--- a/browser/components/extensions/test/browser/browser-common.ini
+++ b/browser/components/extensions/test/browser/browser-common.ini
@@ -130,17 +130,16 @@ disabled = bug 1438663
 [browser_ext_sessions_forgetClosedTab.js]
 [browser_ext_sessions_forgetClosedWindow.js]
 [browser_ext_sessions_getRecentlyClosed.js]
 [browser_ext_sessions_getRecentlyClosed_private.js]
 [browser_ext_sessions_getRecentlyClosed_tabs.js]
 [browser_ext_sessions_restore.js]
 [browser_ext_sessions_window_tab_value.js]
 [browser_ext_settings_overrides_default_search.js]
-[browser_ext_settings_overrides_search.js]
 [browser_ext_sidebarAction.js]
 [browser_ext_sidebarAction_browser_style.js]
 [browser_ext_sidebarAction_context.js]
 [browser_ext_sidebarAction_contextMenu.js]
 [browser_ext_sidebarAction_runtime.js]
 [browser_ext_sidebarAction_tabs.js]
 [browser_ext_sidebarAction_windows.js]
 [browser_ext_simple.js]

rename from browser/components/extensions/test/browser/browser_ext_settings_overrides_search.js
rename to browser/components/extensions/test/xpcshell/test_ext_settings_overrides_search.js
--- a/browser/components/extensions/test/browser/browser_ext_settings_overrides_search.js
+++ b/browser/components/extensions/test/xpcshell/test_ext_settings_overrides_search.js
@@ -1,20 +1,32 @@
 /* -*- Mode: indent-tabs-mode: nil; js-indent-level: 2 -*- */
 /* vim: set sts=2 sw=2 et tw=80: */
 
 "use strict";
 
+ChromeUtils.import("resource://testing-common/AddonTestUtils.jsm");
+ChromeUtils.import("resource://gre/modules/Timer.jsm");
+
+let delay = () => new Promise(resolve => setTimeout(resolve, 0));
 
 const kSearchEngineURL = "https://example.com/?search={searchTerms}";
 const kSearchSuggestURL = "http://example.com/?suggest={searchTerms}";
 const kSearchTerm = "foo";
 const kSearchTermIntl = "日";
 const URLTYPE_SUGGEST_JSON = "application/x-suggestions+json";
 
+AddonTestUtils.init(this);
+AddonTestUtils.createAppInfo("xpcshell@tests.mozilla.org", "XPCShell", "42", "42");
+
+add_task(async function setup() {
+  await AddonTestUtils.promiseStartupManager();
+  Services.search.init();
+});
+
 add_task(async function test_extension_adding_engine() {
   let ext1 = ExtensionTestUtils.loadExtension({
     manifest: {
       "chrome_settings_overrides": {
         "search_provider": {
           "name": "MozSearch",
           "keyword": "MozSearch",
           "search_url": kSearchEngineURL,
@@ -29,21 +41,22 @@ add_task(async function test_extension_a
 
   let engine = Services.search.getEngineByName("MozSearch");
   ok(engine, "Engine should exist.");
 
   let expectedSuggestURL = kSearchSuggestURL.replace("{searchTerms}", kSearchTerm);
   let submissionSuggest = engine.getSubmission(kSearchTerm, URLTYPE_SUGGEST_JSON);
   let encodedSubmissionURL = engine.getSubmission(kSearchTermIntl).uri.spec;
   let testSubmissionURL = kSearchEngineURL.replace("{searchTerms}", encodeURIComponent(kSearchTermIntl));
-  is(encodedSubmissionURL, testSubmissionURL, "Encoded UTF-8 URLs should match");
+  equal(encodedSubmissionURL, testSubmissionURL, "Encoded UTF-8 URLs should match");
 
-  is(submissionSuggest.uri.spec, expectedSuggestURL, "Suggest URLs should match");
+  equal(submissionSuggest.uri.spec, expectedSuggestURL, "Suggest URLs should match");
 
   await ext1.unload();
+  await delay();
 
   engine = Services.search.getEngineByName("MozSearch");
   ok(!engine, "Engine should not exist");
 });
 
 add_task(async function test_extension_adding_engine_with_spaces() {
   let ext1 = ExtensionTestUtils.loadExtension({
     manifest: {
@@ -59,16 +72,17 @@ add_task(async function test_extension_a
   });
 
   await ext1.startup();
 
   let engine = Services.search.getEngineByName("MozSearch");
   ok(engine, "Engine should exist.");
 
   await ext1.unload();
+  await delay();
 
   engine = Services.search.getEngineByName("MozSearch");
   ok(!engine, "Engine should not exist");
 });
 
 
 add_task(async function test_upgrade_default_position_engine() {
   let ext1 = ExtensionTestUtils.loadExtension({
@@ -85,17 +99,23 @@ add_task(async function test_upgrade_def
           "id": "testengine@mozilla.com",
         },
       },
       "version": "0.1",
     },
     useAddonManager: "temporary",
   });
 
-  let ext2 = ExtensionTestUtils.loadExtension({
+  await ext1.startup();
+
+  let engine = Services.search.getEngineByName("MozSearch");
+  Services.search.currentEngine = engine;
+  Services.search.moveEngine(engine, 1);
+
+  await ext1.upgrade({
     manifest: {
       "chrome_settings_overrides": {
         "search_provider": {
           "name": "MozSearch",
           "keyword": "MozSearch",
           "search_url": "https://example.com/?q={searchTerms}",
         },
       },
@@ -104,26 +124,18 @@ add_task(async function test_upgrade_def
           "id": "testengine@mozilla.com",
         },
       },
       "version": "0.2",
     },
     useAddonManager: "temporary",
   });
 
-  await ext1.startup();
-
-  let engine = Services.search.getEngineByName("MozSearch");
-  Services.search.currentEngine = engine;
-  Services.search.moveEngine(engine, 1);
+  engine = Services.search.getEngineByName("MozSearch");
+  equal(Services.search.currentEngine, engine, "Default engine should still be MozSearch");
+  equal(Services.search.getEngines().indexOf(engine), 1, "Engine is in position 1");
 
-  await ext2.startup();
-
-  engine = Services.search.getEngineByName("MozSearch");
-  is(Services.search.currentEngine, engine, "Default engine should still be MozSearch");
-  is(Services.search.getEngines().indexOf(engine), 1, "Engine is in position 1");
-
-  await ext2.unload();
   await ext1.unload();
+  await delay();
 
   engine = Services.search.getEngineByName("MozSearch");
   ok(!engine, "Engine should not exist");
 });

--- a/browser/components/extensions/test/xpcshell/xpcshell-common.ini
+++ b/browser/components/extensions/test/xpcshell/xpcshell-common.ini
@@ -2,11 +2,12 @@
 [test_ext_browsingData.js]
 [test_ext_browsingData_cookies_cache.js]
 [test_ext_browsingData_downloads.js]
 [test_ext_browsingData_passwords.js]
 [test_ext_browsingData_settings.js]
 [test_ext_chrome_settings_overrides_update.js]
 [test_ext_geckoProfiler_control.js]
 [test_ext_history.js]
+[test_ext_settings_overrides_search.js]
 [test_ext_url_overrides_newtab.js]
 [test_ext_url_overrides_newtab_update.js]