Adding upstream version 124.0.1.upstream/124.0.1

Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>

13 files changed, 1431 insertions, 0 deletions

diff --git a/toolkit/components/remotebrowserutils/tests/browser/307redirect.sjs b/toolkit/components/remotebrowserutils/tests/browser/307redirect.sjs
new file mode 100644
index 0000000000..1a28b8c5c3
--- /dev/null
+++ b/toolkit/components/remotebrowserutils/tests/browser/307redirect.sjs
@@ -0,0 +1,6 @@
+function handleRequest(request, response) {
+  response.setStatusLine(request.httpVersion, 307, "Temporary Redirect");
+  let location = request.queryString;
+  response.setHeader("Location", location, false);
+  response.write("Hello world!");
+}
diff --git a/toolkit/components/remotebrowserutils/tests/browser/browser.toml b/toolkit/components/remotebrowserutils/tests/browser/browser.toml
new file mode 100644
index 0000000000..47832d0da4
--- /dev/null
+++ b/toolkit/components/remotebrowserutils/tests/browser/browser.toml
@@ -0,0 +1,22 @@
+[DEFAULT]
+support-files = [
+  "dummy_page.html",
+  "print_postdata.sjs",
+  "307redirect.sjs",
+  "head.js",
+  "coop_header.sjs",
+  "file_postmsg_parent.html",
+]
+
+["browser_RemoteWebNavigation.js"]
+https_first_disabled = true
+
+["browser_documentChannel.js"]
+
+["browser_externalLinkBlanksPage.js"]
+
+["browser_httpCrossOriginOpenerPolicy.js"]
+
+["browser_httpToFileHistory.js"]
+
+["browser_oopProcessSwap.js"]
diff --git a/toolkit/components/remotebrowserutils/tests/browser/browser_RemoteWebNavigation.js b/toolkit/components/remotebrowserutils/tests/browser/browser_RemoteWebNavigation.js
new file mode 100644
index 0000000000..964d7f5373
--- /dev/null
+++ b/toolkit/components/remotebrowserutils/tests/browser/browser_RemoteWebNavigation.js
@@ -0,0 +1,239 @@
+const SYSTEMPRINCIPAL = Services.scriptSecurityManager.getSystemPrincipal();
+const DUMMY1 =
+  "http://test1.example.org/browser/toolkit/modules/tests/browser/dummy_page.html";
+const DUMMY2 =
+  "http://test2.example.org/browser/toolkit/modules/tests/browser/dummy_page.html";
+const LOAD_URI_OPTIONS = { triggeringPrincipal: SYSTEMPRINCIPAL };
+
+function waitForLoad(uri) {
+  return BrowserTestUtils.browserLoaded(gBrowser.selectedBrowser, false, uri);
+}
+
+function waitForPageShow(browser = gBrowser.selectedBrowser) {
+  return BrowserTestUtils.waitForContentEvent(browser, "pageshow", true);
+}
+
+// Tests that loadURI accepts a referrer and it is included in the load.
+add_task(async function test_referrer() {
+  gBrowser.selectedTab = BrowserTestUtils.addTab(gBrowser);
+  let browser = gBrowser.selectedBrowser;
+  let ReferrerInfo = Components.Constructor(
+    "@mozilla.org/referrer-info;1",
+    "nsIReferrerInfo",
+    "init"
+  );
+
+  let loadURIOptionsWithReferrer = {
+    triggeringPrincipal: SYSTEMPRINCIPAL,
+    referrerInfo: new ReferrerInfo(
+      Ci.nsIReferrerInfo.EMPTY,
+      true,
+      Services.io.newURI(DUMMY2)
+    ),
+  };
+  browser.webNavigation.loadURI(
+    Services.io.newURI(DUMMY1),
+    loadURIOptionsWithReferrer
+  );
+  await waitForLoad(DUMMY1);
+
+  await SpecialPowers.spawn(
+    browser,
+    [[DUMMY1, DUMMY2]],
+    function ([dummy1, dummy2]) {
+      function getExpectedReferrer(referrer) {
+        let defaultPolicy = Services.prefs.getIntPref(
+          "network.http.referer.defaultPolicy"
+        );
+        Assert.greater(
+          [2, 3].indexOf(defaultPolicy),
+          -1,
+          "default referrer policy should be either strict-origin-when-cross-origin(2) or no-referrer-when-downgrade(3)"
+        );
+        if (defaultPolicy == 2) {
+          return referrer.match(/https?:\/\/[^\/]+\/?/i)[0];
+        }
+        return referrer;
+      }
+
+      is(content.location.href, dummy1, "Should have loaded the right URL");
+      is(
+        content.document.referrer,
+        getExpectedReferrer(dummy2),
+        "Should have the right referrer"
+      );
+    }
+  );
+
+  gBrowser.removeCurrentTab();
+});
+
+// Tests that remote access to webnavigation.sessionHistory works.
+add_task(async function test_history() {
+  async function checkHistoryIndex(browser, n) {
+    if (!SpecialPowers.Services.appinfo.sessionHistoryInParent) {
+      return SpecialPowers.spawn(browser, [n], function (n) {
+        let history =
+          docShell.browsingContext.childSessionHistory.legacySHistory;
+
+        is(history.index, n, "Should be at the right place in history");
+      });
+    }
+
+    let history = browser.browsingContext.sessionHistory;
+    is(history.index, n, "Should be at the right place in history");
+    return null;
+  }
+
+  gBrowser.selectedTab = BrowserTestUtils.addTab(gBrowser);
+  let browser = gBrowser.selectedBrowser;
+
+  browser.webNavigation.loadURI(Services.io.newURI(DUMMY1), LOAD_URI_OPTIONS);
+  await waitForLoad(DUMMY1);
+
+  browser.webNavigation.loadURI(Services.io.newURI(DUMMY2), LOAD_URI_OPTIONS);
+  await waitForLoad(DUMMY2);
+
+  if (!SpecialPowers.Services.appinfo.sessionHistoryInParent) {
+    await SpecialPowers.spawn(
+      browser,
+      [[DUMMY1, DUMMY2]],
+      function ([dummy1, dummy2]) {
+        let history =
+          docShell.browsingContext.childSessionHistory.legacySHistory;
+
+        is(history.count, 2, "Should be two history items");
+        is(history.index, 1, "Should be at the right place in history");
+        let entry = history.getEntryAtIndex(0);
+        is(entry.URI.spec, dummy1, "Should have the right history entry");
+        entry = history.getEntryAtIndex(1);
+        is(entry.URI.spec, dummy2, "Should have the right history entry");
+      }
+    );
+  } else {
+    let history = browser.browsingContext.sessionHistory;
+
+    is(history.count, 2, "Should be two history items");
+    is(history.index, 1, "Should be at the right place in history");
+    let entry = history.getEntryAtIndex(0);
+    is(entry.URI.spec, DUMMY1, "Should have the right history entry");
+    entry = history.getEntryAtIndex(1);
+    is(entry.URI.spec, DUMMY2, "Should have the right history entry");
+  }
+
+  let promise = waitForPageShow();
+  browser.webNavigation.goBack();
+  await promise;
+  await checkHistoryIndex(browser, 0);
+
+  promise = waitForPageShow();
+  browser.webNavigation.goForward();
+  await promise;
+  await checkHistoryIndex(browser, 1);
+
+  promise = waitForPageShow();
+  browser.webNavigation.gotoIndex(0);
+  await promise;
+  await checkHistoryIndex(browser, 0);
+
+  gBrowser.removeCurrentTab();
+});
+
+// Tests that load flags are passed through to the content process.
+add_task(async function test_flags() {
+  async function checkHistory(browser, { count, index }) {
+    if (!SpecialPowers.Services.appinfo.sessionHistoryInParent) {
+      return SpecialPowers.spawn(
+        browser,
+        [[DUMMY2, count, index]],
+        function ([dummy2, count, index]) {
+          let history =
+            docShell.browsingContext.childSessionHistory.legacySHistory;
+          is(history.count, count, "Should be one history item");
+          is(history.index, index, "Should be at the right place in history");
+          let entry = history.getEntryAtIndex(index);
+          is(entry.URI.spec, dummy2, "Should have the right history entry");
+        }
+      );
+    }
+
+    let history = browser.browsingContext.sessionHistory;
+    is(history.count, count, "Should be one history item");
+    is(history.index, index, "Should be at the right place in history");
+    let entry = history.getEntryAtIndex(index);
+    is(entry.URI.spec, DUMMY2, "Should have the right history entry");
+
+    return null;
+  }
+
+  gBrowser.selectedTab = BrowserTestUtils.addTab(gBrowser);
+  let browser = gBrowser.selectedBrowser;
+
+  browser.webNavigation.loadURI(Services.io.newURI(DUMMY1), LOAD_URI_OPTIONS);
+  await waitForLoad(DUMMY1);
+  let loadURIOptionsReplaceHistory = {
+    triggeringPrincipal: SYSTEMPRINCIPAL,
+    loadFlags: Ci.nsIWebNavigation.LOAD_FLAGS_REPLACE_HISTORY,
+  };
+  browser.webNavigation.loadURI(
+    Services.io.newURI(DUMMY2),
+    loadURIOptionsReplaceHistory
+  );
+  await waitForLoad(DUMMY2);
+  await checkHistory(browser, { count: 1, index: 0 });
+  let loadURIOptionsBypassHistory = {
+    triggeringPrincipal: SYSTEMPRINCIPAL,
+    loadFlags: Ci.nsIWebNavigation.LOAD_FLAGS_BYPASS_HISTORY,
+  };
+  browser.webNavigation.loadURI(
+    Services.io.newURI(DUMMY1),
+    loadURIOptionsBypassHistory
+  );
+  await waitForLoad(DUMMY1);
+  await checkHistory(browser, { count: 1, index: 0 });
+
+  gBrowser.removeCurrentTab();
+});
+
+// Tests that attempts to use unsupported arguments throw an exception.
+add_task(async function test_badarguments() {
+  if (!gMultiProcessBrowser) {
+    return;
+  }
+
+  gBrowser.selectedTab = BrowserTestUtils.addTab(gBrowser);
+  let browser = gBrowser.selectedBrowser;
+
+  try {
+    let loadURIOptionsBadPostData = {
+      triggeringPrincipal: SYSTEMPRINCIPAL,
+      postData: {},
+    };
+    browser.webNavigation.loadURI(
+      Services.io.newURI(DUMMY1),
+      loadURIOptionsBadPostData
+    );
+    ok(
+      false,
+      "Should have seen an exception from trying to pass some postdata"
+    );
+  } catch (e) {
+    ok(true, "Should have seen an exception from trying to pass some postdata");
+  }
+
+  try {
+    let loadURIOptionsBadHeader = {
+      triggeringPrincipal: SYSTEMPRINCIPAL,
+      headers: {},
+    };
+    browser.webNavigation.loadURI(
+      Services.io.newURI(DUMMY1),
+      loadURIOptionsBadHeader
+    );
+    ok(false, "Should have seen an exception from trying to pass some headers");
+  } catch (e) {
+    ok(true, "Should have seen an exception from trying to pass some headers");
+  }
+
+  gBrowser.removeCurrentTab();
+});
diff --git a/toolkit/components/remotebrowserutils/tests/browser/browser_documentChannel.js b/toolkit/components/remotebrowserutils/tests/browser/browser_documentChannel.js
new file mode 100644
index 0000000000..f32216010b
--- /dev/null
+++ b/toolkit/components/remotebrowserutils/tests/browser/browser_documentChannel.js
@@ -0,0 +1,279 @@
+/* eslint-env webextensions */
+"use strict";
+
+const PRINT_POSTDATA = httpURL("print_postdata.sjs");
+const FILE_DUMMY = fileURL("dummy_page.html");
+const DATA_URL = "data:text/html,Hello%2C World!";
+const DATA_STRING = "Hello, World!";
+
+async function performLoad(browser, opts, action) {
+  let loadedPromise = BrowserTestUtils.browserLoaded(
+    browser,
+    false,
+    opts.url,
+    opts.maybeErrorPage
+  );
+  await action();
+  await loadedPromise;
+}
+
+const EXTENSION_DATA = {
+  manifest: {
+    name: "Simple extension test",
+    version: "1.0",
+    manifest_version: 2,
+    description: "",
+
+    permissions: ["proxy", "webRequest", "webRequestBlocking", "<all_urls>"],
+  },
+
+  files: {
+    "dummy.html": "<html>webext dummy</html>",
+    "redirect.html": "<html>webext redirect</html>",
+  },
+
+  extUrl: "",
+
+  async background() {
+    browser.test.log("background script running");
+    browser.webRequest.onAuthRequired.addListener(
+      async details => {
+        browser.test.log("webRequest onAuthRequired");
+
+        // A blocking request that returns a promise exercises a codepath that
+        // sets the notificationCallbacks on the channel to a JS object that we
+        // can't do directly QueryObject on with expected results.
+        // This triggered a crash which was fixed in bug 1528188.
+        return new Promise((resolve, reject) => {
+          setTimeout(resolve, 0);
+        });
+      },
+      { urls: ["*://*/*"] },
+      ["blocking"]
+    );
+    browser.webRequest.onBeforeRequest.addListener(
+      async details => {
+        browser.test.log("webRequest onBeforeRequest");
+        let isRedirect =
+          details.originUrl == browser.runtime.getURL("redirect.html") &&
+          details.url.endsWith("print_postdata.sjs");
+        let url = this.extUrl ? this.extUrl : details.url + "?redirected";
+        return isRedirect ? { redirectUrl: url } : {};
+      },
+      { urls: ["*://*/*"] },
+      ["blocking"]
+    );
+    browser.test.onMessage.addListener(async ({ method, url }) => {
+      if (method == "setRedirectUrl") {
+        this.extUrl = url;
+      }
+      browser.test.sendMessage("done");
+    });
+  },
+};
+
+async function withExtensionDummy(callback) {
+  let extension = ExtensionTestUtils.loadExtension(EXTENSION_DATA);
+  await extension.startup();
+  let rv = await callback(`moz-extension://${extension.uuid}/`, extension);
+  await extension.unload();
+  return rv;
+}
+
+async function postFrom(start, target) {
+  return BrowserTestUtils.withNewTab(
+    {
+      gBrowser,
+      url: start,
+    },
+    async function (browser) {
+      info("Test tab ready: postFrom " + start);
+
+      // Create the form element in our loaded URI.
+      await SpecialPowers.spawn(browser, [{ target }], function ({ target }) {
+        content.document.body.innerHTML = `
+        <form method="post" action="${target}">
+          <input type="text" name="initialRemoteType" value="${Services.appinfo.remoteType}">
+          <input type="submit" id="submit">
+        </form>`;
+      });
+
+      // Perform a form POST submit load.
+      info("Performing POST submission");
+      await performLoad(
+        browser,
+        {
+          url(url) {
+            let enable =
+              url.startsWith(PRINT_POSTDATA) ||
+              url == target ||
+              url == DATA_URL;
+            if (!enable) {
+              info(`url ${url} is invalid to perform load`);
+            }
+            return enable;
+          },
+          maybeErrorPage: true,
+        },
+        async () => {
+          await SpecialPowers.spawn(browser, [], () => {
+            content.document.querySelector("#submit").click();
+          });
+        }
+      );
+
+      // Check that the POST data was submitted.
+      info("Fetching results");
+      return SpecialPowers.spawn(browser, [], () => {
+        return {
+          remoteType: Services.appinfo.remoteType,
+          location: "" + content.location.href,
+          body: content.document.body.textContent,
+        };
+      });
+    }
+  );
+}
+
+async function loadAndGetProcessID(browser, target) {
+  info(`Performing GET load: ${target}`);
+  await performLoad(
+    browser,
+    {
+      maybeErrorPage: true,
+    },
+    () => {
+      BrowserTestUtils.startLoadingURIString(browser, target);
+    }
+  );
+
+  info(`Navigated to: ${target}`);
+  browser = gBrowser.selectedBrowser;
+  let processID = await SpecialPowers.spawn(browser, [], () => {
+    return Services.appinfo.processID;
+  });
+  return processID;
+}
+
+async function testLoadAndRedirect(
+  target,
+  expectedProcessSwitch,
+  testRedirect
+) {
+  let start = httpURL(`dummy_page.html`);
+  return BrowserTestUtils.withNewTab(
+    {
+      gBrowser,
+      url: start,
+    },
+    async function (_browser) {
+      info("Test tab ready: getFrom " + start);
+
+      let browser = gBrowser.selectedBrowser;
+      let firstProcessID = await SpecialPowers.spawn(browser, [], () => {
+        return Services.appinfo.processID;
+      });
+
+      info(`firstProcessID: ${firstProcessID}`);
+
+      let secondProcessID = await loadAndGetProcessID(browser, target);
+
+      info(`secondProcessID: ${secondProcessID}`);
+      Assert.equal(firstProcessID != secondProcessID, expectedProcessSwitch);
+
+      if (!testRedirect) {
+        return;
+      }
+
+      let thirdProcessID = await loadAndGetProcessID(browser, add307(target));
+
+      info(`thirdProcessID: ${thirdProcessID}`);
+      Assert.equal(firstProcessID != thirdProcessID, expectedProcessSwitch);
+      Assert.ok(secondProcessID == thirdProcessID);
+    }
+  );
+}
+
+add_task(async function test_enabled() {
+  // Force only one webIsolated content process to ensure same-origin loads
+  // always end in the same process.
+  await SpecialPowers.pushPrefEnv({
+    set: [["dom.ipc.processCount.webIsolated", 1]],
+  });
+
+  // URIs should correctly switch processes & the POST
+  // should succeed.
+  info("ENABLED -- FILE -- raw URI load");
+  let resp = await postFrom(FILE_DUMMY, PRINT_POSTDATA);
+  ok(E10SUtils.isWebRemoteType(resp.remoteType), "process switch");
+  is(resp.location, PRINT_POSTDATA, "correct location");
+  is(resp.body, "initialRemoteType=file", "correct POST body");
+
+  info("ENABLED -- FILE -- 307-redirect URI load");
+  let resp307 = await postFrom(FILE_DUMMY, add307(PRINT_POSTDATA));
+  ok(E10SUtils.isWebRemoteType(resp307.remoteType), "process switch");
+  is(resp307.location, PRINT_POSTDATA, "correct location");
+  is(resp307.body, "initialRemoteType=file", "correct POST body");
+
+  // Same with extensions
+  await withExtensionDummy(async extOrigin => {
+    info("ENABLED -- EXTENSION -- raw URI load");
+    let respExt = await postFrom(extOrigin + "dummy.html", PRINT_POSTDATA);
+    ok(E10SUtils.isWebRemoteType(respExt.remoteType), "process switch");
+    is(respExt.location, PRINT_POSTDATA, "correct location");
+    is(respExt.body, "initialRemoteType=extension", "correct POST body");
+
+    info("ENABLED -- EXTENSION -- extension-redirect URI load");
+    let respExtRedirect = await postFrom(
+      extOrigin + "redirect.html",
+      PRINT_POSTDATA
+    );
+    ok(E10SUtils.isWebRemoteType(respExtRedirect.remoteType), "process switch");
+    is(
+      respExtRedirect.location,
+      PRINT_POSTDATA + "?redirected",
+      "correct location"
+    );
+    is(
+      respExtRedirect.body,
+      "initialRemoteType=extension?redirected",
+      "correct POST body"
+    );
+
+    info("ENABLED -- EXTENSION -- 307-redirect URI load");
+    let respExt307 = await postFrom(
+      extOrigin + "dummy.html",
+      add307(PRINT_POSTDATA)
+    );
+    ok(E10SUtils.isWebRemoteType(respExt307.remoteType), "process switch");
+    is(respExt307.location, PRINT_POSTDATA, "correct location");
+    is(respExt307.body, "initialRemoteType=extension", "correct POST body");
+  });
+});
+
+async function sendMessage(ext, method, url) {
+  ext.sendMessage({ method, url });
+  await ext.awaitMessage("done");
+}
+
+// TODO: Currently no test framework for ftp://.
+add_task(async function test_protocol() {
+  // TODO: Processes should be switched due to navigation of different origins.
+  await testLoadAndRedirect("data:,foo", false, true);
+
+  // Redirecting to file:// is not allowed.
+  await testLoadAndRedirect(FILE_DUMMY, true, false);
+
+  await withExtensionDummy(async (extOrigin, extension) => {
+    await sendMessage(extension, "setRedirectUrl", DATA_URL);
+
+    let respExtRedirect = await postFrom(
+      extOrigin + "redirect.html",
+      PRINT_POSTDATA
+    );
+
+    ok(E10SUtils.isWebRemoteType(respExtRedirect.remoteType), "process switch");
+    is(respExtRedirect.location, DATA_URL, "correct location");
+    is(respExtRedirect.body, DATA_STRING, "correct POST body");
+  });
+});
diff --git a/toolkit/components/remotebrowserutils/tests/browser/browser_externalLinkBlanksPage.js b/toolkit/components/remotebrowserutils/tests/browser/browser_externalLinkBlanksPage.js
new file mode 100644
index 0000000000..3cdfed48cc
--- /dev/null
+++ b/toolkit/components/remotebrowserutils/tests/browser/browser_externalLinkBlanksPage.js
@@ -0,0 +1,79 @@
+/*
+ * Test that following a link with a scheme that opens externally (like
+ * irc:) does not blank the page (Bug 1630757).
+ */
+
+const { HandlerServiceTestUtils } = ChromeUtils.importESModule(
+  "resource://testing-common/HandlerServiceTestUtils.sys.mjs"
+);
+
+let gHandlerService = Cc["@mozilla.org/uriloader/handler-service;1"].getService(
+  Ci.nsIHandlerService
+);
+
+let Pages = [httpURL("dummy_page.html"), fileURL("dummy_page.html")];
+
+/**
+ * Creates dummy protocol handler
+ */
+function initTestHandlers() {
+  let handlerInfo =
+    HandlerServiceTestUtils.getBlankHandlerInfo("test-proto://");
+
+  let appHandler = Cc[
+    "@mozilla.org/uriloader/local-handler-app;1"
+  ].createInstance(Ci.nsILocalHandlerApp);
+  // This is a dir and not executable, but that's enough for here.
+  appHandler.executable = Services.dirsvc.get("XCurProcD", Ci.nsIFile);
+  handlerInfo.possibleApplicationHandlers.appendElement(appHandler);
+  handlerInfo.preferredApplicationHandler = appHandler;
+  handlerInfo.preferredAction = handlerInfo.useHelperApp;
+  handlerInfo.alwaysAskBeforeHandling = false;
+  gHandlerService.store(handlerInfo);
+
+  registerCleanupFunction(() => {
+    gHandlerService.remove(handlerInfo);
+  });
+}
+
+async function runTest() {
+  initTestHandlers();
+
+  for (let page of Pages) {
+    await BrowserTestUtils.withNewTab(page, async function (aBrowser) {
+      await SpecialPowers.spawn(aBrowser, [], async () => {
+        let h = content.document.createElement("h1");
+        ok(h);
+        h.innerHTML = "My heading";
+        h.id = "my-heading";
+        content.document.body.append(h);
+        is(content.document.getElementById("my-heading"), h, "h exists");
+
+        let a = content.document.createElement("a");
+        ok(a);
+        a.innerHTML = "my link";
+        a.id = "my-link";
+        content.document.body.append(a);
+      });
+
+      await SpecialPowers.spawn(aBrowser, [], async () => {
+        let url = "test-proto://some-thing";
+
+        let a = content.document.getElementById("my-link");
+        ok(a);
+        a.href = url;
+        a.click();
+      });
+
+      await SpecialPowers.spawn(aBrowser, [], async () => {
+        ok(
+          content.document.getElementById("my-heading"),
+          "Page contents not erased"
+        );
+      });
+    });
+  }
+  await SpecialPowers.popPrefEnv();
+}
+
+add_task(runTest);
diff --git a/toolkit/components/remotebrowserutils/tests/browser/browser_httpCrossOriginOpenerPolicy.js b/toolkit/components/remotebrowserutils/tests/browser/browser_httpCrossOriginOpenerPolicy.js
new file mode 100644
index 0000000000..5f3eade823
--- /dev/null
+++ b/toolkit/components/remotebrowserutils/tests/browser/browser_httpCrossOriginOpenerPolicy.js
@@ -0,0 +1,410 @@
+"use strict";
+
+const COOP_PREF = "browser.tabs.remote.useCrossOriginOpenerPolicy";
+
+async function setPref() {
+  await SpecialPowers.pushPrefEnv({
+    set: [[COOP_PREF, true]],
+  });
+}
+
+async function unsetPref() {
+  await SpecialPowers.pushPrefEnv({
+    set: [[COOP_PREF, false]],
+  });
+}
+
+function httpURL(filename, host = "https://example.com") {
+  let root = getRootDirectory(gTestPath).replace(
+    "chrome://mochitests/content",
+    host
+  );
+  return root + filename;
+}
+
+async function performLoad(browser, opts, action) {
+  let loadedPromise = BrowserTestUtils.browserStopped(
+    browser,
+    opts.url,
+    opts.maybeErrorPage
+  );
+  await action();
+  await loadedPromise;
+}
+
+async function test_coop(
+  start,
+  target,
+  expectedProcessSwitch,
+  startRemoteTypeCheck,
+  targetRemoteTypeCheck
+) {
+  return BrowserTestUtils.withNewTab(
+    {
+      gBrowser,
+      url: start,
+      waitForStateStop: true,
+    },
+    async function (_browser) {
+      info(`test_coop: Test tab ready: ${start}`);
+
+      let browser = gBrowser.selectedBrowser;
+      let firstRemoteType = browser.remoteType;
+      let firstBC = browser.browsingContext;
+
+      info(`firstBC: ${firstBC.id} remoteType: ${firstRemoteType}`);
+
+      if (startRemoteTypeCheck) {
+        startRemoteTypeCheck(firstRemoteType);
+      }
+
+      await performLoad(
+        browser,
+        {
+          url: target,
+          maybeErrorPage: false,
+        },
+        async () => BrowserTestUtils.startLoadingURIString(browser, target)
+      );
+
+      info(`Navigated to: ${target}`);
+      browser = gBrowser.selectedBrowser;
+      let secondRemoteType = browser.remoteType;
+      let secondBC = browser.browsingContext;
+
+      info(`secondBC: ${secondBC.id} remoteType: ${secondRemoteType}`);
+      if (targetRemoteTypeCheck) {
+        targetRemoteTypeCheck(secondRemoteType);
+      }
+      if (expectedProcessSwitch) {
+        Assert.notEqual(firstBC.id, secondBC.id, `from: ${start} to ${target}`);
+      } else {
+        Assert.equal(firstBC.id, secondBC.id, `from: ${start} to ${target}`);
+      }
+    }
+  );
+}
+
+function waitForDownloadWindow() {
+  return new Promise(resolve => {
+    var listener = {
+      onOpenWindow: aXULWindow => {
+        info("Download window shown...");
+        Services.wm.removeListener(listener);
+
+        function downloadOnLoad() {
+          domwindow.removeEventListener("load", downloadOnLoad, true);
+
+          is(
+            domwindow.document.location.href,
+            "chrome://mozapps/content/downloads/unknownContentType.xhtml",
+            "Download page appeared"
+          );
+          resolve(domwindow);
+        }
+
+        var domwindow = aXULWindow.docShell.domWindow;
+        domwindow.addEventListener("load", downloadOnLoad, true);
+      },
+      onCloseWindow: aXULWindow => {},
+    };
+
+    Services.wm.addListener(listener);
+  });
+}
+
+async function waitForDownloadUI() {
+  return BrowserTestUtils.waitForEvent(DownloadsPanel.panel, "popupshown");
+}
+
+async function cleanupDownloads(downloadList) {
+  info("cleaning up downloads");
+  let [download] = await downloadList.getAll();
+  await downloadList.remove(download);
+  await download.finalize(true);
+
+  try {
+    if (Services.appinfo.OS === "WINNT") {
+      // We need to make the file writable to delete it on Windows.
+      await IOUtils.setPermissions(download.target.path, 0o600);
+    }
+    await IOUtils.remove(download.target.path);
+  } catch (error) {
+    info("The file " + download.target.path + " is not removed, " + error);
+  }
+
+  if (DownloadsPanel.panel.state !== "closed") {
+    let hiddenPromise = BrowserTestUtils.waitForEvent(
+      DownloadsPanel.panel,
+      "popuphidden"
+    );
+    DownloadsPanel.hidePanel();
+    await hiddenPromise;
+  }
+  is(
+    DownloadsPanel.panel.state,
+    "closed",
+    "Check that the download panel is closed"
+  );
+}
+
+async function test_download_from(initCoop, downloadCoop) {
+  return BrowserTestUtils.withNewTab("about:blank", async function (_browser) {
+    info(`test_download: Test tab ready`);
+
+    let start = httpURL(
+      "coop_header.sjs?downloadPage&coop=" + initCoop,
+      "https://example.com"
+    );
+    await performLoad(
+      _browser,
+      {
+        url: start,
+        maybeErrorPage: false,
+      },
+      async () => {
+        info(`test_download: Loading download page ${start}`);
+        return BrowserTestUtils.startLoadingURIString(_browser, start);
+      }
+    );
+
+    info(`test_download: Download page ready ${start}`);
+    info(`Downloading ${downloadCoop}`);
+
+    let expectDialog = Services.prefs.getBoolPref(
+      "browser.download.always_ask_before_handling_new_types",
+      false
+    );
+    let resultPromise = expectDialog
+      ? waitForDownloadWindow()
+      : waitForDownloadUI();
+    let browser = gBrowser.selectedBrowser;
+    SpecialPowers.spawn(browser, [downloadCoop], downloadCoop => {
+      content.document.getElementById(downloadCoop).click();
+    });
+
+    // if the download page doesn't appear, the promise leads a timeout.
+    if (expectDialog) {
+      let win = await resultPromise;
+      await BrowserTestUtils.closeWindow(win);
+    } else {
+      // verify link target will get automatically downloaded
+      await resultPromise;
+      let downloadList = await Downloads.getList(Downloads.PUBLIC);
+      is((await downloadList.getAll()).length, 1, "Target was downloaded");
+      await cleanupDownloads(downloadList);
+      is((await downloadList.getAll()).length, 0, "Downloads were cleaned up");
+    }
+  });
+}
+
+// Check that multiple navigations of the same tab will only switch processes
+// when it's expected.
+add_task(async function test_multiple_nav_process_switches() {
+  await setPref();
+  await BrowserTestUtils.withNewTab(
+    {
+      gBrowser,
+      url: httpURL("coop_header.sjs", "https://example.org"),
+      waitForStateStop: true,
+    },
+    async function (browser) {
+      let prevBC = browser.browsingContext;
+
+      let target = httpURL("coop_header.sjs?.", "https://example.org");
+      await performLoad(
+        browser,
+        {
+          url: target,
+          maybeErrorPage: false,
+        },
+        async () => BrowserTestUtils.startLoadingURIString(browser, target)
+      );
+
+      Assert.equal(prevBC, browser.browsingContext);
+      prevBC = browser.browsingContext;
+
+      target = httpURL(
+        "coop_header.sjs?coop=same-origin",
+        "https://example.org"
+      );
+      await performLoad(
+        browser,
+        {
+          url: target,
+          maybeErrorPage: false,
+        },
+        async () => BrowserTestUtils.startLoadingURIString(browser, target)
+      );
+
+      Assert.notEqual(prevBC, browser.browsingContext);
+      prevBC = browser.browsingContext;
+
+      target = httpURL(
+        "coop_header.sjs?coop=same-origin",
+        "https://example.com"
+      );
+      await performLoad(
+        browser,
+        {
+          url: target,
+          maybeErrorPage: false,
+        },
+        async () => BrowserTestUtils.startLoadingURIString(browser, target)
+      );
+
+      Assert.notEqual(prevBC, browser.browsingContext);
+      prevBC = browser.browsingContext;
+
+      target = httpURL(
+        "coop_header.sjs?coop=same-origin&index=4",
+        "https://example.com"
+      );
+      await performLoad(
+        browser,
+        {
+          url: target,
+          maybeErrorPage: false,
+        },
+        async () => BrowserTestUtils.startLoadingURIString(browser, target)
+      );
+
+      Assert.equal(prevBC, browser.browsingContext);
+    }
+  );
+});
+
+add_task(async function test_disabled() {
+  await unsetPref();
+  await test_coop(
+    httpURL("coop_header.sjs", "https://example.com"),
+    httpURL("coop_header.sjs", "https://example.com"),
+    false
+  );
+  await test_coop(
+    httpURL("coop_header.sjs?coop=same-origin", "http://example.com"),
+    httpURL("coop_header.sjs", "http://example.com"),
+    false
+  );
+  await test_coop(
+    httpURL("coop_header.sjs", "http://example.com"),
+    httpURL("coop_header.sjs?coop=same-origin", "http://example.com"),
+    false
+  );
+});
+
+add_task(async function test_enabled() {
+  await setPref();
+
+  function checkIsCoopRemoteType(remoteType) {
+    Assert.ok(
+      remoteType.startsWith(E10SUtils.WEB_REMOTE_COOP_COEP_TYPE_PREFIX),
+      `${remoteType} expected to be coop`
+    );
+  }
+
+  function checkIsNotCoopRemoteType(remoteType) {
+    if (gFissionBrowser) {
+      Assert.ok(
+        remoteType.startsWith("webIsolated="),
+        `${remoteType} expected to start with webIsolated=`
+      );
+    } else {
+      Assert.equal(
+        remoteType,
+        E10SUtils.WEB_REMOTE_TYPE,
+        `${remoteType} expected to be web`
+      );
+    }
+  }
+
+  await test_coop(
+    httpURL("coop_header.sjs", "https://example.com"),
+    httpURL("coop_header.sjs", "https://example.com"),
+    false,
+    checkIsNotCoopRemoteType,
+    checkIsNotCoopRemoteType
+  );
+  await test_coop(
+    httpURL("coop_header.sjs", "https://example.com"),
+    httpURL("coop_header.sjs?coop=same-origin", "https://example.org"),
+    true,
+    checkIsNotCoopRemoteType,
+    checkIsNotCoopRemoteType
+  );
+  await test_coop(
+    httpURL("coop_header.sjs?coop=same-origin&index=1", "https://example.com"),
+    httpURL("coop_header.sjs?coop=same-origin&index=1", "https://example.org"),
+    true,
+    checkIsNotCoopRemoteType,
+    checkIsNotCoopRemoteType
+  );
+  await test_coop(
+    httpURL("coop_header.sjs", "https://example.com"),
+    httpURL(
+      "coop_header.sjs?coop=same-origin&coep=require-corp",
+      "https://example.com"
+    ),
+    true,
+    checkIsNotCoopRemoteType,
+    checkIsCoopRemoteType
+  );
+  await test_coop(
+    httpURL(
+      "coop_header.sjs?coop=same-origin&coep=require-corp&index=2",
+      "https://example.com"
+    ),
+    httpURL(
+      "coop_header.sjs?coop=same-origin&coep=require-corp&index=3",
+      "https://example.com"
+    ),
+    false,
+    checkIsCoopRemoteType,
+    checkIsCoopRemoteType
+  );
+  await test_coop(
+    httpURL(
+      "coop_header.sjs?coop=same-origin&coep=require-corp&index=4",
+      "https://example.com"
+    ),
+    httpURL("coop_header.sjs", "https://example.com"),
+    true,
+    checkIsCoopRemoteType,
+    checkIsNotCoopRemoteType
+  );
+  await test_coop(
+    httpURL(
+      "coop_header.sjs?coop=same-origin&coep=require-corp&index=5",
+      "https://example.com"
+    ),
+    httpURL(
+      "coop_header.sjs?coop=same-origin&coep=require-corp&index=6",
+      "https://example.org"
+    ),
+    true,
+    checkIsCoopRemoteType,
+    checkIsCoopRemoteType
+  );
+});
+
+add_task(async function test_download() {
+  requestLongerTimeout(4);
+  await setPref();
+
+  let initCoopArray = ["", "same-origin"];
+
+  let downloadCoopArray = [
+    "no-coop",
+    "same-origin",
+    "same-origin-allow-popups",
+  ];
+
+  // If the coop mismatch between current page and download link, clicking the
+  // download link will make the page empty and popup the download window. That
+  // forces us to reload the page every time.
+  for (var initCoop of initCoopArray) {
+    for (var downloadCoop of downloadCoopArray) {
+      await test_download_from(initCoop, downloadCoop);
+    }
+  }
+});
diff --git a/toolkit/components/remotebrowserutils/tests/browser/browser_httpToFileHistory.js b/toolkit/components/remotebrowserutils/tests/browser/browser_httpToFileHistory.js
new file mode 100644
index 0000000000..1072f5f6d1
--- /dev/null
+++ b/toolkit/components/remotebrowserutils/tests/browser/browser_httpToFileHistory.js
@@ -0,0 +1,115 @@
+const HISTORY = [
+  { url: httpURL("dummy_page.html") },
+  { url: fileURL("dummy_page.html") },
+  { url: httpURL("dummy_page.html") },
+];
+
+function reversed(list) {
+  let copy = list.slice();
+  copy.reverse();
+  return copy;
+}
+
+function butLast(list) {
+  return list.slice(0, -1);
+}
+
+async function runTest() {
+  await BrowserTestUtils.withNewTab({ gBrowser }, async function (aBrowser) {
+    // Perform initial load of each URL in the history.
+    let count = 0;
+    let index = -1;
+    for (let { url } of HISTORY) {
+      BrowserTestUtils.startLoadingURIString(aBrowser, url);
+
+      await BrowserTestUtils.browserLoaded(aBrowser, false, loaded => {
+        return (
+          Services.io.newURI(loaded).scheme == Services.io.newURI(url).scheme
+        );
+      });
+
+      count++;
+      index++;
+      await SpecialPowers.spawn(
+        aBrowser,
+        [{ count, index, url }],
+        async function ({ count, index, url }) {
+          docShell.QueryInterface(Ci.nsIWebNavigation);
+
+          is(
+            docShell.sessionHistory.count,
+            count,
+            "Initial Navigation Count Match"
+          );
+          is(
+            docShell.sessionHistory.index,
+            index,
+            "Initial Navigation Index Match"
+          );
+
+          let real = Services.io.newURI(content.location.href);
+          let expect = Services.io.newURI(url);
+          is(real.scheme, expect.scheme, "Initial Navigation URL Scheme");
+        }
+      );
+    }
+
+    // Go back to the first entry.
+    for (let { url } of reversed(HISTORY).slice(1)) {
+      SpecialPowers.spawn(aBrowser, [], () => {
+        content.history.back();
+      });
+      await BrowserTestUtils.browserLoaded(aBrowser, false, loaded => {
+        return (
+          Services.io.newURI(loaded).scheme == Services.io.newURI(url).scheme
+        );
+      });
+
+      index--;
+      await SpecialPowers.spawn(
+        aBrowser,
+        [{ count, index, url }],
+        async function ({ count, index, url }) {
+          docShell.QueryInterface(Ci.nsIWebNavigation);
+
+          is(docShell.sessionHistory.count, count, "Go Back Count Match");
+          is(docShell.sessionHistory.index, index, "Go Back Index Match");
+
+          let real = Services.io.newURI(content.location.href);
+          let expect = Services.io.newURI(url);
+          is(real.scheme, expect.scheme, "Go Back URL Scheme");
+        }
+      );
+    }
+
+    // Go forward to the last entry.
+    for (let { url } of HISTORY.slice(1)) {
+      SpecialPowers.spawn(aBrowser, [], () => {
+        content.history.forward();
+      });
+      await BrowserTestUtils.browserLoaded(aBrowser, false, loaded => {
+        return (
+          Services.io.newURI(loaded).scheme == Services.io.newURI(url).scheme
+        );
+      });
+
+      index++;
+      await SpecialPowers.spawn(
+        aBrowser,
+        [{ count, index, url }],
+        async function ({ count, index, url }) {
+          docShell.QueryInterface(Ci.nsIWebNavigation);
+
+          is(docShell.sessionHistory.count, count, "Go Forward Count Match");
+          is(docShell.sessionHistory.index, index, "Go Forward Index Match");
+
+          let real = Services.io.newURI(content.location.href);
+          let expect = Services.io.newURI(url);
+          is(real.scheme, expect.scheme, "Go Forward URL Scheme");
+        }
+      );
+    }
+  });
+}
+
+add_task(runTest);
diff --git a/toolkit/components/remotebrowserutils/tests/browser/browser_oopProcessSwap.js b/toolkit/components/remotebrowserutils/tests/browser/browser_oopProcessSwap.js
new file mode 100644
index 0000000000..3286227d37
--- /dev/null
+++ b/toolkit/components/remotebrowserutils/tests/browser/browser_oopProcessSwap.js
@@ -0,0 +1,161 @@
+add_task(async function oopProcessSwap() {
+  const FILE = fileURL("dummy_page.html");
+  const WEB = httpURL("file_postmsg_parent.html");
+
+  let win = await BrowserTestUtils.openNewBrowserWindow({ fission: true });
+
+  await BrowserTestUtils.withNewTab(
+    { gBrowser: win.gBrowser, url: FILE },
+    async browser => {
+      is(browser.browsingContext.children.length, 0);
+
+      info("creating an in-process frame");
+      let frameId = await SpecialPowers.spawn(
+        browser,
+        [{ FILE }],
+        async ({ FILE }) => {
+          let iframe = content.document.createElement("iframe");
+          iframe.setAttribute("src", FILE);
+          content.document.body.appendChild(iframe);
+
+          // The nested URI should be same-process
+          ok(iframe.browsingContext.docShell, "Should be in-process");
+
+          return iframe.browsingContext.id;
+        }
+      );
+
+      is(browser.browsingContext.children.length, 1);
+
+      info("navigating to x-process frame");
+      let oopinfo = await SpecialPowers.spawn(
+        browser,
+        [{ WEB }],
+        async ({ WEB }) => {
+          let iframe = content.document.querySelector("iframe");
+
+          iframe.contentWindow.location = WEB;
+
+          let data = await new Promise(resolve => {
+            content.window.addEventListener(
+              "message",
+              function (evt) {
+                info("oop iframe loaded");
+                is(evt.source, iframe.contentWindow);
+                resolve(evt.data);
+              },
+              { once: true }
+            );
+          });
+
+          is(iframe.browsingContext.docShell, null, "Should be out-of-process");
+          is(
+            iframe.browsingContext.embedderElement,
+            iframe,
+            "correct embedder"
+          );
+
+          return {
+            location: data.location,
+            browsingContextId: iframe.browsingContext.id,
+          };
+        }
+      );
+
+      is(browser.browsingContext.children.length, 1);
+
+      if (Services.prefs.getBoolPref("fission.preserve_browsing_contexts")) {
+        is(
+          frameId,
+          oopinfo.browsingContextId,
+          `BrowsingContext should not have changed (${frameId} != ${oopinfo.browsingContextId})`
+        );
+      }
+      is(oopinfo.location, WEB, "correct location");
+    }
+  );
+
+  await BrowserTestUtils.closeWindow(win);
+});
+
+add_task(async function oopOriginProcessSwap() {
+  const COM_DUMMY = httpURL("dummy_page.html", "https://example.com/");
+  const ORG_POSTMSG = httpURL(
+    "file_postmsg_parent.html",
+    "https://example.org/"
+  );
+
+  let win = await BrowserTestUtils.openNewBrowserWindow({ fission: true });
+
+  await BrowserTestUtils.withNewTab(
+    { gBrowser: win.gBrowser, url: COM_DUMMY },
+    async browser => {
+      is(browser.browsingContext.children.length, 0);
+
+      info("creating an in-process frame");
+      let frameId = await SpecialPowers.spawn(
+        browser,
+        [{ COM_DUMMY }],
+        async ({ COM_DUMMY }) => {
+          let iframe = content.document.createElement("iframe");
+          iframe.setAttribute("src", COM_DUMMY);
+          content.document.body.appendChild(iframe);
+
+          // The nested URI should be same-process
+          ok(iframe.browsingContext.docShell, "Should be in-process");
+
+          return iframe.browsingContext.id;
+        }
+      );
+
+      is(browser.browsingContext.children.length, 1);
+
+      info("navigating to x-process frame");
+      let oopinfo = await SpecialPowers.spawn(
+        browser,
+        [{ ORG_POSTMSG }],
+        async ({ ORG_POSTMSG }) => {
+          let iframe = content.document.querySelector("iframe");
+
+          iframe.contentWindow.location = ORG_POSTMSG;
+
+          let data = await new Promise(resolve => {
+            content.window.addEventListener(
+              "message",
+              function (evt) {
+                info("oop iframe loaded");
+                is(evt.source, iframe.contentWindow);
+                resolve(evt.data);
+              },
+              { once: true }
+            );
+          });
+
+          is(iframe.browsingContext.docShell, null, "Should be out-of-process");
+          is(
+            iframe.browsingContext.embedderElement,
+            iframe,
+            "correct embedder"
+          );
+
+          return {
+            location: data.location,
+            browsingContextId: iframe.browsingContext.id,
+          };
+        }
+      );
+
+      is(browser.browsingContext.children.length, 1);
+      if (Services.prefs.getBoolPref("fission.preserve_browsing_contexts")) {
+        is(
+          frameId,
+          oopinfo.browsingContextId,
+          `BrowsingContext should not have changed (${frameId} != ${oopinfo.browsingContextId})`
+        );
+      }
+      is(oopinfo.location, ORG_POSTMSG, "correct location");
+    }
+  );
+
+  await BrowserTestUtils.closeWindow(win);
+});
diff --git a/toolkit/components/remotebrowserutils/tests/browser/coop_header.sjs b/toolkit/components/remotebrowserutils/tests/browser/coop_header.sjs
new file mode 100644
index 0000000000..03ed73af76
--- /dev/null
+++ b/toolkit/components/remotebrowserutils/tests/browser/coop_header.sjs
@@ -0,0 +1,57 @@
+function handleRequest(request, response) {
+  let query = new URLSearchParams(request.queryString);
+
+  response.setStatusLine(request.httpVersion, 200, "OK");
+
+  // The tests for Cross-Origin-Opener-Policy unfortunately depend on
+  // BFCacheInParent not kicking in, as with that enabled, it is not possible to
+  // tell whether the BrowsingContext switch was caused by the BFCache
+  // navigation or by the COOP mismatch. This header disables BFCache for the
+  // coop documents, and should avoid the issue.
+  response.setHeader("Cache-Control", "no-store", false);
+
+  let isDownloadPage = false;
+  let isDownloadFile = false;
+
+  query.forEach((value, name) => {
+    if (name === "downloadPage") {
+      isDownloadPage = true;
+    } else if (name === "downloadFile") {
+      isDownloadFile = true;
+    } else if (name == "coop") {
+      response.setHeader("Cross-Origin-Opener-Policy", unescape(value), false);
+    } else if (name == "coep") {
+      response.setHeader(
+        "Cross-Origin-Embedder-Policy",
+        unescape(value),
+        false
+      );
+    }
+  });
+
+  let downloadHTML = "";
+  if (isDownloadPage) {
+    ["no-coop", "same-origin", "same-origin-allow-popups"].forEach(coop => {
+      downloadHTML +=
+        '<a href="https://example.com/browser/toolkit/components/remotebrowserutils/tests/browser/coop_header.sjs?downloadFile&' +
+        (coop === "no-coop" ? "" : coop) +
+        '" id="' +
+        coop +
+        '" download>' +
+        unescape(coop) +
+        "</a> <br>";
+    });
+  }
+
+  if (isDownloadFile) {
+    response.setHeader("Content-Type", "application/octet-stream", false);
+    response.write("BINARY_DATA");
+  } else {
+    response.setHeader("Content-Type", "text/html; charset=utf-8", false);
+    response.write(
+      "<!DOCTYPE html><html><body><p>Hello world</p> " +
+        downloadHTML +
+        "</body></html>"
+    );
+  }
+}
diff --git a/toolkit/components/remotebrowserutils/tests/browser/dummy_page.html b/toolkit/components/remotebrowserutils/tests/browser/dummy_page.html
new file mode 100644
index 0000000000..8205e90d5d
--- /dev/null
+++ b/toolkit/components/remotebrowserutils/tests/browser/dummy_page.html
@@ -0,0 +1,13 @@
+<!DOCTYPE html>
+<meta charset="utf-8">
+
+<html>
+<body>
+<p>Page</p>
+    <script>
+        // Prevent this page from being stored in the bfcache for the
+        // browser_httpToFileHistory.js test
+        window.blockBFCache = new RTCPeerConnection();
+    </script>
+</body>
+</html>
diff --git a/toolkit/components/remotebrowserutils/tests/browser/file_postmsg_parent.html b/toolkit/components/remotebrowserutils/tests/browser/file_postmsg_parent.html
new file mode 100644
index 0000000000..d5f640775b
--- /dev/null
+++ b/toolkit/components/remotebrowserutils/tests/browser/file_postmsg_parent.html
@@ -0,0 +1,5 @@
+<!DOCTYPE html>
+<html>
+<body onload="parent.postMessage({location: window.location.href}, '*')">
+</body>
+</html>
diff --git a/toolkit/components/remotebrowserutils/tests/browser/head.js b/toolkit/components/remotebrowserutils/tests/browser/head.js
new file mode 100644
index 0000000000..ffdd9375cf
--- /dev/null
+++ b/toolkit/components/remotebrowserutils/tests/browser/head.js
@@ -0,0 +1,17 @@
+function fileURL(filename) {
+  let ifile = getChromeDir(getResolvedURI(gTestPath));
+  ifile.append(filename);
+  return Services.io.newFileURI(ifile).spec;
+}
+
+function httpURL(filename, host = "https://example.com/") {
+  let root = getRootDirectory(gTestPath).replace(
+    "chrome://mochitests/content/",
+    host
+  );
+  return root + filename;
+}
+
+function add307(url, host = "https://example.com/") {
+  return httpURL("307redirect.sjs?" + url, host);
+}
diff --git a/toolkit/components/remotebrowserutils/tests/browser/print_postdata.sjs b/toolkit/components/remotebrowserutils/tests/browser/print_postdata.sjs
new file mode 100644
index 0000000000..bd9c18f7ea
--- /dev/null
+++ b/toolkit/components/remotebrowserutils/tests/browser/print_postdata.sjs
@@ -0,0 +1,28 @@
+const CC = Components.Constructor;
+const BinaryInputStream = CC(
+  "@mozilla.org/binaryinputstream;1",
+  "nsIBinaryInputStream",
+  "setInputStream"
+);
+
+function handleRequest(request, response) {
+  response.setHeader("Content-Type", "text/plain", false);
+  if (request.method == "GET") {
+    response.write(request.queryString);
+  } else {
+    var body = new BinaryInputStream(request.bodyInputStream);
+
+    var avail;
+    var bytes = [];
+
+    while ((avail = body.available()) > 0) {
+      Array.prototype.push.apply(bytes, body.readByteArray(avail));
+    }
+
+    var data = String.fromCharCode.apply(null, bytes);
+    if (request.queryString) {
+      data = data + "?" + request.queryString;
+    }
+    response.bodyOutputStream.write(data, data.length);
+  }
+}