector("#registered-extension-url-style")
+  );
+  const blobElStyle = getComputedStyle(
+    document.querySelector("#registered-extension-text-style")
+  );
+
+  browser.test.sendMessage("registered-styles-results", {
+    registeredExtensionUrlStyleBG: urlElStyle["background-color"],
+    registeredExtensionBlobStyleBG: blobElStyle["background-color"],
+  });
+}
+
+add_task(async function test_contentscripts_register_css() {
+  async function background() {
+    let cssCode = `
+      #registered-extension-text-style {
+        background-color: blue;
+      }
+    `;
+
+    const matches = ["http://localhost/*/file_sample_registered_styles.html"];
+
+    browser.test.assertThrows(
+      () => {
+        browser.contentScripts.register({
+          matches,
+          unknownParam: "unexpected property",
+        });
+      },
+      /Unexpected property "unknownParam"/,
+      "contentScripts.register throws on unexpected properties"
+    );
+
+    let fileScript = await browser.contentScripts.register({
+      css: [{ file: "registered_ext_style.css" }],
+      matches,
+      runAt: "document_start",
+    });
+
+    let textScript = await browser.contentScripts.register({
+      css: [{ code: cssCode }],
+      matches,
+      runAt: "document_start",
+    });
+
+    browser.test.onMessage.addListener(async msg => {
+      switch (msg) {
+        case "unregister-text":
+          await textScript.unregister().catch(err => {
+            browser.test.fail(
+              `Unexpected exception while unregistering text style: ${err}`
+            );
+          });
+
+          await browser.test.assertRejects(
+            textScript.unregister(),
+            /Content script already unregistered/,
+            "Got the expected rejection on calling script.unregister() multiple times"
+          );
+
+          browser.test.sendMessage("unregister-text:done");
+          break;
+        case "unregister-file":
+          await fileScript.unregister().catch(err => {
+            browser.test.fail(
+              `Unexpected exception while unregistering url style: ${err}`
+            );
+          });
+
+          await browser.test.assertRejects(
+            fileScript.unregister(),
+            /Content script already unregistered/,
+            "Got the expected rejection on calling script.unregister() multiple times"
+          );
+
+          browser.test.sendMessage("unregister-file:done");
+          break;
+        default:
+          browser.test.fail(`Unexpected test message received: ${msg}`);
+      }
+    });
+
+    browser.test.sendMessage("background_ready");
+  }
+
+  let extension = ExtensionTestUtils.loadExtension({
+    manifest: {
+      permissions: [
+        "http://localhost/*/file_sample_registered_styles.html",
+        "<all_urls>",
+      ],
+      content_scripts: [
+        {
+          matches: ["http://localhost/*/file_sample_registered_styles.html"],
+          run_at: "document_idle",
+          js: ["check_applied_styles.js"],
+        },
+      ],
+    },
+    background,
+
+    files: {
+      "check_applied_styles.js": check_applied_styles,
+      "registered_ext_style.css": `
+        #registered-extension-url-style {
+          background-color: red;
+        }
+      `,
+    },
+  });
+
+  await extension.startup();
+
+  await extension.awaitMessage("background_ready");
+
+  // Ensure that a content page running in a content process and which has been
+  // started after the content scripts has been registered, it still receives
+  // and registers the expected content scripts.
+  let contentPage = await ExtensionTestUtils.loadContentPage(`about:blank`);
+
+  await contentPage.loadURL(`${BASE_URL}/file_sample_registered_styles.html`);
+
+  const registeredStylesResults = await extension.awaitMessage(
+    "registered-styles-results"
+  );
+
+  equal(
+    registeredStylesResults.registeredExtensionUrlStyleBG,
+    "rgb(255, 0, 0)",
+    "The expected style has been applied from the registered extension url style"
+  );
+  equal(
+    registeredStylesResults.registeredExtensionBlobStyleBG,
+    "rgb(0, 0, 255)",
+    "The expected style has been applied from the registered extension blob style"
+  );
+
+  extension.sendMessage("unregister-file");
+  await extension.awaitMessage("unregister-file:done");
+
+  await contentPage.loadURL(`${BASE_URL}/file_sample_registered_styles.html`);
+
+  const unregisteredURLStylesResults = await extension.awaitMessage(
+    "registered-styles-results"
+  );
+
+  equal(
+    unregisteredURLStylesResults.registeredExtensionUrlStyleBG,
+    "rgba(0, 0, 0, 0)",
+    "The expected style has been applied once extension url style has been unregistered"
+  );
+  equal(
+    unregisteredURLStylesResults.registeredExtensionBlobStyleBG,
+    "rgb(0, 0, 255)",
+    "The expected style has been applied from the registered extension blob style"
+  );
+
+  extension.sendMessage("unregister-text");
+  await extension.awaitMessage("unregister-text:done");
+
+  await contentPage.loadURL(`${BASE_URL}/file_sample_registered_styles.html`);
+
+  const unregisteredBlobStylesResults = await extension.awaitMessage(
+    "registered-styles-results"
+  );
+
+  equal(
+    unregisteredBlobStylesResults.registeredExtensionUrlStyleBG,
+    "rgba(0, 0, 0, 0)",
+    "The expected style has been applied once extension url style has been unregistered"
+  );
+  equal(
+    unregisteredBlobStylesResults.registeredExtensionBlobStyleBG,
+    "rgba(0, 0, 0, 0)",
+    "The expected style has been applied once extension blob style has been unregistered"
+  );
+
+  await contentPage.close();
+  await extension.unload();
+});
+
+add_task(async function test_contentscripts_unregister_on_context_unload() {
+  async function background() {
+    const frame = document.createElement("iframe");
+    frame.setAttribute("src", "/background-frame.html");
+
+    document.body.appendChild(frame);
+
+    browser.test.onMessage.addListener(msg => {
+      switch (msg) {
+        case "unload-frame":
+          frame.remove();
+          browser.test.sendMessage("unload-frame:done");
+          break;
+        default:
+          browser.test.fail(`Unexpected test message received: ${msg}`);
+      }
+    });
+
+    browser.test.sendMessage("background_ready");
+  }
+
+  async function background_frame() {
+    await browser.contentScripts.register({
+      css: [{ file: "registered_ext_style.css" }],
+      matches: ["http://localhost/*/file_sample_registered_styles.html"],
+      runAt: "document_start",
+    });
+
+    browser.test.sendMessage("background_frame_ready");
+  }
+
+  let extension = ExtensionTestUtils.loadExtension({
+    manifest: {
+      permissions: ["http://localhost/*/file_sample_registered_styles.html"],
+      content_scripts: [
+        {
+          matches: ["http://localhost/*/file_sample_registered_styles.html"],
+          run_at: "document_idle",
+          js: ["check_applied_styles.js"],
+        },
+      ],
+    },
+    background,
+
+    files: {
+      "background-frame.html": `<!DOCTYPE html>
+        <html>
+          <head>
+            <script src="background-frame.js"></script>
+          </head>
+          <body>
+          </body>
+        </html>
+      `,
+      "background-frame.js": background_frame,
+      "check_applied_styles.js": check_applied_styles,
+      "registered_ext_style.css": `
+        #registered-extension-url-style {
+          background-color: red;
+        }
+      `,
+    },
+  });
+
+  await extension.startup();
+
+  await extension.awaitMessage("background_ready");
+
+  // Wait the background frame to have been loaded and its script
+  // executed.
+  await extension.awaitMessage("background_frame_ready");
+
+  // Ensure that a content page running in a content process and which has been
+  // started after the content scripts has been registered, it still receives
+  // and registers the expected content scripts.
+  let contentPage = await ExtensionTestUtils.loadContentPage(`about:blank`);
+
+  await contentPage.loadURL(`${BASE_URL}/file_sample_registered_styles.html`);
+
+  const registeredStylesResults = await extension.awaitMessage(
+    "registered-styles-results"
+  );
+
+  equal(
+    registeredStylesResults.registeredExtensionUrlStyleBG,
+    "rgb(255, 0, 0)",
+    "The expected style has been applied from the registered extension url style"
+  );
+
+  extension.sendMessage("unload-frame");
+  await extension.awaitMessage("unload-frame:done");
+
+  await contentPage.loadURL(`${BASE_URL}/file_sample_registered_styles.html`);
+
+  const unregisteredURLStylesResults = await extension.awaitMessage(
+    "registered-styles-results"
+  );
+
+  equal(
+    unregisteredURLStylesResults.registeredExtensionUrlStyleBG,
+    "rgba(0, 0, 0, 0)",
+    "The expected style has been applied once extension url style has been unregistered"
+  );
+
+  await contentPage.close();
+  await extension.unload();
+});
+
+add_task(async function test_contentscripts_register_js() {
+  async function background() {
+    browser.runtime.onMessage.addListener(
+      ([msg, expectedStates, readyState], sender) => {
+        if (msg == "chrome-namespace-ok") {
+          browser.test.sendMessage(msg);
+          return;
+        }
+
+        browser.test.assertEq("script-run", msg, "message type is correct");
+        browser.test.assertTrue(
+          expectedStates.includes(readyState),
+          `readyState "${readyState}" is one of [${expectedStates}]`
+        );
+        browser.test.sendMessage("script-run-" + expectedStates[0]);
+      }
+    );
+
+    // Raise an exception when the content script cannot be registered
+    // because the extension has no permission to access the specified origin.
+
+    await browser.test.assertRejects(
+      browser.contentScripts.register({
+        matches: ["http://*/*"],
+        js: [
+          {
+            code: 'browser.test.fail("content script with wrong matches should not run")',
+          },
+        ],
+      }),
+      /Permission denied to register a content script for/,
+      "The reject contains the expected error message"
+    );
+
+    // Register a content script from a JS code string.
+
+    function textScriptCodeStart() {
+      browser.runtime.sendMessage([
+        "script-run",
+        ["loading"],
+        document.readyState,
+      ]);
+    }
+    function textScriptCodeEnd() {
+      browser.runtime.sendMessage([
+        "script-run",
+        ["interactive", "complete"],
+        document.readyState,
+      ]);
+    }
+    function textScriptCodeIdle() {
+      browser.runtime.sendMessage([
+        "script-run",
+        ["complete"],
+        document.readyState,
+      ]);
+    }
+
+    // Register content scripts from both extension URLs and plain JS code strings.
+
+    const content_scripts = [
+      // Plain JS code strings.
+      {
+        matches: ["http://localhost/*/file_sample.html"],
+        js: [{ code: `(${textScriptCodeStart})()` }],
+        runAt: "document_start",
+      },
+      {
+        matches: ["http://localhost/*/file_sample.html"],
+        js: [{ code: `(${textScriptCodeEnd})()` }],
+        runAt: "document_end",
+      },
+      {
+        matches: ["http://localhost/*/file_sample.html"],
+        js: [{ code: `(${textScriptCodeIdle})()` }],
+        runAt: "document_idle",
+      },
+      {
+        matches: ["http://localhost/*/file_sample.html"],
+        js: [{ code: `(${textScriptCodeIdle})()` }],
+        runAt: "document_idle",
+        cookieStoreId: "firefox-container-1",
+      },
+      // Extension URLs.
+      {
+        matches: ["http://localhost/*/file_sample.html"],
+        js: [{ file: "content_script_start.js" }],
+        runAt: "document_start",
+      },
+      {
+        matches: ["http://localhost/*/file_sample.html"],
+        js: [{ file: "content_script_end.js" }],
+        runAt: "document_end",
+      },
+      {
+        matches: ["http://localhost/*/file_sample.html"],
+        js: [{ file: "content_script_idle.js" }],
+        runAt: "document_idle",
+      },
+      {
+        matches: ["http://localhost/*/file_sample.html"],
+        js: [{ file: "content_script.js" }],
+        // "runAt" is not specified here to ensure that it defaults to document_idle when missing.
+      },
+      {
+        matches: ["http://localhost/*/file_sample.html"],
+        js: [{ file: "content_script_idle.js" }],
+        runAt: "document_idle",
+        cookieStoreId: "firefox-container-1",
+      },
+    ];
+
+    const expectedAPIs = ["unregister"];
+
+    for (const scriptOptions of content_scripts) {
+      const script = await browser.contentScripts.register(scriptOptions);
+      const actualAPIs = Object.keys(script);
+
+      browser.test.assertEq(
+        JSON.stringify(expectedAPIs),
+        JSON.stringify(actualAPIs),
+        `Got a script API object for ${scriptOptions.js[0]}`
+      );
+    }
+
+    browser.test.sendMessage("background-ready");
+  }
+
+  function contentScriptStart() {
+    browser.runtime.sendMessage([
+      "script-run",
+      ["loading"],
+      document.readyState,
+    ]);
+  }
+  function contentScriptEnd() {
+    browser.runtime.sendMessage([
+      "script-run",
+      ["interactive", "complete"],
+      document.readyState,
+    ]);
+  }
+  function contentScriptIdle() {
+    browser.runtime.sendMessage([
+      "script-run",
+      ["complete"],
+      document.readyState,
+    ]);
+  }
+
+  function contentScript() {
+    let manifest = browser.runtime.getManifest();
+    void manifest.permissions;
+    browser.runtime.sendMessage(["chrome-namespace-ok"]);
+  }
+
+  let extensionData = {
+    manifest: {
+      permissions: ["http://localhost/*/file_sample.html"],
+    },
+    background,
+
+    files: {
+      "content_script_start.js": contentScriptStart,
+      "content_script_end.js": contentScriptEnd,
+      "content_script_idle.js": contentScriptIdle,
+      "content_script.js": contentScript,
+    },
+  };
+
+  let extension = ExtensionTestUtils.loadExtension(extensionData);
+
+  let loadingCount = 0;
+  let interactiveCount = 0;
+  let completeCount = 0;
+  extension.onMessage("script-run-loading", () => {
+    loadingCount++;
+  });
+  extension.onMessage("script-run-interactive", () => {
+    interactiveCount++;
+  });
+
+  let completePromise = new Promise(resolve => {
+    extension.onMessage("script-run-complete", () => {
+      completeCount++;
+      if (completeCount == 2) {
+        resolve();
+      }
+    });
+  });
+
+  let chromeNamespacePromise = extension.awaitMessage("chrome-namespace-ok");
+
+  // Ensure that a content page running in a content process and which has been
+  // already loaded when the content scripts has been registered, it has received
+  // and registered the expected content scripts.
+  let contentPage = await ExtensionTestUtils.loadContentPage(`about:blank`);
+
+  await extension.startup();
+  await extension.awaitMessage("background-ready");
+
+  await contentPage.loadURL(`${BASE_URL}/file_sample.html`);
+
+  await Promise.all([completePromise, chromeNamespacePromise]);
+
+  await contentPage.close();
+
+  // Expect two content scripts to run (one registered using an extension URL
+  // and one registered from plain JS code).
+  equal(loadingCount, 2, "document_start script ran exactly twice");
+  equal(interactiveCount, 2, "document_end script ran exactly twice");
+  equal(completeCount, 2, "document_idle script ran exactly twice");
+
+  await extension.unload();
+});
+
+// Test that the contentScripts.register options are correctly translated
+// into the expected WebExtensionContentScript properties.
+add_task(async function test_contentscripts_register_all_options() {
+  async function background() {
+    await browser.contentScripts.register({
+      js: [{ file: "content_script.js" }],
+      css: [{ file: "content_style.css" }],
+      matches: ["http://localhost/*"],
+      excludeMatches: ["http://localhost/exclude/*"],
+      excludeGlobs: ["*_exclude.html"],
+      includeGlobs: ["*_include.html"],
+      allFrames: true,
+      matchAboutBlank: true,
+      runAt: "document_start",
+    });
+
+    browser.test.sendMessage("background-ready", window.location.origin);
+  }
+
+  const extensionData = {
+    manifest: {
+      permissions: ["http://localhost/*"],
+    },
+    background,
+
+    files: {
+      "content_script.js": "",
+      "content_style.css": "",
+    },
+  };
+
+  const extension = ExtensionTestUtils.loadExtension(extensionData);
+
+  await extension.startup();
+
+  const baseExtURL = await extension.awaitMessage("background-ready");
+
+  const policy = WebExtensionPolicy.getByID(extension.id);
+
+  ok(policy, "Got the WebExtensionPolicy for the test extension");
+  equal(
+    policy.contentScripts.length,
+    1,
+    "Got the expected number of registered content scripts"
+  );
+
+  const script = policy.contentScripts[0];
+  let {
+    allFrames,
+    cssPaths,
+    jsPaths,
+    matchAboutBlank,
+    runAt,
+    originAttributesPatterns,
+  } = script;
+
+  deepEqual(
+    {
+      allFrames,
+      cssPaths,
+      jsPaths,
+      matchAboutBlank,
+      runAt,
+      originAttributesPatterns,
+    },
+    {
+      allFrames: true,
+      cssPaths: [`${baseExtURL}/content_style.css`],
+      jsPaths: [`${baseExtURL}/content_script.js`],
+      matchAboutBlank: true,
+      runAt: "document_start",
+      originAttributesPatterns: null,
+    },
+    "Got the expected content script properties"
+  );
+
+  ok(
+    script.matchesURI(Services.io.newURI("http://localhost/ok_include.html")),
+    "matched and include globs should match"
+  );
+  ok(
+    !script.matchesURI(
+      Services.io.newURI("http://localhost/exclude/ok_include.html")
+    ),
+    "exclude matches should not match"
+  );
+  ok(
+    !script.matchesURI(Services.io.newURI("http://localhost/ok_exclude.html")),
+    "exclude globs should not match"
+  );
+
+  await extension.unload();
+});
+
+add_task(async function test_contentscripts_register_cookieStoreId() {
+  async function background() {
+    let cookieStoreIdCSSArray = [
+      { id: null, color: "rgb(123, 45, 67)" },
+      { id: "firefox-private", color: "rgb(255,255,0)" },
+      { id: "firefox-default", color: "red" },
+      { id: "firefox-container-1", color: "green" },
+      { id: "firefox-container-2", color: "blue" },
+      {
+        id: ["firefox-container-3", "firefox-container-4"],
+        color: "rgb(100,100,0)",
+      },
+    ];
+    const matches = ["http://localhost/*/file_sample_registered_styles.html"];
+
+    for (let { id, color } of cookieStoreIdCSSArray) {
+      await browser.contentScripts.register({
+        css: [
+          {
+            code: `#registered-extension-text-style {
+              background-color: ${color}}`,
+          },
+        ],
+        matches,
+        runAt: "document_start",
+        cookieStoreId: id,
+      });
+    }
+    await browser.test.assertRejects(
+      browser.contentScripts.register({
+        css: [{ code: `body {}` }],
+        matches,
+        cookieStoreId: "not_a_valid_cookieStoreId",
+      }),
+      /Invalid cookieStoreId/,
+      "contentScripts.register with an invalid cookieStoreId"
+    );
+
+    if (!navigator.userAgent.includes("Android")) {
+      await browser.test.assertRejects(
+        browser.contentScripts.register({
+          css: [{ code: `body {}` }],
+          matches,
+          cookieStoreId: "firefox-container-999",
+        }),
+        /Invalid cookieStoreId/,
+        "contentScripts.register with an invalid cookieStoreId"
+      );
+    } else {
+      // On Android, any firefox-container-... is treated as valid, so it doesn't
+      // result in an error.
+      // TODO bug 1743616: Fix implementation and remove this branch.
+      await browser.contentScripts.register({
+        css: [{ code: `body {}` }],
+        matches,
+        cookieStoreId: "firefox-container-999",
+      });
+    }
+
+    await browser.test.assertRejects(
+      browser.contentScripts.register({
+        css: [{ code: `body {}` }],
+        matches,
+        cookieStoreId: "",
+      }),
+      /Invalid cookieStoreId/,
+      "contentScripts.register with an invalid cookieStoreId"
+    );
+
+    browser.test.sendMessage("background_ready");
+  }
+
+  const extensionData = {
+    manifest: {
+      permissions: [
+        "http://localhost/*/file_sample_registered_styles.html",
+        "<all_urls>",
+      ],
+      content_scripts: [
+        {
+          matches: ["http://localhost/*/file_sample_registered_styles.html"],
+          run_at: "document_idle",
+          js: ["check_applied_styles.js"],
+        },
+      ],
+    },
+    background,
+    files: {
+      "check_applied_styles.js": check_applied_styles,
+    },
+  };
+
+  const extension = ExtensionTestUtils.loadExtension({
+    ...extensionData,
+    incognitoOverride: "spanning",
+  });
+
+  await extension.startup();
+  await extension.awaitMessage("background_ready");
+  //  Index 0 is the one from manifest.json.
+  let contentScriptMatchTests = [
+    {
+      contentPageOptions: { userContextId: 5 },
+      expectedStyles: "rgb(123, 45, 67)",
+      originAttributesPatternExpected: null,
+      contentScriptIndex: 1,
+    },
+    {
+      contentPageOptions: { privateBrowsing: true },
+      expectedStyles: "rgb(255, 255, 0)",
+      originAttributesPatternExpected: [
+        {
+          privateBrowsingId: 1,
+          userContextId: 0,
+        },
+      ],
+      contentScriptIndex: 2,
+    },
+    {
+      contentPageOptions: { userContextId: 0 },
+      expectedStyles: "rgb(255, 0, 0)",
+      originAttributesPatternExpected: [
+        {
+          privateBrowsingId: 0,
+          userContextId: 0,
+        },
+      ],
+      contentScriptIndex: 3,
+    },
+    {
+      contentPageOptions: { userContextId: 1 },
+      expectedStyles: "rgb(0, 128, 0)",
+      originAttributesPatternExpected: [{ userContextId: 1 }],
+      contentScriptIndex: 4,
+    },
+    {
+      contentPageOptions: { userContextId: 2 },
+      expectedStyles: "rgb(0, 0, 255)",
+      originAttributesPatternExpected: [{ userContextId: 2 }],
+      contentScriptIndex: 5,
+    },
+    {
+      contentPageOptions: { userContextId: 3 },
+      expectedStyles: "rgb(100, 100, 0)",
+      originAttributesPatternExpected: [
+        { userContextId: 3 },
+        { userContextId: 4 },
+      ],
+      contentScriptIndex: 6,
+    },
+    {
+      contentPageOptions: { userContextId: 4 },
+      expectedStyles: "rgb(100, 100, 0)",
+      originAttributesPatternExpected: [
+        { userContextId: 3 },
+        { userContextId: 4 },
+      ],
+      contentScriptIndex: 6,
+    },
+  ];
+
+  const policy = WebExtensionPolicy.getByID(extension.id);
+
+  for (const testCase of contentScriptMatchTests) {
+    const {
+      contentPageOptions,
+      expectedStyles,
+      originAttributesPatternExpected,
+      contentScriptIndex,
+    } = testCase;
+    const script = policy.contentScripts[contentScriptIndex];
+
+    deepEqual(script.originAttributesPatterns, originAttributesPatternExpected);
+    let contentPage = await ExtensionTestUtils.loadContentPage(
+      `about:blank`,
+      contentPageOptions
+    );
+    await contentPage.loadURL(`${BASE_URL}/file_sample_registered_styles.html`);
+
+    let registeredStylesResults = await extension.awaitMessage(
+      "registered-styles-results"
+    );
+
+    equal(
+      registeredStylesResults.registeredExtensionBlobStyleBG,
+      expectedStyles,
+      `Expected styles applied on content page loaded with options 
+      ${JSON.stringify(contentPageOptions)}`
+    );
+    await contentPage.close();
+  }
+
+  await extension.unload();
+});
diff --git a/toolkit/components/extensions/test/xpcshell/test_ext_content_security_policy.js b/toolkit/components/extensions/test/xpcshell/test_ext_content_security_policy.js
new file mode 100644
index 0000000000..335a278329
--- /dev/null
+++ b/toolkit/components/extensions/test/xpcshell/test_ext_content_security_policy.js
@@ -0,0 +1,362 @@
+"use strict";
+
+Services.prefs.setBoolPref("extensions.manifestV3.enabled", true);
+
+const server = createHttpServer({ hosts: ["example.com"] });
+
+server.registerPathHandler("/dummy", (request, response) => {
+  response.setStatusLine(request.httpVersion, 200, "OK");
+  response.setHeader("Content-Type", "text/html", false);
+  response.write("<!DOCTYPE html><html></html>");
+});
+
+server.registerPathHandler("/worker.js", (request, response) => {
+  response.setStatusLine(request.httpVersion, 200, "OK");
+  response.setHeader("Content-Type", "application/javascript", false);
+  response.write("let x = true;");
+});
+
+const baseCSP = [];
+// Keep in sync with extensions.webextensions.base-content-security-policy
+baseCSP[2] = {
+  "script-src": [
+    "'unsafe-eval'",
+    "'wasm-unsafe-eval'",
+    "'unsafe-inline'",
+    "blob:",
+    "filesystem:",
+    "http://localhost:*",
+    "http://127.0.0.1:*",
+    "https://*",
+    "moz-extension:",
+    "'self'",
+  ],
+};
+// Keep in sync with extensions.webextensions.base-content-security-policy.v3
+baseCSP[3] = {
+  "script-src": ["'self'", "'wasm-unsafe-eval'"],
+};
+
+/**
+ * @typedef TestPolicyExpects
+ * @type {object}
+ * @param {boolean} workerEvalAllowed
+ * @param {boolean} workerImportScriptsAllowed
+ * @param {boolean} workerWasmAllowed
+ */
+
+/**
+ * Tests that content security policies for an add-on are actually applied to *
+ * documents that belong to it. This tests both the base policies and add-on
+ * specific policies, and ensures that the parsed policies applied to the
+ * document's principal match what was specified in the policy string.
+ *
+ * @param {object} options
+ * @param {number} [options.manifest_version]
+ * @param {object} [options.customCSP]
+ * @param {TestPolicyExpects} options.expects
+ */
+async function testPolicy({
+  manifest_version = 2,
+  customCSP = null,
+  expects = {},
+}) {
+  info(
+    `Enter tests for extension CSP with ${JSON.stringify({
+      manifest_version,
+      customCSP,
+    })}`
+  );
+
+  let baseURL;
+
+  let addonCSP = {
+    "script-src": ["'self'"],
+  };
+
+  if (manifest_version < 3) {
+    addonCSP["script-src"].push("'wasm-unsafe-eval'");
+  }
+
+  let content_security_policy = null;
+
+  if (customCSP) {
+    for (let key of Object.keys(customCSP)) {
+      addonCSP[key] = customCSP[key].split(/\s+/);
+    }
+
+    content_security_policy = Object.keys(customCSP)
+      .map(key => `${key} ${customCSP[key]}`)
+      .join("; ");
+  }
+
+  function checkSource(name, policy, expected) {
+    // fallback to script-src when comparing worker-src if policy does not include worker-src
+    let policySrc =
+      name != "worker-src" || policy[name]
+        ? policy[name]
+        : policy["script-src"];
+    equal(
+      JSON.stringify(policySrc.sort()),
+      JSON.stringify(expected[name].sort()),
+      `Expected value for ${name}`
+    );
+  }
+
+  function checkCSP(csp, location) {
+    let policies = csp["csp-policies"];
+
+    info(`Base policy for ${location}`);
+    let base = baseCSP[manifest_version];
+
+    equal(policies[0]["report-only"], false, "Policy is not report-only");
+    for (let key in base) {
+      checkSource(key, policies[0], base);
+    }
+
+    info(`Add-on policy for ${location}`);
+
+    equal(policies[1]["report-only"], false, "Policy is not report-only");
+    for (let key in addonCSP) {
+      checkSource(key, policies[1], addonCSP);
+    }
+  }
+
+  function background() {
+    browser.test.sendMessage(
+      "base-url",
+      browser.runtime.getURL("").replace(/\/$/, "")
+    );
+
+    browser.test.sendMessage("background-csp", window.getCsp());
+  }
+
+  function tabScript() {
+    browser.test.sendMessage("tab-csp", window.getCsp());
+
+    const worker = new Worker("worker.js");
+    worker.onmessage = event => {
+      browser.test.sendMessage("worker-csp", event.data);
+    };
+
+    worker.postMessage({});
+  }
+
+  function testWorker(port) {
+    this.onmessage = () => {
+      let importScriptsAllowed;
+      let evalAllowed;
+      let wasmAllowed;
+
+      try {
+        eval("let y = true;"); // eslint-disable-line no-eval
+        evalAllowed = true;
+      } catch (e) {
+        evalAllowed = false;
+      }
+
+      try {
+        new WebAssembly.Module(
+          new Uint8Array([0, 0x61, 0x73, 0x6d, 0x1, 0, 0, 0])
+        );
+        wasmAllowed = true;
+      } catch (e) {
+        wasmAllowed = false;
+      }
+
+      try {
+        // eslint-disable-next-line no-undef
+        importScripts(`http://127.0.0.1:${port}/worker.js`);
+        importScriptsAllowed = true;
+      } catch (e) {
+        importScriptsAllowed = false;
+      }
+
+      postMessage({ evalAllowed, importScriptsAllowed, wasmAllowed });
+    };
+  }
+
+  let web_accessible_resources = ["content.html", "tab.html"];
+  if (manifest_version == 3) {
+    let extension_pages = content_security_policy;
+    content_security_policy = {
+      extension_pages,
+    };
+    let resources = web_accessible_resources;
+    web_accessible_resources = [
+      { resources, matches: ["http://example.com/*"] },
+    ];
+  }
+
+  let extension = ExtensionTestUtils.loadExtension({
+    background,
+
+    files: {
+      "tab.html": `<html><head><meta charset="utf-8">
+                   <script src="tab.js"></${"script"}></head></html>`,
+
+      "tab.js": tabScript,
+
+      "content.html": `<html><head><meta charset="utf-8"></head></html>`,
+      "worker.js": `(${testWorker})(${server.identity.primaryPort})`,
+    },
+
+    manifest: {
+      manifest_version,
+      content_security_policy,
+      web_accessible_resources,
+    },
+  });
+
+  function frameScript() {
+    // eslint-disable-next-line mozilla/balanced-listeners
+    addEventListener(
+      "DOMWindowCreated",
+      event => {
+        let win = event.target.ownerGlobal;
+        function getCsp() {
+          let { cspJSON } = win.document;
+          return win.wrappedJSObject.JSON.parse(cspJSON);
+        }
+        Cu.exportFunction(getCsp, win, { defineAs: "getCsp" });
+      },
+      true
+    );
+  }
+  let frameScriptURL = `data:,(${encodeURI(frameScript)}).call(this)`;
+  Services.mm.loadFrameScript(frameScriptURL, true, true);
+
+  info(`Testing CSP for policy: ${JSON.stringify(content_security_policy)}`);
+
+  await extension.startup();
+
+  baseURL = await extension.awaitMessage("base-url");
+
+  let tabPage = await ExtensionTestUtils.loadContentPage(
+    `${baseURL}/tab.html`,
+    { extension }
+  );
+
+  let contentPage = await ExtensionTestUtils.loadContentPage(
+    "http://example.com/dummy"
+  );
+
+  let contentCSP = await contentPage.spawn(
+    [`${baseURL}/content.html`],
+    async src => {
+      let doc = this.content.document;
+
+      let frame = doc.createElement("iframe");
+      frame.src = src;
+      doc.body.appendChild(frame);
+
+      await new Promise(resolve => {
+        frame.onload = resolve;
+      });
+
+      return frame.contentWindow.wrappedJSObject.getCsp();
+    }
+  );
+
+  let backgroundCSP = await extension.awaitMessage("background-csp");
+  checkCSP(backgroundCSP, "background page");
+
+  let tabCSP = await extension.awaitMessage("tab-csp");
+  checkCSP(tabCSP, "tab page");
+
+  checkCSP(contentCSP, "content frame");
+
+  let workerCSP = await extension.awaitMessage("worker-csp");
+  equal(
+    workerCSP.importScriptsAllowed,
+    expects.workerImportAllowed,
+    "worker importScript"
+  );
+  equal(workerCSP.evalAllowed, expects.workerEvalAllowed, "worker eval");
+  equal(workerCSP.wasmAllowed, expects.workerWasmAllowed, "worker wasm");
+
+  await contentPage.close();
+  await tabPage.close();
+
+  await extension.unload();
+
+  Services.mm.removeDelayedFrameScript(frameScriptURL);
+}
+
+add_task(async function testCSP() {
+  await testPolicy({
+    manifest_version: 2,
+    customCSP: null,
+    expects: {
+      workerEvalAllowed: false,
+      workerImportAllowed: false,
+      workerWasmAllowed: true,
+    },
+  });
+
+  let hash =
+    "'sha256-NjZhMDQ1YjQ1MjEwMmM1OWQ4NDBlYzA5N2Q1OWQ5NDY3ZTEzYTNmMzRmNjQ5NGU1MzlmZmQzMmMxYmIzNWYxOCAgLQo='";
+
+  await testPolicy({
+    manifest_version: 2,
+    customCSP: {
+      "script-src": `'self' https://*.example.com 'unsafe-eval' ${hash}`,
+    },
+    expects: {
+      workerEvalAllowed: true,
+      workerImportAllowed: false,
+      workerWasmAllowed: true,
+    },
+  });
+
+  await testPolicy({
+    manifest_version: 2,
+    customCSP: {
+      "script-src": `'self'`,
+    },
+    expects: {
+      workerEvalAllowed: false,
+      workerImportAllowed: false,
+      workerWasmAllowed: true,
+    },
+  });
+
+  await testPolicy({
+    manifest_version: 3,
+    customCSP: {
+      "script-src": `'self' ${hash}`,
+      "worker-src": `'self'`,
+    },
+    expects: {
+      workerEvalAllowed: false,
+      workerImportAllowed: false,
+      workerWasmAllowed: false,
+    },
+  });
+
+  await testPolicy({
+    manifest_version: 3,
+    customCSP: {
+      "script-src": `'self'`,
+      "worker-src": `'self'`,
+    },
+    expects: {
+      workerEvalAllowed: false,
+      workerImportAllowed: false,
+      workerWasmAllowed: false,
+    },
+  });
+
+  await testPolicy({
+    manifest_version: 3,
+    customCSP: {
+      "script-src": `'self' 'wasm-unsafe-eval'`,
+      "worker-src": `'self' 'wasm-unsafe-eval'`,
+    },
+    expects: {
+      workerEvalAllowed: false,
+      workerImportAllowed: false,
+      workerWasmAllowed: true,
+    },
+  });
+});
diff --git a/toolkit/components/extensions/test/xpcshell/test_ext_contentscript.js b/toolkit/components/extensions/test/xpcshell/test_ext_contentscript.js
new file mode 100644
index 0000000000..d35f572731
--- /dev/null
+++ b/toolkit/components/extensions/test/xpcshell/test_ext_contentscript.js
@@ -0,0 +1,270 @@
+"use strict";
+
+const server = createHttpServer();
+server.registerDirectory("/data/", do_get_file("data"));
+
+const BASE_URL = `http://localhost:${server.identity.primaryPort}/data`;
+
+// ExtensionContent.jsm needs to know when it's running from xpcshell,
+// to use the right timeout for content scripts executed at document_idle.
+ExtensionTestUtils.mockAppInfo();
+
+add_task(async function test_contentscript_runAt() {
+  function background() {
+    browser.runtime.onMessage.addListener(
+      ([msg, expectedStates, readyState], sender) => {
+        if (msg == "chrome-namespace-ok") {
+          browser.test.sendMessage(msg);
+          return;
+        }
+
+        browser.test.assertEq("script-run", msg, "message type is correct");
+        browser.test.assertTrue(
+          expectedStates.includes(readyState),
+          `readyState "${readyState}" is one of [${expectedStates}]`
+        );
+        browser.test.sendMessage("script-run-" + expectedStates[0]);
+      }
+    );
+  }
+
+  function contentScriptStart() {
+    browser.runtime.sendMessage([
+      "script-run",
+      ["loading"],
+      document.readyState,
+    ]);
+  }
+  function contentScriptEnd() {
+    browser.runtime.sendMessage([
+      "script-run",
+      ["interactive", "complete"],
+      document.readyState,
+    ]);
+  }
+  function contentScriptIdle() {
+    browser.runtime.sendMessage([
+      "script-run",
+      ["complete"],
+      document.readyState,
+    ]);
+  }
+
+  function contentScript() {
+    let manifest = browser.runtime.getManifest();
+    void manifest.applications.gecko.id;
+    browser.runtime.sendMessage(["chrome-namespace-ok"]);
+  }
+
+  let extensionData = {
+    manifest: {
+      browser_specific_settings: {
+        gecko: { id: "contentscript@tests.mozilla.org" },
+      },
+      content_scripts: [
+        {
+          matches: ["http://*/*/file_sample.html"],
+          js: ["content_script_start.js"],
+          run_at: "document_start",
+        },
+        {
+          matches: ["http://*/*/file_sample.html"],
+          js: ["content_script_end.js"],
+          run_at: "document_end",
+        },
+        {
+          matches: ["http://*/*/file_sample.html"],
+          js: ["content_script_idle.js"],
+          run_at: "document_idle",
+        },
+        {
+          matches: ["http://*/*/file_sample.html"],
+          js: ["content_script_idle.js"],
+          // Test default `run_at`.
+        },
+        {
+          matches: ["http://*/*/file_sample.html"],
+          js: ["content_script.js"],
+          run_at: "document_idle",
+        },
+      ],
+    },
+    background,
+
+    files: {
+      "content_script_start.js": contentScriptStart,
+      "content_script_end.js": contentScriptEnd,
+      "content_script_idle.js": contentScriptIdle,
+      "content_script.js": contentScript,
+    },
+  };
+
+  let extension = ExtensionTestUtils.loadExtension(extensionData);
+
+  let loadingCount = 0;
+  let interactiveCount = 0;
+  let completeCount = 0;
+  extension.onMessage("script-run-loading", () => {
+    loadingCount++;
+  });
+  extension.onMessage("script-run-interactive", () => {
+    interactiveCount++;
+  });
+
+  let completePromise = new Promise(resolve => {
+    extension.onMessage("script-run-complete", () => {
+      completeCount++;
+      if (completeCount > 1) {
+        resolve();
+      }
+    });
+  });
+
+  let chromeNamespacePromise = extension.awaitMessage("chrome-namespace-ok");
+
+  await extension.startup();
+
+  let contentPage = await ExtensionTestUtils.loadContentPage(
+    `${BASE_URL}/file_sample.html`
+  );
+
+  await Promise.all([completePromise, chromeNamespacePromise]);
+
+  await contentPage.close();
+
+  equal(loadingCount, 1, "document_start script ran exactly once");
+  equal(interactiveCount, 1, "document_end script ran exactly once");
+  equal(completeCount, 2, "document_idle script ran exactly twice");
+
+  await extension.unload();
+});
+
+add_task(async function test_contentscript_window_open() {
+  if (AppConstants.DEBUG && ExtensionTestUtils.remoteContentScripts) {
+    return;
+  }
+
+  let script = async () => {
+    /* globals x */
+    browser.test.assertEq(1, x, "Should only run once");
+
+    if (top !== window) {
+      // Wait for our parent page to load, then set a timeout to wait for the
+      // document.open call, so we make sure to not tear down the extension
+      // until after we've done the document.open.
+      await new Promise(resolve => {
+        top.addEventListener("load", () => setTimeout(resolve, 0), {
+          once: true,
+        });
+      });
+    }
+
+    browser.test.sendMessage("content-script", [location.href, top === window]);
+  };
+
+  let extension = ExtensionTestUtils.loadExtension({
+    manifest: {
+      browser_specific_settings: {
+        gecko: { id: "contentscript@tests.mozilla.org" },
+      },
+      content_scripts: [
+        {
+          matches: ["<all_urls>"],
+          js: ["content_script.js"],
+          run_at: "document_start",
+          match_about_blank: true,
+          all_frames: true,
+        },
+      ],
+    },
+
+    files: {
+      "content_script.js": `
+        var x = (x || 0) + 1;
+        (${script})();
+      `,
+    },
+  });
+
+  await extension.startup();
+
+  let url = `${BASE_URL}/file_document_open.html`;
+  let contentPage = await ExtensionTestUtils.loadContentPage(url);
+
+  let [pageURL, pageIsTop] = await extension.awaitMessage("content-script");
+
+  // Sometimes we get a content script load for the initial about:blank
+  // top level frame here, sometimes we don't. Either way is fine, as long as we
+  // don't get two loads into the same document.open() document.
+  if (pageURL === "about:blank") {
+    equal(pageIsTop, true);
+    [pageURL, pageIsTop] = await extension.awaitMessage("content-script");
+  }
+
+  Assert.deepEqual([pageURL, pageIsTop], [url, true]);
+
+  let [frameURL, isTop] = await extension.awaitMessage("content-script");
+  Assert.deepEqual([frameURL, isTop], [url, false]);
+
+  await contentPage.close();
+  await extension.unload();
+});
+
+// This test verify that a cached script is still able to catch the document
+// while it is still loading (when we do not block the document parsing as
+// we do for a non cached script).
+add_task(async function test_cached_contentscript_on_document_start() {
+  let extension = ExtensionTestUtils.loadExtension({
+    manifest: {
+      content_scripts: [
+        {
+          matches: ["http://localhost/*/file_document_open.html"],
+          js: ["content_script.js"],
+          run_at: "document_start",
+        },
+      ],
+    },
+
+    files: {
+      "content_script.js": `
+        browser.test.sendMessage("content-script-loaded", {
+          url: window.location.href,
+          documentReadyState: document.readyState,
+        });
+      `,
+    },
+  });
+
+  await extension.startup();
+
+  let url = `${BASE_URL}/file_document_open.html`;
+  let contentPage = await ExtensionTestUtils.loadContentPage(url);
+
+  let msg = await extension.awaitMessage("content-script-loaded");
+  Assert.deepEqual(
+    msg,
+    {
+      url,
+      documentReadyState: "loading",
+    },
+    "Got the expected url and document.readyState from a non cached script"
+  );
+
+  // Reload the page and check that the cached content script is still able to
+  // run on document_start.
+  await contentPage.loadURL(url);
+
+  let msgFromCached = await extension.awaitMessage("content-script-loaded");
+  Assert.deepEqual(
+    msgFromCached,
+    {
+      url,
+      documentReadyState: "loading",
+    },
+    "Got the expected url and document.readyState from a cached script"
+  );
+
+  await extension.unload();
+
+  await contentPage.close();
+});
diff --git a/toolkit/components/extensions/test/xpcshell/test_ext_contentscript_about_blank_start.js b/toolkit/components/extensions/test/xpcshell/test_ext_contentscript_about_blank_start.js
new file mode 100644
index 0000000000..1297f105a1
--- /dev/null
+++ b/toolkit/components/extensions/test/xpcshell/test_ext_contentscript_about_blank_start.js
@@ -0,0 +1,78 @@
+"use strict";
+
+const server = createHttpServer({ hosts: ["example.com"] });
+
+server.registerPathHandler("/blank-iframe.html", (request, response) => {
+  response.setStatusLine(request.httpVersion, 200, "OK");
+  response.setHeader("Content-Type", "text/html; charset=utf-8", false);
+  response.write("<iframe></iframe>");
+});
+
+add_task(async function content_script_at_document_start() {
+  let extensionData = {
+    manifest: {
+      content_scripts: [
+        {
+          matches: ["<all_urls>"],
+          js: ["start.js"],
+          run_at: "document_start",
+          match_about_blank: true,
+        },
+      ],
+    },
+
+    files: {
+      "start.js": function () {
+        browser.test.sendMessage("content-script-done");
+      },
+    },
+  };
+
+  let extension = ExtensionTestUtils.loadExtension(extensionData);
+  await extension.startup();
+  let contentPage = await ExtensionTestUtils.loadContentPage(`about:blank`);
+  await extension.awaitMessage("content-script-done");
+  await contentPage.close();
+  await extension.unload();
+});
+
+add_task(async function content_style_at_document_start() {
+  let extensionData = {
+    manifest: {
+      content_scripts: [
+        {
+          matches: ["<all_urls>"],
+          css: ["start.css"],
+          run_at: "document_start",
+          match_about_blank: true,
+        },
+        {
+          matches: ["<all_urls>"],
+          js: ["end.js"],
+          run_at: "document_end",
+          match_about_blank: true,
+        },
+      ],
+    },
+
+    files: {
+      "start.css": "body { background: red; }",
+      "end.js": function () {
+        let style = window.getComputedStyle(document.body);
+        browser.test.assertEq(
+          "rgb(255, 0, 0)",
+          style.backgroundColor,
+          "document_start style should have been applied"
+        );
+        browser.test.sendMessage("content-script-done");
+      },
+    },
+  };
+
+  let extension = ExtensionTestUtils.loadExtension(extensionData);
+  await extension.startup();
+  let contentPage = await ExtensionTestUtils.loadContentPage(`about:blank`);
+  await extension.awaitMessage("content-script-done");
+  await contentPage.close();
+  await extension.unload();
+});
diff --git a/toolkit/components/extensions/test/xpcshell/test_ext_contentscript_api_injection.js b/toolkit/components/extensions/test/xpcshell/test_ext_contentscript_api_injection.js
new file mode 100644
index 0000000000..4e42181e71
--- /dev/null
+++ b/toolkit/components/extensions/test/xpcshell/test_ext_contentscript_api_injection.js
@@ -0,0 +1,65 @@
+"use strict";
+
+const server = createHttpServer({ hosts: ["example.com"] });
+server.registerDirectory("/data/", do_get_file("data"));
+
+add_task(async function test_contentscript_api_injection() {
+  let extensionData = {
+    manifest: {
+      content_scripts: [
+        {
+          matches: ["http://example.com/data/file_sample.html"],
+          js: ["content_script.js"],
+        },
+      ],
+      web_accessible_resources: ["content_script_iframe.html"],
+    },
+
+    files: {
+      "content_script.js"() {
+        let iframe = document.createElement("iframe");
+        iframe.src = browser.runtime.getURL("content_script_iframe.html");
+        document.body.appendChild(iframe);
+      },
+      "content_script_iframe.js"() {
+        window.location = `http://example.com/data/file_privilege_escalation.html`;
+      },
+      "content_script_iframe.html": `<!DOCTYPE html>
+        <html>
+          <head>
+            <meta charset="utf-8">
+            <script type="text/javascript" src="content_script_iframe.js"></script>
+          </head>
+        </html>`,
+    },
+  };
+
+  let extension = ExtensionTestUtils.loadExtension(extensionData);
+
+  let awaitConsole = new Promise(resolve => {
+    Services.console.registerListener(function listener(message) {
+      if (/WebExt Privilege Escalation/.test(message.message)) {
+        Services.console.unregisterListener(listener);
+        resolve(message);
+      }
+    });
+  });
+
+  await extension.startup();
+
+  let contentPage = await ExtensionTestUtils.loadContentPage(
+    "http://example.com/data/file_sample.html"
+  );
+
+  let message = await awaitConsole;
+  ok(
+    message.message.includes(
+      "WebExt Privilege Escalation: typeof(browser) = undefined"
+    ),
+    "Document does not have `browser` APIs."
+  );
+
+  await contentPage.close();
+
+  await extension.unload();
+});
diff --git a/toolkit/components/extensions/test/xpcshell/test_ext_contentscript_async_loading.js b/toolkit/components/extensions/test/xpcshell/test_ext_contentscript_async_loading.js
new file mode 100644
index 0000000000..cb9a07142d
--- /dev/null
+++ b/toolkit/components/extensions/test/xpcshell/test_ext_contentscript_async_loading.js
@@ -0,0 +1,79 @@
+"use strict";
+
+const server = createHttpServer({ hosts: ["example.com"] });
+
+server.registerPathHandler("/dummy", (request, response) => {
+  response.setStatusLine(request.httpVersion, 200, "OK");
+  response.setHeader("Content-Type", "text/html", false);
+  response.write("<!DOCTYPE html><html></html>");
+});
+
+add_task(async function test_async_loading() {
+  const adder = `(function add(a = 1) { this.count += a; })();\n`;
+
+  const extension = {
+    manifest: {
+      content_scripts: [
+        {
+          run_at: "document_start",
+          matches: ["http://example.com/dummy"],
+          js: ["first.js", "second.js"],
+        },
+        {
+          run_at: "document_end",
+          matches: ["http://example.com/dummy"],
+          js: ["third.js"],
+        },
+      ],
+    },
+    files: {
+      "first.js": `
+        this.count = 0;
+        ${adder.repeat(50000)};  // 2Mb
+        browser.test.assertEq(this.count, 50000, "A 50k line script");
+
+        this.order = (this.order || 0) + 1;
+        browser.test.sendMessage("first", this.order);
+      `,
+      "second.js": `
+        this.order = (this.order || 0) + 1;
+        browser.test.sendMessage("second", this.order);
+      `,
+      "third.js": `
+        this.order = (this.order || 0) + 1;
+        browser.test.sendMessage("third", this.order);
+      `,
+    },
+  };
+
+  async function checkOrder(ext) {
+    const [first, second, third] = await Promise.all([
+      ext.awaitMessage("first"),
+      ext.awaitMessage("second"),
+      ext.awaitMessage("third"),
+    ]);
+
+    equal(first, 1, "first.js finished execution first.");
+    equal(second, 2, "second.js finished execution second.");
+    equal(third, 3, "third.js finished execution third.");
+  }
+
+  info("Test pages observed while extension is running");
+  const observed = ExtensionTestUtils.loadExtension(extension);
+  await observed.startup();
+
+  const contentPage = await ExtensionTestUtils.loadContentPage(
+    "http://example.com/dummy"
+  );
+  await checkOrder(observed);
+  await observed.unload();
+
+  info("Test pages already existing on extension startup");
+  const existing = ExtensionTestUtils.loadExtension(extension);
+
+  await existing.startup();
+  await checkOrder(existing);
+  await existing.unload();
+
+  await contentPage.close();
+});
diff --git a/toolkit/components/extensions/test/xpcshell/test_ext_contentscript_canvas_tainting.js b/toolkit/components/extensions/test/xpcshell/test_ext_contentscript_canvas_tainting.js
new file mode 100644
index 0000000000..4ac22dc700
--- /dev/null
+++ b/toolkit/components/extensions/test/xpcshell/test_ext_contentscript_canvas_tainting.js
@@ -0,0 +1,128 @@
+"use strict";
+
+const server = createHttpServer({
+  hosts: ["green.example.com", "red.example.com"],
+});
+
+server.registerDirectory("/data/", do_get_file("data"));
+
+server.registerPathHandler("/pixel.html", (request, response) => {
+  response.setStatusLine(request.httpVersion, 200, "OK");
+  response.setHeader("Content-Type", "text/html", false);
+  response.write(`<!DOCTYPE html>
+    <script>
+      function readByWeb() {
+        let ctx = document.querySelector("canvas").getContext("2d");
+        let {data} = ctx.getImageData(0, 0, 1, 1);
+        return data.slice(0, 3).join();
+      }
+    </script>
+  `);
+});
+
+add_task(async function test_contentscript_canvas_tainting() {
+  async function contentScript() {
+    let canvas = document.createElement("canvas");
+    let ctx = canvas.getContext("2d");
+    document.body.appendChild(canvas);
+
+    function draw(url) {
+      return new Promise(resolve => {
+        let img = document.createElement("img");
+        img.onload = () => {
+          ctx.drawImage(img, 0, 0, 1, 1);
+          resolve();
+        };
+        img.src = url;
+      });
+    }
+
+    function readByExt() {
+      let { data } = ctx.getImageData(0, 0, 1, 1);
+      return data.slice(0, 3).join();
+    }
+
+    let readByWeb = window.wrappedJSObject.readByWeb;
+
+    // Test reading after drawing an image from the same origin as the web page.
+    await draw("http://green.example.com/data/pixel_green.gif");
+    browser.test.assertEq(
+      readByWeb(),
+      "0,255,0",
+      "Content can read same-origin image"
+    );
+    browser.test.assertEq(
+      readByExt(),
+      "0,255,0",
+      "Extension can read same-origin image"
+    );
+
+    // Test reading after drawing a blue pixel data URI from extension content script.
+    await draw(
+      "data:image/gif;base64,R0lGODlhAQABAIABAAAA/wAAACwAAAAAAQABAAACAkQBADs="
+    );
+    browser.test.assertThrows(
+      readByWeb,
+      /operation is insecure/,
+      "Content can't read extension's image"
+    );
+    browser.test.assertEq(
+      readByExt(),
+      "0,0,255",
+      "Extension can read its own image"
+    );
+
+    // Test after tainting the canvas with an image from a third party domain.
+    await draw("http://red.example.com/data/pixel_red.gif");
+    browser.test.assertThrows(
+      readByWeb,
+      /operation is insecure/,
+      "Content can't read third party image"
+    );
+    browser.test.assertThrows(
+      readByExt,
+      /operation is insecure/,
+      "Extension can't read fully tainted"
+    );
+
+    // Test canvas is still fully tainted after drawing extension's data: image again.
+    await draw(
+      "data:image/gif;base64,R0lGODlhAQABAIABAAAA/wAAACwAAAAAAQABAAACAkQBADs="
+    );
+    browser.test.assertThrows(
+      readByWeb,
+      /operation is insecure/,
+      "Canvas still fully tainted for content"
+    );
+    browser.test.assertThrows(
+      readByExt,
+      /operation is insecure/,
+      "Canvas still fully tainted for extension"
+    );
+
+    browser.test.sendMessage("done");
+  }
+
+  let extension = ExtensionTestUtils.loadExtension({
+    manifest: {
+      content_scripts: [
+        {
+          matches: ["http://green.example.com/pixel.html"],
+          js: ["cs.js"],
+        },
+      ],
+    },
+    files: {
+      "cs.js": contentScript,
+    },
+  });
+
+  await extension.startup();
+  let contentPage = await ExtensionTestUtils.loadContentPage(
+    "http://green.example.com/pixel.html"
+  );
+  await extension.awaitMessage("done");
+
+  await contentPage.close();
+  await extension.unload();
+});
diff --git a/toolkit/components/extensions/test/xpcshell/test_ext_contentscript_context.js b/toolkit/components/extensions/test/xpcshell/test_ext_contentscript_context.js
new file mode 100644
index 0000000000..fc27b84200
--- /dev/null
+++ b/toolkit/components/extensions/test/xpcshell/test_ext_contentscript_context.js
@@ -0,0 +1,359 @@
+"use strict";
+
+/* eslint-disable mozilla/balanced-listeners */
+
+const server = createHttpServer({ hosts: ["example.com", "example.org"] });
+
+server.registerPathHandler("/dummy", (request, response) => {
+  response.setStatusLine(request.httpVersion, 200, "OK");
+  response.setHeader("Content-Type", "text/html", false);
+  response.write("<!DOCTYPE html><html></html>");
+});
+
+function loadExtension() {
+  function contentScript() {
+    browser.test.sendMessage("content-script-ready");
+
+    window.addEventListener(
+      "pagehide",
+      () => {
+        browser.test.sendMessage("content-script-hide");
+      },
+      true
+    );
+    window.addEventListener("pageshow", () => {
+      browser.test.sendMessage("content-script-show");
+    });
+  }
+
+  return ExtensionTestUtils.loadExtension({
+    manifest: {
+      content_scripts: [
+        {
+          matches: ["http://example.com/dummy*"],
+          js: ["content_script.js"],
+          run_at: "document_start",
+        },
+      ],
+    },
+
+    files: {
+      "content_script.js": contentScript,
+    },
+  });
+}
+
+add_task(async function test_contentscript_context() {
+  let extension = loadExtension();
+  await extension.startup();
+
+  let contentPage = await ExtensionTestUtils.loadContentPage(
+    "http://example.com/dummy"
+  );
+  await extension.awaitMessage("content-script-ready");
+  await extension.awaitMessage("content-script-show");
+
+  // Get the content script context and check that it points to the correct window.
+  await contentPage.legacySpawn(extension.id, async extensionId => {
+    const { ExtensionContent } = ChromeUtils.importESModule(
+      "resource://gre/modules/ExtensionContent.sys.mjs"
+    );
+    this.context = ExtensionContent.getContextByExtensionId(
+      extensionId,
+      this.content
+    );
+
+    Assert.ok(this.context, "Got content script context");
+
+    Assert.equal(
+      this.context.contentWindow,
+      this.content,
+      "Context's contentWindow property is correct"
+    );
+
+    // Navigate so that the content page is hidden in the bfcache.
+
+    this.content.location = "http://example.org/dummy";
+  });
+
+  await extension.awaitMessage("content-script-hide");
+
+  await contentPage.legacySpawn(null, async () => {
+    Assert.equal(
+      this.context.contentWindow,
+      null,
+      "Context's contentWindow property is null"
+    );
+
+    // Navigate back so the content page is resurrected from the bfcache.
+    this.content.history.back();
+  });
+
+  await extension.awaitMessage("content-script-show");
+
+  await contentPage.legacySpawn(null, async () => {
+    Assert.equal(
+      this.context.contentWindow,
+      this.content,
+      "Context's contentWindow property is correct"
+    );
+  });
+
+  await contentPage.close();
+  await extension.awaitMessage("content-script-hide");
+  await extension.unload();
+});
+
+add_task(async function test_contentscript_context_incognito_not_allowed() {
+  async function background() {
+    await browser.contentScripts.register({
+      js: [{ file: "registered_script.js" }],
+      matches: ["http://example.com/dummy"],
+      runAt: "document_start",
+    });
+
+    browser.test.sendMessage("background-ready");
+  }
+
+  let extension = ExtensionTestUtils.loadExtension({
+    manifest: {
+      content_scripts: [
+        {
+          matches: ["http://example.com/dummy"],
+          js: ["content_script.js"],
+          run_at: "document_start",
+        },
+      ],
+      permissions: ["http://example.com/*"],
+    },
+    background,
+    files: {
+      "content_script.js": () => {
+        browser.test.notifyFail("content_script_loaded");
+      },
+      "registered_script.js": () => {
+        browser.test.notifyFail("registered_script_loaded");
+      },
+    },
+  });
+
+  // Bug 1715801: Re-enable pbm portion on GeckoView
+  if (AppConstants.platform == "android") {
+    Services.prefs.setBoolPref("dom.security.https_first_pbm", false);
+  }
+
+  await extension.startup();
+  await extension.awaitMessage("background-ready");
+
+  let contentPage = await ExtensionTestUtils.loadContentPage(
+    "http://example.com/dummy",
+    { privateBrowsing: true }
+  );
+
+  await contentPage.legacySpawn(extension.id, async extensionId => {
+    const { ExtensionContent } = ChromeUtils.importESModule(
+      "resource://gre/modules/ExtensionContent.sys.mjs"
+    );
+    let context = ExtensionContent.getContextByExtensionId(
+      extensionId,
+      this.content
+    );
+    Assert.equal(
+      context,
+      null,
+      "Extension unable to use content_script in private browsing window"
+    );
+  });
+
+  await contentPage.close();
+  await extension.unload();
+
+  // Bug 1715801: Re-enable pbm portion on GeckoView
+  if (AppConstants.platform == "android") {
+    Services.prefs.clearUserPref("dom.security.https_first_pbm");
+  }
+});
+
+add_task(async function test_contentscript_context_unload_while_in_bfcache() {
+  let contentPage = await ExtensionTestUtils.loadContentPage(
+    "http://example.com/dummy?first"
+  );
+  let extension = loadExtension();
+  await extension.startup();
+  await extension.awaitMessage("content-script-ready");
+
+  // Get the content script context and check that it points to the correct window.
+  await contentPage.legacySpawn(extension.id, async extensionId => {
+    const { ExtensionContent } = ChromeUtils.importESModule(
+      "resource://gre/modules/ExtensionContent.sys.mjs"
+    );
+    // Save context so we can verify that contentWindow is nulled after unload.
+    this.context = ExtensionContent.getContextByExtensionId(
+      extensionId,
+      this.content
+    );
+
+    Assert.equal(
+      this.context.contentWindow,
+      this.content,
+      "Context's contentWindow property is correct"
+    );
+
+    this.contextUnloadedPromise = new Promise(resolve => {
+      this.context.callOnClose({ close: resolve });
+    });
+    this.pageshownPromise = new Promise(resolve => {
+      this.content.addEventListener(
+        "pageshow",
+        () => {
+          // Yield to the event loop once more to ensure that all pageshow event
+          // handlers have been dispatched before fulfilling the promise.
+          let { setTimeout } = ChromeUtils.importESModule(
+            "resource://gre/modules/Timer.sys.mjs"
+          );
+          setTimeout(resolve, 0);
+        },
+        { once: true, mozSystemGroup: true }
+      );
+    });
+
+    // Navigate so that the content page is hidden in the bfcache.
+    this.content.location = "http://example.org/dummy?second";
+  });
+
+  await extension.awaitMessage("content-script-hide");
+
+  await extension.unload();
+  await contentPage.legacySpawn(null, async () => {
+    await this.contextUnloadedPromise;
+    Assert.equal(this.context.unloaded, true, "Context has been unloaded");
+
+    // Normally, when a page is not in the bfcache, context.contentWindow is
+    // not null when the callOnClose handler is invoked (this is checked by the
+    // previous subtest).
+    // Now wait a little bit and check again to ensure that the contentWindow
+    // property is not somehow restored.
+    await new Promise(resolve => this.content.setTimeout(resolve, 0));
+    Assert.equal(
+      this.context.contentWindow,
+      null,
+      "Context's contentWindow property is null"
+    );
+
+    // Navigate back so the content page is resurrected from the bfcache.
+    this.content.history.back();
+
+    await this.pageshownPromise;
+
+    Assert.equal(
+      this.context.contentWindow,
+      null,
+      "Context's contentWindow property is null after restore from bfcache"
+    );
+  });
+
+  await contentPage.close();
+});
+
+add_task(async function test_contentscript_context_valid_during_execution() {
+  // This test does the following:
+  // - Load page
+  // - Load extension; inject content script.
+  // - Navigate page; pagehide triggered.
+  // - Navigate back; pageshow triggered.
+  // - Close page; pagehide, unload triggered.
+  // At each of these last four events, the validity of the context is checked.
+
+  function contentScript() {
+    browser.test.sendMessage("content-script-ready");
+    window.wrappedJSObject.checkContextIsValid("Context is valid on execution");
+
+    window.addEventListener(
+      "pagehide",
+      () => {
+        window.wrappedJSObject.checkContextIsValid(
+          "Context is valid on pagehide"
+        );
+        browser.test.sendMessage("content-script-hide");
+      },
+      true
+    );
+    window.addEventListener("pageshow", () => {
+      window.wrappedJSObject.checkContextIsValid(
+        "Context is valid on pageshow"
+      );
+
+      // This unload listener is registered after pageshow, to ensure that the
+      // page can be stored in the bfcache at the previous pagehide.
+      window.addEventListener("unload", () => {
+        window.wrappedJSObject.checkContextIsValid(
+          "Context is valid on unload"
+        );
+        browser.test.sendMessage("content-script-unload");
+      });
+
+      browser.test.sendMessage("content-script-show");
+    });
+  }
+
+  let extension = ExtensionTestUtils.loadExtension({
+    manifest: {
+      content_scripts: [
+        {
+          matches: ["http://example.com/dummy*"],
+          js: ["content_script.js"],
+        },
+      ],
+    },
+
+    files: {
+      "content_script.js": contentScript,
+    },
+  });
+
+  let contentPage = await ExtensionTestUtils.loadContentPage(
+    "http://example.com/dummy?first"
+  );
+  await contentPage.legacySpawn(extension.id, async extensionId => {
+    let context;
+    let checkContextIsValid = description => {
+      if (!context) {
+        const { ExtensionContent } = ChromeUtils.importESModule(
+          "resource://gre/modules/ExtensionContent.sys.mjs"
+        );
+        context = ExtensionContent.getContextByExtensionId(
+          extensionId,
+          this.content
+        );
+      }
+      Assert.equal(
+        context.contentWindow,
+        this.content,
+        `${description}: contentWindow`
+      );
+      Assert.equal(context.active, true, `${description}: active`);
+    };
+    Cu.exportFunction(checkContextIsValid, this.content, {
+      defineAs: "checkContextIsValid",
+    });
+  });
+  await extension.startup();
+  await extension.awaitMessage("content-script-ready");
+
+  await contentPage.legacySpawn(extension.id, async extensionId => {
+    // Navigate so that the content page is frozen in the bfcache.
+    this.content.location = "http://example.org/dummy?second";
+  });
+
+  await extension.awaitMessage("content-script-hide");
+  await contentPage.legacySpawn(null, async () => {
+    // Navigate back so the content page is resurrected from the bfcache.
+    this.content.history.back();
+  });
+
+  await extension.awaitMessage("content-script-show");
+  await contentPage.close();
+  await extension.awaitMessage("content-script-hide");
+  await extension.awaitMessage("content-script-unload");
+  await extension.unload();
+});
diff --git a/toolkit/components/extensions/test/xpcshell/test_ext_contentscript_context_isolation.js b/toolkit/components/extensions/test/xpcshell/test_ext_contentscript_context_isolation.js
new file mode 100644
index 0000000000..7794a66d57
--- /dev/null
+++ b/toolkit/components/extensions/test/xpcshell/test_ext_contentscript_context_isolation.js
@@ -0,0 +1,168 @@
+"use strict";
+
+/* globals exportFunction */
+/* eslint-disable mozilla/balanced-listeners */
+
+const server = createHttpServer({ hosts: ["example.com", "example.org"] });
+
+server.registerPathHandler("/dummy", (request, response) => {
+  response.setStatusLine(request.httpVersion, 200, "OK");
+  response.setHeader("Content-Type", "text/html", false);
+  response.write("<!DOCTYPE html><html></html>");
+});
+
+server.registerPathHandler("/bfcachetestpage", (request, response) => {
+  response.setStatusLine(request.httpVersion, 200, "OK");
+  response.setHeader("Content-Type", "text/html;charset=utf-8", false);
+  response.write(`<!DOCTYPE html>
+<script>
+  window.addEventListener("pageshow", (event) => {
+    event.stopImmediatePropagation();
+    if (window.browserTestSendMessage) {
+      browserTestSendMessage("content-script-show");
+    }
+  });
+  window.addEventListener("pagehide", (event) => {
+    event.stopImmediatePropagation();
+    if (window.browserTestSendMessage) {
+      if (event.persisted) {
+        browserTestSendMessage("content-script-hide");
+      } else {
+        browserTestSendMessage("content-script-unload");
+      }
+    }
+  }, true);
+</script>`);
+});
+
+add_task(async function test_contentscript_context_isolation() {
+  function contentScript() {
+    browser.test.sendMessage("content-script-ready");
+
+    exportFunction(browser.test.sendMessage, window, {
+      defineAs: "browserTestSendMessage",
+    });
+
+    window.addEventListener("pageshow", () => {
+      browser.test.fail(
+        "pageshow should have been suppressed by stopImmediatePropagation"
+      );
+    });
+    window.addEventListener(
+      "pagehide",
+      () => {
+        browser.test.fail(
+          "pagehide should have been suppressed by stopImmediatePropagation"
+        );
+      },
+      true
+    );
+  }
+
+  let extension = ExtensionTestUtils.loadExtension({
+    manifest: {
+      content_scripts: [
+        {
+          matches: ["http://example.com/bfcachetestpage"],
+          js: ["content_script.js"],
+        },
+      ],
+    },
+
+    files: {
+      "content_script.js": contentScript,
+    },
+  });
+
+  let contentPage = await ExtensionTestUtils.loadContentPage(
+    "http://example.com/bfcachetestpage"
+  );
+  await extension.startup();
+  await extension.awaitMessage("content-script-ready");
+
+  // Get the content script context and check that it points to the correct window.
+  await contentPage.legacySpawn(extension.id, async extensionId => {
+    const { ExtensionContent } = ChromeUtils.importESModule(
+      "resource://gre/modules/ExtensionContent.sys.mjs"
+    );
+    this.context = ExtensionContent.getContextByExtensionId(
+      extensionId,
+      this.content
+    );
+
+    Assert.ok(this.context, "Got content script context");
+
+    Assert.equal(
+      this.context.contentWindow,
+      this.content,
+      "Context's contentWindow property is correct"
+    );
+
+    // Navigate so that the content page is hidden in the bfcache.
+
+    this.content.location = "http://example.org/dummy?noscripthere1";
+  });
+
+  await extension.awaitMessage("content-script-hide");
+
+  await contentPage.legacySpawn(null, async () => {
+    Assert.equal(
+      this.context.contentWindow,
+      null,
+      "Context's contentWindow property is null"
+    );
+    Assert.ok(this.context.sandbox, "Context's sandbox exists");
+
+    // Navigate back so the content page is resurrected from the bfcache.
+    this.content.history.back();
+  });
+
+  await extension.awaitMessage("content-script-show");
+
+  async function testWithoutBfcache() {
+    return contentPage.legacySpawn(null, async () => {
+      Assert.equal(
+        this.context.contentWindow,
+        this.content,
+        "Context's contentWindow property is correct"
+      );
+      Assert.ok(this.context.sandbox, "Context's sandbox exists before unload");
+
+      let contextUnloadedPromise = new Promise(resolve => {
+        this.context.callOnClose({ close: resolve });
+      });
+
+      // Now add an "unload" event listener, which should prevent a page from entering the bfcache.
+      await new Promise(resolve => {
+        this.content.addEventListener("unload", () => {
+          Assert.equal(
+            this.context.contentWindow,
+            this.content,
+            "Context's contentWindow property should be non-null at unload"
+          );
+          resolve();
+        });
+        this.content.location = "http://example.org/dummy?noscripthere2";
+      });
+
+      await contextUnloadedPromise;
+    });
+  }
+  await runWithPrefs(
+    [["docshell.shistory.bfcache.allow_unload_listeners", false]],
+    testWithoutBfcache
+  );
+
+  await extension.awaitMessage("content-script-unload");
+
+  await contentPage.legacySpawn(null, async () => {
+    Assert.equal(
+      this.context.sandbox,
+      null,
+      "Context's sandbox has been destroyed after unload"
+    );
+  });
+
+  await contentPage.close();
+  await extension.unload();
+});
diff --git a/toolkit/components/extensions/test/xpcshell/test_ext_contentscript_create_iframe.js b/toolkit/components/extensions/test/xpcshell/test_ext_contentscript_create_iframe.js
new file mode 100644
index 0000000000..41d9901c80
--- /dev/null
+++ b/toolkit/components/extensions/test/xpcshell/test_ext_contentscript_create_iframe.js
@@ -0,0 +1,177 @@
+"use strict";
+
+const server = createHttpServer({ hosts: ["example.com"] });
+server.registerDirectory("/data/", do_get_file("data"));
+
+add_task(async function test_contentscript_create_iframe() {
+  function background() {
+    browser.runtime.onMessage.addListener((msg, sender) => {
+      let { name, availableAPIs, manifest, testGetManifest } = msg;
+      let hasExtTabsAPI = availableAPIs.indexOf("tabs") > 0;
+      let hasExtWindowsAPI = availableAPIs.indexOf("windows") > 0;
+
+      browser.test.assertFalse(
+        hasExtTabsAPI,
+        "the created iframe should not be able to use privileged APIs (tabs)"
+      );
+      browser.test.assertFalse(
+        hasExtWindowsAPI,
+        "the created iframe should not be able to use privileged APIs (windows)"
+      );
+
+      let {
+        browser_specific_settings: {
+          gecko: { id: expectedManifestGeckoId },
+        },
+      } = chrome.runtime.getManifest();
+      let {
+        browser_specific_settings: {
+          gecko: { id: actualManifestGeckoId },
+        },
+      } = manifest;
+
+      browser.test.assertEq(
+        actualManifestGeckoId,
+        expectedManifestGeckoId,
+        "the add-on manifest should be accessible from the created iframe"
+      );
+
+      let {
+        browser_specific_settings: {
+          gecko: { id: testGetManifestGeckoId },
+        },
+      } = testGetManifest;
+
+      browser.test.assertEq(
+        testGetManifestGeckoId,
+        expectedManifestGeckoId,
+        "GET_MANIFEST() returns manifest data before extension unload"
+      );
+
+      browser.test.sendMessage(name);
+    });
+  }
+
+  function contentScriptIframe() {
+    window.GET_MANIFEST = browser.runtime.getManifest.bind(null);
+
+    window.testGetManifestException = () => {
+      try {
+        window.GET_MANIFEST();
+      } catch (exception) {
+        return String(exception);
+      }
+    };
+
+    let testGetManifest = window.GET_MANIFEST();
+
+    let manifest = browser.runtime.getManifest();
+    let availableAPIs = Object.keys(browser).filter(key => browser[key]);
+
+    browser.runtime.sendMessage({
+      name: "content-script-iframe-loaded",
+      availableAPIs,
+      manifest,
+      testGetManifest,
+    });
+  }
+
+  const ID = "contentscript@tests.mozilla.org";
+  let extensionData = {
+    manifest: {
+      browser_specific_settings: { gecko: { id: ID } },
+      content_scripts: [
+        {
+          matches: ["http://example.com/data/file_sample.html"],
+          js: ["content_script.js"],
+          run_at: "document_idle",
+        },
+      ],
+      web_accessible_resources: ["content_script_iframe.html"],
+    },
+
+    background,
+
+    files: {
+      "content_script.js"() {
+        let iframe = document.createElement("iframe");
+        iframe.src = browser.runtime.getURL("content_script_iframe.html");
+        document.body.appendChild(iframe);
+      },
+      "content_script_iframe.html": `<!DOCTYPE html>
+        <html>
+          <head>
+            <meta charset="utf-8">
+            <script type="text/javascript" src="content_script_iframe.js"></script>
+          </head>
+        </html>`,
+      "content_script_iframe.js": contentScriptIframe,
+    },
+  };
+
+  let extension = ExtensionTestUtils.loadExtension(extensionData);
+  await extension.startup();
+
+  let contentPage = await ExtensionTestUtils.loadContentPage(
+    "http://example.com/data/file_sample.html"
+  );
+
+  await extension.awaitMessage("content-script-iframe-loaded");
+
+  info("testing APIs availability once the extension is unloaded...");
+
+  await contentPage.legacySpawn(null, () => {
+    this.iframeWindow = this.content[0];
+
+    Assert.ok(this.iframeWindow, "content script enabled iframe found");
+    Assert.ok(
+      /content_script_iframe\.html$/.test(this.iframeWindow.location),
+      "the found iframe has the expected URL"
+    );
+  });
+
+  await extension.unload();
+
+  info(
+    "test content script APIs not accessible from the frame once the extension is unloaded"
+  );
+
+  await contentPage.legacySpawn(null, () => {
+    let win = Cu.waiveXrays(this.iframeWindow);
+    ok(
+      !Cu.isDeadWrapper(win.browser),
+      "the API object should not be a dead object"
+    );
+
+    let manifest;
+    let manifestException;
+    try {
+      manifest = win.browser.runtime.getManifest();
+    } catch (e) {
+      manifestException = e;
+    }
+
+    Assert.ok(!manifest, "manifest should be undefined");
+
+    Assert.equal(
+      manifestException.constructor.name,
+      "TypeError",
+      "expected exception received"
+    );
+
+    Assert.ok(
+      manifestException.message.endsWith("win.browser.runtime is undefined"),
+      "expected exception received"
+    );
+
+    let getManifestException = win.testGetManifestException();
+
+    Assert.equal(
+      getManifestException,
+      "TypeError: can't access dead object",
+      "expected exception received"
+    );
+  });
+
+  await contentPage.close();
+});
diff --git a/toolkit/components/extensions/test/xpcshell/test_ext_contentscript_csp.js b/toolkit/components/extensions/test/xpcshell/test_ext_contentscript_csp.js
new file mode 100644
index 0000000000..6b03f5b0b0
--- /dev/null
+++ b/toolkit/components/extensions/test/xpcshell/test_ext_contentscript_csp.js
@@ -0,0 +1,433 @@
+/* -*- Mode: indent-tabs-mode: nil; js-indent-level: 2 -*- */
+/* vim: set sts=2 sw=2 et tw=80: */
+"use strict";
+
+const { TestUtils } = ChromeUtils.importESModule(
+  "resource://testing-common/TestUtils.sys.mjs"
+);
+
+Services.prefs.setBoolPref("extensions.manifestV3.enabled", true);
+
+const server = createHttpServer({
+  hosts: ["example.com", "csplog.example.net"],
+});
+server.registerDirectory("/data/", do_get_file("data"));
+
+var gDefaultCSP = `default-src 'self' 'report-sample'; script-src 'self' 'report-sample';`;
+var gCSP = gDefaultCSP;
+const pageContent = `<!DOCTYPE html>
+  <html lang="en">
+  <head>
+    <meta charset="UTF-8">
+    <title></title>
+  </head>
+  <body>
+  <img id="testimg">
+  </body>
+  </html>`;
+
+server.registerPathHandler("/plain.html", (request, response) => {
+  response.setStatusLine(request.httpVersion, 200, "OK");
+  response.setHeader("Content-Type", "text/html");
+  if (gCSP) {
+    info(`Content-Security-Policy: ${gCSP}`);
+    response.setHeader("Content-Security-Policy", gCSP);
+  }
+  response.write(pageContent);
+});
+
+const BASE_URL = `http://example.com`;
+const pageURL = `${BASE_URL}/plain.html`;
+
+const CSP_REPORT_PATH = "/csp-report.sjs";
+
+function readUTF8InputStream(stream) {
+  let buffer = NetUtil.readInputStream(stream, stream.available());
+  return new TextDecoder().decode(buffer);
+}
+
+server.registerPathHandler(CSP_REPORT_PATH, (request, response) => {
+  response.setStatusLine(request.httpVersion, 204, "No Content");
+  let data = readUTF8InputStream(request.bodyInputStream);
+  Services.obs.notifyObservers(null, "extension-test-csp-report", data);
+});
+
+async function promiseCSPReport(test) {
+  let res = await TestUtils.topicObserved("extension-test-csp-report", test);
+  return JSON.parse(res[1]);
+}
+
+// Test functions loaded into extension content script.
+function testImage(data = {}) {
+  return new Promise(resolve => {
+    let img = window.document.getElementById("testimg");
+    img.onload = () => resolve(true);
+    img.onerror = () => {
+      browser.test.log(`img error: ${img.src}`);
+      resolve(false);
+    };
+    img.src = data.image_url;
+  });
+}
+
+function testFetch(data = {}) {
+  let f = data.content ? content.fetch : fetch;
+  return f(data.url)
+    .then(() => true)
+    .catch(e => {
+      browser.test.assertEq(
+        e.message,
+        "NetworkError when attempting to fetch resource.",
+        "expected fetch failure"
+      );
+      return false;
+    });
+}
+
+async function testEval(data = {}) {
+  try {
+    // eslint-disable-next-line no-eval
+    let ev = data.content ? window.eval : eval;
+    return ev("true");
+  } catch (e) {
+    return false;
+  }
+}
+
+async function testFunction(data = {}) {
+  try {
+    // eslint-disable-next-line no-eval
+    let fn = data.content ? window.Function : Function;
+    let sum = new fn("a", "b", "return a + b");
+    return sum(1, 1);
+  } catch (e) {
+    return 0;
+  }
+}
+
+function testScriptTag(data) {
+  return new Promise(resolve => {
+    let script = document.createElement("script");
+    script.src = data.url;
+    script.onload = () => {
+      resolve(true);
+    };
+    script.onerror = () => {
+      resolve(false);
+    };
+    document.body.appendChild(script);
+  });
+}
+
+async function testHttpRequestUpgraded(data = {}) {
+  let f = data.content ? content.fetch : fetch;
+  return f(data.url)
+    .then(() => "http:")
+    .catch(() => "https:");
+}
+
+async function testWebSocketUpgraded(data = {}) {
+  let ws = data.content ? content.WebSocket : WebSocket;
+  new ws(data.url);
+}
+
+function webSocketUpgradeListenerBackground() {
+  // Catch websocket requests and send the protocol back to be asserted.
+  browser.webRequest.onBeforeRequest.addListener(
+    details => {
+      // Send the protocol back as test result.
+      // This will either be "wss:", "ws:"
+      browser.test.sendMessage("result", new URL(details.url).protocol);
+      return { cancel: true };
+    },
+    { urls: ["wss://example.com/*", "ws://example.com/*"] },
+    ["blocking"]
+  );
+}
+
+// If the violation source is the extension the securitypolicyviolation event is not fired.
+// If the page is the source, the event is fired and both the content script or page scripts
+// will receive the event.  If we're expecting a moz-extension report  we'll  fail in the
+// event listener if we receive a report.  Otherwise we want to resolve in the listener to
+// ensure we've received the event for the test.
+function contentScript(report) {
+  return new Promise(resolve => {
+    if (!report || report["document-uri"] === "moz-extension") {
+      resolve();
+    }
+    // eslint-disable-next-line mozilla/balanced-listeners
+    document.addEventListener("securitypolicyviolation", e => {
+      browser.test.assertTrue(
+        e.documentURI !== "moz-extension",
+        `securitypolicyviolation: ${e.violatedDirective} ${e.documentURI}`
+      );
+      resolve();
+    });
+  });
+}
+
+let TESTS = [
+  // Image Tests
+  {
+    description:
+      "Image from content script using default extension csp. Image is allowed.",
+    pageCSP: `${gDefaultCSP} img-src 'none';`,
+    script: testImage,
+    data: { image_url: `${BASE_URL}/data/file_image_good.png` },
+    expect: true,
+  },
+  // Fetch Tests
+  {
+    description: "Fetch url in content script uses default extension csp.",
+    pageCSP: `${gDefaultCSP} connect-src 'none';`,
+    script: testFetch,
+    data: { url: `${BASE_URL}/data/file_image_good.png` },
+    expect: true,
+  },
+  {
+    description: "Fetch full url from content script uses page csp.",
+    pageCSP: `${gDefaultCSP} connect-src 'none';`,
+    script: testFetch,
+    data: {
+      content: true,
+      url: `${BASE_URL}/data/file_image_good.png`,
+    },
+    expect: false,
+    report: {
+      "blocked-uri": `${BASE_URL}/data/file_image_good.png`,
+      "document-uri": `${BASE_URL}/plain.html`,
+      "violated-directive": "connect-src",
+    },
+  },
+
+  // Eval tests.
+  {
+    description: "Eval from content script uses page csp with unsafe-eval.",
+    pageCSP: `default-src 'none'; script-src 'unsafe-eval';`,
+    script: testEval,
+    data: { content: true },
+    expect: true,
+  },
+  {
+    description: "Eval from content script uses page csp.",
+    pageCSP: `default-src 'self' 'report-sample'; script-src 'self';`,
+    version: 3,
+    script: testEval,
+    data: { content: true },
+    expect: false,
+    report: {
+      "blocked-uri": "eval",
+      "document-uri": "http://example.com/plain.html",
+      "violated-directive": "script-src",
+    },
+  },
+  {
+    description: "Eval in content script allowed by v2 csp.",
+    pageCSP: `script-src 'self' 'unsafe-eval';`,
+    script: testEval,
+    expect: true,
+  },
+  {
+    description: "Eval in content script disallowed by v3 csp.",
+    pageCSP: `script-src 'self' 'unsafe-eval';`,
+    version: 3,
+    script: testEval,
+    expect: false,
+  },
+  {
+    description: "Wrapped Eval in content script uses page csp.",
+    pageCSP: `script-src 'self' 'unsafe-eval';`,
+    version: 3,
+    script: async () => {
+      return window.wrappedJSObject.eval("true");
+    },
+    expect: true,
+  },
+  {
+    description: "Wrapped Eval in content script denied by page csp.",
+    pageCSP: `script-src 'self';`,
+    version: 3,
+    script: async () => {
+      try {
+        return window.wrappedJSObject.eval("true");
+      } catch (e) {
+        return false;
+      }
+    },
+    expect: false,
+  },
+
+  {
+    description: "Function from content script uses page csp.",
+    pageCSP: `default-src 'self'; script-src 'self' 'unsafe-eval';`,
+    script: testFunction,
+    data: { content: true },
+    expect: 2,
+  },
+  {
+    description: "Function from content script uses page csp.",
+    pageCSP: `default-src 'self' 'report-sample'; script-src 'self';`,
+    version: 3,
+    script: testFunction,
+    data: { content: true },
+    expect: 0,
+    report: {
+      "blocked-uri": "eval",
+      "document-uri": "http://example.com/plain.html",
+      "violated-directive": "script-src",
+    },
+  },
+  {
+    description: "Function in content script uses extension csp.",
+    pageCSP: `default-src 'self'; script-src 'self' 'unsafe-eval';`,
+    version: 3,
+    script: testFunction,
+    expect: 0,
+  },
+
+  // The javascript url tests are not included as we do not execute those,
+  // aparently even with the urlbar filtering pref flipped.
+  // (browser.urlbar.filter.javascript)
+  // https://bugzilla.mozilla.org/show_bug.cgi?id=866522
+
+  // script tag injection tests
+  {
+    description: "remote script in content script passes in v2",
+    version: 2,
+    pageCSP: "script-src http://example.com:*;",
+    script: testScriptTag,
+    data: { url: `${BASE_URL}/data/file_script_good.js` },
+    expect: true,
+  },
+  {
+    description: "remote script in content script fails in v3",
+    version: 3,
+    pageCSP: "script-src http://example.com:*;",
+    script: testScriptTag,
+    data: { url: `${BASE_URL}/data/file_script_good.js` },
+    expect: false,
+  },
+  {
+    description: "content.WebSocket in content script is affected by page csp.",
+    version: 2,
+    pageCSP: `upgrade-insecure-requests;`,
+    data: { content: true, url: "ws://example.com/ws_dummy" },
+    script: testWebSocketUpgraded,
+    expect: "wss:", // we expect the websocket to be upgraded.
+    backgroundScript: webSocketUpgradeListenerBackground,
+  },
+  {
+    description: "WebSocket in content script is not affected by page csp.",
+    version: 2,
+    pageCSP: `upgrade-insecure-requests;`,
+    data: { url: "ws://example.com/ws_dummy" },
+    script: testWebSocketUpgraded,
+    expect: "ws:", // we expect the websocket to not be upgraded.
+    backgroundScript: webSocketUpgradeListenerBackground,
+  },
+  {
+    description: "WebSocket in content script is not affected by page csp. v3",
+    version: 3,
+    pageCSP: `upgrade-insecure-requests;`,
+    data: { url: "ws://example.com/ws_dummy" },
+    script: testWebSocketUpgraded,
+    // TODO bug 1766813: MV3+WebSocket should use content script CSP.
+    expect: "wss:", // TODO: we expect the websocket to not be upgraded (ws:).
+    backgroundScript: webSocketUpgradeListenerBackground,
+  },
+  {
+    description: "Http request in content script is not affected by page csp.",
+    version: 2,
+    pageCSP: `upgrade-insecure-requests;`,
+    data: { url: "http://example.com/plain.html" },
+    script: testHttpRequestUpgraded,
+    expect: "http:", // we expect the request to not be upgraded.
+  },
+  {
+    description:
+      "Http request in content script is not affected by page csp. v3",
+    version: 3,
+    pageCSP: `upgrade-insecure-requests;`,
+    data: { url: "http://example.com/plain.html" },
+    script: testHttpRequestUpgraded,
+    // TODO bug 1766813: MV3+fetch should use content script CSP.
+    expect: "https:", // TODO: we expect the request to not be upgraded (http:).
+  },
+  {
+    description: "content.fetch in content script is affected by page csp.",
+    version: 2,
+    pageCSP: `upgrade-insecure-requests;`,
+    data: { content: true, url: "http://example.com/plain.html" },
+    script: testHttpRequestUpgraded,
+    expect: "https:", // we expect the request to be upgraded.
+  },
+];
+
+async function runCSPTest(test) {
+  // Set the CSP for the page loaded into the tab.
+  gCSP = `${test.pageCSP || gDefaultCSP} report-uri ${CSP_REPORT_PATH}`;
+  let data = {
+    manifest: {
+      manifest_version: test.version || 2,
+      content_scripts: [
+        {
+          matches: ["http://*/plain.html"],
+          run_at: "document_idle",
+          js: ["content_script.js"],
+        },
+      ],
+      permissions: ["webRequest", "webRequestBlocking"],
+      host_permissions: ["<all_urls>"],
+      granted_host_permissions: true,
+      background: { scripts: ["background.js"] },
+    },
+    temporarilyInstalled: true,
+    files: {
+      "content_script.js": `
+      (${contentScript})(${JSON.stringify(test.report)}).then(() => {
+        browser.test.sendMessage("violationEvent");
+      });
+      (${test.script})(${JSON.stringify(test.data)}).then(result => {
+        if(result !== undefined) { 
+          browser.test.sendMessage("result", result);
+        }
+      });
+      `,
+      "background.js": `(${test.backgroundScript || (() => {})})()`,
+      ...test.files,
+    },
+  };
+
+  let extension = ExtensionTestUtils.loadExtension(data);
+  await extension.startup();
+
+  let reportPromise = test.report && promiseCSPReport();
+  let contentPage = await ExtensionTestUtils.loadContentPage(pageURL);
+
+  info(`running: ${test.description}`);
+  await extension.awaitMessage("violationEvent");
+
+  let result = await extension.awaitMessage("result");
+  equal(result, test.expect, test.description);
+
+  if (test.report) {
+    let report = await reportPromise;
+    for (let key of Object.keys(test.report)) {
+      equal(
+        report["csp-report"][key],
+        test.report[key],
+        `csp-report ${key} matches`
+      );
+    }
+  }
+
+  await extension.unload();
+  await contentPage.close();
+  clearCache();
+}
+
+add_task(async function test_contentscript_csp() {
+  for (let test of TESTS) {
+    await runCSPTest(test);
+  }
+});
diff --git a/toolkit/components/extensions/test/xpcshell/test_ext_contentscript_css.js b/toolkit/components/extensions/test/xpcshell/test_ext_contentscript_css.js
new file mode 100644
index 0000000000..a75c397b8c
--- /dev/null
+++ b/toolkit/components/extensions/test/xpcshell/test_ext_contentscript_css.js
@@ -0,0 +1,48 @@
+"use strict";
+
+const server = createHttpServer({ hosts: ["example.com"] });
+
+server.registerPathHandler("/dummy", (request, response) => {
+  response.setStatusLine(request.httpVersion, 200, "OK");
+  response.setHeader("Content-Type", "text/html", false);
+  response.write("<!DOCTYPE html><html></html>");
+});
+
+add_task(async function test_content_script_css() {
+  let extension = ExtensionTestUtils.loadExtension({
+    manifest: {
+      content_scripts: [
+        {
+          matches: ["http://example.com/dummy"],
+          css: ["content.css"],
+          run_at: "document_start",
+        },
+      ],
+    },
+
+    files: {
+      "content.css": "body { max-width: 42px; }",
+    },
+  });
+
+  await extension.startup();
+
+  let contentPage = await ExtensionTestUtils.loadContentPage(
+    "http://example.com/dummy"
+  );
+
+  function task() {
+    let style = this.content.getComputedStyle(this.content.document.body);
+    return style.maxWidth;
+  }
+
+  let maxWidth = await contentPage.spawn([], task);
+  equal(maxWidth, "42px", "Stylesheet correctly applied");
+
+  await extension.unload();
+
+  maxWidth = await contentPage.spawn([], task);
+  equal(maxWidth, "none", "Stylesheet correctly removed");
+
+  await contentPage.close();
+});
diff --git a/toolkit/components/extensions/test/xpcshell/test_ext_contentscript_dynamic_registration.js b/toolkit/components/extensions/test/xpcshell/test_ext_contentscript_dynamic_registration.js
new file mode 100644
index 0000000000..0133b5d86c
--- /dev/null
+++ b/toolkit/components/extensions/test/xpcshell/test_ext_contentscript_dynamic_registration.js
@@ -0,0 +1,205 @@
+"use strict";
+
+const server = createHttpServer();
+server.registerDirectory("/data/", do_get_file("data"));
+
+const BASE_URL = `http://localhost:${server.identity.primaryPort}/data`;
+
+// ExtensionContent.jsm needs to know when it's running from xpcshell, to use
+// the right timeout for content scripts executed at document_idle.
+ExtensionTestUtils.mockAppInfo();
+
+// Do not use preallocated processes.
+Services.prefs.setBoolPref("dom.ipc.processPrelaunch.enabled", false);
+// This is needed for Android.
+Services.prefs.setIntPref("dom.ipc.keepProcessesAlive.web", 0);
+
+const makeExtension = ({ background, manifest }) => {
+  return ExtensionTestUtils.loadExtension({
+    manifest: {
+      ...manifest,
+      permissions:
+        manifest.manifest_version === 3 ? ["scripting"] : ["http://*/*/*.html"],
+    },
+    temporarilyInstalled: true,
+    background,
+    files: {
+      "script.js": () => {
+        browser.test.sendMessage(
+          `script-ran: ${location.pathname.split("/").pop()}`
+        );
+      },
+      "inject_browser.js": () => {
+        browser.userScripts.onBeforeScript.addListener(script => {
+          // Inject `browser.test.sendMessage()` so that it can be used in the
+          // `script.js` defined above when using "user scripts".
+          script.defineGlobals({
+            browser: {
+              test: {
+                sendMessage(msg) {
+                  browser.test.sendMessage(msg);
+                },
+              },
+            },
+          });
+        });
+      },
+    },
+  });
+};
+
+const verifyRegistrationWithNewProcess = async extension => {
+  // We override the `broadcast()` method to reliably verify Bug 1756495: when
+  // a new process is spawned while we register a content script, the script
+  // should be correctly registered and executed in this new process. Below,
+  // when we receive the `Extension:RegisterContentScripts`, we open a new tab
+  // (which is the "new process") and then we invoke the original "broadcast
+  // logic". The expected result is that the content script registered by the
+  // extension will run.
+  const originalBroadcast = Extension.prototype.broadcast;
+
+  let broadcastCalledCount = 0;
+  let secondContentPage;
+
+  extension.extension.broadcast = async function broadcast(msg, data) {
+    if (msg !== "Extension:RegisterContentScripts") {
+      return originalBroadcast.call(this, msg, data);
+    }
+
+    broadcastCalledCount++;
+    Assert.equal(
+      1,
+      broadcastCalledCount,
+      "broadcast override should be called once"
+    );
+
+    await originalBroadcast.call(this, msg, data);
+
+    Assert.equal(extension.id, data.id, "got expected extension ID");
+    Assert.equal(1, data.scripts.length, "expected 1 script to register");
+    Assert.ok(
+      data.scripts[0].options.jsPaths[0].endsWith("script.js"),
+      "got expected js file"
+    );
+
+    const newPids = [];
+    const topic = "ipc:content-created";
+
+    let obs = (subject, topic, data) => {
+      newPids.push(parseInt(data, 10));
+    };
+    Services.obs.addObserver(obs, topic);
+
+    secondContentPage = await ExtensionTestUtils.loadContentPage(
+      `${BASE_URL}/dummy_page.html`
+    );
+
+    const { childID } =
+      secondContentPage.browsingContext.currentWindowGlobal.domProcess;
+
+    Services.obs.removeObserver(obs, topic);
+
+    // We expect to have a new process created for `secondContentPage`.
+    Assert.ok(
+      newPids.includes(childID),
+      `expected PID ${childID} to be in [${newPids.join(", ")}])`
+    );
+  };
+
+  await extension.startup();
+  await extension.awaitMessage("background-done");
+
+  let contentPage = await ExtensionTestUtils.loadContentPage(
+    `${BASE_URL}/file_sample.html`
+  );
+
+  await Promise.all([
+    extension.awaitMessage("script-ran: file_sample.html"),
+    extension.awaitMessage("script-ran: dummy_page.html"),
+  ]);
+
+  // Unload extension first to avoid an issue on Windows platforms.
+  await extension.unload();
+  await contentPage.close();
+  await secondContentPage.close();
+};
+
+add_task(
+  {
+    pref_set: [["extensions.manifestV3.enabled", true]],
+  },
+  async function test_scripting_registerContentScripts() {
+    let extension = makeExtension({
+      manifest: {
+        manifest_version: 3,
+        host_permissions: ["<all_urls>"],
+        granted_host_permissions: true,
+      },
+      async background() {
+        const script = {
+          id: "a-script",
+          js: ["script.js"],
+          matches: ["http://*/*/*.html"],
+          persistAcrossSessions: false,
+        };
+
+        await browser.scripting.registerContentScripts([script]);
+
+        browser.test.sendMessage("background-done");
+      },
+    });
+
+    await verifyRegistrationWithNewProcess(extension);
+  }
+);
+
+add_task(
+  {
+    // We don't have WebIDL bindings for `browser.contentScripts`.
+    skip_if: () => ExtensionTestUtils.isInBackgroundServiceWorkerTests(),
+  },
+  async function test_contentScripts_register() {
+    let extension = makeExtension({
+      manifest: {
+        manifest_version: 2,
+      },
+      async background() {
+        await browser.contentScripts.register({
+          js: [{ file: "script.js" }],
+          matches: ["http://*/*/*.html"],
+        });
+
+        browser.test.sendMessage("background-done");
+      },
+    });
+
+    await verifyRegistrationWithNewProcess(extension);
+  }
+);
+
+add_task(
+  {
+    // We don't have WebIDL bindings for `browser.userScripts`.
+    skip_if: () => ExtensionTestUtils.isInBackgroundServiceWorkerTests(),
+  },
+  async function test_userScripts_register() {
+    let extension = makeExtension({
+      manifest: {
+        manifest_version: 2,
+        user_scripts: {
+          api_script: "inject_browser.js",
+        },
+      },
+      async background() {
+        await browser.userScripts.register({
+          js: [{ file: "script.js" }],
+          matches: ["http://*/*/*.html"],
+        });
+
+        browser.test.sendMessage("background-done");
+      },
+    });
+
+    await verifyRegistrationWithNewProcess(extension);
+  }
+);
diff --git a/toolkit/components/extensions/test/xpcshell/test_ext_contentscript_errors.js b/toolkit/components/extensions/test/xpcshell/test_ext_contentscript_errors.js
new file mode 100644
index 0000000000..6fae3b838a
--- /dev/null
+++ b/toolkit/components/extensions/test/xpcshell/test_ext_contentscript_errors.js
@@ -0,0 +1,150 @@
+"use strict";
+
+const server = createHttpServer();
+server.registerDirectory("/data/", do_get_file("data"));
+
+const BASE_URL = `http://localhost:${server.identity.primaryPort}/data`;
+const TEST_URL_1 = `${BASE_URL}/file_sample.html`;
+const TEST_URL_2 = `${BASE_URL}/file_content_script_errors.html`;
+
+// ExtensionContent.jsm needs to know when it's running from xpcshell,
+// to use the right timeout for content scripts executed at document_idle.
+ExtensionTestUtils.mockAppInfo();
+
+add_task(async function test_cached_contentscript_on_document_start() {
+  let extension = ExtensionTestUtils.loadExtension({
+    manifest: {
+      content_scripts: [
+        // Use distinct content scripts as some will throw and would prevent executing the next script
+        {
+          matches: ["http://*/*/file_content_script_errors.html"],
+          js: ["script1.js"],
+          run_at: "document_start",
+        },
+        {
+          matches: ["http://*/*/file_content_script_errors.html"],
+          js: ["script2.js"],
+          run_at: "document_start",
+        },
+        {
+          matches: ["http://*/*/file_content_script_errors.html"],
+          js: ["script3.js"],
+          run_at: "document_start",
+        },
+        {
+          matches: ["http://*/*/file_content_script_errors.html"],
+          js: ["script4.js"],
+          run_at: "document_start",
+        },
+        {
+          matches: ["http://*/*/file_content_script_errors.html"],
+          js: ["script5.js"],
+          run_at: "document_start",
+        },
+      ],
+    },
+
+    files: {
+      "script1.js": `
+        throw new Error("Object exception");
+      `,
+      "script2.js": `
+        throw "String exception";
+      `,
+      "script3.js": `
+        undefinedSymbol();
+      `,
+      "script4.js": `
+        )
+      `,
+      "script5.js": `
+        Promise.reject("rejected promise");
+
+        (async () => {
+          /* make the async, really async */
+          await new Promise(r => setTimeout(r, 0));
+          throw new Error("async function exception");
+        })();
+
+        setTimeout(() => {
+          asyncUndefinedSymbol();
+        });
+
+        /* Use a delay in order to resume test execution after these async errors */
+        setTimeout(() => {
+          browser.test.sendMessage("content-script-loaded");
+        }, 500);
+      `,
+    },
+  });
+
+  // Error messages, in roughly the order they appear above.
+  let expectedMessages = [
+    "Error: Object exception",
+    "uncaught exception: String exception",
+    "ReferenceError: undefinedSymbol is not defined",
+    "SyntaxError: expected expression, got ')'",
+    "uncaught exception: rejected promise",
+    "Error: async function exception",
+    "ReferenceError: asyncUndefinedSymbol is not defined",
+  ];
+
+  await extension.startup();
+
+  // Load a first page in order to be able to register a console listener in the content process.
+  // This has to be done in the same domain of the second page to stay in the same process.
+  let contentPage = await ExtensionTestUtils.loadContentPage(TEST_URL_1);
+
+  // Listen to the errors logged in the content process.
+  let errorsPromise = ContentTask.spawn(contentPage.browser, {}, async () => {
+    return new Promise(resolve => {
+      function listener(error0) {
+        let error = error0.QueryInterface(Ci.nsIScriptError);
+
+        // Ignore errors from ExtensionContent.jsm
+        if (!error.innerWindowID) {
+          return;
+        }
+
+        this.collectedErrors.push({
+          innerWindowID: error.innerWindowID,
+          message: error.errorMessage,
+        });
+        if (this.collectedErrors.length == 7) {
+          Services.console.unregisterListener(this);
+          resolve(this.collectedErrors);
+        }
+      }
+      listener.collectedErrors = [];
+      Services.console.registerListener(listener);
+    });
+  });
+
+  // Reload the page and check that the cached content script is still able to
+  // run on document_start.
+  await contentPage.loadURL(TEST_URL_2);
+
+  let errors = await errorsPromise;
+
+  await extension.awaitMessage("content-script-loaded");
+
+  equal(errors.length, 7);
+  let messages = [];
+  for (const { innerWindowID, message } of errors) {
+    equal(
+      innerWindowID,
+      contentPage.browser.innerWindowID,
+      `Message ${message} has the innerWindowID set`
+    );
+
+    messages.push(message);
+  }
+
+  messages.sort();
+  expectedMessages.sort();
+  Assert.deepEqual(messages, expectedMessages, "Got the expected errors");
+
+  await extension.unload();
+
+  await contentPage.close();
+});
diff --git a/toolkit/components/extensions/test/xpcshell/test_ext_contentscript_exporthelpers.js b/toolkit/components/extensions/test/xpcshell/test_ext_contentscript_exporthelpers.js
new file mode 100644
index 0000000000..ec3b11ee7d
--- /dev/null
+++ b/toolkit/components/extensions/test/xpcshell/test_ext_contentscript_exporthelpers.js
@@ -0,0 +1,98 @@
+"use strict";
+
+const server = createHttpServer({ hosts: ["example.com"] });
+server.registerDirectory("/data/", do_get_file("data"));
+
+add_task(async function test_contentscript_exportHelpers() {
+  function contentScript() {
+    browser.test.assertTrue(typeof cloneInto === "function");
+    browser.test.assertTrue(typeof createObjectIn === "function");
+    browser.test.assertTrue(typeof exportFunction === "function");
+
+    /* globals exportFunction, precisePi, reportPi */
+    let value = 3.14;
+    exportFunction(() => value, window, { defineAs: "precisePi" });
+
+    browser.test.assertEq(
+      "undefined",
+      typeof precisePi,
+      "exportFunction should export to the page's scope only"
+    );
+
+    browser.test.assertEq(
+      "undefined",
+      typeof window.precisePi,
+      "exportFunction should export to the page's scope only"
+    );
+
+    let results = [];
+    exportFunction(pi => results.push(pi), window, { defineAs: "reportPi" });
+
+    let s = document.createElement("script");
+    s.textContent = `(${function () {
+      let result1 = "unknown 1";
+      let result2 = "unknown 2";
+      try {
+        result1 = precisePi();
+      } catch (e) {
+        result1 = "err:" + e;
+      }
+      try {
+        result2 = window.precisePi();
+      } catch (e) {
+        result2 = "err:" + e;
+      }
+      reportPi(result1);
+      reportPi(result2);
+    }})();`;
+
+    document.documentElement.appendChild(s);
+    // Inline script ought to run synchronously.
+
+    browser.test.assertEq(
+      3.14,
+      results[0],
+      "exportFunction on window should define a global function"
+    );
+    browser.test.assertEq(
+      3.14,
+      results[1],
+      "exportFunction on window should export a property to window."
+    );
+
+    browser.test.assertEq(
+      2,
+      results.length,
+      "Expecting the number of results to match the number of method calls"
+    );
+
+    browser.test.notifyPass("export helper test completed");
+  }
+
+  let extensionData = {
+    manifest: {
+      content_scripts: [
+        {
+          js: ["contentscript.js"],
+          matches: ["http://example.com/data/file_sample.html"],
+          run_at: "document_start",
+        },
+      ],
+    },
+
+    files: {
+      "contentscript.js": contentScript,
+    },
+  };
+
+  let extension = ExtensionTestUtils.loadExtension(extensionData);
+  await extension.startup();
+
+  let contentPage = await ExtensionTestUtils.loadContentPage(
+    "http://example.com/data/file_sample.html"
+  );
+
+  await extension.awaitFinish("export helper test completed");
+  await contentPage.close();
+  await extension.unload();
+});
diff --git a/toolkit/components/extensions/test/xpcshell/test_ext_contentscript_importmap.js b/toolkit/components/extensions/test/xpcshell/test_ext_contentscript_importmap.js
new file mode 100644
index 0000000000..c7762f3afe
--- /dev/null
+++ b/toolkit/components/extensions/test/xpcshell/test_ext_contentscript_importmap.js
@@ -0,0 +1,124 @@
+"use strict";
+
+// Currently import maps are not supported for web extensions, neither for
+// content scripts nor moz-extension documents.
+// For content scripts that's because they use their own sandbox module loaders,
+// which is different from the DOM module loader.
+// As for moz-extension documents, that's because inline script tags is not
+// allowed by CSP. (Currently import maps can be only added through inline
+// script tag.)
+//
+// This test is used to verified import maps are not supported for web
+// extensions.
+// See Bug 1765275: Enable Import maps for web extension content scripts.
+Services.prefs.setBoolPref("dom.importMaps.enabled", true);
+
+const server = createHttpServer({ hosts: ["example.com"] });
+
+const importMapString = `
+  <script type="importmap">
+  {
+    "imports": {
+      "simple": "./simple.js",
+      "simple2": "./simple2.js"
+    }
+  }
+  </script>`;
+
+const importMapHtml = `
+  <!DOCTYPE html>
+  <html>
+  <meta charset=utf-8>
+  <title>Test a simple import map in normal webpage</title>
+  <body>
+  ${importMapString}
+  </body></html>`;
+
+// page.html will load page.js, which will call import();
+const pageHtml = `
+  <!DOCTYPE html>
+  <html>
+  <meta charset=utf-8>
+  <title>Test a simple import map in moz-extension documents</title>
+  <body>
+  ${importMapString}
+  <script src="page.js"></script>
+  </body></html>`;
+
+const simple2JS = `export let foo = 2;`;
+
+server.registerPathHandler("/importmap.html", (request, response) => {
+  response.setStatusLine(request.httpVersion, 200, "OK");
+  response.setHeader("Content-Type", "text/html", false);
+  response.write(importMapHtml);
+});
+
+server.registerPathHandler("/simple.js", (request, response) => {
+  ok(false, "Unexpected request to /simple.js");
+});
+
+server.registerPathHandler("/simple2.js", (request, response) => {
+  response.setStatusLine(request.httpVersion, 200, "OK");
+  response.setHeader("Content-Type", "text/javascript", false);
+  response.write(simple2JS);
+});
+
+add_task(async function test_importMaps_not_supported() {
+  let extension = ExtensionTestUtils.loadExtension({
+    manifest: {
+      content_scripts: [
+        {
+          matches: ["http://example.com/importmap.html"],
+          js: ["main.js"],
+        },
+      ],
+    },
+
+    files: {
+      "main.js": async function () {
+        // Content scripts shouldn't be able to use the bare specifier from
+        // the import map.
+        await browser.test.assertRejects(
+          import("simple"),
+          /The specifier “simple” was a bare specifier/,
+          `should reject import("simple")`
+        );
+
+        browser.test.sendMessage("done");
+      },
+      "page.html": pageHtml,
+      "page.js": async function () {
+        await browser.test.assertRejects(
+          import("simple"),
+          /The specifier “simple” was a bare specifier/,
+          `should reject import("simple")`
+        );
+        browser.test.sendMessage("page-done");
+      },
+    },
+  });
+
+  await extension.startup();
+
+  let contentPage = await ExtensionTestUtils.loadContentPage(
+    "http://example.com/importmap.html"
+  );
+  await extension.awaitMessage("done");
+
+  await contentPage.spawn([], async () => {
+    // Import maps should work for documents.
+    let promise = content.eval(`import("simple2")`);
+    let mod = (await promise.wrappedJSObject).wrappedJSObject;
+    Assert.equal(mod.foo, 2, "mod.foo should be 2");
+  });
+
+  // moz-extension documents doesn't allow inline scripts, so the import map
+  // script tag won't be processed.
+  let url = `moz-extension://${extension.uuid}/page.html`;
+  let page = await ExtensionTestUtils.loadContentPage(url, { extension });
+  await extension.awaitMessage("page-done");
+
+  await page.close();
+  await extension.unload();
+  await contentPage.close();
+});
diff --git a/toolkit/components/extensions/test/xpcshell/test_ext_contentscript_in_background.js b/toolkit/components/extensions/test/xpcshell/test_ext_contentscript_in_background.js
new file mode 100644
index 0000000000..e813b46ca0
--- /dev/null
+++ b/toolkit/components/extensions/test/xpcshell/test_ext_contentscript_in_background.js
@@ -0,0 +1,43 @@
+/* -*- Mode: indent-tabs-mode: nil; js-indent-level: 2 -*- */
+/* vim: set sts=2 sw=2 et tw=80: */
+"use strict";
+
+const server = createHttpServer({ hosts: ["example.com"] });
+server.registerPathHandler("/dummyFrame", (request, response) => {
+  response.setStatusLine(request.httpVersion, 200, "OK");
+  response.setHeader("Content-Type", "text/html; charset=utf-8", false);
+  response.write("");
+});
+
+add_task(async function content_script_in_background_frame() {
+  async function background() {
+    const FRAME_URL = "http://example.com:8888/dummyFrame";
+    await browser.contentScripts.register({
+      matches: ["http://example.com/dummyFrame"],
+      js: [{ file: "contentscript.js" }],
+      allFrames: true,
+    });
+
+    let f = document.createElement("iframe");
+    f.src = FRAME_URL;
+    document.body.appendChild(f);
+  }
+
+  function contentScript() {
+    browser.test.log(`Running content script at ${document.URL}`);
+    browser.test.sendMessage("done_in_content_script");
+  }
+
+  let extension = ExtensionTestUtils.loadExtension({
+    manifest: {
+      permissions: ["http://example.com/*"],
+    },
+    files: {
+      "contentscript.js": contentScript,
+    },
+    background,
+  });
+  await extension.startup();
+  await extension.awaitMessage("done_in_content_script");
+  await extension.unload();
+});
diff --git a/toolkit/components/extensions/test/xpcshell/test_ext_contentscript_json_api.js b/toolkit/components/extensions/test/xpcshell/test_ext_contentscript_json_api.js
new file mode 100644
index 0000000000..ca37e2e951
--- /dev/null
+++ b/toolkit/components/extensions/test/xpcshell/test_ext_contentscript_json_api.js
@@ -0,0 +1,102 @@
+"use strict";
+
+Services.prefs.setBoolPref("extensions.manifestV3.enabled", true);
+
+const server = createHttpServer({ hosts: ["example.com"] });
+server.registerPathHandler("/dummy", (request, response) => {
+  response.setStatusLine(request.httpVersion, 200, "OK");
+  response.write(
+    `<script>
+      // Clobber the JSON API to allow us to confirm that the page's value for
+      // the "JSON" object does not affect the content script's JSON API.
+      window.JSON = new String("overridden by page");
+      window.objFromPage = { serializeMe: "thanks" };
+      window.objWithToJSON = { toJSON: () => "toJSON ran", should_not_see: 1 };
+      </script>
+    `
+  );
+});
+
+async function test_JSON_parse_and_stringify({ manifest_version }) {
+  let extension = ExtensionTestUtils.loadExtension({
+    temporarilyInstalled: true, // Needed for granted_host_permissions
+    manifest: {
+      manifest_version,
+      granted_host_permissions: true, // Test-only: grant permissions in MV3.
+      host_permissions: ["http://example.com/"], // Work-around for bug 1766752.
+      content_scripts: [
+        {
+          matches: ["http://example.com/dummy"],
+          run_at: "document_end",
+          js: ["contentscript.js"],
+        },
+      ],
+    },
+    files: {
+      "contentscript.js"() {
+        let json = `{"a":[123,true,null]}`;
+        browser.test.assertEq(
+          JSON.stringify({ a: [123, true, null] }),
+          json,
+          "JSON.stringify with basic values"
+        );
+        let parsed = JSON.parse(json);
+        browser.test.assertTrue(
+          parsed instanceof Object,
+          "Parsed JSON is an Object"
+        );
+        browser.test.assertTrue(
+          parsed.a instanceof Array,
+          "Parsed JSON has an Array"
+        );
+        browser.test.assertEq(
+          JSON.stringify(parsed),
+          json,
+          "JSON.stringify for parsed JSON returns original input"
+        );
+        browser.test.assertEq(
+          JSON.stringify({ toJSON: () => "overridden", hideme: true }),
+          `"overridden"`,
+          "JSON.parse with toJSON method"
+        );
+
+        browser.test.assertEq(
+          JSON.stringify(window.wrappedJSObject.objFromPage),
+          `{"serializeMe":"thanks"}`,
+          "JSON.parse with value from the page"
+        );
+
+        browser.test.assertEq(
+          JSON.stringify(window.wrappedJSObject.objWithToJSON),
+          `"toJSON ran"`,
+          "JSON.parse with object with toJSON method from the page"
+        );
+
+        browser.test.assertTrue(JSON === globalThis.JSON, "JSON === this.JSON");
+        browser.test.assertTrue(JSON === window.JSON, "JSON === window.JSON");
+        browser.test.assertEq(
+          "overridden by page",
+          window.wrappedJSObject.JSON.toString(),
+          "page's JSON object is still the original value (overridden by page)"
+        );
+        browser.test.sendMessage("done");
+      },
+    },
+  });
+  await extension.startup();
+
+  let contentPage = await ExtensionTestUtils.loadContentPage(
+    "http://example.com/dummy"
+  );
+  await extension.awaitMessage("done");
+  await contentPage.close();
+  await extension.unload();
+}
+
+add_task(async function test_JSON_apis_MV2() {
+  await test_JSON_parse_and_stringify({ manifest_version: 2 });
+});
+
+add_task(async function test_JSON_apis_MV3() {
+  await test_JSON_parse_and_stringify({ manifest_version: 3 });
+});
diff --git a/toolkit/components/extensions/test/xpcshell/test_ext_contentscript_module_import.js b/toolkit/components/extensions/test/xpcshell/test_ext_contentscript_module_import.js
new file mode 100644
index 0000000000..b67ab1bcd9
--- /dev/null
+++ b/toolkit/components/extensions/test/xpcshell/test_ext_contentscript_module_import.js
@@ -0,0 +1,277 @@
+"use strict";
+
+const server = createHttpServer({ hosts: ["example.com"] });
+
+server.registerPathHandler("/dummy", (request, response) => {
+  response.setStatusLine(request.httpVersion, 200, "OK");
+  response.setHeader("Content-Type", "text/html", false);
+  response.write("<!DOCTYPE html><html></html>");
+});
+
+server.registerPathHandler("/script.js", (request, response) => {
+  ok(false, "Unexpected request to /script.js");
+});
+
+/* eslint-disable no-unsanitized/method, no-eval, no-implied-eval */
+
+const MODULE1 = `
+  import {foo} from "./module2.js";
+  export let bar = foo;
+
+  let count = 0;
+
+  export function counter () { return count++; }
+`;
+
+const MODULE2 = `export let foo = 2;`;
+
+add_task(async function test_disallowed_import() {
+  let extension = ExtensionTestUtils.loadExtension({
+    manifest: {
+      content_scripts: [
+        {
+          matches: ["http://example.com/dummy"],
+          js: ["main.js"],
+        },
+      ],
+    },
+
+    files: {
+      "main.js": async function () {
+        let disallowedURLs = [
+          "data:text/javascript,void 0",
+          "javascript:void 0",
+          "http://example.com/script.js",
+          URL.createObjectURL(
+            new Blob(["void 0", { type: "text/javascript" }])
+          ),
+        ];
+
+        for (let url of disallowedURLs) {
+          await browser.test.assertRejects(
+            import(url),
+            /error loading dynamically imported module/,
+            `should reject import("${url}")`
+          );
+        }
+
+        browser.test.sendMessage("done");
+      },
+    },
+  });
+
+  await extension.startup();
+  let contentPage = await ExtensionTestUtils.loadContentPage(
+    "http://example.com/dummy"
+  );
+  await extension.awaitMessage("done");
+  await extension.unload();
+  await contentPage.close();
+});
+
+add_task(async function test_normal_import() {
+  Services.prefs.setBoolPref("extensions.content_web_accessible.enabled", true);
+
+  let extension = ExtensionTestUtils.loadExtension({
+    manifest: {
+      content_scripts: [
+        {
+          matches: ["http://example.com/dummy"],
+          js: ["main.js"],
+        },
+      ],
+    },
+
+    files: {
+      "main.js": async function () {
+        /* global exportFunction */
+        const url = browser.runtime.getURL("module1.js");
+
+        await browser.test.assertRejects(
+          import(url),
+          /error loading dynamically imported module/,
+          "Cannot import script that is not web-accessible from page context"
+        );
+
+        await browser.test.assertRejects(
+          window.eval(`import("${url}")`),
+          /error loading dynamically imported module/,
+          "Cannot import script that is not web-accessible from page context"
+        );
+
+        let promise = new Promise((resolve, reject) => {
+          exportFunction(resolve, window, { defineAs: "resolve" });
+          exportFunction(reject, window, { defineAs: "reject" });
+        });
+
+        window.setTimeout(`import("${url}").then(resolve, reject)`, 0);
+
+        await browser.test.assertRejects(
+          promise,
+          /error loading dynamically imported module/,
+          "Cannot import script that is not web-accessible from page context"
+        );
+
+        browser.test.sendMessage("done");
+      },
+      "module1.js": MODULE1,
+      "module2.js": MODULE2,
+    },
+  });
+
+  await extension.startup();
+  let contentPage = await ExtensionTestUtils.loadContentPage(
+    "http://example.com/dummy"
+  );
+
+  await extension.awaitMessage("done");
+
+  // Web page can not import non-web-accessible files.
+  await contentPage.spawn([extension.uuid], async uuid => {
+    let files = ["main.js", "module1.js", "module2.js"];
+
+    for (let file of files) {
+      let url = `moz-extension://${uuid}/${file}`;
+      await Assert.rejects(
+        content.eval(`import("${url}")`),
+        /error loading dynamically imported module/,
+        "Cannot import script that is not web-accessible"
+      );
+    }
+  });
+
+  await extension.unload();
+  await contentPage.close();
+});
+
+add_task(async function test_import_web_accessible() {
+  let extension = ExtensionTestUtils.loadExtension({
+    manifest: {
+      content_scripts: [
+        {
+          matches: ["http://example.com/dummy"],
+          js: ["main.js"],
+        },
+      ],
+      web_accessible_resources: ["module1.js", "module2.js"],
+    },
+
+    files: {
+      "main.js": async function () {
+        let mod = await import(browser.runtime.getURL("module1.js"));
+        browser.test.assertEq(mod.bar, 2);
+        browser.test.assertEq(mod.counter(), 0);
+        browser.test.sendMessage("done");
+      },
+      "module1.js": MODULE1,
+      "module2.js": MODULE2,
+    },
+  });
+
+  await extension.startup();
+  let contentPage = await ExtensionTestUtils.loadContentPage(
+    "http://example.com/dummy"
+  );
+  await extension.awaitMessage("done");
+
+  // Web page can import web-accessible files,
+  // even after WebExtension imported the same files.
+  await contentPage.spawn([extension.uuid], async uuid => {
+    let base = `moz-extension://${uuid}`;
+
+    await Assert.rejects(
+      content.eval(`import("${base}/main.js")`),
+      /error loading dynamically imported module/,
+      "Cannot import script that is not web-accessible"
+    );
+
+    let promise = content.eval(`import("${base}/module1.js")`);
+    let mod = (await promise.wrappedJSObject).wrappedJSObject;
+    Assert.equal(mod.bar, 2, "exported value should match");
+    Assert.equal(mod.counter(), 0, "Counter should be fresh");
+    Assert.equal(mod.counter(), 1, "Counter should be fresh");
+
+    promise = content.eval(`import("${base}/module2.js")`);
+    mod = (await promise.wrappedJSObject).wrappedJSObject;
+    Assert.equal(mod.foo, 2, "exported value should match");
+  });
+
+  await extension.unload();
+  await contentPage.close();
+});
+
+add_task(async function test_import_web_accessible_after_page() {
+  let extension = ExtensionTestUtils.loadExtension({
+    manifest: {
+      content_scripts: [
+        {
+          matches: ["http://example.com/dummy"],
+          js: ["main.js"],
+        },
+      ],
+      web_accessible_resources: ["module1.js", "module2.js"],
+    },
+
+    files: {
+      "main.js": async function () {
+        browser.test.onMessage.addListener(async msg => {
+          browser.test.assertEq(msg, "import");
+
+          const url = browser.runtime.getURL("module1.js");
+          let mod = await import(url);
+          browser.test.assertEq(mod.bar, 2);
+          browser.test.assertEq(mod.counter(), 0, "Counter should be fresh");
+
+          let promise = window.eval(`import("${url}")`);
+          let mod2 = (await promise.wrappedJSObject).wrappedJSObject;
+          browser.test.assertEq(
+            mod2.counter(),
+            2,
+            "Counter should have been incremented by page"
+          );
+
+          browser.test.sendMessage("done");
+        });
+        browser.test.sendMessage("ready");
+      },
+      "module1.js": MODULE1,
+      "module2.js": MODULE2,
+    },
+  });
+
+  await extension.startup();
+  let contentPage = await ExtensionTestUtils.loadContentPage(
+    "http://example.com/dummy"
+  );
+  await extension.awaitMessage("ready");
+
+  // The web page imports the web-accessible files first,
+  // when the WebExtension imports the same file, they should
+  // not be shared.
+  await contentPage.spawn([extension.uuid], async uuid => {
+    let base = `moz-extension://${uuid}`;
+
+    await Assert.rejects(
+      content.eval(`import("${base}/main.js")`),
+      /error loading dynamically imported module/,
+      "Cannot import script that is not web-accessible"
+    );
+
+    let promise = content.eval(`import("${base}/module1.js")`);
+    let mod = (await promise.wrappedJSObject).wrappedJSObject;
+    Assert.equal(mod.bar, 2, "exported value should match");
+    Assert.equal(mod.counter(), 0);
+    Assert.equal(mod.counter(), 1);
+
+    promise = content.eval(`import("${base}/module2.js")`);
+    mod = (await promise.wrappedJSObject).wrappedJSObject;
+    Assert.equal(mod.foo, 2, "exported value should match");
+  });
+
+  extension.sendMessage("import");
+
+  await extension.awaitMessage("done");
+
+  await extension.unload();
+  await contentPage.close();
+});
diff --git a/toolkit/components/extensions/test/xpcshell/test_ext_contentscript_perf_observers.js b/toolkit/components/extensions/test/xpcshell/test_ext_contentscript_perf_observers.js
new file mode 100644
index 0000000000..2546b257fb
--- /dev/null
+++ b/toolkit/components/extensions/test/xpcshell/test_ext_contentscript_perf_observers.js
@@ -0,0 +1,71 @@
+"use strict";
+
+const server = createHttpServer({
+  hosts: ["a.example.com", "b.example.com", "c.example.com"],
+});
+server.registerDirectory("/data/", do_get_file("data"));
+
+add_task(async function test_perf_observers_cors() {
+  const extension = ExtensionTestUtils.loadExtension({
+    manifest: {
+      permissions: ["http://b.example.com/"],
+      content_scripts: [
+        {
+          matches: ["http://a.example.com/data/file_sample.html"],
+          js: ["cs.js"],
+        },
+      ],
+    },
+    files: {
+      "cs.js"() {
+        let obs = new window.PerformanceObserver(list => {
+          list.getEntries().forEach(e => {
+            browser.test.sendMessage("observed", {
+              url: e.name,
+              time: e.connectEnd,
+              size: e.encodedBodySize,
+            });
+          });
+        });
+        obs.observe({ entryTypes: ["resource"] });
+
+        let b = document.createElement("link");
+        b.rel = "stylesheet";
+
+        // Simulate page including a cross-origin resource from b.example.com.
+        b.wrappedJSObject.href = "http://b.example.com/data/file_download.txt";
+        document.head.appendChild(b);
+
+        let c = document.createElement("link");
+        c.rel = "stylesheet";
+
+        // Simulate page including a cross-origin resource from c.example.com.
+        c.wrappedJSObject.href = "http://c.example.com/data/file_download.txt";
+        document.head.appendChild(c);
+      },
+    },
+  });
+
+  let page = await ExtensionTestUtils.loadContentPage(
+    "http://a.example.com/data/file_sample.html"
+  );
+  await extension.startup();
+
+  let b = await extension.awaitMessage("observed");
+  let c = await extension.awaitMessage("observed");
+
+  if (b.url.startsWith("http://c.")) {
+    [c, b] = [b, c];
+  }
+
+  ok(b.url.startsWith("http://b."), "Observed resource from b.example.com");
+  ok(b.time > 0, "connectionEnd available from b.example.com");
+  equal(b.size, 46, "encodedBodySize available from b.example.com");
+
+  ok(c.url.startsWith("http://c."), "Observed resource from c.example.com");
+  equal(c.time, 0, "connectionEnd == 0 from c.example.com");
+  equal(c.size, 0, "encodedBodySize == 0 from c.example.com");
+
+  await extension.unload();
+  await page.close();
+});
diff --git a/toolkit/components/extensions/test/xpcshell/test_ext_contentscript_permissions_change.js b/toolkit/components/extensions/test/xpcshell/test_ext_contentscript_permissions_change.js
new file mode 100644
index 0000000000..842994858e
--- /dev/null
+++ b/toolkit/components/extensions/test/xpcshell/test_ext_contentscript_permissions_change.js
@@ -0,0 +1,104 @@
+"use strict";
+
+Services.prefs.setBoolPref("extensions.manifestV3.enabled", true);
+
+const server = createHttpServer({ hosts: ["example.com", "example.net"] });
+server.registerDirectory("/data/", do_get_file("data"));
+
+const HOSTS = ["http://example.com/*", "http://example.net/*"];
+
+const { ExtensionPermissions } = ChromeUtils.importESModule(
+  "resource://gre/modules/ExtensionPermissions.sys.mjs"
+);
+
+function grantOptional({ extension: ext }, origins) {
+  return ExtensionPermissions.add(ext.id, { origins, permissions: [] }, ext);
+}
+
+function revokeOptional({ extension: ext }, origins) {
+  return ExtensionPermissions.remove(ext.id, { origins, permissions: [] }, ext);
+}
+
+function makeExtension(id, content_scripts) {
+  return ExtensionTestUtils.loadExtension({
+    manifest: {
+      manifest_version: 3,
+
+      browser_specific_settings: { gecko: { id } },
+      content_scripts,
+
+      permissions: ["scripting"],
+      host_permissions: HOSTS,
+    },
+    files: {
+      "cs.js"() {
+        browser.test.log(`${browser.runtime.id} script on ${location.host}`);
+        browser.test.sendMessage(`${browser.runtime.id}_on_${location.host}`);
+      },
+    },
+    background() {
+      browser.test.onMessage.addListener(async (msg, origins) => {
+        browser.test.log(`${browser.runtime.id} registering content scripts`);
+        await browser.scripting.registerContentScripts([
+          {
+            id: "cs1",
+            persistAcrossSessions: false,
+            matches: origins,
+            js: ["cs.js"],
+          },
+        ]);
+        browser.test.sendMessage("done");
+      });
+    },
+  });
+}
+
+// Test that content scripts in MV3 enforce origin permissions.
+// Test granted optional permissions are available in newly spawned processes.
+add_task(async function test_contentscript_mv3_permissions() {
+  // Alpha lists content scripts in the manifest.
+  let alpha = makeExtension("alpha@test", [{ matches: HOSTS, js: ["cs.js"] }]);
+  let beta = makeExtension("beta@test");
+
+  await grantOptional(alpha, HOSTS);
+  await grantOptional(beta, ["http://example.net/*"]);
+  info("Granted initial permissions for both.");
+
+  await alpha.startup();
+  await beta.startup();
+
+  // Beta registers same content scripts using the scripting api.
+  beta.sendMessage("register", HOSTS);
+  await beta.awaitMessage("done");
+
+  // Only Alpha has origin permissions for example.com.
+  {
+    let page = await ExtensionTestUtils.loadContentPage(
+      `http://example.com/data/file_sample.html`
+    );
+    info("Loaded a page from example.com.");
+
+    await alpha.awaitMessage("alpha@test_on_example.com");
+    info("Got a message from alpha@test on example.com.");
+    await page.close();
+  }
+
+  await revokeOptional(alpha, ["http://example.net/*"]);
+  info("Revoked example.net permissions from Alpha.");
+
+  // Now only Beta has origin permissions for example.net.
+  {
+    let page = await ExtensionTestUtils.loadContentPage(
+      `http://example.net/data/file_sample.html`
+    );
+    info("Loaded a page from example.net.");
+
+    await beta.awaitMessage("beta@test_on_example.net");
+    info("Got a message from beta@test on example.net.");
+    await page.close();
+  }
+
+  info("Done, unloading Alpha and Beta.");
+  await beta.unload();
+  await alpha.unload();
+});
diff --git a/toolkit/components/extensions/test/xpcshell/test_ext_contentscript_permissions_fetch.js b/toolkit/components/extensions/test/xpcshell/test_ext_contentscript_permissions_fetch.js
new file mode 100644
index 0000000000..f9c1b360a0
--- /dev/null
+++ b/toolkit/components/extensions/test/xpcshell/test_ext_contentscript_permissions_fetch.js
@@ -0,0 +1,87 @@
+"use strict";
+
+Services.prefs.setBoolPref("extensions.manifestV3.enabled", true);
+
+const server = createHttpServer({ hosts: ["example.com", "example.net"] });
+server.registerDirectory("/data/", do_get_file("data"));
+
+const { ExtensionPermissions } = ChromeUtils.importESModule(
+  "resource://gre/modules/ExtensionPermissions.sys.mjs"
+);
+
+function grantOptional({ extension: ext }, origins) {
+  return ExtensionPermissions.add(ext.id, { origins, permissions: [] }, ext);
+}
+
+function revokeOptional({ extension: ext }, origins) {
+  return ExtensionPermissions.remove(ext.id, { origins, permissions: [] }, ext);
+}
+
+// Test granted optional permissions work with XHR/fetch in new processes.
+add_task(
+  {
+    pref_set: [["dom.ipc.keepProcessesAlive.extension", 0]],
+  },
+  async function test_fetch_origin_permissions_change() {
+    let extension = ExtensionTestUtils.loadExtension({
+      manifest: {
+        host_permissions: ["http://example.com/*"],
+        optional_permissions: ["http://example.net/*"],
+      },
+      files: {
+        "page.js"() {
+          fetch("http://example.net/data/file_sample.html")
+            .then(req => req.text())
+            .then(text => browser.test.sendMessage("done", { text }))
+            .catch(e => browser.test.sendMessage("done", { error: e.message }));
+        },
+        "page.html": `<!DOCTYPE html><meta charset="utf-8"><script src="page.js"></script>`,
+      },
+    });
+
+    await extension.startup();
+
+    let osPid;
+    {
+      // Grant permissions before extension process exists.
+      await grantOptional(extension, ["http://example.net/*"]);
+
+      let page = await ExtensionTestUtils.loadContentPage(
+        extension.extension.baseURI.resolve("page.html")
+      );
+
+      let { text } = await extension.awaitMessage("done");
+      ok(text.includes("Sample text"), "Can read from granted optional host.");
+
+      osPid = page.browsingContext.currentWindowGlobal.osPid;
+      await page.close();
+    }
+
+    // Release the extension process so that next part starts a new one.
+    Services.ppmm.releaseCachedProcesses();
+
+    {
+      // Revoke permissions and confirm fetch fails.
+      await revokeOptional(extension, ["http://example.net/*"]);
+
+      let page = await ExtensionTestUtils.loadContentPage(
+        extension.extension.baseURI.resolve("page.html")
+      );
+
+      let { error } = await extension.awaitMessage("done");
+      ok(error.includes("NetworkError"), `Expected error: ${error}`);
+
+      if (WebExtensionPolicy.useRemoteWebExtensions) {
+        notEqual(
+          osPid,
+          page.browsingContext.currentWindowGlobal.osPid,
+          "Second part of the test used a new process."
+        );
+      }
+
+      await page.close();
+    }
+
+    await extension.unload();
+  }
+);
diff --git a/toolkit/components/extensions/test/xpcshell/test_ext_contentscript_restrictSchemes.js b/toolkit/components/extensions/test/xpcshell/test_ext_contentscript_restrictSchemes.js
new file mode 100644
index 0000000000..d775bb2cfb
--- /dev/null
+++ b/toolkit/components/extensions/test/xpcshell/test_ext_contentscript_restrictSchemes.js
@@ -0,0 +1,149 @@
+"use strict";
+
+function makeExtension({ id, isPrivileged, withScriptingAPI = false }) {
+  let permissions = [];
+  let content_scripts = [];
+  let background = () => {
+    browser.test.sendMessage("background-ready");
+  };
+
+  if (isPrivileged) {
+    permissions.push("mozillaAddons");
+  }
+
+  if (withScriptingAPI) {
+    permissions.push("scripting");
+    // When we don't use a content script registered via the manifest, we
+    // should add the origin as a permission.
+    permissions.push("resource://foo/file_sample.html");
+
+    // Redefine background script to dynamically register the content script.
+    if (isPrivileged) {
+      background = async () => {
+        await browser.scripting.registerContentScripts([
+          {
+            id: "content_script",
+            js: ["content_script.js"],
+            matches: ["resource://foo/file_sample.html"],
+            persistAcrossSessions: false,
+            runAt: "document_start",
+          },
+        ]);
+
+        let scripts = await browser.scripting.getRegisteredContentScripts();
+        browser.test.assertEq(1, scripts.length, "expected 1 script");
+
+        browser.test.sendMessage("background-ready");
+      };
+    } else {
+      background = async () => {
+        await browser.test.assertRejects(
+          browser.scripting.registerContentScripts([
+            {
+              id: "content_script",
+              js: ["content_script.js"],
+              matches: ["resource://foo/file_sample.html"],
+              persistAcrossSessions: false,
+              runAt: "document_start",
+            },
+          ]),
+          /Invalid url pattern: resource:/,
+          "got expected error"
+        );
+
+        browser.test.sendMessage("background-ready");
+      };
+    }
+  } else {
+    content_scripts.push({
+      js: ["content_script.js"],
+      matches: ["resource://foo/file_sample.html"],
+      run_at: "document_start",
+    });
+  }
+
+  return ExtensionTestUtils.loadExtension({
+    isPrivileged,
+
+    manifest: {
+      manifest_version: 2,
+      browser_specific_settings: { gecko: { id } },
+      content_scripts,
+      permissions,
+    },
+
+    background,
+
+    files: {
+      "content_script.js"() {
+        browser.test.assertEq(
+          "resource://foo/file_sample.html",
+          document.documentURI,
+          `Loaded content script into the correct document (extension: ${browser.runtime.id})`
+        );
+        browser.test.sendMessage(`content-script-${browser.runtime.id}`);
+      },
+    },
+  });
+}
+
+const verifyRestrictSchemes = async ({ withScriptingAPI }) => {
+  let resProto = Services.io
+    .getProtocolHandler("resource")
+    .QueryInterface(Ci.nsIResProtocolHandler);
+  resProto.setSubstitutionWithFlags(
+    "foo",
+    Services.io.newFileURI(do_get_file("data")),
+    resProto.ALLOW_CONTENT_ACCESS
+  );
+
+  let unprivileged = makeExtension({
+    id: "unprivileged@tests.mozilla.org",
+    isPrivileged: false,
+    withScriptingAPI,
+  });
+  let privileged = makeExtension({
+    id: "privileged@tests.mozilla.org",
+    isPrivileged: true,
+    withScriptingAPI,
+  });
+
+  await unprivileged.startup();
+  await unprivileged.awaitMessage("background-ready");
+
+  await privileged.startup();
+  await privileged.awaitMessage("background-ready");
+
+  unprivileged.onMessage(
+    "content-script-unprivileged@tests.mozilla.org",
+    () => {
+      ok(
+        false,
+        "Unprivileged extension executed content script on resource URL"
+      );
+    }
+  );
+
+  let contentPage = await ExtensionTestUtils.loadContentPage(
+    `resource://foo/file_sample.html`
+  );
+
+  await privileged.awaitMessage("content-script-privileged@tests.mozilla.org");
+
+  await contentPage.close();
+
+  await privileged.unload();
+  await unprivileged.unload();
+};
+
+// Bug 1780507: this only works with MV2 currently because MV3's optional
+// permission mechanism lacks `restrictSchemes` flags.
+add_task(async function test_contentscript_restrictSchemes_mv2() {
+  await verifyRestrictSchemes({ withScriptingAPI: false });
+});
+
+// Bug 1780507: this only works with MV2 currently because MV3's optional
+// permission mechanism lacks `restrictSchemes` flags.
+add_task(async function test_contentscript_restrictSchemes_scripting_mv2() {
+  await verifyRestrictSchemes({ withScriptingAPI: true });
+});
diff --git a/toolkit/components/extensions/test/xpcshell/test_ext_contentscript_scriptCreated.js b/toolkit/components/extensions/test/xpcshell/test_ext_contentscript_scriptCreated.js
new file mode 100644
index 0000000000..2f10f8f252
--- /dev/null
+++ b/toolkit/components/extensions/test/xpcshell/test_ext_contentscript_scriptCreated.js
@@ -0,0 +1,61 @@
+"use strict";
+
+const server = createHttpServer();
+server.registerDirectory("/data/", do_get_file("data"));
+
+const BASE_URL = `http://localhost:${server.identity.primaryPort}/data`;
+
+// ExtensionContent.jsm needs to know when it's running from xpcshell,
+// to use the right timeout for content scripts executed at document_idle.
+ExtensionTestUtils.mockAppInfo();
+
+// Test that document_start content scripts don't block script-created
+// parsers.
+add_task(async function test_contentscript_scriptCreated() {
+  let extensionData = {
+    manifest: {
+      content_scripts: [
+        {
+          matches: ["http://*/*/file_document_write.html"],
+          js: ["content_script.js"],
+          run_at: "document_start",
+          match_about_blank: true,
+          all_frames: true,
+        },
+      ],
+    },
+
+    files: {
+      "content_script.js": function () {
+        if (window === top) {
+          addEventListener(
+            "message",
+            msg => {
+              browser.test.assertEq(
+                "ok",
+                msg.data,
+                "document.write() succeeded"
+              );
+              browser.test.sendMessage("content-script-done");
+            },
+            { once: true }
+          );
+        }
+      },
+    },
+  };
+
+  let extension = ExtensionTestUtils.loadExtension(extensionData);
+
+  await extension.startup();
+
+  let contentPage = await ExtensionTestUtils.loadContentPage(
+    `${BASE_URL}/file_document_write.html`
+  );
+
+  await extension.awaitMessage("content-script-done");
+
+  await contentPage.close();
+
+  await extension.unload();
+});
diff --git a/toolkit/components/extensions/test/xpcshell/test_ext_contentscript_teardown.js b/toolkit/components/extensions/test/xpcshell/test_ext_contentscript_teardown.js
new file mode 100644
index 0000000000..9ec72e6455
--- /dev/null
+++ b/toolkit/components/extensions/test/xpcshell/test_ext_contentscript_teardown.js
@@ -0,0 +1,101 @@
+"use strict";
+
+const server = createHttpServer({ hosts: ["example.com"] });
+server.registerDirectory("/data/", do_get_file("data"));
+
+add_task(async function test_contentscript_reload_and_unload() {
+  let extensionData = {
+    manifest: {
+      content_scripts: [
+        {
+          matches: ["http://example.com/data/file_sample.html"],
+          js: ["contentscript.js"],
+        },
+      ],
+    },
+
+    files: {
+      "contentscript.js"() {
+        browser.test.sendMessage("contentscript-run");
+      },
+    },
+  };
+
+  let extension = ExtensionTestUtils.loadExtension(extensionData);
+  await extension.startup();
+
+  let events = [];
+  {
+    const { Management } = ChromeUtils.importESModule(
+      "resource://gre/modules/Extension.sys.mjs"
+    );
+    let record = (type, extensionContext) => {
+      let eventType = type == "proxy-context-load" ? "load" : "unload";
+      let url = extensionContext.uri.spec;
+      let extensionId = extensionContext.extension.id;
+      events.push({ eventType, url, extensionId });
+    };
+
+    Management.on("proxy-context-load", record);
+    Management.on("proxy-context-unload", record);
+    registerCleanupFunction(() => {
+      Management.off("proxy-context-load", record);
+      Management.off("proxy-context-unload", record);
+    });
+  }
+
+  const tabUrl = "http://example.com/data/file_sample.html";
+  let contentPage = await ExtensionTestUtils.loadContentPage(tabUrl);
+
+  await extension.awaitMessage("contentscript-run");
+
+  let contextEvents = events.splice(0);
+  equal(
+    contextEvents.length,
+    1,
+    "ExtensionContext state change after loading a content script"
+  );
+  equal(
+    contextEvents[0].eventType,
+    "load",
+    "Create ExtensionContext for content script"
+  );
+  equal(contextEvents[0].url, tabUrl, "ExtensionContext URL = page");
+
+  await contentPage.spawn([], () => {
+    this.content.location.reload();
+  });
+  await extension.awaitMessage("contentscript-run");
+
+  contextEvents = events.splice(0);
+  equal(
+    contextEvents.length,
+    2,
+    "ExtensionContext state changes after reloading a content script"
+  );
+  equal(contextEvents[0].eventType, "unload", "Unload old ExtensionContext");
+  equal(contextEvents[0].url, tabUrl, "ExtensionContext URL = page");
+  equal(
+    contextEvents[1].eventType,
+    "load",
+    "Create new ExtensionContext for content script"
+  );
+  equal(contextEvents[1].url, tabUrl, "ExtensionContext URL = page");
+
+  await contentPage.close();
+
+  contextEvents = events.splice(0);
+  equal(
+    contextEvents.length,
+    1,
+    "ExtensionContext state change after unloading a content script"
+  );
+  equal(
+    contextEvents[0].eventType,
+    "unload",
+    "Unload ExtensionContext after closing the tab with the content script"
+  );
+  equal(contextEvents[0].url, tabUrl, "ExtensionContext URL = page");
+
+  await extension.unload();
+});
diff --git a/toolkit/components/extensions/test/xpcshell/test_ext_contentscript_triggeringPrincipal.js b/toolkit/components/extensions/test/xpcshell/test_ext_contentscript_triggeringPrincipal.js
new file mode 100644
index 0000000000..115fa77cc5
--- /dev/null
+++ b/toolkit/components/extensions/test/xpcshell/test_ext_contentscript_triggeringPrincipal.js
@@ -0,0 +1,1383 @@
+/* -*- Mode: indent-tabs-mode: nil; js-indent-level: 2 -*- */
+/* vim: set sts=2 sw=2 et tw=80: */
+"use strict";
+
+/**
+ * Tests that various types of inline content elements initiate requests
+ * with the triggering pringipal of the caller that requested the load,
+ * and that the correct security policies are applied to the resulting
+ * loads.
+ */
+
+// Make sure media pre-loading is enabled on Android so that our <audio> and
+// <video> elements trigger the expected requests.
+Services.prefs.setIntPref("media.autoplay.default", Ci.nsIAutoplay.ALLOWED);
+Services.prefs.setIntPref("media.preload.default", 3);
+
+// Increase the length of the code samples included in CSP reports so that we
+// can correctly validate them.
+Services.prefs.setIntPref(
+  "security.csp.reporting.script-sample.max-length",
+  4096
+);
+
+// Do not trunacate the blocked-uri in CSP reports for frame navigations.
+Services.prefs.setBoolPref(
+  "security.csp.truncate_blocked_uri_for_frame_navigations",
+  false
+);
+
+// ExtensionContent.jsm needs to know when it's running from xpcshell,
+// to use the right timeout for content scripts executed at document_idle.
+ExtensionTestUtils.mockAppInfo();
+
+const server = createHttpServer({
+  hosts: ["example.com", "csplog.example.net"],
+});
+
+server.registerDirectory("/data/", do_get_file("data"));
+
+var gContentSecurityPolicy = null;
+
+const BASE_URL = `http://example.com`;
+const CSP_REPORT_PATH = "/csp-report.sjs";
+
+/**
+ * Registers a static HTML document with the given content at the given
+ * path in our test HTTP server.
+ *
+ * @param {string} path
+ * @param {string} content
+ */
+function registerStaticPage(path, content) {
+  server.registerPathHandler(path, (request, response) => {
+    response.setStatusLine(request.httpVersion, 200, "OK");
+    response.setHeader("Content-Type", "text/html");
+    if (gContentSecurityPolicy) {
+      response.setHeader("Content-Security-Policy", gContentSecurityPolicy);
+    }
+    response.write(content);
+  });
+}
+
+/**
+ * A set of tags which are automatically closed in HTML documents, and
+ * do not require an explicit closing tag.
+ */
+const AUTOCLOSE_TAGS = new Set(["img", "input", "link", "source"]);
+
+/**
+ * An object describing the elements to create for a specific test.
+ *
+ * @typedef {object} ElementTestCase
+ * @property {Array} element
+ *        A recursive array, describing the element to create, in the
+ *        following format:
+ *
+ *          ["tagname", {attr: "attrValue"},
+ *            ["child-tagname", {attr: "value"}],
+ *            ...]
+ *
+ *        For each test, a DOM tree will be created with this structure.
+ *        A source attribute, with the name `test.srcAttr` and a value
+ *        based on the values of `test.src` and `opts`, will be added to
+ *        the first leaf node encountered.
+ * @property {string} src
+ *        The relative URL to use as the source of the element. Each
+ *        load of this URL will have a separate set of query parameters
+ *        appended to it, based on the values in `opts`.
+ * @property {string} [srcAttr = "src"]
+ *        The attribute in which to store the element's source URL.
+ * @property {boolean} [liveSrc = false]
+ *        If true, changing the source attribute after the element has
+ *        been inserted into the document is expected to trigger a new
+ *        load, and that configuration will be tested.
+ */
+
+/**
+ * Options for this specific configuration of an element test.
+ *
+ * @typedef {object} ElementTestOptions
+ * @property {string} origin
+ *        The origin with which the content is expected to load. This
+ *        may be one of "page", "contentScript", or "extension". The actual load
+ *        of the URL will be tested against the computed origin strings for
+ *        those two contexts.
+ * @property {string} source
+ *        An arbitrary string which uniquely identifies the source of
+ *        the load. For instance, each of these should have separate
+ *        origin strings:
+ *
+ *         - An element present in the initial page HTML.
+ *         - An element injected by a page script belonging to web
+ *           content.
+ *         - An element injected by an extension content script.
+ */
+
+/**
+ * Data describing a test element, which can be used to create a
+ * corresponding DOM tree.
+ *
+ * @typedef {object} ElementData
+ * @property {string} tagName
+ *        The tag name for the element.
+ * @property {object} attrs
+ *        A property containing key-value pairs for each of the
+ *        attribute's elements.
+ * @property {Array<ElementData>} children
+ *        A possibly empty array of element data for child elements.
+ */
+
+/**
+ * Returns data necessary to create test elements for the given test,
+ * with the given options.
+ *
+ * @param {ElementTestCase} test
+ *        An object describing the elements to create for a specific
+ *        test. This element will be created under various
+ *        circumstances, as described by `opts`.
+ * @param {ElementTestOptions} opts
+ *        Options for this specific configuration of the test.
+ * @returns {ElementData}
+ */
+function getElementData(test, opts) {
+  let baseURL = typeof BASE_URL !== "undefined" ? BASE_URL : location.href;
+
+  let { srcAttr, src } = test;
+
+  // Absolutify the URL, so it passes sanity checks that ignore
+  // triggering principals for relative URLs.
+  src = new URL(
+    src +
+      `?origin=${encodeURIComponent(opts.origin)}&source=${encodeURIComponent(
+        opts.source
+      )}`,
+    baseURL
+  ).href;
+
+  let haveSrc = false;
+  function rec(element) {
+    let [tagName, attrs, ...children] = element;
+
+    if (children.length) {
+      children = children.map(rec);
+    } else if (!haveSrc) {
+      attrs = Object.assign({ [srcAttr]: src }, attrs);
+      haveSrc = true;
+    }
+
+    return { tagName, attrs, children };
+  }
+  return rec(test.element);
+}
+
+/**
+ * The result type of the {@see createElement} function.
+ *
+ * @typedef {object} CreateElementResult
+ * @property {Element} elem
+ *        The root element of the created DOM tree.
+ * @property {Element} srcElem
+ *        The element in the tree to which the source attribute must be
+ *        added.
+ * @property {string} src
+ *        The value of the source element.
+ */
+
+/**
+ * Creates a DOM tree for a given test, in a given configuration, as
+ * understood by {@see getElementData}, but without the `test.srcAttr`
+ * attribute having been set. The caller must set the value of that
+ * attribute to the returned `src` value.
+ *
+ * There are many different ways most source values can be set
+ * (DOM attribute, DOM property, ...) and many different contexts
+ * (content script verses page script). Each test should be run with as
+ * many variants of these as possible.
+ *
+ * @param {ElementTestCase} test
+ *        A test object, as passed to {@see getElementData}.
+ * @param {ElementTestOptions} opts
+ *        An options object, as passed to {@see getElementData}.
+ * @returns {CreateElementResult}
+ */
+function createElement(test, opts) {
+  let srcElem;
+  let src;
+
+  function rec({ tagName, attrs, children }) {
+    let elem = document.createElement(tagName);
+
+    for (let [key, val] of Object.entries(attrs)) {
+      if (key === test.srcAttr) {
+        srcElem = elem;
+        src = val;
+      } else {
+        elem.setAttribute(key, val);
+      }
+    }
+    for (let child of children) {
+      elem.appendChild(rec(child));
+    }
+    return elem;
+  }
+  let elem = rec(getElementData(test, opts));
+
+  return { elem, srcElem, src };
+}
+
+/**
+ * Escapes any occurrences of &, ", < or > with XML entities.
+ *
+ * @param {string} str
+ *        The string to escape.
+ * @returns {string} The escaped string.
+ */
+function escapeXML(str) {
+  let replacements = {
+    "&": "&amp;",
+    '"': "&quot;",
+    "'": "&apos;",
+    "<": "&lt;",
+    ">": "&gt;",
+  };
+  return String(str).replace(/[&"''<>]/g, m => replacements[m]);
+}
+
+/**
+ * A tagged template function which escapes any XML metacharacters in
+ * interpolated values.
+ *
+ * @param {Array<string>} strings
+ *        An array of literal strings extracted from the templates.
+ * @param {Array} values
+ *        An array of interpolated values extracted from the template.
+ * @returns {string}
+ *        The result of the escaped values interpolated with the literal
+ *        strings.
+ */
+function escaped(strings, ...values) {
+  let result = [];
+
+  for (let [i, string] of strings.entries()) {
+    result.push(string);
+    if (i < values.length) {
+      result.push(escapeXML(values[i]));
+    }
+  }
+
+  return result.join("");
+}
+
+/**
+ * Converts the given test data, as accepted by {@see getElementData},
+ * to an HTML representation.
+ *
+ * @param {ElementTestCase} test
+ *        A test object, as passed to {@see getElementData}.
+ * @param {ElementTestOptions} opts
+ *        An options object, as passed to {@see getElementData}.
+ * @returns {string}
+ */
+function toHTML(test, opts) {
+  function rec({ tagName, attrs, children }) {
+    let html = [`<${tagName}`];
+    for (let [key, val] of Object.entries(attrs)) {
+      html.push(escaped` ${key}="${val}"`);
+    }
+
+    html.push(">");
+    if (!AUTOCLOSE_TAGS.has(tagName)) {
+      for (let child of children) {
+        html.push(rec(child));
+      }
+
+      html.push(`</${tagName}>`);
+    }
+    return html.join("");
+  }
+  return rec(getElementData(test, opts));
+}
+
+/**
+ * Injects various permutations of inline CSS into a content page, from both
+ * extension content script and content page contexts, and sends a "css-sources"
+ * message to the test harness describing the injected content for verification.
+ */
+function testInlineCSS() {
+  let urls = [];
+  let sources = [];
+
+  /**
+   * Constructs the URL of an image to be loaded by the given origin, and
+   * returns a CSS url() expression for it.
+   *
+   * The `name` parameter is an arbitrary name which should describe how the URL
+   * is loaded. The `opts` object may contain arbitrary properties which
+   * describe the load. Currently, only `inline` is recognized, and indicates
+   * that the URL is being used in an inline stylesheet which may be blocked by
+   * CSP.
+   *
+   * The URL and its parameters are recorded, and sent to the parent process for
+   * verification.
+   *
+   * @param {string} origin
+   * @param {string} name
+   * @param {object} [opts]
+   * @returns {string}
+   */
+  let i = 0;
+  let url = (origin, name, opts = {}) => {
+    let source = `${origin}-${name}`;
+
+    let { href } = new URL(
+      `css-${i++}.png?origin=${encodeURIComponent(
+        origin
+      )}&source=${encodeURIComponent(source)}`,
+      location.href
+    );
+
+    urls.push(Object.assign({}, opts, { href, origin, source }));
+    return `url("${href}")`;
+  };
+
+  /**
+   * Registers the given inline CSS source as being loaded by the given origin,
+   * and returns that CSS text.
+   *
+   * @param {string} origin
+   * @param {string} css
+   * @returns {string}
+   */
+  let source = (origin, css) => {
+    sources.push({ origin, css });
+    return css;
+  };
+
+  /**
+   * Saves the given function to be run after a short delay, just before sending
+   * the list of loaded sources to the parent process.
+   */
+  let laters = [];
+  let later = fn => {
+    laters.push(fn);
+  };
+
+  // Note: When accessing an element through `wrappedJSObject`, the operations
+  // occur in the content page context, using the content subject principal.
+  // When accessing it through X-ray wrappers, they happen in the content script
+  // context, using its subject principal.
+
+  {
+    let li = document.createElement("li");
+    li.setAttribute(
+      "style",
+      source(
+        "contentScript",
+        `background: ${url("contentScript", "li.style-first")}`
+      )
+    );
+    li.style.wrappedJSObject.listStyleImage = url(
+      "page",
+      "li.style.listStyleImage-second"
+    );
+    document.body.appendChild(li);
+  }
+
+  {
+    let li = document.createElement("li");
+    li.wrappedJSObject.setAttribute(
+      "style",
+      source(
+        "page",
+        `background: ${url("page", "li.style-first", { inline: true })}`
+      )
+    );
+    li.style.listStyleImage = url(
+      "contentScript",
+      "li.style.listStyleImage-second"
+    );
+    document.body.appendChild(li);
+  }
+
+  {
+    let li = document.createElement("li");
+    document.body.appendChild(li);
+    li.setAttribute(
+      "style",
+      source(
+        "contentScript",
+        `background: ${url("contentScript", "li.style-first")}`
+      )
+    );
+    later(() =>
+      li.wrappedJSObject.setAttribute(
+        "style",
+        source(
+          "page",
+          `background: ${url("page", "li.style-second", { inline: true })}`
+        )
+      )
+    );
+  }
+
+  {
+    let li = document.createElement("li");
+    document.body.appendChild(li);
+    li.wrappedJSObject.setAttribute(
+      "style",
+      source(
+        "page",
+        `background: ${url("page", "li.style-first", { inline: true })}`
+      )
+    );
+    later(() =>
+      li.setAttribute(
+        "style",
+        source(
+          "contentScript",
+          `background: ${url("contentScript", "li.style-second")}`
+        )
+      )
+    );
+  }
+
+  {
+    let li = document.createElement("li");
+    document.body.appendChild(li);
+    li.style.cssText = source(
+      "contentScript",
+      `background: ${url("contentScript", "li.style.cssText-first")}`
+    );
+
+    // TODO: This inline style should be blocked, since our style-src does not
+    // include 'unsafe-eval', but that is currently unimplemented.
+    later(() => {
+      li.style.wrappedJSObject.cssText = `background: ${url(
+        "page",
+        "li.style.cssText-second"
+      )}`;
+    });
+  }
+
+  // Creates a new element, inserts it into the page, and returns its CSS selector.
+  let divNum = 0;
+  function getSelector() {
+    let div = document.createElement("div");
+    div.id = `generated-div-${divNum++}`;
+    document.body.appendChild(div);
+    return `#${div.id}`;
+  }
+
+  for (let prop of ["textContent", "innerHTML"]) {
+    // Test creating <style> element from the extension side and then replacing
+    // its contents from the content side.
+    {
+      let sel = getSelector();
+      let style = document.createElement("style");
+      style[prop] = source(
+        "extension",
+        `${sel} { background: ${url("extension", `style-${prop}-first`)}; }`
+      );
+      document.head.appendChild(style);
+
+      later(() => {
+        style.wrappedJSObject[prop] = source(
+          "page",
+          `${sel} { background: ${url("page", `style-${prop}-second`, {
+            inline: true,
+          })}; }`
+        );
+      });
+    }
+
+    // Test creating <style> element from the extension side and then appending
+    // a text node to it. Regardless of whether the append happens from the
+    // content or extension side, this should cause the principal to be
+    // forgotten.
+    let testModifyAfterInject = (name, modifyFunc) => {
+      let sel = getSelector();
+      let style = document.createElement("style");
+      style[prop] = source(
+        "extension",
+        `${sel} { background: ${url(
+          "extension",
+          `style-${name}-${prop}-first`
+        )}; }`
+      );
+      document.head.appendChild(style);
+
+      later(() => {
+        modifyFunc(
+          style,
+          `${sel} { background: ${url("page", `style-${name}-${prop}-second`, {
+            inline: true,
+          })}; }`
+        );
+        source("page", style.textContent);
+      });
+    };
+
+    testModifyAfterInject("appendChild", (style, css) => {
+      style.appendChild(document.createTextNode(css));
+    });
+
+    // Test creating <style> element from the extension side and then appending
+    // to it using insertAdjacentHTML, with the same rules as above.
+    testModifyAfterInject("insertAdjacentHTML", (style, css) => {
+      // eslint-disable-next-line no-unsanitized/method
+      style.insertAdjacentHTML("beforeend", css);
+    });
+
+    // And again using insertAdjacentText.
+    testModifyAfterInject("insertAdjacentText", (style, css) => {
+      style.insertAdjacentText("beforeend", css);
+    });
+
+    // Test creating a style element and then accessing its CSSStyleSheet object.
+    {
+      let sel = getSelector();
+      let style = document.createElement("style");
+      style[prop] = source(
+        "extension",
+        `${sel} { background: ${url("extension", `style-${prop}-sheet`)}; }`
+      );
+      document.head.appendChild(style);
+
+      browser.test.assertThrows(
+        () => style.sheet.wrappedJSObject.cssRules,
+        /Not allowed to access cross-origin stylesheet/,
+        "Page content should not be able to access extension-generated CSS rules"
+      );
+
+      style.sheet.insertRule(
+        source(
+          "extension",
+          `${sel} { border-image: ${url(
+            "extension",
+            `style-${prop}-sheet-insertRule`
+          )}; }`
+        )
+      );
+    }
+  }
+
+  setTimeout(() => {
+    for (let fn of laters) {
+      fn();
+    }
+    browser.test.sendMessage("css-sources", { urls, sources });
+  });
+}
+
+/**
+ * A function which will be stringified, and run both as a page script
+ * and an extension content script, to test element injection under
+ * various configurations.
+ *
+ * @param {Array<ElementTestCase>} tests
+ *        A list of test objects, as understood by {@see getElementData}.
+ * @param {ElementTestOptions} baseOpts
+ *        A base options object, as understood by {@see getElementData},
+ *        which represents the default values for injections under this
+ *        context.
+ */
+function injectElements(tests, baseOpts) {
+  window.addEventListener(
+    "load",
+    () => {
+      if (typeof browser === "object") {
+        try {
+          testInlineCSS();
+        } catch (e) {
+          browser.test.fail(`Error: ${e} :: ${e.stack}`);
+        }
+      }
+
+      // Basic smoke test to check that SVG images do not try to create a document
+      // with an expanded principal, which would cause a crash.
+      let img = document.createElement("img");
+      img.src = "data:image/svg+xml,%3Csvg%2F%3E";
+      document.body.appendChild(img);
+
+      let rand = Math.random();
+
+      // Basic smoke test to check that we don't try to create stylesheets with an
+      // expanded principal, which would cause a crash when loading font sets.
+      let cssText = `
+      @font-face {
+          font-family: "DoesNotExist${rand}";
+          src: url("fonts/DoesNotExist.${rand}.woff") format("woff");
+          font-weight: normal;
+          font-style: normal;
+      }`;
+
+      let link = document.createElement("link");
+      link.rel = "stylesheet";
+      link.href = "data:text/css;base64," + btoa(cssText);
+      document.head.appendChild(link);
+
+      let style = document.createElement("style");
+      style.textContent = cssText;
+      document.head.appendChild(style);
+
+      let overrideOpts = opts => Object.assign({}, baseOpts, opts);
+      let opts = baseOpts;
+
+      // Build the full element with setAttr, then inject.
+      for (let test of tests) {
+        let { elem, srcElem, src } = createElement(test, opts);
+        srcElem.setAttribute(test.srcAttr, src);
+        document.body.appendChild(elem);
+      }
+
+      // Build the full element with a property setter.
+      opts = overrideOpts({ source: `${baseOpts.source}-prop` });
+      for (let test of tests) {
+        let { elem, srcElem, src } = createElement(test, opts);
+        srcElem[test.srcAttr] = src;
+        document.body.appendChild(elem);
+      }
+
+      // Build the element without the source attribute, inject, then set
+      // it.
+      opts = overrideOpts({ source: `${baseOpts.source}-attr-after-inject` });
+      for (let test of tests) {
+        let { elem, srcElem, src } = createElement(test, opts);
+        document.body.appendChild(elem);
+        srcElem.setAttribute(test.srcAttr, src);
+      }
+
+      // Build the element without the source attribute, inject, then set
+      // the corresponding property.
+      opts = overrideOpts({ source: `${baseOpts.source}-prop-after-inject` });
+      for (let test of tests) {
+        let { elem, srcElem, src } = createElement(test, opts);
+        document.body.appendChild(elem);
+        srcElem[test.srcAttr] = src;
+      }
+
+      // Build the element with a relative, rather than absolute, URL, and
+      // make sure it always has the page origin.
+      opts = overrideOpts({
+        source: `${baseOpts.source}-relative-url`,
+        origin: "page",
+      });
+      for (let test of tests) {
+        let { elem, srcElem, src } = createElement(test, opts);
+        // Note: This assumes that the content page and the src URL are
+        // always at the server root. If that changes, the test will
+        // timeout waiting for matching requests.
+        src = src.replace(/.*\//, "");
+        srcElem.setAttribute(test.srcAttr, src);
+        document.body.appendChild(elem);
+      }
+
+      // If we're in an extension content script, do some additional checks.
+      if (typeof browser !== "undefined") {
+        // Build the element without the source attribute, inject, then
+        // have content set it.
+        opts = overrideOpts({
+          source: `${baseOpts.source}-content-attr-after-inject`,
+          origin: "page",
+        });
+
+        for (let test of tests) {
+          let { elem, srcElem, src } = createElement(test, opts);
+
+          document.body.appendChild(elem);
+          window.wrappedJSObject.elem = srcElem;
+          window.wrappedJSObject.eval(
+            `elem.setAttribute(${JSON.stringify(
+              test.srcAttr
+            )}, ${JSON.stringify(src)})`
+          );
+        }
+
+        // Build the full element, then let content inject.
+        opts = overrideOpts({
+          source: `${baseOpts.source}-content-inject-after-attr`,
+        });
+        for (let test of tests) {
+          let { elem, srcElem, src } = createElement(test, opts);
+          srcElem.setAttribute(test.srcAttr, src);
+          window.wrappedJSObject.elem = elem;
+          window.wrappedJSObject.eval(`document.body.appendChild(elem)`);
+        }
+
+        // Build the element without the source attribute, let content set
+        // it, then inject.
+        opts = overrideOpts({
+          source: `${baseOpts.source}-inject-after-content-attr`,
+          origin: "page",
+        });
+
+        for (let test of tests) {
+          let { elem, srcElem, src } = createElement(test, opts);
+          window.wrappedJSObject.elem = srcElem;
+          window.wrappedJSObject.eval(
+            `elem.setAttribute(${JSON.stringify(
+              test.srcAttr
+            )}, ${JSON.stringify(src)})`
+          );
+          document.body.appendChild(elem);
+        }
+
+        // Build the element with a dummy source attribute, inject, then
+        // let content change it.
+        opts = overrideOpts({
+          source: `${baseOpts.source}-content-change-after-inject`,
+          origin: "page",
+        });
+
+        for (let test of tests) {
+          let { elem, srcElem, src } = createElement(test, opts);
+          srcElem.setAttribute(test.srcAttr, "meh.txt");
+          document.body.appendChild(elem);
+          window.wrappedJSObject.elem = srcElem;
+          window.wrappedJSObject.eval(
+            `elem.setAttribute(${JSON.stringify(
+              test.srcAttr
+            )}, ${JSON.stringify(src)})`
+          );
+        }
+      }
+    },
+    { once: true }
+  );
+}
+
+/**
+ * Stringifies the {@see injectElements} function for use as a page or
+ * content script.
+ *
+ * @param {Array<ElementTestCase>} tests
+ *        A list of test objects, as understood by {@see getElementData}.
+ * @param {ElementTestOptions} opts
+ *        A base options object, as understood by {@see getElementData},
+ *        which represents the default values for injections under this
+ *        context.
+ * @returns {string}
+ */
+function getInjectionScript(tests, opts) {
+  return `
+    ${getElementData}
+    ${createElement}
+    ${testInlineCSS}
+    (${injectElements})(${JSON.stringify(tests)},
+                        ${JSON.stringify(opts)});
+  `;
+}
+
+/**
+ * Extracts the "origin" query parameter from the given URL, and returns it,
+ * along with the URL sans origin parameter.
+ *
+ * @param {string} origURL
+ * @returns {object}
+ *        An object with `origin` and `baseURL` properties, containing the value
+ *        or the URL's "origin" query parameter and the URL with that parameter
+ *        removed, respectively.
+ */
+function getOriginBase(origURL) {
+  let url = new URL(origURL);
+  let origin = url.searchParams.get("origin");
+  url.searchParams.delete("origin");
+
+  return { origin, baseURL: url.href };
+}
+
+/**
+ * An object containing sets of base URLs and CSS sources which are present in
+ * the test page, sorted based on how they should be treated by CSP.
+ *
+ * @typedef {object} RequestedURLs
+ * @property {Set<string>} expectedURLs
+ *        A set of URLs which should be successfully requested by the content
+ *        page.
+ * @property {Set<string>} forbiddenURLs
+ *        A set of URLs which are present in the content page, but should never
+ *        generate requests.
+ * @property {Set<string>} blockedURLs
+ *        A set of URLs which are present in the content page, and should be
+ *        blocked by CSP, and reported in a CSP report.
+ * @property {Set<string>} blockedSources
+ *        A set of inline CSS sources which should be blocked by CSP, and
+ *        reported in a CSP report.
+ */
+
+/**
+ * Computes a list of expected and forbidden base URLs for the given
+ * sets of tests and sources. The base URL is the complete request URL
+ * with the `origin` query parameter removed.
+ *
+ * @param {Array<ElementTestCase>} tests
+ *        A list of tests, as understood by {@see getElementData}.
+ * @param {Object<string, object>} expectedSources
+ *        A set of sources for which each of the above tests is expected
+ *        to generate one request, if each of the properties in the
+ *        value object matches the value of the same property in the
+ *        test object.
+ * @param {Object<string, object>} [forbiddenSources = {}]
+ *        A set of sources for which requests should never be sent. Any
+ *        matching requests from these sources will cause the test to
+ *        fail.
+ * @returns {RequestedURLs}
+ */
+function computeBaseURLs(tests, expectedSources, forbiddenSources = {}) {
+  let expectedURLs = new Set();
+  let forbiddenURLs = new Set();
+
+  function* iterSources(test, sources) {
+    for (let [source, attrs] of Object.entries(sources)) {
+      // if a source defines attributes (e.g. liveSrc in PAGE_SOURCES etc.) then all
+      // attributes in the source must be matched by the test (see const TEST).
+      if (Object.keys(attrs).every(attr => attrs[attr] === test[attr])) {
+        yield `${BASE_URL}/${test.src}?source=${source}`;
+      }
+    }
+  }
+
+  for (let test of tests) {
+    for (let urlPrefix of iterSources(test, expectedSources)) {
+      expectedURLs.add(urlPrefix);
+    }
+    for (let urlPrefix of iterSources(test, forbiddenSources)) {
+      forbiddenURLs.add(urlPrefix);
+    }
+  }
+
+  return { expectedURLs, forbiddenURLs, blockedURLs: forbiddenURLs };
+}
+
+/**
+ * @typedef InjectedUrl
+ *        A URL present in styles injected by the content script.
+ * @type {object}
+ * @property {string} origin
+ *        The origin of the URL, one of "page", "contentScript", or "extension".
+ * @param {string} href
+ *        The URL string.
+ * @param {boolean} inline
+ *        If true, the URL is present in an inline stylesheet, which may be
+ *        blocked by CSP prior to parsing, depending on its origin.
+ */
+
+/**
+ * @typedef InjectedSource
+ *        An inline CSS source injected by the content script.
+ * @type {object}
+ * @param {string} origin
+ *        The origin of the CSS, one of "page", "contentScript", or "extension".
+ * @param {string} css
+ *        The CSS source text.
+ */
+
+/**
+ * Generates a set of expected and forbidden URLs and sources based on the CSS
+ * injected by our content script.
+ *
+ * @param {object} message
+ *        The "css-sources" message sent by the content script, containing lists
+ *        of CSS sources injected into the page.
+ * @param {Array<InjectedUrl>} message.urls
+ *        A list of URLs present in styles injected by the content script.
+ * @param {Array<InjectedSource>} message.sources
+ *        A list of inline CSS sources injected by the content script.
+ * @param {boolean} [cspEnabled = false]
+ *        If true, a strict CSP is enabled for this page, and inline page
+ *        sources should be blocked. URLs present in these sources will not be
+ *        expected to generate a CSP report, the inline sources themselves will.
+ * @param {boolean} [contentCspEnabled = false]
+ * @returns {RequestedURLs}
+ */
+function computeExpectedForbiddenURLs(
+  { urls, sources },
+  cspEnabled = false,
+  contentCspEnabled = false
+) {
+  let expectedURLs = new Set();
+  let forbiddenURLs = new Set();
+  let blockedURLs = new Set();
+  let blockedSources = new Set();
+
+  for (let { href, origin, inline } of urls) {
+    let { baseURL } = getOriginBase(href);
+    if (cspEnabled && origin === "page") {
+      if (inline) {
+        forbiddenURLs.add(baseURL);
+      } else {
+        blockedURLs.add(baseURL);
+      }
+    } else if (contentCspEnabled && origin === "contentScript") {
+      if (inline) {
+        forbiddenURLs.add(baseURL);
+      }
+    } else {
+      expectedURLs.add(baseURL);
+    }
+  }
+
+  if (cspEnabled) {
+    for (let { origin, css } of sources) {
+      if (origin === "page") {
+        blockedSources.add(css);
+      }
+    }
+  }
+
+  return { expectedURLs, forbiddenURLs, blockedURLs, blockedSources };
+}
+
+/**
+ * Awaits the content loads for each of the given expected base URLs,
+ * and checks that their origin strings are as expected. Triggers a test
+ * failure if any of the given forbidden URLs is requested.
+ *
+ * @param {Promise<object>} urlsPromise
+ *        A promise which resolves to an object containing expected and
+ *        forbidden URL sets, as returned by {@see computeBaseURLs}.
+ * @param {Object<string, string>} origins
+ *        A mapping of origin parameters as they appear in URL query
+ *        strings to the origin strings returned by corresponding
+ *        principals. These values are used to test requests against
+ *        their expected origins.
+ * @returns {Promise}
+ *        A promise which resolves when all requests have been
+ *        processed.
+ */
+function awaitLoads(urlsPromise, origins) {
+  return new Promise(resolve => {
+    let expectedURLs, forbiddenURLs;
+    let queuedChannels = [];
+
+    let observer;
+
+    function checkChannel(channel) {
+      let origURL = channel.URI.spec;
+      let { baseURL, origin } = getOriginBase(origURL);
+
+      if (forbiddenURLs.has(baseURL)) {
+        ok(false, `Got unexpected request for forbidden URL ${origURL}`);
+      }
+
+      if (expectedURLs.has(baseURL)) {
+        expectedURLs.delete(baseURL);
+
+        equal(
+          channel.loadInfo.triggeringPrincipal.origin,
+          origins[origin],
+          `Got expected origin for URL ${origURL}`
+        );
+
+        if (!expectedURLs.size) {
+          Services.obs.removeObserver(observer, "http-on-modify-request");
+          info("Got all expected requests");
+          resolve();
+        }
+      }
+    }
+
+    urlsPromise.then(urls => {
+      expectedURLs = new Set(urls.expectedURLs);
+      forbiddenURLs = new Set([...urls.forbiddenURLs, ...urls.blockedURLs]);
+
+      for (let channel of queuedChannels.splice(0)) {
+        checkChannel(channel.QueryInterface(Ci.nsIChannel));
+      }
+    });
+
+    observer = (channel, topic, data) => {
+      if (expectedURLs) {
+        checkChannel(channel.QueryInterface(Ci.nsIChannel));
+      } else {
+        queuedChannels.push(channel);
+      }
+    };
+    Services.obs.addObserver(observer, "http-on-modify-request");
+  });
+}
+
+function readUTF8InputStream(stream) {
+  let buffer = NetUtil.readInputStream(stream, stream.available());
+  return new TextDecoder().decode(buffer);
+}
+
+/**
+ * Awaits CSP reports for each of the given forbidden base URLs.
+ * Triggers a test failure if any of the given expected URLs triggers a
+ * report.
+ *
+ * @param {Promise<object>} urlsPromise
+ *        A promise which resolves to an object containing expected and
+ *        forbidden URL sets, as returned by {@see computeBaseURLs}.
+ * @returns {Promise}
+ *        A promise which resolves when all requests have been
+ *        processed.
+ */
+function awaitCSP(urlsPromise) {
+  return new Promise(resolve => {
+    let expectedURLs, blockedURLs, blockedSources;
+    let queuedRequests = [];
+
+    function checkRequest(request) {
+      let body = JSON.parse(readUTF8InputStream(request.bodyInputStream));
+      let report = body["csp-report"];
+
+      let origURL = report["blocked-uri"];
+      if (origURL !== "inline" && origURL !== "") {
+        let { baseURL } = getOriginBase(origURL);
+
+        if (expectedURLs.has(baseURL)) {
+          ok(false, `Got unexpected CSP report for allowed URL ${origURL}`);
+        }
+
+        if (blockedURLs.has(baseURL)) {
+          blockedURLs.delete(baseURL);
+
+          ok(true, `Got CSP report for forbidden URL ${origURL}`);
+        }
+      }
+
+      let source = report["script-sample"];
+      if (source) {
+        if (blockedSources.has(source)) {
+          blockedSources.delete(source);
+
+          ok(
+            true,
+            `Got CSP report for forbidden inline source ${JSON.stringify(
+              source
+            )}`
+          );
+        }
+      }
+
+      if (!blockedURLs.size && !blockedSources.size) {
+        ok(true, "Got all expected CSP reports");
+        resolve();
+      }
+    }
+
+    urlsPromise.then(urls => {
+      blockedURLs = new Set(urls.blockedURLs);
+      blockedSources = new Set(urls.blockedSources);
+      ({ expectedURLs } = urls);
+
+      for (let request of queuedRequests.splice(0)) {
+        checkRequest(request);
+      }
+    });
+
+    server.registerPathHandler(CSP_REPORT_PATH, (request, response) => {
+      response.setStatusLine(request.httpVersion, 204, "No Content");
+
+      if (expectedURLs) {
+        checkRequest(request);
+      } else {
+        queuedRequests.push(request);
+      }
+    });
+  });
+}
+
+/**
+ * A list of tests to run in each context, as understood by
+ * {@see getElementData}.
+ */
+const TESTS = [
+  {
+    element: ["audio", {}],
+    src: "audio.webm",
+  },
+  {
+    element: ["audio", {}, ["source", {}]],
+    src: "audio-source.webm",
+  },
+  // TODO: <frame> element, which requires a frameset document.
+  {
+    // the blocked-uri for frame-navigations is the pre-path URI. For the
+    // purpose of this test we do not strip the blocked-uri by setting the
+    // preference 'truncate_blocked_uri_for_frame_navigations'
+    element: ["iframe", {}],
+    src: "iframe.html",
+  },
+  {
+    element: ["img", {}],
+    src: "img.png",
+  },
+  {
+    element: ["img", {}],
+    src: "imgset.png",
+    srcAttr: "srcset",
+  },
+  {
+    element: ["input", { type: "image" }],
+    src: "input.png",
+  },
+  {
+    element: ["link", { rel: "stylesheet" }],
+    src: "link.css",
+    srcAttr: "href",
+  },
+  {
+    element: ["picture", {}, ["source", {}], ["img", {}]],
+    src: "picture.png",
+    srcAttr: "srcset",
+  },
+  {
+    element: ["script", {}],
+    src: "script.js",
+    liveSrc: false,
+  },
+  {
+    element: ["video", {}],
+    src: "video.webm",
+  },
+  {
+    element: ["video", {}, ["source", {}]],
+    src: "video-source.webm",
+  },
+];
+
+for (let test of TESTS) {
+  if (!test.srcAttr) {
+    test.srcAttr = "src";
+  }
+  if (!("liveSrc" in test)) {
+    test.liveSrc = true;
+  }
+}
+
+/**
+ * A set of sources for which each of the above tests is expected to
+ * generate one request, if each of the properties in the value object
+ * matches the value of the same property in the test object.
+ */
+// Sources which load with the page context.
+const PAGE_SOURCES = {
+  "contentScript-content-attr-after-inject": { liveSrc: true },
+  "contentScript-content-change-after-inject": { liveSrc: true },
+  "contentScript-inject-after-content-attr": {},
+  "contentScript-relative-url": {},
+  pageHTML: {},
+  pageScript: {},
+  "pageScript-attr-after-inject": {},
+  "pageScript-prop": {},
+  "pageScript-prop-after-inject": {},
+  "pageScript-relative-url": {},
+};
+// Sources which load with the extension context.
+const EXTENSION_SOURCES = {
+  contentScript: {},
+  "contentScript-attr-after-inject": { liveSrc: true },
+  "contentScript-content-inject-after-attr": {},
+  "contentScript-prop": {},
+  "contentScript-prop-after-inject": {},
+};
+// When our default content script CSP is applied, only
+// liveSrc: true are loading.  IOW, the "script" test above
+// will fail.
+const EXTENSION_SOURCES_CONTENT_CSP = {
+  contentScript: { liveSrc: true },
+  "contentScript-attr-after-inject": { liveSrc: true },
+  "contentScript-content-inject-after-attr": { liveSrc: true },
+  "contentScript-prop": { liveSrc: true },
+  "contentScript-prop-after-inject": { liveSrc: true },
+};
+// All sources.
+const SOURCES = Object.assign({}, PAGE_SOURCES, EXTENSION_SOURCES);
+
+registerStaticPage(
+  "/page.html",
+  `<!DOCTYPE html>
+  <html lang="en">
+  <head>
+    <meta charset="UTF-8">
+    <title></title>
+    <script nonce="deadbeef">
+      ${getInjectionScript(TESTS, { source: "pageScript", origin: "page" })}
+    </script>
+  </head>
+  <body>
+    ${TESTS.map(test =>
+      toHTML(test, { source: "pageHTML", origin: "page" })
+    ).join("\n  ")}
+  </body>
+  </html>`
+);
+
+function catchViolation() {
+  // eslint-disable-next-line mozilla/balanced-listeners
+  document.addEventListener("securitypolicyviolation", e => {
+    browser.test.assertTrue(
+      e.documentURI !== "moz-extension",
+      `securitypolicyviolation: ${e.violatedDirective} ${e.documentURI}`
+    );
+  });
+}
+
+const EXTENSION_DATA = {
+  manifest: {
+    content_scripts: [
+      {
+        matches: ["http://*/page.html"],
+        run_at: "document_start",
+        js: ["violation.js", "content_script.js"],
+      },
+    ],
+  },
+
+  files: {
+    "violation.js": catchViolation,
+    "content_script.js": getInjectionScript(TESTS, {
+      source: "contentScript",
+      origin: "contentScript",
+    }),
+  },
+};
+
+const pageURL = `${BASE_URL}/page.html`;
+const pageURI = Services.io.newURI(pageURL);
+
+// Merges the sets of expected URL and source data returned by separate
+// computedExpectedForbiddenURLs and computedBaseURLs calls.
+function mergeSources(a, b) {
+  return {
+    expectedURLs: new Set([...a.expectedURLs, ...b.expectedURLs]),
+    forbiddenURLs: new Set([...a.forbiddenURLs, ...b.forbiddenURLs]),
+    blockedURLs: new Set([...a.blockedURLs, ...b.blockedURLs]),
+    blockedSources: a.blockedSources || b.blockedSources,
+  };
+}
+
+// Returns a set of origin strings for the given extension and content page, for
+// use in verifying request triggering principals.
+function getOrigins(extension) {
+  return {
+    page: Services.scriptSecurityManager.createContentPrincipal(pageURI, {})
+      .origin,
+    contentScript: Cu.getObjectPrincipal(
+      Cu.Sandbox([pageURL, extension.principal])
+    ).origin,
+    extension: extension.principal.origin,
+  };
+}
+
+/**
+ * Tests that various types of inline content elements initiate requests
+ * with the triggering pringipal of the caller that requested the load.
+ */
+add_task(async function test_contentscript_triggeringPrincipals() {
+  let extension = ExtensionTestUtils.loadExtension(EXTENSION_DATA);
+  await extension.startup();
+
+  let urlsPromise = extension.awaitMessage("css-sources").then(msg => {
+    return mergeSources(
+      computeExpectedForbiddenURLs(msg),
+      computeBaseURLs(TESTS, SOURCES)
+    );
+  });
+
+  let origins = getOrigins(extension.extension);
+  let finished = awaitLoads(urlsPromise, origins);
+
+  let contentPage = await ExtensionTestUtils.loadContentPage(pageURL);
+
+  await finished;
+
+  await extension.unload();
+  await contentPage.close();
+
+  clearCache();
+});
+
+/**
+ * Tests that the correct CSP is applied to loads of inline content
+ * depending on whether the load was initiated by an extension or the
+ * content page.
+ */
+add_task(async function test_contentscript_csp() {
+  // TODO bug 1408193: We currently don't get the full set of CSP reports when
+  // running in network scheduling chaos mode. It's not entirely clear why.
+  let chaosMode = parseInt(Services.env.get("MOZ_CHAOSMODE"), 16);
+  let checkCSPReports = !(chaosMode === 0 || chaosMode & 0x02);
+
+  gContentSecurityPolicy = `default-src 'none' 'report-sample'; script-src 'nonce-deadbeef' 'unsafe-eval' 'report-sample'; report-uri ${CSP_REPORT_PATH};`;
+
+  let extension = ExtensionTestUtils.loadExtension(EXTENSION_DATA);
+  await extension.startup();
+
+  let urlsPromise = extension.awaitMessage("css-sources").then(msg => {
+    return mergeSources(
+      computeExpectedForbiddenURLs(msg, true),
+      computeBaseURLs(TESTS, EXTENSION_SOURCES, PAGE_SOURCES)
+    );
+  });
+
+  let origins = getOrigins(extension.extension);
+
+  let finished = Promise.all([
+    awaitLoads(urlsPromise, origins),
+    checkCSPReports && awaitCSP(urlsPromise),
+  ]);
+
+  let contentPage = await ExtensionTestUtils.loadContentPage(pageURL);
+
+  await finished;
+
+  await extension.unload();
+  await contentPage.close();
+});
+
+/**
+ * Tests that the correct CSP is applied to loads of inline content
+ * depending on whether the load was initiated by an extension or the
+ * content page.
+ */
+add_task(async function test_extension_contentscript_csp() {
+  Services.prefs.setBoolPref("extensions.manifestV3.enabled", true);
+
+  // TODO bug 1408193: We currently don't get the full set of CSP reports when
+  // running in network scheduling chaos mode. It's not entirely clear why.
+  let chaosMode = parseInt(Services.env.get("MOZ_CHAOSMODE"), 16);
+  let checkCSPReports = !(chaosMode === 0 || chaosMode & 0x02);
+
+  gContentSecurityPolicy = `default-src 'none' 'report-sample'; script-src 'nonce-deadbeef' 'unsafe-eval' 'report-sample'; report-uri ${CSP_REPORT_PATH};`;
+
+  let data = {
+    ...EXTENSION_DATA,
+    manifest: {
+      ...EXTENSION_DATA.manifest,
+      manifest_version: 3,
+      host_permissions: ["http://example.com/*"],
+      granted_host_permissions: true,
+    },
+    temporarilyInstalled: true,
+  };
+
+  let extension = ExtensionTestUtils.loadExtension(data);
+  await extension.startup();
+
+  let urlsPromise = extension.awaitMessage("css-sources").then(msg => {
+    return mergeSources(
+      computeExpectedForbiddenURLs(msg, true, true),
+      computeBaseURLs(TESTS, EXTENSION_SOURCES_CONTENT_CSP, PAGE_SOURCES)
+    );
+  });
+
+  let origins = getOrigins(extension.extension);
+
+  let finished = Promise.all([
+    awaitLoads(urlsPromise, origins),
+    checkCSPReports && awaitCSP(urlsPromise),
+  ]);
+
+  let contentPage = await ExtensionTestUtils.loadContentPage(pageURL);
+
+  await finished;
+
+  await extension.unload();
+  await contentPage.close();
+  Services.prefs.clearUserPref("extensions.manifestV3.enabled");
+});
diff --git a/toolkit/components/extensions/test/xpcshell/test_ext_contentscript_unregister_during_loadContentScript.js b/toolkit/components/extensions/test/xpcshell/test_ext_contentscript_unregister_during_loadContentScript.js
new file mode 100644
index 0000000000..9191f7633e
--- /dev/null
+++ b/toolkit/components/extensions/test/xpcshell/test_ext_contentscript_unregister_during_loadContentScript.js
@@ -0,0 +1,91 @@
+/* Any copyright is dedicated to the Public Domain.
+ * http://creativecommons.org/publicdomain/zero/1.0/ */
+
+"use strict";
+
+const server = createHttpServer();
+server.registerDirectory("/data/", do_get_file("data"));
+
+const BASE_URL = `http://localhost:${server.identity.primaryPort}/data`;
+
+add_task(async function content_script_unregistered_during_loadContentScript() {
+  let content_scripts = [];
+
+  for (let i = 0; i < 10; i++) {
+    content_scripts.push({
+      matches: ["<all_urls>"],
+      js: ["dummy.js"],
+      run_at: "document_start",
+    });
+  }
+
+  let extension = ExtensionTestUtils.loadExtension({
+    manifest: {
+      content_scripts,
+    },
+    files: {
+      "dummy.js": function () {
+        browser.test.sendMessage("content-script-executed");
+      },
+    },
+  });
+
+  await extension.startup();
+
+  let contentPage = await ExtensionTestUtils.loadContentPage(
+    `${BASE_URL}/file_sample.html`
+  );
+  info("Wait for all the content scripts to be executed");
+  await Promise.all(
+    content_scripts.map(() => extension.awaitMessage("content-script-executed"))
+  );
+
+  const promiseDone = contentPage.legacySpawn([extension.id], extensionId => {
+    const { ExtensionProcessScript } = ChromeUtils.importESModule(
+      "resource://gre/modules/ExtensionProcessScript.sys.mjs"
+    );
+
+    return new Promise(resolve => {
+      // This recreates a scenario similar to Bug 1593240 and ensures that the
+      // related fix doesn't regress. Replacing loadContentScript with a
+      // function that unregisters all the content scripts make us sure that
+      // mutating the policy contentScripts doesn't trigger a crash due to
+      // the invalidation of the contentScripts iterator being used by the
+      // caller (ExtensionPolicyService::CheckContentScripts).
+      const { loadContentScript } = ExtensionProcessScript;
+      ExtensionProcessScript.loadContentScript = async (...args) => {
+        const policy = WebExtensionPolicy.getByID(extensionId);
+        let initial = policy.contentScripts.length;
+        let i = initial;
+        while (i) {
+          policy.unregisterContentScript(policy.contentScripts[--i]);
+        }
+        Services.tm.dispatchToMainThread(() =>
+          resolve({
+            initial,
+            final: policy.contentScripts.length,
+          })
+        );
+        // Call the real loadContentScript method.
+        return loadContentScript(...args);
+      };
+    });
+  });
+
+  info("Reload the webpage");
+  await contentPage.loadURL(`${BASE_URL}/file_sample.html`);
+  info("Wait for all the content scripts to be executed again");
+  await Promise.all(
+    content_scripts.map(() => extension.awaitMessage("content-script-executed"))
+  );
+  info("No crash triggered as expected");
+
+  Assert.deepEqual(
+    await promiseDone,
+    { initial: content_scripts.length, final: 0 },
+    "All content scripts unregistered as expected"
+  );
+
+  await contentPage.close();
+  await extension.unload();
+});
diff --git a/toolkit/components/extensions/test/xpcshell/test_ext_contentscript_xml_prettyprint.js b/toolkit/components/extensions/test/xpcshell/test_ext_contentscript_xml_prettyprint.js
new file mode 100644
index 0000000000..0682d30933
--- /dev/null
+++ b/toolkit/components/extensions/test/xpcshell/test_ext_contentscript_xml_prettyprint.js
@@ -0,0 +1,75 @@
+/* Any copyright is dedicated to the Public Domain.
+ * http://creativecommons.org/publicdomain/zero/1.0/ */
+
+"use strict";
+
+Services.prefs.setBoolPref("layout.xml.prettyprint", true);
+
+const BASE_XML = '<?xml version="1.0" encoding="UTF-8"?>';
+const server = createHttpServer({ hosts: ["example.com"] });
+
+server.registerPathHandler("/test.xml", (request, response) => {
+  response.setStatusLine(request.httpVersion, 200, "OK");
+  response.setHeader("Content-Type", "text/xml; charset=utf-8", false);
+  response.write(`${BASE_XML}\n<note></note>`);
+});
+
+// Make sure that XML pretty printer runs after content scripts
+// that runs at document_start (See Bug 1605657).
+add_task(async function content_script_on_xml_prettyprinted_document() {
+  let extension = ExtensionTestUtils.loadExtension({
+    manifest: {
+      content_scripts: [
+        {
+          matches: ["<all_urls>"],
+          js: ["start.js"],
+          run_at: "document_start",
+        },
+      ],
+    },
+    files: {
+      "start.js": async function () {
+        const el = document.createElement("ext-el");
+        document.documentElement.append(el);
+        if (document.readyState !== "complete") {
+          await new Promise(resolve => {
+            document.addEventListener("DOMContentLoaded", resolve, {
+              once: true,
+            });
+          });
+        }
+        browser.test.sendMessage("content-script-done");
+      },
+    },
+  });
+
+  await extension.startup();
+  let contentPage = await ExtensionTestUtils.loadContentPage(
+    "http://example.com/test.xml"
+  );
+
+  info("Wait content script and xml document to be fully loaded");
+  await extension.awaitMessage("content-script-done");
+
+  info("Verify the xml file is still pretty printed");
+  const res = await contentPage.spawn([], () => {
+    const doc = this.content.document;
+    const shadowRoot = doc.documentElement.openOrClosedShadowRoot;
+    const prettyPrintLink =
+      shadowRoot &&
+      shadowRoot.querySelector("link[href*='XMLPrettyPrint.css']");
+    return {
+      hasShadowRoot: !!shadowRoot,
+      hasPrettyPrintLink: !!prettyPrintLink,
+    };
+  });
+
+  Assert.deepEqual(
+    res,
+    { hasShadowRoot: true, hasPrettyPrintLink: true },
+    "The XML file has the pretty print shadowRoot"
+  );
+
+  await contentPage.close();
+  await extension.unload();
+});
diff --git a/toolkit/components/extensions/test/xpcshell/test_ext_contentscript_xorigin_frame.js b/toolkit/components/extensions/test/xpcshell/test_ext_contentscript_xorigin_frame.js
new file mode 100644
index 0000000000..8a58b2475c
--- /dev/null
+++ b/toolkit/components/extensions/test/xpcshell/test_ext_contentscript_xorigin_frame.js
@@ -0,0 +1,62 @@
+"use strict";
+
+const server = createHttpServer({
+  hosts: ["example.net", "example.org"],
+});
+server.registerDirectory("/data/", do_get_file("data"));
+
+add_task(async function test_process_switch_cross_origin_frame() {
+  const extension = ExtensionTestUtils.loadExtension({
+    manifest: {
+      content_scripts: [
+        {
+          matches: ["http://example.org/*/file_iframe.html"],
+          all_frames: true,
+          js: ["cs.js"],
+        },
+      ],
+    },
+
+    files: {
+      "cs.js"() {
+        browser.test.assertEq(
+          location.href,
+          "http://example.org/data/file_iframe.html",
+          "url is ok"
+        );
+
+        // frameId is the BrowsingContext ID in practice.
+        let frameId = browser.runtime.getFrameId(window);
+        browser.test.sendMessage("content-script-loaded", frameId);
+      },
+    },
+  });
+
+  await extension.startup();
+
+  const contentPage = await ExtensionTestUtils.loadContentPage(
+    "http://example.net/data/file_with_xorigin_frame.html"
+  );
+
+  const browserProcessId =
+    contentPage.browser.browsingContext.currentWindowGlobal.domProcess.childID;
+
+  const scriptFrameId = await extension.awaitMessage("content-script-loaded");
+
+  const children = contentPage.browser.browsingContext.children.map(bc => ({
+    browsingContextId: bc.id,
+    processId: bc.currentWindowGlobal.domProcess.childID,
+  }));
+
+  Assert.equal(children.length, 1);
+  Assert.equal(scriptFrameId, children[0].browsingContextId);
+
+  if (contentPage.remoteSubframes) {
+    Assert.notEqual(browserProcessId, children[0].processId);
+  } else {
+    Assert.equal(browserProcessId, children[0].processId);
+  }
+
+  await contentPage.close();
+  await extension.unload();
+});
diff --git a/toolkit/components/extensions/test/xpcshell/test_ext_contentscript_xrays.js b/toolkit/components/extensions/test/xpcshell/test_ext_contentscript_xrays.js
new file mode 100644
index 0000000000..7b92d5c4b7
--- /dev/null
+++ b/toolkit/components/extensions/test/xpcshell/test_ext_contentscript_xrays.js
@@ -0,0 +1,59 @@
+"use strict";
+
+// ExtensionContent.jsm needs to know when it's running from xpcshell,
+// to use the right timeout for content scripts executed at document_idle.
+ExtensionTestUtils.mockAppInfo();
+
+const server = createHttpServer();
+server.registerDirectory("/data/", do_get_file("data"));
+
+const BASE_URL = `http://localhost:${server.identity.primaryPort}/data`;
+
+add_task(async function test_contentscript_xrays() {
+  async function contentScript() {
+    let unwrapped = window.wrappedJSObject;
+
+    browser.test.assertEq(
+      "undefined",
+      typeof test,
+      "Should not have named X-ray property access"
+    );
+    browser.test.assertEq(
+      undefined,
+      window.test,
+      "Should not have named X-ray property access"
+    );
+    browser.test.assertEq(
+      "object",
+      typeof unwrapped.test,
+      "Should always have non-X-ray named property access"
+    );
+
+    browser.test.notifyPass("contentScriptXrays");
+  }
+
+  let extension = ExtensionTestUtils.loadExtension({
+    manifest: {
+      content_scripts: [
+        {
+          matches: ["http://*/*/file_sample.html"],
+          js: ["content_script.js"],
+        },
+      ],
+    },
+
+    files: {
+      "content_script.js": contentScript,
+    },
+  });
+
+  await extension.startup();
+  let contentPage = await ExtensionTestUtils.loadContentPage(
+    `${BASE_URL}/file_sample.html`
+  );
+
+  await extension.awaitFinish("contentScriptXrays");
+
+  await contentPage.close();
+  await extension.unload();
+});
diff --git a/toolkit/components/extensions/test/xpcshell/test_ext_contexts.js b/toolkit/components/extensions/test/xpcshell/test_ext_contexts.js
new file mode 100644
index 0000000000..028f5b5638
--- /dev/null
+++ b/toolkit/components/extensions/test/xpcshell/test_ext_contexts.js
@@ -0,0 +1,201 @@
+"use strict";
+
+const global = this;
+
+var { BaseContext, EventManager, EventEmitter } = ExtensionCommon;
+
+class FakeExtension extends EventEmitter {
+  constructor(id) {
+    super();
+    this.id = id;
+  }
+}
+
+class StubContext extends BaseContext {
+  constructor() {
+    let fakeExtension = new FakeExtension("test@web.extension");
+    super("testEnv", fakeExtension);
+    this.sandbox = Cu.Sandbox(global);
+  }
+
+  logActivity(type, name, data) {
+    // no-op required by subclass
+  }
+
+  get cloneScope() {
+    return this.sandbox;
+  }
+
+  get principal() {
+    return Cu.getObjectPrincipal(this.sandbox);
+  }
+}
+
+add_task(async function test_post_unload_promises() {
+  let context = new StubContext();
+
+  let fail = result => {
+    ok(false, `Unexpected callback: ${result}`);
+  };
+
+  // Make sure promises resolve normally prior to unload.
+  let promises = [
+    context.wrapPromise(Promise.resolve()),
+    context.wrapPromise(Promise.reject({ message: "" })).catch(() => {}),
+  ];
+
+  await Promise.all(promises);
+
+  // Make sure promises that resolve after unload do not trigger
+  // resolution handlers.
+
+  context.wrapPromise(Promise.resolve("resolved")).then(fail);
+
+  context.wrapPromise(Promise.reject({ message: "rejected" })).then(fail, fail);
+
+  context.unload();
+
+  // The `setTimeout` ensures that we return to the event loop after
+  // promise resolution, which means we're guaranteed to return after
+  // any micro-tasks that get enqueued by the resolution handlers above.
+  await new Promise(resolve => setTimeout(resolve, 0));
+});
+
+add_task(async function test_post_unload_listeners() {
+  let context = new StubContext();
+
+  let fire;
+  let manager = new EventManager({
+    context,
+    name: "EventManager",
+    register: _fire => {
+      fire = () => {
+        _fire.async();
+      };
+      return () => {};
+    },
+  });
+
+  let fail = event => {
+    ok(false, `Unexpected event: ${event}`);
+  };
+
+  // Check that event listeners isn't called after it has been removed.
+  manager.addListener(fail);
+
+  let promise = new Promise(resolve => manager.addListener(resolve));
+
+  fire();
+
+  // The `fireSingleton` call ia dispatched asynchronously, so it won't
+  // have fired by this point. The `fail` listener that we remove now
+  // should not be called, even though the event has already been
+  // enqueued.
+  manager.removeListener(fail);
+
+  // Wait for the remaining listener to be called, which should always
+  // happen after the `fail` listener would normally be called.
+  await promise;
+
+  // Check that the event listener isn't called after the context has
+  // unloaded.
+  manager.addListener(fail);
+
+  // The `fire` callback always dispatches events
+  // asynchronously, so we need to test that any pending event callbacks
+  // aren't fired after the context unloads. We also need to test that
+  // any `fire` calls that happen *after* the context is unloaded also
+  // do not trigger callbacks.
+  fire();
+  Promise.resolve().then(fire);
+
+  context.unload();
+
+  // The `setTimeout` ensures that we return to the event loop after
+  // promise resolution, which means we're guaranteed to return after
+  // any micro-tasks that get enqueued by the resolution handlers above.
+  await new Promise(resolve => setTimeout(resolve, 0));
+});
+
+class Context extends BaseContext {
+  constructor(principal) {
+    let fakeExtension = new FakeExtension("test@web.extension");
+    super("testEnv", fakeExtension);
+    Object.defineProperty(this, "principal", {
+      value: principal,
+      configurable: true,
+    });
+    this.sandbox = Cu.Sandbox(principal, { wantXrays: false });
+  }
+
+  logActivity(type, name, data) {
+    // no-op required by subclass
+  }
+
+  get cloneScope() {
+    return this.sandbox;
+  }
+}
+
+let ssm = Services.scriptSecurityManager;
+const PRINCIPAL1 = ssm.createContentPrincipalFromOrigin(
+  "http://www.example.org"
+);
+const PRINCIPAL2 = ssm.createContentPrincipalFromOrigin(
+  "http://www.somethingelse.org"
+);
+
+// Test that toJSON() works in the json sandbox
+add_task(async function test_stringify_toJSON() {
+  let context = new Context(PRINCIPAL1);
+  let obj = Cu.evalInSandbox(
+    "({hidden: true, toJSON() { return {visible: true}; } })",
+    context.sandbox
+  );
+
+  let stringified = context.jsonStringify(obj);
+  let expected = JSON.stringify({ visible: true });
+  equal(
+    stringified,
+    expected,
+    "Stringified object with toJSON() method is as expected"
+  );
+});
+
+// Test that stringifying in inaccessible property throws
+add_task(async function test_stringify_inaccessible() {
+  let context = new Context(PRINCIPAL1);
+  let sandbox = context.sandbox;
+  let sandbox2 = Cu.Sandbox(PRINCIPAL2);
+
+  Cu.waiveXrays(sandbox).subobj = Cu.evalInSandbox(
+    "({ subobject: true })",
+    sandbox2
+  );
+  let obj = Cu.evalInSandbox("({ local: true, nested: subobj })", sandbox);
+  Assert.throws(() => {
+    context.jsonStringify(obj);
+  }, /Permission denied to access property "toJSON"/);
+});
+
+add_task(async function test_stringify_accessible() {
+  // Test that an accessible property from another global is included
+  let principal = Cu.getObjectPrincipal(Cu.Sandbox([PRINCIPAL1, PRINCIPAL2]));
+  let context = new Context(principal);
+  let sandbox = context.sandbox;
+  let sandbox2 = Cu.Sandbox(PRINCIPAL2);
+
+  Cu.waiveXrays(sandbox).subobj = Cu.evalInSandbox(
+    "({ subobject: true })",
+    sandbox2
+  );
+  let obj = Cu.evalInSandbox("({ local: true, nested: subobj })", sandbox);
+  let stringified = context.jsonStringify(obj);
+
+  let expected = JSON.stringify({ local: true, nested: { subobject: true } });
+  equal(
+    stringified,
+    expected,
+    "Stringified object with accessible property is as expected"
+  );
+});
diff --git a/toolkit/components/extensions/test/xpcshell/test_ext_contexts_gc.js b/toolkit/components/extensions/test/xpcshell/test_ext_contexts_gc.js
new file mode 100644
index 0000000000..a828584ced
--- /dev/null
+++ b/toolkit/components/extensions/test/xpcshell/test_ext_contexts_gc.js
@@ -0,0 +1,277 @@
+"use strict";
+
+const server = createHttpServer();
+server.registerDirectory("/data/", do_get_file("data"));
+
+const BASE_URL = `http://localhost:${server.identity.primaryPort}/data`;
+
+// ExtensionContent.jsm needs to know when it's running from xpcshell,
+// to use the right timeout for content scripts executed at document_idle.
+ExtensionTestUtils.mockAppInfo();
+
+// Each of these tests do the following:
+// 1. Load document to create an extension context (instance of BaseContext).
+// 2. Get weak reference to that context.
+// 3. Unload the document.
+// 4. Force GC and check that the weak reference has been invalidated.
+
+async function reloadTopContext(contentPage) {
+  await contentPage.legacySpawn(null, async () => {
+    let { TestUtils } = ChromeUtils.importESModule(
+      "resource://testing-common/TestUtils.sys.mjs"
+    );
+    let windowNukeObserved = TestUtils.topicObserved("inner-window-nuked");
+    info(`Reloading top-level document`);
+    this.content.location.reload();
+    await windowNukeObserved;
+    info(`Reloaded top-level document`);
+  });
+}
+
+async function assertContextReleased(contentPage, description) {
+  await contentPage.legacySpawn(description, async assertionDescription => {
+    // Force GC, see https://searchfox.org/mozilla-central/rev/b0275bc977ad7fda615ef34b822bba938f2b16fd/testing/talos/talos/tests/devtools/addon/content/damp.js#84-98
+    // and https://searchfox.org/mozilla-central/rev/33c21c060b7f3a52477a73d06ebcb2bf313c4431/xpcom/base/nsMemoryReporterManager.cpp#2574-2585,2591-2594
+    let gcCount = 0;
+    while (gcCount < 30 && this.contextWeakRef.get() !== null) {
+      ++gcCount;
+      // The JS engine will sometimes hold IC stubs for function
+      // environments alive across multiple CCs, which can keep
+      // closed-over JS objects alive. A shrinking GC will throw those
+      // stubs away, and therefore side-step the problem.
+      Cu.forceShrinkingGC();
+      Cu.forceCC();
+      Cu.forceGC();
+      await new Promise(resolve => this.content.setTimeout(resolve, 0));
+    }
+
+    // The above loop needs to be repeated at most 3 times according to MinimizeMemoryUsage:
+    // https://searchfox.org/mozilla-central/rev/6f86cc3479f80ace97f62634e2c82a483d1ede40/xpcom/base/nsMemoryReporterManager.cpp#2644-2647
+    Assert.lessOrEqual(
+      gcCount,
+      3,
+      `Context should have been GCd within a few GC attempts.`
+    );
+
+    // Each test will set this.contextWeakRef before unloading the document.
+    Assert.ok(!this.contextWeakRef.get(), assertionDescription);
+  });
+}
+
+add_task(async function test_ContentScriptContextChild_in_child_frame() {
+  let extensionData = {
+    manifest: {
+      content_scripts: [
+        {
+          matches: ["http://*/*/file_iframe.html"],
+          js: ["content_script.js"],
+          all_frames: true,
+        },
+      ],
+    },
+
+    files: {
+      "content_script.js": "browser.test.sendMessage('contentScriptLoaded');",
+    },
+  };
+
+  let extension = ExtensionTestUtils.loadExtension(extensionData);
+  await extension.startup();
+
+  let contentPage = await ExtensionTestUtils.loadContentPage(
+    `${BASE_URL}/file_toplevel.html`
+  );
+  await extension.awaitMessage("contentScriptLoaded");
+
+  await contentPage.legacySpawn(extension.id, async extensionId => {
+    const { ExtensionContent } = ChromeUtils.importESModule(
+      "resource://gre/modules/ExtensionContent.sys.mjs"
+    );
+    let frame = this.content.document.querySelector(
+      "iframe[src*='file_iframe.html']"
+    );
+    let context = ExtensionContent.getContextByExtensionId(
+      extensionId,
+      frame.contentWindow
+    );
+
+    Assert.ok(!!context, "Got content script context");
+
+    this.contextWeakRef = Cu.getWeakReference(context);
+    frame.remove();
+  });
+
+  await assertContextReleased(
+    contentPage,
+    "ContentScriptContextChild should have been released"
+  );
+
+  await contentPage.close();
+  await extension.unload();
+});
+
+add_task(async function test_ContentScriptContextChild_in_toplevel() {
+  let extensionData = {
+    manifest: {
+      content_scripts: [
+        {
+          matches: ["http://*/*/file_sample.html"],
+          js: ["content_script.js"],
+          all_frames: true,
+        },
+      ],
+    },
+
+    files: {
+      "content_script.js": "browser.test.sendMessage('contentScriptLoaded');",
+    },
+  };
+
+  let extension = ExtensionTestUtils.loadExtension(extensionData);
+  await extension.startup();
+
+  let contentPage = await ExtensionTestUtils.loadContentPage(
+    `${BASE_URL}/file_sample.html`
+  );
+  await extension.awaitMessage("contentScriptLoaded");
+
+  await contentPage.legacySpawn(extension.id, async extensionId => {
+    const { ExtensionContent } = ChromeUtils.importESModule(
+      "resource://gre/modules/ExtensionContent.sys.mjs"
+    );
+    let context = ExtensionContent.getContextByExtensionId(
+      extensionId,
+      this.content
+    );
+
+    Assert.ok(!!context, "Got content script context");
+
+    this.contextWeakRef = Cu.getWeakReference(context);
+  });
+
+  await reloadTopContext(contentPage);
+  await extension.awaitMessage("contentScriptLoaded");
+  await assertContextReleased(
+    contentPage,
+    "ContentScriptContextChild should have been released"
+  );
+
+  await contentPage.close();
+  await extension.unload();
+});
+
+add_task(async function test_ExtensionPageContextChild_in_child_frame() {
+  let extensionData = {
+    files: {
+      "iframe.html": `
+        <!DOCTYPE html><meta charset="utf8">
+        <script src="script.js"></script>
+      `,
+      "toplevel.html": `
+        <!DOCTYPE html><meta charset="utf8">
+        <iframe src="iframe.html"></iframe>
+      `,
+      "script.js": "browser.test.sendMessage('extensionPageLoaded');",
+    },
+  };
+
+  let extension = ExtensionTestUtils.loadExtension(extensionData);
+  await extension.startup();
+
+  let contentPage = await ExtensionTestUtils.loadContentPage(
+    `moz-extension://${extension.uuid}/toplevel.html`,
+    {
+      extension,
+      remote: extension.extension.remote,
+    }
+  );
+  await extension.awaitMessage("extensionPageLoaded");
+
+  await contentPage.legacySpawn(extension.id, async extensionId => {
+    let { ExtensionPageChild } = ChromeUtils.importESModule(
+      "resource://gre/modules/ExtensionPageChild.sys.mjs"
+    );
+
+    let frame = this.content.document.querySelector(
+      "iframe[src*='iframe.html']"
+    );
+    let innerWindowID =
+      frame.browsingContext.currentWindowContext.innerWindowId;
+    let context = ExtensionPageChild.extensionContexts.get(innerWindowID);
+
+    Assert.ok(!!context, "Got extension page context for child frame");
+
+    this.contextWeakRef = Cu.getWeakReference(context);
+    frame.remove();
+  });
+
+  await assertContextReleased(
+    contentPage,
+    "ExtensionPageContextChild should have been released"
+  );
+
+  await contentPage.close();
+  await extension.unload();
+});
+
+add_task(async function test_ExtensionPageContextChild_in_toplevel() {
+  let extensionData = {
+    files: {
+      "toplevel.html": `
+        <!DOCTYPE html><meta charset="utf8">
+        <script src="script.js"></script>
+      `,
+      "script.js": "browser.test.sendMessage('extensionPageLoaded');",
+    },
+  };
+
+  let extension = ExtensionTestUtils.loadExtension(extensionData);
+  await extension.startup();
+
+  let contentPage = await ExtensionTestUtils.loadContentPage(
+    `moz-extension://${extension.uuid}/toplevel.html`,
+    {
+      extension,
+      remote: extension.extension.remote,
+    }
+  );
+  await extension.awaitMessage("extensionPageLoaded");
+
+  await contentPage.legacySpawn(extension.id, async extensionId => {
+    let { ExtensionPageChild } = ChromeUtils.importESModule(
+      "resource://gre/modules/ExtensionPageChild.sys.mjs"
+    );
+
+    let innerWindowID = this.content.windowGlobalChild.innerWindowId;
+    let context = ExtensionPageChild.extensionContexts.get(innerWindowID);
+
+    Assert.ok(!!context, "Got extension page context for top-level document");
+
+    this.contextWeakRef = Cu.getWeakReference(context);
+  });
+
+  await reloadTopContext(contentPage);
+  await extension.awaitMessage("extensionPageLoaded");
+  // For some unknown reason, the context cannot forcidbly be released by the
+  // garbage collector unless we wait for a short while.
+  await contentPage.spawn([], async () => {
+    let start = Date.now();
+    // The treshold was found after running this subtest only, 300 times
+    // in a release build (100 of xpcshell, xpcshell-e10s and xpcshell-remote).
+    // With treshold 8, almost half of the tests complete after a 17-18 ms delay.
+    // With treshold 7, over half of the tests complete after a 13-14 ms delay,
+    //  with 12 failures in 300 tests runs.
+    // Let's double that number to have a safety margin.
+    for (let i = 0; i < 15; ++i) {
+      await new Promise(resolve => this.content.setTimeout(resolve, 0));
+    }
+    info(`Going to GC after waiting for ${Date.now() - start} ms.`);
+  });
+  await assertContextReleased(
+    contentPage,
+    "ExtensionPageContextChild should have been released"
+  );
+
+  await contentPage.close();
+  await extension.unload();
+});
diff --git a/toolkit/components/extensions/test/xpcshell/test_ext_contextual_identities.js b/toolkit/components/extensions/test/xpcshell/test_ext_contextual_identities.js
new file mode 100644
index 0000000000..29f8b030ff
--- /dev/null
+++ b/toolkit/components/extensions/test/xpcshell/test_ext_contextual_identities.js
@@ -0,0 +1,588 @@
+"use strict";
+
+ChromeUtils.defineESModuleGetters(this, {
+  ContextualIdentityService:
+    "resource://gre/modules/ContextualIdentityService.sys.mjs",
+  ExtensionPreferencesManager:
+    "resource://gre/modules/ExtensionPreferencesManager.sys.mjs",
+});
+
+const CONTAINERS_PREF = "privacy.userContext.enabled";
+
+AddonTestUtils.init(this);
+AddonTestUtils.overrideCertDB();
+AddonTestUtils.createAppInfo(
+  "xpcshell@tests.mozilla.org",
+  "XPCShell",
+  "42",
+  "42"
+);
+
+add_task(async function startup() {
+  await AddonTestUtils.promiseStartupManager();
+});
+
+add_task(async function test_contextualIdentities_without_permissions() {
+  function background() {
+    browser.test.assertTrue(
+      !browser.contextualIdentities,
+      "contextualIdentities API is not available when the contextualIdentities permission is not required"
+    );
+    browser.test.notifyPass("contextualIdentities_without_permission");
+  }
+
+  let extension = ExtensionTestUtils.loadExtension({
+    useAddonManager: "temporary",
+    background,
+    manifest: {
+      browser_specific_settings: {
+        gecko: { id: "testing@thing.com" },
+      },
+      permissions: [],
+    },
+  });
+
+  await extension.startup();
+  await extension.awaitFinish("contextualIdentities_without_permission");
+  await extension.unload();
+});
+
+add_task(async function test_contextualIdentity_events() {
+  async function background() {
+    function createOneTimeListener(type) {
+      return new Promise((resolve, reject) => {
+        try {
+          browser.test.assertTrue(
+            type in browser.contextualIdentities,
+            `Found API object browser.contextualIdentities.${type}`
+          );
+          const listener = change => {
+            browser.test.assertTrue(
+              "contextualIdentity" in change,
+              `Found identity in change`
+            );
+            browser.contextualIdentities[type].removeListener(listener);
+            resolve(change);
+          };
+          browser.contextualIdentities[type].addListener(listener);
+        } catch (e) {
+          reject(e);
+        }
+      });
+    }
+
+    function assertExpected(expected, container) {
+      // Number of keys that are added by the APIs
+      const createdCount = 2;
+      for (let key of Object.keys(container)) {
+        browser.test.assertTrue(key in expected, `found property ${key}`);
+        browser.test.assertEq(
+          expected[key],
+          container[key],
+          `property value for ${key} is correct`
+        );
+      }
+      const hexMatch = /^#[0-9a-f]{6}$/;
+      browser.test.assertTrue(
+        hexMatch.test(expected.colorCode),
+        "Color code property was expected Hex shape"
+      );
+      const iconMatch = /^resource:\/\/usercontext-content\/[a-z]+[.]svg$/;
+      browser.test.assertTrue(
+        iconMatch.test(expected.iconUrl),
+        "Icon url property was expected shape"
+      );
+      browser.test.assertEq(
+        Object.keys(expected).length,
+        Object.keys(container).length + createdCount,
+        "all expected properties found"
+      );
+    }
+
+    let onCreatePromise = createOneTimeListener("onCreated");
+
+    let containerObj = { name: "foobar", color: "red", icon: "circle" };
+    let ci = await browser.contextualIdentities.create(containerObj);
+    browser.test.assertTrue(!!ci, "We have an identity");
+    const onCreateListenerResponse = await onCreatePromise;
+    const cookieStoreId = ci.cookieStoreId;
+    assertExpected(
+      onCreateListenerResponse.contextualIdentity,
+      Object.assign(containerObj, { cookieStoreId })
+    );
+
+    let onUpdatedPromise = createOneTimeListener("onUpdated");
+    let updateContainerObj = { name: "testing", color: "blue", icon: "dollar" };
+    ci = await browser.contextualIdentities.update(
+      cookieStoreId,
+      updateContainerObj
+    );
+    browser.test.assertTrue(!!ci, "We have an update identity");
+    const onUpdatedListenerResponse = await onUpdatedPromise;
+    assertExpected(
+      onUpdatedListenerResponse.contextualIdentity,
+      Object.assign(updateContainerObj, { cookieStoreId })
+    );
+
+    let onRemovePromise = createOneTimeListener("onRemoved");
+    ci = await browser.contextualIdentities.remove(
+      updateContainerObj.cookieStoreId
+    );
+    browser.test.assertTrue(!!ci, "We have an remove identity");
+    const onRemoveListenerResponse = await onRemovePromise;
+    assertExpected(
+      onRemoveListenerResponse.contextualIdentity,
+      Object.assign(updateContainerObj, { cookieStoreId })
+    );
+
+    browser.test.notifyPass("contextualIdentities_events");
+  }
+
+  let extension = ExtensionTestUtils.loadExtension({
+    background,
+    useAddonManager: "temporary",
+    manifest: {
+      browser_specific_settings: {
+        gecko: { id: "testing@thing.com" },
+      },
+      permissions: ["contextualIdentities"],
+    },
+  });
+
+  Services.prefs.setBoolPref(CONTAINERS_PREF, true);
+
+  await extension.startup();
+  await extension.awaitFinish("contextualIdentities_events");
+  await extension.unload();
+
+  Services.prefs.clearUserPref(CONTAINERS_PREF);
+});
+
+add_task(async function test_contextualIdentity_with_permissions() {
+  const initial = Services.prefs.getBoolPref(CONTAINERS_PREF);
+
+  async function background() {
+    let ci;
+    await browser.test.assertRejects(
+      browser.contextualIdentities.get("foobar"),
+      "Invalid contextual identity: foobar",
+      "API should reject here"
+    );
+    await browser.test.assertRejects(
+      browser.contextualIdentities.update("foobar", { name: "testing" }),
+      "Invalid contextual identity: foobar",
+      "API should reject for unknown updates"
+    );
+    await browser.test.assertRejects(
+      browser.contextualIdentities.remove("foobar"),
+      "Invalid contextual identity: foobar",
+      "API should reject for removing unknown containers"
+    );
+
+    ci = await browser.contextualIdentities.get("firefox-container-1");
+    browser.test.assertTrue(!!ci, "We have an identity");
+    browser.test.assertTrue("name" in ci, "We have an identity.name");
+    browser.test.assertTrue("color" in ci, "We have an identity.color");
+    browser.test.assertTrue("icon" in ci, "We have an identity.icon");
+    browser.test.assertEq("Personal", ci.name, "identity.name is correct");
+    browser.test.assertEq(
+      "firefox-container-1",
+      ci.cookieStoreId,
+      "identity.cookieStoreId is correct"
+    );
+
+    function listenForMessage(messageName, stateChangeBool) {
+      return new Promise(resolve => {
+        browser.test.onMessage.addListener(function listener(msg) {
+          browser.test.log(`Got message from background: ${msg}`);
+          if (msg === messageName + "-response") {
+            browser.test.onMessage.removeListener(listener);
+            resolve();
+          }
+        });
+        browser.test.log(
+          `Sending message to background: ${messageName} ${stateChangeBool}`
+        );
+        browser.test.sendMessage(messageName, stateChangeBool);
+      });
+    }
+
+    await listenForMessage("containers-state-change", false);
+
+    browser.test.assertRejects(
+      browser.contextualIdentities.query({}),
+      "Contextual identities are currently disabled",
+      "Throws when containers are disabled"
+    );
+
+    await listenForMessage("containers-state-change", true);
+
+    let cis = await browser.contextualIdentities.query({});
+    browser.test.assertEq(
+      4,
+      cis.length,
+      "by default we should have 4 containers"
+    );
+
+    cis = await browser.contextualIdentities.query({ name: "Personal" });
+    browser.test.assertEq(
+      1,
+      cis.length,
+      "by default we should have 1 container called Personal"
+    );
+
+    cis = await browser.contextualIdentities.query({ name: "foobar" });
+    browser.test.assertEq(
+      0,
+      cis.length,
+      "by default we should have 0 container called foobar"
+    );
+
+    ci = await browser.contextualIdentities.create({
+      name: "foobar",
+      color: "red",
+      icon: "gift",
+    });
+    browser.test.assertTrue(!!ci, "We have an identity");
+    browser.test.assertEq("foobar", ci.name, "identity.name is correct");
+    browser.test.assertEq("red", ci.color, "identity.color is correct");
+    browser.test.assertEq("gift", ci.icon, "identity.icon is correct");
+    browser.test.assertTrue(
+      !!ci.cookieStoreId,
+      "identity.cookieStoreId is correct"
+    );
+
+    browser.test.assertRejects(
+      browser.contextualIdentities.create({
+        name: "foobar",
+        color: "red",
+        icon: "firefox",
+      }),
+      "Invalid icon firefox for container",
+      "Create container called with an invalid icon"
+    );
+
+    browser.test.assertRejects(
+      browser.contextualIdentities.create({
+        name: "foobar",
+        color: "firefox-orange",
+        icon: "gift",
+      }),
+      "Invalid color name firefox-orange for container",
+      "Create container called with an invalid color"
+    );
+
+    cis = await browser.contextualIdentities.query({});
+    browser.test.assertEq(
+      5,
+      cis.length,
+      "we should still have have 5 containers"
+    );
+
+    ci = await browser.contextualIdentities.get(ci.cookieStoreId);
+    browser.test.assertTrue(!!ci, "We have an identity");
+    browser.test.assertEq("foobar", ci.name, "identity.name is correct");
+    browser.test.assertEq("red", ci.color, "identity.color is correct");
+    browser.test.assertEq("gift", ci.icon, "identity.icon is correct");
+
+    browser.test.assertRejects(
+      browser.contextualIdentities.update(ci.cookieStoreId, {
+        name: "foobar",
+        color: "red",
+        icon: "firefox",
+      }),
+      "Invalid icon firefox for container",
+      "Create container called with an invalid icon"
+    );
+
+    browser.test.assertRejects(
+      browser.contextualIdentities.update(ci.cookieStoreId, {
+        name: "foobar",
+        color: "firefox-orange",
+        icon: "gift",
+      }),
+      "Invalid color name firefox-orange for container",
+      "Create container called with an invalid color"
+    );
+
+    cis = await browser.contextualIdentities.query({});
+    browser.test.assertEq(5, cis.length, "now we have 5 identities");
+
+    ci = await browser.contextualIdentities.update(ci.cookieStoreId, {
+      name: "barfoo",
+      color: "blue",
+      icon: "cart",
+    });
+    browser.test.assertTrue(!!ci, "We have an identity");
+    browser.test.assertEq("barfoo", ci.name, "identity.name is correct");
+    browser.test.assertEq("blue", ci.color, "identity.color is correct");
+    browser.test.assertEq("cart", ci.icon, "identity.icon is correct");
+
+    ci = await browser.contextualIdentities.get(ci.cookieStoreId);
+    browser.test.assertTrue(!!ci, "We have an identity");
+    browser.test.assertEq("barfoo", ci.name, "identity.name is correct");
+    browser.test.assertEq("blue", ci.color, "identity.color is correct");
+    browser.test.assertEq("cart", ci.icon, "identity.icon is correct");
+
+    ci = await browser.contextualIdentities.remove(ci.cookieStoreId);
+    browser.test.assertTrue(!!ci, "We have an identity");
+    browser.test.assertEq("barfoo", ci.name, "identity.name is correct");
+    browser.test.assertEq("blue", ci.color, "identity.color is correct");
+    browser.test.assertEq("cart", ci.icon, "identity.icon is correct");
+
+    cis = await browser.contextualIdentities.query({});
+    browser.test.assertEq(4, cis.length, "we are back to 4 identities");
+
+    browser.test.notifyPass("contextualIdentities");
+  }
+
+  function makeExtension(id) {
+    return ExtensionTestUtils.loadExtension({
+      useAddonManager: "temporary",
+      background,
+      manifest: {
+        browser_specific_settings: {
+          gecko: { id },
+        },
+        permissions: ["contextualIdentities"],
+      },
+    });
+  }
+
+  let extension = makeExtension("containers-test@mozilla.org");
+
+  extension.onMessage("containers-state-change", stateBool => {
+    Cu.reportError(`Got message "containers-state-change", ${stateBool}`);
+    Services.prefs.setBoolPref(CONTAINERS_PREF, stateBool);
+    Cu.reportError("Changed pref");
+    extension.sendMessage("containers-state-change-response");
+  });
+
+  await extension.startup();
+  await extension.awaitFinish("contextualIdentities");
+  equal(
+    Services.prefs.getBoolPref(CONTAINERS_PREF),
+    true,
+    "Pref should now be enabled, whatever it's initial state"
+  );
+  await extension.unload();
+  equal(
+    Services.prefs.getBoolPref(CONTAINERS_PREF),
+    initial,
+    "Pref should now be initial state"
+  );
+
+  Services.prefs.clearUserPref(CONTAINERS_PREF);
+});
+
+add_task(async function test_contextualIdentity_extensions_enable_containers() {
+  const initial = Services.prefs.getBoolPref(CONTAINERS_PREF);
+  async function background() {
+    let ci = await browser.contextualIdentities.get("firefox-container-1");
+    browser.test.assertTrue(!!ci, "We have an identity");
+
+    browser.test.notifyPass("contextualIdentities");
+  }
+  function makeExtension(id) {
+    return ExtensionTestUtils.loadExtension({
+      useAddonManager: "temporary",
+      background,
+      manifest: {
+        browser_specific_settings: {
+          gecko: { id },
+        },
+        permissions: ["contextualIdentities"],
+      },
+    });
+  }
+  async function testSetting(expect, message) {
+    let setting = await ExtensionPreferencesManager.getSetting(
+      "privacy.containers"
+    );
+    if (expect === null) {
+      equal(setting, null, message);
+    } else {
+      equal(setting.value, expect, message);
+    }
+  }
+  function testPref(expect, message) {
+    equal(Services.prefs.getBoolPref(CONTAINERS_PREF), expect, message);
+  }
+
+  let extension = makeExtension("containers-test@mozilla.org");
+  await extension.startup();
+  await extension.awaitFinish("contextualIdentities");
+  equal(
+    Services.prefs.getBoolPref(CONTAINERS_PREF),
+    true,
+    "Pref should now be enabled, whatever it's initial state"
+  );
+  await extension.unload();
+  await testSetting(null, "setting should be unset");
+  testPref(initial, "setting should be initial value");
+
+  // Lets set containers explicitly to be off and test we keep it that way after removal
+  Services.prefs.setBoolPref(CONTAINERS_PREF, false);
+
+  let extension1 = makeExtension("containers-test-1@mozilla.org");
+  await extension1.startup();
+  await extension1.awaitFinish("contextualIdentities");
+  await testSetting(extension1.id, "setting should be controlled");
+  testPref(true, "Pref should now be enabled, whatever it's initial state");
+
+  await extension1.unload();
+  await testSetting(null, "setting should be unset");
+  testPref(false, "Pref should be false");
+
+  // Lets set containers explicitly to be on and test we keep it that way after removal.
+  Services.prefs.setBoolPref(CONTAINERS_PREF, true);
+
+  let extension2 = makeExtension("containers-test-2@mozilla.org");
+  let extension3 = makeExtension("containers-test-3@mozilla.org");
+  await extension2.startup();
+  await extension2.awaitFinish("contextualIdentities");
+  await extension3.startup();
+  await extension3.awaitFinish("contextualIdentities");
+
+  // Flip the ordering to check it's still enabled
+  await testSetting(extension3.id, "setting should still be controlled by 3");
+  testPref(true, "Pref should now be enabled 1");
+  await extension3.unload();
+  await testSetting(extension2.id, "setting should still be controlled by 2");
+  testPref(true, "Pref should now be enabled 2");
+  await extension2.unload();
+  await testSetting(null, "setting should be unset");
+  testPref(true, "Pref should now be enabled 3");
+
+  Services.prefs.clearUserPref(CONTAINERS_PREF);
+});
+
+add_task(async function test_contextualIdentity_preference_change() {
+  async function background() {
+    let extensionInfo = await browser.management.getSelf();
+    if (extensionInfo.version == "1.0.0") {
+      const containers = await browser.contextualIdentities.query({});
+      browser.test.assertEq(
+        containers.length,
+        4,
+        "We still have the original containers"
+      );
+      await browser.contextualIdentities.create({
+        name: "foobar",
+        color: "red",
+        icon: "circle",
+      });
+    }
+    const containers = await browser.contextualIdentities.query({});
+    browser.test.assertEq(containers.length, 5, "We have a new container");
+    if (extensionInfo.version == "1.1.0") {
+      await browser.contextualIdentities.remove(containers[4].cookieStoreId);
+    }
+    browser.test.notifyPass("contextualIdentities");
+  }
+  function makeExtension(id, version) {
+    return ExtensionTestUtils.loadExtension({
+      useAddonManager: "temporary",
+      background,
+      manifest: {
+        version,
+        browser_specific_settings: {
+          gecko: { id },
+        },
+        permissions: ["contextualIdentities"],
+      },
+    });
+  }
+
+  Services.prefs.setBoolPref(CONTAINERS_PREF, false);
+  let extension = makeExtension("containers-pref-test@mozilla.org", "1.0.0");
+  await extension.startup();
+  await extension.awaitFinish("contextualIdentities");
+  equal(
+    Services.prefs.getBoolPref(CONTAINERS_PREF),
+    true,
+    "Pref should now be enabled, whatever it's initial state"
+  );
+
+  let extension2 = makeExtension("containers-pref-test@mozilla.org", "1.1.0");
+  await extension2.startup();
+  await extension2.awaitFinish("contextualIdentities");
+
+  await extension.unload();
+  equal(
+    Services.prefs.getBoolPref(CONTAINERS_PREF),
+    false,
+    "Pref should now be the initial state we set it to."
+  );
+
+  Services.prefs.clearUserPref(CONTAINERS_PREF);
+});
+
+add_task(
+  { pref_set: [["extensions.eventPages.enabled", true]] },
+  async function test_contextualIdentity_event_page() {
+    let extension = ExtensionTestUtils.loadExtension({
+      useAddonManager: "permanent",
+      manifest: {
+        browser_specific_settings: {
+          gecko: { id: "eventpage@mochitest" },
+        },
+        permissions: ["contextualIdentities"],
+        background: { persistent: false },
+      },
+      background() {
+        browser.contextualIdentities.onCreated.addListener(() => {
+          browser.test.sendMessage("created");
+        });
+        browser.contextualIdentities.onUpdated.addListener(() => {});
+        browser.contextualIdentities.onRemoved.addListener(() => {
+          browser.test.sendMessage("removed");
+        });
+        browser.test.sendMessage("ready");
+      },
+    });
+
+    const EVENTS = ["onCreated", "onUpdated", "onRemoved"];
+
+    await extension.startup();
+    await extension.awaitMessage("ready");
+    for (let event of EVENTS) {
+      assertPersistentListeners(extension, "contextualIdentities", event, {
+        primed: false,
+      });
+    }
+
+    await extension.terminateBackground();
+    for (let event of EVENTS) {
+      assertPersistentListeners(extension, "contextualIdentities", event, {
+        primed: true,
+      });
+    }
+
+    // test events waken background
+    let identity = ContextualIdentityService.create("foobar", "circle", "red");
+
+    await extension.awaitMessage("ready");
+    await extension.awaitMessage("created");
+    for (let event of EVENTS) {
+      assertPersistentListeners(extension, "contextualIdentities", event, {
+        primed: false,
+      });
+    }
+
+    ContextualIdentityService.remove(identity.userContextId);
+    await extension.awaitMessage("removed");
+
+    // check primed listeners after startup
+    await AddonTestUtils.promiseRestartManager();
+    await extension.awaitStartup();
+
+    for (let event of EVENTS) {
+      assertPersistentListeners(extension, "contextualIdentities", event, {
+        primed: true,
+      });
+    }
+
+    await extension.unload();
+  }
+);
diff --git a/toolkit/components/extensions/test/xpcshell/test_ext_cookieBehaviors.js b/toolkit/components/extensions/test/xpcshell/test_ext_cookieBehaviors.js
new file mode 100644
index 0000000000..8fa0a7ed0b
--- /dev/null
+++ b/toolkit/components/extensions/test/xpcshell/test_ext_cookieBehaviors.js
@@ -0,0 +1,567 @@
+"use strict";
+
+const { UrlClassifierTestUtils } = ChromeUtils.importESModule(
+  "resource://testing-common/UrlClassifierTestUtils.sys.mjs"
+);
+
+const {
+  // cookieBehavior constants.
+  BEHAVIOR_REJECT,
+  BEHAVIOR_REJECT_TRACKER,
+} = Ci.nsICookieService;
+
+function createPage({ script, body = "" } = {}) {
+  if (script) {
+    body += `<script src="${script}"></script>`;
+  }
+
+  return `<!DOCTYPE html>
+    <html>
+      <head>
+        <meta charset="utf-8">
+      </head>
+      <body>
+        ${body}
+      </body>
+    </html>`;
+}
+
+const server = createHttpServer({ hosts: ["example.com", "itisatracker.org"] });
+server.registerDirectory("/data/", do_get_file("data"));
+server.registerPathHandler("/test-cookies", (request, response) => {
+  response.setHeader("Cache-Control", "no-cache", false);
+  response.setHeader("Content-Type", "text/json", false);
+  response.setHeader("Set-Cookie", "myKey=myCookie", true);
+  response.write('{"success": true}');
+});
+server.registerPathHandler("/subframe.html", (request, response) => {
+  response.write(createPage());
+});
+server.registerPathHandler("/page-with-tracker.html", (request, response) => {
+  response.write(
+    createPage({
+      body: `<iframe src="http://itisatracker.org/test-cookies"></iframe>`,
+    })
+  );
+});
+server.registerPathHandler("/sw.js", (request, response) => {
+  response.setHeader("Content-Type", "text/javascript", false);
+  response.write("");
+});
+
+function assertCookiesForHost(url, cookiesCount, message) {
+  const { host } = new URL(url);
+  const cookies = Services.cookies.cookies.filter(
+    cookie => cookie.host === host
+  );
+  equal(cookies.length, cookiesCount, message);
+  return cookies;
+}
+
+// Test that the indexedDB and localStorage are allowed in an extension page
+// and that the indexedDB is allowed in a extension worker.
+add_task(async function test_ext_page_allowed_storage() {
+  function testWebStorages() {
+    const url = window.location.href;
+
+    try {
+      // In a webpage accessing indexedDB throws on cookiesBehavior reject,
+      // here we verify that doesn't happen for an extension page.
+      browser.test.assertTrue(
+        indexedDB,
+        "IndexedDB global should be accessible"
+      );
+
+      // In a webpage localStorage is undefined on cookiesBehavior reject,
+      // here we verify that doesn't happen for an extension page.
+      browser.test.assertTrue(
+        localStorage,
+        "localStorage global should be defined"
+      );
+
+      const worker = new Worker("worker.js");
+      worker.onmessage = event => {
+        browser.test.assertTrue(
+          event.data.pass,
+          "extension page worker have access to indexedDB"
+        );
+
+        browser.test.sendMessage("test-storage:done", url);
+      };
+
+      worker.postMessage({});
+    } catch (err) {
+      browser.test.fail(`Unexpected error: ${err}`);
+      browser.test.sendMessage("test-storage:done", url);
+    }
+  }
+
+  function testWorker() {
+    this.onmessage = () => {
+      try {
+        void indexedDB;
+        postMessage({ pass: true });
+      } catch (err) {
+        postMessage({ pass: false });
+        throw err;
+      }
+    };
+  }
+
+  async function createExtension() {
+    let extension = ExtensionTestUtils.loadExtension({
+      files: {
+        "test_web_storages.js": testWebStorages,
+        "worker.js": testWorker,
+        "page_subframe.html": createPage({ script: "test_web_storages.js" }),
+        "page_with_subframe.html": createPage({
+          body: '<iframe src="page_subframe.html"></iframe>',
+        }),
+        "page.html": createPage({
+          script: "test_web_storages.js",
+        }),
+      },
+    });
+
+    await extension.startup();
+
+    const EXT_BASE_URL = `moz-extension://${extension.uuid}/`;
+
+    return { extension, EXT_BASE_URL };
+  }
+
+  const cookieBehaviors = [
+    "BEHAVIOR_LIMIT_FOREIGN",
+    "BEHAVIOR_REJECT_FOREIGN",
+    "BEHAVIOR_REJECT",
+    "BEHAVIOR_REJECT_TRACKER",
+    "BEHAVIOR_REJECT_TRACKER_AND_PARTITION_FOREIGN",
+  ];
+  equal(
+    cookieBehaviors.length,
+    Ci.nsICookieService.BEHAVIOR_LAST,
+    "all behaviors should be covered"
+  );
+
+  for (const behavior of cookieBehaviors) {
+    info(
+      `Test extension page access to indexedDB & localStorage with ${behavior}`
+    );
+    ok(
+      behavior in Ci.nsICookieService,
+      `${behavior} is a valid CookieBehavior`
+    );
+    Services.prefs.setIntPref(
+      "network.cookie.cookieBehavior",
+      Ci.nsICookieService[behavior]
+    );
+
+    // Create a new extension to ensure that the cookieBehavior just set is going to be
+    // used for the requests triggered by the extension page.
+    const { extension, EXT_BASE_URL } = await createExtension();
+    const extPage = await ExtensionTestUtils.loadContentPage("about:blank", {
+      extension,
+      remote: extension.extension.remote,
+    });
+
+    info("Test from a top level extension page");
+    await extPage.loadURL(`${EXT_BASE_URL}page.html`);
+
+    let testedFromURL = await extension.awaitMessage("test-storage:done");
+    equal(
+      testedFromURL,
+      `${EXT_BASE_URL}page.html`,
+      "Got the results from the expected url"
+    );
+
+    info("Test from a sub frame extension page");
+    await extPage.loadURL(`${EXT_BASE_URL}page_with_subframe.html`);
+
+    testedFromURL = await extension.awaitMessage("test-storage:done");
+    equal(
+      testedFromURL,
+      `${EXT_BASE_URL}page_subframe.html`,
+      "Got the results from the expected url"
+    );
+
+    await extPage.close();
+    await extension.unload();
+  }
+});
+
+add_task(async function test_ext_page_3rdparty_cookies() {
+  // Disable tracking protection to test cookies on BEHAVIOR_REJECT_TRACKER
+  // (otherwise tracking protection would block the tracker iframe and
+  // we would not be actually checking the cookie behavior).
+  Services.prefs.setBoolPref("privacy.trackingprotection.enabled", false);
+  await UrlClassifierTestUtils.addTestTrackers();
+  registerCleanupFunction(function () {
+    UrlClassifierTestUtils.cleanupTestTrackers();
+    Services.prefs.clearUserPref("privacy.trackingprotection.enabled");
+    Services.cookies.removeAll();
+  });
+
+  function testRequestScript() {
+    browser.test.onMessage.addListener((msg, url) => {
+      const done = () => {
+        browser.test.sendMessage(`${msg}:done`);
+      };
+
+      switch (msg) {
+        case "xhr": {
+          let req = new XMLHttpRequest();
+          req.onload = done;
+          req.open("GET", url);
+          req.send();
+          break;
+        }
+        case "fetch": {
+          window.fetch(url).then(done);
+          break;
+        }
+        case "worker fetch": {
+          const worker = new Worker("test_worker.js");
+          worker.onmessage = evt => {
+            if (evt.data.requestDone) {
+              done();
+            }
+          };
+          worker.postMessage({ url });
+          break;
+        }
+        default: {
+          browser.test.fail(`Received an unexpected message: ${msg}`);
+          done();
+        }
+      }
+    });
+
+    browser.test.sendMessage("testRequestScript:ready", window.location.href);
+  }
+
+  function testWorker() {
+    this.onmessage = evt => {
+      fetch(evt.data.url).then(() => {
+        postMessage({ requestDone: true });
+      });
+    };
+  }
+
+  async function createExtension() {
+    let extension = ExtensionTestUtils.loadExtension({
+      manifest: {
+        permissions: ["http://example.com/*", "http://itisatracker.org/*"],
+      },
+      files: {
+        "test_worker.js": testWorker,
+        "test_request.js": testRequestScript,
+        "page_subframe.html": createPage({ script: "test_request.js" }),
+        "page_with_subframe.html": createPage({
+          body: '<iframe src="page_subframe.html"></iframe>',
+        }),
+        "page.html": createPage({ script: "test_request.js" }),
+      },
+    });
+
+    await extension.startup();
+
+    const EXT_BASE_URL = `moz-extension://${extension.uuid}`;
+
+    return { extension, EXT_BASE_URL };
+  }
+
+  const testUrl = "http://example.com/test-cookies";
+  const testRequests = ["xhr", "fetch", "worker fetch"];
+  const tests = [
+    { behavior: "BEHAVIOR_ACCEPT", cookiesCount: 1 },
+    { behavior: "BEHAVIOR_REJECT_FOREIGN", cookiesCount: 1 },
+    { behavior: "BEHAVIOR_REJECT", cookiesCount: 0 },
+    { behavior: "BEHAVIOR_LIMIT_FOREIGN", cookiesCount: 1 },
+    { behavior: "BEHAVIOR_REJECT_TRACKER", cookiesCount: 1 },
+  ];
+
+  function clearAllCookies() {
+    Services.cookies.removeAll();
+    let cookies = Services.cookies.cookies;
+    equal(cookies.length, 0, "There shouldn't be any cookies after clearing");
+  }
+
+  async function runTestRequests(extension, cookiesCount, msg) {
+    for (const testRequest of testRequests) {
+      clearAllCookies();
+      extension.sendMessage(testRequest, testUrl);
+      await extension.awaitMessage(`${testRequest}:done`);
+      assertCookiesForHost(
+        testUrl,
+        cookiesCount,
+        `${msg}: cookies count on ${testRequest} "${testUrl}"`
+      );
+    }
+  }
+
+  for (const { behavior, cookiesCount } of tests) {
+    info(`Test cookies on http requests with ${behavior}`);
+    ok(
+      behavior in Ci.nsICookieService,
+      `${behavior} is a valid CookieBehavior`
+    );
+    Services.prefs.setIntPref(
+      "network.cookie.cookieBehavior",
+      Ci.nsICookieService[behavior]
+    );
+
+    // Create a new extension to ensure that the cookieBehavior just set is going to be
+    // used for the requests triggered by the extension page.
+    const { extension, EXT_BASE_URL } = await createExtension();
+
+    // Run all the test requests on a top level extension page.
+    let extPage = await ExtensionTestUtils.loadContentPage(
+      `${EXT_BASE_URL}/page.html`,
+      {
+        extension,
+        remote: extension.extension.remote,
+      }
+    );
+    await extension.awaitMessage("testRequestScript:ready");
+    await runTestRequests(
+      extension,
+      cookiesCount,
+      `Test top level extension page on ${behavior}`
+    );
+    await extPage.close();
+
+    // Rerun all the test requests on a sub frame extension page.
+    extPage = await ExtensionTestUtils.loadContentPage(
+      `${EXT_BASE_URL}/page_with_subframe.html`,
+      {
+        extension,
+        remote: extension.extension.remote,
+      }
+    );
+    await extension.awaitMessage("testRequestScript:ready");
+    await runTestRequests(
+      extension,
+      cookiesCount,
+      `Test sub frame extension page on ${behavior}`
+    );
+    await extPage.close();
+
+    await extension.unload();
+  }
+
+  // Test tracking url blocking from a webpage subframe.
+  info(
+    "Testing blocked tracker cookies in webpage subframe on BEHAVIOR_REJECT_TRACKERS"
+  );
+  Services.prefs.setIntPref(
+    "network.cookie.cookieBehavior",
+    BEHAVIOR_REJECT_TRACKER
+  );
+
+  const trackerURL = "http://itisatracker.org/test-cookies";
+  const { extension, EXT_BASE_URL } = await createExtension();
+  const extPage = await ExtensionTestUtils.loadContentPage(
+    `${EXT_BASE_URL}/_generated_background_page.html`,
+    {
+      extension,
+      remote: extension.extension.remote,
+    }
+  );
+  clearAllCookies();
+
+  await extPage.spawn(
+    ["http://example.com/page-with-tracker.html"],
+    async iframeURL => {
+      const iframe = this.content.document.createElement("iframe");
+      iframe.setAttribute("src", iframeURL);
+      return new Promise(resolve => {
+        iframe.onload = () => resolve();
+        this.content.document.body.appendChild(iframe);
+      });
+    }
+  );
+
+  assertCookiesForHost(
+    trackerURL,
+    0,
+    "Test cookies on web subframe inside top level extension page on BEHAVIOR_REJECT_TRACKER"
+  );
+  clearAllCookies();
+
+  await extPage.close();
+  await extension.unload();
+});
+
+// Test that a webpage embedded as a subframe of an extension page is not allowed to use
+// IndexedDB and register a ServiceWorker when it shouldn't be based on the cookieBehavior.
+add_task(
+  async function test_webpage_subframe_storage_respect_cookiesBehavior() {
+    let extension = ExtensionTestUtils.loadExtension({
+      manifest: {
+        permissions: ["http://example.com/*"],
+        web_accessible_resources: ["subframe.html"],
+      },
+      files: {
+        "toplevel.html": createPage({
+          body: `
+          <iframe id="ext" src="subframe.html"></iframe>
+          <iframe id="web" src="http://example.com/subframe.html"></iframe>
+        `,
+        }),
+        "subframe.html": createPage(),
+      },
+    });
+
+    Services.prefs.setIntPref("network.cookie.cookieBehavior", BEHAVIOR_REJECT);
+
+    await extension.startup();
+
+    let extensionPage = await ExtensionTestUtils.loadContentPage(
+      `moz-extension://${extension.uuid}/toplevel.html`,
+      {
+        extension,
+        remote: extension.extension.remote,
+      }
+    );
+
+    let results = await extensionPage.spawn([], async () => {
+      let extFrame = this.content.document.querySelector("iframe#ext");
+      let webFrame = this.content.document.querySelector("iframe#web");
+
+      function testIDB(win) {
+        try {
+          void win.indexedDB;
+          return { success: true };
+        } catch (err) {
+          return { error: `${err}` };
+        }
+      }
+
+      async function testServiceWorker(win) {
+        try {
+          await win.navigator.serviceWorker.register("sw.js");
+          return { success: true };
+        } catch (err) {
+          return { error: `${err}` };
+        }
+      }
+
+      return {
+        extTopLevel: testIDB(this.content),
+        extSubFrame: testIDB(extFrame.contentWindow),
+        webSubFrame: testIDB(webFrame.contentWindow),
+        webServiceWorker: await testServiceWorker(webFrame.contentWindow),
+      };
+    });
+
+    let contentPage = await ExtensionTestUtils.loadContentPage(
+      "http://example.com/subframe.html"
+    );
+
+    results.extSubFrameContent = await contentPage.spawn(
+      [extension.uuid],
+      uuid => {
+        return new Promise(resolve => {
+          let frame = this.content.document.createElement("iframe");
+          frame.setAttribute("src", `moz-extension://${uuid}/subframe.html`);
+          frame.onload = () => {
+            try {
+              void frame.contentWindow.indexedDB;
+              resolve({ success: true });
+            } catch (err) {
+              resolve({ error: `${err}` });
+            }
+          };
+          this.content.document.body.appendChild(frame);
+        });
+      }
+    );
+
+    Assert.deepEqual(
+      results.extTopLevel,
+      { success: true },
+      "IndexedDB allowed in a top level extension page"
+    );
+
+    Assert.deepEqual(
+      results.extSubFrame,
+      { success: true },
+      "IndexedDB allowed in a subframe extension page with a top level extension page"
+    );
+
+    Assert.deepEqual(
+      results.webSubFrame,
+      { error: "SecurityError: The operation is insecure." },
+      "IndexedDB not allowed in a subframe webpage with a top level extension page"
+    );
+    Assert.deepEqual(
+      results.webServiceWorker,
+      { error: "SecurityError: The operation is insecure." },
+      "IndexedDB and Cache not allowed in a service worker registered in the subframe webpage extension page"
+    );
+
+    Assert.deepEqual(
+      results.extSubFrameContent,
+      { success: true },
+      "IndexedDB allowed in a subframe extension page with a top level webpage"
+    );
+
+    await extensionPage.close();
+    await contentPage.close();
+
+    await extension.unload();
+  }
+);
+
+// Test that the webpage's indexedDB and localStorage are still not allowed from a content script
+// when the cookie behavior doesn't allow it, even when they are allowed in the extension pages.
+add_task(async function test_content_script_on_cookieBehaviorReject() {
+  Services.prefs.setIntPref("network.cookie.cookieBehavior", BEHAVIOR_REJECT);
+
+  function contentScript() {
+    // Ensure that when the current cookieBehavior doesn't allow a webpage to use indexedDB
+    // or localStorage, then a WebExtension content script is not allowed to use it as well.
+    browser.test.assertThrows(
+      () => indexedDB,
+      /The operation is insecure/,
+      "a content script can't use indexedDB from a page where it is disallowed"
+    );
+
+    browser.test.assertThrows(
+      () => localStorage,
+      /The operation is insecure/,
+      "a content script can't use localStorage from a page where it is disallowed"
+    );
+
+    browser.test.notifyPass("cs_disallowed_storage");
+  }
+
+  let extension = ExtensionTestUtils.loadExtension({
+    manifest: {
+      content_scripts: [
+        {
+          matches: ["http://*/*/file_sample.html"],
+          js: ["content_script.js"],
+        },
+      ],
+    },
+    files: {
+      "content_script.js": contentScript,
+    },
+  });
+
+  await extension.startup();
+
+  let contentPage = await ExtensionTestUtils.loadContentPage(
+    "http://example.com/data/file_sample.html"
+  );
+
+  await extension.awaitFinish("cs_disallowed_storage");
+
+  await contentPage.close();
+  await extension.unload();
+});
+
+add_task(function clear_cookieBehavior_pref() {
+  Services.prefs.clearUserPref("network.cookie.cookieBehavior");
+});
diff --git a/toolkit/components/extensions/test/xpcshell/test_ext_cookies_errors.js b/toolkit/components/extensions/test/xpcshell/test_ext_cookies_errors.js
new file mode 100644
index 0000000000..1c40f2f73f
--- /dev/null
+++ b/toolkit/components/extensions/test/xpcshell/test_ext_cookies_errors.js
@@ -0,0 +1,168 @@
+"use strict";
+
+add_task(async function setup_cookies() {
+  let extension = ExtensionTestUtils.loadExtension({
+    incognitoOverride: "spanning",
+    async background() {
+      const url = "http://example.com/";
+      const name = "dummyname";
+      await browser.cookies.set({ url, name, value: "from_setup:normal" });
+      await browser.cookies.set({
+        url,
+        name,
+        value: "from_setup:private",
+        storeId: "firefox-private",
+      });
+      await browser.cookies.set({
+        url,
+        name,
+        value: "from_setup:container",
+        storeId: "firefox-container-1",
+      });
+      browser.test.sendMessage("setup_done");
+    },
+    manifest: {
+      permissions: ["cookies", "http://example.com/"],
+    },
+  });
+  await extension.startup();
+  await extension.awaitMessage("setup_done");
+  await extension.unload();
+});
+
+add_task(async function test_error_messages() {
+  async function background() {
+    const url = "http://example.com/";
+    const name = "dummyname";
+    // Shorthands to minimize boilerplate.
+    const set = d => browser.cookies.set({ url, name, value: "x", ...d });
+    const remove = d => browser.cookies.remove({ url, name, ...d });
+    const get = d => browser.cookies.get({ url, name, ...d });
+    const getAll = d => browser.cookies.getAll(d);
+
+    // Host permission permission missing.
+    await browser.test.assertRejects(
+      set({}),
+      /^Permission denied to set cookie \{.*\}$/,
+      "cookies.set without host permissions rejects with error"
+    );
+    browser.test.assertEq(
+      null,
+      await remove({}),
+      "cookies.remove without host permissions does not remove any cookies"
+    );
+    browser.test.assertEq(
+      null,
+      await get({}),
+      "cookies.get without host permissions does not match any cookies"
+    );
+    browser.test.assertEq(
+      "[]",
+      JSON.stringify(await getAll({})),
+      "cookies.getAll without host permissions does not match any cookies"
+    );
+
+    // Private browsing cookies without access to private browsing mode.
+    await browser.test.assertRejects(
+      set({ storeId: "firefox-private" }),
+      "Extension disallowed access to the private cookies storeId.",
+      "cookies.set cannot modify private cookies without permission"
+    );
+    await browser.test.assertRejects(
+      remove({ storeId: "firefox-private" }),
+      "Extension disallowed access to the private cookies storeId.",
+      "cookies.remove cannot modify private cookies without permission"
+    );
+    await browser.test.assertRejects(
+      get({ storeId: "firefox-private" }),
+      "Extension disallowed access to the private cookies storeId.",
+      "cookies.get cannot read private cookies without permission"
+    );
+    await browser.test.assertRejects(
+      getAll({ storeId: "firefox-private" }),
+      "Extension disallowed access to the private cookies storeId.",
+      "cookies.getAll cannot read private cookies without permission"
+    );
+
+    // On Android, any firefox-container-... is treated as valid, so it doesn't
+    // result in an error. However, because the test extension does not have
+    // any host permissions, it will fail with an error any way (but a
+    // different one than expected).
+    // TODO bug 1743616: Fix implementation and this test.
+    const kErrorInvalidContainer = navigator.userAgent.includes("Android")
+      ? /Permission denied to set cookie/
+      : `Invalid cookie store id: "firefox-container-99"`;
+
+    // Invalid storeId.
+    await browser.test.assertRejects(
+      set({ storeId: "firefox-container-99" }),
+      kErrorInvalidContainer,
+      "cookies.set with invalid storeId (non-existent container)"
+    );
+
+    await browser.test.assertRejects(
+      set({ storeId: "0" }),
+      `Invalid cookie store id: "0"`,
+      "cookies.set with invalid storeId (format not recognized)"
+    );
+
+    for (let method of [remove, get, getAll]) {
+      let resultWithInvalidStoreId = method == getAll ? [] : null;
+      browser.test.assertEq(
+        JSON.stringify(await method({ storeId: "firefox-container-99" })),
+        JSON.stringify(resultWithInvalidStoreId),
+        `cookies.${method.name} with invalid storeId (non-existent container)`
+      );
+
+      browser.test.assertEq(
+        JSON.stringify(await method({ storeId: "0" })),
+        JSON.stringify(resultWithInvalidStoreId),
+        `cookies.${method.name} with invalid storeId (format not recognized)`
+      );
+    }
+
+    browser.test.sendMessage("test_done");
+  }
+
+  let extension = ExtensionTestUtils.loadExtension({
+    background,
+    manifest: {
+      permissions: ["cookies"],
+    },
+  });
+  await extension.startup();
+  await extension.awaitMessage("test_done");
+  await extension.unload();
+});
+
+add_task(async function expected_cookies_at_end_of_test() {
+  let extension = ExtensionTestUtils.loadExtension({
+    incognitoOverride: "spanning",
+    async background() {
+      async function checkCookie(storeId, value) {
+        let cookies = await browser.cookies.getAll({ storeId });
+        let index = cookies.findIndex(c => c.value === value);
+        browser.test.assertTrue(index !== -1, `Found cookie: ${value}`);
+        if (index >= 0) {
+          cookies.splice(index, 1);
+        }
+        browser.test.assertEq(
+          "[]",
+          JSON.stringify(cookies),
+          `No more cookies left in cookieStoreId=${storeId}`
+        );
+      }
+      // Added in setup.
+      await checkCookie("firefox-default", "from_setup:normal");
+      await checkCookie("firefox-private", "from_setup:private");
+      await checkCookie("firefox-container-1", "from_setup:container");
+      browser.test.sendMessage("final_check_done");
+    },
+    manifest: {
+      permissions: ["cookies", "<all_urls>"],
+    },
+  });
+  await extension.startup();
+  await extension.awaitMessage("final_check_done");
+  await extension.unload();
+});
diff --git a/toolkit/components/extensions/test/xpcshell/test_ext_cookies_firstParty.js b/toolkit/components/extensions/test/xpcshell/test_ext_cookies_firstParty.js
new file mode 100644
index 0000000000..700794b46c
--- /dev/null
+++ b/toolkit/components/extensions/test/xpcshell/test_ext_cookies_firstParty.js
@@ -0,0 +1,334 @@
+"use strict";
+
+const server = createHttpServer({
+  hosts: ["example.org", "example.net", "example.com"],
+});
+
+function promiseSetCookies() {
+  return new Promise(resolve => {
+    server.registerPathHandler("/setCookies", (request, response) => {
+      response.setStatusLine(request.httpVersion, 200, "OK");
+      response.setHeader("Content-Type", "text/html; charset=utf-8", false);
+      response.setHeader("Set-Cookie", "none=a; sameSite=none", true);
+      response.setHeader("Set-Cookie", "lax=b; sameSite=lax", true);
+      response.setHeader("Set-Cookie", "strict=c; sameSite=strict", true);
+      response.write("<html></html>");
+      resolve();
+    });
+  });
+}
+
+function promiseLoadedCookies() {
+  return new Promise(resolve => {
+    let cookies;
+
+    server.registerPathHandler("/checkCookies", (request, response) => {
+      cookies = request.hasHeader("Cookie") ? request.getHeader("Cookie") : "";
+
+      response.setStatusLine(request.httpVersion, 302, "Moved Permanently");
+      response.setHeader("Content-Type", "text/html; charset=utf-8", false);
+      response.setHeader("Location", "/ready");
+    });
+
+    server.registerPathHandler("/navigate", (request, response) => {
+      cookies = request.hasHeader("Cookie") ? request.getHeader("Cookie") : "";
+
+      response.setStatusLine(request.httpVersion, 200, "OK");
+      response.setHeader("Content-Type", "text/html; charset=utf-8", false);
+      response.write(
+        "<html><script>location = '/checkCookies';</script></html>"
+      );
+    });
+
+    server.registerPathHandler("/fetch", (request, response) => {
+      response.setStatusLine(request.httpVersion, 200, "OK");
+      response.setHeader("Content-Type", "text/html; charset=utf-8", false);
+      response.write("<html><script>fetch('/checkCookies');</script></html>");
+    });
+
+    server.registerPathHandler("/nestedfetch", (request, response) => {
+      response.setStatusLine(request.httpVersion, 200, "OK");
+      response.setHeader("Content-Type", "text/html; charset=utf-8", false);
+      response.write(
+        "<html><iframe src='http://example.net/nestedfetch2'></iframe></html>"
+      );
+    });
+
+    server.registerPathHandler("/nestedfetch2", (request, response) => {
+      response.setStatusLine(request.httpVersion, 200, "OK");
+      response.setHeader("Content-Type", "text/html; charset=utf-8", false);
+      response.write(
+        "<html><iframe src='http://example.org/fetch'></iframe></html>"
+      );
+    });
+
+    server.registerPathHandler("/ready", (request, response) => {
+      response.setStatusLine(request.httpVersion, 200, "OK");
+      response.setHeader("Content-Type", "text/html; charset=utf-8", false);
+      response.write("<html></html>");
+
+      resolve(cookies);
+    });
+  });
+}
+
+add_task(async function setup() {
+  Services.prefs.setIntPref("network.cookie.cookieBehavior", 0);
+  Services.prefs.setBoolPref("network.cookie.sameSite.laxByDefault", true);
+
+  // We don't want to have 'secure' cookies because our test http server doesn't run in https.
+  Services.prefs.setBoolPref(
+    "network.cookie.sameSite.noneRequiresSecure",
+    false
+  );
+
+  // Let's set 3 cookies before loading the extension.
+  let cookiesPromise = promiseSetCookies();
+  let contentPage = await ExtensionTestUtils.loadContentPage(
+    "http://example.org/setCookies"
+  );
+  await cookiesPromise;
+  await contentPage.close();
+  Assert.equal(Services.cookies.cookies.length, 3);
+});
+
+add_task(async function test_cookies_firstParty() {
+  async function pageScript() {
+    const ifr = document.createElement("iframe");
+    ifr.src = "http://example.org/" + location.search.slice(1);
+    document.body.appendChild(ifr);
+  }
+  let extension = ExtensionTestUtils.loadExtension({
+    manifest: {
+      permissions: ["*://example.org/"],
+    },
+    files: {
+      "page.html": `<body><script src="page.js"></script></body>`,
+      "page.js": pageScript,
+    },
+  });
+
+  await extension.startup();
+
+  // This page will load example.org in an iframe.
+  let url = `moz-extension://${extension.uuid}/page.html`;
+  let cookiesPromise = promiseLoadedCookies();
+  let contentPage = await ExtensionTestUtils.loadContentPage(
+    url + "?checkCookies",
+    { extension }
+  );
+
+  // Let's check the cookies received during the last loading.
+  Assert.equal(await cookiesPromise, "none=a; lax=b; strict=c");
+  await contentPage.close();
+
+  // Let's navigate.
+  cookiesPromise = promiseLoadedCookies();
+  contentPage = await ExtensionTestUtils.loadContentPage(url + "?navigate", {
+    extension,
+  });
+
+  // Let's check the cookies received during the last loading.
+  Assert.equal(await cookiesPromise, "none=a; lax=b; strict=c");
+  await contentPage.close();
+
+  // Let's run a fetch()
+  cookiesPromise = promiseLoadedCookies();
+  contentPage = await ExtensionTestUtils.loadContentPage(url + "?fetch", {
+    extension,
+  });
+
+  // Let's check the cookies received during the last loading.
+  Assert.equal(await cookiesPromise, "none=a; lax=b; strict=c");
+  await contentPage.close();
+
+  // Let's run a fetch() from a nested iframe (extension -> example.net ->
+  // example.org -> fetch)
+  cookiesPromise = promiseLoadedCookies();
+  contentPage = await ExtensionTestUtils.loadContentPage(url + "?nestedfetch", {
+    extension,
+  });
+
+  // Let's check the cookies received during the last loading.
+  Assert.equal(await cookiesPromise, "none=a");
+  await contentPage.close();
+
+  // Let's run a fetch() from a nested iframe (extension -> example.org -> fetch)
+  cookiesPromise = promiseLoadedCookies();
+  contentPage = await ExtensionTestUtils.loadContentPage(
+    url + "?nestedfetch2",
+    {
+      extension,
+    }
+  );
+
+  // Let's check the cookies received during the last loading.
+  Assert.equal(await cookiesPromise, "none=a; lax=b; strict=c");
+  await contentPage.close();
+
+  await extension.unload();
+});
+
+add_task(async function test_cookies_iframes() {
+  server.registerPathHandler("/echocookies", (request, response) => {
+    response.setStatusLine(request.httpVersion, 200, "OK");
+    response.setHeader("Content-Type", "text/html; charset=utf-8", false);
+    response.write(
+      request.hasHeader("Cookie") ? request.getHeader("Cookie") : ""
+    );
+  });
+
+  server.registerPathHandler("/contentScriptHere", (request, response) => {
+    response.setStatusLine(request.httpVersion, 200, "OK");
+    response.setHeader("Content-Type", "text/html; charset=utf-8", false);
+    response.write("<html></html>");
+  });
+
+  server.registerPathHandler("/pageWithFrames", (request, response) => {
+    response.setStatusLine(request.httpVersion, 200, "OK");
+    response.setHeader("Content-Type", "text/html; charset=utf-8", false);
+
+    response.write(`
+      <html>
+        <iframe src="http://example.com/contentScriptHere"></iframe>
+        <iframe src="http://example.net/contentScriptHere"></iframe>
+      </html>
+    `);
+  });
+
+  let extension = ExtensionTestUtils.loadExtension({
+    manifest: {
+      permissions: ["*://example.org/"],
+      content_scripts: [
+        {
+          js: ["contentScript.js"],
+          matches: [
+            "*://example.com/contentScriptHere",
+            "*://example.net/contentScriptHere",
+          ],
+          run_at: "document_end",
+          all_frames: true,
+        },
+      ],
+    },
+    files: {
+      "contentScript.js": async () => {
+        const res = await fetch("http://example.org/echocookies");
+        const cookies = await res.text();
+        browser.test.assertEq(
+          "none=a",
+          cookies,
+          "expected cookies in content script"
+        );
+        browser.test.sendMessage("extfetch:" + location.hostname);
+      },
+    },
+  });
+
+  await extension.startup();
+  let contentPage = await ExtensionTestUtils.loadContentPage(
+    "http://example.com/pageWithFrames"
+  );
+  await Promise.all([
+    extension.awaitMessage("extfetch:example.com"),
+    extension.awaitMessage("extfetch:example.net"),
+  ]);
+  await contentPage.close();
+  await extension.unload();
+});
+
+add_task(async function test_cookies_background() {
+  async function background() {
+    const res = await fetch("http://example.org/echocookies", {
+      credentials: "include",
+    });
+    const cookies = await res.text();
+    browser.test.sendMessage("fetchcookies", cookies);
+  }
+
+  const tests = [
+    {
+      permissions: ["http://example.org/*"],
+      cookies: "none=a; lax=b; strict=c",
+    },
+    {
+      permissions: [],
+      cookies: "none=a",
+    },
+  ];
+
+  for (let test of tests) {
+    let extension = ExtensionTestUtils.loadExtension({
+      background,
+      manifest: {
+        permissions: test.permissions,
+      },
+    });
+
+    server.registerPathHandler("/echocookies", (request, response) => {
+      response.setStatusLine(request.httpVersion, 200, "OK");
+      response.setHeader("Content-Type", "text/html; charset=utf-8", false);
+      response.setHeader(
+        "Access-Control-Allow-Origin",
+        `moz-extension://${extension.uuid}`,
+        false
+      );
+      response.setHeader("Access-Control-Allow-Credentials", "true", false);
+      response.write(
+        request.hasHeader("Cookie") ? request.getHeader("Cookie") : ""
+      );
+    });
+
+    await extension.startup();
+    equal(
+      await extension.awaitMessage("fetchcookies"),
+      test.cookies,
+      "extension with permissions can see SameSite-restricted cookies"
+    );
+
+    await extension.unload();
+  }
+});
+
+add_task(async function test_cookies_contentScript() {
+  server.registerPathHandler("/empty", (request, response) => {
+    response.setStatusLine(request.httpVersion, 200, "OK");
+    response.setHeader("Content-Type", "text/html; charset=utf-8", false);
+    response.write("<html><body></body></html>");
+  });
+
+  async function contentScript() {
+    let res = await fetch("http://example.org/checkCookies");
+    browser.test.assertEq(location.origin + "/ready", res.url, "request OK");
+    browser.test.sendMessage("fetch-done");
+  }
+
+  let extension = ExtensionTestUtils.loadExtension({
+    manifest: {
+      content_scripts: [
+        {
+          run_at: "document_end",
+          js: ["contentscript.js"],
+          matches: ["*://*/*"],
+        },
+      ],
+    },
+    files: {
+      "contentscript.js": contentScript,
+    },
+  });
+
+  await extension.startup();
+
+  let cookiesPromise = promiseLoadedCookies();
+  let contentPage = await ExtensionTestUtils.loadContentPage(
+    "http://example.org/empty"
+  );
+  await extension.awaitMessage("fetch-done");
+
+  // Let's check the cookies received during the last loading.
+  Assert.equal(await cookiesPromise, "none=a; lax=b; strict=c");
+  await contentPage.close();
+
+  await extension.unload();
+});
diff --git a/toolkit/components/extensions/test/xpcshell/test_ext_cookies_onChanged.js b/toolkit/components/extensions/test/xpcshell/test_ext_cookies_onChanged.js
new file mode 100644
index 0000000000..6eef222297
--- /dev/null
+++ b/toolkit/components/extensions/test/xpcshell/test_ext_cookies_onChanged.js
@@ -0,0 +1,142 @@
+"use strict";
+
+AddonTestUtils.init(this);
+AddonTestUtils.overrideCertDB();
+
+// In this test, we want to check the behavior of extensions without private
+// browsing access. Privileged add-ons automatically have private browsing
+// access, so make sure that the test add-ons are not privileged.
+AddonTestUtils.usePrivilegedSignatures = false;
+
+add_task(async function setup() {
+  await ExtensionTestUtils.startAddonManager();
+
+  Services.prefs.setBoolPref("extensions.eventPages.enabled", true);
+});
+
+function createTestExtension({ privateAllowed }) {
+  return ExtensionTestUtils.loadExtension({
+    incognitoOverride: privateAllowed ? "spanning" : null,
+    manifest: {
+      permissions: ["cookies"],
+      host_permissions: ["https://example.com/"],
+      background: { persistent: false },
+    },
+    background() {
+      browser.cookies.onChanged.addListener(changeInfo => {
+        browser.test.sendMessage("cookie-event", changeInfo);
+      });
+    },
+  });
+}
+
+function addAndRemoveCookie({ isPrivate }) {
+  const cookie = {
+    name: "cookname",
+    value: "cookvalue",
+    domain: "example.com",
+    hostOnly: true,
+    path: "/",
+    secure: true,
+    httpOnly: false,
+    sameSite: "lax",
+    session: false,
+    firstPartyDomain: "",
+    partitionKey: null,
+    expirationDate: Date.now() + 3600000,
+    storeId: isPrivate ? "firefox-private" : "firefox-default",
+  };
+  const originAttributes = { privateBrowsingId: isPrivate ? 1 : 0 };
+  Services.cookies.add(
+    cookie.domain,
+    cookie.path,
+    cookie.name,
+    cookie.value,
+    cookie.secure,
+    cookie.httpOnly,
+    cookie.session,
+    cookie.expirationDate,
+    originAttributes,
+    Ci.nsICookie.SAMESITE_LAX,
+    Ci.nsICookie.SCHEME_HTTPS
+  );
+  Services.cookies.remove(
+    cookie.domain,
+    cookie.name,
+    cookie.path,
+    originAttributes
+  );
+  return cookie;
+}
+
+add_task(async function test_onChanged_event_page() {
+  let nonPrivateExtension = createTestExtension({ privateAllowed: false });
+  let privateExtension = createTestExtension({ privateAllowed: true });
+  await privateExtension.startup();
+  await nonPrivateExtension.startup();
+  assertPersistentListeners(privateExtension, "cookies", "onChanged", {
+    primed: false,
+  });
+  assertPersistentListeners(nonPrivateExtension, "cookies", "onChanged", {
+    primed: false,
+  });
+
+  // Suspend both event pages.
+  await privateExtension.terminateBackground();
+  assertPersistentListeners(privateExtension, "cookies", "onChanged", {
+    primed: true,
+  });
+  await nonPrivateExtension.terminateBackground();
+  assertPersistentListeners(nonPrivateExtension, "cookies", "onChanged", {
+    primed: true,
+  });
+
+  // Modifying a private cookie should wake up the private extension, but not
+  // the other one that does not have access to private browsing data.
+  let privateCookie = addAndRemoveCookie({ isPrivate: true });
+
+  Assert.deepEqual(
+    await privateExtension.awaitMessage("cookie-event"),
+    { removed: false, cookie: privateCookie, cause: "explicit" },
+    "cookies.onChanged for private cookie creation"
+  );
+  Assert.deepEqual(
+    await privateExtension.awaitMessage("cookie-event"),
+    { removed: true, cookie: privateCookie, cause: "explicit" },
+    "cookies.onChanged for private cookie removal"
+  );
+  // Private extension should have awakened...
+  assertPersistentListeners(privateExtension, "cookies", "onChanged", {
+    primed: false,
+  });
+  // ... but the non-private extension should still be sound asleep.
+  assertPersistentListeners(nonPrivateExtension, "cookies", "onChanged", {
+    primed: true,
+  });
+
+  // A non-private cookie modification should notify both extensions.
+  let nonPrivateCookie = addAndRemoveCookie({ isPrivate: false });
+  Assert.deepEqual(
+    await privateExtension.awaitMessage("cookie-event"),
+    { removed: false, cookie: nonPrivateCookie, cause: "explicit" },
+    "cookies.onChanged for cookie creation in privateExtension"
+  );
+  Assert.deepEqual(
+    await privateExtension.awaitMessage("cookie-event"),
+    { removed: true, cookie: nonPrivateCookie, cause: "explicit" },
+    "cookies.onChanged for cookie removal in privateExtension"
+  );
+  Assert.deepEqual(
+    await nonPrivateExtension.awaitMessage("cookie-event"),
+    { removed: false, cookie: nonPrivateCookie, cause: "explicit" },
+    "cookies.onChanged for cookie creation in nonPrivateExtension"
+  );
+  Assert.deepEqual(
+    await nonPrivateExtension.awaitMessage("cookie-event"),
+    { removed: true, cookie: nonPrivateCookie, cause: "explicit" },
+    "cookies.onChanged for cookie removal in nonPrivateCookie"
+  );
+
+  await privateExtension.unload();
+  await nonPrivateExtension.unload();
+});
diff --git a/toolkit/components/extensions/test/xpcshell/test_ext_cookies_partitionKey.js b/toolkit/components/extensions/test/xpcshell/test_ext_cookies_partitionKey.js
new file mode 100644
index 0000000000..7a4170a51e
--- /dev/null
+++ b/toolkit/components/extensions/test/xpcshell/test_ext_cookies_partitionKey.js
@@ -0,0 +1,895 @@
+"use strict";
+
+/**
+ * This test verifies that the extension API's access to cookies is consistent
+ * with the cookies as seen by web pages under the following modes:
+ * - Every top-level document shares the same cookie jar, every subdocument of
+ *   the top-level document has a distinct cookie jar tied to the site of the
+ *   top-level document (dFPI).
+ * - All documents have a cookie jar keyed by the domain of the top-level
+ *   document (FPI).
+ * - All cookies are in one cookie jar (classic behavior = no FPI nor dFPI)
+ *
+ * FPI and dFPI are implemented using OriginAttributes, and historically the
+ * consequence of not recognizing an origin attribute is that cookies cannot be
+ * deleted. Hence, the functionality of the cookies API is verified as follows,
+ * by the testCookiesAPI/runTestCase methods.
+ *
+ * 1. Load page that creates cookies for the top and a framed document:
+ *    - "delete_me"
+ *    - "edit_me"
+ * 2. cookies.getAll: get all cookies with extension API.
+ * 3. cookies.remove: Remove "delete_me" cookies with the extension API.
+ * 4. cookies.set: Edit "edit_me" cookie with the extension API.
+ * 5. Verify that the web page can see "edit_me" cookie (via document.cookie).
+ * 6. cookies.get: "edit_me" is still present.
+ * 7. cookies.remove: "edit_me" can be removed.
+ * 8. cookies.getAll: no cookies left.
+ */
+
+const FIRST_DOMAIN = "first.example.com";
+const FIRST_DOMAIN_ETLD_PLUS_1 = "example.com";
+const FIRST_DOMAIN_ETLD_PLUS_MANY = "nested.under.first.example.com";
+const THIRD_PARTY_DOMAIN = "third.example.net";
+const server = createHttpServer({
+  hosts: [FIRST_DOMAIN, FIRST_DOMAIN_ETLD_PLUS_MANY, THIRD_PARTY_DOMAIN],
+});
+const LOCAL_IP_AND_PORT = `127.0.0.1:${server.identity.primaryPort}`;
+
+server.registerPathHandler("/top", (request, response) => {
+  response.setHeader("Set-Cookie", `delete_me=top; SameSite=none`);
+  response.setHeader("Set-Cookie", `edit_me=top; SameSite=none`, true);
+  response.setHeader("Content-Type", "text/html; charset=utf-8", false);
+  response.write(
+    `<!DOCTYPE html><iframe src="//third.example.net/framed"></iframe>`
+  );
+});
+server.registerPathHandler("/framed", (request, response) => {
+  response.setHeader("Set-Cookie", `delete_me=frame; SameSite=none`);
+  response.setHeader("Set-Cookie", `edit_me=frame; SameSite=none`, true);
+});
+
+// Background script of the extension that drives the test.
+// It first waits for the content scripts in /top and /framed to connect,
+// in order to verify that cookie operations by the extension API are reflected
+// to the web page (verified through document.cookie from the content script).
+function backgroundScript() {
+  let portsByDomain = new Map();
+
+  async function getDocumentCookies(port) {
+    return new Promise(resolve => {
+      port.onMessage.addListener(function listener(cookieString) {
+        port.onMessage.removeListener(listener);
+        resolve(cookieString);
+      });
+      port.postMessage("get_cookies");
+    });
+  }
+
+  // Stringify cookie identifier for comparisons in assertions.
+  function stringifyCookie(cookie) {
+    if (!cookie) {
+      return "COOKIE MISSING";
+    }
+    let domain = cookie.domain;
+    if (!domain) {
+      // The return value of `cookies.remove` has a URL instead of a domain.
+      domain = new URL(cookie.url).hostname;
+    }
+    return `${cookie.name} domain=${domain} firstPartyDomain=${
+      cookie.firstPartyDomain
+    } partitionKey=${JSON.stringify(cookie.partitionKey)}`;
+  }
+  function stringifyCookies(cookies) {
+    return cookies.map(stringifyCookie).sort().join(" , ");
+  }
+
+  // detailsIn may have partitionKey and firstPartyDomain attributes.
+  // expectedOut has partitionKey and firstPartyDomain attributes.
+  async function runTestCase({ domain, detailsIn, expectedOut }) {
+    const port = portsByDomain.get(domain);
+    browser.test.assertTrue(port, `Got port to document for ${domain}`);
+
+    let allCookies = await browser.cookies.getAll({
+      domain,
+      firstPartyDomain: null,
+      partitionKey: {},
+    });
+
+    let allCookiesWithFPD = await browser.cookies.getAll({
+      domain,
+      ...detailsIn,
+    });
+    browser.test.assertEq(
+      stringifyCookies(allCookies),
+      stringifyCookies(allCookiesWithFPD),
+      "cookies.getAll returns consistent results"
+    );
+
+    for (let [key, expectedValue] of Object.entries(expectedOut)) {
+      expectedValue = JSON.stringify(expectedValue);
+      browser.test.assertTrue(
+        allCookies.every(c => JSON.stringify(c[key]) === expectedValue),
+        `All ${allCookies.length} cookies have ${key}=${expectedValue}`
+      );
+    }
+
+    // delete_me: get, remove, get.
+    const cookieToDelete = {
+      url: `http://${domain}/`,
+      name: "delete_me",
+      ...detailsIn,
+    };
+    const deletedCookie = {
+      ...cookieToDelete,
+      ...expectedOut,
+    };
+    browser.test.assertEq(
+      stringifyCookie(deletedCookie),
+      stringifyCookie(await browser.cookies.get(cookieToDelete)),
+      "delete_me cookie exists before removal"
+    );
+    browser.test.assertEq(
+      stringifyCookie(deletedCookie),
+      stringifyCookie(await browser.cookies.remove(cookieToDelete)),
+      "delete_me cookie has been removed by cookies.remove"
+    );
+    browser.test.assertEq(
+      null,
+      await browser.cookies.get(cookieToDelete),
+      "delete_me cookie does not exist any more"
+    );
+
+    // edit_me: set, retrieve via document.cookie
+    const cookieToEdit = {
+      url: `http://${domain}/`,
+      name: "edit_me",
+      ...detailsIn,
+    };
+    const editedCookie = await browser.cookies.set({
+      ...cookieToEdit,
+      value: `new_value_${domain}`,
+    });
+    browser.test.assertEq(
+      stringifyCookie({ ...cookieToEdit, ...expectedOut }),
+      stringifyCookie(editedCookie),
+      "edit_me cookie updated"
+    );
+    browser.test.assertEq(
+      await getDocumentCookies(port),
+      `edit_me=new_value_${domain}`,
+      "Expected cookies after removing and editing a cookie"
+    );
+
+    // edit_me: get, remove, getAll.
+    browser.test.assertEq(
+      stringifyCookie(editedCookie),
+      stringifyCookie(await browser.cookies.get(cookieToEdit)),
+      "edit_me cookie still exists"
+    );
+    await browser.cookies.remove(cookieToEdit);
+    let allCookiesAtEnd = await browser.cookies.getAll({
+      domain,
+      firstPartyDomain: null,
+      partitionKey: {},
+    });
+    browser.test.assertEq(
+      "[]",
+      JSON.stringify(allCookiesAtEnd),
+      "No cookies left"
+    );
+  }
+
+  let resolveTestReady;
+  let testReadyPromise = new Promise(resolve => {
+    resolveTestReady = resolve;
+  });
+
+  browser.test.onMessage.addListener(async (msg, testCase) => {
+    await testReadyPromise;
+    browser.test.assertEq("runTest", msg, `Starting: ${testCase.description}`);
+    try {
+      await runTestCase(testCase);
+    } catch (e) {
+      browser.test.fail(`Unexpected error: ${e} :: ${e.stack}`);
+    }
+    browser.test.sendMessage("runTest_done");
+  });
+
+  // cookie-checker-contentscript.js will connect.
+  browser.runtime.onConnect.addListener(port => {
+    portsByDomain.set(port.name, port);
+    browser.test.log(`Got port #${portsByDomain.size} ${port.name}`);
+    if (portsByDomain.size === 2) {
+      // The top document and the embedded frame has loaded and the
+      // content script that we use to read cookies is connected.
+      // The test can now start.
+      resolveTestReady();
+    }
+  });
+}
+
+// The primary purpose of this test is to verify that the cookies API can read
+// and write cookies that are actually in use by the web page.
+async function testCookiesAPI({ testCases, topDomain = FIRST_DOMAIN }) {
+  let extension = ExtensionTestUtils.loadExtension({
+    background: backgroundScript,
+    manifest: {
+      permissions: [
+        "cookies",
+        // Remove port to work around bug 1350523.
+        `*://${topDomain.replace(/:\d+$/, "")}/*`,
+        `*://${THIRD_PARTY_DOMAIN}/*`,
+      ],
+      content_scripts: [
+        {
+          js: ["cookie-checker-contentscript.js"],
+          matches: [
+            // Remove port to work around bug 1362809.
+            `*://${topDomain.replace(/:\d+$/, "")}/top`,
+            `*://${THIRD_PARTY_DOMAIN}/framed`,
+          ],
+          all_frames: true,
+          run_at: "document_end",
+        },
+      ],
+    },
+    files: {
+      "cookie-checker-contentscript.js": () => {
+        const port = browser.runtime.connect({ name: location.hostname });
+        port.onMessage.addListener(msg => {
+          browser.test.assertEq(msg, "get_cookies", "Expected port message");
+          port.postMessage(document.cookie);
+        });
+      },
+    },
+  });
+  await extension.startup();
+  let contentPage = await ExtensionTestUtils.loadContentPage(
+    `http://${topDomain}/top`
+  );
+  for (let testCase of testCases) {
+    info(`Running test case: ${testCase.description}`);
+    extension.sendMessage("runTest", testCase);
+    await extension.awaitMessage("runTest_done");
+  }
+  await contentPage.close();
+  await extension.unload();
+}
+
+add_task(async function setup() {
+  // SameSite=none is needed to set cookies in third-party contexts.
+  // SameSite=none usually requires Secure, but the test server doesn't support
+  // https, so disable the Secure requirement for SameSite=none.
+  Services.prefs.setBoolPref(
+    "network.cookie.sameSite.noneRequiresSecure",
+    false
+  );
+});
+
+add_task(async function test_no_partitioning() {
+  const testCases = [
+    {
+      description: "first-party cookies without any partitioning",
+      domain: FIRST_DOMAIN,
+      detailsIn: {
+        firstPartyDomain: "",
+        partitionKey: null,
+      },
+      expectedOut: {
+        firstPartyDomain: "",
+        partitionKey: null,
+      },
+    },
+    {
+      description: "third-party cookies without any partitioning",
+      domain: THIRD_PARTY_DOMAIN,
+      detailsIn: {
+        // Without (d)FPI, firstPartyDomain and partitionKey are optional.
+      },
+      expectedOut: {
+        firstPartyDomain: "",
+        partitionKey: null,
+      },
+    },
+  ];
+  await runWithPrefs(
+    // dFPI is enabled by default on Nightly, disable it.
+    [["network.cookie.cookieBehavior", 4]],
+    () => testCookiesAPI({ testCases })
+  );
+});
+
+add_task(async function test_firstPartyIsolate() {
+  const testCases = [
+    {
+      description: "first-party cookies with FPI",
+      domain: FIRST_DOMAIN,
+      detailsIn: {
+        firstPartyDomain: FIRST_DOMAIN_ETLD_PLUS_1,
+      },
+      expectedOut: {
+        firstPartyDomain: FIRST_DOMAIN_ETLD_PLUS_1,
+        partitionKey: null,
+      },
+    },
+    {
+      description: "third-party cookies with FPI",
+      domain: THIRD_PARTY_DOMAIN,
+      detailsIn: {
+        firstPartyDomain: FIRST_DOMAIN_ETLD_PLUS_1,
+      },
+      expectedOut: {
+        firstPartyDomain: FIRST_DOMAIN_ETLD_PLUS_1,
+        partitionKey: null,
+      },
+    },
+  ];
+  await runWithPrefs(
+    [
+      // FPI is mutually exclusive with dFPI. Disable dFPI.
+      ["network.cookie.cookieBehavior", 4],
+      ["privacy.firstparty.isolate", true],
+    ],
+    () => testCookiesAPI({ testCases })
+  );
+});
+
+add_task(async function test_dfpi() {
+  const testCases = [
+    {
+      description: "first-party cookies with dFPI",
+      domain: FIRST_DOMAIN,
+      detailsIn: {
+        // partitionKey is optional and expected to default to unpartitioned.
+      },
+      expectedOut: {
+        firstPartyDomain: "",
+        partitionKey: null,
+      },
+    },
+    {
+      description: "third-party cookies with dFPI",
+      domain: THIRD_PARTY_DOMAIN,
+      detailsIn: {
+        partitionKey: { topLevelSite: `http://${FIRST_DOMAIN_ETLD_PLUS_1}` },
+      },
+      expectedOut: {
+        firstPartyDomain: "",
+        partitionKey: { topLevelSite: `http://${FIRST_DOMAIN_ETLD_PLUS_1}` },
+      },
+    },
+  ];
+  await runWithPrefs(
+    // Enable dFPI; 5 = BEHAVIOR_REJECT_TRACKER_AND_PARTITION_FOREIGN.
+    [["network.cookie.cookieBehavior", 5]],
+    () => testCookiesAPI({ testCases })
+  );
+});
+
+add_task(async function test_dfpi_with_ip_and_port() {
+  const testCases = [
+    {
+      description: "first-party cookies for IP with port",
+      domain: "127.0.0.1",
+      detailsIn: {
+        partitionKey: null,
+      },
+      expectedOut: {
+        firstPartyDomain: "",
+        partitionKey: null,
+      },
+    },
+    {
+      description: "third-party cookies for IP with port",
+      domain: THIRD_PARTY_DOMAIN,
+      detailsIn: {
+        partitionKey: { topLevelSite: `http://${LOCAL_IP_AND_PORT}` },
+      },
+      expectedOut: {
+        firstPartyDomain: "",
+        partitionKey: { topLevelSite: `http://${LOCAL_IP_AND_PORT}` },
+      },
+    },
+  ];
+  await runWithPrefs(
+    // Enable dFPI; 5 = BEHAVIOR_REJECT_TRACKER_AND_PARTITION_FOREIGN.
+    [["network.cookie.cookieBehavior", 5]],
+    () => testCookiesAPI({ testCases, topDomain: LOCAL_IP_AND_PORT })
+  );
+});
+
+add_task(async function test_dfpi_with_nested_subdomains() {
+  const testCases = [
+    {
+      description: "first-party cookies with DFPI at eTLD+many",
+      domain: FIRST_DOMAIN_ETLD_PLUS_MANY,
+      detailsIn: {
+        partitionKey: null,
+      },
+      expectedOut: {
+        firstPartyDomain: "",
+        partitionKey: null,
+      },
+    },
+    {
+      description: "third-party cookies for first party with eTLD+many",
+      domain: THIRD_PARTY_DOMAIN,
+      detailsIn: {
+        // Partitioned cookies are keyed by eTLD+1, so even if eTLD+many is
+        // passed, then eTLD+1 is stored (and returned).
+        partitionKey: { topLevelSite: `http://${FIRST_DOMAIN_ETLD_PLUS_MANY}` },
+      },
+      expectedOut: {
+        firstPartyDomain: "",
+        partitionKey: { topLevelSite: `http://${FIRST_DOMAIN_ETLD_PLUS_1}` },
+      },
+    },
+  ];
+  await runWithPrefs(
+    // Enable dFPI; 5 = BEHAVIOR_REJECT_TRACKER_AND_PARTITION_FOREIGN.
+    [["network.cookie.cookieBehavior", 5]],
+    () => testCookiesAPI({ testCases, topDomain: FIRST_DOMAIN_ETLD_PLUS_MANY })
+  );
+});
+
+add_task(async function test_dfpi_with_non_default_use_site() {
+  // privacy.dynamic_firstparty.use_site is a pref that can be used to toggle
+  // the internal representation of partitionKey. True (default) means keyed
+  // by site (scheme, host, port); false means keyed by host only.
+  const testCases = [
+    {
+      description: "first-party cookies with dFPI and use_site=false",
+      domain: FIRST_DOMAIN,
+      detailsIn: {
+        partitionKey: null,
+      },
+      expectedOut: {
+        firstPartyDomain: "",
+        partitionKey: null,
+      },
+    },
+    {
+      description: "third-party cookies with dFPI and use_site=false",
+      domain: THIRD_PARTY_DOMAIN,
+      detailsIn: {
+        partitionKey: { topLevelSite: `http://${FIRST_DOMAIN_ETLD_PLUS_1}` },
+      },
+      expectedOut: {
+        firstPartyDomain: "",
+        // When use_site=false, the scheme is not stored, and the
+        // implementation just prepends "https" as a dummy scheme.
+        partitionKey: { topLevelSite: `https://${FIRST_DOMAIN_ETLD_PLUS_1}` },
+      },
+    },
+  ];
+  await runWithPrefs(
+    [
+      // Enable dFPI; 5 = BEHAVIOR_REJECT_TRACKER_AND_PARTITION_FOREIGN.
+      ["network.cookie.cookieBehavior", 5],
+      ["privacy.dynamic_firstparty.use_site", false],
+    ],
+    () => testCookiesAPI({ testCases })
+  );
+});
+add_task(async function test_dfpi_with_ip_and_port_and_non_default_use_site() {
+  // privacy.dynamic_firstparty.use_site is a pref that can be used to toggle
+  // the internal representation of partitionKey. True (default) means keyed
+  // by site (scheme, host, port); false means keyed by host only.
+  const testCases = [
+    {
+      description: "first-party cookies for IP:port with dFPI+use_site=false",
+      domain: "127.0.0.1",
+      detailsIn: {
+        partitionKey: null,
+      },
+      expectedOut: {
+        firstPartyDomain: "",
+        partitionKey: null,
+      },
+    },
+    {
+      description: "third-party cookies for IP:port with dFPI+use_site=false",
+      domain: THIRD_PARTY_DOMAIN,
+      detailsIn: {
+        // When use_site=false, the scheme is not stored in the internal
+        // representation of the partitionKey. So even though the web page
+        // creates the cookie at HTTP, the cookies are still detected when
+        // "https" is used.
+        partitionKey: { topLevelSite: `https://${LOCAL_IP_AND_PORT}` },
+      },
+      expectedOut: {
+        firstPartyDomain: "",
+        // When use_site=false, the scheme and port are not stored.
+        // "https" is used as a dummy scheme, and the port is not used.
+        partitionKey: { topLevelSite: "https://127.0.0.1" },
+      },
+    },
+  ];
+  await runWithPrefs(
+    [
+      // Enable dFPI; 5 = BEHAVIOR_REJECT_TRACKER_AND_PARTITION_FOREIGN.
+      ["network.cookie.cookieBehavior", 5],
+      ["privacy.dynamic_firstparty.use_site", false],
+    ],
+    () => testCookiesAPI({ testCases, topDomain: LOCAL_IP_AND_PORT })
+  );
+});
+
+add_task(async function dfpi_invalid_partitionKey() {
+  AddonTestUtils.init(globalThis);
+  AddonTestUtils.createAppInfo(
+    "xpcshell@tests.mozilla.org",
+    "XPCShell",
+    "1",
+    "42"
+  );
+  // The test below uses the browser.privacy API, which relies on
+  // ExtensionSettingsStore, which in turn depends on AddonManager.
+  await AddonTestUtils.promiseStartupManager();
+
+  let extension = ExtensionTestUtils.loadExtension({
+    useAddonManager: "temporary",
+    manifest: {
+      permissions: ["cookies", "*://example.com/*", "privacy"],
+    },
+    async background() {
+      const url = "http://example.com/";
+      const name = "dfpi_invalid_partitionKey_dummy_name";
+      const value = "1";
+
+      // Shorthands to minimize boilerplate.
+      const set = d => browser.cookies.set({ url, name, value, ...d });
+      const remove = d => browser.cookies.remove({ url, name, ...d });
+      const get = d => browser.cookies.get({ url, name, ...d });
+      const getAll = d => browser.cookies.getAll(d);
+
+      await browser.test.assertRejects(
+        set({ partitionKey: { topLevelSite: "example.net" } }),
+        /Invalid value for 'partitionKey' attribute/,
+        "partitionKey must be a URL, not a domain"
+      );
+      await browser.test.assertRejects(
+        set({ partitionKey: { topLevelSite: "chrome://foo" } }),
+        /Invalid value for 'partitionKey' attribute/,
+        "partitionKey cannot be the chrome:-scheme (canonicalization fails)"
+      );
+      await browser.test.assertRejects(
+        set({ partitionKey: { topLevelSite: "chrome://foo/foo/foo" } }),
+        /Invalid value for 'partitionKey' attribute/,
+        "partitionKey cannot be the chrome:-scheme (canonicalization passes)"
+      );
+      await browser.test.assertRejects(
+        set({ partitionKey: { topLevelSite: "http://[]:" } }),
+        /Invalid value for 'partitionKey' attribute/,
+        "partitionKey must be a valid URL"
+      );
+
+      browser.test.assertThrows(
+        () => get({ partitionKey: "" }),
+        /Error processing partitionKey: Expected object instead of ""/,
+        "cookies.get should reject invalid partitionKey (string)"
+      );
+      browser.test.assertThrows(
+        () => get({ partitionKey: { topLevelSite: "http://x", badkey: 0 } }),
+        /Error processing partitionKey: Unexpected property "badkey"/,
+        "cookies.get should reject unsupported keys in partitionKey"
+      );
+      await browser.test.assertRejects(
+        remove({ partitionKey: { topLevelSite: "invalid" } }),
+        /Invalid value for 'partitionKey' attribute/,
+        "cookies.remove should reject invalid partitionKey.topLevelSite"
+      );
+      await browser.test.assertRejects(
+        get({ partitionKey: { topLevelSite: "invalid" } }),
+        /Invalid value for 'partitionKey' attribute/,
+        "cookies.get should reject invalid partitionKey.topLevelSite"
+      );
+      await browser.test.assertRejects(
+        getAll({ partitionKey: { topLevelSite: "invalid" } }),
+        /Invalid value for 'partitionKey' attribute/,
+        "cookies.getAll should reject invalid partitionKey.topLevelSite"
+      );
+
+      // firstPartyDomain and partitionKey are mutually exclusive, because
+      // FPI and dFPI are mutually exclusive.
+      await browser.test.assertRejects(
+        set({ firstPartyDomain: "example.net", partitionKey: {} }),
+        /Partitioned cookies cannot have a 'firstPartyDomain' attribute./,
+        "partitionKey and firstPartyDomain cannot both be non-empty"
+      );
+
+      // On Nightly, dFPI is enabled by default. We have to disable it first,
+      // before we can enable FPI. Otherwise we would get error:
+      // Can't enable firstPartyIsolate when cookieBehavior is 'reject_trackers_and_partition_foreign'
+      await browser.privacy.websites.cookieConfig.set({
+        value: { behavior: "reject_trackers" },
+      });
+      await browser.privacy.websites.firstPartyIsolate.set({
+        value: true,
+      });
+
+      // FPI and dFPI are mutually exclusive. FPI is documented to require the
+      // firstPartyDomain attribute, let's verify that, despite it being
+      // technically possible to support both attributes.
+      for (let cookiesMethod of [get, getAll, remove, set]) {
+        await browser.test.assertRejects(
+          cookiesMethod({ partitionKey: { topLevelSite: url } }),
+          /First-Party Isolation is enabled, but the required 'firstPartyDomain' attribute was not set./,
+          `cookies.${cookiesMethod.name} requires firstPartyDomain when FPI is enabled`
+        );
+      }
+
+      // The pref changes above (to dFPI/FPI) via the browser.privacy API  will
+      // be undone when the extension unloads.
+
+      browser.test.sendMessage("test_done");
+    },
+  });
+  await extension.startup();
+  await extension.awaitMessage("test_done");
+  await extension.unload();
+
+  await AddonTestUtils.promiseShutdownManager();
+});
+
+add_task(async function dfpi_moz_extension() {
+  let extension = ExtensionTestUtils.loadExtension({
+    manifest: {
+      permissions: ["cookies", "*://example.com/*"],
+    },
+    async background() {
+      let cookie = await browser.cookies.set({
+        url: "http://example.com/",
+        name: "moz_ext_party",
+        value: "1",
+        // moz-extension: URL is passed here, in an attempt to mark the cookie
+        // as part of the "moz-extension:"-partition. Below we will expect ""
+        // because the dFPI implementation treats "moz-extension" as
+        // unpartitioned, see
+        // https://searchfox.org/mozilla-central/rev/ac7da6c7306d86e2f86a302ce1e170ad54b3c1fe/caps/OriginAttributes.cpp#79-82
+        partitionKey: { topLevelSite: browser.runtime.getURL("/") },
+      });
+      browser.test.assertEq(
+        null,
+        cookie.partitionKey,
+        "Cookies in moz-extension:-URL are unpartitioned"
+      );
+      let deletedCookie = await browser.cookies.remove({
+        url: "http://example.com/",
+        name: "moz_ext_party",
+        partitionKey: { topLevelSite: "moz-extension://ignoreme" },
+      });
+      browser.test.assertEq(
+        null,
+        deletedCookie.partitionKey,
+        "moz-extension:-partition key is treated as unpartitioned"
+      );
+      browser.test.sendMessage("test_done");
+    },
+  });
+  await extension.startup();
+  await extension.awaitMessage("test_done");
+  await extension.unload();
+});
+
+add_task(async function dfpi_about_scheme_as_partitionKey() {
+  let extension = ExtensionTestUtils.loadExtension({
+    manifest: {
+      permissions: ["cookies", "*://example.com/*"],
+    },
+    async background() {
+      let cookie = await browser.cookies.set({
+        url: "http://example.com/",
+        name: "moz_ext_party",
+        value: "1",
+        partitionKey: { topLevelSite: "about:blank" },
+      });
+      // It doesn't really make sense to partition in `about:blank` (since it
+      // cannot really be a first party), but for completeness of test coverage
+      // we also check that the use of an about:-scheme results in predictable
+      // behavior. The weird "about://"-URL below is the serialization of the
+      // internal value of the partitionKey attribute:
+      // https://searchfox.org/mozilla-central/rev/ac7da6c7306d86e2f86a302ce1e170ad54b3c1fe/caps/OriginAttributes.cpp#73-77
+      browser.test.assertEq(
+        "about://about.ef2a7dd5-93bc-417f-a698-142c3116864f.mozilla",
+        cookie.partitionKey.topLevelSite,
+        "An URL-like representation of the internal about:-format is returned"
+      );
+      let deletedCookie = await browser.cookies.remove({
+        url: "http://example.com/",
+        name: "moz_ext_party",
+        partitionKey: {
+          topLevelSite:
+            "about://about.ef2a7dd5-93bc-417f-a698-142c3116864f.mozilla",
+        },
+      });
+      browser.test.assertEq(
+        "about://about.ef2a7dd5-93bc-417f-a698-142c3116864f.mozilla",
+        deletedCookie.partitionKey.topLevelSite,
+        "Cookie can be deleted via the dummy about:-scheme"
+      );
+      browser.test.sendMessage("test_done");
+    },
+  });
+  await extension.startup();
+  await extension.awaitMessage("test_done");
+  await extension.unload();
+});
+
+// Same-site frames are expected to be unpartitioned.
+// The cookies API can receive partitionKey and url that are same-site. While
+// such cookies won't be sent to websites in practice, we do want to verify that
+// the behavior is predictable.
+add_task(async function test_url_is_same_site_as_partitionKey() {
+  // This loads a page with a frame at third.example.net (= THIRD_PARTY_DOMAIN).
+  let contentPage = await ExtensionTestUtils.loadContentPage(
+    `http://${THIRD_PARTY_DOMAIN}/top`
+  );
+  await contentPage.close();
+  let extension = ExtensionTestUtils.loadExtension({
+    manifest: {
+      permissions: ["cookies", "*://third.example.net/"],
+    },
+    async background() {
+      // Retrieve all cookies, partitioned and unpartitioned. We expect only
+      // unpartitioned cookies at first because the top frame and the child
+      // frame have the same origin.
+      let initialCookies = await browser.cookies.getAll({ partitionKey: {} });
+      browser.test.assertEq(
+        "delete_me=frame,edit_me=frame",
+        initialCookies.map(c => `${c.name}=${c.value}`).join(),
+        "Same-site frames are in unpartitioned storage; /frame overwrites /top"
+      );
+      browser.test.assertTrue(
+        await browser.cookies.remove({
+          url: "https://third.example.net/",
+          name: "delete_me",
+        }),
+        "Removed unpartitioned cookie"
+      );
+      browser.test.assertEq(
+        "[null,null]",
+        JSON.stringify(initialCookies.map(c => c.partitionKey)),
+        "Cookies in same-site/same-origin frames are not partitioned"
+      );
+
+      // We only have one unpartitioned cookie (edit_cookie) left.
+
+      // Add new cookie whose partitionKey is same-site relative to url.
+      let newCookie = await browser.cookies.set({
+        url: "http://third.example.net/",
+        name: "edit_me",
+        value: "url_is_partitionKey_eTLD+2",
+        partitionKey: { topLevelSite: "http://third.example.net" },
+      });
+      browser.test.assertEq(
+        "http://example.net",
+        newCookie.partitionKey.topLevelSite,
+        "Created cookie with partitionKey=url; eTLD+2 is normalized as eTLD+1"
+      );
+
+      browser.test.assertTrue(
+        await browser.cookies.remove({
+          url: "http://third.example.net/",
+          name: "edit_me",
+          partitionKey: {},
+        }),
+        "Removed unpartitioned cookie when partitionKey: {} is used"
+      );
+
+      browser.test.assertEq(
+        null,
+        await browser.cookies.remove({
+          url: "http://third.example.net/",
+          name: "edit_me",
+          partitionKey: {},
+        }),
+        "No more unpartitioned cookies to remove"
+      );
+
+      browser.test.assertTrue(
+        await browser.cookies.remove({
+          url: "http://third.example.net/",
+          name: "edit_me",
+          partitionKey: { topLevelSite: "http://example.net" },
+        }),
+        "Removed partitioned cookie when partitionKey is passed"
+      );
+
+      browser.test.sendMessage("test_done");
+    },
+  });
+  await extension.startup();
+  await extension.awaitMessage("test_done");
+  await extension.unload();
+});
+
+add_task(async function test_getAll_partitionKey() {
+  let extension = ExtensionTestUtils.loadExtension({
+    manifest: {
+      permissions: ["cookies", "*://third.example.net/"],
+    },
+    async background() {
+      const url = "http://third.example.net";
+      const name = "test_url_is_identical_to_partitionKey";
+      const partitionKey = { topLevelSite: "http://example.com" };
+      const firstPartyDomain = "example.net";
+
+      // Create non-partitioned cookie, create partitioned cookie.
+      await browser.cookies.set({ url, name, value: "no_partition" });
+      await browser.cookies.set({ url, name, value: "fpd", firstPartyDomain });
+      await browser.cookies.set({ url, name, partitionKey, value: "party" });
+      // partitionKey + firstPartyDomain was tested in dfpi_invalid_partitionKey
+
+      async function getAllValues(details) {
+        let cookies = await browser.cookies.getAll(details);
+        let values = cookies.map(c => c.value);
+        return values.sort().join(); // Serialize for use with assertEq.
+      }
+
+      browser.test.assertEq(
+        "no_partition",
+        await getAllValues({}),
+        "getAll() returns unpartitioned by default"
+      );
+
+      browser.test.assertEq(
+        "no_partition,party",
+        await getAllValues({ partitionKey: {} }),
+        "getAll() with partitionKey: {} returns all cookies"
+      );
+
+      browser.test.assertEq(
+        "party",
+        await getAllValues({ partitionKey }),
+        "getAll() with specific partitionKey returns partitionKey cookies only"
+      );
+
+      browser.test.assertEq(
+        "",
+        await getAllValues({ partitionKey: { topLevelSite: url } }),
+        "getAll() with partitionKey set to cookie URL does not match anything"
+      );
+
+      browser.test.assertEq(
+        "",
+        await getAllValues({ partitionKey, firstPartyDomain }),
+        "getAll() with non-empty partitionKey and firstPartyDomain does not match anything"
+      );
+      browser.test.assertEq(
+        "fpd",
+        await getAllValues({ partitionKey: {}, firstPartyDomain }),
+        "getAll() with empty partitionKey and firstPartyDomain matches fpd"
+      );
+
+      browser.test.assertEq(
+        "fpd,no_partition,party",
+        await getAllValues({ partitionKey: {}, firstPartyDomain: null }),
+        "getAll() with empty partitionKey and firstPartyDomain:null matches everything"
+      );
+
+      await browser.cookies.remove({ url, name });
+      await browser.cookies.remove({ url, name, firstPartyDomain });
+      await browser.cookies.remove({ url, name, partitionKey });
+
+      browser.test.sendMessage("test_done");
+    },
+  });
+  await extension.startup();
+  await extension.awaitMessage("test_done");
+  await extension.unload();
+});
+
+add_task(async function no_unexpected_cookies_at_end_of_test() {
+  let results = [];
+  for (const cookie of Services.cookies.cookies) {
+    results.push({
+      name: cookie.name,
+      value: cookie.value,
+      host: cookie.host,
+      originAttributes: cookie.originAttributes,
+    });
+  }
+  Assert.deepEqual(results, [], "Test should not leave any cookies");
+});
diff --git a/toolkit/components/extensions/test/xpcshell/test_ext_cookies_samesite.js b/toolkit/components/extensions/test/xpcshell/test_ext_cookies_samesite.js
new file mode 100644
index 0000000000..618ed820d4
--- /dev/null
+++ b/toolkit/components/extensions/test/xpcshell/test_ext_cookies_samesite.js
@@ -0,0 +1,114 @@
+"use strict";
+
+const server = createHttpServer({ hosts: ["example.org"] });
+server.registerPathHandler("/sameSiteCookiesApiTest", (request, response) => {
+  response.setStatusLine(request.httpVersion, 200, "OK");
+  response.setHeader("Content-Type", "text/html; charset=utf-8", false);
+  response.write("<!DOCTYPE html><html></html>");
+});
+
+add_task(async function test_samesite_cookies() {
+  // Bug 1617611 - Fix all the tests broken by "cookies SameSite=Lax by default"
+  Services.prefs.setBoolPref("network.cookie.sameSite.laxByDefault", false);
+
+  function contentScript() {
+    document.cookie = "test1=whatever";
+    document.cookie = "test2=whatever; SameSite=lax";
+    document.cookie = "test3=whatever; SameSite=strict";
+    browser.runtime.sendMessage("do-check-cookies");
+  }
+  async function background() {
+    await new Promise(resolve => {
+      browser.runtime.onMessage.addListener(msg => {
+        browser.test.assertEq("do-check-cookies", msg, "expected message");
+        resolve();
+      });
+    });
+
+    const url = "https://example.org/";
+
+    // Baseline. Every cookie must have the expected sameSite.
+    let cookie = await browser.cookies.get({ url, name: "test1" });
+    browser.test.assertEq(
+      "no_restriction",
+      cookie.sameSite,
+      "Expected sameSite for test1"
+    );
+
+    cookie = await browser.cookies.get({ url, name: "test2" });
+    browser.test.assertEq(
+      "lax",
+      cookie.sameSite,
+      "Expected sameSite for test2"
+    );
+
+    cookie = await browser.cookies.get({ url, name: "test3" });
+    browser.test.assertEq(
+      "strict",
+      cookie.sameSite,
+      "Expected sameSite for test3"
+    );
+
+    // Testing cookies.getAll + cookies.set
+    let cookies = await browser.cookies.getAll({ url, name: "test3" });
+    browser.test.assertEq(1, cookies.length, "There is only one test3 cookie");
+
+    cookie = await browser.cookies.set({
+      url,
+      name: "test3",
+      value: "newvalue",
+    });
+    browser.test.assertEq(
+      "no_restriction",
+      cookie.sameSite,
+      "sameSite defaults to no_restriction"
+    );
+
+    for (let sameSite of ["no_restriction", "lax", "strict"]) {
+      cookie = await browser.cookies.set({ url, name: "test3", sameSite });
+      browser.test.assertEq(
+        sameSite,
+        cookie.sameSite,
+        `Expected sameSite=${sameSite} in return value of cookies.set`
+      );
+      cookies = await browser.cookies.getAll({ url, name: "test3" });
+      browser.test.assertEq(
+        1,
+        cookies.length,
+        `test3 is still the only cookie after setting sameSite=${sameSite}`
+      );
+      browser.test.assertEq(
+        sameSite,
+        cookies[0].sameSite,
+        `test3 was updated to sameSite=${sameSite}`
+      );
+    }
+
+    browser.test.notifyPass("cookies");
+  }
+  let extension = ExtensionTestUtils.loadExtension({
+    background,
+    manifest: {
+      permissions: ["cookies", "*://example.org/"],
+      content_scripts: [
+        {
+          matches: ["*://example.org/sameSiteCookiesApiTest*"],
+          js: ["contentscript.js"],
+        },
+      ],
+    },
+    files: {
+      "contentscript.js": contentScript,
+    },
+  });
+
+  await extension.startup();
+  let contentPage = await ExtensionTestUtils.loadContentPage(
+    "http://example.org/sameSiteCookiesApiTest"
+  );
+  await extension.awaitFinish("cookies");
+  await contentPage.close();
+  await extension.unload();
+
+  Services.prefs.clearUserPref("network.cookie.sameSite.laxByDefault");
+});
diff --git a/toolkit/components/extensions/test/xpcshell/test_ext_cors_mozextension.js b/toolkit/components/extensions/test/xpcshell/test_ext_cors_mozextension.js
new file mode 100644
index 0000000000..fc50388c77
--- /dev/null
+++ b/toolkit/components/extensions/test/xpcshell/test_ext_cors_mozextension.js
@@ -0,0 +1,220 @@
+"use strict";
+
+const server = createHttpServer({
+  hosts: ["example.com", "x.example.com"],
+});
+server.registerPathHandler("/dummy", (req, res) => {
+  res.write("dummy");
+});
+server.registerPathHandler("/redir", (req, res) => {
+  res.setStatusLine(req.httpVersion, 302, "Found");
+  res.setHeader("Access-Control-Allow-Origin", "http://example.com");
+  res.setHeader("Access-Control-Allow-Credentials", "true");
+  res.setHeader("Location", new URLSearchParams(req.queryString).get("url"));
+});
+
+add_task(async function load_moz_extension_with_and_without_cors() {
+  let extension = ExtensionTestUtils.loadExtension({
+    manifest: {
+      web_accessible_resources: ["ok.js"],
+    },
+    files: {
+      "ok.js": "window.status = 'loaded';",
+      "deny.js": "window.status = 'unexpected load'",
+    },
+  });
+  await extension.startup();
+  const EXT_BASE_URL = `moz-extension://${extension.uuid}`;
+  let contentPage = await ExtensionTestUtils.loadContentPage(
+    "http://example.com/dummy"
+  );
+  await contentPage.spawn([EXT_BASE_URL], async EXT_BASE_URL => {
+    const { document, window } = this.content;
+    async function checkScriptLoad({ setupScript, expectLoad, description }) {
+      const scriptElem = document.createElement("script");
+      setupScript(scriptElem);
+      return new Promise(resolve => {
+        window.status = "initial";
+        scriptElem.onload = () => {
+          Assert.equal(window.status, "loaded", "Script executed upon load");
+          Assert.ok(expectLoad, `Script loaded - ${description}`);
+          resolve();
+        };
+        scriptElem.onerror = () => {
+          Assert.equal(window.status, "initial", "not executed upon error");
+          Assert.ok(!expectLoad, `Script not loaded - ${description}`);
+          resolve();
+        };
+        document.head.append(scriptElem);
+      });
+    }
+
+    function sameOriginRedirectUrl(url) {
+      return `http://example.com/redir?url=` + encodeURIComponent(url);
+    }
+    function crossOriginRedirectUrl(url) {
+      return `http://x.example.com/redir?url=` + encodeURIComponent(url);
+    }
+
+    // Direct load of web-accessible extension script.
+    await checkScriptLoad({
+      setupScript(scriptElem) {
+        scriptElem.src = `${EXT_BASE_URL}/ok.js`;
+      },
+      expectLoad: true,
+      description: "web-accessible script, plain load",
+    });
+    await checkScriptLoad({
+      setupScript(scriptElem) {
+        scriptElem.src = `${EXT_BASE_URL}/ok.js`;
+        scriptElem.crossOrigin = "anonymous";
+      },
+      expectLoad: true,
+      description: "web-accessible script, cors",
+    });
+    await checkScriptLoad({
+      setupScript(scriptElem) {
+        scriptElem.src = `${EXT_BASE_URL}/ok.js`;
+        scriptElem.crossOrigin = "use-credentials";
+      },
+      expectLoad: true,
+      description: "web-accessible script, cors+credentials",
+    });
+
+    // Load of web-accessible extension scripts, after same-origin redirect.
+    await checkScriptLoad({
+      setupScript(scriptElem) {
+        scriptElem.src = sameOriginRedirectUrl(`${EXT_BASE_URL}/ok.js`);
+      },
+      expectLoad: true,
+      description: "same-origin redirect to web-accessible script, plain load",
+    });
+    await checkScriptLoad({
+      setupScript(scriptElem) {
+        scriptElem.src = sameOriginRedirectUrl(`${EXT_BASE_URL}/ok.js`);
+        scriptElem.crossOrigin = "anonymous";
+      },
+      expectLoad: true,
+      description: "same-origin redirect to web-accessible script, cors",
+    });
+    await checkScriptLoad({
+      setupScript(scriptElem) {
+        scriptElem.src = sameOriginRedirectUrl(`${EXT_BASE_URL}/ok.js`);
+        scriptElem.crossOrigin = "use-credentials";
+      },
+      expectLoad: true,
+      description:
+        "same-origin redirect to web-accessible script, cors+credentials",
+    });
+
+    // Load of web-accessible extension scripts, after cross-origin redirect.
+    await checkScriptLoad({
+      setupScript(scriptElem) {
+        scriptElem.src = crossOriginRedirectUrl(`${EXT_BASE_URL}/ok.js`);
+      },
+      expectLoad: true,
+      description: "cross-origin redirect to web-accessible script, plain load",
+    });
+    await checkScriptLoad({
+      setupScript(scriptElem) {
+        scriptElem.src = crossOriginRedirectUrl(`${EXT_BASE_URL}/ok.js`);
+        scriptElem.crossOrigin = "anonymous";
+      },
+      expectLoad: true,
+      description: "cross-origin redirect to web-accessible script, cors",
+    });
+    await checkScriptLoad({
+      setupScript(scriptElem) {
+        scriptElem.src = crossOriginRedirectUrl(`${EXT_BASE_URL}/ok.js`);
+        scriptElem.crossOrigin = "use-credentials";
+      },
+      expectLoad: true,
+      description:
+        "cross-origin redirect to web-accessible script, cors+credentials",
+    });
+
+    // Various loads of non-web-accessible extension script.
+    await checkScriptLoad({
+      setupScript(scriptElem) {
+        scriptElem.src = `${EXT_BASE_URL}/deny.js`;
+      },
+      expectLoad: false,
+      description: "non-accessible script, plain load",
+    });
+    await checkScriptLoad({
+      setupScript(scriptElem) {
+        scriptElem.src = `${EXT_BASE_URL}/deny.js`;
+        scriptElem.crossOrigin = "anonymous";
+      },
+      expectLoad: false,
+      description: "non-accessible script, cors",
+    });
+    await checkScriptLoad({
+      setupScript(scriptElem) {
+        scriptElem.src = sameOriginRedirectUrl(`${EXT_BASE_URL}/deny.js`);
+        scriptElem.crossOrigin = "anonymous";
+      },
+      expectLoad: false,
+      description: "same-origin redirect to non-accessible script, cors",
+    });
+    await checkScriptLoad({
+      setupScript(scriptElem) {
+        scriptElem.src = crossOriginRedirectUrl(`${EXT_BASE_URL}/deny.js`);
+        scriptElem.crossOrigin = "anonymous";
+      },
+      expectLoad: false,
+      description: "cross-origin redirect to non-accessible script, cors",
+    });
+
+    // Sub-resource integrity usually requires CORS. Verify that web-accessible
+    // extension resources are still subjected to SRI.
+    const sriHashOkJs = // SRI hash for "window.status = 'loaded';" (=ok.js).
+      "sha384-EAofaAZpgy6JshegITJJHeE3ROzn9ngGw1GAuuzjSJV1c/YS9PLvHMt9oh4RovrI";
+
+    async function testSRI({ integrityMatches }) {
+      const integrity = integrityMatches ? sriHashOkJs : "sha384-bad-sri-hash";
+      const sriDescription = integrityMatches
+        ? "web-accessible script, good sri, "
+        : "web-accessible script, sri not matching, ";
+      await checkScriptLoad({
+        setupScript(scriptElem) {
+          scriptElem.src = `${EXT_BASE_URL}/ok.js`;
+          scriptElem.integrity = integrity;
+        },
+        expectLoad: integrityMatches,
+        description: `${sriDescription} no cors, plain load`,
+      });
+      await checkScriptLoad({
+        setupScript(scriptElem) {
+          scriptElem.src = `${EXT_BASE_URL}/ok.js`;
+          scriptElem.crossOrigin = "anonymous";
+          scriptElem.integrity = integrity;
+        },
+        expectLoad: integrityMatches,
+        description: `${sriDescription} cors, plain load`,
+      });
+      await checkScriptLoad({
+        setupScript(scriptElem) {
+          scriptElem.src = sameOriginRedirectUrl(`${EXT_BASE_URL}/ok.js`);
+          scriptElem.crossOrigin = "anonymous";
+          scriptElem.integrity = integrity;
+        },
+        expectLoad: integrityMatches,
+        description: `${sriDescription} cors, same-origin redirect`,
+      });
+      await checkScriptLoad({
+        setupScript(scriptElem) {
+          scriptElem.src = crossOriginRedirectUrl(`${EXT_BASE_URL}/ok.js`);
+          scriptElem.crossOrigin = "anonymous";
+          scriptElem.integrity = integrity;
+        },
+        expectLoad: integrityMatches,
+        description: `${sriDescription} cors, cross-origin redirect`,
+      });
+    }
+    await testSRI({ integrityMatches: true });
+    await testSRI({ integrityMatches: false });
+  });
+  await contentPage.close();
+  await extension.unload();
+});
diff --git a/toolkit/components/extensions/test/xpcshell/test_ext_csp_frame_ancestors.js b/toolkit/components/extensions/test/xpcshell/test_ext_csp_frame_ancestors.js
new file mode 100644
index 0000000000..ae931dfe06
--- /dev/null
+++ b/toolkit/components/extensions/test/xpcshell/test_ext_csp_frame_ancestors.js
@@ -0,0 +1,221 @@
+/* Any copyright is dedicated to the Public Domain.
+ * http://creativecommons.org/publicdomain/zero/1.0/ */
+
+"use strict";
+
+const server = createHttpServer({ hosts: ["example.com", "example.net"] });
+server.registerPathHandler("/parent.html", (request, response) => {
+  let frameUrl = new URLSearchParams(request.queryString).get("iframe_src");
+  response.setHeader("Content-Type", "text/html; charset=utf-8", false);
+  response.write(`<!DOCTYPE html><iframe src="${frameUrl}"></iframe>`);
+});
+
+// Loads an extension frame as a frame at ancestorOrigins[0], which in turn is
+// a child of ancestorOrigins[1], etc.
+// The frame should either load successfully, or trigger exactly one failure due
+// to one of the ancestorOrigins being blocked by the content_security_policy.
+async function checkExtensionLoadInFrame({
+  ancestorOrigins,
+  content_security_policy,
+  expectLoad,
+}) {
+  const extensionData = {
+    manifest: {
+      content_security_policy,
+      web_accessible_resources: ["parent.html", "frame.html"],
+    },
+    files: {
+      "frame.html": `<!DOCTYPE html><script src="frame.js"></script>`,
+      "frame.js": () => {
+        browser.test.sendMessage("frame_load_completed");
+      },
+      "parent.html": `<!DOCTYPE html><body><script src="parent.js"></script>`,
+      "parent.js": () => {
+        let iframe = document.createElement("iframe");
+        iframe.src = new URLSearchParams(location.search).get("iframe_src");
+        document.body.append(iframe);
+      },
+    },
+  };
+  let extension = ExtensionTestUtils.loadExtension(extensionData);
+  await extension.startup();
+
+  const EXTENSION_FRAME_URL = `moz-extension://${extension.uuid}/frame.html`;
+
+  // ancestorOrigins is a list of origins, from the parent up to the top frame.
+  let topUrl = EXTENSION_FRAME_URL;
+  for (let origin of ancestorOrigins) {
+    if (origin === "EXTENSION_ORIGIN") {
+      origin = `moz-extension://${extension.uuid}`;
+    }
+    // origin is either the origin for |server| or the test extension. Both
+    // endpoints serve a page at parent.html that embeds iframe_src.
+    topUrl = `${origin}/parent.html?iframe_src=${encodeURIComponent(topUrl)}`;
+  }
+
+  let cspViolationObserver;
+  let cspViolationCount = 0;
+  let frameLoadedCount = 0;
+  let frameLoadOrFailedPromise = new Promise(resolve => {
+    extension.onMessage("frame_load_completed", () => {
+      ++frameLoadedCount;
+      resolve();
+    });
+    cspViolationObserver = {
+      observe(subject, topic, data) {
+        ++cspViolationCount;
+        Assert.equal(data, "frame-ancestors", "CSP violation directive");
+        resolve();
+      },
+    };
+    Services.obs.addObserver(cspViolationObserver, "csp-on-violate-policy");
+  });
+
+  const contentPage = await ExtensionTestUtils.loadContentPage(topUrl);
+
+  // Firstly, wait for the frame load to either complete or fail.
+  await frameLoadOrFailedPromise;
+
+  // Secondly, do a round trip to the content process to make sure that any
+  // unexpected extra load/failures are observed. This is necessary, because
+  // the "csp-on-violate-policy" notification is triggered from the parent,
+  // while it may be possible for the load to continue in the child anyway.
+  //
+  // And while we are at it, this verifies that the CSP does not block regular
+  // reads of a file that's part of web_accessible_resources. For comparable
+  // results, the load should ideally happen in the parent of the extension
+  // frame, but contentPage.fetch only works in the top frame, so this does not
+  // work perfectly in case ancestorOrigins.length > 1.
+  // But that is OK, as we mainly care about unexpected frame loads/failures.
+  equal(
+    await contentPage.fetch(EXTENSION_FRAME_URL),
+    extensionData.files["frame.html"],
+    "web-accessible extension resource can still be read with fetch"
+  );
+
+  // Finally, clean up.
+  Services.obs.removeObserver(cspViolationObserver, "csp-on-violate-policy");
+  await contentPage.close();
+  await extension.unload();
+
+  if (expectLoad) {
+    equal(cspViolationCount, 0, "Expected no CSP violations");
+    equal(
+      frameLoadedCount,
+      1,
+      `Frame should accept ancestors (${ancestorOrigins}) in CSP: ${content_security_policy}`
+    );
+  } else {
+    equal(cspViolationCount, 1, "Expected CSP violation count");
+    equal(
+      frameLoadedCount,
+      0,
+      `Frame should reject one of the ancestors (${ancestorOrigins}) in CSP: ${content_security_policy}`
+    );
+  }
+}
+
+add_task(async function test_frame_ancestors_missing_allows_self() {
+  await checkExtensionLoadInFrame({
+    ancestorOrigins: ["EXTENSION_ORIGIN"],
+    content_security_policy: "default-src 'self'", // missing frame-ancestors.
+    expectLoad: true, // an extension can embed itself by default.
+  });
+});
+
+add_task(async function test_frame_ancestors_self_allows_self() {
+  await checkExtensionLoadInFrame({
+    ancestorOrigins: ["EXTENSION_ORIGIN"],
+    content_security_policy: "default-src 'self'; frame-ancestors 'self'",
+    expectLoad: true,
+  });
+});
+
+add_task(async function test_frame_ancestors_none_blocks_self() {
+  await checkExtensionLoadInFrame({
+    ancestorOrigins: ["EXTENSION_ORIGIN"],
+    content_security_policy: "default-src 'self'; frame-ancestors",
+    expectLoad: false, // frame-ancestors 'none' blocks extension frame.
+  });
+});
+
+add_task(async function test_frame_ancestors_missing_allowed_in_web_page() {
+  await checkExtensionLoadInFrame({
+    ancestorOrigins: ["http://example.com"],
+    content_security_policy: "default-src 'self'", // missing frame-ancestors
+    expectLoad: true, // Web page can embed web-accessible extension frames.
+  });
+});
+
+add_task(async function test_frame_ancestors_self_blocked_in_web_page() {
+  await checkExtensionLoadInFrame({
+    ancestorOrigins: ["http://example.com"],
+    content_security_policy: "default-src 'self'; frame-ancestors 'self'",
+    expectLoad: false,
+  });
+});
+
+add_task(async function test_frame_ancestors_scheme_allowed_in_web_page() {
+  await checkExtensionLoadInFrame({
+    ancestorOrigins: ["http://example.com"],
+    content_security_policy: "default-src 'self'; frame-ancestors http:",
+    expectLoad: true,
+  });
+});
+
+add_task(async function test_frame_ancestors_origin_allowed_in_web_page() {
+  await checkExtensionLoadInFrame({
+    ancestorOrigins: ["http://example.com"],
+    content_security_policy:
+      "default-src 'self'; frame-ancestors http://example.com",
+    expectLoad: true,
+  });
+});
+
+add_task(async function test_frame_ancestors_mismatch_blocked_in_web_page() {
+  await checkExtensionLoadInFrame({
+    ancestorOrigins: ["http://example.com"],
+    content_security_policy:
+      "default-src 'self'; frame-ancestors http://not.example.com",
+    expectLoad: false,
+  });
+});
+
+add_task(async function test_frame_ancestors_top_mismatch_blocked() {
+  await checkExtensionLoadInFrame({
+    ancestorOrigins: ["http://example.com", "http://example.net"],
+    content_security_policy:
+      "default-src 'self'; frame-ancestors http://example.com",
+    // example.com is allowed, but the top origin (example.net) is rejected.
+    expectLoad: false,
+  });
+});
+
+add_task(async function test_frame_ancestors_parent_mismatch_blocked() {
+  await checkExtensionLoadInFrame({
+    ancestorOrigins: ["http://example.net", "http://example.com"],
+    content_security_policy:
+      "default-src 'self'; frame-ancestors http://example.com",
+    // example.com is allowed, but the parent origin (example.net) is rejected.
+    expectLoad: false,
+  });
+});
+
+add_task(async function test_frame_ancestors_middle_rejected() {
+  if (!WebExtensionPolicy.useRemoteWebExtensions) {
+    // This test load http://example.com in an extension page, which fails if
+    // extensions run in the parent process. This is not a default config on
+    // desktop, but see https://bugzilla.mozilla.org/show_bug.cgi?id=1724099
+    info("Web pages cannot be loaded in extension page without OOP extensions");
+    return;
+  }
+  await checkExtensionLoadInFrame({
+    ancestorOrigins: ["http://example.com", "EXTENSION_ORIGIN"],
+    content_security_policy:
+      "default-src 'self'; frame-src http: 'self'; frame-ancestors 'self'",
+    // Although the top frame has the same origin as the extension, the load
+    // should be rejected anyway because there is a non-allowlisted origin in
+    // the middle (child of top frame, parent of extension frame).
+    expectLoad: false,
+  });
+});
diff --git a/toolkit/components/extensions/test/xpcshell/test_ext_csp_upgrade_requests.js b/toolkit/components/extensions/test/xpcshell/test_ext_csp_upgrade_requests.js
new file mode 100644
index 0000000000..6780293f04
--- /dev/null
+++ b/toolkit/components/extensions/test/xpcshell/test_ext_csp_upgrade_requests.js
@@ -0,0 +1,74 @@
+"use strict";
+
+const server = createHttpServer({ hosts: ["example.com"] });
+server.registerPathHandler("/", (req, res) => {
+  res.write("ok");
+});
+
+add_setup(async () => {
+  Services.prefs.setBoolPref("extensions.manifestV3.enabled", true);
+});
+
+add_task(async function test_csp_upgrade() {
+  async function background() {
+    browser.webRequest.onBeforeRequest.addListener(
+      details => {
+        browser.test.assertEq(
+          details.url,
+          "https://example.com/",
+          "request upgraded and sent"
+        );
+        browser.test.notifyPass();
+        return { cancel: true };
+      },
+      {
+        urls: ["https://example.com/*"],
+      },
+      ["blocking"]
+    );
+
+    await browser.test.assertRejects(
+      fetch("http://example.com/"),
+      "NetworkError when attempting to fetch resource.",
+      "request was upgraded"
+    );
+  }
+  let extension = ExtensionTestUtils.loadExtension({
+    background,
+    temporarilyInstalled: true,
+    manifest: {
+      manifest_version: 3,
+      granted_host_permissions: true,
+      host_permissions: ["*://example.com/*"],
+      permissions: ["webRequest", "webRequestBlocking"],
+    },
+  });
+  await extension.startup();
+  await extension.awaitFinish();
+  await extension.unload();
+});
+
+add_task(async function test_csp_noupgrade() {
+  async function background() {
+    let req = await fetch("http://example.com/");
+    browser.test.assertEq(
+      req.url,
+      "http://example.com/",
+      "request not upgraded"
+    );
+    browser.test.notifyPass();
+  }
+  let extension = ExtensionTestUtils.loadExtension({
+    background,
+    temporarilyInstalled: true,
+    allowInsecureRequests: true,
+    manifest: {
+      manifest_version: 3,
+      granted_host_permissions: true,
+      host_permissions: ["*://example.com/*"],
+    },
+  });
+  await extension.startup();
+  await extension.awaitFinish();
+  await extension.unload();
+});
diff --git a/toolkit/components/extensions/test/xpcshell/test_ext_debugging_utils.js b/toolkit/components/extensions/test/xpcshell/test_ext_debugging_utils.js
new file mode 100644
index 0000000000..5fc7f2ba3f
--- /dev/null
+++ b/toolkit/components/extensions/test/xpcshell/test_ext_debugging_utils.js
@@ -0,0 +1,312 @@
+/* -*- Mode: indent-tabs-mode: nil; js-indent-level: 2 -*- */
+/* vim: set sts=2 sw=2 et tw=80: */
+"use strict";
+
+const { ExtensionParent } = ChromeUtils.importESModule(
+  "resource://gre/modules/ExtensionParent.sys.mjs"
+);
+
+add_task(async function testExtensionDebuggingUtilsCleanup() {
+  const extension = ExtensionTestUtils.loadExtension({
+    background() {
+      browser.test.sendMessage("background.ready");
+    },
+  });
+
+  const expectedEmptyDebugUtils = {
+    hiddenXULWindow: null,
+    cacheSize: 0,
+  };
+
+  let { hiddenXULWindow, debugBrowserPromises } = ExtensionParent.DebugUtils;
+
+  deepEqual(
+    { hiddenXULWindow, cacheSize: debugBrowserPromises.size },
+    expectedEmptyDebugUtils,
+    "No ExtensionDebugUtils resources has been allocated yet"
+  );
+
+  await extension.startup();
+
+  await extension.awaitMessage("background.ready");
+
+  hiddenXULWindow = ExtensionParent.DebugUtils.hiddenXULWindow;
+  deepEqual(
+    { hiddenXULWindow, cacheSize: debugBrowserPromises.size },
+    expectedEmptyDebugUtils,
+    "No debugging resources has been yet allocated once the extension is running"
+  );
+
+  const fakeAddonActor = {
+    addonId: extension.id,
+  };
+
+  const anotherAddonActor = {
+    addonId: extension.id,
+  };
+
+  const waitFirstBrowser =
+    ExtensionParent.DebugUtils.getExtensionProcessBrowser(fakeAddonActor);
+  const waitSecondBrowser =
+    ExtensionParent.DebugUtils.getExtensionProcessBrowser(anotherAddonActor);
+
+  const addonDebugBrowser = await waitFirstBrowser;
+  equal(
+    addonDebugBrowser.isRemoteBrowser,
+    extension.extension.remote,
+    "The addon debugging browser has the expected remote type"
+  );
+
+  equal(
+    await waitSecondBrowser,
+    addonDebugBrowser,
+    "Two addon debugging actors related to the same addon get the same browser element "
+  );
+
+  equal(
+    debugBrowserPromises.size,
+    1,
+    "The expected resources has been allocated"
+  );
+
+  const nonExistentAddonActor = {
+    addonId: "non-existent-addon@test",
+  };
+
+  const waitRejection = ExtensionParent.DebugUtils.getExtensionProcessBrowser(
+    nonExistentAddonActor
+  );
+
+  await Assert.rejects(
+    waitRejection,
+    /Extension not found/,
+    "Reject with the expected message for non existent addons"
+  );
+
+  equal(
+    debugBrowserPromises.size,
+    1,
+    "No additional debugging resources has been allocated"
+  );
+
+  await ExtensionParent.DebugUtils.releaseExtensionProcessBrowser(
+    fakeAddonActor
+  );
+
+  equal(
+    debugBrowserPromises.size,
+    1,
+    "The addon debugging browser is cached until all the related actors have released it"
+  );
+
+  await ExtensionParent.DebugUtils.releaseExtensionProcessBrowser(
+    anotherAddonActor
+  );
+
+  hiddenXULWindow = ExtensionParent.DebugUtils.hiddenXULWindow;
+
+  deepEqual(
+    { hiddenXULWindow, cacheSize: debugBrowserPromises.size },
+    expectedEmptyDebugUtils,
+    "All the allocated debugging resources has been cleared"
+  );
+
+  await extension.unload();
+});
+
+add_task(async function testExtensionDebuggingUtilsAddonReloaded() {
+  let extension = ExtensionTestUtils.loadExtension({
+    manifest: {
+      browser_specific_settings: {
+        gecko: {
+          id: "test-reloaded@test.mozilla.com",
+        },
+      },
+    },
+    background() {
+      browser.test.sendMessage("background.ready");
+    },
+  });
+
+  await extension.startup();
+  await extension.awaitMessage("background.ready");
+
+  let fakeAddonActor = {
+    addonId: extension.id,
+  };
+
+  const addonDebugBrowser =
+    await ExtensionParent.DebugUtils.getExtensionProcessBrowser(fakeAddonActor);
+  equal(
+    addonDebugBrowser.isRemoteBrowser,
+    extension.extension.remote,
+    "The addon debugging browser has the expected remote type"
+  );
+  equal(
+    ExtensionParent.DebugUtils.debugBrowserPromises.size,
+    1,
+    "Got the expected number of requested debug browsers"
+  );
+
+  const { chromeDocument } = ExtensionParent.DebugUtils.hiddenXULWindow;
+
+  ok(
+    addonDebugBrowser.parentElement === chromeDocument.documentElement,
+    "The addon debugging browser is part of the hiddenXULWindow chromeDocument"
+  );
+
+  await extension.unload();
+
+  // Install an extension with the same id to recreate for the DebugUtils
+  // conditions similar to an addon reloaded while the Addon Debugger is opened.
+  extension = ExtensionTestUtils.loadExtension({
+    manifest: {
+      browser_specific_settings: {
+        gecko: {
+          id: "test-reloaded@test.mozilla.com",
+        },
+      },
+    },
+    background() {
+      browser.test.sendMessage("background.ready");
+    },
+  });
+
+  await extension.startup();
+  await extension.awaitMessage("background.ready");
+
+  equal(
+    ExtensionParent.DebugUtils.debugBrowserPromises.size,
+    1,
+    "Got the expected number of requested debug browsers"
+  );
+
+  const newAddonDebugBrowser =
+    await ExtensionParent.DebugUtils.getExtensionProcessBrowser(fakeAddonActor);
+
+  equal(
+    addonDebugBrowser,
+    newAddonDebugBrowser,
+    "The existent debugging browser has been reused"
+  );
+
+  equal(
+    newAddonDebugBrowser.isRemoteBrowser,
+    extension.extension.remote,
+    "The addon debugging browser has the expected remote type"
+  );
+
+  await ExtensionParent.DebugUtils.releaseExtensionProcessBrowser(
+    fakeAddonActor
+  );
+
+  equal(
+    ExtensionParent.DebugUtils.debugBrowserPromises.size,
+    0,
+    "All the addon debugging browsers has been released"
+  );
+
+  await extension.unload();
+});
+
+add_task(async function testExtensionDebuggingUtilsWithMultipleAddons() {
+  let extension = ExtensionTestUtils.loadExtension({
+    manifest: {
+      browser_specific_settings: {
+        gecko: {
+          id: "test-addon-1@test.mozilla.com",
+        },
+      },
+    },
+    background() {
+      browser.test.sendMessage("background.ready");
+    },
+  });
+  let anotherExtension = ExtensionTestUtils.loadExtension({
+    manifest: {
+      browser_specific_settings: {
+        gecko: {
+          id: "test-addon-2@test.mozilla.com",
+        },
+      },
+    },
+    background() {
+      browser.test.sendMessage("background.ready");
+    },
+  });
+
+  await extension.startup();
+  await extension.awaitMessage("background.ready");
+
+  await anotherExtension.startup();
+  await anotherExtension.awaitMessage("background.ready");
+
+  const fakeAddonActor = {
+    addonId: extension.id,
+  };
+
+  const anotherFakeAddonActor = {
+    addonId: anotherExtension.id,
+  };
+
+  const { DebugUtils } = ExtensionParent;
+  const debugBrowser = await DebugUtils.getExtensionProcessBrowser(
+    fakeAddonActor
+  );
+  const anotherDebugBrowser = await DebugUtils.getExtensionProcessBrowser(
+    anotherFakeAddonActor
+  );
+
+  const chromeDocument = DebugUtils.hiddenXULWindow.chromeDocument;
+
+  equal(
+    ExtensionParent.DebugUtils.debugBrowserPromises.size,
+    2,
+    "Got the expected number of debug browsers requested"
+  );
+  ok(
+    debugBrowser.parentElement === chromeDocument.documentElement,
+    "The first debug browser is part of the hiddenXUL chromeDocument"
+  );
+  ok(
+    anotherDebugBrowser.parentElement === chromeDocument.documentElement,
+    "The second debug browser is part of the hiddenXUL chromeDocument"
+  );
+
+  await ExtensionParent.DebugUtils.releaseExtensionProcessBrowser(
+    fakeAddonActor
+  );
+
+  equal(
+    ExtensionParent.DebugUtils.debugBrowserPromises.size,
+    1,
+    "Got the expected number of debug browsers requested"
+  );
+
+  ok(
+    anotherDebugBrowser.parentElement === chromeDocument.documentElement,
+    "The second debug browser is still part of the hiddenXUL chromeDocument"
+  );
+
+  ok(
+    debugBrowser.parentElement == null,
+    "The first debug browser has been removed from the hiddenXUL chromeDocument"
+  );
+
+  await ExtensionParent.DebugUtils.releaseExtensionProcessBrowser(
+    anotherFakeAddonActor
+  );
+
+  ok(
+    anotherDebugBrowser.parentElement == null,
+    "The second debug browser has been removed from the hiddenXUL chromeDocument"
+  );
+  equal(
+    ExtensionParent.DebugUtils.debugBrowserPromises.size,
+    0,
+    "All the addon debugging browsers has been released"
+  );
+
+  await extension.unload();
+  await anotherExtension.unload();
+});
diff --git a/toolkit/components/extensions/test/xpcshell/test_ext_dnr_allowAllRequests.js b/toolkit/components/extensions/test/xpcshell/test_ext_dnr_allowAllRequests.js
new file mode 100644
index 0000000000..ccb380180f
--- /dev/null
+++ b/toolkit/components/extensions/test/xpcshell/test_ext_dnr_allowAllRequests.js
@@ -0,0 +1,1231 @@
+"use strict";
+
+// This file tests whether the "allowAllRequests" action is correctly applied
+// to subresource requests. The relative precedence to other actions/extensions
+// is tested in test_ext_dnr_testMatchOutcome.js, specifically by test tasks
+// rule_priority_and_action_type_precedence and
+// action_precedence_between_extensions.
+
+ChromeUtils.defineESModuleGetters(this, {
+  TestUtils: "resource://testing-common/TestUtils.sys.mjs",
+});
+
+add_setup(() => {
+  Services.prefs.setBoolPref("extensions.manifestV3.enabled", true);
+  Services.prefs.setBoolPref("extensions.dnr.enabled", true);
+});
+
+const server = createHttpServer({
+  hosts: ["example.com", "example.net", "example.org"],
+});
+server.registerPathHandler("/never_reached", (req, res) => {
+  Assert.ok(false, "Server should never have been reached");
+});
+server.registerPathHandler("/allowed", (req, res) => {
+  res.setHeader("Access-Control-Allow-Origin", "*");
+  res.setHeader("Access-Control-Max-Age", "0");
+  // Any test that is able to check the response body will be able to assert
+  // the response body's value. Let's use "fetchAllowed" so that the compared
+  // values are obvious when assertEq/assertDeepEq are used.
+  res.write("fetchAllowed");
+});
+server.registerPathHandler("/", (req, res) => {
+  res.write("Dummy page");
+});
+server.registerPathHandler("/echo_html", (req, res) => {
+  let code = decodeURIComponent(req.queryString);
+  res.setHeader("Content-Type", "text/html; charset=utf-8");
+  if (req.hasHeader("prependhtml")) {
+    code = req.getHeader("prependhtml") + code;
+  }
+  res.write(`<!DOCTYPE html>${code}`);
+});
+server.registerPathHandler("/bfcache_test", (req, res) => {
+  res.setHeader("Content-Type", "text/html; charset=utf-8");
+  res.write(`<body><script>
+    // false at initial load, true when loaded from bfcache.
+    onpageshow = e => document.body.textContent = e.persisted;
+  </script>`);
+});
+
+async function waitForRequestAtServer(path) {
+  return new Promise(resolve => {
+    let callCount = 0;
+    server.registerPathHandler(path, (req, res) => {
+      Assert.equal(++callCount, 1, `Got one request for: ${path}`);
+      res.processAsync();
+      resolve({ req, res });
+    });
+  });
+}
+
+// Several tests expect fetch() to fail due to the request being blocked.
+// They can use testLoadInFrame({ ..., expectedError: FETCH_BLOCKED }).
+const FETCH_BLOCKED =
+  "TypeError: NetworkError when attempting to fetch resource.";
+
+function urlEchoHtml(domain, html) {
+  return `http://${domain}/echo_html?${encodeURIComponent(html)}`;
+}
+
+function htmlEscape(html) {
+  return html
+    .replaceAll("&", "&amp;")
+    .replaceAll('"', "&quot;")
+    .replaceAll("'", "&#39;")
+    .replaceAll("<", "&lt;")
+    .replaceAll(">", "&gt;");
+}
+
+// Values for domains in testLoadInFrame.
+const ABOUT_SRCDOC_SAME_ORIGIN = "about:srcdoc (same-origin)";
+const ABOUT_SRCDOC_CROSS_ORIGIN = "about:srcdoc (cross-origin)";
+
+async function testLoadInFrame({
+  description,
+  // domains[0] = main frame, every extra item is a child frame.
+  domains = ["example.com"],
+  htmlPrependedToEachFrame = "",
+  // jsForFrame will be serialized and run in the deepest frame.
+  jsForFrame,
+  // The expected (potentially async) return value of jsForFrame.
+  expectedResult,
+  // The expected (potentially async) error thrown from jsForFrame.
+  expectedError,
+}) {
+  const frameJs = async jsForFrame => {
+    let result = {};
+    try {
+      result.returnValue = await jsForFrame();
+    } catch (e) {
+      result.error = String(e);
+    }
+    // jsForFrame may return "delay_postMessage" to postpone the resolution of
+    // the promise. When the test is ready to resume, `top.postMessage()` can
+    // be called with the result, from any frame. This would also happen if the
+    // URL generated by this testLoadInFrame helper are re-used, e.g. by a new
+    // navigation to the URL that triggers a return value from jsForFrame that
+    // differs from "delay_postMessage".
+    if (result.returnValue !== "delay_postMessage") {
+      top.postMessage(result, "*");
+    }
+  };
+  const frameHtml = `<body><script>(${frameJs})(${jsForFrame})</script>`;
+
+  // Construct the frame tree so that domains[0] is the main frame, and
+  // domains[domains.length - 1] is the deepest level frame (if any).
+
+  const [mainFrameDomain, ...subFramesDomains] = domains;
+
+  // The loop below generates the HTML for the deepest frame first, so we have
+  // to reverse the list of domains.
+  subFramesDomains.reverse();
+
+  let html = frameHtml;
+  for (let domain of subFramesDomains) {
+    html = htmlPrependedToEachFrame + html;
+    if (domain === ABOUT_SRCDOC_SAME_ORIGIN) {
+      html = `<iframe srcdoc="${htmlEscape(html)}"></iframe>`;
+    } else if (domain === ABOUT_SRCDOC_CROSS_ORIGIN) {
+      html = `<iframe srcdoc="${htmlEscape(
+        html
+      )}" sandbox="allow-scripts"></iframe>`;
+    } else {
+      html = `<iframe src="${urlEchoHtml(domain, html)}"></iframe>`;
+    }
+  }
+
+  const mainFrameJs = () => {
+    window.resultPromise = new Promise(resolve => {
+      window.onmessage = e => resolve(e.data);
+    });
+  };
+  const mainFrameHtml = `<script>(${mainFrameJs})()</script>${html}`;
+  const mainFrameUrl = urlEchoHtml(mainFrameDomain, mainFrameHtml);
+
+  let contentPage = await ExtensionTestUtils.loadContentPage(mainFrameUrl);
+  let result = await contentPage.spawn([], () => {
+    return content.wrappedJSObject.resultPromise;
+  });
+  await contentPage.close();
+  if (expectedError) {
+    Assert.deepEqual(result, { error: expectedError }, description);
+  } else {
+    Assert.deepEqual(result, { returnValue: expectedResult }, description);
+  }
+}
+
+async function loadExtensionWithDNRRules(
+  rules,
+  {
+    // host_permissions is only required for modifyHeaders/redirect, or when
+    // "declarativeNetRequestWithHostAccess" is used.
+    host_permissions = [],
+    permissions = ["declarativeNetRequest"],
+  } = {}
+) {
+  async function background(rules) {
+    try {
+      await browser.declarativeNetRequest.updateSessionRules({
+        addRules: rules,
+      });
+    } catch (e) {
+      browser.test.fail(`Failed to register DNR rules: ${e} :: ${e.stack}`);
+    }
+    browser.test.sendMessage("dnr_registered");
+  }
+  let extension = ExtensionTestUtils.loadExtension({
+    background: `(${background})(${JSON.stringify(rules)})`,
+    temporarilyInstalled: true, // Needed for granted_host_permissions
+    manifest: {
+      manifest_version: 3,
+      granted_host_permissions: true,
+      host_permissions,
+      permissions,
+    },
+  });
+  await extension.startup();
+  await extension.awaitMessage("dnr_registered");
+  return extension;
+}
+
+add_task(async function allowAllRequests_allows_request() {
+  let extension = await loadExtensionWithDNRRules([
+    // allowAllRequests should take precedence over block.
+    {
+      id: 1,
+      condition: { resourceTypes: ["main_frame", "xmlhttprequest"] },
+      action: { type: "block" },
+    },
+    {
+      id: 2,
+      condition: { resourceTypes: ["main_frame"] },
+      action: { type: "allowAllRequests" },
+    },
+    {
+      id: 3,
+      priority: 2,
+      // Note: when not specified, main_frame is excluded by default. So
+      // when a main_frame request is triggered, only rules 1 and 2 match.
+      condition: { requestDomains: ["example.com"] },
+      action: { type: "block" },
+    },
+  ]);
+
+  let contentPage = await ExtensionTestUtils.loadContentPage(
+    "http://example.com/"
+  );
+  Assert.equal(
+    await contentPage.spawn([], () => content.document.URL),
+    "http://example.com/",
+    "main_frame request should have been allowed by allowAllRequests"
+  );
+
+  async function checkCanFetch(url) {
+    return contentPage.spawn([url], async url => {
+      try {
+        return await (await content.fetch(url)).text();
+      } catch (e) {
+        return e.toString();
+      }
+    });
+  }
+
+  Assert.equal(
+    await checkCanFetch("http://example.com/never_reached"),
+    FETCH_BLOCKED,
+    "should be blocked by DNR rule 3"
+  );
+  Assert.equal(
+    await checkCanFetch("http://example.net/allowed"),
+    "fetchAllowed",
+    "should not be blocked by block rule due to allowAllRequests rule"
+  );
+
+  await contentPage.close();
+  await extension.unload();
+});
+
+add_task(async function allowAllRequests_in_sub_frame() {
+  const extension = await loadExtensionWithDNRRules([
+    {
+      id: 1,
+      condition: { resourceTypes: ["xmlhttprequest"] },
+      action: { type: "block" },
+    },
+    {
+      id: 2,
+      condition: {
+        requestDomains: ["example.com"],
+        resourceTypes: ["main_frame", "sub_frame"],
+      },
+      action: { type: "allowAllRequests" },
+    },
+  ]);
+
+  const testFetch = async () => {
+    // Should be able to read, unless blocked by DNR rule 1 above.
+    return (await fetch("http://example.com/allowed")).text();
+  };
+
+  // Sanity check: verify that the test result is different (i.e. FETCH_BLOCKED)
+  // when the "allowAllRequests" rule (rule ID 2) is not matched.
+  await testLoadInFrame({
+    description: "allowAllRequests was not matched anywhere, req in subframe",
+    domains: ["example.net", "example.org"],
+    jsForFrame: testFetch,
+    expectedError: FETCH_BLOCKED,
+  });
+
+  // allowAllRequests applied to domains[0], i.e. "main_frame".
+  await testLoadInFrame({
+    description: "allowAllRequests for main frame, req in main frame",
+    domains: ["example.com"],
+    jsForFrame: testFetch,
+    expectedResult: "fetchAllowed",
+  });
+  await testLoadInFrame({
+    description: "allowAllRequests for main frame, req in same-origin frame",
+    domains: ["example.com", "example.com"],
+    jsForFrame: testFetch,
+    expectedResult: "fetchAllowed",
+  });
+  await testLoadInFrame({
+    description: "allowAllRequests for main frame, req in cross-origin frame",
+    domains: ["example.com", "example.net"],
+    jsForFrame: testFetch,
+    expectedResult: "fetchAllowed",
+  });
+
+  // allowAllRequests applied to domains[1], i.e. "sub_frame".
+  await testLoadInFrame({
+    description: "allowAllRequests for subframe, req in same subframe",
+    domains: ["example.net", "example.com"],
+    jsForFrame: testFetch,
+    expectedResult: "fetchAllowed",
+  });
+  await testLoadInFrame({
+    description: "allowAllRequests for subframe, req in same-origin subframe",
+    domains: ["example.net", "example.com", "example.com"],
+    jsForFrame: testFetch,
+    expectedResult: "fetchAllowed",
+  });
+  await testLoadInFrame({
+    description: "allowAllRequests for subframe, req in cross-origin subframe",
+    domains: ["example.net", "example.com", "example.org"],
+    jsForFrame: testFetch,
+    expectedResult: "fetchAllowed",
+  });
+
+  await extension.unload();
+});
+
+add_task(async function allowAllRequests_does_not_affect_other_extension() {
+  const extension = await loadExtensionWithDNRRules([
+    {
+      id: 1,
+      condition: { resourceTypes: ["xmlhttprequest"] },
+      action: { type: "block" },
+    },
+  ]);
+  const otherExtension = await loadExtensionWithDNRRules([
+    {
+      id: 2,
+      condition: { resourceTypes: ["main_frame", "sub_frame"] },
+      action: { type: "allowAllRequests" },
+    },
+  ]);
+
+  const testFetch = async () => {
+    return (await fetch("http://example.com/allowed")).text();
+  };
+
+  // Sanity check: verify that the test result is different (i.e. FETCH_BLOCKED)
+  // when the "allowAllRequests" rule (rule ID 2) is not matched.
+  await testLoadInFrame({
+    description: "block rule from extension not superseded by otherExtension",
+    domains: ["example.net", "example.org"],
+    jsForFrame: testFetch,
+    expectedError: FETCH_BLOCKED,
+  });
+
+  await extension.unload();
+  await otherExtension.unload();
+});
+
+// When there are multiple frames and matching allowAllRequests, we need to
+// use the highest-priority allowAllRequests rule. The selected rule can be
+// observed through interleaved modifyHeaders rules.
+add_task(async function allowAllRequests_multiple_frames_and_modifyHeaders() {
+  const domains = ["example.com", "example.com", "example.net", "example.org"];
+  const rules = [
+    {
+      id: 1,
+      priority: 3,
+      condition: { requestDomains: [domains[1]], resourceTypes: ["sub_frame"] },
+      action: { type: "allowAllRequests" },
+    },
+    {
+      id: 2,
+      priority: 7,
+      condition: { requestDomains: [domains[2]], resourceTypes: ["sub_frame"] },
+      action: { type: "allowAllRequests" },
+    },
+    {
+      id: 3,
+      priority: 5,
+      condition: { requestDomains: [domains[3]], resourceTypes: ["sub_frame"] },
+      action: { type: "allowAllRequests" },
+    },
+    // The loop below will add modifyHeaders rules with priorities 1 - 9.
+  ];
+  for (let i = 1; i <= 9; ++i) {
+    rules.push({
+      id: 10 + i, // not overlapping with any rule in |rules|.
+      priority: i,
+      condition: { resourceTypes: ["xmlhttprequest"] },
+      action: {
+        type: "modifyHeaders",
+        responseHeaders: [
+          {
+            // Expose the header via CORS to allow fetch() to read the header.
+            operation: "set",
+            header: "Access-Control-Expose-Headers",
+            value: "addedByDnr",
+          },
+          { operation: "append", header: "addedByDnr", value: `${i}` },
+        ],
+      },
+    });
+  }
+
+  const extension = await loadExtensionWithDNRRules(rules, {
+    // host_permissions required for "modifyHeaders" action.
+    host_permissions: ["<all_urls>"],
+  });
+
+  await testLoadInFrame({
+    description: "Should select highest-prio allowAllRequests among ancestors",
+    domains,
+    jsForFrame: async () => {
+      let res = await fetch("http://example.com/allowed");
+      return res.headers.get("addedByDnr");
+    },
+    // The fetch request matches all xmlhttprequest rules, which would append
+    // the numbers 1...9 to the results via "modifyHeaders".
+    //
+    // But every frame also has one matching "allowAllRequests" rule. Among
+    // these, we should not select an arbitrary rule, but the one with the
+    // highest priority, i.e. priority 7 (matches domains[2]).
+    //
+    // Given the "allowAllRequests" of priority 7, all rules of lower-or-equal
+    // priority are ignored, so only "modifyHeaders" remain with priority 8 & 9.
+    //
+    // modifyHeaders are applied in the order of priority: "9, 8", not "8, 9".
+    expectedResult: "9, 8",
+  });
+
+  await extension.unload();
+});
+
+add_task(async function allowAllRequests_initiatorDomains() {
+  const rules = [
+    {
+      id: 1,
+      condition: {
+        initiatorDomains: ["example.com"], // Note: in host_permissions below.
+        resourceTypes: ["main_frame", "sub_frame"],
+      },
+      action: { type: "allowAllRequests" },
+    },
+    {
+      id: 2,
+      condition: {
+        initiatorDomains: ["example.net"], // Note: NOT in host_permissions.
+        resourceTypes: ["sub_frame"],
+      },
+      action: { type: "allowAllRequests" },
+    },
+    {
+      id: 3,
+      condition: { resourceTypes: ["xmlhttprequest"] },
+      action: { type: "block" },
+    },
+  ];
+
+  const extension = await loadExtensionWithDNRRules(rules, {
+    // host_permissions matches initiatorDomains from rule 1 (allowAllRequests)
+    // and the origin of the frame that calls testCanFetch.
+    host_permissions: ["*://example.com/*", "*://example.org/*"],
+  });
+
+  const testCanFetch = async () => {
+    return (await fetch("http://example.com/allowed")).text();
+  };
+
+  await testLoadInFrame({
+    description: "main_frame request does not have an initiator",
+    domains: ["example.com"],
+    jsForFrame: testCanFetch,
+    // Rule 1 (initiatorDomains: ["example.com"]) should not match.
+    expectedError: FETCH_BLOCKED,
+  });
+  await testLoadInFrame({
+    description: "sub_frame loaded by initiator in host_permissions",
+    domains: ["example.com", "example.org"],
+    jsForFrame: testCanFetch,
+    // Matched by rule 1 (initiatorDomains: ["example.com"])
+    expectedResult: "fetchAllowed",
+  });
+  await testLoadInFrame({
+    description: "sub_frame loaded by initiator not in host_permissions",
+    domains: ["example.net", "example.org"],
+    jsForFrame: testCanFetch,
+    // Matched by rule 2 (initiatorDomains: ["example.net"]). While example.net
+    // is not in host_permissions, the "allowAllRequests" rule can apply because
+    // the extension does have the "declarativeNetRequest" permission (opposed
+    // to just "declarativeNetRequestWithHostAccess", which is covered by the
+    // allowAllRequests_initiatorDomains_dnrWithHostAccess test task below).
+    expectedResult: "fetchAllowed",
+  });
+
+  // about:srcdoc inherits parent origin.
+  await testLoadInFrame({
+    description: "about:srcdoc with matching initiator",
+    domains: ["example.com", ABOUT_SRCDOC_SAME_ORIGIN],
+    jsForFrame: testCanFetch,
+    // While the "about:srcdoc" frame's initiator is matched by rule 1
+    // (initiatorDomains: ["example.com"]), the frame's URL itself is
+    // "about:srcdoc" and consequently ignored in the matcher.
+    expectedError: FETCH_BLOCKED,
+  });
+  await testLoadInFrame({
+    description: "subframe in about:srcdoc with matching initiator",
+    domains: ["example.com", ABOUT_SRCDOC_SAME_ORIGIN, "example.org"],
+    jsForFrame: testCanFetch,
+    // The parent URL is "about:srcdoc", but its principal is inherit from its
+    // parent, i.e. "example.com". Therefore it matches rule 1.
+    expectedResult: "fetchAllowed",
+  });
+  await testLoadInFrame({
+    description: "subframe in opaque about:srcdoc despite matching initiator",
+    domains: ["example.com", ABOUT_SRCDOC_CROSS_ORIGIN, "example.org"],
+    jsForFrame: testCanFetch,
+    // The parent URL is "about:srcdoc". Because it is sandboxed, it has an
+    // opaque origin and therefore none of the allowAllRequests rules match,
+    // even not rule 1 even though the "about:srcdoc" frame was created by
+    // "example.com".
+    expectedError: FETCH_BLOCKED,
+  });
+
+  await extension.unload();
+});
+
+add_task(async function allowAllRequests_initiatorDomains_dnrWithHostAccess() {
+  const rules = [
+    {
+      id: 1,
+      condition: {
+        // This test shows that it does not matter whether initiatorDomains is
+        // in host_permissions; it only matters if the frame's URL is matched
+        // by host_permissions.
+        initiatorDomains: ["example.net"], // Not in host_permissions.
+        resourceTypes: ["sub_frame"],
+      },
+      action: { type: "allowAllRequests" },
+    },
+    {
+      id: 2,
+      condition: { resourceTypes: ["xmlhttprequest"] },
+      action: { type: "block" },
+    },
+  ];
+
+  const extension = await loadExtensionWithDNRRules(rules, {
+    host_permissions: ["*://example.org/*"],
+    permissions: ["declarativeNetRequestWithHostAccess"],
+  });
+
+  const testCanFetch = async () => {
+    // example.org is in host_permissions above so "xmlhttprequest" rule is
+    // always expected to match this, unless "allowAllRequests" applied.
+    // If "allowAllRequests" applies, then expectedResult: "fetchAllowed".
+    // If "allowAllRequests" did not apply, then expectedError: FETCH_BLOCKED.
+    return (await fetch("http://example.org/allowed")).text();
+  };
+
+  await testLoadInFrame({
+    description:
+      "frame URL in host_permissions despite initiator not in host_permissions",
+    domains: ["example.com", "example.net", "example.org"],
+    jsForFrame: testCanFetch,
+    // The "xmlhttprequest" block rule applies because the request URL
+    // (example.org) and initiator (example.org) are part of host_permissions.
+    //
+    // The "allowAllRequests" rule applies and overrides the block because the
+    // "example.org" frame has "example.net" as initiator (as specified in the
+    // initiatorDomains DNR rule). Despite the lack of host_permissions for
+    // "example.net", the DNR rule is matched because navigation requests do
+    // not require host permissions.
+    expectedResult: "fetchAllowed",
+  });
+
+  await testLoadInFrame({
+    description: "frame URL and initiator not in host_permissions",
+    domains: ["example.net", "example.com", "example.org"],
+    jsForFrame: testCanFetch,
+    // The "xmlhttprequest" block rule applies because the request URL
+    // (example.org) and initiator (example.org) are part of host_permissions.
+    //
+    // The "allowAllRequests" rule does not apply because it would only apply
+    // to the "example.com" frame (that frame has "example.net" as initiator),
+    // but the DNR extension does not have host permissions for example.com.
+    expectedError: FETCH_BLOCKED,
+  });
+
+  await extension.unload();
+});
+
+add_task(async function allowAllRequests_initiator_is_parent() {
+  // The actual initiator of a request is the principal (origin) that triggered
+  // the request. Navigations of subframes are usually triggered by the parent,
+  // except in case of cross-frame/window navigations.
+  //
+  // There are some limits on cross-frame navigations, specified by:
+  // https://html.spec.whatwg.org/multipage/browsing-the-web.html#allowed-to-navigate
+  // An ancestor can always navigate a descendant, so we do that here.
+  //
+  // - example.com (main frame)
+  //   - example.net (sub frame 1)
+  //     - example.org (sub frame 2)
+  //       - example.com (sub frame 3) - will be navigated by sub frame 1.
+  //
+  // "initiatorDomains" is usually matched against the actual initiator of a
+  // request. Since the actual initiator (triggering principal) is not always
+  // known nor obvious, the parent principal (origin) is used instead, when the
+  // conditions for "allowAllRequests" are retroactively checked for a document.
+  const domains = ["example.com", "example.net", "example.org", "example.com"];
+  const rules = [
+    {
+      id: 1,
+      condition: {
+        // Note: restrict to example.org, so that we can verify that the
+        // "allowAllRequests" rule applies to subresource requests within any
+        // child frame of "example.org" (i.e. that rule 3 is ignored).
+        //
+        // Side note: the ultimate navigation request for the child frame
+        // itself has actual initiator "example.net" and does not match this
+        // rule, which we verify by confirming that rule 2 matches.
+        initiatorDomains: ["example.org"],
+        requestDomains: ["example.com"],
+        resourceTypes: ["sub_frame"],
+      },
+      action: { type: "allowAllRequests" },
+    },
+    {
+      id: 2,
+      condition: { resourceTypes: ["xmlhttprequest"] },
+      action: { type: "block" },
+    },
+    // The modifyHeaders rules below are not affected by the "allowAllRequests"
+    // rule above, but are part of the test to serve as a sanity check that the
+    // "initiatorDomains" field of sub_frame navigations are compared against
+    // the actual initiator.
+    {
+      id: 3,
+      priority: 2, // To not be ignored by allowAllRequests (rule 1).
+      condition: {
+        // The initial sub_frame navigation request is initiated by its parent,
+        // i.e. example.org.
+        initiatorDomains: ["example.org"],
+        requestDomains: ["example.com"],
+        resourceTypes: ["sub_frame"],
+      },
+      action: {
+        type: "modifyHeaders",
+        requestHeaders: [
+          {
+            operation: "append",
+            header: "prependhtml",
+            value: "<title>DNR rule 3 for initiator example.org</title>",
+          },
+        ],
+      },
+    },
+    {
+      id: 4,
+      condition: {
+        // The final sub_frame navigation request is initiated by a frame other
+        // than the parent (i.e. example.net).
+        initiatorDomains: ["example.net"],
+        requestDomains: ["example.com"],
+        resourceTypes: ["sub_frame"],
+      },
+      action: {
+        type: "modifyHeaders",
+        requestHeaders: [
+          {
+            operation: "append",
+            header: "prependhtml",
+            value: "<title>DNR rule 4 for initiator example.net</title>",
+          },
+        ],
+      },
+    },
+  ];
+
+  const extension = await loadExtensionWithDNRRules(rules, {
+    // host_permissions needed for allowAllRequests of ancestors
+    // (initiatorDomains & requestDomains) and modifyHeaders.
+    host_permissions: ["<all_urls>"],
+  });
+
+  const jsNavigateOnMessage = () => {
+    window.onmessage = e => {
+      dump(`\nReceived message at ${origin} from ${e.origin}: ${e.data}\n`);
+      e.source.location = e.data;
+    };
+  };
+  const htmlNavigateOnMessage = `<script>(${jsNavigateOnMessage})()</script>`;
+
+  // First: sanity check that the actual initiators are as expected, which we
+  // verify through the modifyHeaders+initiatorDomains rules, observed through
+  // document.title (/echo_html prepends the "prependhtml" header's value).
+  await testLoadInFrame({
+    description: "Sanity check: navigation matches actual initiator (parent)",
+    domains,
+    jsForFrame: () => document.title,
+    expectedResult: "DNR rule 3 for initiator example.org",
+  });
+
+  await testLoadInFrame({
+    description: "Sanity check: navigation matches actual initiator (ancestor)",
+    domains,
+    htmlPrependedToEachFrame: htmlNavigateOnMessage,
+    jsForFrame: () => {
+      if (location.hash !== "#End") {
+        dump("Sanity: Trying to navigate with initiator set to example.net\n");
+        parent.parent.postMessage(document.URL + ".#End", "http://example.net");
+        return "delay_postMessage";
+      }
+      return document.title;
+    },
+    expectedResult: "DNR rule 4 for initiator example.net",
+  });
+
+  // Now the actual test: when fetch() is called, "allowAllRequests" should use
+  // the parent origin for each frame in the frame tree.
+
+  await testLoadInFrame({
+    description: "allowAllRequests matches parent (which is the initiator)",
+    domains,
+    jsForFrame: async () => {
+      return (await fetch("http://example.com/allowed")).text();
+    },
+    expectedResult: "fetchAllowed", // fetch() not blocked, rule 1 > rule 2.
+  });
+
+  // This is where the result differs from what one may expect from
+  // "initiatorDomains". This is consistent with Chrome's behavior,
+  // https://source.chromium.org/chromium/chromium/src/+/main:extensions/browser/api/declarative_net_request/request_params.cc;l=123-130;drc=8a27797c643fb0f2d9ae835f8d8b509e027c97e9
+  await testLoadInFrame({
+    description: "allowAllRequests matches parent (not actual initiator)",
+    domains,
+    htmlPrependedToEachFrame: htmlNavigateOnMessage,
+    jsForFrame: async () => {
+      if (location.hash !== "#End") {
+        dump("Final: Trying to navigate with initiator set to example.net\n");
+        parent.parent.postMessage(document.URL + ".#End", "http://example.net");
+        return "delay_postMessage";
+      }
+      return (await fetch("http://example.com/allowed")).text();
+    },
+    expectedResult: "fetchAllowed", // fetch() not blocked, rule 1 > rule 2.
+  });
+
+  await extension.unload();
+});
+
+// Tests how initiatorDomains applies to document and non-document (fetch)
+// requests triggered from content scripts.
+add_task(async function allowAllRequests_initiatorDomains_content_script() {
+  const rules = [
+    {
+      id: 1,
+      condition: {
+        initiatorDomains: ["example.com"],
+        resourceTypes: ["sub_frame"],
+      },
+      action: { type: "allowAllRequests" },
+    },
+    {
+      id: 2,
+      condition: { resourceTypes: ["xmlhttprequest"] },
+      action: { type: "block" },
+    },
+    {
+      id: 3,
+      condition: {
+        resourceTypes: ["sub_frame"],
+        requestDomains: ["example.com"],
+      },
+      action: {
+        type: "redirect",
+        redirect: { transform: { host: "example.net" } },
+      },
+    },
+  ];
+
+  const extension = await loadExtensionWithDNRRules(rules, {
+    host_permissions: ["*://example.com/*", "*://example.net/*"],
+  });
+
+  let contentScriptExtension = ExtensionTestUtils.loadExtension({
+    manifest: {
+      // Intentionally MV2 because its fetch() is tied to the content script
+      // sandbox, and thus potentially more likely to trigger bugs than the MV3
+      // fetch (fetch in MV3 is the same as the web page due to bug 1578405).
+      manifest_version: 2,
+      content_scripts: [
+        {
+          run_at: "document_end",
+          js: ["contentscript_load_frame.js"],
+          matches: ["http://*/?test_contentscript_load_frame"],
+        },
+        {
+          all_frames: true,
+          run_at: "document_end",
+          js: ["contentscript_in_iframe.js"],
+          matches: ["http://example.net/?test_contentscript_triggered_frame"],
+        },
+      ],
+    },
+    files: {
+      "contentscript_load_frame.js": () => {
+        browser.test.log("Waiting for frame, then contentscript_in_iframe.js");
+        // Created by content script; initiatorDomains should match the page's
+        // domain (and not somehow be confused by the content script principal).
+        // let document = window.document.wrappedJSObject;
+        let f = document.createElement("iframe");
+        f.src = "http://example.com/?test_contentscript_triggered_frame";
+        document.body.append(f);
+      },
+      "contentscript_in_iframe.js": async () => {
+        // When the iframe request was generated by the content script, its
+        // initiator is void because the content script has an ExpandedPrincipal
+        // that is treated as void when the request initiator is computed:
+        // https://searchfox.org/mozilla-central/rev/d85572c1963f72e8bef2787d900e0a8ffd8e6728/toolkit/components/extensions/webrequest/ChannelWrapper.cpp#551
+        // Therefore the initiatorDomains condition of rule 1 (allowAllRequests)
+        // does not match, so rule 3 (redirect to example.net) applies.
+        browser.test.assertEq(
+          "example.net", // instead of the pre-redirect URL (example.com).
+          location.host,
+          "redirect rule matched because initiator is void for content-script-triggered navigation"
+        );
+        async function isFetchOk(fetchPromise) {
+          try {
+            await fetchPromise;
+            return true; // allowAllRequests matched.
+          } catch (e) {
+            await browser.test.assertRejects(fetchPromise, /NetworkError/);
+            return false; // block rule matched because allowAllRequests didn't.
+          }
+        }
+        browser.test.assertTrue(
+          await isFetchOk(content.fetch("http://example.net/allowed")),
+          "frame's parent origin matches initiatorDomains (content script fetch)"
+        );
+        // fetch() in MV2 content script is associated with the content script
+        // sandbox, not the frame, so there are no allowAllRequests rules to
+        // apply. For equivalent request details, see bug 1444729.
+        browser.test.assertFalse(
+          await isFetchOk(fetch("http://example.net/allowed")),
+          "MV2 content script fetch() is not associated with the document"
+        );
+        browser.test.sendMessage("contentscript_initiator");
+      },
+    },
+  });
+  await contentScriptExtension.startup();
+  let contentPage = await ExtensionTestUtils.loadContentPage(
+    "http://example.com/?test_contentscript_load_frame"
+  );
+  info("Waiting for page load, will continue at contentscript_load_frame.js");
+  await contentScriptExtension.awaitMessage("contentscript_initiator");
+  await contentScriptExtension.unload();
+  await contentPage.close();
+  await extension.unload();
+});
+
+// Verifies that allowAllRequests is evaluated against the currently committed
+// document, even if another document load has been initiated.
+add_task(async function allowAllRequests_during_and_after_navigation() {
+  let extension = await loadExtensionWithDNRRules([
+    {
+      id: 1,
+      condition: { resourceTypes: ["xmlhttprequest"] },
+      action: { type: "block" },
+    },
+    {
+      id: 2,
+      condition: { urlFilter: "WITH_AAR", resourceTypes: ["sub_frame"] },
+      action: { type: "allowAllRequests" },
+    },
+  ]);
+
+  const contentPage = await ExtensionTestUtils.loadContentPage(
+    "http://example.com/?dummy_see_iframe_for_interesting_stuff"
+  );
+  await contentPage.spawn([], async () => {
+    let f = content.document.createElement("iframe");
+    f.id = "frame_to_navigate";
+    f.src = "/?init_WITH_AAR"; // allowAllRequests initially applies.
+    await new Promise(resolve => {
+      f.onload = resolve;
+      content.document.body.append(f);
+    });
+  });
+  async function navigateIframe(url) {
+    await contentPage.spawn([url], url => {
+      let f = content.document.getElementById("frame_to_navigate");
+      content.frameLoadedPromise = new Promise(resolve => {
+        f.addEventListener("load", resolve, { once: true });
+      });
+      f.contentWindow.location.href = url;
+    });
+  }
+  async function waitForNavigationCompleted(expectLoad = true) {
+    await contentPage.spawn([expectLoad], async expectLoad => {
+      if (expectLoad) {
+        info("Waiting for frame load - if stuck the load never happened\n");
+        return content.frameLoadedPromise.then(() => {});
+      }
+      // When HTTP 204 No Content is used, onload is not fired.
+      // Here we load another frame, and assume that once this completes, that
+      // any previous load of navigateIframe() would have completed by now.
+      let f = content.document.createElement("iframe");
+      f.src = "/?dummy_no_dnr_matched_" + Math.random();
+      await new Promise(resolve => {
+        f.onload = resolve;
+        content.document.body.append(f);
+      });
+      f.remove();
+    });
+  }
+  async function assertIframePath(expectedPath, description) {
+    let actualPath = await contentPage.spawn([], () => {
+      return content.frames[0].location.pathname;
+    });
+    Assert.equal(actualPath, expectedPath, description);
+  }
+  async function assertHasAAR(expected, description) {
+    let actual = await contentPage.spawn([], async () => {
+      try {
+        await (await content.frames[0].fetch("/allowed")).text();
+        return true; // allowAllRequests overrides block rule.
+      } catch (e) {
+        // Sanity check: NetworkError from fetch(), not a random other error.
+        Assert.equal(
+          e.toString(),
+          "TypeError: NetworkError when attempting to fetch resource.",
+          "Got error for failed fetch"
+        );
+        return false; // blocked by xmlhttprequest block rule.
+      }
+    });
+    Assert.equal(actual, expected, description);
+  }
+  await assertHasAAR(true, "Initial allowAllRequests overrides block rule");
+
+  const PATH_1_NO_AAR = "/delayed/PATH_1_NO_AAR";
+  const PATH_2_WITH_AAR = "/delayed/PATH_2_WITH_AAR";
+  const PATH_3_NO_AAR = "/delayed/PATH_3_NO_AAR";
+  info("First: transition from /?init_WITH_AAR to PATH_NOT_MATCHED_BY_DNR.");
+  {
+    let promisedServerReq = waitForRequestAtServer(PATH_1_NO_AAR);
+    await navigateIframe(PATH_1_NO_AAR);
+    let serverReq = await promisedServerReq;
+    await assertHasAAR(
+      true,
+      "Initial allowAllRequests still applies despite pending navigation"
+    );
+    await assertIframePath("/", "Frame has not navigated yet");
+    serverReq.res.finish();
+    await waitForNavigationCompleted();
+    await assertIframePath(PATH_1_NO_AAR, "Navigated to PATH_1_NO_AAR");
+
+    await assertHasAAR(
+      false,
+      "Old allowAllRequests should no longer apply after navigation to PATH_1_NO_AAR"
+    );
+  }
+
+  info("Second: transition from PATH_1_NO_AAR to PATH_2_WITH_AAR.");
+  {
+    let promisedServerReq = waitForRequestAtServer(PATH_2_WITH_AAR);
+    await navigateIframe(PATH_2_WITH_AAR);
+    let serverReq = await promisedServerReq;
+    await assertHasAAR(
+      false,
+      "No allowAllRequests yet despite pending navigation to PATH_2_WITH_AAR"
+    );
+    await assertIframePath(PATH_1_NO_AAR, "Frame has not navigated yet");
+    serverReq.res.finish();
+    await waitForNavigationCompleted();
+    await assertIframePath(PATH_2_WITH_AAR, "Navigated to PATH_2_WITH_AAR");
+
+    await assertHasAAR(
+      true,
+      "allowAllRequests should apply after navigation to PATH_2_WITH_AAR"
+    );
+  }
+
+  info("Third: AAR still applies after canceling navigation to PATH_3_NO_AAR.");
+  {
+    let promisedServerReq = waitForRequestAtServer(PATH_3_NO_AAR);
+    await navigateIframe(PATH_3_NO_AAR);
+    let serverReq = await promisedServerReq;
+    serverReq.res.setStatusLine(serverReq.req.httpVersion, 204, "No Content");
+    serverReq.res.finish();
+    await waitForNavigationCompleted(/* expectLoad */ false);
+    await assertIframePath(PATH_2_WITH_AAR, "HTTP 204 does not navigate away");
+
+    await assertHasAAR(
+      true,
+      "allowAllRequests still applied after aborted navigation to PATH_3_NO_AAR"
+    );
+  }
+
+  await contentPage.close();
+  await extension.unload();
+});
+
+add_task(
+  {
+    // Ensure that there is room for at least 2 non-evicted bfcache entries.
+    // Note: this pref is ignored (i.e forced 0) when configured (non-default)
+    // with bfcacheInParent=false while SHIP is enabled:
+    // https://searchfox.org/mozilla-central/rev/00ea1649b59d5f427979e2d6ba42be96f62d6e82/docshell/shistory/nsSHistory.cpp#360-363
+    // ... we mainly care about the bfcache here because it triggers interesting
+    // behavior. DNR evaluation is correct regardless of bfcache.
+    pref_set: [["browser.sessionhistory.max_total_viewers", 3]],
+  },
+  async function allowAllRequests_and_bfcache_navigation() {
+    let extension = await loadExtensionWithDNRRules([
+      {
+        id: 1,
+        condition: { resourceTypes: ["xmlhttprequest"] },
+        action: { type: "block" },
+      },
+      {
+        id: 2,
+        condition: { urlFilter: "aar_yes", resourceTypes: ["main_frame"] },
+        action: { type: "allowAllRequests" },
+      },
+    ]);
+
+    info("Navigating to initial URL: 1_aar_no");
+    const contentPage = await ExtensionTestUtils.loadContentPage(
+      "http://example.com/bfcache_test?1_aar_no"
+    );
+    async function navigateBackInHistory(expectedUrl) {
+      await contentPage.spawn([], () => {
+        content.history.back();
+      });
+      await TestUtils.waitForCondition(
+        () => contentPage.browsingContext.currentURI.spec === expectedUrl,
+        `Waiting for history.back() to trigger navigation to ${expectedUrl}`
+      );
+      await contentPage.spawn([expectedUrl], async expectedUrl => {
+        Assert.equal(content.location.href, expectedUrl, "URL after back");
+        Assert.equal(content.document.body.textContent, "true", "from bfcache");
+      });
+    }
+    async function checkCanFetch(url) {
+      return contentPage.spawn([url], async url => {
+        try {
+          return await (await content.fetch(url)).text();
+        } catch (e) {
+          return e.toString();
+        }
+      });
+    }
+
+    info("Navigating from initial URL to: 2_aar_yes");
+    await contentPage.loadURL("http://example.com/bfcache_test?2_aar_yes");
+    info("Navigating from 2_aar_yes to: 3_aar_no");
+    await contentPage.loadURL("http://example.com/bfcache_test?3_aar_no");
+
+    info("Going back in history (from 3_aar_no to 2_aar_yes)");
+    await navigateBackInHistory("http://example.com/bfcache_test?2_aar_yes");
+    Assert.equal(
+      await checkCanFetch("http://example.com/allowed"),
+      "fetchAllowed",
+      "after history.back(), allowAllRequests should apply from 2_aar_yes"
+    );
+
+    info("Going back in history (from 2_aar_yes to 1_aar_no)");
+    await navigateBackInHistory("http://example.com/bfcache_test?1_aar_no");
+    Assert.equal(
+      await checkCanFetch("http://example.net/never_reached"),
+      FETCH_BLOCKED,
+      "after history.back(), no allowAllRequests action applied at 1_aar_no"
+    );
+
+    await contentPage.close();
+    await extension.unload();
+  }
+);
+
+add_task(
+  {
+    // Usually, back/forward navigation to a POST form requires the user to
+    // confirm the form resubmission. Set pref to approve without prompting.
+    pref_set: [["dom.confirm_repost.testing.always_accept", true]],
+  },
+  async function allowAllRequests_navigate_with_http_method_POST() {
+    const rules = [
+      {
+        id: 1,
+        condition: {
+          requestMethods: ["post"],
+          resourceTypes: ["main_frame", "sub_frame"],
+        },
+        action: { type: "allowAllRequests" },
+      },
+      {
+        id: 2,
+        condition: { resourceTypes: ["xmlhttprequest"] },
+        action: { type: "block" },
+      },
+    ];
+
+    if (!Services.appinfo.sessionHistoryInParent) {
+      // POST detection relies on SHIP being enabled. This is true by default,
+      // but there are some test configurations with SHIP disabled. When SHIP
+      // is disabled, all methods are interpreted as GET instead of POST.
+      // Rewrite the rule to specifically match the POST requests that are
+      // misinterpreted as GET, to verify that the request evaluation by DNR is
+      // functional (opposed to throwing errors).
+      rules[0].condition.requestMethods = ["get"];
+      rules[0].condition.urlFilter = "do_post|";
+      info(`WARNING: SHIP is disabled. POST will be misinterpreted as GET`);
+    }
+
+    const extension = await loadExtensionWithDNRRules(rules);
+
+    const contentPage = await ExtensionTestUtils.loadContentPage(
+      "http://example.com/?do_get"
+    );
+    async function checkCanFetch(url) {
+      return contentPage.spawn([url], async url => {
+        try {
+          return await (await content.fetch(url)).text();
+        } catch (e) {
+          return e.toString();
+        }
+      });
+    }
+
+    // Check fetch() with regular GET navigation in main_frame.
+    Assert.equal(
+      await checkCanFetch("http://example.net/never_reached"),
+      FETCH_BLOCKED,
+      "main_frame: non-POST not matched by requestMethods:['post']"
+    );
+
+    // Check fetch() after POST navigation in main_frame.
+    await contentPage.spawn([], () => {
+      let form = content.document.createElement("form");
+      form.action = "/?do_post";
+      form.method = "POST";
+      content.document.body.append(form);
+      form.submit();
+    });
+    await TestUtils.waitForCondition(
+      () => contentPage.browsingContext.currentURI.pathQueryRef === "/?do_post",
+      "Waiting for navigation with POST to complete"
+    );
+    Assert.equal(
+      await checkCanFetch("http://example.net/allowed"),
+      "fetchAllowed",
+      "main_frame: requestMethods:['post'] applies to POST"
+    );
+
+    // Navigate back to the beginning and verify that allowAllRequests does not
+    // match any more.
+    await contentPage.spawn([], () => {
+      content.history.back();
+    });
+    await TestUtils.waitForCondition(
+      () => contentPage.browsingContext.currentURI.pathQueryRef === "/?do_get",
+      "Waiting for (back) navigation to initial GET page to complete"
+    );
+    Assert.equal(
+      await checkCanFetch("http://example.net/never_reached"),
+      FETCH_BLOCKED,
+      "main_frame: back to non-POST not matched by requestMethods:['post']"
+    );
+
+    // Now navigate forwards to verify that the POST method is still seen.
+    await contentPage.spawn([], () => {
+      content.history.forward();
+    });
+    await TestUtils.waitForCondition(
+      () => contentPage.browsingContext.currentURI.pathQueryRef === "/?do_post",
+      "Waiting for (forward) navigation to POST page to complete"
+    );
+
+    Assert.equal(
+      await checkCanFetch("http://example.net/allowed"),
+      "fetchAllowed",
+      "main_frame: requestMethods:['post'] detects POST after history.forward()"
+    );
+
+    // Now check that adding a new history entry drops the POST method.
+    await contentPage.spawn([], () => {
+      content.history.pushState(null, null, "/?hist_p");
+    });
+    await TestUtils.waitForCondition(
+      () => contentPage.browsingContext.currentURI.pathQueryRef === "/?hist_p",
+      "Waiting for history.pushState to have changed the URL"
+    );
+    Assert.equal(
+      await checkCanFetch("http://example.net/never_reached"),
+      FETCH_BLOCKED,
+      "history.pushState drops POST, not matched by requestMethods:['post']"
+    );
+
+    await contentPage.close();
+
+    // Finally, check that POST detection also works for child frames.
+    await testLoadInFrame({
+      description: "sub_frame: non-POST not matched by requestMethods:['post']",
+      domains: ["example.com", "example.com"],
+      jsForFrame: async () => {
+        return (await fetch("http://example.com/allowed")).text();
+      },
+      expectedError: FETCH_BLOCKED,
+    });
+
+    await testLoadInFrame({
+      description: "sub_frame: requestMethods:['post'] applies to POST",
+      domains: ["example.com", "example.com"],
+      jsForFrame: async () => {
+        if (!location.href.endsWith("?do_post")) {
+          dump("Triggering navigation with POST\n");
+          let form = document.createElement("form");
+          form.action = location.href + "?do_post";
+          form.method = "POST";
+          document.body.append(form);
+          form.submit();
+          return "delay_postMessage";
+        }
+        dump("Navigation with POST completed; testing fetch()...\n");
+        return (await fetch("http://example.com/allowed")).text();
+      },
+      expectedResult: "fetchAllowed",
+    });
+    await extension.unload();
+  }
+);
diff --git a/toolkit/components/extensions/test/xpcshell/test_ext_dnr_api.js b/toolkit/components/extensions/test/xpcshell/test_ext_dnr_api.js
new file mode 100644
index 0000000000..0fc92dcb94
--- /dev/null
+++ b/toolkit/components/extensions/test/xpcshell/test_ext_dnr_api.js
@@ -0,0 +1,383 @@
+"use strict";
+
+ChromeUtils.defineESModuleGetters(this, {
+  ExtensionDNRLimits: "resource://gre/modules/ExtensionDNRLimits.sys.mjs",
+});
+
+AddonTestUtils.init(this);
+
+const PREF_DNR_FEEDBACK_DEFAULT_VALUE = Services.prefs.getBoolPref(
+  "extensions.dnr.feedback",
+  false
+);
+
+// To distinguish from testMatchOutcome, undefined vs resolving vs rejecting.
+const kTestMatchOutcomeNotAllowed = "kTestMatchOutcomeNotAllowed";
+
+async function testAvailability({
+  allowDNRFeedback = false,
+  testExpectations,
+  ...extensionData
+}) {
+  async function background(testExpectations) {
+    let {
+      // declarativeNetRequest should be available if "declarativeNetRequest" or
+      // "declarativeNetRequestWithHostAccess" permission is requested.
+      //  (and always unavailable when "extensions.dnr.enabled" pref is false)
+      declarativeNetRequest_available = false,
+      // testMatchOutcome is available when the "declarativeNetRequestFeedback"
+      // permission is granted AND the "extensions.dnr.feedback" pref is true.
+      //  (and always unavailable when "extensions.dnr.enabled" pref is false)
+      // testMatchOutcome_available: true - permission granted + pref true.
+      // testMatchOutcome_available: false - no permission, pref doesn't matter.
+      // testMatchOutcome_available: kTestMatchOutcomeNotAllowed - permission
+      //   granted, but pref is false.
+      testMatchOutcome_available = false,
+    } = testExpectations;
+    browser.test.assertEq(
+      declarativeNetRequest_available,
+      !!browser.declarativeNetRequest,
+      "declarativeNetRequest API namespace availability"
+    );
+
+    // Dummy param for testMatchOutcome:
+    const dummyRequest = { url: "https://example.com/", type: "other" };
+
+    if (!testMatchOutcome_available) {
+      browser.test.assertEq(
+        undefined,
+        browser.declarativeNetRequest?.testMatchOutcome,
+        "declarativeNetRequest.testMatchOutcome availability"
+      );
+    } else if (testMatchOutcome_available === "kTestMatchOutcomeNotAllowed") {
+      await browser.test.assertRejects(
+        browser.declarativeNetRequest.testMatchOutcome(dummyRequest),
+        `declarativeNetRequest.testMatchOutcome is only available when the "extensions.dnr.feedback" preference is set to true.`,
+        "declarativeNetRequest.testMatchOutcome is unavailable"
+      );
+    } else {
+      browser.test.assertDeepEq(
+        { matchedRules: [] },
+        await browser.declarativeNetRequest.testMatchOutcome(dummyRequest),
+        "declarativeNetRequest.testMatchOutcome is available"
+      );
+    }
+    browser.test.sendMessage("done");
+  }
+  let extension = ExtensionTestUtils.loadExtension({
+    ...extensionData,
+    manifest: {
+      manifest_version: 3,
+      ...extensionData.manifest,
+    },
+    background: `(${background})(${JSON.stringify(testExpectations)});`,
+  });
+  Services.prefs.setBoolPref("extensions.dnr.feedback", allowDNRFeedback);
+  try {
+    await extension.startup();
+    await extension.awaitMessage("done");
+    await extension.unload();
+  } finally {
+    Services.prefs.clearUserPref("extensions.dnr.feedback");
+  }
+}
+
+add_setup(async () => {
+  Services.prefs.setBoolPref("extensions.manifestV3.enabled", true);
+
+  // test_optional_declarativeNetRequestFeedback calls permission.request().
+  // We don't care about the UI, only about the effect of being granted.
+  Services.prefs.setBoolPref(
+    "extensions.webextOptionalPermissionPrompts",
+    false
+  );
+});
+
+add_task(
+  {
+    pref_set: [["extensions.dnr.enabled", false]],
+  },
+  async function extensions_dnr_enabled_pref_disabled_dnr_feature() {
+    let { messages } = await promiseConsoleOutput(async () => {
+      await testAvailability({
+        allowDNRFeedback: PREF_DNR_FEEDBACK_DEFAULT_VALUE,
+        testExpectations: {
+          declarativeNetRequest_available: false,
+        },
+        manifest: {
+          permissions: [
+            "declarativeNetRequest",
+            "declarativeNetRequestFeedback",
+            "declarativeNetRequestWithHostAccess",
+          ],
+        },
+      });
+    });
+
+    AddonTestUtils.checkMessages(messages, {
+      expected: [
+        {
+          message:
+            /Reading manifest: Invalid extension permission: declarativeNetRequest$/,
+        },
+        {
+          message:
+            /Reading manifest: Invalid extension permission: declarativeNetRequestFeedback/,
+        },
+        {
+          message:
+            /Reading manifest: Invalid extension permission: declarativeNetRequestWithHostAccess/,
+        },
+      ],
+    });
+  }
+);
+
+add_task(async function dnr_feedback_apis_disabled_by_default() {
+  let { messages } = await promiseConsoleOutput(async () => {
+    await testAvailability({
+      allowDNRFeedback: PREF_DNR_FEEDBACK_DEFAULT_VALUE,
+      testExpectations: {
+        declarativeNetRequest_available: true,
+        testMatchOutcome_available: kTestMatchOutcomeNotAllowed,
+      },
+      manifest: {
+        permissions: [
+          "declarativeNetRequest",
+          "declarativeNetRequestFeedback",
+          "declarativeNetRequestWithHostAccess",
+        ],
+      },
+    });
+  });
+
+  AddonTestUtils.checkMessages(messages, {
+    forbidden: [
+      {
+        message:
+          /Reading manifest: Invalid extension permission: declarativeNetRequest$/,
+      },
+      {
+        message:
+          /Reading manifest: Invalid extension permission: declarativeNetRequestFeedback/,
+      },
+      {
+        message:
+          /Reading manifest: Invalid extension permission: declarativeNetRequestWithHostAccess/,
+      },
+    ],
+  });
+});
+
+add_task(async function dnr_available_in_mv2() {
+  await testAvailability({
+    allowDNRFeedback: true,
+    testExpectations: {
+      declarativeNetRequest_available: true,
+      testMatchOutcome_available: true,
+    },
+    manifest: {
+      manifest_version: 2,
+      permissions: [
+        "declarativeNetRequest",
+        "declarativeNetRequestFeedback",
+        "declarativeNetRequestWithHostAccess",
+      ],
+    },
+  });
+});
+
+add_task(async function with_declarativeNetRequest_permission() {
+  await testAvailability({
+    allowDNRFeedback: true,
+    testExpectations: {
+      declarativeNetRequest_available: true,
+      // feature allowed, but missing declarativeNetRequestFeedback:
+      testMatchOutcome_available: false,
+    },
+    manifest: {
+      permissions: ["declarativeNetRequest"],
+    },
+  });
+});
+
+add_task(async function with_declarativeNetRequestWithHostAccess_permission() {
+  await testAvailability({
+    allowDNRFeedback: true,
+    testExpectations: {
+      declarativeNetRequest_available: true,
+      // feature allowed, but missing declarativeNetRequestFeedback:
+      testMatchOutcome_available: false,
+    },
+    manifest: {
+      permissions: ["declarativeNetRequestWithHostAccess"],
+    },
+  });
+});
+
+add_task(async function with_all_declarativeNetRequest_permissions() {
+  await testAvailability({
+    allowDNRFeedback: true,
+    testExpectations: {
+      declarativeNetRequest_available: true,
+      // feature allowed, but missing declarativeNetRequestFeedback:
+      testMatchOutcome_available: false,
+    },
+    manifest: {
+      permissions: [
+        "declarativeNetRequest",
+        "declarativeNetRequestWithHostAccess",
+      ],
+    },
+  });
+});
+
+add_task(async function no_declarativeNetRequest_permission() {
+  await testAvailability({
+    allowDNRFeedback: true,
+    testExpectations: {
+      // Just declarativeNetRequestFeedback should not unlock the API.
+      declarativeNetRequest_available: false,
+    },
+    manifest: {
+      permissions: ["declarativeNetRequestFeedback"],
+    },
+  });
+});
+
+add_task(async function with_declarativeNetRequestFeedback_permission() {
+  await testAvailability({
+    allowDNRFeedback: true,
+    testExpectations: {
+      declarativeNetRequest_available: true,
+      // feature allowed, and all permissions specified:
+      testMatchOutcome_available: true,
+    },
+    manifest: {
+      permissions: ["declarativeNetRequest", "declarativeNetRequestFeedback"],
+    },
+  });
+});
+
+add_task(async function declarativeNetRequestFeedback_without_feature() {
+  await testAvailability({
+    allowDNRFeedback: false,
+    testExpectations: {
+      declarativeNetRequest_available: true,
+      // all permissions set, but DNR feedback feature not allowed.
+      testMatchOutcome_available: kTestMatchOutcomeNotAllowed,
+    },
+    manifest: {
+      permissions: ["declarativeNetRequest", "declarativeNetRequestFeedback"],
+    },
+  });
+});
+
+add_task(
+  { pref_set: [["extensions.dnr.feedback", true]] },
+  async function declarativeNetRequestFeedback_is_optional() {
+    async function background() {
+      async function assertTestMatchOutcomeEnabled(expected, description) {
+        let enabled;
+        try {
+          // testAvailability already checks the errors etc, so here we only
+          // care about the method working vs not working.
+          await browser.declarativeNetRequest.testMatchOutcome({
+            url: "https://example.com/",
+            type: "other",
+          });
+          enabled = true;
+        } catch (e) {
+          enabled = false;
+        }
+        browser.test.assertEq(expected, enabled, description);
+      }
+
+      await assertTestMatchOutcomeEnabled(false, "disabled when not granted");
+
+      await new Promise(resolve => {
+        // browser.test.withHandlingUserInput would have been simpler, but due
+        // to bug 1598804 it cannot be used.
+        browser.test.onMessage.addListener(async msg => {
+          browser.test.assertEq("withHandlingUserInput_ok", msg, "Resuming");
+          await browser.permissions.request({
+            permissions: ["declarativeNetRequestFeedback"],
+          });
+          browser.test.sendMessage("withHandlingUserInput_done");
+          resolve();
+        });
+        browser.test.sendMessage("withHandlingUserInput_wanted");
+      });
+
+      await assertTestMatchOutcomeEnabled(true, "enabled by permission");
+
+      await browser.permissions.remove({
+        permissions: ["declarativeNetRequestFeedback"],
+      });
+      await assertTestMatchOutcomeEnabled(false, "disabled after perm removal");
+
+      browser.test.sendMessage("done");
+    }
+    let extension = ExtensionTestUtils.loadExtension({
+      background,
+      manifest: {
+        manifest_version: 3,
+        permissions: ["declarativeNetRequestWithHostAccess"],
+        optional_permissions: ["declarativeNetRequestFeedback"],
+      },
+    });
+    await extension.startup();
+    await extension.awaitMessage("withHandlingUserInput_wanted");
+    await withHandlingUserInput(extension, async () => {
+      extension.sendMessage("withHandlingUserInput_ok");
+      await extension.awaitMessage("withHandlingUserInput_done");
+    });
+    await extension.awaitMessage("done");
+    await extension.unload();
+  }
+);
+
+add_task(async function test_dnr_limits_namespace_properties() {
+  let extension = ExtensionTestUtils.loadExtension({
+    manifest: {
+      manifest_version: 3,
+      permissions: ["declarativeNetRequest"],
+    },
+    background() {
+      browser.test.assertEq(
+        "_dynamic",
+        browser.declarativeNetRequest.DYNAMIC_RULESET_ID,
+        "Value of DYNAMIC_RULESET_ID constant"
+      );
+      browser.test.assertEq(
+        "_session",
+        browser.declarativeNetRequest.SESSION_RULESET_ID,
+        "Value of SESSION_RULESET_ID constant"
+      );
+      const {
+        GUARANTEED_MINIMUM_STATIC_RULES,
+        MAX_NUMBER_OF_STATIC_RULESETS,
+        MAX_NUMBER_OF_ENABLED_STATIC_RULESETS,
+        MAX_NUMBER_OF_DYNAMIC_AND_SESSION_RULES,
+        MAX_NUMBER_OF_REGEX_RULES,
+      } = browser.declarativeNetRequest;
+      browser.test.sendMessage("dnr-namespace-properties", {
+        GUARANTEED_MINIMUM_STATIC_RULES,
+        MAX_NUMBER_OF_STATIC_RULESETS,
+        MAX_NUMBER_OF_ENABLED_STATIC_RULESETS,
+        MAX_NUMBER_OF_DYNAMIC_AND_SESSION_RULES,
+        MAX_NUMBER_OF_REGEX_RULES,
+      });
+    },
+  });
+
+  await extension.startup();
+
+  Assert.deepEqual(
+    await extension.awaitMessage("dnr-namespace-properties"),
+    ExtensionDNRLimits,
+    "Got the expected limits values set on the dnr namespace"
+  );
+
+  await extension.unload();
+});
diff --git a/toolkit/components/extensions/test/xpcshell/test_ext_dnr_download.js b/toolkit/components/extensions/test/xpcshell/test_ext_dnr_download.js
new file mode 100644
index 0000000000..cd24b75855
--- /dev/null
+++ b/toolkit/components/extensions/test/xpcshell/test_ext_dnr_download.js
@@ -0,0 +1,193 @@
+"use strict";
+
+let server = createHttpServer({ hosts: ["example.com"] });
+let downloadReqCount = 0;
+server.registerPathHandler("/downloadtest", (req, res) => {
+  ++downloadReqCount;
+});
+
+add_setup(async () => {
+  let downloadDir = await IOUtils.createUniqueDirectory(
+    Services.dirsvc.get("TmpD", Ci.nsIFile).path,
+    "downloadDirForDnrDownloadTest"
+  );
+  info(`Using download directory ${downloadDir.path}`);
+
+  Services.prefs.setIntPref("browser.download.folderList", 2);
+  Services.prefs.setCharPref("browser.download.dir", downloadDir);
+
+  registerCleanupFunction(async () => {
+    Services.prefs.clearUserPref("browser.download.folderList");
+    Services.prefs.clearUserPref("browser.download.dir");
+    try {
+      await IOUtils.remove(downloadDir);
+    } catch (e) {
+      info(`Failed to remove ${downloadDir} because: ${e}`);
+      // Downloaded files should have been deleted by tests.
+      // Clean up + report error otherwise.
+      let children = await IOUtils.getChildren(downloadDir).catch(e => e);
+      ok(false, `Unexpected files in downloadDir: ${children}`);
+      await IOUtils.remove(downloadDir, { recursive: true });
+    }
+  });
+
+  Services.prefs.setBoolPref("extensions.dnr.enabled", true);
+});
+
+// Test for Bug 1579911: Check that download requests created by the
+// downloads.download API can be observed by extensions.
+// The webRequest version is in test_ext_webRequest_download.js.
+add_task(async function test_download_api_can_be_blocked_by_dnr() {
+  let extension = ExtensionTestUtils.loadExtension({
+    manifest: {
+      manifest_version: 3,
+      permissions: ["declarativeNetRequest", "downloads"],
+      // No host_permissions here because neither the downloads nor the DNR API
+      // require host permissions to download and/or block the request.
+    },
+    // Not needed, but to rule out downloads being blocked by CSP:
+    allowInsecureRequests: true,
+    background: async function () {
+      await browser.declarativeNetRequest.updateSessionRules({
+        addRules: [
+          {
+            id: 1,
+            condition: { urlFilter: "|http://example.com/downloadtest" },
+            action: { type: "block" },
+          },
+        ],
+      });
+
+      browser.downloads.onChanged.addListener(delta => {
+        browser.test.assertEq(delta.state.current, "interrupted");
+        browser.test.sendMessage("done");
+      });
+
+      await browser.downloads.download({
+        url: "http://example.com/downloadtest",
+        filename: "example.txt",
+      });
+    },
+  });
+
+  await extension.startup();
+  await extension.awaitMessage("done");
+  await extension.unload();
+
+  Assert.equal(downloadReqCount, 0, "Did not expect any download requests");
+});
+
+add_task(async function test_download_api_ignores_dnr_from_other_extension() {
+  let extension = ExtensionTestUtils.loadExtension({
+    manifest: {
+      manifest_version: 3,
+      permissions: ["declarativeNetRequest"],
+    },
+    background: async function () {
+      await browser.declarativeNetRequest.updateSessionRules({
+        addRules: [
+          {
+            id: 1,
+            condition: { urlFilter: "|http://example.com/downloadtest" },
+            action: { type: "block" },
+          },
+        ],
+      });
+
+      browser.test.sendMessage("dnr_registered");
+    },
+  });
+
+  let otherExtension = ExtensionTestUtils.loadExtension({
+    manifest: {
+      permissions: ["downloads"],
+    },
+    background: async function () {
+      let downloadDonePromise = new Promise(resolve => {
+        browser.downloads.onChanged.addListener(delta => {
+          if (delta.state.current === "interrupted") {
+            browser.test.fail("Download was unexpectedly interrupted");
+            browser.test.notifyFail("done");
+          } else if (delta.state.current === "complete") {
+            resolve();
+          }
+        });
+      });
+
+      // This download should not have been interrupted by the other extension,
+      // because declarativeNetRequest cannot match requests from other
+      // extensions.
+      let downloadId = await browser.downloads.download({
+        url: "http://example.com/downloadtest",
+        filename: "example_from_other_ext.txt",
+      });
+      await downloadDonePromise;
+      browser.test.log("Download completed, removing file...");
+      // TODO bug 1654819: On Windows the file may be recreated.
+      await browser.downloads.removeFile(downloadId);
+      browser.test.notifyPass("done");
+    },
+  });
+
+  await extension.startup();
+  await extension.awaitMessage("dnr_registered");
+
+  await otherExtension.startup();
+  await otherExtension.awaitFinish("done");
+  await otherExtension.unload();
+  await extension.unload();
+
+  Assert.equal(downloadReqCount, 1, "Expected one download request");
+  downloadReqCount = 0;
+});
+
+add_task(
+  {
+    pref_set: [["extensions.dnr.match_requests_from_other_extensions", true]],
+  },
+  async function test_download_api_dnr_blocks_other_extension_with_pref() {
+    let extension = ExtensionTestUtils.loadExtension({
+      manifest: {
+        manifest_version: 3,
+        permissions: ["declarativeNetRequest"],
+      },
+      background: async function () {
+        await browser.declarativeNetRequest.updateSessionRules({
+          addRules: [
+            {
+              id: 1,
+              condition: { urlFilter: "|http://example.com/downloadtest" },
+              action: { type: "block" },
+            },
+          ],
+        });
+
+        browser.test.sendMessage("dnr_registered");
+      },
+    });
+    let otherExtension = ExtensionTestUtils.loadExtension({
+      manifest: {
+        permissions: ["downloads"],
+      },
+      background: async function () {
+        browser.downloads.onChanged.addListener(delta => {
+          browser.test.assertEq(delta.state.current, "interrupted");
+          browser.test.sendMessage("done");
+        });
+        await browser.downloads.download({
+          url: "http://example.com/downloadtest",
+          filename: "example_from_other_ext_with_pref.txt",
+        });
+      },
+    });
+
+    await extension.startup();
+    await extension.awaitMessage("dnr_registered");
+    await otherExtension.startup();
+    await otherExtension.awaitMessage("done");
+    await otherExtension.unload();
+    await extension.unload();
+
+    Assert.equal(downloadReqCount, 0, "Did not expect any download requests");
+  }
+);
diff --git a/toolkit/components/extensions/test/xpcshell/test_ext_dnr_dynamic_rules.js b/toolkit/components/extensions/test/xpcshell/test_ext_dnr_dynamic_rules.js
new file mode 100644
index 0000000000..4ba120852f
--- /dev/null
+++ b/toolkit/components/extensions/test/xpcshell/test_ext_dnr_dynamic_rules.js
@@ -0,0 +1,1245 @@
+/* Any copyright is dedicated to the Public Domain.
+ * http://creativecommons.org/publicdomain/zero/1.0/ */
+
+"use strict";
+
+ChromeUtils.defineESModuleGetters(this, {
+  ExtensionDNR: "resource://gre/modules/ExtensionDNR.sys.mjs",
+  ExtensionDNRLimits: "resource://gre/modules/ExtensionDNRLimits.sys.mjs",
+  ExtensionDNRStore: "resource://gre/modules/ExtensionDNRStore.sys.mjs",
+  TestUtils: "resource://testing-common/TestUtils.sys.mjs",
+});
+
+AddonTestUtils.init(this);
+AddonTestUtils.overrideCertDB();
+AddonTestUtils.createAppInfo(
+  "xpcshell@tests.mozilla.org",
+  "XPCShell",
+  "1",
+  "43"
+);
+
+Services.scriptloader.loadSubScript(
+  Services.io.newFileURI(do_get_file("head_dnr.js")).spec,
+  this
+);
+
+const { promiseStartupManager, promiseRestartManager } = AddonTestUtils;
+
+const server = createHttpServer({ hosts: ["example.com"] });
+server.registerPathHandler("/", (req, res) => {
+  res.setHeader("Access-Control-Allow-Origin", "*");
+  res.write("response from server");
+});
+
+add_setup(async () => {
+  Services.prefs.setBoolPref("extensions.manifestV3.enabled", true);
+  Services.prefs.setBoolPref("extensions.dnr.enabled", true);
+  Services.prefs.setBoolPref("extensions.dnr.feedback", true);
+
+  setupTelemetryForTests();
+
+  await promiseStartupManager();
+});
+
+// This function is serialized and called in the context of the test extension's
+// background page. dnrTestUtils is passed to the background function.
+function makeDnrTestUtils() {
+  const dnrTestUtils = {};
+  const dnr = browser.declarativeNetRequest;
+
+  function serializeForLog(data) {
+    // JSON-stringify, but drop null values (replacing them with undefined
+    // causes JSON.stringify to drop them), so that optional keys with the null
+    // values are hidden.
+    let str = JSON.stringify(data, rep => rep ?? undefined);
+    return str;
+  }
+
+  async function testInvalidRule(rule, expectedError, isSchemaError) {
+    if (isSchemaError) {
+      // Schema validation error = thrown error instead of a rejection.
+      browser.test.assertThrows(
+        () => dnr.updateDynamicRules({ addRules: [rule] }),
+        expectedError,
+        `Rule should be invalid (schema-validated): ${serializeForLog(rule)}`
+      );
+    } else {
+      await browser.test.assertRejects(
+        dnr.updateDynamicRules({ addRules: [rule] }),
+        expectedError,
+        `Rule should be invalid: ${serializeForLog(rule)}`
+      );
+    }
+  }
+
+  Object.assign(dnrTestUtils, {
+    testInvalidRule,
+    serializeForLog,
+  });
+  return dnrTestUtils;
+}
+
+async function runAsDNRExtension({
+  background,
+  unloadTestAtEnd = true,
+  awaitFinish = false,
+  id = "test-dynamic-rules@test-extension",
+}) {
+  const testExtensionParams = {
+    background: `(${background})((${makeDnrTestUtils})())`,
+    useAddonManager: "permanent",
+    manifest: {
+      manifest_version: 3,
+      permissions: ["declarativeNetRequest", "declarativeNetRequestFeedback"],
+      browser_specific_settings: {
+        gecko: { id },
+      },
+    },
+  };
+  const extension = ExtensionTestUtils.loadExtension(testExtensionParams);
+  await extension.startup();
+  if (awaitFinish) {
+    await extension.awaitFinish();
+  }
+  if (unloadTestAtEnd) {
+    await extension.unload();
+  }
+  return { extension, testExtensionParams };
+}
+
+function callTestMessageHandler(extension, testMessage, ...args) {
+  extension.sendMessage(testMessage, ...args);
+  return extension.awaitMessage(`${testMessage}:done`);
+}
+
+add_task(async function test_dynamic_rule_registration() {
+  await runAsDNRExtension({
+    background: async () => {
+      const dnr = browser.declarativeNetRequest;
+
+      await dnr.updateDynamicRules({
+        addRules: [{ id: 1, condition: {}, action: { type: "block" } }],
+      });
+
+      const url = "https://example.com/some-dummy-url";
+      const type = "font";
+      browser.test.assertDeepEq(
+        { matchedRules: [{ ruleId: 1, rulesetId: "_dynamic" }] },
+        await dnr.testMatchOutcome({ url, type }),
+        "Dynamic rule matched after registration"
+      );
+
+      await dnr.updateDynamicRules({
+        removeRuleIds: [
+          1,
+          1234567890, // Invalid rules should be ignored.
+        ],
+        addRules: [{ id: 2, condition: {}, action: { type: "block" } }],
+      });
+      browser.test.assertDeepEq(
+        { matchedRules: [{ ruleId: 2, rulesetId: "_dynamic" }] },
+        await dnr.testMatchOutcome({ url, type }),
+        "Dynamic rule matched after update"
+      );
+
+      await dnr.updateDynamicRules({ removeRuleIds: [2] });
+      browser.test.assertDeepEq(
+        { matchedRules: [] },
+        await dnr.testMatchOutcome({ url, type }),
+        "Dynamic rule not matched after unregistration"
+      );
+
+      browser.test.notifyPass();
+    },
+  });
+});
+
+add_task(async function test_dynamic_rules_count_limits() {
+  await runAsDNRExtension({
+    unloadTestAtEnd: true,
+    awaitFinish: true,
+    background: async () => {
+      const dnr = browser.declarativeNetRequest;
+      const [dyamicRules, sessionRules] = await Promise.all([
+        dnr.getDynamicRules(),
+        dnr.getSessionRules(),
+      ]);
+
+      browser.test.assertDeepEq(
+        { session: [], dynamic: [] },
+        { session: sessionRules, dynamic: dyamicRules },
+        "Expect no session and no dynamic rules"
+      );
+
+      const { MAX_NUMBER_OF_DYNAMIC_AND_SESSION_RULES } = dnr;
+      const DUMMY_RULE = {
+        action: { type: "block" },
+        condition: { resourceTypes: ["main_frame"] },
+      };
+      const rules = [];
+      for (let i = 0; i < MAX_NUMBER_OF_DYNAMIC_AND_SESSION_RULES; i++) {
+        rules.push({ ...DUMMY_RULE, id: i + 1 });
+      }
+
+      await browser.test.assertRejects(
+        dnr.updateDynamicRules({
+          addRules: [
+            ...rules,
+            { ...DUMMY_RULE, id: MAX_NUMBER_OF_DYNAMIC_AND_SESSION_RULES + 1 },
+          ],
+        }),
+        `Number of rules in ruleset "_dynamic" exceeds MAX_NUMBER_OF_DYNAMIC_AND_SESSION_RULES.`,
+        "Got the expected rejection of exceeding the number of dynamic rules allowed"
+      );
+
+      await dnr.updateDynamicRules({
+        addRules: rules,
+      });
+      browser.test.assertEq(
+        5000,
+        (await dnr.getDynamicRules()).length,
+        "Got the expected number of dynamic rules stored"
+      );
+
+      await dnr.updateDynamicRules({
+        removeRuleIds: rules.map(r => r.id),
+      });
+
+      browser.test.assertEq(
+        0,
+        (await dnr.getDynamicRules()).length,
+        "All dynamic rules should have been removed"
+      );
+
+      browser.test.log(
+        "Verify rules count limits with multiple async API calls"
+      );
+
+      const [updateDynamicRulesSingle, updateDynamicRulesTooMany] =
+        await Promise.allSettled([
+          dnr.updateDynamicRules({
+            addRules: [
+              {
+                ...DUMMY_RULE,
+                id: MAX_NUMBER_OF_DYNAMIC_AND_SESSION_RULES + 1,
+              },
+            ],
+          }),
+          dnr.updateDynamicRules({ addRules: rules }),
+        ]);
+
+      browser.test.assertDeepEq(
+        updateDynamicRulesSingle,
+        { status: "fulfilled", value: undefined },
+        "Expect the first updateDynamicRules call to be successful"
+      );
+
+      await browser.test.assertRejects(
+        updateDynamicRulesTooMany?.status === "rejected"
+          ? Promise.reject(updateDynamicRulesTooMany.reason)
+          : Promise.resolve(),
+        `Number of rules in ruleset "_dynamic" exceeds MAX_NUMBER_OF_DYNAMIC_AND_SESSION_RULES.`,
+        "Got the expected rejection on the second call exceeding the number of dynamic rules allowed"
+      );
+
+      browser.test.assertDeepEq(
+        (await dnr.getDynamicRules()).map(rule => rule.id),
+        [MAX_NUMBER_OF_DYNAMIC_AND_SESSION_RULES + 1],
+        "Got the expected dynamic rules"
+      );
+
+      await dnr.updateDynamicRules({
+        removeRuleIds: [MAX_NUMBER_OF_DYNAMIC_AND_SESSION_RULES + 1],
+      });
+
+      const [updateSessionResult, updateDynamicResult] =
+        await Promise.allSettled([
+          dnr.updateSessionRules({ addRules: rules }),
+          dnr.updateDynamicRules({ addRules: rules }),
+        ]);
+
+      browser.test.assertDeepEq(
+        updateDynamicResult,
+        { status: "fulfilled", value: undefined },
+        "Expect the number of dynamic rules to be still allowed, despite the session rule added"
+      );
+
+      // NOTE: In this test we do not exceed the quota of session rules. The
+      // updateSessionRules call here is to verify that the quota of session and
+      // dynamic rules are separate. The limits for session rules are tested
+      // by session_rules_total_rule_limit in test_ext_dnr_session_rules.js.
+      browser.test.assertDeepEq(
+        updateSessionResult,
+        { status: "fulfilled", value: undefined },
+        "Got expected success from the updateSessionRules request"
+      );
+
+      browser.test.assertDeepEq(
+        { sessionRulesCount: 5000, dynamicRulesCount: 5000 },
+        {
+          sessionRulesCount: (await dnr.getSessionRules()).length,
+          dynamicRulesCount: (await dnr.getDynamicRules()).length,
+        },
+        "Got expected session and dynamic rules counts"
+      );
+
+      browser.test.notifyPass();
+    },
+  });
+});
+
+add_task(async function test_stored_dynamic_rules_exceeding_limits() {
+  const { extension } = await runAsDNRExtension({
+    unloadTestAtEnd: false,
+    awaitFinish: false,
+    background: async () => {
+      const dnr = browser.declarativeNetRequest;
+
+      browser.test.onMessage.addListener(async (msg, ...args) => {
+        switch (msg) {
+          case "createDynamicRules": {
+            const [{ updateRuleOptions }] = args;
+            await dnr.updateDynamicRules(updateRuleOptions);
+            break;
+          }
+          case "assertGetDynamicRulesCount": {
+            const [{ expectedRulesCount }] = args;
+            browser.test.assertEq(
+              expectedRulesCount,
+              (await dnr.getDynamicRules()).length,
+              "getDynamicRules() resolves to the expected number of dynamic rules"
+            );
+            break;
+          }
+          default:
+            browser.test.fail(
+              `Got unexpected unhandled test message: "${msg}"`
+            );
+            break;
+        }
+        browser.test.sendMessage(`${msg}:done`);
+      });
+      browser.test.sendMessage("bgpage:ready");
+    },
+  });
+
+  const initialRules = [getDNRRule({ id: 1 })];
+  await extension.awaitMessage("bgpage:ready");
+  await callTestMessageHandler(extension, "createDynamicRules", {
+    updateRuleOptions: { addRules: initialRules },
+  });
+  await callTestMessageHandler(extension, "assertGetDynamicRulesCount", {
+    expectedRulesCount: 1,
+  });
+
+  const extUUID = extension.uuid;
+  const dnrStore = ExtensionDNRStore._getStoreForTesting();
+  await dnrStore._savePromises.get(extUUID);
+  const { storeFile } = dnrStore.getFilePaths(extUUID);
+
+  await extension.addon.disable();
+
+  ok(
+    !dnrStore._dataPromises.has(extUUID),
+    "DNR store read data promise cleared after the extension has been disabled"
+  );
+  ok(
+    !dnrStore._data.has(extUUID),
+    "DNR store data cleared from memory after the extension has been disabled"
+  );
+
+  ok(await IOUtils.exists(storeFile), `DNR storeFile ${storeFile} found`);
+  const dnrDataFromFile = await IOUtils.readJSON(storeFile, {
+    decompress: true,
+  });
+
+  const { MAX_NUMBER_OF_DYNAMIC_AND_SESSION_RULES } = ExtensionDNRLimits;
+
+  const expectedDynamicRules = [];
+  const unexpectedDynamicRules = [];
+
+  for (let i = 0; i < MAX_NUMBER_OF_DYNAMIC_AND_SESSION_RULES + 5; i++) {
+    const rule = getDNRRule({ id: i + 1 });
+    if (i < MAX_NUMBER_OF_DYNAMIC_AND_SESSION_RULES) {
+      expectedDynamicRules.push(rule);
+    } else {
+      unexpectedDynamicRules.push(rule);
+    }
+  }
+
+  const tooManyDynamicRules = [
+    ...expectedDynamicRules,
+    ...unexpectedDynamicRules,
+  ];
+
+  const dnrDataNew = {
+    schemaVersion: dnrDataFromFile.schemaVersion,
+    extVersion: extension.extension.version,
+    staticRulesets: [],
+    dynamicRuleset: getSchemaNormalizedRules(extension, tooManyDynamicRules),
+  };
+
+  await IOUtils.writeJSON(storeFile, dnrDataNew, { compress: true });
+
+  const { messages } = await AddonTestUtils.promiseConsoleOutput(async () => {
+    await extension.addon.enable();
+    await extension.awaitMessage("bgpage:ready");
+  });
+
+  await callTestMessageHandler(extension, "assertGetDynamicRulesCount", {
+    expectedRulesCount: 0,
+  });
+
+  AddonTestUtils.checkMessages(messages, {
+    expected: [
+      {
+        message: new RegExp(
+          `Ignoring dynamic ruleset in extension "${extension.id}" because: Number of rules in ruleset "_dynamic" exceeds MAX_NUMBER_OF_DYNAMIC_AND_SESSION_RULES`
+        ),
+      },
+    ],
+  });
+
+  await extension.unload();
+});
+
+add_task(async function test_save_and_load_dynamic_rules() {
+  let { extension, testExtensionParams } = await runAsDNRExtension({
+    unloadTestAtEnd: false,
+    awaitFinish: false,
+    background: async dnrTestUtils => {
+      const dnr = browser.declarativeNetRequest;
+
+      browser.test.onMessage.addListener(async (msg, ...args) => {
+        switch (msg) {
+          case "assertGetDynamicRules": {
+            const [{ expectedRules }] = args;
+            browser.test.assertDeepEq(
+              expectedRules,
+              await dnr.getDynamicRules(),
+              "getDynamicRules() resolves to the expected dynamic rules"
+            );
+            break;
+          }
+          case "testUpdateDynamicRules": {
+            const [{ updateRulesRequests, expectedRules }] = args;
+            const promiseResults = await Promise.allSettled(
+              updateRulesRequests.map(updateRuleOptions =>
+                dnr.updateDynamicRules(updateRuleOptions)
+              )
+            );
+
+            // All calls should have been resolved successfully.
+            for (const [i, request] of updateRulesRequests.entries()) {
+              browser.test.assertDeepEq(
+                { status: "fulfilled", value: undefined },
+                promiseResults[i],
+                `Expect resolved updateDynamicRules request for ${dnrTestUtils.serializeForLog(
+                  request
+                )}`
+              );
+            }
+
+            browser.test.assertDeepEq(
+              expectedRules,
+              await dnr.getDynamicRules(),
+              "getDynamicRules resolves to the expected updated dynamic rules"
+            );
+            break;
+          }
+          case "testInvalidDynamicAddRule": {
+            const [{ rule, expectedError, isSchemaError, isErrorRegExp }] =
+              args;
+            await dnrTestUtils.testInvalidRule(
+              rule,
+              expectedError,
+              isSchemaError,
+              isErrorRegExp
+            );
+            break;
+          }
+          default:
+            browser.test.fail(
+              `Got unexpected unhandled test message: "${msg}"`
+            );
+            break;
+        }
+
+        browser.test.sendMessage(`${msg}:done`);
+      });
+
+      browser.test.sendMessage("bgpage:ready");
+    },
+  });
+
+  await extension.awaitMessage("bgpage:ready");
+  await callTestMessageHandler(extension, "assertGetDynamicRules", {
+    expectedRules: [],
+  });
+
+  const rules = [
+    getDNRRule({
+      id: 1,
+      action: { type: "allow" },
+      condition: { resourceTypes: ["main_frame"] },
+    }),
+    getDNRRule({
+      id: 2,
+      action: { type: "block" },
+      condition: { resourceTypes: ["main_frame", "script"] },
+    }),
+  ];
+
+  info("Verify updateDynamicRules adding new valid rules");
+  // Send two concurrent API requests, the first one adds 3 rules and the second
+  // one removing a rule defined in the first call, the result of the combined
+  // API calls is expected to only store 2 dynamic rules in the DNR store.
+  await callTestMessageHandler(extension, "testUpdateDynamicRules", {
+    updateRulesRequests: [
+      { addRules: [...rules, getDNRRule({ id: 3 })] },
+      { removeRuleIds: [3] },
+    ],
+    expectedRules: getSchemaNormalizedRules(extension, rules),
+  });
+
+  const extUUID = extension.uuid;
+  const dnrStore = ExtensionDNRStore._getStoreForTesting();
+  await dnrStore._savePromises.get(extUUID);
+  const { storeFile } = dnrStore.getFilePaths(extUUID);
+  const dnrDataFromFile = await IOUtils.readJSON(storeFile, {
+    decompress: true,
+  });
+
+  Assert.deepEqual(
+    dnrDataFromFile.dynamicRuleset,
+    getSchemaNormalizedRules(extension, rules),
+    "Got the expected rules stored on disk"
+  );
+
+  info("Verify updateDynamicRules rejects on new invalid rules");
+  await callTestMessageHandler(extension, "testInvalidDynamicAddRule", {
+    rule: rules[0],
+    expectedError: "Duplicate rule ID: 1",
+    isSchemaError: false,
+  });
+
+  await callTestMessageHandler(extension, "testInvalidDynamicAddRule", {
+    rule: getDNRRule({ action: { type: "invalid-action" } }),
+    expectedError:
+      /addRules.0.action.type: Invalid enumeration value "invalid-action"/,
+    isSchemaError: true,
+  });
+
+  info("Expect dynamic rules to not have been changed");
+  await callTestMessageHandler(extension, "assertGetDynamicRules", {
+    expectedRules: getSchemaNormalizedRules(extension, rules),
+  });
+
+  Assert.deepEqual(
+    dnrStore._data.get(extUUID).dynamicRuleset,
+    getSchemaNormalizedRules(extension, rules),
+    "Got the expected dynamic rules in the DNR store"
+  );
+
+  info("Verify dynamic rules loaded back from disk on addon restart");
+  ok(await IOUtils.exists(storeFile), `DNR storeFile ${storeFile} found`);
+
+  // force deleting the data stored in memory to confirm if it being loaded again from
+  // the files stored on disk.
+  dnrStore._data.delete(extUUID);
+  dnrStore._dataPromises.delete(extUUID);
+
+  const { addon } = extension;
+  await addon.disable();
+
+  ok(
+    !dnrStore._dataPromises.has(extUUID),
+    "DNR store read data promise cleared after the extension has been disabled"
+  );
+  ok(
+    !dnrStore._data.has(extUUID),
+    "DNR store data cleared from memory after the extension has been disabled"
+  );
+
+  await addon.enable();
+  await extension.awaitMessage("bgpage:ready");
+
+  info("Expect dynamic rules to have been loaded back");
+  await callTestMessageHandler(extension, "assertGetDynamicRules", {
+    expectedRules: getSchemaNormalizedRules(extension, rules),
+  });
+
+  Assert.deepEqual(
+    dnrStore._data.get(extUUID).dynamicRuleset,
+    getSchemaNormalizedRules(extension, rules),
+    "Got the expected dynamic rules loaded back from the DNR store after addon restart"
+  );
+
+  info("Verify dynamic rules loaded back as expected on AOM restart");
+  dnrStore._data.delete(extUUID);
+  dnrStore._dataPromises.delete(extUUID);
+
+  // NOTE: promiseRestartManager will not be enough to make sure the
+  // DNR store data for the test extension is going to be loaded from
+  // the DNR startup cache file.
+  // See test_ext_dnr_startup_cache.js for a test case that more completely
+  // simulates ExtensionDNRStore initialization on browser restart.
+  await promiseRestartManager();
+
+  await extension.awaitStartup();
+  await extension.awaitMessage("bgpage:ready");
+
+  await callTestMessageHandler(extension, "assertGetDynamicRules", {
+    expectedRules: getSchemaNormalizedRules(extension, rules),
+  });
+
+  // Verify the dynamic rules are converted back into Rule class instances
+  // as expected when loaded back from the DNR store file
+  Assert.ok(
+    !!dnrStore._data.get(extUUID).dynamicRuleset.length,
+    "Expected dynamic rules to have been loaded back from the DNR store file"
+  );
+  Assert.deepEqual(
+    dnrStore._data
+      .get(extUUID)
+      .dynamicRuleset.filter(rule => rule.constructor.name !== "Rule"),
+    [],
+    "Expect dynamic rules loaded back from the DNR store file to be converted to Rule class instances"
+  );
+
+  Assert.deepEqual(
+    dnrStore._data.get(extUUID).dynamicRuleset,
+    getSchemaNormalizedRules(extension, rules),
+    "Got the expected dynamic rules loaded back from the DNR store after AOM restart"
+  );
+
+  info(
+    "Verify updateDynamicRules adding new valid rules and remove one of the existing"
+  );
+  // Expect the first rule to be removed and a new one being added.
+  const newRule3 = getDNRRule({
+    id: 3,
+    action: { type: "allow" },
+    condition: { resourceTypes: ["main_frame"] },
+  });
+  const updatedRules = [rules[1], newRule3];
+
+  await callTestMessageHandler(extension, "testUpdateDynamicRules", {
+    updateRulesRequests: [{ addRules: [newRule3], removeRuleIds: [1] }],
+    expectedRules: getSchemaNormalizedRules(extension, updatedRules),
+  });
+
+  info("Verify dynamic rules preserved across addon updates");
+
+  const staticRules = [
+    getDNRRule({
+      id: 4,
+      action: { type: "block" },
+      condition: { resourceTypes: ["xmlhttprequest"] },
+    }),
+  ];
+  await extension.upgrade({
+    ...testExtensionParams,
+    manifest: {
+      ...testExtensionParams.manifest,
+      version: "2.0",
+      declarative_net_request: {
+        rule_resources: [
+          {
+            id: "ruleset_1",
+            enabled: true,
+            path: "ruleset_1.json",
+          },
+        ],
+      },
+    },
+    files: { "ruleset_1.json": JSON.stringify(staticRules) },
+  });
+  await extension.awaitMessage("bgpage:ready");
+
+  await callTestMessageHandler(extension, "assertGetDynamicRules", {
+    expectedRules: getSchemaNormalizedRules(extension, updatedRules),
+  });
+
+  info(
+    "Verify static rules included in the new addon version have been loaded"
+  );
+
+  await assertDNRStoreData(dnrStore, extension, {
+    ruleset_1: getSchemaNormalizedRules(extension, staticRules),
+  });
+
+  info("Verify rules after extension downgrade");
+  await extension.upgrade({
+    ...testExtensionParams,
+    manifest: {
+      ...testExtensionParams.manifest,
+      version: "1.0",
+    },
+  });
+  await extension.awaitMessage("bgpage:ready");
+
+  info("Verify stored dynamic rules are unchanged");
+
+  await callTestMessageHandler(extension, "assertGetDynamicRules", {
+    expectedRules: getSchemaNormalizedRules(extension, updatedRules),
+  });
+
+  info(
+    "Verify static rules included in the new addon version are cleared on downgrade to previous version"
+  );
+  await assertDNRStoreData(dnrStore, extension, {});
+
+  info("Verify rules after extension upgrade to one without DNR permissions");
+  await extension.upgrade({
+    ...testExtensionParams,
+    manifest: {
+      ...testExtensionParams.manifest,
+      permissions: [],
+      version: "1.1",
+    },
+    background: async () => {
+      browser.test.assertEq(
+        browser.declarativeNetRequest,
+        undefined,
+        "Expect DNR API namespace to not be available"
+      );
+      browser.test.sendMessage("bgpage:ready");
+    },
+  });
+  await extension.awaitMessage("bgpage:ready");
+  ok(
+    !dnrStore._dataPromises.has(extension.uuid),
+    "Expect dnrStore to not have any promise for the extension DNR data being loaded"
+  );
+  ok(
+    !ExtensionDNR.getRuleManager(
+      extension.extension,
+      false /* createIfMissing */
+    ),
+    "Expect no ruleManager found for the extenson"
+  );
+
+  info(
+    "Verify rules are loaded back after upgrading again to one with DNR permissions"
+  );
+  await extension.upgrade({
+    ...testExtensionParams,
+    manifest: {
+      ...testExtensionParams.manifest,
+      version: "1.2",
+    },
+  });
+  await extension.awaitMessage("bgpage:ready");
+
+  // NOTE: To make sure that the test extension rule manager is removed
+  // on the extension shutdown also when the declarativeNetRequest
+  // ExtensionAPI class instance has not been created at all, this part
+  // on the test is purposely not calling any declarativeNetRequest API method
+  // not calling ExtensionDNR.ensureInitialized, instead we wait for the
+  // RuleManager instance to be created and then we disable the
+  // test extension and assert that the RuleManager has been cleared.
+  let ruleManager = await TestUtils.waitForCondition(
+    () =>
+      ExtensionDNR.getRuleManager(
+        extension.extension,
+        /* createIfMissing= */ false
+      ),
+    "Wait for the test extension RuleManager to have neem created"
+  );
+  Assert.ok(ruleManager, "Rule manager exists before unload");
+  Assert.deepEqual(
+    ruleManager.getDynamicRules(),
+    getSchemaNormalizedRules(extension, updatedRules),
+    "Found the expected dynamic rules in the Rule manager"
+  );
+  await extension.addon.disable();
+  Assert.ok(
+    !ExtensionDNR.getRuleManager(
+      extension.extension,
+      /* createIfMissing= */ false
+    ),
+    "Rule manager erased after unload"
+  );
+
+  await extension.addon.enable();
+  await extension.awaitMessage("bgpage:ready");
+  await callTestMessageHandler(extension, "assertGetDynamicRules", {
+    expectedRules: getSchemaNormalizedRules(extension, updatedRules),
+  });
+
+  info("Verify dynamic rules updates after corrupted storage");
+
+  async function testLoadedRulesAfterDataCorruption({
+    name,
+    asyncWriteStoreFile,
+    expectedCorruptFile,
+  }) {
+    info(`Tampering DNR store data: ${name}`);
+
+    await extension.addon.disable();
+    Assert.ok(
+      !ExtensionDNR.getRuleManager(
+        extension.extension,
+        /* createIfMissing= */ false
+      ),
+      "Rule manager erased after unload"
+    );
+
+    ok(
+      !dnrStore._dataPromises.has(extUUID),
+      "DNR store read data promise cleared after the extension has been disabled"
+    );
+    ok(
+      !dnrStore._data.has(extUUID),
+      "DNR store data cleared from memory after the extension has been disabled"
+    );
+
+    await asyncWriteStoreFile();
+
+    await extension.addon.enable();
+    await extension.awaitMessage("bgpage:ready");
+
+    await TestUtils.waitForCondition(
+      () => IOUtils.exists(`${expectedCorruptFile}`),
+      `Wait for the "${expectedCorruptFile}" file to have been created`
+    );
+
+    ok(
+      !(await IOUtils.exists(storeFile)),
+      "Corrupted store file expected to be removed"
+    );
+
+    await callTestMessageHandler(extension, "assertGetDynamicRules", {
+      expectedRules: [],
+    });
+
+    const newRules = [getDNRRule({ id: 3 })];
+    const expectedRules = getSchemaNormalizedRules(extension, newRules);
+    await callTestMessageHandler(extension, "testUpdateDynamicRules", {
+      updateRulesRequests: [{ addRules: newRules }],
+      expectedRules,
+    });
+
+    await TestUtils.waitForCondition(
+      () => IOUtils.exists(storeFile),
+      `Wait for the "${storeFile}" file to have been created`
+    );
+
+    const newData = await IOUtils.readJSON(storeFile, { decompress: true });
+    Assert.deepEqual(
+      newData.dynamicRuleset,
+      expectedRules,
+      "Expect the new rules to have been stored on disk"
+    );
+  }
+
+  await testLoadedRulesAfterDataCorruption({
+    name: "invalid lz4 header",
+    asyncWriteStoreFile: () =>
+      IOUtils.writeUTF8(storeFile, "not an lz4 compressed file", {
+        compress: false,
+      }),
+    expectedCorruptFile: `${storeFile}.corrupt`,
+  });
+
+  await testLoadedRulesAfterDataCorruption({
+    name: "invalid json data",
+    asyncWriteStoreFile: () =>
+      IOUtils.writeUTF8(storeFile, "invalid json data", { compress: true }),
+    expectedCorruptFile: `${storeFile}-1.corrupt`,
+  });
+
+  await testLoadedRulesAfterDataCorruption({
+    name: "empty json data",
+    asyncWriteStoreFile: () =>
+      IOUtils.writeUTF8(storeFile, "{}", { compress: true }),
+    expectedCorruptFile: `${storeFile}-2.corrupt`,
+  });
+
+  await testLoadedRulesAfterDataCorruption({
+    name: "invalid staticRulesets property type",
+    asyncWriteStoreFile: () =>
+      IOUtils.writeUTF8(
+        storeFile,
+        JSON.stringify({
+          schemaVersion: dnrDataFromFile.schemaVersion,
+          extVersion: extension.extension.version,
+          staticRulesets: "Not an array",
+        }),
+        { compress: true }
+      ),
+    expectedCorruptFile: `${storeFile}-3.corrupt`,
+  });
+
+  await testLoadedRulesAfterDataCorruption({
+    name: "invalid dynamicRuleset property type",
+    asyncWriteStoreFile: () =>
+      IOUtils.writeUTF8(
+        storeFile,
+        JSON.stringify({
+          schemaVersion: dnrDataFromFile.schemaVersion,
+          extVersion: extension.extension.version,
+          staticRulesets: [],
+          dynamicRuleset: "Not an array",
+        }),
+        { compress: true }
+      ),
+    expectedCorruptFile: `${storeFile}-4.corrupt`,
+  });
+
+  await extension.unload();
+});
+
+add_task(async function test_tabId_conditions_invalid_in_dynamic_rules() {
+  await runAsDNRExtension({
+    unloadTestAtEnd: true,
+    awaitFinish: true,
+    background: async dnrTestUtils => {
+      await dnrTestUtils.testInvalidRule(
+        { id: 1, action: { type: "block" }, condition: { tabIds: [1] } },
+        "tabIds and excludedTabIds can only be specified in session rules"
+      );
+      await dnrTestUtils.testInvalidRule(
+        {
+          id: 1,
+          action: { type: "block" },
+          condition: { excludedTabIds: [1] },
+        },
+        "tabIds and excludedTabIds can only be specified in session rules"
+      );
+      browser.test.assertDeepEq(
+        [],
+        await browser.declarativeNetRequest.getDynamicRules(),
+        "Expect the invalid rules to not be enabled"
+      );
+      browser.test.notifyPass();
+    },
+  });
+});
+
+add_task(async function test_dynamic_rules_telemetry() {
+  resetTelemetryData();
+
+  let { extension } = await runAsDNRExtension({
+    unloadTestAtEnd: false,
+    awaitFinish: false,
+    id: "test-dynamic-rules-telemetry@test-extension",
+    background: () => {
+      const dnr = browser.declarativeNetRequest;
+
+      browser.test.onMessage.addListener(async (msg, ...args) => {
+        switch (msg) {
+          case "getDynamicRules": {
+            browser.test.sendMessage(
+              `${msg}:done`,
+              await dnr.getDynamicRules()
+            );
+            break;
+          }
+          case "updateDynamicRules": {
+            const { addRules, removeRuleIds } = args[0];
+            await dnr.updateDynamicRules({
+              addRules,
+              removeRuleIds,
+            });
+            browser.test.sendMessage(
+              `${msg}:done`,
+              await dnr.getDynamicRules()
+            );
+            break;
+          }
+          default: {
+            browser.test.fail(`Unexpected test message: ${msg}`);
+            browser.test.sendMessage(`${msg}:done`);
+            break;
+          }
+        }
+      });
+      browser.test.sendMessage("bgpage:ready");
+    },
+  });
+
+  await extension.awaitMessage("bgpage:ready");
+
+  extension.sendMessage("getDynamicRules");
+  Assert.deepEqual(
+    await extension.awaitMessage("getDynamicRules:done"),
+    [],
+    "Expect no dynamic DNR rules"
+  );
+
+  assertDNRTelemetryMetricsNoSamples(
+    [
+      {
+        metric: "validateRulesTime",
+        mirroredName: "WEBEXT_DNR_VALIDATE_RULES_MS",
+        mirroredType: "histogram",
+      },
+    ],
+    "before test extension have been loaded"
+  );
+
+  const dynamicRules = [
+    getDNRRule({
+      id: 1,
+      action: { type: "block" },
+      condition: {
+        resourceTypes: ["xmlhttprequest"],
+        requestDomains: ["example.com"],
+      },
+    }),
+    getDNRRule({
+      id: 2,
+      action: { type: "block" },
+      condition: {
+        resourceTypes: ["xmlhttprequest"],
+        requestDomains: ["example.org"],
+      },
+    }),
+  ];
+
+  await extension.sendMessage("updateDynamicRules", {
+    addRules: dynamicRules,
+  });
+
+  Assert.deepEqual(
+    await extension.awaitMessage("updateDynamicRules:done"),
+    getSchemaNormalizedRules(extension, dynamicRules),
+    "Expect new dynamic DNR rules to have been added"
+  );
+
+  assertDNRTelemetryMetricsNoSamples(
+    [
+      {
+        metric: "validateRulesTime",
+        mirroredName: "WEBEXT_DNR_VALIDATE_RULES_MS",
+        mirroredType: "histogram",
+      },
+    ],
+    "no additional rule validation expected for dynamic rules pre-validated on a updateDynamicRules API call"
+  );
+
+  extension.sendMessage("updateDynamicRules", {
+    removeRuleIds: [dynamicRules[1].id],
+  });
+
+  Assert.deepEqual(
+    await extension.awaitMessage("updateDynamicRules:done"),
+    getSchemaNormalizedRules(extension, [dynamicRules[0]]),
+    `Expect dynamic DNR rule with id ${dynamicRules[1].id} to have been removed`
+  );
+
+  assertDNRTelemetryMetricsNoSamples(
+    [
+      {
+        metric: "validateRulesTime",
+        mirroredName: "WEBEXT_DNR_VALIDATE_RULES_MS",
+        mirroredType: "histogram",
+      },
+    ],
+    "no additional rule validation expected for dynamic rules removed by a updateDynamicRules API call"
+  );
+
+  info("Disabling test extension");
+  await extension.addon.disable();
+
+  assertDNRTelemetryMetricsNoSamples(
+    [
+      {
+        metric: "validateRulesTime",
+        mirroredName: "WEBEXT_DNR_VALIDATE_RULES_MS",
+        mirroredType: "histogram",
+      },
+    ],
+    "no rule validation hit after disabling the extension"
+  );
+
+  info("Re-enabling test extension");
+  await extension.addon.enable();
+  await extension.awaitMessage("bgpage:ready");
+  info(
+    "Wait for DNR initialization completed for the re-enabled permanently installed extension"
+  );
+  await ExtensionDNR.ensureInitialized(extension.extension);
+
+  assertDNRTelemetryMetricsSamplesCount(
+    [
+      {
+        metric: "validateRulesTime",
+        mirroredName: "WEBEXT_DNR_VALIDATE_RULES_MS",
+        mirroredType: "histogram",
+        expectedSamplesCount: 1,
+      },
+    ],
+    "expected rule validation to be hit on re-loading dynamic rules from DNR store file"
+  );
+  assertDNRTelemetryMetricsNoSamples(
+    [
+      // Expected no startup cache file to be loaded or used on re-enabling a disabled extension.
+      {
+        metric: "startupCacheReadSize",
+        mirroredName: "WEBEXT_DNR_STARTUPCACHE_READ_BYTES",
+        mirroredType: "histogram",
+      },
+      {
+        metric: "startupCacheReadTime",
+        mirroredName: "WEBEXT_DNR_STARTUPCACHE_READ_MS",
+        mirroredType: "histogram",
+      },
+    ],
+    "on loading dnr rules for newly installed extension"
+  );
+
+  info("Verify evaluateRulesCountMax telemetry probe");
+
+  assertDNRTelemetryMetricsNoSamples(
+    [
+      {
+        metric: "evaluateRulesTime",
+        mirroredName: "WEBEXT_DNR_EVALUATE_RULES_MS",
+        mirroredType: "histogram",
+      },
+      {
+        metric: "evaluateRulesCountMax",
+        mirroredName: "extensions.apis.dnr.evaluate_rules_count_max",
+        mirroredType: "scalar",
+      },
+    ],
+    "before any request have been intercepted"
+  );
+
+  Assert.equal(
+    await fetch("http://example.com/").then(res => res.text()),
+    "response from server",
+    "DNR should not block system requests"
+  );
+
+  assertDNRTelemetryMetricsNoSamples(
+    [
+      {
+        metric: "evaluateRulesTime",
+        mirroredName: "WEBEXT_DNR_EVALUATE_RULES_MS",
+        mirroredType: "histogram",
+      },
+      {
+        metric: "evaluateRulesCountMax",
+        mirroredName: "extensions.apis.dnr.evaluate_rules_count_max",
+        mirroredType: "scalar",
+      },
+    ],
+    "after restricted request have been intercepted (but no rules evaluated)"
+  );
+
+  const page = await ExtensionTestUtils.loadContentPage("http://example.com");
+  const callPageFetch = async () => {
+    Assert.equal(
+      await page.spawn([], () => {
+        return this.content.fetch("http://example.com/").then(
+          res => res.text(),
+          err => err.message
+        );
+      }),
+      "NetworkError when attempting to fetch resource.",
+      "DNR should have blocked test request to example.com"
+    );
+  };
+
+  // Expect one sample recorded on evaluating rules for the
+  // top level navigation.
+  let expectedEvaluateRulesTimeSamples = 1;
+  assertDNRTelemetryMetricsSamplesCount(
+    [
+      {
+        metric: "evaluateRulesTime",
+        mirroredName: "WEBEXT_DNR_EVALUATE_RULES_MS",
+        mirroredType: "histogram",
+        expectedSamplesCount: expectedEvaluateRulesTimeSamples,
+      },
+    ],
+    "evaluateRulesTime should be collected after evaluated rulesets"
+  );
+  // Expect same number of rules currently included in the dynamic ruleset.
+  let expectedEvaluateRulesCountMax = 1;
+  assertDNRTelemetryMetricsGetValueEq(
+    [
+      {
+        metric: "evaluateRulesCountMax",
+        mirroredName: "extensions.apis.dnr.evaluate_rules_count_max",
+        mirroredType: "scalar",
+        expectedGetValue: expectedEvaluateRulesCountMax,
+      },
+    ],
+    "evaluateRulesCountMax should be collected after evaluated dynamic rulesets"
+  );
+
+  extension.sendMessage("updateDynamicRules", {
+    addRules: [dynamicRules[1]],
+  });
+
+  Assert.deepEqual(
+    await extension.awaitMessage("updateDynamicRules:done"),
+    getSchemaNormalizedRules(extension, dynamicRules),
+    `Expect second dynamic DNR rules to have been added`
+  );
+
+  await callPageFetch();
+
+  // Expect one new sample reported on evaluating rules for the
+  // first fetch request originated from the test page.
+  expectedEvaluateRulesTimeSamples += 1;
+  assertDNRTelemetryMetricsSamplesCount(
+    [
+      {
+        metric: "evaluateRulesTime",
+        mirroredName: "WEBEXT_DNR_EVALUATE_RULES_MS",
+        mirroredType: "histogram",
+        expectedSamplesCount: expectedEvaluateRulesTimeSamples,
+      },
+    ],
+    "evaluateRulesTime should be collected after evaluated rulesets"
+  );
+
+  // Expect new number of rules currently included in the dynamic ruleset.
+  expectedEvaluateRulesCountMax = dynamicRules.length;
+  assertDNRTelemetryMetricsGetValueEq(
+    [
+      {
+        metric: "evaluateRulesCountMax",
+        mirroredName: "extensions.apis.dnr.evaluate_rules_count_max",
+        mirroredType: "scalar",
+        expectedGetValue: expectedEvaluateRulesCountMax,
+      },
+    ],
+    "evaluateRulesCountMax should be increased after evaluated two dynamic rules"
+  );
+
+  extension.sendMessage("updateDynamicRules", {
+    removeRuleIds: [dynamicRules[1].id],
+  });
+
+  await callPageFetch();
+
+  Assert.deepEqual(
+    await extension.awaitMessage("updateDynamicRules:done"),
+    getSchemaNormalizedRules(extension, [dynamicRules[0]]),
+    `Expect only first dynamic DNR rule to have be available`
+  );
+
+  assertDNRTelemetryMetricsGetValueEq(
+    [
+      {
+        metric: "evaluateRulesCountMax",
+        mirroredName: "extensions.apis.dnr.evaluate_rules_count_max",
+        mirroredType: "scalar",
+        expectedGetValue: expectedEvaluateRulesCountMax,
+      },
+    ],
+    "evaluateRulesCountMax should NOT be decreased after removing one dynamic rules"
+  );
+
+  await page.close();
+
+  await extension.unload();
+});
diff --git a/toolkit/components/extensions/test/xpcshell/test_ext_dnr_modifyHeaders.js b/toolkit/components/extensions/test/xpcshell/test_ext_dnr_modifyHeaders.js
new file mode 100644
index 0000000000..236cda4e37
--- /dev/null
+++ b/toolkit/components/extensions/test/xpcshell/test_ext_dnr_modifyHeaders.js
@@ -0,0 +1,1072 @@
+"use strict";
+
+const server = createHttpServer({
+  hosts: ["dummy", "restricted", "yes", "no", "maybe", "cookietest"],
+});
+server.registerPathHandler("/echoheaders", (req, res) => {
+  res.setHeader("Content-Type", "application/json");
+  const headers = Object.create(null);
+  for (const nameSupports of req.headers) {
+    const name = nameSupports.QueryInterface(Ci.nsISupportsString).data;
+    // httpd.js automatically concats headers with ",", but in some cases it
+    // stores them separately, joined with "\n".
+    // https://searchfox.org/mozilla-central/rev/c1180ea13e73eb985a49b15c0d90e977a1aa919c/netwerk/test/httpserver/httpd.js#5271-5286
+    const values = req.getHeader(name).split("\n");
+    headers[name] = values.length === 1 ? values[0] : values;
+  }
+
+  // Only keep custom headers, so that the test expectations does not have to
+  // enumerate all headers of interest.
+  function dropDefaultHeader(name) {
+    if (!(name in headers)) {
+      Assert.ok(false, `Header unexpectedly not found: ${name}`);
+    }
+    delete headers[name];
+  }
+  dropDefaultHeader("host");
+  dropDefaultHeader("user-agent");
+  dropDefaultHeader("accept");
+  dropDefaultHeader("accept-language");
+  dropDefaultHeader("accept-encoding");
+  dropDefaultHeader("connection");
+
+  res.write(JSON.stringify(headers));
+});
+
+server.registerPathHandler("/host", (req, res) => {
+  res.write(req.getHeader("Host"));
+});
+
+server.registerPathHandler("/csptest", (req, res) => {
+  res.setHeader("Access-Control-Allow-Origin", "*");
+  res.write("EXPECTED_RESPONSE_FOR /csp test");
+});
+server.registerPathHandler("/csp", (req, res) => {
+  // Inserting the ";" just in case something somehow merges the headers by ","
+  // (e.g. to "bla,; default-src http://yes http://maybe ;,bla").
+  // This ensures that the server-set "default-src" CSP is not somehow mangled.
+  res.setHeader(
+    "Content-Security-Policy",
+    "; default-src http://yes http://maybe ;"
+  );
+});
+
+server.registerPathHandler("/responseheadersFixture", (req, res) => {
+  res.setHeader("a", "server_a");
+  res.setHeader("b", "server_b");
+  res.setHeader("c", "server_c");
+  res.setHeader("d", "server_d");
+  res.setHeader("e", "server_e");
+  // www-authenticate and proxy-authenticate are among the few headers where
+  // the test server (httpd.js) allows multiple header lines instead of
+  // automatically concatenating them with ",":
+  // https://searchfox.org/mozilla-central/rev/a4a41aafa80bf38f6e456238a60781fed46f9d08/netwerk/test/httpserver/httpd.js#5280
+  res.setHeader("www-authenticate", "first_line");
+  res.setHeader("www-authenticate", "second_line", /* merge */ true);
+  res.setHeader("proxy-authenticate", "first_line");
+  res.setHeader("proxy-authenticate", "second_line", /* merge */ true);
+});
+
+server.registerPathHandler("/setcookie", (req, res) => {
+  // set-cookie is also allowed to span multiple lines.
+  res.setHeader("Set-Cookie", "food=yummy; max-age=999");
+  res.setHeader("Set-Cookie", "second=serving; max-age=999", /* merge */ true);
+  res.write(req.hasHeader("Cookie") ? req.getHeader("Cookie") : "");
+});
+server.registerPathHandler("/empty", (req, res) => {});
+
+add_setup(() => {
+  Services.prefs.setBoolPref("extensions.manifestV3.enabled", true);
+  Services.prefs.setBoolPref("extensions.dnr.enabled", true);
+
+  // The restrictedDomains pref should be set early, because the pref is read
+  // only once (on first use) by WebExtensionPolicy::IsRestrictedURI.
+  Services.prefs.setCharPref(
+    "extensions.webextensions.restrictedDomains",
+    "restricted"
+  );
+});
+
+// This function is serialized and called in the context of the test extension's
+// background page. dnrTestUtils is passed to the background function.
+function makeDnrTestUtils() {
+  const dnrTestUtils = {};
+  async function fetchAsJson(url, options) {
+    let res = await fetch(url, options);
+    let txt = await res.text();
+    try {
+      return JSON.parse(txt);
+    } catch (e) {
+      return txt;
+    }
+  }
+  Object.assign(dnrTestUtils, {
+    fetchAsJson,
+  });
+  return dnrTestUtils;
+}
+
+async function runAsDNRExtension({
+  background,
+  manifest,
+  unloadTestAtEnd = true,
+}) {
+  let extension = ExtensionTestUtils.loadExtension({
+    background: `(${background})((${makeDnrTestUtils})())`,
+    allowInsecureRequests: true,
+    manifest: {
+      manifest_version: 3,
+      permissions: ["declarativeNetRequest"],
+      host_permissions: ["<all_urls>"],
+      granted_host_permissions: true,
+      ...manifest,
+    },
+    temporarilyInstalled: true, // <-- for granted_host_permissions
+  });
+  await extension.startup();
+  await extension.awaitFinish();
+  if (unloadTestAtEnd) {
+    await extension.unload();
+  }
+  return extension;
+}
+
+add_task(async function modifyHeaders_requestHeaders() {
+  await runAsDNRExtension({
+    background: async dnrTestUtils => {
+      const { fetchAsJson } = dnrTestUtils;
+      await browser.declarativeNetRequest.updateSessionRules({
+        addRules: [
+          {
+            id: 1,
+            condition: { urlFilter: "set_twice" },
+            action: {
+              type: "modifyHeaders",
+              requestHeaders: [
+                { operation: "set", header: "a", value: "a-first" },
+                // second set should be ignored after set.
+                { operation: "set", header: "a", value: "a-second" },
+              ],
+            },
+          },
+          {
+            id: 2,
+            condition: { urlFilter: "set_and_remove" },
+            action: {
+              type: "modifyHeaders",
+              requestHeaders: [
+                { operation: "set", header: "b", value: "b-value" },
+                // remove should be ignored after set.
+                { operation: "remove", header: "b" },
+              ],
+            },
+          },
+          {
+            id: 3,
+            condition: { urlFilter: "remove_and_set" },
+            action: {
+              type: "modifyHeaders",
+              requestHeaders: [
+                { operation: "remove", header: "c" },
+                // set should be ignored after remove.
+                { operation: "set", header: "c", value: "c-value" },
+                // append should be ignored after remove.
+                { operation: "append", header: "c", value: "c-appended" },
+              ],
+            },
+          },
+          {
+            id: 4,
+            condition: { urlFilter: "remove_only" },
+            action: {
+              type: "modifyHeaders",
+              requestHeaders: [{ operation: "remove", header: "d" }],
+            },
+          },
+          {
+            id: 5,
+            condition: { urlFilter: "append_twice" },
+            action: {
+              type: "modifyHeaders",
+              requestHeaders: [
+                { operation: "append", header: "e", value: "e-first" },
+                { operation: "append", header: "e", value: "e-second" },
+              ],
+            },
+          },
+          {
+            id: 6,
+            condition: { urlFilter: "set_and_append" },
+            action: {
+              type: "modifyHeaders",
+              requestHeaders: [
+                { operation: "set", header: "f", value: "f-first" },
+                { operation: "append", header: "f", value: "f-second" },
+              ],
+            },
+          },
+        ],
+      });
+
+      browser.test.assertDeepEq(
+        { existing: "header" },
+        await fetchAsJson(
+          "http://dummy/echoheaders?not_matching_any_dnr_rule",
+          { headers: { existing: "header" } }
+        ),
+        "Sanity check: should echo original headers without matching DNR rules"
+      );
+
+      // Tests set_twice rule:
+
+      browser.test.assertDeepEq(
+        { a: "a-first" },
+        await fetchAsJson("http://dummy/echoheaders?set_twice"),
+        "only the first header should be used when set twice"
+      );
+      browser.test.assertDeepEq(
+        { a: "a-first" },
+        await fetchAsJson("http://dummy/echoheaders?set_twice", {
+          headers: { a: "original" },
+        }),
+        "original header should be overwritten by DNR"
+      );
+
+      // Tests set_and_remove rule:
+
+      browser.test.assertDeepEq(
+        { b: "b-value" },
+        await fetchAsJson("http://dummy/echoheaders?set_and_remove"),
+        "after setting a header, remove should be ignored"
+      );
+      browser.test.assertDeepEq(
+        { b: "b-value" },
+        await fetchAsJson("http://dummy/echoheaders?set_and_remove", {
+          headers: { b: "original" },
+        }),
+        "after overwriting a header, remove should be ignored"
+      );
+
+      // Tests remove_and_set rule:
+
+      browser.test.assertDeepEq(
+        { start: "START", end: "end" },
+        await fetchAsJson("http://dummy/echoheaders?remove_and_set", {
+          headers: { start: "START", c: "remove me", end: "end" },
+        }),
+        "after removing a header, remove should be ignored"
+      );
+      browser.test.assertDeepEq(
+        {},
+        await fetchAsJson("http://dummy/echoheaders?remove_and_set"),
+        "after a remove op (despite no existing header), set should be ignored"
+      );
+
+      // Tests remove_only rule:
+
+      browser.test.assertDeepEq(
+        {},
+        await fetchAsJson("http://dummy/echoheaders?remove_only", {
+          headers: { d: "remove me please" },
+        }),
+        "should remove header"
+      );
+
+      // Tests append_twice rule:
+
+      browser.test.assertDeepEq(
+        { e: "original, e-first, e-second" },
+        await fetchAsJson("http://dummy/echoheaders?append_twice", {
+          headers: { e: "original" },
+        }),
+        "should append headers"
+      );
+      browser.test.assertDeepEq(
+        { e: "e-first, e-second" },
+        await fetchAsJson("http://dummy/echoheaders?append_twice"),
+        "should append headers if there are no existing ones yet"
+      );
+
+      // Tests set_and_append rule:
+
+      browser.test.assertDeepEq(
+        { f: "f-first, f-second" },
+        await fetchAsJson("http://dummy/echoheaders?set_and_append", {
+          headers: { f: "original" },
+        }),
+        "should overwrite and append headers"
+      );
+
+      // All rules together:
+
+      browser.test.assertDeepEq(
+        {
+          a: "a-first",
+          b: "b-value",
+          e: "olde, e-first, e-second",
+          f: "f-first, f-second",
+          extra: "",
+        },
+        await fetchAsJson(
+          "http://dummy/echoheaders?set_twice,set_and_remove,remove_and_set,remove_only,append_twice,set_and_append",
+          {
+            headers: {
+              a: "olda",
+              b: "oldb",
+              c: "oldc",
+              d: "oldd",
+              e: "olde",
+              f: "oldf",
+              extra: "",
+            },
+          }
+        ),
+        "modifyHeaders actions from multiple rules should all apply"
+      );
+
+      browser.test.notifyPass();
+    },
+  });
+});
+
+// Host header is restricted, for details see bug 1467523.
+add_task(async function requestHeaders_set_host_header() {
+  async function background() {
+    const makeModifyHostRule = (id, urlFilter, value) => ({
+      id,
+      condition: { urlFilter },
+      action: {
+        type: "modifyHeaders",
+        requestHeaders: [{ operation: "set", header: "Host", value }],
+      },
+    });
+    await browser.declarativeNetRequest.updateSessionRules({
+      addRules: [
+        makeModifyHostRule(1, "yes_host_permissions", "yes"),
+        makeModifyHostRule(2, "no_host_permissions", "no"),
+        makeModifyHostRule(3, "restricted_domain", "restricted"),
+      ],
+    });
+
+    browser.test.assertEq(
+      "yes",
+      await (await fetch("http://dummy/host?yes_host_permissions")).text(),
+      "Host header value allowed if extension has permission for new value"
+    );
+
+    browser.test.assertEq(
+      "dummy",
+      await (await fetch("http://dummy/host?no_host_permissions")).text(),
+      "Host header value ignored if extension misses permission for new value"
+    );
+
+    browser.test.assertEq(
+      "dummy",
+      await (await fetch("http://dummy/host?restricted_domain")).text(),
+      "Host header value ignored if new host is in restrictedDomains"
+    );
+
+    browser.test.notifyPass();
+  }
+  const { messages } = await promiseConsoleOutput(async () => {
+    await runAsDNRExtension({
+      manifest: {
+        // Note: host_permissions without "*://no/*".
+        host_permissions: ["*://dummy/*", "*://yes/*", "*://restricted/*"],
+      },
+      background,
+    });
+  });
+
+  AddonTestUtils.checkMessages(messages, {
+    expected: [
+      {
+        message:
+          /Failed to apply modifyHeaders action to header "Host" \(DNR rule id 2 from ruleset "_session"\): Error: Unable to set host header, url missing from permissions\./,
+      },
+      {
+        message:
+          /Failed to apply modifyHeaders action to header "Host" \(DNR rule id 3 from ruleset "_session"\): Error: Unable to set host header to restricted url\./,
+      },
+    ],
+  });
+});
+
+add_task(async function requestHeaders_set_host_header_multiple_extensions() {
+  async function background() {
+    const hostHeaderValue = browser.runtime.getManifest().name;
+
+    await browser.declarativeNetRequest.updateSessionRules({
+      addRules: [
+        {
+          id: 1,
+          condition: { resourceTypes: ["xmlhttprequest"] },
+          action: {
+            type: "modifyHeaders",
+            requestHeaders: [
+              { operation: "set", header: "Host", value: hostHeaderValue },
+              // Add a unique header for each request to verify that the
+              // extension can still modify other headers despite failure to
+              // modify the host header.
+              { operation: "set", header: hostHeaderValue, value: "setbydnr" },
+            ],
+          },
+        },
+      ],
+    });
+    browser.test.notifyPass();
+  }
+  // Precedence is in install order, most recent first.
+  // While this extension is permitted to change Host to "maybe", it has a lower
+  // precedence than extensionWithPermissionAndHigherPrecedence.
+  let extensionWithPermissionButLowerPrecedence = await runAsDNRExtension({
+    unloadTestAtEnd: false,
+    manifest: {
+      name: "maybe",
+      host_permissions: ["*://dummy/*", "*://maybe/*"],
+    },
+    background,
+  });
+  // This extension is permitted to change Host to "yes".
+  let extensionWithPermissionAndHigherPrecedence = await runAsDNRExtension({
+    unloadTestAtEnd: false,
+    manifest: { name: "yes", host_permissions: ["*://dummy/*", "*://yes/*"] },
+    background,
+  });
+  // While this extension has the highest precedence by install order, it does
+  // not have permission to change "Host" to "no".
+  let extensionWithoutPermissionForHostHeader = await runAsDNRExtension({
+    unloadTestAtEnd: false,
+    manifest: { name: "no", host_permissions: ["*://dummy/*"] },
+    background,
+  });
+
+  Assert.equal(
+    await ExtensionTestUtils.fetch("http://dummy/", "http://dummy/host"),
+    "yes",
+    "Host header changedby the most recently installed extension with the right permission"
+  );
+
+  const { messages, result } = await promiseConsoleOutput(() =>
+    ExtensionTestUtils.fetch("http://dummy/", "http://dummy/echoheaders")
+  );
+  Assert.equal(
+    result,
+    `{"referer":"http://dummy/","no":"setbydnr","yes":"setbydnr","maybe":"setbydnr"}`,
+    "Host header changedby the most recently installed extension with the right permission"
+  );
+  AddonTestUtils.checkMessages(messages, {
+    expected: [
+      {
+        message:
+          /Failed to apply modifyHeaders action to header "Host" \(DNR rule id 1 from ruleset "_session"\): Error: Unable to set host header, url missing from permissions\./,
+      },
+    ],
+  });
+
+  await extensionWithPermissionButLowerPrecedence.unload();
+  await extensionWithPermissionAndHigherPrecedence.unload();
+  await extensionWithoutPermissionForHostHeader.unload();
+});
+
+add_task(async function modifyHeaders_responseHeaders() {
+  await runAsDNRExtension({
+    background: async () => {
+      await browser.declarativeNetRequest.updateSessionRules({
+        addRules: [
+          {
+            id: 1,
+            condition: { urlFilter: "/responseheadersFixture" },
+            action: {
+              type: "modifyHeaders",
+              responseHeaders: [
+                { operation: "set", header: "a", value: "a-first" },
+                // remove after set should be ignored:
+                { operation: "remove", header: "a" },
+                // Second set should be ignored:
+                { operation: "set", header: "a", value: "a-second" },
+                // But append is permitted:
+                { operation: "append", header: "a", value: "a-third" },
+                // Another append is allowed too:
+                { operation: "append", header: "a", value: "a-fourth" },
+                // An unrelated set is accepted:
+                { operation: "set", header: "b", value: "b-dnr" },
+                // An unrelated remove is also accepted:
+                { operation: "remove", header: "c" },
+                // An unrelated append is also accepted:
+                { operation: "append", header: "d", value: "d-dnr" },
+                // The server also sends the "e" header, we don't touch that.
+
+                // The server sends the www-authenticate header on two lines,
+                // which should be removed.
+                { operation: "remove", header: "www-authenticate" },
+                // The server also sends the proxy-authenticate header on two
+                // lines, but we don't touch that.
+              ],
+            },
+          },
+        ],
+      });
+
+      let { headers } = await fetch("http://dummy/responseheadersFixture");
+      browser.test.assertEq(
+        "a-first, a-third, a-fourth",
+        headers.get("a"),
+        "a set, ignored set + remove, 2x append"
+      );
+      browser.test.assertEq("b-dnr", headers.get("b"), "b set");
+      browser.test.assertEq(null, headers.get("c"), "c removed");
+      browser.test.assertEq("server_d, d-dnr", headers.get("d"), "d appended");
+      browser.test.assertEq("server_e", headers.get("e"), "e not touched");
+      browser.test.assertEq(
+        null,
+        headers.get("www-authenticate"),
+        "multi-line www-authenticate header removed"
+      );
+
+      // Multi-line http headers cannot be tested through fetch/Headers. This is
+      // a known limitation of that API, see e.g. note about Set-Cookie in the
+      // fetch spec - https://fetch.spec.whatwg.org/#headers-class
+      browser.test.assertEq(
+        null, // Note: null because Headers does not see multi-line headers.
+        headers.get("proxy-authenticate"),
+        "multi-line proxy-authenticate header kept (but fetch cannot see it)"
+      );
+
+      // XMLHttpRequest can return multi-line values, so we use that instead.
+      const xhr = new XMLHttpRequest();
+      await new Promise(r => {
+        xhr.onloadend = r;
+        xhr.open("GET", "http://dummy/responseheadersFixture?xhr");
+        xhr.send();
+      });
+      browser.test.assertEq(
+        null,
+        xhr.getResponseHeader("www-authenticate"),
+        "multi-line www-authenticate header removed"
+      );
+      browser.test.assertEq(
+        "first_line\nsecond_line",
+        xhr.getResponseHeader("proxy-authenticate"),
+        "multi-line proxy-authenticate header kept (seen through XHR)"
+      );
+
+      browser.test.notifyPass();
+    },
+  });
+});
+
+add_task(async function responseHeaders_set_content_security_policy_header() {
+  let extension = await runAsDNRExtension({
+    unloadTestAtEnd: false,
+    background: async () => {
+      // By default, a DNR condition excludes the main frame. But to verify that
+      // the CSP works, we have to modify the CSP header of a document request.
+      const resourceTypes = ["main_frame"];
+      await browser.declarativeNetRequest.updateSessionRules({
+        addRules: [
+          {
+            id: 1,
+            condition: { resourceTypes, urlFilter: "/csp?remove" },
+            action: {
+              type: "modifyHeaders",
+              responseHeaders: [
+                { operation: "remove", header: "Content-Security-Policy" },
+              ],
+            },
+          },
+          {
+            id: 2,
+            condition: { resourceTypes, urlFilter: "/csp?append_to_server" },
+            action: {
+              type: "modifyHeaders",
+              responseHeaders: [
+                {
+                  operation: "append",
+                  header: "Content-Security-Policy",
+                  // Server has "default-src http://yes http://maybe". When
+                  // multiple CSP header lines are present, all policies should
+                  // be enforced, thus "http://no" below should be ignored, and
+                  // the "http://maybe" from the server be ignored.
+                  value: "connect-src http://YES http://not-maybe http://no",
+                },
+              ],
+            },
+          },
+          {
+            id: 3,
+            condition: { resourceTypes, urlFilter: "/csp?set_and_append" },
+            action: {
+              type: "modifyHeaders",
+              responseHeaders: [
+                {
+                  operation: "set",
+                  header: "Content-Security-Policy",
+                  value: "connect-src 1-of-2 http://yes http://maybe",
+                },
+                {
+                  operation: "append",
+                  header: "Content-Security-Policy",
+                  value: "connect-src 2-of-2 http://yes",
+                },
+              ],
+            },
+          },
+        ],
+      });
+
+      browser.test.notifyPass();
+    },
+  });
+
+  async function testFetchAndCSP(url) {
+    info(`testFetchAndCSP: ${url}`);
+    let contentPage = await ExtensionTestUtils.loadContentPage(url);
+    let cspTestResults = await contentPage.spawn([], async () => {
+      const { document } = content;
+      async function doFetchAndCheckCSP(url) {
+        const cspTestResult = { url, violatedCSP: [] };
+        let cspListener;
+        let cspEventPromise = new Promise(resolve => {
+          cspListener = e => {
+            cspTestResult.violatedCSP.push(e.originalPolicy);
+            // A CSP violation results in an event for each violated policy,
+            // dispatched after each other. Post a macrotask to ensure that all
+            // violations are caught.
+            content.setTimeout(resolve, 0);
+          };
+        });
+        document.addEventListener("securitypolicyviolation", cspListener);
+        try {
+          let res = await content.fetch(url);
+          let responseText = await res.text();
+          if (responseText !== "EXPECTED_RESPONSE_FOR /csp test") {
+            cspTestResult.unexpectedResponseText = responseText;
+          }
+          // No await cspEventPromise, because we are not expecting any errors.
+          // If there was any CSP violation, we would have ended in catch.
+        } catch (e) {
+          dump(`\nFailed to fetch ${url}, waiting for CSP report/event.\n`);
+          await cspEventPromise;
+        }
+        document.removeEventListener("securitypolicyviolation", cspListener);
+        return cspTestResult;
+      }
+
+      return {
+        yes: await doFetchAndCheckCSP("http://yes/csptest"),
+        maybe: await doFetchAndCheckCSP("http://maybe/csptest"),
+        no: await doFetchAndCheckCSP("http://no/csptest"),
+      };
+    });
+    await contentPage.close();
+    return cspTestResults;
+  }
+
+  // Note: this is derived from the server's policy. The server sends a bit more
+  // in the Content-Security-Policy header (i.e. ";"), but the normalized form
+  // is as follows.
+  const SERVER_DEFAULT_CSP = "default-src http://yes http://maybe";
+
+  // First, sanity check:
+  Assert.deepEqual(
+    await testFetchAndCSP("http://dummy/csp"),
+    {
+      yes: { url: "http://yes/csptest", violatedCSP: [] },
+      maybe: { url: "http://maybe/csptest", violatedCSP: [] },
+      no: { url: "http://no/csptest", violatedCSP: [SERVER_DEFAULT_CSP] },
+    },
+    "Sanity check: Server sends CSP that only allows requests to http://yes."
+  );
+
+  Assert.deepEqual(
+    await testFetchAndCSP("http://dummy/csp?remove"),
+    {
+      yes: { url: "http://yes/csptest", violatedCSP: [] },
+      maybe: { url: "http://maybe/csptest", violatedCSP: [] },
+      no: { url: "http://no/csptest", violatedCSP: [] },
+    },
+    "DNR remove CSP: results in no requests blocked by CSP"
+  );
+
+  Assert.deepEqual(
+    {
+      yes: { url: "http://yes/csptest", violatedCSP: [] },
+      maybe: {
+        url: "http://maybe/csptest",
+        violatedCSP: [
+          // This value was appended by DNR (with upper-case "http://YES", but
+          // the normalized form should be lowercase "http://yes"), and notably
+          // the "yes" request above should still pass.
+          "connect-src http://yes http://not-maybe http://no",
+        ],
+      },
+      no: { url: "http://no/csptest", violatedCSP: [SERVER_DEFAULT_CSP] },
+    },
+    await testFetchAndCSP("http://dummy/csp?append_to_server"),
+    "DNR append CSP: should enforce CSP of server and DNR"
+  );
+
+  Assert.deepEqual(
+    await testFetchAndCSP("http://dummy/csp?set_and_append"),
+    {
+      yes: { url: "http://yes/csptest", violatedCSP: [] },
+      maybe: {
+        url: "http://maybe/csptest",
+        violatedCSP: [
+          // Note: "http://" is before 2-of-2 due to bug 1804145.
+          "connect-src http://2-of-2 http://yes",
+        ],
+      },
+      no: {
+        url: "http://no/csptest",
+        violatedCSP: [
+          // Note: "http://" is before 1-of-2 and 2-of-2 due to bug 1804145.
+          "connect-src http://1-of-2 http://yes http://maybe",
+          "connect-src http://2-of-2 http://yes",
+        ],
+      },
+    },
+    "DNR set + append CSP: should enforce both CSPs from DNR"
+  );
+
+  await extension.unload();
+});
+
+// Set-Cookie is special because it may span multiple lines. This test tests a
+// combination of requestHeaders/responseHeaders and that the DNR-set cookies
+// are really working, i.e. visible to server and/or modifying the client's
+// cookie jar.
+add_task(async function requestHeaders_and_responseHeaders_cookies() {
+  let extension = await runAsDNRExtension({
+    unloadTestAtEnd: false,
+    background: async () => {
+      // By default, a DNR condition excludes the main frame. But this test uses
+      // a document load to verify that cookie header modifications (if any) are
+      // reflected in document.cookie.
+      const resourceTypes = ["main_frame"];
+
+      await browser.declarativeNetRequest.updateSessionRules({
+        addRules: [
+          {
+            id: 1,
+            condition: { resourceTypes, urlFilter: "dnr_resp_drop_cookie" },
+            action: {
+              type: "modifyHeaders",
+              responseHeaders: [{ operation: "remove", header: "set-cookie" }],
+            },
+          },
+          {
+            id: 2,
+            condition: { resourceTypes, urlFilter: "dnr_resp_set_cookie" },
+            action: {
+              type: "modifyHeaders",
+              responseHeaders: [
+                {
+                  operation: "set",
+                  header: "set-cookie",
+                  value: "dnr_res=set; max-age=999",
+                },
+              ],
+            },
+          },
+          {
+            id: 3,
+            condition: { resourceTypes, urlFilter: "dnr_set_cookie_to_req" },
+            action: {
+              type: "modifyHeaders",
+              requestHeaders: [
+                { operation: "set", header: "cookie", value: "dnr_req=1" },
+              ],
+            },
+          },
+          {
+            id: 4,
+            condition: {
+              resourceTypes,
+              urlFilter: "dnr_append_cookie_to_req_and_res",
+            },
+            action: {
+              type: "modifyHeaders",
+              requestHeaders: [
+                // Just for extra coverage, mix upper/lower case.
+                { operation: "append", header: "Cookie", value: "DNR_APP=1" },
+                { operation: "append", header: "cookie", value: "DNR_app=2" },
+              ],
+              responseHeaders: [
+                {
+                  operation: "append",
+                  header: "set-cookie",
+                  value: "dnr_res=appended; max-age=999",
+                },
+              ],
+            },
+          },
+          {
+            id: 5,
+            condition: {
+              resourceTypes,
+              urlFilter: "dnr_set_server_cookies_expired",
+            },
+            action: {
+              type: "modifyHeaders",
+              responseHeaders: [
+                {
+                  operation: "set",
+                  header: "set-cookie",
+                  value: "food=deletedbydnr; second=deletedbydnr; max-age=-1",
+                },
+                {
+                  operation: "append",
+                  header: "set-cookie",
+                  value: "second=deletedbydnr; max-age=-1",
+                },
+              ],
+            },
+          },
+          {
+            id: 6,
+            condition: {
+              resourceTypes,
+              urlFilter: "dnr_resp_append_expired_cookie",
+            },
+            action: {
+              type: "modifyHeaders",
+              responseHeaders: [
+                {
+                  operation: "append",
+                  header: "set-cookie",
+                  value: "dnr_res=deleteme; max-age=-1",
+                },
+              ],
+            },
+          },
+        ],
+      });
+
+      browser.test.notifyPass();
+    },
+  });
+
+  async function loadPageAndGetCookies(pathAndQuery) {
+    const url = `http://cookietest${pathAndQuery}`;
+    info(`loadPageAndGetCookies: ${url}`);
+    let contentPage = await ExtensionTestUtils.loadContentPage(url);
+    let res = await contentPage.spawn([], () => {
+      const { document } = content;
+      const sortCookies = s => s.split("; ").sort().join("; ");
+      return {
+        // Server at /setcookie echos value of Cookie request header.
+        serverSeenCookies: sortCookies(document.body.textContent),
+        clientSeenCookies: sortCookies(document.cookie),
+      };
+    });
+    await contentPage.close();
+    return res;
+  }
+
+  Assert.deepEqual(
+    { serverSeenCookies: "", clientSeenCookies: "" },
+    await loadPageAndGetCookies("/setcookie?dnr_resp_drop_cookie"),
+    "Set-Cookie from server ignored due to DNR (remove Set-Cookie)"
+  );
+  Assert.deepEqual(
+    {
+      serverSeenCookies: "",
+      clientSeenCookies: "dnr_res=set",
+    },
+    await loadPageAndGetCookies("/setcookie?dnr_resp_set_cookie"),
+    "Set-Cookie from server overwritten by DNR (set Set-Cookie)"
+  );
+  Assert.deepEqual(
+    {
+      // No cookies from previous request + request-specific cookie from DNR.
+      serverSeenCookies: "dnr_req=1",
+      // Notably, "dnr_req=1" should be missing from clientSeenCookies, because
+      // it is added in the request, so only seen by the server. Only cookies
+      // set by Set-Cookie are persisted/seen by the client.
+      clientSeenCookies: "dnr_res=set; food=yummy; second=serving",
+    },
+    await loadPageAndGetCookies("/setcookie?dnr_set_cookie_to_req"),
+    "Cookie req header from DNR, shadows existing client-generated Cookie header"
+  );
+  Assert.deepEqual(
+    {
+      // Cookies from previous request + request-specific cookies from DNR.
+      serverSeenCookies:
+        "DNR_APP=1; DNR_app=2; dnr_res=set; food=yummy; second=serving",
+      // NDR_APP and DNR_app are notably missing. dnr_res was modified by DNR,
+      // because an appended cookie with the same name overwrites existing one.
+      clientSeenCookies: "dnr_res=appended; food=yummy; second=serving",
+    },
+    await loadPageAndGetCookies("/setcookie?dnr_append_cookie_to_req_and_res"),
+    "Cookie req header from DNR, merged with existing client cookies; Set-Cookie from server merged with DNR (append Set-Cookie)"
+  );
+  Assert.deepEqual(
+    {
+      // Cookies from previous request (not changed by DNR):
+      serverSeenCookies: "dnr_res=appended; food=yummy; second=serving",
+      // Server cookies removed, only previously added DNR cookie sticks:
+      clientSeenCookies: "dnr_res=appended",
+    },
+    await loadPageAndGetCookies("/setcookie?dnr_set_server_cookies_expired"),
+    "Set-Cookie from server expired by DNR (set Set-Cookie + expire server cookies)"
+  );
+  Assert.deepEqual(
+    {
+      // Cookies from previous request (not changed by DNR):
+      serverSeenCookies: "dnr_res=appended",
+      // Cookies from server; because we used "append", they should merge, and
+      // expire the previous DNR cookie, and create the server-set cookies.
+      clientSeenCookies: "food=yummy; second=serving",
+    },
+    await loadPageAndGetCookies("/setcookie?dnr_resp_append_expired_cookie"),
+    "Set-Cookie from server merged with DNR (append Set-Cookie + expire dnr_res)"
+  );
+  // We've already tested dnr_set_server_cookies_expired before, now we're just
+  // cleaning up.
+  Assert.deepEqual(
+    {
+      serverSeenCookies: "food=yummy; second=serving",
+      clientSeenCookies: "",
+    },
+    await loadPageAndGetCookies("/setcookie?dnr_set_server_cookies_expired"),
+    "DNR cleared remaining cookies (set Set-Cookie + expire server cookies)"
+  );
+
+  await extension.unload();
+});
+
+// This test confirms the effective modifyHeaders actions if multiple extensions
+// have matching modifyHeaders rules. Only one extension is allowed to modify
+// headers.
+add_task(async function modifyHeaders_multiple_extensions() {
+  async function background() {
+    const extName = browser.runtime.getManifest().name;
+    function makeModifyHeadersRule(id, operation, headerName) {
+      const urlFilter = `${extName}_${operation}_${headerName}`;
+      let value;
+      if (operation !== "remove") {
+        // Use the urlFilter as value so that it's obvious which rule added it.
+        value = urlFilter;
+      }
+      return {
+        id,
+        condition: { urlFilter },
+        action: {
+          type: "modifyHeaders",
+          // As the logic of responseHeaders and requestHeaders is shared, it
+          // suffices to only check responseHeaders here.
+          responseHeaders: [{ operation, header: headerName, value }],
+        },
+      };
+    }
+    await browser.declarativeNetRequest.updateSessionRules({
+      addRules: [
+        makeModifyHeadersRule(1, "set", "a"),
+        makeModifyHeadersRule(2, "remove", "a"),
+        makeModifyHeadersRule(3, "append", "a"),
+        makeModifyHeadersRule(4, "set", "b"),
+        makeModifyHeadersRule(5, "remove", "b"),
+        makeModifyHeadersRule(6, "append", "b"),
+      ],
+    });
+    browser.test.notifyPass();
+  }
+
+  // Cross-extension rule precedence is in the order of extension installation.
+  const prioTwoExtension = await runAsDNRExtension({
+    manifest: { name: "prioTwo" },
+    background,
+    unloadTestAtEnd: false,
+  });
+  const prioOneExtension = await runAsDNRExtension({
+    manifest: { name: "prioOne" },
+    background,
+    unloadTestAtEnd: false,
+  });
+
+  let contentPage = await ExtensionTestUtils.loadContentPage(
+    "http://dummy/empty"
+  );
+  async function checkHeaderActionResult(query, expectedHeaders, description) {
+    const url = `/responseheadersFixture?${query}`;
+    const result = await contentPage.spawn([url], async url => {
+      const res = await content.fetch(url);
+      return {
+        a: res.headers.get("a"),
+        b: res.headers.get("b"),
+      };
+    });
+    Assert.deepEqual(
+      result,
+      expectedHeaders,
+      `${description} - Expected headers for ${url}`
+    );
+  }
+
+  await checkHeaderActionResult(
+    "",
+    {
+      a: "server_a",
+      b: "server_b",
+    },
+    "Sanity check: headers should be unmodified without matching DNR rules"
+  );
+
+  // First: verify that "set" is only permitted if there are no other extensions
+  // that have already modified the header. Note that this requirement already
+  // holds for actions within one extension, so they should still be enforced
+  // for modifyHeaders actions from multiple extensions.
+  await checkHeaderActionResult(
+    "prioOne_set_a,prioTwo_set_a,prioTwo_set_b",
+    {
+      a: "prioOne_set_a",
+      b: "prioTwo_set_b",
+    },
+    "set should only be allowed if no other extension has set a header"
+  );
+  await checkHeaderActionResult(
+    "prioOne_remove_a,prioTwo_set_a,prioTwo_set_b",
+    {
+      a: null,
+      b: "prioTwo_set_b",
+    },
+    "set should only be allowed if no other extension has removed the header"
+  );
+  await checkHeaderActionResult(
+    "prioOne_append_a,prioTwo_set_a,prioTwo_set_b",
+    {
+      a: "server_a, prioOne_append_a",
+      b: "prioTwo_set_b",
+    },
+    "set should only be allowed if no other extension has appended the header"
+  );
+
+  // The "remove" operation is not logically conflicting, let's confirm that it
+  // works as usual.
+  await checkHeaderActionResult(
+    "prioOne_remove_a,prioTwo_remove_a,prioTwo_remove_b",
+    {
+      a: null,
+      b: null,
+    },
+    "remove should work, regardless of the number of extensions that use it"
+  );
+
+  // While an extension can specify multiple "append" operations, only one
+  // extension should be able to use it. Another extension is still allowed to
+  // modify an unrelated, not-yet-modified header.
+  await checkHeaderActionResult(
+    "prioOne_append_a,prioTwo_append_a,prioTwo_append_b",
+    {
+      a: "server_a, prioOne_append_a",
+      b: "server_b, prioTwo_append_b",
+    },
+    "Only one extension may modify a specific header"
+  );
+
+  await contentPage.close();
+  await prioOneExtension.unload();
+  await prioTwoExtension.unload();
+});
diff --git a/toolkit/components/extensions/test/xpcshell/test_ext_dnr_private_browsing.js b/toolkit/components/extensions/test/xpcshell/test_ext_dnr_private_browsing.js
new file mode 100644
index 0000000000..e9e7f90b01
--- /dev/null
+++ b/toolkit/components/extensions/test/xpcshell/test_ext_dnr_private_browsing.js
@@ -0,0 +1,130 @@
+"use strict";
+
+const server = createHttpServer({ hosts: ["example.com"] });
+server.registerPathHandler("/", (req, res) => {
+  res.setHeader("Access-Control-Allow-Origin", "*");
+  res.setHeader("Access-Control-Max-Age", "0");
+});
+
+add_setup(() => {
+  Services.prefs.setBoolPref("extensions.manifestV3.enabled", true);
+  Services.prefs.setBoolPref("extensions.dnr.enabled", true);
+});
+
+async function startDNRExtension({ privateBrowsingAllowed }) {
+  let extension = ExtensionTestUtils.loadExtension({
+    incognitoOverride: privateBrowsingAllowed ? "spanning" : undefined,
+    async background() {
+      await browser.declarativeNetRequest.updateSessionRules({
+        addRules: [{ id: 1, condition: {}, action: { type: "block" } }],
+      });
+      browser.test.sendMessage("dnr_registered");
+    },
+    manifest: {
+      manifest_version: 3,
+      permissions: ["declarativeNetRequest"],
+      browser_specific_settings: { gecko: { id: "@dnr-ext" } },
+    },
+  });
+  await extension.startup();
+  await extension.awaitMessage("dnr_registered");
+  return extension;
+}
+
+async function testMatchedByDNR(privateBrowsing) {
+  let contentPage = await ExtensionTestUtils.loadContentPage(
+    "http://example.com/?page",
+    { privateBrowsing }
+  );
+  let wasRequestBlocked = await contentPage.legacySpawn(null, async () => {
+    try {
+      await content.fetch("http://example.com/?fetch");
+      return false;
+    } catch (e) {
+      // Request blocked by DNR rule from startDNRExtension().
+      return true;
+    }
+  });
+  await contentPage.close();
+  return wasRequestBlocked;
+}
+
+add_task(async function private_browsing_not_allowed_by_default() {
+  let extension = await startDNRExtension({ privateBrowsingAllowed: false });
+  Assert.equal(
+    await testMatchedByDNR(false),
+    true,
+    "DNR applies to non-private browsing requests by default"
+  );
+  Assert.equal(
+    await testMatchedByDNR(true),
+    false,
+    "DNR not applied to private browsing requests by default"
+  );
+  await extension.unload();
+});
+
+add_task(async function private_browsing_allowed() {
+  let extension = await startDNRExtension({ privateBrowsingAllowed: true });
+  Assert.equal(
+    await testMatchedByDNR(false),
+    true,
+    "DNR applies to non-private requests regardless of privateBrowsingAllowed"
+  );
+  Assert.equal(
+    await testMatchedByDNR(true),
+    true,
+    "DNR applied to private browsing requests when privateBrowsingAllowed"
+  );
+  await extension.unload();
+});
+
+add_task(
+  { pref_set: [["extensions.dnr.feedback", true]] },
+  async function testMatchOutcome_unaffected_by_privateBrowsing() {
+    let extensionWithoutPrivateBrowsingAllowed = await startDNRExtension({});
+    let extension = ExtensionTestUtils.loadExtension({
+      incognitoOverride: "spanning",
+      manifest: {
+        manifest_version: 3,
+        permissions: ["declarativeNetRequest", "declarativeNetRequestFeedback"],
+      },
+      files: {
+        "page.html": `<!DOCTYPE html><script src="page.js"></script>`,
+        "page.js": async () => {
+          browser.test.assertTrue(
+            browser.extension.inIncognitoContext,
+            "Extension page is opened in a private browsing context"
+          );
+          browser.test.assertDeepEq(
+            {
+              matchedRules: [
+                { ruleId: 1, rulesetId: "_session", extensionId: "@dnr-ext" },
+              ],
+            },
+            // testMatchOutcome does not offer a way to specify the private
+            // browsing mode of a request. Confirm that testMatchOutcome always
+            // simulates requests in normal private browsing mode, even if the
+            // testMatchOutcome method itself is called from an extension page
+            // in private browsing mode.
+            await browser.declarativeNetRequest.testMatchOutcome(
+              { url: "http://example.com/?simulated_request", type: "image" },
+              { includeOtherExtensions: true }
+            ),
+            "testMatchOutcome includes DNR from extensions without pbm access"
+          );
+          browser.test.sendMessage("done");
+        },
+      },
+    });
+    await extension.startup();
+    let contentPage = await ExtensionTestUtils.loadContentPage(
+      `moz-extension://${extension.uuid}/page.html`,
+      { privateBrowsing: true }
+    );
+    await extension.awaitMessage("done");
+    await contentPage.close();
+    await extension.unload();
+    await extensionWithoutPrivateBrowsingAllowed.unload();
+  }
+);
diff --git a/toolkit/components/extensions/test/xpcshell/test_ext_dnr_redirect_transform.js b/toolkit/components/extensions/test/xpcshell/test_ext_dnr_redirect_transform.js
new file mode 100644
index 0000000000..de01169dea
--- /dev/null
+++ b/toolkit/components/extensions/test/xpcshell/test_ext_dnr_redirect_transform.js
@@ -0,0 +1,723 @@
+"use strict";
+
+// The validate_action_redirect_transform task of test_ext_dnr_session_rules.js
+// confirms that redirect transform rules meet some minimum bar of validation.
+// Despite passing validation, there are still interesting cases to explore,
+// ranging from verifying that special characters appear as expected, to
+// verifying that an invalid URL (e.g. too long after the transform) is handled
+// reasonably well.
+
+add_setup(() => {
+  Services.prefs.setBoolPref("extensions.manifestV3.enabled", true);
+  Services.prefs.setBoolPref("extensions.dnr.enabled", true);
+
+  // Allow navigation to URLs with embedded credentials, without prompt.
+  Services.prefs.setBoolPref("network.auth.confirmAuth.enabled", false);
+});
+
+const server = createHttpServer({
+  hosts: ["from", "dest", "127.0.0.127", "[::1]", "xn--stra-yna.de", "fqdn."],
+});
+server.identity.add("http", "dest", 443); // test_redirect_transform_port
+server.identity.add("http", "dest", 700); // test_redirect_transform_port
+server.identity.add("http", "dest", 777); // Dummy port in test cases.
+
+server.registerPrefixHandler("/", (req, res) => {
+  res.setHeader("Access-Control-Allow-Origin", "*");
+  res.write("GOOD_RESPONSE");
+});
+
+// This function is serialized and called in the context of the test extension's
+// background page. dnrTestUtils is passed to the background function.
+function makeDnrTestUtils() {
+  const dnrTestUtils = {};
+  const dnr = browser.declarativeNetRequest;
+  function makeRedirectTransformRule(transform) {
+    return {
+      id: 1,
+      condition: { requestDomains: ["from"] },
+      action: {
+        type: "redirect",
+        // redirect to "dest" by default, different from "from", to avoid an
+        // infinite redirect loop.
+        redirect: { transform: { host: "dest", ...transform } },
+      },
+    };
+  }
+  async function setRedirectTransform(transform) {
+    await dnr.updateSessionRules({
+      removeRuleIds: [1],
+      addRules: [makeRedirectTransformRule(transform)],
+    });
+  }
+  // testFetch is simple/fast, but cannot always be used:
+  // - when the request URL contains embedded credentials.
+  // - when the final URL is supposed to contain a reference fragment.
+  async function testFetch(from, to, description) {
+    let res = await fetch(from);
+    browser.test.assertEq(to, res.url, description);
+    browser.test.assertEq("GOOD_RESPONSE", await res.text(), "expected body");
+  }
+  // testNavigate is the slower, complex version of testFetch. It should be
+  // used in tests where the username, password or fragment components of a URL
+  // are significant.
+  async function testNavigate(from, to, description) {
+    let resultPromise = new Promise(resolve => {
+      browser.test.onMessage.addListener(function listener(msg, result) {
+        if (msg === "test_navigate_result") {
+          browser.test.onMessage.removeListener(listener);
+          // resolve only resolves on the first call, which is ideal because
+          // browser.test.onMessage.removeListener does not work (bug 1428213).
+          resolve(result);
+        }
+      });
+    });
+    browser.test.sendMessage("test_navigate", from);
+    browser.test.assertDeepEq({ from, to }, await resultPromise, description);
+  }
+  Object.assign(dnrTestUtils, {
+    makeRedirectTransformRule,
+    setRedirectTransform,
+    testFetch,
+    testNavigate,
+  });
+  return dnrTestUtils;
+}
+
+async function runAsDNRExtension({ background, manifest }) {
+  let extension = ExtensionTestUtils.loadExtension({
+    background: `(${background})((${makeDnrTestUtils})())`,
+    allowInsecureRequests: true,
+    manifest: {
+      manifest_version: 3,
+      permissions: ["declarativeNetRequest"],
+      host_permissions: ["<all_urls>"],
+      granted_host_permissions: true,
+      web_accessible_resources: [
+        { resources: ["war.txt"], matches: ["http://from/*"] },
+      ],
+      ...manifest,
+    },
+    temporarilyInstalled: true, // <-- for granted_host_permissions
+    files: {
+      "war.txt": "GOOD_RESPONSE",
+      "nowar.txt": "nowar.txt is not in web_accessible_resources",
+    },
+  });
+  extension.onMessage("test_navigate", async url => {
+    // The DNR rule does not redirect the main frame.
+    let contentPage = await ExtensionTestUtils.loadContentPage("http://from/");
+    info(`Loading ${url}`);
+    await contentPage.spawn([url], async url => {
+      let { document } = this.content;
+      let frame = document.createElement("iframe");
+      frame.src = url;
+      await new Promise(resolve => {
+        frame.onload = resolve;
+        document.body.appendChild(frame);
+      });
+    });
+    let finalURL = contentPage.browsingContext.children[0].currentURI.spec;
+    await contentPage.close();
+    extension.sendMessage("test_navigate_result", { from: url, to: finalURL });
+  });
+  await extension.startup();
+  await extension.awaitFinish();
+  await extension.unload();
+}
+
+add_task(async function test_redirect_transform_all_at_once() {
+  await runAsDNRExtension({
+    background: async dnrTestUtils => {
+      const { setRedirectTransform, testFetch, testNavigate } = dnrTestUtils;
+
+      await setRedirectTransform({
+        scheme: "http",
+        username: "a",
+        password: "b",
+        host: "dest",
+        port: "777",
+        path: "/d",
+        query: "?e",
+        queryTransform: null,
+        fragment: "#f",
+      });
+      await testFetch(
+        "https://from",
+        "http://a:b@dest:777/d?e", // note: fetch cannot see '#f'.
+        "Adds components to minimal URL (fetch)"
+      );
+      await testNavigate(
+        "https://from",
+        "http://a:b@dest:777/d?e#f",
+        "Adds components to minimal URL (navigation)"
+      );
+
+      await browser.test.assertRejects(
+        testFetch("https://user:pass@from:777/path?query#ref"),
+        "Window.fetch: https://user:pass@from:777/path?query#ref is an url with embedded credentials.",
+        "fetch does not work with embedded credentials"
+      );
+      await testNavigate(
+        "https://user:pass@from:777/path?query#ref",
+        "http://a:b@dest:777/d?e#f",
+        "Replaces all components in existing URL (navigation)"
+      );
+
+      browser.test.notifyPass();
+    },
+  });
+});
+
+add_task(async function test_redirect_transform_scheme() {
+  await runAsDNRExtension({
+    background: async dnrTestUtils => {
+      const { setRedirectTransform, testFetch, testNavigate } = dnrTestUtils;
+
+      await setRedirectTransform({ scheme: "http" });
+      await testFetch("https://from/", "http://dest/", "scheme change");
+      await testNavigate(
+        "https://user:pass@from:777/path?query#ref",
+        "http://user:pass@dest:777/path?query#ref",
+        "scheme change in complex URL with embedded credentials"
+      );
+
+      await setRedirectTransform({
+        scheme: "moz-extension",
+        host: location.hostname,
+      });
+      await testFetch(
+        "http://from/war.txt",
+        browser.runtime.getURL("war.txt"),
+        "Scheme change to moz-extension:-URL"
+      );
+      await testNavigate(
+        "http://from/war.txt",
+        browser.runtime.getURL("war.txt"),
+        "Scheme change to moz-extension:-URL (navigation)"
+      );
+      // While the initiator (extension) would be allowed to read the resource
+      // due to it being same-origin, the pre-redirect URL (http://from) is not
+      // matching web_accessible_resources[].matches, so the load is rejected.
+      // This scenario is also tested in test_ext_dnr_without_webrequest.js, at
+      // the redirect_request_with_dnr_to_extensionPath task.
+      await browser.test.assertRejects(
+        testFetch("http://from/nowar.txt"),
+        "NetworkError when attempting to fetch resource.",
+        "Cannot load redirect to moz-extension: not in web_accessible_resources"
+      );
+
+      browser.test.notifyPass();
+    },
+  });
+});
+
+add_task(async function test_redirect_transform_username() {
+  await runAsDNRExtension({
+    background: async dnrTestUtils => {
+      const { setRedirectTransform, testFetch, testNavigate } = dnrTestUtils;
+
+      await setRedirectTransform({ username: "" });
+      await testNavigate(
+        "http://user:pass@from:777/path?query#ref",
+        "http://:pass@dest:777/path?query#ref",
+        "username cleared"
+      );
+
+      await setRedirectTransform({ username: "new" });
+      // Cannot pass credentials to fetch, but can read from response.url:
+      await testFetch("http://from/", "http://new@dest/", "username added");
+      await testNavigate("http://from/", "http://new@dest/", "username added");
+      await testNavigate(
+        "http://user:pass@from:777/path?query#ref",
+        "http://new:pass@dest:777/path?query#ref",
+        "username changed"
+      );
+
+      await setRedirectTransform({ username: "new User:name@%%20/" });
+      await testNavigate(
+        "http://user:pass@from:777/path?query#ref",
+        "http://new%20User%3Aname%40%%20%2F:pass@dest:777/path?query#ref",
+        "username changed to complex value"
+      );
+
+      browser.test.notifyPass();
+    },
+  });
+});
+
+add_task(async function test_redirect_transform_password() {
+  await runAsDNRExtension({
+    background: async dnrTestUtils => {
+      const { setRedirectTransform, testFetch, testNavigate } = dnrTestUtils;
+
+      await setRedirectTransform({ password: "" });
+      await testNavigate(
+        "http://user:pass@from:777/path?query#ref",
+        "http://user@dest:777/path?query#ref",
+        "password cleared"
+      );
+
+      await setRedirectTransform({ password: "new" });
+      // Cannot pass credentials to fetch, but can read from response.url:
+      await testFetch("http://from/", "http://:new@dest/", "password added");
+      await testNavigate("http://from/", "http://:new@dest/", "password added");
+      await testNavigate(
+        "http://user:pass@from:777/path?query#ref",
+        "http://user:new@dest:777/path?query#ref",
+        "password changed"
+      );
+
+      await setRedirectTransform({ password: "new Pass:@%%20/" });
+      await testNavigate(
+        "http://user:pass@from:777/path?query#ref",
+        "http://user:new%20Pass%3A%40%%20%2F@dest:777/path?query#ref",
+        "password changed to complex value"
+      );
+      browser.test.notifyPass();
+    },
+  });
+});
+
+add_task(async function test_redirect_transform_host() {
+  await runAsDNRExtension({
+    background: async dnrTestUtils => {
+      const { setRedirectTransform, testFetch, testNavigate } = dnrTestUtils;
+
+      await setRedirectTransform({ host: "dest" });
+      await testFetch(
+        "http://from:777/path?query",
+        "http://dest:777/path?query",
+        "host changed"
+      );
+      await testNavigate(
+        "http://user:pass@from:777/path?query#ref",
+        "http://user:pass@dest:777/path?query#ref",
+        "host changed without affecting embedded credentials"
+      );
+
+      await setRedirectTransform({ host: "DEST" });
+      await testFetch(
+        "http://from/",
+        "http://dest/",
+        "host changed (non-canonical, upper case)"
+      );
+
+      await setRedirectTransform({ host: "%44%65%73%54" }); // "DesT", escaped.
+      await testFetch(
+        "http://from:777/",
+        "http://dest:777/",
+        "host changed (non-canonical, percent-escaped)"
+      );
+
+      await setRedirectTransform({ host: "127.0.0.127" });
+      await testFetch(
+        "http://from/",
+        "http://127.0.0.127/",
+        "host change to IPv4"
+      );
+
+      await setRedirectTransform({ host: "[::1]" });
+      await testFetch("http://from/", "http://[::1]/", "host change to IPv6");
+
+      await setRedirectTransform({ host: "xn--stra-yna.de" });
+      await testFetch(
+        "http://from/",
+        "http://xn--stra-yna.de/",
+        "host change to IDN (internationalized domain name, in punycode)"
+      );
+
+      await setRedirectTransform({ host: "straß.de" });
+      await testFetch(
+        "http://from/",
+        "http://xn--stra-yna.de/",
+        "host change to IDN (not punycode-encoded)"
+      );
+
+      await setRedirectTransform({ host: "fqdn." });
+      await testFetch(
+        "http://from/",
+        "http://fqdn./",
+        "host change to FQDN (fully-qualified domain name)"
+      );
+
+      browser.test.notifyPass();
+    },
+  });
+});
+
+add_task(async function test_redirect_transform_port() {
+  await runAsDNRExtension({
+    background: async dnrTestUtils => {
+      const { setRedirectTransform, testFetch, testNavigate } = dnrTestUtils;
+
+      await setRedirectTransform({ port: "" });
+      await testFetch("http://from:777/", "http://dest/", "port cleared");
+      await testNavigate(
+        "http://user:pass@from:777/path?query#ref",
+        "http://user:pass@dest/path?query#ref",
+        "port cleared from URL with embedded credentials"
+      );
+
+      await setRedirectTransform({ port: "700" });
+      await testFetch("http://from/", "http://dest:700/", "port added");
+      await testFetch("http://from:777/", "http://dest:700/", "port changed");
+
+      // 0-padded should not be misinterpreted as an octal number.
+      await setRedirectTransform({ port: "0700" });
+      await testFetch(
+        "http://from:777/",
+        "http://dest:700/",
+        "port changed (non-canonical, 0-padded port)"
+      );
+
+      await setRedirectTransform({ port: "80" });
+      await testFetch(
+        "http://from:777/",
+        "http://dest/",
+        "port cleared if default protocol"
+      );
+
+      await setRedirectTransform({ scheme: "http", port: "443" });
+      await testFetch(
+        "https://from/",
+        "http://dest:443/",
+        "port added if new port is not default port of new protocol"
+      );
+
+      await setRedirectTransform({ scheme: "http", port: "80" });
+      await testFetch(
+        "https://from:777/",
+        "http://dest/",
+        "port cleared if new port is default port of new protocol"
+      );
+
+      browser.test.notifyPass();
+    },
+  });
+});
+
+add_task(async function test_redirect_transform_path() {
+  await runAsDNRExtension({
+    background: async dnrTestUtils => {
+      const { setRedirectTransform, testFetch, testNavigate } = dnrTestUtils;
+
+      await setRedirectTransform({ path: "" });
+      await testFetch("http://from/path", "http://dest/", "path cleared");
+      await testNavigate(
+        "http://user:pass@from:777/path?query#ref",
+        "http://user:pass@dest:777/?query#ref",
+        "path cleared from URL with embedded credentials"
+      );
+
+      await setRedirectTransform({ path: "/new" });
+      await testFetch("http://from/", "http://dest/new", "path added");
+      await testFetch("http://from/path", "http://dest/new", "path changed");
+
+      await setRedirectTransform({ path: "///" });
+      await testFetch("http://from/", "http://dest///", "path added (///)");
+
+      await setRedirectTransform({ path: "path" });
+      await testFetch(
+        "http://from/",
+        "http://dest/path",
+        "path added (non-canonical, missing slash)"
+      );
+
+      // " " -> "%20" (space)
+      // "\x00" -> "%00" (null byte)
+      // "<>" -> "%3C%3E" (URL encoding of angle brackets)
+      // "%", "%20", "%3A", "%3a" -> not changed (%-encoding kept as-is).
+      await setRedirectTransform({ path: "/Path_%_ _%20_?_#_\x00_<>_%3A%3a" });
+      await testFetch(
+        "http://from/",
+        "http://dest/Path_%_%20_%20_%3F_%23_%00_%3C%3E_%3A%3a",
+        "path added (non-canonical, partial percent encoding)"
+      );
+
+      browser.test.notifyPass();
+    },
+  });
+});
+
+add_task(async function test_redirect_transform_query() {
+  await runAsDNRExtension({
+    background: async dnrTestUtils => {
+      const { setRedirectTransform, testFetch, testNavigate } = dnrTestUtils;
+
+      await setRedirectTransform({ query: "" });
+      await testFetch("http://from/?query", "http://dest/", "query cleared");
+      await testNavigate(
+        "http://user:pass@from:777/path?query#ref",
+        "http://user:pass@dest:777/path#ref",
+        "query cleared from URL with embedded credentials"
+      );
+
+      await setRedirectTransform({ query: "?new" });
+      await testFetch("http://from/", "http://dest/?new", "query added");
+      await testFetch(
+        "http://from/?query",
+        "http://dest/?new",
+        "query changed"
+      );
+
+      await setRedirectTransform({ query: "?" });
+      await testFetch("http://from/", "http://dest/?", "query set to just '?'");
+
+      await setRedirectTransform({ query: "?Query_#_ _%20_%3a%3A_<>_\x00" });
+      await testFetch(
+        "http://from/",
+        "http://dest/?Query_%23_%20_%20_%3a%3A_%3C%3E_%00",
+        "query added (non-canonical, partial percent encoding)"
+      );
+
+      // Now rule.action.redirect.transform.queryTransform:
+      await setRedirectTransform({
+        queryTransform: {
+          removeParams: ["query"],
+        },
+      });
+      await testFetch(
+        "http://from/?query",
+        "http://dest/",
+        "queryTransform removed query"
+      );
+      await testFetch(
+        "http://from/?prefix&query&suffix",
+        "http://dest/?prefix&suffix",
+        "queryTransform removed part of query"
+      );
+      await testFetch(
+        "http://from/?query&aquery&queryb&query=withvalue&not=query&QUERY&",
+        "http://dest/?aquery&queryb&not=query&QUERY&",
+        "queryTransform removed all occurrences of 'query' key"
+      );
+      await testFetch(
+        "http://from/??query",
+        "http://dest/??query",
+        "queryTransform does not match param when it starts with '??'"
+      );
+
+      await setRedirectTransform({
+        queryTransform: {
+          removeParams: ["query"],
+          addOrReplaceParams: [{ key: "query", value: "newvalue" }],
+        },
+      });
+      await testFetch(
+        "http://from/",
+        "http://dest/?query=newvalue",
+        "queryTransform appended query despite new param being in removeParams"
+      );
+      await testFetch(
+        "http://from/?prefix&query&suffix",
+        "http://dest/?prefix&suffix&query=newvalue",
+        "queryTransform removed query, and appended new value"
+      );
+      await testFetch(
+        "http://from/??query",
+        "http://dest/??query&query=newvalue",
+        "queryTransform ignores existing param starting with '??', and appends"
+      );
+
+      await setRedirectTransform({
+        queryTransform: {
+          addOrReplaceParams: [{ key: "query", value: "newvalue" }],
+        },
+      });
+      await testFetch(
+        "http://from/",
+        "http://dest/?query=newvalue",
+        "queryTransform appended query"
+      );
+      await testFetch(
+        "http://from/?prefix&query=oldvalue&query=2&query=3",
+        "http://dest/?prefix&query=newvalue&query=2&query=3",
+        "queryTransform replaced the first occurrence and kept the others"
+      );
+
+      await setRedirectTransform({
+        queryTransform: {
+          addOrReplaceParams: [
+            { key: "r", value: "default" }, // default:false
+            { key: "r", value: "false", replaceOnly: false },
+            { key: "r", value: "true", replaceOnly: true },
+            { key: "r", value: "false2", replaceOnly: false },
+            { key: "r", value: "true2", replaceOnly: true },
+          ],
+        },
+      });
+      // r=true and r=true2 are missing because there are no matching "r".
+      await testFetch(
+        "http://from/",
+        "http://dest/?r=default&r=false&r=false2",
+        "queryTransform appends all except replaceOnly=true"
+      );
+      // r=true2 should be missing because there is no matching "r".
+      await testFetch(
+        "http://from/?r=1&r=2&r=3&___",
+        "http://dest/?r=default&r=false&r=true&___&r=false2",
+        "queryTransform replaced in order and ignores last replaceOnly=true"
+      );
+
+      await setRedirectTransform({
+        queryTransform: {
+          addOrReplaceParams: [
+            { key: "a", value: "appenda" },
+            { key: "b", value: "b1" },
+            { key: "c", value: "c1" },
+            { key: "c", value: "c2" },
+            { key: "c", value: "appendc" },
+            { key: "d", value: "d1" },
+          ],
+        },
+      });
+      // Test case has:         b  c  c       d.
+      // Rule only has: appenda b1 c2 appendc d1.
+      // Expected out :         b1 c2         d1 appenda appendc.
+      await testFetch(
+        "http://from/?b=01&c=02&c=03&d=06",
+        "http://dest/?b=b1&c=c1&c=c2&d=d1&a=appenda&c=appendc",
+        "queryTransform replaces matched queries and appends the rest, in order"
+      );
+
+      await setRedirectTransform({
+        queryTransform: {
+          addOrReplaceParams: [{ key: "query", value: " _+_%00_#" }],
+        },
+      });
+      await testFetch(
+        "http://from/",
+        "http://dest/?query=+_%2B_%2500_%23",
+        "queryTransform urlencodes values"
+      );
+
+      // This part tests how param names with non-alphanumeric characters can be
+      // (and not be) matched and replaced. This follows Chrome's behavior, see
+      // https://bugzilla.mozilla.org/show_bug.cgi?id=1801870#c1
+      await setRedirectTransform({
+        queryTransform: {
+          removeParams: ["?x", "%3Fx", "&x", "%26x"],
+          addOrReplaceParams: [
+            // Internally interpreted as: %3Fp:
+            { key: "?p", value: "rawq", replaceOnly: true },
+            // Internally interpreted as: %253Fp:
+            { key: "%3Fp", value: "escape_upper_q", replaceOnly: true },
+            // Internally interpreted as: %253fp:
+            { key: "%3fp", value: "escape_lower_q", replaceOnly: true },
+            // Internally interpreted as: %26p:
+            { key: "&p", value: "rawa", replaceOnly: true },
+            // Internally interpreted as: %2526p:
+            { key: "%26p", value: "escape_a", replaceOnly: true },
+          ],
+        },
+      });
+      await testFetch(
+        "http://from/?x&x&?x",
+        "http://dest/?x&x&?x",
+        "queryTransform does not match the '?' or '&' separators"
+      );
+      await testFetch(
+        "http://from/??p&&p&?p",
+        "http://dest/??p&&p&?p",
+        "queryTransform cannot match literal '?p' because it is not urlencoded"
+      );
+      await testFetch(
+        "http://from/?%3Fp",
+        "http://dest/?%3Fp=rawq",
+        "queryTransform matches already-urlencoded '%3Fp' with raw '?p'"
+      );
+      await testFetch(
+        "http://from/?%3fp",
+        "http://dest/?%3fp",
+        "queryTransform cannot match non-canonical percent encoding (lowercase)"
+      );
+      await testFetch(
+        "http://from/?%253fp&%253Fp",
+        "http://dest/?%253fp=escape_lower_q&%253Fp=escape_upper_q",
+        "queryTransform matches double-urlencoded '?p' with single-encoded '?p'"
+      );
+      await testFetch(
+        "http://from/?%26p",
+        "http://dest/?%26p=rawa",
+        "queryTransform matches already-urlencoded '%26p' with raw '&p'"
+      );
+
+      browser.test.notifyPass();
+    },
+  });
+});
+
+add_task(async function test_redirect_transform_fragment() {
+  await runAsDNRExtension({
+    background: async dnrTestUtils => {
+      // Note: not using testFetch because it cannot see fragment changes.
+      const { setRedirectTransform, testNavigate } = dnrTestUtils;
+
+      await setRedirectTransform({ fragment: "" });
+      await testNavigate(
+        "http://user:pass@from:777/path?query#ref",
+        "http://user:pass@dest:777/path?query",
+        "fragment cleared from URL with embedded credentials"
+      );
+
+      await setRedirectTransform({ fragment: "#new" });
+      await testNavigate("http://from/", "http://dest/#new", "fragment added");
+      await testNavigate(
+        "http://from/#ref",
+        "http://dest/#new",
+        "fragment changed"
+      );
+      browser.test.notifyPass();
+    },
+  });
+});
+
+add_task(async function test_redirect_transform_failed_at_runtime() {
+  await runAsDNRExtension({
+    background: async dnrTestUtils => {
+      const { setRedirectTransform } = dnrTestUtils;
+
+      // Maximum length of a UTL is 1048576 (network.standard-url.max-length).
+      const network_standard_url_max_length = 1048576;
+      // updateSessionRules does some validation on the limit (as seen by
+      // validate_action_redirect_transform in test_ext_dnr_session_rules.js),
+      // but it is still possible to pass validation and fail in practice when
+      // the existing URL + new component exceeds the limit.
+      const VERY_LONG_STRING = "x".repeat(network_standard_url_max_length - 20);
+
+      // Like testFetch, except truncates URLs in log messages to avoid logspam.
+      async function testFetchPossiblyLongUrl(from, to, body, description) {
+        let res = await fetch(from);
+        const shortx = s => s.replace(/x{10,}/g, xxx => `x{${xxx.length}}`);
+        // VERY_LONG_STRING consists of many 'X'. Shorten to avoid logspam.
+        browser.test.assertEq(shortx(to), shortx(res.url), description);
+        browser.test.assertEq(body, await res.text(), "expected body");
+      }
+
+      await setRedirectTransform({ query: "?" + VERY_LONG_STRING });
+      await testFetchPossiblyLongUrl(
+        "http://from/short",
+        `http://dest/short?${VERY_LONG_STRING}`,
+        // Somehow the httpd server raises NS_ERROR_MALFORMED_URI when it tries
+        // to use newURI to parse the received URL. But the server responding
+        // with that implies that the redirect was successful, so for the
+        // purpose of this test, that response is acceptable.
+        "Bad request\n",
+        "Can redirect to URL near (but not over) url max-length"
+      );
+
+      // This check confirms that not only does the request not redirect to
+      // an invalid URL, but also that the request does not somehow end up in
+      // an infinite redirect loop.
+      await testFetchPossiblyLongUrl(
+        "http://from/1234567890_1234567890",
+        "http://from/1234567890_1234567890",
+        "GOOD_RESPONSE",
+        "Redirect to URL over max length is ignored; request continues"
+      );
+
+      browser.test.notifyPass();
+    },
+  });
+});
diff --git a/toolkit/components/extensions/test/xpcshell/test_ext_dnr_regexFilter.js b/toolkit/components/extensions/test/xpcshell/test_ext_dnr_regexFilter.js
new file mode 100644
index 0000000000..0ee1bff815
--- /dev/null
+++ b/toolkit/components/extensions/test/xpcshell/test_ext_dnr_regexFilter.js
@@ -0,0 +1,590 @@
+"use strict";
+
+// This file provides test coverage for regexFilter and regexSubstitution.
+//
+// The validate_actions task of test_ext_dnr_session_rules.js checks that the
+// basic requirements of regexFilter + regexSubstitution are met.
+//
+// The match_regexFilter task of test_ext_dnr_testMatchOutcome.js verifies that
+// regexFilter is evaluated correctly in testMatchOutcome.
+//
+// The quota on regexFilter is verified in test_ext_dnr_regexFilter_limits.js.
+
+add_setup(() => {
+  Services.prefs.setBoolPref("extensions.manifestV3.enabled", true);
+  Services.prefs.setBoolPref("extensions.dnr.enabled", true);
+  Services.prefs.setBoolPref("extensions.dnr.feedback", true);
+});
+
+const server = createHttpServer({
+  hosts: ["example.com", "example-com", "from", "dest"],
+});
+server.registerPrefixHandler("/", (req, res) => {
+  res.setHeader("Access-Control-Allow-Origin", "*");
+  res.write("GOOD_RESPONSE");
+});
+
+// This function is serialized and called in the context of the test extension's
+// background page. dnrTestUtils is passed to the background function.
+function makeDnrTestUtils() {
+  const dnrTestUtils = {};
+  const dnr = browser.declarativeNetRequest;
+
+  async function testFetch(from, to, description) {
+    let res = await fetch(from);
+    browser.test.assertEq(to, res.url, description);
+    browser.test.assertEq("GOOD_RESPONSE", await res.text(), "expected body");
+  }
+
+  async function _testRegexFilterOrRedirect({
+    description,
+    regexFilter,
+    isUrlFilterCaseSensitive,
+    expectedRedirectUrl = "http://dest/",
+    regexSubstitution = expectedRedirectUrl,
+    urlsMatching,
+    urlsNonMatching,
+  }) {
+    browser.test.log(`Test description: ${description}`);
+    await dnr.updateSessionRules({
+      addRules: [
+        {
+          id: 12345,
+          condition: { regexFilter, isUrlFilterCaseSensitive },
+          action: { type: "redirect", redirect: { regexSubstitution } },
+        },
+      ],
+    });
+    for (let url of urlsMatching) {
+      const description = `regexFilter ${regexFilter} should match: ${url}`;
+      await testFetch(url, expectedRedirectUrl, description);
+    }
+    for (let url of urlsNonMatching) {
+      const description = `regexFilter ${regexFilter} should not match: ${url}`;
+      let expectedUrl = new URL(url);
+      expectedUrl.hash = "";
+      await testFetch(url, expectedUrl.href, description);
+    }
+    await dnr.updateSessionRules({ removeRuleIds: [12345] });
+  }
+
+  async function testValidRegexFilter({
+    description,
+    regexFilter,
+    isUrlFilterCaseSensitive,
+    urlsMatching,
+    urlsNonMatching,
+  }) {
+    browser.test.assertDeepEq(
+      { isSupported: true },
+      await dnr.isRegexSupported({
+        regex: regexFilter,
+        isCaseSensitive: isUrlFilterCaseSensitive,
+      }),
+      `isRegexSupported should detect support for: ${regexFilter}`
+    );
+    await _testRegexFilterOrRedirect({
+      description,
+      regexFilter,
+      isUrlFilterCaseSensitive,
+      expectedRedirectUrl: "http://dest/",
+      regexSubstitution: "http://dest/",
+      urlsMatching,
+      urlsNonMatching,
+    });
+  }
+
+  async function testValidRegexSubstitution({
+    description,
+    regexFilter,
+    regexSubstitution,
+    inputUrl,
+    expectedRedirectUrl,
+  }) {
+    browser.test.assertDeepEq(
+      { isSupported: true },
+      await dnr.isRegexSupported({
+        regex: regexFilter,
+        // requireCapturing option not strictly needed, but included to verify
+        // that the method can take the option without issues.
+        requireCapturing: true,
+      }),
+      `isRegexSupported should accept regexFilter: ${regexFilter}`
+    );
+
+    await _testRegexFilterOrRedirect({
+      description,
+      regexFilter,
+      regexSubstitution,
+      urlsMatching: [inputUrl],
+      urlsNonMatching: [],
+      expectedRedirectUrl,
+    });
+  }
+
+  async function testInvalidRegexFilter(regexFilter, expectedError, msg) {
+    browser.test.assertDeepEq(
+      { isSupported: false, reason: "syntaxError" },
+      await dnr.isRegexSupported({ regex: regexFilter }),
+      `isRegexSupported should detect unsupported regex: ${regexFilter}`
+    );
+    await browser.test.assertRejects(
+      dnr.updateSessionRules({
+        addRules: [
+          { id: 123, condition: { regexFilter }, action: { type: "block" } },
+        ],
+      }),
+      expectedError,
+      `Should reject invalid regexFilter (${regexFilter}) - ${msg}`
+    );
+  }
+
+  async function testInvalidRegexSubstitution(
+    regexSubstitution,
+    expectedError,
+    msg
+  ) {
+    await browser.test.assertRejects(
+      _testRegexFilterOrRedirect({
+        description: `testInvalidRegexSubstitution: "${regexSubstitution}"`,
+        regexFilter: ".",
+        regexSubstitution,
+        urlsMatching: [],
+        urlsNonMatching: [],
+      }),
+      expectedError,
+      msg
+    );
+  }
+
+  async function testRejectedRedirectAtRuntime({ regexSubstitution, url }) {
+    // Some regexSubstitution rules pass validation but the generated redirect
+    // URL is rejected at runtime. That is validated here.
+    await _testRegexFilterOrRedirect({
+      description: `testRejectedRedirectAtRuntime for URL: ${url}`,
+      regexFilter: "http://from/.*",
+      regexSubstitution,
+      // When regexSubstitution is invalid, it should not be redirected:
+      expectedRedirectUrl: url,
+      urlsMatching: [url],
+      urlsNonMatching: [],
+    });
+  }
+
+  Object.assign(dnrTestUtils, {
+    testValidRegexFilter,
+    testValidRegexSubstitution,
+    testInvalidRegexFilter,
+    testInvalidRegexSubstitution,
+    testRejectedRedirectAtRuntime,
+  });
+  return dnrTestUtils;
+}
+
+async function runAsDNRExtension({ background, manifest }) {
+  let extension = ExtensionTestUtils.loadExtension({
+    background: `(${background})((${makeDnrTestUtils})())`,
+    allowInsecureRequests: true,
+    manifest: {
+      manifest_version: 3,
+      permissions: ["declarativeNetRequest"],
+      // host_permissions are needed for the redirect action.
+      host_permissions: ["<all_urls>"],
+      granted_host_permissions: true,
+      ...manifest,
+    },
+    temporarilyInstalled: true, // <-- for granted_host_permissions
+  });
+  await extension.startup();
+  await extension.awaitFinish();
+  await extension.unload();
+}
+
+// The least common denominator across Chrome, Safari and Firefox is Safari, at
+// the time of writing, the supported syntax in Safari's regexFilter is
+// documented at https://webkit.org/blog/3476/content-blockers-first-look/,
+// section "The Regular expression format":
+//
+// - Matching any character with “.”.
+// - Matching ranges with the range syntax [a-b].
+// - Quantifying expressions with “?”, “+” and “*”.
+// - Groups with parenthesis.
+// - ... beginning of line (“^”) and end of line (“$”) marker ...
+//
+// The above syntax is very limited, as expressed at
+// https://github.com/w3c/webextensions/issues/344
+//
+// The tests continue in regexFilter_more_than_basic.
+add_task(async function regexFilter_basic() {
+  await runAsDNRExtension({
+    background: async dnrTestUtils => {
+      const { testValidRegexFilter } = dnrTestUtils;
+
+      await testValidRegexFilter({
+        description: "URL as regexFilter is sometimes a valid regexp",
+        regexFilter: "http://example.com/",
+        urlsMatching: [
+          "http://example.com/",
+          // dot is wildcard.
+          "http://example-com/",
+          // Without ^ anchor, matches substring elsewhere.
+          "http://from/http://example.com/",
+        ],
+        urlsNonMatching: [
+          "http://dest/http://example.com-no-slash-after-.com",
+          // Does not match reference fragment.
+          "http://dest/#http://example.com/",
+        ],
+      });
+
+      await testValidRegexFilter({
+        description: "\\. is literal dot",
+        regexFilter: "http://example\\.com/",
+        urlsMatching: ["http://example.com/"],
+        urlsNonMatching: ["http://example-com/"],
+      });
+
+      await testValidRegexFilter({
+        description: "[a-b] range is supported",
+        regexFilter: "http://from/[a-b]",
+        urlsMatching: ["http://from/a", "http://from/b"],
+        urlsNonMatching: ["http://from/c", "http://from/"],
+      });
+
+      await testValidRegexFilter({
+        description: "groups with parenthesis are supported",
+        regexFilter: "http://from/(a)",
+        urlsMatching: ["http://from/a", "http://from/aa"],
+        urlsNonMatching: ["http://from/b", "http://from/ba"],
+      });
+
+      await testValidRegexFilter({
+        description: "+, * and ? are quantifiers",
+        regexFilter: "a+b*c?d",
+        urlsMatching: [
+          "http://from/ad",
+          "http://from/abcd",
+          "http://from/aaabbcd",
+        ],
+        urlsNonMatching: [
+          "http://from/bcd", // "a+" requires "a" to be specified.
+          "http://from/abccd", // "c?" matches only one c, but got two.
+        ],
+      });
+
+      await testValidRegexFilter({
+        description: ".* matches anything",
+        regexFilter: "a.*b",
+        urlsMatching: ["http://from/ab/", "http://from/aANYTHINGb"],
+        urlsNonMatching: ["http://from/a"],
+      });
+
+      await testValidRegexFilter({
+        description: "^ is start-of-string anchor",
+        regexFilter: "^http://from/",
+        urlsMatching: ["http://from/", "http://from/path"],
+        urlsNonMatching: ["http://dest/^http://from/"],
+      });
+
+      await testValidRegexFilter({
+        description: "$ is end-of-string anchor",
+        regexFilter: "http://from/$",
+        urlsMatching: ["http://from/", "http://dest/http://from/"],
+        urlsNonMatching: ["http://from/path", "http://from/$"],
+      });
+
+      browser.test.notifyPass();
+    },
+  });
+});
+
+// regexFilter_basic lists the bare minimum, this tests more useful features.
+add_task(async function regexFilter_more_than_basic() {
+  await runAsDNRExtension({
+    background: async dnrTestUtils => {
+      const { testValidRegexFilter } = dnrTestUtils;
+
+      // Use cases listed at
+      // https://github.com/w3c/webextensions/issues/344#issuecomment-1430358116
+
+      await testValidRegexFilter({
+        description: "{n,m} quantifier",
+        regexFilter: "http://from/a{2,3}b",
+        urlsMatching: ["http://from/aab", "http://from/aaab"],
+        urlsNonMatching: ["http://from/ab", "http://from/aaaab"],
+      });
+
+      await testValidRegexFilter({
+        description: "{n,} quantifier",
+        regexFilter: "http://from/a{2,}$",
+        urlsMatching: ["http://from/aa", "http://from/aaa", "http://from/aaaa"],
+        urlsNonMatching: ["http://from/a"],
+      });
+
+      await testValidRegexFilter({
+        description: "| disjunction and within groups",
+        regexFilter: "from/a|from/b$|c$",
+        urlsMatching: ["http://from/a", "http://from/b", "http://from/c"],
+        urlsNonMatching: ["http://from/b$|c$"],
+      });
+
+      await testValidRegexFilter({
+        description: "(?!) negative look-ahead",
+        regexFilter: "http://from/a(?!notme|$)",
+        urlsMatching: ["http://from/aOK"],
+        urlsNonMatching: ["http://from/anotme", "http://from/a"],
+      });
+
+      // Features based on
+      // https://github.com/w3c/webextensions/issues/344#issuecomment-1430127543
+      await testValidRegexFilter({
+        description: "Negated character class",
+        regexFilter: "http://from/[^a-z]",
+        urlsMatching: ["http://from/1"],
+        urlsNonMatching: ["http://from/a", "http://from/y", "http://from/"],
+      });
+
+      await testValidRegexFilter({
+        description: "Word character class (\\w)",
+        regexFilter: "http://from/\\w",
+        urlsMatching: ["http://from/1", "http://from/a", "http://from/_"],
+        urlsNonMatching: ["http://from/-", "http://from/%20"],
+      });
+
+      // Rule that leads to "memoryLimitExceeded" in Chrome:
+      // https://github.com/w3c/webextensions/issues/344#issuecomment-1424527627
+      await testValidRegexFilter({
+        description: "regexFilter that triggers memoryLimitExceeded in Chrome",
+        regexFilter: "(https?://)104\\.154\\..{100,}",
+        urlsMatching: ["http://from/http://104.154.0.0/" + "x".repeat(100)],
+        urlsNonMatching: ["http://from/http://104.154.0.0/too-short"],
+      });
+
+      browser.test.notifyPass();
+    },
+  });
+});
+
+// Adds more coverage in addition to what was tested by validate_regexFilter in
+// test_ext_dnr_session_rules.js.
+add_task(async function regexFilter_invalid() {
+  await runAsDNRExtension({
+    background: async dnrTestUtils => {
+      const { testInvalidRegexFilter } = dnrTestUtils;
+
+      await testInvalidRegexFilter(
+        "(",
+        "regexFilter is not a valid regular expression",
+        "( opens a group and should be closed"
+      );
+
+      await testInvalidRegexFilter(
+        "straß.d",
+        "regexFilter should not contain non-ASCII characters",
+        "regexFilter matches the canonical URL which does not contain non-ASCII"
+      );
+
+      browser.test.notifyPass();
+    },
+  });
+});
+
+add_task(async function regexFilter_isUrlFilterCaseSensitive() {
+  await runAsDNRExtension({
+    background: async dnrTestUtils => {
+      const { testValidRegexFilter } = dnrTestUtils;
+
+      await testValidRegexFilter({
+        description: "isUrlFilterCaseSensitive omitted (= false by default)",
+        // isUrlFilterCaseSensitive = false by default.
+        regexFilter: "from/Pa",
+        urlsMatching: ["http://from/Pa", "http://from/pa", "http://from/PA"],
+        urlsNonMatching: [],
+      });
+
+      await testValidRegexFilter({
+        description: "isUrlFilterCaseSensitive: false",
+        isUrlFilterCaseSensitive: false,
+        regexFilter: "from/Pa",
+        urlsMatching: ["http://from/Pa", "http://from/pa", "http://from/PA"],
+        urlsNonMatching: [],
+      });
+
+      await testValidRegexFilter({
+        description: "isUrlFilterCaseSensitive: true",
+        isUrlFilterCaseSensitive: true,
+        regexFilter: "from/Pa",
+        urlsMatching: ["http://from/Pa"],
+        urlsNonMatching: ["http://from/pa", "http://from/PA"],
+      });
+
+      await testValidRegexFilter({
+        description: "Case-sensitive uppercase regexFilter cannot match HOST",
+        isUrlFilterCaseSensitive: true,
+        regexFilter: "FROM",
+        urlsMatching: [],
+        urlsNonMatching: ["http://FROM/canonical_host_is_lowercase"],
+      });
+
+      browser.test.notifyPass();
+    },
+  });
+});
+
+add_task(async function regexSubstitution_invalid() {
+  let { messages } = await promiseConsoleOutput(async () => {
+    await runAsDNRExtension({
+      manifest: { browser_specific_settings: { gecko: { id: "@dnr" } } },
+      background: async dnrTestUtils => {
+        const { testRejectedRedirectAtRuntime, testInvalidRegexSubstitution } =
+          dnrTestUtils;
+
+        await testInvalidRegexSubstitution(
+          "http://dest/\\x20",
+          "redirect.regexSubstitution only allows digit or \\ after \\.",
+          "\\x should not be allowed in regexSubstitution"
+        );
+
+        await testInvalidRegexSubstitution(
+          "http://dest/?\\",
+          "redirect.regexSubstitution only allows digit or \\ after \\.",
+          "\\<end> should not be allowed in regexSubstitution"
+        );
+
+        await testRejectedRedirectAtRuntime({
+          regexSubstitution: "not-URL",
+          url: "http://from/should_not_be_directed_invalid_url",
+        });
+
+        await testRejectedRedirectAtRuntime({
+          regexSubstitution: "javascript://-URL",
+          url: "http://from/should_not_be_directed_javascript_url",
+        });
+
+        // May be allowed once bug 1622986 is fixed.
+        await testRejectedRedirectAtRuntime({
+          regexSubstitution: "data:,redirect-from-dnr",
+          url: "http://from/should_not_be_directed_disallowed_url",
+        });
+
+        await testRejectedRedirectAtRuntime({
+          regexSubstitution: "resource://gre/",
+          url: "http://from/should_not_be_directed_resource_url",
+        });
+
+        browser.test.notifyPass();
+      },
+    });
+  });
+
+  AddonTestUtils.checkMessages(messages, {
+    expected: [
+      {
+        message: /Extension @dnr tried to redirect to an invalid URL: not-URL/,
+      },
+      {
+        message: /Extension @dnr may not redirect to: javascript:\/\/-URL/,
+      },
+      {
+        message: /Extension @dnr may not redirect to: data:,redirect-from-dnr/,
+      },
+      {
+        message: /Extension @dnr may not redirect to: resource:\/\/gre\//,
+      },
+    ],
+  });
+});
+
+add_task(async function regexSubstitution_valid() {
+  await runAsDNRExtension({
+    background: async dnrTestUtils => {
+      const { testValidRegexSubstitution } = dnrTestUtils;
+
+      await testValidRegexSubstitution({
+        description: "All captured groups can be accessed by \\1 - \\9",
+        regexFilter: "from/(.)(.)(.)(.)(.)(.)(.)(.)(.)(.)(.)",
+        regexSubstitution: "http://dest/\\9\\8\\7\\6\\5\\4\\3\\2\\1",
+        inputUrl: "http://from/abcdef?gh-ignoredsuffix",
+        // ^ captured groups:  123456789
+        expectedRedirectUrl: "http://dest/hg?fedcba",
+      });
+
+      await testValidRegexSubstitution({
+        description: "\\0 captures the full match",
+        regexFilter: "from/$",
+        regexSubstitution: "http://dest/\\0/end",
+        inputUrl: "http://from/",
+        expectedRedirectUrl: "http://dest/from//end",
+      });
+
+      await testValidRegexSubstitution({
+        description: "\\10 means: captured group 1 + literal 0",
+        regexFilter: "/(captured)$",
+        regexSubstitution: "http://dest/\\10",
+        inputUrl: "http://from/captured",
+        expectedRedirectUrl: "http://dest/captured0",
+      });
+
+      await testValidRegexSubstitution({
+        description: "\\\\ is an escaped backslash",
+        regexFilter: "/(XXX)",
+        regexSubstitution: "http://dest/?\\1\\\\1\\\\\\\\1\\1",
+        inputUrl: "http://from/XXX",
+        expectedRedirectUrl: "http://dest/?XXX\\1\\\\1XXX",
+      });
+
+      await testValidRegexSubstitution({
+        description: "Captured groups can be repeated",
+        regexFilter: "/(captured)$",
+        regexSubstitution: "http://dest/\\1+\\1",
+        inputUrl: "http://from/captured",
+        expectedRedirectUrl: "http://dest/captured+captured",
+      });
+
+      await testValidRegexSubstitution({
+        description: "Non-matching optional group is an empty string",
+        regexFilter: "(doesnotmatch)?suffix",
+        regexSubstitution: "http://dest/[\\1]=group1_is_optional",
+        inputUrl: "http://from/suffix",
+        expectedRedirectUrl: "http://dest/[]=group1_is_optional",
+      });
+
+      await testValidRegexSubstitution({
+        description: "Non-existing capturing group is an empty string",
+        regexFilter: "(captured)",
+        regexSubstitution: "http://dest/[\\2]=missing_group_2",
+        inputUrl: "http://from/captured",
+        expectedRedirectUrl: "http://dest/[]=missing_group_2",
+      });
+
+      await testValidRegexSubstitution({
+        description: "Non-capturing group is not captured",
+        regexFilter: "(?:non-)(captured)",
+        regexSubstitution: "http://dest/[\\1]=only_captured_group",
+        inputUrl: "http://from/non-captured",
+        expectedRedirectUrl: "http://dest/[captured]=only_captured_group",
+      });
+
+      browser.test.notifyPass();
+    },
+  });
+});
+
+add_task(async function regexSubstitution_redirect_chain() {
+  await runAsDNRExtension({
+    background: async dnrTestUtils => {
+      const { testValidRegexSubstitution } = dnrTestUtils;
+
+      await testValidRegexSubstitution({
+        description: "regexFilter matches intermediate redirect URLs",
+        regexFilter: "^(http://from/)(a|b|c)(.+)",
+        regexSubstitution: "\\1\\3",
+        inputUrl: "http://from/abcdef",
+        // After redirecting three times, we end up here:
+        expectedRedirectUrl: "http://from/def",
+      });
+
+      browser.test.notifyPass();
+    },
+  });
+});
diff --git a/toolkit/components/extensions/test/xpcshell/test_ext_dnr_regexFilter_limits.js b/toolkit/components/extensions/test/xpcshell/test_ext_dnr_regexFilter_limits.js
new file mode 100644
index 0000000000..443f69c2d1
--- /dev/null
+++ b/toolkit/components/extensions/test/xpcshell/test_ext_dnr_regexFilter_limits.js
@@ -0,0 +1,549 @@
+"use strict";
+
+// This file verifies the quota on regexFilter rules for all ruleset.
+//
+// The generic rule limits (not specific to regexFilter) are covered elsewhere:
+// - session_rules_total_rule_limit in test_ext_dnr_session_rules.js
+// - test_dynamic_rules_count_limits in test_ext_dnr_dynamic_rules.js
+//   (also checks that the quota of session and dynamic rules are separate.)
+// - test_getAvailableStaticRulesCountAndLimits and test_static_rulesets_limits
+//   in test_ext_dnr_static_rules.js.
+
+ChromeUtils.defineESModuleGetters(this, {
+  ExtensionDNRLimits: "resource://gre/modules/ExtensionDNRLimits.sys.mjs",
+});
+
+AddonTestUtils.init(this);
+AddonTestUtils.overrideCertDB();
+
+add_setup(async () => {
+  Services.prefs.setBoolPref("extensions.manifestV3.enabled", true);
+  Services.prefs.setBoolPref("extensions.dnr.enabled", true);
+  Services.prefs.setBoolPref("extensions.dnr.feedback", true);
+
+  // We want to install add-ons through the add-on manager in order to be able
+  // to disable / re-enable the add-on.
+  await ExtensionTestUtils.startAddonManager();
+});
+
+const _origDescs = {};
+function restoreDefaultDnrLimit(key) {
+  info(`Restoring original value of ExtensionDNRLimits.${key}`);
+  Object.defineProperty(ExtensionDNRLimits, key, _origDescs[key]);
+}
+function overrideDefaultDnrLimit(key, value) {
+  // Until DNR limits can be customized through prefs (bug 1803370), we need to
+  // overwrite the internals here in the parent process. That is sufficient to
+  // control the limits. Notably, this does NOT affect the values of the
+  // constants exposed through the declarativeNetRequest keyspace, because
+  // their values are directly read from the extension (child) process.
+  if (!_origDescs[key]) {
+    _origDescs[key] = Object.getOwnPropertyDescriptor(ExtensionDNRLimits, key);
+    registerCleanupFunction(() => restoreDefaultDnrLimit(key));
+  }
+  Assert.ok(
+    typeof value === "number" && Number.isInteger(value),
+    `Setting ExtensionDNRLimits.${key} = ${value} (was: ${ExtensionDNRLimits[key]})`
+  );
+  Object.defineProperty(ExtensionDNRLimits, key, {
+    configurable: true,
+    writable: true,
+    enumerable: true,
+    value,
+  });
+}
+
+// Create an extension composed of the given test cases, and start or reload
+// the extension before each test case.
+//
+// testCases is an array of:
+// - name - unique name describing purpose of test
+// - setup - optional function run before (re-)enabling the extension.
+// - backgroundFn - logic to run in the extension's background.
+// - checkConsoleMessages - function to run to verify the console messages
+//   collected between extension (re)startup and the execution of backgroundFn.
+//
+// extensionDataTemplate should be a value for ExtensionTestUtils.loadExtension,
+// without the background key.
+async function startOrReloadExtensionForEach(testCases, extensionDataTemplate) {
+  for (let testCase of testCases) {
+    // Verify that the keys are supported, so that the test does not pass
+    // trivially because of a typo or something.
+    let okKeys = ["name", "setup", "backgroundFn", "checkConsoleMessages"];
+    let keys = Object.keys(testCase).filter(k => !okKeys.includes(k));
+    if (keys.length) {
+      throw new Error(`Unexpected key in testCase ${testCase.name}: ${keys}`);
+    }
+  }
+  if (extensionDataTemplate.background) {
+    // background is generated here, so the template should not specify it.
+    throw new Error("extensionDataTemplate.background should not be set");
+  }
+  function background(testCases) {
+    browser.test.onMessage.addListener(async testName => {
+      try {
+        browser.test.log(`Starting backgroundFn for ${testName}`);
+        await testCases.find(({ name }) => name === testName).backgroundFn();
+      } catch (e) {
+        browser.test.fail(`Unexpected error for ${testName}: ${e}`);
+      }
+      browser.test.log(`Completed backgroundFn for ${testName}`);
+      browser.test.sendMessage(`${testName}:done`);
+    });
+    browser.test.sendMessage("background_started");
+  }
+
+  const serializedTestCases = testCases.map(
+    ({ name, backgroundFn }) => `{name:"${name}",backgroundFn:${backgroundFn}}`
+  );
+  let extension = ExtensionTestUtils.loadExtension({
+    ...extensionDataTemplate,
+    background: `(${background})([${serializedTestCases.join(",")}])`,
+  });
+
+  for (let [i, { name, setup, checkConsoleMessages }] of testCases.entries()) {
+    info(`Running test case: ${name}`);
+    await setup?.();
+
+    let { messages } = await promiseConsoleOutput(async () => {
+      if (i === 0) {
+        await extension.startup();
+      } else {
+        await extension.addon.enable();
+      }
+      await extension.awaitMessage("background_started");
+
+      // DNR rule loading errors should be emitted at startup. But since the
+      // rule loading is async and not blocking background startup, we need to
+      // roundtrip through the DNR API before we can verify the error message.
+      extension.sendMessage(name);
+      await extension.awaitMessage(`${name}:done`);
+    });
+
+    checkConsoleMessages(name, messages);
+
+    if (i === testCases.length - 1) {
+      await extension.unload();
+    } else {
+      await extension.addon.disable();
+    }
+    info(`Completed test case: ${name}`);
+  }
+}
+
+// Create the extensionDataTemplate value (without "background" key!) for use
+// with ExtensionTestUtils.loadExtension, through startOrReloadExtensionForEach.
+function makeExtensionDataTemplate({ manifest, files }) {
+  return {
+    // Note: no "background" key because startOrReloadExtensionForEach adds it.
+    useAddonManager: "permanent",
+    manifest: {
+      manifest_version: 3,
+      permissions: ["declarativeNetRequest", "declarativeNetRequestFeedback"],
+      browser_specific_settings: { gecko: { id: "dnr@ext" } },
+      ...manifest,
+    },
+    files,
+  };
+}
+
+function genStaticRules(count) {
+  let rules = [];
+  for (let i = 1; i <= count; ++i) {
+    rules.push({
+      id: i,
+      condition: { regexFilter: `prefix_${i}_suffix` },
+      action: { type: "block" },
+    });
+  }
+  return JSON.stringify(rules);
+}
+
+add_task(async function session_and_dynamic_regexFilter_limit() {
+  let extensionDataTemplate = makeExtensionDataTemplate({});
+
+  // Note: Every testPart* function will be serialized and be part of the test
+  // extension's background script.
+
+  async function testPart1_session_and_dynamic_quota() {
+    let rules = [];
+    const { MAX_NUMBER_OF_REGEX_RULES } = browser.declarativeNetRequest;
+    for (let i = 1; i <= MAX_NUMBER_OF_REGEX_RULES; ++i) {
+      rules.push({
+        id: i,
+        condition: { regexFilter: `prefix_${i}_suffix` },
+        action: { type: "block" },
+      });
+    }
+    const lastRuleId = rules[rules.length - 1].id;
+
+    browser.test.log(`Adding ${rules.length} regex rules (dynamic)`);
+    await browser.declarativeNetRequest.updateDynamicRules({
+      addRules: rules,
+    });
+
+    browser.test.assertDeepEq(
+      { matchedRules: [{ ruleId: lastRuleId, rulesetId: "_dynamic" }] },
+      await browser.declarativeNetRequest.testMatchOutcome({
+        url: `http://example.com/prefix_${lastRuleId}_suffix`,
+        type: "other",
+      }),
+      "Expected last regexFilter to match the request"
+    );
+
+    // Dynamic and session rules should have a separate quota for regexFilter.
+    browser.test.log(`Adding ${rules.length} regex rules (session)`);
+    await browser.declarativeNetRequest.updateSessionRules({
+      addRules: rules,
+    });
+
+    browser.test.assertDeepEq(
+      { matchedRules: [{ ruleId: lastRuleId, rulesetId: "_session" }] },
+      await browser.declarativeNetRequest.testMatchOutcome({
+        url: `http://example.com/prefix_${lastRuleId}_suffix`,
+        type: "other",
+      }),
+      "Expected registered regexFilter to match"
+    );
+
+    // Now we should not be able to add another one.
+    const newRule = {
+      id: lastRuleId + 1,
+      condition: { regexFilter: "." },
+      action: { type: "block" },
+    };
+    await browser.test.assertRejects(
+      browser.declarativeNetRequest.updateSessionRules({ addRules: [newRule] }),
+      `Number of regexFilter rules in ruleset "_session" exceeds MAX_NUMBER_OF_REGEX_RULES.`,
+      "Should not allow regexFilter over quota for session ruleset"
+    );
+    await browser.test.assertRejects(
+      browser.declarativeNetRequest.updateDynamicRules({ addRules: [newRule] }),
+      `Number of regexFilter rules in ruleset "_dynamic" exceeds MAX_NUMBER_OF_REGEX_RULES.`,
+      "Should not allow regexFilter over quota for dynamic ruleset"
+    );
+  }
+
+  async function testPart2_after_reload() {
+    browser.test.assertEq(
+      0,
+      (await browser.declarativeNetRequest.getSessionRules()).length,
+      "Session rules gone after restart"
+    );
+    let rules = await browser.declarativeNetRequest.getDynamicRules();
+    browser.test.assertEq(
+      browser.declarativeNetRequest.MAX_NUMBER_OF_REGEX_RULES,
+      rules.length,
+      "Dynamic regexFilter rules still there after restart"
+    );
+
+    // This confirms that the quota for session rules is not somehow persisted
+    // somewhere else.
+    browser.test.log(`Verifying that we can add ${rules.length} rules again.`);
+    await browser.declarativeNetRequest.updateSessionRules({
+      addRules: rules,
+    });
+  }
+
+  async function testPart3_too_many_regexFilters_stored_after_lowering_quota() {
+    browser.test.assertEq(
+      0,
+      (await browser.declarativeNetRequest.getDynamicRules()).length,
+      "Ignore all stored dynamic rules when regexFilter quota is exceeded"
+    );
+  }
+
+  async function testPart4_reload_after_quota_back() {
+    // Implementation detail: while the in-memory representation of the
+    // dynamic rules has been wiped at the previous extension load, the disk
+    // representation did not change because we only read the dynamic rules
+    // without anything else triggering a save request.
+    //
+    // Therefore, when the limit was somehow restored, the on-disk data is
+    // now considered valid again.
+    browser.test.assertEq(
+      browser.declarativeNetRequest.MAX_NUMBER_OF_REGEX_RULES,
+      (await browser.declarativeNetRequest.getDynamicRules()).length,
+      "On-disk dynamic rules accepted when regexFilter quota is not exceeded"
+    );
+  }
+
+  // Expected warning in console when there are too many regexFilter rules in
+  // the dynamic ruleset data on disk.
+  const errorMsg = `Ignoring dynamic ruleset in extension "dnr@ext" because: Number of regexFilter rules in ruleset "_dynamic" exceeds MAX_NUMBER_OF_REGEX_RULES.`;
+  function expectError(testName, messages) {
+    Assert.equal(
+      messages.filter(m => m.message.includes(errorMsg)).length,
+      1,
+      `${testName} should trigger the following error in the log: ${errorMsg}`
+    );
+  }
+  function noErrors(testName, messages) {
+    Assert.equal(
+      messages.filter(m => m.message.includes(errorMsg)).length,
+      0,
+      `${testName} should not trigger any logged errors`
+    );
+  }
+
+  const testCases = [
+    {
+      name: "testPart1_session_and_dynamic_quota",
+      backgroundFn: testPart1_session_and_dynamic_quota,
+      checkConsoleMessages: noErrors,
+    },
+    {
+      name: "testPart2_after_reload",
+      backgroundFn: testPart2_after_reload,
+      checkConsoleMessages: noErrors,
+    },
+    {
+      name: "testPart3_too_many_regexFilters_stored_after_lowering_quota",
+      setup() {
+        // Artificially decrease the max number of allowed regexFilter rules,
+        // so that whatever that was stored on disk is no longer within quota.
+        overrideDefaultDnrLimit("MAX_NUMBER_OF_REGEX_RULES", 1);
+      },
+      backgroundFn: testPart3_too_many_regexFilters_stored_after_lowering_quota,
+      checkConsoleMessages: expectError,
+    },
+    {
+      name: "testPart4_reload_after_quota_back",
+      setup() {
+        // Restore the original quota after it was lowered in testPart3.
+        restoreDefaultDnrLimit("MAX_NUMBER_OF_REGEX_RULES");
+      },
+      backgroundFn: testPart4_reload_after_quota_back,
+      checkConsoleMessages: noErrors,
+    },
+  ];
+
+  await startOrReloadExtensionForEach(testCases, extensionDataTemplate);
+});
+
+add_task(async function static_regexFilter_limit() {
+  const { MAX_NUMBER_OF_REGEX_RULES } = ExtensionDNRLimits;
+
+  let extensionDataTemplate = makeExtensionDataTemplate({
+    manifest: {
+      declarative_net_request: {
+        rule_resources: [
+          // limit_plus_1 is over quota, but the other rules should be loaded
+          // if possible.
+          { id: "limit_plus_1", path: "limit_plus_1.json", enabled: true },
+          { id: "just_one", path: "just_one.json", enabled: true },
+          { id: "just_two", path: "just_two.json", enabled: true },
+          { id: "limit_minus_2", path: "limit_minus_2.json", enabled: true },
+          { id: "limit_minus_1", path: "limit_minus_1.json", enabled: false },
+        ],
+      },
+    },
+    files: {
+      "limit_plus_1.json": genStaticRules(MAX_NUMBER_OF_REGEX_RULES + 1),
+      "just_one.json": genStaticRules(1),
+      "just_two.json": genStaticRules(2),
+      "limit_minus_2.json": genStaticRules(MAX_NUMBER_OF_REGEX_RULES - 2),
+      "limit_minus_1.json": genStaticRules(MAX_NUMBER_OF_REGEX_RULES - 1),
+    },
+  });
+
+  // Note: Every testPart* function will be serialized and be part of the test
+  // extension's background script.
+
+  async function testPart1_start_over_static_quota() {
+    browser.test.assertDeepEq(
+      ["just_one", "just_two"],
+      await browser.declarativeNetRequest.getEnabledRulesets(),
+      "Should only load rules that fit in the quota for static rules"
+    );
+  }
+
+  async function testPart2_after_reload() {
+    // Should still be the same.
+    browser.test.assertDeepEq(
+      ["just_one", "just_two"],
+      await browser.declarativeNetRequest.getEnabledRulesets(),
+      "Should only load rules that fit in the quota for static rules (again)"
+    );
+
+    await browser.declarativeNetRequest.updateEnabledRulesets({
+      disableRulesetIds: ["just_one"],
+    });
+
+    browser.test.assertDeepEq(
+      ["just_two"],
+      await browser.declarativeNetRequest.getEnabledRulesets(),
+      "After disabling 'just_one', there should only be one enabled ruleset"
+    );
+  }
+
+  async function testPart3_after_updateEnabledRulesets_within_limit() {
+    browser.test.assertDeepEq(
+      ["just_two"],
+      await browser.declarativeNetRequest.getEnabledRulesets(),
+      "limit_minus_2 should still be disabled because of a previous updateEnabledRulesets call"
+    );
+
+    // This should succeed, as there is now enough space.
+    await browser.declarativeNetRequest.updateEnabledRulesets({
+      enableRulesetIds: ["limit_minus_2"],
+    });
+    browser.test.assertDeepEq(
+      ["just_two", "limit_minus_2"],
+      await browser.declarativeNetRequest.getEnabledRulesets(),
+      "limit_minus_2 should be enabled by updateEnabledRulesets"
+    );
+
+    await browser.test.assertRejects(
+      browser.declarativeNetRequest.updateEnabledRulesets({
+        enableRulesetIds: ["just_one"],
+      }),
+      `Number of regexFilter rules across all enabled static rulesets exceeds MAX_NUMBER_OF_REGEX_RULES if ruleset "just_one" were to be enabled.`,
+      "Should not be able to enable just_one because limit was reached"
+    );
+  }
+
+  async function testPart4_toggling_rulesets_at_quota() {
+    browser.test.assertDeepEq(
+      ["just_two", "limit_minus_2"],
+      await browser.declarativeNetRequest.getEnabledRulesets(),
+      "Should have the two rulesets occupying all quota from the previous run"
+    );
+
+    await browser.declarativeNetRequest.updateEnabledRulesets({
+      disableRulesetIds: ["just_two"],
+      enableRulesetIds: ["just_one"],
+    });
+    browser.test.assertDeepEq(
+      ["just_one", "limit_minus_2"],
+      await browser.declarativeNetRequest.getEnabledRulesets(),
+      "Should be able to replace a ruleset as long as the result is within quota"
+    );
+
+    // Try to enable just_one + just_two (+existing limit_minus_2).
+    await browser.test.assertRejects(
+      browser.declarativeNetRequest.updateEnabledRulesets({
+        disableRulesetIds: ["just_one"],
+        enableRulesetIds: ["just_one", "just_two"],
+      }),
+      `Number of regexFilter rules across all enabled static rulesets exceeds MAX_NUMBER_OF_REGEX_RULES if ruleset "just_two" were to be enabled.`,
+      "Should reject updateEnabledRulesets that would exceed the quota by 1"
+    );
+    browser.test.assertDeepEq(
+      ["just_one", "limit_minus_2"],
+      await browser.declarativeNetRequest.getEnabledRulesets(),
+      "Rulesets should not have changed due to rejection"
+    );
+  }
+
+  async function testPart5_after_doubling_quota() {
+    browser.test.assertDeepEq(
+      ["just_one", "limit_minus_2"],
+      await browser.declarativeNetRequest.getEnabledRulesets(),
+      "Initial ruleset not changed after bumping the quota"
+    );
+    // Explicitly disable before re-enabling them all to see whether the order
+    // of passed-in rulesets has any impact on the evaluation order at startup.
+    await browser.declarativeNetRequest.updateEnabledRulesets({
+      disableRulesetIds: ["limit_minus_2", "just_one"],
+    });
+    await browser.declarativeNetRequest.updateEnabledRulesets({
+      enableRulesetIds: [
+        "limit_minus_2",
+        "just_two",
+        "just_one",
+        "limit_minus_1",
+      ],
+    });
+    browser.test.assertDeepEq(
+      ["just_one", "just_two", "limit_minus_2", "limit_minus_1"],
+      await browser.declarativeNetRequest.getEnabledRulesets(),
+      "All rulesets within new quota - ruleset order should match manifest order"
+    );
+  }
+
+  async function testPart6_after_restoring_original_quota_half() {
+    browser.test.assertDeepEq(
+      ["just_one", "just_two"],
+      await browser.declarativeNetRequest.getEnabledRulesets(),
+      "Should have trimmed excess rules in the manifest order"
+    );
+  }
+
+  const errorMsgPattern =
+    /Ignoring static ruleset "([^"]+)" in extension "dnr@ext" because: Number of regexFilter rules across all enabled static rulesets exceeds MAX_NUMBER_OF_REGEX_RULES if ruleset "\1" were to be enabled./;
+  function checkFailedRulesets(testName, messages, rulesetIds) {
+    let actualRulesetIds = messages
+      .map(m => errorMsgPattern.exec(m.message)?.[1])
+      .filter(Boolean);
+    Assert.deepEqual(
+      rulesetIds,
+      actualRulesetIds,
+      `${testName} should only trigger errors for rejected rulesets at start`
+    );
+  }
+
+  const testCases = [
+    {
+      name: "testPart1_start_over_static_quota",
+      backgroundFn: testPart1_start_over_static_quota,
+      checkConsoleMessages: (n, m) =>
+        checkFailedRulesets(n, m, ["limit_plus_1", "limit_minus_2"]),
+    },
+    {
+      name: "testPart2_after_reload",
+      backgroundFn: testPart2_after_reload,
+      // The extension has not called updateEnabledRulesets, so the "enabled"
+      // state of limit_minus_2 from manifest.json is still the extension's
+      // desired state for the ruleset. When the browser thus tries to enable
+      // the ruleset, it should encounter the same error as before.
+      //
+      // An alternative would be for the latest understanding of "enabled" to
+      // be persisted to disk and used when we load the persisted ruleset state.
+      // But if we do that, then we would not be able to distinguish "disabled
+      // because of a browser limit" from "disabled by extension". And if we
+      // cannot do that, then we would not be able to enable rulesets from
+      // already-installed extensions if we were to bump the limits in a browser
+      // update.
+      //
+      // Note: even if caching is implemented (bug 1803365), the observed
+      // behavior should happen, because the cache is cleared when we disable
+      // the extension.
+      checkConsoleMessages: (n, m) =>
+        checkFailedRulesets(n, m, ["limit_plus_1", "limit_minus_2"]),
+    },
+    {
+      name: "testPart3_after_updateEnabledRulesets_within_limit",
+      backgroundFn: testPart3_after_updateEnabledRulesets_within_limit,
+      checkConsoleMessages: (n, m) => checkFailedRulesets(n, m, []),
+    },
+    {
+      name: "testPart4_toggling_rulesets_at_quota",
+      backgroundFn: testPart4_toggling_rulesets_at_quota,
+      checkConsoleMessages: (n, m) => checkFailedRulesets(n, m, []),
+    },
+    {
+      name: "testPart5_after_doubling_quota",
+      setup() {
+        overrideDefaultDnrLimit(
+          "MAX_NUMBER_OF_REGEX_RULES",
+          2 * MAX_NUMBER_OF_REGEX_RULES
+        );
+      },
+      backgroundFn: testPart5_after_doubling_quota,
+      checkConsoleMessages: (n, m) => checkFailedRulesets(n, m, []),
+    },
+    {
+      name: "testPart6_after_restoring_original_quota_half",
+      setup() {
+        // Restore the original quota after it was raised in testPart5.
+        restoreDefaultDnrLimit("MAX_NUMBER_OF_REGEX_RULES");
+      },
+      backgroundFn: testPart6_after_restoring_original_quota_half,
+      checkConsoleMessages: (n, m) =>
+        checkFailedRulesets(n, m, ["limit_minus_2", "limit_minus_1"]),
+    },
+  ];
+
+  await startOrReloadExtensionForEach(testCases, extensionDataTemplate);
+});
diff --git a/toolkit/components/extensions/test/xpcshell/test_ext_dnr_session_rules.js b/toolkit/components/extensions/test/xpcshell/test_ext_dnr_session_rules.js
new file mode 100644
index 0000000000..5f0b0d72a2
--- /dev/null
+++ b/toolkit/components/extensions/test/xpcshell/test_ext_dnr_session_rules.js
@@ -0,0 +1,1111 @@
+"use strict";
+
+ChromeUtils.defineESModuleGetters(this, {
+  ExtensionDNR: "resource://gre/modules/ExtensionDNR.sys.mjs",
+});
+
+add_setup(() => {
+  Services.prefs.setBoolPref("extensions.manifestV3.enabled", true);
+  Services.prefs.setBoolPref("extensions.dnr.enabled", true);
+});
+
+// This function is serialized and called in the context of the test extension's
+// background page. dnrTestUtils is passed to the background function.
+function makeDnrTestUtils() {
+  const dnrTestUtils = {};
+  const dnr = browser.declarativeNetRequest;
+  dnrTestUtils.makeRuleInput = id => {
+    return {
+      id,
+      condition: {},
+      action: { type: "block" },
+    };
+  };
+  dnrTestUtils.makeRuleOutput = id => {
+    return {
+      id,
+      condition: {
+        urlFilter: null,
+        regexFilter: null,
+        isUrlFilterCaseSensitive: null,
+        initiatorDomains: null,
+        excludedInitiatorDomains: null,
+        requestDomains: null,
+        excludedRequestDomains: null,
+        resourceTypes: null,
+        excludedResourceTypes: null,
+        requestMethods: null,
+        excludedRequestMethods: null,
+        domainType: null,
+        tabIds: null,
+        excludedTabIds: null,
+      },
+      action: {
+        type: "block",
+        redirect: null,
+        requestHeaders: null,
+        responseHeaders: null,
+      },
+      priority: 1,
+    };
+  };
+
+  function serializeForLog(rule) {
+    // JSON-stringify, but drop null values (replacing them with undefined
+    // causes JSON.stringify to drop them), so that optional keys with the null
+    // values are hidden.
+    let str = JSON.stringify(rule, rep => rep ?? undefined);
+    // VERY_LONG_STRING consists of many 'X'. Shorten to avoid logspam.
+    str = str.replace(/x{10,}/g, xxx => `x{${xxx.length}}`);
+    return str;
+  }
+
+  async function testInvalidRule(rule, expectedError, isSchemaError) {
+    if (isSchemaError) {
+      // Schema validation error = thrown error instead of a rejection.
+      browser.test.assertThrows(
+        () => dnr.updateSessionRules({ addRules: [rule] }),
+        expectedError,
+        `Rule should be invalid (schema-validated): ${serializeForLog(rule)}`
+      );
+    } else {
+      await browser.test.assertRejects(
+        dnr.updateSessionRules({ addRules: [rule] }),
+        expectedError,
+        `Rule should be invalid: ${serializeForLog(rule)}`
+      );
+    }
+  }
+  async function testInvalidCondition(condition, expectedError, isSchemaError) {
+    await testInvalidRule(
+      { id: 1, condition, action: { type: "block" } },
+      expectedError,
+      isSchemaError
+    );
+  }
+  async function testInvalidAction(action, expectedError, isSchemaError) {
+    await testInvalidRule(
+      { id: 1, condition: {}, action },
+      expectedError,
+      isSchemaError
+    );
+  }
+
+  // The tests in this file merely verify whether rule registration and
+  // retrieval works. test_ext_dnr_testMatchOutcome.js checks rule evaluation.
+  async function testValidRule(rule) {
+    await dnr.updateSessionRules({ addRules: [rule] });
+
+    // Default rule with null for optional fields.
+    const expectedRule = dnrTestUtils.makeRuleOutput();
+    expectedRule.id = rule.id;
+    Object.assign(expectedRule.condition, rule.condition);
+    Object.assign(expectedRule.action, rule.action);
+    if (rule.action.redirect) {
+      expectedRule.action.redirect = {
+        extensionPath: null,
+        url: null,
+        transform: null,
+        regexSubstitution: null,
+        ...rule.action.redirect,
+      };
+      if (rule.action.redirect.transform) {
+        expectedRule.action.redirect.transform = {
+          scheme: null,
+          username: null,
+          password: null,
+          host: null,
+          port: null,
+          path: null,
+          query: null,
+          queryTransform: null,
+          fragment: null,
+          ...rule.action.redirect.transform,
+        };
+        if (rule.action.redirect.transform.queryTransform) {
+          const qt = {
+            removeParams: null,
+            addOrReplaceParams: null,
+            ...rule.action.redirect.transform.queryTransform,
+          };
+          if (qt.addOrReplaceParams) {
+            qt.addOrReplaceParams = qt.addOrReplaceParams.map(v => ({
+              key: null,
+              value: null,
+              replaceOnly: false,
+              ...v,
+            }));
+          }
+          expectedRule.action.redirect.transform.queryTransform = qt;
+        }
+      }
+    }
+    if (rule.action.requestHeaders) {
+      expectedRule.action.requestHeaders = rule.action.requestHeaders.map(
+        h => ({ header: null, operation: null, value: null, ...h })
+      );
+    }
+    if (rule.action.responseHeaders) {
+      expectedRule.action.responseHeaders = rule.action.responseHeaders.map(
+        h => ({ header: null, operation: null, value: null, ...h })
+      );
+    }
+
+    browser.test.assertDeepEq(
+      [expectedRule],
+      await dnr.getSessionRules(),
+      "Rule should be valid"
+    );
+
+    await dnr.updateSessionRules({ removeRuleIds: [rule.id] });
+  }
+  async function testValidCondition(condition) {
+    await testValidRule({ id: 1, condition, action: { type: "block" } });
+  }
+  async function testValidAction(action) {
+    await testValidRule({ id: 1, condition: {}, action });
+  }
+
+  Object.assign(dnrTestUtils, {
+    testInvalidRule,
+    testInvalidCondition,
+    testInvalidAction,
+    testValidRule,
+    testValidCondition,
+    testValidAction,
+  });
+  return dnrTestUtils;
+}
+
+async function runAsDNRExtension({ background, unloadTestAtEnd = true }) {
+  let extension = ExtensionTestUtils.loadExtension({
+    background: `(${background})((${makeDnrTestUtils})())`,
+    manifest: {
+      manifest_version: 3,
+      permissions: ["declarativeNetRequest", "declarativeNetRequestFeedback"],
+    },
+  });
+  await extension.startup();
+  await extension.awaitFinish();
+  if (unloadTestAtEnd) {
+    await extension.unload();
+  }
+  return extension;
+}
+
+add_task(async function register_and_retrieve_session_rules() {
+  let extension = await runAsDNRExtension({
+    background: async dnrTestUtils => {
+      const dnr = browser.declarativeNetRequest;
+      // Rules input to updateSessionRules:
+      const RULE_1234_IN = dnrTestUtils.makeRuleInput(1234);
+      const RULE_4321_IN = dnrTestUtils.makeRuleInput(4321);
+      const RULE_9001_IN = dnrTestUtils.makeRuleInput(9001);
+      // Rules expected to be returned by getSessionRules:
+      const RULE_1234_OUT = dnrTestUtils.makeRuleOutput(1234);
+      const RULE_4321_OUT = dnrTestUtils.makeRuleOutput(4321);
+      const RULE_9001_OUT = dnrTestUtils.makeRuleOutput(9001);
+
+      await dnr.updateSessionRules({
+        // Deliberately rule 4321 before 1234, see next getSessionRules test.
+        addRules: [RULE_4321_IN, RULE_1234_IN],
+        removeRuleIds: [1234567890], // Invalid rules should be ignored.
+      });
+      browser.test.assertDeepEq(
+        // Order is same as the original input.
+        [RULE_4321_OUT, RULE_1234_OUT],
+        await dnr.getSessionRules(),
+        "getSessionRules() returns all registered session rules"
+      );
+
+      await browser.test.assertRejects(
+        dnr.updateSessionRules({
+          addRules: [RULE_9001_IN, RULE_1234_IN],
+          removeRuleIds: [RULE_4321_IN.id],
+        }),
+        "Duplicate rule ID: 1234",
+        "updateSessionRules of existing rule without removeRuleIds should fail"
+      );
+      browser.test.assertDeepEq(
+        [RULE_4321_OUT, RULE_1234_OUT],
+        await dnr.getSessionRules(),
+        "session rules should not be changed if an error has occurred"
+      );
+
+      // From [4321,1234] to [1234,9001,4321]; 4321 moves to the end because
+      // the rule is deleted before inserted, NOT updated in-place.
+      await dnr.updateSessionRules({
+        addRules: [RULE_9001_IN, RULE_4321_IN],
+        removeRuleIds: [RULE_4321_IN.id],
+      });
+      browser.test.assertDeepEq(
+        [RULE_1234_OUT, RULE_9001_OUT, RULE_4321_OUT],
+        await dnr.getSessionRules(),
+        "existing session rule ID can be re-used for a new rule"
+      );
+
+      await dnr.updateSessionRules({
+        removeRuleIds: [RULE_1234_IN.id, RULE_4321_IN.id, RULE_9001_IN.id],
+      });
+      browser.test.assertDeepEq(
+        [],
+        await dnr.getSessionRules(),
+        "deleted all rules"
+      );
+
+      browser.test.notifyPass();
+    },
+    unloadTestAtEnd: false,
+  });
+
+  const realExtension = extension.extension;
+  Assert.ok(
+    ExtensionDNR.getRuleManager(realExtension, /* createIfMissing= */ false),
+    "Rule manager exists before unload"
+  );
+  await extension.unload();
+  Assert.ok(
+    !ExtensionDNR.getRuleManager(realExtension, /* createIfMissing= */ false),
+    "Rule manager erased after unload"
+  );
+});
+
+add_task(async function validate_resourceTypes() {
+  await runAsDNRExtension({
+    background: async dnrTestUtils => {
+      const {
+        testInvalidCondition,
+        testInvalidRule,
+        testValidRule,
+        testValidCondition,
+      } = dnrTestUtils;
+
+      await testInvalidCondition(
+        { resourceTypes: ["font", "image"], excludedResourceTypes: ["image"] },
+        "resourceTypes and excludedResourceTypes should not overlap"
+      );
+      await testInvalidCondition(
+        { resourceTypes: [], excludedResourceTypes: ["image"] },
+        /resourceTypes: Array requires at least 1 items; you have 0/,
+        /* isSchemaError */ true
+      );
+      await testValidCondition({
+        resourceTypes: ["font"],
+        excludedResourceTypes: ["image"],
+      });
+      await testValidCondition({
+        resourceTypes: ["font"],
+        excludedResourceTypes: [],
+      });
+
+      // Validation specific to allowAllRequests
+      await testInvalidRule(
+        {
+          id: 1,
+          condition: {},
+          action: { type: "allowAllRequests" },
+        },
+        "An allowAllRequests rule must have a non-empty resourceTypes array"
+      );
+      await testInvalidRule(
+        {
+          id: 1,
+          condition: { resourceTypes: [] },
+          action: { type: "allowAllRequests" },
+        },
+        /resourceTypes: Array requires at least 1 items; you have 0/,
+        /* isSchemaError */ true
+      );
+      await testInvalidRule(
+        {
+          id: 1,
+          condition: { resourceTypes: ["main_frame", "image"] },
+          action: { type: "allowAllRequests" },
+        },
+        "An allowAllRequests rule may only include main_frame/sub_frame in resourceTypes"
+      );
+      await testValidRule({
+        id: 1,
+        condition: { resourceTypes: ["main_frame"] },
+        action: { type: "allowAllRequests" },
+      });
+      await testValidRule({
+        id: 1,
+        condition: { resourceTypes: ["sub_frame"] },
+        action: { type: "allowAllRequests" },
+      });
+      browser.test.notifyPass();
+    },
+  });
+});
+
+add_task(async function validate_requestMethods() {
+  await runAsDNRExtension({
+    background: async dnrTestUtils => {
+      const { testInvalidCondition, testValidCondition } = dnrTestUtils;
+
+      await testInvalidCondition(
+        { requestMethods: ["get"], excludedRequestMethods: ["post", "get"] },
+        "requestMethods and excludedRequestMethods should not overlap"
+      );
+      await testInvalidCondition(
+        { requestMethods: [] },
+        /requestMethods: Array requires at least 1 items; you have 0/,
+        /* isSchemaError */ true
+      );
+      await testInvalidCondition(
+        { requestMethods: ["GET"] },
+        "request methods must be in lower case"
+      );
+      await testInvalidCondition(
+        { excludedRequestMethods: ["PUT"] },
+        "request methods must be in lower case"
+      );
+      await testValidCondition({ excludedRequestMethods: [] });
+      await testValidCondition({
+        requestMethods: ["get", "head"],
+        excludedRequestMethods: ["post"],
+      });
+      await testValidCondition({
+        requestMethods: ["connect", "delete", "options", "patch", "put", "xxx"],
+      });
+
+      browser.test.notifyPass();
+    },
+  });
+});
+
+add_task(async function validate_tabIds() {
+  await runAsDNRExtension({
+    background: async dnrTestUtils => {
+      const { testInvalidCondition, testValidCondition } = dnrTestUtils;
+
+      await testInvalidCondition(
+        { tabIds: [1], excludedTabIds: [1] },
+        "tabIds and excludedTabIds should not overlap"
+      );
+      await testInvalidCondition(
+        { tabIds: [] },
+        /tabIds: Array requires at least 1 items; you have 0/,
+        /* isSchemaError */ true
+      );
+      await testValidCondition({ excludedTabIds: [] });
+      await testValidCondition({ tabIds: [-1, 0, 1], excludedTabIds: [2] });
+      await testValidCondition({ tabIds: [Number.MAX_SAFE_INTEGER] });
+
+      browser.test.notifyPass();
+    },
+  });
+});
+
+add_task(async function validate_domains() {
+  await runAsDNRExtension({
+    background: async dnrTestUtils => {
+      const { testInvalidCondition, testValidCondition } = dnrTestUtils;
+
+      await testInvalidCondition(
+        { requestDomains: [] },
+        /requestDomains: Array requires at least 1 items; you have 0/,
+        /* isSchemaError */ true
+      );
+      await testInvalidCondition(
+        { initiatorDomains: [] },
+        /initiatorDomains: Array requires at least 1 items; you have 0/,
+        /* isSchemaError */ true
+      );
+      // The include and exclude overlaps, but the validator doesn't reject it:
+      await testValidCondition({
+        requestDomains: ["example.com"],
+        excludedRequestDomains: ["example.com"],
+        initiatorDomains: ["example.com"],
+        excludedInitiatorDomains: ["example.com"],
+      });
+      await testValidCondition({
+        excludedRequestDomains: [],
+        excludedInitiatorDomains: [],
+      });
+
+      // "null" is valid as a way to match an opaque initiator.
+      await testInvalidCondition(
+        { requestDomains: [null] },
+        /requestDomains\.0: Expected string instead of null/,
+        /* isSchemaError */ true
+      );
+      await testValidCondition({ requestDomains: ["null"] });
+
+      // IPv4 adress should be 4 digits separated by a dot.
+      await testInvalidCondition(
+        { requestDomains: ["1.2"] },
+        /requestDomains\.0: Error: Invalid domain 1.2/,
+        /* isSchemaError */ true
+      );
+      await testValidCondition({ requestDomains: ["0.0.1.2"] });
+
+      // IPv6 should be wrapped in brackets.
+      await testInvalidCondition(
+        { requestDomains: ["::1"] },
+        /requestDomains\.0: Error: Invalid domain ::1/,
+        /* isSchemaError */ true
+      );
+      // IPv6 addresses cannot contain dots.
+      await testInvalidCondition(
+        { requestDomains: ["[::ffff:127.0.0.1]"] },
+        /requestDomains\.0: Error: Invalid domain \[::ffff:127\.0\.0\.1\]/,
+        /* isSchemaError */ true
+      );
+      await testValidCondition({
+        // "[::ffff:7f00:1]" is the canonical form of "[::ffff:127.0.0.1]".
+        requestDomains: ["[::1]", "[::ffff:7f00:1]"],
+      });
+
+      // International Domain Names should be punycode-encoded.
+      await testInvalidCondition(
+        { requestDomains: ["straß.de"] },
+        /requestDomains\.0: Error: Invalid domain straß.de/,
+        /* isSchemaError */ true
+      );
+      await testValidCondition({ requestDomains: ["xn--stra-yna.de"] });
+
+      // Domain may not contain a port.
+      await testInvalidCondition(
+        { requestDomains: ["a.com:1234"] },
+        /requestDomains\.0: Error: Invalid domain a.com:1234/,
+        /* isSchemaError */ true
+      );
+      // Upper case is not canonical.
+      await testInvalidCondition(
+        { requestDomains: ["UPPERCASE"] },
+        /requestDomains\.0: Error: Invalid domain UPPERCASE/,
+        /* isSchemaError */ true
+      );
+      // URL encoded is not canonical.
+      await testInvalidCondition(
+        { requestDomains: ["ex%61mple.com"] },
+        /requestDomains\.0: Error: Invalid domain ex%61mple.com/,
+        /* isSchemaError */ true
+      );
+
+      // Verify that the validation is applied to all domain-related keys.
+      for (let domainsKey of [
+        "initiatorDomains",
+        "excludedInitiatorDomains",
+        "requestDomains",
+        "excludedRequestDomains",
+      ]) {
+        await testInvalidCondition(
+          { [domainsKey]: [""] },
+          new RegExp(String.raw`${domainsKey}\.0: Error: Invalid domain \)`),
+          /* isSchemaError */ true
+        );
+      }
+
+      browser.test.notifyPass();
+    },
+  });
+});
+
+// Basic urlFilter validation; test_ext_dnr_urlFilter.js has more tests.
+add_task(async function validate_urlFilter() {
+  await runAsDNRExtension({
+    background: async dnrTestUtils => {
+      const { testInvalidCondition, testValidCondition } = dnrTestUtils;
+
+      await testInvalidCondition(
+        { urlFilter: "", regexFilter: "" },
+        "urlFilter and regexFilter are mutually exclusive"
+      );
+
+      await testInvalidCondition(
+        { urlFilter: 0 },
+        /urlFilter: Expected string instead of 0/,
+        /* isSchemaError */ true
+      );
+      await testInvalidCondition(
+        { urlFilter: "" },
+        "urlFilter should not be an empty string"
+      );
+      await testInvalidCondition(
+        { urlFilter: "||*" },
+        "urlFilter should not start with '||*'" // should use '*' instead.
+      );
+      await testInvalidCondition(
+        { urlFilter: "||*/" },
+        "urlFilter should not start with '||*'" // should use '*' instead.
+      );
+      await testInvalidCondition(
+        { urlFilter: "straß.de" },
+        "urlFilter should not contain non-ASCII characters"
+      );
+      await testValidCondition({ urlFilter: "xn--stra-yna.de" });
+      await testValidCondition({ urlFilter: "||xn--stra-yna.de/" });
+
+      // The following are all logically equivalent to "||*" (and ""), but are
+      // considered valid in the DNR API implemented/documented by Chrome.
+      await testValidCondition({ urlFilter: "*" });
+      await testValidCondition({ urlFilter: "****************" });
+      await testValidCondition({ urlFilter: "||" });
+      await testValidCondition({ urlFilter: "|" });
+      await testValidCondition({ urlFilter: "|*|" });
+      await testValidCondition({ urlFilter: "^" });
+      await testValidCondition({ urlFilter: null });
+
+      await testValidCondition({ urlFilter: "||example^" });
+      await testValidCondition({ urlFilter: "||example.com" });
+      await testValidCondition({ urlFilter: "||example.com/index^" });
+      await testValidCondition({ urlFilter: ".gif|" });
+      await testValidCondition({ urlFilter: "|https:" });
+      await testValidCondition({ urlFilter: "|https:*" });
+      await testValidCondition({ urlFilter: "e" });
+      await testValidCondition({ urlFilter: "%80" });
+      await testValidCondition({ urlFilter: "*e*" }); // FYI: same as just "e".
+      await testValidCondition({ urlFilter: "*e*|" }); // FYI: same as just "e".
+
+      let validchars = "";
+      for (let i = 0; i < 0x80; ++i) {
+        validchars += String.fromCharCode(i);
+      }
+      await testValidCondition({ urlFilter: validchars });
+      // Confirming that 0x80 and up is invalid.
+      await testInvalidCondition(
+        { urlFilter: "\x80" },
+        "urlFilter should not contain non-ASCII characters"
+      );
+
+      browser.test.notifyPass();
+    },
+  });
+});
+
+// Basic regexFilter validation; test_ext_dnr_regexFilter.js has more tests.
+add_task(async function validate_regexFilter() {
+  await runAsDNRExtension({
+    background: async dnrTestUtils => {
+      const { testInvalidCondition, testValidCondition } = dnrTestUtils;
+
+      // This check is duplicated in validate_urlFilter.
+      await testInvalidCondition(
+        { urlFilter: "", regexFilter: "" },
+        "urlFilter and regexFilter are mutually exclusive"
+      );
+
+      await testInvalidCondition(
+        { regexFilter: /regex/ },
+        /regexFilter: Expected string instead of \{\}/,
+        /* isSchemaError */ true
+      );
+
+      await testInvalidCondition(
+        { regexFilter: "" },
+        "regexFilter should not be an empty string"
+      );
+      await testInvalidCondition(
+        { regexFilter: "*" },
+        "regexFilter is not a valid regular expression"
+      );
+      await testValidCondition(
+        { regexFilter: "^https://example\\.com\\/" },
+        "regexFilter with valid regexp should be accepted"
+      );
+
+      browser.test.notifyPass();
+    },
+  });
+});
+
+add_task(async function validate_actions() {
+  await runAsDNRExtension({
+    background: async dnrTestUtils => {
+      const { testInvalidAction, testValidAction, testValidRule } =
+        dnrTestUtils;
+
+      await testValidAction({ type: "allow" });
+      // Note: allowAllRequests is already covered in validate_resourceTypes
+      await testValidAction({ type: "block" });
+      await testValidAction({ type: "upgradeScheme" });
+      await testValidAction({ type: "block" });
+
+      // redirect actions, invalid cases
+      await testInvalidAction(
+        { type: "redirect" },
+        "A redirect rule must have a non-empty action.redirect object"
+      );
+      await testInvalidAction(
+        { type: "redirect", redirect: {} },
+        "A redirect rule must have a non-empty action.redirect object"
+      );
+      await testInvalidAction(
+        { type: "redirect", redirect: { extensionPath: "/", url: "http://a" } },
+        "redirect.url, redirect.extensionPath, redirect.transform and redirect.regexSubstitution are mutually exclusive"
+      );
+      await testInvalidAction(
+        { type: "redirect", redirect: { extensionPath: "", url: "http://a" } },
+        "redirect.url, redirect.extensionPath, redirect.transform and redirect.regexSubstitution are mutually exclusive"
+      );
+      await testInvalidAction(
+        {
+          type: "redirect",
+          redirect: { regexSubstitution: "", transform: {} },
+        },
+        "redirect.url, redirect.extensionPath, redirect.transform and redirect.regexSubstitution are mutually exclusive"
+      );
+      await testInvalidAction(
+        {
+          type: "redirect",
+          redirect: { regexSubstitution: "x", transform: {}, url: "http://a" },
+        },
+        "redirect.url, redirect.extensionPath, redirect.transform and redirect.regexSubstitution are mutually exclusive"
+      );
+      await testInvalidAction(
+        {
+          type: "redirect",
+          redirect: {
+            url: "http://a",
+            extensionPath: "/",
+            transform: {},
+            regexSubstitution: "http://a",
+          },
+        },
+        "redirect.url, redirect.extensionPath, redirect.transform and redirect.regexSubstitution are mutually exclusive"
+      );
+      await testInvalidAction(
+        { type: "redirect", redirect: { extensionPath: "" } },
+        "redirect.extensionPath should start with a '/'"
+      );
+      await testInvalidAction(
+        {
+          type: "redirect",
+          redirect: { extensionPath: browser.runtime.getURL("/") },
+        },
+        "redirect.extensionPath should start with a '/'"
+      );
+      await testInvalidAction(
+        { type: "redirect", redirect: { url: "javascript:" } },
+        /Access denied for URL javascript:/,
+        /* isSchemaError */ true
+      );
+      await testInvalidAction(
+        { type: "redirect", redirect: { url: "JAVASCRIPT:// Hmmm" } },
+        /Access denied for URL javascript:\/\/ Hmmm/,
+        /* isSchemaError */ true
+      );
+      await testInvalidAction(
+        { type: "redirect", redirect: { url: "about:addons" } },
+        /Access denied for URL about:addons/,
+        /* isSchemaError */ true
+      );
+      // TODO bug 1622986: allow redirects to data:-URLs.
+      await testInvalidAction(
+        { type: "redirect", redirect: { url: "data:," } },
+        /Access denied for URL data:,/,
+        /* isSchemaError */ true
+      );
+      await testInvalidAction(
+        { type: "redirect", redirect: { regexSubstitution: "http:///" } },
+        "redirect.regexSubstitution requires the regexFilter condition to be specified"
+      );
+
+      // redirect actions, valid cases
+      await testValidAction({
+        type: "redirect",
+        redirect: { extensionPath: "/foo.txt" },
+      });
+      await testValidAction({
+        type: "redirect",
+        redirect: { url: "https://example.com/" },
+      });
+      await testValidAction({
+        type: "redirect",
+        redirect: { url: browser.runtime.getURL("/") },
+      });
+      await testValidAction({
+        type: "redirect",
+        redirect: { transform: {} },
+      });
+      // redirect.transform is validated in validate_action_redirect_transform.
+      await testValidRule({
+        id: 1,
+        condition: { regexFilter: ".+" },
+        action: {
+          type: "redirect",
+          redirect: { regexSubstitution: "http://example.com/" },
+        },
+      });
+      // ^ redirect.regexSubstitution is tested by test_ext_dnr_regexFilter.js.
+
+      // modifyHeaders actions, invalid cases
+      await testInvalidAction(
+        { type: "modifyHeaders" },
+        "A modifyHeaders rule must have a non-empty requestHeaders or modifyHeaders list"
+      );
+      await testInvalidAction(
+        { type: "modifyHeaders", requestHeaders: [] },
+        /requestHeaders: Array requires at least 1 items; you have 0/,
+        /* isSchemaError */ true
+      );
+      await testInvalidAction(
+        { type: "modifyHeaders", responseHeaders: [] },
+        /responseHeaders: Array requires at least 1 items; you have 0/,
+        /* isSchemaError */ true
+      );
+      await testInvalidAction(
+        {
+          type: "modifyHeaders",
+          requestHeaders: [{ header: "", operation: "remove" }],
+        },
+        "header must be non-empty"
+      );
+      await testInvalidAction(
+        {
+          type: "modifyHeaders",
+          responseHeaders: [{ header: "", operation: "remove" }],
+        },
+        "header must be non-empty"
+      );
+      await testInvalidAction(
+        {
+          type: "modifyHeaders",
+          responseHeaders: [{ header: "x", operation: "append" }],
+        },
+        "value is required for operations append/set"
+      );
+      await testInvalidAction(
+        {
+          type: "modifyHeaders",
+          responseHeaders: [{ header: "x", operation: "set" }],
+        },
+        "value is required for operations append/set"
+      );
+      await testInvalidAction(
+        {
+          type: "modifyHeaders",
+          responseHeaders: [{ header: "x", operation: "remove", value: "x" }],
+        },
+        "value must not be provided for operation remove"
+      );
+      await testInvalidAction(
+        {
+          type: "modifyHeaders",
+          responseHeaders: [{ header: "x", operation: "REMOVE", value: "x" }],
+        },
+        /operation: Invalid enumeration value "REMOVE"/,
+        /* isSchemaError */ true
+      );
+
+      // modifyHeaders actions, valid cases
+      await testValidAction({
+        type: "modifyHeaders",
+        requestHeaders: [{ header: "x", operation: "set", value: "x" }],
+      });
+      await testValidAction({
+        type: "modifyHeaders",
+        responseHeaders: [{ header: "x", operation: "set", value: "x" }],
+      });
+      await testValidAction({
+        type: "modifyHeaders",
+        requestHeaders: [{ header: "y", operation: "set", value: "y" }],
+        responseHeaders: [{ header: "z", operation: "set", value: "z" }],
+      });
+      await testValidAction({
+        type: "modifyHeaders",
+        requestHeaders: [
+          { header: "reqh", operation: "set", value: "b" },
+          // Note: contrary to Chrome, we support "append" for requestHeaders:
+          // https://bugzilla.mozilla.org/show_bug.cgi?id=1797404#c1
+          { header: "reqh", operation: "append", value: "b" },
+          { header: "reqh", operation: "remove" },
+        ],
+        responseHeaders: [
+          { header: "resh", operation: "set", value: "b" },
+          { header: "resh", operation: "append", value: "b" },
+          { header: "resh", operation: "remove" },
+        ],
+      });
+
+      await testInvalidAction(
+        { type: "MODIFYHEADERS" },
+        /type: Invalid enumeration value "MODIFYHEADERS"/,
+        /* isSchemaError */ true
+      );
+
+      browser.test.notifyPass();
+    },
+  });
+});
+
+// This test task only verifies that a redirect transform is validated upon
+// registration. A transform can result in an invalid redirect despite passing
+// validation (see e.g. VERY_LONG_STRING below).
+// test_ext_dnr_redirect_transform.js will test the behavior of such cases.
+add_task(async function validate_action_redirect_transform() {
+  await runAsDNRExtension({
+    background: async dnrTestUtils => {
+      const { testInvalidAction, testValidAction } = dnrTestUtils;
+
+      const GENERIC_TRANSFORM_ERROR =
+        "redirect.transform does not describe a valid URL transformation";
+
+      const testValidTransform = transform =>
+        testValidAction({ type: "redirect", redirect: { transform } });
+      const testInvalidTransform = (transform, expectedError, isSchemaError) =>
+        testInvalidAction(
+          { type: "redirect", redirect: { transform } },
+          expectedError ?? GENERIC_TRANSFORM_ERROR,
+          isSchemaError
+        );
+
+      // Maximum length of a UTL is 1048576 (network.standard-url.max-length).
+      // Since URLs have other characters (separators), using VERY_LONG_STRING
+      // anywhere in a transform should be rejected. Note that this is mainly
+      // to verify that there is some bounds check on the URL. It is possible
+      // to generate a transform that is borderline valid at validation time,
+      // but invalid when applied to an existing longer URL.
+      const VERY_LONG_STRING = "x".repeat(1048576);
+
+      // An empty transformation is still valid.
+      await testValidTransform({});
+
+      // redirect.transform.scheme
+      await testValidTransform({ scheme: "http" });
+      await testValidTransform({ scheme: "https" });
+      await testValidTransform({ scheme: "moz-extension" });
+      await testInvalidTransform(
+        { scheme: "HTTPS" },
+        /scheme: Invalid enumeration value "HTTPS"/,
+        /* isSchemaError */ true
+      );
+      await testInvalidTransform(
+        { scheme: "javascript" },
+        /scheme: Invalid enumeration value "javascript"/,
+        /* isSchemaError */ true
+      );
+      // "ftp" is unsupported because support for it was dropped in Firefox.
+      // Chrome documents "ftp" as a supported scheme, but in practice it does
+      // not do anything useful, because it cannot handle ftp schemes either.
+      await testInvalidTransform(
+        { scheme: "ftp" },
+        /scheme: Invalid enumeration value "ftp"/,
+        /* isSchemaError */ true
+      );
+
+      // redirect.transform.host
+      await testValidTransform({ host: "example.com" });
+      await testValidTransform({ host: "example.com." });
+      await testValidTransform({ host: "localhost" });
+      await testValidTransform({ host: "127.0.0.1" });
+      await testValidTransform({ host: "[::1]" });
+      await testValidTransform({ host: "." });
+      await testValidTransform({ host: "straß.de" });
+      await testValidTransform({ host: "xn--stra-yna.de" });
+      await testInvalidTransform({ host: "::1" }); // Invalid IPv6.
+      await testInvalidTransform({ host: "[]" }); // Invalid IPv6.
+      await testInvalidTransform({ host: "/" }); // Invalid host
+      await testInvalidTransform({ host: " a" }); // Invalid host
+      await testInvalidTransform({ host: "foo:1234" }); // Port not allowed.
+      await testInvalidTransform({ host: "foo:" }); // Port sep not allowed.
+      await testInvalidTransform({ host: "" }); // Host cannot be empty.
+      await testInvalidTransform({ host: VERY_LONG_STRING });
+
+      // redirect.transform.port
+      await testValidTransform({ port: "" }); // empty = strip port.
+      await testValidTransform({ port: "0" });
+      await testValidTransform({ port: "0700" });
+      await testValidTransform({ port: "65535" });
+      const PORT_ERR = "redirect.transform.port should be empty or an integer";
+      await testInvalidTransform({ port: "65536" }, GENERIC_TRANSFORM_ERROR);
+      await testInvalidTransform({ port: " 0" }, PORT_ERR);
+      await testInvalidTransform({ port: "0 " }, PORT_ERR);
+      await testInvalidTransform({ port: "0." }, PORT_ERR);
+      await testInvalidTransform({ port: "0x1" }, PORT_ERR);
+      await testInvalidTransform({ port: "1.2" }, PORT_ERR);
+      await testInvalidTransform({ port: "-1" }, PORT_ERR);
+      await testInvalidTransform({ port: "a" }, PORT_ERR);
+      // A naive implementation of `host = hostname + ":" + port` could be
+      // misinterpreted as an IPv6 address. Verify that this is not the case.
+      await testInvalidTransform({ host: "[::1", port: "2]" }, PORT_ERR);
+      await testInvalidTransform({ port: VERY_LONG_STRING }, PORT_ERR);
+
+      // redirect.transform.path
+      await testValidTransform({ path: "" }); // empty = strip path.
+      await testValidTransform({ path: "/slash" });
+      await testValidTransform({ path: "/ref#ok" }); // # will be escaped.
+      await testValidTransform({ path: "/\n\t\x00" }); // Will all be escaped.
+      // A path should start with a '/', but the implementation works fine
+      // without it, and Chrome doesn't require it either.
+      await testValidTransform({ path: "noslash" });
+      await testValidTransform({ path: "http://example.com/" });
+      await testInvalidTransform({ path: VERY_LONG_STRING });
+
+      // redirect.transform.query
+      await testValidTransform({ query: "" }); // empty = strip query.
+      await testValidTransform({ query: "?suffix" });
+      await testValidTransform({ query: "?ref#ok" }); // # will be escaped.
+      await testValidTransform({ query: "?\n\t\x00" }); // Will all be escaped.
+      await testInvalidTransform(
+        { query: "noquestionmark" },
+        "redirect.transform.query should be empty or start with a '?'"
+      );
+      await testInvalidTransform({ query: "?" + VERY_LONG_STRING });
+
+      // redirect.transform.queryTransform
+      await testInvalidTransform(
+        { query: "", queryTransform: {} },
+        "redirect.transform.query and redirect.transform.queryTransform are mutually exclusive"
+      );
+      await testValidTransform({ queryTransform: {} });
+      await testValidTransform({ queryTransform: { removeParams: [] } });
+      await testValidTransform({ queryTransform: { removeParams: ["x"] } });
+      await testValidTransform({ queryTransform: { addOrReplaceParams: [] } });
+      await testValidTransform({
+        queryTransform: {
+          addOrReplaceParams: [{ key: "k", value: "v" }],
+        },
+      });
+      await testValidTransform({
+        queryTransform: {
+          addOrReplaceParams: [{ key: "k", value: "v", replaceOnly: true }],
+        },
+      });
+      await testInvalidTransform({
+        queryTransform: {
+          addOrReplaceParams: [{ key: "k", value: VERY_LONG_STRING }],
+        },
+      });
+      await testInvalidTransform(
+        {
+          queryTransform: {
+            addOrReplaceParams: [{ key: "k" }],
+          },
+        },
+        /addOrReplaceParams\.0: Property "value" is required/,
+        /* isSchemaError */ true
+      );
+      await testInvalidTransform(
+        {
+          queryTransform: {
+            addOrReplaceParams: [{ value: "v" }],
+          },
+        },
+        /addOrReplaceParams\.0: Property "key" is required/,
+        /* isSchemaError */ true
+      );
+
+      // redirect.transform.fragment
+      await testValidTransform({ fragment: "" }); // empty = strip fragment.
+      await testValidTransform({ fragment: "#suffix" });
+      await testValidTransform({ fragment: "#\n\t\x00" }); // will be escaped.
+      await testInvalidTransform(
+        { fragment: "nohash" },
+        "redirect.transform.fragment should be empty or start with a '#'"
+      );
+      await testInvalidTransform({ fragment: "#" + VERY_LONG_STRING });
+
+      // redirect.transform.username
+      await testValidTransform({ username: "" }); // empty = strip username.
+      await testValidTransform({ username: "username" });
+      await testValidTransform({ username: "@:" }); // will be escaped.
+      await testInvalidTransform({ username: VERY_LONG_STRING });
+
+      // redirect.transform.password
+      await testValidTransform({ password: "" }); // empty = strip password.
+      await testValidTransform({ password: "pass" });
+      await testValidTransform({ password: "@:" }); // will be escaped.
+      await testInvalidTransform({ password: VERY_LONG_STRING });
+
+      // All together:
+      await testValidTransform({
+        scheme: "http",
+        username: "a",
+        password: "b",
+        host: "c",
+        port: "12345",
+        path: "/d",
+        query: "?e",
+        queryTransform: null,
+        fragment: "#f",
+      });
+
+      browser.test.notifyPass();
+    },
+  });
+});
+
+add_task(async function session_rules_total_rule_limit() {
+  await runAsDNRExtension({
+    background: async dnrTestUtils => {
+      const { MAX_NUMBER_OF_DYNAMIC_AND_SESSION_RULES } =
+        browser.declarativeNetRequest;
+
+      let inputRules = [];
+      let nextRuleId = 1;
+      for (let i = 0; i < MAX_NUMBER_OF_DYNAMIC_AND_SESSION_RULES; ++i) {
+        inputRules.push(dnrTestUtils.makeRuleInput(nextRuleId++));
+      }
+      let excessRule = dnrTestUtils.makeRuleInput(nextRuleId++);
+
+      browser.test.log(`Should be able to add ${inputRules.length} rules.`);
+      await browser.declarativeNetRequest.updateSessionRules({
+        addRules: inputRules,
+      });
+
+      browser.test.assertEq(
+        inputRules.length,
+        (await browser.declarativeNetRequest.getSessionRules()).length,
+        "Added up to MAX_NUMBER_OF_DYNAMIC_AND_SESSION_RULES session rules"
+      );
+
+      await browser.test.assertRejects(
+        browser.declarativeNetRequest.updateSessionRules({
+          addRules: [excessRule],
+        }),
+        `Number of rules in ruleset "_session" exceeds MAX_NUMBER_OF_DYNAMIC_AND_SESSION_RULES.`,
+        "Should not accept more than MAX_NUMBER_OF_DYNAMIC_AND_SESSION_RULES rules"
+      );
+
+      await browser.test.assertRejects(
+        browser.declarativeNetRequest.updateSessionRules({
+          removeRuleIds: [inputRules[0].id],
+          addRules: [inputRules[0], excessRule],
+        }),
+        `Number of rules in ruleset "_session" exceeds MAX_NUMBER_OF_DYNAMIC_AND_SESSION_RULES.`,
+        "Removing one rule is not enough to make space for two rules"
+      );
+
+      browser.test.log("Should be able to replace one rule while at the limit");
+      await browser.declarativeNetRequest.updateSessionRules({
+        removeRuleIds: [inputRules[0].id],
+        addRules: [excessRule],
+      });
+
+      browser.test.log("Should be able to remove many rules, even at quota");
+      await browser.declarativeNetRequest.updateSessionRules({
+        // Note: inputRules[0].id was already removed, but that's fine.
+        removeRuleIds: inputRules.map(r => r.id),
+      });
+
+      browser.test.assertDeepEq(
+        [dnrTestUtils.makeRuleOutput(excessRule.id)],
+        await browser.declarativeNetRequest.getSessionRules(),
+        "Expected one rule after removing all-but-one-rule"
+      );
+
+      await browser.test.assertRejects(
+        browser.declarativeNetRequest.updateSessionRules({
+          addRules: inputRules,
+        }),
+        `Number of rules in ruleset "_session" exceeds MAX_NUMBER_OF_DYNAMIC_AND_SESSION_RULES.`,
+        "Should not be able to add MAX_NUMBER_OF_DYNAMIC_AND_SESSION_RULES when there is already a rule"
+      );
+
+      await browser.declarativeNetRequest.updateSessionRules({
+        removeRuleIds: [excessRule.id],
+      });
+      browser.test.assertDeepEq(
+        [],
+        await browser.declarativeNetRequest.getSessionRules(),
+        "Removed last remaining rule"
+      );
+
+      browser.test.notifyPass();
+    },
+  });
+});
diff --git a/toolkit/components/extensions/test/xpcshell/test_ext_dnr_startup_cache.js b/toolkit/components/extensions/test/xpcshell/test_ext_dnr_startup_cache.js
new file mode 100644
index 0000000000..bcb05eec23
--- /dev/null
+++ b/toolkit/components/extensions/test/xpcshell/test_ext_dnr_startup_cache.js
@@ -0,0 +1,651 @@
+/* Any copyright is dedicated to the Public Domain.
+ * http://creativecommons.org/publicdomain/zero/1.0/ */
+
+"use strict";
+
+const { Schemas } = ChromeUtils.importESModule(
+  "resource://gre/modules/Schemas.sys.mjs"
+);
+
+ChromeUtils.defineESModuleGetters(this, {
+  ExtensionDNR: "resource://gre/modules/ExtensionDNR.sys.mjs",
+  ExtensionDNRStore: "resource://gre/modules/ExtensionDNRStore.sys.mjs",
+  sinon: "resource://testing-common/Sinon.sys.mjs",
+});
+
+XPCOMUtils.defineLazyServiceGetters(this, {
+  aomStartup: [
+    "@mozilla.org/addons/addon-manager-startup;1",
+    "amIAddonManagerStartup",
+  ],
+});
+
+AddonTestUtils.init(this);
+AddonTestUtils.overrideCertDB();
+
+Services.scriptloader.loadSubScript(
+  Services.io.newFileURI(do_get_file("head_dnr.js")).spec,
+  this
+);
+
+const EXT_ID = "test-dnr-store-startup-cache@test-extension";
+const TEMP_EXT_ID = "test-dnr-store-temporarily-installed@test-extension";
+
+// Test rulesets should include fields that are special cased during Rule object deserialization
+// from the plain objects loaded from the StartupCache data objects.
+// In particular regexFilter are included to make sure that RuleValidator.deserializeRule is
+// internally compiling the regexFilter and storing it into the RuleCondition instance as expected
+// (implicitly asserted internally by the test helper assertDNRStoreData in head_dnr.js).
+const RULESET_1_DATA = [
+  getDNRRule({
+    id: 1,
+    action: { type: "allow" },
+    condition: { resourceTypes: ["main_frame"], regexFilter: "http://from/$" },
+  }),
+  getDNRRule({
+    id: 2,
+    action: { type: "allow" },
+    condition: {
+      resourceTypes: ["main_frame"],
+      regexFilter: "http://from2/$",
+      isUrlFilterCaseSensitive: true,
+    },
+  }),
+];
+const RULESET_2_DATA = [
+  getDNRRule({
+    action: { type: "block" },
+    condition: { resourceTypes: ["main_frame", "script"] },
+  }),
+];
+
+function getDNRExtension({
+  id = EXT_ID,
+  version = "1.0",
+  useAddonManager = "permanent",
+  background,
+  rule_resources,
+  declarative_net_request,
+  files,
+}) {
+  // Omit declarative_net_request if rule_resources isn't defined
+  // (because declarative_net_request fails the manifest validation
+  // if rule_resources is missing).
+  const dnr = rule_resources ? { rule_resources } : undefined;
+
+  return {
+    background,
+    useAddonManager,
+    manifest: {
+      manifest_version: 3,
+      version,
+      permissions: ["declarativeNetRequest", "declarativeNetRequestFeedback"],
+      // Needed to make sure the upgraded extension will have the same id and
+      // same uuid (which is mapped based on the extension id).
+      browser_specific_settings: {
+        gecko: { id },
+      },
+      declarative_net_request: declarative_net_request
+        ? { ...declarative_net_request, ...(dnr ?? {}) }
+        : dnr,
+    },
+    files,
+  };
+}
+
+add_setup(async () => {
+  Services.prefs.setBoolPref("extensions.manifestV3.enabled", true);
+  Services.prefs.setBoolPref("extensions.dnr.enabled", true);
+  Services.prefs.setBoolPref("extensions.dnr.feedback", true);
+
+  setupTelemetryForTests();
+
+  await ExtensionTestUtils.startAddonManager();
+});
+
+add_task(async function test_dnr_startup_cache_save_and_load() {
+  resetTelemetryData();
+
+  const rule_resources = [
+    {
+      id: "ruleset_1",
+      enabled: true,
+      path: "ruleset_1.json",
+    },
+    {
+      id: "ruleset_2",
+      enabled: false,
+      path: "ruleset_2.json",
+    },
+  ];
+  const files = {
+    "ruleset_1.json": JSON.stringify(RULESET_1_DATA),
+    "ruleset_2.json": JSON.stringify(RULESET_2_DATA),
+  };
+
+  let dnrStore = ExtensionDNRStore._getStoreForTesting();
+  let sandboxStoreSpies = sinon.createSandbox();
+  const spyScheduleCacheDataSave = sandboxStoreSpies.spy(
+    dnrStore,
+    "scheduleCacheDataSave"
+  );
+
+  const extension = ExtensionTestUtils.loadExtension(
+    getDNRExtension({ rule_resources, files })
+  );
+
+  const temporarilyInstalledExt = ExtensionTestUtils.loadExtension(
+    getDNRExtension({
+      id: TEMP_EXT_ID,
+      useAddonManager: "temporary",
+      rule_resources,
+      files,
+    })
+  );
+
+  assertDNRTelemetryMetricsNoSamples(
+    [
+      {
+        metric: "validateRulesTime",
+        mirroredName: "WEBEXT_DNR_VALIDATE_RULES_MS",
+        mirroredType: "histogram",
+      },
+    ],
+    "before any test extensions have been loaded"
+  );
+
+  await temporarilyInstalledExt.startup();
+  await extension.startup();
+  info(
+    "Wait for DNR initialization completed for the temporarily installed extension"
+  );
+  await ExtensionDNR.ensureInitialized(temporarilyInstalledExt.extension);
+  info(
+    "Wait for DNR initialization completed for the permanently installed extension"
+  );
+  await ExtensionDNR.ensureInitialized(extension.extension);
+
+  assertDNRTelemetryMetricsSamplesCount(
+    [
+      {
+        metric: "validateRulesTime",
+        mirroredName: "WEBEXT_DNR_VALIDATE_RULES_MS",
+        mirroredType: "histogram",
+        expectedSamplesCount: 2,
+      },
+    ],
+    "after two test extensions have been loaded"
+  );
+
+  Assert.equal(
+    spyScheduleCacheDataSave.callCount,
+    1,
+    "Expect ExtensionDNRStore scheduleCacheDataSave method to have been called once"
+  );
+
+  sandboxStoreSpies.restore();
+
+  const extUUID = extension.uuid;
+  const { cacheFile } = dnrStore.getFilePaths(extUUID);
+
+  await assertDNRStoreData(dnrStore, extension, {
+    ruleset_1: getSchemaNormalizedRules(extension, RULESET_1_DATA),
+  });
+
+  assertDNRTelemetryMetricsNoSamples(
+    [
+      {
+        metric: "startupCacheWriteTime",
+        mirroredName: "WEBEXT_DNR_STARTUPCACHE_WRITE_MS",
+        mirroredType: "histogram",
+      },
+      {
+        metric: "startupCacheWriteSize",
+        mirroredName: "WEBEXT_DNR_STARTUPCACHE_WRITE_BYTES",
+        mirroredType: "histogram",
+      },
+      // Expected no startup cache file to be loaded or used for a newly installed extension.
+      {
+        metric: "startupCacheReadSize",
+        mirroredName: "WEBEXT_DNR_STARTUPCACHE_READ_BYTES",
+        mirroredType: "histogram",
+      },
+      {
+        metric: "startupCacheReadTime",
+        mirroredName: "WEBEXT_DNR_STARTUPCACHE_READ_MS",
+        mirroredType: "histogram",
+      },
+      {
+        metric: "startupCacheEntries",
+        label: "miss",
+        mirroredName: "extensions.apis.dnr.startup_cache_entries",
+        mirroredType: "keyedScalar",
+      },
+      {
+        metric: "startupCacheEntries",
+        label: "hit",
+        mirroredName: "extensions.apis.dnr.startup_cache_entries",
+        mirroredType: "keyedScalar",
+      },
+    ],
+    "on loading dnr rules for newly installed extension"
+  );
+  await dnrStore.waitSaveCacheDataForTesting();
+  assertDNRTelemetryMetricsSamplesCount(
+    [
+      {
+        metric: "startupCacheWriteTime",
+        mirroredName: "WEBEXT_DNR_STARTUPCACHE_WRITE_MS",
+        mirroredType: "histogram",
+        expectedSamplesCount: 1,
+      },
+      {
+        metric: "startupCacheWriteSize",
+        mirroredName: "WEBEXT_DNR_STARTUPCACHE_WRITE_BYTES",
+        mirroredType: "histogram",
+        expectedSamplesCount: 1,
+      },
+    ],
+    "after writing DNR startup cache data to disk"
+  );
+
+  ok(
+    await IOUtils.exists(cacheFile),
+    "Expect the DNR store startupCache file exist"
+  );
+
+  const assertDNRStoreDataLoadOnStartup = async ({
+    expectLoadedFromCache,
+    expectClearLastUpdateTagPref,
+  }) => {
+    info(
+      `Mock browser restart and assert DNR rules ${
+        expectLoadedFromCache ? "NOT " : ""
+      }going through Schemas.normalize`
+    );
+    await AddonTestUtils.promiseShutdownManager();
+    // Recreate the DNR store to more easily mock its initial state after a browser restart.
+    dnrStore = ExtensionDNRStore._recreateStoreForTesting();
+    const StoreData = ExtensionDNRStore._getStoreDataClassForTesting();
+
+    let sandbox = sinon.createSandbox();
+    const schemasNormalizeSpy = sandbox.spy(Schemas, "normalize");
+    const ruleValidatorAddRulesSpy = sandbox.spy(
+      ExtensionDNR.RuleValidator.prototype,
+      "addRules"
+    );
+    const deserializeRuleSpy = sandbox.spy(
+      ExtensionDNR.RuleValidator,
+      "deserializeRule"
+    );
+    const clearLastUpdateTagPrefSpy = sandbox.spy(
+      StoreData,
+      "clearLastUpdateTagPref"
+    );
+    const scheduleCacheDataSaveSpy = sandbox.spy(
+      dnrStore,
+      "scheduleCacheDataSave"
+    );
+
+    resetTelemetryData();
+    await AddonTestUtils.promiseStartupManager();
+    await extension.awaitStartup();
+    await ExtensionDNR.ensureInitialized(extension.extension);
+
+    if (expectLoadedFromCache) {
+      assertDNRTelemetryMetricsSamplesCount(
+        [
+          {
+            metric: "startupCacheReadSize",
+            mirroredName: "WEBEXT_DNR_STARTUPCACHE_READ_BYTES",
+            mirroredType: "histogram",
+            expectedSamplesCount: 1,
+          },
+          {
+            metric: "startupCacheReadTime",
+            mirroredName: "WEBEXT_DNR_STARTUPCACHE_READ_MS",
+            mirroredType: "histogram",
+            expectedSamplesCount: 1,
+          },
+        ],
+        "after app startup and expected startup cache hit"
+      );
+      assertDNRTelemetryMetricsGetValueEq(
+        [
+          {
+            metric: "startupCacheEntries",
+            label: "hit",
+            expectedGetValue: 1,
+            mirroredName: "extensions.apis.dnr.startup_cache_entries",
+            mirroredType: "keyedScalar",
+          },
+        ],
+        "after app startup and expected startup cache hit"
+      );
+      assertDNRTelemetryMetricsNoSamples(
+        [
+          {
+            metric: "validateRulesTime",
+            mirroredName: "WEBEXT_DNR_VALIDATE_RULES_MS",
+            mirroredType: "histogram",
+          },
+          {
+            metric: "startupCacheEntries",
+            label: "miss",
+            mirroredName: "extensions.apis.dnr.startup_cache_entries",
+            mirroredType: "keyedScalar",
+          },
+        ],
+        "after DNR store loaded startup cache data"
+      );
+    } else {
+      assertDNRTelemetryMetricsSamplesCount(
+        [
+          {
+            metric: "validateRulesTime",
+            mirroredName: "WEBEXT_DNR_VALIDATE_RULES_MS",
+            mirroredType: "histogram",
+            expectedSamplesCount: 1,
+          },
+          {
+            metric: "startupCacheReadSize",
+            mirroredName: "WEBEXT_DNR_STARTUPCACHE_READ_BYTES",
+            mirroredType: "histogram",
+            expectedSamplesCount: 1,
+          },
+          {
+            metric: "startupCacheReadTime",
+            mirroredName: "WEBEXT_DNR_STARTUPCACHE_READ_MS",
+            mirroredType: "histogram",
+            expectedSamplesCount: 1,
+          },
+        ],
+        "after app startup and expected startup cache miss"
+      );
+      assertDNRTelemetryMetricsGetValueEq(
+        [
+          {
+            metric: "startupCacheEntries",
+            label: "miss",
+            expectedGetValue: 1,
+            mirroredName: "extensions.apis.dnr.startup_cache_entries",
+            mirroredType: "keyedScalar",
+          },
+        ],
+        "after app startup and expected startup cache miss"
+      );
+      assertDNRTelemetryMetricsNoSamples(
+        [
+          {
+            metric: "startupCacheEntries",
+            label: "hit",
+            mirroredName: "extensions.apis.dnr.startup_cache_entries",
+            mirroredType: "keyedScalar",
+          },
+        ],
+        "after DNR store loaded startup cache data"
+      );
+    }
+
+    Assert.equal(
+      scheduleCacheDataSaveSpy.called,
+      !expectLoadedFromCache,
+      "scheduleCacheDataSave to not be called when the extension DNR rules are initialized from startup cache data"
+    );
+
+    Assert.equal(
+      clearLastUpdateTagPrefSpy.callCount,
+      expectClearLastUpdateTagPref ? 1 : 0,
+      "Expect clearLastUpdateTagPrefSpy to have been called the expected number of times"
+    );
+    if (expectClearLastUpdateTagPref === true) {
+      Assert.ok(
+        clearLastUpdateTagPrefSpy.calledWith(extension.uuid),
+        "Expect clearLastUpdateTagPrefSpy to have been called with the test extension uuid"
+      );
+    }
+
+    Assert.equal(
+      schemasNormalizeSpy.calledWith(
+        sinon.match.any,
+        sinon.match("declarativeNetRequest.Rule"),
+        sinon.match.any
+      ),
+      !expectLoadedFromCache,
+      `Expect DNR rules to ${
+        expectLoadedFromCache ? "NOT " : ""
+      }be going through Schemas.normalize`
+    );
+
+    Assert.equal(
+      ruleValidatorAddRulesSpy.called,
+      !expectLoadedFromCache,
+      `Expect DNR rules to ${
+        expectLoadedFromCache ? "NOT " : ""
+      }be going through RuleValidator addRules`
+    );
+
+    Assert.equal(
+      deserializeRuleSpy.called,
+      expectLoadedFromCache,
+      `Expect RuleValidator.deserializeRule to ${
+        expectLoadedFromCache ? "NOT " : ""
+      }be called to convert StartupCache data back into Rule class instances`
+    );
+
+    await assertDNRStoreData(dnrStore, extension, {
+      ruleset_1: getSchemaNormalizedRules(extension, RULESET_1_DATA),
+    });
+
+    sandbox.restore();
+  };
+
+  const expectedLastUpdateTag = ExtensionDNRStore._getLastUpdateTag(
+    extension.uuid
+  );
+
+  Assert.ok(
+    typeof expectedLastUpdateTag == "string" && !!expectedLastUpdateTag.length,
+    `Expect lastUpdateTag for ${extension.id} to be set to a non empty string: ${expectedLastUpdateTag}`
+  );
+
+  Assert.equal(
+    ExtensionDNRStore._getLastUpdateTag(temporarilyInstalledExt.uuid),
+    null,
+    `Expect no lastUpdateTag value set for temporarily installed extensions`
+  );
+
+  await assertDNRStoreDataLoadOnStartup({
+    expectLoadedFromCache: true,
+    expectClearLastUpdateTagPref: false,
+  });
+
+  {
+    const { buffer } = await IOUtils.read(cacheFile);
+    const decodedData = aomStartup.decodeBlob(buffer);
+    Assert.equal(
+      expectedLastUpdateTag,
+      decodedData?.cacheData.get(extension.uuid).lastUpdateTag,
+      "Expect cacheData entry's lastUpdateTag to match the value stored in the related pref"
+    );
+    Assert.equal(
+      decodedData?.cacheData.has(temporarilyInstalledExt.uuid),
+      false,
+      "Expect no cache data entry for temporarily installed extensions"
+    );
+
+    info("Confirm startupCache data dropped if last tag pref value mismatches");
+    ExtensionDNRStore._storeLastUpdateTag(
+      extension.uuid,
+      "mismatching-tag-value"
+    );
+    Assert.notEqual(
+      ExtensionDNRStore._getLastUpdateTag(extension.uuid),
+      decodedData?.cacheData.get(extension.uuid).lastUpdateTag,
+      "Expect cacheData.lastDNRStoreUpdateTag to NOT match the tampered value stored in the related pref"
+    );
+  }
+
+  await assertDNRStoreDataLoadOnStartup({
+    expectLoadedFromCache: false,
+    expectClearLastUpdateTagPref: true,
+  });
+
+  info(
+    "Verify that startupCache data mismatching with the StoreData schema version is being dropped"
+  );
+  await dnrStore.waitSaveCacheDataForTesting();
+  await assertDNRStoreDataLoadOnStartup({
+    expectLoadedFromCache: true,
+    expectClearLastUpdateTagPref: false,
+  });
+
+  {
+    info("Tamper the StoreData version in the startupCache data");
+    const { buffer } = await IOUtils.read(cacheFile);
+    const decodedData = aomStartup.decodeBlob(buffer);
+    decodedData.cacheData.get(extUUID).schemaVersion = -1;
+    await IOUtils.write(
+      cacheFile,
+      new Uint8Array(aomStartup.encodeBlob(decodedData))
+    );
+  }
+
+  await assertDNRStoreDataLoadOnStartup({
+    expectLoadedFromCache: false,
+    expectClearLastUpdateTagPref: true,
+  });
+
+  info(
+    "Verify that startupCache data mismatching with the extension version is being dropped"
+  );
+  await dnrStore.waitSaveCacheDataForTesting();
+  await assertDNRStoreDataLoadOnStartup({
+    expectLoadedFromCache: true,
+    expectClearLastUpdateTagPref: false,
+  });
+
+  {
+    info("Tamper the extension version in the startupCache data");
+    const { buffer } = await IOUtils.read(cacheFile);
+    const decodedData = aomStartup.decodeBlob(buffer);
+    decodedData.cacheData.get(extUUID).extVersion = "0.1";
+    await IOUtils.write(
+      cacheFile,
+      new Uint8Array(aomStartup.encodeBlob(decodedData))
+    );
+  }
+  await assertDNRStoreDataLoadOnStartup({
+    expectLoadedFromCache: false,
+    expectClearLastUpdateTagPref: true,
+  });
+
+  await extension.unload();
+
+  Assert.equal(
+    ExtensionDNRStore._getLastUpdateTag(extension.uuid),
+    null,
+    "LastUpdateTag pref should have been removed after addon uninstall"
+  );
+});
+
+add_task(async function test_detect_and_reschedule_save_cache_on_new_changes() {
+  const rule_resources = [
+    {
+      id: "ruleset_1",
+      enabled: true,
+      path: "ruleset_1.json",
+    },
+  ];
+  const files = {
+    "ruleset_1.json": JSON.stringify(RULESET_1_DATA),
+  };
+
+  let dnrStore = ExtensionDNRStore._getStoreForTesting();
+  let sandboxStore = sinon.createSandbox();
+  const spyScheduleCacheDataSave = sandboxStore.spy(
+    dnrStore,
+    "scheduleCacheDataSave"
+  );
+
+  let extension;
+  const tamperedLastUpdateTag = Services.uuid.generateUUID().toString();
+  let resolvePromiseSaveCacheRescheduled;
+  let promiseSaveCacheRescheduled = new Promise(resolve => {
+    resolvePromiseSaveCacheRescheduled = resolve;
+  });
+  const realDetectStartupCacheDataChanged =
+    dnrStore.detectStartupCacheDataChanged.bind(dnrStore);
+  const stubDetectCacheDataChanges = sandboxStore.stub(
+    dnrStore,
+    "detectStartupCacheDataChanged"
+  );
+
+  stubDetectCacheDataChanges.callsFake(seenLastUpdateTags => {
+    const extData = dnrStore._data.get(extension.extension.uuid);
+    Assert.ok(extData, "Got StoreData instance for the test extension");
+    Assert.ok(
+      typeof extData.lastUpdateTag === "string" &&
+        !!extData.lastUpdateTag.length,
+      "Expect a non empty lastUpdateTag assigned to the extension StoreData"
+    );
+    Assert.deepEqual(
+      Array.from(seenLastUpdateTags),
+      [extData.lastUpdateTag],
+      "Expects the extension storeData lastUpdateTag to have been seen"
+    );
+    if (stubDetectCacheDataChanges.callCount == 1) {
+      Assert.notEqual(
+        extData.lastUpdateTag,
+        tamperedLastUpdateTag,
+        "New tampered lastUpdateTag should not be equal to the one already set"
+      );
+      extData.lastUpdateTag = tamperedLastUpdateTag;
+      Assert.equal(
+        realDetectStartupCacheDataChanged(seenLastUpdateTags),
+        true,
+        "Expect dnrStore.detectStartupCacheDataChanged to detect a change"
+      );
+      return true;
+    }
+    Assert.equal(
+      realDetectStartupCacheDataChanged(seenLastUpdateTags),
+      false,
+      "Expect dnrStore.detectStartupCacheDataChanged to NOT have detected any change"
+    );
+
+    Promise.resolve().then(resolvePromiseSaveCacheRescheduled);
+    return false;
+  });
+
+  extension = ExtensionTestUtils.loadExtension(
+    getDNRExtension({
+      id: "test-reschedule-save-on-detected-changes@test",
+      rule_resources,
+      files,
+    })
+  );
+
+  await extension.startup();
+  info(
+    "Wait for DNR initialization completed for the permanently installed extension"
+  );
+  await ExtensionDNR.ensureInitialized(extension.extension);
+  info("Wait for the saveCacheDataNow task to have been rescheduled");
+  await promiseSaveCacheRescheduled;
+
+  Assert.equal(
+    spyScheduleCacheDataSave.callCount,
+    2,
+    "Expect ExtensionDNRStore scheduleCacheDataSave method to have been called twice"
+  );
+  Assert.equal(
+    stubDetectCacheDataChanges.callCount,
+    2,
+    "Expect ExtensionDNRStore detectStartupCacheDataChanged method to have been called twice"
+  );
+
+  sandboxStore.restore();
+
+  await extension.unload();
+});
diff --git a/toolkit/components/extensions/test/xpcshell/test_ext_dnr_static_rules.js b/toolkit/components/extensions/test/xpcshell/test_ext_dnr_static_rules.js
new file mode 100644
index 0000000000..19c869b149
--- /dev/null
+++ b/toolkit/components/extensions/test/xpcshell/test_ext_dnr_static_rules.js
@@ -0,0 +1,1849 @@
+/* Any copyright is dedicated to the Public Domain.
+ * http://creativecommons.org/publicdomain/zero/1.0/ */
+
+"use strict";
+
+ChromeUtils.defineESModuleGetters(this, {
+  ExtensionDNR: "resource://gre/modules/ExtensionDNR.sys.mjs",
+  ExtensionDNRLimits: "resource://gre/modules/ExtensionDNRLimits.sys.mjs",
+  ExtensionDNRStore: "resource://gre/modules/ExtensionDNRStore.sys.mjs",
+  TestUtils: "resource://testing-common/TestUtils.sys.mjs",
+});
+
+AddonTestUtils.init(this);
+AddonTestUtils.overrideCertDB();
+
+Services.scriptloader.loadSubScript(
+  Services.io.newFileURI(do_get_file("head_dnr.js")).spec,
+  this
+);
+
+const server = createHttpServer({ hosts: ["example.com"] });
+server.registerPathHandler("/", (req, res) => {
+  res.setHeader("Access-Control-Allow-Origin", "*");
+  res.write("response from server");
+});
+
+function backgroundWithDNRAPICallHandlers() {
+  browser.test.onMessage.addListener(async (msg, ...args) => {
+    let result;
+    switch (msg) {
+      case "getEnabledRulesets":
+        result = await browser.declarativeNetRequest.getEnabledRulesets();
+        break;
+      case "getAvailableStaticRuleCount":
+        result =
+          await browser.declarativeNetRequest.getAvailableStaticRuleCount();
+        break;
+      case "testMatchOutcome":
+        result = await browser.declarativeNetRequest
+          .testMatchOutcome(...args)
+          .catch(err =>
+            browser.test.fail(
+              `Unexpected rejection from testMatchOutcome call: ${err}`
+            )
+          );
+        break;
+      case "updateEnabledRulesets":
+        // Run (one or more than one concurrently) updateEnabledRulesets calls
+        // and report back the results.
+        result = await Promise.all(
+          args.map(arg => {
+            return browser.declarativeNetRequest
+              .updateEnabledRulesets(arg)
+              .catch(err => {
+                return { rejectedWithErrorMessage: err.message };
+              });
+          })
+        );
+        break;
+      default:
+        browser.test.fail(`Unexpected test message: ${msg}`);
+        return;
+    }
+
+    browser.test.sendMessage(`${msg}:done`, result);
+  });
+
+  browser.test.sendMessage("bgpage:ready");
+}
+
+function getDNRExtension({
+  id = "test-dnr-static-rules@test-extension",
+  version = "1.0",
+  background = backgroundWithDNRAPICallHandlers,
+  useAddonManager = "permanent",
+  rule_resources,
+  declarative_net_request,
+  files,
+}) {
+  // Omit declarative_net_request if rule_resources isn't defined
+  // (because declarative_net_request fails the manifest validation
+  // if rule_resources is missing).
+  const dnr = rule_resources ? { rule_resources } : undefined;
+
+  return {
+    background,
+    useAddonManager,
+    manifest: {
+      manifest_version: 3,
+      version,
+      permissions: ["declarativeNetRequest", "declarativeNetRequestFeedback"],
+      // Needed to make sure the upgraded extension will have the same id and
+      // same uuid (which is mapped based on the extension id).
+      browser_specific_settings: {
+        gecko: { id },
+      },
+      declarative_net_request: declarative_net_request
+        ? { ...declarative_net_request, ...(dnr ?? {}) }
+        : dnr,
+    },
+    files,
+  };
+}
+
+const assertDNRTestMatchOutcome = async (
+  { extension, testRequest, expected },
+  assertMessage
+) => {
+  extension.sendMessage("testMatchOutcome", testRequest);
+  Assert.deepEqual(
+    expected,
+    await extension.awaitMessage("testMatchOutcome:done"),
+    assertMessage ??
+      "Got the expected matched rules from testMatchOutcome API call"
+  );
+};
+
+const assertDNRGetAvailableStaticRuleCount = async (
+  extensionTestWrapper,
+  expectedCount,
+  assertMessage
+) => {
+  extensionTestWrapper.sendMessage("getAvailableStaticRuleCount");
+  Assert.deepEqual(
+    await extensionTestWrapper.awaitMessage("getAvailableStaticRuleCount:done"),
+    expectedCount,
+    assertMessage ??
+      "Got the expected count value from dnr.getAvailableStaticRuleCount API method"
+  );
+};
+
+const assertDNRGetEnabledRulesets = async (
+  extensionTestWrapper,
+  expectedRulesetIds
+) => {
+  extensionTestWrapper.sendMessage("getEnabledRulesets");
+  Assert.deepEqual(
+    await extensionTestWrapper.awaitMessage("getEnabledRulesets:done"),
+    expectedRulesetIds,
+    "Got the expected enabled ruleset ids from dnr.getEnabledRulesets API method"
+  );
+};
+
+add_setup(async () => {
+  Services.prefs.setBoolPref("extensions.manifestV3.enabled", true);
+  Services.prefs.setBoolPref("extensions.dnr.enabled", true);
+  Services.prefs.setBoolPref("extensions.dnr.feedback", true);
+
+  setupTelemetryForTests();
+
+  await ExtensionTestUtils.startAddonManager();
+});
+
+add_task(async function test_load_static_rules() {
+  const ruleset1Data = [
+    getDNRRule({
+      action: { type: "allow" },
+      condition: { resourceTypes: ["main_frame"] },
+    }),
+  ];
+  const ruleset2Data = [
+    getDNRRule({
+      action: { type: "block" },
+      condition: { resourceTypes: ["main_frame", "script"] },
+    }),
+  ];
+
+  const rule_resources = [
+    {
+      id: "ruleset_1",
+      enabled: true,
+      path: "ruleset_1.json",
+    },
+    {
+      id: "ruleset_2",
+      enabled: true,
+      path: "ruleset_2.json",
+    },
+    {
+      id: "ruleset_3",
+      enabled: false,
+      path: "ruleset_3.json",
+    },
+  ];
+  const files = {
+    // Missing ruleset_3.json on purpose.
+    "ruleset_1.json": JSON.stringify(ruleset1Data),
+    "ruleset_2.json": JSON.stringify(ruleset2Data),
+  };
+
+  const extension = ExtensionTestUtils.loadExtension(
+    getDNRExtension({ rule_resources, files })
+  );
+
+  await extension.startup();
+
+  const extUUID = extension.uuid;
+
+  await extension.awaitMessage("bgpage:ready");
+
+  const dnrStore = ExtensionDNRStore._getStoreForTesting();
+
+  info("Verify DNRStore data for the test extension");
+  await assertDNRGetEnabledRulesets(extension, ["ruleset_1", "ruleset_2"]);
+
+  await assertDNRStoreData(dnrStore, extension, {
+    ruleset_1: getSchemaNormalizedRules(extension, ruleset1Data),
+    ruleset_2: getSchemaNormalizedRules(extension, ruleset2Data),
+  });
+
+  info("Verify matched rules using testMatchOutcome");
+  const testRequestMainFrame = {
+    url: "https://example.com/some-dummy-url",
+    type: "main_frame",
+  };
+  const testRequestScript = {
+    url: "https://example.com/some-dummy-url.js",
+    type: "script",
+  };
+
+  await assertDNRTestMatchOutcome(
+    {
+      extension,
+      testRequest: testRequestMainFrame,
+      expected: {
+        matchedRules: [{ ruleId: 1, rulesetId: "ruleset_1" }],
+      },
+    },
+    "Expect ruleset_1 to be matched on the main-frame test request"
+  );
+  await assertDNRTestMatchOutcome(
+    {
+      extension,
+      testRequest: testRequestScript,
+      expected: {
+        matchedRules: [{ ruleId: 1, rulesetId: "ruleset_2" }],
+      },
+    },
+    "Expect ruleset_2 to be matched on the script test request"
+  );
+
+  info("Verify DNRStore data persisted on disk for the test extension");
+  // The data will not be stored on disk until something is being changed
+  // from what was already available in the manifest and so in this
+  // test we save manually (a test for the updateEnabledRulesets will
+  // take care of asserting that the data has been stored automatically
+  // on disk when it is meant to).
+  await dnrStore.save(extension.extension);
+
+  const { storeFile } = dnrStore.getFilePaths(extUUID);
+
+  ok(await IOUtils.exists(storeFile), `DNR storeFile ${storeFile} found`);
+
+  // force deleting the data stored in memory to confirm if it being loaded again from
+  // the files stored on disk.
+  dnrStore._data.delete(extUUID);
+  dnrStore._dataPromises.delete(extUUID);
+
+  info("Verify the expected DNRStore data persisted on disk is loaded back");
+  const { AddonManager } = ChromeUtils.importESModule(
+    "resource://gre/modules/AddonManager.sys.mjs"
+  );
+  const addon = await AddonManager.getAddonByID(extension.id);
+  await addon.disable();
+
+  ok(
+    !dnrStore._dataPromises.has(extUUID),
+    "DNR store read data promise cleared after the extension has been disabled"
+  );
+  ok(
+    !dnrStore._data.has(extUUID),
+    "DNR store data cleared from memory after the extension has been disabled"
+  );
+
+  await addon.enable();
+  await extension.awaitMessage("bgpage:ready");
+  await assertDNRGetEnabledRulesets(extension, ["ruleset_1", "ruleset_2"]);
+
+  await assertDNRStoreData(dnrStore, extension, {
+    ruleset_1: getSchemaNormalizedRules(extension, ruleset1Data),
+    ruleset_2: getSchemaNormalizedRules(extension, ruleset2Data),
+  });
+
+  info("Verify matched rules using testMatchOutcome");
+  await assertDNRTestMatchOutcome(
+    {
+      extension,
+      testRequest: testRequestMainFrame,
+      expected: {
+        matchedRules: [{ ruleId: 1, rulesetId: "ruleset_1" }],
+      },
+    },
+    "Expect ruleset_1 to be matched on the main-frame test request"
+  );
+
+  info("Verify enabled static rules updated on addon updates");
+  await extension.upgrade(
+    getDNRExtension({
+      version: "2.0",
+      rule_resources: [
+        {
+          id: "ruleset_1",
+          enabled: false,
+          path: "ruleset_1.json",
+        },
+        {
+          id: "ruleset_2",
+          enabled: true,
+          path: "ruleset_2.json",
+        },
+      ],
+      files: {
+        "ruleset_2.json": JSON.stringify(ruleset2Data),
+      },
+    })
+  );
+  await extension.awaitMessage("bgpage:ready");
+  await assertDNRGetEnabledRulesets(extension, ["ruleset_2"]);
+  await assertDNRStoreData(dnrStore, extension, {
+    ruleset_2: getSchemaNormalizedRules(extension, ruleset2Data),
+  });
+
+  info("Verify matched rules using testMatchOutcome");
+  await assertDNRTestMatchOutcome(
+    {
+      extension,
+      testRequest: testRequestMainFrame,
+      expected: {
+        matchedRules: [{ ruleId: 1, rulesetId: "ruleset_2" }],
+      },
+    },
+    "Expect ruleset_2 to be matched on the main-frame test request"
+  );
+
+  info(
+    "Verify enabled static rules updated on addon updates even if version in the manifest did not change"
+  );
+  await extension.upgrade(
+    getDNRExtension({
+      rule_resources: [
+        {
+          id: "ruleset_1",
+          enabled: true,
+          path: "ruleset_1.json",
+        },
+        {
+          id: "ruleset_2",
+          enabled: false,
+          path: "ruleset_2.json",
+        },
+      ],
+      files: {
+        "ruleset_1.json": JSON.stringify(ruleset1Data),
+      },
+    })
+  );
+  await extension.awaitMessage("bgpage:ready");
+  await assertDNRGetEnabledRulesets(extension, ["ruleset_1"]);
+  await assertDNRStoreData(dnrStore, extension, {
+    ruleset_1: getSchemaNormalizedRules(extension, ruleset1Data),
+  });
+
+  info("Verify matched rules using testMatchOutcome");
+  await assertDNRTestMatchOutcome(
+    {
+      extension,
+      testRequest: testRequestMainFrame,
+      expected: {
+        matchedRules: [{ ruleId: 1, rulesetId: "ruleset_1" }],
+      },
+    },
+    "Expect ruleset_2 to be matched on the main-script test request"
+  );
+
+  info(
+    "Verify updated addon version with no static rules but declarativeNetRequest permission granted"
+  );
+  await extension.upgrade(
+    getDNRExtension({
+      version: "3.0",
+      rule_resources: undefined,
+      files: {},
+    })
+  );
+  await extension.awaitMessage("bgpage:ready");
+  await assertDNRGetEnabledRulesets(extension, []);
+  await assertDNRStoreData(dnrStore, extension, {});
+
+  info("Verify matched rules using testMatchOutcome");
+  await assertDNRTestMatchOutcome(
+    {
+      extension,
+      testRequest: testRequestScript,
+      expected: {
+        matchedRules: [],
+      },
+    },
+    "Expect no match on the script test request on test extension without no static rules"
+  );
+
+  info("Verify store file removed on addon uninstall");
+  await extension.unload();
+
+  ok(
+    !dnrStore._dataPromises.has(extUUID),
+    "DNR store read data promise cleared after the extension has been unloaded"
+  );
+  ok(
+    !dnrStore._data.has(extUUID),
+    "DNR store data cleared from memory after the extension has been unloaded"
+  );
+
+  ok(
+    !(await IOUtils.exists(storeFile)),
+    `DNR storeFile ${storeFile} removed on addon uninstalled`
+  );
+});
+
+add_task(async function test_load_from_corrupted_data() {
+  const ruleset1Data = [
+    getDNRRule({
+      action: { type: "allow" },
+      condition: { resourceTypes: ["main_frame"] },
+    }),
+  ];
+
+  const rule_resources = [
+    {
+      id: "ruleset_1",
+      enabled: true,
+      path: "ruleset_1.json",
+    },
+  ];
+
+  const files = {
+    "ruleset_1.json": JSON.stringify(ruleset1Data),
+  };
+
+  const extension = ExtensionTestUtils.loadExtension(
+    getDNRExtension({ rule_resources, files })
+  );
+
+  await extension.startup();
+
+  const extUUID = extension.uuid;
+
+  await extension.awaitMessage("bgpage:ready");
+
+  const dnrStore = ExtensionDNRStore._getStoreForTesting();
+
+  info("Verify DNRStore data for the test extension");
+  await assertDNRGetEnabledRulesets(extension, ["ruleset_1"]);
+
+  await assertDNRStoreData(dnrStore, extension, {
+    ruleset_1: getSchemaNormalizedRules(extension, ruleset1Data),
+  });
+
+  info("Verify DNRStore data after loading corrupted store data");
+  await dnrStore.save(extension.extension);
+
+  const { storeFile } = dnrStore.getFilePaths(extUUID);
+  ok(await IOUtils.exists(storeFile), `DNR storeFile ${storeFile} found`);
+
+  const nonCorruptedData = await IOUtils.readJSON(storeFile, {
+    decompress: true,
+  });
+
+  async function testLoadedRulesAfterDataCorruption({
+    name,
+    asyncWriteStoreFile,
+    expectedCorruptFile,
+  }) {
+    info(`Tempering DNR store data: ${name}`);
+
+    await extension.addon.disable();
+
+    ok(
+      !dnrStore._dataPromises.has(extUUID),
+      "DNR store read data promise cleared after the extension has been disabled"
+    );
+    ok(
+      !dnrStore._data.has(extUUID),
+      "DNR store data cleared from memory after the extension has been disabled"
+    );
+
+    // Make sure we remove a previous corrupt file in case there is one from a previous run.
+    await IOUtils.remove(expectedCorruptFile, { ignoreAbsent: true });
+
+    await asyncWriteStoreFile();
+
+    await extension.addon.enable();
+    await extension.awaitMessage("bgpage:ready");
+
+    info("Verify DNRStore data for the test extension");
+    await assertDNRGetEnabledRulesets(extension, ["ruleset_1"]);
+
+    await assertDNRStoreData(dnrStore, extension, {
+      ruleset_1: getSchemaNormalizedRules(extension, ruleset1Data),
+    });
+
+    await TestUtils.waitForCondition(
+      () => IOUtils.exists(`${expectedCorruptFile}`),
+      `Wait for the "${expectedCorruptFile}" file to have been created`
+    );
+  }
+
+  await testLoadedRulesAfterDataCorruption({
+    name: "invalid lz4 header",
+    asyncWriteStoreFile: () =>
+      IOUtils.writeUTF8(storeFile, "not an lz4 compressed file", {
+        compress: false,
+      }),
+    expectedCorruptFile: `${storeFile}.corrupt`,
+  });
+
+  await testLoadedRulesAfterDataCorruption({
+    name: "invalid json data",
+    asyncWriteStoreFile: () =>
+      IOUtils.writeUTF8(storeFile, "invalid json data", { compress: true }),
+    expectedCorruptFile: `${storeFile}-1.corrupt`,
+  });
+
+  await testLoadedRulesAfterDataCorruption({
+    name: "empty json data",
+    asyncWriteStoreFile: () =>
+      IOUtils.writeUTF8(storeFile, "{}", { compress: true }),
+    expectedCorruptFile: `${storeFile}-2.corrupt`,
+  });
+
+  await testLoadedRulesAfterDataCorruption({
+    name: "invalid staticRulesets property type",
+    asyncWriteStoreFile: () =>
+      IOUtils.writeUTF8(
+        storeFile,
+        JSON.stringify({
+          schemaVersion: nonCorruptedData.schemaVersion,
+          extVersion: extension.extension.version,
+          staticRulesets: "Not an array",
+        }),
+        { compress: true }
+      ),
+    expectedCorruptFile: `${storeFile}-3.corrupt`,
+  });
+
+  await extension.unload();
+});
+
+add_task(async function test_ruleset_validation() {
+  const invalidRulesetIdCases = [
+    {
+      description: "empty ruleset id",
+      rule_resources: [
+        {
+          // Invalid empty ruleset id.
+          id: "",
+          path: "ruleset_0.json",
+          enabled: true,
+        },
+      ],
+      expected: [
+        // Validation error emitted from the manifest schema validation.
+        {
+          message: /rule_resources\.0\.id: String "" must match/,
+        },
+      ],
+    },
+    {
+      description: "invalid ruleset id starting with '_'",
+      rule_resources: [
+        {
+          // Invalid empty ruleset id.
+          id: "_invalid_ruleset_id",
+          path: "ruleset_0.json",
+          enabled: true,
+        },
+      ],
+      expected: [
+        // Validation error emitted from the manifest schema validation.
+        {
+          message:
+            /rule_resources\.0\.id: String "_invalid_ruleset_id" must match/,
+        },
+      ],
+    },
+    {
+      description: "duplicated ruleset ids",
+      rule_resources: [
+        {
+          id: "ruleset_2",
+          path: "ruleset_2.json",
+          enabled: true,
+        },
+        {
+          // Duplicated ruleset id.
+          id: "ruleset_2",
+          path: "duplicated_ruleset_2.json",
+          enabled: true,
+        },
+        {
+          id: "ruleset_3",
+          path: "ruleset_3.json",
+          enabled: true,
+        },
+        {
+          // Other duplicated ruleset id.
+          id: "ruleset_3",
+          path: "duplicated_ruleset_3.json",
+          enabled: true,
+        },
+      ],
+      // NOTE: this is currently a warning logged from onManifestEntry, and so it would actually
+      // fail in test harness due to the manifest warning, because it is too late at that point
+      // the addon is technically already starting at that point.
+      expectInstallFailed: false,
+      expected: [
+        {
+          message:
+            /declarative_net_request: Static ruleset ids should be unique.*: "ruleset_2" at index 1, "ruleset_3" at index 3/,
+        },
+      ],
+    },
+    {
+      description: "missing mandatory path",
+      rule_resources: [
+        {
+          // Missing mandatory path.
+          id: "ruleset_3",
+          enabled: true,
+        },
+      ],
+      expected: [
+        {
+          message: /rule_resources\.0: Property "path" is required/,
+        },
+      ],
+    },
+    {
+      description: "missing mandatory id",
+      rule_resources: [
+        {
+          // Missing mandatory id.
+          enabled: true,
+          path: "missing_ruleset_id.json",
+        },
+      ],
+      expected: [
+        {
+          message: /rule_resources\.0: Property "id" is required/,
+        },
+      ],
+    },
+    {
+      description: "duplicated ruleset path",
+      rule_resources: [
+        {
+          id: "ruleset_2",
+          path: "ruleset_2.json",
+          enabled: true,
+        },
+        {
+          // Duplicate path.
+          id: "ruleset_3",
+          path: "ruleset_2.json",
+          enabled: true,
+        },
+      ],
+      // NOTE: we couldn't get on agreement about making this a manifest validation error, apparently Chrome doesn't validate it and doesn't
+      // even report any warning, and so it is logged only as an informative warning but without triggering an install failure.
+      expectInstallFailed: false,
+      expected: [
+        {
+          message:
+            /declarative_net_request: Static rulesets paths are not unique.*: ".*ruleset_2.json" at index 1/,
+        },
+      ],
+    },
+    {
+      description: "missing mandatory enabled",
+      rule_resources: [
+        {
+          id: "ruleset_without_enabled",
+          path: "ruleset.json",
+        },
+      ],
+      expected: [
+        {
+          message: /rule_resources\.0: Property "enabled" is required/,
+        },
+      ],
+    },
+    {
+      description: "allows and warns additional properties",
+      declarative_net_request: {
+        unexpected_prop: true,
+        rule_resources: [
+          {
+            id: "ruleset1",
+            path: "ruleset1.json",
+            enabled: false,
+            unexpected_prop: true,
+          },
+        ],
+      },
+      expectInstallFailed: false,
+      expected: [
+        {
+          message:
+            /declarative_net_request.unexpected_prop: An unexpected property was found/,
+        },
+        {
+          message:
+            /rule_resources.0.unexpected_prop: An unexpected property was found/,
+        },
+      ],
+    },
+    {
+      description: "invalid ruleset JSON - unexpected comments",
+      rule_resources: [
+        {
+          id: "invalid_ruleset_with_comments",
+          path: "invalid_ruleset_with_comments.json",
+          enabled: true,
+        },
+      ],
+      files: {
+        "invalid_ruleset_with_comments.json":
+          "/* an unexpected inline comment */\n[]",
+      },
+      expectInstallFailed: false,
+      expected: [
+        {
+          message:
+            /Reading declarative_net_request .*invalid_ruleset_with_comments\.json: JSON.parse: unexpected character/,
+        },
+      ],
+    },
+    {
+      description: "invalid ruleset JSON - empty string",
+      rule_resources: [
+        {
+          id: "invalid_ruleset_emptystring",
+          path: "invalid_ruleset_emptystring.json",
+          enabled: true,
+        },
+      ],
+      files: {
+        "invalid_ruleset_emptystring.json": JSON.stringify(""),
+      },
+      expectInstallFailed: false,
+      expected: [
+        {
+          message:
+            /Reading declarative_net_request .*invalid_ruleset_emptystring\.json: rules file must contain an Array/,
+        },
+      ],
+    },
+    {
+      description: "invalid ruleset JSON - object",
+      rule_resources: [
+        {
+          id: "invalid_ruleset_object",
+          path: "invalid_ruleset_object.json",
+          enabled: true,
+        },
+      ],
+      files: {
+        "invalid_ruleset_object.json": JSON.stringify({}),
+      },
+      expectInstallFailed: false,
+      expected: [
+        {
+          message:
+            /Reading declarative_net_request .*invalid_ruleset_object\.json: rules file must contain an Array/,
+        },
+      ],
+    },
+    {
+      description: "invalid ruleset JSON - null",
+      rule_resources: [
+        {
+          id: "invalid_ruleset_null",
+          path: "invalid_ruleset_null.json",
+          enabled: true,
+        },
+      ],
+      files: {
+        "invalid_ruleset_null.json": JSON.stringify(null),
+      },
+      expectInstallFailed: false,
+      expected: [
+        {
+          message:
+            /Reading declarative_net_request .*invalid_ruleset_null\.json: rules file must contain an Array/,
+        },
+      ],
+    },
+  ];
+
+  for (const {
+    description,
+    declarative_net_request,
+    rule_resources,
+    files,
+    expected,
+    expectInstallFailed = true,
+  } of invalidRulesetIdCases) {
+    info(`Test manifest validation: ${description}`);
+    let extension = ExtensionTestUtils.loadExtension(
+      getDNRExtension({ rule_resources, declarative_net_request, files })
+    );
+
+    const { messages } = await AddonTestUtils.promiseConsoleOutput(async () => {
+      ExtensionTestUtils.failOnSchemaWarnings(false);
+      if (expectInstallFailed) {
+        await Assert.rejects(
+          extension.startup(),
+          /Install failed/,
+          "Expected install to fail"
+        );
+      } else {
+        await extension.startup();
+        await extension.awaitMessage("bgpage:ready");
+        await extension.unload();
+      }
+      ExtensionTestUtils.failOnSchemaWarnings(true);
+    });
+
+    AddonTestUtils.checkMessages(messages, { expected });
+  }
+});
+
+add_task(async function test_updateEnabledRuleset_id_validation() {
+  const rule_resources = [
+    {
+      id: "ruleset_1",
+      enabled: true,
+      path: "ruleset_1.json",
+    },
+    {
+      id: "ruleset_2",
+      enabled: false,
+      path: "ruleset_2.json",
+    },
+  ];
+
+  const ruleset1Data = [
+    getDNRRule({
+      action: { type: "allow" },
+      condition: { resourceTypes: ["main_frame"] },
+    }),
+  ];
+  const ruleset2Data = [
+    getDNRRule({
+      action: { type: "block" },
+      condition: { resourceTypes: ["main_frame", "script"] },
+    }),
+  ];
+
+  const files = {
+    "ruleset_1.json": JSON.stringify(ruleset1Data),
+    "ruleset_2.json": JSON.stringify(ruleset2Data),
+  };
+
+  let extension = ExtensionTestUtils.loadExtension(
+    getDNRExtension({ rule_resources, files })
+  );
+
+  await extension.startup();
+  await extension.awaitMessage("bgpage:ready");
+
+  await assertDNRGetEnabledRulesets(extension, ["ruleset_1"]);
+
+  const dnrStore = ExtensionDNRStore._getStoreForTesting();
+  await assertDNRStoreData(dnrStore, extension, {
+    ruleset_1: getSchemaNormalizedRules(extension, ruleset1Data),
+  });
+
+  const invalidStaticRulesetIds = [
+    // The following two are reserved for session and dynamic rules.
+    "_session",
+    "_dynamic",
+    "ruleset_non_existing",
+  ];
+
+  for (const invalidRSId of invalidStaticRulesetIds) {
+    extension.sendMessage(
+      "updateEnabledRulesets",
+      // Only in rulesets to be disabled.
+      { disableRulesetIds: [invalidRSId] },
+      // Only in rulesets to be enabled.
+      { enableRulesetIds: [invalidRSId] },
+      // In both rulesets to be enabled and disabled.
+      { disableRulesetIds: [invalidRSId], enableRulesetIds: [invalidRSId] },
+      // Along with existing rulesets (and expected the existing rulesets
+      // to stay unchanged due to the invalid ruleset ids.)
+      {
+        disableRulesetIds: [invalidRSId, "ruleset_1"],
+        enableRulesetIds: [invalidRSId, "ruleset_2"],
+      }
+    );
+    const [
+      resInDisable,
+      resInEnable,
+      resInEnableAndDisable,
+      resInSameRequestAsValid,
+    ] = await extension.awaitMessage("updateEnabledRulesets:done");
+    await Assert.rejects(
+      Promise.reject(resInDisable?.rejectedWithErrorMessage),
+      new RegExp(`Invalid ruleset id: "${invalidRSId}"`),
+      `Got the expected rejection on invalid ruleset id "${invalidRSId}" in disableRulesetIds`
+    );
+    await Assert.rejects(
+      Promise.reject(resInEnable?.rejectedWithErrorMessage),
+      new RegExp(`Invalid ruleset id: "${invalidRSId}"`),
+      `Got the expected rejection on invalid ruleset id "${invalidRSId}" in enableRulesetIds`
+    );
+    await Assert.rejects(
+      Promise.reject(resInEnableAndDisable?.rejectedWithErrorMessage),
+      new RegExp(`Invalid ruleset id: "${invalidRSId}"`),
+      `Got the expected rejection on invalid ruleset id "${invalidRSId}" in both enable/disableRulesetIds`
+    );
+    await Assert.rejects(
+      Promise.reject(resInSameRequestAsValid?.rejectedWithErrorMessage),
+      new RegExp(`Invalid ruleset id: "${invalidRSId}"`),
+      `Got the expected rejection on invalid ruleset id "${invalidRSId}" along with valid ruleset ids`
+    );
+  }
+
+  // Confirm that the expected rulesets didn't change neither.
+  await assertDNRGetEnabledRulesets(extension, ["ruleset_1"]);
+  await assertDNRStoreData(dnrStore, extension, {
+    ruleset_1: getSchemaNormalizedRules(extension, ruleset1Data),
+  });
+
+  // - List the same ruleset ids more than ones is expected to work and
+  //   to be resulting in the same set of rules being enabled
+  // - Disabling and Enabling the same ruleset id should result in the
+  //   ruleset being enabled.
+  await extension.sendMessage("updateEnabledRulesets", {
+    disableRulesetIds: [
+      "ruleset_1",
+      "ruleset_1",
+      "ruleset_2",
+      "ruleset_2",
+      "ruleset_2",
+    ],
+    enableRulesetIds: ["ruleset_2", "ruleset_2"],
+  });
+  Assert.deepEqual(
+    await extension.awaitMessage("updateEnabledRulesets:done"),
+    [undefined],
+    "Expect the updateEnabledRulesets to result successfully"
+  );
+
+  await assertDNRGetEnabledRulesets(extension, ["ruleset_2"]);
+  await assertDNRStoreData(dnrStore, extension, {
+    ruleset_2: getSchemaNormalizedRules(extension, ruleset2Data),
+  });
+
+  await extension.unload();
+});
+
+add_task(async function test_getAvailableStaticRulesCountAndLimits() {
+  // NOTE: this test is going to load and validate the maximum amount of static rules
+  // that an extension can enable, which on slower builds (in particular in tsan builds,
+  // e.g. see Bug 1803801) have a higher chance that the test extension may have hit the
+  // idle timeout and being suspended by the time the test is going to trigger API method
+  // calls through test API events (which do not expect the lifetime of the event page).
+  Services.prefs.setBoolPref("extensions.background.idle.enabled", false);
+
+  const dnrStore = ExtensionDNRStore._getStoreForTesting();
+  const { GUARANTEED_MINIMUM_STATIC_RULES } = ExtensionDNRLimits;
+  equal(
+    typeof GUARANTEED_MINIMUM_STATIC_RULES,
+    "number",
+    "Expect GUARANTEED_MINIMUM_STATIC_RULES to be a number"
+  );
+
+  const availableStaticRulesCount = GUARANTEED_MINIMUM_STATIC_RULES;
+
+  const rule_resources = [
+    {
+      id: "ruleset_0",
+      path: "/ruleset_0.json",
+      enabled: true,
+    },
+    {
+      id: "ruleset_1",
+      path: "/ruleset_1.json",
+      enabled: true,
+    },
+    // A ruleset initially disabled (to make sure it doesn't count for the
+    // rules count limit).
+    {
+      id: "ruleset_disabled",
+      path: "/ruleset_disabled.json",
+      enabled: false,
+    },
+    // A ruleset including an invalid rule and valid rule.
+    {
+      id: "ruleset_withInvalid",
+      path: "/ruleset_withInvalid.json",
+      enabled: false,
+    },
+    // An empty ruleset (to make sure it can still be enabled/disabled just fine,
+    // e.g. in case on some browser version all rules are technically invalid).
+    {
+      id: "ruleset_empty",
+      path: "/ruleset_empty.json",
+      enabled: false,
+    },
+  ];
+
+  const files = {};
+  const rules = {};
+
+  const rulesetDisabledData = [getDNRRule({ id: 1 })];
+  const ruleValid = getDNRRule({ id: 2, action: { type: "allow" } });
+  const rulesetWithInvalidData = [
+    getDNRRule({ id: 1, action: { type: "invalid_action" } }),
+    ruleValid,
+  ];
+
+  rules.ruleset_0 = [getDNRRule({ id: 1 }), getDNRRule({ id: 2 })];
+
+  rules.ruleset_1 = [];
+  for (let i = 0; i < availableStaticRulesCount; i++) {
+    rules.ruleset_1.push(getDNRRule({ id: i + 1 }));
+  }
+
+  for (const [k, v] of Object.entries(rules)) {
+    files[`${k}.json`] = JSON.stringify(v);
+  }
+  files[`ruleset_disabled.json`] = JSON.stringify(rulesetDisabledData);
+  files[`ruleset_withInvalid.json`] = JSON.stringify(rulesetWithInvalidData);
+  files[`ruleset_empty.json`] = JSON.stringify([]);
+
+  const extension = ExtensionTestUtils.loadExtension(
+    getDNRExtension({
+      id: "dnr-getAvailable-count-@mochitest",
+      rule_resources,
+      files,
+    })
+  );
+
+  await extension.startup();
+  await extension.awaitMessage("bgpage:ready");
+
+  async function updateEnabledRulesets({ expectedErrorMessage, ...options }) {
+    // Note: options = { disableRulesetIds, enableRulesetIds }
+    extension.sendMessage("updateEnabledRulesets", options);
+    let [result] = await extension.awaitMessage("updateEnabledRulesets:done");
+    if (expectedErrorMessage) {
+      Assert.deepEqual(
+        result,
+        { rejectedWithErrorMessage: expectedErrorMessage },
+        "updateEnabledRulesets() should reject with the given error"
+      );
+    } else {
+      Assert.deepEqual(
+        result,
+        undefined,
+        "updateEnabledRulesets() should resolve without error"
+      );
+    }
+  }
+
+  const expectedEnabledRulesets = {};
+  expectedEnabledRulesets.ruleset_0 = getSchemaNormalizedRules(
+    extension,
+    rules.ruleset_0
+  );
+
+  info(
+    "Expect ruleset_1 to not be enabled because along with ruleset_0 exceeded the static rules count limit"
+  );
+  await assertDNRStoreData(dnrStore, extension, expectedEnabledRulesets);
+
+  await assertDNRGetAvailableStaticRuleCount(
+    extension,
+    availableStaticRulesCount - rules.ruleset_0.length,
+    "Got the available static rule count on ruleset_0 initially enabled"
+  );
+
+  // Try to enable ruleset_1 again from the API method.
+  await updateEnabledRulesets({
+    enableRulesetIds: ["ruleset_1"],
+    expectedErrorMessage: `Number of rules across all enabled static rulesets exceeds GUARANTEED_MINIMUM_STATIC_RULES if ruleset "ruleset_1" were to be enabled.`,
+  });
+
+  info(
+    "Expect ruleset_1 to not be enabled because still exceeded the static rules count limit"
+  );
+  await assertDNRGetEnabledRulesets(extension, ["ruleset_0"]);
+  await assertDNRStoreData(dnrStore, extension, expectedEnabledRulesets);
+
+  await assertDNRGetAvailableStaticRuleCount(
+    extension,
+    availableStaticRulesCount - rules.ruleset_0.length,
+    "Got the available static rule count on ruleset_0 still the only one enabled"
+  );
+
+  await updateEnabledRulesets({
+    disableRulesetIds: ["ruleset_0"],
+    enableRulesetIds: ["ruleset_1"],
+  });
+
+  info("Expect ruleset_1 to be enabled along with disabling ruleset_0");
+  await assertDNRGetEnabledRulesets(extension, ["ruleset_1"]);
+  delete expectedEnabledRulesets.ruleset_0;
+  expectedEnabledRulesets.ruleset_1 = getSchemaNormalizedRules(
+    extension,
+    rules.ruleset_1
+  );
+  await assertDNRStoreData(dnrStore, extension, expectedEnabledRulesets, {
+    // Assert total amount of expected rules and only the first and last rule
+    // individually, to avoid generating a huge amount of logs and potential
+    // timeout failures on slower builds.
+    assertIndividualRules: false,
+  });
+
+  await assertDNRGetAvailableStaticRuleCount(
+    extension,
+    0,
+    "Expect no additional static rules count available when ruleset_1 is enabled"
+  );
+
+  info(
+    "Expect ruleset_disabled to stay disabled because along with ruleset_1 exceeeds the limits"
+  );
+  await updateEnabledRulesets({
+    enableRulesetIds: ["ruleset_disabled"],
+    expectedErrorMessage: `Number of rules across all enabled static rulesets exceeds GUARANTEED_MINIMUM_STATIC_RULES if ruleset "ruleset_disabled" were to be enabled.`,
+  });
+  await assertDNRGetEnabledRulesets(extension, ["ruleset_1"]);
+  await assertDNRStoreData(dnrStore, extension, expectedEnabledRulesets, {
+    // Assert total amount of expected rules and only the first and last rule
+    // individually, to avoid generating a huge amount of logs and potential
+    // timeout failures on slower builds.
+    assertIndividualRules: false,
+  });
+  await assertDNRGetAvailableStaticRuleCount(
+    extension,
+    0,
+    "Expect no additional static rules count available"
+  );
+
+  info("Expect ruleset_empty to be enabled despite having reached the limit");
+  await updateEnabledRulesets({
+    enableRulesetIds: ["ruleset_empty"],
+  });
+  await assertDNRGetEnabledRulesets(extension, ["ruleset_1", "ruleset_empty"]);
+  await assertDNRStoreData(
+    dnrStore,
+    extension,
+    {
+      ...expectedEnabledRulesets,
+      ruleset_empty: [],
+    },
+    // Assert total amount of expected rules and only the first and last rule
+    // individually, to avoid generating a huge amount of logs and potential
+    // timeout failures on slower builds.
+    { assertIndividualRules: false }
+  );
+  await assertDNRGetAvailableStaticRuleCount(
+    extension,
+    0,
+    "Expect no additional static rules count available"
+  );
+
+  info("Expect invalid rules to not be counted towards the limits");
+  await updateEnabledRulesets({
+    disableRulesetIds: ["ruleset_1", "ruleset_empty"],
+    enableRulesetIds: ["ruleset_withInvalid"],
+  });
+  await assertDNRGetEnabledRulesets(extension, ["ruleset_withInvalid"]);
+  await assertDNRStoreData(dnrStore, extension, {
+    // Only the valid rule has been actually loaded, and the invalid one
+    // ignored.
+    ruleset_withInvalid: [ruleValid],
+  });
+  await assertDNRGetAvailableStaticRuleCount(
+    extension,
+    availableStaticRulesCount - 1,
+    "Expect only valid rules to be counted"
+  );
+
+  await extension.unload();
+
+  Services.prefs.clearUserPref("extensions.background.idle.enabled");
+});
+
+add_task(async function test_static_rulesets_limits() {
+  const dnrStore = ExtensionDNRStore._getStoreForTesting();
+
+  const getRulesetManifestData = (rulesetNumber, enabled) => {
+    return {
+      id: `ruleset_${rulesetNumber}`,
+      enabled,
+      path: `ruleset_${rulesetNumber}.json`,
+    };
+  };
+  const {
+    MAX_NUMBER_OF_STATIC_RULESETS,
+    MAX_NUMBER_OF_ENABLED_STATIC_RULESETS,
+  } = ExtensionDNRLimits;
+
+  equal(
+    typeof MAX_NUMBER_OF_STATIC_RULESETS,
+    "number",
+    "Expect MAX_NUMBER_OF_STATIC_RULESETS to be a number"
+  );
+  equal(
+    typeof MAX_NUMBER_OF_ENABLED_STATIC_RULESETS,
+    "number",
+    "Expect MAX_NUMBER_OF_ENABLED_STATIC_RULESETS to be a number"
+  );
+  ok(
+    MAX_NUMBER_OF_STATIC_RULESETS > MAX_NUMBER_OF_ENABLED_STATIC_RULESETS,
+    "Expect MAX_NUMBER_OF_STATIC_RULESETS to be greater"
+  );
+
+  const rules = [getDNRRule()];
+
+  const rule_resources = [];
+  const files = {};
+  for (let i = 0; i < MAX_NUMBER_OF_STATIC_RULESETS + 1; i++) {
+    const enabled = i < MAX_NUMBER_OF_ENABLED_STATIC_RULESETS + 1;
+    files[`ruleset_${i}.json`] = JSON.stringify(rules);
+    rule_resources.push(getRulesetManifestData(i, enabled));
+  }
+
+  let extension = ExtensionTestUtils.loadExtension(
+    getDNRExtension({
+      rule_resources,
+      files,
+    })
+  );
+
+  const expectedEnabledRulesets = {};
+
+  const { messages } = await AddonTestUtils.promiseConsoleOutput(async () => {
+    ExtensionTestUtils.failOnSchemaWarnings(false);
+    await extension.startup();
+    ExtensionTestUtils.failOnSchemaWarnings(true);
+    await extension.awaitMessage("bgpage:ready");
+
+    for (let i = 0; i < MAX_NUMBER_OF_ENABLED_STATIC_RULESETS; i++) {
+      expectedEnabledRulesets[`ruleset_${i}`] = getSchemaNormalizedRules(
+        extension,
+        rules
+      );
+    }
+
+    await assertDNRGetEnabledRulesets(
+      extension,
+      Array.from(Object.keys(expectedEnabledRulesets))
+    );
+    await assertDNRStoreData(dnrStore, extension, expectedEnabledRulesets);
+  });
+
+  AddonTestUtils.checkMessages(messages, {
+    expected: [
+      // Warnings emitted from the manifest schema validation.
+      {
+        message:
+          /declarative_net_request: Static rulesets are exceeding the MAX_NUMBER_OF_STATIC_RULESETS limit/,
+      },
+      {
+        message:
+          /declarative_net_request: Enabled static rulesets are exceeding the MAX_NUMBER_OF_ENABLED_STATIC_RULESETS limit .* "ruleset_10"/,
+      },
+      // Error reported on the browser console as part of loading enabled rulesets)
+      // on enabled rulesets being ignored because exceeding the limit.
+      {
+        message:
+          /Ignoring enabled static ruleset exceeding the MAX_NUMBER_OF_ENABLED_STATIC_RULESETS .* "ruleset_10"/,
+      },
+    ],
+  });
+
+  info(
+    "Verify updateEnabledRulesets reject when the request is exceeding the enabled rulesets count limit"
+  );
+  extension.sendMessage("updateEnabledRulesets", {
+    disableRulesetIds: ["ruleset_0"],
+    enableRulesetIds: ["ruleset_10", "ruleset_11"],
+  });
+
+  await Assert.rejects(
+    extension.awaitMessage("updateEnabledRulesets:done").then(results => {
+      if (results[0].rejectedWithErrorMessage) {
+        return Promise.reject(new Error(results[0].rejectedWithErrorMessage));
+      }
+      return results[0];
+    }),
+    /updatedEnabledRulesets request is exceeding MAX_NUMBER_OF_ENABLED_STATIC_RULESETS/,
+    "Expected rejection on updateEnabledRulesets exceeting enabled rulesets count limit"
+  );
+
+  // Confirm that the expected rulesets didn't change neither.
+  await assertDNRGetEnabledRulesets(
+    extension,
+    Array.from(Object.keys(expectedEnabledRulesets))
+  );
+  await assertDNRStoreData(dnrStore, extension, expectedEnabledRulesets);
+
+  info(
+    "Verify updateEnabledRulesets applies the expected changes when resolves successfully"
+  );
+  extension.sendMessage(
+    "updateEnabledRulesets",
+    {
+      disableRulesetIds: ["ruleset_0"],
+      enableRulesetIds: ["ruleset_10"],
+    },
+    {
+      disableRulesetIds: ["ruleset_10"],
+      enableRulesetIds: ["ruleset_11"],
+    }
+  );
+  await extension.awaitMessage("updateEnabledRulesets:done");
+
+  // Expect ruleset_0 disabled, ruleset_10 to be enabled but then disabled by the
+  // second update queued after the first one, and ruleset_11 to be enabled.
+  delete expectedEnabledRulesets.ruleset_0;
+  expectedEnabledRulesets.ruleset_11 = getSchemaNormalizedRules(
+    extension,
+    rules
+  );
+
+  await assertDNRGetEnabledRulesets(
+    extension,
+    Array.from(Object.keys(expectedEnabledRulesets))
+  );
+  await assertDNRStoreData(dnrStore, extension, expectedEnabledRulesets);
+
+  // Ensure all changes were stored and reloaded from disk store and the
+  // DNR store update queue can accept new updates.
+  info("Verify static rules load and updates after extension is restarted");
+
+  // NOTE: promiseRestartManager will not be enough to make sure the
+  // DNR store data for the test extension is going to be loaded from
+  // the DNR startup cache file.
+  // See test_ext_dnr_startup_cache.js for a test case that more completely
+  // simulates ExtensionDNRStore initialization on browser restart.
+  await AddonTestUtils.promiseRestartManager();
+
+  await extension.awaitStartup();
+  await extension.awaitMessage("bgpage:ready");
+  await assertDNRGetEnabledRulesets(
+    extension,
+    Array.from(Object.keys(expectedEnabledRulesets))
+  );
+  await assertDNRStoreData(dnrStore, extension, expectedEnabledRulesets);
+
+  extension.sendMessage("updateEnabledRulesets", {
+    disableRulesetIds: ["ruleset_11"],
+  });
+  await extension.awaitMessage("updateEnabledRulesets:done");
+  delete expectedEnabledRulesets.ruleset_11;
+  await assertDNRGetEnabledRulesets(
+    extension,
+    Array.from(Object.keys(expectedEnabledRulesets))
+  );
+  await assertDNRStoreData(dnrStore, extension, expectedEnabledRulesets);
+
+  await extension.unload();
+});
+
+add_task(async function test_tabId_conditions_invalid_in_static_rules() {
+  const ruleset1_with_tabId_condition = [
+    getDNRRule({ id: 1, condition: { tabIds: [1] } }),
+    getDNRRule({ id: 3, condition: { urlFilter: "valid-ruleset1-rule" } }),
+  ];
+
+  const ruleset2_with_excludeTabId_condition = [
+    getDNRRule({ id: 2, condition: { excludedTabIds: [1] } }),
+    getDNRRule({ id: 3, condition: { urlFilter: "valid-ruleset2-rule" } }),
+  ];
+
+  const rule_resources = [
+    {
+      id: "ruleset1_with_tabId_condition",
+      enabled: true,
+      path: "ruleset1.json",
+    },
+    {
+      id: "ruleset2_with_excludeTabId_condition",
+      enabled: true,
+      path: "ruleset2.json",
+    },
+  ];
+
+  const files = {
+    "ruleset1.json": JSON.stringify(ruleset1_with_tabId_condition),
+    "ruleset2.json": JSON.stringify(ruleset2_with_excludeTabId_condition),
+  };
+
+  const extension = ExtensionTestUtils.loadExtension(
+    getDNRExtension({
+      id: "tabId-invalid-in-session-rules@mochitest",
+      rule_resources,
+      files,
+    })
+  );
+
+  const { messages } = await AddonTestUtils.promiseConsoleOutput(async () => {
+    ExtensionTestUtils.failOnSchemaWarnings(false);
+    await extension.startup();
+    ExtensionTestUtils.failOnSchemaWarnings(true);
+    await extension.awaitMessage("bgpage:ready");
+    await assertDNRGetEnabledRulesets(extension, [
+      "ruleset1_with_tabId_condition",
+      "ruleset2_with_excludeTabId_condition",
+    ]);
+  });
+
+  AddonTestUtils.checkMessages(messages, {
+    expected: [
+      {
+        message:
+          /"ruleset1_with_tabId_condition": tabIds and excludedTabIds can only be specified in session rules/,
+      },
+      {
+        message:
+          /"ruleset2_with_excludeTabId_condition": tabIds and excludedTabIds can only be specified in session rules/,
+      },
+    ],
+  });
+
+  info("Expect the invalid rule to not be enabled");
+  const dnrStore = ExtensionDNRStore._getStoreForTesting();
+  // Expect the two valid rules to have been loaded as expected.
+  await assertDNRStoreData(dnrStore, extension, {
+    ruleset1_with_tabId_condition: getSchemaNormalizedRules(extension, [
+      ruleset1_with_tabId_condition[1],
+    ]),
+    ruleset2_with_excludeTabId_condition: getSchemaNormalizedRules(extension, [
+      ruleset2_with_excludeTabId_condition[1],
+    ]),
+  });
+
+  await extension.unload();
+});
+
+add_task(async function test_dnr_all_rules_disabled_allowed() {
+  const ruleset1 = [
+    getDNRRule({ id: 3, condition: { urlFilter: "valid-ruleset1-rule" } }),
+  ];
+
+  const rule_resources = [
+    {
+      id: "ruleset1",
+      enabled: true,
+      path: "ruleset1.json",
+    },
+  ];
+
+  const files = {
+    "ruleset1.json": JSON.stringify(ruleset1),
+  };
+
+  const extension = ExtensionTestUtils.loadExtension(
+    getDNRExtension({
+      id: "all-static-rulesets-disabled-allowed@mochitest",
+      rule_resources,
+      files,
+    })
+  );
+
+  await extension.startup();
+  await extension.awaitMessage("bgpage:ready");
+
+  await assertDNRGetEnabledRulesets(extension, ["ruleset1"]);
+
+  const dnrStore = ExtensionDNRStore._getStoreForTesting();
+  await assertDNRStoreData(dnrStore, extension, {
+    ruleset1: getSchemaNormalizedRules(extension, ruleset1),
+  });
+
+  info("Disable static ruleset1");
+  extension.sendMessage("updateEnabledRulesets", {
+    disableRulesetIds: ["ruleset1"],
+  });
+  await extension.awaitMessage("updateEnabledRulesets:done");
+  await assertDNRGetEnabledRulesets(extension, []);
+  await assertDNRStoreData(dnrStore, extension, {});
+
+  info("Verify that static ruleset1 is still disable after browser restart");
+
+  // NOTE: promiseRestartManager will not be enough to make sure the
+  // DNR store data for the test extension is going to be loaded from
+  // the DNR startup cache file.
+  // See test_ext_dnr_startup_cache.js for a test case that more completely
+  // simulates ExtensionDNRStore initialization on browser restart.
+  await AddonTestUtils.promiseRestartManager();
+
+  await extension.awaitStartup;
+  await ExtensionDNR.ensureInitialized(extension.extension);
+  await extension.awaitMessage("bgpage:ready");
+
+  await assertDNRGetEnabledRulesets(extension, []);
+  await assertDNRStoreData(dnrStore, extension, {});
+
+  await extension.unload();
+});
+
+add_task(async function test_static_rules_telemetry() {
+  resetTelemetryData();
+
+  const ruleset1 = [
+    getDNRRule({
+      id: 1,
+      action: { type: "block" },
+      condition: {
+        resourceTypes: ["xmlhttprequest"],
+        requestDomains: ["example.com"],
+      },
+    }),
+  ];
+  const ruleset2 = [
+    getDNRRule({
+      id: 1,
+      action: { type: "block" },
+      condition: {
+        resourceTypes: ["xmlhttprequest"],
+        requestDomains: ["example.org"],
+      },
+    }),
+    getDNRRule({
+      id: 2,
+      action: { type: "block" },
+      condition: {
+        resourceTypes: ["xmlhttprequest"],
+        requestDomains: ["example2.org"],
+      },
+    }),
+  ];
+
+  const rule_resources = [
+    {
+      id: "ruleset1",
+      enabled: false,
+      path: "ruleset1.json",
+    },
+    {
+      id: "ruleset2",
+      enabled: false,
+      path: "ruleset2.json",
+    },
+  ];
+
+  const files = {
+    "ruleset1.json": JSON.stringify(ruleset1),
+    "ruleset2.json": JSON.stringify(ruleset2),
+  };
+
+  const extension = ExtensionTestUtils.loadExtension(
+    getDNRExtension({
+      id: "tabId-invalid-in-session-rules@mochitest",
+      rule_resources,
+      files,
+    })
+  );
+
+  assertDNRTelemetryMetricsNoSamples(
+    [
+      {
+        metric: "validateRulesTime",
+        mirroredName: "WEBEXT_DNR_VALIDATE_RULES_MS",
+        mirroredType: "histogram",
+      },
+      {
+        metric: "evaluateRulesTime",
+        mirroredName: "WEBEXT_DNR_EVALUATE_RULES_MS",
+        mirroredType: "histogram",
+      },
+    ],
+    "before test extension have been loaded"
+  );
+
+  await extension.startup();
+  await extension.awaitMessage("bgpage:ready");
+
+  await assertDNRGetEnabledRulesets(extension, []);
+
+  assertDNRTelemetryMetricsNoSamples(
+    [
+      {
+        metric: "validateRulesTime",
+        mirroredName: "WEBEXT_DNR_VALIDATE_RULES_MS",
+        mirroredType: "histogram",
+      },
+    ],
+    "after test extension loaded with all static rulesets disabled"
+  );
+
+  info("Enable static ruleset1");
+  extension.sendMessage("updateEnabledRulesets", {
+    enableRulesetIds: ["ruleset1"],
+  });
+  await extension.awaitMessage("updateEnabledRulesets:done");
+
+  await assertDNRGetEnabledRulesets(extension, ["ruleset1"]);
+
+  // Expect one sample after enabling ruleset1.
+  let expectedValidateRulesTimeSamples = 1;
+  assertDNRTelemetryMetricsSamplesCount(
+    [
+      {
+        metric: "validateRulesTime",
+        mirroredName: "WEBEXT_DNR_VALIDATE_RULES_MS",
+        mirroredType: "histogram",
+        expectedSamplesCount: expectedValidateRulesTimeSamples,
+      },
+    ],
+    "after enabling static rulesets1"
+  );
+
+  info("Enable static ruleset2");
+  extension.sendMessage("updateEnabledRulesets", {
+    enableRulesetIds: ["ruleset2"],
+  });
+  await extension.awaitMessage("updateEnabledRulesets:done");
+
+  await assertDNRGetEnabledRulesets(extension, ["ruleset1", "ruleset2"]);
+
+  // Expect one new sample after enabling ruleset2.
+  expectedValidateRulesTimeSamples += 1;
+  assertDNRTelemetryMetricsSamplesCount(
+    [
+      {
+        metric: "validateRulesTime",
+        mirroredName: "WEBEXT_DNR_VALIDATE_RULES_MS",
+        mirroredType: "histogram",
+        expectedSamplesCount: expectedValidateRulesTimeSamples,
+      },
+    ],
+    "after enabling static rulesets2"
+  );
+
+  await extension.addon.disable();
+
+  assertDNRTelemetryMetricsSamplesCount(
+    [
+      {
+        metric: "validateRulesTime",
+        mirroredName: "WEBEXT_DNR_VALIDATE_RULES_MS",
+        mirroredType: "histogram",
+        expectedSamplesCount: expectedValidateRulesTimeSamples,
+      },
+    ],
+    "no new samples expected after disabling test extension"
+  );
+
+  await extension.addon.enable();
+  await extension.awaitMessage("bgpage:ready");
+  await ExtensionDNR.ensureInitialized(extension.extension);
+
+  // Expect 2 new samples after re-enabling the addon with
+  // the 2 rulesets enabled being loaded from the DNR store file.
+  expectedValidateRulesTimeSamples += 2;
+  assertDNRTelemetryMetricsSamplesCount(
+    [
+      {
+        metric: "validateRulesTime",
+        mirroredName: "WEBEXT_DNR_VALIDATE_RULES_MS",
+        mirroredType: "histogram",
+        expectedSamplesCount: expectedValidateRulesTimeSamples,
+      },
+    ],
+    "after re-enabling test extension"
+  );
+
+  info("Disable static ruleset1");
+
+  extension.sendMessage("updateEnabledRulesets", {
+    disableRulesetIds: ["ruleset1"],
+  });
+  await extension.awaitMessage("updateEnabledRulesets:done");
+
+  await assertDNRGetEnabledRulesets(extension, ["ruleset2"]);
+
+  assertDNRTelemetryMetricsSamplesCount(
+    [
+      {
+        metric: "validateRulesTime",
+        mirroredName: "WEBEXT_DNR_VALIDATE_RULES_MS",
+        mirroredType: "histogram",
+        expectedSamplesCount: expectedValidateRulesTimeSamples,
+      },
+    ],
+    "no new validation should be hit after disabling ruleset1"
+  );
+
+  info("Verify telemetry recorded on rules evaluation");
+  extension.sendMessage("updateEnabledRulesets", {
+    enableRulesetIds: ["ruleset1"],
+    disableRulesetIds: ["ruleset2"],
+  });
+  await extension.awaitMessage("updateEnabledRulesets:done");
+  await assertDNRGetEnabledRulesets(extension, ["ruleset1"]);
+
+  assertDNRTelemetryMetricsNoSamples(
+    [
+      {
+        metric: "evaluateRulesTime",
+        mirroredName: "WEBEXT_DNR_EVALUATE_RULES_MS",
+        mirroredType: "histogram",
+      },
+      {
+        metric: "evaluateRulesCountMax",
+        mirroredName: "extensions.apis.dnr.evaluate_rules_count_max",
+        mirroredType: "scalar",
+      },
+    ],
+    "before any request have been intercepted"
+  );
+
+  Assert.equal(
+    await fetch("http://example.com/").then(res => res.text()),
+    "response from server",
+    "DNR should not block system requests"
+  );
+
+  assertDNRTelemetryMetricsNoSamples(
+    [
+      {
+        metric: "evaluateRulesTime",
+        mirroredName: "WEBEXT_DNR_EVALUATE_RULES_MS",
+        mirroredType: "histogram",
+      },
+      {
+        metric: "evaluateRulesCountMax",
+        mirroredName: "extensions.apis.dnr.evaluate_rules_count_max",
+        mirroredType: "scalar",
+      },
+    ],
+    "after restricted request have been intercepted (but no rules evaluated)"
+  );
+
+  const page = await ExtensionTestUtils.loadContentPage("http://example.com");
+  const callPageFetch = async () => {
+    Assert.equal(
+      await page.spawn([], () => {
+        return this.content.fetch("http://example.com/").then(
+          res => res.text(),
+          err => err.message
+        );
+      }),
+      "NetworkError when attempting to fetch resource.",
+      "DNR should have blocked test request to example.com"
+    );
+  };
+
+  // Expect one sample recorded on evaluating rules for the
+  // top level navigation.
+  let expectedEvaluateRulesTimeSamples = 1;
+  assertDNRTelemetryMetricsSamplesCount(
+    [
+      {
+        metric: "evaluateRulesTime",
+        mirroredName: "WEBEXT_DNR_EVALUATE_RULES_MS",
+        mirroredType: "histogram",
+        expectedSamplesCount: expectedEvaluateRulesTimeSamples,
+      },
+    ],
+    "evaluateRulesTime should be collected after evaluated rulesets"
+  );
+  // Expect same number of rules included in the single ruleset
+  // currently enabled.
+  let expectedEvaluateRulesCountMax = ruleset1.length;
+  assertDNRTelemetryMetricsGetValueEq(
+    [
+      {
+        metric: "evaluateRulesCountMax",
+        mirroredName: "extensions.apis.dnr.evaluate_rules_count_max",
+        mirroredType: "scalar",
+        expectedGetValue: expectedEvaluateRulesCountMax,
+      },
+    ],
+    "evaluateRulesCountMax should be collected after evaluated rulesets1"
+  );
+
+  await callPageFetch();
+
+  // Expect one new sample reported on evaluating rules for the
+  // first fetch request originated from the test page.
+  expectedEvaluateRulesTimeSamples += 1;
+  assertDNRTelemetryMetricsSamplesCount(
+    [
+      {
+        metric: "evaluateRulesTime",
+        mirroredName: "WEBEXT_DNR_EVALUATE_RULES_MS",
+        mirroredType: "histogram",
+        expectedSamplesCount: expectedEvaluateRulesTimeSamples,
+      },
+    ],
+    "evaluateRulesTime should be collected after evaluated rulesets"
+  );
+
+  extension.sendMessage("updateEnabledRulesets", {
+    enableRulesetIds: ["ruleset2"],
+  });
+  await extension.awaitMessage("updateEnabledRulesets:done");
+  await assertDNRGetEnabledRulesets(extension, ["ruleset1", "ruleset2"]);
+
+  await callPageFetch();
+
+  // Expect 3 rules with both rulesets enabled
+  // (1 from ruleset1 and 2 more from ruleset2).
+  expectedEvaluateRulesCountMax += ruleset2.length;
+  assertDNRTelemetryMetricsGetValueEq(
+    [
+      {
+        metric: "evaluateRulesCountMax",
+        mirroredName: "extensions.apis.dnr.evaluate_rules_count_max",
+        mirroredType: "scalar",
+        expectedGetValue: expectedEvaluateRulesCountMax,
+      },
+    ],
+    "evaluateRulesCountMax should have been increased after enabling ruleset2"
+  );
+
+  extension.sendMessage("updateEnabledRulesets", {
+    disableRulesetIds: ["ruleset2"],
+  });
+  await extension.awaitMessage("updateEnabledRulesets:done");
+  await assertDNRGetEnabledRulesets(extension, ["ruleset1"]);
+
+  await callPageFetch();
+
+  assertDNRTelemetryMetricsGetValueEq(
+    [
+      {
+        metric: "evaluateRulesCountMax",
+        mirroredName: "extensions.apis.dnr.evaluate_rules_count_max",
+        mirroredType: "scalar",
+        expectedGetValue: expectedEvaluateRulesCountMax,
+      },
+    ],
+    "evaluateRulesCountMax should have not been decreased after disabling ruleset2"
+  );
+
+  await page.close();
+
+  await extension.unload();
+});
diff --git a/toolkit/components/extensions/test/xpcshell/test_ext_dnr_system_restrictions.js b/toolkit/components/extensions/test/xpcshell/test_ext_dnr_system_restrictions.js
new file mode 100644
index 0000000000..84464d0cba
--- /dev/null
+++ b/toolkit/components/extensions/test/xpcshell/test_ext_dnr_system_restrictions.js
@@ -0,0 +1,283 @@
+"use strict";
+
+const server = createHttpServer({ hosts: ["example.com", "restricted"] });
+server.registerPathHandler("/", (req, res) => {
+  res.setHeader("Access-Control-Allow-Origin", "*");
+  res.write("response from server");
+});
+server.registerPathHandler("/style_with_import.css", (req, res) => {
+  res.setHeader("Content-Type", "text/css");
+  res.setHeader("Access-Control-Allow-Origin", "*");
+  res.write("@import url('http://example.com/imported.css');");
+});
+server.registerPathHandler("/imported.css", (req, res) => {
+  res.setHeader("Content-Type", "text/css");
+  res.setHeader("Access-Control-Allow-Origin", "*");
+  res.write("imported_stylesheet_here { }");
+});
+
+add_setup(() => {
+  Services.prefs.setBoolPref("extensions.manifestV3.enabled", true);
+  Services.prefs.setBoolPref("extensions.dnr.enabled", true);
+  // The restrictedDomains pref should be set early, because the pref is read
+  // only once (on first use) by WebExtensionPolicy::IsRestrictedURI.
+  Services.prefs.setCharPref(
+    "extensions.webextensions.restrictedDomains",
+    "restricted"
+  );
+});
+
+async function startDNRExtension() {
+  let extension = ExtensionTestUtils.loadExtension({
+    async background() {
+      await browser.declarativeNetRequest.updateSessionRules({
+        addRules: [
+          {
+            id: 1,
+            condition: { resourceTypes: ["xmlhttprequest", "stylesheet"] },
+            action: { type: "block" },
+          },
+          {
+            id: 2,
+            condition: { urlFilter: "blockme", resourceTypes: ["main_frame"] },
+            action: { type: "block" },
+          },
+        ],
+      });
+      browser.test.sendMessage("dnr_registered");
+    },
+    manifest: {
+      manifest_version: 3,
+      permissions: ["declarativeNetRequest"],
+    },
+  });
+  await extension.startup();
+  await extension.awaitMessage("dnr_registered");
+  return extension;
+}
+
+add_task(async function dnr_ignores_system_requests() {
+  let extension = await startDNRExtension();
+  Assert.equal(
+    await (await fetch("http://example.com/")).text(),
+    "response from server",
+    "DNR should not block requests from system principal"
+  );
+  await extension.unload();
+});
+
+add_task(async function dnr_ignores_requests_to_restrictedDomains() {
+  let extension = await startDNRExtension();
+  Assert.equal(
+    await ExtensionTestUtils.fetch("http://example.com/", "http://restricted/"),
+    "response from server",
+    "DNR should not block destination in restrictedDomains"
+  );
+  await extension.unload();
+});
+
+add_task(async function dnr_ignores_initiator_from_restrictedDomains() {
+  let extension = await startDNRExtension();
+  Assert.equal(
+    await ExtensionTestUtils.fetch("http://restricted/", "http://example.com/"),
+    "response from server",
+    "DNR should not block requests initiated from a page in restrictedDomains"
+  );
+  await extension.unload();
+});
+
+add_task(async function dnr_ignores_navigation_to_restrictedDomains() {
+  let extension = await startDNRExtension();
+  let contentPage = await ExtensionTestUtils.loadContentPage(
+    "http://restricted/?blockme"
+  );
+  await contentPage.spawn([], () => {
+    const { document } = content;
+    Assert.equal(document.URL, "http://restricted/?blockme", "Same URL");
+    Assert.equal(document.body.textContent, "response from server", "body");
+  });
+  await contentPage.close();
+  await extension.unload();
+});
+
+add_task(async function dnr_ignores_css_import_at_restrictedDomains() {
+  // CSS @import have triggeringPrincipal set to the URL of the stylesheet,
+  // and the loadingPrincipal set to the web page. To verify that access is
+  // indeed being restricted as expected, confirm that none of the stylesheet
+  // requests are blocked by the DNR extension.
+  let extension = await startDNRExtension();
+  let contentPage = await ExtensionTestUtils.loadContentPage(
+    "http://restricted/"
+  );
+  await contentPage.spawn([], async () => {
+    // Use wrappedJSObject so that all operations below are with the principal
+    // of the content instead of the system principal (from this ContentTask).
+    const { document } = content.wrappedJSObject;
+    const style = document.createElement("link");
+    style.rel = "stylesheet";
+    // Note: intentionally not at "http://restricted/" because we want to check
+    // that subresources from a restricted domain are ignored by DNR..
+    style.href = "http://example.com/style_with_import.css";
+    style.crossOrigin = "anonymous";
+    await new Promise(resolve => {
+      info("Waiting for style sheet to load...");
+      style.onload = resolve;
+      document.head.append(style);
+    });
+    const importRule = style.sheet.cssRules[0];
+    Assert.equal(
+      importRule?.cssText,
+      `@import url("http://example.com/imported.css");`,
+      "Not blocked by DNR: Loaded style_with_import.css"
+    );
+    // Waiving Xrays here because we cannot read cssRules despite CORS because
+    // that is not implemented for child stylesheets (loaded via @import):
+    // https://searchfox.org/mozilla-central/rev/55d5c4b9dffe5e59eb6b019c1a930ec9ada47e10/layout/style/Loader.cpp#2052
+    const importedStylesheet = Cu.unwaiveXrays(importRule.styleSheet);
+    Assert.equal(
+      importedStylesheet.cssRules[0]?.cssText,
+      "imported_stylesheet_here { }",
+      "Not blocked by DNR: Loaded import.css"
+    );
+  });
+  await contentPage.close();
+  await extension.unload();
+});
+
+add_task(
+  { pref_set: [["extensions.dnr.feedback", true]] },
+  async function testMatchOutcome_and_restrictedDomains() {
+    let extension = ExtensionTestUtils.loadExtension({
+      async background() {
+        await browser.declarativeNetRequest.updateSessionRules({
+          addRules: [{ id: 1, condition: {}, action: { type: "block" } }],
+        });
+        const type = "other"; // matches the condition of the above rule.
+
+        browser.test.assertDeepEq(
+          { matchedRules: [] },
+          await browser.declarativeNetRequest.testMatchOutcome({
+            url: "http://restricted/",
+            type,
+          }),
+          "testMatchOutcome ignores restricted url"
+        );
+        browser.test.assertDeepEq(
+          { matchedRules: [] },
+          await browser.declarativeNetRequest.testMatchOutcome({
+            url: "http://example.com/",
+            initiator: "http://restricted/",
+            type,
+          }),
+          "testMatchOutcome ignores restricted initiator"
+        );
+        browser.test.sendMessage("done");
+      },
+      manifest: {
+        manifest_version: 3,
+        permissions: ["declarativeNetRequest", "declarativeNetRequestFeedback"],
+      },
+    });
+    await extension.startup();
+    await extension.awaitMessage("done");
+    await extension.unload();
+  }
+);
+
+add_task(
+  // In debug builds, any attempt to load data:-URLs in the parent process
+  // results in a crash or at least a logged error, via
+  // nsContentSecurityUtils::ValidateScriptFilename.
+  //
+  // Xpcshell tests use loadFrameScript with data:-URLs, which could trigger the
+  // above error / crash, when a page is loaded in the parent process.
+  // For example, the following error message (or crash),
+  // "InternalError: unsafe filename: data:text/javascript,//"
+  // "Hit MOZ_CRASH(Blocking a script load data:text/javascript,// from file (None))"
+  // is triggered because of the loadFrameScript call at
+  // https://searchfox.org/mozilla-central/rev/11dbac7f64f509b78037465cbb4427ed71f8b565/testing/modules/XPCShellContentUtils.sys.mjs#308
+  //
+  // This test loads about:logo in the parent, because nsAboutRedirector.cpp
+  // registers about:logo without nsIAboutModule::URI_MUST_LOAD_IN_CHILD.
+  // When about:logo is loaded, the ContentPage test helper also triggers the
+  // above error/crash at:
+  // https://searchfox.org/mozilla-central/rev/11dbac7f64f509b78037465cbb4427ed71f8b565/testing/modules/XPCShellContentUtils.sys.mjs#224,242
+  //
+  // Opt out of the check/crash from ValidateScriptFilename:
+  { pref_set: [["security.allow_parent_unrestricted_js_loads", true]] },
+  async function non_system_request_with_disallowed_scheme() {
+    let extension = await startDNRExtension();
+    Assert.equal(
+      await (await fetch("http://example.com/")).text(),
+      "response from server",
+      "DNR should not block requests from system principal"
+    );
+    // We are loading about:logo for the following reasons:
+    // - It is a regular content principal, NOT a system principal.
+    // - It is an about:-URL that resolves across all builds (part of toolkit/).
+    // - It does not have a CSP (intentional - bug 1587417). That enables us to
+    //   send a fetch() request below.
+    let contentPage = await ExtensionTestUtils.loadContentPage(
+      "about:logo?blockme"
+    );
+    await contentPage.spawn([], async () => {
+      const { document } = content;
+      // To make sure that the test does not pass trivially, we verify that it
+      // is not the system principal (because dnr_ignores_system_requests
+      // already tests that) and not a null principal (because that translates
+      // to a void "initiator" in the DNR API, which would pass access checks).
+      Assert.ok(
+        document.nodePrincipal.isContentPrincipal,
+        "about:logo has content principal (not system or NullPrincipal))"
+      );
+      Assert.equal(document.URL, "about:logo?blockme", "Same URL");
+      Assert.equal(
+        await (await content.fetch("http://example.com/")).text(),
+        "response from server",
+        "fetch() at about:logo not blocked by DNR"
+      );
+    });
+    await contentPage.close();
+    await extension.unload();
+  }
+);
+
+add_task(
+  { pref_set: [["extensions.dnr.feedback", true]] },
+  async function testMatchOutcome_non_system_request_with_disallowed_scheme() {
+    let extension = ExtensionTestUtils.loadExtension({
+      async background() {
+        await browser.declarativeNetRequest.updateSessionRules({
+          addRules: [{ id: 1, condition: {}, action: { type: "block" } }],
+        });
+        const type = "other"; // matches the condition of the above rule.
+
+        browser.test.assertDeepEq(
+          { matchedRules: [] },
+          await browser.declarativeNetRequest.testMatchOutcome({
+            url: "about:logo",
+            type,
+          }),
+          "testMatchOutcome ignores url with disallowed schema"
+        );
+        browser.test.assertDeepEq(
+          { matchedRules: [] },
+          await browser.declarativeNetRequest.testMatchOutcome({
+            url: "http://example.com/",
+            initiator: "about:logo",
+            type,
+          }),
+          "testMatchOutcome ignores initiator with disallowed schema"
+        );
+        browser.test.sendMessage("done");
+      },
+      manifest: {
+        manifest_version: 3,
+        permissions: ["declarativeNetRequest", "declarativeNetRequestFeedback"],
+      },
+    });
+    await extension.startup();
+    await extension.awaitMessage("done");
+    await extension.unload();
+  }
+);
diff --git a/toolkit/components/extensions/test/xpcshell/test_ext_dnr_tabIds.js b/toolkit/components/extensions/test/xpcshell/test_ext_dnr_tabIds.js
new file mode 100644
index 0000000000..84b75bb5be
--- /dev/null
+++ b/toolkit/components/extensions/test/xpcshell/test_ext_dnr_tabIds.js
@@ -0,0 +1,249 @@
+"use strict";
+
+// This test verifies that the internals for associating requests with tabId
+// are only active when a session rule with a tabId rule exists.
+//
+// There are tests for the logic of tabId matching in the match_tabIds task in
+// toolkit/components/extensions/test/xpcshell/test_ext_dnr_testMatchOutcome.js
+//
+// And there are tests that verify matching with real network requests in
+// toolkit/components/extensions/test/mochitest/test_ext_dnr_tabIds.html
+
+const server = createHttpServer({ hosts: ["from", "any", "in", "ex"] });
+server.registerPathHandler("/", (req, res) => {
+  res.setHeader("Access-Control-Allow-Origin", "*");
+});
+
+let gTabLookupSpy;
+
+add_setup(async () => {
+  Services.prefs.setBoolPref("extensions.manifestV3.enabled", true);
+  Services.prefs.setBoolPref("extensions.dnr.enabled", true);
+
+  // Install a spy on WebRequest.getTabIdForChannelWrapper.
+  const { WebRequest } = ChromeUtils.importESModule(
+    "resource://gre/modules/WebRequest.sys.mjs"
+  );
+  const { sinon } = ChromeUtils.importESModule(
+    "resource://testing-common/Sinon.sys.mjs"
+  );
+  gTabLookupSpy = sinon.spy(WebRequest, "getTabIdForChannelWrapper");
+
+  await ExtensionTestUtils.startAddonManager();
+});
+
+function numberOfTabLookupsSinceLastCheck() {
+  let result = gTabLookupSpy.callCount;
+  gTabLookupSpy.resetHistory();
+  return result;
+}
+
+// This test checks that WebRequest.getTabIdForChannelWrapper is only called
+// when there are any registered tabId/excludedTabIds rules. Moreover, it
+// verifies that after unloading (reloading) the extension, that the method is
+// still not called unnecessarily.
+add_task(async function getTabIdForChannelWrapper_only_called_when_needed() {
+  async function background() {
+    const RULE_ANY_TAB_ID = {
+      id: 1,
+      condition: { requestDomains: ["from"] },
+      action: { type: "redirect", redirect: { url: "http://any/" } },
+    };
+    const RULE_INCLUDE_TAB_ID = {
+      id: 2,
+      condition: { requestDomains: ["from"], tabIds: [-1] },
+      action: { type: "redirect", redirect: { url: "http://in/" } },
+      priority: 2,
+    };
+    const RULE_EXCLUDE_TAB_ID = {
+      id: 3,
+      condition: { requestDomains: ["from"], excludedTabIds: [-1] },
+      action: { type: "redirect", redirect: { url: "http://ex/" } },
+      priority: 2,
+    };
+    async function promiseOneMessage(messageName) {
+      return new Promise(resolve => {
+        browser.test.onMessage.addListener(function listener(msg, result) {
+          if (messageName === msg) {
+            browser.test.onMessage.removeListener(listener);
+            resolve(result);
+          }
+        });
+      });
+    }
+    async function numberOfTabLookupsSinceLastCheck() {
+      let promise = promiseOneMessage("tabLookups");
+      browser.test.sendMessage("getTabLookups");
+      return promise;
+    }
+    async function testFetchUrl(url, expectedUrl, expectedCount, description) {
+      let res = await fetch(url);
+      browser.test.assertEq(expectedUrl, res.url, `Final URL for ${url}`);
+      browser.test.assertEq(
+        expectedCount,
+        await numberOfTabLookupsSinceLastCheck(),
+        `Expected number of tab lookups - ${url} - ${description}`
+      );
+    }
+
+    const startupCountPromise = promiseOneMessage("extensionStartupCount");
+    browser.test.sendMessage("extensionStarted");
+    const startupCount = await startupCountPromise;
+    if (startupCount !== 0) {
+      browser.test.assertEq(1, startupCount, "Extension restarted once");
+
+      // Note: declarativeNetRequest.updateSessionRules is intentionally not
+      // called here, because we want to verify that upon unloading the
+      // extension, that the tabId lookup logic was properly cleaned up,
+      // i.e. that NetworkIntegration.maybeUpdateTabIdChecker() was called.
+
+      await testFetchUrl(
+        "http://from/?after-restart-supposedly-no-include-tab",
+        "http://from/?after-restart-supposedly-no-include-tab",
+        0,
+        "No lookup because session rules should have disappeared at reload"
+      );
+
+      browser.test.assertDeepEq(
+        [],
+        await browser.declarativeNetRequest.getSessionRules(),
+        "The session rules have indeed been cleared upon reload."
+      );
+
+      browser.test.sendMessage("test_completed_after_reload");
+      return;
+    }
+
+    browser.test.assertEq(
+      0,
+      await numberOfTabLookupsSinceLastCheck(),
+      "Initially, no tab lookups"
+    );
+
+    await testFetchUrl(
+      "http://from/?no_dnr_rules",
+      "http://from/?no_dnr_rules",
+      0,
+      "No tab lookups without any registered DNR rules"
+    );
+
+    await browser.declarativeNetRequest.updateSessionRules({
+      addRules: [RULE_ANY_TAB_ID],
+    });
+    // Active rules now: RULE_ANY_TAB_ID
+
+    await testFetchUrl(
+      "http://from/?only_dnr_rule_matches_any_tab",
+      "http://any/",
+      0,
+      "No tab lookups when only rule has no tabIds/excludedTabIds conditions"
+    );
+
+    await browser.declarativeNetRequest.updateSessionRules({
+      addRules: [RULE_EXCLUDE_TAB_ID],
+    });
+    // Active rules now: RULE_ANY_TAB_ID, RULE_EXCLUDE_TAB_ID
+
+    await testFetchUrl(
+      "http://from/?dnr_rule_matches_any,dnr_rule_excludes_-1",
+      // should be "any" instead of "ex" because excludedTabIds: [-1] should
+      // exclude the background.
+      "http://any/",
+      2, // initial request + redirect request.
+      "Expected tabId lookup when a tabId rule is registered"
+    );
+
+    await browser.declarativeNetRequest.updateSessionRules({
+      removeRuleIds: [RULE_ANY_TAB_ID.id],
+    });
+    // Active rules now: RULE_EXCLUDE_TAB_ID
+
+    await testFetchUrl(
+      "http://from/?only_dnr_rule_excludes_-1",
+      // Not redirected to "ex" because excludedTabIds: [-1] does not match the
+      // background that has tabId -1.
+      "http://from/?only_dnr_rule_excludes_-1",
+      1,
+      "Expected lookup after unregistering unrelated rule, keeping tabId rule"
+    );
+
+    await browser.declarativeNetRequest.updateSessionRules({
+      addRules: [RULE_INCLUDE_TAB_ID],
+    });
+    // Active rules now: RULE_EXCLUDE_TAB_ID, RULE_INCLUDE_TAB_ID
+    await testFetchUrl(
+      "http://from/?two_dnr_rule_include_and_exclude_-1",
+      "http://in/",
+      2, // initial request + redirect request.
+      "Expecting lookup because of 2 DNR rules with tabId and excludedTabIds"
+    );
+
+    await browser.declarativeNetRequest.updateSessionRules({
+      removeRuleIds: [RULE_EXCLUDE_TAB_ID.id],
+    });
+    // Active rules now: RULE_INCLUDE_TAB_ID
+
+    await testFetchUrl(
+      "http://from/?only_dnr_rule_includes_-1",
+      "http://in/",
+      2, // initial request + redirect request.
+      "Expecting lookup because of remaining tabId DNR rule"
+    );
+
+    await browser.declarativeNetRequest.updateSessionRules({
+      removeRuleIds: [RULE_INCLUDE_TAB_ID.id],
+    });
+    // Active rules now: none
+
+    await testFetchUrl(
+      "http://from/?no_rules_again",
+      "http://from/?no_rules_again",
+      0,
+      "Expected no lookups after unregistering the last remaining rule"
+    );
+
+    await browser.declarativeNetRequest.updateSessionRules({
+      addRules: [RULE_INCLUDE_TAB_ID],
+    });
+    // Active rules now: RULE_INCLUDE_TAB_ID
+
+    await testFetchUrl(
+      "http://from/?again_with-include-1",
+      "http://in/",
+      2, // initial request + redirect request.
+      "Expecting lookup again because of include rule"
+    );
+
+    // Ending test with remaining rule: RULE_INCLUDE_TAB_ID
+    // Reload extension.
+    browser.test.sendMessage("reload_extension");
+  }
+  let extension = ExtensionTestUtils.loadExtension({
+    background,
+    useAddonManager: "temporary", // for reload and granted_host_permissions.
+    allowInsecureRequests: true,
+    manifest: {
+      manifest_version: 3,
+      host_permissions: ["*://from/*"],
+      granted_host_permissions: true,
+      permissions: ["declarativeNetRequest"],
+    },
+  });
+  extension.onMessage("getTabLookups", () => {
+    extension.sendMessage("tabLookups", numberOfTabLookupsSinceLastCheck());
+  });
+  let startupCount = 0;
+  extension.onMessage("extensionStarted", () => {
+    extension.sendMessage("extensionStartupCount", startupCount++);
+  });
+  await extension.startup();
+  await extension.awaitMessage("reload_extension");
+  await extension.addon.reload();
+  await extension.awaitMessage("test_completed_after_reload");
+  Assert.equal(
+    0,
+    numberOfTabLookupsSinceLastCheck(),
+    "No new tab lookups since completion of extension tests"
+  );
+  await extension.unload();
+});
diff --git a/toolkit/components/extensions/test/xpcshell/test_ext_dnr_testMatchOutcome.js b/toolkit/components/extensions/test/xpcshell/test_ext_dnr_testMatchOutcome.js
new file mode 100644
index 0000000000..d9cc523d99
--- /dev/null
+++ b/toolkit/components/extensions/test/xpcshell/test_ext_dnr_testMatchOutcome.js
@@ -0,0 +1,1504 @@
+"use strict";
+
+add_setup(() => {
+  Services.prefs.setBoolPref("extensions.manifestV3.enabled", true);
+  Services.prefs.setBoolPref("extensions.dnr.enabled", true);
+  Services.prefs.setBoolPref("extensions.dnr.feedback", true);
+
+  // Don't turn warnings in errors, to make sure that the parameter validation
+  // tests verify real-world behavior, instead of the stricter test-only mode.
+  ExtensionTestUtils.failOnSchemaWarnings(false);
+});
+
+// This function is serialized and called in the context of the test extension's
+// background page. dnrTestUtils is passed to the background function.
+function makeDnrTestUtils() {
+  const dnrTestUtils = {};
+  const dnr = browser.declarativeNetRequest;
+  function makeDummyAction(type) {
+    switch (type) {
+      case "redirect":
+        return { type, redirect: { url: "https://example.com/dummy" } };
+      case "modifyHeaders":
+        return {
+          type,
+          responseHeaders: [{ operation: "append", header: "x", value: "y" }],
+        };
+      default:
+        return { type };
+    }
+  }
+  function makeDummyRequest() {
+    // A value that matches the condition from makeDummyRule().
+    return { url: "https://example.com/some-dummy-url", type: "main_frame" };
+  }
+  function makeDummyRule(id, actionType) {
+    return {
+      id,
+      // condition matches makeDummyRequest().
+      condition: { resourceTypes: ["main_frame"] },
+      action: makeDummyAction(actionType),
+    };
+  }
+  async function testMatchesRequest(request, ruleIds, description) {
+    browser.test.assertDeepEq(
+      ruleIds,
+      (await dnr.testMatchOutcome(request)).matchedRules.map(mr => mr.ruleId),
+      description
+    );
+  }
+  async function testCanMatchAnyBlock({ matchedRequests, nonMatchedRequests }) {
+    await dnr.updateSessionRules({
+      addRules: [
+        {
+          // A rule that is supposed to match everything.
+          id: 1,
+          condition: { excludedResourceTypes: [] },
+          action: { type: "block" },
+        },
+      ],
+    });
+    for (let request of matchedRequests) {
+      await testMatchesRequest(
+        request,
+        [1],
+        `${JSON.stringify(request)} - should match wildcard DNR block rule`
+      );
+    }
+    for (let request of nonMatchedRequests) {
+      await testMatchesRequest(
+        request,
+        [],
+        `${JSON.stringify(request)} - should not match any DNR rule`
+      );
+    }
+    await dnr.updateSessionRules({ removeRuleIds: [1] });
+  }
+  async function testCanUseAction(type, canUse) {
+    await dnr.updateSessionRules({ addRules: [makeDummyRule(1, type)] });
+    await testMatchesRequest(
+      makeDummyRequest(),
+      canUse ? [1] : [],
+      `${type} - should${canUse ? "" : " not"} match`
+    );
+    await dnr.updateSessionRules({ removeRuleIds: [1] });
+  }
+  Object.assign(dnrTestUtils, {
+    makeDummyAction,
+    makeDummyRequest,
+    makeDummyRule,
+    testMatchesRequest,
+    testCanMatchAnyBlock,
+    testCanUseAction,
+  });
+  return dnrTestUtils;
+}
+
+async function runAsDNRExtension({
+  background,
+  manifest,
+  unloadTestAtEnd = true,
+}) {
+  let extension = ExtensionTestUtils.loadExtension({
+    background: `(${background})((${makeDnrTestUtils})())`,
+    manifest: {
+      manifest_version: 3,
+      permissions: ["declarativeNetRequest", "declarativeNetRequestFeedback"],
+      host_permissions: ["<all_urls>"],
+      granted_host_permissions: true,
+      ...manifest,
+    },
+    temporarilyInstalled: true, // <-- for granted_host_permissions
+  });
+  await extension.startup();
+  await extension.awaitFinish();
+  if (unloadTestAtEnd) {
+    await extension.unload();
+  }
+  return extension;
+}
+
+add_task(async function validate_required_params() {
+  await runAsDNRExtension({
+    background: async () => {
+      const testMatchOutcome = browser.declarativeNetRequest.testMatchOutcome;
+
+      browser.test.assertThrows(
+        () => testMatchOutcome({ type: "image" }),
+        /Type error for parameter request \(Property "url" is required\)/,
+        "url is required"
+      );
+      browser.test.assertThrows(
+        () => testMatchOutcome({ url: "https://example.com/" }),
+        /Type error for parameter request \(Property "type" is required\)/,
+        "resource type is required"
+      );
+
+      browser.test.assertDeepEq(
+        { matchedRules: [] },
+        await testMatchOutcome({ url: "https://example.com/", type: "image" }),
+        "testMatchOutcome with url and type succeeds"
+      );
+
+      browser.test.notifyPass();
+    },
+  });
+});
+
+add_task(async function resource_type_validation() {
+  await runAsDNRExtension({
+    background: async () => {
+      const testMatchOutcome = browser.declarativeNetRequest.testMatchOutcome;
+
+      const url = "https://example.com/some-dummy-url";
+
+      browser.test.assertThrows(
+        () => testMatchOutcome({ url, type: "MAIN_FRAME" }),
+        /Error processing type: Invalid enumeration value "MAIN_FRAME"/,
+        "testMatchOutcome should expects a lowercase type"
+      );
+
+      // Check that at least one ResourceType exists.
+      browser.test.assertEq(
+        "main_frame",
+        browser.declarativeNetRequest.ResourceType.MAIN_FRAME,
+        "ResourceType.MAIN_FRAME exists"
+      );
+
+      for (let type of Object.values(
+        browser.declarativeNetRequest.ResourceType
+      )) {
+        browser.test.assertDeepEq(
+          { matchedRules: [] },
+          await testMatchOutcome({ url, type }),
+          `testMatchOutcome for type=${type} is allowed`
+        );
+      }
+
+      browser.test.notifyPass();
+    },
+  });
+});
+
+add_task(async function url_validation() {
+  await runAsDNRExtension({
+    background: async dnrTestUtils => {
+      const dnr = browser.declarativeNetRequest;
+      const { testMatchesRequest } = dnrTestUtils;
+
+      const type = "other"; // Dummy resource type.
+      await dnr.updateSessionRules({
+        addRules: [{ id: 1, condition: {}, action: { type: "block" } }],
+      });
+
+      const supportedUrls = [
+        // All schemes that are potentially hooked up to the network are here.
+        "http://example.com/",
+        "https://example.com/",
+        // While host permissions permits more (e.g. file:, moz-extension:),
+        // we don't list them here since they are not hooked up to the network.
+        // Trying to match such URLs is undefined behavior for now.
+      ];
+      const supportedInitiators = [
+        // Supported URLs are also supported initiators.
+        ...supportedUrls,
+        // Note: moz-extension: has more tests in match_initiator_moz_extension.
+        `moz-extension://${location.host}`,
+        "file:///tmp/",
+        // data:-URIs have a null principal.
+        "data:text/plain,",
+      ];
+      const disallowedUrlsOrInitiators = [
+        // about:-URI with system principal:
+        "about:config",
+        // Unprivileged about:-URL:
+        "about:logo",
+        "chrome://extensions/content/dummy.xhtml",
+        "resource://pdf.js/web/viewer.html",
+        // Extensions cannot see "view-source", only the result: bug 1683646.
+        "view-source:http://example.com/",
+        "view-source:about:config",
+        // blob:-URLs do not go through the network. An actual network request
+        // will never have a blob-URI as initiator, always the actual principal
+        // URI. We don't try to extract the actual principal from the blob:-URI
+        // because that is expensive and also performs a validation that the
+        // blob:-URI is still valid, so testMatchOutcome could then return
+        // inconsistent results.
+        URL.createObjectURL(new Blob([])),
+      ];
+      const disallowedUrls = [
+        ...disallowedUrlsOrInitiators,
+        // data:-URIs are not hooked up to the network (bug 1631933), so we do
+        // not support it in the testMatchOutcome API, even though the URL
+        // matches "<all_urls>".
+        "data:text/plain,",
+      ];
+      const disallowedInitiator = [
+        ...disallowedUrlsOrInitiators,
+        // "about:blank" inherits the principal or is null. testMatchOutcome
+        // does not offer a way to specify it more precisely.
+        "about:blank",
+        // This is bogus: A principal URL can never be about:srcdoc. It is
+        // always inherit from something.
+        "about:srcdoc",
+        "moz-extension://someone-elses-extension-here",
+      ];
+
+      for (let url of supportedUrls) {
+        await testMatchesRequest({ url, type }, [1], `Supported url: ${url}`);
+      }
+      for (let initiator of supportedInitiators) {
+        await testMatchesRequest(
+          { url: "http://example.com/", type, initiator },
+          [1],
+          `Supported initiator: ${initiator}`
+        );
+      }
+      for (let url of disallowedUrls) {
+        await testMatchesRequest({ type, url }, [], `Disallowed url: ${url}`);
+      }
+      for (let initiator of disallowedInitiator) {
+        await testMatchesRequest(
+          { url: "http://example.com/", type, initiator },
+          [],
+          `Disallowed initiator: ${initiator}`
+        );
+      }
+
+      browser.test.notifyPass();
+    },
+  });
+});
+
+add_task(async function rule_priority_and_action_type_precedence() {
+  await runAsDNRExtension({
+    background: async dnrTestUtils => {
+      const dnr = browser.declarativeNetRequest;
+      const { makeDummyRule, makeDummyRequest } = dnrTestUtils;
+
+      await dnr.updateSessionRules({
+        addRules: [
+          makeDummyRule(1, "allow"),
+          makeDummyRule(2, "allowAllRequests"),
+          makeDummyRule(3, "block"),
+          makeDummyRule(4, "upgradeScheme"),
+          makeDummyRule(5, "redirect"),
+          makeDummyRule(6, "modifyHeaders"),
+          { ...makeDummyRule(7, "modifyHeaders"), priority: 2 },
+          { ...makeDummyRule(8, "allow"), priority: 2 },
+          { ...makeDummyRule(9, "block"), priority: 2 },
+          // Repeat rules so that we can verify that the outcome is due to the
+          // rule action, instead of the rule ID / input order.
+          makeDummyRule(11, "allow"),
+          makeDummyRule(12, "allowAllRequests"),
+          makeDummyRule(13, "block"),
+          makeDummyRule(14, "upgradeScheme"),
+          makeDummyRule(15, "redirect"),
+          makeDummyRule(16, "modifyHeaders"),
+          { ...makeDummyRule(17, "modifyHeaders"), priority: 2 },
+        ],
+      });
+      async function testAndRemove(ruleId, expectedRuleIds, description) {
+        browser.test.assertDeepEq(
+          expectedRuleIds.map(ruleId => ({ ruleId, rulesetId: "_session" })),
+          (await dnr.testMatchOutcome(makeDummyRequest())).matchedRules,
+          description
+        );
+        await dnr.updateSessionRules({ removeRuleIds: [ruleId] });
+      }
+
+      await testAndRemove(8, [8], "highest-prio allow wins");
+      await testAndRemove(9, [9], "highest-prio block wins");
+      // after this point, we only have same-prio rules and two higher-prio
+      // modifyHeaders rules (7 & 17).
+
+      await testAndRemove(
+        1,
+        [1, 7, 17],
+        "1st allow ignores other rules, except for higher-prio modifyHeaders"
+      );
+      await testAndRemove(
+        11,
+        [11, 7, 17],
+        "2nd allow ignores other rules, except for higher-prio modifyHeaders"
+      );
+
+      await testAndRemove(
+        2,
+        [2, 7, 17],
+        "1st allowAllRequests ignores other rules, except for higher-prio modifyHeaders"
+      );
+      await testAndRemove(
+        12,
+        [12, 7, 17],
+        "2nd allowAllRequests ignores other rules, except for higher-prio modifyHeaders"
+      );
+
+      await testAndRemove(3, [3], "1st block > all other actions");
+      await testAndRemove(13, [13], "2nd block > all other actions");
+
+      await testAndRemove(4, [4], "1st upgradeScheme > redirect");
+      await testAndRemove(14, [14], "2nd upgradeScheme > redirect");
+
+      await testAndRemove(5, [5], "1st redirect > modifyHeaders");
+      await testAndRemove(15, [15], "2nd redirect > modifyHeaders");
+
+      await testAndRemove(
+        6,
+        [7, 17, 6, 16],
+        "All modifyHeaders match if there is no other action"
+      );
+
+      // Verify that a new rule takes precedence again.
+      await dnr.updateSessionRules({
+        addRules: [makeDummyRule(11, "allow")],
+      });
+      await testAndRemove(
+        11,
+        [11, 7, 17],
+        "After adding an allow rule, only higher-prio modifyHeaders are shown"
+      );
+
+      browser.test.assertDeepEq(
+        [7, 16, 17],
+        (await dnr.getSessionRules()).map(r => r.id),
+        "Remaining rules at end of test"
+      );
+
+      browser.test.notifyPass();
+    },
+  });
+});
+
+add_task(async function declarativeNetRequest_and_host_permissions() {
+  await runAsDNRExtension({
+    background: async dnrTestUtils => {
+      const { testCanUseAction, testCanMatchAnyBlock } = dnrTestUtils;
+
+      // Unlocked by declarativeNetRequest permission:
+      await testCanUseAction("allow", true);
+      await testCanUseAction("allowAllRequests", true);
+      await testCanUseAction("block", true);
+      await testCanUseAction("upgradeScheme", true);
+      // Unlocked by host permissions:
+      await testCanUseAction("redirect", true);
+      await testCanUseAction("modifyHeaders", true);
+
+      const url = "https://example.com/";
+      await testCanMatchAnyBlock({
+        matchedRequests: [
+          { url, type: "other" },
+          { url, type: "main_frame" },
+          { url, type: "sub_frame" },
+          { url, initiator: url, type: "other" },
+          { url, initiator: url, type: "main_frame" },
+          { url, initiator: url, type: "sub_frame" },
+        ],
+        nonMatchedRequests: [],
+      });
+
+      browser.test.notifyPass();
+    },
+  });
+});
+
+add_task(async function declarativeNetRequest_permission_only() {
+  await runAsDNRExtension({
+    manifest: {
+      host_permissions: [],
+    },
+    background: async dnrTestUtils => {
+      const { testCanUseAction, testCanMatchAnyBlock } = dnrTestUtils;
+
+      // Unlocked by declarativeNetRequest permission:
+      await testCanUseAction("allow", true);
+      await testCanUseAction("allowAllRequests", true);
+      await testCanUseAction("block", true);
+      await testCanUseAction("upgradeScheme", true);
+      // These require host permissions, which we don't have:
+      await testCanUseAction("redirect", false);
+      await testCanUseAction("modifyHeaders", false);
+
+      const url = "https://example.com/";
+      await testCanMatchAnyBlock({
+        matchedRequests: [
+          { url, type: "other" },
+          { url, type: "main_frame" },
+          { url, type: "sub_frame" },
+          { url, initiator: url, type: "other" },
+          { url, initiator: url, type: "main_frame" },
+          { url, initiator: url, type: "sub_frame" },
+        ],
+        nonMatchedRequests: [],
+      });
+
+      browser.test.notifyPass();
+    },
+  });
+});
+
+add_task(async function declarativeNetRequestWithHostAccess_only() {
+  await runAsDNRExtension({
+    manifest: {
+      permissions: [
+        "declarativeNetRequestWithHostAccess",
+        "declarativeNetRequestFeedback",
+      ],
+      host_permissions: [],
+    },
+    background: async dnrTestUtils => {
+      const { testCanUseAction } = dnrTestUtils;
+
+      // declarativeNetRequestWithHostAccess requires host permissions,
+      // which we don't have. So none of the rules should match:
+      await testCanUseAction("allow", false);
+      await testCanUseAction("allowAllRequests", false);
+      await testCanUseAction("block", false);
+      await testCanUseAction("upgradeScheme", false);
+      await testCanUseAction("redirect", false);
+      await testCanUseAction("modifyHeaders", false);
+
+      browser.test.notifyPass();
+    },
+  });
+});
+
+add_task(async function declarativeNetRequestWithHostAccess_and_host_perm() {
+  await runAsDNRExtension({
+    manifest: {
+      permissions: [
+        "declarativeNetRequestWithHostAccess",
+        "declarativeNetRequestFeedback",
+      ],
+      // Origin used by makeDummyRequest() & makeDummyRule():
+      host_permissions: ["https://example.com/"],
+    },
+    background: async dnrTestUtils => {
+      const { testCanUseAction, testCanMatchAnyBlock } = dnrTestUtils;
+
+      // declarativeNetRequestWithHostAccess + host permissions allows all:
+      await testCanUseAction("allow", true);
+      await testCanUseAction("allowAllRequests", true);
+      await testCanUseAction("block", true);
+      await testCanUseAction("upgradeScheme", true);
+      await testCanUseAction("redirect", true);
+      await testCanUseAction("modifyHeaders", true);
+
+      const url = "https://example.com/";
+      const urlNoPerm = "https://example.net/?not_in:host_permissions";
+      await testCanMatchAnyBlock({
+        matchedRequests: [
+          { url, type: "other" },
+          { url, type: "main_frame" },
+          { url, type: "sub_frame" },
+          // Navigations do no require host permissions for initiator.
+          { url, initiator: urlNoPerm, type: "main_frame" },
+          { url, initiator: urlNoPerm, type: "sub_frame" },
+        ],
+        nonMatchedRequests: [
+          // url always requires declarativeNetRequest or host permissions.
+          { url: urlNoPerm, type: "other" },
+          // Non-navigations require host permissions for initiator.
+          { url, initiator: urlNoPerm, type: "other" },
+        ],
+      });
+
+      browser.test.notifyPass();
+    },
+  });
+});
+
+// Tests: resourceTypes, excludedResourceTypes
+// Tests: requestMethods, excludedRequestMethods
+add_task(async function match_condition_types_and_methods() {
+  await runAsDNRExtension({
+    background: async dnrTestUtils => {
+      const dnr = browser.declarativeNetRequest;
+      const { makeDummyAction, testMatchesRequest } = dnrTestUtils;
+
+      // "modifyHeaders" is the only action that allows multiple rule matches.
+      const action = makeDummyAction("modifyHeaders");
+
+      await dnr.updateSessionRules({
+        addRules: [
+          {
+            id: 1,
+            condition: {
+              resourceTypes: ["xmlhttprequest"],
+              requestMethods: ["put"],
+            },
+            action,
+          },
+          {
+            id: 2,
+            condition: {
+              excludedResourceTypes: ["sub_frame"],
+              excludedRequestMethods: ["post"],
+            },
+            action,
+          },
+          {
+            id: 3,
+            condition: {
+              // resourceTypes not specified should imply all-minus-main_frame.
+              requestMethods: ["get", "post"],
+            },
+            action,
+          },
+          {
+            id: 4,
+            condition: {
+              resourceTypes: ["main_frame", "xmlhttprequest"],
+              excludedRequestMethods: ["get"],
+            },
+            action,
+          },
+        ],
+      });
+
+      const url = "https://example.com/some-dummy-url";
+      await testMatchesRequest(
+        { url, type: "main_frame" },
+        [2],
+        "main_frame + GET"
+      );
+
+      await testMatchesRequest(
+        { url, type: "xmlhttprequest" },
+        [2, 3],
+        "xmlhttprequest + GET"
+      );
+
+      await testMatchesRequest(
+        { url, type: "xmlhttprequest", method: "put" },
+        [1, 2, 4],
+        "xmlhttprequest + PUT"
+      );
+
+      await testMatchesRequest(
+        { url, type: "sub_frame", method: "post" },
+        [3],
+        "sub_frame + POST"
+      );
+
+      await testMatchesRequest(
+        { url, type: "sub_frame", method: "post" },
+        [3],
+        "sub_frame + POST"
+      );
+
+      browser.test.notifyPass();
+    },
+  });
+});
+
+// Tests: requestDomains, excludedRequestDomains
+add_task(async function match_request_domains() {
+  await runAsDNRExtension({
+    background: async dnrTestUtils => {
+      const dnr = browser.declarativeNetRequest;
+      const { makeDummyAction, testMatchesRequest } = dnrTestUtils;
+
+      // "modifyHeaders" is the only action that allows multiple rule matches.
+      const action = makeDummyAction("modifyHeaders");
+
+      await dnr.updateSessionRules({
+        addRules: [
+          {
+            id: 1,
+            condition: {
+              requestDomains: ["a.com", "www.b.com"],
+            },
+            action,
+          },
+          {
+            id: 2,
+            condition: {
+              excludedRequestDomains: ["a.com", "www.b.com", "127.0.0.1"],
+            },
+            action,
+          },
+          {
+            id: 3,
+            condition: {
+              requestDomains: ["one.net"],
+              excludedRequestDomains: ["sub.one.net"],
+            },
+            action,
+          },
+          {
+            id: 4,
+            condition: {
+              // This can never match.
+              requestDomains: ["sub.one.net"],
+              excludedRequestDomains: ["one.net"],
+            },
+            action,
+          },
+          {
+            id: 5,
+            condition: {
+              requestDomains: ["127.0.0.1", "[::1]"],
+            },
+            action,
+          },
+          {
+            id: 6,
+            condition: {
+              requestDomains: [
+                "~b.com", // "~" should not be interpreted as pattern negation.
+              ],
+            },
+            action,
+          },
+          {
+            id: 7,
+            condition: {
+              // A canonical domain does not start with a ".". Domains filters
+              // starting with a "." are therefore not matching anything.
+              requestDomains: [".a.com"],
+            },
+            action,
+          },
+        ],
+      });
+
+      const type = "sub_frame";
+      // Tests related to a.com:
+      await testMatchesRequest(
+        { url: "https://a.com:1234/path", type },
+        [1],
+        "a.com: url's domain is equal to a.com"
+      );
+      await testMatchesRequest(
+        { url: "http://sub.a.com/", type },
+        [1],
+        "sub.a.com: url is subdomain of a.com"
+      );
+      await testMatchesRequest(
+        { url: "http://nota.com/a.com?a.com#a.com", type },
+        [2],
+        "nota.com: url's domain does not match a.com"
+      );
+      await testMatchesRequest(
+        { url: "http://a.com.not/a.com?a.com#a.com", type },
+        [2],
+        "a.com.not: url's domain does not match a.com"
+      );
+      await testMatchesRequest(
+        { url: "http://a.com./a.com?a.com#a.com", type },
+        [2],
+        "a.com.: url's domain (ending with dot) does not match a.com"
+      );
+
+      // Tests related to www.b.com:
+      await testMatchesRequest(
+        { url: "http://www.b.com/", type },
+        [1],
+        "www.b.com: url's domain is equal to www.b.com"
+      );
+      await testMatchesRequest(
+        { url: "http://sub.www.b.com", type },
+        [1],
+        "sub.www.b.com: url's domain is a subdomain of www.b.com"
+      );
+      await testMatchesRequest(
+        { url: "http://b.com/", type },
+        [2],
+        "b.com: url's domain is a superdomain, NOT a subdomain of www.b.com"
+      );
+
+      // Tests related to sub.one.net / one.net
+      await testMatchesRequest(
+        { url: "http://one.net/", type },
+        [2, 3],
+        "one.net: url's domain matches one.net, but not sub.one.net"
+      );
+      await testMatchesRequest(
+        { url: "http://sub.one.net/", type },
+        [2], // Rule 4 was a candidate, but excluded anyway.
+        "sub.one.net: url's domain matches sub.one.net, but excluded by one.net"
+      );
+
+      // Tests related to IP addresses
+      await testMatchesRequest(
+        { url: "http://127.0.0.1:8080/", type },
+        [5],
+        "127.0.0.1: IP address is exact match for 127.0.0.1"
+      );
+      await testMatchesRequest(
+        { url: "http://8.8.8.8/", type },
+        [2],
+        "8.8.8.8: not matched by any of the domains"
+      );
+      await testMatchesRequest(
+        { url: "http://9.127.0.0.1/", type },
+        [5],
+        "9.127.0.0.1: while not a valid IP, it looks like a subdomain"
+      );
+      await testMatchesRequest(
+        { url: "http://[::1]/", type },
+        [2, 5],
+        "[::1]: IPv6 matches with bracket"
+      );
+
+      // For completeness, verify that the non-resolving domain "~b.com"
+      // matches the input, so that we know that "~" was not given special
+      // treatment. In filter list syntax, "~" before the domain negates the
+      // meaning, but that should not be supported in DNR.
+      await testMatchesRequest(
+        { url: "http://~b.com/", type },
+        [2, 6],
+        "~b.com: Although a non-resolving domain, it matches the pattern"
+      );
+
+      // match_initiator_domains has more tests; here we just confirm that
+      // requestDomains rules don't match initiator.
+      await testMatchesRequest(
+        { url: "http://url.does.not.match/", type, initiator: "http://a.com/" },
+        [2],
+        "requestDomains should not match initiator URL"
+      );
+
+      browser.test.notifyPass();
+    },
+  });
+});
+
+add_task(async function match_request_domains_punycode() {
+  await runAsDNRExtension({
+    background: async dnrTestUtils => {
+      const dnr = browser.declarativeNetRequest;
+      const { makeDummyAction, testMatchesRequest } = dnrTestUtils;
+
+      // "modifyHeaders" is the only action that allows multiple rule matches.
+      const action = makeDummyAction("modifyHeaders");
+
+      // Note that the non-punycode domains are rejected by schema validation,
+      // and checked by test validate_domains in test_ext_dnr_session_rules.js.
+
+      await dnr.updateSessionRules({
+        addRules: [
+          {
+            id: 1,
+            condition: {
+              // straß.de
+              requestDomains: ["xn--stra-yna.de"],
+            },
+            action,
+          },
+          {
+            id: 2,
+            condition: {
+              // IDNA2003 converted ß to ss. But IDNA2008 requires punycode.
+              requestDomains: ["strass.de", "stras.de"],
+            },
+            action,
+          },
+        ],
+      });
+
+      const type = "sub_frame";
+
+      await testMatchesRequest(
+        { url: "https://straß.de/", type },
+        [1],
+        "straß.de matches"
+      );
+      await testMatchesRequest(
+        { url: "https://xn--stra-yna.de/", type },
+        [1],
+        "xn--stra-yna.de matches"
+      );
+      await testMatchesRequest(
+        { url: "https://strass.de/", type },
+        [2],
+        "strass.de does not match the punycode pattern of straß"
+      );
+      await testMatchesRequest(
+        { url: "https://stras.de/", type },
+        [2],
+        "stras.de does not match the punycode pattern of straß"
+      );
+
+      browser.test.notifyPass();
+    },
+  });
+});
+
+// Tests: initiatorDomains, excludedInitiatorDomains
+// More tests in: match_initiator_moz_extension.
+add_task(async function match_initiator_domains() {
+  await runAsDNRExtension({
+    background: async dnrTestUtils => {
+      const dnr = browser.declarativeNetRequest;
+      const { makeDummyAction, testMatchesRequest } = dnrTestUtils;
+
+      // "modifyHeaders" is the only action that allows multiple rule matches.
+      const action = makeDummyAction("modifyHeaders");
+
+      // The validation of initiatorDomains and requestDomains are shared.
+      // The match_request_domains and match_request_domains_punycode tests
+      // already verify semantics; this test just tests that the conditional
+      // logic works as expected, plus coverage for initiator being void.
+
+      await dnr.updateSessionRules({
+        addRules: [
+          {
+            id: 1,
+            condition: {
+              initiatorDomains: ["a.com"],
+            },
+            action,
+          },
+          {
+            id: 2,
+            condition: {
+              excludedInitiatorDomains: ["a.com"],
+            },
+            action,
+          },
+          {
+            id: 3,
+            condition: {
+              initiatorDomains: ["c.com"],
+              excludedInitiatorDomains: ["c.com"],
+            },
+            action,
+          },
+          {
+            id: 4, // To verify that it does not match a void initiator.
+            condition: {
+              initiatorDomains: ["null"],
+            },
+            action,
+          },
+          {
+            id: 5,
+            condition: {
+              excludedInitiatorDomains: ["null", "undefined"],
+            },
+            action,
+          },
+          {
+            id: 6, // To verify that it does not match a void initiator.
+            condition: {
+              initiatorDomains: ["undefined"],
+            },
+            action,
+          },
+        ],
+      });
+
+      const url = "https://do.not.look.here/look_at_initator_instead";
+      const type = "image";
+      await testMatchesRequest(
+        { url, type, initiator: "http://a.com/" },
+        [1, 5],
+        "initiatorDomains matches"
+      );
+      await testMatchesRequest(
+        { url, type, initiator: "http://b.com/" },
+        [2, 5],
+        "excludedInitiatorDomains does not match, so request matched"
+      );
+      await testMatchesRequest(
+        { url, type, initiator: "http://c.com/" },
+        [2, 5], // 3 is not here, despite containing "c.com".
+        "excludedInitiatorDomains takes precedence over initiatorDomains"
+      );
+      // When initiator is not specified, rules with initiatorDomains should not
+      // match, and rules with excludedInitiatorDomains may match.
+      await testMatchesRequest(
+        { url, type },
+        [2, 5],
+        "request without initiator matches every excludedInitiatorDomains"
+      );
+      // http://null is unlikely to exist in practice. Regardless, verify that
+      // it won't match a void initiators.
+      await testMatchesRequest(
+        { url, type, initiator: "http://null/" },
+        [2, 4],
+        "http://null is matched by the 'null' domain"
+      );
+      await testMatchesRequest(
+        { url, type, initiator: "http://undefined/" },
+        [2, 6],
+        "http://null is matched by the 'undefined' domain"
+      );
+      await testMatchesRequest(
+        { url: "http://a.com/", type },
+        [2, 5],
+        "initiatorDomains should not match the request URL (initiator=null)"
+      );
+
+      browser.test.notifyPass();
+    },
+  });
+});
+
+// Tests: initiatorDomains, excludedInitiatorDomains with moz-extension:-URLs.
+add_task(async function match_initiator_moz_extension() {
+  let extension = await runAsDNRExtension({
+    manifest: { browser_specific_settings: { gecko: { id: "other@ext" } } },
+    background: async dnrTestUtils => {
+      const dnr = browser.declarativeNetRequest;
+      const { makeDummyAction, testMatchesRequest } = dnrTestUtils;
+
+      // "modifyHeaders" is the only action that allows multiple rule matches.
+      // But we cannot use "modifyHeaders" because that feature depends on
+      // access to "triggering principal". Fortunately, the two test rules in
+      // this test case are mutually exclusive, so the block action works.
+      // TODO bug 1825824: change to makeDummyAction("modifyHeaders").
+      const action = makeDummyAction("block");
+
+      const thisExtensionUUID = location.hostname;
+      await dnr.updateSessionRules({
+        addRules: [
+          {
+            id: 1,
+            condition: {
+              initiatorDomains: [thisExtensionUUID],
+            },
+            action,
+          },
+          {
+            id: 2,
+            condition: {
+              excludedInitiatorDomains: [thisExtensionUUID],
+            },
+            action,
+          },
+        ],
+      });
+
+      const url = "https://do.not.look.here/look_at_initator_instead";
+      const type = "other";
+      // Sanity check with non-moz-extension:-schemes as initiator.
+      await testMatchesRequest(
+        { url, type, initiator: `https://${thisExtensionUUID}/` },
+        [1],
+        "https:+UUID matches initiatorDomains"
+      );
+      await testMatchesRequest(
+        { url, type, initiator: "https://random-uuid-here/" },
+        [2],
+        "https:+UUID matches excludedInitiatorDomains"
+      );
+      // Now test with moz-extension: as initiator.
+      await testMatchesRequest(
+        { url, type, initiator: location.origin },
+        [1],
+        "moz-extension: initiator matches when it should"
+      );
+      await testMatchesRequest(
+        { url, type, initiator: `moz-extension://random-uuid-here/` },
+        [],
+        "moz-extension: from unrelated extension cannot match by default"
+      );
+
+      browser.test.onMessage.addListener(async msg => {
+        browser.test.assertEq("test_with_pref", msg, "expected msg");
+        await testMatchesRequest(
+          { url, type, initiator: `moz-extension://random-uuid-here/` },
+          [2],
+          "With pref, moz-extension: from unrelated extension can match"
+        );
+        browser.test.sendMessage("test_with_pref:done");
+      });
+
+      // Notify to continue. We don't exit yet due to unloadTestAtEnd:false
+      browser.test.notifyPass();
+    },
+    // Continue running the DNR extension because we want to test the current
+    // DNR rules with other extensions.
+    unloadTestAtEnd: false,
+  });
+
+  info("Testing foreign moz-extension request within same ext, with pref on");
+  await runWithPrefs(
+    [["extensions.dnr.match_requests_from_other_extensions", true]],
+    async () => {
+      extension.sendMessage("test_with_pref");
+      await extension.awaitMessage("test_with_pref:done");
+    }
+  );
+
+  const otherExtensionUUID = extension.uuid;
+
+  await runAsDNRExtension({
+    manifest: {
+      // Pass the DNR extension UUID to this extension.
+      description: otherExtensionUUID,
+    },
+    background: async () => {
+      const otherExtensionUUID = browser.runtime.getManifest().description;
+      const dnr = browser.declarativeNetRequest;
+
+      const url = "https://do.not.look.here/look_at_initator_instead";
+      const type = "other";
+
+      browser.test.assertDeepEq(
+        { matchedRules: [] },
+        await dnr.testMatchOutcome({ url, type, initiator: location.origin }),
+        "testMatchOutcome excludes other extensions by default"
+      );
+      browser.test.assertDeepEq(
+        { matchedRules: [] },
+        await dnr.testMatchOutcome(
+          { url, type, initiator: location.origin },
+          { includeOtherExtensions: true }
+        ),
+        "No matches when initiator is moz-extension:, different from DNR ext"
+      );
+      browser.test.assertDeepEq(
+        {
+          matchedRules: [
+            { ruleId: 1, rulesetId: "_session", extensionId: "other@ext" },
+          ],
+        },
+        await dnr.testMatchOutcome(
+          { url, type, initiator: `moz-extension://${otherExtensionUUID}` },
+          { includeOtherExtensions: true }
+        ),
+        "Simulated moz-extension: for original extension finds a match"
+      );
+
+      browser.test.notifyPass();
+    },
+  });
+
+  info("Testing foreign moz-extension request in other ext, with pref on");
+  await runWithPrefs(
+    [["extensions.dnr.match_requests_from_other_extensions", true]],
+    async () => {
+      await runAsDNRExtension({
+        manifest: {
+          // Pass the DNR extension UUID to this extension.
+          description: otherExtensionUUID,
+        },
+        background: async () => {
+          const otherExtensionUUID = browser.runtime.getManifest().description;
+          const dnr = browser.declarativeNetRequest;
+
+          const url = "https://do.not.look.here/look_at_initator_instead";
+          const type = "other";
+
+          // Sanity check: testMatchOutcome for moz-extension:-URL different
+          // from the DNR extension and the current test extension.
+          browser.test.assertDeepEq(
+            {
+              matchedRules: [
+                { ruleId: 2, rulesetId: "_session", extensionId: "other@ext" },
+              ],
+            },
+            await dnr.testMatchOutcome(
+              { url, type, initiator: "moz-extension://random-uuid-here/" },
+              { includeOtherExtensions: true }
+            ),
+            "With pref, moz-extension: from unrelated extensions can match"
+          );
+
+          // Usually, DNR does not affect requests from other extensions. That
+          // was checked in the previous test extension (without pref override).
+          // Here, we check that with the pref override, testMatchOutcome can
+          // return matches from other extensions for the given extension UUID.
+          browser.test.assertDeepEq(
+            {
+              matchedRules: [
+                { ruleId: 2, rulesetId: "_session", extensionId: "other@ext" },
+              ],
+            },
+            await dnr.testMatchOutcome(
+              { url, type, initiator: location.origin },
+              { includeOtherExtensions: true }
+            ),
+            "With pref, moz-extension:-initiator different from DNR ext matches"
+          );
+
+          // Identical test as in the previous test extension (that ran without
+          // the pref override). This verifies that the pref does not affect the
+          // behavior of request matching for requests within that extension.
+          browser.test.assertDeepEq(
+            {
+              matchedRules: [
+                { ruleId: 1, rulesetId: "_session", extensionId: "other@ext" },
+              ],
+            },
+            await dnr.testMatchOutcome(
+              { url, type, initiator: `moz-extension://${otherExtensionUUID}` },
+              { includeOtherExtensions: true }
+            ),
+            "With pref, moz-extension: for DNR ext still matches"
+          );
+
+          browser.test.notifyPass();
+        },
+      });
+    }
+  );
+
+  await extension.unload();
+});
+
+// Tests: urlFilter. For more comprehensive tests, see
+// toolkit/components/extensions/test/xpcshell/test_ext_dnr_urlFilter.js
+add_task(async function match_urlFilter() {
+  await runAsDNRExtension({
+    background: async dnrTestUtils => {
+      const dnr = browser.declarativeNetRequest;
+      const { makeDummyAction, testMatchesRequest } = dnrTestUtils;
+
+      // "modifyHeaders" is the only action that allows multiple rule matches.
+      const action = makeDummyAction("modifyHeaders");
+
+      await dnr.updateSessionRules({
+        addRules: [
+          // Some patterns that match literally everything:
+          { id: 1, condition: { urlFilter: "." }, action },
+          { id: 2, condition: { urlFilter: "^" }, action },
+          { id: 3, condition: { urlFilter: "|" }, action },
+          // Patterns that match the test URLs
+          { id: 4, condition: { urlFilter: "https://example.com" }, action },
+          {
+            // urlFilter matches, requestDomains matches.
+            id: 5,
+            condition: { urlFilter: "*", requestDomains: ["example.com"] },
+            action,
+          },
+          {
+            // urlFilter matches, requestDomains does not match.
+            id: 6,
+            condition: { urlFilter: "*", requestDomains: ["notexample.com"] },
+            action,
+          },
+          {
+            // urlFilter does not match, requestDomains matches.
+            id: 7,
+            condition: { urlFilter: "notm", requestDomains: ["example.com"] },
+            action,
+          },
+        ],
+      });
+
+      await testMatchesRequest(
+        { url: "https://example.com/file.txt", type: "font" },
+        [1, 2, 3, 4, 5],
+        "urlFilter should match when needed, and correctly with requestDomains"
+      );
+
+      browser.test.notifyPass();
+    },
+  });
+});
+
+// Tests: regexFilter. For more comprehensive tests, see
+// toolkit/components/extensions/test/xpcshell/test_ext_dnr_regexFilter.js
+add_task(async function match_regexFilter() {
+  await runAsDNRExtension({
+    background: async dnrTestUtils => {
+      const dnr = browser.declarativeNetRequest;
+      const { makeDummyAction, testMatchesRequest } = dnrTestUtils;
+
+      // "modifyHeaders" is the only action that allows multiple rule matches.
+      const action = makeDummyAction("modifyHeaders");
+
+      await dnr.updateSessionRules({
+        addRules: [
+          // Some patterns that match literally everything:
+          { id: 1, condition: { regexFilter: ".*" }, action },
+          { id: 2, condition: { regexFilter: "^" }, action },
+          // Patterns that match the test URLs
+          { id: 3, condition: { regexFilter: "https://.xample\\." }, action },
+          { id: 4, condition: { regexFilter: "https://example.com" }, action },
+          {
+            // regexFilter matches, requestDomains matches.
+            id: 5,
+            condition: { regexFilter: "$", requestDomains: ["example.com"] },
+            action,
+          },
+          {
+            // regexFilter matches, requestDomains does not match.
+            id: 6,
+            condition: { regexFilter: "$", requestDomains: ["notexample.com"] },
+            action,
+          },
+          {
+            // regexFilter does not match, requestDomains matches.
+            id: 7,
+            condition: { regexFilter: "notm", requestDomains: ["example.com"] },
+            action,
+          },
+        ],
+      });
+
+      await testMatchesRequest(
+        { url: "https://example.com/file.txt", type: "font" },
+        [1, 2, 3, 4, 5],
+        "regexFilter should match when needed, and correctly with requestDomains"
+      );
+
+      browser.test.notifyPass();
+    },
+  });
+});
+
+// Tests: tabIds, excludedTabIds
+add_task(async function match_tabIds() {
+  await runAsDNRExtension({
+    background: async dnrTestUtils => {
+      const dnr = browser.declarativeNetRequest;
+      const { makeDummyAction, testMatchesRequest } = dnrTestUtils;
+
+      // "modifyHeaders" is the only action that allows multiple rule matches.
+      const action = makeDummyAction("modifyHeaders");
+
+      await dnr.updateSessionRules({
+        addRules: [
+          {
+            id: 1,
+            condition: {
+              excludedTabIds: [-1, Number.MAX_SAFE_INTEGER],
+            },
+            action,
+          },
+          {
+            id: 2,
+            condition: {
+              tabIds: [1, Number.MAX_SAFE_INTEGER],
+            },
+            action,
+          },
+          {
+            id: 3,
+            condition: {
+              tabIds: [-1],
+            },
+            action,
+          },
+        ],
+      });
+
+      const url = "https://example.com/some-dummy-url";
+      const type = "font";
+      await testMatchesRequest({ url, type }, [3], "tabId defaults to -1");
+      await testMatchesRequest({ url, type, tabId: -1 }, [3], "tabId -1");
+      await testMatchesRequest({ url, type, tabId: 1 }, [1, 2], "tabId 1");
+      await testMatchesRequest(
+        {
+          url,
+          type,
+          tabId: Number.MAX_SAFE_INTEGER,
+        },
+        [2],
+        `tabId high number (MAX_SAFE_INTEGER=${Number.MAX_SAFE_INTEGER})`
+      );
+
+      // tabId -2 is invalid and not encountered in practice, but technically
+      // it matches the first rule.
+      await testMatchesRequest({ url, type, tabId: -2 }, [1], "bad tabId -2");
+
+      browser.test.notifyPass();
+    },
+  });
+});
+
+add_task(async function action_precedence_between_extensions() {
+  // This test is structured as follows:
+  // - otherExtension registers rules for several numeric conditions (tabId).
+  // - otherExtensionNonBlockAndModifyHeaders adds allowAllRequests and
+  //   modifyHeaders to all requests.
+  // - otherExtensionModifyHeaders adds modifyHeaders rules to all requests.
+  // - the main test extension also registers rules, and then simulates requests
+  //   with testMatchOutcome for each tabId, and checks the result.
+
+  let otherExtension = await runAsDNRExtension({
+    manifest: { browser_specific_settings: { gecko: { id: "other@ext" } } },
+    background: async dnrTestUtils => {
+      const { makeDummyAction } = dnrTestUtils;
+
+      // Dummy condition for testing requests in this test.
+      const c = tabId => ({ resourceTypes: ["main_frame"], tabIds: [tabId] });
+
+      await browser.declarativeNetRequest.updateSessionRules({
+        addRules: [
+          { id: 11, condition: c(1), action: makeDummyAction("allow") },
+          { id: 12, condition: c(2), action: makeDummyAction("block") },
+          { id: 13, condition: c(3), action: makeDummyAction("redirect") },
+          { id: 14, condition: c(4), action: makeDummyAction("upgradeScheme") },
+          {
+            id: 15,
+            condition: c(5),
+            action: makeDummyAction("allowAllRequests"),
+          },
+          {
+            id: 16,
+            condition: c(6),
+            action: makeDummyAction("allowAllRequests"),
+          },
+        ],
+      });
+      // Notify to continue. We don't exit yet due to unloadTestAtEnd:false
+      browser.test.notifyPass();
+    },
+    unloadTestAtEnd: false,
+  });
+
+  let otherExtensionNonBlockAndModifyHeaders = await runAsDNRExtension({
+    manifest: { browser_specific_settings: { gecko: { id: "other@ext2" } } },
+    background: async dnrTestUtils => {
+      const { makeDummyAction } = dnrTestUtils;
+
+      // Matches all requests from this test.
+      const condition = { resourceTypes: ["main_frame"] };
+
+      await browser.declarativeNetRequest.updateSessionRules({
+        addRules: [
+          {
+            id: 1000,
+            condition,
+            action: makeDummyAction("modifyHeaders"),
+            // Same-or-lower priority "modifyHeaders" actions are ignored when
+            // an "allowAllRequests" action exists within the same extension.
+            // Since we have such a rule (ID 1001), this modifyHeaders rule must
+            // have "priority: 2" to avoid being ignored.
+            priority: 2,
+          },
+          { id: 1001, condition, action: makeDummyAction("allowAllRequests") },
+          {
+            id: 1002,
+            condition,
+            action: makeDummyAction("modifyHeaders"),
+            priority: 2, // necessary as explained above at rule ID 1000.
+          },
+          // should never appear because the first allowAllRequests rule should
+          // take precedence:
+          { id: 1003, condition, action: makeDummyAction("allowAllRequests") },
+        ],
+      });
+
+      // Notify to continue. We don't exit yet due to unloadTestAtEnd:false
+      browser.test.notifyPass();
+    },
+    unloadTestAtEnd: false,
+  });
+
+  // |otherExtensionModifyHeaders| and |otherExtensionNonBlockAndModifyHeaders|
+  // both have "modifyHeaders" rules. The documented order of rules is for
+  // the most recently installed extension to take precedence when applying
+  // modifyHeaders actions. The "priority" key is extension-specific, so even
+  // though |otherExtensionNonBlockAndModifyHeaders| defines "priority: 2" for
+  // modifyHeaders action (ID 1001), the modifyHeaders below (ID 1337) takes
+  // precedence because the extension was installed later.
+  let otherExtensionModifyHeaders = await runAsDNRExtension({
+    manifest: { browser_specific_settings: { gecko: { id: "other@ext3" } } },
+    background: async dnrTestUtils => {
+      const { makeDummyAction } = dnrTestUtils;
+      await browser.declarativeNetRequest.updateSessionRules({
+        addRules: [
+          {
+            id: 1337,
+            // Matches all requests from this test.
+            condition: { resourceTypes: ["main_frame"] },
+            action: makeDummyAction("modifyHeaders"),
+            // Note: no "priority" key set, so defaults to 1.
+          },
+        ],
+      });
+      // Notify to continue. We don't exit yet due to unloadTestAtEnd:false
+      browser.test.notifyPass();
+    },
+    unloadTestAtEnd: false,
+  });
+
+  await runAsDNRExtension({
+    background: async dnrTestUtils => {
+      const dnr = browser.declarativeNetRequest;
+      const { makeDummyAction } = dnrTestUtils;
+
+      // Dummy condition for testing requests in this test.
+      const c = tabId => ({ resourceTypes: ["main_frame"], tabIds: [tabId] });
+
+      await dnr.updateSessionRules({
+        addRules: [
+          { id: 91, condition: c(1), action: makeDummyAction("block") },
+          { id: 92, condition: c(2), action: makeDummyAction("allow") },
+          { id: 93, condition: c(3), action: makeDummyAction("block") },
+          { id: 94, condition: c(4), action: makeDummyAction("block") },
+          { id: 95, condition: c(5), action: makeDummyAction("allow") },
+          {
+            id: 96,
+            condition: c(6),
+            action: makeDummyAction("allowAllRequests"),
+          },
+        ],
+      });
+
+      const url = "https://example.com/dummy-url";
+      const type = "main_frame";
+      const options = { includeOtherExtensions: true };
+      browser.test.assertDeepEq(
+        [{ ruleId: 91, rulesetId: "_session" }],
+        (await dnr.testMatchOutcome({ url, type, tabId: 1 }, options))
+          .matchedRules,
+        "block takes precedence over allow (from other extension)"
+      );
+
+      browser.test.assertDeepEq(
+        [{ ruleId: 12, rulesetId: "_session", extensionId: "other@ext" }],
+        (await dnr.testMatchOutcome({ url, type, tabId: 2 }, options))
+          .matchedRules,
+        "block (from other extension) takes precedence over allow"
+      );
+      browser.test.assertDeepEq(
+        [{ ruleId: 93, rulesetId: "_session" }],
+        (await dnr.testMatchOutcome({ url, type, tabId: 3 }, options))
+          .matchedRules,
+        "block takes precedence over redirect (from other extension)"
+      );
+      browser.test.assertDeepEq(
+        [{ ruleId: 94, rulesetId: "_session" }],
+        (await dnr.testMatchOutcome({ url, type, tabId: 4 }, options))
+          .matchedRules,
+        "block takes precedence over upgradeScheme (from other extension)"
+      );
+      browser.test.assertDeepEq(
+        [
+          // allow:
+          { ruleId: 95, rulesetId: "_session" },
+          // allowAllRequests (newest install first):
+          { ruleId: 1001, rulesetId: "_session", extensionId: "other@ext2" },
+          { ruleId: 15, rulesetId: "_session", extensionId: "other@ext" },
+          // modifyHeaders (see comment at otherExtensionModifyHeaders):
+          { ruleId: 1337, rulesetId: "_session", extensionId: "other@ext3" },
+          { ruleId: 1000, rulesetId: "_session", extensionId: "other@ext2" },
+          { ruleId: 1002, rulesetId: "_session", extensionId: "other@ext2" },
+        ],
+        (await dnr.testMatchOutcome({ url, type, tabId: 5 }, options))
+          .matchedRules,
+        "When allow matches, allowAllRequests from other extension matches too"
+      );
+      browser.test.assertDeepEq(
+        [
+          // allowAllRequests (newest install first):
+          { ruleId: 96, rulesetId: "_session" },
+          { ruleId: 1001, rulesetId: "_session", extensionId: "other@ext2" },
+          { ruleId: 16, rulesetId: "_session", extensionId: "other@ext" },
+          // modifyHeaders (see comment at otherExtensionModifyHeaders):
+          { ruleId: 1337, rulesetId: "_session", extensionId: "other@ext3" },
+          { ruleId: 1000, rulesetId: "_session", extensionId: "other@ext2" },
+          { ruleId: 1002, rulesetId: "_session", extensionId: "other@ext2" },
+        ],
+        (await dnr.testMatchOutcome({ url, type, tabId: 6 }, options))
+          .matchedRules,
+        "allowAllRequests from all other extensions are matched"
+      );
+
+      browser.test.notifyPass();
+    },
+  });
+
+  await otherExtension.unload();
+  await otherExtensionNonBlockAndModifyHeaders.unload();
+  await otherExtensionModifyHeaders.unload();
+});
diff --git a/toolkit/components/extensions/test/xpcshell/test_ext_dnr_urlFilter.js b/toolkit/components/extensions/test/xpcshell/test_ext_dnr_urlFilter.js
new file mode 100644
index 0000000000..dd12184cbe
--- /dev/null
+++ b/toolkit/components/extensions/test/xpcshell/test_ext_dnr_urlFilter.js
@@ -0,0 +1,1159 @@
+"use strict";
+
+add_setup(() => {
+  Services.prefs.setBoolPref("extensions.manifestV3.enabled", true);
+  Services.prefs.setBoolPref("extensions.dnr.enabled", true);
+  Services.prefs.setBoolPref("extensions.dnr.feedback", true);
+});
+
+// This function is serialized and called in the context of the test extension's
+// background page. dnrTestUtils is passed to the background function.
+function makeDnrTestUtils() {
+  const dnrTestUtils = {};
+  const dnr = browser.declarativeNetRequest;
+
+  const DUMMY_ACTION = {
+    // "modifyHeaders" is the only action that allows multiple rule matches.
+    type: "modifyHeaders",
+    responseHeaders: [{ operation: "append", header: "x", value: "y" }],
+  };
+  async function testMatchesRequest(request, ruleIds, description) {
+    browser.test.assertDeepEq(
+      ruleIds,
+      (await dnr.testMatchOutcome(request)).matchedRules.map(mr => mr.ruleId),
+      description
+    );
+  }
+  async function testMatchesUrlFilter({
+    urlFilter,
+    isUrlFilterCaseSensitive,
+    urls = [],
+    urlsNonMatching = [],
+  }) {
+    // Sanity check: verify that there are no unexpected escaped characters,
+    // because that can surprise.
+    function sanityCheckUrl(url) {
+      const normalizedUrl = new URL(url).href;
+      if (normalizedUrl.split("%").length !== url.split("*").length) {
+        // ^ we only check for %-escapes and not exact URL equality because the
+        // tests imported from Chrome often omit the "/" (path separator).
+        browser.test.assertEq(normalizedUrl, url, "url should be canonical");
+      }
+    }
+
+    await dnr.updateSessionRules({
+      addRules: [
+        {
+          id: 12345,
+          condition: { urlFilter, isUrlFilterCaseSensitive },
+          action: DUMMY_ACTION,
+        },
+      ],
+    });
+    for (let url of urls) {
+      sanityCheckUrl(url);
+      const request = { url, type: "other" };
+      const description = `urlFilter ${urlFilter} should match: ${url}`;
+      await testMatchesRequest(request, [12345], description);
+    }
+    for (let url of urlsNonMatching) {
+      sanityCheckUrl(url);
+      const request = { url, type: "other" };
+      const description = `urlFilter ${urlFilter} should not match: ${url}`;
+      await testMatchesRequest(request, [], description);
+    }
+    await dnr.updateSessionRules({ removeRuleIds: [12345] });
+  }
+  Object.assign(dnrTestUtils, {
+    DUMMY_ACTION,
+    testMatchesRequest,
+    testMatchesUrlFilter,
+  });
+  return dnrTestUtils;
+}
+
+async function runAsDNRExtension({ background, manifest }) {
+  let extension = ExtensionTestUtils.loadExtension({
+    background: `(${background})((${makeDnrTestUtils})())`,
+    manifest: {
+      manifest_version: 3,
+      permissions: ["declarativeNetRequest", "declarativeNetRequestFeedback"],
+      // While testing urlFilter itself does not require any host permissions,
+      // we are asking for host permissions anyway because the "modifyHeaders"
+      // action requires host permissions, and we use the "modifyHeaders" action
+      // to ensure that we can detect when multiple rules match.
+      host_permissions: ["<all_urls>"],
+      granted_host_permissions: true,
+      ...manifest,
+    },
+    temporarilyInstalled: true, // <-- for granted_host_permissions
+  });
+  await extension.startup();
+  await extension.awaitFinish();
+  await extension.unload();
+}
+
+// This test checks various urlFilters with a possibly ambiguous interpretation.
+// In some cases the semantic difference in interpretation can have different
+// outcomes; in these cases we have chosen the behavior as observed in Chrome.
+add_task(async function ambiguous_urlFilter_patterns() {
+  await runAsDNRExtension({
+    background: async dnrTestUtils => {
+      const { testMatchesUrlFilter } = dnrTestUtils;
+
+      // Left anchor, empty pattern: always matches
+      // Ambiguous with Right anchor, but same result.
+      await testMatchesUrlFilter({
+        urlFilter: "|",
+        urls: ["http://a/"],
+        urlsNonMatching: [],
+      });
+
+      // Domain anchor, empty pattern: always matches.
+      // Ambiguous with Left anchor + Right anchor, the latter would not match
+      // anything (only an empty string, but URLs cannot be empty).
+      await testMatchesUrlFilter({
+        urlFilter: "||",
+        urls: ["http://a/"],
+        urlsNonMatching: [],
+      });
+
+      // Domain anchor plus Right separator: never matches.
+      // Ambiguous with Left anchor + | + Right anchor, that is no match either.
+      await testMatchesUrlFilter({
+        urlFilter: "|||",
+        urls: [],
+        urlsNonMatching: ["http://a./|||"],
+      });
+
+      // Repeated separator: ^^^^ matches separator chars (=everything except
+      // alphanumeric, "_", "-", ".", "%"), but when at the end of a string,
+      // the last "^" can also be interpreted as a right anchor (like ^^^|).
+      // Ambiguous: while "^" is defined to match the end of URL, it could also
+      // be interpreted as "^^^^" matching the end of URL 4x, i.e. always.
+      await testMatchesUrlFilter({
+        urlFilter: "^^^^",
+        urls: [
+          // Note: "^" is escaped "%5E" when part of the URL, except after "#".
+          "http://a/#frag^^^^", // four ^ characters ("^^^^").
+          "http://a/#frag^^^", // three ^ characters ("^^^") + end of URL.
+          "http://a/?&#", // four separator characters ("/?&#");
+          "http://a/#^", // three separator characters ("/??") + end of URL.
+          // ^ Note that "^" is after "#" and therefore not %5E. If "^" were to
+          // somehow be %-encoded to "%5E", then the end would become "/#%5E"
+          // and the "/#%" would only be 3 separators followed by alphanum. The
+          // test matching shows that the canonical representation of "^" after
+          // a "#" is "^" and can be matched.
+        ],
+        urlsNonMatching: [
+          "http://a/?", // Just two separator + end of URL, not matching 4x "^".
+          "http://a/____", // _ is specified to not match ^.
+          "http://a/----", // - is specified to not match ^.
+          "http://a/....", // . is specified to not match ^.
+        ],
+      });
+      // Not ambiguous, but for comparison with "^^^^": all http(s) match.
+      await testMatchesUrlFilter({
+        urlFilter: "^^^",
+        urls: ["https://a/"], // "://" always matches "^^^".
+        // Not seen by DNR in practice, but could be passed to testMatchOutcome:
+        urlsNonMatching: ["file:hello/no/three/consecutive/special/characters"],
+      });
+
+      // Separator plus Right anchor: always matches.
+      // Ambiguous: "^" is defined to match the end of URL once, but a right
+      // domain anchor already matches that. A potential interpretation is for
+      // "^" to be required to match a non-alphanumeric (etc.), but in practice
+      // "^" is allowed to match the end of the URL. Effectively "^|" = "|".
+      await testMatchesUrlFilter({
+        urlFilter: "^|",
+        urls: [
+          "http://a/", // "/" matches "^".
+          "http://a/a", // "a" does not match "^", but "^" matches the end.
+        ],
+        urlsNonMatching: [],
+      });
+
+      // Domain anchor plus separator: "^" only matches non-alphanum (etc.)
+      // Ambiguous: "||" is defined to match a domain anchor. There is no
+      // domain part after the trailing "." of a FQDN. Still, "." matches.
+      await testMatchesUrlFilter({
+        urlFilter: "||^",
+        urls: ["http://a./"], // FQDN: "/" after "." matches "^".
+        urlsNonMatching: ["http://a/", "http://a/||"],
+      });
+
+      browser.test.notifyPass();
+    },
+  });
+});
+
+add_task(async function urlFilter_domain_anchor() {
+  await runAsDNRExtension({
+    background: async dnrTestUtils => {
+      const { testMatchesUrlFilter } = dnrTestUtils;
+
+      await testMatchesUrlFilter({
+        // Not a domain anchor, but for comparison with "||ps" below:
+        urlFilter: "ps",
+        urls: [
+          "https://example.com/", // ps in scheme.
+          "http://ps.example.com/", // ps at start of domain.
+          "http://sub.ps.example.com/", // ps at superdomain.
+          "http://ps/", // ps as sole host.
+          "http://example-ps.com/", // ps in middle of domain.
+          "http://ps@example.com/", // ps as user without password.
+          "http://user:ps@example.com/", // ps in password.
+          "http://ps:pass@example.com/", // ps in user.
+          "http://example.com/ps", // ps at end.
+          "http://example.com/#ps", // ps in fragment.
+        ],
+        urlsNonMatching: [
+          "http://example.com/", // no ps anywhere.
+        ],
+      });
+
+      await testMatchesUrlFilter({
+        urlFilter: "||ps",
+        urls: [
+          "http://ps.example.com/", // ps at start of domain.
+          "http://sub.ps.example.com/", // ps at superdomain.
+          "http://ps/", // ps as sole host.
+        ],
+        urlsNonMatching: [
+          "http://example.com/", // no ps anywhere.
+          "https://example.com/", // ps in scheme.
+          "http://example-ps.com/", // ps in middle
+          "http://ps@example.com/", // ps as user without password.
+          "http://user:ps@example.com/", // ps in password.
+          "http://ps:pass@example.com/", // ps in user.
+          "http://example.com/ps", // ps at end.
+        ],
+      });
+
+      await testMatchesUrlFilter({
+        urlFilter: "||1",
+        urls: [
+          "http://127.0.0.1/",
+          "http://2.0.0.1/",
+          "http://www.1example.com/",
+        ],
+        urlsNonMatching: [
+          "http://[::1]/",
+          "http://[1::1]/",
+          "http://hostwithport:1/",
+          "http://host/1",
+          "http://fqdn.:1/",
+          "http://fqdn./1",
+        ],
+      });
+
+      await testMatchesUrlFilter({
+        urlFilter: "||^1",
+        urls: [
+          "http://[1::1]/", // "[1" at start matches "^1".
+          "http://fqdn.:1/", // ":1" matches "^1" and is after a ".".
+          "http://fqdn./1", // "/1" matches "^1" and is after a ".".
+        ],
+        urlsNonMatching: [
+          "http://127.0.0.1/",
+          "http://2.0.0.1/",
+          "http://www.1example.com/",
+          "http://[::1]/",
+          "http://hostwithport:1/",
+          "http://host/1",
+        ],
+      });
+
+      browser.test.notifyPass();
+    },
+  });
+});
+
+// Extreme patterns that should not be used in practice, but are not explicitly
+// documented to be disallowed.
+add_task(
+  // Stuck in ccov: https://bugzilla.mozilla.org/show_bug.cgi?id=1806494#c4
+  { skip_if: () => mozinfo.ccov },
+  async function extreme_urlFilter_patterns() {
+    await runAsDNRExtension({
+      background: async dnrTestUtils => {
+        const { testMatchesRequest, DUMMY_ACTION } = dnrTestUtils;
+
+        await browser.declarativeNetRequest.updateSessionRules({
+          addRules: [
+            {
+              id: 1,
+              condition: {
+                urlFilter: "*".repeat(1e6),
+              },
+              action: DUMMY_ACTION,
+            },
+            {
+              id: 2,
+              condition: {
+                urlFilter: "^".repeat(1e6),
+              },
+              action: DUMMY_ACTION,
+            },
+            {
+              id: 3,
+              condition: {
+                // Note: 2 chars repeat 5e5 instead of 1e6 because newURI limits
+                // the length of the URL (to network.standard-url.max-length),
+                // so we would not be able to verify whether the URL is really
+                // that long.
+                urlFilter: "*^".repeat(5e5),
+              },
+              action: DUMMY_ACTION,
+            },
+            {
+              id: 4,
+              condition: {
+                // Note: well beyond the maximum length of a URL. But as "*" can
+                // match any char (including zero length), this still matches.
+                urlFilter: "h" + "*".repeat(1e7) + "endofurl",
+              },
+              action: DUMMY_ACTION,
+            },
+          ],
+        });
+
+        await testMatchesRequest(
+          { url: "http://example.com/", type: "other" },
+          [1],
+          "urlFilter with 1M wildcard chars matches any URL"
+        );
+
+        await testMatchesRequest(
+          { url: "http://example.com/" + "x".repeat(1e6), type: "other" },
+          [1],
+          "urlFilter with 1M wildcards matches, other '^' do not match alpha"
+        );
+
+        await testMatchesRequest(
+          { url: "http://example.com/" + "/".repeat(1e6), type: "other" },
+          [1, 2, 3],
+          "urlFilter with 1M wildcards, ^ and *^ all match URL with 1M '/' chars"
+        );
+
+        await testMatchesRequest(
+          { url: "http://example.com/" + "x/".repeat(5e5), type: "other" },
+          [1, 3],
+          "urlFilter with 1M wildcards and *^ match URL with 1M 'x/' chars"
+        );
+
+        await testMatchesRequest(
+          { url: "http://example.com/endofurl", type: "other" },
+          [1, 4],
+          "urlFilter with 1M and 10M wildcards matches URL"
+        );
+
+        browser.test.notifyPass();
+      },
+    });
+  }
+);
+
+add_task(async function test_isUrlFilterCaseSensitive() {
+  await runAsDNRExtension({
+    background: async dnrTestUtils => {
+      const { testMatchesUrlFilter } = dnrTestUtils;
+
+      await testMatchesUrlFilter({
+        urlFilter: "AbC",
+        isUrlFilterCaseSensitive: true,
+        urls: [
+          "http://true.example.com/AbC", // Exact match.
+        ],
+        urlsNonMatching: [
+          "http://true.example.com/abc", // All lower.
+          "http://true.example.com/ABC", // All upper.
+          "http://true.example.com/???", // ABC not present at all.
+          "http://true.AbC/", // When canonicalized, the host is lower case.
+        ],
+      });
+      await testMatchesUrlFilter({
+        urlFilter: "AbC",
+        isUrlFilterCaseSensitive: false,
+        urls: [
+          "http://false.example.com/AbC", // Exact match.
+          "http://false.example.com/abc", // All lower.
+          "http://false.example.com/ABC", // All upper.
+          "http://false.AbC/", // When canonicalized, the host is lower case.
+        ],
+        urlsNonMatching: [
+          "http://false.example.com/???", // ABC not present at all.
+        ],
+      });
+
+      // Chrome's initial DNR API specified isUrlFilterCaseSensitive to be true
+      // by default. Later, it became false by default.
+      // https://github.com/w3c/webextensions/issues/269
+      await testMatchesUrlFilter({
+        urlFilter: "AbC",
+        // isUrlFilterCaseSensitive: false, // is implied by default.
+        urls: [
+          "http://default.example.com/AbC", // Exact match.
+          "http://default.example.com/abc", // All lower.
+          "http://default.example.com/ABC", // All upper.
+          "http://default.AbC/", // When canonicalized, the host is lower case.
+        ],
+        urlsNonMatching: [
+          "http://default.example.com/???", // ABC not present at all.
+        ],
+      });
+
+      browser.test.notifyPass();
+    },
+  });
+});
+
+// Imported tests from Chromium from:
+// https://chromium.googlesource.com/chromium/src.git/+/refs/tags/110.0.5442.0/components/url_pattern_index/url_pattern_unittest.cc
+// kAnchorNone -> "" (anywhere in the string)
+// kBoundary -> | (start or end of string)
+// kSubdomain -> || (start of (sub)domain)
+// kMatchCase -> isUrlFilterCaseSensitive: true
+// kDonotMatchCase -> isUrlFilterCaseSensitive: false (this is the default).
+// proto::URL_PATTERN_TYPE_WILDCARDED / proto::URL_PATTERN_TYPE_SUBSTRING -> ""
+//
+// Minus two tests ("", kBoundary, kBoundary) because the resulting pattern is
+// "||" and ambiguous with ("", kSubdomain, "").
+add_task(async function test_chrome_parity() {
+  await runAsDNRExtension({
+    background: async dnrTestUtils => {
+      const { testMatchesUrlFilter } = dnrTestUtils;
+      const testCases = [
+        // {"", proto::URL_PATTERN_TYPE_SUBSTRING}
+        {
+          urlFilter: "*",
+          url: "http://ex.com/",
+          expectMatch: true,
+        },
+        // // {"", proto::URL_PATTERN_TYPE_WILDCARDED}
+        // { // Already tested before.
+        //   urlFilter: "*",
+        //   url: "http://ex.com/",
+        //   expectMatch: true,
+        // },
+        // {"", kBoundary, kAnchorNone}
+        {
+          urlFilter: "|",
+          url: "http://ex.com/",
+          expectMatch: true,
+        },
+        // {"", kSubdomain, kAnchorNone}
+        {
+          urlFilter: "||",
+          url: "http://ex.com/",
+          expectMatch: true,
+        },
+        // // {"", kSubdomain, kAnchorNone}
+        // { // Already tested before.
+        //   urlFilter: "||",
+        //   url: "http://ex.com/",
+        //   expectMatch: true,
+        // },
+        // {"^", kSubdomain, kAnchorNone}
+        {
+          urlFilter: "||^",
+          url: "http://ex.com/",
+          expectMatch: false,
+        },
+        // {".", kSubdomain, kAnchorNone}
+        {
+          urlFilter: "||.",
+          url: "http://ex.com/",
+          expectMatch: false,
+        },
+        // // {"", kAnchorNone, kBoundary}
+        // { // Already tested before.
+        //   urlFilter: "|",
+        //   url: "http://ex.com/",
+        //   expectMatch: true,
+        // },
+        // {"^", kAnchorNone, kBoundary}
+        {
+          urlFilter: "^|",
+          url: "http://ex.com/",
+          expectMatch: true,
+        },
+        // {".", kAnchorNone, kBoundary}
+        {
+          urlFilter: ".|",
+          url: "http://ex.com/",
+          expectMatch: false,
+        },
+        // // {"", kBoundary, kBoundary}
+        // { // "||" is ambiguous, cannot mean Left anchor + Right anchor
+        //   urlFilter: "||",
+        //   url: "http://ex.com/",
+        //   expectMatch: false,
+        // },
+        // {"", kSubdomain, kBoundary}
+        {
+          urlFilter: "|||",
+          url: "http://ex.com/",
+          expectMatch: false,
+        },
+        // {"com/", kSubdomain, kBoundary}
+        {
+          urlFilter: "||com/|",
+          url: "http://ex.com/",
+          expectMatch: true,
+        },
+        // {"xampl", proto::URL_PATTERN_TYPE_SUBSTRING}
+        {
+          urlFilter: "xampl",
+          url: "http://example.com",
+          expectMatch: true,
+        },
+        // {"example", proto::URL_PATTERN_TYPE_SUBSTRING}
+        {
+          urlFilter: "example",
+          url: "http://example.com",
+          expectMatch: true,
+        },
+        // {"/a?a"}
+        {
+          urlFilter: "/a?a",
+          url: "http://ex.com/a?a",
+          expectMatch: true,
+        },
+        // {"^abc"}
+        {
+          urlFilter: "^abc",
+          url: "http://ex.com/abc?a",
+          expectMatch: true,
+        },
+        // {"^abc"}
+        {
+          urlFilter: "^abc",
+          url: "http://ex.com/a?abc",
+          expectMatch: true,
+        },
+        // {"^abc"}
+        {
+          urlFilter: "^abc",
+          url: "http://ex.com/abc?abc",
+          expectMatch: true,
+        },
+        // {"^abc^abc"}
+        {
+          urlFilter: "^abc^abc",
+          url: "http://ex.com/abc?abc",
+          expectMatch: true,
+        },
+        // {"^com^abc^abc"}
+        {
+          urlFilter: "^com^abc^abc",
+          url: "http://ex.com/abc?abc",
+          expectMatch: false,
+        },
+        // {"http://ex", kBoundary, kAnchorNone}
+        {
+          urlFilter: "|http://ex",
+          url: "http://example.com",
+          expectMatch: true,
+        },
+        // {"http://ex", kAnchorNone, kAnchorNone}
+        {
+          urlFilter: "http://ex",
+          url: "http://example.com",
+          expectMatch: true,
+        },
+        // {"mple.com/", kAnchorNone, kBoundary}
+        {
+          urlFilter: "mple.com/|",
+          url: "http://example.com",
+          expectMatch: true,
+        },
+        // {"mple.com/", kAnchorNone, kAnchorNone}
+        {
+          urlFilter: "mple.com/",
+          url: "http://example.com",
+          expectMatch: true,
+        },
+        // {"mple.com/", kSubdomain, kAnchorNone}
+        {
+          urlFilter: "||mple.com/",
+          url: "http://example.com",
+          expectMatch: false,
+        },
+        // {"ex.com", kSubdomain, kAnchorNone}
+        {
+          urlFilter: "||ex.com",
+          url: "http://hex.com",
+          expectMatch: false,
+        },
+        // {"ex.com", kSubdomain, kAnchorNone}
+        {
+          urlFilter: "||ex.com",
+          url: "http://ex.com",
+          expectMatch: true,
+        },
+        // {"ex.com", kSubdomain, kAnchorNone}
+        {
+          urlFilter: "||ex.com",
+          url: "http://hex.ex.com",
+          expectMatch: true,
+        },
+        // {"ex.com", kSubdomain, kAnchorNone}
+        {
+          urlFilter: "||ex.com",
+          url: "http://hex.hex.com",
+          expectMatch: false,
+        },
+        // {"example.com^", kSubdomain, kAnchorNone}
+        {
+          urlFilter: "||example.com^",
+          url: "http://www.example.com",
+          expectMatch: true,
+        },
+        // {"http://*mpl", kBoundary, kAnchorNone}
+        {
+          urlFilter: "|http://*mpl",
+          url: "http://example.com",
+          expectMatch: true,
+        },
+        // {"mpl*com/", kAnchorNone, kBoundary}
+        {
+          urlFilter: "mpl*com/|",
+          url: "http://example.com",
+          expectMatch: true,
+        },
+        // {"example^com"}
+        {
+          urlFilter: "example^com",
+          url: "http://example.com",
+          expectMatch: false,
+        },
+        // {"example^com"}
+        {
+          urlFilter: "example^com",
+          url: "http://example/com",
+          expectMatch: true,
+        },
+        // {"example.com^"}
+        {
+          urlFilter: "example.com^",
+          url: "http://example.com:8080",
+          expectMatch: true,
+        },
+        // {"http*.com/", kBoundary, kBoundary}
+        {
+          urlFilter: "|http*.com/|",
+          url: "http://example.com",
+          expectMatch: true,
+        },
+        // {"http*.org/", kBoundary, kBoundary}
+        {
+          urlFilter: "|http*.org/|",
+          url: "http://example.com",
+          expectMatch: false,
+        },
+        // {"/path?*&p1=*&p2="}
+        {
+          urlFilter: "/path?*&p1=*&p2=",
+          url: "http://ex.com/aaa/path/bbb?k=v&p1=0&p2=1",
+          expectMatch: false,
+        },
+        // {"/path?*&p1=*&p2="}
+        {
+          urlFilter: "/path?*&p1=*&p2=",
+          url: "http://ex.com/aaa/path?k=v&p1=0&p2=1",
+          expectMatch: true,
+        },
+        // {"/path?*&p1=*&p2="}
+        {
+          urlFilter: "/path?*&p1=*&p2=",
+          url: "http://ex.com/aaa/path?k=v&k=v&p1=0&p2=1",
+          expectMatch: true,
+        },
+        // {"/path?*&p1=*&p2="}
+        {
+          urlFilter: "/path?*&p1=*&p2=",
+          url: "http://ex.com/aaa/path?k=v&p1=0&p3=10&p2=1",
+          expectMatch: true,
+        },
+        // {"/path?*&p1=*&p2="}
+        {
+          urlFilter: "/path?*&p1=*&p2=",
+          url: "http://ex.com/aaa/path&p1=0&p2=1",
+          expectMatch: false,
+        },
+        // {"/path?*&p1=*&p2="}
+        {
+          urlFilter: "/path?*&p1=*&p2=",
+          url: "http://ex.com/aaa/path?k=v&p2=0&p1=1",
+          expectMatch: false,
+        },
+        // {"abc*def*ghijk*xyz"}
+        {
+          urlFilter: "abc*def*ghijk*xyz",
+          url: "http://example.com/abcdeffffghijkmmmxyzzz",
+          expectMatch: true,
+        },
+        // {"abc*cdef"}
+        {
+          urlFilter: "abc*cdef",
+          url: "http://example.com/abcdef",
+          expectMatch: false,
+        },
+        // {"^^a^^"}
+        {
+          urlFilter: "^^a^^",
+          url: "http://ex.com/?a=/",
+          expectMatch: true,
+        },
+        // {"^^a^^"}
+        {
+          urlFilter: "^^a^^",
+          url: "http://ex.com/?a=/&b=0",
+          expectMatch: true,
+        },
+        // {"^^a^^"}
+        {
+          urlFilter: "^^a^^",
+          url: "http://ex.com/?a=x",
+          expectMatch: false,
+        },
+        // {"^^a^^"}
+        {
+          urlFilter: "^^a^^",
+          url: "http://ex.com/?a=",
+          expectMatch: true,
+        },
+        // {"ex.com^path^*k=v^"}
+        {
+          urlFilter: "ex.com^path^*k=v^",
+          url: "http://ex.com/path/?k1=v1&ak=v&kk=vv",
+          expectMatch: true,
+        },
+        // {"ex.com^path^*k=v^"}
+        {
+          urlFilter: "ex.com^path^*k=v^",
+          url: "http://ex.com/p/path/?k1=v1&ak=v&kk=vv",
+          expectMatch: false,
+        },
+        // {"a^a&a^a&"}
+        {
+          urlFilter: "a^a&a^a&",
+          url: "http://ex.com/a/a/a/a/?a&a&a&a&a",
+          expectMatch: true,
+        },
+        // {"abc*def^"}
+        {
+          urlFilter: "abc*def^",
+          url: "http://ex.com/abc/a/ddef/",
+          expectMatch: true,
+        },
+        // {"https://example.com/"}
+        {
+          urlFilter: "https://example.com/",
+          url: "http://example.com/",
+          expectMatch: false,
+        },
+        // {"example.com/", kSubdomain, kAnchorNone}
+        {
+          urlFilter: "||example.com/",
+          url: "http://example.com/",
+          expectMatch: true,
+        },
+        // {"examp", kSubdomain, kAnchorNone}
+        {
+          urlFilter: "||examp",
+          url: "http://example.com/",
+          expectMatch: true,
+        },
+        // {"xamp", kSubdomain, kAnchorNone}
+        {
+          urlFilter: "||xamp",
+          url: "http://example.com/",
+          expectMatch: false,
+        },
+        // {"examp", kSubdomain, kAnchorNone}
+        {
+          urlFilter: "||examp",
+          url: "http://test.example.com/",
+          expectMatch: true,
+        },
+        // {"t.examp", kSubdomain, kAnchorNone}
+        {
+          urlFilter: "||t.examp",
+          url: "http://test.example.com/",
+          expectMatch: false,
+        },
+        // {"com^", kSubdomain, kAnchorNone}
+        {
+          urlFilter: "||com^",
+          url: "http://test.example.com/",
+          expectMatch: true,
+        },
+        // {"com^x", kSubdomain, kBoundary}
+        {
+          urlFilter: "||com^x|",
+          url: "http://a.com/x",
+          expectMatch: true,
+        },
+        // {"x.com", kSubdomain, kAnchorNone}
+        {
+          urlFilter: "||x.com",
+          url: "http://ex.com/?url=x.com",
+          expectMatch: false,
+        },
+        // {"ex.com/", kSubdomain, kBoundary}
+        {
+          urlFilter: "||ex.com/|",
+          url: "http://ex.com/",
+          expectMatch: true,
+        },
+        // {"ex.com^", kSubdomain, kBoundary}
+        {
+          urlFilter: "||ex.com^|",
+          url: "http://ex.com/",
+          expectMatch: true,
+        },
+        // {"ex.co", kSubdomain, kBoundary}
+        {
+          urlFilter: "||ex.co|",
+          url: "http://ex.com/",
+          expectMatch: false,
+        },
+        // {"ex.com", kSubdomain, kBoundary}
+        {
+          urlFilter: "||ex.com|",
+          url: "http://rex.com.ex.com/",
+          expectMatch: false,
+        },
+        // {"ex.com/", kSubdomain, kBoundary}
+        {
+          urlFilter: "||ex.com/|",
+          url: "http://rex.com.ex.com/",
+          expectMatch: true,
+        },
+        // {"http", kSubdomain, kBoundary}
+        {
+          urlFilter: "||http|",
+          url: "http://http.com/",
+          expectMatch: false,
+        },
+        // {"http", kSubdomain, kAnchorNone}
+        {
+          urlFilter: "||http",
+          url: "http://http.com/",
+          expectMatch: true,
+        },
+        // {"/example.com", kSubdomain, kBoundary}
+        {
+          urlFilter: "||/example.com|",
+          url: "http://example.com/",
+          expectMatch: false,
+        },
+        // {"/example.com/", kSubdomain, kBoundary}
+        {
+          urlFilter: "||/example.com/|",
+          url: "http://example.com/",
+          expectMatch: false,
+        },
+        // {".", kSubdomain, kAnchorNone}
+        {
+          urlFilter: "||.",
+          url: "http://a..com/",
+          expectMatch: true,
+        },
+        // {"^", kSubdomain, kAnchorNone}
+        {
+          urlFilter: "||^",
+          url: "http://a..com/",
+          expectMatch: false,
+        },
+        // {".", kSubdomain, kAnchorNone}
+        {
+          urlFilter: "||.",
+          url: "http://a.com./",
+          expectMatch: false,
+        },
+        // {"^", kSubdomain, kAnchorNone}
+        {
+          urlFilter: "||^",
+          url: "http://a.com./",
+          expectMatch: true,
+        },
+        // {".", kSubdomain, kAnchorNone}
+        {
+          urlFilter: "||.",
+          url: "http://a.com../",
+          expectMatch: true,
+        },
+        // {"^", kSubdomain, kAnchorNone}
+        {
+          urlFilter: "||^",
+          url: "http://a.com../",
+          expectMatch: true,
+        },
+        // {"/path", kSubdomain, kAnchorNone}
+        {
+          urlFilter: "||/path",
+          url: "http://a.com./path/to/x",
+          expectMatch: true,
+        },
+        // {"^path", kSubdomain, kAnchorNone}
+        {
+          urlFilter: "||^path",
+          url: "http://a.com./path/to/x",
+          expectMatch: true,
+        },
+        // {"/path", kSubdomain, kBoundary}
+        {
+          urlFilter: "||/path|",
+          url: "http://a.com./path",
+          expectMatch: true,
+        },
+        // {"^path", kSubdomain, kBoundary}
+        {
+          urlFilter: "||^path|",
+          url: "http://a.com./path",
+          expectMatch: true,
+        },
+        // {"path", kSubdomain, kBoundary}
+        {
+          urlFilter: "||path|",
+          url: "http://a.com./path",
+          expectMatch: false,
+        },
+        // {"path", proto::URL_PATTERN_TYPE_SUBSTRING, kDonotMatchCase}
+        {
+          urlFilter: "path",
+          url: "http://a.com/PaTh",
+          isUrlFilterCaseSensitive: false,
+          expectMatch: true,
+        },
+        // {"path", proto::URL_PATTERN_TYPE_SUBSTRING, kMatchCase}
+        {
+          urlFilter: "path",
+          url: "http://a.com/PaTh",
+          isUrlFilterCaseSensitive: true,
+          expectMatch: false,
+        },
+        // {"path", proto::URL_PATTERN_TYPE_SUBSTRING, kDonotMatchCase}
+        {
+          urlFilter: "path",
+          url: "http://a.com/path",
+          isUrlFilterCaseSensitive: false,
+          expectMatch: true,
+        },
+        // {"path", proto::URL_PATTERN_TYPE_SUBSTRING, kMatchCase}
+        {
+          urlFilter: "path",
+          url: "http://a.com/path",
+          isUrlFilterCaseSensitive: true,
+          expectMatch: true,
+        },
+        // {"abc*def^", proto::URL_PATTERN_TYPE_WILDCARDED, kMatchCase}
+        {
+          urlFilter: "abc*def^",
+          url: "http://a.com/abcxAdef/vo",
+          isUrlFilterCaseSensitive: true,
+          expectMatch: true,
+        },
+        // {"abc*def^", proto::URL_PATTERN_TYPE_WILDCARDED, kMatchCase}
+        {
+          urlFilter: "abc*def^",
+          url: "http://a.com/aBcxAdeF/vo",
+          isUrlFilterCaseSensitive: true,
+          expectMatch: false,
+        },
+        // {"abc*def^", proto::URL_PATTERN_TYPE_WILDCARDED, kDonotMatchCase}
+        {
+          urlFilter: "abc*def^",
+          url: "http://a.com/aBcxAdeF/vo",
+          isUrlFilterCaseSensitive: false,
+          expectMatch: true,
+        },
+        // {"abc*def^", proto::URL_PATTERN_TYPE_WILDCARDED, kDonotMatchCase}
+        {
+          urlFilter: "abc*def^",
+          url: "http://a.com/abcxAdef/vo",
+          isUrlFilterCaseSensitive: false,
+          expectMatch: true,
+        },
+        // {"abc^", kAnchorNone, kAnchorNone}
+        {
+          urlFilter: "abc^",
+          url: "https://xyz.com/abc/123",
+          expectMatch: true,
+        },
+        // {"abc^", kAnchorNone, kAnchorNone}
+        {
+          urlFilter: "abc^",
+          url: "https://xyz.com/abc",
+          expectMatch: true,
+        },
+        // {"abc^", kAnchorNone, kAnchorNone}
+        {
+          urlFilter: "abc^",
+          url: "https://abc.com",
+          expectMatch: false,
+        },
+        // {"abc^", kAnchorNone, kBoundary}
+        {
+          urlFilter: "abc^|",
+          url: "https://xyz.com/abc/",
+          expectMatch: true,
+        },
+        // {"abc^", kAnchorNone, kBoundary}
+        {
+          urlFilter: "abc^|",
+          url: "https://xyz.com/abc",
+          expectMatch: true,
+        },
+        // {"abc^", kAnchorNone, kBoundary}
+        {
+          urlFilter: "abc^|",
+          url: "https://xyz.com/abc/123",
+          expectMatch: false,
+        },
+        // {"http://abc.com/x^", kBoundary, kAnchorNone}
+        {
+          urlFilter: "|http://abc.com/x^",
+          url: "http://abc.com/x",
+          expectMatch: true,
+        },
+        // {"http://abc.com/x^", kBoundary, kAnchorNone}
+        {
+          urlFilter: "|http://abc.com/x^",
+          url: "http://abc.com/x/",
+          expectMatch: true,
+        },
+        // {"http://abc.com/x^", kBoundary, kAnchorNone}
+        {
+          urlFilter: "|http://abc.com/x^",
+          url: "http://abc.com/x/123",
+          expectMatch: true,
+        },
+        // {"http://abc.com/x^", kBoundary, kBoundary}
+        {
+          urlFilter: "|http://abc.com/x^|",
+          url: "http://abc.com/x",
+          expectMatch: true,
+        },
+        // {"http://abc.com/x^", kBoundary, kBoundary}
+        {
+          urlFilter: "|http://abc.com/x^|",
+          url: "http://abc.com/x/",
+          expectMatch: true,
+        },
+        // {"http://abc.com/x^", kBoundary, kBoundary}
+        {
+          urlFilter: "|http://abc.com/x^|",
+          url: "http://abc.com/x/123",
+          expectMatch: false,
+        },
+        // {"abc.com^", kSubdomain, kAnchorNone}
+        {
+          urlFilter: "||abc.com^",
+          url: "http://xyz.abc.com/123",
+          expectMatch: true,
+        },
+        // {"abc.com^", kSubdomain, kAnchorNone}
+        {
+          urlFilter: "||abc.com^",
+          url: "http://xyz.abc.com",
+          expectMatch: true,
+        },
+        // {"abc.com^", kSubdomain, kAnchorNone}
+        {
+          urlFilter: "||abc.com^",
+          url: "http://abc.com.xyz.com?q=abc.com",
+          expectMatch: false,
+        },
+        // {"abc.com^", kSubdomain, kBoundary}
+        {
+          urlFilter: "||abc.com^|",
+          url: "http://xyz.abc.com/123",
+          expectMatch: false,
+        },
+        // {"abc.com^", kSubdomain, kBoundary}
+        {
+          urlFilter: "||abc.com^|",
+          url: "http://xyz.abc.com",
+          expectMatch: true,
+        },
+        // {"abc.com^", kSubdomain, kBoundary}
+        {
+          urlFilter: "||abc.com^|",
+          url: "http://abc.com.xyz.com?q=abc.com/",
+          expectMatch: false,
+        },
+        // {"abc*^", kAnchorNone, kAnchorNone}
+        {
+          urlFilter: "abc*^",
+          url: "https://abc.com",
+          expectMatch: true,
+        },
+        // {"abc*^", kAnchorNone, kAnchorNone}
+        {
+          urlFilter: "abc*^",
+          url: "https://abc.com?q=123",
+          expectMatch: true,
+        },
+        // {"abc*^", kAnchorNone, kBoundary}
+        {
+          urlFilter: "abc*^|",
+          url: "https://abc.com",
+          expectMatch: true,
+        },
+        // {"abc*^", kAnchorNone, kBoundary}
+        {
+          urlFilter: "abc*^|",
+          url: "https://abc.com?q=123",
+          expectMatch: true,
+        },
+        // {"abc*", kAnchorNone, kBoundary}
+        {
+          urlFilter: "abc*|",
+          url: "https://a.com/abcxyz",
+          expectMatch: true,
+        },
+        // {"*google.com", kBoundary, kAnchorNone}
+        {
+          urlFilter: "|*google.com",
+          url: "https://www.google.com",
+          expectMatch: true,
+        },
+        // {"*", kBoundary, kBoundary}
+        {
+          urlFilter: "|*|",
+          url: "https://example.com",
+          expectMatch: true,
+        },
+        // // {"", kBoundary, kBoundary}
+        // { // "||" is ambiguous, cannot mean Left anchor + Right anchor
+        //   urlFilter: "||",
+        //   url: "https://example.com",
+        //   expectMatch: false,
+        // },
+      ];
+      for (let test of testCases) {
+        let { urlFilter, url, expectMatch, isUrlFilterCaseSensitive } = test;
+        if (expectMatch) {
+          await testMatchesUrlFilter({
+            urlFilter,
+            isUrlFilterCaseSensitive,
+            urls: [url],
+          });
+        } else {
+          await testMatchesUrlFilter({
+            urlFilter,
+            isUrlFilterCaseSensitive,
+            urlsNonMatching: [url],
+          });
+        }
+      }
+
+      browser.test.notifyPass();
+    },
+  });
+});
diff --git a/toolkit/components/extensions/test/xpcshell/test_ext_dnr_webrequest.js b/toolkit/components/extensions/test/xpcshell/test_ext_dnr_webrequest.js
new file mode 100644
index 0000000000..415ab42c5f
--- /dev/null
+++ b/toolkit/components/extensions/test/xpcshell/test_ext_dnr_webrequest.js
@@ -0,0 +1,296 @@
+"use strict";
+
+add_setup(() => {
+  Services.prefs.setBoolPref("extensions.manifestV3.enabled", true);
+  Services.prefs.setBoolPref("extensions.dnr.enabled", true);
+});
+
+const server = createHttpServer({
+  hosts: ["example.com", "redir"],
+});
+server.registerPathHandler("/never_reached", (req, res) => {
+  Assert.ok(false, "Server should never have been reached");
+});
+server.registerPathHandler("/source", (req, res) => {
+  res.setHeader("Access-Control-Allow-Origin", "*");
+});
+server.registerPathHandler("/destination", (req, res) => {
+  res.setHeader("Access-Control-Allow-Origin", "*");
+});
+
+add_task(async function block_request_with_dnr() {
+  async function background() {
+    let onBeforeRequestPromise = new Promise(resolve => {
+      browser.webRequest.onBeforeRequest.addListener(resolve, {
+        urls: ["*://example.com/*"],
+      });
+    });
+    await browser.declarativeNetRequest.updateSessionRules({
+      addRules: [
+        {
+          id: 1,
+          condition: { requestDomains: ["example.com"] },
+          action: { type: "block" },
+        },
+      ],
+    });
+
+    await browser.test.assertRejects(
+      fetch("http://example.com/never_reached"),
+      "NetworkError when attempting to fetch resource.",
+      "blocked by DNR rule"
+    );
+    // DNR is documented to take precedence over webRequest. We should still
+    // receive the webRequest event, however.
+    browser.test.log("Waiting for webRequest.onBeforeRequest...");
+    await onBeforeRequestPromise;
+    browser.test.log("Seen webRequest.onBeforeRequest!");
+
+    browser.test.notifyPass();
+  }
+  let extension = ExtensionTestUtils.loadExtension({
+    background,
+    temporarilyInstalled: true, // Needed for granted_host_permissions
+    allowInsecureRequests: true,
+    manifest: {
+      manifest_version: 3,
+      granted_host_permissions: true,
+      host_permissions: ["*://example.com/*"],
+      permissions: ["declarativeNetRequest", "webRequest"],
+    },
+  });
+  await extension.startup();
+  await extension.awaitFinish();
+  await extension.unload();
+});
+
+add_task(async function upgradeScheme_and_redirect_request_with_dnr() {
+  async function background() {
+    let onBeforeRequestSeen = [];
+    browser.webRequest.onBeforeRequest.addListener(
+      d => {
+        onBeforeRequestSeen.push(d.url);
+        // webRequest cancels, but DNR should actually be taking precedence.
+        return { cancel: true };
+      },
+      { urls: ["*://example.com/*", "http://redir/here"] },
+      ["blocking"]
+    );
+    await browser.declarativeNetRequest.updateSessionRules({
+      addRules: [
+        {
+          id: 1,
+          condition: { requestDomains: ["example.com"] },
+          action: { type: "upgradeScheme" },
+        },
+        {
+          id: 2,
+          condition: { requestDomains: ["example.com"], urlFilter: "|https:*" },
+          action: { type: "redirect", redirect: { url: "http://redir/here" } },
+          // The upgradeScheme and redirect actions have equal precedence. To
+          // make sure that the redirect action is executed when both rules
+          // match, we assign a higher priority to the redirect action.
+          priority: 2,
+        },
+      ],
+    });
+
+    await browser.test.assertRejects(
+      fetch("http://example.com/never_reached"),
+      "NetworkError when attempting to fetch resource.",
+      "although initially redirected by DNR, ultimately blocked by webRequest"
+    );
+    // DNR is documented to take precedence over webRequest.
+    // So we should actually see redirects according to the DNR rules, and
+    // the webRequest listener should still be able to observe all requests.
+    browser.test.assertDeepEq(
+      [
+        "http://example.com/never_reached",
+        "https://example.com/never_reached",
+        "http://redir/here",
+      ],
+      onBeforeRequestSeen,
+      "Expected onBeforeRequest events"
+    );
+
+    browser.test.notifyPass();
+  }
+  let extension = ExtensionTestUtils.loadExtension({
+    background,
+    temporarilyInstalled: true, // Needed for granted_host_permissions
+    manifest: {
+      manifest_version: 3,
+      granted_host_permissions: true,
+      host_permissions: ["*://example.com/*", "*://redir/*"],
+      permissions: [
+        "declarativeNetRequest",
+        "webRequest",
+        "webRequestBlocking",
+      ],
+    },
+  });
+  await extension.startup();
+  await extension.awaitFinish();
+  await extension.unload();
+});
+
+add_task(async function block_request_with_webRequest_after_allow_with_dnr() {
+  async function background() {
+    let onBeforeRequestSeen = [];
+    browser.webRequest.onBeforeRequest.addListener(
+      d => {
+        onBeforeRequestSeen.push(d.url);
+        return { cancel: !d.url.includes("webRequestNoCancel") };
+      },
+      { urls: ["*://example.com/*"] },
+      ["blocking"]
+    );
+    // All DNR actions that do not end up canceling/redirecting the request:
+    await browser.declarativeNetRequest.updateSessionRules({
+      addRules: [
+        {
+          id: 1,
+          condition: { requestMethods: ["get"] },
+          action: { type: "allow" },
+        },
+        {
+          id: 2,
+          condition: { requestMethods: ["put"] },
+          action: {
+            type: "modifyHeaders",
+            requestHeaders: [{ operation: "set", header: "x", value: "y" }],
+          },
+        },
+      ],
+    });
+
+    await browser.test.assertRejects(
+      fetch("http://example.com/never_reached?1", { method: "get" }),
+      "NetworkError when attempting to fetch resource.",
+      "despite DNR 'allow' rule, still blocked by webRequest"
+    );
+    await browser.test.assertRejects(
+      fetch("http://example.com/never_reached?2", { method: "put" }),
+      "NetworkError when attempting to fetch resource.",
+      "despite DNR 'modifyHeaders' rule, still blocked by webRequest"
+    );
+    // Just to rule out the request having been canceled by DNR instead of
+    // webRequest, repeat the requests and verify that they succeed.
+    await fetch("http://example.com/?webRequestNoCancel1", { method: "get" });
+    await fetch("http://example.com/?webRequestNoCancel2", { method: "put" });
+
+    browser.test.assertDeepEq(
+      [
+        "http://example.com/never_reached?1",
+        "http://example.com/never_reached?2",
+        "http://example.com/?webRequestNoCancel1",
+        "http://example.com/?webRequestNoCancel2",
+      ],
+      onBeforeRequestSeen,
+      "Expected onBeforeRequest events"
+    );
+
+    browser.test.notifyPass();
+  }
+  let extension = ExtensionTestUtils.loadExtension({
+    background,
+    temporarilyInstalled: true, // Needed for granted_host_permissions
+    allowInsecureRequests: true,
+    manifest: {
+      manifest_version: 3,
+      granted_host_permissions: true,
+      host_permissions: ["*://example.com/*"],
+      permissions: [
+        "declarativeNetRequest",
+        "webRequest",
+        "webRequestBlocking",
+      ],
+    },
+  });
+  await extension.startup();
+  await extension.awaitFinish();
+  await extension.unload();
+});
+
+add_task(async function redirect_with_webRequest_after_failing_dnr_redirect() {
+  async function background() {
+    // Maximum length of a UTL is 1048576 (network.standard-url.max-length).
+    const network_standard_url_max_length = 1048576;
+    // updateSessionRules does some validation on the limit (as seen by
+    // validate_action_redirect_transform in test_ext_dnr_session_rules.js),
+    // but it is still possible to pass validation and fail in practice when
+    // the existing URL + new component exceeds the limit.
+    const VERY_LONG_STRING = "x".repeat(network_standard_url_max_length - 20);
+
+    browser.webRequest.onBeforeRequest.addListener(
+      d => {
+        return { redirectUrl: "http://redir/destination?by-webrequest" };
+      },
+      { urls: ["*://example.com/*"] },
+      ["blocking"]
+    );
+    await browser.declarativeNetRequest.updateSessionRules({
+      addRules: [
+        {
+          id: 1,
+          condition: { requestDomains: ["example.com"] },
+          action: {
+            type: "redirect",
+            redirect: {
+              transform: {
+                host: "redir",
+                path: "/destination",
+                queryTransform: {
+                  addOrReplaceParams: [
+                    { key: "dnr", value: VERY_LONG_STRING, replaceOnly: true },
+                  ],
+                },
+              },
+            },
+          },
+        },
+      ],
+    });
+
+    // Note: we are not expecting successful DNR redirects below, but in case
+    // that ever changes (e.g. due to VERY_LONG_STRING not resulting in an
+    // invalid URL), we will truncate the URL out of caution.
+    // VERY_LONG_STRING consists of many 'X'. Shorten to avoid logspam.
+    const shortx = s => s.replace(/x{10,}/g, xxx => `x{${xxx.length}}`);
+
+    browser.test.assertEq(
+      "http://redir/destination?1",
+      shortx((await fetch("http://example.com/never_reached?1")).url),
+      "Successful DNR redirect."
+    );
+
+    // DNR redirect failure is expected to be very rare, and only to occur when
+    // an extension intentionally explores the boundaries of the DNR API. When
+    // DNR fails, we fall back to allowing webRequest to take over.
+    browser.test.assertEq(
+      "http://redir/destination?by-webrequest",
+      shortx((await fetch("http://example.com/source?dnr")).url),
+      "When DNR fails, we fall back to webRequest redirect"
+    );
+
+    browser.test.notifyPass();
+  }
+  let extension = ExtensionTestUtils.loadExtension({
+    background,
+    temporarilyInstalled: true, // Needed for granted_host_permissions
+    allowInsecureRequests: true,
+    manifest: {
+      manifest_version: 3,
+      granted_host_permissions: true,
+      host_permissions: ["*://example.com/*"],
+      permissions: [
+        "declarativeNetRequest",
+        "webRequest",
+        "webRequestBlocking",
+      ],
+    },
+  });
+  await extension.startup();
+  await extension.awaitFinish();
+  await extension.unload();
+});
diff --git a/toolkit/components/extensions/test/xpcshell/test_ext_dnr_without_webrequest.js b/toolkit/components/extensions/test/xpcshell/test_ext_dnr_without_webrequest.js
new file mode 100644
index 0000000000..5a69b255d2
--- /dev/null
+++ b/toolkit/components/extensions/test/xpcshell/test_ext_dnr_without_webrequest.js
@@ -0,0 +1,877 @@
+"use strict";
+
+// This test file verifies that the declarativeNetRequest API can modify
+// network requests as expected without the presence of the webRequest API. See
+// test_ext_dnr_webRequest.js for the interaction between webRequest and DNR.
+
+add_setup(() => {
+  Services.prefs.setBoolPref("extensions.manifestV3.enabled", true);
+  Services.prefs.setBoolPref("extensions.dnr.enabled", true);
+});
+
+const server = createHttpServer({
+  hosts: ["example.com", "example.net", "example.org", "redir", "dummy"],
+});
+server.registerPathHandler("/cors_202", (req, res) => {
+  res.setStatusLine(req.httpVersion, 202, "Accepted");
+  // The extensions in this test have minimal permissions, so grant CORS to
+  // allow them to read the response without host permissions.
+  res.setHeader("Access-Control-Allow-Origin", "*");
+  res.setHeader("Access-Control-Max-Age", "0");
+  res.write("cors_response");
+});
+server.registerPathHandler("/never_reached", (req, res) => {
+  Assert.ok(false, "Server should never have been reached");
+  res.setHeader("Access-Control-Allow-Origin", "*");
+  res.setHeader("Access-Control-Max-Age", "0");
+});
+let gPreflightCount = 0;
+server.registerPathHandler("/preflight_count", (req, res) => {
+  res.setHeader("Access-Control-Allow-Origin", "*");
+  res.setHeader("Access-Control-Max-Age", "0");
+  res.setHeader("Access-Control-Allow-Methods", "NONSIMPLE");
+  if (req.method === "OPTIONS") {
+    ++gPreflightCount;
+  } else {
+    // CORS Preflight considers 2xx to be successful. To rule out inadvertent
+    // server opt-in to CORS, respond with a non-2xx response.
+    res.setStatusLine(req.httpVersion, 418, "I'm a teapot");
+    res.write(`count=${gPreflightCount}`);
+  }
+});
+server.registerPathHandler("/", (req, res) => {
+  res.setHeader("Access-Control-Allow-Origin", "*");
+  res.setHeader("Access-Control-Max-Age", "0");
+  res.write("Dummy page");
+});
+
+async function contentFetch(initiatorURL, url, options) {
+  let contentPage = await ExtensionTestUtils.loadContentPage(initiatorURL);
+  // Sanity check: that the initiator is as specified, and not redirected.
+  Assert.equal(
+    await contentPage.spawn([], () => content.document.URL),
+    initiatorURL,
+    `Expected document load at: ${initiatorURL}`
+  );
+  let result = await contentPage.spawn([{ url, options }], async args => {
+    try {
+      let req = await content.fetch(args.url, args.options);
+      return {
+        status: req.status,
+        url: req.url,
+        body: await req.text(),
+      };
+    } catch (e) {
+      return { error: e.message };
+    }
+  });
+  await contentPage.close();
+  return result;
+}
+
+async function checkCanFetchFromOtherExtension() {
+  let otherExtension = ExtensionTestUtils.loadExtension({
+    async background() {
+      let req = await fetch("http://example.com/cors_202", { method: "get" });
+      browser.test.assertEq(202, req.status, "not blocked by other extension");
+      browser.test.assertEq("cors_response", await req.text());
+      browser.test.sendMessage("other_extension_done");
+    },
+  });
+  await otherExtension.startup();
+  await otherExtension.awaitMessage("other_extension_done");
+  await otherExtension.unload();
+}
+
+add_task(async function block_request_with_dnr() {
+  async function background() {
+    await browser.declarativeNetRequest.updateSessionRules({
+      addRules: [
+        {
+          id: 1,
+          condition: { requestMethods: ["get"] },
+          action: { type: "block" },
+        },
+        {
+          id: 2,
+          condition: { requestMethods: ["head"] },
+          action: { type: "allow" },
+        },
+      ],
+    });
+    {
+      // Request not matching DNR.
+      let req = await fetch("http://example.com/cors_202", { method: "post" });
+      browser.test.assertEq(202, req.status, "allowed without DNR rule");
+      browser.test.assertEq("cors_response", await req.text());
+    }
+    {
+      // Request with "allow" DNR action.
+      let req = await fetch("http://example.com/cors_202", { method: "head" });
+      browser.test.assertEq(202, req.status, "allowed by DNR rule");
+      browser.test.assertEq("", await req.text(), "no response for HEAD");
+    }
+
+    // Request with "block" DNR action.
+    await browser.test.assertRejects(
+      fetch("http://example.com/never_reached", { method: "get" }),
+      "NetworkError when attempting to fetch resource.",
+      "blocked by DNR rule"
+    );
+
+    browser.test.sendMessage("tested_dnr_block");
+  }
+  let extension = ExtensionTestUtils.loadExtension({
+    allowInsecureRequests: true,
+    background,
+    manifest: {
+      manifest_version: 3,
+      permissions: ["declarativeNetRequest"],
+    },
+  });
+  await extension.startup();
+  await extension.awaitMessage("tested_dnr_block");
+
+  // DNR should not only work with requests within the extension, but also from
+  // web pages.
+  Assert.deepEqual(
+    await contentFetch("http://dummy/", "http://example.com/never_reached"),
+    { error: "NetworkError when attempting to fetch resource." },
+    "Blocked by DNR with declarativeNetRequestWithHostAccess"
+  );
+
+  // declarativeNetRequest does not allow extensions to block requests from
+  // other extensions.
+  await checkCanFetchFromOtherExtension();
+
+  // Except when the user opts in via a preference. When the pref is on, then:
+  // The declarativeNetRequest permission grants the ability to block requests
+  // from other extensions. (The declarativeNetRequestWithHostAccess permission
+  // does not; see test task block_with_declarativeNetRequestWithHostAccess.)
+  let otherExtension = ExtensionTestUtils.loadExtension({
+    async background() {
+      await browser.test.assertRejects(
+        fetch("http://example.com/never_reached", { method: "get" }),
+        "NetworkError when attempting to fetch resource.",
+        "blocked by different extension with declarativeNetRequest permission"
+      );
+      browser.test.sendMessage("other_extension_done");
+    },
+  });
+  await runWithPrefs(
+    [["extensions.dnr.match_requests_from_other_extensions", true]],
+    async () => {
+      info("Verifying that fetch() from extension is intercepted with pref");
+      await otherExtension.startup();
+      await otherExtension.awaitMessage("other_extension_done");
+      await otherExtension.unload();
+    }
+  );
+
+  await extension.unload();
+});
+
+// Verifies that the "declarativeNetRequestWithHostAccess" permission can only
+// block if it has permission for the initiator.
+add_task(async function block_with_declarativeNetRequestWithHostAccess() {
+  let extension = ExtensionTestUtils.loadExtension({
+    async background() {
+      await browser.declarativeNetRequest.updateSessionRules({
+        addRules: [{ id: 1, condition: {}, action: { type: "block" } }],
+      });
+      browser.test.sendMessage("dnr_registered");
+    },
+    temporarilyInstalled: true, // Needed for granted_host_permissions
+    allowInsecureRequests: true,
+    manifest: {
+      manifest_version: 3,
+      granted_host_permissions: true,
+      host_permissions: ["<all_urls>"],
+      permissions: ["declarativeNetRequestWithHostAccess"],
+    },
+  });
+  await extension.startup();
+  await extension.awaitMessage("dnr_registered");
+
+  // Initiator "http://dummy" does match "<all_urls>", so DNR rule should apply.
+  Assert.deepEqual(
+    await contentFetch("http://dummy/", "http://example.com/never_reached"),
+    { error: "NetworkError when attempting to fetch resource." },
+    "Blocked by DNR with declarativeNetRequestWithHostAccess"
+  );
+
+  // Extensions cannot have permissions for another extension and therefore the
+  // DNR rule never applies.
+  await checkCanFetchFromOtherExtension();
+
+  // Sanity check: even with the pref, the declarativeNetRequestWithHostAccess
+  // permission should not grant access.
+  info("Verifying that access is not allowed, despite the pref being true");
+  await runWithPrefs(
+    [["extensions.dnr.match_requests_from_other_extensions", true]],
+    checkCanFetchFromOtherExtension
+  );
+
+  await extension.unload();
+});
+
+add_task(async function block_in_sandboxed_extension_page() {
+  const filesWithSandbox = {
+    "page_with_sandbox.html": `<!DOCTYPE html><meta charset="utf-8">
+        <script src="page_with_sandbox.js"></script>
+        <iframe src="sandbox.html" sandbox="allow-scripts"></iframe>
+      `,
+    "page_with_sandbox.js": () => {
+      // Sent by sandbox.js:
+      window.onmessage = e => {
+        browser.test.assertEq("null", e.origin, "Sender has opaque origin");
+        browser.test.sendMessage("fetch_result", e.data);
+      };
+    },
+    "sandbox.html": `<script src="sandbox.js"></script>`,
+    "sandbox.js": async () => {
+      try {
+        // Note that the test server responds with CORS headers, so we should
+        // be able to fetch this URL:
+        await fetch("http://example.com/?fetch_by_sandbox");
+        parent.postMessage("FETCH_ALLOWED", "*");
+      } catch (e) {
+        // The only way for this to fail in this test is when DNR blocks it.
+        parent.postMessage("FETCH_BLOCKED", "*");
+      }
+    },
+  };
+  async function checkFetchInSandboxedExtensionPage(ext) {
+    let contentPage = await ExtensionTestUtils.loadContentPage(
+      `moz-extension://${ext.uuid}/page_with_sandbox.html`
+    );
+    let result = await ext.awaitMessage("fetch_result");
+    await contentPage.close();
+    return result;
+  }
+
+  let extension = ExtensionTestUtils.loadExtension({
+    async background() {
+      await browser.declarativeNetRequest.updateSessionRules({
+        addRules: [{ id: 1, condition: {}, action: { type: "block" } }],
+      });
+      browser.test.sendMessage("dnr_registered");
+    },
+    allowInsecureRequests: true,
+    manifest: {
+      manifest_version: 3,
+      permissions: ["declarativeNetRequest"],
+    },
+    files: filesWithSandbox,
+  });
+  await extension.startup();
+  await extension.awaitMessage("dnr_registered");
+
+  Assert.equal(
+    await checkFetchInSandboxedExtensionPage(extension),
+    "FETCH_BLOCKED",
+    "DNR blocks request from sandboxed page in own extension"
+  );
+
+  let otherExtension = ExtensionTestUtils.loadExtension({
+    files: filesWithSandbox,
+  });
+  await otherExtension.startup();
+
+  // Note: In Firefox, webRequest can intercept requests from opaque origins
+  // opened by other extensions. In contrast, that is not the case in Chrome.
+  Assert.equal(
+    await checkFetchInSandboxedExtensionPage(otherExtension),
+    "FETCH_BLOCKED",
+    "DNR can block request from sandboxed page in other extension"
+  );
+
+  await runWithPrefs(
+    [["extensions.dnr.match_requests_from_other_extensions", true]],
+    async () => {
+      info("Verifying that fetch() from extension sandbox is matched via pref");
+      Assert.equal(
+        await checkFetchInSandboxedExtensionPage(otherExtension),
+        "FETCH_BLOCKED",
+        "DNR can block request from sandboxed page in other extension via pref"
+      );
+    }
+  );
+  await extension.unload();
+
+  // As a sanity check, to verify that the tests above do not always return
+  // FETCH_BLOCKED, run a test case that returns FETCH_ALLOWED:
+  Assert.equal(
+    await checkFetchInSandboxedExtensionPage(otherExtension),
+    "FETCH_ALLOWED",
+    "DNR does not affect sandboxed extensions after unloading the DNR extension"
+  );
+
+  await otherExtension.unload();
+});
+
+// Verifies that upgradeScheme works.
+// The HttpServer helper does not support https (bug 1742061), so in this
+// test we just verify whether the upgrade has been attempted. Coverage that
+// verifies that the upgraded request completes is in:
+// toolkit/components/extensions/test/mochitest/test_ext_dnr_upgradeScheme.html
+add_task(async function upgradeScheme_declarativeNetRequestWithHostAccess() {
+  let extension = ExtensionTestUtils.loadExtension({
+    async background() {
+      await browser.declarativeNetRequest.updateSessionRules({
+        addRules: [
+          {
+            id: 1,
+            condition: { excludedRequestDomains: ["dummy"] },
+            action: { type: "upgradeScheme" },
+          },
+          {
+            id: 2,
+            // HttpServer does not support https (bug 1742061).
+            // As a work-around, we just redirect the https:-request to http.
+            condition: { urlFilter: "|https:*" },
+            action: {
+              type: "redirect",
+              redirect: { url: "http://dummy/cors_202?from_https" },
+            },
+            // The upgradeScheme and redirect actions have equal precedence. To
+            // make sure that the redirect action is executed when both rules
+            // match, we assign a higher priority to the redirect action.
+            priority: 2,
+          },
+        ],
+      });
+
+      let req = await fetch("http://redir/never_reached");
+      browser.test.assertEq(
+        "http://dummy/cors_202?from_https",
+        req.url,
+        "upgradeScheme upgraded to https"
+      );
+      browser.test.assertEq("cors_response", await req.text());
+
+      browser.test.sendMessage("tested_dnr_upgradeScheme");
+    },
+    temporarilyInstalled: true, // Needed for granted_host_permissions.
+    allowInsecureRequests: true,
+    manifest: {
+      manifest_version: 3,
+      granted_host_permissions: true,
+      host_permissions: ["*://dummy/*", "*://redir/*"],
+      permissions: ["declarativeNetRequestWithHostAccess"],
+    },
+  });
+  await extension.startup();
+  await extension.awaitMessage("tested_dnr_upgradeScheme");
+
+  // Request to same-origin subresource, which should be upgraded.
+  Assert.equal(
+    (await contentFetch("http://redir/", "http://redir/never_reached")).url,
+    "http://dummy/cors_202?from_https",
+    "upgradeScheme + host access should upgrade (same-origin request)"
+  );
+
+  // Request to cross-origin subresource, which should be upgraded.
+  // Note: after the upgrade, a cross-origin redirect happens. Internally, we
+  // reflect the Origin request header in the Access-Control-Allow-Origin (ACAO)
+  // response header, to ensure that the request is accepted by CORS. See
+  // https://github.com/w3c/webappsec-upgrade-insecure-requests/issues/32
+  Assert.equal(
+    (await contentFetch("http://dummy/", "http://redir/never_reached")).url,
+    "http://dummy/cors_202?from_https",
+    "upgradeScheme + host access should upgrade (cross-origin request)"
+  );
+
+  // The DNR extension does not have example.net in host_permissions.
+  const urlNoHostPerms = "http://example.net/cors_202?missing_host_permission";
+  Assert.equal(
+    (await contentFetch("http://dummy/", urlNoHostPerms)).url,
+    urlNoHostPerms,
+    "upgradeScheme not matched when extension lacks host access"
+  );
+
+  await extension.unload();
+});
+
+add_task(async function redirect_request_with_dnr() {
+  async function background() {
+    await browser.declarativeNetRequest.updateSessionRules({
+      addRules: [
+        {
+          id: 1,
+          condition: {
+            requestDomains: ["example.com"],
+            requestMethods: ["get"],
+          },
+          action: {
+            type: "redirect",
+            redirect: {
+              url: "http://example.net/cors_202?1",
+            },
+          },
+        },
+        {
+          id: 2,
+          // Note: extension does not have example.org host permission.
+          condition: { requestDomains: ["example.org"] },
+          action: {
+            type: "redirect",
+            redirect: {
+              url: "http://example.net/cors_202?2",
+            },
+          },
+        },
+      ],
+    });
+    // The extension only has example.com permission, but the redirects to
+    // example.net are still due to the CORS headers from the server.
+    {
+      // Simple GET request.
+      let req = await fetch("http://example.com/never_reached");
+      browser.test.assertEq(202, req.status, "redirected by DNR (simple)");
+      browser.test.assertEq("http://example.net/cors_202?1", req.url);
+      browser.test.assertEq("cors_response", await req.text());
+    }
+    {
+      // GeT request should be matched despite having a different case.
+      let req = await fetch("http://example.com/never_reached", {
+        method: "GeT",
+      });
+      browser.test.assertEq(202, req.status, "redirected by DNR (GeT)");
+      browser.test.assertEq("http://example.net/cors_202?1", req.url);
+      browser.test.assertEq("cors_response", await req.text());
+    }
+    {
+      // Host permission missing for request, request not redirected by DNR.
+      // Response is readable due to the CORS response headers from the server.
+      let req = await fetch("http://example.org/cors_202?noredir");
+      browser.test.assertEq(202, req.status, "not redirected by DNR");
+      browser.test.assertEq("http://example.org/cors_202?noredir", req.url);
+      browser.test.assertEq("cors_response", await req.text());
+    }
+
+    browser.test.notifyPass();
+  }
+  let extension = ExtensionTestUtils.loadExtension({
+    background,
+    temporarilyInstalled: true, // Needed for granted_host_permissions
+    allowInsecureRequests: true,
+    manifest: {
+      manifest_version: 3,
+      granted_host_permissions: true,
+      host_permissions: ["*://example.com/*"],
+      permissions: ["declarativeNetRequest"],
+    },
+  });
+  await extension.startup();
+  await extension.awaitFinish();
+
+  let otherExtension = ExtensionTestUtils.loadExtension({
+    async background() {
+      // The DNR extension has permissions for example.com, but not for this
+      // extension. Therefore the "redirect" action should not apply.
+      let req = await fetch("http://example.com/cors_202?other_ext");
+      browser.test.assertEq(202, req.status, "not redirected by DNR");
+      browser.test.assertEq("http://example.com/cors_202?other_ext", req.url);
+      browser.test.assertEq("cors_response", await req.text());
+      browser.test.sendMessage("other_extension_done");
+    },
+  });
+  await otherExtension.startup();
+  await otherExtension.awaitMessage("other_extension_done");
+  await otherExtension.unload();
+
+  await extension.unload();
+});
+
+// Verifies that DNR redirects requiring a CORS preflight behave as expected.
+add_task(async function redirect_request_with_dnr_cors_preflight() {
+  // Most other test tasks only test requests within the test extension. This
+  // test intentionally triggers requests outside the extension, to make sure
+  // that the usual CORS mechanisms is triggered (instead of exceptions from
+  // host permissions).
+  async function background() {
+    await browser.declarativeNetRequest.updateSessionRules({
+      addRules: [
+        {
+          id: 1,
+          condition: {
+            requestDomains: ["redir"],
+            excludedRequestMethods: ["options"],
+          },
+          action: {
+            type: "redirect",
+            redirect: {
+              url: "http://example.com/preflight_count",
+            },
+          },
+        },
+        {
+          id: 2,
+          condition: {
+            requestDomains: ["example.net"],
+            excludedRequestMethods: ["nonsimple"], // note: redirects "options"
+          },
+          action: {
+            type: "redirect",
+            redirect: {
+              url: "http://example.com/preflight_count",
+            },
+          },
+        },
+      ],
+    });
+    let req = await fetch("http://redir/never_reached", {
+      method: "NONSIMPLE",
+    });
+    // Extension has permission for "redir", but not for the redirect target.
+    // The request is non-simple (see below for explanation of non-simple), so
+    // a preflight (OPTIONS) request to /preflight_count is expected before the
+    // redirection target is requested.
+    browser.test.assertEq(
+      "count=1",
+      await req.text(),
+      "Got preflight before redirect target because of missing host_permissions"
+    );
+
+    browser.test.sendMessage("continue_preflight_tests");
+  }
+
+  let extension = ExtensionTestUtils.loadExtension({
+    background,
+    temporarilyInstalled: true, // Needed for granted_host_permissions
+    allowInsecureRequests: true,
+    manifest: {
+      manifest_version: 3,
+      granted_host_permissions: true,
+      // "redir" and "example.net" are needed to allow redirection of these.
+      // "dummy" is needed to redirect requests initiated from http://dummy.
+      host_permissions: ["*://redir/*", "*://example.net/*", "*://dummy/*"],
+      permissions: ["declarativeNetRequest"],
+    },
+  });
+  gPreflightCount = 0;
+  await extension.startup();
+  await extension.awaitMessage("continue_preflight_tests");
+  gPreflightCount = 0; // value already checked before continue_preflight_tests.
+
+  // Simple request (i.e. without preflight requirement), that's redirected to
+  // another URL by the DNR rule. The redirect should be accepted, and in
+  // particular not be blocked by the same-origin policy. The redirect target
+  // (/preflight_count) is readable due to the CORS headers from the server.
+  Assert.deepEqual(
+    await contentFetch("http://dummy/", "http://redir/never_reached"),
+    // count=0: A simple request does not trigger a preflight (OPTIONS) request.
+    { status: 418, url: "http://example.com/preflight_count", body: "count=0" },
+    "Simple request should not have a preflight."
+  );
+
+  // Any request method other than "GET", "POST" and "PUT" (e.g "NONSIMPLE") is
+  // a non-simple request that triggers a preflight request ("OPTIONS").
+  //
+  // Usually, this happens (without extension-triggered redirects):
+  // 1. NONSIMPLE /never_reached : is started, but does NOT hit the server yet.
+  // 2. OPTIONS /never_reached + Access-Control-Request-Method: NONSIMPLE
+  // 3. NONSIMPLE /never_reached : reaches the server if allowed by OPTIONS.
+  //
+  // With an extension-initiated redirect to /preflight_count:
+  // 1. NONSIMPLE /never_reached : is started, but does not hit the server yet.
+  // 2. extension redirects to /preflight_count
+  // 3. OPTIONS /preflight_count + Access-Control-Request-Method: NONSIMPLE
+  //    - This is because the redirect preserves the request method/body/etc.
+  // 4. NONSIMPLE /preflight_count : reaches the server if allowed by OPTIONS.
+  Assert.deepEqual(
+    await contentFetch("http://dummy/", "http://redir/never_reached", {
+      method: "NONSIMPLE",
+    }),
+    // Due to excludedRequestMethods: ["options"], the preflight for the
+    // redirect target is not intercepted, so the server sees a preflight.
+    { status: 418, url: "http://example.com/preflight_count", body: "count=1" },
+    "Initial URL redirected, redirection target has preflight"
+  );
+  gPreflightCount = 0;
+
+  // The "example.net" rule has "excludedRequestMethods": ["nonsimple"], so the
+  // initial "NONSIMPLE" request is not immediately redirected. Therefore the
+  // preflight request happens. This OPTIONS request is matched by the DNR rule
+  // and redirected to /preflight_count. While preflight_count offers a very
+  // permissive preflight response, it is not even fetched:
+  // Only a 2xx HTTP status is considered a valid response to a pre-flight.
+  // A redirect is like a 3xx HTTP status, so the whole request is rejected,
+  // and the redirect is not followed for the OPTIONS request.
+  Assert.deepEqual(
+    await contentFetch("http://dummy/", "http://example.net/never_reached", {
+      method: "NONSIMPLE",
+    }),
+    { error: "NetworkError when attempting to fetch resource." },
+    "Redirect of preflight request (OPTIONS) should be a CORS failure"
+  );
+
+  Assert.equal(gPreflightCount, 0, "Preflight OPTIONS has been intercepted");
+
+  await extension.unload();
+});
+
+// Tests that DNR redirect rules can be chained.
+add_task(async function redirect_request_with_dnr_multiple_hops() {
+  async function background() {
+    // Set up redirects from example.com up until dummy.
+    let hosts = ["example.com", "example.net", "example.org", "redir", "dummy"];
+    let rules = [];
+    for (let i = 1; i < hosts.length; ++i) {
+      const from = hosts[i - 1];
+      const to = hosts[i];
+      const end = hosts.length - 1 === i;
+      rules.push({
+        id: i,
+        condition: { requestDomains: [from] },
+        action: {
+          type: "redirect",
+          redirect: {
+            // All intermediate redirects should never hit the server, but the
+            // last one should..
+            url: end ? `http://${to}/?end` : `http://${to}/never_reached`,
+          },
+        },
+      });
+    }
+    await browser.declarativeNetRequest.updateSessionRules({ addRules: rules });
+    let req = await fetch("http://example.com/never_reached");
+    browser.test.assertEq(200, req.status, "redirected by DNR (multiple)");
+    browser.test.assertEq("http://dummy/?end", req.url, "Last URL in chain");
+    browser.test.assertEq("Dummy page", await req.text());
+
+    browser.test.notifyPass();
+  }
+  let extension = ExtensionTestUtils.loadExtension({
+    background,
+    temporarilyInstalled: true, // Needed for granted_host_permissions
+    allowInsecureRequests: true,
+    manifest: {
+      manifest_version: 3,
+      granted_host_permissions: true,
+      host_permissions: ["*://*/*"], // matches all in the |hosts| list.
+      permissions: ["declarativeNetRequest"],
+    },
+  });
+  await extension.startup();
+  await extension.awaitFinish();
+
+  // Test again, but without special extension permissions to verify that DNR
+  // redirects pass CORS checks.
+  Assert.deepEqual(
+    await contentFetch("http://dummy/", "http://redir/never_reached"),
+    { status: 200, url: "http://dummy/?end", body: "Dummy page" },
+    "Multiple redirects by DNR, requested from web origin."
+  );
+
+  await extension.unload();
+});
+
+add_task(async function redirect_request_with_dnr_with_redirect_loop() {
+  async function background() {
+    await browser.declarativeNetRequest.updateSessionRules({
+      addRules: [
+        {
+          id: 1,
+          // requestMethods is mutually exclusive with the other rule.
+          condition: { regexFilter: "^(.+)$", requestMethods: ["post"] },
+          action: {
+            type: "redirect",
+            redirect: {
+              // Appends "?loop" to the request URL
+              regexSubstitution: "\\1?loop",
+            },
+          },
+        },
+        {
+          id: 2,
+          // requestMethods is mutually exclusive with the other rule.
+          condition: { requestDomains: ["redir"], requestMethods: ["get"] },
+          action: {
+            type: "redirect",
+            redirect: {
+              // Despite redirect.url matching the condition, the redirect loop
+              // should be caught because of the obvious fact that the URL did
+              // not change.
+              url: "http://redir/cors_202?loop",
+            },
+          },
+        },
+      ],
+    });
+
+    // Redirect where the redirect URL changes at every redirect.
+    await browser.test.assertRejects(
+      fetch("http://redir/cors_202?loop", { method: "post" }),
+      "NetworkError when attempting to fetch resource.",
+      "Redirect loop caught (redirect target differs at every redirect)"
+    );
+
+    async function assertRedirect(url, expected, description) {
+      // method: "get" could only match rule 2.
+      let res = await fetch(url);
+      browser.test.assertDeepEq(
+        expected,
+        { status: res.status, url: res.url, redirected: res.redirected },
+        description
+      );
+    }
+
+    // Redirect with initially a different URL.
+    await assertRedirect(
+      "http://redir/never_reached?",
+      { status: 202, url: "http://redir/cors_202?loop", redirected: true },
+      "Redirect loop caught (initially different URL)"
+    );
+
+    // Redirect where redirect is exactly the same URL as requested.
+    await assertRedirect(
+      "http://redir/cors_202?loop",
+      { status: 202, url: "http://redir/cors_202?loop", redirected: false },
+      "Redirect loop caught (redirect target same as initial URL)"
+    );
+
+    browser.test.notifyPass();
+  }
+  let extension = ExtensionTestUtils.loadExtension({
+    background,
+    temporarilyInstalled: true, // Needed for granted_host_permissions
+    allowInsecureRequests: true,
+    manifest: {
+      manifest_version: 3,
+      granted_host_permissions: true,
+      host_permissions: ["*://redir/*"],
+      permissions: ["declarativeNetRequest"],
+    },
+  });
+  await extension.startup();
+  await extension.awaitFinish();
+  await extension.unload();
+});
+
+// Tests that redirect to extensionPath works, provided that the initiator is
+// either the extension itself, or in host_permissions. Moreover, the requested
+// resource must match a web_accessible_resources entry for both the initiator
+// AND the pre-redirect URL.
+add_task(async function redirect_request_with_dnr_to_extensionPath() {
+  async function background() {
+    await browser.declarativeNetRequest.updateSessionRules({
+      addRules: [
+        {
+          id: 1,
+          condition: { requestDomains: ["redir"], requestMethods: ["post"] },
+          action: {
+            type: "redirect",
+            redirect: {
+              extensionPath: "/war.txt?1",
+            },
+          },
+        },
+        {
+          id: 2,
+          condition: { requestDomains: ["redir"], requestMethods: ["put"] },
+          action: {
+            type: "redirect",
+            redirect: {
+              extensionPath: "/nonwar.txt?2",
+            },
+          },
+        },
+      ],
+    });
+    {
+      let req = await fetch("http://redir/never_reached", { method: "post" });
+      browser.test.assertEq(200, req.status, "redirected to extensionPath");
+      browser.test.assertEq(`${location.origin}/war.txt?1`, req.url);
+      browser.test.assertEq("war_ext_res", await req.text());
+    }
+    // Redirects to extensionPath that is not in web_accessible_resources.
+    // While the initiator (extension) would be allowed to read the resource
+    // due to it being same-origin, the pre-redirect URL (http://redir) is not
+    // matching web_accessible_resources[].matches, so the load is rejected.
+    //
+    // This behavior differs from Chrome (e.g. at least in Chrome 109) that
+    // does allow the load to complete. Extensions who really care about
+    // exposing a web-accessible resource to the world can just put an all_urls
+    // pattern in web_accessible_resources[].matches.
+    await browser.test.assertRejects(
+      fetch("http://redir/never_reached", { method: "put" }),
+      "NetworkError when attempting to fetch resource.",
+      "Redirect to nowar.txt, but pre-redirect host is not in web_accessible_resources[].matches"
+    );
+
+    browser.test.notifyPass();
+  }
+  let extension = ExtensionTestUtils.loadExtension({
+    background,
+    temporarilyInstalled: true, // Needed for granted_host_permissions
+    allowInsecureRequests: true,
+    manifest: {
+      manifest_version: 3,
+      granted_host_permissions: true,
+      host_permissions: ["*://redir/*", "*://dummy/*"],
+      permissions: ["declarativeNetRequest"],
+      web_accessible_resources: [
+        // *://redir/* is in matches, because that is the pre-redirect host.
+        // *://dummy/* is in matches, because that is an initiator below.
+        { resources: ["war.txt"], matches: ["*://redir/*", "*://dummy/*"] },
+        // without "matches", this is almost equivalent to not being listed in
+        // web_accessible_resources at all. This entry is listed here to verify
+        // that the presence of extension_ids does not somehow allow a request
+        // with an extension initiator to complete.
+        { resources: ["nonwar.txt"], extension_ids: ["*"] },
+      ],
+    },
+    files: {
+      "war.txt": "war_ext_res",
+      "nonwar.txt": "non_war_ext_res",
+    },
+  });
+  await extension.startup();
+  await extension.awaitFinish();
+  const extPrefix = `moz-extension://${extension.uuid}`;
+
+  // Request from origin in host_permissions, for web-accessible resource.
+  Assert.deepEqual(
+    await contentFetch(
+      "http://dummy/", // <-- Matching web_accessible_resources[].matches
+      "http://redir/never_reached", // <-- With matching host_permissions
+      { method: "post" }
+    ),
+    { status: 200, url: `${extPrefix}/war.txt?1`, body: "war_ext_res" },
+    "Should have got redirect to web_accessible_resources (war.txt)"
+  );
+
+  // Request from origin in host_permissions, for non-web-accessible resource.
+  let { messages } = await promiseConsoleOutput(async () => {
+    Assert.deepEqual(
+      await contentFetch(
+        "http://dummy/", // <-- Matching web_accessible_resources[].matches
+        "http://redir/never_reached", // <-- With matching host_permissions
+        { method: "put" }
+      ),
+      { error: "NetworkError when attempting to fetch resource." },
+      "Redirect to nowar.txt, without matching web_accessible_resources[].matches"
+    );
+  });
+  const EXPECTED_SECURITY_ERROR = `Content at http://redir/never_reached may not load or link to ${extPrefix}/nonwar.txt?2.`;
+  Assert.equal(
+    messages.filter(m => m.message.includes(EXPECTED_SECURITY_ERROR)).length,
+    1,
+    `Should log SecurityError: ${EXPECTED_SECURITY_ERROR}`
+  );
+
+  // Request from origin not in host_permissions. DNR rule should not apply.
+  Assert.deepEqual(
+    await contentFetch(
+      "http://dummy/", // <-- Matching web_accessible_resources[].matches
+      "http://example.com/cors_202", // <-- NOT in host_permissions
+      { method: "post" }
+    ),
+    { status: 202, url: "http://example.com/cors_202", body: "cors_response" },
+    "Extension should not have redirected, due to lack of host permissions"
+  );
+
+  await extension.unload();
+});
diff --git a/toolkit/components/extensions/test/xpcshell/test_ext_dns.js b/toolkit/components/extensions/test/xpcshell/test_ext_dns.js
new file mode 100644
index 0000000000..56bd3ae174
--- /dev/null
+++ b/toolkit/components/extensions/test/xpcshell/test_ext_dns.js
@@ -0,0 +1,176 @@
+"use strict";
+
+// Some test machines and android are not returning ipv6, turn it
+// off to get consistent test results.
+Services.prefs.setBoolPref("network.dns.disableIPv6", true);
+
+AddonTestUtils.init(this);
+AddonTestUtils.overrideCertDB();
+
+AddonTestUtils.createAppInfo(
+  "xpcshell@tests.mozilla.org",
+  "XPCShell",
+  "1",
+  "42"
+);
+
+function getExtension(background = undefined) {
+  let manifest = {
+    permissions: ["dns", "proxy"],
+  };
+  return ExtensionTestUtils.loadExtension({
+    manifest,
+    background() {
+      browser.test.onMessage.addListener(async (msg, data) => {
+        if (msg == "proxy") {
+          await browser.proxy.settings.set({ value: data });
+          browser.test.sendMessage("proxied");
+          return;
+        }
+        browser.test.log(`=== dns resolve test ${JSON.stringify(data)}`);
+        browser.dns
+          .resolve(data.hostname, data.flags)
+          .then(result => {
+            browser.test.log(
+              `=== dns resolve result ${JSON.stringify(result)}`
+            );
+            browser.test.sendMessage("resolved", result);
+          })
+          .catch(e => {
+            browser.test.log(`=== dns resolve error ${e.message}`);
+            browser.test.sendMessage("resolved", { message: e.message });
+          });
+      });
+      browser.test.sendMessage("ready");
+    },
+    incognitoOverride: "spanning",
+    useAddonManager: "temporary",
+  });
+}
+
+const tests = [
+  {
+    request: {
+      hostname: "localhost",
+    },
+    expect: {
+      addresses: ["127.0.0.1"], // ipv6 disabled , "::1"
+    },
+  },
+  {
+    request: {
+      hostname: "localhost",
+      flags: ["offline"],
+    },
+    expect: {
+      addresses: ["127.0.0.1"], // ipv6 disabled , "::1"
+    },
+  },
+  {
+    request: {
+      hostname: "test.example",
+    },
+    expect: {
+      // android will error with offline
+      error: /NS_ERROR_UNKNOWN_HOST|NS_ERROR_OFFLINE/,
+    },
+  },
+  {
+    request: {
+      hostname: "127.0.0.1",
+      flags: ["canonical_name"],
+    },
+    expect: {
+      canonicalName: "127.0.0.1",
+      addresses: ["127.0.0.1"],
+    },
+  },
+  {
+    request: {
+      hostname: "localhost",
+      flags: ["disable_ipv6"],
+    },
+    expect: {
+      addresses: ["127.0.0.1"],
+    },
+  },
+];
+
+add_setup(async function startup() {
+  await AddonTestUtils.promiseStartupManager();
+});
+
+add_task(async function test_dns_resolve() {
+  let extension = getExtension();
+  await extension.startup();
+  await extension.awaitMessage("ready");
+
+  for (let test of tests) {
+    extension.sendMessage("resolve", test.request);
+    let result = await extension.awaitMessage("resolved");
+    if (test.expect.error) {
+      ok(
+        test.expect.error.test(result.message),
+        `expected error ${result.message}`
+      );
+    } else {
+      equal(
+        result.canonicalName,
+        test.expect.canonicalName,
+        "canonicalName match"
+      );
+      // It seems there are platform differences happening that make this
+      // testing difficult. We're going to rely on other existing dns tests to validate
+      // the dns service itself works and only validate that we're getting generally
+      // expected results in the webext api.
+      ok(
+        result.addresses.length >= test.expect.addresses.length,
+        "expected number of addresses returned"
+      );
+      if (test.expect.addresses.length && result.addresses.length) {
+        ok(
+          result.addresses.includes(test.expect.addresses[0]),
+          "got expected ip address"
+        );
+      }
+    }
+  }
+
+  await extension.unload();
+});
+
+add_task(async function test_dns_resolve_socks() {
+  let extension = getExtension();
+  await extension.startup();
+  await extension.awaitMessage("ready");
+  extension.sendMessage("proxy", {
+    proxyType: "manual",
+    socks: "127.0.0.1",
+    socksVersion: 5,
+    proxyDNS: true,
+  });
+  await extension.awaitMessage("proxied");
+  equal(
+    Services.prefs.getIntPref("network.proxy.type"),
+    1 /* PROXYCONFIG_MANUAL */,
+    "manual proxy"
+  );
+  equal(
+    Services.prefs.getStringPref("network.proxy.socks"),
+    "127.0.0.1",
+    "socks proxy"
+  );
+  ok(
+    Services.prefs.getBoolPref("network.proxy.socks_remote_dns"),
+    "socks remote dns"
+  );
+  extension.sendMessage("resolve", {
+    hostname: "mozilla.org",
+  });
+  let result = await extension.awaitMessage("resolved");
+  ok(
+    /NS_ERROR_UNKNOWN_PROXY_HOST/.test(result.message),
+    `expected error ${result.message}`
+  );
+  await extension.unload();
+});
diff --git a/toolkit/components/extensions/test/xpcshell/test_ext_downloads.js b/toolkit/components/extensions/test/xpcshell/test_ext_downloads.js
new file mode 100644
index 0000000000..f65df707e1
--- /dev/null
+++ b/toolkit/components/extensions/test/xpcshell/test_ext_downloads.js
@@ -0,0 +1,38 @@
+/* -*- Mode: indent-tabs-mode: nil; js-indent-level: 2 -*- */
+/* vim: set sts=2 sw=2 et tw=80: */
+"use strict";
+
+add_task(async function test_downloads_api_namespace_and_permissions() {
+  function backgroundScript() {
+    browser.test.assertTrue(!!browser.downloads, "`downloads` API is present.");
+    browser.test.assertTrue(
+      !!browser.downloads.FilenameConflictAction,
+      "`downloads.FilenameConflictAction` enum is present."
+    );
+    browser.test.assertTrue(
+      !!browser.downloads.InterruptReason,
+      "`downloads.InterruptReason` enum is present."
+    );
+    browser.test.assertTrue(
+      !!browser.downloads.DangerType,
+      "`downloads.DangerType` enum is present."
+    );
+    browser.test.assertTrue(
+      !!browser.downloads.State,
+      "`downloads.State` enum is present."
+    );
+    browser.test.notifyPass("downloads tests");
+  }
+
+  let extensionData = {
+    background: backgroundScript,
+    manifest: {
+      permissions: ["downloads", "downloads.open"],
+    },
+  };
+
+  let extension = ExtensionTestUtils.loadExtension(extensionData);
+  await extension.startup();
+  await extension.awaitFinish("downloads tests");
+  await extension.unload();
+});
diff --git a/toolkit/components/extensions/test/xpcshell/test_ext_downloads_cookieStoreId.js b/toolkit/components/extensions/test/xpcshell/test_ext_downloads_cookieStoreId.js
new file mode 100644
index 0000000000..e79e3adbfb
--- /dev/null
+++ b/toolkit/components/extensions/test/xpcshell/test_ext_downloads_cookieStoreId.js
@@ -0,0 +1,469 @@
+/* -*- Mode: indent-tabs-mode: nil; js-indent-level: 2 -*- */
+/* vim: set sts=2 sw=2 et tw=80: */
+"use strict";
+
+function cookiesToMime(cookies) {
+  return `dummy/${encodeURIComponent(cookies)}`.toLowerCase();
+}
+
+function mimeToCookies(mime) {
+  return decodeURIComponent(mime.replace("dummy/", ""));
+}
+
+const server = createHttpServer({ hosts: ["example.net"] });
+
+server.registerPathHandler("/download", (request, response) => {
+  response.setStatusLine(request.httpVersion, 200, "OK");
+  let cookies = request.hasHeader("Cookie") ? request.getHeader("Cookie") : "";
+  // Assign the result through the MIME-type, to make it easier to read the
+  // result via the downloads API.
+  response.setHeader("Content-Type", cookiesToMime(cookies));
+  // Response of length 7.
+  response.write("1234567");
+});
+
+const DOWNLOAD_URL = "http://example.net/download";
+
+async function setUpCookies() {
+  Services.cookies.removeAll();
+  let extension = ExtensionTestUtils.loadExtension({
+    incognitoOverride: "spanning",
+    manifest: {
+      permissions: ["cookies", "http://example.net/download"],
+    },
+    async background() {
+      let url = "http://example.net/download";
+      // Add default cookie
+      await browser.cookies.set({
+        url,
+        name: "cookie_normal",
+        value: "1",
+      });
+
+      // Add private cookie
+      await browser.cookies.set({
+        url,
+        storeId: "firefox-private",
+        name: "cookie_private",
+        value: "1",
+      });
+
+      // Add container cookie
+      await browser.cookies.set({
+        url,
+        storeId: "firefox-container-1",
+        name: "cookie_container",
+        value: "1",
+      });
+      browser.test.sendMessage("cookies set");
+    },
+  });
+  await extension.startup();
+  await extension.awaitMessage("cookies set");
+  await extension.unload();
+}
+
+function createDownloadTestExtension(extraPermissions = [], incognito = false) {
+  let extensionOptions = {
+    manifest: {
+      permissions: ["downloads", ...extraPermissions],
+    },
+    background() {
+      browser.test.onMessage.addListener(async (method, data) => {
+        async function getDownload(data) {
+          let donePromise = new Promise(resolve => {
+            browser.downloads.onChanged.addListener(async delta => {
+              if (delta.state?.current === "complete") {
+                resolve(delta.id);
+              }
+            });
+          });
+          let downloadId = await browser.downloads.download(data);
+          browser.test.assertEq(await donePromise, downloadId, "got download");
+          let [download] = await browser.downloads.search({ id: downloadId });
+          browser.test.log(`Download results: ${JSON.stringify(download)}`);
+          // Delete the file since we aren't interested in it.
+          // TODO bug 1654819: On Windows the file may be recreated.
+          await browser.downloads.removeFile(download.id);
+          // Sanity check to verify that we got the result from /download.
+          browser.test.assertEq(7, download.fileSize, "download succeeded");
+          return download;
+        }
+        function checkDownloadError(data) {
+          return browser.test.assertRejects(
+            browser.downloads.download(data.downloadData),
+            data.exceptionRe
+          );
+        }
+        function search(data) {
+          return browser.downloads.search(data);
+        }
+        function erase(data) {
+          return browser.downloads.erase(data);
+        }
+        switch (method) {
+          case "getDownload":
+            return browser.test.sendMessage(method, await getDownload(data));
+          case "checkDownloadError":
+            return browser.test.sendMessage(
+              method,
+              await checkDownloadError(data)
+            );
+          case "search":
+            return browser.test.sendMessage(method, await search(data));
+          case "erase":
+            return browser.test.sendMessage(method, await erase(data));
+        }
+      });
+    },
+  };
+  if (incognito) {
+    extensionOptions.incognitoOverride = "spanning";
+  }
+  return ExtensionTestUtils.loadExtension(extensionOptions);
+}
+
+function getResult(extension, method, data) {
+  extension.sendMessage(method, data);
+  return extension.awaitMessage(method);
+}
+
+async function getCookies(extension, data) {
+  let download = await getResult(extension, "getDownload", data);
+  // The "/download" endpoint mirrors received cookies via Content-Type.
+  let cookies = mimeToCookies(download.mime);
+  return cookies;
+}
+
+async function runTests(extension, containerDownloadAllowed, privateAllowed) {
+  let forcedIncognitoException = null;
+  if (!privateAllowed) {
+    forcedIncognitoException = /private browsing access not allowed/;
+  } else if (!containerDownloadAllowed) {
+    forcedIncognitoException = /No permission for cookieStoreId/;
+  }
+
+  // Test default container download
+  if (containerDownloadAllowed) {
+    equal(
+      await getCookies(extension, {
+        url: DOWNLOAD_URL,
+        cookieStoreId: "firefox-default",
+      }),
+      "cookie_normal=1",
+      "Default container cookies for downloads.download"
+    );
+  } else {
+    await getResult(extension, "checkDownloadError", {
+      exceptionRe: /No permission for cookieStoreId/,
+      downloadData: {
+        url: DOWNLOAD_URL,
+        cookieStoreId: "firefox-default",
+      },
+    });
+  }
+
+  // Test private container download
+  if (privateAllowed && containerDownloadAllowed) {
+    equal(
+      await getCookies(extension, {
+        url: DOWNLOAD_URL,
+        cookieStoreId: "firefox-private",
+        incognito: true,
+      }),
+      "cookie_private=1",
+      "Private container cookies for downloads.download"
+    );
+  } else {
+    await getResult(extension, "checkDownloadError", {
+      exceptionRe: forcedIncognitoException,
+      downloadData: {
+        url: DOWNLOAD_URL,
+        cookieStoreId: "firefox-private",
+        incognito: true,
+      },
+    });
+  }
+
+  // Test firefox-container-1 download
+  if (containerDownloadAllowed) {
+    equal(
+      await getCookies(extension, {
+        url: DOWNLOAD_URL,
+        cookieStoreId: "firefox-container-1",
+      }),
+      "cookie_container=1",
+      "firefox-container-1 cookies for downloads.download"
+    );
+  } else {
+    await getResult(extension, "checkDownloadError", {
+      exceptionRe: /No permission for cookieStoreId/,
+      downloadData: {
+        url: DOWNLOAD_URL,
+        cookieStoreId: "firefox-container-1",
+      },
+    });
+  }
+
+  // Test mismatched incognito and cookieStoreId download
+  await getResult(extension, "checkDownloadError", {
+    exceptionRe: forcedIncognitoException
+      ? forcedIncognitoException
+      : /Illegal to set non-private cookieStoreId in a private window/,
+    downloadData: {
+      url: DOWNLOAD_URL,
+      incognito: true,
+      cookieStoreId: "firefox-container-1",
+    },
+  });
+  await getResult(extension, "checkDownloadError", {
+    exceptionRe: containerDownloadAllowed
+      ? /Illegal to set private cookieStoreId in a non-private window/
+      : /No permission for cookieStoreId/,
+    downloadData: {
+      url: DOWNLOAD_URL,
+      incognito: false,
+      cookieStoreId: "firefox-private",
+    },
+  });
+
+  // Test invalid cookieStoreId download
+  await getResult(extension, "checkDownloadError", {
+    exceptionRe: containerDownloadAllowed
+      ? /Illegal cookieStoreId/
+      : /No permission for cookieStoreId/,
+    downloadData: {
+      url: DOWNLOAD_URL,
+      cookieStoreId: "invalid-invalid-invalid",
+    },
+  });
+
+  let searchRes, searchResDownload;
+  // Test default container search
+  searchRes = await getResult(extension, "search", {
+    cookieStoreId: "firefox-default",
+  });
+  equal(
+    searchRes.length,
+    1,
+    "Default container results length for downloads.search"
+  );
+  [searchResDownload] = searchRes;
+  equal(
+    mimeToCookies(searchResDownload.mime),
+    "cookie_normal=1",
+    "Default container cookies for downloads.search"
+  );
+  // Test default container search with mismatched container
+  searchRes = await getResult(extension, "search", {
+    mime: cookiesToMime("cookie_normal=1"),
+    cookieStoreId: "firefox-container-1",
+  });
+  equal(
+    searchRes.length,
+    0,
+    "Default container results length for downloads.search when container mismatched"
+  );
+
+  // Test private container search
+  searchRes = await getResult(extension, "search", {
+    cookieStoreId: "firefox-private",
+  });
+  if (privateAllowed) {
+    equal(
+      searchRes.length,
+      1,
+      "Private container results length for downloads.search"
+    );
+    [searchResDownload] = searchRes;
+    equal(
+      mimeToCookies(searchResDownload.mime),
+      "cookie_private=1",
+      "Private container cookies for downloads.search"
+    );
+    // Test private container search with mismatched container
+    searchRes = await getResult(extension, "search", {
+      mime: cookiesToMime("cookie_private=1"),
+      cookieStoreId: "firefox-container-1",
+    });
+    equal(
+      searchRes.length,
+      0,
+      "Private container results length for downloads.search when container mismatched"
+    );
+  } else {
+    equal(
+      searchRes.length,
+      0,
+      "Private container results length for downloads.search when private disallowed"
+    );
+  }
+
+  // Test firefox-container-1 search
+  searchRes = await getResult(extension, "search", {
+    cookieStoreId: "firefox-container-1",
+  });
+  equal(
+    searchRes.length,
+    1,
+    "firefox-container-1 results length for downloads.search"
+  );
+  [searchResDownload] = searchRes;
+  equal(
+    mimeToCookies(searchResDownload.mime),
+    "cookie_container=1",
+    "firefox-container-1 cookies for downloads.search"
+  );
+  // Test firefox-container-1 search with mismatched container
+  searchRes = await getResult(extension, "search", {
+    mime: cookiesToMime("cookie_container=1"),
+    cookieStoreId: "firefox-default",
+  });
+  equal(
+    searchRes.length,
+    0,
+    "firefox-container-1 container results length for downloads.search when container mismatched"
+  );
+
+  // Test default container erase with mismatched container
+  await getResult(extension, "erase", {
+    mime: cookiesToMime("cookie_normal=1"),
+    cookieStoreId: "firefox-container-1",
+  });
+  searchRes = await getResult(extension, "search", {
+    mime: cookiesToMime("cookie_normal=1"),
+  });
+  equal(
+    searchRes.length,
+    1,
+    "Default container results length for downloads.search after erase with mismatched container"
+  );
+
+  // Test private container erase with mismatched container
+  await getResult(extension, "erase", {
+    mime: cookiesToMime("cookie_private=1"),
+    cookieStoreId: "firefox-container-1",
+  });
+  searchRes = await getResult(extension, "search", {
+    mime: cookiesToMime("cookie_private=1"),
+  });
+  equal(
+    searchRes.length,
+    privateAllowed ? 1 : 0,
+    "Private container results length for downloads.search after erase with mismatched container"
+  );
+
+  // Test firefox-container-1 erase with mismatched container
+  await getResult(extension, "erase", {
+    mime: cookiesToMime("cookie_container=1"),
+    cookieStoreId: "firefox-default",
+  });
+  searchRes = await getResult(extension, "search", {
+    mime: cookiesToMime("cookie_container=1"),
+  });
+  equal(
+    searchRes.length,
+    1,
+    "firefox-container-1 results length for downloads.search after erase with mismatched container"
+  );
+
+  // Test default container erase
+  await getResult(extension, "erase", {
+    cookieStoreId: "firefox-default",
+  });
+  searchRes = await getResult(extension, "search", {
+    mime: cookiesToMime("cookie_normal=1"),
+  });
+  equal(
+    searchRes.length,
+    0,
+    "Default container results length for downloads.search after erase"
+  );
+
+  // Test private container erase
+  await getResult(extension, "erase", {
+    cookieStoreId: "firefox-private",
+  });
+  searchRes = await getResult(extension, "search", {
+    mime: cookiesToMime("cookie_private=1"),
+  });
+  // The following will also pass when incognito disabled
+  equal(
+    searchRes.length,
+    0,
+    "Private container results length for downloads.search after erase"
+  );
+
+  // Test firefox-container-1 erase
+  await getResult(extension, "erase", {
+    cookieStoreId: "firefox-container-1",
+  });
+  searchRes = await getResult(extension, "search", {
+    mime: cookiesToMime("cookie_container=1"),
+  });
+  equal(
+    searchRes.length,
+    0,
+    "firefox-container-1 results length for downloads.search after erase"
+  );
+}
+
+async function populateDownloads(extension) {
+  await getResult(extension, "erase", {});
+  await getResult(extension, "getDownload", {
+    url: DOWNLOAD_URL,
+  });
+  await getResult(extension, "getDownload", {
+    url: DOWNLOAD_URL,
+    incognito: true,
+  });
+  await getResult(extension, "getDownload", {
+    url: DOWNLOAD_URL,
+    cookieStoreId: "firefox-container-1",
+  });
+}
+
+add_task(async function setup() {
+  const nsIFile = Ci.nsIFile;
+  const downloadDir = FileUtils.getDir("TmpD", ["downloads"]);
+  downloadDir.createUnique(nsIFile.DIRECTORY_TYPE, FileUtils.PERMS_DIRECTORY);
+  Services.prefs.setIntPref("browser.download.folderList", 2);
+  Services.prefs.setComplexValue("browser.download.dir", nsIFile, downloadDir);
+  Services.prefs.setBoolPref("privacy.userContext.enabled", true);
+  await setUpCookies();
+  registerCleanupFunction(() => {
+    Services.cookies.removeAll();
+    Services.prefs.clearUserPref("browser.download.folderList");
+    Services.prefs.clearUserPref("browser.download.dir");
+    downloadDir.remove(false);
+  });
+});
+
+add_task(async function download_cookieStoreId() {
+  // Test extension with cookies permission and incognito enabled
+  let extension = createDownloadTestExtension(["cookies"], true);
+  await extension.startup();
+  await runTests(extension, true, true);
+
+  // Test extension with incognito enabled and no cookies permission
+  await populateDownloads(extension);
+  let noCookiesExtension = createDownloadTestExtension([], true);
+  await noCookiesExtension.startup();
+  await runTests(noCookiesExtension, false, true);
+  await noCookiesExtension.unload();
+
+  // Test extension with incognito disabled and no cookies permission
+  await populateDownloads(extension);
+  let noCookiesAndPrivateExtension = createDownloadTestExtension([], false);
+  await noCookiesAndPrivateExtension.startup();
+  await runTests(noCookiesAndPrivateExtension, false, false);
+  await noCookiesAndPrivateExtension.unload();
+
+  // Verify that incognito disabled test did not delete private download
+  let searchRes = await getResult(extension, "search", {
+    mime: cookiesToMime("cookie_private=1"),
+  });
+  ok(searchRes.length, "Incognito disabled does not delete private download");
+
+  await extension.unload();
+});
diff --git a/toolkit/components/extensions/test/xpcshell/test_ext_downloads_cookies.js b/toolkit/components/extensions/test/xpcshell/test_ext_downloads_cookies.js
new file mode 100644
index 0000000000..8d3984e8e2
--- /dev/null
+++ b/toolkit/components/extensions/test/xpcshell/test_ext_downloads_cookies.js
@@ -0,0 +1,219 @@
+/* -*- Mode: indent-tabs-mode: nil; js-indent-level: 2 -*- */
+/* vim: set sts=2 sw=2 et tw=80: */
+"use strict";
+
+const { UrlClassifierTestUtils } = ChromeUtils.importESModule(
+  "resource://testing-common/UrlClassifierTestUtils.sys.mjs"
+);
+
+// Value for network.cookie.cookieBehavior to reject all third-party cookies.
+const { BEHAVIOR_REJECT_FOREIGN } = Ci.nsICookieService;
+
+const server = createHttpServer({ hosts: ["example.net", "itisatracker.org"] });
+server.registerPathHandler("/setcookies", (request, response) => {
+  response.setHeader("Content-Type", "text/html; charset=utf-8", false);
+  response.setHeader("Set-Cookie", "c_none=1; sameSite=none", true);
+  response.setHeader("Set-Cookie", "c_lax=1; sameSite=lax", true);
+  response.setHeader("Set-Cookie", "c_strict=1; sameSite=strict", true);
+});
+
+server.registerPathHandler("/download", (request, response) => {
+  response.setStatusLine(request.httpVersion, 200, "OK");
+
+  let cookies = request.hasHeader("Cookie") ? request.getHeader("Cookie") : "";
+  // Assign the result through the MIME-type, to make it easier to read the
+  // result via the downloads API.
+  response.setHeader("Content-Type", `dummy/${encodeURIComponent(cookies)}`);
+  // Response of length 7.
+  response.write("1234567");
+});
+
+server.registerPathHandler("/redirect", (request, response) => {
+  response.setStatusLine(request.httpVersion, 302, "Found");
+  response.setHeader("Location", "/download");
+});
+
+function createDownloadTestExtension(extraPermissions = []) {
+  return ExtensionTestUtils.loadExtension({
+    manifest: {
+      permissions: ["downloads", ...extraPermissions],
+    },
+    incognitoOverride: "spanning",
+    background() {
+      async function getCookiesForDownload(url) {
+        let donePromise = new Promise(resolve => {
+          browser.downloads.onChanged.addListener(async delta => {
+            if (delta.state?.current === "complete") {
+              resolve(delta.id);
+            }
+          });
+        });
+        // TODO bug 1653636: Remove this when the correct browsing mode is used.
+        const incognito = browser.extension.inIncognitoContext;
+        let downloadId = await browser.downloads.download({ url, incognito });
+        browser.test.assertEq(await donePromise, downloadId, "got download");
+        let [download] = await browser.downloads.search({ id: downloadId });
+        browser.test.log(`Download results: ${JSON.stringify(download)}`);
+
+        // Delete the file since we aren't interested in it.
+        // TODO bug 1654819: On Windows the file may be recreated.
+        await browser.downloads.removeFile(download.id);
+        // Sanity check to verify that we got the result from /download.
+        browser.test.assertEq(7, download.fileSize, "download succeeded");
+
+        // The "/download" endpoint mirrors received cookies via Content-Type.
+        let cookies = decodeURIComponent(download.mime.replace("dummy/", ""));
+        return cookies;
+      }
+
+      browser.test.onMessage.addListener(async url => {
+        browser.test.sendMessage("result", await getCookiesForDownload(url));
+      });
+    },
+  });
+}
+
+async function downloadAndGetCookies(extension, url) {
+  extension.sendMessage(url);
+  return extension.awaitMessage("result");
+}
+
+add_task(async function setup() {
+  const nsIFile = Ci.nsIFile;
+  const downloadDir = FileUtils.getDir("TmpD", ["downloads"]);
+  downloadDir.createUnique(nsIFile.DIRECTORY_TYPE, FileUtils.PERMS_DIRECTORY);
+  Services.prefs.setIntPref("browser.download.folderList", 2);
+  Services.prefs.setComplexValue("browser.download.dir", nsIFile, downloadDir);
+
+  // Support sameSite=none despite the server using http instead of https.
+  Services.prefs.setBoolPref(
+    "network.cookie.sameSite.noneRequiresSecure",
+    false
+  );
+  async function loadAndClose(url) {
+    let contentPage = await ExtensionTestUtils.loadContentPage(url);
+    await contentPage.close();
+  }
+  // Generate cookies for use in this test.
+  await loadAndClose("http://example.net/setcookies");
+  await loadAndClose("http://itisatracker.org/setcookies");
+
+  await UrlClassifierTestUtils.addTestTrackers();
+  registerCleanupFunction(() => {
+    UrlClassifierTestUtils.cleanupTestTrackers();
+    Services.cookies.removeAll();
+
+    Services.prefs.clearUserPref("browser.download.folderList");
+    Services.prefs.clearUserPref("browser.download.dir");
+
+    downloadDir.remove(false);
+  });
+});
+
+// Checks that (sameSite) cookies are included in download requests.
+add_task(async function download_cookies_basic() {
+  let extension = createDownloadTestExtension(["*://example.net/*"]);
+  await extension.startup();
+
+  equal(
+    await downloadAndGetCookies(extension, "http://example.net/download"),
+    "c_none=1; c_lax=1; c_strict=1",
+    "Cookies for downloads.download with sameSite cookies"
+  );
+
+  equal(
+    await downloadAndGetCookies(extension, "http://example.net/redirect"),
+    "c_none=1; c_lax=1; c_strict=1",
+    "Cookies for downloads.download with redirect"
+  );
+
+  await runWithPrefs(
+    [["network.cookie.cookieBehavior", BEHAVIOR_REJECT_FOREIGN]],
+    async () => {
+      equal(
+        await downloadAndGetCookies(extension, "http://example.net/download"),
+        "c_none=1; c_lax=1; c_strict=1",
+        "Cookies for downloads.download with all third-party cookies disabled"
+      );
+    }
+  );
+
+  await extension.unload();
+});
+
+// Checks that (sameSite) cookies are included even when tracking protection
+// would block cookies from third-party requests.
+add_task(async function download_cookies_from_tracker_url() {
+  let extension = createDownloadTestExtension(["*://itisatracker.org/*"]);
+  await extension.startup();
+
+  equal(
+    await downloadAndGetCookies(extension, "http://itisatracker.org/download"),
+    "c_none=1; c_lax=1; c_strict=1",
+    "Cookies for downloads.download of itisatracker.org"
+  );
+
+  await extension.unload();
+});
+
+// Checks that (sameSite) cookies are included even without host permissions.
+add_task(async function download_cookies_without_host_permissions() {
+  let extension = createDownloadTestExtension();
+  await extension.startup();
+
+  equal(
+    await downloadAndGetCookies(extension, "http://example.net/download"),
+    "c_none=1; c_lax=1; c_strict=1",
+    "Cookies for downloads.download without host permissions"
+  );
+
+  equal(
+    await downloadAndGetCookies(extension, "http://itisatracker.org/download"),
+    "c_none=1; c_lax=1; c_strict=1",
+    "Cookies for downloads.download of itisatracker.org"
+  );
+
+  await runWithPrefs(
+    [["network.cookie.cookieBehavior", BEHAVIOR_REJECT_FOREIGN]],
+    async () => {
+      equal(
+        await downloadAndGetCookies(extension, "http://example.net/download"),
+        "c_none=1; c_lax=1; c_strict=1",
+        "Cookies for downloads.download with all third-party cookies disabled"
+      );
+    }
+  );
+
+  await extension.unload();
+});
+
+// Checks that (sameSite) cookies from private browsing are included.
+add_task(async function download_cookies_in_perma_private_browsing() {
+  Services.prefs.setBoolPref("browser.privatebrowsing.autostart", true);
+  Services.prefs.setBoolPref("dom.security.https_first_pbm", false);
+
+  let extension = createDownloadTestExtension(["*://example.net/*"]);
+  await extension.startup();
+
+  equal(
+    await downloadAndGetCookies(extension, "http://example.net/download"),
+    "",
+    "Initially no cookies in permanent private browsing mode"
+  );
+
+  let contentPage = await ExtensionTestUtils.loadContentPage(
+    "http://example.net/setcookies",
+    { privateBrowsing: true }
+  );
+
+  equal(
+    await downloadAndGetCookies(extension, "http://example.net/download"),
+    "c_none=1; c_lax=1; c_strict=1",
+    "Cookies for downloads.download in perma-private-browsing mode"
+  );
+
+  await extension.unload();
+  await contentPage.close();
+  Services.prefs.clearUserPref("browser.privatebrowsing.autostart");
+  Services.prefs.clearUserPref("dom.security.https_first_pbm");
+});
diff --git a/toolkit/components/extensions/test/xpcshell/test_ext_downloads_download.js b/toolkit/components/extensions/test/xpcshell/test_ext_downloads_download.js
new file mode 100644
index 0000000000..e2867d1f03
--- /dev/null
+++ b/toolkit/components/extensions/test/xpcshell/test_ext_downloads_download.js
@@ -0,0 +1,685 @@
+/* -*- Mode: indent-tabs-mode: nil; js-indent-level: 2 -*- */
+/* vim: set sts=2 sw=2 et tw=80: */
+"use strict";
+
+const { Downloads } = ChromeUtils.importESModule(
+  "resource://gre/modules/Downloads.sys.mjs"
+);
+
+const gServer = createHttpServer();
+gServer.registerDirectory("/data/", do_get_file("data"));
+
+gServer.registerPathHandler("/dir/", (_, res) => res.write("length=8"));
+
+const WINDOWS = AppConstants.platform == "win";
+
+const BASE = `http://localhost:${gServer.identity.primaryPort}/`;
+const FILE_NAME = "file_download.txt";
+const FILE_NAME_W_SPACES = "file   download.txt";
+const FILE_URL = BASE + "data/" + FILE_NAME;
+const FILE_NAME_UNIQUE = "file_download(1).txt";
+const FILE_LEN = 46;
+
+let downloadDir;
+
+function joinPath(...components) {
+  const separator = WINDOWS ? "\\" : "/";
+
+  return components.join(separator);
+}
+
+function setup() {
+  downloadDir = FileUtils.getDir("TmpD", ["downloads"]);
+  downloadDir.createUnique(
+    Ci.nsIFile.DIRECTORY_TYPE,
+    FileUtils.PERMS_DIRECTORY
+  );
+  info(`Using download directory ${downloadDir.path}`);
+
+  Services.prefs.setIntPref("browser.download.folderList", 2);
+  Services.prefs.setComplexValue(
+    "browser.download.dir",
+    Ci.nsIFile,
+    downloadDir
+  );
+
+  registerCleanupFunction(() => {
+    Services.prefs.clearUserPref("browser.download.folderList");
+    Services.prefs.clearUserPref("browser.download.dir");
+
+    let entries = downloadDir.directoryEntries;
+    while (entries.hasMoreElements()) {
+      let entry = entries.nextFile;
+      ok(false, `Leftover file ${entry.path} in download directory`);
+      entry.remove(false);
+    }
+
+    downloadDir.remove(false);
+  });
+}
+
+function backgroundScript() {
+  let blobUrl;
+  browser.test.onMessage.addListener(async (msg, ...args) => {
+    if (msg == "download.request") {
+      let options = args[0];
+
+      if (options.blobme) {
+        let blob = new Blob(options.blobme);
+        delete options.blobme;
+        blobUrl = options.url = window.URL.createObjectURL(blob);
+      }
+
+      try {
+        let id = await browser.downloads.download(options);
+        browser.test.sendMessage("download.done", { status: "success", id });
+      } catch (error) {
+        browser.test.sendMessage("download.done", {
+          status: "error",
+          errmsg: error.message,
+        });
+      }
+    } else if (msg == "killTheBlob") {
+      window.URL.revokeObjectURL(blobUrl);
+      blobUrl = null;
+    }
+  });
+
+  browser.test.sendMessage("ready");
+}
+
+// This function is a bit of a sledgehammer, it looks at every download
+// the browser knows about and waits for all active downloads to complete.
+// But we only start one at a time and only do a handful in total, so
+// this lets us test download() without depending on anything else.
+async function waitForDownloads() {
+  let list = await Downloads.getList(Downloads.ALL);
+  let downloads = await list.getAll();
+
+  let inprogress = downloads.filter(dl => !dl.stopped);
+  return Promise.all(inprogress.map(dl => dl.whenSucceeded()));
+}
+
+// Create a file in the downloads directory.
+function touch(filename) {
+  let file = downloadDir.clone();
+  file.append(filename);
+  file.create(Ci.nsIFile.NORMAL_FILE_TYPE, FileUtils.PERMS_FILE);
+}
+
+// Remove a file in the downloads directory.
+function remove(filename, recursive = false) {
+  let file = downloadDir.clone();
+  file.append(filename);
+  file.remove(recursive);
+}
+
+add_task(async function test_downloads() {
+  setup();
+
+  let extension = ExtensionTestUtils.loadExtension({
+    background: `(${backgroundScript})()`,
+    manifest: {
+      permissions: ["downloads"],
+    },
+    incognitoOverride: "spanning",
+  });
+
+  function download(options) {
+    extension.sendMessage("download.request", options);
+    return extension.awaitMessage("download.done");
+  }
+
+  async function testDownload(options, localFile, expectedSize, description) {
+    let msg = await download(options);
+    equal(
+      msg.status,
+      "success",
+      `downloads.download() works with ${description}`
+    );
+
+    await waitForDownloads();
+
+    let localPath = downloadDir.clone();
+    let parts = Array.isArray(localFile) ? localFile : [localFile];
+
+    parts.map(p => localPath.append(p));
+    equal(
+      localPath.fileSize,
+      expectedSize,
+      "Downloaded file has expected size"
+    );
+    localPath.remove(false);
+  }
+
+  await extension.startup();
+  await extension.awaitMessage("ready");
+  info("extension started");
+
+  // Call download() with just the url property.
+  await testDownload({ url: FILE_URL }, FILE_NAME, FILE_LEN, "just source");
+
+  // Call download() with a filename property.
+  await testDownload(
+    {
+      url: FILE_URL,
+      filename: "newpath.txt",
+    },
+    "newpath.txt",
+    FILE_LEN,
+    "source and filename"
+  );
+
+  // Call download() with a filename with subdirs.
+  await testDownload(
+    {
+      url: FILE_URL,
+      filename: "sub/dir/file",
+    },
+    ["sub", "dir", "file"],
+    FILE_LEN,
+    "source and filename with subdirs"
+  );
+
+  // Call download() with a filename with existing subdirs.
+  await testDownload(
+    {
+      url: FILE_URL,
+      filename: "sub/dir/file2",
+    },
+    ["sub", "dir", "file2"],
+    FILE_LEN,
+    "source and filename with existing subdirs"
+  );
+
+  // Only run Windows path separator test on Windows.
+  if (WINDOWS) {
+    // Call download() with a filename with Windows path separator.
+    await testDownload(
+      {
+        url: FILE_URL,
+        filename: "sub\\dir\\file3",
+      },
+      ["sub", "dir", "file3"],
+      FILE_LEN,
+      "filename with Windows path separator"
+    );
+  }
+  remove("sub", true);
+
+  // Call download(), filename with subdir, skipping parts.
+  await testDownload(
+    {
+      url: FILE_URL,
+      filename: "skip//part",
+    },
+    ["skip", "part"],
+    FILE_LEN,
+    "source, filename, with subdir, skipping parts"
+  );
+  remove("skip", true);
+
+  // Check conflictAction of "uniquify".
+  touch(FILE_NAME);
+  await testDownload(
+    {
+      url: FILE_URL,
+      conflictAction: "uniquify",
+    },
+    FILE_NAME_UNIQUE,
+    FILE_LEN,
+    "conflictAction=uniquify"
+  );
+  // todo check that preexisting file was not modified?
+  remove(FILE_NAME);
+
+  // Check conflictAction of "overwrite".
+  touch(FILE_NAME);
+  await testDownload(
+    {
+      url: FILE_URL,
+      conflictAction: "overwrite",
+    },
+    FILE_NAME,
+    FILE_LEN,
+    "conflictAction=overwrite"
+  );
+
+  // Try to download in invalid url
+  await download({ url: "this is not a valid URL" }).then(msg => {
+    equal(msg.status, "error", "downloads.download() fails with invalid url");
+    ok(
+      /not a valid URL/.test(msg.errmsg),
+      "error message for invalid url is correct"
+    );
+  });
+
+  // Try to download to an empty path.
+  await download({
+    url: FILE_URL,
+    filename: "",
+  }).then(msg => {
+    equal(
+      msg.status,
+      "error",
+      "downloads.download() fails with empty filename"
+    );
+    equal(
+      msg.errmsg,
+      "filename must not be empty",
+      "error message for empty filename is correct"
+    );
+  });
+
+  // Try to download to an absolute path.
+  const absolutePath = PathUtils.join(
+    WINDOWS ? "C:\\tmp" : "/tmp",
+    "file_download.txt"
+  );
+  await download({
+    url: FILE_URL,
+    filename: absolutePath,
+  }).then(msg => {
+    equal(
+      msg.status,
+      "error",
+      "downloads.download() fails with absolute filename"
+    );
+    equal(
+      msg.errmsg,
+      "filename must not be an absolute path",
+      `error message for absolute path (${absolutePath}) is correct`
+    );
+  });
+
+  if (WINDOWS) {
+    await download({
+      url: FILE_URL,
+      filename: "C:\\file_download.txt",
+    }).then(msg => {
+      equal(
+        msg.status,
+        "error",
+        "downloads.download() fails with absolute filename"
+      );
+      equal(
+        msg.errmsg,
+        "filename must not be an absolute path",
+        "error message for absolute path with drive letter is correct"
+      );
+    });
+  }
+
+  // Try to download to a relative path containing ..
+  await download({
+    url: FILE_URL,
+    filename: joinPath("..", "file_download.txt"),
+  }).then(msg => {
+    equal(
+      msg.status,
+      "error",
+      "downloads.download() fails with back-references"
+    );
+    equal(
+      msg.errmsg,
+      "filename must not contain back-references (..)",
+      "error message for back-references is correct"
+    );
+  });
+
+  // Try to download to a long relative path containing ..
+  await download({
+    url: FILE_URL,
+    filename: joinPath("foo", "..", "..", "file_download.txt"),
+  }).then(msg => {
+    equal(
+      msg.status,
+      "error",
+      "downloads.download() fails with back-references"
+    );
+    equal(
+      msg.errmsg,
+      "filename must not contain back-references (..)",
+      "error message for back-references is correct"
+    );
+  });
+
+  // Test illegal characters.
+  await download({
+    url: FILE_URL,
+    filename: "like:this",
+  }).then(msg => {
+    equal(msg.status, "error", "downloads.download() fails with illegal chars");
+    equal(
+      msg.errmsg,
+      "filename must not contain illegal characters",
+      "error message correct"
+    );
+  });
+
+  // Try to download a blob url
+  const BLOB_STRING = "Hello, world";
+  await testDownload(
+    {
+      blobme: [BLOB_STRING],
+      filename: FILE_NAME,
+    },
+    FILE_NAME,
+    BLOB_STRING.length,
+    "blob url"
+  );
+  extension.sendMessage("killTheBlob");
+
+  // Try to download a blob url without a given filename
+  await testDownload(
+    {
+      blobme: [BLOB_STRING],
+    },
+    "download",
+    BLOB_STRING.length,
+    "blob url with no filename"
+  );
+  extension.sendMessage("killTheBlob");
+
+  // Download a normal URL with an empty filename part.
+  await testDownload(
+    {
+      url: BASE + "dir/",
+    },
+    "download",
+    8,
+    "normal url with empty filename"
+  );
+
+  // Download a filename with multiple spaces, url is ignored for this test.
+  await testDownload(
+    {
+      url: FILE_URL,
+      filename: "a   file.txt",
+    },
+    "a   file.txt",
+    FILE_LEN,
+    "filename with multiple spaces"
+  );
+
+  // Download a normal URL with a leafname containing multiple spaces.
+  // Note: spaces are compressed by file name normalization.
+  await testDownload(
+    {
+      url: BASE + "data/" + FILE_NAME_W_SPACES,
+    },
+    FILE_NAME_W_SPACES.replace(/\s+/, " "),
+    FILE_LEN,
+    "leafname with multiple spaces"
+  );
+
+  // Check that the "incognito" property is supported.
+  await testDownload(
+    {
+      url: FILE_URL,
+      incognito: false,
+    },
+    FILE_NAME,
+    FILE_LEN,
+    "incognito=false"
+  );
+
+  await testDownload(
+    {
+      url: FILE_URL,
+      incognito: true,
+    },
+    FILE_NAME,
+    FILE_LEN,
+    "incognito=true"
+  );
+
+  await extension.unload();
+});
+
+async function testHttpErrors(allowHttpErrors) {
+  const server = createHttpServer();
+  const url = `http://localhost:${server.identity.primaryPort}/error`;
+  const content = "HTTP Error test";
+
+  server.registerPathHandler("/error", (request, response) => {
+    response.setStatusLine(
+      "1.1",
+      parseInt(request.queryString, 10),
+      "Some Error"
+    );
+    response.setHeader("Content-Type", "text/plain", false);
+    response.setHeader("Content-Length", content.length.toString());
+    response.write(content);
+  });
+
+  function background(code) {
+    let dlid = 0;
+    let expectedState;
+    browser.test.onMessage.addListener(async options => {
+      try {
+        expectedState = options.allowHttpErrors ? "complete" : "interrupted";
+        dlid = await browser.downloads.download(options);
+      } catch (err) {
+        browser.test.fail(`Unexpected error in downloads.download(): ${err}`);
+      }
+    });
+    function onChanged({ id, state }) {
+      if (dlid !== id || !state || state.current === "in_progress") {
+        return;
+      }
+      browser.test.assertEq(state.current, expectedState, "correct state");
+      browser.downloads.search({ id }).then(([download]) => {
+        browser.test.sendMessage("done", download.error);
+      });
+    }
+    browser.downloads.onChanged.addListener(onChanged);
+  }
+
+  const extension = ExtensionTestUtils.loadExtension({
+    manifest: {
+      permissions: ["downloads"],
+    },
+    background,
+  });
+  await extension.startup();
+
+  async function download(code, expected_when_disallowed) {
+    const options = {
+      url: url + "?" + code,
+      filename: `test-${code}`,
+      conflictAction: "overwrite",
+      allowHttpErrors,
+    };
+    extension.sendMessage(options);
+    const rv = await extension.awaitMessage("done");
+
+    if (allowHttpErrors) {
+      const localPath = downloadDir.clone();
+      localPath.append(options.filename);
+      equal(
+        localPath.fileSize,
+        // The 20x No content errors will not produce any response body,
+        // only "true" errors do.
+        code >= 400 ? content.length : 0,
+        "Downloaded file has expected size" + code
+      );
+      localPath.remove(false);
+
+      ok(!rv, "error must be ignored and hence false-y");
+      return;
+    }
+
+    equal(
+      rv,
+      expected_when_disallowed,
+      "error must have the correct InterruptReason"
+    );
+  }
+
+  await download(204, "SERVER_BAD_CONTENT"); // No Content
+  await download(205, "SERVER_BAD_CONTENT"); // Reset Content
+  await download(404, "SERVER_BAD_CONTENT"); // Not Found
+  await download(403, "SERVER_FORBIDDEN"); // Forbidden
+  await download(402, "SERVER_UNAUTHORIZED"); // Unauthorized
+  await download(407, "SERVER_UNAUTHORIZED"); // Proxy auth required
+  await download(504, "SERVER_FAILED"); //General errors, here Gateway Timeout
+
+  await extension.unload();
+}
+
+add_task(function test_download_disallowed_http_errors() {
+  return testHttpErrors(false);
+});
+
+add_task(function test_download_allowed_http_errors() {
+  return testHttpErrors(true);
+});
+
+add_task(async function test_download_http_details() {
+  const server = createHttpServer();
+  const url = `http://localhost:${server.identity.primaryPort}/post-log`;
+
+  let received;
+  server.registerPathHandler("/post-log", (request, response) => {
+    received = request;
+    response.setHeader("Set-Cookie", "monster=", false);
+  });
+
+  // Confirm received vs. expected values.
+  function confirm(method, headers = {}, body) {
+    equal(received.method, method, "method is correct");
+
+    for (let name in headers) {
+      ok(received.hasHeader(name), `header ${name} received`);
+      equal(
+        received.getHeader(name),
+        headers[name],
+        `header ${name} is correct`
+      );
+    }
+
+    if (body) {
+      const str = NetUtil.readInputStreamToString(
+        received.bodyInputStream,
+        received.bodyInputStream.available()
+      );
+      equal(str, body, "body is correct");
+    }
+  }
+
+  function background() {
+    browser.test.onMessage.addListener(async options => {
+      try {
+        await browser.downloads.download(options);
+      } catch (err) {
+        browser.test.sendMessage("done", { err: err.message });
+      }
+    });
+    browser.downloads.onChanged.addListener(({ state }) => {
+      if (state && state.current === "complete") {
+        browser.test.sendMessage("done", { ok: true });
+      }
+    });
+  }
+
+  const extension = ExtensionTestUtils.loadExtension({
+    manifest: {
+      permissions: ["downloads"],
+    },
+    background,
+    incognitoOverride: "spanning",
+  });
+  await extension.startup();
+
+  function download(options) {
+    options.url = url;
+    options.conflictAction = "overwrite";
+
+    extension.sendMessage(options);
+    return extension.awaitMessage("done");
+  }
+
+  // Test that site cookies are sent with download requests,
+  // and "incognito" downloads use a separate cookie jar.
+  let testDownloadCookie = async function (incognito) {
+    let result = await download({ incognito });
+    ok(result.ok, `preflight to set cookies with incognito=${incognito}`);
+    ok(!received.hasHeader("cookie"), "first request has no cookies");
+
+    result = await download({ incognito });
+    ok(result.ok, `download with cookie with incognito=${incognito}`);
+    equal(
+      received.getHeader("cookie"),
+      "monster=",
+      "correct cookie header sent for second download"
+    );
+  };
+
+  await testDownloadCookie(false);
+  await testDownloadCookie(true);
+
+  // Test method option.
+  let result = await download({});
+  ok(result.ok, "download works without the method option, defaults to GET");
+  confirm("GET");
+
+  result = await download({ method: "PUT" });
+  ok(!result.ok, "download rejected with PUT method");
+  ok(
+    /method: Invalid enumeration/.test(result.err),
+    "descriptive error message"
+  );
+
+  result = await download({ method: "POST" });
+  ok(result.ok, "download works with POST method");
+  confirm("POST");
+
+  // Test body option values.
+  result = await download({ body: [] });
+  ok(!result.ok, "download rejected because of non-string body");
+  ok(/body: Expected string/.test(result.err), "descriptive error message");
+
+  result = await download({ method: "POST", body: "of work" });
+  ok(result.ok, "download works with POST method and body");
+  confirm("POST", { "Content-Length": 7 }, "of work");
+
+  // Test custom headers.
+  result = await download({ headers: [{ name: "X-Custom" }] });
+  ok(!result.ok, "download rejected because of missing header value");
+  ok(/"value" is required/.test(result.err), "descriptive error message");
+
+  result = await download({ headers: [{ name: "X-Custom", value: "13" }] });
+  ok(result.ok, "download works with a custom header");
+  confirm("GET", { "X-Custom": "13" });
+
+  // Test Referer header.
+  const referer = "http://example.org/test";
+  result = await download({ headers: [{ name: "Referer", value: referer }] });
+  ok(result.ok, "download works with Referer header");
+  confirm("GET", { Referer: referer });
+
+  // Test forbidden headers.
+  result = await download({ headers: [{ name: "DNT", value: "1" }] });
+  ok(!result.ok, "download rejected because of forbidden header name DNT");
+  ok(/Forbidden request header/.test(result.err), "descriptive error message");
+
+  result = await download({
+    headers: [{ name: "Proxy-Connection", value: "keep" }],
+  });
+  ok(
+    !result.ok,
+    "download rejected because of forbidden header name prefix Proxy-"
+  );
+  ok(/Forbidden request header/.test(result.err), "descriptive error message");
+
+  result = await download({ headers: [{ name: "Sec-ret", value: "13" }] });
+  ok(
+    !result.ok,
+    "download rejected because of forbidden header name prefix Sec-"
+  );
+  ok(/Forbidden request header/.test(result.err), "descriptive error message");
+
+  remove("post-log");
+  await extension.unload();
+});
diff --git a/toolkit/components/extensions/test/xpcshell/test_ext_downloads_eventpage.js b/toolkit/components/extensions/test/xpcshell/test_ext_downloads_eventpage.js
new file mode 100644
index 0000000000..9c71c63e96
--- /dev/null
+++ b/toolkit/components/extensions/test/xpcshell/test_ext_downloads_eventpage.js
@@ -0,0 +1,162 @@
+"use strict";
+
+AddonTestUtils.init(this);
+AddonTestUtils.overrideCertDB();
+AddonTestUtils.createAppInfo(
+  "xpcshell@tests.mozilla.org",
+  "XPCShell",
+  "42",
+  "42"
+);
+
+const server = createHttpServer();
+server.registerDirectory("/data/", do_get_file("data"));
+
+const BASE = `http://localhost:${server.identity.primaryPort}/data`;
+const TXT_FILE = "file_download.txt";
+const TXT_URL = BASE + "/" + TXT_FILE;
+
+add_task(function setup() {
+  let downloadDir = FileUtils.getDir("TmpD", ["downloads"]);
+  downloadDir.createUnique(
+    Ci.nsIFile.DIRECTORY_TYPE,
+    FileUtils.PERMS_DIRECTORY
+  );
+  info(`Using download directory ${downloadDir.path}`);
+
+  Services.prefs.setIntPref("browser.download.folderList", 2);
+  Services.prefs.setComplexValue(
+    "browser.download.dir",
+    Ci.nsIFile,
+    downloadDir
+  );
+
+  registerCleanupFunction(() => {
+    Services.prefs.clearUserPref("browser.download.folderList");
+    Services.prefs.clearUserPref("browser.download.dir");
+
+    let entries = downloadDir.directoryEntries;
+    while (entries.hasMoreElements()) {
+      let entry = entries.nextFile;
+      ok(false, `Leftover file ${entry.path} in download directory`);
+      entry.remove(false);
+    }
+
+    downloadDir.remove(false);
+  });
+});
+
+add_task(
+  { pref_set: [["extensions.eventPages.enabled", true]] },
+  async function test_downloads_event_page() {
+    await AddonTestUtils.promiseStartupManager();
+
+    // A simple download driving extension
+    let dl_extension = ExtensionTestUtils.loadExtension({
+      manifest: {
+        browser_specific_settings: { gecko: { id: "downloader@mochitest" } },
+        permissions: ["downloads"],
+        background: { persistent: false },
+      },
+      background() {
+        let downloadId;
+        browser.downloads.onChanged.addListener(async info => {
+          if (info.state && info.state.current === "complete") {
+            browser.test.sendMessage("downloadComplete");
+          }
+        });
+        browser.test.onMessage.addListener(async (msg, opts) => {
+          if (msg == "download") {
+            downloadId = await browser.downloads.download(opts);
+          }
+          if (msg == "erase") {
+            await browser.downloads.removeFile(downloadId);
+            await browser.downloads.erase({ id: downloadId });
+          }
+        });
+      },
+    });
+    await dl_extension.startup();
+
+    let extension = ExtensionTestUtils.loadExtension({
+      useAddonManager: "permanent",
+      manifest: {
+        permissions: ["downloads"],
+        background: { persistent: false },
+      },
+      background() {
+        browser.downloads.onChanged.addListener(() => {
+          browser.test.sendMessage("onChanged");
+        });
+        browser.downloads.onCreated.addListener(() => {
+          browser.test.sendMessage("onCreated");
+        });
+        browser.downloads.onErased.addListener(() => {
+          browser.test.sendMessage("onErased");
+        });
+        browser.test.sendMessage("ready");
+      },
+    });
+
+    // onDeterminingFilename is never persisted, it is an empty event handler.
+    const EVENTS = ["onChanged", "onCreated", "onErased"];
+
+    await extension.startup();
+    await extension.awaitMessage("ready");
+    for (let event of EVENTS) {
+      assertPersistentListeners(extension, "downloads", event, {
+        primed: false,
+      });
+    }
+
+    await extension.terminateBackground({ disableResetIdleForTest: true });
+    ok(
+      !extension.extension.backgroundContext,
+      "Background Extension context should have been destroyed"
+    );
+
+    for (let event of EVENTS) {
+      assertPersistentListeners(extension, "downloads", event, {
+        primed: true,
+      });
+    }
+
+    // test download events waken background
+    dl_extension.sendMessage("download", {
+      url: TXT_URL,
+      filename: TXT_FILE,
+    });
+    await extension.awaitMessage("ready");
+    await extension.awaitMessage("onCreated");
+    for (let event of EVENTS) {
+      assertPersistentListeners(extension, "downloads", event, {
+        primed: false,
+      });
+    }
+    await extension.awaitMessage("onChanged");
+
+    await extension.terminateBackground({ disableResetIdleForTest: true });
+    ok(
+      !extension.extension.backgroundContext,
+      "Background Extension context should have been destroyed"
+    );
+
+    await dl_extension.awaitMessage("downloadComplete");
+    dl_extension.sendMessage("erase");
+    await extension.awaitMessage("ready");
+    await extension.awaitMessage("onErased");
+    await dl_extension.unload();
+
+    // check primed listeners after startup
+    await AddonTestUtils.promiseRestartManager();
+    await extension.awaitStartup();
+
+    for (let event of EVENTS) {
+      assertPersistentListeners(extension, "downloads", event, {
+        primed: true,
+      });
+    }
+
+    await extension.unload();
+  }
+);
diff --git a/toolkit/components/extensions/test/xpcshell/test_ext_downloads_misc.js b/toolkit/components/extensions/test/xpcshell/test_ext_downloads_misc.js
new file mode 100644
index 0000000000..d315d37aaa
--- /dev/null
+++ b/toolkit/components/extensions/test/xpcshell/test_ext_downloads_misc.js
@@ -0,0 +1,1169 @@
+/* -*- Mode: indent-tabs-mode: nil; js-indent-level: 2 -*- */
+/* vim: set sts=2 sw=2 et tw=80: */
+"use strict";
+
+const { Downloads } = ChromeUtils.importESModule(
+  "resource://gre/modules/Downloads.sys.mjs"
+);
+
+const { TestUtils } = ChromeUtils.importESModule(
+  "resource://testing-common/TestUtils.sys.mjs"
+);
+
+const server = createHttpServer();
+server.registerDirectory("/data/", do_get_file("data"));
+
+const ROOT = `http://localhost:${server.identity.primaryPort}`;
+const BASE = `${ROOT}/data`;
+const TXT_FILE = "file_download.txt";
+const TXT_URL = BASE + "/" + TXT_FILE;
+
+// Keep these in sync with code in interruptible.sjs
+const INT_PARTIAL_LEN = 15;
+const INT_TOTAL_LEN = 31;
+
+const TEST_DATA = "This is 31 bytes of sample data";
+const TOTAL_LEN = TEST_DATA.length;
+const PARTIAL_LEN = 15;
+
+// A handler to let us systematically test pausing/resuming/canceling
+// of downloads.  This target represents a small text file but a simple
+// GET will stall after sending part of the data, to give the test code
+// a chance to pause or do other operations on an in-progress download.
+// A resumed download (ie, a GET with a Range: header) will allow the
+// download to complete.
+function handleRequest(request, response) {
+  response.setHeader("Content-Type", "text/plain", false);
+
+  if (request.hasHeader("Range")) {
+    let start, end;
+    let matches = request
+      .getHeader("Range")
+      .match(/^\s*bytes=(\d+)?-(\d+)?\s*$/);
+    if (matches != null) {
+      start = matches[1] ? parseInt(matches[1], 10) : 0;
+      end = matches[2] ? parseInt(matches[2], 10) : TOTAL_LEN - 1;
+    }
+
+    if (end == undefined || end >= TOTAL_LEN) {
+      response.setStatusLine(
+        request.httpVersion,
+        416,
+        "Requested Range Not Satisfiable"
+      );
+      response.setHeader("Content-Range", `*/${TOTAL_LEN}`, false);
+      response.finish();
+      return;
+    }
+
+    response.setStatusLine(request.httpVersion, 206, "Partial Content");
+    response.setHeader("Content-Range", `${start}-${end}/${TOTAL_LEN}`, false);
+    response.write(TEST_DATA.slice(start, end + 1));
+  } else if (request.queryString.includes("stream")) {
+    response.processAsync();
+    response.setHeader("Content-Length", "10000", false);
+    response.write("!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!");
+    setInterval(() => {
+      response.write("!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!");
+    }, 50);
+  } else {
+    response.processAsync();
+    response.setHeader("Content-Length", `${TOTAL_LEN}`, false);
+    response.write(TEST_DATA.slice(0, PARTIAL_LEN));
+  }
+
+  registerCleanupFunction(() => {
+    try {
+      response.finish();
+    } catch (e) {
+      // This will throw, but we don't care at this point.
+    }
+  });
+}
+
+server.registerPrefixHandler("/interruptible/", handleRequest);
+
+let interruptibleCount = 0;
+function getInterruptibleUrl(filename = "interruptible.html") {
+  let n = interruptibleCount++;
+  return `${ROOT}/interruptible/${filename}?count=${n}`;
+}
+
+function backgroundScript() {
+  let events = new Set();
+  let eventWaiter = null;
+
+  browser.downloads.onCreated.addListener(data => {
+    events.add({ type: "onCreated", data });
+    if (eventWaiter) {
+      eventWaiter();
+    }
+  });
+
+  browser.downloads.onChanged.addListener(data => {
+    events.add({ type: "onChanged", data });
+    if (eventWaiter) {
+      eventWaiter();
+    }
+  });
+
+  browser.downloads.onErased.addListener(data => {
+    events.add({ type: "onErased", data });
+    if (eventWaiter) {
+      eventWaiter();
+    }
+  });
+
+  // Returns a promise that will resolve when the given list of expected
+  // events have all been seen.  By default, succeeds only if the exact list
+  // of expected events is seen in the given order.  options.exact can be
+  // set to false to allow other events and options.inorder can be set to
+  // false to allow the events to arrive in any order.
+  function waitForEvents(expected, options = {}) {
+    function compare(a, b) {
+      if (typeof b == "object" && b != null) {
+        if (typeof a != "object") {
+          return false;
+        }
+        return Object.keys(b).every(fld => compare(a[fld], b[fld]));
+      }
+      return a == b;
+    }
+
+    const exact = "exact" in options ? options.exact : true;
+    const inorder = "inorder" in options ? options.inorder : true;
+    return new Promise((resolve, reject) => {
+      function check() {
+        function fail(msg) {
+          browser.test.fail(msg);
+          reject(new Error(msg));
+        }
+        if (events.size < expected.length) {
+          return;
+        }
+        if (exact && expected.length < events.size) {
+          fail(
+            `Got ${events.size} events but only expected ${expected.length}`
+          );
+          return;
+        }
+
+        let remaining = new Set(events);
+        if (inorder) {
+          for (let event of events) {
+            if (compare(event, expected[0])) {
+              expected.shift();
+              remaining.delete(event);
+            }
+          }
+        } else {
+          expected = expected.filter(val => {
+            for (let remainingEvent of remaining) {
+              if (compare(remainingEvent, val)) {
+                remaining.delete(remainingEvent);
+                return false;
+              }
+            }
+            return true;
+          });
+        }
+
+        // Events that did occur have been removed from expected so if
+        // expected is empty, we're done.  If we didn't see all the
+        // expected events and we're not looking for an exact match,
+        // then we just may not have seen the event yet, so return without
+        // failing and check() will be called again when a new event arrives.
+        if (!expected.length) {
+          events = remaining;
+          eventWaiter = null;
+          resolve();
+        } else if (exact) {
+          fail(
+            `Mismatched event: expecting ${JSON.stringify(
+              expected[0]
+            )} but got ${JSON.stringify(Array.from(remaining)[0])}`
+          );
+        }
+      }
+      eventWaiter = check;
+      check();
+    });
+  }
+
+  browser.test.onMessage.addListener(async (msg, ...args) => {
+    let match = msg.match(/(\w+).request$/);
+    if (!match) {
+      return;
+    }
+
+    let what = match[1];
+    if (what == "waitForEvents") {
+      try {
+        await waitForEvents(...args);
+        browser.test.sendMessage("waitForEvents.done", { status: "success" });
+      } catch (error) {
+        browser.test.sendMessage("waitForEvents.done", {
+          status: "error",
+          errmsg: error.message,
+        });
+      }
+    } else if (what == "clearEvents") {
+      events = new Set();
+      browser.test.sendMessage("clearEvents.done", { status: "success" });
+    } else {
+      try {
+        let result = await browser.downloads[what](...args);
+        browser.test.sendMessage(`${what}.done`, { status: "success", result });
+      } catch (error) {
+        browser.test.sendMessage(`${what}.done`, {
+          status: "error",
+          errmsg: error.message,
+        });
+      }
+    }
+  });
+
+  browser.test.sendMessage("ready");
+}
+
+let downloadDir;
+let extension;
+
+async function waitForCreatedPartFile(baseFilename = "interruptible.html") {
+  const partFilePath = PathUtils.join(downloadDir.path, `${baseFilename}.part`);
+
+  info(`Wait for ${partFilePath} to be created`);
+  let lastError;
+  await TestUtils.waitForCondition(
+    () =>
+      IOUtils.exists(partFilePath).catch(err => {
+        lastError = err;
+        return false;
+      }),
+    `Wait for the ${partFilePath} to exists before pausing the download`
+  ).catch(err => {
+    if (lastError) {
+      throw lastError;
+    }
+    throw err;
+  });
+}
+
+async function clearDownloads() {
+  let list = await Downloads.getList(Downloads.ALL);
+  let downloads = await list.getAll();
+
+  await Promise.all(
+    downloads.map(async download => {
+      await download.finalize(true);
+      list.remove(download);
+    })
+  );
+
+  return downloads;
+}
+
+function runInExtension(what, ...args) {
+  extension.sendMessage(`${what}.request`, ...args);
+  return extension.awaitMessage(`${what}.done`);
+}
+
+// This is pretty simplistic, it looks for a progress update for a
+// download of the given url in which the total bytes are exactly equal
+// to the given value.  Unless you know exactly how data will arrive from
+// the server (eg see interruptible.sjs), it probably isn't very useful.
+async function waitForProgress(url, testFn) {
+  let list = await Downloads.getList(Downloads.ALL);
+
+  return new Promise(resolve => {
+    const view = {
+      onDownloadChanged(download) {
+        if (download.source.url == url && testFn(download.currentBytes)) {
+          list.removeView(view);
+          resolve(download.currentBytes);
+        }
+      },
+    };
+    list.addView(view);
+  });
+}
+
+add_setup(async () => {
+  const nsIFile = Ci.nsIFile;
+  downloadDir = FileUtils.getDir("TmpD", ["downloads"]);
+  downloadDir.createUnique(nsIFile.DIRECTORY_TYPE, FileUtils.PERMS_DIRECTORY);
+  info(`downloadDir ${downloadDir.path}`);
+
+  Services.prefs.setIntPref("browser.download.folderList", 2);
+  Services.prefs.setComplexValue("browser.download.dir", nsIFile, downloadDir);
+
+  registerCleanupFunction(async () => {
+    Services.prefs.clearUserPref("browser.download.folderList");
+    Services.prefs.clearUserPref("browser.download.dir");
+    await clearDownloads();
+    downloadDir.remove(true);
+  });
+
+  await clearDownloads().then(downloads => {
+    info(`removed ${downloads.length} pre-existing downloads from history`);
+  });
+
+  extension = ExtensionTestUtils.loadExtension({
+    background: backgroundScript,
+    manifest: {
+      permissions: ["downloads"],
+    },
+  });
+
+  await extension.startup();
+  await extension.awaitMessage("ready");
+
+  registerCleanupFunction(async () => {
+    await extension.unload();
+  });
+});
+
+add_task(async function test_events() {
+  let msg = await runInExtension("download", { url: TXT_URL });
+  equal(msg.status, "success", "download() succeeded");
+  const id = msg.result;
+
+  msg = await runInExtension("waitForEvents", [
+    { type: "onCreated", data: { id, url: TXT_URL } },
+    {
+      type: "onChanged",
+      data: {
+        id,
+        state: {
+          previous: "in_progress",
+          current: "complete",
+        },
+      },
+    },
+  ]);
+  equal(msg.status, "success", "got onCreated and onChanged events");
+});
+
+add_task(async function test_cancel() {
+  let url = getInterruptibleUrl();
+  info(url);
+  let msg = await runInExtension("download", { url });
+  equal(msg.status, "success", "download() succeeded");
+  const id = msg.result;
+
+  let progressPromise = waitForProgress(url, bytes => bytes == INT_PARTIAL_LEN);
+
+  msg = await runInExtension("waitForEvents", [
+    { type: "onCreated", data: { id } },
+  ]);
+  equal(msg.status, "success", "got created and changed events");
+
+  await progressPromise;
+  info(`download reached ${INT_PARTIAL_LEN} bytes`);
+
+  msg = await runInExtension("cancel", id);
+  equal(msg.status, "success", "cancel() succeeded");
+
+  // TODO bug 1256243: This sequence of events is bogus
+  msg = await runInExtension("waitForEvents", [
+    {
+      type: "onChanged",
+      data: {
+        state: {
+          previous: "in_progress",
+          current: "interrupted",
+        },
+        paused: {
+          previous: false,
+          current: true,
+        },
+      },
+    },
+    {
+      type: "onChanged",
+      data: {
+        id,
+        error: {
+          previous: null,
+          current: "USER_CANCELED",
+        },
+      },
+    },
+    {
+      type: "onChanged",
+      data: {
+        id,
+        paused: {
+          previous: true,
+          current: false,
+        },
+      },
+    },
+  ]);
+  equal(
+    msg.status,
+    "success",
+    "got onChanged events corresponding to cancel()"
+  );
+
+  msg = await runInExtension("search", { error: "USER_CANCELED" });
+  equal(msg.status, "success", "search() succeeded");
+  equal(msg.result.length, 1, "search() found 1 download");
+  equal(msg.result[0].id, id, "download.id is correct");
+  equal(msg.result[0].state, "interrupted", "download.state is correct");
+  equal(msg.result[0].paused, false, "download.paused is correct");
+  equal(
+    msg.result[0].estimatedEndTime,
+    null,
+    "download.estimatedEndTime is correct"
+  );
+  equal(msg.result[0].canResume, false, "download.canResume is correct");
+  equal(msg.result[0].error, "USER_CANCELED", "download.error is correct");
+  equal(
+    msg.result[0].totalBytes,
+    INT_TOTAL_LEN,
+    "download.totalBytes is correct"
+  );
+  equal(msg.result[0].exists, false, "download.exists is correct");
+
+  msg = await runInExtension("pause", id);
+  equal(msg.status, "error", "cannot pause a canceled download");
+
+  msg = await runInExtension("resume", id);
+  equal(msg.status, "error", "cannot resume a canceled download");
+});
+
+add_task(async function test_pauseresume() {
+  const filename = "pauseresume.html";
+  let url = getInterruptibleUrl(filename);
+  let msg = await runInExtension("download", { url });
+  equal(msg.status, "success", "download() succeeded");
+  const id = msg.result;
+
+  let progressPromise = waitForProgress(url, bytes => bytes == INT_PARTIAL_LEN);
+
+  msg = await runInExtension("waitForEvents", [
+    { type: "onCreated", data: { id } },
+  ]);
+  equal(msg.status, "success", "got created and changed events");
+
+  await progressPromise;
+  info(`download reached ${INT_PARTIAL_LEN} bytes`);
+
+  // Prevent intermittent timeouts due to the part file not yet created
+  // (e.g. see Bug 1573360).
+  await waitForCreatedPartFile(filename);
+
+  info("Pause the download item");
+  msg = await runInExtension("pause", id);
+  equal(msg.status, "success", "pause() succeeded");
+
+  msg = await runInExtension("waitForEvents", [
+    {
+      type: "onChanged",
+      data: {
+        id,
+        state: {
+          previous: "in_progress",
+          current: "interrupted",
+        },
+        paused: {
+          previous: false,
+          current: true,
+        },
+        canResume: {
+          previous: false,
+          current: true,
+        },
+      },
+    },
+    {
+      type: "onChanged",
+      data: {
+        id,
+        error: {
+          previous: null,
+          current: "USER_CANCELED",
+        },
+      },
+    },
+  ]);
+  equal(msg.status, "success", "got onChanged event corresponding to pause");
+
+  msg = await runInExtension("search", { paused: true });
+  equal(msg.status, "success", "search() succeeded");
+  equal(msg.result.length, 1, "search() found 1 download");
+  equal(msg.result[0].id, id, "download.id is correct");
+  equal(msg.result[0].state, "interrupted", "download.state is correct");
+  equal(msg.result[0].paused, true, "download.paused is correct");
+  equal(
+    msg.result[0].estimatedEndTime,
+    null,
+    "download.estimatedEndTime is correct"
+  );
+  equal(msg.result[0].canResume, true, "download.canResume is correct");
+  equal(msg.result[0].error, "USER_CANCELED", "download.error is correct");
+  equal(
+    msg.result[0].bytesReceived,
+    INT_PARTIAL_LEN,
+    "download.bytesReceived is correct"
+  );
+  equal(
+    msg.result[0].totalBytes,
+    INT_TOTAL_LEN,
+    "download.totalBytes is correct"
+  );
+  equal(msg.result[0].exists, false, "download.exists is correct");
+
+  msg = await runInExtension("search", { error: "USER_CANCELED" });
+  equal(msg.status, "success", "search() succeeded");
+  let found = msg.result.filter(item => item.id == id);
+  equal(found.length, 1, "search() by error found the paused download");
+
+  msg = await runInExtension("pause", id);
+  equal(msg.status, "error", "cannot pause an already paused download");
+
+  msg = await runInExtension("resume", id);
+  equal(msg.status, "success", "resume() succeeded");
+
+  msg = await runInExtension("waitForEvents", [
+    {
+      type: "onChanged",
+      data: {
+        id,
+        state: {
+          previous: "interrupted",
+          current: "in_progress",
+        },
+        paused: {
+          previous: true,
+          current: false,
+        },
+        canResume: {
+          previous: true,
+          current: false,
+        },
+        error: {
+          previous: "USER_CANCELED",
+          current: null,
+        },
+      },
+    },
+    {
+      type: "onChanged",
+      data: {
+        id,
+        state: {
+          previous: "in_progress",
+          current: "complete",
+        },
+      },
+    },
+  ]);
+  equal(msg.status, "success", "got onChanged events for resume and complete");
+
+  msg = await runInExtension("search", { id });
+  equal(msg.status, "success", "search() succeeded");
+  equal(msg.result.length, 1, "search() found 1 download");
+  equal(msg.result[0].state, "complete", "download.state is correct");
+  equal(msg.result[0].paused, false, "download.paused is correct");
+  equal(
+    msg.result[0].estimatedEndTime,
+    null,
+    "download.estimatedEndTime is correct"
+  );
+  equal(msg.result[0].canResume, false, "download.canResume is correct");
+  equal(msg.result[0].error, null, "download.error is correct");
+  equal(
+    msg.result[0].bytesReceived,
+    INT_TOTAL_LEN,
+    "download.bytesReceived is correct"
+  );
+  equal(
+    msg.result[0].totalBytes,
+    INT_TOTAL_LEN,
+    "download.totalBytes is correct"
+  );
+  equal(msg.result[0].exists, true, "download.exists is correct");
+
+  msg = await runInExtension("pause", id);
+  equal(msg.status, "error", "cannot pause a completed download");
+
+  msg = await runInExtension("resume", id);
+  equal(msg.status, "error", "cannot resume a completed download");
+});
+
+add_task(async function test_pausecancel() {
+  let url = getInterruptibleUrl();
+  let msg = await runInExtension("download", { url });
+  equal(msg.status, "success", "download() succeeded");
+  const id = msg.result;
+
+  let progressPromise = waitForProgress(url, bytes => bytes == INT_PARTIAL_LEN);
+
+  msg = await runInExtension("waitForEvents", [
+    { type: "onCreated", data: { id } },
+  ]);
+  equal(msg.status, "success", "got created and changed events");
+
+  await progressPromise;
+  info(`download reached ${INT_PARTIAL_LEN} bytes`);
+
+  msg = await runInExtension("pause", id);
+  equal(msg.status, "success", "pause() succeeded");
+
+  msg = await runInExtension("waitForEvents", [
+    {
+      type: "onChanged",
+      data: {
+        id,
+        state: {
+          previous: "in_progress",
+          current: "interrupted",
+        },
+        paused: {
+          previous: false,
+          current: true,
+        },
+        canResume: {
+          previous: false,
+          current: true,
+        },
+      },
+    },
+    {
+      type: "onChanged",
+      data: {
+        id,
+        error: {
+          previous: null,
+          current: "USER_CANCELED",
+        },
+      },
+    },
+  ]);
+  equal(msg.status, "success", "got onChanged event corresponding to pause");
+
+  msg = await runInExtension("search", { paused: true });
+  equal(msg.status, "success", "search() succeeded");
+  equal(msg.result.length, 1, "search() found 1 download");
+  equal(msg.result[0].id, id, "download.id is correct");
+  equal(msg.result[0].state, "interrupted", "download.state is correct");
+  equal(msg.result[0].paused, true, "download.paused is correct");
+  equal(
+    msg.result[0].estimatedEndTime,
+    null,
+    "download.estimatedEndTime is correct"
+  );
+  equal(msg.result[0].canResume, true, "download.canResume is correct");
+  equal(msg.result[0].error, "USER_CANCELED", "download.error is correct");
+  equal(
+    msg.result[0].bytesReceived,
+    INT_PARTIAL_LEN,
+    "download.bytesReceived is correct"
+  );
+  equal(
+    msg.result[0].totalBytes,
+    INT_TOTAL_LEN,
+    "download.totalBytes is correct"
+  );
+  equal(msg.result[0].exists, false, "download.exists is correct");
+
+  msg = await runInExtension("search", { error: "USER_CANCELED" });
+  equal(msg.status, "success", "search() succeeded");
+  let found = msg.result.filter(item => item.id == id);
+  equal(found.length, 1, "search() by error found the paused download");
+
+  msg = await runInExtension("cancel", id);
+  equal(msg.status, "success", "cancel() succeeded");
+
+  msg = await runInExtension("waitForEvents", [
+    {
+      type: "onChanged",
+      data: {
+        id,
+        paused: {
+          previous: true,
+          current: false,
+        },
+        canResume: {
+          previous: true,
+          current: false,
+        },
+      },
+    },
+  ]);
+  equal(msg.status, "success", "got onChanged event for cancel");
+
+  msg = await runInExtension("search", { id });
+  equal(msg.status, "success", "search() succeeded");
+  equal(msg.result.length, 1, "search() found 1 download");
+  equal(msg.result[0].state, "interrupted", "download.state is correct");
+  equal(msg.result[0].paused, false, "download.paused is correct");
+  equal(
+    msg.result[0].estimatedEndTime,
+    null,
+    "download.estimatedEndTime is correct"
+  );
+  equal(msg.result[0].canResume, false, "download.canResume is correct");
+  equal(msg.result[0].error, "USER_CANCELED", "download.error is correct");
+  equal(
+    msg.result[0].totalBytes,
+    INT_TOTAL_LEN,
+    "download.totalBytes is correct"
+  );
+  equal(msg.result[0].exists, false, "download.exists is correct");
+});
+
+add_task(async function test_pause_resume_cancel_badargs() {
+  let BAD_ID = 1000;
+
+  let msg = await runInExtension("pause", BAD_ID);
+  equal(msg.status, "error", "pause() failed with a bad download id");
+  ok(/Invalid download id/.test(msg.errmsg), "error message is descriptive");
+
+  msg = await runInExtension("resume", BAD_ID);
+  equal(msg.status, "error", "resume() failed with a bad download id");
+  ok(/Invalid download id/.test(msg.errmsg), "error message is descriptive");
+
+  msg = await runInExtension("cancel", BAD_ID);
+  equal(msg.status, "error", "cancel() failed with a bad download id");
+  ok(/Invalid download id/.test(msg.errmsg), "error message is descriptive");
+});
+
+add_task(async function test_file_removal() {
+  let msg = await runInExtension("download", { url: TXT_URL });
+  equal(msg.status, "success", "download() succeeded");
+  const id = msg.result;
+
+  msg = await runInExtension("waitForEvents", [
+    { type: "onCreated", data: { id, url: TXT_URL } },
+    {
+      type: "onChanged",
+      data: {
+        id,
+        state: {
+          previous: "in_progress",
+          current: "complete",
+        },
+      },
+    },
+  ]);
+
+  equal(msg.status, "success", "got onCreated and onChanged events");
+
+  msg = await runInExtension("removeFile", id);
+  equal(msg.status, "success", "removeFile() succeeded");
+
+  msg = await runInExtension("removeFile", id);
+  equal(
+    msg.status,
+    "error",
+    "removeFile() fails since the file was already removed."
+  );
+  equal(
+    msg.errmsg,
+    `Could not remove download id ${id} because the file doesn't exist`,
+    "removeFile() failed on removed file."
+  );
+
+  msg = await runInExtension("removeFile", 1000);
+  equal(
+    msg.errmsg,
+    "Invalid download id 1000",
+    "removeFile() failed due to non-existent id"
+  );
+});
+
+add_task(async function test_file_removeFile_permission_failure() {
+  const inputDirname = "subdir_for_download";
+  const inputFilename = "downloaded_filename.txt";
+  const expectedDir = PathUtils.join(downloadDir.path, inputDirname);
+  const expectedPath = PathUtils.join(expectedDir, inputFilename);
+
+  let msg = await runInExtension("download", {
+    url: TXT_URL,
+    filename: `${inputDirname}/${inputFilename}`,
+  });
+  equal(msg.status, "success", "download() succeeded");
+  const id = msg.result;
+
+  msg = await runInExtension("waitForEvents", [
+    { type: "onCreated", data: { id, url: TXT_URL } },
+    {
+      type: "onChanged",
+      data: {
+        id,
+        state: {
+          previous: "in_progress",
+          current: "complete",
+        },
+      },
+    },
+  ]);
+
+  equal(msg.status, "success", "got onCreated and onChanged events");
+
+  msg = await runInExtension("search", { id });
+  equal(msg.status, "success", "search() succeeded");
+  equal(expectedPath, msg.result[0]?.filename, "Got expected filename");
+
+  async function withUndeletableFileUnix(testRemoveFile) {
+    try {
+      // Temporarily make directory unreadable/inaccessible.
+      await IOUtils.setPermissions(expectedDir, 0);
+      // Remove should fail with Unix error 13 (EACCES).
+      await testRemoveFile();
+    } finally {
+      await IOUtils.setPermissions(expectedDir, 0o777);
+    }
+  }
+  async function withUndeletableFileWin(testRemoveFile) {
+    // On Windows, a directory marked as read-only does not prevent the deletion
+    // of its content. So we need an alternative approach here.
+    let stream = Cc["@mozilla.org/network/file-input-stream;1"].createInstance(
+      Ci.nsIFileInputStream
+    );
+    try {
+      // Open a file handle. The file cannot be deleted until it is closed.
+      stream.init(await IOUtils.getFile(expectedPath), -1, 0, 0);
+      // Remove should fail with Win error 32 (ERROR_SHARING_VIOLATION).
+      await testRemoveFile();
+    } finally {
+      stream.close();
+    }
+  }
+
+  const withUndeletableFile =
+    AppConstants.platform === "win"
+      ? withUndeletableFileWin
+      : withUndeletableFileUnix;
+
+  let consoleOutput;
+  await withUndeletableFile(async () => {
+    consoleOutput = await promiseConsoleOutput(async () => {
+      msg = await runInExtension("removeFile", id);
+    });
+  });
+
+  equal(msg.status, "error", "removeFile() fails due to missing dir perms");
+  // Verify that an unexpected error is redacted, with a useful error message
+  // logged to the console.
+  // Note: if we ever decide to make the error for permission failures more
+  // useful, try to add a new test case for unexpected errors, even if
+  // completely artificial such as mocking + breaking an internal API.
+  equal(msg.errmsg, "An unexpected error occurred", "Error message redacted");
+
+  AddonTestUtils.checkMessages(consoleOutput.messages, {
+    expected: [{ message: /NotAllowedError/ }],
+  });
+
+  ok(await IOUtils.exists(expectedPath), "File exists before removeFile()");
+
+  msg = await runInExtension("removeFile", id);
+  equal(msg.status, "success", "removeFile() succeeded");
+
+  equal(await IOUtils.exists(expectedPath), false, "File was really removed");
+
+  // As a bonus: check that the re-created file can be deleted without issues.
+  await IOUtils.writeUTF8(expectedPath, "content here");
+
+  msg = await runInExtension("removeFile", id);
+  equal(msg.status, "success", "removeFile() succeeded after recreation");
+
+  equal(await IOUtils.exists(expectedPath), false, "File was removed again");
+});
+
+add_task(async function test_removal_of_incomplete_download() {
+  const filename = "remove-incomplete.html";
+  let url = getInterruptibleUrl(filename);
+  let msg = await runInExtension("download", { url });
+  equal(msg.status, "success", "download() succeeded");
+  const id = msg.result;
+
+  let progressPromise = waitForProgress(url, bytes => bytes == INT_PARTIAL_LEN);
+
+  msg = await runInExtension("waitForEvents", [
+    { type: "onCreated", data: { id } },
+  ]);
+  equal(msg.status, "success", "got created and changed events");
+
+  await progressPromise;
+  info(`download reached ${INT_PARTIAL_LEN} bytes`);
+
+  // Prevent intermittent timeouts due to the part file not yet created
+  // (e.g. see Bug 1573360).
+  await waitForCreatedPartFile(filename);
+
+  msg = await runInExtension("pause", id);
+  equal(msg.status, "success", "pause() succeeded");
+
+  msg = await runInExtension("waitForEvents", [
+    {
+      type: "onChanged",
+      data: {
+        id,
+        state: {
+          previous: "in_progress",
+          current: "interrupted",
+        },
+        paused: {
+          previous: false,
+          current: true,
+        },
+        canResume: {
+          previous: false,
+          current: true,
+        },
+      },
+    },
+    {
+      type: "onChanged",
+      data: {
+        id,
+        error: {
+          previous: null,
+          current: "USER_CANCELED",
+        },
+      },
+    },
+  ]);
+  equal(msg.status, "success", "got onChanged event corresponding to pause");
+
+  msg = await runInExtension("removeFile", id);
+  equal(msg.status, "error", "removeFile() on paused download failed");
+
+  ok(
+    /Cannot remove incomplete download/.test(msg.errmsg),
+    "removeFile() failed due to download being incomplete"
+  );
+
+  msg = await runInExtension("resume", id);
+  equal(msg.status, "success", "resume() succeeded");
+
+  msg = await runInExtension("waitForEvents", [
+    {
+      type: "onChanged",
+      data: {
+        id,
+        state: {
+          previous: "interrupted",
+          current: "in_progress",
+        },
+        paused: {
+          previous: true,
+          current: false,
+        },
+        canResume: {
+          previous: true,
+          current: false,
+        },
+        error: {
+          previous: "USER_CANCELED",
+          current: null,
+        },
+      },
+    },
+    {
+      type: "onChanged",
+      data: {
+        id,
+        state: {
+          previous: "in_progress",
+          current: "complete",
+        },
+      },
+    },
+  ]);
+  equal(msg.status, "success", "got onChanged events for resume and complete");
+
+  msg = await runInExtension("removeFile", id);
+  equal(
+    msg.status,
+    "success",
+    "removeFile() succeeded following completion of resumed download."
+  );
+});
+
+// Test erase().  We don't do elaborate testing of the query handling
+// since it uses the exact same engine as search() which is tested
+// more thoroughly in test_chrome_ext_downloads_search.html
+add_task(async function test_erase() {
+  await clearDownloads();
+
+  await runInExtension("clearEvents");
+
+  async function download() {
+    let msg = await runInExtension("download", { url: TXT_URL });
+    equal(msg.status, "success", "download succeeded");
+    let id = msg.result;
+
+    msg = await runInExtension(
+      "waitForEvents",
+      [
+        {
+          type: "onChanged",
+          data: { id, state: { current: "complete" } },
+        },
+      ],
+      { exact: false }
+    );
+    equal(msg.status, "success", "download finished");
+
+    return id;
+  }
+
+  let ids = {};
+  ids.dl1 = await download();
+  ids.dl2 = await download();
+  ids.dl3 = await download();
+
+  let msg = await runInExtension("search", {});
+  equal(msg.status, "success", "search succeeded");
+  equal(msg.result.length, 3, "search found 3 downloads");
+
+  msg = await runInExtension("clearEvents");
+
+  msg = await runInExtension("erase", { id: ids.dl1 });
+  equal(msg.status, "success", "erase by id succeeded");
+
+  msg = await runInExtension("waitForEvents", [
+    { type: "onErased", data: ids.dl1 },
+  ]);
+  equal(msg.status, "success", "received onErased event");
+
+  msg = await runInExtension("search", {});
+  equal(msg.status, "success", "search succeeded");
+  equal(msg.result.length, 2, "search found 2 downloads");
+
+  msg = await runInExtension("erase", {});
+  equal(msg.status, "success", "erase everything succeeded");
+
+  msg = await runInExtension(
+    "waitForEvents",
+    [
+      { type: "onErased", data: ids.dl2 },
+      { type: "onErased", data: ids.dl3 },
+    ],
+    { inorder: false }
+  );
+  equal(msg.status, "success", "received 2 onErased events");
+
+  msg = await runInExtension("search", {});
+  equal(msg.status, "success", "search succeeded");
+  equal(msg.result.length, 0, "search found 0 downloads");
+});
+
+function loadImage(img, data) {
+  return new Promise(resolve => {
+    img.src = data;
+    img.onload = resolve;
+  });
+}
+
+add_task(async function test_getFileIcon() {
+  let webNav = Services.appShell.createWindowlessBrowser(false);
+  let docShell = webNav.docShell;
+
+  let system = Services.scriptSecurityManager.getSystemPrincipal();
+  docShell.createAboutBlankContentViewer(system, system);
+
+  let img = webNav.document.createElement("img");
+
+  let msg = await runInExtension("download", { url: TXT_URL });
+  equal(msg.status, "success", "download() succeeded");
+  const id = msg.result;
+
+  msg = await runInExtension("getFileIcon", id);
+  equal(msg.status, "success", "getFileIcon() succeeded");
+  await loadImage(img, msg.result);
+  equal(img.height, 32, "returns an icon with the right height");
+  equal(img.width, 32, "returns an icon with the right width");
+
+  msg = await runInExtension("waitForEvents", [
+    { type: "onCreated", data: { id, url: TXT_URL } },
+    { type: "onChanged" },
+  ]);
+  equal(msg.status, "success", "got events");
+
+  msg = await runInExtension("getFileIcon", id);
+  equal(msg.status, "success", "getFileIcon() succeeded");
+  await loadImage(img, msg.result);
+  equal(img.height, 32, "returns an icon with the right height after download");
+  equal(img.width, 32, "returns an icon with the right width after download");
+
+  msg = await runInExtension("getFileIcon", id + 100);
+  equal(msg.status, "error", "getFileIcon() failed");
+  ok(msg.errmsg.includes("Invalid download id"), "download id is invalid");
+
+  msg = await runInExtension("getFileIcon", id, { size: 127 });
+  equal(msg.status, "success", "getFileIcon() succeeded");
+  await loadImage(img, msg.result);
+  equal(img.height, 127, "returns an icon with the right custom height");
+  equal(img.width, 127, "returns an icon with the right custom width");
+
+  msg = await runInExtension("getFileIcon", id, { size: 1 });
+  equal(msg.status, "success", "getFileIcon() succeeded");
+  await loadImage(img, msg.result);
+  equal(img.height, 1, "returns an icon with the right custom height");
+  equal(img.width, 1, "returns an icon with the right custom width");
+
+  msg = await runInExtension("getFileIcon", id, { size: "foo" });
+  equal(msg.status, "error", "getFileIcon() fails");
+  ok(msg.errmsg.includes("Error processing size"), "size is not a number");
+
+  msg = await runInExtension("getFileIcon", id, { size: 0 });
+  equal(msg.status, "error", "getFileIcon() fails");
+  ok(msg.errmsg.includes("Error processing size"), "size is too small");
+
+  msg = await runInExtension("getFileIcon", id, { size: 128 });
+  equal(msg.status, "error", "getFileIcon() fails");
+  ok(msg.errmsg.includes("Error processing size"), "size is too big");
+
+  webNav.close();
+});
+
+add_task(async function test_estimatedendtime() {
+  // Note we are not testing the actual value calculation of estimatedEndTime,
+  // only whether it is null/non-null at the appropriate times.
+
+  let url = `${getInterruptibleUrl()}&stream=1`;
+  let msg = await runInExtension("download", { url });
+  equal(msg.status, "success", "download() succeeded");
+  const id = msg.result;
+
+  let previousBytes = await waitForProgress(url, bytes => bytes > 0);
+  await waitForProgress(url, bytes => bytes > previousBytes);
+
+  msg = await runInExtension("search", { id });
+  equal(msg.status, "success", "search() succeeded");
+  equal(msg.result.length, 1, "search() found 1 download");
+  ok(msg.result[0].estimatedEndTime, "download.estimatedEndTime is correct");
+  ok(msg.result[0].bytesReceived > 0, "download.bytesReceived is correct");
+
+  msg = await runInExtension("cancel", id);
+
+  msg = await runInExtension("search", { id });
+  equal(msg.status, "success", "search() succeeded");
+  equal(msg.result.length, 1, "search() found 1 download");
+  ok(!msg.result[0].estimatedEndTime, "download.estimatedEndTime is correct");
+});
+
+add_task(async function test_byExtension() {
+  let msg = await runInExtension("download", { url: TXT_URL });
+  equal(msg.status, "success", "download() succeeded");
+  const id = msg.result;
+  msg = await runInExtension("search", { id });
+
+  equal(msg.result.length, 1, "search() found 1 download");
+  equal(
+    msg.result[0].byExtensionName,
+    "Generated extension",
+    "download.byExtensionName is correct"
+  );
+  equal(
+    msg.result[0].byExtensionId,
+    extension.id,
+    "download.byExtensionId is correct"
+  );
+});
diff --git a/toolkit/components/extensions/test/xpcshell/test_ext_downloads_partitionKey.js b/toolkit/components/extensions/test/xpcshell/test_ext_downloads_partitionKey.js
new file mode 100644
index 0000000000..3326ed0ce9
--- /dev/null
+++ b/toolkit/components/extensions/test/xpcshell/test_ext_downloads_partitionKey.js
@@ -0,0 +1,199 @@
+/* -*- Mode: indent-tabs-mode: nil; js-indent-level: 2 -*- */
+/* vim: set sts=2 sw=2 et tw=80: */
+"use strict";
+
+const { Downloads } = ChromeUtils.importESModule(
+  "resource://gre/modules/Downloads.sys.mjs"
+);
+
+const server = createHttpServer();
+server.registerDirectory("/data/", do_get_file("data"));
+
+const BASE = `http://localhost:${server.identity.primaryPort}/data`;
+const TEST_FILE = "file_download.txt";
+const TEST_URL = BASE + "/" + TEST_FILE;
+
+// We use different cookieBehaviors so that we can verify if we use the correct
+// cookieBehavior if option.incognito is set. Note that we need to set a
+// non-default value to the private cookieBehavior because the private
+// cookieBehavior will mirror the regular cookieBehavior if the private pref is
+// default value and the regular pref is non-default value. To avoid affecting
+// the test by mirroring, we set the private cookieBehavior to a non-default
+// value.
+const TEST_REGULAR_COOKIE_BEHAVIOR =
+  Ci.nsICookieService.BEHAVIOR_REJECT_TRACKER;
+const TEST_PRIVATE_COOKIE_BEHAVIOR = Ci.nsICookieService.BEHAVIOR_LIMIT_FOREIGN;
+
+let downloadDir;
+
+function observeDownloadChannel(uri, partitionKey, isPrivate) {
+  return new Promise(resolve => {
+    let observer = {
+      observe(subject, topic, data) {
+        if (topic === "http-on-modify-request") {
+          let httpChannel = subject.QueryInterface(Ci.nsIHttpChannel);
+          if (httpChannel.URI.spec != uri) {
+            return;
+          }
+
+          let reqLoadInfo = httpChannel.loadInfo;
+          let cookieJarSettings = reqLoadInfo.cookieJarSettings;
+
+          // Check the partitionKey of the cookieJarSettings.
+          equal(
+            cookieJarSettings.partitionKey,
+            partitionKey,
+            "The loadInfo has the correct paritionKey"
+          );
+
+          // Check the cookieBehavior of the cookieJarSettings.
+          equal(
+            cookieJarSettings.cookieBehavior,
+            isPrivate
+              ? TEST_PRIVATE_COOKIE_BEHAVIOR
+              : TEST_REGULAR_COOKIE_BEHAVIOR,
+            "The loadInfo has the correct cookieBehavior"
+          );
+
+          Services.obs.removeObserver(observer, "http-on-modify-request");
+          resolve();
+        }
+      },
+    };
+
+    Services.obs.addObserver(observer, "http-on-modify-request");
+  });
+}
+
+async function waitForDownloads() {
+  let list = await Downloads.getList(Downloads.ALL);
+  let downloads = await list.getAll();
+
+  let inprogress = downloads.filter(dl => !dl.stopped);
+  return Promise.all(inprogress.map(dl => dl.whenSucceeded()));
+}
+
+function backgroundScript() {
+  browser.test.onMessage.addListener(async (msg, ...args) => {
+    if (msg == "download.request") {
+      let options = args[0];
+
+      try {
+        let id = await browser.downloads.download(options);
+        browser.test.sendMessage("download.done", { status: "success", id });
+      } catch (error) {
+        browser.test.sendMessage("download.done", {
+          status: "error",
+          errmsg: error.message,
+        });
+      }
+    }
+  });
+
+  browser.test.sendMessage("ready");
+}
+
+// Remove a file in the downloads directory.
+function remove(filename, recursive = false) {
+  let file = downloadDir.clone();
+  file.append(filename);
+  file.remove(recursive);
+}
+
+add_task(function setup() {
+  downloadDir = FileUtils.getDir("TmpD", ["downloads"]);
+  downloadDir.createUnique(
+    Ci.nsIFile.DIRECTORY_TYPE,
+    FileUtils.PERMS_DIRECTORY
+  );
+  info(`Using download directory ${downloadDir.path}`);
+
+  Services.prefs.setIntPref("browser.download.folderList", 2);
+  Services.prefs.setComplexValue(
+    "browser.download.dir",
+    Ci.nsIFile,
+    downloadDir
+  );
+  Services.prefs.setBoolPref("privacy.partition.network_state", true);
+
+  Services.prefs.setIntPref(
+    "network.cookie.cookieBehavior",
+    TEST_REGULAR_COOKIE_BEHAVIOR
+  );
+  Services.prefs.setIntPref(
+    "network.cookie.cookieBehavior.pbmode",
+    TEST_PRIVATE_COOKIE_BEHAVIOR
+  );
+
+  registerCleanupFunction(() => {
+    Services.prefs.clearUserPref("browser.download.folderList");
+    Services.prefs.clearUserPref("browser.download.dir");
+    Services.prefs.clearUserPref("privacy.partition.network_state");
+    Services.prefs.clearUserPref("network.cookie.cookieBehavior");
+    Services.prefs.clearUserPref("network.cookie.cookieBehavior.pbmode");
+
+    let entries = downloadDir.directoryEntries;
+    while (entries.hasMoreElements()) {
+      let entry = entries.nextFile;
+      info(`Leftover file ${entry.path} in download directory`);
+      ok(false, `Leftover file ${entry.path} in download directory`);
+      entry.remove(false);
+    }
+
+    downloadDir.remove(false);
+  });
+});
+
+add_task(async function test() {
+  let extension = ExtensionTestUtils.loadExtension({
+    background: `(${backgroundScript})()`,
+    manifest: {
+      permissions: ["downloads"],
+    },
+    incognitoOverride: "spanning",
+  });
+
+  function download(options) {
+    extension.sendMessage("download.request", options);
+    return extension.awaitMessage("download.done");
+  }
+
+  async function testDownload(url, partitionKey, isPrivate) {
+    let options = { url, incognito: isPrivate };
+
+    let promiseObserveDownloadChannel = observeDownloadChannel(
+      url,
+      partitionKey,
+      isPrivate
+    );
+
+    let msg = await download(options);
+    equal(msg.status, "success", `downloads.download() works`);
+
+    await promiseObserveDownloadChannel;
+    await waitForDownloads();
+  }
+
+  await extension.startup();
+  await extension.awaitMessage("ready");
+  info("extension started");
+
+  // Call download() to check partitionKey of the download channel for the
+  // regular browsing mode.
+  await testDownload(
+    TEST_URL,
+    `(http,localhost,${server.identity.primaryPort})`,
+    false
+  );
+  remove(TEST_FILE);
+
+  // Call download again for the private browsing mode.
+  await testDownload(
+    TEST_URL,
+    `(http,localhost,${server.identity.primaryPort})`,
+    true
+  );
+  remove(TEST_FILE);
+
+  await extension.unload();
+});
diff --git a/toolkit/components/extensions/test/xpcshell/test_ext_downloads_private.js b/toolkit/components/extensions/test/xpcshell/test_ext_downloads_private.js
new file mode 100644
index 0000000000..caf664fb86
--- /dev/null
+++ b/toolkit/components/extensions/test/xpcshell/test_ext_downloads_private.js
@@ -0,0 +1,306 @@
+/* -*- Mode: indent-tabs-mode: nil; js-indent-level: 2 -*- */
+/* vim: set sts=2 sw=2 et tw=80: */
+"use strict";
+
+const server = createHttpServer();
+server.registerDirectory("/data/", do_get_file("data"));
+
+const BASE = `http://localhost:${server.identity.primaryPort}/data`;
+const TXT_FILE = "file_download.txt";
+const TXT_URL = BASE + "/" + TXT_FILE;
+
+add_task(function setup() {
+  let downloadDir = FileUtils.getDir("TmpD", ["downloads"]);
+  downloadDir.createUnique(
+    Ci.nsIFile.DIRECTORY_TYPE,
+    FileUtils.PERMS_DIRECTORY
+  );
+  info(`Using download directory ${downloadDir.path}`);
+
+  Services.prefs.setIntPref("browser.download.folderList", 2);
+  Services.prefs.setComplexValue(
+    "browser.download.dir",
+    Ci.nsIFile,
+    downloadDir
+  );
+
+  registerCleanupFunction(() => {
+    Services.prefs.clearUserPref("browser.download.folderList");
+    Services.prefs.clearUserPref("browser.download.dir");
+
+    let entries = downloadDir.directoryEntries;
+    while (entries.hasMoreElements()) {
+      let entry = entries.nextFile;
+      ok(false, `Leftover file ${entry.path} in download directory`);
+      entry.remove(false);
+    }
+
+    downloadDir.remove(false);
+  });
+});
+
+add_task(async function test_private_download() {
+  let pb_extension = ExtensionTestUtils.loadExtension({
+    background: async function () {
+      function promiseEvent(eventTarget, accept) {
+        return new Promise(resolve => {
+          eventTarget.addListener(function listener(data) {
+            if (accept && !accept(data)) {
+              return;
+            }
+            eventTarget.removeListener(listener);
+            resolve(data);
+          });
+        });
+      }
+      let startTestPromise = promiseEvent(browser.test.onMessage);
+      let removeTestPromise = promiseEvent(
+        browser.test.onMessage,
+        msg => msg == "remove"
+      );
+      let onCreatedPromise = promiseEvent(browser.downloads.onCreated);
+      let onDonePromise = promiseEvent(
+        browser.downloads.onChanged,
+        delta => delta.state && delta.state.current === "complete"
+      );
+
+      browser.test.sendMessage("ready");
+      let { url, filename } = await startTestPromise;
+
+      browser.test.log("Starting private download");
+      let downloadId = await browser.downloads.download({
+        url,
+        filename,
+        incognito: true,
+      });
+      browser.test.sendMessage("downloadId", downloadId);
+
+      browser.test.log("Waiting for downloads.onCreated");
+      let createdItem = await onCreatedPromise;
+
+      browser.test.log("Waiting for completion notification");
+      await onDonePromise;
+
+      // test_ext_downloads_download.js already tests whether the file exists
+      // in the file system. Here we will only verify that the  downloads API
+      // behaves in a meaningful way.
+
+      let [downloadItem] = await browser.downloads.search({ id: downloadId });
+      browser.test.assertEq(url, createdItem.url, "onCreated url should match");
+      browser.test.assertEq(url, downloadItem.url, "download url should match");
+      browser.test.assertTrue(
+        createdItem.incognito,
+        "created download should be private"
+      );
+      browser.test.assertTrue(
+        downloadItem.incognito,
+        "stored download should be private"
+      );
+
+      await removeTestPromise;
+      browser.test.log("Removing downloaded file");
+      browser.test.assertTrue(downloadItem.exists, "downloaded file exists");
+      await browser.downloads.removeFile(downloadId);
+
+      // Disabled because the assertion fails - https://bugzil.la/1381031
+      // let [downloadItem2] = await browser.downloads.search({id: downloadId});
+      // browser.test.assertFalse(downloadItem2.exists, "file should be deleted");
+
+      browser.test.log("Erasing private download from history");
+      let erasePromise = promiseEvent(browser.downloads.onErased);
+      await browser.downloads.erase({ id: downloadId });
+      browser.test.assertEq(
+        downloadId,
+        await erasePromise,
+        "onErased should be fired for the erased private download"
+      );
+
+      browser.test.notifyPass("private download test done");
+    },
+    manifest: {
+      browser_specific_settings: { gecko: { id: "@spanning" } },
+      permissions: ["downloads"],
+    },
+    incognitoOverride: "spanning",
+  });
+
+  let extension = ExtensionTestUtils.loadExtension({
+    manifest: {
+      browser_specific_settings: { gecko: { id: "@not_allowed" } },
+      permissions: ["downloads", "downloads.open"],
+    },
+    background: async function () {
+      browser.downloads.onCreated.addListener(() => {
+        browser.test.fail("download-onCreated");
+      });
+      browser.downloads.onChanged.addListener(() => {
+        browser.test.fail("download-onChanged");
+      });
+      browser.downloads.onErased.addListener(() => {
+        browser.test.fail("download-onErased");
+      });
+      browser.test.onMessage.addListener(async (msg, data) => {
+        if (msg == "download") {
+          let { url, filename, downloadId } = data;
+          await browser.test.assertRejects(
+            browser.downloads.download({
+              url,
+              filename,
+              incognito: true,
+            }),
+            /private browsing access not allowed/,
+            "cannot download using incognito without permission."
+          );
+
+          let downloads = await browser.downloads.search({ id: downloadId });
+          browser.test.assertEq(
+            downloads.length,
+            0,
+            "cannot search for incognito downloads"
+          );
+          let erasing = await browser.downloads.erase({ id: downloadId });
+          browser.test.assertEq(
+            erasing.length,
+            0,
+            "cannot erase incognito download"
+          );
+
+          await browser.test.assertRejects(
+            browser.downloads.removeFile(downloadId),
+            /Invalid download id/,
+            "cannot remove incognito download"
+          );
+          await browser.test.assertRejects(
+            browser.downloads.pause(downloadId),
+            /Invalid download id/,
+            "cannot pause incognito download"
+          );
+          await browser.test.assertRejects(
+            browser.downloads.resume(downloadId),
+            /Invalid download id/,
+            "cannot resume incognito download"
+          );
+          await browser.test.assertRejects(
+            browser.downloads.cancel(downloadId),
+            /Invalid download id/,
+            "cannot cancel incognito download"
+          );
+          await browser.test.assertRejects(
+            browser.downloads.removeFile(downloadId),
+            /Invalid download id/,
+            "cannot remove incognito download"
+          );
+          await browser.test.assertRejects(
+            browser.downloads.show(downloadId),
+            /Invalid download id/,
+            "cannot show incognito download"
+          );
+          await browser.test.assertRejects(
+            browser.downloads.getFileIcon(downloadId),
+            /Invalid download id/,
+            "cannot show incognito download"
+          );
+        }
+        if (msg == "download.open") {
+          let { downloadId } = data;
+          await browser.test.assertRejects(
+            browser.downloads.open(downloadId),
+            /Invalid download id/,
+            "cannot open incognito download"
+          );
+        }
+        browser.test.sendMessage("continue");
+      });
+    },
+  });
+
+  await extension.startup();
+  await pb_extension.startup();
+  await pb_extension.awaitMessage("ready");
+  pb_extension.sendMessage({
+    url: TXT_URL,
+    filename: TXT_FILE,
+  });
+  let downloadId = await pb_extension.awaitMessage("downloadId");
+  extension.sendMessage("download", {
+    url: TXT_URL,
+    filename: TXT_FILE,
+    downloadId,
+  });
+  await extension.awaitMessage("continue");
+  await withHandlingUserInput(extension, async () => {
+    extension.sendMessage("download.open", { downloadId });
+    await extension.awaitMessage("continue");
+  });
+  pb_extension.sendMessage("remove");
+
+  await pb_extension.awaitFinish("private download test done");
+  await pb_extension.unload();
+  await extension.unload();
+});
+
+// Regression test for https://bugzilla.mozilla.org/show_bug.cgi?id=1649463
+add_task(async function download_blob_in_perma_private_browsing() {
+  Services.prefs.setBoolPref("browser.privatebrowsing.autostart", true);
+
+  // This script creates a blob:-URL and checks that the URL can be downloaded.
+  async function testScript() {
+    const blobUrl = URL.createObjectURL(new Blob(["data here"]));
+    const downloadId = await new Promise(resolve => {
+      browser.downloads.onChanged.addListener(delta => {
+        browser.test.log(`downloads.onChanged = ${JSON.stringify(delta)}`);
+        if (delta.state && delta.state.current !== "in_progress") {
+          resolve(delta.id);
+        }
+      });
+      browser.downloads.download({
+        url: blobUrl,
+        filename: "some-blob-download.txt",
+      });
+    });
+
+    let [downloadItem] = await browser.downloads.search({ id: downloadId });
+    browser.test.log(`Downloaded ${JSON.stringify(downloadItem)}`);
+    browser.test.assertEq(downloadItem.url, blobUrl, "expected blob URL");
+    // TODO bug 1653636: should be true because of perma-private browsing.
+    // browser.test.assertTrue(downloadItem.incognito, "download is private");
+    browser.test.assertFalse(
+      downloadItem.incognito,
+      "download is private [skipped - to be fixed in bug 1653636]"
+    );
+    browser.test.assertTrue(downloadItem.exists, "download exists");
+    await browser.downloads.removeFile(downloadId);
+
+    browser.test.sendMessage("downloadDone");
+  }
+  let pb_extension = ExtensionTestUtils.loadExtension({
+    manifest: {
+      browser_specific_settings: { gecko: { id: "@private-download-ext" } },
+      permissions: ["downloads"],
+    },
+    background: testScript,
+    incognitoOverride: "spanning",
+    files: {
+      "test_part2.html": `
+        <!DOCTYPE html><meta charset="utf-8">
+        <script src="test_part2.js"></script>
+      `,
+      "test_part2.js": testScript,
+    },
+  });
+  await pb_extension.startup();
+
+  info("Testing download of blob:-URL from extension's background page");
+  await pb_extension.awaitMessage("downloadDone");
+
+  info("Testing download of blob:-URL with different userContextId");
+  let contentPage = await ExtensionTestUtils.loadContentPage(
+    `moz-extension://${pb_extension.uuid}/test_part2.html`,
+    { extension: pb_extension, userContextId: 2 }
+  );
+  await pb_extension.awaitMessage("downloadDone");
+  await contentPage.close();
+
+  await pb_extension.unload();
+  Services.prefs.clearUserPref("browser.privatebrowsing.autostart");
+});
diff --git a/toolkit/components/extensions/test/xpcshell/test_ext_downloads_search.js b/toolkit/components/extensions/test/xpcshell/test_ext_downloads_search.js
new file mode 100644
index 0000000000..37c497a9b6
--- /dev/null
+++ b/toolkit/components/extensions/test/xpcshell/test_ext_downloads_search.js
@@ -0,0 +1,682 @@
+/* -*- Mode: indent-tabs-mode: nil; js-indent-level: 2 -*- */
+/* vim: set sts=2 sw=2 et tw=80: */
+"use strict";
+
+const { Downloads } = ChromeUtils.importESModule(
+  "resource://gre/modules/Downloads.sys.mjs"
+);
+
+const server = createHttpServer();
+server.registerDirectory("/data/", do_get_file("data"));
+
+const BASE = `http://localhost:${server.identity.primaryPort}/data`;
+const TXT_FILE = "file_download.txt";
+const TXT_URL = BASE + "/" + TXT_FILE;
+const TXT_LEN = 46;
+const HTML_FILE = "file_download.html";
+const HTML_URL = BASE + "/" + HTML_FILE;
+const HTML_LEN = 117;
+const EMPTY_FILE = "empty_file_download.txt";
+const EMPTY_URL = BASE + "/" + EMPTY_FILE;
+const EMPTY_LEN = 0;
+const BIG_LEN = 1000; // something bigger both TXT_LEN and HTML_LEN
+
+function backgroundScript() {
+  let complete = new Map();
+
+  function waitForComplete(id) {
+    if (complete.has(id)) {
+      return complete.get(id).promise;
+    }
+
+    let promise = new Promise(resolve => {
+      complete.set(id, { resolve });
+    });
+    complete.get(id).promise = promise;
+    return promise;
+  }
+
+  browser.downloads.onChanged.addListener(change => {
+    if (change.state && change.state.current == "complete") {
+      // Make sure we have a promise.
+      waitForComplete(change.id);
+      complete.get(change.id).resolve();
+    }
+  });
+
+  browser.test.onMessage.addListener(async (msg, ...args) => {
+    if (msg == "download.request") {
+      try {
+        let id = await browser.downloads.download(args[0]);
+        browser.test.sendMessage("download.done", { status: "success", id });
+      } catch (error) {
+        browser.test.sendMessage("download.done", {
+          status: "error",
+          errmsg: error.message,
+        });
+      }
+    } else if (msg == "search.request") {
+      try {
+        let downloads = await browser.downloads.search(args[0]);
+        browser.test.sendMessage("search.done", {
+          status: "success",
+          downloads,
+        });
+      } catch (error) {
+        browser.test.sendMessage("search.done", {
+          status: "error",
+          errmsg: error.message,
+        });
+      }
+    } else if (msg == "waitForComplete.request") {
+      await waitForComplete(args[0]);
+      browser.test.sendMessage("waitForComplete.done");
+    }
+  });
+
+  browser.test.sendMessage("ready");
+}
+
+async function clearDownloads(callback) {
+  let list = await Downloads.getList(Downloads.ALL);
+  let downloads = await list.getAll();
+
+  await Promise.all(downloads.map(download => list.remove(download)));
+
+  return downloads;
+}
+
+add_task(async function test_search() {
+  const nsIFile = Ci.nsIFile;
+  let downloadDir = FileUtils.getDir("TmpD", ["downloads"]);
+  downloadDir.createUnique(nsIFile.DIRECTORY_TYPE, FileUtils.PERMS_DIRECTORY);
+  info(`downloadDir ${downloadDir.path}`);
+
+  function downloadPath(filename) {
+    let path = downloadDir.clone();
+    path.append(filename);
+    return path.path;
+  }
+
+  Services.prefs.setIntPref("browser.download.folderList", 2);
+  Services.prefs.setComplexValue("browser.download.dir", nsIFile, downloadDir);
+  Services.prefs.setBoolPref("privacy.reduceTimerPrecision", false);
+
+  registerCleanupFunction(async () => {
+    Services.prefs.clearUserPref("browser.download.folderList");
+    Services.prefs.clearUserPref("browser.download.dir");
+    Services.prefs.clearUserPref("privacy.reduceTimerPrecision");
+    await cleanupDir(downloadDir);
+    await clearDownloads();
+  });
+
+  await clearDownloads().then(downloads => {
+    info(`removed ${downloads.length} pre-existing downloads from history`);
+  });
+
+  let extension = ExtensionTestUtils.loadExtension({
+    background: backgroundScript,
+    manifest: {
+      permissions: ["downloads"],
+    },
+  });
+
+  async function download(options) {
+    extension.sendMessage("download.request", options);
+    let result = await extension.awaitMessage("download.done");
+
+    if (result.status == "success") {
+      info(`wait for onChanged event to indicate ${result.id} is complete`);
+      extension.sendMessage("waitForComplete.request", result.id);
+
+      await extension.awaitMessage("waitForComplete.done");
+    }
+
+    return result;
+  }
+
+  function search(query) {
+    extension.sendMessage("search.request", query);
+    return extension.awaitMessage("search.done");
+  }
+
+  await extension.startup();
+  await extension.awaitMessage("ready");
+
+  // Do some downloads...
+  const time1 = new Date();
+
+  let downloadIds = {};
+  let msg = await download({ url: TXT_URL });
+  equal(msg.status, "success", "download() succeeded");
+  downloadIds.txt1 = msg.id;
+
+  const TXT_FILE2 = "NewFile.txt";
+  msg = await download({ url: TXT_URL, filename: TXT_FILE2 });
+  equal(msg.status, "success", "download() succeeded");
+  downloadIds.txt2 = msg.id;
+
+  msg = await download({ url: EMPTY_URL });
+  equal(msg.status, "success", "download() succeeded");
+  downloadIds.txt3 = msg.id;
+
+  const time2 = new Date();
+
+  msg = await download({ url: HTML_URL });
+  equal(msg.status, "success", "download() succeeded");
+  downloadIds.html1 = msg.id;
+
+  const HTML_FILE2 = "renamed.html";
+  msg = await download({ url: HTML_URL, filename: HTML_FILE2 });
+  equal(msg.status, "success", "download() succeeded");
+  downloadIds.html2 = msg.id;
+
+  const time3 = new Date();
+
+  // Search for each individual download and check
+  // the corresponding DownloadItem.
+  async function checkDownloadItem(id, expect) {
+    let item = await search({ id });
+    equal(item.status, "success", "search() succeeded");
+    equal(item.downloads.length, 1, "search() found exactly 1 download");
+
+    Object.keys(expect).forEach(function (field) {
+      equal(
+        item.downloads[0][field],
+        expect[field],
+        `DownloadItem.${field} is correct"`
+      );
+    });
+  }
+  await checkDownloadItem(downloadIds.txt1, {
+    url: TXT_URL,
+    filename: downloadPath(TXT_FILE),
+    mime: "text/plain",
+    state: "complete",
+    bytesReceived: TXT_LEN,
+    totalBytes: TXT_LEN,
+    fileSize: TXT_LEN,
+    exists: true,
+  });
+
+  await checkDownloadItem(downloadIds.txt2, {
+    url: TXT_URL,
+    filename: downloadPath(TXT_FILE2),
+    mime: "text/plain",
+    state: "complete",
+    bytesReceived: TXT_LEN,
+    totalBytes: TXT_LEN,
+    fileSize: TXT_LEN,
+    exists: true,
+  });
+
+  await checkDownloadItem(downloadIds.txt3, {
+    url: EMPTY_URL,
+    filename: downloadPath(EMPTY_FILE),
+    mime: "text/plain",
+    state: "complete",
+    bytesReceived: EMPTY_LEN,
+    totalBytes: EMPTY_LEN,
+    fileSize: EMPTY_LEN,
+    exists: true,
+  });
+
+  await checkDownloadItem(downloadIds.html1, {
+    url: HTML_URL,
+    filename: downloadPath(HTML_FILE),
+    mime: "text/html",
+    state: "complete",
+    bytesReceived: HTML_LEN,
+    totalBytes: HTML_LEN,
+    fileSize: HTML_LEN,
+    exists: true,
+  });
+
+  await checkDownloadItem(downloadIds.html2, {
+    url: HTML_URL,
+    filename: downloadPath(HTML_FILE2),
+    mime: "text/html",
+    state: "complete",
+    bytesReceived: HTML_LEN,
+    totalBytes: HTML_LEN,
+    fileSize: HTML_LEN,
+    exists: true,
+  });
+
+  async function checkSearch(query, expected, description, exact) {
+    let item = await search(query);
+    equal(item.status, "success", "search() succeeded");
+    equal(
+      item.downloads.length,
+      expected.length,
+      `search() for ${description} found exactly ${expected.length} downloads`
+    );
+
+    let receivedIds = item.downloads.map(i => i.id);
+    if (exact) {
+      receivedIds.forEach((id, idx) => {
+        equal(
+          id,
+          downloadIds[expected[idx]],
+          `search() for ${description} returned ${expected[idx]} in position ${idx}`
+        );
+      });
+    } else {
+      Object.keys(downloadIds).forEach(key => {
+        const id = downloadIds[key];
+        const thisExpected = expected.includes(key);
+        equal(
+          receivedIds.includes(id),
+          thisExpected,
+          `search() for ${description} ${
+            thisExpected ? "includes" : "does not include"
+          } ${key}`
+        );
+      });
+    }
+  }
+
+  // Check that search with an invalid id returns nothing.
+  // NB: for now ids are not persistent and we start numbering them at 1
+  //     so a sufficiently large number will be unused.
+  const INVALID_ID = 1000;
+  await checkSearch({ id: INVALID_ID }, [], "invalid id");
+
+  // Check that search on url works.
+  await checkSearch({ url: TXT_URL }, ["txt1", "txt2"], "url");
+
+  // Check that regexp on url works.
+  const HTML_REGEX = "[download]{8}.html+$";
+  await checkSearch({ urlRegex: HTML_REGEX }, ["html1", "html2"], "url regexp");
+
+  // Check that compatible url+regexp works
+  await checkSearch(
+    { url: HTML_URL, urlRegex: HTML_REGEX },
+    ["html1", "html2"],
+    "compatible url+urlRegex"
+  );
+
+  // Check that incompatible url+regexp works
+  await checkSearch(
+    { url: TXT_URL, urlRegex: HTML_REGEX },
+    [],
+    "incompatible url+urlRegex"
+  );
+
+  // Check that search on filename works.
+  await checkSearch({ filename: downloadPath(TXT_FILE) }, ["txt1"], "filename");
+
+  // Check that regexp on filename works.
+  await checkSearch({ filenameRegex: HTML_REGEX }, ["html1"], "filename regex");
+
+  // Check that compatible filename+regexp works
+  await checkSearch(
+    { filename: downloadPath(HTML_FILE), filenameRegex: HTML_REGEX },
+    ["html1"],
+    "compatible filename+filename regex"
+  );
+
+  // Check that incompatible filename+regexp works
+  await checkSearch(
+    { filename: downloadPath(TXT_FILE), filenameRegex: HTML_REGEX },
+    [],
+    "incompatible filename+filename regex"
+  );
+
+  // Check that simple positive search terms work.
+  await checkSearch(
+    { query: ["file_download"] },
+    ["txt1", "txt2", "txt3", "html1", "html2"],
+    "term file_download"
+  );
+  await checkSearch({ query: ["NewFile"] }, ["txt2"], "term NewFile");
+
+  // Check that positive search terms work case-insensitive.
+  await checkSearch({ query: ["nEwfILe"] }, ["txt2"], "term nEwfiLe");
+
+  // Check that negative search terms work.
+  await checkSearch({ query: ["-txt"] }, ["html1", "html2"], "term -txt");
+
+  // Check that positive and negative search terms together work.
+  await checkSearch(
+    { query: ["html", "-renamed"] },
+    ["html1"],
+    "positive and negative terms"
+  );
+
+  async function checkSearchWithDate(query, expected, description) {
+    const fields = Object.keys(query);
+    if (fields.length != 1 || !(query[fields[0]] instanceof Date)) {
+      throw new Error("checkSearchWithDate expects exactly one Date field");
+    }
+    const field = fields[0];
+    const date = query[field];
+
+    let newquery = {};
+
+    // Check as a Date
+    newquery[field] = date;
+    await checkSearch(newquery, expected, `${description} as Date`);
+
+    // Check as numeric milliseconds
+    newquery[field] = date.valueOf();
+    await checkSearch(newquery, expected, `${description} as numeric ms`);
+
+    // Check as stringified milliseconds
+    newquery[field] = date.valueOf().toString();
+    await checkSearch(newquery, expected, `${description} as string ms`);
+
+    // Check as ISO string
+    newquery[field] = date.toISOString();
+    await checkSearch(newquery, expected, `${description} as iso string`);
+  }
+
+  // Check startedBefore
+  await checkSearchWithDate({ startedBefore: time1 }, [], "before time1");
+  await checkSearchWithDate(
+    { startedBefore: time2 },
+    ["txt1", "txt2", "txt3"],
+    "before time2"
+  );
+  await checkSearchWithDate(
+    { startedBefore: time3 },
+    ["txt1", "txt2", "txt3", "html1", "html2"],
+    "before time3"
+  );
+
+  // Check startedAfter
+  await checkSearchWithDate(
+    { startedAfter: time1 },
+    ["txt1", "txt2", "txt3", "html1", "html2"],
+    "after time1"
+  );
+  await checkSearchWithDate(
+    { startedAfter: time2 },
+    ["html1", "html2"],
+    "after time2"
+  );
+  await checkSearchWithDate({ startedAfter: time3 }, [], "after time3");
+
+  // Check simple search on totalBytes
+  await checkSearch({ totalBytes: TXT_LEN }, ["txt1", "txt2"], "totalBytes");
+  await checkSearch({ totalBytes: HTML_LEN }, ["html1", "html2"], "totalBytes");
+
+  // Check simple test on totalBytes{Greater,Less}
+  // (NB: TXT_LEN < HTML_LEN < BIG_LEN)
+  await checkSearch(
+    { totalBytesGreater: 0 },
+    ["txt1", "txt2", "html1", "html2"],
+    "totalBytesGreater than 0"
+  );
+  await checkSearch(
+    { totalBytesGreater: TXT_LEN },
+    ["html1", "html2"],
+    `totalBytesGreater than ${TXT_LEN}`
+  );
+  await checkSearch(
+    { totalBytesGreater: HTML_LEN },
+    [],
+    `totalBytesGreater than ${HTML_LEN}`
+  );
+  await checkSearch(
+    { totalBytesLess: TXT_LEN },
+    ["txt3"],
+    `totalBytesLess than ${TXT_LEN}`
+  );
+  await checkSearch(
+    { totalBytesLess: HTML_LEN },
+    ["txt1", "txt2", "txt3"],
+    `totalBytesLess than ${HTML_LEN}`
+  );
+  await checkSearch(
+    { totalBytesLess: BIG_LEN },
+    ["txt1", "txt2", "txt3", "html1", "html2"],
+    `totalBytesLess than ${BIG_LEN}`
+  );
+
+  // Bug 1503760 check if 0 byte files with no search query are returned.
+  await checkSearch(
+    {},
+    ["txt1", "txt2", "txt3", "html1", "html2"],
+    "totalBytesGreater than -1"
+  );
+
+  // Check good combinations of totalBytes*.
+  await checkSearch(
+    { totalBytes: HTML_LEN, totalBytesGreater: TXT_LEN },
+    ["html1", "html2"],
+    "totalBytes and totalBytesGreater"
+  );
+  await checkSearch(
+    { totalBytes: TXT_LEN, totalBytesLess: HTML_LEN },
+    ["txt1", "txt2"],
+    "totalBytes and totalBytesGreater"
+  );
+  await checkSearch(
+    { totalBytes: HTML_LEN, totalBytesLess: BIG_LEN, totalBytesGreater: 0 },
+    ["html1", "html2"],
+    "totalBytes and totalBytesLess and totalBytesGreater"
+  );
+
+  // Check bad combination of totalBytes*.
+  await checkSearch(
+    { totalBytesLess: TXT_LEN, totalBytesGreater: HTML_LEN },
+    [],
+    "bad totalBytesLess, totalBytesGreater combination"
+  );
+  await checkSearch(
+    { totalBytes: TXT_LEN, totalBytesGreater: HTML_LEN },
+    [],
+    "bad totalBytes, totalBytesGreater combination"
+  );
+  await checkSearch(
+    { totalBytes: HTML_LEN, totalBytesLess: TXT_LEN },
+    [],
+    "bad totalBytes, totalBytesLess combination"
+  );
+
+  // Check mime.
+  await checkSearch(
+    { mime: "text/plain" },
+    ["txt1", "txt2", "txt3"],
+    "mime text/plain"
+  );
+  await checkSearch(
+    { mime: "text/html" },
+    ["html1", "html2"],
+    "mime text/htmlplain"
+  );
+  await checkSearch({ mime: "video/webm" }, [], "mime video/webm");
+
+  // Check fileSize.
+  await checkSearch({ fileSize: TXT_LEN }, ["txt1", "txt2"], "fileSize");
+  await checkSearch({ fileSize: HTML_LEN }, ["html1", "html2"], "fileSize");
+
+  // Fields like bytesReceived, paused, state, exists are meaningful
+  // for downloads that are in progress but have not yet completed.
+  // todo: add tests for these when we have better support for in-progress
+  // downloads (e.g., after pause(), resume() and cancel() are implemented)
+
+  // Check multiple query properties.
+  // We could make this testing arbitrarily complicated...
+  // We already tested combining fields with obvious interactions above
+  // (e.g., filename and filenameRegex or startTime and startedBefore/After)
+  // so now just throw as many fields as we can at a single search and
+  // make sure a simple case still works.
+  await checkSearch(
+    {
+      url: TXT_URL,
+      urlRegex: "download",
+      filename: downloadPath(TXT_FILE),
+      filenameRegex: "download",
+      query: ["download"],
+      startedAfter: time1.valueOf().toString(),
+      startedBefore: time2.valueOf().toString(),
+      totalBytes: TXT_LEN,
+      totalBytesGreater: 0,
+      totalBytesLess: BIG_LEN,
+      mime: "text/plain",
+      fileSize: TXT_LEN,
+    },
+    ["txt1"],
+    "many properties"
+  );
+
+  // Check simple orderBy (forward and backward).
+  await checkSearch(
+    { orderBy: ["startTime"] },
+    ["txt1", "txt2", "txt3", "html1", "html2"],
+    "orderBy startTime",
+    true
+  );
+  await checkSearch(
+    { orderBy: ["-startTime"] },
+    ["html2", "html1", "txt3", "txt2", "txt1"],
+    "orderBy -startTime",
+    true
+  );
+
+  // Check orderBy with multiple fields.
+  // NB: TXT_URL and HTML_URL differ only in extension and .html precedes .txt
+  // EMPTY_URL begins with e which precedes f
+  await checkSearch(
+    { orderBy: ["url", "-startTime"] },
+    ["txt3", "html2", "html1", "txt2", "txt1"],
+    "orderBy with multiple fields",
+    true
+  );
+
+  // Check orderBy with limit.
+  await checkSearch(
+    { orderBy: ["url"], limit: 1 },
+    ["txt3"],
+    "orderBy with limit",
+    true
+  );
+
+  // Check bad arguments.
+  async function checkBadSearch(query, pattern, description) {
+    let item = await search(query);
+    equal(item.status, "error", "search() failed");
+    ok(
+      pattern.test(item.errmsg),
+      `error message for ${description} was correct (${item.errmsg}).`
+    );
+  }
+
+  await checkBadSearch(
+    "myquery",
+    /Incorrect argument type/,
+    "query is not an object"
+  );
+  await checkBadSearch(
+    { bogus: "boo" },
+    /Unexpected property/,
+    "query contains an unknown field"
+  );
+  await checkBadSearch(
+    { query: "query string" },
+    /Expected array/,
+    "query.query is a string"
+  );
+  await checkBadSearch(
+    { startedBefore: "i am not a time" },
+    /Type error/,
+    "query.startedBefore is not a valid time"
+  );
+  await checkBadSearch(
+    { startedAfter: "i am not a time" },
+    /Type error/,
+    "query.startedAfter is not a valid time"
+  );
+  await checkBadSearch(
+    { endedBefore: "i am not a time" },
+    /Type error/,
+    "query.endedBefore is not a valid time"
+  );
+  await checkBadSearch(
+    { endedAfter: "i am not a time" },
+    /Type error/,
+    "query.endedAfter is not a valid time"
+  );
+  await checkBadSearch(
+    { urlRegex: "[" },
+    /Invalid urlRegex/,
+    "query.urlRegexp is not a valid regular expression"
+  );
+  await checkBadSearch(
+    { filenameRegex: "[" },
+    /Invalid filenameRegex/,
+    "query.filenameRegexp is not a valid regular expression"
+  );
+  await checkBadSearch(
+    { orderBy: "startTime" },
+    /Expected array/,
+    "query.orderBy is not an array"
+  );
+  await checkBadSearch(
+    { orderBy: ["bogus"] },
+    /Invalid orderBy field/,
+    "query.orderBy references a non-existent field"
+  );
+
+  await extension.unload();
+});
+
+// Test that downloads with totalBytes of -1 (ie, that have not yet started)
+// work properly.  See bug 1519762 for details of a past regression in
+// this area.
+add_task(async function test_inprogress() {
+  let resume,
+    resumePromise = new Promise(resolve => {
+      resume = resolve;
+    });
+  let hit = false;
+  server.registerPathHandler("/data/slow", async (request, response) => {
+    hit = true;
+    response.processAsync();
+    await resumePromise;
+    response.setHeader("Content-type", "text/plain");
+    response.write("");
+    response.finish();
+  });
+
+  let extension = ExtensionTestUtils.loadExtension({
+    manifest: {
+      permissions: ["downloads"],
+    },
+    background() {
+      browser.test.onMessage.addListener(async (msg, url) => {
+        let id = await browser.downloads.download({ url });
+        let full = await browser.downloads.search({ id });
+
+        browser.test.assertEq(
+          full.length,
+          1,
+          "Found new download in search results"
+        );
+        browser.test.assertEq(
+          full[0].totalBytes,
+          -1,
+          "New download still has totalBytes == -1"
+        );
+
+        browser.downloads.onChanged.addListener(info => {
+          if (info.id == id && info.state && info.state.current == "complete") {
+            browser.test.notifyPass("done");
+          }
+        });
+
+        browser.test.sendMessage("started");
+      });
+    },
+  });
+
+  await extension.startup();
+  extension.sendMessage("go", `${BASE}/slow`);
+  await extension.awaitMessage("started");
+  resume();
+  await extension.awaitFinish("done");
+  await extension.unload();
+  Assert.ok(hit, "slow path was actually hit");
+});
diff --git a/toolkit/components/extensions/test/xpcshell/test_ext_downloads_urlencoded.js b/toolkit/components/extensions/test/xpcshell/test_ext_downloads_urlencoded.js
new file mode 100644
index 0000000000..03288fb5d5
--- /dev/null
+++ b/toolkit/components/extensions/test/xpcshell/test_ext_downloads_urlencoded.js
@@ -0,0 +1,257 @@
+/* -*- Mode: indent-tabs-mode: nil; js-indent-level: 2 -*- */
+/* vim: set sts=2 sw=2 et tw=80: */
+"use strict";
+
+const { Downloads } = ChromeUtils.importESModule(
+  "resource://gre/modules/Downloads.sys.mjs"
+);
+
+function backgroundScript() {
+  let complete = new Map();
+
+  function waitForComplete(id) {
+    if (complete.has(id)) {
+      return complete.get(id).promise;
+    }
+
+    let promise = new Promise(resolve => {
+      complete.set(id, { resolve });
+    });
+    complete.get(id).promise = promise;
+    return promise;
+  }
+
+  browser.downloads.onChanged.addListener(change => {
+    if (change.state && change.state.current == "complete") {
+      // Make sure we have a promise.
+      waitForComplete(change.id);
+      complete.get(change.id).resolve();
+    }
+  });
+
+  browser.test.onMessage.addListener(async (msg, ...args) => {
+    if (msg == "download.request") {
+      try {
+        let id = await browser.downloads.download(args[0]);
+        browser.test.sendMessage("download.done", { status: "success", id });
+      } catch (error) {
+        browser.test.sendMessage("download.done", {
+          status: "error",
+          errmsg: error.message,
+        });
+      }
+    } else if (msg == "search.request") {
+      try {
+        let downloads = await browser.downloads.search(args[0]);
+        browser.test.sendMessage("search.done", {
+          status: "success",
+          downloads,
+        });
+      } catch (error) {
+        browser.test.sendMessage("search.done", {
+          status: "error",
+          errmsg: error.message,
+        });
+      }
+    } else if (msg == "waitForComplete.request") {
+      await waitForComplete(args[0]);
+      browser.test.sendMessage("waitForComplete.done");
+    }
+  });
+
+  browser.test.sendMessage("ready");
+}
+
+async function clearDownloads(callback) {
+  let list = await Downloads.getList(Downloads.ALL);
+  let downloads = await list.getAll();
+
+  await Promise.all(downloads.map(download => list.remove(download)));
+
+  return downloads;
+}
+
+add_task(async function test_decoded_filename_download() {
+  const server = createHttpServer();
+  server.registerPrefixHandler("/data/", (_, res) => res.write("length=8"));
+
+  const BASE = `http://localhost:${server.identity.primaryPort}/data`;
+  const FILE_NAME_ENCODED_1 = "file%2Fencode.txt";
+  const FILE_NAME_DECODED_1 = "file_encode.txt";
+  const FILE_NAME_ENCODED_URL_1 = BASE + "/" + FILE_NAME_ENCODED_1;
+  const FILE_NAME_ENCODED_2 = "file%F0%9F%9A%B2encoded.txt";
+  const FILE_NAME_DECODED_2 = "file\u{0001F6B2}encoded.txt";
+  const FILE_NAME_ENCODED_URL_2 = BASE + "/" + FILE_NAME_ENCODED_2;
+  const FILE_NAME_ENCODED_3 = "file%X%20encode.txt";
+  const FILE_NAME_DECODED_3 = "file%X encode.txt";
+  const FILE_NAME_ENCODED_URL_3 = BASE + "/" + FILE_NAME_ENCODED_3;
+  const FILE_NAME_ENCODED_4 = "file%E3%80%82encode.txt";
+  const FILE_NAME_DECODED_4 = "file\u3002encode.txt";
+  const FILE_NAME_ENCODED_URL_4 = BASE + "/" + FILE_NAME_ENCODED_4;
+  const FILE_ENCODED_LEN = 8;
+
+  const nsIFile = Ci.nsIFile;
+  let downloadDir = FileUtils.getDir("TmpD", ["downloads"]);
+  downloadDir.createUnique(nsIFile.DIRECTORY_TYPE, FileUtils.PERMS_DIRECTORY);
+  info(`downloadDir ${downloadDir.path}`);
+
+  function downloadPath(filename) {
+    let path = downloadDir.clone();
+    path.append(filename);
+    return path.path;
+  }
+
+  Services.prefs.setIntPref("browser.download.folderList", 2);
+  Services.prefs.setComplexValue("browser.download.dir", nsIFile, downloadDir);
+
+  registerCleanupFunction(async () => {
+    Services.prefs.clearUserPref("browser.download.folderList");
+    Services.prefs.clearUserPref("browser.download.dir");
+    await cleanupDir(downloadDir);
+    await clearDownloads();
+  });
+
+  await clearDownloads().then(downloads => {
+    info(`removed ${downloads.length} pre-existing downloads from history`);
+  });
+
+  let extension = ExtensionTestUtils.loadExtension({
+    background: backgroundScript,
+    manifest: {
+      permissions: ["downloads"],
+    },
+  });
+
+  async function download(options) {
+    extension.sendMessage("download.request", options);
+    let result = await extension.awaitMessage("download.done");
+
+    if (result.status == "success") {
+      info(`wait for onChanged event to indicate ${result.id} is complete`);
+      extension.sendMessage("waitForComplete.request", result.id);
+
+      await extension.awaitMessage("waitForComplete.done");
+    }
+
+    return result;
+  }
+
+  function search(query) {
+    extension.sendMessage("search.request", query);
+    return extension.awaitMessage("search.done");
+  }
+
+  await extension.startup();
+  await extension.awaitMessage("ready");
+
+  let downloadIds = {};
+  let msg = await download({ url: FILE_NAME_ENCODED_URL_1 });
+  equal(msg.status, "success", "download() succeeded");
+  downloadIds.fileEncoded1 = msg.id;
+
+  msg = await download({ url: FILE_NAME_ENCODED_URL_2 });
+  equal(msg.status, "success", "download() succeeded");
+  downloadIds.fileEncoded2 = msg.id;
+
+  msg = await download({ url: FILE_NAME_ENCODED_URL_3 });
+  equal(msg.status, "success", "download() succeeded");
+  downloadIds.fileEncoded3 = msg.id;
+
+  msg = await download({ url: FILE_NAME_ENCODED_URL_4 });
+  equal(msg.status, "success", "download() succeeded");
+  downloadIds.fileEncoded4 = msg.id;
+
+  // Search for each individual download and check
+  // the corresponding DownloadItem.
+  async function checkDownloadItem(id, expect) {
+    let item = await search({ id });
+    equal(item.status, "success", "search() succeeded");
+    equal(item.downloads.length, 1, "search() found exactly 1 download");
+    Object.keys(expect).forEach(function (field) {
+      equal(
+        item.downloads[0][field],
+        expect[field],
+        `DownloadItem.${field} is correct"`
+      );
+    });
+  }
+
+  await checkDownloadItem(downloadIds.fileEncoded1, {
+    url: FILE_NAME_ENCODED_URL_1,
+    filename: downloadPath(FILE_NAME_DECODED_1),
+    state: "complete",
+    bytesReceived: FILE_ENCODED_LEN,
+    totalBytes: FILE_ENCODED_LEN,
+    fileSize: FILE_ENCODED_LEN,
+    exists: true,
+  });
+
+  await checkDownloadItem(downloadIds.fileEncoded2, {
+    url: FILE_NAME_ENCODED_URL_2,
+    filename: downloadPath(FILE_NAME_DECODED_2),
+    state: "complete",
+    bytesReceived: FILE_ENCODED_LEN,
+    totalBytes: FILE_ENCODED_LEN,
+    fileSize: FILE_ENCODED_LEN,
+    exists: true,
+  });
+
+  await checkDownloadItem(downloadIds.fileEncoded3, {
+    url: FILE_NAME_ENCODED_URL_3,
+    filename: downloadPath(FILE_NAME_DECODED_3),
+    state: "complete",
+    bytesReceived: FILE_ENCODED_LEN,
+    totalBytes: FILE_ENCODED_LEN,
+    fileSize: FILE_ENCODED_LEN,
+    exists: true,
+  });
+
+  await checkDownloadItem(downloadIds.fileEncoded4, {
+    url: FILE_NAME_ENCODED_URL_4,
+    filename: downloadPath(FILE_NAME_DECODED_4),
+    state: "complete",
+    bytesReceived: FILE_ENCODED_LEN,
+    totalBytes: FILE_ENCODED_LEN,
+    fileSize: FILE_ENCODED_LEN,
+    exists: true,
+  });
+
+  // Searching for downloads by the decoded filename works correctly.
+  async function checkSearch(query, expected, description) {
+    let item = await search(query);
+    equal(item.status, "success", "search() succeeded");
+    equal(
+      item.downloads.length,
+      expected.length,
+      `search() for ${description} found exactly ${expected.length} downloads`
+    );
+    equal(
+      item.downloads[0].id,
+      downloadIds[expected[0]],
+      `search() for ${description} returned ${expected[0]} in position ${0}`
+    );
+  }
+
+  await checkSearch(
+    { filename: downloadPath(FILE_NAME_DECODED_1) },
+    ["fileEncoded1"],
+    "filename"
+  );
+  await checkSearch(
+    { filename: downloadPath(FILE_NAME_DECODED_2) },
+    ["fileEncoded2"],
+    "filename"
+  );
+  await checkSearch(
+    { filename: downloadPath(FILE_NAME_DECODED_3) },
+    ["fileEncoded3"],
+    "filename"
+  );
+  await checkSearch(
+    { filename: downloadPath(FILE_NAME_DECODED_4) },
+    ["fileEncoded4"],
+    "filename"
+  );
+
+  await extension.unload();
+});
diff --git a/toolkit/components/extensions/test/xpcshell/test_ext_error_location.js b/toolkit/components/extensions/test/xpcshell/test_ext_error_location.js
new file mode 100644
index 0000000000..ab18c9c371
--- /dev/null
+++ b/toolkit/components/extensions/test/xpcshell/test_ext_error_location.js
@@ -0,0 +1,48 @@
+/* -*- Mode: indent-tabs-mode: nil; js-indent-level: 2 -*- */
+/* vim: set sts=2 sw=2 et tw=80: */
+"use strict";
+
+add_task(async function test_error_location() {
+  let extension = ExtensionTestUtils.loadExtension({
+    async background() {
+      let { fileName } = new Error();
+
+      browser.test.sendMessage("fileName", fileName);
+
+      browser.runtime.sendMessage("Meh.", () => {});
+
+      await browser.test.assertRejects(
+        browser.runtime.sendMessage("Meh"),
+        error => {
+          return error.fileName === fileName && error.lineNumber === 9;
+        }
+      );
+
+      browser.test.notifyPass("error-location");
+    },
+  });
+
+  let fileName;
+  const { messages } = await promiseConsoleOutput(async () => {
+    await extension.startup();
+
+    fileName = await extension.awaitMessage("fileName");
+
+    await extension.awaitFinish("error-location");
+
+    await extension.unload();
+  });
+
+  let [msg] = messages.filter(m => m.message.includes("Unchecked lastError"));
+
+  equal(msg.sourceName, fileName, "Message source");
+  equal(msg.lineNumber, 6, "Message line");
+
+  let frame = msg.stack;
+  if (frame) {
+    equal(frame.source, fileName, "Frame source");
+    equal(frame.line, 6, "Frame line");
+    equal(frame.column, 23, "Frame column");
+    equal(frame.functionDisplayName, "background", "Frame function name");
+  }
+});
diff --git a/toolkit/components/extensions/test/xpcshell/test_ext_eventpage_idle.js b/toolkit/components/extensions/test/xpcshell/test_ext_eventpage_idle.js
new file mode 100644
index 0000000000..6aade7af1f
--- /dev/null
+++ b/toolkit/components/extensions/test/xpcshell/test_ext_eventpage_idle.js
@@ -0,0 +1,574 @@
+"use strict";
+
+ChromeUtils.defineESModuleGetters(this, {
+  ExtensionPreferencesManager:
+    "resource://gre/modules/ExtensionPreferencesManager.sys.mjs",
+});
+
+AddonTestUtils.init(this);
+AddonTestUtils.overrideCertDB();
+
+AddonTestUtils.createAppInfo(
+  "xpcshell@tests.mozilla.org",
+  "XPCShell",
+  "42",
+  "42"
+);
+
+Services.prefs.setBoolPref("extensions.eventPages.enabled", true);
+// Set minimum idle timeout for testing
+Services.prefs.setIntPref("extensions.background.idle.timeout", 0);
+
+// Expected rejection from the test cases defined in this file.
+PromiseTestUtils.allowMatchingRejectionsGlobally(/expected-test-rejection/);
+PromiseTestUtils.allowMatchingRejectionsGlobally(
+  /Actor 'Conduits' destroyed before query 'RunListener' was resolved/
+);
+
+add_setup(async () => {
+  await AddonTestUtils.promiseStartupManager();
+});
+
+add_task(async function test_eventpage_idle() {
+  clearHistograms();
+
+  assertHistogramEmpty(WEBEXT_EVENTPAGE_RUNNING_TIME_MS);
+  assertKeyedHistogramEmpty(WEBEXT_EVENTPAGE_RUNNING_TIME_MS_BY_ADDONID);
+  assertHistogramEmpty(WEBEXT_EVENTPAGE_IDLE_RESULT_COUNT);
+  assertKeyedHistogramEmpty(WEBEXT_EVENTPAGE_IDLE_RESULT_COUNT_BY_ADDONID);
+
+  let extension = ExtensionTestUtils.loadExtension({
+    useAddonManager: "permanent",
+    manifest: {
+      permissions: ["browserSettings"],
+      background: { persistent: false },
+    },
+    background() {
+      browser.browserSettings.allowPopupsForUserEvents.onChange.addListener(
+        () => {
+          browser.test.sendMessage("allowPopupsForUserEvents");
+        }
+      );
+      browser.runtime.onSuspend.addListener(async () => {
+        let setting =
+          await browser.browserSettings.allowPopupsForUserEvents.get({});
+        browser.test.sendMessage("suspended", setting);
+      });
+    },
+  });
+  await extension.startup();
+  assertPersistentListeners(
+    extension,
+    "browserSettings",
+    "allowPopupsForUserEvents",
+    {
+      primed: false,
+    }
+  );
+
+  info(`test idle timeout after startup`);
+  await extension.awaitMessage("suspended");
+  await promiseExtensionEvent(extension, "shutdown-background-script");
+  assertPersistentListeners(
+    extension,
+    "browserSettings",
+    "allowPopupsForUserEvents",
+    {
+      primed: true,
+    }
+  );
+  ExtensionPreferencesManager.setSetting(
+    extension.id,
+    "allowPopupsForUserEvents",
+    "click"
+  );
+  await extension.awaitMessage("allowPopupsForUserEvents");
+  ok(true, "allowPopupsForUserEvents.onChange fired");
+
+  // again after the event is fired
+  info(`test idle timeout after wakeup`);
+  let setting = await extension.awaitMessage("suspended");
+  equal(setting.value, true, "verify simple async wait works in onSuspend");
+
+  await promiseExtensionEvent(extension, "shutdown-background-script");
+  assertPersistentListeners(
+    extension,
+    "browserSettings",
+    "allowPopupsForUserEvents",
+    {
+      primed: true,
+    }
+  );
+  ExtensionPreferencesManager.setSetting(
+    extension.id,
+    "allowPopupsForUserEvents",
+    false
+  );
+  await extension.awaitMessage("allowPopupsForUserEvents");
+  ok(true, "allowPopupsForUserEvents.onChange fired");
+
+  const { id } = extension;
+  await extension.unload();
+
+  info("Verify eventpage telemetry recorded");
+
+  assertHistogramSnapshot(
+    WEBEXT_EVENTPAGE_RUNNING_TIME_MS,
+    {
+      keyed: false,
+      processSnapshot: snapshot => snapshot.sum > 0,
+      expectedValue: true,
+    },
+    `Expect stored values in the eventpage running time non-keyed histogram snapshot`
+  );
+
+  assertHistogramSnapshot(
+    WEBEXT_EVENTPAGE_RUNNING_TIME_MS_BY_ADDONID,
+    {
+      keyed: true,
+      processSnapshot: snapshot => snapshot[id]?.sum > 0,
+      expectedValue: true,
+    },
+    `Expect stored values for addon with id ${id} in the eventpage running time keyed histogram snapshot`
+  );
+
+  assertHistogramCategoryNotEmpty(WEBEXT_EVENTPAGE_IDLE_RESULT_COUNT, {
+    category: "suspend",
+    categories: HISTOGRAM_EVENTPAGE_IDLE_RESULT_CATEGORIES,
+  });
+
+  assertHistogramCategoryNotEmpty(
+    WEBEXT_EVENTPAGE_IDLE_RESULT_COUNT_BY_ADDONID,
+    {
+      keyed: true,
+      key: id,
+      category: "suspend",
+      categories: HISTOGRAM_EVENTPAGE_IDLE_RESULT_CATEGORIES,
+    }
+  );
+});
+
+add_task(
+  { pref_set: [["extensions.webextensions.runtime.timeout", 500]] },
+  async function test_eventpage_runtime_onSuspend_timeout() {
+    let extension = ExtensionTestUtils.loadExtension({
+      useAddonManager: "permanent",
+      manifest: {
+        background: { persistent: false },
+      },
+      background() {
+        browser.runtime.onSuspend.addListener(() => {
+          // return a promise that never resolves
+          return new Promise(() => {});
+        });
+      },
+    });
+    await extension.startup();
+    await promiseExtensionEvent(extension, "shutdown-background-script");
+    ok(true, "onSuspend did not block background shutdown");
+    await extension.unload();
+  }
+);
+
+add_task(
+  { pref_set: [["extensions.webextensions.runtime.timeout", 500]] },
+  async function test_eventpage_runtime_onSuspend_reject() {
+    let extension = ExtensionTestUtils.loadExtension({
+      useAddonManager: "permanent",
+      manifest: {
+        background: { persistent: false },
+      },
+      background() {
+        browser.runtime.onSuspend.addListener(() => {
+          // Raise an error to test error handling in onSuspend
+          return Promise.reject("testing reject");
+        });
+      },
+    });
+    await extension.startup();
+    await promiseExtensionEvent(extension, "shutdown-background-script");
+    ok(true, "onSuspend did not block background shutdown");
+    await extension.unload();
+  }
+);
+
+add_task(
+  { pref_set: [["extensions.webextensions.runtime.timeout", 1000]] },
+  async function test_eventpage_runtime_onSuspend_canceled() {
+    clearHistograms();
+
+    assertHistogramEmpty(WEBEXT_EVENTPAGE_IDLE_RESULT_COUNT);
+    assertKeyedHistogramEmpty(WEBEXT_EVENTPAGE_IDLE_RESULT_COUNT_BY_ADDONID);
+
+    let extension = ExtensionTestUtils.loadExtension({
+      useAddonManager: "permanent",
+      manifest: {
+        permissions: ["browserSettings"],
+        background: { persistent: false },
+      },
+      background() {
+        let resolveSuspend;
+        browser.browserSettings.allowPopupsForUserEvents.onChange.addListener(
+          () => {
+            browser.test.sendMessage("allowPopupsForUserEvents");
+          }
+        );
+        browser.runtime.onSuspend.addListener(() => {
+          browser.test.sendMessage("suspending");
+          return new Promise(resolve => {
+            resolveSuspend = resolve;
+          });
+        });
+        browser.runtime.onSuspendCanceled.addListener(() => {
+          browser.test.sendMessage("suspendCanceled");
+        });
+        browser.test.onMessage.addListener(() => {
+          resolveSuspend();
+        });
+      },
+    });
+    await extension.startup();
+    await extension.awaitMessage("suspending");
+    // While suspending, cause an event
+    ExtensionPreferencesManager.setSetting(
+      extension.id,
+      "allowPopupsForUserEvents",
+      "click"
+    );
+    extension.sendMessage("resolveSuspend");
+    await extension.awaitMessage("allowPopupsForUserEvents");
+    await extension.awaitMessage("suspendCanceled");
+    ok(true, "event caused suspend-canceled");
+
+    assertHistogramCategoryNotEmpty(WEBEXT_EVENTPAGE_IDLE_RESULT_COUNT, {
+      category: "reset_event",
+      categories: HISTOGRAM_EVENTPAGE_IDLE_RESULT_CATEGORIES,
+    });
+
+    assertHistogramCategoryNotEmpty(
+      WEBEXT_EVENTPAGE_IDLE_RESULT_COUNT_BY_ADDONID,
+      {
+        keyed: true,
+        key: extension.id,
+        category: "reset_event",
+        categories: HISTOGRAM_EVENTPAGE_IDLE_RESULT_CATEGORIES,
+      }
+    );
+
+    await extension.awaitMessage("suspending");
+    await promiseExtensionEvent(extension, "shutdown-background-script");
+    await extension.unload();
+  }
+);
+
+add_task(async function test_terminateBackground_after_extension_hasShutdown() {
+  let extension = ExtensionTestUtils.loadExtension({
+    useAddonManager: "permanent",
+    manifest: {
+      background: { persistent: false },
+    },
+    async background() {
+      browser.runtime.onSuspend.addListener(() => {
+        browser.test.fail(
+          `runtime.onSuspend listener should have not been called`
+        );
+      });
+
+      // Call an API method implemented in the parent process (to be sure runtime.onSuspend
+      // listener is going to be fully registered from a parent process perspective by the
+      // time we will send the "bg-ready" test message).
+      await browser.runtime.getBrowserInfo();
+
+      browser.test.sendMessage("bg-ready");
+    },
+  });
+
+  await extension.startup();
+  await extension.awaitMessage("bg-ready");
+
+  // Fake suspending event page on idle while the extension was being shutdown by manually
+  // setting the hasShutdown flag to true on the Extension class instance object.
+  extension.extension.hasShutdown = true;
+  await extension.terminateBackground();
+  extension.extension.hasShutdown = false;
+
+  await extension.unload();
+});
+
+add_task(async function test_wakeupBackground_after_extension_hasShutdown() {
+  let extension = ExtensionTestUtils.loadExtension({
+    useAddonManager: "permanent",
+    manifest: {
+      background: { persistent: false },
+    },
+    async background() {
+      browser.test.sendMessage("bg-ready");
+    },
+  });
+
+  await extension.startup();
+  await extension.awaitMessage("bg-ready");
+  await extension.terminateBackground();
+
+  // Fake suspending event page on idle while the extension was being shutdown by manually
+  // setting the hasShutdown flag to true on the Extension class instance object.
+  extension.extension.hasShutdown = true;
+  await Assert.rejects(
+    extension.wakeupBackground(),
+    /wakeupBackground called while the extension was already shutting down/,
+    "Got the expected rejection when wakeupBackground is called after extension shutdown"
+  );
+  extension.extension.hasShutdown = false;
+
+  await extension.unload();
+});
+
+async function testSuspendShutdownRace({ manifest_version }) {
+  const extension = ExtensionTestUtils.loadExtension({
+    manifest: {
+      manifest_version,
+      background: manifest_version === 2 ? { persistent: false } : {},
+      permissions: ["webRequest", "webRequestBlocking"],
+      host_permissions: ["*://example.com/*"],
+      granted_host_permissions: true,
+    },
+    // Define an empty background script.
+    background() {},
+  });
+
+  await extension.startup();
+  await extension.extension.promiseBackgroundStarted();
+  const promiseTerminateBackground = extension.extension.terminateBackground();
+  // Wait one tick to leave to terminateBackground async method time to get
+  // past the first check that returns earlier if extension.hasShutdown is true.
+  await Promise.resolve();
+  const promiseUnload = extension.unload();
+
+  await promiseUnload;
+  try {
+    await promiseTerminateBackground;
+    ok(true, "extension.terminateBackground should not have been rejected");
+  } catch (err) {
+    ok(
+      false,
+      `extension.terminateBackground should not have been rejected: ${err} :: ${err.stack}`
+    );
+  }
+}
+
+add_task(function test_mv2_suspend_shutdown_race() {
+  return testSuspendShutdownRace({ manifest_version: 2 });
+});
+
+add_task(
+  {
+    pref_set: [["extensions.manifestV3.enabled", true]],
+  },
+  function test_mv3_suspend_shutdown_race() {
+    return testSuspendShutdownRace({ manifest_version: 3 });
+  }
+);
+
+function createPendingListenerTestExtension() {
+  return ExtensionTestUtils.loadExtension({
+    useAddonManager: "permanent",
+    manifest: {
+      permissions: ["browserSettings"],
+      background: { persistent: false },
+    },
+    background() {
+      let idx = 0;
+      browser.browserSettings.allowPopupsForUserEvents.onChange.addListener(
+        async () => {
+          const currIdx = idx++;
+          await new Promise((resolve, reject) => {
+            browser.test.onMessage.addListener(msg => {
+              switch (`${msg}-${currIdx}`) {
+                case "unblock-promise-0":
+                  resolve();
+                  browser.test.sendMessage("allowPopupsForUserEvents:resolved");
+                  break;
+                case "unblock-promise-1":
+                  reject(new Error("expected-test-rejection"));
+                  browser.test.sendMessage("allowPopupsForUserEvents:rejected");
+                  break;
+                default:
+                  browser.test.fail(`Unexpected test message: ${msg}`);
+              }
+            });
+            browser.test.sendMessage("allowPopupsForUserEvents:awaiting");
+          });
+        }
+      );
+
+      browser.runtime.onSuspend.addListener(() => {
+        // Raise an error to test error handling in onSuspend
+        return browser.test.sendMessage("runtime-on-suspend");
+      });
+
+      browser.test.sendMessage("bg-script-ready");
+    },
+  });
+}
+
+add_task(
+  { pref_set: [["extensions.background.idle.timeout", 500]] },
+  async function test_eventpage_idle_reset_on_async_listener_unresolved() {
+    clearHistograms();
+
+    assertHistogramEmpty(WEBEXT_EVENTPAGE_IDLE_RESULT_COUNT);
+    assertKeyedHistogramEmpty(WEBEXT_EVENTPAGE_IDLE_RESULT_COUNT_BY_ADDONID);
+
+    let extension = createPendingListenerTestExtension();
+    await extension.startup();
+    await extension.awaitMessage("bg-script-ready");
+
+    info("Trigger the first API event listener call");
+    ExtensionPreferencesManager.setSetting(
+      extension.id,
+      "allowPopupsForUserEvents",
+      "click"
+    );
+
+    await extension.awaitMessage("allowPopupsForUserEvents:awaiting");
+
+    info("Trigger the second API event listener call");
+    ExtensionPreferencesManager.setSetting(
+      extension.id,
+      "allowPopupsForUserEvents",
+      "click"
+    );
+
+    await extension.awaitMessage("allowPopupsForUserEvents:awaiting");
+
+    info("Wait for suspend on idle to be reset");
+    const [, resetIdleData] = await promiseExtensionEvent(
+      extension,
+      "background-script-reset-idle"
+    );
+
+    Assert.deepEqual(
+      resetIdleData,
+      {
+        reason: "pendingListeners",
+        pendingListeners: 2,
+      },
+      "Got the expected idle reset reason and pendingListeners count"
+    );
+
+    assertHistogramCategoryNotEmpty(WEBEXT_EVENTPAGE_IDLE_RESULT_COUNT, {
+      category: "reset_listeners",
+      categories: HISTOGRAM_EVENTPAGE_IDLE_RESULT_CATEGORIES,
+    });
+
+    assertHistogramCategoryNotEmpty(
+      WEBEXT_EVENTPAGE_IDLE_RESULT_COUNT_BY_ADDONID,
+      {
+        keyed: true,
+        key: extension.id,
+        category: "reset_listeners",
+        categories: HISTOGRAM_EVENTPAGE_IDLE_RESULT_CATEGORIES,
+      }
+    );
+
+    info(
+      "Resolve the async listener pending on a promise and expect the event page to suspend after the idle timeout"
+    );
+    extension.sendMessage("unblock-promise");
+    // Expect the two promises to be resolved and rejected respectively.
+    await extension.awaitMessage("allowPopupsForUserEvents:resolved");
+    await extension.awaitMessage("allowPopupsForUserEvents:rejected");
+
+    info("Await for the runtime.onSuspend event to be emitted");
+    await extension.awaitMessage("runtime-on-suspend");
+    await extension.unload();
+  }
+);
+
+add_task(
+  { pref_set: [["extensions.background.idle.timeout", 500]] },
+  async function test_pending_async_listeners_promises_rejected_on_shutdown() {
+    let extension = createPendingListenerTestExtension();
+    await extension.startup();
+    await extension.awaitMessage("bg-script-ready");
+
+    info("Trigger the API event listener call");
+    ExtensionPreferencesManager.setSetting(
+      extension.id,
+      "allowPopupsForUserEvents",
+      "click"
+    );
+
+    await extension.awaitMessage("allowPopupsForUserEvents:awaiting");
+
+    const { runListenerPromises } = extension.extension.backgroundContext;
+    equal(
+      runListenerPromises.size,
+      1,
+      "Got the expected number of pending runListener promises"
+    );
+
+    const pendingPromise = Array.from(runListenerPromises)[0];
+
+    // Shutdown the extension while there is still a pending promises being tracked
+    // to verify they gets rejected as expected when the background page browser element
+    // is going to be destroyed.
+    await extension.unload();
+
+    await Assert.rejects(
+      pendingPromise,
+      /Actor 'Conduits' destroyed before query 'RunListener' was resolved/,
+      "Previously pending runListener promise rejected with the expected error"
+    );
+
+    equal(
+      runListenerPromises.size,
+      0,
+      "Expect no remaining pending runListener promises"
+    );
+  }
+);
+
+add_task(
+  { pref_set: [["extensions.background.idle.timeout", 500]] },
+  async function test_eventpage_idle_reset_once_on_pending_async_listeners() {
+    let extension = createPendingListenerTestExtension();
+    await extension.startup();
+    await extension.awaitMessage("bg-script-ready");
+
+    info("Trigger the API event listener call");
+    ExtensionPreferencesManager.setSetting(
+      extension.id,
+      "allowPopupsForUserEvents",
+      "click"
+    );
+
+    await extension.awaitMessage("allowPopupsForUserEvents:awaiting");
+
+    info("Wait for suspend on the first idle timeout to be reset");
+    const [, resetIdleData] = await promiseExtensionEvent(
+      extension,
+      "background-script-reset-idle"
+    );
+
+    Assert.deepEqual(
+      resetIdleData,
+      {
+        reason: "pendingListeners",
+        pendingListeners: 1,
+      },
+      "Got the expected idle reset reason and pendingListeners count"
+    );
+
+    info(
+      "Await for the runtime.onSuspend event to be emitted on the second idle timeout hit"
+    );
+    // We expect this part of the test to trigger a uncaught rejection for the
+    // "Actor 'Conduits' destroyed before query 'RunListener' was resolved" error,
+    // due to the listener left purposely pending in this test
+    // and so that expected rejection is ignored using PromiseTestUtils in the preamble
+    // of this test file.
+    await extension.awaitMessage("runtime-on-suspend");
+    await extension.unload();
+  }
+);
diff --git a/toolkit/components/extensions/test/xpcshell/test_ext_eventpage_settings.js b/toolkit/components/extensions/test/xpcshell/test_ext_eventpage_settings.js
new file mode 100644
index 0000000000..66a6b45020
--- /dev/null
+++ b/toolkit/components/extensions/test/xpcshell/test_ext_eventpage_settings.js
@@ -0,0 +1,166 @@
+"use strict";
+
+ChromeUtils.defineESModuleGetters(this, {
+  Preferences: "resource://gre/modules/Preferences.sys.mjs",
+});
+
+AddonTestUtils.init(this);
+AddonTestUtils.overrideCertDB();
+
+AddonTestUtils.createAppInfo(
+  "xpcshell@tests.mozilla.org",
+  "XPCShell",
+  "42",
+  "42"
+);
+
+Services.prefs.setBoolPref("extensions.eventPages.enabled", true);
+
+ChromeUtils.defineModuleGetter(
+  this,
+  "AboutNewTab",
+  "resource:///modules/AboutNewTab.jsm"
+);
+
+add_task(async function setup() {
+  await AddonTestUtils.promiseStartupManager();
+
+  // Create an object to hold the values to which we will initialize the prefs.
+  const PREFS = {
+    "browser.cache.disk.enable": true,
+    "browser.cache.memory.enable": true,
+  };
+
+  // Set prefs to our initial values.
+  for (let pref in PREFS) {
+    Preferences.set(pref, PREFS[pref]);
+  }
+
+  registerCleanupFunction(() => {
+    // Reset the prefs.
+    for (let pref in PREFS) {
+      Preferences.reset(pref);
+    }
+  });
+});
+
+// Other tests exist for all the settings, this smoke tests that the
+// settings will startup an event page.
+add_task(async function test_browser_settings() {
+  let setExt = ExtensionTestUtils.loadExtension({
+    useAddonManager: "permanent",
+    manifest: {
+      permissions: ["browserSettings", "privacy"],
+    },
+    background() {
+      browser.test.onMessage.addListener(async (msg, apiName, value) => {
+        let apiObj = apiName.split(".").reduce((o, i) => o[i], browser);
+        let result = await apiObj.set({ value });
+        if (msg === "set") {
+          browser.test.assertTrue(result, "set returns true.");
+        } else {
+          browser.test.assertFalse(result, "set returns false for a no-op.");
+        }
+      });
+    },
+  });
+  await setExt.startup();
+
+  let extension = ExtensionTestUtils.loadExtension({
+    useAddonManager: "permanent",
+    manifest: {
+      permissions: ["browserSettings", "privacy"],
+      background: { persistent: false },
+    },
+    background() {
+      browser.browserSettings.cacheEnabled.onChange.addListener(() => {
+        browser.test.log("cacheEnabled received");
+        browser.test.sendMessage("cacheEnabled");
+      });
+      browser.browserSettings.homepageOverride.onChange.addListener(() => {
+        browser.test.sendMessage("homepageOverride");
+      });
+      browser.browserSettings.newTabPageOverride.onChange.addListener(() => {
+        browser.test.sendMessage("newTabPageOverride");
+      });
+      browser.privacy.services.passwordSavingEnabled.onChange.addListener(
+        () => {
+          browser.test.sendMessage("passwordSavingEnabled");
+        }
+      );
+    },
+  });
+  await extension.startup();
+
+  await extension.terminateBackground({ disableResetIdleForTest: true });
+  assertPersistentListeners(extension, "browserSettings", "cacheEnabled", {
+    primed: true,
+  });
+
+  info(`testing cacheEnabled`);
+  setExt.sendMessage("set", "browserSettings.cacheEnabled", false);
+  await extension.awaitMessage("cacheEnabled");
+  ok(true, "cacheEnabled.onChange fired");
+
+  await extension.terminateBackground({ disableResetIdleForTest: true });
+  assertPersistentListeners(extension, "browserSettings", "homepageOverride", {
+    primed: true,
+  });
+
+  info(`testing homepageOverride`);
+  Preferences.set("browser.startup.homepage", "http://homepage.example.com");
+  await extension.awaitMessage("homepageOverride");
+  ok(true, "homepageOverride.onChange fired");
+
+  if (
+    AppConstants.platform !== "android" &&
+    AppConstants.MOZ_APP_NAME !== "thunderbird"
+  ) {
+    await extension.terminateBackground({ disableResetIdleForTest: true });
+    assertPersistentListeners(
+      extension,
+      "browserSettings",
+      "newTabPageOverride",
+      {
+        primed: true,
+      }
+    );
+
+    info(`testing newTabPageOverride`);
+    AboutNewTab.newTabURL = "http://homepage.example.com";
+    await extension.awaitMessage("newTabPageOverride");
+    ok(true, "newTabPageOverride.onChange fired");
+  }
+
+  await extension.terminateBackground({ disableResetIdleForTest: true });
+  assertPersistentListeners(
+    extension,
+    "privacy",
+    "services.passwordSavingEnabled",
+    {
+      primed: true,
+    }
+  );
+
+  info(`testing passwordSavingEnabled`);
+  setExt.sendMessage("set", "privacy.services.passwordSavingEnabled", true);
+  await extension.awaitMessage("passwordSavingEnabled");
+  ok(true, "passwordSavingEnabled.onChange fired");
+
+  await AddonTestUtils.promiseRestartManager();
+  await setExt.awaitStartup();
+  await extension.awaitStartup();
+  Services.obs.notifyObservers(null, "browser-delayed-startup-finished");
+
+  assertPersistentListeners(extension, "browserSettings", "homepageOverride", {
+    primed: true,
+  });
+
+  info(`testing homepageOverride after AOM restart`);
+  Preferences.set("browser.startup.homepage", "http://test.example.com");
+  await extension.awaitMessage("homepageOverride");
+  ok(true, "homepageOverride.onChange fired");
+
+  await extension.unload();
+  await setExt.unload();
+});
diff --git a/toolkit/components/extensions/test/xpcshell/test_ext_eventpage_warning.js b/toolkit/components/extensions/test/xpcshell/test_ext_eventpage_warning.js
new file mode 100644
index 0000000000..82c18e7015
--- /dev/null
+++ b/toolkit/components/extensions/test/xpcshell/test_ext_eventpage_warning.js
@@ -0,0 +1,99 @@
+"use strict";
+
+AddonTestUtils.init(this);
+// This test expects and checks deprecation warnings.
+ExtensionTestUtils.failOnSchemaWarnings(false);
+
+function createEventPageExtension(eventPage) {
+  return ExtensionTestUtils.loadExtension({
+    manifest: {
+      background: eventPage,
+    },
+    files: {
+      "event_page_script.js"() {
+        browser.test.log("running event page as background script");
+        browser.test.sendMessage("running", 1);
+      },
+      "event-page.html": `<!DOCTYPE html>
+        <html><head>
+          <meta charset="utf-8">
+          <script src="event_page_script.js"><\/script>
+        </head></html>`,
+    },
+  });
+}
+
+add_task(
+  {
+    // This test case covers expected warnings emitted when the
+    // event page support is disabled by prefs.
+    pref_set: [["extensions.eventPages.enabled", false]],
+  },
+  async function test_eventpages() {
+    let testCases = [
+      {
+        message: "testing event page running as a background page",
+        eventPage: {
+          page: "event-page.html",
+          persistent: false,
+        },
+      },
+      {
+        message: "testing event page scripts running as a background page",
+        eventPage: {
+          scripts: ["event_page_script.js"],
+          persistent: false,
+        },
+      },
+      {
+        message:
+          "testing additional unrecognized properties on background page",
+        eventPage: {
+          scripts: ["event_page_script.js"],
+          nonExistentProp: true,
+        },
+      },
+      {
+        message: "testing persistent background page",
+        eventPage: {
+          page: "event-page.html",
+          persistent: true,
+        },
+      },
+      {
+        message:
+          "testing scripts with persistent background running as a background page",
+        eventPage: {
+          scripts: ["event_page_script.js"],
+          persistent: true,
+        },
+      },
+    ];
+
+    let { messages } = await promiseConsoleOutput(async () => {
+      for (let test of testCases) {
+        info(test.message);
+
+        let extension = createEventPageExtension(test.eventPage);
+        await extension.startup();
+        let x = await extension.awaitMessage("running");
+        equal(x, 1, "got correct value from extension");
+        await extension.unload();
+      }
+    });
+    AddonTestUtils.checkMessages(
+      messages,
+      {
+        expected: [
+          { message: /Event pages are not currently supported./ },
+          { message: /Event pages are not currently supported./ },
+          {
+            message:
+              /Reading manifest: Warning processing background.nonExistentProp: An unexpected property was found/,
+          },
+        ],
+      },
+      true
+    );
+  }
+);
diff --git a/toolkit/components/extensions/test/xpcshell/test_ext_experiments.js b/toolkit/components/extensions/test/xpcshell/test_ext_experiments.js
new file mode 100644
index 0000000000..802ec69240
--- /dev/null
+++ b/toolkit/components/extensions/test/xpcshell/test_ext_experiments.js
@@ -0,0 +1,377 @@
+"use strict";
+
+/* globals browser */
+const { AddonSettings } = ChromeUtils.importESModule(
+  "resource://gre/modules/addons/AddonSettings.sys.mjs"
+);
+
+AddonTestUtils.init(this);
+AddonTestUtils.overrideCertDB();
+AddonTestUtils.createAppInfo(
+  "xpcshell@tests.mozilla.org",
+  "XPCShell",
+  "1",
+  "42"
+);
+
+add_task(async function setup() {
+  AddonTestUtils.overrideCertDB();
+  await ExtensionTestUtils.startAddonManager();
+});
+
+let fooExperimentAPIs = {
+  foo: {
+    schema: "schema.json",
+    parent: {
+      scopes: ["addon_parent"],
+      script: "parent.js",
+      paths: [["experiments", "foo", "parent"]],
+    },
+    child: {
+      scopes: ["addon_child"],
+      script: "child.js",
+      paths: [["experiments", "foo", "child"]],
+    },
+  },
+};
+
+let fooExperimentFiles = {
+  "schema.json": JSON.stringify([
+    {
+      namespace: "experiments.foo",
+      types: [
+        {
+          id: "Meh",
+          type: "object",
+          properties: {},
+        },
+      ],
+      functions: [
+        {
+          name: "parent",
+          type: "function",
+          async: true,
+          parameters: [],
+        },
+        {
+          name: "child",
+          type: "function",
+          parameters: [],
+          returns: { type: "string" },
+        },
+      ],
+    },
+  ]),
+
+  /* globals ExtensionAPI */
+  "parent.js": () => {
+    this.foo = class extends ExtensionAPI {
+      getAPI(context) {
+        return {
+          experiments: {
+            foo: {
+              parent() {
+                return Promise.resolve("parent");
+              },
+            },
+          },
+        };
+      }
+    };
+  },
+
+  "child.js": () => {
+    this.foo = class extends ExtensionAPI {
+      getAPI(context) {
+        return {
+          experiments: {
+            foo: {
+              child() {
+                return "child";
+              },
+            },
+          },
+        };
+      }
+    };
+  },
+};
+
+async function testFooExperiment() {
+  browser.test.assertEq(
+    "object",
+    typeof browser.experiments,
+    "typeof browser.experiments"
+  );
+
+  browser.test.assertEq(
+    "object",
+    typeof browser.experiments.foo,
+    "typeof browser.experiments.foo"
+  );
+
+  browser.test.assertEq(
+    "function",
+    typeof browser.experiments.foo.child,
+    "typeof browser.experiments.foo.child"
+  );
+
+  browser.test.assertEq(
+    "function",
+    typeof browser.experiments.foo.parent,
+    "typeof browser.experiments.foo.parent"
+  );
+
+  browser.test.assertEq(
+    "child",
+    browser.experiments.foo.child(),
+    "foo.child()"
+  );
+
+  browser.test.assertEq(
+    "parent",
+    await browser.experiments.foo.parent(),
+    "await foo.parent()"
+  );
+}
+
+async function testFooFailExperiment() {
+  browser.test.assertEq(
+    "object",
+    typeof browser.experiments,
+    "typeof browser.experiments"
+  );
+
+  browser.test.assertEq(
+    "undefined",
+    typeof browser.experiments.foo,
+    "typeof browser.experiments.foo"
+  );
+}
+
+add_task(async function test_bundled_experiments() {
+  let testCases = [
+    { isSystem: true, temporarilyInstalled: true, shouldHaveExperiments: true },
+    {
+      isSystem: true,
+      temporarilyInstalled: false,
+      shouldHaveExperiments: true,
+    },
+    {
+      isPrivileged: true,
+      temporarilyInstalled: true,
+      shouldHaveExperiments: true,
+    },
+    {
+      isPrivileged: true,
+      temporarilyInstalled: false,
+      shouldHaveExperiments: true,
+    },
+    {
+      isPrivileged: false,
+      temporarilyInstalled: true,
+      shouldHaveExperiments: AddonSettings.EXPERIMENTS_ENABLED,
+    },
+    {
+      isPrivileged: false,
+      temporarilyInstalled: false,
+      shouldHaveExperiments: AppConstants.MOZ_APP_NAME == "thunderbird",
+    },
+  ];
+
+  async function background(shouldHaveExperiments) {
+    if (shouldHaveExperiments) {
+      await testFooExperiment();
+    } else {
+      await testFooFailExperiment();
+    }
+
+    browser.test.notifyPass("background.experiments.foo");
+  }
+
+  for (let testCase of testCases) {
+    let extension = ExtensionTestUtils.loadExtension({
+      isPrivileged: testCase.isPrivileged,
+      isSystem: testCase.isSystem,
+      temporarilyInstalled: testCase.temporarilyInstalled,
+
+      manifest: {
+        experiment_apis: fooExperimentAPIs,
+      },
+
+      background: `
+        ${testFooExperiment}
+        ${testFooFailExperiment}
+        (${background})(${testCase.shouldHaveExperiments});
+      `,
+
+      files: fooExperimentFiles,
+    });
+
+    if (testCase.temporarilyInstalled && !testCase.shouldHaveExperiments) {
+      ExtensionTestUtils.failOnSchemaWarnings(false);
+      await Assert.rejects(
+        extension.startup(),
+        /Using 'experiment_apis' requires a privileged add-on/,
+        "startup failed without experimental api access"
+      );
+      ExtensionTestUtils.failOnSchemaWarnings(true);
+    } else {
+      await extension.startup();
+
+      await extension.awaitFinish("background.experiments.foo");
+
+      await extension.unload();
+    }
+  }
+});
+
+add_task(async function test_unbundled_experiments() {
+  async function background() {
+    await testFooExperiment();
+
+    browser.test.assertEq(
+      "object",
+      typeof browser.experiments.crunk,
+      "typeof browser.experiments.crunk"
+    );
+
+    browser.test.assertEq(
+      "function",
+      typeof browser.experiments.crunk.child,
+      "typeof browser.experiments.crunk.child"
+    );
+
+    browser.test.assertEq(
+      "function",
+      typeof browser.experiments.crunk.parent,
+      "typeof browser.experiments.crunk.parent"
+    );
+
+    browser.test.assertEq(
+      "crunk-child",
+      browser.experiments.crunk.child(),
+      "crunk.child()"
+    );
+
+    browser.test.assertEq(
+      "crunk-parent",
+      await browser.experiments.crunk.parent(),
+      "await crunk.parent()"
+    );
+
+    browser.test.notifyPass("background.experiments.crunk");
+  }
+
+  let extension = ExtensionTestUtils.loadExtension({
+    isPrivileged: true,
+
+    manifest: {
+      experiment_apis: fooExperimentAPIs,
+
+      permissions: ["experiments.crunk"],
+    },
+
+    background: `
+      ${testFooExperiment}
+      (${background})();
+    `,
+
+    files: fooExperimentFiles,
+  });
+
+  let apiExtension = ExtensionTestUtils.loadExtension({
+    isPrivileged: true,
+
+    manifest: {
+      browser_specific_settings: {
+        gecko: { id: "crunk@experiments.addons.mozilla.org" },
+      },
+
+      experiment_apis: {
+        crunk: {
+          schema: "schema.json",
+          parent: {
+            scopes: ["addon_parent"],
+            script: "parent.js",
+            paths: [["experiments", "crunk", "parent"]],
+          },
+          child: {
+            scopes: ["addon_child"],
+            script: "child.js",
+            paths: [["experiments", "crunk", "child"]],
+          },
+        },
+      },
+    },
+
+    files: {
+      "schema.json": JSON.stringify([
+        {
+          namespace: "experiments.crunk",
+          types: [
+            {
+              id: "Meh",
+              type: "object",
+              properties: {},
+            },
+          ],
+          functions: [
+            {
+              name: "parent",
+              type: "function",
+              async: true,
+              parameters: [],
+            },
+            {
+              name: "child",
+              type: "function",
+              parameters: [],
+              returns: { type: "string" },
+            },
+          ],
+        },
+      ]),
+
+      "parent.js": () => {
+        this.crunk = class extends ExtensionAPI {
+          getAPI(context) {
+            return {
+              experiments: {
+                crunk: {
+                  parent() {
+                    return Promise.resolve("crunk-parent");
+                  },
+                },
+              },
+            };
+          }
+        };
+      },
+
+      "child.js": () => {
+        this.crunk = class extends ExtensionAPI {
+          getAPI(context) {
+            return {
+              experiments: {
+                crunk: {
+                  child() {
+                    return "crunk-child";
+                  },
+                },
+              },
+            };
+          }
+        };
+      },
+    },
+  });
+
+  await apiExtension.startup();
+  await extension.startup();
+
+  await extension.awaitFinish("background.experiments.crunk");
+
+  await extension.unload();
+  await apiExtension.unload();
+});
diff --git a/toolkit/components/extensions/test/xpcshell/test_ext_extension.js b/toolkit/components/extensions/test/xpcshell/test_ext_extension.js
new file mode 100644
index 0000000000..b50d8cd734
--- /dev/null
+++ b/toolkit/components/extensions/test/xpcshell/test_ext_extension.js
@@ -0,0 +1,74 @@
+/* -*- Mode: indent-tabs-mode: nil; js-indent-level: 2 -*- */
+/* vim: set sts=2 sw=2 et tw=80: */
+"use strict";
+
+add_task(async function test_is_allowed_incognito_access() {
+  async function background() {
+    let allowed = await browser.extension.isAllowedIncognitoAccess();
+
+    browser.test.assertEq(true, allowed, "isAllowedIncognitoAccess is true");
+    browser.test.notifyPass("isAllowedIncognitoAccess");
+  }
+
+  let extension = ExtensionTestUtils.loadExtension({
+    background,
+    incognitoOverride: "spanning",
+  });
+
+  await extension.startup();
+  await extension.awaitFinish("isAllowedIncognitoAccess");
+  await extension.unload();
+});
+
+add_task(async function test_is_denied_incognito_access() {
+  async function background() {
+    let allowed = await browser.extension.isAllowedIncognitoAccess();
+
+    browser.test.assertEq(false, allowed, "isAllowedIncognitoAccess is false");
+    browser.test.notifyPass("isNotAllowedIncognitoAccess");
+  }
+
+  let extension = ExtensionTestUtils.loadExtension({
+    background,
+  });
+
+  await extension.startup();
+  await extension.awaitFinish("isNotAllowedIncognitoAccess");
+  await extension.unload();
+});
+
+add_task(async function test_in_incognito_context_false() {
+  function background() {
+    browser.test.assertEq(
+      false,
+      browser.extension.inIncognitoContext,
+      "inIncognitoContext returned false"
+    );
+    browser.test.notifyPass("inIncognitoContext");
+  }
+
+  let extension = ExtensionTestUtils.loadExtension({
+    background,
+  });
+
+  await extension.startup();
+  await extension.awaitFinish("inIncognitoContext");
+  await extension.unload();
+});
+
+add_task(async function test_is_allowed_file_scheme_access() {
+  async function background() {
+    let allowed = await browser.extension.isAllowedFileSchemeAccess();
+
+    browser.test.assertEq(false, allowed, "isAllowedFileSchemeAccess is false");
+    browser.test.notifyPass("isAllowedFileSchemeAccess");
+  }
+
+  let extension = ExtensionTestUtils.loadExtension({
+    background,
+  });
+
+  await extension.startup();
+  await extension.awaitFinish("isAllowedFileSchemeAccess");
+  await extension.unload();
+});
diff --git a/toolkit/components/extensions/test/xpcshell/test_ext_extensionPreferencesManager.js b/toolkit/components/extensions/test/xpcshell/test_ext_extensionPreferencesManager.js
new file mode 100644
index 0000000000..2f6e3dbe14
--- /dev/null
+++ b/toolkit/components/extensions/test/xpcshell/test_ext_extensionPreferencesManager.js
@@ -0,0 +1,877 @@
+/* -*- Mode: indent-tabs-mode: nil; js-indent-level: 2 -*- */
+/* vim: set sts=2 sw=2 et tw=80: */
+"use strict";
+
+ChromeUtils.defineESModuleGetters(this, {
+  ExtensionPreferencesManager:
+    "resource://gre/modules/ExtensionPreferencesManager.sys.mjs",
+  ExtensionSettingsStore:
+    "resource://gre/modules/ExtensionSettingsStore.sys.mjs",
+  Preferences: "resource://gre/modules/Preferences.sys.mjs",
+});
+
+var { PromiseUtils } = ChromeUtils.importESModule(
+  "resource://gre/modules/PromiseUtils.sys.mjs"
+);
+
+const { createAppInfo, promiseShutdownManager, promiseStartupManager } =
+  AddonTestUtils;
+
+AddonTestUtils.init(this);
+
+createAppInfo("xpcshell@tests.mozilla.org", "XPCShell", "1", "42");
+
+let lastSetPref;
+
+const STORE_TYPE = "prefs";
+
+// Test settings to use with the preferences manager.
+const SETTINGS = {
+  multiple_prefs: {
+    prefNames: ["my.pref.1", "my.pref.2", "my.pref.3"],
+
+    initalValues: ["value1", "value2", "value3"],
+
+    valueFn(pref, value) {
+      return `${pref}-${value}`;
+    },
+
+    setCallback(value) {
+      let prefs = {};
+      for (let pref of this.prefNames) {
+        prefs[pref] = this.valueFn(pref, value);
+      }
+      return prefs;
+    },
+  },
+
+  singlePref: {
+    prefNames: ["my.single.pref"],
+
+    initalValues: ["value1"],
+
+    onPrefsChanged(item) {
+      lastSetPref = item;
+    },
+
+    valueFn(pref, value) {
+      return value;
+    },
+
+    setCallback(value) {
+      return { [this.prefNames[0]]: this.valueFn(null, value) };
+    },
+  },
+};
+
+ExtensionPreferencesManager.addSetting(
+  "multiple_prefs",
+  SETTINGS.multiple_prefs
+);
+ExtensionPreferencesManager.addSetting("singlePref", SETTINGS.singlePref);
+
+// Set initial values for prefs.
+for (let setting in SETTINGS) {
+  setting = SETTINGS[setting];
+  for (let i = 0; i < setting.prefNames.length; i++) {
+    Preferences.set(setting.prefNames[i], setting.initalValues[i]);
+  }
+}
+
+function checkPrefs(settingObj, value, msg) {
+  for (let pref of settingObj.prefNames) {
+    equal(Preferences.get(pref), settingObj.valueFn(pref, value), msg);
+  }
+}
+
+function checkOnPrefsChanged(setting, value, msg) {
+  if (value) {
+    deepEqual(lastSetPref, value, msg);
+    lastSetPref = null;
+  } else {
+    ok(!lastSetPref, msg);
+  }
+}
+
+add_task(async function test_preference_manager() {
+  await promiseStartupManager();
+
+  // Create an array of test framework extension wrappers to install.
+  let testExtensions = [
+    ExtensionTestUtils.loadExtension({
+      useAddonManager: "temporary",
+      manifest: {},
+    }),
+    ExtensionTestUtils.loadExtension({
+      useAddonManager: "temporary",
+      manifest: {},
+    }),
+  ];
+
+  for (let extension of testExtensions) {
+    await extension.startup();
+  }
+
+  // Create an array actual Extension objects which correspond to the
+  // test framework extension wrappers.
+  let extensions = testExtensions.map(extension => extension.extension);
+
+  for (let setting in SETTINGS) {
+    let settingObj = SETTINGS[setting];
+    let newValue1 = "newValue1";
+    let levelOfControl = await ExtensionPreferencesManager.getLevelOfControl(
+      extensions[1].id,
+      setting
+    );
+    if (settingObj.onPrefsChanged) {
+      checkOnPrefsChanged(
+        setting,
+        null,
+        "onPrefsChanged has not been called yet"
+      );
+    }
+    equal(
+      levelOfControl,
+      "controllable_by_this_extension",
+      "getLevelOfControl returns correct levelOfControl with no settings set."
+    );
+
+    let prefsChanged = await ExtensionPreferencesManager.setSetting(
+      extensions[1].id,
+      setting,
+      newValue1
+    );
+    ok(prefsChanged, "setSetting returns true when the pref(s) have been set.");
+    checkPrefs(
+      settingObj,
+      newValue1,
+      "setSetting sets the prefs for the first extension."
+    );
+    if (settingObj.onPrefsChanged) {
+      checkOnPrefsChanged(
+        setting,
+        { id: extensions[1].id, value: newValue1, key: setting },
+        "onPrefsChanged is called when pref changes"
+      );
+    }
+    levelOfControl = await ExtensionPreferencesManager.getLevelOfControl(
+      extensions[1].id,
+      setting
+    );
+    equal(
+      levelOfControl,
+      "controlled_by_this_extension",
+      "getLevelOfControl returns correct levelOfControl when a pref has been set."
+    );
+
+    let checkSetting = await ExtensionPreferencesManager.getSetting(setting);
+    equal(
+      checkSetting.value,
+      newValue1,
+      "getSetting returns the expected value."
+    );
+
+    let newValue2 = "newValue2";
+    prefsChanged = await ExtensionPreferencesManager.setSetting(
+      extensions[0].id,
+      setting,
+      newValue2
+    );
+    ok(
+      !prefsChanged,
+      "setSetting returns false when the pref(s) have not been set."
+    );
+    checkPrefs(
+      settingObj,
+      newValue1,
+      "setSetting does not set the pref(s) for an earlier extension."
+    );
+    if (settingObj.onPrefsChanged) {
+      checkOnPrefsChanged(
+        setting,
+        null,
+        "onPrefsChanged isn't called without control change"
+      );
+    }
+
+    prefsChanged = await ExtensionPreferencesManager.disableSetting(
+      extensions[0].id,
+      setting
+    );
+    ok(
+      !prefsChanged,
+      "disableSetting returns false when the pref(s) have not been set."
+    );
+    checkPrefs(
+      settingObj,
+      newValue1,
+      "disableSetting does not change the pref(s) for the non-top extension."
+    );
+    if (settingObj.onPrefsChanged) {
+      checkOnPrefsChanged(
+        setting,
+        null,
+        "onPrefsChanged isn't called without control change on disable"
+      );
+    }
+
+    prefsChanged = await ExtensionPreferencesManager.enableSetting(
+      extensions[0].id,
+      setting
+    );
+    ok(
+      !prefsChanged,
+      "enableSetting returns false when the pref(s) have not been set."
+    );
+    checkPrefs(
+      settingObj,
+      newValue1,
+      "enableSetting does not change the pref(s) for the non-top extension."
+    );
+    if (settingObj.onPrefsChanged) {
+      checkOnPrefsChanged(
+        setting,
+        null,
+        "onPrefsChanged isn't called without control change on enable"
+      );
+    }
+
+    prefsChanged = await ExtensionPreferencesManager.removeSetting(
+      extensions[0].id,
+      setting
+    );
+    ok(
+      !prefsChanged,
+      "removeSetting returns false when the pref(s) have not been set."
+    );
+    checkPrefs(
+      settingObj,
+      newValue1,
+      "removeSetting does not change the pref(s) for the non-top extension."
+    );
+    if (settingObj.onPrefsChanged) {
+      checkOnPrefsChanged(
+        setting,
+        null,
+        "onPrefsChanged isn't called without control change on remove"
+      );
+    }
+
+    prefsChanged = await ExtensionPreferencesManager.setSetting(
+      extensions[0].id,
+      setting,
+      newValue2
+    );
+    ok(
+      !prefsChanged,
+      "setSetting returns false when the pref(s) have not been set."
+    );
+    checkPrefs(
+      settingObj,
+      newValue1,
+      "setSetting does not set the pref(s) for an earlier extension."
+    );
+    if (settingObj.onPrefsChanged) {
+      checkOnPrefsChanged(
+        setting,
+        null,
+        "onPrefsChanged isn't called without control change again"
+      );
+    }
+
+    prefsChanged = await ExtensionPreferencesManager.disableSetting(
+      extensions[1].id,
+      setting
+    );
+    ok(
+      prefsChanged,
+      "disableSetting returns true when the pref(s) have been set."
+    );
+    checkPrefs(
+      settingObj,
+      newValue2,
+      "disableSetting sets the pref(s) to the next value when disabling the top extension."
+    );
+    if (settingObj.onPrefsChanged) {
+      checkOnPrefsChanged(
+        setting,
+        { id: extensions[0].id, key: setting, value: newValue2 },
+        "onPrefsChanged is called when control changes on disable"
+      );
+    }
+
+    prefsChanged = await ExtensionPreferencesManager.enableSetting(
+      extensions[1].id,
+      setting
+    );
+    ok(
+      prefsChanged,
+      "enableSetting returns true when the pref(s) have been set."
+    );
+    checkPrefs(
+      settingObj,
+      newValue1,
+      "enableSetting sets the pref(s) to the previous value(s)."
+    );
+    if (settingObj.onPrefsChanged) {
+      checkOnPrefsChanged(
+        setting,
+        { id: extensions[1].id, key: setting, value: newValue1 },
+        "onPrefsChanged is called when control changes on enable"
+      );
+    }
+
+    prefsChanged = await ExtensionPreferencesManager.removeSetting(
+      extensions[1].id,
+      setting
+    );
+    ok(
+      prefsChanged,
+      "removeSetting returns true when the pref(s) have been set."
+    );
+    checkPrefs(
+      settingObj,
+      newValue2,
+      "removeSetting sets the pref(s) to the next value when removing the top extension."
+    );
+    if (settingObj.onPrefsChanged) {
+      checkOnPrefsChanged(
+        setting,
+        { id: extensions[0].id, key: setting, value: newValue2 },
+        "onPrefsChanged is called when control changes on remove"
+      );
+    }
+
+    prefsChanged = await ExtensionPreferencesManager.removeSetting(
+      extensions[0].id,
+      setting
+    );
+    ok(
+      prefsChanged,
+      "removeSetting returns true when the pref(s) have been set."
+    );
+    if (settingObj.onPrefsChanged) {
+      checkOnPrefsChanged(
+        setting,
+        { key: setting, initialValue: { "my.single.pref": "value1" } },
+        "onPrefsChanged is called when control is entirely removed"
+      );
+    }
+    for (let i = 0; i < settingObj.prefNames.length; i++) {
+      equal(
+        Preferences.get(settingObj.prefNames[i]),
+        settingObj.initalValues[i],
+        "removeSetting sets the pref(s) to the initial value(s) when removing the last extension."
+      );
+    }
+
+    checkSetting = await ExtensionPreferencesManager.getSetting(setting);
+    equal(
+      checkSetting,
+      null,
+      "getSetting returns null when nothing has been set."
+    );
+  }
+
+  // Tests for unsetAll.
+  let newValue3 = "newValue3";
+  for (let setting in SETTINGS) {
+    let settingObj = SETTINGS[setting];
+    await ExtensionPreferencesManager.setSetting(
+      extensions[0].id,
+      setting,
+      newValue3
+    );
+    checkPrefs(settingObj, newValue3, "setSetting set the pref.");
+  }
+
+  let setSettings = await ExtensionSettingsStore.getAllForExtension(
+    extensions[0].id,
+    STORE_TYPE
+  );
+  deepEqual(
+    setSettings,
+    Object.keys(SETTINGS),
+    "Expected settings were set for extension."
+  );
+  await ExtensionPreferencesManager.disableAll(extensions[0].id);
+
+  for (let setting in SETTINGS) {
+    let settingObj = SETTINGS[setting];
+    for (let i = 0; i < settingObj.prefNames.length; i++) {
+      equal(
+        Preferences.get(settingObj.prefNames[i]),
+        settingObj.initalValues[i],
+        "disableAll unset the pref."
+      );
+    }
+  }
+
+  setSettings = await ExtensionSettingsStore.getAllForExtension(
+    extensions[0].id,
+    STORE_TYPE
+  );
+  deepEqual(
+    setSettings,
+    Object.keys(SETTINGS),
+    "disableAll retains the settings."
+  );
+
+  await ExtensionPreferencesManager.enableAll(extensions[0].id);
+  for (let setting in SETTINGS) {
+    let settingObj = SETTINGS[setting];
+    checkPrefs(settingObj, newValue3, "enableAll re-set the pref.");
+  }
+
+  await ExtensionPreferencesManager.removeAll(extensions[0].id);
+
+  for (let setting in SETTINGS) {
+    let settingObj = SETTINGS[setting];
+    for (let i = 0; i < settingObj.prefNames.length; i++) {
+      equal(
+        Preferences.get(settingObj.prefNames[i]),
+        settingObj.initalValues[i],
+        "removeAll unset the pref."
+      );
+    }
+  }
+
+  setSettings = await ExtensionSettingsStore.getAllForExtension(
+    extensions[0].id,
+    STORE_TYPE
+  );
+  deepEqual(setSettings, [], "removeAll removed all settings.");
+
+  // Tests for preventing automatic changes to manually edited prefs.
+  for (let setting in SETTINGS) {
+    let apiValue = "newValue";
+    let manualValue = "something different";
+    let settingObj = SETTINGS[setting];
+    let extension = extensions[1];
+    await ExtensionPreferencesManager.setSetting(
+      extension.id,
+      setting,
+      apiValue
+    );
+
+    let checkResetPrefs = method => {
+      let prefNames = settingObj.prefNames;
+      for (let i = 0; i < prefNames.length; i++) {
+        if (i === 0) {
+          equal(
+            Preferences.get(prefNames[0]),
+            manualValue,
+            `${method} did not change a manually set pref.`
+          );
+        } else {
+          equal(
+            Preferences.get(prefNames[i]),
+            settingObj.valueFn(prefNames[i], apiValue),
+            `${method} did not change another pref when a pref was manually set.`
+          );
+        }
+      }
+    };
+
+    // Manually set the preference to a different value.
+    Preferences.set(settingObj.prefNames[0], manualValue);
+
+    await ExtensionPreferencesManager.disableAll(extension.id);
+    checkResetPrefs("disableAll");
+
+    await ExtensionPreferencesManager.enableAll(extension.id);
+    checkResetPrefs("enableAll");
+
+    await ExtensionPreferencesManager.removeAll(extension.id);
+    checkResetPrefs("removeAll");
+  }
+
+  // Test with an uninitialized pref.
+  let setting = "singlePref";
+  let settingObj = SETTINGS[setting];
+  let pref = settingObj.prefNames[0];
+  let newValue = "newValue";
+  Preferences.reset(pref);
+  await ExtensionPreferencesManager.setSetting(
+    extensions[1].id,
+    setting,
+    newValue
+  );
+  equal(
+    Preferences.get(pref),
+    settingObj.valueFn(pref, newValue),
+    "Uninitialized pref is set."
+  );
+  await ExtensionPreferencesManager.removeSetting(extensions[1].id, setting);
+  ok(!Preferences.has(pref), "removeSetting removed the pref.");
+
+  // Test levelOfControl with a locked pref.
+  setting = "multiple_prefs";
+  let prefToLock = SETTINGS[setting].prefNames[0];
+  Preferences.lock(prefToLock, 1);
+  ok(Preferences.locked(prefToLock), `Preference ${prefToLock} is locked.`);
+  let levelOfControl = await ExtensionPreferencesManager.getLevelOfControl(
+    extensions[1].id,
+    setting
+  );
+  equal(
+    levelOfControl,
+    "not_controllable",
+    "getLevelOfControl returns correct levelOfControl when a pref is locked."
+  );
+
+  for (let extension of testExtensions) {
+    await extension.unload();
+  }
+
+  await promiseShutdownManager();
+});
+
+add_task(async function test_preference_manager_set_when_disabled() {
+  await promiseStartupManager();
+
+  let id = "@set-disabled-pref";
+  let extension = ExtensionTestUtils.loadExtension({
+    useAddonManager: "temporary",
+    manifest: {
+      browser_specific_settings: { gecko: { id } },
+    },
+  });
+
+  await extension.startup();
+
+  // We test both a default pref and a user-set pref.  Get the default
+  // value off the pref we'll use.  We fake the default pref by setting
+  // a value on it before creating the setting.
+  Services.prefs.setBoolPref("bar", true);
+
+  function isUndefinedPref(pref) {
+    try {
+      Services.prefs.getStringPref(pref);
+      return false;
+    } catch (e) {
+      return true;
+    }
+  }
+  ok(isUndefinedPref("foo"), "test pref is not set");
+
+  await ExtensionSettingsStore.initialize();
+  let lastItemChange = PromiseUtils.defer();
+  ExtensionPreferencesManager.addSetting("some-pref", {
+    prefNames: ["foo", "bar"],
+    onPrefsChanged(item) {
+      lastItemChange.resolve(item);
+      lastItemChange = PromiseUtils.defer();
+    },
+    setCallback(value) {
+      return { [this.prefNames[0]]: value, [this.prefNames[1]]: false };
+    },
+  });
+
+  await ExtensionPreferencesManager.setSetting(id, "some-pref", "my value");
+
+  let item = ExtensionSettingsStore.getSetting("prefs", "some-pref");
+  equal(item.value, "my value", "The value has been set");
+  equal(
+    Services.prefs.getStringPref("foo"),
+    "my value",
+    "The user pref has been set"
+  );
+  equal(
+    Services.prefs.getBoolPref("bar"),
+    false,
+    "The default pref has been set"
+  );
+
+  await ExtensionPreferencesManager.disableSetting(id, "some-pref");
+
+  // test that a disabled setting has been returned to the default value.  In this
+  // case the pref is not a default pref, so it will be undefined.
+  item = ExtensionSettingsStore.getSetting("prefs", "some-pref");
+  equal(item.value, undefined, "The value is back to default");
+  equal(item.initialValue.foo, undefined, "The initialValue is correct");
+  ok(isUndefinedPref("foo"), "user pref is not set");
+  equal(
+    Services.prefs.getBoolPref("bar"),
+    true,
+    "The default pref has been restored to the default"
+  );
+
+  // test that setSetting() will enable a disabled setting
+  await ExtensionPreferencesManager.setSetting(id, "some-pref", "new value");
+
+  item = ExtensionSettingsStore.getSetting("prefs", "some-pref");
+  equal(item.value, "new value", "The value is set again");
+  equal(
+    Services.prefs.getStringPref("foo"),
+    "new value",
+    "The user pref is set again"
+  );
+  equal(
+    Services.prefs.getBoolPref("bar"),
+    false,
+    "The default pref has been set again"
+  );
+
+  // Force settings to be serialized and reloaded to mimick what happens
+  // with settings through a restart of Firefox.  Bug 1576266.
+  await ExtensionSettingsStore._reloadFile(true);
+
+  // Now unload the extension to test prefs are reset properly.
+  let promise = lastItemChange.promise;
+  await extension.unload();
+
+  // Test that the pref is unset when an extension is uninstalled.
+  item = await promise;
+  deepEqual(
+    item,
+    { key: "some-pref", initialValue: { bar: true } },
+    "The value has been reset"
+  );
+  ok(isUndefinedPref("foo"), "user pref is not set");
+  equal(
+    Services.prefs.getBoolPref("bar"),
+    true,
+    "The default pref has been restored to the default"
+  );
+  Services.prefs.clearUserPref("bar");
+
+  await promiseShutdownManager();
+});
+
+add_task(async function test_preference_default_upgraded() {
+  await promiseStartupManager();
+
+  let id = "@upgrade-pref";
+  let extension = ExtensionTestUtils.loadExtension({
+    useAddonManager: "temporary",
+    manifest: {
+      browser_specific_settings: { gecko: { id } },
+    },
+  });
+
+  await extension.startup();
+
+  // We set the default value for a pref here so it will be
+  // picked up by EPM.
+  let defaultPrefs = Services.prefs.getDefaultBranch(null);
+  defaultPrefs.setStringPref("bar", "initial default");
+
+  await ExtensionSettingsStore.initialize();
+  ExtensionPreferencesManager.addSetting("some-pref", {
+    prefNames: ["bar"],
+    setCallback(value) {
+      return { [this.prefNames[0]]: value };
+    },
+  });
+
+  await ExtensionPreferencesManager.setSetting(id, "some-pref", "new value");
+  let item = ExtensionSettingsStore.getSetting("prefs", "some-pref");
+  equal(item.value, "new value", "The value is set");
+
+  defaultPrefs.setStringPref("bar", "new default");
+
+  item = ExtensionSettingsStore.getSetting("prefs", "some-pref");
+  equal(item.value, "new value", "The value is still set");
+
+  let prefsChanged = await ExtensionPreferencesManager.removeSetting(
+    id,
+    "some-pref"
+  );
+  ok(prefsChanged, "pref changed on removal of setting.");
+  equal(Preferences.get("bar"), "new default", "default value is correct");
+
+  await extension.unload();
+  await promiseShutdownManager();
+});
+
+add_task(async function test_preference_select() {
+  await promiseStartupManager();
+
+  let extensionData = {
+    useAddonManager: "temporary",
+    manifest: {
+      browser_specific_settings: { gecko: { id: "@one" } },
+    },
+  };
+  let one = ExtensionTestUtils.loadExtension(extensionData);
+
+  await one.startup();
+
+  // We set the default value for a pref here so it will be
+  // picked up by EPM.
+  let defaultPrefs = Services.prefs.getDefaultBranch(null);
+  defaultPrefs.setStringPref("bar", "initial default");
+
+  await ExtensionSettingsStore.initialize();
+  ExtensionPreferencesManager.addSetting("some-pref", {
+    prefNames: ["bar"],
+    setCallback(value) {
+      return { [this.prefNames[0]]: value };
+    },
+  });
+
+  ok(
+    await ExtensionPreferencesManager.setSetting(
+      one.id,
+      "some-pref",
+      "new value"
+    ),
+    "setting was changed"
+  );
+  let item = await ExtensionPreferencesManager.getSetting("some-pref");
+  equal(item.value, "new value", "The value is set");
+
+  // User-set the setting.
+  await ExtensionPreferencesManager.selectSetting(null, "some-pref");
+  item = await ExtensionPreferencesManager.getSetting("some-pref");
+  deepEqual(
+    item,
+    { key: "some-pref", initialValue: {} },
+    "The value is user-set"
+  );
+
+  // Extensions installed before cannot gain control again.
+  let levelOfControl = await ExtensionPreferencesManager.getLevelOfControl(
+    one.id,
+    "some-pref"
+  );
+  equal(
+    levelOfControl,
+    "not_controllable",
+    "getLevelOfControl returns correct levelOfControl when user-set."
+  );
+
+  // Enabling the top-precedence addon does not take over a user-set setting.
+  await ExtensionPreferencesManager.disableSetting(one.id, "some-pref");
+  await ExtensionPreferencesManager.enableSetting(one.id, "some-pref");
+  item = await ExtensionPreferencesManager.getSetting("some-pref");
+  deepEqual(
+    item,
+    { key: "some-pref", initialValue: {} },
+    "The value is user-set"
+  );
+
+  // Upgrading does not override the user-set setting.
+  extensionData.manifest.version = "2.0";
+  extensionData.manifest.incognito = "not_allowed";
+  await one.upgrade(extensionData);
+  levelOfControl = await ExtensionPreferencesManager.getLevelOfControl(
+    one.id,
+    "some-pref"
+  );
+  equal(
+    levelOfControl,
+    "not_controllable",
+    "getLevelOfControl returns correct levelOfControl when user-set after addon upgrade."
+  );
+
+  // We can re-select the extension.
+  await ExtensionPreferencesManager.selectSetting(one.id, "some-pref");
+  item = await ExtensionPreferencesManager.getSetting("some-pref");
+  deepEqual(item.value, "new value", "The value is extension set");
+
+  // An extension installed after user-set can take over the setting.
+  await ExtensionPreferencesManager.selectSetting(null, "some-pref");
+  item = await ExtensionPreferencesManager.getSetting("some-pref");
+  deepEqual(
+    item,
+    { key: "some-pref", initialValue: {} },
+    "The value is user-set"
+  );
+
+  let two = ExtensionTestUtils.loadExtension({
+    useAddonManager: "temporary",
+    manifest: {
+      browser_specific_settings: { gecko: { id: "@two" } },
+    },
+  });
+
+  await two.startup();
+  levelOfControl = await ExtensionPreferencesManager.getLevelOfControl(
+    two.id,
+    "some-pref"
+  );
+  equal(
+    levelOfControl,
+    "controllable_by_this_extension",
+    "getLevelOfControl returns correct levelOfControl when user-set after addon install."
+  );
+
+  await ExtensionPreferencesManager.setSetting(
+    two.id,
+    "some-pref",
+    "another value"
+  );
+  item = ExtensionSettingsStore.getSetting("prefs", "some-pref");
+  equal(item.value, "another value", "The value is set");
+
+  // A new installed extension can override a user selected extension.
+  let three = ExtensionTestUtils.loadExtension({
+    useAddonManager: "temporary",
+    manifest: {
+      browser_specific_settings: { gecko: { id: "@three" } },
+    },
+  });
+
+  // user selects specific extension to take control
+  await ExtensionPreferencesManager.selectSetting(one.id, "some-pref");
+
+  // two cannot control
+  levelOfControl = await ExtensionPreferencesManager.getLevelOfControl(
+    two.id,
+    "some-pref"
+  );
+  equal(
+    levelOfControl,
+    "not_controllable",
+    "getLevelOfControl returns correct levelOfControl when user-set after addon install."
+  );
+
+  // three can control after install
+  await three.startup();
+  levelOfControl = await ExtensionPreferencesManager.getLevelOfControl(
+    three.id,
+    "some-pref"
+  );
+  equal(
+    levelOfControl,
+    "controllable_by_this_extension",
+    "getLevelOfControl returns correct levelOfControl when user-set after addon install."
+  );
+
+  await ExtensionPreferencesManager.setSetting(
+    three.id,
+    "some-pref",
+    "third value"
+  );
+  item = ExtensionSettingsStore.getSetting("prefs", "some-pref");
+  equal(item.value, "third value", "The value is set");
+
+  // We have returned to precedence based settings.
+  await ExtensionPreferencesManager.removeSetting(three.id, "some-pref");
+  await ExtensionPreferencesManager.removeSetting(two.id, "some-pref");
+  item = await ExtensionPreferencesManager.getSetting("some-pref");
+  equal(item.value, "new value", "The value is extension set");
+
+  await one.unload();
+  await two.unload();
+  await three.unload();
+  await promiseShutdownManager();
+});
+
+add_task(async function test_preference_select() {
+  let prefNames = await ExtensionPreferencesManager.getManagedPrefDetails();
+  // Just check a subset of settings that are in this test file.
+  Assert.ok(prefNames.size > 0, "some prefs exist");
+  for (let settingName in SETTINGS) {
+    let setting = SETTINGS[settingName];
+    for (let prefName of setting.prefNames) {
+      Assert.equal(
+        prefNames.get(prefName),
+        settingName,
+        "setting retrieved prefNames"
+      );
+    }
+  }
+});
diff --git a/toolkit/components/extensions/test/xpcshell/test_ext_extensionSettingsStore.js b/toolkit/components/extensions/test/xpcshell/test_ext_extensionSettingsStore.js
new file mode 100644
index 0000000000..720c7f539a
--- /dev/null
+++ b/toolkit/components/extensions/test/xpcshell/test_ext_extensionSettingsStore.js
@@ -0,0 +1,1085 @@
+/* -*- Mode: indent-tabs-mode: nil; js-indent-level: 2 -*- */
+/* vim: set sts=2 sw=2 et tw=80: */
+"use strict";
+
+ChromeUtils.defineESModuleGetters(this, {
+  ExtensionSettingsStore:
+    "resource://gre/modules/ExtensionSettingsStore.sys.mjs",
+});
+
+const { createAppInfo, promiseShutdownManager, promiseStartupManager } =
+  AddonTestUtils;
+
+AddonTestUtils.init(this);
+
+// Allow for unsigned addons.
+AddonTestUtils.overrideCertDB();
+
+createAppInfo("xpcshell@tests.mozilla.org", "XPCShell", "1", "42");
+
+const ITEMS = {
+  key1: [
+    { key: "key1", value: "val1", id: "@first" },
+    { key: "key1", value: "val2", id: "@second" },
+    { key: "key1", value: "val3", id: "@third" },
+  ],
+  key2: [
+    { key: "key2", value: "val1-2", id: "@first" },
+    { key: "key2", value: "val2-2", id: "@second" },
+    { key: "key2", value: "val3-2", id: "@third" },
+  ],
+};
+const KEY_LIST = Object.keys(ITEMS);
+const TEST_TYPE = "myType";
+
+let callbackCount = 0;
+
+function initialValue(key) {
+  callbackCount++;
+  return `key:${key}`;
+}
+
+add_task(async function test_settings_store() {
+  await promiseStartupManager();
+
+  // Create an array of test framework extension wrappers to install.
+  let testExtensions = [
+    ExtensionTestUtils.loadExtension({
+      useAddonManager: "temporary",
+      manifest: {
+        browser_specific_settings: { gecko: { id: "@first" } },
+      },
+    }),
+    ExtensionTestUtils.loadExtension({
+      useAddonManager: "temporary",
+      manifest: {
+        browser_specific_settings: { gecko: { id: "@second" } },
+      },
+    }),
+    ExtensionTestUtils.loadExtension({
+      useAddonManager: "temporary",
+      manifest: {
+        browser_specific_settings: { gecko: { id: "@third" } },
+      },
+    }),
+  ];
+
+  for (let extension of testExtensions) {
+    await extension.startup();
+  }
+
+  // Create an array actual Extension objects which correspond to the
+  // test framework extension wrappers.
+  let extensions = testExtensions.map(extension => extension.extension);
+
+  let expectedCallbackCount = 0;
+
+  await Assert.rejects(
+    ExtensionSettingsStore.getLevelOfControl(1, TEST_TYPE, "key"),
+    /The ExtensionSettingsStore was accessed before the initialize promise resolved/,
+    "Accessing the SettingsStore before it is initialized throws an error."
+  );
+
+  // Initialize the SettingsStore.
+  await ExtensionSettingsStore.initialize();
+
+  // Add a setting for the second oldest extension, where it is the only setting for a key.
+  for (let key of KEY_LIST) {
+    let extensionIndex = 1;
+    let itemToAdd = ITEMS[key][extensionIndex];
+    let levelOfControl = await ExtensionSettingsStore.getLevelOfControl(
+      extensions[extensionIndex].id,
+      TEST_TYPE,
+      key
+    );
+    equal(
+      levelOfControl,
+      "controllable_by_this_extension",
+      "getLevelOfControl returns correct levelOfControl with no settings set for a key."
+    );
+    let item = await ExtensionSettingsStore.addSetting(
+      extensions[extensionIndex].id,
+      TEST_TYPE,
+      itemToAdd.key,
+      itemToAdd.value,
+      initialValue
+    );
+    expectedCallbackCount++;
+    equal(
+      callbackCount,
+      expectedCallbackCount,
+      "initialValueCallback called the expected number of times."
+    );
+    deepEqual(
+      item,
+      itemToAdd,
+      "Adding initial item for a key returns that item."
+    );
+    item = await ExtensionSettingsStore.getSetting(TEST_TYPE, key);
+    deepEqual(
+      item,
+      itemToAdd,
+      "getSetting returns correct item with only one item in the list."
+    );
+    levelOfControl = await ExtensionSettingsStore.getLevelOfControl(
+      extensions[extensionIndex].id,
+      TEST_TYPE,
+      key
+    );
+    equal(
+      levelOfControl,
+      "controlled_by_this_extension",
+      "getLevelOfControl returns correct levelOfControl with only one item in the list."
+    );
+    ok(
+      ExtensionSettingsStore.hasSetting(
+        extensions[extensionIndex].id,
+        TEST_TYPE,
+        key
+      ),
+      "hasSetting returns the correct value when an extension has a setting set."
+    );
+    item = await ExtensionSettingsStore.getSetting(
+      TEST_TYPE,
+      key,
+      extensions[extensionIndex].id
+    );
+    deepEqual(
+      item,
+      itemToAdd,
+      "getSetting with id returns correct item with only one item in the list."
+    );
+  }
+
+  // Add a setting for the oldest extension.
+  for (let key of KEY_LIST) {
+    let extensionIndex = 0;
+    let itemToAdd = ITEMS[key][extensionIndex];
+    let item = await ExtensionSettingsStore.addSetting(
+      extensions[extensionIndex].id,
+      TEST_TYPE,
+      itemToAdd.key,
+      itemToAdd.value,
+      initialValue
+    );
+    equal(
+      callbackCount,
+      expectedCallbackCount,
+      "initialValueCallback called the expected number of times."
+    );
+    equal(
+      item,
+      null,
+      "An older extension adding a setting for a key returns null"
+    );
+    item = await ExtensionSettingsStore.getSetting(TEST_TYPE, key);
+    deepEqual(
+      item,
+      ITEMS[key][1],
+      "getSetting returns correct item with more than one item in the list."
+    );
+    let levelOfControl = await ExtensionSettingsStore.getLevelOfControl(
+      extensions[extensionIndex].id,
+      TEST_TYPE,
+      key
+    );
+    equal(
+      levelOfControl,
+      "controlled_by_other_extensions",
+      "getLevelOfControl returns correct levelOfControl when another extension is in control."
+    );
+    item = await ExtensionSettingsStore.getSetting(
+      TEST_TYPE,
+      key,
+      extensions[extensionIndex].id
+    );
+    deepEqual(
+      item,
+      itemToAdd,
+      "getSetting with id returns correct item with more than one item in the list."
+    );
+  }
+
+  // Reload the settings store to emulate a browser restart.
+  await ExtensionSettingsStore._reloadFile();
+
+  // Add a setting for the newest extension.
+  for (let key of KEY_LIST) {
+    let extensionIndex = 2;
+    let itemToAdd = ITEMS[key][extensionIndex];
+    let levelOfControl = await ExtensionSettingsStore.getLevelOfControl(
+      extensions[extensionIndex].id,
+      TEST_TYPE,
+      key
+    );
+    equal(
+      levelOfControl,
+      "controllable_by_this_extension",
+      "getLevelOfControl returns correct levelOfControl for a more recent extension."
+    );
+    let item = await ExtensionSettingsStore.addSetting(
+      extensions[extensionIndex].id,
+      TEST_TYPE,
+      itemToAdd.key,
+      itemToAdd.value,
+      initialValue
+    );
+    equal(
+      callbackCount,
+      expectedCallbackCount,
+      "initialValueCallback called the expected number of times."
+    );
+    deepEqual(
+      item,
+      itemToAdd,
+      "Adding item for most recent extension returns that item."
+    );
+    item = await ExtensionSettingsStore.getSetting(TEST_TYPE, key);
+    deepEqual(
+      item,
+      itemToAdd,
+      "getSetting returns correct item with more than one item in the list."
+    );
+    levelOfControl = await ExtensionSettingsStore.getLevelOfControl(
+      extensions[extensionIndex].id,
+      TEST_TYPE,
+      key
+    );
+    equal(
+      levelOfControl,
+      "controlled_by_this_extension",
+      "getLevelOfControl returns correct levelOfControl when this extension is in control."
+    );
+    item = await ExtensionSettingsStore.getSetting(
+      TEST_TYPE,
+      key,
+      extensions[extensionIndex].id
+    );
+    deepEqual(
+      item,
+      itemToAdd,
+      "getSetting with id returns correct item with more than one item in the list."
+    );
+  }
+
+  for (let extension of extensions) {
+    let items = await ExtensionSettingsStore.getAllForExtension(
+      extension.id,
+      TEST_TYPE
+    );
+    deepEqual(items, KEY_LIST, "getAllForExtension returns expected keys.");
+  }
+
+  // Attempting to remove a setting that has not been set should *not* throw an exception.
+  let removeResult = await ExtensionSettingsStore.removeSetting(
+    extensions[0].id,
+    "myType",
+    "unset_key"
+  );
+  equal(
+    removeResult,
+    null,
+    "Removing a setting that was not previously set returns null."
+  );
+
+  // Attempting to disable a setting that has not been set should throw an exception.
+  Assert.throws(
+    () =>
+      ExtensionSettingsStore.disable(extensions[0].id, "myType", "unset_key"),
+    /Cannot alter the setting for myType:unset_key as it does not exist/,
+    "disable rejects with an unset key."
+  );
+
+  // Attempting to enable a setting that has not been set should throw an exception.
+  Assert.throws(
+    () =>
+      ExtensionSettingsStore.enable(extensions[0].id, "myType", "unset_key"),
+    /Cannot alter the setting for myType:unset_key as it does not exist/,
+    "enable rejects with an unset key."
+  );
+
+  let expectedKeys = KEY_LIST;
+  // Disable the non-top item for a key.
+  for (let key of KEY_LIST) {
+    let extensionIndex = 0;
+    let item = await ExtensionSettingsStore.addSetting(
+      extensions[extensionIndex].id,
+      TEST_TYPE,
+      key,
+      "new value",
+      initialValue
+    );
+    equal(
+      callbackCount,
+      expectedCallbackCount,
+      "initialValueCallback called the expected number of times."
+    );
+    equal(item, null, "Updating non-top item for a key returns null");
+    item = await ExtensionSettingsStore.disable(
+      extensions[extensionIndex].id,
+      TEST_TYPE,
+      key
+    );
+    equal(item, null, "Disabling non-top item for a key returns null.");
+    let allForExtension = await ExtensionSettingsStore.getAllForExtension(
+      extensions[extensionIndex].id,
+      TEST_TYPE
+    );
+    deepEqual(
+      allForExtension,
+      expectedKeys,
+      "getAllForExtension returns expected keys after a disable."
+    );
+    item = await ExtensionSettingsStore.getSetting(TEST_TYPE, key);
+    deepEqual(
+      item,
+      ITEMS[key][2],
+      "getSetting returns correct item after a disable."
+    );
+    let levelOfControl = await ExtensionSettingsStore.getLevelOfControl(
+      extensions[extensionIndex].id,
+      TEST_TYPE,
+      key
+    );
+    equal(
+      levelOfControl,
+      "controlled_by_other_extensions",
+      "getLevelOfControl returns correct levelOfControl after disabling of non-top item."
+    );
+  }
+
+  // Re-enable the non-top item for a key.
+  for (let key of KEY_LIST) {
+    let extensionIndex = 0;
+    let item = await ExtensionSettingsStore.enable(
+      extensions[extensionIndex].id,
+      TEST_TYPE,
+      key
+    );
+    equal(item, null, "Enabling non-top item for a key returns null.");
+    let allForExtension = await ExtensionSettingsStore.getAllForExtension(
+      extensions[extensionIndex].id,
+      TEST_TYPE
+    );
+    deepEqual(
+      allForExtension,
+      expectedKeys,
+      "getAllForExtension returns expected keys after an enable."
+    );
+    item = await ExtensionSettingsStore.getSetting(TEST_TYPE, key);
+    deepEqual(
+      item,
+      ITEMS[key][2],
+      "getSetting returns correct item after an enable."
+    );
+    let levelOfControl = await ExtensionSettingsStore.getLevelOfControl(
+      extensions[extensionIndex].id,
+      TEST_TYPE,
+      key
+    );
+    equal(
+      levelOfControl,
+      "controlled_by_other_extensions",
+      "getLevelOfControl returns correct levelOfControl after enabling of non-top item."
+    );
+  }
+
+  // Remove the non-top item for a key.
+  for (let key of KEY_LIST) {
+    let extensionIndex = 0;
+    let item = await ExtensionSettingsStore.removeSetting(
+      extensions[extensionIndex].id,
+      TEST_TYPE,
+      key
+    );
+    equal(item, null, "Removing non-top item for a key returns null.");
+    expectedKeys = expectedKeys.filter(expectedKey => expectedKey != key);
+    let allForExtension = await ExtensionSettingsStore.getAllForExtension(
+      extensions[extensionIndex].id,
+      TEST_TYPE
+    );
+    deepEqual(
+      allForExtension,
+      expectedKeys,
+      "getAllForExtension returns expected keys after a removal."
+    );
+    item = await ExtensionSettingsStore.getSetting(TEST_TYPE, key);
+    deepEqual(
+      item,
+      ITEMS[key][2],
+      "getSetting returns correct item after a removal."
+    );
+    let levelOfControl = await ExtensionSettingsStore.getLevelOfControl(
+      extensions[extensionIndex].id,
+      TEST_TYPE,
+      key
+    );
+    equal(
+      levelOfControl,
+      "controlled_by_other_extensions",
+      "getLevelOfControl returns correct levelOfControl after removal of non-top item."
+    );
+    ok(
+      !ExtensionSettingsStore.hasSetting(
+        extensions[extensionIndex].id,
+        TEST_TYPE,
+        key
+      ),
+      "hasSetting returns the correct value when an extension does not have a setting set."
+    );
+  }
+
+  for (let key of KEY_LIST) {
+    // Disable the top item for a key.
+    let item = await ExtensionSettingsStore.disable(
+      extensions[2].id,
+      TEST_TYPE,
+      key
+    );
+    deepEqual(
+      item,
+      ITEMS[key][1],
+      "Disabling top item for a key returns the new top item."
+    );
+    item = await ExtensionSettingsStore.getSetting(TEST_TYPE, key);
+    deepEqual(
+      item,
+      ITEMS[key][1],
+      "getSetting returns correct item after a disable."
+    );
+    let levelOfControl = await ExtensionSettingsStore.getLevelOfControl(
+      extensions[2].id,
+      TEST_TYPE,
+      key
+    );
+    equal(
+      levelOfControl,
+      "controllable_by_this_extension",
+      "getLevelOfControl returns correct levelOfControl after disabling of top item."
+    );
+
+    // Re-enable the top item for a key.
+    item = await ExtensionSettingsStore.enable(
+      extensions[2].id,
+      TEST_TYPE,
+      key
+    );
+    deepEqual(
+      item,
+      ITEMS[key][2],
+      "Re-enabling top item for a key returns the old top item."
+    );
+    item = await ExtensionSettingsStore.getSetting(TEST_TYPE, key);
+    deepEqual(
+      item,
+      ITEMS[key][2],
+      "getSetting returns correct item after an enable."
+    );
+    levelOfControl = await ExtensionSettingsStore.getLevelOfControl(
+      extensions[2].id,
+      TEST_TYPE,
+      key
+    );
+    equal(
+      levelOfControl,
+      "controlled_by_this_extension",
+      "getLevelOfControl returns correct levelOfControl after re-enabling top item."
+    );
+
+    // Remove the top item for a key.
+    item = await ExtensionSettingsStore.removeSetting(
+      extensions[2].id,
+      TEST_TYPE,
+      key
+    );
+    deepEqual(
+      item,
+      ITEMS[key][1],
+      "Removing top item for a key returns the new top item."
+    );
+    item = await ExtensionSettingsStore.getSetting(TEST_TYPE, key);
+    deepEqual(
+      item,
+      ITEMS[key][1],
+      "getSetting returns correct item after a removal."
+    );
+    levelOfControl = await ExtensionSettingsStore.getLevelOfControl(
+      extensions[2].id,
+      TEST_TYPE,
+      key
+    );
+    equal(
+      levelOfControl,
+      "controllable_by_this_extension",
+      "getLevelOfControl returns correct levelOfControl after removal of top item."
+    );
+
+    // Add a setting for the current top item.
+    let itemToAdd = { key, value: `new-${key}`, id: "@second" };
+    item = await ExtensionSettingsStore.addSetting(
+      extensions[1].id,
+      TEST_TYPE,
+      itemToAdd.key,
+      itemToAdd.value,
+      initialValue
+    );
+    equal(
+      callbackCount,
+      expectedCallbackCount,
+      "initialValueCallback called the expected number of times."
+    );
+    deepEqual(
+      item,
+      itemToAdd,
+      "Updating top item for a key returns that item."
+    );
+    item = await ExtensionSettingsStore.getSetting(TEST_TYPE, key);
+    deepEqual(
+      item,
+      itemToAdd,
+      "getSetting returns correct item after updating."
+    );
+    levelOfControl = await ExtensionSettingsStore.getLevelOfControl(
+      extensions[1].id,
+      TEST_TYPE,
+      key
+    );
+    equal(
+      levelOfControl,
+      "controlled_by_this_extension",
+      "getLevelOfControl returns correct levelOfControl after updating."
+    );
+
+    // Disable the last remaining item for a key.
+    let expectedItem = { key, initialValue: initialValue(key) };
+    // We're using the callback to set the expected value, so we need to increment the
+    // expectedCallbackCount.
+    expectedCallbackCount++;
+    item = await ExtensionSettingsStore.disable(
+      extensions[1].id,
+      TEST_TYPE,
+      key
+    );
+    deepEqual(
+      item,
+      expectedItem,
+      "Disabling last item for a key returns the initial value."
+    );
+    item = await ExtensionSettingsStore.getSetting(TEST_TYPE, key);
+    deepEqual(
+      item,
+      expectedItem,
+      "getSetting returns the initial value after all are disabled."
+    );
+    levelOfControl = await ExtensionSettingsStore.getLevelOfControl(
+      extensions[1].id,
+      TEST_TYPE,
+      key
+    );
+    equal(
+      levelOfControl,
+      "controllable_by_this_extension",
+      "getLevelOfControl returns correct levelOfControl after all are disabled."
+    );
+
+    // Re-enable the last remaining item for a key.
+    item = await ExtensionSettingsStore.enable(
+      extensions[1].id,
+      TEST_TYPE,
+      key
+    );
+    deepEqual(
+      item,
+      itemToAdd,
+      "Re-enabling last item for a key returns the old value."
+    );
+    item = await ExtensionSettingsStore.getSetting(TEST_TYPE, key);
+    deepEqual(
+      item,
+      itemToAdd,
+      "getSetting returns expected value after re-enabling."
+    );
+    levelOfControl = await ExtensionSettingsStore.getLevelOfControl(
+      extensions[1].id,
+      TEST_TYPE,
+      key
+    );
+    equal(
+      levelOfControl,
+      "controlled_by_this_extension",
+      "getLevelOfControl returns correct levelOfControl after re-enabling."
+    );
+
+    // Remove the last remaining item for a key.
+    item = await ExtensionSettingsStore.removeSetting(
+      extensions[1].id,
+      TEST_TYPE,
+      key
+    );
+    deepEqual(
+      item,
+      expectedItem,
+      "Removing last item for a key returns the initial value."
+    );
+    item = await ExtensionSettingsStore.getSetting(TEST_TYPE, key);
+    deepEqual(item, null, "getSetting returns null after all are removed.");
+    levelOfControl = await ExtensionSettingsStore.getLevelOfControl(
+      extensions[1].id,
+      TEST_TYPE,
+      key
+    );
+    equal(
+      levelOfControl,
+      "controllable_by_this_extension",
+      "getLevelOfControl returns correct levelOfControl after all are removed."
+    );
+
+    // Attempting to remove a setting that has had all extensions removed should *not* throw an exception.
+    removeResult = await ExtensionSettingsStore.removeSetting(
+      extensions[1].id,
+      TEST_TYPE,
+      key
+    );
+    equal(
+      removeResult,
+      null,
+      "Removing a setting that has had all extensions removed returns null."
+    );
+  }
+
+  // Test adding a setting with a value in callbackArgument.
+  let extensionIndex = 0;
+  let testKey = "callbackArgumentKey";
+  let callbackArgumentValue = Date.now();
+  // Add the setting.
+  let item = await ExtensionSettingsStore.addSetting(
+    extensions[extensionIndex].id,
+    TEST_TYPE,
+    testKey,
+    1,
+    initialValue,
+    callbackArgumentValue
+  );
+  expectedCallbackCount++;
+  equal(
+    callbackCount,
+    expectedCallbackCount,
+    "initialValueCallback called the expected number of times."
+  );
+  // Remove the setting which should return the initial value.
+  let expectedItem = {
+    key: testKey,
+    initialValue: initialValue(callbackArgumentValue),
+  };
+  // We're using the callback to set the expected value, so we need to increment the
+  // expectedCallbackCount.
+  expectedCallbackCount++;
+  item = await ExtensionSettingsStore.removeSetting(
+    extensions[extensionIndex].id,
+    TEST_TYPE,
+    testKey
+  );
+  deepEqual(
+    item,
+    expectedItem,
+    "Removing last item for a key returns the initial value."
+  );
+  item = await ExtensionSettingsStore.getSetting(TEST_TYPE, testKey);
+  deepEqual(item, null, "getSetting returns null after all are removed.");
+
+  item = await ExtensionSettingsStore.getSetting(TEST_TYPE, "not a key");
+  equal(
+    item,
+    null,
+    "getSetting returns a null item if the setting does not have any records."
+  );
+  let levelOfControl = await ExtensionSettingsStore.getLevelOfControl(
+    extensions[1].id,
+    TEST_TYPE,
+    "not a key"
+  );
+  equal(
+    levelOfControl,
+    "controllable_by_this_extension",
+    "getLevelOfControl returns correct levelOfControl if the setting does not have any records."
+  );
+
+  for (let extension of testExtensions) {
+    await extension.unload();
+  }
+
+  await promiseShutdownManager();
+});
+
+add_task(async function test_settings_store_setByUser() {
+  await promiseStartupManager();
+
+  // Create an array of test framework extension wrappers to install.
+  let testExtensions = [
+    ExtensionTestUtils.loadExtension({
+      useAddonManager: "temporary",
+      manifest: {
+        browser_specific_settings: { gecko: { id: "@first" } },
+      },
+    }),
+    ExtensionTestUtils.loadExtension({
+      useAddonManager: "temporary",
+      manifest: {
+        browser_specific_settings: { gecko: { id: "@second" } },
+      },
+    }),
+  ];
+
+  let type = "some_type";
+  let key = "some_key";
+
+  for (let extension of testExtensions) {
+    await extension.startup();
+  }
+
+  // Create an array actual Extension objects which correspond to the
+  // test framework extension wrappers.
+  let [one, two] = testExtensions.map(extension => extension.extension);
+  let initialCallback = () => "initial";
+
+  // Initialize the SettingsStore.
+  await ExtensionSettingsStore.initialize();
+
+  equal(
+    null,
+    ExtensionSettingsStore.getSetting(type, key),
+    "getSetting is initially null"
+  );
+
+  let item = await ExtensionSettingsStore.addSetting(
+    one.id,
+    type,
+    key,
+    "one",
+    initialCallback
+  );
+  deepEqual(
+    { key, value: "one", id: one.id },
+    item,
+    "addSetting returns the first set item"
+  );
+
+  item = await ExtensionSettingsStore.addSetting(
+    two.id,
+    type,
+    key,
+    "two",
+    initialCallback
+  );
+  deepEqual(
+    { key, value: "two", id: two.id },
+    item,
+    "addSetting returns the second set item"
+  );
+
+  // a user-set selection reverts to precedence order when new
+  // extension sets the setting.
+  ExtensionSettingsStore.select(
+    ExtensionSettingsStore.SETTING_USER_SET,
+    type,
+    key
+  );
+  deepEqual(
+    { key, initialValue: "initial" },
+    ExtensionSettingsStore.getSetting(type, key),
+    "getSetting returns the initial value after being set by user"
+  );
+
+  let three = ExtensionTestUtils.loadExtension({
+    useAddonManager: "temporary",
+    manifest: {
+      browser_specific_settings: { gecko: { id: "@third" } },
+    },
+  });
+  await three.startup();
+
+  item = await ExtensionSettingsStore.addSetting(
+    three.id,
+    type,
+    key,
+    "three",
+    initialCallback
+  );
+  deepEqual(
+    { key, value: "three", id: three.id },
+    item,
+    "addSetting returns the third set item"
+  );
+  deepEqual(
+    item,
+    ExtensionSettingsStore.getSetting(type, key),
+    "getSetting returns the third set item"
+  );
+
+  ExtensionSettingsStore.select(
+    ExtensionSettingsStore.SETTING_USER_SET,
+    type,
+    key
+  );
+  deepEqual(
+    { key, initialValue: "initial" },
+    ExtensionSettingsStore.getSetting(type, key),
+    "getSetting returns the initial value after being set by user"
+  );
+
+  item = ExtensionSettingsStore.select(one.id, type, key);
+  deepEqual(
+    { key, value: "one", id: one.id },
+    item,
+    "selecting an extension returns the first set item after enable"
+  );
+
+  // Disabling a selected item returns to precedence order
+  ExtensionSettingsStore.disable(one.id, type, key);
+  deepEqual(
+    { key, value: "three", id: three.id },
+    ExtensionSettingsStore.getSetting(type, key),
+    "returning to precedence order sets the third set item"
+  );
+
+  // Test that disabling all then enabling one does not take over a user-set setting.
+  ExtensionSettingsStore.select(
+    ExtensionSettingsStore.SETTING_USER_SET,
+    type,
+    key
+  );
+  deepEqual(
+    { key, initialValue: "initial" },
+    ExtensionSettingsStore.getSetting(type, key),
+    "getSetting returns the initial value after being set by user"
+  );
+
+  ExtensionSettingsStore.disable(three.id, type, key);
+  ExtensionSettingsStore.disable(two.id, type, key);
+  deepEqual(
+    { key, initialValue: "initial" },
+    ExtensionSettingsStore.getSetting(type, key),
+    "getSetting returns the initial value after disabling all extensions"
+  );
+
+  ExtensionSettingsStore.enable(three.id, type, key);
+  deepEqual(
+    { key, initialValue: "initial" },
+    ExtensionSettingsStore.getSetting(type, key),
+    "getSetting returns the initial value after enabling one extension"
+  );
+
+  // Ensure that calling addSetting again will not reset a user-set value when
+  // the extension install date is older than the user-set date.
+  item = await ExtensionSettingsStore.addSetting(
+    three.id,
+    type,
+    key,
+    "three",
+    initialCallback
+  );
+  deepEqual(
+    { key, initialValue: "initial" },
+    ExtensionSettingsStore.getSetting(type, key),
+    "getSetting returns the initial value after calling addSetting for old addon"
+  );
+
+  item = ExtensionSettingsStore.enable(three.id, type, key);
+  equal(undefined, item, "enabling the active item does not return an item");
+  deepEqual(
+    { key, initialValue: "initial" },
+    ExtensionSettingsStore.getSetting(type, key),
+    "getSetting returns the initial value after enabling one extension"
+  );
+
+  ExtensionSettingsStore.removeSetting(three.id, type, key);
+  ExtensionSettingsStore.removeSetting(two.id, type, key);
+  ExtensionSettingsStore.removeSetting(one.id, type, key);
+
+  equal(
+    null,
+    ExtensionSettingsStore.getSetting(type, key),
+    "getSetting returns null after removing all settings"
+  );
+
+  for (let extension of testExtensions) {
+    await extension.unload();
+  }
+
+  await promiseShutdownManager();
+});
+
+add_task(async function test_settings_store_add_disabled() {
+  await promiseStartupManager();
+
+  let id = "@add-on-disable";
+  let extension = ExtensionTestUtils.loadExtension({
+    useAddonManager: "temporary",
+    manifest: {
+      browser_specific_settings: { gecko: { id } },
+    },
+  });
+
+  await extension.startup();
+  await ExtensionSettingsStore.initialize();
+
+  await ExtensionSettingsStore.addSetting(
+    id,
+    "foo",
+    "bar",
+    "set",
+    () => "not set"
+  );
+
+  let item = ExtensionSettingsStore.getSetting("foo", "bar");
+  equal(item.id, id, "The add-on is in control");
+  equal(item.value, "set", "The value is set");
+
+  ExtensionSettingsStore.disable(id, "foo", "bar");
+  item = ExtensionSettingsStore.getSetting("foo", "bar");
+  equal(item.id, undefined, "The add-on is not in control");
+  equal(item.initialValue, "not set", "The value is not set");
+
+  await ExtensionSettingsStore.addSetting(
+    id,
+    "foo",
+    "bar",
+    "set",
+    () => "not set"
+  );
+  item = ExtensionSettingsStore.getSetting("foo", "bar");
+  equal(item.id, id, "The add-on is in control");
+  equal(item.value, "set", "The value is set");
+
+  await extension.unload();
+
+  await promiseShutdownManager();
+});
+
+add_task(async function test_settings_uninstall_remove() {
+  await promiseStartupManager();
+
+  let id = "@add-on-uninstall";
+  let extension = ExtensionTestUtils.loadExtension({
+    useAddonManager: "temporary",
+    manifest: {
+      browser_specific_settings: { gecko: { id } },
+    },
+  });
+
+  await extension.startup();
+  await ExtensionSettingsStore.initialize();
+
+  await ExtensionSettingsStore.addSetting(
+    id,
+    "foo",
+    "bar",
+    "set",
+    () => "not set"
+  );
+
+  let item = ExtensionSettingsStore.getSetting("foo", "bar");
+  equal(item.id, id, "The add-on is in control");
+  equal(item.value, "set", "The value is set");
+
+  await extension.unload();
+
+  await promiseShutdownManager();
+
+  item = ExtensionSettingsStore.getSetting("foo", "bar");
+  equal(item, null, "The add-on setting was removed");
+});
+
+add_task(async function test_exceptions() {
+  await ExtensionSettingsStore.initialize();
+
+  await Assert.rejects(
+    ExtensionSettingsStore.addSetting(
+      1,
+      TEST_TYPE,
+      "key_not_a_function",
+      "val1",
+      "not a function"
+    ),
+    /initialValueCallback must be a function/,
+    "addSetting rejects with a callback that is not a function."
+  );
+});
+
+add_task(async function test_get_all_settings() {
+  await promiseStartupManager();
+
+  let testExtensions = [
+    ExtensionTestUtils.loadExtension({
+      useAddonManager: "temporary",
+      manifest: {
+        browser_specific_settings: { gecko: { id: "@first" } },
+      },
+    }),
+    ExtensionTestUtils.loadExtension({
+      useAddonManager: "temporary",
+      manifest: {
+        browser_specific_settings: { gecko: { id: "@second" } },
+      },
+    }),
+  ];
+
+  for (let extension of testExtensions) {
+    await extension.startup();
+  }
+
+  await ExtensionSettingsStore.initialize();
+
+  let items = ExtensionSettingsStore.getAllSettings("foo", "bar");
+  equal(items.length, 0, "There are no addons controlling this setting yet");
+
+  await ExtensionSettingsStore.addSetting(
+    "@first",
+    "foo",
+    "bar",
+    "set",
+    () => "not set"
+  );
+
+  items = ExtensionSettingsStore.getAllSettings("foo", "bar");
+  equal(items.length, 1, "The add-on setting has 1 addon trying to control it");
+
+  await ExtensionSettingsStore.addSetting(
+    "@second",
+    "foo",
+    "bar",
+    "setting",
+    () => "not set"
+  );
+
+  let item = ExtensionSettingsStore.getSetting("foo", "bar");
+  equal(item.id, "@second", "The second add-on is in control");
+  equal(item.value, "setting", "The second value is set");
+
+  items = ExtensionSettingsStore.getAllSettings("foo", "bar");
+  equal(
+    items.length,
+    2,
+    "The add-on setting has 2 addons trying to control it"
+  );
+
+  await ExtensionSettingsStore.removeSetting("@first", "foo", "bar");
+
+  items = ExtensionSettingsStore.getAllSettings("foo", "bar");
+  equal(items.length, 1, "There is only 1 addon controlling this setting");
+
+  await ExtensionSettingsStore.removeSetting("@second", "foo", "bar");
+
+  items = ExtensionSettingsStore.getAllSettings("foo", "bar");
+  equal(
+    items.length,
+    0,
+    "There is no longer any addon controlling this setting"
+  );
+
+  for (let extension of testExtensions) {
+    await extension.unload();
+  }
+
+  await promiseShutdownManager();
+});
diff --git a/toolkit/components/extensions/test/xpcshell/test_ext_extension_content_telemetry.js b/toolkit/components/extensions/test/xpcshell/test_ext_extension_content_telemetry.js
new file mode 100644
index 0000000000..ee5eb84907
--- /dev/null
+++ b/toolkit/components/extensions/test/xpcshell/test_ext_extension_content_telemetry.js
@@ -0,0 +1,146 @@
+/* -*- Mode: indent-tabs-mode: nil; js-indent-level: 2 -*- */
+/* vim: set sts=2 sw=2 et tw=80: */
+"use strict";
+
+const HISTOGRAM = "WEBEXT_CONTENT_SCRIPT_INJECTION_MS";
+const HISTOGRAM_KEYED = "WEBEXT_CONTENT_SCRIPT_INJECTION_MS_BY_ADDONID";
+
+const server = createHttpServer();
+server.registerDirectory("/data/", do_get_file("data"));
+
+const BASE_URL = `http://localhost:${server.identity.primaryPort}/data`;
+
+add_task(async function test_telemetry() {
+  function contentScript() {
+    browser.test.sendMessage("content-script-run");
+  }
+
+  let extension1 = ExtensionTestUtils.loadExtension({
+    manifest: {
+      content_scripts: [
+        {
+          matches: ["http://*/*/file_sample.html"],
+          js: ["content_script.js"],
+          run_at: "document_end",
+        },
+      ],
+    },
+
+    files: {
+      "content_script.js": contentScript,
+    },
+  });
+  let extension2 = ExtensionTestUtils.loadExtension({
+    manifest: {
+      content_scripts: [
+        {
+          matches: ["http://*/*/file_sample.html"],
+          js: ["content_script.js"],
+          run_at: "document_end",
+        },
+      ],
+    },
+
+    files: {
+      "content_script.js": contentScript,
+    },
+  });
+
+  clearHistograms();
+
+  let process = IS_OOP ? "content" : "parent";
+  ok(
+    !(HISTOGRAM in getSnapshots(process)),
+    `No data recorded for histogram: ${HISTOGRAM}.`
+  );
+  ok(
+    !(HISTOGRAM_KEYED in getKeyedSnapshots(process)),
+    `No data recorded for keyed histogram: ${HISTOGRAM_KEYED}.`
+  );
+
+  await extension1.startup();
+  let extensionId = extension1.extension.id;
+
+  info(`Started extension with id ${extensionId}`);
+
+  ok(
+    !(HISTOGRAM in getSnapshots(process)),
+    `No data recorded for histogram after startup: ${HISTOGRAM}.`
+  );
+  ok(
+    !(HISTOGRAM_KEYED in getKeyedSnapshots(process)),
+    `No data recorded for keyed histogram: ${HISTOGRAM_KEYED}.`
+  );
+
+  let contentPage = await ExtensionTestUtils.loadContentPage(
+    `${BASE_URL}/file_sample.html`
+  );
+  await extension1.awaitMessage("content-script-run");
+  await promiseTelemetryRecorded(HISTOGRAM, process, 1);
+  await promiseKeyedTelemetryRecorded(HISTOGRAM_KEYED, process, extensionId, 1);
+
+  equal(
+    valueSum(getSnapshots(process)[HISTOGRAM].values),
+    1,
+    `Data recorded for histogram: ${HISTOGRAM}.`
+  );
+  equal(
+    valueSum(getKeyedSnapshots(process)[HISTOGRAM_KEYED][extensionId].values),
+    1,
+    `Data recorded for histogram: ${HISTOGRAM_KEYED} with key ${extensionId}.`
+  );
+
+  await contentPage.close();
+  await extension1.unload();
+
+  await extension2.startup();
+  let extensionId2 = extension2.extension.id;
+
+  info(`Started extension with id ${extensionId2}`);
+
+  equal(
+    valueSum(getSnapshots(process)[HISTOGRAM].values),
+    1,
+    `No new data recorded for histogram after extension2 startup: ${HISTOGRAM}.`
+  );
+  equal(
+    valueSum(getKeyedSnapshots(process)[HISTOGRAM_KEYED][extensionId].values),
+    1,
+    `No new data recorded for histogram after extension2 startup: ${HISTOGRAM_KEYED} with key ${extensionId}.`
+  );
+  ok(
+    !(extensionId2 in getKeyedSnapshots(process)[HISTOGRAM_KEYED]),
+    `No data recorded for histogram after startup: ${HISTOGRAM_KEYED} with key ${extensionId2}.`
+  );
+
+  contentPage = await ExtensionTestUtils.loadContentPage(
+    `${BASE_URL}/file_sample.html`
+  );
+  await extension2.awaitMessage("content-script-run");
+  await promiseTelemetryRecorded(HISTOGRAM, process, 2);
+  await promiseKeyedTelemetryRecorded(
+    HISTOGRAM_KEYED,
+    process,
+    extensionId2,
+    1
+  );
+
+  equal(
+    valueSum(getSnapshots(process)[HISTOGRAM].values),
+    2,
+    `Data recorded for histogram: ${HISTOGRAM}.`
+  );
+  equal(
+    valueSum(getKeyedSnapshots(process)[HISTOGRAM_KEYED][extensionId].values),
+    1,
+    `No new data recorded for histogram: ${HISTOGRAM_KEYED} with key ${extensionId}.`
+  );
+  equal(
+    valueSum(getKeyedSnapshots(process)[HISTOGRAM_KEYED][extensionId2].values),
+    1,
+    `Data recorded for histogram: ${HISTOGRAM_KEYED} with key ${extensionId2}.`
+  );
+
+  await contentPage.close();
+  await extension2.unload();
+});
diff --git a/toolkit/components/extensions/test/xpcshell/test_ext_extension_page_navigated.js b/toolkit/components/extensions/test/xpcshell/test_ext_extension_page_navigated.js
new file mode 100644
index 0000000000..e573595afb
--- /dev/null
+++ b/toolkit/components/extensions/test/xpcshell/test_ext_extension_page_navigated.js
@@ -0,0 +1,341 @@
+/* Any copyright is dedicated to the Public Domain.
+ * http://creativecommons.org/publicdomain/zero/1.0/ */
+
+"use strict";
+
+AddonTestUtils.init(this);
+AddonTestUtils.createAppInfo(
+  "xpcshell@tests.mozilla.org",
+  "XPCShell",
+  "42",
+  "42"
+);
+
+const server = AddonTestUtils.createHttpServer({ hosts: ["example.com"] });
+
+server.registerPathHandler("/", (request, response) => {
+  response.write(`<!DOCTYPE html>
+    <html>
+      <head>
+       <meta charset="utf-8">
+       <title>test webpage</title>
+      </head>
+    </html>
+  `);
+});
+
+function createTestExtPage({ script }) {
+  return `<!DOCTYPE html>
+    <html>
+      <head>
+       <meta charset="utf-8">
+       <script src="${script}"></script>
+      </head>
+    </html>
+  `;
+}
+
+function createTestExtPageScript(name) {
+  return `(${async function (pageName) {
+    browser.webRequest.onBeforeRequest.addListener(
+      details => {
+        browser.test.log(
+          `${pageName} got a webRequest.onBeforeRequest event: ${details.url}`
+        );
+        browser.test.sendMessage(`event-received:${pageName}`);
+      },
+      { urls: ["http://example.com/request*"] }
+    );
+
+    // Calling an API implemented in the parent process to make sure
+    // the webRequest.onBeforeRequest listener is got registered in
+    // the parent process by the time the test is going to expect that
+    // listener to intercept a test web request.
+    await browser.runtime.getBrowserInfo();
+    browser.test.sendMessage(`page-loaded:${pageName}`);
+  }})("${name}");`;
+}
+
+const getExtensionContextIdAndURL = extensionId => {
+  const { ExtensionProcessScript } = ChromeUtils.importESModule(
+    "resource://gre/modules/ExtensionProcessScript.sys.mjs"
+  );
+  let extWindow = this.content.window;
+  let extChild = ExtensionProcessScript.getExtensionChild(extensionId);
+
+  let contextIds = [];
+  let contextURLs = [];
+  for (let ctx of extChild.views) {
+    if (ctx.contentWindow === extWindow) {
+      // Only one is expected, but we collect details from all
+      // the ones that match to make sure the test will fails
+      // in case there are unexpected multiple extension contexts
+      // associated to the same contentWindow.
+      contextIds.push(ctx.contextId);
+      contextURLs.push(ctx.contentWindow.location.href);
+    }
+  }
+  return { contextIds, contextURLs };
+};
+
+const getExtensionContextStatusByContextId = (
+  extensionId,
+  extPageContextId
+) => {
+  const { ExtensionProcessScript } = ChromeUtils.importESModule(
+    "resource://gre/modules/ExtensionProcessScript.sys.mjs"
+  );
+  let extChild = ExtensionProcessScript.getExtensionChild(extensionId);
+
+  let context;
+  for (let ctx of extChild.views) {
+    if (ctx.contextId === extPageContextId) {
+      context = ctx;
+    }
+  }
+  return context?.active;
+};
+
+add_task(async function test_extension_page_sameprocess_navigation() {
+  const extension = ExtensionTestUtils.loadExtension({
+    manifest: {
+      permissions: ["webRequest", "http://example.com/*"],
+    },
+    files: {
+      "extpage1.html": createTestExtPage({ script: "extpage1.js" }),
+      "extpage1.js": createTestExtPageScript("extpage1"),
+      "extpage2.html": createTestExtPage({ script: "extpage2.js" }),
+      "extpage2.js": createTestExtPageScript("extpage2"),
+    },
+  });
+
+  await extension.startup();
+
+  const policy = WebExtensionPolicy.getByID(extension.id);
+
+  const extPageURL1 = policy.extension.baseURI.resolve("extpage1.html");
+  const extPageURL2 = policy.extension.baseURI.resolve("extpage2.html");
+
+  info("Opening extension page in a first browser element");
+  const extPage = await ExtensionTestUtils.loadContentPage(extPageURL1);
+  await extension.awaitMessage("page-loaded:extpage1");
+
+  const { contextIds, contextURLs } = await extPage.spawn(
+    [extension.id],
+    getExtensionContextIdAndURL
+  );
+
+  Assert.deepEqual(
+    contextURLs,
+    [extPageURL1],
+    `Found an extension context with the expected page url`
+  );
+
+  ok(
+    contextIds[0],
+    `Found an extension context with contextId ${contextIds[0]}`
+  );
+  ok(
+    contextIds.length,
+    `There should be only one extension context for a given content window, found ${contextIds.length}`
+  );
+
+  const [contextId] = contextIds;
+
+  await ExtensionTestUtils.fetch(
+    "http://example.com",
+    "http://example.com/request1"
+  );
+  await extension.awaitMessage("event-received:extpage1");
+
+  info("Load a second extension page in the same browser element");
+  await extPage.loadURL(extPageURL2);
+  await extension.awaitMessage("page-loaded:extpage2");
+
+  let active;
+
+  let { messages } = await AddonTestUtils.promiseConsoleOutput(async () => {
+    // We only expect extpage2 to be able to receive API events.
+    await ExtensionTestUtils.fetch(
+      "http://example.com",
+      "http://example.com/request2"
+    );
+    await extension.awaitMessage("event-received:extpage2");
+
+    active = await extPage.spawn(
+      [extension.id, contextId],
+      getExtensionContextStatusByContextId
+    );
+  });
+
+  if (
+    Services.appinfo.sessionHistoryInParent &&
+    WebExtensionPolicy.isExtensionProcess
+  ) {
+    // When the extension are running in the main process while the webpages run
+    // in a separate child process, the extension page doesn't enter the BFCache
+    // because nsFrameLoader::changeRemotenessCommon bails out due to retainPaint
+    // being computed as true (see
+    // https://searchfox.org/mozilla-central/rev/24c1cdc33ccce692612276cd0d3e9a44f6c22fd3/dom/base/nsFrameLoaderOwner.cpp#185-196
+    // ).
+    equal(active, undefined, "extension page context should not exist anymore");
+  } else {
+    equal(
+      active,
+      false,
+      "extension page context is expected to be inactive while moved into the BFCache"
+    );
+  }
+
+  if (typeof active === "boolean") {
+    AddonTestUtils.checkMessages(
+      messages,
+      {
+        forbidden: [
+          // We should not have tried to deserialize the event data for the extension page
+          // that got moved into the BFCache (See Bug 1499129).
+          {
+            message:
+              /StructureCloneHolder.deserialize: Argument 1 is not an object/,
+          },
+        ],
+        expected: [
+          // If the extension page is expected to be in the BFCache, then we expect to see
+          // a warning message logged for the ignored listener.
+          {
+            message:
+              /Ignored listener for inactive context .* path=webRequest.onBeforeRequest/,
+          },
+        ],
+      },
+      "Expect no StructureCloneHolder error due to trying to send the event to inactive context"
+    );
+  }
+
+  await extPage.close();
+  await extension.unload();
+});
+
+add_task(async function test_extension_page_context_navigated_to_web_page() {
+  const extension = ExtensionTestUtils.loadExtension({
+    files: {
+      "extpage.html": createTestExtPage({ script: "extpage.js" }),
+      "extpage.js": function () {
+        dump("loaded extension page\n");
+        window.addEventListener(
+          "pageshow",
+          () => {
+            browser.test.log("Extension page got a pageshow event");
+            browser.test.sendMessage("extpage:pageshow");
+          },
+          { once: true }
+        );
+        window.addEventListener(
+          "pagehide",
+          () => {
+            browser.test.log("Extension page got a pagehide event");
+            browser.test.sendMessage("extpage:pagehide");
+          },
+          { once: true }
+        );
+      },
+    },
+  });
+
+  await extension.startup();
+
+  const policy = WebExtensionPolicy.getByID(extension.id);
+
+  const extPageURL = policy.extension.baseURI.resolve("extpage.html");
+  const webPageURL = "http://example.com/";
+
+  info("Opening extension page in a browser element");
+  const extPage = await ExtensionTestUtils.loadContentPage(extPageURL);
+  await extension.awaitMessage("extpage:pageshow");
+
+  const { contextIds, contextURLs } = await extPage.spawn(
+    [extension.id],
+    getExtensionContextIdAndURL
+  );
+
+  Assert.deepEqual(
+    contextURLs,
+    [extPageURL],
+    `Found an extension context with the expected page url`
+  );
+
+  ok(
+    contextIds[0],
+    `Found an extension context with contextId ${contextIds[0]}`
+  );
+  ok(
+    contextIds.length,
+    `There should be only one extension context for a given content window, found ${contextIds.length}`
+  );
+
+  const [contextId] = contextIds;
+
+  info("Load a webpage in the same browser element");
+  await extPage.loadURL(webPageURL);
+  await extension.awaitMessage("extpage:pagehide");
+
+  info("Open extension page in a second browser element");
+  const extPage2 = await ExtensionTestUtils.loadContentPage(extPageURL);
+  await extension.awaitMessage("extpage:pageshow");
+
+  let active = await extPage2.spawn(
+    [extension.id, contextId],
+    getExtensionContextStatusByContextId
+  );
+
+  if (WebExtensionPolicy.isExtensionProcess) {
+    // When the extension are running in the main process while the webpages run
+    // in a separate child process, the extension page doesn't enter the BFCache
+    // because nsFrameLoader::changeRemotenessCommon bails out due to retainPaint
+    // being computed as true (see
+    // https://searchfox.org/mozilla-central/rev/24c1cdc33ccce692612276cd0d3e9a44f6c22fd3/dom/base/nsFrameLoaderOwner.cpp#185-196
+    // ).
+    equal(active, undefined, "extension page context should not exist anymore");
+  } else if (Services.appinfo.sessionHistoryInParent) {
+    // When SHIP is enabled and the extensions runs in their own child extension
+    // process, the BFCache is managed entirely from the parent process and the
+    // extension page is expected to be able to enter the BFCache.
+    equal(
+      active,
+      false,
+      "extension page context is expected to be inactive while moved into the BFCache"
+    );
+  } else {
+    // With the extension running in a separate child process but fission disabled,
+    // we expect the extension page to don't enter the BFCache.
+    equal(active, undefined, "extension page context should not exist anymore");
+  }
+
+  if (active === false) {
+    info(
+      "Navigating to more web pages to confirm the extension page have been evicted from the BFCache"
+    );
+    for (let i = 2; i < 5; i++) {
+      const url = `${webPageURL}/page${i}`;
+      info(`Navigating to ${url}`);
+      await extPage.loadURL(url);
+    }
+    equal(
+      await extPage2.spawn(
+        [extension.id, contextId],
+        getExtensionContextStatusByContextId
+      ),
+      undefined,
+      "extension page context should have been evicted"
+    );
+  }
+
+  info("Cleanup and exit test");
+
+  await Promise.all([
+    extPage.close(),
+    extPage2.close(),
+    extension.awaitMessage("extpage:pagehide"),
+  ]);
+  await extension.unload();
+});
diff --git a/toolkit/components/extensions/test/xpcshell/test_ext_extension_startup_failure.js b/toolkit/components/extensions/test/xpcshell/test_ext_extension_startup_failure.js
new file mode 100644
index 0000000000..abd81a7ce3
--- /dev/null
+++ b/toolkit/components/extensions/test/xpcshell/test_ext_extension_startup_failure.js
@@ -0,0 +1,46 @@
+/* -*- Mode: indent-tabs-mode: nil; js-indent-level: 2 -*- */
+/* vim: set sts=2 sw=2 et tw=80: */
+"use strict";
+
+const { ExtensionTestCommon } = ChromeUtils.importESModule(
+  "resource://testing-common/ExtensionTestCommon.sys.mjs"
+);
+
+add_task(async function extension_startup_early_error() {
+  const EXTENSION_ID = "@extension-with-package-error";
+  let extension = ExtensionTestCommon.generate({
+    manifest: {
+      browser_specific_settings: { gecko: { id: EXTENSION_ID } },
+    },
+  });
+
+  extension.initLocale = async function () {
+    // Simulate error that happens during startup.
+    extension.packagingError("dummy error");
+  };
+
+  let startupPromise = extension.startup();
+
+  let policy = WebExtensionPolicy.getByID(EXTENSION_ID);
+  ok(policy, "WebExtensionPolicy instantiated at startup");
+  let readyPromise = policy.readyPromise;
+  ok(readyPromise, "WebExtensionPolicy.readyPromise is set");
+
+  await Assert.rejects(
+    startupPromise,
+    /dummy error/,
+    "Extension with packaging error should fail to load"
+  );
+
+  Assert.equal(
+    WebExtensionPolicy.getByID(EXTENSION_ID),
+    null,
+    "WebExtensionPolicy should be unregistered"
+  );
+
+  Assert.equal(
+    await readyPromise,
+    null,
+    "policy.readyPromise should be resolved with null"
+  );
+});
diff --git a/toolkit/components/extensions/test/xpcshell/test_ext_extension_startup_telemetry.js b/toolkit/components/extensions/test/xpcshell/test_ext_extension_startup_telemetry.js
new file mode 100644
index 0000000000..b65c772174
--- /dev/null
+++ b/toolkit/components/extensions/test/xpcshell/test_ext_extension_startup_telemetry.js
@@ -0,0 +1,87 @@
+/* -*- Mode: indent-tabs-mode: nil; js-indent-level: 2 -*- */
+/* vim: set sts=2 sw=2 et tw=80: */
+"use strict";
+
+const HISTOGRAM = "WEBEXT_EXTENSION_STARTUP_MS";
+const HISTOGRAM_KEYED = "WEBEXT_EXTENSION_STARTUP_MS_BY_ADDONID";
+
+function processSnapshot(snapshot) {
+  return snapshot.sum > 0;
+}
+
+function processKeyedSnapshot(snapshot) {
+  let res = {};
+  for (let key of Object.keys(snapshot)) {
+    res[key] = snapshot[key].sum > 0;
+  }
+  return res;
+}
+
+add_task(async function test_telemetry() {
+  let extension1 = ExtensionTestUtils.loadExtension({});
+  let extension2 = ExtensionTestUtils.loadExtension({});
+
+  clearHistograms();
+
+  assertHistogramEmpty(HISTOGRAM);
+  assertKeyedHistogramEmpty(HISTOGRAM_KEYED);
+
+  await extension1.startup();
+
+  assertHistogramSnapshot(
+    HISTOGRAM,
+    { processSnapshot, expectedValue: true },
+    `Data recorded for first extension for histogram: ${HISTOGRAM}.`
+  );
+
+  assertHistogramSnapshot(
+    HISTOGRAM_KEYED,
+    {
+      keyed: true,
+      processSnapshot: processKeyedSnapshot,
+      expectedValue: {
+        [extension1.extension.id]: true,
+      },
+    },
+    `Data recorded for first extension for histogram ${HISTOGRAM_KEYED}`
+  );
+
+  let histogram = Services.telemetry.getHistogramById(HISTOGRAM);
+  let histogramKeyed =
+    Services.telemetry.getKeyedHistogramById(HISTOGRAM_KEYED);
+  let histogramSum = histogram.snapshot().sum;
+  let histogramSumExt1 = histogramKeyed.snapshot()[extension1.extension.id].sum;
+
+  await extension2.startup();
+
+  assertHistogramSnapshot(
+    HISTOGRAM,
+    {
+      processSnapshot: snapshot => snapshot.sum > histogramSum,
+      expectedValue: true,
+    },
+    `Data recorded for second extension for histogram: ${HISTOGRAM}.`
+  );
+
+  assertHistogramSnapshot(
+    HISTOGRAM_KEYED,
+    {
+      keyed: true,
+      processSnapshot: processKeyedSnapshot,
+      expectedValue: {
+        [extension1.extension.id]: true,
+        [extension2.extension.id]: true,
+      },
+    },
+    `Data recorded for second extension for histogram ${HISTOGRAM_KEYED}`
+  );
+
+  equal(
+    histogramKeyed.snapshot()[extension1.extension.id].sum,
+    histogramSumExt1,
+    `Data recorder for first extension is unchanged on the keyed histogram ${HISTOGRAM_KEYED}`
+  );
+
+  await extension1.unload();
+  await extension2.unload();
+});
diff --git a/toolkit/components/extensions/test/xpcshell/test_ext_file_access.js b/toolkit/components/extensions/test/xpcshell/test_ext_file_access.js
new file mode 100644
index 0000000000..c05188cd38
--- /dev/null
+++ b/toolkit/components/extensions/test/xpcshell/test_ext_file_access.js
@@ -0,0 +1,193 @@
+"use strict";
+
+const FILE_DUMMY_URL = Services.io.newFileURI(
+  do_get_file("data/dummy_page.html")
+).spec;
+
+// ExtensionContent.jsm needs to know when it's running from xpcshell,
+// to use the right timeout for content scripts executed at document_idle.
+ExtensionTestUtils.mockAppInfo();
+
+// XHR/fetch from content script to the page itself is allowed.
+add_task(async function content_script_xhr_to_self() {
+  let extension = ExtensionTestUtils.loadExtension({
+    manifest: {
+      content_scripts: [
+        {
+          matches: ["file:///*"],
+          js: ["content_script.js"],
+        },
+      ],
+    },
+    files: {
+      "content_script.js": async () => {
+        let response = await fetch(document.URL);
+        browser.test.assertEq(200, response.status, "expected load");
+        let responseText = await response.text();
+        browser.test.assertTrue(
+          responseText.includes("<p>Page</p>"),
+          `expected file content in response of ${response.url}`
+        );
+
+        // Now with content.fetch:
+        response = await content.fetch(document.URL);
+        browser.test.assertEq(200, response.status, "expected load (content)");
+
+        browser.test.sendMessage("done");
+      },
+    },
+  });
+
+  await extension.startup();
+
+  let contentPage = await ExtensionTestUtils.loadContentPage(FILE_DUMMY_URL);
+  await extension.awaitMessage("done");
+  await contentPage.close();
+
+  await extension.unload();
+});
+
+// XHR/fetch for other file is not allowed, even with file://-permissions.
+add_task(async function content_script_xhr_to_other_file_not_allowed() {
+  let extension = ExtensionTestUtils.loadExtension({
+    manifest: {
+      permissions: ["file:///*"],
+      content_scripts: [
+        {
+          matches: ["file:///*"],
+          js: ["content_script.js"],
+        },
+      ],
+    },
+    files: {
+      "content_script.js": async () => {
+        let otherFileUrl = document.URL.replace(
+          "dummy_page.html",
+          "file_sample.html"
+        );
+        let x = new XMLHttpRequest();
+        x.open("GET", otherFileUrl);
+        await new Promise(resolve => {
+          x.onloadend = resolve;
+          x.send();
+        });
+        browser.test.assertEq(0, x.status, "expected error");
+        browser.test.assertEq("", x.responseText, "request should fail");
+
+        // Now with content.XMLHttpRequest.
+        x = new content.XMLHttpRequest();
+        x.open("GET", otherFileUrl);
+        x.onloadend = () => {
+          browser.test.assertEq(0, x.status, "expected error (content)");
+          browser.test.sendMessage("done");
+        };
+        x.send();
+      },
+    },
+  });
+
+  await extension.startup();
+
+  let contentPage = await ExtensionTestUtils.loadContentPage(FILE_DUMMY_URL);
+  await extension.awaitMessage("done");
+  await contentPage.close();
+
+  await extension.unload();
+});
+
+// "file://" permission does not grant access to files in the extension page.
+add_task(async function file_access_from_extension_page_not_allowed() {
+  let extension = ExtensionTestUtils.loadExtension({
+    manifest: {
+      permissions: ["file:///*"],
+      description: FILE_DUMMY_URL,
+    },
+    async background() {
+      const FILE_DUMMY_URL = browser.runtime.getManifest().description;
+
+      await browser.test.assertRejects(
+        fetch(FILE_DUMMY_URL),
+        /NetworkError when attempting to fetch resource/,
+        "block request to file from background page despite file permission"
+      );
+
+      // Regression test for bug 1420296 .
+      await browser.test.assertRejects(
+        fetch(FILE_DUMMY_URL, { mode: "same-origin" }),
+        /NetworkError when attempting to fetch resource/,
+        "block request to file from background page despite 'same-origin' mode"
+      );
+
+      browser.test.sendMessage("done");
+    },
+  });
+
+  await extension.startup();
+
+  await extension.awaitMessage("done");
+
+  await extension.unload();
+});
+
+// webRequest listeners should see subresource requests from file:-principals.
+add_task(async function webRequest_script_request_from_file_principals() {
+  // Extension without file:-permission should not see the request.
+  let extensionWithoutFilePermission = ExtensionTestUtils.loadExtension({
+    manifest: {
+      permissions: ["http://example.net/", "webRequest"],
+    },
+    background() {
+      browser.webRequest.onBeforeRequest.addListener(
+        details => {
+          browser.test.fail(`Unexpected request from ${details.originUrl}`);
+        },
+        { urls: ["http://example.net/intercept_by_webRequest.js"] }
+      );
+    },
+  });
+
+  // Extension with <all_urls> (which matches the resource URL at example.net
+  // and the origin at file://*/*) can see the request.
+  let extension = ExtensionTestUtils.loadExtension({
+    manifest: {
+      permissions: ["<all_urls>", "webRequest", "webRequestBlocking"],
+      web_accessible_resources: ["testDONE.html"],
+    },
+    background() {
+      browser.webRequest.onBeforeRequest.addListener(
+        ({ originUrl }) => {
+          browser.test.assertTrue(
+            /^file:.*file_do_load_script_subresource.html/.test(originUrl),
+            `expected script to be loaded from a local file (${originUrl})`
+          );
+          let redirectUrl = browser.runtime.getURL("testDONE.html");
+          return {
+            redirectUrl: `data:text/javascript,location.href='${redirectUrl}';`,
+          };
+        },
+        { urls: ["http://example.net/intercept_by_webRequest.js"] },
+        ["blocking"]
+      );
+    },
+    files: {
+      "testDONE.html": `<!DOCTYPE html><script src="testDONE.js"></script>`,
+      "testDONE.js"() {
+        browser.test.sendMessage("webRequest_redirect_completed");
+      },
+    },
+  });
+
+  await extensionWithoutFilePermission.startup();
+  await extension.startup();
+
+  let contentPage = await ExtensionTestUtils.loadContentPage(
+    Services.io.newFileURI(
+      do_get_file("data/file_do_load_script_subresource.html")
+    ).spec
+  );
+  await extension.awaitMessage("webRequest_redirect_completed");
+  await contentPage.close();
+
+  await extension.unload();
+  await extensionWithoutFilePermission.unload();
+});
diff --git a/toolkit/components/extensions/test/xpcshell/test_ext_geckoProfiler_control.js b/toolkit/components/extensions/test/xpcshell/test_ext_geckoProfiler_control.js
new file mode 100644
index 0000000000..fa2759b7f0
--- /dev/null
+++ b/toolkit/components/extensions/test/xpcshell/test_ext_geckoProfiler_control.js
@@ -0,0 +1,205 @@
+/* -*- Mode: indent-tabs-mode: nil; js-indent-level: 2 -*- */
+/* vim: set sts=2 sw=2 et tw=80: */
+"use strict";
+
+let getExtension = () => {
+  return ExtensionTestUtils.loadExtension({
+    background: async function () {
+      const runningListener = isRunning => {
+        if (isRunning) {
+          browser.test.sendMessage("started");
+        } else {
+          browser.test.sendMessage("stopped");
+        }
+      };
+
+      browser.test.onMessage.addListener(async (message, data) => {
+        let result;
+        switch (message) {
+          case "start":
+            result = await browser.geckoProfiler.start({
+              bufferSize: 10000,
+              windowLength: 20,
+              interval: 0.5,
+              features: ["js"],
+              threads: ["GeckoMain"],
+            });
+            browser.test.assertEq(undefined, result, "start returns nothing.");
+            break;
+          case "stop":
+            result = await browser.geckoProfiler.stop();
+            browser.test.assertEq(undefined, result, "stop returns nothing.");
+            break;
+          case "pause":
+            result = await browser.geckoProfiler.pause();
+            browser.test.assertEq(undefined, result, "pause returns nothing.");
+            browser.test.sendMessage("paused");
+            break;
+          case "resume":
+            result = await browser.geckoProfiler.resume();
+            browser.test.assertEq(undefined, result, "resume returns nothing.");
+            browser.test.sendMessage("resumed");
+            break;
+          case "test profile":
+            result = await browser.geckoProfiler.getProfile();
+            browser.test.assertTrue(
+              "libs" in result,
+              "The profile contains libs."
+            );
+            browser.test.assertTrue(
+              "meta" in result,
+              "The profile contains meta."
+            );
+            browser.test.assertTrue(
+              "threads" in result,
+              "The profile contains threads."
+            );
+            browser.test.assertTrue(
+              result.threads.some(t => t.name == "GeckoMain"),
+              "The profile contains a GeckoMain thread."
+            );
+            browser.test.sendMessage("tested profile");
+            break;
+          case "test dump to file":
+            try {
+              await browser.geckoProfiler.dumpProfileToFile(data.fileName);
+              browser.test.sendMessage("tested dump to file", {});
+            } catch (e) {
+              browser.test.sendMessage("tested dump to file", {
+                error: e.message,
+              });
+            }
+            break;
+          case "test profile as array buffer":
+            let arrayBuffer =
+              await browser.geckoProfiler.getProfileAsArrayBuffer();
+            browser.test.assertTrue(
+              arrayBuffer.byteLength >= 2,
+              "The profile array buffer contains data."
+            );
+            let textDecoder = new TextDecoder();
+            let profile = JSON.parse(textDecoder.decode(arrayBuffer));
+            browser.test.assertTrue(
+              "libs" in profile,
+              "The profile contains libs."
+            );
+            browser.test.assertTrue(
+              "meta" in profile,
+              "The profile contains meta."
+            );
+            browser.test.assertTrue(
+              "threads" in profile,
+              "The profile contains threads."
+            );
+            browser.test.assertTrue(
+              profile.threads.some(t => t.name == "GeckoMain"),
+              "The profile contains a GeckoMain thread."
+            );
+            browser.test.sendMessage("tested profile as array buffer");
+            break;
+          case "remove runningListener":
+            browser.geckoProfiler.onRunning.removeListener(runningListener);
+            browser.test.sendMessage("removed runningListener");
+            break;
+        }
+      });
+
+      browser.test.sendMessage("ready");
+
+      browser.geckoProfiler.onRunning.addListener(runningListener);
+    },
+
+    manifest: {
+      permissions: ["geckoProfiler"],
+      browser_specific_settings: {
+        gecko: {
+          id: "profilertest@mozilla.com",
+        },
+      },
+    },
+  });
+};
+
+let verifyProfileData = profile => {
+  ok("libs" in profile, "The profile contains libs.");
+  ok("meta" in profile, "The profile contains meta.");
+  ok("threads" in profile, "The profile contains threads.");
+  ok(
+    profile.threads.some(t => t.name == "GeckoMain"),
+    "The profile contains a GeckoMain thread."
+  );
+};
+
+add_task(async function testProfilerControl() {
+  const acceptedExtensionIdsPref =
+    "extensions.geckoProfiler.acceptedExtensionIds";
+  Services.prefs.setCharPref(
+    acceptedExtensionIdsPref,
+    "profilertest@mozilla.com"
+  );
+
+  let extension = getExtension();
+  await extension.startup();
+  await extension.awaitMessage("ready");
+  await extension.awaitMessage("stopped");
+
+  extension.sendMessage("start");
+  await extension.awaitMessage("started");
+
+  extension.sendMessage("test profile");
+  await extension.awaitMessage("tested profile");
+
+  const profilerPath = PathUtils.join(PathUtils.profileDir, "profiler");
+  let data, fileName, targetPath;
+
+  // test with file name only
+  fileName = "bar.profile";
+  targetPath = PathUtils.join(profilerPath, fileName);
+  extension.sendMessage("test dump to file", { fileName });
+  data = await extension.awaitMessage("tested dump to file");
+  equal(data.error, undefined, "No error thrown");
+  ok(await IOUtils.exists(targetPath), "Saved gecko profile exists.");
+  verifyProfileData(await IOUtils.readJSON(targetPath));
+
+  // test overwriting the formerly created file
+  extension.sendMessage("test dump to file", { fileName });
+  data = await extension.awaitMessage("tested dump to file");
+  equal(data.error, undefined, "No error thrown");
+  ok(await IOUtils.exists(targetPath), "Saved gecko profile exists.");
+  verifyProfileData(await IOUtils.readJSON(targetPath));
+
+  // test with a POSIX path, which is not allowed
+  fileName = "foo/bar.profile";
+  targetPath = PathUtils.join(profilerPath, ...fileName.split("/"));
+  extension.sendMessage("test dump to file", { fileName });
+  data = await extension.awaitMessage("tested dump to file");
+  equal(data.error, "Path cannot contain a subdirectory.");
+  ok(!(await IOUtils.exists(targetPath)), "Gecko profile hasn't been saved.");
+
+  // test with a non POSIX path which is not allowed
+  fileName = "foo\\bar.profile";
+  targetPath = PathUtils.join(profilerPath, ...fileName.split("\\"));
+  extension.sendMessage("test dump to file", { fileName });
+  data = await extension.awaitMessage("tested dump to file");
+  equal(data.error, "Path cannot contain a subdirectory.");
+  ok(!(await IOUtils.exists(targetPath)), "Gecko profile hasn't been saved.");
+
+  extension.sendMessage("test profile as array buffer");
+  await extension.awaitMessage("tested profile as array buffer");
+
+  extension.sendMessage("pause");
+  await extension.awaitMessage("paused");
+
+  extension.sendMessage("resume");
+  await extension.awaitMessage("resumed");
+
+  extension.sendMessage("stop");
+  await extension.awaitMessage("stopped");
+
+  extension.sendMessage("remove runningListener");
+  await extension.awaitMessage("removed runningListener");
+
+  await extension.unload();
+
+  Services.prefs.clearUserPref(acceptedExtensionIdsPref);
+});
diff --git a/toolkit/components/extensions/test/xpcshell/test_ext_geckoProfiler_schema.js b/toolkit/components/extensions/test/xpcshell/test_ext_geckoProfiler_schema.js
new file mode 100644
index 0000000000..6d96731a3c
--- /dev/null
+++ b/toolkit/components/extensions/test/xpcshell/test_ext_geckoProfiler_schema.js
@@ -0,0 +1,68 @@
+"use strict";
+
+add_task(async function () {
+  // The startupCache is removed whenever the buildid changes by code that runs
+  // during Firefox startup but not during xpcshell startup, remove it by hand
+  // before running this test to avoid failures with --conditioned-profile
+  let file = PathUtils.join(
+    Services.dirsvc.get("ProfLD", Ci.nsIFile).path,
+    "startupCache",
+    "webext.sc.lz4"
+  );
+  await IOUtils.remove(file, { ignoreAbsent: true });
+
+  const acceptedExtensionIdsPref =
+    "extensions.geckoProfiler.acceptedExtensionIds";
+  Services.prefs.setCharPref(
+    acceptedExtensionIdsPref,
+    "profilertest@mozilla.com"
+  );
+
+  let extension = ExtensionTestUtils.loadExtension({
+    background: () => {
+      browser.test.sendMessage(
+        "features",
+        Object.values(browser.geckoProfiler.ProfilerFeature)
+      );
+    },
+    manifest: {
+      permissions: ["geckoProfiler"],
+      browser_specific_settings: {
+        gecko: {
+          id: "profilertest@mozilla.com",
+        },
+      },
+    },
+  });
+
+  await extension.startup();
+  let acceptedFeatures = await extension.awaitMessage("features");
+  await extension.unload();
+
+  Services.prefs.clearUserPref(acceptedExtensionIdsPref);
+
+  const allFeaturesAcceptedByProfiler = Services.profiler.GetAllFeatures();
+  ok(
+    allFeaturesAcceptedByProfiler.length >= 2,
+    "Either we've massively reduced the profiler's feature set, or something is wrong."
+  );
+
+  // Check that the list of available values in the ProfilerFeature enum
+  // matches the list of features supported by the profiler.
+  for (const feature of allFeaturesAcceptedByProfiler) {
+    // If this fails, check the lists in {,Base}ProfilerState.h and geckoProfiler.json.
+    ok(
+      acceptedFeatures.includes(feature),
+      `The schema of the geckoProfiler.start() method should accept the "${feature}" feature.`
+    );
+  }
+  for (const feature of acceptedFeatures) {
+    // If this fails, check the lists in {,Base}ProfilerState.h and geckoProfiler.json.
+    ok(
+      // Bug 1594566 - ignore Responsiveness until the extension is updated
+      allFeaturesAcceptedByProfiler.includes(feature) ||
+        feature == "responsiveness",
+      `The schema of the geckoProfiler.start() method mentions a "${feature}" feature which is not supported by the profiler.`
+    );
+  }
+});
diff --git a/toolkit/components/extensions/test/xpcshell/test_ext_geturl.js b/toolkit/components/extensions/test/xpcshell/test_ext_geturl.js
new file mode 100644
index 0000000000..b9048787d5
--- /dev/null
+++ b/toolkit/components/extensions/test/xpcshell/test_ext_geturl.js
@@ -0,0 +1,64 @@
+"use strict";
+
+const server = createHttpServer({ hosts: ["example.com"] });
+server.registerDirectory("/data/", do_get_file("data"));
+
+add_task(async function test_contentscript() {
+  let extension = ExtensionTestUtils.loadExtension({
+    background() {
+      browser.runtime.onMessage.addListener(([url1, url2]) => {
+        let url3 = browser.runtime.getURL("test_file.html");
+        let url4 = browser.extension.getURL("test_file.html");
+
+        browser.test.assertTrue(url1 !== undefined, "url1 defined");
+
+        browser.test.assertTrue(
+          url1.startsWith("moz-extension://"),
+          "url1 has correct scheme"
+        );
+        browser.test.assertTrue(
+          url1.endsWith("test_file.html"),
+          "url1 has correct leaf name"
+        );
+
+        browser.test.assertEq(url1, url2, "url2 matches");
+        browser.test.assertEq(url1, url3, "url3 matches");
+        browser.test.assertEq(url1, url4, "url4 matches");
+
+        browser.test.notifyPass("geturl");
+      });
+    },
+
+    manifest: {
+      content_scripts: [
+        {
+          matches: ["http://example.com/data/file_sample.html"],
+          js: ["content_script.js"],
+          run_at: "document_idle",
+        },
+      ],
+    },
+
+    files: {
+      "content_script.js"() {
+        let url1 = browser.runtime.getURL("test_file.html");
+        let url2 = browser.extension.getURL("test_file.html");
+        browser.runtime.sendMessage([url1, url2]);
+      },
+    },
+  });
+  // Turn off warning as errors to pass for deprecated APIs
+  ExtensionTestUtils.failOnSchemaWarnings(false);
+  await extension.startup();
+
+  let contentPage = await ExtensionTestUtils.loadContentPage(
+    "http://example.com/data/file_sample.html"
+  );
+
+  await extension.awaitFinish("geturl");
+
+  await contentPage.close();
+
+  await extension.unload();
+  ExtensionTestUtils.failOnSchemaWarnings(true);
+});
diff --git a/toolkit/components/extensions/test/xpcshell/test_ext_i18n.js b/toolkit/components/extensions/test/xpcshell/test_ext_i18n.js
new file mode 100644
index 0000000000..048e675a3e
--- /dev/null
+++ b/toolkit/components/extensions/test/xpcshell/test_ext_i18n.js
@@ -0,0 +1,571 @@
+"use strict";
+
+const { Preferences } = ChromeUtils.importESModule(
+  "resource://gre/modules/Preferences.sys.mjs"
+);
+
+// ExtensionContent.jsm needs to know when it's running from xpcshell,
+// to use the right timeout for content scripts executed at document_idle.
+ExtensionTestUtils.mockAppInfo();
+
+const server = createHttpServer();
+server.registerDirectory("/data/", do_get_file("data"));
+
+const BASE_URL = `http://localhost:${server.identity.primaryPort}/data`;
+
+var originalReqLocales = Services.locale.requestedLocales;
+
+registerCleanupFunction(() => {
+  Preferences.reset("intl.accept_languages");
+  Services.locale.requestedLocales = originalReqLocales;
+});
+
+add_task(async function test_i18n() {
+  function runTests(assertEq) {
+    let _ = browser.i18n.getMessage.bind(browser.i18n);
+
+    let url = browser.runtime.getURL("/");
+    assertEq(
+      url,
+      `moz-extension://${_("@@extension_id")}/`,
+      "@@extension_id builtin message"
+    );
+
+    assertEq("Foo.", _("Foo"), "Simple message in selected locale.");
+
+    assertEq("(bar)", _("bar"), "Simple message fallback in default locale.");
+
+    assertEq("", _("some-unknown-locale-string"), "Unknown locale string.");
+
+    assertEq("", _("@@unknown_builtin_string"), "Unknown built-in string.");
+    assertEq(
+      "",
+      _("@@bidi_unknown_builtin_string"),
+      "Unknown built-in bidi string."
+    );
+
+    assertEq("Føo.", _("Föo"), "Multi-byte message in selected locale.");
+
+    let substitutions = [];
+    substitutions[4] = "5";
+    substitutions[13] = "14";
+
+    assertEq(
+      "'$0' '14' '' '5' '$$$$' '$'.",
+      _("basic_substitutions", substitutions),
+      "Basic numeric substitutions"
+    );
+
+    assertEq(
+      "'$0' '' 'just a string' '' '$$$$' '$'.",
+      _("basic_substitutions", "just a string"),
+      "Basic numeric substitutions, with non-array value"
+    );
+
+    let values = _("named_placeholder_substitutions", [
+      "(subst $1 $2)",
+      "(2 $1 $2)",
+    ]).split("\n");
+
+    assertEq(
+      "_foo_ (subst $1 $2) _bar_",
+      values[0],
+      "Named and numeric substitution"
+    );
+
+    assertEq(
+      "(2 $1 $2)",
+      values[1],
+      "Numeric substitution amid named placeholders"
+    );
+
+    assertEq("$bad name$", values[2], "Named placeholder with invalid key");
+
+    assertEq("", values[3], "Named placeholder with an invalid value");
+
+    assertEq(
+      "Accepted, but shouldn't break.",
+      values[4],
+      "Named placeholder with a strange content value"
+    );
+
+    assertEq("$foo", values[5], "Non-placeholder token that should be ignored");
+  }
+
+  let extension = ExtensionTestUtils.loadExtension({
+    manifest: {
+      default_locale: "jp",
+
+      content_scripts: [
+        { matches: ["http://*/*/file_sample.html"], js: ["content.js"] },
+      ],
+    },
+
+    files: {
+      "_locales/en_US/messages.json": {
+        foo: {
+          message: "Foo.",
+          description: "foo",
+        },
+
+        föo: {
+          message: "Føo.",
+          description: "foo",
+        },
+
+        basic_substitutions: {
+          message: "'$0' '$14' '$1' '$5' '$$$$$' '$$'.",
+          description: "foo",
+        },
+
+        Named_placeholder_substitutions: {
+          message:
+            "$Foo$\n$2\n$bad name$\n$bad_value$\n$bad_content_value$\n$foo",
+          description: "foo",
+          placeholders: {
+            foO: {
+              content: "_foo_ $1 _bar_",
+              description: "foo",
+            },
+
+            "bad name": {
+              content: "Nope.",
+              description: "bad name",
+            },
+
+            bad_value: "Nope.",
+
+            bad_content_value: {
+              content: ["Accepted, but shouldn't break."],
+              description: "bad value",
+            },
+          },
+        },
+
+        broken_placeholders: {
+          message: "$broken$",
+          description: "broken placeholders",
+          placeholders: "foo.",
+        },
+      },
+
+      "_locales/jp/messages.json": {
+        foo: {
+          message: "(foo)",
+          description: "foo",
+        },
+
+        bar: {
+          message: "(bar)",
+          description: "bar",
+        },
+      },
+
+      "content.js":
+        "new " +
+        function (runTestsFn) {
+          runTestsFn((...args) => {
+            browser.runtime.sendMessage(["assertEq", ...args]);
+          });
+
+          browser.runtime.sendMessage(["content-script-finished"]);
+        } +
+        `(${runTests})`,
+    },
+
+    background:
+      "new " +
+      function (runTestsFn) {
+        browser.runtime.onMessage.addListener(([msg, ...args]) => {
+          if (msg == "assertEq") {
+            browser.test.assertEq(...args);
+          } else {
+            browser.test.sendMessage(msg, ...args);
+          }
+        });
+
+        runTestsFn(browser.test.assertEq.bind(browser.test));
+      } +
+      `(${runTests})`,
+  });
+
+  await extension.startup();
+
+  let contentPage = await ExtensionTestUtils.loadContentPage(
+    `${BASE_URL}/file_sample.html`
+  );
+  await extension.awaitMessage("content-script-finished");
+  await contentPage.close();
+
+  await extension.unload();
+});
+
+add_task(async function test_i18n_negotiation() {
+  function runTests(expected) {
+    let _ = browser.i18n.getMessage.bind(browser.i18n);
+
+    browser.test.assertEq(expected, _("foo"), "Got expected message");
+  }
+
+  let extensionData = {
+    manifest: {
+      default_locale: "en_US",
+
+      content_scripts: [
+        { matches: ["http://*/*/file_sample.html"], js: ["content.js"] },
+      ],
+    },
+
+    files: {
+      "_locales/en_US/messages.json": {
+        foo: {
+          message: "English.",
+          description: "foo",
+        },
+      },
+
+      "_locales/jp/messages.json": {
+        foo: {
+          message: "\u65e5\u672c\u8a9e",
+          description: "foo",
+        },
+      },
+
+      "content.js":
+        "new " +
+        function (runTestsFn) {
+          browser.test.onMessage.addListener(expected => {
+            runTestsFn(expected);
+
+            browser.test.sendMessage("content-script-finished");
+          });
+          browser.test.sendMessage("content-ready");
+        } +
+        `(${runTests})`,
+    },
+
+    background:
+      "new " +
+      function (runTestsFn) {
+        browser.test.onMessage.addListener(expected => {
+          runTestsFn(expected);
+
+          browser.test.sendMessage("background-script-finished");
+        });
+      } +
+      `(${runTests})`,
+  };
+
+  // At the moment extension language negotiation is tied to Firefox language
+  // negotiation result. That means that to test an extension in `fr`, we need
+  // to mock `fr` being available in Firefox and then request it.
+  //
+  // In the future, we should provide some way for tests to decouple their
+  // language selection from that of Firefox.
+  Services.locale.availableLocales = ["en-US", "fr", "jp"];
+
+  let contentPage = await ExtensionTestUtils.loadContentPage(
+    `${BASE_URL}/file_sample.html`
+  );
+
+  for (let [lang, msg] of [
+    ["en-US", "English."],
+    ["jp", "\u65e5\u672c\u8a9e"],
+  ]) {
+    Services.locale.requestedLocales = [lang];
+
+    let extension = ExtensionTestUtils.loadExtension(extensionData);
+    await extension.startup();
+    await extension.awaitMessage("content-ready");
+
+    extension.sendMessage(msg);
+    await extension.awaitMessage("background-script-finished");
+    await extension.awaitMessage("content-script-finished");
+
+    await extension.unload();
+  }
+  Services.locale.requestedLocales = originalReqLocales;
+
+  await contentPage.close();
+});
+
+add_task(async function test_get_accept_languages() {
+  function checkResults(source, results, expected) {
+    browser.test.assertEq(
+      expected.length,
+      results.length,
+      `got expected number of languages in ${source}`
+    );
+    results.forEach((lang, index) => {
+      browser.test.assertEq(
+        expected[index],
+        lang,
+        `got expected language in ${source}`
+      );
+    });
+  }
+
+  function background(checkResultsFn) {
+    browser.test.onMessage.addListener(([msg, expected]) => {
+      browser.i18n.getAcceptLanguages().then(results => {
+        checkResultsFn("background", results, expected);
+
+        browser.test.sendMessage("background-done");
+      });
+    });
+  }
+
+  function content(checkResultsFn) {
+    browser.test.onMessage.addListener(([msg, expected]) => {
+      browser.i18n.getAcceptLanguages().then(results => {
+        checkResultsFn("contentScript", results, expected);
+
+        browser.test.sendMessage("content-done");
+      });
+    });
+    browser.test.sendMessage("content-loaded");
+  }
+
+  let extension = ExtensionTestUtils.loadExtension({
+    manifest: {
+      content_scripts: [
+        {
+          matches: ["http://*/*/file_sample.html"],
+          run_at: "document_start",
+          js: ["content_script.js"],
+        },
+      ],
+    },
+
+    background: `(${background})(${checkResults})`,
+
+    files: {
+      "content_script.js": `(${content})(${checkResults})`,
+    },
+  });
+
+  let contentPage = await ExtensionTestUtils.loadContentPage(
+    `${BASE_URL}/file_sample.html`
+  );
+
+  await extension.startup();
+  await extension.awaitMessage("content-loaded");
+
+  // TODO bug 1765375: ", en" is missing on Android.
+  let expectedLangs =
+    AppConstants.platform == "android" ? ["en-US"] : ["en-US", "en"];
+  extension.sendMessage(["expect-results", expectedLangs]);
+  await extension.awaitMessage("background-done");
+  await extension.awaitMessage("content-done");
+
+  expectedLangs = ["en-US", "en", "fr-CA", "fr"];
+  Preferences.set("intl.accept_languages", expectedLangs.toString());
+  extension.sendMessage(["expect-results", expectedLangs]);
+  await extension.awaitMessage("background-done");
+  await extension.awaitMessage("content-done");
+  Preferences.reset("intl.accept_languages");
+
+  await contentPage.close();
+
+  await extension.unload();
+});
+
+add_task(async function test_get_ui_language() {
+  function getResults() {
+    return {
+      getUILanguage: browser.i18n.getUILanguage(),
+      getMessage: browser.i18n.getMessage("@@ui_locale"),
+    };
+  }
+
+  function checkResults(source, results, expected) {
+    browser.test.assertEq(
+      expected,
+      results.getUILanguage,
+      `Got expected getUILanguage result in ${source}`
+    );
+    browser.test.assertEq(
+      expected,
+      results.getMessage,
+      `Got expected getMessage result in ${source}`
+    );
+  }
+
+  function background(getResultsFn, checkResultsFn) {
+    browser.test.onMessage.addListener(([msg, expected]) => {
+      checkResultsFn("background", getResultsFn(), expected);
+
+      browser.test.sendMessage("background-done");
+    });
+  }
+
+  function content(getResultsFn, checkResultsFn) {
+    browser.test.onMessage.addListener(([msg, expected]) => {
+      checkResultsFn("contentScript", getResultsFn(), expected);
+
+      browser.test.sendMessage("content-done");
+    });
+    browser.test.sendMessage("content-loaded");
+  }
+
+  let extension = ExtensionTestUtils.loadExtension({
+    manifest: {
+      content_scripts: [
+        {
+          matches: ["http://*/*/file_sample.html"],
+          run_at: "document_start",
+          js: ["content_script.js"],
+        },
+      ],
+    },
+
+    background: `(${background})(${getResults}, ${checkResults})`,
+
+    files: {
+      "content_script.js": `(${content})(${getResults}, ${checkResults})`,
+    },
+  });
+
+  let contentPage = await ExtensionTestUtils.loadContentPage(
+    `${BASE_URL}/file_sample.html`
+  );
+
+  await extension.startup();
+  await extension.awaitMessage("content-loaded");
+
+  extension.sendMessage(["expect-results", "en-US"]);
+
+  await extension.awaitMessage("background-done");
+  await extension.awaitMessage("content-done");
+
+  // We don't currently have a good way to mock this.
+  if (false) {
+    Services.locale.requestedLocales = ["he"];
+
+    extension.sendMessage(["expect-results", "he"]);
+
+    await extension.awaitMessage("background-done");
+    await extension.awaitMessage("content-done");
+  }
+
+  await contentPage.close();
+
+  await extension.unload();
+});
+
+add_task(async function test_detect_language() {
+  const af_string =
+    " aam skukuza die naam beteken hy wat skoonvee of hy wat alles onderstebo keer wysig " +
+    "bosveldkampe boskampe is kleiner afgeleë ruskampe wat oor min fasiliteite beskik daar is geen restaurante " +
+    "of winkels nie en slegs oornagbesoekers word toegelaat bateleur";
+  // String with intermixed French/English text
+  const fr_en_string =
+    "France is the largest country in Western Europe and the third-largest in Europe as a whole. " +
+    "A accès aux chiens et aux frontaux qui lui ont été il peut consulter et modifier ses collections et exporter " +
+    "Cet article concerne le pays européen aujourd’hui appelé République française. Pour d’autres usages du nom France, " +
+    "Pour une aide rapide et effective, veuiller trouver votre aide dans le menu ci-dessus." +
+    "Motoring events began soon after the construction of the first successful gasoline-fueled automobiles. The quick brown fox jumped over the lazy dog";
+
+  function checkResult(source, result, expected) {
+    browser.test.assertEq(
+      expected.isReliable,
+      result.isReliable,
+      "result.confident is true"
+    );
+    browser.test.assertEq(
+      expected.languages.length,
+      result.languages.length,
+      `result.languages contains the expected number of languages in ${source}`
+    );
+    expected.languages.forEach((lang, index) => {
+      browser.test.assertEq(
+        lang.percentage,
+        result.languages[index].percentage,
+        `element ${index} of result.languages array has the expected percentage in ${source}`
+      );
+      browser.test.assertEq(
+        lang.language,
+        result.languages[index].language,
+        `element ${index} of result.languages array has the expected language in ${source}`
+      );
+    });
+  }
+
+  function backgroundScript(checkResultFn) {
+    browser.test.onMessage.addListener(([msg, expected]) => {
+      browser.i18n.detectLanguage(msg).then(result => {
+        checkResultFn("background", result, expected);
+        browser.test.sendMessage("background-done");
+      });
+    });
+  }
+
+  function content(checkResultFn) {
+    browser.test.onMessage.addListener(([msg, expected]) => {
+      browser.i18n.detectLanguage(msg).then(result => {
+        checkResultFn("contentScript", result, expected);
+        browser.test.sendMessage("content-done");
+      });
+    });
+    browser.test.sendMessage("content-loaded");
+  }
+
+  let extension = ExtensionTestUtils.loadExtension({
+    manifest: {
+      content_scripts: [
+        {
+          matches: ["http://*/*/file_sample.html"],
+          run_at: "document_start",
+          js: ["content_script.js"],
+        },
+      ],
+    },
+
+    background: `(${backgroundScript})(${checkResult})`,
+
+    files: {
+      "content_script.js": `(${content})(${checkResult})`,
+    },
+  });
+
+  let contentPage = await ExtensionTestUtils.loadContentPage(
+    `${BASE_URL}/file_sample.html`
+  );
+
+  await extension.startup();
+  await extension.awaitMessage("content-loaded");
+
+  let expected = {
+    isReliable: true,
+    languages: [
+      {
+        language: "fr",
+        percentage: 67,
+      },
+      {
+        language: "en",
+        percentage: 32,
+      },
+    ],
+  };
+  extension.sendMessage([fr_en_string, expected]);
+  await extension.awaitMessage("background-done");
+  await extension.awaitMessage("content-done");
+
+  expected = {
+    isReliable: true,
+    languages: [
+      {
+        language: "af",
+        percentage: 99,
+      },
+    ],
+  };
+  extension.sendMessage([af_string, expected]);
+  await extension.awaitMessage("background-done");
+  await extension.awaitMessage("content-done");
+
+  await contentPage.close();
+
+  await extension.unload();
+});
diff --git a/toolkit/components/extensions/test/xpcshell/test_ext_i18n_css.js b/toolkit/components/extensions/test/xpcshell/test_ext_i18n_css.js
new file mode 100644
index 0000000000..e02ae09e11
--- /dev/null
+++ b/toolkit/components/extensions/test/xpcshell/test_ext_i18n_css.js
@@ -0,0 +1,194 @@
+"use strict";
+
+const { Preferences } = ChromeUtils.importESModule(
+  "resource://gre/modules/Preferences.sys.mjs"
+);
+
+const server = createHttpServer();
+server.registerDirectory("/data/", do_get_file("data"));
+
+const BASE_URL = `http://localhost:${server.identity.primaryPort}/data`;
+
+const { createAppInfo, promiseShutdownManager, promiseStartupManager } =
+  AddonTestUtils;
+
+AddonTestUtils.init(this);
+
+createAppInfo("xpcshell@tests.mozilla.org", "XPCShell", "1", "42");
+
+// Some multibyte characters. This sample was taken from the encoding/api-basics.html web platform test.
+const MULTIBYTE_STRING = "z\xA2\u6C34\uD834\uDD1E\uF8FF\uDBFF\uDFFD\uFFFE";
+let getCSS = (a, b) => `a { content: '${a}'; } b { content: '${b}'; }`;
+
+let extensionData = {
+  background: function () {
+    function backgroundFetch(url) {
+      return new Promise((resolve, reject) => {
+        let xhr = new XMLHttpRequest();
+        xhr.overrideMimeType("text/plain");
+        xhr.open("GET", url);
+        xhr.onload = () => {
+          resolve(xhr.responseText);
+        };
+        xhr.onerror = reject;
+        xhr.send();
+      });
+    }
+
+    Promise.all([
+      backgroundFetch("foo.css"),
+      backgroundFetch("bar.CsS?x#y"),
+      backgroundFetch("foo.txt"),
+    ]).then(results => {
+      browser.test.assertEq(
+        "body { max-width: 42px; }",
+        results[0],
+        "CSS file localized"
+      );
+      browser.test.assertEq(
+        "body { max-width: 42px; }",
+        results[1],
+        "CSS file localized"
+      );
+
+      browser.test.assertEq(
+        "body { __MSG_foo__; }",
+        results[2],
+        "Text file not localized"
+      );
+
+      browser.test.notifyPass("i18n-css");
+    });
+
+    browser.test.sendMessage("ready", browser.runtime.getURL("/"));
+  },
+
+  manifest: {
+    browser_specific_settings: {
+      gecko: {
+        id: "i18n_css@mochi.test",
+      },
+    },
+
+    web_accessible_resources: [
+      "foo.css",
+      "foo.txt",
+      "locale.css",
+      "multibyte.css",
+    ],
+
+    content_scripts: [
+      {
+        matches: ["http://*/*/file_sample.html"],
+        css: ["foo.css"],
+        run_at: "document_start",
+      },
+      {
+        matches: ["http://*/*/file_sample.html"],
+        js: ["content.js"],
+      },
+    ],
+
+    default_locale: "en",
+  },
+
+  files: {
+    "_locales/en/messages.json": JSON.stringify({
+      foo: {
+        message: "max-width: 42px",
+        description: "foo",
+      },
+      multibyteKey: {
+        message: MULTIBYTE_STRING,
+      },
+    }),
+
+    "content.js": function () {
+      let style = getComputedStyle(document.body);
+      browser.test.sendMessage("content-maxWidth", style.maxWidth);
+    },
+
+    "foo.css": "body { __MSG_foo__; }",
+    "bar.CsS": "body { __MSG_foo__; }",
+    "foo.txt": "body { __MSG_foo__; }",
+    "locale.css":
+      '* { content: "__MSG_@@ui_locale__ __MSG_@@bidi_dir__ __MSG_@@bidi_reversed_dir__ __MSG_@@bidi_start_edge__ __MSG_@@bidi_end_edge__" }',
+    "multibyte.css": getCSS("__MSG_multibyteKey__", MULTIBYTE_STRING),
+  },
+};
+
+async function test_i18n_css(options = {}) {
+  extensionData.useAddonManager = options.useAddonManager;
+  let extension = ExtensionTestUtils.loadExtension(extensionData);
+
+  await extension.startup();
+  let baseURL = await extension.awaitMessage("ready");
+
+  let contentPage = await ExtensionTestUtils.loadContentPage(
+    `${BASE_URL}/file_sample.html`
+  );
+
+  let css = await contentPage.fetch(baseURL + "foo.css");
+
+  equal(
+    css,
+    "body { max-width: 42px; }",
+    "CSS file localized in mochitest scope"
+  );
+
+  let maxWidth = await extension.awaitMessage("content-maxWidth");
+
+  equal(maxWidth, "42px", "stylesheet correctly applied");
+
+  css = await contentPage.fetch(baseURL + "locale.css");
+  equal(
+    css,
+    '* { content: "en-US ltr rtl left right" }',
+    "CSS file localized in mochitest scope"
+  );
+
+  css = await contentPage.fetch(baseURL + "multibyte.css");
+  equal(
+    css,
+    getCSS(MULTIBYTE_STRING, MULTIBYTE_STRING),
+    "CSS file contains multibyte string"
+  );
+
+  await contentPage.close();
+
+  // We don't currently have a good way to mock this.
+  if (false) {
+    const DIR = "intl.l10n.pseudo";
+
+    // We don't wind up actually switching the chrome registry locale, since we
+    // don't have a chrome package for Hebrew. So just override it, and force
+    // RTL directionality.
+    const origReqLocales = Services.locale.requestedLocales;
+    Services.locale.requestedLocales = ["he"];
+    Preferences.set(DIR, "bidi");
+
+    css = await fetch(baseURL + "locale.css");
+    equal(
+      css,
+      '* { content: "he rtl ltr right left" }',
+      "CSS file localized in mochitest scope"
+    );
+
+    Services.locale.requestedLocales = origReqLocales;
+    Preferences.reset(DIR);
+  }
+
+  await extension.awaitFinish("i18n-css");
+  await extension.unload();
+}
+
+add_task(async function startup() {
+  await promiseStartupManager();
+});
+add_task(test_i18n_css);
+add_task(async function test_i18n_css_xpi() {
+  await test_i18n_css({ useAddonManager: "temporary" });
+});
+add_task(async function startup() {
+  await promiseShutdownManager();
+});
diff --git a/toolkit/components/extensions/test/xpcshell/test_ext_idle.js b/toolkit/components/extensions/test/xpcshell/test_ext_idle.js
new file mode 100644
index 0000000000..6398224f1a
--- /dev/null
+++ b/toolkit/components/extensions/test/xpcshell/test_ext_idle.js
@@ -0,0 +1,361 @@
+/* -*- Mode: indent-tabs-mode: nil; js-indent-level: 2 -*- */
+/* vim: set sts=2 sw=2 et tw=80: */
+"use strict";
+
+const { MockRegistrar } = ChromeUtils.importESModule(
+  "resource://testing-common/MockRegistrar.sys.mjs"
+);
+
+AddonTestUtils.init(this);
+AddonTestUtils.overrideCertDB();
+AddonTestUtils.createAppInfo(
+  "xpcshell@tests.mozilla.org",
+  "XPCShell",
+  "42",
+  "42"
+);
+
+let idleService = {
+  _observers: new Set(),
+  _activity: {
+    addCalls: [],
+    removeCalls: [],
+    observerFires: [],
+  },
+  _reset: function () {
+    this._observers.clear();
+    this._activity.addCalls = [];
+    this._activity.removeCalls = [];
+    this._activity.observerFires = [];
+  },
+  _fireObservers: function (state) {
+    for (let observer of this._observers.values()) {
+      observer.observe(observer, state, null);
+      this._activity.observerFires.push(state);
+    }
+  },
+  QueryInterface: ChromeUtils.generateQI(["nsIUserIdleService"]),
+  idleTime: 19999,
+  addIdleObserver: function (observer, time) {
+    this._observers.add(observer);
+    this._activity.addCalls.push(time);
+  },
+  removeIdleObserver: function (observer, time) {
+    this._observers.delete(observer);
+    this._activity.removeCalls.push(time);
+  },
+};
+
+function checkActivity(expectedActivity) {
+  let { expectedAdd, expectedRemove, expectedFires } = expectedActivity;
+  let { addCalls, removeCalls, observerFires } = idleService._activity;
+  equal(
+    expectedAdd.length,
+    addCalls.length,
+    "idleService.addIdleObserver was called the expected number of times"
+  );
+  equal(
+    expectedRemove.length,
+    removeCalls.length,
+    "idleService.removeIdleObserver was called the expected number of times"
+  );
+  equal(
+    expectedFires.length,
+    observerFires.length,
+    "idle observer was fired the expected number of times"
+  );
+  deepEqual(
+    addCalls,
+    expectedAdd,
+    "expected interval passed to idleService.addIdleObserver"
+  );
+  deepEqual(
+    removeCalls,
+    expectedRemove,
+    "expected interval passed to idleService.removeIdleObserver"
+  );
+  deepEqual(
+    observerFires,
+    expectedFires,
+    "expected topic passed to idle observer"
+  );
+}
+
+add_task(async function setup() {
+  let fakeIdleService = MockRegistrar.register(
+    "@mozilla.org/widget/useridleservice;1",
+    idleService
+  );
+  registerCleanupFunction(() => {
+    MockRegistrar.unregister(fakeIdleService);
+  });
+});
+
+add_task(async function testQueryStateActive() {
+  function background() {
+    browser.idle.queryState(20).then(
+      status => {
+        browser.test.assertEq("active", status, "Idle status is active");
+        browser.test.notifyPass("idle");
+      },
+      err => {
+        browser.test.fail(`Error: ${err} :: ${err.stack}`);
+        browser.test.notifyFail("idle");
+      }
+    );
+  }
+
+  let extension = ExtensionTestUtils.loadExtension({
+    background,
+    manifest: {
+      permissions: ["idle"],
+    },
+  });
+
+  await extension.startup();
+  await extension.awaitFinish("idle");
+  await extension.unload();
+});
+
+add_task(async function testQueryStateIdle() {
+  function background() {
+    browser.idle.queryState(15).then(
+      status => {
+        browser.test.assertEq("idle", status, "Idle status is idle");
+        browser.test.notifyPass("idle");
+      },
+      err => {
+        browser.test.fail(`Error: ${err} :: ${err.stack}`);
+        browser.test.notifyFail("idle");
+      }
+    );
+  }
+
+  let extension = ExtensionTestUtils.loadExtension({
+    background,
+    manifest: {
+      permissions: ["idle"],
+    },
+  });
+
+  await extension.startup();
+  await extension.awaitFinish("idle");
+  await extension.unload();
+});
+
+add_task(async function testOnlySetDetectionInterval() {
+  function background() {
+    browser.idle.setDetectionInterval(99);
+    browser.test.sendMessage("detectionIntervalSet");
+  }
+
+  let extension = ExtensionTestUtils.loadExtension({
+    background,
+    manifest: {
+      permissions: ["idle"],
+    },
+  });
+
+  idleService._reset();
+  await extension.startup();
+  await extension.awaitMessage("detectionIntervalSet");
+  idleService._fireObservers("idle");
+  checkActivity({ expectedAdd: [], expectedRemove: [], expectedFires: [] });
+  await extension.unload();
+});
+
+add_task(async function testSetDetectionIntervalBeforeAddingListener() {
+  function background() {
+    browser.idle.setDetectionInterval(99);
+    browser.idle.onStateChanged.addListener(newState => {
+      browser.test.assertEq(
+        "idle",
+        newState,
+        "listener fired with the expected state"
+      );
+      browser.test.sendMessage("listenerFired");
+    });
+    browser.test.sendMessage("listenerAdded");
+  }
+
+  let extension = ExtensionTestUtils.loadExtension({
+    background,
+    manifest: {
+      permissions: ["idle"],
+    },
+  });
+
+  idleService._reset();
+  await extension.startup();
+  await extension.awaitMessage("listenerAdded");
+  idleService._fireObservers("idle");
+  await extension.awaitMessage("listenerFired");
+  checkActivity({
+    expectedAdd: [99],
+    expectedRemove: [],
+    expectedFires: ["idle"],
+  });
+  // Defer unloading the extension so the asynchronous event listener
+  // reply finishes.
+  await new Promise(resolve => setTimeout(resolve, 0));
+  await extension.unload();
+});
+
+add_task(async function testSetDetectionIntervalAfterAddingListener() {
+  function background() {
+    browser.idle.onStateChanged.addListener(newState => {
+      browser.test.assertEq(
+        "idle",
+        newState,
+        "listener fired with the expected state"
+      );
+      browser.test.sendMessage("listenerFired");
+    });
+    browser.idle.setDetectionInterval(99);
+    browser.test.sendMessage("detectionIntervalSet");
+  }
+
+  let extension = ExtensionTestUtils.loadExtension({
+    background,
+    manifest: {
+      permissions: ["idle"],
+    },
+  });
+
+  idleService._reset();
+  await extension.startup();
+  await extension.awaitMessage("detectionIntervalSet");
+  idleService._fireObservers("idle");
+  await extension.awaitMessage("listenerFired");
+  checkActivity({
+    expectedAdd: [60, 99],
+    expectedRemove: [60],
+    expectedFires: ["idle"],
+  });
+
+  // Defer unloading the extension so the asynchronous event listener
+  // reply finishes.
+  await new Promise(resolve => setTimeout(resolve, 0));
+  await extension.unload();
+});
+
+add_task(async function testOnlyAddingListener() {
+  function background() {
+    browser.idle.onStateChanged.addListener(newState => {
+      browser.test.assertEq(
+        "active",
+        newState,
+        "listener fired with the expected state"
+      );
+      browser.test.sendMessage("listenerFired");
+    });
+    browser.test.sendMessage("listenerAdded");
+  }
+
+  let extension = ExtensionTestUtils.loadExtension({
+    background,
+    manifest: {
+      permissions: ["idle"],
+    },
+  });
+
+  idleService._reset();
+  await extension.startup();
+  await extension.awaitMessage("listenerAdded");
+  idleService._fireObservers("active");
+  await extension.awaitMessage("listenerFired");
+  // check that "idle-daily" topic does not cause a listener to fire
+  idleService._fireObservers("idle-daily");
+  checkActivity({
+    expectedAdd: [60],
+    expectedRemove: [],
+    expectedFires: ["active", "idle-daily"],
+  });
+
+  // Defer unloading the extension so the asynchronous event listener
+  // reply finishes.
+  await new Promise(resolve => setTimeout(resolve, 0));
+  await extension.unload();
+});
+
+add_task(
+  { pref_set: [["extensions.eventPages.enabled", true]] },
+  async function test_idle_event_page() {
+    await AddonTestUtils.promiseStartupManager();
+
+    let extension = ExtensionTestUtils.loadExtension({
+      useAddonManager: "permanent",
+      manifest: {
+        permissions: ["idle"],
+        background: { persistent: false },
+      },
+      background() {
+        browser.idle.setDetectionInterval(99);
+        browser.idle.onStateChanged.addListener(newState => {
+          browser.test.assertEq(
+            "active",
+            newState,
+            "listener fired with the expected state"
+          );
+          browser.test.sendMessage("listenerFired");
+        });
+      },
+    });
+
+    idleService._reset();
+    await extension.startup();
+    assertPersistentListeners(extension, "idle", "onStateChanged", {
+      primed: false,
+    });
+    checkActivity({
+      expectedAdd: [99],
+      expectedRemove: [],
+      expectedFires: [],
+    });
+
+    idleService._reset();
+    await extension.terminateBackground();
+    assertPersistentListeners(extension, "idle", "onStateChanged", {
+      primed: true,
+    });
+    checkActivity({
+      expectedAdd: [99],
+      expectedRemove: [99],
+      expectedFires: [],
+    });
+
+    // Fire an idle notification to wake up the background.
+    idleService._fireObservers("active");
+    await extension.awaitMessage("listenerFired");
+    checkActivity({
+      expectedAdd: [99],
+      expectedRemove: [99],
+      expectedFires: ["active"],
+    });
+
+    // Verify the set idle time is used with the persisted listener.
+    idleService._reset();
+    await AddonTestUtils.promiseRestartManager();
+    await extension.awaitStartup();
+
+    assertPersistentListeners(extension, "idle", "onStateChanged", {
+      primed: true,
+    });
+    checkActivity({
+      expectedAdd: [99], // 99 should have been persisted
+      expectedRemove: [99], // remove is from AOM shutdown
+      expectedFires: [],
+    });
+
+    // Fire an idle notification to wake up the background.
+    idleService._fireObservers("active");
+    await extension.awaitMessage("listenerFired");
+    checkActivity({
+      expectedAdd: [99],
+      expectedRemove: [99],
+      expectedFires: ["active"],
+    });
+
+    await extension.unload();
+  }
+);
diff --git a/toolkit/components/extensions/test/xpcshell/test_ext_incognito.js b/toolkit/components/extensions/test/xpcshell/test_ext_incognito.js
new file mode 100644
index 0000000000..b4b00e7db4
--- /dev/null
+++ b/toolkit/components/extensions/test/xpcshell/test_ext_incognito.js
@@ -0,0 +1,127 @@
+/* -*- Mode: indent-tabs-mode: nil; js-indent-level: 2 -*- */
+/* vim: set sts=2 sw=2 et tw=80: */
+"use strict";
+
+AddonTestUtils.init(this);
+AddonTestUtils.overrideCertDB();
+AddonTestUtils.createAppInfo(
+  "xpcshell@tests.mozilla.org",
+  "XPCShell",
+  "1",
+  "42"
+);
+AddonTestUtils.usePrivilegedSignatures = id => id.startsWith("privileged");
+
+add_task(async function setup() {
+  await AddonTestUtils.promiseStartupManager();
+});
+
+async function runIncognitoTest(extensionData, privateBrowsingAllowed) {
+  let wrapper = ExtensionTestUtils.loadExtension(extensionData);
+  await wrapper.startup();
+  let { extension } = wrapper;
+
+  equal(
+    extension.permissions.has("internal:privateBrowsingAllowed"),
+    privateBrowsingAllowed,
+    "privateBrowsingAllowed in serialized extension"
+  );
+  equal(
+    extension.privateBrowsingAllowed,
+    privateBrowsingAllowed,
+    "privateBrowsingAllowed in extension"
+  );
+  equal(
+    extension.policy.privateBrowsingAllowed,
+    privateBrowsingAllowed,
+    "privateBrowsingAllowed on policy"
+  );
+
+  await wrapper.unload();
+}
+
+add_task(async function test_extension_incognito_spanning() {
+  await runIncognitoTest({}, false);
+});
+
+// Test that when we are restricted, we can override the restriction for tests.
+add_task(async function test_extension_incognito_override_spanning() {
+  let extensionData = {
+    incognitoOverride: "spanning",
+  };
+  await runIncognitoTest(extensionData, true);
+});
+
+// This tests that a privileged extension will always have private browsing.
+add_task(async function test_extension_incognito_privileged() {
+  let extensionData = {
+    isPrivileged: true,
+  };
+  await runIncognitoTest(extensionData, true);
+});
+
+add_task(async function test_extension_privileged_not_allowed() {
+  let addonId = "privileged_not_allowed@mochi.test";
+  let extensionData = {
+    manifest: {
+      version: "1.0",
+      browser_specific_settings: { gecko: { id: addonId } },
+      incognito: "not_allowed",
+    },
+    useAddonManager: "permanent",
+    isPrivileged: true,
+  };
+  let wrapper = ExtensionTestUtils.loadExtension(extensionData);
+  await wrapper.startup();
+  let policy = WebExtensionPolicy.getByID(addonId);
+  equal(
+    policy.extension.isPrivileged,
+    true,
+    "The test extension is privileged"
+  );
+  equal(
+    policy.privateBrowsingAllowed,
+    false,
+    "privateBrowsingAllowed is false"
+  );
+
+  await wrapper.unload();
+});
+
+// Test that we remove pb permission if an extension is updated to not_allowed.
+add_task(async function test_extension_upgrade_not_allowed() {
+  let addonId = "upgrade@mochi.test";
+  let extensionData = {
+    manifest: {
+      version: "1.0",
+      browser_specific_settings: { gecko: { id: addonId } },
+      incognito: "spanning",
+    },
+    useAddonManager: "permanent",
+    incognitoOverride: "spanning",
+  };
+  let wrapper = ExtensionTestUtils.loadExtension(extensionData);
+  await wrapper.startup();
+
+  let policy = WebExtensionPolicy.getByID(addonId);
+
+  equal(
+    policy.privateBrowsingAllowed,
+    true,
+    "privateBrowsingAllowed in extension"
+  );
+
+  extensionData.manifest.version = "2.0";
+  extensionData.manifest.incognito = "not_allowed";
+  await wrapper.upgrade(extensionData);
+
+  equal(wrapper.version, "2.0", "Expected extension version");
+  policy = WebExtensionPolicy.getByID(addonId);
+  equal(
+    policy.privateBrowsingAllowed,
+    false,
+    "privateBrowsingAllowed is false"
+  );
+
+  await wrapper.unload();
+});
diff --git a/toolkit/components/extensions/test/xpcshell/test_ext_indexedDB_principal.js b/toolkit/components/extensions/test/xpcshell/test_ext_indexedDB_principal.js
new file mode 100644
index 0000000000..f355b1d43a
--- /dev/null
+++ b/toolkit/components/extensions/test/xpcshell/test_ext_indexedDB_principal.js
@@ -0,0 +1,147 @@
+"use strict";
+
+AddonTestUtils.init(this);
+AddonTestUtils.createAppInfo(
+  "xpcshell@tests.mozilla.org",
+  "XPCShell",
+  "1",
+  "42"
+);
+
+add_task(async function test_indexedDB_principal() {
+  Services.prefs.setBoolPref("privacy.firstparty.isolate", true);
+
+  await AddonTestUtils.promiseStartupManager();
+
+  let extension = ExtensionTestUtils.loadExtension({
+    useAddonManager: "temporary",
+    manifest: {},
+    async background() {
+      browser.test.onMessage.addListener(async msg => {
+        if (msg == "create-storage") {
+          let request = window.indexedDB.open("TestDatabase");
+          request.onupgradeneeded = function (e) {
+            let db = e.target.result;
+            db.createObjectStore("TestStore");
+          };
+          request.onsuccess = function (e) {
+            let db = e.target.result;
+            let tx = db.transaction("TestStore", "readwrite");
+            let store = tx.objectStore("TestStore");
+            tx.oncomplete = () => browser.test.sendMessage("storage-created");
+            store.add("foo", "bar");
+            tx.onerror = function (e) {
+              browser.test.fail(`Failed with error ${tx.error.message}`);
+              // Don't wait for timeout
+              browser.test.sendMessage("storage-created");
+            };
+          };
+          request.onerror = function (e) {
+            browser.test.fail(`Failed with error ${request.error.message}`);
+            // Don't wait for timeout
+            browser.test.sendMessage("storage-created");
+          };
+          return;
+        }
+        if (msg == "check-storage") {
+          let dbRequest = window.indexedDB.open("TestDatabase");
+          dbRequest.onupgradeneeded = function () {
+            browser.test.fail("Database should exist");
+            browser.test.notifyFail("done");
+          };
+          dbRequest.onsuccess = function (e) {
+            let db = e.target.result;
+            let transaction = db.transaction("TestStore");
+            transaction.onerror = function (e) {
+              browser.test.fail(
+                `Failed with error ${transaction.error.message}`
+              );
+              browser.test.notifyFail("done");
+            };
+            let objectStore = transaction.objectStore("TestStore");
+            let request = objectStore.get("bar");
+            request.onsuccess = function (event) {
+              browser.test.assertEq(
+                request.result,
+                "foo",
+                "Got the expected data"
+              );
+              browser.test.notifyPass("done");
+            };
+            request.onerror = function (e) {
+              browser.test.fail(`Failed with error ${request.error.message}`);
+              browser.test.notifyFail("done");
+            };
+          };
+          dbRequest.onerror = function (e) {
+            browser.test.fail(`Failed with error ${dbRequest.error.message}`);
+            browser.test.notifyFail("done");
+          };
+        }
+      });
+    },
+  });
+
+  await extension.startup();
+  extension.sendMessage("create-storage");
+  await extension.awaitMessage("storage-created");
+
+  await extension.addon.disable();
+
+  Services.prefs.setBoolPref("privacy.firstparty.isolate", false);
+
+  await extension.addon.enable();
+  await extension.awaitStartup();
+
+  extension.sendMessage("check-storage");
+  await extension.awaitFinish("done");
+
+  await extension.unload();
+  Services.prefs.clearUserPref("privacy.firstparty.isolate");
+});
+
+add_task(async function test_indexedDB_ext_privateBrowsing() {
+  Services.prefs.setBoolPref("dom.indexedDB.privateBrowsing.enabled", true);
+
+  let extension = ExtensionTestUtils.loadExtension({
+    useAddonManager: "temporary",
+    incognitoOverride: "spanning",
+    files: {
+      "extpage.html": `<!DOCTYPE><script src="extpage.js"></script>`,
+      "extpage.js": async function () {
+        try {
+          const request = window.indexedDB.open("TestDatabasePrivateBrowsing");
+          await new Promise((resolve, reject) => {
+            request.onupgradeneeded = resolve;
+            request.onsuccess = resolve;
+            request.onerror = () => {
+              reject(request.error);
+            };
+          });
+          browser.test.notifyFail("indexedDB-expect-error-on-open");
+        } catch (err) {
+          browser.test.assertEq(
+            "InvalidStateError",
+            err.name,
+            "Expect an error raised on openeing indexedDB"
+          );
+          browser.test.notifyPass("indexedDB-expect-error-on-open");
+        }
+      },
+    },
+  });
+
+  await extension.startup();
+
+  const page = await ExtensionTestUtils.loadContentPage(
+    extension.extension.baseURI.resolve("extpage.html"),
+    { privateBrowsing: true }
+  );
+
+  await extension.awaitFinish("indexedDB-expect-error-on-open");
+
+  await page.close();
+  await extension.unload();
+
+  Services.prefs.clearUserPref("dom.indexedDB.privateBrowsing.enabled");
+});
diff --git a/toolkit/components/extensions/test/xpcshell/test_ext_ipcBlob.js b/toolkit/components/extensions/test/xpcshell/test_ext_ipcBlob.js
new file mode 100644
index 0000000000..dd90d9bbc8
--- /dev/null
+++ b/toolkit/components/extensions/test/xpcshell/test_ext_ipcBlob.js
@@ -0,0 +1,150 @@
+"use strict";
+
+const server = createHttpServer();
+server.registerDirectory("/data/", do_get_file("data"));
+
+const BASE_URL = `http://localhost:${server.identity.primaryPort}/data`;
+
+// ExtensionContent.jsm needs to know when it's running from xpcshell,
+// to use the right timeout for content scripts executed at document_idle.
+ExtensionTestUtils.mockAppInfo();
+
+add_task(async function test_parent_to_child() {
+  async function background() {
+    const dbName = "broken-blob";
+    const dbStore = "blob-store";
+    const dbVersion = 1;
+    const blobContent = "Hello World!";
+
+    let db = await new Promise((resolve, reject) => {
+      let dbOpen = indexedDB.open(dbName, dbVersion);
+      dbOpen.onerror = event => {
+        browser.test.fail(`Error opening the DB: ${event.target.error}`);
+        browser.test.notifyFail("test-completed");
+        reject();
+      };
+      dbOpen.onsuccess = event => {
+        resolve(event.target.result);
+      };
+      dbOpen.onupgradeneeded = event => {
+        let dbobj = event.target.result;
+        dbobj.onerror = error => {
+          browser.test.fail(`Error updating the DB: ${error.target.error}`);
+          browser.test.notifyFail("test-completed");
+          reject();
+        };
+        dbobj.createObjectStore(dbStore);
+      };
+    });
+
+    async function save(blob) {
+      let txn = db.transaction([dbStore], "readwrite");
+      let store = txn.objectStore(dbStore);
+      let req = store.put(blob, "key");
+
+      return new Promise((resolve, reject) => {
+        req.onsuccess = () => {
+          resolve();
+        };
+        req.onerror = event => {
+          browser.test.fail(
+            `Error saving the blob into the DB: ${event.target.error}`
+          );
+          browser.test.notifyFail("test-completed");
+          reject();
+        };
+      });
+    }
+
+    async function load() {
+      let txn = db.transaction([dbStore], "readonly");
+      let store = txn.objectStore(dbStore);
+      let req = store.getAll();
+
+      return new Promise((resolve, reject) => {
+        req.onsuccess = () => resolve(req.result);
+        req.onerror = () => reject(req.error);
+      })
+        .then(loadDetails => {
+          let blobs = [];
+          loadDetails.forEach(details => {
+            blobs.push(details);
+          });
+          return blobs[0];
+        })
+        .catch(err => {
+          browser.test.fail(
+            `Error loading the blob from the DB: ${err} :: ${err.stack}`
+          );
+          browser.test.notifyFail("test-completed");
+        });
+    }
+
+    browser.test.log("Blob creation");
+    await save(new Blob([blobContent]));
+    let blob = await load();
+
+    db.close();
+
+    browser.runtime.onMessage.addListener(([msg, what]) => {
+      browser.test.log("Message received from content: " + msg);
+      if (msg == "script-ready") {
+        return Promise.resolve({ blob });
+      }
+
+      if (msg == "script-value") {
+        browser.test.assertEq(blobContent, what, "blob content matches");
+        browser.test.notifyPass("test-completed");
+        return;
+      }
+
+      browser.test.fail(`Unexpected test message received: ${msg}`);
+    });
+
+    browser.test.sendMessage("bg-ready");
+  }
+
+  function contentScriptStart() {
+    browser.runtime.sendMessage(["script-ready"], response => {
+      let reader = new FileReader();
+      reader.addEventListener(
+        "load",
+        () => {
+          browser.runtime.sendMessage(["script-value", reader.result]);
+        },
+        { once: true }
+      );
+      reader.readAsText(response.blob);
+    });
+  }
+
+  let extensionData = {
+    background,
+    manifest: {
+      content_scripts: [
+        {
+          matches: ["http://*/*/file_sample.html"],
+          js: ["content_script_start.js"],
+          run_at: "document_start",
+        },
+      ],
+    },
+    files: {
+      "content_script_start.js": contentScriptStart,
+    },
+  };
+
+  let extension = ExtensionTestUtils.loadExtension(extensionData);
+  await extension.startup();
+
+  await extension.awaitMessage("bg-ready");
+
+  let contentPage = await ExtensionTestUtils.loadContentPage(
+    `${BASE_URL}/file_sample.html`
+  );
+
+  await extension.awaitFinish("test-completed");
+
+  await contentPage.close();
+  await extension.unload();
+});
diff --git a/toolkit/components/extensions/test/xpcshell/test_ext_json_parser.js b/toolkit/components/extensions/test/xpcshell/test_ext_json_parser.js
new file mode 100644
index 0000000000..aba25173d7
--- /dev/null
+++ b/toolkit/components/extensions/test/xpcshell/test_ext_json_parser.js
@@ -0,0 +1,108 @@
+/* -*- Mode: indent-tabs-mode: nil; js-indent-level: 2 -*- */
+/* vim: set sts=2 sw=2 et tw=80: */
+"use strict";
+
+add_task(async function test_json_parser() {
+  const ID = "json@test.web.extension";
+
+  let xpi = AddonTestUtils.createTempWebExtensionFile({
+    files: {
+      "manifest.json": String.raw`{
+        // This is a manifest.
+        "manifest_version": 2,
+        "browser_specific_settings": {"gecko": {"id": "${ID}"}},
+        "name": "This \" is // not a comment",
+        "version": "0.1\\" // , "description": "This is not a description"
+      }`,
+    },
+  });
+
+  let expectedManifest = {
+    manifest_version: 2,
+    browser_specific_settings: { gecko: { id: ID } },
+    name: 'This " is // not a comment',
+    version: "0.1\\",
+  };
+
+  let fileURI = Services.io.newFileURI(xpi);
+  let uri = NetUtil.newURI(`jar:${fileURI.spec}!/`);
+
+  let extension = new ExtensionData(uri, false);
+
+  await extension.parseManifest();
+
+  Assert.deepEqual(
+    extension.rawManifest,
+    expectedManifest,
+    "Manifest with correctly-filtered comments"
+  );
+
+  Services.obs.notifyObservers(xpi, "flush-cache-entry");
+});
+
+add_task(async function test_getExtensionVersionWithoutValidation() {
+  let xpi = AddonTestUtils.createTempWebExtensionFile({
+    files: {
+      "manifest.json": String.raw`{
+        // This is valid JSON but not a valid manifest.
+        "version": ["This is not a valid version"]
+      }`,
+    },
+  });
+  let fileURI = Services.io.newFileURI(xpi);
+  let uri = NetUtil.newURI(`jar:${fileURI.spec}!/`);
+  let extension = new ExtensionData(uri, false);
+
+  let rawVersion = await extension.getExtensionVersionWithoutValidation();
+  Assert.deepEqual(
+    rawVersion,
+    ["This is not a valid version"],
+    "Got the raw value of the 'version' key from an (invalid) manifest file"
+  );
+
+  // The manifest lacks several required properties and manifest_version is
+  // invalid. The exact error here doesn't matter, as long as it shows that the
+  // manifest is invalid.
+  await Assert.rejects(
+    extension.parseManifest(),
+    /Unexpected params.manifestVersion value: undefined/,
+    "parseManifest() should reject an invalid manifest"
+  );
+
+  Services.obs.notifyObservers(xpi, "flush-cache-entry");
+});
+
+add_task(
+  {
+    pref_set: [
+      ["extensions.manifestV3.enabled", true],
+      ["extensions.webextensions.warnings-as-errors", false],
+    ],
+  },
+  async function test_applications_no_longer_valid_in_mv3() {
+    let id = "some@id";
+    let xpi = AddonTestUtils.createTempWebExtensionFile({
+      files: {
+        "manifest.json": JSON.stringify({
+          manifest_version: 3,
+          name: "some name",
+          version: "0.1",
+          applications: { gecko: { id } },
+        }),
+      },
+    });
+
+    let fileURI = Services.io.newFileURI(xpi);
+    let uri = NetUtil.newURI(`jar:${fileURI.spec}!/`);
+
+    let extension = new ExtensionData(uri, false);
+
+    const { manifest } = await extension.parseManifest();
+    ok(
+      !Object.keys(manifest).includes("applications"),
+      "expected no applications key in manifest"
+    );
+
+    Services.obs.notifyObservers(xpi, "flush-cache-entry");
+  }
+);
diff --git a/toolkit/components/extensions/test/xpcshell/test_ext_l10n.js b/toolkit/components/extensions/test/xpcshell/test_ext_l10n.js
new file mode 100644
index 0000000000..96cc124348
--- /dev/null
+++ b/toolkit/components/extensions/test/xpcshell/test_ext_l10n.js
@@ -0,0 +1,165 @@
+"use strict";
+
+const { FileUtils } = ChromeUtils.importESModule(
+  "resource://gre/modules/FileUtils.sys.mjs"
+);
+
+add_setup(async function setup() {
+  // Add a test .ftl file
+  // (Note: other tests do this by patching L10nRegistry.load() but in
+  // this test L10nRegistry is also loaded in the extension process --
+  // just adding a new resource is easier than trying to patch
+  // L10nRegistry in all processes)
+  let dir = FileUtils.getDir("TmpD", ["l10ntest"]);
+  dir.createUnique(Ci.nsIFile.DIRECTORY_TYPE, FileUtils.PERMS_DIRECTORY);
+
+  await IOUtils.writeUTF8(
+    PathUtils.join(dir.path, "test.ftl"),
+    "key = value\n"
+  );
+
+  let target = Services.io.newFileURI(dir);
+  let resProto = Services.io
+    .getProtocolHandler("resource")
+    .QueryInterface(Ci.nsIResProtocolHandler);
+
+  resProto.setSubstitution("l10ntest", target);
+
+  const source = new L10nFileSource(
+    "test",
+    "app",
+    Services.locale.requestedLocales,
+    "resource://l10ntest/"
+  );
+  L10nRegistry.getInstance().registerSources([source]);
+});
+
+// Test that privileged extensions can use fluent to get strings from
+// language packs (and that unprivileged extensions cannot)
+add_task(async function test_l10n_dom() {
+  const PAGE = `<!DOCTYPE html>
+                <html><head>
+                  <meta charset="utf8">
+                  <link rel="localization" href="test.ftl"/>
+                  <script src="page.js"></script>
+                </head></html>`;
+
+  function SCRIPT() {
+    window.addEventListener(
+      "load",
+      async () => {
+        try {
+          await document.l10n.ready;
+          let result = await document.l10n.formatValue("key");
+          browser.test.sendMessage("result", { success: true, result });
+        } catch (err) {
+          browser.test.sendMessage("result", {
+            success: false,
+            msg: err.message,
+          });
+        }
+      },
+      { once: true }
+    );
+  }
+
+  async function runTest(isPrivileged) {
+    let extension = ExtensionTestUtils.loadExtension({
+      background() {
+        browser.test.sendMessage("ready", browser.runtime.getURL("page.html"));
+      },
+      manifest: {
+        web_accessible_resources: ["page.html"],
+      },
+      isPrivileged,
+      files: {
+        "page.html": PAGE,
+        "page.js": SCRIPT,
+      },
+    });
+
+    await extension.startup();
+    let url = await extension.awaitMessage("ready");
+    let page = await ExtensionTestUtils.loadContentPage(url, { extension });
+    let results = await extension.awaitMessage("result");
+    await page.close();
+    await extension.unload();
+
+    return results;
+  }
+
+  // Everything should work for a privileged extension
+  let results = await runTest(true);
+  equal(results.success, true, "Translation succeeded in privileged extension");
+  equal(results.result, "value", "Translation got the right value");
+
+  // In an unprivileged extension, document.l10n shouldn't show up
+  results = await runTest(false);
+  equal(results.success, false, "Translation failed in unprivileged extension");
+  equal(
+    results.msg.endsWith("document.l10n is undefined"),
+    true,
+    "Translation failed due to missing document.l10n"
+  );
+});
+
+add_task(async function test_l10n_manifest() {
+  // Fluent can't be used to localize properties that the AddonManager
+  // reads (see comment inside ExtensionData.parseManifest for details)
+  // so test by localizing a property that only the extension framework
+  // cares about: page_action.  This means we can only do this test from
+  // browser.
+  if (AppConstants.MOZ_BUILD_APP != "browser") {
+    return;
+  }
+
+  AddonTestUtils.initializeURLPreloader();
+
+  async function runTest({
+    isPrivileged = false,
+    temporarilyInstalled = false,
+  } = {}) {
+    let extension = ExtensionTestUtils.loadExtension({
+      isPrivileged,
+      temporarilyInstalled,
+      manifest: {
+        l10n_resources: ["test.ftl"],
+        page_action: {
+          default_title: "__MSG_key__",
+        },
+      },
+    });
+
+    if (temporarilyInstalled && !isPrivileged) {
+      ExtensionTestUtils.failOnSchemaWarnings(false);
+      await Assert.rejects(
+        extension.startup(),
+        /Using 'l10n_resources' requires a privileged add-on/,
+        "startup failed without privileged api access"
+      );
+      ExtensionTestUtils.failOnSchemaWarnings(true);
+      return;
+    }
+    await extension.startup();
+    let title = extension.extension.manifest.page_action.default_title;
+    await extension.unload();
+    return title;
+  }
+
+  let title = await runTest({ isPrivileged: true });
+  equal(
+    title,
+    "value",
+    "Manifest key localized with fluent in privileged extension"
+  );
+
+  title = await runTest();
+  equal(
+    title,
+    "__MSG_key__",
+    "Manifest key not localized in unprivileged extension"
+  );
+
+  title = await runTest({ temporarilyInstalled: true });
+  equal(title, undefined, "Startup fails with temporarilyInstalled extension");
+});
diff --git a/toolkit/components/extensions/test/xpcshell/test_ext_localStorage.js b/toolkit/components/extensions/test/xpcshell/test_ext_localStorage.js
new file mode 100644
index 0000000000..9adb549afe
--- /dev/null
+++ b/toolkit/components/extensions/test/xpcshell/test_ext_localStorage.js
@@ -0,0 +1,50 @@
+/* -*- Mode: indent-tabs-mode: nil; js-indent-level: 2 -*- */
+/* vim: set sts=2 sw=2 et tw=80: */
+"use strict";
+
+function backgroundScript() {
+  let hasRun = localStorage.getItem("has-run");
+  let result;
+  if (!hasRun) {
+    localStorage.setItem("has-run", "yup");
+    localStorage.setItem("test-item", "item1");
+    result = "item1";
+  } else {
+    let data = localStorage.getItem("test-item");
+    if (data == "item1") {
+      localStorage.setItem("test-item", "item2");
+      result = "item2";
+    } else if (data == "item2") {
+      localStorage.removeItem("test-item");
+      result = "deleted";
+    } else if (!data) {
+      localStorage.clear();
+      result = "cleared";
+    }
+  }
+  browser.test.sendMessage("result", result);
+  browser.test.notifyPass("localStorage");
+}
+
+const ID = "test-webextension@mozilla.com";
+let extensionData = {
+  manifest: { browser_specific_settings: { gecko: { id: ID } } },
+  background: backgroundScript,
+};
+
+add_task(async function test_localStorage() {
+  const RESULTS = ["item1", "item2", "deleted", "cleared", "item1"];
+
+  for (let expected of RESULTS) {
+    let extension = ExtensionTestUtils.loadExtension(extensionData);
+
+    await extension.startup();
+
+    let actual = await extension.awaitMessage("result");
+
+    await extension.awaitFinish("localStorage");
+    await extension.unload();
+
+    equal(actual, expected, "got expected localStorage data");
+  }
+});
diff --git a/toolkit/components/extensions/test/xpcshell/test_ext_management.js b/toolkit/components/extensions/test/xpcshell/test_ext_management.js
new file mode 100644
index 0000000000..8fb6b0d9a1
--- /dev/null
+++ b/toolkit/components/extensions/test/xpcshell/test_ext_management.js
@@ -0,0 +1,339 @@
+/* -*- Mode: indent-tabs-mode: nil; js-indent-level: 2 -*- */
+/* vim: set sts=2 sw=2 et tw=80: */
+"use strict";
+
+AddonTestUtils.init(this);
+AddonTestUtils.overrideCertDB();
+AddonTestUtils.createAppInfo(
+  "xpcshell@tests.mozilla.org",
+  "XPCShell",
+  "42",
+  "42"
+);
+
+add_task(async function setup() {
+  Services.prefs.setBoolPref(
+    "extensions.webextOptionalPermissionPrompts",
+    false
+  );
+  registerCleanupFunction(() => {
+    Services.prefs.clearUserPref("extensions.webextOptionalPermissionPrompts");
+  });
+  await ExtensionTestUtils.startAddonManager();
+});
+
+add_task(async function test_management_permission() {
+  async function background() {
+    const permObj = { permissions: ["management"] };
+
+    let hasPerm = await browser.permissions.contains(permObj);
+    browser.test.assertTrue(!hasPerm, "does not have management permission");
+    browser.test.assertTrue(
+      !!browser.management,
+      "management namespace exists"
+    );
+    // These require permission
+    let requires_permission = [
+      "getAll",
+      "get",
+      "install",
+      "setEnabled",
+      "onDisabled",
+      "onEnabled",
+      "onInstalled",
+      "onUninstalled",
+    ];
+
+    async function testAvailable() {
+      // These are always available regardless of permission.
+      for (let fn of ["getSelf", "uninstallSelf"]) {
+        browser.test.assertTrue(
+          !!browser.management[fn],
+          `management.${fn} exists`
+        );
+      }
+
+      let hasPerm = await browser.permissions.contains(permObj);
+      for (let fn of requires_permission) {
+        browser.test.assertEq(
+          hasPerm,
+          !!browser.management[fn],
+          `management.${fn} does not exist`
+        );
+      }
+    }
+
+    await testAvailable();
+
+    browser.test.onMessage.addListener(async msg => {
+      browser.test.log("test with permission");
+
+      // get permission
+      await browser.permissions.request(permObj);
+      let hasPerm = await browser.permissions.contains(permObj);
+      browser.test.assertTrue(
+        hasPerm,
+        "management permission.request accepted"
+      );
+      await testAvailable();
+
+      browser.management.onInstalled.addListener(() => {
+        browser.test.fail("onInstalled listener invoked");
+      });
+
+      browser.test.log("test without permission");
+      // remove permission
+      await browser.permissions.remove(permObj);
+      hasPerm = await browser.permissions.contains(permObj);
+      browser.test.assertFalse(
+        hasPerm,
+        "management permission.request removed"
+      );
+      await testAvailable();
+
+      browser.test.sendMessage("done");
+    });
+
+    browser.test.sendMessage("started");
+  }
+
+  let extension = ExtensionTestUtils.loadExtension({
+    manifest: {
+      browser_specific_settings: {
+        gecko: {
+          id: "management@test",
+        },
+      },
+      optional_permissions: ["management"],
+    },
+    background,
+    useAddonManager: "temporary",
+  });
+
+  await extension.startup();
+  await extension.awaitMessage("started");
+  await withHandlingUserInput(extension, async () => {
+    extension.sendMessage("request");
+  });
+  await extension.awaitMessage("done");
+
+  // Verify the onInstalled listener does not get used.
+  // The listener will make the test fail if fired.
+  let ext2 = ExtensionTestUtils.loadExtension({
+    manifest: {
+      browser_specific_settings: {
+        gecko: {
+          id: "on-installed@test",
+        },
+      },
+      optional_permissions: ["management"],
+    },
+    useAddonManager: "temporary",
+  });
+  await ext2.startup();
+  await ext2.unload();
+
+  await extension.unload();
+});
+
+add_task(async function test_management_getAll() {
+  const id1 = "get_all_test1@tests.mozilla.com";
+  const id2 = "get_all_test2@tests.mozilla.com";
+
+  function getManifest(id) {
+    return {
+      browser_specific_settings: {
+        gecko: {
+          id,
+        },
+      },
+      name: id,
+      version: "1.0",
+      short_name: id,
+      permissions: ["management"],
+    };
+  }
+
+  async function background() {
+    browser.test.onMessage.addListener(async (msg, id) => {
+      let addon = await browser.management.get(id);
+      browser.test.sendMessage("addon", addon);
+    });
+
+    let addons = await browser.management.getAll();
+    browser.test.assertEq(
+      2,
+      addons.length,
+      "management.getAll returned correct number of add-ons."
+    );
+    browser.test.sendMessage("addons", addons);
+  }
+
+  let extension1 = ExtensionTestUtils.loadExtension({
+    manifest: getManifest(id1),
+    useAddonManager: "temporary",
+  });
+
+  let extension2 = ExtensionTestUtils.loadExtension({
+    manifest: getManifest(id2),
+    background,
+    useAddonManager: "temporary",
+  });
+
+  await extension1.startup();
+  await extension2.startup();
+
+  let addons = await extension2.awaitMessage("addons");
+  for (let id of [id1, id2]) {
+    let addon = addons.find(a => {
+      return a.id === id;
+    });
+    equal(
+      addon.name,
+      id,
+      `The extension with id ${id} was returned by getAll.`
+    );
+    equal(addon.shortName, id, "Additional extension metadata was correct");
+  }
+
+  extension2.sendMessage("getAddon", id1);
+  let addon = await extension2.awaitMessage("addon");
+  equal(addon.name, id1, `The extension with id ${id1} was returned by get.`);
+  equal(addon.shortName, id1, "Additional extension metadata was correct");
+
+  extension2.sendMessage("getAddon", id2);
+  addon = await extension2.awaitMessage("addon");
+  equal(addon.name, id2, `The extension with id ${id2} was returned by get.`);
+  equal(addon.shortName, id2, "Additional extension metadata was correct");
+
+  await extension2.unload();
+  await extension1.unload();
+});
+
+add_task(
+  { pref_set: [["extensions.eventPages.enabled", true]] },
+  async function test_management_event_page() {
+    let extension = ExtensionTestUtils.loadExtension({
+      useAddonManager: "permanent",
+      manifest: {
+        permissions: ["management"],
+        background: { persistent: false },
+      },
+      background() {
+        browser.management.onInstalled.addListener(details => {
+          browser.test.sendMessage("onInstalled", details);
+        });
+        browser.management.onUninstalled.addListener(details => {
+          browser.test.sendMessage("onUninstalled", details);
+        });
+        browser.management.onEnabled.addListener(() => {
+          browser.test.sendMessage("onEnabled");
+        });
+        browser.management.onDisabled.addListener(() => {
+          browser.test.sendMessage("onDisabled");
+        });
+      },
+    });
+
+    await extension.startup();
+    let events = ["onInstalled", "onUninstalled", "onEnabled", "onDisabled"];
+    for (let event of events) {
+      assertPersistentListeners(extension, "management", event, {
+        primed: false,
+      });
+    }
+
+    await extension.terminateBackground();
+    for (let event of events) {
+      assertPersistentListeners(extension, "management", event, {
+        primed: true,
+      });
+    }
+
+    let testExt = ExtensionTestUtils.loadExtension({
+      useAddonManager: "permanent",
+      manifest: {
+        browser_specific_settings: { gecko: { id: "test-ext@mochitest" } },
+      },
+      background() {},
+    });
+    await testExt.startup();
+
+    let details = await extension.awaitMessage("onInstalled");
+    equal(testExt.id, details.id, "got onInstalled event");
+
+    await AddonTestUtils.promiseRestartManager();
+    await extension.awaitStartup();
+    await testExt.awaitStartup();
+
+    for (let event of events) {
+      assertPersistentListeners(extension, "management", event, {
+        primed: true,
+      });
+    }
+
+    // Test uninstalling an addon wakes up the watching extension.
+    let uninstalled = testExt.unload();
+
+    details = await extension.awaitMessage("onUninstalled");
+    equal(testExt.id, details.id, "got onUninstalled event");
+
+    await extension.unload();
+    await uninstalled;
+  }
+);
+
+// Sanity check that Addon listeners are removed on context close.
+add_task(
+  {
+    // __AddonManagerInternal__ is exposed for debug builds only.
+    skip_if: () => !AppConstants.DEBUG,
+  },
+  async function test_management_unregister_listener() {
+    let extension = ExtensionTestUtils.loadExtension({
+      manifest: {
+        permissions: ["management"],
+      },
+      files: {
+        "extpage.html": `<!DOCTYPE html><script src="extpage.js"></script>`,
+        "extpage.js": function () {
+          browser.management.onInstalled.addListener(() => {});
+        },
+      },
+    });
+
+    await extension.startup();
+
+    const page = await ExtensionTestUtils.loadContentPage(
+      `moz-extension://${extension.uuid}/extpage.html`
+    );
+
+    const { AddonManager } = ChromeUtils.importESModule(
+      "resource://gre/modules/AddonManager.sys.mjs"
+    );
+    function assertManagementAPIAddonListener(expect) {
+      let found = false;
+      for (const addonListener of AddonManager.__AddonManagerInternal__
+        ?.addonListeners || []) {
+        if (
+          Object.getPrototypeOf(addonListener).constructor.name ===
+          "ManagementAddonListener"
+        ) {
+          found = true;
+        }
+      }
+      equal(
+        found,
+        expect,
+        `${
+          expect ? "Should" : "Should not"
+        } have found an AOM addonListener registered by the management API`
+      );
+    }
+
+    assertManagementAPIAddonListener(true);
+    await page.close();
+    assertManagementAPIAddonListener(false);
+    await extension.unload();
+  }
+);
diff --git a/toolkit/components/extensions/test/xpcshell/test_ext_management_uninstall_self.js b/toolkit/components/extensions/test/xpcshell/test_ext_management_uninstall_self.js
new file mode 100644
index 0000000000..45c981811b
--- /dev/null
+++ b/toolkit/components/extensions/test/xpcshell/test_ext_management_uninstall_self.js
@@ -0,0 +1,146 @@
+/* -*- Mode: indent-tabs-mode: nil; js-indent-level: 2 -*- */
+/* vim: set sts=2 sw=2 et tw=80: */
+"use strict";
+
+const { AddonManager } = ChromeUtils.importESModule(
+  "resource://gre/modules/AddonManager.sys.mjs"
+);
+const { MockRegistrar } = ChromeUtils.importESModule(
+  "resource://testing-common/MockRegistrar.sys.mjs"
+);
+
+const id = "uninstall_self_test@tests.mozilla.com";
+
+const manifest = {
+  browser_specific_settings: {
+    gecko: {
+      id,
+    },
+  },
+  name: "test extension name",
+  version: "1.0",
+};
+
+const waitForUninstalled = () =>
+  new Promise(resolve => {
+    const listener = {
+      onUninstalled: async addon => {
+        equal(addon.id, id, "The expected add-on has been uninstalled");
+        let checkedAddon = await AddonManager.getAddonByID(addon.id);
+        equal(checkedAddon, null, "Add-on no longer exists");
+        AddonManager.removeAddonListener(listener);
+        resolve();
+      },
+    };
+    AddonManager.addAddonListener(listener);
+  });
+
+let promptService = {
+  _response: null,
+  QueryInterface: ChromeUtils.generateQI(["nsIPromptService"]),
+  confirmEx: function (...args) {
+    this._confirmExArgs = args;
+    return this._response;
+  },
+};
+
+AddonTestUtils.init(this);
+
+add_task(async function setup() {
+  let fakePromptService = MockRegistrar.register(
+    "@mozilla.org/prompter;1",
+    promptService
+  );
+  registerCleanupFunction(() => {
+    MockRegistrar.unregister(fakePromptService);
+  });
+  await ExtensionTestUtils.startAddonManager();
+});
+
+add_task(async function test_management_uninstall_no_prompt() {
+  function background() {
+    browser.test.onMessage.addListener(msg => {
+      browser.management.uninstallSelf();
+    });
+  }
+
+  let extension = ExtensionTestUtils.loadExtension({
+    manifest,
+    background,
+    useAddonManager: "temporary",
+  });
+
+  await extension.startup();
+  let addon = await AddonManager.getAddonByID(id);
+  notEqual(addon, null, "Add-on is installed");
+  extension.sendMessage("uninstall");
+  await waitForUninstalled();
+  Services.obs.notifyObservers(extension.extension.file, "flush-cache-entry");
+});
+
+add_task(async function test_management_uninstall_prompt_uninstall() {
+  promptService._response = 0;
+
+  function background() {
+    browser.test.onMessage.addListener(msg => {
+      browser.management.uninstallSelf({ showConfirmDialog: true });
+    });
+  }
+
+  let extension = ExtensionTestUtils.loadExtension({
+    manifest,
+    background,
+    useAddonManager: "temporary",
+  });
+
+  await extension.startup();
+  let addon = await AddonManager.getAddonByID(id);
+  notEqual(addon, null, "Add-on is installed");
+  extension.sendMessage("uninstall");
+  await waitForUninstalled();
+
+  // Test localization strings
+  equal(promptService._confirmExArgs[1], `Uninstall ${manifest.name}`);
+  equal(
+    promptService._confirmExArgs[2],
+    `The extension “${manifest.name}” is requesting to be uninstalled. What would you like to do?`
+  );
+  equal(promptService._confirmExArgs[4], "Uninstall");
+  equal(promptService._confirmExArgs[5], "Keep Installed");
+  Services.obs.notifyObservers(extension.extension.file, "flush-cache-entry");
+});
+
+add_task(async function test_management_uninstall_prompt_keep() {
+  promptService._response = 1;
+
+  function background() {
+    browser.test.onMessage.addListener(async msg => {
+      await browser.test.assertRejects(
+        browser.management.uninstallSelf({ showConfirmDialog: true }),
+        "User cancelled uninstall of extension",
+        "Expected rejection when user declines uninstall"
+      );
+
+      browser.test.sendMessage("uninstall-rejected");
+    });
+  }
+
+  let extension = ExtensionTestUtils.loadExtension({
+    manifest,
+    background,
+    useAddonManager: "temporary",
+  });
+
+  await extension.startup();
+
+  let addon = await AddonManager.getAddonByID(id);
+  notEqual(addon, null, "Add-on is installed");
+
+  extension.sendMessage("uninstall");
+  await extension.awaitMessage("uninstall-rejected");
+
+  addon = await AddonManager.getAddonByID(id);
+  notEqual(addon, null, "Add-on remains installed");
+
+  await extension.unload();
+});
diff --git a/toolkit/components/extensions/test/xpcshell/test_ext_manifest.js b/toolkit/components/extensions/test/xpcshell/test_ext_manifest.js
new file mode 100644
index 0000000000..4b9300fd40
--- /dev/null
+++ b/toolkit/components/extensions/test/xpcshell/test_ext_manifest.js
@@ -0,0 +1,460 @@
+/* -*- Mode: indent-tabs-mode: nil; js-indent-level: 2 -*- */
+/* vim: set sts=2 sw=2 et tw=80: */
+"use strict";
+
+ChromeUtils.defineESModuleGetters(this, {
+  AddonManager: "resource://gre/modules/AddonManager.sys.mjs",
+});
+
+AddonTestUtils.init(this);
+AddonTestUtils.createAppInfo(
+  "xpcshell@tests.mozilla.org",
+  "XPCShell",
+  "1",
+  "42"
+);
+
+async function testManifest(manifest, expectedError) {
+  ExtensionTestUtils.failOnSchemaWarnings(false);
+  let normalized = await ExtensionTestUtils.normalizeManifest(manifest);
+  ExtensionTestUtils.failOnSchemaWarnings(true);
+
+  if (expectedError) {
+    ok(
+      expectedError.test(normalized.error),
+      `Should have an error for ${JSON.stringify(manifest)}, got ${
+        normalized.error
+      }`
+    );
+  } else {
+    ok(
+      !normalized.error,
+      `Should not have an error ${JSON.stringify(manifest)}, ${
+        normalized.error
+      }`
+    );
+  }
+  return normalized.errors;
+}
+
+async function testIconPaths(icon, manifest, expectedError) {
+  let normalized = await ExtensionTestUtils.normalizeManifest(manifest);
+
+  if (expectedError) {
+    ok(
+      expectedError.test(normalized.error),
+      `Should have an error for ${JSON.stringify(icon)}`
+    );
+  } else {
+    ok(!normalized.error, `Should not have an error ${JSON.stringify(icon)}`);
+  }
+}
+
+add_setup(async () => {
+  await AddonTestUtils.promiseStartupManager();
+});
+
+add_task(async function test_manifest() {
+  let badpaths = ["", " ", "\t", "http://foo.com/icon.png"];
+  for (let path of badpaths) {
+    await testIconPaths(
+      path,
+      {
+        icons: path,
+      },
+      /Error processing icons/
+    );
+
+    await testIconPaths(
+      path,
+      {
+        icons: {
+          16: path,
+        },
+      },
+      /Error processing icons/
+    );
+  }
+
+  let paths = [
+    "icon.png",
+    "/icon.png",
+    "./icon.png",
+    "path to an icon.png",
+    " icon.png",
+  ];
+  for (let path of paths) {
+    // manifest.icons is an object
+    await testIconPaths(
+      path,
+      {
+        icons: path,
+      },
+      /Error processing icons/
+    );
+
+    await testIconPaths(path, {
+      icons: {
+        16: path,
+      },
+    });
+  }
+});
+
+add_task(async function test_manifest_warnings_on_unexpected_props() {
+  let extension = await ExtensionTestUtils.loadExtension({
+    manifest: {
+      background: {
+        scripts: ["bg.js"],
+        wrong_prop: true,
+      },
+    },
+    files: {
+      "bg.js": "",
+    },
+  });
+
+  ExtensionTestUtils.failOnSchemaWarnings(false);
+  await extension.startup();
+  ExtensionTestUtils.failOnSchemaWarnings(true);
+
+  // Retrieve the warning message collected by the Extension class
+  // packagingWarning method.
+  const { warnings } = extension.extension;
+  equal(warnings.length, 1, "Got the expected number of manifest warnings");
+
+  const expectedMessage =
+    "Reading manifest: Warning processing background.wrong_prop";
+  ok(
+    warnings[0].startsWith(expectedMessage),
+    "Got the expected warning message format"
+  );
+
+  await extension.unload();
+});
+
+add_task(async function test_mv2_scripting_permission_always_enabled() {
+  let warnings = await testManifest({
+    manifest_version: 2,
+    permissions: ["scripting"],
+  });
+
+  Assert.deepEqual(warnings, [], "Got no warnings");
+});
+
+add_task(
+  {
+    pref_set: [["extensions.manifestV3.enabled", true]],
+  },
+  async function test_mv3_scripting_permission_always_enabled() {
+    let warnings = await testManifest({
+      manifest_version: 3,
+      permissions: ["scripting"],
+    });
+
+    Assert.deepEqual(warnings, [], "Got no warnings");
+  }
+);
+
+add_task(async function test_simpler_version_format() {
+  const TEST_CASES = [
+    // Valid cases
+    { version: "0", expectWarning: false },
+    { version: "0.0", expectWarning: false },
+    { version: "0.0.0", expectWarning: false },
+    { version: "0.0.0.0", expectWarning: false },
+    { version: "0.0.0.1", expectWarning: false },
+    { version: "0.0.0.999999999", expectWarning: false },
+    { version: "0.0.1.0", expectWarning: false },
+    { version: "0.0.999999999", expectWarning: false },
+    { version: "0.1.0.0", expectWarning: false },
+    { version: "0.999999999", expectWarning: false },
+    { version: "1", expectWarning: false },
+    { version: "1.0", expectWarning: false },
+    { version: "1.0.0", expectWarning: false },
+    { version: "1.0.0.0", expectWarning: false },
+    { version: "1.2.3.4", expectWarning: false },
+    { version: "999999999", expectWarning: false },
+    {
+      version: "999999999.999999999.999999999.999999999",
+      expectWarning: false,
+    },
+    // Invalid cases
+    { version: ".", expectWarning: true },
+    { version: ".999999999", expectWarning: true },
+    { version: "0.0.0.0.0", expectWarning: true },
+    { version: "0.0.0.00001", expectWarning: true },
+    { version: "0.0.0.0010", expectWarning: true },
+    { version: "0.0.00001", expectWarning: true },
+    { version: "0.0.001", expectWarning: true },
+    { version: "0.0.01.0", expectWarning: true },
+    { version: "0.01.0", expectWarning: true },
+    { version: "00001", expectWarning: true },
+    { version: "0001", expectWarning: true },
+    { version: "001", expectWarning: true },
+    { version: "01", expectWarning: true },
+    { version: "01.0", expectWarning: true },
+    { version: "099999", expectWarning: true },
+    { version: "0999999999", expectWarning: true },
+    { version: "1.00000", expectWarning: true },
+    { version: "1.1.-1", expectWarning: true },
+    { version: "1.1000000000", expectWarning: true },
+    { version: "1.1pre1aa", expectWarning: true },
+    { version: "1.2.1000000000", expectWarning: true },
+    { version: "1.2.3.4-a", expectWarning: true },
+    { version: "1.2.3.4.5", expectWarning: true },
+    { version: "1000000000", expectWarning: true },
+    { version: "1000000000.0.0.0", expectWarning: true },
+    { version: "999999999.", expectWarning: true },
+  ];
+
+  for (const { version, expectWarning } of TEST_CASES) {
+    const normalized = await ExtensionTestUtils.normalizeManifest({ version });
+
+    if (expectWarning) {
+      Assert.deepEqual(
+        normalized.errors,
+        [
+          `Warning processing version: version must be a version string ` +
+            `consisting of at most 4 integers of at most 9 digits without ` +
+            `leading zeros, and separated with dots`,
+        ],
+        `expected warning for version: ${version}`
+      );
+    } else {
+      Assert.deepEqual(
+        normalized.errors,
+        [],
+        `expected no warning for version: ${version}`
+      );
+    }
+  }
+});
+
+add_task(async function test_applications() {
+  const id = "some@id";
+  const updateURL = "https://example.com/updates/";
+
+  let extension = await ExtensionTestUtils.loadExtension({
+    manifest: {
+      manifest_version: 2,
+      applications: {
+        gecko: { id, update_url: updateURL },
+      },
+    },
+    useAddonManager: "temporary",
+  });
+
+  ExtensionTestUtils.failOnSchemaWarnings(false);
+  await extension.startup();
+  ExtensionTestUtils.failOnSchemaWarnings(true);
+
+  Assert.deepEqual(extension.extension.warnings, [], "expected no warnings");
+
+  const addon = await AddonManager.getAddonByID(extension.id);
+  ok(addon, "got an add-on");
+  equal(addon.id, id, "got expected ID");
+  equal(addon.updateURL, updateURL, "got expected update URL");
+
+  await extension.unload();
+});
+
+add_task(
+  {
+    pref_set: [["extensions.manifestV3.enabled", true]],
+  },
+  async function test_applications_key_mv3() {
+    let warnings = await testManifest({
+      manifest_version: 3,
+      applications: {},
+    });
+
+    Assert.deepEqual(
+      warnings,
+      [`Property "applications" is unsupported in Manifest Version 3`],
+      `Manifest v3 with "applications" key logs an error.`
+    );
+  }
+);
+
+add_task(async function test_bss_gecko_android() {
+  const addonId = "some@id";
+  const isAndroid = AppConstants.platform == "android";
+
+  const TEST_CASES = [
+    {
+      title: "gecko_android overrides gecko",
+      browser_specific_settings: {
+        gecko: {
+          id: addonId,
+          strict_min_version: "2",
+          strict_max_version: "2",
+        },
+        gecko_android: {
+          strict_min_version: "1",
+          strict_max_version: "1",
+        },
+      },
+      expectedError: isAndroid
+        ? `Add-on ${addonId} is not compatible with application version. add-on minVersion: 1. add-on maxVersion: 1.`
+        : `Add-on ${addonId} is not compatible with application version. add-on minVersion: 2. add-on maxVersion: 2.`,
+    },
+    {
+      title:
+        "strict_min_version in gecko_android overrides gecko.strict_min_version",
+      browser_specific_settings: {
+        gecko: {
+          id: addonId,
+          strict_min_version: "2",
+          strict_max_version: "3",
+        },
+        gecko_android: {
+          strict_min_version: "3",
+        },
+      },
+      expectedError: isAndroid
+        ? `Add-on ${addonId} is not compatible with application version. add-on minVersion: 3. add-on maxVersion: 3.`
+        : `Add-on ${addonId} is not compatible with application version. add-on minVersion: 2. add-on maxVersion: 3.`,
+    },
+    {
+      title:
+        "strict_max_version in gecko_android overrides gecko.strict_max_version",
+      browser_specific_settings: {
+        gecko: {
+          id: addonId,
+          strict_min_version: "2",
+          strict_max_version: "2",
+        },
+        gecko_android: {
+          strict_max_version: "3",
+        },
+      },
+      expectedError: isAndroid
+        ? `Add-on ${addonId} is not compatible with application version. add-on minVersion: 2. add-on maxVersion: 3.`
+        : `Add-on ${addonId} is not compatible with application version. add-on minVersion: 2. add-on maxVersion: 2.`,
+    },
+    {
+      title: "no gecko_android",
+      browser_specific_settings: {
+        gecko: {
+          id: addonId,
+          strict_min_version: "2",
+          strict_max_version: "2",
+        },
+      },
+      expectedError: `Add-on ${addonId} is not compatible with application version. add-on minVersion: 2. add-on maxVersion: 2.`,
+    },
+    {
+      title: "empty gecko_android",
+      browser_specific_settings: {
+        gecko: {
+          id: addonId,
+          strict_min_version: "2",
+          strict_max_version: "2",
+        },
+        gecko_android: {},
+      },
+      expectedError: `Add-on ${addonId} is not compatible with application version. add-on minVersion: 2. add-on maxVersion: 2.`,
+    },
+    {
+      title: "empty strict min/max versions in gecko_android",
+      browser_specific_settings: {
+        gecko: {
+          id: addonId,
+          strict_min_version: "2",
+          strict_max_version: "2",
+        },
+        gecko_android: {
+          strict_min_version: "",
+          strict_max_version: "",
+        },
+      },
+      expectedError: `Add-on ${addonId} is not compatible with application version. add-on minVersion: 2. add-on maxVersion: 2.`,
+    },
+    {
+      title: "unsupported prop in gecko_android",
+      browser_specific_settings: {
+        gecko: {
+          id: addonId,
+          strict_min_version: "2",
+          strict_max_version: "2",
+        },
+        gecko_android: {
+          aPropThatIsNotSupported: "aPropThatIsNotSupported",
+        },
+      },
+      expectedError: `Add-on ${addonId} is not compatible with application version. add-on minVersion: 2. add-on maxVersion: 2.`,
+    },
+    {
+      title: "only strict min/max version in gecko_android",
+      browser_specific_settings: {
+        gecko: {
+          id: addonId,
+        },
+        gecko_android: {
+          strict_min_version: "3",
+          strict_max_version: "4",
+        },
+      },
+      expectedError: isAndroid
+        ? `Add-on ${addonId} is not compatible with application version. add-on minVersion: 3. add-on maxVersion: 4.`
+        : null,
+    },
+    {
+      title: "only strict_min_version in gecko_android",
+      browser_specific_settings: {
+        gecko: {
+          id: addonId,
+        },
+        gecko_android: {
+          // The app version is set to `42` at the top of the file.
+          strict_min_version: "100",
+        },
+      },
+      expectedError: isAndroid
+        ? `Add-on ${addonId} is not compatible with application version. add-on minVersion: 100.`
+        : null,
+    },
+  ];
+
+  for (const {
+    title,
+    browser_specific_settings,
+    expectedError,
+  } of TEST_CASES) {
+    info(`verifying: ${title}`);
+
+    // This task is mainly about verifying `bss.gecko_android` and some test
+    // cases require a "valid" compatibility range by default, which would
+    // break the assumption below (that the install is going to fail). This is
+    // why we skip null errors, but only on non-Android builds.
+    if (expectedError === null) {
+      notEqual(
+        AppConstants.platform,
+        "android",
+        `${title} - expected no error on a non-Android build`
+      );
+      continue;
+    }
+
+    const manifest = {
+      manifest_version: 2,
+      version: "1.0",
+      browser_specific_settings,
+    };
+
+    const extension = ExtensionTestUtils.loadExtension({
+      manifest,
+      useAddonManager: "temporary",
+    });
+
+    await Assert.rejects(
+      extension.startup(),
+      new RegExp(expectedError),
+      `${title} - expected error: ${expectedError}`
+    );
+
+    const addon = await AddonManager.getAddonByID(addonId);
+    equal(addon, null, "add-on is not installed");
+  }
+});
diff --git a/toolkit/components/extensions/test/xpcshell/test_ext_manifest_content_security_policy.js b/toolkit/components/extensions/test/xpcshell/test_ext_manifest_content_security_policy.js
new file mode 100644
index 0000000000..a6e3f91a6b
--- /dev/null
+++ b/toolkit/components/extensions/test/xpcshell/test_ext_manifest_content_security_policy.js
@@ -0,0 +1,114 @@
+/* -*- Mode: indent-tabs-mode: nil; js-indent-level: 2 -*- */
+/* vim: set sts=2 sw=2 et tw=80: */
+"use strict";
+
+Services.prefs.setBoolPref("extensions.manifestV3.enabled", true);
+
+add_task(async function test_manifest_csp() {
+  let normalized = await ExtensionTestUtils.normalizeManifest({
+    content_security_policy: "script-src 'self'; object-src 'none'",
+  });
+
+  equal(normalized.error, undefined, "Should not have an error");
+  equal(normalized.errors.length, 0, "Should not have warnings");
+  equal(
+    normalized.value.content_security_policy,
+    "script-src 'self'; object-src 'none'",
+    "Should have the expected policy string"
+  );
+
+  ExtensionTestUtils.failOnSchemaWarnings(false);
+  normalized = await ExtensionTestUtils.normalizeManifest({
+    content_security_policy: "object-src 'none'",
+  });
+  ExtensionTestUtils.failOnSchemaWarnings(true);
+
+  equal(normalized.error, undefined, "Should not have an error");
+
+  Assert.deepEqual(
+    normalized.errors,
+    [
+      "Error processing content_security_policy: Policy is missing a required ‘script-src’ directive",
+    ],
+    "Should have the expected warning"
+  );
+
+  equal(
+    normalized.value.content_security_policy,
+    null,
+    "Invalid policy string should be omitted"
+  );
+
+  ExtensionTestUtils.failOnSchemaWarnings(false);
+  normalized = await ExtensionTestUtils.normalizeManifest({
+    manifest_version: 2,
+    content_security_policy: {
+      extension_pages: "script-src 'self'; object-src 'none'",
+    },
+  });
+  ExtensionTestUtils.failOnSchemaWarnings(true);
+
+  Assert.deepEqual(
+    normalized.errors,
+    [
+      `Error processing content_security_policy: Expected string instead of {"extension_pages":"script-src 'self'; object-src 'none'"}`,
+    ],
+    "Should have the expected warning"
+  );
+});
+
+add_task(async function test_manifest_csp_v3() {
+  ExtensionTestUtils.failOnSchemaWarnings(false);
+  let normalized = await ExtensionTestUtils.normalizeManifest({
+    manifest_version: 3,
+    content_security_policy: "script-src 'self'; object-src 'none'",
+  });
+  ExtensionTestUtils.failOnSchemaWarnings(true);
+
+  Assert.deepEqual(
+    normalized.errors,
+    [
+      `Error processing content_security_policy: Expected object instead of "script-src 'self'; object-src 'none'"`,
+    ],
+    "Should have the expected warning"
+  );
+
+  normalized = await ExtensionTestUtils.normalizeManifest({
+    manifest_version: 3,
+    content_security_policy: {
+      extension_pages: "script-src 'self' 'unsafe-eval'; object-src 'none'",
+    },
+  });
+
+  Assert.deepEqual(
+    normalized.errors,
+    [
+      "Error processing content_security_policy.extension_pages: ‘script-src’ directive contains a forbidden 'unsafe-eval' keyword",
+    ],
+    "Should have the expected warning"
+  );
+  equal(
+    normalized.value.content_security_policy.extension_pages,
+    null,
+    "Should have the expected policy string"
+  );
+
+  ExtensionTestUtils.failOnSchemaWarnings(false);
+  normalized = await ExtensionTestUtils.normalizeManifest({
+    manifest_version: 3,
+    content_security_policy: {
+      extension_pages: "object-src 'none'",
+    },
+  });
+  ExtensionTestUtils.failOnSchemaWarnings(true);
+
+  equal(normalized.error, undefined, "Should not have an error");
+  equal(normalized.errors.length, 1, "Should have warnings");
+  Assert.deepEqual(
+    normalized.errors,
+    [
+      "Error processing content_security_policy.extension_pages: Policy is missing a required ‘script-src’ directive",
+    ],
+    "Should have the expected warning for extension_pages CSP"
+  );
+});
diff --git a/toolkit/components/extensions/test/xpcshell/test_ext_manifest_incognito.js b/toolkit/components/extensions/test/xpcshell/test_ext_manifest_incognito.js
new file mode 100644
index 0000000000..4330e1b681
--- /dev/null
+++ b/toolkit/components/extensions/test/xpcshell/test_ext_manifest_incognito.js
@@ -0,0 +1,45 @@
+/* -*- Mode: indent-tabs-mode: nil; js-indent-level: 2 -*- */
+/* vim: set sts=2 sw=2 et tw=80: */
+"use strict";
+
+add_task(async function test_manifest_incognito() {
+  let normalized = await ExtensionTestUtils.normalizeManifest({
+    incognito: "spanning",
+  });
+
+  equal(normalized.error, undefined, "Should not have an error");
+  equal(normalized.errors.length, 0, "Should not have warnings");
+  equal(
+    normalized.value.incognito,
+    "spanning",
+    "Should have the expected incognito string"
+  );
+
+  normalized = await ExtensionTestUtils.normalizeManifest({
+    incognito: "not_allowed",
+  });
+
+  equal(normalized.error, undefined, "Should not have an error");
+  equal(normalized.errors.length, 0, "Should not have warnings");
+  equal(
+    normalized.value.incognito,
+    "not_allowed",
+    "Should have the expected incognito string"
+  );
+
+  normalized = await ExtensionTestUtils.normalizeManifest({
+    incognito: "split",
+  });
+
+  equal(
+    normalized.error,
+    'Error processing incognito: Invalid enumeration value "split"',
+    "Should have an error"
+  );
+  Assert.deepEqual(normalized.errors, [], "Should not have a warning");
+  equal(
+    normalized.value,
+    undefined,
+    "Invalid incognito string should be undefined"
+  );
+});
diff --git a/toolkit/components/extensions/test/xpcshell/test_ext_manifest_minimum_chrome_version.js b/toolkit/components/extensions/test/xpcshell/test_ext_manifest_minimum_chrome_version.js
new file mode 100644
index 0000000000..39119513fb
--- /dev/null
+++ b/toolkit/components/extensions/test/xpcshell/test_ext_manifest_minimum_chrome_version.js
@@ -0,0 +1,12 @@
+/* -*- Mode: indent-tabs-mode: nil; js-indent-level: 2 -*- */
+/* vim: set sts=2 sw=2 et tw=80: */
+"use strict";
+
+add_task(async function test_manifest_minimum_chrome_version() {
+  let normalized = await ExtensionTestUtils.normalizeManifest({
+    minimum_chrome_version: "42",
+  });
+
+  equal(normalized.error, undefined, "Should not have an error");
+  equal(normalized.errors.length, 0, "Should not have warnings");
+});
diff --git a/toolkit/components/extensions/test/xpcshell/test_ext_manifest_minimum_opera_version.js b/toolkit/components/extensions/test/xpcshell/test_ext_manifest_minimum_opera_version.js
new file mode 100644
index 0000000000..943e8b7270
--- /dev/null
+++ b/toolkit/components/extensions/test/xpcshell/test_ext_manifest_minimum_opera_version.js
@@ -0,0 +1,12 @@
+/* -*- Mode: indent-tabs-mode: nil; js-indent-level: 2 -*- */
+/* vim: set sts=2 sw=2 et tw=80: */
+"use strict";
+
+add_task(async function test_manifest_minimum_opera_version() {
+  let normalized = await ExtensionTestUtils.normalizeManifest({
+    minimum_opera_version: "48",
+  });
+
+  equal(normalized.error, undefined, "Should not have an error");
+  equal(normalized.errors.length, 0, "Should not have warnings");
+});
diff --git a/toolkit/components/extensions/test/xpcshell/test_ext_manifest_themes.js b/toolkit/components/extensions/test/xpcshell/test_ext_manifest_themes.js
new file mode 100644
index 0000000000..8cd44f06dc
--- /dev/null
+++ b/toolkit/components/extensions/test/xpcshell/test_ext_manifest_themes.js
@@ -0,0 +1,35 @@
+/* -*- Mode: indent-tabs-mode: nil; js-indent-level: 2 -*- */
+/* vim: set sts=2 sw=2 et tw=80: */
+"use strict";
+
+async function test_theme_property(property) {
+  let normalized = await ExtensionTestUtils.normalizeManifest(
+    {
+      theme: {
+        [property]: {},
+      },
+    },
+    "manifest.ThemeManifest"
+  );
+
+  if (property === "unrecognized_key") {
+    const expectedWarning = `Warning processing theme.${property}`;
+    ok(
+      normalized.errors[0].includes(expectedWarning),
+      `The manifest warning ${JSON.stringify(
+        normalized.errors[0]
+      )} must contain ${JSON.stringify(expectedWarning)}`
+    );
+  } else {
+    equal(normalized.errors.length, 0, "Should have a warning");
+  }
+  equal(normalized.error, undefined, "Should not have an error");
+}
+
+add_task(async function test_manifest_themes() {
+  await test_theme_property("images");
+  await test_theme_property("colors");
+  ExtensionTestUtils.failOnSchemaWarnings(false);
+  await test_theme_property("unrecognized_key");
+  ExtensionTestUtils.failOnSchemaWarnings(true);
+});
diff --git a/toolkit/components/extensions/test/xpcshell/test_ext_messaging_startup.js b/toolkit/components/extensions/test/xpcshell/test_ext_messaging_startup.js
new file mode 100644
index 0000000000..120bebb431
--- /dev/null
+++ b/toolkit/components/extensions/test/xpcshell/test_ext_messaging_startup.js
@@ -0,0 +1,277 @@
+"use strict";
+
+const server = createHttpServer({ hosts: ["example.com"] });
+server.registerDirectory("/data/", do_get_file("data"));
+
+AddonTestUtils.init(this);
+AddonTestUtils.overrideCertDB();
+AddonTestUtils.createAppInfo(
+  "xpcshell@tests.mozilla.org",
+  "XPCShell",
+  "1",
+  "43"
+);
+
+let { promiseRestartManager, promiseShutdownManager, promiseStartupManager } =
+  AddonTestUtils;
+
+const PAGE_HTML = `<!DOCTYPE html><meta charset="utf-8"><script src="script.js"></script>`;
+
+function trackEvents(wrapper) {
+  let events = new Map();
+  for (let event of ["background-script-event", "start-background-script"]) {
+    events.set(event, false);
+    wrapper.extension.once(event, () => events.set(event, true));
+  }
+  return events;
+}
+
+async function test(what, background, script) {
+  await promiseStartupManager();
+
+  let extension = ExtensionTestUtils.loadExtension({
+    useAddonManager: "permanent",
+
+    manifest: {
+      content_scripts: [
+        {
+          matches: ["http://example.com/*"],
+          js: ["script.js"],
+        },
+      ],
+    },
+
+    files: {
+      "page.html": PAGE_HTML,
+      "script.js": script,
+    },
+
+    background,
+  });
+
+  info(`Set up ${what} listener`);
+  await extension.startup();
+  await extension.awaitMessage("bg-ran");
+
+  info(`Test wakeup for ${what} from an extension page`);
+  await promiseRestartManager({ earlyStartup: false });
+  await extension.awaitStartup();
+
+  function awaitBgEvent() {
+    return new Promise(resolve =>
+      extension.extension.once("background-script-event", resolve)
+    );
+  }
+
+  let events = trackEvents(extension);
+
+  let url = extension.extension.baseURI.resolve("page.html");
+
+  let [, page] = await Promise.all([
+    awaitBgEvent(),
+    ExtensionTestUtils.loadContentPage(url, { extension }),
+  ]);
+
+  equal(
+    events.get("background-script-event"),
+    true,
+    "Should have gotten a background page event"
+  );
+  equal(
+    events.get("start-background-script"),
+    false,
+    "Background page should not be started"
+  );
+
+  equal(extension.messageQueue.size, 0, "Have not yet received bg-ran message");
+
+  let promise = extension.awaitMessage("bg-ran");
+  AddonTestUtils.notifyEarlyStartup();
+  await promise;
+
+  equal(
+    events.get("start-background-script"),
+    true,
+    "Should have gotten start-background-script event"
+  );
+
+  await extension.awaitFinish("messaging-test");
+  ok(true, "Background page loaded and received message from extension page");
+
+  await page.close();
+
+  info(`Test wakeup for ${what} from a content script`);
+  await promiseRestartManager({ earlyStartup: false });
+  await extension.awaitStartup();
+
+  events = trackEvents(extension);
+
+  [, page] = await Promise.all([
+    awaitBgEvent(),
+    ExtensionTestUtils.loadContentPage(
+      "http://example.com/data/file_sample.html"
+    ),
+  ]);
+
+  equal(
+    events.get("background-script-event"),
+    true,
+    "Should have gotten a background script event"
+  );
+  equal(
+    events.get("start-background-script"),
+    false,
+    "Background script should not be started"
+  );
+
+  equal(extension.messageQueue.size, 0, "Have not yet received bg-ran message");
+
+  promise = extension.awaitMessage("bg-ran");
+  AddonTestUtils.notifyEarlyStartup();
+  await promise;
+
+  equal(
+    events.get("start-background-script"),
+    true,
+    "Should have gotten start-background-script event"
+  );
+
+  await extension.awaitFinish("messaging-test");
+  ok(true, "Background page loaded and received message from content script");
+
+  await page.close();
+  await extension.unload();
+
+  await promiseShutdownManager();
+}
+
+add_task(function test_onMessage() {
+  function script() {
+    browser.runtime.sendMessage("ping").then(reply => {
+      browser.test.assertEq(
+        reply,
+        "pong",
+        "Extension page received pong reply"
+      );
+      browser.test.notifyPass("messaging-test");
+    });
+  }
+
+  async function background() {
+    browser.runtime.onMessage.addListener((msg, sender) => {
+      browser.test.assertEq(
+        msg,
+        "ping",
+        "Background page received ping message"
+      );
+      return Promise.resolve("pong");
+    });
+
+    // addListener() returns right away but make a round trip to the
+    // main process to ensure the persistent onMessage listener is recorded.
+    await browser.runtime.getBrowserInfo();
+    browser.test.sendMessage("bg-ran");
+  }
+
+  return test("onMessage", background, script);
+});
+
+add_task(function test_onConnect() {
+  function script() {
+    let port = browser.runtime.connect();
+    port.onMessage.addListener(msg => {
+      browser.test.assertEq(msg, "pong", "Extension page received pong reply");
+      browser.test.notifyPass("messaging-test");
+    });
+    port.postMessage("ping");
+  }
+
+  async function background() {
+    browser.runtime.onConnect.addListener(port => {
+      port.onMessage.addListener(msg => {
+        browser.test.assertEq(
+          msg,
+          "ping",
+          "Background page received ping message"
+        );
+        port.postMessage("pong");
+      });
+    });
+
+    // addListener() returns right away but make a round trip to the
+    // main process to ensure the persistent onMessage listener is recorded.
+    await browser.runtime.getBrowserInfo();
+    browser.test.sendMessage("bg-ran");
+  }
+
+  return test("onConnect", background, script);
+});
+
+// Test that messaging works if the background page is started before
+// any messages are exchanged.  (See bug 1467136 for an example of how
+// this broke at one point).
+add_task(async function test_other_startup() {
+  await promiseStartupManager();
+
+  let extension = ExtensionTestUtils.loadExtension({
+    useAddonManager: "permanent",
+
+    async background() {
+      browser.runtime.onMessage.addListener(msg => {
+        browser.test.notifyPass("startup");
+      });
+
+      // addListener() returns right away but make a round trip to the
+      // main process to ensure the persistent onMessage listener is recorded.
+      await browser.runtime.getBrowserInfo();
+      browser.test.sendMessage("bg-ran");
+    },
+
+    files: {
+      "page.html": PAGE_HTML,
+      "script.js"() {
+        browser.runtime.sendMessage("ping");
+      },
+    },
+  });
+
+  await extension.startup();
+  await extension.awaitMessage("bg-ran");
+
+  await promiseRestartManager({ lateStartup: false });
+  await extension.awaitStartup();
+  let events = trackEvents(extension);
+
+  equal(
+    events.get("background-script-event"),
+    false,
+    "Should not have gotten a background page event"
+  );
+  equal(
+    events.get("start-background-script"),
+    false,
+    "Background page should not be started"
+  );
+
+  // Start the background page.  No message have been sent at this point.
+  await AddonTestUtils.notifyLateStartup();
+  equal(
+    events.get("start-background-script"),
+    true,
+    "Background page should be started"
+  );
+
+  await extension.awaitMessage("bg-ran");
+
+  // Now that the background page is fully started, load a new page that
+  // sends a message to the background page.
+  let url = extension.extension.baseURI.resolve("page.html");
+  let page = await ExtensionTestUtils.loadContentPage(url, { extension });
+
+  await extension.awaitFinish("startup");
+
+  await page.close();
+  await extension.unload();
+
+  await promiseShutdownManager();
+});
diff --git a/toolkit/components/extensions/test/xpcshell/test_ext_native_messaging.js b/toolkit/components/extensions/test/xpcshell/test_ext_native_messaging.js
new file mode 100644
index 0000000000..cb08a70151
--- /dev/null
+++ b/toolkit/components/extensions/test/xpcshell/test_ext_native_messaging.js
@@ -0,0 +1,1111 @@
+/* -*- Mode: indent-tabs-mode: nil; js-indent-level: 2 -*- */
+/* vim: set sts=2 sw=2 et tw=80: */
+"use strict";
+
+/* globals chrome */
+
+const { TestUtils } = ChromeUtils.importESModule(
+  "resource://testing-common/TestUtils.sys.mjs"
+);
+
+const PREF_MAX_READ = "webextensions.native-messaging.max-input-message-bytes";
+const PREF_MAX_WRITE =
+  "webextensions.native-messaging.max-output-message-bytes";
+
+AddonTestUtils.init(this);
+AddonTestUtils.overrideCertDB();
+AddonTestUtils.createAppInfo(
+  "xpcshell@tests.mozilla.org",
+  "XPCShell",
+  "1",
+  "42"
+);
+
+const server = createHttpServer({ hosts: ["example.com"] });
+
+server.registerPathHandler("/dummy", (request, response) => {
+  response.setStatusLine(request.httpVersion, 200, "OK");
+  response.setHeader("Content-Type", "text/html", false);
+  response.write("<!DOCTYPE html><html></html>");
+});
+
+const ECHO_BODY = String.raw`
+  import struct
+  import sys
+
+  stdin = getattr(sys.stdin, 'buffer', sys.stdin)
+  stdout = getattr(sys.stdout, 'buffer', sys.stdout)
+
+  while True:
+    rawlen = stdin.read(4)
+    if len(rawlen) == 0:
+      sys.exit(0)
+    msglen = struct.unpack('@I', rawlen)[0]
+    msg = stdin.read(msglen)
+
+    stdout.write(struct.pack('@I', msglen))
+    stdout.write(msg)
+`;
+
+const INFO_BODY = String.raw`
+  import json
+  import os
+  import struct
+  import sys
+
+  msg = json.dumps({"args": sys.argv, "cwd": os.getcwd()})
+  if sys.version_info >= (3,):
+    sys.stdout.buffer.write(struct.pack('@I', len(msg)))
+  else:
+    sys.stdout.write(struct.pack('@I', len(msg)))
+  sys.stdout.write(msg)
+  sys.exit(0)
+`;
+
+const DELAYED_ECHO_BODY = String.raw`
+  import atexit
+  import json
+  import os
+  import struct
+  import sys
+  import time
+
+  stdin = getattr(sys.stdin, 'buffer', sys.stdin)
+  stdout = getattr(sys.stdout, 'buffer', sys.stdout)
+  pid = os.getpid()
+
+  sys.stderr.write("nativeapp with pid %d is running\n" % pid)
+
+  def onexit():
+    sys.stderr.write("nativeapp with pid %d is exiting\n" % pid)
+
+  atexit.register(onexit)
+
+  while True:
+    rawlen = stdin.read(4)
+    if len(rawlen) == 0:
+      sys.exit(0)
+    msglen = struct.unpack('@I', rawlen)[0]
+    msg = stdin.read(msglen)
+
+    sys.stderr.write(
+      "nativeapp with pid %d delaying echoing message '%s'\n" %
+      (pid, str(msg, 'utf-8'))
+    )
+
+    time.sleep(5)
+    stdout.write(struct.pack('@I', msglen))
+    stdout.write(msg)
+
+    sys.stderr.write(
+      "nativeapp with pid %d replied to message '%s'\n" %
+      (pid, str(msg, 'utf-8'))
+    )
+`;
+
+const STDERR_LINES = ["hello stderr", "this should be a separate line"];
+let STDERR_MSG = STDERR_LINES.join("\\n");
+
+const STDERR_BODY = String.raw`
+  import sys
+  sys.stderr.write("${STDERR_MSG}")
+`;
+
+const PLATFORM_PATH_SEP = AppConstants.platform == "win" ? "\\" : "/";
+
+let SCRIPTS = [
+  {
+    name: "echo",
+    description: "a native app that echoes back messages it receives",
+    script: ECHO_BODY.replace(/^ {2}/gm, ""),
+  },
+  {
+    name: "relative.echo",
+    description: "a native app that echoes; relative path instead of absolute",
+    script: ECHO_BODY.replace(/^ {2}/gm, ""),
+    _hookModifyManifest(manifest) {
+      manifest.path = PathUtils.filename(manifest.path);
+    },
+  },
+  {
+    name: "relative_dotdot.echo",
+    description: "a native app that echos; relative path with dot dot",
+    script: ECHO_BODY.replace(/^ {2}/gm, ""),
+    _hookModifyManifest(manifest) {
+      // Set to ..\NativeMessagingHosts\relative_dotdot.bat (Windows)
+      manifest.path = [
+        "..",
+        ...manifest.path.split(PLATFORM_PATH_SEP).slice(-2),
+      ].join(PLATFORM_PATH_SEP);
+    },
+  },
+  {
+    name: "renamed.echo",
+    description: "invalid manifest due to name mismatch",
+    script: ECHO_BODY.replace(/^ {2}/gm, ""),
+    _hookModifyManifest(manifest) {
+      manifest.name = "renamed_name_mismatch";
+    },
+  },
+  {
+    name: "nonstdio.echo",
+    description: "invalid manifest due to non-stdio type",
+    script: ECHO_BODY.replace(/^ {2}/gm, ""),
+    _hookModifyManifest(manifest) {
+      // schema only permits "stdio" or "pkcs11". Change from "stdio":
+      manifest.type = "pkcs11";
+    },
+  },
+  {
+    name: "forwardslash.echo",
+    description: "a native app that echos; with forward slash in path",
+    script: ECHO_BODY.replace(/^ {2}/gm, ""),
+    _hookModifyManifest(manifest) {
+      // On Linux/macOS, this doesn't change anything.
+      // On Windows, this turns C:\Program Files\... in C:/Program Files/...
+      manifest.path = manifest.path.replaceAll("\\", "/");
+    },
+  },
+  {
+    name: "dot.echo",
+    description: "a native app that echos; with dot slash in path",
+    script: ECHO_BODY.replace(/^ {2}/gm, ""),
+    _hookModifyManifest(manifest) {
+      // Replace / with /./ (or \ with \.\ on Windows).
+      manifest.path = manifest.path.replaceAll(
+        PLATFORM_PATH_SEP,
+        PLATFORM_PATH_SEP + "." + PLATFORM_PATH_SEP
+      );
+    },
+  },
+  {
+    name: "dotdot.echo",
+    description: "a native app that echos; with dot dot slash in path",
+    script: ECHO_BODY.replace(/^ {2}/gm, ""),
+    _hookModifyManifest(manifest) {
+      // The binary is in a directory called "TYPE_SLUG". Turn
+      // /TYPE_SLUG/ in /TYPE_SLUG/../TYPE_SLUG/ to have equivalent directories
+      // that ought to be considered a valid absolute path.
+      const dirWithSlashes = PLATFORM_PATH_SEP + TYPE_SLUG + PLATFORM_PATH_SEP;
+      manifest.path = manifest.path.replace(
+        dirWithSlashes,
+        dirWithSlashes + ".." + dirWithSlashes
+      );
+    },
+  },
+  {
+    name: "delayedecho",
+    description:
+      "a native app that echo messages received with a small artificial delay",
+    script: DELAYED_ECHO_BODY.replace(/^ {2}/gm, ""),
+  },
+  {
+    name: "info",
+    description: "a native app that gives some info about how it was started",
+    script: INFO_BODY.replace(/^ {2}/gm, ""),
+  },
+  {
+    name: "stderr",
+    description: "a native app that writes to stderr and then exits",
+    script: STDERR_BODY.replace(/^ {2}/gm, ""),
+  },
+];
+
+if (AppConstants.platform == "win") {
+  SCRIPTS.push({
+    name: "echocmd",
+    description: "echo but using a .cmd file",
+    scriptExtension: "cmd",
+    script: ECHO_BODY.replace(/^ {2}/gm, ""),
+  });
+}
+
+add_setup(async function setup() {
+  optionalPermissionsPromptHandler.init();
+  optionalPermissionsPromptHandler.acceptPrompt = true;
+  await AddonTestUtils.promiseStartupManager();
+
+  await setupHosts(SCRIPTS);
+});
+
+// Test the basic operation of native messaging with a simple
+// script that echoes back whatever message is sent to it.
+add_task(async function test_happy_path() {
+  async function background() {
+    let port;
+    browser.test.onMessage.addListener(async (what, payload) => {
+      if (what == "request") {
+        await browser.permissions.request({ permissions: ["nativeMessaging"] });
+        // connectNative requires permission
+        port = browser.runtime.connectNative("echo");
+        port.onMessage.addListener(msg => {
+          browser.test.sendMessage("message", msg);
+        });
+        browser.test.sendMessage("ready");
+      } else if (what == "send") {
+        if (payload._json) {
+          let json = payload._json;
+          payload.toJSON = () => json;
+          delete payload._json;
+        }
+        port.postMessage(payload);
+      }
+    });
+  }
+
+  let extension = ExtensionTestUtils.loadExtension({
+    background,
+    manifest: {
+      browser_specific_settings: { gecko: { id: ID } },
+      optional_permissions: ["nativeMessaging"],
+    },
+    useAddonManager: "temporary",
+  });
+
+  await extension.startup();
+  await withHandlingUserInput(extension, async () => {
+    extension.sendMessage("request");
+    await extension.awaitMessage("ready");
+  });
+  const tests = [
+    {
+      data: "this is a string",
+      what: "simple string",
+    },
+    {
+      data: "Это юникода",
+      what: "unicode string",
+    },
+    {
+      data: { test: "hello" },
+      what: "simple object",
+    },
+    {
+      data: {
+        what: "An object with a few properties",
+        number: 123,
+        bool: true,
+        nested: { what: "another object" },
+      },
+      what: "object with several properties",
+    },
+
+    {
+      data: {
+        ignoreme: true,
+        _json: { data: "i have a tojson method" },
+      },
+      expected: { data: "i have a tojson method" },
+      what: "object with toJSON() method",
+    },
+  ];
+  for (let test of tests) {
+    extension.sendMessage("send", test.data);
+    let response = await extension.awaitMessage("message");
+    let expected = test.expected || test.data;
+    deepEqual(response, expected, `Echoed a message of type ${test.what}`);
+  }
+
+  let procCount = await getSubprocessCount();
+  equal(procCount, 1, "subprocess is still running");
+  let exitPromise = waitForSubprocessExit();
+  await extension.unload();
+  await exitPromise;
+});
+
+// Just test that the given app (which should be the echo script above)
+// can be started.  Used to test corner cases in how the native application
+// is located/launched.
+async function simpleTest(app) {
+  function background(appname) {
+    let port = browser.runtime.connectNative(appname);
+    let MSG = "test";
+    port.onMessage.addListener(msg => {
+      browser.test.assertEq(MSG, msg, "Got expected message back");
+      browser.test.sendMessage("done");
+    });
+    port.postMessage(MSG);
+  }
+
+  let extension = ExtensionTestUtils.loadExtension({
+    background: `(${background})(${JSON.stringify(app)});`,
+    manifest: {
+      browser_specific_settings: { gecko: { id: ID } },
+      permissions: ["nativeMessaging"],
+    },
+  });
+
+  await extension.startup();
+  await extension.awaitMessage("done");
+
+  let procCount = await getSubprocessCount();
+  equal(procCount, 1, "subprocess is still running");
+  let exitPromise = waitForSubprocessExit();
+  await extension.unload();
+  await exitPromise;
+}
+
+async function testBrokenApp({
+  extensionId = ID,
+  appname,
+  expectedError,
+  expectedConsoleMessages,
+}) {
+  let extension = ExtensionTestUtils.loadExtension({
+    background() {
+      browser.test.onMessage.addListener(async (appname, expectedError) => {
+        await browser.test.assertRejects(
+          browser.runtime.sendNativeMessage(appname, "dummymsg"),
+          expectedError,
+          "Expected sendNativeMessage error"
+        );
+        browser.test.sendMessage("done");
+      });
+    },
+    manifest: {
+      browser_specific_settings: { gecko: { id: extensionId } },
+      permissions: ["nativeMessaging"],
+    },
+  });
+
+  await extension.startup();
+  let { messages } = await promiseConsoleOutput(async () => {
+    extension.sendMessage(appname, expectedError);
+    await extension.awaitMessage("done");
+  });
+  await extension.unload();
+
+  let procCount = await getSubprocessCount();
+  equal(procCount, 0, "No child process was started");
+
+  // Because we're using forbidUnexpected:true below, we have to account for
+  // all logged messages. RemoteSettings may try (and fail) to load remote
+  // settings - ignore the "NetworkError: Network request failed" error.
+  // To avoid having to update this filter all the time, select the specific
+  // modules relevant to native messaging from where we expect errors.
+  messages = messages.filter(m => {
+    return /NativeMessaging|NativeManifests|Subprocess/.test(m.message);
+  });
+
+  // On Linux/macOS, the setupHosts helper registers the same manifest file in
+  // multiple locations, which can result in the same error being printed
+  // multiple times. We de-duplicate that here.
+  let deduplicatedMessages = messages.filter(
+    (msg, i) => i === messages.findIndex(m => m.message === msg.message)
+  );
+
+  // Now check that all the log messages exist, in the expected order too.
+  AddonTestUtils.checkMessages(
+    deduplicatedMessages,
+    {
+      expected: expectedConsoleMessages.map(message => ({ message })),
+      forbidUnexpected: true,
+    },
+    "Expected messages in the console"
+  );
+}
+
+if (AppConstants.platform == "win") {
+  // "relative.echo" has a relative path in the host manifest.
+  add_task(function test_relative_path() {
+    // Note: relative paths only supported on Windows.
+    // For non-Windows, see test_relative_path_unsupported instead.
+    return simpleTest("relative.echo");
+  });
+
+  add_task(function test_relative_dotdot_path() {
+    // Note: relative paths only supported on Windows.
+    // For non-Windows, see test_relative_dotdot_path_unsupported instead.
+    return simpleTest("relative_dotdot.echo");
+  });
+
+  // "echocmd" uses a .cmd file instead of a .bat file
+  add_task(function test_cmd_file() {
+    return simpleTest("echocmd");
+  });
+} else {
+  // On non-Windows, relative paths are not supported.
+  add_task(function test_relative_path_unsupported() {
+    return testBrokenApp({
+      appname: "relative.echo",
+      expectedError: "An unexpected error occurred",
+      expectedConsoleMessages: [
+        /NativeApp requires absolute path to command on this platform/,
+      ],
+    });
+  });
+  add_task(function test_relative_dotdot_path_unsupported() {
+    return testBrokenApp({
+      appname: "relative_dotdot.echo",
+      expectedError: "An unexpected error occurred",
+      expectedConsoleMessages: [
+        /NativeApp requires absolute path to command on this platform/,
+      ],
+    });
+  });
+}
+
+add_task(async function test_absolute_path_dot_one() {
+  return simpleTest("dot.echo");
+});
+
+add_task(async function test_absolute_path_dotdot() {
+  return simpleTest("dotdot.echo");
+});
+
+add_task(async function test_error_name_mismatch() {
+  await testBrokenApp({
+    appname: "renamed.echo",
+    expectedError: "No such native application renamed.echo",
+    expectedConsoleMessages: [
+      /Native manifest .+ has name property renamed_name_mismatch \(expected renamed\.echo\)/,
+      /No such native application renamed\.echo/,
+    ],
+  });
+});
+
+add_task(async function test_invalid_manifest_type_not_stdio() {
+  await testBrokenApp({
+    appname: "nonstdio.echo",
+    expectedError: "No such native application nonstdio.echo",
+    expectedConsoleMessages: [
+      /Native manifest .+ has type property pkcs11 \(expected stdio\)/,
+      /No such native application nonstdio\.echo/,
+    ],
+  });
+});
+
+add_task(async function test_forward_slashes_in_path_works() {
+  await simpleTest("forwardslash.echo");
+});
+
+// Test sendNativeMessage()
+add_task(async function test_sendNativeMessage() {
+  async function background() {
+    let MSG = { test: "hello world" };
+
+    // Check error handling
+    await browser.test.assertRejects(
+      browser.runtime.sendNativeMessage("nonexistent", MSG),
+      "No such native application nonexistent",
+      "sendNativeMessage() to a nonexistent app failed"
+    );
+
+    // Check regular message exchange
+    let reply = await browser.runtime.sendNativeMessage("echo", MSG);
+
+    let expected = JSON.stringify(MSG);
+    let received = JSON.stringify(reply);
+    browser.test.assertEq(expected, received, "Received echoed native message");
+
+    browser.test.sendMessage("finished");
+  }
+
+  let extension = ExtensionTestUtils.loadExtension({
+    background,
+    manifest: {
+      browser_specific_settings: { gecko: { id: ID } },
+      permissions: ["nativeMessaging"],
+    },
+  });
+
+  await extension.startup();
+  await extension.awaitMessage("finished");
+
+  // With sendNativeMessage(), the subprocess should be disconnected
+  // after exchanging a single message.
+  await waitForSubprocessExit();
+
+  await extension.unload();
+});
+
+// Test calling Port.disconnect()
+add_task(async function test_disconnect() {
+  function background() {
+    let port = browser.runtime.connectNative("echo");
+    port.onMessage.addListener((msg, msgPort) => {
+      browser.test.assertEq(
+        port,
+        msgPort,
+        "onMessage handler should receive the port as the second argument"
+      );
+      browser.test.sendMessage("message", msg);
+    });
+    port.onDisconnect.addListener(msgPort => {
+      browser.test.fail("onDisconnect should not be called for disconnect()");
+    });
+    browser.test.onMessage.addListener((what, payload) => {
+      if (what == "send") {
+        if (payload._json) {
+          let json = payload._json;
+          payload.toJSON = () => json;
+          delete payload._json;
+        }
+        port.postMessage(payload);
+      } else if (what == "disconnect") {
+        try {
+          port.disconnect();
+          browser.test.assertThrows(
+            () => port.postMessage("void"),
+            "Attempt to postMessage on disconnected port"
+          );
+          browser.test.sendMessage("disconnect-result", { success: true });
+        } catch (err) {
+          browser.test.sendMessage("disconnect-result", {
+            success: false,
+            errmsg: err.message,
+          });
+        }
+      }
+    });
+    browser.test.sendMessage("ready");
+  }
+
+  let extension = ExtensionTestUtils.loadExtension({
+    background,
+    manifest: {
+      browser_specific_settings: { gecko: { id: ID } },
+      permissions: ["nativeMessaging"],
+    },
+  });
+
+  await extension.startup();
+  await extension.awaitMessage("ready");
+
+  extension.sendMessage("send", "test");
+  let response = await extension.awaitMessage("message");
+  equal(response, "test", "Echoed a string");
+
+  let procCount = await getSubprocessCount();
+  equal(procCount, 1, "subprocess is running");
+
+  extension.sendMessage("disconnect");
+  response = await extension.awaitMessage("disconnect-result");
+  equal(response.success, true, "disconnect succeeded");
+
+  info("waiting for subprocess to exit");
+  await waitForSubprocessExit();
+  procCount = await getSubprocessCount();
+  equal(procCount, 0, "subprocess is no longer running");
+
+  extension.sendMessage("disconnect");
+  response = await extension.awaitMessage("disconnect-result");
+  equal(response.success, true, "second call to disconnect silently ignored");
+
+  await extension.unload();
+});
+
+// Test the limit on message size for writing
+add_task(async function test_write_limit() {
+  Services.prefs.setIntPref(PREF_MAX_WRITE, 10);
+  function clearPref() {
+    Services.prefs.clearUserPref(PREF_MAX_WRITE);
+  }
+  registerCleanupFunction(clearPref);
+
+  function background() {
+    const PAYLOAD = "0123456789A";
+    let port = browser.runtime.connectNative("echo");
+    try {
+      port.postMessage(PAYLOAD);
+      browser.test.sendMessage("result", null);
+    } catch (ex) {
+      browser.test.sendMessage("result", ex.message);
+    }
+  }
+
+  let extension = ExtensionTestUtils.loadExtension({
+    background,
+    manifest: {
+      browser_specific_settings: { gecko: { id: ID } },
+      permissions: ["nativeMessaging"],
+    },
+  });
+
+  await extension.startup();
+
+  let errmsg = await extension.awaitMessage("result");
+  notEqual(
+    errmsg,
+    null,
+    "native postMessage() failed for overly large message"
+  );
+
+  await extension.unload();
+  await waitForSubprocessExit();
+
+  clearPref();
+});
+
+// Test the limit on message size for reading
+add_task(async function test_read_limit() {
+  Services.prefs.setIntPref(PREF_MAX_READ, 10);
+  function clearPref() {
+    Services.prefs.clearUserPref(PREF_MAX_READ);
+  }
+  registerCleanupFunction(clearPref);
+
+  function background() {
+    const PAYLOAD = "0123456789A";
+    let port = browser.runtime.connectNative("echo");
+    port.onDisconnect.addListener(msgPort => {
+      browser.test.assertEq(
+        port,
+        msgPort,
+        "onDisconnect handler should receive the port as the first argument"
+      );
+      browser.test.assertEq(
+        "Native application tried to send a message of 13 bytes, which exceeds the limit of 10 bytes.",
+        port.error && port.error.message
+      );
+      browser.test.sendMessage("result", "disconnected");
+    });
+    port.onMessage.addListener(msg => {
+      browser.test.sendMessage("result", "message");
+    });
+    port.postMessage(PAYLOAD);
+  }
+
+  let extension = ExtensionTestUtils.loadExtension({
+    background,
+    manifest: {
+      browser_specific_settings: { gecko: { id: ID } },
+      permissions: ["nativeMessaging"],
+    },
+  });
+
+  await extension.startup();
+
+  let result = await extension.awaitMessage("result");
+  equal(
+    result,
+    "disconnected",
+    "native port disconnected on receiving large message"
+  );
+
+  await extension.unload();
+  await waitForSubprocessExit();
+
+  clearPref();
+});
+
+// Test that an extension without the nativeMessaging permission cannot
+// use native messaging.
+add_task(async function test_ext_permission() {
+  function background() {
+    browser.test.assertEq(
+      chrome.runtime.connectNative,
+      undefined,
+      "chrome.runtime.connectNative does not exist without nativeMessaging permission"
+    );
+    browser.test.assertEq(
+      browser.runtime.connectNative,
+      undefined,
+      "browser.runtime.connectNative does not exist without nativeMessaging permission"
+    );
+    browser.test.assertEq(
+      chrome.runtime.sendNativeMessage,
+      undefined,
+      "chrome.runtime.sendNativeMessage does not exist without nativeMessaging permission"
+    );
+    browser.test.assertEq(
+      browser.runtime.sendNativeMessage,
+      undefined,
+      "browser.runtime.sendNativeMessage does not exist without nativeMessaging permission"
+    );
+    browser.test.sendMessage("finished");
+  }
+
+  let extension = ExtensionTestUtils.loadExtension({
+    background,
+    manifest: {},
+  });
+
+  await extension.startup();
+  await extension.awaitMessage("finished");
+  await extension.unload();
+});
+
+// Test that an extension that is not listed in allowed_extensions for
+// a native application cannot use that application.
+add_task(async function test_app_permission() {
+  await testBrokenApp({
+    extensionId: "@id-that-is-not-in-the-allowed_extensions-list",
+    appname: "echo",
+    expectedError: "No such native application echo",
+    expectedConsoleMessages: [
+      /This extension does not have permission to use native manifest .+echo\.json/,
+      /No such native application echo/,
+    ],
+  });
+});
+
+// Test that the command-line arguments and working directory for the
+// native application are as expected.
+add_task(async function test_child_process() {
+  function background() {
+    let port = browser.runtime.connectNative("info");
+    port.onMessage.addListener(msg => {
+      browser.test.sendMessage("result", msg);
+    });
+  }
+
+  let extension = ExtensionTestUtils.loadExtension({
+    background,
+    manifest: {
+      browser_specific_settings: { gecko: { id: ID } },
+      permissions: ["nativeMessaging"],
+    },
+  });
+
+  await extension.startup();
+
+  let msg = await extension.awaitMessage("result");
+  equal(msg.args.length, 3, "Received two command line arguments");
+  equal(
+    msg.args[1],
+    getPath("info.json"),
+    "Command line argument is the path to the native host manifest"
+  );
+  equal(
+    msg.args[2],
+    ID,
+    "Second command line argument is the ID of the calling extension"
+  );
+  equal(
+    msg.cwd.replace(/^\/private\//, "/"),
+    PathUtils.join(tmpDir.path, TYPE_SLUG),
+    "Working directory is the directory containing the native appliation"
+  );
+
+  let exitPromise = waitForSubprocessExit();
+  await extension.unload();
+  await exitPromise;
+});
+
+add_task(async function test_stderr() {
+  function background() {
+    let port = browser.runtime.connectNative("stderr");
+    port.onDisconnect.addListener(msgPort => {
+      browser.test.assertEq(
+        port,
+        msgPort,
+        "onDisconnect handler should receive the port as the first argument"
+      );
+      browser.test.assertEq(
+        null,
+        port.error,
+        "Normal application exit is not an error"
+      );
+      browser.test.sendMessage("finished");
+    });
+  }
+
+  let { messages } = await promiseConsoleOutput(async function () {
+    let extension = ExtensionTestUtils.loadExtension({
+      background,
+      manifest: {
+        browser_specific_settings: { gecko: { id: ID } },
+        permissions: ["nativeMessaging"],
+      },
+    });
+
+    await extension.startup();
+    await extension.awaitMessage("finished");
+    await extension.unload();
+
+    await waitForSubprocessExit();
+  });
+
+  let lines = STDERR_LINES.map(line =>
+    messages.findIndex(msg => msg.message.includes(line))
+  );
+  notEqual(lines[0], -1, "Saw first line of stderr output on the console");
+  notEqual(lines[1], -1, "Saw second line of stderr output on the console");
+  notEqual(
+    lines[0],
+    lines[1],
+    "Stderr output lines are separated in the console"
+  );
+});
+
+// Test that calling connectNative() multiple times works
+// (see bug 1313980 for a previous regression in this area)
+add_task(async function test_multiple_connects() {
+  async function background() {
+    function once() {
+      return new Promise(resolve => {
+        let MSG = "hello";
+        let port = browser.runtime.connectNative("echo");
+
+        port.onMessage.addListener(msg => {
+          browser.test.assertEq(MSG, msg, "Got expected message back");
+          port.disconnect();
+          resolve();
+        });
+        port.postMessage(MSG);
+      });
+    }
+
+    await once();
+    await once();
+    browser.test.notifyPass("multiple-connect");
+  }
+
+  let extension = ExtensionTestUtils.loadExtension({
+    background,
+    manifest: {
+      browser_specific_settings: { gecko: { id: ID } },
+      permissions: ["nativeMessaging"],
+    },
+  });
+
+  await extension.startup();
+  await extension.awaitFinish("multiple-connect");
+  await extension.unload();
+});
+
+// Test that native messaging is always rejected on content scripts
+add_task(async function test_connect_native_from_content_script() {
+  async function testScript() {
+    let port = browser.runtime.connectNative("echo");
+    port.onDisconnect.addListener(msgPort => {
+      browser.test.assertEq(
+        port,
+        msgPort,
+        "onDisconnect handler should receive the port as the first argument"
+      );
+      browser.test.assertEq(
+        "An unexpected error occurred",
+        port.error && port.error.message
+      );
+      browser.test.sendMessage("result", "disconnected");
+    });
+    port.onMessage.addListener(msg => {
+      browser.test.sendMessage("result", "message");
+    });
+    port.postMessage({ test: "test" });
+  }
+
+  let extension = ExtensionTestUtils.loadExtension({
+    manifest: {
+      content_scripts: [
+        {
+          run_at: "document_end",
+          js: ["test.js"],
+          matches: ["http://example.com/dummy"],
+        },
+      ],
+      browser_specific_settings: { gecko: { id: ID } },
+      permissions: ["nativeMessaging"],
+    },
+    files: {
+      "test.js": testScript,
+    },
+  });
+
+  await extension.startup();
+
+  const page = await ExtensionTestUtils.loadContentPage(
+    "http://example.com/dummy"
+  );
+
+  let result = await extension.awaitMessage("result");
+  equal(result, "disconnected", "connectNative() failed from content script");
+
+  await page.close();
+  await extension.unload();
+
+  let procCount = await getSubprocessCount();
+  equal(procCount, 0, "No child process was started");
+});
+
+// Testing native app messaging against idle timeout.
+async function startupExtensionAndRequestPermission() {
+  const extension = ExtensionTestUtils.loadExtension({
+    useAddonManager: "temporary",
+    manifest: {
+      browser_specific_settings: { gecko: { id: ID } },
+      optional_permissions: ["nativeMessaging"],
+      background: { persistent: false },
+    },
+    async background() {
+      browser.runtime.onSuspend.addListener(() => {
+        browser.test.sendMessage("bgpage:suspending");
+      });
+
+      let port;
+      browser.test.onMessage.addListener(async (msg, ...args) => {
+        switch (msg) {
+          case "request-permission": {
+            await browser.permissions.request({
+              permissions: ["nativeMessaging"],
+            });
+            break;
+          }
+          case "delayedecho-sendmessage": {
+            browser.runtime
+              .sendNativeMessage("delayedecho", args[0])
+              .then(msg =>
+                browser.test.sendMessage(
+                  `delayedecho-sendmessage:got-reply`,
+                  msg
+                )
+              );
+            break;
+          }
+          case "connectNative": {
+            if (port) {
+              browser.test.fail(`Unexpected already connected NativeApp port`);
+            } else {
+              port = browser.runtime.connectNative("echo");
+            }
+            break;
+          }
+          case "disconnectNative": {
+            if (!port) {
+              browser.test.fail(`Unexpected undefined NativeApp port`);
+            }
+            port?.disconnect();
+            break;
+          }
+          default:
+            browser.test.fail(`Got an unexpected test message: ${msg}`);
+        }
+
+        browser.test.sendMessage(`${msg}:done`);
+      });
+      browser.test.sendMessage("bg:ready");
+    },
+  });
+  await extension.startup();
+  await extension.awaitMessage("bg:ready");
+  const contextId = extension.extension.backgroundContext.contextId;
+  notEqual(contextId, undefined, "Got a contextId for the background context");
+
+  await withHandlingUserInput(extension, async () => {
+    extension.sendMessage("request-permission");
+    await extension.awaitMessage("request-permission:done");
+  });
+
+  return { extension, contextId };
+}
+
+async function expectTerminateBackgroundToResetIdle({ extension, contextId }) {
+  info("Wait for hasActiveNativeAppPorts to become true");
+  await TestUtils.waitForCondition(
+    () => extension.extension.backgroundContext,
+    "Parent proxy context should be active"
+  );
+
+  await TestUtils.waitForCondition(
+    () => extension.extension.backgroundContext?.hasActiveNativeAppPorts,
+    "Parent proxy context should have active native app ports tracked"
+  );
+
+  clearHistograms();
+  assertHistogramEmpty(WEBEXT_EVENTPAGE_IDLE_RESULT_COUNT);
+  assertKeyedHistogramEmpty(WEBEXT_EVENTPAGE_IDLE_RESULT_COUNT_BY_ADDONID);
+
+  info("Trigger background script idle timeout and expect to be reset");
+  const promiseResetIdle = promiseExtensionEvent(
+    extension,
+    "background-script-reset-idle"
+  );
+  await extension.terminateBackground();
+  info("Wait for 'background-script-reset-idle' event to be emitted");
+  await promiseResetIdle;
+  equal(
+    extension.extension.backgroundContext.contextId,
+    contextId,
+    "Initial background context is still available as expected"
+  );
+
+  assertHistogramCategoryNotEmpty(WEBEXT_EVENTPAGE_IDLE_RESULT_COUNT, {
+    category: "reset_nativeapp",
+    categories: HISTOGRAM_EVENTPAGE_IDLE_RESULT_CATEGORIES,
+  });
+
+  assertHistogramCategoryNotEmpty(
+    WEBEXT_EVENTPAGE_IDLE_RESULT_COUNT_BY_ADDONID,
+    {
+      keyed: true,
+      key: extension.id,
+      category: "reset_nativeapp",
+      categories: HISTOGRAM_EVENTPAGE_IDLE_RESULT_CATEGORIES,
+    }
+  );
+}
+
+async function testSendNativeMessage({ extension, contextId }) {
+  extension.sendMessage("delayedecho-sendmessage", "delayed-echo");
+  await extension.awaitMessage("delayedecho-sendmessage:done");
+
+  await expectTerminateBackgroundToResetIdle({ extension, contextId });
+
+  // We expect exactly two replies (one for the previous queued message
+  // and one more for the last message sent right above).
+  equal(
+    await extension.awaitMessage("delayedecho-sendmessage:got-reply"),
+    "delayed-echo",
+    "Got the expected reply for the first message sent"
+  );
+
+  await TestUtils.waitForCondition(
+    () => !extension.extension.backgroundContext?.hasActiveNativeAppPorts,
+    "Parent proxy context should not have any active native app ports tracked"
+  );
+
+  info("terminating the background script");
+  await extension.terminateBackground();
+  info("wait for runtime.onSuspend listener to have been called");
+  await extension.awaitMessage("bgpage:suspending");
+}
+
+async function testConnectNative({ extension, contextId }) {
+  extension.sendMessage("connectNative");
+  await extension.awaitMessage("connectNative:done");
+
+  await expectTerminateBackgroundToResetIdle({ extension, contextId });
+
+  // Disconnect the NativeApp and confirm that the background page
+  // will be suspending as expected.
+  extension.sendMessage("disconnectNative");
+  await extension.awaitMessage("disconnectNative:done");
+
+  await TestUtils.waitForCondition(
+    () => !extension.extension.backgroundContext?.hasActiveNativeAppPorts,
+    "Parent proxy context should not have any active native app ports tracked"
+  );
+
+  info("terminating the background script");
+  await extension.terminateBackground();
+  info("wait for runtime.onSuspend listener to have been called");
+  await extension.awaitMessage("bgpage:suspending");
+}
+
+add_task(
+  {
+    pref_set: [["extensions.eventPages.enabled", true]],
+  },
+  async function test_pending_sendNativeMessageReply_resets_bgscript_idle_timeout() {
+    const { extension, contextId } =
+      await startupExtensionAndRequestPermission();
+    await testSendNativeMessage({ extension, contextId });
+    await waitForSubprocessExit();
+    await extension.unload();
+  }
+);
+
+add_task(
+  {
+    pref_set: [["extensions.eventPages.enabled", true]],
+  },
+  async function test_open_connectNativePort_resets_bgscript_idle_timeout() {
+    const { extension, contextId } =
+      await startupExtensionAndRequestPermission();
+    await testConnectNative({ extension, contextId });
+    await waitForSubprocessExit();
+    await extension.unload();
+  }
+);
diff --git a/toolkit/components/extensions/test/xpcshell/test_ext_native_messaging_perf.js b/toolkit/components/extensions/test/xpcshell/test_ext_native_messaging_perf.js
new file mode 100644
index 0000000000..7c5d09dc39
--- /dev/null
+++ b/toolkit/components/extensions/test/xpcshell/test_ext_native_messaging_perf.js
@@ -0,0 +1,130 @@
+/* -*- Mode: indent-tabs-mode: nil; js-indent-level: 2 -*- */
+/* vim: set sts=2 sw=2 et tw=80: */
+"use strict";
+
+const MAX_ROUND_TRIP_TIME_MS =
+  AppConstants.DEBUG || AppConstants.ASAN ? 60 : 30;
+const MAX_RETRIES = 5;
+
+const ECHO_BODY = String.raw`
+  import struct
+  import sys
+
+  stdin = getattr(sys.stdin, 'buffer', sys.stdin)
+  stdout = getattr(sys.stdout, 'buffer', sys.stdout)
+
+  while True:
+    rawlen = stdin.read(4)
+    if len(rawlen) == 0:
+      sys.exit(0)
+
+    msglen = struct.unpack('@I', rawlen)[0]
+    msg = stdin.read(msglen)
+
+    stdout.write(struct.pack('@I', msglen))
+    stdout.write(msg)
+`;
+
+const SCRIPTS = [
+  {
+    name: "echo",
+    description: "A native app that echoes back messages it receives",
+    script: ECHO_BODY.replace(/^ {2}/gm, ""),
+  },
+];
+
+add_task(async function setup() {
+  await setupHosts(SCRIPTS);
+});
+
+add_task(async function test_round_trip_perf() {
+  let extension = ExtensionTestUtils.loadExtension({
+    background() {
+      browser.test.onMessage.addListener(msg => {
+        if (msg != "run-tests") {
+          return;
+        }
+
+        let port = browser.runtime.connectNative("echo");
+
+        function next() {
+          port.postMessage({
+            Lorem: {
+              ipsum: {
+                dolor: [
+                  "sit amet",
+                  "consectetur adipiscing elit",
+                  "sed do eiusmod tempor incididunt ut labore et dolore magna aliqua.",
+                ],
+                "Ut enim": [
+                  "ad minim veniam",
+                  "quis nostrud exercitation ullamco",
+                  "laboris nisi ut aliquip ex ea commodo consequat.",
+                ],
+                Duis: [
+                  "aute irure dolor in reprehenderit in",
+                  "voluptate velit esse cillum dolore eu",
+                  "fugiat nulla pariatur.",
+                ],
+                Excepteur: [
+                  "sint occaecat cupidatat non proident",
+                  "sunt in culpa qui officia deserunt",
+                  "mollit anim id est laborum.",
+                ],
+              },
+            },
+          });
+        }
+
+        const COUNT = 1000;
+        let now;
+        function finish() {
+          let roundTripTime = (Date.now() - now) / COUNT;
+
+          port.disconnect();
+          browser.test.sendMessage("result", roundTripTime);
+        }
+
+        let count = 0;
+        port.onMessage.addListener(() => {
+          if (count == 0) {
+            // Skip the first round, since it includes the time it takes
+            // the app to start up.
+            now = Date.now();
+          }
+
+          if (count++ <= COUNT) {
+            next();
+          } else {
+            finish();
+          }
+        });
+
+        next();
+      });
+    },
+    manifest: {
+      browser_specific_settings: { gecko: { id: ID } },
+      permissions: ["nativeMessaging"],
+    },
+  });
+
+  await extension.startup();
+
+  let roundTripTime = Infinity;
+  for (
+    let i = 0;
+    i < MAX_RETRIES && roundTripTime > MAX_ROUND_TRIP_TIME_MS;
+    i++
+  ) {
+    extension.sendMessage("run-tests");
+    roundTripTime = await extension.awaitMessage("result");
+  }
+
+  await extension.unload();
+
+  ok(
+    roundTripTime <= MAX_ROUND_TRIP_TIME_MS,
+    `Expected round trip time (${roundTripTime}ms) to be less than ${MAX_ROUND_TRIP_TIME_MS}ms`
+  );
+});
diff --git a/toolkit/components/extensions/test/xpcshell/test_ext_native_messaging_unresponsive.js b/toolkit/components/extensions/test/xpcshell/test_ext_native_messaging_unresponsive.js
new file mode 100644
index 0000000000..5b30a06a23
--- /dev/null
+++ b/toolkit/components/extensions/test/xpcshell/test_ext_native_messaging_unresponsive.js
@@ -0,0 +1,85 @@
+/* -*- Mode: indent-tabs-mode: nil; js-indent-level: 2 -*- */
+/* vim: set sts=2 sw=2 et tw=80: */
+"use strict";
+
+const WONTDIE_BODY = String.raw`
+  import signal
+  import struct
+  import sys
+  import time
+
+  signal.signal(signal.SIGTERM, signal.SIG_IGN)
+
+  stdin = getattr(sys.stdin, 'buffer', sys.stdin)
+  stdout = getattr(sys.stdout, 'buffer', sys.stdout)
+
+  def spin():
+    while True:
+      try:
+        signal.pause()
+      except AttributeError:
+        time.sleep(5)
+
+  while True:
+    rawlen = stdin.read(4)
+    if len(rawlen) == 0:
+      spin()
+
+    msglen = struct.unpack('@I', rawlen)[0]
+    msg = stdin.read(msglen)
+
+    stdout.write(struct.pack('@I', msglen))
+    stdout.write(msg)
+`;
+
+const SCRIPTS = [
+  {
+    name: "wontdie",
+    description:
+      "a native app that does not exit when stdin closes or on SIGTERM",
+    script: WONTDIE_BODY.replace(/^ {2}/gm, ""),
+  },
+];
+
+add_task(async function setup() {
+  await setupHosts(SCRIPTS);
+});
+
+// Test that an unresponsive native application still gets killed eventually
+add_task(async function test_unresponsive_native_app() {
+  // XXX expose GRACEFUL_SHUTDOWN_TIME as a pref and reduce it
+  // just for this test?
+
+  function background() {
+    let port = browser.runtime.connectNative("wontdie");
+
+    const MSG = "echo me";
+    // bounce a message to make sure the process actually starts
+    port.onMessage.addListener(msg => {
+      browser.test.assertEq(msg, MSG, "Received echoed message");
+      browser.test.sendMessage("ready");
+    });
+    port.postMessage(MSG);
+  }
+
+  let extension = ExtensionTestUtils.loadExtension({
+    background,
+    manifest: {
+      browser_specific_settings: { gecko: { id: ID } },
+      permissions: ["nativeMessaging"],
+    },
+  });
+
+  await extension.startup();
+  await extension.awaitMessage("ready");
+
+  let procCount = await getSubprocessCount();
+  equal(procCount, 1, "subprocess is running");
+
+  let exitPromise = waitForSubprocessExit();
+  await extension.unload();
+  await exitPromise;
+
+  procCount = await getSubprocessCount();
+  equal(procCount, 0, "subprocess was successfully killed");
+});
diff --git a/toolkit/components/extensions/test/xpcshell/test_ext_networkStatus.js b/toolkit/components/extensions/test/xpcshell/test_ext_networkStatus.js
new file mode 100644
index 0000000000..5d94a1534d
--- /dev/null
+++ b/toolkit/components/extensions/test/xpcshell/test_ext_networkStatus.js
@@ -0,0 +1,209 @@
+"use strict";
+
+const Cm = Components.manager;
+
+const uuidGenerator = Services.uuid;
+
+AddonTestUtils.init(this);
+
+var mockNetworkStatusService = {
+  contractId: "@mozilla.org/network/network-link-service;1",
+
+  _mockClassId: uuidGenerator.generateUUID(),
+
+  _originalClassId: "",
+
+  QueryInterface: ChromeUtils.generateQI(["nsINetworkLinkService"]),
+
+  createInstance(iiD) {
+    return this.QueryInterface(iiD);
+  },
+
+  register() {
+    let registrar = Cm.QueryInterface(Ci.nsIComponentRegistrar);
+    if (!registrar.isCIDRegistered(this._mockClassId)) {
+      this._originalClassId = registrar.contractIDToCID(this.contractId);
+      registrar.registerFactory(
+        this._mockClassId,
+        "Unregister after testing",
+        this.contractId,
+        this
+      );
+    }
+  },
+
+  unregister() {
+    let registrar = Cm.QueryInterface(Ci.nsIComponentRegistrar);
+    registrar.unregisterFactory(this._mockClassId, this);
+    registrar.registerFactory(this._originalClassId, "", this.contractId, null);
+  },
+
+  _isLinkUp: true,
+  _linkStatusKnown: false,
+  _linkType: Ci.nsINetworkLinkService.LINK_TYPE_UNKNOWN,
+
+  get isLinkUp() {
+    return this._isLinkUp;
+  },
+
+  get linkStatusKnown() {
+    return this._linkStatusKnown;
+  },
+
+  setLinkStatus(status) {
+    switch (status) {
+      case "up":
+        this._isLinkUp = true;
+        this._linkStatusKnown = true;
+        this._networkID = "foo";
+        break;
+      case "down":
+        this._isLinkUp = false;
+        this._linkStatusKnown = true;
+        this._linkType = Ci.nsINetworkLinkService.LINK_TYPE_UNKNOWN;
+        this._networkID = undefined;
+        break;
+      case "changed":
+        this._linkStatusKnown = true;
+        this._networkID = "foo";
+        break;
+      case "unknown":
+        this._linkStatusKnown = false;
+        this._linkType = Ci.nsINetworkLinkService.LINK_TYPE_UNKNOWN;
+        this._networkID = undefined;
+        break;
+    }
+    Services.obs.notifyObservers(null, "network:link-status-changed", status);
+  },
+
+  get linkType() {
+    return this._linkType;
+  },
+
+  setLinkType(val) {
+    this._linkType = val;
+    this._linkStatusKnown = true;
+    this._isLinkUp = true;
+    this._networkID = "bar";
+    Services.obs.notifyObservers(
+      null,
+      "network:link-type-changed",
+      this._linkType
+    );
+  },
+
+  get networkID() {
+    return this._networkID;
+  },
+};
+
+// nsINetworkLinkService is not directly testable. With the mock service above,
+// we just exercise a couple small things here to validate the api works somewhat.
+add_task(async function test_networkStatus() {
+  mockNetworkStatusService.register();
+  let extension = ExtensionTestUtils.loadExtension({
+    manifest: {
+      browser_specific_settings: {
+        gecko: { id: "networkstatus@tests.mozilla.org" },
+      },
+      permissions: ["networkStatus"],
+    },
+    isPrivileged: true,
+    async background() {
+      browser.networkStatus.onConnectionChanged.addListener(async details => {
+        browser.test.log(`connection status ${JSON.stringify(details)}`);
+        browser.test.sendMessage("connect-changed", {
+          details,
+          linkInfo: await browser.networkStatus.getLinkInfo(),
+        });
+      });
+      browser.test.sendMessage(
+        "linkdata",
+        await browser.networkStatus.getLinkInfo()
+      );
+    },
+  });
+
+  async function test(expected, change) {
+    if (change.status) {
+      info(`test link change status to ${change.status}`);
+      mockNetworkStatusService.setLinkStatus(change.status);
+    } else if (change.link) {
+      info(`test link change type to ${change.link}`);
+      mockNetworkStatusService.setLinkType(change.link);
+    }
+    let { details, linkInfo } = await extension.awaitMessage("connect-changed");
+    equal(details.type, expected.type, "network type is correct");
+    equal(details.status, expected.status, `network status is correct`);
+    equal(details.id, expected.id, "network id");
+    Assert.deepEqual(
+      linkInfo,
+      details,
+      "getLinkInfo should resolve to the same details received from onConnectionChanged"
+    );
+  }
+
+  await extension.startup();
+
+  let data = await extension.awaitMessage("linkdata");
+  equal(data.type, "unknown", "network type is unknown");
+  equal(data.status, "unknown", `network status is ${data.status}`);
+  equal(data.id, undefined, "network id");
+
+  await test(
+    { type: "unknown", status: "up", id: "foo" },
+    { status: "changed" }
+  );
+
+  await test(
+    { type: "wifi", status: "up", id: "bar" },
+    { link: Ci.nsINetworkLinkService.LINK_TYPE_WIFI }
+  );
+
+  await test({ type: "unknown", status: "down" }, { status: "down" });
+
+  await test({ type: "unknown", status: "unknown" }, { status: "unknown" });
+
+  await extension.unload();
+  mockNetworkStatusService.unregister();
+});
+
+add_task(
+  {
+    // Some builds (e.g. thunderbird) have experiments enabled by default.
+    pref_set: [["extensions.experiments.enabled", false]],
+  },
+  async function test_networkStatus_permission() {
+    let extension = ExtensionTestUtils.loadExtension({
+      temporarilyInstalled: true,
+      isPrivileged: false,
+      manifest: {
+        browser_specific_settings: {
+          gecko: { id: "networkstatus-permission@tests.mozilla.org" },
+        },
+        permissions: ["networkStatus"],
+      },
+    });
+    ExtensionTestUtils.failOnSchemaWarnings(false);
+    let { messages } = await promiseConsoleOutput(async () => {
+      await Assert.rejects(
+        extension.startup(),
+        /Using the privileged permission/,
+        "Startup failed with privileged permission"
+      );
+    });
+    ExtensionTestUtils.failOnSchemaWarnings(true);
+    AddonTestUtils.checkMessages(
+      messages,
+      {
+        expected: [
+          {
+            message:
+              /Using the privileged permission 'networkStatus' requires a privileged add-on/,
+          },
+        ],
+      },
+      true
+    );
+  }
+);
diff --git a/toolkit/components/extensions/test/xpcshell/test_ext_notifications_incognito.js b/toolkit/components/extensions/test/xpcshell/test_ext_notifications_incognito.js
new file mode 100644
index 0000000000..fda60c3a82
--- /dev/null
+++ b/toolkit/components/extensions/test/xpcshell/test_ext_notifications_incognito.js
@@ -0,0 +1,105 @@
+/* -*- Mode: indent-tabs-mode: nil; js-indent-level: 2 -*- */
+/* vim: set sts=2 sw=2 et tw=80: */
+"use strict";
+
+const ALERTS_SERVICE_CONTRACT_ID = "@mozilla.org/alerts-service;1";
+
+const createdAlerts = [];
+
+const mockAlertsService = {
+  showPersistentNotification(persistentData, alert, alertListener) {
+    this.showAlert(alert, alertListener);
+  },
+
+  showAlert(alert, listener) {
+    createdAlerts.push(alert);
+    listener.observe(null, "alertfinished", alert.cookie);
+  },
+
+  showAlertNotification(
+    imageUrl,
+    title,
+    text,
+    textClickable,
+    cookie,
+    alertListener,
+    name,
+    dir,
+    lang,
+    data,
+    principal,
+    privateBrowsing
+  ) {
+    this.showAlert({ cookie, title, text, privateBrowsing }, alertListener);
+  },
+
+  closeAlert(name) {
+    // This mock immediately close the alert on show, so this is empty.
+  },
+
+  QueryInterface: ChromeUtils.generateQI(["nsIAlertsService"]),
+
+  createInstance(iid) {
+    return this.QueryInterface(iid);
+  },
+};
+
+const registrar = Components.manager.QueryInterface(Ci.nsIComponentRegistrar);
+registrar.registerFactory(
+  Components.ID("{173a036a-d678-4415-9cff-0baff6bfe554}"),
+  "alerts service",
+  ALERTS_SERVICE_CONTRACT_ID,
+  mockAlertsService
+);
+
+add_task(async function test_notification_privateBrowsing_flag() {
+  let extension = ExtensionTestUtils.loadExtension({
+    incognitoOverride: "spanning",
+    manifest: {
+      permissions: ["notifications"],
+    },
+    files: {
+      "page.html": `<meta charset="utf-8"><script src="page.js"></script>`,
+      async "page.js"() {
+        let closedPromise = new Promise(resolve => {
+          browser.notifications.onClosed.addListener(resolve);
+        });
+        let createdId = await browser.notifications.create("notifid", {
+          type: "basic",
+          title: "titl",
+          message: "msg",
+        });
+        let closedId = await closedPromise;
+        browser.test.assertEq(createdId, closedId, "ID of closed notification");
+        browser.test.assertEq(
+          "{}",
+          JSON.stringify(await browser.notifications.getAll()),
+          "no notifications left"
+        );
+        browser.test.sendMessage("notification_closed");
+      },
+    },
+  });
+  await extension.startup();
+
+  async function checkPrivateBrowsingFlag(privateBrowsing) {
+    let contentPage = await ExtensionTestUtils.loadContentPage(
+      `moz-extension://${extension.uuid}/page.html`,
+      { extension, remote: extension.extension.remote, privateBrowsing }
+    );
+    await extension.awaitMessage("notification_closed");
+    await contentPage.close();
+
+    Assert.equal(createdAlerts.length, 1, "expected one alert");
+    let notification = createdAlerts.shift();
+    Assert.equal(notification.cookie, "notifid", "notification id");
+    Assert.equal(notification.title, "titl", "notification title");
+    Assert.equal(notification.text, "msg", "notification text");
+    Assert.equal(notification.privateBrowsing, privateBrowsing, "pbm flag");
+  }
+
+  await checkPrivateBrowsingFlag(false);
+  await checkPrivateBrowsingFlag(true);
+
+  await extension.unload();
+});
diff --git a/toolkit/components/extensions/test/xpcshell/test_ext_notifications_unsupported.js b/toolkit/components/extensions/test/xpcshell/test_ext_notifications_unsupported.js
new file mode 100644
index 0000000000..1213ae4f23
--- /dev/null
+++ b/toolkit/components/extensions/test/xpcshell/test_ext_notifications_unsupported.js
@@ -0,0 +1,41 @@
+/* -*- Mode: indent-tabs-mode: nil; js-indent-level: 2 -*- */
+/* vim: set sts=2 sw=2 et tw=80: */
+"use strict";
+
+const ALERTS_SERVICE_CONTRACT_ID = "@mozilla.org/alerts-service;1";
+const registrar = Components.manager.QueryInterface(Ci.nsIComponentRegistrar);
+registrar.registerFactory(
+  Components.ID("{18f25bb4-ab12-4e24-b3b0-69215056160b}"),
+  "unsupported alerts service",
+  ALERTS_SERVICE_CONTRACT_ID,
+  {} // This object lacks an implementation of nsIAlertsService.
+);
+
+add_task(async function test_notification_unsupported_backend() {
+  let extension = ExtensionTestUtils.loadExtension({
+    manifest: {
+      permissions: ["notifications"],
+    },
+    async background() {
+      let closedPromise = new Promise(resolve => {
+        browser.notifications.onClosed.addListener(resolve);
+      });
+      let createdId = await browser.notifications.create("notifid", {
+        type: "basic",
+        title: "titl",
+        message: "msg",
+      });
+      let closedId = await closedPromise;
+      browser.test.assertEq(createdId, closedId, "ID of closed notification");
+      browser.test.assertEq(
+        "{}",
+        JSON.stringify(await browser.notifications.getAll()),
+        "no notifications left"
+      );
+      browser.test.sendMessage("notification_closed");
+    },
+  });
+  await extension.startup();
+  await extension.awaitMessage("notification_closed");
+  await extension.unload();
+});
diff --git a/toolkit/components/extensions/test/xpcshell/test_ext_onmessage_removelistener.js b/toolkit/components/extensions/test/xpcshell/test_ext_onmessage_removelistener.js
new file mode 100644
index 0000000000..c6d258c96c
--- /dev/null
+++ b/toolkit/components/extensions/test/xpcshell/test_ext_onmessage_removelistener.js
@@ -0,0 +1,30 @@
+/* -*- Mode: indent-tabs-mode: nil; js-indent-level: 2 -*- */
+/* vim: set sts=2 sw=2 et tw=80: */
+"use strict";
+
+function backgroundScript() {
+  function listener() {
+    browser.test.notifyFail("listener should not be invoked");
+  }
+
+  browser.runtime.onMessage.addListener(listener);
+  browser.runtime.onMessage.removeListener(listener);
+  browser.runtime.sendMessage("hello");
+
+  // Make sure that, if we somehow fail to remove the listener, then we'll run
+  // the listener before the test is marked as passing.
+  setTimeout(function () {
+    browser.test.notifyPass("onmessage_removelistener");
+  }, 0);
+}
+
+let extensionData = {
+  background: backgroundScript,
+};
+
+add_task(async function test_contentscript() {
+  let extension = ExtensionTestUtils.loadExtension(extensionData);
+  await extension.startup();
+  await extension.awaitFinish("onmessage_removelistener");
+  await extension.unload();
+});
diff --git a/toolkit/components/extensions/test/xpcshell/test_ext_performance_counters.js b/toolkit/components/extensions/test/xpcshell/test_ext_performance_counters.js
new file mode 100644
index 0000000000..1a14ff6eb6
--- /dev/null
+++ b/toolkit/components/extensions/test/xpcshell/test_ext_performance_counters.js
@@ -0,0 +1,86 @@
+/* -*- Mode: indent-tabs-mode: nil; js-indent-level: 2 -*- */
+/* vim: set sts=2 sw=2 et tw=80: */
+"use strict";
+
+const { ExtensionParent } = ChromeUtils.importESModule(
+  "resource://gre/modules/ExtensionParent.sys.mjs"
+);
+
+const ENABLE_COUNTER_PREF =
+  "extensions.webextensions.enablePerformanceCounters";
+const TIMING_MAX_AGE = "extensions.webextensions.performanceCountersMaxAge";
+
+let { ParentAPIManager } = ExtensionParent;
+
+function sleep(ms) {
+  return new Promise(resolve => setTimeout(resolve, ms)); // eslint-disable-line mozilla/no-arbitrary-setTimeout
+}
+
+async function retrieveSpecificCounter(apiName, expectedCount) {
+  let currentCount = 0;
+  let data;
+  while (currentCount < expectedCount) {
+    data = await ParentAPIManager.retrievePerformanceCounters();
+    for (let [console, counters] of data) {
+      for (let [api, counter] of counters) {
+        if (api == apiName) {
+          currentCount += counter.calls;
+        }
+      }
+    }
+    await sleep(100);
+  }
+  return data;
+}
+
+async function test_counter() {
+  async function background() {
+    // creating a bookmark is done in the parent
+    let folder = await browser.bookmarks.create({ title: "Folder" });
+    await browser.bookmarks.create({
+      title: "Bookmark",
+      url: "http://example.com",
+      parentId: folder.id,
+    });
+
+    // getURL() is done in the child, let do three
+    browser.runtime.getURL("beasts/frog.html");
+    browser.runtime.getURL("beasts/frog2.html");
+    browser.runtime.getURL("beasts/frog3.html");
+    browser.test.sendMessage("done");
+  }
+
+  let extensionData = {
+    background,
+    manifest: {
+      permissions: ["bookmarks"],
+    },
+  };
+
+  let extension = ExtensionTestUtils.loadExtension(extensionData);
+  await extension.startup();
+  await extension.awaitMessage("done");
+
+  let counters = await retrieveSpecificCounter("getURL", 3);
+  await extension.unload();
+
+  // check that the bookmarks.create API was tracked
+  let counter = counters.get(extension.id).get("bookmarks.create");
+  ok(counter.calls > 0);
+  ok(counter.duration > 0);
+
+  // check that the getURL API was tracked
+  counter = counters.get(extension.id).get("getURL");
+  ok(counter.calls > 0);
+  ok(counter.duration > 0);
+}
+
+add_task(function test_performance_counter() {
+  return runWithPrefs(
+    [
+      [ENABLE_COUNTER_PREF, true],
+      [TIMING_MAX_AGE, 1],
+    ],
+    test_counter
+  );
+});
diff --git a/toolkit/components/extensions/test/xpcshell/test_ext_permission_warnings.js b/toolkit/components/extensions/test/xpcshell/test_ext_permission_warnings.js
new file mode 100644
index 0000000000..33248611fd
--- /dev/null
+++ b/toolkit/components/extensions/test/xpcshell/test_ext_permission_warnings.js
@@ -0,0 +1,845 @@
+"use strict";
+
+let { ExtensionTestCommon } = ChromeUtils.importESModule(
+  "resource://testing-common/ExtensionTestCommon.sys.mjs"
+);
+
+const {
+  PERMISSION_L10N_ID_OVERRIDES,
+  PERMISSIONS_WITH_MESSAGE,
+  permissionToL10nId,
+} = ChromeUtils.importESModule(
+  "resource://gre/modules/ExtensionPermissionMessages.sys.mjs"
+);
+
+const EXTENSION_L10N_PATHS = [
+  "toolkit/global/extensions.ftl",
+  "toolkit/global/extensionPermissions.ftl",
+  "branding/brand.ftl",
+];
+
+// For Android, these strings are only used in tests. In the actual UI, the
+// warnings are in Android-Components, as explained in bug 1671453.
+const l10n = new Localization(EXTENSION_L10N_PATHS, true);
+
+// nativeMessaging is in PRIVILEGED_PERMS on Android.
+const IS_NATIVE_MESSAGING_PRIVILEGED = AppConstants.platform == "android";
+
+const { createAppInfo } = AddonTestUtils;
+
+AddonTestUtils.init(this);
+AddonTestUtils.overrideCertDB();
+AddonTestUtils.usePrivilegedSignatures = id => id.startsWith("privileged");
+createAppInfo("xpcshell@tests.mozilla.org", "XPCShell", "1", "42");
+
+Services.prefs.setBoolPref("extensions.manifestV3.enabled", true);
+
+async function getManifestPermissions(extensionData) {
+  let extension = ExtensionTestCommon.generate(extensionData);
+  // Some tests contain invalid permissions; ignore the warnings about their invalidity.
+  ExtensionTestUtils.failOnSchemaWarnings(false);
+  await extension.loadManifest();
+  ExtensionTestUtils.failOnSchemaWarnings(true);
+  let result = extension.manifestPermissions;
+
+  if (extension.manifest.manifest_version >= 3) {
+    // In MV3, host permissions are optional by default.
+    deepEqual(result.origins, [], "No origins by default in MV3");
+    let optional = extension.manifestOptionalPermissions;
+    deepEqual(optional.permissions, [], "No tests use optional_permissions");
+    result.origins = optional.origins;
+  }
+
+  await extension.cleanupGeneratedFile();
+  return result;
+}
+
+function getPermissionWarnings(permissions, options) {
+  let { msgs } = ExtensionData.formatPermissionStrings(
+    { permissions },
+    options
+  );
+  return msgs;
+}
+
+async function getPermissionWarningsForUpdate(
+  oldExtensionData,
+  newExtensionData
+) {
+  let oldPerms = await getManifestPermissions(oldExtensionData);
+  let newPerms = await getManifestPermissions(newExtensionData);
+  let difference = Extension.comparePermissions(oldPerms, newPerms);
+  return getPermissionWarnings(difference);
+}
+
+// Tests that the callers of ExtensionData.formatPermissionStrings can customize the
+// mapping between the permission names and related localized strings.
+add_task(async function customized_permission_keys_mapping() {
+  const mockLocalization = {
+    formatMessagesSync: args =>
+      args.map(arg => ({
+        value: `Fake localized ${arg.id ?? arg}`,
+        attributes: [],
+      })),
+    formatValueSync: key => `Fake localized ${key}`,
+    formatValuesSync: args =>
+      args.map(arg => `Fake localized ${arg.id ?? arg}`),
+  };
+
+  // Define a non-default mapping for permission names -> locale keys.
+  const getKeyForPermission = perm => `custom-webext-perms-description-${perm}`;
+
+  const manifest = {
+    permissions: ["downloads", "proxy"],
+  };
+  const expectedWarnings = mockLocalization.formatValuesSync(
+    manifest.permissions.map(getKeyForPermission)
+  );
+
+  try {
+    for (let perm of manifest.permissions) {
+      PERMISSION_L10N_ID_OVERRIDES.set(perm, getKeyForPermission(perm));
+    }
+    const manifestPermissions = await getManifestPermissions({ manifest });
+
+    // Pass the callback function for the non-default key mapping to
+    // ExtensionData.formatPermissionStrings() and verify it being used.
+    const warnings = getPermissionWarnings(manifestPermissions, {
+      localization: mockLocalization,
+    });
+    deepEqual(
+      warnings,
+      expectedWarnings,
+      "Got the expected string from customized permission mapping"
+    );
+  } finally {
+    for (let perm of manifest.permissions) {
+      PERMISSION_L10N_ID_OVERRIDES.delete(perm);
+    }
+  }
+});
+
+// Tests that permission description data is internally consistent
+add_task(async function permission_message_consistence() {
+  for (let perm of PERMISSIONS_WITH_MESSAGE) {
+    ok(permissionToL10nId(perm), `Message is provided for ${perm}`);
+  }
+  for (let [perm] of PERMISSION_L10N_ID_OVERRIDES) {
+    ok(permissionToL10nId(perm), `Message is provided for ${perm}`);
+  }
+});
+
+// Tests that the expected permission warnings are generated for various
+// combinations of host permissions.
+add_task(async function host_permissions() {
+  let permissionTestCases = [
+    {
+      description: "Empty manifest without permissions",
+      manifest: {},
+      expectedOrigins: [],
+      expectedWarnings: [],
+    },
+    {
+      description: "Invalid match patterns",
+      manifest: {
+        permissions: [
+          "https:///",
+          "https://",
+          "https://*",
+          "about:ugh",
+          "about:*",
+          "about://*/",
+          "resource://*/",
+        ],
+      },
+      expectedOrigins: [],
+      expectedWarnings: [],
+    },
+    {
+      description: "moz-extension: permissions",
+      manifest: {
+        permissions: ["moz-extension://*/*", "moz-extension://uuid/"],
+      },
+      // moz-extension:-origin does not appear in the permission list,
+      // but it is implicitly granted anyway.
+      expectedOrigins: [],
+      expectedWarnings: [],
+    },
+    {
+      description: "*. host permission",
+      manifest: {
+        // This permission is rejected by the manifest and ignored.
+        permissions: ["http://*./"],
+      },
+      expectedOrigins: [],
+      expectedWarnings: [],
+    },
+    {
+      description: "<all_urls> permission",
+      manifest: {
+        permissions: ["<all_urls>"],
+      },
+      expectedOrigins: ["<all_urls>"],
+      expectedWarnings: [
+        l10n.formatValueSync("webext-perms-host-description-all-urls"),
+      ],
+    },
+    {
+      description: "file: permissions",
+      manifest: {
+        permissions: ["file://*/"],
+      },
+      expectedOrigins: ["file://*/"],
+      expectedWarnings: [
+        l10n.formatValueSync("webext-perms-host-description-all-urls"),
+      ],
+    },
+    {
+      description: "http: permission",
+      manifest: {
+        permissions: ["http://*/"],
+      },
+      expectedOrigins: ["http://*/"],
+      expectedWarnings: [
+        l10n.formatValueSync("webext-perms-host-description-all-urls"),
+      ],
+    },
+    {
+      description: "*://*/ permission",
+      manifest: {
+        permissions: ["*://*/"],
+      },
+      expectedOrigins: ["*://*/"],
+      expectedWarnings: [
+        l10n.formatValueSync("webext-perms-host-description-all-urls"),
+      ],
+    },
+    {
+      description: "content_script[*].matches",
+      manifest: {
+        content_scripts: [
+          {
+            // This test uses the manifest file without loading the content script
+            // file, so we can use a non-existing dummy file.
+            js: ["dummy.js"],
+            matches: ["https://*/"],
+          },
+        ],
+      },
+      expectedOrigins: ["https://*/"],
+      expectedWarnings: [
+        l10n.formatValueSync("webext-perms-host-description-all-urls"),
+      ],
+    },
+    {
+      description: "A few host permissions",
+      manifest: {
+        permissions: ["http://a/", "http://*.b/", "http://c/*"],
+      },
+      expectedOrigins: ["http://a/", "http://*.b/", "http://c/*"],
+      expectedWarnings: l10n.formatValuesSync([
+        // Wildcard hosts take precedence in the permission list.
+        {
+          id: "webext-perms-host-description-wildcard",
+          args: { domain: "b" },
+        },
+        {
+          id: "webext-perms-host-description-one-site",
+          args: { domain: "a" },
+        },
+        {
+          id: "webext-perms-host-description-one-site",
+          args: { domain: "c" },
+        },
+      ]),
+    },
+    {
+      description: "many host permission",
+      manifest: {
+        permissions: [
+          "http://a/",
+          "http://b/",
+          "http://c/",
+          "http://d/",
+          "http://e/*",
+          "http://*.1/",
+          "http://*.2/",
+          "http://*.3/",
+          "http://*.4/",
+        ],
+      },
+      expectedOrigins: [
+        "http://a/",
+        "http://b/",
+        "http://c/",
+        "http://d/",
+        "http://e/*",
+        "http://*.1/",
+        "http://*.2/",
+        "http://*.3/",
+        "http://*.4/",
+      ],
+      expectedWarnings: l10n.formatValuesSync([
+        // Wildcard hosts take precedence in the permission list.
+        {
+          id: "webext-perms-host-description-wildcard",
+          args: { domain: "1" },
+        },
+        {
+          id: "webext-perms-host-description-wildcard",
+          args: { domain: "2" },
+        },
+        {
+          id: "webext-perms-host-description-wildcard",
+          args: { domain: "3" },
+        },
+        {
+          id: "webext-perms-host-description-wildcard",
+          args: { domain: "4" },
+        },
+        {
+          id: "webext-perms-host-description-one-site",
+          args: { domain: "a" },
+        },
+        {
+          id: "webext-perms-host-description-one-site",
+          args: { domain: "b" },
+        },
+        {
+          id: "webext-perms-host-description-one-site",
+          args: { domain: "c" },
+        },
+        {
+          id: "webext-perms-host-description-too-many-sites",
+          args: { domainCount: 2 },
+        },
+      ]),
+      options: {
+        collapseOrigins: true,
+      },
+    },
+    {
+      description:
+        "many host permissions without item limit in the warning list",
+      manifest: {
+        permissions: [
+          "http://a/",
+          "http://b/",
+          "http://c/",
+          "http://d/",
+          "http://e/*",
+          "http://*.1/",
+          "http://*.2/",
+          "http://*.3/",
+          "http://*.4/",
+          "http://*.5/",
+        ],
+      },
+      expectedOrigins: [
+        "http://a/",
+        "http://b/",
+        "http://c/",
+        "http://d/",
+        "http://e/*",
+        "http://*.1/",
+        "http://*.2/",
+        "http://*.3/",
+        "http://*.4/",
+        "http://*.5/",
+      ],
+      expectedWarnings: l10n.formatValuesSync([
+        { id: "webext-perms-host-description-wildcard", args: { domain: "1" } },
+        { id: "webext-perms-host-description-wildcard", args: { domain: "2" } },
+        { id: "webext-perms-host-description-wildcard", args: { domain: "3" } },
+        { id: "webext-perms-host-description-wildcard", args: { domain: "4" } },
+        { id: "webext-perms-host-description-wildcard", args: { domain: "5" } },
+        { id: "webext-perms-host-description-one-site", args: { domain: "a" } },
+        { id: "webext-perms-host-description-one-site", args: { domain: "b" } },
+        { id: "webext-perms-host-description-one-site", args: { domain: "c" } },
+        { id: "webext-perms-host-description-one-site", args: { domain: "d" } },
+        { id: "webext-perms-host-description-one-site", args: { domain: "e" } },
+      ]),
+    },
+  ];
+  for (let manifest_version of [2, 3]) {
+    for (let {
+      description,
+      manifest,
+      expectedOrigins,
+      expectedWarnings,
+      options,
+    } of permissionTestCases) {
+      manifest = Object.assign({}, manifest, { manifest_version });
+      if (manifest_version > 2) {
+        manifest.host_permissions = manifest.permissions;
+        manifest.permissions = [];
+      }
+
+      let manifestPermissions = await getManifestPermissions({ manifest });
+
+      deepEqual(
+        manifestPermissions.origins,
+        expectedOrigins,
+        `Expected origins (${description})`
+      );
+      deepEqual(
+        manifestPermissions.permissions,
+        [],
+        `Expected no non-host permissions (${description})`
+      );
+
+      let warnings = getPermissionWarnings(manifestPermissions, options);
+      deepEqual(
+        warnings,
+        expectedWarnings,
+        `Expected warnings (${description})`
+      );
+    }
+  }
+});
+
+// Tests that the expected permission warnings are generated for a mix of host
+// permissions and API permissions.
+add_task(async function api_permissions() {
+  let manifestPermissions = await getManifestPermissions({
+    isPrivileged: IS_NATIVE_MESSAGING_PRIVILEGED,
+    manifest: {
+      permissions: [
+        "activeTab",
+        "webNavigation",
+        "tabs",
+        "nativeMessaging",
+        "http://x/",
+        "http://*.x/",
+        "http://*.tld/",
+      ],
+    },
+  });
+
+  deepEqual(
+    manifestPermissions,
+    {
+      origins: ["http://x/", "http://*.x/", "http://*.tld/"],
+      permissions: ["activeTab", "webNavigation", "tabs", "nativeMessaging"],
+    },
+    "Expected origins and permissions"
+  );
+
+  deepEqual(
+    getPermissionWarnings(manifestPermissions),
+    l10n.formatValuesSync([
+      // Host permissions first, with wildcards on top.
+      { id: "webext-perms-host-description-wildcard", args: { domain: "x" } },
+      { id: "webext-perms-host-description-wildcard", args: { domain: "tld" } },
+      { id: "webext-perms-host-description-one-site", args: { domain: "x" } },
+      // nativeMessaging permission warning first of all permissions.
+      "webext-perms-description-nativeMessaging",
+      // Other permissions in alphabetical order.
+      // Note: activeTab has no permission warning string.
+      "webext-perms-description-tabs",
+      "webext-perms-description-webNavigation",
+    ]),
+    "Expected warnings"
+  );
+});
+
+add_task(async function nativeMessaging_permission() {
+  let manifestPermissions = await getManifestPermissions({
+    // isPrivileged: false, by default.
+    manifest: {
+      permissions: ["nativeMessaging"],
+    },
+  });
+
+  if (IS_NATIVE_MESSAGING_PRIVILEGED) {
+    // The behavior of nativeMessaging for unprivileged extensions on Android
+    // is covered in
+    // mobile/android/components/extensions/test/xpcshell/test_ext_native_messaging_permissions.js
+    deepEqual(
+      manifestPermissions,
+      { origins: [], permissions: [] },
+      "nativeMessaging perm ignored for unprivileged extensions on Android"
+    );
+  } else {
+    deepEqual(
+      manifestPermissions,
+      { origins: [], permissions: ["nativeMessaging"] },
+      "nativeMessaging permission recognized for unprivileged extensions"
+    );
+  }
+});
+
+add_task(
+  { pref_set: [["extensions.dnr.enabled", true]] },
+  async function declarativeNetRequest_permission_with_warning() {
+    let manifestPermissions = await getManifestPermissions({
+      manifest: {
+        manifest_version: 3,
+        permissions: ["declarativeNetRequest", "declarativeNetRequestFeedback"],
+      },
+    });
+
+    deepEqual(
+      manifestPermissions,
+      {
+        origins: [],
+        permissions: ["declarativeNetRequest", "declarativeNetRequestFeedback"],
+      },
+      "Expected origins and permissions"
+    );
+
+    deepEqual(
+      getPermissionWarnings(manifestPermissions),
+      l10n.formatValuesSync([
+        "webext-perms-description-declarativeNetRequest",
+        "webext-perms-description-declarativeNetRequestFeedback",
+      ]),
+      "Expected warnings"
+    );
+  }
+);
+
+add_task(
+  { pref_set: [["extensions.dnr.enabled", true]] },
+  async function declarativeNetRequest_permission_without_warning() {
+    let manifestPermissions = await getManifestPermissions({
+      manifest: {
+        manifest_version: 3,
+        permissions: ["declarativeNetRequestWithHostAccess"],
+      },
+    });
+
+    deepEqual(
+      manifestPermissions,
+      { origins: [], permissions: ["declarativeNetRequestWithHostAccess"] },
+      "Expected origins and permissions"
+    );
+
+    deepEqual(getPermissionWarnings(manifestPermissions), [], "No warnings");
+  }
+);
+
+// Tests that the expected permission warnings are generated for a mix of host
+// permissions and API permissions, for a privileged extension that uses the
+// mozillaAddons permission.
+add_task(async function privileged_with_mozillaAddons() {
+  let manifestPermissions = await getManifestPermissions({
+    isPrivileged: true,
+    manifest: {
+      permissions: [
+        "mozillaAddons",
+        "mozillaAddons",
+        "mozillaAddons",
+        "resource://x/*",
+        "http://a/",
+        "about:reader*",
+      ],
+    },
+  });
+  deepEqual(
+    manifestPermissions,
+    {
+      origins: ["resource://x/*", "http://a/", "about:reader*"],
+      permissions: ["mozillaAddons"],
+    },
+    "Expected origins and permissions for privileged add-on with mozillaAddons"
+  );
+
+  deepEqual(
+    getPermissionWarnings(manifestPermissions),
+    [l10n.formatValueSync("webext-perms-host-description-all-urls")],
+    "Expected warnings for privileged add-on with mozillaAddons permission."
+  );
+});
+
+// Similar to the privileged_with_mozillaAddons test, except the test extension
+// is unprivileged and not allowed to use the mozillaAddons permission.
+add_task(async function unprivileged_with_mozillaAddons() {
+  let manifestPermissions = await getManifestPermissions({
+    manifest: {
+      permissions: [
+        "mozillaAddons",
+        "mozillaAddons",
+        "mozillaAddons",
+        "resource://x/*",
+        "http://a/",
+        "about:reader*",
+      ],
+    },
+  });
+  deepEqual(
+    manifestPermissions,
+    {
+      origins: ["http://a/"],
+      permissions: [],
+    },
+    "Expected origins and permissions for unprivileged add-on with mozillaAddons"
+  );
+
+  deepEqual(
+    getPermissionWarnings(manifestPermissions),
+    [
+      l10n.formatValueSync("webext-perms-host-description-one-site", {
+        domain: "a",
+      }),
+    ],
+    "Expected warnings for unprivileged add-on with mozillaAddons permission."
+  );
+});
+
+// Tests that an update with less permissions has no warning.
+add_task(async function update_drop_permission() {
+  let warnings = await getPermissionWarningsForUpdate(
+    {
+      manifest: {
+        permissions: ["<all_urls>", "https://a/", "http://b/"],
+      },
+    },
+    {
+      manifest: {
+        permissions: [
+          "https://a/",
+          "http://b/",
+          "ftp://host_matching_all_urls/",
+        ],
+      },
+    }
+  );
+  deepEqual(
+    warnings,
+    [],
+    "An update with fewer permissions should not have any warnings"
+  );
+});
+
+// Tests that an update that switches from "*://*/*" to "<all_urls>" does not
+// result in additional permission warnings.
+add_task(async function update_all_urls_permission() {
+  let warnings = await getPermissionWarningsForUpdate(
+    {
+      manifest: {
+        permissions: ["*://*/*"],
+      },
+    },
+    {
+      manifest: {
+        permissions: ["<all_urls>"],
+      },
+    }
+  );
+  deepEqual(
+    warnings,
+    [],
+    "An update from a wildcard host to <all_urls> should not have any warnings"
+  );
+});
+
+// Tests that an update where a new permission whose domain overlaps with
+// an existing permission does not result in additional permission warnings.
+add_task(async function update_change_permissions() {
+  let warnings = await getPermissionWarningsForUpdate(
+    {
+      manifest: {
+        permissions: ["https://a/", "http://*.b/", "http://c/", "http://f/"],
+      },
+    },
+    {
+      manifest: {
+        permissions: [
+          // (no new warning) Unchanged permission from old extension.
+          "https://a/",
+          // (no new warning) Different schemes, host should match "*.b" wildcard.
+          "ftp://ftp.b/",
+          "ws://ws.b/",
+          "wss://wss.b",
+          "https://https.b/",
+          "http://http.b/",
+          "*://*.b/",
+          "http://b/",
+
+          // (expect warning) Wildcard was added.
+          "http://*.c/",
+          // (no new warning) file:-scheme, but host "f" is same as "http://f/".
+          "file://f/",
+          // (expect warning) New permission was added.
+          "proxy",
+        ],
+      },
+    }
+  );
+  deepEqual(
+    warnings,
+    l10n.formatValuesSync([
+      { id: "webext-perms-host-description-wildcard", args: { domain: "c" } },
+      "webext-perms-description-proxy",
+    ]),
+    "Expected permission warnings for new permissions only"
+  );
+});
+
+// Tests that a privileged extension with the mozillaAddons permission can be
+// updated without errors.
+add_task(async function update_privileged_with_mozillaAddons() {
+  let warnings = await getPermissionWarningsForUpdate(
+    {
+      isPrivileged: true,
+      manifest: {
+        permissions: ["mozillaAddons", "resource://a/"],
+      },
+    },
+    {
+      isPrivileged: true,
+      manifest: {
+        permissions: ["mozillaAddons", "resource://a/", "resource://b/"],
+      },
+    }
+  );
+  deepEqual(
+    warnings,
+    [
+      l10n.formatValueSync("webext-perms-host-description-one-site", {
+        domain: "b",
+      }),
+    ],
+    "Expected permission warnings for new host only"
+  );
+});
+
+// Tests that an unprivileged extension cannot get privileged permissions
+// through an update.
+add_task(async function update_unprivileged_with_mozillaAddons() {
+  // Unprivileged
+  let warnings = await getPermissionWarningsForUpdate(
+    {
+      manifest: {
+        permissions: ["mozillaAddons", "resource://a/"],
+      },
+    },
+    {
+      manifest: {
+        permissions: ["mozillaAddons", "resource://a/", "resource://b/"],
+      },
+    }
+  );
+  deepEqual(
+    warnings,
+    [],
+    "resource:-scheme is unsupported for unprivileged extensions"
+  );
+});
+
+// Tests that invalid permission warning for privileged permissions requested
+// are not emitted for privileged extensions, only for unprivileged extensions.
+add_task(
+  async function test_invalid_permission_warning_on_privileged_permission() {
+    await AddonTestUtils.promiseStartupManager();
+
+    const MANIFEST_WARNINGS = [
+      "Reading manifest: Invalid extension permission: mozillaAddons",
+      "Reading manifest: Invalid extension permission: resource://x/",
+      "Reading manifest: Invalid extension permission: about:reader*",
+    ];
+
+    async function testInvalidPermissionWarning({ isPrivileged }) {
+      let id = isPrivileged
+        ? "privileged-addon@mochi.test"
+        : "nonprivileged-addon@mochi.test";
+
+      let expectedWarnings = isPrivileged ? [] : MANIFEST_WARNINGS;
+
+      const ext = ExtensionTestUtils.loadExtension({
+        useAddonManager: "permanent",
+        manifest: {
+          permissions: ["mozillaAddons", "resource://x/", "about:reader*"],
+          browser_specific_settings: { gecko: { id } },
+        },
+        background() {},
+      });
+
+      await ext.startup();
+      const { warnings } = ext.extension;
+      Assert.deepEqual(
+        warnings,
+        expectedWarnings,
+        `Got the expected warning for ${id}`
+      );
+      await ext.unload();
+    }
+
+    await testInvalidPermissionWarning({ isPrivileged: false });
+    await testInvalidPermissionWarning({ isPrivileged: true });
+
+    info("Test invalid permission warning on ExtensionData instance");
+    // Generate an extension (just to be able to reuse its rootURI for the
+    // ExtensionData instance created below).
+    let generatedExt = ExtensionTestCommon.generate({
+      manifest: {
+        permissions: ["mozillaAddons", "resource://x/", "about:reader*"],
+        browser_specific_settings: {
+          gecko: { id: "extension-data@mochi.test" },
+        },
+      },
+    });
+
+    // Verify that XPIInstall.jsm will not collect the warning for the
+    // privileged permission as expected.
+    async function getWarningsFromExtensionData({ isPrivileged }) {
+      let extData;
+      if (typeof isPrivileged == "function") {
+        // isPrivileged expected to be computed asynchronously.
+        extData = await ExtensionData.constructAsync({
+          rootURI: generatedExt.rootURI,
+          checkPrivileged: isPrivileged,
+        });
+      } else {
+        extData = new ExtensionData(generatedExt.rootURI, isPrivileged);
+      }
+      await extData.loadManifest();
+
+      // This assertion is just meant to prevent the test to pass if there were
+      // no warnings because some errors prevented the warnings to be
+      // collected).
+      Assert.deepEqual(
+        extData.errors,
+        [],
+        "No errors collected by the ExtensionData instance"
+      );
+      return extData.warnings;
+    }
+
+    Assert.deepEqual(
+      await getWarningsFromExtensionData({ isPrivileged: undefined }),
+      MANIFEST_WARNINGS,
+      "Got warnings about privileged permissions by default"
+    );
+
+    Assert.deepEqual(
+      await getWarningsFromExtensionData({ isPrivileged: false }),
+      MANIFEST_WARNINGS,
+      "Got warnings about privileged permissions for non-privileged extensions"
+    );
+
+    Assert.deepEqual(
+      await getWarningsFromExtensionData({ isPrivileged: true }),
+      [],
+      "No warnings about privileged permissions on privileged extensions"
+    );
+
+    Assert.deepEqual(
+      await getWarningsFromExtensionData({ isPrivileged: async () => false }),
+      MANIFEST_WARNINGS,
+      "Got warnings about privileged permissions for non-privileged extensions (async)"
+    );
+
+    Assert.deepEqual(
+      await getWarningsFromExtensionData({ isPrivileged: async () => true }),
+      [],
+      "No warnings about privileged permissions on privileged extensions (async)"
+    );
+
+    // Cleanup the generated xpi file.
+    await generatedExt.cleanupGeneratedFile();
+
+    await AddonTestUtils.promiseShutdownManager();
+  }
+);
diff --git a/toolkit/components/extensions/test/xpcshell/test_ext_permission_xhr.js b/toolkit/components/extensions/test/xpcshell/test_ext_permission_xhr.js
new file mode 100644
index 0000000000..88afd36dcc
--- /dev/null
+++ b/toolkit/components/extensions/test/xpcshell/test_ext_permission_xhr.js
@@ -0,0 +1,240 @@
+"use strict";
+
+// This file tests the behavior of fetch/XMLHttpRequest in content scripts, in
+// relation to permissions, in MV2.
+// In MV3, the expectations are different, test coverage for that is in
+// test_ext_xhr_cors.js (along with CORS tests that also apply to MV2).
+
+const server = createHttpServer({
+  hosts: ["xpcshell.test", "example.com", "example.org"],
+});
+server.registerDirectory("/data/", do_get_file("data"));
+
+server.registerPathHandler("/example.txt", (request, response) => {
+  response.setStatusLine(request.httpVersion, 200, "OK");
+  response.write("ok");
+});
+
+server.registerPathHandler("/return_headers.sjs", (request, response) => {
+  response.setHeader("Content-Type", "text/plain", false);
+
+  let headers = {};
+  for (let { data: header } of request.headers) {
+    headers[header.toLowerCase()] = request.getHeader(header);
+  }
+
+  response.write(JSON.stringify(headers));
+});
+
+/* eslint-disable mozilla/balanced-listeners */
+
+add_task(async function test_simple() {
+  async function runTests(cx) {
+    function xhr(XMLHttpRequest) {
+      return url => {
+        return new Promise((resolve, reject) => {
+          let req = new XMLHttpRequest();
+          req.open("GET", url);
+          req.addEventListener("load", resolve);
+          req.addEventListener("error", reject);
+          req.send();
+        });
+      };
+    }
+
+    function run(shouldFail, fetch) {
+      function passListener() {
+        browser.test.succeed(`${cx}.${fetch.name} pass listener`);
+      }
+
+      function failListener() {
+        browser.test.fail(`${cx}.${fetch.name} fail listener`);
+      }
+
+      /* eslint-disable no-else-return */
+      if (shouldFail) {
+        return fetch("http://example.org/example.txt").then(
+          failListener,
+          passListener
+        );
+      } else {
+        return fetch("http://example.com/example.txt").then(
+          passListener,
+          failListener
+        );
+      }
+      /* eslint-enable no-else-return */
+    }
+
+    try {
+      await run(true, xhr(XMLHttpRequest));
+      await run(false, xhr(XMLHttpRequest));
+      await run(true, xhr(window.XMLHttpRequest));
+      await run(false, xhr(window.XMLHttpRequest));
+      await run(true, fetch);
+      await run(false, fetch);
+      await run(true, window.fetch);
+      await run(false, window.fetch);
+    } catch (err) {
+      browser.test.fail(`Error: ${err} :: ${err.stack}`);
+      browser.test.notifyFail("permission_xhr");
+    }
+  }
+
+  async function background(runTestsFn) {
+    await runTestsFn("bg");
+    browser.test.notifyPass("permission_xhr");
+  }
+
+  let extensionData = {
+    background: `(${background})(${runTests})`,
+    manifest: {
+      permissions: ["http://example.com/"],
+      content_scripts: [
+        {
+          matches: ["http://xpcshell.test/data/file_permission_xhr.html"],
+          js: ["content.js"],
+        },
+      ],
+    },
+    files: {
+      "content.js": `(${async runTestsFn => {
+        await runTestsFn("content");
+
+        window.wrappedJSObject.privilegedFetch = fetch;
+        window.wrappedJSObject.privilegedXHR = XMLHttpRequest;
+
+        window.addEventListener("message", function rcv({ data }) {
+          switch (data.msg) {
+            case "test":
+              break;
+
+            case "assertTrue":
+              browser.test.assertTrue(data.condition, data.description);
+              break;
+
+            case "finish":
+              window.removeEventListener("message", rcv);
+              browser.test.sendMessage("content-script-finished");
+              break;
+          }
+        });
+        window.postMessage("test", "*");
+      }})(${runTests})`,
+    },
+  };
+
+  let extension = ExtensionTestUtils.loadExtension(extensionData);
+  await extension.startup();
+
+  let contentPage = await ExtensionTestUtils.loadContentPage(
+    "http://xpcshell.test/data/file_permission_xhr.html"
+  );
+  await extension.awaitMessage("content-script-finished");
+  await contentPage.close();
+
+  await extension.awaitFinish("permission_xhr");
+  await extension.unload();
+});
+
+// This test case ensures that a WebExtension content script can still use the same
+// XMLHttpRequest and fetch APIs that the webpage can use and be recognized from
+// the target server with the same origin and referer headers of the target webpage
+// (see Bug 1295660 for a rationale).
+add_task(async function test_page_xhr() {
+  async function contentScript() {
+    const content = this.content;
+
+    const { webpageFetchResult, webpageXhrResult } = await new Promise(
+      resolve => {
+        const listenPageMessage = event => {
+          if (!event.data || event.data.type !== "testPageGlobals") {
+            return;
+          }
+
+          window.removeEventListener("message", listenPageMessage);
+
+          browser.test.assertEq(
+            true,
+            !!content.XMLHttpRequest,
+            "The content script should have access to content.XMLHTTPRequest"
+          );
+          browser.test.assertEq(
+            true,
+            !!content.fetch,
+            "The content script should have access to window.pageFetch"
+          );
+
+          resolve(event.data);
+        };
+
+        window.addEventListener("message", listenPageMessage);
+
+        window.postMessage({}, "*");
+      }
+    );
+
+    const url = new URL("/return_headers.sjs", location).href;
+
+    await Promise.all([
+      new Promise((resolve, reject) => {
+        const req = new content.XMLHttpRequest();
+        req.open("GET", url);
+        req.addEventListener("load", () =>
+          resolve(JSON.parse(req.responseText))
+        );
+        req.addEventListener("error", reject);
+        req.send();
+      }),
+      content.fetch(url).then(res => res.json()),
+    ])
+      .then(async ([xhrResult, fetchResult]) => {
+        browser.test.assertEq(
+          webpageFetchResult.referer,
+          fetchResult.referer,
+          "window.pageFetch referrer is the same of a webpage fetch request"
+        );
+        browser.test.assertEq(
+          webpageFetchResult.origin,
+          fetchResult.origin,
+          "window.pageFetch origin is the same of a webpage fetch request"
+        );
+
+        browser.test.assertEq(
+          webpageXhrResult.referer,
+          xhrResult.referer,
+          "content.XMLHttpRequest referrer is the same of a webpage fetch request"
+        );
+      })
+      .catch(error => {
+        browser.test.fail(`Unexpected error: ${error}`);
+      });
+
+    browser.test.notifyPass("content-script-page-xhr");
+  }
+
+  let extensionData = {
+    manifest: {
+      content_scripts: [
+        {
+          matches: ["http://xpcshell.test/*"],
+          js: ["content.js"],
+        },
+      ],
+    },
+    files: {
+      "content.js": `(${contentScript})()`,
+    },
+  };
+
+  let extension = ExtensionTestUtils.loadExtension(extensionData);
+  await extension.startup();
+
+  let contentPage = await ExtensionTestUtils.loadContentPage(
+    "http://xpcshell.test/data/file_page_xhr.html"
+  );
+  await extension.awaitFinish("content-script-page-xhr");
+  await contentPage.close();
+
+  await extension.unload();
+});
diff --git a/toolkit/components/extensions/test/xpcshell/test_ext_permissions.js b/toolkit/components/extensions/test/xpcshell/test_ext_permissions.js
new file mode 100644
index 0000000000..68253c03e9
--- /dev/null
+++ b/toolkit/components/extensions/test/xpcshell/test_ext_permissions.js
@@ -0,0 +1,1035 @@
+"use strict";
+
+const { AddonManager } = ChromeUtils.importESModule(
+  "resource://gre/modules/AddonManager.sys.mjs"
+);
+const { permissionToL10nId } = ChromeUtils.importESModule(
+  "resource://gre/modules/ExtensionPermissionMessages.sys.mjs"
+);
+const { ExtensionPermissions } = ChromeUtils.importESModule(
+  "resource://gre/modules/ExtensionPermissions.sys.mjs"
+);
+
+Services.prefs.setBoolPref("extensions.manifestV3.enabled", true);
+
+// ExtensionParent.jsm is being imported lazily because when it is imported Services.appinfo will be
+// retrieved and cached (as a side-effect of Schemas.jsm being imported), and so Services.appinfo
+// will not be returning the version set by AddonTestUtils.createAppInfo and this test will
+// fail on non-nightly builds (because the cached appinfo.version will be undefined and
+// AddonManager startup will fail).
+ChromeUtils.defineESModuleGetters(this, {
+  ExtensionParent: "resource://gre/modules/ExtensionParent.sys.mjs",
+});
+
+const l10n = new Localization([
+  "toolkit/global/extensions.ftl",
+  "toolkit/global/extensionPermissions.ftl",
+  "branding/brand.ftl",
+]);
+// Localization resources need to be first iterated outside a test
+l10n.formatValue("webext-perms-sideload-text");
+
+AddonTestUtils.init(this);
+AddonTestUtils.overrideCertDB();
+AddonTestUtils.createAppInfo(
+  "xpcshell@tests.mozilla.org",
+  "XPCShell",
+  "1",
+  "42"
+);
+
+add_setup(async () => {
+  // Bug 1646182: Force ExtensionPermissions to run in rkv mode, the legacy
+  // storage mode will run in xpcshell-legacy-ep.ini
+  await ExtensionPermissions._uninit();
+
+  optionalPermissionsPromptHandler.init();
+
+  await AddonTestUtils.promiseStartupManager();
+  AddonTestUtils.usePrivilegedSignatures = false;
+});
+
+add_task(async function test_permissions_on_startup() {
+  let extensionId = "@permissionTest";
+  let extension = ExtensionTestUtils.loadExtension({
+    manifest: {
+      browser_specific_settings: {
+        gecko: { id: extensionId },
+      },
+      permissions: ["tabs"],
+    },
+    useAddonManager: "permanent",
+    async background() {
+      let perms = await browser.permissions.getAll();
+      browser.test.sendMessage("permissions", perms);
+    },
+  });
+  let adding = {
+    permissions: ["internal:privateBrowsingAllowed"],
+    origins: [],
+  };
+  await extension.startup();
+  let perms = await extension.awaitMessage("permissions");
+  equal(perms.permissions.length, 1, "one permission");
+  equal(perms.permissions[0], "tabs", "internal permission not present");
+
+  const { StartupCache } = ExtensionParent;
+
+  // StartupCache.permissions will not contain the extension permissions.
+  let manifestData = await StartupCache.permissions.get(extensionId, () => {
+    return { permissions: [], origins: [] };
+  });
+  equal(manifestData.permissions.length, 0, "no permission");
+
+  perms = await ExtensionPermissions.get(extensionId);
+  equal(perms.permissions.length, 0, "no permissions");
+  await ExtensionPermissions.add(extensionId, adding);
+
+  // Restart the extension and re-test the permissions.
+  await ExtensionPermissions._uninit();
+  await AddonTestUtils.promiseRestartManager();
+  let restarted = extension.awaitMessage("permissions");
+  await extension.awaitStartup();
+  perms = await restarted;
+
+  manifestData = await StartupCache.permissions.get(extensionId, () => {
+    return { permissions: [], origins: [] };
+  });
+  deepEqual(
+    manifestData.permissions,
+    adding.permissions,
+    "StartupCache.permissions contains permission"
+  );
+
+  equal(perms.permissions.length, 1, "one permission");
+  equal(perms.permissions[0], "tabs", "internal permission not present");
+  let added = await ExtensionPermissions._get(extensionId);
+  deepEqual(added, adding, "permissions were retained");
+
+  await extension.unload();
+});
+
+async function test_permissions({
+  manifest_version,
+  granted_host_permissions,
+  useAddonManager,
+  expectAllGranted,
+}) {
+  const REQUIRED_PERMISSIONS = ["downloads"];
+  const REQUIRED_ORIGINS = ["*://site.com/", "*://*.domain.com/"];
+  const REQUIRED_ORIGINS_EXPECTED = expectAllGranted
+    ? ["*://site.com/*", "*://*.domain.com/*"]
+    : [];
+
+  const OPTIONAL_PERMISSIONS = ["idle", "clipboardWrite"];
+  const OPTIONAL_ORIGINS = [
+    "http://optionalsite.com/",
+    "https://*.optionaldomain.com/",
+  ];
+  const OPTIONAL_ORIGINS_NORMALIZED = [
+    "http://optionalsite.com/*",
+    "https://*.optionaldomain.com/*",
+  ];
+
+  function background() {
+    browser.test.onMessage.addListener(async (method, arg) => {
+      if (method == "getAll") {
+        let perms = await browser.permissions.getAll();
+        let url = browser.runtime.getURL("*");
+        perms.origins = perms.origins.filter(i => i != url);
+        browser.test.sendMessage("getAll.result", perms);
+      } else if (method == "contains") {
+        let result = await browser.permissions.contains(arg);
+        browser.test.sendMessage("contains.result", result);
+      } else if (method == "request") {
+        try {
+          let result = await browser.permissions.request(arg);
+          browser.test.sendMessage("request.result", {
+            status: "success",
+            result,
+          });
+        } catch (err) {
+          browser.test.sendMessage("request.result", {
+            status: "error",
+            message: err.message,
+          });
+        }
+      } else if (method == "remove") {
+        let result = await browser.permissions.remove(arg);
+        browser.test.sendMessage("remove.result", result);
+      }
+    });
+  }
+
+  let extension = ExtensionTestUtils.loadExtension({
+    background,
+    manifest: {
+      manifest_version,
+      permissions: REQUIRED_PERMISSIONS,
+      host_permissions: REQUIRED_ORIGINS,
+      optional_permissions: [...OPTIONAL_PERMISSIONS, ...OPTIONAL_ORIGINS],
+      granted_host_permissions,
+    },
+    useAddonManager,
+  });
+
+  await extension.startup();
+
+  function call(method, arg) {
+    extension.sendMessage(method, arg);
+    return extension.awaitMessage(`${method}.result`);
+  }
+
+  let result = await call("getAll");
+  deepEqual(result.permissions, REQUIRED_PERMISSIONS);
+  deepEqual(result.origins, REQUIRED_ORIGINS_EXPECTED);
+
+  for (let perm of REQUIRED_PERMISSIONS) {
+    result = await call("contains", { permissions: [perm] });
+    equal(result, true, `contains() returns true for fixed permission ${perm}`);
+  }
+  for (let origin of REQUIRED_ORIGINS) {
+    result = await call("contains", { origins: [origin] });
+    equal(
+      result,
+      expectAllGranted,
+      `contains() returns true for fixed origin ${origin}`
+    );
+  }
+
+  // None of the optional permissions should be available yet
+  for (let perm of OPTIONAL_PERMISSIONS) {
+    result = await call("contains", { permissions: [perm] });
+    equal(result, false, `contains() returns false for permission ${perm}`);
+  }
+  for (let origin of OPTIONAL_ORIGINS) {
+    result = await call("contains", { origins: [origin] });
+    equal(result, false, `contains() returns false for origin ${origin}`);
+  }
+
+  result = await call("contains", {
+    permissions: [...REQUIRED_PERMISSIONS, ...OPTIONAL_PERMISSIONS],
+  });
+  equal(
+    result,
+    false,
+    "contains() returns false for a mix of available and unavailable permissions"
+  );
+
+  let perm = OPTIONAL_PERMISSIONS[0];
+  result = await call("request", { permissions: [perm] });
+  equal(
+    result.status,
+    "error",
+    "request() fails if not called from an event handler"
+  );
+  ok(
+    /request may only be called from a user input handler/.test(result.message),
+    "error message for calling request() outside an event handler is reasonable"
+  );
+  result = await call("contains", { permissions: [perm] });
+  equal(
+    result,
+    false,
+    "Permission requested outside an event handler was not granted"
+  );
+
+  await withHandlingUserInput(extension, async () => {
+    result = await call("request", { permissions: ["notifications"] });
+    equal(
+      result.status,
+      "error",
+      "request() for permission not in optional_permissions should fail"
+    );
+    ok(
+      /since it was not declared in optional_permissions/.test(result.message),
+      "error message for undeclared optional_permission is reasonable"
+    );
+
+    // Check request() when the prompt is canceled.
+    optionalPermissionsPromptHandler.acceptPrompt = false;
+    result = await call("request", { permissions: [perm] });
+    equal(result.status, "success", "request() returned cleanly");
+    equal(
+      result.result,
+      false,
+      "request() returned false for rejected permission"
+    );
+
+    result = await call("contains", { permissions: [perm] });
+    equal(result, false, "Rejected permission was not granted");
+
+    // Call request() and accept the prompt
+    optionalPermissionsPromptHandler.acceptPrompt = true;
+    let allOptional = {
+      permissions: OPTIONAL_PERMISSIONS,
+      origins: OPTIONAL_ORIGINS,
+    };
+    result = await call("request", allOptional);
+    equal(result.status, "success", "request() returned cleanly");
+    equal(
+      result.result,
+      true,
+      "request() returned true for accepted permissions"
+    );
+
+    // Verify that requesting a permission/origin in the wrong field fails
+    let originsAsPerms = {
+      permissions: OPTIONAL_ORIGINS,
+    };
+    let permsAsOrigins = {
+      origins: OPTIONAL_PERMISSIONS,
+    };
+
+    result = await call("request", originsAsPerms);
+    equal(
+      result.status,
+      "error",
+      "Requesting an origin as a permission should fail"
+    );
+    ok(
+      /Type error for parameter permissions \(Error processing permissions/.test(
+        result.message
+      ),
+      "Error message for origin as permission is reasonable"
+    );
+
+    result = await call("request", permsAsOrigins);
+    equal(
+      result.status,
+      "error",
+      "Requesting a permission as an origin should fail"
+    );
+    ok(
+      /Type error for parameter permissions \(Error processing origins/.test(
+        result.message
+      ),
+      "Error message for permission as origin is reasonable"
+    );
+  });
+
+  let allPermissions = {
+    permissions: [...REQUIRED_PERMISSIONS, ...OPTIONAL_PERMISSIONS],
+    origins: [...REQUIRED_ORIGINS_EXPECTED, ...OPTIONAL_ORIGINS_NORMALIZED],
+  };
+
+  result = await call("getAll");
+  deepEqual(
+    result,
+    allPermissions,
+    "getAll() returns required and runtime requested permissions"
+  );
+
+  result = await call("contains", allPermissions);
+  equal(
+    result,
+    true,
+    "contains() returns true for runtime requested permissions"
+  );
+
+  async function restart() {
+    if (useAddonManager === "permanent") {
+      await AddonTestUtils.promiseRestartManager();
+    } else {
+      // Manually reload for temporarily loaded.
+      await extension.addon.reload();
+    }
+    await extension.awaitBackgroundStarted();
+  }
+
+  // Restart extension, verify permissions are still present.
+  await restart();
+
+  result = await call("getAll");
+  deepEqual(
+    result,
+    allPermissions,
+    "Runtime requested permissions are still present after restart"
+  );
+
+  // Check remove()
+  result = await call("remove", { permissions: OPTIONAL_PERMISSIONS });
+  equal(result, true, "remove() succeeded");
+
+  let perms = {
+    permissions: REQUIRED_PERMISSIONS,
+    origins: [...REQUIRED_ORIGINS_EXPECTED, ...OPTIONAL_ORIGINS_NORMALIZED],
+  };
+
+  result = await call("getAll");
+  deepEqual(result, perms, "Expected permissions remain after removing some");
+
+  result = await call("remove", { origins: OPTIONAL_ORIGINS });
+  equal(result, true, "remove() succeeded");
+
+  perms.origins = REQUIRED_ORIGINS_EXPECTED;
+  result = await call("getAll");
+  deepEqual(result, perms, "Back to default permissions after removing more");
+
+  if (granted_host_permissions && expectAllGranted) {
+    // Check that all (granted) host permissions in MV3 can be revoked.
+
+    result = await call("remove", { origins: REQUIRED_ORIGINS });
+    equal(result, true, "remove() succeeded");
+    perms.origins = [];
+
+    result = await call("getAll");
+    deepEqual(
+      result,
+      perms,
+      "Expected only api permissions remain after removing all origins in mv3."
+    );
+  }
+
+  // Clear cache to confirm same result after rebuilding it (after an update).
+  await ExtensionParent.StartupCache.clearAddonData(extension.id);
+
+  // Restart again, verify optional permissions state is still preserved.
+  await restart();
+
+  result = await call("getAll");
+  deepEqual(result, perms, "Expected the same permissions after restart.");
+
+  await extension.unload();
+}
+
+add_task(function test_normal_mv2() {
+  return test_permissions({
+    manifest_version: 2,
+    useAddonManager: "permanent",
+    expectAllGranted: true,
+  });
+});
+
+add_task(function test_normal_mv3() {
+  return test_permissions({
+    manifest_version: 3,
+    useAddonManager: "permanent",
+    expectAllGranted: false,
+  });
+});
+
+add_task(function test_granted_for_temporary_mv3() {
+  return test_permissions({
+    manifest_version: 3,
+    granted_host_permissions: true,
+    useAddonManager: "temporary",
+    expectAllGranted: true,
+  });
+});
+
+add_task(async function test_granted_only_for_privileged_mv3() {
+  try {
+    // For permanent non-privileged, granted_host_permissions does nothing.
+    await test_permissions({
+      manifest_version: 3,
+      granted_host_permissions: true,
+      useAddonManager: "permanent",
+      expectAllGranted: false,
+    });
+
+    // Make extensions loaded with addon manager privileged.
+    AddonTestUtils.usePrivilegedSignatures = true;
+
+    await test_permissions({
+      manifest_version: 3,
+      granted_host_permissions: true,
+      useAddonManager: "permanent",
+      expectAllGranted: true,
+    });
+  } finally {
+    AddonTestUtils.usePrivilegedSignatures = false;
+  }
+});
+
+add_task(async function test_startup() {
+  async function background() {
+    browser.test.onMessage.addListener(async perms => {
+      await browser.permissions.request(perms);
+      browser.test.sendMessage("requested");
+    });
+
+    let all = await browser.permissions.getAll();
+    let url = browser.runtime.getURL("*");
+    all.origins = all.origins.filter(i => i != url);
+    browser.test.sendMessage("perms", all);
+  }
+
+  const PERMS1 = {
+    permissions: ["clipboardRead", "tabs"],
+  };
+  const PERMS2 = {
+    origins: ["https://site2.com/*"],
+  };
+
+  let extension1 = ExtensionTestUtils.loadExtension({
+    background,
+    manifest: {
+      optional_permissions: PERMS1.permissions,
+    },
+    useAddonManager: "permanent",
+  });
+  let extension2 = ExtensionTestUtils.loadExtension({
+    background,
+    manifest: {
+      optional_permissions: PERMS2.origins,
+    },
+    useAddonManager: "permanent",
+  });
+
+  await extension1.startup();
+  await extension2.startup();
+
+  let perms = await extension1.awaitMessage("perms");
+  perms = await extension2.awaitMessage("perms");
+
+  await withHandlingUserInput(extension1, async () => {
+    extension1.sendMessage(PERMS1);
+    await extension1.awaitMessage("requested");
+  });
+
+  await withHandlingUserInput(extension2, async () => {
+    extension2.sendMessage(PERMS2);
+    await extension2.awaitMessage("requested");
+  });
+
+  // Restart everything, and force the permissions store to be
+  // re-read on startup
+  await ExtensionPermissions._uninit();
+  await AddonTestUtils.promiseRestartManager();
+  await extension1.awaitStartup();
+  await extension2.awaitStartup();
+
+  async function checkPermissions(extension, permissions) {
+    perms = await extension.awaitMessage("perms");
+    let expect = Object.assign({ permissions: [], origins: [] }, permissions);
+    deepEqual(perms, expect, "Extension got correct permissions on startup");
+  }
+
+  await checkPermissions(extension1, PERMS1);
+  await checkPermissions(extension2, PERMS2);
+
+  await extension1.unload();
+  await extension2.unload();
+});
+
+// Test that we don't prompt for permissions an extension already has.
+async function test_alreadyGranted(manifest_version) {
+  const REQUIRED_PERMISSIONS = ["geolocation"];
+  const REQUIRED_ORIGINS = [
+    "*://required-host.com/",
+    "*://*.required-domain.com/",
+  ];
+  const OPTIONAL_PERMISSIONS = [
+    ...REQUIRED_PERMISSIONS,
+    ...REQUIRED_ORIGINS,
+    "clipboardRead",
+    "*://optional-host.com/",
+    "*://*.optional-domain.com/",
+  ];
+
+  function pageScript() {
+    browser.test.onMessage.addListener(async (msg, arg) => {
+      if (msg == "request") {
+        let result = await browser.permissions.request(arg);
+        browser.test.sendMessage("request.result", result);
+      } else if (msg == "remove") {
+        let result = await browser.permissions.remove(arg);
+        browser.test.sendMessage("remove.result", result);
+      } else if (msg == "close") {
+        window.close();
+      }
+    });
+
+    browser.test.sendMessage("page-ready");
+  }
+
+  let extension = ExtensionTestUtils.loadExtension({
+    background() {
+      browser.test.sendMessage("ready", browser.runtime.getURL("page.html"));
+    },
+
+    manifest: {
+      manifest_version,
+      permissions: REQUIRED_PERMISSIONS,
+      host_permissions: REQUIRED_ORIGINS,
+      optional_permissions: OPTIONAL_PERMISSIONS,
+      granted_host_permissions: true,
+    },
+    temporarilyInstalled: true,
+    startupReason: "ADDON_INSTALL",
+    files: {
+      "page.html": `<html><head>
+          <script src="page.js"><\/script>
+        </head></html>`,
+
+      "page.js": pageScript,
+    },
+  });
+
+  await extension.startup();
+
+  await withHandlingUserInput(extension, async () => {
+    let url = await extension.awaitMessage("ready");
+    let page = await ExtensionTestUtils.loadContentPage(url, { extension });
+    await extension.awaitMessage("page-ready");
+
+    async function checkRequest(arg, expectPrompt, msg) {
+      optionalPermissionsPromptHandler.sawPrompt = false;
+      extension.sendMessage("request", arg);
+      let result = await extension.awaitMessage("request.result");
+      ok(result, "request() call succeeded");
+      equal(
+        optionalPermissionsPromptHandler.sawPrompt,
+        expectPrompt,
+        `Got ${expectPrompt ? "" : "no "}permission prompt for ${msg}`
+      );
+    }
+
+    await checkRequest(
+      { permissions: ["geolocation"] },
+      false,
+      "required permission from manifest"
+    );
+    await checkRequest(
+      { origins: ["http://required-host.com/"] },
+      false,
+      "origin permission from manifest"
+    );
+    await checkRequest(
+      { origins: ["http://host.required-domain.com/"] },
+      false,
+      "wildcard origin permission from manifest"
+    );
+
+    await checkRequest(
+      { permissions: ["clipboardRead"] },
+      true,
+      "optional permission"
+    );
+    await checkRequest(
+      { permissions: ["clipboardRead"] },
+      false,
+      "already granted optional permission"
+    );
+
+    await checkRequest(
+      { origins: ["http://optional-host.com/"] },
+      true,
+      "optional origin"
+    );
+    await checkRequest(
+      { origins: ["http://optional-host.com/"] },
+      false,
+      "already granted origin permission"
+    );
+
+    await checkRequest(
+      { origins: ["http://*.optional-domain.com/"] },
+      true,
+      "optional wildcard origin"
+    );
+    await checkRequest(
+      { origins: ["http://*.optional-domain.com/"] },
+      false,
+      "already granted optional wildcard origin"
+    );
+    await checkRequest(
+      { origins: ["http://host.optional-domain.com/"] },
+      false,
+      "host matching optional wildcard origin"
+    );
+    await page.close();
+  });
+
+  await extension.unload();
+}
+add_task(async function test_alreadyGranted_mv2() {
+  return test_alreadyGranted(2);
+});
+add_task(async function test_alreadyGranted_mv3() {
+  return test_alreadyGranted(3);
+});
+
+// IMPORTANT: Do not change this list without review from a Web Extensions peer!
+
+const GRANTED_WITHOUT_USER_PROMPT = [
+  "activeTab",
+  "activityLog",
+  "alarms",
+  "captivePortal",
+  "contextMenus",
+  "contextualIdentities",
+  "cookies",
+  "declarativeNetRequestWithHostAccess",
+  "dns",
+  "geckoProfiler",
+  "identity",
+  "idle",
+  "menus",
+  "menus.overrideContext",
+  "mozillaAddons",
+  "networkStatus",
+  "normandyAddonStudy",
+  "scripting",
+  "search",
+  "storage",
+  "telemetry",
+  "theme",
+  "unlimitedStorage",
+  "urlbar",
+  "webRequest",
+  "webRequestBlocking",
+  "webRequestFilterResponse",
+  "webRequestFilterResponse.serviceWorkerScript",
+];
+
+add_task(async function test_permissions_have_localization_strings() {
+  let noPromptNames = Schemas.getPermissionNames([
+    "PermissionNoPrompt",
+    "OptionalPermissionNoPrompt",
+    "PermissionPrivileged",
+  ]);
+  Assert.deepEqual(
+    GRANTED_WITHOUT_USER_PROMPT,
+    noPromptNames,
+    "List of no-prompt permissions is correct."
+  );
+
+  for (const perm of Schemas.getPermissionNames()) {
+    const permId = permissionToL10nId(perm);
+    if (permId) {
+      const str = await l10n.formatValue(permId);
+      ok(str.length, `Found localization string for '${perm}' permission`);
+    } else {
+      ok(
+        GRANTED_WITHOUT_USER_PROMPT.includes(perm),
+        `Permission '${perm}' intentionally granted without prompting the user`
+      );
+    }
+  }
+});
+
+// Check <all_urls> used as an optional API permission.
+add_task(async function test_optional_all_urls() {
+  let extension = ExtensionTestUtils.loadExtension({
+    manifest: {
+      optional_permissions: ["<all_urls>"],
+    },
+
+    background() {
+      browser.test.onMessage.addListener(async () => {
+        let before = !!browser.tabs.captureVisibleTab;
+        let granted = await browser.permissions.request({
+          origins: ["<all_urls>"],
+        });
+        let after = !!browser.tabs.captureVisibleTab;
+
+        browser.test.sendMessage("results", [before, granted, after]);
+      });
+    },
+  });
+
+  await extension.startup();
+
+  await withHandlingUserInput(extension, async () => {
+    extension.sendMessage("request");
+    let [before, granted, after] = await extension.awaitMessage("results");
+
+    equal(
+      before,
+      false,
+      "captureVisibleTab() unavailable before optional permission request()"
+    );
+    equal(granted, true, "request() for optional permissions granted");
+    equal(
+      after,
+      true,
+      "captureVisibleTab() available after optional permission request()"
+    );
+  });
+
+  await extension.unload();
+});
+
+// Check when content_script match patterns are treated as optional origins.
+async function test_content_script_is_optional(manifest_version) {
+  function background() {
+    browser.test.onMessage.addListener(async (msg, arg) => {
+      if (msg == "request") {
+        try {
+          let result = await browser.permissions.request(arg);
+          browser.test.sendMessage("result", result);
+        } catch (e) {
+          browser.test.sendMessage("result", e.message);
+        }
+      }
+      if (msg === "getAll") {
+        let result = await browser.permissions.getAll(arg);
+        browser.test.sendMessage("granted", result);
+      }
+    });
+  }
+
+  const CS_ORIGIN = "https://test2.example.com/*";
+
+  let extension = ExtensionTestUtils.loadExtension({
+    background,
+    manifest: {
+      manifest_version,
+      content_scripts: [
+        {
+          matches: [CS_ORIGIN],
+          js: [],
+        },
+      ],
+    },
+  });
+
+  await extension.startup();
+
+  extension.sendMessage("getAll");
+  let initial = await extension.awaitMessage("granted");
+  deepEqual(initial.origins, [], "Nothing granted on install.");
+
+  await withHandlingUserInput(extension, async () => {
+    extension.sendMessage("request", {
+      permissions: [],
+      origins: [CS_ORIGIN],
+    });
+    let result = await extension.awaitMessage("result");
+    if (manifest_version < 3) {
+      equal(
+        result,
+        `Cannot request origin permission for ${CS_ORIGIN} since it was not declared in the manifest`,
+        "Content script match pattern is not a requestable optional origin in MV2"
+      );
+    } else {
+      equal(result, true, "request() for optional permissions succeeded");
+    }
+  });
+
+  extension.sendMessage("getAll");
+  let granted = await extension.awaitMessage("granted");
+  deepEqual(
+    granted.origins,
+    manifest_version < 3 ? [] : [CS_ORIGIN],
+    "Granted content script origin in MV3."
+  );
+
+  await extension.unload();
+}
+add_task(() => test_content_script_is_optional(2));
+add_task(() => test_content_script_is_optional(3));
+
+// Check that optional permissions are not included in update prompts
+async function test_permissions_prompt(manifest_version) {
+  function background() {
+    browser.test.onMessage.addListener(async (msg, arg) => {
+      if (msg == "request") {
+        let result = await browser.permissions.request(arg);
+        browser.test.sendMessage("result", result);
+      }
+      if (msg === "getAll") {
+        let result = await browser.permissions.getAll(arg);
+        browser.test.sendMessage("granted", result);
+      }
+    });
+  }
+
+  let extension = ExtensionTestUtils.loadExtension({
+    background,
+    manifest: {
+      name: "permissions test",
+      description: "permissions test",
+      manifest_version,
+      version: "1.0",
+
+      permissions: ["tabs"],
+      host_permissions: ["https://test1.example.com/*"],
+      optional_permissions: ["clipboardWrite", "<all_urls>"],
+
+      content_scripts: [
+        {
+          matches: ["https://test2.example.com/*"],
+          js: [],
+        },
+      ],
+    },
+    useAddonManager: "permanent",
+  });
+
+  await extension.startup();
+
+  await withHandlingUserInput(extension, async () => {
+    extension.sendMessage("request", {
+      permissions: ["clipboardWrite"],
+      origins: ["https://test2.example.com/*"],
+    });
+    let result = await extension.awaitMessage("result");
+    equal(result, true, "request() for optional permissions succeeded");
+  });
+
+  if (manifest_version >= 3) {
+    await withHandlingUserInput(extension, async () => {
+      extension.sendMessage("request", {
+        origins: ["https://test1.example.com/*"],
+      });
+      let result = await extension.awaitMessage("result");
+      equal(result, true, "request() for host_permissions in mv3 succeeded");
+    });
+  }
+
+  const PERMS = ["history", "tabs"];
+  const ORIGINS = ["https://test1.example.com/*", "https://test3.example.com/"];
+  let xpi = AddonTestUtils.createTempWebExtensionFile({
+    background,
+    manifest: {
+      name: "permissions test",
+      description: "permissions test",
+      manifest_version,
+      version: "2.0",
+
+      browser_specific_settings: { gecko: { id: extension.id } },
+
+      permissions: PERMS,
+      host_permissions: ORIGINS,
+      optional_permissions: ["clipboardWrite", "<all_urls>"],
+    },
+  });
+
+  let install = await AddonManager.getInstallForFile(xpi);
+
+  let perminfo;
+  install.promptHandler = info => {
+    perminfo = info;
+    return Promise.resolve();
+  };
+
+  await AddonTestUtils.promiseCompleteInstall(install);
+  await extension.awaitStartup();
+
+  notEqual(perminfo, undefined, "Permission handler was invoked");
+  let perms = perminfo.addon.userPermissions;
+  deepEqual(
+    perms.permissions,
+    PERMS,
+    "Update details includes only manifest api permissions"
+  );
+  deepEqual(
+    perms.origins,
+    manifest_version < 3 ? ORIGINS : [],
+    "Update details includes only manifest origin permissions"
+  );
+
+  let EXPECTED = ["https://test1.example.com/*", "https://test2.example.com/*"];
+  if (manifest_version < 3) {
+    EXPECTED.push("https://test3.example.com/*");
+  }
+
+  extension.sendMessage("getAll");
+  let granted = await extension.awaitMessage("granted");
+  deepEqual(
+    granted.origins.sort(),
+    EXPECTED,
+    "Granted origins persisted after update."
+  );
+
+  await extension.unload();
+}
+add_task(async function test_permissions_prompt_mv2() {
+  return test_permissions_prompt(2);
+});
+add_task(async function test_permissions_prompt_mv3() {
+  return test_permissions_prompt(3);
+});
+
+// Check that internal permissions can not be set and are not returned by the API.
+add_task(async function test_internal_permissions() {
+  function background() {
+    browser.test.onMessage.addListener(async (method, arg) => {
+      try {
+        if (method == "getAll") {
+          let perms = await browser.permissions.getAll();
+          browser.test.sendMessage("getAll.result", perms);
+        } else if (method == "contains") {
+          let result = await browser.permissions.contains(arg);
+          browser.test.sendMessage("contains.result", {
+            status: "success",
+            result,
+          });
+        } else if (method == "request") {
+          let result = await browser.permissions.request(arg);
+          browser.test.sendMessage("request.result", {
+            status: "success",
+            result,
+          });
+        } else if (method == "remove") {
+          let result = await browser.permissions.remove(arg);
+          browser.test.sendMessage("remove.result", result);
+        }
+      } catch (err) {
+        browser.test.sendMessage(`${method}.result`, {
+          status: "error",
+          message: err.message,
+        });
+      }
+    });
+  }
+
+  let extension = ExtensionTestUtils.loadExtension({
+    background,
+    manifest: {
+      name: "permissions test",
+      description: "permissions test",
+      manifest_version: 2,
+      version: "1.0",
+      permissions: [],
+    },
+    useAddonManager: "permanent",
+    incognitoOverride: "spanning",
+  });
+
+  let perm = "internal:privateBrowsingAllowed";
+
+  await extension.startup();
+
+  function call(method, arg) {
+    extension.sendMessage(method, arg);
+    return extension.awaitMessage(`${method}.result`);
+  }
+
+  let result = await call("getAll");
+  ok(!result.permissions.includes(perm), "internal not returned");
+
+  result = await call("contains", { permissions: [perm] });
+  ok(
+    /Type error for parameter permissions \(Error processing permissions/.test(
+      result.message
+    ),
+    `Unable to check for internal permission: ${result.message}`
+  );
+
+  result = await call("remove", { permissions: [perm] });
+  ok(
+    /Type error for parameter permissions \(Error processing permissions/.test(
+      result.message
+    ),
+    `Unable to remove for internal permission ${result.message}`
+  );
+
+  await withHandlingUserInput(extension, async () => {
+    result = await call("request", {
+      permissions: [perm],
+      origins: [],
+    });
+    ok(
+      /Type error for parameter permissions \(Error processing permissions/.test(
+        result.message
+      ),
+      `Unable to request internal permission ${result.message}`
+    );
+  });
+
+  await extension.unload();
+});
diff --git a/toolkit/components/extensions/test/xpcshell/test_ext_permissions_api.js b/toolkit/components/extensions/test/xpcshell/test_ext_permissions_api.js
new file mode 100644
index 0000000000..526f0a720e
--- /dev/null
+++ b/toolkit/components/extensions/test/xpcshell/test_ext_permissions_api.js
@@ -0,0 +1,464 @@
+"use strict";
+
+const { AddonManager } = ChromeUtils.importESModule(
+  "resource://gre/modules/AddonManager.sys.mjs"
+);
+const { ExtensionPermissions } = ChromeUtils.importESModule(
+  "resource://gre/modules/ExtensionPermissions.sys.mjs"
+);
+
+ChromeUtils.defineESModuleGetters(this, {
+  ExtensionParent: "resource://gre/modules/ExtensionParent.sys.mjs",
+});
+
+AddonTestUtils.init(this);
+AddonTestUtils.overrideCertDB();
+AddonTestUtils.createAppInfo(
+  "xpcshell@tests.mozilla.org",
+  "XPCShell",
+  "1",
+  "42"
+);
+
+let OptionalPermissions;
+
+add_task(async function setup() {
+  // Bug 1646182: Force ExtensionPermissions to run in rkv mode, the legacy
+  // storage mode will run in xpcshell-legacy-ep.ini
+  await ExtensionPermissions._uninit();
+
+  Services.prefs.setBoolPref(
+    "extensions.webextOptionalPermissionPrompts",
+    false
+  );
+  registerCleanupFunction(() => {
+    Services.prefs.clearUserPref("extensions.webextOptionalPermissionPrompts");
+  });
+  await AddonTestUtils.promiseStartupManager();
+  AddonTestUtils.usePrivilegedSignatures = false;
+
+  // We want to get a list of optional permissions prior to loading an extension,
+  // so we'll get ExtensionParent to do that for us.
+  await ExtensionParent.apiManager.lazyInit();
+
+  // These permissions have special behaviors and/or are not mapped directly to an
+  // api namespace.  They will have their own tests for specific behavior.
+  let ignore = [
+    "activeTab",
+    "clipboardRead",
+    "clipboardWrite",
+    "declarativeNetRequestFeedback",
+    "devtools",
+    "downloads.open",
+    "geolocation",
+    "management",
+    "menus.overrideContext",
+    "nativeMessaging",
+    "scripting",
+    "search",
+    "tabHide",
+    "tabs",
+    "webRequestBlocking",
+    "webRequestFilterResponse",
+    "webRequestFilterResponse.serviceWorkerScript",
+  ];
+  OptionalPermissions = Schemas.getPermissionNames([
+    "OptionalPermission",
+    "OptionalPermissionNoPrompt",
+  ]).filter(n => !ignore.includes(n));
+});
+
+add_task(async function test_api_on_permissions_changed() {
+  async function background() {
+    let manifest = browser.runtime.getManifest();
+    let permObj = { permissions: manifest.optional_permissions, origins: [] };
+
+    function verifyPermissions(enabled) {
+      for (let perm of manifest.optional_permissions) {
+        browser.test.assertEq(
+          enabled,
+          !!browser[perm],
+          `${perm} API is ${
+            enabled ? "injected" : "removed"
+          } after permission request`
+        );
+      }
+    }
+
+    browser.permissions.onAdded.addListener(details => {
+      browser.test.assertEq(
+        JSON.stringify(details.permissions),
+        JSON.stringify(manifest.optional_permissions),
+        "expected permissions added"
+      );
+      verifyPermissions(true);
+      browser.test.sendMessage("added");
+    });
+
+    browser.permissions.onRemoved.addListener(details => {
+      browser.test.assertEq(
+        JSON.stringify(details.permissions),
+        JSON.stringify(manifest.optional_permissions),
+        "expected permissions removed"
+      );
+      verifyPermissions(false);
+      browser.test.sendMessage("removed");
+    });
+
+    browser.test.onMessage.addListener((msg, enabled) => {
+      if (msg === "request") {
+        browser.permissions.request(permObj);
+      } else if (msg === "verify_access") {
+        verifyPermissions(enabled);
+        browser.test.sendMessage("verified");
+      } else if (msg === "revoke") {
+        browser.permissions.remove(permObj);
+      }
+    });
+  }
+
+  let extension = ExtensionTestUtils.loadExtension({
+    background,
+    manifest: {
+      optional_permissions: OptionalPermissions,
+    },
+    useAddonManager: "permanent",
+  });
+  await extension.startup();
+
+  function addPermissions() {
+    extension.sendMessage("request");
+    return extension.awaitMessage("added");
+  }
+
+  function removePermissions() {
+    extension.sendMessage("revoke");
+    return extension.awaitMessage("removed");
+  }
+
+  function verifyPermissions(enabled) {
+    extension.sendMessage("verify_access", enabled);
+    return extension.awaitMessage("verified");
+  }
+
+  await withHandlingUserInput(extension, async () => {
+    await addPermissions();
+    await removePermissions();
+    await addPermissions();
+  });
+
+  // reset handlingUserInput for the restart
+  extensionHandlers.delete(extension);
+
+  // Verify access on restart
+  await AddonTestUtils.promiseRestartManager();
+  await extension.awaitBackgroundStarted();
+  await verifyPermissions(true);
+
+  await withHandlingUserInput(extension, async () => {
+    await removePermissions();
+  });
+
+  // Add private browsing to be sure it doesn't come through.
+  let permObj = {
+    permissions: OptionalPermissions.concat("internal:privateBrowsingAllowed"),
+    origins: [],
+  };
+
+  // enable the permissions while the addon is running
+  await ExtensionPermissions.add(extension.id, permObj, extension.extension);
+  await extension.awaitMessage("added");
+  await verifyPermissions(true);
+
+  // disable the permissions while the addon is running
+  await ExtensionPermissions.remove(extension.id, permObj, extension.extension);
+  await extension.awaitMessage("removed");
+  await verifyPermissions(false);
+
+  // Add private browsing to test internal permission.  If it slips through,
+  // we would get an error for an additional added message.
+  await ExtensionPermissions.add(
+    extension.id,
+    { permissions: ["internal:privateBrowsingAllowed"], origins: [] },
+    extension.extension
+  );
+
+  // disable the addon and re-test revoking permissions.
+  await withHandlingUserInput(extension, async () => {
+    await addPermissions();
+  });
+  let addon = await AddonManager.getAddonByID(extension.id);
+  await addon.disable();
+  await ExtensionPermissions.remove(extension.id, permObj);
+  await addon.enable();
+  await extension.awaitStartup();
+
+  await verifyPermissions(false);
+  let perms = await ExtensionPermissions.get(extension.id);
+  equal(perms.permissions.length, 0, "no permissions on startup");
+
+  await extension.unload();
+});
+
+add_task(async function test_geo_permissions() {
+  async function background() {
+    const permObj = { permissions: ["geolocation"] };
+    browser.test.onMessage.addListener(async msg => {
+      if (msg === "request") {
+        await browser.permissions.request(permObj);
+      } else if (msg === "remove") {
+        await browser.permissions.remove(permObj);
+      }
+      let result = await browser.permissions.contains(permObj);
+      browser.test.sendMessage("done", result);
+    });
+  }
+
+  let extension = ExtensionTestUtils.loadExtension({
+    background,
+    manifest: {
+      browser_specific_settings: { gecko: { id: "geo-test@test" } },
+      optional_permissions: ["geolocation"],
+    },
+    useAddonManager: "permanent",
+  });
+  await extension.startup();
+
+  let policy = WebExtensionPolicy.getByID(extension.id);
+  let principal = policy.extension.principal;
+  equal(
+    Services.perms.testPermissionFromPrincipal(principal, "geo"),
+    Services.perms.UNKNOWN_ACTION,
+    "geolocation not allowed on install"
+  );
+
+  await withHandlingUserInput(extension, async () => {
+    extension.sendMessage("request");
+    ok(await extension.awaitMessage("done"), "permission granted");
+    equal(
+      Services.perms.testPermissionFromPrincipal(principal, "geo"),
+      Services.perms.ALLOW_ACTION,
+      "geolocation allowed after requested"
+    );
+
+    extension.sendMessage("remove");
+    ok(!(await extension.awaitMessage("done")), "permission revoked");
+
+    equal(
+      Services.perms.testPermissionFromPrincipal(principal, "geo"),
+      Services.perms.UNKNOWN_ACTION,
+      "geolocation not allowed after removed"
+    );
+
+    // re-grant to test update removal
+    extension.sendMessage("request");
+    ok(await extension.awaitMessage("done"), "permission granted");
+    equal(
+      Services.perms.testPermissionFromPrincipal(principal, "geo"),
+      Services.perms.ALLOW_ACTION,
+      "geolocation allowed after re-requested"
+    );
+  });
+
+  // We should not have geo permission after this upgrade.
+  await extension.upgrade({
+    manifest: {
+      browser_specific_settings: { gecko: { id: "geo-test@test" } },
+    },
+    useAddonManager: "permanent",
+  });
+
+  equal(
+    Services.perms.testPermissionFromPrincipal(principal, "geo"),
+    Services.perms.UNKNOWN_ACTION,
+    "geolocation not allowed after upgrade"
+  );
+
+  await extension.unload();
+});
+
+add_task(async function test_browserSetting_permissions() {
+  async function background() {
+    const permObj = { permissions: ["browserSettings"] };
+    browser.test.onMessage.addListener(async msg => {
+      if (msg === "request") {
+        await browser.permissions.request(permObj);
+        await browser.browserSettings.cacheEnabled.set({ value: false });
+      } else if (msg === "remove") {
+        await browser.permissions.remove(permObj);
+      }
+      browser.test.sendMessage("done");
+    });
+  }
+
+  function cacheIsEnabled() {
+    return (
+      Services.prefs.getBoolPref("browser.cache.disk.enable") &&
+      Services.prefs.getBoolPref("browser.cache.memory.enable")
+    );
+  }
+
+  let extension = ExtensionTestUtils.loadExtension({
+    background,
+    manifest: {
+      optional_permissions: ["browserSettings"],
+    },
+    useAddonManager: "permanent",
+  });
+  await extension.startup();
+  ok(cacheIsEnabled(), "setting is not set after startup");
+
+  await withHandlingUserInput(extension, async () => {
+    extension.sendMessage("request");
+    await extension.awaitMessage("done");
+    ok(!cacheIsEnabled(), "setting was set after request");
+
+    extension.sendMessage("remove");
+    await extension.awaitMessage("done");
+    ok(cacheIsEnabled(), "setting is reset after remove");
+
+    extension.sendMessage("request");
+    await extension.awaitMessage("done");
+    ok(!cacheIsEnabled(), "setting was set after request");
+  });
+
+  await ExtensionPermissions._uninit();
+  extensionHandlers.delete(extension);
+  await AddonTestUtils.promiseRestartManager();
+  await extension.awaitBackgroundStarted();
+
+  await withHandlingUserInput(extension, async () => {
+    extension.sendMessage("remove");
+    await extension.awaitMessage("done");
+    ok(cacheIsEnabled(), "setting is reset after remove");
+  });
+
+  await extension.unload();
+});
+
+add_task(async function test_privacy_permissions() {
+  async function background() {
+    const permObj = { permissions: ["privacy"] };
+    browser.test.onMessage.addListener(async msg => {
+      if (msg === "request") {
+        await browser.permissions.request(permObj);
+        await browser.privacy.websites.trackingProtectionMode.set({
+          value: "always",
+        });
+      } else if (msg === "remove") {
+        await browser.permissions.remove(permObj);
+      }
+      browser.test.sendMessage("done");
+    });
+  }
+
+  function hasSetting() {
+    return Services.prefs.getBoolPref("privacy.trackingprotection.enabled");
+  }
+
+  let extension = ExtensionTestUtils.loadExtension({
+    background,
+    manifest: {
+      optional_permissions: ["privacy"],
+    },
+    useAddonManager: "permanent",
+  });
+  await extension.startup();
+  ok(!hasSetting(), "setting is not set after startup");
+
+  await withHandlingUserInput(extension, async () => {
+    extension.sendMessage("request");
+    await extension.awaitMessage("done");
+    ok(hasSetting(), "setting was set after request");
+
+    extension.sendMessage("remove");
+    await extension.awaitMessage("done");
+    ok(!hasSetting(), "setting is reset after remove");
+
+    extension.sendMessage("request");
+    await extension.awaitMessage("done");
+    ok(hasSetting(), "setting was set after request");
+  });
+
+  await ExtensionPermissions._uninit();
+  extensionHandlers.delete(extension);
+  await AddonTestUtils.promiseRestartManager();
+  await extension.awaitBackgroundStarted();
+
+  await withHandlingUserInput(extension, async () => {
+    extension.sendMessage("remove");
+    await extension.awaitMessage("done");
+    ok(!hasSetting(), "setting is reset after remove");
+  });
+
+  await extension.unload();
+});
+
+add_task(
+  { pref_set: [["extensions.eventPages.enabled", true]] },
+  async function test_permissions_event_page() {
+    let extension = ExtensionTestUtils.loadExtension({
+      useAddonManager: "permanent",
+      manifest: {
+        optional_permissions: ["privacy"],
+        background: { persistent: false },
+      },
+      background() {
+        browser.permissions.onAdded.addListener(details => {
+          browser.test.sendMessage("added", details);
+        });
+
+        browser.permissions.onRemoved.addListener(details => {
+          browser.test.sendMessage("removed", details);
+        });
+      },
+    });
+
+    await extension.startup();
+    let events = ["onAdded", "onRemoved"];
+    for (let event of events) {
+      assertPersistentListeners(extension, "permissions", event, {
+        primed: false,
+      });
+    }
+
+    await extension.terminateBackground();
+    for (let event of events) {
+      assertPersistentListeners(extension, "permissions", event, {
+        primed: true,
+      });
+    }
+
+    let permObj = {
+      permissions: ["privacy"],
+      origins: [],
+    };
+
+    // enable the permissions while the background is stopped
+    await ExtensionPermissions.add(extension.id, permObj, extension.extension);
+    let details = await extension.awaitMessage("added");
+    Assert.deepEqual(permObj, details, "got added event");
+
+    // Restart and test that permission removal wakes the background.
+    await AddonTestUtils.promiseRestartManager();
+    await extension.awaitStartup();
+
+    for (let event of events) {
+      assertPersistentListeners(extension, "permissions", event, {
+        primed: true,
+      });
+    }
+
+    // remove the permissions while the background is stopped
+    await ExtensionPermissions.remove(
+      extension.id,
+      permObj,
+      extension.extension
+    );
+
+    details = await extension.awaitMessage("removed");
+    Assert.deepEqual(permObj, details, "got removed event");
+
+    await extension.unload();
+  }
+);
diff --git a/toolkit/components/extensions/test/xpcshell/test_ext_permissions_migrate.js b/toolkit/components/extensions/test/xpcshell/test_ext_permissions_migrate.js
new file mode 100644
index 0000000000..969304676f
--- /dev/null
+++ b/toolkit/components/extensions/test/xpcshell/test_ext_permissions_migrate.js
@@ -0,0 +1,268 @@
+"use strict";
+
+const { ExtensionPermissions } = ChromeUtils.importESModule(
+  "resource://gre/modules/ExtensionPermissions.sys.mjs"
+);
+
+AddonTestUtils.init(this);
+AddonTestUtils.overrideCertDB();
+AddonTestUtils.createAppInfo(
+  "xpcshell@tests.mozilla.org",
+  "XPCShell",
+  "1",
+  "42"
+);
+
+add_task(async function setup() {
+  // Bug 1646182: Force ExtensionPermissions to run in rkv mode, the legacy
+  // storage mode will run in xpcshell-legacy-ep.ini
+  await ExtensionPermissions._uninit();
+
+  Services.prefs.setBoolPref(
+    "extensions.webextOptionalPermissionPrompts",
+    false
+  );
+  registerCleanupFunction(() => {
+    Services.prefs.clearUserPref("extensions.webextOptionalPermissionPrompts");
+  });
+  await AddonTestUtils.promiseStartupManager();
+  AddonTestUtils.usePrivilegedSignatures = false;
+});
+
+async function test_migrated_permission_to_optional({ manifest_version }) {
+  let id = "permission-upgrade@test";
+  let extensionData = {
+    manifest: {
+      version: "1.0",
+      browser_specific_settings: { gecko: { id } },
+      permissions: [
+        "webRequest",
+        "tabs",
+        "http://example.net/*",
+        "http://example.com/*",
+      ],
+    },
+    useAddonManager: "permanent",
+  };
+
+  function checkPermissions() {
+    let policy = WebExtensionPolicy.getByID(id);
+    ok(policy.hasPermission("webRequest"), "addon has webRequest permission");
+    ok(policy.hasPermission("tabs"), "addon has tabs permission");
+    ok(
+      policy.canAccessURI(Services.io.newURI("http://example.net/")),
+      "addon has example.net host permission"
+    );
+    ok(
+      policy.canAccessURI(Services.io.newURI("http://example.com/")),
+      "addon has example.com host permission"
+    );
+    ok(
+      !policy.canAccessURI(Services.io.newURI("http://other.com/")),
+      "addon does not have other.com host permission"
+    );
+  }
+
+  let extension = ExtensionTestUtils.loadExtension(extensionData);
+  await extension.startup();
+  checkPermissions();
+
+  extensionData.manifest.manifest_version = manifest_version;
+
+  // Move to using optional permission
+  extensionData.manifest.version = "2.0";
+  extensionData.manifest.permissions = ["tabs"];
+
+  // The ExtensionTestCommon.generateFiles() test helper will normalize (move)
+  // host permissions into the `permissions` key for the MV2 test.
+  extensionData.manifest.host_permissions = ["http://example.net/*"];
+
+  extensionData.manifest.optional_permissions = [
+    "webRequest",
+    "http://example.com/*",
+    "http://other.com/*",
+  ];
+
+  // Restart the addon manager to flush the AddonInternal instance created
+  // when installing the addon above.  See bug 1622117.
+  await AddonTestUtils.promiseRestartManager();
+  await extension.upgrade(extensionData);
+
+  equal(extension.version, "2.0", "Expected extension version");
+  checkPermissions();
+
+  await extension.unload();
+}
+
+add_task(function test_migrated_permission_to_optional_mv2() {
+  return test_migrated_permission_to_optional({ manifest_version: 2 });
+});
+
+// Test migration of mv2 (required) to mv3 (optional) host permissions.
+add_task(function test_migrated_permission_to_optional_mv3() {
+  return test_migrated_permission_to_optional({ manifest_version: 3 });
+});
+
+// This tests that settings are removed if a required permission is removed.
+// We use two settings APIs to make sure the one we keep permission to is not
+// removed inadvertantly.
+add_task(async function test_required_permissions_removed() {
+  function cacheIsEnabled() {
+    return (
+      Services.prefs.getBoolPref("browser.cache.disk.enable") &&
+      Services.prefs.getBoolPref("browser.cache.memory.enable")
+    );
+  }
+
+  let extData = {
+    background() {
+      if (browser.browserSettings) {
+        browser.browserSettings.cacheEnabled.set({ value: false });
+      }
+      browser.privacy.services.passwordSavingEnabled.set({ value: false });
+    },
+    manifest: {
+      browser_specific_settings: { gecko: { id: "pref-test@test" } },
+      permissions: ["tabs", "browserSettings", "privacy", "http://test.com/*"],
+    },
+    useAddonManager: "permanent",
+  };
+  let extension = ExtensionTestUtils.loadExtension(extData);
+  ok(
+    Services.prefs.getBoolPref("signon.rememberSignons"),
+    "privacy setting intial value as expected"
+  );
+  await extension.startup();
+  ok(!cacheIsEnabled(), "setting is set after startup");
+
+  extData.manifest.permissions = ["tabs"];
+  extData.manifest.optional_permissions = ["privacy"];
+  await extension.upgrade(extData);
+  ok(cacheIsEnabled(), "setting is reset after upgrade");
+  ok(
+    !Services.prefs.getBoolPref("signon.rememberSignons"),
+    "privacy setting is still set after upgrade"
+  );
+
+  await extension.unload();
+});
+
+// This tests that settings are removed if a granted permission is removed.
+// We use two settings APIs to make sure the one we keep permission to is not
+// removed inadvertantly.
+add_task(async function test_granted_permissions_removed() {
+  function cacheIsEnabled() {
+    return (
+      Services.prefs.getBoolPref("browser.cache.disk.enable") &&
+      Services.prefs.getBoolPref("browser.cache.memory.enable")
+    );
+  }
+
+  let extData = {
+    async background() {
+      browser.test.onMessage.addListener(async msg => {
+        await browser.permissions.request({ permissions: msg.permissions });
+        if (browser.browserSettings) {
+          browser.browserSettings.cacheEnabled.set({ value: false });
+        }
+        browser.privacy.services.passwordSavingEnabled.set({ value: false });
+        browser.test.sendMessage("done");
+      });
+    },
+    // "tabs" is never granted, it is included to exercise the removal code
+    // that called during the upgrade.
+    manifest: {
+      browser_specific_settings: { gecko: { id: "pref-test@test" } },
+      optional_permissions: [
+        "tabs",
+        "browserSettings",
+        "privacy",
+        "http://test.com/*",
+      ],
+    },
+    useAddonManager: "permanent",
+  };
+  let extension = ExtensionTestUtils.loadExtension(extData);
+  ok(
+    Services.prefs.getBoolPref("signon.rememberSignons"),
+    "privacy setting intial value as expected"
+  );
+  await extension.startup();
+  await withHandlingUserInput(extension, async () => {
+    extension.sendMessage({ permissions: ["browserSettings", "privacy"] });
+    await extension.awaitMessage("done");
+  });
+  ok(!cacheIsEnabled(), "setting is set after startup");
+
+  extData.manifest.permissions = ["privacy"];
+  delete extData.manifest.optional_permissions;
+  await extension.upgrade(extData);
+  ok(cacheIsEnabled(), "setting is reset after upgrade");
+  ok(
+    !Services.prefs.getBoolPref("signon.rememberSignons"),
+    "privacy setting is still set after upgrade"
+  );
+
+  await extension.unload();
+});
+
+// Test an update where an add-on becomes a theme.
+add_task(async function test_addon_to_theme_update() {
+  let id = "theme-test@test";
+  let extData = {
+    manifest: {
+      browser_specific_settings: { gecko: { id } },
+      version: "1.0",
+      optional_permissions: ["tabs"],
+    },
+    async background() {
+      browser.test.onMessage.addListener(async msg => {
+        await browser.permissions.request({ permissions: msg.permissions });
+        browser.test.sendMessage("done");
+      });
+    },
+    useAddonManager: "permanent",
+  };
+  let extension = ExtensionTestUtils.loadExtension(extData);
+  await extension.startup();
+
+  await withHandlingUserInput(extension, async () => {
+    extension.sendMessage({ permissions: ["tabs"] });
+    await extension.awaitMessage("done");
+  });
+
+  let policy = WebExtensionPolicy.getByID(id);
+  ok(policy.hasPermission("tabs"), "addon has tabs permission");
+
+  await extension.upgrade({
+    manifest: {
+      browser_specific_settings: { gecko: { id } },
+      version: "2.0",
+      theme: {
+        images: {
+          theme_frame: "image1.png",
+        },
+      },
+    },
+    useAddonManager: "permanent",
+  });
+  // When a theme is installed, it starts off in disabled mode, as seen in
+  //  toolkit/mozapps/extensions/test/xpcshell/test_update_theme.js .
+  // But if we upgrade from an enabled extension, the theme is enabled.
+  equal(extension.addon.userDisabled, false, "Theme is enabled");
+
+  policy = WebExtensionPolicy.getByID(id);
+  ok(!policy.hasPermission("tabs"), "addon tabs permission was removed");
+  let perms = await ExtensionPermissions._get(id);
+  ok(!perms?.permissions?.length, "no retained permissions");
+
+  extData.manifest.version = "3.0";
+  extData.manifest.permissions = ["privacy"];
+  await extension.upgrade(extData);
+
+  policy = WebExtensionPolicy.getByID(id);
+  ok(!policy.hasPermission("tabs"), "addon tabs permission not added");
+  ok(policy.hasPermission("privacy"), "addon privacy permission added");
+
+  await extension.unload();
+});
diff --git a/toolkit/components/extensions/test/xpcshell/test_ext_permissions_uninstall.js b/toolkit/components/extensions/test/xpcshell/test_ext_permissions_uninstall.js
new file mode 100644
index 0000000000..d123575cc5
--- /dev/null
+++ b/toolkit/components/extensions/test/xpcshell/test_ext_permissions_uninstall.js
@@ -0,0 +1,157 @@
+"use strict";
+
+const { ExtensionPermissions } = ChromeUtils.importESModule(
+  "resource://gre/modules/ExtensionPermissions.sys.mjs"
+);
+
+AddonTestUtils.init(this);
+AddonTestUtils.overrideCertDB();
+AddonTestUtils.createAppInfo(
+  "xpcshell@tests.mozilla.org",
+  "XPCShell",
+  "1",
+  "42"
+);
+
+// This test doesn't need the test extensions to be detected as privileged,
+// disabling it to avoid having to keep the list of expected "internal:*"
+// permissions that are added automatically to privileged extensions
+// and already covered by other tests.
+AddonTestUtils.usePrivilegedSignatures = false;
+
+// Look up the cached permissions, if any.
+async function getCachedPermissions(extensionId) {
+  const NotFound = Symbol("extension ID not found in permissions cache");
+  try {
+    return await ExtensionParent.StartupCache.permissions.get(
+      extensionId,
+      () => {
+        // Throw error to prevent the key from being created.
+        throw NotFound;
+      }
+    );
+  } catch (e) {
+    if (e === NotFound) {
+      return null;
+    }
+    throw e;
+  }
+}
+
+// Look up the permissions from the file. Internal methods are used to avoid
+// inadvertently changing the permissions in the cache or the database.
+async function getStoredPermissions(extensionId) {
+  if (await ExtensionPermissions._has(extensionId)) {
+    return ExtensionPermissions._get(extensionId);
+  }
+  return null;
+}
+
+add_task(async function setup() {
+  // Bug 1646182: Force ExtensionPermissions to run in rkv mode, the legacy
+  // storage mode will run in xpcshell-legacy-ep.ini
+  await ExtensionPermissions._uninit();
+
+  optionalPermissionsPromptHandler.init();
+  optionalPermissionsPromptHandler.acceptPrompt = true;
+
+  await AddonTestUtils.promiseStartupManager();
+  registerCleanupFunction(async () => {
+    await AddonTestUtils.promiseShutdownManager();
+  });
+});
+
+// This test must run before any restart of the addonmanager so the
+// ExtensionAddonObserver works.
+add_task(async function test_permissions_removed() {
+  let extension = ExtensionTestUtils.loadExtension({
+    manifest: {
+      optional_permissions: ["idle"],
+    },
+    background() {
+      browser.test.onMessage.addListener(async (msg, arg) => {
+        if (msg == "request") {
+          try {
+            let result = await browser.permissions.request(arg);
+            browser.test.sendMessage("request.result", result);
+          } catch (err) {
+            browser.test.sendMessage("request.result", err.message);
+          }
+        }
+      });
+    },
+    useAddonManager: "temporary",
+  });
+
+  await extension.startup();
+
+  await withHandlingUserInput(extension, async () => {
+    extension.sendMessage("request", { permissions: ["idle"], origins: [] });
+    let result = await extension.awaitMessage("request.result");
+    equal(result, true, "request() for optional permissions succeeded");
+  });
+
+  let id = extension.id;
+  let perms = await ExtensionPermissions.get(id);
+  equal(
+    perms.permissions.length,
+    1,
+    `optional permission added (${JSON.stringify(perms.permissions)})`
+  );
+
+  Assert.deepEqual(
+    await getCachedPermissions(id),
+    {
+      permissions: ["idle"],
+      origins: [],
+    },
+    "Optional permission added to cache"
+  );
+  Assert.deepEqual(
+    await getStoredPermissions(id),
+    {
+      permissions: ["idle"],
+      origins: [],
+    },
+    "Optional permission added to persistent file"
+  );
+
+  await extension.unload();
+
+  // Directly read from the internals instead of using ExtensionPermissions.get,
+  // because the latter will lazily cache the extension ID.
+  Assert.deepEqual(
+    await getCachedPermissions(id),
+    null,
+    "Cached permissions removed"
+  );
+  Assert.deepEqual(
+    await getStoredPermissions(id),
+    null,
+    "Stored permissions removed"
+  );
+
+  perms = await ExtensionPermissions.get(id);
+  equal(
+    perms.permissions.length,
+    0,
+    `no permissions after uninstall (${JSON.stringify(perms.permissions)})`
+  );
+  equal(
+    perms.origins.length,
+    0,
+    `no origin permissions after uninstall (${JSON.stringify(perms.origins)})`
+  );
+
+  // The public ExtensionPermissions.get method should not store (empty)
+  // permissions in the persistent database. Polluting the cache is not ideal,
+  // but acceptable since the cache will eventually be cleared, and non-test
+  // code is not likely to call ExtensionPermissions.get() for non-installed
+  // extensions anyway.
+  Assert.deepEqual(await getCachedPermissions(id), perms, "Permissions cached");
+  Assert.deepEqual(
+    await getStoredPermissions(id),
+    null,
+    "Permissions not saved"
+  );
+});
diff --git a/toolkit/components/extensions/test/xpcshell/test_ext_persistent_events.js b/toolkit/components/extensions/test/xpcshell/test_ext_persistent_events.js
new file mode 100644
index 0000000000..6f903ddeac
--- /dev/null
+++ b/toolkit/components/extensions/test/xpcshell/test_ext_persistent_events.js
@@ -0,0 +1,1636 @@
+"use strict";
+
+// Delay loading until createAppInfo is called and setup.
+ChromeUtils.defineESModuleGetters(this, {
+  AddonManager: "resource://gre/modules/AddonManager.sys.mjs",
+});
+
+const { ExtensionAPI } = ExtensionCommon;
+
+// The code in this class does not actually run in this test scope, it is
+// serialized into a string which is later loaded by the WebExtensions
+// framework in the same context as other extension APIs.  By writing it
+// this way rather than as a big string constant we get lint coverage.
+// But eslint doesn't understand that this code runs in a different context
+// where the EventManager class is available so just tell it here:
+/* global EventManager */
+const API = class extends ExtensionAPI {
+  static namespace = undefined;
+  primeListener(event, fire, params, isInStartup) {
+    if (isInStartup && event == "nonBlockingEvent") {
+      return;
+    }
+    // eslint-disable-next-line no-undef
+    let { eventName, throwError, ignoreListener } =
+      this.constructor.testOptions || {};
+    let { namespace } = this.constructor;
+
+    if (eventName == event) {
+      if (throwError) {
+        throw new Error(throwError);
+      }
+      if (ignoreListener) {
+        return;
+      }
+    }
+
+    Services.obs.notifyObservers(
+      { namespace, event, fire, params },
+      "prime-event-listener"
+    );
+
+    const FIRE_TOPIC = `fire-${namespace}.${event}`;
+
+    async function listener(subject, topic, data) {
+      try {
+        if (subject.wrappedJSObject.waitForBackground) {
+          await fire.wakeup();
+        }
+        await fire.async(subject.wrappedJSObject.listenerArgs);
+      } catch (err) {
+        let errSubject = { namespace, event, errorMessage: err.toString() };
+        Services.obs.notifyObservers(errSubject, "listener-callback-exception");
+      }
+    }
+    Services.obs.addObserver(listener, FIRE_TOPIC);
+
+    return {
+      unregister() {
+        Services.obs.notifyObservers(
+          { namespace, event, params },
+          "unregister-primed-listener"
+        );
+        Services.obs.removeObserver(listener, FIRE_TOPIC);
+      },
+      convert(_fire) {
+        Services.obs.notifyObservers(
+          { namespace, event, params },
+          "convert-event-listener"
+        );
+        fire = _fire;
+      },
+    };
+  }
+
+  getAPI(context) {
+    let self = this;
+    let { namespace } = this.constructor;
+    return {
+      [namespace]: {
+        testOptions(options) {
+          // We want to be able to test errors on startup.
+          // We use a global here because we test restarting AOM,
+          // which causes the instance of this class to be destroyed.
+          // eslint-disable-next-line no-undef
+          self.constructor.testOptions = options;
+        },
+        onEvent1: new EventManager({
+          context,
+          module: namespace,
+          event: "onEvent1",
+          register: (fire, ...params) => {
+            let data = { namespace, event: "onEvent1", params };
+            Services.obs.notifyObservers(data, "register-event-listener");
+            return () => {
+              Services.obs.notifyObservers(data, "unregister-event-listener");
+            };
+          },
+        }).api(),
+
+        onEvent2: new EventManager({
+          context,
+          module: namespace,
+          event: "onEvent2",
+          register: (fire, ...params) => {
+            let data = { namespace, event: "onEvent2", params };
+            Services.obs.notifyObservers(data, "register-event-listener");
+            return () => {
+              Services.obs.notifyObservers(data, "unregister-event-listener");
+            };
+          },
+        }).api(),
+
+        onEvent3: new EventManager({
+          context,
+          module: namespace,
+          event: "onEvent3",
+          register: (fire, ...params) => {
+            let data = { namespace, event: "onEvent3", params };
+            Services.obs.notifyObservers(data, "register-event-listener");
+            return () => {
+              Services.obs.notifyObservers(data, "unregister-event-listener");
+            };
+          },
+        }).api(),
+
+        nonBlockingEvent: new EventManager({
+          context,
+          module: namespace,
+          event: "nonBlockingEvent",
+          register: (fire, ...params) => {
+            let data = { namespace, event: "nonBlockingEvent", params };
+            Services.obs.notifyObservers(data, "register-event-listener");
+            return () => {
+              Services.obs.notifyObservers(data, "unregister-event-listener");
+            };
+          },
+        }).api(),
+      },
+    };
+  }
+};
+
+function makeModule(namespace, options = {}) {
+  const SCHEMA = [
+    {
+      namespace,
+      functions: [
+        {
+          name: "testOptions",
+          type: "function",
+          async: true,
+          parameters: [
+            {
+              name: "options",
+              type: "object",
+              additionalProperties: {
+                type: "any",
+              },
+            },
+          ],
+        },
+      ],
+      events: [
+        {
+          name: "onEvent1",
+          type: "function",
+          extraParameters: [{ type: "any", optional: true }],
+        },
+        {
+          name: "onEvent2",
+          type: "function",
+          extraParameters: [{ type: "any", optional: true }],
+        },
+        {
+          name: "onEvent3",
+          type: "function",
+          extraParameters: [
+            { type: "object", optional: true, additionalProperties: true },
+            { type: "any", optional: true },
+          ],
+        },
+        {
+          name: "nonBlockingEvent",
+          type: "function",
+          extraParameters: [{ type: "any", optional: true }],
+        },
+      ],
+    },
+  ];
+
+  const API_SCRIPT = `
+    this.${namespace} = ${API.toString()};
+    this.${namespace}.namespace = "${namespace}";
+  `;
+
+  // MODULE_INFO for registerModules
+  let { startupBlocking } = options;
+  return {
+    schema: `data:,${JSON.stringify(SCHEMA)}`,
+    scopes: ["addon_parent"],
+    paths: [[namespace]],
+    startupBlocking,
+    url: URL.createObjectURL(new Blob([API_SCRIPT])),
+  };
+}
+
+// Two modules, primary test module is startupBlocking
+const MODULE_INFO = {
+  startupBlocking: makeModule("startupBlocking", { startupBlocking: true }),
+  nonStartupBlocking: makeModule("nonStartupBlocking"),
+};
+
+const global = this;
+
+// Wait for the given event (topic) to occur a specific number of times
+// (count).  If fn is not supplied, the Promise returned from this function
+// resolves as soon as that many instances of the event have been observed.
+// If fn is supplied, this function also waits for the Promise that fn()
+// returns to complete and ensures that the given event does not occur more
+// than `count` times before then.  On success, resolves with an array
+// of the subjects from each of the observed events.
+async function promiseObservable(topic, count, fn = null) {
+  let _countResolve;
+  let results = [];
+  function listener(subject, _topic, data) {
+    const eventDetails = subject.wrappedJSObject;
+    results.push(eventDetails);
+    if (results.length > count) {
+      ok(
+        false,
+        `Got unexpected ${topic} event with ${JSON.stringify(eventDetails)}`
+      );
+    } else if (results.length == count) {
+      _countResolve();
+    }
+  }
+  Services.obs.addObserver(listener, topic);
+
+  try {
+    await Promise.all([
+      new Promise(resolve => {
+        _countResolve = resolve;
+      }),
+      fn && fn(),
+    ]);
+  } finally {
+    Services.obs.removeObserver(listener, topic);
+  }
+
+  return results;
+}
+
+function trackEvents(wrapper) {
+  let events = new Map();
+  for (let event of ["background-script-event", "start-background-script"]) {
+    events.set(event, false);
+    wrapper.extension.once(event, () => events.set(event, true));
+  }
+  return events;
+}
+
+const server = createHttpServer({ hosts: ["example.com"] });
+server.registerDirectory("/data/", do_get_file("data"));
+
+add_setup(async function setup() {
+  // The blob:-URL registered above in MODULE_INFO gets loaded at
+  // https://searchfox.org/mozilla-central/rev/0fec57c05d3996cc00c55a66f20dd5793a9bfb5d/toolkit/components/extensions/ExtensionCommon.jsm#1649
+  Services.prefs.setBoolPref(
+    "security.allow_parent_unrestricted_js_loads",
+    true
+  );
+  registerCleanupFunction(() => {
+    Services.prefs.clearUserPref("security.allow_parent_unrestricted_js_loads");
+  });
+
+  AddonTestUtils.init(global);
+  AddonTestUtils.overrideCertDB();
+  AddonTestUtils.createAppInfo(
+    "xpcshell@tests.mozilla.org",
+    "XPCShell",
+    "42",
+    "42"
+  );
+
+  ExtensionParent.apiManager.registerModules(MODULE_INFO);
+});
+
+add_task(async function test_persistent_events() {
+  await AddonTestUtils.promiseStartupManager();
+
+  let extension = ExtensionTestUtils.loadExtension({
+    useAddonManager: "permanent",
+    background() {
+      let register1 = true,
+        register2 = true;
+      if (localStorage.getItem("skip1")) {
+        register1 = false;
+      }
+      if (localStorage.getItem("skip2")) {
+        register2 = false;
+      }
+
+      let listener1 = arg => browser.test.sendMessage("listener1", arg);
+      let listener2 = arg => browser.test.sendMessage("listener2", arg);
+      let listener3 = arg => browser.test.sendMessage("listener3", arg);
+
+      if (register1) {
+        browser.startupBlocking.onEvent1.addListener(listener1, "listener1");
+      }
+      if (register2) {
+        browser.startupBlocking.onEvent1.addListener(listener2, "listener2");
+        browser.startupBlocking.onEvent2.addListener(listener3, "listener3");
+      }
+
+      browser.test.onMessage.addListener(msg => {
+        if (msg == "unregister2") {
+          browser.startupBlocking.onEvent2.removeListener(listener3);
+          localStorage.setItem("skip2", true);
+        } else if (msg == "unregister1") {
+          localStorage.setItem("skip1", true);
+          browser.test.sendMessage("unregistered");
+        }
+      });
+
+      browser.test.sendMessage("ready");
+    },
+  });
+
+  function check(
+    info,
+    what,
+    { listener1 = true, listener2 = true, listener3 = true } = {}
+  ) {
+    let count = (listener1 ? 1 : 0) + (listener2 ? 1 : 0) + (listener3 ? 1 : 0);
+    equal(info.length, count, `Got ${count} ${what} events`);
+
+    let i = 0;
+    if (listener1) {
+      equal(info[i].event, "onEvent1", `Got ${what} on event1 for listener 1`);
+      deepEqual(
+        info[i].params,
+        ["listener1"],
+        `Got event1 ${what} args for listener 1`
+      );
+      ++i;
+    }
+
+    if (listener2) {
+      equal(info[i].event, "onEvent1", `Got ${what} on event1 for listener 2`);
+      deepEqual(
+        info[i].params,
+        ["listener2"],
+        `Got event1 ${what} args for listener 2`
+      );
+      ++i;
+    }
+
+    if (listener3) {
+      equal(info[i].event, "onEvent2", `Got ${what} on event2 for listener 3`);
+      deepEqual(
+        info[i].params,
+        ["listener3"],
+        `Got event2 ${what} args for listener 3`
+      );
+      ++i;
+    }
+  }
+
+  // Check that the regular event registration process occurs when
+  // the extension is installed.
+  let [observed] = await Promise.all([
+    promiseObservable("register-event-listener", 3),
+    extension.startup(),
+  ]);
+  check(observed, "register");
+
+  await extension.awaitMessage("ready");
+
+  // Check that the regular unregister process occurs when
+  // the browser shuts down.
+  [observed] = await Promise.all([
+    promiseObservable("unregister-event-listener", 3),
+    new Promise(resolve => extension.extension.once("shutdown", resolve)),
+    AddonTestUtils.promiseShutdownManager(),
+  ]);
+  check(observed, "unregister");
+
+  // Check that listeners are primed at the next browser startup.
+  [observed] = await Promise.all([
+    promiseObservable("prime-event-listener", 3),
+    AddonTestUtils.promiseStartupManager(),
+  ]);
+  check(observed, "prime");
+
+  assertPersistentListeners(extension, "startupBlocking", "onEvent1", {
+    primed: true,
+    primedListenersCount: 2,
+  });
+
+  assertPersistentListeners(extension, "startupBlocking", "onEvent2", {
+    primed: true,
+    primedListenersCount: 1,
+  });
+
+  // Check that primed listeners are converted to regular listeners
+  // when the background page is started after browser startup.
+  let p = promiseObservable("convert-event-listener", 3);
+  AddonTestUtils.notifyLateStartup();
+  observed = await p;
+
+  check(observed, "convert");
+
+  await extension.awaitMessage("ready");
+
+  // Check that when the event is triggered, all the plumbing worked
+  // correctly for the primed-then-converted listener.
+  let listenerArgs = { test: "kaboom" };
+  Services.obs.notifyObservers(
+    { listenerArgs },
+    "fire-startupBlocking.onEvent1"
+  );
+
+  let details = await extension.awaitMessage("listener1");
+  deepEqual(details, listenerArgs, "Listener 1 fired");
+  details = await extension.awaitMessage("listener2");
+  deepEqual(details, listenerArgs, "Listener 2 fired");
+
+  // Check that the converted listener is properly unregistered at
+  // browser shutdown.
+  [observed] = await Promise.all([
+    promiseObservable("unregister-primed-listener", 3),
+    AddonTestUtils.promiseShutdownManager(),
+  ]);
+  check(observed, "unregister");
+
+  // Start up again, listener should be primed
+  [observed] = await Promise.all([
+    promiseObservable("prime-event-listener", 3),
+    AddonTestUtils.promiseStartupManager(),
+  ]);
+  check(observed, "prime");
+
+  // Check that triggering the event before the listener has been converted
+  // causes the background page to be loaded and the listener to be converted,
+  // and the listener is invoked.
+  p = promiseObservable("convert-event-listener", 3);
+  listenerArgs.test = "startup event";
+  Services.obs.notifyObservers(
+    { listenerArgs },
+    "fire-startupBlocking.onEvent2"
+  );
+  observed = await p;
+
+  check(observed, "convert");
+
+  details = await extension.awaitMessage("listener3");
+  deepEqual(details, listenerArgs, "Listener 3 fired for event during startup");
+
+  await extension.awaitMessage("ready");
+
+  // Check that triggering onEvent1 emits calls to both listener1 and listener2
+  // (See Bug 1795801).
+  [observed] = await Promise.all([
+    promiseObservable("unregister-primed-listener", 3),
+    AddonTestUtils.promiseShutdownManager(),
+  ]);
+  check(observed, "unregister");
+  [observed] = await Promise.all([
+    promiseObservable("prime-event-listener", 3),
+    AddonTestUtils.promiseStartupManager(),
+  ]);
+  check(observed, "prime");
+  assertPersistentListeners(extension, "startupBlocking", "onEvent1", {
+    primed: true,
+    primedListenersCount: 2,
+  });
+  assertPersistentListeners(extension, "startupBlocking", "onEvent2", {
+    primed: true,
+    primedListenersCount: 1,
+  });
+
+  p = promiseObservable("convert-event-listener", 3);
+  listenerArgs.test = "startup event";
+  Services.obs.notifyObservers(
+    { listenerArgs },
+    "fire-startupBlocking.onEvent1"
+  );
+  observed = await p;
+
+  check(observed, "convert");
+
+  const [detailsListener1Call, detailsListener2Call] = await Promise.all([
+    extension.awaitMessage("listener1"),
+    extension.awaitMessage("listener2"),
+  ]);
+  deepEqual(
+    detailsListener1Call,
+    listenerArgs,
+    "Listener 1 fired for event during startup"
+  );
+  deepEqual(
+    detailsListener2Call,
+    listenerArgs,
+    "Listener 2 fired for event during startup"
+  );
+
+  await extension.awaitMessage("ready");
+
+  // Check that the unregister process works when we manually remove
+  // a listener.
+  p = promiseObservable("unregister-primed-listener", 1);
+  extension.sendMessage("unregister2");
+  observed = await p;
+  check(observed, "unregister", { listener1: false, listener2: false });
+
+  // Check that we only get unregisters for the remaining events after
+  // one listener has been removed.
+  observed = await promiseObservable("unregister-primed-listener", 2, () =>
+    AddonTestUtils.promiseShutdownManager()
+  );
+  check(observed, "unregister", { listener3: false });
+
+  // Check that after restart, only listeners that were present at
+  // the end of the last session are primed.
+  observed = await promiseObservable("prime-event-listener", 2, () =>
+    AddonTestUtils.promiseStartupManager()
+  );
+  check(observed, "prime", { listener3: false });
+
+  // Check that if the background script does not re-register listeners,
+  // the primed listeners are unregistered after the background page
+  // starts up.
+  p = promiseObservable("unregister-primed-listener", 1, () =>
+    extension.awaitMessage("ready")
+  );
+
+  AddonTestUtils.notifyLateStartup();
+  observed = await p;
+  check(observed, "unregister", { listener1: false, listener3: false });
+
+  // Just listener1 should be registered now, fire event1 to confirm.
+  listenerArgs.test = "third time";
+  Services.obs.notifyObservers(
+    { listenerArgs },
+    "fire-startupBlocking.onEvent1"
+  );
+  details = await extension.awaitMessage("listener1");
+  deepEqual(details, listenerArgs, "Listener 1 fired");
+
+  // Tell the extension not to re-register listener1 on the next startup
+  extension.sendMessage("unregister1");
+  await extension.awaitMessage("unregistered");
+
+  // Shut down, start up
+  observed = await promiseObservable("unregister-primed-listener", 1, () =>
+    AddonTestUtils.promiseShutdownManager()
+  );
+  check(observed, "unregister", { listener2: false, listener3: false });
+
+  observed = await promiseObservable("prime-event-listener", 1, () =>
+    AddonTestUtils.promiseStartupManager()
+  );
+  check(observed, "register", { listener2: false, listener3: false });
+
+  // Check that firing event1 causes the listener fire callback to
+  // reject.
+  p = promiseObservable("listener-callback-exception", 1);
+  Services.obs.notifyObservers(
+    { listenerArgs, waitForBackground: true },
+    "fire-startupBlocking.onEvent1"
+  );
+  equal(
+    (await p)[0].errorMessage,
+    "Error: primed listener startupBlocking.onEvent1 not re-registered",
+    "Primed listener that was not re-registered received an error when event was triggered during startup"
+  );
+
+  await extension.awaitMessage("ready");
+
+  await extension.unload();
+
+  await AddonTestUtils.promiseShutdownManager();
+});
+
+// This test checks whether primed listeners are correctly unregistered when
+// a background page load is interrupted. In particular, it verifies that the
+// fire.wakeup() and fire.async() promises settle eventually.
+add_task(async function test_shutdown_before_background_loaded() {
+  await AddonTestUtils.promiseStartupManager();
+
+  let extension = ExtensionTestUtils.loadExtension({
+    useAddonManager: "permanent",
+    background() {
+      let listener = arg => browser.test.sendMessage("triggered", arg);
+      browser.startupBlocking.onEvent1.addListener(listener, "triggered");
+      browser.test.sendMessage("bg_started");
+    },
+  });
+  await Promise.all([
+    promiseObservable("register-event-listener", 1),
+    extension.startup(),
+  ]);
+  await extension.awaitMessage("bg_started");
+
+  await Promise.all([
+    promiseObservable("unregister-event-listener", 1),
+    new Promise(resolve => extension.extension.once("shutdown", resolve)),
+    AddonTestUtils.promiseShutdownManager(),
+  ]);
+
+  let primeListenerPromise = promiseObservable("prime-event-listener", 1);
+  let fire;
+  let fireWakeupBeforeBgFail;
+  let fireAsyncBeforeBgFail;
+
+  let bgAbortedPromise = new Promise(resolve => {
+    let Management = ExtensionParent.apiManager;
+    Management.once("extension-browser-inserted", (eventName, browser) => {
+      browser.fixupAndLoadURIString = async () => {
+        // The fire.wakeup/fire.async promises created while loading the
+        // background page should settle when the page fails to load.
+        fire = (await primeListenerPromise)[0].fire;
+        fireWakeupBeforeBgFail = fire.wakeup();
+        fireAsyncBeforeBgFail = fire.async();
+
+        extension.extension.once("background-script-aborted", resolve);
+        info("Forcing the background load to fail");
+        browser.remove();
+      };
+    });
+  });
+
+  let unregisterPromise = promiseObservable("unregister-primed-listener", 1);
+
+  await Promise.all([
+    primeListenerPromise,
+    AddonTestUtils.promiseStartupManager(),
+  ]);
+  await bgAbortedPromise;
+  info("Loaded extension and aborted load of background page");
+
+  await unregisterPromise;
+  info("Primed listener has been unregistered");
+
+  await fireWakeupBeforeBgFail;
+  info("fire.wakeup() before background load failure should settle");
+
+  await Assert.rejects(
+    fireAsyncBeforeBgFail,
+    /Error: listener not re-registered/,
+    "fire.async before background load failure should be rejected"
+  );
+
+  await fire.wakeup();
+  info("fire.wakeup() after background load failure should settle");
+
+  await Assert.rejects(
+    fire.async(),
+    /Error: primed listener startupBlocking.onEvent1 not re-registered/,
+    "fire.async after background load failure should be rejected"
+  );
+
+  await AddonTestUtils.promiseShutdownManager();
+
+  // End of the abnormal shutdown test. Now restart the extension to verify
+  // that the persistent listeners have not been unregistered.
+
+  // Suppress background page start until an explicit notification.
+  await Promise.all([
+    promiseObservable("prime-event-listener", 1),
+    AddonTestUtils.promiseStartupManager({ earlyStartup: false }),
+  ]);
+  info("Triggering persistent event to force the background page to start");
+  Services.obs.notifyObservers(
+    { listenerArgs: 123 },
+    "fire-startupBlocking.onEvent1"
+  );
+  AddonTestUtils.notifyEarlyStartup();
+  await extension.awaitMessage("bg_started");
+  equal(await extension.awaitMessage("triggered"), 123, "triggered event");
+
+  await Promise.all([
+    promiseObservable("unregister-primed-listener", 1),
+    AddonTestUtils.promiseShutdownManager(),
+  ]);
+
+  // And lastly, verify that a primed listener is correctly removed when the
+  // extension unloads normally before the delayed background page can load.
+  await Promise.all([
+    promiseObservable("prime-event-listener", 1),
+    AddonTestUtils.promiseStartupManager({ earlyStartup: false }),
+  ]);
+
+  info("Unloading extension before background page has loaded");
+  await Promise.all([
+    promiseObservable("unregister-primed-listener", 1),
+    extension.unload(),
+  ]);
+
+  await AddonTestUtils.promiseShutdownManager();
+});
+
+// This test checks whether primed listeners are correctly primed to
+// restart the background once the background has been shutdown or
+// put to sleep.
+add_task(async function test_background_restarted() {
+  await AddonTestUtils.promiseStartupManager();
+
+  let extension = ExtensionTestUtils.loadExtension({
+    useAddonManager: "permanent",
+    background() {
+      let listener = arg => browser.test.sendMessage("triggered", arg);
+      browser.startupBlocking.onEvent1.addListener(listener, "triggered");
+      browser.test.sendMessage("bg_started");
+    },
+  });
+  await Promise.all([
+    promiseObservable("register-event-listener", 1),
+    extension.startup(),
+  ]);
+  await extension.awaitMessage("bg_started");
+  assertPersistentListeners(extension, "startupBlocking", "onEvent1", {
+    primed: false,
+  });
+
+  // Shutdown the background page
+  await Promise.all([
+    promiseObservable("unregister-event-listener", 1),
+    extension.terminateBackground(),
+  ]);
+  // When sleeping the background, its events should become persisted
+  assertPersistentListeners(extension, "startupBlocking", "onEvent1", {
+    primed: true,
+  });
+
+  info("Triggering persistent event to force the background page to start");
+  Services.obs.notifyObservers(
+    { listenerArgs: 123 },
+    "fire-startupBlocking.onEvent1"
+  );
+  await extension.awaitMessage("bg_started");
+  equal(await extension.awaitMessage("triggered"), 123, "triggered event");
+
+  await extension.unload();
+  await AddonTestUtils.promiseShutdownManager();
+});
+
+// This test checks whether primed listeners are correctly primed to
+// restart the background once the background has been shutdown or
+// put to sleep.
+add_task(
+  { pref_set: [["extensions.eventPages.enabled", true]] },
+  async function test_eventpage_startup() {
+    await AddonTestUtils.promiseStartupManager();
+
+    let extension = ExtensionTestUtils.loadExtension({
+      useAddonManager: "permanent",
+      manifest: {
+        browser_specific_settings: { gecko: { id: "eventpage@test" } },
+        background: { persistent: false },
+      },
+      background() {
+        let listener = arg => browser.test.sendMessage("triggered", arg);
+        browser.startupBlocking.onEvent1.addListener(listener, "triggered");
+        let listenerNs = arg => browser.test.sendMessage("triggered-et2", arg);
+        browser.nonStartupBlocking.onEvent1.addListener(
+          listenerNs,
+          "triggered-et2"
+        );
+        browser.test.onMessage.addListener(() => {
+          let listener = arg => browser.test.sendMessage("triggered2", arg);
+          browser.startupBlocking.onEvent2.addListener(listener, "triggered2");
+          browser.test.sendMessage("async-registered-listener");
+        });
+        browser.test.sendMessage("bg_started");
+      },
+    });
+    await Promise.all([
+      promiseObservable("register-event-listener", 2),
+      extension.startup(),
+    ]);
+    await extension.awaitMessage("bg_started");
+    extension.sendMessage("async-register-listener");
+    await extension.awaitMessage("async-registered-listener");
+
+    async function testAfterRestart() {
+      assertPersistentListeners(extension, "startupBlocking", "onEvent1", {
+        primed: true,
+      });
+      // async registration should not be primed or persisted
+      assertPersistentListeners(extension, "startupBlocking", "onEvent2", {
+        primed: false,
+        persisted: false,
+      });
+
+      let events = trackEvents(extension);
+      ok(
+        !events.get("background-script-event"),
+        "Should not have received a background script event"
+      );
+      ok(
+        !events.get("start-background-script"),
+        "Background script should not be started"
+      );
+
+      info("Triggering persistent event to force the background page to start");
+      let converted = promiseObservable("convert-event-listener", 1);
+      Services.obs.notifyObservers(
+        { listenerArgs: 123 },
+        "fire-startupBlocking.onEvent1"
+      );
+      await extension.awaitMessage("bg_started");
+      await converted;
+      equal(await extension.awaitMessage("triggered"), 123, "triggered event");
+      ok(
+        events.get("background-script-event"),
+        "Should have received a background script event"
+      );
+      ok(
+        events.get("start-background-script"),
+        "Background script should be started"
+      );
+    }
+
+    // Shutdown the background page
+    await Promise.all([
+      promiseObservable("unregister-event-listener", 3),
+      new Promise(resolve => extension.extension.once("shutdown", resolve)),
+      AddonTestUtils.promiseShutdownManager(),
+    ]);
+    await AddonTestUtils.promiseStartupManager({ lateStartup: false });
+    await extension.awaitStartup();
+    assertPersistentListeners(extension, "nonStartupBlocking", "onEvent1", {
+      primed: false,
+      persisted: true,
+    });
+    await testAfterRestart();
+
+    extension.sendMessage("async-register-listener");
+    await extension.awaitMessage("async-registered-listener");
+
+    // We sleep twice to ensure startup and shutdown work correctly
+    info("test event listener registration during termination");
+    let registrationEvents = Promise.all([
+      promiseObservable("unregister-event-listener", 2),
+      promiseObservable("unregister-primed-listener", 1),
+      promiseObservable("prime-event-listener", 2),
+    ]);
+    await extension.terminateBackground();
+    await registrationEvents;
+
+    assertPersistentListeners(extension, "nonStartupBlocking", "onEvent1", {
+      primed: true,
+      persisted: true,
+    });
+
+    // Ensure onEvent2 does not fire, testAfterRestart will fail otherwise.
+    Services.obs.notifyObservers(
+      { listenerArgs: 123 },
+      "fire-startupBlocking.onEvent2"
+    );
+    await testAfterRestart();
+
+    registrationEvents = Promise.all([
+      promiseObservable("unregister-primed-listener", 2),
+      promiseObservable("prime-event-listener", 2),
+    ]);
+    await extension.terminateBackground();
+    await registrationEvents;
+    await testAfterRestart();
+
+    await extension.unload();
+    await AddonTestUtils.promiseShutdownManager();
+  }
+);
+
+// This test verifies primeListener behavior for errors or ignored listeners.
+add_task(async function test_background_primeListener_errors() {
+  await AddonTestUtils.promiseStartupManager();
+
+  // The internal APIs to shutdown the background work with any
+  // background, and in the shutdown case, events will be persisted
+  // and primed for a restart.
+  let extension = ExtensionTestUtils.loadExtension({
+    useAddonManager: "permanent",
+    background() {
+      // Listen for options being set so a restart will have them.
+      browser.test.onMessage.addListener(async (message, options) => {
+        if (message == "set-options") {
+          await browser.startupBlocking.testOptions(options);
+          browser.test.sendMessage("set-options:done");
+        }
+      });
+      let listener = arg => browser.test.sendMessage("triggered", arg);
+      browser.startupBlocking.onEvent1.addListener(listener, "triggered");
+      let listener2 = arg => browser.test.sendMessage("triggered", arg);
+      browser.startupBlocking.onEvent2.addListener(listener2, "triggered");
+      browser.test.sendMessage("bg_started");
+    },
+  });
+  await Promise.all([
+    promiseObservable("register-event-listener", 1),
+    extension.startup(),
+  ]);
+  await extension.awaitMessage("bg_started");
+  assertPersistentListeners(extension, "startupBlocking", "onEvent1", {
+    primed: false,
+  });
+
+  // If an event is removed from an api, a permission is removed,
+  // or some other option prevents priming, ensure that
+  // primelistener works correctly.
+  // In this scenario we are testing that an event is not renewed
+  // on startup because the API does not re-prime it.  The result
+  // is that the event is also not persisted.  However the other
+  // events that are renewed should still be primed and persisted.
+  extension.sendMessage("set-options", {
+    eventName: "onEvent1",
+    ignoreListener: true,
+  });
+  await extension.awaitMessage("set-options:done");
+
+  // Shutdown the background page
+  await Promise.all([
+    promiseObservable("unregister-event-listener", 2),
+    extension.terminateBackground(),
+  ]);
+  // startupBlocking.onEvent1 was not re-primed and should not be persisted, but
+  // onEvent2 should still be primed and persisted.
+  assertPersistentListeners(extension, "startupBlocking", "onEvent1", {
+    primed: false,
+    persisted: false,
+  });
+  assertPersistentListeners(extension, "startupBlocking", "onEvent2", {
+    primed: true,
+  });
+
+  info("Triggering persistent event to force the background page to start");
+  Services.obs.notifyObservers(
+    { listenerArgs: 123 },
+    "fire-startupBlocking.onEvent2"
+  );
+  await extension.awaitMessage("bg_started");
+  equal(await extension.awaitMessage("triggered"), 123, "triggered event");
+
+  // On restart, test an exception, it should not be re-primed.
+  extension.sendMessage("set-options", {
+    eventName: "onEvent1",
+    throwError: "error",
+  });
+  await extension.awaitMessage("set-options:done");
+
+  // Shutdown the background page
+  await Promise.all([
+    promiseObservable("unregister-event-listener", 1),
+    extension.terminateBackground(),
+  ]);
+  // startupBlocking.onEvent1 failed and should not be persisted
+  assertPersistentListeners(extension, "startupBlocking", "onEvent1", {
+    primed: false,
+    persisted: false,
+  });
+
+  info("Triggering event to verify background starts after prior error");
+  Services.obs.notifyObservers(
+    { listenerArgs: 123 },
+    "fire-startupBlocking.onEvent2"
+  );
+  await extension.awaitMessage("bg_started");
+  equal(await extension.awaitMessage("triggered"), 123, "triggered event");
+
+  info("reset options for next test");
+  extension.sendMessage("set-options", {});
+  await extension.awaitMessage("set-options:done");
+
+  // Test errors on app restart
+  info("Test errors during app startup");
+  await AddonTestUtils.promiseRestartManager();
+  await extension.awaitStartup();
+  await extension.awaitMessage("bg_started");
+
+  info("restart AOM and verify primed listener");
+  await AddonTestUtils.promiseRestartManager({ earlyStartup: false });
+  await extension.awaitStartup();
+  assertPersistentListeners(extension, "startupBlocking", "onEvent1", {
+    primed: true,
+    persisted: true,
+  });
+  AddonTestUtils.notifyEarlyStartup();
+
+  Services.obs.notifyObservers(
+    { listenerArgs: 123 },
+    "fire-startupBlocking.onEvent1"
+  );
+  await extension.awaitMessage("bg_started");
+  equal(await extension.awaitMessage("triggered"), 123, "triggered event");
+
+  // Test that an exception happening during priming clears the
+  // event from being persisted when restarting the browser, and that
+  // the background correctly starts.
+  info("test exception during primeListener on startup");
+  extension.sendMessage("set-options", {
+    eventName: "onEvent1",
+    throwError: "error",
+  });
+  await extension.awaitMessage("set-options:done");
+
+  await AddonTestUtils.promiseRestartManager({ earlyStartup: false });
+  await extension.awaitStartup();
+  AddonTestUtils.notifyEarlyStartup();
+
+  // At this point, the exception results in the persisted entry
+  // being cleared.
+  assertPersistentListeners(extension, "startupBlocking", "onEvent1", {
+    primed: false,
+    persisted: false,
+  });
+
+  AddonTestUtils.notifyLateStartup();
+
+  await extension.awaitMessage("bg_started");
+
+  // The background added the listener back during top level execution,
+  // verify it is in the persisted list.
+  assertPersistentListeners(extension, "startupBlocking", "onEvent1", {
+    primed: false,
+    persisted: true,
+  });
+
+  // reset options
+  extension.sendMessage("set-options", {});
+  await extension.awaitMessage("set-options:done");
+  await extension.unload();
+  await AddonTestUtils.promiseShutdownManager();
+});
+
+add_task(async function test_non_background_context_listener_not_persisted() {
+  await AddonTestUtils.promiseStartupManager();
+
+  let extension = ExtensionTestUtils.loadExtension({
+    useAddonManager: "permanent",
+    background() {
+      let listener = arg => browser.test.sendMessage("triggered", arg);
+      browser.startupBlocking.onEvent1.addListener(listener, "triggered");
+      browser.test.sendMessage(
+        "bg_started",
+        browser.runtime.getURL("extpage.html")
+      );
+    },
+    files: {
+      "extpage.html": `<script src="extpage.js"></script>`,
+      "extpage.js": function () {
+        let listener = arg =>
+          browser.test.sendMessage("extpage-triggered", arg);
+        browser.startupBlocking.onEvent2.addListener(
+          listener,
+          "extpage-triggered"
+        );
+        // Send a message to signal the extpage has registered the listener,
+        // after calling an async method and wait it to be resolved to make sure
+        // the addListener call to have been handled in the parent process by
+        // the time we will assert the persisted listeners.
+        browser.runtime.getPlatformInfo().then(() => {
+          browser.test.sendMessage("extpage_started");
+        });
+      },
+    },
+  });
+
+  await extension.startup();
+  const extpage_url = await extension.awaitMessage("bg_started");
+
+  assertPersistentListeners(extension, "startupBlocking", "onEvent1", {
+    persisted: true,
+    primed: false,
+  });
+
+  assertPersistentListeners(extension, "startupBlocking", "onEvent2", {
+    persisted: false,
+  });
+
+  const page = await ExtensionTestUtils.loadContentPage(extpage_url);
+  await extension.awaitMessage("extpage_started");
+
+  // Expect the onEvent2 listener subscribed by the extpage to not be persisted.
+  assertPersistentListeners(extension, "startupBlocking", "onEvent2", {
+    persisted: false,
+  });
+
+  await page.close();
+  await extension.unload();
+  await AddonTestUtils.promiseShutdownManager();
+});
+
+// Test support for event page tests
+const background = async function () {
+  let listener2 = () =>
+    browser.test.sendMessage("triggered:non-startupblocking");
+  browser.startupBlocking.onEvent1.addListener(() => {});
+  browser.startupBlocking.nonBlockingEvent.addListener(() => {});
+  browser.nonStartupBlocking.onEvent2.addListener(listener2);
+  browser.test.sendMessage("bg_started");
+};
+
+const background_update = async function () {
+  browser.startupBlocking.onEvent1.addListener(() => {});
+  browser.nonStartupBlocking.onEvent2.addListener(() => {});
+  browser.test.sendMessage("updated_bg_started");
+};
+
+function testPersistentListeners(extension, expect) {
+  for (let [ns, event, persisted, primed] of expect) {
+    assertPersistentListeners(extension, ns, event, {
+      persisted,
+      primed,
+    });
+  }
+}
+
+add_task(
+  { pref_set: [["extensions.eventPages.enabled", true]] },
+  async function test_startupblocking_behavior() {
+    await AddonTestUtils.promiseStartupManager();
+
+    let extension = ExtensionTestUtils.loadExtension({
+      useAddonManager: "permanent",
+      manifest: {
+        background: { persistent: false },
+      },
+      background,
+    });
+
+    await extension.startup();
+    await extension.awaitMessage("bg_started");
+
+    // All are persisted on startup
+    testPersistentListeners(extension, [
+      ["startupBlocking", "onEvent1", true, false],
+      ["startupBlocking", "nonBlockingEvent", true, false],
+      ["nonStartupBlocking", "onEvent2", true, false],
+    ]);
+
+    info("Test after mocked browser restart");
+    await Promise.all([
+      new Promise(resolve => extension.extension.once("shutdown", resolve)),
+      AddonTestUtils.promiseShutdownManager(),
+    ]);
+    await AddonTestUtils.promiseStartupManager({ lateStartup: false });
+    await extension.awaitStartup();
+
+    testPersistentListeners(extension, [
+      // Startup blocking event is expected to be persisted and primed.
+      ["startupBlocking", "onEvent1", true, true],
+      // A non-startup-blocking event shouldn't be primed yet.
+      ["startupBlocking", "nonBlockingEvent", true, false],
+      // Non "Startup blocking" event is expected to be persisted but not primed yet.
+      ["nonStartupBlocking", "onEvent2", true, false],
+    ]);
+
+    // Complete the browser startup and fire the startup blocking event
+    // to let the backgrund script to run.
+    AddonTestUtils.notifyLateStartup();
+    Services.obs.notifyObservers({}, "fire-startupBlocking.onEvent1");
+    await extension.awaitMessage("bg_started");
+
+    info("Test after terminate background script");
+    await extension.terminateBackground();
+
+    // After the background is terminated, all are persisted and primed.
+    testPersistentListeners(extension, [
+      ["startupBlocking", "onEvent1", true, true],
+      ["startupBlocking", "nonBlockingEvent", true, true],
+      ["nonStartupBlocking", "onEvent2", true, true],
+    ]);
+
+    info("Notify event for the non-startupBlocking API event");
+    Services.obs.notifyObservers({}, "fire-nonStartupBlocking.onEvent2");
+    await extension.awaitMessage("bg_started");
+    await extension.awaitMessage("triggered:non-startupblocking");
+
+    await extension.unload();
+    await AddonTestUtils.promiseShutdownManager();
+  }
+);
+
+add_task(
+  { pref_set: [["extensions.eventPages.enabled", true]] },
+  async function test_startupblocking_behavior_upgrade() {
+    let id = "persistent-upgrade@test";
+    await AddonTestUtils.promiseStartupManager();
+
+    let extensionData = {
+      useAddonManager: "permanent",
+      manifest: {
+        version: "1.0",
+        browser_specific_settings: {
+          gecko: { id },
+        },
+        background: { persistent: false },
+      },
+      background,
+    };
+    let extension = ExtensionTestUtils.loadExtension(extensionData);
+    await extension.startup();
+    await extension.awaitMessage("bg_started");
+
+    // All are persisted on startup
+    testPersistentListeners(extension, [
+      ["startupBlocking", "onEvent1", true, false],
+      ["startupBlocking", "nonBlockingEvent", true, false],
+      ["nonStartupBlocking", "onEvent2", true, false],
+    ]);
+
+    // Prepare the extension that will be updated.
+    extensionData.manifest.version = "2.0";
+    extensionData.background = background_update;
+
+    info("Test after a upgrade");
+    await extension.upgrade(extensionData);
+    // upgrade should start the background
+    await extension.awaitMessage("updated_bg_started");
+
+    // Nothing should be primed at this point after the background
+    // has started.  We look specifically for nonBlockingEvent to
+    // no longer be a part of the persisted listeners.
+    testPersistentListeners(extension, [
+      ["startupBlocking", "onEvent1", true, false],
+      ["startupBlocking", "nonBlockingEvent", false, false],
+      ["nonStartupBlocking", "onEvent2", true, false],
+    ]);
+
+    await extension.unload();
+    await AddonTestUtils.promiseShutdownManager();
+  }
+);
+
+add_task(
+  { pref_set: [["extensions.eventPages.enabled", true]] },
+  async function test_startupblocking_behavior_staged_upgrade() {
+    AddonManager.checkUpdateSecurity = false;
+    let id = "persistent-staged-upgrade@test";
+
+    // register an update file.
+    AddonTestUtils.registerJSON(server, "/test_update.json", {
+      addons: {
+        [id]: {
+          updates: [
+            {
+              version: "2.0",
+              update_link:
+                "http://example.com/addons/test_settings_staged_restart.xpi",
+            },
+          ],
+        },
+      },
+    });
+
+    let extensionData = {
+      useAddonManager: "permanent",
+      manifest: {
+        version: "2.0",
+        browser_specific_settings: {
+          gecko: { id, update_url: `http://example.com/test_update.json` },
+        },
+        background: { persistent: false },
+      },
+      background: background_update,
+    };
+
+    // Prepare the update first.
+    server.registerFile(
+      `/addons/test_settings_staged_restart.xpi`,
+      AddonTestUtils.createTempWebExtensionFile(extensionData)
+    );
+
+    // Prepare the extension that will be updated.
+    extensionData.manifest.version = "1.0";
+    extensionData.background = async function () {
+      // we're testing persistence, not operation, so no action in listeners.
+      browser.startupBlocking.onEvent1.addListener(() => {});
+      // nonBlockingEvent will be removed on upgrade
+      browser.startupBlocking.nonBlockingEvent.addListener(() => {});
+      browser.nonStartupBlocking.onEvent2.addListener(() => {});
+
+      // Force a staged updated.
+      browser.runtime.onUpdateAvailable.addListener(async details => {
+        // This should be the version of the pending update.
+        browser.test.assertEq("2.0", details.version, "correct version");
+        browser.test.sendMessage("delay");
+      });
+
+      browser.test.sendMessage("bg_started");
+    };
+
+    await AddonTestUtils.promiseStartupManager();
+    let extension = ExtensionTestUtils.loadExtension(extensionData);
+
+    await extension.startup();
+    await extension.awaitMessage("bg_started");
+
+    // All are persisted but not primed on startup
+    testPersistentListeners(extension, [
+      ["startupBlocking", "onEvent1", true, false],
+      ["startupBlocking", "nonBlockingEvent", true, false],
+      ["nonStartupBlocking", "onEvent2", true, false],
+    ]);
+
+    info("Test after a staged update");
+    // first, deal with getting and staging an upgrade
+    let addon = await AddonManager.getAddonByID(id);
+    Assert.equal(addon.version, "1.0", "1.0 is loaded");
+
+    let update = await AddonTestUtils.promiseFindAddonUpdates(addon);
+    let install = update.updateAvailable;
+    Assert.ok(install, `install is available ${update.error}`);
+
+    await AddonTestUtils.promiseCompleteAllInstalls([install]);
+
+    Assert.equal(
+      install.state,
+      AddonManager.STATE_POSTPONED,
+      "update is staged for install"
+    );
+    await extension.awaitMessage("delay");
+
+    await AddonTestUtils.promiseShutdownManager();
+
+    // restarting allows upgrade to proceed
+    await AddonTestUtils.promiseStartupManager();
+    // upgrade should always start the background
+    await extension.awaitMessage("updated_bg_started");
+
+    // Since this is an upgraded addon, the background will have started
+    // and we no longer have primed listeners.  Check only the persisted
+    // values, and that nonBlockingEvent is not persisted.
+    testPersistentListeners(extension, [
+      ["startupBlocking", "onEvent1", true, false],
+      ["startupBlocking", "nonBlockingEvent", false, false],
+      ["nonStartupBlocking", "onEvent2", true, false],
+    ]);
+
+    await extension.unload();
+    await AddonTestUtils.promiseShutdownManager();
+  }
+);
+
+// Regression test for Bug 1795801:
+// - verifies that multiple listeners sharing the same event and set of extra
+//   params are being stored in the startupData and then all primed on the next
+//   startup
+// - verifies behaviors expected when startupData stored from an older
+//   Firefox version (one that didn't include Bug 1795801 changes) is
+//   loaded from a new Firefox version
+// - a small smoke test to also verify the behaviors when startupData stored
+//   by a newer version is being loaded by an older one (where Bug 1795801
+//   changes have not been introduced yet).
+add_task(async function test_migrate_startupData_to_new_format() {
+  await AddonTestUtils.promiseStartupManager();
+
+  const extension = ExtensionTestUtils.loadExtension({
+    useAddonManager: "permanent",
+    manifest: {
+      background: { persistent: false },
+    },
+    background() {
+      const eventParams = [
+        { fromCustomParam1: "value1" },
+        ["fromCustomParam2"],
+      ];
+      const otherEventParams = [
+        { fromCustomParam1: "value2" },
+        ["fromCustomParam2Other"],
+      ];
+      browser.nonStartupBlocking.onEvent3.addListener(function listener1(arg) {
+        browser.test.log("listener1 called on nonStartupBlocking.onEvent3");
+        browser.test.sendMessage("listener1", arg);
+      }, ...eventParams);
+      browser.nonStartupBlocking.onEvent3.addListener(function listener2(arg) {
+        browser.test.log("listener2 called on nonStartupBlocking.onEvent3");
+        browser.test.sendMessage("listener2", arg);
+      }, ...eventParams);
+      browser.nonStartupBlocking.onEvent3.addListener(function listener3(arg) {
+        browser.test.log("listener3 called on nonStartupBlocking.onEvent3");
+        browser.test.sendMessage("listener3", arg);
+      }, ...otherEventParams);
+      browser.test.sendMessage("ready");
+    },
+  });
+
+  // Data expected to be stored in the extension startupData with the new
+  // format and old format.
+  const STARTUP_DATA = {
+    newPersistentListenersFormat: {
+      nonStartupBlocking: {
+        onEvent3: [
+          // 2 listeners registered with the same set of extra params
+          [{ fromCustomParam1: "value1" }, ["fromCustomParam2"]],
+          [{ fromCustomParam1: "value1" }, ["fromCustomParam2"]],
+          // 1 listener registered with different set of extra params
+          [{ fromCustomParam1: "value2" }, ["fromCustomParam2Other"]],
+        ],
+      },
+    },
+    oldPersistentListenersFormat: {
+      nonStartupBlocking: {
+        onEvent3: [
+          [{ fromCustomParam1: "value1" }, ["fromCustomParam2"]],
+          [{ fromCustomParam1: "value2" }, ["fromCustomParam2Other"]],
+        ],
+      },
+    },
+  };
+
+  function getXPIStatesFilePath() {
+    let { path } = ChromeUtils.import(
+      "resource://gre/modules/addons/XPIProvider.jsm"
+    ).XPIInternal.XPIStates._jsonFile;
+    ok(
+      typeof path === "string" && !!path.length,
+      `Found XPIStates file path: ${path}`
+    );
+    return path;
+  }
+
+  async function tamperStartupData(testExtensionWrapper) {
+    const { startupData } = testExtensionWrapper.extension;
+    Assert.deepEqual(
+      startupData.persistentListeners,
+      STARTUP_DATA.newPersistentListenersFormat,
+      "Got data stored from extension.startupData.persistentListeners"
+    );
+
+    startupData.persistentListeners = STARTUP_DATA.oldPersistentListenersFormat;
+
+    // Force the data to be stored on disk (by requesting AddonTestUtils to flush
+    // the XPIStates after having tampered them to make sure they are in the
+    // format we expect from older Firefox versions).
+    testExtensionWrapper.extension.saveStartupData();
+    await AddonTestUtils.loadAddonsList(/* flush */ true);
+    const { XPIInternal } = ChromeUtils.import(
+      "resource://gre/modules/addons/XPIProvider.jsm"
+    );
+    XPIInternal.XPIStates.save();
+    await XPIInternal.XPIStates._jsonFile._save();
+    return getXPIStatesFilePath();
+  }
+
+  async function assertDiskStoredPersistentListeners(
+    extensionId,
+    xpiStatesPath,
+    expectedData
+  ) {
+    const xpiStatesData = await IOUtils.readJSON(xpiStatesPath, {
+      decompress: true,
+    });
+    const startupData =
+      xpiStatesData["app-profile"]?.addons[extensionId]?.startupData;
+    ok(startupData, `Found startupData for test extension ${extensionId}`);
+    Assert.deepEqual(
+      startupData.persistentListeners,
+      expectedData,
+      "Got the expected tampered addon startupData stored on disk"
+    );
+  }
+
+  await extension.startup();
+
+  await extension.awaitMessage("ready");
+  assertPersistentListeners(extension, "nonStartupBlocking", "onEvent3", {
+    persisted: true,
+  });
+
+  info(
+    "Manually tampering startupData.persistentListeners to match the format older Firefox format"
+  );
+  const xpiStatesFilePath = await tamperStartupData(extension);
+  await AddonTestUtils.promiseShutdownManager();
+  await assertDiskStoredPersistentListeners(
+    extension.id,
+    xpiStatesFilePath,
+    STARTUP_DATA.oldPersistentListenersFormat
+  );
+
+  info(
+    "Confirm that the expected listeners have been primed and the startupData migrated to the new format"
+  );
+
+  {
+    await AddonTestUtils.promiseStartupManager();
+    await extension.awaitStartup;
+
+    assertPersistentListeners(extension, "nonStartupBlocking", "onEvent3", {
+      primed: true,
+      // Old format of startupData.persistentListeners did not have a listenersCount
+      // property and so only two primed listeners are expected on the first startup
+      // after the addon startupData have been tampered to match the format expected
+      // by an older Firefox version.
+      primedListenersCount: 2,
+    });
+
+    const promiseListenersConverted = promiseObservable(
+      "convert-event-listener",
+      2
+    );
+    Services.obs.notifyObservers(
+      { listenerArgs: "test-startup" },
+      "fire-nonStartupBlocking.onEvent3"
+    );
+    await promiseListenersConverted;
+
+    deepEqual(
+      await extension.awaitMessage("listener1"),
+      "test-startup",
+      "Listener1 fired for event during startup"
+    );
+
+    deepEqual(
+      await extension.awaitMessage("listener3"),
+      "test-startup",
+      "Listener3 fired for event during startup"
+    );
+
+    await extension.awaitMessage("ready");
+
+    Assert.deepEqual(
+      extension.extension.startupData.persistentListeners,
+      STARTUP_DATA.newPersistentListenersFormat,
+      "Got startupData.persistentListeners migrated to the new format"
+    );
+  }
+
+  info(
+    "Confirm that the startupData written on disk have been migrated to the new format"
+  );
+
+  await AddonTestUtils.promiseShutdownManager();
+  await assertDiskStoredPersistentListeners(
+    extension.id,
+    xpiStatesFilePath,
+    STARTUP_DATA.newPersistentListenersFormat
+  );
+
+  info(
+    "Verify that both listeners are called after migrating to the new format"
+  );
+  {
+    await AddonTestUtils.promiseStartupManager();
+    await extension.awaitStartup;
+
+    assertPersistentListeners(extension, "nonStartupBlocking", "onEvent3", {
+      primed: true,
+      primedListenersCount: 3,
+    });
+
+    const promiseListenersConverted = promiseObservable(
+      "convert-event-listener",
+      2
+    );
+    Services.obs.notifyObservers(
+      { listenerArgs: "test-startup" },
+      "fire-nonStartupBlocking.onEvent3"
+    );
+    await promiseListenersConverted;
+
+    // Now we expect both the listeners to have been called.
+    deepEqual(
+      await extension.awaitMessage("listener1"),
+      "test-startup",
+      "Listener1 fired for event during startup"
+    );
+
+    deepEqual(
+      await extension.awaitMessage("listener2"),
+      "test-startup",
+      "Listener2 fired for event during startup"
+    );
+
+    deepEqual(
+      await extension.awaitMessage("listener3"),
+      "test-startup",
+      "Listener3 fired for event during startup"
+    );
+
+    await extension.awaitMessage("ready");
+  }
+
+  await extension.unload();
+  await AddonTestUtils.promiseShutdownManager();
+
+  // The additional assertions below are meant to provide a smoke test covering
+  // the behavior we would expect if an older Firefox versions (one that would
+  // expect the old format) is loading persistentListeners from startupData
+  // using the new format.
+  info("Verify backward compatibility with old format");
+
+  const { ExtensionUtils } = ChromeUtils.importESModule(
+    "resource://gre/modules/ExtensionUtils.sys.mjs"
+  );
+  const { DefaultMap } = ExtensionUtils;
+  const loadedListeners = new DefaultMap(() => new DefaultMap(() => new Map()));
+
+  // Logic from older Firefox versions expecting the old format
+  // (https://searchfox.org/mozilla-central/rev/cd2121e7d8/toolkit/components/extensions/ExtensionCommon.jsm#2360-2371)
+  let found = false;
+  for (let [module, entry] of Object.entries(
+    STARTUP_DATA.newPersistentListenersFormat
+  )) {
+    for (let [event, paramlists] of Object.entries(entry)) {
+      for (let paramlist of paramlists) {
+        let key = uneval(paramlist);
+        loadedListeners.get(module).get(event).set(key, { params: paramlist });
+        found = true;
+      }
+    }
+  }
+
+  Assert.ok(
+    found,
+    "Expect persistentListeners to have been found from the old loading logic"
+  );
+
+  // We expect the older Firefox version to don't choke on loading
+  // the new format, a primed listener is still expected to be
+  // found because the old Firefox version will be overriding a single
+  // entry in the inmemory Map with the multiple entries from the
+  // ondisk format listing the same extra params for multiple listeners,
+  // Bug 1795801 would still be hit, but no other change in behavior is
+  // expected to be hit with the old logic.
+  Assert.ok(
+    loadedListeners
+      .get("nonStartupBlocking")
+      .get("onEvent3")
+      .has(uneval([{ fromCustomParam1: "value1" }, ["fromCustomParam2"]])),
+    "Expect the listener params key to be found in older Firefox versions"
+  );
+});
diff --git a/toolkit/components/extensions/test/xpcshell/test_ext_privacy.js b/toolkit/components/extensions/test/xpcshell/test_ext_privacy.js
new file mode 100644
index 0000000000..1d5f2a8b30
--- /dev/null
+++ b/toolkit/components/extensions/test/xpcshell/test_ext_privacy.js
@@ -0,0 +1,979 @@
+/* -*- Mode: indent-tabs-mode: nil; js-indent-level: 2 -*- */
+/* vim: set sts=2 sw=2 et tw=80: */
+"use strict";
+
+ChromeUtils.defineESModuleGetters(this, {
+  ExtensionPreferencesManager:
+    "resource://gre/modules/ExtensionPreferencesManager.sys.mjs",
+  Preferences: "resource://gre/modules/Preferences.sys.mjs",
+});
+
+const { createAppInfo, promiseShutdownManager, promiseStartupManager } =
+  AddonTestUtils;
+
+AddonTestUtils.init(this);
+AddonTestUtils.overrideCertDB();
+
+createAppInfo("xpcshell@tests.mozilla.org", "XPCShell", "1", "42");
+
+// Currently security.tls.version.min has a different default
+// value in Nightly and Beta as opposed to Release builds.
+const tlsMinPref = Services.prefs.getIntPref("security.tls.version.min");
+if (tlsMinPref != 1 && tlsMinPref != 3) {
+  ok(false, "This test expects security.tls.version.min set to 1 or 3.");
+}
+const tlsMinVer = tlsMinPref === 3 ? "TLSv1.2" : "TLSv1";
+const READ_ONLY = true;
+
+add_task(async function test_privacy() {
+  // Create an object to hold the values to which we will initialize the prefs.
+  const SETTINGS = {
+    "network.networkPredictionEnabled": {
+      "network.predictor.enabled": true,
+      "network.prefetch-next": true,
+      // This pref starts with a numerical value and we need to use whatever the
+      // default is or we encounter issues when the pref is reset during the test.
+      "network.http.speculative-parallel-limit":
+        ExtensionPreferencesManager.getDefaultValue(
+          "network.http.speculative-parallel-limit"
+        ),
+      "network.dns.disablePrefetch": false,
+    },
+    "websites.hyperlinkAuditingEnabled": {
+      "browser.send_pings": true,
+    },
+  };
+
+  async function background() {
+    browser.test.onMessage.addListener(async (msg, data, setting) => {
+      // The second argument is the end of the api name,
+      // e.g., "network.networkPredictionEnabled".
+      let apiObj = setting.split(".").reduce((o, i) => o[i], browser.privacy);
+      let settingData;
+      switch (msg) {
+        case "get":
+          settingData = await apiObj.get(data);
+          browser.test.sendMessage("gotData", settingData);
+          break;
+
+        case "set":
+          await apiObj.set(data);
+          settingData = await apiObj.get({});
+          browser.test.sendMessage("afterSet", settingData);
+          break;
+
+        case "clear":
+          await apiObj.clear(data);
+          settingData = await apiObj.get({});
+          browser.test.sendMessage("afterClear", settingData);
+          break;
+      }
+    });
+  }
+
+  // Set prefs to our initial values.
+  for (let setting in SETTINGS) {
+    for (let pref in SETTINGS[setting]) {
+      Preferences.set(pref, SETTINGS[setting][pref]);
+    }
+  }
+
+  registerCleanupFunction(() => {
+    // Reset the prefs.
+    for (let setting in SETTINGS) {
+      for (let pref in SETTINGS[setting]) {
+        Preferences.reset(pref);
+      }
+    }
+  });
+
+  await promiseStartupManager();
+
+  // Create an array of extensions to install.
+  let testExtensions = [
+    ExtensionTestUtils.loadExtension({
+      background,
+      manifest: {
+        permissions: ["privacy"],
+      },
+      useAddonManager: "temporary",
+    }),
+
+    ExtensionTestUtils.loadExtension({
+      background,
+      manifest: {
+        permissions: ["privacy"],
+      },
+      useAddonManager: "temporary",
+    }),
+  ];
+
+  for (let extension of testExtensions) {
+    await extension.startup();
+  }
+
+  for (let setting in SETTINGS) {
+    testExtensions[0].sendMessage("get", {}, setting);
+    let data = await testExtensions[0].awaitMessage("gotData");
+    ok(data.value, "get returns expected value.");
+    equal(
+      data.levelOfControl,
+      "controllable_by_this_extension",
+      "get returns expected levelOfControl."
+    );
+
+    testExtensions[0].sendMessage("get", { incognito: true }, setting);
+    data = await testExtensions[0].awaitMessage("gotData");
+    ok(data.value, "get returns expected value with incognito.");
+    equal(
+      data.levelOfControl,
+      "not_controllable",
+      "get returns expected levelOfControl with incognito."
+    );
+
+    // Change the value to false.
+    testExtensions[0].sendMessage("set", { value: false }, setting);
+    data = await testExtensions[0].awaitMessage("afterSet");
+    ok(!data.value, "get returns expected value after setting.");
+    equal(
+      data.levelOfControl,
+      "controlled_by_this_extension",
+      "get returns expected levelOfControl after setting."
+    );
+
+    // Verify the prefs have been set to match the "false" setting.
+    for (let pref in SETTINGS[setting]) {
+      let msg = `${pref} set correctly for ${setting}`;
+      if (pref === "network.http.speculative-parallel-limit") {
+        equal(Preferences.get(pref), 0, msg);
+      } else {
+        equal(Preferences.get(pref), !SETTINGS[setting][pref], msg);
+      }
+    }
+
+    // Change the value with a newer extension.
+    testExtensions[1].sendMessage("set", { value: true }, setting);
+    data = await testExtensions[1].awaitMessage("afterSet");
+    ok(
+      data.value,
+      "get returns expected value after setting via newer extension."
+    );
+    equal(
+      data.levelOfControl,
+      "controlled_by_this_extension",
+      "get returns expected levelOfControl after setting."
+    );
+
+    // Verify the prefs have been set to match the "true" setting.
+    for (let pref in SETTINGS[setting]) {
+      let msg = `${pref} set correctly for ${setting}`;
+      if (pref === "network.http.speculative-parallel-limit") {
+        equal(
+          Preferences.get(pref),
+          ExtensionPreferencesManager.getDefaultValue(pref),
+          msg
+        );
+      } else {
+        equal(Preferences.get(pref), SETTINGS[setting][pref], msg);
+      }
+    }
+
+    // Change the value with an older extension.
+    testExtensions[0].sendMessage("set", { value: false }, setting);
+    data = await testExtensions[0].awaitMessage("afterSet");
+    ok(data.value, "Newer extension remains in control.");
+    equal(
+      data.levelOfControl,
+      "controlled_by_other_extensions",
+      "get returns expected levelOfControl when controlled by other."
+    );
+
+    // Clear the value of the newer extension.
+    testExtensions[1].sendMessage("clear", {}, setting);
+    data = await testExtensions[1].awaitMessage("afterClear");
+    ok(!data.value, "Older extension gains control.");
+    equal(
+      data.levelOfControl,
+      "controllable_by_this_extension",
+      "Expected levelOfControl returned after clearing."
+    );
+
+    testExtensions[0].sendMessage("get", {}, setting);
+    data = await testExtensions[0].awaitMessage("gotData");
+    ok(!data.value, "Current, older extension has control.");
+    equal(
+      data.levelOfControl,
+      "controlled_by_this_extension",
+      "Expected levelOfControl returned after clearing."
+    );
+
+    // Set the value again with the newer extension.
+    testExtensions[1].sendMessage("set", { value: true }, setting);
+    data = await testExtensions[1].awaitMessage("afterSet");
+    ok(
+      data.value,
+      "get returns expected value after setting via newer extension."
+    );
+    equal(
+      data.levelOfControl,
+      "controlled_by_this_extension",
+      "get returns expected levelOfControl after setting."
+    );
+
+    // Unload the newer extension. Expect the older extension to regain control.
+    await testExtensions[1].unload();
+    testExtensions[0].sendMessage("get", {}, setting);
+    data = await testExtensions[0].awaitMessage("gotData");
+    ok(!data.value, "Older extension regained control.");
+    equal(
+      data.levelOfControl,
+      "controlled_by_this_extension",
+      "Expected levelOfControl returned after unloading."
+    );
+
+    // Reload the extension for the next iteration of the loop.
+    testExtensions[1] = ExtensionTestUtils.loadExtension({
+      background,
+      manifest: {
+        permissions: ["privacy"],
+      },
+      useAddonManager: "temporary",
+    });
+    await testExtensions[1].startup();
+
+    // Clear the value of the older extension.
+    testExtensions[0].sendMessage("clear", {}, setting);
+    data = await testExtensions[0].awaitMessage("afterClear");
+    ok(data.value, "Setting returns to original value when all are cleared.");
+    equal(
+      data.levelOfControl,
+      "controllable_by_this_extension",
+      "Expected levelOfControl returned after clearing."
+    );
+
+    // Verify that our initial values were restored.
+    for (let pref in SETTINGS[setting]) {
+      equal(
+        Preferences.get(pref),
+        SETTINGS[setting][pref],
+        `${pref} was reset to its initial value.`
+      );
+    }
+  }
+
+  for (let extension of testExtensions) {
+    await extension.unload();
+  }
+
+  await promiseShutdownManager();
+});
+
+add_task(async function test_privacy_other_prefs() {
+  registerCleanupFunction(() => {
+    Services.prefs.clearUserPref("security.tls.version.min");
+    Services.prefs.clearUserPref("security.tls.version.max");
+  });
+
+  const cookieSvc = Ci.nsICookieService;
+
+  // Create an object to hold the values to which we will initialize the prefs.
+  const SETTINGS = {
+    "network.webRTCIPHandlingPolicy": {
+      "media.peerconnection.ice.default_address_only": false,
+      "media.peerconnection.ice.no_host": false,
+      "media.peerconnection.ice.proxy_only_if_behind_proxy": false,
+      "media.peerconnection.ice.proxy_only": false,
+    },
+    "network.tlsVersionRestriction": {
+      "security.tls.version.min": tlsMinPref,
+      "security.tls.version.max": 4,
+    },
+    "network.peerConnectionEnabled": {
+      "media.peerconnection.enabled": true,
+    },
+    "services.passwordSavingEnabled": {
+      "signon.rememberSignons": true,
+    },
+    "websites.referrersEnabled": {
+      "network.http.sendRefererHeader": 2,
+    },
+    "websites.resistFingerprinting": {
+      "privacy.resistFingerprinting": true,
+    },
+    "websites.firstPartyIsolate": {
+      "privacy.firstparty.isolate": false,
+    },
+    "websites.cookieConfig": {
+      "network.cookie.cookieBehavior": cookieSvc.BEHAVIOR_ACCEPT,
+    },
+  };
+
+  let defaultPrefs = new Preferences({ defaultBranch: true });
+  let defaultCookieBehavior = defaultPrefs.get("network.cookie.cookieBehavior");
+  let defaultBehavior;
+  switch (defaultCookieBehavior) {
+    case cookieSvc.BEHAVIOR_ACCEPT:
+      defaultBehavior = "allow_all";
+      break;
+    case cookieSvc.BEHAVIOR_REJECT_FOREIGN:
+      defaultBehavior = "reject_third_party";
+      break;
+    case cookieSvc.BEHAVIOR_REJECT:
+      defaultBehavior = "reject_all";
+      break;
+    case cookieSvc.BEHAVIOR_LIMIT_FOREIGN:
+      defaultBehavior = "allow_visited";
+      break;
+    case cookieSvc.BEHAVIOR_REJECT_TRACKER:
+      defaultBehavior = "reject_trackers";
+      break;
+    case cookieSvc.BEHAVIOR_REJECT_TRACKER_AND_PARTITION_FOREIGN:
+      defaultBehavior = "reject_trackers_and_partition_foreign";
+      break;
+    default:
+      ok(
+        false,
+        `Unexpected cookie behavior encountered: ${defaultCookieBehavior}`
+      );
+      break;
+  }
+
+  async function background() {
+    let listeners = new Set([]);
+    browser.test.onMessage.addListener(async (msg, data, setting, readOnly) => {
+      // The second argument is the end of the api name,
+      // e.g., "network.webRTCIPHandlingPolicy".
+      let apiObj = setting.split(".").reduce((o, i) => o[i], browser.privacy);
+      if (msg == "get") {
+        browser.test.sendMessage("gettingData", await apiObj.get({}));
+        return;
+      }
+
+      // Don't add more than one listener per apiName.  We leave the
+      // listener to ensure we do not get more calls than we expect.
+      if (!listeners.has(setting)) {
+        apiObj.onChange.addListener(details => {
+          browser.test.sendMessage("settingData", details);
+        });
+        listeners.add(setting);
+      }
+      try {
+        await apiObj.set(data);
+      } catch (e) {
+        browser.test.sendMessage("settingThrowsException", {
+          message: e.message,
+        });
+      }
+      // Readonly settings will not trigger onChange, return the setting now.
+      if (readOnly) {
+        browser.test.sendMessage("settingData", await apiObj.get({}));
+      }
+    });
+  }
+
+  // Set prefs to our initial values.
+  for (let setting in SETTINGS) {
+    for (let pref in SETTINGS[setting]) {
+      Preferences.set(pref, SETTINGS[setting][pref]);
+    }
+  }
+
+  registerCleanupFunction(() => {
+    // Reset the prefs.
+    for (let setting in SETTINGS) {
+      for (let pref in SETTINGS[setting]) {
+        Preferences.reset(pref);
+      }
+    }
+  });
+
+  await promiseStartupManager();
+
+  let extension = ExtensionTestUtils.loadExtension({
+    background,
+    manifest: {
+      permissions: ["privacy"],
+    },
+    useAddonManager: "temporary",
+  });
+
+  await extension.startup();
+
+  async function testSetting(setting, value, expected, expectedValue = value) {
+    extension.sendMessage("set", { value: value }, setting);
+    let data = await extension.awaitMessage("settingData");
+    deepEqual(
+      data.value,
+      expectedValue,
+      `Got expected result on setting ${setting} to ${uneval(value)}`
+    );
+    for (let pref in expected) {
+      equal(
+        Preferences.get(pref),
+        expected[pref],
+        `${pref} set correctly for ${expected[pref]}`
+      );
+    }
+  }
+
+  async function testSettingException(setting, value, expected) {
+    extension.sendMessage("set", { value: value }, setting);
+    let data = await extension.awaitMessage("settingThrowsException");
+    equal(data.message, expected);
+  }
+
+  async function testGetting(getting, expected, expectedValue) {
+    extension.sendMessage("get", null, getting);
+    let data = await extension.awaitMessage("gettingData");
+    deepEqual(
+      data.value,
+      expectedValue,
+      `Got expected result on getting ${getting}`
+    );
+    for (let pref in expected) {
+      equal(
+        Preferences.get(pref),
+        expected[pref],
+        `${pref} get correctly for ${expected[pref]}`
+      );
+    }
+  }
+
+  await testSetting(
+    "network.webRTCIPHandlingPolicy",
+    "default_public_and_private_interfaces",
+    {
+      "media.peerconnection.ice.default_address_only": true,
+      "media.peerconnection.ice.no_host": false,
+      "media.peerconnection.ice.proxy_only_if_behind_proxy": false,
+      "media.peerconnection.ice.proxy_only": false,
+    }
+  );
+  await testSetting(
+    "network.webRTCIPHandlingPolicy",
+    "default_public_interface_only",
+    {
+      "media.peerconnection.ice.default_address_only": true,
+      "media.peerconnection.ice.no_host": true,
+      "media.peerconnection.ice.proxy_only_if_behind_proxy": false,
+      "media.peerconnection.ice.proxy_only": false,
+    }
+  );
+  await testSetting(
+    "network.webRTCIPHandlingPolicy",
+    "disable_non_proxied_udp",
+    {
+      "media.peerconnection.ice.default_address_only": true,
+      "media.peerconnection.ice.no_host": true,
+      "media.peerconnection.ice.proxy_only_if_behind_proxy": true,
+      "media.peerconnection.ice.proxy_only": false,
+    }
+  );
+  await testSetting("network.webRTCIPHandlingPolicy", "proxy_only", {
+    "media.peerconnection.ice.default_address_only": false,
+    "media.peerconnection.ice.no_host": false,
+    "media.peerconnection.ice.proxy_only_if_behind_proxy": false,
+    "media.peerconnection.ice.proxy_only": true,
+  });
+  await testSetting("network.webRTCIPHandlingPolicy", "default", {
+    "media.peerconnection.ice.default_address_only": false,
+    "media.peerconnection.ice.no_host": false,
+    "media.peerconnection.ice.proxy_only_if_behind_proxy": false,
+    "media.peerconnection.ice.proxy_only": false,
+  });
+
+  await testSetting("network.peerConnectionEnabled", false, {
+    "media.peerconnection.enabled": false,
+  });
+  await testSetting("network.peerConnectionEnabled", true, {
+    "media.peerconnection.enabled": true,
+  });
+
+  await testSetting("websites.referrersEnabled", false, {
+    "network.http.sendRefererHeader": 0,
+  });
+  await testSetting("websites.referrersEnabled", true, {
+    "network.http.sendRefererHeader": 2,
+  });
+
+  await testSetting("websites.resistFingerprinting", false, {
+    "privacy.resistFingerprinting": false,
+  });
+  await testSetting("websites.resistFingerprinting", true, {
+    "privacy.resistFingerprinting": true,
+  });
+
+  await testSetting("websites.trackingProtectionMode", "always", {
+    "privacy.trackingprotection.enabled": true,
+    "privacy.trackingprotection.pbmode.enabled": true,
+  });
+  await testSetting("websites.trackingProtectionMode", "never", {
+    "privacy.trackingprotection.enabled": false,
+    "privacy.trackingprotection.pbmode.enabled": false,
+  });
+  await testSetting("websites.trackingProtectionMode", "private_browsing", {
+    "privacy.trackingprotection.enabled": false,
+    "privacy.trackingprotection.pbmode.enabled": true,
+  });
+
+  await testSetting("services.passwordSavingEnabled", false, {
+    "signon.rememberSignons": false,
+  });
+  await testSetting("services.passwordSavingEnabled", true, {
+    "signon.rememberSignons": true,
+  });
+
+  await testSetting(
+    "websites.cookieConfig",
+    { behavior: "reject_third_party", nonPersistentCookies: true },
+    {
+      "network.cookie.cookieBehavior": cookieSvc.BEHAVIOR_REJECT_FOREIGN,
+    },
+    { behavior: "reject_third_party", nonPersistentCookies: false }
+  );
+  // A missing nonPersistentCookies property should default to false.
+  await testSetting(
+    "websites.cookieConfig",
+    { behavior: "reject_third_party" },
+    {
+      "network.cookie.cookieBehavior": cookieSvc.BEHAVIOR_REJECT_FOREIGN,
+    },
+    { behavior: "reject_third_party", nonPersistentCookies: false }
+  );
+  // A missing behavior property should reset the pref.
+  await testSetting(
+    "websites.cookieConfig",
+    { nonPersistentCookies: true },
+    {
+      "network.cookie.cookieBehavior": defaultCookieBehavior,
+    },
+    { behavior: defaultBehavior, nonPersistentCookies: false }
+  );
+  await testSetting(
+    "websites.cookieConfig",
+    { behavior: "reject_all" },
+    {
+      "network.cookie.cookieBehavior": cookieSvc.BEHAVIOR_REJECT,
+    },
+    { behavior: "reject_all", nonPersistentCookies: false }
+  );
+  await testSetting(
+    "websites.cookieConfig",
+    { behavior: "allow_visited" },
+    {
+      "network.cookie.cookieBehavior": cookieSvc.BEHAVIOR_LIMIT_FOREIGN,
+    },
+    { behavior: "allow_visited", nonPersistentCookies: false }
+  );
+  await testSetting(
+    "websites.cookieConfig",
+    { behavior: "allow_all" },
+    {
+      "network.cookie.cookieBehavior": cookieSvc.BEHAVIOR_ACCEPT,
+    },
+    { behavior: "allow_all", nonPersistentCookies: false }
+  );
+  await testSetting(
+    "websites.cookieConfig",
+    { nonPersistentCookies: true },
+    {
+      "network.cookie.cookieBehavior": defaultCookieBehavior,
+    },
+    { behavior: defaultBehavior, nonPersistentCookies: false }
+  );
+  await testSetting(
+    "websites.cookieConfig",
+    { nonPersistentCookies: false },
+    {
+      "network.cookie.cookieBehavior": defaultCookieBehavior,
+    },
+    { behavior: defaultBehavior, nonPersistentCookies: false }
+  );
+  await testSetting(
+    "websites.cookieConfig",
+    { behavior: "reject_trackers" },
+    {
+      "network.cookie.cookieBehavior": cookieSvc.BEHAVIOR_REJECT_TRACKER,
+    },
+    { behavior: "reject_trackers", nonPersistentCookies: false }
+  );
+  await testSetting(
+    "websites.cookieConfig",
+    { behavior: "reject_trackers_and_partition_foreign" },
+    {
+      "network.cookie.cookieBehavior":
+        cookieSvc.BEHAVIOR_REJECT_TRACKER_AND_PARTITION_FOREIGN,
+    },
+    {
+      behavior: "reject_trackers_and_partition_foreign",
+      nonPersistentCookies: false,
+    }
+  );
+
+  // 1. Can't enable FPI when cookie behavior is "reject_trackers_and_partition_foreign"
+  await testSettingException(
+    "websites.firstPartyIsolate",
+    true,
+    "Can't enable firstPartyIsolate when cookieBehavior is 'reject_trackers_and_partition_foreign'"
+  );
+
+  // 2. Change cookieConfig to reject_trackers should work normally.
+  await testSetting(
+    "websites.cookieConfig",
+    { behavior: "reject_trackers" },
+    {
+      "network.cookie.cookieBehavior": cookieSvc.BEHAVIOR_REJECT_TRACKER,
+    },
+    { behavior: "reject_trackers", nonPersistentCookies: false }
+  );
+
+  // 3. Enable FPI
+  await testSetting("websites.firstPartyIsolate", true, {
+    "privacy.firstparty.isolate": true,
+  });
+
+  // 4. When FPI is enabled, change setting to "reject_trackers_and_partition_foreign" is invalid
+  await testSettingException(
+    "websites.cookieConfig",
+    { behavior: "reject_trackers_and_partition_foreign" },
+    "Invalid cookieConfig 'reject_trackers_and_partition_foreign' when firstPartyIsolate is enabled"
+  );
+
+  // 5. Set conflict settings manually and check prefs.
+  Preferences.set("network.cookie.cookieBehavior", 5);
+  await testGetting(
+    "websites.firstPartyIsolate",
+    { "privacy.firstparty.isolate": true },
+    true
+  );
+  await testGetting(
+    "websites.cookieConfig",
+    {
+      "network.cookie.cookieBehavior":
+        cookieSvc.BEHAVIOR_REJECT_TRACKER_AND_PARTITION_FOREIGN,
+    },
+    {
+      behavior: "reject_trackers_and_partition_foreign",
+      nonPersistentCookies: false,
+    }
+  );
+
+  // 6. It is okay to set current saved value.
+  await testSetting("websites.firstPartyIsolate", true, {
+    "privacy.firstparty.isolate": true,
+  });
+  await testSetting(
+    "websites.cookieConfig",
+    { behavior: "reject_trackers_and_partition_foreign" },
+    {
+      "network.cookie.cookieBehavior":
+        cookieSvc.BEHAVIOR_REJECT_TRACKER_AND_PARTITION_FOREIGN,
+    },
+    {
+      behavior: "reject_trackers_and_partition_foreign",
+      nonPersistentCookies: false,
+    }
+  );
+
+  await testSetting("websites.firstPartyIsolate", false, {
+    "privacy.firstparty.isolate": false,
+  });
+
+  await testSetting(
+    "network.tlsVersionRestriction",
+    {
+      minimum: "TLSv1.2",
+      maximum: "TLSv1.3",
+    },
+    {
+      "security.tls.version.min": 3,
+      "security.tls.version.max": 4,
+    }
+  );
+
+  // Single values
+  await testSetting(
+    "network.tlsVersionRestriction",
+    {
+      minimum: "TLSv1.3",
+    },
+    {
+      "security.tls.version.min": 4,
+      "security.tls.version.max": 4,
+    },
+    {
+      minimum: "TLSv1.3",
+      maximum: "TLSv1.3",
+    }
+  );
+
+  // Single values
+  await testSetting(
+    "network.tlsVersionRestriction",
+    {
+      minimum: "TLSv1.3",
+    },
+    {
+      "security.tls.version.min": 4,
+      "security.tls.version.max": 4,
+    },
+    {
+      minimum: "TLSv1.3",
+      maximum: "TLSv1.3",
+    }
+  );
+
+  // Invalid values.
+  await testSettingException(
+    "network.tlsVersionRestriction",
+    {
+      minimum: "invalid",
+      maximum: "invalid",
+    },
+    "Setting TLS version invalid is not allowed for security reasons."
+  );
+
+  // Invalid values.
+  await testSettingException(
+    "network.tlsVersionRestriction",
+    {
+      minimum: "invalid2",
+    },
+    "Setting TLS version invalid2 is not allowed for security reasons."
+  );
+
+  // Invalid values.
+  await testSettingException(
+    "network.tlsVersionRestriction",
+    {
+      maximum: "invalid3",
+    },
+    "Setting TLS version invalid3 is not allowed for security reasons."
+  );
+
+  await testSetting(
+    "network.tlsVersionRestriction",
+    {
+      minimum: "TLSv1.2",
+    },
+    {
+      "security.tls.version.min": 3,
+      "security.tls.version.max": 4,
+    },
+    {
+      minimum: "TLSv1.2",
+      maximum: "TLSv1.3",
+    }
+  );
+
+  await testSetting(
+    "network.tlsVersionRestriction",
+    {
+      maximum: "TLSv1.2",
+    },
+    {
+      "security.tls.version.min": tlsMinPref,
+      "security.tls.version.max": 3,
+    },
+    {
+      minimum: tlsMinVer,
+      maximum: "TLSv1.2",
+    }
+  );
+
+  // Not supported version.
+  if (tlsMinPref === 3) {
+    await testSettingException(
+      "network.tlsVersionRestriction",
+      {
+        minimum: "TLSv1",
+      },
+      "Setting TLS version TLSv1 is not allowed for security reasons."
+    );
+
+    await testSettingException(
+      "network.tlsVersionRestriction",
+      {
+        minimum: "TLSv1.1",
+      },
+      "Setting TLS version TLSv1.1 is not allowed for security reasons."
+    );
+
+    await testSettingException(
+      "network.tlsVersionRestriction",
+      {
+        maximum: "TLSv1",
+      },
+      "Setting TLS version TLSv1 is not allowed for security reasons."
+    );
+
+    await testSettingException(
+      "network.tlsVersionRestriction",
+      {
+        maximum: "TLSv1.1",
+      },
+      "Setting TLS version TLSv1.1 is not allowed for security reasons."
+    );
+  }
+
+  // Min vs Max
+  await testSettingException(
+    "network.tlsVersionRestriction",
+    {
+      minimum: "TLSv1.3",
+      maximum: "TLSv1.2",
+    },
+    "Setting TLS min version grater than the max version is not allowed."
+  );
+
+  // Min vs Max (with default max)
+  await testSetting(
+    "network.tlsVersionRestriction",
+    {
+      minimum: "TLSv1.2",
+      maximum: "TLSv1.2",
+    },
+    {
+      "security.tls.version.min": 3,
+      "security.tls.version.max": 3,
+    }
+  );
+  await testSettingException(
+    "network.tlsVersionRestriction",
+    {
+      minimum: "TLSv1.3",
+    },
+    "Setting TLS min version grater than the max version is not allowed."
+  );
+
+  // Max vs Min
+  await testSetting(
+    "network.tlsVersionRestriction",
+    {
+      minimum: "TLSv1.3",
+      maximum: "TLSv1.3",
+    },
+    {
+      "security.tls.version.min": 4,
+      "security.tls.version.max": 4,
+    }
+  );
+  await testSettingException(
+    "network.tlsVersionRestriction",
+    {
+      maximum: "TLSv1.2",
+    },
+    "Setting TLS max version lower than the min version is not allowed."
+  );
+
+  // Empty value.
+  await testSetting(
+    "network.tlsVersionRestriction",
+    {},
+    {
+      "security.tls.version.min": tlsMinPref,
+      "security.tls.version.max": 4,
+    },
+    {
+      minimum: tlsMinVer,
+      maximum: "TLSv1.3",
+    }
+  );
+
+  const GLOBAL_PRIVACY_CONTROL_PREF_NAME =
+    "privacy.globalprivacycontrol.enabled";
+
+  Preferences.set(GLOBAL_PRIVACY_CONTROL_PREF_NAME, false);
+  await testGetting("network.globalPrivacyControl", {}, false);
+
+  Preferences.set(GLOBAL_PRIVACY_CONTROL_PREF_NAME, true);
+  await testGetting("network.globalPrivacyControl", {}, true);
+
+  // trying to "set" should have no effect when readonly!
+  extension.sendMessage(
+    "set",
+    { value: !Preferences.get(GLOBAL_PRIVACY_CONTROL_PREF_NAME) },
+    "network.globalPrivacyControl",
+    READ_ONLY
+  );
+  let readOnlyGPCData = await extension.awaitMessage("settingData");
+  equal(
+    readOnlyGPCData.value,
+    Preferences.get(GLOBAL_PRIVACY_CONTROL_PREF_NAME),
+    "extension cannot set globalPrivacyControl"
+  );
+
+  equal(Preferences.get(GLOBAL_PRIVACY_CONTROL_PREF_NAME), true);
+
+  const HTTPS_ONLY_PREF_NAME = "dom.security.https_only_mode";
+  const HTTPS_ONLY_PBM_PREF_NAME = "dom.security.https_only_mode_pbm";
+
+  Preferences.set(HTTPS_ONLY_PREF_NAME, false);
+  Preferences.set(HTTPS_ONLY_PBM_PREF_NAME, false);
+  await testGetting("network.httpsOnlyMode", {}, "never");
+
+  Preferences.set(HTTPS_ONLY_PREF_NAME, true);
+  Preferences.set(HTTPS_ONLY_PBM_PREF_NAME, false);
+  await testGetting("network.httpsOnlyMode", {}, "always");
+
+  Preferences.set(HTTPS_ONLY_PREF_NAME, false);
+  Preferences.set(HTTPS_ONLY_PBM_PREF_NAME, true);
+  await testGetting("network.httpsOnlyMode", {}, "private_browsing");
+
+  // Please note that if https_only_mode = true, then
+  // https_only_mode_pbm has no effect.
+  Preferences.set(HTTPS_ONLY_PREF_NAME, true);
+  Preferences.set(HTTPS_ONLY_PBM_PREF_NAME, true);
+  await testGetting("network.httpsOnlyMode", {}, "always");
+
+  // trying to "set" should have no effect when readonly!
+  extension.sendMessage(
+    "set",
+    { value: "never" },
+    "network.httpsOnlyMode",
+    READ_ONLY
+  );
+  let readOnlyData = await extension.awaitMessage("settingData");
+  equal(readOnlyData.value, "always");
+
+  equal(Preferences.get(HTTPS_ONLY_PREF_NAME), true);
+  equal(Preferences.get(HTTPS_ONLY_PBM_PREF_NAME), true);
+
+  await extension.unload();
+
+  await promiseShutdownManager();
+});
+
+add_task(async function test_exceptions() {
+  async function background() {
+    await browser.test.assertRejects(
+      browser.privacy.network.networkPredictionEnabled.set({
+        value: true,
+        scope: "regular_only",
+      }),
+      "Firefox does not support the regular_only settings scope.",
+      "Expected rejection calling set with invalid scope."
+    );
+
+    await browser.test.assertRejects(
+      browser.privacy.network.networkPredictionEnabled.clear({
+        scope: "incognito_persistent",
+      }),
+      "Firefox does not support the incognito_persistent settings scope.",
+      "Expected rejection calling clear with invalid scope."
+    );
+
+    browser.test.notifyPass("exceptionTests");
+  }
+
+  let extension = ExtensionTestUtils.loadExtension({
+    background,
+    manifest: {
+      permissions: ["privacy"],
+    },
+  });
+
+  await extension.startup();
+  await extension.awaitFinish("exceptionTests");
+  await extension.unload();
+});
diff --git a/toolkit/components/extensions/test/xpcshell/test_ext_privacy_disable.js b/toolkit/components/extensions/test/xpcshell/test_ext_privacy_disable.js
new file mode 100644
index 0000000000..637751f473
--- /dev/null
+++ b/toolkit/components/extensions/test/xpcshell/test_ext_privacy_disable.js
@@ -0,0 +1,180 @@
+/* -*- Mode: indent-tabs-mode: nil; js-indent-level: 2 -*- */
+/* vim: set sts=2 sw=2 et tw=80: */
+"use strict";
+
+ChromeUtils.defineESModuleGetters(this, {
+  AddonManager: "resource://gre/modules/AddonManager.sys.mjs",
+  ExtensionPreferencesManager:
+    "resource://gre/modules/ExtensionPreferencesManager.sys.mjs",
+  Management: "resource://gre/modules/Extension.sys.mjs",
+  Preferences: "resource://gre/modules/Preferences.sys.mjs",
+});
+
+const { createAppInfo, promiseShutdownManager, promiseStartupManager } =
+  AddonTestUtils;
+
+AddonTestUtils.init(this);
+
+createAppInfo("xpcshell@tests.mozilla.org", "XPCShell", "1", "42");
+
+function awaitEvent(eventName) {
+  return new Promise(resolve => {
+    let listener = (_eventName, ...args) => {
+      if (_eventName === eventName) {
+        Management.off(eventName, listener);
+        resolve(...args);
+      }
+    };
+
+    Management.on(eventName, listener);
+  });
+}
+
+function awaitPrefChange(prefName) {
+  return new Promise(resolve => {
+    let listener = args => {
+      Preferences.ignore(prefName, listener);
+      resolve();
+    };
+
+    Preferences.observe(prefName, listener);
+  });
+}
+
+add_task(async function test_disable() {
+  const OLD_ID = "old_id@tests.mozilla.org";
+  const NEW_ID = "new_id@tests.mozilla.org";
+
+  const PREF_TO_WATCH = "network.http.speculative-parallel-limit";
+
+  // Create an object to hold the values to which we will initialize the prefs.
+  const PREFS = {
+    "network.predictor.enabled": true,
+    "network.prefetch-next": true,
+    "network.http.speculative-parallel-limit": 10,
+    "network.dns.disablePrefetch": false,
+  };
+
+  // Set prefs to our initial values.
+  for (let pref in PREFS) {
+    Preferences.set(pref, PREFS[pref]);
+  }
+
+  registerCleanupFunction(() => {
+    // Reset the prefs.
+    for (let pref in PREFS) {
+      Preferences.reset(pref);
+    }
+  });
+
+  function checkPrefs(expected) {
+    for (let pref in PREFS) {
+      let msg = `${pref} set correctly.`;
+      let expectedValue = expected ? PREFS[pref] : !PREFS[pref];
+      if (pref === "network.http.speculative-parallel-limit") {
+        expectedValue = expected
+          ? ExtensionPreferencesManager.getDefaultValue(pref)
+          : 0;
+      }
+      equal(Preferences.get(pref), expectedValue, msg);
+    }
+  }
+
+  async function background() {
+    browser.test.onMessage.addListener(async (msg, data) => {
+      await browser.privacy.network.networkPredictionEnabled.set(data);
+      let settingData =
+        await browser.privacy.network.networkPredictionEnabled.get({});
+      browser.test.sendMessage("privacyData", settingData);
+    });
+  }
+
+  await promiseStartupManager();
+
+  let testExtensions = [
+    ExtensionTestUtils.loadExtension({
+      background,
+      manifest: {
+        browser_specific_settings: {
+          gecko: {
+            id: OLD_ID,
+          },
+        },
+        permissions: ["privacy"],
+      },
+      useAddonManager: "temporary",
+    }),
+
+    ExtensionTestUtils.loadExtension({
+      background,
+      manifest: {
+        browser_specific_settings: {
+          gecko: {
+            id: NEW_ID,
+          },
+        },
+        permissions: ["privacy"],
+      },
+      useAddonManager: "temporary",
+    }),
+  ];
+
+  for (let extension of testExtensions) {
+    await extension.startup();
+  }
+
+  // Set the value to true for the older extension.
+  testExtensions[0].sendMessage("set", { value: true });
+  let data = await testExtensions[0].awaitMessage("privacyData");
+  ok(data.value, "Value set to true for the older extension.");
+
+  // Set the value to false for the newest extension.
+  testExtensions[1].sendMessage("set", { value: false });
+  data = await testExtensions[1].awaitMessage("privacyData");
+  ok(!data.value, "Value set to false for the newest extension.");
+
+  // Verify the prefs have been set to match the "false" setting.
+  checkPrefs(false);
+
+  // Disable the newest extension.
+  let disabledPromise = awaitPrefChange(PREF_TO_WATCH);
+  let newAddon = await AddonManager.getAddonByID(NEW_ID);
+  await newAddon.disable();
+  await disabledPromise;
+
+  // Verify the prefs have been set to match the "true" setting.
+  checkPrefs(true);
+
+  // Disable the older extension.
+  disabledPromise = awaitPrefChange(PREF_TO_WATCH);
+  let oldAddon = await AddonManager.getAddonByID(OLD_ID);
+  await oldAddon.disable();
+  await disabledPromise;
+
+  // Verify the prefs have reverted back to their initial values.
+  for (let pref in PREFS) {
+    equal(Preferences.get(pref), PREFS[pref], `${pref} reset correctly.`);
+  }
+
+  // Re-enable the newest extension.
+  let enabledPromise = awaitEvent("ready");
+  await newAddon.enable();
+  await enabledPromise;
+
+  // Verify the prefs have been set to match the "false" setting.
+  checkPrefs(false);
+
+  // Re-enable the older extension.
+  enabledPromise = awaitEvent("ready");
+  await oldAddon.enable();
+  await enabledPromise;
+
+  // Verify the prefs have remained set to match the "false" setting.
+  checkPrefs(false);
+
+  for (let extension of testExtensions) {
+    await extension.unload();
+  }
+
+  await promiseShutdownManager();
+});
diff --git a/toolkit/components/extensions/test/xpcshell/test_ext_privacy_nonPersistentCookies.js b/toolkit/components/extensions/test/xpcshell/test_ext_privacy_nonPersistentCookies.js
new file mode 100644
index 0000000000..91f0feaa82
--- /dev/null
+++ b/toolkit/components/extensions/test/xpcshell/test_ext_privacy_nonPersistentCookies.js
@@ -0,0 +1,54 @@
+"use strict";
+
+const { promiseShutdownManager, promiseStartupManager } = AddonTestUtils;
+
+AddonTestUtils.init(this);
+AddonTestUtils.overrideCertDB();
+AddonTestUtils.createAppInfo(
+  "xpcshell@tests.mozilla.org",
+  "XPCShell",
+  "1",
+  "42"
+);
+
+add_task(async function test_nonPersistentCookies_is_deprecated() {
+  await promiseStartupManager();
+
+  let extension = ExtensionTestUtils.loadExtension({
+    manifest: {
+      permissions: ["privacy"],
+    },
+    useAddonManager: "temporary",
+    async background() {
+      for (const nonPersistentCookies of [true, false]) {
+        await browser.privacy.websites.cookieConfig.set({
+          value: {
+            behavior: "reject_third_party",
+            nonPersistentCookies,
+          },
+        });
+      }
+
+      browser.test.sendMessage("background-done");
+    },
+  });
+
+  let { messages } = await promiseConsoleOutput(async () => {
+    await extension.startup();
+    await extension.awaitMessage("background-done");
+    await extension.unload();
+  });
+
+  const expectedMessage =
+    /"'nonPersistentCookies' has been deprecated and it has no effect anymore."/;
+
+  AddonTestUtils.checkMessages(
+    messages,
+    {
+      expected: [{ message: expectedMessage }, { message: expectedMessage }],
+    },
+    true
+  );
+
+  await promiseShutdownManager();
+});
diff --git a/toolkit/components/extensions/test/xpcshell/test_ext_privacy_update.js b/toolkit/components/extensions/test/xpcshell/test_ext_privacy_update.js
new file mode 100644
index 0000000000..5dcbca9d63
--- /dev/null
+++ b/toolkit/components/extensions/test/xpcshell/test_ext_privacy_update.js
@@ -0,0 +1,163 @@
+/* -*- Mode: indent-tabs-mode: nil; js-indent-level: 2 -*- */
+/* vim: set sts=2 sw=2 et tw=80: */
+"use strict";
+
+ChromeUtils.defineESModuleGetters(this, {
+  Preferences: "resource://gre/modules/Preferences.sys.mjs",
+});
+
+const {
+  createAppInfo,
+  createTempWebExtensionFile,
+  promiseCompleteAllInstalls,
+  promiseFindAddonUpdates,
+  promiseShutdownManager,
+  promiseStartupManager,
+} = AddonTestUtils;
+
+AddonTestUtils.init(this);
+
+// Allow for unsigned addons.
+AddonTestUtils.overrideCertDB();
+
+createAppInfo("xpcshell@tests.mozilla.org", "XPCShell", "42", "42");
+
+add_task(async function test_privacy_update() {
+  // Create a object to hold the values to which we will initialize the prefs.
+  const PREFS = {
+    "network.predictor.enabled": true,
+    "network.prefetch-next": true,
+    "network.http.speculative-parallel-limit": 10,
+    "network.dns.disablePrefetch": false,
+  };
+
+  const EXTENSION_ID = "test_privacy_addon_update@tests.mozilla.org";
+  const PREF_EM_CHECK_UPDATE_SECURITY = "extensions.checkUpdateSecurity";
+
+  // Set prefs to our initial values.
+  for (let pref in PREFS) {
+    Preferences.set(pref, PREFS[pref]);
+  }
+
+  registerCleanupFunction(() => {
+    // Reset the prefs.
+    for (let pref in PREFS) {
+      Preferences.reset(pref);
+    }
+  });
+
+  async function background() {
+    browser.test.onMessage.addListener(async (msg, data) => {
+      let settingData;
+      switch (msg) {
+        case "get":
+          settingData =
+            await browser.privacy.network.networkPredictionEnabled.get({});
+          browser.test.sendMessage("privacyData", settingData);
+          break;
+
+        case "set":
+          await browser.privacy.network.networkPredictionEnabled.set(data);
+          settingData =
+            await browser.privacy.network.networkPredictionEnabled.get({});
+          browser.test.sendMessage("privacyData", settingData);
+          break;
+      }
+    });
+  }
+
+  const testServer = createHttpServer();
+  const port = testServer.identity.primaryPort;
+
+  // The test extension uses an insecure update url.
+  Services.prefs.setBoolPref(PREF_EM_CHECK_UPDATE_SECURITY, false);
+
+  testServer.registerPathHandler("/test_update.json", (request, response) => {
+    response.write(`{
+      "addons": {
+        "${EXTENSION_ID}": {
+          "updates": [
+            {
+              "version": "2.0",
+              "update_link": "http://localhost:${port}/addons/test_privacy-2.0.xpi"
+            }
+          ]
+        }
+      }
+    }`);
+  });
+
+  let webExtensionFile = createTempWebExtensionFile({
+    manifest: {
+      version: "2.0",
+      browser_specific_settings: {
+        gecko: {
+          id: EXTENSION_ID,
+        },
+      },
+      permissions: ["privacy"],
+    },
+    background,
+  });
+
+  testServer.registerFile("/addons/test_privacy-2.0.xpi", webExtensionFile);
+
+  await promiseStartupManager();
+
+  let extension = ExtensionTestUtils.loadExtension({
+    useAddonManager: "permanent",
+    manifest: {
+      version: "1.0",
+      browser_specific_settings: {
+        gecko: {
+          id: EXTENSION_ID,
+          update_url: `http://localhost:${port}/test_update.json`,
+        },
+      },
+      permissions: ["privacy"],
+    },
+    background,
+  });
+
+  await extension.startup();
+
+  // Change the value to false.
+  extension.sendMessage("set", { value: false });
+  let data = await extension.awaitMessage("privacyData");
+  ok(!data.value, "get returns expected value after setting.");
+
+  equal(
+    extension.version,
+    "1.0",
+    "The installed addon has the expected version."
+  );
+
+  let update = await promiseFindAddonUpdates(extension.addon);
+  let install = update.updateAvailable;
+
+  await promiseCompleteAllInstalls([install]);
+
+  await extension.awaitStartup();
+
+  equal(
+    extension.version,
+    "2.0",
+    "The updated addon has the expected version."
+  );
+
+  extension.sendMessage("get");
+  data = await extension.awaitMessage("privacyData");
+  ok(!data.value, "get returns expected value after updating.");
+
+  // Verify the prefs are still set to match the "false" setting.
+  for (let pref in PREFS) {
+    let msg = `${pref} set correctly.`;
+    let expectedValue =
+      pref === "network.http.speculative-parallel-limit" ? 0 : !PREFS[pref];
+    equal(Preferences.get(pref), expectedValue, msg);
+  }
+
+  await extension.unload();
+
+  await promiseShutdownManager();
+});
diff --git a/toolkit/components/extensions/test/xpcshell/test_ext_proxy_authorization_via_proxyinfo.js b/toolkit/components/extensions/test/xpcshell/test_ext_proxy_authorization_via_proxyinfo.js
new file mode 100644
index 0000000000..27f537b73b
--- /dev/null
+++ b/toolkit/components/extensions/test/xpcshell/test_ext_proxy_authorization_via_proxyinfo.js
@@ -0,0 +1,116 @@
+"use strict";
+
+XPCOMUtils.defineLazyServiceGetter(
+  this,
+  "authManager",
+  "@mozilla.org/network/http-auth-manager;1",
+  "nsIHttpAuthManager"
+);
+
+const proxy = createHttpServer();
+const proxyToken = "this_is_my_pass";
+
+// accept proxy connections for mozilla.org
+proxy.identity.add("http", "mozilla.org", 80);
+
+proxy.registerPathHandler("/", (request, response) => {
+  if (request.hasHeader("Proxy-Authorization")) {
+    response.setStatusLine(request.httpVersion, 200, "OK");
+    response.setHeader("Content-Type", "text/plain", false);
+    response.write(request.getHeader("Proxy-Authorization"));
+  } else {
+    response.setStatusLine(
+      request.httpVersion,
+      407,
+      "Proxy authentication required"
+    );
+    response.setHeader("Content-Type", "text/plain", false);
+    response.setHeader("Proxy-Authenticate", "UnknownMeantToFail", false);
+    response.write("auth required");
+  }
+});
+
+function getExtension(background) {
+  return ExtensionTestUtils.loadExtension({
+    manifest: {
+      permissions: ["proxy", "webRequest", "webRequestBlocking", "<all_urls>"],
+    },
+    background: `(${background})(${proxy.identity.primaryPort}, "${proxyToken}")`,
+  });
+}
+
+add_task(async function test_webRequest_auth_proxy() {
+  function background(port, proxyToken) {
+    browser.webRequest.onCompleted.addListener(
+      details => {
+        browser.test.log(`onCompleted ${JSON.stringify(details)}\n`);
+        browser.test.assertEq(
+          "localhost",
+          details.proxyInfo.host,
+          "proxy host"
+        );
+        browser.test.assertEq(port, details.proxyInfo.port, "proxy port");
+        browser.test.assertEq("http", details.proxyInfo.type, "proxy type");
+        browser.test.assertEq(
+          "",
+          details.proxyInfo.username,
+          "proxy username not set"
+        );
+        browser.test.assertEq(
+          proxyToken,
+          details.proxyInfo.proxyAuthorizationHeader,
+          "proxy authorization header"
+        );
+        browser.test.assertEq(
+          proxyToken,
+          details.proxyInfo.connectionIsolationKey,
+          "proxy connection isolation"
+        );
+
+        browser.test.notifyPass("requestCompleted");
+      },
+      { urls: ["<all_urls>"] }
+    );
+
+    browser.webRequest.onAuthRequired.addListener(
+      details => {
+        // Using proxyAuthorizationHeader should prevent an auth request coming to us in the extension.
+        browser.test.fail("onAuthRequired");
+      },
+      { urls: ["<all_urls>"] },
+      ["blocking"]
+    );
+
+    // Handle the proxy request.
+    browser.proxy.onRequest.addListener(
+      details => {
+        browser.test.log(`onRequest ${JSON.stringify(details)}`);
+        return [
+          {
+            host: "localhost",
+            port,
+            type: "http",
+            proxyAuthorizationHeader: proxyToken,
+            connectionIsolationKey: proxyToken,
+          },
+        ];
+      },
+      { urls: ["<all_urls>"] },
+      ["requestHeaders"]
+    );
+  }
+
+  let extension = getExtension(background);
+
+  await extension.startup();
+
+  authManager.clearAll();
+
+  let contentPage = await ExtensionTestUtils.loadContentPage(
+    `http://mozilla.org/`
+  );
+
+  await extension.awaitFinish("requestCompleted");
+  await contentPage.close();
+  await extension.unload();
+});
diff --git a/toolkit/components/extensions/test/xpcshell/test_ext_proxy_config.js b/toolkit/components/extensions/test/xpcshell/test_ext_proxy_config.js
new file mode 100644
index 0000000000..490de51d3a
--- /dev/null
+++ b/toolkit/components/extensions/test/xpcshell/test_ext_proxy_config.js
@@ -0,0 +1,614 @@
+/* -*- Mode: indent-tabs-mode: nil; js-indent-level: 2 -*- */
+/* vim: set sts=2 sw=2 et tw=80: */
+"use strict";
+
+ChromeUtils.defineESModuleGetters(this, {
+  Preferences: "resource://gre/modules/Preferences.sys.mjs",
+});
+
+const { ExtensionPermissions } = ChromeUtils.importESModule(
+  "resource://gre/modules/ExtensionPermissions.sys.mjs"
+);
+
+AddonTestUtils.init(this);
+AddonTestUtils.overrideCertDB();
+
+AddonTestUtils.createAppInfo(
+  "xpcshell@tests.mozilla.org",
+  "XPCShell",
+  "1",
+  "42"
+);
+
+// Start a server for `pac.example.com` to intercept attempts to connect to it
+// to load a PAC URL. We won't serve anything, but this prevents attempts at
+// non-local connections if this domain is registered.
+AddonTestUtils.createHttpServer({ hosts: ["pac.example.com"] });
+
+add_task(async function setup() {
+  // Bug 1646182: Force ExtensionPermissions to run in rkv mode, the legacy
+  // storage mode will run in xpcshell-legacy-ep.ini
+  await ExtensionPermissions._uninit();
+
+  Services.prefs.setBoolPref(
+    "extensions.webextOptionalPermissionPrompts",
+    false
+  );
+  registerCleanupFunction(() => {
+    Services.prefs.clearUserPref("extensions.webextOptionalPermissionPrompts");
+  });
+
+  await AddonTestUtils.promiseStartupManager();
+});
+
+add_task(async function test_browser_settings() {
+  const proxySvc = Ci.nsIProtocolProxyService;
+
+  // Create an object to hold the values to which we will initialize the prefs.
+  const PREFS = {
+    "network.proxy.type": proxySvc.PROXYCONFIG_SYSTEM,
+    "network.proxy.http": "",
+    "network.proxy.http_port": 0,
+    "network.proxy.share_proxy_settings": false,
+    "network.proxy.ssl": "",
+    "network.proxy.ssl_port": 0,
+    "network.proxy.socks": "",
+    "network.proxy.socks_port": 0,
+    "network.proxy.socks_version": 5,
+    "network.proxy.socks_remote_dns": false,
+    "network.proxy.no_proxies_on": "",
+    "network.proxy.autoconfig_url": "",
+    "signon.autologin.proxy": false,
+  };
+
+  async function background() {
+    browser.test.onMessage.addListener(async (msg, value) => {
+      let apiObj = browser.proxy.settings;
+      let result = await apiObj.set({ value });
+      if (msg === "set") {
+        browser.test.assertTrue(result, "set returns true.");
+        browser.test.sendMessage("settingData", await apiObj.get({}));
+      } else {
+        browser.test.assertFalse(result, "set returns false for a no-op.");
+        browser.test.sendMessage("no-op set");
+      }
+    });
+  }
+
+  // Set prefs to our initial values.
+  for (let pref in PREFS) {
+    Preferences.set(pref, PREFS[pref]);
+  }
+
+  registerCleanupFunction(() => {
+    // Reset the prefs.
+    for (let pref in PREFS) {
+      Preferences.reset(pref);
+    }
+  });
+
+  let extension = ExtensionTestUtils.loadExtension({
+    background,
+    manifest: {
+      permissions: ["proxy"],
+    },
+    incognitoOverride: "spanning",
+    useAddonManager: "temporary",
+  });
+
+  await extension.startup();
+
+  async function testSetting(value, expected, expectedValue = value) {
+    extension.sendMessage("set", value);
+    let data = await extension.awaitMessage("settingData");
+    deepEqual(data.value, expectedValue, `The setting has the expected value.`);
+    equal(
+      data.levelOfControl,
+      "controlled_by_this_extension",
+      `The setting has the expected levelOfControl.`
+    );
+    for (let pref in expected) {
+      equal(
+        Preferences.get(pref),
+        expected[pref],
+        `${pref} set correctly for ${value}`
+      );
+    }
+  }
+
+  async function testProxy(config, expectedPrefs, expectedConfig = config) {
+    // proxy.settings is not supported on Android.
+    if (AppConstants.platform === "android") {
+      return Promise.resolve();
+    }
+
+    let proxyConfig = {
+      proxyType: "none",
+      autoConfigUrl: "",
+      autoLogin: false,
+      proxyDNS: false,
+      httpProxyAll: false,
+      socksVersion: 5,
+      passthrough: "",
+      http: "",
+      ssl: "",
+      socks: "",
+      respectBeConservative: true,
+    };
+
+    expectedConfig.proxyType = expectedConfig.proxyType || "system";
+
+    return testSetting(
+      config,
+      expectedPrefs,
+      Object.assign(proxyConfig, expectedConfig)
+    );
+  }
+
+  await testProxy(
+    { proxyType: "none" },
+    { "network.proxy.type": proxySvc.PROXYCONFIG_DIRECT }
+  );
+
+  await testProxy(
+    {
+      proxyType: "autoDetect",
+      autoLogin: true,
+      proxyDNS: true,
+    },
+    {
+      "network.proxy.type": proxySvc.PROXYCONFIG_WPAD,
+      "signon.autologin.proxy": true,
+      "network.proxy.socks_remote_dns": true,
+    }
+  );
+
+  await testProxy(
+    {
+      proxyType: "system",
+      autoLogin: false,
+      proxyDNS: false,
+    },
+    {
+      "network.proxy.type": proxySvc.PROXYCONFIG_SYSTEM,
+      "signon.autologin.proxy": false,
+      "network.proxy.socks_remote_dns": false,
+    }
+  );
+
+  // Verify that proxyType is optional and it defaults to "system".
+  await testProxy(
+    {
+      autoLogin: false,
+      proxyDNS: false,
+    },
+    {
+      "network.proxy.type": proxySvc.PROXYCONFIG_SYSTEM,
+      "signon.autologin.proxy": false,
+      "network.proxy.socks_remote_dns": false,
+      "network.http.proxy.respect-be-conservative": true,
+    }
+  );
+
+  await testProxy(
+    {
+      proxyType: "autoConfig",
+      autoConfigUrl: "http://pac.example.com",
+    },
+    {
+      "network.proxy.type": proxySvc.PROXYCONFIG_PAC,
+      "network.proxy.autoconfig_url": "http://pac.example.com",
+      "network.http.proxy.respect-be-conservative": true,
+    }
+  );
+
+  await testProxy(
+    {
+      proxyType: "manual",
+      http: "http://www.mozilla.org",
+      autoConfigUrl: "",
+    },
+    {
+      "network.proxy.type": proxySvc.PROXYCONFIG_MANUAL,
+      "network.proxy.http": "www.mozilla.org",
+      "network.proxy.http_port": 80,
+      "network.proxy.autoconfig_url": "",
+    },
+    {
+      proxyType: "manual",
+      http: "www.mozilla.org:80",
+      autoConfigUrl: "",
+    }
+  );
+
+  // When using proxyAll, we expect all proxies to be set to
+  // be the same as http.
+  await testProxy(
+    {
+      proxyType: "manual",
+      http: "http://www.mozilla.org:8080",
+      httpProxyAll: true,
+    },
+    {
+      "network.proxy.type": proxySvc.PROXYCONFIG_MANUAL,
+      "network.proxy.http": "www.mozilla.org",
+      "network.proxy.http_port": 8080,
+      "network.proxy.ssl": "www.mozilla.org",
+      "network.proxy.ssl_port": 8080,
+      "network.proxy.share_proxy_settings": true,
+    },
+    {
+      proxyType: "manual",
+      http: "www.mozilla.org:8080",
+      ssl: "www.mozilla.org:8080",
+      socks: "",
+      httpProxyAll: true,
+    }
+  );
+
+  await testProxy(
+    {
+      proxyType: "manual",
+      http: "www.mozilla.org:8080",
+      httpProxyAll: false,
+      ftp: "www.mozilla.org:8081",
+      ssl: "www.mozilla.org:8082",
+      socks: "mozilla.org:8083",
+      socksVersion: 4,
+      passthrough: ".mozilla.org",
+      respectBeConservative: true,
+    },
+    {
+      "network.proxy.type": proxySvc.PROXYCONFIG_MANUAL,
+      "network.proxy.http": "www.mozilla.org",
+      "network.proxy.http_port": 8080,
+      "network.proxy.share_proxy_settings": false,
+      "network.proxy.ssl": "www.mozilla.org",
+      "network.proxy.ssl_port": 8082,
+      "network.proxy.socks": "mozilla.org",
+      "network.proxy.socks_port": 8083,
+      "network.proxy.socks_version": 4,
+      "network.proxy.no_proxies_on": ".mozilla.org",
+      "network.http.proxy.respect-be-conservative": true,
+    },
+    {
+      proxyType: "manual",
+      http: "www.mozilla.org:8080",
+      httpProxyAll: false,
+      // ftp: "www.mozilla.org:8081", // This line should not be sent back
+      ssl: "www.mozilla.org:8082",
+      socks: "mozilla.org:8083",
+      socksVersion: 4,
+      passthrough: ".mozilla.org",
+      respectBeConservative: true,
+    }
+  );
+
+  await testProxy(
+    {
+      proxyType: "manual",
+      http: "http://www.mozilla.org",
+      ssl: "https://www.mozilla.org",
+      socks: "mozilla.org",
+      socksVersion: 4,
+      passthrough: ".mozilla.org",
+      respectBeConservative: false,
+    },
+    {
+      "network.proxy.type": proxySvc.PROXYCONFIG_MANUAL,
+      "network.proxy.http": "www.mozilla.org",
+      "network.proxy.http_port": 80,
+      "network.proxy.share_proxy_settings": false,
+      "network.proxy.ssl": "www.mozilla.org",
+      "network.proxy.ssl_port": 443,
+      "network.proxy.socks": "mozilla.org",
+      "network.proxy.socks_port": 1080,
+      "network.proxy.socks_version": 4,
+      "network.proxy.no_proxies_on": ".mozilla.org",
+      "network.http.proxy.respect-be-conservative": false,
+    },
+    {
+      proxyType: "manual",
+      http: "www.mozilla.org:80",
+      httpProxyAll: false,
+      ssl: "www.mozilla.org:443",
+      socks: "mozilla.org:1080",
+      socksVersion: 4,
+      passthrough: ".mozilla.org",
+      respectBeConservative: false,
+    }
+  );
+
+  await testProxy(
+    {
+      proxyType: "manual",
+      http: "http://www.mozilla.org:80",
+      ssl: "https://www.mozilla.org:443",
+      socks: "mozilla.org:1080",
+      socksVersion: 4,
+      passthrough: ".mozilla.org",
+      respectBeConservative: true,
+    },
+    {
+      "network.proxy.type": proxySvc.PROXYCONFIG_MANUAL,
+      "network.proxy.http": "www.mozilla.org",
+      "network.proxy.http_port": 80,
+      "network.proxy.share_proxy_settings": false,
+      "network.proxy.ssl": "www.mozilla.org",
+      "network.proxy.ssl_port": 443,
+      "network.proxy.socks": "mozilla.org",
+      "network.proxy.socks_port": 1080,
+      "network.proxy.socks_version": 4,
+      "network.proxy.no_proxies_on": ".mozilla.org",
+      "network.http.proxy.respect-be-conservative": true,
+    },
+    {
+      proxyType: "manual",
+      http: "www.mozilla.org:80",
+      httpProxyAll: false,
+      ssl: "www.mozilla.org:443",
+      socks: "mozilla.org:1080",
+      socksVersion: 4,
+      passthrough: ".mozilla.org",
+      respectBeConservative: true,
+    }
+  );
+
+  await testProxy(
+    {
+      proxyType: "manual",
+      http: "http://www.mozilla.org:80",
+      ssl: "https://www.mozilla.org:80",
+      socks: "mozilla.org:80",
+      socksVersion: 4,
+      passthrough: ".mozilla.org",
+      respectBeConservative: false,
+    },
+    {
+      "network.proxy.type": proxySvc.PROXYCONFIG_MANUAL,
+      "network.proxy.http": "www.mozilla.org",
+      "network.proxy.http_port": 80,
+      "network.proxy.share_proxy_settings": false,
+      "network.proxy.ssl": "www.mozilla.org",
+      "network.proxy.ssl_port": 80,
+      "network.proxy.socks": "mozilla.org",
+      "network.proxy.socks_port": 80,
+      "network.proxy.socks_version": 4,
+      "network.proxy.no_proxies_on": ".mozilla.org",
+      "network.http.proxy.respect-be-conservative": false,
+    },
+    {
+      proxyType: "manual",
+      http: "www.mozilla.org:80",
+      httpProxyAll: false,
+      ssl: "www.mozilla.org:80",
+      socks: "mozilla.org:80",
+      socksVersion: 4,
+      passthrough: ".mozilla.org",
+      respectBeConservative: false,
+    }
+  );
+
+  // Test resetting values.
+  await testProxy(
+    {
+      proxyType: "none",
+      http: "",
+      ssl: "",
+      socks: "",
+      socksVersion: 5,
+      passthrough: "",
+      respectBeConservative: true,
+    },
+    {
+      "network.proxy.type": proxySvc.PROXYCONFIG_DIRECT,
+      "network.proxy.http": "",
+      "network.proxy.http_port": 0,
+      "network.proxy.ssl": "",
+      "network.proxy.ssl_port": 0,
+      "network.proxy.socks": "",
+      "network.proxy.socks_port": 0,
+      "network.proxy.socks_version": 5,
+      "network.proxy.no_proxies_on": "",
+      "network.http.proxy.respect-be-conservative": true,
+    }
+  );
+
+  await extension.unload();
+});
+
+add_task(async function test_bad_value_proxy_config() {
+  let background =
+    AppConstants.platform === "android"
+      ? async () => {
+          await browser.test.assertRejects(
+            browser.proxy.settings.set({
+              value: {
+                proxyType: "none",
+              },
+            }),
+            /proxy.settings is not supported on android/,
+            "proxy.settings.set rejects on Android."
+          );
+
+          await browser.test.assertRejects(
+            browser.proxy.settings.get({}),
+            /proxy.settings is not supported on android/,
+            "proxy.settings.get rejects on Android."
+          );
+
+          await browser.test.assertRejects(
+            browser.proxy.settings.clear({}),
+            /proxy.settings is not supported on android/,
+            "proxy.settings.clear rejects on Android."
+          );
+
+          browser.test.sendMessage("done");
+        }
+      : async () => {
+          await browser.test.assertRejects(
+            browser.proxy.settings.set({
+              value: {
+                proxyType: "abc",
+              },
+            }),
+            /abc is not a valid value for proxyType/,
+            "proxy.settings.set rejects with an invalid proxyType value."
+          );
+
+          await browser.test.assertRejects(
+            browser.proxy.settings.set({
+              value: {
+                proxyType: "autoConfig",
+              },
+            }),
+            /undefined is not a valid value for autoConfigUrl/,
+            "proxy.settings.set for type autoConfig rejects with an empty autoConfigUrl value."
+          );
+
+          await browser.test.assertRejects(
+            browser.proxy.settings.set({
+              value: {
+                proxyType: "autoConfig",
+                autoConfigUrl: "abc",
+              },
+            }),
+            /abc is not a valid value for autoConfigUrl/,
+            "proxy.settings.set rejects with an invalid autoConfigUrl value."
+          );
+
+          await browser.test.assertRejects(
+            browser.proxy.settings.set({
+              value: {
+                proxyType: "manual",
+                socksVersion: "abc",
+              },
+            }),
+            /abc is not a valid value for socksVersion/,
+            "proxy.settings.set rejects with an invalid socksVersion value."
+          );
+
+          await browser.test.assertRejects(
+            browser.proxy.settings.set({
+              value: {
+                proxyType: "manual",
+                socksVersion: 3,
+              },
+            }),
+            /3 is not a valid value for socksVersion/,
+            "proxy.settings.set rejects with an invalid socksVersion value."
+          );
+
+          browser.test.sendMessage("done");
+        };
+
+  let extension = ExtensionTestUtils.loadExtension({
+    background,
+    manifest: {
+      permissions: ["proxy"],
+    },
+    incognitoOverride: "spanning",
+  });
+
+  await extension.startup();
+  await extension.awaitMessage("done");
+  await extension.unload();
+});
+
+// Verify proxy prefs are unset on permission removal.
+add_task(async function test_proxy_settings_permissions() {
+  async function background() {
+    const permObj = { permissions: ["proxy"] };
+    browser.test.onMessage.addListener(async (msg, value) => {
+      if (msg === "request") {
+        browser.test.log("requesting proxy permission");
+        await browser.permissions.request(permObj);
+        browser.test.log("setting proxy values");
+        await browser.proxy.settings.set({ value });
+        browser.test.sendMessage("set");
+      } else if (msg === "remove") {
+        await browser.permissions.remove(permObj);
+        browser.test.sendMessage("removed");
+      }
+    });
+  }
+
+  let prefNames = [
+    "network.proxy.type",
+    "network.proxy.http",
+    "network.proxy.http_port",
+    "network.proxy.ssl",
+    "network.proxy.ssl_port",
+    "network.proxy.socks",
+    "network.proxy.socks_port",
+    "network.proxy.socks_version",
+    "network.proxy.no_proxies_on",
+  ];
+
+  function checkSettings(msg, expectUserValue = false) {
+    info(msg);
+    for (let pref of prefNames) {
+      equal(
+        expectUserValue,
+        Services.prefs.prefHasUserValue(pref),
+        `${pref} set as expected ${Preferences.get(pref)}`
+      );
+    }
+  }
+
+  let extension = ExtensionTestUtils.loadExtension({
+    background,
+    manifest: {
+      optional_permissions: ["proxy"],
+    },
+    incognitoOverride: "spanning",
+    useAddonManager: "permanent",
+  });
+  await extension.startup();
+  checkSettings("setting is not set after startup");
+
+  await withHandlingUserInput(extension, async () => {
+    extension.sendMessage("request", {
+      proxyType: "manual",
+      http: "www.mozilla.org:8080",
+      httpProxyAll: false,
+      ssl: "www.mozilla.org:8082",
+      socks: "mozilla.org:8083",
+      socksVersion: 4,
+      passthrough: ".mozilla.org",
+    });
+    await extension.awaitMessage("set");
+    checkSettings("setting was set after request", true);
+
+    extension.sendMessage("remove");
+    await extension.awaitMessage("removed");
+    checkSettings("setting is reset after remove");
+
+    // Set again to test after restart
+    extension.sendMessage("request", {
+      proxyType: "manual",
+      http: "www.mozilla.org:8080",
+      httpProxyAll: false,
+      ssl: "www.mozilla.org:8082",
+      socks: "mozilla.org:8083",
+      socksVersion: 4,
+      passthrough: ".mozilla.org",
+    });
+    await extension.awaitMessage("set");
+    checkSettings("setting was set after request", true);
+  });
+
+  // force the permissions store to be re-read on startup
+  await ExtensionPermissions._uninit();
+  resetHandlingUserInput();
+  await AddonTestUtils.promiseRestartManager();
+  await extension.awaitBackgroundStarted();
+
+  await withHandlingUserInput(extension, async () => {
+    extension.sendMessage("remove");
+    await extension.awaitMessage("removed");
+    checkSettings("setting is reset after remove");
+  });
+
+  await extension.unload();
+});
diff --git a/toolkit/components/extensions/test/xpcshell/test_ext_proxy_containerIsolation.js b/toolkit/components/extensions/test/xpcshell/test_ext_proxy_containerIsolation.js
new file mode 100644
index 0000000000..9a375f68a9
--- /dev/null
+++ b/toolkit/components/extensions/test/xpcshell/test_ext_proxy_containerIsolation.js
@@ -0,0 +1,59 @@
+"use strict";
+
+const server = createHttpServer({ hosts: ["example.com"] });
+
+server.registerPathHandler("/dummy", (request, response) => {
+  response.setStatusLine(request.httpVersion, 200, "OK");
+  response.setHeader("Content-Type", "text/html", false);
+  response.write("<!DOCTYPE html><html></html>");
+});
+
+add_task(async function test_userContextId_proxy() {
+  Services.prefs.setBoolPref("extensions.userContextIsolation.enabled", true);
+  let extension = ExtensionTestUtils.loadExtension({
+    manifest: {
+      permissions: ["proxy", "<all_urls>"],
+    },
+    background() {
+      browser.proxy.onRequest.addListener(
+        async details => {
+          browser.test.assertEq(
+            "firefox-container-2",
+            details.cookieStoreId,
+            "cookieStoreId is set"
+          );
+          browser.test.notifyPass("allowed");
+        },
+        { urls: ["http://example.com/dummy"] }
+      );
+    },
+  });
+
+  Services.prefs.setCharPref(
+    "extensions.userContextIsolation.defaults.restricted",
+    "[1]"
+  );
+  await extension.startup();
+
+  let restrictedPage = await ExtensionTestUtils.loadContentPage(
+    "http://example.com/dummy",
+    { userContextId: 1 }
+  );
+
+  let allowedPage = await ExtensionTestUtils.loadContentPage(
+    "http://example.com/dummy",
+    {
+      userContextId: 2,
+    }
+  );
+  await extension.awaitFinish("allowed");
+
+  await extension.unload();
+  await restrictedPage.close();
+  await allowedPage.close();
+
+  Services.prefs.clearUserPref("extensions.userContextIsolation.enabled");
+  Services.prefs.clearUserPref(
+    "extensions.userContextIsolation.defaults.restricted"
+  );
+});
diff --git a/toolkit/components/extensions/test/xpcshell/test_ext_proxy_onauthrequired.js b/toolkit/components/extensions/test/xpcshell/test_ext_proxy_onauthrequired.js
new file mode 100644
index 0000000000..db041d20d0
--- /dev/null
+++ b/toolkit/components/extensions/test/xpcshell/test_ext_proxy_onauthrequired.js
@@ -0,0 +1,302 @@
+"use strict";
+
+XPCOMUtils.defineLazyServiceGetter(
+  this,
+  "authManager",
+  "@mozilla.org/network/http-auth-manager;1",
+  "nsIHttpAuthManager"
+);
+
+const proxy = createHttpServer();
+
+// accept proxy connections for mozilla.org
+proxy.identity.add("http", "mozilla.org", 80);
+proxy.identity.add("https", "407.example.com", 443);
+
+proxy.registerPathHandler("CONNECT", (request, response) => {
+  Assert.equal(request.method, "CONNECT");
+  switch (request.host) {
+    case "407.example.com":
+      response.setStatusLine(request.httpVersion, 407, "Authenticate");
+      response.setHeader("Content-Type", "text/plain", false);
+      response.setHeader("Proxy-Authenticate", 'Basic realm="foobar"', false);
+      response.write("auth required");
+      break;
+    default:
+      response.setStatusLine(request.httpVersion, 500, "I am dumb");
+  }
+});
+
+proxy.registerPathHandler("/", (request, response) => {
+  if (request.hasHeader("Proxy-Authorization")) {
+    response.setStatusLine(request.httpVersion, 200, "OK");
+    response.setHeader("Content-Type", "text/plain", false);
+    response.write("ok, got proxy auth");
+  } else {
+    response.setStatusLine(
+      request.httpVersion,
+      407,
+      "Proxy authentication required"
+    );
+    response.setHeader("Content-Type", "text/plain", false);
+    response.setHeader("Proxy-Authenticate", 'Basic realm="foobar"', false);
+    response.write("auth required");
+  }
+});
+
+function getExtension(background) {
+  return ExtensionTestUtils.loadExtension({
+    manifest: {
+      permissions: ["proxy", "webRequest", "webRequestBlocking", "<all_urls>"],
+    },
+    background: `(${background})(${proxy.identity.primaryPort})`,
+  });
+}
+
+add_task(async function test_webRequest_auth_proxy() {
+  async function background(port) {
+    let expecting = [
+      "onBeforeSendHeaders",
+      "onSendHeaders",
+      "onAuthRequired",
+      "onBeforeSendHeaders",
+      "onSendHeaders",
+      "onCompleted",
+    ];
+    browser.webRequest.onBeforeSendHeaders.addListener(
+      details => {
+        browser.test.log(`onBeforeSendHeaders ${JSON.stringify(details)}\n`);
+        browser.test.assertEq(
+          "onBeforeSendHeaders",
+          expecting.shift(),
+          "got expected event"
+        );
+        browser.test.assertEq(
+          "localhost",
+          details.proxyInfo.host,
+          "proxy host"
+        );
+        browser.test.assertEq(port, details.proxyInfo.port, "proxy port");
+        browser.test.assertEq("http", details.proxyInfo.type, "proxy type");
+        browser.test.assertEq(
+          "",
+          details.proxyInfo.username,
+          "proxy username not set"
+        );
+      },
+      { urls: ["<all_urls>"] }
+    );
+
+    browser.webRequest.onSendHeaders.addListener(
+      details => {
+        browser.test.log(`onSendHeaders ${JSON.stringify(details)}\n`);
+        browser.test.assertEq(
+          "onSendHeaders",
+          expecting.shift(),
+          "got expected event"
+        );
+      },
+      { urls: ["<all_urls>"] }
+    );
+
+    browser.webRequest.onAuthRequired.addListener(
+      details => {
+        browser.test.log(`onAuthRequired ${JSON.stringify(details)}\n`);
+        browser.test.assertEq(
+          "onAuthRequired",
+          expecting.shift(),
+          "got expected event"
+        );
+        browser.test.assertTrue(details.isProxy, "proxied request");
+        browser.test.assertEq(
+          "localhost",
+          details.proxyInfo.host,
+          "proxy host"
+        );
+        browser.test.assertEq(port, details.proxyInfo.port, "proxy port");
+        browser.test.assertEq("http", details.proxyInfo.type, "proxy type");
+        browser.test.assertEq(
+          "localhost",
+          details.challenger.host,
+          "proxy host"
+        );
+        browser.test.assertEq(port, details.challenger.port, "proxy port");
+        return { authCredentials: { username: "puser", password: "ppass" } };
+      },
+      { urls: ["<all_urls>"] },
+      ["blocking"]
+    );
+
+    browser.webRequest.onCompleted.addListener(
+      details => {
+        browser.test.log(`onCompleted ${JSON.stringify(details)}\n`);
+        browser.test.assertEq(
+          "onCompleted",
+          expecting.shift(),
+          "got expected event"
+        );
+        browser.test.assertEq(
+          "localhost",
+          details.proxyInfo.host,
+          "proxy host"
+        );
+        browser.test.assertEq(port, details.proxyInfo.port, "proxy port");
+        browser.test.assertEq("http", details.proxyInfo.type, "proxy type");
+        browser.test.assertEq(
+          "",
+          details.proxyInfo.username,
+          "proxy username not set by onAuthRequired"
+        );
+        browser.test.assertEq(
+          undefined,
+          details.proxyInfo.password,
+          "no proxy password"
+        );
+        browser.test.assertEq(expecting.length, 0, "got all expected events");
+        browser.test.sendMessage("done");
+      },
+      { urls: ["<all_urls>"] }
+    );
+
+    // Handle the proxy request.
+    browser.proxy.onRequest.addListener(
+      details => {
+        browser.test.log(`onRequest ${JSON.stringify(details)}`);
+        return [{ host: "localhost", port, type: "http" }];
+      },
+      { urls: ["<all_urls>"] },
+      ["requestHeaders"]
+    );
+    browser.test.sendMessage("ready");
+  }
+
+  let handlingExt = getExtension(background);
+
+  await handlingExt.startup();
+  await handlingExt.awaitMessage("ready");
+
+  authManager.clearAll();
+
+  let contentPage = await ExtensionTestUtils.loadContentPage(
+    `http://mozilla.org/`
+  );
+
+  await handlingExt.awaitMessage("done");
+  await contentPage.close();
+  await handlingExt.unload();
+});
+
+add_task(async function test_webRequest_auth_proxy_https() {
+  async function background(port) {
+    let authReceived = false;
+
+    browser.webRequest.onBeforeSendHeaders.addListener(
+      details => {
+        if (authReceived) {
+          browser.test.sendMessage("done");
+          return { cancel: true };
+        }
+      },
+      { urls: ["<all_urls>"] },
+      ["blocking"]
+    );
+
+    browser.webRequest.onAuthRequired.addListener(
+      details => {
+        authReceived = true;
+        return { authCredentials: { username: "puser", password: "ppass" } };
+      },
+      { urls: ["<all_urls>"] },
+      ["blocking"]
+    );
+
+    // Handle the proxy request.
+    browser.proxy.onRequest.addListener(
+      details => {
+        browser.test.log(`onRequest ${JSON.stringify(details)}`);
+        return [{ host: "localhost", port, type: "http" }];
+      },
+      { urls: ["<all_urls>"] },
+      ["requestHeaders"]
+    );
+    browser.test.sendMessage("ready");
+  }
+
+  let handlingExt = getExtension(background);
+
+  await handlingExt.startup();
+  await handlingExt.awaitMessage("ready");
+
+  authManager.clearAll();
+
+  let contentPage = await ExtensionTestUtils.loadContentPage(
+    `https://407.example.com/`
+  );
+
+  await handlingExt.awaitMessage("done");
+  await contentPage.close();
+  await handlingExt.unload();
+});
+
+add_task(async function test_webRequest_auth_proxy_system() {
+  async function background(port) {
+    browser.webRequest.onBeforeRequest.addListener(
+      details => {
+        browser.test.fail("onBeforeRequest");
+      },
+      { urls: ["<all_urls>"] }
+    );
+
+    browser.webRequest.onAuthRequired.addListener(
+      details => {
+        browser.test.sendMessage("onAuthRequired");
+        // cancel is silently ignored, if it were not (e.g someone messes up in
+        // WebRequest.jsm and allows cancel) this test would fail.
+        return {
+          cancel: true,
+          authCredentials: { username: "puser", password: "ppass" },
+        };
+      },
+      { urls: ["<all_urls>"] },
+      ["blocking"]
+    );
+
+    // Handle the proxy request.
+    browser.proxy.onRequest.addListener(
+      details => {
+        browser.test.log(`onRequest ${JSON.stringify(details)}`);
+        return { host: "localhost", port, type: "http" };
+      },
+      { urls: ["<all_urls>"] }
+    );
+    browser.test.sendMessage("ready");
+  }
+
+  let handlingExt = getExtension(background);
+
+  await handlingExt.startup();
+  await handlingExt.awaitMessage("ready");
+
+  authManager.clearAll();
+
+  function fetch(url) {
+    return new Promise((resolve, reject) => {
+      let xhr = new XMLHttpRequest();
+      xhr.mozBackgroundRequest = true;
+      xhr.open("GET", url);
+      xhr.onload = () => {
+        resolve(xhr.responseText);
+      };
+      xhr.onerror = () => {
+        reject(xhr.status);
+      };
+      xhr.send();
+    });
+  }
+
+  await Promise.all([
+    handlingExt.awaitMessage("onAuthRequired"),
+    fetch("http://mozilla.org"),
+  ]);
+  await handlingExt.unload();
+});
diff --git a/toolkit/components/extensions/test/xpcshell/test_ext_proxy_settings.js b/toolkit/components/extensions/test/xpcshell/test_ext_proxy_settings.js
new file mode 100644
index 0000000000..8c558d6aa5
--- /dev/null
+++ b/toolkit/components/extensions/test/xpcshell/test_ext_proxy_settings.js
@@ -0,0 +1,104 @@
+"use strict";
+
+ChromeUtils.defineModuleGetter(
+  this,
+  "HttpServer",
+  "resource://testing-common/httpd.js"
+);
+
+const { createAppInfo, promiseShutdownManager, promiseStartupManager } =
+  AddonTestUtils;
+
+AddonTestUtils.init(this);
+
+createAppInfo("xpcshell@tests.mozilla.org", "XPCShell", "1", "42");
+
+// We cannot use createHttpServer because it also messes with proxies.  We want
+// httpChannel to pick up the prefs we set and use those to proxy to our server.
+// If this were to fail, we would get an error about making a request out to
+// the network.
+const proxy = new HttpServer();
+proxy.start(-1);
+proxy.registerPathHandler("/fubar", (request, response) => {
+  response.setStatusLine(request.httpVersion, 200, "OK");
+  response.write("ok");
+});
+registerCleanupFunction(() => {
+  return new Promise(resolve => {
+    proxy.stop(resolve);
+  });
+});
+
+add_task(async function test_proxy_settings() {
+  async function background(host, port) {
+    browser.webRequest.onBeforeRequest.addListener(
+      details => {
+        browser.test.assertEq(
+          host,
+          details.proxyInfo.host,
+          "proxy host matched"
+        );
+        browser.test.assertEq(
+          port,
+          details.proxyInfo.port,
+          "proxy port matched"
+        );
+      },
+      { urls: ["http://example.com/*"] }
+    );
+    browser.webRequest.onCompleted.addListener(
+      details => {
+        browser.test.notifyPass("proxytest");
+      },
+      { urls: ["http://example.com/*"] }
+    );
+    browser.webRequest.onErrorOccurred.addListener(
+      details => {
+        browser.test.notifyFail("proxytest");
+      },
+      { urls: ["http://example.com/*"] }
+    );
+
+    // Wait for the settings before testing a request.
+    await browser.proxy.settings.set({
+      value: {
+        proxyType: "manual",
+        http: `${host}:${port}`,
+      },
+    });
+    browser.test.sendMessage("ready");
+  }
+
+  let extension = ExtensionTestUtils.loadExtension({
+    manifest: {
+      browser_specific_settings: { gecko: { id: "proxy.settings@mochi.test" } },
+      permissions: ["proxy", "webRequest", "<all_urls>"],
+    },
+    incognitoOverride: "spanning",
+    useAddonManager: "temporary",
+    background: `(${background})("${proxy.identity.primaryHost}", ${proxy.identity.primaryPort})`,
+  });
+
+  await promiseStartupManager();
+  await extension.startup();
+  await extension.awaitMessage("ready");
+  equal(
+    Services.prefs.getStringPref("network.proxy.http"),
+    proxy.identity.primaryHost,
+    "proxy address is set"
+  );
+  equal(
+    Services.prefs.getIntPref("network.proxy.http_port"),
+    proxy.identity.primaryPort,
+    "proxy port is set"
+  );
+  let ok = extension.awaitFinish("proxytest");
+  let contentPage = await ExtensionTestUtils.loadContentPage(
+    "http://example.com/fubar"
+  );
+  await ok;
+
+  await contentPage.close();
+  await extension.unload();
+  await promiseShutdownManager();
+});
diff --git a/toolkit/components/extensions/test/xpcshell/test_ext_proxy_socks.js b/toolkit/components/extensions/test/xpcshell/test_ext_proxy_socks.js
new file mode 100644
index 0000000000..6ebd9fbfcc
--- /dev/null
+++ b/toolkit/components/extensions/test/xpcshell/test_ext_proxy_socks.js
@@ -0,0 +1,660 @@
+"use strict";
+
+/* globals TCPServerSocket */
+
+const CC = Components.Constructor;
+
+const BinaryInputStream = CC(
+  "@mozilla.org/binaryinputstream;1",
+  "nsIBinaryInputStream",
+  "setInputStream"
+);
+
+const currentThread =
+  Cc["@mozilla.org/thread-manager;1"].getService().currentThread;
+
+// Most of the socks logic here is copied and upgraded to support authentication
+// for socks5. The original test is from netwerk/test/unit/test_socks.js
+
+// Socks 4 support was left in place for future tests.
+
+const STATE_WAIT_GREETING = 1;
+const STATE_WAIT_SOCKS4_REQUEST = 2;
+const STATE_WAIT_SOCKS4_USERNAME = 3;
+const STATE_WAIT_SOCKS4_HOSTNAME = 4;
+const STATE_WAIT_SOCKS5_GREETING = 5;
+const STATE_WAIT_SOCKS5_REQUEST = 6;
+const STATE_WAIT_SOCKS5_AUTH = 7;
+const STATE_WAIT_INPUT = 8;
+const STATE_FINISHED = 9;
+
+/**
+ * A basic socks proxy setup that handles a single http response page.  This
+ * is used for testing socks auth with webrequest.  We don't bother making
+ * sure we buffer ondata, etc., we'll never get anything but tiny chunks here.
+ */
+class SocksClient {
+  constructor(server, socket) {
+    this.server = server;
+    this.type = "";
+    this.username = "";
+    this.dest_name = "";
+    this.dest_addr = [];
+    this.dest_port = [];
+
+    this.inbuf = [];
+    this.state = STATE_WAIT_GREETING;
+    this.socket = socket;
+
+    socket.onclose = event => {
+      this.server.requestCompleted(this);
+    };
+    socket.ondata = event => {
+      let len = event.data.byteLength;
+
+      if (len == 0 && this.state == STATE_FINISHED) {
+        this.close();
+        this.server.requestCompleted(this);
+        return;
+      }
+
+      this.inbuf = new Uint8Array(event.data);
+      Promise.resolve().then(() => {
+        this.callState();
+      });
+    };
+  }
+
+  callState() {
+    switch (this.state) {
+      case STATE_WAIT_GREETING:
+        this.checkSocksGreeting();
+        break;
+      case STATE_WAIT_SOCKS4_REQUEST:
+        this.checkSocks4Request();
+        break;
+      case STATE_WAIT_SOCKS4_USERNAME:
+        this.checkSocks4Username();
+        break;
+      case STATE_WAIT_SOCKS4_HOSTNAME:
+        this.checkSocks4Hostname();
+        break;
+      case STATE_WAIT_SOCKS5_GREETING:
+        this.checkSocks5Greeting();
+        break;
+      case STATE_WAIT_SOCKS5_REQUEST:
+        this.checkSocks5Request();
+        break;
+      case STATE_WAIT_SOCKS5_AUTH:
+        this.checkSocks5Auth();
+        break;
+      case STATE_WAIT_INPUT:
+        this.checkRequest();
+        break;
+      default:
+        do_throw("server: read in invalid state!");
+    }
+  }
+
+  write(buf) {
+    this.socket.send(new Uint8Array(buf).buffer);
+  }
+
+  checkSocksGreeting() {
+    if (!this.inbuf.length) {
+      return;
+    }
+
+    if (this.inbuf[0] == 4) {
+      this.type = "socks4";
+      this.state = STATE_WAIT_SOCKS4_REQUEST;
+      this.checkSocks4Request();
+    } else if (this.inbuf[0] == 5) {
+      this.type = "socks";
+      this.state = STATE_WAIT_SOCKS5_GREETING;
+      this.checkSocks5Greeting();
+    } else {
+      do_throw("Unknown socks protocol!");
+    }
+  }
+
+  checkSocks4Request() {
+    if (this.inbuf.length < 8) {
+      return;
+    }
+
+    this.dest_port = this.inbuf.slice(2, 4);
+    this.dest_addr = this.inbuf.slice(4, 8);
+
+    this.inbuf = this.inbuf.slice(8);
+    this.state = STATE_WAIT_SOCKS4_USERNAME;
+    this.checkSocks4Username();
+  }
+
+  readString() {
+    let i = this.inbuf.indexOf(0);
+    let str = null;
+
+    if (i >= 0) {
+      let decoder = new TextDecoder();
+      str = decoder.decode(this.inbuf.slice(0, i));
+      this.inbuf = this.inbuf.slice(i + 1);
+    }
+
+    return str;
+  }
+
+  checkSocks4Username() {
+    let str = this.readString();
+
+    if (str == null) {
+      return;
+    }
+
+    this.username = str;
+    if (
+      this.dest_addr[0] == 0 &&
+      this.dest_addr[1] == 0 &&
+      this.dest_addr[2] == 0 &&
+      this.dest_addr[3] != 0
+    ) {
+      this.state = STATE_WAIT_SOCKS4_HOSTNAME;
+      this.checkSocks4Hostname();
+    } else {
+      this.sendSocks4Response();
+    }
+  }
+
+  checkSocks4Hostname() {
+    let str = this.readString();
+
+    if (str == null) {
+      return;
+    }
+
+    this.dest_name = str;
+    this.sendSocks4Response();
+  }
+
+  sendSocks4Response() {
+    this.state = STATE_WAIT_INPUT;
+    this.inbuf = [];
+    this.write([0, 0x5a, 0, 0, 0, 0, 0, 0]);
+  }
+
+  /**
+   * checks authentication information.
+   *
+   * buf[0] socks version
+   * buf[1] number of auth methods supported
+   * buf[2+nmethods] value for each auth method
+   *
+   * Response is
+   * byte[0] socks version
+   * byte[1] desired auth method
+   *
+   * For whatever reason, Firefox does not present auth method 0x02 however
+   * responding with that does cause Firefox to send authentication if
+   * the nsIProxyInfo instance has the data.  IUUC Firefox should send
+   * supported methods, but I'm no socks expert.
+   */
+  checkSocks5Greeting() {
+    if (this.inbuf.length < 2) {
+      return;
+    }
+    let nmethods = this.inbuf[1];
+    if (this.inbuf.length < 2 + nmethods) {
+      return;
+    }
+
+    // See comment above, keeping for future update.
+    // let methods = this.inbuf.slice(2, 2 + nmethods);
+
+    this.inbuf = [];
+    if (this.server.password || this.server.username) {
+      this.state = STATE_WAIT_SOCKS5_AUTH;
+      this.write([5, 2]);
+    } else {
+      this.state = STATE_WAIT_SOCKS5_REQUEST;
+      this.write([5, 0]);
+    }
+  }
+
+  checkSocks5Auth() {
+    equal(this.inbuf[0], 0x01, "subnegotiation version");
+    let uname_len = this.inbuf[1];
+    let pass_len = this.inbuf[2 + uname_len];
+    let unnamebuf = this.inbuf.slice(2, 2 + uname_len);
+    let pass_start = 2 + uname_len + 1;
+    let pwordbuf = this.inbuf.slice(pass_start, pass_start + pass_len);
+    let decoder = new TextDecoder();
+    let username = decoder.decode(unnamebuf);
+    let password = decoder.decode(pwordbuf);
+    this.inbuf = [];
+    equal(username, this.server.username, "socks auth username");
+    equal(password, this.server.password, "socks auth password");
+    if (username == this.server.username && password == this.server.password) {
+      this.state = STATE_WAIT_SOCKS5_REQUEST;
+      // x00 is success, any other value closes the connection
+      this.write([1, 0]);
+      return;
+    }
+    this.state = STATE_FINISHED;
+    this.write([1, 1]);
+  }
+
+  checkSocks5Request() {
+    if (this.inbuf.length < 4) {
+      return;
+    }
+
+    let atype = this.inbuf[3];
+    let len;
+    let name = false;
+
+    switch (atype) {
+      case 0x01:
+        len = 4;
+        break;
+      case 0x03:
+        len = this.inbuf[4];
+        name = true;
+        break;
+      case 0x04:
+        len = 16;
+        break;
+      default:
+        do_throw("Unknown address type " + atype);
+    }
+
+    if (name) {
+      if (this.inbuf.length < 4 + len + 1 + 2) {
+        return;
+      }
+
+      let buf = this.inbuf.slice(5, 5 + len);
+      let decoder = new TextDecoder();
+      this.dest_name = decoder.decode(buf);
+      len += 1;
+    } else {
+      if (this.inbuf.length < 4 + len + 2) {
+        return;
+      }
+
+      this.dest_addr = this.inbuf.slice(4, 4 + len);
+    }
+
+    len += 4;
+    this.dest_port = this.inbuf.slice(len, len + 2);
+    this.inbuf = this.inbuf.slice(len + 2);
+    this.sendSocks5Response();
+  }
+
+  sendSocks5Response() {
+    let buf;
+    if (this.dest_addr.length == 16) {
+      // send a successful response with the address, [::1]:80
+      buf = [5, 0, 0, 4, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 1, 0, 80];
+    } else {
+      // send a successful response with the address, 127.0.0.1:80
+      buf = [5, 0, 0, 1, 127, 0, 0, 1, 0, 80];
+    }
+    this.state = STATE_WAIT_INPUT;
+    this.inbuf = [];
+    this.write(buf);
+  }
+
+  checkRequest() {
+    let decoder = new TextDecoder();
+    let request = decoder.decode(this.inbuf);
+
+    if (request == "PING!") {
+      this.state = STATE_FINISHED;
+      this.socket.send("PONG!");
+    } else if (request.startsWith("GET / HTTP/1.1")) {
+      this.socket.send(
+        "HTTP/1.1 200 OK\r\n" +
+          "Content-Length: 2\r\n" +
+          "Content-Type: text/html\r\n" +
+          "\r\nOK"
+      );
+      this.state = STATE_FINISHED;
+    }
+  }
+
+  close() {
+    this.socket.close();
+  }
+}
+
+class SocksTestServer {
+  constructor() {
+    this.client_connections = new Set();
+    this.listener = new TCPServerSocket(-1, { binaryType: "arraybuffer" }, -1);
+    this.listener.onconnect = event => {
+      let client = new SocksClient(this, event.socket);
+      this.client_connections.add(client);
+    };
+  }
+
+  requestCompleted(client) {
+    this.client_connections.delete(client);
+  }
+
+  close() {
+    for (let client of this.client_connections) {
+      client.close();
+    }
+    this.client_connections = new Set();
+    if (this.listener) {
+      this.listener.close();
+      this.listener = null;
+    }
+  }
+
+  setUserPass(username, password) {
+    this.username = username;
+    this.password = password;
+  }
+}
+
+/**
+ * Tests the basic socks logic using a simple socket connection and the
+ * protocol proxy service.  Before 902346, TCPSocket has no way to tie proxy
+ * data to it, so we go old school here.
+ */
+class SocksTestClient {
+  constructor(socks, dest, resolve, reject) {
+    let pps = Cc["@mozilla.org/network/protocol-proxy-service;1"].getService(
+      Ci.nsIProtocolProxyService
+    );
+    let sts = Cc["@mozilla.org/network/socket-transport-service;1"].getService(
+      Ci.nsISocketTransportService
+    );
+
+    let pi_flags = 0;
+    if (socks.dns == "remote") {
+      pi_flags = Ci.nsIProxyInfo.TRANSPARENT_PROXY_RESOLVES_HOST;
+    }
+
+    let pi = pps.newProxyInfoWithAuth(
+      socks.version,
+      socks.host,
+      socks.port,
+      socks.username,
+      socks.password,
+      "",
+      "",
+      pi_flags,
+      -1,
+      null
+    );
+
+    this.trans = sts.createTransport([], dest.host, dest.port, pi, null);
+    this.input = this.trans.openInputStream(
+      Ci.nsITransport.OPEN_BLOCKING,
+      0,
+      0
+    );
+    this.output = this.trans.openOutputStream(
+      Ci.nsITransport.OPEN_BLOCKING,
+      0,
+      0
+    );
+    this.outbuf = String();
+    this.resolve = resolve;
+    this.reject = reject;
+
+    this.write("PING!");
+    this.input.asyncWait(this, 0, 0, currentThread);
+  }
+
+  onInputStreamReady(stream) {
+    let len = 0;
+    try {
+      len = stream.available();
+    } catch (e) {
+      // This will happen on auth failure.
+      this.reject(e);
+      return;
+    }
+    let bin = new BinaryInputStream(stream);
+    let data = bin.readByteArray(len);
+    let decoder = new TextDecoder();
+    let result = decoder.decode(data);
+    if (result == "PONG!") {
+      this.resolve(result);
+    } else {
+      this.reject();
+    }
+  }
+
+  write(buf) {
+    this.outbuf += buf;
+    this.output.asyncWait(this, 0, 0, currentThread);
+  }
+
+  onOutputStreamReady(stream) {
+    let len = stream.write(this.outbuf, this.outbuf.length);
+    if (len != this.outbuf.length) {
+      this.outbuf = this.outbuf.substring(len);
+      stream.asyncWait(this, 0, 0, currentThread);
+    } else {
+      this.outbuf = String();
+    }
+  }
+
+  close() {
+    this.output.close();
+  }
+}
+
+const socksServer = new SocksTestServer();
+socksServer.setUserPass("foo", "bar");
+registerCleanupFunction(() => {
+  socksServer.close();
+});
+
+// A simple ping/pong to test the socks server.
+add_task(async function test_socks_server() {
+  let socks = {
+    version: "socks",
+    host: "127.0.0.1",
+    port: socksServer.listener.localPort,
+    username: "foo",
+    password: "bar",
+    dns: false,
+  };
+  let dest = {
+    host: "localhost",
+    port: 8888,
+  };
+
+  new Promise((resolve, reject) => {
+    new SocksTestClient(socks, dest, resolve, reject);
+  })
+    .then(result => {
+      equal("PONG!", result, "socks test ok");
+    })
+    .catch(result => {
+      ok(false, `socks test failed ${result}`);
+    });
+});
+
+// Register a proxy to be used by TCPSocket connections later.
+function registerProxy(socks) {
+  let pps = Cc["@mozilla.org/network/protocol-proxy-service;1"].getService(
+    Ci.nsIProtocolProxyService
+  );
+  let filter = {
+    QueryInterface: ChromeUtils.generateQI(["nsIProtocolProxyFilter"]),
+    applyFilter(uri, proxyInfo, callback) {
+      callback.onProxyFilterResult(
+        pps.newProxyInfoWithAuth(
+          socks.version,
+          socks.host,
+          socks.port,
+          socks.username,
+          socks.password,
+          "",
+          "",
+          socks.dns == "remote"
+            ? Ci.nsIProxyInfo.TRANSPARENT_PROXY_RESOLVES_HOST
+            : 0,
+          -1,
+          null
+        )
+      );
+    },
+  };
+  pps.registerFilter(filter, 0);
+  registerCleanupFunction(() => {
+    pps.unregisterFilter(filter);
+  });
+}
+
+// A simple ping/pong to test the socks server with TCPSocket.
+add_task(async function test_tcpsocket_proxy() {
+  let socks = {
+    version: "socks",
+    host: "127.0.0.1",
+    port: socksServer.listener.localPort,
+    username: "foo",
+    password: "bar",
+    dns: false,
+  };
+  let dest = {
+    host: "localhost",
+    port: 8888,
+  };
+
+  registerProxy(socks);
+  await new Promise((resolve, reject) => {
+    let client = new TCPSocket(dest.host, dest.port);
+    client.onopen = () => {
+      client.send("PING!");
+    };
+    client.ondata = e => {
+      equal("PONG!", e.data, "socks test ok");
+      resolve();
+    };
+    client.onerror = () => reject();
+  });
+});
+
+add_task(async function test_webRequest_socks_proxy() {
+  async function background(port) {
+    function checkProxyData(details) {
+      browser.test.assertEq("127.0.0.1", details.proxyInfo.host, "proxy host");
+      browser.test.assertEq(port, details.proxyInfo.port, "proxy port");
+      browser.test.assertEq("socks", details.proxyInfo.type, "proxy type");
+      browser.test.assertEq(
+        "foo",
+        details.proxyInfo.username,
+        "proxy username not set"
+      );
+      browser.test.assertEq(
+        undefined,
+        details.proxyInfo.password,
+        "no proxy password passed to webrequest"
+      );
+    }
+    browser.webRequest.onBeforeRequest.addListener(
+      details => {
+        checkProxyData(details);
+      },
+      { urls: ["<all_urls>"] }
+    );
+    browser.webRequest.onAuthRequired.addListener(
+      details => {
+        // We should never get onAuthRequired for socks proxy
+        browser.test.fail("onAuthRequired");
+      },
+      { urls: ["<all_urls>"] },
+      ["blocking"]
+    );
+    browser.webRequest.onCompleted.addListener(
+      details => {
+        checkProxyData(details);
+        browser.test.sendMessage("done");
+      },
+      { urls: ["<all_urls>"] }
+    );
+    browser.proxy.onRequest.addListener(
+      () => {
+        return [
+          {
+            type: "socks",
+            host: "127.0.0.1",
+            port,
+            username: "foo",
+            password: "bar",
+          },
+        ];
+      },
+      { urls: ["<all_urls>"] }
+    );
+  }
+
+  let handlingExt = ExtensionTestUtils.loadExtension({
+    manifest: {
+      permissions: ["proxy", "webRequest", "webRequestBlocking", "<all_urls>"],
+    },
+    background: `(${background})(${socksServer.listener.localPort})`,
+  });
+
+  // proxy.register is deprecated - bug 1443259.
+  ExtensionTestUtils.failOnSchemaWarnings(false);
+  await handlingExt.startup();
+  ExtensionTestUtils.failOnSchemaWarnings(true);
+
+  let contentPage = await ExtensionTestUtils.loadContentPage(
+    `http://localhost/`
+  );
+
+  await handlingExt.awaitMessage("done");
+  await contentPage.close();
+  await handlingExt.unload();
+});
+
+add_task(async function test_onRequest_tcpsocket_proxy() {
+  async function background(port) {
+    browser.proxy.onRequest.addListener(
+      () => {
+        return [
+          {
+            type: "socks",
+            host: "127.0.0.1",
+            port,
+            username: "foo",
+            password: "bar",
+          },
+        ];
+      },
+      { urls: ["<all_urls>"] }
+    );
+  }
+
+  let handlingExt = ExtensionTestUtils.loadExtension({
+    manifest: {
+      permissions: ["proxy", "webRequest", "webRequestBlocking", "<all_urls>"],
+    },
+    background: `(${background})(${socksServer.listener.localPort})`,
+  });
+
+  await handlingExt.startup();
+
+  await new Promise((resolve, reject) => {
+    let client = new TCPSocket("localhost", 8888);
+    client.onopen = () => {
+      client.send("PING!");
+    };
+    client.ondata = e => {
+      equal("PONG!", e.data, "socks test ok");
+      resolve();
+    };
+    client.onerror = () => reject();
+  });
+
+  await handlingExt.unload();
+});
diff --git a/toolkit/components/extensions/test/xpcshell/test_ext_proxy_speculative.js b/toolkit/components/extensions/test/xpcshell/test_ext_proxy_speculative.js
new file mode 100644
index 0000000000..25b7030671
--- /dev/null
+++ b/toolkit/components/extensions/test/xpcshell/test_ext_proxy_speculative.js
@@ -0,0 +1,53 @@
+"use strict";
+
+const { ExtensionUtils } = ChromeUtils.importESModule(
+  "resource://gre/modules/ExtensionUtils.sys.mjs"
+);
+
+const proxy = createHttpServer();
+
+add_task(async function test_speculative_connect() {
+  function background() {
+    // Handle the proxy request.
+    browser.proxy.onRequest.addListener(
+      details => {
+        browser.test.log(`onRequest ${JSON.stringify(details)}`);
+        browser.test.assertEq(
+          details.type,
+          "speculative",
+          "Should have seen a speculative proxy request."
+        );
+        return [{ type: "direct" }];
+      },
+      { urls: ["<all_urls>"], types: ["speculative"] }
+    );
+  }
+
+  let handlingExt = ExtensionTestUtils.loadExtension({
+    manifest: {
+      permissions: ["proxy", "<all_urls>"],
+    },
+    background: `(${background})()`,
+  });
+
+  Services.prefs.setBoolPref("network.http.debug-observations", true);
+
+  await handlingExt.startup();
+
+  let notificationPromise = ExtensionUtils.promiseObserved(
+    "speculative-connect-request"
+  );
+
+  let uri = Services.io.newURI(
+    `http://${proxy.identity.primaryHost}:${proxy.identity.primaryPort}`
+  );
+  Services.io.speculativeConnect(
+    uri,
+    Services.scriptSecurityManager.getSystemPrincipal(),
+    null,
+    false
+  );
+  await notificationPromise;
+
+  await handlingExt.unload();
+});
diff --git a/toolkit/components/extensions/test/xpcshell/test_ext_proxy_startup.js b/toolkit/components/extensions/test/xpcshell/test_ext_proxy_startup.js
new file mode 100644
index 0000000000..d6a016a594
--- /dev/null
+++ b/toolkit/components/extensions/test/xpcshell/test_ext_proxy_startup.js
@@ -0,0 +1,144 @@
+"use strict";
+
+AddonTestUtils.init(this);
+AddonTestUtils.overrideCertDB();
+AddonTestUtils.createAppInfo(
+  "xpcshell@tests.mozilla.org",
+  "XPCShell",
+  "1",
+  "43"
+);
+
+let { promiseRestartManager, promiseShutdownManager, promiseStartupManager } =
+  AddonTestUtils;
+
+let nonProxiedRequests = 0;
+const nonProxiedServer = createHttpServer({ hosts: ["example.com"] });
+nonProxiedServer.registerPathHandler("/", (request, response) => {
+  nonProxiedRequests++;
+  response.setStatusLine(request.httpVersion, 200, "OK");
+  response.write("ok");
+});
+
+// No hosts defined to avoid proxy filter setup.
+let proxiedRequests = 0;
+const server = createHttpServer();
+server.identity.add("http", "proxied.example.com", 80);
+server.registerPathHandler("/", (request, response) => {
+  proxiedRequests++;
+  response.setStatusLine(request.httpVersion, 200, "OK");
+  response.write("ok");
+});
+
+function trackEvents(wrapper) {
+  let events = new Map();
+  for (let event of ["background-script-event", "start-background-script"]) {
+    events.set(event, false);
+    wrapper.extension.once(event, () => events.set(event, true));
+  }
+  return events;
+}
+
+// Test that a proxy listener during startup does not immediately
+// start the background page, but the event is queued until the background
+// page is started.
+add_task(async function test_proxy_startup() {
+  await promiseStartupManager();
+
+  function background(proxyInfo) {
+    browser.proxy.onRequest.addListener(
+      details => {
+        // ignore speculative requests
+        if (details.type == "xmlhttprequest") {
+          browser.test.sendMessage("saw-request");
+        }
+        return proxyInfo;
+      },
+      { urls: ["<all_urls>"] }
+    );
+  }
+
+  let proxyInfo = {
+    host: server.identity.primaryHost,
+    port: server.identity.primaryPort,
+    type: "http",
+  };
+
+  let extension = ExtensionTestUtils.loadExtension({
+    useAddonManager: "permanent",
+    manifest: {
+      permissions: ["proxy", "http://proxied.example.com/*"],
+    },
+    background: `(${background})(${JSON.stringify(proxyInfo)})`,
+  });
+
+  await extension.startup();
+
+  // Initial requests to test the proxy and non-proxied servers.
+  await Promise.all([
+    extension.awaitMessage("saw-request"),
+    ExtensionTestUtils.fetch("http://proxied.example.com/?a=0"),
+  ]);
+  equal(1, proxiedRequests, "proxied request ok");
+  equal(0, nonProxiedRequests, "non proxied request ok");
+
+  await ExtensionTestUtils.fetch("http://example.com/?a=0");
+  equal(1, proxiedRequests, "proxied request ok");
+  equal(1, nonProxiedRequests, "non proxied request ok");
+
+  await promiseRestartManager({ earlyStartup: false });
+  await extension.awaitStartup();
+
+  let events = trackEvents(extension);
+
+  // Initiate a non-proxied request to make sure the startup listeners are using
+  // the extensions filters/etc.
+  await ExtensionTestUtils.fetch("http://example.com/?a=1");
+  equal(1, proxiedRequests, "proxied request ok");
+  equal(2, nonProxiedRequests, "non proxied request ok");
+
+  equal(
+    events.get("background-script-event"),
+    false,
+    "Should not have gotten a background script event"
+  );
+
+  // Make a request that the extension will proxy once it is started.
+  let request = Promise.all([
+    extension.awaitMessage("saw-request"),
+    ExtensionTestUtils.fetch("http://proxied.example.com/?a=1"),
+  ]);
+
+  await promiseExtensionEvent(extension, "background-script-event");
+  equal(
+    events.get("background-script-event"),
+    true,
+    "Should have gotten a background script event"
+  );
+
+  // Test the background page startup.
+  equal(
+    events.get("start-background-script"),
+    false,
+    "Should have gotten a background script event"
+  );
+
+  AddonTestUtils.notifyEarlyStartup();
+  await new Promise(executeSoon);
+
+  equal(
+    events.get("start-background-script"),
+    true,
+    "Should have gotten a background script event"
+  );
+
+  // Verify our proxied request finishes properly and that the
+  // request was not handled via our non-proxied server.
+  await request;
+  equal(2, proxiedRequests, "proxied request ok");
+  equal(2, nonProxiedRequests, "non proxied requests ok");
+
+  await extension.unload();
+
+  await promiseShutdownManager();
+});
diff --git a/toolkit/components/extensions/test/xpcshell/test_ext_redirects.js b/toolkit/components/extensions/test/xpcshell/test_ext_redirects.js
new file mode 100644
index 0000000000..7b950355f3
--- /dev/null
+++ b/toolkit/components/extensions/test/xpcshell/test_ext_redirects.js
@@ -0,0 +1,660 @@
+"use strict";
+
+// Tests whether we can redirect to a moz-extension: url.
+ChromeUtils.defineESModuleGetters(this, {
+  TestUtils: "resource://testing-common/TestUtils.sys.mjs",
+});
+
+const server = createHttpServer();
+const gServerUrl = `http://localhost:${server.identity.primaryPort}`;
+
+server.registerPathHandler("/redirect", (request, response) => {
+  let params = new URLSearchParams(request.queryString);
+  response.setStatusLine(request.httpVersion, 302, "Moved Temporarily");
+  response.setHeader("Location", params.get("redirect_uri"));
+  response.write("redirecting");
+});
+
+server.registerPathHandler("/dummy", (request, response) => {
+  response.setStatusLine(request.httpVersion, 200, "OK");
+  response.write("ok");
+});
+
+server.registerPathHandler("/dummy-2", (request, response) => {
+  response.setStatusLine(request.httpVersion, 200, "OK");
+  response.write("ok");
+});
+
+function onStopListener(channel) {
+  return new Promise(resolve => {
+    let orig = channel.QueryInterface(Ci.nsITraceableChannel).setNewListener({
+      QueryInterface: ChromeUtils.generateQI([
+        "nsIRequestObserver",
+        "nsIStreamListener",
+      ]),
+      getFinalURI(request) {
+        let { loadInfo } = request;
+        return (loadInfo && loadInfo.resultPrincipalURI) || request.originalURI;
+      },
+      onDataAvailable(...args) {
+        orig.onDataAvailable(...args);
+      },
+      onStartRequest(request) {
+        orig.onStartRequest(request);
+      },
+      onStopRequest(request, statusCode) {
+        orig.onStopRequest(request, statusCode);
+        let URI = this.getFinalURI(request.QueryInterface(Ci.nsIChannel));
+        resolve(URI && URI.spec);
+      },
+    });
+  });
+}
+
+async function onModifyListener(originUrl, redirectToUrl) {
+  return TestUtils.topicObserved("http-on-modify-request", (subject, data) => {
+    let channel = subject.QueryInterface(Ci.nsIHttpChannel);
+    return channel.URI && channel.URI.spec == originUrl;
+  }).then(([subject, data]) => {
+    let channel = subject.QueryInterface(Ci.nsIHttpChannel);
+    if (redirectToUrl) {
+      channel.redirectTo(Services.io.newURI(redirectToUrl));
+    }
+    return channel;
+  });
+}
+
+function getExtension(
+  accessible = false,
+  background = undefined,
+  blocking = true
+) {
+  let manifest = {
+    permissions: ["webRequest", "<all_urls>"],
+  };
+  if (blocking) {
+    manifest.permissions.push("webRequestBlocking");
+  }
+  if (accessible) {
+    manifest.web_accessible_resources = ["finished.html"];
+  }
+  if (!background) {
+    background = () => {
+      // send the extensions public uri to the test.
+      let exturi = browser.runtime.getURL("finished.html");
+      browser.test.sendMessage("redirectURI", exturi);
+    };
+  }
+  return ExtensionTestUtils.loadExtension({
+    manifest,
+    files: {
+      "finished.html": `
+        <!DOCTYPE html>
+        <html>
+          <head>
+            <meta charset="utf-8">
+          </head>
+          <body>
+            <h1>redirected!</h1>
+          </body>
+        </html>
+      `.trim(),
+    },
+    background,
+  });
+}
+
+async function redirection_test(url, channelRedirectUrl) {
+  // setup our observer
+  let watcher = onModifyListener(url, channelRedirectUrl).then(channel => {
+    return onStopListener(channel);
+  });
+  let xhr = new XMLHttpRequest();
+  xhr.open("GET", url);
+  xhr.send();
+  return watcher;
+}
+
+// This test verifies failure without web_accessible_resources.
+add_task(async function test_redirect_to_non_accessible_resource() {
+  let extension = getExtension();
+  await extension.startup();
+  let redirectUrl = await extension.awaitMessage("redirectURI");
+  let url = `${gServerUrl}/redirect?redirect_uri=${redirectUrl}`;
+  let result = await redirection_test(url);
+  equal(result, url, `expected no redirect`);
+  await extension.unload();
+});
+
+// This test makes a request against a server that redirects with a 302.
+add_task(async function test_302_redirect_to_extension() {
+  let extension = getExtension(true);
+  await extension.startup();
+  let redirectUrl = await extension.awaitMessage("redirectURI");
+  let url = `${gServerUrl}/redirect?redirect_uri=${redirectUrl}`;
+  let result = await redirection_test(url);
+  equal(result, redirectUrl, "redirect request is finished");
+  await extension.unload();
+});
+
+// This test uses channel.redirectTo during http-on-modify to redirect to the
+// moz-extension url.
+add_task(async function test_channel_redirect_to_extension() {
+  let extension = getExtension(true);
+  await extension.startup();
+  let redirectUrl = await extension.awaitMessage("redirectURI");
+  let url = `${gServerUrl}/dummy?r=${Math.random()}`;
+  let result = await redirection_test(url, redirectUrl);
+  equal(result, redirectUrl, "redirect request is finished");
+  await extension.unload();
+});
+
+// This test verifies failure without web_accessible_resources.
+add_task(async function test_content_redirect_to_non_accessible_resource() {
+  let extension = getExtension();
+  await extension.startup();
+  let redirectUrl = await extension.awaitMessage("redirectURI");
+  let url = `${gServerUrl}/redirect?redirect_uri=${redirectUrl}`;
+  let watcher = onModifyListener(url).then(channel => {
+    return onStopListener(channel);
+  });
+  let contentPage = await ExtensionTestUtils.loadContentPage(url, {
+    redirectUrl: "about:blank",
+  });
+  equal(
+    contentPage.browser.documentURI.spec,
+    "about:blank",
+    `expected no redirect`
+  );
+  equal(await watcher, url, "expected no redirect");
+  await contentPage.close();
+  await extension.unload();
+});
+
+// This test makes a request against a server that redirects with a 302.
+add_task(async function test_content_302_redirect_to_extension() {
+  let extension = getExtension(true);
+  await extension.startup();
+  let redirectUrl = await extension.awaitMessage("redirectURI");
+  let url = `${gServerUrl}/redirect?redirect_uri=${redirectUrl}`;
+  let contentPage = await ExtensionTestUtils.loadContentPage(url, {
+    redirectUrl,
+  });
+  equal(contentPage.browser.documentURI.spec, redirectUrl, `expected redirect`);
+  await contentPage.close();
+  await extension.unload();
+});
+
+// This test uses channel.redirectTo during http-on-modify to redirect to the
+// moz-extension url.
+add_task(async function test_content_channel_redirect_to_extension() {
+  let extension = getExtension(true);
+  await extension.startup();
+  let redirectUrl = await extension.awaitMessage("redirectURI");
+  let url = `${gServerUrl}/dummy?r=${Math.random()}`;
+  onModifyListener(url, redirectUrl);
+  let contentPage = await ExtensionTestUtils.loadContentPage(url, {
+    redirectUrl,
+  });
+  equal(contentPage.browser.documentURI.spec, redirectUrl, `expected redirect`);
+  await contentPage.close();
+  await extension.unload();
+});
+
+// This test makes a request against a server and tests redirect to another server page.
+add_task(async function test_extension_302_redirect_web() {
+  function background(serverUrl) {
+    let expectedUrls = ["/redirect", "/dummy"];
+    let expected = [
+      "onBeforeRequest",
+      "onHeadersReceived",
+      "onBeforeRedirect",
+      "onBeforeRequest",
+      "onHeadersReceived",
+      "onResponseStarted",
+      "onCompleted",
+    ];
+    browser.webRequest.onBeforeRequest.addListener(
+      details => {
+        browser.test.assertTrue(
+          details.url.includes(expectedUrls.shift()),
+          "onBeforeRequest url matches"
+        );
+        browser.test.assertEq(
+          expected.shift(),
+          "onBeforeRequest",
+          "onBeforeRequest matches"
+        );
+      },
+      { urls: [serverUrl] }
+    );
+    browser.webRequest.onHeadersReceived.addListener(
+      details => {
+        browser.test.assertEq(
+          expected.shift(),
+          "onHeadersReceived",
+          "onHeadersReceived matches"
+        );
+      },
+      { urls: [serverUrl] }
+    );
+    browser.webRequest.onResponseStarted.addListener(
+      details => {
+        browser.test.assertEq(
+          expected.shift(),
+          "onResponseStarted",
+          "onResponseStarted matches"
+        );
+      },
+      { urls: [serverUrl] }
+    );
+    browser.webRequest.onBeforeRedirect.addListener(
+      details => {
+        browser.test.assertTrue(
+          details.redirectUrl.includes("/dummy"),
+          "onBeforeRedirect matches redirectUrl"
+        );
+        browser.test.assertEq(
+          expected.shift(),
+          "onBeforeRedirect",
+          "onBeforeRedirect matches"
+        );
+      },
+      { urls: [serverUrl] }
+    );
+    browser.webRequest.onCompleted.addListener(
+      details => {
+        browser.test.assertTrue(
+          details.url.includes("/dummy"),
+          "onCompleted expected url received"
+        );
+        browser.test.assertEq(
+          expected.shift(),
+          "onCompleted",
+          "onCompleted matches"
+        );
+        browser.test.notifyPass("requestCompleted");
+      },
+      { urls: [serverUrl] }
+    );
+    browser.webRequest.onErrorOccurred.addListener(
+      details => {
+        browser.test.log(`onErrorOccurred ${JSON.stringify(details)}`);
+        browser.test.notifyFail("requestCompleted");
+      },
+      { urls: [serverUrl] }
+    );
+  }
+  let extension = getExtension(
+    false,
+    `(${background})("*://${server.identity.primaryHost}/*")`,
+    false
+  );
+  await extension.startup();
+  let redirectUrl = `${gServerUrl}/dummy`;
+  let completed = extension.awaitFinish("requestCompleted");
+  let url = `${gServerUrl}/redirect?r=${Math.random()}&redirect_uri=${redirectUrl}`;
+  let contentPage = await ExtensionTestUtils.loadContentPage(url, {
+    redirectUrl,
+  });
+  equal(
+    contentPage.browser.documentURI.spec,
+    redirectUrl,
+    `expected content redirect`
+  );
+  await completed;
+  await contentPage.close();
+  await extension.unload();
+});
+
+// This test makes a request against a server and tests redirect to another server page, without
+// onBeforeRedirect.  Bug 1448599
+add_task(async function test_extension_302_redirect_opening() {
+  let redirectUrl = `${gServerUrl}/dummy`;
+  let expectData = [
+    {
+      event: "onBeforeRequest",
+      url: `${gServerUrl}/redirect`,
+    },
+    {
+      event: "onBeforeRequest",
+      url: redirectUrl,
+    },
+  ];
+  function background(serverUrl, expected) {
+    browser.webRequest.onBeforeRequest.addListener(
+      details => {
+        let expect = expected.shift();
+        browser.test.assertEq(
+          expect.event,
+          "onBeforeRequest",
+          "onBeforeRequest event matches"
+        );
+        browser.test.assertTrue(
+          details.url.startsWith(expect.url),
+          "onBeforeRequest url matches"
+        );
+        if (expected.length === 0) {
+          browser.test.notifyPass("requestCompleted");
+        }
+      },
+      { urls: [serverUrl] }
+    );
+  }
+  let extension = getExtension(
+    false,
+    `(${background})("*://${server.identity.primaryHost}/*", ${JSON.stringify(
+      expectData
+    )})`,
+    false
+  );
+  await extension.startup();
+  let completed = extension.awaitFinish("requestCompleted");
+  let url = `${gServerUrl}/redirect?r=${Math.random()}&redirect_uri=${redirectUrl}`;
+  let contentPage = await ExtensionTestUtils.loadContentPage(url, {
+    redirectUrl,
+  });
+  equal(
+    contentPage.browser.documentURI.spec,
+    redirectUrl,
+    `expected content redirect`
+  );
+  await completed;
+  await contentPage.close();
+  await extension.unload();
+});
+
+// This test makes a request against a server and tests redirect to another server page, without
+// onBeforeRedirect.  Bug 1448599
+add_task(async function test_extension_302_redirect_modify() {
+  let redirectUrl = `${gServerUrl}/dummy`;
+  let expectData = [
+    {
+      event: "onHeadersReceived",
+      url: `${gServerUrl}/redirect`,
+    },
+    {
+      event: "onHeadersReceived",
+      url: redirectUrl,
+    },
+  ];
+  function background(serverUrl, expected) {
+    browser.webRequest.onHeadersReceived.addListener(
+      details => {
+        let expect = expected.shift();
+        browser.test.assertEq(
+          expect.event,
+          "onHeadersReceived",
+          "onHeadersReceived event matches"
+        );
+        browser.test.assertTrue(
+          details.url.startsWith(expect.url),
+          "onHeadersReceived url matches"
+        );
+        if (expected.length === 0) {
+          browser.test.notifyPass("requestCompleted");
+        }
+      },
+      { urls: ["<all_urls>"] }
+    );
+  }
+  let extension = getExtension(
+    false,
+    `(${background})("*://${server.identity.primaryHost}/*", ${JSON.stringify(
+      expectData
+    )})`,
+    false
+  );
+  await extension.startup();
+  let completed = extension.awaitFinish("requestCompleted");
+  let url = `${gServerUrl}/redirect?r=${Math.random()}&redirect_uri=${redirectUrl}`;
+  let contentPage = await ExtensionTestUtils.loadContentPage(url, {
+    redirectUrl,
+  });
+  equal(
+    contentPage.browser.documentURI.spec,
+    redirectUrl,
+    `expected content redirect`
+  );
+  await completed;
+  await contentPage.close();
+  await extension.unload();
+});
+
+// This test makes a request against a server and tests redirect to another server page, without
+// onBeforeRedirect.  Bug 1448599
+add_task(async function test_extension_302_redirect_tracing() {
+  let redirectUrl = `${gServerUrl}/dummy`;
+  let expectData = [
+    {
+      event: "onCompleted",
+      url: redirectUrl,
+    },
+  ];
+  function background(serverUrl, expected) {
+    browser.webRequest.onCompleted.addListener(
+      details => {
+        let expect = expected.shift();
+        browser.test.assertEq(
+          expect.event,
+          "onCompleted",
+          "onCompleted event matches"
+        );
+        browser.test.assertTrue(
+          details.url.startsWith(expect.url),
+          "onCompleted url matches"
+        );
+        if (expected.length === 0) {
+          browser.test.notifyPass("requestCompleted");
+        }
+      },
+      { urls: [serverUrl] }
+    );
+  }
+  let extension = getExtension(
+    false,
+    `(${background})("*://${server.identity.primaryHost}/*", ${JSON.stringify(
+      expectData
+    )})`,
+    false
+  );
+  await extension.startup();
+  let completed = extension.awaitFinish("requestCompleted");
+  let url = `${gServerUrl}/redirect?r=${Math.random()}&redirect_uri=${redirectUrl}`;
+  let contentPage = await ExtensionTestUtils.loadContentPage(url, {
+    redirectUrl,
+  });
+  equal(
+    contentPage.browser.documentURI.spec,
+    redirectUrl,
+    `expected content redirect`
+  );
+  await completed;
+  await contentPage.close();
+  await extension.unload();
+});
+
+// This test makes a request against a server and tests webrequest.  Currently
+// disabled due to NS_BINDING_ABORTED happening.
+add_task(async function test_extension_302_redirect() {
+  let extension = getExtension(true, () => {
+    let myuri = browser.runtime.getURL("*");
+    let exturi = browser.runtime.getURL("finished.html");
+    browser.webRequest.onBeforeRedirect.addListener(
+      details => {
+        browser.test.assertEq(details.redirectUrl, exturi, "redirect matches");
+      },
+      { urls: ["<all_urls>", myuri] }
+    );
+    browser.webRequest.onCompleted.addListener(
+      details => {
+        browser.test.assertEq(details.url, exturi, "expected url received");
+        browser.test.notifyPass("requestCompleted");
+      },
+      { urls: ["<all_urls>", myuri] }
+    );
+    browser.webRequest.onErrorOccurred.addListener(
+      details => {
+        browser.test.log(`onErrorOccurred ${JSON.stringify(details)}`);
+        browser.test.notifyFail("requestCompleted");
+      },
+      { urls: ["<all_urls>", myuri] }
+    );
+    // send the extensions public uri to the test.
+    browser.test.sendMessage("redirectURI", exturi);
+  });
+  await extension.startup();
+  let redirectUrl = await extension.awaitMessage("redirectURI");
+  let completed = extension.awaitFinish("requestCompleted");
+  let url = `${gServerUrl}/redirect?r=${Math.random()}&redirect_uri=${redirectUrl}`;
+  let contentPage = await ExtensionTestUtils.loadContentPage(url, {
+    redirectUrl,
+  });
+  equal(
+    contentPage.browser.documentURI.spec,
+    redirectUrl,
+    `expected content redirect`
+  );
+  await completed;
+  await contentPage.close();
+  await extension.unload();
+}).skip();
+
+// This test makes a request and uses onBeforeRequet to redirect to moz-ext.
+// Currently disabled due to NS_BINDING_ABORTED happening.
+add_task(async function test_extension_redirect() {
+  let extension = getExtension(true, () => {
+    let myuri = browser.runtime.getURL("*");
+    let exturi = browser.runtime.getURL("finished.html");
+    browser.webRequest.onBeforeRequest.addListener(
+      details => {
+        return { redirectUrl: exturi };
+      },
+      { urls: ["<all_urls>", myuri] },
+      ["blocking"]
+    );
+    browser.webRequest.onBeforeRedirect.addListener(
+      details => {
+        browser.test.assertEq(details.redirectUrl, exturi, "redirect matches");
+      },
+      { urls: ["<all_urls>", myuri] }
+    );
+    browser.webRequest.onCompleted.addListener(
+      details => {
+        browser.test.assertEq(details.url, exturi, "expected url received");
+        browser.test.notifyPass("requestCompleted");
+      },
+      { urls: ["<all_urls>", myuri] }
+    );
+    browser.webRequest.onErrorOccurred.addListener(
+      details => {
+        browser.test.log(`onErrorOccurred ${JSON.stringify(details)}`);
+        browser.test.notifyFail("requestCompleted");
+      },
+      { urls: ["<all_urls>", myuri] }
+    );
+    // send the extensions public uri to the test.
+    browser.test.sendMessage("redirectURI", exturi);
+  });
+  await extension.startup();
+  let redirectUrl = await extension.awaitMessage("redirectURI");
+  let completed = extension.awaitFinish("requestCompleted");
+  let url = `${gServerUrl}/dummy?r=${Math.random()}`;
+  let contentPage = await ExtensionTestUtils.loadContentPage(url, {
+    redirectUrl,
+  });
+  equal(contentPage.browser.documentURI.spec, redirectUrl, `expected redirect`);
+  await completed;
+  await contentPage.close();
+  await extension.unload();
+}).skip();
+
+add_task(async function test_redirect_with_onHeadersReceived() {
+  let redirectUrl = `${gServerUrl}/dummy-2`;
+
+  function background(initialUrl, redirectUrl) {
+    browser.webRequest.onCompleted.addListener(
+      () => {
+        browser.test.notifyPass("requestCompleted");
+      },
+      { urls: ["<all_urls>"] }
+    );
+
+    browser.webRequest.onHeadersReceived.addListener(
+      () => {
+        // Redirect to a different URL when we receive the headers of the
+        // initial request.
+        return { redirectUrl };
+      },
+      { urls: [initialUrl] },
+      ["blocking"]
+    );
+  }
+  let extension = getExtension(
+    false,
+    `(${background})("*://${server.identity.primaryHost}/dummy", "${redirectUrl}")`
+  );
+  await extension.startup();
+
+  let contentPage = await ExtensionTestUtils.loadContentPage(
+    `${gServerUrl}/dummy`
+  );
+  await extension.awaitFinish("requestCompleted");
+  equal(contentPage.browser.documentURI.spec, redirectUrl, "expected redirect");
+
+  await contentPage.close();
+  await extension.unload();
+});
+
+add_task(async function test_no_redirect_with_location_in_onHeadersReceived() {
+  function background(initialUrl, redirectUrl) {
+    browser.webRequest.onCompleted.addListener(
+      ({ responseHeaders }) => {
+        // Make sure that the `Location` header is set by `onHeadersReceived`.
+        browser.test.assertTrue(
+          responseHeaders.some(({ name, value }) => {
+            return name.toLowerCase() === "location" && value === redirectUrl;
+          }),
+          "Location header is set"
+        );
+
+        browser.test.notifyPass("requestCompleted");
+      },
+      { urls: ["<all_urls>"] },
+      ["responseHeaders"]
+    );
+
+    browser.webRequest.onHeadersReceived.addListener(
+      ({ responseHeaders }) => {
+        return {
+          responseHeaders: [
+            ...responseHeaders,
+            // Although we set a Location header here, the request shouldn't be
+            // redirected to `redirectUrl` because the status code hasn't been
+            // change (and cannot be changed from there).
+            { name: "Location", value: redirectUrl },
+          ],
+        };
+      },
+      { urls: [initialUrl] },
+      ["blocking", "responseHeaders"]
+    );
+  }
+  let extension = getExtension(
+    false,
+    `(${background})("*://${server.identity.primaryHost}/dummy", "${gServerUrl}/dummy-2")`
+  );
+  await extension.startup();
+
+  let initialUrl = `${gServerUrl}/dummy`;
+  let contentPage = await ExtensionTestUtils.loadContentPage(initialUrl);
+  await extension.awaitFinish("requestCompleted");
+  equal(
+    contentPage.browser.documentURI.spec,
+    initialUrl,
+    "expected no redirect"
+  );
+
+  await contentPage.close();
+  await extension.unload();
+});
diff --git a/toolkit/components/extensions/test/xpcshell/test_ext_runtime_connect_no_receiver.js b/toolkit/components/extensions/test/xpcshell/test_ext_runtime_connect_no_receiver.js
new file mode 100644
index 0000000000..e42f45c019
--- /dev/null
+++ b/toolkit/components/extensions/test/xpcshell/test_ext_runtime_connect_no_receiver.js
@@ -0,0 +1,26 @@
+/* -*- Mode: indent-tabs-mode: nil; js-indent-level: 2 -*- */
+/* vim: set sts=2 sw=2 et tw=80: */
+"use strict";
+
+add_task(async function test_connect_without_listener() {
+  function background() {
+    let port = browser.runtime.connect();
+    port.onDisconnect.addListener(() => {
+      browser.test.assertEq(
+        "Could not establish connection. Receiving end does not exist.",
+        port.error && port.error.message
+      );
+      browser.test.notifyPass("port.onDisconnect was called");
+    });
+  }
+  let extensionData = {
+    background,
+  };
+
+  let extension = ExtensionTestUtils.loadExtension(extensionData);
+  await extension.startup();
+
+  await extension.awaitFinish("port.onDisconnect was called");
+
+  await extension.unload();
+});
diff --git a/toolkit/components/extensions/test/xpcshell/test_ext_runtime_getBackgroundPage.js b/toolkit/components/extensions/test/xpcshell/test_ext_runtime_getBackgroundPage.js
new file mode 100644
index 0000000000..5af0bab639
--- /dev/null
+++ b/toolkit/components/extensions/test/xpcshell/test_ext_runtime_getBackgroundPage.js
@@ -0,0 +1,172 @@
+"use strict";
+
+AddonTestUtils.init(this);
+AddonTestUtils.overrideCertDB();
+AddonTestUtils.createAppInfo(
+  "xpcshell@tests.mozilla.org",
+  "XPCShell",
+  "1",
+  "43"
+);
+
+add_task(async function setup() {
+  await AddonTestUtils.promiseStartupManager();
+
+  Services.prefs.setBoolPref("dom.serviceWorkers.testing.enabled", true);
+
+  registerCleanupFunction(() => {
+    Services.prefs.clearUserPref("dom.serviceWorkers.testing.enabled");
+    Services.prefs.clearUserPref("dom.serviceWorkers.idle_timeout");
+  });
+});
+
+add_task(async function test_getBackgroundPage_noBackground() {
+  async function testBackground() {
+    let page = await browser.runtime.getBackgroundPage();
+    browser.test.assertEq(
+      page,
+      null,
+      "getBackgroundPage returned null as expected"
+    );
+    browser.test.sendMessage("page-ready");
+  }
+
+  let extension = ExtensionTestUtils.loadExtension({
+    files: {
+      "page.html": `
+      <!DOCTYPE html>
+      <html>
+      <head><meta charset="utf-8"></head>
+      <body>
+      <script src="page.js"></script>
+      </body></html>
+      `,
+
+      "page.js": testBackground,
+    },
+  });
+  await extension.startup();
+  let contentPage = await ExtensionTestUtils.loadContentPage(
+    `moz-extension://${extension.uuid}//page.html`
+  );
+  await extension.awaitMessage("page-ready");
+  await contentPage.close();
+
+  await extension.unload();
+});
+
+add_task(
+  {
+    pref_set: [["extensions.eventPages.enabled", true]],
+    skip_if: () =>
+      Services.prefs.getBoolPref(
+        "extensions.backgroundServiceWorker.forceInTestExtension",
+        false
+      ),
+  },
+  async function test_getBackgroundPage_eventpage() {
+    async function wakeupBackground() {
+      let page = await browser.runtime.getBackgroundPage();
+      page.hello();
+      browser.test.sendMessage("page-ready");
+    }
+
+    let extension = ExtensionTestUtils.loadExtension({
+      useAddonManager: "temporary", // To automatically show sidebar on load.
+      manifest: {
+        background: { persistent: false },
+      },
+
+      files: {
+        "page.html": `
+      <!DOCTYPE html>
+      <html>
+      <head><meta charset="utf-8"></head>
+      <body>
+      <script src="page.js"></script>
+      </body></html>
+      `,
+
+        "page.js": wakeupBackground,
+      },
+      async background() {
+        // eslint-disable-next-line no-unused-vars
+        window.hello = () => {
+          browser.test.sendMessage("hello");
+        };
+
+        browser.test.sendMessage("ready");
+      },
+    });
+
+    await extension.startup();
+    await extension.awaitMessage("ready");
+
+    await extension.terminateBackground();
+
+    // wake up the background
+    let contentPage = await ExtensionTestUtils.loadContentPage(
+      `moz-extension://${extension.uuid}//page.html`
+    );
+    await extension.awaitMessage("ready");
+    await extension.awaitMessage("hello");
+    await extension.awaitMessage("page-ready");
+    await contentPage.close();
+
+    ok(true, "getBackgroundPage wakes up background");
+
+    await extension.unload();
+  }
+);
+
+add_task(
+  {
+    skip_if: () => {
+      return !WebExtensionPolicy.backgroundServiceWorkerEnabled;
+    },
+  },
+  async function test_getBackgroundPage_serviceWorker() {
+    async function testBackground() {
+      let page = await browser.runtime.getBackgroundPage();
+      browser.test.assertEq(
+        page,
+        null,
+        "getBackgroundPage returned null as expected"
+      );
+      browser.test.sendMessage("page-ready");
+    }
+
+    let extension = ExtensionTestUtils.loadExtension({
+      useAddonManager: "temporary",
+      manifest: {
+        version: "1.0",
+        background: {
+          service_worker: "sw.js",
+        },
+        browser_specific_settings: { gecko: { id: "test-bg-sw@mochi.test" } },
+      },
+
+      files: {
+        "sw.js": "dump('Background ServiceWorker - executed\\n');",
+        "page.html": `
+      <!DOCTYPE html>
+      <html>
+      <head><meta charset="utf-8"></head>
+      <body>
+      <script src="page.js"></script>
+      </body></html>
+      `,
+
+        "page.js": testBackground,
+      },
+    });
+    await extension.startup();
+    let contentPage = await ExtensionTestUtils.loadContentPage(
+      `moz-extension://${extension.uuid}//page.html`
+    );
+    await extension.awaitMessage("page-ready");
+    await contentPage.close();
+
+    await extension.unload();
+  }
+);
diff --git a/toolkit/components/extensions/test/xpcshell/test_ext_runtime_getBrowserInfo.js b/toolkit/components/extensions/test/xpcshell/test_ext_runtime_getBrowserInfo.js
new file mode 100644
index 0000000000..3f3b8f8e95
--- /dev/null
+++ b/toolkit/components/extensions/test/xpcshell/test_ext_runtime_getBrowserInfo.js
@@ -0,0 +1,26 @@
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+"use strict";
+
+add_task(async function setup() {
+  ExtensionTestUtils.mockAppInfo();
+});
+
+add_task(async function test_getBrowserInfo() {
+  async function background() {
+    let info = await browser.runtime.getBrowserInfo();
+
+    browser.test.assertEq(info.name, "XPCShell", "name is valid");
+    browser.test.assertEq(info.vendor, "Mozilla", "vendor is Mozilla");
+    browser.test.assertEq(info.version, "48", "version is correct");
+    browser.test.assertEq(info.buildID, "20160315", "buildID is correct");
+
+    browser.test.notifyPass("runtime.getBrowserInfo");
+  }
+
+  const extension = ExtensionTestUtils.loadExtension({ background });
+  await extension.startup();
+  await extension.awaitFinish("runtime.getBrowserInfo");
+  await extension.unload();
+});
diff --git a/toolkit/components/extensions/test/xpcshell/test_ext_runtime_getPlatformInfo.js b/toolkit/components/extensions/test/xpcshell/test_ext_runtime_getPlatformInfo.js
new file mode 100644
index 0000000000..7d0dde2f8a
--- /dev/null
+++ b/toolkit/components/extensions/test/xpcshell/test_ext_runtime_getPlatformInfo.js
@@ -0,0 +1,36 @@
+/* -*- Mode: indent-tabs-mode: nil; js-indent-level: 2 -*- */
+/* vim: set sts=2 sw=2 et tw=80: */
+"use strict";
+
+function backgroundScript() {
+  browser.runtime.getPlatformInfo(info => {
+    let validOSs = ["mac", "win", "android", "cros", "linux", "openbsd"];
+    let validArchs = [
+      "aarch64",
+      "arm",
+      "ppc64",
+      "s390x",
+      "sparc64",
+      "x86-32",
+      "x86-64",
+    ];
+
+    browser.test.assertTrue(validOSs.includes(info.os), "OS is valid");
+    browser.test.assertTrue(
+      validArchs.includes(info.arch),
+      "Architecture is valid"
+    );
+    browser.test.notifyPass("runtime.getPlatformInfo");
+  });
+}
+
+let extensionData = {
+  background: backgroundScript,
+};
+
+add_task(async function () {
+  let extension = ExtensionTestUtils.loadExtension(extensionData);
+  await extension.startup();
+  await extension.awaitFinish("runtime.getPlatformInfo");
+  await extension.unload();
+});
diff --git a/toolkit/components/extensions/test/xpcshell/test_ext_runtime_id.js b/toolkit/components/extensions/test/xpcshell/test_ext_runtime_id.js
new file mode 100644
index 0000000000..6967e81232
--- /dev/null
+++ b/toolkit/components/extensions/test/xpcshell/test_ext_runtime_id.js
@@ -0,0 +1,46 @@
+"use strict";
+
+const server = createHttpServer({ hosts: ["example.com"] });
+server.registerDirectory("/data/", do_get_file("data"));
+
+add_task(async function test_runtime_id() {
+  let extension = ExtensionTestUtils.loadExtension({
+    manifest: {
+      content_scripts: [
+        {
+          matches: ["http://example.com/data/file_sample.html"],
+          js: ["content_script.js"],
+        },
+      ],
+    },
+
+    background() {
+      browser.test.sendMessage("background-id", browser.runtime.id);
+    },
+
+    files: {
+      "content_script.js"() {
+        browser.test.sendMessage("content-id", browser.runtime.id);
+      },
+    },
+  });
+
+  await extension.startup();
+
+  let contentPage = await ExtensionTestUtils.loadContentPage(
+    "http://example.com/data/file_sample.html"
+  );
+
+  let backgroundId = await extension.awaitMessage("background-id");
+  equal(
+    backgroundId,
+    extension.id,
+    "runtime.id from background script is correct"
+  );
+
+  let contentId = await extension.awaitMessage("content-id");
+  equal(contentId, extension.id, "runtime.id from content script is correct");
+
+  await contentPage.close();
+  await extension.unload();
+});
diff --git a/toolkit/components/extensions/test/xpcshell/test_ext_runtime_messaging_self.js b/toolkit/components/extensions/test/xpcshell/test_ext_runtime_messaging_self.js
new file mode 100644
index 0000000000..254387dc6b
--- /dev/null
+++ b/toolkit/components/extensions/test/xpcshell/test_ext_runtime_messaging_self.js
@@ -0,0 +1,84 @@
+/* -*- Mode: indent-tabs-mode: nil; js-indent-level: 2 -*- */
+/* vim: set sts=2 sw=2 et tw=80: */
+"use strict";
+
+add_task(
+  async function test_messaging_to_self_should_not_trigger_onMessage_onConnect() {
+    async function background() {
+      browser.runtime.onMessage.addListener(msg => {
+        browser.test.assertEq("msg from child", msg);
+        browser.test.sendMessage(
+          "sendMessage did not call same-frame onMessage"
+        );
+      });
+
+      browser.test.onMessage.addListener(msg => {
+        browser.test.assertEq(
+          "sendMessage with a listener in another frame",
+          msg
+        );
+        browser.runtime.sendMessage("should only reach another frame");
+      });
+
+      await browser.test.assertRejects(
+        browser.runtime.sendMessage("should not trigger same-frame onMessage"),
+        "Could not establish connection. Receiving end does not exist."
+      );
+
+      browser.runtime.onConnect.addListener(port => {
+        browser.test.assertEq("from-frame", port.name);
+        browser.runtime.connect({ name: "from-bg-2" });
+      });
+
+      await new Promise(resolve => {
+        let port = browser.runtime.connect({ name: "from-bg-1" });
+        port.onDisconnect.addListener(() => {
+          browser.test.assertEq(
+            "Could not establish connection. Receiving end does not exist.",
+            port.error.message
+          );
+          resolve();
+        });
+      });
+
+      let anotherFrame = document.createElement("iframe");
+      anotherFrame.src = browser.runtime.getURL("extensionpage.html");
+      document.body.appendChild(anotherFrame);
+    }
+
+    function lastScript() {
+      browser.runtime.onMessage.addListener(msg => {
+        browser.test.assertEq("should only reach another frame", msg);
+        browser.runtime.sendMessage("msg from child");
+      });
+      browser.test.sendMessage("sendMessage callback called");
+
+      browser.runtime.onConnect.addListener(port => {
+        browser.test.assertEq("from-bg-2", port.name);
+        browser.test.sendMessage("connect did not call same-frame onConnect");
+      });
+      browser.runtime.connect({ name: "from-frame" });
+    }
+
+    let extensionData = {
+      background,
+      files: {
+        "lastScript.js": lastScript,
+        "extensionpage.html": `<!DOCTYPE html><meta charset="utf-8"><script src="lastScript.js"></script>`,
+      },
+    };
+
+    let extension = ExtensionTestUtils.loadExtension(extensionData);
+    await extension.startup();
+
+    await extension.awaitMessage("sendMessage callback called");
+    extension.sendMessage("sendMessage with a listener in another frame");
+
+    await Promise.all([
+      extension.awaitMessage("connect did not call same-frame onConnect"),
+      extension.awaitMessage("sendMessage did not call same-frame onMessage"),
+    ]);
+
+    await extension.unload();
+  }
+);
diff --git a/toolkit/components/extensions/test/xpcshell/test_ext_runtime_onInstalled_and_onStartup.js b/toolkit/components/extensions/test/xpcshell/test_ext_runtime_onInstalled_and_onStartup.js
new file mode 100644
index 0000000000..c330aaafde
--- /dev/null
+++ b/toolkit/components/extensions/test/xpcshell/test_ext_runtime_onInstalled_and_onStartup.js
@@ -0,0 +1,599 @@
+/* -*- Mode: indent-tabs-mode: nil; js-indent-level: 2 -*- */
+/* vim: set sts=2 sw=2 et tw=80: */
+"use strict";
+
+const { AddonManager } = ChromeUtils.importESModule(
+  "resource://gre/modules/AddonManager.sys.mjs"
+);
+const { Preferences } = ChromeUtils.importESModule(
+  "resource://gre/modules/Preferences.sys.mjs"
+);
+
+const {
+  createAppInfo,
+  createTempWebExtensionFile,
+  promiseAddonEvent,
+  promiseCompleteAllInstalls,
+  promiseFindAddonUpdates,
+  promiseRestartManager,
+  promiseShutdownManager,
+  promiseStartupManager,
+} = AddonTestUtils;
+
+AddonTestUtils.init(this);
+
+// Allow for unsigned addons.
+AddonTestUtils.overrideCertDB();
+
+createAppInfo("xpcshell@tests.mozilla.org", "XPCShell", "42", "42");
+
+function background() {
+  let onInstalledDetails = null;
+  let onStartupFired = false;
+  let eventPage = browser.runtime.getManifest().background.persistent === false;
+
+  browser.runtime.onInstalled.addListener(details => {
+    onInstalledDetails = details;
+  });
+
+  browser.runtime.onStartup.addListener(() => {
+    onStartupFired = true;
+  });
+
+  browser.test.onMessage.addListener(message => {
+    if (message === "get-on-installed-details") {
+      onInstalledDetails = onInstalledDetails || { fired: false };
+      browser.test.sendMessage("on-installed-details", onInstalledDetails);
+    } else if (message === "did-on-startup-fire") {
+      browser.test.sendMessage("on-startup-fired", onStartupFired);
+    } else if (message === "reload-extension") {
+      browser.runtime.reload();
+    }
+  });
+
+  browser.runtime.onUpdateAvailable.addListener(details => {
+    browser.test.sendMessage("reloading");
+    browser.runtime.reload();
+  });
+
+  if (eventPage) {
+    browser.runtime.onSuspend.addListener(() => {
+      browser.test.sendMessage("suspended");
+    });
+    // an event we use to restart the background
+    browser.browserSettings.homepageOverride.onChange.addListener(() => {
+      browser.test.sendMessage("homepageOverride");
+    });
+  }
+}
+
+async function expectEvents(
+  extension,
+  {
+    onStartupFired,
+    onInstalledFired,
+    onInstalledReason,
+    onInstalledTemporary,
+    onInstalledPrevious,
+  }
+) {
+  extension.sendMessage("get-on-installed-details");
+  let details = await extension.awaitMessage("on-installed-details");
+  if (onInstalledFired) {
+    equal(
+      details.reason,
+      onInstalledReason,
+      "runtime.onInstalled fired with the correct reason"
+    );
+    equal(
+      details.temporary,
+      onInstalledTemporary,
+      "runtime.onInstalled fired with the correct temporary flag"
+    );
+    if (onInstalledPrevious) {
+      equal(
+        details.previousVersion,
+        onInstalledPrevious,
+        "runtime.onInstalled after update with correct previousVersion"
+      );
+    }
+  } else {
+    equal(
+      details.fired,
+      onInstalledFired,
+      "runtime.onInstalled should not have fired"
+    );
+  }
+
+  extension.sendMessage("did-on-startup-fire");
+  let fired = await extension.awaitMessage("on-startup-fired");
+  equal(
+    fired,
+    onStartupFired,
+    `Expected runtime.onStartup to ${onStartupFired ? "" : "not "} fire`
+  );
+}
+
+add_task(async function test_should_fire_on_addon_update() {
+  Preferences.set("extensions.logging.enabled", false);
+
+  await promiseStartupManager();
+
+  const EXTENSION_ID =
+    "test_runtime_on_installed_addon_update@tests.mozilla.org";
+
+  const PREF_EM_CHECK_UPDATE_SECURITY = "extensions.checkUpdateSecurity";
+
+  // The test extension uses an insecure update url.
+  Services.prefs.setBoolPref(PREF_EM_CHECK_UPDATE_SECURITY, false);
+
+  const testServer = createHttpServer();
+  const port = testServer.identity.primaryPort;
+
+  let extension = ExtensionTestUtils.loadExtension({
+    useAddonManager: "permanent",
+    manifest: {
+      version: "1.0",
+      browser_specific_settings: {
+        gecko: {
+          id: EXTENSION_ID,
+          update_url: `http://localhost:${port}/test_update.json`,
+        },
+      },
+    },
+    background,
+  });
+
+  testServer.registerPathHandler("/test_update.json", (request, response) => {
+    response.write(`{
+      "addons": {
+        "${EXTENSION_ID}": {
+          "updates": [
+            {
+              "version": "2.0",
+              "update_link": "http://localhost:${port}/addons/test_runtime_on_installed-2.0.xpi"
+            }
+          ]
+        }
+      }
+    }`);
+  });
+
+  let webExtensionFile = createTempWebExtensionFile({
+    manifest: {
+      version: "2.0",
+      browser_specific_settings: {
+        gecko: {
+          id: EXTENSION_ID,
+        },
+      },
+    },
+    background,
+  });
+
+  testServer.registerFile(
+    "/addons/test_runtime_on_installed-2.0.xpi",
+    webExtensionFile
+  );
+
+  await extension.startup();
+
+  await expectEvents(extension, {
+    onStartupFired: false,
+    onInstalledFired: true,
+    onInstalledTemporary: false,
+    onInstalledReason: "install",
+  });
+
+  let addon = await AddonManager.getAddonByID(EXTENSION_ID);
+  equal(addon.version, "1.0", "The installed addon has the correct version");
+
+  let update = await promiseFindAddonUpdates(addon);
+  let install = update.updateAvailable;
+
+  let promiseInstalled = promiseAddonEvent("onInstalled");
+  await promiseCompleteAllInstalls([install]);
+
+  await extension.awaitMessage("reloading");
+
+  let [updated_addon] = await promiseInstalled;
+  equal(
+    updated_addon.version,
+    "2.0",
+    "The updated addon has the correct version"
+  );
+
+  await extension.awaitStartup();
+
+  await expectEvents(extension, {
+    onStartupFired: false,
+    onInstalledFired: true,
+    onInstalledTemporary: false,
+    onInstalledReason: "update",
+    onInstalledPrevious: "1.0",
+  });
+
+  await extension.unload();
+
+  await promiseShutdownManager();
+});
+
+add_task(async function test_should_fire_on_browser_update() {
+  const EXTENSION_ID =
+    "test_runtime_on_installed_browser_update@tests.mozilla.org";
+
+  await promiseStartupManager("1");
+
+  let extension = ExtensionTestUtils.loadExtension({
+    useAddonManager: "permanent",
+    manifest: {
+      version: "1.0",
+      browser_specific_settings: {
+        gecko: {
+          id: EXTENSION_ID,
+        },
+      },
+    },
+    background,
+  });
+
+  await extension.startup();
+
+  await expectEvents(extension, {
+    onStartupFired: false,
+    onInstalledFired: true,
+    onInstalledTemporary: false,
+    onInstalledReason: "install",
+  });
+
+  // Restart the browser.
+  await promiseRestartManager("1");
+  await extension.awaitBackgroundStarted();
+
+  await expectEvents(extension, {
+    onStartupFired: true,
+    onInstalledFired: false,
+  });
+
+  // Update the browser.
+  await promiseRestartManager("2");
+  await extension.awaitBackgroundStarted();
+
+  await expectEvents(extension, {
+    onStartupFired: true,
+    onInstalledFired: true,
+    onInstalledTemporary: false,
+    onInstalledReason: "browser_update",
+  });
+
+  // Restart the browser.
+  await promiseRestartManager("2");
+  await extension.awaitBackgroundStarted();
+
+  await expectEvents(extension, {
+    onStartupFired: true,
+    onInstalledFired: false,
+  });
+
+  // Update the browser again.
+  await promiseRestartManager("3");
+  await extension.awaitBackgroundStarted();
+
+  await expectEvents(extension, {
+    onStartupFired: true,
+    onInstalledFired: true,
+    onInstalledTemporary: false,
+    onInstalledReason: "browser_update",
+  });
+
+  await extension.unload();
+
+  await promiseShutdownManager();
+});
+
+add_task(async function test_should_not_fire_on_reload() {
+  const EXTENSION_ID = "test_runtime_on_installed_reload@tests.mozilla.org";
+
+  await promiseStartupManager();
+
+  let extension = ExtensionTestUtils.loadExtension({
+    useAddonManager: "permanent",
+    manifest: {
+      version: "1.0",
+      browser_specific_settings: {
+        gecko: {
+          id: EXTENSION_ID,
+        },
+      },
+    },
+    background,
+  });
+
+  await extension.startup();
+
+  await expectEvents(extension, {
+    onStartupFired: false,
+    onInstalledFired: true,
+    onInstalledTemporary: false,
+    onInstalledReason: "install",
+  });
+
+  extension.sendMessage("reload-extension");
+  extension.setRestarting();
+  await extension.awaitStartup();
+
+  await expectEvents(extension, {
+    onStartupFired: false,
+    onInstalledFired: false,
+  });
+
+  await extension.unload();
+  await promiseShutdownManager();
+});
+
+add_task(async function test_should_not_fire_on_restart() {
+  const EXTENSION_ID = "test_runtime_on_installed_restart@tests.mozilla.org";
+
+  await promiseStartupManager();
+
+  let extension = ExtensionTestUtils.loadExtension({
+    useAddonManager: "permanent",
+    manifest: {
+      version: "1.0",
+      browser_specific_settings: {
+        gecko: {
+          id: EXTENSION_ID,
+        },
+      },
+    },
+    background,
+  });
+
+  await extension.startup();
+
+  await expectEvents(extension, {
+    onStartupFired: false,
+    onInstalledFired: true,
+    onInstalledTemporary: false,
+    onInstalledReason: "install",
+  });
+
+  let addon = await AddonManager.getAddonByID(EXTENSION_ID);
+  await addon.disable();
+  await addon.enable();
+  await extension.awaitStartup();
+
+  await expectEvents(extension, {
+    onStartupFired: false,
+    onInstalledFired: false,
+  });
+
+  await extension.unload();
+  await promiseShutdownManager();
+});
+
+add_task(async function test_temporary_installation() {
+  const EXTENSION_ID =
+    "test_runtime_on_installed_addon_temporary@tests.mozilla.org";
+
+  await promiseStartupManager();
+
+  let extension = ExtensionTestUtils.loadExtension({
+    useAddonManager: "temporary",
+    manifest: {
+      version: "1.0",
+      browser_specific_settings: {
+        gecko: {
+          id: EXTENSION_ID,
+        },
+      },
+    },
+    background,
+  });
+
+  await extension.startup();
+
+  await expectEvents(extension, {
+    onStartupFired: false,
+    onInstalledFired: true,
+    onInstalledReason: "install",
+    onInstalledTemporary: true,
+  });
+
+  await extension.unload();
+  await promiseShutdownManager();
+});
+
+add_task(
+  {
+    pref_set: [["extensions.eventPages.enabled", true]],
+  },
+  async function test_runtime_eventpage() {
+    const EXTENSION_ID = "test_runtime_eventpage@tests.mozilla.org";
+
+    await promiseStartupManager("1");
+
+    let extension = ExtensionTestUtils.loadExtension({
+      useAddonManager: "permanent",
+      manifest: {
+        version: "1.0",
+        browser_specific_settings: {
+          gecko: {
+            id: EXTENSION_ID,
+          },
+        },
+        permissions: ["browserSettings"],
+        background: {
+          persistent: false,
+        },
+      },
+      background,
+    });
+
+    await extension.startup();
+
+    await expectEvents(extension, {
+      onStartupFired: false,
+      onInstalledFired: true,
+      onInstalledReason: "install",
+      onInstalledTemporary: false,
+    });
+
+    info(`test onInstall does not fire after suspend`);
+    // we do enough here that idle timeout causes intermittent failure.
+    // using terminateBackground results in the same code path tested.
+    extension.terminateBackground();
+    await extension.awaitMessage("suspended");
+    await promiseExtensionEvent(extension, "shutdown-background-script");
+
+    Services.prefs.setStringPref(
+      "browser.startup.homepage",
+      "http://test.example.com"
+    );
+    await extension.awaitMessage("homepageOverride");
+    // onStartup remains persisted, but not primed
+    assertPersistentListeners(extension, "runtime", "onStartup", {
+      primed: false,
+      persisted: true,
+    });
+
+    await expectEvents(extension, {
+      onStartupFired: false,
+      onInstalledFired: false,
+    });
+
+    info("test onStartup is not primed but background starts automatically");
+    await promiseRestartManager();
+    // onStartup is a bit special.  During APP_STARTUP we do not
+    // prime this, we just start since it needs to.
+    assertPersistentListeners(extension, "runtime", "onStartup", {
+      primed: false,
+      persisted: true,
+    });
+    await extension.awaitBackgroundStarted();
+
+    info("test expectEvents");
+    await expectEvents(extension, {
+      onStartupFired: true,
+      onInstalledFired: false,
+    });
+
+    info("test onInstalled fired during browser update");
+    await promiseRestartManager("2");
+    assertPersistentListeners(extension, "runtime", "onStartup", {
+      primed: false,
+      persisted: true,
+    });
+    await extension.awaitBackgroundStarted();
+
+    await expectEvents(extension, {
+      onStartupFired: true,
+      onInstalledFired: true,
+      onInstalledReason: "browser_update",
+      onInstalledTemporary: false,
+    });
+
+    info(`test onStarted does not fire after suspend`);
+    extension.terminateBackground();
+    await extension.awaitMessage("suspended");
+    await promiseExtensionEvent(extension, "shutdown-background-script");
+
+    Services.prefs.setStringPref(
+      "browser.startup.homepage",
+      "http://homepage.example.com"
+    );
+    await extension.awaitMessage("homepageOverride");
+    // onStartup remains persisted, but not primed
+    assertPersistentListeners(extension, "runtime", "onStartup", {
+      primed: false,
+      persisted: true,
+    });
+
+    await expectEvents(extension, {
+      onStartupFired: false,
+      onInstalledFired: false,
+    });
+
+    await extension.unload();
+    await promiseShutdownManager();
+  }
+);
+
+// Verify we don't regress the issue related to runtime.onStartup persistent
+// listener being cleared from the startup data as part of priming all listeners
+// while terminating the event page on idle timeout (Bug 1796586).
+add_task(
+  {
+    pref_set: [["extensions.eventPages.enabled", true]],
+  },
+  async function test_runtime_onStartup_eventpage() {
+    const EXTENSION_ID = "test_eventpage_onStartup@tests.mozilla.org";
+
+    await promiseStartupManager();
+
+    let extension = ExtensionTestUtils.loadExtension({
+      useAddonManager: "permanent",
+      manifest: {
+        version: "1.0",
+        browser_specific_settings: {
+          gecko: {
+            id: EXTENSION_ID,
+          },
+        },
+        permissions: ["browserSettings"],
+        background: {
+          persistent: false,
+        },
+      },
+      background,
+    });
+
+    await extension.startup();
+
+    await expectEvents(extension, {
+      onStartupFired: false,
+      onInstalledFired: true,
+      onInstalledReason: "install",
+      onInstalledTemporary: false,
+    });
+
+    info("Simulated idle timeout");
+    extension.terminateBackground();
+    await extension.awaitMessage("suspended");
+    await promiseExtensionEvent(extension, "shutdown-background-script");
+
+    // onStartup remains persisted, but not primed
+    assertPersistentListeners(extension, "runtime", "onStartup", {
+      primed: false,
+      persisted: true,
+    });
+
+    info(`test onStartup after restart`);
+    await promiseRestartManager();
+
+    // onStartup is a bit special.  During APP_STARTUP we do not
+    // prime this, we just start since it needs to.
+    assertPersistentListeners(extension, "runtime", "onStartup", {
+      primed: false,
+      persisted: true,
+    });
+    await extension.awaitBackgroundStarted();
+
+    info("test expectEvents");
+    await expectEvents(extension, {
+      onStartupFired: true,
+      onInstalledFired: false,
+    });
+
+    extension.terminateBackground();
+    await extension.awaitMessage("suspended");
+    await promiseExtensionEvent(extension, "shutdown-background-script");
+    assertPersistentListeners(extension, "runtime", "onStartup", {
+      primed: false,
+      persisted: true,
+    });
+
+    await extension.unload();
+    await promiseShutdownManager();
+  }
+);
diff --git a/toolkit/components/extensions/test/xpcshell/test_ext_runtime_ports.js b/toolkit/components/extensions/test/xpcshell/test_ext_runtime_ports.js
new file mode 100644
index 0000000000..7365a13f93
--- /dev/null
+++ b/toolkit/components/extensions/test/xpcshell/test_ext_runtime_ports.js
@@ -0,0 +1,69 @@
+"use strict";
+
+add_task(async function test_port_disconnected_from_wrong_window() {
+  let extensionData = {
+    background() {
+      let num = 0;
+      let ports = {};
+      let done = false;
+
+      browser.runtime.onConnect.addListener(port => {
+        num++;
+        ports[num] = port;
+
+        port.onMessage.addListener(msg => {
+          browser.test.assertEq(msg, "port-2-response", "Got port 2 response");
+          browser.test.sendMessage(msg + "-received");
+          done = true;
+        });
+
+        port.onDisconnect.addListener(err => {
+          if (port === ports[1]) {
+            browser.test.log("Port 1 disconnected, sending message via port 2");
+            ports[2].postMessage("port-2-msg");
+          } else {
+            browser.test.assertTrue(
+              done,
+              "Port 2 disconnected only after a full roundtrip received"
+            );
+          }
+        });
+
+        browser.test.sendMessage("port-connect-" + num);
+      });
+    },
+    files: {
+      "page.html": `
+        <!DOCTYPE html><meta charset="utf8">
+        <script src="script.js"></script>
+      `,
+      "script.js"() {
+        let port = browser.runtime.connect();
+        port.onMessage.addListener(msg => {
+          browser.test.assertEq(msg, "port-2-msg", "Got message via port 2");
+          port.postMessage("port-2-response");
+        });
+      },
+    },
+  };
+
+  let extension = ExtensionTestUtils.loadExtension(extensionData);
+  let url = `moz-extension://${extension.uuid}/page.html`;
+  await extension.startup();
+
+  let page1 = await ExtensionTestUtils.loadContentPage(url, { extension });
+  await extension.awaitMessage("port-connect-1");
+  info("First page opened port 1");
+
+  let page2 = await ExtensionTestUtils.loadContentPage(url, { extension });
+  await extension.awaitMessage("port-connect-2");
+  info("Second page opened port 2");
+
+  info("Closing the first page should not close port 2");
+  await page1.close();
+  await extension.awaitMessage("port-2-response-received");
+  info("Roundtrip message through port 2 received");
+
+  await page2.close();
+  await extension.unload();
+});
diff --git a/toolkit/components/extensions/test/xpcshell/test_ext_runtime_ports_gc.js b/toolkit/components/extensions/test/xpcshell/test_ext_runtime_ports_gc.js
new file mode 100644
index 0000000000..dd47744a97
--- /dev/null
+++ b/toolkit/components/extensions/test/xpcshell/test_ext_runtime_ports_gc.js
@@ -0,0 +1,170 @@
+"use strict";
+
+let gcExperimentAPIs = {
+  gcHelper: {
+    schema: "schema.json",
+    child: {
+      scopes: ["addon_child"],
+      script: "child.js",
+      paths: [["gcHelper"]],
+    },
+  },
+};
+
+let gcExperimentFiles = {
+  "schema.json": JSON.stringify([
+    {
+      namespace: "gcHelper",
+      functions: [
+        {
+          name: "forceGarbageCollect",
+          type: "function",
+          parameters: [],
+          async: true,
+        },
+        {
+          name: "registerWitness",
+          type: "function",
+          parameters: [
+            {
+              name: "obj",
+              // Expected type is "object", but using "any" here to ensure that
+              // the parameter is untouched (not normalized).
+              type: "any",
+            },
+          ],
+          returns: { type: "number" },
+        },
+        {
+          name: "isGarbageCollected",
+          type: "function",
+          parameters: [
+            {
+              name: "witnessId",
+              description: "return value of registerWitness",
+              type: "number",
+            },
+          ],
+          returns: { type: "boolean" },
+        },
+      ],
+    },
+  ]),
+  "child.js": () => {
+    let { setTimeout } = ChromeUtils.importESModule(
+      "resource://gre/modules/Timer.sys.mjs"
+    );
+    /* globals ExtensionAPI */
+    this.gcHelper = class extends ExtensionAPI {
+      getAPI(context) {
+        let witnesses = new Map();
+        return {
+          gcHelper: {
+            async forceGarbageCollect() {
+              // Logic copied from test_ext_contexts_gc.js
+              for (let i = 0; i < 3; ++i) {
+                Cu.forceShrinkingGC();
+                Cu.forceCC();
+                Cu.forceGC();
+                await new Promise(resolve => setTimeout(resolve, 0));
+              }
+            },
+            registerWitness(obj) {
+              let witnessId = witnesses.size;
+              witnesses.set(witnessId, Cu.getWeakReference(obj));
+              return witnessId;
+            },
+            isGarbageCollected(witnessId) {
+              return witnesses.get(witnessId).get() === null;
+            },
+          },
+        };
+      }
+    };
+  },
+};
+
+// Verify that the experiment is working as intended before using it in tests.
+add_task(async function test_gc_experiment() {
+  let extension = ExtensionTestUtils.loadExtension({
+    isPrivileged: true,
+    manifest: {
+      experiment_apis: gcExperimentAPIs,
+    },
+    files: gcExperimentFiles,
+    async background() {
+      let obj1 = {};
+      let obj2 = {};
+      let witness1 = browser.gcHelper.registerWitness(obj1);
+      let witness2 = browser.gcHelper.registerWitness(obj2);
+      obj1 = null;
+      await browser.gcHelper.forceGarbageCollect();
+      browser.test.assertTrue(
+        browser.gcHelper.isGarbageCollected(witness1),
+        "obj1 should have been garbage-collected"
+      );
+      browser.test.assertFalse(
+        browser.gcHelper.isGarbageCollected(witness2),
+        "obj2 should not have been garbage-collected"
+      );
+
+      browser.test.sendMessage("done");
+    },
+  });
+
+  await extension.startup();
+  await extension.awaitMessage("done");
+  await extension.unload();
+});
+
+add_task(async function test_port_gc() {
+  let extension = ExtensionTestUtils.loadExtension({
+    isPrivileged: true,
+    manifest: {
+      experiment_apis: gcExperimentAPIs,
+    },
+    files: gcExperimentFiles,
+    async background() {
+      let witnessPortSender;
+      let witnessPortReceiver;
+
+      browser.runtime.onConnect.addListener(port => {
+        browser.test.assertEq("daName", port.name, "expected port");
+        witnessPortReceiver = browser.gcHelper.registerWitness(port);
+        port.disconnect();
+      });
+
+      // runtime.connect() only triggers onConnect for different contexts,
+      // so create a frame to have a different context.
+      // A blank frame in a moz-extension:-document will have access to the
+      // extension APIs.
+      let frameWindow = await new Promise(resolve => {
+        let f = document.createElement("iframe");
+        f.onload = () => resolve(f.contentWindow);
+        document.body.append(f);
+      });
+      await new Promise(resolve => {
+        let port = frameWindow.browser.runtime.connect({ name: "daName" });
+        witnessPortSender = browser.gcHelper.registerWitness(port);
+        port.onDisconnect.addListener(() => resolve());
+      });
+
+      await browser.gcHelper.forceGarbageCollect();
+
+      browser.test.assertTrue(
+        browser.gcHelper.isGarbageCollected(witnessPortSender),
+        "runtime.connect() port should have been garbage-collected"
+      );
+      browser.test.assertTrue(
+        browser.gcHelper.isGarbageCollected(witnessPortReceiver),
+        "runtime.onConnect port should have been garbage-collected"
+      );
+
+      browser.test.sendMessage("done");
+    },
+  });
+
+  await extension.startup();
+  await extension.awaitMessage("done");
+  await extension.unload();
+});
diff --git a/toolkit/components/extensions/test/xpcshell/test_ext_runtime_sendMessage.js b/toolkit/components/extensions/test/xpcshell/test_ext_runtime_sendMessage.js
new file mode 100644
index 0000000000..2bbc9864d7
--- /dev/null
+++ b/toolkit/components/extensions/test/xpcshell/test_ext_runtime_sendMessage.js
@@ -0,0 +1,462 @@
+/* -*- Mode: indent-tabs-mode: nil; js-indent-level: 2 -*- */
+/* vim: set sts=2 sw=2 et tw=80: */
+"use strict";
+
+const server = createHttpServer();
+server.registerDirectory("/data/", do_get_file("data"));
+const BASE_URL = `http://localhost:${server.identity.primaryPort}/data`;
+
+add_task(async function runtimeSendMessageReply() {
+  function background() {
+    browser.runtime.onMessage.addListener((msg, sender, respond) => {
+      if (msg == "respond-now") {
+        respond(msg);
+      } else if (msg == "respond-soon") {
+        setTimeout(() => {
+          respond(msg);
+        }, 0);
+        return true;
+      } else if (msg == "respond-promise") {
+        return Promise.resolve(msg);
+      } else if (msg == "respond-promise-false") {
+        return Promise.resolve(false);
+      } else if (msg == "respond-false") {
+        // return false means that respond() is not expected to be called.
+        setTimeout(() => respond("should be ignored"));
+        return false;
+      } else if (msg == "respond-never") {
+        return undefined;
+      } else if (msg == "respond-error") {
+        return Promise.reject(new Error(msg));
+      } else if (msg == "throw-error") {
+        throw new Error(msg);
+      } else if (msg === "respond-uncloneable") {
+        return Promise.resolve(window);
+      } else if (msg === "reject-uncloneable") {
+        return Promise.reject(window);
+      } else if (msg == "reject-undefined") {
+        return Promise.reject();
+      } else if (msg == "throw-undefined") {
+        throw undefined; // eslint-disable-line no-throw-literal
+      }
+    });
+
+    browser.runtime.onMessage.addListener((msg, sender, respond) => {
+      if (msg == "respond-now") {
+        respond("hello");
+      } else if (msg == "respond-now-2") {
+        respond(msg);
+      }
+    });
+
+    browser.runtime.onMessage.addListener((msg, sender, respond) => {
+      if (msg == "respond-now") {
+        // If a response from another listener is received first, this
+        // exception should be ignored.  Test fails if it is not.
+
+        // All this is of course stupid, but some extensions depend on it.
+        msg.blah.this.throws();
+      }
+    });
+
+    let childFrame = document.createElement("iframe");
+    childFrame.src = "extensionpage.html";
+    document.body.appendChild(childFrame);
+  }
+
+  function senderScript() {
+    Promise.all([
+      browser.runtime.sendMessage("respond-now"),
+      browser.runtime.sendMessage("respond-now-2"),
+      new Promise(resolve =>
+        browser.runtime.sendMessage("respond-soon", resolve)
+      ),
+      browser.runtime.sendMessage("respond-promise"),
+      browser.runtime.sendMessage("respond-promise-false"),
+      browser.runtime.sendMessage("respond-false"),
+      browser.runtime.sendMessage("respond-never"),
+      new Promise(resolve => {
+        browser.runtime.sendMessage("respond-never", response => {
+          resolve(response);
+        });
+      }),
+
+      browser.runtime
+        .sendMessage("respond-error")
+        .catch(error => Promise.resolve({ error })),
+      browser.runtime
+        .sendMessage("throw-error")
+        .catch(error => Promise.resolve({ error })),
+
+      browser.runtime
+        .sendMessage("respond-uncloneable")
+        .catch(error => Promise.resolve({ error })),
+      browser.runtime
+        .sendMessage("reject-uncloneable")
+        .catch(error => Promise.resolve({ error })),
+      browser.runtime
+        .sendMessage("reject-undefined")
+        .catch(error => Promise.resolve({ error })),
+      browser.runtime
+        .sendMessage("throw-undefined")
+        .catch(error => Promise.resolve({ error })),
+    ])
+      .then(
+        ([
+          respondNow,
+          respondNow2,
+          respondSoon,
+          respondPromise,
+          respondPromiseFalse,
+          respondFalse,
+          respondNever,
+          respondNever2,
+          respondError,
+          throwError,
+          respondUncloneable,
+          rejectUncloneable,
+          rejectUndefined,
+          throwUndefined,
+        ]) => {
+          browser.test.assertEq(
+            "respond-now",
+            respondNow,
+            "Got the expected immediate response"
+          );
+          browser.test.assertEq(
+            "respond-now-2",
+            respondNow2,
+            "Got the expected immediate response from the second listener"
+          );
+          browser.test.assertEq(
+            "respond-soon",
+            respondSoon,
+            "Got the expected delayed response"
+          );
+          browser.test.assertEq(
+            "respond-promise",
+            respondPromise,
+            "Got the expected promise response"
+          );
+          browser.test.assertEq(
+            false,
+            respondPromiseFalse,
+            "Got the expected false value as a promise result"
+          );
+          browser.test.assertEq(
+            undefined,
+            respondFalse,
+            "Got the expected no-response when onMessage returns false"
+          );
+          browser.test.assertEq(
+            undefined,
+            respondNever,
+            "Got the expected no-response resolution"
+          );
+          browser.test.assertEq(
+            undefined,
+            respondNever2,
+            "Got the expected no-response resolution"
+          );
+
+          browser.test.assertEq(
+            "respond-error",
+            respondError.error.message,
+            "Got the expected error response"
+          );
+          browser.test.assertEq(
+            "throw-error",
+            throwError.error.message,
+            "Got the expected thrown error response"
+          );
+
+          browser.test.assertEq(
+            "Could not establish connection. Receiving end does not exist.",
+            respondUncloneable.error.message,
+            "An uncloneable response should be ignored"
+          );
+          browser.test.assertEq(
+            "An unexpected error occurred",
+            rejectUncloneable.error.message,
+            "Got the expected error for a rejection with an uncloneable value"
+          );
+          browser.test.assertEq(
+            "An unexpected error occurred",
+            rejectUndefined.error.message,
+            "Got the expected error for a void rejection"
+          );
+          browser.test.assertEq(
+            "An unexpected error occurred",
+            throwUndefined.error.message,
+            "Got the expected error for a void throw"
+          );
+
+          browser.test.notifyPass("sendMessage");
+        }
+      )
+      .catch(e => {
+        browser.test.fail(`Error: ${e} :: ${e.stack}`);
+        browser.test.notifyFail("sendMessage");
+      });
+  }
+
+  let extension = ExtensionTestUtils.loadExtension({
+    background,
+    files: {
+      "senderScript.js": senderScript,
+      "extensionpage.html": `<!DOCTYPE html><meta charset="utf-8"><script src="senderScript.js"></script>`,
+    },
+  });
+
+  await extension.startup();
+  await extension.awaitFinish("sendMessage");
+  await extension.unload();
+});
+
+add_task(async function runtimeSendMessageBlob() {
+  function background() {
+    browser.runtime.onMessage.addListener(msg => {
+      // eslint-disable-next-line mozilla/use-isInstance -- this function runs in an extension
+      browser.test.assertTrue(msg.blob instanceof Blob, "Message is a blob");
+      return Promise.resolve(msg);
+    });
+
+    let childFrame = document.createElement("iframe");
+    childFrame.src = "extensionpage.html";
+    document.body.appendChild(childFrame);
+  }
+
+  function senderScript() {
+    browser.runtime
+      .sendMessage({ blob: new Blob(["hello"]) })
+      .then(response => {
+        browser.test.assertTrue(
+          // eslint-disable-next-line mozilla/use-isInstance -- this function runs in an extension
+          response.blob instanceof Blob,
+          "Response is a blob"
+        );
+        browser.test.notifyPass("sendBlob");
+      });
+  }
+
+  let extension = ExtensionTestUtils.loadExtension({
+    background,
+    files: {
+      "senderScript.js": senderScript,
+      "extensionpage.html": `<!DOCTYPE html><meta charset="utf-8"><script src="senderScript.js"></script>`,
+    },
+  });
+
+  await extension.startup();
+  await extension.awaitFinish("sendBlob");
+  await extension.unload();
+});
+
+add_task(async function sendMessageResponseGC() {
+  function background() {
+    let savedResolve, savedRespond;
+
+    browser.runtime.onMessage.addListener((msg, _, respond) => {
+      browser.test.log(`Got request: ${msg}`);
+      switch (msg) {
+        case "ping":
+          respond("pong");
+          return;
+
+        case "promise-save":
+          return new Promise(resolve => {
+            savedResolve = resolve;
+          });
+        case "promise-resolve":
+          savedResolve("saved-resolve");
+          return;
+        case "promise-never":
+          return new Promise(r => {});
+
+        case "callback-save":
+          savedRespond = respond;
+          return true;
+        case "callback-call":
+          savedRespond("saved-respond");
+          return;
+        case "callback-never":
+          return true;
+      }
+    });
+
+    const frame = document.createElement("iframe");
+    frame.src = "page.html";
+    document.body.appendChild(frame);
+  }
+
+  function page() {
+    browser.test.onMessage.addListener(msg => {
+      browser.runtime.sendMessage(msg).then(
+        response => {
+          if (response) {
+            browser.test.log(`Got response: ${response}`);
+            browser.test.sendMessage(response);
+          }
+        },
+        error => {
+          browser.test.assertEq(
+            "Promised response from onMessage listener went out of scope",
+            error.message,
+            `Promise rejected with the correct error message`
+          );
+
+          browser.test.assertTrue(
+            /^moz-extension:\/\/[\w-]+\/%7B[\w-]+%7D\.js/.test(error.fileName),
+            `Promise rejected with the correct error filename: ${error.fileName}`
+          );
+
+          browser.test.assertEq(
+            4,
+            error.lineNumber,
+            `Promise rejected with the correct error line number`
+          );
+
+          browser.test.assertTrue(
+            /moz-extension:\/\/[\w-]+\/%7B[\w-]+%7D\.js:4/.test(error.stack),
+            `Promise rejected with the correct error stack: ${error.stack}`
+          );
+          browser.test.sendMessage("rejected");
+        }
+      );
+    });
+    browser.test.sendMessage("ready");
+  }
+
+  let extension = ExtensionTestUtils.loadExtension({
+    background,
+    files: {
+      "page.html":
+        "<!DOCTYPE html><meta charset=utf-8><script src=page.js></script>",
+      "page.js": page,
+    },
+  });
+
+  await extension.startup();
+  await extension.awaitMessage("ready");
+
+  // Setup long-running tasks before GC.
+  extension.sendMessage("promise-save");
+  extension.sendMessage("callback-save");
+
+  // Test returning a Promise that can never resolve.
+  extension.sendMessage("promise-never");
+
+  extension.sendMessage("ping");
+  await extension.awaitMessage("pong");
+
+  Services.prefs.setBoolPref(
+    "security.allow_parent_unrestricted_js_loads",
+    true
+  );
+  Services.ppmm.loadProcessScript("data:,Components.utils.forceGC()", false);
+  await extension.awaitMessage("rejected");
+
+  // Test returning `true` without holding the response handle.
+  extension.sendMessage("callback-never");
+
+  extension.sendMessage("ping");
+  await extension.awaitMessage("pong");
+
+  Services.ppmm.loadProcessScript("data:,Components.utils.forceGC()", false);
+  Services.prefs.setBoolPref(
+    "security.allow_parent_unrestricted_js_loads",
+    false
+  );
+  await extension.awaitMessage("rejected");
+
+  // Test that promises from long-running tasks didn't get GCd.
+  extension.sendMessage("promise-resolve");
+  await extension.awaitMessage("saved-resolve");
+
+  extension.sendMessage("callback-call");
+  await extension.awaitMessage("saved-respond");
+
+  ok("Long running tasks responded");
+  await extension.unload();
+});
+
+add_task(async function sendMessage_async_response_multiple_contexts() {
+  let extension = ExtensionTestUtils.loadExtension({
+    background() {
+      browser.runtime.onMessage.addListener((msg, _, respond) => {
+        browser.test.log(`Background got request: ${msg}`);
+
+        switch (msg) {
+          case "ask-bg-fast":
+            respond("bg-respond");
+            return true;
+
+          case "ask-bg-slow":
+            return new Promise(r => setTimeout(() => r("bg-promise")), 1000);
+        }
+      });
+      browser.test.sendMessage("bg-ready");
+    },
+
+    manifest: {
+      content_scripts: [
+        {
+          matches: ["http://localhost/*/file_sample.html"],
+          js: ["cs.js"],
+        },
+      ],
+    },
+
+    files: {
+      "page.html":
+        "<!DOCTYPE html><meta charset=utf-8><script src=page.js></script>",
+      "page.js"() {
+        browser.runtime.onMessage.addListener((msg, _, respond) => {
+          browser.test.log(`Page got request: ${msg}`);
+
+          switch (msg) {
+            case "ask-page-fast":
+              respond("page-respond");
+              return true;
+
+            case "ask-page-slow":
+              return new Promise(r => setTimeout(() => r("page-promise")), 500);
+          }
+        });
+        browser.test.sendMessage("page-ready");
+      },
+
+      "cs.js"() {
+        Promise.all([
+          browser.runtime.sendMessage("ask-bg-fast"),
+          browser.runtime.sendMessage("ask-bg-slow"),
+          browser.runtime.sendMessage("ask-page-fast"),
+          browser.runtime.sendMessage("ask-page-slow"),
+        ]).then(responses => {
+          browser.test.assertEq(
+            responses.join(),
+            ["bg-respond", "bg-promise", "page-respond", "page-promise"].join(),
+            "Got all expected responses from correct contexts"
+          );
+          browser.test.notifyPass("cs-done");
+        });
+      },
+    },
+  });
+
+  await extension.startup();
+  await extension.awaitMessage("bg-ready");
+
+  let url = `moz-extension://${extension.uuid}/page.html`;
+  let page = await ExtensionTestUtils.loadContentPage(url, { extension });
+  await extension.awaitMessage("page-ready");
+
+  let content = await ExtensionTestUtils.loadContentPage(
+    BASE_URL + "/file_sample.html"
+  );
+  await extension.awaitFinish("cs-done");
+  await content.close();
+
+  await page.close();
+  await extension.unload();
+});
diff --git a/toolkit/components/extensions/test/xpcshell/test_ext_runtime_sendMessage_args.js b/toolkit/components/extensions/test/xpcshell/test_ext_runtime_sendMessage_args.js
new file mode 100644
index 0000000000..2c0b889ba3
--- /dev/null
+++ b/toolkit/components/extensions/test/xpcshell/test_ext_runtime_sendMessage_args.js
@@ -0,0 +1,118 @@
+/* -*- Mode: indent-tabs-mode: nil; js-indent-level: 2 -*- */
+/* vim: set sts=2 sw=2 et tw=80: */
+"use strict";
+
+add_task(async function () {
+  const ID1 = "sendMessage1@tests.mozilla.org";
+  const ID2 = "sendMessage2@tests.mozilla.org";
+
+  let extension1 = ExtensionTestUtils.loadExtension({
+    background() {
+      browser.test.onMessage.addListener((...args) => {
+        browser.runtime.sendMessage(...args);
+      });
+
+      let frame = document.createElement("iframe");
+      frame.src = "page.html";
+      document.body.appendChild(frame);
+    },
+    manifest: { browser_specific_settings: { gecko: { id: ID1 } } },
+    files: {
+      "page.js": function () {
+        browser.runtime.onMessage.addListener((msg, sender) => {
+          browser.test.sendMessage("received-page", { msg, sender });
+        });
+        // Let them know we're done loading the page.
+        browser.test.sendMessage("page-ready");
+      },
+      "page.html": `<!DOCTYPE html><meta charset="utf-8"><script src="page.js"></script>`,
+    },
+  });
+
+  let extension2 = ExtensionTestUtils.loadExtension({
+    background() {
+      browser.runtime.onMessageExternal.addListener((msg, sender) => {
+        browser.test.sendMessage("received-external", { msg, sender });
+      });
+    },
+    manifest: { browser_specific_settings: { gecko: { id: ID2 } } },
+  });
+
+  await Promise.all([extension1.startup(), extension2.startup()]);
+  await extension1.awaitMessage("page-ready");
+
+  // Check that a message was sent within extension1.
+  async function checkLocalMessage(msg) {
+    let result = await extension1.awaitMessage("received-page");
+    deepEqual(result.msg, msg, "Received internal message");
+    equal(result.sender.id, ID1, "Received correct sender id");
+  }
+
+  // Check that a message was sent from extension1 to extension2.
+  async function checkRemoteMessage(msg) {
+    let result = await extension2.awaitMessage("received-external");
+    deepEqual(result.msg, msg, "Received cross-extension message");
+    equal(result.sender.id, ID1, "Received correct sender id");
+  }
+
+  // sendMessage() takes 3 arguments:
+  //  optional extensionID
+  //  mandatory message
+  //  optional options
+  // Due to this insane design we parse its arguments manually.  This
+  // test is meant to cover all the combinations.
+
+  // A single null or undefined argument is allowed, and represents the message
+  extension1.sendMessage(null);
+  await checkLocalMessage(null);
+
+  // With one argument, it must be just the message
+  extension1.sendMessage("message");
+  await checkLocalMessage("message");
+
+  // With two arguments, these cases should be treated as (extensionID, message)
+  extension1.sendMessage(ID2, "message");
+  await checkRemoteMessage("message");
+
+  extension1.sendMessage(ID2, { msg: "message" });
+  await checkRemoteMessage({ msg: "message" });
+
+  // And these should be (message, options)
+  extension1.sendMessage("message", {});
+  await checkLocalMessage("message");
+
+  // or (message, non-callback), pick your poison
+  extension1.sendMessage("message", undefined);
+  await checkLocalMessage("message");
+
+  // With three arguments, we send a cross-extension message
+  extension1.sendMessage(ID2, "message", {});
+  await checkRemoteMessage("message");
+
+  // Even when the last one is null or undefined
+  extension1.sendMessage(ID2, "message", undefined);
+  await checkRemoteMessage("message");
+
+  // The four params case is unambigous, so we allow null as a (non-) callback
+  extension1.sendMessage(ID2, "message", {}, null);
+  await checkRemoteMessage("message");
+
+  await Promise.all([extension1.unload(), extension2.unload()]);
+});
+
+add_task(async function test_sendMessage_to_badid() {
+  const extension = ExtensionTestUtils.loadExtension({
+    async background() {
+      await browser.test.assertRejects(
+        browser.runtime.sendMessage("badid@test-extension", "fake-message"),
+        /Could not establish connection. Receiving end does not exist./,
+        "Got the expected error message on sendMessage to badid ext"
+      );
+      browser.test.sendMessage("test-done");
+    },
+  });
+
+  await extension.startup();
+  await extension.awaitMessage("test-done");
+  await extension.unload();
+});
diff --git a/toolkit/components/extensions/test/xpcshell/test_ext_runtime_sendMessage_errors.js b/toolkit/components/extensions/test/xpcshell/test_ext_runtime_sendMessage_errors.js
new file mode 100644
index 0000000000..d78197f9e4
--- /dev/null
+++ b/toolkit/components/extensions/test/xpcshell/test_ext_runtime_sendMessage_errors.js
@@ -0,0 +1,66 @@
+/* -*- Mode: indent-tabs-mode: nil; js-indent-level: 2 -*- */
+/* vim: set sts=2 sw=2 et tw=80: */
+"use strict";
+
+add_task(async function test_sendMessage_error() {
+  async function background() {
+    let circ = {};
+    circ.circ = circ;
+    let testCases = [
+      // [arguments, expected error string],
+      [[], "runtime.sendMessage's message argument is missing"],
+      [
+        [null, null, null, 42],
+        "runtime.sendMessage's last argument is not a function",
+      ],
+      [[null, null, 1], "runtime.sendMessage's options argument is invalid"],
+      [
+        [1, null, null],
+        "runtime.sendMessage's extensionId argument is invalid",
+      ],
+      [
+        [null, null, null, null, null],
+        "runtime.sendMessage received too many arguments",
+      ],
+
+      // Even when the parameters are accepted, we still expect an error
+      // because there is no onMessage listener.
+      [
+        [null, null, null],
+        "Could not establish connection. Receiving end does not exist.",
+      ],
+
+      // Structured cloning doesn't work with DOM objects
+      [[null, location, null], "Location object could not be cloned."],
+      [[null, [circ, location], null], "Location object could not be cloned."],
+    ];
+
+    // Repeat all tests with the undefined value instead of null.
+    for (let [args, expectedError] of testCases.slice()) {
+      args = args.map(arg => (arg === null ? undefined : arg));
+      testCases.push([args, expectedError]);
+    }
+
+    for (let [args, expectedError] of testCases) {
+      let description = `runtime.sendMessage(${args.map(String).join(", ")})`;
+
+      await browser.test.assertRejects(
+        browser.runtime.sendMessage(...args),
+        expectedError,
+        `expected error message for ${description}`
+      );
+    }
+
+    browser.test.notifyPass("sendMessage parameter validation");
+  }
+  let extensionData = {
+    background,
+  };
+
+  let extension = ExtensionTestUtils.loadExtension(extensionData);
+  await extension.startup();
+
+  await extension.awaitFinish("sendMessage parameter validation");
+
+  await extension.unload();
+});
diff --git a/toolkit/components/extensions/test/xpcshell/test_ext_runtime_sendMessage_multiple.js b/toolkit/components/extensions/test/xpcshell/test_ext_runtime_sendMessage_multiple.js
new file mode 100644
index 0000000000..9827a329e3
--- /dev/null
+++ b/toolkit/components/extensions/test/xpcshell/test_ext_runtime_sendMessage_multiple.js
@@ -0,0 +1,67 @@
+/* -*- Mode: indent-tabs-mode: nil; js-indent-level: 2 -*- */
+/* vim: set sts=2 sw=2 et tw=80: */
+"use strict";
+
+// Regression test for bug 1655624: When there are multiple onMessage receivers
+// that both handle the response asynchronously, destroying the context of one
+// recipient should not prevent the other recipient from sending a reply.
+add_task(async function onMessage_ignores_destroyed_contexts() {
+  let extension = ExtensionTestUtils.loadExtension({
+    background() {
+      browser.test.onMessage.addListener(async msg => {
+        if (msg !== "startTest") {
+          return;
+        }
+        try {
+          let res = await browser.runtime.sendMessage("msg_from_bg");
+          browser.test.assertEq(0, res, "Result from onMessage");
+          browser.test.notifyPass("handled_onMessage");
+        } catch (e) {
+          browser.test.fail(`Unexpected error: ${e.message} :: ${e.stack}`);
+          browser.test.notifyFail("handled_onMessage");
+        }
+      });
+    },
+    files: {
+      "tab.html": `
+        <!DOCTYPE html><meta charset="utf-8">
+        <script src="tab.js"></script>
+      `,
+      "tab.js": () => {
+        let where = location.search.slice(1);
+        let resolveOnMessage;
+        browser.runtime.onMessage.addListener(async msg => {
+          browser.test.assertEq("msg_from_bg", msg, `onMessage at ${where}`);
+          browser.test.sendMessage(`received:${where}`);
+          return new Promise(resolve => {
+            resolveOnMessage = resolve;
+          });
+        });
+        browser.test.onMessage.addListener(msg => {
+          if (msg === `resolveOnMessage:${where}`) {
+            resolveOnMessage(0);
+          }
+        });
+      },
+    },
+  });
+  await extension.startup();
+  let tabToCloseEarly = await ExtensionTestUtils.loadContentPage(
+    `moz-extension://${extension.uuid}/tab.html?tabToCloseEarly`,
+    { extension }
+  );
+  let tabToRespond = await ExtensionTestUtils.loadContentPage(
+    `moz-extension://${extension.uuid}/tab.html?tabToRespond`,
+    { extension }
+  );
+  extension.sendMessage("startTest");
+  await Promise.all([
+    extension.awaitMessage("received:tabToCloseEarly"),
+    extension.awaitMessage("received:tabToRespond"),
+  ]);
+  await tabToCloseEarly.close();
+  extension.sendMessage("resolveOnMessage:tabToRespond");
+  await extension.awaitFinish("handled_onMessage");
+  await tabToRespond.close();
+  await extension.unload();
+});
diff --git a/toolkit/components/extensions/test/xpcshell/test_ext_runtime_sendMessage_no_receiver.js b/toolkit/components/extensions/test/xpcshell/test_ext_runtime_sendMessage_no_receiver.js
new file mode 100644
index 0000000000..23d8b05f83
--- /dev/null
+++ b/toolkit/components/extensions/test/xpcshell/test_ext_runtime_sendMessage_no_receiver.js
@@ -0,0 +1,93 @@
+/* -*- Mode: indent-tabs-mode: nil; js-indent-level: 2 -*- */
+/* vim: set sts=2 sw=2 et tw=80: */
+"use strict";
+
+add_task(async function test_sendMessage_without_listener() {
+  async function background() {
+    await browser.test.assertRejects(
+      browser.runtime.sendMessage("msg"),
+      "Could not establish connection. Receiving end does not exist.",
+      "Correct error when there are no receivers from background"
+    );
+
+    browser.test.sendMessage("sendMessage-error-bg");
+  }
+  let extensionData = {
+    background,
+    files: {
+      "page.html": `<!doctype><meta charset=utf-8><script src="page.js"></script>`,
+      async "page.js"() {
+        await browser.test.assertRejects(
+          browser.runtime.sendMessage("msg"),
+          "Could not establish connection. Receiving end does not exist.",
+          "Correct error when there are no receivers from extension page"
+        );
+
+        browser.test.notifyPass("sendMessage-error-page");
+      },
+    },
+  };
+
+  let extension = ExtensionTestUtils.loadExtension(extensionData);
+  await extension.startup();
+  await extension.awaitMessage("sendMessage-error-bg");
+
+  let url = `moz-extension://${extension.uuid}/page.html`;
+  let page = await ExtensionTestUtils.loadContentPage(url, { extension });
+  await extension.awaitFinish("sendMessage-error-page");
+  await page.close();
+
+  await extension.unload();
+});
+
+add_task(async function test_chrome_sendMessage_without_listener() {
+  function background() {
+    /* globals chrome */
+    browser.test.assertEq(
+      null,
+      chrome.runtime.lastError,
+      "no lastError before call"
+    );
+    let retval = chrome.runtime.sendMessage("msg");
+    browser.test.assertEq(
+      null,
+      chrome.runtime.lastError,
+      "no lastError after call"
+    );
+    browser.test.assertEq(
+      undefined,
+      retval,
+      "return value of chrome.runtime.sendMessage without callback"
+    );
+
+    let isAsyncCall = false;
+    retval = chrome.runtime.sendMessage("msg", reply => {
+      browser.test.assertEq(undefined, reply, "no reply");
+      browser.test.assertTrue(
+        isAsyncCall,
+        "chrome.runtime.sendMessage's callback must be called asynchronously"
+      );
+      browser.test.assertEq(
+        undefined,
+        retval,
+        "return value of chrome.runtime.sendMessage with callback"
+      );
+      browser.test.assertEq(
+        "Could not establish connection. Receiving end does not exist.",
+        chrome.runtime.lastError.message
+      );
+      browser.test.notifyPass("finished chrome.runtime.sendMessage");
+    });
+    isAsyncCall = true;
+  }
+  let extensionData = {
+    background,
+  };
+
+  let extension = ExtensionTestUtils.loadExtension(extensionData);
+  await extension.startup();
+
+  await extension.awaitFinish("finished chrome.runtime.sendMessage");
+
+  await extension.unload();
+});
diff --git a/toolkit/components/extensions/test/xpcshell/test_ext_same_site_cookies.js b/toolkit/components/extensions/test/xpcshell/test_ext_same_site_cookies.js
new file mode 100644
index 0000000000..7d768b47c4
--- /dev/null
+++ b/toolkit/components/extensions/test/xpcshell/test_ext_same_site_cookies.js
@@ -0,0 +1,131 @@
+"use strict";
+
+const server = createHttpServer({ hosts: ["example.com"] });
+
+const WIN = `<html><body>dummy page setting a same-site cookie</body></html>`;
+
+// Small red image.
+const IMG_BYTES = atob(
+  "iVBORw0KGgoAAAANSUhEUgAAAAUAAAAFCAYAAACNbyblAAAAHElEQVQI12" +
+    "P4//8/w38GIAXDIBKE0DHxgljNBAAO9TXL0Y4OHwAAAABJRU5ErkJggg=="
+);
+
+server.registerPathHandler("/same_site_cookies", (request, response) => {
+  // avoid confusing cache behaviors
+  response.setHeader("Cache-Control", "no-cache", false);
+
+  if (request.queryString === "loadWin") {
+    response.write(WIN);
+    return;
+  }
+
+  // using startsWith and discard the math random
+  if (request.queryString.startsWith("loadImage")) {
+    response.setHeader(
+      "Set-Cookie",
+      "myKey=mySameSiteExtensionCookie; samesite=strict",
+      true
+    );
+    response.setHeader("Content-Type", "image/png");
+    response.write(IMG_BYTES);
+    return;
+  }
+
+  if (request.queryString === "loadXHR") {
+    let cookie = "noCookie";
+    if (request.hasHeader("Cookie")) {
+      cookie = request.getHeader("Cookie");
+    }
+    response.setHeader("Content-Type", "text/plain");
+    response.write(cookie);
+    return;
+  }
+
+  // We should never get here, but just in case return something unexpected.
+  response.write("D'oh");
+});
+
+/* Description of the test:
+ * (1) We load an image from mochi.test which sets a same site cookie
+ * (2) We have the web extension perform an XHR request to mochi.test
+ * (3) We verify the web-extension can access the same-site cookie
+ */
+
+add_task(async function test_webRequest_same_site_cookie_access() {
+  let extension = ExtensionTestUtils.loadExtension({
+    manifest: {
+      permissions: ["http://example.com/*"],
+      content_scripts: [
+        {
+          matches: ["http://example.com/*"],
+          run_at: "document_end",
+          js: ["content_script.js"],
+        },
+      ],
+    },
+
+    background() {
+      browser.test.onMessage.addListener(msg => {
+        if (msg === "verify-same-site-cookie-moz-extension") {
+          let xhr = new XMLHttpRequest();
+          try {
+            xhr.open(
+              "GET",
+              "http://example.com/same_site_cookies?loadXHR",
+              true
+            );
+            xhr.onload = function () {
+              browser.test.assertEq(
+                "myKey=mySameSiteExtensionCookie",
+                xhr.responseText,
+                "cookie should be accessible from moz-extension context"
+              );
+              browser.test.sendMessage("same-site-cookie-test-done");
+            };
+            xhr.onerror = function () {
+              browser.test.fail("xhr onerror");
+              browser.test.sendMessage("same-site-cookie-test-done");
+            };
+          } catch (e) {
+            browser.test.fail("xhr failure: " + e);
+          }
+          xhr.send();
+        }
+      });
+    },
+
+    files: {
+      "content_script.js": function () {
+        let myImage = document.createElement("img");
+        // Set the src via wrappedJSObject so the load is triggered with the
+        // content page's principal rather than ours.
+        myImage.wrappedJSObject.setAttribute(
+          "src",
+          "http://example.com/same_site_cookies?loadImage" + Math.random()
+        );
+        myImage.onload = function () {
+          browser.test.log("image onload");
+          browser.test.sendMessage("image-loaded-and-same-site-cookie-set");
+        };
+        myImage.onerror = function () {
+          browser.test.log("image onerror");
+        };
+        document.body.appendChild(myImage);
+      },
+    },
+  });
+
+  await extension.startup();
+
+  let contentPage = await ExtensionTestUtils.loadContentPage(
+    "http://example.com/same_site_cookies?loadWin"
+  );
+
+  await extension.awaitMessage("image-loaded-and-same-site-cookie-set");
+
+  extension.sendMessage("verify-same-site-cookie-moz-extension");
+  await extension.awaitMessage("same-site-cookie-test-done");
+
+  await contentPage.close();
+  await extension.unload();
+});
diff --git a/toolkit/components/extensions/test/xpcshell/test_ext_same_site_redirects.js b/toolkit/components/extensions/test/xpcshell/test_ext_same_site_redirects.js
new file mode 100644
index 0000000000..df77f8b0dd
--- /dev/null
+++ b/toolkit/components/extensions/test/xpcshell/test_ext_same_site_redirects.js
@@ -0,0 +1,233 @@
+"use strict";
+
+/**
+ * This test tests various redirection scenarios, and checks whether sameSite
+ * cookies are sent.
+ *
+ * The file has the following tests:
+ * - verify_firstparty_web_behavior - base case, confirms normal web behavior.
+ * - samesite_is_foreign_without_host_permissions
+ * - wildcard_host_permissions_enable_samesite_cookies
+ * - explicit_host_permissions_enable_samesite_cookies
+ * - some_host_permissions_enable_some_samesite_cookies
+ */
+
+// This simulates a common pattern used for sites that require authentication.
+// After logging in, there may be multiple redirects, HTTP and scripted.
+const SITE_START = "start.example.net";
+// set "start" cookies + 302 redirects to found.
+const SITE_FOUND = "found.example.net";
+// set "found" cookies + uses a HTML redirect to redir.
+const SITE_REDIR = "redir.example.net";
+// set "redir" cookies + 302 redirects to final.
+const SITE_FINAL = "final.example.net";
+
+const SITE = "example.net";
+
+const URL_START = `http://${SITE_START}/start`;
+
+const server = createHttpServer({
+  hosts: [SITE_START, SITE_FOUND, SITE_REDIR, SITE_FINAL],
+});
+
+function getCookies(request) {
+  return request.hasHeader("Cookie") ? request.getHeader("Cookie") : "";
+}
+
+function sendCookies(response, prefix, suffix = "") {
+  const cookies = [
+    prefix + "-none=1; sameSite=none; domain=" + SITE + suffix,
+    prefix + "-lax=1; sameSite=lax; domain=" + SITE + suffix,
+    prefix + "-strict=1; sameSite=strict; domain=" + SITE + suffix,
+  ];
+  for (let cookie of cookies) {
+    response.setHeader("Set-Cookie", cookie, true);
+  }
+}
+
+function deleteCookies(response, prefix) {
+  sendCookies(response, prefix, "; expires=Thu, 01 Jan 1970 00:00:00 GMT");
+}
+
+var receivedCookies = [];
+
+server.registerPathHandler("/start", (request, response) => {
+  Assert.equal(request.host, SITE_START);
+  Assert.equal(getCookies(request), "", "No cookies at start of test");
+
+  response.setStatusLine(request.httpVersion, 302, "Found");
+  sendCookies(response, "start");
+  response.setHeader("Location", `http://${SITE_FOUND}/found`);
+});
+
+server.registerPathHandler("/found", (request, response) => {
+  Assert.equal(request.host, SITE_FOUND);
+  receivedCookies.push(getCookies(request));
+
+  response.setHeader("Content-Type", "text/html; charset=utf-8", false);
+  deleteCookies(response, "start");
+  sendCookies(response, "found");
+  response.write(`<script>location = "http://${SITE_REDIR}/redir";</script>`);
+});
+
+server.registerPathHandler("/redir", (request, response) => {
+  Assert.equal(request.host, SITE_REDIR);
+  receivedCookies.push(getCookies(request));
+
+  response.setStatusLine(request.httpVersion, 302, "Found");
+  deleteCookies(response, "found");
+  sendCookies(response, "redir");
+  response.setHeader("Location", `http://${SITE_FINAL}/final`);
+});
+
+server.registerPathHandler("/final", (request, response) => {
+  Assert.equal(request.host, SITE_FINAL);
+  receivedCookies.push(getCookies(request));
+
+  response.setStatusLine(request.httpVersion, 302, "Found");
+  deleteCookies(response, "redir");
+  // In test some_host_permissions_enable_some_samesite_cookies, the cookies
+  // from the start haven't been cleared due to the lack of host permissions.
+  // Do that here instead.
+  deleteCookies(response, "start");
+  response.setHeader("Location", "/final_and_clean");
+});
+
+// Should be called before any request is made.
+function promiseFinalResponse() {
+  Assert.deepEqual(receivedCookies, [], "Test starts without observed cookies");
+  return new Promise(resolve => {
+    server.registerPathHandler("/final_and_clean", (request, response) => {
+      Assert.equal(request.host, SITE_FINAL);
+      Assert.equal(getCookies(request), "", "Cookies cleaned up");
+      resolve(receivedCookies.splice(0));
+    });
+  });
+}
+
+// Load the page as a child frame of an extension, for the given permissions.
+async function getCookiesForLoadInExtension({ permissions }) {
+  let extension = ExtensionTestUtils.loadExtension({
+    manifest: {
+      permissions,
+    },
+    files: {
+      "embedder.html": `<iframe src="${URL_START}"></iframe>`,
+    },
+  });
+  await extension.startup();
+  let cookiesPromise = promiseFinalResponse();
+  let contentPage = await ExtensionTestUtils.loadContentPage(
+    `moz-extension://${extension.uuid}/embedder.html`,
+    { extension }
+  );
+  let cookies = await cookiesPromise;
+  await contentPage.close();
+  await extension.unload();
+  return cookies;
+}
+
+add_task(async function setup() {
+  Services.prefs.setIntPref("network.cookie.cookieBehavior", 0);
+  Services.prefs.setBoolPref("network.cookie.sameSite.laxByDefault", true);
+
+  // Test server runs on http, so disable Secure requirement of sameSite=none.
+  Services.prefs.setBoolPref(
+    "network.cookie.sameSite.noneRequiresSecure",
+    false
+  );
+});
+
+// First verify that our expectations match with the actual behavior on the web.
+add_task(async function verify_firstparty_web_behavior() {
+  let cookiesPromise = promiseFinalResponse();
+  let contentPage = await ExtensionTestUtils.loadContentPage(URL_START);
+  let cookies = await cookiesPromise;
+  await contentPage.close();
+  Assert.deepEqual(
+    cookies,
+    // Same expectations as in host_permissions_enable_samesite_cookies
+    [
+      "start-none=1; start-lax=1; start-strict=1",
+      "found-none=1; found-lax=1; found-strict=1",
+      "redir-none=1; redir-lax=1; redir-strict=1",
+    ],
+    "Expected cookies from a first-party load on the web"
+  );
+});
+
+// Verify that an extension without permission behaves like a third-party page.
+add_task(async function samesite_is_foreign_without_host_permissions() {
+  let cookies = await getCookiesForLoadInExtension({
+    permissions: [],
+  });
+
+  Assert.deepEqual(
+    cookies,
+    ["start-none=1", "found-none=1", "redir-none=1"],
+    "SameSite cookies excluded without permissions"
+  );
+});
+
+// When an extension has permissions for the site, cookies should be included.
+add_task(async function wildcard_host_permissions_enable_samesite_cookies() {
+  let cookies = await getCookiesForLoadInExtension({
+    permissions: ["*://*.example.net/*"], // = *.SITE
+  });
+
+  Assert.deepEqual(
+    cookies,
+    // Same expectations as in verify_firstparty_web_behavior.
+    [
+      "start-none=1; start-lax=1; start-strict=1",
+      "found-none=1; found-lax=1; found-strict=1",
+      "redir-none=1; redir-lax=1; redir-strict=1",
+    ],
+    "Expected cookies from a load in an extension frame"
+  );
+});
+
+// When an extension has permissions for the site, cookies should be included.
+add_task(async function explicit_host_permissions_enable_samesite_cookies() {
+  let cookies = await getCookiesForLoadInExtension({
+    permissions: [
+      "*://start.example.net/*",
+      "*://found.example.net/*",
+      "*://redir.example.net/*",
+      "*://final.example.net/*",
+    ],
+  });
+
+  Assert.deepEqual(
+    cookies,
+    // Same expectations as in verify_firstparty_web_behavior.
+    [
+      "start-none=1; start-lax=1; start-strict=1",
+      "found-none=1; found-lax=1; found-strict=1",
+      "redir-none=1; redir-lax=1; redir-strict=1",
+    ],
+    "Expected cookies from a load in an extension frame"
+  );
+});
+
+// When an extension does not have host permissions for all sites, but only
+// some, then same-site cookies are only included in requests with the right
+// permissions.
+add_task(async function some_host_permissions_enable_some_samesite_cookies() {
+  let cookies = await getCookiesForLoadInExtension({
+    permissions: ["*://start.example.net/*", "*://final.example.net/*"],
+  });
+
+  Assert.deepEqual(
+    cookies,
+    [
+      // Missing permission for "found.example.net":
+      "start-none=1",
+      // Missing permission for "redir.example.net":
+      "found-none=1",
+      // "final.example.net" can see cookies from "start.example.net":
+      "start-lax=1; start-strict=1; redir-none=1",
+    ],
+    "Expected some cookies from a load in an extension frame"
+  );
+});
diff --git a/toolkit/components/extensions/test/xpcshell/test_ext_sandbox_var.js b/toolkit/components/extensions/test/xpcshell/test_ext_sandbox_var.js
new file mode 100644
index 0000000000..0a8a5acdef
--- /dev/null
+++ b/toolkit/components/extensions/test/xpcshell/test_ext_sandbox_var.js
@@ -0,0 +1,42 @@
+"use strict";
+
+const server = createHttpServer();
+server.registerDirectory("/data/", do_get_file("data"));
+
+const BASE_URL = `http://localhost:${server.identity.primaryPort}/data`;
+
+function contentScript() {
+  window.x = 12;
+  browser.test.assertEq(window.x, 12, "x is 12");
+  browser.test.notifyPass("background test passed");
+}
+
+let extensionData = {
+  manifest: {
+    content_scripts: [
+      {
+        matches: ["http://localhost/*/file_sample.html"],
+        js: ["content_script.js"],
+        run_at: "document_idle",
+      },
+    ],
+  },
+
+  files: {
+    "content_script.js": contentScript,
+  },
+};
+
+add_task(async function test_contentscript() {
+  let extension = ExtensionTestUtils.loadExtension(extensionData);
+  await extension.startup();
+
+  let contentPage = await ExtensionTestUtils.loadContentPage(
+    `${BASE_URL}/file_sample.html`
+  );
+
+  await extension.awaitFinish();
+  await contentPage.close();
+
+  await extension.unload();
+});
diff --git a/toolkit/components/extensions/test/xpcshell/test_ext_sandboxed_resource.js b/toolkit/components/extensions/test/xpcshell/test_ext_sandboxed_resource.js
new file mode 100644
index 0000000000..05489d753d
--- /dev/null
+++ b/toolkit/components/extensions/test/xpcshell/test_ext_sandboxed_resource.js
@@ -0,0 +1,55 @@
+"use strict";
+
+// Test that an extension page which is sandboxed may load resources
+// from itself without relying on web acessible resources.
+add_task(async function test_webext_background_sandbox_privileges() {
+  function backgroundSubframeScript() {
+    window.parent.postMessage(typeof browser, "*");
+  }
+
+  function backgroundScript() {
+    /* eslint-disable-next-line mozilla/balanced-listeners */
+    window.addEventListener("message", event => {
+      if (event.data == "undefined") {
+        browser.test.notifyPass("webext-background-sandbox-privileges");
+      } else {
+        browser.test.notifyFail("webext-background-sandbox-privileges");
+      }
+    });
+  }
+
+  let extensionData = {
+    manifest: {
+      background: {
+        page: "background.html",
+      },
+    },
+    files: {
+      "background.html": `<!DOCTYPE>
+        <html>
+          <head>
+            <meta charset="utf-8">
+          </head>
+          <body>
+            <script src="background.js"><\/script>
+            <iframe src="background-subframe.html" sandbox="allow-scripts"></iframe>
+          </body>
+        </html>`,
+      "background-subframe.html": `<!DOCTYPE>
+        <html>
+          <head>
+            <meta charset="utf-8">
+            <script src="background-subframe.js"><\/script>
+          </head>
+        </html>`,
+      "background-subframe.js": backgroundSubframeScript,
+      "background.js": backgroundScript,
+    },
+  };
+  let extension = ExtensionTestUtils.loadExtension(extensionData);
+
+  await extension.startup();
+
+  await extension.awaitFinish("webext-background-sandbox-privileges");
+  await extension.unload();
+});
diff --git a/toolkit/components/extensions/test/xpcshell/test_ext_schema.js b/toolkit/components/extensions/test/xpcshell/test_ext_schema.js
new file mode 100644
index 0000000000..913aa4f9ab
--- /dev/null
+++ b/toolkit/components/extensions/test/xpcshell/test_ext_schema.js
@@ -0,0 +1,80 @@
+"use strict";
+
+AddonTestUtils.init(this);
+
+add_task(async function testEmptySchema() {
+  function background() {
+    browser.test.assertEq(
+      undefined,
+      browser.manifest,
+      "browser.manifest is not defined"
+    );
+    browser.test.assertTrue(
+      !!browser.storage,
+      "browser.storage should be defined"
+    );
+    browser.test.assertEq(
+      undefined,
+      browser.contextMenus,
+      "browser.contextMenus should not be defined"
+    );
+    browser.test.notifyPass("schema");
+  }
+
+  let extension = ExtensionTestUtils.loadExtension({
+    background,
+    manifest: {
+      permissions: ["storage"],
+    },
+  });
+
+  await extension.startup();
+  await extension.awaitFinish("schema");
+  await extension.unload();
+});
+
+add_task(async function test_warnings_as_errors() {
+  let extension = ExtensionTestUtils.loadExtension({
+    manifest: { unrecognized_property_that_should_be_treated_as_a_warning: 1 },
+  });
+
+  // Tests should be run with extensions.webextensions.warnings-as-errors=true
+  // by default, and prevent extensions with manifest warnings from loading.
+  await Assert.rejects(
+    extension.startup(),
+    /unrecognized_property_that_should_be_treated_as_a_warning/,
+    "extension with invalid manifest should not load if warnings-as-errors=true"
+  );
+  // When ExtensionTestUtils.failOnSchemaWarnings(false) is called, startup is
+  // expected to succeed, as shown by the next "testUnknownProperties" test.
+});
+
+add_task(async function testUnknownProperties() {
+  let extension = ExtensionTestUtils.loadExtension({
+    manifest: {
+      permissions: ["unknownPermission"],
+
+      unknown_property: {},
+    },
+
+    background() {},
+  });
+
+  let { messages } = await promiseConsoleOutput(async () => {
+    ExtensionTestUtils.failOnSchemaWarnings(false);
+    await extension.startup();
+    ExtensionTestUtils.failOnSchemaWarnings(true);
+  });
+
+  AddonTestUtils.checkMessages(messages, {
+    expected: [
+      { message: /processing permissions\.0: Value "unknownPermission"/ },
+      {
+        message:
+          /processing unknown_property: An unexpected property was found in the WebExtension manifest/,
+      },
+    ],
+  });
+
+  await extension.unload();
+});
diff --git a/toolkit/components/extensions/test/xpcshell/test_ext_schemas.js b/toolkit/components/extensions/test/xpcshell/test_ext_schemas.js
new file mode 100644
index 0000000000..a89ddf0728
--- /dev/null
+++ b/toolkit/components/extensions/test/xpcshell/test_ext_schemas.js
@@ -0,0 +1,2118 @@
+"use strict";
+
+const global = this;
+
+let json = [
+  {
+    namespace: "testing",
+
+    properties: {
+      PROP1: { value: 20 },
+      prop2: { type: "string" },
+      prop3: {
+        $ref: "submodule",
+      },
+      prop4: {
+        $ref: "submodule",
+        unsupported: true,
+      },
+    },
+
+    types: [
+      {
+        id: "type1",
+        type: "string",
+        enum: ["value1", "value2", "value3"],
+      },
+
+      {
+        id: "type2",
+        type: "object",
+        properties: {
+          prop1: { type: "integer" },
+          prop2: { type: "array", items: { $ref: "type1" } },
+        },
+      },
+
+      {
+        id: "basetype1",
+        type: "object",
+        properties: {
+          prop1: { type: "string" },
+        },
+      },
+
+      {
+        id: "basetype2",
+        choices: [{ type: "integer" }],
+      },
+
+      {
+        $extend: "basetype1",
+        properties: {
+          prop2: { type: "string" },
+        },
+      },
+
+      {
+        $extend: "basetype2",
+        choices: [{ type: "string" }],
+      },
+
+      {
+        id: "basetype3",
+        type: "object",
+        properties: {
+          baseprop: { type: "string" },
+        },
+      },
+
+      {
+        id: "derivedtype1",
+        type: "object",
+        $import: "basetype3",
+        properties: {
+          derivedprop: { type: "string" },
+        },
+      },
+
+      {
+        id: "derivedtype2",
+        type: "object",
+        $import: "basetype3",
+        properties: {
+          derivedprop: { type: "integer" },
+        },
+      },
+
+      {
+        id: "submodule",
+        type: "object",
+        functions: [
+          {
+            name: "sub_foo",
+            type: "function",
+            parameters: [],
+            returns: { type: "integer" },
+          },
+        ],
+      },
+    ],
+
+    functions: [
+      {
+        name: "foo",
+        type: "function",
+        parameters: [
+          { name: "arg1", type: "integer", optional: true, default: 99 },
+          { name: "arg2", type: "boolean", optional: true },
+        ],
+      },
+
+      {
+        name: "bar",
+        type: "function",
+        parameters: [
+          { name: "arg1", type: "integer", optional: true },
+          { name: "arg2", type: "boolean" },
+        ],
+      },
+
+      {
+        name: "baz",
+        type: "function",
+        parameters: [
+          {
+            name: "arg1",
+            type: "object",
+            properties: {
+              prop1: { type: "string" },
+              prop2: { type: "integer", optional: true },
+              prop3: { type: "integer", unsupported: true },
+            },
+          },
+        ],
+      },
+
+      {
+        name: "qux",
+        type: "function",
+        parameters: [{ name: "arg1", $ref: "type1" }],
+      },
+
+      {
+        name: "quack",
+        type: "function",
+        parameters: [{ name: "arg1", $ref: "type2" }],
+      },
+
+      {
+        name: "quora",
+        type: "function",
+        parameters: [{ name: "arg1", type: "function" }],
+      },
+
+      {
+        name: "quileute",
+        type: "function",
+        parameters: [
+          { name: "arg1", type: "integer", optional: true },
+          { name: "arg2", type: "integer" },
+        ],
+      },
+
+      {
+        name: "queets",
+        type: "function",
+        unsupported: true,
+        parameters: [],
+      },
+
+      {
+        name: "quintuplets",
+        type: "function",
+        parameters: [
+          {
+            name: "obj",
+            type: "object",
+            properties: [],
+            additionalProperties: { type: "integer" },
+          },
+        ],
+      },
+
+      {
+        name: "quasar",
+        type: "function",
+        parameters: [
+          {
+            name: "abc",
+            type: "object",
+            properties: {
+              func: {
+                type: "function",
+                parameters: [{ name: "x", type: "integer" }],
+              },
+            },
+          },
+        ],
+      },
+
+      {
+        name: "quosimodo",
+        type: "function",
+        parameters: [
+          {
+            name: "xyz",
+            type: "object",
+            additionalProperties: { type: "any" },
+          },
+        ],
+      },
+
+      {
+        name: "patternprop",
+        type: "function",
+        parameters: [
+          {
+            name: "obj",
+            type: "object",
+            properties: { prop1: { type: "string", pattern: "^\\d+$" } },
+            patternProperties: {
+              "(?i)^prop\\d+$": { type: "string" },
+              "^foo\\d+$": { type: "string" },
+            },
+          },
+        ],
+      },
+
+      {
+        name: "pattern",
+        type: "function",
+        parameters: [
+          { name: "arg", type: "string", pattern: "(?i)^[0-9a-f]+$" },
+        ],
+      },
+
+      {
+        name: "format",
+        type: "function",
+        parameters: [
+          {
+            name: "arg",
+            type: "object",
+            properties: {
+              hostname: { type: "string", format: "hostname", optional: true },
+              canonicalDomain: {
+                type: "string",
+                format: "canonicalDomain",
+                optional: "omit-key-if-missing",
+              },
+              url: { type: "string", format: "url", optional: true },
+              origin: { type: "string", format: "origin", optional: true },
+              relativeUrl: {
+                type: "string",
+                format: "relativeUrl",
+                optional: true,
+              },
+              strictRelativeUrl: {
+                type: "string",
+                format: "strictRelativeUrl",
+                optional: true,
+              },
+              imageDataOrStrictRelativeUrl: {
+                type: "string",
+                format: "imageDataOrStrictRelativeUrl",
+                optional: true,
+              },
+            },
+          },
+        ],
+      },
+
+      {
+        name: "formatDate",
+        type: "function",
+        parameters: [
+          {
+            name: "arg",
+            type: "object",
+            properties: {
+              date: { type: "string", format: "date", optional: true },
+            },
+          },
+        ],
+      },
+
+      {
+        name: "deep",
+        type: "function",
+        parameters: [
+          {
+            name: "arg",
+            type: "object",
+            properties: {
+              foo: {
+                type: "object",
+                properties: {
+                  bar: {
+                    type: "array",
+                    items: {
+                      type: "object",
+                      properties: {
+                        baz: {
+                          type: "object",
+                          properties: {
+                            required: { type: "integer" },
+                            optional: { type: "string", optional: true },
+                          },
+                        },
+                      },
+                    },
+                  },
+                },
+              },
+            },
+          },
+        ],
+      },
+
+      {
+        name: "errors",
+        type: "function",
+        parameters: [
+          {
+            name: "arg",
+            type: "object",
+            properties: {
+              warn: {
+                type: "string",
+                pattern: "^\\d+$",
+                optional: true,
+                onError: "warn",
+              },
+              ignore: {
+                type: "string",
+                pattern: "^\\d+$",
+                optional: true,
+                onError: "ignore",
+              },
+              default: {
+                type: "string",
+                pattern: "^\\d+$",
+                optional: true,
+              },
+            },
+          },
+        ],
+      },
+
+      {
+        name: "localize",
+        type: "function",
+        parameters: [
+          {
+            name: "arg",
+            type: "object",
+            properties: {
+              foo: { type: "string", preprocess: "localize", optional: true },
+              bar: { type: "string", optional: true },
+              url: {
+                type: "string",
+                preprocess: "localize",
+                format: "url",
+                optional: true,
+              },
+            },
+          },
+        ],
+      },
+
+      {
+        name: "extended1",
+        type: "function",
+        parameters: [{ name: "val", $ref: "basetype1" }],
+      },
+
+      {
+        name: "extended2",
+        type: "function",
+        parameters: [{ name: "val", $ref: "basetype2" }],
+      },
+
+      {
+        name: "callderived1",
+        type: "function",
+        parameters: [{ name: "value", $ref: "derivedtype1" }],
+      },
+
+      {
+        name: "callderived2",
+        type: "function",
+        parameters: [{ name: "value", $ref: "derivedtype2" }],
+      },
+    ],
+
+    events: [
+      {
+        name: "onFoo",
+        type: "function",
+      },
+
+      {
+        name: "onBar",
+        type: "function",
+        extraParameters: [
+          {
+            name: "filter",
+            type: "integer",
+            optional: true,
+            default: 1,
+          },
+        ],
+      },
+    ],
+  },
+  {
+    namespace: "foreign",
+    properties: {
+      foreignRef: { $ref: "testing.submodule" },
+    },
+  },
+  {
+    namespace: "inject",
+    properties: {
+      PROP1: { value: "should inject" },
+    },
+  },
+  {
+    namespace: "do-not-inject",
+    properties: {
+      PROP1: { value: "should not inject" },
+    },
+  },
+];
+
+add_task(async function () {
+  let wrapper = getContextWrapper();
+  let url = "data:," + JSON.stringify(json);
+  Schemas._rootSchema = null;
+  await Schemas.load(url);
+
+  let root = {};
+  Schemas.inject(root, wrapper);
+
+  Assert.equal(root.testing.PROP1, 20, "simple value property");
+  Assert.equal(root.testing.type1.VALUE1, "value1", "enum type");
+  Assert.equal(root.testing.type1.VALUE2, "value2", "enum type");
+
+  Assert.equal("inject" in root, true, "namespace 'inject' should be injected");
+  Assert.equal(
+    root["do-not-inject"],
+    undefined,
+    "namespace 'do-not-inject' should not be injected"
+  );
+
+  root.testing.foo(11, true);
+  wrapper.verify("call", "testing", "foo", [11, true]);
+
+  root.testing.foo(true);
+  wrapper.verify("call", "testing", "foo", [99, true]);
+
+  root.testing.foo(null, true);
+  wrapper.verify("call", "testing", "foo", [99, true]);
+
+  root.testing.foo(undefined, true);
+  wrapper.verify("call", "testing", "foo", [99, true]);
+
+  root.testing.foo(11);
+  wrapper.verify("call", "testing", "foo", [11, null]);
+
+  Assert.throws(
+    () => root.testing.bar(11),
+    /Incorrect argument types/,
+    "should throw without required arg"
+  );
+
+  Assert.throws(
+    () => root.testing.bar(11, true, 10),
+    /Incorrect argument types/,
+    "should throw with too many arguments"
+  );
+
+  root.testing.bar(true);
+  wrapper.verify("call", "testing", "bar", [null, true]);
+
+  root.testing.baz({ prop1: "hello", prop2: 22 });
+  wrapper.verify("call", "testing", "baz", [{ prop1: "hello", prop2: 22 }]);
+
+  root.testing.baz({ prop1: "hello" });
+  wrapper.verify("call", "testing", "baz", [{ prop1: "hello", prop2: null }]);
+
+  root.testing.baz({ prop1: "hello", prop2: null });
+  wrapper.verify("call", "testing", "baz", [{ prop1: "hello", prop2: null }]);
+
+  Assert.throws(
+    () => root.testing.baz({ prop2: 12 }),
+    /Property "prop1" is required/,
+    "should throw without required property"
+  );
+
+  Assert.throws(
+    () => root.testing.baz({ prop1: "hi", prop3: 12 }),
+    /Property "prop3" is unsupported by Firefox/,
+    "should throw with unsupported property"
+  );
+
+  Assert.throws(
+    () => root.testing.baz({ prop1: "hi", prop4: 12 }),
+    /Unexpected property "prop4"/,
+    "should throw with unexpected property"
+  );
+
+  Assert.throws(
+    () => root.testing.baz({ prop1: 12 }),
+    /Expected string instead of 12/,
+    "should throw with wrong type"
+  );
+
+  root.testing.qux("value2");
+  wrapper.verify("call", "testing", "qux", ["value2"]);
+
+  Assert.throws(
+    () => root.testing.qux("value4"),
+    /Invalid enumeration value "value4"/,
+    "should throw for invalid enum value"
+  );
+
+  root.testing.quack({ prop1: 12, prop2: ["value1", "value3"] });
+  wrapper.verify("call", "testing", "quack", [
+    { prop1: 12, prop2: ["value1", "value3"] },
+  ]);
+
+  Assert.throws(
+    () =>
+      root.testing.quack({ prop1: 12, prop2: ["value1", "value3", "value4"] }),
+    /Invalid enumeration value "value4"/,
+    "should throw for invalid array type"
+  );
+
+  function f() {}
+  root.testing.quora(f);
+  Assert.equal(
+    JSON.stringify(wrapper.tallied.slice(0, -1)),
+    JSON.stringify(["call", "testing", "quora"])
+  );
+  Assert.equal(wrapper.tallied[3][0], f);
+  wrapper.tallied = null;
+
+  let g = () => 0;
+  root.testing.quora(g);
+  Assert.equal(
+    JSON.stringify(wrapper.tallied.slice(0, -1)),
+    JSON.stringify(["call", "testing", "quora"])
+  );
+  Assert.equal(wrapper.tallied[3][0], g);
+  wrapper.tallied = null;
+
+  root.testing.quileute(10);
+  wrapper.verify("call", "testing", "quileute", [null, 10]);
+
+  Assert.throws(
+    () => root.testing.queets(),
+    /queets is not a function/,
+    "should throw for unsupported functions"
+  );
+
+  root.testing.quintuplets({ a: 10, b: 20, c: 30 });
+  wrapper.verify("call", "testing", "quintuplets", [{ a: 10, b: 20, c: 30 }]);
+
+  Assert.throws(
+    () => root.testing.quintuplets({ a: 10, b: 20, c: 30, d: "hi" }),
+    /Expected integer instead of "hi"/,
+    "should throw for wrong additionalProperties type"
+  );
+
+  root.testing.quasar({ func: f });
+  Assert.equal(
+    JSON.stringify(wrapper.tallied.slice(0, -1)),
+    JSON.stringify(["call", "testing", "quasar"])
+  );
+  Assert.equal(wrapper.tallied[3][0].func, f);
+
+  root.testing.quosimodo({ a: 10, b: 20, c: 30 });
+  wrapper.verify("call", "testing", "quosimodo", [{ a: 10, b: 20, c: 30 }]);
+
+  Assert.throws(
+    () => root.testing.quosimodo(10),
+    /Incorrect argument types/,
+    "should throw for wrong type"
+  );
+
+  root.testing.patternprop({
+    prop1: "12",
+    prop2: "42",
+    Prop3: "43",
+    foo1: "x",
+  });
+  wrapper.verify("call", "testing", "patternprop", [
+    { prop1: "12", prop2: "42", Prop3: "43", foo1: "x" },
+  ]);
+
+  root.testing.patternprop({ prop1: "12" });
+  wrapper.verify("call", "testing", "patternprop", [{ prop1: "12" }]);
+
+  Assert.throws(
+    () => root.testing.patternprop({ prop1: "12", foo1: null }),
+    /Expected string instead of null/,
+    "should throw for wrong property type"
+  );
+
+  Assert.throws(
+    () => root.testing.patternprop({ prop1: "xx", prop2: "yy" }),
+    /String "xx" must match \/\^\\d\+\$\//,
+    "should throw for wrong property type"
+  );
+
+  Assert.throws(
+    () => root.testing.patternprop({ prop1: "12", prop2: 42 }),
+    /Expected string instead of 42/,
+    "should throw for wrong property type"
+  );
+
+  Assert.throws(
+    () => root.testing.patternprop({ prop1: "12", prop2: null }),
+    /Expected string instead of null/,
+    "should throw for wrong property type"
+  );
+
+  Assert.throws(
+    () => root.testing.patternprop({ prop1: "12", propx: "42" }),
+    /Unexpected property "propx"/,
+    "should throw for unexpected property"
+  );
+
+  Assert.throws(
+    () => root.testing.patternprop({ prop1: "12", Foo1: "x" }),
+    /Unexpected property "Foo1"/,
+    "should throw for unexpected property"
+  );
+
+  root.testing.pattern("DEADbeef");
+  wrapper.verify("call", "testing", "pattern", ["DEADbeef"]);
+
+  Assert.throws(
+    () => root.testing.pattern("DEADcow"),
+    /String "DEADcow" must match \/\^\[0-9a-f\]\+\$\/i/,
+    "should throw for non-match"
+  );
+
+  root.testing.format({ hostname: "foo" });
+  wrapper.verify("call", "testing", "format", [
+    {
+      hostname: "foo",
+      imageDataOrStrictRelativeUrl: null,
+      origin: null,
+      relativeUrl: null,
+      strictRelativeUrl: null,
+      url: null,
+    },
+  ]);
+
+  for (let invalid of ["", " ", "http://foo", "foo/bar", "foo.com/", "foo?"]) {
+    Assert.throws(
+      () => root.testing.format({ hostname: invalid }),
+      /Invalid hostname/,
+      "should throw for invalid hostname"
+    );
+    Assert.throws(
+      () => root.testing.format({ canonicalDomain: invalid }),
+      /Invalid domain /,
+      `should throw for invalid canonicalDomain (${invalid})`
+    );
+  }
+
+  for (let invalid of [
+    "%61", // ASCII should not be URL-encoded.
+    "foo:12345", // It is a common mistake to use .host instead of .hostname.
+    "2", // Single digit is an IPv4 address, but should be written as 0.0.0.2.
+    "::1", // IPv6 addresses should have brackets.
+    "[::1A]", // not lowercase.
+    "[::ffff:127.0.0.1]", // not a canonical IPv6 representation.
+    "UPPERCASE", // not lowercase.
+    "straß.de", // not punycode.
+  ]) {
+    Assert.throws(
+      () => root.testing.format({ canonicalDomain: invalid }),
+      /Invalid domain /,
+      `should throw for invalid canonicalDomain (${invalid})`
+    );
+  }
+
+  for (let valid of ["0.0.0.2", "[::1]", "[::1a]", "lowercase", "."]) {
+    root.testing.format({ canonicalDomain: valid });
+    wrapper.verify("call", "testing", "format", [
+      {
+        canonicalDomain: valid,
+        hostname: null,
+        imageDataOrStrictRelativeUrl: null,
+        origin: null,
+        relativeUrl: null,
+        strictRelativeUrl: null,
+        url: null,
+      },
+    ]);
+  }
+
+  for (let valid of [
+    "https://example.com",
+    "http://example.com",
+    "https://foo.bar.栃木.jp",
+  ]) {
+    root.testing.format({ origin: valid });
+  }
+
+  for (let invalid of [
+    "https://example.com/testing",
+    "file:/foo/bar",
+    "file:///foo/bar",
+    "",
+    " ",
+    "https://foo.bar.栃木.jp/",
+    "https://user:pass@example.com",
+    "https://*.example.com",
+    "https://example.com#test",
+    "https://example.com?test",
+  ]) {
+    Assert.throws(
+      () => root.testing.format({ origin: invalid }),
+      /Invalid origin/,
+      "should throw for invalid origin"
+    );
+  }
+
+  root.testing.format({ url: "http://foo/bar", relativeUrl: "http://foo/bar" });
+  wrapper.verify("call", "testing", "format", [
+    {
+      hostname: null,
+      imageDataOrStrictRelativeUrl: null,
+      origin: null,
+      relativeUrl: "http://foo/bar",
+      strictRelativeUrl: null,
+      url: "http://foo/bar",
+    },
+  ]);
+
+  root.testing.format({
+    relativeUrl: "foo.html",
+    strictRelativeUrl: "foo.html",
+  });
+  wrapper.verify("call", "testing", "format", [
+    {
+      hostname: null,
+      imageDataOrStrictRelativeUrl: null,
+      origin: null,
+      relativeUrl: `${wrapper.url}foo.html`,
+      strictRelativeUrl: `${wrapper.url}foo.html`,
+      url: null,
+    },
+  ]);
+
+  root.testing.format({
+    imageDataOrStrictRelativeUrl: "data:image/png;base64,A",
+  });
+  wrapper.verify("call", "testing", "format", [
+    {
+      hostname: null,
+      imageDataOrStrictRelativeUrl: "data:image/png;base64,A",
+      origin: null,
+      relativeUrl: null,
+      strictRelativeUrl: null,
+      url: null,
+    },
+  ]);
+
+  root.testing.format({
+    imageDataOrStrictRelativeUrl: "data:image/jpeg;base64,A",
+  });
+  wrapper.verify("call", "testing", "format", [
+    {
+      hostname: null,
+      imageDataOrStrictRelativeUrl: "data:image/jpeg;base64,A",
+      origin: null,
+      relativeUrl: null,
+      strictRelativeUrl: null,
+      url: null,
+    },
+  ]);
+
+  root.testing.format({ imageDataOrStrictRelativeUrl: "foo.html" });
+  wrapper.verify("call", "testing", "format", [
+    {
+      hostname: null,
+      imageDataOrStrictRelativeUrl: `${wrapper.url}foo.html`,
+      origin: null,
+      relativeUrl: null,
+      strictRelativeUrl: null,
+      url: null,
+    },
+  ]);
+
+  for (let format of ["url", "relativeUrl"]) {
+    Assert.throws(
+      () => root.testing.format({ [format]: "chrome://foo/content/" }),
+      /Access denied/,
+      "should throw for access denied"
+    );
+  }
+
+  for (let urlString of ["//foo.html", "http://foo/bar.html"]) {
+    Assert.throws(
+      () => root.testing.format({ strictRelativeUrl: urlString }),
+      /must be a relative URL/,
+      "should throw for non-relative URL"
+    );
+  }
+
+  Assert.throws(
+    () =>
+      root.testing.format({
+        imageDataOrStrictRelativeUrl: "data:image/svg+xml;utf8,A",
+      }),
+    /must be a relative or PNG or JPG data:image URL/,
+    "should throw for non-relative or non PNG/JPG data URL"
+  );
+
+  const dates = [
+    "2016-03-04",
+    "2016-03-04T08:00:00Z",
+    "2016-03-04T08:00:00.000Z",
+    "2016-03-04T08:00:00-08:00",
+    "2016-03-04T08:00:00.000-08:00",
+    "2016-03-04T08:00:00+08:00",
+    "2016-03-04T08:00:00.000+08:00",
+    "2016-03-04T08:00:00+0800",
+    "2016-03-04T08:00:00-0800",
+  ];
+  dates.forEach(str => {
+    root.testing.formatDate({ date: str });
+    wrapper.verify("call", "testing", "formatDate", [{ date: str }]);
+  });
+
+  // Make sure that a trivial change to a valid date invalidates it.
+  dates.forEach(str => {
+    Assert.throws(
+      () => root.testing.formatDate({ date: "0" + str }),
+      /Invalid date string/,
+      "should throw for invalid iso date string"
+    );
+    Assert.throws(
+      () => root.testing.formatDate({ date: str + "0" }),
+      /Invalid date string/,
+      "should throw for invalid iso date string"
+    );
+  });
+
+  const badDates = [
+    "I do not look anything like a date string",
+    "2016-99-99",
+    "2016-03-04T25:00:00Z",
+  ];
+  badDates.forEach(str => {
+    Assert.throws(
+      () => root.testing.formatDate({ date: str }),
+      /Invalid date string/,
+      "should throw for invalid iso date string"
+    );
+  });
+
+  root.testing.deep({
+    foo: { bar: [{ baz: { required: 12, optional: "42" } }] },
+  });
+  wrapper.verify("call", "testing", "deep", [
+    { foo: { bar: [{ baz: { optional: "42", required: 12 } }] } },
+  ]);
+
+  Assert.throws(
+    () => root.testing.deep({ foo: { bar: [{ baz: { optional: "42" } }] } }),
+    /Type error for parameter arg \(Error processing foo\.bar\.0\.baz: Property "required" is required\) for testing\.deep/,
+    "should throw with the correct object path"
+  );
+
+  Assert.throws(
+    () =>
+      root.testing.deep({
+        foo: { bar: [{ baz: { optional: 42, required: 12 } }] },
+      }),
+    /Type error for parameter arg \(Error processing foo\.bar\.0\.baz\.optional: Expected string instead of 42\) for testing\.deep/,
+    "should throw with the correct object path"
+  );
+
+  wrapper.talliedErrors.length = 0;
+
+  root.testing.errors({ default: "0123", ignore: "0123", warn: "0123" });
+  wrapper.verify("call", "testing", "errors", [
+    { default: "0123", ignore: "0123", warn: "0123" },
+  ]);
+  wrapper.checkErrors([]);
+
+  root.testing.errors({ default: "0123", ignore: "x123", warn: "0123" });
+  wrapper.verify("call", "testing", "errors", [
+    { default: "0123", ignore: null, warn: "0123" },
+  ]);
+  wrapper.checkErrors([]);
+
+  ExtensionTestUtils.failOnSchemaWarnings(false);
+  root.testing.errors({ default: "0123", ignore: "0123", warn: "x123" });
+  ExtensionTestUtils.failOnSchemaWarnings(true);
+  wrapper.verify("call", "testing", "errors", [
+    { default: "0123", ignore: "0123", warn: null },
+  ]);
+  wrapper.checkErrors(['String "x123" must match /^\\d+$/']);
+
+  root.testing.onFoo.addListener(f);
+  Assert.equal(
+    JSON.stringify(wrapper.tallied.slice(0, -1)),
+    JSON.stringify(["addListener", "testing", "onFoo"])
+  );
+  Assert.equal(wrapper.tallied[3][0], f);
+  Assert.equal(JSON.stringify(wrapper.tallied[3][1]), JSON.stringify([]));
+  wrapper.tallied = null;
+
+  root.testing.onFoo.removeListener(f);
+  Assert.equal(
+    JSON.stringify(wrapper.tallied.slice(0, -1)),
+    JSON.stringify(["removeListener", "testing", "onFoo"])
+  );
+  Assert.equal(wrapper.tallied[3][0], f);
+  wrapper.tallied = null;
+
+  root.testing.onFoo.hasListener(f);
+  Assert.equal(
+    JSON.stringify(wrapper.tallied.slice(0, -1)),
+    JSON.stringify(["hasListener", "testing", "onFoo"])
+  );
+  Assert.equal(wrapper.tallied[3][0], f);
+  wrapper.tallied = null;
+
+  Assert.throws(
+    () => root.testing.onFoo.addListener(10),
+    /Invalid listener/,
+    "addListener with non-function should throw"
+  );
+
+  root.testing.onBar.addListener(f, 10);
+  Assert.equal(
+    JSON.stringify(wrapper.tallied.slice(0, -1)),
+    JSON.stringify(["addListener", "testing", "onBar"])
+  );
+  Assert.equal(wrapper.tallied[3][0], f);
+  Assert.equal(JSON.stringify(wrapper.tallied[3][1]), JSON.stringify([10]));
+  wrapper.tallied = null;
+
+  root.testing.onBar.addListener(f);
+  Assert.equal(
+    JSON.stringify(wrapper.tallied.slice(0, -1)),
+    JSON.stringify(["addListener", "testing", "onBar"])
+  );
+  Assert.equal(wrapper.tallied[3][0], f);
+  Assert.equal(JSON.stringify(wrapper.tallied[3][1]), JSON.stringify([1]));
+  wrapper.tallied = null;
+
+  Assert.throws(
+    () => root.testing.onBar.addListener(f, "hi"),
+    /Incorrect argument types/,
+    "addListener with wrong extra parameter should throw"
+  );
+
+  let target = { prop1: 12, prop2: ["value1", "value3"] };
+  let proxy = new Proxy(target, {});
+  Assert.throws(
+    () => root.testing.quack(proxy),
+    /Expected a plain JavaScript object, got a Proxy/,
+    "should throw when passing a Proxy"
+  );
+
+  if (Symbol.toStringTag) {
+    let stringTarget = { prop1: 12, prop2: ["value1", "value3"] };
+    stringTarget[Symbol.toStringTag] = () => "[object Object]";
+    let stringProxy = new Proxy(stringTarget, {});
+    Assert.throws(
+      () => root.testing.quack(stringProxy),
+      /Expected a plain JavaScript object, got a Proxy/,
+      "should throw when passing a Proxy"
+    );
+  }
+
+  root.testing.localize({
+    foo: "__MSG_foo__",
+    bar: "__MSG_foo__",
+    url: "__MSG_http://example.com/__",
+  });
+  wrapper.verify("call", "testing", "localize", [
+    { bar: "__MSG_foo__", foo: "FOO", url: "http://example.com/" },
+  ]);
+
+  Assert.throws(
+    () => root.testing.localize({ url: "__MSG_/foo/bar__" }),
+    /\/FOO\/BAR is not a valid URL\./,
+    "should throw for invalid URL"
+  );
+
+  root.testing.extended1({ prop1: "foo", prop2: "bar" });
+  wrapper.verify("call", "testing", "extended1", [
+    { prop1: "foo", prop2: "bar" },
+  ]);
+
+  Assert.throws(
+    () => root.testing.extended1({ prop1: "foo", prop2: 12 }),
+    /Expected string instead of 12/,
+    "should throw for wrong property type"
+  );
+
+  Assert.throws(
+    () => root.testing.extended1({ prop1: "foo" }),
+    /Property "prop2" is required/,
+    "should throw for missing property"
+  );
+
+  Assert.throws(
+    () => root.testing.extended1({ prop1: "foo", prop2: "bar", prop3: "xxx" }),
+    /Unexpected property "prop3"/,
+    "should throw for extra property"
+  );
+
+  root.testing.extended2("foo");
+  wrapper.verify("call", "testing", "extended2", ["foo"]);
+
+  root.testing.extended2(12);
+  wrapper.verify("call", "testing", "extended2", [12]);
+
+  Assert.throws(
+    () => root.testing.extended2(true),
+    /Incorrect argument types/,
+    "should throw for wrong argument type"
+  );
+
+  root.testing.prop3.sub_foo();
+  wrapper.verify("call", "testing.prop3", "sub_foo", []);
+
+  Assert.throws(
+    () => root.testing.prop4.sub_foo(),
+    /root.testing.prop4 is undefined/,
+    "should throw for unsupported submodule"
+  );
+
+  root.foreign.foreignRef.sub_foo();
+  wrapper.verify("call", "foreign.foreignRef", "sub_foo", []);
+
+  root.testing.callderived1({ baseprop: "s1", derivedprop: "s2" });
+  wrapper.verify("call", "testing", "callderived1", [
+    { baseprop: "s1", derivedprop: "s2" },
+  ]);
+
+  Assert.throws(
+    () => root.testing.callderived1({ baseprop: "s1", derivedprop: 42 }),
+    /Error processing derivedprop: Expected string/,
+    "Two different objects may $import the same base object"
+  );
+  Assert.throws(
+    () => root.testing.callderived1({ baseprop: "s1" }),
+    /Property "derivedprop" is required/,
+    "Object using $import has its local properites"
+  );
+  Assert.throws(
+    () => root.testing.callderived1({ derivedprop: "s2" }),
+    /Property "baseprop" is required/,
+    "Object using $import has imported properites"
+  );
+
+  root.testing.callderived2({ baseprop: "s1", derivedprop: 42 });
+  wrapper.verify("call", "testing", "callderived2", [
+    { baseprop: "s1", derivedprop: 42 },
+  ]);
+
+  Assert.throws(
+    () => root.testing.callderived2({ baseprop: "s1", derivedprop: "s2" }),
+    /Error processing derivedprop: Expected integer/,
+    "Two different objects may $import the same base object"
+  );
+  Assert.throws(
+    () => root.testing.callderived2({ baseprop: "s1" }),
+    /Property "derivedprop" is required/,
+    "Object using $import has its local properites"
+  );
+  Assert.throws(
+    () => root.testing.callderived2({ derivedprop: 42 }),
+    /Property "baseprop" is required/,
+    "Object using $import has imported properites"
+  );
+});
+
+let deprecatedJson = [
+  {
+    namespace: "deprecated",
+
+    properties: {
+      accessor: {
+        type: "string",
+        writable: true,
+        deprecated: "This is not the property you are looking for",
+      },
+    },
+
+    types: [
+      {
+        id: "Type",
+        type: "string",
+      },
+    ],
+
+    functions: [
+      {
+        name: "property",
+        type: "function",
+        parameters: [
+          {
+            name: "arg",
+            type: "object",
+            properties: {
+              foo: {
+                type: "string",
+              },
+            },
+            additionalProperties: {
+              type: "any",
+              deprecated: "Unknown property",
+            },
+          },
+        ],
+      },
+
+      {
+        name: "value",
+        type: "function",
+        parameters: [
+          {
+            name: "arg",
+            choices: [
+              {
+                type: "integer",
+              },
+              {
+                type: "string",
+                deprecated: "Please use an integer, not ${value}",
+              },
+            ],
+          },
+        ],
+      },
+
+      {
+        name: "choices",
+        type: "function",
+        parameters: [
+          {
+            name: "arg",
+            deprecated: "You have no choices",
+            choices: [
+              {
+                type: "integer",
+              },
+            ],
+          },
+        ],
+      },
+
+      {
+        name: "ref",
+        type: "function",
+        parameters: [
+          {
+            name: "arg",
+            choices: [
+              {
+                $ref: "Type",
+                deprecated: "Deprecated alias",
+              },
+            ],
+          },
+        ],
+      },
+
+      {
+        name: "method",
+        type: "function",
+        deprecated: "Do not call this method",
+        parameters: [],
+      },
+    ],
+
+    events: [
+      {
+        name: "onDeprecated",
+        type: "function",
+        deprecated: "This event does not work",
+      },
+    ],
+  },
+];
+
+add_task(async function testDeprecation() {
+  let wrapper = getContextWrapper();
+  // This whole test expects deprecation warnings.
+  ExtensionTestUtils.failOnSchemaWarnings(false);
+
+  let url = "data:," + JSON.stringify(deprecatedJson);
+  Schemas._rootSchema = null;
+  await Schemas.load(url);
+
+  let root = {};
+  Schemas.inject(root, wrapper);
+
+  root.deprecated.property({ foo: "bar", xxx: "any", yyy: "property" });
+  wrapper.verify("call", "deprecated", "property", [
+    { foo: "bar", xxx: "any", yyy: "property" },
+  ]);
+  wrapper.checkErrors([
+    "Warning processing xxx: Unknown property",
+    "Warning processing yyy: Unknown property",
+  ]);
+
+  root.deprecated.value(12);
+  wrapper.verify("call", "deprecated", "value", [12]);
+  wrapper.checkErrors([]);
+
+  root.deprecated.value("12");
+  wrapper.verify("call", "deprecated", "value", ["12"]);
+  wrapper.checkErrors(['Please use an integer, not "12"']);
+
+  root.deprecated.choices(12);
+  wrapper.verify("call", "deprecated", "choices", [12]);
+  wrapper.checkErrors(["You have no choices"]);
+
+  root.deprecated.ref("12");
+  wrapper.verify("call", "deprecated", "ref", ["12"]);
+  wrapper.checkErrors(["Deprecated alias"]);
+
+  root.deprecated.method();
+  wrapper.verify("call", "deprecated", "method", []);
+  wrapper.checkErrors(["Do not call this method"]);
+
+  void root.deprecated.accessor;
+  wrapper.verify("get", "deprecated", "accessor", null);
+  wrapper.checkErrors(["This is not the property you are looking for"]);
+
+  root.deprecated.accessor = "x";
+  wrapper.verify("set", "deprecated", "accessor", "x");
+  wrapper.checkErrors(["This is not the property you are looking for"]);
+
+  root.deprecated.onDeprecated.addListener(() => {});
+  wrapper.checkErrors(["This event does not work"]);
+
+  root.deprecated.onDeprecated.removeListener(() => {});
+  wrapper.checkErrors(["This event does not work"]);
+
+  root.deprecated.onDeprecated.hasListener(() => {});
+  wrapper.checkErrors(["This event does not work"]);
+
+  ExtensionTestUtils.failOnSchemaWarnings(true);
+
+  Assert.throws(
+    () => root.deprecated.onDeprecated.hasListener(() => {}),
+    /This event does not work/,
+    "Deprecation warning with extensions.webextensions.warnings-as-errors=true"
+  );
+});
+
+let choicesJson = [
+  {
+    namespace: "choices",
+
+    types: [],
+
+    functions: [
+      {
+        name: "meh",
+        type: "function",
+        parameters: [
+          {
+            name: "arg",
+            choices: [
+              {
+                type: "string",
+                enum: ["foo", "bar", "baz"],
+              },
+              {
+                type: "string",
+                pattern: "florg.*meh",
+              },
+              {
+                type: "integer",
+                minimum: 12,
+                maximum: 42,
+              },
+            ],
+          },
+        ],
+      },
+
+      {
+        name: "foo",
+        type: "function",
+        parameters: [
+          {
+            name: "arg",
+            choices: [
+              {
+                type: "object",
+                properties: {
+                  blurg: {
+                    type: "string",
+                    unsupported: true,
+                    optional: true,
+                  },
+                },
+                additionalProperties: {
+                  type: "string",
+                },
+              },
+              {
+                type: "string",
+              },
+              {
+                type: "array",
+                minItems: 2,
+                maxItems: 3,
+                items: {
+                  type: "integer",
+                },
+              },
+            ],
+          },
+        ],
+      },
+
+      {
+        name: "bar",
+        type: "function",
+        parameters: [
+          {
+            name: "arg",
+            choices: [
+              {
+                type: "object",
+                properties: {
+                  baz: {
+                    type: "string",
+                  },
+                },
+              },
+              {
+                type: "array",
+                items: {
+                  type: "integer",
+                },
+              },
+            ],
+          },
+        ],
+      },
+    ],
+  },
+];
+
+add_task(async function testChoices() {
+  let wrapper = getContextWrapper();
+  let url = "data:," + JSON.stringify(choicesJson);
+  Schemas._rootSchema = null;
+  await Schemas.load(url);
+
+  let root = {};
+  Schemas.inject(root, wrapper);
+
+  Assert.throws(
+    () => root.choices.meh("frog"),
+    /Value "frog" must either: be one of \["foo", "bar", "baz"\], match the pattern \/florg\.\*meh\/, or be an integer value/
+  );
+
+  Assert.throws(
+    () => root.choices.meh(4),
+    /be a string value, or be at least 12/
+  );
+
+  Assert.throws(
+    () => root.choices.meh(43),
+    /be a string value, or be no greater than 42/
+  );
+
+  Assert.throws(
+    () => root.choices.foo([]),
+    /be an object value, be a string value, or have at least 2 items/
+  );
+
+  Assert.throws(
+    () => root.choices.foo([1, 2, 3, 4]),
+    /be an object value, be a string value, or have at most 3 items/
+  );
+
+  Assert.throws(
+    () => root.choices.foo({ foo: 12 }),
+    /.foo must be a string value, be a string value, or be an array value/
+  );
+
+  Assert.throws(
+    () => root.choices.foo({ blurg: "foo" }),
+    /not contain an unsupported "blurg" property, be a string value, or be an array value/
+  );
+
+  Assert.throws(
+    () => root.choices.bar({}),
+    /contain the required "baz" property, or be an array value/
+  );
+
+  Assert.throws(
+    () => root.choices.bar({ baz: "x", quux: "y" }),
+    /not contain an unexpected "quux" property, or be an array value/
+  );
+
+  Assert.throws(
+    () => root.choices.bar({ baz: "x", quux: "y", foo: "z" }),
+    /not contain the unexpected properties \[foo, quux\], or be an array value/
+  );
+});
+
+let permissionsJson = [
+  {
+    namespace: "noPerms",
+
+    types: [],
+
+    functions: [
+      {
+        name: "noPerms",
+        type: "function",
+        parameters: [],
+      },
+
+      {
+        name: "fooPerm",
+        type: "function",
+        permissions: ["foo"],
+        parameters: [],
+      },
+    ],
+  },
+
+  {
+    namespace: "fooPerm",
+
+    permissions: ["foo"],
+
+    types: [],
+
+    functions: [
+      {
+        name: "noPerms",
+        type: "function",
+        parameters: [],
+      },
+
+      {
+        name: "fooBarPerm",
+        type: "function",
+        permissions: ["foo.bar"],
+        parameters: [],
+      },
+    ],
+  },
+];
+
+add_task(async function testPermissions() {
+  let url = "data:," + JSON.stringify(permissionsJson);
+  Schemas._rootSchema = null;
+  await Schemas.load(url);
+
+  let wrapper = getContextWrapper();
+
+  let root = {};
+  Schemas.inject(root, wrapper);
+
+  equal(typeof root.noPerms, "object", "noPerms namespace should exist");
+  equal(
+    typeof root.noPerms.noPerms,
+    "function",
+    "noPerms.noPerms method should exist"
+  );
+
+  equal(
+    root.noPerms.fooPerm,
+    undefined,
+    "noPerms.fooPerm should not method exist"
+  );
+
+  equal(root.fooPerm, undefined, "fooPerm namespace should not exist");
+
+  info('Add "foo" permission');
+  wrapper.permissions.add("foo");
+
+  root = {};
+  Schemas.inject(root, wrapper);
+
+  equal(typeof root.noPerms, "object", "noPerms namespace should exist");
+  equal(
+    typeof root.noPerms.noPerms,
+    "function",
+    "noPerms.noPerms method should exist"
+  );
+  equal(
+    typeof root.noPerms.fooPerm,
+    "function",
+    "noPerms.fooPerm method should exist"
+  );
+
+  equal(typeof root.fooPerm, "object", "fooPerm namespace should exist");
+  equal(
+    typeof root.fooPerm.noPerms,
+    "function",
+    "noPerms.noPerms method should exist"
+  );
+
+  equal(
+    root.fooPerm.fooBarPerm,
+    undefined,
+    "fooPerm.fooBarPerm method should not exist"
+  );
+
+  info('Add "foo.bar" permission');
+  wrapper.permissions.add("foo.bar");
+
+  root = {};
+  Schemas.inject(root, wrapper);
+
+  equal(typeof root.noPerms, "object", "noPerms namespace should exist");
+  equal(
+    typeof root.noPerms.noPerms,
+    "function",
+    "noPerms.noPerms method should exist"
+  );
+  equal(
+    typeof root.noPerms.fooPerm,
+    "function",
+    "noPerms.fooPerm method should exist"
+  );
+
+  equal(typeof root.fooPerm, "object", "fooPerm namespace should exist");
+  equal(
+    typeof root.fooPerm.noPerms,
+    "function",
+    "noPerms.noPerms method should exist"
+  );
+  equal(
+    typeof root.fooPerm.fooBarPerm,
+    "function",
+    "noPerms.fooBarPerm method should exist"
+  );
+});
+
+let nestedNamespaceJson = [
+  {
+    namespace: "nested.namespace",
+    types: [
+      {
+        id: "CustomType",
+        type: "object",
+        events: [
+          {
+            name: "onEvent",
+            type: "function",
+          },
+        ],
+        properties: {
+          url: {
+            type: "string",
+          },
+        },
+        functions: [
+          {
+            name: "functionOnCustomType",
+            type: "function",
+            parameters: [
+              {
+                name: "title",
+                type: "string",
+              },
+            ],
+          },
+        ],
+      },
+    ],
+    properties: {
+      instanceOfCustomType: {
+        $ref: "CustomType",
+      },
+    },
+    functions: [
+      {
+        name: "create",
+        type: "function",
+        parameters: [
+          {
+            name: "title",
+            type: "string",
+          },
+        ],
+      },
+    ],
+  },
+];
+
+add_task(async function testNestedNamespace() {
+  let url = "data:," + JSON.stringify(nestedNamespaceJson);
+  let wrapper = getContextWrapper();
+
+  Schemas._rootSchema = null;
+  await Schemas.load(url);
+
+  let root = {};
+  Schemas.inject(root, wrapper);
+
+  ok(root.nested, "The root object contains the first namespace level");
+  ok(
+    root.nested.namespace,
+    "The first level object contains the second namespace level"
+  );
+
+  ok(
+    root.nested.namespace.create,
+    "Got the expected function in the nested namespace"
+  );
+  equal(
+    typeof root.nested.namespace.create,
+    "function",
+    "The property is a function as expected"
+  );
+
+  let { instanceOfCustomType } = root.nested.namespace;
+
+  ok(
+    instanceOfCustomType,
+    "Got the expected instance of the CustomType defined in the schema"
+  );
+  ok(
+    instanceOfCustomType.functionOnCustomType,
+    "Got the expected method in the CustomType instance"
+  );
+  ok(
+    instanceOfCustomType.onEvent &&
+      instanceOfCustomType.onEvent.addListener &&
+      typeof instanceOfCustomType.onEvent.addListener == "function",
+    "Got the expected event defined in the CustomType instance"
+  );
+
+  instanceOfCustomType.functionOnCustomType("param_value");
+  wrapper.verify(
+    "call",
+    "nested.namespace.instanceOfCustomType",
+    "functionOnCustomType",
+    ["param_value"]
+  );
+
+  let fakeListener = () => {};
+  instanceOfCustomType.onEvent.addListener(fakeListener);
+  wrapper.verify(
+    "addListener",
+    "nested.namespace.instanceOfCustomType",
+    "onEvent",
+    [fakeListener, []]
+  );
+  instanceOfCustomType.onEvent.removeListener(fakeListener);
+  wrapper.verify(
+    "removeListener",
+    "nested.namespace.instanceOfCustomType",
+    "onEvent",
+    [fakeListener]
+  );
+
+  // TODO: test support properties in a SubModuleType defined in the schema,
+  // once implemented, e.g.:
+  // ok("url" in instanceOfCustomType,
+  //   "Got the expected property defined in the CustomType instance");
+});
+
+let $importJson = [
+  {
+    namespace: "from_the",
+    $import: "future",
+  },
+  {
+    namespace: "future",
+    properties: {
+      PROP1: { value: "original value" },
+      PROP2: { value: "second original" },
+    },
+    types: [
+      {
+        id: "Colour",
+        type: "string",
+        enum: ["red", "white", "blue"],
+      },
+    ],
+    functions: [
+      {
+        name: "dye",
+        type: "function",
+        parameters: [{ name: "arg", $ref: "Colour" }],
+      },
+    ],
+  },
+  {
+    namespace: "embrace",
+    $import: "future",
+    properties: {
+      PROP2: { value: "overridden value" },
+    },
+    types: [
+      {
+        id: "Colour",
+        type: "string",
+        enum: ["blue", "orange"],
+      },
+    ],
+  },
+];
+
+add_task(async function test_$import() {
+  let wrapper = getContextWrapper();
+  let url = "data:," + JSON.stringify($importJson);
+  Schemas._rootSchema = null;
+  await Schemas.load(url);
+
+  let root = {};
+  Schemas.inject(root, wrapper);
+
+  equal(root.from_the.PROP1, "original value", "imported property");
+  equal(root.from_the.PROP2, "second original", "second imported property");
+  equal(root.from_the.Colour.RED, "red", "imported enum type");
+  equal(typeof root.from_the.dye, "function", "imported function");
+
+  root.from_the.dye("white");
+  wrapper.verify("call", "from_the", "dye", ["white"]);
+
+  Assert.throws(
+    () => root.from_the.dye("orange"),
+    /Invalid enumeration value/,
+    "original imported argument type Colour doesn't include 'orange'"
+  );
+
+  equal(root.embrace.PROP1, "original value", "imported property");
+  equal(root.embrace.PROP2, "overridden value", "overridden property");
+  equal(root.embrace.Colour.ORANGE, "orange", "overridden enum type");
+  equal(typeof root.embrace.dye, "function", "imported function");
+
+  root.embrace.dye("orange");
+  wrapper.verify("call", "embrace", "dye", ["orange"]);
+
+  Assert.throws(
+    () => root.embrace.dye("white"),
+    /Invalid enumeration value/,
+    "overridden argument type Colour doesn't include 'white'"
+  );
+});
+
+add_task(async function testLocalAPIImplementation() {
+  let countGet2 = 0;
+  let countProp3 = 0;
+  let countProp3SubFoo = 0;
+
+  let testingApiObj = {
+    get PROP1() {
+      // PROP1 is a schema-defined constant.
+      throw new Error("Unexpected get PROP1");
+    },
+    get prop2() {
+      ++countGet2;
+      return "prop2 val";
+    },
+    get prop3() {
+      throw new Error("Unexpected get prop3");
+    },
+    set prop3(v) {
+      // prop3 is a submodule, defined as a function, so the API should not pass
+      // through assignment to prop3.
+      throw new Error("Unexpected set prop3");
+    },
+  };
+  let submoduleApiObj = {
+    get sub_foo() {
+      ++countProp3;
+      return () => {
+        return ++countProp3SubFoo;
+      };
+    },
+  };
+
+  let localWrapper = {
+    manifestVersion: 2,
+    cloneScope: global,
+    shouldInject(ns, name) {
+      return name == "testing" || ns == "testing" || ns == "testing.prop3";
+    },
+    getImplementation(ns, name) {
+      Assert.ok(ns == "testing" || ns == "testing.prop3");
+      if (ns == "testing.prop3" && name == "sub_foo") {
+        // It is fine to use `null` here because we don't call async functions.
+        return new LocalAPIImplementation(submoduleApiObj, name, null);
+      }
+      // It is fine to use `null` here because we don't call async functions.
+      return new LocalAPIImplementation(testingApiObj, name, null);
+    },
+  };
+
+  let root = {};
+  Schemas.inject(root, localWrapper);
+  Assert.equal(countGet2, 0);
+  Assert.equal(countProp3, 0);
+  Assert.equal(countProp3SubFoo, 0);
+
+  Assert.equal(root.testing.PROP1, 20);
+
+  Assert.equal(root.testing.prop2, "prop2 val");
+  Assert.equal(countGet2, 1);
+
+  Assert.equal(root.testing.prop2, "prop2 val");
+  Assert.equal(countGet2, 2);
+
+  info(JSON.stringify(root.testing));
+  Assert.equal(root.testing.prop3.sub_foo(), 1);
+  Assert.equal(countProp3, 1);
+  Assert.equal(countProp3SubFoo, 1);
+
+  Assert.equal(root.testing.prop3.sub_foo(), 2);
+  Assert.equal(countProp3, 2);
+  Assert.equal(countProp3SubFoo, 2);
+
+  root.testing.prop3.sub_foo = () => {
+    return "overwritten";
+  };
+  Assert.equal(root.testing.prop3.sub_foo(), "overwritten");
+
+  root.testing.prop3 = {
+    sub_foo() {
+      return "overwritten again";
+    },
+  };
+  Assert.equal(root.testing.prop3.sub_foo(), "overwritten again");
+  Assert.equal(countProp3SubFoo, 2);
+});
+
+let defaultsJson = [
+  {
+    namespace: "defaultsJson",
+
+    types: [],
+
+    functions: [
+      {
+        name: "defaultFoo",
+        type: "function",
+        parameters: [
+          {
+            name: "arg",
+            type: "object",
+            optional: true,
+            properties: {
+              prop1: { type: "integer", optional: true },
+            },
+            default: { prop1: 1 },
+          },
+        ],
+        returns: {
+          type: "object",
+          additionalProperties: true,
+        },
+      },
+    ],
+  },
+];
+
+add_task(async function testDefaults() {
+  let url = "data:," + JSON.stringify(defaultsJson);
+  Schemas._rootSchema = null;
+  await Schemas.load(url);
+
+  let testingApiObj = {
+    defaultFoo: function (arg) {
+      if (Object.keys(arg) != "prop1") {
+        throw new Error(
+          `Received the expected default object, default: ${JSON.stringify(
+            arg
+          )}`
+        );
+      }
+      arg.newProp = 1;
+      return arg;
+    },
+  };
+
+  let localWrapper = {
+    manifestVersion: 2,
+    cloneScope: global,
+    shouldInject(ns) {
+      return true;
+    },
+    getImplementation(ns, name) {
+      return new LocalAPIImplementation(testingApiObj, name, null);
+    },
+  };
+
+  let root = {};
+  Schemas.inject(root, localWrapper);
+
+  deepEqual(root.defaultsJson.defaultFoo(), { prop1: 1, newProp: 1 });
+  deepEqual(root.defaultsJson.defaultFoo({ prop1: 2 }), {
+    prop1: 2,
+    newProp: 1,
+  });
+  deepEqual(root.defaultsJson.defaultFoo(), { prop1: 1, newProp: 1 });
+});
+
+let returnsJson = [
+  {
+    namespace: "returns",
+    types: [
+      {
+        id: "Widget",
+        type: "object",
+        properties: {
+          size: { type: "integer" },
+          colour: { type: "string", optional: true },
+        },
+      },
+    ],
+    functions: [
+      {
+        name: "complete",
+        type: "function",
+        returns: { $ref: "Widget" },
+        parameters: [],
+      },
+      {
+        name: "optional",
+        type: "function",
+        returns: { $ref: "Widget" },
+        parameters: [],
+      },
+      {
+        name: "invalid",
+        type: "function",
+        returns: { $ref: "Widget" },
+        parameters: [],
+      },
+    ],
+  },
+];
+
+add_task(async function testReturns() {
+  const url = "data:," + JSON.stringify(returnsJson);
+  Schemas._rootSchema = null;
+  await Schemas.load(url);
+
+  const apiObject = {
+    complete() {
+      return { size: 3, colour: "orange" };
+    },
+    optional() {
+      return { size: 4 };
+    },
+    invalid() {
+      return {};
+    },
+  };
+
+  const localWrapper = {
+    manifestVersion: 2,
+    cloneScope: global,
+    shouldInject(ns) {
+      return true;
+    },
+    getImplementation(ns, name) {
+      return new LocalAPIImplementation(apiObject, name, null);
+    },
+  };
+
+  const root = {};
+  Schemas.inject(root, localWrapper);
+
+  deepEqual(root.returns.complete(), { size: 3, colour: "orange" });
+  deepEqual(
+    root.returns.optional(),
+    { size: 4 },
+    "Missing optional properties is allowed"
+  );
+
+  if (AppConstants.DEBUG) {
+    Assert.throws(
+      () => root.returns.invalid(),
+      /Type error for result value \(Property "size" is required\)/,
+      "Should throw for invalid result in DEBUG builds"
+    );
+  } else {
+    deepEqual(
+      root.returns.invalid(),
+      {},
+      "Doesn't throw for invalid result value in release builds"
+    );
+  }
+});
+
+let booleanEnumJson = [
+  {
+    namespace: "booleanEnum",
+
+    types: [
+      {
+        id: "enumTrue",
+        type: "boolean",
+        enum: [true],
+      },
+    ],
+    functions: [
+      {
+        name: "paramMustBeTrue",
+        type: "function",
+        parameters: [{ name: "arg", $ref: "enumTrue" }],
+      },
+    ],
+  },
+];
+
+add_task(async function testBooleanEnum() {
+  let wrapper = getContextWrapper();
+
+  let url = "data:," + JSON.stringify(booleanEnumJson);
+  Schemas._rootSchema = null;
+  await Schemas.load(url);
+
+  let root = {};
+  Schemas.inject(root, wrapper);
+
+  ok(root.booleanEnum, "namespace exists");
+  root.booleanEnum.paramMustBeTrue(true);
+  wrapper.verify("call", "booleanEnum", "paramMustBeTrue", [true]);
+  Assert.throws(
+    () => root.booleanEnum.paramMustBeTrue(false),
+    /Type error for parameter arg \(Invalid value false\) for booleanEnum\.paramMustBeTrue\./,
+    "should throw because enum of the type restricts parameter to true"
+  );
+});
+
+let xoriginJson = [
+  {
+    namespace: "xorigin",
+    types: [],
+    functions: [
+      {
+        name: "foo",
+        type: "function",
+        parameters: [
+          {
+            name: "arg",
+            type: "any",
+          },
+        ],
+      },
+      {
+        name: "crossFoo",
+        type: "function",
+        allowCrossOriginArguments: true,
+        parameters: [
+          {
+            name: "arg",
+            type: "any",
+          },
+        ],
+      },
+    ],
+  },
+];
+
+add_task(async function testCrossOriginArguments() {
+  let url = "data:," + JSON.stringify(xoriginJson);
+  Schemas._rootSchema = null;
+  await Schemas.load(url);
+
+  let sandbox = new Cu.Sandbox("http://test.com");
+
+  let testingApiObj = {
+    foo(arg) {
+      sandbox.result = JSON.stringify(arg);
+    },
+    crossFoo(arg) {
+      sandbox.xResult = JSON.stringify(arg);
+    },
+  };
+
+  let localWrapper = {
+    manifestVersion: 2,
+    cloneScope: sandbox,
+    shouldInject(ns) {
+      return true;
+    },
+    getImplementation(ns, name) {
+      return new LocalAPIImplementation(testingApiObj, name, null);
+    },
+  };
+
+  let root = {};
+  Schemas.inject(root, localWrapper);
+
+  Assert.throws(
+    () => root.xorigin.foo({ key: 13 }),
+    /Permission denied to pass object/
+  );
+  equal(sandbox.result, undefined, "Foo can't read cross origin object.");
+
+  root.xorigin.crossFoo({ answer: 42 });
+  equal(sandbox.xResult, '{"answer":42}', "Can read cross origin object.");
+});
diff --git a/toolkit/components/extensions/test/xpcshell/test_ext_schemas_allowed_contexts.js b/toolkit/components/extensions/test/xpcshell/test_ext_schemas_allowed_contexts.js
new file mode 100644
index 0000000000..16743049d0
--- /dev/null
+++ b/toolkit/components/extensions/test/xpcshell/test_ext_schemas_allowed_contexts.js
@@ -0,0 +1,160 @@
+"use strict";
+
+const { Schemas } = ChromeUtils.importESModule(
+  "resource://gre/modules/Schemas.sys.mjs"
+);
+
+const global = this;
+
+let schemaJson = [
+  {
+    namespace: "noAllowedContexts",
+    properties: {
+      prop1: { type: "object" },
+      prop2: { type: "object", allowedContexts: ["test_zero", "test_one"] },
+      prop3: { type: "number", value: 1 },
+      prop4: { type: "number", value: 1, allowedContexts: ["numeric_one"] },
+    },
+  },
+  {
+    namespace: "defaultContexts",
+    defaultContexts: ["test_two"],
+    properties: {
+      prop1: { type: "object" },
+      prop2: { type: "object", allowedContexts: ["test_three"] },
+      prop3: { type: "number", value: 1 },
+      prop4: { type: "number", value: 1, allowedContexts: ["numeric_two"] },
+    },
+  },
+  {
+    namespace: "withAllowedContexts",
+    allowedContexts: ["test_four"],
+    properties: {
+      prop1: { type: "object" },
+      prop2: { type: "object", allowedContexts: ["test_five"] },
+      prop3: { type: "number", value: 1 },
+      prop4: { type: "number", value: 1, allowedContexts: ["numeric_three"] },
+    },
+  },
+  {
+    namespace: "withAllowedContextsAndDefault",
+    allowedContexts: ["test_six"],
+    defaultContexts: ["test_seven"],
+    properties: {
+      prop1: { type: "object" },
+      prop2: { type: "object", allowedContexts: ["test_eight"] },
+      prop3: { type: "number", value: 1 },
+      prop4: { type: "number", value: 1, allowedContexts: ["numeric_four"] },
+    },
+  },
+  {
+    namespace: "with_submodule",
+    defaultContexts: ["test_nine"],
+    types: [
+      {
+        id: "subtype",
+        type: "object",
+        functions: [
+          {
+            name: "noAllowedContexts",
+            type: "function",
+            parameters: [],
+          },
+          {
+            name: "allowedContexts",
+            allowedContexts: ["test_ten"],
+            type: "function",
+            parameters: [],
+          },
+        ],
+      },
+    ],
+    properties: {
+      prop1: { $ref: "subtype" },
+      prop2: { $ref: "subtype", allowedContexts: ["test_eleven"] },
+    },
+  },
+];
+
+add_task(async function testRestrictions() {
+  let url = "data:," + JSON.stringify(schemaJson);
+  await Schemas.load(url);
+  let results = {};
+  let localWrapper = {
+    manifestVersion: 2,
+    cloneScope: global,
+    shouldInject(ns, name, allowedContexts) {
+      name = ns ? ns + "." + name : name;
+      results[name] = allowedContexts.join(",");
+      return true;
+    },
+    getImplementation() {
+      // The actual implementation is not significant for this test.
+      // Let's take this opportunity to see if schema generation is free of
+      // exceptions even when somehow getImplementation does not return an
+      // implementation.
+    },
+  };
+
+  let root = {};
+  Schemas.inject(root, localWrapper);
+
+  function verify(path, expected) {
+    let obj = root;
+    for (let thing of path.split(".")) {
+      try {
+        obj = obj[thing];
+      } catch (e) {
+        // Blech.
+      }
+    }
+
+    let result = results[path];
+    equal(result, expected, path);
+  }
+
+  verify("noAllowedContexts", "");
+  verify("noAllowedContexts.prop1", "");
+  verify("noAllowedContexts.prop2", "test_zero,test_one");
+  verify("noAllowedContexts.prop3", "");
+  verify("noAllowedContexts.prop4", "numeric_one");
+
+  verify("defaultContexts", "");
+  verify("defaultContexts.prop1", "test_two");
+  verify("defaultContexts.prop2", "test_three");
+  verify("defaultContexts.prop3", "test_two");
+  verify("defaultContexts.prop4", "numeric_two");
+
+  verify("withAllowedContexts", "test_four");
+  verify("withAllowedContexts.prop1", "");
+  verify("withAllowedContexts.prop2", "test_five");
+  verify("withAllowedContexts.prop3", "");
+  verify("withAllowedContexts.prop4", "numeric_three");
+
+  verify("withAllowedContextsAndDefault", "test_six");
+  verify("withAllowedContextsAndDefault.prop1", "test_seven");
+  verify("withAllowedContextsAndDefault.prop2", "test_eight");
+  verify("withAllowedContextsAndDefault.prop3", "test_seven");
+  verify("withAllowedContextsAndDefault.prop4", "numeric_four");
+
+  verify("with_submodule", "");
+  verify("with_submodule.prop1", "test_nine");
+  verify("with_submodule.prop1.noAllowedContexts", "test_nine");
+  verify("with_submodule.prop1.allowedContexts", "test_ten");
+  verify("with_submodule.prop2", "test_eleven");
+  // Note: test_nine inherits allowed contexts from the namespace, not from
+  // submodule. There is no "defaultContexts" for submodule types to not
+  // complicate things.
+  verify("with_submodule.prop1.noAllowedContexts", "test_nine");
+  verify("with_submodule.prop1.allowedContexts", "test_ten");
+
+  // This is a constant, so it does not matter that getImplementation does not
+  // return an implementation since the API injector should take care of it.
+  equal(root.noAllowedContexts.prop3, 1);
+
+  Assert.throws(
+    () => root.noAllowedContexts.prop1,
+    /undefined/,
+    "Should throw when the implementation is absent."
+  );
+});
diff --git a/toolkit/components/extensions/test/xpcshell/test_ext_schemas_async.js b/toolkit/components/extensions/test/xpcshell/test_ext_schemas_async.js
new file mode 100644
index 0000000000..2613593771
--- /dev/null
+++ b/toolkit/components/extensions/test/xpcshell/test_ext_schemas_async.js
@@ -0,0 +1,352 @@
+"use strict";
+
+const { Schemas } = ChromeUtils.importESModule(
+  "resource://gre/modules/Schemas.sys.mjs"
+);
+
+let { BaseContext, LocalAPIImplementation } = ExtensionCommon;
+
+let schemaJson = [
+  {
+    namespace: "testnamespace",
+    types: [
+      {
+        id: "Widget",
+        type: "object",
+        properties: {
+          size: { type: "integer" },
+          colour: { type: "string", optional: true },
+        },
+      },
+    ],
+    functions: [
+      {
+        name: "one_required",
+        type: "function",
+        parameters: [
+          {
+            name: "first",
+            type: "function",
+            parameters: [],
+          },
+        ],
+      },
+      {
+        name: "one_optional",
+        type: "function",
+        parameters: [
+          {
+            name: "first",
+            type: "function",
+            parameters: [],
+            optional: true,
+          },
+        ],
+      },
+      {
+        name: "async_required",
+        type: "function",
+        async: "first",
+        parameters: [
+          {
+            name: "first",
+            type: "function",
+            parameters: [],
+          },
+        ],
+      },
+      {
+        name: "async_optional",
+        type: "function",
+        async: "first",
+        parameters: [
+          {
+            name: "first",
+            type: "function",
+            parameters: [],
+            optional: true,
+          },
+        ],
+      },
+      {
+        name: "async_result",
+        type: "function",
+        async: "callback",
+        parameters: [
+          {
+            name: "callback",
+            type: "function",
+            parameters: [
+              {
+                name: "widget",
+                $ref: "Widget",
+              },
+            ],
+          },
+        ],
+      },
+    ],
+  },
+];
+
+const global = this;
+class StubContext extends BaseContext {
+  constructor() {
+    let fakeExtension = { id: "test@web.extension" };
+    super("testEnv", fakeExtension);
+    this.sandbox = Cu.Sandbox(global);
+  }
+
+  get cloneScope() {
+    return this.sandbox;
+  }
+
+  get principal() {
+    return Cu.getObjectPrincipal(this.sandbox);
+  }
+}
+
+let context;
+
+function generateAPIs(extraWrapper, apiObj) {
+  context = new StubContext();
+  let localWrapper = {
+    manifestVersion: 2,
+    cloneScope: global,
+    shouldInject() {
+      return true;
+    },
+    getImplementation(namespace, name) {
+      return new LocalAPIImplementation(apiObj, name, context);
+    },
+  };
+  Object.assign(localWrapper, extraWrapper);
+
+  let root = {};
+  Schemas.inject(root, localWrapper);
+  return root.testnamespace;
+}
+
+add_task(async function testParameterValidation() {
+  await Schemas.load("data:," + JSON.stringify(schemaJson));
+
+  let testnamespace;
+  function assertThrows(name, ...args) {
+    Assert.throws(
+      () => testnamespace[name](...args),
+      /Incorrect argument types/,
+      `Expected testnamespace.${name}(${args.map(String).join(", ")}) to throw.`
+    );
+  }
+  function assertNoThrows(name, ...args) {
+    try {
+      testnamespace[name](...args);
+    } catch (e) {
+      info(
+        `testnamespace.${name}(${args
+          .map(String)
+          .join(", ")}) unexpectedly threw.`
+      );
+      throw new Error(e);
+    }
+  }
+  let cb = () => {};
+
+  for (let isChromeCompat of [true, false]) {
+    info(`Testing API validation with isChromeCompat=${isChromeCompat}`);
+    testnamespace = generateAPIs(
+      {
+        isChromeCompat,
+      },
+      {
+        one_required() {},
+        one_optional() {},
+        async_required() {},
+        async_optional() {},
+      }
+    );
+
+    assertThrows("one_required");
+    assertThrows("one_required", null);
+    assertNoThrows("one_required", cb);
+    assertThrows("one_required", cb, null);
+    assertThrows("one_required", cb, cb);
+
+    assertNoThrows("one_optional");
+    assertNoThrows("one_optional", null);
+    assertNoThrows("one_optional", cb);
+    assertThrows("one_optional", cb, null);
+    assertThrows("one_optional", cb, cb);
+
+    // Schema-based validation happens before an async method is called, so
+    // errors should be thrown synchronously.
+
+    // The parameter was declared as required, but there was also an "async"
+    // attribute with the same value as the parameter name, so the callback
+    // parameter is actually optional.
+    assertNoThrows("async_required");
+    assertNoThrows("async_required", null);
+    assertNoThrows("async_required", cb);
+    assertThrows("async_required", cb, null);
+    assertThrows("async_required", cb, cb);
+
+    assertNoThrows("async_optional");
+    assertNoThrows("async_optional", null);
+    assertNoThrows("async_optional", cb);
+    assertThrows("async_optional", cb, null);
+    assertThrows("async_optional", cb, cb);
+  }
+});
+
+add_task(async function testCheckAsyncResults() {
+  await Schemas.load("data:," + JSON.stringify(schemaJson));
+
+  const complete = generateAPIs(
+    {},
+    {
+      async_result: async () => ({ size: 5, colour: "green" }),
+    }
+  );
+
+  const optional = generateAPIs(
+    {},
+    {
+      async_result: async () => ({ size: 6 }),
+    }
+  );
+
+  const invalid = generateAPIs(
+    {},
+    {
+      async_result: async () => ({}),
+    }
+  );
+
+  deepEqual(await complete.async_result(), { size: 5, colour: "green" });
+
+  deepEqual(
+    await optional.async_result(),
+    { size: 6 },
+    "Missing optional properties is allowed"
+  );
+
+  if (AppConstants.DEBUG) {
+    await Assert.rejects(
+      invalid.async_result(),
+      /Type error for widget value \(Property "size" is required\)/,
+      "Should throw for invalid callback argument in DEBUG builds"
+    );
+  } else {
+    deepEqual(
+      await invalid.async_result(),
+      {},
+      "Invalid callback argument doesn't throw in release builds"
+    );
+  }
+});
+
+add_task(async function testAsyncResults() {
+  await Schemas.load("data:," + JSON.stringify(schemaJson));
+  function runWithCallback(func) {
+    info(`Calling testnamespace.${func.name}, expecting callback with result`);
+    return new Promise(resolve => {
+      let result = "uninitialized value";
+      let returnValue = func(reply => {
+        result = reply;
+        resolve(result);
+      });
+      // When a callback is given, the return value must be missing.
+      Assert.equal(returnValue, undefined);
+      // Callback must be called asynchronously.
+      Assert.equal(result, "uninitialized value");
+    });
+  }
+
+  function runFailCallback(func) {
+    info(`Calling testnamespace.${func.name}, expecting callback with error`);
+    return new Promise(resolve => {
+      func(reply => {
+        Assert.equal(reply, undefined);
+        resolve(context.lastError.message); // eslint-disable-line no-undef
+      });
+    });
+  }
+
+  for (let isChromeCompat of [true, false]) {
+    info(`Testing API invocation with isChromeCompat=${isChromeCompat}`);
+    let testnamespace = generateAPIs(
+      {
+        isChromeCompat,
+      },
+      {
+        async_required(cb) {
+          Assert.equal(cb, undefined);
+          return Promise.resolve(1);
+        },
+        async_optional(cb) {
+          Assert.equal(cb, undefined);
+          return Promise.resolve(2);
+        },
+      }
+    );
+    if (!isChromeCompat) {
+      // No promises for chrome.
+      info("testnamespace.async_required should be a Promise");
+      let promise = testnamespace.async_required();
+      Assert.ok(promise instanceof context.cloneScope.Promise);
+      Assert.equal(await promise, 1);
+
+      info("testnamespace.async_optional should be a Promise");
+      promise = testnamespace.async_optional();
+      Assert.ok(promise instanceof context.cloneScope.Promise);
+      Assert.equal(await promise, 2);
+    }
+
+    Assert.equal(await runWithCallback(testnamespace.async_required), 1);
+    Assert.equal(await runWithCallback(testnamespace.async_optional), 2);
+
+    let otherSandbox = Cu.Sandbox(null, {});
+    let errorFactories = [
+      msg => {
+        throw new context.cloneScope.Error(msg);
+      },
+      msg => context.cloneScope.Promise.reject({ message: msg }),
+      msg => Cu.evalInSandbox(`throw new Error("${msg}")`, otherSandbox),
+      msg =>
+        Cu.evalInSandbox(`Promise.reject({message: "${msg}"})`, otherSandbox),
+    ];
+    for (let makeError of errorFactories) {
+      info(`Testing callback/promise with error caused by: ${makeError}`);
+      testnamespace = generateAPIs(
+        {
+          isChromeCompat,
+        },
+        {
+          async_required() {
+            return makeError("ONE");
+          },
+          async_optional() {
+            return makeError("TWO");
+          },
+        }
+      );
+
+      if (!isChromeCompat) {
+        // No promises for chrome.
+        await Assert.rejects(
+          testnamespace.async_required(),
+          /ONE/,
+          "should reject testnamespace.async_required()"
+        );
+        await Assert.rejects(
+          testnamespace.async_optional(),
+          /TWO/,
+          "should reject testnamespace.async_optional()"
+        );
+      }
+
+      Assert.equal(await runFailCallback(testnamespace.async_required), "ONE");
+      Assert.equal(await runFailCallback(testnamespace.async_optional), "TWO");
+    }
+  }
+});
diff --git a/toolkit/components/extensions/test/xpcshell/test_ext_schemas_interactive.js b/toolkit/components/extensions/test/xpcshell/test_ext_schemas_interactive.js
new file mode 100644
index 0000000000..986dc74bc5
--- /dev/null
+++ b/toolkit/components/extensions/test/xpcshell/test_ext_schemas_interactive.js
@@ -0,0 +1,173 @@
+"use strict";
+
+const { ExtensionProcessScript } = ChromeUtils.importESModule(
+  "resource://gre/modules/ExtensionProcessScript.sys.mjs"
+);
+
+let experimentAPIs = {
+  userinputtest: {
+    schema: "schema.json",
+    parent: {
+      scopes: ["addon_parent"],
+      script: "parent.js",
+      paths: [["userinputtest"]],
+    },
+    child: {
+      scopes: ["addon_child"],
+      script: "child.js",
+      paths: [["userinputtest", "child"]],
+    },
+  },
+};
+
+let experimentFiles = {
+  "schema.json": JSON.stringify([
+    {
+      namespace: "userinputtest",
+      functions: [
+        {
+          name: "test",
+          type: "function",
+          async: true,
+          requireUserInput: true,
+          parameters: [],
+        },
+        {
+          name: "child",
+          type: "function",
+          async: true,
+          requireUserInput: true,
+          parameters: [],
+        },
+      ],
+    },
+  ]),
+
+  /* globals ExtensionAPI */
+  "parent.js": () => {
+    this.userinputtest = class extends ExtensionAPI {
+      getAPI(context) {
+        return {
+          userinputtest: {
+            test() {},
+          },
+        };
+      }
+    };
+  },
+
+  "child.js": () => {
+    this.userinputtest = class extends ExtensionAPI {
+      getAPI(context) {
+        return {
+          userinputtest: {
+            child() {},
+          },
+        };
+      }
+    };
+  },
+};
+
+// Set the "handlingUserInput" flag for the given extension's background page.
+// Returns an RAIIHelper that should be destruct()ed eventually.
+function setHandlingUserInput(extension) {
+  let extensionChild = ExtensionProcessScript.getExtensionChild(extension.id);
+  let bgwin = null;
+  for (let view of extensionChild.views) {
+    if (view.viewType == "background") {
+      bgwin = view.contentWindow;
+      break;
+    }
+  }
+  notEqual(bgwin, null, "Found background window for the test extension");
+  let winutils = bgwin.windowUtils;
+  return winutils.setHandlingUserInput(true);
+}
+
+// Test that the schema requireUserInput flag works correctly for
+// proxied api implementations.
+add_task(async function test_proxy() {
+  let extension = ExtensionTestUtils.loadExtension({
+    isPrivileged: true,
+    background() {
+      browser.test.onMessage.addListener(async () => {
+        try {
+          await browser.userinputtest.test();
+          browser.test.sendMessage("result", null);
+        } catch (err) {
+          browser.test.sendMessage("result", err.message);
+        }
+      });
+    },
+    manifest: {
+      permissions: ["experiments.userinputtest"],
+      experiment_apis: experimentAPIs,
+    },
+    files: experimentFiles,
+  });
+
+  await extension.startup();
+
+  extension.sendMessage("test");
+  let result = await extension.awaitMessage("result");
+  ok(
+    /test may only be called from a user input handler/.test(result),
+    `function failed when not called from a user input handler: ${result}`
+  );
+
+  let handle = setHandlingUserInput(extension);
+  extension.sendMessage("test");
+  result = await extension.awaitMessage("result");
+  equal(
+    result,
+    null,
+    "function succeeded when called from a user input handler"
+  );
+  handle.destruct();
+
+  await extension.unload();
+});
+
+// Test that the schema requireUserInput flag works correctly for
+// non-proxied api implementations.
+add_task(async function test_local() {
+  let extension = ExtensionTestUtils.loadExtension({
+    isPrivileged: true,
+    background() {
+      browser.test.onMessage.addListener(async () => {
+        try {
+          await browser.userinputtest.child();
+          browser.test.sendMessage("result", null);
+        } catch (err) {
+          browser.test.sendMessage("result", err.message);
+        }
+      });
+    },
+    manifest: {
+      experiment_apis: experimentAPIs,
+    },
+    files: experimentFiles,
+  });
+
+  await extension.startup();
+
+  extension.sendMessage("test");
+  let result = await extension.awaitMessage("result");
+  ok(
+    /child may only be called from a user input handler/.test(result),
+    `function failed when not called from a user input handler: ${result}`
+  );
+
+  let handle = setHandlingUserInput(extension);
+  extension.sendMessage("test");
+  result = await extension.awaitMessage("result");
+  equal(
+    result,
+    null,
+    "function succeeded when called from a user input handler"
+  );
+  handle.destruct();
+
+  await extension.unload();
+});
diff --git a/toolkit/components/extensions/test/xpcshell/test_ext_schemas_manifest_permissions.js b/toolkit/components/extensions/test/xpcshell/test_ext_schemas_manifest_permissions.js
new file mode 100644
index 0000000000..562ab5c36d
--- /dev/null
+++ b/toolkit/components/extensions/test/xpcshell/test_ext_schemas_manifest_permissions.js
@@ -0,0 +1,171 @@
+"use strict";
+
+const { ExtensionAPI } = ExtensionCommon;
+
+add_task(async function () {
+  const schema = [
+    {
+      namespace: "manifest",
+      types: [
+        {
+          $extend: "WebExtensionManifest",
+          properties: {
+            a_manifest_property: {
+              type: "object",
+              optional: true,
+              properties: {
+                nested: {
+                  optional: true,
+                  type: "any",
+                },
+              },
+              additionalProperties: { $ref: "UnrecognizedProperty" },
+            },
+          },
+        },
+      ],
+    },
+    {
+      namespace: "testManifestPermission",
+      permissions: ["manifest:a_manifest_property"],
+      functions: [
+        {
+          name: "testMethod",
+          type: "function",
+          async: true,
+          parameters: [],
+          permissions: ["manifest:a_manifest_property.nested"],
+        },
+      ],
+    },
+  ];
+
+  class FakeAPI extends ExtensionAPI {
+    getAPI(context) {
+      return {
+        testManifestPermission: {
+          get testProperty() {
+            return "value";
+          },
+          testMethod() {
+            return Promise.resolve("value");
+          },
+        },
+      };
+    }
+  }
+
+  const modules = {
+    testNamespace: {
+      url: URL.createObjectURL(new Blob([FakeAPI.toString()])),
+      schema: `data:,${JSON.stringify(schema)}`,
+      scopes: ["addon_parent", "addon_child"],
+      paths: [["testManifestPermission"]],
+    },
+  };
+
+  Services.catMan.addCategoryEntry(
+    "webextension-modules",
+    "test-manifest-permission",
+    `data:,${JSON.stringify(modules)}`,
+    false,
+    false
+  );
+
+  async function testExtension(extensionDef, assertFn) {
+    let extension = ExtensionTestUtils.loadExtension(extensionDef);
+
+    await extension.startup();
+    await assertFn(extension);
+    await extension.unload();
+  }
+
+  await testExtension(
+    {
+      manifest: {
+        a_manifest_property: {},
+      },
+      background() {
+        // Test hasPermission method implemented in ExtensionChild.jsm.
+        browser.test.assertTrue(
+          "testManifestPermission" in browser,
+          "The API namespace is defined as expected"
+        );
+        browser.test.assertEq(
+          undefined,
+          browser.testManifestPermission &&
+            browser.testManifestPermission.testMethod,
+          "The property with nested manifest property permission should not be available "
+        );
+        browser.test.notifyPass("test-extension-manifest-without-nested-prop");
+      },
+    },
+    async extension => {
+      await extension.awaitFinish(
+        "test-extension-manifest-without-nested-prop"
+      );
+
+      // Test hasPermission method implemented in Extension.jsm.
+      equal(
+        extension.extension.hasPermission("manifest:a_manifest_property"),
+        true,
+        "Got the expected Extension's hasPermission result on existing property"
+      );
+      equal(
+        extension.extension.hasPermission(
+          "manifest:a_manifest_property.nested"
+        ),
+        false,
+        "Got the expected Extension's hasPermission result on existing subproperty"
+      );
+    }
+  );
+
+  await testExtension(
+    {
+      manifest: {
+        a_manifest_property: {
+          nested: {},
+        },
+      },
+      background() {
+        // Test hasPermission method implemented in ExtensionChild.jsm.
+        browser.test.assertTrue(
+          "testManifestPermission" in browser,
+          "The API namespace is defined as expected"
+        );
+        browser.test.assertEq(
+          "function",
+          browser.testManifestPermission &&
+            typeof browser.testManifestPermission.testMethod,
+          "The property with nested manifest property permission should be available "
+        );
+        browser.test.notifyPass("test-extension-manifest-with-nested-prop");
+      },
+    },
+    async extension => {
+      await extension.awaitFinish("test-extension-manifest-with-nested-prop");
+
+      // Test hasPermission method implemented in Extension.jsm.
+      equal(
+        extension.extension.hasPermission("manifest:a_manifest_property"),
+        true,
+        "Got the expected Extension's hasPermission result on existing property"
+      );
+      equal(
+        extension.extension.hasPermission(
+          "manifest:a_manifest_property.nested"
+        ),
+        true,
+        "Got the expected Extension's hasPermission result on existing subproperty"
+      );
+      equal(
+        extension.extension.hasPermission(
+          "manifest:a_manifest_property.unexisting"
+        ),
+        false,
+        "Got the expected Extension's hasPermission result on non existing subproperty"
+      );
+    }
+  );
+});
diff --git a/toolkit/components/extensions/test/xpcshell/test_ext_schemas_privileged.js b/toolkit/components/extensions/test/xpcshell/test_ext_schemas_privileged.js
new file mode 100644
index 0000000000..e2da7e5a74
--- /dev/null
+++ b/toolkit/components/extensions/test/xpcshell/test_ext_schemas_privileged.js
@@ -0,0 +1,161 @@
+"use strict";
+
+const { ExtensionAPI } = ExtensionCommon;
+
+AddonTestUtils.init(this);
+AddonTestUtils.overrideCertDB();
+AddonTestUtils.usePrivilegedSignatures = false;
+AddonTestUtils.createAppInfo(
+  "xpcshell@tests.mozilla.org",
+  "XPCShell",
+  "1",
+  "42"
+);
+
+add_setup(async () => {
+  const schema = [
+    {
+      namespace: "privileged",
+      permissions: ["mozillaAddons"],
+      properties: {
+        test: {
+          type: "any",
+        },
+      },
+    },
+  ];
+
+  class API extends ExtensionAPI {
+    getAPI(context) {
+      return {
+        privileged: {
+          test: "hello",
+        },
+      };
+    }
+  }
+
+  const modules = {
+    privileged: {
+      url: URL.createObjectURL(new Blob([API.toString()])),
+      schema: `data:,${JSON.stringify(schema)}`,
+      scopes: ["addon_parent"],
+      paths: [["privileged"]],
+    },
+  };
+
+  Services.catMan.addCategoryEntry(
+    "webextension-modules",
+    "test-privileged",
+    `data:,${JSON.stringify(modules)}`,
+    false,
+    false
+  );
+
+  await AddonTestUtils.promiseStartupManager();
+
+  registerCleanupFunction(async () => {
+    await AddonTestUtils.promiseShutdownManager();
+    Services.catMan.deleteCategoryEntry(
+      "webextension-modules",
+      "test-privileged",
+      false
+    );
+  });
+});
+
+add_task(
+  {
+    // Some builds (e.g. thunderbird) have experiments enabled by default.
+    pref_set: [["extensions.experiments.enabled", false]],
+  },
+  async function test_privileged_namespace_disallowed() {
+    // Try accessing the privileged namespace.
+    async function testOnce({
+      isPrivileged = false,
+      temporarilyInstalled = false,
+    } = {}) {
+      let extension = ExtensionTestUtils.loadExtension({
+        manifest: {
+          permissions: ["mozillaAddons", "tabs"],
+        },
+        background() {
+          browser.test.sendMessage(
+            "result",
+            browser.privileged instanceof Object
+          );
+        },
+        isPrivileged,
+        temporarilyInstalled,
+      });
+
+      if (temporarilyInstalled && !isPrivileged) {
+        ExtensionTestUtils.failOnSchemaWarnings(false);
+        let { messages } = await promiseConsoleOutput(async () => {
+          await Assert.rejects(
+            extension.startup(),
+            /Using the privileged permission/,
+            "Startup failed with privileged permission"
+          );
+        });
+        ExtensionTestUtils.failOnSchemaWarnings(true);
+        AddonTestUtils.checkMessages(
+          messages,
+          {
+            expected: [
+              {
+                message:
+                  /Using the privileged permission 'mozillaAddons' requires a privileged add-on/,
+              },
+            ],
+          },
+          true
+        );
+        return null;
+      }
+      await extension.startup();
+      let result = await extension.awaitMessage("result");
+      await extension.unload();
+      return result;
+    }
+
+    // Prevents startup
+    let result = await testOnce({ temporarilyInstalled: true });
+    equal(
+      result,
+      null,
+      "Privileged namespace should not be accessible to a regular webextension"
+    );
+
+    result = await testOnce({ isPrivileged: true });
+    equal(
+      result,
+      true,
+      "Privileged namespace should be accessible to a webextension signed with Mozilla Extensions"
+    );
+
+    // Allows startup, no access
+    result = await testOnce();
+    equal(
+      result,
+      false,
+      "Privileged namespace should not be accessible to a regular webextension"
+    );
+  }
+);
+
+// Test that Extension.jsm and schema correctly match.
+add_task(function test_privileged_permissions_match() {
+  const { PRIVILEGED_PERMS } = ChromeUtils.importESModule(
+    "resource://gre/modules/Extension.sys.mjs"
+  );
+  let perms = Schemas.getPermissionNames(["PermissionPrivileged"]);
+  if (AppConstants.platform == "android") {
+    perms.push("nativeMessaging");
+  }
+  Assert.deepEqual(
+    Array.from(PRIVILEGED_PERMS).sort(),
+    perms.sort(),
+    "List of privileged permissions is correct."
+  );
+});
diff --git a/toolkit/components/extensions/test/xpcshell/test_ext_schemas_revoke.js b/toolkit/components/extensions/test/xpcshell/test_ext_schemas_revoke.js
new file mode 100644
index 0000000000..5b4df1e671
--- /dev/null
+++ b/toolkit/components/extensions/test/xpcshell/test_ext_schemas_revoke.js
@@ -0,0 +1,507 @@
+/* -*- Mode: indent-tabs-mode: nil; js-indent-level: 2 -*- */
+/* vim: set sts=2 sw=2 et tw=80: */
+"use strict";
+
+const { Schemas } = ChromeUtils.importESModule(
+  "resource://gre/modules/Schemas.sys.mjs"
+);
+
+let { SchemaAPIInterface } = ExtensionCommon;
+
+const global = this;
+
+let json = [
+  {
+    namespace: "revokableNs",
+
+    permissions: ["revokableNs"],
+
+    properties: {
+      stringProp: {
+        type: "string",
+        writable: true,
+      },
+
+      revokableStringProp: {
+        type: "string",
+        permissions: ["revokableProp"],
+        writable: true,
+      },
+
+      submoduleProp: {
+        $ref: "submodule",
+      },
+
+      revokableSubmoduleProp: {
+        $ref: "submodule",
+        permissions: ["revokableProp"],
+      },
+    },
+
+    types: [
+      {
+        id: "submodule",
+        type: "object",
+        functions: [
+          {
+            name: "sub_foo",
+            type: "function",
+            parameters: [],
+            returns: { type: "integer" },
+          },
+        ],
+      },
+    ],
+
+    functions: [
+      {
+        name: "func",
+        type: "function",
+        parameters: [],
+      },
+
+      {
+        name: "revokableFunc",
+        type: "function",
+        parameters: [],
+        permissions: ["revokableFunc"],
+      },
+    ],
+
+    events: [
+      {
+        name: "onEvent",
+        type: "function",
+      },
+
+      {
+        name: "onRevokableEvent",
+        type: "function",
+        permissions: ["revokableEvent"],
+      },
+    ],
+  },
+];
+
+let recorded = [];
+
+function record(...args) {
+  recorded.push(args);
+}
+
+function verify(expected) {
+  for (let [i, rec] of expected.entries()) {
+    Assert.deepEqual(recorded[i], rec, `Record ${i} matches`);
+  }
+
+  equal(recorded.length, expected.length, "Got expected number of records");
+
+  recorded.length = 0;
+}
+
+registerCleanupFunction(() => {
+  equal(recorded.length, 0, "No unchecked recorded events at shutdown");
+});
+
+let permissions = new Set();
+
+class APIImplementation extends SchemaAPIInterface {
+  constructor(namespace, name) {
+    super();
+    this.namespace = namespace;
+    this.name = name;
+  }
+
+  record(method, args) {
+    record(method, this.namespace, this.name, args);
+  }
+
+  revoke(...args) {
+    this.record("revoke", args);
+  }
+
+  callFunction(...args) {
+    this.record("callFunction", args);
+    if (this.name === "sub_foo") {
+      return 13;
+    }
+  }
+
+  callFunctionNoReturn(...args) {
+    this.record("callFunctionNoReturn", args);
+  }
+
+  getProperty(...args) {
+    this.record("getProperty", args);
+  }
+
+  setProperty(...args) {
+    this.record("setProperty", args);
+  }
+
+  addListener(...args) {
+    this.record("addListener", args);
+  }
+
+  removeListener(...args) {
+    this.record("removeListener", args);
+  }
+
+  hasListener(...args) {
+    this.record("hasListener", args);
+  }
+}
+
+let context = {
+  manifestVersion: 2,
+  cloneScope: global,
+
+  permissionsChanged: null,
+
+  setPermissionsChangedCallback(callback) {
+    this.permissionsChanged = callback;
+  },
+
+  hasPermission(permission) {
+    return permissions.has(permission);
+  },
+
+  isPermissionRevokable(permission) {
+    return permission.startsWith("revokable");
+  },
+
+  getImplementation(namespace, name) {
+    return new APIImplementation(namespace, name);
+  },
+
+  shouldInject() {
+    return true;
+  },
+};
+
+function ignoreError(fn) {
+  try {
+    fn();
+  } catch (e) {
+    // Meh.
+  }
+}
+
+add_task(async function () {
+  let url = "data:," + JSON.stringify(json);
+  await Schemas.load(url);
+
+  let root = {};
+  Schemas.inject(root, context);
+  equal(recorded.length, 0, "No recorded events");
+
+  let listener = () => {};
+  let captured = {};
+
+  function checkRecorded() {
+    let possible = [
+      ["revokableNs", ["getProperty", "revokableNs", "stringProp", []]],
+      [
+        "revokableProp",
+        ["getProperty", "revokableNs", "revokableStringProp", []],
+      ],
+
+      [
+        "revokableNs",
+        ["setProperty", "revokableNs", "stringProp", ["stringProp"]],
+      ],
+      [
+        "revokableProp",
+        [
+          "setProperty",
+          "revokableNs",
+          "revokableStringProp",
+          ["revokableStringProp"],
+        ],
+      ],
+
+      ["revokableNs", ["callFunctionNoReturn", "revokableNs", "func", [[]]]],
+      [
+        "revokableFunc",
+        ["callFunctionNoReturn", "revokableNs", "revokableFunc", [[]]],
+      ],
+
+      [
+        "revokableNs",
+        ["callFunction", "revokableNs.submoduleProp", "sub_foo", [[]]],
+      ],
+      [
+        "revokableProp",
+        ["callFunction", "revokableNs.revokableSubmoduleProp", "sub_foo", [[]]],
+      ],
+
+      [
+        "revokableNs",
+        ["addListener", "revokableNs", "onEvent", [listener, []]],
+      ],
+      ["revokableNs", ["removeListener", "revokableNs", "onEvent", [listener]]],
+      ["revokableNs", ["hasListener", "revokableNs", "onEvent", [listener]]],
+
+      [
+        "revokableEvent",
+        ["addListener", "revokableNs", "onRevokableEvent", [listener, []]],
+      ],
+      [
+        "revokableEvent",
+        ["removeListener", "revokableNs", "onRevokableEvent", [listener]],
+      ],
+      [
+        "revokableEvent",
+        ["hasListener", "revokableNs", "onRevokableEvent", [listener]],
+      ],
+    ];
+
+    let expected = [];
+    if (permissions.has("revokableNs")) {
+      for (let [perm, recording] of possible) {
+        if (!perm || permissions.has(perm)) {
+          expected.push(recording);
+        }
+      }
+    }
+
+    verify(expected);
+  }
+
+  function check() {
+    info(`Check normal access (permissions: [${Array.from(permissions)}])`);
+
+    let ns = root.revokableNs;
+
+    void ns.stringProp;
+    void ns.revokableStringProp;
+
+    ns.stringProp = "stringProp";
+    ns.revokableStringProp = "revokableStringProp";
+
+    ns.func();
+
+    if (ns.revokableFunc) {
+      ns.revokableFunc();
+    }
+
+    ns.submoduleProp.sub_foo();
+    if (ns.revokableSubmoduleProp) {
+      ns.revokableSubmoduleProp.sub_foo();
+    }
+
+    ns.onEvent.addListener(listener);
+    ns.onEvent.removeListener(listener);
+    ns.onEvent.hasListener(listener);
+
+    if (ns.onRevokableEvent) {
+      ns.onRevokableEvent.addListener(listener);
+      ns.onRevokableEvent.removeListener(listener);
+      ns.onRevokableEvent.hasListener(listener);
+    }
+
+    checkRecorded();
+  }
+
+  function capture() {
+    info("Capture values");
+
+    let ns = root.revokableNs;
+
+    captured = { ns };
+    captured.revokableStringProp = Object.getOwnPropertyDescriptor(
+      ns,
+      "revokableStringProp"
+    );
+
+    captured.revokableSubmoduleProp = ns.revokableSubmoduleProp;
+    if (ns.revokableSubmoduleProp) {
+      captured.sub_foo = ns.revokableSubmoduleProp.sub_foo;
+    }
+
+    captured.revokableFunc = ns.revokableFunc;
+
+    captured.onRevokableEvent = ns.onRevokableEvent;
+    if (ns.onRevokableEvent) {
+      captured.addListener = ns.onRevokableEvent.addListener;
+      captured.removeListener = ns.onRevokableEvent.removeListener;
+      captured.hasListener = ns.onRevokableEvent.hasListener;
+    }
+  }
+
+  function checkCaptured() {
+    info(
+      `Check captured value access (permissions: [${Array.from(permissions)}])`
+    );
+
+    let { ns } = captured;
+
+    void ns.stringProp;
+    ignoreError(() => captured.revokableStringProp.get());
+    if (!permissions.has("revokableProp")) {
+      void ns.revokableStringProp;
+    }
+
+    ns.stringProp = "stringProp";
+    ignoreError(() => captured.revokableStringProp.set("revokableStringProp"));
+    if (!permissions.has("revokableProp")) {
+      ns.revokableStringProp = "revokableStringProp";
+    }
+
+    ignoreError(() => ns.func());
+    ignoreError(() => captured.revokableFunc());
+    if (!permissions.has("revokableFunc")) {
+      ignoreError(() => ns.revokableFunc());
+    }
+
+    ignoreError(() => ns.submoduleProp.sub_foo());
+
+    ignoreError(() => captured.sub_foo());
+    if (!permissions.has("revokableProp")) {
+      ignoreError(() => captured.revokableSubmoduleProp.sub_foo());
+      ignoreError(() => ns.revokableSubmoduleProp.sub_foo());
+    }
+
+    ignoreError(() => ns.onEvent.addListener(listener));
+    ignoreError(() => ns.onEvent.removeListener(listener));
+    ignoreError(() => ns.onEvent.hasListener(listener));
+
+    ignoreError(() => captured.addListener(listener));
+    ignoreError(() => captured.removeListener(listener));
+    ignoreError(() => captured.hasListener(listener));
+    if (!permissions.has("revokableEvent")) {
+      ignoreError(() => captured.onRevokableEvent.addListener(listener));
+      ignoreError(() => captured.onRevokableEvent.removeListener(listener));
+      ignoreError(() => captured.onRevokableEvent.hasListener(listener));
+
+      ignoreError(() => ns.onRevokableEvent.addListener(listener));
+      ignoreError(() => ns.onRevokableEvent.removeListener(listener));
+      ignoreError(() => ns.onRevokableEvent.hasListener(listener));
+    }
+
+    checkRecorded();
+  }
+
+  permissions.add("revokableNs");
+  permissions.add("revokableProp");
+  permissions.add("revokableFunc");
+  permissions.add("revokableEvent");
+
+  check();
+  capture();
+  checkCaptured();
+
+  permissions.delete("revokableProp");
+  context.permissionsChanged();
+  verify([
+    ["revoke", "revokableNs", "revokableStringProp", []],
+    ["revoke", "revokableNs.revokableSubmoduleProp", "sub_foo", []],
+  ]);
+
+  check();
+  checkCaptured();
+
+  permissions.delete("revokableFunc");
+  context.permissionsChanged();
+  verify([["revoke", "revokableNs", "revokableFunc", []]]);
+
+  check();
+  checkCaptured();
+
+  permissions.delete("revokableEvent");
+  context.permissionsChanged();
+
+  verify([["revoke", "revokableNs", "onRevokableEvent", []]]);
+
+  check();
+  checkCaptured();
+
+  permissions.delete("revokableNs");
+  context.permissionsChanged();
+  verify([
+    ["revoke", "revokableNs", "stringProp", []],
+    ["revoke", "revokableNs", "func", []],
+    ["revoke", "revokableNs.submoduleProp", "sub_foo", []],
+    ["revoke", "revokableNs", "onEvent", []],
+  ]);
+
+  checkCaptured();
+
+  permissions.add("revokableNs");
+  permissions.add("revokableProp");
+  permissions.add("revokableFunc");
+  permissions.add("revokableEvent");
+  context.permissionsChanged();
+
+  check();
+  capture();
+  checkCaptured();
+
+  permissions.delete("revokableProp");
+  permissions.delete("revokableFunc");
+  permissions.delete("revokableEvent");
+  context.permissionsChanged();
+  verify([
+    ["revoke", "revokableNs", "revokableStringProp", []],
+    ["revoke", "revokableNs", "revokableFunc", []],
+    ["revoke", "revokableNs.revokableSubmoduleProp", "sub_foo", []],
+    ["revoke", "revokableNs", "onRevokableEvent", []],
+  ]);
+
+  check();
+  checkCaptured();
+
+  permissions.add("revokableProp");
+  permissions.add("revokableFunc");
+  permissions.add("revokableEvent");
+  context.permissionsChanged();
+
+  check();
+  capture();
+  checkCaptured();
+
+  permissions.delete("revokableNs");
+  context.permissionsChanged();
+  verify([
+    ["revoke", "revokableNs", "stringProp", []],
+    ["revoke", "revokableNs", "revokableStringProp", []],
+    ["revoke", "revokableNs", "func", []],
+    ["revoke", "revokableNs", "revokableFunc", []],
+    ["revoke", "revokableNs.submoduleProp", "sub_foo", []],
+    ["revoke", "revokableNs.revokableSubmoduleProp", "sub_foo", []],
+    ["revoke", "revokableNs", "onEvent", []],
+    ["revoke", "revokableNs", "onRevokableEvent", []],
+  ]);
+
+  equal(root.revokableNs, undefined, "Namespace is not defined");
+  checkCaptured();
+});
+
+add_task(async function test_neuter() {
+  context.permissionsChanged = null;
+
+  let root = {};
+  Schemas.inject(root, context);
+  equal(recorded.length, 0, "No recorded events");
+
+  permissions.add("revokableNs");
+  permissions.add("revokableProp");
+  permissions.add("revokableFunc");
+  permissions.add("revokableEvent");
+
+  let ns = root.revokableNs;
+  let { submoduleProp } = ns;
+
+  let lazyGetter = Object.getOwnPropertyDescriptor(submoduleProp, "sub_foo");
+
+  permissions.delete("revokableNs");
+  context.permissionsChanged();
+  verify([]);
+
+  equal(root.revokableNs, undefined, "Should have no revokableNs");
+  equal(ns.submoduleProp, undefined, "Should have no ns.submoduleProp");
+
+  equal(submoduleProp.sub_foo, undefined, "No sub_foo");
+  lazyGetter.get.call(submoduleProp);
+  equal(submoduleProp.sub_foo, undefined, "No sub_foo");
+});
diff --git a/toolkit/components/extensions/test/xpcshell/test_ext_schemas_roots.js b/toolkit/components/extensions/test/xpcshell/test_ext_schemas_roots.js
new file mode 100644
index 0000000000..21434228a3
--- /dev/null
+++ b/toolkit/components/extensions/test/xpcshell/test_ext_schemas_roots.js
@@ -0,0 +1,242 @@
+/* -*- Mode: indent-tabs-mode: nil; js-indent-level: 2 -*- */
+/* vim: set sts=2 sw=2 et tw=80: */
+"use strict";
+
+const { SchemaRoot } = ChromeUtils.importESModule(
+  "resource://gre/modules/Schemas.sys.mjs"
+);
+
+let { SchemaAPIInterface } = ExtensionCommon;
+
+const global = this;
+
+let baseSchemaJSON = [
+  {
+    namespace: "base",
+
+    properties: {
+      PROP1: { value: 42 },
+    },
+
+    types: [
+      {
+        id: "type1",
+        type: "string",
+        enum: ["value1", "value2", "value3"],
+      },
+    ],
+
+    functions: [
+      {
+        name: "foo",
+        type: "function",
+        parameters: [{ name: "arg1", $ref: "type1" }],
+      },
+    ],
+  },
+];
+
+let experimentFooJSON = [
+  {
+    namespace: "experiments.foo",
+    types: [
+      {
+        id: "typeFoo",
+        type: "string",
+        enum: ["foo1", "foo2", "foo3"],
+      },
+    ],
+
+    functions: [
+      {
+        name: "foo",
+        type: "function",
+        parameters: [
+          { name: "arg1", $ref: "typeFoo" },
+          { name: "arg2", $ref: "base.type1" },
+        ],
+      },
+    ],
+  },
+];
+
+let experimentBarJSON = [
+  {
+    namespace: "experiments.bar",
+    types: [
+      {
+        id: "typeBar",
+        type: "string",
+        enum: ["bar1", "bar2", "bar3"],
+      },
+    ],
+
+    functions: [
+      {
+        name: "bar",
+        type: "function",
+        parameters: [
+          { name: "arg1", $ref: "typeBar" },
+          { name: "arg2", $ref: "base.type1" },
+        ],
+      },
+    ],
+  },
+];
+
+let tallied = null;
+
+function tally(kind, ns, name, args) {
+  tallied = [kind, ns, name, args];
+}
+
+function verify(...args) {
+  equal(JSON.stringify(tallied), JSON.stringify(args));
+  tallied = null;
+}
+
+let talliedErrors = [];
+
+let permissions = new Set();
+
+class TallyingAPIImplementation extends SchemaAPIInterface {
+  constructor(namespace, name) {
+    super();
+    this.namespace = namespace;
+    this.name = name;
+  }
+
+  callFunction(args) {
+    tally("call", this.namespace, this.name, args);
+    if (this.name === "sub_foo") {
+      return 13;
+    }
+  }
+
+  callFunctionNoReturn(args) {
+    tally("call", this.namespace, this.name, args);
+  }
+
+  getProperty() {
+    tally("get", this.namespace, this.name);
+  }
+
+  setProperty(value) {
+    tally("set", this.namespace, this.name, value);
+  }
+
+  addListener(listener, args) {
+    tally("addListener", this.namespace, this.name, [listener, args]);
+  }
+
+  removeListener(listener) {
+    tally("removeListener", this.namespace, this.name, [listener]);
+  }
+
+  hasListener(listener) {
+    tally("hasListener", this.namespace, this.name, [listener]);
+  }
+}
+
+let wrapper = {
+  url: "moz-extension://b66e3509-cdb3-44f6-8eb8-c8b39b3a1d27/",
+  manifestVersion: 2,
+
+  cloneScope: global,
+
+  checkLoadURL(url) {
+    return !url.startsWith("chrome:");
+  },
+
+  preprocessors: {
+    localize(value, context) {
+      return value.replace(/__MSG_(.*?)__/g, (m0, m1) => `${m1.toUpperCase()}`);
+    },
+  },
+
+  logError(message) {
+    talliedErrors.push(message);
+  },
+
+  hasPermission(permission) {
+    return permissions.has(permission);
+  },
+
+  shouldInject(ns, name) {
+    return name != "do-not-inject";
+  },
+
+  getImplementation(namespace, name) {
+    return new TallyingAPIImplementation(namespace, name);
+  },
+};
+
+add_task(async function () {
+  let baseSchemas = new Map([["resource://schemas/base.json", baseSchemaJSON]]);
+  let experimentSchemas = new Map([
+    ["resource://experiment-foo/schema.json", experimentFooJSON],
+    ["resource://experiment-bar/schema.json", experimentBarJSON],
+  ]);
+
+  let baseSchema = new SchemaRoot(null, baseSchemas);
+  let schema = new SchemaRoot(baseSchema, experimentSchemas);
+
+  baseSchema.parseSchemas();
+  schema.parseSchemas();
+
+  let root = {};
+  let base = {};
+
+  tallied = null;
+
+  baseSchema.inject(base, wrapper);
+  schema.inject(root, wrapper);
+
+  equal(typeof base.base, "object", "base.base exists");
+  equal(typeof root.base, "object", "root.base exists");
+  equal(typeof base.experiments, "undefined", "base.experiments exists not");
+  equal(typeof root.experiments, "object", "root.experiments exists");
+  equal(typeof root.experiments.foo, "object", "root.experiments.foo exists");
+  equal(typeof root.experiments.bar, "object", "root.experiments.bar exists");
+
+  equal(tallied, null);
+
+  equal(root.base.PROP1, 42, "root.base.PROP1");
+  equal(base.base.PROP1, 42, "root.base.PROP1");
+
+  root.base.foo("value2");
+  verify("call", "base", "foo", ["value2"]);
+
+  base.base.foo("value3");
+  verify("call", "base", "foo", ["value3"]);
+
+  root.experiments.foo.foo("foo2", "value1");
+  verify("call", "experiments.foo", "foo", ["foo2", "value1"]);
+
+  root.experiments.bar.bar("bar2", "value1");
+  verify("call", "experiments.bar", "bar", ["bar2", "value1"]);
+
+  Assert.throws(
+    () => root.base.foo("Meh."),
+    /Type error for parameter arg1/,
+    "root.base.foo()"
+  );
+
+  Assert.throws(
+    () => base.base.foo("Meh."),
+    /Type error for parameter arg1/,
+    "base.base.foo()"
+  );
+
+  Assert.throws(
+    () => root.experiments.foo.foo("Meh."),
+    /Incorrect argument types/,
+    "root.experiments.foo.foo()"
+  );
+
+  Assert.throws(
+    () => root.experiments.bar.bar("Meh."),
+    /Incorrect argument types/,
+    "root.experiments.bar.bar()"
+  );
+});
diff --git a/toolkit/components/extensions/test/xpcshell/test_ext_schemas_versioned.js b/toolkit/components/extensions/test/xpcshell/test_ext_schemas_versioned.js
new file mode 100644
index 0000000000..3dddbbc41b
--- /dev/null
+++ b/toolkit/components/extensions/test/xpcshell/test_ext_schemas_versioned.js
@@ -0,0 +1,714 @@
+"use strict";
+
+let json = [
+  {
+    namespace: "MV2",
+    max_manifest_version: 2,
+
+    properties: {
+      PROP1: { value: 20 },
+    },
+  },
+  {
+    namespace: "MV3",
+    min_manifest_version: 3,
+    properties: {
+      PROP1: { value: 20 },
+    },
+  },
+  {
+    namespace: "mixed",
+
+    properties: {
+      PROP_any: { value: 20 },
+      PROP_mv3: {
+        $ref: "submodule",
+      },
+    },
+    types: [
+      {
+        id: "manifestTest",
+        type: "object",
+        properties: {
+          // An example of extending the base type for permissions
+          permissions: {
+            type: "array",
+            items: {
+              $ref: "BaseType",
+            },
+            optional: true,
+            default: [],
+          },
+          // An example of differentiating versions of a manifest entry
+          multiple_choice: {
+            optional: true,
+            choices: [
+              {
+                max_manifest_version: 2,
+                type: "array",
+                items: {
+                  type: "string",
+                },
+              },
+              {
+                min_manifest_version: 3,
+                type: "array",
+                items: {
+                  type: "boolean",
+                },
+              },
+              {
+                type: "array",
+                items: {
+                  type: "object",
+                  properties: {
+                    value: { type: "boolean" },
+                  },
+                },
+              },
+            ],
+          },
+          accepting_unrecognized_props: {
+            optional: true,
+            type: "object",
+            properties: {
+              mv2_only_prop: {
+                type: "string",
+                optional: true,
+                max_manifest_version: 2,
+              },
+              mv3_only_prop: {
+                type: "string",
+                optional: true,
+                min_manifest_version: 3,
+              },
+              mv2_only_prop_with_default: {
+                type: "string",
+                optional: true,
+                default: "only in MV2",
+                max_manifest_version: 2,
+              },
+              mv3_only_prop_with_default: {
+                type: "string",
+                optional: true,
+                default: "only in MV3",
+                min_manifest_version: 3,
+              },
+            },
+            additionalProperties: { $ref: "UnrecognizedProperty" },
+          },
+        },
+      },
+      {
+        id: "submodule",
+        type: "object",
+        min_manifest_version: 3,
+        functions: [
+          {
+            name: "sub_foo",
+            type: "function",
+            parameters: [],
+            returns: { type: "integer" },
+          },
+          {
+            name: "sub_no_match",
+            type: "function",
+            max_manifest_version: 2,
+            parameters: [],
+            returns: { type: "integer" },
+          },
+        ],
+      },
+      {
+        id: "BaseType",
+        choices: [
+          {
+            type: "string",
+            enum: ["base"],
+          },
+        ],
+      },
+      {
+        id: "type_any",
+        type: "string",
+        enum: ["value1", "value2", "value3"],
+      },
+      {
+        id: "type_mv2",
+        max_manifest_version: 2,
+        type: "string",
+        enum: ["value1", "value2", "value3"],
+      },
+      {
+        id: "type_mv3",
+        min_manifest_version: 3,
+        type: "string",
+        enum: ["value1", "value2", "value3"],
+      },
+      {
+        id: "param_type_changed",
+        type: "array",
+        items: {
+          choices: [
+            { max_manifest_version: 2, type: "string" },
+            {
+              min_manifest_version: 3,
+              type: "boolean",
+            },
+          ],
+        },
+      },
+      {
+        id: "object_type_changed",
+        type: "object",
+        properties: {
+          prop_mv2: {
+            type: "string",
+            max_manifest_version: 2,
+          },
+          prop_mv3: {
+            type: "string",
+            min_manifest_version: 3,
+          },
+          prop_any: {
+            type: "string",
+          },
+        },
+      },
+      {
+        id: "no_valid_choices",
+        type: "array",
+        items: {
+          choices: [
+            { max_manifest_version: 1, type: "string" },
+            {
+              min_manifest_version: 4,
+              type: "boolean",
+            },
+          ],
+        },
+      },
+    ],
+
+    functions: [
+      {
+        name: "fun_param_type_versioned",
+        type: "function",
+        parameters: [{ name: "arg1", $ref: "param_type_changed" }],
+      },
+      {
+        name: "fun_mv2",
+        max_manifest_version: 2,
+        type: "function",
+        parameters: [
+          { name: "arg1", type: "integer", optional: true, default: 99 },
+          { name: "arg2", type: "boolean", optional: true },
+        ],
+      },
+      {
+        name: "fun_mv3",
+        min_manifest_version: 3,
+        type: "function",
+        parameters: [
+          { name: "arg1", type: "integer", optional: true, default: 99 },
+          { name: "arg2", type: "boolean", optional: true },
+        ],
+      },
+      {
+        name: "fun_param_change",
+        type: "function",
+        parameters: [{ name: "arg1", $ref: "object_type_changed" }],
+      },
+      {
+        name: "fun_no_valid_param",
+        type: "function",
+        parameters: [{ name: "arg1", $ref: "no_valid_choices" }],
+      },
+    ],
+    events: [
+      {
+        name: "onEvent_any",
+        type: "function",
+      },
+      {
+        name: "onEvent_mv2",
+        max_manifest_version: 2,
+        type: "function",
+      },
+      {
+        name: "onEvent_mv3",
+        min_manifest_version: 3,
+        type: "function",
+      },
+    ],
+  },
+  {
+    namespace: "mixed",
+    types: [
+      {
+        $extend: "BaseType",
+        choices: [
+          {
+            min_manifest_version: 3,
+            type: "string",
+            enum: ["extended"],
+          },
+        ],
+      },
+    ],
+  },
+  {
+    namespace: "mixed",
+    types: [
+      {
+        $extend: "manifestTest",
+        properties: {
+          versioned_extend: {
+            optional: true,
+            // just a simple type here
+            type: "string",
+            max_manifest_version: 2,
+          },
+        },
+      },
+    ],
+  },
+];
+
+add_task(async function setup() {
+  let url = "data:," + JSON.stringify(json);
+  Schemas._rootSchema = null;
+  await Schemas.load(url);
+
+  // We want the actual errors thrown here, and not warnings recast as errors.
+  ExtensionTestUtils.failOnSchemaWarnings(false);
+});
+
+add_task(async function test_inject_V2() {
+  // Test injecting into a V2 context.
+  let wrapper = getContextWrapper(2);
+
+  let root = {};
+  Schemas.inject(root, wrapper);
+
+  // Test elements available to both
+  Assert.equal(root.mixed.type_any.VALUE1, "value1", "type_any exists");
+  Assert.equal(root.mixed.PROP_any, 20, "mixed value property");
+
+  // Test elements available to MV2
+  Assert.equal(root.MV2.PROP1, 20, "MV2 value property");
+  Assert.equal(root.mixed.type_mv2.VALUE2, "value2", "type_mv2 exists");
+
+  // Test MV3 elements not available
+  Assert.equal(root.MV3, undefined, "MV3 not injected");
+  Assert.ok(!("MV3" in root), "MV3 not enumerable");
+  Assert.equal(
+    root.mixed.PROP_mv3,
+    undefined,
+    "mixed submodule property does not exist"
+  );
+  Assert.ok(
+    !("PROP_mv3" in root.mixed),
+    "mixed submodule property not enumerable"
+  );
+  Assert.equal(root.mixed.type_mv3, undefined, "type_mv3 does not exist");
+
+  // Function tests
+  Assert.ok(
+    "fun_param_type_versioned" in root.mixed,
+    "fun_param_type_versioned exists"
+  );
+  Assert.ok(
+    !!root.mixed.fun_param_type_versioned,
+    "fun_param_type_versioned exists"
+  );
+  Assert.ok("fun_mv2" in root.mixed, "fun_mv2 exists");
+  Assert.ok(!!root.mixed.fun_mv2, "fun_mv2 exists");
+  Assert.ok(!("fun_mv3" in root.mixed), "fun_mv3 does not exist");
+  Assert.ok(!root.mixed.fun_mv3, "fun_mv3 does not exist");
+
+  // Event tests
+  Assert.ok("onEvent_any" in root.mixed, "onEvent_any exists");
+  Assert.ok(!!root.mixed.onEvent_any, "onEvent_any exists");
+  Assert.ok("onEvent_mv2" in root.mixed, "onEvent_mv2 exists");
+  Assert.ok(!!root.mixed.onEvent_mv2, "onEvent_mv2 exists");
+  Assert.ok(!("onEvent_mv3" in root.mixed), "onEvent_mv3 does not exist");
+  Assert.ok(!root.mixed.onEvent_mv3, "onEvent_mv3 does not exist");
+
+  // Function call tests
+  root.mixed.fun_param_type_versioned(["hello"]);
+  wrapper.verify("call", "mixed", "fun_param_type_versioned", [["hello"]]);
+  Assert.throws(
+    () => root.mixed.fun_param_type_versioned([true]),
+    /Expected string instead of true/,
+    "fun_param_type_versioned should throw for invalid type"
+  );
+
+  let propObj = { prop_any: "prop_any", prop_mv2: "prop_mv2" };
+  root.mixed.fun_param_change(propObj);
+  wrapper.verify("call", "mixed", "fun_param_change", [propObj]);
+
+  // Still throw same error as we did before we knew of the MV3 property.
+  Assert.throws(
+    () => root.mixed.fun_param_change({ prop_mv3: "prop_mv3", ...propObj }),
+    /Type error for parameter arg1 \(Unexpected property "prop_mv3"\)/,
+    "generic unexpected property message for MV3 property in MV2 extension"
+  );
+
+  // But print the more specific and descriptive warning message to console.
+  wrapper.checkErrors([
+    `Property "prop_mv3" is unsupported in Manifest Version 2`,
+  ]);
+
+  Assert.throws(
+    () => root.mixed.fun_no_valid_param("anything"),
+    /Incorrect argument types for mixed.fun_no_valid_param/,
+    "fun_no_valid_param should throw for versioned type"
+  );
+});
+
+function normalizeTest(manifest, test, wrapper) {
+  let normalized = Schemas.normalize(manifest, "mixed.manifestTest", wrapper);
+  test(normalized);
+  // The test function should call wrapper.checkErrors if it expected errors.
+  // Here we call checkErrors again to ensure that there are not any unexpected
+  // errors left.
+  wrapper.checkErrors([]);
+}
+
+add_task(async function test_normalize_V2() {
+  let wrapper = getContextWrapper(2);
+
+  // Test normalize additions to the manifest structure
+  normalizeTest(
+    {
+      versioned_extend: "test",
+    },
+    normalized => {
+      Assert.equal(
+        normalized.value.versioned_extend,
+        "test",
+        "resources normalized"
+      );
+    },
+    wrapper
+  );
+
+  // Test normalizing baseType
+  normalizeTest(
+    {
+      permissions: ["base"],
+    },
+    normalized => {
+      Assert.equal(
+        normalized.value.permissions[0],
+        "base",
+        "resources normalized"
+      );
+    },
+    wrapper
+  );
+
+  normalizeTest(
+    {
+      permissions: ["extended"],
+    },
+    normalized => {
+      Assert.ok(
+        normalized.error.startsWith("Error processing permissions.0"),
+        `manifest normalized error ${normalized.error}`
+      );
+    },
+    wrapper
+  );
+
+  // Test normalizing a value
+  normalizeTest(
+    {
+      multiple_choice: ["foo.html"],
+    },
+    normalized => {
+      Assert.equal(
+        normalized.value.multiple_choice[0],
+        "foo.html",
+        "resources normalized"
+      );
+    },
+    wrapper
+  );
+
+  normalizeTest(
+    {
+      multiple_choice: [true],
+    },
+    normalized => {
+      Assert.ok(
+        normalized.error.startsWith("Error processing multiple_choice"),
+        "manifest error"
+      );
+    },
+    wrapper
+  );
+
+  normalizeTest(
+    {
+      multiple_choice: [
+        {
+          value: true,
+        },
+      ],
+    },
+    normalized => {
+      Assert.ok(
+        normalized.value.multiple_choice[0].value,
+        "resources normalized"
+      );
+    },
+    wrapper
+  );
+
+  // Tests that object definitions including additionalProperties can
+  // successfully accept objects from another manifest version, while ignoring
+  // the actual value from the non-matching manifest value.
+  normalizeTest(
+    {
+      accepting_unrecognized_props: {
+        mv2_only_prop: "mv2 here",
+        mv3_only_prop: "mv3 here",
+      },
+    },
+    normalized => {
+      equal(normalized.error, undefined, "no normalization error");
+      Assert.deepEqual(
+        normalized.value.accepting_unrecognized_props,
+        {
+          mv2_only_prop: "mv2 here",
+          mv2_only_prop_with_default: "only in MV2",
+        },
+        "Normalized object for MV2, without MV3-specific props"
+      );
+      wrapper.checkErrors([
+        `Property "mv3_only_prop" is unsupported in Manifest Version 2`,
+      ]);
+    },
+    wrapper
+  );
+});
+
+add_task(async function test_inject_V3() {
+  // Test injecting into a V3 context.
+  let wrapper = getContextWrapper(3);
+
+  let root = {};
+  Schemas.inject(root, wrapper);
+
+  // Test elements available to both
+  Assert.equal(root.mixed.type_any.VALUE1, "value1", "type_any exists");
+  Assert.equal(root.mixed.PROP_any, 20, "mixed value property");
+
+  // Test elements available to MV2
+  Assert.equal(root.MV2, undefined, "MV2 value property");
+  Assert.ok(!("MV2" in root), "MV2 not enumerable");
+  Assert.equal(root.mixed.type_mv2, undefined, "type_mv2 does not exist");
+  Assert.ok(!("type_mv2" in root.mixed), "type_mv2 not enumerable");
+
+  // Test MV3 elements not available
+  Assert.equal(root.MV3.PROP1, 20, "MV3 injected");
+  Assert.ok(!!root.mixed.PROP_mv3, "mixed submodule property exists");
+  Assert.equal(root.mixed.type_mv3.VALUE3, "value3", "type_mv3 exists");
+
+  // Versioned submodule
+  Assert.ok(!!root.mixed.PROP_mv3.sub_foo, "mixed submodule sub_foo exists");
+  Assert.ok(
+    !root.mixed.PROP_mv3.sub_no_match,
+    "mixed submodule sub_no_match does not exist"
+  );
+  Assert.ok(
+    !("sub_no_match" in root.mixed.PROP_mv3),
+    "mixed submodule sub_no_match is not enumerable"
+  );
+
+  // Function tests
+  Assert.ok(
+    "fun_param_type_versioned" in root.mixed,
+    "fun_param_type_versioned exists"
+  );
+  Assert.ok(
+    !!root.mixed.fun_param_type_versioned,
+    "fun_param_type_versioned exists"
+  );
+  Assert.ok(!("fun_mv2" in root.mixed), "fun_mv2 does not exist");
+  Assert.ok(!root.mixed.fun_mv2, "fun_mv2 does not exist");
+  Assert.ok("fun_mv3" in root.mixed, "fun_mv3 exists");
+  Assert.ok(!!root.mixed.fun_mv3, "fun_mv3 exists");
+
+  // Event tests
+  Assert.ok("onEvent_any" in root.mixed, "onEvent_any exists");
+  Assert.ok(!!root.mixed.onEvent_any, "onEvent_any exists");
+  Assert.ok(!("onEvent_mv2" in root.mixed), "onEvent_mv2 not enumerable");
+  Assert.ok(!root.mixed.onEvent_mv2, "onEvent_mv2 does not exist");
+  Assert.ok("onEvent_mv3" in root.mixed, "onEvent_mv3 exists");
+  Assert.ok(!!root.mixed.onEvent_mv3, "onEvent_mv3 exists");
+
+  // Function call tests
+  root.mixed.fun_param_type_versioned([true]);
+  wrapper.verify("call", "mixed", "fun_param_type_versioned", [[true]]);
+  Assert.throws(
+    () => root.mixed.fun_param_type_versioned(["hello"]),
+    /Expected boolean instead of "hello"/,
+    "should throw for invalid type"
+  );
+
+  let propObj = { prop_any: "prop_any", prop_mv3: "prop_mv3" };
+  root.mixed.fun_param_change(propObj);
+  wrapper.verify("call", "mixed", "fun_param_change", [propObj]);
+  Assert.throws(
+    () => root.mixed.fun_param_change({ prop_mv2: "prop_mv2", ...propObj }),
+    /Unexpected property "prop_mv2"/,
+    "should throw for versioned type"
+  );
+  wrapper.checkErrors([
+    `Property "prop_mv2" is unsupported in Manifest Version 3`,
+  ]);
+
+  root.mixed.PROP_mv3.sub_foo();
+  wrapper.verify("call", "mixed.PROP_mv3", "sub_foo", []);
+  Assert.throws(
+    () => root.mixed.PROP_mv3.sub_no_match(),
+    /TypeError: root.mixed.PROP_mv3.sub_no_match is not a function/,
+    "sub_no_match should throw"
+  );
+});
+
+add_task(async function test_normalize_V3() {
+  let wrapper = getContextWrapper(3);
+
+  // Test normalize additions to the manifest structure
+  normalizeTest(
+    {
+      versioned_extend: "test",
+    },
+    normalized => {
+      Assert.equal(
+        normalized.error,
+        `Unexpected property "versioned_extend"`,
+        "expected manifest error"
+      );
+      wrapper.checkErrors([
+        `Property "versioned_extend" is unsupported in Manifest Version 3`,
+      ]);
+    },
+    wrapper
+  );
+
+  // Test normalizing baseType
+  normalizeTest(
+    {
+      permissions: ["base"],
+    },
+    normalized => {
+      Assert.equal(
+        normalized.value.permissions[0],
+        "base",
+        "resources normalized"
+      );
+    },
+    wrapper
+  );
+
+  normalizeTest(
+    {
+      permissions: ["extended"],
+    },
+    normalized => {
+      Assert.equal(
+        normalized.value.permissions[0],
+        "extended",
+        "resources normalized"
+      );
+    },
+    wrapper
+  );
+
+  // Test normalizing a value
+  normalizeTest(
+    {
+      multiple_choice: ["foo.html"],
+    },
+    normalized => {
+      Assert.ok(
+        normalized.error.startsWith("Error processing multiple_choice"),
+        "manifest error"
+      );
+    },
+    wrapper
+  );
+
+  normalizeTest(
+    {
+      multiple_choice: [true],
+    },
+    normalized => {
+      Assert.equal(
+        normalized.value.multiple_choice[0],
+        true,
+        "resources normalized"
+      );
+    },
+    wrapper
+  );
+
+  normalizeTest(
+    {
+      multiple_choice: [
+        {
+          value: true,
+        },
+      ],
+    },
+    normalized => {
+      Assert.ok(
+        normalized.value.multiple_choice[0].value,
+        "resources normalized"
+      );
+    },
+    wrapper
+  );
+
+  wrapper.tallied = null;
+
+  normalizeTest(
+    {},
+    normalized => {
+      ok(!normalized.error, "manifest normalized");
+    },
+    wrapper
+  );
+
+  // Tests that object definitions including additionalProperties can
+  // successfully accept objects from another manifest version, while ignoring
+  // the actual value from the non-matching manifest value.
+  normalizeTest(
+    {
+      accepting_unrecognized_props: {
+        mv2_only_prop: "mv2 here",
+        mv3_only_prop: "mv3 here",
+      },
+    },
+    normalized => {
+      equal(normalized.error, undefined, "no normalization error");
+      Assert.deepEqual(
+        normalized.value.accepting_unrecognized_props,
+        {
+          mv3_only_prop: "mv3 here",
+          mv3_only_prop_with_default: "only in MV3",
+        },
+        "Normalized object for MV3, without MV2-specific props"
+      );
+      wrapper.checkErrors([
+        `Property "mv2_only_prop" is unsupported in Manifest Version 3`,
+      ]);
+    },
+    wrapper
+  );
+});
diff --git a/toolkit/components/extensions/test/xpcshell/test_ext_script_filenames.js b/toolkit/components/extensions/test/xpcshell/test_ext_script_filenames.js
new file mode 100644
index 0000000000..8e2f6c7b0d
--- /dev/null
+++ b/toolkit/components/extensions/test/xpcshell/test_ext_script_filenames.js
@@ -0,0 +1,366 @@
+"use strict";
+
+// There is a rejection emitted when a JS file fails to load. On Android,
+// extensions run on the main process and this rejection causes test failures,
+// which is essentially why we need to allow the rejection below.
+PromiseTestUtils.allowMatchingRejectionsGlobally(
+  /Unable to load script.*content_script/
+);
+
+const server = createHttpServer();
+server.registerDirectory("/data/", do_get_file("data"));
+
+const BASE_URL = `http://localhost:${server.identity.primaryPort}/data`;
+
+function computeSHA256Hash(text) {
+  const hasher = Cc["@mozilla.org/security/hash;1"].createInstance(
+    Ci.nsICryptoHash
+  );
+  hasher.init(Ci.nsICryptoHash.SHA256);
+  hasher.update(
+    text.split("").map(c => c.charCodeAt(0)),
+    text.length
+  );
+  return hasher.finish(true);
+}
+
+// This function represents a dummy content or background script that the test
+// cases below should attempt to load but it shouldn't be loaded because we
+// check the extensions of JavaScript files in `nsJARChannel`.
+function scriptThatShouldNotBeLoaded() {
+  browser.test.fail("this should not be executed");
+}
+
+function scriptThatAlwaysRuns() {
+  browser.test.sendMessage("content-script-loaded");
+}
+
+// We use these variables in combination with `scriptThatAlwaysRuns()` to send a
+// signal to the extension and avoid the page to be closed too soon.
+const alwaysRunsFileName = "always_run.js";
+const alwaysRunsContentScript = {
+  matches: ["<all_urls>"],
+  js: [alwaysRunsFileName],
+  run_at: "document_start",
+};
+
+add_task(async function test_content_script_filename_without_extension() {
+  // Filenames without any extension should not be loaded.
+  let invalidFileName = "content_script";
+  let extensionData = {
+    manifest: {
+      content_scripts: [
+        alwaysRunsContentScript,
+        {
+          matches: ["<all_urls>"],
+          js: [invalidFileName],
+        },
+      ],
+    },
+    files: {
+      [invalidFileName]: scriptThatShouldNotBeLoaded,
+      [alwaysRunsFileName]: scriptThatAlwaysRuns,
+    },
+  };
+
+  let extension = ExtensionTestUtils.loadExtension(extensionData);
+  await extension.startup();
+
+  let contentPage = await ExtensionTestUtils.loadContentPage(
+    `${BASE_URL}/file_sample.html`
+  );
+
+  await extension.awaitMessage("content-script-loaded");
+
+  await contentPage.close();
+  await extension.unload();
+});
+
+add_task(async function test_content_script_filename_with_invalid_extension() {
+  let validFileName = "content_script.js";
+  let invalidFileName = "content_script.xyz";
+  let extensionData = {
+    manifest: {
+      content_scripts: [
+        alwaysRunsContentScript,
+        {
+          matches: ["<all_urls>"],
+          js: [validFileName, invalidFileName],
+        },
+      ],
+    },
+    files: {
+      // This makes sure that, when one of the content scripts fails to load,
+      // none of the content scripts are executed.
+      [validFileName]: scriptThatShouldNotBeLoaded,
+      [invalidFileName]: scriptThatShouldNotBeLoaded,
+      [alwaysRunsFileName]: scriptThatAlwaysRuns,
+    },
+  };
+
+  let extension = ExtensionTestUtils.loadExtension(extensionData);
+  await extension.startup();
+
+  let contentPage = await ExtensionTestUtils.loadContentPage(
+    `${BASE_URL}/file_sample.html`
+  );
+
+  await extension.awaitMessage("content-script-loaded");
+
+  await contentPage.close();
+  await extension.unload();
+});
+
+add_task(async function test_bg_script_injects_script_with_invalid_ext() {
+  function backgroundScript() {
+    browser.test.sendMessage("background-script-loaded");
+  }
+
+  let validFileName = "background.js";
+  let invalidFileName = "invalid_background.xyz";
+  let extensionData = {
+    background() {
+      const script = document.createElement("script");
+      script.src = "./invalid_background.xyz";
+      document.head.appendChild(script);
+
+      const validScript = document.createElement("script");
+      validScript.src = "./background.js";
+      document.head.appendChild(validScript);
+    },
+    files: {
+      [invalidFileName]: scriptThatShouldNotBeLoaded,
+      [validFileName]: backgroundScript,
+    },
+  };
+
+  let extension = ExtensionTestUtils.loadExtension(extensionData);
+  await extension.startup();
+
+  await extension.awaitMessage("background-script-loaded");
+
+  await extension.unload();
+});
+
+add_task(async function test_background_scripts() {
+  function backgroundScript() {
+    browser.test.sendMessage("background-script-loaded");
+  }
+
+  let validFileName = "background.js";
+  let invalidFileName = "invalid_background.xyz";
+  let extensionData = {
+    manifest: {
+      background: {
+        scripts: [invalidFileName, validFileName],
+      },
+    },
+    files: {
+      [invalidFileName]: scriptThatShouldNotBeLoaded,
+      [validFileName]: backgroundScript,
+    },
+  };
+
+  let extension = ExtensionTestUtils.loadExtension(extensionData);
+  await extension.startup();
+
+  await extension.awaitMessage("background-script-loaded");
+
+  await extension.unload();
+});
+
+add_task(async function test_background_page_injects_scripts_inline() {
+  function injectedBackgroundScript() {
+    browser.test.log(
+      "inline script injectedBackgroundScript has been executed"
+    );
+    browser.test.sendMessage("background-script-loaded");
+  }
+
+  let backgroundHtmlPage = "background_page.html";
+  let validFileName = "injected_background.js";
+  let invalidFileName = "invalid_background.xyz";
+
+  let inlineScript = `(${function () {
+    const script = document.createElement("script");
+    script.src = "./invalid_background.xyz";
+    document.head.appendChild(script);
+    const validScript = document.createElement("script");
+    validScript.src = "./injected_background.js";
+    document.head.appendChild(validScript);
+  }})()`;
+
+  const inlineScriptSHA256 = computeSHA256Hash(inlineScript);
+
+  info(
+    `Computed sha256 for the inline script injectedBackgroundScript: ${inlineScriptSHA256}`
+  );
+
+  let extensionData = {
+    manifest: {
+      background: { page: backgroundHtmlPage },
+      content_security_policy: [
+        "script-src",
+        "'self'",
+        `'sha256-${inlineScriptSHA256}'`,
+        ";",
+      ].join(" "),
+    },
+    files: {
+      [invalidFileName]: scriptThatShouldNotBeLoaded,
+      [validFileName]: injectedBackgroundScript,
+      "pre-script.js": () => {
+        window.onsecuritypolicyviolation = evt => {
+          const { violatedDirective, originalPolicy } = evt;
+          browser.test.fail(
+            `Unexpected csp violation: ${JSON.stringify({
+              violatedDirective,
+              originalPolicy,
+            })}`
+          );
+          // Let the test to fail immediately when an unexpected csp violation
+          // prevented the inline script from being executed successfully.
+          browser.test.sendMessage("background-script-loaded");
+        };
+      },
+      [backgroundHtmlPage]: `
+        <!DOCTYPE html>
+        <html>
+          <head>
+            <meta charset="utf-8"></head>
+            <script src="pre-script.js"></script>
+            <script>${inlineScript}</script>
+          </head>
+        </html>`,
+    },
+  };
+
+  let extension = ExtensionTestUtils.loadExtension(extensionData);
+  await extension.startup();
+
+  await extension.awaitMessage("background-script-loaded");
+
+  await extension.unload();
+});
+
+add_task(async function test_background_page_injects_scripts() {
+  // This is the initial background script loaded in the HTML page.
+  function backgroundScript() {
+    const script = document.createElement("script");
+    script.src = "./invalid_background.xyz";
+    document.head.appendChild(script);
+
+    const validScript = document.createElement("script");
+    validScript.src = "./injected_background.js";
+    document.head.appendChild(validScript);
+  }
+
+  // This is the script injected by the script defined in `backgroundScript()`.
+  function injectedBackgroundScript() {
+    browser.test.sendMessage("background-script-loaded");
+  }
+
+  let backgroundHtmlPage = "background_page.html";
+  let validFileName = "injected_background.js";
+  let invalidFileName = "invalid_background.xyz";
+  let extensionData = {
+    manifest: {
+      background: { page: backgroundHtmlPage },
+    },
+    files: {
+      [invalidFileName]: scriptThatShouldNotBeLoaded,
+      [validFileName]: injectedBackgroundScript,
+      [backgroundHtmlPage]: `
+        <html>
+          <head>
+            <meta charset="utf-8"></head>
+            <script src="./background.js"></script>
+          </head>
+        </html>`,
+      "background.js": backgroundScript,
+    },
+  };
+
+  let extension = ExtensionTestUtils.loadExtension(extensionData);
+  await extension.startup();
+
+  await extension.awaitMessage("background-script-loaded");
+
+  await extension.unload();
+});
+
+add_task(async function test_background_script_registers_content_script() {
+  let invalidFileName = "content_script";
+  let extensionData = {
+    manifest: {
+      permissions: ["<all_urls>"],
+    },
+    async background() {
+      await browser.contentScripts.register({
+        js: [{ file: "/content_script" }],
+        matches: ["<all_urls>"],
+      });
+      browser.test.sendMessage("background-script-loaded");
+    },
+    files: {
+      [invalidFileName]: scriptThatShouldNotBeLoaded,
+    },
+  };
+
+  let extension = ExtensionTestUtils.loadExtension(extensionData);
+  await extension.startup();
+
+  let contentPage = await ExtensionTestUtils.loadContentPage(
+    `${BASE_URL}/file_sample.html`
+  );
+
+  await extension.awaitMessage("background-script-loaded");
+
+  await contentPage.close();
+  await extension.unload();
+});
+
+add_task(async function test_web_accessible_resources() {
+  function contentScript() {
+    const script = document.createElement("script");
+    script.src = browser.runtime.getURL("content_script.css");
+    script.onerror = () => {
+      browser.test.sendMessage("second-content-script-loaded");
+    };
+
+    document.head.appendChild(script);
+  }
+
+  let contentScriptFileName = "content_script.js";
+  let invalidFileName = "content_script.css";
+  let extensionData = {
+    manifest: {
+      web_accessible_resources: [invalidFileName],
+      content_scripts: [
+        alwaysRunsContentScript,
+        {
+          matches: ["<all_urls>"],
+          js: [contentScriptFileName],
+        },
+      ],
+    },
+    files: {
+      [invalidFileName]: scriptThatShouldNotBeLoaded,
+      [contentScriptFileName]: contentScript,
+      [alwaysRunsFileName]: scriptThatAlwaysRuns,
+    },
+  };
+
+  let extension = ExtensionTestUtils.loadExtension(extensionData);
+  await extension.startup();
+
+  let contentPage = await ExtensionTestUtils.loadContentPage(
+    `${BASE_URL}/file_sample.html`
+  );
+
+  await extension.awaitMessage("content-script-loaded");
+  await extension.awaitMessage("second-content-script-loaded");
+
+  await contentPage.close();
+  await extension.unload();
+});
diff --git a/toolkit/components/extensions/test/xpcshell/test_ext_scripting_contentScripts.js b/toolkit/components/extensions/test/xpcshell/test_ext_scripting_contentScripts.js
new file mode 100644
index 0000000000..464c6bd31d
--- /dev/null
+++ b/toolkit/components/extensions/test/xpcshell/test_ext_scripting_contentScripts.js
@@ -0,0 +1,412 @@
+"use strict";
+
+const server = createHttpServer();
+server.registerDirectory("/data/", do_get_file("data"));
+
+const BASE_URL = `http://localhost:${server.identity.primaryPort}/data`;
+
+// ExtensionContent.jsm needs to know when it's running from xpcshell, to use
+// the right timeout for content scripts executed at document_idle.
+ExtensionTestUtils.mockAppInfo();
+
+Services.prefs.setBoolPref("extensions.manifestV3.enabled", true);
+
+const makeExtension = ({ manifest: manifestProps, ...otherProps }) => {
+  return ExtensionTestUtils.loadExtension({
+    manifest: {
+      manifest_version: 3,
+      permissions: ["scripting"],
+      host_permissions: ["http://localhost/*"],
+      granted_host_permissions: true,
+      ...manifestProps,
+    },
+    temporarilyInstalled: true,
+    ...otherProps,
+  });
+};
+
+add_task(async function test_registerContentScripts_runAt() {
+  let extension = makeExtension({
+    async background() {
+      const TEST_CASES = [
+        {
+          title: "runAt: document_idle",
+          params: [
+            {
+              id: "script-idle",
+              js: ["script-idle.js"],
+              matches: ["http://*/*/file_sample.html"],
+              runAt: "document_idle",
+              persistAcrossSessions: false,
+            },
+          ],
+        },
+        {
+          title: "no runAt specified",
+          params: [
+            {
+              id: "script-idle-default",
+              js: ["script-idle-default.js"],
+              matches: ["http://*/*/file_sample.html"],
+              // `runAt` defaults to `document_idle`.
+              persistAcrossSessions: false,
+            },
+          ],
+        },
+        {
+          title: "runAt: document_end",
+          params: [
+            {
+              id: "script-end",
+              js: ["script-end.js"],
+              matches: ["http://*/*/file_sample.html"],
+              runAt: "document_end",
+              persistAcrossSessions: false,
+            },
+          ],
+        },
+        {
+          title: "runAt: document_start",
+          params: [
+            {
+              id: "script-start",
+              js: ["script-start.js"],
+              matches: ["http://*/*/file_sample.html"],
+              runAt: "document_start",
+              persistAcrossSessions: false,
+            },
+          ],
+        },
+      ];
+
+      let scripts = await browser.scripting.getRegisteredContentScripts();
+      browser.test.assertEq(0, scripts.length, "expected no registered script");
+
+      for (const { title, params } of TEST_CASES) {
+        const res = await browser.scripting.registerContentScripts(params);
+        browser.test.assertEq(undefined, res, `${title} - expected no result`);
+      }
+
+      scripts = await browser.scripting.getRegisteredContentScripts();
+      browser.test.assertEq(
+        TEST_CASES.length,
+        scripts.length,
+        `expected ${TEST_CASES.length} registered scripts`
+      );
+      browser.test.assertEq(
+        JSON.stringify([
+          {
+            id: "script-idle",
+            allFrames: false,
+            matches: ["http://*/*/file_sample.html"],
+            runAt: "document_idle",
+            persistAcrossSessions: false,
+            js: ["script-idle.js"],
+          },
+          {
+            id: "script-idle-default",
+            allFrames: false,
+            matches: ["http://*/*/file_sample.html"],
+            runAt: "document_idle",
+            persistAcrossSessions: false,
+            js: ["script-idle-default.js"],
+          },
+          {
+            id: "script-end",
+            allFrames: false,
+            matches: ["http://*/*/file_sample.html"],
+            runAt: "document_end",
+            persistAcrossSessions: false,
+            js: ["script-end.js"],
+          },
+          {
+            id: "script-start",
+            allFrames: false,
+            matches: ["http://*/*/file_sample.html"],
+            runAt: "document_start",
+            persistAcrossSessions: false,
+            js: ["script-start.js"],
+          },
+        ]),
+        JSON.stringify(scripts),
+        "got expected scripts"
+      );
+
+      browser.test.sendMessage("background-ready");
+    },
+    files: {
+      "script-start.js": () => {
+        browser.test.assertEq(
+          "loading",
+          document.readyState,
+          "expected state 'loading' at document_start"
+        );
+        browser.test.sendMessage("script-ran", "script-start.js");
+      },
+      "script-end.js": () => {
+        browser.test.assertTrue(
+          ["interactive", "complete"].includes(document.readyState),
+          `expected state 'interactive' or 'complete' at document_end, got: ${document.readyState}`
+        );
+        browser.test.sendMessage("script-ran", "script-end.js");
+      },
+      "script-idle.js": () => {
+        browser.test.assertEq(
+          "complete",
+          document.readyState,
+          "expected state 'complete' at document_idle"
+        );
+        browser.test.sendMessage("script-ran", "script-idle.js");
+      },
+      "script-idle-default.js": () => {
+        browser.test.assertEq(
+          "complete",
+          document.readyState,
+          "expected state 'complete' at document_idle"
+        );
+        browser.test.sendMessage("script-ran", "script-idle-default.js");
+      },
+    },
+  });
+
+  let scriptsRan = [];
+  let completePromise = new Promise(resolve => {
+    extension.onMessage("script-ran", result => {
+      scriptsRan.push(result);
+
+      // The value below should be updated when TEST_CASES above is changed.
+      if (scriptsRan.length === 4) {
+        resolve();
+      }
+    });
+  });
+
+  await extension.startup();
+  await extension.awaitMessage("background-ready");
+
+  let contentPage = await ExtensionTestUtils.loadContentPage(
+    `${BASE_URL}/file_sample.html`
+  );
+
+  await completePromise;
+
+  Assert.deepEqual(
+    [
+      "script-start.js",
+      "script-end.js",
+      "script-idle.js",
+      "script-idle-default.js",
+    ],
+    scriptsRan,
+    "got expected executed scripts"
+  );
+
+  await contentPage.close();
+  await extension.unload();
+});
+
+add_task(async function test_register_and_unregister() {
+  let extension = makeExtension({
+    async background() {
+      const script = {
+        id: "a-script",
+        js: ["script.js"],
+        matches: ["http://*/*/file_sample.html"],
+        persistAcrossSessions: false,
+      };
+
+      let results = await Promise.allSettled([
+        browser.scripting.registerContentScripts([script]),
+        browser.scripting.unregisterContentScripts(),
+      ]);
+
+      browser.test.assertEq(
+        2,
+        results.filter(result => result.status === "fulfilled").length,
+        "got expected number of fulfilled promises"
+      );
+
+      let scripts = await browser.scripting.getRegisteredContentScripts();
+      browser.test.assertEq(0, scripts.length, "expected no registered script");
+
+      browser.test.sendMessage("background-done");
+    },
+    files: {
+      "script.js": "",
+    },
+  });
+
+  await extension.startup();
+  await extension.awaitMessage("background-done");
+
+  // Verify that the registered content scripts on the extension are correct.
+  let contentScripts = Array.from(
+    extension.extension.registeredContentScripts.values()
+  );
+  Assert.equal(0, contentScripts.length, "expected no registered scripts");
+
+  await extension.unload();
+});
+
+add_task(async function test_register_and_unregister_multiple_times() {
+  let extension = makeExtension({
+    async background() {
+      // We use the same script `id` on purpose in this test.
+      let results = await Promise.allSettled([
+        browser.scripting.registerContentScripts([
+          {
+            id: "a-script",
+            js: ["script-1.js"],
+            matches: ["http://*/*/file_sample.html"],
+            persistAcrossSessions: false,
+          },
+        ]),
+        browser.scripting.unregisterContentScripts(),
+        browser.scripting.registerContentScripts([
+          {
+            id: "a-script",
+            js: ["script-2.js"],
+            matches: ["http://*/*/file_sample.html"],
+            persistAcrossSessions: false,
+          },
+        ]),
+        browser.scripting.unregisterContentScripts(),
+        browser.scripting.registerContentScripts([
+          {
+            id: "a-script",
+            js: ["script-3.js"],
+            matches: ["http://*/*/file_sample.html"],
+            persistAcrossSessions: false,
+          },
+        ]),
+      ]);
+
+      browser.test.assertEq(
+        5,
+        results.filter(result => result.status === "fulfilled").length,
+        "got expected number of fulfilled promises"
+      );
+
+      let scripts = await browser.scripting.getRegisteredContentScripts();
+      browser.test.assertEq(1, scripts.length, "expected 1 registered script");
+
+      browser.test.sendMessage("background-done");
+    },
+    files: {
+      "script-1.js": "",
+      "script-2.js": "",
+      "script-3.js": "",
+    },
+  });
+
+  await extension.startup();
+  await extension.awaitMessage("background-done");
+
+  // Verify that the registered content scripts on the extension are correct.
+  let contentScripts = Array.from(
+    extension.extension.registeredContentScripts.values()
+  );
+  Assert.equal(1, contentScripts.length, "expected 1 registered script");
+  Assert.ok(
+    contentScripts[0].jsPaths[0].endsWith("script-3.js"),
+    "got expected js file"
+  );
+
+  await extension.unload();
+});
+
+add_task(async function test_register_update_and_unregister() {
+  let extension = makeExtension({
+    async background() {
+      const script = {
+        id: "a-script",
+        js: ["script-1.js"],
+        matches: ["http://*/*/file_sample.html"],
+        persistAcrossSessions: false,
+      };
+      const updatedScript1 = { ...script, js: ["script-2.js"] };
+      const updatedScript2 = { ...script, js: ["script-3.js"] };
+
+      let results = await Promise.allSettled([
+        browser.scripting.registerContentScripts([script]),
+        browser.scripting.updateContentScripts([updatedScript1]),
+        browser.scripting.updateContentScripts([updatedScript2]),
+        browser.scripting.getRegisteredContentScripts(),
+        browser.scripting.unregisterContentScripts(),
+        browser.scripting.updateContentScripts([script]),
+      ]);
+
+      browser.test.assertEq(6, results.length, "expected 6 results");
+      browser.test.assertEq(
+        "fulfilled",
+        results[0].status,
+        "expected fulfilled promise (registeredContentScripts)"
+      );
+      browser.test.assertEq(
+        "fulfilled",
+        results[1].status,
+        "expected fulfilled promise (updateContentScripts)"
+      );
+      browser.test.assertEq(
+        "fulfilled",
+        results[2].status,
+        "expected fulfilled promise (updateContentScripts)"
+      );
+      browser.test.assertEq(
+        "fulfilled",
+        results[3].status,
+        "expected fulfilled promise (getRegisteredContentScripts)"
+      );
+      browser.test.assertEq(
+        JSON.stringify([
+          {
+            id: "a-script",
+            allFrames: false,
+            matches: ["http://*/*/file_sample.html"],
+            runAt: "document_idle",
+            persistAcrossSessions: false,
+            js: ["script-3.js"],
+          },
+        ]),
+        JSON.stringify(results[3].value),
+        "expected updated content script"
+      );
+      browser.test.assertEq(
+        "fulfilled",
+        results[4].status,
+        "expected fulfilled promise (unregisterContentScripts)"
+      );
+      browser.test.assertEq(
+        "rejected",
+        results[5].status,
+        "expected rejected promise because script should have been unregistered"
+      );
+      browser.test.assertEq(
+        `Content script with id "${script.id}" does not exist.`,
+        results[5].reason.message,
+        "expected error message about script not found"
+      );
+
+      let scripts = await browser.scripting.getRegisteredContentScripts();
+      browser.test.assertEq(0, scripts.length, "expected no registered script");
+
+      browser.test.sendMessage("background-done");
+    },
+    files: {
+      "script-1.js": "",
+      "script-2.js": "",
+      "script-3.js": "",
+    },
+  });
+
+  await extension.startup();
+  await extension.awaitMessage("background-done");
+
+  // Verify that the registered content scripts on the extension are correct.
+  let contentScripts = Array.from(
+    extension.extension.registeredContentScripts.values()
+  );
+  Assert.equal(0, contentScripts.length, "expected no registered scripts");
+
+  await extension.unload();
+});
diff --git a/toolkit/components/extensions/test/xpcshell/test_ext_scripting_contentScripts_css.js b/toolkit/components/extensions/test/xpcshell/test_ext_scripting_contentScripts_css.js
new file mode 100644
index 0000000000..21190d2d59
--- /dev/null
+++ b/toolkit/components/extensions/test/xpcshell/test_ext_scripting_contentScripts_css.js
@@ -0,0 +1,331 @@
+"use strict";
+
+const server = createHttpServer();
+server.registerDirectory("/data/", do_get_file("data"));
+
+const BASE_URL = `http://localhost:${server.identity.primaryPort}/data`;
+
+// ExtensionContent.jsm needs to know when it's running from xpcshell, to use
+// the right timeout for content scripts executed at document_idle.
+ExtensionTestUtils.mockAppInfo();
+
+Services.prefs.setBoolPref("extensions.manifestV3.enabled", true);
+
+const makeExtension = ({ manifest: manifestProps, ...otherProps }) => {
+  return ExtensionTestUtils.loadExtension({
+    manifest: {
+      manifest_version: 3,
+      permissions: ["scripting"],
+      host_permissions: ["http://localhost/*"],
+      granted_host_permissions: true,
+      ...manifestProps,
+    },
+    allowInsecureRequests: true,
+    temporarilyInstalled: true,
+    ...otherProps,
+  });
+};
+
+add_task(async function test_registerContentScripts_css() {
+  let extension = makeExtension({
+    async background() {
+      // This script is injected in all frames after the styles so that we can
+      // verify the registered styles.
+      const checkAppliedStyleScript = {
+        id: "check-applied-styles",
+        allFrames: true,
+        matches: ["http://*/*/*.html"],
+        runAt: "document_idle",
+        persistAcrossSessions: false,
+        js: ["check-applied-styles.js"],
+      };
+
+      // Listen to the `load-test-case` message and unregister/register new
+      // content scripts.
+      browser.test.onMessage.addListener(async (msg, data) => {
+        switch (msg) {
+          case "load-test-case":
+            const { title, params, skipCheckScriptRegistration } = data;
+            const expectedScripts = [];
+
+            await browser.scripting.unregisterContentScripts();
+
+            if (!skipCheckScriptRegistration) {
+              await browser.scripting.registerContentScripts([
+                checkAppliedStyleScript,
+              ]);
+
+              expectedScripts.push(checkAppliedStyleScript);
+            }
+
+            expectedScripts.push(...params);
+
+            const res = await browser.scripting.registerContentScripts(params);
+            browser.test.assertEq(
+              res,
+              undefined,
+              `${title} - expected no result`
+            );
+            const scripts =
+              await browser.scripting.getRegisteredContentScripts();
+            browser.test.assertEq(
+              expectedScripts.length,
+              scripts.length,
+              `${title} - expected ${expectedScripts.length} registered scripts`
+            );
+            browser.test.assertEq(
+              JSON.stringify(expectedScripts),
+              JSON.stringify(scripts),
+              `${title} - got expected registered scripts`
+            );
+
+            browser.test.sendMessage(`${msg}-done`);
+            break;
+          default:
+            browser.test.fail(`received unexpected message: ${msg}`);
+        }
+      });
+
+      browser.test.sendMessage("background-ready");
+    },
+    files: {
+      "check-applied-styles.js": () => {
+        browser.test.sendMessage(
+          `background-color-${location.pathname.split("/").pop()}`,
+          getComputedStyle(document.querySelector("#test")).backgroundColor
+        );
+      },
+      "style-1.css": "#test { background-color: rgb(255, 0, 0); }",
+      "style-2.css": "#test { background-color: rgb(0, 0, 255); }",
+      "style-3.css": "html  { background-color: rgb(0, 255, 0); }",
+      "script-document-start.js": async () => {
+        const testElement = document.querySelector("html");
+
+        browser.test.assertEq(
+          "rgb(0, 255, 0)",
+          getComputedStyle(testElement).backgroundColor,
+          "got expected style in script-document-start.js"
+        );
+
+        testElement.style.backgroundColor = "rgb(4, 4, 4)";
+      },
+      "check-applied-styles-document-start.js": () => {
+        browser.test.sendMessage(
+          `background-color-${location.pathname.split("/").pop()}`,
+          getComputedStyle(document.querySelector("html")).backgroundColor
+        );
+      },
+      "script-document-end-and-idle.js": () => {
+        const testElement = document.querySelector("#test");
+
+        browser.test.assertEq(
+          "rgb(255, 0, 0)",
+          getComputedStyle(testElement).backgroundColor,
+          "got expected style in script-document-end-and-idle.js"
+        );
+
+        testElement.style.backgroundColor = "rgb(5, 5, 5)";
+      },
+    },
+  });
+
+  const TEST_CASES = [
+    {
+      title: "a css file",
+      params: [
+        {
+          id: "style-1",
+          allFrames: false,
+          matches: ["http://*/*/*.html"],
+          // TODO: Bug 1759117 - runAt should not affect css injection
+          runAt: "document_start",
+          persistAcrossSessions: false,
+          css: ["style-1.css"],
+        },
+      ],
+      expected: ["rgb(255, 0, 0)", "rgba(0, 0, 0, 0)"],
+    },
+    {
+      title: "css and allFrames: true",
+      params: [
+        {
+          id: "style-1",
+          allFrames: true,
+          matches: ["http://*/*/*.html"],
+          // TODO: Bug 1759117 - runAt should not affect css injection
+          runAt: "document_start",
+          persistAcrossSessions: false,
+          css: ["style-1.css"],
+        },
+      ],
+      expected: ["rgb(255, 0, 0)", "rgb(255, 0, 0)"],
+    },
+    {
+      title: "css and allFrames: true but matches restricted to top frame",
+      params: [
+        {
+          id: "style-1",
+          allFrames: true,
+          matches: ["http://*/*/file_with_iframe.html"],
+          // TODO: Bug 1759117 - runAt should not affect css injection
+          runAt: "document_start",
+          persistAcrossSessions: false,
+          css: ["style-1.css"],
+        },
+      ],
+      expected: ["rgb(255, 0, 0)", "rgba(0, 0, 0, 0)"],
+    },
+    {
+      title: "css and excludeMatches set",
+      params: [
+        {
+          id: "style-1",
+          allFrames: true,
+          matches: ["http://*/*/*.html"],
+          // TODO: Bug 1759117 - runAt should not affect css injection
+          runAt: "document_start",
+          persistAcrossSessions: false,
+          css: ["style-1.css"],
+          excludeMatches: ["http://*/*/file_with_iframe.html"],
+        },
+      ],
+      expected: ["rgba(0, 0, 0, 0)", "rgb(255, 0, 0)"],
+    },
+    {
+      title: "two css files",
+      params: [
+        {
+          id: "style-1-and-2",
+          allFrames: false,
+          matches: ["http://*/*/*.html"],
+          // TODO: Bug 1759117 - runAt should not affect css injection
+          runAt: "document_start",
+          persistAcrossSessions: false,
+          css: ["style-1.css", "style-2.css"],
+        },
+      ],
+      expected: ["rgb(0, 0, 255)", "rgba(0, 0, 0, 0)"],
+    },
+    {
+      title: "two scripts with css",
+      params: [
+        {
+          id: "style-1",
+          allFrames: false,
+          matches: ["http://*/*/*.html"],
+          runAt: "document_end",
+          persistAcrossSessions: false,
+          css: ["style-1.css"],
+        },
+        {
+          id: "style-2",
+          allFrames: false,
+          matches: ["http://*/*/*.html"],
+          runAt: "document_start",
+          persistAcrossSessions: false,
+          css: ["style-2.css"],
+        },
+      ],
+      // TODO: Bug 1759117 - The expected value should be `rgb(0, 0, 255)`
+      // because runAt should not affect css injection and therefore the two
+      // styles should be applied one after the other.
+      expected: ["rgb(255, 0, 0)", "rgba(0, 0, 0, 0)"],
+    },
+    {
+      title: "js and css with runAt: document_start",
+      params: [
+        {
+          id: "js-and-style-start",
+          allFrames: true,
+          matches: ["http://*/*/*.html"],
+          runAt: "document_start",
+          persistAcrossSessions: false,
+          css: ["style-3.css"],
+          // Inject the check script last to be able to send a message back to
+          // the test case. This works with `skipCheckScriptRegistration: true`
+          // below.
+          js: [
+            "script-document-start.js",
+            "check-applied-styles-document-start.js",
+          ],
+        },
+      ],
+      expected: ["rgb(4, 4, 4)", "rgb(4, 4, 4)"],
+      skipCheckScriptRegistration: true,
+    },
+    {
+      title: "js and css with runAt: document_end",
+      params: [
+        {
+          id: "js-and-style-end",
+          allFrames: true,
+          matches: ["http://*/*/*.html"],
+          runAt: "document_end",
+          persistAcrossSessions: false,
+          css: ["style-1.css"],
+          // Inject the check script last to be able to send a message back to
+          // the test case. This works with `skipCheckScriptRegistration: true`
+          // below.
+          js: ["script-document-end-and-idle.js", "check-applied-styles.js"],
+        },
+      ],
+      expected: ["rgb(5, 5, 5)", "rgb(5, 5, 5)"],
+      skipCheckScriptRegistration: true,
+    },
+    {
+      title: "js and css with runAt: document_idle",
+      params: [
+        {
+          id: "js-and-style-idle",
+          allFrames: true,
+          matches: ["http://*/*/*.html"],
+          runAt: "document_idle",
+          persistAcrossSessions: false,
+          css: ["style-1.css"],
+          // Inject the check script last to be able to send a message back to
+          // the test case. This works with `skipCheckScriptRegistration: true`
+          // below.
+          js: ["script-document-end-and-idle.js", "check-applied-styles.js"],
+        },
+      ],
+      expected: ["rgb(5, 5, 5)", "rgb(5, 5, 5)"],
+      skipCheckScriptRegistration: true,
+    },
+  ];
+
+  await extension.startup();
+  await extension.awaitMessage("background-ready");
+
+  for (const {
+    title,
+    params,
+    expected,
+    skipCheckScriptRegistration,
+  } of TEST_CASES) {
+    extension.sendMessage("load-test-case", {
+      title,
+      params,
+      skipCheckScriptRegistration,
+    });
+    await extension.awaitMessage("load-test-case-done");
+
+    let contentPage = await ExtensionTestUtils.loadContentPage(
+      `${BASE_URL}/file_with_iframe.html`
+    );
+
+    const backgroundColors = [
+      await extension.awaitMessage("background-color-file_with_iframe.html"),
+      await extension.awaitMessage("background-color-file_sample.html"),
+    ];
+
+    Assert.deepEqual(
+      expected,
+      backgroundColors,
+      `${title} - got expected colors`
+    );
+
+    await contentPage.close();
+  }
+
+  await extension.unload();
+});
diff --git a/toolkit/components/extensions/test/xpcshell/test_ext_scripting_contentScripts_file.js b/toolkit/components/extensions/test/xpcshell/test_ext_scripting_contentScripts_file.js
new file mode 100644
index 0000000000..3c806439ce
--- /dev/null
+++ b/toolkit/components/extensions/test/xpcshell/test_ext_scripting_contentScripts_file.js
@@ -0,0 +1,77 @@
+"use strict";
+
+const FILE_DUMMY_URL = Services.io.newFileURI(
+  do_get_file("data/dummy_page.html")
+).spec;
+
+// ExtensionContent.jsm needs to know when it's running from xpcshell, to use
+// the right timeout for content scripts executed at document_idle.
+ExtensionTestUtils.mockAppInfo();
+
+Services.prefs.setBoolPref("extensions.manifestV3.enabled", true);
+
+const makeExtension = ({ manifest: manifestProps, ...otherProps }) => {
+  return ExtensionTestUtils.loadExtension({
+    manifest: {
+      manifest_version: 3,
+      permissions: ["scripting"],
+      host_permissions: ["<all_urls>"],
+      granted_host_permissions: true,
+      ...manifestProps,
+    },
+    temporarilyInstalled: true,
+    ...otherProps,
+  });
+};
+
+add_task(async function test_registered_content_script_with_files() {
+  let extension = makeExtension({
+    async background() {
+      const MATCHES = [
+        { id: "script-1", matches: ["<all_urls>"] },
+        { id: "script-2", matches: ["file:///*"] },
+        { id: "script-3", matches: ["file://*/*dummy_page.html"] },
+        { id: "fail-if-executed", matches: ["*://*/*"] },
+      ];
+
+      await browser.scripting.registerContentScripts(
+        MATCHES.map(({ id, matches }) => ({
+          id,
+          js: [`${id}.js`],
+          matches,
+          persistAcrossSessions: false,
+        }))
+      );
+
+      browser.test.sendMessage("background-ready");
+    },
+    files: {
+      "script-1.js": () => {
+        browser.test.sendMessage("script-1-ran");
+      },
+      "script-2.js": () => {
+        browser.test.sendMessage("script-2-ran");
+      },
+      "script-3.js": () => {
+        browser.test.sendMessage("script-3-ran");
+      },
+      "fail-if-executed.js": () => {
+        browser.test.fail("this script should not be executed");
+      },
+    },
+  });
+
+  await extension.startup();
+  await extension.awaitMessage("background-ready");
+
+  let contentPage = await ExtensionTestUtils.loadContentPage(FILE_DUMMY_URL);
+
+  await Promise.all([
+    extension.awaitMessage("script-1-ran"),
+    extension.awaitMessage("script-2-ran"),
+    extension.awaitMessage("script-3-ran"),
+  ]);
+
+  await contentPage.close();
+  await extension.unload();
+});
diff --git a/toolkit/components/extensions/test/xpcshell/test_ext_scripting_mv2.js b/toolkit/components/extensions/test/xpcshell/test_ext_scripting_mv2.js
new file mode 100644
index 0000000000..53fb77c4da
--- /dev/null
+++ b/toolkit/components/extensions/test/xpcshell/test_ext_scripting_mv2.js
@@ -0,0 +1,23 @@
+"use strict";
+
+add_task(async function test_scripting_enabled_in_mv2() {
+  const extension = ExtensionTestUtils.loadExtension({
+    manifest: {
+      manifest_version: 2,
+      permissions: ["scripting"],
+    },
+    background() {
+      browser.test.assertEq(
+        "object",
+        typeof browser.scripting,
+        "expected scripting namespace to be defined"
+      );
+
+      browser.test.sendMessage("background-done");
+    },
+  });
+
+  await extension.startup();
+  await extension.awaitMessage("background-done");
+  await extension.unload();
+});
diff --git a/toolkit/components/extensions/test/xpcshell/test_ext_scripting_persistAcrossSessions.js b/toolkit/components/extensions/test/xpcshell/test_ext_scripting_persistAcrossSessions.js
new file mode 100644
index 0000000000..cae09b5d2e
--- /dev/null
+++ b/toolkit/components/extensions/test/xpcshell/test_ext_scripting_persistAcrossSessions.js
@@ -0,0 +1,760 @@
+"use strict";
+
+Services.prefs.setBoolPref("extensions.manifestV3.enabled", true);
+
+AddonTestUtils.init(this);
+AddonTestUtils.overrideCertDB();
+AddonTestUtils.createAppInfo(
+  "xpcshell@tests.mozilla.org",
+  "XPCShell",
+  "1",
+  "42"
+);
+
+const { ExtensionScriptingStore } = ChromeUtils.importESModule(
+  "resource://gre/modules/ExtensionScriptingStore.sys.mjs"
+);
+const { TestUtils } = ChromeUtils.importESModule(
+  "resource://testing-common/TestUtils.sys.mjs"
+);
+
+const makeExtension = ({ manifest: manifestProps, ...otherProps }) => {
+  return ExtensionTestUtils.loadExtension({
+    manifest: {
+      manifest_version: 2,
+      permissions: ["scripting"],
+      ...manifestProps,
+    },
+    useAddonManager: "permanent",
+    ...otherProps,
+  });
+};
+
+const assertNumScriptsInStore = async (extension, expectedNum) => {
+  // `registerContentScripts`/`updateContentScripts()`/`unregisterContentScripts`
+  // call `ExtensionScriptingStore.persistAll()` without awaiting it, which
+  // isn't a problem in practice but this becomes a problem in this test given
+  // that we should make sure the startup cache is updated before checking it.
+  await TestUtils.waitForCondition(async () => {
+    let scripts =
+      await ExtensionScriptingStore._getStoreForTesting().getByExtensionId(
+        extension.id
+      );
+    return scripts.length === expectedNum;
+  }, "wait until the store is updated with the expected number of scripts");
+
+  let scripts =
+    await ExtensionScriptingStore._getStoreForTesting().getByExtensionId(
+      extension.id
+    );
+  Assert.equal(
+    scripts.length,
+    expectedNum,
+    `expected ${expectedNum} script in store`
+  );
+};
+
+const verifyRegisterContentScripts = async manifestVersion => {
+  await AddonTestUtils.promiseStartupManager();
+
+  let extension = makeExtension({
+    manifest: {
+      manifest_version: manifestVersion,
+    },
+    async background() {
+      let scripts = await browser.scripting.getRegisteredContentScripts();
+
+      // Only register the content script if it wasn't registered before. Since
+      // there is only one script, we don't check its ID.
+      if (!scripts.length) {
+        const script = {
+          id: "script",
+          js: ["script.js"],
+          matches: ["http://*/*/file_sample.html"],
+          persistAcrossSessions: true,
+        };
+
+        await browser.scripting.registerContentScripts([script]);
+        browser.test.sendMessage("script-registered");
+        return;
+      }
+
+      browser.test.assertEq(1, scripts.length, "expected 1 registered script");
+      browser.test.sendMessage("script-already-registered");
+    },
+    files: {
+      "script.js": "",
+    },
+  });
+
+  await extension.startup();
+  await extension.awaitMessage("script-registered");
+  await assertNumScriptsInStore(extension, 1);
+
+  await AddonTestUtils.promiseRestartManager();
+  await assertNumScriptsInStore(extension, 1);
+
+  await extension.awaitStartup();
+  await extension.awaitMessage("script-already-registered");
+
+  await extension.unload();
+  await AddonTestUtils.promiseShutdownManager();
+  await assertNumScriptsInStore(extension, 0);
+};
+
+add_task(async function test_registerContentScripts_mv2() {
+  await verifyRegisterContentScripts(2);
+});
+
+add_task(async function test_registerContentScripts_mv3() {
+  await verifyRegisterContentScripts(3);
+});
+
+const verifyUpdateContentScripts = async manifestVersion => {
+  await AddonTestUtils.promiseStartupManager();
+
+  let extension = makeExtension({
+    manifest: {
+      manifest_version: manifestVersion,
+    },
+    async background() {
+      let scripts = await browser.scripting.getRegisteredContentScripts();
+
+      // Only register the content script if it wasn't registered before. Since
+      // there is only one script, we don't check its ID.
+      if (!scripts.length) {
+        const script = {
+          id: "script",
+          js: ["script.js"],
+          matches: ["http://*/*/file_sample.html"],
+          persistAcrossSessions: true,
+        };
+
+        await browser.scripting.registerContentScripts([script]);
+        browser.test.sendMessage("script-registered");
+        return;
+      }
+
+      browser.test.assertEq(1, scripts.length, "expected 1 registered script");
+      await browser.scripting.updateContentScripts([
+        { id: scripts[0].id, persistAcrossSessions: false },
+      ]);
+      browser.test.sendMessage("script-updated");
+    },
+    files: {
+      "script.js": "",
+    },
+  });
+
+  await extension.startup();
+  await extension.awaitMessage("script-registered");
+  await assertNumScriptsInStore(extension, 1);
+
+  // Simulate a new session.
+  await AddonTestUtils.promiseRestartManager();
+  await assertNumScriptsInStore(extension, 1);
+
+  await extension.awaitStartup();
+  await extension.awaitMessage("script-updated");
+  await assertNumScriptsInStore(extension, 0);
+
+  // Simulate another new session.
+  await AddonTestUtils.promiseRestartManager();
+
+  await extension.awaitStartup();
+  await extension.awaitMessage("script-registered");
+  await assertNumScriptsInStore(extension, 1);
+
+  await extension.unload();
+  await AddonTestUtils.promiseShutdownManager();
+  await assertNumScriptsInStore(extension, 0);
+};
+
+add_task(async function test_updateContentScripts() {
+  await verifyUpdateContentScripts(2);
+});
+
+add_task(async function test_updateContentScripts_mv3() {
+  await verifyUpdateContentScripts(3);
+});
+
+const verifyUnregisterContentScripts = async manifestVersion => {
+  await AddonTestUtils.promiseStartupManager();
+
+  let extension = makeExtension({
+    manifest: {
+      manifest_version: manifestVersion,
+    },
+    async background() {
+      let scripts = await browser.scripting.getRegisteredContentScripts();
+
+      // Only register the content script if it wasn't registered before. Since
+      // there is only one script, we don't check its ID.
+      if (!scripts.length) {
+        const script = {
+          id: "script",
+          js: ["script.js"],
+          matches: ["http://*/*/file_sample.html"],
+          persistAcrossSessions: true,
+        };
+
+        await browser.scripting.registerContentScripts([script]);
+        browser.test.sendMessage("script-registered");
+        return;
+      }
+
+      browser.test.assertEq(1, scripts.length, "expected 1 registered script");
+      await browser.scripting.unregisterContentScripts();
+      browser.test.sendMessage("script-unregistered");
+    },
+    files: {
+      "script.js": "",
+    },
+  });
+
+  await extension.startup();
+  await extension.awaitMessage("script-registered");
+  await assertNumScriptsInStore(extension, 1);
+
+  // Simulate a new session.
+  await AddonTestUtils.promiseRestartManager();
+
+  // Script should be still persisted...
+  await assertNumScriptsInStore(extension, 1);
+  await extension.awaitStartup();
+  // ...and we should now enter the second branch of the background script.
+  await extension.awaitMessage("script-unregistered");
+  await assertNumScriptsInStore(extension, 0);
+
+  // Simulate another new session.
+  await AddonTestUtils.promiseRestartManager();
+
+  await extension.awaitStartup();
+  await extension.awaitMessage("script-registered");
+  await assertNumScriptsInStore(extension, 1);
+
+  await extension.unload();
+  await AddonTestUtils.promiseShutdownManager();
+  await assertNumScriptsInStore(extension, 0);
+};
+
+add_task(async function test_unregisterContentScripts() {
+  await verifyUnregisterContentScripts(2);
+});
+
+add_task(async function test_unregisterContentScripts_mv3() {
+  await verifyUnregisterContentScripts(3);
+});
+
+add_task(async function test_reload_extension() {
+  await AddonTestUtils.promiseStartupManager();
+
+  let extension = makeExtension({
+    async background() {
+      browser.test.onMessage.addListener(msg => {
+        browser.test.assertEq("reload-extension", msg, `expected msg: ${msg}`);
+        browser.runtime.reload();
+      });
+
+      let scripts = await browser.scripting.getRegisteredContentScripts();
+
+      // Only register the content script if it wasn't registered before. Since
+      // there is only one script, we don't check its ID.
+      if (!scripts.length) {
+        const script = {
+          id: "script",
+          js: ["script.js"],
+          matches: ["http://*/*/file_sample.html"],
+          persistAcrossSessions: true,
+        };
+
+        await browser.scripting.registerContentScripts([script]);
+        browser.test.sendMessage("script-registered");
+        return;
+      }
+
+      browser.test.assertEq(1, scripts.length, "expected 1 registered script");
+      browser.test.sendMessage("script-already-registered");
+    },
+    files: {
+      "script.js": "",
+    },
+  });
+
+  await extension.startup();
+  await extension.awaitMessage("script-registered");
+  await assertNumScriptsInStore(extension, 1);
+
+  extension.sendMessage("reload-extension");
+  // Wait for extension to restart, to make sure reloads works.
+  await AddonTestUtils.promiseWebExtensionStartup(extension.id);
+  await extension.awaitMessage("script-already-registered");
+  await assertNumScriptsInStore(extension, 1);
+
+  await extension.unload();
+  await AddonTestUtils.promiseShutdownManager();
+  await assertNumScriptsInStore(extension, 0);
+});
+
+add_task(async function test_disable_and_reenable_extension() {
+  await AddonTestUtils.promiseStartupManager();
+
+  let extension = makeExtension({
+    async background() {
+      let scripts = await browser.scripting.getRegisteredContentScripts();
+
+      // Only register the content script if it wasn't registered before. Since
+      // there is only one script, we don't check its ID.
+      if (!scripts.length) {
+        const script = {
+          id: "script",
+          js: ["script.js"],
+          matches: ["http://*/*/file_sample.html"],
+          persistAcrossSessions: true,
+        };
+
+        await browser.scripting.registerContentScripts([script]);
+        browser.test.sendMessage("script-registered");
+        return;
+      }
+
+      browser.test.assertEq(1, scripts.length, "expected 1 registered script");
+      browser.test.sendMessage("script-already-registered");
+    },
+    files: {
+      "script.js": "",
+    },
+  });
+
+  await extension.startup();
+  await extension.awaitMessage("script-registered");
+  await assertNumScriptsInStore(extension, 1);
+
+  // Disable...
+  await extension.addon.disable();
+  // then re-enable the extension.
+  await extension.addon.enable();
+
+  await extension.awaitMessage("script-already-registered");
+  await assertNumScriptsInStore(extension, 1);
+
+  await extension.unload();
+  await AddonTestUtils.promiseShutdownManager();
+  await assertNumScriptsInStore(extension, 0);
+});
+
+add_task(async function test_updateContentScripts_persistAcrossSessions_true() {
+  await AddonTestUtils.promiseStartupManager();
+
+  let extension = makeExtension({
+    async background() {
+      const script = {
+        id: "script",
+        js: ["script-1.js"],
+        matches: ["http://*/*/file_sample.html"],
+        persistAcrossSessions: false,
+      };
+
+      const scripts = await browser.scripting.getRegisteredContentScripts();
+
+      browser.test.onMessage.addListener(async msg => {
+        switch (msg) {
+          case "persist-script":
+            await browser.scripting.updateContentScripts([
+              { id: script.id, persistAcrossSessions: true },
+            ]);
+            browser.test.sendMessage(`${msg}-done`);
+            break;
+
+          case "add-new-js":
+            await browser.scripting.updateContentScripts([
+              { id: script.id, js: ["script-1.js", "script-2.js"] },
+            ]);
+            browser.test.sendMessage(`${msg}-done`);
+            break;
+
+          case "verify-script":
+            // We expect a single registered script, which is the one declared
+            // above but at this point we should have 2 JS files and the
+            // `persistAcrossSessions` option set to `true`.
+            browser.test.assertEq(
+              JSON.stringify([
+                {
+                  id: script.id,
+                  allFrames: false,
+                  matches: script.matches,
+                  runAt: "document_idle",
+                  persistAcrossSessions: true,
+                  js: ["script-1.js", "script-2.js"],
+                },
+              ]),
+              JSON.stringify(scripts),
+              "expected scripts"
+            );
+            browser.test.sendMessage(`${msg}-done`);
+            break;
+
+          default:
+            browser.test.fail(`unexpected message: ${msg}`);
+        }
+      });
+
+      // Only register the content script if it wasn't registered before. Since
+      // there is only one script, we don't check its ID.
+      if (!scripts.length) {
+        await browser.scripting.registerContentScripts([script]);
+        browser.test.sendMessage("script-registered");
+      } else {
+        browser.test.sendMessage("script-already-registered");
+      }
+    },
+    files: {
+      "script-1.js": "",
+      "script-2.js": "",
+    },
+  });
+
+  await extension.startup();
+  await extension.awaitMessage("script-registered");
+  await assertNumScriptsInStore(extension, 0);
+
+  // Simulate a new session.
+  await AddonTestUtils.promiseRestartManager();
+  await assertNumScriptsInStore(extension, 0);
+
+  // We expect the script to be registered again because it isn't persisted.
+  await extension.awaitStartup();
+  await extension.awaitMessage("script-registered");
+  await assertNumScriptsInStore(extension, 0);
+
+  // We now tell the background script to update the script to persist it
+  // across sessions.
+  extension.sendMessage("persist-script");
+  await extension.awaitMessage("persist-script-done");
+
+  // Simulate another new session. We expect the content script to be already
+  // registered since it was persisted in the previous (simulated) session.
+  await AddonTestUtils.promiseRestartManager();
+  await assertNumScriptsInStore(extension, 1);
+
+  await extension.awaitStartup();
+  await extension.awaitMessage("script-already-registered");
+  await assertNumScriptsInStore(extension, 1);
+
+  // We tell the background script to update the content script with a new JS
+  // file and we don't change the `persistAcrossSessions` option.
+  extension.sendMessage("add-new-js");
+  await extension.awaitMessage("add-new-js-done");
+
+  // Simulate another new session. We expect the content script to have 2 JS
+  // files and to be registered since it was persisted in the previous
+  // (simulated) session and we didn't update the option.
+  await AddonTestUtils.promiseRestartManager();
+  await assertNumScriptsInStore(extension, 1);
+
+  await extension.awaitStartup();
+  await extension.awaitMessage("script-already-registered");
+  await assertNumScriptsInStore(extension, 1);
+
+  // Let's verify that the script fetched by the background script is the one
+  // we expect at this point: it should have two JS files.
+  extension.sendMessage("verify-script");
+  await extension.awaitMessage("verify-script-done");
+
+  await extension.unload();
+  await AddonTestUtils.promiseShutdownManager();
+  await assertNumScriptsInStore(extension, 0);
+});
+
+add_task(async function test_multiple_extensions_and_scripts() {
+  await AddonTestUtils.promiseStartupManager();
+
+  let extension1 = makeExtension({
+    async background() {
+      let scripts = await browser.scripting.getRegisteredContentScripts();
+
+      if (!scripts.length) {
+        await browser.scripting.registerContentScripts([
+          {
+            id: "0",
+            js: ["script-1.js"],
+            matches: ["http://*/*/file_sample.html"],
+            // We should persist this script by default.
+          },
+          {
+            id: "/",
+            js: ["script-2.js"],
+            matches: ["http://*/*/file_sample.html"],
+            persistAcrossSessions: true,
+          },
+          {
+            id: "3",
+            js: ["script-3.js"],
+            matches: ["http://*/*/file_sample.html"],
+            persistAcrossSessions: false,
+          },
+        ]);
+        browser.test.sendMessage("scripts-registered");
+        return;
+      }
+
+      browser.test.assertEq(2, scripts.length, "expected 2 registered scripts");
+      browser.test.sendMessage("scripts-already-registered");
+    },
+    files: {
+      "script-1.js": "",
+      "script-2.js": "",
+      "script-3.js": "",
+    },
+  });
+
+  let extension2 = makeExtension({
+    async background() {
+      let scripts = await browser.scripting.getRegisteredContentScripts();
+
+      if (!scripts.length) {
+        await browser.scripting.registerContentScripts([
+          {
+            id: "1",
+            js: ["script-1.js"],
+            matches: ["http://*/*/file_sample.html"],
+            // We should persist this script by default.
+          },
+          {
+            id: "2",
+            js: ["script-2.js"],
+            matches: ["http://*/*/file_sample.html"],
+            persistAcrossSessions: false,
+          },
+          {
+            id: "\uFFFD 🍕 Boö",
+            js: ["script-3.js"],
+            matches: ["http://*/*/file_sample.html"],
+            persistAcrossSessions: true,
+          },
+        ]);
+        browser.test.sendMessage("scripts-registered");
+        return;
+      }
+
+      browser.test.assertEq(2, scripts.length, "expected 2 registered scripts");
+      browser.test.assertEq(
+        JSON.stringify(["script-1.js"]),
+        JSON.stringify(scripts[0].js),
+        "expected a single 'script-1.js' js file"
+      );
+      browser.test.assertEq(
+        "\uFFFD 🍕 Boö",
+        scripts[1].id,
+        "expected correct ID"
+      );
+      browser.test.sendMessage("scripts-already-registered");
+    },
+    files: {
+      "script-1.js": "",
+      "script-2.js": "",
+      "script-3.js": "",
+    },
+  });
+
+  await Promise.all([extension1.startup(), extension2.startup()]);
+
+  await Promise.all([
+    extension1.awaitMessage("scripts-registered"),
+    extension2.awaitMessage("scripts-registered"),
+  ]);
+  await assertNumScriptsInStore(extension1, 2);
+  await assertNumScriptsInStore(extension2, 2);
+
+  await AddonTestUtils.promiseRestartManager();
+  await assertNumScriptsInStore(extension1, 2);
+  await assertNumScriptsInStore(extension2, 2);
+
+  await Promise.all([extension1.awaitStartup(), extension2.awaitStartup()]);
+  await Promise.all([
+    extension1.awaitMessage("scripts-already-registered"),
+    extension2.awaitMessage("scripts-already-registered"),
+  ]);
+
+  await Promise.all([extension1.unload(), extension2.unload()]);
+  await AddonTestUtils.promiseShutdownManager();
+  await assertNumScriptsInStore(extension1, 0);
+  await assertNumScriptsInStore(extension2, 0);
+});
+
+add_task(async function test_persisted_scripts_cleared_on_addon_updates() {
+  await AddonTestUtils.promiseStartupManager();
+
+  function background() {
+    browser.test.onMessage.addListener(async (msg, ...args) => {
+      switch (msg) {
+        case "registerContentScripts":
+          await browser.scripting.registerContentScripts(...args);
+          break;
+        case "unregisterContentScripts":
+          await browser.scripting.unregisterContentScripts(...args);
+          break;
+        default:
+          browser.test.fail(`Unexpected test message: ${msg}`);
+      }
+      browser.test.sendMessage(`${msg}:done`);
+    });
+  }
+
+  async function registerContentScript(ext, scriptFileName) {
+    ext.sendMessage("registerContentScripts", [
+      {
+        id: scriptFileName,
+        js: [scriptFileName],
+        matches: ["http://*/*/file_sample.html"],
+        persistAcrossSessions: true,
+      },
+    ]);
+    await ext.awaitMessage("registerContentScripts:done");
+  }
+
+  let extension1Data = {
+    manifest: {
+      manifest_version: 2,
+      permissions: ["scripting"],
+      version: "1.0",
+      browser_specific_settings: {
+        // Set an explicit extension id so that extension.upgrade
+        // will trigger the extension to be started with the expected
+        // "ADDON_UPGRADE" / "ADDON_DOWNGRADE" extension.startupReason.
+        gecko: { id: "extension1@mochi.test" },
+      },
+    },
+    useAddonManager: "permanent",
+    background,
+    files: {
+      "script-1.js": "",
+    },
+  };
+
+  let extension1 = ExtensionTestUtils.loadExtension(extension1Data);
+
+  let extension2 = ExtensionTestUtils.loadExtension({
+    manifest: {
+      manifest_version: 2,
+      permissions: ["scripting"],
+      browser_specific_settings: {
+        gecko: { id: "extension2@mochi.test" },
+      },
+    },
+    useAddonManager: "permanent",
+    background,
+    files: {
+      "script-2.js": "",
+    },
+  });
+
+  await extension1.startup();
+  await assertNumScriptsInStore(extension1, 0);
+  await assertIsPersistentScriptsCachedFlag(extension1, false);
+
+  await extension2.startup();
+  await assertNumScriptsInStore(extension2, 0);
+  await assertIsPersistentScriptsCachedFlag(extension2, false);
+
+  await registerContentScript(extension1, "script-1.js");
+  await assertNumScriptsInStore(extension1, 1);
+  await assertIsPersistentScriptsCachedFlag(extension1, true);
+
+  await registerContentScript(extension2, "script-2.js");
+  await assertNumScriptsInStore(extension2, 1);
+  await assertIsPersistentScriptsCachedFlag(extension2, true);
+
+  info("Verify that scripts are still registered on a browser startup");
+  await AddonTestUtils.promiseRestartManager();
+  await extension1.awaitStartup();
+  await extension2.awaitStartup();
+  equal(
+    extension1.extension.startupReason,
+    "APP_STARTUP",
+    "Got the expected startupReason on AOM restart"
+  );
+
+  await assertNumScriptsInStore(extension1, 1);
+  await assertIsPersistentScriptsCachedFlag(extension1, true);
+  await assertNumScriptsInStore(extension2, 1);
+  await assertIsPersistentScriptsCachedFlag(extension2, true);
+
+  async function testOnAddonUpdates(
+    extensionUpdateData,
+    expectedStartupReason
+  ) {
+    await extension1.upgrade(extensionUpdateData);
+    equal(
+      extension1.extension.startupReason,
+      expectedStartupReason,
+      "Got the expected startupReason on upgrade"
+    );
+
+    await assertNumScriptsInStore(extension1, 0);
+    await assertIsPersistentScriptsCachedFlag(extension1, false);
+    await assertNumScriptsInStore(extension2, 1);
+    await assertIsPersistentScriptsCachedFlag(extension2, true);
+  }
+
+  info("Verify that scripts are cleared on upgrade");
+  await testOnAddonUpdates(
+    {
+      ...extension1Data,
+      manifest: {
+        ...extension1Data.manifest,
+        version: "2.0",
+      },
+    },
+    "ADDON_UPGRADE"
+  );
+
+  await registerContentScript(extension1, "script-1.js");
+  await assertNumScriptsInStore(extension1, 1);
+
+  info("Verify that scripts are cleared on downgrade");
+  await testOnAddonUpdates(extension1Data, "ADDON_DOWNGRADE");
+
+  await registerContentScript(extension1, "script-1.js");
+  await assertNumScriptsInStore(extension1, 1);
+
+  info("Verify that scripts are cleared on upgrade to same version");
+  await testOnAddonUpdates(extension1Data, "ADDON_UPGRADE");
+
+  await extension1.unload();
+  await extension2.unload();
+
+  await assertNumScriptsInStore(extension1, 0);
+  await assertIsPersistentScriptsCachedFlag(extension1, undefined);
+  await assertNumScriptsInStore(extension2, 0);
+  await assertIsPersistentScriptsCachedFlag(extension2, undefined);
+
+  info("Verify stale persisted scripts cleared on re-install");
+  // Inject a stale persisted script into the store.
+  await ExtensionScriptingStore._getStoreForTesting().writeMany(extension1.id, [
+    {
+      id: "script-1.js",
+      allFrames: false,
+      matches: ["http://*/*/file_sample.html"],
+      runAt: "document_idle",
+      persistAcrossSessions: true,
+      js: ["script-1.js"],
+    },
+  ]);
+  await assertNumScriptsInStore(extension1, 1);
+  const extension1Reinstalled =
+    ExtensionTestUtils.loadExtension(extension1Data);
+  await extension1Reinstalled.startup();
+  equal(
+    extension1Reinstalled.extension.startupReason,
+    "ADDON_INSTALL",
+    "Got the expected startupReason on re-install"
+  );
+  await assertNumScriptsInStore(extension1Reinstalled, 0);
+  await assertIsPersistentScriptsCachedFlag(extension1Reinstalled, false);
+  await extension1Reinstalled.unload();
+  await assertNumScriptsInStore(extension1Reinstalled, 0);
+  await assertIsPersistentScriptsCachedFlag(extension1Reinstalled, undefined);
+
+  await AddonTestUtils.promiseShutdownManager();
+});
diff --git a/toolkit/components/extensions/test/xpcshell/test_ext_scripting_startupCache.js b/toolkit/components/extensions/test/xpcshell/test_ext_scripting_startupCache.js
new file mode 100644
index 0000000000..07445dafbe
--- /dev/null
+++ b/toolkit/components/extensions/test/xpcshell/test_ext_scripting_startupCache.js
@@ -0,0 +1,167 @@
+/* Any copyright is dedicated to the Public Domain.
+ * http://creativecommons.org/publicdomain/zero/1.0/ */
+
+"use strict";
+
+AddonTestUtils.init(this);
+AddonTestUtils.overrideCertDB();
+AddonTestUtils.createAppInfo(
+  "xpcshell@tests.mozilla.org",
+  "XPCShell",
+  "1",
+  "42"
+);
+
+const { ExtensionScriptingStore } = ChromeUtils.importESModule(
+  "resource://gre/modules/ExtensionScriptingStore.sys.mjs"
+);
+const { TestUtils } = ChromeUtils.importESModule(
+  "resource://testing-common/TestUtils.sys.mjs"
+);
+
+const { sinon } = ChromeUtils.importESModule(
+  "resource://testing-common/Sinon.sys.mjs"
+);
+
+add_task(async function test_hasPersistedScripts_startup_cache() {
+  let extension1 = ExtensionTestUtils.loadExtension({
+    manifest: {
+      manifest_version: 2,
+      permissions: ["scripting"],
+    },
+    // Set the startup reason to "APP_STARTUP", used to be able to simulate
+    // the behavior expected on calls to `ExtensionScriptingStore.init(extension)`
+    // when the addon has not been just installed, but it is being loaded as part
+    // of the browser application starting up.
+    startupReason: "APP_STARTUP",
+    background() {
+      browser.test.onMessage.addListener(async (msg, ...args) => {
+        switch (msg) {
+          case "registerContentScripts":
+            await browser.scripting.registerContentScripts(...args);
+            break;
+          case "unregisterContentScripts":
+            await browser.scripting.unregisterContentScripts(...args);
+            break;
+          default:
+            browser.test.fail(`Unexpected test message: ${msg}`);
+        }
+        browser.test.sendMessage(`${msg}:done`);
+      });
+    },
+    files: {
+      "script-1.js": "",
+    },
+  });
+
+  await extension1.startup();
+
+  info(`Checking StartupCache for ${extension1.id} ${extension1.version}`);
+  await assertHasPersistedScriptsCachedFlag(extension1);
+  await assertIsPersistentScriptsCachedFlag(extension1, false);
+
+  const store = ExtensionScriptingStore._getStoreForTesting();
+
+  extension1.sendMessage("registerContentScripts", [
+    {
+      id: "some-script-id",
+      js: ["script-1.js"],
+      matches: ["http://*/*/file_sample.html"],
+      persistAcrossSessions: true,
+    },
+  ]);
+  await extension1.awaitMessage("registerContentScripts:done");
+
+  // `registerContentScripts()` calls `ExtensionScriptingStore.persistAll()`
+  // without await it, which isn't a problem in practice but this becomes a
+  // problem in this test given that we should make sure the startup cache
+  // is updated before checking it.
+  await TestUtils.waitForCondition(async () => {
+    const scripts = await store.getAll(extension1.id);
+    return !!scripts.length;
+  }, "Wait for stored scripts list to not be empty");
+  await assertIsPersistentScriptsCachedFlag(extension1, true);
+
+  extension1.sendMessage("unregisterContentScripts", {
+    ids: ["some-script-id"],
+  });
+  await extension1.awaitMessage("unregisterContentScripts:done");
+
+  await TestUtils.waitForCondition(async () => {
+    const scripts = await store.getAll(extension1.id);
+    return !scripts.length;
+  }, "Wait for stored scripts list to be empty");
+  await assertIsPersistentScriptsCachedFlag(extension1, false);
+
+  const storeGetAllSpy = sinon.spy(store, "getAll");
+  const cleanupSpies = () => {
+    storeGetAllSpy.restore();
+  };
+
+  // NOTE: ExtensionScriptingStore.initExtension is usually only called once
+  // during the extension startup.
+  //
+  // This test calls the method after startup was completed, which does not
+  // happen in practice, but it allows us to simulate what happens under different
+  // store and startup cache conditions and more explicitly cover the expectation
+  // that store.getAll isn't going to be called more than once internally
+  // when the hasPersistedScripts boolean flag wasn't in the StartupCache
+  // and had to be recomputed.
+  equal(
+    extension1.extension.startupReason,
+    "APP_STARTUP",
+    "Got the expected extension.startupReason"
+  );
+  await ExtensionScriptingStore.initExtension(extension1.extension);
+  equal(storeGetAllSpy.callCount, 0, "Expect store.getAll to not be called");
+
+  Services.obs.notifyObservers(null, "startupcache-invalidate");
+
+  await ExtensionScriptingStore.initExtension(extension1.extension);
+  equal(storeGetAllSpy.callCount, 1, "Expect store.getAll to be called once");
+
+  extension1.sendMessage("registerContentScripts", [
+    {
+      id: "some-script-id",
+      js: ["script-1.js"],
+      matches: ["http://*/*/file_sample.html"],
+      persistAcrossSessions: true,
+    },
+  ]);
+  await extension1.awaitMessage("registerContentScripts:done");
+
+  await TestUtils.waitForCondition(async () => {
+    const scripts = await store.getAll(extension1.id);
+    return !!scripts.length;
+  }, "Wait for stored scripts list to not be empty");
+  await assertIsPersistentScriptsCachedFlag(extension1, true);
+
+  // Make sure getAll is only called once when we don't have
+  // scripting.hasPersistedScripts flag cached.
+  storeGetAllSpy.resetHistory();
+  Services.obs.notifyObservers(null, "startupcache-invalidate");
+  await ExtensionScriptingStore.initExtension(extension1.extension);
+  equal(storeGetAllSpy.callCount, 1, "Expect store.getAll to be called once");
+
+  cleanupSpies();
+
+  const extId = extension1.id;
+  const extVersion = extension1.version;
+  await assertIsPersistentScriptsCachedFlag(
+    { id: extId, version: extVersion },
+    true
+  );
+  await extension1.unload();
+  await assertIsPersistentScriptsCachedFlag(
+    { id: extId, version: extVersion },
+    undefined
+  );
+
+  const { StartupCache } = ExtensionParent;
+  const allCachedGeneral = StartupCache._data.get("general");
+  equal(
+    allCachedGeneral.has(extId),
+    false,
+    "Expect the extension to have been removed from the StartupCache"
+  );
+});
diff --git a/toolkit/components/extensions/test/xpcshell/test_ext_scripting_updateContentScripts.js b/toolkit/components/extensions/test/xpcshell/test_ext_scripting_updateContentScripts.js
new file mode 100644
index 0000000000..9d3bf1576c
--- /dev/null
+++ b/toolkit/components/extensions/test/xpcshell/test_ext_scripting_updateContentScripts.js
@@ -0,0 +1,114 @@
+"use strict";
+
+const server = createHttpServer();
+server.registerDirectory("/data/", do_get_file("data"));
+
+const BASE_URL = `http://localhost:${server.identity.primaryPort}/data`;
+
+// ExtensionContent.jsm needs to know when it's running from xpcshell, to use
+// the right timeout for content scripts executed at document_idle.
+ExtensionTestUtils.mockAppInfo();
+
+Services.prefs.setBoolPref("extensions.manifestV3.enabled", true);
+
+const makeExtension = ({ manifest: manifestProps, ...otherProps }) => {
+  return ExtensionTestUtils.loadExtension({
+    manifest: {
+      manifest_version: 3,
+      permissions: ["scripting"],
+      host_permissions: ["http://localhost/*"],
+      granted_host_permissions: true,
+      ...manifestProps,
+    },
+    temporarilyInstalled: true,
+    ...otherProps,
+  });
+};
+
+add_task(async function test_scripting_updateContentScripts() {
+  let extension = makeExtension({
+    async background() {
+      const script = {
+        id: "a-script",
+        js: ["script-1.js"],
+        matches: ["http://*/*/*.html"],
+        persistAcrossSessions: false,
+      };
+
+      await browser.scripting.registerContentScripts([script]);
+      await browser.scripting.updateContentScripts([
+        {
+          id: script.id,
+          js: ["script-2.js"],
+        },
+      ]);
+      let scripts = await browser.scripting.getRegisteredContentScripts();
+      browser.test.assertEq(1, scripts.length, "expected 1 registered script");
+
+      browser.test.sendMessage("background-ready");
+    },
+    files: {
+      "script-1.js": () => {
+        browser.test.fail("script-1 should not be executed");
+      },
+      "script-2.js": () => {
+        browser.test.sendMessage(
+          `script-2 executed in ${location.pathname.split("/").pop()}`
+        );
+      },
+    },
+  });
+
+  await extension.startup();
+  await extension.awaitMessage("background-ready");
+
+  let contentPage = await ExtensionTestUtils.loadContentPage(
+    `${BASE_URL}/file_sample.html`
+  );
+
+  await extension.awaitMessage("script-2 executed in file_sample.html");
+
+  await extension.unload();
+  await contentPage.close();
+});
+
+add_task(
+  async function test_scripting_updateContentScripts_non_default_values() {
+    let extension = makeExtension({
+      async background() {
+        const script = {
+          id: "a-script",
+          allFrames: true,
+          matches: ["http://*/*/*.html"],
+          runAt: "document_start",
+          persistAcrossSessions: false,
+          css: ["style.js"],
+          excludeMatches: ["http://*/*/foobar.html"],
+          js: ["script.js"],
+        };
+
+        await browser.scripting.registerContentScripts([script]);
+
+        // This should not modify the previously registered script.
+        await browser.scripting.updateContentScripts([{ id: script.id }]);
+
+        let scripts = await browser.scripting.getRegisteredContentScripts();
+        browser.test.assertEq(
+          JSON.stringify([script]),
+          JSON.stringify(scripts),
+          "expected unmodified registered script"
+        );
+
+        browser.test.sendMessage("background-done");
+      },
+      files: {
+        "script.js": "",
+        "style.css": "",
+      },
+    });
+
+    await extension.startup();
+    await extension.awaitMessage("background-done");
+    await extension.unload();
+  }
+);
diff --git a/toolkit/components/extensions/test/xpcshell/test_ext_secfetch.js b/toolkit/components/extensions/test/xpcshell/test_ext_secfetch.js
new file mode 100644
index 0000000000..e8b3dcfca8
--- /dev/null
+++ b/toolkit/components/extensions/test/xpcshell/test_ext_secfetch.js
@@ -0,0 +1,352 @@
+/* -*- Mode: indent-tabs-mode: nil; js-indent-level: 2 -*- */
+/* vim: set sts=2 sw=2 et tw=80: */
+"use strict";
+
+Services.prefs.setBoolPref("extensions.manifestV3.enabled", true);
+
+const server = createHttpServer({
+  // We need the 127.0.0.1 proxy because the sec-fetch headers are not sent to
+  // "127.0.0.1:<any port other than 80 or 443>".
+  hosts: ["127.0.0.1", "127.0.0.2"],
+});
+
+server.registerPathHandler("/page.html", (request, response) => {
+  response.setStatusLine(request.httpVersion, 200, "OK");
+  response.setHeader("Access-Control-Allow-Origin", "*");
+});
+
+server.registerPathHandler("/return_headers", (request, response) => {
+  response.setStatusLine(request.httpVersion, 200, "OK");
+  response.setHeader("Content-Type", "text/plain");
+  response.setHeader("Access-Control-Allow-Origin", "*");
+  if (request.method === "OPTIONS") {
+    // Handle CORS preflight request.
+    response.setHeader("Access-Control-Allow-Methods", "GET, PUT");
+    return;
+  }
+
+  let headers = {};
+  for (let header of [
+    "sec-fetch-site",
+    "sec-fetch-dest",
+    "sec-fetch-mode",
+    "sec-fetch-user",
+  ]) {
+    if (request.hasHeader(header)) {
+      headers[header] = request.getHeader(header);
+    }
+  }
+
+  if (request.hasHeader("origin")) {
+    headers.origin = request
+      .getHeader("origin")
+      .replace(/moz-extension:\/\/[^\/]+/, "moz-extension://<placeholder>");
+  }
+
+  response.write(JSON.stringify(headers));
+});
+
+async function contentScript() {
+  let content_fetch;
+  if (browser.runtime.getManifest().manifest_version === 2) {
+    content_fetch = content.fetch;
+  } else {
+    // In MV3, there is no content variable.
+    browser.test.assertEq(typeof content, "undefined", "no .content in MV3");
+    // In MV3, window.fetch is the original fetch with the page's principal.
+    content_fetch = window.fetch.bind(window);
+  }
+  let results = await Promise.allSettled([
+    // A cross-origin request from the content script.
+    fetch("http://127.0.0.1/return_headers").then(res => res.json()),
+    // A cross-origin request that behaves as if it was sent by the content it
+    // self.
+    content_fetch("http://127.0.0.1/return_headers").then(res => res.json()),
+    // A same-origin request that behaves as if it was sent by the content it
+    // self.
+    content_fetch("http://127.0.0.2/return_headers").then(res => res.json()),
+    // A same-origin request from the content script.
+    fetch("http://127.0.0.2/return_headers").then(res => res.json()),
+    // Non GET or HEAD request, triggers CORS preflight.
+    fetch("http://127.0.0.2/return_headers", { method: "PUT" }).then(res =>
+      res.json()
+    ),
+  ]);
+
+  results = results.map(({ value, reason }) => value ?? reason.message);
+
+  browser.test.sendMessage("content_results", results);
+}
+
+async function runSecFetchTest(test) {
+  let data = {
+    async background() {
+      let site = await new Promise(resolve => {
+        browser.test.onMessage.addListener(msg => {
+          resolve(msg);
+        });
+      });
+
+      let results = await Promise.all([
+        fetch(`${site}/return_headers`).then(res => res.json()),
+        // Non GET or HEAD request, triggers CORS preflight.
+        fetch(`${site}/return_headers`, { method: "PUT" }).then(res =>
+          res.json()
+        ),
+      ]);
+      browser.test.sendMessage("background_results", results);
+    },
+    manifest: {
+      manifest_version: test.manifest_version,
+      content_scripts: [
+        {
+          matches: ["http://127.0.0.2/*"],
+          js: ["content_script.js"],
+        },
+      ],
+    },
+    files: {
+      "content_script.js": contentScript,
+    },
+  };
+
+  if (data.manifest.manifest_version == 3) {
+    // Automatically grant permissions so that the content script can run.
+    data.manifest.granted_host_permissions = true;
+    // Needed to use granted_host_permissions in tests:
+    data.temporarilyInstalled = true;
+    // Work-around for bug 1766752:
+    data.manifest.host_permissions = ["http://127.0.0.2/*"];
+    // (note: ^ host_permissions may be replaced/extended below).
+  }
+
+  // The sec-fetch-* headers are only send to potentially trust worthy origins.
+  // We use 127.0.0.1 to avoid setting up an https server.
+  const site = "http://127.0.0.1";
+
+  if (test.permission) {
+    // MV3 requires permissions to be set in permissions. ExtensionTestCommon
+    // will replace host_permissions with permissions in MV2.
+    data.manifest.host_permissions = ["http://127.0.0.2/*", `${site}/*`];
+  }
+
+  let extension = ExtensionTestUtils.loadExtension(data);
+  await extension.startup();
+
+  extension.sendMessage(site);
+  let backgroundResults = await extension.awaitMessage("background_results");
+  Assert.deepEqual(backgroundResults, test.expectedBackgroundHeaders);
+
+  let contentPage = await ExtensionTestUtils.loadContentPage(
+    `http://127.0.0.2/page.html`
+  );
+  let contentResults = await extension.awaitMessage("content_results");
+  Assert.deepEqual(contentResults, test.expectedContentHeaders);
+  await contentPage.close();
+
+  await extension.unload();
+}
+
+add_task(async function test_fetch_without_permissions_mv2() {
+  await runSecFetchTest({
+    manifest_version: 2,
+    permission: false,
+    expectedBackgroundHeaders: [
+      {
+        "sec-fetch-site": "cross-site",
+        "sec-fetch-mode": "cors",
+        "sec-fetch-dest": "empty",
+        origin: "moz-extension://<placeholder>",
+      },
+      {
+        "sec-fetch-site": "cross-site",
+        "sec-fetch-mode": "cors",
+        "sec-fetch-dest": "empty",
+        origin: "moz-extension://<placeholder>",
+      },
+    ],
+    expectedContentHeaders: [
+      // TODO bug 1605197: Support cors without permissions in MV2.
+      "NetworkError when attempting to fetch resource.",
+      // Expectation:
+      // {
+      //   "sec-fetch-site": "cross-site",
+      //   "sec-fetch-mode": "cors",
+      //   "sec-fetch-dest": "empty",
+      // },
+      {
+        "sec-fetch-site": "cross-site",
+        "sec-fetch-mode": "cors",
+        "sec-fetch-dest": "empty",
+        origin: "http://127.0.0.2",
+      },
+      {
+        "sec-fetch-site": "same-origin",
+        "sec-fetch-mode": "cors",
+        "sec-fetch-dest": "empty",
+      },
+      {
+        "sec-fetch-site": "same-origin",
+        "sec-fetch-mode": "cors",
+        "sec-fetch-dest": "empty",
+      },
+      {
+        "sec-fetch-site": "same-origin",
+        "sec-fetch-mode": "cors",
+        "sec-fetch-dest": "empty",
+      },
+    ],
+  });
+});
+
+add_task(async function test_fetch_with_permissions_mv2() {
+  await runSecFetchTest({
+    manifest_version: 2,
+    permission: true,
+    expectedBackgroundHeaders: [
+      {
+        "sec-fetch-site": "same-origin",
+        "sec-fetch-mode": "cors",
+        "sec-fetch-dest": "empty",
+      },
+      {
+        "sec-fetch-site": "same-origin",
+        "sec-fetch-mode": "cors",
+        "sec-fetch-dest": "empty",
+        origin: "moz-extension://<placeholder>",
+      },
+    ],
+    expectedContentHeaders: [
+      {
+        "sec-fetch-site": "cross-site",
+        "sec-fetch-mode": "cors",
+        "sec-fetch-dest": "empty",
+      },
+      {
+        "sec-fetch-site": "cross-site",
+        "sec-fetch-mode": "cors",
+        "sec-fetch-dest": "empty",
+        origin: "http://127.0.0.2",
+      },
+      {
+        "sec-fetch-site": "same-origin",
+        "sec-fetch-mode": "cors",
+        "sec-fetch-dest": "empty",
+      },
+      {
+        "sec-fetch-site": "same-origin",
+        "sec-fetch-mode": "cors",
+        "sec-fetch-dest": "empty",
+      },
+      {
+        "sec-fetch-site": "same-origin",
+        "sec-fetch-mode": "cors",
+        "sec-fetch-dest": "empty",
+      },
+    ],
+  });
+});
+
+add_task(async function test_fetch_without_permissions_mv3() {
+  await runSecFetchTest({
+    manifest_version: 3,
+    permission: false,
+    expectedBackgroundHeaders: [
+      // Same as in test_fetch_without_permissions_mv2.
+      {
+        "sec-fetch-site": "cross-site",
+        "sec-fetch-mode": "cors",
+        "sec-fetch-dest": "empty",
+        origin: "moz-extension://<placeholder>",
+      },
+      {
+        "sec-fetch-site": "cross-site",
+        "sec-fetch-mode": "cors",
+        "sec-fetch-dest": "empty",
+        origin: "moz-extension://<placeholder>",
+      },
+    ],
+    expectedContentHeaders: [
+      {
+        "sec-fetch-site": "cross-site",
+        "sec-fetch-mode": "cors",
+        "sec-fetch-dest": "empty",
+        origin: "http://127.0.0.2",
+      },
+      {
+        "sec-fetch-site": "cross-site",
+        "sec-fetch-mode": "cors",
+        "sec-fetch-dest": "empty",
+        origin: "http://127.0.0.2",
+      },
+      {
+        "sec-fetch-site": "same-origin",
+        "sec-fetch-mode": "cors",
+        "sec-fetch-dest": "empty",
+      },
+      {
+        "sec-fetch-site": "same-origin",
+        "sec-fetch-mode": "cors",
+        "sec-fetch-dest": "empty",
+      },
+      {
+        "sec-fetch-site": "same-origin",
+        "sec-fetch-mode": "cors",
+        "sec-fetch-dest": "empty",
+        origin: "http://127.0.0.2",
+      },
+    ],
+  });
+});
+
+add_task(async function test_fetch_with_permissions_mv3() {
+  await runSecFetchTest({
+    manifest_version: 3,
+    permission: true,
+    expectedBackgroundHeaders: [
+      {
+        // Same as in test_fetch_with_permissions_mv2.
+        "sec-fetch-site": "same-origin",
+        "sec-fetch-mode": "cors",
+        "sec-fetch-dest": "empty",
+      },
+      {
+        "sec-fetch-site": "same-origin",
+        "sec-fetch-mode": "cors",
+        "sec-fetch-dest": "empty",
+        origin: "moz-extension://<placeholder>",
+      },
+    ],
+    expectedContentHeaders: [
+      // All expectations the same as in test_fetch_without_permissions_mv3.
+      {
+        "sec-fetch-site": "cross-site",
+        "sec-fetch-mode": "cors",
+        "sec-fetch-dest": "empty",
+        origin: "http://127.0.0.2",
+      },
+      {
+        "sec-fetch-site": "cross-site",
+        "sec-fetch-mode": "cors",
+        "sec-fetch-dest": "empty",
+        origin: "http://127.0.0.2",
+      },
+      {
+        "sec-fetch-site": "same-origin",
+        "sec-fetch-mode": "cors",
+        "sec-fetch-dest": "empty",
+      },
+      {
+        "sec-fetch-site": "same-origin",
+        "sec-fetch-mode": "cors",
+        "sec-fetch-dest": "empty",
+      },
+      {
+        "sec-fetch-site": "same-origin",
+        "sec-fetch-mode": "cors",
+        "sec-fetch-dest": "empty",
+        origin: "http://127.0.0.2",
+      },
+    ],
+  });
+});
diff --git a/toolkit/components/extensions/test/xpcshell/test_ext_shadowdom.js b/toolkit/components/extensions/test/xpcshell/test_ext_shadowdom.js
new file mode 100644
index 0000000000..626d8de22d
--- /dev/null
+++ b/toolkit/components/extensions/test/xpcshell/test_ext_shadowdom.js
@@ -0,0 +1,59 @@
+"use strict";
+
+// ExtensionContent.jsm needs to know when it's running from xpcshell,
+// to use the right timeout for content scripts executed at document_idle.
+ExtensionTestUtils.mockAppInfo();
+
+const server = createHttpServer();
+server.registerDirectory("/data/", do_get_file("data"));
+
+const BASE_URL = `http://localhost:${server.identity.primaryPort}/data`;
+
+add_task(async function test_contentscript_shadowDOM() {
+  function backgroundScript() {
+    browser.test.assertTrue(
+      "openOrClosedShadowRoot" in document.documentElement,
+      "Should have openOrClosedShadowRoot in Element in background script."
+    );
+  }
+
+  function contentScript() {
+    let host = document.getElementById("host");
+    browser.test.assertTrue(
+      "openOrClosedShadowRoot" in host,
+      "Should have openOrClosedShadowRoot in Element."
+    );
+    let shadowRoot = host.openOrClosedShadowRoot;
+    browser.test.assertEq(
+      shadowRoot.mode,
+      "closed",
+      "Should have closed ShadowRoot."
+    );
+    browser.test.sendMessage("contentScript");
+  }
+
+  let extension = ExtensionTestUtils.loadExtension({
+    manifest: {
+      content_scripts: [
+        {
+          matches: ["http://*/*/file_shadowdom.html"],
+          js: ["content_script.js"],
+        },
+      ],
+    },
+    background: backgroundScript,
+    files: {
+      "content_script.js": contentScript,
+    },
+  });
+
+  await extension.startup();
+
+  let contentPage = await ExtensionTestUtils.loadContentPage(
+    `${BASE_URL}/file_shadowdom.html`
+  );
+  await extension.awaitMessage("contentScript");
+
+  await contentPage.close();
+  await extension.unload();
+});
diff --git a/toolkit/components/extensions/test/xpcshell/test_ext_shared_array_buffer.js b/toolkit/components/extensions/test/xpcshell/test_ext_shared_array_buffer.js
new file mode 100644
index 0000000000..b2a9d81a27
--- /dev/null
+++ b/toolkit/components/extensions/test/xpcshell/test_ext_shared_array_buffer.js
@@ -0,0 +1,104 @@
+/* Any copyright is dedicated to the Public Domain.
+ * http://creativecommons.org/publicdomain/zero/1.0/ */
+
+"use strict";
+
+add_task(async function test_shared_array_buffer_worker() {
+  const extension_description = {
+    isPrivileged: null,
+    async background() {
+      browser.test.onMessage.addListener(async isPrivileged => {
+        const worker = new Worker("worker.js");
+        worker.isPrivileged = isPrivileged;
+        worker.onmessage = function (e) {
+          const msg = `${
+            this.isPrivileged
+              ? "privileged addon can"
+              : "non-privileged addon can't"
+          } instantiate a SharedArrayBuffer
+          in a worker`;
+          if (e.data === this.isPrivileged) {
+            browser.test.succeed(msg);
+          } else {
+            browser.test.fail(msg);
+          }
+          browser.test.sendMessage("test-sab-worker:done");
+        };
+      });
+    },
+    files: {
+      "worker.js": function () {
+        try {
+          new SharedArrayBuffer(1);
+          this.postMessage(true);
+        } catch (e) {
+          this.postMessage(false);
+        }
+      },
+    },
+  };
+
+  // This test attempts to verify that a worker inside a privileged addon
+  // is allowed to instantiate a SharedArrayBuffer
+  extension_description.isPrivileged = true;
+  let extension = ExtensionTestUtils.loadExtension(extension_description);
+  await extension.startup();
+  extension.sendMessage(extension_description.isPrivileged);
+  await extension.awaitMessage("test-sab-worker:done");
+  await extension.unload();
+
+  // This test attempts to verify that a worker inside a non privileged addon
+  // is not allowed to instantiate a SharedArrayBuffer
+  extension_description.isPrivileged = false;
+  extension = ExtensionTestUtils.loadExtension(extension_description);
+  await extension.startup();
+  extension.sendMessage(extension_description.isPrivileged);
+  await extension.awaitMessage("test-sab-worker:done");
+  await extension.unload();
+});
+
+add_task(async function test_shared_array_buffer_content() {
+  let extension_description = {
+    isPrivileged: null,
+    async background() {
+      browser.test.onMessage.addListener(async isPrivileged => {
+        let succeed = null;
+        try {
+          new SharedArrayBuffer(1);
+          succeed = true;
+        } catch (e) {
+          succeed = false;
+        } finally {
+          const msg = `${
+            isPrivileged ? "privileged addon can" : "non-privileged addon can't"
+          } instantiate a SharedArrayBuffer
+          in the main thread`;
+          if (succeed === isPrivileged) {
+            browser.test.succeed(msg);
+          } else {
+            browser.test.fail(msg);
+          }
+          browser.test.sendMessage("test-sab-content:done");
+        }
+      });
+    },
+  };
+
+  // This test attempts to verify that a non privileged addon
+  // is allowed to instantiate a sharedarraybuffer
+  extension_description.isPrivileged = true;
+  let extension = ExtensionTestUtils.loadExtension(extension_description);
+  await extension.startup();
+  extension.sendMessage(extension_description.isPrivileged);
+  await extension.awaitMessage("test-sab-content:done");
+  await extension.unload();
+
+  // This test attempts to verify that a non privileged addon
+  // is not allowed to instantiate a sharedarraybuffer
+  extension_description.isPrivileged = false;
+  extension = ExtensionTestUtils.loadExtension(extension_description);
+  await extension.startup();
+  extension.sendMessage(extension_description.isPrivileged);
+  await extension.awaitMessage("test-sab-content:done");
+  await extension.unload();
+});
diff --git a/toolkit/components/extensions/test/xpcshell/test_ext_shared_workers.js b/toolkit/components/extensions/test/xpcshell/test_ext_shared_workers.js
new file mode 100644
index 0000000000..54c14e5524
--- /dev/null
+++ b/toolkit/components/extensions/test/xpcshell/test_ext_shared_workers.js
@@ -0,0 +1,40 @@
+/* Any copyright is dedicated to the Public Domain.
+ * http://creativecommons.org/publicdomain/zero/1.0/ */
+
+"use strict";
+
+// This test attemps to verify that:
+// - SharedWorkers can be created and successfully spawned by web extensions
+//   when web-extensions run in their own child process.
+add_task(async function test_spawn_shared_worker() {
+  if (!WebExtensionPolicy.useRemoteWebExtensions) {
+    // Ensure RemoteWorkerService has been initialized in the main
+    // process.
+    Services.obs.notifyObservers(null, "profile-after-change");
+  }
+
+  const background = async function () {
+    const worker = new SharedWorker("worker.js");
+    await new Promise(resolve => {
+      worker.port.onmessage = resolve;
+      worker.port.postMessage("bgpage->worker");
+    });
+    browser.test.sendMessage("test-shared-worker:done");
+  };
+
+  const extension = ExtensionTestUtils.loadExtension({
+    background,
+    files: {
+      "worker.js": function () {
+        self.onconnect = evt => {
+          const port = evt.ports[0];
+          port.onmessage = () => port.postMessage("worker-reply");
+        };
+      },
+    },
+  });
+
+  await extension.startup();
+  await extension.awaitMessage("test-shared-worker:done");
+  await extension.unload();
+});
diff --git a/toolkit/components/extensions/test/xpcshell/test_ext_shutdown_cleanup.js b/toolkit/components/extensions/test/xpcshell/test_ext_shutdown_cleanup.js
new file mode 100644
index 0000000000..f423ccbe97
--- /dev/null
+++ b/toolkit/components/extensions/test/xpcshell/test_ext_shutdown_cleanup.js
@@ -0,0 +1,43 @@
+/* -*- Mode: indent-tabs-mode: nil; js-indent-level: 2 -*- */
+/* vim: set sts=2 sw=2 et tw=80: */
+
+"use strict";
+
+const {
+  ExtensionParent: { GlobalManager },
+} = ChromeUtils.importESModule(
+  "resource://gre/modules/ExtensionParent.sys.mjs"
+);
+
+add_task(async function test_global_manager_shutdown_cleanup() {
+  equal(
+    GlobalManager.initialized,
+    false,
+    "GlobalManager start as not initialized"
+  );
+
+  function background() {
+    browser.test.notifyPass("background page loaded");
+  }
+
+  let extension = ExtensionTestUtils.loadExtension({
+    background,
+  });
+
+  await extension.startup();
+  await extension.awaitFinish("background page loaded");
+
+  equal(
+    GlobalManager.initialized,
+    true,
+    "GlobalManager has been initialized once an extension is started"
+  );
+
+  await extension.unload();
+
+  equal(
+    GlobalManager.initialized,
+    false,
+    "GlobalManager has been uninitialized once all the webextensions have been stopped"
+  );
+});
diff --git a/toolkit/components/extensions/test/xpcshell/test_ext_simple.js b/toolkit/components/extensions/test/xpcshell/test_ext_simple.js
new file mode 100644
index 0000000000..ad74d80ede
--- /dev/null
+++ b/toolkit/components/extensions/test/xpcshell/test_ext_simple.js
@@ -0,0 +1,208 @@
+/* -*- Mode: indent-tabs-mode: nil; js-indent-level: 2 -*- */
+/* vim: set sts=2 sw=2 et tw=80: */
+"use strict";
+
+AddonTestUtils.init(this);
+AddonTestUtils.overrideCertDB();
+AddonTestUtils.createAppInfo(
+  "xpcshell@tests.mozilla.org",
+  "XPCShell",
+  "1",
+  "43"
+);
+
+add_task(async function test_simple() {
+  let extensionData = {
+    manifest: {
+      name: "Simple extension test",
+      version: "1.0",
+      manifest_version: 2,
+      description: "",
+    },
+  };
+
+  let extension = ExtensionTestUtils.loadExtension(extensionData);
+  await extension.startup();
+  await extension.unload();
+});
+
+add_task(async function test_manifest_V3_disabled() {
+  Services.prefs.setBoolPref("extensions.manifestV3.enabled", false);
+  let extensionData = {
+    manifest: {
+      manifest_version: 3,
+    },
+  };
+
+  let extension = ExtensionTestUtils.loadExtension(extensionData);
+  await Assert.rejects(
+    extension.startup(),
+    /Unsupported manifest version: 3/,
+    "manifest V3 cannot be loaded"
+  );
+  Services.prefs.clearUserPref("extensions.manifestV3.enabled");
+});
+
+add_task(async function test_manifest_V3_enabled() {
+  Services.prefs.setBoolPref("extensions.manifestV3.enabled", true);
+  let extensionData = {
+    manifest: {
+      manifest_version: 3,
+    },
+  };
+
+  let extension = ExtensionTestUtils.loadExtension(extensionData);
+  await extension.startup();
+  equal(extension.extension.manifest.manifest_version, 3, "manifest V3 loads");
+  await extension.unload();
+  Services.prefs.clearUserPref("extensions.manifestV3.enabled");
+});
+
+add_task(async function test_background() {
+  function background() {
+    browser.test.log("running background script");
+
+    browser.test.onMessage.addListener((x, y) => {
+      browser.test.assertEq(x, 10, "x is 10");
+      browser.test.assertEq(y, 20, "y is 20");
+
+      browser.test.notifyPass("background test passed");
+    });
+
+    browser.test.sendMessage("running", 1);
+  }
+
+  let extensionData = {
+    background,
+    manifest: {
+      name: "Simple extension test",
+      version: "1.0",
+      manifest_version: 2,
+      description: "",
+    },
+  };
+
+  let extension = ExtensionTestUtils.loadExtension(extensionData);
+
+  let [, x] = await Promise.all([
+    extension.startup(),
+    extension.awaitMessage("running"),
+  ]);
+  equal(x, 1, "got correct value from extension");
+
+  extension.sendMessage(10, 20);
+  await extension.awaitFinish();
+  await extension.unload();
+});
+
+add_task(async function test_extensionTypes() {
+  let extensionData = {
+    background: function () {
+      browser.test.assertEq(
+        typeof browser.extensionTypes,
+        "object",
+        "browser.extensionTypes exists"
+      );
+      browser.test.assertEq(
+        typeof browser.extensionTypes.RunAt,
+        "object",
+        "browser.extensionTypes.RunAt exists"
+      );
+      browser.test.notifyPass("extentionTypes test passed");
+    },
+  };
+
+  let extension = ExtensionTestUtils.loadExtension(extensionData);
+
+  await extension.startup();
+  await extension.awaitFinish();
+  await extension.unload();
+});
+
+add_task(async function test_policy_temporarilyInstalled() {
+  await AddonTestUtils.promiseStartupManager();
+
+  let extensionData = {
+    manifest: {
+      manifest_version: 2,
+    },
+  };
+
+  async function runTest(useAddonManager) {
+    let extension = ExtensionTestUtils.loadExtension({
+      ...extensionData,
+      useAddonManager,
+    });
+
+    const expected = useAddonManager === "temporary";
+    await extension.startup();
+    const { temporarilyInstalled } = WebExtensionPolicy.getByID(extension.id);
+    equal(
+      temporarilyInstalled,
+      expected,
+      `Got the expected WebExtensionPolicy.temporarilyInstalled value on "${useAddonManager}"`
+    );
+    await extension.unload();
+  }
+
+  await runTest("temporary");
+  await runTest("permanent");
+});
+
+add_task(async function test_manifest_allowInsecureRequests() {
+  Services.prefs.setBoolPref("extensions.manifestV3.enabled", true);
+  let extensionData = {
+    allowInsecureRequests: true,
+    manifest: {
+      manifest_version: 3,
+    },
+  };
+
+  let extension = ExtensionTestUtils.loadExtension(extensionData);
+  await extension.startup();
+  equal(
+    extension.extension.manifest.content_security_policy.extension_pages,
+    `script-src 'self'`,
+    "insecure allowed"
+  );
+  await extension.unload();
+  Services.prefs.clearUserPref("extensions.manifestV3.enabled");
+});
+
+add_task(async function test_manifest_allowInsecureRequests_throws() {
+  Services.prefs.setBoolPref("extensions.manifestV3.enabled", true);
+  let extensionData = {
+    allowInsecureRequests: true,
+    manifest: {
+      manifest_version: 3,
+      content_security_policy: {
+        extension_pages: `script-src 'self'`,
+      },
+    },
+  };
+
+  await Assert.throws(
+    () => ExtensionTestUtils.loadExtension(extensionData),
+    /allowInsecureRequests cannot be used with manifest.content_security_policy/,
+    "allowInsecureRequests with content_security_policy cannot be loaded"
+  );
+  Services.prefs.clearUserPref("extensions.manifestV3.enabled");
+});
+
+add_task(async function test_gecko_android_key_in_applications() {
+  const extensionData = {
+    manifest: {
+      manifest_version: 2,
+      applications: {
+        gecko_android: {},
+      },
+    },
+  };
+  const extension = ExtensionTestUtils.loadExtension(extensionData);
+
+  await Assert.rejects(
+    extension.startup(),
+    /applications: Property "gecko_android" is unsupported by Firefox/,
+    "expected applications.gecko_android to be invalid"
+  );
+});
diff --git a/toolkit/components/extensions/test/xpcshell/test_ext_startupData.js b/toolkit/components/extensions/test/xpcshell/test_ext_startupData.js
new file mode 100644
index 0000000000..df51fa9abf
--- /dev/null
+++ b/toolkit/components/extensions/test/xpcshell/test_ext_startupData.js
@@ -0,0 +1,55 @@
+"use strict";
+
+AddonTestUtils.init(this);
+AddonTestUtils.overrideCertDB();
+AddonTestUtils.createAppInfo(
+  "xpcshell@tests.mozilla.org",
+  "XPCShell",
+  "1",
+  "1"
+);
+
+// Tests that startupData is persisted and is available at startup
+add_task(async function test_startupData() {
+  await AddonTestUtils.promiseStartupManager();
+
+  let wrapper = ExtensionTestUtils.loadExtension({
+    useAddonManager: "permanent",
+  });
+  await wrapper.startup();
+
+  let { extension } = wrapper;
+
+  deepEqual(
+    extension.startupData,
+    {},
+    "startupData for a new extension defaults to empty object"
+  );
+
+  const DATA = { test: "i am some startup data" };
+  extension.startupData = DATA;
+  extension.saveStartupData();
+
+  await AddonTestUtils.promiseRestartManager();
+  await wrapper.startupPromise;
+
+  ({ extension } = wrapper);
+  deepEqual(extension.startupData, DATA, "startupData is present on restart");
+
+  const DATA2 = { other: "this is different data" };
+  extension.startupData = DATA2;
+  extension.saveStartupData();
+
+  await AddonTestUtils.promiseRestartManager();
+  await wrapper.startupPromise;
+
+  ({ extension } = wrapper);
+  deepEqual(
+    extension.startupData,
+    DATA2,
+    "updated startupData is present on restart"
+  );
+
+  await wrapper.unload();
+  await AddonTestUtils.promiseShutdownManager();
+});
diff --git a/toolkit/components/extensions/test/xpcshell/test_ext_startup_cache.js b/toolkit/components/extensions/test/xpcshell/test_ext_startup_cache.js
new file mode 100644
index 0000000000..ac815d6010
--- /dev/null
+++ b/toolkit/components/extensions/test/xpcshell/test_ext_startup_cache.js
@@ -0,0 +1,178 @@
+/* -*- Mode: indent-tabs-mode: nil; js-indent-level: 2 -*- */
+/* vim: set sts=2 sw=2 et tw=80: */
+"use strict";
+
+const { AddonManager } = ChromeUtils.importESModule(
+  "resource://gre/modules/AddonManager.sys.mjs"
+);
+const { Preferences } = ChromeUtils.importESModule(
+  "resource://gre/modules/Preferences.sys.mjs"
+);
+
+const { TestUtils } = ChromeUtils.importESModule(
+  "resource://testing-common/TestUtils.sys.mjs"
+);
+
+AddonTestUtils.init(this);
+AddonTestUtils.overrideCertDB();
+
+AddonTestUtils.createAppInfo(
+  "xpcshell@tests.mozilla.org",
+  "XPCShell",
+  "42",
+  "42"
+);
+
+const ADDON_ID = "test-startup-cache@xpcshell.mozilla.org";
+
+function makeExtension(opts) {
+  return {
+    useAddonManager: "permanent",
+
+    manifest: {
+      version: opts.version,
+      browser_specific_settings: { gecko: { id: ADDON_ID } },
+
+      name: "__MSG_name__",
+
+      default_locale: "en_US",
+    },
+
+    files: {
+      "_locales/en_US/messages.json": {
+        name: {
+          message: `en-US ${opts.version}`,
+          description: "Name.",
+        },
+      },
+      "_locales/fr/messages.json": {
+        name: {
+          message: `fr ${opts.version}`,
+          description: "Name.",
+        },
+      },
+    },
+
+    background() {
+      browser.test.onMessage.addListener(msg => {
+        if (msg === "get-manifest") {
+          browser.test.sendMessage("manifest", browser.runtime.getManifest());
+        }
+      });
+    },
+  };
+}
+
+add_task(async function test_langpack_startup_cache() {
+  Preferences.set("extensions.logging.enabled", false);
+  await AddonTestUtils.promiseStartupManager();
+
+  // Install langpacks to get proper locale startup.
+  let langpack = {
+    "manifest.json": {
+      name: "test Language Pack",
+      version: "1.0",
+      manifest_version: 2,
+      browser_specific_settings: {
+        gecko: {
+          id: "@test-langpack",
+          strict_min_version: "42.0",
+          strict_max_version: "42.0",
+        },
+      },
+      langpack_id: "fr",
+      languages: {
+        fr: {
+          chrome_resources: {
+            global: "chrome/fr/locale/fr/global/",
+          },
+          version: "20171001190118",
+        },
+      },
+      sources: {
+        browser: {
+          base_path: "browser/",
+        },
+      },
+    },
+  };
+
+  let [, { addon }] = await Promise.all([
+    TestUtils.topicObserved("webextension-langpack-startup"),
+    AddonTestUtils.promiseInstallXPI(langpack),
+  ]);
+
+  let extension = ExtensionTestUtils.loadExtension(
+    makeExtension({ version: "1.0" })
+  );
+
+  function getManifest() {
+    extension.sendMessage("get-manifest");
+    return extension.awaitMessage("manifest");
+  }
+
+  // At the moment extension language negotiation is tied to Firefox language
+  // negotiation result. That means that to test an extension in `fr`, we need
+  // to mock `fr` being available in Firefox and then request it.
+  //
+  // In the future, we should provide some way for tests to decouple their
+  // language selection from that of Firefox.
+  ok(Services.locale.availableLocales.includes("fr"), "fr locale is avialable");
+
+  await extension.startup();
+
+  equal(extension.version, "1.0", "Expected extension version");
+  let manifest = await getManifest();
+  equal(manifest.name, "en-US 1.0", "Got expected manifest name");
+
+  info("Restart and re-check");
+  await AddonTestUtils.promiseRestartManager();
+  await extension.awaitBackgroundStarted();
+
+  equal(extension.version, "1.0", "Expected extension version");
+  manifest = await getManifest();
+  equal(manifest.name, "en-US 1.0", "Got expected manifest name");
+
+  info("Change locale to 'fr' and restart");
+  Services.locale.requestedLocales = ["fr"];
+  await AddonTestUtils.promiseRestartManager();
+  await extension.awaitBackgroundStarted();
+
+  equal(extension.version, "1.0", "Expected extension version");
+  manifest = await getManifest();
+  equal(manifest.name, "fr 1.0", "Got expected manifest name");
+
+  info("Update to version 1.1");
+  await extension.upgrade(makeExtension({ version: "1.1" }));
+
+  equal(extension.version, "1.1", "Expected extension version");
+  manifest = await getManifest();
+  equal(manifest.name, "fr 1.1", "Got expected manifest name");
+
+  info("Change locale to 'en-US' and restart");
+  Services.locale.requestedLocales = ["en-US"];
+  await AddonTestUtils.promiseRestartManager();
+  await extension.awaitBackgroundStarted();
+
+  equal(extension.version, "1.1", "Expected extension version");
+  manifest = await getManifest();
+  equal(manifest.name, "en-US 1.1", "Got expected manifest name");
+
+  info("Disable locale 'fr'");
+  addon = await AddonManager.getAddonByID("@test-langpack");
+
+  // We disable the installed langpack instead of uninstalling it
+  // because the xpi file may technically be still in use by the
+  // time the XPIProvider will try to remove the file and will
+  // make this test to fail intermittently on windows.
+  //
+  // Disabling the addon is equivalent from the perspective of this
+  // test case, and the langpack xpi will be uninstalled automatically
+  // at the end of this test case by AddonTestUtils (from its
+  // cleanupTempXPIs method, which will also force a GC if the
+  // file fails to be removed after we flushed the jar cache).
+  await addon.disable();
+  ok(!Services.locale.availableLocales.includes("fr"), "fr locale is removed");
+
+  await extension.unload();
+});
diff --git a/toolkit/components/extensions/test/xpcshell/test_ext_startup_cache_telemetry.js b/toolkit/components/extensions/test/xpcshell/test_ext_startup_cache_telemetry.js
new file mode 100644
index 0000000000..f26e917220
--- /dev/null
+++ b/toolkit/components/extensions/test/xpcshell/test_ext_startup_cache_telemetry.js
@@ -0,0 +1,162 @@
+/* Any copyright is dedicated to the Public Domain.
+ * http://creativecommons.org/publicdomain/zero/1.0/ */
+
+"use strict";
+
+ChromeUtils.defineESModuleGetters(this, {
+  ExtensionParent: "resource://gre/modules/ExtensionParent.sys.mjs",
+  TelemetryTestUtils: "resource://testing-common/TelemetryTestUtils.sys.mjs",
+});
+
+AddonTestUtils.init(this);
+AddonTestUtils.overrideCertDB();
+
+AddonTestUtils.createAppInfo(
+  "xpcshell@tests.mozilla.org",
+  "XPCShell",
+  "42",
+  "42"
+);
+
+const ADDON_ID = "test-startup-cache-telemetry@xpcshell.mozilla.org";
+
+add_setup(async () => {
+  // FOG needs a profile directory to put its data in.
+  do_get_profile();
+  // FOG needs to be initialized in order for data to flow.
+  Services.fog.initializeFOG();
+
+  await AddonTestUtils.promiseStartupManager();
+});
+
+add_task(async function test_startupCache_write_byteLength() {
+  const extension = ExtensionTestUtils.loadExtension({
+    useAddonManager: "permanent",
+    manifest: {
+      browser_specific_settings: { gecko: { id: ADDON_ID } },
+    },
+  });
+
+  await extension.startup();
+
+  const { StartupCache } = ExtensionParent;
+
+  const aomStartup = Cc[
+    "@mozilla.org/addons/addon-manager-startup;1"
+  ].getService(Ci.amIAddonManagerStartup);
+
+  let expectedByteLength = new Uint8Array(
+    aomStartup.encodeBlob(StartupCache._data)
+  ).byteLength;
+
+  equal(
+    typeof expectedByteLength,
+    "number",
+    "Got a numeric byteLength for the expected startupCache data"
+  );
+  ok(expectedByteLength > 0, "Got a non-zero byteLength as expected");
+  await StartupCache._saveNow();
+
+  let scalars = TelemetryTestUtils.getProcessScalars("parent");
+  equal(
+    scalars["extensions.startupCache.write_byteLength"],
+    expectedByteLength,
+    "Got the expected value set in the 'extensions.startupCache.write_byteLength' scalar"
+  );
+
+  await extension.unload();
+});
+
+add_task(async function test_startupCache_read_errors() {
+  const { StartupCache } = ExtensionParent;
+
+  // Clear any pre-existing keyed scalar.
+  TelemetryTestUtils.getProcessScalars("parent", /* keyed */ true, true);
+
+  // Temporarily point StartupCache._file to a path that is
+  // not going to exist for sure.
+  Assert.notEqual(
+    StartupCache.file,
+    null,
+    "Got a StartupCache._file non-null property as expected"
+  );
+  const oldFile = StartupCache.file;
+  const restoreStartupCacheFile = () => (StartupCache.file = oldFile);
+  StartupCache.file = `${StartupCache.file}.non_existing_file.${Math.random()}`;
+  registerCleanupFunction(restoreStartupCacheFile);
+
+  // Make sure the _readData has been called and we can expect
+  // the extensions.startupCache.read_errors scalar to have
+  // been recorded.
+  await StartupCache._readData();
+
+  let scalars = TelemetryTestUtils.getProcessScalars(
+    "parent",
+    /* keyed */ true
+  );
+  Assert.deepEqual(
+    scalars["extensions.startupCache.read_errors"],
+    {
+      NotFoundError: 1,
+    },
+    "Got the expected value set in the 'extensions.startupCache.read_errors' keyed scalar"
+  );
+
+  restoreStartupCacheFile();
+});
+
+async function test_startupCache_load_timestamps() {
+  const { StartupCache } = ExtensionParent;
+
+  // Clear any pre-existing keyed scalar and Glean metrics data.
+  TelemetryTestUtils.getProcessScalars("parent", false, true);
+  Services.fog.testResetFOG();
+
+  let gleanMetric = Glean.extensions.startupCacheLoadTime.testGetValue();
+  equal(
+    typeof gleanMetric,
+    "undefined",
+    "Expect extensions.startup_cache_load_time Glean metric to be initially undefined"
+  );
+
+  // Make sure the _readData has been called and we can expect
+  // the startupCache load telemetry timestamps to have been
+  // recorded.
+  await StartupCache._readData();
+
+  info(
+    "Verify telemetry recorded for the 'extensions.startup_cache_load_time' Glean metric"
+  );
+
+  gleanMetric = Glean.extensions.startupCacheLoadTime.testGetValue();
+  equal(
+    typeof gleanMetric,
+    "number",
+    "Expect extensions.startup_cache_load_time Glean metric to be set to a number"
+  );
+
+  info(
+    "Verify telemetry mirrored into the 'extensions.startupCache.load_time' scalar"
+  );
+
+  const scalars = TelemetryTestUtils.getProcessScalars("parent", false, true);
+
+  equal(
+    typeof scalars["extensions.startupCache.load_time"],
+    "number",
+    "Expect extensions.startupCache.load_time mirrored scalar to be set to a number"
+  );
+
+  equal(
+    scalars["extensions.startupCache.load_time"],
+    gleanMetric,
+    "Expect the glean metric and mirrored scalar to be set to the same value"
+  );
+}
+
+add_task(
+  // Bug 1752139: this test can be re-enabled once Services.fog.testResetFOG()
+  // is implemented also on Android.
+  { skip_if: () => AppConstants.platform === "android" },
+  test_startupCache_load_timestamps
+);
diff --git a/toolkit/components/extensions/test/xpcshell/test_ext_startup_perf.js b/toolkit/components/extensions/test/xpcshell/test_ext_startup_perf.js
new file mode 100644
index 0000000000..e7108ce100
--- /dev/null
+++ b/toolkit/components/extensions/test/xpcshell/test_ext_startup_perf.js
@@ -0,0 +1,70 @@
+/* -*- Mode: indent-tabs-mode: nil; js-indent-level: 2 -*- */
+/* vim: set sts=2 sw=2 et tw=80: */
+"use strict";
+
+const STARTUP_APIS = ["backgroundPage"];
+
+const STARTUP_MODULES = new Set([
+  "resource://gre/modules/Extension.sys.mjs",
+  "resource://gre/modules/ExtensionCommon.sys.mjs",
+  "resource://gre/modules/ExtensionParent.sys.mjs",
+  // FIXME: This is only loaded at startup for new extension installs.
+  // Otherwise the data comes from the startup cache. We should test for
+  // this.
+  "resource://gre/modules/ExtensionPermissions.sys.mjs",
+  "resource://gre/modules/ExtensionProcessScript.sys.mjs",
+  "resource://gre/modules/ExtensionUtils.sys.mjs",
+  "resource://gre/modules/ExtensionTelemetry.sys.mjs",
+]);
+
+if (!Services.prefs.getBoolPref("extensions.webextensions.remote")) {
+  STARTUP_MODULES.add("resource://gre/modules/ExtensionChild.sys.mjs");
+  STARTUP_MODULES.add("resource://gre/modules/ExtensionPageChild.sys.mjs");
+}
+
+if (AppConstants.MOZ_APP_NAME == "thunderbird") {
+  // Imported via mail/components/extensions/processScript.js.
+  STARTUP_MODULES.add("resource://gre/modules/ExtensionChild.sys.mjs");
+  STARTUP_MODULES.add("resource://gre/modules/ExtensionContent.sys.mjs");
+  STARTUP_MODULES.add("resource://gre/modules/ExtensionPageChild.sys.mjs");
+}
+
+AddonTestUtils.init(this);
+
+// Tests that only the minimal set of API scripts and modules are loaded at
+// startup for a simple extension.
+add_task(async function test_loaded_scripts() {
+  await ExtensionTestUtils.startAddonManager();
+
+  let extension = ExtensionTestUtils.loadExtension({
+    useAddonManager: "temporary",
+    background() {},
+    manifest: {},
+  });
+
+  await extension.startup();
+
+  const { apiManager } = ExtensionParent;
+
+  const loadedAPIs = Array.from(apiManager.modules.values())
+    .filter(m => m.loaded || m.asyncLoaded)
+    .map(m => m.namespaceName);
+
+  deepEqual(
+    loadedAPIs.sort(),
+    STARTUP_APIS,
+    "No extra APIs should be loaded at startup for a simple extension"
+  );
+
+  let loadedModules = Cu.loadedJSModules
+    .concat(Cu.loadedESModules)
+    .filter(url => url.startsWith("resource://gre/modules/Extension"));
+
+  deepEqual(
+    loadedModules.sort(),
+    Array.from(STARTUP_MODULES).sort(),
+    "No extra extension modules should be loaded at startup for a simple extension"
+  );
+
+  await extension.unload();
+});
diff --git a/toolkit/components/extensions/test/xpcshell/test_ext_startup_request_handler.js b/toolkit/components/extensions/test/xpcshell/test_ext_startup_request_handler.js
new file mode 100644
index 0000000000..2311f76105
--- /dev/null
+++ b/toolkit/components/extensions/test/xpcshell/test_ext_startup_request_handler.js
@@ -0,0 +1,64 @@
+"use strict";
+
+function delay(time) {
+  return new Promise(resolve => {
+    // eslint-disable-next-line mozilla/no-arbitrary-setTimeout
+    setTimeout(resolve, time);
+  });
+}
+
+const { Extension } = ChromeUtils.importESModule(
+  "resource://gre/modules/Extension.sys.mjs"
+);
+
+add_task(async function test_startup_request_handler() {
+  const ID = "request-startup@xpcshell.mozilla.org";
+
+  let extension = ExtensionTestUtils.loadExtension({
+    manifest: {
+      browser_specific_settings: { gecko: { id: ID } },
+    },
+
+    files: {
+      "meh.txt": "Meh.",
+    },
+  });
+
+  let ready = false;
+  let resolvePromise;
+  let promise = new Promise(resolve => {
+    resolvePromise = resolve;
+  });
+  promise.then(() => {
+    ready = true;
+  });
+
+  let origInitLocale = Extension.prototype.initLocale;
+  Extension.prototype.initLocale = async function initLocale() {
+    await promise;
+    return origInitLocale.call(this);
+  };
+
+  let startupPromise = extension.startup();
+
+  await delay(0);
+  let policy = WebExtensionPolicy.getByID(ID);
+  let url = policy.getURL("meh.txt");
+
+  let resp = ExtensionTestUtils.fetch(url, url);
+  resp.then(() => {
+    ok(ready, "Shouldn't get response before extension is ready");
+  });
+
+  await delay(2000);
+
+  resolvePromise();
+  await startupPromise;
+
+  let body = await resp;
+  equal(body, "Meh.", "Got the correct response");
+
+  await extension.unload();
+
+  Extension.prototype.initLocale = origInitLocale;
+});
diff --git a/toolkit/components/extensions/test/xpcshell/test_ext_storage_content_local.js b/toolkit/components/extensions/test/xpcshell/test_ext_storage_content_local.js
new file mode 100644
index 0000000000..4ba8cc596b
--- /dev/null
+++ b/toolkit/components/extensions/test/xpcshell/test_ext_storage_content_local.js
@@ -0,0 +1,39 @@
+"use strict";
+
+const { ExtensionStorageIDB } = ChromeUtils.importESModule(
+  "resource://gre/modules/ExtensionStorageIDB.sys.mjs"
+);
+
+PromiseTestUtils.allowMatchingRejectionsGlobally(
+  /WebExtension context not found/
+);
+
+const server = createHttpServer({ hosts: ["example.com"] });
+server.registerDirectory("/data/", do_get_file("data"));
+
+// The storage API in content scripts should behave identical to the storage API
+// in background pages.
+
+AddonTestUtils.init(this);
+
+add_task(async function setup() {
+  await ExtensionTestUtils.startAddonManager();
+});
+
+add_task(async function test_contentscript_storage_local_file_backend() {
+  return runWithPrefs([[ExtensionStorageIDB.BACKEND_ENABLED_PREF, false]], () =>
+    test_contentscript_storage("local")
+  );
+});
+
+add_task(async function test_contentscript_storage_local_idb_backend() {
+  return runWithPrefs([[ExtensionStorageIDB.BACKEND_ENABLED_PREF, true]], () =>
+    test_contentscript_storage("local")
+  );
+});
+
+add_task(async function test_contentscript_storage_local_idb_no_bytes_in_use() {
+  return runWithPrefs([[ExtensionStorageIDB.BACKEND_ENABLED_PREF, true]], () =>
+    test_contentscript_storage_area_no_bytes_in_use("local")
+  );
+});
diff --git a/toolkit/components/extensions/test/xpcshell/test_ext_storage_content_sync.js b/toolkit/components/extensions/test/xpcshell/test_ext_storage_content_sync.js
new file mode 100644
index 0000000000..6b1695417d
--- /dev/null
+++ b/toolkit/components/extensions/test/xpcshell/test_ext_storage_content_sync.js
@@ -0,0 +1,31 @@
+"use strict";
+
+Services.prefs.setBoolPref("webextensions.storage.sync.kinto", false);
+
+PromiseTestUtils.allowMatchingRejectionsGlobally(
+  /WebExtension context not found/
+);
+
+const server = createHttpServer({ hosts: ["example.com"] });
+server.registerDirectory("/data/", do_get_file("data"));
+
+// The storage API in content scripts should behave identical to the storage API
+// in background pages.
+
+AddonTestUtils.init(this);
+
+add_task(async function setup() {
+  await ExtensionTestUtils.startAddonManager();
+});
+
+add_task(async function test_contentscript_storage_sync() {
+  return runWithPrefs([[STORAGE_SYNC_PREF, true]], () =>
+    test_contentscript_storage("sync")
+  );
+});
+
+add_task(async function test_contentscript_bytes_in_use_sync() {
+  return runWithPrefs([[STORAGE_SYNC_PREF, true]], () =>
+    test_contentscript_storage_area_with_bytes_in_use("sync", true)
+  );
+});
diff --git a/toolkit/components/extensions/test/xpcshell/test_ext_storage_content_sync_kinto.js b/toolkit/components/extensions/test/xpcshell/test_ext_storage_content_sync_kinto.js
new file mode 100644
index 0000000000..92ec405520
--- /dev/null
+++ b/toolkit/components/extensions/test/xpcshell/test_ext_storage_content_sync_kinto.js
@@ -0,0 +1,31 @@
+"use strict";
+
+Services.prefs.setBoolPref("webextensions.storage.sync.kinto", true);
+
+PromiseTestUtils.allowMatchingRejectionsGlobally(
+  /WebExtension context not found/
+);
+
+const server = createHttpServer({ hosts: ["example.com"] });
+server.registerDirectory("/data/", do_get_file("data"));
+
+// The storage API in content scripts should behave identical to the storage API
+// in background pages.
+
+AddonTestUtils.init(this);
+
+add_task(async function setup() {
+  await ExtensionTestUtils.startAddonManager();
+});
+
+add_task(async function test_contentscript_storage_sync() {
+  return runWithPrefs([[STORAGE_SYNC_PREF, true]], () =>
+    test_contentscript_storage("sync")
+  );
+});
+
+add_task(async function test_contentscript_storage_no_bytes_in_use() {
+  return runWithPrefs([[STORAGE_SYNC_PREF, true]], () =>
+    test_contentscript_storage_area_with_bytes_in_use("sync", false)
+  );
+});
diff --git a/toolkit/components/extensions/test/xpcshell/test_ext_storage_idb_data_migration.js b/toolkit/components/extensions/test/xpcshell/test_ext_storage_idb_data_migration.js
new file mode 100644
index 0000000000..8a426c3669
--- /dev/null
+++ b/toolkit/components/extensions/test/xpcshell/test_ext_storage_idb_data_migration.js
@@ -0,0 +1,790 @@
+/* -*- Mode: indent-tabs-mode: nil; js-indent-level: 2 -*- */
+/* vim: set sts=2 sw=2 et tw=80: */
+"use strict";
+
+// This test file verifies various scenarios related to the data migration
+// from the JSONFile backend to the IDB backend.
+
+AddonTestUtils.init(this);
+
+// Create appInfo before importing any other jsm file, to prevent
+// Services.appinfo to be cached before an appInfo.version is
+// actually defined (which prevent failures to be triggered when
+// the test run in a non nightly build).
+AddonTestUtils.createAppInfo(
+  "xpcshell@tests.mozilla.org",
+  "XPCShell",
+  "1",
+  "42"
+);
+
+const { getTrimmedString } = ChromeUtils.importESModule(
+  "resource://gre/modules/ExtensionTelemetry.sys.mjs"
+);
+const { ExtensionStorage } = ChromeUtils.importESModule(
+  "resource://gre/modules/ExtensionStorage.sys.mjs"
+);
+const { ExtensionStorageIDB } = ChromeUtils.importESModule(
+  "resource://gre/modules/ExtensionStorageIDB.sys.mjs"
+);
+const { TelemetryController } = ChromeUtils.importESModule(
+  "resource://gre/modules/TelemetryController.sys.mjs"
+);
+const { TelemetryTestUtils } = ChromeUtils.importESModule(
+  "resource://testing-common/TelemetryTestUtils.sys.mjs"
+);
+
+const { promiseShutdownManager, promiseStartupManager } = AddonTestUtils;
+
+const { IDB_MIGRATED_PREF_BRANCH, IDB_MIGRATE_RESULT_HISTOGRAM } =
+  ExtensionStorageIDB;
+const CATEGORIES = ["success", "failure"];
+const EVENT_CATEGORY = "extensions.data";
+const EVENT_OBJECT = "storageLocal";
+const EVENT_METHOD = "migrateResult";
+const LEAVE_STORAGE_PREF = "extensions.webextensions.keepStorageOnUninstall";
+const LEAVE_UUID_PREF = "extensions.webextensions.keepUuidOnUninstall";
+const TELEMETRY_EVENTS_FILTER = {
+  category: "extensions.data",
+  method: "migrateResult",
+  object: "storageLocal",
+};
+
+async function createExtensionJSONFileWithData(extensionId, data) {
+  await ExtensionStorage.set(extensionId, data);
+  const jsonFile = await ExtensionStorage.getFile(extensionId);
+  await jsonFile._save();
+  const oldStorageFilename = ExtensionStorage.getStorageFile(extensionId);
+  equal(
+    await IOUtils.exists(oldStorageFilename),
+    true,
+    "The old json file has been created"
+  );
+
+  return { jsonFile, oldStorageFilename };
+}
+
+function clearMigrationHistogram() {
+  const histogram = Services.telemetry.getHistogramById(
+    IDB_MIGRATE_RESULT_HISTOGRAM
+  );
+  histogram.clear();
+  equal(
+    histogram.snapshot().sum,
+    0,
+    `No data recorded for histogram ${IDB_MIGRATE_RESULT_HISTOGRAM}`
+  );
+}
+
+function assertMigrationHistogramCount(category, expectedCount) {
+  const histogram = Services.telemetry.getHistogramById(
+    IDB_MIGRATE_RESULT_HISTOGRAM
+  );
+
+  equal(
+    histogram.snapshot().values[CATEGORIES.indexOf(category)],
+    expectedCount,
+    `Got the expected count on category "${category}" for histogram ${IDB_MIGRATE_RESULT_HISTOGRAM}`
+  );
+}
+
+function assertTelemetryEvents(expectedEvents) {
+  TelemetryTestUtils.assertEvents(expectedEvents, {
+    category: EVENT_CATEGORY,
+    method: EVENT_METHOD,
+    object: EVENT_OBJECT,
+  });
+}
+
+add_setup(async function setup() {
+  Services.prefs.setBoolPref(ExtensionStorageIDB.BACKEND_ENABLED_PREF, true);
+
+  await promiseStartupManager();
+
+  // Telemetry test setup needed to ensure that the builtin events are defined
+  // and they can be collected and verified.
+  await TelemetryController.testSetup();
+
+  // This is actually only needed on Android, because it does not properly support unified telemetry
+  // and so, if not enabled explicitly here, it would make these tests to fail when running on a
+  // non-Nightly build.
+  const oldCanRecordBase = Services.telemetry.canRecordBase;
+  Services.telemetry.canRecordBase = true;
+  registerCleanupFunction(() => {
+    Services.telemetry.canRecordBase = oldCanRecordBase;
+  });
+
+  // Clear any telemetry events collected so far.
+  Services.telemetry.clearEvents();
+});
+
+// Test that for newly installed extension the IDB backend is enabled without
+// any data migration.
+add_task(async function test_no_migration_for_newly_installed_extensions() {
+  const EXTENSION_ID = "test-no-data-migration@mochi.test";
+
+  await createExtensionJSONFileWithData(EXTENSION_ID, {
+    test_old_data: "test_old_value",
+  });
+
+  const extension = ExtensionTestUtils.loadExtension({
+    useAddonManager: "temporary",
+    manifest: {
+      permissions: ["storage"],
+      browser_specific_settings: { gecko: { id: EXTENSION_ID } },
+    },
+    async background() {
+      const data = await browser.storage.local.get();
+      browser.test.assertEq(
+        Object.keys(data).length,
+        0,
+        "Expect the storage.local store to be empty"
+      );
+      browser.test.sendMessage("test-stored-data:done");
+    },
+  });
+
+  await extension.startup();
+  equal(
+    ExtensionStorageIDB.isMigratedExtension(extension),
+    true,
+    "The newly installed test extension is marked as migrated"
+  );
+  await extension.awaitMessage("test-stored-data:done");
+  await extension.unload();
+
+  // Verify that no data migration have been needed on the newly installed
+  // extension, by asserting that no telemetry events has been collected.
+  await TelemetryTestUtils.assertEvents([], TELEMETRY_EVENTS_FILTER);
+});
+
+// Test that the data migration is still running for a newly installed extension
+// if keepStorageOnUninstall is true.
+add_task(async function test_data_migration_on_keep_storage_on_uninstall() {
+  Services.prefs.setBoolPref(LEAVE_STORAGE_PREF, true);
+
+  // Store some fake data in the storage.local file backend before starting the extension.
+  const EXTENSION_ID = "new-extension-on-keep-storage-on-uninstall@mochi.test";
+  await createExtensionJSONFileWithData(EXTENSION_ID, {
+    test_key_string: "test_value",
+  });
+
+  const extension = ExtensionTestUtils.loadExtension({
+    useAddonManager: "temporary",
+    manifest: {
+      permissions: ["storage"],
+      browser_specific_settings: { gecko: { id: EXTENSION_ID } },
+    },
+    async background() {
+      const storedData = await browser.storage.local.get();
+      browser.test.assertEq(
+        "test_value",
+        storedData.test_key_string,
+        "Got the expected data after the storage.local data migration"
+      );
+      browser.test.sendMessage("storage-local-data-migrated");
+    },
+  });
+
+  await extension.startup();
+  await extension.awaitMessage("storage-local-data-migrated");
+  equal(
+    ExtensionStorageIDB.isMigratedExtension(extension),
+    true,
+    "The newly installed test extension is marked as migrated"
+  );
+  await extension.unload();
+
+  // Verify that the expected telemetry has been recorded.
+  await TelemetryTestUtils.assertEvents(
+    [
+      {
+        method: "migrateResult",
+        value: EXTENSION_ID,
+        extra: {
+          backend: "IndexedDB",
+          data_migrated: "y",
+          has_jsonfile: "y",
+          has_olddata: "y",
+        },
+      },
+    ],
+    TELEMETRY_EVENTS_FILTER
+  );
+
+  Services.prefs.clearUserPref(LEAVE_STORAGE_PREF);
+});
+
+// Test that the old data is migrated successfully to the new storage backend
+// and that the original JSONFile has been renamed.
+add_task(async function test_storage_local_data_migration() {
+  const EXTENSION_ID = "extension-to-be-migrated@mozilla.org";
+
+  // Keep the extension storage and the uuid on uninstall, to verify that no telemetry events
+  // are being sent for an already migrated extension.
+  Services.prefs.setBoolPref(LEAVE_STORAGE_PREF, true);
+  Services.prefs.setBoolPref(LEAVE_UUID_PREF, true);
+
+  const data = {
+    test_key_string: "test_value1",
+    test_key_number: 1000,
+    test_nested_data: {
+      nested_key: true,
+    },
+  };
+
+  // Store some fake data in the storage.local file backend before starting the extension.
+  const { oldStorageFilename } = await createExtensionJSONFileWithData(
+    EXTENSION_ID,
+    data
+  );
+
+  async function background() {
+    const storedData = await browser.storage.local.get();
+
+    browser.test.assertEq(
+      "test_value1",
+      storedData.test_key_string,
+      "Got the expected data after the storage.local data migration"
+    );
+    browser.test.assertEq(
+      1000,
+      storedData.test_key_number,
+      "Got the expected data after the storage.local data migration"
+    );
+    browser.test.assertEq(
+      true,
+      storedData.test_nested_data.nested_key,
+      "Got the expected data after the storage.local data migration"
+    );
+
+    browser.test.sendMessage("storage-local-data-migrated");
+  }
+
+  clearMigrationHistogram();
+
+  let extensionDefinition = {
+    useAddonManager: "temporary",
+    manifest: {
+      permissions: ["storage"],
+      browser_specific_settings: {
+        gecko: {
+          id: EXTENSION_ID,
+        },
+      },
+    },
+  };
+
+  let extension = ExtensionTestUtils.loadExtension(extensionDefinition);
+
+  // Install the extension while the storage.local IDB backend is disabled.
+  Services.prefs.setBoolPref(ExtensionStorageIDB.BACKEND_ENABLED_PREF, false);
+  await extension.startup();
+
+  ok(
+    !ExtensionStorageIDB.isMigratedExtension(extension),
+    "The test extension should be using the JSONFile backend"
+  );
+
+  // Enabled the storage.local IDB backend and upgrade the extension.
+  Services.prefs.setBoolPref(ExtensionStorageIDB.BACKEND_ENABLED_PREF, true);
+  await extension.upgrade({
+    ...extensionDefinition,
+    background,
+  });
+
+  await extension.awaitMessage("storage-local-data-migrated");
+
+  ok(
+    ExtensionStorageIDB.isMigratedExtension(extension),
+    "The test extension should be using the IndexedDB backend"
+  );
+
+  const storagePrincipal = ExtensionStorageIDB.getStoragePrincipal(
+    extension.extension
+  );
+
+  const idbConn = await ExtensionStorageIDB.open(storagePrincipal);
+
+  equal(
+    await idbConn.isEmpty(extension.extension),
+    false,
+    "Data stored in the ExtensionStorageIDB backend as expected"
+  );
+
+  equal(
+    await IOUtils.exists(oldStorageFilename),
+    false,
+    "The old json storage file name should not exist anymore"
+  );
+
+  equal(
+    await IOUtils.exists(`${oldStorageFilename}.migrated`),
+    true,
+    "The old json storage file name should have been renamed as .migrated"
+  );
+
+  equal(
+    Services.prefs.getBoolPref(
+      `${IDB_MIGRATED_PREF_BRANCH}.${EXTENSION_ID}`,
+      false
+    ),
+    true,
+    `Got the ${IDB_MIGRATED_PREF_BRANCH} preference set to true as expected`
+  );
+
+  assertMigrationHistogramCount("success", 1);
+  assertMigrationHistogramCount("failure", 0);
+
+  assertTelemetryEvents([
+    {
+      method: "migrateResult",
+      value: EXTENSION_ID,
+      extra: {
+        backend: "IndexedDB",
+        data_migrated: "y",
+        has_jsonfile: "y",
+        has_olddata: "y",
+      },
+    },
+  ]);
+
+  equal(
+    Services.prefs.getBoolPref(
+      `${IDB_MIGRATED_PREF_BRANCH}.${EXTENSION_ID}`,
+      false
+    ),
+    true,
+    `${IDB_MIGRATED_PREF_BRANCH} should still be true on keepStorageOnUninstall=true`
+  );
+
+  // Upgrade the extension and check that no telemetry events are being sent
+  // for an already migrated extension.
+  await extension.upgrade({
+    ...extensionDefinition,
+    background,
+  });
+
+  await extension.awaitMessage("storage-local-data-migrated");
+
+  // The histogram values are unmodified.
+  assertMigrationHistogramCount("success", 1);
+  assertMigrationHistogramCount("failure", 0);
+
+  // No new telemetry events recorded for the extension.
+  const snapshot = Services.telemetry.snapshotEvents(
+    Ci.nsITelemetry.DATASET_PRERELEASE_CHANNELS,
+    true
+  );
+  const filterByCategory = ([timestamp, category]) =>
+    category === EVENT_CATEGORY;
+
+  ok(
+    !snapshot.parent || snapshot.parent.filter(filterByCategory).length === 0,
+    "No telemetry events should be recorded for an already migrated extension"
+  );
+
+  Services.prefs.setBoolPref(LEAVE_STORAGE_PREF, false);
+  Services.prefs.setBoolPref(LEAVE_UUID_PREF, false);
+
+  await extension.unload();
+
+  equal(
+    Services.prefs.getPrefType(`${IDB_MIGRATED_PREF_BRANCH}.${EXTENSION_ID}`),
+    Services.prefs.PREF_INVALID,
+    `Got the ${IDB_MIGRATED_PREF_BRANCH} preference has been cleared on addon uninstall`
+  );
+});
+
+// Test that the extensionId included in the telemetry event is being trimmed down to 80 chars
+// as expected.
+add_task(async function test_extensionId_trimmed_in_telemetry_event() {
+  // Generated extensionId in email-like format, longer than 80 chars.
+  const EXTENSION_ID = `long.extension.id@${Array(80).fill("a").join("")}`;
+
+  const data = { test_key_string: "test_value" };
+
+  // Store some fake data in the storage.local file backend before starting the extension.
+  await createExtensionJSONFileWithData(EXTENSION_ID, data);
+
+  async function background() {
+    const storedData = await browser.storage.local.get("test_key_string");
+
+    browser.test.assertEq(
+      "test_value",
+      storedData.test_key_string,
+      "Got the expected data after the storage.local data migration"
+    );
+
+    browser.test.sendMessage("storage-local-data-migrated");
+  }
+
+  let extension = ExtensionTestUtils.loadExtension({
+    manifest: {
+      permissions: ["storage"],
+      browser_specific_settings: {
+        gecko: {
+          id: EXTENSION_ID,
+        },
+      },
+    },
+    background,
+    // We don't want the (default) startupReason ADDON_INSTALL because
+    // that automatically sets the migrated pref and skips migration.
+    startupReason: "APP_STARTUP",
+  });
+
+  await extension.startup();
+
+  await extension.awaitMessage("storage-local-data-migrated");
+
+  const expectedTrimmedExtensionId = getTrimmedString(EXTENSION_ID);
+
+  equal(
+    expectedTrimmedExtensionId.length,
+    80,
+    "The trimmed version of the extensionId should be 80 chars long"
+  );
+
+  assertTelemetryEvents([
+    {
+      method: "migrateResult",
+      value: expectedTrimmedExtensionId,
+      extra: {
+        backend: "IndexedDB",
+        data_migrated: "y",
+        has_jsonfile: "y",
+        has_olddata: "y",
+      },
+    },
+  ]);
+
+  await extension.unload();
+});
+
+// Test that if the old JSONFile data file is corrupted and the old data
+// can't be successfully migrated to the new storage backend, then:
+// - the new storage backend for that extension is still initialized and enabled
+// - any new data is being stored in the new backend
+// - the old file is being renamed (with the `.corrupted` suffix that JSONFile.sys.mjs
+//   adds when it fails to load the data file) and still available on disk.
+add_task(async function test_storage_local_corrupted_data_migration() {
+  const EXTENSION_ID = "extension-corrupted-data-migration@mozilla.org";
+
+  const invalidData = `{"test_key_string": "test_value1"`;
+  const oldStorageFilename = ExtensionStorage.getStorageFile(EXTENSION_ID);
+
+  await IOUtils.makeDirectory(
+    PathUtils.join(PathUtils.profileDir, "browser-extension-data", EXTENSION_ID)
+  );
+
+  // Write the json file with some invalid data.
+  await IOUtils.writeUTF8(oldStorageFilename, invalidData, { flush: true });
+  equal(
+    await IOUtils.readUTF8(oldStorageFilename),
+    invalidData,
+    "The old json file has been overwritten with invalid data"
+  );
+
+  async function background() {
+    const storedData = await browser.storage.local.get();
+
+    browser.test.assertEq(
+      Object.keys(storedData).length,
+      0,
+      "No data should be found on invalid data migration"
+    );
+
+    await browser.storage.local.set({
+      test_key_string_on_IDBBackend: "expected-value",
+    });
+
+    browser.test.sendMessage("storage-local-data-migrated-and-set");
+  }
+
+  clearMigrationHistogram();
+
+  let extension = ExtensionTestUtils.loadExtension({
+    manifest: {
+      permissions: ["storage"],
+      browser_specific_settings: {
+        gecko: {
+          id: EXTENSION_ID,
+        },
+      },
+    },
+    background,
+    // We don't want the (default) startupReason ADDON_INSTALL because
+    // that automatically sets the migrated pref and skips migration.
+    startupReason: "APP_STARTUP",
+  });
+
+  await extension.startup();
+
+  await extension.awaitMessage("storage-local-data-migrated-and-set");
+
+  const storagePrincipal = ExtensionStorageIDB.getStoragePrincipal(
+    extension.extension
+  );
+
+  const idbConn = await ExtensionStorageIDB.open(storagePrincipal);
+
+  equal(
+    await idbConn.isEmpty(extension.extension),
+    false,
+    "Data stored in the ExtensionStorageIDB backend as expected"
+  );
+
+  equal(
+    await IOUtils.exists(`${oldStorageFilename}.corrupt`),
+    true,
+    "The old json storage should still be available if failed to be read"
+  );
+
+  // The extension is still migrated successfully to the new backend if the file from the
+  // original json file was corrupted.
+
+  equal(
+    Services.prefs.getBoolPref(
+      `${IDB_MIGRATED_PREF_BRANCH}.${EXTENSION_ID}`,
+      false
+    ),
+    true,
+    `Got the ${IDB_MIGRATED_PREF_BRANCH} preference set to true as expected`
+  );
+
+  assertMigrationHistogramCount("success", 1);
+  assertMigrationHistogramCount("failure", 0);
+
+  assertTelemetryEvents([
+    {
+      method: "migrateResult",
+      value: EXTENSION_ID,
+      extra: {
+        backend: "IndexedDB",
+        data_migrated: "y",
+        has_jsonfile: "y",
+        has_olddata: "n",
+      },
+    },
+  ]);
+
+  await extension.unload();
+});
+
+// Test that if the data migration fails to store the old data into the IndexedDB backend
+// then the expected telemetry histogram is being updated.
+add_task(async function test_storage_local_data_migration_failure() {
+  const EXTENSION_ID = "extension-data-migration-failure@mozilla.org";
+
+  // Create the file under the expected directory tree.
+  const { jsonFile, oldStorageFilename } =
+    await createExtensionJSONFileWithData(EXTENSION_ID, {});
+
+  // Store a fake invalid value which is going to fail to be saved into IndexedDB
+  // (because it can't be cloned and it is going to raise a DataCloneError), which
+  // will trigger a data migration failure that we expect to increment the related
+  // telemetry histogram.
+  jsonFile.data.set("fake_invalid_key", function () {});
+
+  async function background() {
+    await browser.storage.local.set({
+      test_key_string_on_JSONFileBackend: "expected-value",
+    });
+    browser.test.sendMessage("storage-local-data-migrated-and-set");
+  }
+
+  clearMigrationHistogram();
+
+  let extension = ExtensionTestUtils.loadExtension({
+    manifest: {
+      permissions: ["storage"],
+      browser_specific_settings: {
+        gecko: {
+          id: EXTENSION_ID,
+        },
+      },
+    },
+    background,
+    // We don't want the (default) startupReason ADDON_INSTALL because
+    // that automatically sets the migrated pref and skips migration.
+    startupReason: "APP_STARTUP",
+  });
+
+  await extension.startup();
+
+  await extension.awaitMessage("storage-local-data-migrated-and-set");
+
+  const storagePrincipal = ExtensionStorageIDB.getStoragePrincipal(
+    extension.extension
+  );
+
+  const idbConn = await ExtensionStorageIDB.open(storagePrincipal);
+  equal(
+    await idbConn.isEmpty(extension.extension),
+    true,
+    "No data stored in the ExtensionStorageIDB backend as expected"
+  );
+  equal(
+    await IOUtils.exists(oldStorageFilename),
+    true,
+    "The old json storage should still be available if failed to be read"
+  );
+
+  await extension.unload();
+
+  assertTelemetryEvents([
+    {
+      method: "migrateResult",
+      value: EXTENSION_ID,
+      extra: {
+        backend: "JSONFile",
+        data_migrated: "n",
+        error_name: "DataCloneError",
+        has_jsonfile: "y",
+        has_olddata: "y",
+      },
+    },
+  ]);
+
+  assertMigrationHistogramCount("success", 0);
+  assertMigrationHistogramCount("failure", 1);
+});
+
+add_task(async function test_migration_aborted_on_shutdown() {
+  const EXTENSION_ID = "test-migration-aborted-on-shutdown@mochi.test";
+  let extension = ExtensionTestUtils.loadExtension({
+    manifest: {
+      permissions: ["storage"],
+      browser_specific_settings: {
+        gecko: {
+          id: EXTENSION_ID,
+        },
+      },
+    },
+    // We don't want the (default) startupReason ADDON_INSTALL because
+    // that automatically sets the migrated pref and skips migration.
+    startupReason: "APP_STARTUP",
+  });
+
+  await extension.startup();
+
+  equal(
+    extension.extension.hasShutdown,
+    false,
+    "The extension is still running"
+  );
+
+  await extension.unload();
+  equal(extension.extension.hasShutdown, true, "The extension has shutdown");
+
+  // Trigger a data migration after the extension has been unloaded.
+  const result = await ExtensionStorageIDB.selectBackend({
+    extension: extension.extension,
+  });
+  Assert.deepEqual(
+    result,
+    { backendEnabled: false },
+    "Expect migration to have been aborted"
+  );
+  TelemetryTestUtils.assertEvents(
+    [
+      {
+        value: EXTENSION_ID,
+        extra: {
+          backend: "JSONFile",
+          error_name: "DataMigrationAbortedError",
+        },
+      },
+    ],
+    TELEMETRY_EVENTS_FILTER
+  );
+});
+
+add_task(async function test_storage_local_data_migration_clear_pref() {
+  Services.prefs.clearUserPref(LEAVE_STORAGE_PREF);
+  Services.prefs.clearUserPref(LEAVE_UUID_PREF);
+  Services.prefs.clearUserPref(ExtensionStorageIDB.BACKEND_ENABLED_PREF);
+  await promiseShutdownManager();
+  await TelemetryController.testShutdown();
+});
+
+add_task(async function setup_quota_manager_testing_prefs() {
+  Services.prefs.setBoolPref("dom.quotaManager.testing", true);
+  Services.prefs.setIntPref(
+    "dom.quotaManager.temporaryStorage.fixedLimit",
+    100
+  );
+  await promiseQuotaManagerServiceReset();
+});
+
+add_task(
+  // TODO: temporarily disabled because it currently perma-fails on
+  // android builds (Bug 1564871)
+  { skip_if: () => AppConstants.platform === "android" },
+  // eslint-disable-next-line no-use-before-define
+  test_quota_exceeded_while_migrating_data
+);
+async function test_quota_exceeded_while_migrating_data() {
+  const EXT_ID = "test-data-migration-stuck@mochi.test";
+  const dataSize = 1000 * 1024;
+
+  await createExtensionJSONFileWithData(EXT_ID, {
+    data: new Array(dataSize).fill("x").join(""),
+  });
+
+  const extension = ExtensionTestUtils.loadExtension({
+    manifest: {
+      permissions: ["storage"],
+      browser_specific_settings: { gecko: { id: EXT_ID } },
+    },
+    background() {
+      browser.test.onMessage.addListener(async (msg, dataSize) => {
+        if (msg !== "verify-stored-data") {
+          return;
+        }
+        const res = await browser.storage.local.get();
+        browser.test.assertEq(
+          res.data && res.data.length,
+          dataSize,
+          "Got the expected data"
+        );
+        browser.test.sendMessage("verify-stored-data:done");
+      });
+
+      browser.test.sendMessage("bg-page:ready");
+    },
+    // We don't want the (default) startupReason ADDON_INSTALL because
+    // that automatically sets the migrated pref and skips migration.
+    startupReason: "APP_STARTUP",
+  });
+
+  await extension.startup();
+  await extension.awaitMessage("bg-page:ready");
+
+  extension.sendMessage("verify-stored-data", dataSize);
+  await extension.awaitMessage("verify-stored-data:done");
+
+  await ok(
+    !ExtensionStorageIDB.isMigratedExtension(extension),
+    "The extension falls back to the JSONFile backend because of the migration failure"
+  );
+  await extension.unload();
+
+  TelemetryTestUtils.assertEvents(
+    [
+      {
+        value: EXT_ID,
+        extra: {
+          backend: "JSONFile",
+          error_name: "QuotaExceededError",
+        },
+      },
+    ],
+    TELEMETRY_EVENTS_FILTER
+  );
+
+  Services.prefs.clearUserPref("dom.quotaManager.temporaryStorage.fixedLimit");
+  await promiseQuotaManagerServiceClear();
+  Services.prefs.clearUserPref("dom.quotaManager.testing");
+}
diff --git a/toolkit/components/extensions/test/xpcshell/test_ext_storage_local.js b/toolkit/components/extensions/test/xpcshell/test_ext_storage_local.js
new file mode 100644
index 0000000000..c846494f0c
--- /dev/null
+++ b/toolkit/components/extensions/test/xpcshell/test_ext_storage_local.js
@@ -0,0 +1,83 @@
+/* -*- Mode: indent-tabs-mode: nil; js-indent-level: 2 -*- */
+/* vim: set sts=2 sw=2 et tw=80: */
+"use strict";
+
+ChromeUtils.defineESModuleGetters(this, {
+  ExtensionStorageIDB: "resource://gre/modules/ExtensionStorageIDB.sys.mjs",
+});
+
+AddonTestUtils.init(this);
+
+add_task(async function setup() {
+  await ExtensionTestUtils.startAddonManager();
+});
+
+add_task(async function test_local_cache_invalidation() {
+  function background(checkGet) {
+    browser.test.onMessage.addListener(async msg => {
+      if (msg === "set-initial") {
+        await browser.storage.local.set({
+          "test-prop1": "value1",
+          "test-prop2": "value2",
+        });
+        browser.test.sendMessage("set-initial-done");
+      } else if (msg === "check") {
+        await checkGet("local", "test-prop1", "value1");
+        await checkGet("local", "test-prop2", "value2");
+        browser.test.sendMessage("check-done");
+      }
+    });
+
+    browser.test.sendMessage("ready");
+  }
+
+  let extension = ExtensionTestUtils.loadExtension({
+    manifest: {
+      permissions: ["storage"],
+    },
+    background: `(${background})(${checkGetImpl})`,
+  });
+
+  await extension.startup();
+  await extension.awaitMessage("ready");
+
+  extension.sendMessage("set-initial");
+  await extension.awaitMessage("set-initial-done");
+
+  Services.obs.notifyObservers(null, "extension-invalidate-storage-cache");
+
+  extension.sendMessage("check");
+  await extension.awaitMessage("check-done");
+
+  await extension.unload();
+});
+
+add_task(function test_storage_local_file_backend() {
+  return runWithPrefs([[ExtensionStorageIDB.BACKEND_ENABLED_PREF, false]], () =>
+    test_background_page_storage("local")
+  );
+});
+
+add_task(function test_storage_local_idb_backend() {
+  return runWithPrefs([[ExtensionStorageIDB.BACKEND_ENABLED_PREF, true]], () =>
+    test_background_page_storage("local")
+  );
+});
+
+add_task(function test_storage_local_idb_bytes_in_use() {
+  return runWithPrefs([[ExtensionStorageIDB.BACKEND_ENABLED_PREF, true]], () =>
+    test_background_storage_area_no_bytes_in_use("local")
+  );
+});
+
+add_task(function test_storage_local_onChanged_event_page() {
+  return runWithPrefs([[ExtensionStorageIDB.BACKEND_ENABLED_PREF, true]], () =>
+    test_storage_change_event_page("local")
+  );
+});
+
+add_task(async function test_storage_local_empty_events() {
+  return runWithPrefs([[ExtensionStorageIDB.BACKEND_ENABLED_PREF, true]], () =>
+    test_storage_empty_events("local")
+  );
+});
diff --git a/toolkit/components/extensions/test/xpcshell/test_ext_storage_managed.js b/toolkit/components/extensions/test/xpcshell/test_ext_storage_managed.js
new file mode 100644
index 0000000000..5bf6dcc3bc
--- /dev/null
+++ b/toolkit/components/extensions/test/xpcshell/test_ext_storage_managed.js
@@ -0,0 +1,212 @@
+"use strict";
+
+ChromeUtils.defineESModuleGetters(this, {
+  MockRegistry: "resource://testing-common/MockRegistry.sys.mjs",
+});
+
+const MANIFEST = {
+  name: "test-storage-managed@mozilla.com",
+  description: "",
+  type: "storage",
+  data: {
+    null: null,
+    str: "hello",
+    obj: {
+      a: [2, 3],
+      b: true,
+    },
+  },
+};
+
+AddonTestUtils.init(this);
+
+const server = createHttpServer({ hosts: ["example.com"] });
+server.registerDirectory("/data/", do_get_file("data"));
+
+add_task(async function setup() {
+  await ExtensionTestUtils.startAddonManager();
+
+  let tmpDir = FileUtils.getDir("TmpD", ["native-manifests"]);
+  tmpDir.createUnique(Ci.nsIFile.DIRECTORY_TYPE, FileUtils.PERMS_DIRECTORY);
+
+  let dirProvider = {
+    getFile(property) {
+      if (property.endsWith("NativeManifests")) {
+        return tmpDir.clone();
+      }
+    },
+  };
+  Services.dirsvc.registerProvider(dirProvider);
+
+  let typeSlug =
+    AppConstants.platform === "linux" ? "managed-storage" : "ManagedStorage";
+  await IOUtils.makeDirectory(PathUtils.join(tmpDir.path, typeSlug));
+
+  let path = PathUtils.join(tmpDir.path, typeSlug, `${MANIFEST.name}.json`);
+  await IOUtils.writeJSON(path, MANIFEST);
+
+  let registry;
+  if (AppConstants.platform === "win") {
+    registry = new MockRegistry();
+    registry.setValue(
+      Ci.nsIWindowsRegKey.ROOT_KEY_CURRENT_USER,
+      `Software\\\Mozilla\\\ManagedStorage\\${MANIFEST.name}`,
+      "",
+      path
+    );
+  }
+
+  registerCleanupFunction(() => {
+    Services.dirsvc.unregisterProvider(dirProvider);
+    tmpDir.remove(true);
+    if (registry) {
+      registry.shutdown();
+    }
+  });
+});
+
+add_task(async function test_storage_managed() {
+  let extension = ExtensionTestUtils.loadExtension({
+    manifest: {
+      browser_specific_settings: { gecko: { id: MANIFEST.name } },
+      permissions: ["storage"],
+    },
+
+    async background() {
+      await browser.test.assertRejects(
+        browser.storage.managed.set({ a: 1 }),
+        /storage.managed is read-only/,
+        "browser.storage.managed.set() rejects because it's read only"
+      );
+
+      await browser.test.assertRejects(
+        browser.storage.managed.remove("str"),
+        /storage.managed is read-only/,
+        "browser.storage.managed.remove() rejects because it's read only"
+      );
+
+      await browser.test.assertRejects(
+        browser.storage.managed.clear(),
+        /storage.managed is read-only/,
+        "browser.storage.managed.clear() rejects because it's read only"
+      );
+
+      browser.test.sendMessage(
+        "results",
+        await Promise.all([
+          browser.storage.managed.get(),
+          browser.storage.managed.get("str"),
+          browser.storage.managed.get(["null", "obj"]),
+          browser.storage.managed.get({ str: "a", num: 2 }),
+        ])
+      );
+    },
+  });
+
+  await extension.startup();
+  deepEqual(await extension.awaitMessage("results"), [
+    MANIFEST.data,
+    { str: "hello" },
+    { null: null, obj: MANIFEST.data.obj },
+    { str: "hello", num: 2 },
+  ]);
+  await extension.unload();
+});
+
+add_task(async function test_storage_managed_from_content_script() {
+  let extension = ExtensionTestUtils.loadExtension({
+    manifest: {
+      browser_specific_settings: { gecko: { id: MANIFEST.name } },
+      permissions: ["storage"],
+      content_scripts: [
+        {
+          js: ["contentscript.js"],
+          matches: ["*://*/*"],
+          run_at: "document_end",
+        },
+      ],
+    },
+
+    files: {
+      "contentscript.js": async function () {
+        browser.test.sendMessage(
+          "results",
+          await browser.storage.managed.get()
+        );
+      },
+    },
+  });
+
+  await extension.startup();
+  let contentPage = await ExtensionTestUtils.loadContentPage(
+    "http://example.com/data/file_sample.html"
+  );
+  deepEqual(await extension.awaitMessage("results"), MANIFEST.data);
+  await contentPage.close();
+  await extension.unload();
+});
+
+add_task(async function test_manifest_not_found() {
+  let extension = ExtensionTestUtils.loadExtension({
+    manifest: {
+      permissions: ["storage"],
+    },
+
+    async background() {
+      await browser.test.assertRejects(
+        browser.storage.managed.get({ a: 1 }),
+        /Managed storage manifest not found/,
+        "browser.storage.managed.get() rejects when without manifest"
+      );
+
+      browser.test.notifyPass();
+    },
+  });
+
+  await extension.startup();
+  await extension.awaitFinish();
+  await extension.unload();
+});
+
+add_task(async function test_manifest_not_found() {
+  let extension = ExtensionTestUtils.loadExtension({
+    manifest: {
+      permissions: ["storage"],
+    },
+
+    async background() {
+      const dummyListener = () => {};
+      browser.storage.managed.onChanged.addListener(dummyListener);
+      browser.test.assertTrue(
+        browser.storage.managed.onChanged.hasListener(dummyListener),
+        "addListener works according to hasListener"
+      );
+      browser.storage.managed.onChanged.removeListener(dummyListener);
+
+      // We should get a warning for each registration.
+      browser.storage.managed.onChanged.addListener(() => {});
+      browser.storage.managed.onChanged.addListener(() => {});
+      browser.storage.managed.onChanged.addListener(() => {});
+
+      // Invoke the storage.managed API to make sure that we have made a
+      // round trip to the parent process and back. This is because event
+      // registration is async but we cannot await (bug 1300234).
+      await browser.test.assertRejects(
+        browser.storage.managed.get({ a: 1 }),
+        /Managed storage manifest not found/,
+        "browser.storage.managed.get() rejects when without manifest"
+      );
+
+      browser.test.notifyPass();
+    },
+  });
+
+  let { messages } = await promiseConsoleOutput(async () => {
+    await extension.startup();
+    await extension.awaitFinish();
+    await extension.unload();
+  });
+  const UNSUP_EVENT_WARNING = `attempting to use listener "storage.managed.onChanged", which is unimplemented`;
+  messages = messages.filter(msg => msg.message.includes(UNSUP_EVENT_WARNING));
+  Assert.equal(messages.length, 4, "Expected msg for each addListener call");
+});
diff --git a/toolkit/components/extensions/test/xpcshell/test_ext_storage_managed_policy.js b/toolkit/components/extensions/test/xpcshell/test_ext_storage_managed_policy.js
new file mode 100644
index 0000000000..169bef4139
--- /dev/null
+++ b/toolkit/components/extensions/test/xpcshell/test_ext_storage_managed_policy.js
@@ -0,0 +1,44 @@
+"use strict";
+
+const { EnterprisePolicyTesting } = ChromeUtils.importESModule(
+  "resource://testing-common/EnterprisePolicyTesting.sys.mjs"
+);
+
+// Load policy engine
+Services.policies; // eslint-disable-line no-unused-expressions
+
+AddonTestUtils.init(this);
+
+add_task(async function test_storage_managed_policy() {
+  await ExtensionTestUtils.startAddonManager();
+
+  await EnterprisePolicyTesting.setupPolicyEngineWithJson({
+    policies: {
+      "3rdparty": {
+        Extensions: {
+          "test-storage-managed-policy@mozilla.com": {
+            string: "value",
+          },
+        },
+      },
+    },
+  });
+
+  let extension = ExtensionTestUtils.loadExtension({
+    manifest: {
+      browser_specific_settings: {
+        gecko: { id: "test-storage-managed-policy@mozilla.com" },
+      },
+      permissions: ["storage"],
+    },
+
+    async background() {
+      let str = await browser.storage.managed.get("string");
+      browser.test.sendMessage("results", str);
+    },
+  });
+
+  await extension.startup();
+  deepEqual(await extension.awaitMessage("results"), { string: "value" });
+  await extension.unload();
+});
diff --git a/toolkit/components/extensions/test/xpcshell/test_ext_storage_quota_exceeded_errors.js b/toolkit/components/extensions/test/xpcshell/test_ext_storage_quota_exceeded_errors.js
new file mode 100644
index 0000000000..b03646d939
--- /dev/null
+++ b/toolkit/components/extensions/test/xpcshell/test_ext_storage_quota_exceeded_errors.js
@@ -0,0 +1,80 @@
+/* -*- Mode: indent-tabs-mode: nil; js-indent-level: 2 -*- */
+/* vim: set sts=2 sw=2 et tw=80: */
+
+"use strict";
+
+ChromeUtils.defineESModuleGetters(this, {
+  ExtensionStorageIDB: "resource://gre/modules/ExtensionStorageIDB.sys.mjs",
+});
+
+const LEAVE_STORAGE_PREF = "extensions.webextensions.keepStorageOnUninstall";
+const LEAVE_UUID_PREF = "extensions.webextensions.keepUuidOnUninstall";
+
+AddonTestUtils.init(this);
+
+add_task(async function setup() {
+  // Ensure that the IDB backend is enabled.
+  Services.prefs.setBoolPref("ExtensionStorageIDB.BACKEND_ENABLED_PREF", true);
+
+  Services.prefs.setBoolPref("dom.quotaManager.testing", true);
+  Services.prefs.setIntPref(
+    "dom.quotaManager.temporaryStorage.fixedLimit",
+    100
+  );
+  await promiseQuotaManagerServiceReset();
+
+  await ExtensionTestUtils.startAddonManager();
+});
+
+add_task(async function test_storage_local_set_quota_exceeded_error() {
+  const EXT_ID = "test-quota-exceeded@mochi.test";
+
+  const extensionDef = {
+    manifest: {
+      permissions: ["storage"],
+      browser_specific_settings: { gecko: { id: EXT_ID } },
+    },
+    async background() {
+      const data = new Array(1000 * 1024).fill("x").join("");
+      await browser.test.assertRejects(
+        browser.storage.local.set({ data }),
+        /QuotaExceededError/,
+        "Got a rejection with the expected error message"
+      );
+      browser.test.sendMessage("data-stored");
+    },
+  };
+
+  Services.prefs.setBoolPref(LEAVE_STORAGE_PREF, true);
+  Services.prefs.setBoolPref(LEAVE_UUID_PREF, true);
+  registerCleanupFunction(() => {
+    Services.prefs.clearUserPref(LEAVE_STORAGE_PREF);
+    Services.prefs.clearUserPref(LEAVE_UUID_PREF);
+  });
+
+  const extension = ExtensionTestUtils.loadExtension(extensionDef);
+
+  // Run test on a test extension being migrated to the IDB backend.
+  await extension.startup();
+  await extension.awaitMessage("data-stored");
+
+  ok(
+    ExtensionStorageIDB.isMigratedExtension(extension),
+    "The extension has been successfully migrated to the IDB backend"
+  );
+  await extension.unload();
+
+  // Run again on a test extension already already migrated to the IDB backend.
+  const extensionUpdated = ExtensionTestUtils.loadExtension(extensionDef);
+  await extensionUpdated.startup();
+  ok(
+    ExtensionStorageIDB.isMigratedExtension(extension),
+    "The extension has been successfully migrated to the IDB backend"
+  );
+  await extensionUpdated.awaitMessage("data-stored");
+
+  await extensionUpdated.unload();
+
+  Services.prefs.clearUserPref("dom.quotaManager.temporaryStorage.fixedLimit");
+  await promiseQuotaManagerServiceClear();
+});
diff --git a/toolkit/components/extensions/test/xpcshell/test_ext_storage_sanitizer.js b/toolkit/components/extensions/test/xpcshell/test_ext_storage_sanitizer.js
new file mode 100644
index 0000000000..6c69ad1a4c
--- /dev/null
+++ b/toolkit/components/extensions/test/xpcshell/test_ext_storage_sanitizer.js
@@ -0,0 +1,107 @@
+/* -*- Mode: indent-tabs-mode: nil; js-indent-level: 2 -*- */
+/* vim: set sts=2 sw=2 et tw=80: */
+
+"use strict";
+
+ChromeUtils.defineESModuleGetters(this, {
+  Sanitizer: "resource:///modules/Sanitizer.sys.mjs",
+});
+
+async function test_sanitize_offlineApps(storageHelpersScript) {
+  const extension = ExtensionTestUtils.loadExtension({
+    manifest: {
+      permissions: ["storage"],
+      background: {
+        scripts: ["storageHelpers.js", "background.js"],
+      },
+    },
+    files: {
+      "storageHelpers.js": storageHelpersScript,
+      "background.js": function () {
+        browser.test.onMessage.addListener(async (msg, args) => {
+          let result = {};
+          switch (msg) {
+            case "set-storage-data":
+              await window.testWriteKey(...args);
+              break;
+            case "get-storage-data":
+              const value = await window.testReadKey(args[0]);
+              browser.test.assertEq(args[1], value, "Got the expected value");
+              break;
+            default:
+              browser.test.fail(`Unexpected test message received: ${msg}`);
+          }
+
+          browser.test.sendMessage(`${msg}:done`, result);
+        });
+      },
+    },
+  });
+
+  await extension.startup();
+
+  extension.sendMessage("set-storage-data", ["aKey", "aValue"]);
+  await extension.awaitMessage("set-storage-data:done");
+
+  await extension.sendMessage("get-storage-data", ["aKey", "aValue"]);
+  await extension.awaitMessage("get-storage-data:done");
+
+  info("Verify the extension data not cleared by offlineApps Sanitizer");
+  await Sanitizer.sanitize(["offlineApps"]);
+  await extension.sendMessage("get-storage-data", ["aKey", "aValue"]);
+  await extension.awaitMessage("get-storage-data:done");
+
+  await extension.unload();
+}
+
+add_task(async function test_sanitize_offlineApps_extension_indexedDB() {
+  await test_sanitize_offlineApps(function indexedDBStorageHelpers() {
+    const getIDBStore = () =>
+      new Promise(resolve => {
+        let dbreq = window.indexedDB.open("TestDB");
+        dbreq.onupgradeneeded = () =>
+          dbreq.result.createObjectStore("TestStore");
+        dbreq.onsuccess = () => resolve(dbreq.result);
+      });
+
+    // Export writeKey and readKey storage test helpers.
+    window.testWriteKey = (k, v) =>
+      getIDBStore().then(db => {
+        const tx = db.transaction("TestStore", "readwrite");
+        const store = tx.objectStore("TestStore");
+        return new Promise((resolve, reject) => {
+          tx.oncomplete = evt => resolve(evt.target.result);
+          tx.onerror = evt => reject(evt.target.error);
+          store.add(v, k);
+        });
+      });
+    window.testReadKey = k =>
+      getIDBStore().then(db => {
+        const tx = db.transaction("TestStore");
+        const store = tx.objectStore("TestStore");
+        return new Promise((resolve, reject) => {
+          const req = store.get(k);
+          tx.oncomplete = evt => resolve(req.result);
+          tx.onerror = evt => reject(evt.target.error);
+        });
+      });
+  });
+});
+
+add_task(
+  {
+    // Skip this test if LSNG is not enabled (because this test is only
+    // going to pass when nextgen local storage is being used).
+    skip_if: () =>
+      Services.prefs.getBoolPref(
+        "dom.storage.enable_unsupported_legacy_implementation"
+      ),
+  },
+  async function test_sanitize_offlineApps_extension_localStorage() {
+    await test_sanitize_offlineApps(function indexedDBStorageHelpers() {
+      // Export writeKey and readKey storage test helpers.
+      window.testWriteKey = (k, v) => window.localStorage.setItem(k, v);
+      window.testReadKey = k => window.localStorage.getItem(k);
+    });
+  }
+);
diff --git a/toolkit/components/extensions/test/xpcshell/test_ext_storage_session.js b/toolkit/components/extensions/test/xpcshell/test_ext_storage_session.js
new file mode 100644
index 0000000000..9dc0aa5af9
--- /dev/null
+++ b/toolkit/components/extensions/test/xpcshell/test_ext_storage_session.js
@@ -0,0 +1,97 @@
+"use strict";
+
+AddonTestUtils.init(this);
+
+const server = createHttpServer({ hosts: ["example.com"] });
+server.registerDirectory("/data/", do_get_file("data"));
+
+add_setup(async function setup() {
+  await ExtensionTestUtils.startAddonManager();
+});
+
+add_task(async function test_storage_session() {
+  await test_background_page_storage("session");
+});
+
+add_task(async function test_storage_session_onChanged_event_page() {
+  await test_storage_change_event_page("session");
+});
+
+add_task(async function test_storage_session_persistance() {
+  await test_storage_after_reload("session", { expectPersistency: false });
+});
+
+add_task(async function test_storage_session_empty_events() {
+  await test_storage_empty_events("session");
+});
+
+add_task(async function test_storage_session_contentscript() {
+  let extensionData = {
+    manifest: {
+      content_scripts: [
+        {
+          matches: ["http://example.com/data/file_sample.html"],
+          js: ["content_script.js"],
+        },
+      ],
+      permissions: ["storage"],
+    },
+    background() {
+      let events = [];
+      browser.storage.onChanged.addListener((_, area) => {
+        events.push(area);
+      });
+      browser.test.onMessage.addListener(_msg => {
+        browser.test.sendMessage("bg-events", events.join());
+      });
+      browser.runtime.onMessage.addListener(async _msg => {
+        await browser.storage.local.set({ foo: "local" });
+        await browser.storage.session.set({ foo: "session" });
+        await browser.storage.sync.set({ foo: "sync" });
+        browser.test.sendMessage("done");
+      });
+    },
+    files: {
+      "content_script.js"() {
+        let events = [];
+        browser.storage.onChanged.addListener((_, area) => {
+          events.push(area);
+        });
+        browser.test.onMessage.addListener(_msg => {
+          browser.test.sendMessage("cs-events", events.join());
+        });
+
+        browser.test.assertEq(
+          typeof browser.storage.session,
+          "undefined",
+          "Expect storage.session to not be available in content scripts"
+        );
+        browser.runtime.sendMessage("ready");
+      },
+    },
+  };
+
+  let extension = ExtensionTestUtils.loadExtension(extensionData);
+  await extension.startup();
+
+  let contentPage = await ExtensionTestUtils.loadContentPage(
+    "http://example.com/data/file_sample.html"
+  );
+
+  await extension.awaitMessage("done");
+  extension.sendMessage("_getEvents");
+
+  equal(
+    "local,sync",
+    await extension.awaitMessage("cs-events"),
+    "Content script doesn't see storage.onChanged events from the session area."
+  );
+  equal(
+    "local,session,sync",
+    await extension.awaitMessage("bg-events"),
+    "Background receives onChanged events from all storage areas."
+  );
+
+  await extension.unload();
+  await contentPage.close();
+});
diff --git a/toolkit/components/extensions/test/xpcshell/test_ext_storage_sync.js b/toolkit/components/extensions/test/xpcshell/test_ext_storage_sync.js
new file mode 100644
index 0000000000..e28af80d0a
--- /dev/null
+++ b/toolkit/components/extensions/test/xpcshell/test_ext_storage_sync.js
@@ -0,0 +1,35 @@
+/* -*- Mode: indent-tabs-mode: nil; js-indent-level: 2 -*- */
+/* vim: set sts=2 sw=2 et tw=80: */
+"use strict";
+
+Services.prefs.setBoolPref("webextensions.storage.sync.kinto", false);
+
+AddonTestUtils.init(this);
+
+add_task(async function setup() {
+  await ExtensionTestUtils.startAddonManager();
+});
+
+add_task(test_config_flag_needed);
+
+add_task(test_sync_reloading_extensions_works);
+
+add_task(function test_storage_sync() {
+  return runWithPrefs([[STORAGE_SYNC_PREF, true]], () =>
+    test_background_page_storage("sync")
+  );
+});
+
+add_task(test_storage_sync_requires_real_id);
+
+add_task(function test_bytes_in_use() {
+  return runWithPrefs([[STORAGE_SYNC_PREF, true]], () =>
+    test_background_storage_area_with_bytes_in_use("sync", true)
+  );
+});
+
+add_task(function test_storage_onChanged_event_page() {
+  return runWithPrefs([[STORAGE_SYNC_PREF, true]], () =>
+    test_storage_change_event_page("sync")
+  );
+});
diff --git a/toolkit/components/extensions/test/xpcshell/test_ext_storage_sync_kinto.js b/toolkit/components/extensions/test/xpcshell/test_ext_storage_sync_kinto.js
new file mode 100644
index 0000000000..7e92eb862c
--- /dev/null
+++ b/toolkit/components/extensions/test/xpcshell/test_ext_storage_sync_kinto.js
@@ -0,0 +1,2318 @@
+/* Any copyright is dedicated to the Public Domain.
+ * http://creativecommons.org/publicdomain/zero/1.0/ */
+
+"use strict";
+
+// This is a kinto-specific test...
+Services.prefs.setBoolPref("webextensions.storage.sync.kinto", true);
+
+do_get_profile(); // so we can use FxAccounts
+
+const { HttpServer } = ChromeUtils.import("resource://testing-common/httpd.js");
+const { CommonUtils } = ChromeUtils.importESModule(
+  "resource://services-common/utils.sys.mjs"
+);
+const {
+  ExtensionStorageSyncKinto: ExtensionStorageSync,
+  KintoStorageTestUtils: {
+    cleanUpForContext,
+    CollectionKeyEncryptionRemoteTransformer,
+    CryptoCollection,
+    idToKey,
+    keyToId,
+    KeyRingEncryptionRemoteTransformer,
+  },
+} = ChromeUtils.importESModule(
+  "resource://gre/modules/ExtensionStorageSyncKinto.sys.mjs"
+);
+const { BulkKeyBundle } = ChromeUtils.importESModule(
+  "resource://services-sync/keys.sys.mjs"
+);
+const { FxAccountsKeys } = ChromeUtils.importESModule(
+  "resource://gre/modules/FxAccountsKeys.sys.mjs"
+);
+const { Utils } = ChromeUtils.importESModule(
+  "resource://services-sync/util.sys.mjs"
+);
+
+const { createAppInfo, promiseStartupManager } = AddonTestUtils;
+
+AddonTestUtils.init(this);
+
+createAppInfo("xpcshell@tests.mozilla.org", "XPCShell", "1", "69");
+
+function handleCannedResponse(cannedResponse, request, response) {
+  response.setStatusLine(
+    null,
+    cannedResponse.status.status,
+    cannedResponse.status.statusText
+  );
+  // send the headers
+  for (let headerLine of cannedResponse.sampleHeaders) {
+    let headerElements = headerLine.split(":");
+    response.setHeader(headerElements[0], headerElements[1].trimLeft());
+  }
+  response.setHeader("Date", new Date().toUTCString());
+
+  response.write(cannedResponse.responseBody);
+}
+
+function collectionPath(collectionId) {
+  return `/buckets/default/collections/${collectionId}`;
+}
+
+function collectionRecordsPath(collectionId) {
+  return `/buckets/default/collections/${collectionId}/records`;
+}
+
+class KintoServer {
+  constructor() {
+    // Set up an HTTP Server
+    this.httpServer = new HttpServer();
+    this.httpServer.start(-1);
+
+    // Set<Object> corresponding to records that might be served.
+    // The format of these objects is defined in the documentation for #addRecord.
+    this.records = [];
+
+    // Collections that we have set up access to (see `installCollection`).
+    this.collections = new Set();
+
+    // ETag to serve with responses
+    this.etag = 1;
+
+    this.port = this.httpServer.identity.primaryPort;
+
+    // POST requests we receive from the client go here
+    this.posts = [];
+    // DELETEd buckets will go here.
+    this.deletedBuckets = [];
+    // Anything in here will force the next POST to generate a conflict
+    this.conflicts = [];
+    // If this is true, reject the next request with a 401
+    this.rejectNextAuthResponse = false;
+    this.failedAuths = [];
+
+    this.installConfigPath();
+    this.installBatchPath();
+    this.installCatchAll();
+  }
+
+  clearPosts() {
+    this.posts = [];
+  }
+
+  getPosts() {
+    return this.posts;
+  }
+
+  getDeletedBuckets() {
+    return this.deletedBuckets;
+  }
+
+  rejectNextAuthWith(response) {
+    this.rejectNextAuthResponse = response;
+  }
+
+  checkAuth(request, response) {
+    equal(request.getHeader("Authorization"), "Bearer some-access-token");
+
+    if (this.rejectNextAuthResponse) {
+      response.setStatusLine(null, 401, "Unauthorized");
+      response.write(this.rejectNextAuthResponse);
+      this.rejectNextAuthResponse = false;
+      this.failedAuths.push(request);
+      return true;
+    }
+    return false;
+  }
+
+  installConfigPath() {
+    const configPath = "/v1/";
+    const responseBody = JSON.stringify({
+      settings: { batch_max_requests: 25 },
+      url: `http://localhost:${this.port}/v1/`,
+      documentation: "https://kinto.readthedocs.org/",
+      version: "1.5.1",
+      commit: "cbc6f58",
+      hello: "kinto",
+    });
+    const configResponse = {
+      sampleHeaders: [
+        "Access-Control-Allow-Origin: *",
+        "Access-Control-Expose-Headers: Retry-After, Content-Length, Alert, Backoff",
+        "Content-Type: application/json; charset=UTF-8",
+        "Server: waitress",
+      ],
+      status: { status: 200, statusText: "OK" },
+      responseBody: responseBody,
+    };
+
+    function handleGetConfig(request, response) {
+      if (request.method != "GET") {
+        dump(`ARGH, got ${request.method}\n`);
+      }
+      return handleCannedResponse(configResponse, request, response);
+    }
+
+    this.httpServer.registerPathHandler(configPath, handleGetConfig);
+  }
+
+  installBatchPath() {
+    const batchPath = "/v1/batch";
+
+    function handlePost(request, response) {
+      if (this.checkAuth(request, response)) {
+        return;
+      }
+
+      let bodyStr = CommonUtils.readBytesFromInputStream(
+        request.bodyInputStream
+      );
+      let body = JSON.parse(bodyStr);
+      let defaults = body.defaults;
+      for (let req of body.requests) {
+        let headers = Object.assign(
+          {},
+          (defaults && defaults.headers) || {},
+          req.headers
+        );
+        this.posts.push(Object.assign({}, req, { headers }));
+      }
+
+      response.setStatusLine(null, 200, "OK");
+      response.setHeader("Content-Type", "application/json; charset=UTF-8");
+      response.setHeader("Date", new Date().toUTCString());
+
+      let postResponse = {
+        responses: body.requests.map(req => {
+          let oneBody;
+          if (req.method == "DELETE") {
+            let id = req.path.match(
+              /^\/buckets\/default\/collections\/.+\/records\/(.+)$/
+            )[1];
+            oneBody = {
+              data: {
+                deleted: true,
+                id: id,
+                last_modified: this.etag,
+              },
+            };
+          } else {
+            oneBody = {
+              data: Object.assign({}, req.body.data, {
+                last_modified: this.etag,
+              }),
+              permissions: [],
+            };
+          }
+
+          return {
+            path: req.path,
+            status: 201, // FIXME -- only for new posts??
+            headers: { ETag: 3000 }, // FIXME???
+            body: oneBody,
+          };
+        }),
+      };
+
+      if (this.conflicts.length) {
+        const nextConflict = this.conflicts.shift();
+        if (!nextConflict.transient) {
+          this.records.push(nextConflict);
+        }
+        const { data } = nextConflict;
+        postResponse = {
+          responses: body.requests.map(req => {
+            return {
+              path: req.path,
+              status: 412,
+              headers: { ETag: this.etag }, // is this correct??
+              body: {
+                details: {
+                  existing: data,
+                },
+              },
+            };
+          }),
+        };
+      }
+
+      response.write(JSON.stringify(postResponse));
+
+      //   "sampleHeaders": [
+      //     "Access-Control-Allow-Origin: *",
+      //     "Access-Control-Expose-Headers: Retry-After, Content-Length, Alert, Backoff",
+      //     "Server: waitress",
+      //     "Etag: \"4000\""
+      //   ],
+    }
+
+    this.httpServer.registerPathHandler(batchPath, handlePost.bind(this));
+  }
+
+  installCatchAll() {
+    this.httpServer.registerPathHandler("/", (request, response) => {
+      dump(
+        `got request: ${request.method}:${request.path}?${request.queryString}\n`
+      );
+      dump(
+        `${CommonUtils.readBytesFromInputStream(request.bodyInputStream)}\n`
+      );
+    });
+  }
+
+  /**
+   * Add a record to those that can be served by this server.
+   *
+   * @param {object} properties  An object describing the record that
+   *   should be served. The properties of this object are:
+   * - collectionId {string} This record should only be served if a
+   *   request is for this collection.
+   * - predicate {Function} If present, this record should only be served if the
+   *   predicate returns true. The predicate will be called with
+   *   {request: Request, response: Response, since: number, server: KintoServer}.
+   * - data {string} The record to serve.
+   * - conflict {boolean} If present and true, this record is added to
+   *   "conflicts" and won't be served, but will cause a conflict on
+   *   the next push.
+   */
+  addRecord(properties) {
+    if (!properties.conflict) {
+      this.records.push(properties);
+    } else {
+      this.conflicts.push(properties);
+    }
+
+    this.installCollection(properties.collectionId);
+  }
+
+  /**
+   * Tell the server to set up a route for this collection.
+   *
+   * This will automatically be called for any collection to which you `addRecord`.
+   *
+   * @param {string} collectionId   the collection whose route we
+   *    should set up.
+   */
+  installCollection(collectionId) {
+    if (this.collections.has(collectionId)) {
+      return;
+    }
+    this.collections.add(collectionId);
+    const remoteCollectionPath =
+      "/v1" + collectionPath(encodeURIComponent(collectionId));
+    this.httpServer.registerPathHandler(
+      remoteCollectionPath,
+      this.handleGetCollection.bind(this, collectionId)
+    );
+    const remoteRecordsPath =
+      "/v1" + collectionRecordsPath(encodeURIComponent(collectionId));
+    this.httpServer.registerPathHandler(
+      remoteRecordsPath,
+      this.handleGetRecords.bind(this, collectionId)
+    );
+  }
+
+  handleGetCollection(collectionId, request, response) {
+    if (this.checkAuth(request, response)) {
+      return;
+    }
+
+    response.setStatusLine(null, 200, "OK");
+    response.setHeader("Content-Type", "application/json; charset=UTF-8");
+    response.setHeader("Date", new Date().toUTCString());
+    response.write(
+      JSON.stringify({
+        data: {
+          id: collectionId,
+        },
+      })
+    );
+  }
+
+  handleGetRecords(collectionId, request, response) {
+    if (this.checkAuth(request, response)) {
+      return;
+    }
+
+    if (request.method != "GET") {
+      do_throw(`only GET is supported on ${request.path}`);
+    }
+
+    let sinceMatch = request.queryString.match(/(^|&)_since=(\d+)/);
+    let since = sinceMatch && parseInt(sinceMatch[2], 10);
+
+    response.setStatusLine(null, 200, "OK");
+    response.setHeader("Content-Type", "application/json; charset=UTF-8");
+    response.setHeader("Date", new Date().toUTCString());
+    response.setHeader("ETag", this.etag.toString());
+
+    const records = this.records
+      .filter(properties => {
+        if (properties.collectionId != collectionId) {
+          return false;
+        }
+
+        if (properties.predicate) {
+          const predAllowed = properties.predicate({
+            request: request,
+            response: response,
+            since: since,
+            server: this,
+          });
+          if (!predAllowed) {
+            return false;
+          }
+        }
+
+        return true;
+      })
+      .map(properties => properties.data);
+
+    const body = JSON.stringify({
+      data: records,
+    });
+    response.write(body);
+  }
+
+  installDeleteBucket() {
+    this.httpServer.registerPrefixHandler(
+      "/v1/buckets/",
+      (request, response) => {
+        if (request.method != "DELETE") {
+          dump(
+            `got a non-delete action on bucket: ${request.method} ${request.path}\n`
+          );
+          return;
+        }
+
+        const noPrefix = request.path.slice("/v1/buckets/".length);
+        const [bucket, afterBucket] = noPrefix.split("/", 1);
+        if (afterBucket && afterBucket != "") {
+          dump(
+            `got a delete for a non-bucket: ${request.method} ${request.path}\n`
+          );
+        }
+
+        this.deletedBuckets.push(bucket);
+        // Fake like this actually deletes the records.
+        this.records = [];
+
+        response.write(
+          JSON.stringify({
+            data: {
+              deleted: true,
+              last_modified: 1475161309026,
+              id: "b09f1618-d789-302d-696e-74ec53ee18a8", // FIXME
+            },
+          })
+        );
+      }
+    );
+  }
+
+  // Utility function to install a keyring at the start of a test.
+  async installKeyRing(fxaService, keysData, salts, etag, properties) {
+    const keysRecord = {
+      id: "keys",
+      keys: keysData,
+      salts: salts,
+      last_modified: etag,
+    };
+    this.etag = etag;
+    const transformer = new KeyRingEncryptionRemoteTransformer(fxaService);
+    return this.encryptAndAddRecord(
+      transformer,
+      Object.assign({}, properties, {
+        collectionId: "storage-sync-crypto",
+        data: keysRecord,
+      })
+    );
+  }
+
+  encryptAndAddRecord(transformer, properties) {
+    return transformer.encode(properties.data).then(encrypted => {
+      this.addRecord(Object.assign({}, properties, { data: encrypted }));
+    });
+  }
+
+  stop() {
+    this.httpServer.stop(() => {});
+  }
+}
+
+/**
+ * Predicate that represents a record appearing at some time.
+ * Requests with "_since" before this time should see this record,
+ * unless the server itself isn't at this time yet (etag is before
+ * this time).
+ *
+ * Requests with _since after this time shouldn't see this record any
+ * more, since it hasn't changed after this time.
+ *
+ * @param {int} startTime  the etag at which time this record should
+ *    start being available (and thus, the predicate should start
+ *    returning true)
+ * @returns {Function}
+ */
+function appearsAt(startTime) {
+  return function ({ since, server }) {
+    return since < startTime && startTime < server.etag;
+  };
+}
+
+// Run a block of code with access to a KintoServer.
+async function withServer(f) {
+  let server = new KintoServer();
+  // Point the sync.storage client to use the test server we've just started.
+  Services.prefs.setCharPref(
+    "webextensions.storage.sync.serverURL",
+    `http://localhost:${server.port}/v1`
+  );
+  try {
+    await f(server);
+  } finally {
+    server.stop();
+  }
+}
+
+// Run a block of code with access to both a sync context and a
+// KintoServer. This is meant as a workaround for eslint's refusal to
+// let me have 5 nested callbacks.
+async function withContextAndServer(f) {
+  await withSyncContext(async function (context) {
+    await withServer(async function (server) {
+      await f(context, server);
+    });
+  });
+}
+
+// Run a block of code with fxa mocked out to return a specific user.
+// Calls the given function with an ExtensionStorageSync instance that
+// was constructed using a mocked FxAccounts instance.
+async function withSignedInUser(user, f) {
+  let fxaServiceMock = {
+    getSignedInUser() {
+      return Promise.resolve({ uid: user.uid });
+    },
+    getOAuthToken() {
+      return Promise.resolve("some-access-token");
+    },
+    checkAccountStatus() {
+      return Promise.resolve(true);
+    },
+    removeCachedOAuthToken() {
+      return Promise.resolve();
+    },
+    keys: {
+      getKeyForScope(scope) {
+        return Promise.resolve({ ...user.scopedKeys[scope] });
+      },
+      kidAsHex(jwk) {
+        return new FxAccountsKeys({}).kidAsHex(jwk);
+      },
+    },
+  };
+
+  let telemetryMock = {
+    _calls: [],
+    _histograms: {},
+    scalarSet(name, value) {
+      this._calls.push({ method: "scalarSet", name, value });
+    },
+    keyedScalarSet(name, key, value) {
+      this._calls.push({ method: "keyedScalarSet", name, key, value });
+    },
+    getKeyedHistogramById(name) {
+      let self = this;
+      return {
+        add(key, value) {
+          if (!self._histograms[name]) {
+            self._histograms[name] = [];
+          }
+          self._histograms[name].push(value);
+        },
+      };
+    },
+  };
+  let extensionStorageSync = new ExtensionStorageSync(
+    fxaServiceMock,
+    telemetryMock
+  );
+  await f(extensionStorageSync, fxaServiceMock);
+}
+
+// Some assertions that make it easier to write tests about what was
+// posted and when.
+
+// Assert that a post in a batch was made with the correct access token.
+// This should be true of all requests, so this is usually called from
+// another assertion.
+function assertAuthenticatedPost(post) {
+  equal(post.headers.Authorization, "Bearer some-access-token");
+}
+
+// Assert that this post was made with the correct request headers to
+// create a new resource while protecting against someone else
+// creating it at the same time (in other words, "If-None-Match: *").
+// Also calls assertAuthenticatedPost(post).
+function assertPostedNewRecord(post) {
+  assertAuthenticatedPost(post);
+  equal(post.headers["If-None-Match"], "*");
+}
+
+// Assert that this post was made with the correct request headers to
+// update an existing resource while protecting against concurrent
+// modification (in other words, `If-Match: "${etag}"`).
+// Also calls assertAuthenticatedPost(post).
+function assertPostedUpdatedRecord(post, since) {
+  assertAuthenticatedPost(post);
+  equal(post.headers["If-Match"], `"${since}"`);
+}
+
+// Assert that this post was an encrypted keyring, and produce the
+// decrypted body. Sanity check the body while we're here.
+const assertPostedEncryptedKeys = async function (fxaService, post) {
+  equal(post.path, collectionRecordsPath("storage-sync-crypto") + "/keys");
+
+  let body = await new KeyRingEncryptionRemoteTransformer(fxaService).decode(
+    post.body.data
+  );
+  ok(body.keys, `keys object should be present in decoded body`);
+  ok(body.keys.default, `keys object should have a default key`);
+  ok(body.salts, `salts object should be present in decoded body`);
+  return body;
+};
+
+// assertEqual, but for keyring[extensionId] == key.
+function assertKeyRingKey(keyRing, extensionId, expectedKey, message) {
+  if (!message) {
+    message = `expected keyring's key for ${extensionId} to match ${expectedKey.keyPairB64}`;
+  }
+  ok(
+    keyRing.hasKeysFor([extensionId]),
+    `expected keyring to have a key for ${extensionId}\n`
+  );
+  deepEqual(
+    keyRing.keyForCollection(extensionId).keyPairB64,
+    expectedKey.keyPairB64,
+    message
+  );
+}
+
+// Assert that this post was posted for a given extension.
+const assertExtensionRecord = async function (
+  fxaService,
+  post,
+  extension,
+  key
+) {
+  const extensionId = extension.id;
+  const cryptoCollection = new CryptoCollection(fxaService);
+  const hashedId =
+    "id-" +
+    (await cryptoCollection.hashWithExtensionSalt(keyToId(key), extensionId));
+  const collectionId = await cryptoCollection.extensionIdToCollectionId(
+    extensionId
+  );
+  const transformer = new CollectionKeyEncryptionRemoteTransformer(
+    cryptoCollection,
+    await cryptoCollection.getKeyRing(),
+    extensionId
+  );
+  equal(
+    post.path,
+    `${collectionRecordsPath(collectionId)}/${hashedId}`,
+    "decrypted data should be posted to path corresponding to its key"
+  );
+  let decoded = await transformer.decode(post.body.data);
+  equal(
+    decoded.key,
+    key,
+    "decrypted data should have a key attribute corresponding to the extension data key"
+  );
+  return decoded;
+};
+
+// Tests using this ID will share keys in local storage, so be careful.
+const defaultExtensionId = "{13bdde76-4dc7-11e6-9bdc-54ee758d6342}";
+const defaultExtension = { id: defaultExtensionId };
+
+const loggedInUser = {
+  uid: "0123456789abcdef0123456789abcdef",
+  scopedKeys: {
+    "sync:addon_storage": {
+      kid: "1234567890123-I1DLqPztWi-647HxgLr4YPePZUK-975wn9qWzT49yAA",
+      k: "Y_kFdXfAS7u58MP9hbXUAytg4T7cH43TCb9DBdZvLMMS3eFs5GAhpJb3E5UNCmxWbOGBUhpEcm576Xz1d7MbMQ",
+      kty: "oct",
+    },
+  },
+  oauthTokens: {
+    "sync:addon_storage": {
+      token: "some-access-token",
+    },
+  },
+};
+
+function uuid() {
+  const uuidgen = Services.uuid;
+  return uuidgen.generateUUID().toString();
+}
+
+add_task(async function test_setup() {
+  await promiseStartupManager();
+});
+
+add_task(async function test_single_initialization() {
+  // Check if we're calling openConnection too often.
+  const { FirefoxAdapter } = ChromeUtils.importESModule(
+    "resource://services-common/kinto-storage-adapter.sys.mjs"
+  );
+  const origOpenConnection = FirefoxAdapter.openConnection;
+  let callCount = 0;
+  FirefoxAdapter.openConnection = function (...args) {
+    ++callCount;
+    return origOpenConnection.apply(this, args);
+  };
+  function background() {
+    let promises = ["foo", "bar", "baz", "quux"].map(key =>
+      browser.storage.sync.get(key)
+    );
+    Promise.all(promises).then(() =>
+      browser.test.notifyPass("initialize once")
+    );
+  }
+  try {
+    let extension = ExtensionTestUtils.loadExtension({
+      manifest: {
+        permissions: ["storage"],
+      },
+      background: `(${background})()`,
+    });
+
+    await extension.startup();
+    await extension.awaitFinish("initialize once");
+    await extension.unload();
+    equal(
+      callCount,
+      1,
+      "Initialized FirefoxAdapter connection and Kinto exactly once"
+    );
+  } finally {
+    FirefoxAdapter.openConnection = origOpenConnection;
+  }
+});
+
+add_task(async function test_key_to_id() {
+  equal(keyToId("foo"), "key-foo");
+  equal(keyToId("my-new-key"), "key-my_2D_new_2D_key");
+  equal(keyToId(""), "key-");
+  equal(keyToId("™"), "key-_2122_");
+  equal(keyToId("\b"), "key-_8_");
+  equal(keyToId("abc\ndef"), "key-abc_A_def");
+  equal(keyToId("Kinto's fancy_string"), "key-Kinto_27_s_20_fancy_5F_string");
+
+  const KEYS = ["foo", "my-new-key", "", "Kinto's fancy_string", "™", "\b"];
+  for (let key of KEYS) {
+    equal(idToKey(keyToId(key)), key);
+  }
+
+  equal(idToKey("hi"), null);
+  equal(idToKey("-key-hi"), null);
+  equal(idToKey("key--abcd"), null);
+  equal(idToKey("key-%"), null);
+  equal(idToKey("key-_HI"), null);
+  equal(idToKey("key-_HI_"), null);
+  equal(idToKey("key-"), "");
+  equal(idToKey("key-1"), "1");
+  equal(idToKey("key-_2D_"), "-");
+});
+
+add_task(async function test_extension_id_to_collection_id() {
+  const extensionId = "{9419cce6-5435-11e6-84bf-54ee758d6342}";
+  // FIXME: this doesn't actually require the signed in user, but the
+  // extensionIdToCollectionId method exists on CryptoCollection,
+  // which needs an fxaService to be instantiated.
+  await withSignedInUser(
+    loggedInUser,
+    async function (extensionStorageSync, fxaService) {
+      // Fake a static keyring since the server doesn't exist.
+      const salt = "Scgx8RJ8Y0rxMGFYArUiKeawlW+0zJyFmtTDvro9qPo=";
+      const cryptoCollection = new CryptoCollection(fxaService);
+      await cryptoCollection._setSalt(extensionId, salt);
+
+      equal(
+        await cryptoCollection.extensionIdToCollectionId(extensionId),
+        "ext-0_QHA1P93_yJoj7ONisrR0lW6uN4PZ3Ii-rT-QOjtvo"
+      );
+    }
+  );
+});
+
+add_task(async function ensureCanSync_clearAll() {
+  // A test extension that will not have any active context around
+  // but it is returned from a call to AddonManager.getExtensionsByType.
+  const extensionId = "test-wipe-on-enabled-and-synced@mochi.test";
+  const testExtension = ExtensionTestUtils.loadExtension({
+    useAddonManager: "temporary",
+    manifest: {
+      permissions: ["storage"],
+      browser_specific_settings: { gecko: { id: extensionId } },
+    },
+  });
+
+  await testExtension.startup();
+
+  // Retrieve the Extension class instance from the test extension.
+  const { extension } = testExtension;
+
+  // Another test extension that will have an active extension context.
+  const extensionId2 = "test-wipe-on-active-context@mochi.test";
+  const extension2 = { id: extensionId2 };
+
+  await withContextAndServer(async function (context, server) {
+    await withSignedInUser(
+      loggedInUser,
+      async function (extensionStorageSync, fxaService) {
+        async function assertSetAndGetData(extension, data) {
+          await extensionStorageSync.set(extension, data, context);
+          let storedData = await extensionStorageSync.get(
+            extension,
+            Object.keys(data),
+            context
+          );
+          const extId = extensionId;
+          deepEqual(
+            storedData,
+            data,
+            `${extId} should get back the data we set`
+          );
+        }
+
+        async function assertDataCleared(extension, keys) {
+          const storedData = await extensionStorageSync.get(
+            extension,
+            keys,
+            context
+          );
+          deepEqual(
+            storedData,
+            {},
+            `${extension.id} should have lost the data`
+          );
+        }
+
+        server.installCollection("storage-sync-crypto");
+        server.etag = 1000;
+
+        let newKeys = await extensionStorageSync.ensureCanSync([
+          extensionId,
+          extensionId2,
+        ]);
+        ok(
+          newKeys.hasKeysFor([extensionId]),
+          `key isn't present for ${extensionId}`
+        );
+        ok(
+          newKeys.hasKeysFor([extensionId2]),
+          `key isn't present for ${extensionId2}`
+        );
+
+        let posts = server.getPosts();
+        equal(posts.length, 1);
+        assertPostedNewRecord(posts[0]);
+
+        await assertSetAndGetData(extension, { "my-key": 1 });
+        await assertSetAndGetData(extension2, { "my-key": 2 });
+
+        // Call cleanup for the first extension, to double check it has
+        // been wiped out even without an active extension context.
+        cleanUpForContext(extension, context);
+
+        // clear everything.
+        await extensionStorageSync.clearAll();
+
+        // Assert that the data is gone for both the extensions.
+        await assertDataCleared(extension, ["my-key"]);
+        await assertDataCleared(extension2, ["my-key"]);
+
+        // should have been no posts caused by the clear.
+        posts = server.getPosts();
+        equal(posts.length, 1);
+      }
+    );
+  });
+
+  await testExtension.unload();
+});
+
+add_task(async function ensureCanSync_posts_new_keys() {
+  const extensionId = uuid();
+  await withContextAndServer(async function (context, server) {
+    await withSignedInUser(
+      loggedInUser,
+      async function (extensionStorageSync, fxaService) {
+        server.installCollection("storage-sync-crypto");
+        server.etag = 1000;
+
+        let newKeys = await extensionStorageSync.ensureCanSync([extensionId]);
+        ok(
+          newKeys.hasKeysFor([extensionId]),
+          `key isn't present for ${extensionId}`
+        );
+
+        let posts = server.getPosts();
+        equal(posts.length, 1);
+        const post = posts[0];
+        assertPostedNewRecord(post);
+        const body = await assertPostedEncryptedKeys(fxaService, post);
+        const oldSalt = body.salts[extensionId];
+        ok(
+          body.keys.collections[extensionId],
+          `keys object should have a key for ${extensionId}`
+        );
+        ok(oldSalt, `salts object should have a salt for ${extensionId}`);
+
+        // Try adding another key to make sure that the first post was
+        // OK, even on a new profile.
+        await extensionStorageSync.cryptoCollection._clear();
+        server.clearPosts();
+        // Restore the first posted keyring, but add a last_modified date
+        const firstPostedKeyring = Object.assign({}, post.body.data, {
+          last_modified: server.etag,
+        });
+        server.addRecord({
+          data: firstPostedKeyring,
+          collectionId: "storage-sync-crypto",
+          predicate: appearsAt(250),
+        });
+        const extensionId2 = uuid();
+        newKeys = await extensionStorageSync.ensureCanSync([extensionId2]);
+        ok(
+          newKeys.hasKeysFor([extensionId]),
+          `didn't forget key for ${extensionId}`
+        );
+        ok(
+          newKeys.hasKeysFor([extensionId2]),
+          `new key generated for ${extensionId2}`
+        );
+
+        posts = server.getPosts();
+        equal(posts.length, 1);
+        const newPost = posts[posts.length - 1];
+        const newBody = await assertPostedEncryptedKeys(fxaService, newPost);
+        ok(
+          newBody.keys.collections[extensionId],
+          `keys object should have a key for ${extensionId}`
+        );
+        ok(
+          newBody.keys.collections[extensionId2],
+          `keys object should have a key for ${extensionId2}`
+        );
+        ok(
+          newBody.salts[extensionId],
+          `salts object should have a key for ${extensionId}`
+        );
+        ok(
+          newBody.salts[extensionId2],
+          `salts object should have a key for ${extensionId2}`
+        );
+        equal(
+          oldSalt,
+          newBody.salts[extensionId],
+          `old salt should be preserved in post`
+        );
+      }
+    );
+  });
+});
+
+add_task(async function ensureCanSync_pulls_key() {
+  // ensureCanSync is implemented by adding a key to our local record
+  // and doing a sync. This means that if the same key exists
+  // remotely, we get a "conflict". Ensure that we handle this
+  // correctly -- we keep the server key (since presumably it's
+  // already been used to encrypt records) and we don't wipe out other
+  // collections' keys.
+  const extensionId = uuid();
+  const extensionId2 = uuid();
+  const extensionOnlyKey = uuid();
+  const extensionOnlySalt = uuid();
+  const DEFAULT_KEY = new BulkKeyBundle("[default]");
+  await DEFAULT_KEY.generateRandom();
+  const RANDOM_KEY = new BulkKeyBundle(extensionId);
+  await RANDOM_KEY.generateRandom();
+  await withContextAndServer(async function (context, server) {
+    await withSignedInUser(
+      loggedInUser,
+      async function (extensionStorageSync, fxaService) {
+        // FIXME: generating a random salt probably shouldn't require a CryptoCollection?
+        const cryptoCollection = new CryptoCollection(fxaService);
+        const RANDOM_SALT = cryptoCollection.getNewSalt();
+        await extensionStorageSync.cryptoCollection._clear();
+        const keysData = {
+          default: DEFAULT_KEY.keyPairB64,
+          collections: {
+            [extensionId]: RANDOM_KEY.keyPairB64,
+          },
+        };
+        const saltData = {
+          [extensionId]: RANDOM_SALT,
+        };
+        await server.installKeyRing(fxaService, keysData, saltData, 950, {
+          predicate: appearsAt(900),
+        });
+
+        let collectionKeys = await extensionStorageSync.ensureCanSync([
+          extensionId,
+        ]);
+        assertKeyRingKey(collectionKeys, extensionId, RANDOM_KEY);
+
+        let posts = server.getPosts();
+        equal(
+          posts.length,
+          0,
+          "ensureCanSync shouldn't push when the server keyring has the right key"
+        );
+
+        // Another client generates a key for extensionId2
+        const newKey = new BulkKeyBundle(extensionId2);
+        await newKey.generateRandom();
+        keysData.collections[extensionId2] = newKey.keyPairB64;
+        saltData[extensionId2] = cryptoCollection.getNewSalt();
+        await server.installKeyRing(fxaService, keysData, saltData, 1050, {
+          predicate: appearsAt(1000),
+        });
+
+        let newCollectionKeys = await extensionStorageSync.ensureCanSync([
+          extensionId,
+          extensionId2,
+        ]);
+        assertKeyRingKey(newCollectionKeys, extensionId2, newKey);
+        assertKeyRingKey(
+          newCollectionKeys,
+          extensionId,
+          RANDOM_KEY,
+          `ensureCanSync shouldn't lose the old key for ${extensionId}`
+        );
+
+        posts = server.getPosts();
+        equal(
+          posts.length,
+          0,
+          "ensureCanSync shouldn't push when updating keys"
+        );
+
+        // Another client generates a key, but not a salt, for extensionOnlyKey
+        const onlyKey = new BulkKeyBundle(extensionOnlyKey);
+        await onlyKey.generateRandom();
+        keysData.collections[extensionOnlyKey] = onlyKey.keyPairB64;
+        await server.installKeyRing(fxaService, keysData, saltData, 1150, {
+          predicate: appearsAt(1100),
+        });
+
+        let withNewKey = await extensionStorageSync.ensureCanSync([
+          extensionId,
+          extensionOnlyKey,
+        ]);
+        dump(`got ${JSON.stringify(withNewKey.asWBO().cleartext)}\n`);
+        assertKeyRingKey(withNewKey, extensionOnlyKey, onlyKey);
+        assertKeyRingKey(
+          withNewKey,
+          extensionId,
+          RANDOM_KEY,
+          `ensureCanSync shouldn't lose the old key for ${extensionId}`
+        );
+
+        posts = server.getPosts();
+        equal(
+          posts.length,
+          1,
+          "ensureCanSync should push when generating a new salt"
+        );
+        const withNewKeyRecord = await assertPostedEncryptedKeys(
+          fxaService,
+          posts[0]
+        );
+        // We don't a priori know what the new salt is
+        dump(`${JSON.stringify(withNewKeyRecord)}\n`);
+        ok(
+          withNewKeyRecord.salts[extensionOnlyKey],
+          `ensureCanSync should generate a salt for an extension that only had a key`
+        );
+
+        // Another client generates a key, but not a salt, for extensionOnlyKey
+        const newSalt = cryptoCollection.getNewSalt();
+        saltData[extensionOnlySalt] = newSalt;
+        await server.installKeyRing(fxaService, keysData, saltData, 1250, {
+          predicate: appearsAt(1200),
+        });
+
+        let withOnlySaltKey = await extensionStorageSync.ensureCanSync([
+          extensionId,
+          extensionOnlySalt,
+        ]);
+        assertKeyRingKey(
+          withOnlySaltKey,
+          extensionId,
+          RANDOM_KEY,
+          `ensureCanSync shouldn't lose the old key for ${extensionId}`
+        );
+        // We don't a priori know what the new key is
+        ok(
+          withOnlySaltKey.hasKeysFor([extensionOnlySalt]),
+          `ensureCanSync generated a key for an extension that only had a salt`
+        );
+
+        posts = server.getPosts();
+        equal(
+          posts.length,
+          2,
+          "ensureCanSync should push when generating a new key"
+        );
+        const withNewSaltRecord = await assertPostedEncryptedKeys(
+          fxaService,
+          posts[1]
+        );
+        equal(
+          withNewSaltRecord.salts[extensionOnlySalt],
+          newSalt,
+          "ensureCanSync should keep the existing salt when generating only a key"
+        );
+      }
+    );
+  });
+});
+
+add_task(async function ensureCanSync_handles_conflicts() {
+  // Syncing is done through a pull followed by a push of any merged
+  // changes. Accordingly, the only way to have a "true" conflict --
+  // i.e. with the server rejecting a change -- is if
+  // someone pushes changes between our pull and our push. Ensure that
+  // if this happens, we still behave sensibly (keep the remote key).
+  const extensionId = uuid();
+  const DEFAULT_KEY = new BulkKeyBundle("[default]");
+  await DEFAULT_KEY.generateRandom();
+  const RANDOM_KEY = new BulkKeyBundle(extensionId);
+  await RANDOM_KEY.generateRandom();
+  await withContextAndServer(async function (context, server) {
+    await withSignedInUser(
+      loggedInUser,
+      async function (extensionStorageSync, fxaService) {
+        // FIXME: generating salts probably shouldn't rely on a CryptoCollection
+        const cryptoCollection = new CryptoCollection(fxaService);
+        const RANDOM_SALT = cryptoCollection.getNewSalt();
+        const keysData = {
+          default: DEFAULT_KEY.keyPairB64,
+          collections: {
+            [extensionId]: RANDOM_KEY.keyPairB64,
+          },
+        };
+        const saltData = {
+          [extensionId]: RANDOM_SALT,
+        };
+        await server.installKeyRing(fxaService, keysData, saltData, 765, {
+          conflict: true,
+        });
+
+        await extensionStorageSync.cryptoCollection._clear();
+
+        let collectionKeys = await extensionStorageSync.ensureCanSync([
+          extensionId,
+        ]);
+        assertKeyRingKey(
+          collectionKeys,
+          extensionId,
+          RANDOM_KEY,
+          `syncing keyring should keep the server key for ${extensionId}`
+        );
+
+        let posts = server.getPosts();
+        equal(
+          posts.length,
+          1,
+          "syncing keyring should have tried to post a keyring"
+        );
+        const failedPost = posts[0];
+        assertPostedNewRecord(failedPost);
+        let body = await assertPostedEncryptedKeys(fxaService, failedPost);
+        // This key will be the one the client generated locally, so
+        // we don't know what its value will be
+        ok(
+          body.keys.collections[extensionId],
+          `decrypted failed post should have a key for ${extensionId}`
+        );
+        notEqual(
+          body.keys.collections[extensionId],
+          RANDOM_KEY.keyPairB64,
+          `decrypted failed post should have a randomly-generated key for ${extensionId}`
+        );
+      }
+    );
+  });
+});
+
+add_task(async function ensureCanSync_handles_deleted_conflicts() {
+  // A keyring can be deleted, and this changes the format of the 412
+  // Conflict response from the Kinto server. Make sure we handle it correctly.
+  const extensionId = uuid();
+  const extensionId2 = uuid();
+  await withContextAndServer(async function (context, server) {
+    server.installCollection("storage-sync-crypto");
+    server.installDeleteBucket();
+    await withSignedInUser(
+      loggedInUser,
+      async function (extensionStorageSync, fxaService) {
+        server.etag = 700;
+        await extensionStorageSync.cryptoCollection._clear();
+
+        // Generate keys that we can check for later.
+        let collectionKeys = await extensionStorageSync.ensureCanSync([
+          extensionId,
+        ]);
+        const extensionKey = collectionKeys.keyForCollection(extensionId);
+        server.clearPosts();
+
+        // This is the response that the Kinto server return when the
+        // keyring has been deleted.
+        server.addRecord({
+          collectionId: "storage-sync-crypto",
+          conflict: true,
+          transient: true,
+          data: null,
+          etag: 765,
+        });
+
+        // Try to add a new extension to trigger a sync of the keyring.
+        let collectionKeys2 = await extensionStorageSync.ensureCanSync([
+          extensionId2,
+        ]);
+
+        assertKeyRingKey(
+          collectionKeys2,
+          extensionId,
+          extensionKey,
+          `syncing keyring should keep our local key for ${extensionId}`
+        );
+
+        deepEqual(
+          server.getDeletedBuckets(),
+          ["default"],
+          "Kinto server should have been wiped when keyring was thrown away"
+        );
+
+        let posts = server.getPosts();
+        equal(
+          posts.length,
+          2,
+          "syncing keyring should have tried to post a keyring twice"
+        );
+        // The first post got a conflict.
+        const failedPost = posts[0];
+        assertPostedUpdatedRecord(failedPost, 700);
+        let body = await assertPostedEncryptedKeys(fxaService, failedPost);
+
+        deepEqual(
+          body.keys.collections[extensionId],
+          extensionKey.keyPairB64,
+          `decrypted failed post should have the key for ${extensionId}`
+        );
+
+        // The second post was after the wipe, and succeeded.
+        const afterWipePost = posts[1];
+        assertPostedNewRecord(afterWipePost);
+        let afterWipeBody = await assertPostedEncryptedKeys(
+          fxaService,
+          afterWipePost
+        );
+
+        deepEqual(
+          afterWipeBody.keys.collections[extensionId],
+          extensionKey.keyPairB64,
+          `decrypted new post should have preserved the key for ${extensionId}`
+        );
+      }
+    );
+  });
+});
+
+add_task(async function ensureCanSync_handles_flushes() {
+  // See Bug 1359879 and Bug 1350088. One of the ways that 1359879 presents is
+  // as 1350088. This seems to be the symptom that results when the user had
+  // two devices, one of which was not syncing at the time the keyring was
+  // lost. Ensure we can recover for these users as well.
+  const extensionId = uuid();
+  const extensionId2 = uuid();
+  await withContextAndServer(async function (context, server) {
+    server.installCollection("storage-sync-crypto");
+    server.installDeleteBucket();
+    await withSignedInUser(
+      loggedInUser,
+      async function (extensionStorageSync, fxaService) {
+        server.etag = 700;
+        // Generate keys that we can check for later.
+        let collectionKeys = await extensionStorageSync.ensureCanSync([
+          extensionId,
+        ]);
+        const extensionKey = collectionKeys.keyForCollection(extensionId);
+        server.clearPosts();
+
+        // last_modified is new, but there is no data.
+        server.etag = 800;
+
+        // Try to add a new extension to trigger a sync of the keyring.
+        let collectionKeys2 = await extensionStorageSync.ensureCanSync([
+          extensionId2,
+        ]);
+
+        assertKeyRingKey(
+          collectionKeys2,
+          extensionId,
+          extensionKey,
+          `syncing keyring should keep our local key for ${extensionId}`
+        );
+
+        deepEqual(
+          server.getDeletedBuckets(),
+          ["default"],
+          "Kinto server should have been wiped when keyring was thrown away"
+        );
+
+        let posts = server.getPosts();
+        equal(
+          posts.length,
+          1,
+          "syncing keyring should have tried to post a keyring once"
+        );
+
+        const post = posts[0];
+        assertPostedNewRecord(post);
+        let postBody = await assertPostedEncryptedKeys(fxaService, post);
+
+        deepEqual(
+          postBody.keys.collections[extensionId],
+          extensionKey.keyPairB64,
+          `decrypted new post should have preserved the key for ${extensionId}`
+        );
+      }
+    );
+  });
+});
+
+add_task(async function checkSyncKeyRing_reuploads_keys() {
+  // Verify that when keys are present, they are reuploaded with the
+  // new kbHash when we call touchKeys().
+  const extensionId = uuid();
+  let extensionKey, extensionSalt;
+  await withContextAndServer(async function (context, server) {
+    await withSignedInUser(
+      loggedInUser,
+      async function (extensionStorageSync, fxaService) {
+        server.installCollection("storage-sync-crypto");
+        server.etag = 765;
+
+        await extensionStorageSync.cryptoCollection._clear();
+
+        // Do an `ensureCanSync` to generate some keys.
+        let collectionKeys = await extensionStorageSync.ensureCanSync([
+          extensionId,
+        ]);
+        ok(
+          collectionKeys.hasKeysFor([extensionId]),
+          `ensureCanSync should return a keyring that has a key for ${extensionId}`
+        );
+        extensionKey = collectionKeys.keyForCollection(extensionId).keyPairB64;
+        equal(
+          server.getPosts().length,
+          1,
+          "generating a key that doesn't exist on the server should post it"
+        );
+        const body = await assertPostedEncryptedKeys(
+          fxaService,
+          server.getPosts()[0]
+        );
+        extensionSalt = body.salts[extensionId];
+      }
+    );
+
+    // The user changes their password. This is their new kbHash, with
+    // the last character changed.
+    const newUser = Object.assign({}, loggedInUser, {
+      scopedKeys: {
+        "sync:addon_storage": {
+          kid: "1234567890123-I1DLqPztWi-647HxgLr4YPePZUK-975wn9qWzT49yAE",
+          k: "Y_kFdXfAS7u58MP9hbXUAytg4T7cH43TCb9DBdZvLMMS3eFs5GAhpJb3E5UNCmxWbOGBUhpEcm576Xz1d7MbMA",
+          kty: "oct",
+        },
+      },
+    });
+    let postedKeys;
+    await withSignedInUser(
+      newUser,
+      async function (extensionStorageSync, fxaService) {
+        await extensionStorageSync.checkSyncKeyRing();
+
+        let posts = server.getPosts();
+        equal(
+          posts.length,
+          2,
+          "when kBHash changes, checkSyncKeyRing should post the keyring reencrypted with the new kBHash"
+        );
+        postedKeys = posts[1];
+        assertPostedUpdatedRecord(postedKeys, 765);
+
+        let body = await assertPostedEncryptedKeys(fxaService, postedKeys);
+        deepEqual(
+          body.keys.collections[extensionId],
+          extensionKey,
+          `the posted keyring should have the same key for ${extensionId} as the old one`
+        );
+        deepEqual(
+          body.salts[extensionId],
+          extensionSalt,
+          `the posted keyring should have the same salt for ${extensionId} as the old one`
+        );
+      }
+    );
+
+    // Verify that with the old kBHash, we can't decrypt the record.
+    await withSignedInUser(
+      loggedInUser,
+      async function (extensionStorageSync, fxaService) {
+        let error;
+        try {
+          await new KeyRingEncryptionRemoteTransformer(fxaService).decode(
+            postedKeys.body.data
+          );
+        } catch (e) {
+          error = e;
+        }
+        ok(error, "decrypting the keyring with the old kBHash should fail");
+        ok(
+          Utils.isHMACMismatch(error) ||
+            KeyRingEncryptionRemoteTransformer.isOutdatedKB(error),
+          "decrypting the keyring with the old kBHash should throw an HMAC mismatch"
+        );
+      }
+    );
+  });
+});
+
+add_task(async function checkSyncKeyRing_overwrites_on_conflict() {
+  // If there is already a record on the server that was encrypted
+  // with a different kbHash, we wipe the server, clear sync state, and
+  // overwrite it with our keys.
+  const extensionId = uuid();
+  let extensionKey;
+  await withSyncContext(async function (context) {
+    await withServer(async function (server) {
+      // The old device has this kbHash, which is very similar to the
+      // current kbHash but with the last character changed.
+      const oldUser = Object.assign({}, loggedInUser, {
+        scopedKeys: {
+          "sync:addon_storage": {
+            kid: "1234567890123-I1DLqPztWi-647HxgLr4YPePZUK-975wn9qWzT49yAE",
+            k: "Y_kFdXfAS7u58MP9hbXUAytg4T7cH43TCb9DBdZvLMMS3eFs5GAhpJb3E5UNCmxWbOGBUhpEcm576Xz1d7MbMA",
+            kty: "oct",
+          },
+        },
+      });
+      server.installDeleteBucket();
+      await withSignedInUser(
+        oldUser,
+        async function (extensionStorageSync, fxaService) {
+          await server.installKeyRing(fxaService, {}, {}, 765);
+        }
+      );
+
+      // Now we have this new user with a different kbHash.
+      await withSignedInUser(
+        loggedInUser,
+        async function (extensionStorageSync, fxaService) {
+          await extensionStorageSync.cryptoCollection._clear();
+
+          // Do an `ensureCanSync` to generate some keys.
+          // This will try to sync, notice that the record is
+          // undecryptable, and clear the server.
+          let collectionKeys = await extensionStorageSync.ensureCanSync([
+            extensionId,
+          ]);
+          ok(
+            collectionKeys.hasKeysFor([extensionId]),
+            `ensureCanSync should always return a keyring with a key for ${extensionId}`
+          );
+          extensionKey =
+            collectionKeys.keyForCollection(extensionId).keyPairB64;
+
+          deepEqual(
+            server.getDeletedBuckets(),
+            ["default"],
+            "Kinto server should have been wiped when keyring was thrown away"
+          );
+
+          let posts = server.getPosts();
+          equal(posts.length, 1, "new keyring should have been uploaded");
+          const postedKeys = posts[0];
+          // The POST was to an empty server, so etag shouldn't be respected
+          equal(
+            postedKeys.headers.Authorization,
+            "Bearer some-access-token",
+            "keyring upload should be authorized"
+          );
+          equal(
+            postedKeys.headers["If-None-Match"],
+            "*",
+            "keyring upload should be to empty Kinto server"
+          );
+          equal(
+            postedKeys.path,
+            collectionRecordsPath("storage-sync-crypto") + "/keys",
+            "keyring upload should be to keyring path"
+          );
+
+          let body = await new KeyRingEncryptionRemoteTransformer(
+            fxaService
+          ).decode(postedKeys.body.data);
+          ok(body.uuid, "new keyring should have a UUID");
+          equal(typeof body.uuid, "string", "keyring UUIDs should be strings");
+          notEqual(
+            body.uuid,
+            "abcd",
+            "new keyring should not have the same UUID as previous keyring"
+          );
+          ok(body.keys, "new keyring should have a keys attribute");
+          ok(body.keys.default, "new keyring should have a default key");
+          // We should keep the extension key that was in our uploaded version.
+          deepEqual(
+            extensionKey,
+            body.keys.collections[extensionId],
+            "ensureCanSync should have returned keyring with the same key that was uploaded"
+          );
+
+          // This should be a no-op; the keys were uploaded as part of ensurekeysfor
+          await extensionStorageSync.checkSyncKeyRing();
+          equal(
+            server.getPosts().length,
+            1,
+            "checkSyncKeyRing should not need to post keys after they were reuploaded"
+          );
+        }
+      );
+    });
+  });
+});
+
+add_task(async function checkSyncKeyRing_flushes_on_uuid_change() {
+  // If we can decrypt the record, but the UUID has changed, that
+  // means another client has wiped the server and reuploaded a
+  // keyring, so reset sync state and reupload everything.
+  const extensionId = uuid();
+  const extension = { id: extensionId };
+  await withSyncContext(async function (context) {
+    await withServer(async function (server) {
+      server.installCollection("storage-sync-crypto");
+      server.installDeleteBucket();
+      await withSignedInUser(
+        loggedInUser,
+        async function (extensionStorageSync, fxaService) {
+          const cryptoCollection = new CryptoCollection(fxaService);
+          const transformer = new KeyRingEncryptionRemoteTransformer(
+            fxaService
+          );
+          await extensionStorageSync.cryptoCollection._clear();
+
+          // Do an `ensureCanSync` to get access to keys and salt.
+          let collectionKeys = await extensionStorageSync.ensureCanSync([
+            extensionId,
+          ]);
+          const collectionId = await cryptoCollection.extensionIdToCollectionId(
+            extensionId
+          );
+          server.installCollection(collectionId);
+
+          ok(
+            collectionKeys.hasKeysFor([extensionId]),
+            `ensureCanSync should always return a keyring that has a key for ${extensionId}`
+          );
+          const extensionKey =
+            collectionKeys.keyForCollection(extensionId).keyPairB64;
+
+          // Set something to make sure that it gets re-uploaded when
+          // uuid changes.
+          await extensionStorageSync.set(extension, { "my-key": 5 }, context);
+          await extensionStorageSync.syncAll();
+
+          let posts = server.getPosts();
+          equal(
+            posts.length,
+            2,
+            "should have posted a new keyring and an extension datum"
+          );
+          const postedKeys = posts[0];
+          equal(
+            postedKeys.path,
+            collectionRecordsPath("storage-sync-crypto") + "/keys",
+            "should have posted keyring to /keys"
+          );
+
+          let body = await transformer.decode(postedKeys.body.data);
+          ok(body.uuid, "keyring should have a UUID");
+          ok(body.keys, "keyring should have a keys attribute");
+          ok(body.keys.default, "keyring should have a default key");
+          ok(
+            body.salts[extensionId],
+            `keyring should have a salt for ${extensionId}`
+          );
+          const extensionSalt = body.salts[extensionId];
+          deepEqual(
+            extensionKey,
+            body.keys.collections[extensionId],
+            "new keyring should have the same key that we uploaded"
+          );
+
+          // Another client comes along and replaces the UUID.
+          // In real life, this would mean changing the keys too, but
+          // this test verifies that just changing the UUID is enough.
+          const newKeyRingData = Object.assign({}, body, {
+            uuid: "abcd",
+            // Technically, last_modified should be served outside the
+            // object, but the transformer will pass it through in
+            // either direction, so this is OK.
+            last_modified: 765,
+          });
+          server.etag = 1000;
+          await server.encryptAndAddRecord(transformer, {
+            collectionId: "storage-sync-crypto",
+            data: newKeyRingData,
+            predicate: appearsAt(800),
+          });
+
+          // Fake adding another extension just so that the keyring will
+          // really get synced.
+          const newExtension = uuid();
+          const newKeyRing = await extensionStorageSync.ensureCanSync([
+            newExtension,
+          ]);
+
+          // This should have detected the UUID change and flushed everything.
+          // The keyring should, however, be the same, since we just
+          // changed the UUID of the previously POSTed one.
+          deepEqual(
+            newKeyRing.keyForCollection(extensionId).keyPairB64,
+            extensionKey,
+            "ensureCanSync should have pulled down a new keyring with the same keys"
+          );
+
+          // Syncing should reupload the data for the extension.
+          await extensionStorageSync.syncAll();
+          posts = server.getPosts();
+          equal(
+            posts.length,
+            4,
+            "should have posted keyring for new extension and reuploaded extension data"
+          );
+
+          const finalKeyRingPost = posts[2];
+          const reuploadedPost = posts[3];
+
+          equal(
+            finalKeyRingPost.path,
+            collectionRecordsPath("storage-sync-crypto") + "/keys",
+            "keyring for new extension should have been posted to /keys"
+          );
+          let finalKeyRing = await transformer.decode(
+            finalKeyRingPost.body.data
+          );
+          equal(
+            finalKeyRing.uuid,
+            "abcd",
+            "newly uploaded keyring should preserve UUID from replacement keyring"
+          );
+          deepEqual(
+            finalKeyRing.salts[extensionId],
+            extensionSalt,
+            "newly uploaded keyring should preserve salts from existing salts"
+          );
+
+          // Confirm that the data got reuploaded
+          let reuploadedData = await assertExtensionRecord(
+            fxaService,
+            reuploadedPost,
+            extension,
+            "my-key"
+          );
+          equal(
+            reuploadedData.data,
+            5,
+            "extension data should have a data attribute corresponding to the extension data value"
+          );
+        }
+      );
+    });
+  });
+});
+
+add_task(async function test_storage_sync_pulls_changes() {
+  const extensionId = defaultExtensionId;
+  const extension = defaultExtension;
+  await withContextAndServer(async function (context, server) {
+    await withSignedInUser(
+      loggedInUser,
+      async function (extensionStorageSync, fxaService) {
+        const cryptoCollection = new CryptoCollection(fxaService);
+        server.installCollection("storage-sync-crypto");
+
+        let calls = [];
+        await extensionStorageSync.addOnChangedListener(
+          extension,
+          function () {
+            calls.push(arguments);
+          },
+          context
+        );
+
+        await extensionStorageSync.ensureCanSync([extensionId]);
+        const collectionId = await cryptoCollection.extensionIdToCollectionId(
+          extensionId
+        );
+        let transformer = new CollectionKeyEncryptionRemoteTransformer(
+          cryptoCollection,
+          await cryptoCollection.getKeyRing(),
+          extensionId
+        );
+        await server.encryptAndAddRecord(transformer, {
+          collectionId,
+          data: {
+            id: "key-remote_2D_key",
+            key: "remote-key",
+            data: 6,
+          },
+          predicate: appearsAt(850),
+        });
+        server.etag = 900;
+
+        await extensionStorageSync.syncAll();
+        const remoteValue = (
+          await extensionStorageSync.get(extension, "remote-key", context)
+        )["remote-key"];
+        equal(
+          remoteValue,
+          6,
+          "ExtensionStorageSync.get() returns value retrieved from sync"
+        );
+
+        equal(calls.length, 1, "syncing calls on-changed listener");
+        deepEqual(calls[0][0], { "remote-key": { newValue: 6 } });
+        calls = [];
+
+        // Syncing again doesn't do anything
+        await extensionStorageSync.syncAll();
+
+        equal(
+          calls.length,
+          0,
+          "syncing again shouldn't call on-changed listener"
+        );
+
+        // Updating the server causes us to pull down the new value
+        server.etag = 1000;
+        await server.encryptAndAddRecord(transformer, {
+          collectionId,
+          data: {
+            id: "key-remote_2D_key",
+            key: "remote-key",
+            data: 7,
+          },
+          predicate: appearsAt(950),
+        });
+
+        await extensionStorageSync.syncAll();
+        const remoteValue2 = (
+          await extensionStorageSync.get(extension, "remote-key", context)
+        )["remote-key"];
+        equal(
+          remoteValue2,
+          7,
+          "ExtensionStorageSync.get() returns value updated from sync"
+        );
+
+        equal(calls.length, 1, "syncing calls on-changed listener on update");
+        deepEqual(calls[0][0], { "remote-key": { oldValue: 6, newValue: 7 } });
+      }
+    );
+  });
+});
+
+// Tests that an enabled extension which have been synced before it is going
+// to be synced on ExtensionStorageSync.syncAll even if there is no active
+// context that is currently using the API.
+add_task(async function test_storage_sync_on_no_active_context() {
+  const extensionId = "sync@mochi.test";
+  const extension = ExtensionTestUtils.loadExtension({
+    useAddonManager: "temporary",
+    manifest: {
+      permissions: ["storage"],
+      browser_specific_settings: { gecko: { id: extensionId } },
+    },
+    files: {
+      "ext-page.html": `<!DOCTYPE html>
+        <html>
+          <head>
+            <script src="ext-page.js"></script>
+          </head>
+        </html>
+      `,
+      "ext-page.js": function () {
+        const { browser } = this;
+        browser.test.onMessage.addListener(async msg => {
+          if (msg === "get-sync-data") {
+            browser.test.sendMessage(
+              "get-sync-data:done",
+              await browser.storage.sync.get(["remote-key"])
+            );
+          }
+        });
+      },
+    },
+  });
+
+  await extension.startup();
+
+  await withServer(async server => {
+    await withSignedInUser(
+      loggedInUser,
+      async function (extensionStorageSync, fxaService) {
+        const cryptoCollection = new CryptoCollection(fxaService);
+        server.installCollection("storage-sync-crypto");
+
+        await extensionStorageSync.ensureCanSync([extensionId]);
+        const collectionId = await cryptoCollection.extensionIdToCollectionId(
+          extensionId
+        );
+        let transformer = new CollectionKeyEncryptionRemoteTransformer(
+          cryptoCollection,
+          await cryptoCollection.getKeyRing(),
+          extensionId
+        );
+        await server.encryptAndAddRecord(transformer, {
+          collectionId,
+          data: {
+            id: "key-remote_2D_key",
+            key: "remote-key",
+            data: 6,
+          },
+          predicate: appearsAt(850),
+        });
+
+        server.etag = 1000;
+        await extensionStorageSync.syncAll();
+      }
+    );
+  });
+
+  const extPage = await ExtensionTestUtils.loadContentPage(
+    `moz-extension://${extension.uuid}/ext-page.html`,
+    { extension }
+  );
+
+  await extension.sendMessage("get-sync-data");
+  const res = await extension.awaitMessage("get-sync-data:done");
+  Assert.deepEqual(res, { "remote-key": 6 }, "Got the expected sync data");
+
+  await extPage.close();
+
+  await extension.unload();
+});
+
+add_task(async function test_storage_sync_pushes_changes() {
+  // FIXME: This test relies on the fact that previous tests pushed
+  // keys and salts for the default extension ID
+  const extension = defaultExtension;
+  const extensionId = defaultExtensionId;
+  await withContextAndServer(async function (context, server) {
+    await withSignedInUser(
+      loggedInUser,
+      async function (extensionStorageSync, fxaService) {
+        const cryptoCollection = new CryptoCollection(fxaService);
+        const collectionId = await cryptoCollection.extensionIdToCollectionId(
+          extensionId
+        );
+        server.installCollection(collectionId);
+        server.installCollection("storage-sync-crypto");
+        server.etag = 1000;
+
+        await extensionStorageSync.set(extension, { "my-key": 5 }, context);
+
+        // install this AFTER we set the key to 5...
+        let calls = [];
+        extensionStorageSync.addOnChangedListener(
+          extension,
+          function () {
+            calls.push(arguments);
+          },
+          context
+        );
+
+        await extensionStorageSync.syncAll();
+        const localValue = (
+          await extensionStorageSync.get(extension, "my-key", context)
+        )["my-key"];
+        equal(
+          localValue,
+          5,
+          "pushing an ExtensionStorageSync value shouldn't change local value"
+        );
+        const hashedId =
+          "id-" +
+          (await cryptoCollection.hashWithExtensionSalt(
+            "key-my_2D_key",
+            extensionId
+          ));
+
+        let posts = server.getPosts();
+        // FIXME: Keys were pushed in a previous test
+        equal(
+          posts.length,
+          1,
+          "pushing a value should cause a post to the server"
+        );
+        const post = posts[0];
+        assertPostedNewRecord(post);
+        equal(
+          post.path,
+          `${collectionRecordsPath(collectionId)}/${hashedId}`,
+          "pushing a value should have a path corresponding to its id"
+        );
+
+        const encrypted = post.body.data;
+        ok(
+          encrypted.ciphertext,
+          "pushing a value should post an encrypted record"
+        );
+        ok(
+          !encrypted.data,
+          "pushing a value should not have any plaintext data"
+        );
+        equal(
+          encrypted.id,
+          hashedId,
+          "pushing a value should use a kinto-friendly record ID"
+        );
+
+        const record = await assertExtensionRecord(
+          fxaService,
+          post,
+          extension,
+          "my-key"
+        );
+        equal(
+          record.data,
+          5,
+          "when decrypted, a pushed value should have a data field corresponding to its storage.sync value"
+        );
+        equal(
+          record.id,
+          "key-my_2D_key",
+          "when decrypted, a pushed value should have an id field corresponding to its record ID"
+        );
+
+        equal(
+          calls.length,
+          0,
+          "pushing a value shouldn't call the on-changed listener"
+        );
+
+        await extensionStorageSync.set(extension, { "my-key": 6 }, context);
+        await extensionStorageSync.syncAll();
+
+        // Doesn't push keys because keys were pushed by a previous test.
+        posts = server.getPosts();
+        equal(posts.length, 2, "updating a value should trigger another push");
+        const updatePost = posts[1];
+        assertPostedUpdatedRecord(updatePost, 1000);
+        equal(
+          updatePost.path,
+          `${collectionRecordsPath(collectionId)}/${hashedId}`,
+          "pushing an updated value should go to the same path"
+        );
+
+        const updateEncrypted = updatePost.body.data;
+        ok(
+          updateEncrypted.ciphertext,
+          "pushing an updated value should still be encrypted"
+        );
+        ok(
+          !updateEncrypted.data,
+          "pushing an updated value should not have any plaintext visible"
+        );
+        equal(
+          updateEncrypted.id,
+          hashedId,
+          "pushing an updated value should maintain the same ID"
+        );
+      }
+    );
+  });
+});
+
+add_task(async function test_storage_sync_retries_failed_auth() {
+  const extensionId = uuid();
+  const extension = { id: extensionId };
+  await withContextAndServer(async function (context, server) {
+    await withSignedInUser(
+      loggedInUser,
+      async function (extensionStorageSync, fxaService) {
+        const cryptoCollection = new CryptoCollection(fxaService);
+        server.installCollection("storage-sync-crypto");
+
+        await extensionStorageSync.ensureCanSync([extensionId]);
+        await extensionStorageSync.set(extension, { "my-key": 5 }, context);
+        const collectionId = await cryptoCollection.extensionIdToCollectionId(
+          extensionId
+        );
+        let transformer = new CollectionKeyEncryptionRemoteTransformer(
+          cryptoCollection,
+          await cryptoCollection.getKeyRing(),
+          extensionId
+        );
+        // Put a remote record just to verify that eventually we succeeded
+        await server.encryptAndAddRecord(transformer, {
+          collectionId,
+          data: {
+            id: "key-remote_2D_key",
+            key: "remote-key",
+            data: 6,
+          },
+          predicate: appearsAt(850),
+        });
+        server.etag = 900;
+
+        // This is a typical response from a production stack if your
+        // bearer token is bad.
+        server.rejectNextAuthWith(
+          '{"code": 401, "errno": 104, "error": "Unauthorized", "message": "Please authenticate yourself to use this endpoint"}'
+        );
+        await extensionStorageSync.syncAll();
+
+        equal(server.failedAuths.length, 1, "an auth was failed");
+
+        const remoteValue = (
+          await extensionStorageSync.get(extension, "remote-key", context)
+        )["remote-key"];
+        equal(
+          remoteValue,
+          6,
+          "ExtensionStorageSync.get() returns value retrieved from sync"
+        );
+
+        // Try again with an emptier JSON body to make sure this still
+        // works with a less-cooperative server.
+        await server.encryptAndAddRecord(transformer, {
+          collectionId,
+          data: {
+            id: "key-remote_2D_key",
+            key: "remote-key",
+            data: 7,
+          },
+          predicate: appearsAt(950),
+        });
+        server.etag = 1000;
+        // Need to write a JSON response.
+        // kinto.js 9.0.2 doesn't throw unless there's json.
+        // See https://github.com/Kinto/kinto-http.js/issues/192.
+        server.rejectNextAuthWith("{}");
+
+        await extensionStorageSync.syncAll();
+
+        equal(server.failedAuths.length, 2, "an auth was failed");
+
+        const newRemoteValue = (
+          await extensionStorageSync.get(extension, "remote-key", context)
+        )["remote-key"];
+        equal(
+          newRemoteValue,
+          7,
+          "ExtensionStorageSync.get() returns value retrieved from sync"
+        );
+      }
+    );
+  });
+});
+
+add_task(async function test_storage_sync_pulls_conflicts() {
+  const extensionId = uuid();
+  const extension = { id: extensionId };
+  await withContextAndServer(async function (context, server) {
+    await withSignedInUser(
+      loggedInUser,
+      async function (extensionStorageSync, fxaService) {
+        const cryptoCollection = new CryptoCollection(fxaService);
+        server.installCollection("storage-sync-crypto");
+
+        await extensionStorageSync.ensureCanSync([extensionId]);
+        const collectionId = await cryptoCollection.extensionIdToCollectionId(
+          extensionId
+        );
+        let transformer = new CollectionKeyEncryptionRemoteTransformer(
+          cryptoCollection,
+          await cryptoCollection.getKeyRing(),
+          extensionId
+        );
+        await server.encryptAndAddRecord(transformer, {
+          collectionId,
+          data: {
+            id: "key-remote_2D_key",
+            key: "remote-key",
+            data: 6,
+          },
+          predicate: appearsAt(850),
+        });
+        server.etag = 900;
+
+        await extensionStorageSync.set(extension, { "remote-key": 8 }, context);
+
+        let calls = [];
+        await extensionStorageSync.addOnChangedListener(
+          extension,
+          function () {
+            calls.push(arguments);
+          },
+          context
+        );
+
+        await extensionStorageSync.syncAll();
+        const remoteValue = (
+          await extensionStorageSync.get(extension, "remote-key", context)
+        )["remote-key"];
+        equal(remoteValue, 8, "locally set value overrides remote value");
+
+        equal(calls.length, 1, "conflicts manifest in on-changed listener");
+        deepEqual(calls[0][0], { "remote-key": { newValue: 8 } });
+        calls = [];
+
+        // Syncing again doesn't do anything
+        await extensionStorageSync.syncAll();
+
+        equal(
+          calls.length,
+          0,
+          "syncing again shouldn't call on-changed listener"
+        );
+
+        // Updating the server causes us to pull down the new value
+        server.etag = 1000;
+        await server.encryptAndAddRecord(transformer, {
+          collectionId,
+          data: {
+            id: "key-remote_2D_key",
+            key: "remote-key",
+            data: 7,
+          },
+          predicate: appearsAt(950),
+        });
+
+        await extensionStorageSync.syncAll();
+        const remoteValue2 = (
+          await extensionStorageSync.get(extension, "remote-key", context)
+        )["remote-key"];
+        equal(
+          remoteValue2,
+          7,
+          "conflicts do not prevent retrieval of new values"
+        );
+
+        equal(calls.length, 1, "syncing calls on-changed listener on update");
+        deepEqual(calls[0][0], { "remote-key": { oldValue: 8, newValue: 7 } });
+      }
+    );
+  });
+});
+
+add_task(async function test_storage_sync_pulls_deletes() {
+  const extension = defaultExtension;
+  await withContextAndServer(async function (context, server) {
+    await withSignedInUser(
+      loggedInUser,
+      async function (extensionStorageSync, fxaService) {
+        const cryptoCollection = new CryptoCollection(fxaService);
+        const collectionId = await cryptoCollection.extensionIdToCollectionId(
+          defaultExtensionId
+        );
+        server.installCollection(collectionId);
+        server.installCollection("storage-sync-crypto");
+
+        await extensionStorageSync.set(extension, { "my-key": 5 }, context);
+        await extensionStorageSync.syncAll();
+        server.clearPosts();
+
+        let calls = [];
+        await extensionStorageSync.addOnChangedListener(
+          extension,
+          function () {
+            calls.push(arguments);
+          },
+          context
+        );
+
+        const transformer = new CollectionKeyEncryptionRemoteTransformer(
+          new CryptoCollection(fxaService),
+          await cryptoCollection.getKeyRing(),
+          extension.id
+        );
+        await server.encryptAndAddRecord(transformer, {
+          collectionId,
+          data: {
+            id: "key-my_2D_key",
+            data: 6,
+            _status: "deleted",
+          },
+        });
+
+        await extensionStorageSync.syncAll();
+        const remoteValues = await extensionStorageSync.get(
+          extension,
+          "my-key",
+          context
+        );
+        ok(
+          !remoteValues["my-key"],
+          "ExtensionStorageSync.get() shows value was deleted by sync"
+        );
+
+        equal(
+          server.getPosts().length,
+          0,
+          "pulling the delete shouldn't cause posts"
+        );
+
+        equal(calls.length, 1, "syncing calls on-changed listener");
+        deepEqual(calls[0][0], { "my-key": { oldValue: 5 } });
+        calls = [];
+
+        // Syncing again doesn't do anything
+        await extensionStorageSync.syncAll();
+
+        equal(
+          calls.length,
+          0,
+          "syncing again shouldn't call on-changed listener"
+        );
+      }
+    );
+  });
+});
+
+add_task(async function test_storage_sync_pushes_deletes() {
+  const extensionId = uuid();
+  const extension = { id: extensionId };
+  await withContextAndServer(async function (context, server) {
+    await withSignedInUser(
+      loggedInUser,
+      async function (extensionStorageSync, fxaService) {
+        const cryptoCollection = new CryptoCollection(fxaService);
+        await cryptoCollection._clear();
+        await cryptoCollection._setSalt(
+          extensionId,
+          cryptoCollection.getNewSalt()
+        );
+        const collectionId = await cryptoCollection.extensionIdToCollectionId(
+          extensionId
+        );
+
+        server.installCollection(collectionId);
+        server.installCollection("storage-sync-crypto");
+        server.etag = 1000;
+
+        await extensionStorageSync.set(extension, { "my-key": 5 }, context);
+
+        let calls = [];
+        extensionStorageSync.addOnChangedListener(
+          extension,
+          function () {
+            calls.push(arguments);
+          },
+          context
+        );
+
+        await extensionStorageSync.syncAll();
+        let posts = server.getPosts();
+        equal(
+          posts.length,
+          2,
+          "pushing a non-deleted value should post keys and post the value to the server"
+        );
+
+        await extensionStorageSync.remove(extension, ["my-key"], context);
+        equal(
+          calls.length,
+          1,
+          "deleting a value should call the on-changed listener"
+        );
+
+        await extensionStorageSync.syncAll();
+        equal(
+          calls.length,
+          1,
+          "pushing a deleted value shouldn't call the on-changed listener"
+        );
+
+        // Doesn't push keys because keys were pushed by a previous test.
+        const hashedId =
+          "id-" +
+          (await cryptoCollection.hashWithExtensionSalt(
+            "key-my_2D_key",
+            extensionId
+          ));
+        posts = server.getPosts();
+        equal(posts.length, 3, "deleting a value should trigger another push");
+        const post = posts[2];
+        assertPostedUpdatedRecord(post, 1000);
+        equal(
+          post.path,
+          `${collectionRecordsPath(collectionId)}/${hashedId}`,
+          "pushing a deleted value should go to the same path"
+        );
+        ok(post.method, "PUT");
+        ok(
+          post.body.data.ciphertext,
+          "deleting a value should have an encrypted body"
+        );
+        const decoded = await new CollectionKeyEncryptionRemoteTransformer(
+          cryptoCollection,
+          await cryptoCollection.getKeyRing(),
+          extensionId
+        ).decode(post.body.data);
+        equal(decoded._status, "deleted");
+        // Ideally, we'd check that decoded.deleted is not true, because
+        // the encrypted record shouldn't have it, but the decoder will
+        // add it when it sees _status == deleted
+      }
+    );
+  });
+});
+
+// Some sync tests shared between implementations.
+add_task(test_config_flag_needed);
+
+add_task(test_sync_reloading_extensions_works);
+
+add_task(function test_storage_sync() {
+  return runWithPrefs([[STORAGE_SYNC_PREF, true]], () =>
+    test_background_page_storage("sync")
+  );
+});
+
+add_task(test_storage_sync_requires_real_id);
+
+add_task(function test_storage_sync_with_bytes_in_use() {
+  return runWithPrefs([[STORAGE_SYNC_PREF, true]], () =>
+    test_background_storage_area_with_bytes_in_use("sync", false)
+  );
+});
+
+add_task(function test_storage_onChanged_event_page() {
+  return runWithPrefs([[STORAGE_SYNC_PREF, true]], () =>
+    test_storage_change_event_page("sync")
+  );
+});
diff --git a/toolkit/components/extensions/test/xpcshell/test_ext_storage_sync_kinto_crypto.js b/toolkit/components/extensions/test/xpcshell/test_ext_storage_sync_kinto_crypto.js
new file mode 100644
index 0000000000..8d99083fa8
--- /dev/null
+++ b/toolkit/components/extensions/test/xpcshell/test_ext_storage_sync_kinto_crypto.js
@@ -0,0 +1,122 @@
+/* Any copyright is dedicated to the Public Domain.
+ * http://creativecommons.org/publicdomain/zero/1.0/ */
+
+"use strict";
+
+// This is a kinto-specific test...
+Services.prefs.setBoolPref("webextensions.storage.sync.kinto", true);
+
+const {
+  KintoStorageTestUtils: { EncryptionRemoteTransformer },
+} = ChromeUtils.importESModule(
+  "resource://gre/modules/ExtensionStorageSyncKinto.sys.mjs"
+);
+const { CryptoUtils } = ChromeUtils.importESModule(
+  "resource://services-crypto/utils.sys.mjs"
+);
+const { Utils } = ChromeUtils.importESModule(
+  "resource://services-sync/util.sys.mjs"
+);
+
+/**
+ * Like Assert.throws, but for generators.
+ *
+ * @param {string | object | Function} constraint
+ *        What to use to check the exception.
+ * @param {Function} f
+ *        The function to call.
+ */
+async function throwsGen(constraint, f) {
+  let threw = false;
+  let exception;
+  try {
+    await f();
+  } catch (e) {
+    threw = true;
+    exception = e;
+  }
+
+  ok(threw, "did not throw an exception");
+
+  const debuggingMessage = `got ${exception}, expected ${constraint}`;
+
+  if (typeof constraint === "function") {
+    ok(constraint(exception), debuggingMessage);
+  } else {
+    let message = exception;
+    if (typeof exception === "object") {
+      message = exception.message;
+    }
+    ok(constraint === message, debuggingMessage);
+  }
+}
+
+/**
+ * An EncryptionRemoteTransformer that uses a fixed key bundle,
+ * suitable for testing.
+ */
+class StaticKeyEncryptionRemoteTransformer extends EncryptionRemoteTransformer {
+  constructor(keyBundle) {
+    super();
+    this.keyBundle = keyBundle;
+  }
+
+  getKeys() {
+    return Promise.resolve(this.keyBundle);
+  }
+}
+const BORING_KB =
+  "0123456789abcdef0123456789abcdef0123456789abcdef0123456789abcdef";
+let transformer;
+add_task(async function setup() {
+  const STRETCHED_KEY = await CryptoUtils.hkdfLegacy(
+    BORING_KB,
+    undefined,
+    `testing storage.sync encryption`,
+    2 * 32
+  );
+  const KEY_BUNDLE = {
+    hmacKey: STRETCHED_KEY.slice(0, 32),
+    encryptionKeyB64: btoa(STRETCHED_KEY.slice(32, 64)),
+  };
+  transformer = new StaticKeyEncryptionRemoteTransformer(KEY_BUNDLE);
+});
+
+add_task(async function test_encryption_transformer_roundtrip() {
+  const POSSIBLE_DATAS = [
+    "string",
+    2, // number
+    [1, 2, 3], // array
+    { key: "value" }, // object
+  ];
+
+  for (let data of POSSIBLE_DATAS) {
+    const record = { data, id: "key-some_2D_key", key: "some-key" };
+
+    deepEqual(
+      record,
+      await transformer.decode(await transformer.encode(record))
+    );
+  }
+});
+
+add_task(async function test_refuses_to_decrypt_tampered() {
+  const encryptedRecord = await transformer.encode({
+    data: [1, 2, 3],
+    id: "key-some_2D_key",
+    key: "some-key",
+  });
+  const tamperedHMAC = Object.assign({}, encryptedRecord, {
+    hmac: "0000000000000000000000000000000000000000000000000000000000000001",
+  });
+  await throwsGen(Utils.isHMACMismatch, async function () {
+    await transformer.decode(tamperedHMAC);
+  });
+
+  const tamperedIV = Object.assign({}, encryptedRecord, {
+    IV: "aaaaaaaaaaaaaaaaaaaaaa==",
+  });
+  await throwsGen(Utils.isHMACMismatch, async function () {
+    await transformer.decode(tamperedIV);
+  });
+});
diff --git a/toolkit/components/extensions/test/xpcshell/test_ext_storage_tab.js b/toolkit/components/extensions/test/xpcshell/test_ext_storage_tab.js
new file mode 100644
index 0000000000..cfa49c334b
--- /dev/null
+++ b/toolkit/components/extensions/test/xpcshell/test_ext_storage_tab.js
@@ -0,0 +1,245 @@
+"use strict";
+
+const { ExtensionStorageIDB } = ChromeUtils.importESModule(
+  "resource://gre/modules/ExtensionStorageIDB.sys.mjs"
+);
+
+async function test_multiple_pages() {
+  let extension = ExtensionTestUtils.loadExtension({
+    async background() {
+      function awaitMessage(expectedMsg, api = "test") {
+        return new Promise(resolve => {
+          browser[api].onMessage.addListener(function listener(msg) {
+            if (msg === expectedMsg) {
+              browser[api].onMessage.removeListener(listener);
+              resolve();
+            }
+          });
+        });
+      }
+
+      let tabReady = awaitMessage("tab-ready", "runtime");
+
+      try {
+        let storage = browser.storage.local;
+
+        browser.test.sendMessage(
+          "load-page",
+          browser.runtime.getURL("tab.html")
+        );
+        await awaitMessage("page-loaded");
+        await tabReady;
+
+        let result = await storage.get("key");
+        browser.test.assertEq(undefined, result.key, "Key should be undefined");
+
+        await browser.runtime.sendMessage("tab-set-key");
+
+        result = await storage.get("key");
+        browser.test.assertEq(
+          JSON.stringify({ foo: { bar: "baz" } }),
+          JSON.stringify(result.key),
+          "Key should be set to the value from the tab"
+        );
+
+        browser.test.sendMessage("remove-page");
+        await awaitMessage("page-removed");
+
+        result = await storage.get("key");
+        browser.test.assertEq(
+          JSON.stringify({ foo: { bar: "baz" } }),
+          JSON.stringify(result.key),
+          "Key should still be set to the value from the tab"
+        );
+
+        browser.test.notifyPass("storage-multiple");
+      } catch (e) {
+        browser.test.fail(`Error: ${e} :: ${e.stack}`);
+        browser.test.notifyFail("storage-multiple");
+      }
+    },
+
+    files: {
+      "tab.html": `<!DOCTYPE html>
+        <html>
+          <head>
+            <meta charset="utf-8">
+            <script src="tab.js"></script>
+          </head>
+        </html>`,
+
+      "tab.js"() {
+        browser.test.log("tab");
+        browser.runtime.onMessage.addListener(msg => {
+          if (msg == "tab-set-key") {
+            return browser.storage.local.set({ key: { foo: { bar: "baz" } } });
+          }
+        });
+
+        browser.runtime.sendMessage("tab-ready");
+      },
+    },
+
+    manifest: {
+      permissions: ["storage"],
+    },
+  });
+
+  let contentPage;
+  extension.onMessage("load-page", async url => {
+    contentPage = await ExtensionTestUtils.loadContentPage(url, { extension });
+    extension.sendMessage("page-loaded");
+  });
+  extension.onMessage("remove-page", async url => {
+    await contentPage.close();
+    extension.sendMessage("page-removed");
+  });
+
+  await extension.startup();
+  await extension.awaitFinish("storage-multiple");
+  await extension.unload();
+}
+
+add_task(async function test_storage_local_file_backend_from_tab() {
+  return runWithPrefs(
+    [[ExtensionStorageIDB.BACKEND_ENABLED_PREF, false]],
+    test_multiple_pages
+  );
+});
+
+add_task(async function test_storage_local_idb_backend_from_tab() {
+  return runWithPrefs(
+    [[ExtensionStorageIDB.BACKEND_ENABLED_PREF, true]],
+    test_multiple_pages
+  );
+});
+
+async function test_storage_local_call_from_destroying_context() {
+  let extension = ExtensionTestUtils.loadExtension({
+    async background() {
+      let numberOfChanges = 0;
+      browser.storage.onChanged.addListener((changes, areaName) => {
+        if (areaName !== "local") {
+          browser.test.fail(
+            `Received unexpected storage changes for "${areaName}"`
+          );
+        }
+
+        numberOfChanges++;
+      });
+
+      browser.test.onMessage.addListener(async ({ msg, values }) => {
+        switch (msg) {
+          case "storage-set": {
+            await browser.storage.local.set(values);
+            browser.test.sendMessage("storage-set:done");
+            break;
+          }
+          case "storage-get": {
+            const res = await browser.storage.local.get();
+            browser.test.sendMessage("storage-get:done", res);
+            break;
+          }
+          case "storage-changes": {
+            browser.test.sendMessage("storage-changes-count", numberOfChanges);
+            break;
+          }
+          default:
+            browser.test.fail(`Received unexpected message: ${msg}`);
+        }
+      });
+
+      browser.test.sendMessage(
+        "ext-page-url",
+        browser.runtime.getURL("tab.html")
+      );
+    },
+    files: {
+      "tab.html": `<!DOCTYPE html>
+        <html>
+          <head>
+            <meta charset="utf-8">
+            <script src="tab.js"></script>
+          </head>
+        </html>`,
+
+      "tab.js"() {
+        browser.test.log("Extension tab - calling storage.local API method");
+        // Call the storage.local API from a tab that is going to be quickly closed.
+        browser.storage.local.set({
+          "test-key-from-destroying-context": "testvalue2",
+        });
+        // Navigate away from the extension page, so that the storage.local API call will be unable
+        // to send the call to the caller context (because it has been destroyed in the meantime).
+        window.location = "about:blank";
+      },
+    },
+    manifest: {
+      permissions: ["storage"],
+    },
+  });
+
+  await extension.startup();
+  const url = await extension.awaitMessage("ext-page-url");
+
+  let contentPage = await ExtensionTestUtils.loadContentPage(url, {
+    extension,
+  });
+  let expectedBackgroundPageData = {
+    "test-key-from-background-page": "test-value",
+  };
+  let expectedTabData = { "test-key-from-destroying-context": "testvalue2" };
+
+  info(
+    "Call storage.local.set from the background page and wait it to be completed"
+  );
+  extension.sendMessage({
+    msg: "storage-set",
+    values: expectedBackgroundPageData,
+  });
+  await extension.awaitMessage("storage-set:done");
+
+  info(
+    "Call storage.local.get from the background page and wait it to be completed"
+  );
+  extension.sendMessage({ msg: "storage-get" });
+  let res = await extension.awaitMessage("storage-get:done");
+
+  Assert.deepEqual(
+    res,
+    {
+      ...expectedBackgroundPageData,
+      ...expectedTabData,
+    },
+    "Got the expected data set in the storage.local backend"
+  );
+
+  extension.sendMessage({ msg: "storage-changes" });
+  equal(
+    await extension.awaitMessage("storage-changes-count"),
+    2,
+    "Got the expected number of storage.onChanged event received"
+  );
+
+  contentPage.close();
+
+  await extension.unload();
+}
+
+add_task(
+  async function test_storage_local_file_backend_destroyed_context_promise() {
+    return runWithPrefs(
+      [[ExtensionStorageIDB.BACKEND_ENABLED_PREF, false]],
+      test_storage_local_call_from_destroying_context
+    );
+  }
+);
+
+add_task(
+  async function test_storage_local_idb_backend_destroyed_context_promise() {
+    return runWithPrefs(
+      [[ExtensionStorageIDB.BACKEND_ENABLED_PREF, true]],
+      test_storage_local_call_from_destroying_context
+    );
+  }
+);
diff --git a/toolkit/components/extensions/test/xpcshell/test_ext_storage_telemetry.js b/toolkit/components/extensions/test/xpcshell/test_ext_storage_telemetry.js
new file mode 100644
index 0000000000..9bc4281624
--- /dev/null
+++ b/toolkit/components/extensions/test/xpcshell/test_ext_storage_telemetry.js
@@ -0,0 +1,362 @@
+/* -*- Mode: indent-tabs-mode: nil; js-indent-level: 2 -*- */
+/* vim: set sts=2 sw=2 et tw=80: */
+"use strict";
+
+const { ExtensionStorageIDB } = ChromeUtils.importESModule(
+  "resource://gre/modules/ExtensionStorageIDB.sys.mjs"
+);
+const { getTrimmedString } = ChromeUtils.importESModule(
+  "resource://gre/modules/ExtensionTelemetry.sys.mjs"
+);
+const { TelemetryController } = ChromeUtils.importESModule(
+  "resource://gre/modules/TelemetryController.sys.mjs"
+);
+const { TelemetryTestUtils } = ChromeUtils.importESModule(
+  "resource://testing-common/TelemetryTestUtils.sys.mjs"
+);
+
+const HISTOGRAM_JSON_IDS = [
+  "WEBEXT_STORAGE_LOCAL_SET_MS",
+  "WEBEXT_STORAGE_LOCAL_GET_MS",
+];
+const KEYED_HISTOGRAM_JSON_IDS = [
+  "WEBEXT_STORAGE_LOCAL_SET_MS_BY_ADDONID",
+  "WEBEXT_STORAGE_LOCAL_GET_MS_BY_ADDONID",
+];
+
+const HISTOGRAM_IDB_IDS = [
+  "WEBEXT_STORAGE_LOCAL_IDB_SET_MS",
+  "WEBEXT_STORAGE_LOCAL_IDB_GET_MS",
+];
+const KEYED_HISTOGRAM_IDB_IDS = [
+  "WEBEXT_STORAGE_LOCAL_IDB_SET_MS_BY_ADDONID",
+  "WEBEXT_STORAGE_LOCAL_IDB_GET_MS_BY_ADDONID",
+];
+
+const HISTOGRAM_IDS = [].concat(HISTOGRAM_JSON_IDS, HISTOGRAM_IDB_IDS);
+const KEYED_HISTOGRAM_IDS = [].concat(
+  KEYED_HISTOGRAM_JSON_IDS,
+  KEYED_HISTOGRAM_IDB_IDS
+);
+
+const EXTENSION_ID1 = "@test-extension1";
+const EXTENSION_ID2 = "@test-extension2";
+
+async function test_telemetry_background() {
+  const expectedEmptyHistograms = ExtensionStorageIDB.isBackendEnabled
+    ? HISTOGRAM_JSON_IDS
+    : HISTOGRAM_IDB_IDS;
+  const expectedEmptyKeyedHistograms = ExtensionStorageIDB.isBackendEnabled
+    ? KEYED_HISTOGRAM_JSON_IDS
+    : KEYED_HISTOGRAM_IDB_IDS;
+
+  const expectedNonEmptyHistograms = ExtensionStorageIDB.isBackendEnabled
+    ? HISTOGRAM_IDB_IDS
+    : HISTOGRAM_JSON_IDS;
+  const expectedNonEmptyKeyedHistograms = ExtensionStorageIDB.isBackendEnabled
+    ? KEYED_HISTOGRAM_IDB_IDS
+    : KEYED_HISTOGRAM_JSON_IDS;
+
+  const server = createHttpServer();
+  server.registerDirectory("/data/", do_get_file("data"));
+
+  const BASE_URL = `http://localhost:${server.identity.primaryPort}/data`;
+
+  async function contentScript() {
+    await browser.storage.local.set({ a: "b" });
+    await browser.storage.local.get("a");
+    browser.test.sendMessage("contentDone");
+  }
+
+  let baseManifest = {
+    permissions: ["storage"],
+    content_scripts: [
+      {
+        matches: ["http://*/*/file_sample.html"],
+        js: ["content_script.js"],
+      },
+    ],
+  };
+
+  let baseExtInfo = {
+    async background() {
+      await browser.storage.local.set({ a: "b" });
+      await browser.storage.local.get("a");
+      browser.test.sendMessage("backgroundDone");
+    },
+    files: {
+      "content_script.js": contentScript,
+    },
+  };
+
+  let extension1 = ExtensionTestUtils.loadExtension({
+    ...baseExtInfo,
+    manifest: {
+      ...baseManifest,
+      browser_specific_settings: {
+        gecko: { id: EXTENSION_ID1 },
+      },
+    },
+  });
+  let extension2 = ExtensionTestUtils.loadExtension({
+    ...baseExtInfo,
+    manifest: {
+      ...baseManifest,
+      browser_specific_settings: {
+        gecko: { id: EXTENSION_ID2 },
+      },
+    },
+  });
+
+  clearHistograms();
+
+  let process = IS_OOP ? "extension" : "parent";
+  let snapshots = getSnapshots(process);
+  let keyedSnapshots = getKeyedSnapshots(process);
+
+  for (let id of HISTOGRAM_IDS) {
+    ok(!(id in snapshots), `No data recorded for histogram: ${id}.`);
+  }
+
+  for (let id of KEYED_HISTOGRAM_IDS) {
+    Assert.deepEqual(
+      Object.keys(keyedSnapshots[id] || {}),
+      [],
+      `No data recorded for histogram: ${id}.`
+    );
+  }
+
+  await extension1.startup();
+  await extension1.awaitMessage("backgroundDone");
+  for (let id of expectedNonEmptyHistograms) {
+    await promiseTelemetryRecorded(id, process, 1);
+  }
+  for (let id of expectedNonEmptyKeyedHistograms) {
+    await promiseKeyedTelemetryRecorded(id, process, EXTENSION_ID1, 1);
+  }
+
+  // Telemetry from extension1's background page should be recorded.
+  snapshots = getSnapshots(process);
+  keyedSnapshots = getKeyedSnapshots(process);
+
+  for (let id of expectedNonEmptyHistograms) {
+    equal(
+      valueSum(snapshots[id].values),
+      1,
+      `Data recorded for histogram: ${id}.`
+    );
+  }
+
+  for (let id of expectedNonEmptyKeyedHistograms) {
+    Assert.deepEqual(
+      Object.keys(keyedSnapshots[id]),
+      [EXTENSION_ID1],
+      `Data recorded for histogram: ${id}.`
+    );
+    equal(
+      valueSum(keyedSnapshots[id][EXTENSION_ID1].values),
+      1,
+      `Data recorded for histogram: ${id}.`
+    );
+  }
+
+  await extension2.startup();
+  await extension2.awaitMessage("backgroundDone");
+
+  for (let id of expectedNonEmptyHistograms) {
+    await promiseTelemetryRecorded(id, process, 2);
+  }
+  for (let id of expectedNonEmptyKeyedHistograms) {
+    await promiseKeyedTelemetryRecorded(id, process, EXTENSION_ID2, 1);
+  }
+
+  // Telemetry from extension2's background page should be recorded.
+  snapshots = getSnapshots(process);
+  keyedSnapshots = getKeyedSnapshots(process);
+
+  for (let id of expectedNonEmptyHistograms) {
+    equal(
+      valueSum(snapshots[id].values),
+      2,
+      `Additional data recorded for histogram: ${id}.`
+    );
+  }
+
+  for (let id of expectedNonEmptyKeyedHistograms) {
+    Assert.deepEqual(
+      Object.keys(keyedSnapshots[id]).sort(),
+      [EXTENSION_ID1, EXTENSION_ID2],
+      `Additional data recorded for histogram: ${id}.`
+    );
+    equal(
+      valueSum(keyedSnapshots[id][EXTENSION_ID2].values),
+      1,
+      `Additional data recorded for histogram: ${id}.`
+    );
+  }
+
+  await extension2.unload();
+
+  // Run a content script.
+  process = IS_OOP ? "content" : "parent";
+  let expectedCount = IS_OOP ? 1 : 3;
+  let expectedKeyedCount = IS_OOP ? 1 : 2;
+
+  let contentPage = await ExtensionTestUtils.loadContentPage(
+    `${BASE_URL}/file_sample.html`
+  );
+  await extension1.awaitMessage("contentDone");
+
+  for (let id of expectedNonEmptyHistograms) {
+    await promiseTelemetryRecorded(id, process, expectedCount);
+  }
+  for (let id of expectedNonEmptyKeyedHistograms) {
+    await promiseKeyedTelemetryRecorded(
+      id,
+      process,
+      EXTENSION_ID1,
+      expectedKeyedCount
+    );
+  }
+
+  // Telemetry from extension1's content script should be recorded.
+  snapshots = getSnapshots(process);
+  keyedSnapshots = getKeyedSnapshots(process);
+
+  for (let id of expectedNonEmptyHistograms) {
+    equal(
+      valueSum(snapshots[id].values),
+      expectedCount,
+      `Data recorded in content script for histogram: ${id}.`
+    );
+  }
+
+  for (let id of expectedNonEmptyKeyedHistograms) {
+    Assert.deepEqual(
+      Object.keys(keyedSnapshots[id]).sort(),
+      IS_OOP ? [EXTENSION_ID1] : [EXTENSION_ID1, EXTENSION_ID2],
+      `Additional data recorded for histogram: ${id}.`
+    );
+    equal(
+      valueSum(keyedSnapshots[id][EXTENSION_ID1].values),
+      expectedKeyedCount,
+      `Additional data recorded for histogram: ${id}.`
+    );
+  }
+
+  await extension1.unload();
+
+  // Telemetry for histograms that we expect to be empty.
+  for (let id of expectedEmptyHistograms) {
+    ok(!(id in snapshots), `No data recorded for histogram: ${id}.`);
+  }
+
+  for (let id of expectedEmptyKeyedHistograms) {
+    Assert.deepEqual(
+      Object.keys(keyedSnapshots[id] || {}),
+      [],
+      `No data recorded for histogram: ${id}.`
+    );
+  }
+
+  await contentPage.close();
+}
+
+add_task(async function setup() {
+  // Telemetry test setup needed to ensure that the builtin events are defined
+  // and they can be collected and verified.
+  await TelemetryController.testSetup();
+
+  // This is actually only needed on Android, because it does not properly support unified telemetry
+  // and so, if not enabled explicitly here, it would make these tests to fail when running on a
+  // non-Nightly build.
+  const oldCanRecordBase = Services.telemetry.canRecordBase;
+  Services.telemetry.canRecordBase = true;
+  registerCleanupFunction(() => {
+    Services.telemetry.canRecordBase = oldCanRecordBase;
+  });
+});
+
+add_task(function test_telemetry_background_file_backend() {
+  return runWithPrefs(
+    [[ExtensionStorageIDB.BACKEND_ENABLED_PREF, false]],
+    test_telemetry_background
+  );
+});
+
+add_task(function test_telemetry_background_idb_backend() {
+  return runWithPrefs(
+    [
+      [ExtensionStorageIDB.BACKEND_ENABLED_PREF, true],
+      // Set the migrated preference for the two test extension, because the
+      // first storage.local call fallbacks to run in the parent process when we
+      // don't know which is the selected backend during the extension startup
+      // and so we can't choose the telemetry histogram to use.
+      [
+        `${ExtensionStorageIDB.IDB_MIGRATED_PREF_BRANCH}.${EXTENSION_ID1}`,
+        true,
+      ],
+      [
+        `${ExtensionStorageIDB.IDB_MIGRATED_PREF_BRANCH}.${EXTENSION_ID2}`,
+        true,
+      ],
+    ],
+    test_telemetry_background
+  );
+});
+
+// This test verifies that we do record the expected telemetry event when we
+// normalize the error message for an unexpected error (an error raised internally
+// by the QuotaManager and/or IndexedDB, which it is being normalized into the generic
+// "An unexpected error occurred" error message).
+add_task(async function test_telemetry_storage_local_unexpected_error() {
+  // Clear any telemetry events collected so far.
+  Services.telemetry.clearEvents();
+
+  const methods = ["clear", "get", "remove", "set"];
+  const veryLongErrorName = `VeryLongErrorName${Array(200).fill(0).join("")}`;
+  const otherError = new Error("an error recorded as OtherError");
+
+  const recordedErrors = [
+    new DOMException("error message", "UnexpectedDOMException"),
+    new DOMException("error message", veryLongErrorName),
+    otherError,
+  ];
+
+  // We expect the following errors to not be recorded in telemetry (because they
+  // are raised on scenarios that we already expect).
+  const nonRecordedErrors = [
+    new DOMException("error message", "QuotaExceededError"),
+    new DOMException("error message", "DataCloneError"),
+  ];
+
+  const expectedEvents = [];
+
+  const errors = [].concat(recordedErrors, nonRecordedErrors);
+
+  for (let i = 0; i < errors.length; i++) {
+    const error = errors[i];
+    const storageMethod = methods[i] || "set";
+    ExtensionStorageIDB.normalizeStorageError({
+      error: errors[i],
+      extensionId: EXTENSION_ID1,
+      storageMethod,
+    });
+
+    if (recordedErrors.includes(error)) {
+      let error_name =
+        error === otherError ? "OtherError" : getTrimmedString(error.name);
+
+      expectedEvents.push({
+        value: EXTENSION_ID1,
+        object: storageMethod,
+        extra: { error_name },
+      });
+    }
+  }
+
+  await TelemetryTestUtils.assertEvents(expectedEvents, {
+    category: "extensions.data",
+    method: "storageLocalError",
+  });
+});
diff --git a/toolkit/components/extensions/test/xpcshell/test_ext_tab_teardown.js b/toolkit/components/extensions/test/xpcshell/test_ext_tab_teardown.js
new file mode 100644
index 0000000000..538ce9d8fc
--- /dev/null
+++ b/toolkit/components/extensions/test/xpcshell/test_ext_tab_teardown.js
@@ -0,0 +1,97 @@
+"use strict";
+
+add_task(async function test_extension_page_tabs_create_reload_and_close() {
+  let events = [];
+  {
+    const { Management } = ChromeUtils.importESModule(
+      "resource://gre/modules/Extension.sys.mjs"
+    );
+    let record = (type, extensionContext) => {
+      let eventType = type == "proxy-context-load" ? "load" : "unload";
+      let url = extensionContext.uri.spec;
+      let extensionId = extensionContext.extension.id;
+      events.push({ eventType, url, extensionId });
+    };
+
+    Management.on("proxy-context-load", record);
+    Management.on("proxy-context-unload", record);
+    registerCleanupFunction(() => {
+      Management.off("proxy-context-load", record);
+      Management.off("proxy-context-unload", record);
+    });
+  }
+
+  let extension = ExtensionTestUtils.loadExtension({
+    background() {
+      browser.test.sendMessage("tab-url", browser.runtime.getURL("page.html"));
+    },
+    files: {
+      "page.html": `<!DOCTYPE html><meta charset="utf-8"><script src="page.js"></script>`,
+      "page.js"() {
+        browser.test.sendMessage("extension page loaded", document.URL);
+      },
+    },
+  });
+
+  await extension.startup();
+  let tabURL = await extension.awaitMessage("tab-url");
+  events.splice(0);
+
+  let contentPage = await ExtensionTestUtils.loadContentPage(tabURL, {
+    extension,
+  });
+  let extensionPageURL = await extension.awaitMessage("extension page loaded");
+  equal(extensionPageURL, tabURL, "Loaded the expected URL");
+
+  let contextEvents = events.splice(0);
+  equal(contextEvents.length, 1, "ExtensionContext change for opening a tab");
+  equal(contextEvents[0].eventType, "load", "create ExtensionContext for tab");
+  equal(
+    contextEvents[0].url,
+    extensionPageURL,
+    "ExtensionContext URL after tab creation should be tab URL"
+  );
+
+  await contentPage.spawn([], () => {
+    this.content.location.reload();
+  });
+  let extensionPageURL2 = await extension.awaitMessage("extension page loaded");
+
+  equal(
+    extensionPageURL,
+    extensionPageURL2,
+    "The tab's URL is expected to not change after a page reload"
+  );
+
+  contextEvents = events.splice(0);
+  equal(contextEvents.length, 2, "ExtensionContext change after tab reload");
+  equal(contextEvents[0].eventType, "unload", "unload old ExtensionContext");
+  equal(
+    contextEvents[0].url,
+    extensionPageURL,
+    "ExtensionContext URL before reload should be tab URL"
+  );
+  equal(
+    contextEvents[1].eventType,
+    "load",
+    "create new ExtensionContext for tab"
+  );
+  equal(
+    contextEvents[1].url,
+    extensionPageURL2,
+    "ExtensionContext URL after reload should be tab URL"
+  );
+
+  await contentPage.close();
+
+  contextEvents = events.splice(0);
+  equal(contextEvents.length, 1, "ExtensionContext after closing tab");
+  equal(contextEvents[0].eventType, "unload", "unload tab's ExtensionContext");
+  equal(
+    contextEvents[0].url,
+    extensionPageURL2,
+    "ExtensionContext URL at closing tab should be tab URL"
+  );
+
+  await extension.unload();
+});
diff --git a/toolkit/components/extensions/test/xpcshell/test_ext_telemetry.js b/toolkit/components/extensions/test/xpcshell/test_ext_telemetry.js
new file mode 100644
index 0000000000..c651e46732
--- /dev/null
+++ b/toolkit/components/extensions/test/xpcshell/test_ext_telemetry.js
@@ -0,0 +1,917 @@
+"use strict";
+
+const { TelemetryArchive } = ChromeUtils.importESModule(
+  "resource://gre/modules/TelemetryArchive.sys.mjs"
+);
+const { TelemetryUtils } = ChromeUtils.importESModule(
+  "resource://gre/modules/TelemetryUtils.sys.mjs"
+);
+const { TelemetryTestUtils } = ChromeUtils.importESModule(
+  "resource://testing-common/TelemetryTestUtils.sys.mjs"
+);
+
+const { TelemetryArchiveTesting } = ChromeUtils.importESModule(
+  "resource://testing-common/TelemetryArchiveTesting.sys.mjs"
+);
+
+const { TestUtils } = ChromeUtils.importESModule(
+  "resource://testing-common/TestUtils.sys.mjs"
+);
+
+// All tests run privileged unless otherwise specified not to.
+function createExtension(
+  backgroundScript,
+  permissions,
+  isPrivileged = true,
+  telemetry
+) {
+  let extensionData = {
+    background: backgroundScript,
+    manifest: { permissions, telemetry },
+    isPrivileged,
+  };
+
+  return ExtensionTestUtils.loadExtension(extensionData);
+}
+
+async function run(test) {
+  let extension = createExtension(
+    test.backgroundScript,
+    test.permissions || ["telemetry"],
+    test.isPrivileged,
+    test.telemetry
+  );
+  await extension.startup();
+  await extension.awaitFinish(test.doneSignal);
+  await extension.unload();
+}
+
+// Currently unsupported on Android: blocked on 1220177.
+// See 1280234 c67 for discussion.
+if (AppConstants.MOZ_BUILD_APP === "browser") {
+  add_task(async function test_telemetry_without_telemetry_permission() {
+    await run({
+      backgroundScript: () => {
+        browser.test.assertTrue(
+          !browser.telemetry,
+          "'telemetry' permission is required"
+        );
+        browser.test.notifyPass("telemetry_permission");
+      },
+      permissions: [],
+      doneSignal: "telemetry_permission",
+      isPrivileged: false,
+    });
+  });
+
+  add_task(
+    async function test_telemetry_without_telemetry_permission_privileged() {
+      await run({
+        backgroundScript: () => {
+          browser.test.assertTrue(
+            !browser.telemetry,
+            "'telemetry' permission is required"
+          );
+          browser.test.notifyPass("telemetry_permission");
+        },
+        permissions: [],
+        doneSignal: "telemetry_permission",
+      });
+    }
+  );
+
+  add_task(async function test_telemetry_scalar_add() {
+    Services.telemetry.clearScalars();
+    await run({
+      backgroundScript: async () => {
+        await browser.telemetry.scalarAdd(
+          "telemetry.test.unsigned_int_kind",
+          1
+        );
+        browser.test.notifyPass("scalar_add");
+      },
+      doneSignal: "scalar_add",
+    });
+    TelemetryTestUtils.assertScalar(
+      TelemetryTestUtils.getProcessScalars("parent", false, true),
+      "telemetry.test.unsigned_int_kind",
+      1
+    );
+  });
+
+  add_task(async function test_telemetry_scalar_add_unknown_name() {
+    let { messages } = await promiseConsoleOutput(async () => {
+      await run({
+        backgroundScript: async () => {
+          await browser.telemetry.scalarAdd("telemetry.test.does_not_exist", 1);
+          browser.test.notifyPass("scalar_add_unknown_name");
+        },
+        doneSignal: "scalar_add_unknown_name",
+      });
+    });
+    Assert.ok(
+      messages.find(({ message }) => message.includes("Unknown scalar")),
+      "Telemetry should warn if an unknown scalar is incremented"
+    );
+  });
+
+  add_task(async function test_telemetry_scalar_add_illegal_value() {
+    await run({
+      backgroundScript: () => {
+        browser.test.assertThrows(
+          () =>
+            browser.telemetry.scalarAdd("telemetry.test.unsigned_int_kind", {}),
+          /Incorrect argument types for telemetry.scalarAdd/,
+          "The second 'value' argument to scalarAdd must be an integer, string, or boolean"
+        );
+        browser.test.notifyPass("scalar_add_illegal_value");
+      },
+      doneSignal: "scalar_add_illegal_value",
+    });
+  });
+
+  add_task(async function test_telemetry_scalar_add_invalid_keyed_scalar() {
+    let { messages } = await promiseConsoleOutput(async function () {
+      await run({
+        backgroundScript: async () => {
+          await browser.telemetry.scalarAdd(
+            "telemetry.test.keyed_unsigned_int",
+            1
+          );
+          browser.test.notifyPass("scalar_add_invalid_keyed_scalar");
+        },
+        doneSignal: "scalar_add_invalid_keyed_scalar",
+      });
+    });
+    Assert.ok(
+      messages.find(({ message }) =>
+        message.includes("Attempting to manage a keyed scalar as a scalar")
+      ),
+      "Telemetry should warn if a scalarAdd is called for a keyed scalar"
+    );
+  });
+
+  add_task(async function test_telemetry_scalar_set_bool_true() {
+    Services.telemetry.clearScalars();
+    await run({
+      backgroundScript: async () => {
+        await browser.telemetry.scalarSet("telemetry.test.boolean_kind", true);
+        browser.test.notifyPass("scalar_set_bool_true");
+      },
+      doneSignal: "scalar_set_bool_true",
+    });
+    TelemetryTestUtils.assertScalar(
+      TelemetryTestUtils.getProcessScalars("parent", false, true),
+      "telemetry.test.boolean_kind",
+      true
+    );
+  });
+
+  add_task(async function test_telemetry_scalar_set_bool_false() {
+    Services.telemetry.clearScalars();
+    await run({
+      backgroundScript: async () => {
+        await browser.telemetry.scalarSet("telemetry.test.boolean_kind", false);
+        browser.test.notifyPass("scalar_set_bool_false");
+      },
+      doneSignal: "scalar_set_bool_false",
+    });
+    TelemetryTestUtils.assertScalar(
+      TelemetryTestUtils.getProcessScalars("parent", false, true),
+      "telemetry.test.boolean_kind",
+      false
+    );
+  });
+
+  add_task(async function test_telemetry_scalar_unset_bool() {
+    Services.telemetry.clearScalars();
+    TelemetryTestUtils.assertScalarUnset(
+      TelemetryTestUtils.getProcessScalars("parent", false, true),
+      "telemetry.test.boolean_kind"
+    );
+  });
+
+  add_task(async function test_telemetry_scalar_set_unknown_name() {
+    let { messages } = await promiseConsoleOutput(async function () {
+      await run({
+        backgroundScript: async () => {
+          await browser.telemetry.scalarSet(
+            "telemetry.test.does_not_exist",
+            true
+          );
+          browser.test.notifyPass("scalar_set_unknown_name");
+        },
+        doneSignal: "scalar_set_unknown_name",
+      });
+    });
+    Assert.ok(
+      messages.find(({ message }) => message.includes("Unknown scalar")),
+      "Telemetry should warn if an unknown scalar is set"
+    );
+  });
+
+  add_task(async function test_telemetry_scalar_set_zero() {
+    Services.telemetry.clearScalars();
+    await run({
+      backgroundScript: async () => {
+        await browser.telemetry.scalarSet(
+          "telemetry.test.unsigned_int_kind",
+          0
+        );
+        browser.test.notifyPass("scalar_set_zero");
+      },
+      doneSignal: "scalar_set_zero",
+    });
+    TelemetryTestUtils.assertScalar(
+      TelemetryTestUtils.getProcessScalars("parent", false, true),
+      "telemetry.test.unsigned_int_kind",
+      0
+    );
+  });
+
+  add_task(async function test_telemetry_scalar_set_maximum() {
+    Services.telemetry.clearScalars();
+    await run({
+      backgroundScript: async () => {
+        await browser.telemetry.scalarSetMaximum(
+          "telemetry.test.unsigned_int_kind",
+          123
+        );
+        browser.test.notifyPass("scalar_set_maximum");
+      },
+      doneSignal: "scalar_set_maximum",
+    });
+    TelemetryTestUtils.assertScalar(
+      TelemetryTestUtils.getProcessScalars("parent", false, true),
+      "telemetry.test.unsigned_int_kind",
+      123
+    );
+  });
+
+  add_task(async function test_telemetry_scalar_set_maximum_unknown_name() {
+    let { messages } = await promiseConsoleOutput(async function () {
+      await run({
+        backgroundScript: async () => {
+          await browser.telemetry.scalarSetMaximum(
+            "telemetry.test.does_not_exist",
+            1
+          );
+          browser.test.notifyPass("scalar_set_maximum_unknown_name");
+        },
+        doneSignal: "scalar_set_maximum_unknown_name",
+      });
+    });
+    Assert.ok(
+      messages.find(({ message }) => message.includes("Unknown scalar")),
+      "Telemetry should warn if an unknown scalar is set"
+    );
+  });
+
+  add_task(async function test_telemetry_scalar_set_maximum_illegal_value() {
+    await run({
+      backgroundScript: () => {
+        browser.test.assertThrows(
+          () =>
+            browser.telemetry.scalarSetMaximum(
+              "telemetry.test.unsigned_int_kind",
+              "string"
+            ),
+          /Incorrect argument types for telemetry.scalarSetMaximum/,
+          "The second 'value' argument to scalarSetMaximum must be a scalar"
+        );
+        browser.test.notifyPass("scalar_set_maximum_illegal_value");
+      },
+      doneSignal: "scalar_set_maximum_illegal_value",
+    });
+  });
+
+  add_task(async function test_telemetry_keyed_scalar_add() {
+    Services.telemetry.clearScalars();
+    await run({
+      backgroundScript: async () => {
+        await browser.telemetry.keyedScalarAdd(
+          "telemetry.test.keyed_unsigned_int",
+          "foo",
+          1
+        );
+        browser.test.notifyPass("keyed_scalar_add");
+      },
+      doneSignal: "keyed_scalar_add",
+    });
+    TelemetryTestUtils.assertKeyedScalar(
+      TelemetryTestUtils.getProcessScalars("parent", true, true),
+      "telemetry.test.keyed_unsigned_int",
+      "foo",
+      1
+    );
+  });
+
+  add_task(async function test_telemetry_keyed_scalar_add_unknown_name() {
+    let { messages } = await promiseConsoleOutput(async () => {
+      await run({
+        backgroundScript: async () => {
+          await browser.telemetry.keyedScalarAdd(
+            "telemetry.test.does_not_exist",
+            "foo",
+            1
+          );
+          browser.test.notifyPass("keyed_scalar_add_unknown_name");
+        },
+        doneSignal: "keyed_scalar_add_unknown_name",
+      });
+    });
+    Assert.ok(
+      messages.find(({ message }) => message.includes("Unknown scalar")),
+      "Telemetry should warn if an unknown keyed scalar is incremented"
+    );
+  });
+
+  add_task(async function test_telemetry_keyed_scalar_add_illegal_value() {
+    await run({
+      backgroundScript: () => {
+        browser.test.assertThrows(
+          () =>
+            browser.telemetry.keyedScalarAdd(
+              "telemetry.test.keyed_unsigned_int",
+              "foo",
+              {}
+            ),
+          /Incorrect argument types for telemetry.keyedScalarAdd/,
+          "The second 'value' argument to keyedScalarAdd must be an integer, string, or boolean"
+        );
+        browser.test.notifyPass("keyed_scalar_add_illegal_value");
+      },
+      doneSignal: "keyed_scalar_add_illegal_value",
+    });
+  });
+
+  add_task(async function test_telemetry_keyed_scalar_add_invalid_scalar() {
+    let { messages } = await promiseConsoleOutput(async function () {
+      await run({
+        backgroundScript: async () => {
+          await browser.telemetry.keyedScalarAdd(
+            "telemetry.test.unsigned_int_kind",
+            "foo",
+            1
+          );
+          browser.test.notifyPass("keyed_scalar_add_invalid_scalar");
+        },
+        doneSignal: "keyed_scalar_add_invalid_scalar",
+      });
+    });
+    Assert.ok(
+      messages.find(({ message }) =>
+        message.includes(
+          "Attempting to manage a keyed scalar as a scalar (or vice-versa)"
+        )
+      ),
+      "Telemetry should warn if a scalar is incremented as a keyed scalar"
+    );
+  });
+
+  add_task(async function test_telemetry_keyed_scalar_add_long_key() {
+    let { messages } = await promiseConsoleOutput(async () => {
+      await run({
+        backgroundScript: async () => {
+          await browser.telemetry.keyedScalarAdd(
+            "telemetry.test.keyed_unsigned_int",
+            "X".repeat(73),
+            1
+          );
+          browser.test.notifyPass("keyed_scalar_add_long_key");
+        },
+        doneSignal: "keyed_scalar_add_long_key",
+      });
+    });
+    Assert.ok(
+      messages.find(({ message }) =>
+        message.includes("The key length must be limited to 72 characters.")
+      ),
+      "Telemetry should warn if keyed scalar's key is too long"
+    );
+  });
+
+  add_task(async function test_telemetry_keyed_scalar_set() {
+    Services.telemetry.clearScalars();
+    await run({
+      backgroundScript: async () => {
+        await browser.telemetry.keyedScalarSet(
+          "telemetry.test.keyed_boolean_kind",
+          "foo",
+          true
+        );
+        browser.test.notifyPass("keyed_scalar_set");
+      },
+      doneSignal: "keyed_scalar_set",
+    });
+    TelemetryTestUtils.assertKeyedScalar(
+      TelemetryTestUtils.getProcessScalars("parent", true, true),
+      "telemetry.test.keyed_boolean_kind",
+      "foo",
+      true
+    );
+  });
+
+  add_task(async function test_telemetry_keyed_scalar_set_unknown_name() {
+    let { messages } = await promiseConsoleOutput(async function () {
+      await run({
+        backgroundScript: async () => {
+          await browser.telemetry.keyedScalarSet(
+            "telemetry.test.does_not_exist",
+            "foo",
+            true
+          );
+          browser.test.notifyPass("keyed_scalar_set_unknown_name");
+        },
+        doneSignal: "keyed_scalar_set_unknown_name",
+      });
+    });
+    Assert.ok(
+      messages.find(({ message }) => message.includes("Unknown scalar")),
+      "Telemetry should warn if an unknown keyed scalar is incremented"
+    );
+  });
+
+  add_task(async function test_telemetry_keyed_scalar_set_long_key() {
+    let { messages } = await promiseConsoleOutput(async () => {
+      await run({
+        backgroundScript: async () => {
+          await browser.telemetry.keyedScalarSet(
+            "telemetry.test.keyed_unsigned_int",
+            "X".repeat(73),
+            1
+          );
+          browser.test.notifyPass("keyed_scalar_set_long_key");
+        },
+        doneSignal: "keyed_scalar_set_long_key",
+      });
+    });
+    Assert.ok(
+      messages.find(({ message }) =>
+        message.includes("The key length must be limited to 72 characters")
+      ),
+      "Telemetry should warn if keyed scalar's key is too long"
+    );
+  });
+
+  add_task(async function test_telemetry_keyed_scalar_set_maximum() {
+    Services.telemetry.clearScalars();
+    await run({
+      backgroundScript: async () => {
+        await browser.telemetry.keyedScalarSetMaximum(
+          "telemetry.test.keyed_unsigned_int",
+          "foo",
+          123
+        );
+        browser.test.notifyPass("keyed_scalar_set_maximum");
+      },
+      doneSignal: "keyed_scalar_set_maximum",
+    });
+    TelemetryTestUtils.assertKeyedScalar(
+      TelemetryTestUtils.getProcessScalars("parent", true, true),
+      "telemetry.test.keyed_unsigned_int",
+      "foo",
+      123
+    );
+  });
+
+  add_task(
+    async function test_telemetry_keyed_scalar_set_maximum_unknown_name() {
+      let { messages } = await promiseConsoleOutput(async function () {
+        await run({
+          backgroundScript: async () => {
+            await browser.telemetry.keyedScalarSetMaximum(
+              "telemetry.test.does_not_exist",
+              "foo",
+              1
+            );
+            browser.test.notifyPass("keyed_scalar_set_maximum_unknown_name");
+          },
+          doneSignal: "keyed_scalar_set_maximum_unknown_name",
+        });
+      });
+      Assert.ok(
+        messages.find(({ message }) => message.includes("Unknown scalar")),
+        "Telemetry should warn if an unknown keyed scalar is set"
+      );
+    }
+  );
+
+  add_task(
+    async function test_telemetry_keyed_scalar_set_maximum_illegal_value() {
+      await run({
+        backgroundScript: () => {
+          browser.test.assertThrows(
+            () =>
+              browser.telemetry.keyedScalarSetMaximum(
+                "telemetry.test.keyed_unsigned_int",
+                "foo",
+                "string"
+              ),
+            /Incorrect argument types for telemetry.keyedScalarSetMaximum/,
+            "The third 'value' argument to keyedScalarSetMaximum must be a scalar"
+          );
+          browser.test.notifyPass("keyed_scalar_set_maximum_illegal_value");
+        },
+        doneSignal: "keyed_scalar_set_maximum_illegal_value",
+      });
+    }
+  );
+
+  add_task(async function test_telemetry_keyed_scalar_set_maximum_long_key() {
+    let { messages } = await promiseConsoleOutput(async () => {
+      await run({
+        backgroundScript: async () => {
+          await browser.telemetry.keyedScalarSetMaximum(
+            "telemetry.test.keyed_unsigned_int",
+            "X".repeat(73),
+            1
+          );
+          browser.test.notifyPass("keyed_scalar_set_maximum_long_key");
+        },
+        doneSignal: "keyed_scalar_set_maximum_long_key",
+      });
+    });
+    Assert.ok(
+      messages.find(({ message }) =>
+        message.includes("The key length must be limited to 72 characters")
+      ),
+      "Telemetry should warn if keyed scalar's key is too long"
+    );
+  });
+
+  add_task(async function test_telemetry_record_event() {
+    Services.telemetry.clearEvents();
+    Services.telemetry.setEventRecordingEnabled("telemetry.test", true);
+
+    await run({
+      backgroundScript: async () => {
+        await browser.telemetry.recordEvent(
+          "telemetry.test",
+          "test1",
+          "object1"
+        );
+        browser.test.notifyPass("record_event_ok");
+      },
+      doneSignal: "record_event_ok",
+    });
+
+    TelemetryTestUtils.assertEvents(
+      [
+        {
+          category: "telemetry.test",
+          method: "test1",
+          object: "object1",
+        },
+      ],
+      { category: "telemetry.test" }
+    );
+
+    Services.telemetry.setEventRecordingEnabled("telemetry.test", false);
+    Services.telemetry.clearEvents();
+  });
+
+  // Bug 1536877
+  add_task(async function test_telemetry_record_event_value_must_be_string() {
+    Services.telemetry.clearEvents();
+    Services.telemetry.setEventRecordingEnabled("telemetry.test", true);
+
+    await run({
+      backgroundScript: async () => {
+        try {
+          await browser.telemetry.recordEvent(
+            "telemetry.test",
+            "test1",
+            "object1",
+            "value1"
+          );
+          browser.test.notifyPass("record_event_string_value");
+        } catch (ex) {
+          browser.test.fail(
+            `Unexpected exception raised during record_event_value_must_be_string: ${ex}`
+          );
+          browser.test.notifyPass("record_event_string_value");
+          throw ex;
+        }
+      },
+      doneSignal: "record_event_string_value",
+    });
+
+    TelemetryTestUtils.assertEvents(
+      [
+        {
+          category: "telemetry.test",
+          method: "test1",
+          object: "object1",
+          value: "value1",
+        },
+      ],
+      { category: "telemetry.test" }
+    );
+
+    Services.telemetry.setEventRecordingEnabled("telemetry.test", false);
+    Services.telemetry.clearEvents();
+  });
+
+  add_task(async function test_telemetry_register_scalars_string() {
+    Services.telemetry.clearScalars();
+    await run({
+      backgroundScript: async () => {
+        await browser.telemetry.registerScalars("telemetry.test.dynamic", {
+          webext_string: {
+            kind: browser.telemetry.ScalarType.STRING,
+            keyed: false,
+            record_on_release: true,
+          },
+        });
+        await browser.telemetry.scalarSet(
+          "telemetry.test.dynamic.webext_string",
+          "hello"
+        );
+        browser.test.notifyPass("register_scalars_string");
+      },
+      doneSignal: "register_scalars_string",
+    });
+    TelemetryTestUtils.assertScalar(
+      TelemetryTestUtils.getProcessScalars("dynamic", false, true),
+      "telemetry.test.dynamic.webext_string",
+      "hello"
+    );
+  });
+
+  add_task(async function test_telemetry_register_scalars_multiple() {
+    Services.telemetry.clearScalars();
+    await run({
+      backgroundScript: async () => {
+        await browser.telemetry.registerScalars("telemetry.test.dynamic", {
+          webext_string: {
+            kind: browser.telemetry.ScalarType.STRING,
+            keyed: false,
+            record_on_release: true,
+          },
+          webext_string_too: {
+            kind: browser.telemetry.ScalarType.STRING,
+            keyed: false,
+            record_on_release: true,
+          },
+        });
+        await browser.telemetry.scalarSet(
+          "telemetry.test.dynamic.webext_string",
+          "hello"
+        );
+        await browser.telemetry.scalarSet(
+          "telemetry.test.dynamic.webext_string_too",
+          "world"
+        );
+        browser.test.notifyPass("register_scalars_multiple");
+      },
+      doneSignal: "register_scalars_multiple",
+    });
+    const scalars = TelemetryTestUtils.getProcessScalars(
+      "dynamic",
+      false,
+      true
+    );
+    TelemetryTestUtils.assertScalar(
+      scalars,
+      "telemetry.test.dynamic.webext_string",
+      "hello"
+    );
+    TelemetryTestUtils.assertScalar(
+      scalars,
+      "telemetry.test.dynamic.webext_string_too",
+      "world"
+    );
+  });
+
+  add_task(async function test_telemetry_register_scalars_boolean() {
+    Services.telemetry.clearScalars();
+    await run({
+      backgroundScript: async () => {
+        await browser.telemetry.registerScalars("telemetry.test.dynamic", {
+          webext_boolean: {
+            kind: browser.telemetry.ScalarType.BOOLEAN,
+            keyed: false,
+            record_on_release: true,
+          },
+        });
+        await browser.telemetry.scalarSet(
+          "telemetry.test.dynamic.webext_boolean",
+          true
+        );
+        browser.test.notifyPass("register_scalars_boolean");
+      },
+      doneSignal: "register_scalars_boolean",
+    });
+    TelemetryTestUtils.assertScalar(
+      TelemetryTestUtils.getProcessScalars("dynamic", false, true),
+      "telemetry.test.dynamic.webext_boolean",
+      true
+    );
+  });
+
+  add_task(async function test_telemetry_register_scalars_count() {
+    Services.telemetry.clearScalars();
+    await run({
+      backgroundScript: async () => {
+        await browser.telemetry.registerScalars("telemetry.test.dynamic", {
+          webext_count: {
+            kind: browser.telemetry.ScalarType.COUNT,
+            keyed: false,
+            record_on_release: true,
+          },
+        });
+        await browser.telemetry.scalarSet(
+          "telemetry.test.dynamic.webext_count",
+          123
+        );
+        browser.test.notifyPass("register_scalars_count");
+      },
+      doneSignal: "register_scalars_count",
+    });
+    TelemetryTestUtils.assertScalar(
+      TelemetryTestUtils.getProcessScalars("dynamic", false, true),
+      "telemetry.test.dynamic.webext_count",
+      123
+    );
+  });
+
+  add_task(async function test_telemetry_register_events() {
+    Services.telemetry.clearEvents();
+
+    await run({
+      backgroundScript: async () => {
+        await browser.telemetry.registerEvents("telemetry.test.dynamic", {
+          test1: {
+            methods: ["test1"],
+            objects: ["object1"],
+            extra_keys: [],
+          },
+        });
+        await browser.telemetry.recordEvent(
+          "telemetry.test.dynamic",
+          "test1",
+          "object1"
+        );
+        browser.test.notifyPass("register_events");
+      },
+      doneSignal: "register_events",
+    });
+
+    TelemetryTestUtils.assertEvents(
+      [
+        {
+          category: "telemetry.test.dynamic",
+          method: "test1",
+          object: "object1",
+        },
+      ],
+      { category: "telemetry.test.dynamic" },
+      { process: "dynamic" }
+    );
+  });
+
+  add_task(async function test_telemetry_submit_ping() {
+    let archiveTester = new TelemetryArchiveTesting.Checker();
+    await archiveTester.promiseInit();
+
+    await run({
+      backgroundScript: async () => {
+        await browser.telemetry.submitPing("webext-test", {}, {});
+        browser.test.notifyPass("submit_ping");
+      },
+      doneSignal: "submit_ping",
+    });
+
+    await TestUtils.waitForCondition(
+      () => archiveTester.promiseFindPing("webext-test", []),
+      "Failed to find the webext-test ping"
+    );
+  });
+
+  add_task(async function test_telemetry_submit_encrypted_ping() {
+    await run({
+      backgroundScript: async () => {
+        try {
+          await browser.telemetry.submitEncryptedPing(
+            { payload: "encrypted-webext-test" },
+            {
+              schemaName: "schema-name",
+              schemaVersion: 123,
+            }
+          );
+          browser.test.fail(
+            "Expected exception without required manifest entries set."
+          );
+        } catch (e) {
+          browser.test.assertTrue(
+            e,
+            /Encrypted telemetry pings require ping_type and public_key to be set in manifest./
+          );
+          browser.test.notifyPass("submit_encrypted_ping_fail");
+        }
+      },
+      doneSignal: "submit_encrypted_ping_fail",
+    });
+
+    const telemetryManifestEntries = {
+      ping_type: "encrypted-webext-ping",
+      schemaNamespace: "schema-namespace",
+      public_key: {
+        id: "pioneer-dev-20200423",
+        key: {
+          crv: "P-256",
+          kty: "EC",
+          x: "Qqihp7EryDN2-qQ-zuDPDpy5mJD5soFBDZmzPWTmjwk",
+          y: "PiEQVUlywi2bEsA3_5D0VFrCHClCyUlLW52ajYs-5uc",
+        },
+      },
+    };
+
+    await run({
+      backgroundScript: async () => {
+        await browser.telemetry.submitEncryptedPing(
+          {
+            payload: "encrypted-webext-test",
+          },
+          {
+            schemaName: "schema-name",
+            schemaVersion: 123,
+          }
+        );
+        browser.test.notifyPass("submit_encrypted_ping_pass");
+      },
+      permissions: ["telemetry"],
+      doneSignal: "submit_encrypted_ping_pass",
+      isPrivileged: true,
+      telemetry: telemetryManifestEntries,
+    });
+
+    telemetryManifestEntries.pioneer_id = true;
+    telemetryManifestEntries.study_name = "test123";
+    Services.prefs.setStringPref("toolkit.telemetry.pioneerId", "test123");
+
+    await run({
+      backgroundScript: async () => {
+        await browser.telemetry.submitEncryptedPing(
+          { payload: "encrypted-webext-test" },
+          {
+            schemaName: "schema-name",
+            schemaVersion: 123,
+          }
+        );
+        browser.test.notifyPass("submit_encrypted_ping_pass");
+      },
+      permissions: ["telemetry"],
+      doneSignal: "submit_encrypted_ping_pass",
+      isPrivileged: true,
+      telemetry: telemetryManifestEntries,
+    });
+
+    let pings;
+    await TestUtils.waitForCondition(async function () {
+      pings = await TelemetryArchive.promiseArchivedPingList();
+      return pings.length >= 3;
+    }, "Wait until we have at least 3 pings in the telemetry archive");
+
+    equal(pings.length, 3);
+    equal(pings[1].type, "encrypted-webext-ping");
+    equal(pings[2].type, "encrypted-webext-ping");
+  });
+
+  add_task(async function test_telemetry_can_upload_enabled() {
+    Services.prefs.setBoolPref(
+      TelemetryUtils.Preferences.FhrUploadEnabled,
+      true
+    );
+
+    await run({
+      backgroundScript: async () => {
+        const result = await browser.telemetry.canUpload();
+        browser.test.assertTrue(result);
+        browser.test.notifyPass("can_upload_enabled");
+      },
+      doneSignal: "can_upload_enabled",
+    });
+
+    Services.prefs.clearUserPref(TelemetryUtils.Preferences.FhrUploadEnabled);
+  });
+
+  add_task(async function test_telemetry_can_upload_disabled() {
+    Services.prefs.setBoolPref(
+      TelemetryUtils.Preferences.FhrUploadEnabled,
+      false
+    );
+
+    await run({
+      backgroundScript: async () => {
+        const result = await browser.telemetry.canUpload();
+        browser.test.assertFalse(result);
+        browser.test.notifyPass("can_upload_disabled");
+      },
+      doneSignal: "can_upload_disabled",
+    });
+
+    Services.prefs.clearUserPref(TelemetryUtils.Preferences.FhrUploadEnabled);
+  });
+}
diff --git a/toolkit/components/extensions/test/xpcshell/test_ext_test_mock.js b/toolkit/components/extensions/test/xpcshell/test_ext_test_mock.js
new file mode 100644
index 0000000000..81e07d9a9b
--- /dev/null
+++ b/toolkit/components/extensions/test/xpcshell/test_ext_test_mock.js
@@ -0,0 +1,55 @@
+/* -*- Mode: indent-tabs-mode: nil; js-indent-level: 2 -*- */
+/* vim: set sts=2 sw=2 et tw=80: */
+"use strict";
+
+// This test verifies that the extension mocks behave consistently, regardless
+// of test type (xpcshell vs browser test).
+// See also toolkit/components/extensions/test/browser/browser_ext_test_mock.js
+
+// Check the state of the extension object. This should be consistent between
+// browser tests and xpcshell tests.
+async function checkExtensionStartupAndUnload(ext) {
+  await ext.startup();
+  Assert.ok(ext.id, "Extension ID should be available");
+  Assert.ok(ext.uuid, "Extension UUID should be available");
+  await ext.unload();
+  // Once set nothing clears the UUID.
+  Assert.ok(ext.uuid, "Extension UUID exists after unload");
+}
+
+AddonTestUtils.init(this);
+
+add_task(async function setup() {
+  await ExtensionTestUtils.startAddonManager();
+});
+
+add_task(async function test_MockExtension() {
+  let ext = ExtensionTestUtils.loadExtension({
+    useAddonManager: "temporary",
+    manifest: {},
+  });
+
+  Assert.equal(ext.constructor.name, "InstallableWrapper", "expected class");
+  Assert.ok(!ext.id, "Extension ID is initially unavailable");
+  Assert.ok(!ext.uuid, "Extension UUID is initially unavailable");
+  await checkExtensionStartupAndUnload(ext);
+  // When useAddonManager is set, AOMExtensionWrapper clears the ID upon unload.
+  // TODO: Fix AOMExtensionWrapper to not clear the ID after unload, and move
+  // this assertion inside |checkExtensionStartupAndUnload| (since then the
+  // behavior will be consistent across all test types).
+  Assert.ok(!ext.id, "Extension ID is cleared after unload");
+});
+
+add_task(async function test_generated_Extension() {
+  let ext = ExtensionTestUtils.loadExtension({
+    manifest: {},
+  });
+
+  Assert.equal(ext.constructor.name, "ExtensionWrapper", "expected class");
+  // Without "useAddonManager", an Extension is generated and their IDs are
+  // immediately available.
+  Assert.ok(ext.id, "Extension ID is initially available");
+  Assert.ok(ext.uuid, "Extension UUID is initially available");
+  await checkExtensionStartupAndUnload(ext);
+  Assert.ok(ext.id, "Extension ID exists after unload");
+});
diff --git a/toolkit/components/extensions/test/xpcshell/test_ext_test_wrapper.js b/toolkit/components/extensions/test/xpcshell/test_ext_test_wrapper.js
new file mode 100644
index 0000000000..b4b1b87ee5
--- /dev/null
+++ b/toolkit/components/extensions/test/xpcshell/test_ext_test_wrapper.js
@@ -0,0 +1,60 @@
+"use strict";
+
+Services.prefs.setBoolPref("extensions.blocklist.enabled", false);
+
+ChromeUtils.defineESModuleGetters(this, {
+  AddonManager: "resource://gre/modules/AddonManager.sys.mjs",
+});
+
+AddonTestUtils.init(this);
+AddonTestUtils.overrideCertDB();
+AddonTestUtils.createAppInfo(
+  "xpcshell@tests.mozilla.org",
+  "XPCShell",
+  "1",
+  "43"
+);
+
+const TEST_ADDON_ID = "@some-permanent-test-addon";
+
+// Load a permanent extension that eventually unloads the extension immediately
+// after add-on startup, to set the stage as a regression test for bug 1575190.
+add_task(async function setup_wrapper() {
+  let extension = ExtensionTestUtils.loadExtension({
+    useAddonManager: "permanent",
+    manifest: {
+      browser_specific_settings: { gecko: { id: TEST_ADDON_ID } },
+    },
+    background() {
+      browser.test.sendMessage("started_up");
+    },
+  });
+
+  await AddonTestUtils.promiseStartupManager();
+  await extension.startup();
+  await extension.awaitBackgroundStarted();
+  await AddonTestUtils.promiseShutdownManager();
+
+  // Check message because it is expected to be received while `startup()` was
+  // pending resolution.
+  info("Awaiting expected started_up message 1");
+  await extension.awaitMessage("started_up");
+
+  // Load AddonManager, and unload the extension as soon as it has started.
+  await AddonTestUtils.promiseStartupManager();
+  await extension.awaitBackgroundStarted();
+  await extension.unload();
+  await AddonTestUtils.promiseShutdownManager();
+
+  // Confirm that the extension has started when promiseStartupManager returned.
+  info("Awaiting expected started_up message 2");
+  await extension.awaitMessage("started_up");
+});
+
+// Check that the add-on from the previous test has indeed been uninstalled.
+add_task(async function restart_addon_manager_after_extension_unload() {
+  await AddonTestUtils.promiseStartupManager();
+  let addon = await AddonManager.getAddonByID(TEST_ADDON_ID);
+  equal(addon, null, "Test add-on should have been removed");
+  await AddonTestUtils.promiseShutdownManager();
+});
diff --git a/toolkit/components/extensions/test/xpcshell/test_ext_theme_experiments.js b/toolkit/components/extensions/test/xpcshell/test_ext_theme_experiments.js
new file mode 100644
index 0000000000..4c3bf7b4d9
--- /dev/null
+++ b/toolkit/components/extensions/test/xpcshell/test_ext_theme_experiments.js
@@ -0,0 +1,109 @@
+/* Any copyright is dedicated to the Public Domain.
+   http://creativecommons.org/publicdomain/zero/1.0/ */
+
+"use strict";
+
+const { TestUtils } = ChromeUtils.importESModule(
+  "resource://testing-common/TestUtils.sys.mjs"
+);
+
+AddonTestUtils.init(this);
+AddonTestUtils.overrideCertDB();
+AddonTestUtils.usePrivilegedSignatures = id => id.startsWith("privileged");
+AddonTestUtils.createAppInfo(
+  "xpcshell@tests.mozilla.org",
+  "XPCShell",
+  "1",
+  "42"
+);
+
+add_task(async function setup() {
+  await ExtensionTestUtils.startAddonManager();
+});
+
+// This test checks whether the theme experiments work for privileged static themes
+// and are ignored for unprivileged static themes.
+async function test_experiment_static_theme({ privileged }) {
+  let extensionManifest = {
+    theme: {
+      colors: {},
+      images: {},
+      properties: {},
+    },
+    theme_experiment: {
+      colors: {},
+      images: {},
+      properties: {},
+    },
+  };
+
+  const addonId = `${
+    privileged ? "privileged" : "unprivileged"
+  }-static-theme@test-extension`;
+  const themeFiles = {
+    "manifest.json": {
+      name: "test theme",
+      version: "1.0",
+      manifest_version: 2,
+      browser_specific_settings: {
+        gecko: { id: addonId },
+      },
+      ...extensionManifest,
+    },
+  };
+
+  const promiseThemeUpdated = TestUtils.topicObserved(
+    "lightweight-theme-styling-update"
+  );
+
+  let themeAddon;
+  const { messages } = await AddonTestUtils.promiseConsoleOutput(async () => {
+    let { addon } = await AddonTestUtils.promiseInstallXPI(themeFiles);
+    // Enable the newly installed static theme.
+    await addon.enable();
+    themeAddon = addon;
+  });
+
+  const themeExperimentNotAllowed = {
+    message: /This extension is not allowed to run theme experiments/,
+  };
+  AddonTestUtils.checkMessages(messages, {
+    forbidden: privileged ? [themeExperimentNotAllowed] : [],
+    expected: privileged ? [] : [themeExperimentNotAllowed],
+  });
+
+  if (privileged) {
+    // ext-theme.js Theme class constructor doesn't call Theme.prototype.load
+    // if the static theme includes theme_experiment but isn't allowed to.
+    info("Wait for theme updated observer service topic to be notified");
+    const [topicSubject] = await promiseThemeUpdated;
+    let themeData = topicSubject.wrappedJSObject;
+    ok(
+      themeData.experiment,
+      "Expect theme experiment property to be defined in theme update data"
+    );
+  }
+
+  const policy = WebExtensionPolicy.getByID(themeAddon.id);
+  equal(
+    policy.extension.isPrivileged,
+    privileged,
+    `The static theme should be ${privileged ? "privileged" : "unprivileged"}`
+  );
+
+  await themeAddon.uninstall();
+}
+
+add_task(function test_privileged_theme() {
+  return test_experiment_static_theme({ privileged: true });
+});
+
+add_task(
+  {
+    // Some builds (e.g. thunderbird) have experiments enabled by default.
+    pref_set: [["extensions.experiments.enabled", false]],
+  },
+  function test_unprivileged_theme() {
+    return test_experiment_static_theme({ privileged: false });
+  }
+);
diff --git a/toolkit/components/extensions/test/xpcshell/test_ext_trustworthy_origin.js b/toolkit/components/extensions/test/xpcshell/test_ext_trustworthy_origin.js
new file mode 100644
index 0000000000..f509ae1749
--- /dev/null
+++ b/toolkit/components/extensions/test/xpcshell/test_ext_trustworthy_origin.js
@@ -0,0 +1,20 @@
+"use strict";
+
+/**
+ * This test is asserting that moz-extension: URLs are recognized as trustworthy local origins
+ */
+
+add_task(
+  function test_isOriginPotentiallyTrustworthnsIContentSecurityManagery() {
+    let uri = NetUtil.newURI("moz-extension://foobar/something.html");
+    let principal = Services.scriptSecurityManager.createContentPrincipal(
+      uri,
+      {}
+    );
+    Assert.equal(
+      principal.isOriginPotentiallyTrustworthy,
+      true,
+      "it is potentially trustworthy"
+    );
+  }
+);
diff --git a/toolkit/components/extensions/test/xpcshell/test_ext_unknown_permissions.js b/toolkit/components/extensions/test/xpcshell/test_ext_unknown_permissions.js
new file mode 100644
index 0000000000..aa4a309a52
--- /dev/null
+++ b/toolkit/components/extensions/test/xpcshell/test_ext_unknown_permissions.js
@@ -0,0 +1,60 @@
+"use strict";
+
+// This test expects and checks warnings for unknown permissions.
+ExtensionTestUtils.failOnSchemaWarnings(false);
+
+add_task(async function test_unknown_permissions() {
+  let extension = ExtensionTestUtils.loadExtension({
+    manifest: {
+      permissions: [
+        "activeTab",
+        "fooUnknownPermission",
+        "http://*/",
+        "chrome://favicon/",
+      ],
+      optional_permissions: ["chrome://favicon/", "https://example.com/"],
+    },
+  });
+
+  let { messages } = await promiseConsoleOutput(() => extension.startup());
+
+  const { WebExtensionPolicy } = Cu.getGlobalForObject(
+    ChromeUtils.importESModule("resource://gre/modules/Extension.sys.mjs")
+  );
+
+  let policy = WebExtensionPolicy.getByID(extension.id);
+  Assert.deepEqual(Array.from(policy.permissions).sort(), ["activeTab"]);
+
+  Assert.deepEqual(extension.extension.manifest.optional_permissions, [
+    "https://example.com/",
+  ]);
+
+  ok(
+    messages.some(message =>
+      /Error processing permissions\.1: Value "fooUnknownPermission" must/.test(
+        message
+      )
+    ),
+    'Got expected error for "fooUnknownPermission"'
+  );
+
+  ok(
+    messages.some(message =>
+      /Error processing permissions\.3: Value "chrome:\/\/favicon\/" must/.test(
+        message
+      )
+    ),
+    'Got expected error for "chrome://favicon/"'
+  );
+
+  ok(
+    messages.some(message =>
+      /Error processing optional_permissions\.0: Value "chrome:\/\/favicon\/" must/.test(
+        message
+      )
+    ),
+    "Got expected error from optional_permissions"
+  );
+
+  await extension.unload();
+});
diff --git a/toolkit/components/extensions/test/xpcshell/test_ext_unlimitedStorage.js b/toolkit/components/extensions/test/xpcshell/test_ext_unlimitedStorage.js
new file mode 100644
index 0000000000..77eb0c89f7
--- /dev/null
+++ b/toolkit/components/extensions/test/xpcshell/test_ext_unlimitedStorage.js
@@ -0,0 +1,211 @@
+"use strict";
+
+const {
+  createAppInfo,
+  promiseStartupManager,
+  promiseRestartManager,
+  promiseWebExtensionStartup,
+} = AddonTestUtils;
+
+AddonTestUtils.init(this);
+AddonTestUtils.overrideCertDB();
+
+createAppInfo("xpcshell@tests.mozilla.org", "XPCShell", "42", "42");
+
+const STORAGE_SITE_PERMISSIONS = [
+  "WebExtensions-unlimitedStorage",
+  "persistent-storage",
+];
+
+function checkSitePermissions(principal, expectedPermAction, assertMessage) {
+  for (const permName of STORAGE_SITE_PERMISSIONS) {
+    const actualPermAction = Services.perms.testPermissionFromPrincipal(
+      principal,
+      permName
+    );
+
+    equal(
+      actualPermAction,
+      expectedPermAction,
+      `The extension "${permName}" SitePermission ${assertMessage} as expected`
+    );
+  }
+}
+
+add_task(async function test_unlimitedStorage_restored_on_app_startup() {
+  const id = "test-unlimitedStorage-removed-on-app-shutdown@mozilla";
+
+  let extension = ExtensionTestUtils.loadExtension({
+    manifest: {
+      permissions: ["unlimitedStorage"],
+      browser_specific_settings: {
+        gecko: { id },
+      },
+    },
+
+    useAddonManager: "permanent",
+  });
+
+  await promiseStartupManager();
+  await extension.startup();
+
+  const policy = WebExtensionPolicy.getByID(extension.id);
+  const principal = policy.extension.principal;
+
+  checkSitePermissions(
+    principal,
+    Services.perms.ALLOW_ACTION,
+    "has been allowed"
+  );
+
+  // Remove site permissions as it would happen if Firefox is shutting down
+  // with the "clear site permissions" setting.
+
+  Services.perms.removeFromPrincipal(
+    principal,
+    "WebExtensions-unlimitedStorage"
+  );
+  Services.perms.removeFromPrincipal(principal, "persistent-storage");
+
+  checkSitePermissions(principal, Services.perms.UNKNOWN_ACTION, "is not set");
+
+  const onceExtensionStarted = promiseWebExtensionStartup(id);
+  await promiseRestartManager();
+  await onceExtensionStarted;
+
+  // The site permissions should have been granted again.
+  checkSitePermissions(
+    principal,
+    Services.perms.ALLOW_ACTION,
+    "has been allowed"
+  );
+
+  await extension.unload();
+});
+
+add_task(async function test_unlimitedStorage_removed_on_update() {
+  const id = "test-unlimitedStorage-removed-on-update@mozilla";
+
+  function background() {
+    browser.test.onMessage.addListener(async msg => {
+      switch (msg) {
+        case "set-storage":
+          browser.test.log(`storing data in storage.local`);
+          await browser.storage.local.set({ akey: "somevalue" });
+          browser.test.log(`data stored in storage.local successfully`);
+          break;
+        case "has-storage": {
+          browser.test.log(`checking data stored in storage.local`);
+          const data = await browser.storage.local.get(["akey"]);
+          browser.test.assertEq(
+            data.akey,
+            "somevalue",
+            "Got storage.local data"
+          );
+          break;
+        }
+        default:
+          browser.test.fail(`Unexpected test message: ${msg}`);
+      }
+
+      browser.test.sendMessage(`${msg}:done`);
+    });
+  }
+
+  let extension = ExtensionTestUtils.loadExtension({
+    background,
+    manifest: {
+      permissions: ["unlimitedStorage", "storage"],
+      browser_specific_settings: { gecko: { id } },
+      version: "1",
+    },
+    useAddonManager: "permanent",
+  });
+
+  await extension.startup();
+
+  const policy = WebExtensionPolicy.getByID(extension.id);
+  const principal = policy.extension.principal;
+
+  checkSitePermissions(
+    principal,
+    Services.perms.ALLOW_ACTION,
+    "has been allowed"
+  );
+
+  extension.sendMessage("set-storage");
+  await extension.awaitMessage("set-storage:done");
+  extension.sendMessage("has-storage");
+  await extension.awaitMessage("has-storage:done");
+
+  // Simulate an update which do not require the unlimitedStorage permission.
+  await extension.upgrade({
+    background,
+    manifest: {
+      permissions: ["storage"],
+      browser_specific_settings: { gecko: { id } },
+      version: "2",
+    },
+    useAddonManager: "permanent",
+  });
+
+  const newPolicy = WebExtensionPolicy.getByID(extension.id);
+  const newPrincipal = newPolicy.extension.principal;
+
+  equal(
+    principal.spec,
+    newPrincipal.spec,
+    "upgraded extension has the expected principal"
+  );
+
+  checkSitePermissions(
+    principal,
+    Services.perms.UNKNOWN_ACTION,
+    "has been cleared"
+  );
+
+  // Verify that the previously stored data has not been
+  // removed as a side effect of removing the unlimitedStorage
+  // permission.
+  extension.sendMessage("has-storage");
+  await extension.awaitMessage("has-storage:done");
+
+  await extension.unload();
+});
+
+add_task(async function test_unlimitedStorage_origin_attributes() {
+  Services.prefs.setBoolPref("privacy.firstparty.isolate", true);
+
+  const id = "test-unlimitedStorage-origin-attributes@mozilla";
+
+  let extension = ExtensionTestUtils.loadExtension({
+    manifest: {
+      permissions: ["unlimitedStorage"],
+      browser_specific_settings: { gecko: { id } },
+    },
+  });
+
+  await extension.startup();
+
+  let policy = WebExtensionPolicy.getByID(extension.id);
+  let principal = policy.extension.principal;
+
+  ok(
+    !principal.firstPartyDomain,
+    "extension principal has no firstPartyDomain"
+  );
+
+  let perm = Services.perms.testExactPermissionFromPrincipal(
+    principal,
+    "persistent-storage"
+  );
+  equal(
+    perm,
+    Services.perms.ALLOW_ACTION,
+    "Should have the correct permission without OAs"
+  );
+
+  await extension.unload();
+
+  Services.prefs.clearUserPref("privacy.firstparty.isolate");
+});
diff --git a/toolkit/components/extensions/test/xpcshell/test_ext_unload_frame.js b/toolkit/components/extensions/test/xpcshell/test_ext_unload_frame.js
new file mode 100644
index 0000000000..fee33e8815
--- /dev/null
+++ b/toolkit/components/extensions/test/xpcshell/test_ext_unload_frame.js
@@ -0,0 +1,230 @@
+"use strict";
+
+const server = createHttpServer({ hosts: ["example.com"] });
+server.registerDirectory("/data/", do_get_file("data"));
+
+server.registerPathHandler("/dummy", (request, response) => {
+  response.setStatusLine(request.httpVersion, 200, "OK");
+  response.setHeader("Content-Type", "text/html", false);
+  response.write("<!DOCTYPE html><html></html>");
+});
+
+// Background and content script for testSendMessage_*
+function sendMessage_background(delayedNotifyPass) {
+  browser.runtime.onMessage.addListener((msg, sender, sendResponse) => {
+    browser.test.assertEq("from frame", msg, "Expected message from frame");
+    sendResponse("msg from back"); // Should not throw or anything like that.
+    delayedNotifyPass("Received sendMessage from closing frame");
+  });
+}
+function sendMessage_contentScript(testType) {
+  browser.runtime.sendMessage("from frame", reply => {
+    // The frame has been removed, so we should not get this callback!
+    browser.test.fail(`Unexpected reply: ${reply}`);
+  });
+  if (testType == "frame") {
+    frameElement.remove();
+  } else {
+    browser.test.sendMessage("close-window");
+  }
+}
+
+// Background and content script for testConnect_*
+function connect_background(delayedNotifyPass) {
+  browser.runtime.onConnect.addListener(port => {
+    browser.test.assertEq("port from frame", port.name);
+
+    let disconnected = false;
+    let hasMessage = false;
+    port.onDisconnect.addListener(() => {
+      browser.test.assertFalse(disconnected, "onDisconnect should fire once");
+      disconnected = true;
+      browser.test.assertTrue(
+        hasMessage,
+        "Expected onMessage before onDisconnect"
+      );
+      browser.test.assertEq(
+        null,
+        port.error,
+        "The port is implicitly closed without errors when the other context unloads"
+      );
+      delayedNotifyPass("Received onDisconnect from closing frame");
+    });
+    port.onMessage.addListener(msg => {
+      browser.test.assertFalse(hasMessage, "onMessage should fire once");
+      hasMessage = true;
+      browser.test.assertFalse(
+        disconnected,
+        "Should get message before disconnect"
+      );
+      browser.test.assertEq("from frame", msg, "Expected message from frame");
+    });
+
+    port.postMessage("reply to closing frame");
+  });
+}
+function connect_contentScript(testType) {
+  let isUnloading = false;
+  addEventListener(
+    "pagehide",
+    () => {
+      isUnloading = true;
+    },
+    { once: true }
+  );
+
+  let port = browser.runtime.connect({ name: "port from frame" });
+  port.onMessage.addListener(msg => {
+    // The background page sends a reply as soon as we call runtime.connect().
+    // It is possible that the reply reaches this frame before the
+    // window.close() request has been processed.
+    if (!isUnloading) {
+      browser.test.log(
+        `Ignorting unexpected reply ("${msg}") because the page is not being unloaded.`
+      );
+      return;
+    }
+
+    // The frame has been removed, so we should not get a reply.
+    browser.test.fail(`Unexpected reply: ${msg}`);
+  });
+  port.postMessage("from frame");
+
+  // Removing the frame or window should disconnect the port.
+  if (testType == "frame") {
+    frameElement.remove();
+  } else {
+    browser.test.sendMessage("close-window");
+  }
+}
+
+// `testType` is "window" or "frame".
+function createTestExtension(testType, backgroundScript, contentScript) {
+  // Make a roundtrip between the background page and the test runner (which is
+  // in the same process as the content script) to make sure that we record a
+  // failure in case the content script's sendMessage or onMessage handlers are
+  // called even after the frame or window was removed.
+  function delayedNotifyPass(msg) {
+    browser.test.onMessage.addListener((type, echoMsg) => {
+      if (type == "pong") {
+        browser.test.assertEq(msg, echoMsg, "Echoed reply should be the same");
+        browser.test.notifyPass(msg);
+      }
+    });
+    browser.test.log("Starting ping-pong to flush messages...");
+    browser.test.sendMessage("ping", msg);
+  }
+  let extension = ExtensionTestUtils.loadExtension({
+    background: `(${backgroundScript})(${delayedNotifyPass});`,
+    manifest: {
+      content_scripts: [
+        {
+          js: ["contentscript.js"],
+          all_frames: testType == "frame",
+          matches: ["http://example.com/data/file_sample.html"],
+        },
+      ],
+    },
+    files: {
+      "contentscript.js": `(${contentScript})("${testType}");`,
+    },
+  });
+  extension.awaitMessage("ping").then(msg => {
+    extension.sendMessage("pong", msg);
+  });
+  return extension;
+}
+
+add_task(async function testSendMessage_and_remove_frame() {
+  let extension = createTestExtension(
+    "frame",
+    sendMessage_background,
+    sendMessage_contentScript
+  );
+  await extension.startup();
+
+  let contentPage = await ExtensionTestUtils.loadContentPage(
+    "http://example.com/dummy"
+  );
+
+  await contentPage.spawn([], () => {
+    let { document } = this.content;
+    let frame = document.createElement("iframe");
+    frame.src = "/data/file_sample.html";
+    document.body.appendChild(frame);
+  });
+
+  await extension.awaitFinish("Received sendMessage from closing frame");
+  await contentPage.close();
+  await extension.unload();
+});
+
+add_task(async function testConnect_and_remove_frame() {
+  let extension = createTestExtension(
+    "frame",
+    connect_background,
+    connect_contentScript
+  );
+  await extension.startup();
+
+  let contentPage = await ExtensionTestUtils.loadContentPage(
+    "http://example.com/dummy"
+  );
+
+  await contentPage.spawn([], () => {
+    let { document } = this.content;
+    let frame = document.createElement("iframe");
+    frame.src = "/data/file_sample.html";
+    document.body.appendChild(frame);
+  });
+
+  await extension.awaitFinish("Received onDisconnect from closing frame");
+  await contentPage.close();
+  await extension.unload();
+});
+
+add_task(async function testSendMessage_and_remove_window() {
+  if (AppConstants.MOZ_BUILD_APP !== "browser") {
+    // We can't rely on this timing on Android.
+    return;
+  }
+
+  let extension = createTestExtension(
+    "window",
+    sendMessage_background,
+    sendMessage_contentScript
+  );
+  await extension.startup();
+
+  let contentPage = await ExtensionTestUtils.loadContentPage(
+    "http://example.com/data/file_sample.html"
+  );
+  await extension.awaitMessage("close-window");
+  await contentPage.close();
+
+  await extension.awaitFinish("Received sendMessage from closing frame");
+  await extension.unload();
+});
+
+add_task(async function testConnect_and_remove_window() {
+  if (AppConstants.MOZ_BUILD_APP !== "browser") {
+    // We can't rely on this timing on Android.
+    return;
+  }
+
+  let extension = createTestExtension(
+    "window",
+    connect_background,
+    connect_contentScript
+  );
+  await extension.startup();
+
+  let contentPage = await ExtensionTestUtils.loadContentPage(
+    "http://example.com/data/file_sample.html"
+  );
+  await extension.awaitMessage("close-window");
+  await contentPage.close();
+
+  await extension.awaitFinish("Received onDisconnect from closing frame");
+  await extension.unload();
+});
diff --git a/toolkit/components/extensions/test/xpcshell/test_ext_userScripts.js b/toolkit/components/extensions/test/xpcshell/test_ext_userScripts.js
new file mode 100644
index 0000000000..a44711e26d
--- /dev/null
+++ b/toolkit/components/extensions/test/xpcshell/test_ext_userScripts.js
@@ -0,0 +1,729 @@
+"use strict";
+
+const PROCESS_COUNT_PREF = "dom.ipc.processCount";
+
+const { createAppInfo } = AddonTestUtils;
+
+AddonTestUtils.init(this);
+
+createAppInfo("xpcshell@tests.mozilla.org", "XPCShell", "1", "49");
+
+const server = createHttpServer();
+server.registerDirectory("/data/", do_get_file("data"));
+
+const BASE_URL = `http://localhost:${server.identity.primaryPort}/data`;
+
+add_task(async function setup_test_environment() {
+  if (ExtensionTestUtils.remoteContentScripts) {
+    // Start with one content process so that we can increase the number
+    // later and test the behavior of a fresh content process.
+    Services.prefs.setIntPref(PROCESS_COUNT_PREF, 1);
+  }
+
+  // Grant the optional permissions requested.
+  function permissionObserver(subject, topic, data) {
+    if (topic == "webextension-optional-permission-prompt") {
+      let { resolve } = subject.wrappedJSObject;
+      resolve(true);
+    }
+  }
+  Services.obs.addObserver(
+    permissionObserver,
+    "webextension-optional-permission-prompt"
+  );
+  registerCleanupFunction(() => {
+    Services.obs.removeObserver(
+      permissionObserver,
+      "webextension-optional-permission-prompt"
+    );
+  });
+});
+
+// Test that there is no userScripts API namespace when the manifest doesn't include a user_scripts
+// property.
+add_task(async function test_userScripts_manifest_property_required() {
+  function background() {
+    browser.test.assertEq(
+      undefined,
+      browser.userScripts,
+      "userScripts API namespace should be undefined in the extension page"
+    );
+    browser.test.sendMessage("background-page:done");
+  }
+
+  async function contentScript() {
+    browser.test.assertEq(
+      undefined,
+      browser.userScripts,
+      "userScripts API namespace should be undefined in the content script"
+    );
+    browser.test.sendMessage("content-script:done");
+  }
+
+  let extension = ExtensionTestUtils.loadExtension({
+    background,
+    manifest: {
+      permissions: ["http://*/*/file_sample.html"],
+      content_scripts: [
+        {
+          matches: ["http://*/*/file_sample.html"],
+          js: ["content_script.js"],
+          run_at: "document_start",
+        },
+      ],
+    },
+    files: {
+      "content_script.js": contentScript,
+    },
+  });
+
+  await extension.startup();
+  await extension.awaitMessage("background-page:done");
+
+  let url = `${BASE_URL}/file_sample.html`;
+  let contentPage = await ExtensionTestUtils.loadContentPage(url);
+
+  await extension.awaitMessage("content-script:done");
+
+  await extension.unload();
+  await contentPage.close();
+});
+
+// Test that userScripts can only matches origins that are subsumed by the extension permissions,
+// and that more origins can be allowed by requesting an optional permission.
+add_task(async function test_userScripts_matches_denied() {
+  async function background() {
+    async function registerUserScriptWithMatches(matches) {
+      const scripts = await browser.userScripts.register({
+        js: [{ code: "" }],
+        matches,
+      });
+      await scripts.unregister();
+    }
+
+    // These matches are supposed to be denied until the extension has been granted the
+    // <all_urls> origin permission.
+    const testMatches = [
+      "<all_urls>",
+      "file://*/*",
+      "https://localhost/*",
+      "http://example.com/*",
+    ];
+
+    browser.test.onMessage.addListener(async msg => {
+      if (msg === "test-denied-matches") {
+        for (let testMatch of testMatches) {
+          await browser.test.assertRejects(
+            registerUserScriptWithMatches([testMatch]),
+            /Permission denied to register a user script for/,
+            "Got the expected rejection when the extension permission does not subsume the userScript matches"
+          );
+        }
+      } else if (msg === "grant-all-urls") {
+        await browser.permissions.request({ origins: ["<all_urls>"] });
+      } else if (msg === "test-allowed-matches") {
+        for (let testMatch of testMatches) {
+          try {
+            await registerUserScriptWithMatches([testMatch]);
+          } catch (err) {
+            browser.test.fail(
+              `Unexpected rejection ${err} on matching ${JSON.stringify(
+                testMatch
+              )}`
+            );
+          }
+        }
+      } else {
+        browser.test.fail(`Received an unexpected ${msg} test message`);
+      }
+
+      browser.test.sendMessage(`${msg}:done`);
+    });
+
+    browser.test.sendMessage("background-ready");
+  }
+
+  let extension = ExtensionTestUtils.loadExtension({
+    manifest: {
+      permissions: ["http://localhost/*"],
+      optional_permissions: ["<all_urls>"],
+      user_scripts: {},
+    },
+    background,
+  });
+
+  await extension.startup();
+
+  await extension.awaitMessage("background-ready");
+
+  // Test that the matches not subsumed by the extension permissions are being denied.
+  extension.sendMessage("test-denied-matches");
+  await extension.awaitMessage("test-denied-matches:done");
+
+  // Grant the optional <all_urls> permission.
+  await withHandlingUserInput(extension, async () => {
+    extension.sendMessage("grant-all-urls");
+    await extension.awaitMessage("grant-all-urls:done");
+  });
+
+  // Test that all the matches are now subsumed by the extension permissions.
+  extension.sendMessage("test-allowed-matches");
+  await extension.awaitMessage("test-allowed-matches:done");
+
+  await extension.unload();
+});
+
+// Test that userScripts sandboxes:
+// - can be registered/unregistered from an extension page (and they are registered on both new and
+//   existing processes).
+// - have no WebExtensions APIs available
+// - are able to access the target window and document
+add_task(async function test_userScripts_no_webext_apis() {
+  async function background() {
+    const matches = ["http://localhost/*/file_sample.html*"];
+
+    const sharedCode = {
+      code: 'console.log("js code shared by multiple userScripts");',
+    };
+
+    const userScriptOptions = {
+      js: [
+        sharedCode,
+        {
+          code: `
+          window.addEventListener("load", () => {
+            const webextAPINamespaces = this.browser ? Object.keys(this.browser) : undefined;
+            document.body.innerHTML = "userScript loaded - " + JSON.stringify(webextAPINamespaces);
+          }, {once: true});
+        `,
+        },
+      ],
+      runAt: "document_start",
+      matches,
+      scriptMetadata: {
+        name: "test-user-script",
+        arrayProperty: ["el1"],
+        objectProperty: { nestedProp: "nestedValue" },
+        nullProperty: null,
+      },
+    };
+
+    let script = await browser.userScripts.register(userScriptOptions);
+
+    // Unregister and then register the same js code again, to verify that the last registered
+    // userScript doesn't get assigned a revoked blob url (otherwise Extensioncontent.jsm
+    // ScriptCache raises an error because it fails to compile the revoked blob url and the user
+    // script will never be loaded).
+    script.unregister();
+    script = await browser.userScripts.register(userScriptOptions);
+
+    browser.test.onMessage.addListener(async msg => {
+      if (msg !== "register-new-script") {
+        return;
+      }
+
+      await script.unregister();
+      await browser.userScripts.register({
+        ...userScriptOptions,
+        scriptMetadata: { name: "test-new-script" },
+        js: [
+          sharedCode,
+          {
+            code: `
+          window.addEventListener("load", () => {
+            const webextAPINamespaces = this.browser ? Object.keys(this.browser) : undefined;
+            document.body.innerHTML = "new userScript loaded - " + JSON.stringify(webextAPINamespaces);
+          }, {once: true});
+        `,
+          },
+        ],
+      });
+
+      browser.test.sendMessage("script-registered");
+    });
+
+    const scriptToRemove = await browser.userScripts.register({
+      js: [
+        sharedCode,
+        {
+          code: `
+          window.addEventListener("load", () => {
+            document.body.innerHTML = "unexpected unregistered userScript loaded";
+          }, {once: true});
+        `,
+        },
+      ],
+      runAt: "document_start",
+      matches,
+      scriptMetadata: {
+        name: "user-script-to-remove",
+      },
+    });
+
+    browser.test.assertTrue(
+      "unregister" in script,
+      "Got an unregister method on the userScript API object"
+    );
+
+    // Remove the last registered user script.
+    await scriptToRemove.unregister();
+
+    browser.test.sendMessage("background-ready");
+  }
+
+  let extensionData = {
+    manifest: {
+      permissions: ["http://localhost/*/file_sample.html"],
+      user_scripts: {},
+    },
+    background,
+  };
+
+  let extension = ExtensionTestUtils.loadExtension(extensionData);
+
+  await extension.startup();
+
+  await extension.awaitMessage("background-ready");
+
+  let url = `${BASE_URL}/file_sample.html?testpage=1`;
+  let contentPage = await ExtensionTestUtils.loadContentPage(
+    url,
+    ExtensionTestUtils.remoteContentScripts ? { remote: true } : undefined
+  );
+  let result = await contentPage.spawn([], async () => {
+    return {
+      textContent: this.content.document.body.textContent,
+      url: this.content.location.href,
+      readyState: this.content.document.readyState,
+    };
+  });
+  Assert.deepEqual(
+    result,
+    {
+      textContent: "userScript loaded - undefined",
+      url,
+      readyState: "complete",
+    },
+    "The userScript executed on the expected url and no access to the WebExtensions APIs"
+  );
+
+  // If the tests is running with "remote content process" mode, test that the userScript
+  // are being correctly registered in newly created processes (received as part of the sharedData).
+  if (ExtensionTestUtils.remoteContentScripts) {
+    info(
+      "Test content script are correctly created on a newly created process"
+    );
+
+    await extension.sendMessage("register-new-script");
+    await extension.awaitMessage("script-registered");
+
+    // Update the process count preference, so that we can test that the newly registered user script
+    // is propagated as expected into the newly created process.
+    Services.prefs.setIntPref(PROCESS_COUNT_PREF, 2);
+
+    const url2 = `${BASE_URL}/file_sample.html?testpage=2`;
+    let contentPage2 = await ExtensionTestUtils.loadContentPage(url2, {
+      remote: true,
+    });
+    let result2 = await contentPage2.spawn([], async () => {
+      return {
+        textContent: this.content.document.body.textContent,
+        url: this.content.location.href,
+        readyState: this.content.document.readyState,
+      };
+    });
+    Assert.deepEqual(
+      result2,
+      {
+        textContent: "new userScript loaded - undefined",
+        url: url2,
+        readyState: "complete",
+      },
+      "The userScript executed on the expected url and no access to the WebExtensions APIs"
+    );
+
+    await contentPage2.close();
+  }
+
+  await contentPage.close();
+
+  await extension.unload();
+});
+
+// This test verify that a cached script is still able to catch the document
+// while it is still loading (when we do not block the document parsing as
+// we do for a non cached script).
+add_task(async function test_cached_userScript_on_document_start() {
+  function apiScript() {
+    browser.userScripts.onBeforeScript.addListener(script => {
+      script.defineGlobals({
+        sendTestMessage(name, params) {
+          return browser.test.sendMessage(name, params);
+        },
+      });
+    });
+  }
+
+  async function background() {
+    function userScript() {
+      this.sendTestMessage("user-script-loaded", {
+        url: window.location.href,
+        documentReadyState: document.readyState,
+      });
+    }
+
+    await browser.userScripts.register({
+      js: [
+        {
+          code: `(${userScript})();`,
+        },
+      ],
+      runAt: "document_start",
+      matches: ["http://localhost/*/file_sample.html"],
+    });
+
+    browser.test.sendMessage("user-script-registered");
+  }
+
+  let extension = ExtensionTestUtils.loadExtension({
+    manifest: {
+      permissions: ["http://localhost/*/file_sample.html"],
+      user_scripts: {
+        api_script: "api-script.js",
+        // The following is an unexpected manifest property, that we expect to be ignored and
+        // to not prevent the test extension from being installed and run as expected.
+        unexpected_manifest_key: "test-unexpected-key",
+      },
+    },
+    background,
+    files: {
+      "api-script.js": apiScript,
+    },
+  });
+
+  ExtensionTestUtils.failOnSchemaWarnings(false);
+  await extension.startup();
+  ExtensionTestUtils.failOnSchemaWarnings(true);
+  await extension.awaitMessage("user-script-registered");
+
+  let url = `${BASE_URL}/file_sample.html`;
+  let contentPage = await ExtensionTestUtils.loadContentPage(url);
+
+  let msg = await extension.awaitMessage("user-script-loaded");
+  Assert.deepEqual(
+    msg,
+    {
+      url,
+      documentReadyState: "loading",
+    },
+    "Got the expected url and document.readyState from a non cached user script"
+  );
+
+  // Reload the page and check that the cached content script is still able to
+  // run on document_start.
+  await contentPage.loadURL(url);
+
+  let msgFromCached = await extension.awaitMessage("user-script-loaded");
+  Assert.deepEqual(
+    msgFromCached,
+    {
+      url,
+      documentReadyState: "loading",
+    },
+    "Got the expected url and document.readyState from a cached user script"
+  );
+
+  await contentPage.close();
+  await extension.unload();
+});
+
+add_task(async function test_userScripts_pref_disabled() {
+  async function run_userScript_on_pref_disabled_test() {
+    async function background() {
+      let promise = (async () => {
+        await browser.userScripts.register({
+          js: [
+            {
+              code: "throw new Error('This userScripts should not be registered')",
+            },
+          ],
+          runAt: "document_start",
+          matches: ["<all_urls>"],
+        });
+      })();
+
+      await browser.test.assertRejects(
+        promise,
+        /userScripts APIs are currently experimental/,
+        "Got the expected error from userScripts.register when the userScripts API is disabled"
+      );
+
+      browser.test.sendMessage("background-page:done");
+    }
+
+    async function contentScript() {
+      let promise = (async () => {
+        browser.userScripts.onBeforeScript.addListener(() => {});
+      })();
+      await browser.test.assertRejects(
+        promise,
+        /userScripts APIs are currently experimental/,
+        "Got the expected error from userScripts.onBeforeScript when the userScripts API is disabled"
+      );
+
+      browser.test.sendMessage("content-script:done");
+    }
+
+    let extension = ExtensionTestUtils.loadExtension({
+      background,
+      manifest: {
+        permissions: ["http://*/*/file_sample.html"],
+        user_scripts: { api_script: "" },
+        content_scripts: [
+          {
+            matches: ["http://*/*/file_sample.html"],
+            js: ["content_script.js"],
+            run_at: "document_start",
+          },
+        ],
+      },
+      files: {
+        "content_script.js": contentScript,
+      },
+    });
+
+    await extension.startup();
+
+    await extension.awaitMessage("background-page:done");
+
+    let url = `${BASE_URL}/file_sample.html`;
+    let contentPage = await ExtensionTestUtils.loadContentPage(url);
+
+    await extension.awaitMessage("content-script:done");
+
+    await extension.unload();
+    await contentPage.close();
+  }
+
+  await runWithPrefs(
+    [["extensions.webextensions.userScripts.enabled", false]],
+    run_userScript_on_pref_disabled_test
+  );
+});
+
+// This test verify that userScripts.onBeforeScript API Event is not available without
+// a "user_scripts.api_script" property in the manifest.
+add_task(async function test_user_script_api_script_required() {
+  let extension = ExtensionTestUtils.loadExtension({
+    manifest: {
+      content_scripts: [
+        {
+          matches: ["http://localhost/*/file_sample.html"],
+          js: ["content_script.js"],
+          run_at: "document_start",
+        },
+      ],
+      user_scripts: {},
+    },
+    files: {
+      "content_script.js": function () {
+        browser.test.assertEq(
+          undefined,
+          browser.userScripts && browser.userScripts.onBeforeScript,
+          "Got an undefined onBeforeScript property as expected"
+        );
+        browser.test.sendMessage("no-onBeforeScript:done");
+      },
+    },
+  });
+
+  await extension.startup();
+
+  let url = `${BASE_URL}/file_sample.html`;
+  let contentPage = await ExtensionTestUtils.loadContentPage(url);
+
+  await extension.awaitMessage("no-onBeforeScript:done");
+
+  await extension.unload();
+  await contentPage.close();
+});
+
+add_task(async function test_scriptMetaData() {
+  function getTestCases(isUserScriptsRegister) {
+    return [
+      // When scriptMetadata is not set (or undefined), it is treated as if it were null.
+      // In the API script, the metadata is then expected to be null.
+      isUserScriptsRegister ? undefined : null,
+
+      // Falsey
+      null,
+      "",
+      false,
+      0,
+
+      // Truthy
+      true,
+      1,
+      "non-empty string",
+
+      // Objects
+      ["some array with value"],
+      { "some object": "with value" },
+    ];
+  }
+
+  async function background() {
+    for (let scriptMetadata of getTestCases(true)) {
+      await browser.userScripts.register({
+        js: [{ file: "userscript.js" }],
+        runAt: "document_end",
+        matches: ["http://localhost/*/file_sample.html"],
+        scriptMetadata,
+      });
+    }
+
+    browser.test.sendMessage("background-page:done");
+  }
+
+  function apiScript() {
+    let testCases = getTestCases(false);
+    let i = 0;
+
+    browser.userScripts.onBeforeScript.addListener(script => {
+      script.defineGlobals({
+        checkMetadata() {
+          let expectation = testCases[i];
+          let metadata = script.metadata;
+          if (typeof expectation === "object" && expectation !== null) {
+            // Non-primitive values cannot be compared with assertEq,
+            // so serialize both and just verify that they are equal.
+            expectation = JSON.stringify(expectation);
+            metadata = JSON.stringify(script.metadata);
+          }
+
+          browser.test.assertEq(
+            expectation,
+            metadata,
+            `Expected metadata at call ${i}`
+          );
+          if (++i === testCases.length) {
+            browser.test.sendMessage("apiscript:done");
+          }
+        },
+      });
+    });
+  }
+
+  let extension = ExtensionTestUtils.loadExtension({
+    background: `${getTestCases};(${background})()`,
+    manifest: {
+      permissions: ["http://*/*/file_sample.html"],
+      user_scripts: {
+        api_script: "apiscript.js",
+      },
+    },
+    files: {
+      "apiscript.js": `${getTestCases};(${apiScript})()`,
+      "userscript.js": "checkMetadata();",
+    },
+  });
+
+  await extension.startup();
+
+  await extension.awaitMessage("background-page:done");
+
+  const pageUrl = `${BASE_URL}/file_sample.html`;
+  info(`Load content page: ${pageUrl}`);
+  const page = await ExtensionTestUtils.loadContentPage(pageUrl);
+
+  await extension.awaitMessage("apiscript:done");
+
+  await page.close();
+
+  await extension.unload();
+});
+
+add_task(async function test_userScriptOptions_js_property_required() {
+  function background() {
+    const userScriptOptions = {
+      runAt: "document_start",
+      matches: ["http://*/*/file_sample.html"],
+    };
+
+    browser.test.assertThrows(
+      () => browser.userScripts.register(userScriptOptions),
+      /Type error for parameter userScriptOptions \(Property \"js\" is required\)/,
+      "Got the expected error from userScripts.register when js property is missing"
+    );
+
+    browser.test.sendMessage("done");
+  }
+
+  let extension = ExtensionTestUtils.loadExtension({
+    background,
+    manifest: {
+      permissions: ["http://*/*/file_sample.html"],
+      user_scripts: {},
+    },
+  });
+
+  await extension.startup();
+  await extension.awaitMessage("done");
+  await extension.unload();
+});
+
+add_task(async function test_userScripts_are_unregistered_on_unload() {
+  let extension = ExtensionTestUtils.loadExtension({
+    manifest: {
+      permissions: ["http://*/*/file_sample.html"],
+      user_scripts: {
+        api_script: "api_script.js",
+      },
+    },
+    files: {
+      "userscript.js": "",
+      "extpage.html": `<!DOCTYPE html><script src="extpage.js"></script>`,
+      "extpage.js": async function extPage() {
+        await browser.userScripts.register({
+          js: [{ file: "userscript.js" }],
+          matches: ["http://localhost/*/file_sample.html"],
+        });
+
+        browser.test.sendMessage("user-script-registered");
+      },
+    },
+  });
+
+  await extension.startup();
+
+  equal(
+    // In order to read the `registeredContentScripts` map, we need to access
+    // the extension embedded in the `ExtensionWrapper` first.
+    extension.extension.registeredContentScripts.size,
+    0,
+    "no user scripts registered yet"
+  );
+
+  const url = `moz-extension://${extension.uuid}/extpage.html`;
+  info(`loading extension page: ${url}`);
+  const page = await ExtensionTestUtils.loadContentPage(url);
+
+  info("waiting for the user script to be registered");
+  await extension.awaitMessage("user-script-registered");
+
+  equal(
+    extension.extension.registeredContentScripts.size,
+    1,
+    "got registered user scripts in the extension content scripts map"
+  );
+
+  await page.close();
+
+  equal(
+    extension.extension.registeredContentScripts.size,
+    0,
+    "user scripts unregistered from the extension content scripts map"
+  );
+
+  await extension.unload();
+});
diff --git a/toolkit/components/extensions/test/xpcshell/test_ext_userScripts_exports.js b/toolkit/components/extensions/test/xpcshell/test_ext_userScripts_exports.js
new file mode 100644
index 0000000000..5950377f85
--- /dev/null
+++ b/toolkit/components/extensions/test/xpcshell/test_ext_userScripts_exports.js
@@ -0,0 +1,1108 @@
+"use strict";
+
+const { createAppInfo } = AddonTestUtils;
+
+AddonTestUtils.init(this);
+
+createAppInfo("xpcshell@tests.mozilla.org", "XPCShell", "1", "49");
+
+const server = createHttpServer();
+server.registerDirectory("/data/", do_get_file("data"));
+
+const BASE_URL = `http://localhost:${server.identity.primaryPort}/data`;
+
+// A small utility function used to test the expected behaviors of the userScripts API method
+// wrapper.
+async function test_userScript_APIMethod({
+  apiScript,
+  userScript,
+  userScriptMetadata,
+  testFn,
+  runtimeMessageListener,
+}) {
+  async function backgroundScript(
+    userScriptFn,
+    scriptMetadata,
+    messageListener
+  ) {
+    await browser.userScripts.register({
+      js: [
+        {
+          code: `(${userScriptFn})();`,
+        },
+      ],
+      runAt: "document_end",
+      matches: ["http://localhost/*/file_sample.html"],
+      scriptMetadata,
+    });
+
+    if (messageListener) {
+      browser.runtime.onMessage.addListener(messageListener);
+    }
+
+    browser.test.sendMessage("background-ready");
+  }
+
+  function notifyFinish(failureReason) {
+    browser.test.assertEq(
+      undefined,
+      failureReason,
+      "should be completed without errors"
+    );
+    browser.test.sendMessage("test_userScript_APIMethod:done");
+  }
+
+  function assertTrue(val, message) {
+    browser.test.assertTrue(val, message);
+    if (!val) {
+      browser.test.sendMessage("test_userScript_APIMethod:done");
+      throw message;
+    }
+  }
+
+  let extension = ExtensionTestUtils.loadExtension({
+    manifest: {
+      permissions: ["http://localhost/*/file_sample.html"],
+      user_scripts: {
+        api_script: "api-script.js",
+      },
+    },
+    // Defines a background script that receives all the needed test parameters.
+    background: `
+        const metadata = ${JSON.stringify(userScriptMetadata)};
+        (${backgroundScript})(${userScript}, metadata, ${runtimeMessageListener})
+     `,
+    files: {
+      "api-script.js": `(${apiScript})({
+        assertTrue: ${assertTrue},
+        notifyFinish: ${notifyFinish}
+      })`,
+    },
+  });
+
+  // Load a page in a content process, register the user script and then load a
+  // new page in the existing content process.
+  let url = `${BASE_URL}/file_sample.html`;
+  let contentPage = await ExtensionTestUtils.loadContentPage(`about:blank`);
+
+  await extension.startup();
+  await extension.awaitMessage("background-ready");
+  await contentPage.loadURL(url);
+
+  // Run any additional test-specific assertions.
+  if (testFn) {
+    await testFn({ extension, contentPage, url });
+  }
+
+  await extension.awaitMessage("test_userScript_APIMethod:done");
+
+  await extension.unload();
+  await contentPage.close();
+}
+
+add_task(async function test_apiScript_exports_simple_sync_method() {
+  function apiScript(sharedTestAPIMethods) {
+    browser.userScripts.onBeforeScript.addListener(script => {
+      const scriptMetadata = script.metadata;
+
+      script.defineGlobals({
+        ...sharedTestAPIMethods,
+        testAPIMethod(
+          stringParam,
+          numberParam,
+          boolParam,
+          nullParam,
+          undefinedParam,
+          arrayParam
+        ) {
+          browser.test.assertEq(
+            "test-user-script-exported-apis",
+            scriptMetadata.name,
+            "Got the expected value for a string scriptMetadata property"
+          );
+          browser.test.assertEq(
+            null,
+            scriptMetadata.nullProperty,
+            "Got the expected value for a null scriptMetadata property"
+          );
+          browser.test.assertTrue(
+            scriptMetadata.arrayProperty &&
+              scriptMetadata.arrayProperty.length === 1 &&
+              scriptMetadata.arrayProperty[0] === "el1",
+            "Got the expected value for an array scriptMetadata property"
+          );
+          browser.test.assertTrue(
+            scriptMetadata.objectProperty &&
+              scriptMetadata.objectProperty.nestedProp === "nestedValue",
+            "Got the expected value for an object scriptMetadata property"
+          );
+
+          browser.test.assertEq(
+            "param1",
+            stringParam,
+            "Got the expected string parameter value"
+          );
+          browser.test.assertEq(
+            123,
+            numberParam,
+            "Got the expected number parameter value"
+          );
+          browser.test.assertEq(
+            true,
+            boolParam,
+            "Got the expected boolean parameter value"
+          );
+          browser.test.assertEq(
+            null,
+            nullParam,
+            "Got the expected null parameter value"
+          );
+          browser.test.assertEq(
+            undefined,
+            undefinedParam,
+            "Got the expected undefined parameter value"
+          );
+
+          browser.test.assertEq(
+            3,
+            arrayParam.length,
+            "Got the expected length on the array param"
+          );
+          browser.test.assertTrue(
+            arrayParam.includes(1),
+            "Got the expected result when calling arrayParam.includes"
+          );
+
+          return "returned_value";
+        },
+      });
+    });
+  }
+
+  function userScript() {
+    const { assertTrue, notifyFinish, testAPIMethod } = this;
+
+    // Redefine the includes method on the Array prototype, to explicitly verify that the method
+    // redefined in the userScript is not used when accessing arrayParam.includes from the API script.
+    // eslint-disable-next-line no-extend-native
+    Array.prototype.includes = () => {
+      throw new Error("Unexpected prototype leakage");
+    };
+    const arrayParam = new Array(1, 2, 3); // eslint-disable-line no-array-constructor
+    const result = testAPIMethod(
+      "param1",
+      123,
+      true,
+      null,
+      undefined,
+      arrayParam
+    );
+
+    assertTrue(
+      result === "returned_value",
+      `userScript got an unexpected result value: ${result}`
+    );
+
+    notifyFinish();
+  }
+
+  const userScriptMetadata = {
+    name: "test-user-script-exported-apis",
+    arrayProperty: ["el1"],
+    objectProperty: { nestedProp: "nestedValue" },
+    nullProperty: null,
+  };
+
+  await test_userScript_APIMethod({
+    userScript,
+    apiScript,
+    userScriptMetadata,
+  });
+});
+
+add_task(async function test_apiScript_async_method() {
+  function apiScript(sharedTestAPIMethods) {
+    browser.userScripts.onBeforeScript.addListener(script => {
+      script.defineGlobals({
+        ...sharedTestAPIMethods,
+        testAPIMethod(param, cb, cb2, objWithCb) {
+          browser.test.assertEq(
+            "function",
+            typeof cb,
+            "Got a callback function parameter"
+          );
+          browser.test.assertTrue(
+            cb === cb2,
+            "Got the same cloned function for the same function parameter"
+          );
+
+          browser.runtime.sendMessage(param).then(bgPageRes => {
+            const cbResult = cb(script.export(bgPageRes));
+            browser.test.sendMessage("user-script-callback-return", cbResult);
+          });
+
+          return "resolved_value";
+        },
+      });
+    });
+  }
+
+  async function userScript() {
+    // Redefine Promise to verify that it doesn't break the WebExtensions internals
+    // that are going to use them.
+    const { Promise } = this;
+    Promise.resolve = function () {
+      throw new Error("Promise.resolve poisoning");
+    };
+    this.Promise = function () {
+      throw new Error("Promise constructor poisoning");
+    };
+
+    const { assertTrue, notifyFinish, testAPIMethod } = this;
+
+    const cb = cbParam => {
+      return `callback param: ${JSON.stringify(cbParam)}`;
+    };
+    const cb2 = cb;
+    const asyncAPIResult = await testAPIMethod("param3", cb, cb2);
+
+    assertTrue(
+      asyncAPIResult === "resolved_value",
+      `userScript got an unexpected resolved value: ${asyncAPIResult}`
+    );
+
+    notifyFinish();
+  }
+
+  async function runtimeMessageListener(param) {
+    if (param !== "param3") {
+      browser.test.fail(`Got an unexpected message: ${param}`);
+    }
+
+    return { bgPageReply: true };
+  }
+
+  await test_userScript_APIMethod({
+    userScript,
+    apiScript,
+    runtimeMessageListener,
+    async testFn({ extension }) {
+      const res = await extension.awaitMessage("user-script-callback-return");
+      equal(
+        res,
+        `callback param: ${JSON.stringify({ bgPageReply: true })}`,
+        "Got the expected userScript callback return value"
+      );
+    },
+  });
+});
+
+add_task(async function test_apiScript_method_with_webpage_objects_params() {
+  function apiScript(sharedTestAPIMethods) {
+    browser.userScripts.onBeforeScript.addListener(script => {
+      script.defineGlobals({
+        ...sharedTestAPIMethods,
+        testAPIMethod(windowParam, documentParam) {
+          browser.test.assertEq(
+            window,
+            windowParam,
+            "Got a reference to the native window as first param"
+          );
+          browser.test.assertEq(
+            window.document,
+            documentParam,
+            "Got a reference to the native document as second param"
+          );
+
+          // Return an uncloneable webpage object, which checks that if the returned object is from a principal
+          // that is subsumed by the userScript sandbox principal, it is returned without being cloned.
+          return windowParam;
+        },
+      });
+    });
+  }
+
+  async function userScript() {
+    const { assertTrue, notifyFinish, testAPIMethod } = this;
+
+    const result = testAPIMethod(window, document);
+
+    // We expect the returned value to be the uncloneable window object.
+    assertTrue(
+      result === window,
+      `userScript got an unexpected returned value: ${result}`
+    );
+    notifyFinish();
+  }
+
+  await test_userScript_APIMethod({
+    userScript,
+    apiScript,
+  });
+});
+
+add_task(async function test_apiScript_method_got_param_with_methods() {
+  function apiScript(sharedTestAPIMethods) {
+    browser.userScripts.onBeforeScript.addListener(script => {
+      const scriptGlobal = script.global;
+      const ScriptFunction = scriptGlobal.Function;
+
+      script.defineGlobals({
+        ...sharedTestAPIMethods,
+        testAPIMethod(objWithMethods) {
+          browser.test.assertEq(
+            "objPropertyValue",
+            objWithMethods && objWithMethods.objProperty,
+            "Got the expected property on the object passed as a parameter"
+          );
+          browser.test.assertEq(
+            undefined,
+            objWithMethods?.objMethod,
+            "XrayWrapper should deny access to a callable property"
+          );
+
+          browser.test.assertTrue(
+            objWithMethods &&
+              objWithMethods.wrappedJSObject &&
+              objWithMethods.wrappedJSObject.objMethod instanceof
+                ScriptFunction.wrappedJSObject,
+            "The callable property is accessible on the wrappedJSObject"
+          );
+
+          browser.test.assertEq(
+            "objMethodResult: p1",
+            objWithMethods &&
+              objWithMethods.wrappedJSObject &&
+              objWithMethods.wrappedJSObject.objMethod("p1"),
+            "Got the expected result when calling the method on the wrappedJSObject"
+          );
+          return true;
+        },
+      });
+    });
+  }
+
+  async function userScript() {
+    const { assertTrue, notifyFinish, testAPIMethod } = this;
+
+    let result = testAPIMethod({
+      objProperty: "objPropertyValue",
+      objMethod(param) {
+        return `objMethodResult: ${param}`;
+      },
+    });
+
+    assertTrue(
+      result === true,
+      `userScript got an unexpected returned value: ${result}`
+    );
+    notifyFinish();
+  }
+
+  await test_userScript_APIMethod({
+    userScript,
+    apiScript,
+  });
+});
+
+add_task(async function test_apiScript_method_throws_errors() {
+  function apiScript({ notifyFinish }) {
+    let proxyTrapsCount = 0;
+
+    browser.userScripts.onBeforeScript.addListener(script => {
+      const scriptGlobals = {
+        Error: script.global.Error,
+        TypeError: script.global.TypeError,
+        Proxy: script.global.Proxy,
+      };
+
+      script.defineGlobals({
+        notifyFinish,
+        testAPIMethod(errorTestName, returnRejectedPromise) {
+          let err;
+
+          switch (errorTestName) {
+            case "apiScriptError":
+              err = new Error(`${errorTestName} message`);
+              break;
+            case "apiScriptThrowsPlainString":
+              err = `${errorTestName} message`;
+              break;
+            case "apiScriptThrowsNull":
+              err = null;
+              break;
+            case "userScriptError":
+              err = new scriptGlobals.Error(`${errorTestName} message`);
+              break;
+            case "userScriptTypeError":
+              err = new scriptGlobals.TypeError(`${errorTestName} message`);
+              break;
+            case "userScriptProxyObject":
+              let proxyTarget = script.export({
+                name: "ProxyObject",
+                message: "ProxyObject message",
+              });
+              let proxyHandlers = script.export({
+                get(target, prop) {
+                  proxyTrapsCount++;
+                  switch (prop) {
+                    case "name":
+                      return "ProxyObjectGetName";
+                    case "message":
+                      return "ProxyObjectGetMessage";
+                  }
+                  return undefined;
+                },
+                getPrototypeOf() {
+                  proxyTrapsCount++;
+                  return scriptGlobals.TypeError;
+                },
+              });
+              err = new scriptGlobals.Proxy(proxyTarget, proxyHandlers);
+              break;
+            default:
+              browser.test.fail(`Unknown ${errorTestName} error testname`);
+              return undefined;
+          }
+
+          if (returnRejectedPromise) {
+            return Promise.reject(err);
+          }
+
+          throw err;
+        },
+        assertNoProxyTrapTriggered() {
+          browser.test.assertEq(
+            0,
+            proxyTrapsCount,
+            "Proxy traps should not be triggered"
+          );
+        },
+        resetProxyTrapCounter() {
+          proxyTrapsCount = 0;
+        },
+        sendResults(results) {
+          browser.test.sendMessage("test-results", results);
+        },
+      });
+    });
+  }
+
+  async function userScript() {
+    const {
+      assertNoProxyTrapTriggered,
+      notifyFinish,
+      resetProxyTrapCounter,
+      sendResults,
+      testAPIMethod,
+    } = this;
+
+    let apiThrowResults = {};
+    let apiThrowTestCases = [
+      "apiScriptError",
+      "apiScriptThrowsPlainString",
+      "apiScriptThrowsNull",
+      "userScriptError",
+      "userScriptTypeError",
+      "userScriptProxyObject",
+    ];
+    for (let errorTestName of apiThrowTestCases) {
+      try {
+        testAPIMethod(errorTestName);
+      } catch (err) {
+        // We expect that no proxy traps have been triggered by the WebExtensions internals.
+        if (errorTestName === "userScriptProxyObject") {
+          assertNoProxyTrapTriggered();
+        }
+
+        if (err instanceof Error) {
+          apiThrowResults[errorTestName] = {
+            name: err.name,
+            message: err.message,
+          };
+        } else {
+          apiThrowResults[errorTestName] = {
+            name: err && err.name,
+            message: err && err.message,
+            typeOf: typeof err,
+            value: err,
+          };
+        }
+      }
+    }
+
+    sendResults(apiThrowResults);
+
+    resetProxyTrapCounter();
+
+    let apiRejectsResults = {};
+    for (let errorTestName of apiThrowTestCases) {
+      try {
+        await testAPIMethod(errorTestName, true);
+      } catch (err) {
+        // We expect that no proxy traps have been triggered by the WebExtensions internals.
+        if (errorTestName === "userScriptProxyObject") {
+          assertNoProxyTrapTriggered();
+        }
+
+        if (err instanceof Error) {
+          apiRejectsResults[errorTestName] = {
+            name: err.name,
+            message: err.message,
+          };
+        } else {
+          apiRejectsResults[errorTestName] = {
+            name: err && err.name,
+            message: err && err.message,
+            typeOf: typeof err,
+            value: err,
+          };
+        }
+      }
+    }
+
+    sendResults(apiRejectsResults);
+
+    notifyFinish();
+  }
+
+  await test_userScript_APIMethod({
+    userScript,
+    apiScript,
+    async testFn({ extension }) {
+      const expectedResults = {
+        // Any error not explicitly raised as a userScript objects or error instance is
+        // expected to be turned into a generic error message.
+        apiScriptError: {
+          name: "Error",
+          message: "An unexpected apiScript error occurred",
+        },
+
+        // When the api script throws a primitive value, we expect to receive it unmodified on
+        // the userScript side.
+        apiScriptThrowsPlainString: {
+          typeOf: "string",
+          value: "apiScriptThrowsPlainString message",
+          name: undefined,
+          message: undefined,
+        },
+        apiScriptThrowsNull: {
+          typeOf: "object",
+          value: null,
+          name: undefined,
+          message: undefined,
+        },
+
+        // Error messages that the apiScript has explicitly created as userScript's Error
+        // global instances are expected to be passing through unmodified.
+        userScriptError: { name: "Error", message: "userScriptError message" },
+        userScriptTypeError: {
+          name: "TypeError",
+          message: "userScriptTypeError message",
+        },
+
+        // Error raised from the apiScript as userScript proxy objects are expected to
+        // be passing through unmodified.
+        userScriptProxyObject: {
+          typeOf: "object",
+          name: "ProxyObjectGetName",
+          message: "ProxyObjectGetMessage",
+        },
+      };
+
+      info(
+        "Checking results from errors raised from an apiScript exported function"
+      );
+
+      const apiThrowResults = await extension.awaitMessage("test-results");
+
+      for (let [key, expected] of Object.entries(expectedResults)) {
+        Assert.deepEqual(
+          apiThrowResults[key],
+          expected,
+          `Got the expected error object for test case "${key}"`
+        );
+      }
+
+      Assert.deepEqual(
+        Object.keys(expectedResults).sort(),
+        Object.keys(apiThrowResults).sort(),
+        "the expected and actual test case names matches"
+      );
+
+      info(
+        "Checking expected results from errors raised from an apiScript exported function"
+      );
+
+      // Verify expected results from rejected promises returned from an apiScript exported function.
+      const apiThrowRejections = await extension.awaitMessage("test-results");
+
+      for (let [key, expected] of Object.entries(expectedResults)) {
+        Assert.deepEqual(
+          apiThrowRejections[key],
+          expected,
+          `Got the expected rejected object for test case "${key}"`
+        );
+      }
+
+      Assert.deepEqual(
+        Object.keys(expectedResults).sort(),
+        Object.keys(apiThrowRejections).sort(),
+        "the expected and actual test case names matches"
+      );
+    },
+  });
+});
+
+add_task(
+  async function test_apiScript_method_ensure_xraywrapped_proxy_in_params() {
+    function apiScript(sharedTestAPIMethods) {
+      browser.userScripts.onBeforeScript.addListener(script => {
+        script.defineGlobals({
+          ...sharedTestAPIMethods,
+          testAPIMethod(...args) {
+            // Proxies are opaque when wrapped in Xrays, and the proto of an opaque object
+            // is supposed to be Object.prototype.
+            browser.test.assertEq(
+              script.global.Object.prototype,
+              Object.getPrototypeOf(args[0]),
+              "Calling getPrototypeOf on the XrayWrapped proxy object doesn't run the proxy trap"
+            );
+
+            browser.test.assertTrue(
+              Array.isArray(args[0]),
+              "Got an array object for the XrayWrapped proxy object param"
+            );
+            browser.test.assertEq(
+              undefined,
+              args[0].length,
+              "XrayWrappers deny access to the length property"
+            );
+            browser.test.assertEq(
+              undefined,
+              args[0][0],
+              "Got the expected item in the array object"
+            );
+            return true;
+          },
+        });
+      });
+    }
+
+    async function userScript() {
+      const { assertTrue, notifyFinish, testAPIMethod } = this;
+
+      let proxy = new Proxy(["expectedArrayValue"], {
+        getPrototypeOf() {
+          throw new Error("Proxy's getPrototypeOf trap");
+        },
+        get(target, prop, receiver) {
+          throw new Error("Proxy's get trap");
+        },
+      });
+
+      let result = testAPIMethod(proxy);
+
+      assertTrue(
+        result,
+        `userScript got an unexpected returned value: ${result}`
+      );
+      notifyFinish();
+    }
+
+    await test_userScript_APIMethod({
+      userScript,
+      apiScript,
+    });
+  }
+);
+
+add_task(async function test_apiScript_method_return_proxy_object() {
+  function apiScript(sharedTestAPIMethods) {
+    let proxyTrapsCount = 0;
+    let scriptTrapsCount = 0;
+
+    browser.userScripts.onBeforeScript.addListener(script => {
+      script.defineGlobals({
+        ...sharedTestAPIMethods,
+        testAPIMethodError() {
+          return new Proxy(["expectedArrayValue"], {
+            getPrototypeOf(target) {
+              proxyTrapsCount++;
+              return Object.getPrototypeOf(target);
+            },
+          });
+        },
+        testAPIMethodOk() {
+          return new script.global.Proxy(
+            script.export(["expectedArrayValue"]),
+            script.export({
+              getPrototypeOf(target) {
+                scriptTrapsCount++;
+                return script.global.Object.getPrototypeOf(target);
+              },
+            })
+          );
+        },
+        assertNoProxyTrapTriggered() {
+          browser.test.assertEq(
+            0,
+            proxyTrapsCount,
+            "Proxy traps should not be triggered"
+          );
+        },
+        assertScriptProxyTrapsCount(expected) {
+          browser.test.assertEq(
+            expected,
+            scriptTrapsCount,
+            "Script Proxy traps should have been triggered"
+          );
+        },
+      });
+    });
+  }
+
+  async function userScript() {
+    const {
+      assertTrue,
+      assertNoProxyTrapTriggered,
+      assertScriptProxyTrapsCount,
+      notifyFinish,
+      testAPIMethodError,
+      testAPIMethodOk,
+    } = this;
+
+    let error;
+    try {
+      let result = testAPIMethodError();
+      notifyFinish(
+        `Unexpected returned value while expecting error: ${result}`
+      );
+      return;
+    } catch (err) {
+      error = err;
+    }
+
+    assertTrue(
+      error &&
+        error.message.includes("Return value not accessible to the userScript"),
+      `Got an unexpected error message: ${error}`
+    );
+
+    error = undefined;
+    try {
+      let result = testAPIMethodOk();
+      assertScriptProxyTrapsCount(0);
+      if (!(result instanceof Array)) {
+        notifyFinish(`Got an unexpected result: ${result}`);
+        return;
+      }
+      assertScriptProxyTrapsCount(1);
+    } catch (err) {
+      error = err;
+    }
+
+    assertTrue(!error, `Got an unexpected error: ${error}`);
+
+    assertNoProxyTrapTriggered();
+
+    notifyFinish();
+  }
+
+  await test_userScript_APIMethod({
+    userScript,
+    apiScript,
+  });
+});
+
+add_task(async function test_apiScript_returns_functions() {
+  function apiScript(sharedTestAPIMethods) {
+    browser.userScripts.onBeforeScript.addListener(script => {
+      script.defineGlobals({
+        ...sharedTestAPIMethods,
+        testAPIReturnsFunction() {
+          // Return a function with provides the same kind of behavior
+          // of the API methods exported as globals.
+          return script.export(() => window);
+        },
+        testAPIReturnsObjWithMethod() {
+          return script.export({
+            getWindow() {
+              return window;
+            },
+          });
+        },
+      });
+    });
+  }
+
+  async function userScript() {
+    const {
+      assertTrue,
+      notifyFinish,
+      testAPIReturnsFunction,
+      testAPIReturnsObjWithMethod,
+    } = this;
+
+    let resultFn = testAPIReturnsFunction();
+    assertTrue(
+      typeof resultFn === "function",
+      `userScript got an unexpected returned value: ${typeof resultFn}`
+    );
+
+    let fnRes = resultFn();
+    assertTrue(
+      fnRes === window,
+      `Got an unexpected value from the returned function: ${fnRes}`
+    );
+
+    let resultObj = testAPIReturnsObjWithMethod();
+    let actualTypeof = resultObj && typeof resultObj.getWindow;
+    assertTrue(
+      actualTypeof === "function",
+      `Returned object does not have the expected getWindow method: ${actualTypeof}`
+    );
+
+    let methodRes = resultObj.getWindow();
+    assertTrue(
+      methodRes === window,
+      `Got an unexpected value from the returned method: ${methodRes}`
+    );
+
+    notifyFinish();
+  }
+
+  await test_userScript_APIMethod({
+    userScript,
+    apiScript,
+  });
+});
+
+add_task(
+  async function test_apiScript_method_clone_non_subsumed_returned_values() {
+    function apiScript(sharedTestAPIMethods) {
+      browser.userScripts.onBeforeScript.addListener(script => {
+        script.defineGlobals({
+          ...sharedTestAPIMethods,
+          testAPIMethodReturnOk() {
+            return script.export({
+              objKey1: {
+                nestedProp: "nestedvalue",
+              },
+              window,
+            });
+          },
+          testAPIMethodExplicitlyClonedError() {
+            let result = script.export({ apiScopeObject: undefined });
+
+            browser.test.assertThrows(
+              () => {
+                result.apiScopeObject = { disallowedProp: "disallowedValue" };
+              },
+              /Not allowed to define cross-origin object as property on .* XrayWrapper/,
+              "Assigning a property to a xRayWrapper is expected to throw"
+            );
+
+            // Let the exception to be raised, so that we check that the actual underlying
+            // error message is not leaking in the userScript (replaced by the generic
+            // "An unexpected apiScript error occurred" error message).
+            result.apiScopeObject = { disallowedProp: "disallowedValue" };
+          },
+        });
+      });
+    }
+
+    async function userScript() {
+      const {
+        assertTrue,
+        notifyFinish,
+        testAPIMethodReturnOk,
+        testAPIMethodExplicitlyClonedError,
+      } = this;
+
+      let result = testAPIMethodReturnOk();
+
+      assertTrue(
+        result &&
+          "objKey1" in result &&
+          result.objKey1.nestedProp === "nestedvalue",
+        `userScript got an unexpected returned value: ${result}`
+      );
+
+      assertTrue(
+        result.window === window,
+        `userScript should have access to the window property: ${result.window}`
+      );
+
+      let error;
+      try {
+        result = testAPIMethodExplicitlyClonedError();
+        notifyFinish(
+          `Unexpected returned value while expecting error: ${result}`
+        );
+        return;
+      } catch (err) {
+        error = err;
+      }
+
+      // We expect the generic "unexpected apiScript error occurred" to be raised to the
+      // userScript code.
+      assertTrue(
+        error &&
+          error.message.includes("An unexpected apiScript error occurred"),
+        `Got an unexpected error message: ${error}`
+      );
+
+      notifyFinish();
+    }
+
+    await test_userScript_APIMethod({
+      userScript,
+      apiScript,
+    });
+  }
+);
+
+add_task(async function test_apiScript_method_export_primitive_types() {
+  function apiScript(sharedTestAPIMethods) {
+    browser.userScripts.onBeforeScript.addListener(script => {
+      script.defineGlobals({
+        ...sharedTestAPIMethods,
+        testAPIMethod(typeToExport) {
+          switch (typeToExport) {
+            case "boolean":
+              return script.export(true);
+            case "number":
+              return script.export(123);
+            case "string":
+              return script.export("a string");
+            case "symbol":
+              return script.export(Symbol("a symbol"));
+          }
+          return undefined;
+        },
+      });
+    });
+  }
+
+  async function userScript() {
+    const { assertTrue, notifyFinish, testAPIMethod } = this;
+
+    let v = testAPIMethod("boolean");
+    assertTrue(v === true, `Should export a boolean`);
+
+    v = testAPIMethod("number");
+    assertTrue(v === 123, `Should export a number`);
+
+    v = testAPIMethod("string");
+    assertTrue(v === "a string", `Should export a string`);
+
+    v = testAPIMethod("symbol");
+    assertTrue(typeof v === "symbol", `Should export a symbol`);
+
+    notifyFinish();
+  }
+
+  await test_userScript_APIMethod({
+    userScript,
+    apiScript,
+  });
+});
+
+add_task(
+  async function test_apiScript_method_avoid_unnecessary_params_cloning() {
+    function apiScript(sharedTestAPIMethods) {
+      browser.userScripts.onBeforeScript.addListener(script => {
+        script.defineGlobals({
+          ...sharedTestAPIMethods,
+          testAPIMethodReturnsParam(param) {
+            return param;
+          },
+          testAPIMethodReturnsUnwrappedParam(param) {
+            return param.wrappedJSObject;
+          },
+        });
+      });
+    }
+
+    async function userScript() {
+      const {
+        assertTrue,
+        notifyFinish,
+        testAPIMethodReturnsParam,
+        testAPIMethodReturnsUnwrappedParam,
+      } = this;
+
+      let obj = {};
+
+      let result = testAPIMethodReturnsParam(obj);
+
+      assertTrue(
+        result === obj,
+        `Expect returned value to be strictly equal to the API method parameter`
+      );
+
+      result = testAPIMethodReturnsUnwrappedParam(obj);
+
+      assertTrue(
+        result === obj,
+        `Expect returned value to be strictly equal to the unwrapped API method parameter`
+      );
+
+      notifyFinish();
+    }
+
+    await test_userScript_APIMethod({
+      userScript,
+      apiScript,
+    });
+  }
+);
+
+add_task(async function test_apiScript_method_export_sparse_arrays() {
+  function apiScript(sharedTestAPIMethods) {
+    browser.userScripts.onBeforeScript.addListener(script => {
+      script.defineGlobals({
+        ...sharedTestAPIMethods,
+        testAPIMethod() {
+          const sparseArray = [];
+          sparseArray[3] = "third-element";
+          sparseArray[5] = "fifth-element";
+          return script.export(sparseArray);
+        },
+      });
+    });
+  }
+
+  async function userScript() {
+    const { assertTrue, notifyFinish, testAPIMethod } = this;
+
+    const result = testAPIMethod(window, document);
+
+    // We expect the returned value to be the uncloneable window object.
+    assertTrue(
+      result && result.length === 6,
+      `the returned value should be an array of the expected length: ${result}`
+    );
+    assertTrue(
+      result[3] === "third-element",
+      `the third array element should have the expected value: ${result[3]}`
+    );
+    assertTrue(
+      result[5] === "fifth-element",
+      `the fifth array element should have the expected value: ${result[5]}`
+    );
+    assertTrue(
+      result[0] === undefined,
+      `the first array element should have the expected value: ${result[0]}`
+    );
+    assertTrue(!("0" in result), "Holey array should still be holey");
+
+    notifyFinish();
+  }
+
+  await test_userScript_APIMethod({
+    userScript,
+    apiScript,
+  });
+});
diff --git a/toolkit/components/extensions/test/xpcshell/test_ext_userScripts_register.js b/toolkit/components/extensions/test/xpcshell/test_ext_userScripts_register.js
new file mode 100644
index 0000000000..fd57cd2736
--- /dev/null
+++ b/toolkit/components/extensions/test/xpcshell/test_ext_userScripts_register.js
@@ -0,0 +1,142 @@
+"use strict";
+
+const { createAppInfo } = AddonTestUtils;
+
+AddonTestUtils.init(this);
+
+createAppInfo("xpcshell@tests.mozilla.org", "XPCShell", "1", "49");
+
+const server = createHttpServer();
+server.registerDirectory("/data/", do_get_file("data"));
+
+const BASE_URL = `http://localhost:${server.identity.primaryPort}/data`;
+
+add_task(async function test_userscripts_register_cookieStoreId() {
+  async function background() {
+    const matches = ["<all_urls>"];
+
+    await browser.test.assertRejects(
+      browser.userScripts.register({
+        js: [{ code: "" }],
+        matches,
+        cookieStoreId: "not_a_valid_cookieStoreId",
+      }),
+      /Invalid cookieStoreId/,
+      "userScript.register with an invalid cookieStoreId"
+    );
+
+    await browser.test.assertRejects(
+      browser.userScripts.register({
+        js: [{ code: "" }],
+        matches,
+        cookieStoreId: "",
+      }),
+      /Invalid cookieStoreId/,
+      "userScripts.register with an invalid cookieStoreId"
+    );
+
+    let cookieStoreIdJSArray = [
+      {
+        id: "firefox-container-1",
+        code: `document.body.textContent += "1"`,
+      },
+      {
+        id: ["firefox-container-2", "firefox-container-3"],
+        code: `document.body.textContent += "2-3"`,
+      },
+      {
+        id: "firefox-private",
+        code: `document.body.textContent += "private"`,
+      },
+      {
+        id: "firefox-default",
+        code: `document.body.textContent += "default"`,
+      },
+    ];
+
+    for (let { id, code } of cookieStoreIdJSArray) {
+      await browser.userScripts.register({
+        js: [{ code }],
+        matches,
+        runAt: "document_end",
+        cookieStoreId: id,
+      });
+    }
+
+    await browser.contentScripts.register({
+      js: [
+        {
+          code: `browser.test.sendMessage("last-content-script");`,
+        },
+      ],
+      matches,
+      runAt: "document_end",
+    });
+
+    browser.test.sendMessage("background_ready");
+  }
+
+  const extension = ExtensionTestUtils.loadExtension({
+    manifest: {
+      permissions: ["<all_urls>"],
+      user_scripts: {},
+    },
+    background,
+    incognitoOverride: "spanning",
+  });
+
+  await extension.startup();
+  await extension.awaitMessage("background_ready");
+
+  registerCleanupFunction(() => extension.unload());
+
+  let testCases = [
+    {
+      contentPageOptions: { userContextId: 0 },
+      expectedTextContent: "default",
+    },
+    {
+      contentPageOptions: { userContextId: 1 },
+      expectedTextContent: "1",
+    },
+    {
+      contentPageOptions: { userContextId: 2 },
+      expectedTextContent: "2-3",
+    },
+    {
+      contentPageOptions: { userContextId: 3 },
+      expectedTextContent: "2-3",
+    },
+    {
+      contentPageOptions: { userContextId: 4 },
+      expectedTextContent: "",
+    },
+    {
+      contentPageOptions: { privateBrowsing: true },
+      expectedTextContent: "private",
+    },
+  ];
+
+  for (let test of testCases) {
+    let contentPage = await ExtensionTestUtils.loadContentPage(
+      `${BASE_URL}/file_sample.html`,
+      test.contentPageOptions
+    );
+
+    await extension.awaitMessage("last-content-script");
+
+    let result = await contentPage.spawn([], () => {
+      let textContent = content.document.body.textContent;
+      // Omit the default content from file_sample.html.
+      return textContent.replace("\n\nSample text\n\n\n\n", "");
+    });
+
+    await contentPage.close();
+
+    equal(
+      result,
+      test.expectedTextContent,
+      `Expected textContent on content page`
+    );
+  }
+});
diff --git a/toolkit/components/extensions/test/xpcshell/test_ext_wasm.js b/toolkit/components/extensions/test/xpcshell/test_ext_wasm.js
new file mode 100644
index 0000000000..1a41361491
--- /dev/null
+++ b/toolkit/components/extensions/test/xpcshell/test_ext_wasm.js
@@ -0,0 +1,135 @@
+/* -*- Mode: indent-tabs-mode: nil; js-indent-level: 2 -*- */
+/* vim: set sts=2 sw=2 et tw=80: */
+"use strict";
+
+Services.prefs.setBoolPref("extensions.manifestV3.enabled", true);
+
+// Common code snippet of background script in this test.
+function background() {
+  globalThis.onsecuritypolicyviolation = event => {
+    browser.test.assertEq("wasm-eval", event.blockedURI, "blockedURI");
+    if (browser.runtime.getManifest().version === 2) {
+      // In MV2, wasm eval violations are advisory only, as a transition tool.
+      browser.test.assertEq(event.disposition, "report", "MV2 disposition");
+    } else {
+      browser.test.assertEq(event.disposition, "enforce", "MV3 disposition");
+    }
+    browser.test.sendMessage("violated_csp", event.originalPolicy);
+  };
+  try {
+    let wasm = new WebAssembly.Module(
+      new Uint8Array([0, 0x61, 0x73, 0x6d, 0x1, 0, 0, 0])
+    );
+    browser.test.assertEq(wasm.toString(), "[object WebAssembly.Module]");
+    browser.test.sendMessage("result", "allowed");
+  } catch (e) {
+    browser.test.assertEq(
+      "call to WebAssembly.Module() blocked by CSP",
+      e.message,
+      "Expected error when blocked"
+    );
+    browser.test.sendMessage("result", "blocked");
+  }
+}
+
+add_task(async function test_wasm_v2() {
+  let extension = ExtensionTestUtils.loadExtension({
+    background,
+    manifest: {
+      manifest_version: 2,
+    },
+  });
+
+  await extension.startup();
+  equal(await extension.awaitMessage("result"), "allowed");
+  await extension.unload();
+});
+
+add_task(async function test_wasm_v2_explicit() {
+  let extension = ExtensionTestUtils.loadExtension({
+    background,
+    manifest: {
+      manifest_version: 2,
+      content_security_policy: `object-src; script-src 'self' 'wasm-unsafe-eval'`,
+    },
+  });
+
+  await extension.startup();
+  equal(await extension.awaitMessage("result"), "allowed");
+  await extension.unload();
+});
+
+// MV3 counterpart is test_wasm_v3_blocked_by_custom_csp.
+add_task(async function test_wasm_v2_blocked_in_report_only_mode() {
+  let extension = ExtensionTestUtils.loadExtension({
+    background,
+    manifest: {
+      manifest_version: 2,
+      content_security_policy: `object-src; script-src 'self'`,
+    },
+  });
+
+  await extension.startup();
+  // "allowed" because wasm-unsafe-eval in MV2 is in report-only mode.
+  equal(await extension.awaitMessage("result"), "allowed");
+  equal(
+    await extension.awaitMessage("violated_csp"),
+    "object-src 'none'; script-src 'self'"
+  );
+  await extension.unload();
+});
+
+add_task(async function test_wasm_v3_blocked_by_default() {
+  let extension = ExtensionTestUtils.loadExtension({
+    background,
+    manifest: {
+      manifest_version: 3,
+    },
+  });
+
+  await extension.startup();
+  equal(await extension.awaitMessage("result"), "blocked");
+  equal(
+    await extension.awaitMessage("violated_csp"),
+    "script-src 'self'; upgrade-insecure-requests",
+    "WASM usage violates default CSP in MV3"
+  );
+  await extension.unload();
+});
+
+// MV2 counterpart is test_wasm_v2_blocked_in_report_only_mode.
+add_task(async function test_wasm_v3_blocked_by_custom_csp() {
+  let extension = ExtensionTestUtils.loadExtension({
+    background,
+    manifest: {
+      manifest_version: 3,
+      content_security_policy: {
+        extension_pages: "object-src; script-src 'self'",
+      },
+    },
+  });
+
+  await extension.startup();
+  equal(await extension.awaitMessage("result"), "blocked");
+  equal(
+    await extension.awaitMessage("violated_csp"),
+    "object-src 'none'; script-src 'self'"
+  );
+  await extension.unload();
+});
+
+add_task(async function test_wasm_v3_allowed() {
+  let extension = ExtensionTestUtils.loadExtension({
+    background,
+    manifest: {
+      manifest_version: 3,
+      content_security_policy: {
+        extension_pages: `script-src 'self' 'wasm-unsafe-eval'; object-src 'self'`,
+      },
+    },
+  });
+
+  await extension.startup();
+  equal(await extension.awaitMessage("result"), "allowed");
+  await extension.unload();
+});
diff --git a/toolkit/components/extensions/test/xpcshell/test_ext_webRequest_auth.js b/toolkit/components/extensions/test/xpcshell/test_ext_webRequest_auth.js
new file mode 100644
index 0000000000..c616d162a5
--- /dev/null
+++ b/toolkit/components/extensions/test/xpcshell/test_ext_webRequest_auth.js
@@ -0,0 +1,425 @@
+"use strict";
+
+const HOSTS = new Set(["example.com"]);
+
+const server = createHttpServer({ hosts: HOSTS });
+
+const BASE_URL = "http://example.com";
+
+// Save seen realms for cache checking.
+let realms = new Set([]);
+
+server.registerPathHandler("/authenticate.sjs", (request, response) => {
+  let url = new URL(`${BASE_URL}${request.path}?${request.queryString}`);
+  let realm = url.searchParams.get("realm") || "mochitest";
+  let proxy_realm = url.searchParams.get("proxy_realm");
+
+  function checkAuthorization(authorization) {
+    let expected_user = url.searchParams.get("user");
+    if (!expected_user) {
+      return true;
+    }
+    let expected_pass = url.searchParams.get("pass");
+    let actual_user, actual_pass;
+    let authHeader = request.getHeader("Authorization");
+    let match = /Basic (.+)/.exec(authHeader);
+    if (match.length != 2) {
+      throw new Error("Couldn't parse auth header: " + authHeader);
+    }
+    let userpass = atob(match[1]); // no atob() :-(
+    match = /(.*):(.*)/.exec(userpass);
+    if (match.length != 3) {
+      throw new Error("Couldn't decode auth header: " + userpass);
+    }
+    actual_user = match[1];
+    actual_pass = match[2];
+    return expected_user === actual_user && expected_pass === actual_pass;
+  }
+
+  response.setHeader("Content-Type", "text/plain; charset=UTF-8", false);
+  if (proxy_realm && !request.hasHeader("Proxy-Authorization")) {
+    // We're not testing anything that requires checking the proxy auth user/password.
+    response.setStatusLine("1.0", 407, "Proxy authentication required");
+    response.setHeader(
+      "Proxy-Authenticate",
+      `basic realm="${proxy_realm}"`,
+      true
+    );
+    response.write("proxy auth required");
+  } else if (
+    !(
+      realms.has(realm) &&
+      request.hasHeader("Authorization") &&
+      checkAuthorization()
+    )
+  ) {
+    realms.add(realm);
+    response.setStatusLine(request.httpVersion, 401, "Authentication required");
+    response.setHeader("WWW-Authenticate", `basic realm="${realm}"`, true);
+    response.write("auth required");
+  } else {
+    response.setStatusLine(request.httpVersion, 200, "OK");
+    response.write("ok, got authorization");
+  }
+});
+
+function getExtension(bgConfig) {
+  function background(config) {
+    let path = config.path;
+    browser.webRequest.onBeforeRequest.addListener(
+      details => {
+        browser.test.log(
+          `onBeforeRequest called with ${details.requestId} ${details.url}`
+        );
+        browser.test.sendMessage("onBeforeRequest");
+        return (
+          config.onBeforeRequest.hasOwnProperty("result") &&
+          config.onBeforeRequest.result
+        );
+      },
+      { urls: [path] },
+      config.onBeforeRequest.hasOwnProperty("extra")
+        ? config.onBeforeRequest.extra
+        : []
+    );
+    browser.webRequest.onAuthRequired.addListener(
+      details => {
+        browser.test.log(
+          `onAuthRequired called with ${details.requestId} ${details.url}`
+        );
+        browser.test.assertEq(
+          config.realm,
+          details.realm,
+          "providing www authorization"
+        );
+        browser.test.sendMessage("onAuthRequired");
+        return (
+          config.onAuthRequired.hasOwnProperty("result") &&
+          config.onAuthRequired.result
+        );
+      },
+      { urls: [path] },
+      config.onAuthRequired.hasOwnProperty("extra")
+        ? config.onAuthRequired.extra
+        : []
+    );
+    browser.webRequest.onCompleted.addListener(
+      details => {
+        browser.test.log(
+          `onCompleted called with ${details.requestId} ${details.url}`
+        );
+        browser.test.sendMessage("onCompleted");
+      },
+      { urls: [path] }
+    );
+    browser.webRequest.onErrorOccurred.addListener(
+      details => {
+        browser.test.log(
+          `onErrorOccurred called with ${JSON.stringify(details)}`
+        );
+        browser.test.sendMessage("onErrorOccurred");
+      },
+      { urls: [path] }
+    );
+  }
+
+  return ExtensionTestUtils.loadExtension({
+    manifest: {
+      permissions: ["webRequest", "webRequestBlocking", bgConfig.path],
+    },
+    background: `(${background})(${JSON.stringify(bgConfig)})`,
+  });
+}
+
+add_task(async function test_webRequest_auth() {
+  let config = {
+    path: `${BASE_URL}/*`,
+    realm: `webRequest_auth${Math.random()}`,
+    onBeforeRequest: {
+      extra: ["blocking"],
+    },
+    onAuthRequired: {
+      extra: ["blocking"],
+      result: {
+        authCredentials: {
+          username: "testuser",
+          password: "testpass",
+        },
+      },
+    },
+  };
+
+  let extension = getExtension(config);
+  await extension.startup();
+
+  let requestUrl = `${BASE_URL}/authenticate.sjs?realm=${config.realm}`;
+  let contentPage = await ExtensionTestUtils.loadContentPage(requestUrl);
+  await Promise.all([
+    extension.awaitMessage("onBeforeRequest"),
+    extension.awaitMessage("onAuthRequired").then(() => {
+      return Promise.all([
+        extension.awaitMessage("onBeforeRequest"),
+        extension.awaitMessage("onCompleted"),
+      ]);
+    }),
+  ]);
+  await contentPage.close();
+
+  // Second time around to test cached credentials
+  contentPage = await ExtensionTestUtils.loadContentPage(requestUrl);
+  await Promise.all([
+    extension.awaitMessage("onBeforeRequest"),
+    extension.awaitMessage("onCompleted"),
+  ]);
+
+  await contentPage.close();
+  await extension.unload();
+});
+
+add_task(async function test_webRequest_auth_cancelled() {
+  // Test that any auth listener can cancel.
+  let config = {
+    path: `${BASE_URL}/*`,
+    realm: `webRequest_auth${Math.random()}`,
+    onBeforeRequest: {
+      extra: ["blocking"],
+    },
+    onAuthRequired: {
+      extra: ["blocking"],
+      result: {
+        authCredentials: {
+          username: "testuser",
+          password: "testpass",
+        },
+      },
+    },
+  };
+
+  let ex1 = getExtension(config);
+  config.onAuthRequired.result = { cancel: true };
+  let ex2 = getExtension(config);
+  await ex1.startup();
+  await ex2.startup();
+
+  let requestUrl = `${BASE_URL}/authenticate.sjs?realm=${config.realm}`;
+  let contentPage = await ExtensionTestUtils.loadContentPage(requestUrl);
+  await Promise.all([
+    ex1.awaitMessage("onBeforeRequest"),
+    ex1.awaitMessage("onAuthRequired"),
+    ex1.awaitMessage("onErrorOccurred"),
+    ex2.awaitMessage("onBeforeRequest"),
+    ex2.awaitMessage("onAuthRequired"),
+    ex2.awaitMessage("onErrorOccurred"),
+  ]);
+
+  await contentPage.close();
+  await ex1.unload();
+  await ex2.unload();
+});
+
+add_task(async function test_webRequest_auth_nonblocking() {
+  let config = {
+    path: `${BASE_URL}/*`,
+    realm: `webRequest_auth${Math.random()}`,
+    onBeforeRequest: {
+      extra: ["blocking"],
+    },
+    onAuthRequired: {
+      extra: ["blocking"],
+      result: {
+        authCredentials: {
+          username: "testuser",
+          password: "testpass",
+        },
+      },
+    },
+  };
+
+  let ex1 = getExtension(config);
+  // non-blocking ext tries to cancel but cannot.
+  delete config.onBeforeRequest.extra;
+  delete config.onAuthRequired.extra;
+  config.onAuthRequired.result = { cancel: true };
+  let ex2 = getExtension(config);
+  await ex1.startup();
+  await ex2.startup();
+
+  let requestUrl = `${BASE_URL}/authenticate.sjs?realm=${config.realm}`;
+  let contentPage = await ExtensionTestUtils.loadContentPage(requestUrl);
+  await Promise.all([
+    ex1.awaitMessage("onBeforeRequest"),
+    ex1.awaitMessage("onAuthRequired").then(() => {
+      return Promise.all([
+        ex1.awaitMessage("onBeforeRequest"),
+        ex1.awaitMessage("onCompleted"),
+      ]);
+    }),
+    ex2.awaitMessage("onBeforeRequest"),
+    ex2.awaitMessage("onAuthRequired").then(() => {
+      return Promise.all([
+        ex2.awaitMessage("onBeforeRequest"),
+        ex2.awaitMessage("onCompleted"),
+      ]);
+    }),
+  ]);
+
+  await contentPage.close();
+  Services.obs.notifyObservers(null, "net:clear-active-logins");
+  await ex1.unload();
+  await ex2.unload();
+});
+
+add_task(async function test_webRequest_auth_blocking_noreturn() {
+  // The first listener is blocking but doesn't return anything.  The second
+  // listener cancels the request.
+  let config = {
+    path: `${BASE_URL}/*`,
+    realm: `webRequest_auth${Math.random()}`,
+    onBeforeRequest: {
+      extra: ["blocking"],
+    },
+    onAuthRequired: {
+      extra: ["blocking"],
+    },
+  };
+
+  let ex1 = getExtension(config);
+  config.onAuthRequired.result = { cancel: true };
+  let ex2 = getExtension(config);
+  await ex1.startup();
+  await ex2.startup();
+
+  let requestUrl = `${BASE_URL}/authenticate.sjs?realm=${config.realm}`;
+  let contentPage = await ExtensionTestUtils.loadContentPage(requestUrl);
+  await Promise.all([
+    ex1.awaitMessage("onBeforeRequest"),
+    ex1.awaitMessage("onAuthRequired"),
+    ex1.awaitMessage("onErrorOccurred"),
+    ex2.awaitMessage("onBeforeRequest"),
+    ex2.awaitMessage("onAuthRequired"),
+    ex2.awaitMessage("onErrorOccurred"),
+  ]);
+
+  await contentPage.close();
+  await ex1.unload();
+  await ex2.unload();
+});
+
+add_task(async function test_webRequest_duelingAuth() {
+  let config = {
+    path: `${BASE_URL}/*`,
+    realm: `webRequest_auth${Math.random()}`,
+    onBeforeRequest: {
+      extra: ["blocking"],
+    },
+    onAuthRequired: {
+      extra: ["blocking"],
+    },
+  };
+  let exNone = getExtension(config);
+  await exNone.startup();
+
+  let authCredentials = {
+    username: `testuser_da1${Math.random()}`,
+    password: `testpass_da1${Math.random()}`,
+  };
+  config.onAuthRequired.result = { authCredentials };
+  let ex1 = getExtension(config);
+  await ex1.startup();
+
+  config.onAuthRequired.result = {};
+  let exEmpty = getExtension(config);
+  await exEmpty.startup();
+
+  config.onAuthRequired.result = {
+    authCredentials: {
+      username: `testuser_da2${Math.random()}`,
+      password: `testpass_da2${Math.random()}`,
+    },
+  };
+  let ex2 = getExtension(config);
+  await ex2.startup();
+
+  let requestUrl = `${BASE_URL}/authenticate.sjs?realm=${config.realm}&user=${authCredentials.username}&pass=${authCredentials.password}`;
+  let contentPage = await ExtensionTestUtils.loadContentPage(requestUrl);
+  await Promise.all([
+    exNone.awaitMessage("onBeforeRequest"),
+    exNone.awaitMessage("onAuthRequired").then(() => {
+      return Promise.all([
+        exNone.awaitMessage("onBeforeRequest"),
+        exNone.awaitMessage("onCompleted"),
+      ]);
+    }),
+    exEmpty.awaitMessage("onBeforeRequest"),
+    exEmpty.awaitMessage("onAuthRequired").then(() => {
+      return Promise.all([
+        exEmpty.awaitMessage("onBeforeRequest"),
+        exEmpty.awaitMessage("onCompleted"),
+      ]);
+    }),
+    ex1.awaitMessage("onBeforeRequest"),
+    ex1.awaitMessage("onAuthRequired").then(() => {
+      return Promise.all([
+        ex1.awaitMessage("onBeforeRequest"),
+        ex1.awaitMessage("onCompleted"),
+      ]);
+    }),
+    ex2.awaitMessage("onBeforeRequest"),
+    ex2.awaitMessage("onAuthRequired").then(() => {
+      return Promise.all([
+        ex2.awaitMessage("onBeforeRequest"),
+        ex2.awaitMessage("onCompleted"),
+      ]);
+    }),
+  ]);
+
+  await Promise.all([
+    await contentPage.close(),
+    exNone.unload(),
+    exEmpty.unload(),
+    ex1.unload(),
+    ex2.unload(),
+  ]);
+});
+
+add_task(async function test_webRequest_auth_proxy() {
+  function background(permissionPath) {
+    let proxyOk = false;
+    browser.webRequest.onAuthRequired.addListener(
+      details => {
+        browser.test.log(
+          `handlingExt onAuthRequired called with ${details.requestId} ${details.url}`
+        );
+        if (details.isProxy) {
+          browser.test.succeed("providing proxy authorization");
+          proxyOk = true;
+          return { authCredentials: { username: "puser", password: "ppass" } };
+        }
+        browser.test.assertTrue(
+          proxyOk,
+          "providing www authorization after proxy auth"
+        );
+        browser.test.sendMessage("done");
+        return { authCredentials: { username: "auser", password: "apass" } };
+      },
+      { urls: [permissionPath] },
+      ["blocking"]
+    );
+  }
+
+  let handlingExt = ExtensionTestUtils.loadExtension({
+    manifest: {
+      permissions: ["webRequest", "webRequestBlocking", `${BASE_URL}/*`],
+    },
+    background: `(${background})("${BASE_URL}/*")`,
+  });
+
+  await handlingExt.startup();
+
+  let requestUrl = `${BASE_URL}/authenticate.sjs?realm=webRequest_auth${Math.random()}&proxy_realm=proxy_auth${Math.random()}`;
+  let contentPage = await ExtensionTestUtils.loadContentPage(requestUrl);
+
+  await handlingExt.awaitMessage("done");
+  await contentPage.close();
+  await handlingExt.unload();
+});
diff --git a/toolkit/components/extensions/test/xpcshell/test_ext_webRequest_cached.js b/toolkit/components/extensions/test/xpcshell/test_ext_webRequest_cached.js
new file mode 100644
index 0000000000..c18c75a580
--- /dev/null
+++ b/toolkit/components/extensions/test/xpcshell/test_ext_webRequest_cached.js
@@ -0,0 +1,311 @@
+"use strict";
+
+const BASE_URL = "http://example.com";
+const FETCH_ORIGIN = "http://example.com/data/file_sample.html";
+
+const server = createHttpServer({ hosts: ["example.com"] });
+server.registerDirectory("/data/", do_get_file("data"));
+server.registerPathHandler("/status", (request, response) => {
+  let IfNoneMatch = request.hasHeader("If-None-Match")
+    ? request.getHeader("If-None-Match")
+    : "";
+
+  switch (IfNoneMatch) {
+    case "1234567890":
+      response.setStatusLine("1.1", 304, "Not Modified");
+      response.setHeader("Content-Type", "text/html", false);
+      response.setHeader("Etag", "1234567890", false);
+      break;
+    case "":
+      response.setStatusLine("1.1", 200, "OK");
+      response.setHeader("Content-Type", "text/html", false);
+      response.setHeader("Etag", "1234567890", false);
+      response.write("ok");
+      break;
+    default:
+      throw new Error(`Unexpected If-None-Match: ${IfNoneMatch}`);
+  }
+});
+
+// This test initialises a cache entry with a CSP header, then
+// loads the cached entry and replaces the CSP header with
+// a new one.  We test in onResponseStarted that the header
+// is what we expect.
+add_task(async function test_replaceResponseHeaders() {
+  Services.prefs.setBoolPref("network.http.rcwn.enabled", false);
+
+  let extension = ExtensionTestUtils.loadExtension({
+    background() {
+      function replaceHeader(headers, newHeader) {
+        headers = headers.filter(header => header.name !== newHeader.name);
+        headers.push(newHeader);
+        return headers;
+      }
+      let testHeaders = [
+        {
+          name: "Content-Security-Policy",
+          value: "object-src 'none'; script-src 'none'",
+        },
+        {
+          name: "Content-Security-Policy",
+          value: "object-src 'none'; script-src https:",
+        },
+      ];
+      browser.webRequest.onHeadersReceived.addListener(
+        details => {
+          if (!details.fromCache) {
+            // Add a CSP header on the initial request
+            details.responseHeaders.push(testHeaders[0]);
+            return {
+              responseHeaders: details.responseHeaders,
+            };
+          }
+          // Test that the header added during the initial request is
+          // now in the cached response.
+          let header = details.responseHeaders.filter(header => {
+            browser.test.log(`header ${header.name} = ${header.value}`);
+            return header.name == "Content-Security-Policy";
+          });
+          browser.test.assertEq(
+            header[0].value,
+            testHeaders[0].value,
+            "pre-cached header exists"
+          );
+          // Replace the cached value so we can test overriding the header that was cached.
+          return {
+            responseHeaders: replaceHeader(
+              details.responseHeaders,
+              testHeaders[1]
+            ),
+          };
+        },
+        {
+          urls: ["http://example.com/*/file_sample.html?r=*"],
+        },
+        ["blocking", "responseHeaders"]
+      );
+      browser.webRequest.onResponseStarted.addListener(
+        details => {
+          let needle = details.fromCache ? testHeaders[1] : testHeaders[0];
+          let header = details.responseHeaders.filter(header => {
+            browser.test.log(`header ${header.name} = ${header.value}`);
+            return header.name == needle.name && header.value == needle.value;
+          });
+          browser.test.assertEq(
+            header.length,
+            1,
+            "header exists with correct value"
+          );
+          if (details.fromCache) {
+            browser.test.sendMessage("from-cache");
+          }
+        },
+        {
+          urls: ["http://example.com/*/file_sample.html?r=*"],
+        },
+        ["responseHeaders"]
+      );
+    },
+
+    manifest: {
+      permissions: ["webRequest", "webRequestBlocking", "http://example.com/"],
+    },
+  });
+
+  await extension.startup();
+
+  let url = `${BASE_URL}/data/file_sample.html?r=${Math.random()}`;
+  await ExtensionTestUtils.fetch(FETCH_ORIGIN, url);
+  await ExtensionTestUtils.fetch(FETCH_ORIGIN, url);
+  await extension.awaitMessage("from-cache");
+
+  await extension.unload();
+});
+
+// This test initialises a cache entry with a CSP header, then
+// loads the cached entry and adds a second CSP header.  We also
+// test that the browser has the CSP entries we expect.
+add_task(async function test_addCSPHeaders() {
+  Services.prefs.setBoolPref("network.http.rcwn.enabled", false);
+
+  let extension = ExtensionTestUtils.loadExtension({
+    background() {
+      let testHeaders = [
+        {
+          name: "Content-Security-Policy",
+          value: "object-src 'none'; script-src 'none'",
+        },
+        {
+          name: "Content-Security-Policy",
+          value: "object-src 'none'; script-src https:",
+        },
+      ];
+      browser.webRequest.onHeadersReceived.addListener(
+        details => {
+          if (!details.fromCache) {
+            details.responseHeaders.push(testHeaders[0]);
+            return {
+              responseHeaders: details.responseHeaders,
+            };
+          }
+          browser.test.log("cached request received");
+          details.responseHeaders.push(testHeaders[1]);
+          return {
+            responseHeaders: details.responseHeaders,
+          };
+        },
+        {
+          urls: ["http://example.com/*/file_sample.html?r=*"],
+        },
+        ["blocking", "responseHeaders"]
+      );
+      browser.webRequest.onCompleted.addListener(
+        details => {
+          let { name, value } = testHeaders[0];
+          if (details.fromCache) {
+            value = `${value}, ${testHeaders[1].value}`;
+          }
+          let header = details.responseHeaders.filter(header => {
+            browser.test.log(`header ${header.name} = ${header.value}`);
+            return header.name == name && header.value == value;
+          });
+          browser.test.assertEq(
+            header.length,
+            1,
+            "header exists with correct value"
+          );
+          if (details.fromCache) {
+            browser.test.sendMessage("from-cache");
+          }
+        },
+        {
+          urls: ["http://example.com/*/file_sample.html?r=*"],
+        },
+        ["responseHeaders"]
+      );
+    },
+
+    manifest: {
+      permissions: ["webRequest", "webRequestBlocking", "http://example.com/"],
+    },
+  });
+
+  await extension.startup();
+
+  let url = `${BASE_URL}/data/file_sample.html?r=${Math.random()}`;
+  let contentPage = await ExtensionTestUtils.loadContentPage(url);
+  equal(contentPage.browser.csp.policyCount, 1, "expected 1 policy");
+  equal(
+    contentPage.browser.csp.getPolicy(0),
+    "object-src 'none'; script-src 'none'",
+    "expected policy"
+  );
+  await contentPage.close();
+
+  contentPage = await ExtensionTestUtils.loadContentPage(url);
+  equal(contentPage.browser.csp.policyCount, 2, "expected 2 policies");
+  equal(
+    contentPage.browser.csp.getPolicy(0),
+    "object-src 'none'; script-src 'none'",
+    "expected first policy"
+  );
+  equal(
+    contentPage.browser.csp.getPolicy(1),
+    "object-src 'none'; script-src https:",
+    "expected second policy"
+  );
+
+  await extension.awaitMessage("from-cache");
+  await contentPage.close();
+
+  await extension.unload();
+});
+
+// This test verifies that a content type changed during
+// onHeadersReceived is cached.  We initialize the cache,
+// then load against a url that will specifically return
+// a 304 status code.
+add_task(async function test_addContentTypeHeaders() {
+  Services.prefs.setBoolPref("network.http.rcwn.enabled", false);
+
+  let extension = ExtensionTestUtils.loadExtension({
+    background() {
+      browser.webRequest.onBeforeSendHeaders.addListener(
+        details => {
+          browser.test.log(`onBeforeSendHeaders ${JSON.stringify(details)}\n`);
+        },
+        {
+          urls: ["http://example.com/status*"],
+        },
+        ["blocking", "requestHeaders"]
+      );
+      browser.webRequest.onHeadersReceived.addListener(
+        details => {
+          browser.test.log(`onHeadersReceived ${JSON.stringify(details)}\n`);
+          if (!details.fromCache) {
+            browser.test.sendMessage("statusCode", details.statusCode);
+            const mime = details.responseHeaders.find(header => {
+              return header.value && header.name === "content-type";
+            });
+            if (mime) {
+              mime.value = "text/plain";
+            } else {
+              details.responseHeaders.push({
+                name: "content-type",
+                value: "text/plain",
+              });
+            }
+            return {
+              responseHeaders: details.responseHeaders,
+            };
+          }
+        },
+        {
+          urls: ["http://example.com/status*"],
+        },
+        ["blocking", "responseHeaders"]
+      );
+      browser.webRequest.onCompleted.addListener(
+        details => {
+          browser.test.log(`onCompleted ${JSON.stringify(details)}\n`);
+          const mime = details.responseHeaders.find(header => {
+            return header.value && header.name === "content-type";
+          });
+          browser.test.sendMessage("contentType", mime.value);
+        },
+        {
+          urls: ["http://example.com/status*"],
+        },
+        ["responseHeaders"]
+      );
+    },
+
+    manifest: {
+      permissions: ["webRequest", "webRequestBlocking", "http://example.com/"],
+    },
+  });
+
+  await extension.startup();
+
+  let contentPage = await ExtensionTestUtils.loadContentPage(
+    `${BASE_URL}/status`
+  );
+  equal(await extension.awaitMessage("statusCode"), "200", "status OK");
+  equal(
+    await extension.awaitMessage("contentType"),
+    "text/plain",
+    "plain text header"
+  );
+  await contentPage.close();
+
+  contentPage = await ExtensionTestUtils.loadContentPage(`${BASE_URL}/status`);
+  equal(await extension.awaitMessage("statusCode"), "304", "not modified");
+  equal(
+    await extension.awaitMessage("contentType"),
+    "text/plain",
+    "plain text header"
+  );
+  await contentPage.close();
+
+  await extension.unload();
+});
diff --git a/toolkit/components/extensions/test/xpcshell/test_ext_webRequest_cancelWithReason.js b/toolkit/components/extensions/test/xpcshell/test_ext_webRequest_cancelWithReason.js
new file mode 100644
index 0000000000..a8405e5962
--- /dev/null
+++ b/toolkit/components/extensions/test/xpcshell/test_ext_webRequest_cancelWithReason.js
@@ -0,0 +1,68 @@
+"use strict";
+
+const server = createHttpServer();
+const gServerUrl = `http://localhost:${server.identity.primaryPort}`;
+
+server.registerPathHandler("/dummy", (request, response) => {
+  response.setStatusLine(request.httpVersion, 200, "OK");
+  response.write("ok");
+});
+
+add_task(async function test_cancel_with_reason() {
+  let ext = ExtensionTestUtils.loadExtension({
+    manifest: {
+      browser_specific_settings: { gecko: { id: "cancel@test" } },
+      permissions: ["webRequest", "webRequestBlocking", "<all_urls>"],
+    },
+
+    background() {
+      browser.webRequest.onBeforeRequest.addListener(
+        () => {
+          return { cancel: true };
+        },
+        { urls: ["*://*/*"] },
+        ["blocking"]
+      );
+    },
+  });
+  await ext.startup();
+
+  let data = await new Promise(resolve => {
+    let ssm = Services.scriptSecurityManager;
+
+    let channel = NetUtil.newChannel({
+      uri: `${gServerUrl}/dummy`,
+      loadingPrincipal:
+        ssm.createContentPrincipalFromOrigin("http://localhost"),
+      contentPolicyType: Ci.nsIContentPolicy.TYPE_XMLHTTPREQUEST,
+      securityFlags: Ci.nsILoadInfo.SEC_ALLOW_CROSS_ORIGIN_SEC_CONTEXT_IS_NULL,
+    });
+
+    channel.asyncOpen({
+      QueryInterface: ChromeUtils.generateQI(["nsIStreamListener"]),
+
+      onStartRequest(request) {},
+
+      onStopRequest(request, statusCode) {
+        let properties = request.QueryInterface(Ci.nsIPropertyBag);
+        let id = properties.getProperty("cancelledByExtension");
+        let reason = request.loadInfo.requestBlockingReason;
+        resolve({ reason, id });
+      },
+
+      onDataAvailable() {},
+    });
+  });
+
+  Assert.equal(
+    Ci.nsILoadInfo.BLOCKING_REASON_EXTENSION_WEBREQUEST,
+    data.reason,
+    "extension cancelled request"
+  );
+  Assert.equal(
+    ext.id,
+    data.id,
+    "extension id attached to channel property bag"
+  );
+  await ext.unload();
+});
diff --git a/toolkit/components/extensions/test/xpcshell/test_ext_webRequest_containerIsolation.js b/toolkit/components/extensions/test/xpcshell/test_ext_webRequest_containerIsolation.js
new file mode 100644
index 0000000000..53a23fc149
--- /dev/null
+++ b/toolkit/components/extensions/test/xpcshell/test_ext_webRequest_containerIsolation.js
@@ -0,0 +1,59 @@
+"use strict";
+
+const server = createHttpServer({ hosts: ["example.com"] });
+
+server.registerPathHandler("/dummy", (request, response) => {
+  response.setStatusLine(request.httpVersion, 200, "OK");
+  response.setHeader("Content-Type", "text/html", false);
+  response.write("<!DOCTYPE html><html></html>");
+});
+
+add_task(async function test_userContextId_webRequest() {
+  Services.prefs.setBoolPref("extensions.userContextIsolation.enabled", true);
+  let extension = ExtensionTestUtils.loadExtension({
+    manifest: {
+      permissions: ["webRequest", "<all_urls>"],
+    },
+    background() {
+      browser.webRequest.onBeforeRequest.addListener(
+        async details => {
+          browser.test.assertEq(
+            "firefox-container-2",
+            details.cookieStoreId,
+            "cookieStoreId is set"
+          );
+          browser.test.notifyPass("allowed");
+        },
+        { urls: ["http://example.com/dummy"] }
+      );
+    },
+  });
+
+  Services.prefs.setCharPref(
+    "extensions.userContextIsolation.defaults.restricted",
+    "[1]"
+  );
+  await extension.startup();
+
+  let restrictedPage = await ExtensionTestUtils.loadContentPage(
+    "http://example.com/dummy",
+    { userContextId: 1 }
+  );
+
+  let allowedPage = await ExtensionTestUtils.loadContentPage(
+    "http://example.com/dummy",
+    {
+      userContextId: 2,
+    }
+  );
+  await extension.awaitFinish("allowed");
+
+  await extension.unload();
+  await restrictedPage.close();
+  await allowedPage.close();
+
+  Services.prefs.clearUserPref("extensions.userContextIsolation.enabled");
+  Services.prefs.clearUserPref(
+    "extensions.userContextIsolation.defaults.restricted"
+  );
+});
diff --git a/toolkit/components/extensions/test/xpcshell/test_ext_webRequest_download.js b/toolkit/components/extensions/test/xpcshell/test_ext_webRequest_download.js
new file mode 100644
index 0000000000..3485996f56
--- /dev/null
+++ b/toolkit/components/extensions/test/xpcshell/test_ext_webRequest_download.js
@@ -0,0 +1,44 @@
+"use strict";
+
+// Test for Bug 1579911: Check that download requests created by the
+// downloads.download API can be observed by extensions.
+// The DNR version is in test_ext_dnr_download.js.
+add_task(async function testDownload() {
+  let extension = ExtensionTestUtils.loadExtension({
+    manifest: {
+      permissions: [
+        "webRequest",
+        "webRequestBlocking",
+        "downloads",
+        "https://example.com/*",
+      ],
+    },
+    background: async function () {
+      browser.webRequest.onBeforeRequest.addListener(
+        details => {
+          browser.test.sendMessage("request_intercepted");
+          return { cancel: true };
+        },
+        {
+          urls: ["https://example.com/downloadtest"],
+        },
+        ["blocking"]
+      );
+
+      browser.downloads.onChanged.addListener(delta => {
+        browser.test.assertEq(delta.state.current, "interrupted");
+        browser.test.sendMessage("done");
+      });
+
+      await browser.downloads.download({
+        url: "https://example.com/downloadtest",
+        filename: "example.txt",
+      });
+    },
+  });
+
+  await extension.startup();
+  await extension.awaitMessage("request_intercepted");
+  await extension.awaitMessage("done");
+  await extension.unload();
+});
diff --git a/toolkit/components/extensions/test/xpcshell/test_ext_webRequest_eventPage_StreamFilter.js b/toolkit/components/extensions/test/xpcshell/test_ext_webRequest_eventPage_StreamFilter.js
new file mode 100644
index 0000000000..23c29aa155
--- /dev/null
+++ b/toolkit/components/extensions/test/xpcshell/test_ext_webRequest_eventPage_StreamFilter.js
@@ -0,0 +1,350 @@
+/* Any copyright is dedicated to the Public Domain.
+ * http://creativecommons.org/publicdomain/zero/1.0/ */
+
+"use strict";
+
+AddonTestUtils.init(this);
+AddonTestUtils.createAppInfo(
+  "xpcshell@tests.mozilla.org",
+  "XPCShell",
+  "42",
+  "42"
+);
+
+const server = createHttpServer({ hosts: ["example.com"] });
+
+let clearLastPendingRequest;
+
+server.registerPathHandler("/pending_request", (request, response) => {
+  response.processAsync();
+  response.setHeader("Content-Length", "10000", false);
+  response.write("somedata\n");
+  let intervalID = setInterval(() => response.write("continue\n"), 50);
+
+  const clearPendingRequest = () => {
+    try {
+      clearInterval(intervalID);
+      response.finish();
+    } catch (e) {
+      // This will throw, but we don't care at this point.
+    }
+  };
+
+  clearLastPendingRequest = clearPendingRequest;
+  registerCleanupFunction(clearPendingRequest);
+});
+
+server.registerPathHandler("/completed_request", (request, response) => {
+  response.write("somedata\n");
+});
+
+add_setup(async () => {
+  await AddonTestUtils.promiseStartupManager();
+});
+
+async function test_idletimeout_on_streamfilter({
+  manifest_version,
+  expectResetIdle,
+  expectStreamFilterStop,
+  requestUrlPath,
+}) {
+  const extension = ExtensionTestUtils.loadExtension({
+    background: `(${async function (urlPath) {
+      browser.webRequest.onBeforeRequest.addListener(
+        request => {
+          browser.test.log(`webRequest request intercepted: ${request.url}`);
+          const filter = browser.webRequest.filterResponseData(
+            request.requestId
+          );
+          const decoder = new TextDecoder("utf-8");
+          const encoder = new TextEncoder();
+          filter.onstart = () => {
+            browser.test.sendMessage("streamfilter:started");
+          };
+          filter.ondata = event => {
+            let str = decoder.decode(event.data, { stream: true });
+            filter.write(encoder.encode(str));
+          };
+          filter.onstop = () => {
+            filter.close();
+            browser.test.sendMessage("streamfilter:stopped");
+          };
+        },
+        {
+          urls: [`http://example.com/${urlPath}`],
+        },
+        ["blocking"]
+      );
+      browser.test.sendMessage("bg:ready");
+    }})("${requestUrlPath}")`,
+
+    useAddonManager: "temporary",
+    manifest: {
+      manifest_version,
+      background: manifest_version >= 3 ? {} : { persistent: false },
+      granted_host_permissions: manifest_version >= 3,
+      permissions:
+        manifest_version >= 3
+          ? ["webRequest", "webRequestBlocking", "webRequestFilterResponse"]
+          : ["webRequest", "webRequestBlocking"],
+      // host_permissions are merged with permissions on a MV2 test extension.
+      host_permissions: ["http://example.com/*"],
+    },
+  });
+
+  await extension.startup();
+  await extension.awaitMessage("bg:ready");
+  const { contextId } = extension.extension.backgroundContext;
+  notEqual(contextId, undefined, "Got a contextId for the background context");
+
+  info("Trigger a webRequest");
+  const testURL = `http://example.com/${requestUrlPath}`;
+  const promiseRequestCompleted = ExtensionTestUtils.fetch(
+    "http://example.com/",
+    testURL
+  ).catch(err => {
+    // This request is expected to be aborted when cleared after the test is exiting,
+    // otherwise rethrow the error to trigger an explicit failure.
+    if (/The operation was aborted/.test(err.message)) {
+      info(`Test webRequest fetching "${testURL}" aborted`);
+    } else {
+      ok(
+        false,
+        `Unexpected rejection triggered by the test webRequest fetching "${testURL}": ${err.message}`
+      );
+      throw err;
+    }
+  });
+
+  info("Wait for the stream filter to be started");
+  await extension.awaitMessage("streamfilter:started");
+
+  if (expectStreamFilterStop) {
+    await extension.awaitMessage("streamfilter:stopped");
+  }
+
+  info("Terminate the background script (simulated idle timeout)");
+
+  if (expectResetIdle) {
+    const promiseResetIdle = promiseExtensionEvent(
+      extension,
+      "background-script-reset-idle"
+    );
+
+    clearHistograms();
+    assertHistogramEmpty(WEBEXT_EVENTPAGE_IDLE_RESULT_COUNT);
+    assertKeyedHistogramEmpty(WEBEXT_EVENTPAGE_IDLE_RESULT_COUNT_BY_ADDONID);
+
+    await extension.terminateBackground();
+    info("Wait for 'background-script-reset-idle' event to be emitted");
+    await promiseResetIdle;
+    equal(
+      extension.extension.backgroundContext.contextId,
+      contextId,
+      "Initial background context is still available as expected"
+    );
+
+    assertHistogramCategoryNotEmpty(WEBEXT_EVENTPAGE_IDLE_RESULT_COUNT, {
+      category: "reset_streamfilter",
+      categories: HISTOGRAM_EVENTPAGE_IDLE_RESULT_CATEGORIES,
+    });
+
+    assertHistogramCategoryNotEmpty(
+      WEBEXT_EVENTPAGE_IDLE_RESULT_COUNT_BY_ADDONID,
+      {
+        keyed: true,
+        key: extension.id,
+        category: "reset_streamfilter",
+        categories: HISTOGRAM_EVENTPAGE_IDLE_RESULT_CATEGORIES,
+      }
+    );
+  } else {
+    const { Management } = ChromeUtils.importESModule(
+      "resource://gre/modules/Extension.sys.mjs"
+    );
+    const promiseProxyContextUnloaded = new Promise(resolve => {
+      function listener(evt, context) {
+        if (context.extension.id === extension.id) {
+          Management.off("proxy-context-unload", listener);
+          resolve();
+        }
+      }
+      Management.on("proxy-context-unload", listener);
+    });
+    await extension.terminateBackground();
+    await promiseProxyContextUnloaded;
+    equal(
+      extension.extension.backgroundContext,
+      undefined,
+      "Initial background context should have been terminated as expected"
+    );
+  }
+
+  await extension.unload();
+  clearLastPendingRequest();
+  await promiseRequestCompleted;
+}
+
+add_task(
+  {
+    pref_set: [["extensions.eventPages.enabled", true]],
+  },
+  async function test_idletimeout_on_active_streamfilter_mv2_eventpage() {
+    await test_idletimeout_on_streamfilter({
+      manifest_version: 2,
+      requestUrlPath: "pending_request",
+      expectStreamFilterStop: false,
+      expectResetIdle: true,
+    });
+  }
+);
+
+add_task(
+  {
+    pref_set: [["extensions.manifestV3.enabled", true]],
+  },
+  async function test_idletimeout_on_active_streamfilter_mv3() {
+    await test_idletimeout_on_streamfilter({
+      manifest_version: 3,
+      requestUrlPath: "pending_request",
+      expectStreamFilterStop: false,
+      expectResetIdle: true,
+    });
+  }
+);
+
+add_task(
+  {
+    pref_set: [["extensions.eventPages.enabled", true]],
+  },
+  async function test_idletimeout_on_inactive_streamfilter_mv2_eventpage() {
+    await test_idletimeout_on_streamfilter({
+      manifest_version: 2,
+      requestUrlPath: "completed_request",
+      expectStreamFilterStop: true,
+      expectResetIdle: false,
+    });
+  }
+);
+
+add_task(
+  {
+    pref_set: [["extensions.manifestV3.enabled", true]],
+  },
+  async function test_idletimeout_on_inactive_streamfilter_mv3() {
+    await test_idletimeout_on_streamfilter({
+      manifest_version: 3,
+      requestUrlPath: "completed_request",
+      expectStreamFilterStop: true,
+      expectResetIdle: false,
+    });
+  }
+);
+
+async function test_create_new_streamfilter_while_suspending({
+  manifest_version,
+}) {
+  const extension = ExtensionTestUtils.loadExtension({
+    async background() {
+      let interceptedRequestId;
+      let resolvePendingWebRequest;
+
+      browser.runtime.onSuspend.addListener(async () => {
+        await browser.test.assertThrows(
+          () => browser.webRequest.filterResponseData(interceptedRequestId),
+          /forbidden while background extension global is suspending/,
+          "Got the expected exception raised from filterResponseData calls while suspending"
+        );
+        browser.test.sendMessage("suspend-listener");
+      });
+
+      browser.runtime.onSuspendCanceled.addListener(async () => {
+        // Once onSuspendCanceled is emitted, filterResponseData
+        // is expected to don't throw.
+        const filter =
+          browser.webRequest.filterResponseData(interceptedRequestId);
+        resolvePendingWebRequest();
+        filter.onstop = () => {
+          filter.disconnect();
+          browser.test.sendMessage("suspend-canceled-listener");
+        };
+      });
+
+      browser.webRequest.onBeforeRequest.addListener(
+        request => {
+          browser.test.log(`webRequest request intercepted: ${request.url}`);
+          interceptedRequestId = request.requestId;
+          return new Promise(resolve => {
+            resolvePendingWebRequest = resolve;
+            browser.test.sendMessage("webrequest-listener:done");
+          });
+        },
+        {
+          urls: [`http://example.com/completed_request`],
+        },
+        ["blocking"]
+      );
+      browser.test.sendMessage("bg:ready");
+    },
+
+    useAddonManager: "temporary",
+    manifest: {
+      manifest_version,
+      background: manifest_version >= 3 ? {} : { persistent: false },
+      granted_host_permissions: manifest_version >= 3,
+      permissions:
+        manifest_version >= 3
+          ? ["webRequest", "webRequestBlocking", "webRequestFilterResponse"]
+          : ["webRequest", "webRequestBlocking"],
+      // host_permissions are merged with permissions on a MV2 test extension.
+      host_permissions: ["http://example.com/*"],
+    },
+  });
+
+  await extension.startup();
+  await extension.awaitMessage("bg:ready");
+  const { contextId } = extension.extension.backgroundContext;
+  notEqual(contextId, undefined, "Got a contextId for the background context");
+
+  info("Trigger a webRequest");
+  ExtensionTestUtils.fetch(
+    "http://example.com/",
+    `http://example.com/completed_request`
+  );
+
+  info("Wait for the web request to be intercepted and suspended");
+  await extension.awaitMessage("webrequest-listener:done");
+
+  info("Terminate the background script (simulated idle timeout)");
+
+  extension.terminateBackground({ disableResetIdleForTest: true });
+  await extension.awaitMessage("suspend-listener");
+
+  info("Simulated idle timeout canceled");
+  extension.extension.emit("background-script-reset-idle");
+  await extension.awaitMessage("suspend-canceled-listener");
+
+  await extension.unload();
+}
+
+add_task(
+  {
+    pref_set: [["extensions.eventPages.enabled", true]],
+  },
+  async function test_error_creating_new_streamfilter_while_suspending_mv2_eventpage() {
+    await test_create_new_streamfilter_while_suspending({
+      manifest_version: 2,
+    });
+  }
+);
+
+add_task(
+  {
+    pref_set: [["extensions.manifestV3.enabled", true]],
+  },
+  async function test_error_creating_new_streamfilter_while_suspending_mv3() {
+    await test_create_new_streamfilter_while_suspending({
+      manifest_version: 3,
+    });
+  }
+);
diff --git a/toolkit/components/extensions/test/xpcshell/test_ext_webRequest_filterResponseData.js b/toolkit/components/extensions/test/xpcshell/test_ext_webRequest_filterResponseData.js
new file mode 100644
index 0000000000..0b826be08f
--- /dev/null
+++ b/toolkit/components/extensions/test/xpcshell/test_ext_webRequest_filterResponseData.js
@@ -0,0 +1,607 @@
+"use strict";
+
+const HOSTS = new Set(["example.com", "example.org", "example.net"]);
+
+const server = createHttpServer({ hosts: HOSTS });
+
+const FETCH_ORIGIN = "http://example.com/dummy";
+
+server.registerDirectory("/data/", do_get_file("data"));
+
+server.registerPathHandler("/redirect", (request, response) => {
+  let params = new URLSearchParams(request.queryString);
+  response.setStatusLine(request.httpVersion, 302, "Moved Temporarily");
+  response.setHeader("Location", params.get("redirect_uri"));
+  response.setHeader("Access-Control-Allow-Origin", "*");
+});
+
+server.registerPathHandler("/redirect301", (request, response) => {
+  let params = new URLSearchParams(request.queryString);
+  response.setStatusLine(request.httpVersion, 301, "Moved Permanently");
+  response.setHeader("Location", params.get("redirect_uri"));
+  response.setHeader("Access-Control-Allow-Origin", "*");
+});
+
+server.registerPathHandler("/script302.js", (request, response) => {
+  response.setStatusLine(request.httpVersion, 302, "Moved Temporarily");
+  response.setHeader("Location", "http://example.com/script.js");
+});
+
+server.registerPathHandler("/script.js", (request, response) => {
+  response.setStatusLine(request.httpVersion, 200, "OK");
+  response.setHeader("Content-Type", "application/javascript");
+  response.write(String.raw`console.log("HELLO!");`);
+});
+
+server.registerPathHandler("/302.html", (request, response) => {
+  response.setStatusLine(request.httpVersion, 200, "OK");
+  response.setHeader("Content-Type", "text/html");
+  response.write(String.raw`
+    <script type="application/javascript" src="http://example.com/script302.js"></script>
+  `);
+});
+
+server.registerPathHandler("/dummy", (request, response) => {
+  response.setStatusLine(request.httpVersion, 200, "OK");
+  response.setHeader("Access-Control-Allow-Origin", "*");
+  response.write("ok");
+});
+
+server.registerPathHandler("/dummy.xhtml", (request, response) => {
+  response.setStatusLine(request.httpVersion, 200, "OK");
+  response.setHeader("Content-Type", "application/xhtml+xml");
+  response.write(String.raw`<?xml version="1.0"?>
+    <html xml:lang="en" xmlns="http://www.w3.org/1999/xhtml">
+      <head/>
+      <body/>
+    </html>
+  `);
+});
+
+server.registerPathHandler("/lorem.html.gz", async (request, response) => {
+  response.processAsync();
+
+  response.setHeader(
+    "Content-Type",
+    "Content-Type: text/html; charset=utf-8",
+    false
+  );
+  response.setHeader("Content-Encoding", "gzip", false);
+
+  let data = await IOUtils.read(do_get_file("data/lorem.html.gz").path);
+  response.write(String.fromCharCode(...data));
+
+  response.finish();
+});
+
+// Test re-encoding the data stream for bug 1590898.
+add_task(async function test_stream_encoding_data() {
+  let extension = ExtensionTestUtils.loadExtension({
+    background() {
+      browser.webRequest.onBeforeRequest.addListener(
+        request => {
+          let filter = browser.webRequest.filterResponseData(request.requestId);
+          let decoder = new TextDecoder("utf-8");
+          let encoder = new TextEncoder();
+
+          filter.ondata = event => {
+            let str = decoder.decode(event.data, { stream: true });
+            filter.write(encoder.encode(str));
+            filter.disconnect();
+          };
+        },
+        {
+          urls: ["http://example.com/lorem.html.gz"],
+          types: ["main_frame"],
+        },
+        ["blocking"]
+      );
+    },
+
+    manifest: {
+      permissions: ["webRequest", "webRequestBlocking", "http://example.com/"],
+    },
+  });
+
+  await extension.startup();
+
+  let contentPage = await ExtensionTestUtils.loadContentPage(
+    "http://example.com/lorem.html.gz"
+  );
+
+  let content = await contentPage.spawn([], () => {
+    return this.content.document.body.textContent;
+  });
+
+  ok(
+    content.includes("Lorem ipsum dolor sit amet"),
+    `expected content received`
+  );
+
+  await contentPage.close();
+  await extension.unload();
+});
+
+// Tests that the stream filter request is added to the document's load
+// group, and blocks an XML document's load event until after the filter
+// stops sending data.
+add_task(async function test_xml_document_loadgroup_blocking() {
+  let extension = ExtensionTestUtils.loadExtension({
+    background() {
+      browser.webRequest.onBeforeRequest.addListener(
+        request => {
+          let filter = browser.webRequest.filterResponseData(request.requestId);
+
+          let data = [];
+          filter.ondata = event => {
+            data.push(event.data);
+          };
+          filter.onstop = async () => {
+            browser.test.sendMessage("phase", "original-onstop");
+
+            // Make a few trips through the event loop.
+            for (let i = 0; i < 10; i++) {
+              await new Promise(resolve => setTimeout(resolve, 0));
+            }
+
+            for (let buffer of data) {
+              filter.write(buffer);
+            }
+            browser.test.sendMessage("phase", "filter-onstop");
+            filter.close();
+          };
+        },
+        {
+          urls: ["http://example.com/dummy.xhtml"],
+        },
+        ["blocking"]
+      );
+    },
+
+    files: {
+      "content_script.js"() {
+        browser.test.sendMessage("phase", "content-script-start");
+        window.addEventListener(
+          "DOMContentLoaded",
+          () => {
+            browser.test.sendMessage("phase", "content-script-domload");
+          },
+          { once: true }
+        );
+        window.addEventListener(
+          "load",
+          () => {
+            browser.test.sendMessage("phase", "content-script-load");
+          },
+          { once: true }
+        );
+      },
+    },
+
+    manifest: {
+      permissions: ["webRequest", "webRequestBlocking", "http://example.com/"],
+
+      content_scripts: [
+        {
+          matches: ["http://example.com/dummy.xhtml"],
+          run_at: "document_start",
+          js: ["content_script.js"],
+        },
+      ],
+    },
+  });
+
+  await extension.startup();
+
+  const EXPECTED = [
+    "original-onstop",
+    "filter-onstop",
+    "content-script-start",
+    "content-script-domload",
+    "content-script-load",
+  ];
+
+  let done = new Promise(resolve => {
+    let phases = [];
+    extension.onMessage("phase", phase => {
+      phases.push(phase);
+      if (phases.length === EXPECTED.length) {
+        resolve(phases);
+      }
+    });
+  });
+
+  let contentPage = await ExtensionTestUtils.loadContentPage(
+    "http://example.com/dummy.xhtml"
+  );
+
+  deepEqual(await done, EXPECTED, "Things happened, and in the right order");
+
+  await contentPage.close();
+  await extension.unload();
+});
+
+add_task(async function test_filter_content_fetch() {
+  let extension = ExtensionTestUtils.loadExtension({
+    background() {
+      let pending = [];
+
+      browser.webRequest.onBeforeRequest.addListener(
+        data => {
+          let filter = browser.webRequest.filterResponseData(data.requestId);
+
+          let url = new URL(data.url);
+
+          if (url.searchParams.get("redirect_uri")) {
+            pending.push(
+              new Promise(resolve => {
+                filter.onerror = resolve;
+              }).then(() => {
+                browser.test.assertEq(
+                  "Channel redirected",
+                  filter.error,
+                  "Got correct error for redirected filter"
+                );
+              })
+            );
+          }
+
+          filter.onstart = () => {
+            filter.write(new TextEncoder().encode(data.url));
+          };
+          filter.ondata = event => {
+            let str = new TextDecoder().decode(event.data);
+            browser.test.assertEq(
+              "ok",
+              str,
+              `Got unfiltered data for ${data.url}`
+            );
+          };
+          filter.onstop = () => {
+            filter.close();
+          };
+        },
+        {
+          urls: ["<all_urls>"],
+        },
+        ["blocking"]
+      );
+
+      browser.test.onMessage.addListener(async msg => {
+        if (msg === "done") {
+          await Promise.all(pending);
+          browser.test.notifyPass("stream-filter");
+        }
+      });
+    },
+
+    manifest: {
+      permissions: [
+        "webRequest",
+        "webRequestBlocking",
+        "http://example.com/",
+        "http://example.org/",
+      ],
+    },
+  });
+
+  await extension.startup();
+
+  let results = [
+    ["http://example.com/dummy", "http://example.com/dummy"],
+    ["http://example.org/dummy", "http://example.org/dummy"],
+    ["http://example.net/dummy", "ok"],
+    [
+      "http://example.com/redirect?redirect_uri=http://example.com/dummy",
+      "http://example.com/dummy",
+    ],
+    [
+      "http://example.com/redirect?redirect_uri=http://example.org/dummy",
+      "http://example.org/dummy",
+    ],
+    ["http://example.com/redirect?redirect_uri=http://example.net/dummy", "ok"],
+    [
+      "http://example.net/redirect?redirect_uri=http://example.com/dummy",
+      "http://example.com/dummy",
+    ],
+  ].map(async ([url, expectedResponse]) => {
+    let text = await ExtensionTestUtils.fetch(FETCH_ORIGIN, url);
+    equal(text, expectedResponse, `Expected response for ${url}`);
+  });
+
+  await Promise.all(results);
+
+  extension.sendMessage("done");
+  await extension.awaitFinish("stream-filter");
+  await extension.unload();
+});
+
+add_task(async function test_filter_301() {
+  let extension = ExtensionTestUtils.loadExtension({
+    background() {
+      browser.webRequest.onHeadersReceived.addListener(
+        data => {
+          if (data.statusCode !== 200) {
+            return;
+          }
+          let filter = browser.webRequest.filterResponseData(data.requestId);
+
+          filter.onstop = () => {
+            filter.close();
+            browser.test.notifyPass("stream-filter");
+          };
+          filter.onerror = () => {
+            browser.test.fail(`unexpected ${filter.error}`);
+          };
+        },
+        {
+          urls: ["<all_urls>"],
+        },
+        ["blocking"]
+      );
+    },
+
+    manifest: {
+      permissions: [
+        "webRequest",
+        "webRequestBlocking",
+        "http://example.com/",
+        "http://example.org/",
+      ],
+    },
+  });
+
+  await extension.startup();
+
+  let contentPage = await ExtensionTestUtils.loadContentPage(
+    "http://example.com/redirect301?redirect_uri=http://example.org/dummy"
+  );
+
+  await extension.awaitFinish("stream-filter");
+
+  await contentPage.close();
+  await extension.unload();
+});
+
+add_task(async function test_filter_302() {
+  let extension = ExtensionTestUtils.loadExtension({
+    background() {
+      browser.webRequest.onBeforeRequest.addListener(
+        details => {
+          let filter = browser.webRequest.filterResponseData(details.requestId);
+          browser.test.sendMessage("filter-created");
+
+          filter.ondata = event => {
+            const script = "forceError();";
+            filter.write(new Uint8Array(new TextEncoder().encode(script)));
+            filter.close();
+            browser.test.sendMessage("filter-ondata");
+          };
+
+          filter.onerror = () => {
+            browser.test.assertEq(filter.error, "Channel redirected");
+            browser.test.sendMessage("filter-redirect");
+          };
+        },
+        {
+          urls: ["http://example.com/*.js"],
+        },
+        ["blocking"]
+      );
+    },
+
+    manifest: {
+      permissions: ["webRequest", "webRequestBlocking", "http://example.com/"],
+    },
+  });
+
+  await extension.startup();
+
+  let { messages } = await promiseConsoleOutput(async () => {
+    let contentPage = await ExtensionTestUtils.loadContentPage(
+      "http://example.com/302.html"
+    );
+
+    await extension.awaitMessage("filter-created");
+    await extension.awaitMessage("filter-redirect");
+    await extension.awaitMessage("filter-created");
+    await extension.awaitMessage("filter-ondata");
+    await contentPage.close();
+  });
+  AddonTestUtils.checkMessages(messages, {
+    expected: [{ message: /forceError is not defined/ }],
+  });
+
+  await extension.unload();
+});
+
+add_task(async function test_alternate_cached_data() {
+  Services.prefs.setBoolPref("dom.script_loader.bytecode_cache.enabled", true);
+  Services.prefs.setIntPref("dom.script_loader.bytecode_cache.strategy", -1);
+
+  let extension = ExtensionTestUtils.loadExtension({
+    background() {
+      browser.webRequest.onBeforeRequest.addListener(
+        details => {
+          let filter = browser.webRequest.filterResponseData(details.requestId);
+          let decoder = new TextDecoder("utf-8");
+          let encoder = new TextEncoder();
+
+          filter.ondata = event => {
+            let str = decoder.decode(event.data, { stream: true });
+            filter.write(encoder.encode(str));
+            filter.disconnect();
+            browser.test.assertTrue(
+              str.startsWith(`"use strict";`),
+              "ondata received decoded data"
+            );
+            browser.test.sendMessage("onBeforeRequest");
+          };
+
+          filter.onerror = () => {
+            // onBeforeRequest will always beat the cache race, so we should always
+            // get valid data in ondata.
+            browser.test.fail("error-received", filter.error);
+          };
+        },
+        {
+          urls: ["http://example.com/data/file_script_good.js"],
+        },
+        ["blocking"]
+      );
+      browser.webRequest.onHeadersReceived.addListener(
+        details => {
+          let filter = browser.webRequest.filterResponseData(details.requestId);
+          let decoder = new TextDecoder("utf-8");
+          let encoder = new TextEncoder();
+
+          // Because cache is always a race, intermittently we will succesfully
+          // beat the cache, in which case we pass in ondata.  If cache wins,
+          // we pass in onerror.
+          // Running the test with --verify hits this cache race issue, as well
+          // it seems that the cache primarily looses on linux1804.
+          let gotone = false;
+          filter.ondata = event => {
+            browser.test.assertFalse(gotone, "cache lost the race");
+            gotone = true;
+            let str = decoder.decode(event.data, { stream: true });
+            filter.write(encoder.encode(str));
+            filter.disconnect();
+            browser.test.assertTrue(
+              str.startsWith(`"use strict";`),
+              "ondata received decoded data"
+            );
+            browser.test.sendMessage("onHeadersReceived");
+          };
+
+          filter.onerror = () => {
+            browser.test.assertFalse(gotone, "cache won the race");
+            gotone = true;
+            browser.test.assertEq(
+              filter.error,
+              "Channel is delivering cached alt-data"
+            );
+            browser.test.sendMessage("onHeadersReceived");
+          };
+        },
+        {
+          urls: ["http://example.com/data/file_script_bad.js"],
+        },
+        ["blocking"]
+      );
+    },
+
+    manifest: {
+      permissions: ["webRequest", "webRequestBlocking", "http://example.com/*"],
+    },
+  });
+
+  // Prime the cache so we have the script byte-cached.
+  let contentPage = await ExtensionTestUtils.loadContentPage(
+    "http://example.com/data/file_script.html"
+  );
+  await contentPage.close();
+
+  await extension.startup();
+
+  let page_cached = await await ExtensionTestUtils.loadContentPage(
+    "http://example.com/data/file_script.html"
+  );
+  await Promise.all([
+    extension.awaitMessage("onBeforeRequest"),
+    extension.awaitMessage("onHeadersReceived"),
+  ]);
+  await page_cached.close();
+  await extension.unload();
+
+  Services.prefs.clearUserPref("dom.script_loader.bytecode_cache.enabled");
+  Services.prefs.clearUserPref("dom.script_loader.bytecode_cache.strategy");
+});
+
+add_task(async function test_webRequestFilterResponse_permission() {
+  function background() {
+    browser.test.onMessage.addListener(async (msg, ...args) => {
+      if (msg !== "testFilterResponseData") {
+        browser.test.fail(`Unexpected test message: ${msg}`);
+        return;
+      }
+
+      const [{ expectMissingPermissionError }] = args;
+
+      if (expectMissingPermissionError) {
+        browser.test.assertThrows(
+          () => browser.webRequest.filterResponseData("fake-response-id"),
+          /Missing required "webRequestFilterResponse" permission/,
+          "Expected missing webRequestFilterResponse permission error"
+        );
+      } else {
+        // Expect the generic error raised on invalid response id
+        // if the missing permission error isn't expected.
+        browser.test.assertTrue(
+          browser.webRequest.filterResponseData("fake-response-id"),
+          "Expected no missing webRequestFilterResponse permission error"
+        );
+      }
+
+      browser.test.notifyPass();
+    });
+  }
+
+  info(
+    "Verify MV2 extension does not require webRequestFilterResponse permission"
+  );
+  const extMV2 = ExtensionTestUtils.loadExtension({
+    background,
+    manifest: {
+      manifest_version: 2,
+      permissions: ["webRequest", "webRequestBlocking"],
+    },
+  });
+
+  await extMV2.startup();
+  extMV2.sendMessage("testFilterResponseData", {
+    expectMissingPermissionError: false,
+  });
+  await extMV2.awaitFinish();
+  await extMV2.unload();
+
+  info(
+    "Verify filterResponseData throws on MV3 extension without webRequestFilterResponse permission"
+  );
+  const extMV3NoPerm = ExtensionTestUtils.loadExtension({
+    background,
+    manifest: {
+      manifest_version: 3,
+      permissions: ["webRequest", "webRequestBlocking"],
+    },
+  });
+
+  await extMV3NoPerm.startup();
+  extMV3NoPerm.sendMessage("testFilterResponseData", {
+    expectMissingPermissionError: true,
+  });
+  await extMV3NoPerm.awaitFinish();
+  await extMV3NoPerm.unload();
+
+  info(
+    "Verify filterResponseData does not throw on MV3 extension without webRequestFilterResponse permission"
+  );
+  const extMV3WithPerm = ExtensionTestUtils.loadExtension({
+    background,
+    manifest: {
+      manifest_version: 3,
+      permissions: [
+        "webRequest",
+        "webRequestBlocking",
+        "webRequestFilterResponse",
+      ],
+    },
+  });
+
+  await extMV3WithPerm.startup();
+  extMV3WithPerm.sendMessage("testFilterResponseData", {
+    expectMissingPermissionError: false,
+  });
+  await extMV3WithPerm.awaitFinish();
+  await extMV3WithPerm.unload();
+});
diff --git a/toolkit/components/extensions/test/xpcshell/test_ext_webRequest_filterTypes.js b/toolkit/components/extensions/test/xpcshell/test_ext_webRequest_filterTypes.js
new file mode 100644
index 0000000000..be5b5ec9bf
--- /dev/null
+++ b/toolkit/components/extensions/test/xpcshell/test_ext_webRequest_filterTypes.js
@@ -0,0 +1,87 @@
+"use strict";
+
+AddonTestUtils.init(this);
+
+AddonTestUtils.createAppInfo(
+  "xpcshell@tests.mozilla.org",
+  "XPCShell",
+  "1",
+  "42"
+);
+
+const server = createHttpServer({ hosts: ["example.com"] });
+server.registerPathHandler("/", (request, response) => {
+  response.setHeader("Content-Tpe", "text/plain", false);
+  response.write("OK");
+});
+
+add_task(async function test_all_webRequest_ResourceTypes() {
+  let extension = ExtensionTestUtils.loadExtension({
+    manifest: {
+      permissions: ["webRequest", "webRequestBlocking", "*://example.com/*"],
+    },
+    background() {
+      browser.test.onMessage.addListener(async msg => {
+        browser.webRequest[msg.event].addListener(
+          () => {},
+          { urls: ["*://example.com/*"], ...msg.filter },
+          ["blocking"]
+        );
+        // Call an API method implemented in the parent process to
+        // be sure that the webRequest listener has been registered
+        // in the parent process as well.
+        await browser.runtime.getBrowserInfo();
+        browser.test.sendMessage(`webRequest-listener-registered`);
+      });
+    },
+  });
+
+  await extension.startup();
+
+  const { Schemas } = ChromeUtils.importESModule(
+    "resource://gre/modules/Schemas.sys.mjs"
+  );
+  const webRequestSchema = Schemas.privilegedSchemaJSON
+    .get("chrome://extensions/content/schemas/web_request.json")
+    .deserialize({});
+  const ResourceType = webRequestSchema[1].types.filter(
+    type => type.id == "ResourceType"
+  )[0];
+  ok(
+    ResourceType && ResourceType.enum,
+    "Found ResourceType in the web_request.json schema"
+  );
+  info(
+    "Register webRequest.onBeforeRequest event listener for all supported ResourceType"
+  );
+
+  let { messages } = await promiseConsoleOutput(async () => {
+    ExtensionTestUtils.failOnSchemaWarnings(false);
+    extension.sendMessage({
+      event: "onBeforeRequest",
+      filter: {
+        // Verify that the resourceType not supported is going to be ignored
+        // and all the ones supported does not trigger a ChannelWrapper.matches
+        // exception once the listener is being triggered.
+        types: [].concat(ResourceType.enum, "not-supported-resource-type"),
+      },
+    });
+    await extension.awaitMessage("webRequest-listener-registered");
+    ExtensionTestUtils.failOnSchemaWarnings();
+
+    await ExtensionTestUtils.fetch(
+      "http://example.com/dummy",
+      "http://example.com"
+    );
+  });
+
+  AddonTestUtils.checkMessages(messages, {
+    expected: [
+      { message: /Warning processing types: .* "not-supported-resource-type"/ },
+    ],
+    forbidden: [{ message: /JavaScript Error: "ChannelWrapper.matches/ }],
+  });
+  info("No ChannelWrapper.matches errors have been logged");
+
+  await extension.unload();
+});
diff --git a/toolkit/components/extensions/test/xpcshell/test_ext_webRequest_filter_urls.js b/toolkit/components/extensions/test/xpcshell/test_ext_webRequest_filter_urls.js
new file mode 100644
index 0000000000..af0d8594f4
--- /dev/null
+++ b/toolkit/components/extensions/test/xpcshell/test_ext_webRequest_filter_urls.js
@@ -0,0 +1,35 @@
+/* Any copyright is dedicated to the Public Domain.
+http://creativecommons.org/publicdomain/zero/1.0/ */
+
+"use strict";
+
+AddonTestUtils.init(this);
+
+add_task(async function test_invalid_urls_in_webRequest_filter() {
+  let extension = ExtensionTestUtils.loadExtension({
+    manifest: {
+      permissions: ["webRequest", "https://example.com/*"],
+    },
+    background() {
+      browser.webRequest.onBeforeRequest.addListener(() => {}, {
+        urls: ["htt:/example.com/*"],
+        types: ["main_frame"],
+      });
+    },
+  });
+  let { messages } = await promiseConsoleOutput(async () => {
+    await extension.startup();
+    await extension.unload();
+  });
+  AddonTestUtils.checkMessages(
+    messages,
+    {
+      expected: [
+        {
+          message: /ExtensionError: Invalid url pattern: htt:\/example.com\/*/,
+        },
+      ],
+    },
+    true
+  );
+});
diff --git a/toolkit/components/extensions/test/xpcshell/test_ext_webRequest_from_extension_page.js b/toolkit/components/extensions/test/xpcshell/test_ext_webRequest_from_extension_page.js
new file mode 100644
index 0000000000..7a648d7e31
--- /dev/null
+++ b/toolkit/components/extensions/test/xpcshell/test_ext_webRequest_from_extension_page.js
@@ -0,0 +1,57 @@
+"use strict";
+
+const server = createHttpServer({ hosts: ["example.com"] });
+server.registerPathHandler("/HELLO", (req, res) => {
+  res.write("BYE");
+});
+
+add_task(async function request_from_extension_page() {
+  let extension = ExtensionTestUtils.loadExtension({
+    manifest: {
+      permissions: ["http://example.com/", "webRequest", "webRequestBlocking"],
+    },
+    files: {
+      "tab.html": `<!DOCTYPE html><script src="tab.js"></script>`,
+      "tab.js": async function () {
+        browser.webRequest.onHeadersReceived.addListener(
+          details => {
+            let { responseHeaders } = details;
+            responseHeaders.push({
+              name: "X-Added-by-Test",
+              value: "TheValue",
+            });
+            return { responseHeaders };
+          },
+          {
+            urls: ["http://example.com/HELLO"],
+          },
+          ["blocking", "responseHeaders"]
+        );
+
+        // Ensure that listener is registered (workaround for bug 1300234).
+        await browser.runtime.getPlatformInfo();
+
+        let response = await fetch("http://example.com/HELLO");
+        browser.test.assertEq(
+          "TheValue",
+          response.headers.get("X-added-by-test"),
+          "expected response header from webRequest listener"
+        );
+        browser.test.assertEq(
+          await response.text(),
+          "BYE",
+          "Expected response from server"
+        );
+        browser.test.sendMessage("done");
+      },
+    },
+  });
+  await extension.startup();
+  let contentPage = await ExtensionTestUtils.loadContentPage(
+    `moz-extension://${extension.uuid}/tab.html`,
+    { extension }
+  );
+  await extension.awaitMessage("done");
+  await contentPage.close();
+  await extension.unload();
+});
diff --git a/toolkit/components/extensions/test/xpcshell/test_ext_webRequest_host.js b/toolkit/components/extensions/test/xpcshell/test_ext_webRequest_host.js
new file mode 100644
index 0000000000..425d83560d
--- /dev/null
+++ b/toolkit/components/extensions/test/xpcshell/test_ext_webRequest_host.js
@@ -0,0 +1,99 @@
+"use strict";
+
+const HOSTS = new Set(["example.com", "example.org"]);
+
+const server = createHttpServer({ hosts: HOSTS });
+
+const BASE_URL = "http://example.com";
+const FETCH_ORIGIN = "http://example.com/dummy";
+
+server.registerPathHandler("/return_headers.sjs", (request, response) => {
+  response.setHeader("Content-Type", "text/plain", false);
+
+  let headers = {};
+  for (let { data: header } of request.headers) {
+    headers[header] = request.getHeader(header);
+  }
+
+  response.write(JSON.stringify(headers));
+});
+
+server.registerPathHandler("/dummy", (request, response) => {
+  response.setStatusLine(request.httpVersion, 200, "OK");
+  response.write("ok");
+});
+
+function getExtension(permission = "<all_urls>") {
+  return ExtensionTestUtils.loadExtension({
+    manifest: {
+      permissions: ["webRequest", "webRequestBlocking", permission],
+    },
+    background() {
+      browser.webRequest.onBeforeSendHeaders.addListener(
+        details => {
+          details.requestHeaders.push({ name: "Host", value: "example.org" });
+          return { requestHeaders: details.requestHeaders };
+        },
+        { urls: ["<all_urls>"] },
+        ["blocking", "requestHeaders"]
+      );
+    },
+  });
+}
+
+add_task(async function test_host_header_accepted() {
+  let extension = getExtension();
+  await extension.startup();
+  let headers = JSON.parse(
+    await ExtensionTestUtils.fetch(
+      FETCH_ORIGIN,
+      `${BASE_URL}/return_headers.sjs`
+    )
+  );
+
+  equal(headers.host, "example.org", "Host header was set on request");
+
+  await extension.unload();
+});
+
+add_task(async function test_host_header_denied() {
+  let extension = getExtension(`${BASE_URL}/`);
+
+  await extension.startup();
+
+  let headers = JSON.parse(
+    await ExtensionTestUtils.fetch(
+      FETCH_ORIGIN,
+      `${BASE_URL}/return_headers.sjs`
+    )
+  );
+
+  equal(headers.host, "example.com", "Host header was not set on request");
+
+  await extension.unload();
+});
+
+add_task(async function test_host_header_restricted() {
+  Services.prefs.setCharPref(
+    "extensions.webextensions.restrictedDomains",
+    "example.org"
+  );
+  registerCleanupFunction(() => {
+    Services.prefs.clearUserPref("extensions.webextensions.restrictedDomains");
+  });
+
+  let extension = getExtension();
+
+  await extension.startup();
+
+  let headers = JSON.parse(
+    await ExtensionTestUtils.fetch(
+      FETCH_ORIGIN,
+      `${BASE_URL}/return_headers.sjs`
+    )
+  );
+
+  equal(headers.host, "example.com", "Host header was not set on request");
+
+  await extension.unload();
+});
diff --git a/toolkit/components/extensions/test/xpcshell/test_ext_webRequest_incognito.js b/toolkit/components/extensions/test/xpcshell/test_ext_webRequest_incognito.js
new file mode 100644
index 0000000000..fe3b6a8cf8
--- /dev/null
+++ b/toolkit/components/extensions/test/xpcshell/test_ext_webRequest_incognito.js
@@ -0,0 +1,88 @@
+"use strict";
+
+const server = createHttpServer({ hosts: ["example.com"] });
+
+server.registerPathHandler("/dummy", (request, response) => {
+  response.setStatusLine(request.httpVersion, 200, "OK");
+  response.setHeader("Content-Type", "text/html", false);
+  response.write("<!DOCTYPE html><html></html>");
+});
+
+add_task(async function test_incognito_webrequest_access() {
+  let pb_extension = ExtensionTestUtils.loadExtension({
+    incognitoOverride: "spanning",
+    manifest: {
+      permissions: ["webRequest", "webRequestBlocking", "<all_urls>"],
+    },
+    background() {
+      browser.webRequest.onBeforeRequest.addListener(
+        async details => {
+          browser.test.assertTrue(details.incognito, "incognito flag is set");
+        },
+        { urls: ["<all_urls>"], incognito: true },
+        ["blocking"]
+      );
+
+      browser.webRequest.onBeforeRequest.addListener(
+        async details => {
+          browser.test.assertFalse(
+            details.incognito,
+            "incognito flag is not set"
+          );
+          browser.test.notifyPass("webRequest.spanning");
+        },
+        { urls: ["<all_urls>"], incognito: false },
+        ["blocking"]
+      );
+    },
+  });
+
+  // Bug 1715801: Re-enable pbm portion on GeckoView
+  if (AppConstants.platform == "android") {
+    Services.prefs.setBoolPref("dom.security.https_first_pbm", false);
+  }
+
+  await pb_extension.startup();
+
+  let extension = ExtensionTestUtils.loadExtension({
+    manifest: {
+      permissions: ["webRequest", "webRequestBlocking", "<all_urls>"],
+    },
+    background() {
+      browser.webRequest.onBeforeRequest.addListener(
+        async details => {
+          browser.test.assertFalse(
+            details.incognito,
+            "incognito flag is not set"
+          );
+          browser.test.notifyPass("webRequest");
+        },
+        { urls: ["<all_urls>"] },
+        ["blocking"]
+      );
+    },
+  });
+  // Load non-incognito extension to check that private requests are invisible to it.
+  await extension.startup();
+
+  let contentPage = await ExtensionTestUtils.loadContentPage(
+    "http://example.com/dummy",
+    { privateBrowsing: true }
+  );
+  await contentPage.close();
+
+  contentPage = await ExtensionTestUtils.loadContentPage(
+    "http://example.com/dummy"
+  );
+  await extension.awaitFinish("webRequest");
+  await pb_extension.awaitFinish("webRequest.spanning");
+  await contentPage.close();
+
+  await pb_extension.unload();
+  await extension.unload();
+
+  // Bug 1715801: Re-enable pbm portion on GeckoView
+  if (AppConstants.platform == "android") {
+    Services.prefs.clearUserPref("dom.security.https_first_pbm");
+  }
+});
diff --git a/toolkit/components/extensions/test/xpcshell/test_ext_webRequest_mergecsp.js b/toolkit/components/extensions/test/xpcshell/test_ext_webRequest_mergecsp.js
new file mode 100644
index 0000000000..402f54ca5e
--- /dev/null
+++ b/toolkit/components/extensions/test/xpcshell/test_ext_webRequest_mergecsp.js
@@ -0,0 +1,545 @@
+/* -*- Mode: indent-tabs-mode: nil; js-indent-level: 2 -*- */
+/* vim: set sts=2 sw=2 et tw=80: */
+"use strict";
+
+Services.prefs.setBoolPref("extensions.manifestV3.enabled", true);
+
+AddonTestUtils.init(this);
+AddonTestUtils.createAppInfo(
+  "xpcshell@tests.mozilla.org",
+  "XPCShell",
+  "1",
+  "43"
+);
+
+const server = createHttpServer({
+  hosts: ["example.net", "example.com"],
+});
+server.registerDirectory("/data/", do_get_file("data"));
+
+const pageContent = `<!DOCTYPE html>
+  <script id="script1" src="/data/file_script_good.js"></script>
+  <script id="script3" src="//example.com/data/file_script_bad.js"></script>
+  <img id="img1" src='/data/file_image_good.png'>
+  <img id="img3" src='//example.com/data/file_image_good.png'>
+`;
+
+server.registerPathHandler("/", (request, response) => {
+  response.setStatusLine(request.httpVersion, 200, "OK");
+  response.setHeader("Content-Type", "text/html");
+  if (request.queryString) {
+    response.setHeader(
+      "Content-Security-Policy",
+      decodeURIComponent(request.queryString)
+    );
+  }
+  response.write(pageContent);
+});
+
+let extensionData = {
+  manifest: {
+    permissions: ["webRequest", "webRequestBlocking", "*://example.net/*"],
+  },
+  background() {
+    let csp_value = undefined;
+    browser.test.onMessage.addListener(function (msg) {
+      csp_value = msg;
+      browser.test.sendMessage("csp-set");
+    });
+    browser.webRequest.onHeadersReceived.addListener(
+      e => {
+        browser.test.log(`onHeadersReceived ${e.requestId} ${e.url}`);
+        if (csp_value === undefined) {
+          browser.test.assertTrue(false, "extension called before CSP was set");
+        }
+        if (csp_value !== null) {
+          e.responseHeaders = e.responseHeaders.filter(
+            i => i.name.toLowerCase() != "content-security-policy"
+          );
+          if (csp_value !== "") {
+            e.responseHeaders.push({
+              name: "Content-Security-Policy",
+              value: csp_value,
+            });
+          }
+        }
+        return { responseHeaders: e.responseHeaders };
+      },
+      { urls: ["*://example.net/*"] },
+      ["blocking", "responseHeaders"]
+    );
+  },
+};
+
+/**
+ * @typedef {object} ExpectedResourcesToLoad
+ * @property {object} img1_loaded    image from a first party origin.
+ * @property {object} img3_loaded    image from a third party origin.
+ * @property {object} script1_loaded script from a first party origin.
+ * @property {object} script3_loaded script from a third party origin.
+ * @property {object} [cspJSON] expected final document CSP (in JSON format, See dom/webidl/CSPDictionaries.webidl).
+ */
+
+/**
+ * Test a combination of Content Security Policies against first/third party images/scripts.
+ *
+ * @param {object} opts
+ * @param {string} opts.site_csp The CSP to be sent by the site, or null.
+ * @param {string} opts.ext1_csp The CSP to be sent by the first extension,
+ *                          "" to remove the header, or null to not modify it.
+ * @param {string} opts.ext2_csp The CSP to be sent by the first extension,
+ *                          "" to remove the header, or null to not modify it.
+ * @param {ExpectedResourcesToLoad} opts.expect
+ *                          Object containing information which resources are expected to be loaded.
+ * @param {object} [opts.ext1_data] first test extension definition data (defaults to extensionData).
+ * @param {object} [opts.ext2_data] second test extension definition data (defaults to extensionData).
+ */
+async function test_csp({
+  site_csp,
+  ext1_csp,
+  ext2_csp,
+  expect,
+  ext1_data = extensionData,
+  ext2_data = extensionData,
+}) {
+  let extension1 = await ExtensionTestUtils.loadExtension(ext1_data);
+  let extension2 = await ExtensionTestUtils.loadExtension(ext2_data);
+  await extension1.startup();
+  await extension2.startup();
+  extension1.sendMessage(ext1_csp);
+  extension2.sendMessage(ext2_csp);
+  await extension1.awaitMessage("csp-set");
+  await extension2.awaitMessage("csp-set");
+
+  let csp_value = encodeURIComponent(site_csp || "");
+  let contentPage = await ExtensionTestUtils.loadContentPage(
+    `http://example.net/?${csp_value}`
+  );
+  let results = await contentPage.spawn([], async () => {
+    let img1 = this.content.document.getElementById("img1");
+    let img3 = this.content.document.getElementById("img3");
+    let cspJSON = JSON.parse(this.content.document.cspJSON);
+    return {
+      img1_loaded: img1.complete && img1.naturalWidth > 0,
+      img3_loaded: img3.complete && img3.naturalWidth > 0,
+      // Note: "good" and "bad" are just placeholders; they don't mean anything.
+      script1_loaded: !!this.content.document.getElementById("good"),
+      script3_loaded: !!this.content.document.getElementById("bad"),
+      cspJSON,
+    };
+  });
+
+  await contentPage.close();
+  await extension1.unload();
+  await extension2.unload();
+
+  let action = {
+    true: "loaded",
+    false: "blocked",
+  };
+
+  info(
+    `test_csp: From "${site_csp}" to ${JSON.stringify(
+      ext1_csp
+    )} to ${JSON.stringify(ext2_csp)}`
+  );
+
+  equal(
+    expect.img1_loaded,
+    results.img1_loaded,
+    `expected first party image to be ${action[expect.img1_loaded]}`
+  );
+  equal(
+    expect.img3_loaded,
+    results.img3_loaded,
+    `expected third party image to be ${action[expect.img3_loaded]}`
+  );
+  equal(
+    expect.script1_loaded,
+    results.script1_loaded,
+    `expected first party script to be ${action[expect.script1_loaded]}`
+  );
+  equal(
+    expect.script3_loaded,
+    results.script3_loaded,
+    `expected third party script to be ${action[expect.script3_loaded]}`
+  );
+
+  if (expect.cspJSON) {
+    Assert.deepEqual(
+      expect.cspJSON,
+      results.cspJSON["csp-policies"],
+      `Got the expected final CSP set on the content document`
+    );
+  }
+}
+
+add_setup(async () => {
+  await AddonTestUtils.promiseStartupManager();
+});
+
+// Test that merging csp header on both mv2 and mv3 extensions
+// (and combination of both).
+add_task(async function test_webRequest_mergecsp() {
+  const testCases = [
+    {
+      site_csp: "default-src *",
+      ext1_csp: "script-src 'none'",
+      ext2_csp: null,
+      expect: {
+        img1_loaded: true,
+        img3_loaded: true,
+        script1_loaded: false,
+        script3_loaded: false,
+      },
+    },
+    {
+      site_csp: null,
+      ext1_csp: "script-src 'none'",
+      ext2_csp: null,
+      expect: {
+        img1_loaded: true,
+        img3_loaded: true,
+        script1_loaded: false,
+        script3_loaded: false,
+      },
+    },
+    {
+      site_csp: "default-src *",
+      ext1_csp: "script-src 'none'",
+      ext2_csp: "img-src 'none'",
+      expect: {
+        img1_loaded: false,
+        img3_loaded: false,
+        script1_loaded: false,
+        script3_loaded: false,
+      },
+    },
+    {
+      site_csp: null,
+      ext1_csp: "script-src 'none'",
+      ext2_csp: "img-src 'none'",
+      expect: {
+        img1_loaded: false,
+        img3_loaded: false,
+        script1_loaded: false,
+        script3_loaded: false,
+      },
+    },
+    {
+      site_csp: "default-src *",
+      ext1_csp: "img-src example.com",
+      ext2_csp: "img-src example.org",
+      expect: {
+        img1_loaded: false,
+        img3_loaded: false,
+        script1_loaded: true,
+        script3_loaded: true,
+      },
+    },
+  ];
+
+  const extMV2Data = { ...extensionData };
+  const extMV3Data = {
+    ...extensionData,
+    useAddonManager: "temporary",
+    manifest: {
+      ...extensionData.manifest,
+      manifest_version: 3,
+      permissions: ["webRequest", "webRequestBlocking"],
+      host_permissions: ["*://example.net/*"],
+      granted_host_permissions: true,
+    },
+  };
+
+  info("Run all test cases on ext1 MV2 and ext2 MV2");
+  for (const testCase of testCases) {
+    await test_csp({
+      ...testCase,
+      ext1_data: extMV2Data,
+      ext2_data: extMV2Data,
+    });
+  }
+
+  info("Run all test cases on ext1 MV3 and ext2 MV3");
+  for (const testCase of testCases) {
+    await test_csp({
+      ...testCase,
+      ext1_data: extMV3Data,
+      ext2_data: extMV3Data,
+    });
+  }
+
+  info("Run all test cases on ext1 MV3 and ext2 MV2");
+  for (const testCase of testCases) {
+    await test_csp({
+      ...testCase,
+      ext1_data: extMV3Data,
+      ext2_data: extMV2Data,
+    });
+  }
+
+  info("Run all test cases on ext1 MV2 and ext2 MV3");
+  for (const testCase of testCases) {
+    await test_csp({
+      ...testCase,
+      ext1_data: extMV2Data,
+      ext2_data: extMV3Data,
+    });
+  }
+});
+
+add_task(async function test_remove_and_replace_csp_mv2() {
+  // CSP removed, CSP added.
+  await test_csp({
+    site_csp: "img-src 'self'",
+    ext1_csp: "",
+    ext2_csp: "img-src example.com",
+    expect: {
+      img1_loaded: false,
+      img3_loaded: true,
+      script1_loaded: true,
+      script3_loaded: true,
+    },
+  });
+
+  // CSP removed, CSP added.
+  await test_csp({
+    site_csp: "default-src 'none'",
+    ext1_csp: "",
+    ext2_csp: "img-src example.com",
+    expect: {
+      img1_loaded: false,
+      img3_loaded: true,
+      script1_loaded: true,
+      script3_loaded: true,
+    },
+  });
+
+  // CSP replaced - regression test for bug 1635781.
+  await test_csp({
+    site_csp: "default-src 'none'",
+    ext1_csp: "img-src example.com",
+    ext2_csp: null,
+    expect: {
+      img1_loaded: false,
+      img3_loaded: true,
+      script1_loaded: true,
+      script3_loaded: true,
+    },
+  });
+
+  // CSP unchanged, CSP replaced - regression test for bug 1635781.
+  await test_csp({
+    site_csp: "default-src 'none'",
+    ext1_csp: null,
+    ext2_csp: "img-src example.com",
+    expect: {
+      img1_loaded: false,
+      img3_loaded: true,
+      script1_loaded: true,
+      script3_loaded: true,
+    },
+  });
+
+  // CSP replaced, CSP removed.
+  await test_csp({
+    site_csp: "default-src 'none'",
+    ext1_csp: "img-src example.com",
+    ext2_csp: "",
+    expect: {
+      img1_loaded: true,
+      img3_loaded: true,
+      script1_loaded: true,
+      script3_loaded: true,
+    },
+  });
+});
+
+// Test that fully replace the website csp header from an mv3 extension
+// isn't allowed and it is considered a no-op.
+add_task(async function test_remove_and_replace_csp_mv3() {
+  const extMV2Data = { ...extensionData };
+
+  const extMV3Data = {
+    ...extensionData,
+    useAddonManager: "temporary",
+    manifest: {
+      ...extensionData.manifest,
+      manifest_version: 3,
+      permissions: ["webRequest", "webRequestBlocking"],
+      host_permissions: ["*://example.net/*"],
+      granted_host_permissions: true,
+    },
+  };
+
+  await test_csp({
+    // site: CSP strict on images, lax on default and script src.
+    site_csp: "img-src 'self'",
+    // ext1: MV3 extension which return an empty CSP header (which is a no-op).
+    ext1_csp: "",
+    // ext2: MV3 extension which return a CSP header (which is expected to be merged).
+    ext2_csp: "img-src example.com",
+    expect: {
+      img1_loaded: false,
+      img3_loaded: false,
+      script1_loaded: true,
+      script3_loaded: true,
+      cspJSON: [
+        { "img-src": ["'self'"], "report-only": false },
+        { "img-src": ["http://example.com"], "report-only": false },
+      ],
+    },
+    ext1_data: extMV3Data,
+    ext2_data: extMV3Data,
+  });
+
+  await test_csp({
+    // site: CSP strict on default-src.
+    site_csp: "default-src 'none'",
+    // ext1: MV3 extension which return an empty CSP header (which is a no-op).
+    ext1_csp: "",
+    // ext2: MV3 extension which return a CSP header (which is expected to be merged).
+    ext2_csp: "img-src example.com",
+    expect: {
+      img1_loaded: false,
+      img3_loaded: false,
+      script1_loaded: false,
+      script3_loaded: false,
+      cspJSON: [
+        { "default-src": ["'none'"], "report-only": false },
+        { "img-src": ["http://example.com"], "report-only": false },
+      ],
+    },
+    ext1_data: extMV3Data,
+    ext2_data: extMV3Data,
+  });
+
+  await test_csp({
+    // site: CSP strict on default-src.
+    site_csp: "default-src 'none'",
+    // ext1: MV3 extension which return a CSP header (which is expected to be merged and to
+    // not be able to make it less strict).
+    ext1_csp: "img-src example.com",
+    // ext2: MV3 extension which leaves the header unmodified.
+    ext2_csp: null,
+    expect: {
+      img1_loaded: false,
+      img3_loaded: false,
+      script1_loaded: false,
+      script3_loaded: false,
+      cspJSON: [
+        { "default-src": ["'none'"], "report-only": false },
+        { "img-src": ["http://example.com"], "report-only": false },
+      ],
+    },
+    ext1_data: extMV3Data,
+    ext2_data: extMV3Data,
+  });
+
+  await test_csp({
+    // site: CSP strict on default-src.
+    site_csp: "default-src 'none'",
+    // ext1: MV3 extension which merges additional directive into the site csp (and can't make
+    // it less strict).
+    ext1_csp: "img-src example.com",
+    // ext2: MV3 extension which merges an empty CSP header (which is a no-op, unlike with MV2).
+    ext2_csp: "",
+    expect: {
+      img1_loaded: false,
+      img3_loaded: false,
+      script1_loaded: false,
+      script3_loaded: false,
+      cspJSON: [
+        { "default-src": ["'none'"], "report-only": false },
+        { "img-src": ["http://example.com"], "report-only": false },
+      ],
+    },
+    ext1_data: extMV3Data,
+    ext2_data: extMV3Data,
+  });
+
+  await test_csp({
+    // site: lax CSP (which is expected to be made stricted by the ext1 extension).
+    site_csp: "default-src *",
+    // ext1: MV3 extension which wants to set a stricter CSP (expected to work fine with the MV3 extension)
+    ext1_csp: "default-src 'none'",
+    // ext2: MV3 extension which leaves it unchanged.
+    ext2_csp: null,
+    expect: {
+      img1_loaded: false,
+      img3_loaded: false,
+      script1_loaded: false,
+      script3_loaded: false,
+      cspJSON: [
+        { "default-src": ["*"], "report-only": false },
+        { "default-src": ["'none'"], "report-only": false },
+      ],
+    },
+    ext1_data: extMV3Data,
+    ext2_data: extMV3Data,
+  });
+
+  await test_csp({
+    // site: CSP strict on default-src.
+    site_csp: "default-src 'none'",
+    // ext1: MV3 extension and tries to replace the strict site csp with this lax one
+    // (but as an MV3 extension that is going to be merged to the site csp and the
+    // resulting site CSP is expected to stay strict).
+    ext1_csp: "default-src *",
+    // ext2: MV3 extension which leaves it unchanged.
+    ext2_csp: null,
+    expect: {
+      // strict site csp merged with the lax one from ext1 stays strict.
+      img1_loaded: false,
+      img3_loaded: false,
+      script1_loaded: false,
+      script3_loaded: false,
+      cspJSON: [
+        { "default-src": ["'none'"], "report-only": false },
+        { "default-src": ["*"], "report-only": false },
+      ],
+    },
+    ext1_data: extMV3Data,
+    ext2_data: extMV3Data,
+  });
+
+  await test_csp({
+    // site: CSP strict on default-src.
+    site_csp: "default-src 'none'",
+    // ext1: MV3 extension which return an empty CSP (expected to be a no-op for an MV3 extension).
+    ext1_csp: "",
+    // ext2: MV2 exension which wants to replace the site csp with a lax one (and still be allowed to
+    // because the empty one from the MV3 extension is expected to be a no-op).
+    ext2_csp: "default-src *",
+    expect: {
+      img1_loaded: true,
+      img3_loaded: true,
+      script1_loaded: true,
+      script3_loaded: true,
+      cspJSON: [{ "default-src": ["*"], "report-only": false }],
+    },
+    ext1_data: extMV3Data,
+    ext2_data: extMV2Data,
+  });
+
+  await test_csp({
+    // site: CSP strict on default-src.
+    site_csp: "default-src 'none'",
+    // ext1: MV3 extension which return an empty CSP (which is expected to be a no-op).
+    ext1_csp: "",
+    // ext2: MV2 extension which also returns an empty CSP (which for an MV2 extension is expected
+    // to clear the CSP).
+    ext2_csp: "",
+    expect: {
+      img1_loaded: true,
+      img3_loaded: true,
+      script1_loaded: true,
+      script3_loaded: true,
+      // Expect the resulting final document CSP to be empty (due to the MV2 extension clearing it).
+      cspJSON: [],
+    },
+    ext1_data: extMV3Data,
+    ext2_data: extMV2Data,
+  });
+});
diff --git a/toolkit/components/extensions/test/xpcshell/test_ext_webRequest_permission.js b/toolkit/components/extensions/test/xpcshell/test_ext_webRequest_permission.js
new file mode 100644
index 0000000000..bfb4b55856
--- /dev/null
+++ b/toolkit/components/extensions/test/xpcshell/test_ext_webRequest_permission.js
@@ -0,0 +1,153 @@
+"use strict";
+
+const HOSTS = new Set(["example.com", "example.org"]);
+
+const server = createHttpServer({ hosts: HOSTS });
+
+const BASE_URL = "http://example.com";
+
+server.registerDirectory("/data/", do_get_file("data"));
+
+server.registerPathHandler("/dummy", (request, response) => {
+  response.setStatusLine(request.httpVersion, 200, "OK");
+  response.setHeader("Content-Type", "text/html", false);
+  response.write("<!DOCTYPE html><html></html>");
+});
+
+function sendMessage(page, msg, data) {
+  return MessageChannel.sendMessage(page.browser.messageManager, msg, data);
+}
+
+add_task(async function test_permissions() {
+  function background() {
+    browser.webRequest.onBeforeRequest.addListener(
+      details => {
+        if (details.url.includes("_original")) {
+          let redirectUrl = details.url
+            .replace("example.org", "example.com")
+            .replace("_original", "_redirected");
+          return { redirectUrl };
+        }
+        return {};
+      },
+      { urls: ["<all_urls>"] },
+      ["blocking"]
+    );
+  }
+
+  let extensionData = {
+    manifest: {
+      permissions: ["webRequest", "webRequestBlocking", "<all_urls>"],
+    },
+    background,
+  };
+
+  let extension = ExtensionTestUtils.loadExtension(extensionData);
+  await extension.startup();
+
+  const frameScript = () => {
+    const messageListener = {
+      async receiveMessage({ target, messageName, recipient, data, name }) {
+        /* globals content */
+        let doc = content.document;
+        let iframe = doc.createElement("iframe");
+        doc.body.appendChild(iframe);
+
+        let promise = new Promise(resolve => {
+          let listener = event => {
+            content.removeEventListener("message", listener);
+            resolve(event.data);
+          };
+          content.addEventListener("message", listener);
+        });
+
+        iframe.setAttribute(
+          "src",
+          "http://example.com/data/file_WebRequest_permission_original.html"
+        );
+        let result = await promise;
+        doc.body.removeChild(iframe);
+        return result;
+      },
+    };
+
+    const { MessageChannel } = ChromeUtils.importESModule(
+      "resource://testing-common/MessageChannel.sys.mjs"
+    );
+    MessageChannel.addListener(this, "Test:Check", messageListener);
+  };
+
+  let contentPage = await ExtensionTestUtils.loadContentPage(
+    `${BASE_URL}/dummy`
+  );
+  await contentPage.loadFrameScript(frameScript);
+
+  let results = await sendMessage(contentPage, "Test:Check", {});
+  equal(
+    results.page,
+    "redirected",
+    "Regular webRequest redirect works on an unprivileged page"
+  );
+  equal(
+    results.script,
+    "redirected",
+    "Regular webRequest redirect works from an unprivileged page"
+  );
+
+  Services.prefs.setBoolPref("extensions.webapi.testing", true);
+  Services.prefs.setBoolPref("extensions.webapi.testing.http", true);
+
+  results = await sendMessage(contentPage, "Test:Check", {});
+  equal(
+    results.page,
+    "original",
+    "webRequest redirect fails on a privileged page"
+  );
+  equal(
+    results.script,
+    "original",
+    "webRequest redirect fails from a privileged page"
+  );
+
+  await extension.unload();
+  await contentPage.close();
+});
+
+add_task(async function test_no_webRequestBlocking_error() {
+  function background() {
+    const expectedError =
+      "Using webRequest.addListener with the blocking option " +
+      "requires the 'webRequestBlocking' permission.";
+
+    const blockingEvents = [
+      "onBeforeRequest",
+      "onBeforeSendHeaders",
+      "onHeadersReceived",
+      "onAuthRequired",
+    ];
+
+    for (let eventName of blockingEvents) {
+      browser.test.assertThrows(
+        () => {
+          browser.webRequest[eventName].addListener(
+            details => {},
+            { urls: ["<all_urls>"] },
+            ["blocking"]
+          );
+        },
+        expectedError,
+        `Got the expected exception for a blocking webRequest.${eventName} listener`
+      );
+    }
+  }
+
+  const extensionData = {
+    manifest: { permissions: ["webRequest", "<all_urls>"] },
+    background,
+  };
+
+  const extension = ExtensionTestUtils.loadExtension(extensionData);
+
+  await extension.startup();
+  await extension.unload();
+});
diff --git a/toolkit/components/extensions/test/xpcshell/test_ext_webRequest_redirectProperty.js b/toolkit/components/extensions/test/xpcshell/test_ext_webRequest_redirectProperty.js
new file mode 100644
index 0000000000..5a448abb2a
--- /dev/null
+++ b/toolkit/components/extensions/test/xpcshell/test_ext_webRequest_redirectProperty.js
@@ -0,0 +1,64 @@
+"use strict";
+
+const server = createHttpServer();
+const gServerUrl = `http://localhost:${server.identity.primaryPort}`;
+
+server.registerPathHandler("/dummy", (request, response) => {
+  response.setStatusLine(request.httpVersion, 200, "OK");
+  response.write("ok");
+});
+
+add_task(async function test_redirect_property() {
+  function background(serverUrl) {
+    browser.webRequest.onBeforeRequest.addListener(
+      () => {
+        return { redirectUrl: `${serverUrl}/dummy` };
+      },
+      { urls: ["*://localhost/*"] },
+      ["blocking"]
+    );
+  }
+
+  let ext = ExtensionTestUtils.loadExtension({
+    manifest: {
+      browser_specific_settings: { gecko: { id: "redirect@test" } },
+      permissions: ["webRequest", "webRequestBlocking", "<all_urls>"],
+    },
+    background: `(${background})("${gServerUrl}")`,
+  });
+  await ext.startup();
+
+  let data = await new Promise(resolve => {
+    let ssm = Services.scriptSecurityManager;
+
+    let channel = NetUtil.newChannel({
+      uri: `${gServerUrl}/redirect`,
+      loadingPrincipal:
+        ssm.createContentPrincipalFromOrigin("http://localhost"),
+      contentPolicyType: Ci.nsIContentPolicy.TYPE_XMLHTTPREQUEST,
+      securityFlags: Ci.nsILoadInfo.SEC_ALLOW_CROSS_ORIGIN_SEC_CONTEXT_IS_NULL,
+    });
+
+    channel.asyncOpen({
+      QueryInterface: ChromeUtils.generateQI(["nsIStreamListener"]),
+
+      onStartRequest(request) {},
+
+      onStopRequest(request, statusCode) {
+        let properties = request.QueryInterface(Ci.nsIPropertyBag);
+        let id = properties.getProperty("redirectedByExtension");
+        resolve({ id, url: request.QueryInterface(Ci.nsIChannel).URI.spec });
+      },
+
+      onDataAvailable() {},
+    });
+  });
+
+  Assert.equal(`${gServerUrl}/dummy`, data.url, "request redirected");
+  Assert.equal(
+    ext.id,
+    data.id,
+    "extension id attached to channel property bag"
+  );
+  await ext.unload();
+});
diff --git a/toolkit/components/extensions/test/xpcshell/test_ext_webRequest_redirect_StreamFilter.js b/toolkit/components/extensions/test/xpcshell/test_ext_webRequest_redirect_StreamFilter.js
new file mode 100644
index 0000000000..8153a596a3
--- /dev/null
+++ b/toolkit/components/extensions/test/xpcshell/test_ext_webRequest_redirect_StreamFilter.js
@@ -0,0 +1,129 @@
+"use strict";
+
+// StreamFilters should be closed upon a redirect.
+//
+// Some redirects are already tested in other tests:
+// - test_ext_webRequest_filterResponseData.js tests fetch requests.
+// - test_ext_webRequest_viewsource_StreamFilter.js tests view-source documents.
+//
+// Usually, redirects are caught in StreamFilterParent::OnStartRequest, but due
+// to the fact that AttachStreamFilter is deferred for document requests, OSR is
+// not called and the cleanup is triggered from nsHttpChannel::ReleaseListeners.
+
+const server = createHttpServer({ hosts: ["example.com", "example.org"] });
+
+server.registerPathHandler("/redir", (request, response) => {
+  response.setStatusLine(request.httpVersion, 302, "Found");
+  response.setHeader("Location", "/target");
+});
+server.registerPathHandler("/target", (request, response) => {
+  response.setStatusLine(request.httpVersion, 200, "OK");
+  response.write("ok");
+});
+server.registerPathHandler("/RedirectToRedir.html", (request, response) => {
+  response.setStatusLine(request.httpVersion, 200, "OK");
+  response.setHeader("Content-Type", "text/html; charset=utf-8");
+  response.write("<script>location.href='http://example.com/redir';</script>");
+});
+server.registerPathHandler("/iframeWithRedir.html", (request, response) => {
+  response.setStatusLine(request.httpVersion, 200, "OK");
+  response.setHeader("Content-Type", "text/html; charset=utf-8");
+  response.write("<iframe src='http://example.com/redir'></iframe>");
+});
+
+function loadRedirectCatcherExtension() {
+  return ExtensionTestUtils.loadExtension({
+    manifest: {
+      permissions: ["webRequest", "webRequestBlocking", "*://*/*"],
+    },
+    background() {
+      const closeCounts = {};
+      browser.webRequest.onBeforeRequest.addListener(
+        details => {
+          let expectedError = "Channel redirected";
+          if (details.type === "main_frame" || details.type === "sub_frame") {
+            // Message differs for the reason stated at the top of this file.
+            // TODO bug 1683862: Make error message more accurate.
+            expectedError = "Invalid request ID";
+          }
+
+          closeCounts[details.requestId] = 0;
+
+          let filter = browser.webRequest.filterResponseData(details.requestId);
+          filter.onstart = () => {
+            filter.disconnect();
+            browser.test.fail("Unexpected filter.onstart");
+          };
+          filter.onerror = function () {
+            closeCounts[details.requestId]++;
+            browser.test.assertEq(expectedError, filter.error, "filter.error");
+          };
+        },
+        { urls: ["*://*/redir"] },
+        ["blocking"]
+      );
+      browser.webRequest.onCompleted.addListener(
+        details => {
+          // filter.onerror from the redirect request should be called before
+          // webRequest.onCompleted of the redirection target. Regression test
+          // for bug 1683189.
+          browser.test.assertEq(
+            1,
+            closeCounts[details.requestId],
+            "filter from initial, redirected request should have been closed"
+          );
+          browser.test.log("Intentionally canceling view-source request");
+          browser.test.sendMessage("req_end", details.type);
+        },
+        { urls: ["*://*/target"] }
+      );
+    },
+  });
+}
+
+add_task(async function redirect_document() {
+  let extension = loadRedirectCatcherExtension();
+  await extension.startup();
+
+  {
+    let contentPage = await ExtensionTestUtils.loadContentPage(
+      "http://example.com/redir"
+    );
+    equal(await extension.awaitMessage("req_end"), "main_frame", "is top doc");
+    await contentPage.close();
+  }
+
+  {
+    let contentPage = await ExtensionTestUtils.loadContentPage(
+      "http://example.com/iframeWithRedir.html"
+    );
+    equal(await extension.awaitMessage("req_end"), "sub_frame", "is sub doc");
+    await contentPage.close();
+  }
+
+  await extension.unload();
+});
+
+// Cross-origin redirect = process switch.
+add_task(async function redirect_document_cross_origin() {
+  let extension = loadRedirectCatcherExtension();
+  await extension.startup();
+
+  {
+    let contentPage = await ExtensionTestUtils.loadContentPage(
+      "http://example.org/RedirectToRedir.html"
+    );
+    equal(await extension.awaitMessage("req_end"), "main_frame", "is top doc");
+    await contentPage.close();
+  }
+
+  {
+    let contentPage = await ExtensionTestUtils.loadContentPage(
+      "http://example.org/iframeWithRedir.html"
+    );
+    equal(await extension.awaitMessage("req_end"), "sub_frame", "is sub doc");
+    await contentPage.close();
+  }
+
+  await extension.unload();
+});
diff --git a/toolkit/components/extensions/test/xpcshell/test_ext_webRequest_redirect_mozextension.js b/toolkit/components/extensions/test/xpcshell/test_ext_webRequest_redirect_mozextension.js
new file mode 100644
index 0000000000..e390e3348e
--- /dev/null
+++ b/toolkit/components/extensions/test/xpcshell/test_ext_webRequest_redirect_mozextension.js
@@ -0,0 +1,47 @@
+"use strict";
+
+// See: https://bugzilla.mozilla.org/show_bug.cgi?id=1573456
+add_task(async function test_mozextension_page_loaded_in_extension_process() {
+  let extension = ExtensionTestUtils.loadExtension({
+    manifest: {
+      permissions: [
+        "webRequest",
+        "webRequestBlocking",
+        "https://example.com/*",
+      ],
+      web_accessible_resources: ["test.html"],
+    },
+    files: {
+      "test.html": '<!DOCTYPE html><script src="test.js"></script>',
+      "test.js": () => {
+        browser.test.assertTrue(
+          browser.webRequest,
+          "webRequest API should be available"
+        );
+
+        browser.test.sendMessage("test_done");
+      },
+    },
+    background: () => {
+      browser.webRequest.onBeforeRequest.addListener(
+        () => {
+          return {
+            redirectUrl: browser.runtime.getURL("test.html"),
+          };
+        },
+        { urls: ["*://*/redir"] },
+        ["blocking"]
+      );
+    },
+  });
+  await extension.startup();
+
+  let contentPage = await ExtensionTestUtils.loadContentPage(
+    "https://example.com/redir"
+  );
+
+  await extension.awaitMessage("test_done");
+
+  await extension.unload();
+  await contentPage.close();
+});
diff --git a/toolkit/components/extensions/test/xpcshell/test_ext_webRequest_requestSize.js b/toolkit/components/extensions/test/xpcshell/test_ext_webRequest_requestSize.js
new file mode 100644
index 0000000000..69238fb057
--- /dev/null
+++ b/toolkit/components/extensions/test/xpcshell/test_ext_webRequest_requestSize.js
@@ -0,0 +1,57 @@
+"use strict";
+
+const server = createHttpServer();
+const gServerUrl = `http://localhost:${server.identity.primaryPort}`;
+
+const EXTENSION_DATA = {
+  manifest: {
+    name: "Simple extension test",
+    version: "1.0",
+    manifest_version: 2,
+    description: "",
+
+    permissions: ["webRequest", "<all_urls>"],
+  },
+
+  async background() {
+    browser.test.log("background script running");
+
+    browser.webRequest.onBeforeSendHeaders.addListener(
+      async details => {
+        browser.test.assertTrue(details.requestSize == 0, "no requestSize");
+        browser.test.assertTrue(details.responseSize == 0, "no responseSize");
+        browser.test.log(`details.requestSize: ${details.requestSize}`);
+        browser.test.log(`details.responseSize: ${details.responseSize}`);
+        browser.test.sendMessage("check");
+      },
+      { urls: ["*://*/*"] }
+    );
+
+    browser.webRequest.onCompleted.addListener(
+      async details => {
+        browser.test.assertTrue(details.requestSize > 100, "have requestSize");
+        browser.test.assertTrue(
+          details.responseSize > 100,
+          "have responseSize"
+        );
+        browser.test.log(`details.requestSize: ${details.requestSize}`);
+        browser.test.log(`details.responseSize: ${details.responseSize}`);
+        browser.test.sendMessage("done");
+      },
+      { urls: ["*://*/*"] }
+    );
+  },
+};
+
+add_task(async function test_request_response_size() {
+  let ext = ExtensionTestUtils.loadExtension(EXTENSION_DATA);
+  await ext.startup();
+
+  let contentPage = await ExtensionTestUtils.loadContentPage(
+    `${gServerUrl}/dummy`
+  );
+  await ext.awaitMessage("check");
+  await ext.awaitMessage("done");
+  await contentPage.close();
+  await ext.unload();
+});
diff --git a/toolkit/components/extensions/test/xpcshell/test_ext_webRequest_responseBody.js b/toolkit/components/extensions/test/xpcshell/test_ext_webRequest_responseBody.js
new file mode 100644
index 0000000000..8995870ba6
--- /dev/null
+++ b/toolkit/components/extensions/test/xpcshell/test_ext_webRequest_responseBody.js
@@ -0,0 +1,764 @@
+"use strict";
+
+/* eslint-disable mozilla/no-arbitrary-setTimeout */
+/* eslint-disable no-shadow */
+
+const { ExtensionTestCommon } = ChromeUtils.importESModule(
+  "resource://testing-common/ExtensionTestCommon.sys.mjs"
+);
+
+const HOSTS = new Set(["example.com"]);
+
+const server = createHttpServer({ hosts: HOSTS });
+
+const BASE_URL = "http://example.com";
+const FETCH_ORIGIN = "http://example.com/data/file_sample.html";
+
+const SEQUENTIAL = false;
+
+const PARTS = [
+  `<!DOCTYPE html>
+    <html lang="en">
+    <head>
+      <meta charset="UTF-8">
+      <title></title>
+    </head>
+    <body>`,
+  "Lorem ipsum dolor sit amet, <br>",
+  "consectetur adipiscing elit, <br>",
+  "sed do eiusmod tempor incididunt ut labore et dolore magna aliqua. <br>",
+  "Ut enim ad minim veniam, quis nostrud exercitation ullamco laboris nisi ut aliquip ex ea commodo consequat. <br>",
+  "Duis aute irure dolor in reprehenderit in voluptate velit esse cillum dolore eu fugiat nulla pariatur. <br>",
+  "Excepteur sint occaecat cupidatat non proident, <br>",
+  "sunt in culpa qui officia deserunt mollit anim id est laborum.<br>",
+  `
+    </body>
+    </html>`,
+].map(part => `${part}\n`);
+
+const TIMEOUT = AppConstants.DEBUG ? 4000 : 800;
+
+function delay(timeout = TIMEOUT) {
+  return new Promise(resolve => setTimeout(resolve, timeout));
+}
+
+server.registerPathHandler("/slow_response.sjs", async (request, response) => {
+  response.processAsync();
+
+  response.setHeader("Content-Type", "text/html", false);
+  response.setHeader("Cache-Control", "no-cache", false);
+
+  await delay();
+
+  for (let part of PARTS) {
+    try {
+      response.write(part);
+    } catch (e) {
+      // This fails if we attempt to write data after the connection has
+      // been closed.
+      break;
+    }
+    await delay();
+  }
+
+  response.finish();
+});
+
+server.registerPathHandler("/lorem.html.gz", async (request, response) => {
+  response.processAsync();
+
+  response.setHeader(
+    "Content-Type",
+    "Content-Type: text/html; charset=utf-8",
+    false
+  );
+  response.setHeader("Content-Encoding", "gzip", false);
+
+  let data = await IOUtils.read(do_get_file("data/lorem.html.gz").path);
+  response.write(String.fromCharCode(...data));
+
+  response.finish();
+});
+
+server.registerPathHandler("/multipart", async (request, response) => {
+  response.processAsync();
+
+  response.setHeader(
+    "Content-Type",
+    'Content-Type: multipart/x-mixed-replace; boundary="testingtesting"',
+    false
+  );
+
+  response.write("--testingtesting\n");
+  response.write(PARTS.join(""));
+  response.write("--testingtesting--\n");
+
+  response.finish();
+});
+
+server.registerPathHandler("/multipart2", async (request, response) => {
+  response.processAsync();
+
+  response.setHeader(
+    "Content-Type",
+    'Content-Type: multipart/x-mixed-replace; boundary="testingtesting"',
+    false
+  );
+
+  response.write("--testingtesting\n");
+  response.write(PARTS.join(""));
+  response.write("--testingtesting\n");
+  response.write(PARTS.join(""));
+  response.write("--testingtesting--\n");
+
+  response.finish();
+});
+
+server.registerDirectory("/data/", do_get_file("data"));
+
+const TASKS = [
+  {
+    url: "slow_response.sjs",
+    task(filter, resolve, num) {
+      let decoder = new TextDecoder("utf-8");
+
+      browser.test.assertEq(
+        "uninitialized",
+        filter.status,
+        `(${num}): Got expected initial status`
+      );
+
+      filter.onstart = event => {
+        browser.test.assertEq(
+          "transferringdata",
+          filter.status,
+          `(${num}): Got expected onStart status`
+        );
+      };
+
+      filter.onstop = event => {
+        browser.test.fail(
+          `(${num}): Got unexpected onStop event while disconnected`
+        );
+      };
+
+      let n = 0;
+      filter.ondata = async event => {
+        let str = decoder.decode(event.data, { stream: true });
+
+        if (n < 3) {
+          browser.test.assertEq(
+            JSON.stringify(PARTS[n]),
+            JSON.stringify(str),
+            `(${num}): Got expected part`
+          );
+        }
+        n++;
+
+        filter.write(event.data);
+
+        if (n == 3) {
+          filter.suspend();
+
+          browser.test.assertEq(
+            "suspended",
+            filter.status,
+            `(${num}): Got expected suspended status`
+          );
+
+          let fail = () => {
+            browser.test.fail(
+              `(${num}): Got unexpected data event while suspended`
+            );
+          };
+          filter.addEventListener("data", fail);
+
+          await delay(TIMEOUT * 3);
+
+          browser.test.assertEq(
+            "suspended",
+            filter.status,
+            `(${num}): Got expected suspended status`
+          );
+
+          filter.removeEventListener("data", fail);
+          filter.resume();
+          browser.test.assertEq(
+            "transferringdata",
+            filter.status,
+            `(${num}): Got expected resumed status`
+          );
+        } else if (n > 4) {
+          filter.disconnect();
+
+          filter.addEventListener("data", () => {
+            browser.test.fail(
+              `(${num}): Got unexpected data event while disconnected`
+            );
+          });
+
+          browser.test.assertEq(
+            "disconnected",
+            filter.status,
+            `(${num}): Got expected disconnected status`
+          );
+
+          resolve();
+        }
+      };
+
+      filter.onerror = event => {
+        browser.test.fail(
+          `(${num}): Got unexpected error event: ${filter.error}`
+        );
+      };
+    },
+    verify(response) {
+      equal(response, PARTS.join(""), "Got expected final HTML");
+    },
+  },
+  {
+    url: "slow_response.sjs",
+    task(filter, resolve, num) {
+      let decoder = new TextDecoder("utf-8");
+
+      filter.onstop = event => {
+        browser.test.fail(
+          `(${num}): Got unexpected onStop event while disconnected`
+        );
+      };
+
+      let n = 0;
+      filter.ondata = async event => {
+        let str = decoder.decode(event.data, { stream: true });
+
+        if (n < 3) {
+          browser.test.assertEq(
+            JSON.stringify(PARTS[n]),
+            JSON.stringify(str),
+            `(${num}): Got expected part`
+          );
+        }
+        n++;
+
+        filter.write(event.data);
+
+        if (n == 3) {
+          filter.suspend();
+
+          await delay(TIMEOUT * 3);
+
+          filter.disconnect();
+
+          resolve();
+        }
+      };
+
+      filter.onerror = event => {
+        browser.test.fail(
+          `(${num}): Got unexpected error event: ${filter.error}`
+        );
+      };
+    },
+    verify(response) {
+      equal(response, PARTS.join(""), "Got expected final HTML");
+    },
+  },
+  {
+    url: "slow_response.sjs",
+    task(filter, resolve, num) {
+      let encoder = new TextEncoder();
+
+      filter.onstop = event => {
+        browser.test.fail(
+          `(${num}): Got unexpected onStop event while disconnected`
+        );
+      };
+
+      let n = 0;
+      filter.ondata = async event => {
+        n++;
+
+        filter.write(event.data);
+
+        function checkState(state) {
+          browser.test.assertEq(
+            state,
+            filter.status,
+            `(${num}): Got expected status`
+          );
+        }
+        if (n == 3) {
+          filter.resume();
+          checkState("transferringdata");
+          filter.suspend();
+          checkState("suspended");
+          filter.suspend();
+          checkState("suspended");
+          filter.resume();
+          checkState("transferringdata");
+          filter.suspend();
+          checkState("suspended");
+
+          await delay(TIMEOUT * 3);
+
+          checkState("suspended");
+          filter.disconnect();
+          checkState("disconnected");
+
+          for (let method of ["suspend", "resume", "close"]) {
+            browser.test.assertThrows(
+              () => {
+                filter[method]();
+              },
+              /.*/,
+              `(${num}): ${method}() should throw while disconnected`
+            );
+          }
+
+          browser.test.assertThrows(
+            () => {
+              filter.write(encoder.encode("Foo bar"));
+            },
+            /.*/,
+            `(${num}): write() should throw while disconnected`
+          );
+
+          filter.disconnect();
+
+          resolve();
+        }
+      };
+
+      filter.onerror = event => {
+        browser.test.fail(
+          `(${num}): Got unexpected error event: ${filter.error}`
+        );
+      };
+    },
+    verify(response) {
+      equal(response, PARTS.join(""), "Got expected final HTML");
+    },
+  },
+  {
+    url: "slow_response.sjs",
+    task(filter, resolve, num) {
+      let encoder = new TextEncoder();
+      let decoder = new TextDecoder("utf-8");
+
+      filter.onstop = event => {
+        browser.test.fail(`(${num}): Got unexpected onStop event while closed`);
+      };
+
+      browser.test.assertThrows(
+        () => {
+          filter.write(encoder.encode("Foo bar"));
+        },
+        /.*/,
+        `(${num}): write() should throw prior to connection`
+      );
+
+      let n = 0;
+      filter.ondata = async event => {
+        n++;
+
+        filter.write(event.data);
+
+        browser.test.log(
+          `(${num}): Got part ${n}: ${JSON.stringify(
+            decoder.decode(event.data)
+          )}`
+        );
+
+        function checkState(state) {
+          browser.test.assertEq(
+            state,
+            filter.status,
+            `(${num}): Got expected status`
+          );
+        }
+        if (n == 3) {
+          filter.close();
+
+          checkState("closed");
+
+          for (let method of ["suspend", "resume", "disconnect"]) {
+            browser.test.assertThrows(
+              () => {
+                filter[method]();
+              },
+              /.*/,
+              `(${num}): ${method}() should throw while closed`
+            );
+          }
+
+          browser.test.assertThrows(
+            () => {
+              filter.write(encoder.encode("Foo bar"));
+            },
+            /.*/,
+            `(${num}): write() should throw while closed`
+          );
+
+          filter.close();
+
+          resolve();
+        }
+      };
+
+      filter.onerror = event => {
+        browser.test.fail(
+          `(${num}): Got unexpected error event: ${filter.error}`
+        );
+      };
+    },
+    verify(response) {
+      equal(response, PARTS.slice(0, 3).join(""), "Got expected final HTML");
+    },
+  },
+  {
+    url: "lorem.html.gz",
+    task(filter, resolve, num) {
+      let response = "";
+      let decoder = new TextDecoder("utf-8");
+
+      filter.onstart = event => {
+        browser.test.log(`(${num}): Request start`);
+      };
+
+      filter.onstop = event => {
+        browser.test.assertEq(
+          "finishedtransferringdata",
+          filter.status,
+          `(${num}): Got expected onStop status`
+        );
+
+        filter.close();
+        browser.test.assertEq(
+          "closed",
+          filter.status,
+          `Got expected closed status`
+        );
+
+        browser.test.assertEq(
+          JSON.stringify(PARTS.join("")),
+          JSON.stringify(response),
+          `(${num}): Got expected response`
+        );
+
+        resolve();
+      };
+
+      filter.ondata = event => {
+        let str = decoder.decode(event.data, { stream: true });
+        response += str;
+
+        filter.write(event.data);
+      };
+
+      filter.onerror = event => {
+        browser.test.fail(
+          `(${num}): Got unexpected error event: ${filter.error}`
+        );
+      };
+    },
+    verify(response) {
+      equal(response, PARTS.join(""), "Got expected final HTML");
+    },
+  },
+  {
+    url: "multipart",
+    task(filter, resolve, num) {
+      filter.onstart = event => {
+        browser.test.log(`(${num}): Request start`);
+      };
+
+      filter.onstop = event => {
+        filter.disconnect();
+        resolve();
+      };
+
+      filter.ondata = event => {
+        filter.write(event.data);
+      };
+
+      filter.onerror = event => {
+        browser.test.fail(
+          `(${num}): Got unexpected error event: ${filter.error}`
+        );
+      };
+    },
+    verify(response) {
+      equal(
+        response,
+        "--testingtesting\n" + PARTS.join("") + "--testingtesting--\n",
+        "Got expected final HTML"
+      );
+    },
+  },
+  {
+    url: "multipart2",
+    task(filter, resolve, num) {
+      filter.onstart = event => {
+        browser.test.log(`(${num}): Request start`);
+      };
+
+      filter.onstop = event => {
+        filter.disconnect();
+        resolve();
+      };
+
+      filter.ondata = event => {
+        filter.write(event.data);
+      };
+
+      filter.onerror = event => {
+        browser.test.fail(
+          `(${num}): Got unexpected error event: ${filter.error}`
+        );
+      };
+    },
+    verify(response) {
+      equal(
+        response,
+        "--testingtesting\n" +
+          PARTS.join("") +
+          "--testingtesting\n" +
+          PARTS.join("") +
+          "--testingtesting--\n",
+        "Got expected final HTML"
+      );
+    },
+  },
+];
+
+function serializeTest(test, num) {
+  let url = `${test.url}?test_num=${num}`;
+  let task = ExtensionTestCommon.serializeFunction(test.task);
+
+  return `{url: ${JSON.stringify(url)}, task: ${task}}`;
+}
+
+add_task(async function () {
+  function background(TASKS) {
+    async function runTest(test, num, details) {
+      browser.test.log(`Running test #${num}: ${details.url}`);
+
+      let filter = browser.webRequest.filterResponseData(details.requestId);
+
+      try {
+        await new Promise(resolve => {
+          test.task(filter, resolve, num, details);
+        });
+      } catch (e) {
+        browser.test.fail(
+          `Task #${num} threw an unexpected exception: ${e} :: ${e.stack}`
+        );
+      }
+
+      browser.test.log(`Finished test #${num}: ${details.url}`);
+      browser.test.sendMessage(`finished-${num}`);
+    }
+
+    browser.webRequest.onBeforeRequest.addListener(
+      details => {
+        for (let [num, test] of TASKS.entries()) {
+          if (details.url.endsWith(test.url)) {
+            runTest(test, num, details);
+            break;
+          }
+        }
+      },
+      {
+        urls: ["http://example.com/*?test_num=*"],
+      },
+      ["blocking"]
+    );
+  }
+
+  let extension = ExtensionTestUtils.loadExtension({
+    background: `
+      const PARTS = ${JSON.stringify(PARTS)};
+      const TIMEOUT = ${TIMEOUT};
+
+      ${delay}
+
+      (${background})([${TASKS.map(serializeTest)}])
+    `,
+
+    manifest: {
+      permissions: ["webRequest", "webRequestBlocking", "http://example.com/"],
+    },
+  });
+
+  await extension.startup();
+
+  async function runTest(test, num) {
+    let url = `${BASE_URL}/${test.url}?test_num=${num}`;
+
+    let body = await ExtensionTestUtils.fetch(FETCH_ORIGIN, url);
+
+    await extension.awaitMessage(`finished-${num}`);
+
+    info(`Verifying test #${num}: ${url}`);
+    await test.verify(body);
+  }
+
+  if (SEQUENTIAL) {
+    for (let [num, test] of TASKS.entries()) {
+      await runTest(test, num);
+    }
+  } else {
+    await Promise.all(TASKS.map(runTest));
+  }
+
+  await extension.unload();
+});
+
+// Test that registering a listener for a cached response does not cause a crash.
+add_task(async function test_cachedResponse() {
+  if (AppConstants.platform === "android") {
+    return;
+  }
+  Services.prefs.setBoolPref("network.http.rcwn.enabled", false);
+
+  let extension = ExtensionTestUtils.loadExtension({
+    background() {
+      browser.webRequest.onHeadersReceived.addListener(
+        data => {
+          let filter = browser.webRequest.filterResponseData(data.requestId);
+
+          filter.onstop = event => {
+            filter.close();
+          };
+          filter.ondata = event => {
+            filter.write(event.data);
+          };
+
+          if (data.fromCache) {
+            browser.test.sendMessage("from-cache");
+          }
+        },
+        {
+          urls: ["http://example.com/*/file_sample.html?r=*"],
+        },
+        ["blocking"]
+      );
+    },
+
+    manifest: {
+      permissions: ["webRequest", "webRequestBlocking", "http://example.com/"],
+    },
+  });
+
+  await extension.startup();
+
+  let url = `${BASE_URL}/data/file_sample.html?r=${Math.random()}`;
+  await ExtensionTestUtils.fetch(FETCH_ORIGIN, url);
+  await ExtensionTestUtils.fetch(FETCH_ORIGIN, url);
+  await extension.awaitMessage("from-cache");
+
+  await extension.unload();
+});
+
+// Test that finishing transferring data doesn't overwrite an existing closing/closed state.
+add_task(async function test_late_close() {
+  let extension = ExtensionTestUtils.loadExtension({
+    background() {
+      browser.webRequest.onBeforeRequest.addListener(
+        data => {
+          let filter = browser.webRequest.filterResponseData(data.requestId);
+
+          filter.onstop = event => {
+            browser.test.fail("Should not receive onstop after close()");
+            browser.test.assertEq(
+              "closed",
+              filter.status,
+              "Filter status should still be 'closed'"
+            );
+            browser.test.assertThrows(() => {
+              filter.close();
+            });
+          };
+          filter.ondata = event => {
+            filter.write(event.data);
+            filter.close();
+
+            browser.test.sendMessage(`done-${data.url}`);
+          };
+        },
+        {
+          urls: ["http://example.com/*/file_sample.html?*"],
+        },
+        ["blocking"]
+      );
+    },
+
+    manifest: {
+      permissions: ["webRequest", "webRequestBlocking", "http://example.com/"],
+    },
+  });
+
+  await extension.startup();
+
+  // This issue involves a race, so several requests in parallel to increase
+  // the chances of triggering it.
+  let urls = [];
+  for (let i = 0; i < 32; i++) {
+    urls.push(`${BASE_URL}/data/file_sample.html?r=${Math.random()}`);
+  }
+
+  await Promise.all(
+    urls.map(url => ExtensionTestUtils.fetch(FETCH_ORIGIN, url))
+  );
+  await Promise.all(urls.map(url => extension.awaitMessage(`done-${url}`)));
+
+  await extension.unload();
+});
+
+add_task(async function test_permissions() {
+  let extension = ExtensionTestUtils.loadExtension({
+    background() {
+      browser.test.assertEq(
+        undefined,
+        browser.webRequest.filterResponseData,
+        "filterResponseData is undefined without blocking permissions"
+      );
+    },
+
+    manifest: {
+      permissions: ["webRequest", "http://example.com/"],
+    },
+  });
+
+  await extension.startup();
+  await extension.unload();
+});
+
+add_task(async function test_invalidId() {
+  let extension = ExtensionTestUtils.loadExtension({
+    async background() {
+      let filter = browser.webRequest.filterResponseData("34159628");
+
+      await new Promise(resolve => {
+        filter.onerror = resolve;
+      });
+
+      browser.test.assertEq(
+        "Invalid request ID",
+        filter.error,
+        "Got expected error"
+      );
+
+      browser.test.notifyPass("invalid-request-id");
+    },
+
+    manifest: {
+      permissions: ["webRequest", "webRequestBlocking", "http://example.com/"],
+    },
+  });
+
+  await extension.startup();
+  await extension.awaitFinish("invalid-request-id");
+  await extension.unload();
+});
diff --git a/toolkit/components/extensions/test/xpcshell/test_ext_webRequest_restrictedHeaders.js b/toolkit/components/extensions/test/xpcshell/test_ext_webRequest_restrictedHeaders.js
new file mode 100644
index 0000000000..471bae0493
--- /dev/null
+++ b/toolkit/components/extensions/test/xpcshell/test_ext_webRequest_restrictedHeaders.js
@@ -0,0 +1,252 @@
+/* -*- Mode: indent-tabs-mode: nil; js-indent-level: 2 -*- */
+/* vim: set sts=2 sw=2 et tw=80: */
+"use strict";
+
+Services.prefs.setBoolPref("extensions.manifestV3.enabled", true);
+
+AddonTestUtils.init(this);
+AddonTestUtils.createAppInfo(
+  "xpcshell@tests.mozilla.org",
+  "XPCShell",
+  "1",
+  "43"
+);
+
+const server = createHttpServer({
+  hosts: ["example.net"],
+});
+server.registerPathHandler("/test/response-header", (req, res) => {
+  let headerName;
+  let headerValue;
+  if (req.queryString) {
+    let params = new URLSearchParams(req.queryString);
+    headerName = params.get("name");
+    headerValue = params.get("value");
+    res.setHeader(headerName, headerValue, false);
+    res.setHeader("test", `${headerName}=${headerValue}`, false);
+  }
+  res.write("");
+});
+
+const extensionData = {
+  useAddonManager: "temporary",
+  background() {
+    const { manifest_version } = browser.runtime.getManifest();
+    let headerToSet = undefined;
+    browser.test.onMessage.addListener(function (msg, arg) {
+      if (msg !== "header-to-set") {
+        return;
+      }
+      headerToSet = arg;
+      browser.test.sendMessage("header-to-set:done");
+    });
+    browser.webRequest.onHeadersReceived.addListener(
+      e => {
+        browser.test.log(`onHeadersReceived ${e.requestId} ${e.url}`);
+        if (headerToSet === undefined) {
+          browser.test.fail(
+            "extension called before headerToSet option was set"
+          );
+        }
+        if (typeof headerToSet?.name == "string") {
+          const existingHeader = e.responseHeaders.filter(
+            i => i.name.toLowerCase() === headerToSet.name
+          )[0];
+          e.responseHeaders = e.responseHeaders.filter(
+            i => i.name.toLowerCase() != headerToSet.name
+          );
+          // Omit the header if the value isn't set, change the header otherwise.
+          if (headerToSet.value != null) {
+            e.responseHeaders.push({
+              name: headerToSet.name,
+              value: headerToSet.value,
+            });
+          }
+          browser.test.log(
+            `Test Extension MV${manifest_version} (${browser.runtime.id}) sets responseHeader: "${headerToSet.name}"="${headerToSet.value}" (was originally set to "${existingHeader?.value})"`
+          );
+        }
+        return { responseHeaders: e.responseHeaders };
+      },
+      { urls: ["*://example.net/test/*"] },
+      ["blocking", "responseHeaders"]
+    );
+    browser.webRequest.onCompleted.addListener(
+      e => {
+        browser.test.log(`onCompletedReceived ${e.requestId} ${e.url}`);
+        const responseHeaders = e.responseHeaders.filter(
+          i => i.name.toLowerCase() === headerToSet.name
+        );
+
+        browser.test.sendMessage(
+          "on-completed:response-headers",
+          responseHeaders
+        );
+      },
+      { urls: ["*://example.net/test/*"] },
+      ["responseHeaders"]
+    );
+    browser.test.sendMessage("bgpage:ready");
+  },
+};
+
+const extDataMV2 = {
+  ...extensionData,
+  manifest: {
+    manifest_version: 2,
+    permissions: ["webRequest", "webRequestBlocking", "*://example.net/test/*"],
+  },
+};
+
+const extDataMV3 = {
+  ...extensionData,
+  manifest: {
+    manifest_version: 3,
+    permissions: ["webRequest", "webRequestBlocking"],
+    host_permissions: ["*://example.net/test/*"],
+    granted_host_permissions: true,
+  },
+};
+
+add_setup(async () => {
+  await AddonTestUtils.promiseStartupManager();
+});
+
+async function test_restricted_response_headers_changes({
+  firstExtData,
+  secondExtData,
+  headerName,
+  firstExtHeaderChange,
+  secondExtHeaderChange,
+  siteHeaderValue,
+  expectedHeaderValue,
+}) {
+  const ext1 = ExtensionTestUtils.loadExtension(firstExtData);
+  const ext2 = secondExtData && ExtensionTestUtils.loadExtension(secondExtData);
+
+  await ext1.startup();
+  await ext1.awaitMessage("bgpage:ready");
+
+  await ext2?.startup();
+  await ext2?.awaitMessage("bgpage:ready");
+
+  ext1.sendMessage("header-to-set", {
+    name: headerName,
+    value: firstExtHeaderChange,
+  });
+  await ext1.awaitMessage("header-to-set:done");
+  ext2?.sendMessage("header-to-set", {
+    name: headerName,
+    value: secondExtHeaderChange,
+  });
+  await ext2?.awaitMessage("header-to-set:done");
+
+  if (siteHeaderValue) {
+    await ExtensionTestUtils.fetch(
+      "http://example.net/",
+      `http://example.net/test/response-header?name=${headerName}&value=${siteHeaderValue}`
+    );
+  } else {
+    await ExtensionTestUtils.fetch(
+      "http://example.net/",
+      "http://example.net/test/response-header"
+    );
+  }
+
+  const [finalSiteHeaders] = await Promise.all([
+    ext1.awaitMessage("on-completed:response-headers"),
+    ext2?.awaitMessage("on-completed:response-headers"),
+  ]);
+
+  Assert.deepEqual(
+    finalSiteHeaders,
+    expectedHeaderValue
+      ? [{ name: headerName, value: expectedHeaderValue }]
+      : [],
+    "Got the expected response header"
+  );
+
+  await ext1.unload();
+  await ext2?.unload();
+}
+
+add_task(async function test_changes_to_restricted_response_headers() {
+  const testCases = [
+    {
+      headerName: "cross-origin-embedder-policy",
+      siteHeaderValue: "require-corp",
+      firstExtHeaderChange: "credentialless",
+      secondExtHeaderChange: "unsafe-none",
+    },
+    {
+      headerName: "cross-origin-opener-policy",
+      siteHeaderValue: "same-origin",
+      firstExtHeaderChange: "same-origin-allow-popups",
+      secondExtHeaderChange: "unsafe-none",
+    },
+    {
+      headerName: "cross-origin-resource-policy",
+      siteHeaderValue: "same-origin",
+      firstExtHeaderChange: "same-site",
+      secondExtHeaderChange: "cross-origin",
+    },
+    {
+      headerName: "x-frame-options",
+      siteHeaderValue: "deny",
+      firstExtHeaderChange: "sameorigin",
+      secondExtHeaderChange: "allow-from=http://example.com",
+    },
+    {
+      headerName: "access-control-allow-credentials",
+      siteHeaderValue: "true",
+      firstExtHeaderChange: "false",
+      secondExtHeaderChange: "false",
+    },
+    {
+      headerName: "access-control-allow-methods",
+      siteHeaderValue: "*",
+      firstExtHeaderChange: "",
+      secondExtHeaderChange: "GET",
+    },
+  ];
+
+  for (const testCase of testCases) {
+    info(
+      `Test MV3 extension disallowed to change restricted header if already set by the website: "${testCase.headerName}"="${testCase.siteHeaderValue}`
+    );
+    await test_restricted_response_headers_changes({
+      ...testCase,
+      firstExtData: extDataMV3,
+      // Expect the value set by the server to be preserved.
+      expectedHeaderValue: testCase.siteHeaderValue,
+    });
+  }
+
+  for (const testCase of testCases) {
+    info(
+      `Test MV3 extension disallowed to change restricted header also if not set by the website: "${testCase.headerName}`
+    );
+    await test_restricted_response_headers_changes({
+      ...testCase,
+      siteHeaderValue: null,
+      firstExtData: extDataMV3,
+      // Expect the value set by the server to be preserved.
+      expectedHeaderValue: null,
+    });
+  }
+
+  for (const testCase of testCases) {
+    info(
+      `Test MV2 extension allowed to change restricted header if already set by the website: ${JSON.stringify(
+        testCase.siteHeader
+      )}`
+    );
+    await test_restricted_response_headers_changes({
+      ...testCase,
+      firstExtData: extDataMV3,
+      secondExtData: extDataMV2,
+      // Expect the value set by the server to be preserved.
+      expectedHeaderValue: testCase.secondExtHeaderChange,
+    });
+  }
+});
diff --git a/toolkit/components/extensions/test/xpcshell/test_ext_webRequest_set_cookie.js b/toolkit/components/extensions/test/xpcshell/test_ext_webRequest_set_cookie.js
new file mode 100644
index 0000000000..e40bc4f8b4
--- /dev/null
+++ b/toolkit/components/extensions/test/xpcshell/test_ext_webRequest_set_cookie.js
@@ -0,0 +1,308 @@
+"use strict";
+
+const HOSTS = new Set(["example.com"]);
+
+const server = createHttpServer({ hosts: HOSTS });
+
+server.registerDirectory("/data/", do_get_file("data"));
+
+server.registerPathHandler(
+  "/file_webrequestblocking_set_cookie.html",
+  (request, response) => {
+    response.setStatusLine(request.httpVersion, 200, "OK");
+    response.setHeader("Content-Type", "text/html", false);
+    response.setHeader("Set-Cookie", "reqcookie=reqvalue", false);
+    response.write("<!DOCTYPE html><html></html>");
+  }
+);
+
+add_task(async function test_modifying_cookies_from_onHeadersReceived() {
+  async function background() {
+    /**
+     * Check that all the cookies described by `prefixes` are in the cookie jar.
+     *
+     * @param {Array.string} prefixes
+     *   Zero or more prefixes, describing cookies that are expected to be set
+     *   in the current cookie jar.  Each prefix describes both a cookie
+     *   name and corresponding value.  For example, if the string "ext"
+     *   is passed as an argument, then this function expects to see
+     *   a cookie called "extcookie" and corresponding value of "extvalue".
+     */
+    async function checkCookies(prefixes) {
+      const numPrefixes = prefixes.length;
+      const currentCookies = await browser.cookies.getAll({});
+      browser.test.assertEq(
+        numPrefixes,
+        currentCookies.length,
+        `${numPrefixes} cookies were set`
+      );
+
+      for (let cookiePrefix of prefixes) {
+        let cookieName = `${cookiePrefix}cookie`;
+        let expectedCookieValue = `${cookiePrefix}value`;
+        let fetchedCookie = await browser.cookies.getAll({ name: cookieName });
+        browser.test.assertEq(
+          1,
+          fetchedCookie.length,
+          `Found 1 cookie with name "${cookieName}"`
+        );
+        browser.test.assertEq(
+          expectedCookieValue,
+          fetchedCookie[0] && fetchedCookie[0].value,
+          `Cookie "${cookieName}" has expected value of "${expectedCookieValue}"`
+        );
+      }
+    }
+
+    function awaitMessage(expectedMsg) {
+      return new Promise(resolve => {
+        browser.test.onMessage.addListener(function listener(msg) {
+          if (msg === expectedMsg) {
+            browser.test.onMessage.removeListener(listener);
+            resolve();
+          }
+        });
+      });
+    }
+
+    /**
+     * Opens the given test file as a content page.
+     *
+     * @param {string} filename
+     *   The name of a html file relative to the test server root.
+     *
+     * @returns {Promise}
+     */
+    function openContentPage(filename) {
+      let promise = awaitMessage("url-loaded");
+      browser.test.sendMessage(
+        "load-url",
+        `http://example.com/${filename}?nocache=${Math.random()}`
+      );
+      return promise;
+    }
+
+    /**
+     * Tests that expected cookies are in the cookie jar after opening a file.
+     *
+     * @param {string} filename
+     *   The name of a html file in the
+     *   "toolkit/components/extensions/test/mochitest" directory.
+     * @param {?Array.string} prefixes
+     *   Zero or more prefixes, describing cookies that are expected to be set
+     *   in the current cookie jar.  Each prefix describes both a cookie
+     *   name and corresponding value.  For example, if the string "ext"
+     *   is passed as an argument, then this function expects to see
+     *   a cookie called "extcookie" and corresponding value of "extvalue".
+     *   If undefined, then no checks are automatically performed, and the
+     *   caller should provide a callback to perform the checks.
+     * @param {?Function} callback
+     *   An optional async callback function that, if provided, will be called
+     *   with an object that contains windowId and tabId parameters.
+     *   Callers can use this callback to apply extra tests about the state of
+     *   the cookie jar, or to query the state of the opened page.
+     */
+    async function testCookiesWithFile(filename, prefixes, callback) {
+      await browser.browsingData.removeCookies({});
+      await openContentPage(filename);
+
+      if (prefixes !== undefined) {
+        await checkCookies(prefixes);
+      }
+
+      if (callback !== undefined) {
+        await callback();
+      }
+      let promise = awaitMessage("url-unloaded");
+      browser.test.sendMessage("unload-url");
+      await promise;
+    }
+
+    const filter = {
+      urls: ["<all_urls>"],
+      types: ["main_frame", "sub_frame"],
+    };
+
+    const headersReceivedInfoSpec = ["blocking", "responseHeaders"];
+
+    const onHeadersReceived = details => {
+      details.responseHeaders.push({
+        name: "Set-Cookie",
+        value: "extcookie=extvalue",
+      });
+
+      return {
+        responseHeaders: details.responseHeaders,
+      };
+    };
+    browser.webRequest.onHeadersReceived.addListener(
+      onHeadersReceived,
+      filter,
+      headersReceivedInfoSpec
+    );
+
+    // First, perform a request that should not set any cookies, and check
+    // that the cookie the extension sets is the only cookie in the
+    // cookie jar.
+    await testCookiesWithFile("data/file_sample.html", ["ext"]);
+
+    // Next, perform a request that will set on cookie (reqcookie=reqvalue)
+    // and check that two cookies wind up in the cookie jar (the request
+    // set cookie, and the extension set cookie).
+    await testCookiesWithFile("file_webrequestblocking_set_cookie.html", [
+      "ext",
+      "req",
+    ]);
+
+    // Third, register another onHeadersReceived handler that also
+    // sets a cookie (thirdcookie=thirdvalue), to make sure modifications from
+    // multiple onHeadersReceived listeners are merged correctly.
+    const thirdOnHeadersRecievedListener = details => {
+      details.responseHeaders.push({
+        name: "Set-Cookie",
+        value: "thirdcookie=thirdvalue",
+      });
+
+      browser.test.log(JSON.stringify(details.responseHeaders));
+
+      return {
+        responseHeaders: details.responseHeaders,
+      };
+    };
+    browser.webRequest.onHeadersReceived.addListener(
+      thirdOnHeadersRecievedListener,
+      filter,
+      headersReceivedInfoSpec
+    );
+    await testCookiesWithFile("file_webrequestblocking_set_cookie.html", [
+      "ext",
+      "req",
+      "third",
+    ]);
+    browser.webRequest.onHeadersReceived.removeListener(onHeadersReceived);
+    browser.webRequest.onHeadersReceived.removeListener(
+      thirdOnHeadersRecievedListener
+    );
+
+    // Fourth, test to make sure that extensions can remove cookies
+    // using onHeadersReceived too, by 1. making a request that
+    // sets a cookie (reqcookie=reqvalue), 2. having the extension remove
+    // that cookie by removing that header, and 3. adding a new cookie
+    // (extcookie=extvalue).
+    const fourthOnHeadersRecievedListener = details => {
+      // Remove the cookie set by the request (reqcookie=reqvalue).
+      const newHeaders = details.responseHeaders.filter(
+        cookie => cookie.name !== "set-cookie"
+      );
+
+      // And then add a new cookie in its place (extcookie=extvalue).
+      newHeaders.push({
+        name: "Set-Cookie",
+        value: "extcookie=extvalue",
+      });
+
+      return {
+        responseHeaders: newHeaders,
+      };
+    };
+    browser.webRequest.onHeadersReceived.addListener(
+      fourthOnHeadersRecievedListener,
+      filter,
+      headersReceivedInfoSpec
+    );
+    await testCookiesWithFile("file_webrequestblocking_set_cookie.html", [
+      "ext",
+    ]);
+    browser.webRequest.onHeadersReceived.removeListener(
+      fourthOnHeadersRecievedListener
+    );
+
+    // Fifth, check that extensions are able to overwrite headers set by
+    // pages. In this test, make a request that will set "reqcookie=reqvalue",
+    // and add a listener that sets "reqcookie=changedvalue".  Check
+    // to make sure that the cookie jar contains "reqcookie=changedvalue"
+    // and not "reqcookie=reqvalue".
+    const fifthOnHeadersRecievedListener = details => {
+      // Remove the cookie set by the request (reqcookie=reqvalue).
+      const newHeaders = details.responseHeaders.filter(
+        cookie => cookie.name !== "set-cookie"
+      );
+
+      // And then add a new cookie in its place (reqcookie=changedvalue).
+      newHeaders.push({
+        name: "Set-Cookie",
+        value: "reqcookie=changedvalue",
+      });
+
+      return {
+        responseHeaders: newHeaders,
+      };
+    };
+    browser.webRequest.onHeadersReceived.addListener(
+      fifthOnHeadersRecievedListener,
+      filter,
+      headersReceivedInfoSpec
+    );
+
+    await testCookiesWithFile(
+      "file_webrequestblocking_set_cookie.html",
+      undefined,
+      async () => {
+        const currentCookies = await browser.cookies.getAll({});
+        browser.test.assertEq(1, currentCookies.length, `1 cookie was set`);
+
+        const cookieName = "reqcookie";
+        const expectedCookieValue = "changedvalue";
+        const fetchedCookie = await browser.cookies.getAll({
+          name: cookieName,
+        });
+
+        browser.test.assertEq(
+          1,
+          fetchedCookie.length,
+          `Found 1 cookie with name "${cookieName}"`
+        );
+        browser.test.assertEq(
+          expectedCookieValue,
+          fetchedCookie[0] && fetchedCookie[0].value,
+          `Cookie "${cookieName}" has expected value of "${expectedCookieValue}"`
+        );
+      }
+    );
+    browser.webRequest.onHeadersReceived.removeListener(
+      fifthOnHeadersRecievedListener
+    );
+
+    browser.test.notifyPass("cookie modifying extension");
+  }
+
+  let extension = ExtensionTestUtils.loadExtension({
+    manifest: {
+      permissions: [
+        "browsingData",
+        "cookies",
+        "webNavigation",
+        "webRequest",
+        "webRequestBlocking",
+        "<all_urls>",
+      ],
+    },
+    background,
+  });
+
+  let contentPage = null;
+  extension.onMessage("load-url", async url => {
+    ok(!contentPage, "Should have no content page to unload");
+    contentPage = await ExtensionTestUtils.loadContentPage(url);
+    extension.sendMessage("url-loaded");
+  });
+  extension.onMessage("unload-url", async () => {
+    await contentPage.close();
+    contentPage = null;
+    extension.sendMessage("url-unloaded");
+  });
+
+  await extension.startup();
+  await extension.awaitFinish("cookie modifying extension");
+  await extension.unload();
+});
diff --git a/toolkit/components/extensions/test/xpcshell/test_ext_webRequest_startup.js b/toolkit/components/extensions/test/xpcshell/test_ext_webRequest_startup.js
new file mode 100644
index 0000000000..616dc1fb50
--- /dev/null
+++ b/toolkit/components/extensions/test/xpcshell/test_ext_webRequest_startup.js
@@ -0,0 +1,751 @@
+"use strict";
+
+// Delay loading until createAppInfo is called and setup.
+ChromeUtils.defineESModuleGetters(this, {
+  AddonManager: "resource://gre/modules/AddonManager.sys.mjs",
+});
+
+AddonTestUtils.init(this);
+AddonTestUtils.overrideCertDB();
+
+// The app and platform version here should be >= of the version set in the extensions.webExtensionsMinPlatformVersion preference,
+// otherwise test_persistent_listener_after_staged_update will fail because no compatible updates will be found.
+AddonTestUtils.createAppInfo(
+  "xpcshell@tests.mozilla.org",
+  "XPCShell",
+  "42",
+  "42"
+);
+
+let { promiseShutdownManager, promiseStartupManager, promiseRestartManager } =
+  AddonTestUtils;
+
+const server = createHttpServer({ hosts: ["example.com"] });
+server.registerDirectory("/data/", do_get_file("data"));
+
+let scopes = AddonManager.SCOPE_PROFILE | AddonManager.SCOPE_APPLICATION;
+Services.prefs.setIntPref("extensions.enabledScopes", scopes);
+
+function trackEvents(wrapper) {
+  let events = new Map();
+  for (let event of ["background-script-event", "start-background-script"]) {
+    events.set(event, false);
+    wrapper.extension.once(event, () => events.set(event, true));
+  }
+  return events;
+}
+
+/**
+ * That that we get the expected events
+ *
+ * @param {Extension} extension
+ * @param {Map} events
+ * @param {object} expect
+ * @param {boolean} expect.background   delayed startup event expected
+ * @param {boolean} expect.started      background has already started
+ * @param {boolean} expect.delayedStart startup is delayed, notify start and
+ *                                      expect the starting event
+ * @param {boolean} expect.request      wait for the request event
+ */
+async function testPersistentRequestStartup(extension, events, expect = {}) {
+  equal(
+    events.get("background-script-event"),
+    !!expect.background,
+    "Should have gotten a background script event"
+  );
+  equal(
+    events.get("start-background-script"),
+    !!expect.started,
+    "Background script should be started"
+  );
+
+  if (!expect.started) {
+    AddonTestUtils.notifyEarlyStartup();
+    await ExtensionParent.browserPaintedPromise;
+
+    equal(
+      events.get("start-background-script"),
+      !!expect.delayedStart,
+      "Should have gotten start-background-script event"
+    );
+  }
+
+  if (expect.request) {
+    await extension.awaitMessage("got-request");
+    ok(true, "Background page loaded and received webRequest event");
+  }
+}
+
+// Test that a non-blocking listener does not start the background on
+// startup, but that it does work after startup.
+add_task(async function test_nonblocking() {
+  await promiseStartupManager();
+
+  let extension = ExtensionTestUtils.loadExtension({
+    useAddonManager: "permanent",
+    manifest: {
+      permissions: ["webRequest", "http://example.com/"],
+    },
+
+    background() {
+      browser.webRequest.onBeforeRequest.addListener(
+        details => {
+          browser.test.sendMessage("got-request");
+        },
+        { urls: ["http://example.com/data/file_sample.html"] }
+      );
+      browser.test.sendMessage("ready");
+    },
+  });
+
+  // First install runs background immediately, this sets persistent listeners
+  await extension.startup();
+  await extension.awaitMessage("ready");
+
+  // Restart to get APP_STARTUP, the background should not start
+  await promiseRestartManager({ lateStartup: false });
+  await extension.awaitStartup();
+  assertPersistentListeners(extension, "webRequest", "onBeforeRequest", {
+    primed: false,
+  });
+
+  // Test an early startup event
+  let events = trackEvents(extension);
+
+  await ExtensionTestUtils.fetch(
+    "http://example.com/",
+    "http://example.com/data/file_sample.html"
+  );
+
+  await testPersistentRequestStartup(extension, events, {
+    background: false,
+    delayedStart: false,
+    request: false,
+  });
+
+  AddonTestUtils.notifyLateStartup();
+  await extension.awaitMessage("ready");
+  assertPersistentListeners(extension, "webRequest", "onBeforeRequest", {
+    primed: false,
+  });
+
+  // Test an event after startup
+  await ExtensionTestUtils.fetch(
+    "http://example.com/",
+    "http://example.com/data/file_sample.html"
+  );
+
+  await testPersistentRequestStartup(extension, events, {
+    background: false,
+    started: true,
+    request: true,
+  });
+
+  await extension.unload();
+
+  await promiseShutdownManager();
+});
+
+// Test that a non-blocking listener does not start the background on
+// startup, but that it does work after startup.
+add_task(async function test_eventpage_nonblocking() {
+  Services.prefs.setBoolPref("extensions.eventPages.enabled", true);
+  await promiseStartupManager();
+
+  let id = "event-nonblocking@test";
+  let extension = ExtensionTestUtils.loadExtension({
+    useAddonManager: "permanent",
+    manifest: {
+      browser_specific_settings: { gecko: { id } },
+      permissions: ["webRequest", "http://example.com/"],
+      background: { persistent: false },
+    },
+
+    background() {
+      browser.webRequest.onBeforeRequest.addListener(
+        details => {
+          browser.test.sendMessage("got-request");
+        },
+        { urls: ["http://example.com/data/file_sample.html"] }
+      );
+    },
+  });
+
+  // First install runs background immediately, this sets persistent listeners
+  await extension.startup();
+
+  // Restart to get APP_STARTUP, the background should not start
+  await promiseRestartManager({ lateStartup: false });
+  await extension.awaitStartup();
+  assertPersistentListeners(extension, "webRequest", "onBeforeRequest", {
+    primed: false,
+  });
+
+  // Test an early startup event
+  let events = trackEvents(extension);
+
+  await ExtensionTestUtils.fetch(
+    "http://example.com/",
+    "http://example.com/data/file_sample.html"
+  );
+
+  await testPersistentRequestStartup(extension, events);
+
+  await AddonTestUtils.notifyLateStartup();
+  // After late startup, event page listeners should be primed.
+  assertPersistentListeners(extension, "webRequest", "onBeforeRequest", {
+    primed: true,
+  });
+
+  // We should not have seen any events yet.
+  await testPersistentRequestStartup(extension, events);
+
+  // Test an event after startup
+  await ExtensionTestUtils.fetch(
+    "http://example.com/",
+    "http://example.com/data/file_sample.html"
+  );
+
+  // Now the event page should be started and we'll see the request.
+  await testPersistentRequestStartup(extension, events, {
+    background: true,
+    started: true,
+    request: true,
+  });
+
+  await extension.unload();
+
+  await promiseShutdownManager();
+  Services.prefs.setBoolPref("extensions.eventPages.enabled", false);
+});
+
+// Tests that filters are handled properly: if we have a blocking listener
+// with a filter, a request that does not match the filter does not get
+// suspended and does not start the background page.
+add_task(async function test_persistent_blocking() {
+  await promiseStartupManager();
+
+  let extension = ExtensionTestUtils.loadExtension({
+    useAddonManager: "permanent",
+    manifest: {
+      permissions: [
+        "webRequest",
+        "webRequestBlocking",
+        "http://test1.example.com/",
+      ],
+    },
+
+    background() {
+      browser.webRequest.onBeforeRequest.addListener(
+        details => {
+          browser.test.fail("Listener should not have been called");
+        },
+        { urls: ["http://test1.example.com/*"] },
+        ["blocking"]
+      );
+    },
+  });
+
+  await extension.startup();
+  assertPersistentListeners(extension, "webRequest", "onBeforeRequest", {
+    primed: false,
+  });
+
+  await promiseRestartManager({ lateStartup: false });
+  await extension.awaitStartup();
+  assertPersistentListeners(extension, "webRequest", "onBeforeRequest", {
+    primed: true,
+  });
+
+  let events = trackEvents(extension);
+
+  await ExtensionTestUtils.fetch(
+    "http://example.com/",
+    "http://example.com/data/file_sample.html"
+  );
+
+  await testPersistentRequestStartup(extension, events, {
+    background: false,
+    delayedStart: false,
+    request: false,
+  });
+
+  AddonTestUtils.notifyLateStartup();
+
+  await extension.unload();
+  await promiseShutdownManager();
+});
+
+// Tests that moving permission to optional retains permission and that the
+// persistent listeners are used as expected.
+add_task(async function test_persistent_listener_after_sideload_upgrade() {
+  let id = "permission-sideload-upgrade@test";
+  let extensionData = {
+    useAddonManager: "permanent",
+    manifest: {
+      version: "1.0",
+      browser_specific_settings: { gecko: { id } },
+      permissions: ["webRequest", "webRequestBlocking", "http://example.com/"],
+    },
+
+    background() {
+      browser.webRequest.onBeforeRequest.addListener(
+        details => {
+          browser.test.sendMessage("got-request");
+        },
+        { urls: ["http://example.com/data/file_sample.html"] },
+        ["blocking"]
+      );
+    },
+  };
+  let xpi = AddonTestUtils.createTempWebExtensionFile(extensionData);
+
+  let extension = ExtensionTestUtils.expectExtension(id);
+  await AddonTestUtils.manuallyInstall(xpi);
+  await promiseStartupManager();
+  await extension.awaitStartup();
+  // Sideload install does not prime listeners
+  assertPersistentListeners(extension, "webRequest", "onBeforeRequest", {
+    primed: false,
+  });
+
+  await ExtensionTestUtils.fetch(
+    "http://example.com/",
+    "http://example.com/data/file_sample.html"
+  );
+  await extension.awaitMessage("got-request");
+
+  await promiseShutdownManager();
+
+  // Prepare a sideload update for the extension.
+  extensionData.manifest.version = "2.0";
+  extensionData.manifest.permissions = ["http://example.com/"];
+  extensionData.manifest.optional_permissions = [
+    "webRequest",
+    "webRequestBlocking",
+  ];
+  xpi = AddonTestUtils.createTempWebExtensionFile(extensionData);
+  await AddonTestUtils.manuallyInstall(xpi);
+
+  await promiseStartupManager();
+  await extension.awaitStartup();
+  // Upgrades start the background when the extension is loaded, so
+  // primed listeners are cleared already and background events are
+  // already completed.
+  assertPersistentListeners(extension, "webRequest", "onBeforeRequest", {
+    primed: false,
+    persisted: true,
+  });
+
+  await extension.unload();
+  await promiseShutdownManager();
+});
+
+// Utility to install builtin addon
+async function installBuiltinExtension(extensionData) {
+  let xpi = await AddonTestUtils.createTempWebExtensionFile(extensionData);
+
+  // The built-in location requires a resource: URL that maps to a
+  // jar: or file: URL.  This would typically be something bundled
+  // into omni.ja but for testing we just use a temp file.
+  let base = Services.io.newURI(`jar:file:${xpi.path}!/`);
+  let resProto = Services.io
+    .getProtocolHandler("resource")
+    .QueryInterface(Ci.nsIResProtocolHandler);
+  resProto.setSubstitution("ext-test", base);
+  return AddonManager.installBuiltinAddon("resource://ext-test/");
+}
+
+function promisePostponeInstall(install) {
+  return new Promise((resolve, reject) => {
+    let listener = {
+      onInstallFailed: () => {
+        install.removeListener(listener);
+        reject(new Error("extension installation should not have failed"));
+      },
+      onInstallEnded: () => {
+        install.removeListener(listener);
+        reject(
+          new Error(
+            `extension installation should not have ended for ${install.addon.id}`
+          )
+        );
+      },
+      onInstallPostponed: () => {
+        install.removeListener(listener);
+        resolve();
+      },
+    };
+
+    install.addListener(listener);
+    install.install();
+  });
+}
+
+// Tests that moving permission to optional retains permission and that the
+// persistent listeners are used as expected.
+add_task(
+  async function test_persistent_listener_after_builtin_location_upgrade() {
+    let id = "permission-builtin-upgrade@test";
+    let extensionData = {
+      useAddonManager: "permanent",
+      manifest: {
+        version: "1.0",
+        browser_specific_settings: { gecko: { id } },
+        permissions: [
+          "webRequest",
+          "webRequestBlocking",
+          "http://example.com/",
+        ],
+      },
+
+      async background() {
+        browser.runtime.onUpdateAvailable.addListener(() => {
+          browser.test.sendMessage("postponed");
+        });
+
+        browser.webRequest.onBeforeRequest.addListener(
+          details => {
+            browser.test.sendMessage("got-request");
+          },
+          { urls: ["http://example.com/data/file_sample.html"] },
+          ["blocking"]
+        );
+      },
+    };
+    await promiseStartupManager();
+    // If we use an extension wrapper via ExtensionTestUtils.expectExtension
+    // it will continue to handle messages even after the update, resulting
+    // in errors when it receives additional messages without any awaitMessage.
+    let promiseExtension = AddonTestUtils.promiseWebExtensionStartup(id);
+    await installBuiltinExtension(extensionData);
+    let extv1 = await promiseExtension;
+    assertPersistentListeners(
+      { extension: extv1 },
+      "webRequest",
+      "onBeforeRequest",
+      {
+        primed: false,
+      }
+    );
+
+    // Prepare an update for the extension.
+    extensionData.manifest.version = "2.0";
+    let xpi = AddonTestUtils.createTempWebExtensionFile(extensionData);
+    let install = await AddonManager.getInstallForFile(xpi);
+
+    // Install the update and wait for the onUpdateAvailable event to complete.
+    let promiseUpdate = new Promise(resolve =>
+      extv1.once("test-message", (kind, msg) => {
+        if (msg == "postponed") {
+          resolve();
+        }
+      })
+    );
+    await Promise.all([promisePostponeInstall(install), promiseUpdate]);
+    await promiseShutdownManager();
+
+    // restarting allows upgrade to proceed
+    let extension = ExtensionTestUtils.expectExtension(id);
+    await promiseStartupManager();
+    await extension.awaitStartup();
+    // Upgrades start the background when the extension is loaded, so
+    // primed listeners are cleared already and background events are
+    // already completed.
+    assertPersistentListeners(extension, "webRequest", "onBeforeRequest", {
+      primed: false,
+      persisted: true,
+    });
+
+    await extension.unload();
+
+    // remove the builtin addon which will have restarted now.
+    let addon = await AddonManager.getAddonByID(id);
+    await addon.uninstall();
+
+    await promiseShutdownManager();
+  }
+);
+
+// Tests that moving permission to optional during a staged upgrade retains permission
+// and that the persistent listeners are used as expected.
+add_task(async function test_persistent_listener_after_staged_upgrade() {
+  AddonManager.checkUpdateSecurity = false;
+  let id = "persistent-staged-upgrade@test";
+
+  // register an update file.
+  AddonTestUtils.registerJSON(server, "/test_update.json", {
+    addons: {
+      "persistent-staged-upgrade@test": {
+        updates: [
+          {
+            version: "2.0",
+            update_link:
+              "http://example.com/addons/test_settings_staged_restart.xpi",
+          },
+        ],
+      },
+    },
+  });
+
+  let extensionData = {
+    useAddonManager: "permanent",
+    manifest: {
+      version: "2.0",
+      browser_specific_settings: {
+        gecko: { id, update_url: `http://example.com/test_update.json` },
+      },
+      permissions: ["http://example.com/"],
+      optional_permissions: ["webRequest", "webRequestBlocking"],
+    },
+
+    background() {
+      browser.webRequest.onBeforeRequest.addListener(
+        details => {
+          browser.test.sendMessage("got-request");
+        },
+        { urls: ["http://example.com/data/file_sample.html"] },
+        ["blocking"]
+      );
+      browser.webRequest.onSendHeaders.addListener(
+        details => {
+          browser.test.sendMessage("got-sendheaders");
+        },
+        { urls: ["http://example.com/data/file_sample.html"] }
+      );
+      // Force a staged updated.
+      browser.runtime.onUpdateAvailable.addListener(async details => {
+        if (details && details.version) {
+          // This should be the version of the pending update.
+          browser.test.assertEq("2.0", details.version, "correct version");
+          browser.test.sendMessage("delay");
+        }
+      });
+    },
+  };
+
+  // Prepare the update first.
+  server.registerFile(
+    `/addons/test_settings_staged_restart.xpi`,
+    AddonTestUtils.createTempWebExtensionFile(extensionData)
+  );
+
+  // Prepare the extension that will be updated.
+  extensionData.manifest.version = "1.0";
+  extensionData.manifest.permissions = [
+    "webRequest",
+    "webRequestBlocking",
+    "http://example.com/",
+  ];
+  delete extensionData.manifest.optional_permissions;
+  extensionData.background = function () {
+    browser.webRequest.onBeforeRequest.addListener(
+      details => {
+        browser.test.sendMessage("got-request");
+      },
+      { urls: ["http://example.com/data/file_sample.html"] },
+      ["blocking"]
+    );
+    browser.webRequest.onBeforeSendHeaders.addListener(
+      details => {
+        browser.test.sendMessage("got-beforesendheaders");
+      },
+      { urls: ["http://example.com/data/file_sample.html"] }
+    );
+    browser.webRequest.onSendHeaders.addListener(
+      details => {
+        browser.test.sendMessage("got-sendheaders");
+      },
+      { urls: ["http://example.com/data/file_sample.html"] }
+    );
+    // Force a staged updated.
+    browser.runtime.onUpdateAvailable.addListener(async details => {
+      if (details && details.version) {
+        // This should be the version of the pending update.
+        browser.test.assertEq("2.0", details.version, "correct version");
+        browser.test.sendMessage("delay");
+      }
+    });
+  };
+
+  await promiseStartupManager();
+  let extension = ExtensionTestUtils.loadExtension(extensionData);
+  await extension.startup();
+  assertPersistentListeners(extension, "webRequest", "onBeforeRequest", {
+    primed: false,
+  });
+  assertPersistentListeners(extension, "webRequest", "onBeforeSendHeaders", {
+    primed: false,
+  });
+  assertPersistentListeners(extension, "webRequest", "onSendHeaders", {
+    primed: false,
+  });
+
+  await ExtensionTestUtils.fetch(
+    "http://example.com/",
+    "http://example.com/data/file_sample.html"
+  );
+  await extension.awaitMessage("got-request");
+  await extension.awaitMessage("got-beforesendheaders");
+  await extension.awaitMessage("got-sendheaders");
+  ok(true, "Initial version received webRequest event");
+
+  let addon = await AddonManager.getAddonByID(id);
+  Assert.equal(addon.version, "1.0", "1.0 is loaded");
+
+  let update = await AddonTestUtils.promiseFindAddonUpdates(addon);
+  let install = update.updateAvailable;
+  Assert.ok(install, `install is available ${update.error}`);
+
+  await AddonTestUtils.promiseCompleteAllInstalls([install]);
+
+  Assert.equal(
+    install.state,
+    AddonManager.STATE_POSTPONED,
+    "update is staged for install"
+  );
+  await extension.awaitMessage("delay");
+
+  await promiseShutdownManager();
+
+  // restarting allows upgrade to proceed
+  await promiseStartupManager();
+  await extension.awaitStartup();
+
+  // Upgrades start the background when the extension is loaded, so
+  // primed listeners are cleared already and background events are
+  // already completed.
+  assertPersistentListeners(extension, "webRequest", "onBeforeRequest", {
+    primed: false,
+    persisted: true,
+  });
+  // this was removed in the upgrade background, should not be persisted.
+  assertPersistentListeners(extension, "webRequest", "onBeforeSendHeaders", {
+    primed: false,
+    persisted: false,
+  });
+  assertPersistentListeners(extension, "webRequest", "onSendHeaders", {
+    primed: false,
+    persisted: true,
+  });
+
+  await extension.unload();
+  await promiseShutdownManager();
+  AddonManager.checkUpdateSecurity = true;
+});
+
+// Tests that removing the permission releases the persistent listener.
+add_task(async function test_persistent_listener_after_permission_removal() {
+  AddonManager.checkUpdateSecurity = false;
+  let id = "persistent-staged-remove@test";
+
+  // register an update file.
+  AddonTestUtils.registerJSON(server, "/test_remove.json", {
+    addons: {
+      "persistent-staged-remove@test": {
+        updates: [
+          {
+            version: "2.0",
+            update_link:
+              "http://example.com/addons/test_settings_staged_remove.xpi",
+          },
+        ],
+      },
+    },
+  });
+
+  let extensionData = {
+    useAddonManager: "permanent",
+    manifest: {
+      version: "2.0",
+      browser_specific_settings: {
+        gecko: { id, update_url: `http://example.com/test_remove.json` },
+      },
+      permissions: ["tabs", "http://example.com/"],
+    },
+
+    background() {
+      browser.test.sendMessage("loaded");
+    },
+  };
+
+  // Prepare the update first.
+  server.registerFile(
+    `/addons/test_settings_staged_remove.xpi`,
+    AddonTestUtils.createTempWebExtensionFile(extensionData)
+  );
+
+  await promiseStartupManager();
+  let extension = ExtensionTestUtils.loadExtension({
+    useAddonManager: "permanent",
+    manifest: {
+      version: "1.0",
+      browser_specific_settings: {
+        gecko: { id, update_url: `http://example.com/test_remove.json` },
+      },
+      permissions: ["webRequest", "webRequestBlocking", "http://example.com/"],
+    },
+
+    background() {
+      browser.webRequest.onBeforeRequest.addListener(
+        details => {
+          browser.test.sendMessage("got-request");
+        },
+        { urls: ["http://example.com/data/file_sample.html"] },
+        ["blocking"]
+      );
+      // Force a staged updated.
+      browser.runtime.onUpdateAvailable.addListener(async details => {
+        if (details && details.version) {
+          // This should be the version of the pending update.
+          browser.test.assertEq("2.0", details.version, "correct version");
+          browser.test.sendMessage("delay");
+        }
+      });
+    },
+  });
+
+  await extension.startup();
+
+  await ExtensionTestUtils.fetch(
+    "http://example.com/",
+    "http://example.com/data/file_sample.html"
+  );
+  await extension.awaitMessage("got-request");
+  ok(true, "Initial version received webRequest event");
+
+  let addon = await AddonManager.getAddonByID(id);
+  Assert.equal(addon.version, "1.0", "1.0 is loaded");
+
+  let update = await AddonTestUtils.promiseFindAddonUpdates(addon);
+  let install = update.updateAvailable;
+  Assert.ok(install, `install is available ${update.error}`);
+
+  await AddonTestUtils.promiseCompleteAllInstalls([install]);
+
+  Assert.equal(
+    install.state,
+    AddonManager.STATE_POSTPONED,
+    "update is staged for install"
+  );
+  await extension.awaitMessage("delay");
+
+  await promiseShutdownManager();
+
+  // restarting allows upgrade to proceed
+  await promiseStartupManager({ lateStartup: false });
+  await extension.awaitStartup();
+  await extension.awaitMessage("loaded");
+
+  // Upgrades start the background when the extension is loaded, so
+  // primed listeners are cleared already and background events are
+  // already completed.
+  assertPersistentListeners(extension, "webRequest", "onBeforeRequest", {
+    primed: false,
+    persisted: false,
+  });
+
+  await extension.unload();
+  await promiseShutdownManager();
+  AddonManager.checkUpdateSecurity = true;
+});
diff --git a/toolkit/components/extensions/test/xpcshell/test_ext_webRequest_startup_StreamFilter.js b/toolkit/components/extensions/test/xpcshell/test_ext_webRequest_startup_StreamFilter.js
new file mode 100644
index 0000000000..4972719b43
--- /dev/null
+++ b/toolkit/components/extensions/test/xpcshell/test_ext_webRequest_startup_StreamFilter.js
@@ -0,0 +1,76 @@
+"use strict";
+
+AddonTestUtils.init(this);
+AddonTestUtils.overrideCertDB();
+AddonTestUtils.createAppInfo(
+  "xpcshell@tests.mozilla.org",
+  "XPCShell",
+  "1",
+  "43"
+);
+
+let { promiseRestartManager, promiseShutdownManager, promiseStartupManager } =
+  AddonTestUtils;
+
+const server = createHttpServer({ hosts: ["example.com"] });
+server.registerDirectory("/data/", do_get_file("data"));
+
+// Test that a blocking listener that uses filterResponseData() works
+// properly (i.e., that the delayed call to registerTraceableChannel
+// works properly).
+add_task(async function test_StreamFilter_at_restart() {
+  const DATA = `<!DOCTYPE html>
+<html>
+<body>
+  <h1>This is a modified page</h1>
+</body>
+</html>`;
+
+  function background(data) {
+    browser.webRequest.onBeforeRequest.addListener(
+      details => {
+        let filter = browser.webRequest.filterResponseData(details.requestId);
+        filter.onstop = () => {
+          let encoded = new TextEncoder().encode(data);
+          filter.write(encoded);
+          filter.close();
+        };
+      },
+      { urls: ["http://example.com/data/file_sample.html"] },
+      ["blocking"]
+    );
+  }
+
+  await promiseStartupManager();
+
+  let extension = ExtensionTestUtils.loadExtension({
+    useAddonManager: "permanent",
+    manifest: {
+      permissions: ["webRequest", "webRequestBlocking", "http://example.com/"],
+    },
+
+    background: `(${background})(${uneval(DATA)})`,
+  });
+
+  await extension.startup();
+
+  await promiseRestartManager();
+  await extension.awaitStartup();
+
+  let dataPromise = ExtensionTestUtils.fetch(
+    "http://example.com/",
+    "http://example.com/data/file_sample.html"
+  );
+
+  Services.obs.notifyObservers(null, "browser-delayed-startup-finished");
+  let data = await dataPromise;
+
+  equal(
+    data,
+    DATA,
+    "Stream filter was properly installed for a load during startup"
+  );
+
+  await extension.unload();
+  await promiseShutdownManager();
+});
diff --git a/toolkit/components/extensions/test/xpcshell/test_ext_webRequest_style_cache.js b/toolkit/components/extensions/test/xpcshell/test_ext_webRequest_style_cache.js
new file mode 100644
index 0000000000..296bee3685
--- /dev/null
+++ b/toolkit/components/extensions/test/xpcshell/test_ext_webRequest_style_cache.js
@@ -0,0 +1,49 @@
+"use strict";
+
+const BASE = "http://example.com/data/";
+
+const server = createHttpServer({ hosts: ["example.com"] });
+
+server.registerDirectory("/data/", do_get_file("data"));
+
+add_task(async function test_stylesheet_cache() {
+  let extension = ExtensionTestUtils.loadExtension({
+    manifest: {
+      permissions: ["webRequest", "webRequestBlocking", "<all_urls>"],
+    },
+    background() {
+      const SHEET_URI = "http://example.com/data/file_stylesheet_cache.css";
+      let firstFound = false;
+      browser.webRequest.onBeforeRequest.addListener(
+        details => {
+          browser.test.assertEq(
+            details.url,
+            firstFound ? SHEET_URI + "?2" : SHEET_URI
+          );
+          firstFound = true;
+          browser.test.sendMessage("stylesheet found");
+        },
+        { urls: ["<all_urls>"], types: ["stylesheet"] },
+        ["blocking"]
+      );
+    },
+  });
+
+  await extension.startup();
+
+  let cp = await ExtensionTestUtils.loadContentPage(
+    BASE + "file_stylesheet_cache.html"
+  );
+
+  await extension.awaitMessage("stylesheet found");
+
+  // Need to use the same ContentPage so that the remote process the page ends
+  // up in is the same.
+  await cp.loadURL(BASE + "file_stylesheet_cache_2.html");
+
+  await extension.awaitMessage("stylesheet found");
+
+  await cp.close();
+
+  await extension.unload();
+});
diff --git a/toolkit/components/extensions/test/xpcshell/test_ext_webRequest_suspend.js b/toolkit/components/extensions/test/xpcshell/test_ext_webRequest_suspend.js
new file mode 100644
index 0000000000..f8116aced0
--- /dev/null
+++ b/toolkit/components/extensions/test/xpcshell/test_ext_webRequest_suspend.js
@@ -0,0 +1,289 @@
+"use strict";
+
+const HOSTS = new Set(["example.com"]);
+
+const server = createHttpServer({ hosts: HOSTS });
+
+const BASE_URL = "http://example.com";
+const FETCH_ORIGIN = "http://example.com/dummy";
+
+server.registerPathHandler("/return_headers.sjs", (request, response) => {
+  response.setHeader("Content-Type", "text/plain", false);
+
+  let headers = {};
+  for (let { data: header } of request.headers) {
+    headers[header.toLowerCase()] = request.getHeader(header);
+  }
+
+  response.write(JSON.stringify(headers));
+});
+
+server.registerPathHandler("/dummy", (request, response) => {
+  response.setStatusLine(request.httpVersion, 200, "OK");
+  response.write("ok");
+});
+
+add_task(async function test_suspend() {
+  let extension = ExtensionTestUtils.loadExtension({
+    manifest: {
+      permissions: ["webRequest", "webRequestBlocking", `${BASE_URL}/`],
+    },
+
+    background() {
+      browser.webRequest.onBeforeSendHeaders.addListener(
+        details => {
+          // Make sure that returning undefined or a promise that resolves to
+          // undefined does not break later handlers.
+        },
+        { urls: ["<all_urls>"] },
+        ["blocking", "requestHeaders"]
+      );
+
+      browser.webRequest.onBeforeSendHeaders.addListener(
+        details => {
+          return Promise.resolve();
+        },
+        { urls: ["<all_urls>"] },
+        ["blocking", "requestHeaders"]
+      );
+
+      browser.webRequest.onBeforeSendHeaders.addListener(
+        details => {
+          let requestHeaders = details.requestHeaders.concat({
+            name: "Foo",
+            value: "Bar",
+          });
+
+          return new Promise(resolve => {
+            // eslint-disable-next-line mozilla/no-arbitrary-setTimeout
+            setTimeout(resolve, 500);
+          }).then(() => {
+            return { requestHeaders };
+          });
+        },
+        { urls: ["<all_urls>"] },
+        ["blocking", "requestHeaders"]
+      );
+    },
+  });
+
+  await extension.startup();
+
+  let headers = JSON.parse(
+    await ExtensionTestUtils.fetch(
+      FETCH_ORIGIN,
+      `${BASE_URL}/return_headers.sjs`
+    )
+  );
+
+  equal(
+    headers.foo,
+    "Bar",
+    "Request header was correctly set on suspended request"
+  );
+
+  await extension.unload();
+});
+
+// Test that requests that were canceled while suspended for a blocking
+// listener are correctly resumed.
+add_task(async function test_error_resume() {
+  let observer = channel => {
+    if (
+      channel instanceof Ci.nsIHttpChannel &&
+      channel.URI.spec === "http://example.com/dummy"
+    ) {
+      Services.obs.removeObserver(observer, "http-on-before-connect");
+
+      // Wait until the next tick to make sure this runs after WebRequest observers.
+      Promise.resolve().then(() => {
+        channel.cancel(Cr.NS_BINDING_ABORTED);
+      });
+    }
+  };
+
+  Services.obs.addObserver(observer, "http-on-before-connect");
+
+  let extension = ExtensionTestUtils.loadExtension({
+    manifest: {
+      permissions: ["webRequest", "webRequestBlocking", `${BASE_URL}/`],
+    },
+
+    background() {
+      browser.webRequest.onBeforeSendHeaders.addListener(
+        details => {
+          browser.test.log(`onBeforeSendHeaders({url: ${details.url}})`);
+
+          if (details.url === "http://example.com/dummy") {
+            browser.test.sendMessage("got-before-send-headers");
+          }
+        },
+        { urls: ["<all_urls>"] },
+        ["blocking"]
+      );
+
+      browser.webRequest.onErrorOccurred.addListener(
+        details => {
+          browser.test.log(`onErrorOccurred({url: ${details.url}})`);
+
+          if (details.url === "http://example.com/dummy") {
+            browser.test.sendMessage("got-error-occurred");
+          }
+        },
+        { urls: ["<all_urls>"] }
+      );
+    },
+  });
+
+  await extension.startup();
+
+  try {
+    await ExtensionTestUtils.fetch(FETCH_ORIGIN, `${BASE_URL}/dummy`);
+    ok(false, "Fetch should have failed.");
+  } catch (e) {
+    ok(true, "Got expected error.");
+  }
+
+  await extension.awaitMessage("got-before-send-headers");
+  await extension.awaitMessage("got-error-occurred");
+
+  // Wait for the next tick so the onErrorRecurred response can be
+  // processed before shutting down the extension.
+  await new Promise(resolve => executeSoon(resolve));
+
+  await extension.unload();
+});
+
+// Test that response header modifications take effect before onStartRequest fires.
+add_task(async function test_set_responseHeaders() {
+  let extension = ExtensionTestUtils.loadExtension({
+    manifest: {
+      permissions: ["webRequest", "webRequestBlocking", "http://example.com/"],
+    },
+
+    background() {
+      browser.webRequest.onHeadersReceived.addListener(
+        details => {
+          browser.test.log(`onHeadersReceived({url: ${details.url}})`);
+
+          details.responseHeaders.push({ name: "foo", value: "bar" });
+
+          return { responseHeaders: details.responseHeaders };
+        },
+        { urls: ["http://example.com/?modify_headers"] },
+        ["blocking", "responseHeaders"]
+      );
+    },
+  });
+
+  await extension.startup();
+
+  await new Promise(resolve => setTimeout(resolve, 0));
+
+  let resolveHeaderPromise;
+  let headerPromise = new Promise(resolve => {
+    resolveHeaderPromise = resolve;
+  });
+  {
+    let ssm = Services.scriptSecurityManager;
+
+    let channel = NetUtil.newChannel({
+      uri: "http://example.com/?modify_headers",
+      loadingPrincipal:
+        ssm.createContentPrincipalFromOrigin("http://example.com"),
+      contentPolicyType: Ci.nsIContentPolicy.TYPE_XMLHTTPREQUEST,
+      securityFlags: Ci.nsILoadInfo.SEC_ALLOW_CROSS_ORIGIN_SEC_CONTEXT_IS_NULL,
+    });
+
+    channel.asyncOpen({
+      QueryInterface: ChromeUtils.generateQI(["nsIStreamListener"]),
+
+      onStartRequest(request) {
+        request.QueryInterface(Ci.nsIHttpChannel);
+
+        try {
+          resolveHeaderPromise(request.getResponseHeader("foo"));
+        } catch (e) {
+          resolveHeaderPromise(null);
+        }
+        request.cancel(Cr.NS_BINDING_ABORTED);
+      },
+
+      onStopRequest() {},
+
+      onDataAvailable() {
+        throw new Components.Exception("", Cr.NS_ERROR_FAILURE);
+      },
+    });
+  }
+
+  let headerValue = await headerPromise;
+  equal(headerValue, "bar", "Expected Foo header value");
+
+  await extension.unload();
+});
+
+// Test that exceptions raised from a blocking webRequest listener that returns
+// a promise are logged as expected.
+add_task(async function test_logged_error_on_promise_result() {
+  let extension = ExtensionTestUtils.loadExtension({
+    manifest: {
+      permissions: ["webRequest", "webRequestBlocking", `${BASE_URL}/`],
+    },
+
+    background() {
+      async function onBeforeRequest() {
+        throw new Error("Expected webRequest exception from a promise result");
+      }
+
+      let exceptionRaised = false;
+
+      browser.webRequest.onBeforeRequest.addListener(
+        () => {
+          if (exceptionRaised) {
+            return;
+          }
+
+          // We only need to raise the exception once.
+          exceptionRaised = true;
+          return onBeforeRequest();
+        },
+        {
+          urls: ["http://example.com/*"],
+          types: ["main_frame"],
+        },
+        ["blocking"]
+      );
+
+      browser.webRequest.onBeforeRequest.addListener(
+        () => {
+          browser.test.sendMessage("web-request-event-received");
+        },
+        {
+          urls: ["http://example.com/*"],
+          types: ["main_frame"],
+        },
+        ["blocking"]
+      );
+    },
+  });
+
+  let { messages } = await promiseConsoleOutput(async () => {
+    await extension.startup();
+
+    let contentPage = await ExtensionTestUtils.loadContentPage(
+      `${BASE_URL}/dummy`
+    );
+    await extension.awaitMessage("web-request-event-received");
+    await contentPage.close();
+  });
+
+  ok(
+    messages.some(msg =>
+      /Expected webRequest exception from a promise result/.test(msg.message)
+    ),
+    "Got expected console message"
+  );
+
+  await extension.unload();
+});
diff --git a/toolkit/components/extensions/test/xpcshell/test_ext_webRequest_urlclassification.js b/toolkit/components/extensions/test/xpcshell/test_ext_webRequest_urlclassification.js
new file mode 100644
index 0000000000..de2d059d96
--- /dev/null
+++ b/toolkit/components/extensions/test/xpcshell/test_ext_webRequest_urlclassification.js
@@ -0,0 +1,45 @@
+"use strict";
+
+const { Schemas } = ChromeUtils.importESModule(
+  "resource://gre/modules/Schemas.sys.mjs"
+);
+
+/**
+ * If this test fails, likely nsIClassifiedChannel has added or changed a
+ * CLASSIFIED_* flag.  Those changes must be in sync with
+ * ChannelWrapper.webidl/cpp and the web_request.json schema file.
+ */
+add_task(async function test_webrequest_url_classification_enum() {
+  // The startupCache is removed whenever the buildid changes by code that runs
+  // during Firefox startup but not during xpcshell startup, remove it by hand
+  // before running this test to avoid failures with --conditioned-profile
+  let file = PathUtils.join(
+    Services.dirsvc.get("ProfLD", Ci.nsIFile).path,
+    "startupCache",
+    "webext.sc.lz4"
+  );
+  await IOUtils.remove(file, { ignoreAbsent: true });
+
+  // use normalizeManifest to get the schema loaded.
+  await ExtensionTestUtils.normalizeManifest({ permissions: ["webRequest"] });
+
+  let ns = Schemas.getNamespace("webRequest");
+  let schema_enum = ns.get("UrlClassificationFlags").enumeration;
+  ok(
+    !!schema_enum.length,
+    `UrlClassificationFlags: ${JSON.stringify(schema_enum)}`
+  );
+
+  let prefix = /^(?:CLASSIFIED_)/;
+  let entries = 0;
+  for (let c of Object.keys(Ci.nsIClassifiedChannel).filter(name =>
+    prefix.test(name)
+  )) {
+    let entry = c.replace(prefix, "").toLowerCase();
+    if (!entry.startsWith("socialtracking")) {
+      ok(schema_enum.includes(entry), `schema ${entry} is in IDL`);
+      entries++;
+    }
+  }
+  equal(schema_enum.length, entries, "same number of entries");
+});
diff --git a/toolkit/components/extensions/test/xpcshell/test_ext_webRequest_userContextId.js b/toolkit/components/extensions/test/xpcshell/test_ext_webRequest_userContextId.js
new file mode 100644
index 0000000000..9710aa5990
--- /dev/null
+++ b/toolkit/components/extensions/test/xpcshell/test_ext_webRequest_userContextId.js
@@ -0,0 +1,41 @@
+"use strict";
+
+const server = createHttpServer({ hosts: ["example.com"] });
+
+server.registerPathHandler("/dummy", (request, response) => {
+  response.setStatusLine(request.httpVersion, 200, "OK");
+  response.setHeader("Content-Type", "text/html", false);
+  response.write("<!DOCTYPE html><html></html>");
+});
+
+add_task(async function test_userContextId_webrequest() {
+  let extension = ExtensionTestUtils.loadExtension({
+    manifest: {
+      permissions: ["webRequest", "webRequestBlocking", "<all_urls>"],
+    },
+    background() {
+      browser.webRequest.onBeforeRequest.addListener(
+        async details => {
+          browser.test.assertEq(
+            details.cookieStoreId,
+            "firefox-container-2",
+            "cookieStoreId is set"
+          );
+          browser.test.notifyPass("webRequest");
+        },
+        { urls: ["<all_urls>"] },
+        ["blocking"]
+      );
+    },
+  });
+  await extension.startup();
+
+  let contentPage = await ExtensionTestUtils.loadContentPage(
+    "http://example.com/dummy",
+    { userContextId: 2 }
+  );
+  await extension.awaitFinish("webRequest");
+
+  await extension.unload();
+  await contentPage.close();
+});
diff --git a/toolkit/components/extensions/test/xpcshell/test_ext_webRequest_viewsource.js b/toolkit/components/extensions/test/xpcshell/test_ext_webRequest_viewsource.js
new file mode 100644
index 0000000000..35b713e59b
--- /dev/null
+++ b/toolkit/components/extensions/test/xpcshell/test_ext_webRequest_viewsource.js
@@ -0,0 +1,95 @@
+"use strict";
+
+const server = createHttpServer({ hosts: ["example.com"] });
+
+server.registerPathHandler("/dummy", (request, response) => {
+  response.setStatusLine(request.httpVersion, 200, "OK");
+  response.write("ok");
+});
+
+add_task(async function test_webRequest_viewsource() {
+  function background(serverPort) {
+    browser.proxy.onRequest.addListener(
+      details => {
+        if (details.url === `http://example.com:${serverPort}/dummy`) {
+          browser.test.assertTrue(
+            true,
+            "viewsource protocol worked in proxy request"
+          );
+          browser.test.sendMessage("proxied");
+        }
+      },
+      { urls: ["<all_urls>"] }
+    );
+
+    browser.webRequest.onBeforeRequest.addListener(
+      details => {
+        browser.test.assertEq(
+          `http://example.com:${serverPort}/redirect`,
+          details.url,
+          "viewsource protocol worked in webRequest"
+        );
+        browser.test.sendMessage("viewed");
+        return { redirectUrl: `http://example.com:${serverPort}/dummy` };
+      },
+      { urls: ["http://example.com/redirect"] },
+      ["blocking"]
+    );
+
+    browser.webRequest.onBeforeRequest.addListener(
+      details => {
+        browser.test.assertEq(
+          `http://example.com:${serverPort}/dummy`,
+          details.url,
+          "viewsource protocol worked in webRequest"
+        );
+        browser.test.sendMessage("redirected");
+        return { cancel: true };
+      },
+      { urls: ["http://example.com/dummy"] },
+      ["blocking"]
+    );
+
+    browser.webRequest.onCompleted.addListener(
+      details => {
+        // If cancel fails we get onCompleted.
+        browser.test.fail("onCompleted received");
+      },
+      { urls: ["http://example.com/dummy"] }
+    );
+
+    browser.webRequest.onErrorOccurred.addListener(
+      details => {
+        browser.test.assertEq(
+          details.error,
+          "NS_ERROR_ABORT",
+          "request cancelled"
+        );
+        browser.test.sendMessage("cancelled");
+      },
+      { urls: ["http://example.com/dummy"] }
+    );
+  }
+
+  let extension = ExtensionTestUtils.loadExtension({
+    manifest: {
+      permissions: ["proxy", "webRequest", "webRequestBlocking", "<all_urls>"],
+    },
+    background: `(${background})(${server.identity.primaryPort})`,
+  });
+  await extension.startup();
+
+  let contentPage = await ExtensionTestUtils.loadContentPage(
+    `view-source:http://example.com:${server.identity.primaryPort}/redirect`
+  );
+
+  await Promise.all([
+    extension.awaitMessage("proxied"),
+    extension.awaitMessage("viewed"),
+    extension.awaitMessage("redirected"),
+    extension.awaitMessage("cancelled"),
+  ]);
+
+  await contentPage.close();
+  await extension.unload();
+});
diff --git a/toolkit/components/extensions/test/xpcshell/test_ext_webRequest_viewsource_StreamFilter.js b/toolkit/components/extensions/test/xpcshell/test_ext_webRequest_viewsource_StreamFilter.js
new file mode 100644
index 0000000000..c624de4280
--- /dev/null
+++ b/toolkit/components/extensions/test/xpcshell/test_ext_webRequest_viewsource_StreamFilter.js
@@ -0,0 +1,144 @@
+"use strict";
+
+const server = createHttpServer();
+const BASE_URL = `http://127.0.0.1:${server.identity.primaryPort}`;
+
+server.registerPathHandler("/dummy", (request, response) => {
+  response.setStatusLine(request.httpVersion, 200, "OK");
+  response.write("ok");
+});
+
+server.registerPathHandler("/redir", (request, response) => {
+  response.setStatusLine(request.httpVersion, 303, "See Other");
+  response.setHeader("Location", `${BASE_URL}/dummy`);
+});
+
+async function testViewSource(viewSourceUrl) {
+  function background(BASE_URL) {
+    browser.webRequest.onBeforeRequest.addListener(
+      details => {
+        browser.test.assertEq(`${BASE_URL}/dummy`, details.url, "expected URL");
+        browser.test.assertEq("main_frame", details.type, "details.type");
+
+        let filter = browser.webRequest.filterResponseData(details.requestId);
+        filter.onstart = () => {
+          filter.write(new TextEncoder().encode("PREFIX_"));
+        };
+        filter.ondata = event => {
+          filter.write(event.data);
+        };
+        filter.onstop = () => {
+          filter.write(new TextEncoder().encode("_SUFFIX"));
+          filter.disconnect();
+          browser.test.notifyPass("filter_end");
+        };
+        filter.onerror = () => {
+          browser.test.fail(`Unexpected error: ${filter.error}`);
+          browser.test.notifyFail("filter_end");
+        };
+      },
+      { urls: ["*://*/dummy"] },
+      ["blocking"]
+    );
+    browser.webRequest.onBeforeRequest.addListener(
+      details => {
+        browser.test.assertEq(`${BASE_URL}/redir`, details.url, "Got redirect");
+
+        let filter = browser.webRequest.filterResponseData(details.requestId);
+        filter.onstop = () => {
+          filter.disconnect();
+          browser.test.fail("Unexpected onstop for redirect");
+          browser.test.sendMessage("redirect_done");
+        };
+        filter.onerror = () => {
+          browser.test.assertEq(
+            // TODO bug 1683862: must be "Channel redirected", but it is not
+            // because document requests are handled differently compared to
+            // other requests, see the comment at the top of
+            // test_ext_webRequest_redirect_StreamFilter.js.
+            "Invalid request ID",
+            filter.error,
+            "Expected error in filter.onerror"
+          );
+          browser.test.sendMessage("redirect_done");
+        };
+      },
+      { urls: ["*://*/redir"] },
+      ["blocking"]
+    );
+  }
+  let extension = ExtensionTestUtils.loadExtension({
+    manifest: {
+      permissions: ["webRequest", "webRequestBlocking", "*://*/*"],
+    },
+    background: `(${background})(${JSON.stringify(BASE_URL)})`,
+  });
+  await extension.startup();
+  let contentPage = await ExtensionTestUtils.loadContentPage(viewSourceUrl);
+  if (viewSourceUrl.includes("/redir")) {
+    info("Awaiting observed completion of redirection request");
+    await extension.awaitMessage("redirect_done");
+  }
+  info("Awaiting completion of StreamFilter on request");
+  await extension.awaitFinish("filter_end");
+  let contentText = await contentPage.spawn([], () => {
+    return this.content.document.body.textContent;
+  });
+  equal(contentText, "PREFIX_ok_SUFFIX", "view-source response body");
+  await contentPage.close();
+  await extension.unload();
+}
+
+add_task(async function test_StreamFilter_viewsource() {
+  await testViewSource(`view-source:${BASE_URL}/dummy`);
+});
+
+add_task(async function test_StreamFilter_viewsource_redirect_target() {
+  await testViewSource(`view-source:${BASE_URL}/redir`);
+});
+
+// Sanity check: nothing bad happens if the underlying response is aborted.
+add_task(async function test_StreamFilter_viewsource_cancel() {
+  let extension = ExtensionTestUtils.loadExtension({
+    manifest: {
+      permissions: ["webRequest", "webRequestBlocking", "*://*/*"],
+    },
+    background() {
+      browser.webRequest.onBeforeRequest.addListener(
+        details => {
+          let filter = browser.webRequest.filterResponseData(details.requestId);
+          filter.onstart = () => {
+            filter.disconnect();
+            browser.test.fail("Unexpected filter.onstart");
+            browser.test.notifyFail("filter_end");
+          };
+          filter.onerror = () => {
+            browser.test.assertEq("Invalid request ID", filter.error, "Error?");
+            browser.test.notifyPass("filter_end");
+          };
+        },
+        { urls: ["*://*/dummy"] },
+        ["blocking"]
+      );
+      browser.webRequest.onHeadersReceived.addListener(
+        () => {
+          browser.test.log("Intentionally canceling view-source request");
+          return { cancel: true };
+        },
+        { urls: ["*://*/dummy"] },
+        ["blocking"]
+      );
+    },
+  });
+  await extension.startup();
+  let contentPage = await ExtensionTestUtils.loadContentPage(
+    `${BASE_URL}/dummy`
+  );
+  await extension.awaitFinish("filter_end");
+  let contentText = await contentPage.spawn([], () => {
+    return this.content.document.body.textContent;
+  });
+  equal(contentText, "", "view-source request should have been canceled");
+  await contentPage.close();
+  await extension.unload();
+});
diff --git a/toolkit/components/extensions/test/xpcshell/test_ext_webRequest_webSocket.js b/toolkit/components/extensions/test/xpcshell/test_ext_webRequest_webSocket.js
new file mode 100644
index 0000000000..7e34d2b0b3
--- /dev/null
+++ b/toolkit/components/extensions/test/xpcshell/test_ext_webRequest_webSocket.js
@@ -0,0 +1,55 @@
+"use strict";
+
+const HOSTS = new Set(["example.com"]);
+
+const server = createHttpServer({ hosts: HOSTS });
+
+server.registerPathHandler("/dummy", (request, response) => {
+  response.setStatusLine(request.httpVersion, 200, "OK");
+  response.write("ok");
+});
+
+add_task(async function test_webSocket() {
+  let extension = ExtensionTestUtils.loadExtension({
+    manifest: {
+      permissions: ["webRequest", "webRequestBlocking", "<all_urls>"],
+    },
+    background() {
+      browser.webRequest.onBeforeRequest.addListener(
+        details => {
+          browser.test.assertEq(
+            "ws:",
+            new URL(details.url).protocol,
+            "ws protocol worked"
+          );
+          browser.test.notifyPass("websocket");
+        },
+        { urls: ["ws://example.com/*"] },
+        ["blocking"]
+      );
+
+      browser.test.onMessage.addListener(msg => {
+        let ws = new WebSocket("ws://example.com/dummy");
+        ws.onopen = e => {
+          ws.send("data");
+        };
+        ws.onclose = e => {};
+        ws.onerror = e => {};
+        ws.onmessage = e => {
+          ws.close();
+        };
+      });
+      browser.test.sendMessage("ready");
+    },
+  });
+  await extension.startup();
+  await extension.awaitMessage("ready");
+  extension.sendMessage("go");
+  await extension.awaitFinish("websocket");
+
+  // Wait until the next tick so that listener responses are processed
+  // before we unload.
+  await new Promise(executeSoon);
+
+  await extension.unload();
+});
diff --git a/toolkit/components/extensions/test/xpcshell/test_ext_webSocket.js b/toolkit/components/extensions/test/xpcshell/test_ext_webSocket.js
new file mode 100644
index 0000000000..d5aab3c7f6
--- /dev/null
+++ b/toolkit/components/extensions/test/xpcshell/test_ext_webSocket.js
@@ -0,0 +1,162 @@
+"use strict";
+
+const HOSTS = new Set(["example.com"]);
+
+Services.prefs.setBoolPref("extensions.manifestV3.enabled", true);
+
+const server = createHttpServer({ hosts: HOSTS });
+
+const BASE_URL = `http://example.com`;
+const pageURL = `${BASE_URL}/plain.html`;
+
+server.registerPathHandler("/plain.html", (request, response) => {
+  response.setStatusLine(request.httpVersion, 200, "OK");
+  response.setHeader("Content-Type", "text/html");
+  response.setHeader("Content-Security-Policy", "upgrade-insecure-requests;");
+  response.write("<!DOCTYPE html><html></html>");
+});
+
+async function testWebSocketInFrameUpgraded() {
+  const frame = document.createElement("iframe");
+  frame.src = browser.runtime.getURL("frame.html");
+  document.documentElement.appendChild(frame);
+}
+
+// testIframe = true: open WebSocket from iframe (original test case).
+// testIframe = false: open WebSocket from content script.
+async function test_webSocket({
+  manifest_version,
+  useIframe,
+  content_security_policy,
+  expectUpgrade,
+}) {
+  let web_accessible_resources =
+    manifest_version == 2
+      ? ["frame.html"]
+      : [{ resources: ["frame.html"], matches: ["*://example.com/*"] }];
+
+  let extension = ExtensionTestUtils.loadExtension({
+    manifest: {
+      manifest_version,
+      permissions: ["webRequest", "webRequestBlocking"],
+      host_permissions: ["<all_urls>"],
+      granted_host_permissions: true,
+      web_accessible_resources,
+      content_security_policy,
+      content_scripts: [
+        {
+          matches: ["http://*/plain.html"],
+          run_at: "document_idle",
+          js: [useIframe ? "content_script.js" : "load_WebSocket.js"],
+        },
+      ],
+    },
+    temporarilyInstalled: true,
+    background() {
+      browser.webRequest.onBeforeSendHeaders.addListener(
+        details => {
+          let header = details.requestHeaders.find(h => h.name === "Origin");
+          browser.test.sendMessage("ws_request", {
+            ws_scheme: new URL(details.url).protocol,
+            originHeader: header?.value,
+          });
+        },
+        { urls: ["wss://example.com/*", "ws://example.com/*"] },
+        ["requestHeaders", "blocking"]
+      );
+    },
+    files: {
+      "frame.html": `
+<html>
+    <head>
+        <meta charset="utf-8"/>
+        <script src="load_WebSocket.js"></script>
+    </head>
+    <body>
+    </body>
+</html>
+	  `,
+      "load_WebSocket.js": `new WebSocket("ws://example.com/ws_dummy");`,
+      "content_script.js": `
+      (${testWebSocketInFrameUpgraded})()
+      `,
+    },
+  });
+
+  await extension.startup();
+
+  let contentPage = await ExtensionTestUtils.loadContentPage(pageURL);
+  let { ws_scheme, originHeader } = await extension.awaitMessage("ws_request");
+
+  if (expectUpgrade) {
+    Assert.equal(ws_scheme, "wss:", "ws:-request should have been upgraded");
+  } else {
+    Assert.equal(ws_scheme, "ws:", "ws:-request should not have been upgraded");
+  }
+
+  if (useIframe) {
+    Assert.equal(
+      originHeader,
+      `moz-extension://${extension.uuid}`,
+      "Origin header of WebSocket request from extension page"
+    );
+  } else {
+    Assert.equal(
+      originHeader,
+      manifest_version == 2 ? "null" : "http://example.com",
+      "Origin header of WebSocket request from content script"
+    );
+  }
+  await contentPage.close();
+  await extension.unload();
+}
+
+// Page CSP does not affect extension iframes.
+add_task(async function test_webSocket_upgrade_iframe_mv2() {
+  await test_webSocket({
+    manifest_version: 2,
+    useIframe: true,
+    expectUpgrade: false,
+  });
+});
+
+// Page CSP does not affect extension iframes, however upgrade-insecure-requests causes this
+// request to be upgraded in the iframe.
+add_task(async function test_webSocket_upgrade_iframe_mv3() {
+  await test_webSocket({
+    manifest_version: 3,
+    useIframe: true,
+    expectUpgrade: true,
+  });
+});
+
+// Test that removing upgrade-insecure-requests allows http request in the iframe.
+add_task(async function test_webSocket_noupgrade_iframe_mv3() {
+  let content_security_policy = {
+    extension_pages: `script-src 'self'`,
+  };
+  await test_webSocket({
+    manifest_version: 3,
+    content_security_policy,
+    useIframe: true,
+    expectUpgrade: false,
+  });
+});
+
+// Page CSP does not affect MV2 in the content script.
+add_task(async function test_webSocket_upgrade_in_contentscript_mv2() {
+  await test_webSocket({
+    manifest_version: 2,
+    useIframe: false,
+    expectUpgrade: false,
+  });
+});
+
+// Page CSP affects MV3 in the content script.
+add_task(async function test_webSocket_upgrade_in_contentscript_mv3() {
+  await test_webSocket({
+    manifest_version: 3,
+    useIframe: false,
+    expectUpgrade: true,
+  });
+});
diff --git a/toolkit/components/extensions/test/xpcshell/test_ext_web_accessible_resources.js b/toolkit/components/extensions/test/xpcshell/test_ext_web_accessible_resources.js
new file mode 100644
index 0000000000..0b34dd8127
--- /dev/null
+++ b/toolkit/components/extensions/test/xpcshell/test_ext_web_accessible_resources.js
@@ -0,0 +1,148 @@
+"use strict";
+
+const server = createHttpServer({ hosts: ["example.com", "example.org"] });
+server.registerDirectory("/data/", do_get_file("data"));
+
+let image = atob(
+  "iVBORw0KGgoAAAANSUhEUgAAAAEAAAABAQMAAAAl21bKAAAAA1BMVEUAA" +
+    "ACnej3aAAAAAXRSTlMAQObYZgAAAApJREFUCNdjYAAAAAIAAeIhvDMAAAAASUVORK5CYII="
+);
+const IMAGE_ARRAYBUFFER = Uint8Array.from(image, byte =>
+  byte.charCodeAt(0)
+).buffer;
+
+async function testImageLoading(src, expectedAction) {
+  let imageLoadingPromise = new Promise((resolve, reject) => {
+    let cleanupListeners;
+    let testImage = document.createElement("img");
+    // Set the src via wrappedJSObject so the load is triggered with the
+    // content page's principal rather than ours.
+    testImage.wrappedJSObject.setAttribute("src", src);
+
+    let loadListener = () => {
+      cleanupListeners();
+      resolve(expectedAction === "loaded");
+    };
+
+    let errorListener = () => {
+      cleanupListeners();
+      resolve(expectedAction === "blocked");
+    };
+
+    cleanupListeners = () => {
+      testImage.removeEventListener("load", loadListener);
+      testImage.removeEventListener("error", errorListener);
+    };
+
+    testImage.addEventListener("load", loadListener);
+    testImage.addEventListener("error", errorListener);
+
+    document.body.appendChild(testImage);
+  });
+
+  let success = await imageLoadingPromise;
+  browser.runtime.sendMessage({
+    name: "image-loading",
+    expectedAction,
+    success,
+  });
+}
+
+add_task(async function test_web_accessible_resources_csp() {
+  function background() {
+    browser.runtime.onMessage.addListener((msg, sender) => {
+      if (msg.name === "image-loading") {
+        browser.test.assertTrue(msg.success, `Image was ${msg.expectedAction}`);
+        browser.test.sendMessage(`image-${msg.expectedAction}`);
+      } else {
+        browser.test.sendMessage(msg);
+      }
+    });
+
+    browser.test.sendMessage("background-ready");
+  }
+
+  function content() {
+    window.addEventListener("message", function rcv(event) {
+      browser.runtime.sendMessage("script-ran");
+      window.removeEventListener("message", rcv);
+    });
+
+    testImageLoading(browser.runtime.getURL("image.png"), "loaded");
+
+    let testScriptElement = document.createElement("script");
+    // Set the src via wrappedJSObject so the load is triggered with the
+    // content page's principal rather than ours.
+    testScriptElement.wrappedJSObject.setAttribute(
+      "src",
+      browser.runtime.getURL("test_script.js")
+    );
+    document.head.appendChild(testScriptElement);
+    browser.runtime.sendMessage("script-loaded");
+  }
+
+  function testScript() {
+    window.postMessage("test-script-loaded", "*");
+  }
+
+  let extension = ExtensionTestUtils.loadExtension({
+    manifest: {
+      content_scripts: [
+        {
+          matches: ["http://example.com/*/file_csp.html"],
+          run_at: "document_end",
+          js: ["content_script_helper.js", "content_script.js"],
+        },
+      ],
+      web_accessible_resources: ["image.png", "test_script.js"],
+    },
+    background,
+    files: {
+      "content_script_helper.js": `${testImageLoading}`,
+      "content_script.js": content,
+      "test_script.js": testScript,
+      "image.png": IMAGE_ARRAYBUFFER,
+    },
+  });
+
+  await Promise.all([
+    extension.startup(),
+    extension.awaitMessage("background-ready"),
+  ]);
+
+  let page = await ExtensionTestUtils.loadContentPage(
+    `http://example.com/data/file_sample.html`
+  );
+  await page.legacySpawn(null, () => {
+    this.obs = {
+      events: [],
+      observe(subject, topic, data) {
+        this.events.push(subject.QueryInterface(Ci.nsIURI).spec);
+      },
+      done() {
+        Services.obs.removeObserver(this, "csp-on-violate-policy");
+        return this.events;
+      },
+    };
+    Services.obs.addObserver(this.obs, "csp-on-violate-policy");
+    content.location.href = "http://example.com/data/file_csp.html";
+  });
+
+  await Promise.all([
+    extension.awaitMessage("image-loaded"),
+    extension.awaitMessage("script-loaded"),
+    extension.awaitMessage("script-ran"),
+  ]);
+
+  let events = await page.legacySpawn(null, () => this.obs.done());
+  equal(events.length, 2, "Two items were rejected by CSP");
+  for (let url of events) {
+    ok(
+      url.includes("file_image_bad.png") || url.includes("file_script_bad.js"),
+      `Expected file: ${url} rejected by CSP`
+    );
+  }
+
+  await page.close();
+  await extension.unload();
+});
diff --git a/toolkit/components/extensions/test/xpcshell/test_ext_web_accessible_resources_matches.js b/toolkit/components/extensions/test/xpcshell/test_ext_web_accessible_resources_matches.js
new file mode 100644
index 0000000000..1cd5074780
--- /dev/null
+++ b/toolkit/components/extensions/test/xpcshell/test_ext_web_accessible_resources_matches.js
@@ -0,0 +1,546 @@
+"use strict";
+
+Services.prefs.setBoolPref("extensions.manifestV3.enabled", true);
+
+const server = createHttpServer({ hosts: ["example.com", "example.org"] });
+server.registerDirectory("/data/", do_get_file("data"));
+
+let image = atob(
+  "iVBORw0KGgoAAAANSUhEUgAAAAEAAAABAQMAAAAl21bKAAAAA1BMVEUAA" +
+    "ACnej3aAAAAAXRSTlMAQObYZgAAAApJREFUCNdjYAAAAAIAAeIhvDMAAAAASUVORK5CYII="
+);
+const IMAGE_ARRAYBUFFER = Uint8Array.from(image, byte =>
+  byte.charCodeAt(0)
+).buffer;
+
+add_task(async function test_web_accessible_resources_matching() {
+  let extension = ExtensionTestUtils.loadExtension({
+    manifest: {
+      manifest_version: 3,
+      web_accessible_resources: [
+        {
+          resources: ["/accessible.html"],
+        },
+      ],
+    },
+  });
+
+  await Assert.rejects(
+    extension.startup(),
+    /web_accessible_resources requires one of "matches" or "extension_ids"/,
+    "web_accessible_resources object format incorrect"
+  );
+
+  extension = ExtensionTestUtils.loadExtension({
+    manifest: {
+      manifest_version: 3,
+      web_accessible_resources: [
+        {
+          resources: ["/accessible.html"],
+          matches: ["http://example.com/data/*"],
+        },
+      ],
+    },
+  });
+
+  await extension.startup();
+  ok(true, "web_accessible_resources with matches loads");
+  await extension.unload();
+
+  extension = ExtensionTestUtils.loadExtension({
+    manifest: {
+      manifest_version: 3,
+      web_accessible_resources: [
+        {
+          resources: ["/accessible.html"],
+          extension_ids: ["foo@mochitest"],
+        },
+      ],
+    },
+  });
+
+  await extension.startup();
+  ok(true, "web_accessible_resources with extensions loads");
+  await extension.unload();
+
+  extension = ExtensionTestUtils.loadExtension({
+    manifest: {
+      manifest_version: 3,
+      web_accessible_resources: [
+        {
+          resources: ["/accessible.html"],
+          matches: ["http://example.com/data/*"],
+          extension_ids: ["foo@mochitest"],
+        },
+      ],
+    },
+  });
+
+  await extension.startup();
+  ok(true, "web_accessible_resources with matches and extensions loads");
+  await extension.unload();
+
+  extension = ExtensionTestUtils.loadExtension({
+    manifest: {
+      manifest_version: 3,
+      web_accessible_resources: [
+        {
+          resources: ["/accessible.html"],
+          extension_ids: [],
+        },
+      ],
+    },
+  });
+
+  await extension.startup();
+  ok(true, "web_accessible_resources with empty extensions loads");
+  await extension.unload();
+
+  extension = ExtensionTestUtils.loadExtension({
+    manifest: {
+      manifest_version: 3,
+      web_accessible_resources: [
+        {
+          resources: ["/accessible.html"],
+          matches: ["http://example.com/data/*"],
+          extension_ids: [],
+        },
+      ],
+    },
+  });
+
+  await extension.startup();
+  ok(true, "web_accessible_resources with matches and empty extensions loads");
+  await extension.unload();
+});
+
+add_task(async function test_web_accessible_resources() {
+  async function contentScript() {
+    let canLoad = window.location.href.startsWith("http://example.com");
+    let urls = [
+      {
+        name: "iframe",
+        path: "accessible.html",
+        shouldLoad: canLoad,
+      },
+      {
+        name: "iframe",
+        path: "inaccessible.html",
+        shouldLoad: false,
+      },
+      {
+        name: "img",
+        path: "image.png",
+        shouldLoad: true,
+      },
+      {
+        name: "script",
+        path: "script.js",
+        shouldLoad: canLoad,
+      },
+    ];
+
+    function test_element_src(name, url) {
+      return new Promise(resolve => {
+        let elem = document.createElement(name);
+        // Set the src via wrappedJSObject so the load is triggered with the
+        // content page's principal rather than ours.
+        elem.wrappedJSObject.setAttribute("src", url);
+        elem.addEventListener(
+          "load",
+          () => {
+            resolve(true);
+          },
+          { once: true }
+        );
+        elem.addEventListener(
+          "error",
+          () => {
+            resolve(false);
+          },
+          { once: true }
+        );
+        document.body.appendChild(elem);
+      });
+    }
+    for (let test of urls) {
+      let loaded = await test_element_src(
+        test.name,
+        browser.runtime.getURL(test.path)
+      );
+      browser.test.assertEq(
+        loaded,
+        test.shouldLoad,
+        `resource loaded ${test.path} in ${window.location.href}`
+      );
+    }
+    browser.test.sendMessage("complete");
+  }
+
+  let extension = ExtensionTestUtils.loadExtension({
+    manifest: {
+      manifest_version: 3,
+      content_scripts: [
+        {
+          matches: ["http://example.com/data/*", "http://example.org/data/*"],
+          js: ["content_script.js"],
+          run_at: "document_idle",
+        },
+      ],
+      host_permissions: ["http://example.com/*", "http://example.org/*"],
+      granted_host_permissions: true,
+
+      web_accessible_resources: [
+        {
+          resources: ["/accessible.html", "/script.js"],
+          matches: ["http://example.com/data/*"],
+        },
+        {
+          resources: ["/image.png"],
+          matches: ["<all_urls>"],
+        },
+      ],
+    },
+    temporarilyInstalled: true,
+
+    files: {
+      "content_script.js": contentScript,
+
+      "accessible.html": `<html><head>
+          <meta charset="utf-8">
+        </head></html>`,
+
+      "inaccessible.html": `<html><head>
+          <meta charset="utf-8">
+        </head></html>`,
+
+      "image.png": IMAGE_ARRAYBUFFER,
+      "script.js": () => {
+        // empty script
+      },
+    },
+  });
+
+  await extension.startup();
+
+  let page = await ExtensionTestUtils.loadContentPage(
+    "http://example.com/data/"
+  );
+
+  await extension.awaitMessage("complete");
+  await page.close();
+
+  // None of the test resources are loadable in example.org
+  page = await ExtensionTestUtils.loadContentPage("http://example.org/data/");
+
+  await extension.awaitMessage("complete");
+
+  await page.close();
+  await extension.unload();
+});
+
+async function pageScript() {
+  function test_element_src(data) {
+    return new Promise(resolve => {
+      let elem = document.createElement(data.elem);
+      let elemContext =
+        data.content_context && elem.wrappedJSObject
+          ? elem.wrappedJSObject
+          : elem;
+      elemContext.setAttribute("src", data.url);
+      elem.addEventListener(
+        "load",
+        () => {
+          browser.test.log(`got load event for ${data.url}`);
+          resolve(true);
+        },
+        { once: true }
+      );
+      elem.addEventListener(
+        "error",
+        () => {
+          browser.test.log(`got error event for ${data.url}`);
+          resolve(false);
+        },
+        { once: true }
+      );
+      document.body.appendChild(elem);
+    });
+  }
+  browser.test.onMessage.addListener(async msg => {
+    browser.test.log(`testing ${JSON.stringify(msg)}`);
+    let loaded = await test_element_src(msg);
+    browser.test.assertEq(loaded, msg.shouldLoad, `${msg.name} loaded`);
+    browser.test.sendMessage("web-accessible-resources");
+  });
+  browser.test.sendMessage("page-loaded");
+}
+
+add_task(async function test_web_accessible_resources_extensions() {
+  let other = ExtensionTestUtils.loadExtension({
+    manifest: {
+      browser_specific_settings: { gecko: { id: "other@mochitest" } },
+    },
+    files: {
+      "page.js": pageScript,
+
+      "page.html": `<html><head>
+          <meta charset="utf-8">
+          <script src="page.js"></script>
+        </head></html>`,
+    },
+  });
+
+  let extension = ExtensionTestUtils.loadExtension({
+    manifest: {
+      manifest_version: 3,
+      browser_specific_settings: { gecko: { id: "this@mochitest" } },
+      web_accessible_resources: [
+        {
+          resources: ["/image.png"],
+          extension_ids: ["other@mochitest"],
+        },
+      ],
+    },
+
+    files: {
+      "image.png": IMAGE_ARRAYBUFFER,
+      "inaccessible.png": IMAGE_ARRAYBUFFER,
+      "page.js": pageScript,
+
+      "page.html": `<html><head>
+          <meta charset="utf-8">
+          <script src="page.js"></script>
+        </head></html>`,
+    },
+  });
+
+  await extension.startup();
+  let extensionUrl = `moz-extension://${extension.uuid}/`;
+
+  await other.startup();
+  let pageUrl = `moz-extension://${other.uuid}/page.html`;
+
+  let page = await ExtensionTestUtils.loadContentPage(pageUrl);
+  await other.awaitMessage("page-loaded");
+
+  other.sendMessage({
+    name: "accessible resource",
+    elem: "img",
+    url: `${extensionUrl}image.png`,
+    shouldLoad: true,
+  });
+  await other.awaitMessage("web-accessible-resources");
+
+  other.sendMessage({
+    name: "inaccessible resource",
+    elem: "img",
+    url: `${extensionUrl}inaccessible.png`,
+    shouldLoad: false,
+  });
+  await other.awaitMessage("web-accessible-resources");
+
+  await page.close();
+
+  // test that the extension may load it's own web accessible resource
+  page = await ExtensionTestUtils.loadContentPage(`${extensionUrl}page.html`);
+  await extension.awaitMessage("page-loaded");
+
+  extension.sendMessage({
+    name: "accessible resource",
+    elem: "img",
+    url: `${extensionUrl}image.png`,
+    shouldLoad: true,
+  });
+  await extension.awaitMessage("web-accessible-resources");
+
+  await page.close();
+  await extension.unload();
+  await other.unload();
+});
+
+// test that a web page not in matches cannot load the resource
+add_task(async function test_web_accessible_resources_inaccessible() {
+  let extension = ExtensionTestUtils.loadExtension({
+    temporarilyInstalled: true,
+    manifest: {
+      manifest_version: 3,
+      browser_specific_settings: { gecko: { id: "web@mochitest" } },
+      content_scripts: [
+        {
+          matches: ["http://example.com/data/*"],
+          js: ["page.js"],
+          run_at: "document_idle",
+        },
+      ],
+      web_accessible_resources: [
+        {
+          resources: ["/image.png"],
+          extension_ids: ["some_other_ext@mochitest"],
+        },
+      ],
+      host_permissions: ["*://example.com/*"],
+      granted_host_permissions: true,
+    },
+
+    files: {
+      "image.png": IMAGE_ARRAYBUFFER,
+      "page.js": pageScript,
+
+      "page.html": `<html><head>
+          <meta charset="utf-8">
+          <script src="page.js"></script>
+        </head></html>`,
+    },
+  });
+
+  await extension.startup();
+  let extensionUrl = `moz-extension://${extension.uuid}/`;
+  let page = await ExtensionTestUtils.loadContentPage(
+    "http://example.com/data/"
+  );
+  await extension.awaitMessage("page-loaded");
+
+  extension.sendMessage({
+    name: "cannot access resource",
+    elem: "img",
+    url: `${extensionUrl}image.png`,
+    content_context: true,
+    shouldLoad: false,
+  });
+  await extension.awaitMessage("web-accessible-resources");
+
+  await page.close();
+  await extension.unload();
+});
+
+add_task(async function test_web_accessible_resources_empty_extension_ids() {
+  let extension = ExtensionTestUtils.loadExtension({
+    manifest: {
+      manifest_version: 3,
+      web_accessible_resources: [
+        {
+          resources: ["/file.txt"],
+          matches: ["http://example.com/data/*"],
+          extension_ids: [],
+        },
+      ],
+    },
+
+    files: {
+      "file.txt": "some content",
+    },
+  });
+  let secondExtension = ExtensionTestUtils.loadExtension({
+    files: {
+      "page.html": "",
+    },
+  });
+
+  await extension.startup();
+  await secondExtension.startup();
+
+  const fileURL = extension.extension.baseURI.resolve("file.txt");
+  Assert.equal(
+    await ExtensionTestUtils.fetch("http://example.com/data/", fileURL),
+    "some content",
+    "expected access to the extension's resource"
+  );
+
+  await Assert.rejects(
+    ExtensionTestUtils.fetch(
+      secondExtension.extension.baseURI.resolve("page.html"),
+      fileURL
+    ),
+    e => e?.message === "NetworkError when attempting to fetch resource.",
+    "other extension should not be able to fetch when extension_ids is empty"
+  );
+
+  await extension.unload();
+  await secondExtension.unload();
+});
+
+add_task(async function test_web_accessible_resources_empty_array() {
+  let extension = ExtensionTestUtils.loadExtension({
+    manifest: {
+      manifest_version: 3,
+      web_accessible_resources: [],
+    },
+  });
+  await extension.startup();
+  ok(true, "empty web_accessible_resources loads");
+  await extension.unload();
+});
+
+add_task(async function test_web_accessible_resources_empty_resources() {
+  let extension = ExtensionTestUtils.loadExtension({
+    manifest: {
+      manifest_version: 3,
+      web_accessible_resources: [{ resources: [], matches: ["*://*/*"] }],
+    },
+  });
+  await extension.startup();
+  ok(true, "empty web_accessible_resources[0].resources loads");
+  await extension.unload();
+});
+
+add_task(async function test_web_accessible_resources_empty_everything() {
+  let extension = ExtensionTestUtils.loadExtension({
+    manifest: {
+      manifest_version: 3,
+      web_accessible_resources: [
+        { resources: [], matches: [], extension_ids: [] },
+      ],
+    },
+  });
+  await extension.startup();
+  ok(true, "empty resources, matches & extension_ids loads");
+  await extension.unload();
+});
+
+add_task(async function test_web_accessible_resources_empty_matches() {
+  let extension = ExtensionTestUtils.loadExtension({
+    manifest: {
+      manifest_version: 3,
+      web_accessible_resources: [{ resources: ["file.txt"], matches: [] }],
+    },
+    files: {
+      "file.txt": "some content",
+    },
+  });
+  await extension.startup();
+  ok(true, "empty web_accessible_resources[0].matches loads");
+
+  const fileURL = extension.extension.baseURI.resolve("file.txt");
+  await Assert.rejects(
+    ExtensionTestUtils.fetch("http://example.com", fileURL),
+    e => e?.message === "NetworkError when attempting to fetch resource.",
+    "empty matches[] = not web-accessible"
+  );
+  await extension.unload();
+});
+
+add_task(async function test_web_accessible_resources_unknown_property() {
+  let extension = ExtensionTestUtils.loadExtension({
+    manifest: {
+      manifest_version: 3,
+      web_accessible_resources: [{ resources: [], matches: [], idk: null }],
+    },
+  });
+
+  let { messages } = await promiseConsoleOutput(async () => {
+    ExtensionTestUtils.failOnSchemaWarnings(false);
+    await extension.startup();
+    ExtensionTestUtils.failOnSchemaWarnings(true);
+  });
+
+  AddonTestUtils.checkMessages(messages, {
+    expected: [
+      {
+        message:
+          /Reading manifest: Warning processing web_accessible_resources.0.idk: An unexpected property was found in the WebExtension manifest./,
+      },
+    ],
+  });
+  await extension.unload();
+});
diff --git a/toolkit/components/extensions/test/xpcshell/test_ext_xhr_capabilities.js b/toolkit/components/extensions/test/xpcshell/test_ext_xhr_capabilities.js
new file mode 100644
index 0000000000..0728946817
--- /dev/null
+++ b/toolkit/components/extensions/test/xpcshell/test_ext_xhr_capabilities.js
@@ -0,0 +1,72 @@
+"use strict";
+
+const server = createHttpServer({ hosts: ["example.com"] });
+server.registerDirectory("/data/", do_get_file("data"));
+
+add_task(async function test_xhr_capabilities() {
+  let extension = ExtensionTestUtils.loadExtension({
+    background() {
+      let xhr = new XMLHttpRequest();
+      xhr.open("GET", browser.runtime.getURL("bad.xml"));
+
+      browser.test.sendMessage("result", {
+        name: "Background script XHRs should not be privileged",
+        result: xhr.channel === undefined,
+      });
+
+      xhr.onload = () => {
+        browser.test.sendMessage("result", {
+          name: "Background script XHRs should not yield <parsererrors>",
+          result: xhr.responseXML === null,
+        });
+      };
+      xhr.send();
+    },
+
+    manifest: {
+      content_scripts: [
+        {
+          matches: ["http://example.com/data/file_sample.html"],
+          js: ["content_script.js"],
+        },
+      ],
+      web_accessible_resources: ["bad.xml"],
+    },
+
+    files: {
+      "bad.xml": "<xml",
+      "content_script.js"() {
+        let xhr = new XMLHttpRequest();
+        xhr.open("GET", browser.runtime.getURL("bad.xml"));
+
+        browser.test.sendMessage("result", {
+          name: "Content script XHRs should not be privileged",
+          result: xhr.channel === undefined,
+        });
+
+        xhr.onload = () => {
+          browser.test.sendMessage("result", {
+            name: "Content script XHRs should not yield <parsererrors>",
+            result: xhr.responseXML === null,
+          });
+        };
+        xhr.send();
+      },
+    },
+  });
+
+  await extension.startup();
+
+  let contentPage = await ExtensionTestUtils.loadContentPage(
+    "http://example.com/data/file_sample.html"
+  );
+
+  // We expect four test results from the content/background scripts.
+  for (let i = 0; i < 4; ++i) {
+    let result = await extension.awaitMessage("result");
+    ok(result.result, result.name);
+  }
+
+  await contentPage.close();
+  await extension.unload();
+});
diff --git a/toolkit/components/extensions/test/xpcshell/test_ext_xhr_cors.js b/toolkit/components/extensions/test/xpcshell/test_ext_xhr_cors.js
new file mode 100644
index 0000000000..983fe1c542
--- /dev/null
+++ b/toolkit/components/extensions/test/xpcshell/test_ext_xhr_cors.js
@@ -0,0 +1,223 @@
+"use strict";
+
+// The purpose of this test is to show that the XMLHttpRequest API behaves
+// similarly in MV2 and MV3, except for intentional differences related to
+// permission handling.
+
+Services.prefs.setBoolPref("extensions.manifestV3.enabled", true);
+
+const server = createHttpServer({
+  hosts: ["example.com", "example.net", "example.org"],
+});
+server.registerPathHandler("/dummy", (req, res) => {
+  res.setStatusLine(req.httpVersion, 200, "OK");
+  res.setHeader("Content-Type", "text/html; charset=utf-8");
+
+  // A very strict CSP.
+  res.setHeader(
+    "Content-Security-Policy",
+    "default-src; script-src 'nonce-kindasecret'; connect-src http:"
+  );
+
+  res.write(
+    `<script id="id_of_some_element" nonce="kindasecret">
+      // Clobber XMLHttpRequest API to allow us to verify that the page's value
+      // for it does not affect the XMLHttpRequest API in the content script.
+      window.XMLHttpRequest = "This is not XMLHttpRequest";
+      </script>
+    `
+  );
+});
+server.registerPathHandler("/dummy.json", (req, res) => {
+  res.write(`{"mykey": "kvalue"}`);
+});
+server.registerPathHandler("/nocors", (req, res) => {
+  res.write("no cors");
+});
+server.registerPathHandler("/cors-enabled", (req, res) => {
+  res.setHeader("Access-Control-Allow-Origin", "http://example.com");
+  res.write("cors_response");
+});
+server.registerPathHandler("/return-origin", (req, res) => {
+  res.setHeader("Content-Type", "text/plain");
+  res.setHeader("Access-Control-Allow-Origin", "*");
+  res.setHeader("Access-Control-Allow-Methods", "*");
+  res.write(req.hasHeader("Origin") ? req.getHeader("Origin") : "undefined");
+});
+
+// We just need to test XHR; fetch is already covered by test_ext_secfetch.js.
+async function test_xhr({ manifest_version }) {
+  async function contentScript(manifest_version) {
+    function runXHR(url, extraXHRProps, method = "GET") {
+      return new Promise(resolve => {
+        let x = new XMLHttpRequest();
+        x.open(method, url);
+        Object.assign(x, extraXHRProps);
+        x.onloadend = () => resolve(x);
+        x.send();
+      });
+    }
+    async function checkXHR({
+      description,
+      url,
+      extraXHRProps,
+      method,
+      expected,
+    }) {
+      let { status, response } = expected;
+      let x = await runXHR(url, extraXHRProps, method);
+      browser.test.assertEq(status, x.status, `${description} - status`);
+      browser.test.assertEq(response, x.response, `${description} - body`);
+    }
+
+    await checkXHR({
+      description: "Same-origin",
+      url: "http://example.com/nocors",
+      expected: { status: 200, response: "no cors" },
+    });
+
+    await checkXHR({
+      description: "Cross-origin without CORS",
+      url: "http://example.org/nocors",
+      expected: { status: 0, response: "" },
+    });
+
+    await checkXHR({
+      description: "Cross-origin with CORS",
+      url: "http://example.org/cors-enabled",
+      expected:
+        manifest_version === 2
+          ? // Bug 1605197: MV2 cannot fall back to CORS.
+            { status: 0, response: "" }
+          : { status: 200, response: "cors_response" },
+    });
+
+    // MV2 allowed cross-origin requests in content scripts with host
+    // permissions, but MV3 does not.
+    await checkXHR({
+      description: "Cross-origin without CORS, with permission",
+      url: "http://example.net/nocors",
+      expected:
+        manifest_version === 2
+          ? { status: 200, response: "no cors" }
+          : { status: 0, response: "" },
+    });
+
+    await checkXHR({
+      description: "Cross-origin with CORS (and permission)",
+      url: "http://example.net/cors-enabled",
+      expected: { status: 200, response: "cors_response" },
+    });
+
+    // MV2 has a XMLHttpRequest instance specific to the sandbox.
+    // MV3 uses the page's XMLHttpRequest and currently enforces the page's CSP.
+    // TODO bug 1766813: Enforce content script CSP instead.
+    await checkXHR({
+      description: "data:-URL while page blocks data: via CSP",
+      url: "data:,data-url",
+      expected:
+        // Should be "data-url" in MV3 too.
+        manifest_version === 2
+          ? { status: 200, response: "data-url" }
+          : { status: 0, response: "" },
+    });
+
+    {
+      let x = await runXHR("http://example.com/dummy.json", {
+        responseType: "json",
+      });
+      browser.test.assertTrue(x.response instanceof Object, "is JSON object");
+      browser.test.assertEq(x.response.mykey, "kvalue", "can read parsed JSON");
+    }
+
+    {
+      let x = await runXHR("http://example.com/dummy", {
+        responseType: "document",
+      });
+      browser.test.assertTrue(HTMLDocument.isInstance(x.response), "is doc");
+      browser.test.assertTrue(
+        x.response.querySelector("#id_of_some_element"),
+        "got parsed document"
+      );
+    }
+
+    await checkXHR({
+      description: "Same-origin Origin header",
+      url: "http://example.com/return-origin",
+      expected: { status: 200, response: "undefined" },
+    });
+
+    await checkXHR({
+      description: "Same-origin POST Origin header",
+      url: "http://example.com/return-origin",
+      method: "POST",
+      expected:
+        manifest_version === 2
+          ? { status: 200, response: "undefined" }
+          : { status: 200, response: "http://example.com" },
+    });
+
+    await checkXHR({
+      description: "Cross-origin (CORS) Origin header",
+      url: "http://example.org/return-origin",
+      expected:
+        manifest_version === 2
+          ? // Bug 1605197: MV2 cannot fall back to CORS.
+            { status: 0, response: "" }
+          : { status: 200, response: "http://example.com" },
+    });
+
+    await checkXHR({
+      description: "Cross-origin (CORS) POST Origin header",
+      url: "http://example.org/return-origin",
+      method: "POST",
+      expected:
+        manifest_version === 2
+          ? // Bug 1605197: MV2 cannot fall back to CORS.
+            { status: 0, response: "" }
+          : { status: 200, response: "http://example.com" },
+    });
+
+    browser.test.sendMessage("done");
+  }
+  let extension = ExtensionTestUtils.loadExtension({
+    temporarilyInstalled: true, // Needed for granted_host_permissions
+    manifest: {
+      manifest_version,
+      granted_host_permissions: true, // Test-only: grant permissions in MV3.
+      host_permissions: [
+        "http://example.net/",
+        // Work-around for bug 1766752.
+        "http://example.com/",
+        // "http://example.org/" is intentionally missing.
+      ],
+      content_scripts: [
+        {
+          matches: ["http://example.com/dummy"],
+          run_at: "document_end",
+          js: ["contentscript.js"],
+        },
+      ],
+    },
+    files: {
+      "contentscript.js": `(${contentScript})(${manifest_version})`,
+    },
+  });
+  await extension.startup();
+
+  let contentPage = await ExtensionTestUtils.loadContentPage(
+    "http://example.com/dummy"
+  );
+  await extension.awaitMessage("done");
+  await contentPage.close();
+
+  await extension.unload();
+}
+
+add_task(async function test_XHR_MV2() {
+  await test_xhr({ manifest_version: 2 });
+});
+
+add_task(async function test_XHR_MV3() {
+  await test_xhr({ manifest_version: 3 });
+});
diff --git a/toolkit/components/extensions/test/xpcshell/test_extension_permissions_migrate_kvstore_path.js b/toolkit/components/extensions/test/xpcshell/test_extension_permissions_migrate_kvstore_path.js
new file mode 100644
index 0000000000..5f1c73dd3b
--- /dev/null
+++ b/toolkit/components/extensions/test/xpcshell/test_extension_permissions_migrate_kvstore_path.js
@@ -0,0 +1,234 @@
+"use strict";
+
+const {
+  ExtensionPermissions,
+  OLD_RKV_DIRNAME,
+  RKV_DIRNAME,
+  VERSION_KEY,
+  VERSION_VALUE,
+} = ChromeUtils.importESModule(
+  "resource://gre/modules/ExtensionPermissions.sys.mjs"
+);
+const { FileTestUtils } = ChromeUtils.importESModule(
+  "resource://testing-common/FileTestUtils.sys.mjs"
+);
+const { FileUtils } = ChromeUtils.importESModule(
+  "resource://gre/modules/FileUtils.sys.mjs"
+);
+const { KeyValueService } = ChromeUtils.importESModule(
+  "resource://gre/modules/kvstore.sys.mjs"
+);
+
+add_setup(async () => {
+  // Bug 1646182: Force ExtensionPermissions to run in rkv mode, because this
+  // test does not make sense with the legacy method (which will be removed in
+  // the above bug).
+  ExtensionPermissions._useLegacyStorageBackend = false;
+  await ExtensionPermissions._uninit();
+});
+
+// NOTE: this test lives in its own test file to make sure it is isolated
+// from other tests that would be creating the kvstore instance and
+// would prevent this test to properly simulate the kvstore path migration.
+add_task(async function test_migrate_to_separate_kvstore_store_path() {
+  const ADDON_ID_01 = "test-addon-01@test-extension";
+  const ADDON_ID_02 = "test-addon-02@test-extension";
+  // This third test extension is only used as the one that should
+  // have some content scripts stored in ExtensionScriptingStore.
+  const ADDON_ID_03 = "test-addon-03@test-extension";
+
+  const oldStorePath = FileUtils.getDir("ProfD", [OLD_RKV_DIRNAME]).path;
+  const newStorePath = FileUtils.getDir("ProfD", [RKV_DIRNAME]).path;
+
+  // Verify that we are going to be using the expected backend, and that
+  // the rkv path migration is only enabled by default in Nightly builds.
+  info("Verify test environment match the expected pre-conditions");
+
+  const permsStore = ExtensionPermissions._getStore();
+  equal(
+    permsStore.constructor.name,
+    "PermissionStore",
+    "active ExtensionPermissions store should be an instance of PermissionStore"
+  );
+
+  equal(
+    permsStore._shouldMigrateFromOldKVStorePath,
+    AppConstants.NIGHTLY_BUILD,
+    "ExtensionPermissions rkv migration expected to be enabled by default only in Nightly"
+  );
+
+  info(
+    "Uninitialize ExtensionPermissions and make sure no existing kvstore dir"
+  );
+  await ExtensionPermissions._uninit({ recreateStore: false });
+  equal(
+    ExtensionPermissions._getStore(),
+    null,
+    "PermissionStore has been nullified"
+  );
+  await IOUtils.remove(oldStorePath, { ignoreAbsent: true, recursive: true });
+  await IOUtils.remove(newStorePath, { ignoreAbsent: true, recursive: true });
+
+  info("Create an existing kvstore dir on the old path");
+
+  // Populated the kvstore with some expected permissions.
+  const expectedPermsAddon01 = {
+    permissions: ["tabs"],
+    origins: ["http://*/*"],
+  };
+  const expectedPermsAddon02 = {
+    permissions: ["proxy"],
+    origins: ["https://*/*"],
+  };
+
+  const expectedScriptAddon01 = {
+    id: "script-addon-01",
+    allFrames: false,
+    matches: ["<all_urls>"],
+    js: ["/test-script-addon-01.js"],
+    persistAcrossSessions: true,
+    runAt: "document_end",
+  };
+
+  const expectedScriptAddon02 = {
+    id: "script-addon-02",
+    allFrames: false,
+    matches: ["<all_urls"],
+    css: ["/test-script-addon-02.css"],
+    persistAcrossSessions: true,
+    runAt: "document_start",
+  };
+
+  {
+    // Make sure the folder exists
+    await IOUtils.makeDirectory(oldStorePath, { ignoreExisting: true });
+    // Create a permission kvstore dir on the old file path.
+    const kvstore = await KeyValueService.getOrCreate(
+      oldStorePath,
+      "permissions"
+    );
+    await kvstore.writeMany([
+      ["_version", 1],
+      [`id-${ADDON_ID_01}`, JSON.stringify(expectedPermsAddon01)],
+      [`id-${ADDON_ID_02}`, JSON.stringify(expectedPermsAddon02)],
+    ]);
+  }
+
+  {
+    // Add also scripting kvstore data into the same temp dir path.
+    const kvstore = await KeyValueService.getOrCreate(
+      oldStorePath,
+      "scripting-contentScripts"
+    );
+    await kvstore.writeMany([
+      [
+        `${ADDON_ID_03}/${expectedScriptAddon01.id}`,
+        JSON.stringify(expectedScriptAddon01),
+      ],
+      [
+        `${ADDON_ID_03}/${expectedScriptAddon02.id}`,
+        JSON.stringify(expectedScriptAddon02),
+      ],
+    ]);
+  }
+
+  ok(
+    await IOUtils.exists(oldStorePath),
+    "Found kvstore dir for the old store path"
+  );
+  ok(
+    !(await IOUtils.exists(newStorePath)),
+    "Expect kvstore dir for the new store path to don't exist yet"
+  );
+
+  info("Re-initialize the ExtensionPermission store and assert migrated data");
+  await ExtensionPermissions._uninit({ recreateStore: true });
+
+  // Explicitly enable migration (needed to make sure we hit the migration code
+  // that is only enabled by default on Nightly).
+  if (!AppConstants.NIGHTLY_BUILD) {
+    info("Enable ExtensionPermissions rkv migration on non-nightly channel");
+    const newStoreInstance = ExtensionPermissions._getStore();
+    newStoreInstance._shouldMigrateFromOldKVStorePath = true;
+  }
+
+  const permsAddon01 = await ExtensionPermissions._get(ADDON_ID_01);
+  const permsAddon02 = await ExtensionPermissions._get(ADDON_ID_02);
+
+  Assert.deepEqual(
+    { permsAddon01, permsAddon02 },
+    {
+      permsAddon01: expectedPermsAddon01,
+      permsAddon02: expectedPermsAddon02,
+    },
+    "Got the expected permissions migrated to the new store file path"
+  );
+
+  await ExtensionPermissions._uninit({ recreateStore: false });
+
+  ok(
+    await IOUtils.exists(newStorePath),
+    "Found kvstore dir for the new store path"
+  );
+
+  {
+    const newKVStore = await KeyValueService.getOrCreate(
+      newStorePath,
+      "permissions"
+    );
+    Assert.equal(
+      await newKVStore.get(VERSION_KEY),
+      VERSION_VALUE,
+      "Got the expected value set on the kvstore _version key"
+    );
+  }
+
+  // kvstore internally caching behavior doesn't make it easy to make sure
+  // we would be hitting a failure if the ExtensionPermissions kvstore migration
+  // would be mistakenly removing the old kvstore dir as part of that migration,
+  // and so the test case is explicitly verifying that the directory does still
+  // exist and then it copies it into a new path to confirm that the expected
+  // data have been kept in the old kvstore dir.
+  ok(
+    await IOUtils.exists(oldStorePath),
+    "Found kvstore dir for the old store path"
+  );
+  const oldStoreCopiedPath = FileTestUtils.getTempFile("kvstore-dir").path;
+  await IOUtils.copy(oldStorePath, oldStoreCopiedPath, { recursive: true });
+
+  // Confirm that the content scripts have not been copied into
+  // the new kvstore path.
+  async function assertStoredContentScripts(storePath, expectedKeys) {
+    const kvstore = await KeyValueService.getOrCreate(
+      storePath,
+      "scripting-contentScripts"
+    );
+    const enumerator = await kvstore.enumerate();
+    const keys = [];
+    while (enumerator.hasMoreElements()) {
+      keys.push(enumerator.getNext().key);
+    }
+    Assert.deepEqual(
+      keys,
+      expectedKeys,
+      `Got the expected scripts in the kvstore path ${storePath}`
+    );
+  }
+
+  info(
+    "Verify that no content scripts are stored in the new kvstore dir reserved for permissions"
+  );
+  await assertStoredContentScripts(newStorePath, []);
+  info(
+    "Verify that existing content scripts have been not been removed old kvstore dir"
+  );
+  await assertStoredContentScripts(oldStoreCopiedPath, [
+    `${ADDON_ID_03}/${expectedScriptAddon01.id}`,
+    `${ADDON_ID_03}/${expectedScriptAddon02.id}`,
+  ]);
+
+  await ExtensionPermissions._uninit({ recreateStore: true });
+
+  await IOUtils.remove(newStorePath, { recursive: true });
+  await IOUtils.remove(oldStorePath, { recursive: true });
+});
diff --git a/toolkit/components/extensions/test/xpcshell/test_extension_permissions_migration.js b/toolkit/components/extensions/test/xpcshell/test_extension_permissions_migration.js
new file mode 100644
index 0000000000..aa05377e0e
--- /dev/null
+++ b/toolkit/components/extensions/test/xpcshell/test_extension_permissions_migration.js
@@ -0,0 +1,112 @@
+"use strict";
+
+const {
+  ExtensionPermissions,
+  OLD_JSON_FILENAME,
+  OLD_RKV_DIRNAME,
+  RKV_DIRNAME,
+} = ChromeUtils.importESModule(
+  "resource://gre/modules/ExtensionPermissions.sys.mjs"
+);
+
+const GOOD_JSON_FILE = {
+  "wikipedia@search.mozilla.org": {
+    permissions: ["internal:privateBrowsingAllowed"],
+    origins: [],
+  },
+  "amazon@search.mozilla.org": {
+    permissions: ["internal:privateBrowsingAllowed"],
+    origins: [],
+  },
+  "doh-rollout@mozilla.org": {
+    permissions: ["internal:privateBrowsingAllowed"],
+    origins: [],
+  },
+};
+
+const BAD_JSON_FILE = {
+  "test@example.org": "what",
+};
+
+const BAD_FILE = "what is this { } {";
+
+const gOldJSONPath = FileUtils.getDir("ProfD", [OLD_JSON_FILENAME]).path;
+const gOldRkvPath = FileUtils.getDir("ProfD", [OLD_RKV_DIRNAME]).path;
+const gNewRkvPath = FileUtils.getDir("ProfD", [RKV_DIRNAME]).path;
+
+async function test_file(json, extensionIds, expected, fileDeleted) {
+  await ExtensionPermissions._resetVersion();
+  await ExtensionPermissions._uninit();
+
+  await IOUtils.writeUTF8(gOldJSONPath, json);
+
+  for (let extensionId of extensionIds) {
+    let permissions = await ExtensionPermissions.get(extensionId);
+    Assert.deepEqual(permissions, expected, "permissions match");
+  }
+
+  Assert.equal(
+    await IOUtils.exists(gOldJSONPath),
+    !fileDeleted,
+    "old file was deleted"
+  );
+
+  Assert.ok(
+    await IOUtils.exists(gNewRkvPath),
+    "found the store at the new rkv path"
+  );
+
+  Assert.ok(
+    !(await IOUtils.exists(gOldRkvPath)),
+    "expect old rkv path to not exist"
+  );
+}
+
+add_setup(async () => {
+  // Bug 1646182: Force ExtensionPermissions to run in rkv mode, because this
+  // test does not make sense with the legacy method (which will be removed in
+  // the above bug).
+  await ExtensionPermissions._uninit();
+});
+
+add_task(async function test_migrate_good_json() {
+  let expected = {
+    permissions: ["internal:privateBrowsingAllowed"],
+    origins: [],
+  };
+
+  await test_file(
+    JSON.stringify(GOOD_JSON_FILE),
+    [
+      "wikipedia@search.mozilla.org",
+      "amazon@search.mozilla.org",
+      "doh-rollout@mozilla.org",
+    ],
+    expected,
+    /* fileDeleted */ true
+  );
+});
+
+add_task(async function test_migrate_bad_json() {
+  let expected = { permissions: [], origins: [] };
+
+  await test_file(
+    BAD_FILE,
+    ["test@example.org"],
+    expected,
+    /* fileDeleted */ false
+  );
+  await IOUtils.remove(gOldJSONPath);
+});
+
+add_task(async function test_migrate_bad_file() {
+  let expected = { permissions: [], origins: [] };
+
+  await test_file(
+    JSON.stringify(BAD_JSON_FILE),
+    ["test2@example.org"],
+    expected,
+    /* fileDeleted */ false
+  );
+  await IOUtils.remove(gOldJSONPath);
+});
diff --git a/toolkit/components/extensions/test/xpcshell/test_load_all_api_modules.js b/toolkit/components/extensions/test/xpcshell/test_load_all_api_modules.js
new file mode 100644
index 0000000000..32299fb04e
--- /dev/null
+++ b/toolkit/components/extensions/test/xpcshell/test_load_all_api_modules.js
@@ -0,0 +1,171 @@
+"use strict";
+
+const { Schemas } = ChromeUtils.importESModule(
+  "resource://gre/modules/Schemas.sys.mjs"
+);
+
+const BASE_SCHEMA = "chrome://extensions/content/schemas/manifest.json";
+
+const CATEGORY_EXTENSION_MODULES = "webextension-modules";
+const CATEGORY_EXTENSION_SCHEMAS = "webextension-schemas";
+const CATEGORY_EXTENSION_SCRIPTS = "webextension-scripts";
+
+const CATEGORY_EXTENSION_SCRIPTS_ADDON = "webextension-scripts-addon";
+const CATEGORY_EXTENSION_SCRIPTS_CONTENT = "webextension-scripts-content";
+const CATEGORY_EXTENSION_SCRIPTS_DEVTOOLS = "webextension-scripts-devtools";
+
+let schemaURLs = new Set();
+schemaURLs.add("chrome://extensions/content/schemas/experiments.json");
+
+// Helper class used to load the API modules similarly to the apiManager
+// defined in ExtensionParent.jsm.
+class FakeAPIManager extends ExtensionCommon.SchemaAPIManager {
+  constructor(processType = "main") {
+    super(processType, Schemas);
+    this.initialized = false;
+  }
+
+  getModuleJSONURLs() {
+    return Array.from(
+      Services.catMan.enumerateCategory(CATEGORY_EXTENSION_MODULES),
+      ({ value }) => value
+    );
+  }
+
+  async lazyInit() {
+    if (this.initialized) {
+      return;
+    }
+
+    this.initialized = true;
+
+    let modulesPromise = this.loadModuleJSON(this.getModuleJSONURLs());
+
+    let scriptURLs = [];
+    for (let { value } of Services.catMan.enumerateCategory(
+      CATEGORY_EXTENSION_SCRIPTS
+    )) {
+      scriptURLs.push(value);
+    }
+
+    let scripts = await Promise.all(
+      scriptURLs.map(url => ChromeUtils.compileScript(url))
+    );
+
+    this.initModuleData(await modulesPromise);
+
+    this.initGlobal();
+    for (let script of scripts) {
+      script.executeInGlobal(this.global);
+    }
+
+    // Load order matters here. The base manifest defines types which are
+    // extended by other schemas, so needs to be loaded first.
+    await Schemas.load(BASE_SCHEMA).then(() => {
+      let promises = [];
+      for (let { value } of Services.catMan.enumerateCategory(
+        CATEGORY_EXTENSION_SCHEMAS
+      )) {
+        promises.push(Schemas.load(value));
+      }
+      for (let [url, { content }] of this.schemaURLs) {
+        promises.push(Schemas.load(url, content));
+      }
+      for (let url of schemaURLs) {
+        promises.push(Schemas.load(url));
+      }
+      return Promise.all(promises).then(() => {
+        Schemas.updateSharedSchemas();
+      });
+    });
+  }
+
+  async loadAllModules(reverseOrder = false) {
+    await this.lazyInit();
+
+    let apiModuleNames = Array.from(this.modules.keys())
+      .filter(moduleName => {
+        let moduleDesc = this.modules.get(moduleName);
+        return moduleDesc && !!moduleDesc.url;
+      })
+      .sort();
+
+    apiModuleNames = reverseOrder ? apiModuleNames.reverse() : apiModuleNames;
+
+    for (let apiModule of apiModuleNames) {
+      info(
+        `Loading apiModule ${apiModule}: ${this.modules.get(apiModule).url}`
+      );
+      await this.asyncLoadModule(apiModule);
+    }
+  }
+}
+
+// Specialized helper class used to test loading "child process" modules (similarly to the
+// SchemaAPIManagers sub-classes defined in ExtensionPageChild.jsm and ExtensionContent.jsm).
+class FakeChildProcessAPIManager extends FakeAPIManager {
+  constructor({ processType, categoryScripts }) {
+    super(processType, Schemas);
+
+    this.categoryScripts = categoryScripts;
+  }
+
+  async lazyInit() {
+    if (!this.initialized) {
+      this.initialized = true;
+      this.initGlobal();
+      for (let { value } of Services.catMan.enumerateCategory(
+        this.categoryScripts
+      )) {
+        await this.loadScript(value);
+      }
+    }
+  }
+}
+
+async function test_loading_api_modules(createAPIManager) {
+  let fakeAPIManager;
+
+  info("Load API modules in alphabetic order");
+
+  fakeAPIManager = createAPIManager();
+  await fakeAPIManager.loadAllModules();
+
+  info("Load API modules in reverse order");
+
+  fakeAPIManager = createAPIManager();
+  await fakeAPIManager.loadAllModules(true);
+}
+
+add_task(function test_loading_main_process_api_modules() {
+  return test_loading_api_modules(() => {
+    return new FakeAPIManager();
+  });
+});
+
+add_task(function test_loading_extension_process_modules() {
+  return test_loading_api_modules(() => {
+    return new FakeChildProcessAPIManager({
+      processType: "addon",
+      categoryScripts: CATEGORY_EXTENSION_SCRIPTS_ADDON,
+    });
+  });
+});
+
+add_task(function test_loading_devtools_modules() {
+  return test_loading_api_modules(() => {
+    return new FakeChildProcessAPIManager({
+      processType: "devtools",
+      categoryScripts: CATEGORY_EXTENSION_SCRIPTS_DEVTOOLS,
+    });
+  });
+});
+
+add_task(async function test_loading_content_process_modules() {
+  return test_loading_api_modules(() => {
+    return new FakeChildProcessAPIManager({
+      processType: "content",
+      categoryScripts: CATEGORY_EXTENSION_SCRIPTS_CONTENT,
+    });
+  });
+});
diff --git a/toolkit/components/extensions/test/xpcshell/test_locale_converter.js b/toolkit/components/extensions/test/xpcshell/test_locale_converter.js
new file mode 100644
index 0000000000..2c57b6bf31
--- /dev/null
+++ b/toolkit/components/extensions/test/xpcshell/test_locale_converter.js
@@ -0,0 +1,146 @@
+"use strict";
+
+const convService = Cc["@mozilla.org/streamConverters;1"].getService(
+  Ci.nsIStreamConverterService
+);
+
+const UUID = "72b61ee3-aceb-476c-be1b-0822b036c9f1";
+const ADDON_ID = "test@web.extension";
+const URI = NetUtil.newURI(`moz-extension://${UUID}/file.css`);
+
+const FROM_TYPE = "application/vnd.mozilla.webext.unlocalized";
+const TO_TYPE = "text/css";
+
+function StringStream(string) {
+  let stream = Cc["@mozilla.org/io/string-input-stream;1"].createInstance(
+    Ci.nsIStringInputStream
+  );
+
+  stream.data = string;
+  return stream;
+}
+
+// Initialize the policy service with a stub localizer for our
+// add-on ID.
+add_task(async function init() {
+  let policy = new WebExtensionPolicy({
+    id: ADDON_ID,
+    mozExtensionHostname: UUID,
+    baseURL: "file:///",
+
+    allowedOrigins: new MatchPatternSet([]),
+
+    localizeCallback(string) {
+      return string.replace(/__MSG_(.*?)__/g, "<localized-$1>");
+    },
+  });
+
+  policy.active = true;
+
+  registerCleanupFunction(() => {
+    policy.active = false;
+  });
+});
+
+// Test that the synchronous converter works as expected with a
+// simple string.
+add_task(async function testSynchronousConvert() {
+  let stream = StringStream("Foo __MSG_xxx__ bar __MSG_yyy__ baz");
+
+  let resultStream = convService.convert(stream, FROM_TYPE, TO_TYPE, URI);
+
+  let result = NetUtil.readInputStreamToString(
+    resultStream,
+    resultStream.available()
+  );
+
+  equal(result, "Foo <localized-xxx> bar <localized-yyy> baz");
+});
+
+// Test that the asynchronous converter works as expected with input
+// split into multiple chunks, and a boundary in the middle of a
+// replacement token.
+add_task(async function testAsyncConvert() {
+  let listener;
+  let awaitResult = new Promise((resolve, reject) => {
+    listener = {
+      QueryInterface: ChromeUtils.generateQI(["nsIStreamListener"]),
+
+      onDataAvailable(request, inputStream, offset, count) {
+        this.resultParts.push(
+          NetUtil.readInputStreamToString(inputStream, count)
+        );
+      },
+
+      onStartRequest() {
+        ok(!("resultParts" in this));
+        this.resultParts = [];
+      },
+
+      onStopRequest(request, context, statusCode) {
+        if (!Components.isSuccessCode(statusCode)) {
+          reject(new Error(statusCode));
+        }
+
+        resolve(this.resultParts.join("\n"));
+      },
+    };
+  });
+
+  let parts = ["Foo __MSG_x", "xx__ bar __MSG_yyy__ baz"];
+
+  let converter = convService.asyncConvertData(
+    FROM_TYPE,
+    TO_TYPE,
+    listener,
+    URI
+  );
+  converter.onStartRequest(null, null);
+
+  for (let part of parts) {
+    converter.onDataAvailable(null, StringStream(part), 0, part.length);
+  }
+
+  converter.onStopRequest(null, null, Cr.NS_OK);
+
+  let result = await awaitResult;
+  equal(result, "Foo <localized-xxx> bar <localized-yyy> baz");
+});
+
+// Test that attempting to initialize a converter with the URI of a
+// nonexistent WebExtension fails.
+add_task(async function testInvalidUUID() {
+  let uri = NetUtil.newURI(
+    "moz-extension://eb4f3be8-41c9-4970-aa6d-b84d1ecc02b2/file.css"
+  );
+  let stream = StringStream("Foo __MSG_xxx__ bar __MSG_yyy__ baz");
+
+  // Assert.throws raise a TypeError exception when the expected param
+  // is an arrow function. (See Bug 1237961 for rationale)
+  let expectInvalidContextException = function (e) {
+    return e.result === Cr.NS_ERROR_INVALID_ARG && /Invalid context/.test(e);
+  };
+
+  Assert.throws(() => {
+    convService.convert(stream, FROM_TYPE, TO_TYPE, uri);
+  }, expectInvalidContextException);
+
+  Assert.throws(() => {
+    let listener = {
+      QueryInterface: ChromeUtils.generateQI(["nsIStreamListener"]),
+    };
+
+    convService.asyncConvertData(FROM_TYPE, TO_TYPE, listener, uri);
+  }, expectInvalidContextException);
+});
+
+// Test that an empty stream does not throw an NS_ERROR_ILLEGAL_VALUE.
+add_task(async function testEmptyStream() {
+  let stream = StringStream("");
+  let resultStream = convService.convert(stream, FROM_TYPE, TO_TYPE, URI);
+  equal(
+    resultStream.available(),
+    0,
+    "Size of output stream should match size of input stream"
+  );
+});
diff --git a/toolkit/components/extensions/test/xpcshell/test_locale_data.js b/toolkit/components/extensions/test/xpcshell/test_locale_data.js
new file mode 100644
index 0000000000..31468e91d3
--- /dev/null
+++ b/toolkit/components/extensions/test/xpcshell/test_locale_data.js
@@ -0,0 +1,221 @@
+"use strict";
+
+AddonTestUtils.init(this);
+AddonTestUtils.overrideCertDB();
+AddonTestUtils.createAppInfo(
+  "xpcshell@tests.mozilla.org",
+  "XPCShell",
+  "1",
+  "42"
+);
+
+const { ExtensionData } = ChromeUtils.importESModule(
+  "resource://gre/modules/Extension.sys.mjs"
+);
+
+async function generateAddon(data) {
+  let xpi = AddonTestUtils.createTempWebExtensionFile(data);
+
+  let fileURI = Services.io.newFileURI(xpi);
+  let jarURI = NetUtil.newURI(`jar:${fileURI.spec}!/`);
+
+  let extension = new ExtensionData(jarURI, false);
+  await extension.loadManifest();
+
+  return extension;
+}
+
+add_task(async function testMissingDefaultLocale() {
+  let extension = await generateAddon({
+    files: {
+      "_locales/en_US/messages.json": {},
+    },
+  });
+
+  equal(extension.errors.length, 0, "No errors reported");
+
+  await extension.initAllLocales();
+
+  equal(extension.errors.length, 1, "One error reported");
+
+  info(`Got error: ${extension.errors[0]}`);
+
+  ok(
+    extension.errors[0].includes('"default_locale" property is required'),
+    "Got missing default_locale error"
+  );
+});
+
+add_task(async function testInvalidDefaultLocale() {
+  let extension = await generateAddon({
+    manifest: {
+      default_locale: "en",
+    },
+
+    files: {
+      "_locales/en_US/messages.json": {},
+    },
+  });
+
+  equal(extension.errors.length, 1, "One error reported");
+
+  info(`Got error: ${extension.errors[0]}`);
+
+  ok(
+    extension.errors[0].includes(
+      "Loading locale file _locales/en/messages.json"
+    ),
+    "Got invalid default_locale error"
+  );
+
+  await extension.initAllLocales();
+
+  equal(extension.errors.length, 2, "Two errors reported");
+
+  info(`Got error: ${extension.errors[1]}`);
+
+  ok(
+    extension.errors[1].includes('"default_locale" property must correspond'),
+    "Got invalid default_locale error"
+  );
+});
+
+add_task(async function testUnexpectedDefaultLocale() {
+  let extension = await generateAddon({
+    manifest: {
+      default_locale: "en_US",
+    },
+  });
+
+  equal(extension.errors.length, 1, "One error reported");
+
+  info(`Got error: ${extension.errors[0]}`);
+
+  ok(
+    extension.errors[0].includes(
+      "Loading locale file _locales/en-US/messages.json"
+    ),
+    "Got invalid default_locale error"
+  );
+
+  await extension.initAllLocales();
+
+  equal(extension.errors.length, 2, "One error reported");
+
+  info(`Got error: ${extension.errors[1]}`);
+
+  ok(
+    extension.errors[1].includes('"default_locale" property must correspond'),
+    "Got unexpected default_locale error"
+  );
+});
+
+add_task(async function testInvalidSyntax() {
+  let extension = await generateAddon({
+    manifest: {
+      default_locale: "en_US",
+    },
+
+    files: {
+      "_locales/en_US/messages.json":
+        '{foo: {message: "bar", description: "baz"}}',
+    },
+  });
+
+  equal(extension.errors.length, 1, "No errors reported");
+
+  info(`Got error: ${extension.errors[0]}`);
+
+  ok(
+    extension.errors[0].includes(
+      "Loading locale file _locales/en_US/messages.json: SyntaxError"
+    ),
+    "Got syntax error"
+  );
+
+  await extension.initAllLocales();
+
+  equal(extension.errors.length, 2, "One error reported");
+
+  info(`Got error: ${extension.errors[1]}`);
+
+  ok(
+    extension.errors[1].includes(
+      "Loading locale file _locales/en_US/messages.json: SyntaxError"
+    ),
+    "Got syntax error"
+  );
+});
+
+add_task(async function testExtractLocalizedManifest() {
+  let extension = await generateAddon({
+    manifest: {
+      name: "__MSG_extensionName__",
+      default_locale: "en_US",
+      icons: {
+        16: "__MSG_extensionIcon__",
+      },
+    },
+
+    files: {
+      "_locales/en_US/messages.json": `{
+        "extensionName": {"message": "foo"},
+        "extensionIcon": {"message": "icon-en.png"}
+      }`,
+      "_locales/de_DE/messages.json": `{
+        "extensionName": {"message": "bar"},
+        "extensionIcon": {"message": "icon-de.png"}
+      }`,
+    },
+  });
+
+  await extension.loadManifest();
+  equal(extension.manifest.name, "foo", "name localized");
+  equal(extension.manifest.icons["16"], "icon-en.png", "icons localized");
+
+  let manifest = await extension.getLocalizedManifest("de-DE");
+  ok(extension.localeData.has("de-DE"), "has de_DE locale");
+  equal(manifest.name, "bar", "name localized");
+  equal(manifest.icons["16"], "icon-de.png", "icons localized");
+
+  await Assert.rejects(
+    extension.getLocalizedManifest("xx-XX"),
+    /does not contain the locale xx-XX/,
+    "xx-XX does not exist"
+  );
+});
+
+add_task(async function testRestartThenExtractLocalizedManifest() {
+  await AddonTestUtils.promiseStartupManager();
+
+  let wrapper = ExtensionTestUtils.loadExtension({
+    manifest: {
+      name: "__MSG_extensionName__",
+      default_locale: "en_US",
+    },
+    useAddonManager: "permanent",
+    files: {
+      "_locales/en_US/messages.json": '{"extensionName": {"message": "foo"}}',
+      "_locales/de_DE/messages.json": '{"extensionName": {"message": "bar"}}',
+    },
+  });
+
+  await wrapper.startup();
+
+  await AddonTestUtils.promiseRestartManager();
+  await wrapper.startupPromise;
+
+  let { extension } = wrapper;
+  let manifest = await extension.getLocalizedManifest("de-DE");
+  ok(extension.localeData.has("de-DE"), "has de_DE locale");
+  equal(manifest.name, "bar", "name localized");
+
+  await Assert.rejects(
+    extension.getLocalizedManifest("xx-XX"),
+    /does not contain the locale xx-XX/,
+    "xx-XX does not exist"
+  );
+
+  await wrapper.unload();
+  await AddonTestUtils.promiseShutdownManager();
+});
diff --git a/toolkit/components/extensions/test/xpcshell/test_native_manifests.js b/toolkit/components/extensions/test/xpcshell/test_native_manifests.js
new file mode 100644
index 0000000000..d28e692a08
--- /dev/null
+++ b/toolkit/components/extensions/test/xpcshell/test_native_manifests.js
@@ -0,0 +1,541 @@
+"use strict";
+
+const { AsyncShutdown } = ChromeUtils.importESModule(
+  "resource://gre/modules/AsyncShutdown.sys.mjs"
+);
+const { NativeManifests } = ChromeUtils.importESModule(
+  "resource://gre/modules/NativeManifests.sys.mjs"
+);
+const { FileUtils } = ChromeUtils.importESModule(
+  "resource://gre/modules/FileUtils.sys.mjs"
+);
+const { Schemas } = ChromeUtils.importESModule(
+  "resource://gre/modules/Schemas.sys.mjs"
+);
+const { Subprocess } = ChromeUtils.importESModule(
+  "resource://gre/modules/Subprocess.sys.mjs"
+);
+const { NativeApp } = ChromeUtils.importESModule(
+  "resource://gre/modules/NativeMessaging.sys.mjs"
+);
+
+let registry = null;
+if (AppConstants.platform == "win") {
+  var { MockRegistry } = ChromeUtils.importESModule(
+    "resource://testing-common/MockRegistry.sys.mjs"
+  );
+  registry = new MockRegistry();
+  registerCleanupFunction(() => {
+    registry.shutdown();
+  });
+  ChromeUtils.defineESModuleGetters(this, {
+    SubprocessImpl: "resource://gre/modules/subprocess/subprocess_win.sys.mjs",
+  });
+} else {
+  ChromeUtils.defineESModuleGetters(this, {
+    SubprocessImpl: "resource://gre/modules/subprocess/subprocess_unix.sys.mjs",
+  });
+}
+
+const REGPATH = "Software\\Mozilla\\NativeMessagingHosts";
+
+const BASE_SCHEMA = "chrome://extensions/content/schemas/manifest.json";
+
+const TYPE_SLUG =
+  AppConstants.platform === "linux"
+    ? "native-messaging-hosts"
+    : "NativeMessagingHosts";
+
+let dir = FileUtils.getDir("TmpD", ["NativeManifests"]);
+dir.createUnique(Ci.nsIFile.DIRECTORY_TYPE, FileUtils.PERMS_DIRECTORY);
+
+let userDir = dir.clone();
+userDir.append("user");
+userDir.create(Ci.nsIFile.DIRECTORY_TYPE, FileUtils.PERMS_DIRECTORY);
+
+let globalDir = dir.clone();
+globalDir.append("global");
+globalDir.create(Ci.nsIFile.DIRECTORY_TYPE, FileUtils.PERMS_DIRECTORY);
+
+add_setup(async function setup() {
+  await IOUtils.makeDirectory(PathUtils.join(userDir.path, TYPE_SLUG));
+  await IOUtils.makeDirectory(PathUtils.join(globalDir.path, TYPE_SLUG));
+});
+
+let dirProvider = {
+  getFile(property) {
+    if (property == "XREUserNativeManifests") {
+      return userDir.clone();
+    } else if (property == "XRESysNativeManifests") {
+      return globalDir.clone();
+    }
+    return null;
+  },
+};
+
+Services.dirsvc.registerProvider(dirProvider);
+
+registerCleanupFunction(() => {
+  Services.dirsvc.unregisterProvider(dirProvider);
+  dir.remove(true);
+});
+
+function writeManifest(path, manifest) {
+  if (typeof manifest != "string") {
+    manifest = JSON.stringify(manifest);
+  }
+  return IOUtils.writeUTF8(path, manifest);
+}
+
+let PYTHON;
+add_task(async function setup() {
+  await Schemas.load(BASE_SCHEMA);
+
+  try {
+    PYTHON = await Subprocess.pathSearch(Services.env.get("PYTHON"));
+  } catch (e) {
+    notEqual(
+      PYTHON,
+      null,
+      `Can't find a suitable python interpreter ${e.message}`
+    );
+  }
+});
+
+let global = this;
+
+// Test of NativeManifests.lookupApplication() begin here...
+let context = {
+  extension: {
+    id: "extension@tests.mozilla.org",
+  },
+  manifestVersion: 2,
+  envType: "addon_parent",
+  url: null,
+  jsonStringify(...args) {
+    return JSON.stringify(...args);
+  },
+  cloneScope: global,
+  logError() {},
+  preprocessors: {},
+  callOnClose: () => {},
+  forgetOnClose: () => {},
+};
+
+class MockContext extends ExtensionCommon.BaseContext {
+  constructor(extensionId) {
+    let fakeExtension = { id: extensionId, manifestVersion: 2 };
+    super("addon_parent", fakeExtension);
+    this.sandbox = Cu.Sandbox(global);
+  }
+
+  get cloneScope() {
+    return global;
+  }
+
+  get principal() {
+    return Cu.getObjectPrincipal(this.sandbox);
+  }
+}
+
+let templateManifest = {
+  name: "test",
+  description: "this is only a test",
+  path: "/bin/cat",
+  type: "stdio",
+  allowed_extensions: ["extension@tests.mozilla.org"],
+};
+
+function lookupApplication(app, ctx) {
+  return NativeManifests.lookupManifest("stdio", app, ctx);
+}
+
+add_task(async function test_nonexistent_manifest() {
+  let result = await lookupApplication("test", context);
+  equal(
+    result,
+    null,
+    "lookupApplication returns null for non-existent application"
+  );
+});
+
+const USER_TEST_JSON = PathUtils.join(userDir.path, TYPE_SLUG, "test.json");
+
+add_task(async function test_nonexistent_manifest_with_registry_entry() {
+  if (registry) {
+    registry.setValue(
+      Ci.nsIWindowsRegKey.ROOT_KEY_CURRENT_USER,
+      `${REGPATH}\\test`,
+      "",
+      USER_TEST_JSON
+    );
+  }
+
+  await IOUtils.remove(USER_TEST_JSON);
+  let { messages, result } = await promiseConsoleOutput(() =>
+    lookupApplication("test", context)
+  );
+  equal(
+    result,
+    null,
+    "lookupApplication returns null for non-existent manifest"
+  );
+
+  let noSuchFileErrors = messages.filter(logMessage =>
+    logMessage.message.includes(
+      "file is referenced in the registry but does not exist"
+    )
+  );
+
+  if (registry) {
+    equal(
+      noSuchFileErrors.length,
+      1,
+      "lookupApplication logs a non-existent manifest file pointed to by the registry"
+    );
+  } else {
+    equal(
+      noSuchFileErrors.length,
+      0,
+      "lookupApplication does not log about registry on non-windows platforms"
+    );
+  }
+});
+
+add_task(async function test_good_manifest() {
+  await writeManifest(USER_TEST_JSON, templateManifest);
+  if (registry) {
+    registry.setValue(
+      Ci.nsIWindowsRegKey.ROOT_KEY_CURRENT_USER,
+      `${REGPATH}\\test`,
+      "",
+      USER_TEST_JSON
+    );
+  }
+
+  let result = await lookupApplication("test", context);
+  notEqual(result, null, "lookupApplication finds a good manifest");
+  equal(
+    result.path,
+    USER_TEST_JSON,
+    "lookupApplication returns the correct path"
+  );
+  deepEqual(
+    result.manifest,
+    templateManifest,
+    "lookupApplication returns the manifest contents"
+  );
+});
+
+add_task(
+  { skip_if: () => AppConstants.platform != "win" },
+  async function test_forward_slashes_instead_of_backslashes_in_registry() {
+    Assert.ok(USER_TEST_JSON.includes("\\"), `Path has \\: ${USER_TEST_JSON}`);
+    const manifest = { ...templateManifest, name: "testslash" };
+    await writeManifest(USER_TEST_JSON, manifest);
+    registry.setValue(
+      Ci.nsIWindowsRegKey.ROOT_KEY_CURRENT_USER,
+      `${REGPATH}\\testslash`,
+      "",
+      USER_TEST_JSON.replaceAll("\\", "/")
+    );
+
+    let result = await lookupApplication("testslash", context);
+    notEqual(result, null, "lookupApplication finds the manifest despite /");
+    equal(
+      result.path,
+      USER_TEST_JSON,
+      "lookupApplication returns the correct path with platform-native slash"
+    );
+    // Side note: manifest.path does not contain a platform-native path,
+    // but it is normalized when used in NativeMessaging.jsm.
+    deepEqual(
+      result.manifest,
+      manifest,
+      "lookupApplication returns the manifest contents"
+    );
+  }
+);
+
+add_task(async function test_manifest_with_utf8_byte_order_mark() {
+  const manifest = { ...templateManifest, description: "had BOM at start" };
+  const manifestString = JSON.stringify(manifest);
+
+  // "123" to have a placeholder where we'll fill in the 3 BOM bytes.
+  const manifestBytes = new TextEncoder().encode("123" + manifestString);
+  manifestBytes.set([0xef, 0xbb, 0xbf]);
+
+  // Sanity check: verify that the bytes prepended above have the special
+  // meaning of being a UTF-8 BOM. That is, when parsed as UTF-8, the bytes can
+  // be removed without loss of meaning.
+  equal(
+    new TextDecoder().decode(manifestBytes),
+    manifestString,
+    "Sanity check: input bytes has UTF-8 BOM that is ordinarily stripped"
+  );
+
+  await IOUtils.write(USER_TEST_JSON, manifestBytes);
+  if (registry) {
+    registry.setValue(
+      Ci.nsIWindowsRegKey.ROOT_KEY_CURRENT_USER,
+      `${REGPATH}\\test`,
+      "",
+      USER_TEST_JSON
+    );
+  }
+  let result = await lookupApplication("test", context);
+  notEqual(result, null, "lookupApplication finds a good manifest despite BOM");
+  deepEqual(
+    result.manifest,
+    manifest,
+    "lookupApplication returns the manifest contents"
+  );
+});
+
+add_task(async function test_manifest_with_invalid_utf_8() {
+  const manifest = { ...templateManifest, description: "bad bytes" };
+  const manifestString = JSON.stringify(manifest);
+  const manifestBytes = Uint8Array.from(manifestString, c => c.charCodeAt(0));
+  // manifestString ends with `bad bytes"}`. Replace the `s` with a bad byte:
+  manifestBytes.set([0xff], manifestBytes.byteLength - 3);
+
+  await IOUtils.write(USER_TEST_JSON, manifestBytes);
+  if (registry) {
+    registry.setValue(
+      Ci.nsIWindowsRegKey.ROOT_KEY_CURRENT_USER,
+      `${REGPATH}\\test`,
+      "",
+      USER_TEST_JSON
+    );
+  }
+  // Note: most content failures (malformed JSON, etc.) do not result in a
+  // rejection, but in the manifest file being ignored (and on non-Windows:
+  // looking for manifests in the next location).
+  //
+  // It is inconsistent to reject instead of be returning null here, but that
+  // behavior seems long-standing in Firefox.
+  await Assert.rejects(
+    lookupApplication("test", context),
+    /NotReadableError: Could not read file.* because it is not UTF-8 encoded/,
+    "lookupApplication should reject file with invalid UTF8"
+  );
+});
+
+add_task(async function test_invalid_json() {
+  await writeManifest(USER_TEST_JSON, "this is not valid json");
+  let result = await lookupApplication("test", context);
+  equal(result, null, "lookupApplication ignores bad json");
+});
+
+add_task(async function test_invalid_name() {
+  let manifest = Object.assign({}, templateManifest);
+  manifest.name = "../test";
+  await writeManifest(USER_TEST_JSON, manifest);
+  let result = await lookupApplication("test", context);
+  equal(result, null, "lookupApplication ignores an invalid name");
+});
+
+add_task(async function test_name_mismatch() {
+  let manifest = Object.assign({}, templateManifest);
+  manifest.name = "not test";
+  await writeManifest(USER_TEST_JSON, manifest);
+  let result = await lookupApplication("test", context);
+  let what = AppConstants.platform == "win" ? "registry key" : "json filename";
+  equal(
+    result,
+    null,
+    `lookupApplication ignores mistmatch between ${what} and name property`
+  );
+});
+
+add_task(async function test_missing_props() {
+  const PROPS = ["name", "description", "path", "type", "allowed_extensions"];
+  for (let prop of PROPS) {
+    let manifest = Object.assign({}, templateManifest);
+    delete manifest[prop];
+
+    await writeManifest(USER_TEST_JSON, manifest);
+    let result = await lookupApplication("test", context);
+    equal(result, null, `lookupApplication ignores missing ${prop}`);
+  }
+});
+
+add_task(async function test_invalid_type() {
+  let manifest = Object.assign({}, templateManifest);
+  manifest.type = "bogus";
+  await writeManifest(USER_TEST_JSON, manifest);
+  let result = await lookupApplication("test", context);
+  equal(result, null, "lookupApplication ignores invalid type");
+});
+
+add_task(async function test_no_allowed_extensions() {
+  let manifest = Object.assign({}, templateManifest);
+  manifest.allowed_extensions = [];
+  await writeManifest(USER_TEST_JSON, manifest);
+  let result = await lookupApplication("test", context);
+  equal(
+    result,
+    null,
+    "lookupApplication ignores manifest with no allowed_extensions"
+  );
+});
+
+const GLOBAL_TEST_JSON = PathUtils.join(globalDir.path, TYPE_SLUG, "test.json");
+let globalManifest = Object.assign({}, templateManifest);
+globalManifest.description = "This manifest is from the systemwide directory";
+
+add_task(async function good_manifest_system_dir() {
+  await IOUtils.remove(USER_TEST_JSON);
+  await writeManifest(GLOBAL_TEST_JSON, globalManifest);
+  if (registry) {
+    registry.setValue(
+      Ci.nsIWindowsRegKey.ROOT_KEY_CURRENT_USER,
+      `${REGPATH}\\test`,
+      "",
+      null
+    );
+    registry.setValue(
+      Ci.nsIWindowsRegKey.ROOT_KEY_LOCAL_MACHINE,
+      `${REGPATH}\\test`,
+      "",
+      GLOBAL_TEST_JSON
+    );
+  }
+
+  let where =
+    AppConstants.platform == "win" ? "registry location" : "directory";
+  let result = await lookupApplication("test", context);
+  notEqual(
+    result,
+    null,
+    `lookupApplication finds a manifest in the system-wide ${where}`
+  );
+  equal(
+    result.path,
+    GLOBAL_TEST_JSON,
+    `lookupApplication returns path in the system-wide ${where}`
+  );
+  deepEqual(
+    result.manifest,
+    globalManifest,
+    `lookupApplication returns manifest contents from the system-wide ${where}`
+  );
+});
+
+add_task(async function test_user_dir_precedence() {
+  await writeManifest(USER_TEST_JSON, templateManifest);
+  if (registry) {
+    registry.setValue(
+      Ci.nsIWindowsRegKey.ROOT_KEY_CURRENT_USER,
+      `${REGPATH}\\test`,
+      "",
+      USER_TEST_JSON
+    );
+  }
+  // global test.json and LOCAL_MACHINE registry key on windows are
+  // still present from the previous test
+
+  let result = await lookupApplication("test", context);
+  notEqual(
+    result,
+    null,
+    "lookupApplication finds a manifest when entries exist in both user-specific and system-wide locations"
+  );
+  equal(
+    result.path,
+    USER_TEST_JSON,
+    "lookupApplication returns the user-specific path when user-specific and system-wide entries both exist"
+  );
+  deepEqual(
+    result.manifest,
+    templateManifest,
+    "lookupApplication returns user-specific manifest contents with user-specific and system-wide entries both exist"
+  );
+});
+
+// Test shutdown handling in NativeApp
+add_task(async function test_native_app_shutdown() {
+  const SCRIPT = String.raw`
+import signal
+import struct
+import sys
+
+signal.signal(signal.SIGTERM, signal.SIG_IGN)
+
+stdin = getattr(sys.stdin, 'buffer', sys.stdin)
+stdout = getattr(sys.stdout, 'buffer', sys.stdout)
+
+while True:
+    rawlen = stdin.read(4)
+    if len(rawlen) == 0:
+        signal.pause()
+    msglen = struct.unpack('@I', rawlen)[0]
+    msg = stdin.read(msglen)
+
+    stdout.write(struct.pack('@I', msglen))
+    stdout.write(msg)
+`;
+
+  let scriptPath = PathUtils.join(userDir.path, TYPE_SLUG, "wontdie.py");
+  let manifestPath = PathUtils.join(userDir.path, TYPE_SLUG, "wontdie.json");
+
+  const ID = "native@tests.mozilla.org";
+  let manifest = {
+    name: "wontdie",
+    description: "test async shutdown of native apps",
+    type: "stdio",
+    allowed_extensions: [ID],
+  };
+
+  if (AppConstants.platform == "win") {
+    await IOUtils.writeUTF8(scriptPath, SCRIPT);
+
+    let batPath = PathUtils.join(userDir.path, TYPE_SLUG, "wontdie.bat");
+    let batBody = `@ECHO OFF\n${PYTHON} -u "${scriptPath}" %*\n`;
+    await IOUtils.writeUTF8(batPath, batBody);
+    await IOUtils.setPermissions(batPath, 0o755);
+
+    manifest.path = batPath;
+    await writeManifest(manifestPath, manifest);
+
+    registry.setValue(
+      Ci.nsIWindowsRegKey.ROOT_KEY_CURRENT_USER,
+      `${REGPATH}\\wontdie`,
+      "",
+      manifestPath
+    );
+  } else {
+    await IOUtils.writeUTF8(scriptPath, `#!${PYTHON} -u\n${SCRIPT}`);
+    await IOUtils.setPermissions(scriptPath, 0o755);
+    manifest.path = scriptPath;
+    await writeManifest(manifestPath, manifest);
+  }
+
+  let mockContext = new MockContext(ID);
+  let app = new NativeApp(mockContext, "wontdie");
+
+  // send a message and wait for the reply to make sure the app is running
+  let MSG = "test";
+  let recvPromise = new Promise(resolve => {
+    let listener = (what, msg) => {
+      equal(msg, MSG, "Received test message");
+      app.off("message", listener);
+      resolve();
+    };
+    app.on("message", listener);
+  });
+
+  let buffer = NativeApp.encodeMessage(mockContext, MSG);
+  app.send(new StructuredCloneHolder("", null, buffer));
+  await recvPromise;
+
+  app._cleanup();
+
+  info("waiting for async shutdown");
+  Services.prefs.setBoolPref("toolkit.asyncshutdown.testing", true);
+  AsyncShutdown.profileBeforeChange._trigger();
+  Services.prefs.clearUserPref("toolkit.asyncshutdown.testing");
+
+  let procs = await SubprocessImpl.Process.getWorker().call("getProcesses", []);
+  equal(procs.size, 0, "native process exited");
+});
diff --git a/toolkit/components/extensions/test/xpcshell/test_proxy_failover.js b/toolkit/components/extensions/test/xpcshell/test_proxy_failover.js
new file mode 100644
index 0000000000..e584f142fa
--- /dev/null
+++ b/toolkit/components/extensions/test/xpcshell/test_proxy_failover.js
@@ -0,0 +1,323 @@
+"use strict";
+
+AddonTestUtils.init(this);
+AddonTestUtils.overrideCertDB();
+AddonTestUtils.createAppInfo(
+  "xpcshell@tests.mozilla.org",
+  "XPCShell",
+  "1",
+  "43"
+);
+
+// Necessary for the pac script to proxy localhost requests
+Services.prefs.setBoolPref("network.proxy.allow_hijacking_localhost", true);
+
+// Pref is not builtin if direct failover is disabled in compile config.
+XPCOMUtils.defineLazyGetter(this, "directFailoverDisabled", () => {
+  return (
+    Services.prefs.getPrefType("network.proxy.failover_direct") ==
+    Ci.nsIPrefBranch.PREF_INVALID
+  );
+});
+
+const { ServiceRequest } = ChromeUtils.importESModule(
+  "resource://gre/modules/ServiceRequest.sys.mjs"
+);
+
+// Prevent the request from reaching out to the network.
+const { HttpServer } = ChromeUtils.import("resource://testing-common/httpd.js");
+
+// No hosts defined to avoid the default proxy filter setup.
+const nonProxiedServer = createHttpServer();
+nonProxiedServer.registerPathHandler("/", (request, response) => {
+  response.setStatusLine(request.httpVersion, 200, "OK");
+  response.write("ok!");
+});
+const { primaryHost, primaryPort } = nonProxiedServer.identity;
+
+function getProxyData(channel) {
+  if (!(channel instanceof Ci.nsIProxiedChannel) || !channel.proxyInfo) {
+    return;
+  }
+  let { type, host, port, sourceId } = channel.proxyInfo;
+  return { type, host, port, sourceId };
+}
+
+// Get a free port with no listener to use in the proxyinfo.
+function getBadProxyPort() {
+  let server = new HttpServer();
+  server.start(-1);
+  const badPort = server.identity.primaryPort;
+  server.stop();
+  return badPort;
+}
+
+function xhr(url, options = { beConservative: true, bypassProxy: false }) {
+  return new Promise((resolve, reject) => {
+    let req = new XMLHttpRequest();
+    req.open("GET", `${url}?t=${Math.random()}`);
+    req.channel.QueryInterface(Ci.nsIHttpChannelInternal).beConservative =
+      options.beConservative;
+    req.channel.QueryInterface(Ci.nsIHttpChannelInternal).bypassProxy =
+      options.bypassProxy;
+    req.onload = () => {
+      resolve({ text: req.responseText, proxy: getProxyData(req.channel) });
+    };
+    req.onerror = () => {
+      reject({ status: req.status, proxy: getProxyData(req.channel) });
+    };
+    req.send();
+  });
+}
+
+// Same as the above xhr call, but ServiceRequest is always beConservative.
+// This is here to specifically test bypassProxy with ServiceRequest.
+function serviceRequest(url, options = { bypassProxy: false }) {
+  return new Promise((resolve, reject) => {
+    let req = new ServiceRequest();
+    req.open("GET", `${url}?t=${Math.random()}`, options);
+    req.onload = () => {
+      resolve({ text: req.responseText, proxy: getProxyData(req.channel) });
+    };
+    req.onerror = () => {
+      reject({ status: req.status, proxy: getProxyData(req.channel) });
+    };
+    req.send();
+  });
+}
+
+add_task(async function setup() {
+  await AddonTestUtils.promiseStartupManager();
+});
+
+async function getProxyExtension(proxyDetails) {
+  async function background(proxyDetails) {
+    browser.proxy.onRequest.addListener(
+      details => {
+        return proxyDetails;
+      },
+      { urls: ["<all_urls>"] }
+    );
+
+    browser.test.sendMessage("proxied");
+  }
+  let extensionData = {
+    manifest: {
+      permissions: ["proxy", "<all_urls>"],
+    },
+    background: `(${background})(${JSON.stringify(proxyDetails)})`,
+    incognitoOverride: "spanning",
+    useAddonManager: "temporary",
+  };
+
+  let extension = ExtensionTestUtils.loadExtension(extensionData);
+  await extension.startup();
+  await extension.awaitMessage("proxied");
+  return extension;
+}
+
+add_task(async function test_failover_content_direct() {
+  // load a content page for fetch and non-system principal, expect
+  // failover to direct will work.
+  const proxyDetails = [
+    { type: "http", host: "127.0.0.1", port: getBadProxyPort() },
+    { type: "direct" },
+  ];
+
+  // We need to load the content page before loading the proxy extension
+  // to ensure that we have a valid content page to run fetch from.
+  let contentUrl = `http://${primaryHost}:${primaryPort}/`;
+  let page = await ExtensionTestUtils.loadContentPage(contentUrl);
+
+  let extension = await getProxyExtension(proxyDetails);
+
+  await ExtensionTestUtils.fetch(contentUrl, `${contentUrl}?t=${Math.random()}`)
+    .then(text => {
+      equal(text, "ok!", "fetch completed");
+    })
+    .catch(() => {
+      ok(false, "fetch failed");
+    });
+
+  await extension.unload();
+  await page.close();
+});
+
+add_task(
+  { skip_if: () => directFailoverDisabled },
+  async function test_failover_content() {
+    // load a content page for fetch and non-system principal, expect
+    // no failover
+    const proxyDetails = [
+      { type: "http", host: "127.0.0.1", port: getBadProxyPort() },
+    ];
+
+    // We need to load the content page before loading the proxy extension
+    // to ensure that we have a valid content page to run fetch from.
+    let contentUrl = `http://${primaryHost}:${primaryPort}/`;
+    let page = await ExtensionTestUtils.loadContentPage(contentUrl);
+
+    let extension = await getProxyExtension(proxyDetails);
+
+    await ExtensionTestUtils.fetch(
+      contentUrl,
+      `${contentUrl}?t=${Math.random()}`
+    )
+      .then(text => {
+        ok(false, "xhr unexpectedly completed");
+      })
+      .catch(e => {
+        equal(
+          e.message,
+          "NetworkError when attempting to fetch resource.",
+          "fetch failed"
+        );
+      });
+
+    await extension.unload();
+    await page.close();
+  }
+);
+
+add_task(
+  { skip_if: () => directFailoverDisabled },
+  async function test_failover_system() {
+    const proxyDetails = [
+      { type: "http", host: "127.0.0.1", port: getBadProxyPort() },
+      { type: "http", host: "127.0.0.1", port: getBadProxyPort() },
+    ];
+
+    let extension = await getProxyExtension(proxyDetails);
+
+    await xhr(`http://${primaryHost}:${primaryPort}/`)
+      .then(req => {
+        equal(req.proxy.type, "direct", "proxy failover to direct");
+        equal(req.text, "ok!", "xhr completed");
+      })
+      .catch(req => {
+        ok(false, "xhr failed");
+      });
+
+    await extension.unload();
+  }
+);
+
+add_task(
+  {
+    skip_if: () =>
+      AppConstants.platform === "android" || directFailoverDisabled,
+  },
+  async function test_failover_pac() {
+    const badPort = getBadProxyPort();
+
+    async function background(badPort) {
+      let pac = `function FindProxyForURL(url, host) { return "PROXY 127.0.0.1:${badPort}"; }`;
+      let proxySettings = {
+        proxyType: "autoConfig",
+        autoConfigUrl: `data:application/x-ns-proxy-autoconfig;charset=utf-8,${encodeURIComponent(
+          pac
+        )}`,
+      };
+
+      await browser.proxy.settings.set({ value: proxySettings });
+      browser.test.sendMessage("proxied");
+    }
+    let extensionData = {
+      manifest: {
+        permissions: ["proxy", "<all_urls>"],
+      },
+      background: `(${background})(${badPort})`,
+      incognitoOverride: "spanning",
+      useAddonManager: "temporary",
+    };
+
+    let extension = ExtensionTestUtils.loadExtension(extensionData);
+    await extension.startup();
+    await extension.awaitMessage("proxied");
+    equal(
+      Services.prefs.getIntPref("network.proxy.type"),
+      2,
+      "autoconfig type set"
+    );
+    ok(
+      Services.prefs.getStringPref("network.proxy.autoconfig_url"),
+      "autoconfig url set"
+    );
+
+    await xhr(`http://${primaryHost}:${primaryPort}/`)
+      .then(req => {
+        equal(req.proxy.type, "direct", "proxy failover to direct");
+        equal(req.text, "ok!", "xhr completed");
+      })
+      .catch(() => {
+        ok(false, "xhr failed");
+      });
+
+    await extension.unload();
+  }
+);
+
+add_task(async function test_bypass_proxy() {
+  const proxyDetails = [
+    { type: "http", host: "127.0.0.1", port: getBadProxyPort() },
+  ];
+
+  let extension = await getProxyExtension(proxyDetails);
+
+  await xhr(`http://${primaryHost}:${primaryPort}/`, { bypassProxy: true })
+    .then(req => {
+      equal(req.proxy, undefined, "no proxy used");
+      ok(true, "xhr completed");
+    })
+    .catch(req => {
+      equal(req.proxy, undefined, "no proxy used");
+      ok(false, "xhr error");
+    });
+
+  await extension.unload();
+});
+
+add_task(async function test_bypass_proxy() {
+  const proxyDetails = [
+    { type: "http", host: "127.0.0.1", port: getBadProxyPort() },
+  ];
+
+  let extension = await getProxyExtension(proxyDetails);
+
+  await serviceRequest(`http://${primaryHost}:${primaryPort}/`, {
+    bypassProxy: true,
+  })
+    .then(req => {
+      equal(req.proxy, undefined, "no proxy used");
+      ok(true, "xhr completed");
+    })
+    .catch(req => {
+      equal(req.proxy, undefined, "no proxy used");
+      ok(false, "xhr error");
+    });
+
+  await extension.unload();
+});
+
+add_task(async function test_failover_system_off() {
+  // Test test failover failures, uncomment and set pref to false
+  Services.prefs.setBoolPref("network.proxy.failover_direct", false);
+
+  const proxyDetails = [
+    { type: "http", host: "127.0.0.1", port: getBadProxyPort() },
+  ];
+
+  let extension = await getProxyExtension(proxyDetails);
+
+  await xhr(`http://${primaryHost}:${primaryPort}/`)
+    .then(req => {
+      equal(req.proxy.sourceId, extension.id, "extension matches");
+      ok(false, "xhr completed");
+    })
+    .catch(req => {
+      equal(req.proxy.sourceId, extension.id, "extension matches");
+      equal(req.status, 0, "xhr failed");
+    });
+
+  await extension.unload();
+});
diff --git a/toolkit/components/extensions/test/xpcshell/test_proxy_incognito.js b/toolkit/components/extensions/test/xpcshell/test_proxy_incognito.js
new file mode 100644
index 0000000000..a37996c221
--- /dev/null
+++ b/toolkit/components/extensions/test/xpcshell/test_proxy_incognito.js
@@ -0,0 +1,95 @@
+"use strict";
+
+/* eslint no-unused-vars: ["error", {"args": "none", "varsIgnorePattern": "^(FindProxyForURL)$"}] */
+
+const server = createHttpServer({ hosts: ["example.com"] });
+
+server.registerPathHandler("/dummy", (request, response) => {
+  response.setStatusLine(request.httpVersion, 200, "OK");
+  response.setHeader("Content-Type", "text/html", false);
+  response.write("<!DOCTYPE html><html></html>");
+});
+
+add_task(async function test_incognito_proxy_onRequest_access() {
+  // This extension will fail if it gets a private request.
+  let extension = ExtensionTestUtils.loadExtension({
+    manifest: {
+      permissions: ["proxy", "<all_urls>"],
+    },
+    async background() {
+      browser.proxy.onRequest.addListener(
+        async details => {
+          browser.test.assertFalse(
+            details.incognito,
+            "incognito flag is not set"
+          );
+          browser.test.notifyPass("proxy.onRequest");
+        },
+        { urls: ["<all_urls>"], types: ["main_frame"] }
+      );
+
+      // Actual call arguments do not matter here.
+      await browser.test.assertRejects(
+        browser.proxy.settings.set({
+          value: {
+            proxyType: "none",
+          },
+        }),
+        /proxy.settings requires private browsing permission/,
+        "proxy.settings requires private browsing permission."
+      );
+
+      browser.test.sendMessage("ready");
+    },
+  });
+  await extension.startup();
+  await extension.awaitMessage("ready");
+
+  let pextension = ExtensionTestUtils.loadExtension({
+    incognitoOverride: "spanning",
+    manifest: {
+      permissions: ["proxy", "<all_urls>"],
+    },
+    background() {
+      browser.proxy.onRequest.addListener(
+        async details => {
+          browser.test.assertTrue(
+            details.incognito,
+            "incognito flag is set with filter"
+          );
+          browser.test.sendMessage("proxy.onRequest.private");
+        },
+        { urls: ["<all_urls>"], types: ["main_frame"], incognito: true }
+      );
+
+      browser.proxy.onRequest.addListener(
+        async details => {
+          browser.test.assertFalse(
+            details.incognito,
+            "incognito flag is not set with filter"
+          );
+          browser.test.notifyPass("proxy.onRequest.spanning");
+        },
+        { urls: ["<all_urls>"], types: ["main_frame"], incognito: false }
+      );
+    },
+  });
+  await pextension.startup();
+
+  let contentPage = await ExtensionTestUtils.loadContentPage(
+    "https://example.com/dummy",
+    { privateBrowsing: true }
+  );
+  await pextension.awaitMessage("proxy.onRequest.private");
+  await contentPage.close();
+
+  contentPage = await ExtensionTestUtils.loadContentPage(
+    "https://example.com/dummy"
+  );
+  await extension.awaitFinish("proxy.onRequest");
+  await pextension.awaitFinish("proxy.onRequest.spanning");
+  await contentPage.close();
+
+  await pextension.unload();
+  await extension.unload();
+});
diff --git a/toolkit/components/extensions/test/xpcshell/test_proxy_info_results.js b/toolkit/components/extensions/test/xpcshell/test_proxy_info_results.js
new file mode 100644
index 0000000000..0a7e1422d2
--- /dev/null
+++ b/toolkit/components/extensions/test/xpcshell/test_proxy_info_results.js
@@ -0,0 +1,462 @@
+"use strict";
+
+XPCOMUtils.defineLazyServiceGetter(
+  this,
+  "gProxyService",
+  "@mozilla.org/network/protocol-proxy-service;1",
+  "nsIProtocolProxyService"
+);
+
+const TRANSPARENT_PROXY_RESOLVES_HOST =
+  Ci.nsIProxyInfo.TRANSPARENT_PROXY_RESOLVES_HOST;
+
+let extension;
+add_task(async function setup() {
+  let extensionData = {
+    manifest: {
+      permissions: ["proxy", "<all_urls>"],
+    },
+    background() {
+      let settings = { proxy: null };
+
+      browser.proxy.onError.addListener(error => {
+        browser.test.log(`error received ${error.message}`);
+        browser.test.sendMessage("proxy-error-received", error);
+      });
+      browser.test.onMessage.addListener((message, data) => {
+        if (message === "set-proxy") {
+          settings.proxy = data.proxy;
+          browser.test.sendMessage("proxy-set", settings.proxy);
+        }
+      });
+      browser.proxy.onRequest.addListener(
+        () => {
+          return settings.proxy;
+        },
+        { urls: ["<all_urls>"] }
+      );
+    },
+  };
+  extension = ExtensionTestUtils.loadExtension(extensionData);
+  await extension.startup();
+});
+
+async function setupProxyResult(proxy) {
+  extension.sendMessage("set-proxy", { proxy });
+  let proxyInfoSent = await extension.awaitMessage("proxy-set");
+  deepEqual(
+    proxyInfoSent,
+    proxy,
+    "got back proxy data from the proxy listener"
+  );
+}
+
+async function testProxyResolution(test) {
+  let { uri, proxy, expected } = test;
+  let errorMsg;
+  if (expected.error) {
+    errorMsg = extension.awaitMessage("proxy-error-received");
+  }
+  let proxyInfo = await new Promise((resolve, reject) => {
+    let channel = NetUtil.newChannel({
+      uri,
+      loadUsingSystemPrincipal: true,
+    });
+
+    gProxyService.asyncResolve(channel, 0, {
+      onProxyAvailable(req, uri, pi, status) {
+        resolve(pi && pi.QueryInterface(Ci.nsIProxyInfo));
+      },
+    });
+  });
+
+  let expectedProxyInfo = expected.proxyInfo;
+  if (expected.error) {
+    equal(proxyInfo, null, "Expected proxyInfo to be null");
+    equal((await errorMsg).message, expected.error, "error received");
+  } else if (proxy == null) {
+    equal(proxyInfo, expectedProxyInfo, "proxy is direct");
+  } else {
+    for (
+      let proxyUsed = proxyInfo;
+      proxyUsed;
+      proxyUsed = proxyUsed.failoverProxy
+    ) {
+      let { type, host, port, username, password, proxyDNS, failoverTimeout } =
+        expectedProxyInfo;
+      equal(proxyUsed.host, host, `Expected proxy host to be ${host}`);
+      equal(proxyUsed.port, port, `Expected proxy port to be ${port}`);
+      equal(proxyUsed.type, type, `Expected proxy type to be ${type}`);
+      // May be null or undefined depending on use of newProxyInfoWithAuth or newProxyInfo
+      equal(
+        proxyUsed.username || "",
+        username || "",
+        `Expected proxy username to be ${username}`
+      );
+      equal(
+        proxyUsed.password || "",
+        password || "",
+        `Expected proxy password to be ${password}`
+      );
+      equal(
+        proxyUsed.flags,
+        proxyDNS == undefined ? 0 : proxyDNS,
+        `Expected proxyDNS to be ${proxyDNS}`
+      );
+      // Default timeout is 10
+      equal(
+        proxyUsed.failoverTimeout,
+        failoverTimeout || 10,
+        `Expected failoverTimeout to be ${failoverTimeout}`
+      );
+      expectedProxyInfo = expectedProxyInfo.failoverProxy;
+    }
+  }
+}
+
+add_task(async function test_proxyInfo_results() {
+  let tests = [
+    {
+      proxy: 5,
+      expected: {
+        error: "ProxyInfoData: proxyData must be an object or array of objects",
+      },
+    },
+    {
+      proxy: "INVALID",
+      expected: {
+        error: "ProxyInfoData: proxyData must be an object or array of objects",
+      },
+    },
+    {
+      proxy: {
+        type: "socks",
+      },
+      expected: {
+        error: 'ProxyInfoData: Invalid proxy server host: "undefined"',
+      },
+    },
+    {
+      proxy: [
+        {
+          type: "pptp",
+          host: "foo.bar",
+          port: 1080,
+          username: "mungosantamaria",
+          password: "pass123",
+          proxyDNS: true,
+          failoverTimeout: 3,
+        },
+        {
+          type: "http",
+          host: "192.168.1.1",
+          port: 1128,
+          username: "mungosantamaria",
+          password: "word321",
+        },
+      ],
+      expected: {
+        error: 'ProxyInfoData: Invalid proxy server type: "pptp"',
+      },
+    },
+    {
+      proxy: [
+        {
+          type: "http",
+          host: "foo.bar",
+          port: 65536,
+          username: "mungosantamaria",
+          password: "pass123",
+          proxyDNS: true,
+          failoverTimeout: 3,
+        },
+        {
+          type: "http",
+          host: "192.168.1.1",
+          port: 3128,
+          username: "mungosantamaria",
+          password: "word321",
+        },
+      ],
+      expected: {
+        error:
+          "ProxyInfoData: Proxy server port 65536 outside range 1 to 65535",
+      },
+    },
+    {
+      proxy: [
+        {
+          type: "http",
+          host: "foo.bar",
+          port: 3128,
+          proxyAuthorizationHeader: "test",
+        },
+      ],
+      expected: {
+        error: 'ProxyInfoData: ProxyAuthorizationHeader requires type "https"',
+      },
+    },
+    {
+      proxy: [
+        {
+          type: "http",
+          host: "foo.bar",
+          port: 3128,
+          connectionIsolationKey: 1234,
+        },
+      ],
+      expected: {
+        error: 'ProxyInfoData: Invalid proxy connection isolation key: "1234"',
+      },
+    },
+    {
+      proxy: [{ type: "direct" }],
+      expected: {
+        proxyInfo: null,
+      },
+    },
+    {
+      proxy: {
+        host: "1.2.3.4",
+        port: "8080",
+        type: "http",
+        failoverProxy: null,
+      },
+      expected: {
+        proxyInfo: {
+          host: "1.2.3.4",
+          port: "8080",
+          type: "http",
+          failoverProxy: null,
+        },
+      },
+    },
+    {
+      uri: "ftp://mozilla.org",
+      proxy: {
+        host: "1.2.3.4",
+        port: "8180",
+        type: "http",
+        failoverProxy: null,
+      },
+      expected: {
+        proxyInfo: {
+          host: "1.2.3.4",
+          port: "8180",
+          type: "http",
+          failoverProxy: null,
+        },
+      },
+    },
+    {
+      proxy: {
+        host: "2.3.4.5",
+        port: "8181",
+        type: "http",
+        failoverProxy: null,
+      },
+      expected: {
+        proxyInfo: {
+          host: "2.3.4.5",
+          port: "8181",
+          type: "http",
+          failoverProxy: null,
+        },
+      },
+    },
+    {
+      proxy: {
+        host: "1.2.3.4",
+        port: "8080",
+        type: "http",
+        failoverProxy: {
+          host: "4.4.4.4",
+          port: "9000",
+          type: "socks",
+          failoverProxy: {
+            type: "direct",
+            host: null,
+            port: -1,
+          },
+        },
+      },
+      expected: {
+        proxyInfo: {
+          host: "1.2.3.4",
+          port: "8080",
+          type: "http",
+          failoverProxy: {
+            host: "4.4.4.4",
+            port: "9000",
+            type: "socks",
+            failoverProxy: {
+              type: "direct",
+              host: null,
+              port: -1,
+            },
+          },
+        },
+      },
+    },
+    {
+      proxy: [{ type: "http", host: "foo.bar", port: 3128 }],
+      expected: {
+        proxyInfo: {
+          host: "foo.bar",
+          port: "3128",
+          type: "http",
+        },
+      },
+    },
+    {
+      proxy: {
+        host: "foo.bar",
+        port: "1080",
+        type: "socks",
+      },
+      expected: {
+        proxyInfo: {
+          host: "foo.bar",
+          port: "1080",
+          type: "socks",
+        },
+      },
+    },
+    {
+      proxy: {
+        host: "foo.bar",
+        port: "1080",
+        type: "socks4",
+      },
+      expected: {
+        proxyInfo: {
+          host: "foo.bar",
+          port: "1080",
+          type: "socks4",
+        },
+      },
+    },
+    {
+      proxy: [{ type: "https", host: "foo.bar", port: 3128 }],
+      expected: {
+        proxyInfo: {
+          host: "foo.bar",
+          port: "3128",
+          type: "https",
+        },
+      },
+    },
+    {
+      proxy: [
+        {
+          type: "socks",
+          host: "foo.bar",
+          port: 1080,
+          username: "mungo",
+          password: "santamaria123",
+          proxyDNS: true,
+          failoverTimeout: 5,
+        },
+      ],
+      expected: {
+        proxyInfo: {
+          type: "socks",
+          host: "foo.bar",
+          port: 1080,
+          username: "mungo",
+          password: "santamaria123",
+          failoverTimeout: 5,
+          failoverProxy: null,
+          proxyDNS: TRANSPARENT_PROXY_RESOLVES_HOST,
+        },
+      },
+    },
+    {
+      proxy: [
+        {
+          type: "socks",
+          host: "foo.bar",
+          port: 1080,
+          username: "johnsmith",
+          password: "pass123",
+          proxyDNS: true,
+          failoverTimeout: 3,
+        },
+        { type: "http", host: "192.168.1.1", port: 3128 },
+        { type: "https", host: "192.168.1.2", port: 1121, failoverTimeout: 1 },
+        {
+          type: "socks",
+          host: "192.168.1.3",
+          port: 1999,
+          proxyDNS: true,
+          username: "mungosantamaria",
+          password: "foobar",
+        },
+      ],
+      expected: {
+        proxyInfo: {
+          type: "socks",
+          host: "foo.bar",
+          port: 1080,
+          proxyDNS: true,
+          username: "johnsmith",
+          password: "pass123",
+          failoverTimeout: 3,
+          failoverProxy: {
+            host: "192.168.1.1",
+            port: 3128,
+            type: "http",
+            failoverProxy: {
+              host: "192.168.1.2",
+              port: 1121,
+              type: "https",
+              failoverTimeout: 1,
+              failoverProxy: {
+                host: "192.168.1.3",
+                port: 1999,
+                type: "socks",
+                proxyDNS: TRANSPARENT_PROXY_RESOLVES_HOST,
+                username: "mungosantamaria",
+                password: "foobar",
+                failoverProxy: {
+                  type: "direct",
+                },
+              },
+            },
+          },
+        },
+      },
+    },
+    {
+      proxy: [
+        {
+          type: "https",
+          host: "foo.bar",
+          port: 3128,
+          proxyAuthorizationHeader: "test",
+          connectionIsolationKey: "key",
+        },
+      ],
+      expected: {
+        proxyInfo: {
+          host: "foo.bar",
+          port: "3128",
+          type: "https",
+          proxyAuthorizationHeader: "test",
+          connectionIsolationKey: "key",
+        },
+      },
+    },
+  ];
+  for (let test of tests) {
+    await setupProxyResult(test.proxy);
+    if (!test.uri) {
+      test.uri = "http://www.mozilla.org/";
+    }
+    await testProxyResolution(test);
+  }
+});
+
+add_task(async function shutdown() {
+  await extension.unload();
+});
diff --git a/toolkit/components/extensions/test/xpcshell/test_proxy_listener.js b/toolkit/components/extensions/test/xpcshell/test_proxy_listener.js
new file mode 100644
index 0000000000..8cc46d45e7
--- /dev/null
+++ b/toolkit/components/extensions/test/xpcshell/test_proxy_listener.js
@@ -0,0 +1,298 @@
+"use strict";
+
+XPCOMUtils.defineLazyServiceGetter(
+  this,
+  "gProxyService",
+  "@mozilla.org/network/protocol-proxy-service;1",
+  "nsIProtocolProxyService"
+);
+
+const TRANSPARENT_PROXY_RESOLVES_HOST =
+  Ci.nsIProxyInfo.TRANSPARENT_PROXY_RESOLVES_HOST;
+
+function getProxyInfo(url = "http://www.mozilla.org/") {
+  return new Promise((resolve, reject) => {
+    let channel = NetUtil.newChannel({
+      uri: url,
+      loadUsingSystemPrincipal: true,
+    });
+
+    gProxyService.asyncResolve(channel, 0, {
+      onProxyAvailable(req, uri, pi, status) {
+        resolve(pi);
+      },
+    });
+  });
+}
+
+const testData = [
+  {
+    // An ExtensionError is thrown for this, but we are unable to catch it as we
+    // do with the PAC script api.  In this case, we expect null for proxyInfo.
+    proxyInfo: "not_defined",
+    expected: {
+      proxyInfo: null,
+    },
+  },
+  {
+    proxyInfo: 1,
+    expected: {
+      error: {
+        message:
+          "ProxyInfoData: proxyData must be an object or array of objects",
+      },
+    },
+  },
+  {
+    proxyInfo: [
+      {
+        type: "socks",
+        host: "foo.bar",
+        port: 1080,
+        username: "johnsmith",
+        password: "pass123",
+        proxyDNS: true,
+        failoverTimeout: 3,
+      },
+      { type: "http", host: "192.168.1.1", port: 3128 },
+      { type: "https", host: "192.168.1.2", port: 1121, failoverTimeout: 1 },
+      {
+        type: "socks",
+        host: "192.168.1.3",
+        port: 1999,
+        proxyDNS: true,
+        username: "mungosantamaria",
+        password: "foobar",
+      },
+      { type: "direct" },
+    ],
+    expected: {
+      proxyInfo: {
+        type: "socks",
+        host: "foo.bar",
+        port: 1080,
+        proxyDNS: true,
+        username: "johnsmith",
+        password: "pass123",
+        failoverTimeout: 3,
+        failoverProxy: {
+          host: "192.168.1.1",
+          port: 3128,
+          type: "http",
+          failoverProxy: {
+            host: "192.168.1.2",
+            port: 1121,
+            type: "https",
+            failoverTimeout: 1,
+            failoverProxy: {
+              host: "192.168.1.3",
+              port: 1999,
+              type: "socks",
+              proxyDNS: TRANSPARENT_PROXY_RESOLVES_HOST,
+              username: "mungosantamaria",
+              password: "foobar",
+              failoverProxy: {
+                type: "direct",
+              },
+            },
+          },
+        },
+      },
+    },
+  },
+];
+
+add_task(async function test_proxy_listener() {
+  let extensionData = {
+    manifest: {
+      permissions: ["proxy", "<all_urls>"],
+    },
+    background() {
+      // Some tests generate multiple errors, we'll just rely on the first.
+      let seenError = false;
+      let proxyInfo;
+      browser.proxy.onError.addListener(error => {
+        if (!seenError) {
+          browser.test.sendMessage("proxy-error-received", error);
+          seenError = true;
+        }
+      });
+
+      browser.proxy.onRequest.addListener(
+        details => {
+          browser.test.log(`onRequest ${JSON.stringify(details)}`);
+          if (proxyInfo == "not_defined") {
+            return not_defined; // eslint-disable-line no-undef
+          }
+          return proxyInfo;
+        },
+        { urls: ["<all_urls>"] }
+      );
+
+      browser.test.onMessage.addListener((message, data) => {
+        if (message === "set-proxy") {
+          seenError = false;
+          proxyInfo = data.proxyInfo;
+        }
+      });
+
+      browser.test.sendMessage("ready");
+    },
+  };
+
+  let extension = ExtensionTestUtils.loadExtension(extensionData);
+  await extension.startup();
+  await extension.awaitMessage("ready");
+
+  for (let test of testData) {
+    extension.sendMessage("set-proxy", test);
+    let testError = test.expected.error;
+    let errorWait = testError && extension.awaitMessage("proxy-error-received");
+
+    let proxyInfo = await getProxyInfo();
+    let expectedProxyInfo = test.expected.proxyInfo;
+
+    if (testError) {
+      info("waiting for error data");
+      let error = await errorWait;
+      equal(error.message, testError.message, "Correct error message received");
+      equal(proxyInfo, null, "no proxyInfo received");
+    } else if (expectedProxyInfo === null) {
+      equal(proxyInfo, null, "no proxyInfo received");
+    } else {
+      for (
+        let proxyUsed = proxyInfo;
+        proxyUsed;
+        proxyUsed = proxyUsed.failoverProxy
+      ) {
+        let {
+          type,
+          host,
+          port,
+          username,
+          password,
+          proxyDNS,
+          failoverTimeout,
+        } = expectedProxyInfo;
+        equal(proxyUsed.host, host, `Expected proxy host to be ${host}`);
+        equal(proxyUsed.port, port || -1, `Expected proxy port to be ${port}`);
+        equal(proxyUsed.type, type, `Expected proxy type to be ${type}`);
+        // May be null or undefined depending on use of newProxyInfoWithAuth or newProxyInfo
+        equal(
+          proxyUsed.username || "",
+          username || "",
+          `Expected proxy username to be ${username}`
+        );
+        equal(
+          proxyUsed.password || "",
+          password || "",
+          `Expected proxy password to be ${password}`
+        );
+        equal(
+          proxyUsed.flags,
+          proxyDNS == undefined ? 0 : proxyDNS,
+          `Expected proxyDNS to be ${proxyDNS}`
+        );
+        // Default timeout is 10
+        equal(
+          proxyUsed.failoverTimeout,
+          failoverTimeout || 10,
+          `Expected failoverTimeout to be ${failoverTimeout}`
+        );
+        expectedProxyInfo = expectedProxyInfo.failoverProxy;
+      }
+      ok(!expectedProxyInfo, "no left over failoverProxy");
+    }
+  }
+
+  await extension.unload();
+});
+
+async function getExtension(expectedProxyInfo) {
+  function background(proxyInfo) {
+    browser.test.log(
+      `testing proxy.onRequest with proxyInfo = ${JSON.stringify(proxyInfo)}`
+    );
+    browser.proxy.onRequest.addListener(
+      details => {
+        return proxyInfo;
+      },
+      { urls: ["<all_urls>"] }
+    );
+  }
+  let extensionData = {
+    manifest: {
+      permissions: ["proxy", "<all_urls>"],
+    },
+    background: `(${background})(${JSON.stringify(expectedProxyInfo)})`,
+  };
+  let extension = ExtensionTestUtils.loadExtension(extensionData);
+  await extension.startup();
+  return extension;
+}
+
+add_task(async function test_passthrough() {
+  let ext1 = await getExtension(null);
+  let ext2 = await getExtension({ host: "1.2.3.4", port: 8888, type: "https" });
+
+  // Also use a restricted url to test the ability to proxy those.
+  let proxyInfo = await getProxyInfo("https://addons.mozilla.org/");
+
+  equal(proxyInfo.host, "1.2.3.4", `second extension won`);
+  equal(proxyInfo.port, "8888", `second extension won`);
+  equal(proxyInfo.type, "https", `second extension won`);
+
+  await ext2.unload();
+
+  proxyInfo = await getProxyInfo();
+  equal(proxyInfo, null, `expected no proxy`);
+  await ext1.unload();
+});
+
+add_task(async function test_ftp_disabled() {
+  let extension = await getExtension({
+    host: "1.2.3.4",
+    port: 8888,
+    type: "http",
+  });
+
+  let proxyInfo = await getProxyInfo("ftp://somewhere.mozilla.org/");
+
+  equal(
+    proxyInfo,
+    null,
+    `proxy of ftp request is not available when ftp is disabled`
+  );
+
+  await extension.unload();
+});
+
+add_task(async function test_ws() {
+  let proxyRequestCount = 0;
+  let proxy = createHttpServer();
+  proxy.registerPathHandler("CONNECT", (request, response) => {
+    response.setStatusLine(request.httpVersion, 404, "Proxy not found");
+    ++proxyRequestCount;
+  });
+
+  let extension = await getExtension({
+    host: proxy.identity.primaryHost,
+    port: proxy.identity.primaryPort,
+    type: "http",
+  });
+
+  // We need a page to use the WebSocket constructor, so let's use an extension.
+  let dummy = ExtensionTestUtils.loadExtension({
+    background() {
+      // The connection will not be upgraded to WebSocket, so it will close.
+      let ws = new WebSocket("wss://example.net/");
+      ws.onclose = () => browser.test.sendMessage("websocket_closed");
+    },
+  });
+  await dummy.startup();
+  await dummy.awaitMessage("websocket_closed");
+  await dummy.unload();
+
+  equal(proxyRequestCount, 1, "Expected one proxy request");
+  await extension.unload();
+});
diff --git a/toolkit/components/extensions/test/xpcshell/test_proxy_userContextId.js b/toolkit/components/extensions/test/xpcshell/test_proxy_userContextId.js
new file mode 100644
index 0000000000..5dea560e02
--- /dev/null
+++ b/toolkit/components/extensions/test/xpcshell/test_proxy_userContextId.js
@@ -0,0 +1,43 @@
+"use strict";
+
+const server = createHttpServer({ hosts: ["example.com"] });
+
+server.registerPathHandler("/dummy", (request, response) => {
+  response.setStatusLine(request.httpVersion, 200, "OK");
+  response.setHeader("Content-Type", "text/html", false);
+  response.write("<!DOCTYPE html><html></html>");
+});
+
+add_task(async function test_userContextId_proxy_onRequest() {
+  // This extension will succeed if it gets a request
+  let extension = ExtensionTestUtils.loadExtension({
+    manifest: {
+      permissions: ["proxy", "<all_urls>"],
+    },
+    background() {
+      browser.proxy.onRequest.addListener(
+        async details => {
+          if (details.url != "http://example.com/dummy") {
+            return;
+          }
+          browser.test.assertEq(
+            details.cookieStoreId,
+            "firefox-container-2",
+            "cookieStoreId is set"
+          );
+          browser.test.notifyPass("proxy.onRequest");
+        },
+        { urls: ["<all_urls>"] }
+      );
+    },
+  });
+  await extension.startup();
+
+  let contentPage = await ExtensionTestUtils.loadContentPage(
+    "http://example.com/dummy",
+    { userContextId: 2 }
+  );
+  await extension.awaitFinish("proxy.onRequest");
+  await extension.unload();
+  await contentPage.close();
+});
diff --git a/toolkit/components/extensions/test/xpcshell/test_resistfingerprinting_exempt.js b/toolkit/components/extensions/test/xpcshell/test_resistfingerprinting_exempt.js
new file mode 100644
index 0000000000..6440a470bf
--- /dev/null
+++ b/toolkit/components/extensions/test/xpcshell/test_resistfingerprinting_exempt.js
@@ -0,0 +1,40 @@
+/* -*- Mode: indent-tabs-mode: nil; js-indent-level: 2 -*- */
+/* vim: set sts=2 sw=2 et tw=80: */
+"use strict";
+
+async function queryAppName() {
+  let extension = ExtensionTestUtils.loadExtension({
+    background() {
+      browser.test.sendMessage("result", { appName: navigator.appName });
+    },
+  });
+  await extension.startup();
+  let result = await extension.awaitMessage("result");
+  await extension.unload();
+  return result.appName;
+}
+
+const APPNAME_OVERRIDE = "MyTestAppName";
+
+add_task(
+  {
+    pref_set: [["general.appname.override", APPNAME_OVERRIDE]],
+  },
+  async function test_appName_normal() {
+    let appName = await queryAppName();
+    Assert.equal(appName, APPNAME_OVERRIDE);
+  }
+);
+
+add_task(
+  {
+    pref_set: [
+      ["general.appname.override", APPNAME_OVERRIDE],
+      ["privacy.resistFingerprinting", true],
+    ],
+  },
+  async function test_appName_resistFingerprinting() {
+    let appName = await queryAppName();
+    Assert.equal(appName, APPNAME_OVERRIDE);
+  }
+);
diff --git a/toolkit/components/extensions/test/xpcshell/test_site_permissions.js b/toolkit/components/extensions/test/xpcshell/test_site_permissions.js
new file mode 100644
index 0000000000..652c9ae3ac
--- /dev/null
+++ b/toolkit/components/extensions/test/xpcshell/test_site_permissions.js
@@ -0,0 +1,385 @@
+/* -*- Mode: indent-tabs-mode: nil; js-indent-level: 2 -*- */
+/* vim: set sts=2 sw=2 et tw=80: */
+"use strict";
+
+// TODO(Bug 1789718): adapt to synthetic addon type implemented by the SitePermAddonProvider
+// or remove if redundant, after the deprecated XPIProvider-based implementation is also removed.
+
+const { AddonManager } = ChromeUtils.importESModule(
+  "resource://gre/modules/AddonManager.sys.mjs"
+);
+const { TestUtils } = ChromeUtils.importESModule(
+  "resource://testing-common/TestUtils.sys.mjs"
+);
+
+const { TelemetryController } = ChromeUtils.importESModule(
+  "resource://gre/modules/TelemetryController.sys.mjs"
+);
+const { TelemetryTestUtils } = ChromeUtils.importESModule(
+  "resource://testing-common/TelemetryTestUtils.sys.mjs"
+);
+
+AddonTestUtils.init(this);
+AddonTestUtils.overrideCertDB();
+AddonTestUtils.createAppInfo(
+  "xpcshell@tests.mozilla.org",
+  "XPCShell",
+  "42",
+  "42"
+);
+
+const l10n = new Localization([
+  "toolkit/global/extensions.ftl",
+  "toolkit/global/extensionPermissions.ftl",
+  "branding/brand.ftl",
+]);
+// Localization resources need to be first iterated outside a test
+l10n.formatValue("webext-perms-sideload-text");
+
+// Lazily import ExtensionParent to allow AddonTestUtils.createAppInfo to
+// override Services.appinfo.
+ChromeUtils.defineESModuleGetters(this, {
+  ExtensionParent: "resource://gre/modules/ExtensionParent.sys.mjs",
+});
+
+async function _test_manifest(manifest, expectedError) {
+  ExtensionTestUtils.failOnSchemaWarnings(false);
+  let normalized = await ExtensionTestUtils.normalizeManifest(
+    manifest,
+    "manifest.WebExtensionSitePermissionsManifest"
+  );
+  ExtensionTestUtils.failOnSchemaWarnings(true);
+
+  if (expectedError) {
+    ok(
+      normalized.error.includes(expectedError),
+      `The manifest error ${JSON.stringify(
+        normalized.error
+      )} must contain ${JSON.stringify(expectedError)}`
+    );
+  } else {
+    equal(normalized.error, undefined, "Should not have an error");
+  }
+  equal(normalized.errors.length, 0, "Should have no warning");
+}
+
+add_setup(async () => {
+  // Telemetry test setup needed to ensure that the builtin events are defined
+  // and they can be collected and verified.
+  await TelemetryController.testSetup();
+
+  // This is actually only needed on Android, because it does not properly support unified telemetry
+  // and so, if not enabled explicitly here, it would make these tests to fail when running on
+  // release builds.
+  const oldCanRecordBase = Services.telemetry.canRecordBase;
+  Services.telemetry.canRecordBase = true;
+  registerCleanupFunction(() => {
+    Services.telemetry.canRecordBase = oldCanRecordBase;
+  });
+});
+
+add_task(async function test_manifest_site_permissions() {
+  await _test_manifest({
+    site_permissions: ["midi"],
+    install_origins: ["http://example.com"],
+  });
+  await _test_manifest({
+    site_permissions: ["midi-sysex"],
+    install_origins: ["http://example.com"],
+  });
+  await _test_manifest(
+    {
+      site_permissions: ["unknown_site_permission"],
+      install_origins: ["http://example.com"],
+    },
+    `Error processing site_permissions.0: Invalid enumeration value "unknown_site_permission"`
+  );
+  await _test_manifest(
+    {
+      site_permissions: ["unknown_site_permission"],
+      install_origins: [],
+    },
+    `Error processing install_origins: Array requires at least 1 items;`
+  );
+  await _test_manifest(
+    {
+      site_permissions: ["unknown_site_permission"],
+    },
+    `Property "install_origins" is required`
+  );
+  await _test_manifest(
+    {
+      install_origins: ["http://example.com"],
+    },
+    `Property "site_permissions" is required`
+  );
+  // test any extra manifest entries not part of a site permissions addon will cause an error.
+  await _test_manifest(
+    {
+      site_permissions: ["midi"],
+      install_origins: ["http://example.com"],
+      permissions: ["webRequest"],
+    },
+    `Unexpected property`
+  );
+});
+
+add_task(async function test_sitepermission_telemetry() {
+  await AddonTestUtils.promiseStartupManager();
+
+  Services.telemetry.clearEvents();
+
+  const addon_id = "webmidi@test";
+  const origin = "https://example.com";
+  const permName = "midi";
+
+  let site_permission = {
+    "manifest.json": {
+      name: "test Site Permission",
+      version: "1.0",
+      manifest_version: 2,
+      browser_specific_settings: {
+        gecko: { id: addon_id },
+      },
+      install_origins: [origin],
+      site_permissions: [permName],
+    },
+  };
+
+  let [, { addon }] = await Promise.all([
+    TestUtils.topicObserved("webextension-sitepermissions-startup"),
+    AddonTestUtils.promiseInstallXPI(site_permission),
+  ]);
+
+  await addon.uninstall();
+
+  await TelemetryTestUtils.assertEvents(
+    [
+      [
+        "addonsManager",
+        "install",
+        "siteperm_deprecated",
+        /.*/,
+        {
+          step: "started",
+          addon_id,
+        },
+      ],
+      [
+        "addonsManager",
+        "install",
+        "siteperm_deprecated",
+        /.*/,
+        {
+          step: "completed",
+          addon_id,
+        },
+      ],
+      ["addonsManager", "uninstall", "siteperm_deprecated", addon_id],
+    ],
+    {
+      category: "addonsManager",
+      method: /^install|uninstall$/,
+    }
+  );
+
+  await AddonTestUtils.promiseShutdownManager();
+});
+
+async function _test_ext_site_permissions(site_permissions, install_origins) {
+  ExtensionTestUtils.failOnSchemaWarnings(false);
+  let extension = ExtensionTestUtils.loadExtension({
+    manifest: {
+      install_origins,
+      site_permissions,
+    },
+  });
+  await extension.startup();
+  await extension.unload();
+  ExtensionTestUtils.failOnSchemaWarnings(true);
+}
+
+add_task(async function test_ext_site_permissions() {
+  await _test_ext_site_permissions(["midi"], ["http://example.com"]);
+
+  await _test_ext_site_permissions(
+    ["midi"],
+    ["http://example.com", "http://foo.com"]
+  ).catch(e => {
+    Assert.ok(
+      e.message.includes(
+        "Error processing install_origins: Array requires at most 1 items; you have 2"
+      ),
+      "Site permissions can only contain one install origin: "
+    );
+  });
+});
+
+add_task(async function test_sitepermission_type() {
+  await AddonTestUtils.promiseStartupManager();
+
+  // Test more than one perm to make sure both are added.
+  // While this is allowed, midi-sysex overrides.
+  let perms = ["midi", "midi-sysex"];
+  let id = "@test-permission";
+  let origin = "http://example.com";
+  let uri = Services.io.newURI(origin);
+  let principal = Services.scriptSecurityManager.createContentPrincipal(
+    uri,
+    {}
+  );
+
+  // give the site some other permission (geo)
+  Services.perms.addFromPrincipal(
+    principal,
+    "geo",
+    Services.perms.ALLOW_ACTION,
+    Services.perms.EXPIRE_NEVER
+  );
+
+  let assertGeo = () => {
+    Assert.equal(
+      Services.perms.testExactPermissionFromPrincipal(principal, "geo"),
+      Ci.nsIPermissionManager.ALLOW_ACTION,
+      "site still has geo permission"
+    );
+  };
+
+  let checkPerms = (perms, action, msg) => {
+    for (let permName of perms) {
+      let permission = Services.perms.testExactPermissionFromPrincipal(
+        principal,
+        permName
+      );
+      Assert.equal(permission, action, `${permName}: ${msg}`);
+    }
+  };
+
+  checkPerms(
+    perms,
+    Ci.nsIPermissionManager.UNKNOWN_ACTION,
+    "no permission for site"
+  );
+
+  let site_permission = {
+    "manifest.json": {
+      name: "test Site Permission",
+      version: "1.0",
+      manifest_version: 2,
+      browser_specific_settings: {
+        gecko: {
+          id,
+        },
+      },
+      install_origins: [origin],
+      site_permissions: perms,
+    },
+  };
+
+  let [, { addon }] = await Promise.all([
+    TestUtils.topicObserved("webextension-sitepermissions-startup"),
+    AddonTestUtils.promiseInstallXPI(site_permission),
+  ]);
+
+  checkPerms(
+    perms,
+    Ci.nsIPermissionManager.ALLOW_ACTION,
+    "extension enabled permission for site"
+  );
+  assertGeo();
+
+  // Test the permission is retained on restart.
+  await AddonTestUtils.promiseRestartManager();
+  addon = await AddonManager.getAddonByID(id);
+
+  checkPerms(
+    perms,
+    Ci.nsIPermissionManager.ALLOW_ACTION,
+    "extension enabled permission for site"
+  );
+  assertGeo();
+
+  // Test that a removed permission is added on restart
+  Services.perms.removeFromPrincipal(principal, perms[0]);
+  await AddonTestUtils.promiseRestartManager();
+  addon = await AddonManager.getAddonByID(id);
+
+  checkPerms(
+    perms,
+    Ci.nsIPermissionManager.ALLOW_ACTION,
+    "extension enabled permission for site"
+  );
+  assertGeo();
+
+  // Test that a changed permission is not changed on restart
+  Services.perms.addFromPrincipal(
+    principal,
+    perms[0],
+    Services.perms.DENY_ACTION,
+    Services.perms.EXPIRE_NEVER
+  );
+
+  await AddonTestUtils.promiseRestartManager();
+  addon = await AddonManager.getAddonByID(id);
+
+  checkPerms(
+    [perms[0]],
+    Ci.nsIPermissionManager.DENY_ACTION,
+    "extension enabled permission for site"
+  );
+  checkPerms(
+    [perms[1]],
+    Ci.nsIPermissionManager.ALLOW_ACTION,
+    "extension enabled permission for site"
+  );
+  assertGeo();
+
+  // Test permission removal when addon disabled
+  await addon.disable();
+
+  checkPerms(
+    perms,
+    Ci.nsIPermissionManager.UNKNOWN_ACTION,
+    "no permission for site"
+  );
+  assertGeo();
+
+  // Enabling an addon will always force ALLOW_ACTION
+  await addon.enable();
+
+  checkPerms(
+    perms,
+    Ci.nsIPermissionManager.ALLOW_ACTION,
+    "extension enabled permission for site"
+  );
+  assertGeo();
+
+  // Test permission removal when addon uninstalled
+  await addon.uninstall();
+
+  checkPerms(
+    perms,
+    Ci.nsIPermissionManager.UNKNOWN_ACTION,
+    "no permission for site"
+  );
+  assertGeo();
+});
+
+add_task(async function test_site_permissions_have_localization_strings() {
+  await ExtensionParent.apiManager.lazyInit();
+  const SCHEMA_SITE_PERMISSIONS = Schemas.getPermissionNames([
+    "SitePermission",
+  ]);
+  ok(SCHEMA_SITE_PERMISSIONS.length, "we have site permissions");
+
+  for (const perm of SCHEMA_SITE_PERMISSIONS) {
+    const l10nId = `webext-site-perms-${perm}`;
+    try {
+      const str = await l10n.formatValue(l10nId);
+
+      ok(str.length, `Found localization string for '${perm}' site permission`);
+    } catch (e) {
+      ok(false, `Site permission missing '${perm}'`);
+    }
+  }
+});
diff --git a/toolkit/components/extensions/test/xpcshell/test_webRequest_ancestors.js b/toolkit/components/extensions/test/xpcshell/test_webRequest_ancestors.js
new file mode 100644
index 0000000000..43e2d11872
--- /dev/null
+++ b/toolkit/components/extensions/test/xpcshell/test_webRequest_ancestors.js
@@ -0,0 +1,79 @@
+"use strict";
+
+var { WebRequest } = ChromeUtils.importESModule(
+  "resource://gre/modules/WebRequest.sys.mjs"
+);
+var { PromiseUtils } = ChromeUtils.importESModule(
+  "resource://gre/modules/PromiseUtils.sys.mjs"
+);
+var { ExtensionParent } = ChromeUtils.importESModule(
+  "resource://gre/modules/ExtensionParent.sys.mjs"
+);
+
+const server = createHttpServer({ hosts: ["example.com"] });
+server.registerDirectory("/data/", do_get_file("data"));
+
+add_task(async function setup() {
+  // When WebRequest.jsm is used directly instead of through ext-webRequest.js,
+  // ExtensionParent.apiManager is not automatically initialized. Do it here.
+  await ExtensionParent.apiManager.lazyInit();
+});
+
+add_task(async function test_ancestors_exist() {
+  let deferred = PromiseUtils.defer();
+  function onBeforeRequest(details) {
+    info(`onBeforeRequest ${details.url}`);
+    ok(
+      typeof details.frameAncestors === "object",
+      `ancestors exists [${typeof details.frameAncestors}]`
+    );
+    deferred.resolve();
+  }
+
+  WebRequest.onBeforeRequest.addListener(
+    onBeforeRequest,
+    { urls: new MatchPatternSet(["http://example.com/*"]) },
+    ["blocking"]
+  );
+
+  let contentPage = await ExtensionTestUtils.loadContentPage(
+    "http://example.com/data/file_sample.html"
+  );
+  await deferred.promise;
+  await contentPage.close();
+
+  WebRequest.onBeforeRequest.removeListener(onBeforeRequest);
+});
+
+add_task(async function test_ancestors_null() {
+  let deferred = PromiseUtils.defer();
+  function onBeforeRequest(details) {
+    info(`onBeforeRequest ${details.url}`);
+    ok(details.frameAncestors === undefined, "ancestors do not exist");
+    deferred.resolve();
+  }
+
+  WebRequest.onBeforeRequest.addListener(onBeforeRequest, null, ["blocking"]);
+
+  function fetch(url) {
+    return new Promise((resolve, reject) => {
+      let xhr = new XMLHttpRequest();
+      xhr.mozBackgroundRequest = true;
+      xhr.open("GET", url);
+      xhr.onload = () => {
+        resolve(xhr.responseText);
+      };
+      xhr.onerror = () => {
+        reject(xhr.status);
+      };
+      // use a different contextId to avoid auth cache.
+      xhr.setOriginAttributes({ userContextId: 1 });
+      xhr.send();
+    });
+  }
+
+  await fetch("http://example.com/data/file_sample.html");
+  await deferred.promise;
+
+  WebRequest.onBeforeRequest.removeListener(onBeforeRequest);
+});
diff --git a/toolkit/components/extensions/test/xpcshell/test_webRequest_cookies.js b/toolkit/components/extensions/test/xpcshell/test_webRequest_cookies.js
new file mode 100644
index 0000000000..53ed465786
--- /dev/null
+++ b/toolkit/components/extensions/test/xpcshell/test_webRequest_cookies.js
@@ -0,0 +1,102 @@
+"use strict";
+
+var { WebRequest } = ChromeUtils.importESModule(
+  "resource://gre/modules/WebRequest.sys.mjs"
+);
+
+var { ExtensionParent } = ChromeUtils.importESModule(
+  "resource://gre/modules/ExtensionParent.sys.mjs"
+);
+
+const server = createHttpServer({ hosts: ["example.com"] });
+server.registerPathHandler("/", (request, response) => {
+  response.setStatusLine(request.httpVersion, 200, "OK");
+  if (request.hasHeader("Cookie")) {
+    let value = request.getHeader("Cookie");
+    if (value == "blinky=1") {
+      response.setHeader("Set-Cookie", "dinky=1", false);
+    }
+    response.write("cookie-present");
+  } else {
+    response.setHeader("Set-Cookie", "foopy=1", false);
+    response.write("cookie-not-present");
+  }
+});
+
+const URL = "http://example.com/";
+
+var countBefore = 0;
+var countAfter = 0;
+
+function onBeforeSendHeaders(details) {
+  if (details.url != URL) {
+    return undefined;
+  }
+
+  countBefore++;
+
+  info(`onBeforeSendHeaders ${details.url}`);
+  let found = false;
+  let headers = [];
+  for (let { name, value } of details.requestHeaders) {
+    info(`Saw header ${name} '${value}'`);
+    if (name == "Cookie") {
+      equal(value, "foopy=1", "Cookie is correct");
+      headers.push({ name, value: "blinky=1" });
+      found = true;
+    } else {
+      headers.push({ name, value });
+    }
+  }
+  ok(found, "Saw cookie header");
+  equal(countBefore, 1, "onBeforeSendHeaders hit once");
+
+  return { requestHeaders: headers };
+}
+
+function onResponseStarted(details) {
+  if (details.url != URL) {
+    return;
+  }
+
+  countAfter++;
+
+  info(`onResponseStarted ${details.url}`);
+  let found = false;
+  for (let { name, value } of details.responseHeaders) {
+    info(`Saw header ${name} '${value}'`);
+    if (name == "set-cookie") {
+      equal(value, "dinky=1", "Cookie is correct");
+      found = true;
+    }
+  }
+  ok(found, "Saw cookie header");
+  equal(countAfter, 1, "onResponseStarted hit once");
+}
+
+add_task(async function setup() {
+  // When WebRequest.jsm is used directly instead of through ext-webRequest.js,
+  // ExtensionParent.apiManager is not automatically initialized. Do it here.
+  await ExtensionParent.apiManager.lazyInit();
+});
+
+add_task(async function filter_urls() {
+  // First load the URL so that we set cookie foopy=1.
+  let contentPage = await ExtensionTestUtils.loadContentPage(URL);
+  await contentPage.close();
+
+  // Now load with WebRequest set up.
+  WebRequest.onBeforeSendHeaders.addListener(onBeforeSendHeaders, null, [
+    "blocking",
+    "requestHeaders",
+  ]);
+  WebRequest.onResponseStarted.addListener(onResponseStarted, null, [
+    "responseHeaders",
+  ]);
+
+  contentPage = await ExtensionTestUtils.loadContentPage(URL);
+  await contentPage.close();
+
+  WebRequest.onBeforeSendHeaders.removeListener(onBeforeSendHeaders);
+  WebRequest.onResponseStarted.removeListener(onResponseStarted);
+});
diff --git a/toolkit/components/extensions/test/xpcshell/test_webRequest_filtering.js b/toolkit/components/extensions/test/xpcshell/test_webRequest_filtering.js
new file mode 100644
index 0000000000..a7157f19a4
--- /dev/null
+++ b/toolkit/components/extensions/test/xpcshell/test_webRequest_filtering.js
@@ -0,0 +1,182 @@
+"use strict";
+
+var { WebRequest } = ChromeUtils.importESModule(
+  "resource://gre/modules/WebRequest.sys.mjs"
+);
+
+var { ExtensionParent } = ChromeUtils.importESModule(
+  "resource://gre/modules/ExtensionParent.sys.mjs"
+);
+
+const server = createHttpServer({ hosts: ["example.com"] });
+server.registerDirectory("/data/", do_get_file("data"));
+
+const BASE = "http://example.com/data/";
+const URL = BASE + "/file_WebRequest_page2.html";
+
+var requested = [];
+
+function onBeforeRequest(details) {
+  info(`onBeforeRequest ${details.url}`);
+  if (details.url.startsWith(BASE)) {
+    requested.push(details.url);
+  }
+}
+
+var sendHeaders = [];
+
+function onBeforeSendHeaders(details) {
+  info(`onBeforeSendHeaders ${details.url}`);
+  if (details.url.startsWith(BASE)) {
+    sendHeaders.push(details.url);
+  }
+}
+
+var completed = [];
+
+function onResponseStarted(details) {
+  if (details.url.startsWith(BASE)) {
+    completed.push(details.url);
+  }
+}
+
+const expected_urls = [
+  BASE + "/file_style_good.css",
+  BASE + "/file_style_bad.css",
+  BASE + "/file_style_redirect.css",
+];
+
+function resetExpectations() {
+  requested.length = 0;
+  sendHeaders.length = 0;
+  completed.length = 0;
+}
+
+function removeDupes(list) {
+  let j = 0;
+  for (let i = 1; i < list.length; i++) {
+    if (list[i] != list[j]) {
+      j++;
+      if (i != j) {
+        list[j] = list[i];
+      }
+    }
+  }
+  list.length = j + 1;
+}
+
+function compareLists(list1, list2, kind) {
+  list1.sort();
+  removeDupes(list1);
+  list2.sort();
+  removeDupes(list2);
+  equal(String(list1), String(list2), `${kind} URLs correct`);
+}
+
+async function openAndCloseContentPage(url) {
+  let contentPage = await ExtensionTestUtils.loadContentPage(URL);
+  // Clear the sheet cache so that it doesn't interact with following tests: A
+  // stylesheet with the same URI loaded from the same origin doesn't otherwise
+  // guarantee that onBeforeRequest and so on happen, because it may not need
+  // to go through necko at all.
+  await contentPage.spawn([], () =>
+    content.windowUtils.clearSharedStyleSheetCache()
+  );
+  await contentPage.close();
+}
+
+add_task(async function setup() {
+  // Disable rcwn to make cache behavior deterministic.
+  Services.prefs.setBoolPref("network.http.rcwn.enabled", false);
+
+  // When WebRequest.jsm is used directly instead of through ext-webRequest.js,
+  // ExtensionParent.apiManager is not automatically initialized. Do it here.
+  await ExtensionParent.apiManager.lazyInit();
+});
+
+add_task(async function filter_urls() {
+  let filter = { urls: new MatchPatternSet(["*://*/*_style_*"]) };
+
+  WebRequest.onBeforeRequest.addListener(onBeforeRequest, filter, ["blocking"]);
+  WebRequest.onBeforeSendHeaders.addListener(onBeforeSendHeaders, filter, [
+    "blocking",
+  ]);
+  WebRequest.onResponseStarted.addListener(onResponseStarted, filter);
+
+  await openAndCloseContentPage(URL);
+
+  compareLists(requested, expected_urls, "requested");
+  compareLists(sendHeaders, expected_urls, "sendHeaders");
+  compareLists(completed, expected_urls, "completed");
+
+  WebRequest.onBeforeRequest.removeListener(onBeforeRequest);
+  WebRequest.onBeforeSendHeaders.removeListener(onBeforeSendHeaders);
+  WebRequest.onResponseStarted.removeListener(onResponseStarted);
+});
+
+add_task(async function filter_types() {
+  resetExpectations();
+  let filter = { types: ["stylesheet"] };
+
+  WebRequest.onBeforeRequest.addListener(onBeforeRequest, filter, ["blocking"]);
+  WebRequest.onBeforeSendHeaders.addListener(onBeforeSendHeaders, filter, [
+    "blocking",
+  ]);
+  WebRequest.onResponseStarted.addListener(onResponseStarted, filter);
+
+  await openAndCloseContentPage(URL);
+
+  compareLists(requested, expected_urls, "requested");
+  compareLists(sendHeaders, expected_urls, "sendHeaders");
+  compareLists(completed, expected_urls, "completed");
+
+  WebRequest.onBeforeRequest.removeListener(onBeforeRequest);
+  WebRequest.onBeforeSendHeaders.removeListener(onBeforeSendHeaders);
+  WebRequest.onResponseStarted.removeListener(onResponseStarted);
+});
+
+add_task(async function filter_windowId() {
+  resetExpectations();
+  // Check that adding windowId will exclude non-matching requests.
+  // test_ext_webrequest_filter.html provides coverage for matching requests.
+  let filter = { urls: new MatchPatternSet(["*://*/*_style_*"]), windowId: 0 };
+
+  WebRequest.onBeforeRequest.addListener(onBeforeRequest, filter, ["blocking"]);
+  WebRequest.onBeforeSendHeaders.addListener(onBeforeSendHeaders, filter, [
+    "blocking",
+  ]);
+  WebRequest.onResponseStarted.addListener(onResponseStarted, filter);
+
+  await openAndCloseContentPage(URL);
+
+  compareLists(requested, [], "requested");
+  compareLists(sendHeaders, [], "sendHeaders");
+  compareLists(completed, [], "completed");
+
+  WebRequest.onBeforeRequest.removeListener(onBeforeRequest);
+  WebRequest.onBeforeSendHeaders.removeListener(onBeforeSendHeaders);
+  WebRequest.onResponseStarted.removeListener(onResponseStarted);
+});
+
+add_task(async function filter_tabId() {
+  resetExpectations();
+  // Check that adding tabId will exclude non-matching requests.
+  // test_ext_webrequest_filter.html provides coverage for matching requests.
+  let filter = { urls: new MatchPatternSet(["*://*/*_style_*"]), tabId: 0 };
+
+  WebRequest.onBeforeRequest.addListener(onBeforeRequest, filter, ["blocking"]);
+  WebRequest.onBeforeSendHeaders.addListener(onBeforeSendHeaders, filter, [
+    "blocking",
+  ]);
+  WebRequest.onResponseStarted.addListener(onResponseStarted, filter);
+
+  await openAndCloseContentPage(URL);
+
+  compareLists(requested, [], "requested");
+  compareLists(sendHeaders, [], "sendHeaders");
+  compareLists(completed, [], "completed");
+
+  WebRequest.onBeforeRequest.removeListener(onBeforeRequest);
+  WebRequest.onBeforeSendHeaders.removeListener(onBeforeSendHeaders);
+  WebRequest.onResponseStarted.removeListener(onResponseStarted);
+});
diff --git a/toolkit/components/extensions/test/xpcshell/webidl-api/.eslintrc.js b/toolkit/components/extensions/test/xpcshell/webidl-api/.eslintrc.js
new file mode 100644
index 0000000000..3622fff4f6
--- /dev/null
+++ b/toolkit/components/extensions/test/xpcshell/webidl-api/.eslintrc.js
@@ -0,0 +1,9 @@
+"use strict";
+
+module.exports = {
+  env: {
+    // The tests in this folder are testing based on WebExtensions, so lets
+    // just define the webextensions environment here.
+    webextensions: true,
+  },
+};
diff --git a/toolkit/components/extensions/test/xpcshell/webidl-api/head_webidl_api.js b/toolkit/components/extensions/test/xpcshell/webidl-api/head_webidl_api.js
new file mode 100644
index 0000000000..3e8e094a20
--- /dev/null
+++ b/toolkit/components/extensions/test/xpcshell/webidl-api/head_webidl_api.js
@@ -0,0 +1,306 @@
+/* import-globals-from ../head.js */
+
+/* exported getBackgroundServiceWorkerRegistration, waitForTerminatedWorkers,
+ *          runExtensionAPITest */
+
+"use strict";
+
+ChromeUtils.defineESModuleGetters(this, {
+  ExtensionTestCommon: "resource://testing-common/ExtensionTestCommon.sys.mjs",
+  TestUtils: "resource://testing-common/TestUtils.sys.mjs",
+});
+
+add_setup(function checkExtensionsWebIDLEnabled() {
+  equal(
+    AppConstants.MOZ_WEBEXT_WEBIDL_ENABLED,
+    true,
+    "WebExtensions WebIDL bindings build time flag should be enabled"
+  );
+});
+
+function getBackgroundServiceWorkerRegistration(extension) {
+  const swm = Cc["@mozilla.org/serviceworkers/manager;1"].getService(
+    Ci.nsIServiceWorkerManager
+  );
+
+  const swRegs = swm.getAllRegistrations();
+  const scope = `moz-extension://${extension.uuid}/`;
+
+  for (let i = 0; i < swRegs.length; i++) {
+    let regInfo = swRegs.queryElementAt(i, Ci.nsIServiceWorkerRegistrationInfo);
+    if (regInfo.scope === scope) {
+      return regInfo;
+    }
+  }
+}
+
+function waitForTerminatedWorkers(swRegInfo) {
+  info(`Wait all ${swRegInfo.scope} workers to be terminated`);
+  return TestUtils.waitForCondition(() => {
+    const { evaluatingWorker, installingWorker, waitingWorker, activeWorker } =
+      swRegInfo;
+    return !(
+      evaluatingWorker ||
+      installingWorker ||
+      waitingWorker ||
+      activeWorker
+    );
+  }, `wait workers for scope ${swRegInfo.scope} to be terminated`);
+}
+
+function unmockHandleAPIRequest(extPage) {
+  return extPage.spawn([], () => {
+    const { ExtensionAPIRequestHandler } = ChromeUtils.importESModule(
+      "resource://gre/modules/ExtensionProcessScript.sys.mjs"
+    );
+
+    // Unmock ExtensionAPIRequestHandler.
+    if (ExtensionAPIRequestHandler._handleAPIRequest_orig) {
+      ExtensionAPIRequestHandler.handleAPIRequest =
+        ExtensionAPIRequestHandler._handleAPIRequest_orig;
+      delete ExtensionAPIRequestHandler._handleAPIRequest_orig;
+    }
+  });
+}
+
+function mockHandleAPIRequest(extPage, mockHandleAPIRequest) {
+  mockHandleAPIRequest =
+    mockHandleAPIRequest ||
+    ((policy, request) => {
+      const ExtError = request.window?.Error || Error;
+      return {
+        type: Ci.mozIExtensionAPIRequestResult.EXTENSION_ERROR,
+        value: new ExtError(
+          "mockHandleAPIRequest not defined by this test case"
+        ),
+      };
+    });
+
+  return extPage.legacySpawn(
+    [ExtensionTestCommon.serializeFunction(mockHandleAPIRequest)],
+    mockFnText => {
+      const { ExtensionAPIRequestHandler } = ChromeUtils.importESModule(
+        "resource://gre/modules/ExtensionProcessScript.sys.mjs"
+      );
+
+      mockFnText = `(() => {
+        return (${mockFnText});
+      })();`;
+      // eslint-disable-next-line no-eval
+      const mockFn = eval(mockFnText);
+
+      // Mock ExtensionAPIRequestHandler.
+      if (!ExtensionAPIRequestHandler._handleAPIRequest_orig) {
+        ExtensionAPIRequestHandler._handleAPIRequest_orig =
+          ExtensionAPIRequestHandler.handleAPIRequest;
+      }
+
+      ExtensionAPIRequestHandler.handleAPIRequest = function (policy, request) {
+        if (request.apiNamespace === "test") {
+          return this._handleAPIRequest_orig(policy, request);
+        }
+        return mockFn.call(this, policy, request);
+      };
+    }
+  );
+}
+
+/**
+ * An helper function used to run unit test that are meant to test the
+ * Extension API webidl bindings helpers shared by all the webextensions
+ * API namespaces.
+ *
+ * @param {string} testDescription
+ *        Brief description of the test.
+ * @param {object} [options]
+ * @param {Function} options.backgroundScript
+ *        Test function running in the extension global. This function
+ *        does receive a parameter of type object with the following
+ *        properties:
+ *        - testLog(message): log a message on the terminal
+ *        - testAsserts:
+ *          - isErrorInstance(err): throw if err is not an Error instance
+ *          - isInstanceOf(value, globalContructorName): throws if value
+ *            is not an instance of global[globalConstructorName]
+ *          - equal(val, exp, msg): throw an error including msg if
+ *            val is not strictly equal to exp.
+ * @param {Function} options.assertResults
+ *        Function to be provided to assert the result returned by
+ *        `backgroundScript`, or assert the error if it did throw.
+ *        This function does receive a parameter of type object with
+ *        the following properties:
+ *        - testResult: the result returned (and resolved if the return
+ *          value was a promise) from the call to `backgroundScript`
+ *        - testError: the error raised (or rejected if the return value
+ *          value was a promise) from the call to `backgroundScript`
+ *        - extension: the extension wrapper created by this helper.
+ * @param {Function} options.mockAPIRequestHandler
+ *        Function to be used to mock mozIExtensionAPIRequestHandler.handleAPIRequest
+ *        for the purpose of the test.
+ *        This function received the same parameter that are listed in the idl
+ *        definition (mozIExtensionAPIRequestHandling.webidl).
+ * @param {string} [options.extensionId]
+ *        Optional extension id for the test extension.
+ */
+async function runExtensionAPITest(
+  testDescription,
+  {
+    backgroundScript,
+    assertResults,
+    mockAPIRequestHandler,
+    extensionId = "test-ext-api-request-forward@mochitest",
+  }
+) {
+  // Wraps the `backgroundScript` function to be execute in the target
+  // extension global (currently only in a background service worker,
+  // in follow-ups the same function should also be execute in
+  // other supported extension globals, e.g. an extension page and
+  // a content script).
+  //
+  // The test wrapper does also provide to `backgroundScript` some
+  // helpers to be used as part of the test, these tests are meant to
+  // only cover internals shared by all webidl API bindings through a
+  // mock API namespace only available in tests (and so none of the tests
+  // written with this helpers should be using the browser.test API namespace).
+  function backgroundScriptWrapper(testParams, testFn) {
+    const testLog = msg => {
+      // console messages emitted by workers are not visible in the test logs if not
+      // explicitly collected, and so this testLog helper method does use dump for now
+      // (this way the logs will be visibile as part of the test logs).
+      dump(`"${testParams.extensionId}": ${msg}\n`);
+    };
+
+    const testAsserts = {
+      isErrorInstance(err) {
+        if (!(err instanceof Error)) {
+          throw new Error("Unexpected error: not an instance of Error");
+        }
+        return true;
+      },
+      isInstanceOf(value, globalConstructorName) {
+        if (!(value instanceof self[globalConstructorName])) {
+          throw new Error(
+            `Unexpected error: expected instance of ${globalConstructorName}`
+          );
+        }
+        return true;
+      },
+      equal(val, exp, msg) {
+        if (val !== exp) {
+          throw new Error(
+            `Unexpected error: expected ${exp} but got ${val}. ${msg}`
+          );
+        }
+      },
+    };
+
+    testLog(`Evaluating - test case "${testParams.testDescription}"`);
+    self.onmessage = async evt => {
+      testLog(`Running test case "${testParams.testDescription}"`);
+
+      let testError = null;
+      let testResult;
+      try {
+        testResult = await testFn({ testLog, testAsserts });
+      } catch (err) {
+        testError = { message: err.message, stack: err.stack };
+        testLog(`Unexpected test error: ${err} :: ${err.stack}\n`);
+      }
+
+      evt.ports[0].postMessage({ success: !testError, testError, testResult });
+
+      testLog(`Test case "${testParams.testDescription}" executed`);
+    };
+    testLog(`Wait onmessage event - test case "${testParams.testDescription}"`);
+  }
+
+  async function assertTestResult(result) {
+    if (assertResults) {
+      await assertResults(result);
+    } else {
+      equal(result.testError, undefined, "Expect no errors");
+      ok(result.success, "Test completed successfully");
+    }
+  }
+
+  async function runTestCaseInWorker({ page, extension }) {
+    info(`*** Run test case in an extension service worker`);
+    const result = await page.legacySpawn([], async () => {
+      const { active } = await content.navigator.serviceWorker.ready;
+      const { port1, port2 } = new MessageChannel();
+
+      return new Promise(resolve => {
+        port1.onmessage = evt => resolve(evt.data);
+        active.postMessage("run-test", [port2]);
+      });
+    });
+    info(`*** Assert test case results got from extension service worker`);
+    await assertTestResult({ ...result, extension });
+  }
+
+  // NOTE: prefixing this with `function ` is needed because backgroundScript
+  // is an object property and so it is going to be stringified as
+  // `backgroundScript() { ... }` (which would be detected as a syntax error
+  // on the worker script evaluation phase).
+  const scriptFnParam = ExtensionTestCommon.serializeFunction(backgroundScript);
+  const testOptsParam = `${JSON.stringify({ testDescription, extensionId })}`;
+
+  const testExtData = {
+    useAddonManager: "temporary",
+    manifest: {
+      version: "1",
+      background: {
+        service_worker: "test-sw.js",
+      },
+      browser_specific_settings: {
+        gecko: { id: extensionId },
+      },
+    },
+    files: {
+      "page.html": `<!DOCTYPE html>
+        <head><meta charset="utf-8"></head>
+        <body>
+          <script src="test-sw.js"></script>
+        </body>`,
+      "test-sw.js": `
+        (${backgroundScriptWrapper})(${testOptsParam}, ${scriptFnParam});
+      `,
+    },
+  };
+
+  let cleanupCalled = false;
+  let extension;
+  let page;
+  let swReg;
+
+  async function testCleanup() {
+    if (cleanupCalled) {
+      return;
+    }
+
+    cleanupCalled = true;
+    await unmockHandleAPIRequest(page);
+    await page.close();
+    await extension.unload();
+    await waitForTerminatedWorkers(swReg);
+  }
+
+  info(`Start test case "${testDescription}"`);
+  extension = ExtensionTestUtils.loadExtension(testExtData);
+  await extension.startup();
+
+  swReg = getBackgroundServiceWorkerRegistration(extension);
+  ok(swReg, "Extension background.service_worker should be registered");
+
+  page = await ExtensionTestUtils.loadContentPage(
+    `moz-extension://${extension.uuid}/page.html`,
+    { extension }
+  );
+
+  registerCleanupFunction(testCleanup);
+
+  await mockHandleAPIRequest(page, mockAPIRequestHandler);
+  await runTestCaseInWorker({ page, extension });
+  await testCleanup();
+  info(`End test case "${testDescription}"`);
+}
diff --git a/toolkit/components/extensions/test/xpcshell/webidl-api/test_ext_webidl_api.js b/toolkit/components/extensions/test/xpcshell/webidl-api/test_ext_webidl_api.js
new file mode 100644
index 0000000000..489cc3a754
--- /dev/null
+++ b/toolkit/components/extensions/test/xpcshell/webidl-api/test_ext_webidl_api.js
@@ -0,0 +1,486 @@
+/* -*- Mode: indent-tabs-mode: nil; js-indent-level: 2 -*- */
+/* vim: set sts=2 sw=2 et tw=80: */
+"use strict";
+
+AddonTestUtils.init(this);
+AddonTestUtils.createAppInfo(
+  "xpcshell@tests.mozilla.org",
+  "XPCShell",
+  "1",
+  "42"
+);
+
+add_task(async function setup() {
+  await AddonTestUtils.promiseStartupManager();
+});
+
+add_task(async function test_ext_context_does_have_webidl_bindings() {
+  await runExtensionAPITest("should have a browser global object", {
+    backgroundScript() {
+      const { browser, chrome } = self;
+
+      return {
+        hasExtensionAPI: !!browser,
+        hasExtensionMockAPI: !!browser?.mockExtensionAPI,
+        hasChromeCompatGlobal: !!chrome,
+        hasChromeMockAPI: !!chrome?.mockExtensionAPI,
+      };
+    },
+    assertResults({ testResult, testError }) {
+      Assert.deepEqual(testError, undefined);
+      Assert.deepEqual(
+        testResult,
+        {
+          hasExtensionAPI: true,
+          hasExtensionMockAPI: true,
+          hasChromeCompatGlobal: true,
+          hasChromeMockAPI: true,
+        },
+        "browser and browser.test WebIDL API bindings found"
+      );
+    },
+  });
+});
+
+add_task(async function test_propagated_extension_error() {
+  await runExtensionAPITest(
+    "should throw an extension error on ResultType::EXTENSION_ERROR",
+    {
+      backgroundScript({ testAsserts }) {
+        try {
+          const api = self.browser.mockExtensionAPI;
+          api.methodSyncWithReturn("arg0", 1, { value: "arg2" });
+        } catch (err) {
+          testAsserts.isErrorInstance(err);
+          throw err;
+        }
+      },
+      mockAPIRequestHandler(policy, request) {
+        return {
+          type: Ci.mozIExtensionAPIRequestResult.EXTENSION_ERROR,
+          value: new Error("Fake Extension Error"),
+        };
+      },
+      assertResults({ testError }) {
+        Assert.deepEqual(testError?.message, "Fake Extension Error");
+      },
+    }
+  );
+});
+
+add_task(async function test_system_errors_donot_leak() {
+  function assertResults({ testError }) {
+    ok(
+      testError?.message?.match(/An unexpected error occurred/),
+      `Got the general unexpected error as expected: ${testError?.message}`
+    );
+  }
+
+  function mockAPIRequestHandler(policy, request) {
+    throw new Error("Fake handleAPIRequest exception");
+  }
+
+  const msg =
+    "should throw an unexpected error occurred if handleAPIRequest throws";
+
+  await runExtensionAPITest(`sync method ${msg}`, {
+    backgroundScript({ testAsserts }) {
+      try {
+        self.browser.mockExtensionAPI.methodSyncWithReturn("arg0");
+      } catch (err) {
+        testAsserts.isErrorInstance(err);
+        throw err;
+      }
+    },
+    mockAPIRequestHandler,
+    assertResults,
+  });
+
+  await runExtensionAPITest(`async method ${msg}`, {
+    backgroundScript({ testAsserts }) {
+      try {
+        self.browser.mockExtensionAPI.methodAsync("arg0");
+      } catch (err) {
+        testAsserts.isErrorInstance(err);
+        throw err;
+      }
+    },
+    mockAPIRequestHandler,
+    assertResults,
+  });
+
+  await runExtensionAPITest(`no return method ${msg}`, {
+    backgroundScript({ testAsserts }) {
+      try {
+        self.browser.mockExtensionAPI.methodNoReturn("arg0");
+      } catch (err) {
+        testAsserts.isErrorInstance(err);
+        throw err;
+      }
+    },
+    mockAPIRequestHandler,
+    assertResults,
+  });
+});
+
+add_task(async function test_call_sync_function_result() {
+  await runExtensionAPITest(
+    "sync API methods should support structured clonable return values",
+    {
+      backgroundScript({ testAsserts }) {
+        const api = self.browser.mockExtensionAPI;
+        const results = {
+          string: api.methodSyncWithReturn("string-result"),
+          nested_prop: api.methodSyncWithReturn({
+            string: "123",
+            number: 123,
+            date: new Date("2020-09-20"),
+            map: new Map([
+              ["a", 1],
+              ["b", 2],
+            ]),
+          }),
+        };
+
+        testAsserts.isInstanceOf(results.nested_prop.date, "Date");
+        testAsserts.isInstanceOf(results.nested_prop.map, "Map");
+        return results;
+      },
+      mockAPIRequestHandler(policy, request) {
+        if (request.apiName === "methodSyncWithReturn") {
+          // Return the first argument unmodified, which will be checked in the
+          // resultAssertFn above.
+          return {
+            type: Ci.mozIExtensionAPIRequestResult.RETURN_VALUE,
+            value: request.args[0],
+          };
+        }
+        throw new Error("Unexpected API method");
+      },
+      assertResults({ testResult, testError }) {
+        Assert.deepEqual(testError, null, "Got no error as expected");
+        Assert.deepEqual(testResult, {
+          string: "string-result",
+          nested_prop: {
+            string: "123",
+            number: 123,
+            date: new Date("2020-09-20"),
+            map: new Map([
+              ["a", 1],
+              ["b", 2],
+            ]),
+          },
+        });
+      },
+    }
+  );
+});
+
+add_task(async function test_call_sync_fn_missing_return() {
+  await runExtensionAPITest(
+    "should throw an unexpected error occurred on missing return value",
+    {
+      backgroundScript() {
+        self.browser.mockExtensionAPI.methodSyncWithReturn("arg0");
+      },
+      mockAPIRequestHandler(policy, request) {
+        return undefined;
+      },
+      assertResults({ testError }) {
+        ok(
+          testError?.message?.match(/An unexpected error occurred/),
+          `Got the general unexpected error as expected: ${testError?.message}`
+        );
+      },
+    }
+  );
+});
+
+add_task(async function test_call_async_throw_extension_error() {
+  await runExtensionAPITest(
+    "an async function can throw an error occurred for param validation errors",
+    {
+      backgroundScript({ testAsserts }) {
+        try {
+          self.browser.mockExtensionAPI.methodAsync("arg0");
+        } catch (err) {
+          testAsserts.isErrorInstance(err);
+          throw err;
+        }
+      },
+      mockAPIRequestHandler(policy, request) {
+        return {
+          type: Ci.mozIExtensionAPIRequestResult.EXTENSION_ERROR,
+          value: new Error("Fake Param Validation Error"),
+        };
+      },
+      assertResults({ testError }) {
+        Assert.deepEqual(testError?.message, "Fake Param Validation Error");
+      },
+    }
+  );
+});
+
+add_task(async function test_call_async_reject_error() {
+  await runExtensionAPITest(
+    "an async function rejected promise should propagate extension errors",
+    {
+      async backgroundScript({ testAsserts }) {
+        try {
+          await self.browser.mockExtensionAPI.methodAsync("arg0");
+        } catch (err) {
+          testAsserts.isErrorInstance(err);
+          throw err;
+        }
+      },
+      mockAPIRequestHandler(policy, request) {
+        return {
+          type: Ci.mozIExtensionAPIRequestResult.RETURN_VALUE,
+          value: Promise.reject(new Error("Fake API rejected error object")),
+        };
+      },
+      assertResults({ testError }) {
+        Assert.deepEqual(testError?.message, "Fake API rejected error object");
+      },
+    }
+  );
+});
+
+add_task(async function test_call_async_function_result() {
+  await runExtensionAPITest(
+    "async API methods should support structured clonable resolved values",
+    {
+      async backgroundScript({ testAsserts }) {
+        const api = self.browser.mockExtensionAPI;
+        const results = {
+          string: await api.methodAsync("string-result"),
+          nested_prop: await api.methodAsync({
+            string: "123",
+            number: 123,
+            date: new Date("2020-09-20"),
+            map: new Map([
+              ["a", 1],
+              ["b", 2],
+            ]),
+          }),
+        };
+
+        testAsserts.isInstanceOf(results.nested_prop.date, "Date");
+        testAsserts.isInstanceOf(results.nested_prop.map, "Map");
+        return results;
+      },
+      mockAPIRequestHandler(policy, request) {
+        if (request.apiName === "methodAsync") {
+          // Return the first argument unmodified, which will be checked in the
+          // resultAssertFn above.
+          return {
+            type: Ci.mozIExtensionAPIRequestResult.RETURN_VALUE,
+            value: Promise.resolve(request.args[0]),
+          };
+        }
+        throw new Error("Unexpected API method");
+      },
+      assertResults({ testResult, testError }) {
+        Assert.deepEqual(testError, null, "Got no error as expected");
+        Assert.deepEqual(testResult, {
+          string: "string-result",
+          nested_prop: {
+            string: "123",
+            number: 123,
+            date: new Date("2020-09-20"),
+            map: new Map([
+              ["a", 1],
+              ["b", 2],
+            ]),
+          },
+        });
+      },
+    }
+  );
+});
+
+add_task(async function test_call_no_return_throw_extension_error() {
+  await runExtensionAPITest(
+    "no return function call throw an error occurred for param validation errors",
+    {
+      backgroundScript({ testAsserts }) {
+        try {
+          self.browser.mockExtensionAPI.methodNoReturn("arg0");
+        } catch (err) {
+          testAsserts.isErrorInstance(err);
+          throw err;
+        }
+      },
+      mockAPIRequestHandler(policy, request) {
+        return {
+          type: Ci.mozIExtensionAPIRequestResult.EXTENSION_ERROR,
+          value: new Error("Fake Param Validation Error"),
+        };
+      },
+      assertResults({ testError }) {
+        Assert.deepEqual(testError?.message, "Fake Param Validation Error");
+      },
+    }
+  );
+});
+
+add_task(async function test_call_no_return_without_errors() {
+  await runExtensionAPITest(
+    "handleAPIHandler can return undefined on api calls to methods with no return",
+    {
+      backgroundScript() {
+        self.browser.mockExtensionAPI.methodNoReturn("arg0");
+      },
+      mockAPIRequestHandler(policy, request) {
+        return undefined;
+      },
+      assertResults({ testError }) {
+        Assert.deepEqual(testError, null, "Got no error as expected");
+      },
+    }
+  );
+});
+
+add_task(async function test_async_method_chrome_compatible_callback() {
+  function mockAPIRequestHandler(policy, request) {
+    if (request.args[0] === "fake-async-method-failure") {
+      return {
+        type: Ci.mozIExtensionAPIRequestResult.RETURN_VALUE,
+        value: Promise.reject("this-should-not-be-passed-to-cb-as-parameter"),
+      };
+    }
+
+    return {
+      type: Ci.mozIExtensionAPIRequestResult.RETURN_VALUE,
+      value: Promise.resolve(request.args),
+    };
+  }
+
+  await runExtensionAPITest(
+    "async method should support an optional chrome-compatible callback",
+    {
+      mockAPIRequestHandler,
+      async backgroundScript({ testAsserts }) {
+        const api = self.browser.mockExtensionAPI;
+        const success_cb_params = await new Promise(resolve => {
+          const res = api.methodAsync(
+            { prop: "fake-async-method-success" },
+            (...results) => {
+              resolve(results);
+            }
+          );
+          testAsserts.equal(res, undefined, "no promise should be returned");
+        });
+        const error_cb_params = await new Promise(resolve => {
+          const res = api.methodAsync(
+            "fake-async-method-failure",
+            (...results) => {
+              resolve(results);
+            }
+          );
+          testAsserts.equal(res, undefined, "no promise should be returned");
+        });
+        return { success_cb_params, error_cb_params };
+      },
+      assertResults({ testError, testResult }) {
+        Assert.deepEqual(testError, null, "Got no error as expected");
+        Assert.deepEqual(
+          testResult,
+          {
+            success_cb_params: [[{ prop: "fake-async-method-success" }]],
+            error_cb_params: [],
+          },
+          "Got the expected results from the chrome compatible callbacks"
+        );
+      },
+    }
+  );
+
+  await runExtensionAPITest(
+    "async method with ambiguous args called with a chrome-compatible callback",
+    {
+      mockAPIRequestHandler,
+      async backgroundScript({ testAsserts }) {
+        const api = self.browser.mockExtensionAPI;
+        const success_cb_params = await new Promise(resolve => {
+          const res = api.methodAmbiguousArgsAsync(
+            "arg0",
+            { prop: "arg1" },
+            3,
+            (...results) => {
+              resolve(results);
+            }
+          );
+          testAsserts.equal(res, undefined, "no promise should be returned");
+        });
+        const error_cb_params = await new Promise(resolve => {
+          const res = api.methodAmbiguousArgsAsync(
+            "fake-async-method-failure",
+            (...results) => {
+              resolve(results);
+            }
+          );
+          testAsserts.equal(res, undefined, "no promise should be returned");
+        });
+        return { success_cb_params, error_cb_params };
+      },
+      assertResults({ testError, testResult }) {
+        Assert.deepEqual(testError, null, "Got no error as expected");
+        Assert.deepEqual(
+          testResult,
+          {
+            success_cb_params: [["arg0", { prop: "arg1" }, 3]],
+            error_cb_params: [],
+          },
+          "Got the expected results from the chrome compatible callbacks"
+        );
+      },
+    }
+  );
+});
+
+add_task(async function test_get_property() {
+  await runExtensionAPITest(
+    "getProperty API request does return a value synchrously",
+    {
+      backgroundScript() {
+        return self.browser.mockExtensionAPI.propertyAsString;
+      },
+      mockAPIRequestHandler(policy, request) {
+        return {
+          type: Ci.mozIExtensionAPIRequestResult.RETURN_VALUE,
+          value: "property-value",
+        };
+      },
+      assertResults({ testError, testResult }) {
+        Assert.deepEqual(testError, null, "Got no error as expected");
+        Assert.deepEqual(
+          testResult,
+          "property-value",
+          "Got the expected result"
+        );
+      },
+    }
+  );
+
+  await runExtensionAPITest(
+    "getProperty API request can return an error object",
+    {
+      backgroundScript({ testAsserts }) {
+        const errObj = self.browser.mockExtensionAPI.propertyAsErrorObject;
+        testAsserts.isErrorInstance(errObj);
+        testAsserts.equal(errObj.message, "fake extension error");
+      },
+      mockAPIRequestHandler(policy, request) {
+        let savedFrame = request.calledSavedFrame;
+        return {
+          type: Ci.mozIExtensionAPIRequestResult.RETURN_VALUE,
+          value: ChromeUtils.createError("fake extension error", savedFrame),
+        };
+      },
+      assertResults({ testError, testResult }) {
+        Assert.deepEqual(testError, null, "Got no error as expected");
+      },
+    }
+  );
+});
diff --git a/toolkit/components/extensions/test/xpcshell/webidl-api/test_ext_webidl_api_event_callback.js b/toolkit/components/extensions/test/xpcshell/webidl-api/test_ext_webidl_api_event_callback.js
new file mode 100644
index 0000000000..576ec760d3
--- /dev/null
+++ b/toolkit/components/extensions/test/xpcshell/webidl-api/test_ext_webidl_api_event_callback.js
@@ -0,0 +1,575 @@
+/* -*- Mode: indent-tabs-mode: nil; js-indent-level: 2 -*- */
+/* vim: set sts=2 sw=2 et tw=80: */
+"use strict";
+
+/* import-globals-from ../head_service_worker.js */
+
+AddonTestUtils.init(this);
+AddonTestUtils.createAppInfo(
+  "xpcshell@tests.mozilla.org",
+  "XPCShell",
+  "1",
+  "42"
+);
+
+add_task(async function setup() {
+  await AddonTestUtils.promiseStartupManager();
+});
+
+add_task(async function test_api_event_manager_methods() {
+  await runExtensionAPITest("extension event manager methods", {
+    backgroundScript({ testAsserts, testLog }) {
+      const api = browser.mockExtensionAPI;
+      const listener = () => {};
+
+      function assertHasListener(expect) {
+        testAsserts.equal(
+          api.onTestEvent.hasListeners(),
+          expect,
+          `onTestEvent.hasListeners should return {expect}`
+        );
+        testAsserts.equal(
+          api.onTestEvent.hasListener(listener),
+          expect,
+          `onTestEvent.hasListeners should return {expect}`
+        );
+      }
+
+      assertHasListener(false);
+      api.onTestEvent.addListener(listener);
+      assertHasListener(true);
+      api.onTestEvent.removeListener(listener);
+      assertHasListener(false);
+    },
+    mockAPIRequestHandler(policy, request) {
+      if (!request.eventListener) {
+        throw new Error(
+          "Unexpected Error: missing ExtensionAPIRequest.eventListener"
+        );
+      }
+    },
+    assertResults({ testError, testResult }) {
+      Assert.deepEqual(testError, null, "Got no error as expected");
+    },
+  });
+});
+
+add_task(async function test_api_event_eventListener_call() {
+  await runExtensionAPITest(
+    "extension event eventListener wrapper does forward calls parameters",
+    {
+      backgroundScript({ testAsserts, testLog }) {
+        const api = browser.mockExtensionAPI;
+        let listener;
+
+        return new Promise((resolve, reject) => {
+          testLog("addListener and wait for event to be fired");
+          listener = (...args) => {
+            testLog("onTestEvent");
+            // Make sure the extension code can access the arguments.
+            try {
+              testAsserts.equal(args[1], "arg1");
+              resolve(args);
+            } catch (err) {
+              reject(err);
+            }
+          };
+          api.onTestEvent.addListener(listener);
+        });
+      },
+      mockAPIRequestHandler(policy, request) {
+        if (!request.eventListener) {
+          throw new Error(
+            "Unexpected Error: missing ExtensionAPIRequest.eventListener"
+          );
+        }
+        if (request.requestType === "addListener") {
+          let args = [{ arg: 0 }, "arg1"];
+          request.eventListener.callListener(args);
+        }
+      },
+      assertResults({ testError, testResult }) {
+        Assert.deepEqual(testError, null, "Got no error as expected");
+        Assert.deepEqual(
+          testResult,
+          [{ arg: 0 }, "arg1"],
+          "Got the expected result"
+        );
+      },
+    }
+  );
+});
+
+add_task(async function test_api_event_eventListener_call_with_result() {
+  await runExtensionAPITest(
+    "extension event eventListener wrapper forwarded call result",
+    {
+      backgroundScript({ testAsserts, testLog }) {
+        const api = browser.mockExtensionAPI;
+        let listener;
+
+        return new Promise((resolve, reject) => {
+          testLog("addListener and wait for event to be fired");
+          listener = (msg, value) => {
+            testLog(`onTestEvent received: ${msg}`);
+            switch (msg) {
+              case "test-result-value":
+                return value;
+              case "test-promise-resolve":
+                return Promise.resolve(value);
+              case "test-promise-reject":
+                return Promise.reject(new Error("test-reject"));
+              case "test-done":
+                resolve(value);
+                break;
+              default:
+                reject(new Error(`Unexpected onTestEvent message: ${msg}`));
+            }
+          };
+          api.onTestEvent.addListener(listener);
+        });
+      },
+      assertResults({ testError, testResult }) {
+        Assert.deepEqual(testError, null, "Got no error as expected");
+        Assert.deepEqual(
+          testResult?.resSync,
+          { prop: "retval" },
+          "Got result from eventListener returning a plain return value"
+        );
+        Assert.deepEqual(
+          testResult?.resAsync,
+          { prop: "promise" },
+          "Got result from eventListener returning a resolved promise"
+        );
+        Assert.deepEqual(
+          testResult?.resAsyncReject,
+          {
+            isInstanceOfError: true,
+            errorMessage: "test-reject",
+          },
+          "got result from eventListener returning a rejected promise"
+        );
+      },
+      mockAPIRequestHandler(policy, request) {
+        if (!request.eventListener) {
+          throw new Error(
+            "Unexpected Error: missing ExtensionAPIRequest.eventListener"
+          );
+        }
+
+        if (request.requestType === "addListener") {
+          Promise.resolve().then(async () => {
+            try {
+              dump(`calling listener, expect a plain return value\n`);
+              const resSync = await request.eventListener.callListener([
+                "test-result-value",
+                { prop: "retval" },
+              ]);
+
+              dump(
+                `calling listener, expect a resolved promise return value\n`
+              );
+              const resAsync = await request.eventListener.callListener([
+                "test-promise-resolve",
+                { prop: "promise" },
+              ]);
+
+              dump(
+                `calling listener, expect a rejected promise return value\n`
+              );
+              const resAsyncReject = await request.eventListener
+                .callListener(["test-promise-reject"])
+                .catch(err => err);
+
+              // call API listeners once more to complete the test
+              let args = {
+                resSync,
+                resAsync,
+                resAsyncReject: {
+                  isInstanceOfError: resAsyncReject instanceof Error,
+                  errorMessage: resAsyncReject?.message,
+                },
+              };
+              request.eventListener.callListener(["test-done", args]);
+            } catch (err) {
+              dump(`Unexpected error: ${err} :: ${err.stack}\n`);
+              throw err;
+            }
+          });
+        }
+      },
+    }
+  );
+});
+
+add_task(async function test_api_event_eventListener_result_rejected() {
+  await runExtensionAPITest(
+    "extension event eventListener throws (mozIExtensionCallback.call)",
+    {
+      backgroundScript({ testAsserts, testLog }) {
+        const api = browser.mockExtensionAPI;
+        let listener;
+
+        return new Promise((resolve, reject) => {
+          testLog("addListener and wait for event to be fired");
+          listener = (msg, arg1) => {
+            if (msg === "test-done") {
+              testLog(`Resolving result: ${JSON.stringify(arg1)}`);
+              resolve(arg1);
+              return;
+            }
+            throw new Error("FAKE eventListener exception");
+          };
+          api.onTestEvent.addListener(listener);
+        });
+      },
+      assertResults({ testError, testResult }) {
+        Assert.deepEqual(testError, null, "Got no error as expected");
+        Assert.deepEqual(
+          testResult,
+          {
+            isPromise: true,
+            rejectIsError: true,
+            errorMessage: "FAKE eventListener exception",
+          },
+          "Got the expected rejected promise"
+        );
+      },
+      mockAPIRequestHandler(policy, request) {
+        if (!request.eventListener) {
+          throw new Error(
+            "Unexpected Error: missing ExtensionAPIRequest.eventListener"
+          );
+        }
+
+        if (request.requestType === "addListener") {
+          Promise.resolve().then(async () => {
+            const promiseResult = request.eventListener.callListener([]);
+            const isPromise = promiseResult instanceof Promise;
+            const err = await promiseResult.catch(e => e);
+            const rejectIsError = err instanceof Error;
+            request.eventListener.callListener([
+              "test-done",
+              { isPromise, rejectIsError, errorMessage: err?.message },
+            ]);
+          });
+        }
+      },
+    }
+  );
+});
+
+add_task(async function test_api_event_eventListener_throws_on_call() {
+  await runExtensionAPITest(
+    "extension event eventListener throws (mozIExtensionCallback.call)",
+    {
+      backgroundScript({ testAsserts, testLog }) {
+        const api = browser.mockExtensionAPI;
+        let listener;
+
+        return new Promise(resolve => {
+          testLog("addListener and wait for event to be fired");
+          listener = (msg, arg1) => {
+            if (msg === "test-done") {
+              testLog(`Resolving result: ${JSON.stringify(arg1)}`);
+              resolve();
+              return;
+            }
+            throw new Error("FAKE eventListener exception");
+          };
+          api.onTestEvent.addListener(listener);
+        });
+      },
+      assertResults({ testError, testResult }) {
+        Assert.deepEqual(testError, null, "Got no error as expected");
+      },
+      mockAPIRequestHandler(policy, request) {
+        if (!request.eventListener) {
+          throw new Error(
+            "Unexpected Error: missing ExtensionAPIRequest.eventListener"
+          );
+        }
+
+        if (request.requestType === "addListener") {
+          Promise.resolve().then(async () => {
+            request.eventListener.callListener([]);
+            request.eventListener.callListener(["test-done"]);
+          });
+        }
+      },
+    }
+  );
+});
+
+add_task(async function test_send_response_eventListener() {
+  await runExtensionAPITest(
+    "extension event eventListener sendResponse eventListener argument",
+    {
+      backgroundScript({ testAsserts, testLog }) {
+        const api = browser.mockExtensionAPI;
+        let listener;
+
+        return new Promise(resolve => {
+          testLog("addListener and wait for event to be fired");
+          listener = (msg, sendResponse) => {
+            if (msg === "call-sendResponse") {
+              // eslint-disable-next-line mozilla/no-arbitrary-setTimeout
+              setTimeout(() => sendResponse("sendResponse-value"), 20);
+              return true;
+            }
+
+            resolve(msg);
+          };
+          api.onTestEvent.addListener(listener);
+        });
+      },
+      assertResults({ testError, testResult }) {
+        Assert.deepEqual(testError, null, "Got no error as expected");
+        Assert.equal(testResult, "sendResponse-value", "Got expected value");
+      },
+      mockAPIRequestHandler(policy, request) {
+        if (!request.eventListener) {
+          throw new Error(
+            "Unexpected Error: missing ExtensionAPIRequest.eventListener"
+          );
+        }
+
+        if (request.requestType === "addListener") {
+          Promise.resolve().then(async () => {
+            const res = await request.eventListener.callListener(
+              ["call-sendResponse"],
+              {
+                callbackType:
+                  Ci.mozIExtensionListenerCallOptions.CALLBACK_SEND_RESPONSE,
+              }
+            );
+            request.eventListener.callListener([res]);
+          });
+        }
+      },
+    }
+  );
+});
+
+add_task(async function test_send_response_multiple_eventListener() {
+  await runExtensionAPITest("multiple extension event eventListeners", {
+    backgroundScript({ testAsserts, testLog }) {
+      const api = browser.mockExtensionAPI;
+      let listenerNoReply;
+      let listenerSendResponseReply;
+
+      return new Promise(resolve => {
+        testLog("addListener and wait for event to be fired");
+        listenerNoReply = (msg, sendResponse) => {
+          return false;
+        };
+        listenerSendResponseReply = (msg, sendResponse) => {
+          if (msg === "call-sendResponse") {
+            // eslint-disable-next-line mozilla/no-arbitrary-setTimeout
+            setTimeout(() => sendResponse("sendResponse-value"), 20);
+            return true;
+          }
+
+          resolve(msg);
+        };
+        api.onTestEvent.addListener(listenerNoReply);
+        api.onTestEvent.addListener(listenerSendResponseReply);
+      });
+    },
+    assertResults({ testError, testResult }) {
+      Assert.deepEqual(testError, null, "Got no error as expected");
+      Assert.equal(testResult, "sendResponse-value", "Got expected value");
+    },
+    mockAPIRequestHandler(policy, request) {
+      if (!request.eventListener) {
+        throw new Error(
+          "Unexpected Error: missing ExtensionAPIRequest.eventListener"
+        );
+      }
+
+      if (request.requestType === "addListener") {
+        this._listeners = this._listeners || [];
+        this._listeners.push(request.eventListener);
+        if (this._listeners.length === 2) {
+          Promise.resolve().then(async () => {
+            const { _listeners } = this;
+            this._listeners = undefined;
+
+            // Reference to the listener to which we should send the
+            // final message to complete the test.
+            const replyListener = _listeners[1];
+
+            const res = await Promise.race(
+              _listeners.map(l =>
+                l.callListener(["call-sendResponse"], {
+                  callbackType:
+                    Ci.mozIExtensionListenerCallOptions.CALLBACK_SEND_RESPONSE,
+                })
+              )
+            );
+            replyListener.callListener([res]);
+          });
+        }
+      }
+    },
+  });
+});
+
+// Unit test nsIServiceWorkerManager.wakeForExtensionAPIEvent method.
+add_task(async function test_serviceworkermanager_wake_for_api_event_helper() {
+  const extension = ExtensionTestUtils.loadExtension({
+    useAddonManager: "temporary",
+    manifest: {
+      version: "1.0",
+      background: {
+        service_worker: "sw.js",
+      },
+      browser_specific_settings: {
+        gecko: { id: "test-bg-sw-wakeup@mochi.test" },
+      },
+    },
+    files: {
+      "sw.js": `
+        dump("Background ServiceWorker - executing\\n");
+        const lifecycleEvents = [];
+        self.oninstall = () => {
+          dump('Background ServiceWorker - oninstall\\n');
+          lifecycleEvents.push("install");
+        };
+        self.onactivate = () => {
+          dump('Background ServiceWorker - onactivate\\n');
+          lifecycleEvents.push("activate");
+        };
+        browser.test.onMessage.addListener(msg => {
+          if (msg === "bgsw-getSWEvents") {
+            browser.test.sendMessage("bgsw-gotSWEvents", lifecycleEvents);
+            return;
+          }
+
+          browser.test.fail("Got unexpected test message: " + msg);
+        });
+
+        const fakeListener01 = () => {};
+        const fakeListener02 = () => {};
+
+        // Adding and removing the same listener, and so we expect
+        // ExtensionEventWakeupMap to not have any wakeup listener
+        // for the runtime.onInstalled event.
+        browser.runtime.onInstalled.addListener(fakeListener01);
+        browser.runtime.onInstalled.removeListener(fakeListener01);
+        // Removing the same listener more than ones should make any
+        // difference, and it shouldn't trigger any assertion in
+        // debug builds.
+        browser.runtime.onInstalled.removeListener(fakeListener01);
+
+        browser.runtime.onStartup.addListener(fakeListener02);
+        // Removing an unrelated listener, runtime.onStartup is expected to
+        // still have one wakeup listener tracked by ExtensionEventWakeupMap.
+        browser.runtime.onStartup.removeListener(fakeListener01);
+
+        browser.test.sendMessage("bgsw-executed");
+        dump("Background ServiceWorker - executed\\n");
+      `,
+    },
+  });
+
+  const testWorkerWatcher = new TestWorkerWatcher("../data");
+  let watcher = await testWorkerWatcher.watchExtensionServiceWorker(extension);
+
+  await extension.startup();
+
+  info("Wait for the background service worker to be spawned");
+  ok(
+    await watcher.promiseWorkerSpawned,
+    "The extension service worker has been spawned as expected"
+  );
+
+  await extension.awaitMessage("bgsw-executed");
+
+  extension.sendMessage("bgsw-getSWEvents");
+  let lifecycleEvents = await extension.awaitMessage("bgsw-gotSWEvents");
+  Assert.deepEqual(
+    lifecycleEvents,
+    ["install", "activate"],
+    "Got install and activate lifecycle events as expected"
+  );
+
+  info("Wait for the background service worker to be terminated");
+  ok(
+    await watcher.terminate(),
+    "The extension service worker has been terminated as expected"
+  );
+
+  const swReg = testWorkerWatcher.getRegistration(extension);
+  ok(swReg, "Got a service worker registration");
+  ok(swReg?.activeWorker, "Got an active worker");
+
+  watcher = await testWorkerWatcher.watchExtensionServiceWorker(extension);
+
+  const extensionBaseURL = extension.extension.baseURI.spec;
+
+  async function testWakeupOnAPIEvent(eventName, expectedResult) {
+    const result = await testWorkerWatcher.swm.wakeForExtensionAPIEvent(
+      extensionBaseURL,
+      "runtime",
+      eventName
+    );
+    equal(
+      result,
+      expectedResult,
+      `Got expected result from wakeForExtensionAPIEvent for ${eventName}`
+    );
+    info(
+      `Wait for the background service worker to be spawned for ${eventName}`
+    );
+    ok(
+      await watcher.promiseWorkerSpawned,
+      "The extension service worker has been spawned as expected"
+    );
+    await extension.awaitMessage("bgsw-executed");
+  }
+
+  info("Wake up active worker for API event");
+  // Extension API event listener has been added and removed synchronously by
+  // the worker script, and so we expect the promise to resolve successfully
+  // to `false`.
+  await testWakeupOnAPIEvent("onInstalled", false);
+
+  extension.sendMessage("bgsw-getSWEvents");
+  lifecycleEvents = await extension.awaitMessage("bgsw-gotSWEvents");
+  Assert.deepEqual(
+    lifecycleEvents,
+    [],
+    "No install and activate lifecycle events expected on spawning active worker"
+  );
+
+  info("Wait for the background service worker to be terminated");
+  ok(
+    await watcher.terminate(),
+    "The extension service worker has been terminated as expected"
+  );
+
+  info("Wakeup again with an API event that has been subscribed");
+  // Extension API event listener has been added synchronously (and not removed)
+  // by the worker script, and so we expect the promise to resolve successfully
+  // to `true`.
+  await testWakeupOnAPIEvent("onStartup", true);
+
+  info("Wait for the background service worker to be terminated");
+  ok(
+    await watcher.terminate(),
+    "The extension service worker has been terminated as expected"
+  );
+
+  await extension.unload();
+
+  await Assert.rejects(
+    testWorkerWatcher.swm.wakeForExtensionAPIEvent(
+      extensionBaseURL,
+      "runtime",
+      "onStartup"
+    ),
+    /Not an extension principal or extension disabled/,
+    "Got the expected rejection on wakeForExtensionAPIEvent called for an uninstalled extension"
+  );
+});
diff --git a/toolkit/components/extensions/test/xpcshell/webidl-api/test_ext_webidl_api_request_handler.js b/toolkit/components/extensions/test/xpcshell/webidl-api/test_ext_webidl_api_request_handler.js
new file mode 100644
index 0000000000..070a45fa95
--- /dev/null
+++ b/toolkit/components/extensions/test/xpcshell/webidl-api/test_ext_webidl_api_request_handler.js
@@ -0,0 +1,443 @@
+/* -*- Mode: indent-tabs-mode: nil; js-indent-level: 2 -*- */
+/* vim: set sts=2 sw=2 et tw=80: */
+"use strict";
+
+AddonTestUtils.init(this);
+AddonTestUtils.createAppInfo(
+  "xpcshell@tests.mozilla.org",
+  "XPCShell",
+  "1",
+  "42"
+);
+
+add_task(async function setup() {
+  await AddonTestUtils.promiseStartupManager();
+});
+
+// Verify ExtensionAPIRequestHandler handling API requests for
+// an ext-*.js API module running in the local process
+// (toolkit/components/extensions/child/ext-test.js).
+add_task(async function test_sw_api_request_handling_local_process_api() {
+  const extension = ExtensionTestUtils.loadExtension({
+    useAddonManager: "temporary",
+    manifest: {
+      background: {
+        service_worker: "sw.js",
+      },
+      browser_specific_settings: { gecko: { id: "test-bg-sw@mochi.test" } },
+    },
+    files: {
+      "page.html": "<!DOCTYPE html><body></body>",
+      "sw.js": async function () {
+        browser.test.onMessage.addListener(async msg => {
+          browser.test.succeed("call to test.succeed");
+          browser.test.assertTrue(true, "call to test.assertTrue");
+          browser.test.assertFalse(false, "call to test.assertFalse");
+          // Smoke test assertEq (more complete coverage of the behavior expected
+          // by the test API will be introduced in test_ext_test.html as part of
+          // Bug 1723785).
+          const errorObject = new Error("fake_error_message");
+          browser.test.assertEq(
+            errorObject,
+            errorObject,
+            "call to test.assertEq"
+          );
+
+          // Smoke test for assertThrows/assertRejects.
+          const errorMatchingTestCases = [
+            ["expected error instance", errorObject],
+            ["expected error message string", "fake_error_message"],
+            ["expected regexp", /fake_error/],
+            ["matching function", error => errorObject === error],
+            ["matching Constructor", Error],
+          ];
+
+          browser.test.log("run assertThrows smoke tests");
+
+          const throwFn = () => {
+            throw errorObject;
+          };
+          for (const [msg, expected] of errorMatchingTestCases) {
+            browser.test.assertThrows(
+              throwFn,
+              expected,
+              `call to assertThrow with ${msg}`
+            );
+          }
+
+          browser.test.log("run assertRejects smoke tests");
+
+          const rejectedPromise = Promise.reject(errorObject);
+          for (const [msg, expected] of errorMatchingTestCases) {
+            await browser.test.assertRejects(
+              rejectedPromise,
+              expected,
+              `call to assertRejects with ${msg}`
+            );
+          }
+
+          browser.test.notifyPass("test-completed");
+        });
+        browser.test.sendMessage("bgsw-ready");
+      },
+    },
+  });
+
+  await extension.startup();
+  await extension.awaitMessage("bgsw-ready");
+  extension.sendMessage("test-message-ok");
+  await extension.awaitFinish();
+  await extension.unload();
+});
+
+// Verify ExtensionAPIRequestHandler handling API requests for
+// an ext-*.js API module running in the main process
+// (toolkit/components/extensions/parent/ext-alarms.js).
+add_task(async function test_sw_api_request_handling_main_process_api() {
+  const extension = ExtensionTestUtils.loadExtension({
+    useAddonManager: "temporary",
+    manifest: {
+      background: {
+        service_worker: "sw.js",
+      },
+      permissions: ["alarms"],
+      browser_specific_settings: { gecko: { id: "test-bg-sw@mochi.test" } },
+    },
+    files: {
+      "page.html": "<!DOCTYPE html><body></body>",
+      "sw.js": async function () {
+        browser.alarms.create("test-alarm", { when: Date.now() + 2000000 });
+        const all = await browser.alarms.getAll();
+        if (all.length === 1 && all[0].name === "test-alarm") {
+          browser.test.succeed("Got the expected alarms");
+        } else {
+          browser.test.fail(
+            `browser.alarms.create didn't create the expected alarm: ${JSON.stringify(
+              all
+            )}`
+          );
+        }
+
+        browser.alarms.onAlarm.addListener(alarm => {
+          if (alarm.name === "test-onAlarm") {
+            browser.test.succeed("Got the expected onAlarm event");
+          } else {
+            browser.test.fail(`Got unexpected onAlarm event: ${alarm.name}`);
+          }
+          browser.test.sendMessage("test-completed");
+        });
+
+        browser.alarms.create("test-onAlarm", { when: Date.now() + 1000 });
+      },
+    },
+  });
+
+  await extension.startup();
+  await extension.awaitMessage("test-completed");
+  await extension.unload();
+});
+
+add_task(async function test_sw_api_request_bgsw_runtime_onMessage() {
+  const extension = ExtensionTestUtils.loadExtension({
+    useAddonManager: "temporary",
+    manifest: {
+      background: {
+        service_worker: "sw.js",
+      },
+      permissions: [],
+      browser_specific_settings: {
+        gecko: { id: "test-bg-sw-on-message@mochi.test" },
+      },
+    },
+    files: {
+      "page.html": '<!DOCTYPE html><script src="page.js"></script>',
+      "page.js": async function () {
+        browser.test.onMessage.addListener(msg => {
+          if (msg !== "extpage-send-message") {
+            browser.test.fail(`Unexpected message received: ${msg}`);
+            return;
+          }
+          browser.runtime.sendMessage("extpage-send-message");
+        });
+      },
+      "sw.js": async function () {
+        browser.runtime.onMessage.addListener(msg => {
+          browser.test.sendMessage("bgsw-on-message", msg);
+        });
+        const extURL = browser.runtime.getURL("/");
+        browser.test.sendMessage("ext-url", extURL);
+      },
+    },
+  });
+
+  await extension.startup();
+  const extURL = await extension.awaitMessage("ext-url");
+  equal(
+    extURL,
+    `moz-extension://${extension.uuid}/`,
+    "Got the expected extension url"
+  );
+
+  const extPage = await ExtensionTestUtils.loadContentPage(
+    `${extURL}/page.html`,
+    { extension }
+  );
+  extension.sendMessage("extpage-send-message");
+
+  const msg = await extension.awaitMessage("bgsw-on-message");
+  equal(msg, "extpage-send-message", "Got the expected message");
+  await extPage.close();
+  await extension.unload();
+});
+
+add_task(async function test_sw_api_request_bgsw_runtime_sendMessage() {
+  const extension = ExtensionTestUtils.loadExtension({
+    useAddonManager: "temporary",
+    manifest: {
+      background: {
+        service_worker: "sw.js",
+      },
+      permissions: [],
+      browser_specific_settings: {
+        gecko: { id: "test-bg-sw-sendMessage@mochi.test" },
+      },
+    },
+    files: {
+      "page.html": '<!DOCTYPE html><script src="page.js"></script>',
+      "page.js": async function () {
+        browser.runtime.onMessage.addListener(msg => {
+          browser.test.sendMessage("extpage-on-message", msg);
+        });
+
+        browser.test.sendMessage("extpage-ready");
+      },
+      "sw.js": async function () {
+        browser.test.onMessage.addListener(msg => {
+          if (msg !== "bgsw-send-message") {
+            browser.test.fail(`Unexpected message received: ${msg}`);
+            return;
+          }
+          browser.runtime.sendMessage("bgsw-send-message");
+        });
+        const extURL = browser.runtime.getURL("/");
+        browser.test.sendMessage("ext-url", extURL);
+      },
+    },
+  });
+
+  await extension.startup();
+  const extURL = await extension.awaitMessage("ext-url");
+  equal(
+    extURL,
+    `moz-extension://${extension.uuid}/`,
+    "Got the expected extension url"
+  );
+
+  const extPage = await ExtensionTestUtils.loadContentPage(
+    `${extURL}/page.html`,
+    { extension }
+  );
+  await extension.awaitMessage("extpage-ready");
+  extension.sendMessage("bgsw-send-message");
+
+  const msg = await extension.awaitMessage("extpage-on-message");
+  equal(msg, "bgsw-send-message", "Got the expected message");
+  await extPage.close();
+  await extension.unload();
+});
+
+// Verify ExtensionAPIRequestHandler handling API requests that
+// returns a runtinme.Port API object.
+add_task(async function test_sw_api_request_bgsw_connnect_runtime_port() {
+  const extension = ExtensionTestUtils.loadExtension({
+    useAddonManager: "temporary",
+    manifest: {
+      background: {
+        service_worker: "sw.js",
+      },
+      permissions: [],
+      browser_specific_settings: { gecko: { id: "test-bg-sw@mochi.test" } },
+    },
+    files: {
+      "page.html": '<!DOCTYPE html><script src="page.js"></script>',
+      "page.js": async function () {
+        browser.runtime.onConnect.addListener(port => {
+          browser.test.sendMessage("page-got-port-from-sw");
+          port.postMessage("page-to-sw");
+        });
+        browser.test.sendMessage("page-waiting-port");
+      },
+      "sw.js": async function () {
+        browser.test.onMessage.addListener(msg => {
+          if (msg !== "connect-port") {
+            return;
+          }
+          const port = browser.runtime.connect();
+          if (!port) {
+            browser.test.fail("Got an undefined port");
+          }
+          port.onMessage.addListener((msg, portArgument) => {
+            browser.test.assertTrue(
+              port === portArgument,
+              "Got the expected runtime.Port instance"
+            );
+            browser.test.sendMessage("test-done", msg);
+          });
+          browser.test.sendMessage("sw-waiting-port-message");
+        });
+
+        const portWithError = browser.runtime.connect();
+        portWithError.onDisconnect.addListener(() => {
+          const portError = portWithError.error;
+          browser.test.sendMessage("port-error", {
+            isError: portError instanceof Error,
+            message: portError?.message,
+          });
+        });
+
+        const extURL = browser.runtime.getURL("/");
+        browser.test.sendMessage("ext-url", extURL);
+        browser.test.sendMessage("ext-id", browser.runtime.id);
+      },
+    },
+  });
+
+  await extension.startup();
+  const extURL = await extension.awaitMessage("ext-url");
+  equal(
+    extURL,
+    `moz-extension://${extension.uuid}/`,
+    "Got the expected extension url"
+  );
+
+  const extId = await extension.awaitMessage("ext-id");
+  equal(extId, extension.id, "Got the expected extension id");
+
+  const lastError = await extension.awaitMessage("port-error");
+  Assert.deepEqual(
+    lastError,
+    {
+      isError: true,
+      message: "Could not establish connection. Receiving end does not exist.",
+    },
+    "Got the expected lastError value"
+  );
+
+  const extPage = await ExtensionTestUtils.loadContentPage(
+    `${extURL}/page.html`,
+    { extension }
+  );
+  await extension.awaitMessage("page-waiting-port");
+
+  info("bgsw connect port");
+  extension.sendMessage("connect-port");
+  await extension.awaitMessage("sw-waiting-port-message");
+  info("bgsw waiting port message");
+  await extension.awaitMessage("page-got-port-from-sw");
+  info("page got port from sw, wait to receive event");
+  const msg = await extension.awaitMessage("test-done");
+  equal(msg, "page-to-sw", "Got the expected message");
+  await extPage.close();
+  await extension.unload();
+});
+
+// Verify ExtensionAPIRequestHandler handling API events that should
+// get a runtinme.Port API object as an event argument.
+add_task(async function test_sw_api_request_bgsw_runtime_onConnect() {
+  const extension = ExtensionTestUtils.loadExtension({
+    useAddonManager: "temporary",
+    manifest: {
+      background: {
+        service_worker: "sw.js",
+      },
+      permissions: [],
+      browser_specific_settings: {
+        gecko: { id: "test-bg-sw-onConnect@mochi.test" },
+      },
+    },
+    files: {
+      "page.html": '<!DOCTYPE html><script src="page.js"></script>',
+      "page.js": async function () {
+        browser.test.onMessage.addListener(msg => {
+          if (msg !== "connect-port") {
+            return;
+          }
+          const port = browser.runtime.connect();
+          port.onMessage.addListener(msg => {
+            browser.test.sendMessage("test-done", msg);
+          });
+          browser.test.sendMessage("page-waiting-port-message");
+        });
+      },
+      "sw.js": async function () {
+        try {
+          const extURL = browser.runtime.getURL("/");
+          browser.test.sendMessage("ext-url", extURL);
+
+          browser.runtime.onConnect.addListener(port => {
+            browser.test.sendMessage("bgsw-got-port-from-page");
+            port.postMessage("sw-to-page");
+          });
+          browser.test.sendMessage("bgsw-waiting-port");
+        } catch (err) {
+          browser.test.fail(`Error on runtime.onConnect: ${err}`);
+        }
+      },
+    },
+  });
+
+  await extension.startup();
+  const extURL = await extension.awaitMessage("ext-url");
+  equal(
+    extURL,
+    `moz-extension://${extension.uuid}/`,
+    "Got the expected extension url"
+  );
+  await extension.awaitMessage("bgsw-waiting-port");
+
+  const extPage = await ExtensionTestUtils.loadContentPage(
+    `${extURL}/page.html`,
+    { extension }
+  );
+  info("ext page connect port");
+  extension.sendMessage("connect-port");
+
+  await extension.awaitMessage("page-waiting-port-message");
+  info("page waiting port message");
+  await extension.awaitMessage("bgsw-got-port-from-page");
+  info("bgsw got port from page, page wait to receive event");
+  const msg = await extension.awaitMessage("test-done");
+  equal(msg, "sw-to-page", "Got the expected message");
+  await extPage.close();
+  await extension.unload();
+});
+
+add_task(async function test_sw_runtime_lastError() {
+  const extension = ExtensionTestUtils.loadExtension({
+    useAddonManager: "temporary",
+    manifest: {
+      background: {
+        service_worker: "sw.js",
+      },
+      browser_specific_settings: { gecko: { id: "test-bg-sw@mochi.test" } },
+    },
+    files: {
+      "page.html": "<!DOCTYPE html><body></body>",
+      "sw.js": async function () {
+        browser.runtime.sendMessage(() => {
+          const lastError = browser.runtime.lastError;
+          if (!(lastError instanceof Error)) {
+            browser.test.fail(
+              `lastError isn't an Error instance: ${lastError}`
+            );
+          }
+          browser.test.sendMessage("test-lastError-completed");
+        });
+      },
+    },
+  });
+
+  await extension.startup();
+  await extension.awaitMessage("test-lastError-completed");
+  await extension.unload();
+});
diff --git a/toolkit/components/extensions/test/xpcshell/webidl-api/test_ext_webidl_api_schema_errors.js b/toolkit/components/extensions/test/xpcshell/webidl-api/test_ext_webidl_api_schema_errors.js
new file mode 100644
index 0000000000..d8684c1574
--- /dev/null
+++ b/toolkit/components/extensions/test/xpcshell/webidl-api/test_ext_webidl_api_schema_errors.js
@@ -0,0 +1,202 @@
+/* -*- Mode: indent-tabs-mode: nil; js-indent-level: 2 -*- */
+/* vim: set sts=2 sw=2 et tw=80: */
+"use strict";
+
+const { ExtensionAPI } = ExtensionCommon;
+
+AddonTestUtils.init(this);
+AddonTestUtils.createAppInfo(
+  "xpcshell@tests.mozilla.org",
+  "XPCShell",
+  "1",
+  "42"
+);
+
+// Because the `mockExtensionAPI` is currently the only "mock" API that has
+// WebIDL bindings, this is the only namespace we can use in our tests. There
+// is no JSON schema for this namespace so we add one here that is tailored for
+// our testing needs.
+const API = class extends ExtensionAPI {
+  getAPI(context) {
+    return {
+      mockExtensionAPI: {
+        methodAsync: () => {
+          return "some-value";
+        },
+      },
+    };
+  }
+};
+
+const SCHEMA = [
+  {
+    namespace: "mockExtensionAPI",
+    functions: [
+      {
+        name: "methodAsync",
+        type: "function",
+        async: true,
+        parameters: [
+          {
+            name: "arg",
+            type: "string",
+            enum: ["THE_ONLY_VALUE_ALLOWED"],
+          },
+        ],
+      },
+    ],
+  },
+];
+
+add_setup(async function () {
+  await AddonTestUtils.promiseStartupManager();
+
+  // The blob:-URL registered in `registerModules()` below gets loaded at:
+  // https://searchfox.org/mozilla-central/rev/0fec57c05d3996cc00c55a66f20dd5793a9bfb5d/toolkit/components/extensions/ExtensionCommon.jsm#1649
+  Services.prefs.setBoolPref(
+    "security.allow_parent_unrestricted_js_loads",
+    true
+  );
+
+  ExtensionParent.apiManager.registerModules({
+    mockExtensionAPI: {
+      schema: `data:,${JSON.stringify(SCHEMA)}`,
+      scopes: ["addon_parent"],
+      paths: [["mockExtensionAPI"]],
+      url: URL.createObjectURL(
+        new Blob([`this.mockExtensionAPI = ${API.toString()}`])
+      ),
+    },
+  });
+});
+
+add_task(async function test_schema_error_is_propagated_to_extension() {
+  await runExtensionAPITest("should throw an extension error", {
+    backgroundScript() {
+      return browser.mockExtensionAPI.methodAsync("UNEXPECTED_VALUE");
+    },
+    mockAPIRequestHandler(policy, request) {
+      return this._handleAPIRequest_orig(policy, request);
+    },
+    assertResults({ testError }) {
+      Assert.ok(
+        /Invalid enumeration value "UNEXPECTED_VALUE"/.test(testError.message)
+      );
+    },
+  });
+});
+
+add_task(async function test_schema_error_no_error_with_expected_value() {
+  await runExtensionAPITest("should not throw any error", {
+    backgroundScript() {
+      return browser.mockExtensionAPI.methodAsync("THE_ONLY_VALUE_ALLOWED");
+    },
+    mockAPIRequestHandler(policy, request) {
+      return this._handleAPIRequest_orig(policy, request);
+    },
+    assertResults({ testError, testResult }) {
+      Assert.deepEqual(testError, undefined);
+      Assert.deepEqual(testResult, "some-value");
+    },
+  });
+});
+
+add_task(async function test_schema_data_not_found_or_unexpected_schema_type() {
+  const { Schemas } = ChromeUtils.importESModule(
+    "resource://gre/modules/Schemas.sys.mjs"
+  );
+
+  const mockSchemaExtContext = {};
+
+  const testSchemasErrorOnWebIDLRequest = testCase => {
+    if (testCase.expectedExceptions) {
+      const expectedExceptions = Array.isArray(testCase.expectedExceptions)
+        ? testCase.expectedExceptions
+        : [testCase.expectedExceptions];
+      expectedExceptions.forEach(expectedException =>
+        Assert.throws(
+          () =>
+            Schemas.checkWebIDLRequestParameters(
+              testCase.mockSchemaExtContext,
+              testCase.mockWebIDLAPIRequest
+            ),
+          expectedException,
+          `Got the expected error on ${testCase.description}`
+        )
+      );
+    } else {
+      throw new Error(
+        `Test case ${testCase.description} is missing mandatory expectedExceptions test case property`
+      );
+    }
+  };
+
+  const TEST_CASES = [
+    {
+      description:
+        "callFunction API request for non existing nested API namespace",
+      mockSchemaExtContext,
+      mockWebIDLAPIRequest: {
+        apiNamespace: "browserSettings.unknownNamespace",
+        apiName: "get",
+        requestType: "callFunction",
+      },
+      expectedExceptions:
+        /API Schema not found for browserSettings\.unknownNamespace/,
+    },
+    {
+      description:
+        "addListener API request for non existing API event property",
+      mockSchemaExtContext,
+      mockWebIDLAPIRequest: {
+        apiNamespace: "browserSettings.nonExistingSetting",
+        apiName: "onChange",
+        requestType: "addListener",
+      },
+      expectedExceptions:
+        /API Schema not found for browserSettings\.nonExistingSetting/,
+    },
+    {
+      description:
+        "callFunction on non existing method from existing nested API namespace",
+      mockSchemaExtContext,
+      mockWebIDLAPIRequest: {
+        apiNamespace: "browserSettings.colorManagement.mode",
+        apiName: "nonExistingMethod",
+        requestType: "callFunction",
+      },
+      expectedExceptions: [
+        /API Schema for "nonExistingMethod" not found in browserSettings\.colorManagement\.mode/,
+        /\(browserSettings\.colorManagement\.mode type is SubModuleProperty\)/,
+      ],
+    },
+    {
+      description:
+        "callFunction on non existing method from existing API namespace",
+      mockSchemaExtContext,
+      mockWebIDLAPIRequest: {
+        apiNamespace: "browserSettings",
+        apiName: "nonExistingMethod",
+        requestType: "callFunction",
+      },
+      expectedExceptions:
+        /API Schema not found for browserSettings\.nonExistingMethod/,
+    },
+    {
+      description:
+        "callFunction on existing property but unexpected schema type",
+      mockSchemaExtContext,
+      mockWebIDLAPIRequest: {
+        apiNamespace: "tabs",
+        apiName: "TAB_ID_NONE",
+        requestType: "callFunction",
+      },
+      expectedExceptions: [
+        /Unexpected API Schema type for tabs.TAB_ID_NONE/,
+        /tabs.TAB_ID_NONE type is ValueProperty/,
+      ],
+    },
+  ];
+
+  TEST_CASES.forEach(testSchemasErrorOnWebIDLRequest);
+});
diff --git a/toolkit/components/extensions/test/xpcshell/webidl-api/test_ext_webidl_api_schema_formatters.js b/toolkit/components/extensions/test/xpcshell/webidl-api/test_ext_webidl_api_schema_formatters.js
new file mode 100644
index 0000000000..a7310f345e
--- /dev/null
+++ b/toolkit/components/extensions/test/xpcshell/webidl-api/test_ext_webidl_api_schema_formatters.js
@@ -0,0 +1,99 @@
+/* -*- Mode: indent-tabs-mode: nil; js-indent-level: 2 -*- */
+/* vim: set sts=2 sw=2 et tw=80: */
+"use strict";
+
+const { ExtensionAPI } = ExtensionCommon;
+
+AddonTestUtils.init(this);
+AddonTestUtils.createAppInfo(
+  "xpcshell@tests.mozilla.org",
+  "XPCShell",
+  "1",
+  "42"
+);
+
+// Because the `mockExtensionAPI` is currently the only "mock" API that has
+// WebIDL bindings, this is the only namespace we can use in our tests. There
+// is no JSON schema for this namespace so we add one here that is tailored for
+// our testing needs.
+const API = class extends ExtensionAPI {
+  getAPI(context) {
+    return {
+      mockExtensionAPI: {
+        methodAsync: files => {
+          return files;
+        },
+      },
+    };
+  }
+};
+
+const SCHEMA = [
+  {
+    namespace: "mockExtensionAPI",
+    functions: [
+      {
+        name: "methodAsync",
+        type: "function",
+        async: true,
+        parameters: [
+          {
+            name: "files",
+            type: "array",
+            items: { $ref: "manifest.ExtensionURL" },
+          },
+        ],
+      },
+    ],
+  },
+];
+
+add_setup(async function () {
+  await AddonTestUtils.promiseStartupManager();
+
+  // The blob:-URL registered in `registerModules()` below gets loaded at:
+  // https://searchfox.org/mozilla-central/rev/0fec57c05d3996cc00c55a66f20dd5793a9bfb5d/toolkit/components/extensions/ExtensionCommon.jsm#1649
+  Services.prefs.setBoolPref(
+    "security.allow_parent_unrestricted_js_loads",
+    true
+  );
+
+  ExtensionParent.apiManager.registerModules({
+    mockExtensionAPI: {
+      schema: `data:,${JSON.stringify(SCHEMA)}`,
+      scopes: ["addon_parent"],
+      paths: [["mockExtensionAPI"]],
+      url: URL.createObjectURL(
+        new Blob([`this.mockExtensionAPI = ${API.toString()}`])
+      ),
+    },
+  });
+});
+
+add_task(async function test_relative_urls() {
+  await runExtensionAPITest(
+    "should format arguments with the relativeUrl formatter",
+    {
+      backgroundScript() {
+        return browser.mockExtensionAPI.methodAsync([
+          "script-1.js",
+          "script-2.js",
+        ]);
+      },
+      mockAPIRequestHandler(policy, request) {
+        return this._handleAPIRequest_orig(policy, request);
+      },
+      assertResults({ testResult, testError, extension }) {
+        Assert.deepEqual(
+          testResult,
+          [
+            `moz-extension://${extension.uuid}/script-1.js`,
+            `moz-extension://${extension.uuid}/script-2.js`,
+          ],
+          "expected correct url"
+        );
+        Assert.deepEqual(testError, undefined, "expected no error");
+      },
+    }
+  );
+});
diff --git a/toolkit/components/extensions/test/xpcshell/webidl-api/test_ext_webidl_runtime_port.js b/toolkit/components/extensions/test/xpcshell/webidl-api/test_ext_webidl_runtime_port.js
new file mode 100644
index 0000000000..0d88014f32
--- /dev/null
+++ b/toolkit/components/extensions/test/xpcshell/webidl-api/test_ext_webidl_runtime_port.js
@@ -0,0 +1,220 @@
+/* -*- Mode: indent-tabs-mode: nil; js-indent-level: 2 -*- */
+/* vim: set sts=2 sw=2 et tw=80: */
+"use strict";
+
+AddonTestUtils.init(this);
+AddonTestUtils.createAppInfo(
+  "xpcshell@tests.mozilla.org",
+  "XPCShell",
+  "1",
+  "42"
+);
+
+add_task(async function setup() {
+  await AddonTestUtils.promiseStartupManager();
+});
+
+add_task(async function test_method_return_runtime_port() {
+  await runExtensionAPITest("API method returns an ExtensionPort instance", {
+    backgroundScript({ testAsserts, testLog }) {
+      try {
+        browser.mockExtensionAPI.methodReturnsPort("port-create-error");
+        throw new Error("methodReturnsPort should have raised an exception");
+      } catch (err) {
+        testAsserts.equal(
+          err?.message,
+          "An unexpected error occurred",
+          "Got the expected error"
+        );
+      }
+      const port = browser.mockExtensionAPI.methodReturnsPort(
+        "port-create-success"
+      );
+      testAsserts.equal(!!port, true, "Got a port");
+      testAsserts.equal(
+        typeof port.name,
+        "string",
+        "port.name should be a string"
+      );
+      testAsserts.equal(
+        typeof port.sender,
+        "object",
+        "port.sender should be an object"
+      );
+      testAsserts.equal(
+        typeof port.disconnect,
+        "function",
+        "port.disconnect method"
+      );
+      testAsserts.equal(
+        typeof port.postMessage,
+        "function",
+        "port.postMessage method"
+      );
+      testAsserts.equal(
+        typeof port.onDisconnect?.addListener,
+        "function",
+        "port.onDisconnect.addListener method"
+      );
+      testAsserts.equal(
+        typeof port.onMessage?.addListener,
+        "function",
+        "port.onDisconnect.addListener method"
+      );
+      return new Promise(resolve => {
+        let messages = [];
+        port.onDisconnect.addListener(() => resolve(messages));
+        port.onMessage.addListener((...args) => {
+          messages.push(args);
+        });
+      });
+    },
+    assertResults({ testError, testResult }) {
+      Assert.deepEqual(testError, null, "Got no error as expected");
+      Assert.deepEqual(
+        testResult,
+        [
+          [1, 2],
+          [3, 4],
+          [5, 6],
+        ],
+        "Got the expected results"
+      );
+    },
+    mockAPIRequestHandler(policy, request) {
+      if (request.apiName == "methodReturnsPort") {
+        if (request.args[0] == "port-create-error") {
+          return {
+            type: Ci.mozIExtensionAPIRequestResult.RETURN_VALUE,
+            value: "not-a-valid-port",
+          };
+        }
+        return {
+          type: Ci.mozIExtensionAPIRequestResult.RETURN_VALUE,
+          value: {
+            portId: "port-id-1",
+            name: "a-port-name",
+          },
+        };
+      } else if (request.requestType == "addListener") {
+        if (request.apiObjectType !== "Port") {
+          throw new Error(`Unexpected objectType ${request}`);
+        }
+
+        switch (request.apiName) {
+          case "onDisconnect":
+            this._onDisconnectCb = request.eventListener;
+            return;
+          case "onMessage":
+            Promise.resolve().then(async () => {
+              await request.eventListener.callListener([1, 2]);
+              await request.eventListener.callListener([3, 4]);
+              await request.eventListener.callListener([5, 6]);
+              this._onDisconnectCb.callListener([]);
+            });
+            return;
+        }
+      } else if (
+        request.requestType == "getProperty" &&
+        request.apiObjectType == "Port" &&
+        request.apiName == "sender"
+      ) {
+        return {
+          type: Ci.mozIExtensionAPIRequestResult.RETURN_VALUE,
+          value: { id: "fake-sender-id-prop" },
+        };
+      }
+
+      throw new Error(`Unexpected request: ${request}`);
+    },
+  });
+});
+
+add_task(async function test_port_as_event_listener_eventListener_param() {
+  await runExtensionAPITest(
+    "API event eventListener received an ExtensionPort parameter",
+    {
+      backgroundScript({ testAsserts, testLog }) {
+        const api = browser.mockExtensionAPI;
+        let listener;
+
+        return new Promise((resolve, reject) => {
+          testLog("addListener and wait for event to be fired");
+          listener = port => {
+            try {
+              testAsserts.equal(!!port, true, "Got a port parameter");
+              testAsserts.equal(
+                port.name,
+                "a-port-name-2",
+                "Got expected port.name value"
+              );
+              testAsserts.equal(
+                typeof port.disconnect,
+                "function",
+                "port.disconnect method"
+              );
+              testAsserts.equal(
+                typeof port.postMessage,
+                "function",
+                "port.disconnect method"
+              );
+              port.onMessage.addListener((msg, portArg) => {
+                if (msg === "test-done") {
+                  testLog("Got a port.onMessage event");
+                  testAsserts.equal(
+                    portArg?.name,
+                    "a-port-name-2",
+                    "Got port as last argument"
+                  );
+                  testAsserts.equal(
+                    portArg === port,
+                    true,
+                    "Got the same port instance as expected"
+                  );
+                  resolve();
+                } else {
+                  reject(
+                    new Error(
+                      `port.onMessage got an unexpected message: ${msg}`
+                    )
+                  );
+                }
+              });
+            } catch (err) {
+              reject(err);
+            }
+          };
+          api.onTestEvent.addListener(listener);
+        });
+      },
+      assertResults({ testError }) {
+        Assert.deepEqual(testError, null, "Got no error as expected");
+      },
+      mockAPIRequestHandler(policy, request) {
+        if (
+          request.requestType == "addListener" &&
+          request.apiName == "onTestEvent"
+        ) {
+          request.eventListener.callListener(["arg0", "arg1"], {
+            apiObjectType: Ci.mozIExtensionListenerCallOptions.RUNTIME_PORT,
+            apiObjectDescriptor: { portId: "port-id-2", name: "a-port-name-2" },
+            apiObjectPrepended: true,
+          });
+          return;
+        } else if (
+          request.requestType == "addListener" &&
+          request.apiObjectType == "Port" &&
+          request.apiObjectId == "port-id-2"
+        ) {
+          request.eventListener.callListener(["test-done"], {
+            apiObjectType: Ci.mozIExtensionListenerCallOptions.RUNTIME_PORT,
+            apiObjectDescriptor: { portId: "port-id-2", name: "a-port-name-2" },
+          });
+          return;
+        }
+
+        throw new Error(`Unexpected request: ${request}`);
+      },
+    }
+  );
+});
diff --git a/toolkit/components/extensions/test/xpcshell/webidl-api/xpcshell.ini b/toolkit/components/extensions/test/xpcshell/webidl-api/xpcshell.ini
new file mode 100644
index 0000000000..465f913917
--- /dev/null
+++ b/toolkit/components/extensions/test/xpcshell/webidl-api/xpcshell.ini
@@ -0,0 +1,32 @@
+[DEFAULT]
+head = ../head.js ../head_remote.js ../head_service_worker.js head_webidl_api.js
+firefox-appdir = browser
+tags = webextensions webextensions-webidl-api
+
+prefs =
+  # Enable support for the extension background service worker.
+  extensions.backgroundServiceWorker.enabled=true
+  # Enable Extensions API WebIDL bindings for extension windows.
+  extensions.webidl-api.enabled=true
+  # Enable ExtensionMockAPI WebIDL bindings used for unit tests
+  # related to the API request forwarding and not tied to a particular
+  # extension API.
+  extensions.webidl-api.expose_mock_interface=true
+  # Make sure that loading the default settings for url-classifier-skip-urls
+  # doesn't interfere with running our tests while IDB operations are in
+  # flight by overriding the remote settings server URL to
+  # ensure that the IDB database isn't created in the first place.
+  services.settings.server=data:,#remote-settings-dummy/v1
+
+# NOTE: these tests seems to be timing out because it takes too much time to
+# run all tests and then fully exiting the test.
+skip-if = os == "android" && verify
+
+[test_ext_webidl_api.js]
+[test_ext_webidl_api_event_callback.js]
+skip-if =
+  os == "android" && processor == "x86_64" && debug # Bug 1716308
+[test_ext_webidl_api_request_handler.js]
+[test_ext_webidl_api_schema_errors.js]
+[test_ext_webidl_api_schema_formatters.js]
+[test_ext_webidl_runtime_port.js]
diff --git a/toolkit/components/extensions/test/xpcshell/xpcshell-common-e10s.ini b/toolkit/components/extensions/test/xpcshell/xpcshell-common-e10s.ini
new file mode 100644
index 0000000000..635c89dbbc
--- /dev/null
+++ b/toolkit/components/extensions/test/xpcshell/xpcshell-common-e10s.ini
@@ -0,0 +1,21 @@
+# Similar to xpcshell-common.ini, except tests here only run
+# when e10s is enabled (with or without out-of-process extensions).
+
+[test_ext_webRequest_eventPage_StreamFilter.js]
+[test_ext_webRequest_filterResponseData.js]
+# tsan failure is for test_filter_301 timing out, bug 1674773
+skip-if =
+  tsan || os == "android" && debug
+  apple_silicon # Disabled due to bleedover with other tests when run in regular suites; passes in "failures" jobs
+  fission # Bug 1762638
+[test_ext_webRequest_redirect_StreamFilter.js]
+[test_ext_webRequest_responseBody.js]
+skip-if = os == "android" && debug
+[test_ext_webRequest_startup_StreamFilter.js]
+skip-if = os == "android" && debug
+[test_ext_webRequest_viewsource_StreamFilter.js]
+skip-if =
+  tsan # Bug 1683730
+  apple_silicon # Disabled due to bleedover with other tests when run in regular suites; passes in "failures" jobs
+  fission # Bug 1762638
+
diff --git a/toolkit/components/extensions/test/xpcshell/xpcshell-common.ini b/toolkit/components/extensions/test/xpcshell/xpcshell-common.ini
new file mode 100644
index 0000000000..f76456124d
--- /dev/null
+++ b/toolkit/components/extensions/test/xpcshell/xpcshell-common.ini
@@ -0,0 +1,436 @@
+[DEFAULT]
+# Some tests of downloads.download() expect a file picker, which is only shown
+# by default when the browser.download.useDownloadDir pref is set to true. This
+# is the case on desktop Firefox, but not on Thunderbird.
+# Force pref value to true to get download tests to pass on Thunderbird.
+prefs = browser.download.useDownloadDir=true
+
+[test_change_remote_mode.js]
+[test_ext_MessageManagerProxy.js]
+skip-if = os == "android" # Bug 1545439
+[test_ext_activityLog.js]
+[test_ext_alarms.js]
+[test_ext_alarms_does_not_fire.js]
+[test_ext_alarms_periodic.js]
+[test_ext_alarms_replaces.js]
+[test_ext_api_permissions.js]
+[test_ext_api_events_listener_calls_exceptions.js]
+[test_ext_asyncAPICall_isHandlingUserInput.js]
+[test_ext_background_api_injection.js]
+skip-if = os == "android" # Bug 1700482
+[test_ext_background_early_shutdown.js]
+[test_ext_background_generated_load_events.js]
+[test_ext_background_generated_reload.js]
+[test_ext_background_global_history.js]
+skip-if = os == "android" # Android does not use Places for history.
+[test_ext_background_private_browsing.js]
+[test_ext_background_runtime_connect_params.js]
+[test_ext_background_sub_windows.js]
+[test_ext_background_teardown.js]
+[test_ext_background_telemetry.js]
+[test_ext_background_type_module.js]
+[test_ext_background_window_properties.js]
+skip-if = os == "android"
+[test_ext_browserSettings.js]
+[test_ext_browserSettings_homepage.js]
+skip-if =
+  appname == "thunderbird"
+  os == "android"
+[test_ext_browsingData.js]
+[test_ext_browsingData_cookies_cache.js]
+skip-if =
+  os == "win" && os_version == "6.1" # Skip on Azure - frequent failure
+[test_ext_browsingData_cookies_cookieStoreId.js]
+[test_ext_browser_style_deprecation.js]
+skip-if = appname == "thunderbird"
+[test_ext_cache_api.js]
+[test_ext_captivePortal.js]
+# As with test_captive_portal_service.js, we use the same limits here.
+skip-if =
+  appname == "thunderbird"
+  os == "android" # CP service is disabled on Android
+  os == "mac" && debug # macosx1014/debug due to 1564534
+run-sequentially = node server exceptions dont replay well
+[test_ext_captivePortal_url.js]
+# As with test_captive_portal_service.js, we use the same limits here.
+skip-if =
+  appname == "thunderbird"
+  os == "android" # CP service is disabled on Android,
+  os == "mac" && debug # macosx1014/debug due to 1564534
+run-sequentially = node server exceptions dont replay well
+[test_ext_cookieBehaviors.js]
+skip-if =
+  appname == "thunderbird"
+  os == "android" # Bug 1683730, Android: Bug 1700482
+  apple_silicon # Disabled due to bleedover with other tests when run in regular suites; passes in "failures" jobs
+  tsan
+  fission # Bug 1762638
+[test_ext_cookies_errors.js]
+[test_ext_cookies_firstParty.js]
+skip-if =
+  appname == "thunderbird"
+  os == "android"  # Android: Bug 1680132.
+  tsan
+[test_ext_cookies_onChanged.js]
+[test_ext_cookies_partitionKey.js]
+[test_ext_cookies_samesite.js]
+skip-if = os == "android" # Android: Bug 1680132
+[test_ext_content_security_policy.js]
+skip-if =
+  os == "win" # Bug 1762638
+[test_ext_contentscript_api_injection.js]
+[test_ext_contentscript_async_loading.js]
+skip-if =
+  os == "android" && debug # The generated script takes too long to load on Android debug
+  fission # Bug 1762638
+[test_ext_contentscript_context.js]
+skip-if =
+  tsan # Bug 1683730
+  apple_silicon # Disabled due to bleedover with other tests when run in regular suites; passes in "failures" jobs
+  sessionHistoryInParent # Bug 1762638
+[test_ext_contentscript_context_isolation.js]
+skip-if =
+  tsan # Bug 1683730
+  apple_silicon # Disabled due to bleedover with other tests when run in regular suites; passes in "failures" jobs
+  sessionHistoryInParent # Bug 1762638
+[test_ext_contentscript_create_iframe.js]
+[test_ext_contentscript_csp.js]
+run-sequentially = very high failure rate in parallel
+skip-if =
+  os == "win" && os_version == "6.1" # Skip on Azure - frequent failure
+[test_ext_contentscript_css.js]
+skip-if =
+  os == "linux" && fission # Bug 1762638
+  os == "mac" && debug # Bug 1762638
+[test_ext_contentscript_dynamic_registration.js]
+[test_ext_contentscript_exporthelpers.js]
+[test_ext_contentscript_importmap.js]
+[test_ext_contentscript_in_background.js]
+skip-if = os == "android" # Bug 1700482
+[test_ext_contentscript_json_api.js]
+[test_ext_contentscript_module_import.js]
+[test_ext_contentscript_restrictSchemes.js]
+[test_ext_contentscript_teardown.js]
+skip-if =
+  tsan # Bug 1683730
+[test_ext_contentscript_unregister_during_loadContentScript.js]
+[test_ext_contentscript_xml_prettyprint.js]
+[test_ext_contextual_identities.js]
+skip-if =
+  appname == "thunderbird"
+  os == "android" # Containers are not exposed to android.
+[test_ext_cors_mozextension.js]
+[test_ext_csp_frame_ancestors.js]
+[test_ext_csp_upgrade_requests.js]
+[test_ext_debugging_utils.js]
+[test_ext_dnr_allowAllRequests.js]
+[test_ext_dnr_api.js]
+[test_ext_dnr_download.js]
+skip-if = os == "android" # Android: Bug 1680132; downloads.download goes through the embedder app instead of Gecko.
+[test_ext_dnr_dynamic_rules.js]
+[test_ext_dnr_modifyHeaders.js]
+[test_ext_dnr_private_browsing.js]
+[test_ext_dnr_redirect_transform.js]
+[test_ext_dnr_regexFilter.js]
+[test_ext_dnr_regexFilter_limits.js]
+[test_ext_dnr_session_rules.js]
+[test_ext_dnr_startup_cache.js]
+[test_ext_dnr_static_rules.js]
+[test_ext_dnr_system_restrictions.js]
+[test_ext_dnr_testMatchOutcome.js]
+[test_ext_dnr_tabIds.js]
+[test_ext_dnr_urlFilter.js]
+[test_ext_dnr_webrequest.js]
+[test_ext_dnr_without_webrequest.js]
+[test_ext_dns.js]
+skip-if = os == "android" # Android needs alternative for proxy.settings - bug 1723523
+[test_ext_downloads.js]
+[test_ext_downloads_cookies.js]
+skip-if =
+  os == "android" # downloads API needs to be implemented in GeckoView - bug 1538348
+  win10_2004 # Bug 1718292
+  win11_2009 # Bug 1797751
+  os == "win" && os_version == "6.1" # Skip on Azure - frequent failure
+[test_ext_downloads_cookieStoreId.js]
+skip-if =
+  os == "android"
+  win10_2004 # Bug 1718292
+[test_ext_downloads_download.js]
+skip-if =
+  tsan # Bug 1683730
+  appname == "thunderbird"
+  os == "android"
+  os == "win" && os_version == "6.1" # Skip on Azure - frequent failure
+[test_ext_downloads_eventpage.js]
+skip-if = os == "android"
+[test_ext_downloads_misc.js]
+skip-if =
+  os == "android"
+  tsan # Bug 1683730
+  os == "win" && os_version == "6.1" # Skip on Azure - frequent failure
+[test_ext_downloads_partitionKey.js]
+skip-if = os == "android"
+[test_ext_downloads_private.js]
+skip-if = os == "android"
+[test_ext_downloads_search.js]
+skip-if = os == "android" || tsan # tsan: bug 1612707
+[test_ext_downloads_urlencoded.js]
+skip-if = os == "android"
+[test_ext_error_location.js]
+[test_ext_eventpage_idle.js]
+[test_ext_eventpage_warning.js]
+[test_ext_eventpage_settings.js]
+[test_ext_experiments.js]
+[test_ext_extension.js]
+[test_ext_extension_page_navigated.js]
+[test_ext_extensionPreferencesManager.js]
+[test_ext_extensionSettingsStore.js]
+[test_ext_extension_content_telemetry.js]
+skip-if = os == "android" # checking for telemetry needs to be updated: 1384923
+[test_ext_extension_startup_failure.js]
+[test_ext_extension_startup_telemetry.js]
+[test_ext_file_access.js]
+[test_ext_geckoProfiler_control.js]
+skip-if = os == "android" || tsan # Not shipped on Android. tsan: bug 1612707
+[test_ext_geturl.js]
+[test_ext_idle.js]
+[test_ext_incognito.js]
+skip-if = appname == "thunderbird"
+[test_ext_l10n.js]
+[test_ext_localStorage.js]
+[test_ext_management.js]
+skip-if =
+  os == "win" && !debug # Bug 1419183 disable on Windows
+[test_ext_management_uninstall_self.js]
+[test_ext_messaging_startup.js]
+skip-if =
+  appname == "thunderbird"
+  os == "android" && debug
+[test_ext_networkStatus.js]
+[test_ext_notifications_incognito.js]
+skip-if = appname == "thunderbird"
+[test_ext_notifications_unsupported.js]
+[test_ext_onmessage_removelistener.js]
+skip-if = true # This test no longer tests what it is meant to test.
+[test_ext_permission_xhr.js]
+[test_ext_persistent_events.js]
+[test_ext_privacy.js]
+skip-if =
+  appname == "thunderbird"
+  os == "android" && debug
+  os == "linux" && !debug # Bug 1625455
+[test_ext_privacy_disable.js]
+skip-if = appname == "thunderbird"
+[test_ext_privacy_nonPersistentCookies.js]
+[test_ext_privacy_update.js]
+[test_ext_proxy_authorization_via_proxyinfo.js]
+skip-if = true # Bug 1622433 needs h2 proxy implementation
+[test_ext_proxy_config.js]
+skip-if =
+  appname == "thunderbird"
+  os == "android" # Android: Bug 1680132
+[test_ext_proxy_containerIsolation.js]
+[test_ext_proxy_onauthrequired.js]
+[test_ext_proxy_settings.js]
+skip-if =
+  appname == "thunderbird"
+  os == "android" # proxy settings are not supported on android
+[test_ext_proxy_socks.js]
+skip-if = socketprocess_networking
+run-sequentially = TCPServerSocket fails otherwise
+[test_ext_proxy_speculative.js]
+skip-if =
+  ccov && os == "linux" # bug 1607581
+[test_ext_proxy_startup.js]
+skip-if =
+  ccov && os == "linux" # bug 1607581
+[test_ext_redirects.js]
+skip-if =
+  os == "android" && debug
+[test_ext_runtime_connect_no_receiver.js]
+[test_ext_runtime_getBackgroundPage.js]
+[test_ext_runtime_getBrowserInfo.js]
+[test_ext_runtime_getPlatformInfo.js]
+[test_ext_runtime_id.js]
+skip-if =
+  ccov && os == "linux" # bug 1607581
+[test_ext_runtime_messaging_self.js]
+[test_ext_runtime_onInstalled_and_onStartup.js]
+[test_ext_runtime_ports.js]
+[test_ext_runtime_ports_gc.js]
+[test_ext_runtime_sendMessage.js]
+skip-if =
+  os == "win" && bits == 32 && fission && !debug # Bug 1762638; win7 issue
+[test_ext_runtime_sendMessage_errors.js]
+[test_ext_runtime_sendMessage_multiple.js]
+[test_ext_runtime_sendMessage_no_receiver.js]
+[test_ext_same_site_cookies.js]
+[test_ext_same_site_redirects.js]
+skip-if = os == "android" # Android: Bug 1700482
+[test_ext_sandbox_var.js]
+[test_ext_sandboxed_resource.js]
+[test_ext_schema.js]
+[test_ext_script_filenames.js]
+run-sequentially = very high failure rate in parallel
+skip-if =
+  os == "win" && os_version == "6.1" # Skip on Azure - frequent failure
+[test_ext_scripting_contentScripts.js]
+[test_ext_scripting_contentScripts_css.js]
+skip-if =
+  os == "linux" && debug && fission # Bug 1762638
+  os == "mac" && debug && fission # Bug 1762638
+run-sequentially = very high failure rate in parallel
+[test_ext_scripting_contentScripts_file.js]
+[test_ext_scripting_mv2.js]
+[test_ext_scripting_persistAcrossSessions.js]
+[test_ext_scripting_startupCache.js]
+[test_ext_scripting_updateContentScripts.js]
+[test_ext_shared_workers.js]
+[test_ext_shutdown_cleanup.js]
+[test_ext_simple.js]
+[test_ext_startupData.js]
+[test_ext_startup_cache.js]
+skip-if = os == "android"
+[test_ext_startup_perf.js]
+[test_ext_startup_request_handler.js]
+skip-if = os == "android" # Bug 1700482
+[test_ext_storage_local.js]
+skip-if = os == "android" && debug
+[test_ext_storage_idb_data_migration.js]
+skip-if =
+  appname == "thunderbird"
+  os == "android" && debug
+[test_ext_storage_content_local.js]
+skip-if = os == "android" && debug
+[test_ext_storage_content_sync.js]
+skip-if = os == "android" # Android: Bug 1680132
+[test_ext_storage_content_sync_kinto.js]
+skip-if = os == "android" && debug
+[test_ext_storage_quota_exceeded_errors.js]
+skip-if = os == "android" # Bug 1564871
+[test_ext_storage_managed.js]
+skip-if = os == "android"
+[test_ext_storage_managed_policy.js]
+skip-if =
+  appname == "thunderbird"
+  os == "android"
+[test_ext_storage_sanitizer.js]
+skip-if =
+  appname == "thunderbird"
+  os == "android" # Sanitizer.jsm is not in toolkit.
+[test_ext_storage_session.js]
+[test_ext_storage_sync.js]
+skip-if = os == "android" # Bug 1680132 ; SessionStoreFunctions.sys.mjs relies on SessionStore.sys.mjs that does not exist on Android.
+[test_ext_storage_sync_kinto.js]
+skip-if =
+  appname == "thunderbird"
+  os == "android"
+[test_ext_storage_sync_kinto_crypto.js]
+skip-if =
+  appname == "thunderbird"
+  os == "android"
+[test_ext_storage_tab.js]
+[test_ext_storage_telemetry.js]
+skip-if = os == "android" # checking for telemetry needs to be updated: 1384923
+[test_ext_tab_teardown.js]
+skip-if = os == "android" # Bug 1258975 on android.
+[test_ext_telemetry.js]
+[test_ext_theme_experiments.js]
+[test_ext_trustworthy_origin.js]
+[test_ext_unlimitedStorage.js]
+[test_ext_unload_frame.js]
+skip-if = true # Too frequent intermittent failures
+[test_ext_userScripts.js]
+skip-if = os == "android" # Bug 1700482
+run-sequentially = very high failure rate in parallel
+[test_ext_userScripts_exports.js]
+run-sequentially = very high failure rate in parallel
+[test_ext_userScripts_register.js]
+skip-if =
+  os == "linux" && !fission # Bug 1763197
+  os == "android" # Bug 1763197
+[test_ext_wasm.js]
+[test_ext_webRequest_auth.js]
+skip-if =
+  os == "android" && debug
+[test_ext_webRequest_cached.js]
+skip-if = os == "android" # Bug 1573511
+[test_ext_webRequest_cancelWithReason.js]
+skip-if =
+  os == "android" && processor == 'x86_64' # Bug 1683253
+[test_ext_webRequest_containerIsolation.js]
+[test_ext_webRequest_download.js]
+skip-if = os == "android" # Android: Bug 1680132; downloads.download goes through the embedder app instead of Gecko.
+[test_ext_webRequest_filterTypes.js]
+[test_ext_webRequest_from_extension_page.js]
+[test_ext_webRequest_incognito.js]
+skip-if = os == "android" && debug
+[test_ext_webRequest_filter_urls.js]
+[test_ext_webRequest_host.js]
+skip-if = os == "android" && debug
+[test_ext_webRequest_mergecsp.js]
+skip-if = tsan # Bug 1683730
+[test_ext_webRequest_permission.js]
+skip-if = os == "android" && debug
+[test_ext_webRequest_redirectProperty.js]
+skip-if =
+  os == "android" && processor == 'x86_64' # Bug 1683253
+[test_ext_webRequest_redirect_mozextension.js]
+skip-if = os == "android" # Android: Bug 1680132
+[test_ext_webRequest_requestSize.js]
+[test_ext_webRequest_restrictedHeaders.js]
+[test_ext_webRequest_set_cookie.js]
+skip-if = appname == "thunderbird"
+[test_ext_webRequest_startup.js]
+skip-if = os == "android" # bug 1683159
+[test_ext_webRequest_style_cache.js]
+skip-if = os == "android" # Android: Bug 1680132
+[test_ext_webRequest_suspend.js]
+[test_ext_webRequest_userContextId.js]
+[test_ext_webRequest_viewsource.js]
+[test_ext_webSocket.js]
+run-sequentially = very high failure rate in parallel
+[test_ext_webRequest_webSocket.js]
+skip-if = appname == "thunderbird"
+[test_ext_xhr_capabilities.js]
+[test_ext_xhr_cors.js]
+run-sequentially = very high failure rate in parallel
+[test_native_manifests.js]
+subprocess = true
+skip-if = os == "android"
+[test_ext_permissions.js]
+skip-if =
+  appname == "thunderbird"
+  os == "android" # Bug 1350559
+[test_ext_permissions_api.js]
+skip-if =
+  appname == "thunderbird"
+  os == "android" # Bug 1350559
+[test_ext_permissions_migrate.js]
+skip-if =
+  appname == "thunderbird"
+  os == "android" # Bug 1350559
+[test_ext_permissions_uninstall.js]
+skip-if =
+  appname == "thunderbird"
+  os == "android" # Bug 1350559
+[test_proxy_failover.js]
+[test_proxy_listener.js]
+skip-if = appname == "thunderbird"
+[test_proxy_incognito.js]
+skip-if = os == "android" # incognito not supported on android
+[test_proxy_info_results.js]
+skip-if = os == "win" # bug 1802704
+[test_proxy_userContextId.js]
+[test_QuarantinedDomains.js]
+[test_site_permissions.js]
+[test_webRequest_ancestors.js]
+[test_webRequest_cookies.js]
+[test_webRequest_filtering.js]
+[test_ext_brokenlinks.js]
+skip-if = os == "android" # Android: Bug 1680132
+[test_ext_performance_counters.js]
+skip-if =
+  appname == "thunderbird"
+  os == "android"
+[test_resistfingerprinting_exempt.js]
diff --git a/toolkit/components/extensions/test/xpcshell/xpcshell-content.ini b/toolkit/components/extensions/test/xpcshell/xpcshell-content.ini
new file mode 100644
index 0000000000..54074f4608
--- /dev/null
+++ b/toolkit/components/extensions/test/xpcshell/xpcshell-content.ini
@@ -0,0 +1,70 @@
+[test_ext_i18n.js]
+skip-if = (os == "win" && debug) || (os == "linux")
+[test_ext_i18n_css.js]
+skip-if =
+  os == "mac" && debug && fission # Bug 1762638
+  (socketprocess_networking || fission) && (os == "linux" && debug) # Bug 1759035
+run-sequentially = very high failure rate in parallel
+[test_ext_contentscript.js]
+skip-if =
+  socketprocess_networking # Bug 1759035
+run-sequentially = very high failure rate in parallel
+[test_ext_contentscript_errors.js]
+skip-if =
+  socketprocess_networking # Bug 1759035
+  os == "win" && os_version == "6.1" # Skip on Azure - frequent failure
+run-sequentially = very high failure rate in parallel
+[test_ext_contentscript_about_blank_start.js]
+[test_ext_contentscript_canvas_tainting.js]
+skip-if =
+  os == "linux" && socketprocess_networking && !fission && debug # Bug 1759035
+run-sequentially = very high failure rate in parallel
+
+[test_ext_contentscript_permissions_change.js]
+skip-if =
+  os == "linux" && socketprocess_networking && !fission && debug # Bug 1759035
+  os == "linux" && tsan && fission # bug 1762638
+[test_ext_contentscript_permissions_fetch.js]
+skip-if =
+  os == "linux" && socketprocess_networking && !fission && debug # Bug 1759035
+[test_ext_contentscript_scriptCreated.js]
+skip-if =
+  os == "linux" && socketprocess_networking && !fission && debug # Bug 1759035
+[test_ext_contentscript_triggeringPrincipal.js]
+skip-if =
+  os == "android" # Bug 1680132
+  (os == "win" && debug) # Bug 1438796
+  tsan # Bug 1612707
+  os == "linux" && socketprocess_networking && !fission && debug # Bug 1759035
+  os == "linux" && fission && debug # Bug 1762638
+[test_ext_contentscript_xrays.js]
+skip-if =
+  os == "linux" && socketprocess_networking && !fission && debug # Bug 1759035
+run-sequentially = very high failure rate in parallel
+[test_ext_contentScripts_register.js]
+skip-if =
+  os == "linux" && socketprocess_networking && !fission && debug # Bug 1759035
+  fission # Bug 1762638
+[test_ext_contexts_gc.js]
+skip-if =
+  os == "linux" && socketprocess_networking && !fission && debug # Bug 1759035
+run-sequentially = very high failure rate in parallel
+[test_ext_adoption_with_xrays.js]
+skip-if =
+  os == "linux" && socketprocess_networking && !fission && debug # Bug 1759035
+[test_ext_adoption_with_private_field_xrays.js]
+skip-if = !nightly_build
+  os == "linux" && socketprocess_networking && !fission && debug # Bug 1759035
+run-sequentially = very high failure rate in parallel
+[test_ext_shadowdom.js]
+skip-if = ccov && os == 'linux' # bug 1607581
+  os == "linux" && socketprocess_networking && !fission && debug # Bug 1759035
+[test_ext_web_accessible_resources.js]
+skip-if =
+  apple_silicon # Disabled due to bleedover with other tests when run in regular suites; passes in "failures" jobs
+  os == "linux" && socketprocess_networking && !fission && debug # Bug 1759035
+  sessionHistoryInParent # Bug 1762638
+[test_ext_web_accessible_resources_matches.js]
+skip-if =
+  os == "linux" && socketprocess_networking && !fission && debug # Bug 1759035
+run-sequentially = very high failure rate in parallel
diff --git a/toolkit/components/extensions/test/xpcshell/xpcshell-e10s.ini b/toolkit/components/extensions/test/xpcshell/xpcshell-e10s.ini
new file mode 100644
index 0000000000..b84e3354c5
--- /dev/null
+++ b/toolkit/components/extensions/test/xpcshell/xpcshell-e10s.ini
@@ -0,0 +1,30 @@
+[DEFAULT]
+head = head.js head_e10s.js head_telemetry.js
+tail =
+firefox-appdir = browser
+skip-if = appname == "thunderbird" || os == "android"
+dupe-manifest =
+support-files =
+  data/**
+  xpcshell-content.ini
+tags = webextensions webextensions-e10s
+
+# Make sure that loading the default settings for url-classifier-skip-urls
+# doesn't interfere with running our tests while IDB operations are in
+# flight by overriding the remote settings server URL to
+# ensure that the IDB database isn't created in the first place.
+prefs =
+  services.settings.server=data:,#remote-settings-dummy/v1
+
+[include:xpcshell-common-e10s.ini]
+skip-if =
+  socketprocess_networking # Bug 1759035
+[include:xpcshell-content.ini]
+skip-if =
+  socketprocess_networking && fission # Bug 1759035
+
+# Tests that need to run with e10s only must NOT be placed here,
+# but in xpcshell-common-e10s.ini.
+# A test here will only run on one configuration, e10s + in-process extensions,
+# while the primary target is e10s + out-of-process extensions.
+# xpcshell-common-e10s.ini runs in both configurations.
diff --git a/toolkit/components/extensions/test/xpcshell/xpcshell-legacy-ep.ini b/toolkit/components/extensions/test/xpcshell/xpcshell-legacy-ep.ini
new file mode 100644
index 0000000000..af26762346
--- /dev/null
+++ b/toolkit/components/extensions/test/xpcshell/xpcshell-legacy-ep.ini
@@ -0,0 +1,21 @@
+[DEFAULT]
+head = head.js head_remote.js head_e10s.js head_legacy_ep.js
+tail =
+firefox-appdir = browser
+skip-if = appname == "thunderbird" || os == "android"
+dupe-manifest =
+
+# Make sure that loading the default settings for url-classifier-skip-urls
+# doesn't interfere with running our tests while IDB operations are in
+# flight by overriding the remote settings server URL to
+# ensure that the IDB database isn't created in the first place.
+prefs =
+  services.settings.server=data:,#remote-settings-dummy/v1
+
+# Bug 1646182: Test the legacy ExtensionPermission backend until we fully
+# migrate to rkv
+[test_ext_permissions.js]
+[test_ext_permissions_api.js]
+[test_ext_permissions_migrate.js]
+[test_ext_permissions_uninstall.js]
+[test_ext_proxy_config.js]
diff --git a/toolkit/components/extensions/test/xpcshell/xpcshell-remote.ini b/toolkit/components/extensions/test/xpcshell/xpcshell-remote.ini
new file mode 100644
index 0000000000..b6055bca46
--- /dev/null
+++ b/toolkit/components/extensions/test/xpcshell/xpcshell-remote.ini
@@ -0,0 +1,42 @@
+[DEFAULT]
+head = head.js head_remote.js head_e10s.js head_telemetry.js head_sync.js head_storage.js
+tail =
+firefox-appdir = browser
+skip-if =
+  os == "android"
+  os == "win" && socketprocess_networking && fission # Bug 1759035
+  os == "mac" && socketprocess_networking && fission # Bug 1759035
+  # I would put linux here, but debug has too many chunks and only runs this manifest, so I need 1 test to pass
+dupe-manifest =
+support-files =
+  data/**
+  head_dnr.js
+  xpcshell-content.ini
+tags = webextensions remote-webextensions
+
+# Make sure that loading the default settings for url-classifier-skip-urls
+# doesn't interfere with running our tests while IDB operations are in
+# flight by overriding the remote settings server URL to
+# ensure that the IDB database isn't created in the first place.
+prefs =
+  services.settings.server=data:,#remote-settings-dummy/v1
+
+[include:xpcshell-common.ini]
+skip-if =
+  os == "linux" && socketprocess_networking # Bug 1759035
+[include:xpcshell-common-e10s.ini]
+skip-if =
+  os == "linux" && socketprocess_networking # Bug 1759035
+[include:xpcshell-content.ini]
+skip-if =
+  os == "linux" && socketprocess_networking # Bug 1759035
+[test_ext_contentscript_perf_observers.js] # Inexplicably, PerformanceObserver used in the test doesn't fire in non-e10s mode.
+skip-if = tsan
+  os == "linux" && socketprocess_networking # Bug 1759035
+[test_ext_contentscript_xorigin_frame.js]
+skip-if =
+  os == "linux" && socketprocess_networking # Bug 1759035
+[test_WebExtensionContentScript.js]
+[test_ext_ipcBlob.js]
+skip-if = os == 'android' && processor == 'x86_64'
+  os == "linux" && socketprocess_networking # Bug 1759035
diff --git a/toolkit/components/extensions/test/xpcshell/xpcshell-serviceworker.ini b/toolkit/components/extensions/test/xpcshell/xpcshell-serviceworker.ini
new file mode 100644
index 0000000000..d8f029ab2d
--- /dev/null
+++ b/toolkit/components/extensions/test/xpcshell/xpcshell-serviceworker.ini
@@ -0,0 +1,37 @@
+[DEFAULT]
+head = head.js head_remote.js head_e10s.js head_telemetry.js head_sync.js head_storage.js head_service_worker.js
+tail =
+firefox-appdir = browser
+skip-if = os == "android"
+dupe-manifest = true
+support-files =
+  data/**
+tags = webextensions sw-webextensions
+run-sequentially = Bug 1760041 pass logged after tests when running multiple ini files
+
+prefs =
+  extensions.backgroundServiceWorker.enabled=true
+  extensions.backgroundServiceWorker.forceInTestExtension=true
+  extensions.webextensions.remote=true
+
+[test_ext_alarms.js]
+[test_ext_alarms_does_not_fire.js]
+[test_ext_alarms_periodic.js]
+[test_ext_alarms_replaces.js]
+[test_ext_background_service_worker.js]
+[test_ext_browserSettings.js]
+[test_ext_browserSettings_homepage.js]
+skip-if =
+  appname == "thunderbird"
+  os == "android"
+[test_ext_contentscript_dynamic_registration.js]
+[test_ext_dns.js]
+[test_ext_runtime_getBackgroundPage.js]
+[test_ext_scripting_contentScripts.js]
+[test_ext_scripting_contentScripts_css.js]
+skip-if =
+  os == "linux" && debug && fission # Bug 1762638
+  os == "mac" && debug && fission # Bug 1762638
+run-sequentially = very high failure rate in parallel
+[test_ext_scripting_contentScripts_file.js]
+[test_ext_scripting_updateContentScripts.js]
diff --git a/toolkit/components/extensions/test/xpcshell/xpcshell.ini b/toolkit/components/extensions/test/xpcshell/xpcshell.ini
new file mode 100644
index 0000000000..f42349d7fc
--- /dev/null
+++ b/toolkit/components/extensions/test/xpcshell/xpcshell.ini
@@ -0,0 +1,101 @@
+[DEFAULT]
+head = head.js head_telemetry.js head_sync.js head_storage.js
+firefox-appdir = browser
+dupe-manifest =
+support-files =
+  data/**
+  head_dnr.js
+  xpcshell-content.ini
+tags = webextensions in-process-webextensions condprof
+
+# Make sure that loading the default settings for url-classifier-skip-urls
+# doesn't interfere with running our tests while IDB operations are in
+# flight by overriding the remote settings server URL to
+# ensure that the IDB database isn't created in the first place.
+prefs =
+  services.settings.server=data:,#remote-settings-dummy/v1
+
+# This file contains tests which are not affected by multi-process
+# configuration, or do not support out-of-process content or extensions
+# for one reason or another.
+#
+# Tests which are affected by remote content or remote extensions should
+# go in one of:
+#
+#  - xpcshell-common.ini
+#    For tests which should run in all configurations.
+#  - xpcshell-common-e10s.ini
+#    For tests which should run in all configurations where e10s is enabled.
+#  - xpcshell-remote.ini
+#    For tests which should only run with both remote extensions and remote content.
+#  - xpcshell-content.ini
+#    For tests which rely on content pages, and should run in all configurations.
+#  - xpcshell-e10s.ini
+#    For tests which rely on content pages, and should only run with remote content
+#    but in-process extensions.
+
+[test_ExtensionShortcutKeyMap.js]
+[test_ExtensionStorageSync_migration_kinto.js]
+skip-if = os == 'android' # Not shipped on Android
+  condprof  # Bug 1769184 - by design for now
+[test_MatchPattern.js]
+[test_StorageSyncService.js]
+skip-if = os == 'android' && processor == 'x86_64'
+[test_WebExtensionPolicy.js]
+
+[test_csp_custom_policies.js]
+[test_csp_validator.js]
+[test_ext_clear_cached_resources.js]
+[test_ext_contexts.js]
+[test_ext_json_parser.js]
+[test_ext_geckoProfiler_schema.js]
+skip-if = os == 'android' # Not shipped on Android
+[test_ext_manifest.js]
+[test_ext_manifest_content_security_policy.js]
+[test_ext_manifest_incognito.js]
+[test_ext_indexedDB_principal.js]
+[test_ext_manifest_minimum_chrome_version.js]
+[test_ext_manifest_minimum_opera_version.js]
+[test_ext_manifest_themes.js]
+[test_ext_permission_warnings.js]
+[test_ext_schemas.js]
+head = head.js head_schemas.js
+[test_ext_schemas_roots.js]
+[test_ext_schemas_async.js]
+[test_ext_schemas_allowed_contexts.js]
+[test_ext_schemas_interactive.js]
+[test_ext_schemas_manifest_permissions.js]
+skip-if =
+  condprof  # Bug 1769184 - by design for now
+[test_ext_schemas_privileged.js]
+skip-if =
+  condprof  # Bug 1769184 - by design for now
+[test_ext_schemas_revoke.js]
+[test_ext_schemas_versioned.js]
+head = head.js head_schemas.js
+[test_ext_secfetch.js]
+skip-if =
+  socketprocess_networking # Bug 1759035
+run-sequentially = very high failure rate in parallel
+[test_ext_shared_array_buffer.js]
+[test_ext_startup_cache_telemetry.js]
+[test_ext_test_mock.js]
+[test_ext_test_wrapper.js]
+[test_ext_unknown_permissions.js]
+[test_ext_webRequest_urlclassification.js]
+[test_extension_permissions_migration.js]
+skip-if =
+  condprof  # Bug 1769184 - by design for now
+[test_extension_permissions_migrate_kvstore_path.js]
+skip-if =
+  condprof  # Bug 1769184 - by design for now
+[test_load_all_api_modules.js]
+[test_locale_converter.js]
+[test_locale_data.js]
+
+[test_ext_runtime_sendMessage_args.js]
+
+[include:xpcshell-common.ini]
+run-if = os == 'android' # Android has no remote extensions, Bug 1535365
+[include:xpcshell-content.ini]
+run-if = os == 'android' # Android has no remote extensions, Bug 1535365