Adding upstream version 115.8.0esr.upstream/115.8.0esr

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

16 files changed, 2744 insertions, 0 deletions

diff --git a/uriloader/exthandler/tests/unit/handlers.json b/uriloader/exthandler/tests/unit/handlers.json
new file mode 100644
index 0000000000..51ce581d83
--- /dev/null
+++ b/uriloader/exthandler/tests/unit/handlers.json
@@ -0,0 +1,83 @@
+{
+  "defaultHandlersVersion": {
+    "en-US": 999
+  },
+  "mimeTypes": {
+    "example/type.handleinternally": {
+      "unknownProperty": "preserved",
+      "action": 3,
+      "extensions": ["example_one"]
+    },
+    "example/type.savetodisk": {
+      "action": 0,
+      "ask": true,
+      "handlers": [
+        {
+          "name": "Example Default Handler",
+          "uriTemplate": "https://www.example.com/?url=%s"
+        }
+      ],
+      "extensions": ["example_two", "example_three"]
+    },
+    "example/type.usehelperapp": {
+      "action": 2,
+      "ask": true,
+      "handlers": [
+        {
+          "name": "Example Default Handler",
+          "uriTemplate": "https://www.example.com/?url=%s"
+        },
+        {
+          "name": "Example Possible Handler One",
+          "uriTemplate": "http://www.example.com/?id=1&url=%s"
+        },
+        {
+          "name": "Example Possible Handler Two",
+          "uriTemplate": "http://www.example.com/?id=2&url=%s"
+        }
+      ],
+      "extensions": ["example_two", "example_three"]
+    },
+    "example/type.usesystemdefault": {
+      "action": 4,
+      "handlers": [
+        null,
+        {
+          "name": "Example Possible Handler",
+          "uriTemplate": "http://www.example.com/?url=%s"
+        }
+      ]
+    }
+  },
+  "schemes": {
+    "examplescheme.usehelperapp": {
+      "action": 2,
+      "ask": true,
+      "handlers": [
+        {
+          "name": "Example Default Handler",
+          "uriTemplate": "https://www.example.com/?url=%s"
+        },
+        {
+          "name": "Example Possible Handler One",
+          "uriTemplate": "http://www.example.com/?id=1&url=%s"
+        },
+        {
+          "name": "Example Possible Handler Two",
+          "uriTemplate": "http://www.example.com/?id=2&url=%s"
+        }
+      ]
+    },
+    "examplescheme.usesystemdefault": {
+      "action": 4,
+      "handlers": [
+        null,
+        {
+          "name": "Example Possible Handler",
+          "uriTemplate": "http://www.example.com/?url=%s"
+        }
+      ]
+    }
+  },
+  "isDownloadsImprovementsAlreadyMigrated": true
+}
diff --git a/uriloader/exthandler/tests/unit/head.js b/uriloader/exthandler/tests/unit/head.js
new file mode 100644
index 0000000000..2f65582ae9
--- /dev/null
+++ b/uriloader/exthandler/tests/unit/head.js
@@ -0,0 +1,82 @@
+/* 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/. */
+
+/*
+ * Initialization for tests related to invoking external handler applications.
+ */
+
+"use strict";
+
+var { AppConstants } = ChromeUtils.importESModule(
+  "resource://gre/modules/AppConstants.sys.mjs"
+);
+var { FileUtils } = ChromeUtils.importESModule(
+  "resource://gre/modules/FileUtils.sys.mjs"
+);
+var { NetUtil } = ChromeUtils.import("resource://gre/modules/NetUtil.jsm");
+var { XPCOMUtils } = ChromeUtils.importESModule(
+  "resource://gre/modules/XPCOMUtils.sys.mjs"
+);
+
+const { HandlerServiceTestUtils } = ChromeUtils.importESModule(
+  "resource://testing-common/HandlerServiceTestUtils.sys.mjs"
+);
+var { TestUtils } = ChromeUtils.importESModule(
+  "resource://testing-common/TestUtils.sys.mjs"
+);
+
+XPCOMUtils.defineLazyServiceGetter(
+  this,
+  "gHandlerService",
+  "@mozilla.org/uriloader/handler-service;1",
+  "nsIHandlerService"
+);
+
+do_get_profile();
+
+let jsonPath = PathUtils.join(PathUtils.profileDir, "handlers.json");
+
+/**
+ * Unloads the nsIHandlerService data store, so the back-end file can be
+ * accessed or modified, and the new data will be loaded at the next access.
+ */
+let unloadHandlerStore = async function () {
+  // If this function is called before the nsIHandlerService instance has been
+  // initialized for the first time, the observer below will not be registered.
+  // We have to force initialization to prevent the function from stalling.
+  gHandlerService;
+
+  let promise = TestUtils.topicObserved("handlersvc-json-replace-complete");
+  Services.obs.notifyObservers(null, "handlersvc-json-replace");
+  await promise;
+};
+
+/**
+ * Unloads the data store and deletes it.
+ */
+let deleteHandlerStore = async function () {
+  await unloadHandlerStore();
+
+  await IOUtils.remove(jsonPath, { ignoreAbsent: true });
+
+  Services.prefs.clearUserPref("gecko.handlerService.defaultHandlersVersion");
+};
+
+/**
+ * Unloads the data store and replaces it with the test data file.
+ */
+let copyTestDataToHandlerStore = async function () {
+  await unloadHandlerStore();
+
+  await IOUtils.copy(do_get_file("handlers.json").path, jsonPath);
+
+  Services.prefs.setIntPref("gecko.handlerService.defaultHandlersVersion", 100);
+};
+
+/**
+ * Ensures the files are removed and the services unloaded when the tests end.
+ */
+registerCleanupFunction(async function test_terminate() {
+  await deleteHandlerStore();
+});
diff --git a/uriloader/exthandler/tests/unit/mailcap b/uriloader/exthandler/tests/unit/mailcap
new file mode 100644
index 0000000000..dc93ef8042
--- /dev/null
+++ b/uriloader/exthandler/tests/unit/mailcap
@@ -0,0 +1,2 @@
+text/plain; cat '%s'; needsterminal
+text/plain; sed '%s'
diff --git a/uriloader/exthandler/tests/unit/test_badMIMEType.js b/uriloader/exthandler/tests/unit/test_badMIMEType.js
new file mode 100644
index 0000000000..49c5e8d848
--- /dev/null
+++ b/uriloader/exthandler/tests/unit/test_badMIMEType.js
@@ -0,0 +1,29 @@
+/* -*- indent-tabs-mode: nil; js-indent-level: 2 -*-
+ * 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/. */
+
+function run_test() {
+  // "text/plain" has an 0xFF character appended to it.  This means it's an
+  // invalid string, which is tricky to enter using a text editor (I used
+  // emacs' hexl-mode).  It also means an ordinary text editor might drop it
+  // or convert it to something that *is* valid (in UTF8).  So we measure
+  // its length to make sure this hasn't happened.
+  var badMimeType = "text/plainÿ";
+  Assert.equal(badMimeType.length, 11);
+  try {
+    Cc["@mozilla.org/mime;1"]
+      .getService(Ci.nsIMIMEService)
+      .getFromTypeAndExtension(badMimeType, "txt");
+  } catch (e) {
+    if (
+      !(e instanceof Ci.nsIException) ||
+      e.result != Cr.NS_ERROR_NOT_AVAILABLE
+    ) {
+      throw e;
+    }
+    // This is an expected exception, thrown if the type can't be determined
+  }
+  // Not crashing is good enough
+  Assert.equal(true, true);
+}
diff --git a/uriloader/exthandler/tests/unit/test_defaults_handlerService.js b/uriloader/exthandler/tests/unit/test_defaults_handlerService.js
new file mode 100644
index 0000000000..47fd18a642
--- /dev/null
+++ b/uriloader/exthandler/tests/unit/test_defaults_handlerService.js
@@ -0,0 +1,159 @@
+/* Any copyright is dedicated to the Public Domain.
+http://creativecommons.org/publicdomain/zero/1.0/ */
+
+"use strict";
+
+XPCOMUtils.defineLazyServiceGetter(
+  this,
+  "gExternalProtocolService",
+  "@mozilla.org/uriloader/external-protocol-service;1",
+  "nsIExternalProtocolService"
+);
+ChromeUtils.defineESModuleGetters(this, {
+  kHandlerList: "resource://gre/modules/handlers/HandlerList.sys.mjs",
+});
+
+add_task(async function test_check_defaults_get_added() {
+  let protocols = Object.keys(kHandlerList.default.schemes);
+  for (let protocol of protocols) {
+    let protocolHandlerCount =
+      kHandlerList.default.schemes[protocol].handlers.length;
+    Assert.ok(
+      gHandlerService.wrappedJSObject._store.data.schemes[protocol].stubEntry,
+      `Expect stub for ${protocol}`
+    );
+    let info = gExternalProtocolService.getProtocolHandlerInfo(protocol, {});
+    Assert.ok(
+      info,
+      `Should be able to get protocol handler info for ${protocol}`
+    );
+    let handlers = Array.from(
+      info.possibleApplicationHandlers.enumerate(Ci.nsIHandlerApp)
+    );
+    handlers = handlers.filter(h => h instanceof Ci.nsIWebHandlerApp);
+    Assert.equal(
+      handlers.length,
+      protocolHandlerCount,
+      `Default web handlers for ${protocol} should match`
+    );
+    let { alwaysAskBeforeHandling, preferredAction } = info;
+    // Actually store something, pretending there was a change:
+    let infoToWrite = gExternalProtocolService.getProtocolHandlerInfo(
+      protocol,
+      {}
+    );
+    gHandlerService.store(infoToWrite);
+    ok(
+      !gHandlerService.wrappedJSObject._store.data.schemes[protocol].stubEntry,
+      "Expect stub entry info to go away"
+    );
+
+    let newInfo = gExternalProtocolService.getProtocolHandlerInfo(protocol, {});
+    Assert.equal(
+      alwaysAskBeforeHandling,
+      newInfo.alwaysAskBeforeHandling,
+      protocol + " - always ask shouldn't change"
+    );
+    Assert.equal(
+      preferredAction,
+      newInfo.preferredAction,
+      protocol + " - preferred action shouldn't change"
+    );
+    await deleteHandlerStore();
+  }
+});
+
+add_task(async function test_check_default_modification() {
+  Assert.ok(
+    true,
+    JSON.stringify(gHandlerService.wrappedJSObject._store.data.schemes.mailto)
+  );
+  Assert.ok(
+    gHandlerService.wrappedJSObject._store.data.schemes.mailto.stubEntry,
+    "Expect stub for mailto"
+  );
+  let mailInfo = gExternalProtocolService.getProtocolHandlerInfo("mailto", {});
+  mailInfo.alwaysAskBeforeHandling = false;
+  mailInfo.preferredAction = Ci.nsIHandlerInfo.useSystemDefault;
+  gHandlerService.store(mailInfo);
+  Assert.ok(
+    !gHandlerService.wrappedJSObject._store.data.schemes.mailto.stubEntry,
+    "Stub entry should be removed immediately."
+  );
+  let newMail = gExternalProtocolService.getProtocolHandlerInfo("mailto", {});
+  Assert.equal(newMail.preferredAction, Ci.nsIHandlerInfo.useSystemDefault);
+  Assert.equal(newMail.alwaysAskBeforeHandling, false);
+  await deleteHandlerStore();
+});
+
+add_task(async function test_migrations() {
+  const kTestData = [
+    ["A", "http://compose.mail.yahoo.co.jp/ym/Compose?To=%s"],
+    ["B", "http://www.inbox.lv/rfc2368/?value=%s"],
+    ["C", "http://poczta.interia.pl/mh/?mailto=%s"],
+    ["D", "http://win.mail.ru/cgi-bin/sentmsg?mailto=%s"],
+  ];
+  // Set up the test handlers. This doesn't use prefs like the previous test,
+  // because we now refuse to import insecure handler prefs. They can only
+  // exist if they were added into the handler store before this restriction
+  // was created (bug 1526890).
+  gHandlerService.wrappedJSObject._injectDefaultProtocolHandlers();
+  let handler = gExternalProtocolService.getProtocolHandlerInfo("mailto");
+  while (handler.possibleApplicationHandlers.length) {
+    handler.possibleApplicationHandlers.removeElementAt(0);
+  }
+  for (let [name, uriTemplate] of kTestData) {
+    let app = Cc["@mozilla.org/uriloader/web-handler-app;1"].createInstance(
+      Ci.nsIWebHandlerApp
+    );
+    app.uriTemplate = uriTemplate;
+    app.name = name;
+    handler.possibleApplicationHandlers.appendElement(app);
+  }
+  gHandlerService.store(handler);
+
+  // Now migrate them:
+  Services.prefs.setCharPref("browser.handlers.migrations", "blah,secure-mail");
+  gHandlerService.wrappedJSObject._migrateProtocolHandlersIfNeeded();
+
+  // Now check the result:
+  handler = gExternalProtocolService.getProtocolHandlerInfo("mailto");
+
+  let expectedURIs = new Set([
+    "https://mail.yahoo.co.jp/compose/?To=%s",
+    "https://mail.inbox.lv/compose?to=%s",
+    "https://poczta.interia.pl/mh/?mailto=%s",
+    "https://e.mail.ru/cgi-bin/sentmsg?mailto=%s",
+  ]);
+
+  let possibleApplicationHandlers = Array.from(
+    handler.possibleApplicationHandlers.enumerate(Ci.nsIWebHandlerApp)
+  );
+  // Set iterators are stable to deletion, so this works:
+  for (let expected of expectedURIs) {
+    for (let app of possibleApplicationHandlers) {
+      if (app instanceof Ci.nsIWebHandlerApp && app.uriTemplate == expected) {
+        Assert.ok(true, "Found handler with URI " + expected);
+        // ... even when we remove items.
+        expectedURIs.delete(expected);
+        break;
+      }
+    }
+  }
+  Assert.equal(expectedURIs.size, 0, "Should have seen all the expected URIs.");
+
+  for (let app of possibleApplicationHandlers) {
+    if (app instanceof Ci.nsIWebHandlerApp) {
+      Assert.ok(
+        !kTestData.some(n => n[1] == app.uriTemplate),
+        "Should not be any of the original handlers"
+      );
+    }
+  }
+
+  Assert.ok(
+    !handler.preferredApplicationHandler,
+    "Shouldn't have preferred handler initially."
+  );
+  await deleteHandlerStore();
+});
diff --git a/uriloader/exthandler/tests/unit/test_downloads_improvements_migration.js b/uriloader/exthandler/tests/unit/test_downloads_improvements_migration.js
new file mode 100644
index 0000000000..49e4493b23
--- /dev/null
+++ b/uriloader/exthandler/tests/unit/test_downloads_improvements_migration.js
@@ -0,0 +1,244 @@
+/* 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/. */
+
+const handlerSvc = Cc["@mozilla.org/uriloader/handler-service;1"].getService(
+  Ci.nsIHandlerService
+);
+
+const mimeSvc = Cc["@mozilla.org/mime;1"].getService(Ci.nsIMIMEService);
+
+const { Integration } = ChromeUtils.importESModule(
+  "resource://gre/modules/Integration.sys.mjs"
+);
+
+/* global DownloadIntegration */
+Integration.downloads.defineESModuleGetter(
+  this,
+  "DownloadIntegration",
+  "resource://gre/modules/DownloadIntegration.sys.mjs"
+);
+
+/**
+ * Tests that the migration runs and that only
+ * files with preferredAction alwaysAsk are updated.
+ */
+add_task(async function test_migration() {
+  // Create mock implementation of shouldDownloadInternally for test case
+  let oldShouldViewDownloadInternally =
+    DownloadIntegration.shouldViewDownloadInternally;
+  DownloadIntegration.shouldViewDownloadInternally = (mimeType, extension) => {
+    let downloadTypesViewableInternally = [
+      {
+        extension: "pdf",
+        mimeTypes: ["application/pdf"],
+      },
+      {
+        extension: "webp",
+        mimeTypes: ["image/webp"],
+      },
+    ];
+
+    for (const mockHandler of downloadTypesViewableInternally) {
+      if (mockHandler.mimeTypes.includes(mimeType)) {
+        return true;
+      }
+    }
+
+    return false;
+  };
+
+  registerCleanupFunction(async function () {
+    Services.prefs.clearUserPref(
+      "browser.download.improvements_to_download_panel"
+    );
+    DownloadIntegration.shouldViewDownloadInternally =
+      oldShouldViewDownloadInternally;
+  });
+
+  // For setup, set pref to false. Will be enabled later.
+  Services.prefs.setBoolPref(
+    "browser.download.improvements_to_download_panel",
+    false
+  );
+
+  // Plain text file
+  let txtHandlerInfo = mimeSvc.getFromTypeAndExtension("text/plain", "txt");
+  txtHandlerInfo.preferredAction = Ci.nsIHandlerInfo.alwaysAsk;
+  txtHandlerInfo.alwaysAskBeforeHandling = true;
+  // PDF file
+  let pdfHandlerInfo = mimeSvc.getFromTypeAndExtension(
+    "application/pdf",
+    "pdf"
+  );
+  pdfHandlerInfo.preferredAction = Ci.nsIHandlerInfo.alwaysAsk;
+  pdfHandlerInfo.alwaysAskBeforeHandling = true;
+  // WebP file
+  let webpHandlerInfo = mimeSvc.getFromTypeAndExtension("image/webp", "webp");
+  webpHandlerInfo.preferredAction = Ci.nsIHandlerInfo.useSystemDefault;
+  webpHandlerInfo.alwaysAskBeforeHandling = false;
+
+  handlerSvc.store(txtHandlerInfo);
+  handlerSvc.store(pdfHandlerInfo);
+  handlerSvc.store(webpHandlerInfo);
+
+  Services.prefs.setBoolPref(
+    "browser.download.improvements_to_download_panel",
+    true
+  );
+  gHandlerService.wrappedJSObject._migrateDownloadsImprovementsIfNeeded();
+
+  txtHandlerInfo = mimeSvc.getFromTypeAndExtension("text/plain", "txt");
+  pdfHandlerInfo = mimeSvc.getFromTypeAndExtension("application/pdf", "pdf");
+  webpHandlerInfo = mimeSvc.getFromTypeAndExtension("image/webp", "webp");
+  let data = gHandlerService.wrappedJSObject._store.data;
+  Assert.equal(
+    data.isDownloadsImprovementsAlreadyMigrated,
+    true,
+    "isDownloadsImprovementsAlreadyMigrated should be set to true"
+  );
+  Assert.equal(
+    pdfHandlerInfo.preferredAction,
+    Ci.nsIHandlerInfo.handleInternally,
+    "application/pdf - preferredAction should be handleInternally"
+  );
+  Assert.equal(
+    pdfHandlerInfo.alwaysAskBeforeHandling,
+    false,
+    "application/pdf - alwaysAskBeforeHandling should be false"
+  );
+  Assert.equal(
+    webpHandlerInfo.preferredAction,
+    Ci.nsIHandlerInfo.useSystemDefault,
+    "image/webp - preferredAction should be useSystemDefault"
+  );
+  Assert.equal(
+    webpHandlerInfo.alwaysAskBeforeHandling,
+    false,
+    "image/webp - alwaysAskBeforeHandling should be false"
+  );
+  Assert.equal(
+    txtHandlerInfo.preferredAction,
+    Ci.nsIHandlerInfo.saveToDisk,
+    "text/plain - preferredAction should be saveToDisk"
+  );
+  Assert.equal(
+    txtHandlerInfo.alwaysAskBeforeHandling,
+    false,
+    "text/plain - alwaysAskBeforeHandling should be false"
+  );
+});
+
+/**
+ * Tests that the migration does not run if the migration was already run.
+ */
+add_task(async function test_migration_already_run() {
+  let data = gHandlerService.wrappedJSObject._store.data;
+  data.isDownloadsImprovementsAlreadyMigrated = true;
+
+  // Plain text file
+  let txtHandlerInfo = mimeSvc.getFromTypeAndExtension("text/plain", "txt");
+  txtHandlerInfo.preferredAction = Ci.nsIHandlerInfo.alwaysAsk;
+  txtHandlerInfo.alwaysAskBeforeHandling = true;
+  // PDF file
+  let pdfHandlerInfo = mimeSvc.getFromTypeAndExtension(
+    "application/pdf",
+    "pdf"
+  );
+  pdfHandlerInfo.preferredAction = Ci.nsIHandlerInfo.alwaysAsk;
+  pdfHandlerInfo.alwaysAskBeforeHandling = true;
+
+  handlerSvc.store(txtHandlerInfo);
+  handlerSvc.store(pdfHandlerInfo);
+
+  gHandlerService.wrappedJSObject._migrateDownloadsImprovementsIfNeeded();
+
+  txtHandlerInfo = mimeSvc.getFromTypeAndExtension("text/plain", "txt");
+  pdfHandlerInfo = mimeSvc.getFromTypeAndExtension("application/pdf", "pdf");
+  data = gHandlerService.wrappedJSObject._store.data;
+  Assert.equal(
+    pdfHandlerInfo.preferredAction,
+    Ci.nsIHandlerInfo.alwaysAsk,
+    "application/pdf - preferredAction should be alwaysAsk"
+  );
+  Assert.equal(
+    pdfHandlerInfo.alwaysAskBeforeHandling,
+    true,
+    "application/pdf - alwaysAskBeforeHandling should be true"
+  );
+  Assert.equal(
+    txtHandlerInfo.preferredAction,
+    Ci.nsIHandlerInfo.alwaysAsk,
+    "text/plain - preferredAction should be alwaysAsk"
+  );
+  Assert.equal(
+    txtHandlerInfo.alwaysAskBeforeHandling,
+    true,
+    "text/plain - alwaysAskBeforeHandling should be true"
+  );
+});
+
+/**
+ * Test migration of SVG and XML info.
+ */
+add_task(async function test_migration_xml_svg() {
+  let data = gHandlerService.wrappedJSObject._store.data;
+  // Plain text file
+  let txtHandlerInfo = mimeSvc.getFromTypeAndExtension("text/plain", "txt");
+  txtHandlerInfo.preferredAction = Ci.nsIHandlerInfo.alwaysAsk;
+  txtHandlerInfo.alwaysAskBeforeHandling = true;
+  // SVG file
+  let svgHandlerInfo = mimeSvc.getFromTypeAndExtension("image/svg+xml", "svg");
+  svgHandlerInfo.preferredAction = Ci.nsIHandlerInfo.handleInternally;
+  svgHandlerInfo.alwaysAskBeforeHandling = false;
+  // XML file
+  let xmlHandlerInfo = mimeSvc.getFromTypeAndExtension("text/xml", "xml");
+  xmlHandlerInfo.preferredAction = Ci.nsIHandlerInfo.handleInternally;
+  xmlHandlerInfo.alwaysAskBeforeHandling = false;
+
+  handlerSvc.store(txtHandlerInfo);
+  handlerSvc.store(svgHandlerInfo);
+  handlerSvc.store(xmlHandlerInfo);
+
+  gHandlerService.wrappedJSObject._migrateSVGXMLIfNeeded();
+
+  txtHandlerInfo = mimeSvc.getFromTypeAndExtension("text/plain", "txt");
+  svgHandlerInfo = mimeSvc.getFromTypeAndExtension("image/svg+xml", "svg");
+  xmlHandlerInfo = mimeSvc.getFromTypeAndExtension("text/xml", "xml");
+  data = gHandlerService.wrappedJSObject._store.data;
+  Assert.equal(
+    svgHandlerInfo.preferredAction,
+    Ci.nsIHandlerInfo.saveToDisk,
+    "image/svg+xml - preferredAction should be saveToDisk"
+  );
+  Assert.equal(
+    svgHandlerInfo.alwaysAskBeforeHandling,
+    false,
+    "image/svg+xml - alwaysAskBeforeHandling should be false"
+  );
+  Assert.equal(
+    xmlHandlerInfo.preferredAction,
+    Ci.nsIHandlerInfo.saveToDisk,
+    "text/xml - preferredAction should be saveToDisk"
+  );
+  Assert.equal(
+    xmlHandlerInfo.alwaysAskBeforeHandling,
+    false,
+    "text/xml - alwaysAskBeforeHandling should be false"
+  );
+  Assert.equal(
+    txtHandlerInfo.preferredAction,
+    Ci.nsIHandlerInfo.alwaysAsk,
+    "text/plain - preferredAction should be alwaysAsk"
+  );
+  Assert.equal(
+    txtHandlerInfo.alwaysAskBeforeHandling,
+    true,
+    "text/plain - alwaysAskBeforeHandling should be true"
+  );
+
+  ok(
+    data.isSVGXMLAlreadyMigrated,
+    "Should have stored migration state on the data object."
+  );
+});
diff --git a/uriloader/exthandler/tests/unit/test_filename_sanitize.js b/uriloader/exthandler/tests/unit/test_filename_sanitize.js
new file mode 100644
index 0000000000..d8ab12c266
--- /dev/null
+++ b/uriloader/exthandler/tests/unit/test_filename_sanitize.js
@@ -0,0 +1,398 @@
+/* Any copyright is dedicated to the Public Domain.
+http://creativecommons.org/publicdomain/zero/1.0/ */
+
+// This test verifies that
+// nsIMIMEService.validateFileNameForSaving sanitizes filenames
+// properly with different flags.
+
+"use strict";
+
+add_task(async function validate_filename_method() {
+  let mimeService = Cc["@mozilla.org/mime;1"].getService(Ci.nsIMIMEService);
+
+  function checkFilename(filename, flags, mime = "image/png") {
+    return mimeService.validateFileNameForSaving(filename, mime, flags);
+  }
+
+  Assert.equal(checkFilename("basicfile.png", 0), "basicfile.png");
+  Assert.equal(checkFilename("  whitespace.png  ", 0), "whitespace.png");
+  Assert.equal(
+    checkFilename(" .whitespaceanddots.png...", 0),
+    "whitespaceanddots.png"
+  );
+  Assert.equal(
+    checkFilename("  \u00a0 \u00a0 extrawhitespace.png  \u00a0 \u00a0 ", 0),
+    "extrawhitespace.png"
+  );
+  Assert.equal(
+    checkFilename("  filename  with  whitespace.png  ", 0),
+    "filename with whitespace.png"
+  );
+  Assert.equal(checkFilename("\\path.png", 0), "_path.png");
+  Assert.equal(
+    checkFilename("\\path*and/$?~file.png", 0),
+    "_path and_$ ~file.png"
+  );
+  Assert.equal(
+    checkFilename(" \u180e whit\u180ee.png \u180e", 0),
+    "whit\u180ee.png"
+  );
+  Assert.equal(checkFilename("簡単簡単簡単", 0), "簡単簡単簡単.png");
+  Assert.equal(checkFilename(" happy\u061c\u2069.png", 0), "happy__.png");
+  Assert.equal(
+    checkFilename("12345678".repeat(31) + "abcdefgh.png", 0),
+    "12345678".repeat(31) + "ab.png"
+  );
+  Assert.equal(
+    checkFilename("簡単".repeat(41) + ".png", 0),
+    "簡単".repeat(41) + ".png"
+  );
+  Assert.equal(
+    checkFilename("a" + "簡単".repeat(42) + ".png", 0),
+    "a" + "簡単".repeat(40) + "簡.png"
+  );
+  Assert.equal(
+    checkFilename("a" + "簡単".repeat(56) + ".png", 0),
+    "a" + "簡単".repeat(40) + ".png"
+  );
+  Assert.equal(checkFilename("café.png", 0), "café.png");
+  Assert.equal(
+    checkFilename("café".repeat(50) + ".png", 0),
+    "café".repeat(50) + ".png"
+  );
+  Assert.equal(
+    checkFilename("café".repeat(51) + ".png", 0),
+    "café".repeat(49) + "caf.png"
+  );
+
+  Assert.equal(
+    checkFilename("\u{100001}\u{100002}.png", 0),
+    "\u{100001}\u{100002}.png"
+  );
+  Assert.equal(
+    checkFilename("\u{100001}\u{100002}".repeat(31) + ".png", 0),
+    "\u{100001}\u{100002}".repeat(31) + ".png"
+  );
+  Assert.equal(
+    checkFilename("\u{100001}\u{100002}".repeat(32) + ".png", 0),
+    "\u{100001}\u{100002}".repeat(30) + "\u{100001}.png"
+  );
+
+  Assert.equal(
+    checkFilename("noextensionfile".repeat(16), 0),
+    "noextensionfile".repeat(16) + ".png"
+  );
+  Assert.equal(
+    checkFilename("noextensionfile".repeat(17), 0),
+    "noextensionfile".repeat(16) + "noextensio.png"
+  );
+  Assert.equal(
+    checkFilename("noextensionfile".repeat(16) + "noextensionfil.", 0),
+    "noextensionfile".repeat(16) + "noextensio.png"
+  );
+
+  Assert.equal(checkFilename("  first  .png  ", 0), "first .png");
+  Assert.equal(
+    checkFilename(
+      "  second  .png  ",
+      mimeService.VALIDATE_DONT_COLLAPSE_WHITESPACE
+    ),
+    "second  .png"
+  );
+
+  // For whatever reason, the Android mime handler accepts the .jpeg
+  // extension for image/png, so skip this test there.
+  if (AppConstants.platform != "android") {
+    Assert.equal(checkFilename("thi/*rd.jpeg", 0), "thi_ rd.png");
+  }
+
+  Assert.equal(
+    checkFilename("f*\\ourth  file.jpg", mimeService.VALIDATE_SANITIZE_ONLY),
+    "f _ourth file.jpg"
+  );
+  Assert.equal(
+    checkFilename(
+      "f*\\ift  h.jpe*\\g",
+      mimeService.VALIDATE_SANITIZE_ONLY |
+        mimeService.VALIDATE_DONT_COLLAPSE_WHITESPACE
+    ),
+    "f _ift  h.jpe _g"
+  );
+  Assert.equal(checkFilename("sixth.j  pe/*g", 0), "sixth.png");
+
+  let repeatStr = "12345678".repeat(31);
+  Assert.equal(
+    checkFilename(
+      repeatStr + "seventh.png",
+      mimeService.VALIDATE_DONT_TRUNCATE
+    ),
+    repeatStr + "seventh.png"
+  );
+  Assert.equal(
+    checkFilename(repeatStr + "seventh.png", 0),
+    repeatStr + "se.png"
+  );
+
+  // no filename, so index is used by default.
+  Assert.equal(checkFilename(".png", 0), "png.png");
+
+  // sanitization only, so Untitled is not added, but initial period is stripped.
+  Assert.equal(
+    checkFilename(".png", mimeService.VALIDATE_SANITIZE_ONLY),
+    "png"
+  );
+
+  // correct .png extension is applied.
+  Assert.equal(checkFilename(".butterpecan.icecream", 0), "butterpecan.png");
+
+  // sanitization only, so extension is not modified, but initial period is stripped.
+  Assert.equal(
+    checkFilename(".butterpecan.icecream", mimeService.VALIDATE_SANITIZE_ONLY),
+    "butterpecan.icecream"
+  );
+
+  let ext = ".fairlyLongExtension";
+  Assert.equal(
+    checkFilename(repeatStr + ext, mimeService.VALIDATE_SANITIZE_ONLY),
+    repeatStr.substring(0, 254 - ext.length) + ext
+  );
+
+  ext = "lo%?n/ginvalid? ch\\ars";
+  Assert.equal(
+    checkFilename(repeatStr + ext, mimeService.VALIDATE_SANITIZE_ONLY),
+    repeatStr + "lo% n_"
+  );
+
+  ext = ".long/invalid%? ch\\ars";
+  Assert.equal(
+    checkFilename(repeatStr + ext, mimeService.VALIDATE_SANITIZE_ONLY),
+    repeatStr.substring(0, 233) + ".long_invalid% ch_ars"
+  );
+
+  Assert.equal(
+    checkFilename("test_ﾃｽﾄ_T\x83E\\S\x83T.png", 0),
+    "test_ﾃｽﾄ_T E_S T.png"
+  );
+  Assert.equal(
+    checkFilename("test_ﾃｽﾄ_T\x83E\\S\x83T.pﾃ\x83ng", 0),
+    "test_ﾃｽﾄ_T E_S T.png"
+  );
+
+  // Check we don't invalidate surrogate pairs when trimming.
+  Assert.equal(checkFilename("test😀", 0, ""), "test😀");
+  Assert.equal(checkFilename("test😀😀", 0, ""), "test😀😀");
+
+  // Now check some media types
+  Assert.equal(
+    mimeService.validateFileNameForSaving("video.ogg", "video/ogg", 0),
+    "video.ogg",
+    "video.ogg"
+  );
+  Assert.equal(
+    mimeService.validateFileNameForSaving("video.ogv", "video/ogg", 0),
+    "video.ogv",
+    "video.ogv"
+  );
+  Assert.equal(
+    mimeService.validateFileNameForSaving("video.ogt", "video/ogg", 0),
+    "video.ogv",
+    "video.ogt"
+  );
+
+  Assert.equal(
+    mimeService.validateFileNameForSaving("audio.mp3", "audio/mpeg", 0),
+    "audio.mp3",
+    "audio.mp3"
+  );
+  Assert.equal(
+    mimeService.validateFileNameForSaving("audio.mpega", "audio/mpeg", 0),
+    "audio.mpega",
+    "audio.mpega"
+  );
+  Assert.equal(
+    mimeService.validateFileNameForSaving("audio.mp2", "audio/mpeg", 0),
+    "audio.mp2",
+    "audio.mp2"
+  );
+
+  let expected = "audio.mp3";
+  if (AppConstants.platform == "linux") {
+    expected = "audio.mpga";
+  } else if (AppConstants.platform == "android") {
+    expected = "audio.mp4";
+  }
+
+  Assert.equal(
+    mimeService.validateFileNameForSaving("audio.mp4", "audio/mpeg", 0),
+    expected,
+    "audio.mp4"
+  );
+
+  Assert.equal(
+    mimeService.validateFileNameForSaving("sound.m4a", "audio/mp4", 0),
+    "sound.m4a",
+    "sound.m4a"
+  );
+  Assert.equal(
+    mimeService.validateFileNameForSaving("sound.m4b", "audio/mp4", 0),
+    AppConstants.platform == "android" ? "sound.m4a" : "sound.m4b",
+    "sound.m4b"
+  );
+  Assert.equal(
+    mimeService.validateFileNameForSaving("sound.m4c", "audio/mp4", 0),
+    AppConstants.platform == "macosx" ? "sound.mp4" : "sound.m4a",
+    "sound.mpc"
+  );
+
+  // This has a long filename with a 13 character extension. The end of the filename should be
+  // cropped to fit into 255 bytes.
+  Assert.equal(
+    mimeService.validateFileNameForSaving(
+      "라이브9.9만 시청컬처렐 다이제스티브 3박스 - 3박스 더 (뚱랑이 굿즈 증정) - 선물용 쇼핑백 2장컬처렐 다이제스티브 3박스 - 3박스 더 (뚱랑이 굿즈 증정) - 선물용 쇼핑백 2장24%102 000원 브랜드데이 앵콜 🎁 1.등 유산균 컬처렐 특가!",
+      "text/unknown",
+      mimeService.VALIDATE_SANITIZE_ONLY
+    ),
+    "라이브9.9만 시청컬처렐 다이제스티브 3박스 - 3박스 더 (뚱랑이 굿즈 증정) - 선물용 쇼핑백 2장컬처렐 다이제스티브 3박스 - 3박스 더 (뚱랑이 굿즈 .등 유산균 컬처렐 특가!",
+    "very long filename with extension"
+  );
+
+  // This filename has a very long extension, almost the entire filename.
+  Assert.equal(
+    mimeService.validateFileNameForSaving(
+      "라이브9.9만 시청컬처렐 다이제스티브 3박스 - 3박스 더 (뚱랑이 굿즈 증정) - 선물용 쇼핑백 2장컬처렐 다이제스티브 3박스 - 3박스 더 (뚱랑이 굿즈 증정) - 선물용 쇼핑백 2장24%102 000원 브랜드데이 앵콜 🎁 1등 유산균 컬처렐 특가!",
+      "text/unknown",
+      mimeService.VALIDATE_SANITIZE_ONLY
+    ),
+    "라이브9",
+    "another very long filename with long extension"
+  );
+
+  // This filename is cropped at 254 bytes.
+  Assert.equal(
+    mimeService.validateFileNameForSaving(
+      ".라이브99만 시청컬처렐 다이제스티브 3박스 - 3박스 더 (뚱랑이 굿즈 증정) - 선물용 쇼핑백 2장컬처렐 다이제스티브 3박스 - 3박스 더 (뚱랑이 굿즈 증정) - 선물용 쇼핑백 2장24%102 000원 브랜드데이 앵콜 🎁 1등 유산균 컬처렐 특가!",
+      "text/unknown",
+      mimeService.VALIDATE_SANITIZE_ONLY
+    ),
+    "라이브99만 시청컬처렐 다이제스티브 3박스 - 3박스 더 (뚱랑이 굿즈 증정) - 선물용 쇼핑백 2장컬처렐 다이제스티브 3박스 - 3박스 더 (뚱랑이 굿즈 증정) - 선물용 쇼핑백 2장24%102 000원 브랜드데",
+    "very filename with extension only"
+  );
+
+  Assert.equal(
+    mimeService.validateFileNameForSaving("filename.LNK", "text/unknown", 0),
+    "filename.LNK.download",
+    "filename.LNK"
+  );
+  Assert.equal(
+    mimeService.validateFileNameForSaving("filename.local", "text/unknown", 0),
+    "filename.local.download",
+    "filename.local"
+  );
+  Assert.equal(
+    mimeService.validateFileNameForSaving("filename.url", "text/unknown", 0),
+    "filename.url.download",
+    "filename.url"
+  );
+  Assert.equal(
+    mimeService.validateFileNameForSaving("filename.URl", "text/unknown", 0),
+    "filename.URl.download",
+    "filename.URl"
+  );
+  Assert.equal(
+    mimeService.validateFileNameForSaving("filename.scf", "text/unknown", 0),
+    "filename.scf.download",
+    "filename.scf"
+  );
+  Assert.equal(
+    mimeService.validateFileNameForSaving("filename.sCF", "text/unknown", 0),
+    "filename.sCF.download",
+    "filename.sCF"
+  );
+
+  Assert.equal(
+    mimeService.validateFileNameForSaving("filename.lnk\n", "text/unknown", 0),
+    "filename.lnk.download",
+    "filename.lnk with newline"
+  );
+
+  Assert.equal(
+    mimeService.validateFileNameForSaving(
+      "filename.lnk\n  ",
+      "text/unknown",
+      0
+    ),
+    "filename.lnk.download",
+    "filename.lnk with newline"
+  );
+
+  Assert.equal(
+    mimeService.validateFileNameForSaving(
+      "filename.\n\t  lnk",
+      "text/unknown",
+      0
+    ),
+    "filename. lnk",
+    "filename.lnk with space and newline"
+  );
+
+  Assert.equal(
+    mimeService.validateFileNameForSaving(
+      "filename.local\u180e\u180e\u180e",
+      "text/unknown",
+      0
+    ),
+    "filename.local.download",
+    "filename.lnk with vowel separators"
+  );
+
+  Assert.equal(
+    mimeService.validateFileNameForSaving(
+      "filename.LNK",
+      "text/unknown",
+      mimeService.VALIDATE_SANITIZE_ONLY
+    ),
+    "filename.LNK.download",
+    "filename.LNK sanitize only"
+  );
+
+  Assert.equal(
+    mimeService.validateFileNameForSaving(
+      "filename.LNK\n",
+      "text/unknown",
+      mimeService.VALIDATE_ALLOW_INVALID_FILENAMES
+    ),
+    "filename.LNK",
+    "filename.LNK allow invalid"
+  );
+
+  Assert.equal(
+    mimeService.validateFileNameForSaving(
+      "filename.URL\n",
+      "text/unknown",
+      mimeService.VALIDATE_SANITIZE_ONLY |
+        mimeService.VALIDATE_ALLOW_INVALID_FILENAMES
+    ),
+    "filename.URL",
+    "filename.URL allow invalid, sanitize only"
+  );
+
+  Assert.equal(
+    mimeService.validateFileNameForSaving(
+      "filename.desktop",
+      "text/unknown",
+      mimeService.VALIDATE_SANITIZE_ONLY
+    ),
+    "filename.desktop.download",
+    "filename.desktop sanitize only"
+  );
+  Assert.equal(
+    mimeService.validateFileNameForSaving(
+      "filename.DESKTOP\n",
+      "text/unknown",
+      mimeService.VALIDATE_SANITIZE_ONLY |
+        mimeService.VALIDATE_ALLOW_INVALID_FILENAMES
+    ),
+    "filename.DESKTOP",
+    "filename.DESKTOP allow invalid, sanitize only"
+  );
+});
diff --git a/uriloader/exthandler/tests/unit/test_getFromTypeAndExtension.js b/uriloader/exthandler/tests/unit/test_getFromTypeAndExtension.js
new file mode 100644
index 0000000000..6f4fe52a49
--- /dev/null
+++ b/uriloader/exthandler/tests/unit/test_getFromTypeAndExtension.js
@@ -0,0 +1,17 @@
+/* Any copyright is dedicated to the Public Domain.
+http://creativecommons.org/publicdomain/zero/1.0/ */
+
+"use strict";
+
+add_task(async function test_utf8_extension() {
+  const mimeService = Cc["@mozilla.org/mime;1"].getService(Ci.nsIMIMEService);
+  let someMIME = mimeService.getFromTypeAndExtension(
+    "application/x-nonsense",
+    ".тест"
+  );
+  Assert.stringContains(someMIME.description, "тест");
+  // primary extension isn't set on macOS or android, see bug 1721181
+  if (AppConstants.platform != "macosx" && AppConstants.platform != "android") {
+    Assert.equal(someMIME.primaryExtension, ".тест");
+  }
+});
diff --git a/uriloader/exthandler/tests/unit/test_getMIMEInfo_pdf.js b/uriloader/exthandler/tests/unit/test_getMIMEInfo_pdf.js
new file mode 100644
index 0000000000..03b0cea25e
--- /dev/null
+++ b/uriloader/exthandler/tests/unit/test_getMIMEInfo_pdf.js
@@ -0,0 +1,30 @@
+/* Any copyright is dedicated to the Public Domain.
+http://creativecommons.org/publicdomain/zero/1.0/ */
+
+"use strict";
+
+XPCOMUtils.defineLazyServiceGetter(
+  this,
+  "gMIMEService",
+  "@mozilla.org/mime;1",
+  "nsIMIMEService"
+);
+
+// PDF files should always have a generic description instead
+// of relying on what is registered with the Operating System.
+add_task(async function test_check_unknown_mime_type() {
+  const mimeService = Cc["@mozilla.org/mime;1"].getService(Ci.nsIMIMEService);
+  let pdfType = mimeService.getTypeFromExtension("pdf");
+  Assert.equal(pdfType, "application/pdf");
+  let extension = mimeService.getPrimaryExtension("application/pdf", "");
+  Assert.equal(extension, "pdf", "Expect pdf extension when given mime");
+  let mimeInfo = gMIMEService.getFromTypeAndExtension("", "pdf");
+  let stringBundle = Services.strings.createBundle(
+    "chrome://mozapps/locale/downloads/unknownContentType.properties"
+  );
+  Assert.equal(
+    mimeInfo.description,
+    stringBundle.GetStringFromName("pdfExtHandlerDescription"),
+    "PDF has generic description"
+  );
+});
diff --git a/uriloader/exthandler/tests/unit/test_getMIMEInfo_unknown_mime_type.js b/uriloader/exthandler/tests/unit/test_getMIMEInfo_unknown_mime_type.js
new file mode 100644
index 0000000000..9beef9d9c5
--- /dev/null
+++ b/uriloader/exthandler/tests/unit/test_getMIMEInfo_unknown_mime_type.js
@@ -0,0 +1,32 @@
+/* Any copyright is dedicated to the Public Domain.
+http://creativecommons.org/publicdomain/zero/1.0/ */
+
+"use strict";
+
+// Zip files can be opened by Windows explorer, so we should always be able to
+// determine a description and default handler for them. However, things can
+// get messy if they are sent to us with a mime type other than what Windows
+// considers the "right" mimetype (application/x-zip-compressed), like
+// application/zip, which is what most places (IANA, macOS, probably all linux
+// distros, Apache, etc.) think is the "right" mimetype.
+add_task(async function test_check_unknown_mime_type() {
+  const mimeService = Cc["@mozilla.org/mime;1"].getService(Ci.nsIMIMEService);
+  let zipType = mimeService.getTypeFromExtension("zip");
+  Assert.equal(zipType, "application/x-zip-compressed");
+  try {
+    let extension = mimeService.getPrimaryExtension("application/zip", "");
+    Assert.equal(
+      extension,
+      "zip",
+      "Expect our own info to provide an extension for zip files."
+    );
+  } catch (ex) {
+    Assert.ok(false, "We shouldn't throw when getting zip info.");
+  }
+  let found = {};
+  let mimeInfo = mimeService.getMIMEInfoFromOS("application/zip", "zip", found);
+  Assert.ok(
+    mimeInfo.hasDefaultHandler,
+    "Should have a default app for zip files"
+  );
+});
diff --git a/uriloader/exthandler/tests/unit/test_getTypeFromExtension_ext_to_type_mapping.js b/uriloader/exthandler/tests/unit/test_getTypeFromExtension_ext_to_type_mapping.js
new file mode 100644
index 0000000000..7202db58de
--- /dev/null
+++ b/uriloader/exthandler/tests/unit/test_getTypeFromExtension_ext_to_type_mapping.js
@@ -0,0 +1,65 @@
+/* -*- indent-tabs-mode: nil; js-indent-level: 2 -*-
+ * 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/. */
+
+/**
+ * Test for bug 508030 <https://bugzilla.mozilla.org/show_bug.cgi?id=508030>:
+ * nsIMIMEService.getTypeFromExtension fails to find a match in the
+ * "ext-to-type-mapping" category if the provided extension is not lowercase.
+ */
+function run_test() {
+  // --- Common services ---
+
+  const mimeService = Cc["@mozilla.org/mime;1"].getService(Ci.nsIMIMEService);
+
+  const categoryManager = Services.catMan;
+
+  // --- Test procedure ---
+
+  const kTestExtension = "testextension";
+  const kTestExtensionMixedCase = "testExtensIon";
+  const kTestMimeType = "application/x-testextension";
+
+  // Ensure that the test extension is not initially recognized by the operating
+  // system or the "ext-to-type-mapping" category.
+  try {
+    // Try and get the MIME type associated with the extension.
+    mimeService.getTypeFromExtension(kTestExtension);
+    // The line above should have thrown an exception.
+    do_throw("nsIMIMEService.getTypeFromExtension succeeded unexpectedly");
+  } catch (e) {
+    if (
+      !(e instanceof Ci.nsIException) ||
+      e.result != Cr.NS_ERROR_NOT_AVAILABLE
+    ) {
+      throw e;
+    }
+    // This is an expected exception, thrown if the type can't be determined.
+    // Any other exception would cause the test to fail.
+  }
+
+  // Add a temporary category entry mapping the extension to the MIME type.
+  categoryManager.addCategoryEntry(
+    "ext-to-type-mapping",
+    kTestExtension,
+    kTestMimeType,
+    false,
+    true
+  );
+
+  // Check that the mapping is recognized in the simple case.
+  var type = mimeService.getTypeFromExtension(kTestExtension);
+  Assert.equal(type, kTestMimeType);
+
+  // Check that the mapping is recognized even if the extension has mixed case.
+  type = mimeService.getTypeFromExtension(kTestExtensionMixedCase);
+  Assert.equal(type, kTestMimeType);
+
+  // Clean up after ourselves.
+  categoryManager.deleteCategoryEntry(
+    "ext-to-type-mapping",
+    kTestExtension,
+    false
+  );
+}
diff --git a/uriloader/exthandler/tests/unit/test_getTypeFromExtension_with_empty_Content_Type.js b/uriloader/exthandler/tests/unit/test_getTypeFromExtension_with_empty_Content_Type.js
new file mode 100644
index 0000000000..5076a57738
--- /dev/null
+++ b/uriloader/exthandler/tests/unit/test_getTypeFromExtension_with_empty_Content_Type.js
@@ -0,0 +1,218 @@
+/* -*- indent-tabs-mode: nil; js-indent-level: 2 -*-
+ * 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/. */
+
+/**
+ * Test for bug 484579 <https://bugzilla.mozilla.org/show_bug.cgi?id=484579>:
+ * nsIMIMEService.getTypeFromExtension may fail unexpectedly on Windows when
+ * "Content Type" is empty in the registry.
+ */
+
+// We must use a file extension that isn't listed in nsExternalHelperAppService's
+// defaultMimeEntries, otherwise the code takes a shortcut skipping the registry.
+const FILE_EXTENSION = ".nfo";
+// This is used to ensure the test properly used the mock, so that if we change
+// the underlying code, it won't be skipped.
+let gTestUsedOurMock = false;
+
+function run_test() {
+  // Activate the override of the file association data in the registry.
+  registerMockWindowsRegKeyFactory();
+
+  // Check the mock has been properly activated.
+  let regKey = Cc["@mozilla.org/windows-registry-key;1"].createInstance(
+    Ci.nsIWindowsRegKey
+  );
+  regKey.open(
+    Ci.nsIWindowsRegKey.ROOT_KEY_CLASSES_ROOT,
+    FILE_EXTENSION,
+    Ci.nsIWindowsRegKey.ACCESS_QUERY_VALUE
+  );
+  Assert.equal(
+    regKey.readStringValue("content type"),
+    "",
+    "Check the mock replied as expected."
+  );
+  Assert.ok(gTestUsedOurMock, "The test properly used the mock registry");
+  // Reset gTestUsedOurMock, because we just used it.
+  gTestUsedOurMock = false;
+  // Try and get the MIME type associated with the extension. If this
+  // operation does not throw an unexpected exception, the test succeeds.
+  Assert.throws(
+    () => {
+      Cc["@mozilla.org/mime;1"]
+        .getService(Ci.nsIMIMEService)
+        .getTypeFromExtension(FILE_EXTENSION);
+    },
+    /NS_ERROR_NOT_AVAILABLE/,
+    "Should throw a NOT_AVAILABLE exception"
+  );
+
+  Assert.ok(gTestUsedOurMock, "The test properly used the mock registry");
+}
+
+/**
+ * Constructs a new mock registry key by wrapping the provided object.
+ *
+ * This mock implementation is tailored for this test, and forces consumers
+ * of the readStringValue method to believe that the "Content Type" value of
+ * the FILE_EXTENSION key under HKEY_CLASSES_ROOT is an empty string.
+ *
+ * The same value read from "HKEY_LOCAL_MACHINE\SOFTWARE\Classes" is not
+ * affected.
+ *
+ * @param aWrappedObject   An actual nsIWindowsRegKey implementation.
+ */
+function MockWindowsRegKey(aWrappedObject) {
+  this._wrappedObject = aWrappedObject;
+
+  // This function creates a forwarding function for wrappedObject
+  function makeForwardingFunction(functionName) {
+    return function () {
+      return aWrappedObject[functionName].apply(aWrappedObject, arguments);
+    };
+  }
+
+  // Forward all the functions that are not explicitly overridden
+  for (var propertyName in aWrappedObject) {
+    if (!(propertyName in this)) {
+      if (typeof aWrappedObject[propertyName] == "function") {
+        this[propertyName] = makeForwardingFunction(propertyName);
+      } else {
+        this[propertyName] = aWrappedObject[propertyName];
+      }
+    }
+  }
+}
+
+MockWindowsRegKey.prototype = {
+  // --- Overridden nsISupports interface functions ---
+
+  QueryInterface: ChromeUtils.generateQI(["nsIWindowsRegKey"]),
+
+  // --- Overridden nsIWindowsRegKey interface functions ---
+
+  open(aRootKey, aRelPath, aMode) {
+    // Remember the provided root key and path
+    this._rootKey = aRootKey;
+    this._relPath = aRelPath;
+
+    // Create the actual registry key
+    return this._wrappedObject.open(aRootKey, aRelPath, aMode);
+  },
+
+  openChild(aRelPath, aMode) {
+    // Open the child key and wrap it
+    var innerKey = this._wrappedObject.openChild(aRelPath, aMode);
+    var key = new MockWindowsRegKey(innerKey);
+
+    // Set the properties of the child key and return it
+    key._rootKey = this._rootKey;
+    key._relPath = this._relPath + aRelPath;
+    return key;
+  },
+
+  createChild(aRelPath, aMode) {
+    // Create the child key and wrap it
+    var innerKey = this._wrappedObject.createChild(aRelPath, aMode);
+    var key = new MockWindowsRegKey(innerKey);
+
+    // Set the properties of the child key and return it
+    key._rootKey = this._rootKey;
+    key._relPath = this._relPath + aRelPath;
+    return key;
+  },
+
+  get childCount() {
+    return this._wrappedObject.childCount;
+  },
+
+  get valueCount() {
+    return this._wrappedObject.valueCount;
+  },
+
+  readStringValue(aName) {
+    // If this is the key under test, return a fake value
+    if (
+      this._rootKey == Ci.nsIWindowsRegKey.ROOT_KEY_CLASSES_ROOT &&
+      this._relPath.toLowerCase() == FILE_EXTENSION &&
+      aName.toLowerCase() == "content type"
+    ) {
+      gTestUsedOurMock = true;
+      return "";
+    }
+    // Return the real value from the registry
+    return this._wrappedObject.readStringValue(aName);
+  },
+};
+
+function registerMockWindowsRegKeyFactory() {
+  const kMockCID = Components.ID("{9b23dfe9-296b-4740-ba1c-d39c9a16e55e}");
+  const kWindowsRegKeyContractID = "@mozilla.org/windows-registry-key;1";
+  // Preserve the original CID.
+  let originalWindowsRegKeyCID = Cc[kWindowsRegKeyContractID].number;
+
+  // See bug 1694345 - nsNotifyAddrListener::CheckAdaptersAddresses might
+  // attempt to use the registry off the main thread, so we disable that
+  // feature while the mock registry is active.
+  let oldSuffixListPref = Services.prefs.getBoolPref(
+    "network.notify.dnsSuffixList"
+  );
+  Services.prefs.setBoolPref("network.notify.dnsSuffixList", false);
+
+  let oldCheckForProxiesPref = Services.prefs.getBoolPref(
+    "network.notify.checkForProxies"
+  );
+  Services.prefs.setBoolPref("network.notify.checkForProxies", false);
+
+  let oldCheckForNRPTPref = Services.prefs.getBoolPref(
+    "network.notify.checkForNRPT"
+  );
+  Services.prefs.setBoolPref("network.notify.checkForNRPT", false);
+
+  info("Create a mock RegKey factory");
+  let originalRegKey = Cc["@mozilla.org/windows-registry-key;1"].createInstance(
+    Ci.nsIWindowsRegKey
+  );
+  let mockWindowsRegKeyFactory = {
+    createInstance(iid) {
+      info("Create a mock wrapper around RegKey");
+      var key = new MockWindowsRegKey(originalRegKey);
+      return key.QueryInterface(iid);
+    },
+  };
+  info("Register the mock RegKey factory");
+  let registrar = Components.manager.QueryInterface(Ci.nsIComponentRegistrar);
+  registrar.registerFactory(
+    kMockCID,
+    "Mock Windows Registry Key Implementation",
+    kWindowsRegKeyContractID,
+    mockWindowsRegKeyFactory
+  );
+
+  registerCleanupFunction(() => {
+    // Free references to the mock factory
+    registrar.unregisterFactory(kMockCID, mockWindowsRegKeyFactory);
+    // Restore the original factory
+    registrar.registerFactory(
+      Components.ID(originalWindowsRegKeyCID),
+      "",
+      kWindowsRegKeyContractID,
+      null
+    );
+
+    Services.prefs.setBoolPref(
+      "network.notify.dnsSuffixList",
+      oldSuffixListPref
+    );
+    Services.prefs.setBoolPref(
+      "network.notify.checkForProxies",
+      oldCheckForProxiesPref
+    );
+    Services.prefs.setBoolPref(
+      "network.notify.checkForNRPT",
+      oldCheckForNRPTPref
+    );
+  });
+}
diff --git a/uriloader/exthandler/tests/unit/test_handlerService.js b/uriloader/exthandler/tests/unit/test_handlerService.js
new file mode 100644
index 0000000000..46a4d9fdd9
--- /dev/null
+++ b/uriloader/exthandler/tests/unit/test_handlerService.js
@@ -0,0 +1,467 @@
+/* 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/. */
+
+function run_test() {
+  //* *************************************************************************//
+  // Constants
+
+  const handlerSvc = Cc["@mozilla.org/uriloader/handler-service;1"].getService(
+    Ci.nsIHandlerService
+  );
+
+  const mimeSvc = Cc["@mozilla.org/mime;1"].getService(Ci.nsIMIMEService);
+
+  const protoSvc = Cc[
+    "@mozilla.org/uriloader/external-protocol-service;1"
+  ].getService(Ci.nsIExternalProtocolService);
+
+  const prefSvc = Services.prefs;
+
+  let noMailto = false;
+  if (mozinfo.os == "win") {
+    // Check mailto handler from registry.
+    // If registry entry is nothing, no mailto handler
+    let regSvc = Cc["@mozilla.org/windows-registry-key;1"].createInstance(
+      Ci.nsIWindowsRegKey
+    );
+    try {
+      regSvc.open(regSvc.ROOT_KEY_CLASSES_ROOT, "mailto", regSvc.ACCESS_READ);
+      noMailto = false;
+    } catch (ex) {
+      noMailto = true;
+    }
+    regSvc.close();
+  }
+
+  if (mozinfo.os == "linux") {
+    // Check mailto handler from GIO
+    // If there isn't one, then we have no mailto handler
+    let gIOSvc = Cc["@mozilla.org/gio-service;1"].createInstance(
+      Ci.nsIGIOService
+    );
+    try {
+      gIOSvc.getAppForURIScheme("mailto");
+      noMailto = false;
+    } catch (ex) {
+      noMailto = true;
+    }
+  }
+
+  //* *************************************************************************//
+  // Sample Data
+
+  // It doesn't matter whether or not this nsIFile is actually executable,
+  // only that it has a path and exists.  Since we don't know any executable
+  // that exists on all platforms (except possibly the application being
+  // tested, but there doesn't seem to be a way to get a reference to that
+  // from the directory service), we use the temporary directory itself.
+  var executable = Services.dirsvc.get("TmpD", Ci.nsIFile);
+  // XXX We could, of course, create an actual executable in the directory:
+  // executable.append("localhandler");
+  // if (!executable.exists())
+  //  executable.create(Ci.nsIFile.NORMAL_FILE_TYPE, 0o755);
+
+  var localHandler = Cc[
+    "@mozilla.org/uriloader/local-handler-app;1"
+  ].createInstance(Ci.nsILocalHandlerApp);
+  localHandler.name = "Local Handler";
+  localHandler.executable = executable;
+
+  var webHandler = Cc[
+    "@mozilla.org/uriloader/web-handler-app;1"
+  ].createInstance(Ci.nsIWebHandlerApp);
+  webHandler.name = "Web Handler";
+  webHandler.uriTemplate = "http://www.example.com/?%s";
+
+  // FIXME: these tests create and manipulate enough variables that it would
+  // make sense to move each test into its own scope so we don't run the risk
+  // of one test stomping on another's data.
+
+  //* *************************************************************************//
+  // Test Default Properties
+
+  // Get a handler info for a MIME type that neither the application nor
+  // the OS knows about and make sure its properties are set to the proper
+  // default values.
+
+  var handlerInfo = mimeSvc.getFromTypeAndExtension("nonexistent/type", null);
+
+  // Make sure it's also an nsIHandlerInfo.
+  Assert.ok(handlerInfo instanceof Ci.nsIHandlerInfo);
+
+  Assert.equal(handlerInfo.type, "nonexistent/type");
+
+  // Deprecated property, but we should still make sure it's set correctly.
+  Assert.equal(handlerInfo.MIMEType, "nonexistent/type");
+
+  // These properties are the ones the handler service knows how to store.
+  Assert.equal(handlerInfo.preferredAction, Ci.nsIHandlerInfo.saveToDisk);
+  Assert.equal(handlerInfo.preferredApplicationHandler, null);
+  Assert.equal(handlerInfo.possibleApplicationHandlers.length, 0);
+  Assert.equal(
+    handlerInfo.alwaysAskBeforeHandling,
+    prefSvc.getBoolPref(
+      "browser.download.always_ask_before_handling_new_types",
+      false
+    )
+  );
+
+  // These properties are initialized to default values by the service,
+  // so we might as well make sure they're initialized to the right defaults.
+  Assert.equal(handlerInfo.description, "");
+  Assert.equal(handlerInfo.hasDefaultHandler, false);
+  Assert.equal(handlerInfo.defaultDescription, "");
+
+  const kExternalWarningDefault =
+    "network.protocol-handler.warn-external-default";
+  prefSvc.setBoolPref(kExternalWarningDefault, true);
+
+  // XXX add more thorough protocol info property checking
+
+  // no OS default handler exists
+  var protoInfo = protoSvc.getProtocolHandlerInfo("x-moz-rheet");
+  Assert.equal(protoInfo.preferredAction, protoInfo.alwaysAsk);
+  Assert.ok(protoInfo.alwaysAskBeforeHandling);
+
+  // OS default exists, injected default does not exist,
+  // explicit warning pref: false
+  const kExternalWarningPrefPrefix = "network.protocol-handler.warn-external.";
+  prefSvc.setBoolPref(kExternalWarningPrefPrefix + "http", false);
+  protoInfo = protoSvc.getProtocolHandlerInfo("http");
+  Assert.equal(0, protoInfo.possibleApplicationHandlers.length);
+  // NOTE: this assertion will fail if the system executing the test does not
+  // have a handler registered for the http protocol. This is very unlikely to
+  // actually happen except on certain configurations of Linux, but one of
+  // those configurations is the default WSL Ubuntu install. So, if you are
+  // running this test locally and seeing a failure here, it might not be
+  // anything to really worry about.
+  Assert.ok(!protoInfo.alwaysAskBeforeHandling);
+
+  // OS default exists, injected default does not exist,
+  // explicit warning pref: true
+  prefSvc.setBoolPref(kExternalWarningPrefPrefix + "http", true);
+  protoInfo = protoSvc.getProtocolHandlerInfo("http");
+  // OS handler isn't included in possibleApplicationHandlers, so length is 0
+  // Once they become instances of nsILocalHandlerApp, this number will need
+  // to change.
+  Assert.equal(0, protoInfo.possibleApplicationHandlers.length);
+  Assert.ok(protoInfo.alwaysAskBeforeHandling);
+
+  // OS default exists, injected default exists, explicit warning pref: false
+  prefSvc.setBoolPref(kExternalWarningPrefPrefix + "mailto", false);
+  protoInfo = protoSvc.getProtocolHandlerInfo("mailto");
+  if (AppConstants.MOZ_APP_NAME == "thunderbird") {
+    Assert.equal(0, protoInfo.possibleApplicationHandlers.length);
+  } else {
+    Assert.equal(1, protoInfo.possibleApplicationHandlers.length);
+  }
+
+  // Win7+ or Linux's GIO might not have a default mailto: handler
+  if (noMailto) {
+    Assert.ok(protoInfo.alwaysAskBeforeHandling);
+  } else {
+    Assert.ok(!protoInfo.alwaysAskBeforeHandling);
+  }
+
+  // OS default exists, injected default exists, explicit warning pref: true
+  prefSvc.setBoolPref(kExternalWarningPrefPrefix + "mailto", true);
+  protoInfo = protoSvc.getProtocolHandlerInfo("mailto");
+  if (AppConstants.MOZ_APP_NAME == "thunderbird") {
+    Assert.equal(0, protoInfo.possibleApplicationHandlers.length);
+  } else {
+    Assert.equal(1, protoInfo.possibleApplicationHandlers.length);
+    // Win7+ or Linux's GIO may have no default mailto: handler, so we'd ask
+    // anyway. Otherwise, the default handlers will not have stored preferred
+    // actions etc., so re-requesting them after the warning pref has changed
+    // will use the updated pref value. So both when we have and do not have
+    // a default mailto: handler, we'll ask:
+    Assert.ok(protoInfo.alwaysAskBeforeHandling);
+    // As soon as anyone actually stores updated defaults into the profile
+    // database, that default will stop tracking the warning pref.
+  }
+  // Now set the value stored in RDF to true, and the pref to false, to make
+  // sure we still get the right value. (Basically, same thing as above but
+  // with the values reversed.)
+  prefSvc.setBoolPref(kExternalWarningPrefPrefix + "mailto", false);
+  protoInfo.alwaysAskBeforeHandling = true;
+  handlerSvc.store(protoInfo);
+  protoInfo = protoSvc.getProtocolHandlerInfo("mailto");
+  if (AppConstants.MOZ_APP_NAME == "thunderbird") {
+    Assert.equal(0, protoInfo.possibleApplicationHandlers.length);
+  } else {
+    Assert.equal(1, protoInfo.possibleApplicationHandlers.length);
+    Assert.ok(protoInfo.alwaysAskBeforeHandling);
+  }
+
+  //* *************************************************************************//
+  // Test Round-Trip Data Integrity
+
+  // Test round-trip data integrity by setting the properties of the handler
+  // info object to different values, telling the handler service to store the
+  // object, and then retrieving a new info object for the same type and making
+  // sure its properties are identical.
+
+  handlerInfo.preferredAction = Ci.nsIHandlerInfo.useHelperApp;
+  handlerInfo.preferredApplicationHandler = localHandler;
+  handlerInfo.alwaysAskBeforeHandling = false;
+
+  handlerSvc.store(handlerInfo);
+
+  handlerInfo = mimeSvc.getFromTypeAndExtension("nonexistent/type", null);
+
+  Assert.equal(handlerInfo.preferredAction, Ci.nsIHandlerInfo.useHelperApp);
+
+  Assert.notEqual(handlerInfo.preferredApplicationHandler, null);
+  var preferredHandler = handlerInfo.preferredApplicationHandler;
+  Assert.equal(typeof preferredHandler, "object");
+  Assert.equal(preferredHandler.name, "Local Handler");
+  Assert.ok(preferredHandler instanceof Ci.nsILocalHandlerApp);
+  preferredHandler.QueryInterface(Ci.nsILocalHandlerApp);
+  Assert.equal(preferredHandler.executable.path, localHandler.executable.path);
+
+  Assert.ok(!handlerInfo.alwaysAskBeforeHandling);
+
+  // Make sure the handler service's enumerate method lists all known handlers.
+  var handlerInfo2 = mimeSvc.getFromTypeAndExtension("nonexistent/type2", null);
+  handlerSvc.store(handlerInfo2);
+  var handlerTypes = ["nonexistent/type", "nonexistent/type2"];
+  handlerTypes.push("mailto");
+  for (let handler of handlerSvc.enumerate()) {
+    Assert.notEqual(handlerTypes.indexOf(handler.type), -1);
+    handlerTypes.splice(handlerTypes.indexOf(handler.type), 1);
+  }
+  Assert.equal(handlerTypes.length, 0);
+  // Make sure the handler service's remove method removes a handler record.
+  handlerSvc.remove(handlerInfo2);
+  let handlers = handlerSvc.enumerate();
+  while (handlers.hasMoreElements()) {
+    Assert.notEqual(
+      handlers.getNext().QueryInterface(Ci.nsIHandlerInfo).type,
+      handlerInfo2.type
+    );
+  }
+
+  // Make sure we can store and retrieve a handler info object with no preferred
+  // handler.
+  var noPreferredHandlerInfo = mimeSvc.getFromTypeAndExtension(
+    "nonexistent/no-preferred-handler",
+    null
+  );
+  handlerSvc.store(noPreferredHandlerInfo);
+  noPreferredHandlerInfo = mimeSvc.getFromTypeAndExtension(
+    "nonexistent/no-preferred-handler",
+    null
+  );
+  Assert.equal(noPreferredHandlerInfo.preferredApplicationHandler, null);
+
+  // Make sure that the handler service removes an existing handler record
+  // if we store a handler info object with no preferred handler.
+  var removePreferredHandlerInfo = mimeSvc.getFromTypeAndExtension(
+    "nonexistent/rem-preferred-handler",
+    null
+  );
+  removePreferredHandlerInfo.preferredApplicationHandler = localHandler;
+  handlerSvc.store(removePreferredHandlerInfo);
+  removePreferredHandlerInfo = mimeSvc.getFromTypeAndExtension(
+    "nonexistent/rem-preferred-handler",
+    null
+  );
+  removePreferredHandlerInfo.preferredApplicationHandler = null;
+  handlerSvc.store(removePreferredHandlerInfo);
+  removePreferredHandlerInfo = mimeSvc.getFromTypeAndExtension(
+    "nonexistent/rem-preferred-handler",
+    null
+  );
+  Assert.equal(removePreferredHandlerInfo.preferredApplicationHandler, null);
+
+  // Make sure we can store and retrieve a handler info object with possible
+  // handlers.  We test both adding and removing handlers.
+
+  // Get a handler info and make sure it has no possible handlers.
+  var possibleHandlersInfo = mimeSvc.getFromTypeAndExtension(
+    "nonexistent/possible-handlers",
+    null
+  );
+  Assert.equal(possibleHandlersInfo.possibleApplicationHandlers.length, 0);
+
+  // Store and re-retrieve the handler and make sure it still has no possible
+  // handlers.
+  handlerSvc.store(possibleHandlersInfo);
+  possibleHandlersInfo = mimeSvc.getFromTypeAndExtension(
+    "nonexistent/possible-handlers",
+    null
+  );
+  Assert.equal(possibleHandlersInfo.possibleApplicationHandlers.length, 0);
+
+  // Add two handlers, store the object, re-retrieve it, and make sure it has
+  // two handlers.
+  possibleHandlersInfo.possibleApplicationHandlers.appendElement(localHandler);
+  possibleHandlersInfo.possibleApplicationHandlers.appendElement(webHandler);
+  handlerSvc.store(possibleHandlersInfo);
+  possibleHandlersInfo = mimeSvc.getFromTypeAndExtension(
+    "nonexistent/possible-handlers",
+    null
+  );
+  Assert.equal(possibleHandlersInfo.possibleApplicationHandlers.length, 2);
+
+  // Figure out which is the local and which is the web handler and the index
+  // in the array of the local handler, which is the one we're going to remove
+  // to test removal of a handler.
+  var handler1 =
+    possibleHandlersInfo.possibleApplicationHandlers.queryElementAt(
+      0,
+      Ci.nsIHandlerApp
+    );
+  var handler2 =
+    possibleHandlersInfo.possibleApplicationHandlers.queryElementAt(
+      1,
+      Ci.nsIHandlerApp
+    );
+  var localPossibleHandler, webPossibleHandler, localIndex;
+  if (handler1 instanceof Ci.nsILocalHandlerApp) {
+    [localPossibleHandler, webPossibleHandler, localIndex] = [
+      handler1,
+      handler2,
+      0,
+    ];
+  } else {
+    [localPossibleHandler, webPossibleHandler, localIndex] = [
+      handler2,
+      handler1,
+      1,
+    ];
+  }
+  localPossibleHandler.QueryInterface(Ci.nsILocalHandlerApp);
+  webPossibleHandler.QueryInterface(Ci.nsIWebHandlerApp);
+
+  // Make sure the two handlers are the ones we stored.
+  Assert.equal(localPossibleHandler.name, localHandler.name);
+  Assert.ok(localPossibleHandler.equals(localHandler));
+  Assert.equal(webPossibleHandler.name, webHandler.name);
+  Assert.ok(webPossibleHandler.equals(webHandler));
+
+  // Remove a handler, store the object, re-retrieve it, and make sure
+  // it only has one handler.
+  possibleHandlersInfo.possibleApplicationHandlers.removeElementAt(localIndex);
+  handlerSvc.store(possibleHandlersInfo);
+  possibleHandlersInfo = mimeSvc.getFromTypeAndExtension(
+    "nonexistent/possible-handlers",
+    null
+  );
+  Assert.equal(possibleHandlersInfo.possibleApplicationHandlers.length, 1);
+
+  // Make sure the handler is the one we didn't remove.
+  webPossibleHandler =
+    possibleHandlersInfo.possibleApplicationHandlers.queryElementAt(
+      0,
+      Ci.nsIWebHandlerApp
+    );
+  Assert.equal(webPossibleHandler.name, webHandler.name);
+  Assert.ok(webPossibleHandler.equals(webHandler));
+
+  // ////////////////////////////////////////////////////
+  // handler info command line parameters and equality
+  var localApp = Cc[
+    "@mozilla.org/uriloader/local-handler-app;1"
+  ].createInstance(Ci.nsILocalHandlerApp);
+  var handlerApp = localApp.QueryInterface(Ci.nsIHandlerApp);
+
+  Assert.ok(handlerApp.equals(localApp));
+
+  localApp.executable = executable;
+
+  Assert.equal(0, localApp.parameterCount);
+  localApp.appendParameter("-test1");
+  Assert.equal(1, localApp.parameterCount);
+  localApp.appendParameter("-test2");
+  Assert.equal(2, localApp.parameterCount);
+  Assert.ok(localApp.parameterExists("-test1"));
+  Assert.ok(localApp.parameterExists("-test2"));
+  Assert.ok(!localApp.parameterExists("-false"));
+  localApp.clearParameters();
+  Assert.equal(0, localApp.parameterCount);
+
+  var localApp2 = Cc[
+    "@mozilla.org/uriloader/local-handler-app;1"
+  ].createInstance(Ci.nsILocalHandlerApp);
+
+  localApp2.executable = executable;
+
+  localApp.clearParameters();
+  Assert.ok(localApp.equals(localApp2));
+
+  // equal:
+  // cut -d 1 -f 2
+  // cut -d 1 -f 2
+
+  localApp.appendParameter("-test1");
+  localApp.appendParameter("-test2");
+  localApp.appendParameter("-test3");
+  localApp2.appendParameter("-test1");
+  localApp2.appendParameter("-test2");
+  localApp2.appendParameter("-test3");
+  Assert.ok(localApp.equals(localApp2));
+
+  // not equal:
+  // cut -d 1 -f 2
+  // cut -f 1 -d 2
+
+  localApp.clearParameters();
+  localApp2.clearParameters();
+
+  localApp.appendParameter("-test1");
+  localApp.appendParameter("-test2");
+  localApp.appendParameter("-test3");
+  localApp2.appendParameter("-test2");
+  localApp2.appendParameter("-test1");
+  localApp2.appendParameter("-test3");
+  Assert.ok(!localApp2.equals(localApp));
+
+  var str;
+  str = localApp.getParameter(0);
+  Assert.equal(str, "-test1");
+  str = localApp.getParameter(1);
+  Assert.equal(str, "-test2");
+  str = localApp.getParameter(2);
+  Assert.equal(str, "-test3");
+
+  // FIXME: test round trip integrity for a protocol.
+  // FIXME: test round trip integrity for a handler info with a web handler.
+
+  //* *************************************************************************//
+  // getTypeFromExtension tests
+
+  // test nonexistent extension
+  var lolType = handlerSvc.getTypeFromExtension("lolcat");
+  Assert.equal(lolType, "");
+
+  // add a handler for the extension
+  var lolHandler = mimeSvc.getFromTypeAndExtension("application/lolcat", null);
+
+  Assert.ok(!lolHandler.extensionExists("lolcat"));
+  lolHandler.preferredAction = Ci.nsIHandlerInfo.useHelperApp;
+  lolHandler.preferredApplicationHandler = localHandler;
+  lolHandler.alwaysAskBeforeHandling = false;
+  lolHandler.appendExtension("lolcat");
+
+  // store the handler
+  Assert.ok(!handlerSvc.exists(lolHandler));
+  handlerSvc.store(lolHandler);
+  Assert.ok(handlerSvc.exists(lolHandler));
+
+  // test now-existent extension
+  lolType = handlerSvc.getTypeFromExtension("lolcat");
+  Assert.equal(lolType, "application/lolcat");
+
+  // test mailcap entries with needsterminal are ignored on non-Windows non-Mac.
+  if (mozinfo.os != "win" && mozinfo.os != "mac") {
+    prefSvc.setStringPref(
+      "helpers.private_mailcap_file",
+      do_get_file("mailcap").path
+    );
+    handlerInfo = mimeSvc.getFromTypeAndExtension("text/plain", null);
+    Assert.equal(handlerInfo.preferredAction, Ci.nsIHandlerInfo.saveToDisk);
+    Assert.equal(handlerInfo.defaultDescription, "sed");
+  }
+}
diff --git a/uriloader/exthandler/tests/unit/test_handlerService_store.js b/uriloader/exthandler/tests/unit/test_handlerService_store.js
new file mode 100644
index 0000000000..03573dbc2c
--- /dev/null
+++ b/uriloader/exthandler/tests/unit/test_handlerService_store.js
@@ -0,0 +1,752 @@
+/* Any copyright is dedicated to the Public Domain.
+ * http://creativecommons.org/publicdomain/zero/1.0/ */
+
+/*
+ * Tests the nsIHandlerService interface.
+ */
+
+// Set up an nsIWebHandlerApp instance that can be used in multiple tests.
+let webHandlerApp = Cc[
+  "@mozilla.org/uriloader/web-handler-app;1"
+].createInstance(Ci.nsIWebHandlerApp);
+webHandlerApp.name = "Web Handler";
+webHandlerApp.uriTemplate = "https://www.example.com/?url=%s";
+let expectedWebHandlerApp = {
+  name: webHandlerApp.name,
+  uriTemplate: webHandlerApp.uriTemplate,
+};
+
+// Set up an nsILocalHandlerApp instance that can be used in multiple tests. The
+// executable should exist, but it doesn't need to point to an actual file, so
+// we simply initialize it to the path of an existing directory.
+let localHandlerApp = Cc[
+  "@mozilla.org/uriloader/local-handler-app;1"
+].createInstance(Ci.nsILocalHandlerApp);
+localHandlerApp.name = "Local Handler";
+localHandlerApp.executable = FileUtils.getFile("TmpD", []);
+let expectedLocalHandlerApp = {
+  name: localHandlerApp.name,
+  executable: localHandlerApp.executable,
+};
+
+/**
+ * Returns a new nsIHandlerInfo instance initialized to known values that don't
+ * depend on the platform and are easier to verify later.
+ *
+ * @param type
+ *        Because the "preferredAction" is initialized to saveToDisk, this
+ *        should represent a MIME type rather than a protocol.
+ */
+function getKnownHandlerInfo(type) {
+  let handlerInfo = HandlerServiceTestUtils.getBlankHandlerInfo(type);
+  handlerInfo.preferredAction = Ci.nsIHandlerInfo.saveToDisk;
+  handlerInfo.alwaysAskBeforeHandling = false;
+  return handlerInfo;
+}
+
+/**
+ * Checks that the information stored in the handler service instance under
+ * testing matches the test data files.
+ */
+function assertAllHandlerInfosMatchTestData() {
+  let handlerInfos = HandlerServiceTestUtils.getAllHandlerInfos();
+
+  // It's important that the MIME types we check here do not exist at the
+  // operating system level, otherwise the list of handlers and file extensions
+  // will be merged. The current implementation avoids duplicate entries.
+
+  HandlerServiceTestUtils.assertHandlerInfoMatches(handlerInfos.shift(), {
+    type: "example/type.handleinternally",
+    preferredAction: Ci.nsIHandlerInfo.handleInternally,
+    alwaysAskBeforeHandling: false,
+    fileExtensions: ["example_one"],
+  });
+
+  HandlerServiceTestUtils.assertHandlerInfoMatches(handlerInfos.shift(), {
+    type: "example/type.savetodisk",
+    preferredAction: Ci.nsIHandlerInfo.saveToDisk,
+    alwaysAskBeforeHandling: true,
+    preferredApplicationHandler: {
+      name: "Example Default Handler",
+      uriTemplate: "https://www.example.com/?url=%s",
+    },
+    possibleApplicationHandlers: [
+      {
+        name: "Example Default Handler",
+        uriTemplate: "https://www.example.com/?url=%s",
+      },
+    ],
+    fileExtensions: ["example_two", "example_three"],
+  });
+
+  HandlerServiceTestUtils.assertHandlerInfoMatches(handlerInfos.shift(), {
+    type: "example/type.usehelperapp",
+    preferredAction: Ci.nsIHandlerInfo.useHelperApp,
+    alwaysAskBeforeHandling: true,
+    preferredApplicationHandler: {
+      name: "Example Default Handler",
+      uriTemplate: "https://www.example.com/?url=%s",
+    },
+    possibleApplicationHandlers: [
+      {
+        name: "Example Default Handler",
+        uriTemplate: "https://www.example.com/?url=%s",
+      },
+      {
+        name: "Example Possible Handler One",
+        uriTemplate: "http://www.example.com/?id=1&url=%s",
+      },
+      {
+        name: "Example Possible Handler Two",
+        uriTemplate: "http://www.example.com/?id=2&url=%s",
+      },
+    ],
+    fileExtensions: ["example_two", "example_three"],
+  });
+
+  HandlerServiceTestUtils.assertHandlerInfoMatches(handlerInfos.shift(), {
+    type: "example/type.usesystemdefault",
+    preferredAction: Ci.nsIHandlerInfo.useSystemDefault,
+    alwaysAskBeforeHandling: false,
+    possibleApplicationHandlers: [
+      {
+        name: "Example Possible Handler",
+        uriTemplate: "http://www.example.com/?url=%s",
+      },
+    ],
+  });
+
+  HandlerServiceTestUtils.assertHandlerInfoMatches(handlerInfos.shift(), {
+    type: "examplescheme.usehelperapp",
+    preferredAction: Ci.nsIHandlerInfo.useHelperApp,
+    alwaysAskBeforeHandling: true,
+    preferredApplicationHandler: {
+      name: "Example Default Handler",
+      uriTemplate: "https://www.example.com/?url=%s",
+    },
+    possibleApplicationHandlers: [
+      {
+        name: "Example Default Handler",
+        uriTemplate: "https://www.example.com/?url=%s",
+      },
+      {
+        name: "Example Possible Handler One",
+        uriTemplate: "http://www.example.com/?id=1&url=%s",
+      },
+      {
+        name: "Example Possible Handler Two",
+        uriTemplate: "http://www.example.com/?id=2&url=%s",
+      },
+    ],
+  });
+
+  HandlerServiceTestUtils.assertHandlerInfoMatches(handlerInfos.shift(), {
+    type: "examplescheme.usesystemdefault",
+    preferredAction: Ci.nsIHandlerInfo.useSystemDefault,
+    alwaysAskBeforeHandling: false,
+    possibleApplicationHandlers: [
+      {
+        name: "Example Possible Handler",
+        uriTemplate: "http://www.example.com/?url=%s",
+      },
+    ],
+  });
+
+  Assert.equal(handlerInfos.length, 0);
+}
+
+/**
+ * Loads data from a file in a predefined format, verifying that the format is
+ * recognized and all the known properties are loaded and saved.
+ */
+add_task(async function test_store_fillHandlerInfo_predefined() {
+  // Test that the file format used in previous versions can be loaded.
+  await copyTestDataToHandlerStore();
+  await assertAllHandlerInfosMatchTestData();
+
+  // Keep a copy of the nsIHandlerInfo instances, then delete the handler store
+  // and populate it with the known data. Since the handler store is empty, the
+  // default handlers for the current locale are also injected, so we have to
+  // delete them manually before adding the other nsIHandlerInfo instances.
+  let testHandlerInfos = HandlerServiceTestUtils.getAllHandlerInfos();
+  await deleteHandlerStore();
+  for (let handlerInfo of HandlerServiceTestUtils.getAllHandlerInfos()) {
+    gHandlerService.remove(handlerInfo);
+  }
+  for (let handlerInfo of testHandlerInfos) {
+    gHandlerService.store(handlerInfo);
+  }
+
+  // Test that the known data still matches after saving it and reloading.
+  await unloadHandlerStore();
+  await assertAllHandlerInfosMatchTestData();
+});
+
+/**
+ * Check that "store" is able to add new instances, that "remove" and "exists"
+ * work, and that "fillHandlerInfo" throws when the instance does not exist.
+ */
+add_task(async function test_store_remove_exists() {
+  // Test both MIME types and protocols.
+  for (let type of [
+    "example/type.usehelperapp",
+    "examplescheme.usehelperapp",
+  ]) {
+    // Create new nsIHandlerInfo instances before loading the test data.
+    await deleteHandlerStore();
+    let handlerInfoPresent = HandlerServiceTestUtils.getHandlerInfo(type);
+    let handlerInfoAbsent = HandlerServiceTestUtils.getHandlerInfo(type + "2");
+
+    // Set up known properties that we can verify later.
+    handlerInfoAbsent.preferredAction = Ci.nsIHandlerInfo.saveToDisk;
+    handlerInfoAbsent.alwaysAskBeforeHandling = false;
+
+    await copyTestDataToHandlerStore();
+
+    Assert.ok(gHandlerService.exists(handlerInfoPresent));
+    Assert.ok(!gHandlerService.exists(handlerInfoAbsent));
+
+    gHandlerService.store(handlerInfoAbsent);
+    gHandlerService.remove(handlerInfoPresent);
+
+    await unloadHandlerStore();
+
+    Assert.ok(!gHandlerService.exists(handlerInfoPresent));
+    Assert.ok(gHandlerService.exists(handlerInfoAbsent));
+
+    Assert.throws(
+      () => gHandlerService.fillHandlerInfo(handlerInfoPresent, ""),
+      ex => ex.result == Cr.NS_ERROR_NOT_AVAILABLE
+    );
+
+    let actualHandlerInfo = HandlerServiceTestUtils.getHandlerInfo(type + "2");
+    HandlerServiceTestUtils.assertHandlerInfoMatches(actualHandlerInfo, {
+      type: type + "2",
+      preferredAction: Ci.nsIHandlerInfo.saveToDisk,
+      alwaysAskBeforeHandling: false,
+    });
+  }
+});
+
+/**
+ * Tests that it is possible to save an nsIHandlerInfo instance with a
+ * "preferredAction" that is either a valid or an unknown value, and the
+ * action always takes on an appropriate value when reloading.
+ */
+add_task(async function test_store_preferredAction() {
+  await deleteHandlerStore();
+
+  let handlerInfo = getKnownHandlerInfo("example/new");
+  // Valid action values should all remain unchanged across a refresh, except
+  // for alwaysAsk which may be overridden with useHelperApp depending on prefs.
+  // Invalid action values should always convert to useHelperApp.
+  const actions = [
+    {
+      preferred: Ci.nsIHandlerInfo.alwaysAsk,
+      expected: Ci.nsIHandlerInfo.alwaysAsk,
+    },
+    {
+      preferred: Ci.nsIHandlerInfo.handleInternally,
+      expected: Ci.nsIHandlerInfo.handleInternally,
+    },
+    { preferred: 999, expected: Ci.nsIHandlerInfo.useHelperApp },
+  ];
+
+  for (let action of actions) {
+    handlerInfo.preferredAction = action.preferred;
+    gHandlerService.store(handlerInfo);
+    gHandlerService.fillHandlerInfo(handlerInfo, "");
+    Assert.equal(handlerInfo.preferredAction, action.expected);
+  }
+});
+
+/**
+ * Tests that it is possible to save an nsIHandlerInfo instance containing an
+ * nsILocalHandlerApp instance pointing to an executable that doesn't exist, but
+ * this entry is ignored when reloading.
+ */
+add_task(async function test_store_localHandlerApp_missing() {
+  if (!("@mozilla.org/uriloader/dbus-handler-app;1" in Cc)) {
+    info("Skipping test because it does not apply to this platform.");
+    return;
+  }
+
+  let missingHandlerApp = Cc[
+    "@mozilla.org/uriloader/local-handler-app;1"
+  ].createInstance(Ci.nsILocalHandlerApp);
+  missingHandlerApp.name = "Non-existing Handler";
+  missingHandlerApp.executable = FileUtils.getFile("TmpD", ["nonexisting"]);
+
+  await deleteHandlerStore();
+
+  let handlerInfo = getKnownHandlerInfo("example/new");
+  handlerInfo.preferredApplicationHandler = missingHandlerApp;
+  handlerInfo.possibleApplicationHandlers.appendElement(missingHandlerApp);
+  handlerInfo.possibleApplicationHandlers.appendElement(webHandlerApp);
+  gHandlerService.store(handlerInfo);
+
+  await unloadHandlerStore();
+
+  let actualHandlerInfo = HandlerServiceTestUtils.getHandlerInfo("example/new");
+  HandlerServiceTestUtils.assertHandlerInfoMatches(actualHandlerInfo, {
+    type: "example/new",
+    preferredAction: Ci.nsIHandlerInfo.saveToDisk,
+    alwaysAskBeforeHandling: false,
+    possibleApplicationHandlers: [expectedWebHandlerApp],
+  });
+});
+
+/**
+ * Test saving and reloading an instance of nsIDBusHandlerApp.
+ */
+add_task(async function test_store_dBusHandlerApp() {
+  if (!("@mozilla.org/uriloader/dbus-handler-app;1" in Cc)) {
+    info("Skipping test because it does not apply to this platform.");
+    return;
+  }
+
+  // Set up an nsIDBusHandlerApp instance for testing.
+  let dBusHandlerApp = Cc[
+    "@mozilla.org/uriloader/dbus-handler-app;1"
+  ].createInstance(Ci.nsIDBusHandlerApp);
+  dBusHandlerApp.name = "DBus Handler";
+  dBusHandlerApp.service = "test.method.server";
+  dBusHandlerApp.method = "Method";
+  dBusHandlerApp.dBusInterface = "test.method.Type";
+  dBusHandlerApp.objectPath = "/test/method/Object";
+  let expectedDBusHandlerApp = {
+    name: dBusHandlerApp.name,
+    service: dBusHandlerApp.service,
+    method: dBusHandlerApp.method,
+    dBusInterface: dBusHandlerApp.dBusInterface,
+    objectPath: dBusHandlerApp.objectPath,
+  };
+
+  await deleteHandlerStore();
+
+  let handlerInfo = getKnownHandlerInfo("example/new");
+  handlerInfo.preferredApplicationHandler = dBusHandlerApp;
+  handlerInfo.possibleApplicationHandlers.appendElement(dBusHandlerApp);
+  gHandlerService.store(handlerInfo);
+
+  await unloadHandlerStore();
+
+  let actualHandlerInfo = HandlerServiceTestUtils.getHandlerInfo("example/new");
+  HandlerServiceTestUtils.assertHandlerInfoMatches(actualHandlerInfo, {
+    type: "example/new",
+    preferredAction: Ci.nsIHandlerInfo.saveToDisk,
+    alwaysAskBeforeHandling: false,
+    preferredApplicationHandler: expectedDBusHandlerApp,
+    possibleApplicationHandlers: [expectedDBusHandlerApp],
+  });
+});
+
+/**
+ * Tests that it is possible to save an nsIHandlerInfo instance with a
+ * "preferredApplicationHandler" and no "possibleApplicationHandlers", but the
+ * former is always included in the latter list when reloading.
+ */
+add_task(
+  async function test_store_possibleApplicationHandlers_includes_preferred() {
+    await deleteHandlerStore();
+
+    let handlerInfo = getKnownHandlerInfo("example/new");
+    handlerInfo.preferredApplicationHandler = localHandlerApp;
+    gHandlerService.store(handlerInfo);
+
+    await unloadHandlerStore();
+
+    let actualHandlerInfo =
+      HandlerServiceTestUtils.getHandlerInfo("example/new");
+    HandlerServiceTestUtils.assertHandlerInfoMatches(actualHandlerInfo, {
+      type: "example/new",
+      preferredAction: Ci.nsIHandlerInfo.saveToDisk,
+      alwaysAskBeforeHandling: false,
+      preferredApplicationHandler: expectedLocalHandlerApp,
+      possibleApplicationHandlers: [expectedLocalHandlerApp],
+    });
+  }
+);
+
+/**
+ * Tests that it is possible to save an nsIHandlerInfo instance with a
+ * "preferredApplicationHandler" that is not the first element in
+ * "possibleApplicationHandlers", but the former is always included as the first
+ * element of the latter list when reloading.
+ */
+add_task(
+  async function test_store_possibleApplicationHandlers_preferred_first() {
+    await deleteHandlerStore();
+
+    let handlerInfo = getKnownHandlerInfo("example/new");
+    handlerInfo.preferredApplicationHandler = webHandlerApp;
+    // The preferred handler is appended after the other one.
+    handlerInfo.possibleApplicationHandlers.appendElement(localHandlerApp);
+    handlerInfo.possibleApplicationHandlers.appendElement(webHandlerApp);
+    gHandlerService.store(handlerInfo);
+
+    await unloadHandlerStore();
+
+    let actualHandlerInfo =
+      HandlerServiceTestUtils.getHandlerInfo("example/new");
+    HandlerServiceTestUtils.assertHandlerInfoMatches(actualHandlerInfo, {
+      type: "example/new",
+      preferredAction: Ci.nsIHandlerInfo.saveToDisk,
+      alwaysAskBeforeHandling: false,
+      preferredApplicationHandler: expectedWebHandlerApp,
+      possibleApplicationHandlers: [
+        expectedWebHandlerApp,
+        expectedLocalHandlerApp,
+      ],
+    });
+  }
+);
+
+/**
+ * Tests that it is possible to save an nsIHandlerInfo instance with an
+ * uppercase file extension, but it is converted to lowercase when reloading.
+ */
+add_task(async function test_store_fileExtensions_lowercase() {
+  await deleteHandlerStore();
+
+  let handlerInfo = getKnownHandlerInfo("example/new");
+  handlerInfo.appendExtension("extension_test1");
+  handlerInfo.appendExtension("EXTENSION_test2");
+  gHandlerService.store(handlerInfo);
+
+  await unloadHandlerStore();
+
+  let actualHandlerInfo = HandlerServiceTestUtils.getHandlerInfo("example/new");
+  HandlerServiceTestUtils.assertHandlerInfoMatches(actualHandlerInfo, {
+    type: "example/new",
+    preferredAction: Ci.nsIHandlerInfo.saveToDisk,
+    alwaysAskBeforeHandling: false,
+    fileExtensions: ["extension_test1", "extension_test2"],
+  });
+});
+
+/**
+ * Tests that appendExtension doesn't add duplicates, and that anyway duplicates
+ * from possibleApplicationHandlers are removed when saving and reloading.
+ */
+add_task(async function test_store_no_duplicates() {
+  await deleteHandlerStore();
+
+  let handlerInfo = getKnownHandlerInfo("example/new");
+  handlerInfo.preferredApplicationHandler = webHandlerApp;
+  handlerInfo.possibleApplicationHandlers.appendElement(webHandlerApp);
+  handlerInfo.possibleApplicationHandlers.appendElement(localHandlerApp);
+  handlerInfo.possibleApplicationHandlers.appendElement(localHandlerApp);
+  handlerInfo.possibleApplicationHandlers.appendElement(webHandlerApp);
+  handlerInfo.appendExtension("extension_test1");
+  handlerInfo.appendExtension("extension_test2");
+  handlerInfo.appendExtension("extension_test1");
+  handlerInfo.appendExtension("EXTENSION_test1");
+  Assert.deepEqual(Array.from(handlerInfo.getFileExtensions()), [
+    "extension_test1",
+    "extension_test2",
+  ]);
+  gHandlerService.store(handlerInfo);
+
+  await unloadHandlerStore();
+
+  let actualHandlerInfo = HandlerServiceTestUtils.getHandlerInfo("example/new");
+  HandlerServiceTestUtils.assertHandlerInfoMatches(actualHandlerInfo, {
+    type: "example/new",
+    preferredAction: Ci.nsIHandlerInfo.saveToDisk,
+    alwaysAskBeforeHandling: false,
+    preferredApplicationHandler: expectedWebHandlerApp,
+    possibleApplicationHandlers: [
+      expectedWebHandlerApp,
+      expectedLocalHandlerApp,
+    ],
+    fileExtensions: ["extension_test1", "extension_test2"],
+  });
+});
+
+/**
+ * Tests that setFileExtensions doesn't add duplicates.
+ */
+add_task(async function test_setFileExtensions_no_duplicates() {
+  await deleteHandlerStore();
+
+  let handlerInfo = getKnownHandlerInfo("example/new");
+  handlerInfo.setFileExtensions("a,b,A,b,c,a");
+  let expected = ["a", "b", "c"];
+  Assert.deepEqual(Array.from(handlerInfo.getFileExtensions()), expected);
+  // Test empty extensions, also at begin and end.
+  handlerInfo.setFileExtensions(",a,,b,A,c,");
+  Assert.deepEqual(Array.from(handlerInfo.getFileExtensions()), expected);
+});
+
+/**
+ * Tests that "store" deletes properties that have their default values from
+ * the data store.
+ *
+ * File extensions are never deleted once they have been associated.
+ */
+add_task(async function test_store_deletes_properties_except_extensions() {
+  await deleteHandlerStore();
+
+  // Prepare an nsIHandlerInfo instance with all the properties set to values
+  // that will result in deletions. The preferredAction is also set to a defined
+  // value so we can more easily verify it later.
+  let handlerInfo = HandlerServiceTestUtils.getBlankHandlerInfo(
+    "example/type.savetodisk"
+  );
+  handlerInfo.preferredAction = Ci.nsIHandlerInfo.saveToDisk;
+  handlerInfo.alwaysAskBeforeHandling = false;
+
+  // All the properties for "example/type.savetodisk" are present in the test
+  // data, so we load the data before overwriting their values.
+  await copyTestDataToHandlerStore();
+  gHandlerService.store(handlerInfo);
+
+  // Now we can reload the data and verify that no extra values have been kept.
+  await unloadHandlerStore();
+  let actualHandlerInfo = HandlerServiceTestUtils.getHandlerInfo(
+    "example/type.savetodisk"
+  );
+  HandlerServiceTestUtils.assertHandlerInfoMatches(actualHandlerInfo, {
+    type: "example/type.savetodisk",
+    preferredAction: Ci.nsIHandlerInfo.saveToDisk,
+    alwaysAskBeforeHandling: false,
+    fileExtensions: ["example_two", "example_three"],
+  });
+});
+
+/**
+ * Tests the "overrideType" argument of "fillHandlerInfo".
+ */
+add_task(async function test_fillHandlerInfo_overrideType() {
+  // Test both MIME types and protocols.
+  for (let type of [
+    "example/type.usesystemdefault",
+    "examplescheme.usesystemdefault",
+  ]) {
+    await deleteHandlerStore();
+
+    // Create new nsIHandlerInfo instances before loading the test data.
+    let handlerInfoAbsent = HandlerServiceTestUtils.getHandlerInfo(type + "2");
+
+    // Fill the nsIHandlerInfo instance using the type that actually exists.
+    await copyTestDataToHandlerStore();
+    gHandlerService.fillHandlerInfo(handlerInfoAbsent, type);
+    HandlerServiceTestUtils.assertHandlerInfoMatches(handlerInfoAbsent, {
+      // While the data is populated from another type, the type is unchanged.
+      type: type + "2",
+      preferredAction: Ci.nsIHandlerInfo.useSystemDefault,
+      alwaysAskBeforeHandling: false,
+      possibleApplicationHandlers: [
+        {
+          name: "Example Possible Handler",
+          uriTemplate: "http://www.example.com/?url=%s",
+        },
+      ],
+    });
+  }
+});
+
+/**
+ * Tests "getTypeFromExtension" including unknown extensions.
+ */
+add_task(async function test_getTypeFromExtension() {
+  await copyTestDataToHandlerStore();
+
+  Assert.equal(gHandlerService.getTypeFromExtension(""), "");
+  Assert.equal(gHandlerService.getTypeFromExtension("example_unknown"), "");
+  Assert.equal(
+    gHandlerService.getTypeFromExtension("example_one"),
+    "example/type.handleinternally"
+  );
+  Assert.equal(
+    gHandlerService.getTypeFromExtension("EXAMPLE_one"),
+    "example/type.handleinternally"
+  );
+});
+
+/**
+ * Checks that the information stored in the handler service instance under
+ * testing matches the default handlers for the English locale.
+ */
+function assertAllHandlerInfosMatchDefaultHandlers() {
+  let handlerInfos = HandlerServiceTestUtils.getAllHandlerInfos();
+
+  HandlerServiceTestUtils.assertHandlerInfoMatches(handlerInfos.shift(), {
+    type: "mailto",
+    preferredActionOSDependent: true,
+    possibleApplicationHandlers: [
+      {
+        name: "Gmail",
+        uriTemplate: "https://mail.google.com/mail/?extsrc=mailto&url=%s",
+      },
+    ],
+  });
+
+  Assert.equal(handlerInfos.length, 0);
+}
+
+/**
+ * Tests the default protocol handlers imported from the locale-specific data.
+ */
+add_task(
+  { skip_if: () => AppConstants.MOZ_APP_NAME == "thunderbird" },
+  async function test_default_protocol_handlers() {
+    if (
+      !Services.prefs.getPrefType("gecko.handlerService.defaultHandlersVersion")
+    ) {
+      info("This platform or locale does not have default handlers.");
+      return;
+    }
+
+    // This will inject the default protocol handlers for the current locale.
+    await deleteHandlerStore();
+
+    await assertAllHandlerInfosMatchDefaultHandlers();
+  }
+);
+
+/**
+ * Tests that the default protocol handlers are not imported again from the
+ * locale-specific data if they already exist.
+ */
+add_task(
+  { skip_if: () => AppConstants.MOZ_APP_NAME == "thunderbird" },
+  async function test_default_protocol_handlers_no_duplicates() {
+    if (
+      !Services.prefs.getPrefType("gecko.handlerService.defaultHandlersVersion")
+    ) {
+      info("This platform or locale does not have default handlers.");
+      return;
+    }
+
+    // This will inject the default protocol handlers for the current locale.
+    await deleteHandlerStore();
+
+    // Clear the preference to force injecting again.
+    Services.prefs.clearUserPref("gecko.handlerService.defaultHandlersVersion");
+
+    await unloadHandlerStore();
+
+    // There should be no duplicate handlers in the protocols.
+    assertAllHandlerInfosMatchDefaultHandlers();
+  }
+);
+
+/**
+ * Ensures forward compatibility by checking that the "store" method preserves
+ * unknown properties in the test data.
+ */
+add_task(async function test_store_keeps_unknown_properties() {
+  // Create a new nsIHandlerInfo instance before loading the test data.
+  await deleteHandlerStore();
+  let handlerInfo = HandlerServiceTestUtils.getHandlerInfo(
+    "example/type.handleinternally"
+  );
+
+  await copyTestDataToHandlerStore();
+  gHandlerService.store(handlerInfo);
+
+  await unloadHandlerStore();
+  let data = await IOUtils.readJSON(jsonPath);
+  Assert.equal(
+    data.mimeTypes["example/type.handleinternally"].unknownProperty,
+    "preserved"
+  );
+});
+
+/**
+ * Runs the asyncInit method, ensuring that it successfully inits the store
+ * and calls the handlersvc-store-initialized topic.
+ */
+add_task(async function test_async_init() {
+  await deleteHandlerStore();
+  await copyTestDataToHandlerStore();
+  gHandlerService.asyncInit();
+  await TestUtils.topicObserved("handlersvc-store-initialized");
+  await assertAllHandlerInfosMatchTestData();
+
+  await unloadHandlerStore();
+});
+
+/**
+ * Races the asyncInit method against the sync init (implicit in enumerate),
+ * to ensure that the store will be synchronously initialized without any
+ * ill effects.
+ */
+add_task(async function test_race_async_init() {
+  await deleteHandlerStore();
+  await copyTestDataToHandlerStore();
+  let storeInitialized = false;
+  // Pass a callback to synchronously observe the topic, as a promise would
+  // resolve asynchronously
+  TestUtils.topicObserved("handlersvc-store-initialized", () => {
+    storeInitialized = true;
+    return true;
+  });
+  gHandlerService.asyncInit();
+  Assert.ok(!storeInitialized);
+  gHandlerService.enumerate();
+  Assert.ok(storeInitialized);
+  await assertAllHandlerInfosMatchTestData();
+
+  await unloadHandlerStore();
+});
+
+/**
+ * Test saving and reloading an instance of nsIGIOMimeApp.
+ */
+add_task(async function test_store_gioHandlerApp() {
+  if (!("@mozilla.org/gio-service;1" in Cc)) {
+    info("Skipping test because it does not apply to this platform.");
+    return;
+  }
+
+  // Create dummy exec file that following won't fail because file not found error
+  let dummyHandlerFile = FileUtils.getFile("TmpD", ["dummyHandler"]);
+  dummyHandlerFile.createUnique(
+    Ci.nsIFile.NORMAL_FILE_TYPE,
+    parseInt("777", 8)
+  );
+
+  // Set up an nsIGIOMimeApp instance for testing.
+  let handlerApp = Cc["@mozilla.org/gio-service;1"]
+    .getService(Ci.nsIGIOService)
+    .createAppFromCommand(dummyHandlerFile.path, "Dummy GIO handler");
+  let expectedGIOMimeHandlerApp = {
+    name: handlerApp.name,
+    command: handlerApp.command,
+  };
+
+  await deleteHandlerStore();
+
+  let handlerInfo = getKnownHandlerInfo("example/new");
+  handlerInfo.preferredApplicationHandler = handlerApp;
+  handlerInfo.possibleApplicationHandlers.appendElement(handlerApp);
+  handlerInfo.possibleApplicationHandlers.appendElement(webHandlerApp);
+  gHandlerService.store(handlerInfo);
+
+  await unloadHandlerStore();
+
+  let actualHandlerInfo = HandlerServiceTestUtils.getHandlerInfo("example/new");
+  HandlerServiceTestUtils.assertHandlerInfoMatches(actualHandlerInfo, {
+    type: "example/new",
+    preferredAction: Ci.nsIHandlerInfo.saveToDisk,
+    alwaysAskBeforeHandling: false,
+    preferredApplicationHandler: expectedGIOMimeHandlerApp,
+    possibleApplicationHandlers: [expectedGIOMimeHandlerApp, webHandlerApp],
+  });
+
+  await IOUtils.remove(dummyHandlerFile.path);
+
+  // After removing dummyHandlerFile, the handler should disappear from the
+  // list of possibleApplicationHandlers and preferredAppHandler should be null.
+  actualHandlerInfo = HandlerServiceTestUtils.getHandlerInfo("example/new");
+  HandlerServiceTestUtils.assertHandlerInfoMatches(actualHandlerInfo, {
+    type: "example/new",
+    preferredAction: Ci.nsIHandlerInfo.saveToDisk,
+    alwaysAskBeforeHandling: false,
+    preferredApplicationHandler: null,
+    possibleApplicationHandlers: [webHandlerApp],
+  });
+});
diff --git a/uriloader/exthandler/tests/unit/test_punycodeURIs.js b/uriloader/exthandler/tests/unit/test_punycodeURIs.js
new file mode 100644
index 0000000000..949c9914ec
--- /dev/null
+++ b/uriloader/exthandler/tests/unit/test_punycodeURIs.js
@@ -0,0 +1,126 @@
+/* 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/. */
+
+// Encoded test URI to work on all platforms/independent of file encoding
+const kTestURI = "http://\u65e5\u672c\u8a93.jp/";
+const kExpectedURI = "http://xn--wgv71a309e.jp/";
+const kOutputFile = "result.txt";
+
+// Try several times in case the box we're running on is slow.
+const kMaxCheckExistAttempts = 30; // seconds
+var gCheckExistsAttempts = 0;
+
+const tempDir = do_get_tempdir();
+
+function checkFile() {
+  // This is where we expect the output
+  var tempFile = tempDir.clone();
+  tempFile.append(kOutputFile);
+
+  if (!tempFile.exists()) {
+    if (gCheckExistsAttempts >= kMaxCheckExistAttempts) {
+      do_throw(
+        "Expected File " +
+          tempFile.path +
+          " does not exist after " +
+          kMaxCheckExistAttempts +
+          " seconds"
+      );
+    } else {
+      ++gCheckExistsAttempts;
+      // Wait a bit longer then try again
+      do_timeout(1000, checkFile);
+      return;
+    }
+  }
+
+  // Now read it
+  var fstream = Cc["@mozilla.org/network/file-input-stream;1"].createInstance(
+    Ci.nsIFileInputStream
+  );
+  var sstream = Cc["@mozilla.org/scriptableinputstream;1"].createInstance(
+    Ci.nsIScriptableInputStream
+  );
+  fstream.init(tempFile, -1, 0, 0);
+  sstream.init(fstream);
+
+  // Read the first line only as that's the one we expect WriteArguments
+  // to be writing the argument to.
+  var data = sstream.read(4096);
+
+  sstream.close();
+  fstream.close();
+
+  // Now remove the old file
+  tempFile.remove(false);
+
+  // This currently fails on Mac with an argument like -psn_0_nnnnnn
+  // This seems to be to do with how the executable is called, but I couldn't
+  // find a way around it.
+  // Additionally the lack of OS detection in xpcshell tests sucks, so we'll
+  // have to check for the argument mac gives us.
+  if (data.substring(0, 7) != "-psn_0_") {
+    Assert.equal(data, kExpectedURI);
+  }
+
+  do_test_finished();
+}
+
+function run_test() {
+  if (mozinfo.os == "mac") {
+    dump("INFO | test_punycodeURIs.js | Skipping test on mac, bug 599475");
+    return;
+  }
+
+  // set up the uri to test with
+  var ioService = Services.io;
+
+  // set up the local handler object
+  var localHandler = Cc[
+    "@mozilla.org/uriloader/local-handler-app;1"
+  ].createInstance(Ci.nsILocalHandlerApp);
+  localHandler.name = "Test Local Handler App";
+
+  // WriteArgument will just dump its arguments to a file for us.
+  var processDir = do_get_cwd();
+  var exe = processDir.clone();
+  exe.append("WriteArgument");
+
+  if (!exe.exists()) {
+    // Maybe we are on windows
+    exe.leafName = "WriteArgument.exe";
+    if (!exe.exists()) {
+      do_throw("Could not locate the WriteArgument tests executable\n");
+    }
+  }
+
+  var outFile = tempDir.clone();
+  outFile.append(kOutputFile);
+
+  // Set an environment variable for WriteArgument to pick up
+  // The Write Argument file needs to know where its libraries are, so
+  // just force the path variable
+  // For mac
+  var greDir = Services.dirsvc.get("GreD", Ci.nsIFile);
+
+  Services.env.set("DYLD_LIBRARY_PATH", greDir.path);
+  // For Linux
+  Services.env.set("LD_LIBRARY_PATH", greDir.path);
+  // XXX: handle windows
+
+  // Now tell it where we want the file.
+  Services.env.set("WRITE_ARGUMENT_FILE", outFile.path);
+
+  var uri = ioService.newURI(kTestURI);
+
+  // Just check we've got these matching, if we haven't there's a problem
+  // with ascii spec or our test case.
+  Assert.equal(uri.asciiSpec, kExpectedURI);
+
+  localHandler.executable = exe;
+  localHandler.launchWithURI(uri);
+
+  do_test_pending();
+  do_timeout(1000, checkFile);
+}
diff --git a/uriloader/exthandler/tests/unit/xpcshell.ini b/uriloader/exthandler/tests/unit/xpcshell.ini
new file mode 100644
index 0000000000..57215d1dc5
--- /dev/null
+++ b/uriloader/exthandler/tests/unit/xpcshell.ini
@@ -0,0 +1,40 @@
+[DEFAULT]
+head = head.js
+run-sequentially = Bug 912235 - Intermittent failures
+firefox-appdir = browser
+
+[test_defaults_handlerService.js]
+# No default stored handlers on android given lack of support.
+# No default stored handlers on Thunderbird.
+skip-if =
+    os == "android"
+    appname == "thunderbird"
+[test_downloads_improvements_migration.js]
+# No default stored handlers on android given lack of support.
+# No default stored handlers on Thunderbird.
+skip-if =
+    os == "android"
+    appname == "thunderbird"
+[test_filename_sanitize.js]
+skip-if =
+  os == 'mac' # Bug 1817727
+[test_getFromTypeAndExtension.js]
+[test_getMIMEInfo_pdf.js]
+[test_getMIMEInfo_unknown_mime_type.js]
+run-if = os == "win" # Windows only test
+[test_getTypeFromExtension_ext_to_type_mapping.js]
+[test_getTypeFromExtension_with_empty_Content_Type.js]
+run-if = os == "win" # Windows only test
+[test_badMIMEType.js]
+run-if = buildapp == "browser"
+[test_handlerService.js]
+support-files = mailcap
+# Bug 676997: test consistently fails on Android
+fail-if = os == "android"
+[test_handlerService_store.js]
+# Disabled for 1563343 -- the app should determine possible handlers in GV.
+fail-if = os == "android"
+support-files = handlers.json
+[test_punycodeURIs.js]
+skip-if =
+  os == 'win' && msix # https://bugzilla.mozilla.org/show_bug.cgi?id=1809485