Adding upstream version 110.0.1.upstream/110.0.1upstream

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

16 files changed, 11444 insertions, 0 deletions

diff --git a/browser/components/urlbar/tests/quicksuggest/unit/head.js b/browser/components/urlbar/tests/quicksuggest/unit/head.js
new file mode 100644
index 0000000000..0001f624be
--- /dev/null
+++ b/browser/components/urlbar/tests/quicksuggest/unit/head.js
@@ -0,0 +1,227 @@
+/* Any copyright is dedicated to the Public Domain.
+ * http://creativecommons.org/publicdomain/zero/1.0/ */
+
+/* import-globals-from ../../unit/head.js */
+
+ChromeUtils.defineESModuleGetters(this, {
+  QuickSuggest: "resource:///modules/QuickSuggest.sys.mjs",
+  RemoteSettingsClient:
+    "resource:///modules/urlbar/private/RemoteSettingsClient.sys.mjs",
+  TelemetryTestUtils: "resource://testing-common/TelemetryTestUtils.sys.mjs",
+  UrlbarProviderAutofill: "resource:///modules/UrlbarProviderAutofill.sys.mjs",
+  UrlbarProviderQuickSuggest:
+    "resource:///modules/UrlbarProviderQuickSuggest.sys.mjs",
+});
+
+add_setup(async function setUpQuickSuggestXpcshellTest() {
+  // Initializing TelemetryEnvironment in an xpcshell environment requires
+  // jumping through a bunch of hoops. Suggest's use of TelemetryEnvironment is
+  // tested in browser tests, and there's no other necessary reason to wait for
+  // TelemetryEnvironment initialization in xpcshell tests, so just skip it.
+  UrlbarPrefs._testSkipTelemetryEnvironmentInit = true;
+});
+
+/**
+ * Tests quick suggest prefs migrations.
+ *
+ * @param {object} options
+ *   The options object.
+ * @param {object} options.testOverrides
+ *   An object that modifies how migration is performed. It has the following
+ *   properties, and all are optional:
+ *
+ *   {number} migrationVersion
+ *     Migration will stop at this version, so for example you can test
+ *     migration only up to version 1 even when the current actual version is
+ *     larger than 1.
+ *   {object} defaultPrefs
+ *     An object that maps pref names (relative to `browser.urlbar`) to
+ *     default-branch values. These should be the default prefs for the given
+ *     `migrationVersion` and will be set as defaults before migration occurs.
+ *
+ * @param {string} options.scenario
+ *   The scenario to set at the time migration occurs.
+ * @param {object} options.expectedPrefs
+ *   The expected prefs after migration: `{ defaultBranch, userBranch }`
+ *   Pref names should be relative to `browser.urlbar`.
+ * @param {object} [options.initialUserBranch]
+ *   Prefs to set on the user branch before migration ocurs. Use these to
+ *   simulate user actions like disabling prefs or opting in or out of the
+ *   online modal. Pref names should be relative to `browser.urlbar`.
+ */
+async function doMigrateTest({
+  testOverrides,
+  scenario,
+  expectedPrefs,
+  initialUserBranch = {},
+}) {
+  info(
+    "Testing migration: " +
+      JSON.stringify({
+        testOverrides,
+        initialUserBranch,
+        scenario,
+        expectedPrefs,
+      })
+  );
+
+  function setPref(branch, name, value) {
+    switch (typeof value) {
+      case "boolean":
+        branch.setBoolPref(name, value);
+        break;
+      case "number":
+        branch.setIntPref(name, value);
+        break;
+      case "string":
+        branch.setCharPref(name, value);
+        break;
+      default:
+        Assert.ok(
+          false,
+          `Pref type not handled for setPref: ${name} = ${value}`
+        );
+        break;
+    }
+  }
+
+  function getPref(branch, name) {
+    let type = typeof UrlbarPrefs.get(name);
+    switch (type) {
+      case "boolean":
+        return branch.getBoolPref(name);
+      case "number":
+        return branch.getIntPref(name);
+      case "string":
+        return branch.getCharPref(name);
+      default:
+        Assert.ok(false, `Pref type not handled for getPref: ${name} ${type}`);
+        break;
+    }
+    return null;
+  }
+
+  let defaultBranch = Services.prefs.getDefaultBranch("browser.urlbar.");
+  let userBranch = Services.prefs.getBranch("browser.urlbar.");
+
+  // Set initial prefs. `initialDefaultBranch` are firefox.js values, i.e.,
+  // defaults immediately after startup and before any scenario update and
+  // migration happens.
+  UrlbarPrefs._updatingFirefoxSuggestScenario = true;
+  UrlbarPrefs.clear("quicksuggest.migrationVersion");
+  let initialDefaultBranch = {
+    "suggest.quicksuggest.nonsponsored": false,
+    "suggest.quicksuggest.sponsored": false,
+    "quicksuggest.dataCollection.enabled": false,
+  };
+  for (let name of Object.keys(initialDefaultBranch)) {
+    userBranch.clearUserPref(name);
+  }
+  for (let [branch, prefs] of [
+    [defaultBranch, initialDefaultBranch],
+    [userBranch, initialUserBranch],
+  ]) {
+    for (let [name, value] of Object.entries(prefs)) {
+      if (value !== undefined) {
+        setPref(branch, name, value);
+      }
+    }
+  }
+  UrlbarPrefs._updatingFirefoxSuggestScenario = false;
+
+  // Update the scenario and check prefs twice. The first time the migration
+  // should happen, and the second time the migration should not happen and
+  // all the prefs should stay the same.
+  for (let i = 0; i < 2; i++) {
+    info(`Calling updateFirefoxSuggestScenario, i=${i}`);
+
+    // Do the scenario update and set `isStartup` to simulate startup.
+    await UrlbarPrefs.updateFirefoxSuggestScenario({
+      ...testOverrides,
+      scenario,
+      isStartup: true,
+    });
+
+    // Check expected pref values. Store expected effective values as we go so
+    // we can check them afterward. For a given pref, the expected effective
+    // value is the user value, or if there's not a user value, the default
+    // value.
+    let expectedEffectivePrefs = {};
+    let {
+      defaultBranch: expectedDefaultBranch,
+      userBranch: expectedUserBranch,
+    } = expectedPrefs;
+    expectedDefaultBranch = expectedDefaultBranch || {};
+    expectedUserBranch = expectedUserBranch || {};
+    for (let [branch, prefs, branchType] of [
+      [defaultBranch, expectedDefaultBranch, "default"],
+      [userBranch, expectedUserBranch, "user"],
+    ]) {
+      let entries = Object.entries(prefs);
+      if (!entries.length) {
+        continue;
+      }
+
+      info(
+        `Checking expected prefs on ${branchType} branch after updating scenario`
+      );
+      for (let [name, value] of entries) {
+        expectedEffectivePrefs[name] = value;
+        if (branch == userBranch) {
+          Assert.ok(
+            userBranch.prefHasUserValue(name),
+            `Pref ${name} is on user branch`
+          );
+        }
+        Assert.equal(
+          getPref(branch, name),
+          value,
+          `Pref ${name} value on ${branchType} branch`
+        );
+      }
+    }
+
+    info(
+      `Making sure prefs on the default branch without expected user-branch values are not on the user branch`
+    );
+    for (let name of Object.keys(initialDefaultBranch)) {
+      if (!expectedUserBranch.hasOwnProperty(name)) {
+        Assert.ok(
+          !userBranch.prefHasUserValue(name),
+          `Pref ${name} is not on user branch`
+        );
+      }
+    }
+
+    info(`Checking expected effective prefs`);
+    for (let [name, value] of Object.entries(expectedEffectivePrefs)) {
+      Assert.equal(
+        UrlbarPrefs.get(name),
+        value,
+        `Pref ${name} effective value`
+      );
+    }
+
+    let currentVersion =
+      testOverrides?.migrationVersion === undefined
+        ? UrlbarPrefs.FIREFOX_SUGGEST_MIGRATION_VERSION
+        : testOverrides.migrationVersion;
+    Assert.equal(
+      UrlbarPrefs.get("quicksuggest.migrationVersion"),
+      currentVersion,
+      "quicksuggest.migrationVersion is correct after migration"
+    );
+  }
+
+  // Clean up.
+  UrlbarPrefs._updatingFirefoxSuggestScenario = true;
+  UrlbarPrefs.clear("quicksuggest.migrationVersion");
+  let userBranchNames = [
+    ...Object.keys(initialUserBranch),
+    ...Object.keys(expectedPrefs.userBranch || {}),
+  ];
+  for (let name of userBranchNames) {
+    userBranch.clearUserPref(name);
+  }
+  UrlbarPrefs._updatingFirefoxSuggestScenario = false;
+}
diff --git a/browser/components/urlbar/tests/quicksuggest/unit/test_merinoClient.js b/browser/components/urlbar/tests/quicksuggest/unit/test_merinoClient.js
new file mode 100644
index 0000000000..a9b55c3dd1
--- /dev/null
+++ b/browser/components/urlbar/tests/quicksuggest/unit/test_merinoClient.js
@@ -0,0 +1,652 @@
+/* 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 MerinoClient.
+
+"use strict";
+
+ChromeUtils.defineESModuleGetters(this, {
+  MerinoClient: "resource:///modules/MerinoClient.sys.mjs",
+});
+
+XPCOMUtils.defineLazyModuleGetters(this, {
+  ExperimentFakes: "resource://testing-common/NimbusTestUtils.jsm",
+  NimbusFeatures: "resource://nimbus/ExperimentAPI.jsm",
+});
+
+// Set the `merino.timeoutMs` pref to a large value so that the client will not
+// inadvertently time out during fetches. This is especially important on CI and
+// when running this test in verify mode. Tasks that specifically test timeouts
+// may need to set a more reasonable value for their duration.
+const TEST_TIMEOUT_MS = 30000;
+
+// The expected suggestion objects returned from `MerinoClient.fetch()`.
+const EXPECTED_MERINO_SUGGESTIONS = [];
+
+const { SEARCH_PARAMS } = MerinoClient;
+
+let gClient;
+
+add_setup(async function init() {
+  UrlbarPrefs.set("merino.timeoutMs", TEST_TIMEOUT_MS);
+  registerCleanupFunction(() => {
+    UrlbarPrefs.clear("merino.timeoutMs");
+  });
+
+  gClient = new MerinoClient();
+  await MerinoTestUtils.server.start();
+
+  for (let suggestion of MerinoTestUtils.server.response.body.suggestions) {
+    EXPECTED_MERINO_SUGGESTIONS.push({
+      ...suggestion,
+      request_id: MerinoTestUtils.server.response.body.request_id,
+      source: "merino",
+    });
+  }
+});
+
+// Checks client names.
+add_task(async function name() {
+  Assert.equal(
+    gClient.name,
+    "anonymous",
+    "gClient name is 'anonymous' since it wasn't given a name"
+  );
+
+  let client = new MerinoClient("New client");
+  Assert.equal(client.name, "New client", "newClient name is correct");
+});
+
+// Does a successful fetch.
+add_task(async function success() {
+  let histograms = MerinoTestUtils.getAndClearHistograms();
+
+  await fetchAndCheckSuggestions({
+    expected: EXPECTED_MERINO_SUGGESTIONS,
+  });
+
+  Assert.equal(
+    gClient.lastFetchStatus,
+    "success",
+    "The request successfully finished"
+  );
+  MerinoTestUtils.checkAndClearHistograms({
+    histograms,
+    response: "success",
+    latencyRecorded: true,
+    client: gClient,
+  });
+});
+
+// Does a successful fetch that doesn't return any suggestions.
+add_task(async function noSuggestions() {
+  let { suggestions } = MerinoTestUtils.server.response.body;
+  MerinoTestUtils.server.response.body.suggestions = [];
+
+  let histograms = MerinoTestUtils.getAndClearHistograms();
+
+  await fetchAndCheckSuggestions({
+    expected: [],
+  });
+
+  Assert.equal(
+    gClient.lastFetchStatus,
+    "no_suggestion",
+    "The request successfully finished without suggestions"
+  );
+  MerinoTestUtils.checkAndClearHistograms({
+    histograms,
+    response: "no_suggestion",
+    latencyRecorded: true,
+    client: gClient,
+  });
+
+  MerinoTestUtils.server.response.body.suggestions = suggestions;
+});
+
+// Checks a response that's valid but also has some unexpected properties.
+add_task(async function unexpectedResponseProperties() {
+  let histograms = MerinoTestUtils.getAndClearHistograms();
+
+  MerinoTestUtils.server.response.body.unexpectedString = "some value";
+  MerinoTestUtils.server.response.body.unexpectedArray = ["a", "b", "c"];
+  MerinoTestUtils.server.response.body.unexpectedObject = { foo: "bar" };
+
+  await fetchAndCheckSuggestions({
+    expected: EXPECTED_MERINO_SUGGESTIONS,
+  });
+
+  Assert.equal(
+    gClient.lastFetchStatus,
+    "success",
+    "The request successfully finished"
+  );
+  MerinoTestUtils.checkAndClearHistograms({
+    histograms,
+    response: "success",
+    latencyRecorded: true,
+    client: gClient,
+  });
+});
+
+// Checks some responses with unexpected response bodies.
+add_task(async function unexpectedResponseBody() {
+  let histograms = MerinoTestUtils.getAndClearHistograms();
+
+  let responses = [
+    { body: {} },
+    { body: { bogus: [] } },
+    { body: { suggestions: {} } },
+    { body: { suggestions: [] } },
+    { body: "" },
+    { body: "bogus", contentType: "text/html" },
+  ];
+
+  for (let r of responses) {
+    info("Testing response: " + JSON.stringify(r));
+
+    MerinoTestUtils.server.response = r;
+    await fetchAndCheckSuggestions({ expected: [] });
+
+    Assert.equal(
+      gClient.lastFetchStatus,
+      "no_suggestion",
+      "The request successfully finished without suggestions"
+    );
+    MerinoTestUtils.checkAndClearHistograms({
+      histograms,
+      response: "no_suggestion",
+      latencyRecorded: true,
+      client: gClient,
+    });
+  }
+
+  MerinoTestUtils.server.reset();
+});
+
+// Tests with a network error.
+add_task(async function networkError() {
+  let histograms = MerinoTestUtils.getAndClearHistograms();
+
+  // This promise will be resolved when the client processes the network error.
+  let responsePromise = gClient.waitForNextResponse();
+
+  await MerinoTestUtils.server.withNetworkError(async () => {
+    await fetchAndCheckSuggestions({ expected: [] });
+  });
+
+  // The client should have nulled out the timeout timer before `fetch()`
+  // returned.
+  Assert.strictEqual(
+    gClient._test_timeoutTimer,
+    null,
+    "timeoutTimer does not exist after fetch finished"
+  );
+
+  // Wait for the client to process the network error.
+  await responsePromise;
+
+  Assert.equal(
+    gClient.lastFetchStatus,
+    "network_error",
+    "The request failed with a network error"
+  );
+  MerinoTestUtils.checkAndClearHistograms({
+    histograms,
+    response: "network_error",
+    latencyRecorded: false,
+    client: gClient,
+  });
+});
+
+// Tests with an HTTP error.
+add_task(async function httpError() {
+  let histograms = MerinoTestUtils.getAndClearHistograms();
+
+  MerinoTestUtils.server.response = { status: 500 };
+  await fetchAndCheckSuggestions({ expected: [] });
+
+  Assert.equal(
+    gClient.lastFetchStatus,
+    "http_error",
+    "The request failed with an HTTP error"
+  );
+  MerinoTestUtils.checkAndClearHistograms({
+    histograms,
+    response: "http_error",
+    latencyRecorded: true,
+    client: gClient,
+  });
+
+  MerinoTestUtils.server.reset();
+});
+
+// Tests a client timeout.
+add_task(async function clientTimeout() {
+  await doClientTimeoutTest({
+    prefTimeoutMs: 200,
+    responseDelayMs: 400,
+  });
+});
+
+// Tests a client timeout followed by an HTTP error. Only the timeout should be
+// recorded.
+add_task(async function clientTimeoutFollowedByHTTPError() {
+  MerinoTestUtils.server.response = { status: 500 };
+  await doClientTimeoutTest({
+    prefTimeoutMs: 200,
+    responseDelayMs: 400,
+    expectedResponseStatus: 500,
+  });
+});
+
+// Tests a client timeout when a timeout value is passed to `fetch()`, which
+// should override the value in the `merino.timeoutMs` pref.
+add_task(async function timeoutPassedToFetch() {
+  // Set up a timeline like this:
+  //
+  //     1ms: The timeout passed to `fetch()` elapses
+  //   400ms: Merino returns a response
+  // 30000ms: The timeout in the pref elapses
+  //
+  // The expected behavior is that the 1ms timeout is hit, the request fails
+  // with a timeout, and Merino later returns a response. If the 1ms timeout is
+  // not hit, then Merino will return a response before the 30000ms timeout
+  // elapses and the request will complete successfully.
+
+  await doClientTimeoutTest({
+    prefTimeoutMs: 30000,
+    responseDelayMs: 400,
+    fetchArgs: { query: "search", timeoutMs: 1 },
+  });
+});
+
+async function doClientTimeoutTest({
+  prefTimeoutMs,
+  responseDelayMs,
+  fetchArgs = { query: "search" },
+  expectedResponseStatus = 200,
+} = {}) {
+  let histograms = MerinoTestUtils.getAndClearHistograms();
+
+  let originalPrefTimeoutMs = UrlbarPrefs.get("merino.timeoutMs");
+  UrlbarPrefs.set("merino.timeoutMs", prefTimeoutMs);
+
+  // Make the server return a delayed response so the client times out waiting
+  // for it.
+  MerinoTestUtils.server.response.delay = responseDelayMs;
+
+  let responsePromise = gClient.waitForNextResponse();
+  await fetchAndCheckSuggestions({ args: fetchArgs, expected: [] });
+
+  Assert.equal(gClient.lastFetchStatus, "timeout", "The request timed out");
+
+  // The client should have nulled out the timeout timer.
+  Assert.strictEqual(
+    gClient._test_timeoutTimer,
+    null,
+    "timeoutTimer does not exist after fetch finished"
+  );
+
+  // The fetch controller should still exist because the fetch should remain
+  // ongoing.
+  Assert.ok(
+    gClient._test_fetchController,
+    "fetchController still exists after fetch finished"
+  );
+  Assert.ok(
+    !gClient._test_fetchController.signal.aborted,
+    "fetchController is not aborted"
+  );
+
+  // The latency histogram should not be updated since the response has not been
+  // received.
+  MerinoTestUtils.checkAndClearHistograms({
+    histograms,
+    response: "timeout",
+    latencyRecorded: false,
+    latencyStopwatchRunning: true,
+    client: gClient,
+  });
+
+  // Wait for the client to receive the response.
+  let httpResponse = await responsePromise;
+  Assert.ok(httpResponse, "Response was received");
+  Assert.equal(httpResponse.status, expectedResponseStatus, "Response status");
+
+  // The client should have nulled out the fetch controller.
+  Assert.ok(!gClient._test_fetchController, "fetchController no longer exists");
+
+  // The `checkAndClearHistograms()` call above cleared the histograms. After
+  // that, nothing else should have been recorded for the response.
+  MerinoTestUtils.checkAndClearHistograms({
+    histograms,
+    response: null,
+    latencyRecorded: true,
+    client: gClient,
+  });
+
+  MerinoTestUtils.server.reset();
+  UrlbarPrefs.set("merino.timeoutMs", originalPrefTimeoutMs);
+}
+
+// By design, when a fetch times out, the client allows it to finish so we can
+// record its latency. But when a second fetch starts before the first finishes,
+// the client should abort the first so that there is at most one fetch at a
+// time.
+add_task(async function newFetchAbortsPrevious() {
+  let histograms = MerinoTestUtils.getAndClearHistograms();
+
+  // Make the server return a very delayed response so that it would time out
+  // and we can start a second fetch that will abort the first fetch.
+  MerinoTestUtils.server.response.delay =
+    100 * UrlbarPrefs.get("merino.timeoutMs");
+
+  // Do the first fetch.
+  await fetchAndCheckSuggestions({ expected: [] });
+
+  // At this point, the timeout timer has fired, causing our `fetch()` call to
+  // return. However, the client's internal fetch should still be ongoing.
+
+  Assert.equal(gClient.lastFetchStatus, "timeout", "The request timed out");
+
+  // The client should have nulled out the timeout timer.
+  Assert.strictEqual(
+    gClient._test_timeoutTimer,
+    null,
+    "timeoutTimer does not exist after first fetch finished"
+  );
+
+  // The fetch controller should still exist because the fetch should remain
+  // ongoing.
+  Assert.ok(
+    gClient._test_fetchController,
+    "fetchController still exists after first fetch finished"
+  );
+  Assert.ok(
+    !gClient._test_fetchController.signal.aborted,
+    "fetchController is not aborted"
+  );
+
+  // The latency histogram should not be updated since the fetch is still
+  // ongoing.
+  MerinoTestUtils.checkAndClearHistograms({
+    histograms,
+    response: "timeout",
+    latencyRecorded: false,
+    latencyStopwatchRunning: true,
+    client: gClient,
+  });
+
+  // Do the second fetch. This time don't delay the response.
+  delete MerinoTestUtils.server.response.delay;
+  await fetchAndCheckSuggestions({
+    expected: EXPECTED_MERINO_SUGGESTIONS,
+  });
+
+  Assert.equal(
+    gClient.lastFetchStatus,
+    "success",
+    "The request finished successfully"
+  );
+
+  // The fetch was successful, so the client should have nulled out both
+  // properties.
+  Assert.ok(
+    !gClient._test_fetchController,
+    "fetchController does not exist after second fetch finished"
+  );
+  Assert.strictEqual(
+    gClient._test_timeoutTimer,
+    null,
+    "timeoutTimer does not exist after second fetch finished"
+  );
+
+  MerinoTestUtils.checkAndClearHistograms({
+    histograms,
+    response: "success",
+    latencyRecorded: true,
+    client: gClient,
+  });
+
+  MerinoTestUtils.server.reset();
+});
+
+// The client should not include the `clientVariants` and `providers` search
+// params when they are not set.
+add_task(async function clientVariants_providers_notSet() {
+  UrlbarPrefs.set("merino.clientVariants", "");
+  UrlbarPrefs.set("merino.providers", "");
+
+  await fetchAndCheckSuggestions({
+    expected: EXPECTED_MERINO_SUGGESTIONS,
+  });
+
+  MerinoTestUtils.server.checkAndClearRequests([
+    {
+      params: {
+        [SEARCH_PARAMS.QUERY]: "search",
+        [SEARCH_PARAMS.SEQUENCE_NUMBER]: 0,
+      },
+    },
+  ]);
+
+  UrlbarPrefs.clear("merino.clientVariants");
+  UrlbarPrefs.clear("merino.providers");
+});
+
+// The client should include the `clientVariants` and `providers` search params
+// when they are set using preferences.
+add_task(async function clientVariants_providers_preferences() {
+  UrlbarPrefs.set("merino.clientVariants", "green");
+  UrlbarPrefs.set("merino.providers", "pink");
+
+  await fetchAndCheckSuggestions({
+    expected: EXPECTED_MERINO_SUGGESTIONS,
+  });
+
+  MerinoTestUtils.server.checkAndClearRequests([
+    {
+      params: {
+        [SEARCH_PARAMS.QUERY]: "search",
+        [SEARCH_PARAMS.SEQUENCE_NUMBER]: 0,
+        [SEARCH_PARAMS.CLIENT_VARIANTS]: "green",
+        [SEARCH_PARAMS.PROVIDERS]: "pink",
+      },
+    },
+  ]);
+
+  UrlbarPrefs.clear("merino.clientVariants");
+  UrlbarPrefs.clear("merino.providers");
+});
+
+// The client should include the `providers` search param when it's set by
+// passing in the `providers` argument to `fetch()`. The argument should
+// override the pref. This tests a single provider.
+add_task(async function providers_arg_single() {
+  UrlbarPrefs.set("merino.providers", "prefShouldNotBeUsed");
+
+  await fetchAndCheckSuggestions({
+    args: { query: "search", providers: ["argShouldBeUsed"] },
+    expected: EXPECTED_MERINO_SUGGESTIONS,
+  });
+
+  MerinoTestUtils.server.checkAndClearRequests([
+    {
+      params: {
+        [SEARCH_PARAMS.QUERY]: "search",
+        [SEARCH_PARAMS.SEQUENCE_NUMBER]: 0,
+        [SEARCH_PARAMS.PROVIDERS]: "argShouldBeUsed",
+      },
+    },
+  ]);
+
+  UrlbarPrefs.clear("merino.providers");
+});
+
+// The client should include the `providers` search param when it's set by
+// passing in the `providers` argument to `fetch()`. The argument should
+// override the pref. This tests multiple providers.
+add_task(async function providers_arg_many() {
+  UrlbarPrefs.set("merino.providers", "prefShouldNotBeUsed");
+
+  await fetchAndCheckSuggestions({
+    args: { query: "search", providers: ["one", "two", "three"] },
+    expected: EXPECTED_MERINO_SUGGESTIONS,
+  });
+
+  MerinoTestUtils.server.checkAndClearRequests([
+    {
+      params: {
+        [SEARCH_PARAMS.QUERY]: "search",
+        [SEARCH_PARAMS.SEQUENCE_NUMBER]: 0,
+        [SEARCH_PARAMS.PROVIDERS]: "one,two,three",
+      },
+    },
+  ]);
+
+  UrlbarPrefs.clear("merino.providers");
+});
+
+// The client should include the `providers` search param when it's set by
+// passing in the `providers` argument to `fetch()` even when it's an empty
+// array. The argument should override the pref.
+add_task(async function providers_arg_empty() {
+  UrlbarPrefs.set("merino.providers", "prefShouldNotBeUsed");
+
+  await fetchAndCheckSuggestions({
+    args: { query: "search", providers: [] },
+    expected: EXPECTED_MERINO_SUGGESTIONS,
+  });
+
+  MerinoTestUtils.server.checkAndClearRequests([
+    {
+      params: {
+        [SEARCH_PARAMS.QUERY]: "search",
+        [SEARCH_PARAMS.SEQUENCE_NUMBER]: 0,
+        [SEARCH_PARAMS.PROVIDERS]: "",
+      },
+    },
+  ]);
+
+  UrlbarPrefs.clear("merino.providers");
+});
+
+// Passes invalid `providers` arguments to `fetch()`.
+add_task(async function providers_arg_invalid() {
+  let providersValues = ["", "nonempty", {}];
+
+  for (let providers of providersValues) {
+    info("Calling fetch() with providers: " + JSON.stringify(providers));
+
+    // `Assert.throws()` doesn't seem to work with async functions...
+    let error;
+    try {
+      await gClient.fetch({ providers, query: "search" });
+    } catch (e) {
+      error = e;
+    }
+    Assert.ok(error, "fetch() threw an error");
+    Assert.equal(
+      error.message,
+      "providers must be an array if given",
+      "Expected error was thrown"
+    );
+  }
+});
+
+// Tests setting the endpoint URL and query parameters via Nimbus.
+add_task(async function nimbus() {
+  // Clear the endpoint pref so we know the URL is not being fetched from it.
+  let originalEndpointURL = UrlbarPrefs.get("merino.endpointURL");
+  UrlbarPrefs.set("merino.endpointURL", "");
+
+  await UrlbarTestUtils.initNimbusFeature();
+
+  // First, with the endpoint pref set to an empty string, make sure no Merino
+  // suggestion are returned.
+  await fetchAndCheckSuggestions({ expected: null });
+
+  // Now install an experiment that sets the endpoint and other Merino-related
+  // variables. Make sure a suggestion is returned and the request includes the
+  // correct query params.
+
+  // `param`: The param name in the request URL
+  // `value`: The value to use for the param
+  // `variable`: The name of the Nimbus variable corresponding to the param
+  let expectedParams = [
+    {
+      param: SEARCH_PARAMS.CLIENT_VARIANTS,
+      value: "test-client-variants",
+      variable: "merinoClientVariants",
+    },
+    {
+      param: SEARCH_PARAMS.PROVIDERS,
+      value: "test-providers",
+      variable: "merinoProviders",
+    },
+  ];
+
+  // Set up the Nimbus variable values to create the experiment with.
+  let experimentValues = {
+    merinoEndpointURL: MerinoTestUtils.server.url.toString(),
+  };
+  for (let { variable, value } of expectedParams) {
+    experimentValues[variable] = value;
+  }
+
+  await withExperiment(experimentValues, async () => {
+    await fetchAndCheckSuggestions({ expected: EXPECTED_MERINO_SUGGESTIONS });
+
+    let params = {
+      [SEARCH_PARAMS.QUERY]: "search",
+      [SEARCH_PARAMS.SEQUENCE_NUMBER]: 0,
+    };
+    for (let { param, value } of expectedParams) {
+      params[param] = value;
+    }
+    MerinoTestUtils.server.checkAndClearRequests([{ params }]);
+  });
+
+  UrlbarPrefs.set("merino.endpointURL", originalEndpointURL);
+});
+
+async function fetchAndCheckSuggestions({
+  expected,
+  args = {
+    query: "search",
+  },
+}) {
+  let actual = await gClient.fetch(args);
+  Assert.deepEqual(actual, expected, "Expected suggestions");
+  gClient.resetSession();
+}
+
+async function withExperiment(values, callback) {
+  let {
+    enrollmentPromise,
+    doExperimentCleanup,
+  } = ExperimentFakes.enrollmentHelper(
+    ExperimentFakes.recipe("mock-experiment", {
+      active: true,
+      branches: [
+        {
+          slug: "treatment",
+          features: [
+            {
+              featureId: NimbusFeatures.urlbar.featureId,
+              value: {
+                enabled: true,
+                ...values,
+              },
+            },
+          ],
+        },
+      ],
+    })
+  );
+  await enrollmentPromise;
+  await callback();
+  await doExperimentCleanup();
+}
diff --git a/browser/components/urlbar/tests/quicksuggest/unit/test_merinoClient_sessions.js b/browser/components/urlbar/tests/quicksuggest/unit/test_merinoClient_sessions.js
new file mode 100644
index 0000000000..70e970af8a
--- /dev/null
+++ b/browser/components/urlbar/tests/quicksuggest/unit/test_merinoClient_sessions.js
@@ -0,0 +1,402 @@
+/* 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 MerinoClient sessions.
+
+"use strict";
+
+const { MerinoClient } = ChromeUtils.importESModule(
+  "resource:///modules/MerinoClient.sys.mjs"
+);
+
+const { SEARCH_PARAMS } = MerinoClient;
+
+let gClient;
+
+add_task(async function init() {
+  gClient = new MerinoClient();
+  await MerinoTestUtils.server.start();
+});
+
+// In a single session, all requests should use the same session ID and the
+// sequence number should be incremented.
+add_task(async function singleSession() {
+  for (let i = 0; i < 3; i++) {
+    let query = "search" + i;
+    await gClient.fetch({ query });
+
+    MerinoTestUtils.server.checkAndClearRequests([
+      {
+        params: {
+          [SEARCH_PARAMS.QUERY]: query,
+          [SEARCH_PARAMS.SEQUENCE_NUMBER]: i,
+        },
+      },
+    ]);
+  }
+
+  gClient.resetSession();
+});
+
+// Different sessions should use different session IDs and the sequence number
+// should be reset.
+add_task(async function manySessions() {
+  for (let i = 0; i < 3; i++) {
+    let query = "search" + i;
+    await gClient.fetch({ query });
+
+    MerinoTestUtils.server.checkAndClearRequests([
+      {
+        params: {
+          [SEARCH_PARAMS.QUERY]: query,
+          [SEARCH_PARAMS.SEQUENCE_NUMBER]: 0,
+        },
+      },
+    ]);
+
+    gClient.resetSession();
+  }
+});
+
+// Tests two consecutive fetches:
+//
+// 1. Start a fetch
+// 2. Wait for the mock Merino server to receive the request
+// 3. Start a second fetch before the client receives the response
+//
+// The first fetch will be canceled by the second but the sequence number in the
+// second fetch should still be incremented.
+add_task(async function twoFetches_wait() {
+  for (let i = 0; i < 3; i++) {
+    // Send the first response after a delay to make sure the client will not
+    // receive it before we start the second fetch.
+    MerinoTestUtils.server.response.delay = UrlbarPrefs.get("merino.timeoutMs");
+
+    // Start the first fetch but don't wait for it to finish.
+    let requestPromise = MerinoTestUtils.server.waitForNextRequest();
+    let query1 = "search" + i;
+    gClient.fetch({ query: query1 });
+
+    // Wait until the first request is received before starting the second
+    // fetch, which will cancel the first. The response doesn't need to be
+    // delayed, so remove it to make the test run faster.
+    await requestPromise;
+    delete MerinoTestUtils.server.response.delay;
+    let query2 = query1 + "again";
+    await gClient.fetch({ query: query2 });
+
+    // The sequence number should have been incremented for each fetch.
+    MerinoTestUtils.server.checkAndClearRequests([
+      {
+        params: {
+          [SEARCH_PARAMS.QUERY]: query1,
+          [SEARCH_PARAMS.SEQUENCE_NUMBER]: 2 * i,
+        },
+      },
+      {
+        params: {
+          [SEARCH_PARAMS.QUERY]: query2,
+          [SEARCH_PARAMS.SEQUENCE_NUMBER]: 2 * i + 1,
+        },
+      },
+    ]);
+  }
+
+  gClient.resetSession();
+});
+
+// Tests two consecutive fetches:
+//
+// 1. Start a fetch
+// 2. Immediately start a second fetch
+//
+// The first fetch will be canceled by the second but the sequence number in the
+// second fetch should still be incremented.
+add_task(async function twoFetches_immediate() {
+  for (let i = 0; i < 3; i++) {
+    // Send the first response after a delay to make sure the client will not
+    // receive it before we start the second fetch.
+    MerinoTestUtils.server.response.delay =
+      100 * UrlbarPrefs.get("merino.timeoutMs");
+
+    // Start the first fetch but don't wait for it to finish.
+    let query1 = "search" + i;
+    gClient.fetch({ query: query1 });
+
+    // Immediately do a second fetch that cancels the first. The response
+    // doesn't need to be delayed, so remove it to make the test run faster.
+    delete MerinoTestUtils.server.response.delay;
+    let query2 = query1 + "again";
+    await gClient.fetch({ query: query2 });
+
+    // The sequence number should have been incremented for each fetch, but the
+    // first won't have reached the server since it was immediately canceled.
+    MerinoTestUtils.server.checkAndClearRequests([
+      {
+        params: {
+          [SEARCH_PARAMS.QUERY]: query2,
+          [SEARCH_PARAMS.SEQUENCE_NUMBER]: 2 * i + 1,
+        },
+      },
+    ]);
+  }
+
+  gClient.resetSession();
+});
+
+// When a network error occurs, the sequence number should still be incremented.
+add_task(async function networkError() {
+  for (let i = 0; i < 3; i++) {
+    // Do a fetch that fails with a network error.
+    let query1 = "search" + i;
+    await MerinoTestUtils.server.withNetworkError(async () => {
+      await gClient.fetch({ query: query1 });
+    });
+
+    Assert.equal(
+      gClient.lastFetchStatus,
+      "network_error",
+      "The request failed with a network error"
+    );
+
+    // Do another fetch that successfully finishes.
+    let query2 = query1 + "again";
+    await gClient.fetch({ query: query2 });
+
+    Assert.equal(
+      gClient.lastFetchStatus,
+      "success",
+      "The request completed successfully"
+    );
+
+    // Only the second request should have been received but the sequence number
+    // should have been incremented for each.
+    MerinoTestUtils.server.checkAndClearRequests([
+      {
+        params: {
+          [SEARCH_PARAMS.QUERY]: query2,
+          [SEARCH_PARAMS.SEQUENCE_NUMBER]: 2 * i + 1,
+        },
+      },
+    ]);
+  }
+
+  gClient.resetSession();
+});
+
+// When the server returns a response with an HTTP error, the sequence number
+// should be incremented.
+add_task(async function httpError() {
+  for (let i = 0; i < 3; i++) {
+    // Do a fetch that fails with an HTTP error.
+    MerinoTestUtils.server.response.status = 500;
+    let query1 = "search" + i;
+    await gClient.fetch({ query: query1 });
+
+    Assert.equal(
+      gClient.lastFetchStatus,
+      "http_error",
+      "The last request failed with a network error"
+    );
+
+    // Do another fetch that successfully finishes.
+    MerinoTestUtils.server.response.status = 200;
+    let query2 = query1 + "again";
+    await gClient.fetch({ query: query2 });
+
+    Assert.equal(
+      gClient.lastFetchStatus,
+      "success",
+      "The last request completed successfully"
+    );
+
+    // Both requests should have been received and the sequence number should
+    // have been incremented for each.
+    MerinoTestUtils.server.checkAndClearRequests([
+      {
+        params: {
+          [SEARCH_PARAMS.QUERY]: query1,
+          [SEARCH_PARAMS.SEQUENCE_NUMBER]: 2 * i,
+        },
+      },
+      {
+        params: {
+          [SEARCH_PARAMS.QUERY]: query2,
+          [SEARCH_PARAMS.SEQUENCE_NUMBER]: 2 * i + 1,
+        },
+      },
+    ]);
+
+    MerinoTestUtils.server.reset();
+  }
+
+  gClient.resetSession();
+});
+
+// When the client times out waiting for a response but later receives it and no
+// other fetch happens in the meantime, the sequence number should be
+// incremented.
+add_task(async function clientTimeout_wait() {
+  for (let i = 0; i < 3; i++) {
+    // Do a fetch that causes the client to time out.
+    MerinoTestUtils.server.response.delay =
+      2 * UrlbarPrefs.get("merino.timeoutMs");
+    let responsePromise = gClient.waitForNextResponse();
+    let query1 = "search" + i;
+    await gClient.fetch({ query: query1 });
+
+    Assert.equal(
+      gClient.lastFetchStatus,
+      "timeout",
+      "The last request failed with a client timeout"
+    );
+
+    // Wait for the client to receive the response.
+    await responsePromise;
+
+    // Do another fetch that successfully finishes.
+    delete MerinoTestUtils.server.response.delay;
+    let query2 = query1 + "again";
+    await gClient.fetch({ query: query2 });
+
+    Assert.equal(
+      gClient.lastFetchStatus,
+      "success",
+      "The last request completed successfully"
+    );
+
+    MerinoTestUtils.server.checkAndClearRequests([
+      {
+        params: {
+          [SEARCH_PARAMS.QUERY]: query1,
+          [SEARCH_PARAMS.SEQUENCE_NUMBER]: 2 * i,
+        },
+      },
+      {
+        params: {
+          [SEARCH_PARAMS.QUERY]: query2,
+          [SEARCH_PARAMS.SEQUENCE_NUMBER]: 2 * i + 1,
+        },
+      },
+    ]);
+  }
+
+  gClient.resetSession();
+});
+
+// When the client times out waiting for a response and a second fetch starts
+// before the response is received, the first fetch should be canceled but the
+// sequence number should still be incremented.
+add_task(async function clientTimeout_canceled() {
+  for (let i = 0; i < 3; i++) {
+    // Do a fetch that causes the client to time out.
+    MerinoTestUtils.server.response.delay =
+      2 * UrlbarPrefs.get("merino.timeoutMs");
+    let query1 = "search" + i;
+    await gClient.fetch({ query: query1 });
+
+    Assert.equal(
+      gClient.lastFetchStatus,
+      "timeout",
+      "The last request failed with a client timeout"
+    );
+
+    // Do another fetch that successfully finishes.
+    delete MerinoTestUtils.server.response.delay;
+    let query2 = query1 + "again";
+    await gClient.fetch({ query: query2 });
+
+    Assert.equal(
+      gClient.lastFetchStatus,
+      "success",
+      "The last request completed successfully"
+    );
+
+    MerinoTestUtils.server.checkAndClearRequests([
+      {
+        params: {
+          [SEARCH_PARAMS.QUERY]: query1,
+          [SEARCH_PARAMS.SEQUENCE_NUMBER]: 2 * i,
+        },
+      },
+      {
+        params: {
+          [SEARCH_PARAMS.QUERY]: query2,
+          [SEARCH_PARAMS.SEQUENCE_NUMBER]: 2 * i + 1,
+        },
+      },
+    ]);
+  }
+
+  gClient.resetSession();
+});
+
+// When the session times out, the next fetch should use a new session ID and
+// the sequence number should be reset.
+add_task(async function sessionTimeout() {
+  // Set the session timeout to something reasonable to test.
+  let originalTimeoutMs = gClient.sessionTimeoutMs;
+  gClient.sessionTimeoutMs = 500;
+
+  // Do a fetch.
+  let query1 = "search";
+  await gClient.fetch({ query: query1 });
+
+  // Wait for the session to time out.
+  await gClient.waitForNextSessionReset();
+
+  Assert.strictEqual(
+    gClient.sessionID,
+    null,
+    "sessionID is null after session timeout"
+  );
+  Assert.strictEqual(
+    gClient.sequenceNumber,
+    0,
+    "sequenceNumber is zero after session timeout"
+  );
+  Assert.strictEqual(
+    gClient._test_sessionTimer,
+    null,
+    "sessionTimer is null after session timeout"
+  );
+
+  // Do another fetch.
+  let query2 = query1 + "again";
+  await gClient.fetch({ query: query2 });
+
+  // The second request's sequence number should be zero due to the session
+  // timeout.
+  MerinoTestUtils.server.checkAndClearRequests([
+    {
+      params: {
+        [SEARCH_PARAMS.QUERY]: query1,
+        [SEARCH_PARAMS.SEQUENCE_NUMBER]: 0,
+      },
+    },
+    {
+      params: {
+        [SEARCH_PARAMS.QUERY]: query2,
+        [SEARCH_PARAMS.SEQUENCE_NUMBER]: 0,
+      },
+    },
+  ]);
+
+  Assert.ok(
+    gClient.sessionID,
+    "sessionID is non-null after first request in a new session"
+  );
+  Assert.equal(
+    gClient.sequenceNumber,
+    1,
+    "sequenceNumber is one after first request in a new session"
+  );
+  Assert.ok(
+    gClient._test_sessionTimer,
+    "sessionTimer is non-null after first request in a new session"
+  );
+
+  gClient.sessionTimeoutMs = originalTimeoutMs;
+  gClient.resetSession();
+});
diff --git a/browser/components/urlbar/tests/quicksuggest/unit/test_quicksuggest.js b/browser/components/urlbar/tests/quicksuggest/unit/test_quicksuggest.js
new file mode 100644
index 0000000000..0789e6e742
--- /dev/null
+++ b/browser/components/urlbar/tests/quicksuggest/unit/test_quicksuggest.js
@@ -0,0 +1,1280 @@
+/* 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/. */
+
+// Basic tests for the quick suggest provider using the remote settings source.
+// See also test_quicksuggest_merino.js.
+
+"use strict";
+
+const TELEMETRY_REMOTE_SETTINGS_LATENCY =
+  "FX_URLBAR_QUICK_SUGGEST_REMOTE_SETTINGS_LATENCY_MS";
+
+const SPONSORED_SEARCH_STRING = "frab";
+const NONSPONSORED_SEARCH_STRING = "nonspon";
+
+const HTTP_SEARCH_STRING = "http prefix";
+const HTTPS_SEARCH_STRING = "https prefix";
+const PREFIX_SUGGESTIONS_STRIPPED_URL = "example.com/prefix-test";
+
+const { TIMESTAMP_TEMPLATE, TIMESTAMP_LENGTH } = QuickSuggest;
+const TIMESTAMP_SEARCH_STRING = "timestamp";
+const TIMESTAMP_SUGGESTION_URL = `http://example.com/timestamp-${TIMESTAMP_TEMPLATE}`;
+const TIMESTAMP_SUGGESTION_CLICK_URL = `http://click.reporting.test.com/timestamp-${TIMESTAMP_TEMPLATE}-foo`;
+
+const REMOTE_SETTINGS_RESULTS = [
+  {
+    id: 1,
+    url: "http://test.com/q=frabbits",
+    title: "frabbits",
+    keywords: [SPONSORED_SEARCH_STRING],
+    click_url: "http://click.reporting.test.com/",
+    impression_url: "http://impression.reporting.test.com/",
+    advertiser: "TestAdvertiser",
+    iab_category: "22 - Shopping",
+  },
+  {
+    id: 2,
+    url: "http://test.com/?q=nonsponsored",
+    title: "Non-Sponsored",
+    keywords: [NONSPONSORED_SEARCH_STRING],
+    click_url: "http://click.reporting.test.com/nonsponsored",
+    impression_url: "http://impression.reporting.test.com/nonsponsored",
+    advertiser: "TestAdvertiserNonSponsored",
+    iab_category: "5 - Education",
+  },
+  {
+    id: 3,
+    url: "http://" + PREFIX_SUGGESTIONS_STRIPPED_URL,
+    title: "http suggestion",
+    keywords: [HTTP_SEARCH_STRING],
+    click_url: "http://click.reporting.test.com/prefix",
+    impression_url: "http://impression.reporting.test.com/prefix",
+    advertiser: "TestAdvertiserPrefix",
+    iab_category: "22 - Shopping",
+  },
+  {
+    id: 4,
+    url: "https://" + PREFIX_SUGGESTIONS_STRIPPED_URL,
+    title: "https suggestion",
+    keywords: [HTTPS_SEARCH_STRING],
+    click_url: "http://click.reporting.test.com/prefix",
+    impression_url: "http://impression.reporting.test.com/prefix",
+    advertiser: "TestAdvertiserPrefix",
+    iab_category: "22 - Shopping",
+  },
+  {
+    id: 5,
+    url: TIMESTAMP_SUGGESTION_URL,
+    title: "Timestamp suggestion",
+    keywords: [TIMESTAMP_SEARCH_STRING],
+    click_url: TIMESTAMP_SUGGESTION_CLICK_URL,
+    impression_url: "http://impression.reporting.test.com/timestamp",
+    advertiser: "TestAdvertiserTimestamp",
+    iab_category: "22 - Shopping",
+  },
+];
+
+const EXPECTED_SPONSORED_RESULT = {
+  type: UrlbarUtils.RESULT_TYPE.URL,
+  source: UrlbarUtils.RESULT_SOURCE.SEARCH,
+  heuristic: false,
+  payload: {
+    qsSuggestion: "frab",
+    title: "frabbits",
+    url: "http://test.com/q=frabbits",
+    originalUrl: "http://test.com/q=frabbits",
+    icon: null,
+    sponsoredImpressionUrl: "http://impression.reporting.test.com/",
+    sponsoredClickUrl: "http://click.reporting.test.com/",
+    sponsoredBlockId: 1,
+    sponsoredAdvertiser: "TestAdvertiser",
+    sponsoredIabCategory: "22 - Shopping",
+    isSponsored: true,
+    helpUrl: QuickSuggest.HELP_URL,
+    helpL10n: { id: "firefox-suggest-urlbar-learn-more" },
+    isBlockable: false,
+    blockL10n: { id: "firefox-suggest-urlbar-block" },
+    displayUrl: "http://test.com/q=frabbits",
+    source: "remote-settings",
+  },
+};
+
+const EXPECTED_NONSPONSORED_RESULT = {
+  type: UrlbarUtils.RESULT_TYPE.URL,
+  source: UrlbarUtils.RESULT_SOURCE.SEARCH,
+  heuristic: false,
+  payload: {
+    qsSuggestion: "nonspon",
+    title: "Non-Sponsored",
+    url: "http://test.com/?q=nonsponsored",
+    originalUrl: "http://test.com/?q=nonsponsored",
+    icon: null,
+    sponsoredImpressionUrl: "http://impression.reporting.test.com/nonsponsored",
+    sponsoredClickUrl: "http://click.reporting.test.com/nonsponsored",
+    sponsoredBlockId: 2,
+    sponsoredAdvertiser: "TestAdvertiserNonSponsored",
+    sponsoredIabCategory: "5 - Education",
+    isSponsored: false,
+    helpUrl: QuickSuggest.HELP_URL,
+    helpL10n: { id: "firefox-suggest-urlbar-learn-more" },
+    isBlockable: false,
+    blockL10n: { id: "firefox-suggest-urlbar-block" },
+    displayUrl: "http://test.com/?q=nonsponsored",
+    source: "remote-settings",
+  },
+};
+
+const EXPECTED_HTTP_RESULT = {
+  type: UrlbarUtils.RESULT_TYPE.URL,
+  source: UrlbarUtils.RESULT_SOURCE.SEARCH,
+  heuristic: false,
+  payload: {
+    qsSuggestion: HTTP_SEARCH_STRING,
+    title: "http suggestion",
+    url: "http://" + PREFIX_SUGGESTIONS_STRIPPED_URL,
+    originalUrl: "http://" + PREFIX_SUGGESTIONS_STRIPPED_URL,
+    icon: null,
+    sponsoredImpressionUrl: "http://impression.reporting.test.com/prefix",
+    sponsoredClickUrl: "http://click.reporting.test.com/prefix",
+    sponsoredBlockId: 3,
+    sponsoredAdvertiser: "TestAdvertiserPrefix",
+    sponsoredIabCategory: "22 - Shopping",
+    isSponsored: true,
+    helpUrl: QuickSuggest.HELP_URL,
+    helpL10n: { id: "firefox-suggest-urlbar-learn-more" },
+    isBlockable: false,
+    blockL10n: { id: "firefox-suggest-urlbar-block" },
+    displayUrl: "http://" + PREFIX_SUGGESTIONS_STRIPPED_URL,
+    source: "remote-settings",
+  },
+};
+
+const EXPECTED_HTTPS_RESULT = {
+  type: UrlbarUtils.RESULT_TYPE.URL,
+  source: UrlbarUtils.RESULT_SOURCE.SEARCH,
+  heuristic: false,
+  payload: {
+    qsSuggestion: HTTPS_SEARCH_STRING,
+    title: "https suggestion",
+    url: "https://" + PREFIX_SUGGESTIONS_STRIPPED_URL,
+    originalUrl: "https://" + PREFIX_SUGGESTIONS_STRIPPED_URL,
+    icon: null,
+    sponsoredImpressionUrl: "http://impression.reporting.test.com/prefix",
+    sponsoredClickUrl: "http://click.reporting.test.com/prefix",
+    sponsoredBlockId: 4,
+    sponsoredAdvertiser: "TestAdvertiserPrefix",
+    sponsoredIabCategory: "22 - Shopping",
+    isSponsored: true,
+    helpUrl: QuickSuggest.HELP_URL,
+    helpL10n: { id: "firefox-suggest-urlbar-learn-more" },
+    isBlockable: false,
+    blockL10n: { id: "firefox-suggest-urlbar-block" },
+    displayUrl: PREFIX_SUGGESTIONS_STRIPPED_URL,
+    source: "remote-settings",
+  },
+};
+
+let cleanUpQuickSuggest;
+
+add_task(async function init() {
+  UrlbarPrefs.set("quicksuggest.enabled", true);
+  UrlbarPrefs.set("quicksuggest.shouldShowOnboardingDialog", false);
+  UrlbarPrefs.set("quicksuggest.remoteSettings.enabled", true);
+  UrlbarPrefs.set("merino.enabled", false);
+
+  // Install a default test engine.
+  let engine = await addTestSuggestionsEngine();
+  await Services.search.setDefault(
+    engine,
+    Ci.nsISearchService.CHANGE_REASON_UNKNOWN
+  );
+
+  cleanUpQuickSuggest = await QuickSuggestTestUtils.ensureQuickSuggestInit({
+    remoteSettingsResults: REMOTE_SETTINGS_RESULTS,
+  });
+});
+
+// Tests with only non-sponsored suggestions enabled with a matching search
+// string.
+add_task(async function nonsponsoredOnly_match() {
+  UrlbarPrefs.set("suggest.quicksuggest.nonsponsored", true);
+  UrlbarPrefs.set("suggest.quicksuggest.sponsored", false);
+
+  let context = createContext(NONSPONSORED_SEARCH_STRING, {
+    providers: [UrlbarProviderQuickSuggest.name],
+    isPrivate: false,
+  });
+  await check_results({
+    context,
+    matches: [EXPECTED_NONSPONSORED_RESULT],
+  });
+});
+
+// Tests with only non-sponsored suggestions enabled with a non-matching search
+// string.
+add_task(async function nonsponsoredOnly_noMatch() {
+  UrlbarPrefs.set("suggest.quicksuggest.nonsponsored", true);
+  UrlbarPrefs.set("suggest.quicksuggest.sponsored", false);
+
+  let context = createContext(SPONSORED_SEARCH_STRING, {
+    providers: [UrlbarProviderQuickSuggest.name],
+    isPrivate: false,
+  });
+  await check_results({ context, matches: [] });
+});
+
+// Tests with only sponsored suggestions enabled with a matching search string.
+add_task(async function sponsoredOnly_sponsored() {
+  UrlbarPrefs.set("suggest.quicksuggest.nonsponsored", false);
+  UrlbarPrefs.set("suggest.quicksuggest.sponsored", true);
+
+  let context = createContext(SPONSORED_SEARCH_STRING, {
+    providers: [UrlbarProviderQuickSuggest.name],
+    isPrivate: false,
+  });
+  await check_results({
+    context,
+    matches: [EXPECTED_SPONSORED_RESULT],
+  });
+});
+
+// Tests with only sponsored suggestions enabled with a non-matching search
+// string.
+add_task(async function sponsoredOnly_nonsponsored() {
+  UrlbarPrefs.set("suggest.quicksuggest.nonsponsored", false);
+  UrlbarPrefs.set("suggest.quicksuggest.sponsored", true);
+
+  let context = createContext(NONSPONSORED_SEARCH_STRING, {
+    providers: [UrlbarProviderQuickSuggest.name],
+    isPrivate: false,
+  });
+  await check_results({ context, matches: [] });
+});
+
+// Tests with both sponsored and non-sponsored suggestions enabled with a
+// search string that matches the sponsored suggestion.
+add_task(async function both_sponsored() {
+  UrlbarPrefs.set("suggest.quicksuggest.nonsponsored", true);
+  UrlbarPrefs.set("suggest.quicksuggest.sponsored", true);
+
+  let context = createContext(SPONSORED_SEARCH_STRING, {
+    providers: [UrlbarProviderQuickSuggest.name],
+    isPrivate: false,
+  });
+  await check_results({
+    context,
+    matches: [EXPECTED_SPONSORED_RESULT],
+  });
+});
+
+// Tests with both sponsored and non-sponsored suggestions enabled with a
+// search string that matches the non-sponsored suggestion.
+add_task(async function both_nonsponsored() {
+  UrlbarPrefs.set("suggest.quicksuggest.nonsponsored", true);
+  UrlbarPrefs.set("suggest.quicksuggest.sponsored", true);
+
+  let context = createContext(NONSPONSORED_SEARCH_STRING, {
+    providers: [UrlbarProviderQuickSuggest.name],
+    isPrivate: false,
+  });
+  await check_results({
+    context,
+    matches: [EXPECTED_NONSPONSORED_RESULT],
+  });
+});
+
+// Tests with both sponsored and non-sponsored suggestions enabled with a
+// search string that doesn't match either suggestion.
+add_task(async function both_noMatch() {
+  UrlbarPrefs.set("suggest.quicksuggest.nonsponsored", true);
+  UrlbarPrefs.set("suggest.quicksuggest.sponsored", true);
+
+  let context = createContext("this doesn't match anything", {
+    providers: [UrlbarProviderQuickSuggest.name],
+    isPrivate: false,
+  });
+  await check_results({ context, matches: [] });
+});
+
+// Tests with both the main and sponsored prefs disabled with a search string
+// that matches the sponsored suggestion.
+add_task(async function neither_sponsored() {
+  UrlbarPrefs.set("suggest.quicksuggest.nonsponsored", false);
+  UrlbarPrefs.set("suggest.quicksuggest.sponsored", false);
+
+  let context = createContext(SPONSORED_SEARCH_STRING, {
+    providers: [UrlbarProviderQuickSuggest.name],
+    isPrivate: false,
+  });
+  await check_results({ context, matches: [] });
+});
+
+// Tests with both the main and sponsored prefs disabled with a search string
+// that matches the non-sponsored suggestion.
+add_task(async function neither_nonsponsored() {
+  UrlbarPrefs.set("suggest.quicksuggest.nonsponsored", false);
+  UrlbarPrefs.set("suggest.quicksuggest.sponsored", false);
+
+  let context = createContext(NONSPONSORED_SEARCH_STRING, {
+    providers: [UrlbarProviderQuickSuggest.name],
+    isPrivate: false,
+  });
+  await check_results({ context, matches: [] });
+});
+
+// Search string matching should be case insensitive and ignore leading spaces.
+add_task(async function caseInsensitiveAndLeadingSpaces() {
+  UrlbarPrefs.set("suggest.quicksuggest.nonsponsored", true);
+  UrlbarPrefs.set("suggest.quicksuggest.sponsored", true);
+
+  let context = createContext("  " + SPONSORED_SEARCH_STRING.toUpperCase(), {
+    providers: [UrlbarProviderQuickSuggest.name],
+    isPrivate: false,
+  });
+  await check_results({
+    context,
+    matches: [EXPECTED_SPONSORED_RESULT],
+  });
+});
+
+// Results should be returned even when `browser.search.suggest.enabled` is
+// false.
+add_task(async function browser_search_suggest_enabled() {
+  UrlbarPrefs.set("suggest.quicksuggest.nonsponsored", true);
+  UrlbarPrefs.set("suggest.quicksuggest.sponsored", true);
+  UrlbarPrefs.set("browser.search.suggest.enabled", false);
+
+  let context = createContext(SPONSORED_SEARCH_STRING, {
+    providers: [UrlbarProviderQuickSuggest.name],
+    isPrivate: false,
+  });
+  await check_results({
+    context,
+    matches: [EXPECTED_SPONSORED_RESULT],
+  });
+
+  UrlbarPrefs.clear("browser.search.suggest.enabled");
+});
+
+// Results should be returned even when `browser.urlbar.suggest.searches` is
+// false.
+add_task(async function browser_search_suggest_enabled() {
+  UrlbarPrefs.set("suggest.quicksuggest.nonsponsored", true);
+  UrlbarPrefs.set("suggest.quicksuggest.sponsored", true);
+  UrlbarPrefs.set("suggest.searches", false);
+
+  let context = createContext(SPONSORED_SEARCH_STRING, {
+    providers: [UrlbarProviderQuickSuggest.name],
+    isPrivate: false,
+  });
+  await check_results({
+    context,
+    matches: [EXPECTED_SPONSORED_RESULT],
+  });
+
+  UrlbarPrefs.clear("suggest.searches");
+});
+
+// Neither sponsored nor non-sponsored results should appear in private contexts
+// even when suggestions in private windows are enabled.
+add_task(async function privateContext() {
+  UrlbarPrefs.set("suggest.quicksuggest.nonsponsored", true);
+  UrlbarPrefs.set("suggest.quicksuggest.sponsored", true);
+
+  for (let privateSuggestionsEnabled of [true, false]) {
+    UrlbarPrefs.set(
+      "browser.search.suggest.enabled.private",
+      privateSuggestionsEnabled
+    );
+    let context = createContext(SPONSORED_SEARCH_STRING, {
+      providers: [UrlbarProviderQuickSuggest.name],
+      isPrivate: true,
+    });
+    await check_results({
+      context,
+      matches: [],
+    });
+  }
+
+  UrlbarPrefs.clear("browser.search.suggest.enabled.private");
+});
+
+// When search suggestions come before general results and the only general
+// result is a quick suggest result, it should come last.
+add_task(async function suggestionsBeforeGeneral_only() {
+  UrlbarPrefs.set("suggest.quicksuggest.nonsponsored", true);
+  UrlbarPrefs.set("suggest.quicksuggest.sponsored", true);
+  UrlbarPrefs.set("browser.search.suggest.enabled", true);
+  UrlbarPrefs.set("suggest.searches", true);
+  UrlbarPrefs.set("showSearchSuggestionsFirst", true);
+
+  let context = createContext(SPONSORED_SEARCH_STRING, { isPrivate: false });
+  await check_results({
+    context,
+    matches: [
+      makeSearchResult(context, {
+        heuristic: true,
+        query: SPONSORED_SEARCH_STRING,
+        engineName: Services.search.defaultEngine.name,
+      }),
+      makeSearchResult(context, {
+        query: SPONSORED_SEARCH_STRING,
+        suggestion: SPONSORED_SEARCH_STRING + " foo",
+        engineName: Services.search.defaultEngine.name,
+      }),
+      makeSearchResult(context, {
+        query: SPONSORED_SEARCH_STRING,
+        suggestion: SPONSORED_SEARCH_STRING + " bar",
+        engineName: Services.search.defaultEngine.name,
+      }),
+      EXPECTED_SPONSORED_RESULT,
+    ],
+  });
+
+  UrlbarPrefs.clear("browser.search.suggest.enabled");
+  UrlbarPrefs.clear("suggest.searches");
+  UrlbarPrefs.clear("showSearchSuggestionsFirst");
+});
+
+// When search suggestions come before general results and there are other
+// general results besides quick suggest, the quick suggest result should come
+// last.
+add_task(async function suggestionsBeforeGeneral_others() {
+  UrlbarPrefs.set("suggest.quicksuggest.nonsponsored", true);
+  UrlbarPrefs.set("suggest.quicksuggest.sponsored", true);
+  UrlbarPrefs.set("browser.search.suggest.enabled", true);
+  UrlbarPrefs.set("suggest.searches", true);
+  UrlbarPrefs.set("showSearchSuggestionsFirst", true);
+
+  let context = createContext(SPONSORED_SEARCH_STRING, { isPrivate: false });
+
+  // Add some history that will match our query below.
+  let maxResults = UrlbarPrefs.get("maxRichResults");
+  let historyResults = [];
+  for (let i = 0; i < maxResults; i++) {
+    let url = "http://example.com/" + SPONSORED_SEARCH_STRING + i;
+    historyResults.push(
+      makeVisitResult(context, {
+        uri: url,
+        title: "test visit for " + url,
+      })
+    );
+    await PlacesTestUtils.addVisits(url);
+  }
+  historyResults = historyResults.reverse().slice(0, historyResults.length - 4);
+
+  await check_results({
+    context,
+    matches: [
+      makeSearchResult(context, {
+        heuristic: true,
+        query: SPONSORED_SEARCH_STRING,
+        engineName: Services.search.defaultEngine.name,
+      }),
+      makeSearchResult(context, {
+        query: SPONSORED_SEARCH_STRING,
+        suggestion: SPONSORED_SEARCH_STRING + " foo",
+        engineName: Services.search.defaultEngine.name,
+      }),
+      makeSearchResult(context, {
+        query: SPONSORED_SEARCH_STRING,
+        suggestion: SPONSORED_SEARCH_STRING + " bar",
+        engineName: Services.search.defaultEngine.name,
+      }),
+      ...historyResults,
+      EXPECTED_SPONSORED_RESULT,
+    ],
+  });
+
+  UrlbarPrefs.clear("browser.search.suggest.enabled");
+  UrlbarPrefs.clear("suggest.searches");
+  UrlbarPrefs.clear("showSearchSuggestionsFirst");
+  await PlacesUtils.history.clear();
+});
+
+// When general results come before search suggestions and the only general
+// result is a quick suggest result, it should come before suggestions.
+add_task(async function generalBeforeSuggestions_only() {
+  UrlbarPrefs.set("suggest.quicksuggest.nonsponsored", true);
+  UrlbarPrefs.set("suggest.quicksuggest.sponsored", true);
+  UrlbarPrefs.set("browser.search.suggest.enabled", true);
+  UrlbarPrefs.set("suggest.searches", true);
+  UrlbarPrefs.set("showSearchSuggestionsFirst", false);
+
+  let context = createContext(SPONSORED_SEARCH_STRING, { isPrivate: false });
+  await check_results({
+    context,
+    matches: [
+      makeSearchResult(context, {
+        heuristic: true,
+        query: SPONSORED_SEARCH_STRING,
+        engineName: Services.search.defaultEngine.name,
+      }),
+      EXPECTED_SPONSORED_RESULT,
+      makeSearchResult(context, {
+        query: SPONSORED_SEARCH_STRING,
+        suggestion: SPONSORED_SEARCH_STRING + " foo",
+        engineName: Services.search.defaultEngine.name,
+      }),
+      makeSearchResult(context, {
+        query: SPONSORED_SEARCH_STRING,
+        suggestion: SPONSORED_SEARCH_STRING + " bar",
+        engineName: Services.search.defaultEngine.name,
+      }),
+    ],
+  });
+
+  UrlbarPrefs.clear("browser.search.suggest.enabled");
+  UrlbarPrefs.clear("suggest.searches");
+  UrlbarPrefs.clear("showSearchSuggestionsFirst");
+});
+
+// When general results come before search suggestions and there are other
+// general results besides quick suggest, the quick suggest result should be the
+// last general result.
+add_task(async function generalBeforeSuggestions_others() {
+  UrlbarPrefs.set("suggest.quicksuggest.nonsponsored", true);
+  UrlbarPrefs.set("suggest.quicksuggest.sponsored", true);
+  UrlbarPrefs.set("browser.search.suggest.enabled", true);
+  UrlbarPrefs.set("suggest.searches", true);
+  UrlbarPrefs.set("showSearchSuggestionsFirst", false);
+
+  let context = createContext(SPONSORED_SEARCH_STRING, { isPrivate: false });
+
+  // Add some history that will match our query below.
+  let maxResults = UrlbarPrefs.get("maxRichResults");
+  let historyResults = [];
+  for (let i = 0; i < maxResults; i++) {
+    let url = "http://example.com/" + SPONSORED_SEARCH_STRING + i;
+    historyResults.push(
+      makeVisitResult(context, {
+        uri: url,
+        title: "test visit for " + url,
+      })
+    );
+    await PlacesTestUtils.addVisits(url);
+  }
+  historyResults = historyResults.reverse().slice(0, historyResults.length - 4);
+
+  await check_results({
+    context,
+    matches: [
+      makeSearchResult(context, {
+        heuristic: true,
+        query: SPONSORED_SEARCH_STRING,
+        engineName: Services.search.defaultEngine.name,
+      }),
+      ...historyResults,
+      EXPECTED_SPONSORED_RESULT,
+      makeSearchResult(context, {
+        query: SPONSORED_SEARCH_STRING,
+        suggestion: SPONSORED_SEARCH_STRING + " foo",
+        engineName: Services.search.defaultEngine.name,
+      }),
+      makeSearchResult(context, {
+        query: SPONSORED_SEARCH_STRING,
+        suggestion: SPONSORED_SEARCH_STRING + " bar",
+        engineName: Services.search.defaultEngine.name,
+      }),
+    ],
+  });
+
+  UrlbarPrefs.clear("browser.search.suggest.enabled");
+  UrlbarPrefs.clear("suggest.searches");
+  UrlbarPrefs.clear("showSearchSuggestionsFirst");
+  await PlacesUtils.history.clear();
+});
+
+add_task(async function dedupeAgainstURL_samePrefix() {
+  await doDedupeAgainstURLTest({
+    searchString: HTTP_SEARCH_STRING,
+    expectedQuickSuggestResult: EXPECTED_HTTP_RESULT,
+    otherPrefix: "http://",
+    expectOther: false,
+  });
+});
+
+add_task(async function dedupeAgainstURL_higherPrefix() {
+  await doDedupeAgainstURLTest({
+    searchString: HTTPS_SEARCH_STRING,
+    expectedQuickSuggestResult: EXPECTED_HTTPS_RESULT,
+    otherPrefix: "http://",
+    expectOther: false,
+  });
+});
+
+add_task(async function dedupeAgainstURL_lowerPrefix() {
+  await doDedupeAgainstURLTest({
+    searchString: HTTP_SEARCH_STRING,
+    expectedQuickSuggestResult: EXPECTED_HTTP_RESULT,
+    otherPrefix: "https://",
+    expectOther: true,
+  });
+});
+
+/**
+ * Tests how the muxer dedupes URL results against quick suggest results.
+ * Depending on prefix rank, quick suggest results should be preferred over
+ * other URL results with the same stripped URL: Other results should be
+ * discarded when their prefix rank is lower than the prefix rank of the quick
+ * suggest. They should not be discarded when their prefix rank is higher, and
+ * in that case both results should be included.
+ *
+ * This function adds a visit to the URL formed by the given `otherPrefix` and
+ * `PREFIX_SUGGESTIONS_STRIPPED_URL`. The visit's title will be set to the given
+ * `searchString` so that both the visit and the quick suggest will match it.
+ *
+ * @param {object} options
+ *   Options object.
+ * @param {string} options.searchString
+ *   The search string that should trigger one of the mock prefix-test quick
+ *   suggest results.
+ * @param {object} options.expectedQuickSuggestResult
+ *   The expected quick suggest result.
+ * @param {string} options.otherPrefix
+ *   The visit will be created with a URL with this prefix, e.g., "http://".
+ * @param {boolean} options.expectOther
+ *   Whether the visit result should appear in the final results.
+ */
+async function doDedupeAgainstURLTest({
+  searchString,
+  expectedQuickSuggestResult,
+  otherPrefix,
+  expectOther,
+}) {
+  // Disable search suggestions.
+  UrlbarPrefs.set("suggest.searches", false);
+
+  // Add a visit that will match our query below.
+  let otherURL = otherPrefix + PREFIX_SUGGESTIONS_STRIPPED_URL;
+  await PlacesTestUtils.addVisits({ uri: otherURL, title: searchString });
+
+  // First, do a search with quick suggest disabled to make sure the search
+  // string matches the visit.
+  info("Doing first query");
+  UrlbarPrefs.set("suggest.quicksuggest.nonsponsored", false);
+  UrlbarPrefs.set("suggest.quicksuggest.sponsored", false);
+  let context = createContext(searchString, { isPrivate: false });
+  await check_results({
+    context,
+    matches: [
+      makeSearchResult(context, {
+        heuristic: true,
+        query: searchString,
+        engineName: Services.search.defaultEngine.name,
+      }),
+      makeVisitResult(context, {
+        uri: otherURL,
+        title: searchString,
+      }),
+    ],
+  });
+
+  // Now do another search with quick suggest enabled.
+  UrlbarPrefs.set("suggest.quicksuggest.nonsponsored", true);
+  UrlbarPrefs.set("suggest.quicksuggest.sponsored", true);
+
+  context = createContext(searchString, { isPrivate: false });
+
+  let expectedResults = [
+    makeSearchResult(context, {
+      heuristic: true,
+      query: searchString,
+      engineName: Services.search.defaultEngine.name,
+    }),
+  ];
+  if (expectOther) {
+    expectedResults.push(
+      makeVisitResult(context, {
+        uri: otherURL,
+        title: searchString,
+      })
+    );
+  }
+  expectedResults.push(expectedQuickSuggestResult);
+
+  info("Doing second query");
+  await check_results({ context, matches: expectedResults });
+
+  UrlbarPrefs.clear("suggest.quicksuggest.nonsponsored");
+  UrlbarPrefs.clear("suggest.quicksuggest.sponsored");
+  UrlbarPrefs.clear("suggest.searches");
+  await PlacesUtils.history.clear();
+}
+
+// Tests the remote settings latency histogram.
+add_task(async function latencyTelemetry() {
+  UrlbarPrefs.set("suggest.quicksuggest.nonsponsored", true);
+  UrlbarPrefs.set("suggest.quicksuggest.sponsored", true);
+
+  let histogram = Services.telemetry.getHistogramById(
+    TELEMETRY_REMOTE_SETTINGS_LATENCY
+  );
+  histogram.clear();
+
+  let context = createContext(SPONSORED_SEARCH_STRING, {
+    providers: [UrlbarProviderQuickSuggest.name],
+    isPrivate: false,
+  });
+  await check_results({
+    context,
+    matches: [EXPECTED_SPONSORED_RESULT],
+  });
+
+  // In the latency histogram, there should be a single value across all
+  // buckets.
+  Assert.deepEqual(
+    Object.values(histogram.snapshot().values).filter(v => v > 0),
+    [1],
+    "Latency histogram updated after search"
+  );
+  Assert.ok(
+    !TelemetryStopwatch.running(TELEMETRY_REMOTE_SETTINGS_LATENCY, context),
+    "Stopwatch not running after search"
+  );
+});
+
+// Tests setup and teardown of the remote settings client depending on whether
+// quick suggest is enabled.
+add_task(async function setupAndTeardown() {
+  // Disable the suggest prefs so the settings client starts out torn down.
+  UrlbarPrefs.set("suggest.quicksuggest.nonsponsored", false);
+  UrlbarPrefs.set("suggest.quicksuggest.sponsored", false);
+  await QuickSuggest.remoteSettings.readyPromise;
+  Assert.ok(
+    !QuickSuggest.remoteSettings._test_rs,
+    "Settings client is null after disabling suggest prefs"
+  );
+
+  // Setting one of the suggest prefs should cause the client to be set up. We
+  // assume all previous tasks left `quicksuggest.enabled` true (from the init
+  // task).
+  UrlbarPrefs.set("suggest.quicksuggest.nonsponsored", true);
+  await QuickSuggest.remoteSettings.readyPromise;
+  Assert.ok(
+    QuickSuggest.remoteSettings._test_rs,
+    "Settings client is non-null after enabling suggest.quicksuggest.nonsponsored"
+  );
+
+  UrlbarPrefs.set("suggest.quicksuggest.nonsponsored", false);
+  await QuickSuggest.remoteSettings.readyPromise;
+  Assert.ok(
+    !QuickSuggest.remoteSettings._test_rs,
+    "Settings client is null after disabling suggest.quicksuggest.nonsponsored"
+  );
+
+  UrlbarPrefs.set("suggest.quicksuggest.sponsored", true);
+  await QuickSuggest.remoteSettings.readyPromise;
+  Assert.ok(
+    QuickSuggest.remoteSettings._test_rs,
+    "Settings client is non-null after enabling suggest.quicksuggest.sponsored"
+  );
+
+  UrlbarPrefs.set("suggest.quicksuggest.nonsponsored", true);
+  await QuickSuggest.remoteSettings.readyPromise;
+  Assert.ok(
+    QuickSuggest.remoteSettings._test_rs,
+    "Settings client remains non-null after enabling suggest.quicksuggest.nonsponsored"
+  );
+
+  UrlbarPrefs.set("suggest.quicksuggest.nonsponsored", false);
+  await QuickSuggest.remoteSettings.readyPromise;
+  Assert.ok(
+    QuickSuggest.remoteSettings._test_rs,
+    "Settings client remains non-null after disabling suggest.quicksuggest.nonsponsored"
+  );
+
+  UrlbarPrefs.set("suggest.quicksuggest.sponsored", false);
+  await QuickSuggest.remoteSettings.readyPromise;
+  Assert.ok(
+    !QuickSuggest.remoteSettings._test_rs,
+    "Settings client is null after disabling suggest.quicksuggest.sponsored"
+  );
+
+  UrlbarPrefs.set("suggest.quicksuggest.nonsponsored", true);
+  await QuickSuggest.remoteSettings.readyPromise;
+  Assert.ok(
+    QuickSuggest.remoteSettings._test_rs,
+    "Settings client is non-null after enabling suggest.quicksuggest.nonsponsored"
+  );
+
+  UrlbarPrefs.set("quicksuggest.enabled", false);
+  await QuickSuggest.remoteSettings.readyPromise;
+  Assert.ok(
+    !QuickSuggest.remoteSettings._test_rs,
+    "Settings client is null after disabling quicksuggest.enabled"
+  );
+
+  // Leave the prefs in the same state as when the task started.
+  UrlbarPrefs.clear("suggest.quicksuggest.nonsponsored");
+  UrlbarPrefs.clear("suggest.quicksuggest.sponsored");
+  UrlbarPrefs.set("quicksuggest.enabled", true);
+  await QuickSuggest.remoteSettings.readyPromise;
+  Assert.ok(
+    !QuickSuggest.remoteSettings._test_rs,
+    "Settings client remains null at end of task"
+  );
+});
+
+// Timestamp templates in URLs should be replaced with real timestamps.
+add_task(async function timestamps() {
+  UrlbarPrefs.set("suggest.quicksuggest.nonsponsored", true);
+  UrlbarPrefs.set("suggest.quicksuggest.sponsored", true);
+
+  // Do a search.
+  let context = createContext(TIMESTAMP_SEARCH_STRING, {
+    providers: [UrlbarProviderQuickSuggest.name],
+    isPrivate: false,
+  });
+  let controller = UrlbarTestUtils.newMockController({
+    input: {
+      isPrivate: context.isPrivate,
+      onFirstResult() {
+        return false;
+      },
+      getSearchSource() {
+        return "dummy-search-source";
+      },
+      window: {
+        location: {
+          href: AppConstants.BROWSER_CHROME_URL,
+        },
+      },
+    },
+  });
+  await controller.startQuery(context);
+
+  // Should be one quick suggest result.
+  Assert.equal(context.results.length, 1, "One result returned");
+  let result = context.results[0];
+
+  QuickSuggestTestUtils.assertTimestampsReplaced(result, {
+    url: TIMESTAMP_SUGGESTION_URL,
+    sponsoredClickUrl: TIMESTAMP_SUGGESTION_CLICK_URL,
+  });
+});
+
+// Real quick suggest URLs include a timestamp template that
+// UrlbarProviderQuickSuggest fills in when it fetches suggestions. When the
+// user picks a quick suggest, its URL with its particular timestamp is added to
+// history. If the user triggers the quick suggest again later, its new
+// timestamp may be different from the one in the user's history. In that case,
+// the two URLs should be treated as dupes and only the quick suggest should be
+// shown, not the URL from history.
+add_task(async function dedupeAgainstURL_timestamps() {
+  // Disable search suggestions.
+  UrlbarPrefs.set("suggest.searches", false);
+
+  // Add a visit that will match the query below and dupe the quick suggest.
+  let dupeURL = TIMESTAMP_SUGGESTION_URL.replace(
+    TIMESTAMP_TEMPLATE,
+    "2013051113"
+  );
+
+  // Add other visits that will match the query and almost dupe the quick
+  // suggest but not quite because they have invalid timestamps.
+  let badTimestamps = [
+    // not numeric digits
+    "x".repeat(TIMESTAMP_LENGTH),
+    // too few digits
+    "5".repeat(TIMESTAMP_LENGTH - 1),
+    // empty string, too few digits
+    "",
+  ];
+  let badTimestampURLs = badTimestamps.map(str =>
+    TIMESTAMP_SUGGESTION_URL.replace(TIMESTAMP_TEMPLATE, str)
+  );
+
+  await PlacesTestUtils.addVisits(
+    [dupeURL, ...badTimestampURLs].map(uri => ({
+      uri,
+      title: TIMESTAMP_SEARCH_STRING,
+    }))
+  );
+
+  // First, do a search with quick suggest disabled to make sure the search
+  // string matches all the other URLs.
+  info("Doing first query");
+  UrlbarPrefs.set("suggest.quicksuggest.nonsponsored", false);
+  UrlbarPrefs.set("suggest.quicksuggest.sponsored", false);
+  let context = createContext(TIMESTAMP_SEARCH_STRING, { isPrivate: false });
+
+  let expectedHeuristic = makeSearchResult(context, {
+    heuristic: true,
+    query: TIMESTAMP_SEARCH_STRING,
+    engineName: Services.search.defaultEngine.name,
+  });
+  let expectedDupeResult = makeVisitResult(context, {
+    uri: dupeURL,
+    title: TIMESTAMP_SEARCH_STRING,
+  });
+  let expectedBadTimestampResults = [...badTimestampURLs].reverse().map(uri =>
+    makeVisitResult(context, {
+      uri,
+      title: TIMESTAMP_SEARCH_STRING,
+    })
+  );
+
+  await check_results({
+    context,
+    matches: [
+      expectedHeuristic,
+      ...expectedBadTimestampResults,
+      expectedDupeResult,
+    ],
+  });
+
+  // Now do another search with quick suggest enabled.
+  info("Doing second query");
+  UrlbarPrefs.set("suggest.quicksuggest.nonsponsored", true);
+  UrlbarPrefs.set("suggest.quicksuggest.sponsored", true);
+  context = createContext(TIMESTAMP_SEARCH_STRING, { isPrivate: false });
+
+  // The expected quick suggest result without the timestamp-related payload
+  // properties.
+  let expectedQuickSuggest = {
+    type: UrlbarUtils.RESULT_TYPE.URL,
+    source: UrlbarUtils.RESULT_SOURCE.SEARCH,
+    heuristic: false,
+    payload: {
+      originalUrl: TIMESTAMP_SUGGESTION_URL,
+      qsSuggestion: TIMESTAMP_SEARCH_STRING,
+      title: "Timestamp suggestion",
+      icon: null,
+      sponsoredImpressionUrl: "http://impression.reporting.test.com/timestamp",
+      sponsoredBlockId: 5,
+      sponsoredAdvertiser: "TestAdvertiserTimestamp",
+      sponsoredIabCategory: "22 - Shopping",
+      isSponsored: true,
+      helpUrl: QuickSuggest.HELP_URL,
+      helpL10n: { id: "firefox-suggest-urlbar-learn-more" },
+      isBlockable: false,
+      blockL10n: { id: "firefox-suggest-urlbar-block" },
+      source: "remote-settings",
+    },
+  };
+
+  let expectedResults = [
+    expectedHeuristic,
+    ...expectedBadTimestampResults,
+    expectedQuickSuggest,
+  ];
+
+  let controller = UrlbarTestUtils.newMockController({
+    input: {
+      isPrivate: false,
+      onFirstResult() {
+        return false;
+      },
+      getSearchSource() {
+        return "dummy-search-source";
+      },
+      window: {
+        location: {
+          href: AppConstants.BROWSER_CHROME_URL,
+        },
+      },
+    },
+  });
+  await controller.startQuery(context);
+  info("Actual results: " + JSON.stringify(context.results));
+
+  Assert.equal(
+    context.results.length,
+    expectedResults.length,
+    "Found the expected number of results"
+  );
+
+  function getPayload(result, keysToIgnore = []) {
+    let payload = {};
+    for (let [key, value] of Object.entries(result.payload)) {
+      if (value !== undefined && !keysToIgnore.includes(key)) {
+        payload[key] = value;
+      }
+    }
+    return payload;
+  }
+
+  // Check actual vs. expected result properties.
+  for (let i = 0; i < expectedResults.length; i++) {
+    let actual = context.results[i];
+    let expected = expectedResults[i];
+    info(
+      `Comparing results at index ${i}:` +
+        " actual=" +
+        JSON.stringify(actual) +
+        " expected=" +
+        JSON.stringify(expected)
+    );
+    Assert.equal(
+      actual.type,
+      expected.type,
+      `result.type at result index ${i}`
+    );
+    Assert.equal(
+      actual.source,
+      expected.source,
+      `result.source at result index ${i}`
+    );
+    Assert.equal(
+      actual.heuristic,
+      expected.heuristic,
+      `result.heuristic at result index ${i}`
+    );
+
+    // Check payloads except for the last result, which should be the quick
+    // suggest.
+    if (i != expectedResults.length - 1) {
+      Assert.deepEqual(
+        getPayload(context.results[i]),
+        getPayload(expectedResults[i]),
+        "Payload at index " + i
+      );
+    }
+  }
+
+  // Check the quick suggest's payload excluding the timestamp-related
+  // properties.
+  let actualQuickSuggest = context.results[context.results.length - 1];
+  let timestampKeys = [
+    "displayUrl",
+    "sponsoredClickUrl",
+    "url",
+    "urlTimestampIndex",
+  ];
+  Assert.deepEqual(
+    getPayload(actualQuickSuggest, timestampKeys),
+    getPayload(expectedQuickSuggest, timestampKeys),
+    "Quick suggest payload excluding timestamp-related keys"
+  );
+
+  // Now check the timestamps in the payload.
+  QuickSuggestTestUtils.assertTimestampsReplaced(actualQuickSuggest, {
+    url: TIMESTAMP_SUGGESTION_URL,
+    sponsoredClickUrl: TIMESTAMP_SUGGESTION_CLICK_URL,
+  });
+
+  // Clean up.
+  UrlbarPrefs.clear("suggest.quicksuggest.nonsponsored");
+  UrlbarPrefs.clear("suggest.quicksuggest.sponsored");
+  UrlbarPrefs.clear("suggest.searches");
+  await PlacesUtils.history.clear();
+});
+
+// Tests the API for blocking suggestions and the backing pref.
+add_task(async function blockedSuggestionsAPI() {
+  // Start with no blocked suggestions.
+  await QuickSuggest.blockedSuggestions.clear();
+  Assert.equal(
+    QuickSuggest.blockedSuggestions._test_digests.size,
+    0,
+    "blockedSuggestions._test_digests is empty"
+  );
+  Assert.equal(
+    UrlbarPrefs.get("quicksuggest.blockedDigests"),
+    "",
+    "quicksuggest.blockedDigests is an empty string"
+  );
+
+  // Make some URLs.
+  let urls = [];
+  for (let i = 0; i < 3; i++) {
+    urls.push("http://example.com/" + i);
+  }
+
+  // Block each URL in turn and make sure previously blocked URLs are still
+  // blocked and the remaining URLs are not blocked.
+  for (let i = 0; i < urls.length; i++) {
+    await QuickSuggest.blockedSuggestions.add(urls[i]);
+    for (let j = 0; j < urls.length; j++) {
+      Assert.equal(
+        await QuickSuggest.blockedSuggestions.has(urls[j]),
+        j <= i,
+        `Suggestion at index ${j} is blocked or not as expected`
+      );
+    }
+  }
+
+  // Make sure all URLs are blocked for good measure.
+  for (let url of urls) {
+    Assert.ok(
+      await QuickSuggest.blockedSuggestions.has(url),
+      `Suggestion is blocked: ${url}`
+    );
+  }
+
+  // Check `blockedSuggestions._test_digests` and `quicksuggest.blockedDigests`.
+  Assert.equal(
+    QuickSuggest.blockedSuggestions._test_digests.size,
+    urls.length,
+    "blockedSuggestions._test_digests has correct size"
+  );
+  let array = JSON.parse(UrlbarPrefs.get("quicksuggest.blockedDigests"));
+  Assert.ok(Array.isArray(array), "Parsed value of pref is an array");
+  Assert.equal(array.length, urls.length, "Array has correct length");
+
+  // Write some junk to `quicksuggest.blockedDigests`.
+  // `blockedSuggestions._test_digests` should not be changed and all previously
+  // blocked URLs should remain blocked.
+  UrlbarPrefs.set("quicksuggest.blockedDigests", "not a json array");
+  await QuickSuggest.blockedSuggestions._test_readyPromise;
+  for (let url of urls) {
+    Assert.ok(
+      await QuickSuggest.blockedSuggestions.has(url),
+      `Suggestion remains blocked: ${url}`
+    );
+  }
+  Assert.equal(
+    QuickSuggest.blockedSuggestions._test_digests.size,
+    urls.length,
+    "blockedSuggestions._test_digests still has correct size"
+  );
+
+  // Block a new URL. All URLs should remain blocked and the pref should be
+  // updated.
+  let newURL = "http://example.com/new-block";
+  await QuickSuggest.blockedSuggestions.add(newURL);
+  urls.push(newURL);
+  for (let url of urls) {
+    Assert.ok(
+      await QuickSuggest.blockedSuggestions.has(url),
+      `Suggestion is blocked: ${url}`
+    );
+  }
+  Assert.equal(
+    QuickSuggest.blockedSuggestions._test_digests.size,
+    urls.length,
+    "blockedSuggestions._test_digests has correct size"
+  );
+  array = JSON.parse(UrlbarPrefs.get("quicksuggest.blockedDigests"));
+  Assert.ok(Array.isArray(array), "Parsed value of pref is an array");
+  Assert.equal(array.length, urls.length, "Array has correct length");
+
+  // Add a new URL digest directly to the JSON'ed array in the pref.
+  newURL = "http://example.com/direct-to-pref";
+  urls.push(newURL);
+  array = JSON.parse(UrlbarPrefs.get("quicksuggest.blockedDigests"));
+  array.push(await QuickSuggest.blockedSuggestions._test_getDigest(newURL));
+  UrlbarPrefs.set("quicksuggest.blockedDigests", JSON.stringify(array));
+  await QuickSuggest.blockedSuggestions._test_readyPromise;
+
+  // All URLs should remain blocked and the new URL should be blocked.
+  for (let url of urls) {
+    Assert.ok(
+      await QuickSuggest.blockedSuggestions.has(url),
+      `Suggestion is blocked: ${url}`
+    );
+  }
+  Assert.equal(
+    QuickSuggest.blockedSuggestions._test_digests.size,
+    urls.length,
+    "blockedSuggestions._test_digests has correct size"
+  );
+
+  // Clear the pref. All URLs should be unblocked.
+  UrlbarPrefs.clear("quicksuggest.blockedDigests");
+  await QuickSuggest.blockedSuggestions._test_readyPromise;
+  for (let url of urls) {
+    Assert.ok(
+      !(await QuickSuggest.blockedSuggestions.has(url)),
+      `Suggestion is no longer blocked: ${url}`
+    );
+  }
+  Assert.equal(
+    QuickSuggest.blockedSuggestions._test_digests.size,
+    0,
+    "blockedSuggestions._test_digests is now empty"
+  );
+
+  // Block all the URLs again and test `blockedSuggestions.clear()`.
+  for (let url of urls) {
+    await QuickSuggest.blockedSuggestions.add(url);
+  }
+  for (let url of urls) {
+    Assert.ok(
+      await QuickSuggest.blockedSuggestions.has(url),
+      `Suggestion is blocked: ${url}`
+    );
+  }
+  await QuickSuggest.blockedSuggestions.clear();
+  for (let url of urls) {
+    Assert.ok(
+      !(await QuickSuggest.blockedSuggestions.has(url)),
+      `Suggestion is no longer blocked: ${url}`
+    );
+  }
+  Assert.equal(
+    QuickSuggest.blockedSuggestions._test_digests.size,
+    0,
+    "blockedSuggestions._test_digests is now empty"
+  );
+});
+
+// Test whether the blocking for remote settings results works.
+add_task(async function block() {
+  for (const result of REMOTE_SETTINGS_RESULTS) {
+    await QuickSuggest.blockedSuggestions.add(result.url);
+  }
+
+  for (const result of REMOTE_SETTINGS_RESULTS) {
+    const context = createContext(result.keywords[0], {
+      providers: [UrlbarProviderQuickSuggest.name],
+      isPrivate: false,
+    });
+    await check_results({
+      context,
+      matches: [],
+    });
+  }
+
+  await QuickSuggest.blockedSuggestions.clear();
+});
+
+// Makes sure remote settings data is fetched using the correct `type` based on
+// the value of the `quickSuggestRemoteSettingsDataType` Nimbus variable.
+add_task(async function remoteSettingsDataType() {
+  // `QuickSuggestTestUtils.ensureQuickSuggestInit()` stubs
+  // `QuickSuggest.remoteSettings._queueSettingsSync()`, which we want to test
+  // below, so remove the stub by calling the cleanup function it returned.
+  await cleanUpQuickSuggest();
+
+  // We need to spy on `QuickSuggest.remoteSettings.#rs.get()`, but `#rs` is
+  // created lazily. Set `suggest.quicksuggest.sponsored` to trigger its
+  // creation.
+  UrlbarPrefs.set("suggest.quicksuggest.sponsored", true);
+  await QuickSuggest.remoteSettings.readyPromise;
+
+  let sandbox = sinon.createSandbox();
+  let spy = sandbox.spy(QuickSuggest.remoteSettings._test_rs, "get");
+
+  for (let dataType of [undefined, "test-data-type"]) {
+    // Set up a mock Nimbus rollout with the data type.
+    let value = {};
+    if (dataType) {
+      value.quickSuggestRemoteSettingsDataType = dataType;
+    }
+    let cleanUpNimbus = await UrlbarTestUtils.initNimbusFeature(value);
+
+    // Re-enable remote settings to trigger `remoteSettings.#rs.get()`.
+    await QuickSuggest.remoteSettings.enable(false);
+    await QuickSuggest.remoteSettings.enable(true);
+    await QuickSuggest.remoteSettings.readyPromise;
+
+    let expectedDataType = dataType || "data";
+    Assert.ok(
+      spy.calledWith({ filters: { type: expectedDataType } }),
+      "#rs.get() called with expected data type: " + expectedDataType
+    );
+
+    spy.resetHistory();
+    await cleanUpNimbus();
+  }
+
+  sandbox.restore();
+
+  // Restore the stub for the remainder of the test.
+  cleanUpQuickSuggest = await QuickSuggestTestUtils.ensureQuickSuggestInit(
+    REMOTE_SETTINGS_RESULTS
+  );
+});
diff --git a/browser/components/urlbar/tests/quicksuggest/unit/test_quicksuggest_addResults.js b/browser/components/urlbar/tests/quicksuggest/unit/test_quicksuggest_addResults.js
new file mode 100644
index 0000000000..024f5526a6
--- /dev/null
+++ b/browser/components/urlbar/tests/quicksuggest/unit/test_quicksuggest_addResults.js
@@ -0,0 +1,158 @@
+/* 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/. */
+
+// Tests the chunking feature of `RemoteSettingsClient.#addResults()`.
+
+"use strict";
+
+XPCOMUtils.defineLazyModuleGetters(this, {
+  ObjectUtils: "resource://gre/modules/ObjectUtils.jsm",
+});
+
+// This overrides `QuickSuggest.remoteSettings._addResultsChunkSize`. Testing
+// the actual value can make the test run too long. This is OK because the
+// correctness of the chunking behavior doesn't depend on the chunk size.
+const TEST_ADD_RESULTS_CHUNK_SIZE = 100;
+
+add_task(async function init() {
+  UrlbarPrefs.set("quicksuggest.enabled", true);
+  await QuickSuggestTestUtils.ensureQuickSuggestInit();
+
+  // Sanity check the actual `_addResultsChunkSize` value.
+  Assert.equal(
+    typeof QuickSuggest.remoteSettings._addResultsChunkSize,
+    "number",
+    "Sanity check: _addResultsChunkSize is a number"
+  );
+  Assert.greater(
+    QuickSuggest.remoteSettings._addResultsChunkSize,
+    0,
+    "Sanity check: _addResultsChunkSize > 0"
+  );
+
+  // Set our test value.
+  QuickSuggest.remoteSettings._addResultsChunkSize = TEST_ADD_RESULTS_CHUNK_SIZE;
+});
+
+// Tests many results with one keyword each.
+add_task(async function chunking_singleKeyword() {
+  let resultCounts = [
+    1 * QuickSuggest.remoteSettings._addResultsChunkSize - 1,
+    1 * QuickSuggest.remoteSettings._addResultsChunkSize,
+    1 * QuickSuggest.remoteSettings._addResultsChunkSize + 1,
+    2 * QuickSuggest.remoteSettings._addResultsChunkSize - 1,
+    2 * QuickSuggest.remoteSettings._addResultsChunkSize,
+    2 * QuickSuggest.remoteSettings._addResultsChunkSize + 1,
+    3 * QuickSuggest.remoteSettings._addResultsChunkSize - 1,
+    3 * QuickSuggest.remoteSettings._addResultsChunkSize,
+    3 * QuickSuggest.remoteSettings._addResultsChunkSize + 1,
+  ];
+  for (let count of resultCounts) {
+    await doChunkingTest(count, 1);
+  }
+});
+
+// Tests a small number of results with many keywords each.
+add_task(async function chunking_manyKeywords() {
+  let keywordCounts = [
+    1 * QuickSuggest.remoteSettings._addResultsChunkSize - 1,
+    1 * QuickSuggest.remoteSettings._addResultsChunkSize,
+    1 * QuickSuggest.remoteSettings._addResultsChunkSize + 1,
+    2 * QuickSuggest.remoteSettings._addResultsChunkSize - 1,
+    2 * QuickSuggest.remoteSettings._addResultsChunkSize,
+    2 * QuickSuggest.remoteSettings._addResultsChunkSize + 1,
+    3 * QuickSuggest.remoteSettings._addResultsChunkSize - 1,
+    3 * QuickSuggest.remoteSettings._addResultsChunkSize,
+    3 * QuickSuggest.remoteSettings._addResultsChunkSize + 1,
+  ];
+  for (let resultCount = 1; resultCount <= 3; resultCount++) {
+    for (let keywordCount of keywordCounts) {
+      await doChunkingTest(resultCount, keywordCount);
+    }
+  }
+});
+
+async function doChunkingTest(resultCount, keywordCountPerResult) {
+  info(
+    "Running chunking test: " +
+      JSON.stringify({ resultCount, keywordCountPerResult })
+  );
+
+  // Create `resultCount` results, each with `keywordCountPerResult` keywords.
+  let results = [];
+  for (let i = 0; i < resultCount; i++) {
+    let keywords = [];
+    for (let k = 0; k < keywordCountPerResult; k++) {
+      keywords.push(`keyword-${i}-${k}`);
+    }
+    results.push({
+      keywords,
+      id: i,
+      url: "http://example.com/" + i,
+      title: "Suggestion " + i,
+      click_url: "http://example.com/click",
+      impression_url: "http://example.com/impression",
+      advertiser: "TestAdvertiser",
+      iab_category: "22 - Shopping",
+    });
+  }
+
+  // Add the results.
+  QuickSuggest.remoteSettings._test_resultsByKeyword.clear();
+  await QuickSuggest.remoteSettings._test_addResults(results);
+
+  // Make sure all keyword-result pairs have been added.
+  for (let i = 0; i < resultCount; i++) {
+    for (let k = 0; k < keywordCountPerResult; k++) {
+      let keyword = `keyword-${i}-${k}`;
+
+      // Check the resultsByKeyword map. Logging all assertions takes a ton of
+      // time and makes the test run much longer than it otherwise would,
+      // especially if `_addResultsChunkSize` is large, so only log failing
+      // assertions.
+      let actualResult = QuickSuggest.remoteSettings._test_resultsByKeyword.get(
+        keyword
+      );
+      if (!ObjectUtils.deepEqual(actualResult, results[i])) {
+        Assert.deepEqual(
+          actualResult,
+          results[i],
+          `Result ${i} is in _test_resultsByKeyword for keyword ${keyword}`
+        );
+      }
+
+      // Call `query()` and make sure a suggestion is returned for the result.
+      // Computing the expected value of `full_keyword` is kind of a pain and
+      // it's not important to check it, so first delete it from the returned
+      // suggestion.
+      let actualSuggestions = await QuickSuggest.remoteSettings.fetch(keyword);
+      for (let s of actualSuggestions) {
+        delete s.full_keyword;
+      }
+      let expectedSuggestions = [
+        {
+          block_id: i,
+          url: "http://example.com/" + i,
+          title: "Suggestion " + i,
+          click_url: "http://example.com/click",
+          impression_url: "http://example.com/impression",
+          advertiser: "TestAdvertiser",
+          iab_category: "22 - Shopping",
+          is_sponsored: true,
+          score: RemoteSettingsClient.DEFAULT_SUGGESTION_SCORE,
+          source: "remote-settings",
+          icon: null,
+          position: undefined,
+        },
+      ];
+      if (!ObjectUtils.deepEqual(actualSuggestions, expectedSuggestions)) {
+        Assert.deepEqual(
+          actualSuggestions,
+          expectedSuggestions,
+          `query() returns a suggestion for result ${i} with keyword ${keyword}`
+        );
+      }
+    }
+  }
+}
diff --git a/browser/components/urlbar/tests/quicksuggest/unit/test_quicksuggest_bestMatch.js b/browser/components/urlbar/tests/quicksuggest/unit/test_quicksuggest_bestMatch.js
new file mode 100644
index 0000000000..120162256b
--- /dev/null
+++ b/browser/components/urlbar/tests/quicksuggest/unit/test_quicksuggest_bestMatch.js
@@ -0,0 +1,449 @@
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+// Tests best match quick suggest results.
+
+"use strict";
+
+const MAX_RESULT_COUNT = UrlbarPrefs.get("maxRichResults");
+
+// This search string length needs to be >= 4 to trigger its suggestion as a
+// best match instead of a usual quick suggest.
+const BEST_MATCH_POSITION_SEARCH_STRING = "bestmatchposition";
+const BEST_MATCH_POSITION = Math.round(MAX_RESULT_COUNT / 2);
+
+const REMOTE_SETTINGS_RESULTS = [
+  {
+    id: 1,
+    url: "http://example.com/",
+    title: "Fullkeyword title",
+    keywords: [
+      "fu",
+      "ful",
+      "full",
+      "fullk",
+      "fullke",
+      "fullkey",
+      "fullkeyw",
+      "fullkeywo",
+      "fullkeywor",
+      "fullkeyword",
+      "example",
+    ],
+    click_url: "http://example.com/click",
+    impression_url: "http://example.com/impression",
+    advertiser: "TestAdvertiser",
+  },
+  {
+    id: 2,
+    url: "http://example.com/best-match-position",
+    title: `${BEST_MATCH_POSITION_SEARCH_STRING} title`,
+    keywords: [BEST_MATCH_POSITION_SEARCH_STRING],
+    click_url: "http://example.com/click",
+    impression_url: "http://example.com/impression",
+    advertiser: "TestAdvertiser",
+    position: BEST_MATCH_POSITION,
+  },
+];
+
+const EXPECTED_BEST_MATCH_URLBAR_RESULT = {
+  type: UrlbarUtils.RESULT_TYPE.URL,
+  source: UrlbarUtils.RESULT_SOURCE.SEARCH,
+  heuristic: false,
+  isBestMatch: true,
+  payload: {
+    url: "http://example.com/",
+    originalUrl: "http://example.com/",
+    title: "Fullkeyword title",
+    icon: null,
+    isSponsored: true,
+    sponsoredImpressionUrl: "http://example.com/impression",
+    sponsoredClickUrl: "http://example.com/click",
+    sponsoredBlockId: 1,
+    sponsoredAdvertiser: "TestAdvertiser",
+    helpUrl: QuickSuggest.HELP_URL,
+    helpL10n: { id: "firefox-suggest-urlbar-learn-more" },
+    isBlockable: false,
+    blockL10n: { id: "firefox-suggest-urlbar-block" },
+    displayUrl: "http://example.com",
+    source: "remote-settings",
+  },
+};
+
+const EXPECTED_NON_BEST_MATCH_URLBAR_RESULT = {
+  type: UrlbarUtils.RESULT_TYPE.URL,
+  source: UrlbarUtils.RESULT_SOURCE.SEARCH,
+  heuristic: false,
+  payload: {
+    url: "http://example.com/",
+    originalUrl: "http://example.com/",
+    title: "Fullkeyword title",
+    qsSuggestion: "fullkeyword",
+    icon: null,
+    isSponsored: true,
+    sponsoredImpressionUrl: "http://example.com/impression",
+    sponsoredClickUrl: "http://example.com/click",
+    sponsoredBlockId: 1,
+    sponsoredAdvertiser: "TestAdvertiser",
+    helpUrl: QuickSuggest.HELP_URL,
+    helpL10n: { id: "firefox-suggest-urlbar-learn-more" },
+    isBlockable: false,
+    blockL10n: { id: "firefox-suggest-urlbar-block" },
+    displayUrl: "http://example.com",
+    source: "remote-settings",
+  },
+};
+
+const EXPECTED_BEST_MATCH_POSITION_URLBAR_RESULT = {
+  type: UrlbarUtils.RESULT_TYPE.URL,
+  source: UrlbarUtils.RESULT_SOURCE.SEARCH,
+  heuristic: false,
+  isBestMatch: true,
+  payload: {
+    url: "http://example.com/best-match-position",
+    originalUrl: "http://example.com/best-match-position",
+    title: `${BEST_MATCH_POSITION_SEARCH_STRING} title`,
+    icon: null,
+    isSponsored: true,
+    sponsoredImpressionUrl: "http://example.com/impression",
+    sponsoredClickUrl: "http://example.com/click",
+    sponsoredBlockId: 2,
+    sponsoredAdvertiser: "TestAdvertiser",
+    helpUrl: QuickSuggest.HELP_URL,
+    helpL10n: { id: "firefox-suggest-urlbar-learn-more" },
+    isBlockable: false,
+    blockL10n: { id: "firefox-suggest-urlbar-block" },
+    displayUrl: "http://example.com/best-match-position",
+    source: "remote-settings",
+  },
+};
+
+add_task(async function init() {
+  UrlbarPrefs.set("quicksuggest.enabled", true);
+  UrlbarPrefs.set("bestMatch.enabled", true);
+  UrlbarPrefs.set("suggest.quicksuggest.nonsponsored", true);
+  UrlbarPrefs.set("suggest.quicksuggest.sponsored", true);
+  UrlbarPrefs.set("suggest.bestmatch", true);
+
+  // Disable search suggestions so we don't hit the network.
+  Services.prefs.setBoolPref("browser.search.suggest.enabled", false);
+
+  await QuickSuggestTestUtils.ensureQuickSuggestInit({
+    remoteSettingsResults: REMOTE_SETTINGS_RESULTS,
+  });
+});
+
+// Tests a best match result.
+add_task(async function bestMatch() {
+  let context = createContext("fullkeyword", {
+    providers: [UrlbarProviderQuickSuggest.name],
+    isPrivate: false,
+  });
+  await check_results({
+    context,
+    matches: [EXPECTED_BEST_MATCH_URLBAR_RESULT],
+  });
+
+  let result = context.results[0];
+
+  // The title should not include the full keyword and em dash, and the part of
+  // the title that the search string matches should be highlighted.
+  Assert.equal(result.title, "Fullkeyword title", "result.title");
+  Assert.deepEqual(
+    result.titleHighlights,
+    [[0, "fullkeyword".length]],
+    "result.titleHighlights"
+  );
+
+  Assert.equal(result.suggestedIndex, 1, "result.suggestedIndex");
+  Assert.equal(
+    !!result.isSuggestedIndexRelativeToGroup,
+    false,
+    "result.isSuggestedIndexRelativeToGroup"
+  );
+});
+
+// Tests a usual, non-best match quick suggest result.
+add_task(async function nonBestMatch() {
+  // Search for a substring of the full search string so we can test title
+  // highlights.
+  let context = createContext("fu", {
+    providers: [UrlbarProviderQuickSuggest.name],
+    isPrivate: false,
+  });
+  await check_results({
+    context,
+    matches: [EXPECTED_NON_BEST_MATCH_URLBAR_RESULT],
+  });
+
+  let result = context.results[0];
+
+  // The title should include the full keyword and em dash, and the part of the
+  // title that the search string does not match should be highlighted.
+  Assert.equal(result.title, "fullkeyword — Fullkeyword title", "result.title");
+  Assert.deepEqual(
+    result.titleHighlights,
+    [["fu".length, "fullkeyword".length - "fu".length]],
+    "result.titleHighlights"
+  );
+
+  Assert.equal(result.suggestedIndex, -1, "result.suggestedIndex");
+  Assert.equal(
+    result.isSuggestedIndexRelativeToGroup,
+    true,
+    "result.isSuggestedIndexRelativeToGroup"
+  );
+});
+
+// Tests prefix keywords leading up to a best match.
+add_task(async function prefixKeywords() {
+  let sawNonBestMatch = false;
+  let sawBestMatch = false;
+  for (let keyword of REMOTE_SETTINGS_RESULTS[0].keywords) {
+    info(`Searching for "${keyword}"`);
+    let context = createContext(keyword, {
+      providers: [UrlbarProviderQuickSuggest.name],
+      isPrivate: false,
+    });
+
+    let expectedResult;
+    if (keyword.length < 4) {
+      expectedResult = EXPECTED_NON_BEST_MATCH_URLBAR_RESULT;
+      sawNonBestMatch = true;
+    } else {
+      expectedResult = EXPECTED_BEST_MATCH_URLBAR_RESULT;
+      sawBestMatch = true;
+    }
+
+    await check_results({
+      context,
+      matches: [expectedResult],
+    });
+  }
+
+  Assert.ok(sawNonBestMatch, "Sanity check: Saw a non-best match");
+  Assert.ok(sawBestMatch, "Sanity check: Saw a best match");
+});
+
+// When tab-to-search is shown in the same search, both it and the best match
+// will have a `suggestedIndex` value of 1. The TTS should appear first.
+add_task(async function tabToSearch() {
+  // Disable tab-to-search onboarding results so we get a regular TTS result,
+  // which we can test a little more easily with `makeSearchResult()`.
+  UrlbarPrefs.set("tabToSearch.onboard.interactionsLeft", 0);
+
+  // Install a test engine. The main part of its domain name needs to match the
+  // best match result too so we can trigger both its TTS and the best match.
+  let engineURL = "https://foo.fullkeyword.com/";
+  let extension = await SearchTestUtils.installSearchExtension(
+    {
+      name: "Test",
+      search_url: engineURL,
+    },
+    { skipUnload: true }
+  );
+  let engine = Services.search.getEngineByName("Test");
+
+  // Also need to add a visit to trigger TTS.
+  await PlacesTestUtils.addVisits(engineURL);
+
+  let context = createContext("fullkeyword", {
+    isPrivate: false,
+  });
+  await check_results({
+    context,
+    matches: [
+      // search heuristic
+      makeSearchResult(context, {
+        engineName: Services.search.defaultEngine.name,
+        engineIconUri: Services.search.defaultEngine.iconURI?.spec,
+        heuristic: true,
+      }),
+      // tab to search
+      makeSearchResult(context, {
+        engineName: engine.name,
+        engineIconUri: UrlbarUtils.ICON.SEARCH_GLASS,
+        uri: UrlbarUtils.stripPublicSuffixFromHost(engine.getResultDomain()),
+        providesSearchMode: true,
+        query: "",
+        providerName: "TabToSearch",
+        satisfiesAutofillThreshold: true,
+      }),
+      // best match
+      EXPECTED_BEST_MATCH_URLBAR_RESULT,
+      // visit
+      makeVisitResult(context, {
+        uri: engineURL,
+        title: `test visit for ${engineURL}`,
+      }),
+    ],
+  });
+
+  await cleanupPlaces();
+  await extension.unload();
+
+  UrlbarPrefs.clear("tabToSearch.onboard.interactionsLeft");
+});
+
+// When the best match feature gate is disabled, quick suggest results should be
+// shown as the usual non-best match results.
+add_task(async function disabled_featureGate() {
+  UrlbarPrefs.set("bestMatch.enabled", false);
+  await doDisabledTest();
+  UrlbarPrefs.set("bestMatch.enabled", true);
+});
+
+// When the best match suggestions are disabled, quick suggest results should be
+// shown as the usual non-best match results.
+add_task(async function disabled_suggestions() {
+  UrlbarPrefs.set("suggest.bestmatch", false);
+  await doDisabledTest();
+  UrlbarPrefs.set("suggest.bestmatch", true);
+});
+
+// When best match is disabled, quick suggest results should be shown as the
+// usual, non-best match results.
+async function doDisabledTest() {
+  let context = createContext("fullkeywor", {
+    providers: [UrlbarProviderQuickSuggest.name],
+    isPrivate: false,
+  });
+  await check_results({
+    context,
+    matches: [EXPECTED_NON_BEST_MATCH_URLBAR_RESULT],
+  });
+
+  let result = context.results[0];
+
+  // The title should include the full keyword and em dash, and the part of the
+  // title that the search string does not match should be highlighted.
+  Assert.equal(result.title, "fullkeyword — Fullkeyword title", "result.title");
+  Assert.deepEqual(
+    result.titleHighlights,
+    [["fullkeywor".length, 1]],
+    "result.titleHighlights"
+  );
+
+  Assert.equal(result.suggestedIndex, -1, "result.suggestedIndex");
+  Assert.equal(
+    result.isSuggestedIndexRelativeToGroup,
+    true,
+    "result.isSuggestedIndexRelativeToGroup"
+  );
+}
+
+// `suggestion.position` should be ignored when the suggestion is a best match.
+add_task(async function position() {
+  Assert.greater(
+    BEST_MATCH_POSITION,
+    1,
+    "Precondition: `suggestion.position` > the best match index"
+  );
+
+  UrlbarPrefs.set("quicksuggest.allowPositionInSuggestions", true);
+
+  let context = createContext(BEST_MATCH_POSITION_SEARCH_STRING, {
+    isPrivate: false,
+  });
+
+  // Add some visits to fill up the view.
+  let maxResultCount = UrlbarPrefs.get("maxRichResults");
+  let visitResults = [];
+  for (let i = 0; i < maxResultCount; i++) {
+    let url = `http://example.com/${BEST_MATCH_POSITION_SEARCH_STRING}-${i}`;
+    await PlacesTestUtils.addVisits(url);
+    visitResults.unshift(
+      makeVisitResult(context, {
+        uri: url,
+        title: `test visit for ${url}`,
+      })
+    );
+  }
+
+  // Do a search.
+  await check_results({
+    context,
+    matches: [
+      // search heuristic
+      makeSearchResult(context, {
+        engineName: Services.search.defaultEngine.name,
+        engineIconUri: Services.search.defaultEngine.iconURI?.spec,
+        heuristic: true,
+      }),
+      // best match whose backing suggestion has a `position`
+      EXPECTED_BEST_MATCH_POSITION_URLBAR_RESULT,
+      // visits
+      ...visitResults.slice(0, MAX_RESULT_COUNT - 2),
+    ],
+  });
+
+  await cleanupPlaces();
+  UrlbarPrefs.clear("quicksuggest.allowPositionInSuggestions");
+});
+
+// Tests a suggestion that is blocked from being a best match.
+add_task(async function blockedAsBestMatch() {
+  let config = QuickSuggestTestUtils.DEFAULT_CONFIG;
+  config.best_match.blocked_suggestion_ids = [1];
+  await QuickSuggestTestUtils.withConfig({
+    config,
+    callback: async () => {
+      let context = createContext("fullkeyword", {
+        providers: [UrlbarProviderQuickSuggest.name],
+        isPrivate: false,
+      });
+      await check_results({
+        context,
+        matches: [EXPECTED_NON_BEST_MATCH_URLBAR_RESULT],
+      });
+    },
+  });
+});
+
+// Tests without a best_match config to make sure nothing breaks.
+add_task(async function noConfig() {
+  await QuickSuggestTestUtils.withConfig({
+    config: {},
+    callback: async () => {
+      let context = createContext("fullkeyword", {
+        providers: [UrlbarProviderQuickSuggest.name],
+        isPrivate: false,
+      });
+      await check_results({
+        context,
+        matches: [EXPECTED_NON_BEST_MATCH_URLBAR_RESULT],
+      });
+    },
+  });
+});
+
+// Test that bestMatch results are not shown when there is a heuristic
+// result for the same domain.
+add_task(async function hueristicDeduplication() {
+  let scenarios = [
+    ["http://example.com/", false],
+    ["http://www.example.com/", false],
+    ["http://exampledomain.com/", true],
+  ];
+
+  for (let [url, expectBestMatch] of scenarios) {
+    await PlacesTestUtils.addVisits(url);
+    let context = createContext("example", {
+      providers: [UrlbarProviderQuickSuggest.name, UrlbarProviderAutofill.name],
+      isPrivate: false,
+    });
+    const EXPECTED_AUTOFILL_RESULT = makeVisitResult(context, {
+      uri: url,
+      title: `test visit for ${url}`,
+      heuristic: true,
+    });
+    await check_results({
+      context,
+      matches: expectBestMatch
+        ? [EXPECTED_AUTOFILL_RESULT, EXPECTED_BEST_MATCH_URLBAR_RESULT]
+        : [EXPECTED_AUTOFILL_RESULT],
+    });
+    await PlacesUtils.history.clear();
+  }
+});
diff --git a/browser/components/urlbar/tests/quicksuggest/unit/test_quicksuggest_impressionCaps.js b/browser/components/urlbar/tests/quicksuggest/unit/test_quicksuggest_impressionCaps.js
new file mode 100644
index 0000000000..66285fa19e
--- /dev/null
+++ b/browser/components/urlbar/tests/quicksuggest/unit/test_quicksuggest_impressionCaps.js
@@ -0,0 +1,3865 @@
+/* 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/. */
+
+// Tests impression frequency capping for quick suggest results.
+
+"use strict";
+
+ChromeUtils.defineESModuleGetters(this, {
+  AsyncShutdown: "resource://gre/modules/AsyncShutdown.sys.mjs",
+  setTimeout: "resource://gre/modules/Timer.sys.mjs",
+});
+
+const REMOTE_SETTINGS_RESULTS = [
+  {
+    id: 1,
+    url: "http://example.com/sponsored",
+    title: "Sponsored suggestion",
+    keywords: ["sponsored"],
+    click_url: "http://example.com/click",
+    impression_url: "http://example.com/impression",
+    advertiser: "TestAdvertiser",
+    iab_category: "22 - Shopping",
+  },
+  {
+    id: 2,
+    url: "http://example.com/nonsponsored",
+    title: "Non-sponsored suggestion",
+    keywords: ["nonsponsored"],
+    click_url: "http://example.com/click",
+    impression_url: "http://example.com/impression",
+    advertiser: "TestAdvertiser",
+    iab_category: "5 - Education",
+  },
+];
+
+const EXPECTED_SPONSORED_URLBAR_RESULT = {
+  type: UrlbarUtils.RESULT_TYPE.URL,
+  source: UrlbarUtils.RESULT_SOURCE.SEARCH,
+  heuristic: false,
+  payload: {
+    url: "http://example.com/sponsored",
+    originalUrl: "http://example.com/sponsored",
+    displayUrl: "http://example.com/sponsored",
+    title: "Sponsored suggestion",
+    qsSuggestion: "sponsored",
+    icon: null,
+    isSponsored: true,
+    sponsoredImpressionUrl: "http://example.com/impression",
+    sponsoredClickUrl: "http://example.com/click",
+    sponsoredBlockId: 1,
+    sponsoredAdvertiser: "TestAdvertiser",
+    sponsoredIabCategory: "22 - Shopping",
+    helpUrl: QuickSuggest.HELP_URL,
+    helpL10n: { id: "firefox-suggest-urlbar-learn-more" },
+    isBlockable: false,
+    blockL10n: { id: "firefox-suggest-urlbar-block" },
+    source: "remote-settings",
+  },
+};
+
+const EXPECTED_NONSPONSORED_URLBAR_RESULT = {
+  type: UrlbarUtils.RESULT_TYPE.URL,
+  source: UrlbarUtils.RESULT_SOURCE.SEARCH,
+  heuristic: false,
+  payload: {
+    url: "http://example.com/nonsponsored",
+    originalUrl: "http://example.com/nonsponsored",
+    displayUrl: "http://example.com/nonsponsored",
+    title: "Non-sponsored suggestion",
+    qsSuggestion: "nonsponsored",
+    icon: null,
+    isSponsored: false,
+    sponsoredImpressionUrl: "http://example.com/impression",
+    sponsoredClickUrl: "http://example.com/click",
+    sponsoredBlockId: 2,
+    sponsoredAdvertiser: "TestAdvertiser",
+    sponsoredIabCategory: "5 - Education",
+    helpUrl: QuickSuggest.HELP_URL,
+    helpL10n: { id: "firefox-suggest-urlbar-learn-more" },
+    isBlockable: false,
+    blockL10n: { id: "firefox-suggest-urlbar-block" },
+    source: "remote-settings",
+  },
+};
+
+let gSandbox;
+let gDateNowStub;
+let gStartupDateMsStub;
+
+add_task(async function init() {
+  UrlbarPrefs.set("quicksuggest.enabled", true);
+  UrlbarPrefs.set("quicksuggest.impressionCaps.sponsoredEnabled", true);
+  UrlbarPrefs.set("quicksuggest.impressionCaps.nonSponsoredEnabled", true);
+  UrlbarPrefs.set("suggest.quicksuggest.nonsponsored", true);
+  UrlbarPrefs.set("suggest.quicksuggest.sponsored", true);
+  UrlbarPrefs.set("bestMatch.enabled", false);
+
+  // Disable search suggestions so we don't hit the network.
+  Services.prefs.setBoolPref("browser.search.suggest.enabled", false);
+
+  await QuickSuggestTestUtils.ensureQuickSuggestInit({
+    remoteSettingsResults: REMOTE_SETTINGS_RESULTS,
+  });
+
+  // Set up a sinon stub for the `Date.now()` implementation inside of
+  // UrlbarProviderQuickSuggest. This lets us test searches performed at
+  // specific times. See `doTimedCallbacks()` for more info.
+  gSandbox = sinon.createSandbox();
+  gDateNowStub = gSandbox.stub(
+    Cu.getGlobalForObject(UrlbarProviderQuickSuggest).Date,
+    "now"
+  );
+
+  // Set up a sinon stub for `UrlbarProviderQuickSuggest._getStartupDateMs()` to
+  // let the test override the startup date.
+  gStartupDateMsStub = gSandbox.stub(
+    QuickSuggest.impressionCaps,
+    "_getStartupDateMs"
+  );
+  gStartupDateMsStub.returns(0);
+});
+
+// Tests a single interval.
+add_task(async function oneInterval() {
+  await doTest({
+    config: {
+      impression_caps: {
+        sponsored: {
+          custom: [{ interval_s: 3, max_count: 1 }],
+        },
+      },
+    },
+    callback: async () => {
+      await doTimedSearches("sponsored", {
+        0: {
+          results: [[EXPECTED_SPONSORED_URLBAR_RESULT], []],
+          telemetry: {
+            events: [
+              {
+                object: "hit",
+                extra: {
+                  eventDate: "0",
+                  intervalSeconds: "3",
+                  maxCount: "1",
+                  startDate: "0",
+                  impressionDate: "0",
+                  count: "1",
+                  type: "sponsored",
+                  eventCount: "1",
+                },
+              },
+            ],
+          },
+        },
+        1: {
+          results: [[]],
+        },
+        2: {
+          results: [[]],
+        },
+        3: {
+          results: [[EXPECTED_SPONSORED_URLBAR_RESULT], []],
+          telemetry: {
+            events: [
+              {
+                object: "reset",
+                extra: {
+                  eventDate: "3000",
+                  intervalSeconds: "3",
+                  maxCount: "1",
+                  startDate: "0",
+                  impressionDate: "0",
+                  count: "1",
+                  type: "sponsored",
+                  eventCount: "1",
+                },
+              },
+              {
+                object: "hit",
+                extra: {
+                  eventDate: "3000",
+                  intervalSeconds: "3",
+                  maxCount: "1",
+                  startDate: "3000",
+                  impressionDate: "3000",
+                  count: "1",
+                  type: "sponsored",
+                  eventCount: "1",
+                },
+              },
+            ],
+          },
+        },
+        4: {
+          results: [[]],
+        },
+        5: {
+          results: [[]],
+        },
+      });
+    },
+  });
+});
+
+// Tests multiple intervals.
+add_task(async function multipleIntervals() {
+  await doTest({
+    config: {
+      impression_caps: {
+        sponsored: {
+          custom: [
+            { interval_s: 1, max_count: 1 },
+            { interval_s: 5, max_count: 3 },
+            { interval_s: 10, max_count: 5 },
+          ],
+        },
+      },
+    },
+    callback: async () => {
+      await doTimedSearches("sponsored", {
+        // 0s: 1 new impression; 1 impression total
+        0: {
+          results: [[EXPECTED_SPONSORED_URLBAR_RESULT], []],
+          telemetry: {
+            events: [
+              // hit: interval_s: 1, max_count: 1
+              {
+                object: "hit",
+                extra: {
+                  eventDate: "0",
+                  intervalSeconds: "1",
+                  maxCount: "1",
+                  startDate: "0",
+                  impressionDate: "0",
+                  count: "1",
+                  type: "sponsored",
+                  eventCount: "1",
+                },
+              },
+            ],
+          },
+        },
+        // 1s: 1 new impression; 2 impressions total
+        1: {
+          results: [[EXPECTED_SPONSORED_URLBAR_RESULT], []],
+          telemetry: {
+            events: [
+              // reset: interval_s: 1, max_count: 1
+              {
+                object: "reset",
+                extra: {
+                  eventDate: "1000",
+                  intervalSeconds: "1",
+                  maxCount: "1",
+                  startDate: "0",
+                  impressionDate: "0",
+                  count: "1",
+                  type: "sponsored",
+                  eventCount: "1",
+                },
+              },
+              // hit: interval_s: 1, max_count: 1
+              {
+                object: "hit",
+                extra: {
+                  eventDate: "1000",
+                  intervalSeconds: "1",
+                  maxCount: "1",
+                  startDate: "1000",
+                  impressionDate: "1000",
+                  count: "1",
+                  type: "sponsored",
+                  eventCount: "1",
+                },
+              },
+            ],
+          },
+        },
+        // 2s: 1 new impression; 3 impressions total
+        2: {
+          results: [[EXPECTED_SPONSORED_URLBAR_RESULT], []],
+          telemetry: {
+            events: [
+              // reset: interval_s: 1, max_count: 1
+              {
+                object: "reset",
+                extra: {
+                  eventDate: "2000",
+                  intervalSeconds: "1",
+                  maxCount: "1",
+                  startDate: "1000",
+                  impressionDate: "1000",
+                  count: "1",
+                  type: "sponsored",
+                  eventCount: "1",
+                },
+              },
+              // hit: interval_s: 1, max_count: 1
+              {
+                object: "hit",
+                extra: {
+                  eventDate: "2000",
+                  intervalSeconds: "1",
+                  maxCount: "1",
+                  startDate: "2000",
+                  impressionDate: "2000",
+                  count: "1",
+                  type: "sponsored",
+                  eventCount: "1",
+                },
+              },
+              // hit: interval_s: 5, max_count: 3
+              {
+                object: "hit",
+                extra: {
+                  eventDate: "2000",
+                  intervalSeconds: "5",
+                  maxCount: "3",
+                  startDate: "0",
+                  impressionDate: "2000",
+                  count: "3",
+                  type: "sponsored",
+                  eventCount: "1",
+                },
+              },
+            ],
+          },
+        },
+        // 3s: no new impressions; 3 impressions total
+        3: {
+          results: [[]],
+          telemetry: {
+            events: [
+              // reset: interval_s: 1, max_count: 1
+              {
+                object: "reset",
+                extra: {
+                  eventDate: "3000",
+                  intervalSeconds: "1",
+                  maxCount: "1",
+                  startDate: "2000",
+                  impressionDate: "2000",
+                  count: "1",
+                  type: "sponsored",
+                  eventCount: "1",
+                },
+              },
+            ],
+          },
+        },
+        // 4s: no new impressions; 3 impressions total
+        4: {
+          results: [[]],
+          telemetry: {
+            events: [
+              // reset: interval_s: 1, max_count: 1
+              {
+                object: "reset",
+                extra: {
+                  eventDate: "4000",
+                  intervalSeconds: "1",
+                  maxCount: "1",
+                  startDate: "3000",
+                  impressionDate: "2000",
+                  count: "0",
+                  type: "sponsored",
+                  eventCount: "1",
+                },
+              },
+            ],
+          },
+        },
+        // 5s: 1 new impression; 4 impressions total
+        5: {
+          results: [[EXPECTED_SPONSORED_URLBAR_RESULT], []],
+          telemetry: {
+            events: [
+              // reset: interval_s: 1, max_count: 1
+              {
+                object: "reset",
+                extra: {
+                  eventDate: "5000",
+                  intervalSeconds: "1",
+                  maxCount: "1",
+                  startDate: "4000",
+                  impressionDate: "2000",
+                  count: "0",
+                  type: "sponsored",
+                  eventCount: "1",
+                },
+              },
+              // reset: interval_s: 5, max_count: 3
+              {
+                object: "reset",
+                extra: {
+                  eventDate: "5000",
+                  intervalSeconds: "5",
+                  maxCount: "3",
+                  startDate: "0",
+                  impressionDate: "2000",
+                  count: "3",
+                  type: "sponsored",
+                  eventCount: "1",
+                },
+              },
+              // hit: interval_s: 1, max_count: 1
+              {
+                object: "hit",
+                extra: {
+                  eventDate: "5000",
+                  intervalSeconds: "1",
+                  maxCount: "1",
+                  startDate: "5000",
+                  impressionDate: "5000",
+                  count: "1",
+                  type: "sponsored",
+                  eventCount: "1",
+                },
+              },
+            ],
+          },
+        },
+        // 6s: 1 new impression; 5 impressions total
+        6: {
+          results: [[EXPECTED_SPONSORED_URLBAR_RESULT], []],
+          telemetry: {
+            events: [
+              // reset: interval_s: 1, max_count: 1
+              {
+                object: "reset",
+                extra: {
+                  eventDate: "6000",
+                  intervalSeconds: "1",
+                  maxCount: "1",
+                  startDate: "5000",
+                  impressionDate: "5000",
+                  count: "1",
+                  type: "sponsored",
+                  eventCount: "1",
+                },
+              },
+              // hit: interval_s: 1, max_count: 1
+              {
+                object: "hit",
+                extra: {
+                  eventDate: "6000",
+                  intervalSeconds: "1",
+                  maxCount: "1",
+                  startDate: "6000",
+                  impressionDate: "6000",
+                  count: "1",
+                  type: "sponsored",
+                  eventCount: "1",
+                },
+              },
+              // hit: interval_s: 10, max_count: 5
+              {
+                object: "hit",
+                extra: {
+                  eventDate: "6000",
+                  intervalSeconds: "10",
+                  maxCount: "5",
+                  startDate: "0",
+                  impressionDate: "6000",
+                  count: "5",
+                  type: "sponsored",
+                  eventCount: "1",
+                },
+              },
+            ],
+          },
+        },
+        // 7s: no new impressions; 5 impressions total
+        7: {
+          results: [[]],
+          telemetry: {
+            events: [
+              // reset: interval_s: 1, max_count: 1
+              {
+                object: "reset",
+                extra: {
+                  eventDate: "7000",
+                  intervalSeconds: "1",
+                  maxCount: "1",
+                  startDate: "6000",
+                  impressionDate: "6000",
+                  count: "1",
+                  type: "sponsored",
+                  eventCount: "1",
+                },
+              },
+            ],
+          },
+        },
+        // 8s: no new impressions; 5 impressions total
+        8: {
+          results: [[]],
+          telemetry: {
+            events: [
+              // reset: interval_s: 1, max_count: 1
+              {
+                object: "reset",
+                extra: {
+                  eventDate: "8000",
+                  intervalSeconds: "1",
+                  maxCount: "1",
+                  startDate: "7000",
+                  impressionDate: "6000",
+                  count: "0",
+                  type: "sponsored",
+                  eventCount: "1",
+                },
+              },
+            ],
+          },
+        },
+        // 9s: no new impressions; 5 impressions total
+        9: {
+          results: [[]],
+          telemetry: {
+            events: [
+              // reset: interval_s: 1, max_count: 1
+              {
+                object: "reset",
+                extra: {
+                  eventDate: "9000",
+                  intervalSeconds: "1",
+                  maxCount: "1",
+                  startDate: "8000",
+                  impressionDate: "6000",
+                  count: "0",
+                  type: "sponsored",
+                  eventCount: "1",
+                },
+              },
+            ],
+          },
+        },
+        // 10s: 1 new impression; 6 impressions total
+        10: {
+          results: [[EXPECTED_SPONSORED_URLBAR_RESULT], []],
+          telemetry: {
+            events: [
+              // reset: interval_s: 1, max_count: 1
+              {
+                object: "reset",
+                extra: {
+                  eventDate: "10000",
+                  intervalSeconds: "1",
+                  maxCount: "1",
+                  startDate: "9000",
+                  impressionDate: "6000",
+                  count: "0",
+                  type: "sponsored",
+                  eventCount: "1",
+                },
+              },
+              // reset: interval_s: 5, max_count: 3
+              {
+                object: "reset",
+                extra: {
+                  eventDate: "10000",
+                  intervalSeconds: "5",
+                  maxCount: "3",
+                  startDate: "5000",
+                  impressionDate: "6000",
+                  count: "2",
+                  type: "sponsored",
+                  eventCount: "1",
+                },
+              },
+              // reset: interval_s: 10, max_count: 5
+              {
+                object: "reset",
+                extra: {
+                  eventDate: "10000",
+                  intervalSeconds: "10",
+                  maxCount: "5",
+                  startDate: "0",
+                  impressionDate: "6000",
+                  count: "5",
+                  type: "sponsored",
+                  eventCount: "1",
+                },
+              },
+              // hit: interval_s: 1, max_count: 1
+              {
+                object: "hit",
+                extra: {
+                  eventDate: "10000",
+                  intervalSeconds: "1",
+                  maxCount: "1",
+                  startDate: "10000",
+                  impressionDate: "10000",
+                  count: "1",
+                  type: "sponsored",
+                  eventCount: "1",
+                },
+              },
+            ],
+          },
+        },
+        // 11s: 1 new impression; 7 impressions total
+        11: {
+          results: [[EXPECTED_SPONSORED_URLBAR_RESULT], []],
+          telemetry: {
+            events: [
+              // reset: interval_s: 1, max_count: 1
+              {
+                object: "reset",
+                extra: {
+                  eventDate: "11000",
+                  intervalSeconds: "1",
+                  maxCount: "1",
+                  startDate: "10000",
+                  impressionDate: "10000",
+                  count: "1",
+                  type: "sponsored",
+                  eventCount: "1",
+                },
+              },
+              // hit: interval_s: 1, max_count: 1
+              {
+                object: "hit",
+                extra: {
+                  eventDate: "11000",
+                  intervalSeconds: "1",
+                  maxCount: "1",
+                  startDate: "11000",
+                  impressionDate: "11000",
+                  count: "1",
+                  type: "sponsored",
+                  eventCount: "1",
+                },
+              },
+            ],
+          },
+        },
+        // 12s: 1 new impression; 8 impressions total
+        12: {
+          results: [[EXPECTED_SPONSORED_URLBAR_RESULT], []],
+          telemetry: {
+            events: [
+              // reset: interval_s: 1, max_count: 1
+              {
+                object: "reset",
+                extra: {
+                  eventDate: "12000",
+                  intervalSeconds: "1",
+                  maxCount: "1",
+                  startDate: "11000",
+                  impressionDate: "11000",
+                  count: "1",
+                  type: "sponsored",
+                  eventCount: "1",
+                },
+              },
+              // hit: interval_s: 1, max_count: 1
+              {
+                object: "hit",
+                extra: {
+                  eventDate: "12000",
+                  intervalSeconds: "1",
+                  maxCount: "1",
+                  startDate: "12000",
+                  impressionDate: "12000",
+                  count: "1",
+                  type: "sponsored",
+                  eventCount: "1",
+                },
+              },
+              // hit: interval_s: 5, max_count: 3
+              {
+                object: "hit",
+                extra: {
+                  eventDate: "12000",
+                  intervalSeconds: "5",
+                  maxCount: "3",
+                  startDate: "10000",
+                  impressionDate: "12000",
+                  count: "3",
+                  type: "sponsored",
+                  eventCount: "1",
+                },
+              },
+            ],
+          },
+        },
+        // 13s: no new impressions; 8 impressions total
+        13: {
+          results: [[]],
+          telemetry: {
+            events: [
+              // reset: interval_s: 1, max_count: 1
+              {
+                object: "reset",
+                extra: {
+                  eventDate: "13000",
+                  intervalSeconds: "1",
+                  maxCount: "1",
+                  startDate: "12000",
+                  impressionDate: "12000",
+                  count: "1",
+                  type: "sponsored",
+                  eventCount: "1",
+                },
+              },
+            ],
+          },
+        },
+        // 14s: no new impressions; 8 impressions total
+        14: {
+          results: [[]],
+          telemetry: {
+            events: [
+              // reset: interval_s: 1, max_count: 1
+              {
+                object: "reset",
+                extra: {
+                  eventDate: "14000",
+                  intervalSeconds: "1",
+                  maxCount: "1",
+                  startDate: "13000",
+                  impressionDate: "12000",
+                  count: "0",
+                  type: "sponsored",
+                  eventCount: "1",
+                },
+              },
+            ],
+          },
+        },
+        // 15s: 1 new impression; 9 impressions total
+        15: {
+          results: [[EXPECTED_SPONSORED_URLBAR_RESULT], []],
+          telemetry: {
+            events: [
+              // reset: interval_s: 1, max_count: 1
+              {
+                object: "reset",
+                extra: {
+                  eventDate: "15000",
+                  intervalSeconds: "1",
+                  maxCount: "1",
+                  startDate: "14000",
+                  impressionDate: "12000",
+                  count: "0",
+                  type: "sponsored",
+                  eventCount: "1",
+                },
+              },
+              // reset: interval_s: 5, max_count: 3
+              {
+                object: "reset",
+                extra: {
+                  eventDate: "15000",
+                  intervalSeconds: "5",
+                  maxCount: "3",
+                  startDate: "10000",
+                  impressionDate: "12000",
+                  count: "3",
+                  type: "sponsored",
+                  eventCount: "1",
+                },
+              },
+              // hit: interval_s: 1, max_count: 1
+              {
+                object: "hit",
+                extra: {
+                  eventDate: "15000",
+                  intervalSeconds: "1",
+                  maxCount: "1",
+                  startDate: "15000",
+                  impressionDate: "15000",
+                  count: "1",
+                  type: "sponsored",
+                  eventCount: "1",
+                },
+              },
+            ],
+          },
+        },
+        // 16s: 1 new impression; 10 impressions total
+        16: {
+          results: [[EXPECTED_SPONSORED_URLBAR_RESULT], []],
+          telemetry: {
+            events: [
+              // reset: interval_s: 1, max_count: 1
+              {
+                object: "reset",
+                extra: {
+                  eventDate: "16000",
+                  intervalSeconds: "1",
+                  maxCount: "1",
+                  startDate: "15000",
+                  impressionDate: "15000",
+                  count: "1",
+                  type: "sponsored",
+                  eventCount: "1",
+                },
+              },
+              // hit: interval_s: 1, max_count: 1
+              {
+                object: "hit",
+                extra: {
+                  eventDate: "16000",
+                  intervalSeconds: "1",
+                  maxCount: "1",
+                  startDate: "16000",
+                  impressionDate: "16000",
+                  count: "1",
+                  type: "sponsored",
+                  eventCount: "1",
+                },
+              },
+              // hit: interval_s: 10, max_count: 5
+              {
+                object: "hit",
+                extra: {
+                  eventDate: "16000",
+                  intervalSeconds: "10",
+                  maxCount: "5",
+                  startDate: "10000",
+                  impressionDate: "16000",
+                  count: "5",
+                  type: "sponsored",
+                  eventCount: "1",
+                },
+              },
+            ],
+          },
+        },
+        // 17s: no new impressions; 10 impressions total
+        17: {
+          results: [[]],
+          telemetry: {
+            events: [
+              // reset: interval_s: 1, max_count: 1
+              {
+                object: "reset",
+                extra: {
+                  eventDate: "17000",
+                  intervalSeconds: "1",
+                  maxCount: "1",
+                  startDate: "16000",
+                  impressionDate: "16000",
+                  count: "1",
+                  type: "sponsored",
+                  eventCount: "1",
+                },
+              },
+            ],
+          },
+        },
+        // 18s: no new impressions; 10 impressions total
+        18: {
+          results: [[]],
+          telemetry: {
+            events: [
+              // reset: interval_s: 1, max_count: 1
+              {
+                object: "reset",
+                extra: {
+                  eventDate: "18000",
+                  intervalSeconds: "1",
+                  maxCount: "1",
+                  startDate: "17000",
+                  impressionDate: "16000",
+                  count: "0",
+                  type: "sponsored",
+                  eventCount: "1",
+                },
+              },
+            ],
+          },
+        },
+        // 19s: no new impressions; 10 impressions total
+        19: {
+          results: [[]],
+          telemetry: {
+            events: [
+              // reset: interval_s: 1, max_count: 1
+              {
+                object: "reset",
+                extra: {
+                  eventDate: "19000",
+                  intervalSeconds: "1",
+                  maxCount: "1",
+                  startDate: "18000",
+                  impressionDate: "16000",
+                  count: "0",
+                  type: "sponsored",
+                  eventCount: "1",
+                },
+              },
+            ],
+          },
+        },
+        // 20s: 1 new impression; 11 impressions total
+        20: {
+          results: [[EXPECTED_SPONSORED_URLBAR_RESULT], []],
+          telemetry: {
+            events: [
+              // reset: interval_s: 1, max_count: 1
+              {
+                object: "reset",
+                extra: {
+                  eventDate: "20000",
+                  intervalSeconds: "1",
+                  maxCount: "1",
+                  startDate: "19000",
+                  impressionDate: "16000",
+                  count: "0",
+                  type: "sponsored",
+                  eventCount: "1",
+                },
+              },
+              // reset: interval_s: 5, max_count: 3
+              {
+                object: "reset",
+                extra: {
+                  eventDate: "20000",
+                  intervalSeconds: "5",
+                  maxCount: "3",
+                  startDate: "15000",
+                  impressionDate: "16000",
+                  count: "2",
+                  type: "sponsored",
+                  eventCount: "1",
+                },
+              },
+              // reset: interval_s: 10, max_count: 5
+              {
+                object: "reset",
+                extra: {
+                  eventDate: "20000",
+                  intervalSeconds: "10",
+                  maxCount: "5",
+                  startDate: "10000",
+                  impressionDate: "16000",
+                  count: "5",
+                  type: "sponsored",
+                  eventCount: "1",
+                },
+              },
+              // hit: interval_s: 1, max_count: 1
+              {
+                object: "hit",
+                extra: {
+                  eventDate: "20000",
+                  intervalSeconds: "1",
+                  maxCount: "1",
+                  startDate: "20000",
+                  impressionDate: "20000",
+                  count: "1",
+                  type: "sponsored",
+                  eventCount: "1",
+                },
+              },
+            ],
+          },
+        },
+      });
+    },
+  });
+});
+
+// Tests a lifetime cap.
+add_task(async function lifetime() {
+  await doTest({
+    config: {
+      impression_caps: {
+        sponsored: {
+          lifetime: 3,
+        },
+      },
+    },
+    callback: async () => {
+      await doTimedSearches("sponsored", {
+        0: {
+          results: [
+            [EXPECTED_SPONSORED_URLBAR_RESULT],
+            [EXPECTED_SPONSORED_URLBAR_RESULT],
+            [EXPECTED_SPONSORED_URLBAR_RESULT],
+            [],
+          ],
+          telemetry: {
+            events: [
+              {
+                object: "hit",
+                extra: {
+                  eventDate: "0",
+                  intervalSeconds: "Infinity",
+                  maxCount: "3",
+                  startDate: "0",
+                  impressionDate: "0",
+                  count: "3",
+                  type: "sponsored",
+                  eventCount: "1",
+                },
+              },
+            ],
+          },
+        },
+        1: {
+          results: [[]],
+        },
+      });
+    },
+  });
+});
+
+// Tests one interval and a lifetime cap together.
+add_task(async function intervalAndLifetime() {
+  await doTest({
+    config: {
+      impression_caps: {
+        sponsored: {
+          lifetime: 3,
+          custom: [{ interval_s: 1, max_count: 1 }],
+        },
+      },
+    },
+    callback: async () => {
+      await doTimedSearches("sponsored", {
+        // 0s: 1 new impression; 1 impression total
+        0: {
+          results: [[EXPECTED_SPONSORED_URLBAR_RESULT], []],
+          telemetry: {
+            events: [
+              // hit: interval_s: 1, max_count: 1
+              {
+                object: "hit",
+                extra: {
+                  eventDate: "0",
+                  intervalSeconds: "1",
+                  maxCount: "1",
+                  startDate: "0",
+                  impressionDate: "0",
+                  count: "1",
+                  type: "sponsored",
+                  eventCount: "1",
+                },
+              },
+            ],
+          },
+        },
+        // 1s: 1 new impression; 2 impressions total
+        1: {
+          results: [[EXPECTED_SPONSORED_URLBAR_RESULT], []],
+          telemetry: {
+            events: [
+              // reset: interval_s: 1, max_count: 1
+              {
+                object: "reset",
+                extra: {
+                  eventDate: "1000",
+                  intervalSeconds: "1",
+                  maxCount: "1",
+                  startDate: "0",
+                  impressionDate: "0",
+                  count: "1",
+                  type: "sponsored",
+                  eventCount: "1",
+                },
+              },
+              // hit: interval_s: 1, max_count: 1
+              {
+                object: "hit",
+                extra: {
+                  eventDate: "1000",
+                  intervalSeconds: "1",
+                  maxCount: "1",
+                  startDate: "1000",
+                  impressionDate: "1000",
+                  count: "1",
+                  type: "sponsored",
+                  eventCount: "1",
+                },
+              },
+            ],
+          },
+        },
+        // 2s: 1 new impression; 3 impressions total
+        2: {
+          results: [[EXPECTED_SPONSORED_URLBAR_RESULT], []],
+          telemetry: {
+            events: [
+              // reset: interval_s: 1, max_count: 1
+              {
+                object: "reset",
+                extra: {
+                  eventDate: "2000",
+                  intervalSeconds: "1",
+                  maxCount: "1",
+                  startDate: "1000",
+                  impressionDate: "1000",
+                  count: "1",
+                  type: "sponsored",
+                  eventCount: "1",
+                },
+              },
+              // hit: interval_s: 1, max_count: 1
+              {
+                object: "hit",
+                extra: {
+                  eventDate: "2000",
+                  intervalSeconds: "1",
+                  maxCount: "1",
+                  startDate: "2000",
+                  impressionDate: "2000",
+                  count: "1",
+                  type: "sponsored",
+                  eventCount: "1",
+                },
+              },
+              // hit: interval_s: Infinity, max_count: 3
+              {
+                object: "hit",
+                extra: {
+                  eventDate: "2000",
+                  intervalSeconds: "Infinity",
+                  maxCount: "3",
+                  startDate: "0",
+                  impressionDate: "2000",
+                  count: "3",
+                  type: "sponsored",
+                  eventCount: "1",
+                },
+              },
+            ],
+          },
+        },
+        3: {
+          results: [[]],
+          telemetry: {
+            events: [
+              // reset: interval_s: 1, max_count: 1
+              {
+                object: "reset",
+                extra: {
+                  eventDate: "3000",
+                  intervalSeconds: "1",
+                  maxCount: "1",
+                  startDate: "2000",
+                  impressionDate: "2000",
+                  count: "1",
+                  type: "sponsored",
+                  eventCount: "1",
+                },
+              },
+            ],
+          },
+        },
+      });
+    },
+  });
+});
+
+// Tests multiple intervals and a lifetime cap together.
+add_task(async function multipleIntervalsAndLifetime() {
+  await doTest({
+    config: {
+      impression_caps: {
+        sponsored: {
+          lifetime: 4,
+          custom: [
+            { interval_s: 1, max_count: 1 },
+            { interval_s: 5, max_count: 3 },
+          ],
+        },
+      },
+    },
+    callback: async () => {
+      await doTimedSearches("sponsored", {
+        // 0s: 1 new impression; 1 impression total
+        0: {
+          results: [[EXPECTED_SPONSORED_URLBAR_RESULT], []],
+          telemetry: {
+            events: [
+              // hit: interval_s: 1, max_count: 1
+              {
+                object: "hit",
+                extra: {
+                  eventDate: "0",
+                  intervalSeconds: "1",
+                  maxCount: "1",
+                  startDate: "0",
+                  impressionDate: "0",
+                  count: "1",
+                  type: "sponsored",
+                  eventCount: "1",
+                },
+              },
+            ],
+          },
+        },
+        // 1s: 1 new impression; 2 impressions total
+        1: {
+          results: [[EXPECTED_SPONSORED_URLBAR_RESULT], []],
+          telemetry: {
+            events: [
+              // reset: interval_s: 1, max_count: 1
+              {
+                object: "reset",
+                extra: {
+                  eventDate: "1000",
+                  intervalSeconds: "1",
+                  maxCount: "1",
+                  startDate: "0",
+                  impressionDate: "0",
+                  count: "1",
+                  type: "sponsored",
+                  eventCount: "1",
+                },
+              },
+              // hit: interval_s: 1, max_count: 1
+              {
+                object: "hit",
+                extra: {
+                  eventDate: "1000",
+                  intervalSeconds: "1",
+                  maxCount: "1",
+                  startDate: "1000",
+                  impressionDate: "1000",
+                  count: "1",
+                  type: "sponsored",
+                  eventCount: "1",
+                },
+              },
+            ],
+          },
+        },
+        // 2s: 1 new impression; 3 impressions total
+        2: {
+          results: [[EXPECTED_SPONSORED_URLBAR_RESULT], []],
+          telemetry: {
+            events: [
+              // reset: interval_s: 1, max_count: 1
+              {
+                object: "reset",
+                extra: {
+                  eventDate: "2000",
+                  intervalSeconds: "1",
+                  maxCount: "1",
+                  startDate: "1000",
+                  impressionDate: "1000",
+                  count: "1",
+                  type: "sponsored",
+                  eventCount: "1",
+                },
+              },
+              // hit: interval_s: 1, max_count: 1
+              {
+                object: "hit",
+                extra: {
+                  eventDate: "2000",
+                  intervalSeconds: "1",
+                  maxCount: "1",
+                  startDate: "2000",
+                  impressionDate: "2000",
+                  count: "1",
+                  type: "sponsored",
+                  eventCount: "1",
+                },
+              },
+              // hit: interval_s: 5, max_count: 3
+              {
+                object: "hit",
+                extra: {
+                  eventDate: "2000",
+                  intervalSeconds: "5",
+                  maxCount: "3",
+                  startDate: "0",
+                  impressionDate: "2000",
+                  count: "3",
+                  type: "sponsored",
+                  eventCount: "1",
+                },
+              },
+            ],
+          },
+        },
+        // 3s: no new impressions; 3 impressions total
+        3: {
+          results: [[]],
+          telemetry: {
+            events: [
+              // reset: interval_s: 1, max_count: 1
+              {
+                object: "reset",
+                extra: {
+                  eventDate: "3000",
+                  intervalSeconds: "1",
+                  maxCount: "1",
+                  startDate: "2000",
+                  impressionDate: "2000",
+                  count: "1",
+                  type: "sponsored",
+                  eventCount: "1",
+                },
+              },
+            ],
+          },
+        },
+        // 4s: no new impressions; 3 impressions total
+        4: {
+          results: [[]],
+          telemetry: {
+            events: [
+              // reset: interval_s: 1, max_count: 1
+              {
+                object: "reset",
+                extra: {
+                  eventDate: "4000",
+                  intervalSeconds: "1",
+                  maxCount: "1",
+                  startDate: "3000",
+                  impressionDate: "2000",
+                  count: "0",
+                  type: "sponsored",
+                  eventCount: "1",
+                },
+              },
+            ],
+          },
+        },
+        // 5s: 1 new impression; 4 impressions total
+        5: {
+          results: [[EXPECTED_SPONSORED_URLBAR_RESULT], []],
+          telemetry: {
+            events: [
+              // reset: interval_s: 1, max_count: 1
+              {
+                object: "reset",
+                extra: {
+                  eventDate: "5000",
+                  intervalSeconds: "1",
+                  maxCount: "1",
+                  startDate: "4000",
+                  impressionDate: "2000",
+                  count: "0",
+                  type: "sponsored",
+                  eventCount: "1",
+                },
+              },
+              // reset: interval_s: 5, max_count: 3
+              {
+                object: "reset",
+                extra: {
+                  eventDate: "5000",
+                  intervalSeconds: "5",
+                  maxCount: "3",
+                  startDate: "0",
+                  impressionDate: "2000",
+                  count: "3",
+                  type: "sponsored",
+                  eventCount: "1",
+                },
+              },
+              // hit: interval_s: 1, max_count: 1
+              {
+                object: "hit",
+                extra: {
+                  eventDate: "5000",
+                  intervalSeconds: "1",
+                  maxCount: "1",
+                  startDate: "5000",
+                  impressionDate: "5000",
+                  count: "1",
+                  type: "sponsored",
+                  eventCount: "1",
+                },
+              },
+              // hit: interval_s: Infinity, max_count: 4
+              {
+                object: "hit",
+                extra: {
+                  eventDate: "5000",
+                  intervalSeconds: "Infinity",
+                  maxCount: "4",
+                  startDate: "0",
+                  impressionDate: "5000",
+                  count: "4",
+                  type: "sponsored",
+                  eventCount: "1",
+                },
+              },
+            ],
+          },
+        },
+        // 6s: no new impressions; 4 impressions total
+        6: {
+          results: [[]],
+          telemetry: {
+            events: [
+              // reset: interval_s: 1, max_count: 1
+              {
+                object: "reset",
+                extra: {
+                  eventDate: "6000",
+                  intervalSeconds: "1",
+                  maxCount: "1",
+                  startDate: "5000",
+                  impressionDate: "5000",
+                  count: "1",
+                  type: "sponsored",
+                  eventCount: "1",
+                },
+              },
+            ],
+          },
+        },
+        // 7s: no new impressions; 4 impressions total
+        7: {
+          results: [[]],
+          telemetry: {
+            events: [
+              // reset: interval_s: 1, max_count: 1
+              {
+                object: "reset",
+                extra: {
+                  eventDate: "7000",
+                  intervalSeconds: "1",
+                  maxCount: "1",
+                  startDate: "6000",
+                  impressionDate: "5000",
+                  count: "0",
+                  type: "sponsored",
+                  eventCount: "1",
+                },
+              },
+            ],
+          },
+        },
+      });
+    },
+  });
+});
+
+// Smoke test for non-sponsored caps. Most tasks use sponsored results and caps,
+// but sponsored and non-sponsored should behave the same since they use the
+// same code paths.
+add_task(async function nonsponsored() {
+  await doTest({
+    config: {
+      impression_caps: {
+        nonsponsored: {
+          lifetime: 4,
+          custom: [
+            { interval_s: 1, max_count: 1 },
+            { interval_s: 5, max_count: 3 },
+          ],
+        },
+      },
+    },
+    callback: async () => {
+      await doTimedSearches("nonsponsored", {
+        // 0s: 1 new impression; 1 impression total
+        0: {
+          results: [[EXPECTED_NONSPONSORED_URLBAR_RESULT], []],
+          telemetry: {
+            events: [
+              // hit: interval_s: 1, max_count: 1
+              {
+                object: "hit",
+                extra: {
+                  eventDate: "0",
+                  intervalSeconds: "1",
+                  maxCount: "1",
+                  startDate: "0",
+                  impressionDate: "0",
+                  count: "1",
+                  type: "nonsponsored",
+                  eventCount: "1",
+                },
+              },
+            ],
+          },
+        },
+        // 1s: 1 new impression; 2 impressions total
+        1: {
+          results: [[EXPECTED_NONSPONSORED_URLBAR_RESULT], []],
+          telemetry: {
+            events: [
+              // reset: interval_s: 1, max_count: 1
+              {
+                object: "reset",
+                extra: {
+                  eventDate: "1000",
+                  intervalSeconds: "1",
+                  maxCount: "1",
+                  startDate: "0",
+                  impressionDate: "0",
+                  count: "1",
+                  type: "nonsponsored",
+                  eventCount: "1",
+                },
+              },
+              // hit: interval_s: 1, max_count: 1
+              {
+                object: "hit",
+                extra: {
+                  eventDate: "1000",
+                  intervalSeconds: "1",
+                  maxCount: "1",
+                  startDate: "1000",
+                  impressionDate: "1000",
+                  count: "1",
+                  type: "nonsponsored",
+                  eventCount: "1",
+                },
+              },
+            ],
+          },
+        },
+        // 2s: 1 new impression; 3 impressions total
+        2: {
+          results: [[EXPECTED_NONSPONSORED_URLBAR_RESULT], []],
+          telemetry: {
+            events: [
+              // reset: interval_s: 1, max_count: 1
+              {
+                object: "reset",
+                extra: {
+                  eventDate: "2000",
+                  intervalSeconds: "1",
+                  maxCount: "1",
+                  startDate: "1000",
+                  impressionDate: "1000",
+                  count: "1",
+                  type: "nonsponsored",
+                  eventCount: "1",
+                },
+              },
+              // hit: interval_s: 1, max_count: 1
+              {
+                object: "hit",
+                extra: {
+                  eventDate: "2000",
+                  intervalSeconds: "1",
+                  maxCount: "1",
+                  startDate: "2000",
+                  impressionDate: "2000",
+                  count: "1",
+                  type: "nonsponsored",
+                  eventCount: "1",
+                },
+              },
+              // hit: interval_s: 5, max_count: 3
+              {
+                object: "hit",
+                extra: {
+                  eventDate: "2000",
+                  intervalSeconds: "5",
+                  maxCount: "3",
+                  startDate: "0",
+                  impressionDate: "2000",
+                  count: "3",
+                  type: "nonsponsored",
+                  eventCount: "1",
+                },
+              },
+            ],
+          },
+        },
+        // 3s: no new impressions; 3 impressions total
+        3: {
+          results: [[]],
+          telemetry: {
+            events: [
+              // reset: interval_s: 1, max_count: 1
+              {
+                object: "reset",
+                extra: {
+                  eventDate: "3000",
+                  intervalSeconds: "1",
+                  maxCount: "1",
+                  startDate: "2000",
+                  impressionDate: "2000",
+                  count: "1",
+                  type: "nonsponsored",
+                  eventCount: "1",
+                },
+              },
+            ],
+          },
+        },
+        // 4s: no new impressions; 3 impressions total
+        4: {
+          results: [[]],
+          telemetry: {
+            events: [
+              // reset: interval_s: 1, max_count: 1
+              {
+                object: "reset",
+                extra: {
+                  eventDate: "4000",
+                  intervalSeconds: "1",
+                  maxCount: "1",
+                  startDate: "3000",
+                  impressionDate: "2000",
+                  count: "0",
+                  type: "nonsponsored",
+                  eventCount: "1",
+                },
+              },
+            ],
+          },
+        },
+        // 5s: 1 new impression; 4 impressions total
+        5: {
+          results: [[EXPECTED_NONSPONSORED_URLBAR_RESULT], []],
+          telemetry: {
+            events: [
+              // reset: interval_s: 1, max_count: 1
+              {
+                object: "reset",
+                extra: {
+                  eventDate: "5000",
+                  intervalSeconds: "1",
+                  maxCount: "1",
+                  startDate: "4000",
+                  impressionDate: "2000",
+                  count: "0",
+                  type: "nonsponsored",
+                  eventCount: "1",
+                },
+              },
+              // reset: interval_s: 5, max_count: 3
+              {
+                object: "reset",
+                extra: {
+                  eventDate: "5000",
+                  intervalSeconds: "5",
+                  maxCount: "3",
+                  startDate: "0",
+                  impressionDate: "2000",
+                  count: "3",
+                  type: "nonsponsored",
+                  eventCount: "1",
+                },
+              },
+              // hit: interval_s: 1, max_count: 1
+              {
+                object: "hit",
+                extra: {
+                  eventDate: "5000",
+                  intervalSeconds: "1",
+                  maxCount: "1",
+                  startDate: "5000",
+                  impressionDate: "5000",
+                  count: "1",
+                  type: "nonsponsored",
+                  eventCount: "1",
+                },
+              },
+              // hit: interval_s: Infinity, max_count: 4
+              {
+                object: "hit",
+                extra: {
+                  eventDate: "5000",
+                  intervalSeconds: "Infinity",
+                  maxCount: "4",
+                  startDate: "0",
+                  impressionDate: "5000",
+                  count: "4",
+                  type: "nonsponsored",
+                  eventCount: "1",
+                },
+              },
+            ],
+          },
+        },
+        // 6s: no new impressions; 4 impressions total
+        6: {
+          results: [[]],
+          telemetry: {
+            events: [
+              // reset: interval_s: 1, max_count: 1
+              {
+                object: "reset",
+                extra: {
+                  eventDate: "6000",
+                  intervalSeconds: "1",
+                  maxCount: "1",
+                  startDate: "5000",
+                  impressionDate: "5000",
+                  count: "1",
+                  type: "nonsponsored",
+                  eventCount: "1",
+                },
+              },
+            ],
+          },
+        },
+        // 7s: no new impressions; 4 impressions total
+        7: {
+          results: [[]],
+          telemetry: {
+            events: [
+              // reset: interval_s: 1, max_count: 1
+              {
+                object: "reset",
+                extra: {
+                  eventDate: "7000",
+                  intervalSeconds: "1",
+                  maxCount: "1",
+                  startDate: "6000",
+                  impressionDate: "5000",
+                  count: "0",
+                  type: "nonsponsored",
+                  eventCount: "1",
+                },
+              },
+            ],
+          },
+        },
+      });
+    },
+  });
+});
+
+// Smoke test for sponsored and non-sponsored caps together. Most tasks use only
+// sponsored results and caps, but sponsored and non-sponsored should behave the
+// same since they use the same code paths.
+add_task(async function sponsoredAndNonsponsored() {
+  await doTest({
+    config: {
+      impression_caps: {
+        sponsored: {
+          lifetime: 2,
+        },
+        nonsponsored: {
+          lifetime: 3,
+        },
+      },
+    },
+    callback: async () => {
+      // 1st searches
+      await checkSearch({
+        name: "sponsored 1",
+        searchString: "sponsored",
+        expectedResults: [EXPECTED_SPONSORED_URLBAR_RESULT],
+      });
+      await checkSearch({
+        name: "nonsponsored 1",
+        searchString: "nonsponsored",
+        expectedResults: [EXPECTED_NONSPONSORED_URLBAR_RESULT],
+      });
+      await checkTelemetryEvents([]);
+
+      // 2nd searches
+      await checkSearch({
+        name: "sponsored 2",
+        searchString: "sponsored",
+        expectedResults: [EXPECTED_SPONSORED_URLBAR_RESULT],
+      });
+      await checkSearch({
+        name: "nonsponsored 2",
+        searchString: "nonsponsored",
+        expectedResults: [EXPECTED_NONSPONSORED_URLBAR_RESULT],
+      });
+      await checkTelemetryEvents([
+        {
+          object: "hit",
+          extra: {
+            eventDate: "0",
+            intervalSeconds: "Infinity",
+            maxCount: "2",
+            startDate: "0",
+            impressionDate: "0",
+            count: "2",
+            type: "sponsored",
+            eventCount: "1",
+          },
+        },
+      ]);
+
+      // 3rd searches
+      await checkSearch({
+        name: "sponsored 3",
+        searchString: "sponsored",
+        expectedResults: [],
+      });
+      await checkSearch({
+        name: "nonsponsored 3",
+        searchString: "nonsponsored",
+        expectedResults: [EXPECTED_NONSPONSORED_URLBAR_RESULT],
+      });
+      await checkTelemetryEvents([
+        {
+          object: "hit",
+          extra: {
+            eventDate: "0",
+            intervalSeconds: "Infinity",
+            maxCount: "3",
+            startDate: "0",
+            impressionDate: "0",
+            count: "3",
+            type: "nonsponsored",
+            eventCount: "1",
+          },
+        },
+      ]);
+
+      // 4th searches
+      await checkSearch({
+        name: "sponsored 4",
+        searchString: "sponsored",
+        expectedResults: [],
+      });
+      await checkSearch({
+        name: "nonsponsored 4",
+        searchString: "nonsponsored",
+        expectedResults: [],
+      });
+      await checkTelemetryEvents([]);
+    },
+  });
+});
+
+// Tests with an empty config to make sure results are not capped.
+add_task(async function emptyConfig() {
+  await doTest({
+    config: {},
+    callback: async () => {
+      for (let i = 0; i < 2; i++) {
+        await checkSearch({
+          name: "sponsored " + i,
+          searchString: "sponsored",
+          expectedResults: [EXPECTED_SPONSORED_URLBAR_RESULT],
+        });
+        await checkSearch({
+          name: "nonsponsored " + i,
+          searchString: "nonsponsored",
+          expectedResults: [EXPECTED_NONSPONSORED_URLBAR_RESULT],
+        });
+      }
+      await checkTelemetryEvents([]);
+    },
+  });
+});
+
+// Tests with sponsored caps disabled. Non-sponsored should still be capped.
+add_task(async function sponsoredCapsDisabled() {
+  UrlbarPrefs.set("quicksuggest.impressionCaps.sponsoredEnabled", false);
+  await doTest({
+    config: {
+      impression_caps: {
+        sponsored: {
+          lifetime: 0,
+        },
+        nonsponsored: {
+          lifetime: 3,
+        },
+      },
+    },
+    callback: async () => {
+      for (let i = 0; i < 3; i++) {
+        await checkSearch({
+          name: "sponsored " + i,
+          searchString: "sponsored",
+          expectedResults: [EXPECTED_SPONSORED_URLBAR_RESULT],
+        });
+        await checkSearch({
+          name: "nonsponsored " + i,
+          searchString: "nonsponsored",
+          expectedResults: [EXPECTED_NONSPONSORED_URLBAR_RESULT],
+        });
+      }
+      await checkTelemetryEvents([
+        {
+          object: "hit",
+          extra: {
+            eventDate: "0",
+            intervalSeconds: "Infinity",
+            maxCount: "3",
+            startDate: "0",
+            impressionDate: "0",
+            count: "3",
+            type: "nonsponsored",
+            eventCount: "1",
+          },
+        },
+      ]);
+
+      await checkSearch({
+        name: "sponsored additional",
+        searchString: "sponsored",
+        expectedResults: [EXPECTED_SPONSORED_URLBAR_RESULT],
+      });
+      await checkSearch({
+        name: "nonsponsored additional",
+        searchString: "nonsponsored",
+        expectedResults: [],
+      });
+      await checkTelemetryEvents([]);
+    },
+  });
+  UrlbarPrefs.set("quicksuggest.impressionCaps.sponsoredEnabled", true);
+});
+
+// Tests with non-sponsored caps disabled. Sponsored should still be capped.
+add_task(async function nonsponsoredCapsDisabled() {
+  UrlbarPrefs.set("quicksuggest.impressionCaps.nonSponsoredEnabled", false);
+  await doTest({
+    config: {
+      impression_caps: {
+        sponsored: {
+          lifetime: 3,
+        },
+        nonsponsored: {
+          lifetime: 0,
+        },
+      },
+    },
+    callback: async () => {
+      for (let i = 0; i < 3; i++) {
+        await checkSearch({
+          name: "sponsored " + i,
+          searchString: "sponsored",
+          expectedResults: [EXPECTED_SPONSORED_URLBAR_RESULT],
+        });
+        await checkSearch({
+          name: "nonsponsored " + i,
+          searchString: "nonsponsored",
+          expectedResults: [EXPECTED_NONSPONSORED_URLBAR_RESULT],
+        });
+      }
+      await checkTelemetryEvents([
+        {
+          object: "hit",
+          extra: {
+            eventDate: "0",
+            intervalSeconds: "Infinity",
+            maxCount: "3",
+            startDate: "0",
+            impressionDate: "0",
+            count: "3",
+            type: "sponsored",
+            eventCount: "1",
+          },
+        },
+      ]);
+
+      await checkSearch({
+        name: "sponsored additional",
+        searchString: "sponsored",
+        expectedResults: [],
+      });
+      await checkSearch({
+        name: "nonsponsored additional",
+        searchString: "nonsponsored",
+        expectedResults: [EXPECTED_NONSPONSORED_URLBAR_RESULT],
+      });
+      await checkTelemetryEvents([]);
+    },
+  });
+  UrlbarPrefs.set("quicksuggest.impressionCaps.nonSponsoredEnabled", true);
+});
+
+// Tests a config change: 1 interval -> same interval with lower cap, with the
+// old cap already reached
+add_task(async function configChange_sameIntervalLowerCap_1() {
+  await doTest({
+    config: {
+      impression_caps: {
+        sponsored: {
+          custom: [{ interval_s: 3, max_count: 3 }],
+        },
+      },
+    },
+    callback: async () => {
+      await doTimedCallbacks({
+        0: async () => {
+          for (let i = 0; i < 3; i++) {
+            await checkSearch({
+              name: "0s " + i,
+              searchString: "sponsored",
+              expectedResults: [EXPECTED_SPONSORED_URLBAR_RESULT],
+            });
+          }
+          await checkSearch({
+            name: "0s additional",
+            searchString: "sponsored",
+            expectedResults: [],
+          });
+          await checkTelemetryEvents([
+            {
+              object: "hit",
+              extra: {
+                eventDate: "0",
+                intervalSeconds: "3",
+                maxCount: "3",
+                startDate: "0",
+                impressionDate: "0",
+                count: "3",
+                type: "sponsored",
+                eventCount: "1",
+              },
+            },
+          ]);
+          QuickSuggestTestUtils.setConfig({
+            impression_caps: {
+              sponsored: {
+                custom: [{ interval_s: 3, max_count: 1 }],
+              },
+            },
+          });
+        },
+        1: async () => {
+          await checkSearch({
+            name: "1s",
+            searchString: "sponsored",
+            expectedResults: [],
+          });
+          await checkTelemetryEvents([]);
+        },
+        3: async () => {
+          await checkSearch({
+            name: "3s 0",
+            searchString: "sponsored",
+            expectedResults: [EXPECTED_SPONSORED_URLBAR_RESULT],
+          });
+          await checkSearch({
+            name: "3s additional",
+            searchString: "sponsored",
+            expectedResults: [],
+          });
+          await checkTelemetryEvents([
+            {
+              object: "reset",
+              extra: {
+                eventDate: "3000",
+                intervalSeconds: "3",
+                maxCount: "1",
+                startDate: "0",
+                impressionDate: "0",
+                count: "3",
+                type: "sponsored",
+                eventCount: "1",
+              },
+            },
+            {
+              object: "hit",
+              extra: {
+                eventDate: "3000",
+                intervalSeconds: "3",
+                maxCount: "1",
+                startDate: "3000",
+                impressionDate: "3000",
+                count: "1",
+                type: "sponsored",
+                eventCount: "1",
+              },
+            },
+          ]);
+        },
+      });
+    },
+  });
+});
+
+// Tests a config change: 1 interval -> same interval with lower cap, with the
+// old cap not reached
+add_task(async function configChange_sameIntervalLowerCap_2() {
+  await doTest({
+    config: {
+      impression_caps: {
+        sponsored: {
+          custom: [{ interval_s: 3, max_count: 3 }],
+        },
+      },
+    },
+    callback: async () => {
+      await doTimedCallbacks({
+        0: async () => {
+          for (let i = 0; i < 2; i++) {
+            await checkSearch({
+              name: "0s " + i,
+              searchString: "sponsored",
+              expectedResults: [EXPECTED_SPONSORED_URLBAR_RESULT],
+            });
+          }
+          await checkTelemetryEvents([]);
+          QuickSuggestTestUtils.setConfig({
+            impression_caps: {
+              sponsored: {
+                custom: [{ interval_s: 3, max_count: 1 }],
+              },
+            },
+          });
+        },
+        1: async () => {
+          await checkSearch({
+            name: "1s",
+            searchString: "sponsored",
+            expectedResults: [],
+          });
+        },
+        3: async () => {
+          await checkSearch({
+            name: "3s 0",
+            searchString: "sponsored",
+            expectedResults: [EXPECTED_SPONSORED_URLBAR_RESULT],
+          });
+          await checkSearch({
+            name: "3s additional",
+            searchString: "sponsored",
+            expectedResults: [],
+          });
+          await checkTelemetryEvents([
+            {
+              object: "reset",
+              extra: {
+                eventDate: "3000",
+                intervalSeconds: "3",
+                maxCount: "1",
+                startDate: "0",
+                impressionDate: "0",
+                count: "2",
+                type: "sponsored",
+                eventCount: "1",
+              },
+            },
+            {
+              object: "hit",
+              extra: {
+                eventDate: "3000",
+                intervalSeconds: "3",
+                maxCount: "1",
+                startDate: "3000",
+                impressionDate: "3000",
+                count: "1",
+                type: "sponsored",
+                eventCount: "1",
+              },
+            },
+          ]);
+        },
+      });
+    },
+  });
+});
+
+// Tests a config change: 1 interval -> same interval with higher cap
+add_task(async function configChange_sameIntervalHigherCap() {
+  await doTest({
+    config: {
+      impression_caps: {
+        sponsored: {
+          custom: [{ interval_s: 3, max_count: 3 }],
+        },
+      },
+    },
+    callback: async () => {
+      await doTimedCallbacks({
+        0: async () => {
+          for (let i = 0; i < 3; i++) {
+            await checkSearch({
+              name: "0s " + i,
+              searchString: "sponsored",
+              expectedResults: [EXPECTED_SPONSORED_URLBAR_RESULT],
+            });
+          }
+          await checkSearch({
+            name: "0s additional",
+            searchString: "sponsored",
+            expectedResults: [],
+          });
+          await checkTelemetryEvents([
+            {
+              object: "hit",
+              extra: {
+                eventDate: "0",
+                intervalSeconds: "3",
+                maxCount: "3",
+                startDate: "0",
+                impressionDate: "0",
+                count: "3",
+                type: "sponsored",
+                eventCount: "1",
+              },
+            },
+          ]);
+          QuickSuggestTestUtils.setConfig({
+            impression_caps: {
+              sponsored: {
+                custom: [{ interval_s: 3, max_count: 5 }],
+              },
+            },
+          });
+        },
+        1: async () => {
+          for (let i = 0; i < 2; i++) {
+            await checkSearch({
+              name: "1s " + i,
+              searchString: "sponsored",
+              expectedResults: [EXPECTED_SPONSORED_URLBAR_RESULT],
+            });
+          }
+          await checkSearch({
+            name: "1s additional",
+            searchString: "sponsored",
+            expectedResults: [],
+          });
+          await checkTelemetryEvents([
+            {
+              object: "hit",
+              extra: {
+                eventDate: "1000",
+                intervalSeconds: "3",
+                maxCount: "5",
+                startDate: "0",
+                impressionDate: "1000",
+                count: "5",
+                type: "sponsored",
+                eventCount: "1",
+              },
+            },
+          ]);
+        },
+        3: async () => {
+          for (let i = 0; i < 5; i++) {
+            await checkSearch({
+              name: "3s " + i,
+              searchString: "sponsored",
+              expectedResults: [EXPECTED_SPONSORED_URLBAR_RESULT],
+            });
+          }
+          await checkSearch({
+            name: "3s additional",
+            searchString: "sponsored",
+            expectedResults: [],
+          });
+          await checkTelemetryEvents([
+            {
+              object: "reset",
+              extra: {
+                eventDate: "3000",
+                intervalSeconds: "3",
+                maxCount: "5",
+                startDate: "0",
+                impressionDate: "1000",
+                count: "5",
+                type: "sponsored",
+                eventCount: "1",
+              },
+            },
+            {
+              object: "hit",
+              extra: {
+                eventDate: "3000",
+                intervalSeconds: "3",
+                maxCount: "5",
+                startDate: "3000",
+                impressionDate: "3000",
+                count: "5",
+                type: "sponsored",
+                eventCount: "1",
+              },
+            },
+          ]);
+        },
+      });
+    },
+  });
+});
+
+// Tests a config change: 1 interval -> 2 new intervals with higher timeouts.
+// Impression counts for the old interval should contribute to the new
+// intervals.
+add_task(async function configChange_1IntervalTo2NewIntervalsHigher() {
+  await doTest({
+    config: {
+      impression_caps: {
+        sponsored: {
+          custom: [{ interval_s: 3, max_count: 3 }],
+        },
+      },
+    },
+    callback: async () => {
+      await doTimedCallbacks({
+        0: async () => {
+          for (let i = 0; i < 3; i++) {
+            await checkSearch({
+              name: "0s " + i,
+              searchString: "sponsored",
+              expectedResults: [EXPECTED_SPONSORED_URLBAR_RESULT],
+            });
+          }
+          await checkTelemetryEvents([
+            {
+              object: "hit",
+              extra: {
+                eventDate: "0",
+                intervalSeconds: "3",
+                maxCount: "3",
+                startDate: "0",
+                impressionDate: "0",
+                count: "3",
+                type: "sponsored",
+                eventCount: "1",
+              },
+            },
+          ]);
+          QuickSuggestTestUtils.setConfig({
+            impression_caps: {
+              sponsored: {
+                custom: [
+                  { interval_s: 5, max_count: 3 },
+                  { interval_s: 10, max_count: 5 },
+                ],
+              },
+            },
+          });
+        },
+        3: async () => {
+          await checkSearch({
+            name: "3s",
+            searchString: "sponsored",
+            expectedResults: [],
+          });
+          await checkTelemetryEvents([]);
+        },
+        4: async () => {
+          await checkSearch({
+            name: "4s",
+            searchString: "sponsored",
+            expectedResults: [],
+          });
+          await checkTelemetryEvents([]);
+        },
+        5: async () => {
+          for (let i = 0; i < 2; i++) {
+            await checkSearch({
+              name: "5s " + i,
+              searchString: "sponsored",
+              expectedResults: [EXPECTED_SPONSORED_URLBAR_RESULT],
+            });
+          }
+          await checkSearch({
+            name: "5s additional",
+            searchString: "sponsored",
+            expectedResults: [],
+          });
+          await checkTelemetryEvents([
+            {
+              object: "reset",
+              extra: {
+                eventDate: "5000",
+                intervalSeconds: "5",
+                maxCount: "3",
+                startDate: "0",
+                impressionDate: "0",
+                count: "3",
+                type: "sponsored",
+                eventCount: "1",
+              },
+            },
+            {
+              object: "hit",
+              extra: {
+                eventDate: "5000",
+                intervalSeconds: "10",
+                maxCount: "5",
+                startDate: "0",
+                impressionDate: "5000",
+                count: "5",
+                type: "sponsored",
+                eventCount: "1",
+              },
+            },
+          ]);
+        },
+      });
+    },
+  });
+});
+
+// Tests a config change: 2 intervals -> 1 new interval with higher timeout.
+// Impression counts for the old intervals should contribute to the new
+// interval.
+add_task(async function configChange_2IntervalsTo1NewIntervalHigher() {
+  await doTest({
+    config: {
+      impression_caps: {
+        sponsored: {
+          custom: [
+            { interval_s: 2, max_count: 2 },
+            { interval_s: 4, max_count: 4 },
+          ],
+        },
+      },
+    },
+    callback: async () => {
+      await doTimedCallbacks({
+        0: async () => {
+          for (let i = 0; i < 2; i++) {
+            await checkSearch({
+              name: "0s " + i,
+              searchString: "sponsored",
+              expectedResults: [EXPECTED_SPONSORED_URLBAR_RESULT],
+            });
+          }
+          await checkTelemetryEvents([
+            {
+              object: "hit",
+              extra: {
+                eventDate: "0",
+                intervalSeconds: "2",
+                maxCount: "2",
+                startDate: "0",
+                impressionDate: "0",
+                count: "2",
+                type: "sponsored",
+                eventCount: "1",
+              },
+            },
+          ]);
+        },
+        2: async () => {
+          for (let i = 0; i < 2; i++) {
+            await checkSearch({
+              name: "2s " + i,
+              searchString: "sponsored",
+              expectedResults: [EXPECTED_SPONSORED_URLBAR_RESULT],
+            });
+          }
+          await checkTelemetryEvents([
+            {
+              object: "reset",
+              extra: {
+                eventDate: "2000",
+                intervalSeconds: "2",
+                maxCount: "2",
+                startDate: "0",
+                impressionDate: "0",
+                count: "2",
+                type: "sponsored",
+                eventCount: "1",
+              },
+            },
+            {
+              object: "hit",
+              extra: {
+                eventDate: "2000",
+                intervalSeconds: "2",
+                maxCount: "2",
+                startDate: "2000",
+                impressionDate: "2000",
+                count: "2",
+                type: "sponsored",
+                eventCount: "1",
+              },
+            },
+            {
+              object: "hit",
+              extra: {
+                eventDate: "2000",
+                intervalSeconds: "4",
+                maxCount: "4",
+                startDate: "0",
+                impressionDate: "2000",
+                count: "4",
+                type: "sponsored",
+                eventCount: "1",
+              },
+            },
+          ]);
+          QuickSuggestTestUtils.setConfig({
+            impression_caps: {
+              sponsored: {
+                custom: [{ interval_s: 6, max_count: 5 }],
+              },
+            },
+          });
+        },
+        4: async () => {
+          await checkSearch({
+            name: "4s 0",
+            searchString: "sponsored",
+            expectedResults: [EXPECTED_SPONSORED_URLBAR_RESULT],
+          });
+          await checkSearch({
+            name: "4s 1",
+            searchString: "sponsored",
+            expectedResults: [],
+          });
+          await checkTelemetryEvents([
+            {
+              object: "hit",
+              extra: {
+                eventDate: "4000",
+                intervalSeconds: "6",
+                maxCount: "5",
+                startDate: "0",
+                impressionDate: "4000",
+                count: "5",
+                type: "sponsored",
+                eventCount: "1",
+              },
+            },
+          ]);
+        },
+        5: async () => {
+          await checkSearch({
+            name: "5s",
+            searchString: "sponsored",
+            expectedResults: [],
+          });
+          await checkTelemetryEvents([]);
+        },
+        6: async () => {
+          for (let i = 0; i < 5; i++) {
+            await checkSearch({
+              name: "6s " + i,
+              searchString: "sponsored",
+              expectedResults: [EXPECTED_SPONSORED_URLBAR_RESULT],
+            });
+          }
+          await checkSearch({
+            name: "6s additional",
+            searchString: "sponsored",
+            expectedResults: [],
+          });
+          await checkTelemetryEvents([
+            {
+              object: "reset",
+              extra: {
+                eventDate: "6000",
+                intervalSeconds: "6",
+                maxCount: "5",
+                startDate: "0",
+                impressionDate: "4000",
+                count: "5",
+                type: "sponsored",
+                eventCount: "1",
+              },
+            },
+            {
+              object: "hit",
+              extra: {
+                eventDate: "6000",
+                intervalSeconds: "6",
+                maxCount: "5",
+                startDate: "6000",
+                impressionDate: "6000",
+                count: "5",
+                type: "sponsored",
+                eventCount: "1",
+              },
+            },
+          ]);
+        },
+      });
+    },
+  });
+});
+
+// Tests a config change: 1 interval -> 1 new interval with lower timeout.
+// Impression counts for the old interval should not contribute to the new
+// interval since the new interval has a lower timeout.
+add_task(async function configChange_1IntervalTo1NewIntervalLower() {
+  await doTest({
+    config: {
+      impression_caps: {
+        sponsored: {
+          custom: [{ interval_s: 5, max_count: 3 }],
+        },
+      },
+    },
+    callback: async () => {
+      await doTimedCallbacks({
+        0: async () => {
+          for (let i = 0; i < 3; i++) {
+            await checkSearch({
+              name: "0s " + i,
+              searchString: "sponsored",
+              expectedResults: [EXPECTED_SPONSORED_URLBAR_RESULT],
+            });
+          }
+          await checkTelemetryEvents([
+            {
+              object: "hit",
+              extra: {
+                eventDate: "0",
+                intervalSeconds: "5",
+                maxCount: "3",
+                startDate: "0",
+                impressionDate: "0",
+                count: "3",
+                type: "sponsored",
+                eventCount: "1",
+              },
+            },
+          ]);
+          QuickSuggestTestUtils.setConfig({
+            impression_caps: {
+              sponsored: {
+                custom: [{ interval_s: 3, max_count: 3 }],
+              },
+            },
+          });
+        },
+        1: async () => {
+          for (let i = 0; i < 3; i++) {
+            await checkSearch({
+              name: "3s " + i,
+              searchString: "sponsored",
+              expectedResults: [EXPECTED_SPONSORED_URLBAR_RESULT],
+            });
+          }
+          await checkSearch({
+            name: "3s additional",
+            searchString: "sponsored",
+            expectedResults: [],
+          });
+          await checkTelemetryEvents([
+            {
+              object: "hit",
+              extra: {
+                eventDate: "1000",
+                intervalSeconds: "3",
+                maxCount: "3",
+                startDate: "0",
+                impressionDate: "1000",
+                count: "3",
+                type: "sponsored",
+                eventCount: "1",
+              },
+            },
+          ]);
+        },
+      });
+    },
+  });
+});
+
+// Tests a config change: 1 interval -> lifetime.
+// Impression counts for the old interval should contribute to the new lifetime
+// cap.
+add_task(async function configChange_1IntervalToLifetime() {
+  await doTest({
+    config: {
+      impression_caps: {
+        sponsored: {
+          custom: [{ interval_s: 3, max_count: 3 }],
+        },
+      },
+    },
+    callback: async () => {
+      await doTimedCallbacks({
+        0: async () => {
+          for (let i = 0; i < 3; i++) {
+            await checkSearch({
+              name: "0s " + i,
+              searchString: "sponsored",
+              expectedResults: [EXPECTED_SPONSORED_URLBAR_RESULT],
+            });
+          }
+          await checkTelemetryEvents([
+            {
+              object: "hit",
+              extra: {
+                eventDate: "0",
+                intervalSeconds: "3",
+                maxCount: "3",
+                startDate: "0",
+                impressionDate: "0",
+                count: "3",
+                type: "sponsored",
+                eventCount: "1",
+              },
+            },
+          ]);
+          QuickSuggestTestUtils.setConfig({
+            impression_caps: {
+              sponsored: {
+                lifetime: 3,
+              },
+            },
+          });
+        },
+        3: async () => {
+          await checkSearch({
+            name: "3s",
+            searchString: "sponsored",
+            expectedResults: [],
+          });
+          await checkTelemetryEvents([]);
+        },
+      });
+    },
+  });
+});
+
+// Tests a config change: lifetime cap -> higher lifetime cap
+add_task(async function configChange_lifetimeCapHigher() {
+  await doTest({
+    config: {
+      impression_caps: {
+        sponsored: {
+          lifetime: 3,
+        },
+      },
+    },
+    callback: async () => {
+      await doTimedCallbacks({
+        0: async () => {
+          for (let i = 0; i < 3; i++) {
+            await checkSearch({
+              name: "0s " + i,
+              searchString: "sponsored",
+              expectedResults: [EXPECTED_SPONSORED_URLBAR_RESULT],
+            });
+          }
+          await checkSearch({
+            name: "0s additional",
+            searchString: "sponsored",
+            expectedResults: [],
+          });
+          await checkTelemetryEvents([
+            {
+              object: "hit",
+              extra: {
+                eventDate: "0",
+                intervalSeconds: "Infinity",
+                maxCount: "3",
+                startDate: "0",
+                impressionDate: "0",
+                count: "3",
+                type: "sponsored",
+                eventCount: "1",
+              },
+            },
+          ]);
+          QuickSuggestTestUtils.setConfig({
+            impression_caps: {
+              sponsored: {
+                lifetime: 5,
+              },
+            },
+          });
+        },
+        1: async () => {
+          for (let i = 0; i < 2; i++) {
+            await checkSearch({
+              name: "1s " + i,
+              searchString: "sponsored",
+              expectedResults: [EXPECTED_SPONSORED_URLBAR_RESULT],
+            });
+          }
+          await checkSearch({
+            name: "1s additional",
+            searchString: "sponsored",
+            expectedResults: [],
+          });
+          await checkTelemetryEvents([
+            {
+              object: "hit",
+              extra: {
+                eventDate: "1000",
+                intervalSeconds: "Infinity",
+                maxCount: "5",
+                startDate: "0",
+                impressionDate: "1000",
+                count: "5",
+                type: "sponsored",
+                eventCount: "1",
+              },
+            },
+          ]);
+        },
+      });
+    },
+  });
+});
+
+// Tests a config change: lifetime cap -> lower lifetime cap
+add_task(async function configChange_lifetimeCapLower() {
+  await doTest({
+    config: {
+      impression_caps: {
+        sponsored: {
+          lifetime: 3,
+        },
+      },
+    },
+    callback: async () => {
+      await doTimedCallbacks({
+        0: async () => {
+          for (let i = 0; i < 3; i++) {
+            await checkSearch({
+              name: "0s " + i,
+              searchString: "sponsored",
+              expectedResults: [EXPECTED_SPONSORED_URLBAR_RESULT],
+            });
+          }
+          await checkSearch({
+            name: "0s additional",
+            searchString: "sponsored",
+            expectedResults: [],
+          });
+          await checkTelemetryEvents([
+            {
+              object: "hit",
+              extra: {
+                eventDate: "0",
+                intervalSeconds: "Infinity",
+                maxCount: "3",
+                startDate: "0",
+                impressionDate: "0",
+                count: "3",
+                type: "sponsored",
+                eventCount: "1",
+              },
+            },
+          ]);
+          QuickSuggestTestUtils.setConfig({
+            impression_caps: {
+              sponsored: {
+                lifetime: 1,
+              },
+            },
+          });
+        },
+        1: async () => {
+          await checkSearch({
+            name: "1s",
+            searchString: "sponsored",
+            expectedResults: [],
+          });
+          await checkTelemetryEvents([]);
+        },
+      });
+    },
+  });
+});
+
+// Makes sure stats are serialized to and from the pref correctly.
+add_task(async function prefSync() {
+  await doTest({
+    config: {
+      impression_caps: {
+        sponsored: {
+          lifetime: 5,
+          custom: [
+            { interval_s: 3, max_count: 2 },
+            { interval_s: 5, max_count: 4 },
+          ],
+        },
+      },
+    },
+    callback: async () => {
+      for (let i = 0; i < 2; i++) {
+        await checkSearch({
+          name: i,
+          searchString: "sponsored",
+          expectedResults: [EXPECTED_SPONSORED_URLBAR_RESULT],
+        });
+      }
+
+      let json = UrlbarPrefs.get("quicksuggest.impressionCaps.stats");
+      Assert.ok(json, "JSON is non-empty");
+      Assert.deepEqual(
+        JSON.parse(json),
+        {
+          sponsored: [
+            {
+              intervalSeconds: 3,
+              count: 2,
+              maxCount: 2,
+              startDateMs: 0,
+              impressionDateMs: 0,
+            },
+            {
+              intervalSeconds: 5,
+              count: 2,
+              maxCount: 4,
+              startDateMs: 0,
+              impressionDateMs: 0,
+            },
+            {
+              intervalSeconds: null,
+              count: 2,
+              maxCount: 5,
+              startDateMs: 0,
+              impressionDateMs: 0,
+            },
+          ],
+        },
+        "JSON is correct"
+      );
+
+      QuickSuggest.impressionCaps._test_reloadStats();
+      Assert.deepEqual(
+        QuickSuggest.impressionCaps._test_stats,
+        {
+          sponsored: [
+            {
+              intervalSeconds: 3,
+              count: 2,
+              maxCount: 2,
+              startDateMs: 0,
+              impressionDateMs: 0,
+            },
+            {
+              intervalSeconds: 5,
+              count: 2,
+              maxCount: 4,
+              startDateMs: 0,
+              impressionDateMs: 0,
+            },
+            {
+              intervalSeconds: Infinity,
+              count: 2,
+              maxCount: 5,
+              startDateMs: 0,
+              impressionDateMs: 0,
+            },
+          ],
+        },
+        "Impression stats were properly restored from the pref"
+      );
+    },
+  });
+});
+
+// Tests direct changes to the stats pref.
+add_task(async function prefDirectlyChanged() {
+  await doTest({
+    config: {
+      impression_caps: {
+        sponsored: {
+          lifetime: 5,
+          custom: [{ interval_s: 3, max_count: 3 }],
+        },
+      },
+    },
+    callback: async () => {
+      let expectedStats = {
+        sponsored: [
+          {
+            intervalSeconds: 3,
+            count: 0,
+            maxCount: 3,
+            startDateMs: 0,
+            impressionDateMs: 0,
+          },
+          {
+            intervalSeconds: Infinity,
+            count: 0,
+            maxCount: 5,
+            startDateMs: 0,
+            impressionDateMs: 0,
+          },
+        ],
+      };
+
+      UrlbarPrefs.set("quicksuggest.impressionCaps.stats", "bogus");
+      Assert.deepEqual(
+        QuickSuggest.impressionCaps._test_stats,
+        expectedStats,
+        "Expected stats for 'bogus'"
+      );
+
+      UrlbarPrefs.set("quicksuggest.impressionCaps.stats", JSON.stringify({}));
+      Assert.deepEqual(
+        QuickSuggest.impressionCaps._test_stats,
+        expectedStats,
+        "Expected stats for {}"
+      );
+
+      UrlbarPrefs.set(
+        "quicksuggest.impressionCaps.stats",
+        JSON.stringify({ sponsored: "bogus" })
+      );
+      Assert.deepEqual(
+        QuickSuggest.impressionCaps._test_stats,
+        expectedStats,
+        "Expected stats for { sponsored: 'bogus' }"
+      );
+
+      UrlbarPrefs.set(
+        "quicksuggest.impressionCaps.stats",
+        JSON.stringify({
+          sponsored: [
+            {
+              intervalSeconds: 3,
+              count: 0,
+              maxCount: 3,
+              startDateMs: 0,
+              impressionDateMs: 0,
+            },
+            {
+              intervalSeconds: "bogus",
+              count: 0,
+              maxCount: 99,
+              startDateMs: 0,
+              impressionDateMs: 0,
+            },
+            {
+              intervalSeconds: Infinity,
+              count: 0,
+              maxCount: 5,
+              startDateMs: 0,
+              impressionDateMs: 0,
+            },
+          ],
+        })
+      );
+      Assert.deepEqual(
+        QuickSuggest.impressionCaps._test_stats,
+        expectedStats,
+        "Expected stats with intervalSeconds: 'bogus'"
+      );
+
+      UrlbarPrefs.set(
+        "quicksuggest.impressionCaps.stats",
+        JSON.stringify({
+          sponsored: [
+            {
+              intervalSeconds: 3,
+              count: 0,
+              maxCount: 123,
+              startDateMs: 0,
+              impressionDateMs: 0,
+            },
+            {
+              intervalSeconds: Infinity,
+              count: 0,
+              maxCount: 456,
+              startDateMs: 0,
+              impressionDateMs: 0,
+            },
+          ],
+        })
+      );
+      Assert.deepEqual(
+        QuickSuggest.impressionCaps._test_stats,
+        expectedStats,
+        "Expected stats with `maxCount` values different from caps"
+      );
+
+      let stats = {
+        sponsored: [
+          {
+            intervalSeconds: 3,
+            count: 1,
+            maxCount: 3,
+            startDateMs: 99,
+            impressionDateMs: 99,
+          },
+          {
+            intervalSeconds: Infinity,
+            count: 7,
+            maxCount: 5,
+            startDateMs: 1337,
+            impressionDateMs: 1337,
+          },
+        ],
+      };
+      UrlbarPrefs.set(
+        "quicksuggest.impressionCaps.stats",
+        JSON.stringify(stats)
+      );
+      Assert.deepEqual(
+        QuickSuggest.impressionCaps._test_stats,
+        stats,
+        "Expected stats with valid JSON"
+      );
+    },
+  });
+});
+
+// Tests multiple interval periods where the cap is not hit. Telemetry should be
+// recorded for these periods.
+add_task(async function intervalsElapsedButCapNotHit() {
+  await doTest({
+    config: {
+      impression_caps: {
+        sponsored: {
+          custom: [{ interval_s: 1, max_count: 3 }],
+        },
+      },
+    },
+    callback: async () => {
+      await doTimedCallbacks({
+        // 1s
+        1: async () => {
+          await checkSearch({
+            name: "1s",
+            searchString: "sponsored",
+            expectedResults: [EXPECTED_SPONSORED_URLBAR_RESULT],
+          });
+        },
+        // 10s
+        10: async () => {
+          QuickSuggest.impressionCaps._test_resetElapsedCounters();
+          let expectedEvents = [
+            // 1s: reset with count = 0
+            {
+              object: "reset",
+              extra: {
+                eventDate: "1000",
+                intervalSeconds: "1",
+                maxCount: "3",
+                startDate: "0",
+                impressionDate: "0",
+                count: "0",
+                type: "sponsored",
+                eventCount: "1",
+              },
+            },
+            // 2-10s: reset with count = 1, eventCount = 9
+            {
+              object: "reset",
+              extra: {
+                eventDate: "10000",
+                intervalSeconds: "1",
+                maxCount: "3",
+                startDate: "1000",
+                impressionDate: "1000",
+                count: "1",
+                type: "sponsored",
+                eventCount: "9",
+              },
+            },
+          ];
+          await checkTelemetryEvents(expectedEvents);
+        },
+      });
+    },
+  });
+});
+
+// Simulates reset events across a restart with the following:
+//
+//   S                      S                          R
+//   >----|----|----|----|----|----|----|----|----|----|
+//   0s   1    2    3    4    5    6    7    8    9   10
+//
+//   1. Startup at 0s
+//   2. Caps and stats initialized with interval_s: 1
+//   3. Startup at 4.5s
+//   4. Reset triggered at 10s
+//
+// Expected:
+//   At 10s: 6 batched resets for periods starting at 4s
+add_task(async function restart_1() {
+  await doTest({
+    config: {
+      impression_caps: {
+        sponsored: {
+          custom: [{ interval_s: 1, max_count: 1 }],
+        },
+      },
+    },
+    callback: async () => {
+      gStartupDateMsStub.returns(4500);
+      await doTimedCallbacks({
+        // 10s: 6 batched resets for periods starting at 4s
+        10: async () => {
+          QuickSuggest.impressionCaps._test_resetElapsedCounters();
+          await checkTelemetryEvents([
+            {
+              object: "reset",
+              extra: {
+                eventDate: "10000",
+                intervalSeconds: "1",
+                maxCount: "1",
+                startDate: "4000",
+                impressionDate: "0",
+                count: "0",
+                type: "sponsored",
+                eventCount: "6",
+              },
+            },
+          ]);
+        },
+      });
+    },
+  });
+  gStartupDateMsStub.returns(0);
+});
+
+// Simulates reset events across a restart with the following:
+//
+//   S                        S                        R
+//   >----|----|----|----|----|----|----|----|----|----|
+//   0s   1    2    3    4    5    6    7    8    9   10
+//
+//   1. Startup at 0s
+//   2. Caps and stats initialized with interval_s: 1
+//   3. Startup at 5s
+//   4. Reset triggered at 10s
+//
+// Expected:
+//   At 10s: 5 batched resets for periods starting at 5s
+add_task(async function restart_2() {
+  await doTest({
+    config: {
+      impression_caps: {
+        sponsored: {
+          custom: [{ interval_s: 1, max_count: 1 }],
+        },
+      },
+    },
+    callback: async () => {
+      gStartupDateMsStub.returns(5000);
+      await doTimedCallbacks({
+        // 10s: 5 batched resets for periods starting at 5s
+        10: async () => {
+          QuickSuggest.impressionCaps._test_resetElapsedCounters();
+          await checkTelemetryEvents([
+            {
+              object: "reset",
+              extra: {
+                eventDate: "10000",
+                intervalSeconds: "1",
+                maxCount: "1",
+                startDate: "5000",
+                impressionDate: "0",
+                count: "0",
+                type: "sponsored",
+                eventCount: "5",
+              },
+            },
+          ]);
+        },
+      });
+    },
+  });
+  gStartupDateMsStub.returns(0);
+});
+
+// Simulates reset events across a restart with the following:
+//
+//   S                           S                     R
+//   >----|----|----|----|----|----|----|----|----|----|
+//   0s   1    2    3    4    5    6    7    8    9   10
+//
+//   1. Startup at 0s
+//   2. Caps and stats initialized with interval_s: 1
+//   3. Startup at 5.5s
+//   4. Reset triggered at 10s
+//
+// Expected:
+//   At 10s: 5 batched resets for periods starting at 5s
+add_task(async function restart_3() {
+  await doTest({
+    config: {
+      impression_caps: {
+        sponsored: {
+          custom: [{ interval_s: 1, max_count: 1 }],
+        },
+      },
+    },
+    callback: async () => {
+      gStartupDateMsStub.returns(5500);
+      await doTimedCallbacks({
+        // 10s: 5 batched resets for periods starting at 5s
+        10: async () => {
+          QuickSuggest.impressionCaps._test_resetElapsedCounters();
+          await checkTelemetryEvents([
+            {
+              object: "reset",
+              extra: {
+                eventDate: "10000",
+                intervalSeconds: "1",
+                maxCount: "1",
+                startDate: "5000",
+                impressionDate: "0",
+                count: "0",
+                type: "sponsored",
+                eventCount: "5",
+              },
+            },
+          ]);
+        },
+      });
+    },
+  });
+  gStartupDateMsStub.returns(0);
+});
+
+// Simulates reset events across a restart with the following:
+//
+//   S    S   RR        RR
+//   >---------|---------|
+//   0s       10        20
+//
+//   1. Startup at 0s
+//   2. Caps and stats initialized with interval_s: 10
+//   3. Startup at 5s
+//   4. Resets triggered at 9s, 10s, 19s, 20s
+//
+// Expected:
+//   At 10s: 1 reset for period starting at 0s
+//   At 20s: 1 reset for period starting at 10s
+add_task(async function restart_4() {
+  await doTest({
+    config: {
+      impression_caps: {
+        sponsored: {
+          custom: [{ interval_s: 10, max_count: 1 }],
+        },
+      },
+    },
+    callback: async () => {
+      gStartupDateMsStub.returns(5000);
+      await doTimedCallbacks({
+        // 9s: no resets
+        9: async () => {
+          QuickSuggest.impressionCaps._test_resetElapsedCounters();
+          await checkTelemetryEvents([]);
+        },
+        // 10s: 1 reset for period starting at 0s
+        10: async () => {
+          QuickSuggest.impressionCaps._test_resetElapsedCounters();
+          await checkTelemetryEvents([
+            {
+              object: "reset",
+              extra: {
+                eventDate: "10000",
+                intervalSeconds: "10",
+                maxCount: "1",
+                startDate: "0",
+                impressionDate: "0",
+                count: "0",
+                type: "sponsored",
+                eventCount: "1",
+              },
+            },
+          ]);
+        },
+        // 19s: no resets
+        19: async () => {
+          QuickSuggest.impressionCaps._test_resetElapsedCounters();
+          await checkTelemetryEvents([]);
+        },
+        // 20s: 1 reset for period starting at 10s
+        20: async () => {
+          QuickSuggest.impressionCaps._test_resetElapsedCounters();
+          await checkTelemetryEvents([
+            {
+              object: "reset",
+              extra: {
+                eventDate: "20000",
+                intervalSeconds: "10",
+                maxCount: "1",
+                startDate: "10000",
+                impressionDate: "0",
+                count: "0",
+                type: "sponsored",
+                eventCount: "1",
+              },
+            },
+          ]);
+        },
+      });
+    },
+  });
+  gStartupDateMsStub.returns(0);
+});
+
+// Simulates reset events across a restart with the following:
+//
+//   S    S              R
+//   >---------|---------|
+//   0s       10        20
+//
+//   1. Startup at 0s
+//   2. Caps and stats initialized with interval_s: 10
+//   3. Startup at 5s
+//   4. Reset triggered at 20s
+//
+// Expected:
+//   At 20s: 2 batched resets for periods starting at 0s
+add_task(async function restart_5() {
+  await doTest({
+    config: {
+      impression_caps: {
+        sponsored: {
+          custom: [{ interval_s: 10, max_count: 1 }],
+        },
+      },
+    },
+    callback: async () => {
+      gStartupDateMsStub.returns(5000);
+      await doTimedCallbacks({
+        // 20s: 2 batches resets for periods starting at 0s
+        20: async () => {
+          QuickSuggest.impressionCaps._test_resetElapsedCounters();
+          await checkTelemetryEvents([
+            {
+              object: "reset",
+              extra: {
+                eventDate: "20000",
+                intervalSeconds: "10",
+                maxCount: "1",
+                startDate: "0",
+                impressionDate: "0",
+                count: "0",
+                type: "sponsored",
+                eventCount: "2",
+              },
+            },
+          ]);
+        },
+      });
+    },
+  });
+  gStartupDateMsStub.returns(0);
+});
+
+// Simulates reset events across a restart with the following:
+//
+//   S              S   RR        RR
+//   >---------|---------|---------|
+//   0s       10        20        30
+//
+//   1. Startup at 0s
+//   2. Caps and stats initialized with interval_s: 10
+//   3. Startup at 15s
+//   4. Resets triggered at 19s, 20s, 29s, 30s
+//
+// Expected:
+//   At 20s: 1 reset for period starting at 10s
+//   At 30s: 1 reset for period starting at 20s
+add_task(async function restart_6() {
+  await doTest({
+    config: {
+      impression_caps: {
+        sponsored: {
+          custom: [{ interval_s: 10, max_count: 1 }],
+        },
+      },
+    },
+    callback: async () => {
+      gStartupDateMsStub.returns(15000);
+      await doTimedCallbacks({
+        // 19s: no resets
+        19: async () => {
+          QuickSuggest.impressionCaps._test_resetElapsedCounters();
+          await checkTelemetryEvents([]);
+        },
+        // 20s: 1 reset for period starting at 10s
+        20: async () => {
+          QuickSuggest.impressionCaps._test_resetElapsedCounters();
+          await checkTelemetryEvents([
+            {
+              object: "reset",
+              extra: {
+                eventDate: "20000",
+                intervalSeconds: "10",
+                maxCount: "1",
+                startDate: "10000",
+                impressionDate: "0",
+                count: "0",
+                type: "sponsored",
+                eventCount: "1",
+              },
+            },
+          ]);
+        },
+        // 29s: no resets
+        29: async () => {
+          QuickSuggest.impressionCaps._test_resetElapsedCounters();
+          await checkTelemetryEvents([]);
+        },
+        // 30s: 1 reset for period starting at 20s
+        30: async () => {
+          QuickSuggest.impressionCaps._test_resetElapsedCounters();
+          await checkTelemetryEvents([
+            {
+              object: "reset",
+              extra: {
+                eventDate: "30000",
+                intervalSeconds: "10",
+                maxCount: "1",
+                startDate: "20000",
+                impressionDate: "0",
+                count: "0",
+                type: "sponsored",
+                eventCount: "1",
+              },
+            },
+          ]);
+        },
+      });
+    },
+  });
+  gStartupDateMsStub.returns(0);
+});
+
+// Simulates reset events across a restart with the following:
+//
+//   S              S              R
+//   >---------|---------|---------|
+//   0s       10        20        30
+//
+//   1. Startup at 0s
+//   2. Caps and stats initialized with interval_s: 10
+//   3. Startup at 15s
+//   4. Reset triggered at 30s
+//
+// Expected:
+//   At 30s: 2 batched resets for periods starting at 10s
+add_task(async function restart_7() {
+  await doTest({
+    config: {
+      impression_caps: {
+        sponsored: {
+          custom: [{ interval_s: 10, max_count: 1 }],
+        },
+      },
+    },
+    callback: async () => {
+      gStartupDateMsStub.returns(15000);
+      await doTimedCallbacks({
+        // 30s: 2 batched resets for periods starting at 10s
+        30: async () => {
+          QuickSuggest.impressionCaps._test_resetElapsedCounters();
+          await checkTelemetryEvents([
+            {
+              object: "reset",
+              extra: {
+                eventDate: "30000",
+                intervalSeconds: "10",
+                maxCount: "1",
+                startDate: "10000",
+                impressionDate: "0",
+                count: "0",
+                type: "sponsored",
+                eventCount: "2",
+              },
+            },
+          ]);
+        },
+      });
+    },
+  });
+  gStartupDateMsStub.returns(0);
+});
+
+// Tests reset telemetry recorded on shutdown.
+add_task(async function shutdown() {
+  await doTest({
+    config: {
+      impression_caps: {
+        sponsored: {
+          custom: [{ interval_s: 1, max_count: 1 }],
+        },
+      },
+    },
+    callback: async () => {
+      // Make `Date.now()` return 10s. Since the cap's `interval_s` is 1s and
+      // before this `Date.now()` returned 0s, 10 reset events should be
+      // recorded on shutdown.
+      gDateNowStub.returns(10000);
+
+      // Simulate shutdown.
+      Services.prefs.setBoolPref("toolkit.asyncshutdown.testing", true);
+      AsyncShutdown.profileChangeTeardown._trigger();
+
+      await checkTelemetryEvents([
+        {
+          object: "reset",
+          extra: {
+            eventDate: "10000",
+            intervalSeconds: "1",
+            maxCount: "1",
+            startDate: "0",
+            impressionDate: "0",
+            count: "0",
+            type: "sponsored",
+            eventCount: "10",
+          },
+        },
+      ]);
+
+      gDateNowStub.returns(0);
+      Services.prefs.clearUserPref("toolkit.asyncshutdown.testing");
+    },
+  });
+});
+
+// Tests the reset interval in realtime.
+add_task(async function resetInterval() {
+  // Remove the test stubs so we can test in realtime.
+  gDateNowStub.restore();
+  gStartupDateMsStub.restore();
+
+  await doTest({
+    config: {
+      impression_caps: {
+        sponsored: {
+          custom: [{ interval_s: 0.1, max_count: 1 }],
+        },
+      },
+    },
+    callback: async () => {
+      // Restart the reset interval now with a 1s period. Since the cap's
+      // `interval_s` is 0.1s, at least 10 reset events should be recorded the
+      // first time the reset interval fires. The exact number depends on timing
+      // and the machine running the test: how many 0.1s intervals elapse
+      // between when the config is set to when the reset interval fires. For
+      // that reason, we allow some leeway when checking `eventCount` below to
+      // avoid intermittent failures.
+      QuickSuggest.impressionCaps._test_setCountersResetInterval(1000);
+
+      // eslint-disable-next-line mozilla/no-arbitrary-setTimeout
+      await new Promise(r => setTimeout(r, 1100));
+
+      // Restore the reset interval to its default.
+      QuickSuggest.impressionCaps._test_setCountersResetInterval();
+
+      await checkTelemetryEvents([
+        {
+          object: "reset",
+          extra: {
+            eventDate: /^[0-9]+$/,
+            intervalSeconds: "0.1",
+            maxCount: "1",
+            startDate: /^[0-9]+$/,
+            impressionDate: "0",
+            count: "0",
+            type: "sponsored",
+            // See comment above on allowing leeway for `eventCount`.
+            eventCount: str => {
+              info(`Checking 'eventCount': ${str}`);
+              let count = parseInt(str);
+              return 10 <= count && count < 20;
+            },
+          },
+        },
+      ]);
+    },
+  });
+
+  // Recreate the test stubs.
+  gDateNowStub = gSandbox.stub(
+    Cu.getGlobalForObject(UrlbarProviderQuickSuggest).Date,
+    "now"
+  );
+  gStartupDateMsStub = gSandbox.stub(
+    QuickSuggest.impressionCaps,
+    "_getStartupDateMs"
+  );
+  gStartupDateMsStub.returns(0);
+});
+
+/**
+ * Main test helper. Sets up state, calls your callback, and resets state.
+ *
+ * @param {object} options
+ *   Options object.
+ * @param {object} options.config
+ *   The quick suggest config to use during the test.
+ * @param {Function} options.callback
+ *   The callback that will be run with the {@link config}
+ */
+async function doTest({ config, callback }) {
+  Services.telemetry.clearEvents();
+
+  // Make `Date.now()` return 0 to start with. It's necessary to do this before
+  // calling `withConfig()` because when a new config is set, the provider
+  // validates its impression stats, whose `startDateMs` values depend on
+  // `Date.now()`.
+  gDateNowStub.returns(0);
+
+  info(`Clearing stats and setting config`);
+  UrlbarPrefs.clear("quicksuggest.impressionCaps.stats");
+  QuickSuggest.impressionCaps._test_reloadStats();
+  await QuickSuggestTestUtils.withConfig({ config, callback });
+}
+
+/**
+ * Does a series of timed searches and checks their results and telemetry. This
+ * function relies on `doTimedCallbacks()`, so it may be helpful to look at it
+ * too.
+ *
+ * @param {string} searchString
+ *   The query that should be timed
+ * @param {object} expectedBySecond
+ *   An object that maps from seconds to objects that describe the searches to
+ *   perform, their expected results, and the expected telemetry. For a given
+ *   entry `S -> E` in this object, searches are performed S seconds after this
+ *   function is called. `E` is an object that looks like this:
+ *
+ *     { results, telemetry }
+ *
+ *     {array} results
+ *       An array of arrays. A search is performed for each sub-array in
+ *       `results`, and the contents of the sub-array are the expected results
+ *       for that search.
+ *     {object} telemetry
+ *       An object like this: { events }
+ *       {array} events
+ *         An array of expected telemetry events after all searches are done.
+ *         Telemetry events are cleared after checking these. If not present,
+ *         then it will be asserted that no events were recorded.
+ *
+ *   Example:
+ *
+ *     {
+ *       0: {
+ *         results: [[R1], []],
+ *         telemetry: {
+ *           events: [
+ *             someExpectedEvent,
+ *           ],
+ *         },
+ *       }
+ *       1: {
+ *         results: [[]],
+ *       },
+ *     }
+ *
+ *     0 seconds after `doTimedSearches()` is called, two searches are
+ *     performed. The first one is expected to return a single result R1, and
+ *     the second search is expected to return no results. After the searches
+ *     are done, one telemetry event is expected to be recorded.
+ *
+ *     1 second after `doTimedSearches()` is called, one search is performed.
+ *     It's expected to return no results, and no telemetry is expected to be
+ *     recorded.
+ */
+async function doTimedSearches(searchString, expectedBySecond) {
+  await doTimedCallbacks(
+    Object.entries(expectedBySecond).reduce(
+      (memo, [second, { results, telemetry }]) => {
+        memo[second] = async () => {
+          for (let i = 0; i < results.length; i++) {
+            let expectedResults = results[i];
+            await checkSearch({
+              searchString,
+              expectedResults,
+              name: `${second}s search ${i + 1} of ${results.length}`,
+            });
+          }
+          let { events } = telemetry || {};
+          await checkTelemetryEvents(events || []);
+        };
+        return memo;
+      },
+      {}
+    )
+  );
+}
+
+/**
+ * Takes a series a callbacks and times at which they should be called, and
+ * calls them accordingly. This function is specifically designed for
+ * UrlbarProviderQuickSuggest and its impression capping implementation because
+ * it works by stubbing `Date.now()` within UrlbarProviderQuickSuggest. The
+ * callbacks are not actually called at the given times but instead `Date.now()`
+ * is stubbed so that UrlbarProviderQuickSuggest will think they are being
+ * called at the given times.
+ *
+ * A more general implementation of this helper function that isn't tailored to
+ * UrlbarProviderQuickSuggest is commented out below, and unfortunately it
+ * doesn't work properly on macOS.
+ *
+ * @param {object} callbacksBySecond
+ *   An object that maps from seconds to callback functions. For a given entry
+ *   `S -> F` in this object, the callback F is called S seconds after
+ *   `doTimedCallbacks()` is called.
+ */
+async function doTimedCallbacks(callbacksBySecond) {
+  let entries = Object.entries(callbacksBySecond).sort(([t1], [t2]) => t1 - t2);
+  for (let [timeoutSeconds, callback] of entries) {
+    gDateNowStub.returns(1000 * timeoutSeconds);
+    await callback();
+  }
+}
+
+/*
+// This is the original implementation of `doTimedCallbacks()`, left here for
+// reference or in case the macOS problem described below is fixed. Instead of
+// stubbing `Date.now()` within UrlbarProviderQuickSuggest, it starts parallel
+// timers so that the callbacks are actually called at appropriate times. This
+// version of `doTimedCallbacks()` is therefore more generally useful, but it
+// has the drawback that your test has to run in real time. e.g., if one of your
+// callbacks needs to run 10s from now, the test must actually wait 10s.
+//
+// Unfortunately macOS seems to have some kind of limit of ~33 total 1-second
+// timers during any xpcshell test -- not 33 simultaneous timers but 33 total
+// timers. After that, timers fire randomly and with huge timeout periods that
+// are often exactly 10s greater than the specified period, as if some 10s
+// timeout internal to macOS is being hit. This problem does not seem to happen
+// when running the full browser, only during xpcshell tests. In fact the
+// problem can be reproduced in an xpcshell test that simply creates an interval
+// timer whose period is 1s (e.g., using `setInterval()` from Timer.sys.mjs).
+// After ~33 ticks, the timer's period jumps to ~10s.
+async function doTimedCallbacks(callbacksBySecond) {
+  await Promise.all(
+    Object.entries(callbacksBySecond).map(
+      ([timeoutSeconds, callback]) => new Promise(
+        resolve => setTimeout(
+          () => callback().then(resolve),
+          1000 * parseInt(timeoutSeconds)
+        )
+      )
+    )
+  );
+}
+*/
+
+/**
+ * Does a search, triggers an engagement, and checks the results.
+ *
+ * @param {object} options
+ *   Options object.
+ * @param {string} options.name
+ *   This value is the name of the search and will be logged in messages to make
+ *   debugging easier.
+ * @param {string} options.searchString
+ *   The query that should be searched.
+ * @param {Array} options.expectedResults
+ *   The results that are expected from the search.
+ */
+async function checkSearch({ name, searchString, expectedResults }) {
+  info(`Preparing search "${name}" with search string "${searchString}"`);
+  let context = createContext(searchString, {
+    providers: [UrlbarProviderQuickSuggest.name],
+    isPrivate: false,
+  });
+  info(`Doing search: ${name}`);
+  await check_results({
+    context,
+    matches: expectedResults,
+  });
+  info(`Finished search: ${name}`);
+
+  // Impression stats are updated only on engagement, so force one now.
+  // `selIndex` doesn't really matter but since we're not trying to simulate a
+  // click on the suggestion, pass in -1 to ensure we don't record a click. Pass
+  // in true for `isPrivate` so we don't attempt to record the impression ping
+  // because otherwise the following PingCentre error is logged:
+  // "Structured Ingestion ping failure with error: undefined"
+  let isPrivate = true;
+  if (UrlbarProviderQuickSuggest._resultFromLastQuery) {
+    UrlbarProviderQuickSuggest._resultFromLastQuery.isVisible = true;
+  }
+  UrlbarProviderQuickSuggest.onEngagement(isPrivate, "engagement", context, {
+    selIndex: -1,
+  });
+}
+
+async function checkTelemetryEvents(expectedEvents) {
+  QuickSuggestTestUtils.assertEvents(
+    expectedEvents.map(event => ({
+      ...event,
+      category: QuickSuggest.TELEMETRY_EVENT_CATEGORY,
+      method: "impression_cap",
+    })),
+    // Filter in only impression_cap events.
+    { method: "impression_cap" }
+  );
+}
diff --git a/browser/components/urlbar/tests/quicksuggest/unit/test_quicksuggest_merino.js b/browser/components/urlbar/tests/quicksuggest/unit/test_quicksuggest_merino.js
new file mode 100644
index 0000000000..e0c47d9151
--- /dev/null
+++ b/browser/components/urlbar/tests/quicksuggest/unit/test_quicksuggest_merino.js
@@ -0,0 +1,711 @@
+/* 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/. */
+
+// Tests Merino integration with UrlbarProviderQuickSuggest.
+
+"use strict";
+
+// relative to `browser.urlbar`
+const PREF_DATA_COLLECTION_ENABLED = "quicksuggest.dataCollection.enabled";
+const PREF_MERINO_ENABLED = "merino.enabled";
+const PREF_REMOTE_SETTINGS_ENABLED = "quicksuggest.remoteSettings.enabled";
+
+const SEARCH_STRING = "frab";
+
+const REMOTE_SETTINGS_RESULTS = [
+  {
+    id: 1,
+    url: "http://test.com/q=frabbits",
+    title: "frabbits",
+    keywords: [SEARCH_STRING],
+    click_url: "http://click.reporting.test.com/",
+    impression_url: "http://impression.reporting.test.com/",
+    advertiser: "TestAdvertiser",
+  },
+];
+
+const EXPECTED_REMOTE_SETTINGS_URLBAR_RESULT = {
+  type: UrlbarUtils.RESULT_TYPE.URL,
+  source: UrlbarUtils.RESULT_SOURCE.SEARCH,
+  heuristic: false,
+  payload: {
+    qsSuggestion: SEARCH_STRING,
+    title: "frabbits",
+    url: "http://test.com/q=frabbits",
+    originalUrl: "http://test.com/q=frabbits",
+    icon: null,
+    sponsoredImpressionUrl: "http://impression.reporting.test.com/",
+    sponsoredClickUrl: "http://click.reporting.test.com/",
+    sponsoredBlockId: 1,
+    sponsoredAdvertiser: "TestAdvertiser",
+    isSponsored: true,
+    helpUrl: QuickSuggest.HELP_URL,
+    helpL10n: { id: "firefox-suggest-urlbar-learn-more" },
+    isBlockable: false,
+    blockL10n: { id: "firefox-suggest-urlbar-block" },
+    displayUrl: "http://test.com/q=frabbits",
+    source: "remote-settings",
+  },
+};
+
+const EXPECTED_MERINO_URLBAR_RESULT = {
+  type: UrlbarUtils.RESULT_TYPE.URL,
+  source: UrlbarUtils.RESULT_SOURCE.SEARCH,
+  heuristic: false,
+  payload: {
+    qsSuggestion: "full_keyword",
+    title: "title",
+    url: "url",
+    originalUrl: "url",
+    icon: null,
+    sponsoredImpressionUrl: "impression_url",
+    sponsoredClickUrl: "click_url",
+    sponsoredBlockId: 1,
+    sponsoredAdvertiser: "advertiser",
+    isSponsored: true,
+    helpUrl: QuickSuggest.HELP_URL,
+    helpL10n: { id: "firefox-suggest-urlbar-learn-more" },
+    isBlockable: false,
+    blockL10n: { id: "firefox-suggest-urlbar-block" },
+    displayUrl: "url",
+    requestId: "request_id",
+    source: "merino",
+  },
+};
+
+// `UrlbarProviderQuickSuggest._merino` is lazily created on the first Merino
+// fetch, so it's easiest to create `gClient` lazily too.
+XPCOMUtils.defineLazyGetter(
+  this,
+  "gClient",
+  () => UrlbarProviderQuickSuggest._merino
+);
+
+add_task(async function init() {
+  UrlbarPrefs.set("quicksuggest.enabled", true);
+  UrlbarPrefs.set("suggest.quicksuggest.nonsponsored", true);
+  UrlbarPrefs.set("suggest.quicksuggest.sponsored", true);
+  UrlbarPrefs.set("quicksuggest.shouldShowOnboardingDialog", false);
+
+  await MerinoTestUtils.server.start();
+
+  // Set up the remote settings client with the test data.
+  await QuickSuggestTestUtils.ensureQuickSuggestInit({
+    remoteSettingsResults: REMOTE_SETTINGS_RESULTS,
+  });
+
+  Assert.equal(
+    typeof RemoteSettingsClient.DEFAULT_SUGGESTION_SCORE,
+    "number",
+    "Sanity check: DEFAULT_SUGGESTION_SCORE is defined"
+  );
+});
+
+// Tests with Merino enabled and remote settings disabled.
+add_task(async function oneEnabled_merino() {
+  UrlbarPrefs.set(PREF_MERINO_ENABLED, true);
+  UrlbarPrefs.set(PREF_REMOTE_SETTINGS_ENABLED, false);
+  UrlbarPrefs.set(PREF_DATA_COLLECTION_ENABLED, true);
+
+  let histograms = MerinoTestUtils.getAndClearHistograms();
+
+  // Use a score lower than the remote settings score to make sure the
+  // suggestion is included regardless.
+  MerinoTestUtils.server.response.body.suggestions[0].score =
+    RemoteSettingsClient.DEFAULT_SUGGESTION_SCORE / 2;
+
+  let context = createContext(SEARCH_STRING, {
+    providers: [UrlbarProviderQuickSuggest.name],
+    isPrivate: false,
+  });
+  await check_results({
+    context,
+    matches: [EXPECTED_MERINO_URLBAR_RESULT],
+  });
+
+  MerinoTestUtils.checkAndClearHistograms({
+    histograms,
+    response: "success",
+    latencyRecorded: true,
+    client: gClient,
+  });
+
+  MerinoTestUtils.server.reset();
+  gClient.resetSession();
+});
+
+// Tests with Merino disabled and remote settings enabled.
+add_task(async function oneEnabled_remoteSettings() {
+  UrlbarPrefs.set(PREF_MERINO_ENABLED, false);
+  UrlbarPrefs.set(PREF_REMOTE_SETTINGS_ENABLED, true);
+  UrlbarPrefs.set(PREF_DATA_COLLECTION_ENABLED, true);
+
+  let histograms = MerinoTestUtils.getAndClearHistograms();
+
+  let context = createContext(SEARCH_STRING, {
+    providers: [UrlbarProviderQuickSuggest.name],
+    isPrivate: false,
+  });
+  await check_results({
+    context,
+    matches: [EXPECTED_REMOTE_SETTINGS_URLBAR_RESULT],
+  });
+
+  MerinoTestUtils.checkAndClearHistograms({
+    histograms,
+    response: null,
+    latencyRecorded: false,
+    client: gClient,
+  });
+});
+
+// Tests with Merino enabled but with data collection disabled. Results should
+// not be fetched from Merino in that case. Also tests with remote settings
+// enabled.
+add_task(async function dataCollectionDisabled() {
+  UrlbarPrefs.set(PREF_MERINO_ENABLED, true);
+  UrlbarPrefs.set(PREF_REMOTE_SETTINGS_ENABLED, true);
+  UrlbarPrefs.set(PREF_DATA_COLLECTION_ENABLED, false);
+
+  let context = createContext(SEARCH_STRING, {
+    providers: [UrlbarProviderQuickSuggest.name],
+    isPrivate: false,
+  });
+  await check_results({
+    context,
+    matches: [EXPECTED_REMOTE_SETTINGS_URLBAR_RESULT],
+  });
+});
+
+// When the Merino suggestion has a higher score than the remote settings
+// suggestion, the Merino suggestion should be used.
+add_task(async function higherScore() {
+  UrlbarPrefs.set(PREF_MERINO_ENABLED, true);
+  UrlbarPrefs.set(PREF_REMOTE_SETTINGS_ENABLED, true);
+  UrlbarPrefs.set(PREF_DATA_COLLECTION_ENABLED, true);
+
+  let histograms = MerinoTestUtils.getAndClearHistograms();
+
+  MerinoTestUtils.server.response.body.suggestions[0].score =
+    2 * RemoteSettingsClient.DEFAULT_SUGGESTION_SCORE;
+
+  let context = createContext(SEARCH_STRING, {
+    providers: [UrlbarProviderQuickSuggest.name],
+    isPrivate: false,
+  });
+  await check_results({
+    context,
+    matches: [EXPECTED_MERINO_URLBAR_RESULT],
+  });
+
+  MerinoTestUtils.checkAndClearHistograms({
+    histograms,
+    response: "success",
+    latencyRecorded: true,
+    client: gClient,
+  });
+
+  MerinoTestUtils.server.reset();
+  gClient.resetSession();
+});
+
+// When the Merino suggestion has a lower score than the remote settings
+// suggestion, the remote settings suggestion should be used.
+add_task(async function lowerScore() {
+  UrlbarPrefs.set(PREF_MERINO_ENABLED, true);
+  UrlbarPrefs.set(PREF_REMOTE_SETTINGS_ENABLED, true);
+  UrlbarPrefs.set(PREF_DATA_COLLECTION_ENABLED, true);
+
+  let histograms = MerinoTestUtils.getAndClearHistograms();
+
+  MerinoTestUtils.server.response.body.suggestions[0].score =
+    RemoteSettingsClient.DEFAULT_SUGGESTION_SCORE / 2;
+
+  let context = createContext(SEARCH_STRING, {
+    providers: [UrlbarProviderQuickSuggest.name],
+    isPrivate: false,
+  });
+  await check_results({
+    context,
+    matches: [EXPECTED_REMOTE_SETTINGS_URLBAR_RESULT],
+  });
+
+  MerinoTestUtils.checkAndClearHistograms({
+    histograms,
+    response: "success",
+    latencyRecorded: true,
+    client: gClient,
+  });
+
+  MerinoTestUtils.server.reset();
+  gClient.resetSession();
+});
+
+// When the Merino and remote settings suggestions have the same score, the
+// remote settings suggestion should be used.
+add_task(async function sameScore() {
+  UrlbarPrefs.set(PREF_MERINO_ENABLED, true);
+  UrlbarPrefs.set(PREF_REMOTE_SETTINGS_ENABLED, true);
+  UrlbarPrefs.set(PREF_DATA_COLLECTION_ENABLED, true);
+
+  let histograms = MerinoTestUtils.getAndClearHistograms();
+
+  MerinoTestUtils.server.response.body.suggestions[0].score =
+    RemoteSettingsClient.DEFAULT_SUGGESTION_SCORE;
+
+  let context = createContext(SEARCH_STRING, {
+    providers: [UrlbarProviderQuickSuggest.name],
+    isPrivate: false,
+  });
+  await check_results({
+    context,
+    matches: [EXPECTED_REMOTE_SETTINGS_URLBAR_RESULT],
+  });
+
+  MerinoTestUtils.checkAndClearHistograms({
+    histograms,
+    response: "success",
+    latencyRecorded: true,
+    client: gClient,
+  });
+
+  MerinoTestUtils.server.reset();
+  gClient.resetSession();
+});
+
+// When the Merino suggestion does not include a score, the remote settings
+// suggestion should be used.
+add_task(async function noMerinoScore() {
+  UrlbarPrefs.set(PREF_MERINO_ENABLED, true);
+  UrlbarPrefs.set(PREF_REMOTE_SETTINGS_ENABLED, true);
+  UrlbarPrefs.set(PREF_DATA_COLLECTION_ENABLED, true);
+
+  let histograms = MerinoTestUtils.getAndClearHistograms();
+
+  Assert.equal(
+    typeof MerinoTestUtils.server.response.body.suggestions[0].score,
+    "number",
+    "Sanity check: First suggestion has a score"
+  );
+  delete MerinoTestUtils.server.response.body.suggestions[0].score;
+
+  let context = createContext(SEARCH_STRING, {
+    providers: [UrlbarProviderQuickSuggest.name],
+    isPrivate: false,
+  });
+  await check_results({
+    context,
+    matches: [EXPECTED_REMOTE_SETTINGS_URLBAR_RESULT],
+  });
+
+  MerinoTestUtils.checkAndClearHistograms({
+    histograms,
+    response: "success",
+    latencyRecorded: true,
+    client: gClient,
+  });
+
+  MerinoTestUtils.server.reset();
+  gClient.resetSession();
+});
+
+// When remote settings doesn't return a suggestion but Merino does, the Merino
+// suggestion should be used.
+add_task(async function noSuggestion_remoteSettings() {
+  UrlbarPrefs.set(PREF_MERINO_ENABLED, true);
+  UrlbarPrefs.set(PREF_REMOTE_SETTINGS_ENABLED, true);
+  UrlbarPrefs.set(PREF_DATA_COLLECTION_ENABLED, true);
+
+  let histograms = MerinoTestUtils.getAndClearHistograms();
+
+  let context = createContext("this doesn't match remote settings", {
+    providers: [UrlbarProviderQuickSuggest.name],
+    isPrivate: false,
+  });
+  await check_results({
+    context,
+    matches: [EXPECTED_MERINO_URLBAR_RESULT],
+  });
+
+  MerinoTestUtils.checkAndClearHistograms({
+    histograms,
+    response: "success",
+    latencyRecorded: true,
+    client: gClient,
+  });
+
+  MerinoTestUtils.server.reset();
+  gClient.resetSession();
+});
+
+// When Merino doesn't return a suggestion but remote settings does, the remote
+// settings suggestion should be used.
+add_task(async function noSuggestion_merino() {
+  UrlbarPrefs.set(PREF_MERINO_ENABLED, true);
+  UrlbarPrefs.set(PREF_REMOTE_SETTINGS_ENABLED, true);
+  UrlbarPrefs.set(PREF_DATA_COLLECTION_ENABLED, true);
+
+  let histograms = MerinoTestUtils.getAndClearHistograms();
+
+  MerinoTestUtils.server.response.body.suggestions = [];
+
+  let context = createContext(SEARCH_STRING, {
+    providers: [UrlbarProviderQuickSuggest.name],
+    isPrivate: false,
+  });
+  await check_results({
+    context,
+    matches: [EXPECTED_REMOTE_SETTINGS_URLBAR_RESULT],
+  });
+
+  MerinoTestUtils.checkAndClearHistograms({
+    histograms,
+    response: "no_suggestion",
+    latencyRecorded: true,
+    client: gClient,
+  });
+
+  MerinoTestUtils.server.reset();
+  gClient.resetSession();
+});
+
+// Tests with both Merino and remote settings disabled.
+add_task(async function bothDisabled() {
+  UrlbarPrefs.set(PREF_MERINO_ENABLED, false);
+  UrlbarPrefs.set(PREF_REMOTE_SETTINGS_ENABLED, false);
+  UrlbarPrefs.set(PREF_DATA_COLLECTION_ENABLED, true);
+
+  let histograms = MerinoTestUtils.getAndClearHistograms();
+
+  let context = createContext(SEARCH_STRING, {
+    providers: [UrlbarProviderQuickSuggest.name],
+    isPrivate: false,
+  });
+  await check_results({ context, matches: [] });
+
+  MerinoTestUtils.checkAndClearHistograms({
+    histograms,
+    response: null,
+    latencyRecorded: false,
+    client: gClient,
+  });
+});
+
+// When Merino returns multiple suggestions, the one with the largest score
+// should be used.
+add_task(async function multipleMerinoSuggestions() {
+  UrlbarPrefs.set(PREF_MERINO_ENABLED, true);
+  UrlbarPrefs.set(PREF_REMOTE_SETTINGS_ENABLED, false);
+  UrlbarPrefs.set(PREF_DATA_COLLECTION_ENABLED, true);
+
+  let histograms = MerinoTestUtils.getAndClearHistograms();
+
+  MerinoTestUtils.server.response.body.suggestions = [
+    {
+      full_keyword: "multipleMerinoSuggestions 0 full_keyword",
+      title: "multipleMerinoSuggestions 0 title",
+      url: "multipleMerinoSuggestions 0 url",
+      icon: "multipleMerinoSuggestions 0 icon",
+      impression_url: "multipleMerinoSuggestions 0 impression_url",
+      click_url: "multipleMerinoSuggestions 0 click_url",
+      block_id: 0,
+      advertiser: "multipleMerinoSuggestions 0 advertiser",
+      is_sponsored: true,
+      score: 0.1,
+    },
+    {
+      full_keyword: "multipleMerinoSuggestions 1 full_keyword",
+      title: "multipleMerinoSuggestions 1 title",
+      url: "multipleMerinoSuggestions 1 url",
+      icon: "multipleMerinoSuggestions 1 icon",
+      impression_url: "multipleMerinoSuggestions 1 impression_url",
+      click_url: "multipleMerinoSuggestions 1 click_url",
+      block_id: 1,
+      advertiser: "multipleMerinoSuggestions 1 advertiser",
+      is_sponsored: true,
+      score: 1,
+    },
+    {
+      full_keyword: "multipleMerinoSuggestions 2 full_keyword",
+      title: "multipleMerinoSuggestions 2 title",
+      url: "multipleMerinoSuggestions 2 url",
+      icon: "multipleMerinoSuggestions 2 icon",
+      impression_url: "multipleMerinoSuggestions 2 impression_url",
+      click_url: "multipleMerinoSuggestions 2 click_url",
+      block_id: 2,
+      advertiser: "multipleMerinoSuggestions 2 advertiser",
+      is_sponsored: true,
+      score: 0.2,
+    },
+  ];
+
+  let context = createContext("test", {
+    providers: [UrlbarProviderQuickSuggest.name],
+    isPrivate: false,
+  });
+  await check_results({
+    context,
+    matches: [
+      {
+        type: UrlbarUtils.RESULT_TYPE.URL,
+        source: UrlbarUtils.RESULT_SOURCE.SEARCH,
+        heuristic: false,
+        payload: {
+          qsSuggestion: "multipleMerinoSuggestions 1 full_keyword",
+          title: "multipleMerinoSuggestions 1 title",
+          url: "multipleMerinoSuggestions 1 url",
+          originalUrl: "multipleMerinoSuggestions 1 url",
+          icon: "multipleMerinoSuggestions 1 icon",
+          sponsoredImpressionUrl: "multipleMerinoSuggestions 1 impression_url",
+          sponsoredClickUrl: "multipleMerinoSuggestions 1 click_url",
+          sponsoredBlockId: 1,
+          sponsoredAdvertiser: "multipleMerinoSuggestions 1 advertiser",
+          isSponsored: true,
+          helpUrl: QuickSuggest.HELP_URL,
+          helpL10n: { id: "firefox-suggest-urlbar-learn-more" },
+          isBlockable: false,
+          blockL10n: { id: "firefox-suggest-urlbar-block" },
+          displayUrl: "multipleMerinoSuggestions 1 url",
+          requestId: "request_id",
+          source: "merino",
+        },
+      },
+    ],
+  });
+
+  MerinoTestUtils.checkAndClearHistograms({
+    histograms,
+    response: "success",
+    latencyRecorded: true,
+    client: gClient,
+  });
+
+  MerinoTestUtils.server.reset();
+  gClient.resetSession();
+});
+
+// Timestamp templates in URLs should be replaced with real timestamps.
+add_task(async function timestamps() {
+  UrlbarPrefs.set(PREF_MERINO_ENABLED, true);
+  UrlbarPrefs.set(PREF_REMOTE_SETTINGS_ENABLED, false);
+  UrlbarPrefs.set(PREF_DATA_COLLECTION_ENABLED, true);
+
+  // Set up the Merino response with template URLs.
+  let suggestion = MerinoTestUtils.server.response.body.suggestions[0];
+  let { TIMESTAMP_TEMPLATE } = QuickSuggest;
+
+  suggestion.url = `http://example.com/time-${TIMESTAMP_TEMPLATE}`;
+  suggestion.click_url = `http://example.com/time-${TIMESTAMP_TEMPLATE}-foo`;
+
+  // Do a search.
+  let context = createContext("test", {
+    providers: [UrlbarProviderQuickSuggest.name],
+    isPrivate: false,
+  });
+  let controller = UrlbarTestUtils.newMockController({
+    input: {
+      isPrivate: context.isPrivate,
+      onFirstResult() {
+        return false;
+      },
+      getSearchSource() {
+        return "dummy-search-source";
+      },
+      window: {
+        location: {
+          href: AppConstants.BROWSER_CHROME_URL,
+        },
+      },
+    },
+  });
+  await controller.startQuery(context);
+
+  // Should be one quick suggest result.
+  Assert.equal(context.results.length, 1, "One result returned");
+  let result = context.results[0];
+
+  QuickSuggestTestUtils.assertTimestampsReplaced(result, {
+    url: suggestion.click_url,
+    sponsoredClickUrl: suggestion.click_url,
+  });
+
+  MerinoTestUtils.server.reset();
+  gClient.resetSession();
+});
+
+// When both suggestion types are disabled but data collection is enabled, we
+// should still send requests to Merino, and the requests should include an
+// empty `providers` to tell Merino not to fetch any suggestions.
+add_task(async function suggestedDisabled_dataCollectionEnabled() {
+  UrlbarPrefs.set(PREF_MERINO_ENABLED, true);
+  UrlbarPrefs.set(PREF_REMOTE_SETTINGS_ENABLED, false);
+  UrlbarPrefs.set(PREF_DATA_COLLECTION_ENABLED, true);
+  UrlbarPrefs.set("suggest.quicksuggest.nonsponsored", false);
+  UrlbarPrefs.set("suggest.quicksuggest.sponsored", false);
+
+  let histograms = MerinoTestUtils.getAndClearHistograms();
+
+  let context = createContext("test", {
+    providers: [UrlbarProviderQuickSuggest.name],
+    isPrivate: false,
+  });
+  await check_results({
+    context,
+    matches: [],
+  });
+
+  // Check that the request is received and includes an empty `providers`.
+  MerinoTestUtils.server.checkAndClearRequests([
+    {
+      params: {
+        [MerinoTestUtils.SEARCH_PARAMS.QUERY]: "test",
+        [MerinoTestUtils.SEARCH_PARAMS.SEQUENCE_NUMBER]: 0,
+        [MerinoTestUtils.SEARCH_PARAMS.PROVIDERS]: "",
+      },
+    },
+  ]);
+
+  MerinoTestUtils.checkAndClearHistograms({
+    histograms,
+    response: "success",
+    latencyRecorded: true,
+    client: gClient,
+  });
+
+  UrlbarPrefs.set("suggest.quicksuggest.nonsponsored", true);
+  UrlbarPrefs.set("suggest.quicksuggest.sponsored", true);
+  gClient.resetSession();
+});
+
+// Test whether the blocking for Merino results works.
+add_task(async function block() {
+  UrlbarPrefs.set(PREF_MERINO_ENABLED, true);
+  UrlbarPrefs.set(PREF_REMOTE_SETTINGS_ENABLED, true);
+  UrlbarPrefs.set(PREF_DATA_COLLECTION_ENABLED, true);
+
+  for (const suggestion of MerinoTestUtils.server.response.body.suggestions) {
+    await QuickSuggest.blockedSuggestions.add(suggestion.url);
+  }
+
+  const context = createContext(SEARCH_STRING, {
+    providers: [UrlbarProviderQuickSuggest.name],
+    isPrivate: false,
+  });
+
+  await check_results({
+    context,
+    matches: [EXPECTED_REMOTE_SETTINGS_URLBAR_RESULT],
+  });
+
+  await QuickSuggest.blockedSuggestions.clear();
+  MerinoTestUtils.server.reset();
+  gClient.resetSession();
+});
+
+// Tests a Merino suggestion that is a best match.
+add_task(async function bestMatch() {
+  UrlbarPrefs.set(PREF_MERINO_ENABLED, true);
+  UrlbarPrefs.set(PREF_REMOTE_SETTINGS_ENABLED, false);
+  UrlbarPrefs.set(PREF_DATA_COLLECTION_ENABLED, true);
+
+  // Simply enabling the best match feature should make the mock suggestion a
+  // best match because the search string length is greater than the required
+  // best match length.
+  UrlbarPrefs.set("bestMatch.enabled", true);
+  UrlbarPrefs.set("suggest.bestmatch", true);
+
+  let expectedResult = { ...EXPECTED_MERINO_URLBAR_RESULT };
+  expectedResult.payload = { ...EXPECTED_MERINO_URLBAR_RESULT.payload };
+  expectedResult.isBestMatch = true;
+  delete expectedResult.payload.qsSuggestion;
+
+  let context = createContext(SEARCH_STRING, {
+    providers: [UrlbarProviderQuickSuggest.name],
+    isPrivate: false,
+  });
+  await check_results({
+    context,
+    matches: [expectedResult],
+  });
+
+  // This isn't necessary since `check_results()` checks `isBestMatch`, but
+  // check it here explicitly for good measure.
+  Assert.ok(context.results[0].isBestMatch, "Result is a best match");
+
+  UrlbarPrefs.clear("bestMatch.enabled");
+  UrlbarPrefs.clear("suggest.bestmatch");
+
+  MerinoTestUtils.server.reset();
+  gClient.resetSession();
+});
+
+add_task(async function topPick() {
+  UrlbarPrefs.set(PREF_MERINO_ENABLED, true);
+  UrlbarPrefs.set(PREF_REMOTE_SETTINGS_ENABLED, false);
+  UrlbarPrefs.set(PREF_DATA_COLLECTION_ENABLED, true);
+  UrlbarPrefs.set("bestMatch.enabled", true);
+  UrlbarPrefs.set("suggest.bestmatch", true);
+
+  let topPickSuggestion = createSuggestion(2, 2);
+  topPickSuggestion.is_top_pick = true;
+
+  MerinoTestUtils.server.response.body = {
+    request_id: "request_id",
+    suggestions: [
+      createSuggestion(0, 0.1),
+      createSuggestion(1, 1),
+      topPickSuggestion,
+    ],
+  };
+
+  let context = createContext(SEARCH_STRING, {
+    providers: [UrlbarProviderQuickSuggest.name],
+    isPrivate: false,
+  });
+  await check_results({
+    context,
+    matches: [
+      {
+        type: UrlbarUtils.RESULT_TYPE.URL,
+        source: UrlbarUtils.RESULT_SOURCE.SEARCH,
+        heuristic: false,
+        isBestMatch: true,
+        payload: {
+          title: "multipleMerinoSuggestions 2 title",
+          url: "multipleMerinoSuggestions 2 url",
+          originalUrl: "multipleMerinoSuggestions 2 url",
+          icon: "multipleMerinoSuggestions 2 icon",
+          sponsoredImpressionUrl: "multipleMerinoSuggestions 2 impression_url",
+          sponsoredClickUrl: "multipleMerinoSuggestions 2 click_url",
+          sponsoredBlockId: 2,
+          sponsoredAdvertiser: "multipleMerinoSuggestions 2 advertiser",
+          isSponsored: true,
+          helpUrl: QuickSuggest.HELP_URL,
+          helpL10n: { id: "firefox-suggest-urlbar-learn-more" },
+          isBlockable: false,
+          blockL10n: { id: "firefox-suggest-urlbar-block" },
+          displayUrl: "multipleMerinoSuggestions 2 url",
+          requestId: "request_id",
+          source: "merino",
+        },
+      },
+    ],
+  });
+
+  UrlbarPrefs.clear("bestMatch.enabled");
+  UrlbarPrefs.clear("suggest.bestmatch");
+});
+
+let createSuggestion = (n, score) => ({
+  full_keyword: `multipleMerinoSuggestions ${n} full_keyword`,
+  title: `multipleMerinoSuggestions ${n} title`,
+  url: `multipleMerinoSuggestions ${n} url`,
+  icon: `multipleMerinoSuggestions ${n} icon`,
+  impression_url: `multipleMerinoSuggestions ${n} impression_url`,
+  click_url: `multipleMerinoSuggestions ${n} click_url`,
+  block_id: n,
+  advertiser: `multipleMerinoSuggestions ${n} advertiser`,
+  is_sponsored: true,
+  score,
+});
diff --git a/browser/components/urlbar/tests/quicksuggest/unit/test_quicksuggest_merinoSessions.js b/browser/components/urlbar/tests/quicksuggest/unit/test_quicksuggest_merinoSessions.js
new file mode 100644
index 0000000000..bb77bed595
--- /dev/null
+++ b/browser/components/urlbar/tests/quicksuggest/unit/test_quicksuggest_merinoSessions.js
@@ -0,0 +1,174 @@
+/* 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/. */
+
+// Tests Merino session integration with UrlbarProviderQuickSuggest.
+
+"use strict";
+
+// `UrlbarProviderQuickSuggest._merino` is lazily created on the first Merino
+// fetch, so it's easiest to create `gClient` lazily too.
+XPCOMUtils.defineLazyGetter(
+  this,
+  "gClient",
+  () => UrlbarProviderQuickSuggest._merino
+);
+
+add_task(async function init() {
+  UrlbarPrefs.set("quicksuggest.enabled", true);
+  UrlbarPrefs.set("suggest.quicksuggest.sponsored", true);
+  UrlbarPrefs.set("merino.enabled", true);
+  UrlbarPrefs.set("quicksuggest.remoteSettings.enabled", false);
+  UrlbarPrefs.set("quicksuggest.dataCollection.enabled", true);
+
+  await MerinoTestUtils.server.start();
+  await QuickSuggestTestUtils.ensureQuickSuggestInit();
+});
+
+// In a single engagement, all requests should use the same session ID and the
+// sequence number should be incremented.
+add_task(async function singleEngagement() {
+  let controller = UrlbarTestUtils.newMockController();
+
+  for (let i = 0; i < 3; i++) {
+    let searchString = "search" + i;
+    await controller.startQuery(
+      createContext(searchString, {
+        providers: [UrlbarProviderQuickSuggest.name],
+        isPrivate: false,
+      })
+    );
+
+    MerinoTestUtils.server.checkAndClearRequests([
+      {
+        params: {
+          [MerinoTestUtils.SEARCH_PARAMS.QUERY]: searchString,
+          [MerinoTestUtils.SEARCH_PARAMS.SEQUENCE_NUMBER]: i,
+        },
+      },
+    ]);
+  }
+
+  // End the engagement to reset the session for the next test.
+  endEngagement();
+});
+
+// New engagements should not use the same session ID as previous engagements
+// and the sequence number should be reset. This task completes each engagement
+// successfully.
+add_task(async function manyEngagements_engagement() {
+  await doManyEngagementsTest("engagement");
+});
+
+// New engagements should not use the same session ID as previous engagements
+// and the sequence number should be reset. This task abandons each engagement.
+add_task(async function manyEngagements_abandonment() {
+  await doManyEngagementsTest("abandonment");
+});
+
+async function doManyEngagementsTest(state) {
+  let controller = UrlbarTestUtils.newMockController();
+
+  for (let i = 0; i < 3; i++) {
+    let searchString = "search" + i;
+    let context = createContext(searchString, {
+      providers: [UrlbarProviderQuickSuggest.name],
+      isPrivate: false,
+    });
+    await controller.startQuery(context);
+
+    MerinoTestUtils.server.checkAndClearRequests([
+      {
+        params: {
+          [MerinoTestUtils.SEARCH_PARAMS.QUERY]: searchString,
+          [MerinoTestUtils.SEARCH_PARAMS.SEQUENCE_NUMBER]: 0,
+        },
+      },
+    ]);
+
+    endEngagement(context, state);
+  }
+}
+
+// When a search is canceled after the request is sent and before the Merino
+// response is received, the sequence number should still be incremented.
+add_task(async function canceledQueries() {
+  let controller = UrlbarTestUtils.newMockController();
+
+  for (let i = 0; i < 3; i++) {
+    // Send the first response after a delay to make sure the client will not
+    // receive it before we start the second fetch.
+    MerinoTestUtils.server.response.delay = UrlbarPrefs.get("merino.timeoutMs");
+
+    // Start the first search.
+    let requestPromise = MerinoTestUtils.server.waitForNextRequest();
+    let searchString1 = "search" + i;
+    controller.startQuery(
+      createContext(searchString1, {
+        providers: [UrlbarProviderQuickSuggest.name],
+        isPrivate: false,
+      })
+    );
+
+    // Wait until the first request is received before starting the second
+    // search. If we started the second search immediately, the first would be
+    // canceled before the provider is even called due to the urlbar's 50ms
+    // delay (see `browser.urlbar.delay`) so the sequence number would not be
+    // incremented for it. Here we want to test the case where the first search
+    // is canceled after the request is sent and the number is incremented.
+    await requestPromise;
+    delete MerinoTestUtils.server.response.delay;
+
+    // Now do a second search that cancels the first.
+    let searchString2 = searchString1 + "again";
+    await controller.startQuery(
+      createContext(searchString2, {
+        providers: [UrlbarProviderQuickSuggest.name],
+        isPrivate: false,
+      })
+    );
+
+    // The sequence number should have been incremented for each search.
+    MerinoTestUtils.server.checkAndClearRequests([
+      {
+        params: {
+          [MerinoTestUtils.SEARCH_PARAMS.QUERY]: searchString1,
+          [MerinoTestUtils.SEARCH_PARAMS.SEQUENCE_NUMBER]: 2 * i,
+        },
+      },
+      {
+        params: {
+          [MerinoTestUtils.SEARCH_PARAMS.QUERY]: searchString2,
+          [MerinoTestUtils.SEARCH_PARAMS.SEQUENCE_NUMBER]: 2 * i + 1,
+        },
+      },
+    ]);
+  }
+
+  // End the engagement to reset the session for the next test.
+  endEngagement();
+});
+
+function endEngagement(context = null, state = "engagement") {
+  UrlbarProviderQuickSuggest.onEngagement(
+    false,
+    state,
+    context ||
+      createContext("endEngagement", {
+        providers: [UrlbarProviderQuickSuggest.name],
+        isPrivate: false,
+      }),
+    { selIndex: -1 }
+  );
+
+  Assert.strictEqual(
+    gClient.sessionID,
+    null,
+    "sessionID is null after engagement"
+  );
+  Assert.strictEqual(
+    gClient._test_sessionTimer,
+    null,
+    "sessionTimer is null after engagement"
+  );
+}
diff --git a/browser/components/urlbar/tests/quicksuggest/unit/test_quicksuggest_migrate_v1.js b/browser/components/urlbar/tests/quicksuggest/unit/test_quicksuggest_migrate_v1.js
new file mode 100644
index 0000000000..a7fcf9ee04
--- /dev/null
+++ b/browser/components/urlbar/tests/quicksuggest/unit/test_quicksuggest_migrate_v1.js
@@ -0,0 +1,490 @@
+/* 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/. */
+
+// Tests quick suggest prefs migration from unversioned prefs to version 1.
+
+"use strict";
+
+// Expected version 1 default-branch prefs
+const DEFAULT_PREFS = {
+  history: {
+    "quicksuggest.enabled": false,
+  },
+  offline: {
+    "quicksuggest.enabled": true,
+    "quicksuggest.dataCollection.enabled": false,
+    "quicksuggest.shouldShowOnboardingDialog": false,
+    "suggest.quicksuggest.nonsponsored": true,
+    "suggest.quicksuggest.sponsored": true,
+  },
+  online: {
+    "quicksuggest.enabled": true,
+    "quicksuggest.dataCollection.enabled": false,
+    "quicksuggest.shouldShowOnboardingDialog": true,
+    "suggest.quicksuggest.nonsponsored": false,
+    "suggest.quicksuggest.sponsored": false,
+  },
+};
+
+// Migration will use these values to migrate only up to version 1 instead of
+// the current version.
+const TEST_OVERRIDES = {
+  migrationVersion: 1,
+  defaultPrefs: DEFAULT_PREFS,
+};
+
+add_task(async function init() {
+  await UrlbarTestUtils.initNimbusFeature();
+});
+
+// The following tasks test OFFLINE TO OFFLINE
+
+// Migrating from:
+// * Offline (suggestions on by default)
+// * User did not override any defaults
+//
+// Scenario when migration occurs:
+// * Offline
+//
+// Expected:
+// * Non-sponsored suggestions: remain on
+// * Sponsored suggestions: remain on
+// * Data collection: off
+add_task(async function() {
+  await doMigrateTest({
+    testOverrides: TEST_OVERRIDES,
+    scenario: "offline",
+    expectedPrefs: {
+      defaultBranch: DEFAULT_PREFS.offline,
+    },
+  });
+});
+
+// Migrating from:
+// * Offline (suggestions on by default)
+// * Main suggestions pref: user left on
+// * Sponsored suggestions: user turned off
+//
+// Scenario when migration occurs:
+// * Offline
+//
+// Expected:
+// * Non-sponsored suggestions: on
+// * Sponsored suggestions: remain off
+// * Data collection: off
+add_task(async function() {
+  await doMigrateTest({
+    testOverrides: TEST_OVERRIDES,
+    initialUserBranch: {
+      "suggest.quicksuggest.sponsored": false,
+    },
+    scenario: "offline",
+    expectedPrefs: {
+      defaultBranch: DEFAULT_PREFS.offline,
+      userBranch: {
+        "suggest.quicksuggest.sponsored": false,
+      },
+    },
+  });
+});
+
+// Migrating from:
+// * Offline (suggestions on by default)
+// * Main suggestions pref: user turned off
+// * Sponsored suggestions: user left on (but ignored since main was off)
+//
+// Scenario when migration occurs:
+// * Offline
+//
+// Expected:
+// * Non-sponsored suggestions: off
+// * Sponsored suggestions: off
+// * Data collection: off
+add_task(async function() {
+  await doMigrateTest({
+    testOverrides: TEST_OVERRIDES,
+    initialUserBranch: {
+      "suggest.quicksuggest": false,
+    },
+    scenario: "offline",
+    expectedPrefs: {
+      defaultBranch: DEFAULT_PREFS.offline,
+      userBranch: {
+        "suggest.quicksuggest.nonsponsored": false,
+        "suggest.quicksuggest.sponsored": false,
+      },
+    },
+  });
+});
+
+// Migrating from:
+// * Offline (suggestions on by default)
+// * Main suggestions pref: user turned off
+// * Sponsored suggestions: user turned off
+//
+// Scenario when migration occurs:
+// * Offline
+//
+// Expected:
+// * Non-sponsored suggestions: off
+// * Sponsored suggestions: off
+// * Data collection: off
+add_task(async function() {
+  await doMigrateTest({
+    testOverrides: TEST_OVERRIDES,
+    initialUserBranch: {
+      "suggest.quicksuggest": false,
+      "suggest.quicksuggest.sponsored": false,
+    },
+    scenario: "offline",
+    expectedPrefs: {
+      defaultBranch: DEFAULT_PREFS.offline,
+      userBranch: {
+        "suggest.quicksuggest.nonsponsored": false,
+        "suggest.quicksuggest.sponsored": false,
+      },
+    },
+  });
+});
+
+// The following tasks test OFFLINE TO ONLINE
+
+// Migrating from:
+// * Offline (suggestions on by default)
+// * User did not override any defaults
+//
+// Scenario when migration occurs:
+// * Online
+//
+// Expected:
+// * Non-sponsored suggestions: off
+// * Sponsored suggestions: off
+// * Data collection: off
+add_task(async function() {
+  await doMigrateTest({
+    testOverrides: TEST_OVERRIDES,
+    scenario: "online",
+    expectedPrefs: {
+      defaultBranch: DEFAULT_PREFS.online,
+    },
+  });
+});
+
+// Migrating from:
+// * Offline (suggestions on by default)
+// * Main suggestions pref: user left on
+// * Sponsored suggestions: user turned off
+//
+// Scenario when migration occurs:
+// * Online
+//
+// Expected:
+// * Non-sponsored suggestions: off
+// * Sponsored suggestions: off
+// * Data collection: off
+add_task(async function() {
+  await doMigrateTest({
+    testOverrides: TEST_OVERRIDES,
+    initialUserBranch: {
+      "suggest.quicksuggest.sponsored": false,
+    },
+    scenario: "online",
+    expectedPrefs: {
+      defaultBranch: DEFAULT_PREFS.online,
+      userBranch: {
+        "suggest.quicksuggest.sponsored": false,
+      },
+    },
+  });
+});
+
+// Migrating from:
+// * Offline (suggestions on by default)
+// * Main suggestions pref: user turned off
+// * Sponsored suggestions: user left on (but ignored since main was off)
+//
+// Scenario when migration occurs:
+// * Online
+//
+// Expected:
+// * Non-sponsored suggestions: off
+// * Sponsored suggestions: off
+// * Data collection: off
+add_task(async function() {
+  await doMigrateTest({
+    testOverrides: TEST_OVERRIDES,
+    initialUserBranch: {
+      "suggest.quicksuggest": false,
+    },
+    scenario: "online",
+    expectedPrefs: {
+      defaultBranch: DEFAULT_PREFS.online,
+      userBranch: {
+        "suggest.quicksuggest.nonsponsored": false,
+      },
+    },
+  });
+});
+
+// Migrating from:
+// * Offline (suggestions on by default)
+// * Main suggestions pref: user turned off
+// * Sponsored suggestions: user turned off
+//
+// Scenario when migration occurs:
+// * Online
+//
+// Expected:
+// * Non-sponsored suggestions: off
+// * Sponsored suggestions: off
+// * Data collection: off
+add_task(async function() {
+  await doMigrateTest({
+    testOverrides: TEST_OVERRIDES,
+    initialUserBranch: {
+      "suggest.quicksuggest": false,
+      "suggest.quicksuggest.sponsored": false,
+    },
+    scenario: "online",
+    expectedPrefs: {
+      defaultBranch: DEFAULT_PREFS.online,
+      userBranch: {
+        "suggest.quicksuggest.nonsponsored": false,
+        "suggest.quicksuggest.sponsored": false,
+      },
+    },
+  });
+});
+
+// The following tasks test ONLINE TO OFFLINE
+
+// Migrating from:
+// * Online (suggestions off by default)
+// * User did not override any defaults
+//
+// Scenario when migration occurs:
+// * Offline
+//
+// Expected:
+// * Non-sponsored suggestions: on (since main pref had default value)
+// * Sponsored suggestions: on (since main & sponsored prefs had default values)
+// * Data collection: off
+add_task(async function() {
+  await doMigrateTest({
+    testOverrides: TEST_OVERRIDES,
+    scenario: "offline",
+    expectedPrefs: {
+      defaultBranch: DEFAULT_PREFS.offline,
+    },
+  });
+});
+
+// Migrating from:
+// * Online (suggestions off by default)
+// * Main suggestions pref: user left off
+// * Sponsored suggestions: user turned on (but ignored since main was off)
+//
+// Scenario when migration occurs:
+// * Offline
+//
+// Expected:
+// * Non-sponsored suggestions: off
+// * Sponsored suggestions: on (see below)
+// * Data collection: off
+//
+// It's unfortunate that sponsored suggestions are ultimately on since before
+// the migration no suggestions were shown to the user. There's nothing we can
+// do about it, aside from forcing off suggestions in more cases than we want.
+// The reason is that at the time of migration we can't tell that the previous
+// scenario was online -- or more precisely that it wasn't history. If we knew
+// it wasn't history, then we'd know to turn sponsored off; if we knew it *was*
+// history, then we'd know to turn sponsored -- and non-sponsored -- on, since
+// the scenario at the time of migration is offline, where suggestions should be
+// enabled by default.
+//
+// This is the reason we now record `quicksuggest.scenario` on the user branch
+// and not the default branch as we previously did.
+add_task(async function() {
+  await doMigrateTest({
+    testOverrides: TEST_OVERRIDES,
+    initialUserBranch: {
+      "suggest.quicksuggest.sponsored": true,
+    },
+    scenario: "offline",
+    expectedPrefs: {
+      defaultBranch: DEFAULT_PREFS.offline,
+      userBranch: {
+        "suggest.quicksuggest.sponsored": true,
+      },
+    },
+  });
+});
+
+// Migrating from:
+// * Online (suggestions off by default)
+// * Main suggestions pref: user turned on
+// * Sponsored suggestions: user left off
+//
+// Scenario when migration occurs:
+// * Offline
+//
+// Expected:
+// * Non-sponsored suggestions: remain on
+// * Sponsored suggestions: remain off
+// * Data collection: off (since scenario is offline)
+add_task(async function() {
+  await doMigrateTest({
+    testOverrides: TEST_OVERRIDES,
+    initialUserBranch: {
+      "suggest.quicksuggest": true,
+    },
+    scenario: "offline",
+    expectedPrefs: {
+      defaultBranch: DEFAULT_PREFS.offline,
+      userBranch: {
+        "suggest.quicksuggest.nonsponsored": true,
+      },
+    },
+  });
+});
+
+// Migrating from:
+// * Online (suggestions off by default)
+// * Main suggestions pref: user turned on
+// * Sponsored suggestions: user turned on
+//
+// Scenario when migration occurs:
+// * Online
+//
+// Expected:
+// * Non-sponsored suggestions: remain on
+// * Sponsored suggestions: remain on
+// * Data collection: off (since scenario is offline)
+add_task(async function() {
+  await doMigrateTest({
+    testOverrides: TEST_OVERRIDES,
+    initialUserBranch: {
+      "suggest.quicksuggest": true,
+      "suggest.quicksuggest.sponsored": true,
+    },
+    scenario: "offline",
+    expectedPrefs: {
+      defaultBranch: DEFAULT_PREFS.offline,
+      userBranch: {
+        "suggest.quicksuggest.nonsponsored": true,
+        "suggest.quicksuggest.sponsored": true,
+      },
+    },
+  });
+});
+
+// The following tasks test ONLINE TO ONLINE
+
+// Migrating from:
+// * Online (suggestions off by default)
+// * User did not override any defaults
+//
+// Scenario when migration occurs:
+// * Online
+//
+// Expected:
+// * Non-sponsored suggestions: off
+// * Sponsored suggestions: off
+// * Data collection: off
+add_task(async function() {
+  await doMigrateTest({
+    testOverrides: TEST_OVERRIDES,
+    scenario: "online",
+    expectedPrefs: {
+      defaultBranch: DEFAULT_PREFS.online,
+    },
+  });
+});
+
+// Migrating from:
+// * Online (suggestions off by default)
+// * Main suggestions pref: user left off
+// * Sponsored suggestions: user turned on (but ignored since main was off)
+//
+// Scenario when migration occurs:
+// * Online
+//
+// Expected:
+// * Non-sponsored suggestions: remain off
+// * Sponsored suggestions: off
+// * Data collection: off
+add_task(async function() {
+  await doMigrateTest({
+    testOverrides: TEST_OVERRIDES,
+    initialUserBranch: {
+      "suggest.quicksuggest.sponsored": true,
+    },
+    scenario: "online",
+    expectedPrefs: {
+      defaultBranch: DEFAULT_PREFS.online,
+    },
+  });
+});
+
+// Migrating from:
+// * Online (suggestions off by default)
+// * Main suggestions pref: user turned on
+// * Sponsored suggestions: user left off
+//
+// Scenario when migration occurs:
+// * Online
+//
+// Expected:
+// * Non-sponsored suggestions: remain on
+// * Sponsored suggestions: remain off
+// * Data collection: ON (since user effectively opted in by turning on
+//   suggestions)
+add_task(async function() {
+  await doMigrateTest({
+    testOverrides: TEST_OVERRIDES,
+    initialUserBranch: {
+      "suggest.quicksuggest": true,
+    },
+    scenario: "online",
+    expectedPrefs: {
+      defaultBranch: DEFAULT_PREFS.online,
+      userBranch: {
+        "suggest.quicksuggest.nonsponsored": true,
+        "quicksuggest.dataCollection.enabled": true,
+      },
+    },
+  });
+});
+
+// Migrating from:
+// * Online (suggestions off by default)
+// * Main suggestions pref: user turned on
+// * Sponsored suggestions: user turned on
+//
+// Scenario when migration occurs:
+// * Online
+//
+// Expected:
+// * Non-sponsored suggestions: remain on
+// * Sponsored suggestions: remain on
+// * Data collection: ON (since user effectively opted in by turning on
+//   suggestions)
+add_task(async function() {
+  await doMigrateTest({
+    testOverrides: TEST_OVERRIDES,
+    initialUserBranch: {
+      "suggest.quicksuggest": true,
+      "suggest.quicksuggest.sponsored": true,
+    },
+    scenario: "online",
+    expectedPrefs: {
+      defaultBranch: DEFAULT_PREFS.online,
+      userBranch: {
+        "suggest.quicksuggest.nonsponsored": true,
+        "suggest.quicksuggest.sponsored": true,
+        "quicksuggest.dataCollection.enabled": true,
+      },
+    },
+  });
+});
diff --git a/browser/components/urlbar/tests/quicksuggest/unit/test_quicksuggest_migrate_v2.js b/browser/components/urlbar/tests/quicksuggest/unit/test_quicksuggest_migrate_v2.js
new file mode 100644
index 0000000000..9b22a366dd
--- /dev/null
+++ b/browser/components/urlbar/tests/quicksuggest/unit/test_quicksuggest_migrate_v2.js
@@ -0,0 +1,1357 @@
+/* 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/. */
+
+// Tests quick suggest prefs migration to version 2.
+
+"use strict";
+
+XPCOMUtils.defineLazyModuleGetters(this, {
+  ExperimentFakes: "resource://testing-common/NimbusTestUtils.jsm",
+  NimbusFeatures: "resource://nimbus/ExperimentAPI.jsm",
+});
+
+// Expected version 2 default-branch prefs
+const DEFAULT_PREFS = {
+  history: {
+    "quicksuggest.enabled": false,
+  },
+  offline: {
+    "quicksuggest.enabled": true,
+    "quicksuggest.dataCollection.enabled": false,
+    "quicksuggest.shouldShowOnboardingDialog": false,
+    "suggest.quicksuggest.nonsponsored": true,
+    "suggest.quicksuggest.sponsored": true,
+  },
+  online: {
+    "quicksuggest.enabled": true,
+    "quicksuggest.dataCollection.enabled": false,
+    "quicksuggest.shouldShowOnboardingDialog": true,
+    "suggest.quicksuggest.nonsponsored": true,
+    "suggest.quicksuggest.sponsored": true,
+  },
+};
+
+// Migration will use these values to migrate only up to version 1 instead of
+// the current version.
+// Currently undefined because version 2 is the current migration version and we
+// want migration to use its actual values, not overrides. When version 3 is
+// added, set this to an object like the one in test_quicksuggest_migrate_v1.js.
+const TEST_OVERRIDES = undefined;
+
+add_task(async function init() {
+  await UrlbarTestUtils.initNimbusFeature();
+});
+
+// The following tasks test OFFLINE UNVERSIONED to OFFLINE
+
+// Migrating from:
+// * Unversioned prefs
+// * Offline
+// * Main suggestions pref: user left on
+// * Sponsored suggestions: user left on
+//
+// Scenario when migration occurs:
+// * Offline
+//
+// Expected:
+// * Non-sponsored suggestions: on
+// * Sponsored suggestions: on
+// * Data collection: off
+add_task(async function() {
+  await doMigrateTest({
+    testOverrides: TEST_OVERRIDES,
+    scenario: "offline",
+    expectedPrefs: {
+      defaultBranch: DEFAULT_PREFS.offline,
+    },
+  });
+});
+
+// Migrating from:
+// * Unversioned prefs
+// * Offline
+// * Main suggestions pref: user turned off
+// * Sponsored suggestions: user left on (but ignored since main was off)
+//
+// Scenario when migration occurs:
+// * Offline
+//
+// Expected:
+// * Non-sponsored suggestions: off
+// * Sponsored suggestions: off
+// * Data collection: off
+add_task(async function() {
+  await doMigrateTest({
+    testOverrides: TEST_OVERRIDES,
+    initialUserBranch: {
+      "suggest.quicksuggest": false,
+    },
+    scenario: "offline",
+    expectedPrefs: {
+      defaultBranch: DEFAULT_PREFS.offline,
+      userBranch: {
+        "suggest.quicksuggest.nonsponsored": false,
+        "suggest.quicksuggest.sponsored": false,
+      },
+    },
+  });
+});
+
+// Migrating from:
+// * Unversioned prefs
+// * Offline
+// * Main suggestions pref: user left on
+// * Sponsored suggestions: user turned off
+//
+// Scenario when migration occurs:
+// * Offline
+//
+// Expected:
+// * Non-sponsored suggestions: on
+// * Sponsored suggestions: off
+// * Data collection: off
+add_task(async function() {
+  await doMigrateTest({
+    testOverrides: TEST_OVERRIDES,
+    initialUserBranch: {
+      "suggest.quicksuggest.sponsored": false,
+    },
+    scenario: "offline",
+    expectedPrefs: {
+      defaultBranch: DEFAULT_PREFS.offline,
+      userBranch: {
+        "suggest.quicksuggest.sponsored": false,
+      },
+    },
+  });
+});
+
+// Migrating from:
+// * Unversioned prefs
+// * Offline
+// * Main suggestions pref: user turned off
+// * Sponsored suggestions: user turned off
+//
+// Scenario when migration occurs:
+// * Offline
+//
+// Expected:
+// * Non-sponsored suggestions: off
+// * Sponsored suggestions: off
+// * Data collection: off
+add_task(async function() {
+  await doMigrateTest({
+    testOverrides: TEST_OVERRIDES,
+    initialUserBranch: {
+      "suggest.quicksuggest": false,
+      "suggest.quicksuggest.sponsored": false,
+    },
+    scenario: "offline",
+    expectedPrefs: {
+      defaultBranch: DEFAULT_PREFS.offline,
+      userBranch: {
+        "suggest.quicksuggest.nonsponsored": false,
+        "suggest.quicksuggest.sponsored": false,
+      },
+    },
+  });
+});
+
+// The following tasks test OFFLINE UNVERSIONED to ONLINE
+
+// Migrating from:
+// * Unversioned prefs
+// * Offline
+// * Main suggestions pref: user left on
+// * Sponsored suggestions: user left on
+//
+// Scenario when migration occurs:
+// * Online
+//
+// Expected:
+// * Non-sponsored suggestions: on
+// * Sponsored suggestions: on
+// * Data collection: off
+add_task(async function() {
+  await doMigrateTest({
+    testOverrides: TEST_OVERRIDES,
+    scenario: "online",
+    expectedPrefs: {
+      defaultBranch: DEFAULT_PREFS.online,
+    },
+  });
+});
+
+// Migrating from:
+// * Unversioned prefs
+// * Offline
+// * Main suggestions pref: user turned off
+// * Sponsored suggestions: user left on (but ignored since main was off)
+//
+// Scenario when migration occurs:
+// * Online
+//
+// Expected:
+// * Non-sponsored suggestions: off
+// * Sponsored suggestions: off
+// * Data collection: off
+add_task(async function() {
+  await doMigrateTest({
+    testOverrides: TEST_OVERRIDES,
+    initialUserBranch: {
+      "suggest.quicksuggest": false,
+    },
+    scenario: "online",
+    expectedPrefs: {
+      defaultBranch: DEFAULT_PREFS.online,
+      userBranch: {
+        "suggest.quicksuggest.nonsponsored": false,
+        "suggest.quicksuggest.sponsored": false,
+      },
+    },
+  });
+});
+
+// Migrating from:
+// * Unversioned prefs
+// * Offline
+// * Main suggestions pref: user left on
+// * Sponsored suggestions: user turned off
+//
+// Scenario when migration occurs:
+// * Online
+//
+// Expected:
+// * Non-sponsored suggestions: on
+// * Sponsored suggestions: off
+// * Data collection: off
+add_task(async function() {
+  await doMigrateTest({
+    testOverrides: TEST_OVERRIDES,
+    initialUserBranch: {
+      "suggest.quicksuggest.sponsored": false,
+    },
+    scenario: "online",
+    expectedPrefs: {
+      defaultBranch: DEFAULT_PREFS.online,
+      userBranch: {
+        "suggest.quicksuggest.sponsored": false,
+      },
+    },
+  });
+});
+
+// Migrating from:
+// * Unversioned prefs
+// * Offline
+// * Main suggestions pref: user turned off
+// * Sponsored suggestions: user turned off
+//
+// Scenario when migration occurs:
+// * Online
+//
+// Expected:
+// * Non-sponsored suggestions: off
+// * Sponsored suggestions: off
+// * Data collection: off
+add_task(async function() {
+  await doMigrateTest({
+    testOverrides: TEST_OVERRIDES,
+    initialUserBranch: {
+      "suggest.quicksuggest": false,
+      "suggest.quicksuggest.sponsored": false,
+    },
+    scenario: "online",
+    expectedPrefs: {
+      defaultBranch: DEFAULT_PREFS.online,
+      userBranch: {
+        "suggest.quicksuggest.nonsponsored": false,
+        "suggest.quicksuggest.sponsored": false,
+      },
+    },
+  });
+});
+
+// The following tasks test ONLINE UNVERSIONED to ONLINE when the user was NOT
+// SHOWN THE MODAL (e.g., because they didn't restart)
+
+// Migrating from:
+// * Unversioned prefs
+// * Online
+// * Modal shown: no
+// * User enrolled in online where suggestions were disabled by default, did not
+//   turn on either type of suggestion, was not shown the modal (e.g., because
+//   they didn't restart), and upgraded to v2
+//
+// Scenario when migration occurs:
+// * Online
+//
+// Expected:
+// * Non-sponsored suggestions: off
+// * Sponsored suggestions: off
+// * Data collection: off
+add_task(async function() {
+  await withOnlineExperiment(async () => {
+    await doMigrateTest({
+      testOverrides: TEST_OVERRIDES,
+      scenario: "online",
+      expectedPrefs: {
+        defaultBranch: DEFAULT_PREFS.online,
+      },
+    });
+  });
+});
+
+// Migrating from:
+// * Unversioned prefs
+// * Online
+// * Modal shown: no
+// * User enrolled in online where suggestions were disabled by default, turned
+//   on main suggestions pref and left off sponsored suggestions, was not shown
+//   the modal (e.g., because they didn't restart), and upgraded to v2
+//
+// Scenario when migration occurs:
+// * Online
+//
+// Expected:
+// * Non-sponsored suggestions: on
+// * Sponsored suggestions: off
+// * Data collection: on (since they opted in by checking the main checkbox
+//   while in online)
+add_task(async function() {
+  await withOnlineExperiment(async () => {
+    await doMigrateTest({
+      testOverrides: TEST_OVERRIDES,
+      initialUserBranch: {
+        "suggest.quicksuggest": true,
+      },
+      scenario: "online",
+      expectedPrefs: {
+        defaultBranch: DEFAULT_PREFS.online,
+        userBranch: {
+          "suggest.quicksuggest.nonsponsored": true,
+        },
+      },
+    });
+  });
+});
+
+// Migrating from:
+// * Unversioned prefs
+// * Online
+// * Modal shown: no
+// * User enrolled in online where suggestions were disabled by default, left
+//   off main suggestions pref and turned on sponsored suggestions, was not
+//   shown the modal (e.g., because they didn't restart), and upgraded to v2
+//
+// Scenario when migration occurs:
+// * Online
+//
+// Expected:
+// * Non-sponsored suggestions: off
+// * Sponsored suggestions: off
+// * Data collection: off
+add_task(async function() {
+  await withOnlineExperiment(async () => {
+    await doMigrateTest({
+      testOverrides: TEST_OVERRIDES,
+      initialUserBranch: {
+        "suggest.quicksuggest.sponsored": true,
+      },
+      scenario: "online",
+      expectedPrefs: {
+        defaultBranch: DEFAULT_PREFS.online,
+        userBranch: {
+          "suggest.quicksuggest.sponsored": true,
+        },
+      },
+    });
+  });
+});
+
+// Migrating from:
+// * Unversioned prefs
+// * Online
+// * Modal shown: no
+// * User enrolled in online where suggestions were disabled by default, turned
+//   on main suggestions pref and sponsored suggestions, was not shown the
+//   modal (e.g., because they didn't restart), and upgraded to v2
+//
+// Scenario when migration occurs:
+// * Online
+//
+// Expected:
+// * Non-sponsored suggestions: on
+// * Sponsored suggestions: on
+// * Data collection: on (since they opted in by checking the main checkbox
+//   while in online)
+add_task(async function() {
+  await withOnlineExperiment(async () => {
+    await doMigrateTest({
+      testOverrides: TEST_OVERRIDES,
+      initialUserBranch: {
+        "suggest.quicksuggest": true,
+        "suggest.quicksuggest.sponsored": true,
+      },
+      scenario: "online",
+      expectedPrefs: {
+        defaultBranch: DEFAULT_PREFS.online,
+        userBranch: {
+          "suggest.quicksuggest.nonsponsored": true,
+          "suggest.quicksuggest.sponsored": true,
+        },
+      },
+    });
+  });
+});
+
+// The following tasks test ONLINE UNVERSIONED to ONLINE when the user WAS SHOWN
+// THE MODAL
+
+// Migrating from:
+// * Unversioned prefs
+// * Online
+// * Modal shown: yes
+// * The following end up with same prefs and are covered by this task:
+//   1. User did not opt in and left off both the main suggestions pref and
+//      sponsored suggestions
+//   2. User opted in but then later turned off both the main suggestions pref
+//      and sponsored suggestions
+//
+// Scenario when migration occurs:
+// * Online
+//
+// Expected:
+// * Non-sponsored suggestions: off
+// * Sponsored suggestions: off
+// * Data collection: off
+add_task(async function() {
+  await doMigrateTest({
+    testOverrides: TEST_OVERRIDES,
+    initialUserBranch: {
+      "quicksuggest.showedOnboardingDialog": true,
+    },
+    scenario: "online",
+    expectedPrefs: {
+      defaultBranch: DEFAULT_PREFS.online,
+      userBranch: {
+        "suggest.quicksuggest.nonsponsored": false,
+        "suggest.quicksuggest.sponsored": false,
+        "quicksuggest.dataCollection.enabled": false,
+      },
+    },
+  });
+});
+
+// Migrating from:
+// * Unversioned prefs
+// * Online
+// * Modal shown: yes
+// * The following end up with same prefs and are covered by this task:
+//   1. User did not opt in but then later turned on the main suggestions pref
+//   2. User opted in but then later turned off sponsored suggestions
+//
+// Scenario when migration occurs:
+// * Online
+//
+// Expected:
+// * Non-sponsored suggestions: on
+// * Sponsored suggestions: off
+// * Data collection: on
+add_task(async function() {
+  await doMigrateTest({
+    testOverrides: TEST_OVERRIDES,
+    initialUserBranch: {
+      "quicksuggest.showedOnboardingDialog": true,
+      "suggest.quicksuggest": true,
+    },
+    scenario: "online",
+    expectedPrefs: {
+      defaultBranch: DEFAULT_PREFS.online,
+      userBranch: {
+        "suggest.quicksuggest.nonsponsored": true,
+        "suggest.quicksuggest.sponsored": false,
+        "quicksuggest.dataCollection.enabled": true,
+      },
+    },
+  });
+});
+
+// Migrating from:
+// * Unversioned prefs
+// * Online
+// * Modal shown: yes
+// * The following end up with same prefs and are covered by this task:
+//   1. User did not opt in but then later turned on sponsored suggestions
+//   2. User opted in but then later turned off the main suggestions pref
+//
+// Scenario when migration occurs:
+// * Online
+//
+// Expected:
+// * Non-sponsored suggestions: off
+// * Sponsored suggestions: off
+// * Data collection: off
+add_task(async function() {
+  await doMigrateTest({
+    testOverrides: TEST_OVERRIDES,
+    initialUserBranch: {
+      "quicksuggest.showedOnboardingDialog": true,
+      "suggest.quicksuggest.sponsored": true,
+    },
+    scenario: "online",
+    expectedPrefs: {
+      defaultBranch: DEFAULT_PREFS.online,
+      userBranch: {
+        "suggest.quicksuggest.nonsponsored": false,
+        "suggest.quicksuggest.sponsored": false,
+        "quicksuggest.dataCollection.enabled": false,
+      },
+    },
+  });
+});
+
+// Migrating from:
+// * Unversioned prefs
+// * Online
+// * Modal shown: yes
+// * The following end up with same prefs and are covered by this task:
+//   1. User did not opt in but then later turned on both the main suggestions
+//      pref and sponsored suggestions
+//   2. User opted in and left on both the main suggestions pref and sponsored
+//      suggestions
+//
+// Scenario when migration occurs:
+// * Online
+//
+// Expected:
+// * Non-sponsored suggestions: on
+// * Sponsored suggestions: on
+// * Data collection: on
+add_task(async function() {
+  await doMigrateTest({
+    testOverrides: TEST_OVERRIDES,
+    initialUserBranch: {
+      "quicksuggest.showedOnboardingDialog": true,
+      "suggest.quicksuggest": true,
+      "suggest.quicksuggest.sponsored": true,
+    },
+    scenario: "online",
+    expectedPrefs: {
+      defaultBranch: DEFAULT_PREFS.online,
+      userBranch: {
+        "suggest.quicksuggest.nonsponsored": true,
+        "suggest.quicksuggest.sponsored": true,
+        "quicksuggest.dataCollection.enabled": true,
+      },
+    },
+  });
+});
+
+// The following tasks test OFFLINE VERSION 1 to OFFLINE
+
+// Migrating from:
+// * Version 1 prefs
+// * Offline
+// * Non-sponsored suggestions: user left on
+// * Sponsored suggestions: user left on
+// * Data collection: user left off
+//
+// Scenario when migration occurs:
+// * Offline
+//
+// Expected:
+// * Non-sponsored suggestions: on
+// * Sponsored suggestions: on
+// * Data collection: off
+add_task(async function() {
+  await doMigrateTest({
+    testOverrides: TEST_OVERRIDES,
+    initialUserBranch: {
+      "quicksuggest.migrationVersion": 1,
+      "quicksuggest.scenario": "offline",
+    },
+    scenario: "offline",
+    expectedPrefs: {
+      defaultBranch: DEFAULT_PREFS.offline,
+    },
+  });
+});
+
+// Migrating from:
+// * Version 1 prefs
+// * Offline
+// * Non-sponsored suggestions: user left on
+// * Sponsored suggestions: user left on
+// * Data collection: user turned on
+//
+// Scenario when migration occurs:
+// * Offline
+//
+// Expected:
+// * Non-sponsored suggestions: on
+// * Sponsored suggestions: on
+// * Data collection: on
+add_task(async function() {
+  await doMigrateTest({
+    testOverrides: TEST_OVERRIDES,
+    initialUserBranch: {
+      "quicksuggest.migrationVersion": 1,
+      "quicksuggest.scenario": "offline",
+      "quicksuggest.dataCollection.enabled": true,
+    },
+    scenario: "offline",
+    expectedPrefs: {
+      defaultBranch: DEFAULT_PREFS.offline,
+      userBranch: {
+        "quicksuggest.dataCollection.enabled": true,
+      },
+    },
+  });
+});
+
+// Migrating from:
+// * Version 1 prefs
+// * Offline
+// * Non-sponsored suggestions: user left on
+// * Sponsored suggestions: user turned off
+// * Data collection: user left off
+//
+// Scenario when migration occurs:
+// * Offline
+//
+// Expected:
+// * Non-sponsored suggestions: on
+// * Sponsored suggestions: off
+// * Data collection: off
+add_task(async function() {
+  await doMigrateTest({
+    testOverrides: TEST_OVERRIDES,
+    initialUserBranch: {
+      "quicksuggest.migrationVersion": 1,
+      "quicksuggest.scenario": "offline",
+      "suggest.quicksuggest.sponsored": false,
+    },
+    scenario: "offline",
+    expectedPrefs: {
+      defaultBranch: DEFAULT_PREFS.offline,
+      userBranch: {
+        "suggest.quicksuggest.sponsored": false,
+      },
+    },
+  });
+});
+
+// Migrating from:
+// * Version 1 prefs
+// * Offline
+// * Non-sponsored suggestions: user turned off
+// * Sponsored suggestions: user turned off
+// * Data collection: user left off
+//
+// Scenario when migration occurs:
+// * Offline
+//
+// Expected:
+// * Non-sponsored suggestions: off
+// * Sponsored suggestions: off
+// * Data collection: off
+add_task(async function() {
+  await doMigrateTest({
+    testOverrides: TEST_OVERRIDES,
+    initialUserBranch: {
+      "quicksuggest.migrationVersion": 1,
+      "quicksuggest.scenario": "offline",
+      "suggest.quicksuggest.nonsponsored": false,
+      "suggest.quicksuggest.sponsored": false,
+    },
+    scenario: "offline",
+    expectedPrefs: {
+      defaultBranch: DEFAULT_PREFS.offline,
+      userBranch: {
+        "suggest.quicksuggest.nonsponsored": false,
+        "suggest.quicksuggest.sponsored": false,
+      },
+    },
+  });
+});
+
+// The following tasks test OFFLINE VERSION 1 to ONLINE
+
+// Migrating from:
+// * Version 1 prefs
+// * Offline
+// * Non-sponsored suggestions: user left on
+// * Sponsored suggestions: user left on
+// * Data collection: user left off
+//
+// Scenario when migration occurs:
+// * Online
+//
+// Expected:
+// * Non-sponsored suggestions: on
+// * Sponsored suggestions: on
+// * Data collection: off
+add_task(async function() {
+  await doMigrateTest({
+    testOverrides: TEST_OVERRIDES,
+    initialUserBranch: {
+      "quicksuggest.migrationVersion": 1,
+      "quicksuggest.scenario": "offline",
+    },
+    scenario: "online",
+    expectedPrefs: {
+      defaultBranch: DEFAULT_PREFS.online,
+    },
+  });
+});
+
+// Migrating from:
+// * Version 1 prefs
+// * Offline
+// * Non-sponsored suggestions: user left on
+// * Sponsored suggestions: user turned off
+// * Data collection: user left off
+//
+// Scenario when migration occurs:
+// * Online
+//
+// Expected:
+// * Non-sponsored suggestions: on
+// * Sponsored suggestions: off
+// * Data collection: off
+add_task(async function() {
+  await doMigrateTest({
+    testOverrides: TEST_OVERRIDES,
+    initialUserBranch: {
+      "quicksuggest.migrationVersion": 1,
+      "quicksuggest.scenario": "offline",
+      "suggest.quicksuggest.sponsored": false,
+    },
+    scenario: "online",
+    expectedPrefs: {
+      defaultBranch: DEFAULT_PREFS.online,
+      userBranch: {
+        "suggest.quicksuggest.sponsored": false,
+      },
+    },
+  });
+});
+
+// Migrating from:
+// * Version 1 prefs
+// * Offline
+// * Non-sponsored suggestions: user turned off
+// * Sponsored suggestions: user turned off
+// * Data collection: user left off
+//
+// Scenario when migration occurs:
+// * Online
+//
+// Expected:
+// * Non-sponsored suggestions: on
+// * Sponsored suggestions: off
+// * Data collection: off
+add_task(async function() {
+  await doMigrateTest({
+    testOverrides: TEST_OVERRIDES,
+    initialUserBranch: {
+      "quicksuggest.migrationVersion": 1,
+      "quicksuggest.scenario": "offline",
+      "suggest.quicksuggest.nonsponsored": false,
+      "suggest.quicksuggest.sponsored": false,
+    },
+    scenario: "online",
+    expectedPrefs: {
+      defaultBranch: DEFAULT_PREFS.online,
+      userBranch: {
+        "suggest.quicksuggest.nonsponsored": false,
+        "suggest.quicksuggest.sponsored": false,
+      },
+    },
+  });
+});
+
+// The following tasks test ONLINE VERSION 1 to ONLINE when the user was NOT
+// SHOWN THE MODAL (e.g., because they didn't restart)
+
+// Migrating from:
+// * Version 1 prefs
+// * Online
+// * Modal shown: no
+// * Non-sponsored suggestions: user left off
+// * Sponsored suggestions: user left off
+// * Data collection: user left off
+//
+// Scenario when migration occurs:
+// * Online
+//
+// Expected:
+// * Non-sponsored suggestions: off
+// * Sponsored suggestions: off
+// * Data collection: off
+add_task(async function() {
+  await doMigrateTest({
+    testOverrides: TEST_OVERRIDES,
+    initialUserBranch: {
+      "quicksuggest.migrationVersion": 1,
+      "quicksuggest.scenario": "online",
+    },
+    scenario: "online",
+    expectedPrefs: {
+      defaultBranch: DEFAULT_PREFS.online,
+      userBranch: {
+        "suggest.quicksuggest.nonsponsored": false,
+        "suggest.quicksuggest.sponsored": false,
+      },
+    },
+  });
+});
+
+// Migrating from:
+// * Version 1 prefs
+// * Online
+// * Modal shown: no
+// * Non-sponsored suggestions: user left off
+// * Sponsored suggestions: user left off
+// * Data collection: user turned on
+//
+// Scenario when migration occurs:
+// * Online
+//
+// Expected:
+// * Non-sponsored suggestions: off
+// * Sponsored suggestions: off
+// * Data collection: on
+add_task(async function() {
+  await doMigrateTest({
+    testOverrides: TEST_OVERRIDES,
+    initialUserBranch: {
+      "quicksuggest.migrationVersion": 1,
+      "quicksuggest.scenario": "online",
+      "quicksuggest.dataCollection.enabled": true,
+    },
+    scenario: "online",
+    expectedPrefs: {
+      defaultBranch: DEFAULT_PREFS.online,
+      userBranch: {
+        "suggest.quicksuggest.nonsponsored": false,
+        "suggest.quicksuggest.sponsored": false,
+        "quicksuggest.dataCollection.enabled": true,
+      },
+    },
+  });
+});
+
+// Migrating from:
+// * Version 1 prefs
+// * Online
+// * Modal shown: no
+// * Non-sponsored suggestions: user left off
+// * Sponsored suggestions: user turned on
+// * Data collection: user left off
+//
+// Scenario when migration occurs:
+// * Online
+//
+// Expected:
+// * Non-sponsored suggestions: off
+// * Sponsored suggestions: on
+// * Data collection: off
+add_task(async function() {
+  await doMigrateTest({
+    testOverrides: TEST_OVERRIDES,
+    initialUserBranch: {
+      "quicksuggest.migrationVersion": 1,
+      "quicksuggest.scenario": "online",
+      "suggest.quicksuggest.sponsored": true,
+    },
+    scenario: "online",
+    expectedPrefs: {
+      defaultBranch: DEFAULT_PREFS.online,
+      userBranch: {
+        "suggest.quicksuggest.nonsponsored": false,
+        "suggest.quicksuggest.sponsored": true,
+      },
+    },
+  });
+});
+
+// Migrating from:
+// * Version 1 prefs
+// * Online
+// * Modal shown: no
+// * Non-sponsored suggestions: user left off
+// * Sponsored suggestions: user turned on
+// * Data collection: user turned on
+//
+// Scenario when migration occurs:
+// * Online
+//
+// Expected:
+// * Non-sponsored suggestions: off
+// * Sponsored suggestions: on
+// * Data collection: on
+add_task(async function() {
+  await doMigrateTest({
+    testOverrides: TEST_OVERRIDES,
+    initialUserBranch: {
+      "quicksuggest.migrationVersion": 1,
+      "quicksuggest.scenario": "online",
+      "suggest.quicksuggest.sponsored": true,
+      "quicksuggest.dataCollection.enabled": true,
+    },
+    scenario: "online",
+    expectedPrefs: {
+      defaultBranch: DEFAULT_PREFS.online,
+      userBranch: {
+        "suggest.quicksuggest.nonsponsored": false,
+        "suggest.quicksuggest.sponsored": true,
+        "quicksuggest.dataCollection.enabled": true,
+      },
+    },
+  });
+});
+
+// Migrating from:
+// * Version 1 prefs
+// * Online
+// * Modal shown: no
+// * Non-sponsored suggestions: user turned on
+// * Sponsored suggestions: user left off
+// * Data collection: user left off
+//
+// Scenario when migration occurs:
+// * Online
+//
+// Expected:
+// * Non-sponsored suggestions: on
+// * Sponsored suggestions: off
+// * Data collection: off
+add_task(async function() {
+  await doMigrateTest({
+    testOverrides: TEST_OVERRIDES,
+    initialUserBranch: {
+      "quicksuggest.migrationVersion": 1,
+      "quicksuggest.scenario": "online",
+      "suggest.quicksuggest.nonsponsored": true,
+    },
+    scenario: "online",
+    expectedPrefs: {
+      defaultBranch: DEFAULT_PREFS.online,
+      userBranch: {
+        "suggest.quicksuggest.nonsponsored": true,
+        "suggest.quicksuggest.sponsored": false,
+      },
+    },
+  });
+});
+
+// Migrating from:
+// * Version 1 prefs
+// * Online
+// * Modal shown: no
+// * Non-sponsored suggestions: user turned on
+// * Sponsored suggestions: user left off
+// * Data collection: user turned on
+//
+// Scenario when migration occurs:
+// * Online
+//
+// Expected:
+// * Non-sponsored suggestions: on
+// * Sponsored suggestions: off
+// * Data collection: on
+add_task(async function() {
+  await doMigrateTest({
+    testOverrides: TEST_OVERRIDES,
+    initialUserBranch: {
+      "quicksuggest.migrationVersion": 1,
+      "quicksuggest.scenario": "online",
+      "suggest.quicksuggest.nonsponsored": true,
+      "quicksuggest.dataCollection.enabled": true,
+    },
+    scenario: "online",
+    expectedPrefs: {
+      defaultBranch: DEFAULT_PREFS.online,
+      userBranch: {
+        "suggest.quicksuggest.nonsponsored": true,
+        "suggest.quicksuggest.sponsored": false,
+        "quicksuggest.dataCollection.enabled": true,
+      },
+    },
+  });
+});
+
+// Migrating from:
+// * Version 1 prefs
+// * Online
+// * Modal shown: no
+// * Non-sponsored suggestions: user turned on
+// * Sponsored suggestions: user turned on
+// * Data collection: user left off
+//
+// Scenario when migration occurs:
+// * Online
+//
+// Expected:
+// * Non-sponsored suggestions: on
+// * Sponsored suggestions: on
+// * Data collection: off
+add_task(async function() {
+  await doMigrateTest({
+    testOverrides: TEST_OVERRIDES,
+    initialUserBranch: {
+      "quicksuggest.migrationVersion": 1,
+      "quicksuggest.scenario": "online",
+      "suggest.quicksuggest.nonsponsored": true,
+      "suggest.quicksuggest.sponsored": true,
+    },
+    scenario: "online",
+    expectedPrefs: {
+      defaultBranch: DEFAULT_PREFS.online,
+      userBranch: {
+        "suggest.quicksuggest.nonsponsored": true,
+        "suggest.quicksuggest.sponsored": true,
+      },
+    },
+  });
+});
+
+// Migrating from:
+// * Version 1 prefs
+// * Online
+// * Modal shown: no
+// * Non-sponsored suggestions: user turned on
+// * Sponsored suggestions: user turned on
+// * Data collection: user turned on
+//
+// Scenario when migration occurs:
+// * Online
+//
+// Expected:
+// * Non-sponsored suggestions: on
+// * Sponsored suggestions: on
+// * Data collection: on
+add_task(async function() {
+  await doMigrateTest({
+    testOverrides: TEST_OVERRIDES,
+    initialUserBranch: {
+      "quicksuggest.migrationVersion": 1,
+      "quicksuggest.scenario": "online",
+      "suggest.quicksuggest.nonsponsored": true,
+      "suggest.quicksuggest.sponsored": true,
+      "quicksuggest.dataCollection.enabled": true,
+    },
+    scenario: "online",
+    expectedPrefs: {
+      defaultBranch: DEFAULT_PREFS.online,
+      userBranch: {
+        "suggest.quicksuggest.nonsponsored": true,
+        "suggest.quicksuggest.sponsored": true,
+        "quicksuggest.dataCollection.enabled": true,
+      },
+    },
+  });
+});
+
+// The following tasks test ONLINE VERSION 1 to ONLINE when the user WAS SHOWN
+// THE MODAL WHILE PREFS WERE UNVERSIONED
+
+// Migrating from:
+// * Version 1 prefs
+// * Online
+// * Modal shown: yes, while prefs were unversioned
+// * User opted in: no
+// * Non-sponsored suggestions: user left off
+// * Sponsored suggestions: user left off
+// * Data collection: user left off
+//
+// Scenario when migration occurs:
+// * Online
+//
+// Expected:
+// * Non-sponsored suggestions: off
+// * Sponsored suggestions: off
+// * Data collection: off
+add_task(async function() {
+  await doMigrateTest({
+    testOverrides: TEST_OVERRIDES,
+    initialUserBranch: {
+      "quicksuggest.migrationVersion": 1,
+      "quicksuggest.scenario": "online",
+      "quicksuggest.showedOnboardingDialog": true,
+    },
+    scenario: "online",
+    expectedPrefs: {
+      defaultBranch: DEFAULT_PREFS.online,
+      userBranch: {
+        "suggest.quicksuggest.nonsponsored": false,
+        "suggest.quicksuggest.sponsored": false,
+      },
+    },
+  });
+});
+
+// Migrating from:
+// * Version 1 prefs
+// * Online
+// * Modal shown: yes, while prefs were unversioned
+// * User opted in: no
+// * Non-sponsored suggestions: user turned on
+// * Sponsored suggestions: user left off
+// * Data collection: user left off
+//
+// Scenario when migration occurs:
+// * Online
+//
+// Expected:
+// * Non-sponsored suggestions: on
+// * Sponsored suggestions: off
+// * Data collection: off
+add_task(async function() {
+  await doMigrateTest({
+    testOverrides: TEST_OVERRIDES,
+    initialUserBranch: {
+      "quicksuggest.migrationVersion": 1,
+      "quicksuggest.scenario": "online",
+      "quicksuggest.showedOnboardingDialog": true,
+      "suggest.quicksuggest.nonsponsored": true,
+    },
+    scenario: "online",
+    expectedPrefs: {
+      defaultBranch: DEFAULT_PREFS.online,
+      userBranch: {
+        "suggest.quicksuggest.nonsponsored": true,
+        "suggest.quicksuggest.sponsored": false,
+      },
+    },
+  });
+});
+
+// Migrating from:
+// * Version 1 prefs
+// * Online
+// * Modal shown: yes, while prefs were unversioned
+// * User opted in: yes
+// * Non-sponsored suggestions: user left on
+// * Sponsored suggestions: user left on
+// * Data collection: user left on
+//
+// Scenario when migration occurs:
+// * Online
+//
+// Expected:
+// * Non-sponsored suggestions: on
+// * Sponsored suggestions: on
+// * Data collection: on
+add_task(async function() {
+  await doMigrateTest({
+    testOverrides: TEST_OVERRIDES,
+    initialUserBranch: {
+      "quicksuggest.migrationVersion": 1,
+      "quicksuggest.scenario": "online",
+      "quicksuggest.showedOnboardingDialog": true,
+      "suggest.quicksuggest.nonsponsored": true,
+      "suggest.quicksuggest.sponsored": true,
+      "quicksuggest.dataCollection.enabled": true,
+    },
+    scenario: "online",
+    expectedPrefs: {
+      defaultBranch: DEFAULT_PREFS.online,
+      userBranch: {
+        "suggest.quicksuggest.nonsponsored": true,
+        "suggest.quicksuggest.sponsored": true,
+        "quicksuggest.dataCollection.enabled": true,
+      },
+    },
+  });
+});
+
+// Migrating from:
+// * Version 1 prefs
+// * Online
+// * Modal shown: yes, while prefs were unversioned
+// * User opted in: yes
+// * Non-sponsored suggestions: user turned off
+// * Sponsored suggestions: user left on
+// * Data collection: user left on
+//
+// Scenario when migration occurs:
+// * Online
+//
+// Expected:
+// * Non-sponsored suggestions: off
+// * Sponsored suggestions: on
+// * Data collection: on
+add_task(async function() {
+  await doMigrateTest({
+    testOverrides: TEST_OVERRIDES,
+    initialUserBranch: {
+      "quicksuggest.migrationVersion": 1,
+      "quicksuggest.scenario": "online",
+      "quicksuggest.showedOnboardingDialog": true,
+      "suggest.quicksuggest.sponsored": true,
+      "quicksuggest.dataCollection.enabled": true,
+    },
+    scenario: "online",
+    expectedPrefs: {
+      defaultBranch: DEFAULT_PREFS.online,
+      userBranch: {
+        "suggest.quicksuggest.nonsponsored": false,
+        "suggest.quicksuggest.sponsored": true,
+        "quicksuggest.dataCollection.enabled": true,
+      },
+    },
+  });
+});
+
+// Migrating from:
+// * Version 1 prefs
+// * Online
+// * Modal shown: yes, while prefs were unversioned
+// * User opted in: yes
+// * Non-sponsored suggestions: user left on
+// * Sponsored suggestions: user left on
+// * Data collection: user turned off
+//
+// Scenario when migration occurs:
+// * Online
+//
+// Expected:
+// * Non-sponsored suggestions: on
+// * Sponsored suggestions: on
+// * Data collection: on
+add_task(async function() {
+  await doMigrateTest({
+    testOverrides: TEST_OVERRIDES,
+    initialUserBranch: {
+      "quicksuggest.migrationVersion": 1,
+      "quicksuggest.scenario": "online",
+      "quicksuggest.showedOnboardingDialog": true,
+      "suggest.quicksuggest.nonsponsored": true,
+      "suggest.quicksuggest.sponsored": true,
+      "quicksuggest.dataCollection.enabled": false,
+    },
+    scenario: "online",
+    expectedPrefs: {
+      defaultBranch: DEFAULT_PREFS.online,
+      userBranch: {
+        "suggest.quicksuggest.nonsponsored": true,
+        "suggest.quicksuggest.sponsored": true,
+        "quicksuggest.dataCollection.enabled": false,
+      },
+    },
+  });
+});
+
+// The following tasks test ONLINE VERSION 1 to ONLINE when the user WAS SHOWN
+// THE MODAL WHILE PREFS WERE VERSION 1
+
+// Migrating from:
+// * Version 1 prefs
+// * Online
+// * Modal shown: yes, while prefs were version 1
+// * User opted in: no
+// * Non-sponsored suggestions: user left off
+// * Sponsored suggestions: user left off
+// * Data collection: user left off
+//
+// Scenario when migration occurs:
+// * Online
+//
+// Expected:
+// * Non-sponsored suggestions: off
+// * Sponsored suggestions: off
+// * Data collection: off
+add_task(async function() {
+  await doMigrateTest({
+    testOverrides: TEST_OVERRIDES,
+    initialUserBranch: {
+      "quicksuggest.migrationVersion": 1,
+      "quicksuggest.scenario": "online",
+      "quicksuggest.showedOnboardingDialog": true,
+      "quicksuggest.onboardingDialogChoice": "not_now_link",
+      "suggest.quicksuggest.nonsponsored": false,
+      "suggest.quicksuggest.sponsored": false,
+      "quicksuggest.dataCollection.enabled": false,
+    },
+    scenario: "online",
+    expectedPrefs: {
+      defaultBranch: DEFAULT_PREFS.online,
+      userBranch: {
+        "suggest.quicksuggest.nonsponsored": false,
+        "suggest.quicksuggest.sponsored": false,
+        "quicksuggest.dataCollection.enabled": false,
+      },
+    },
+  });
+});
+
+// Migrating from:
+// * Version 1 prefs
+// * Online
+// * Modal shown: yes, while prefs were version 1
+// * User opted in: yes
+// * Non-sponsored suggestions: user left on
+// * Sponsored suggestions: user left on
+// * Data collection: user left on
+//
+// Scenario when migration occurs:
+// * Online
+//
+// Expected:
+// * Non-sponsored suggestions: on
+// * Sponsored suggestions: on
+// * Data collection: on
+add_task(async function() {
+  await doMigrateTest({
+    testOverrides: TEST_OVERRIDES,
+    initialUserBranch: {
+      "quicksuggest.migrationVersion": 1,
+      "quicksuggest.scenario": "online",
+      "quicksuggest.showedOnboardingDialog": true,
+      "quicksuggest.onboardingDialogChoice": "accept",
+      "suggest.quicksuggest.nonsponsored": true,
+      "suggest.quicksuggest.sponsored": true,
+      "quicksuggest.dataCollection.enabled": true,
+    },
+    scenario: "online",
+    expectedPrefs: {
+      defaultBranch: DEFAULT_PREFS.online,
+      userBranch: {
+        "suggest.quicksuggest.nonsponsored": true,
+        "suggest.quicksuggest.sponsored": true,
+        "quicksuggest.dataCollection.enabled": true,
+      },
+    },
+  });
+});
+
+async function withOnlineExperiment(callback) {
+  let {
+    enrollmentPromise,
+    doExperimentCleanup,
+  } = ExperimentFakes.enrollmentHelper(
+    ExperimentFakes.recipe("firefox-suggest-offline-vs-online", {
+      active: true,
+      branches: [
+        {
+          slug: "treatment",
+          features: [
+            {
+              featureId: NimbusFeatures.urlbar.featureId,
+              value: {
+                enabled: true,
+              },
+            },
+          ],
+        },
+      ],
+    })
+  );
+  await enrollmentPromise;
+  await callback();
+  await doExperimentCleanup();
+}
diff --git a/browser/components/urlbar/tests/quicksuggest/unit/test_quicksuggest_nonUniqueKeywords.js b/browser/components/urlbar/tests/quicksuggest/unit/test_quicksuggest_nonUniqueKeywords.js
new file mode 100644
index 0000000000..6526de7e24
--- /dev/null
+++ b/browser/components/urlbar/tests/quicksuggest/unit/test_quicksuggest_nonUniqueKeywords.js
@@ -0,0 +1,283 @@
+/* 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/. */
+
+// Tests non-unique keywords, i.e., keywords used by multiple suggestions.
+
+"use strict";
+
+// For each of these objects, the test creates a quick suggest result (the kind
+// stored in the remote settings data, not a urlbar result), the corresponding
+// expected quick suggest suggestion, and the corresponding expected urlbar
+// result. The test assumes results and suggestions are returned in the order
+// listed here.
+let SUGGESTIONS_DATA = [
+  {
+    keywords: ["aaa"],
+    isSponsored: true,
+  },
+  {
+    keywords: ["aaa", "bbb"],
+    isSponsored: false,
+    score: 2 * RemoteSettingsClient.DEFAULT_SUGGESTION_SCORE,
+  },
+  {
+    keywords: ["bbb"],
+    isSponsored: true,
+    score: 4 * RemoteSettingsClient.DEFAULT_SUGGESTION_SCORE,
+  },
+  {
+    keywords: ["bbb"],
+    isSponsored: false,
+    score: 3 * RemoteSettingsClient.DEFAULT_SUGGESTION_SCORE,
+  },
+  {
+    keywords: ["ccc"],
+    isSponsored: true,
+  },
+];
+
+// Test cases. In this object, keywords map to subtest cases. For each keyword,
+// the test calls `fetch(keyword)` and checks that the indexes (relative to
+// `SUGGESTIONS_DATA`) of the returned quick suggest results are the ones in
+// `expectedIndexes`. Then the test does a series of urlbar searches using the
+// keyword as the search string, one search per object in `searches`. Sponsored
+// and non-sponsored urlbar results are enabled as defined by `sponsored` and
+// `nonsponsored`. `expectedIndex` is the expected index (relative to
+// `SUGGESTIONS_DATA`) of the returned urlbar result.
+let TESTS = {
+  aaa: {
+    // 0: sponsored
+    // 1: nonsponsored, score = 2x
+    expectedIndexes: [0, 1],
+    searches: [
+      {
+        sponsored: true,
+        nonsponsored: true,
+        expectedIndex: 1,
+      },
+      {
+        sponsored: false,
+        nonsponsored: true,
+        expectedIndex: 1,
+      },
+      {
+        sponsored: true,
+        nonsponsored: false,
+        expectedIndex: 0,
+      },
+      {
+        sponsored: false,
+        nonsponsored: false,
+        expectedIndex: undefined,
+      },
+    ],
+  },
+  bbb: {
+    // 1: nonsponsored, score = 2x
+    // 2: sponsored, score = 4x,
+    // 3: nonsponsored, score = 3x
+    expectedIndexes: [1, 2, 3],
+    searches: [
+      {
+        sponsored: true,
+        nonsponsored: true,
+        expectedIndex: 2,
+      },
+      {
+        sponsored: false,
+        nonsponsored: true,
+        expectedIndex: 3,
+      },
+      {
+        sponsored: true,
+        nonsponsored: false,
+        expectedIndex: 2,
+      },
+      {
+        sponsored: false,
+        nonsponsored: false,
+        expectedIndex: undefined,
+      },
+    ],
+  },
+  ccc: {
+    // 4: sponsored
+    expectedIndexes: [4],
+    searches: [
+      {
+        sponsored: true,
+        nonsponsored: true,
+        expectedIndex: 4,
+      },
+      {
+        sponsored: false,
+        nonsponsored: true,
+        expectedIndex: undefined,
+      },
+      {
+        sponsored: true,
+        nonsponsored: false,
+        expectedIndex: 4,
+      },
+      {
+        sponsored: false,
+        nonsponsored: false,
+        expectedIndex: undefined,
+      },
+    ],
+  },
+};
+
+add_task(async function() {
+  UrlbarPrefs.set("quicksuggest.enabled", true);
+
+  // Create results and suggestions based on `SUGGESTIONS_DATA`.
+  let qsResults = [];
+  let qsSuggestions = [];
+  let urlbarResults = [];
+  for (let i = 0; i < SUGGESTIONS_DATA.length; i++) {
+    let { keywords, isSponsored, score } = SUGGESTIONS_DATA[i];
+
+    // quick suggest result
+    let qsResult = {
+      keywords,
+      score,
+      id: i,
+      url: "http://example.com/" + i,
+      title: "Title " + i,
+      click_url: "http://example.com/click",
+      impression_url: "http://example.com/impression",
+      advertiser: "TestAdvertiser",
+      iab_category: isSponsored ? "22 - Shopping" : "5 - Education",
+    };
+    qsResults.push(qsResult);
+
+    // expected quick suggest suggestion
+    let qsSuggestion = {
+      ...qsResult,
+      block_id: qsResult.id,
+      is_sponsored: isSponsored,
+      score:
+        typeof score == "number"
+          ? score
+          : RemoteSettingsClient.DEFAULT_SUGGESTION_SCORE,
+      source: "remote-settings",
+      icon: null,
+      position: undefined,
+    };
+    delete qsSuggestion.keywords;
+    delete qsSuggestion.id;
+    qsSuggestions.push(qsSuggestion);
+
+    // expected urlbar result
+    urlbarResults.push({
+      type: UrlbarUtils.RESULT_TYPE.URL,
+      source: UrlbarUtils.RESULT_SOURCE.SEARCH,
+      heuristic: false,
+      payload: {
+        isSponsored,
+        sponsoredBlockId: qsResult.id,
+        url: qsResult.url,
+        originalUrl: qsResult.url,
+        displayUrl: qsResult.url,
+        title: qsResult.title,
+        sponsoredClickUrl: qsResult.click_url,
+        sponsoredImpressionUrl: qsResult.impression_url,
+        sponsoredAdvertiser: qsResult.advertiser,
+        sponsoredIabCategory: qsResult.iab_category,
+        icon: null,
+        helpUrl: QuickSuggest.HELP_URL,
+        helpL10n: { id: "firefox-suggest-urlbar-learn-more" },
+        isBlockable: false,
+        blockL10n: { id: "firefox-suggest-urlbar-block" },
+        source: "remote-settings",
+      },
+    });
+  }
+
+  await QuickSuggestTestUtils.ensureQuickSuggestInit({
+    remoteSettingsResults: qsResults,
+  });
+
+  // Run a test for each keyword.
+  for (let [keyword, test] of Object.entries(TESTS)) {
+    info("Running subtest " + JSON.stringify({ keyword, test }));
+
+    let { expectedIndexes, searches } = test;
+
+    // Call `fetch()`.
+    Assert.deepEqual(
+      await QuickSuggest.remoteSettings.fetch(keyword),
+      expectedIndexes.map(i => ({
+        ...qsSuggestions[i],
+        full_keyword: keyword,
+      })),
+      `fetch() for ${keyword}`
+    );
+
+    // Make sure the expected result object(s) are stored correctly.
+    let mapValue = QuickSuggest.remoteSettings._test_resultsByKeyword.get(
+      keyword
+    );
+    if (expectedIndexes.length == 1) {
+      Assert.ok(!Array.isArray(mapValue), "The map value is not an array");
+      Assert.deepEqual(
+        mapValue,
+        qsResults[expectedIndexes[0]],
+        "The map value is the expected result object"
+      );
+    } else {
+      Assert.ok(Array.isArray(mapValue), "The map value is an array");
+      Assert.greater(mapValue.length, 0, "The array is not empty");
+      Assert.deepEqual(
+        mapValue,
+        expectedIndexes.map(i => qsResults[i]),
+        "The map value is the expected array of result objects"
+      );
+    }
+
+    // Now do a urlbar search for the keyword with all possible combinations of
+    // sponsored and non-sponsored suggestions enabled and disabled.
+    for (let sponsored of [true, false]) {
+      for (let nonsponsored of [true, false]) {
+        // Find the matching `searches` object.
+        let search = searches.find(
+          s => s.sponsored == sponsored && s.nonsponsored == nonsponsored
+        );
+        Assert.ok(
+          search,
+          "Sanity check: Search test case specified for " +
+            JSON.stringify({ keyword, sponsored, nonsponsored })
+        );
+
+        info(
+          "Running urlbar search subtest " +
+            JSON.stringify({ keyword, expectedIndexes, search })
+        );
+
+        UrlbarPrefs.set("suggest.quicksuggest.sponsored", sponsored);
+        UrlbarPrefs.set("suggest.quicksuggest.nonsponsored", nonsponsored);
+
+        // Set up the search and do it.
+        let context = createContext(keyword, {
+          providers: [UrlbarProviderQuickSuggest.name],
+          isPrivate: false,
+        });
+
+        let matches = [];
+        if (search.expectedIndex !== undefined) {
+          matches.push({
+            ...urlbarResults[search.expectedIndex],
+            payload: {
+              ...urlbarResults[search.expectedIndex].payload,
+              qsSuggestion: keyword,
+            },
+          });
+        }
+
+        await check_results({ context, matches });
+      }
+    }
+  }
+});
diff --git a/browser/components/urlbar/tests/quicksuggest/unit/test_quicksuggest_offlineDefault.js b/browser/components/urlbar/tests/quicksuggest/unit/test_quicksuggest_offlineDefault.js
new file mode 100644
index 0000000000..7330dd4fd5
--- /dev/null
+++ b/browser/components/urlbar/tests/quicksuggest/unit/test_quicksuggest_offlineDefault.js
@@ -0,0 +1,127 @@
+/* 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/. */
+
+// Tests `UrlbarPrefs.updateFirefoxSuggestScenario` in isolation under the
+// assumption that the offline scenario should be enabled by default for US en.
+
+"use strict";
+
+ChromeUtils.defineESModuleGetters(this, {
+  Region: "resource://gre/modules/Region.sys.mjs",
+});
+
+// All the prefs that `updateFirefoxSuggestScenario` sets along with the
+// expected default-branch values when offline is enabled and when it's not
+// enabled.
+const PREFS = [
+  {
+    name: "browser.urlbar.quicksuggest.enabled",
+    get: "getBoolPref",
+    set: "setBoolPref",
+    expectedOfflineValue: true,
+    expectedOtherValue: false,
+  },
+  {
+    name: "browser.urlbar.quicksuggest.shouldShowOnboardingDialog",
+    get: "getBoolPref",
+    set: "setBoolPref",
+    expectedOfflineValue: false,
+    expectedOtherValue: true,
+  },
+  {
+    name: "browser.urlbar.suggest.quicksuggest.nonsponsored",
+    get: "getBoolPref",
+    set: "setBoolPref",
+    expectedOfflineValue: true,
+    expectedOtherValue: false,
+  },
+  {
+    name: "browser.urlbar.suggest.quicksuggest.sponsored",
+    get: "getBoolPref",
+    set: "setBoolPref",
+    expectedOfflineValue: true,
+    expectedOtherValue: false,
+  },
+];
+
+add_task(async function init() {
+  await UrlbarTestUtils.initNimbusFeature();
+});
+
+add_task(async function test() {
+  let tests = [
+    { locale: "en-US", home: "US", expectedOfflineDefault: true },
+    { locale: "en-US", home: "CA", expectedOfflineDefault: false },
+    { locale: "en-CA", home: "US", expectedOfflineDefault: true },
+    { locale: "en-CA", home: "CA", expectedOfflineDefault: false },
+    { locale: "en-GB", home: "US", expectedOfflineDefault: true },
+    { locale: "en-GB", home: "GB", expectedOfflineDefault: false },
+    { locale: "de", home: "US", expectedOfflineDefault: false },
+    { locale: "de", home: "DE", expectedOfflineDefault: false },
+  ];
+  for (let { locale, home, expectedOfflineDefault } of tests) {
+    await doTest({ locale, home, expectedOfflineDefault });
+  }
+});
+
+/**
+ * Sets the app's locale and region, calls
+ * `UrlbarPrefs.updateFirefoxSuggestScenario`, and asserts that the pref values
+ * are correct.
+ *
+ * @param {object} options
+ *   Options object.
+ * @param {string} options.locale
+ *   The locale to simulate.
+ * @param {string} options.home
+ *   The "home" region to simulate.
+ * @param {boolean} options.expectedOfflineDefault
+ *   The expected value of whether offline should be enabled by default given
+ *   the locale and region.
+ */
+async function doTest({ locale, home, expectedOfflineDefault }) {
+  // Setup: Clear any user values and save original default-branch values.
+  for (let pref of PREFS) {
+    Services.prefs.clearUserPref(pref.name);
+    pref.originalDefault = Services.prefs
+      .getDefaultBranch(pref.name)
+      [pref.get]("");
+  }
+
+  // Set the region and locale, call the function, check the pref values.
+  Region._setHomeRegion(home, false);
+  await QuickSuggestTestUtils.withLocales([locale], async () => {
+    await UrlbarPrefs.updateFirefoxSuggestScenario();
+    for (let { name, get, expectedOfflineValue, expectedOtherValue } of PREFS) {
+      let expectedValue = expectedOfflineDefault
+        ? expectedOfflineValue
+        : expectedOtherValue;
+
+      // Check the default-branch value.
+      Assert.strictEqual(
+        Services.prefs.getDefaultBranch(name)[get](""),
+        expectedValue,
+        `Default pref value for ${name}, locale ${locale}, home ${home}`
+      );
+
+      // For good measure, also check the return value of `UrlbarPrefs.get`
+      // since we use it everywhere. The value should be the same as the
+      // default-branch value.
+      UrlbarPrefs.get(
+        name.replace("browser.urlbar.", ""),
+        expectedValue,
+        `UrlbarPrefs.get() value for ${name}, locale ${locale}, home ${home}`
+      );
+    }
+  });
+
+  // Teardown: Restore original default-branch values for the next task.
+  for (let { name, originalDefault, set } of PREFS) {
+    if (originalDefault === undefined) {
+      Services.prefs.deleteBranch(name);
+    } else {
+      Services.prefs.getDefaultBranch(name)[set]("", originalDefault);
+    }
+  }
+}
diff --git a/browser/components/urlbar/tests/quicksuggest/unit/test_quicksuggest_positionInSuggestions.js b/browser/components/urlbar/tests/quicksuggest/unit/test_quicksuggest_positionInSuggestions.js
new file mode 100644
index 0000000000..cba86b71a1
--- /dev/null
+++ b/browser/components/urlbar/tests/quicksuggest/unit/test_quicksuggest_positionInSuggestions.js
@@ -0,0 +1,485 @@
+/* Any copyright is dedicated to the Public Domain.
+ * http://creativecommons.org/publicdomain/zero/1.0/ */
+
+"use strict";
+
+/**
+ * Tests for quick suggest result position specified in suggestions.
+ */
+
+ChromeUtils.defineESModuleGetters(this, {
+  UrlbarProviderHeuristicFallback:
+    "resource:///modules/UrlbarProviderHeuristicFallback.sys.mjs",
+  UrlbarProviderPlaces: "resource:///modules/UrlbarProviderPlaces.sys.mjs",
+  UrlbarProviderTabToSearch:
+    "resource:///modules/UrlbarProviderTabToSearch.sys.mjs",
+});
+
+const SPONSORED_SECOND_POSITION_RESULT = {
+  id: 1,
+  url: "http://example.com/?q=sponsored-second",
+  title: "sponsored second",
+  keywords: ["s-s"],
+  click_url: "http://click.reporting.test.com/",
+  impression_url: "http://impression.reporting.test.com/",
+  advertiser: "TestAdvertiser",
+  iab_category: "22 - Shopping",
+  position: 1,
+};
+const SPONSORED_NORMAL_POSITION_RESULT = {
+  id: 2,
+  url: "http://example.com/?q=sponsored-normal",
+  title: "sponsored normal",
+  keywords: ["s-n"],
+  click_url: "http://click.reporting.test.com/",
+  impression_url: "http://impression.reporting.test.com/",
+  advertiser: "TestAdvertiser",
+  iab_category: "22 - Shopping",
+};
+const NONSPONSORED_SECOND_POSITION_RESULT = {
+  id: 3,
+  url: "http://example.com/?q=nonsponsored-second",
+  title: "nonsponsored second",
+  keywords: ["n-s"],
+  click_url: "http://click.reporting.test.com/nonsponsored",
+  impression_url: "http://impression.reporting.test.com/nonsponsored",
+  advertiser: "TestAdvertiserNonSponsored",
+  iab_category: "5 - Education",
+  position: 1,
+};
+const NONSPONSORED_NORMAL_POSITION_RESULT = {
+  id: 4,
+  url: "http://example.com/?q=nonsponsored-normal",
+  title: "nonsponsored normal",
+  keywords: ["n-n"],
+  click_url: "http://click.reporting.test.com/nonsponsored",
+  impression_url: "http://impression.reporting.test.com/nonsponsored",
+  advertiser: "TestAdvertiserNonSponsored",
+  iab_category: "5 - Education",
+};
+const FIRST_POSITION_RESULT = {
+  id: 5,
+  url: "http://example.com/?q=first-position",
+  title: "first position suggest",
+  keywords: ["first-position"],
+  click_url: "http://click.reporting.test.com/first-position",
+  impression_url: "http://impression.reporting.test.com/first-position",
+  advertiser: "TestAdvertiserFirstPositionQuickSuggest",
+  iab_category: "22 - Shopping",
+  position: 0,
+};
+const SECOND_POSITION_RESULT = {
+  id: 6,
+  url: "http://example.com/?q=second-position",
+  title: "second position suggest",
+  keywords: ["second-position"],
+  click_url: "http://click.reporting.test.com/second-position",
+  impression_url: "http://impression.reporting.test.com/second-position",
+  advertiser: "TestAdvertiserSecondPositionQuickSuggest",
+  iab_category: "22 - Shopping",
+  position: 1,
+};
+const THIRD_POSITION_RESULT = {
+  id: 7,
+  url: "http://example.com/?q=third-position",
+  title: "third position suggest",
+  keywords: ["third-position"],
+  click_url: "http://click.reporting.test.com/third-position",
+  impression_url: "http://impression.reporting.test.com/third-position",
+  advertiser: "TestAdvertiserThirdPositionQuickSuggest",
+  iab_category: "22 - Shopping",
+  position: 2,
+};
+
+const TABTOSEARCH_ENGINE_DOMAIN_FOR_FIRST_POSITION_TEST =
+  "first-position.example.com";
+const TABTOSEARCH_ENGINE_DOMAIN_FOR_SECOND_POSITION_TEST =
+  "second-position.example.com";
+
+const SECOND_POSITION_INTERVENTION_RESULT = new UrlbarResult(
+  UrlbarUtils.RESULT_TYPE.URL,
+  UrlbarUtils.RESULT_SOURCE.HISTORY,
+  { url: "http://mozilla.org/a" }
+);
+SECOND_POSITION_INTERVENTION_RESULT.suggestedIndex = 1;
+const SECOND_POSITION_INTERVENTION_RESULT_PROVIDER = new UrlbarTestUtils.TestProvider(
+  {
+    results: [SECOND_POSITION_INTERVENTION_RESULT],
+    priority: 0,
+    name: "second_position_intervention_provider",
+  }
+);
+
+const EXPECTED_GENERAL_HEURISTIC_RESULT = {
+  providerName: UrlbarProviderHeuristicFallback.name,
+  type: UrlbarUtils.RESULT_TYPE.SEARCH,
+  source: UrlbarUtils.RESULT_SOURCE.SEARCH,
+  heuristic: true,
+};
+
+const EXPECTED_GENERAL_PLACES_RESULT = {
+  providerName: UrlbarProviderPlaces.name,
+  type: UrlbarUtils.RESULT_TYPE.URL,
+  source: UrlbarUtils.RESULT_SOURCE.HISTORY,
+  heuristic: false,
+};
+
+const EXPECTED_GENERAL_TABTOSEARCH_RESULT = {
+  providerName: UrlbarProviderTabToSearch.name,
+  type: UrlbarUtils.RESULT_TYPE.DYNAMIC,
+  source: UrlbarUtils.RESULT_SOURCE.SEARCH,
+  heuristic: false,
+};
+
+const EXPECTED_GENERAL_INTERVENTION_RESULT = {
+  providerName: SECOND_POSITION_INTERVENTION_RESULT_PROVIDER.name,
+  type: UrlbarUtils.RESULT_TYPE.URL,
+  source: UrlbarUtils.RESULT_SOURCE.HISTORY,
+  heuristic: false,
+};
+
+function createExpectedQuickSuggestResult(suggest) {
+  return {
+    providerName: UrlbarProviderQuickSuggest.name,
+    type: UrlbarUtils.RESULT_TYPE.URL,
+    source: UrlbarUtils.RESULT_SOURCE.SEARCH,
+    heuristic: false,
+    payload: {
+      qsSuggestion: suggest.keywords[0],
+      title: suggest.title,
+      url: suggest.url,
+      originalUrl: suggest.url,
+      icon: null,
+      sponsoredImpressionUrl: suggest.impression_url,
+      sponsoredClickUrl: suggest.click_url,
+      sponsoredBlockId: suggest.id,
+      sponsoredAdvertiser: suggest.advertiser,
+      sponsoredIabCategory: suggest.iab_category,
+      isSponsored: suggest.iab_category !== "5 - Education",
+      helpUrl: QuickSuggest.HELP_URL,
+      helpL10n: { id: "firefox-suggest-urlbar-learn-more" },
+      isBlockable: false,
+      blockL10n: { id: "firefox-suggest-urlbar-block" },
+      displayUrl: suggest.url,
+      source: "remote-settings",
+    },
+  };
+}
+
+const TEST_CASES = [
+  {
+    description: "Test for second placable sponsored suggest",
+    input: SPONSORED_SECOND_POSITION_RESULT.keywords[0],
+    prefs: {
+      "quicksuggest.allowPositionInSuggestions": true,
+      "suggest.quicksuggest.sponsored": true,
+    },
+    providers: [
+      UrlbarProviderHeuristicFallback.name,
+      UrlbarProviderQuickSuggest.name,
+      UrlbarProviderPlaces.name,
+    ],
+    expected: [
+      EXPECTED_GENERAL_HEURISTIC_RESULT,
+      createExpectedQuickSuggestResult(SPONSORED_SECOND_POSITION_RESULT),
+      EXPECTED_GENERAL_PLACES_RESULT,
+    ],
+  },
+  {
+    description: "Test for normal sponsored suggest",
+    input: SPONSORED_NORMAL_POSITION_RESULT.keywords[0],
+    prefs: {
+      "quicksuggest.allowPositionInSuggestions": true,
+      "suggest.quicksuggest.sponsored": true,
+    },
+    providers: [
+      UrlbarProviderHeuristicFallback.name,
+      UrlbarProviderQuickSuggest.name,
+      UrlbarProviderPlaces.name,
+    ],
+    expected: [
+      EXPECTED_GENERAL_HEURISTIC_RESULT,
+      EXPECTED_GENERAL_PLACES_RESULT,
+      createExpectedQuickSuggestResult(SPONSORED_NORMAL_POSITION_RESULT),
+    ],
+  },
+  {
+    description: "Test for second placable nonsponsored suggest",
+    input: NONSPONSORED_SECOND_POSITION_RESULT.keywords[0],
+    prefs: {
+      "quicksuggest.allowPositionInSuggestions": true,
+      "suggest.quicksuggest.nonsponsored": true,
+    },
+    providers: [
+      UrlbarProviderHeuristicFallback.name,
+      UrlbarProviderQuickSuggest.name,
+      UrlbarProviderPlaces.name,
+    ],
+    expected: [
+      EXPECTED_GENERAL_HEURISTIC_RESULT,
+      createExpectedQuickSuggestResult(NONSPONSORED_SECOND_POSITION_RESULT),
+      EXPECTED_GENERAL_PLACES_RESULT,
+    ],
+  },
+  {
+    description: "Test for normal nonsponsored suggest",
+    input: NONSPONSORED_NORMAL_POSITION_RESULT.keywords[0],
+    prefs: {
+      "quicksuggest.allowPositionInSuggestions": true,
+      "suggest.quicksuggest.nonsponsored": true,
+    },
+    providers: [
+      UrlbarProviderHeuristicFallback.name,
+      UrlbarProviderQuickSuggest.name,
+      UrlbarProviderPlaces.name,
+    ],
+    expected: [
+      EXPECTED_GENERAL_HEURISTIC_RESULT,
+      EXPECTED_GENERAL_PLACES_RESULT,
+      createExpectedQuickSuggestResult(NONSPONSORED_NORMAL_POSITION_RESULT),
+    ],
+  },
+  {
+    description:
+      "Test for second placable sponsored suggest but secondPosition pref is disabled",
+    input: SPONSORED_SECOND_POSITION_RESULT.keywords[0],
+    prefs: {
+      "quicksuggest.allowPositionInSuggestions": false,
+      "suggest.quicksuggest.sponsored": true,
+    },
+    providers: [
+      UrlbarProviderHeuristicFallback.name,
+      UrlbarProviderQuickSuggest.name,
+      UrlbarProviderPlaces.name,
+    ],
+    expected: [
+      EXPECTED_GENERAL_HEURISTIC_RESULT,
+      EXPECTED_GENERAL_PLACES_RESULT,
+      createExpectedQuickSuggestResult(SPONSORED_SECOND_POSITION_RESULT),
+    ],
+  },
+  {
+    description: "Test the results with multi providers having same index",
+    input: SECOND_POSITION_RESULT.keywords[0],
+    prefs: {
+      "quicksuggest.allowPositionInSuggestions": true,
+      "suggest.quicksuggest.sponsored": true,
+    },
+    providers: [
+      UrlbarProviderQuickSuggest.name,
+      UrlbarProviderTabToSearch.name,
+      SECOND_POSITION_INTERVENTION_RESULT_PROVIDER.name,
+    ],
+    expected: [
+      EXPECTED_GENERAL_TABTOSEARCH_RESULT,
+      createExpectedQuickSuggestResult(SECOND_POSITION_RESULT),
+      EXPECTED_GENERAL_INTERVENTION_RESULT,
+    ],
+  },
+  {
+    description: "Test the results with tab-to-search",
+    input: SECOND_POSITION_RESULT.keywords[0],
+    prefs: {
+      "quicksuggest.allowPositionInSuggestions": true,
+      "suggest.quicksuggest.sponsored": true,
+    },
+    providers: [
+      UrlbarProviderTabToSearch.name,
+      UrlbarProviderQuickSuggest.name,
+    ],
+    expected: [
+      EXPECTED_GENERAL_TABTOSEARCH_RESULT,
+      createExpectedQuickSuggestResult(SECOND_POSITION_RESULT),
+    ],
+  },
+  {
+    description: "Test the results with another intervention",
+    input: SECOND_POSITION_RESULT.keywords[0],
+    prefs: {
+      "quicksuggest.allowPositionInSuggestions": true,
+      "suggest.quicksuggest.sponsored": true,
+    },
+    providers: [
+      UrlbarProviderQuickSuggest.name,
+      SECOND_POSITION_INTERVENTION_RESULT_PROVIDER.name,
+    ],
+    expected: [
+      createExpectedQuickSuggestResult(SECOND_POSITION_RESULT),
+      EXPECTED_GENERAL_INTERVENTION_RESULT,
+    ],
+  },
+  {
+    description: "Test the results with heuristic and tab-to-search",
+    input: SECOND_POSITION_RESULT.keywords[0],
+    prefs: {
+      "quicksuggest.allowPositionInSuggestions": true,
+      "suggest.quicksuggest.sponsored": true,
+    },
+    providers: [
+      UrlbarProviderHeuristicFallback.name,
+      UrlbarProviderTabToSearch.name,
+      UrlbarProviderQuickSuggest.name,
+    ],
+    expected: [
+      EXPECTED_GENERAL_HEURISTIC_RESULT,
+      EXPECTED_GENERAL_TABTOSEARCH_RESULT,
+      createExpectedQuickSuggestResult(SECOND_POSITION_RESULT),
+    ],
+  },
+  {
+    description: "Test the results with heuristic tab-to-search and places",
+    input: SECOND_POSITION_RESULT.keywords[0],
+    prefs: {
+      "quicksuggest.allowPositionInSuggestions": true,
+      "suggest.quicksuggest.sponsored": true,
+    },
+    providers: [
+      UrlbarProviderHeuristicFallback.name,
+      UrlbarProviderTabToSearch.name,
+      UrlbarProviderQuickSuggest.name,
+      UrlbarProviderPlaces.name,
+    ],
+    expected: [
+      EXPECTED_GENERAL_HEURISTIC_RESULT,
+      EXPECTED_GENERAL_TABTOSEARCH_RESULT,
+      createExpectedQuickSuggestResult(SECOND_POSITION_RESULT),
+      EXPECTED_GENERAL_PLACES_RESULT,
+    ],
+  },
+  {
+    description: "Test the results with heuristic and another intervention",
+    input: SECOND_POSITION_RESULT.keywords[0],
+    prefs: {
+      "quicksuggest.allowPositionInSuggestions": true,
+      "suggest.quicksuggest.sponsored": true,
+    },
+    providers: [
+      UrlbarProviderHeuristicFallback.name,
+      UrlbarProviderQuickSuggest.name,
+      SECOND_POSITION_INTERVENTION_RESULT_PROVIDER.name,
+    ],
+    expected: [
+      EXPECTED_GENERAL_HEURISTIC_RESULT,
+      createExpectedQuickSuggestResult(SECOND_POSITION_RESULT),
+      EXPECTED_GENERAL_INTERVENTION_RESULT,
+    ],
+  },
+  {
+    description:
+      "Test the results with heuristic, another intervention and places",
+    input: SECOND_POSITION_RESULT.keywords[0],
+    prefs: {
+      "quicksuggest.allowPositionInSuggestions": true,
+      "suggest.quicksuggest.sponsored": true,
+    },
+    providers: [
+      UrlbarProviderHeuristicFallback.name,
+      UrlbarProviderQuickSuggest.name,
+      SECOND_POSITION_INTERVENTION_RESULT_PROVIDER.name,
+      UrlbarProviderPlaces.name,
+    ],
+    expected: [
+      EXPECTED_GENERAL_HEURISTIC_RESULT,
+      createExpectedQuickSuggestResult(SECOND_POSITION_RESULT),
+      EXPECTED_GENERAL_INTERVENTION_RESULT,
+      EXPECTED_GENERAL_PLACES_RESULT,
+    ],
+  },
+  {
+    description: "Test for 0 indexed quick suggest",
+    input: FIRST_POSITION_RESULT.keywords[0],
+    prefs: {
+      "quicksuggest.allowPositionInSuggestions": true,
+      "suggest.quicksuggest.sponsored": true,
+    },
+    providers: [
+      UrlbarProviderTabToSearch.name,
+      UrlbarProviderQuickSuggest.name,
+    ],
+    expected: [
+      createExpectedQuickSuggestResult(FIRST_POSITION_RESULT),
+      EXPECTED_GENERAL_TABTOSEARCH_RESULT,
+    ],
+  },
+  {
+    description: "Test for 2 indexed quick suggest",
+    input: THIRD_POSITION_RESULT.keywords[0],
+    prefs: {
+      "quicksuggest.allowPositionInSuggestions": true,
+      "suggest.quicksuggest.sponsored": true,
+    },
+    providers: [
+      UrlbarProviderQuickSuggest.name,
+      SECOND_POSITION_INTERVENTION_RESULT_PROVIDER.name,
+    ],
+    expected: [
+      EXPECTED_GENERAL_INTERVENTION_RESULT,
+      createExpectedQuickSuggestResult(THIRD_POSITION_RESULT),
+    ],
+  },
+];
+
+add_task(async function setup() {
+  UrlbarPrefs.set("quicksuggest.enabled", true);
+
+  // Setup for quick suggest result.
+  await QuickSuggestTestUtils.ensureQuickSuggestInit({
+    remoteSettingsResults: [
+      SPONSORED_SECOND_POSITION_RESULT,
+      SPONSORED_NORMAL_POSITION_RESULT,
+      NONSPONSORED_SECOND_POSITION_RESULT,
+      NONSPONSORED_NORMAL_POSITION_RESULT,
+      FIRST_POSITION_RESULT,
+      SECOND_POSITION_RESULT,
+      THIRD_POSITION_RESULT,
+    ],
+  });
+
+  // Setup for places result.
+  await PlacesUtils.history.clear();
+  await PlacesTestUtils.addVisits([
+    "http://example.com/" + SPONSORED_SECOND_POSITION_RESULT.keywords[0],
+    "http://example.com/" + SPONSORED_NORMAL_POSITION_RESULT.keywords[0],
+    "http://example.com/" + NONSPONSORED_SECOND_POSITION_RESULT.keywords[0],
+    "http://example.com/" + NONSPONSORED_NORMAL_POSITION_RESULT.keywords[0],
+    "http://example.com/" + SECOND_POSITION_RESULT.keywords[0],
+  ]);
+
+  // Setup for tab-to-search result.
+  await SearchTestUtils.installSearchExtension({
+    name: "first",
+    search_url: `https://${TABTOSEARCH_ENGINE_DOMAIN_FOR_FIRST_POSITION_TEST}/`,
+  });
+  await SearchTestUtils.installSearchExtension({
+    name: "second",
+    search_url: `https://${TABTOSEARCH_ENGINE_DOMAIN_FOR_SECOND_POSITION_TEST}/`,
+  });
+
+  /// Setup for another intervention result.
+  UrlbarProvidersManager.registerProvider(
+    SECOND_POSITION_INTERVENTION_RESULT_PROVIDER
+  );
+});
+
+add_task(async function basic() {
+  for (const { description, input, prefs, providers, expected } of TEST_CASES) {
+    info(description);
+
+    for (let name in prefs) {
+      UrlbarPrefs.set(name, prefs[name]);
+    }
+
+    const context = createContext(input, {
+      providers,
+      isPrivate: false,
+    });
+    await check_results({
+      context,
+      matches: expected,
+    });
+
+    for (let name in prefs) {
+      UrlbarPrefs.clear(name);
+    }
+  }
+});
diff --git a/browser/components/urlbar/tests/quicksuggest/unit/test_weather.js b/browser/components/urlbar/tests/quicksuggest/unit/test_weather.js
new file mode 100644
index 0000000000..c07fcef599
--- /dev/null
+++ b/browser/components/urlbar/tests/quicksuggest/unit/test_weather.js
@@ -0,0 +1,765 @@
+/* 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/. */
+
+// Tests the quick suggest weather feature.
+
+"use strict";
+
+const HISTOGRAM_LATENCY = "FX_URLBAR_MERINO_LATENCY_WEATHER_MS";
+const HISTOGRAM_RESPONSE = "FX_URLBAR_MERINO_RESPONSE_WEATHER";
+
+const { WEATHER_SUGGESTION } = MerinoTestUtils;
+
+add_task(async function init() {
+  await QuickSuggestTestUtils.ensureQuickSuggestInit();
+  UrlbarPrefs.set("quicksuggest.enabled", true);
+
+  await MerinoTestUtils.initWeather();
+});
+
+// The feature should be properly uninitialized when it's disabled and then
+// re-initialized when it's re-enabled. This task disables the feature using the
+// feature gate pref.
+add_task(async function disableAndEnable_featureGate() {
+  await doBasicDisableAndEnableTest("weather.featureGate");
+});
+
+// The feature should be properly uninitialized when it's disabled and then
+// re-initialized when it's re-enabled. This task disables the feature using the
+// suggest pref.
+add_task(async function disableAndEnable_suggestPref() {
+  await doBasicDisableAndEnableTest("suggest.weather");
+});
+
+async function doBasicDisableAndEnableTest(pref) {
+  // Sanity check initial state.
+  assertEnabled({
+    message: "Sanity check initial state",
+    hasSuggestion: true,
+    pendingFetchCount: 0,
+  });
+
+  // Disable the feature. It should be immediately uninitialized.
+  UrlbarPrefs.set(pref, false);
+  assertDisabled({
+    message: "After disabling",
+    pendingFetchCount: 0,
+  });
+
+  // No suggestion should be returned for a search.
+  let context = createContext("", {
+    providers: [UrlbarProviderQuickSuggest.name],
+    isPrivate: false,
+  });
+  await check_results({
+    context,
+    matches: [],
+  });
+
+  let histograms = MerinoTestUtils.getAndClearHistograms({
+    extraLatency: HISTOGRAM_LATENCY,
+    extraResponse: HISTOGRAM_RESPONSE,
+  });
+
+  // Re-enable the feature. It should be immediately initialized and a fetch
+  // should start.
+  info("Re-enable the feature");
+  let fetchPromise = QuickSuggest.weather.waitForFetches();
+  UrlbarPrefs.set(pref, true);
+  assertEnabled({
+    message: "Immediately after re-enabling",
+    hasSuggestion: false,
+    pendingFetchCount: 1,
+  });
+
+  await fetchPromise;
+  assertEnabled({
+    message: "After awaiting fetch",
+    hasSuggestion: true,
+    pendingFetchCount: 0,
+  });
+
+  Assert.equal(
+    QuickSuggest.weather._test_merino.lastFetchStatus,
+    "success",
+    "The request successfully finished"
+  );
+  MerinoTestUtils.checkAndClearHistograms({
+    histograms,
+    response: "success",
+    latencyRecorded: true,
+    client: QuickSuggest.weather._test_merino,
+  });
+
+  // The suggestion should be returned for a search.
+  context = createContext("", {
+    providers: [UrlbarProviderQuickSuggest.name],
+    isPrivate: false,
+  });
+  await check_results({
+    context,
+    matches: [makeExpectedResult()],
+  });
+}
+
+// Disables and re-enables the feature without waiting for any intermediate
+// fetches to complete, using the following steps:
+//
+// 1. Disable
+// 2. Enable
+// 3. Disable again
+//
+// At this point, the fetch from step 2 will remain ongoing but once it finishes
+// it should be discarded since the feature is disabled.
+add_task(async function disableAndEnable_immediate1() {
+  // Sanity check initial state.
+  assertEnabled({
+    message: "Sanity check initial state",
+    hasSuggestion: true,
+    pendingFetchCount: 0,
+  });
+
+  // Disable the feature. It should be immediately uninitialized.
+  UrlbarPrefs.set("weather.featureGate", false);
+  assertDisabled({
+    message: "After disabling",
+    pendingFetchCount: 0,
+  });
+
+  // Re-enable the feature. It should be immediately initialized and a fetch
+  // should start.
+  let fetchPromise = QuickSuggest.weather.waitForFetches();
+  UrlbarPrefs.set("weather.featureGate", true);
+  assertEnabled({
+    message: "Immediately after re-enabling",
+    hasSuggestion: false,
+    pendingFetchCount: 1,
+  });
+
+  // Disable it again. The fetch will remain ongoing since pending fetches
+  // aren't stopped when the feature is disabled.
+  UrlbarPrefs.set("weather.featureGate", false);
+  assertDisabled({
+    message: "After disabling again",
+    pendingFetchCount: 1,
+  });
+
+  // Wait for the fetch to finish.
+  await fetchPromise;
+
+  // The fetched suggestion should be discarded and the feature should remain
+  // uninitialized.
+  assertDisabled({
+    message: "After awaiting fetch",
+    pendingFetchCount: 0,
+  });
+
+  // Clean up by re-enabling the feature for the remaining tasks.
+  fetchPromise = QuickSuggest.weather.waitForFetches();
+  UrlbarPrefs.set("weather.featureGate", true);
+  await fetchPromise;
+  assertEnabled({
+    message: "On cleanup",
+    hasSuggestion: true,
+    pendingFetchCount: 0,
+  });
+});
+
+// Disables and re-enables the feature without waiting for any intermediate
+// fetches to complete, using the following steps:
+//
+// 1. Disable
+// 2. Enable
+// 3. Disable again
+// 4. Enable again
+//
+// At this point, the fetches from steps 2 and 4 will remain ongoing. The fetch
+// from step 2 should be discarded.
+add_task(async function disableAndEnable_immediate2() {
+  // Sanity check initial state.
+  assertEnabled({
+    message: "Sanity check initial state",
+    hasSuggestion: true,
+    pendingFetchCount: 0,
+  });
+
+  // Disable the feature. It should be immediately uninitialized.
+  UrlbarPrefs.set("weather.featureGate", false);
+  assertDisabled({
+    message: "After disabling",
+    pendingFetchCount: 0,
+  });
+
+  // Re-enable the feature. It should be immediately initialized and a fetch
+  // should start.
+  UrlbarPrefs.set("weather.featureGate", true);
+  assertEnabled({
+    message: "Immediately after re-enabling",
+    hasSuggestion: false,
+    pendingFetchCount: 1,
+  });
+
+  // Disable it again. The fetch will remain ongoing since pending fetches
+  // aren't stopped when the feature is disabled.
+  UrlbarPrefs.set("weather.featureGate", false);
+  assertDisabled({
+    message: "After disabling again",
+    pendingFetchCount: 1,
+  });
+
+  // Re-enable it. A new fetch should start, so now there will be two pending
+  // fetches.
+  let fetchPromise = QuickSuggest.weather.waitForFetches();
+  UrlbarPrefs.set("weather.featureGate", true);
+  assertEnabled({
+    message: "Immediately after re-enabling again",
+    hasSuggestion: false,
+    pendingFetchCount: 2,
+  });
+
+  // Wait for both fetches to finish.
+  await fetchPromise;
+  assertEnabled({
+    message: "Immediately after re-enabling again",
+    hasSuggestion: true,
+    pendingFetchCount: 0,
+  });
+});
+
+// A fetch that doesn't return a suggestion should cause the last-fetched
+// suggestion to be discarded.
+add_task(async function noSuggestion() {
+  assertEnabled({
+    message: "Sanity check initial state",
+    hasSuggestion: true,
+    pendingFetchCount: 0,
+  });
+
+  let histograms = MerinoTestUtils.getAndClearHistograms({
+    extraLatency: HISTOGRAM_LATENCY,
+    extraResponse: HISTOGRAM_RESPONSE,
+  });
+
+  let { suggestions } = MerinoTestUtils.server.response.body;
+  MerinoTestUtils.server.response.body.suggestions = [];
+
+  await QuickSuggest.weather._test_fetch();
+
+  assertEnabled({
+    message: "After fetch",
+    hasSuggestion: false,
+    pendingFetchCount: 0,
+  });
+  Assert.equal(
+    QuickSuggest.weather._test_merino.lastFetchStatus,
+    "no_suggestion",
+    "The request successfully finished without suggestions"
+  );
+  MerinoTestUtils.checkAndClearHistograms({
+    histograms,
+    response: "no_suggestion",
+    latencyRecorded: true,
+    client: QuickSuggest.weather._test_merino,
+  });
+
+  let context = createContext("", {
+    providers: [UrlbarProviderQuickSuggest.name],
+    isPrivate: false,
+  });
+  await check_results({
+    context,
+    matches: [],
+  });
+
+  MerinoTestUtils.server.response.body.suggestions = suggestions;
+
+  // Clean up by forcing another fetch so the suggestion is non-null for the
+  // remaining tasks.
+  await QuickSuggest.weather._test_fetch();
+  assertEnabled({
+    message: "On cleanup",
+    hasSuggestion: true,
+    pendingFetchCount: 0,
+  });
+});
+
+// A network error should cause the last-fetched suggestion to be discarded.
+add_task(async function networkError() {
+  assertEnabled({
+    message: "Sanity check initial state",
+    hasSuggestion: true,
+    pendingFetchCount: 0,
+  });
+
+  let histograms = MerinoTestUtils.getAndClearHistograms({
+    extraLatency: HISTOGRAM_LATENCY,
+    extraResponse: HISTOGRAM_RESPONSE,
+  });
+
+  // Set the weather fetch timeout high enough that the network error exception
+  // will happen first. See `MerinoTestUtils.withNetworkError()`.
+  QuickSuggest.weather._test_setTimeoutMs(10000);
+
+  await MerinoTestUtils.server.withNetworkError(async () => {
+    await QuickSuggest.weather._test_fetch();
+  });
+
+  QuickSuggest.weather._test_setTimeoutMs(-1);
+
+  assertEnabled({
+    message: "After fetch",
+    hasSuggestion: false,
+    pendingFetchCount: 0,
+  });
+  Assert.equal(
+    QuickSuggest.weather._test_merino.lastFetchStatus,
+    "network_error",
+    "The request failed with a network error"
+  );
+  MerinoTestUtils.checkAndClearHistograms({
+    histograms,
+    response: "network_error",
+    latencyRecorded: false,
+    client: QuickSuggest.weather._test_merino,
+  });
+
+  let context = createContext("", {
+    providers: [UrlbarProviderQuickSuggest.name],
+    isPrivate: false,
+  });
+  await check_results({
+    context,
+    matches: [],
+  });
+
+  // Clean up by forcing another fetch so the suggestion is non-null for the
+  // remaining tasks.
+  await QuickSuggest.weather._test_fetch();
+  assertEnabled({
+    message: "On cleanup",
+    hasSuggestion: true,
+    pendingFetchCount: 0,
+  });
+});
+
+// An HTTP error should cause the last-fetched suggestion to be discarded.
+add_task(async function httpError() {
+  assertEnabled({
+    message: "Sanity check initial state",
+    hasSuggestion: true,
+    pendingFetchCount: 0,
+  });
+
+  let histograms = MerinoTestUtils.getAndClearHistograms({
+    extraLatency: HISTOGRAM_LATENCY,
+    extraResponse: HISTOGRAM_RESPONSE,
+  });
+
+  MerinoTestUtils.server.response = { status: 500 };
+  await QuickSuggest.weather._test_fetch();
+
+  assertEnabled({
+    message: "After fetch",
+    hasSuggestion: false,
+    pendingFetchCount: 0,
+  });
+  Assert.equal(
+    QuickSuggest.weather._test_merino.lastFetchStatus,
+    "http_error",
+    "The request failed with an HTTP error"
+  );
+  MerinoTestUtils.checkAndClearHistograms({
+    histograms,
+    response: "http_error",
+    latencyRecorded: true,
+    client: QuickSuggest.weather._test_merino,
+  });
+
+  let context = createContext("", {
+    providers: [UrlbarProviderQuickSuggest.name],
+    isPrivate: false,
+  });
+  await check_results({
+    context,
+    matches: [],
+  });
+
+  // Clean up by forcing another fetch so the suggestion is non-null for the
+  // remaining tasks.
+  MerinoTestUtils.server.reset();
+  MerinoTestUtils.server.response.body.suggestions = [WEATHER_SUGGESTION];
+  await QuickSuggest.weather._test_fetch();
+  assertEnabled({
+    message: "On cleanup",
+    hasSuggestion: true,
+    pendingFetchCount: 0,
+  });
+});
+
+// A fetch that doesn't return a suggestion due to a client timeout should cause
+// the last-fetched suggestion to be discarded.
+add_task(async function clientTimeout() {
+  assertEnabled({
+    message: "Sanity check initial state",
+    hasSuggestion: true,
+    pendingFetchCount: 0,
+  });
+
+  let histograms = MerinoTestUtils.getAndClearHistograms({
+    extraLatency: HISTOGRAM_LATENCY,
+    extraResponse: HISTOGRAM_RESPONSE,
+  });
+
+  // Make the server return a delayed response so the Merino client times out
+  // waiting for it.
+  MerinoTestUtils.server.response.delay = 400;
+
+  // Make the client time out immediately.
+  QuickSuggest.weather._test_setTimeoutMs(1);
+
+  // Set up a promise that will be resolved when the client finally receives the
+  // response.
+  let responsePromise = QuickSuggest.weather._test_merino.waitForNextResponse();
+
+  await QuickSuggest.weather._test_fetch();
+
+  assertEnabled({
+    message: "After fetch",
+    hasSuggestion: false,
+    pendingFetchCount: 0,
+  });
+  Assert.equal(
+    QuickSuggest.weather._test_merino.lastFetchStatus,
+    "timeout",
+    "The request timed out"
+  );
+  MerinoTestUtils.checkAndClearHistograms({
+    histograms,
+    response: "timeout",
+    latencyRecorded: false,
+    latencyStopwatchRunning: true,
+    client: QuickSuggest.weather._test_merino,
+  });
+
+  let context = createContext("", {
+    providers: [UrlbarProviderQuickSuggest.name],
+    isPrivate: false,
+  });
+  await check_results({
+    context,
+    matches: [],
+  });
+
+  // Await the response.
+  await responsePromise;
+
+  // The `checkAndClearHistograms()` call above cleared the histograms. After
+  // that, nothing else should have been recorded for the response.
+  MerinoTestUtils.checkAndClearHistograms({
+    histograms,
+    response: null,
+    latencyRecorded: true,
+    client: QuickSuggest.weather._test_merino,
+  });
+
+  QuickSuggest.weather._test_setTimeoutMs(-1);
+  delete MerinoTestUtils.server.response.delay;
+
+  // Clean up by forcing another fetch so the suggestion is non-null for the
+  // remaining tasks.
+  await QuickSuggest.weather._test_fetch();
+  assertEnabled({
+    message: "On cleanup",
+    hasSuggestion: true,
+    pendingFetchCount: 0,
+  });
+});
+
+// Locale task for when this test runs on an en-US OS.
+add_task(async function locale_enUS() {
+  await doLocaleTest({
+    shouldRunTask: osLocale => osLocale == "en-US",
+    osUnit: "f",
+    unitsByLocale: {
+      "en-US": "f",
+      // When the app's locale is set to any en-* locale, F will be used because
+      // `regionalPrefsLocales` will prefer the en-US OS locale.
+      "en-CA": "f",
+      "en-GB": "f",
+      de: "c",
+    },
+  });
+});
+
+// Locale task for when this test runs on a non-US English OS.
+add_task(async function locale_nonUSEnglish() {
+  await doLocaleTest({
+    shouldRunTask: osLocale => osLocale.startsWith("en") && osLocale != "en-US",
+    osUnit: "c",
+    unitsByLocale: {
+      // When the app's locale is set to en-US, C will be used because
+      // `regionalPrefsLocales` will prefer the non-US English OS locale.
+      "en-US": "c",
+      "en-CA": "c",
+      "en-GB": "c",
+      de: "c",
+    },
+  });
+});
+
+// Locale task for when this test runs on a non-English OS.
+add_task(async function locale_nonEnglish() {
+  await doLocaleTest({
+    shouldRunTask: osLocale => !osLocale.startsWith("en"),
+    osUnit: "c",
+    unitsByLocale: {
+      "en-US": "f",
+      "en-CA": "c",
+      "en-GB": "c",
+      de: "c",
+    },
+  });
+});
+
+/**
+ * Testing locales is tricky due to the weather feature's use of
+ * `Services.locale.regionalPrefsLocales`. By default `regionalPrefsLocales`
+ * prefers the OS locale if its language is the same as the app locale's
+ * language; otherwise it prefers the app locale. For example, assuming the OS
+ * locale is en-CA, then if the app locale is en-US it will prefer en-CA since
+ * both are English, but if the app locale is de it will prefer de. If the pref
+ * `intl.regional_prefs.use_os_locales` is set, then the OS locale is always
+ * preferred.
+ *
+ * This function tests a given set of locales with and without
+ * `intl.regional_prefs.use_os_locales` set.
+ *
+ * @param {object} options
+ *   Options
+ * @param {Function} options.shouldRunTask
+ *   Called with the OS locale. Should return true if the function should run.
+ *   Use this to skip tasks that don't target a desired OS locale.
+ * @param {string} options.osUnit
+ *   The expected "c" or "f" unit for the OS locale.
+ * @param {object} options.unitsByLocale
+ *   The expected "c" or "f" unit when the app's locale is set to particular
+ *   locales. This should be an object that maps locales to expected units. For
+ *   each locale in the object, the app's locale is set to that locale and the
+ *   actual unit is expected to be the unit in the object.
+ */
+async function doLocaleTest({ shouldRunTask, osUnit, unitsByLocale }) {
+  Services.prefs.setBoolPref("intl.regional_prefs.use_os_locales", true);
+  let osLocale = Services.locale.regionalPrefsLocales[0];
+  Services.prefs.clearUserPref("intl.regional_prefs.use_os_locales");
+
+  if (!shouldRunTask(osLocale)) {
+    info("Skipping task, should not run for this OS locale");
+    return;
+  }
+
+  assertEnabled({
+    message: "Sanity check initial state",
+    hasSuggestion: true,
+    pendingFetchCount: 0,
+  });
+
+  // Sanity check initial locale info.
+  Assert.equal(
+    Services.locale.appLocaleAsBCP47,
+    "en-US",
+    "Initial app locale should be en-US"
+  );
+  Assert.ok(
+    !Services.prefs.getBoolPref("intl.regional_prefs.use_os_locales"),
+    "intl.regional_prefs.use_os_locales should be false initially"
+  );
+
+  // Check locales.
+  for (let [locale, expectedUnit] of Object.entries(unitsByLocale)) {
+    await QuickSuggestTestUtils.withLocales([locale], async () => {
+      info("Checking locale: " + locale);
+      await check_results({
+        context: createContext("", {
+          providers: [UrlbarProviderQuickSuggest.name],
+          isPrivate: false,
+        }),
+        matches: [makeExpectedResult(expectedUnit)],
+      });
+
+      info(
+        "Checking locale with intl.regional_prefs.use_os_locales: " + locale
+      );
+      Services.prefs.setBoolPref("intl.regional_prefs.use_os_locales", true);
+      await check_results({
+        context: createContext("", {
+          providers: [UrlbarProviderQuickSuggest.name],
+          isPrivate: false,
+        }),
+        matches: [makeExpectedResult(osUnit)],
+      });
+      Services.prefs.clearUserPref("intl.regional_prefs.use_os_locales");
+    });
+  }
+}
+
+// A weather suggestion should not be returned for a non-empty search string.
+add_task(async function nonEmptySearchString() {
+  assertEnabled({
+    message: "Sanity check initial state",
+    hasSuggestion: true,
+    pendingFetchCount: 0,
+  });
+
+  // Do a search.
+  let context = createContext("this shouldn't match anything", {
+    providers: [UrlbarProviderQuickSuggest.name],
+    isPrivate: false,
+  });
+  await check_results({
+    context,
+    matches: [],
+  });
+});
+
+// Blocks a result and makes sure the weather pref is disabled.
+add_task(async function block() {
+  // Sanity check initial state.
+  assertEnabled({
+    message: "Sanity check initial state",
+    hasSuggestion: true,
+    pendingFetchCount: 0,
+  });
+  Assert.ok(
+    UrlbarPrefs.get("suggest.weather"),
+    "Sanity check: suggest.weather is true initially"
+  );
+
+  // Do a search so we can get an actual result.
+  let context = createContext("", {
+    providers: [UrlbarProviderQuickSuggest.name],
+    isPrivate: false,
+  });
+  await check_results({
+    context,
+    matches: [makeExpectedResult()],
+  });
+
+  // Block the result.
+  UrlbarProviderQuickSuggest.blockResult(context, context.results[0]);
+  Assert.ok(
+    !UrlbarPrefs.get("suggest.weather"),
+    "suggest.weather is false after blocking the result"
+  );
+
+  // Do a second search. Nothing should be returned.
+  context = createContext("", {
+    providers: [UrlbarProviderQuickSuggest.name],
+    isPrivate: false,
+  });
+  await check_results({
+    context,
+    matches: [],
+  });
+
+  // Re-enable the pref and clean up.
+  let fetchPromise = QuickSuggest.weather.waitForFetches();
+  UrlbarPrefs.set("suggest.weather", true);
+  await fetchPromise;
+  assertEnabled({
+    message: "On cleanup",
+    hasSuggestion: true,
+    pendingFetchCount: 0,
+  });
+});
+
+function assertEnabled({ message, hasSuggestion, pendingFetchCount }) {
+  info("Asserting feature is enabled");
+  if (message) {
+    info(message);
+  }
+
+  Assert.equal(
+    !!QuickSuggest.weather.suggestion,
+    hasSuggestion,
+    "Suggestion is null or non-null as expected"
+  );
+  Assert.notEqual(
+    QuickSuggest.weather._test_fetchInterval,
+    0,
+    "Fetch interval is non-zero"
+  );
+  Assert.ok(QuickSuggest.weather._test_merino, "Merino client is non-null");
+  Assert.equal(
+    QuickSuggest.weather._test_pendingFetchCount,
+    pendingFetchCount,
+    "Expected pending fetch count"
+  );
+}
+
+function assertDisabled({ message, pendingFetchCount }) {
+  info("Asserting feature is disabled");
+  if (message) {
+    info(message);
+  }
+
+  Assert.strictEqual(
+    QuickSuggest.weather.suggestion,
+    null,
+    "Suggestion is null"
+  );
+  Assert.strictEqual(
+    QuickSuggest.weather._test_fetchInterval,
+    0,
+    "Fetch interval is zero"
+  );
+  Assert.strictEqual(
+    QuickSuggest.weather._test_merino,
+    null,
+    "Merino client is null"
+  );
+  Assert.equal(
+    QuickSuggest.weather._test_pendingFetchCount,
+    pendingFetchCount,
+    "Expected pending fetch count"
+  );
+}
+
+function makeExpectedResult(temperatureUnit = undefined) {
+  if (!temperatureUnit) {
+    temperatureUnit =
+      Services.locale.regionalPrefsLocales[0] == "en-US" ? "f" : "c";
+  }
+
+  return {
+    type: UrlbarUtils.RESULT_TYPE.DYNAMIC,
+    source: UrlbarUtils.RESULT_SOURCE.SEARCH,
+    heuristic: false,
+    payload: {
+      temperatureUnit,
+      url: WEATHER_SUGGESTION.url,
+      iconId: "6",
+      helpUrl: QuickSuggest.HELP_URL,
+      helpL10n: {
+        id: "firefox-suggest-urlbar-learn-more",
+      },
+      isBlockable: true,
+      blockL10n: {
+        id: "firefox-suggest-urlbar-block",
+      },
+      requestId: MerinoTestUtils.server.response.body.request_id,
+      source: "merino",
+      merinoProvider: "accuweather",
+      dynamicType: "weather",
+      city: WEATHER_SUGGESTION.city_name,
+      temperature:
+        WEATHER_SUGGESTION.current_conditions.temperature[temperatureUnit],
+      currentConditions: WEATHER_SUGGESTION.current_conditions.summary,
+      forecast: WEATHER_SUGGESTION.forecast.summary,
+      high: WEATHER_SUGGESTION.forecast.high[temperatureUnit],
+      low: WEATHER_SUGGESTION.forecast.low[temperatureUnit],
+      isWeather: true,
+      shouldNavigate: true,
+    },
+  };
+}
diff --git a/browser/components/urlbar/tests/quicksuggest/unit/xpcshell.ini b/browser/components/urlbar/tests/quicksuggest/unit/xpcshell.ini
new file mode 100644
index 0000000000..eb45db1db8
--- /dev/null
+++ b/browser/components/urlbar/tests/quicksuggest/unit/xpcshell.ini
@@ -0,0 +1,19 @@
+[DEFAULT]
+skip-if = toolkit == 'android' # bug 1730213
+head = ../../unit/head.js head.js
+firefox-appdir = browser
+
+[test_merinoClient.js]
+[test_merinoClient_sessions.js]
+[test_quicksuggest.js]
+[test_quicksuggest_addResults.js]
+[test_quicksuggest_bestMatch.js]
+[test_quicksuggest_impressionCaps.js]
+[test_quicksuggest_merino.js]
+[test_quicksuggest_merinoSessions.js]
+[test_quicksuggest_migrate_v1.js]
+[test_quicksuggest_migrate_v2.js]
+[test_quicksuggest_nonUniqueKeywords.js]
+[test_quicksuggest_offlineDefault.js]
+[test_quicksuggest_positionInSuggestions.js]
+[test_weather.js]