diff --git a/browser/components/aboutlogins/tests/browser/browser_loginItemErrors.js b/browser/components/aboutlogins/tests/browser/browser_loginItemErrors.js
--- a/browser/components/aboutlogins/tests/browser/browser_loginItemErrors.js
+++ b/browser/components/aboutlogins/tests/browser/browser_loginItemErrors.js
@@ -19,11 +19,11 @@
     "https://example.com",
     null,
     "user2",
     "pass2"
   );
-  LOGIN_TO_UPDATE = Services.logins.addLogin(LOGIN_TO_UPDATE);
+  LOGIN_TO_UPDATE = await Services.logins.addLoginAsync(LOGIN_TO_UPDATE);
   EXPECTED_ERROR_MESSAGE = "This login already exists.";
   const LOGIN_UPDATES = {
     origin: "https://example.com",
     password: "my1GoodPassword",
     username: "user1",
diff --git a/browser/components/aboutlogins/tests/browser/browser_openFiltered.js b/browser/components/aboutlogins/tests/browser/browser_openFiltered.js
--- a/browser/components/aboutlogins/tests/browser/browser_openFiltered.js
+++ b/browser/components/aboutlogins/tests/browser/browser_openFiltered.js
@@ -4,17 +4,17 @@
 add_setup(async function() {
   let storageChangedPromised = TestUtils.topicObserved(
     "passwordmgr-storage-changed",
     (_, data) => data == "addLogin"
   );
-  TEST_LOGIN1 = Services.logins.addLogin(TEST_LOGIN1);
+  TEST_LOGIN1 = await Services.logins.addLoginAsync(TEST_LOGIN1);
   await storageChangedPromised;
   storageChangedPromised = TestUtils.topicObserved(
     "passwordmgr-storage-changed",
     (_, data) => data == "addLogin"
   );
-  TEST_LOGIN2 = Services.logins.addLogin(TEST_LOGIN2);
+  TEST_LOGIN2 = await Services.logins.addLoginAsync(TEST_LOGIN2);
   await storageChangedPromised;
   let tabOpenedPromise = BrowserTestUtils.waitForNewTab(
     gBrowser,
     "about:logins?filter=" + encodeURIComponent(TEST_LOGIN1.origin),
     true
diff --git a/browser/components/aboutlogins/tests/browser/head.js b/browser/components/aboutlogins/tests/browser/head.js
--- a/browser/components/aboutlogins/tests/browser/head.js
+++ b/browser/components/aboutlogins/tests/browser/head.js
@@ -52,21 +52,16 @@
   "password"
 );
 TEST_LOGIN3.QueryInterface(Ci.nsILoginMetaInfo).timePasswordChanged = 123456;
 
 async function addLogin(login) {
-  let storageChangedPromised = TestUtils.topicObserved(
-    "passwordmgr-storage-changed",
-    (_, data) => data == "addLogin"
-  );
-  login = Services.logins.addLogin(login);
-  await storageChangedPromised;
+  const result = await Services.logins.addLoginAsync(login);
   registerCleanupFunction(() => {
     let matchData = Cc["@mozilla.org/hash-property-bag;1"].createInstance(
       Ci.nsIWritablePropertyBag2
     );
-    matchData.setPropertyAsAUTF8String("guid", login.guid);
+    matchData.setPropertyAsAUTF8String("guid", result.guid);
 
     let logins = Services.logins.searchLogins(matchData);
     if (!logins.length) {
       return;
     }
@@ -74,11 +69,11 @@
     // in case the initial login object was changed by the test code,
     // since removeLogin makes sure that the login argument exactly
     // matches the login that it will be removing.
     Services.logins.removeLogin(logins[0]);
   });
-  return login;
+  return result;
 }
 
 let EXPECTED_BREACH = null;
 let EXPECTED_ERROR_MESSAGE = null;
 add_setup(async function setup_head() {
diff --git a/browser/components/aboutlogins/tests/unit/test_getPotentialBreachesByLoginGUID.js b/browser/components/aboutlogins/tests/unit/test_getPotentialBreachesByLoginGUID.js
--- a/browser/components/aboutlogins/tests/unit/test_getPotentialBreachesByLoginGUID.js
+++ b/browser/components/aboutlogins/tests/unit/test_getPotentialBreachesByLoginGUID.js
@@ -108,11 +108,11 @@
   password: "password",
   timePasswordChanged: new Date("2018-12-15").getTime(),
 });
 
 add_task(async function test_notBreachedLogin() {
-  Services.logins.addLogin(NOT_BREACHED_LOGIN);
+  await Services.logins.addLoginAsync(NOT_BREACHED_LOGIN);
   const breachesByLoginGUID = await LoginBreaches.getPotentialBreachesByLoginGUID(
     [NOT_BREACHED_LOGIN],
     TEST_BREACHES
   );
   Assert.strictEqual(
@@ -121,11 +121,11 @@
     "Should be 0 breached logins."
   );
 });
 
 add_task(async function test_breachedLogin() {
-  Services.logins.addLogin(BREACHED_LOGIN);
+  await Services.logins.addLoginAsync(BREACHED_LOGIN);
   const breachesByLoginGUID = await LoginBreaches.getPotentialBreachesByLoginGUID(
     [NOT_BREACHED_LOGIN, BREACHED_LOGIN],
     TEST_BREACHES
   );
   Assert.strictEqual(
@@ -139,11 +139,11 @@
     "Breach alert link should be equal to the breachAlertURL"
   );
 });
 
 add_task(async function test_breachedLoginAfterCrashingUriLogin() {
-  Services.logins.addLogin(CRASHING_URI_LOGIN);
+  await Services.logins.addLoginAsync(CRASHING_URI_LOGIN);
 
   const breachesByLoginGUID = await LoginBreaches.getPotentialBreachesByLoginGUID(
     [CRASHING_URI_LOGIN, BREACHED_LOGIN],
     TEST_BREACHES
   );
@@ -158,11 +158,11 @@
     "Breach alert link should be equal to the breachAlertURL"
   );
 });
 
 add_task(async function test_notBreachedSubdomain() {
-  Services.logins.addLogin(NOT_BREACHED_SUBDOMAIN_LOGIN);
+  await Services.logins.addLoginAsync(NOT_BREACHED_SUBDOMAIN_LOGIN);
 
   const breachesByLoginGUID = await LoginBreaches.getPotentialBreachesByLoginGUID(
     [NOT_BREACHED_LOGIN, NOT_BREACHED_SUBDOMAIN_LOGIN],
     TEST_BREACHES
   );
@@ -172,11 +172,11 @@
     "Should be 0 breached logins."
   );
 });
 
 add_task(async function test_breachedSubdomain() {
-  Services.logins.addLogin(BREACHED_SUBDOMAIN_LOGIN);
+  await Services.logins.addLoginAsync(BREACHED_SUBDOMAIN_LOGIN);
 
   const breachesByLoginGUID = await LoginBreaches.getPotentialBreachesByLoginGUID(
     [NOT_BREACHED_SUBDOMAIN_LOGIN, BREACHED_SUBDOMAIN_LOGIN],
     TEST_BREACHES
   );
@@ -186,11 +186,13 @@
     "Should be 1 breached login: " + BREACHED_SUBDOMAIN_LOGIN.origin
   );
 });
 
 add_task(async function test_breachedSiteWithoutPasswords() {
-  Services.logins.addLogin(LOGIN_FOR_BREACHED_SITE_WITHOUT_PASSWORDS);
+  await Services.logins.addLoginAsync(
+    LOGIN_FOR_BREACHED_SITE_WITHOUT_PASSWORDS
+  );
 
   const breachesByLoginGUID = await LoginBreaches.getPotentialBreachesByLoginGUID(
     [LOGIN_FOR_BREACHED_SITE_WITHOUT_PASSWORDS],
     TEST_BREACHES
   );
@@ -250,11 +252,11 @@
       BREACHED_LOGIN.origin
   );
 });
 
 add_task(async function test_ExceptionsThrownByNonStandardURIsAreCaught() {
-  Services.logins.addLogin(LOGIN_WITH_NON_STANDARD_URI);
+  await Services.logins.addLoginAsync(LOGIN_WITH_NON_STANDARD_URI);
 
   const breachesByLoginGUID = await LoginBreaches.getPotentialBreachesByLoginGUID(
     [LOGIN_WITH_NON_STANDARD_URI, BREACHED_LOGIN],
     TEST_BREACHES
   );
diff --git a/browser/components/extensions/test/xpcshell/test_ext_browsingData_passwords.js b/browser/components/extensions/test/xpcshell/test_ext_browsingData_passwords.js
--- a/browser/components/extensions/test/xpcshell/test_ext_browsingData_passwords.js
+++ b/browser/components/extensions/test/xpcshell/test_ext_browsingData_passwords.js
@@ -8,35 +8,35 @@
 const OLD_HOST = "http://mozilla.org";
 const NEW_HOST = "http://mozilla.com";
 const FXA_HOST = "chrome://FirefoxAccounts";
 
 function checkLoginExists(host, shouldExist) {
-  let logins = Services.logins.findLogins(host, "", null);
+  const logins = Services.logins.findLogins(host, "", null);
   equal(
     logins.length,
     shouldExist ? 1 : 0,
     `Login was ${shouldExist ? "" : "not "} found.`
   );
 }
 
-function addLogin(host, timestamp) {
+async function addLogin(host, timestamp) {
   checkLoginExists(host, false);
   let login = Cc["@mozilla.org/login-manager/loginInfo;1"].createInstance(
     Ci.nsILoginInfo
   );
   login.init(host, "", null, LOGIN_USERNAME, LOGIN_PASSWORD);
   login.QueryInterface(Ci.nsILoginMetaInfo);
   login.timePasswordChanged = timestamp;
-  Services.logins.addLogin(login);
+  await Services.logins.addLoginAsync(login);
   checkLoginExists(host, true);
 }
 
 async function setupPasswords() {
   Services.logins.removeAllUserFacingLogins();
-  addLogin(FXA_HOST, REFERENCE_DATE);
-  addLogin(NEW_HOST, REFERENCE_DATE);
-  addLogin(OLD_HOST, REFERENCE_DATE - 10000);
+  await addLogin(FXA_HOST, REFERENCE_DATE);
+  await addLogin(NEW_HOST, REFERENCE_DATE);
+  await addLogin(OLD_HOST, REFERENCE_DATE - 10000);
 }
 
 add_task(async function testPasswords() {
   function background() {
     browser.test.onMessage.addListener(async (msg, options) => {
@@ -47,11 +47,11 @@
       }
       browser.test.sendMessage("passwordsRemoved");
     });
   }
 
-  let extension = ExtensionTestUtils.loadExtension({
+  const extension = ExtensionTestUtils.loadExtension({
     background,
     manifest: {
       permissions: ["browsingData"],
     },
   });
diff --git a/browser/components/migration/tests/marionette/test_refresh_firefox.py b/browser/components/migration/tests/marionette/test_refresh_firefox.py
--- a/browser/components/migration/tests/marionette/test_refresh_firefox.py
+++ b/browser/components/migration/tests/marionette/test_refresh_firefox.py
@@ -38,22 +38,24 @@
     _formAutofillAddressGuid = None
 
     _expectedURLs = ["about:robots", "about:mozilla"]
 
     def savePassword(self):
-        self.runCode(
+        self.runAsyncCode(
             """
+          let [username, password, resolve] = arguments;
           let myLogin = new global.LoginInfo(
             "test.marionette.mozilla.com",
             "http://test.marionette.mozilla.com/some/form/",
             null,
-            arguments[0],
-            arguments[1],
+            username,
+            password,
             "username",
             "password"
           );
-          Services.logins.addLogin(myLogin)
+          Services.logins.addLoginAsync(myLogin)
+            .then(() => resolve(false), resolve);
         """,
             script_args=(self._username, self._password),
         )
 
     def createBookmarkInMenu(self):
diff --git a/browser/components/migration/tests/unit/test_Chrome_passwords.js b/browser/components/migration/tests/unit/test_Chrome_passwords.js
--- a/browser/components/migration/tests/unit/test_Chrome_passwords.js
+++ b/browser/components/migration/tests/unit/test_Chrome_passwords.js
@@ -102,16 +102,16 @@
 
 var loginCrypto;
 var dbConn;
 
 async function promiseSetPassword(login) {
-  let encryptedString = await loginCrypto.encryptData(
+  const encryptedString = await loginCrypto.encryptData(
     login.password,
     login.version
   );
   info(`promiseSetPassword: ${encryptedString}`);
-  let passwordValue = new Uint8Array(
+  const passwordValue = new Uint8Array(
     loginCrypto.stringToArray(encryptedString)
   );
   return dbConn.execute(
     `UPDATE logins
                          SET password_value = :password_value
@@ -175,11 +175,11 @@
     "The two logins ID " + id + " have the same timesUsed"
   );
 }
 
 function generateDifferentLogin(login) {
-  let newLogin = Cc["@mozilla.org/login-manager/loginInfo;1"].createInstance(
+  const newLogin = Cc["@mozilla.org/login-manager/loginInfo;1"].createInstance(
     Ci.nsILoginInfo
   );
 
   newLogin.init(
     login.origin,
@@ -204,17 +204,17 @@
 
   // Use a mock service and account name to avoid a Keychain auth. prompt that
   // would block the test from finishing if Chrome has already created a matching
   // Keychain entry. This allows us to still exercise the keychain lookup code.
   // The mock encryption passphrase is used when the Keychain item isn't found.
-  let mockMacOSKeychain = {
+  const mockMacOSKeychain = {
     passphrase: "bW96aWxsYWZpcmVmb3g=",
     serviceName: "TESTING Chrome Safe Storage",
     accountName: "TESTING Chrome",
   };
   if (AppConstants.platform == "macosx") {
-    let { ChromeMacOSLoginCrypto } = ChromeUtils.importESModule(
+    const { ChromeMacOSLoginCrypto } = ChromeUtils.importESModule(
       "resource:///modules/ChromeMacOSLoginCrypto.sys.mjs"
     );
     loginCrypto = new ChromeMacOSLoginCrypto(
       mockMacOSKeychain.serviceName,
       mockMacOSKeychain.accountName,
@@ -228,11 +228,11 @@
       "Chrome",
       "Default",
       "Login Data",
     ];
   } else if (AppConstants.platform == "win") {
-    let { ChromeWindowsLoginCrypto } = ChromeUtils.importESModule(
+    const { ChromeWindowsLoginCrypto } = ChromeUtils.importESModule(
       "resource:///modules/ChromeWindowsLoginCrypto.sys.mjs"
     );
     loginCrypto = new ChromeWindowsLoginCrypto("Chrome");
     dirSvcPath = "AppData/Local/";
     pathId = "LocalAppData";
@@ -244,22 +244,22 @@
       "Login Data",
     ];
   } else {
     throw new Error("Not implemented");
   }
-  let dirSvcFile = do_get_file(dirSvcPath);
+  const dirSvcFile = do_get_file(dirSvcPath);
   registerFakePath(pathId, dirSvcFile);
 
   info(PathUtils.join(dirSvcFile.path, ...profilePathSegments));
-  let loginDataFilePath = PathUtils.join(
+  const loginDataFilePath = PathUtils.join(
     dirSvcFile.path,
     ...profilePathSegments
   );
   dbConn = await Sqlite.openConnection({ path: loginDataFilePath });
 
   if (AppConstants.platform == "macosx") {
-    let migrator = await MigrationUtils.getMigrator("chrome");
+    const migrator = await MigrationUtils.getMigrator("chrome");
     Object.assign(migrator, {
       _keychainServiceName: mockMacOSKeychain.serviceName,
       _keychainAccountName: mockMacOSKeychain.accountName,
       _keychainMockPassphrase: mockMacOSKeychain.passphrase,
     });
@@ -273,15 +273,15 @@
     return dbConn.close();
   });
 });
 
 add_task(async function test_importIntoEmptyDB() {
-  for (let login of TEST_LOGINS) {
+  for (const login of TEST_LOGINS) {
     await promiseSetPassword(login);
   }
 
-  let migrator = await MigrationUtils.getMigrator("chrome");
+  const migrator = await MigrationUtils.getMigrator("chrome");
   Assert.ok(
     await migrator.isSourceAvailable(),
     "Sanity check the source exists"
   );
 
@@ -313,11 +313,11 @@
   }
 });
 
 // Test that existing logins for the same primary key don't get overwritten
 add_task(async function test_importExistingLogins() {
-  let migrator = await MigrationUtils.getMigrator("chrome");
+  const migrator = await MigrationUtils.getMigrator("chrome");
   Assert.ok(
     await migrator.isSourceAvailable(),
     "Sanity check the source exists"
   );
 
@@ -327,11 +327,11 @@
     logins.length,
     0,
     "There are no logins after removing all of them"
   );
 
-  let newLogins = [];
+  const newLogins = [];
 
   // Create 3 new logins that are different but where the key properties are still the same.
   for (let i = 0; i < 3; i++) {
     newLogins.push(generateDifferentLogin(TEST_LOGINS[i]));
     Services.logins.addLogin(newLogins[i]);
diff --git a/browser/components/protections/test/browser/browser_protections_lockwise.js b/browser/components/protections/test/browser/browser_protections_lockwise.js
--- a/browser/components/protections/test/browser/browser_protections_lockwise.js
+++ b/browser/components/protections/test/browser/browser_protections_lockwise.js
@@ -10,15 +10,15 @@
   "resource:///actors/AboutProtectionsParent.sys.mjs"
 );
 const ABOUT_LOGINS_URL = "about:logins";
 
 add_task(async function testNoLoginsLockwiseCardUI() {
-  let tab = await BrowserTestUtils.openNewForegroundTab({
+  const tab = await BrowserTestUtils.openNewForegroundTab({
     url: "about:protections",
     gBrowser,
   });
-  let aboutLoginsPromise = BrowserTestUtils.waitForNewTab(
+  const aboutLoginsPromise = BrowserTestUtils.waitForNewTab(
     gBrowser,
     ABOUT_LOGINS_URL
   );
 
   info(
@@ -74,30 +74,30 @@
     info(
       "Click on the save passwords button and check that it opens about:logins in a new tab"
     );
     savePasswordsButton.click();
   });
-  let loginsTab = await aboutLoginsPromise;
+  const loginsTab = await aboutLoginsPromise;
   info("about:logins was successfully opened in a new tab");
   gBrowser.removeTab(loginsTab);
   gBrowser.removeTab(tab);
 });
 
 add_task(async function testLockwiseCardUIWithLogins() {
-  let tab = await BrowserTestUtils.openNewForegroundTab({
+  const tab = await BrowserTestUtils.openNewForegroundTab({
     url: "about:protections",
     gBrowser,
   });
-  let aboutLoginsPromise = BrowserTestUtils.waitForNewTab(
+  const aboutLoginsPromise = BrowserTestUtils.waitForNewTab(
     gBrowser,
     ABOUT_LOGINS_URL
   );
 
   info(
     "Add a login and check that lockwise card content for a logged in user is displayed correctly"
   );
-  Services.logins.addLogin(TEST_LOGIN1);
+  await Services.logins.addLoginAsync(TEST_LOGIN1);
   await BrowserTestUtils.reloadTab(tab);
 
   await SpecialPowers.spawn(tab.linkedBrowser, [], async function() {
     await ContentTaskUtils.waitForCondition(() => {
       const hasLogins = content.document.querySelector(".lockwise-card");
@@ -170,18 +170,18 @@
     info(
       "Click on the manage passwords button and check that it opens about:logins in a new tab"
     );
     managePasswordsButton.click();
   });
-  let loginsTab = await aboutLoginsPromise;
+  const loginsTab = await aboutLoginsPromise;
   info("about:logins was successfully opened in a new tab");
   gBrowser.removeTab(loginsTab);
 
   info(
     "Add another login and check that the scanned text about stored logins is updated after reload."
   );
-  Services.logins.addLogin(TEST_LOGIN2);
+  await Services.logins.addLoginAsync(TEST_LOGIN2);
   await BrowserTestUtils.reloadTab(tab);
 
   await SpecialPowers.spawn(tab.linkedBrowser, [], async function() {
     const lockwiseScannedText = content.document.querySelector(
       "#lockwise-scanned-text"
@@ -202,15 +202,15 @@
 
 add_task(async function testLockwiseCardUIWithBreachedLogins() {
   info(
     "Add a breached login and test that the lockwise scanned text is displayed correctly"
   );
-  let tab = await BrowserTestUtils.openNewForegroundTab({
+  const tab = await BrowserTestUtils.openNewForegroundTab({
     url: "about:protections",
     gBrowser,
   });
-  Services.logins.addLogin(TEST_LOGIN1);
+  await Services.logins.addLoginAsync(TEST_LOGIN1);
 
   info("Mock monitor data with a breached login to test the Lockwise UI");
   AboutProtectionsParent.setTestOverride(
     mockGetLoginDataWithSyncedDevices(false, 1)
   );
@@ -259,11 +259,11 @@
   Services.logins.removeLogin(TEST_LOGIN1);
   gBrowser.removeTab(tab);
 });
 
 add_task(async function testLockwiseCardPref() {
-  let tab = await BrowserTestUtils.openNewForegroundTab({
+  const tab = await BrowserTestUtils.openNewForegroundTab({
     url: "about:protections",
     gBrowser,
   });
 
   info("Disable showing the Lockwise card.");
diff --git a/browser/components/protections/test/browser/browser_protections_monitor.js b/browser/components/protections/test/browser/browser_protections_monitor.js
--- a/browser/components/protections/test/browser/browser_protections_monitor.js
+++ b/browser/components/protections/test/browser/browser_protections_monitor.js
@@ -16,18 +16,18 @@
   numBreaches: 11,
   numBreachesResolved: 0,
 };
 
 add_task(async function() {
-  let tab = await BrowserTestUtils.openNewForegroundTab({
+  const tab = await BrowserTestUtils.openNewForegroundTab({
     url: "about:protections",
     gBrowser,
   });
 
   await BrowserTestUtils.reloadTab(tab);
 
-  let monitorCardEnabled = Services.prefs.getBoolPref(
+  const monitorCardEnabled = Services.prefs.getBoolPref(
     "browser.contentblocking.report.monitor.enabled"
   );
 
   // Only run monitor card tests if it's enabled.
   if (monitorCardEnabled) {
@@ -37,11 +37,11 @@
     await checkNoLoginsContentIsDisplayed(tab, "monitor-sign-up");
 
     info(
       "Check that the correct content is displayed for users with monitor data."
     );
-    Services.logins.addLogin(TEST_LOGIN1);
+    await Services.logins.addLoginAsync(TEST_LOGIN1);
     AboutProtectionsParent.setTestOverride(mockGetMonitorData(mockMonitorData));
     await BrowserTestUtils.reloadTab(tab);
 
     Assert.ok(
       true,
diff --git a/browser/components/protections/test/browser/browser_protections_telemetry.js b/browser/components/protections/test/browser/browser_protections_telemetry.js
--- a/browser/components/protections/test/browser/browser_protections_telemetry.js
+++ b/browser/components/protections/test/browser/browser_protections_telemetry.js
@@ -205,11 +205,11 @@
     url: "about:protections",
     gBrowser,
   });
 
   // Add user logins.
-  Services.logins.addLogin(TEST_LOGIN1);
+  await Services.logins.addLoginAsync(TEST_LOGIN1);
   await BrowserTestUtils.reloadTab(tab);
   await SpecialPowers.spawn(tab.linkedBrowser, [], async function() {
     const managePasswordsButton = await ContentTaskUtils.waitForCondition(
       () => {
         return content.document.getElementById("manage-passwords-button");
diff --git a/dom/ipc/tests/browser_wpi_base.js b/dom/ipc/tests/browser_wpi_base.js
--- a/dom/ipc/tests/browser_wpi_base.js
+++ b/dom/ipc/tests/browser_wpi_base.js
@@ -188,11 +188,11 @@
       let LoginInfo = new Components.Constructor(
         "@mozilla.org/login-manager/loginInfo;1",
         Ci.nsILoginInfo,
         "init"
       );
-      Services.logins.addLogin(
+      await Services.logins.addLoginAsync(
         new LoginInfo(COM_ORIGIN, "", null, "username", "password", "", "")
       );
 
       // Init login detection service to trigger fetching logins
       let loginDetection = Cc[
diff --git a/services/fxaccounts/tests/xpcshell/test_loginmgr_storage.js b/services/fxaccounts/tests/xpcshell/test_loginmgr_storage.js
--- a/services/fxaccounts/tests/xpcshell/test_loginmgr_storage.js
+++ b/services/fxaccounts/tests/xpcshell/test_loginmgr_storage.js
@@ -303,11 +303,11 @@
     "foo@bar.com", // aUsername
     JSON.stringify(contents), // aPassword
     "", // aUsernameField
     ""
   ); // aPasswordField
-  Services.logins.addLogin(login);
+  await Services.logins.addLoginAsync(login);
 
   // ensure we read it.
   let storage = new LoginManagerStorage();
   let got = await storage.get("uid", "foo@bar.com");
   Assert.deepEqual(got, contents);
diff --git a/services/sync/tests/unit/test_engine_changes_during_sync.js b/services/sync/tests/unit/test_engine_changes_during_sync.js
--- a/services/sync/tests/unit/test_engine_changes_during_sync.js
+++ b/services/sync/tests/unit/test_engine_changes_during_sync.js
@@ -141,11 +141,11 @@
         "username",
         "password",
         "",
         ""
       );
-      Services.logins.addLogin(login);
+      await Services.logins.addLoginAsync(login);
       await engine._tracker.asyncObserver.promiseObserversComplete();
     }
   };
 
   engine._tracker.start();
diff --git a/services/sync/tests/unit/test_password_engine.js b/services/sync/tests/unit/test_password_engine.js
--- a/services/sync/tests/unit/test_password_engine.js
+++ b/services/sync/tests/unit/test_password_engine.js
@@ -43,11 +43,11 @@
   let server = await serverForFoo(engine);
   await SyncTestingInfrastructure(server);
 
   enableValidationPrefs();
 
-  let login = Services.logins.addLogin(
+  let login = await Services.logins.addLoginAsync(
     new LoginInfo(
       "https://example.com",
       "",
       null,
       "username",
@@ -95,11 +95,11 @@
   enableValidationPrefs();
 
   engine._tracker.start();
 
   try {
-    let login = Services.logins.addLogin(
+    let login = await Services.logins.addLoginAsync(
       new LoginInfo(
         FXA_PWDMGR_HOST,
         null,
         FXA_PWDMGR_REALM,
         "fxa-uid",
@@ -144,11 +144,11 @@
       "username",
       "password",
       "",
       ""
     );
-    Services.logins.addLogin(login);
+    await Services.logins.addLoginAsync(login);
 
     let logins = Services.logins.findLogins("https://example.com", "", "");
     equal(logins.length, 1, "Should find new login in login manager");
     newLogin = logins[0].QueryInterface(Ci.nsILoginMetaInfo);
 
@@ -179,11 +179,11 @@
       "us3r",
       "0ldpa55",
       "",
       ""
     );
-    Services.logins.addLogin(login);
+    await Services.logins.addLoginAsync(login);
 
     let props = new PropertyBag();
     let localPasswordChangeTime = Date.now() - 1 * 60 * 60 * 24 * 1000;
     props.setProperty("timePasswordChanged", localPasswordChangeTime);
     Services.logins.modifyLogin(login, props);
diff --git a/services/sync/tests/unit/test_password_tracker.js b/services/sync/tests/unit/test_password_tracker.js
--- a/services/sync/tests/unit/test_password_tracker.js
+++ b/services/sync/tests/unit/test_password_tracker.js
@@ -37,11 +37,11 @@
       usernameField: "username",
       passwordField: "password",
     };
     recordNum++;
     let login = store._nsLoginInfoFromRecord(record);
-    Services.logins.addLogin(login);
+    await Services.logins.addLoginAsync(login);
     await tracker.asyncObserver.promiseObserversComplete();
   }
 
   try {
     _(
@@ -124,11 +124,11 @@
       usernameField: "username",
       passwordField: "password",
     };
     recordNum++;
     let login = store._nsLoginInfoFromRecord(record);
-    Services.logins.addLogin(login);
+    await Services.logins.addLoginAsync(login);
     await tracker.asyncObserver.promiseObserversComplete();
   }
   try {
     _("Tell tracker to start tracking changes");
     tracker.start();
diff --git a/toolkit/components/cleardata/tests/unit/test_passwords.js b/toolkit/components/cleardata/tests/unit/test_passwords.js
--- a/toolkit/components/cleardata/tests/unit/test_passwords.js
+++ b/toolkit/components/cleardata/tests/unit/test_passwords.js
@@ -18,11 +18,11 @@
     username: "admin",
     password: "12345678",
     usernameField: "field_username",
     passwordField: "field_password",
   });
-  Services.logins.addLogin(loginInfo);
+  await Services.logins.addLoginAsync(loginInfo);
 
   Assert.equal(countLogins(URL), 1);
 
   let uri = Services.io.newURI(URL);
   let principal = Services.scriptSecurityManager.createContentPrincipal(
@@ -55,11 +55,11 @@
     username: "admin",
     password: "12345678",
     usernameField: "field_username",
     passwordField: "field_password",
   });
-  Services.logins.addLogin(loginInfo);
+  await Services.logins.addLoginAsync(loginInfo);
 
   Assert.equal(countLogins(URL), 1);
 
   await new Promise(resolve => {
     Services.clearData.deleteData(
diff --git a/toolkit/components/forgetaboutsite/test/unit/test_removeDataFromDomain.js b/toolkit/components/forgetaboutsite/test/unit/test_removeDataFromDomain.js
--- a/toolkit/components/forgetaboutsite/test/unit/test_removeDataFromDomain.js
+++ b/toolkit/components/forgetaboutsite/test/unit/test_removeDataFromDomain.js
@@ -105,11 +105,11 @@
  * Adds a login for the specified host to the login manager.
  *
  * @param aHost
  *        The host to add the login for.
  */
-function add_login(aHost) {
+async function add_login(aHost) {
   check_login_exists(aHost, false);
   let login = Cc["@mozilla.org/login-manager/loginInfo;1"].createInstance(
     Ci.nsILoginInfo
   );
   login.init(
@@ -119,11 +119,11 @@
     LOGIN_USERNAME,
     LOGIN_PASSWORD,
     LOGIN_USERNAME_FIELD,
     LOGIN_PASSWORD_FIELD
   );
-  Services.logins.addLogin(login);
+  await Services.logins.addLoginAsync(login);
   check_login_exists(aHost, true);
 }
 
 /**
  * Checks to see if a login exists for a host.
@@ -310,25 +310,25 @@
   check_disabled_host(TEST_HOST, false);
 }
 
 async function test_login_manager_logins_cleared_with_direct_match() {
   const TEST_HOST = "http://mozilla.org";
-  add_login(TEST_HOST);
+  await add_login(TEST_HOST);
   await ForgetAboutSite.removeDataFromDomain("mozilla.org");
   check_login_exists(TEST_HOST, true);
 }
 
 async function test_login_manager_logins_cleared_with_subdomain() {
   const TEST_HOST = "http://www.mozilla.org";
-  add_login(TEST_HOST);
+  await add_login(TEST_HOST);
   await ForgetAboutSite.removeDataFromDomain("mozilla.org");
   check_login_exists(TEST_HOST, true);
 }
 
 async function test_login_manager_logins_not_cleared_with_uri_contains_domain() {
   const TEST_HOST = "http://ilovemozilla.org";
-  add_login(TEST_HOST);
+  await add_login(TEST_HOST);
   await ForgetAboutSite.removeDataFromDomain("mozilla.org");
   check_login_exists(TEST_HOST, true);
 
   Services.logins.removeAllUserFacingLogins();
   check_login_exists(TEST_HOST, false);
diff --git a/toolkit/components/passwordmgr/test/LoginTestUtils.sys.mjs b/toolkit/components/passwordmgr/test/LoginTestUtils.sys.mjs
--- a/toolkit/components/passwordmgr/test/LoginTestUtils.sys.mjs
+++ b/toolkit/components/passwordmgr/test/LoginTestUtils.sys.mjs
@@ -62,17 +62,11 @@
       origin,
       formActionOrigin: formActionOrigin || origin,
       username,
       password,
     });
-    let storageChangedPromised = TestUtils.topicObserved(
-      "passwordmgr-storage-changed",
-      (_, data) => data == "addLogin"
-    );
-    Services.logins.addLogin(login);
-    let [savedLogin] = await storageChangedPromised;
-    return savedLogin;
+    return Services.logins.addLoginAsync(login);
   },
 
   async modifyLogin(oldLogin, newLogin) {
     const storageChangedPromise = TestUtils.topicObserved(
       "passwordmgr-storage-changed",
diff --git a/toolkit/components/passwordmgr/test/browser/browser_autocomplete_autofocus_with_frame.js b/toolkit/components/passwordmgr/test/browser/browser_autocomplete_autofocus_with_frame.js
--- a/toolkit/components/passwordmgr/test/browser/browser_autocomplete_autofocus_with_frame.js
+++ b/toolkit/components/passwordmgr/test/browser/browser_autocomplete_autofocus_with_frame.js
@@ -5,18 +5,18 @@
     origin: "https://example.org",
     formActionOrigin: "https://example.org",
     username: "username1",
     password: "password1",
   });
-  Services.logins.addLogin(login);
+  await Services.logins.addLoginAsync(login);
   login = LoginTestUtils.testData.formLogin({
     origin: "https://example.org",
     formActionOrigin: "https://example.org",
     username: "username2",
     password: "password2",
   });
-  Services.logins.addLogin(login);
+  await Services.logins.addLoginAsync(login);
 });
 
 // Verify that the autocomplete popup opens when the username field in autofocused.
 add_task(async function test_autofocus_autocomplete() {
   let popup = document.getElementById("PopupAutoComplete");
diff --git a/toolkit/components/passwordmgr/test/browser/browser_autocomplete_disabled_readonly_passwordField.js b/toolkit/components/passwordmgr/test/browser/browser_autocomplete_disabled_readonly_passwordField.js
--- a/toolkit/components/passwordmgr/test/browser/browser_autocomplete_disabled_readonly_passwordField.js
+++ b/toolkit/components/passwordmgr/test/browser/browser_autocomplete_disabled_readonly_passwordField.js
@@ -20,12 +20,11 @@
     formActionOrigin: "https://example.org",
     username: "username2",
     password: "password2",
   });
 
-  Services.logins.addLogin(login1);
-  Services.logins.addLogin(login2);
+  await Services.logins.addLogins([login1, login2]);
 });
 
 add_task(
   async function test_autocomplete_for_usernameField_with_disabled_passwordField() {
     await BrowserTestUtils.withNewTab(
diff --git a/toolkit/components/passwordmgr/test/browser/browser_autocomplete_footer.js b/toolkit/components/passwordmgr/test/browser/browser_autocomplete_footer.js
--- a/toolkit/components/passwordmgr/test/browser/browser_autocomplete_footer.js
+++ b/toolkit/components/passwordmgr/test/browser/browser_autocomplete_footer.js
@@ -27,13 +27,11 @@
   Services.prefs.setBoolPref("signon.showAutoCompleteFooter", true);
   registerCleanupFunction(() => {
     Services.prefs.clearUserPref("signon.showAutoCompleteFooter");
   });
 
-  for (let login of loginList()) {
-    Services.logins.addLogin(login);
-  }
+  await Services.logins.addLogins(loginList());
 });
 
 add_task(async function test_autocomplete_footer_onclick() {
   let url = TEST_ORIGIN + BASIC_FORM_PAGE_PATH;
   await BrowserTestUtils.withNewTab(
diff --git a/toolkit/components/passwordmgr/test/browser/browser_autocomplete_primary_password.js b/toolkit/components/passwordmgr/test/browser/browser_autocomplete_primary_password.js
--- a/toolkit/components/passwordmgr/test/browser/browser_autocomplete_primary_password.js
+++ b/toolkit/components/passwordmgr/test/browser/browser_autocomplete_primary_password.js
@@ -28,11 +28,11 @@
     origin: "https://example.com",
     formActionOrigin: "https://example.com",
     username: "username",
     password: "password",
   });
-  Services.logins.addLogin(login);
+  await Services.logins.addLoginAsync(login);
   LoginTestUtils.primaryPassword.enable();
 
   registerCleanupFunction(function() {
     LoginTestUtils.primaryPassword.disable();
   });
@@ -80,14 +80,14 @@
   // Wait for initial primary password dialog after adding the login.
   let dialogShown = waitForDialog();
 
   let win = await BrowserTestUtils.openNewBrowserWindow();
 
-  Services.tm.dispatchToMainThread(() => {
+  Services.tm.dispatchToMainThread(async () => {
     try {
       // Trigger a MP prompt in the new window by saving a login
-      Services.logins.addLogin(LoginTestUtils.testData.formLogin());
+      await Services.logins.addLoginAsync(LoginTestUtils.testData.formLogin());
     } catch (e) {
       // Handle throwing from MP cancellation
     }
   });
   let { close } = await dialogShown;
diff --git a/toolkit/components/passwordmgr/test/browser/browser_autofill_hidden_document.js b/toolkit/components/passwordmgr/test/browser/browser_autofill_hidden_document.js
--- a/toolkit/components/passwordmgr/test/browser/browser_autofill_hidden_document.js
+++ b/toolkit/components/passwordmgr/test/browser/browser_autofill_hidden_document.js
@@ -33,11 +33,11 @@
     origin: "https://example.org",
     formActionOrigin: "https://example.org",
     username: "user1",
     password: "pass1",
   });
-  Services.logins.addLogin(login);
+  await Services.logins.addLoginAsync(login);
 });
 
 testUrlsWithForm.forEach(testUrl => {
   add_task(async function test_processed_form_fired() {
     // Sanity check. If this doesnt work any results for the subsequent tasks are suspect
diff --git a/toolkit/components/passwordmgr/test/browser/browser_autofill_http.js b/toolkit/components/passwordmgr/test/browser/browser_autofill_http.js
--- a/toolkit/components/passwordmgr/test/browser/browser_autofill_http.js
+++ b/toolkit/components/passwordmgr/test/browser/browser_autofill_http.js
@@ -1,23 +1,22 @@
 const TEST_URL_PATH =
   "://example.org/browser/toolkit/components/passwordmgr/test/browser/";
 
 add_setup(async function() {
-  let login = LoginTestUtils.testData.formLogin({
+  const login1 = LoginTestUtils.testData.formLogin({
     origin: "http://example.org",
     formActionOrigin: "http://example.org",
     username: "username",
     password: "password",
   });
-  Services.logins.addLogin(login);
-  login = LoginTestUtils.testData.formLogin({
+  const login2 = LoginTestUtils.testData.formLogin({
     origin: "http://example.org",
     formActionOrigin: "http://example.com",
     username: "username",
     password: "password",
   });
-  Services.logins.addLogin(login);
+  await Services.logins.addLogins([login1, login2]);
   await SpecialPowers.pushPrefEnv({
     set: [["signon.autofillForms.http", false]],
   });
 });
 
diff --git a/toolkit/components/passwordmgr/test/browser/browser_autofill_track_filled_logins.js b/toolkit/components/passwordmgr/test/browser/browser_autofill_track_filled_logins.js
--- a/toolkit/components/passwordmgr/test/browser/browser_autofill_track_filled_logins.js
+++ b/toolkit/components/passwordmgr/test/browser/browser_autofill_track_filled_logins.js
@@ -29,11 +29,11 @@
       "bob",
       "mypassword",
       "form-basic-username",
       "form-basic-password"
     );
-    login = Services.logins.addLogin(login);
+    login = await Services.logins.addLoginAsync(login);
     Assert.equal(
       login.timesUsed,
       1,
       "The timesUsed should be 1 after creation"
     );
diff --git a/toolkit/components/passwordmgr/test/browser/browser_context_menu.js b/toolkit/components/passwordmgr/test/browser/browser_context_menu.js
--- a/toolkit/components/passwordmgr/test/browser/browser_context_menu.js
+++ b/toolkit/components/passwordmgr/test/browser/browser_context_menu.js
@@ -24,13 +24,11 @@
   registerCleanupFunction(() => {
     Services.prefs.clearUserPref("signon.autofillForms");
     Services.prefs.clearUserPref("signon.schemeUpgrades");
     Services.prefs.clearUserPref("signon.usernameOnlyForm.enabled");
   });
-  for (let login of loginList()) {
-    Services.logins.addLogin(login);
-  }
+  await Services.logins.addLogins(loginList());
 });
 
 /**
  * Check if the context menu is populated with the right
  * menuitems for the target password input field.
diff --git a/toolkit/components/passwordmgr/test/browser/browser_context_menu_autocomplete_interaction.js b/toolkit/components/passwordmgr/test/browser/browser_context_menu_autocomplete_interaction.js
--- a/toolkit/components/passwordmgr/test/browser/browser_context_menu_autocomplete_interaction.js
+++ b/toolkit/components/passwordmgr/test/browser/browser_context_menu_autocomplete_interaction.js
@@ -20,13 +20,11 @@
     autocompletePopup.removeEventListener(
       "popupshowing",
       autocompleteUnexpectedPopupShowing
     );
   });
-  for (let login of loginList()) {
-    Services.logins.addLogin(login);
-  }
+  await Services.logins.addLogins(loginList());
   autocompletePopup.addEventListener(
     "popupshowing",
     autocompleteUnexpectedPopupShowing
   );
 });
diff --git a/toolkit/components/passwordmgr/test/browser/browser_context_menu_generated_password.js b/toolkit/components/passwordmgr/test/browser/browser_context_menu_generated_password.js
--- a/toolkit/components/passwordmgr/test/browser/browser_context_menu_generated_password.js
+++ b/toolkit/components/passwordmgr/test/browser/browser_context_menu_generated_password.js
@@ -258,11 +258,11 @@
   });
   let storageChangedPromised = TestUtils.topicObserved(
     "passwordmgr-storage-changed",
     (_, data) => data == "addLogin"
   );
-  Services.logins.addLogin(login);
+  await Services.logins.addLoginAsync(login);
   await storageChangedPromised;
 
   let formFilled = listenForTestNotification("FormProcessed");
 
   await BrowserTestUtils.withNewTab(
diff --git a/toolkit/components/passwordmgr/test/browser/browser_context_menu_iframe.js b/toolkit/components/passwordmgr/test/browser/browser_context_menu_iframe.js
--- a/toolkit/components/passwordmgr/test/browser/browser_context_menu_iframe.js
+++ b/toolkit/components/passwordmgr/test/browser/browser_context_menu_iframe.js
@@ -19,13 +19,11 @@
   Services.prefs.setBoolPref("signon.schemeUpgrades", true);
   registerCleanupFunction(() => {
     Services.prefs.clearUserPref("signon.autofillForms");
     Services.prefs.clearUserPref("signon.schemeUpgrades");
   });
-  for (let login of loginList()) {
-    Services.logins.addLogin(login);
-  }
+  await Services.logins.addLogins(loginList());
 });
 
 /**
  * Check if the password field is correctly filled when it's in an iframe.
  */
diff --git a/toolkit/components/passwordmgr/test/browser/browser_deleteLoginsBackup.js b/toolkit/components/passwordmgr/test/browser/browser_deleteLoginsBackup.js
--- a/toolkit/components/passwordmgr/test/browser/browser_deleteLoginsBackup.js
+++ b/toolkit/components/passwordmgr/test/browser/browser_deleteLoginsBackup.js
@@ -80,14 +80,14 @@
     );
     info("Adding two logins: fxa key and one user facing login");
     let storageUpdatePromise = TestUtils.topicObserved(
       "password-storage-updated"
     );
-    Services.logins.addLogin(login1);
+    await Services.logins.addLoginAsync(login1);
     Assert.ok(true, "added login1");
     await loginStoreExists();
-    Services.logins.addLogin(fxaKey);
+    await Services.logins.addLoginAsync(fxaKey);
     Assert.ok(true, "added fxaKey");
     await loginBackupExists();
     Assert.ok(true, "logins-backup.json now exists");
     await storageUpdatePromise;
     info("Writes to storage are complete for addLogin calls");
@@ -121,16 +121,16 @@
 
   let storageUpdatePromise = TestUtils.topicObserved(
     "password-storage-updated"
   );
   info("Add a login to create logins.json");
-  Services.logins.addLogin(login1);
+  await Services.logins.addLoginAsync(login1);
   await loginStoreExists();
   Assert.ok(true, "logins.json now exists");
 
   info("Add a second login to create logins-backup.json");
-  Services.logins.addLogin(login2);
+  await Services.logins.addLoginAsync(login2);
   await loginBackupExists();
   info("logins-backup.json now exists");
 
   await storageUpdatePromise;
   info("Writes to storage are complete for addLogin calls");
@@ -164,15 +164,15 @@
 
   let storageUpdatePromise = TestUtils.topicObserved(
     "password-storage-updated"
   );
   info("Add a login to create logins.json");
-  Services.logins.addLogin(login1);
+  await Services.logins.addLoginAsync(login1);
   Assert.ok(true, "added login1");
   await loginStoreExists();
   Assert.ok(true, "logins.json now exists");
-  Services.logins.addLogin(login2);
+  await Services.logins.addLoginAsync(login2);
   Assert.ok(true, "added login2");
   await loginBackupExists();
   info("logins-backup.json now exists");
 
   await storageUpdatePromise;
@@ -191,13 +191,13 @@
   );
   await IOUtils.remove(loginStorePath);
 
   info("Testing the removeAllLogins() case when FxA key is present");
   storageUpdatePromise = TestUtils.topicObserved("password-storage-updated");
-  Services.logins.addLogin(login1);
+  await Services.logins.addLoginAsync(login1);
   await loginStoreExists();
-  Services.logins.addLogin(fxaKey);
+  await Services.logins.addLoginAsync(fxaKey);
   await loginBackupExists();
   info("logins-backup.json now exists");
   await storageUpdatePromise;
   info("Write to storage are complete for addLogin calls");
 
@@ -223,13 +223,13 @@
   info("Testing the removeLogin() case when there is no saved fxa key");
   info("Adding two logins");
   let storageUpdatePromise = TestUtils.topicObserved(
     "password-storage-updated"
   );
-  Services.logins.addLogin(login1);
+  await Services.logins.addLoginAsync(login1);
   await loginStoreExists();
-  Services.logins.addLogin(login2);
+  await Services.logins.addLoginAsync(login2);
   await loginBackupExists();
   info("logins-backup.json now exists");
 
   await storageUpdatePromise;
   info("Writes to storage are complete for addLogin calls");
@@ -253,13 +253,13 @@
   await IOUtils.remove(loginStorePath);
 
   info("Testing the removeLogin() case when there is a saved fxa key");
   info("Adding two logins: one user facing and the fxa key");
   storageUpdatePromise = TestUtils.topicObserved("password-storage-updated");
-  Services.logins.addLogin(login1);
+  await Services.logins.addLoginAsync(login1);
   await loginStoreExists();
-  Services.logins.addLogin(fxaKey);
+  await Services.logins.addLoginAsync(fxaKey);
   await loginBackupExists();
   info("logins-backup.json now exists");
 
   await storageUpdatePromise;
   info("Writes to storage are complete for addLogin calls");
diff --git a/toolkit/components/passwordmgr/test/browser/browser_doorhanger_autocomplete_values.js b/toolkit/components/passwordmgr/test/browser/browser_doorhanger_autocomplete_values.js
--- a/toolkit/components/passwordmgr/test/browser/browser_doorhanger_autocomplete_values.js
+++ b/toolkit/components/passwordmgr/test/browser/browser_doorhanger_autocomplete_values.js
@@ -136,19 +136,20 @@
   await SpecialPowers.pushPrefEnv({
     set: [["signon.capture.inputChanges.enabled", true]],
   });
 }
 
-function _addSavedLogin(username) {
-  Services.logins.addLogin(
+async function _addSavedLogins(logins) {
+  let loginsData = logins.map(({ username }) =>
     LoginTestUtils.testData.formLogin({
       origin: "https://example.com",
       formActionOrigin: "https://example.com",
       username,
       password: "Saved login passwords not used in this test",
     })
   );
+  await Services.logins.addLogins(loginsData);
 }
 
 async function _clickDropmarker(document, notificationElement) {
   let acPopup = document.querySelector(AUTOCOMPLETE_POPUP_SELECTOR);
   let acPopupShown = BrowserTestUtils.waitForEvent(acPopup, "popupshown");
@@ -178,16 +179,13 @@
     await cleanupDoorhanger();
     await cleanupPasswordNotifications();
     Services.logins.removeAllUserFacingLogins();
 
     // Create the pre-existing logins when needed.
-    info("Adding any saved logins");
     if (testCase.savedLogins) {
-      for (let login of testCase.savedLogins) {
-        info("Adding login " + JSON.stringify(login));
-        _addSavedLogin(login.username);
-      }
+      info("Adding logins " + JSON.stringify(testCase.savedLogins));
+      await _addSavedLogins(testCase.savedLogins);
     }
 
     info("Opening tab");
     await BrowserTestUtils.withNewTab(
       {
diff --git a/toolkit/components/passwordmgr/test/browser/browser_doorhanger_dismissed_for_ccnumber.js b/toolkit/components/passwordmgr/test/browser/browser_doorhanger_dismissed_for_ccnumber.js
--- a/toolkit/components/passwordmgr/test/browser/browser_doorhanger_dismissed_for_ccnumber.js
+++ b/toolkit/components/passwordmgr/test/browser/browser_doorhanger_dismissed_for_ccnumber.js
@@ -164,11 +164,11 @@
         "4111111111111111",
         "111", // password looks like a card security code
         "form-basic-username",
         "form-basic-password"
       );
-      Services.logins.addLogin(login);
+      await Services.logins.addLoginAsync(login);
 
       let passwordFilledPromise = listenForTestNotification(
         "PasswordEditedOrGenerated"
       );
 
diff --git a/toolkit/components/passwordmgr/test/browser/browser_doorhanger_httpsUpgrade.js b/toolkit/components/passwordmgr/test/browser/browser_doorhanger_httpsUpgrade.js
--- a/toolkit/components/passwordmgr/test/browser/browser_doorhanger_httpsUpgrade.js
+++ b/toolkit/components/passwordmgr/test/browser/browser_doorhanger_httpsUpgrade.js
@@ -28,11 +28,11 @@
 
 add_task(async function test_httpsUpgradeCaptureFields_noChange() {
   info(
     "Check that we don't prompt to remember when capturing an upgraded login with no change"
   );
-  Services.logins.addLogin(login1);
+  await Services.logins.addLoginAsync(login1);
   // Sanity check the HTTP login exists.
   let logins = Services.logins.getAllLogins();
   Assert.equal(logins.length, 1, "Should have the HTTP login");
 
   await testSubmittingLoginForm(
@@ -71,11 +71,11 @@
 
 add_task(async function test_httpsUpgradeCaptureFields_changePW() {
   info(
     "Check that we prompt to change when capturing an upgraded login with a new PW"
   );
-  Services.logins.addLogin(login1);
+  await Services.logins.addLoginAsync(login1);
   // Sanity check the HTTP login exists.
   let logins = Services.logins.getAllLogins();
   Assert.equal(logins.length, 1, "Should have the HTTP login");
 
   await testSubmittingLoginForm(
@@ -129,12 +129,11 @@
 add_task(
   async function test_httpsUpgradeCaptureFields_changePWWithBothSchemesSaved() {
     info(
       "Check that we prompt to change and properly save when capturing an upgraded login with a new PW when an http login also exists for that username"
     );
-    Services.logins.addLogin(login1);
-    Services.logins.addLogin(login1HTTPS);
+    await Services.logins.addLogins([login1, login1HTTPS]);
 
     let logins = Services.logins.getAllLogins();
     Assert.equal(logins.length, 2, "Should have both HTTP and HTTPS logins");
 
     await testSubmittingLoginForm(
@@ -211,11 +210,11 @@
   }
 );
 
 add_task(async function test_httpsUpgradeCaptureFields_captureMatchingHTTP() {
   info("Capture a new HTTP login which matches a stored HTTPS one.");
-  Services.logins.addLogin(login1HTTPS);
+  await Services.logins.addLoginAsync(login1HTTPS);
 
   await testSubmittingLoginFormHTTP(
     "subtst_notifications_1.html",
     async function(fieldValues) {
       Assert.equal(
diff --git a/toolkit/components/passwordmgr/test/browser/browser_doorhanger_multipage_form.js b/toolkit/components/passwordmgr/test/browser/browser_doorhanger_multipage_form.js
--- a/toolkit/components/passwordmgr/test/browser/browser_doorhanger_multipage_form.js
+++ b/toolkit/components/passwordmgr/test/browser/browser_doorhanger_multipage_form.js
@@ -94,11 +94,11 @@
     password,
     expectOutcome,
   } = testData;
   // Add a login for the origin of the form if testing a change notification.
   if (oldPassword) {
-    Services.logins.addLogin(
+    await Services.logins.addLoginAsync(
       LoginTestUtils.testData.formLogin({
         origin: "https://example.com",
         formActionOrigin: "https://example.com",
         username: typeof oldUsername !== "undefined" ? oldUsername : username,
         password: oldPassword,
diff --git a/toolkit/components/passwordmgr/test/browser/browser_doorhanger_password_edits.js b/toolkit/components/passwordmgr/test/browser/browser_doorhanger_password_edits.js
--- a/toolkit/components/passwordmgr/test/browser/browser_doorhanger_password_edits.js
+++ b/toolkit/components/passwordmgr/test/browser/browser_doorhanger_password_edits.js
@@ -69,22 +69,22 @@
     await cleanupDoorhanger();
     await cleanupPasswordNotifications();
 
     // Create the pre-existing logins when needed.
     if (testCase.usernameInPageExists) {
-      Services.logins.addLogin(
+      await Services.logins.addLoginAsync(
         LoginTestUtils.testData.formLogin({
           origin: "https://example.com",
           formActionOrigin: "https://example.com",
           username: testCase.usernameInPage,
           password: testCase.passwordInStorage,
         })
       );
     }
 
     if (testCase.usernameChangedToExists) {
-      Services.logins.addLogin(
+      await Services.logins.addLoginAsync(
         LoginTestUtils.testData.formLogin({
           origin: "https://example.com",
           formActionOrigin: "https://example.com",
           username: testCase.usernameChangedTo,
           password: testCase.passwordChangedTo,
diff --git a/toolkit/components/passwordmgr/test/browser/browser_doorhanger_remembering.js b/toolkit/components/passwordmgr/test/browser/browser_doorhanger_remembering.js
--- a/toolkit/components/passwordmgr/test/browser/browser_doorhanger_remembering.js
+++ b/toolkit/components/passwordmgr/test/browser/browser_doorhanger_remembering.js
@@ -417,11 +417,11 @@
   );
 });
 
 add_task(async function test_pwOnlyNewLoginMatchesUPForm() {
   info("Check for update popup when new existing pw-only login matches form.");
-  Services.logins.addLogin(login2);
+  await Services.logins.addLoginAsync(login2);
   await testSubmittingLoginFormHTTP(
     "subtst_notifications_1.html",
     async function(fieldValues) {
       Assert.equal(
         fieldValues.username,
@@ -471,11 +471,11 @@
   Services.logins.removeLogin(login);
 });
 
 add_task(async function test_pwOnlyOldLoginMatchesUPForm() {
   info("Check for update popup when old existing pw-only login matches form.");
-  Services.logins.addLogin(login2);
+  await Services.logins.addLoginAsync(login2);
 
   // Change the timePasswordChanged to be old so that the password won't be
   // revealed in the doorhanger.
   let oldTimeMS = new Date("2009-11-15").getTime();
   Services.logins.modifyLogin(
@@ -540,11 +540,11 @@
 
 add_task(async function test_pwOnlyFormMatchesLogin() {
   info(
     "Check for no notification popup when pw-only form matches existing login."
   );
-  Services.logins.addLogin(login1);
+  await Services.logins.addLoginAsync(login1);
 
   await testSubmittingLoginFormHTTP("subtst_notifications_6.html", function(
     fieldValues
   ) {
     Assert.equal(fieldValues.username, "null", "Checking submitted username");
@@ -569,11 +569,11 @@
 
 add_task(async function test_pwOnlyFormDoesntMatchExisting() {
   info(
     "Check for notification popup when pw-only form doesn't match existing login."
   );
-  Services.logins.addLogin(login1B);
+  await Services.logins.addLoginAsync(login1B);
 
   await testSubmittingLoginFormHTTP(
     "subtst_notifications_6.html",
     async function(fieldValues) {
       Assert.equal(fieldValues.username, "null", "Checking submitted username");
@@ -599,11 +599,11 @@
   Services.logins.removeLogin(login1B);
 });
 
 add_task(async function test_changeUPLoginOnUPForm_dont() {
   info("Check for change-password popup, u+p login on u+p form. (not changed)");
-  Services.logins.addLogin(login1);
+  await Services.logins.addLoginAsync(login1);
 
   await testSubmittingLoginFormHTTP(
     "subtst_notifications_8.html",
     async function(fieldValues) {
       Assert.equal(
@@ -640,11 +640,11 @@
   Services.logins.removeLogin(login1);
 });
 
 add_task(async function test_changeUPLoginOnUPForm_remove() {
   info("Check for change-password popup, u+p login on u+p form. (remove)");
-  Services.logins.addLogin(login1);
+  await Services.logins.addLoginAsync(login1);
 
   await testSubmittingLoginFormHTTP(
     "subtst_notifications_8.html",
     async function(fieldValues, browser) {
       Assert.equal(
@@ -681,11 +681,11 @@
   Assert.equal(logins.length, 0, "Should have 0 logins");
 });
 
 add_task(async function test_changeUPLoginOnUPForm_change() {
   info("Check for change-password popup, u+p login on u+p form.");
-  Services.logins.addLogin(login1);
+  await Services.logins.addLoginAsync(login1);
 
   await testSubmittingLoginFormHTTP(
     "subtst_notifications_8.html",
     async function(fieldValues) {
       Assert.equal(
@@ -737,11 +737,11 @@
   login1.password = "notifyp1";
 });
 
 add_task(async function test_changePLoginOnUPForm() {
   info("Check for change-password popup, p-only login on u+p form (empty u).");
-  Services.logins.addLogin(login2);
+  await Services.logins.addLoginAsync(login2);
 
   await testSubmittingLoginFormHTTP(
     "subtst_notifications_9.html",
     async function(fieldValues) {
       Assert.equal(fieldValues.username, "", "Checking submitted username");
@@ -925,11 +925,11 @@
   info(
     "Check for notification popup when a form with 2 password fields (no username) " +
       "is submitted and there is a saved login with a username and different password."
   );
 
-  Services.logins.addLogin(login1B);
+  await Services.logins.addLoginAsync(login1B);
 
   await testSubmittingLoginFormHTTP(
     "subtst_notifications_2pw_0un.html",
     async function(fieldValues) {
       Assert.equal(fieldValues.username, "null", "Checking submitted username");
@@ -959,11 +959,11 @@
   info(
     "Check for notification popup when a form with 2 password fields (no username) " +
       "is submitted and there is a saved login with no username and different password."
   );
 
-  Services.logins.addLogin(login2B);
+  await Services.logins.addLoginAsync(login2B);
 
   await testSubmittingLoginFormHTTP(
     "subtst_notifications_2pw_0un.html",
     async function(fieldValues) {
       Assert.equal(fieldValues.username, "null", "Checking submitted username");
@@ -993,11 +993,11 @@
   info(
     "Check for no notification popup when a form with 2 password fields (no username) " +
       "is submitted and there is a saved login with a username and the same password."
   );
 
-  Services.logins.addLogin(login2);
+  await Services.logins.addLoginAsync(login2);
 
   await testSubmittingLoginFormHTTP(
     "subtst_notifications_2pw_0un.html",
     function(fieldValues) {
       Assert.equal(fieldValues.username, "null", "Checking submitted username");
@@ -1023,11 +1023,11 @@
   Services.logins.removeLogin(login2);
 });
 
 add_task(async function test_changeUPLoginOnPUpdateForm() {
   info("Check for change-password popup, u+p login on password update form.");
-  Services.logins.addLogin(login1);
+  await Services.logins.addLoginAsync(login1);
 
   await testSubmittingLoginFormHTTP(
     "subtst_notifications_change_p.html",
     async function(fieldValues) {
       Assert.equal(fieldValues.username, "null", "Checking submitted username");
diff --git a/toolkit/components/passwordmgr/test/browser/browser_doorhanger_save_password.js b/toolkit/components/passwordmgr/test/browser/browser_doorhanger_save_password.js
--- a/toolkit/components/passwordmgr/test/browser/browser_doorhanger_save_password.js
+++ b/toolkit/components/passwordmgr/test/browser/browser_doorhanger_save_password.js
@@ -87,11 +87,11 @@
     password,
     expectOutcome,
   } = testData;
   // Add a login for the origin of the form if testing a change notification.
   if (oldPassword) {
-    Services.logins.addLogin(
+    await Services.logins.addLoginAsync(
       LoginTestUtils.testData.formLogin({
         origin: "https://example.com",
         formActionOrigin: "https://example.com",
         username: typeof oldUsername !== "undefined" ? oldUsername : username,
         password: oldPassword,
diff --git a/toolkit/components/passwordmgr/test/browser/browser_doorhanger_submit_telemetry.js b/toolkit/components/passwordmgr/test/browser/browser_doorhanger_submit_telemetry.js
--- a/toolkit/components/passwordmgr/test/browser/browser_doorhanger_submit_telemetry.js
+++ b/toolkit/components/passwordmgr/test/browser/browser_doorhanger_submit_telemetry.js
@@ -274,11 +274,11 @@
   }
 }
 
 async function test_submit_telemetry(tc) {
   if (tc.savedLogin) {
-    Services.logins.addLogin(
+    await Services.logins.addLoginAsync(
       LoginTestUtils.testData.formLogin({
         origin: "https://example.com",
         formActionOrigin: "https://example.com",
         username: tc.savedLogin.username,
         password: tc.savedLogin.password,
diff --git a/toolkit/components/passwordmgr/test/browser/browser_doorhanger_username_edits.js b/toolkit/components/passwordmgr/test/browser/browser_doorhanger_username_edits.js
--- a/toolkit/components/passwordmgr/test/browser/browser_doorhanger_username_edits.js
+++ b/toolkit/components/passwordmgr/test/browser/browser_doorhanger_username_edits.js
@@ -55,22 +55,22 @@
     await cleanupDoorhanger();
     await cleanupPasswordNotifications();
 
     // Create the pre-existing logins when needed.
     if (testCase.usernameInPageExists) {
-      Services.logins.addLogin(
+      await Services.logins.addLoginAsync(
         LoginTestUtils.testData.formLogin({
           origin: "https://example.com",
           formActionOrigin: "https://example.com",
           username: testCase.usernameInPage,
           password: "old password",
         })
       );
     }
 
     if (testCase.usernameChangedToExists) {
-      Services.logins.addLogin(
+      await Services.logins.addLoginAsync(
         LoginTestUtils.testData.formLogin({
           origin: "https://example.com",
           formActionOrigin: "https://example.com",
           username: testCase.usernameChangedTo,
           password: "old password",
diff --git a/toolkit/components/passwordmgr/test/browser/browser_focus_before_first_DOMContentLoaded.js b/toolkit/components/passwordmgr/test/browser/browser_focus_before_first_DOMContentLoaded.js
--- a/toolkit/components/passwordmgr/test/browser/browser_focus_before_first_DOMContentLoaded.js
+++ b/toolkit/components/passwordmgr/test/browser/browser_focus_before_first_DOMContentLoaded.js
@@ -3,11 +3,11 @@
  * focused before DOMContentLoaded in a new browser and process.
  */
 
 "use strict";
 
-add_setup(function() {
+add_setup(async () => {
   let nsLoginInfo = Components.Constructor(
     "@mozilla.org/login-manager/loginInfo;1",
     Ci.nsILoginInfo,
     "init"
   );
@@ -28,12 +28,11 @@
     null,
     "testuser2",
     "testpass2"
   );
 
-  Services.logins.addLogin(login1);
-  Services.logins.addLogin(login2);
+  await Services.logins.addLogins([login1, login2]);
 });
 
 add_task(async function test_autocompleteFromUsername() {
   let autocompletePopup = document.getElementById("PopupAutoComplete");
   let autocompletePopupShown = BrowserTestUtils.waitForEvent(
diff --git a/toolkit/components/passwordmgr/test/browser/browser_localip_frame.js b/toolkit/components/passwordmgr/test/browser/browser_localip_frame.js
--- a/toolkit/components/passwordmgr/test/browser/browser_localip_frame.js
+++ b/toolkit/components/passwordmgr/test/browser/browser_localip_frame.js
@@ -1,23 +1,21 @@
 "use strict";
 
-add_setup(async function() {
-  let login = LoginTestUtils.testData.formLogin({
+add_setup(async () => {
+  const login1 = LoginTestUtils.testData.formLogin({
     origin: "http://10.0.0.0",
     formActionOrigin: "https://example.org",
     username: "username1",
     password: "password1",
   });
-  Services.logins.addLogin(login);
-
-  login = LoginTestUtils.testData.formLogin({
+  const login2 = LoginTestUtils.testData.formLogin({
     origin: "https://example.org",
     formActionOrigin: "https://example.org",
     username: "username2",
     password: "password2",
   });
-  Services.logins.addLogin(login);
+  await Services.logins.addLogins([login1, login2]);
 });
 
 add_task(async function test_warningForLocalIP() {
   let tests = [
     /* when the url of top-level and iframe are both ip address, do not show insecure warning */
diff --git a/toolkit/components/passwordmgr/test/browser/browser_private_window.js b/toolkit/components/passwordmgr/test/browser/browser_private_window.js
--- a/toolkit/components/passwordmgr/test/browser/browser_private_window.js
+++ b/toolkit/components/passwordmgr/test/browser/browser_private_window.js
@@ -326,11 +326,11 @@
     "test 3: run with a login, outside of private mode, " +
       "match existing username/password: no popup notification should appear"
   );
 
   Services.logins.removeAllUserFacingLogins();
-  Services.logins.addLogin(login);
+  await Services.logins.addLoginAsync(login);
   let allLogins = Services.logins.getAllLogins();
   // Sanity check the HTTP login exists.
   Assert.equal(allLogins.length, 1, "Should have the HTTP login");
   let timeLastUsed = allLogins[0].timeLastUsed;
   let loginGuid = allLogins[0].guid;
@@ -385,11 +385,11 @@
     "test 3b: run with a login, in private mode," +
       " match existing username/password: no popup notification should appear"
   );
 
   Services.logins.removeAllUserFacingLogins();
-  Services.logins.addLogin(login);
+  await Services.logins.addLoginAsync(login);
   let allLogins = Services.logins.getAllLogins();
   // Sanity check the HTTP login exists.
   Assert.equal(allLogins.length, 1, "Should have the HTTP login");
   let timeLastUsed = allLogins[0].timeLastUsed;
   let loginGuid = allLogins[0].guid;
@@ -445,11 +445,11 @@
   info(
     "test 4: run with a login, outside of private mode," +
       " add a new password: popup notification should appear"
   );
   Services.logins.removeAllUserFacingLogins();
-  Services.logins.addLogin(login);
+  await Services.logins.addLoginAsync(login);
   let allLogins = Services.logins.getAllLogins();
   // Sanity check the HTTP login exists.
   Assert.equal(allLogins.length, 1, "Should have the HTTP login");
   let timeLastUsed = allLogins[0].timeLastUsed;
   let loginGuid = allLogins[0].guid;
@@ -618,11 +618,11 @@
   );
 });
 
 add_task(async function test_normal_autofilled_7() {
   info("test 7: verify that the user/pass pair was autofilled");
-  Services.logins.addLogin(login);
+  await Services.logins.addLoginAsync(login);
 
   // Sanity check the HTTP login exists.
   Assert.equal(
     Services.logins.getAllLogins().length,
     1,
diff --git a/toolkit/components/passwordmgr/test/browser/browser_username_select_dialog.js b/toolkit/components/passwordmgr/test/browser/browser_username_select_dialog.js
--- a/toolkit/components/passwordmgr/test/browser/browser_username_select_dialog.js
+++ b/toolkit/components/passwordmgr/test/browser/browser_username_select_dialog.js
@@ -57,12 +57,11 @@
 
 add_task(async function test_changeUPLoginOnPUpdateForm_accept() {
   info(
     "Select an u+p login from multiple logins, on password update form, and accept."
   );
-  Services.logins.addLogin(login1);
-  Services.logins.addLogin(login1B);
+  await Services.logins.addLogins([login1, login1B]);
 
   let selectDialogPromise = TestUtils.topicObserved("select-dialog-loaded");
 
   await testSubmittingLoginForm(
     "subtst_notifications_change_p.html",
@@ -120,12 +119,11 @@
 
 add_task(async function test_changeUPLoginOnPUpdateForm_cancel() {
   info(
     "Select an u+p login from multiple logins, on password update form, and cancel."
   );
-  Services.logins.addLogin(login1);
-  Services.logins.addLogin(login1B);
+  await Services.logins.addLogins([login1, login1B]);
 
   let selectDialogPromise = TestUtils.topicObserved("select-dialog-loaded");
 
   await testSubmittingLoginForm(
     "subtst_notifications_change_p.html",
diff --git a/toolkit/components/passwordmgr/test/mochitest/pwmgr_common.js b/toolkit/components/passwordmgr/test/mochitest/pwmgr_common.js
--- a/toolkit/components/passwordmgr/test/mochitest/pwmgr_common.js
+++ b/toolkit/components/passwordmgr/test/mochitest/pwmgr_common.js
@@ -705,31 +705,29 @@
 
 /** Initialize with a list of logins. The logins are added within the parent chrome process.
  * @param {array} aLogins - a list of logins to add. Each login is an array of the arguments
  *                          that would be passed to nsLoginInfo.init().
  */
-function addLoginsInParent(...aLogins) {
+async function addLoginsInParent(...aLogins) {
   let script = runInParent(function addLoginsInParentInner() {
     /* eslint-env mozilla/chrome-script */
-    addMessageListener("addLogins", logins => {
+    addMessageListener("addLogins", async logins => {
       let nsLoginInfo = Components.Constructor(
         "@mozilla.org/login-manager/loginInfo;1",
         Ci.nsILoginInfo,
         "init"
       );
 
-      for (let login of logins) {
-        let loginInfo = new nsLoginInfo(...login);
-        try {
-          Services.logins.addLogin(loginInfo);
-        } catch (e) {
-          assert.ok(false, "addLogin threw: " + e);
-        }
+      const loginInfos = logins.map(login => new nsLoginInfo(...login));
+      try {
+        await Services.logins.addLogins(loginInfos);
+      } catch (e) {
+        assert.ok(false, "addLogins threw: " + e);
       }
     });
   });
-  script.sendQuery("addLogins", aLogins);
+  await script.sendQuery("addLogins", aLogins);
   return script;
 }
 
 /*
  * gTestDependsOnDeprecatedLogin Set this global to true if your test relies
diff --git a/toolkit/components/passwordmgr/test/mochitest/pwmgr_common_parent.js b/toolkit/components/passwordmgr/test/mochitest/pwmgr_common_parent.js
--- a/toolkit/components/passwordmgr/test/mochitest/pwmgr_common_parent.js
+++ b/toolkit/components/passwordmgr/test/mochitest/pwmgr_common_parent.js
@@ -38,11 +38,11 @@
  * Init with a common login
  * If selfFilling is true or non-undefined, fires an event at the page so that
  * the test can start checking filled-in values. Tests that check observer
  * notifications might be confused by this.
  */
-function commonInit(selfFilling, testDependsOnDeprecatedLogin) {
+async function commonInit(selfFilling, testDependsOnDeprecatedLogin) {
   var pwmgr = Services.logins;
   assert.ok(pwmgr != null, "Access LoginManager");
 
   // Check that initial state has no logins
   var logins = pwmgr.getAllLogins();
@@ -67,11 +67,11 @@
       "testuser",
       "testpass",
       "uname",
       "pword"
     );
-    pwmgr.addLogin(login);
+    await pwmgr.addLoginAsync(login);
   }
 
   // Last sanity check
   logins = pwmgr.getAllLogins();
   assert.equal(
@@ -143,12 +143,15 @@
 
 // Begin message listeners
 
 addMessageListener(
   "setupParent",
-  ({ selfFilling = false, testDependsOnDeprecatedLogin = false } = {}) => {
-    commonInit(selfFilling, testDependsOnDeprecatedLogin);
+  async ({
+    selfFilling = false,
+    testDependsOnDeprecatedLogin = false,
+  } = {}) => {
+    await commonInit(selfFilling, testDependsOnDeprecatedLogin);
     sendAsyncMessage("doneSetup");
   }
 );
 
 addMessageListener("loadRecipes", async function(recipes) {
diff --git a/toolkit/components/passwordmgr/test/mochitest/test_DOMInputPasswordAdded_fired_between_DOMContentLoaded_and_load_events.html b/toolkit/components/passwordmgr/test/mochitest/test_DOMInputPasswordAdded_fired_between_DOMContentLoaded_and_load_events.html
--- a/toolkit/components/passwordmgr/test/mochitest/test_DOMInputPasswordAdded_fired_between_DOMContentLoaded_and_load_events.html
+++ b/toolkit/components/passwordmgr/test/mochitest/test_DOMInputPasswordAdded_fired_between_DOMContentLoaded_and_load_events.html
@@ -38,11 +38,11 @@
   await DOMContentLoadedPromise;
 }
 
 async function test_password_autofilled() {
   info("Adding one login for the page");
-  addLoginsInParent([DEFAULT_ORIGIN, DEFAULT_ORIGIN, null, "user", "omgsecret!"]);
+  await addLoginsInParent([DEFAULT_ORIGIN, DEFAULT_ORIGIN, null, "user", "omgsecret!"]);
 
   let numLogins = await LoginManager.countLogins(DEFAULT_ORIGIN, DEFAULT_ORIGIN, null);
   is(numLogins, 1, "Correct number of logins");
 
   let win = window.open("about:blank");
diff --git a/toolkit/components/passwordmgr/test/mochitest/test_LoginManagerContent_passwordEditedOrGenerated.html b/toolkit/components/passwordmgr/test/mochitest/test_LoginManagerContent_passwordEditedOrGenerated.html
--- a/toolkit/components/passwordmgr/test/mochitest/test_LoginManagerContent_passwordEditedOrGenerated.html
+++ b/toolkit/components/passwordmgr/test/mochitest/test_LoginManagerContent_passwordEditedOrGenerated.html
@@ -9,16 +9,16 @@
   <script src="pwmgr_common.js"></script>
   <link rel="stylesheet" href="/tests/SimpleTest/test.css"/>
 </head>
 <body>
 <script>
-let readyPromise = registerRunTests(1);
-
-let origin = window.location.origin;
-addLoginsInParent(
-  [origin, "https://autofill", null, "user1", "pass1"],
-  [origin, "https://autofill", null, "user2", "pass2"]);
+const origin = window.location.origin;
+const readyPromise = registerRunTests(1)
+    .then(() => addLoginsInParent(
+      [origin, "https://autofill", null, "user1", "pass1"],
+      [origin, "https://autofill", null, "user2", "pass2"]
+    ));
 
 function preventDefaultAndStopProgagation(event) {
   event.preventDefault();
   event.stopImmediatePropagation();
 }
diff --git a/toolkit/components/passwordmgr/test/mochitest/test_autocomplete_autofill_related_realms_no_dupes.html b/toolkit/components/passwordmgr/test/mochitest/test_autocomplete_autofill_related_realms_no_dupes.html
--- a/toolkit/components/passwordmgr/test/mochitest/test_autocomplete_autofill_related_realms_no_dupes.html
+++ b/toolkit/components/passwordmgr/test/mochitest/test_autocomplete_autofill_related_realms_no_dupes.html
@@ -9,26 +9,10 @@
   <script type="text/javascript" src="pwmgr_common.js"></script>
   <link rel="stylesheet" href="/tests/SimpleTest/test.css"/>
 </head>
 <body>
 Login Manager test: no duplicate logins when using autofill and autocomplete with related realms
-<script>
-  addLoginsInParent(
-    // Simple related domain relationship where example.com and other-example.com are in the related domains list
-    ["https://other-example.com", "https://other-example.com", null, "relatedUser1", "relatedPass1", "uname", "pword"],
-
-    // Example.com and example.co.uk are related, so sub.example.co.uk should appear on example.com's autocomplete dropdown
-    // The intent is to cover the ebay.com/ebay.co.uk and all other country TLD cases
-    // where the sign in page is actually signin.ebay.com/signin.ebay.co.uk but credentials could have manually been entered
-    // for ebay.com/ebay.co.uk or automatically stored as signin.ebay.com/sigin.ebay.co.uk
-    ["https://sub.example.co.uk", "https://sub.example.co.uk", null, "subUser1", "subPass1", "uname", "pword"],
-
-    // Ensures there are no duplicates for the exact domain that the user is on
-    ["https://example.com", "https://example.com", null, "exactUser1", "exactPass1", "uname", "pword"],
-    ["https://www.example.com", "https://www.example.com", null, "exactWWWUser1", "exactWWWPass1", "uname", "pword"],
-    );
-</script>
 <p id="display"></p>
 <div id="content">
   <form id="form1" action="https://www.example.com" onsubmit="return false;">
     <input type="text" name="uname">
     <input type="password" name="pword">
@@ -50,44 +34,58 @@
   pword.value = "";
   uname.focus();
 }
 
 function sendFakeAutocompleteEvent(element) {
-  var acEvent = document.createEvent("HTMLEvents");
+  const acEvent = document.createEvent("HTMLEvents");
   acEvent.initEvent("DOMAutoComplete", true, false);
   element.dispatchEvent(acEvent);
 }
 
 function spinEventLoop() {
   return Promise.resolve();
 }
 
 async function promiseACPopupClosed() {
   return SimpleTest.promiseWaitForCondition(async () => {
-    let popupState = await getPopupState();
+    const popupState = await getPopupState();
     return !popupState.open;
   }, "Wait for AC popup to be closed");
 }
 
 add_setup(async () => {
+  await addLoginsInParent(
+    // Simple related domain relationship where example.com and other-example.com are in the related domains list
+    ["https://other-example.com", "https://other-example.com", null, "relatedUser1", "relatedPass1", "uname", "pword"],
+
+    // Example.com and example.co.uk are related, so sub.example.co.uk should appear on example.com's autocomplete dropdown
+    // The intent is to cover the ebay.com/ebay.co.uk and all other country TLD cases
+    // where the sign in page is actually signin.ebay.com/signin.ebay.co.uk but credentials could have manually been entered
+    // for ebay.com/ebay.co.uk or automatically stored as signin.ebay.com/sigin.ebay.co.uk
+    ["https://sub.example.co.uk", "https://sub.example.co.uk", null, "subUser1", "subPass1", "uname", "pword"],
+
+    // Ensures there are no duplicates for the exact domain that the user is on
+    ["https://example.com", "https://example.com", null, "exactUser1", "exactPass1", "uname", "pword"],
+    ["https://www.example.com", "https://www.example.com", null, "exactWWWUser1", "exactWWWPass1", "uname", "pword"],
+  );
   listenForUnexpectedPopupShown();
 });
 
 add_task(async function test_no_duplicates_autocomplete_autofill() {
   await promiseFormsProcessedInSameProcess();
   await SimpleTest.promiseFocus(window);
-  let results = await popupBy(() => {
+  const results = await popupBy(() => {
     checkLoginForm(uname, "exactUser1", pword, "exactPass1")
     restoreForm();
   });
 
-  let popupState = await getPopupState();
+  const popupState = await getPopupState();
   is(popupState.selectedIndex, -1, "Check no entires are selected upon opening");
-  let expectedMenuItems = ["exactUser1", "exactWWWUser1", "relatedUser1", "subUser1"];
+  const expectedMenuItems = ["exactUser1", "exactWWWUser1", "relatedUser1", "subUser1"];
   checkAutoCompleteResults(results, expectedMenuItems, window.location.host, "Check all menuitems are displayed correctly");
 
-  let acEvents = await getTelemetryEvents({ process: "parent", filterProps: TelemetryFilterPropsAC, clear: true });
+  const acEvents = await getTelemetryEvents({ process: "parent", filterProps: TelemetryFilterPropsAC, clear: true });
   is(acEvents.length, 1, "One autocomplete event");
   checkACTelemetryEvent(acEvents[0], uname, {
     "hadPrevious": "0",
     "login": expectedMenuItems.length + "",
     "loginsFooter": "1"
diff --git a/toolkit/components/passwordmgr/test/mochitest/test_autocomplete_basic_form.html b/toolkit/components/passwordmgr/test/mochitest/test_autocomplete_basic_form.html
--- a/toolkit/components/passwordmgr/test/mochitest/test_autocomplete_basic_form.html
+++ b/toolkit/components/passwordmgr/test/mochitest/test_autocomplete_basic_form.html
@@ -22,11 +22,11 @@
   let script = runInParent(function addLoginsInParentInner() {
     let loginsMap = {};
 
     let initialCount = 5;
 
-    addMessageListener("initLogins", logins => {
+    addMessageListener("initLogins", async logins => {
       let nsLoginInfo = Components.Constructor(
         "@mozilla.org/login-manager/loginInfo;1",
         Ci.nsILoginInfo,
         "init"
       );
@@ -35,23 +35,23 @@
         let loginInfo = new nsLoginInfo(...login[1]);
 
         // Only add the first 'initialCount' number of logins.
         if (initialCount-- > 0) {
           try {
-            Services.logins.addLogin(loginInfo);
+            await Services.logins.addLoginAsync(loginInfo);
           } catch (e) {
             assert.ok(false, "addLogin threw: " + e);
           }
         }
         loginsMap[login[0]] = loginInfo;
       }
     });
 
-    addMessageListener("addLogin", loginVariableName => {
+    addMessageListener("addLogin", async loginVariableName => {
       let login = loginsMap[loginVariableName];
       assert.ok(!!login, "Login to add is defined: " + loginVariableName);
-      Services.logins.addLogin(login);
+      await Services.logins.addLoginAsync(login);
     });
     addMessageListener("removeLogin", loginVariableName => {
       let login = loginsMap[loginVariableName];
       assert.ok(!!login, "Login to delete is defined: " + loginVariableName);
       Services.logins.removeLogin(login);
diff --git a/toolkit/components/passwordmgr/test/mochitest/test_autocomplete_basic_form_formActionOrigin.html b/toolkit/components/passwordmgr/test/mochitest/test_autocomplete_basic_form_formActionOrigin.html
--- a/toolkit/components/passwordmgr/test/mochitest/test_autocomplete_basic_form_formActionOrigin.html
+++ b/toolkit/components/passwordmgr/test/mochitest/test_autocomplete_basic_form_formActionOrigin.html
@@ -11,14 +11,11 @@
 </head>
 <body>
 Login Manager test: logins with non-matching formActionOrigin appear in autocomplete dropdown
 
 <script>
-var chromeScript = runChecksAfterCommonInit();
-
-addLoginsInParent([window.location.origin, "https://differentFormSubmitURL", null,
-                  "dfsu1", "dfsp1", "uname", "pword"]);
+const chromeScript = runChecksAfterCommonInit();
 </script>
 <p id="display"></p>
 
 <!-- we presumably can't hide the content for this test. -->
 <div id="content">
@@ -48,19 +45,22 @@
 function spinEventLoop() {
   return Promise.resolve();
 }
 
 add_setup(async () => {
+  await addLoginsInParent(
+    [window.location.origin, "https://differentFormSubmitURL", null, "dfsu1", "dfsp1", "uname", "pword"]
+  );
   listenForUnexpectedPopupShown();
 });
 
 add_task(async function test_form1_initial_empty() {
   await SimpleTest.promiseFocus(window);
 
   // Make sure initial form is empty.
   checkLoginForm(uname, "", pword, "");
-  let popupState = await getPopupState();
+  const popupState = await getPopupState();
   is(popupState.open, false, "Check popup is initially closed");
 });
 
 /* For this testcase, the only login that exists for this origin
  * is one with a different formActionOrigin, so the login will appear
@@ -70,14 +70,14 @@
   await SimpleTest.promiseFocus(window);
   // Trigger autocomplete popup
   restoreForm();
   const autocompleteItems = await popupByArrowDown();
 
-  let popupState = await getPopupState();
+  const popupState = await getPopupState();
   is(popupState.selectedIndex, -1, "Check no entries are selected upon opening");
 
-  let expectedMenuItems = ["dfsu1"];
+  const expectedMenuItems = ["dfsu1"];
   checkAutoCompleteResults(autocompleteItems, expectedMenuItems, window.location.host, "Check all menuitems are displayed correctly.");
 
   synthesizeKey("KEY_ArrowDown"); // first item
   checkLoginForm(uname, "", pword, ""); // value shouldn't update just by selecting
 
diff --git a/toolkit/components/passwordmgr/test/mochitest/test_autocomplete_basic_form_insecure.html b/toolkit/components/passwordmgr/test/mochitest/test_autocomplete_basic_form_insecure.html
--- a/toolkit/components/passwordmgr/test/mochitest/test_autocomplete_basic_form_insecure.html
+++ b/toolkit/components/passwordmgr/test/mochitest/test_autocomplete_basic_form_insecure.html
@@ -10,13 +10,13 @@
   <link rel="stylesheet" type="text/css" href="/tests/SimpleTest/test.css" />
 </head>
 <body>
 
 <script>
-var chromeScript = runChecksAfterCommonInit();
+const chromeScript = runChecksAfterCommonInit();
 
-var setupScript = runInParent(function setup() {
+const setupScript = runInParent(async function setup() {
   // Create some logins just for this form, since we'll be deleting them.
   var nsLoginInfo = Components.Constructor("@mozilla.org/login-manager/loginInfo;1",
                                            Ci.nsILoginInfo, "init");
   assert.ok(nsLoginInfo != null, "nsLoginInfo constructor");
 
@@ -60,27 +60,25 @@
   logins.login10 = new nsLoginInfo("http://mochi.test:8888", "http://autocomplete7", null,
                                    "testuser10", "testpass10", "uname", "pword");
 
 
   // try/catch in case someone runs the tests manually, twice.
-  try {
-    Services.logins.addLogin(logins.login0);
-    Services.logins.addLogin(logins.login1);
-    Services.logins.addLogin(logins.login2);
-    Services.logins.addLogin(logins.login3);
-    Services.logins.addLogin(logins.login4);
-  } catch (e) {
-    assert.ok(false, "addLogin threw: " + e);
-  }
+  await Services.logins.addLogins([
+    logins.login0,
+    logins.login1,
+    logins.login2,
+    logins.login3,
+    logins.login4,
+  ]);
 
   addMessageListener("addLogin", loginVariableName => {
-    let login = logins[loginVariableName];
+    const login = logins[loginVariableName];
     assert.ok(!!login, "Login to add is defined: " + loginVariableName);
     Services.logins.addLogin(login);
   });
   addMessageListener("removeLogin", loginVariableName => {
-    let login = logins[loginVariableName];
+    const login = logins[loginVariableName];
     assert.ok(!!login, "Login to delete is defined: " + loginVariableName);
     Services.logins.removeLogin(login);
   });
 });
 </script>
diff --git a/toolkit/components/passwordmgr/test/mochitest/test_autocomplete_basic_form_related_realms.html b/toolkit/components/passwordmgr/test/mochitest/test_autocomplete_basic_form_related_realms.html
--- a/toolkit/components/passwordmgr/test/mochitest/test_autocomplete_basic_form_related_realms.html
+++ b/toolkit/components/passwordmgr/test/mochitest/test_autocomplete_basic_form_related_realms.html
@@ -9,23 +9,10 @@
   <script type="text/javascript" src="pwmgr_common.js"></script>
   <link rel="stylesheet" href="/tests/SimpleTest/test.css"/>
 </head>
 <body>
 Login Manager test: related realms autocomplete
-
-<script>
-  addLoginsInParent(
-    // Simple related domain relationship where example.com and other-example.com are in the related domains list
-    ["https://other-example.com", "https://other-example.com", null, "relatedUser1", "relatedPass1", "uname", "pword"],
-
-    // Example.com and example.co.uk are related, so sub.example.co.uk should appear on example.com's autocomplete dropdown
-    // The intent is to cover the ebay.com/ebay.co.uk and all other country TLD cases
-    // where the sign in page is actually signin.ebay.com/signin.ebay.co.uk but credentials could have manually been entered
-    // for ebay.com/ebay.co.uk or automatically stored as signin.ebay.com/sigin.ebay.co.uk
-    ["https://sub.example.co.uk", "https://sub.example.co.uk", null, "subUser1", "subPass1", "uname", "pword"],
-    );
-</script>
 <p id="display"></p>
 <div id="content">
   <form id="form1" onsubmit="return false;">
     <input type="text" name="uname">
     <input type="password" name="pword">
@@ -64,10 +51,20 @@
     return !popupState.open;
   }, "Wait for AC popup to be closed");
 }
 
 add_setup(async () => {
+  await addLoginsInParent(
+    // Simple related domain relationship where example.com and other-example.com are in the related domains list
+    ["https://other-example.com", "https://other-example.com", null, "relatedUser1", "relatedPass1", "uname", "pword"],
+
+    // Example.com and example.co.uk are related, so sub.example.co.uk should appear on example.com's autocomplete dropdown
+    // The intent is to cover the ebay.com/ebay.co.uk and all other country TLD cases
+    // where the sign in page is actually signin.ebay.com/signin.ebay.co.uk but credentials could have manually been entered
+    // for ebay.com/ebay.co.uk or automatically stored as signin.ebay.com/sigin.ebay.co.uk
+    ["https://sub.example.co.uk", "https://sub.example.co.uk", null, "subUser1", "subPass1", "uname", "pword"],
+  );
   listenForUnexpectedPopupShown();
 });
 
 add_task(async function test_form1_initial_empty() {
   await SimpleTest.promiseFocus(window);
diff --git a/toolkit/components/passwordmgr/test/mochitest/test_autocomplete_basic_form_subdomain.html b/toolkit/components/passwordmgr/test/mochitest/test_autocomplete_basic_form_subdomain.html
--- a/toolkit/components/passwordmgr/test/mochitest/test_autocomplete_basic_form_subdomain.html
+++ b/toolkit/components/passwordmgr/test/mochitest/test_autocomplete_basic_form_subdomain.html
@@ -9,38 +9,10 @@
   <script type="text/javascript" src="pwmgr_common.js"></script>
   <link rel="stylesheet" type="text/css" href="/tests/SimpleTest/test.css" />
 </head>
 <body>
 Login Manager test: logins with non-exact match origin appear in autocomplete dropdown
-
-<script>
-let origin = window.location.origin;
-let lastDot = origin.lastIndexOf(".");
-let suffix = origin.slice(lastDot);
-
-let baseHost = "http://example" + suffix;
-let baseSecureHost = "https://example" + suffix;
-let oldHost = "http://old.example" + suffix;
-let oldSecureHost = "https://old.example" + suffix;
-let newHost = "https://new.example" + suffix;
-
-addLoginsInParent(
-  // The first two logins should never be visible on https: versions of
-  // *.example.com since the login is for http: and an https: login exists for this username.
-  [oldHost, oldSecureHost, null, "dsdu1", "dsdp1new", "uname", "pword"],
-  [baseHost, baseSecureHost, null, "dsdu1", "dsdp1", "uname", "pword"],
-  [oldSecureHost, oldSecureHost, null, "dsdu1", "dsdp1", "uname", "pword"],
-  [baseSecureHost, baseSecureHost, null, "dsdu1", "dsdp1", "uname", "pword"],
-  [newHost, newHost, null, "dsdu1", "dsdp1prime", "uname", "pword"]);
-
-var setupScript = runInParent(function setup() {
-  addMessageListener("getDateString", () => {
-    let dateAndTimeFormatter = new Services.intl.DateTimeFormat(undefined, { dateStyle: "medium" });
-    return dateAndTimeFormatter.format(new Date());
-  });
-});
-</script>
 <p id="display"></p>
 
 <!-- we presumably can't hide the content for this test. -->
 <div id="content">
 
@@ -66,11 +38,38 @@
 
 function spinEventLoop() {
   return Promise.resolve();
 }
 
+const setupScript = runInParent(function setup() {
+  addMessageListener("getDateString", () => {
+    const dateAndTimeFormatter = new Services.intl.DateTimeFormat(undefined, { dateStyle: "medium" });
+    return dateAndTimeFormatter.format(new Date());
+  });
+});
+
 add_setup(async () => {
+  const origin = window.location.origin;
+  const lastDot = origin.lastIndexOf(".");
+  const suffix = origin.slice(lastDot);
+
+  const baseHost = "http://example" + suffix;
+  const baseSecureHost = "https://example" + suffix;
+  const oldHost = "http://old.example" + suffix;
+  const oldSecureHost = "https://old.example" + suffix;
+  const newHost = "https://new.example" + suffix;
+
+  await addLoginsInParent(
+    // The first two logins should never be visible on https: versions of
+    // *.example.com since the login is for http: and an https: login exists for this username.
+    [oldHost, oldSecureHost, null, "dsdu1", "dsdp1new", "uname", "pword"],
+    [baseHost, baseSecureHost, null, "dsdu1", "dsdp1", "uname", "pword"],
+    [oldSecureHost, oldSecureHost, null, "dsdu1", "dsdp1", "uname", "pword"],
+    [baseSecureHost, baseSecureHost, null, "dsdu1", "dsdp1", "uname", "pword"],
+    [newHost, newHost, null, "dsdu1", "dsdp1prime", "uname", "pword"]
+  );
+
   await SpecialPowers.pushPrefEnv({
     set: [
       ["signon.includeOtherSubdomainsInLookup", true],
     ],
   });
@@ -80,11 +79,11 @@
 add_task(async function test_form1_initial_empty() {
   await SimpleTest.promiseFocus(window);
 
   // Make sure initial form is empty.
   checkLoginForm(uname, "", pword, "");
-  let popupState = await getPopupState();
+  const popupState = await getPopupState();
   is(popupState.open, false, "Check popup is initially closed");
 });
 
 /* For this testcase, there exists two logins for this origin
  * on different subdomains but with different passwords. Both logins
@@ -94,17 +93,17 @@
   await SimpleTest.promiseFocus(window);
   // Trigger autocomplete popup
   restoreForm();
   const autocompleteItems = await popupByArrowDown();
 
-  let popupState = await getPopupState();
+  const popupState = await getPopupState();
   is(popupState.selectedIndex, -1, "Check no entries are selected upon opening");
 
   // The logins are added "today" and since they are duplicates, the date that they were last
   // changed will be appended.
-  let dateString = await setupScript.sendQuery("getDateString");
-  let username = `dsdu1 (${dateString})`;
+  const dateString = await setupScript.sendQuery("getDateString");
+  const username = `dsdu1 (${dateString})`;
 
   checkAutoCompleteResults(autocompleteItems, [username, username], window.location.host, "Check all menuitems are displayed correctly.");
 
   synthesizeKey("KEY_ArrowDown"); // first item
   checkLoginForm(uname, "", pword, ""); // value shouldn't update just by selecting
diff --git a/toolkit/components/passwordmgr/test/mochitest/test_autocomplete_hasBeenTypePassword.html b/toolkit/components/passwordmgr/test/mochitest/test_autocomplete_hasBeenTypePassword.html
--- a/toolkit/components/passwordmgr/test/mochitest/test_autocomplete_hasBeenTypePassword.html
+++ b/toolkit/components/passwordmgr/test/mochitest/test_autocomplete_hasBeenTypePassword.html
@@ -9,17 +9,10 @@
   <script type="text/javascript" src="pwmgr_common.js"></script>
   <link rel="stylesheet" type="text/css" href="/tests/SimpleTest/test.css" />
 </head>
 <body>
 Login Manager test: Test that passwords are autocompleted into fields that were previously type=password
-
-<script>
-let origin = window.location.origin;
-addLoginsInParent(
-  [origin, origin, null, "user1", "pass1"],
-  [origin, origin, null, "user2", "pass2"]);
-</script>
 <p id="display"></p>
 
 <!-- we presumably can't hide the content for this test. -->
 <div id="content">
 
@@ -46,19 +39,24 @@
 function spinEventLoop() {
   return Promise.resolve();
 }
 
 add_setup(async () => {
+  const origin = window.location.origin;
+  await addLoginsInParent(
+    [origin, origin, null, "user1", "pass1"],
+    [origin, origin, null, "user2", "pass2"]
+  );
   listenForUnexpectedPopupShown();
 });
 
 add_task(async function test_form1_initial_empty() {
   await SimpleTest.promiseFocus(window);
 
   // Make sure initial form is empty.
   checkLoginForm(uname, "", pword, "");
-  let popupState = await getPopupState();
+  const popupState = await getPopupState();
   is(popupState.open, false, "Check popup is initially closed");
 });
 
 add_task(async function test_form1_password_to_type_text() {
   await SimpleTest.promiseFocus(window);
@@ -68,11 +66,11 @@
 
   // Trigger autocomplete popup
   restoreForm();
   const autocompleteItems =  await popupByArrowDown();
 
-  let popupState = await getPopupState();
+  const popupState = await getPopupState();
   is(popupState.selectedIndex, -1, "Check no entries are selected upon opening");
 
   checkAutoCompleteResults(autocompleteItems, ["user1", "user2"], window.location.host,
     "Check all menuitems are displayed correctly.");
 
diff --git a/toolkit/components/passwordmgr/test/mochitest/test_autocomplete_highlight.html b/toolkit/components/passwordmgr/test/mochitest/test_autocomplete_highlight.html
--- a/toolkit/components/passwordmgr/test/mochitest/test_autocomplete_highlight.html
+++ b/toolkit/components/passwordmgr/test/mochitest/test_autocomplete_highlight.html
@@ -7,42 +7,36 @@
   <script src="/tests/SimpleTest/EventUtils.js"></script>
   <script type="text/javascript" src="../../../satchel/test/satchel_common.js"></script>
   <script type="text/javascript" src="pwmgr_common.js"></script>
   <link rel="stylesheet" type="text/css" href="/tests/SimpleTest/test.css"/>
 </head>
-<script>
-let readyPromise = registerRunTests(1);
-
-let origin = window.location.origin;
-addLoginsInParent(
-  [origin, "https://autocomplete", null, "user1", "pass1", "", ""],
-  [origin, "https://autocomplete", null, "user2", "pass2", "", ""]);
-
-</script>
 <body>
 <p id="display"></p>
 <div id="content">
   <form id="form1" action="https://autocomplete" onsubmit="return false;">
     <input  type="text"       id="uname">
     <input  type="password"   id="pword">
     <button type="submit">Submit</button>
   </form>
 <pre id="test">
 <script>
-let { ContentTaskUtils } = SpecialPowers.ChromeUtils.import(
+const { ContentTaskUtils } = SpecialPowers.ChromeUtils.import(
   "resource://testing-common/ContentTaskUtils.jsm"
 );
 
 add_setup(async () => {
-  ok(readyPromise, "check promise is available");
-  await readyPromise;
+  const origin = window.location.origin;
+  await addLoginsInParent(
+    [origin, "https://autocomplete", null, "user1", "pass1", "", ""],
+    [origin, "https://autocomplete", null, "user2", "pass2", "", ""]
+  );
 });
 
 add_task(async function test_field_highlight_on_autocomplete() {
   // Test username autocomplete.
-  let username = document.getElementById("uname");
-  let password = document.getElementById("pword");
+  const username = document.getElementById("uname");
+  const password = document.getElementById("pword");
 
   await openPopupOn(username);
   synthesizeKey("KEY_ArrowDown");
   await synthesizeKey("KEY_Enter");
 
diff --git a/toolkit/components/passwordmgr/test/mochitest/test_autocomplete_highlight_username_only_form.html b/toolkit/components/passwordmgr/test/mochitest/test_autocomplete_highlight_username_only_form.html
--- a/toolkit/components/passwordmgr/test/mochitest/test_autocomplete_highlight_username_only_form.html
+++ b/toolkit/components/passwordmgr/test/mochitest/test_autocomplete_highlight_username_only_form.html
@@ -7,35 +7,29 @@
   <script src="/tests/SimpleTest/EventUtils.js"></script>
   <script type="text/javascript" src="../../../satchel/test/satchel_common.js"></script>
   <script type="text/javascript" src="pwmgr_common.js"></script>
   <link rel="stylesheet" type="text/css" href="/tests/SimpleTest/test.css"/>
 </head>
-<script>
-let readyPromise = registerRunTests(1);
-
-let origin = window.location.origin;
-addLoginsInParent(
-  [origin, "https://autocomplete", null, "user1", "pass1", "", ""],
-  [origin, "https://autocomplete", null, "user2", "pass2", "", ""]);
-
-</script>
 <body>
 <p id="display"></p>
 <div id="content">
   <form id="form" action="https://autocomplete" onsubmit="return false;">
     <input  type="text" id="uname" autocomplete="username">
     <button type="submit">Submit</button>
   </form>
 <pre id="test">
 <script>
-let { ContentTaskUtils } = SpecialPowers.ChromeUtils.import(
+const { ContentTaskUtils } = SpecialPowers.ChromeUtils.import(
   "resource://testing-common/ContentTaskUtils.jsm"
 );
 
 add_setup(async () => {
-  ok(readyPromise, "check promise is available");
-  await readyPromise;
+  const origin = window.location.origin;
+  await addLoginsInParent(
+    [origin, "https://autocomplete", null, "user1", "pass1", "", ""],
+    [origin, "https://autocomplete", null, "user2", "pass2", "", ""]
+  );
 });
 
 add_task(async function test_username_field_in_username_only_form_highlight_on_autocomplete() {
   // Test username autocomplete.
   const username = document.getElementById("uname");
diff --git a/toolkit/components/passwordmgr/test/mochitest/test_autofill_password-only.html b/toolkit/components/passwordmgr/test/mochitest/test_autofill_password-only.html
--- a/toolkit/components/passwordmgr/test/mochitest/test_autofill_password-only.html
+++ b/toolkit/components/passwordmgr/test/mochitest/test_autofill_password-only.html
@@ -12,39 +12,31 @@
 <script>
 PWMGR_COMMON_PARENT.sendAsyncMessage("setupParent", { selfFilling: true });
 
 SimpleTest.waitForExplicitFinish();
 
-let chromeScript = runInParent(function chromeSetup() {
-  let login1A  = Cc["@mozilla.org/login-manager/loginInfo;1"].
-                 createInstance(Ci.nsILoginInfo);
-  let login1B  = Cc["@mozilla.org/login-manager/loginInfo;1"].
-                 createInstance(Ci.nsILoginInfo);
-  let login2A  = Cc["@mozilla.org/login-manager/loginInfo;1"].
-                 createInstance(Ci.nsILoginInfo);
-  let login2B  = Cc["@mozilla.org/login-manager/loginInfo;1"].
-                 createInstance(Ci.nsILoginInfo);
-  let login2C  = Cc["@mozilla.org/login-manager/loginInfo;1"].
-                 createInstance(Ci.nsILoginInfo);
+const chromeScript = runInParent(async function chromeSetup() {
+  const login1A = Cc["@mozilla.org/login-manager/loginInfo;1"].createInstance(Ci.nsILoginInfo);
+  const login1B = Cc["@mozilla.org/login-manager/loginInfo;1"].createInstance(Ci.nsILoginInfo);
+  const login2A = Cc["@mozilla.org/login-manager/loginInfo;1"].createInstance(Ci.nsILoginInfo);
+  const login2B = Cc["@mozilla.org/login-manager/loginInfo;1"].createInstance(Ci.nsILoginInfo);
+  const login2C = Cc["@mozilla.org/login-manager/loginInfo;1"].createInstance(Ci.nsILoginInfo);
+
+  login1A.init("http://mochi.test:8888", "http://bug444968-1", null, "testuser1A", "testpass1A", "", "");
+  login1B.init("http://mochi.test:8888", "http://bug444968-1", null, "", "testpass1B", "", "");
 
-  login1A.init("http://mochi.test:8888", "http://bug444968-1", null,
-               "testuser1A", "testpass1A", "", "");
-  login1B.init("http://mochi.test:8888", "http://bug444968-1", null,
-               "", "testpass1B", "", "");
+  login2A.init("http://mochi.test:8888", "http://bug444968-2", null, "testuser2A", "testpass2A", "", "");
+  login2B.init("http://mochi.test:8888", "http://bug444968-2", null, "", "testpass2B", "", "");
+  login2C.init("http://mochi.test:8888", "http://bug444968-2", null, "testuser2C", "testpass2C", "", "");
 
-  login2A.init("http://mochi.test:8888", "http://bug444968-2", null,
-               "testuser2A", "testpass2A", "", "");
-  login2B.init("http://mochi.test:8888", "http://bug444968-2", null,
-               "", "testpass2B", "", "");
-  login2C.init("http://mochi.test:8888", "http://bug444968-2", null,
-               "testuser2C", "testpass2C", "", "");
-
-  Services.logins.addLogin(login1A);
-  Services.logins.addLogin(login1B);
-  Services.logins.addLogin(login2A);
-  Services.logins.addLogin(login2B);
-  Services.logins.addLogin(login2C);
+  await Services.logins.addLogins([
+    login1A,
+    login1B,
+    login2A,
+    login2B,
+    login2C,
+  ]);
 
   addMessageListener("removeLogins", function removeLogins() {
     Services.logins.removeLogin(login1A);
     Services.logins.removeLogin(login1B);
     Services.logins.removeLogin(login2A);
@@ -61,17 +53,17 @@
 <p id="display"></p>
 <div id="content" style="display: none">
 </div>
 <pre id="test">
 <script class="testbody" type="text/javascript">
-let DEFAULT_ORIGIN = window.location.origin;
+const DEFAULT_ORIGIN = window.location.origin;
 
 /* Test for Login Manager: 444968 (password-only forms should prefer a
  * password-only login when present )
  */
 async function startTest() {
-  let win = window.open("about:blank");
+  const win = window.open("about:blank");
   SimpleTest.registerCleanupFunction(() => win.close());
   await loadFormIntoWindow(DEFAULT_ORIGIN, `
     <!-- first 3 forms have matching user+pass and pass-only logins -->
 
     <!-- user+pass form. -->
diff --git a/toolkit/components/passwordmgr/test/mochitest/test_autofill_sandboxed.html b/toolkit/components/passwordmgr/test/mochitest/test_autofill_sandboxed.html
--- a/toolkit/components/passwordmgr/test/mochitest/test_autofill_sandboxed.html
+++ b/toolkit/components/passwordmgr/test/mochitest/test_autofill_sandboxed.html
@@ -10,23 +10,21 @@
   <link rel="stylesheet" type="text/css" href="/tests/SimpleTest/test.css" />
 </head>
 <body>
 
 <script>
-var chromeScript = runChecksAfterCommonInit();
+const chromeScript = runChecksAfterCommonInit();
 
-var setupScript = runInParent(function setup() {
-  var nsLoginInfo = Components.Constructor("@mozilla.org/login-manager/loginInfo;1",
-                                           Ci.nsILoginInfo, "init");
+const setupScript = runInParent(async function setup() {
+  const nsLoginInfo = Components.Constructor("@mozilla.org/login-manager/loginInfo;1", Ci.nsILoginInfo, "init");
   assert.ok(nsLoginInfo != null, "nsLoginInfo constructor");
 
-  var login1 = new nsLoginInfo("https://example.com", "", null,
-                               "tempuser1", "temppass1", "uname", "pword");
+  const login1 = new nsLoginInfo("https://example.com", "", null, "tempuser1", "temppass1", "uname", "pword");
 
   // try/catch in case someone runs the tests manually, twice.
   try {
-    Services.logins.addLogin(login1);
+    await Services.logins.addLogin(login1);
   } catch (e) {
     assert.ok(false, "addLogin threw: " + e);
   }
 });
 </script>
@@ -40,22 +38,22 @@
 <pre id="test">
 <script class="testbody" type="text/javascript">
 
 /** Test for Login Manager: form field autofill in sandboxed documents (null principal) **/
 
-let sandboxed = document.getElementById("sandboxed");
+const sandboxed = document.getElementById("sandboxed");
 let uname;
 let pword;
 
 function promiseExecuteSoon() {
   return new Promise(SimpleTest.executeSoon);
 }
 
 add_task(async function test_no_autofill_in_form() {
   sandboxed.src = "form_basic.html";
-  let frameWindow = SpecialPowers.wrap(sandboxed).contentWindow;
-  let DOMFormHasPasswordPromise = new Promise(resolve => {
+  const frameWindow = SpecialPowers.wrap(sandboxed).contentWindow;
+  const DOMFormHasPasswordPromise = new Promise(resolve => {
     SpecialPowers.addChromeEventListener("DOMFormHasPassword", function onDFHP() {
       SpecialPowers.removeChromeEventListener("DOMFormHasPassword", onDFHP);
       resolve();
     });
   });
@@ -64,11 +62,11 @@
     return frameWindow.document.readyState == "complete" &&
              frameWindow.location.href.endsWith("form_basic.html");
   }, "Check frame is loaded");
   info("frame loaded");
   await DOMFormHasPasswordPromise;
-  let frameDoc = SpecialPowers.wrap(sandboxed).contentDocument;
+  const frameDoc = SpecialPowers.wrap(sandboxed).contentDocument;
 
   uname = frameDoc.getElementById("form-basic-username");
   pword = frameDoc.getElementById("form-basic-password");
 
   await promiseExecuteSoon();
@@ -86,12 +84,12 @@
   checkLoginForm(uname, "tempuser1", pword, "");
 });
 
 add_task(async function test_no_autofill_outside_form() {
   sandboxed.src = "formless_basic.html";
-  let frameWindow = SpecialPowers.wrap(sandboxed).contentWindow;
-  let DOMInputPasswordAddedPromise = new Promise(resolve => {
+  const frameWindow = SpecialPowers.wrap(sandboxed).contentWindow;
+  const DOMInputPasswordAddedPromise = new Promise(resolve => {
     SpecialPowers.addChromeEventListener("DOMInputPasswordAdded", function onDIPA() {
       SpecialPowers.removeChromeEventListener("DOMInputPasswordAdded", onDIPA);
       resolve();
     });
   });
@@ -100,11 +98,11 @@
     return frameWindow.document.readyState == "complete" &&
              frameWindow.location.href.endsWith("formless_basic.html");
   }, "Check frame is loaded");
   info("frame loaded");
   await DOMInputPasswordAddedPromise;
-  let frameDoc = SpecialPowers.wrap(sandboxed).contentDocument;
+  const frameDoc = SpecialPowers.wrap(sandboxed).contentDocument;
 
   uname = frameDoc.getElementById("form-basic-username");
   pword = frameDoc.getElementById("form-basic-password");
 
   await promiseExecuteSoon();
diff --git a/toolkit/components/passwordmgr/test/mochitest/test_basic_form_html5.html b/toolkit/components/passwordmgr/test/mochitest/test_basic_form_html5.html
--- a/toolkit/components/passwordmgr/test/mochitest/test_basic_form_html5.html
+++ b/toolkit/components/passwordmgr/test/mochitest/test_basic_form_html5.html
@@ -10,23 +10,18 @@
 <body>
 Login Manager test: html5 input types (email, tel, url, etc.)
 <script>
 runChecksAfterCommonInit(() => startTest());
 
-let DEFAULT_ORIGIN = window.location.origin;
+const DEFAULT_ORIGIN = window.location.origin;
 
-runInParent(function setup() {
-  let login1 = Cc["@mozilla.org/login-manager/loginInfo;1"].
-               createInstance(Ci.nsILoginInfo);
-  let login2 = Cc["@mozilla.org/login-manager/loginInfo;1"].
-               createInstance(Ci.nsILoginInfo);
-  let login3 = Cc["@mozilla.org/login-manager/loginInfo;1"].
-               createInstance(Ci.nsILoginInfo);
-  let login4 = Cc["@mozilla.org/login-manager/loginInfo;1"].
-               createInstance(Ci.nsILoginInfo);
-  let login5 = Cc["@mozilla.org/login-manager/loginInfo;1"].
-               createInstance(Ci.nsILoginInfo);
+runInParent(async function setup() {
+  const login1 = Cc["@mozilla.org/login-manager/loginInfo;1"].createInstance(Ci.nsILoginInfo);
+  const login2 = Cc["@mozilla.org/login-manager/loginInfo;1"].createInstance(Ci.nsILoginInfo);
+  const login3 = Cc["@mozilla.org/login-manager/loginInfo;1"].createInstance(Ci.nsILoginInfo);
+  const login4 = Cc["@mozilla.org/login-manager/loginInfo;1"].createInstance(Ci.nsILoginInfo);
+  const login5 = Cc["@mozilla.org/login-manager/loginInfo;1"].createInstance(Ci.nsILoginInfo);
 
   login1.init("http://mochi.test:8888", "http://bug600551-1", null,
               "testuser@example.com", "testpass1", "", "");
   login2.init("http://mochi.test:8888", "http://bug600551-2", null,
               "555-555-5555", "testpass2", "", "");
@@ -35,15 +30,17 @@
   login4.init("http://mochi.test:8888", "http://bug600551-4", null,
               "123456789", "testpass4", "", "");
   login5.init("http://mochi.test:8888", "http://bug600551-5", null,
               "test", "test", "", "");
 
-  Services.logins.addLogin(login1);
-  Services.logins.addLogin(login2);
-  Services.logins.addLogin(login3);
-  Services.logins.addLogin(login4);
-  Services.logins.addLogin(login5);
+  await Services.logins.addLogins([
+    login1,
+    login2,
+    login3,
+    login4,
+    login5,
+  ]);
 });
 </script>
 
 <p id="display"></p>
 <div id="content" style="display: none">
@@ -53,11 +50,11 @@
 
 /* Test for Login Manager: 600551
   (Password manager not working with input type=email)
  */
 async function startTest() {
-  let win = window.open("about:blank");
+  const win = window.open("about:blank");
   SimpleTest.registerCleanupFunction(() => win.close());
   await loadFormIntoWindow(DEFAULT_ORIGIN, `
     <form id="form1" action="http://bug600551-1">
       <input  type="email"    name="uname">
       <input  type="password" name="pword">
diff --git a/toolkit/components/passwordmgr/test/mochitest/test_basic_form_pwonly.html b/toolkit/components/passwordmgr/test/mochitest/test_basic_form_pwonly.html
--- a/toolkit/components/passwordmgr/test/mochitest/test_basic_form_pwonly.html
+++ b/toolkit/components/passwordmgr/test/mochitest/test_basic_form_pwonly.html
@@ -9,47 +9,35 @@
 </head>
 <body>
 Login Manager test: forms and logins without a username.
 <script>
 gTestDependsOnDeprecatedLogin = true;
-runChecksAfterCommonInit(() => startTest());
-runInParent(() => {
-  var nsLoginInfo = Components.Constructor("@mozilla.org/login-manager/loginInfo;1", Ci.nsILoginInfo);
-
-  // pwlogin1 uses a unique formActionOrigin, to check forms where no other logins
-  // will apply. pwlogin2 uses the normal formActionOrigin, so that we can test
+runChecksAfterCommonInit(async () => {
+  // The first login uses a unique formActionOrigin, to check forms where no other logins
+  // will apply. The second login uses the normal formActionOrigin, so that we can test
   // forms with a mix of username and non-username logins that might apply.
   //
-  // Note: pwlogin2 is deleted at the end of the test.
-
-  let pwlogin1 = new nsLoginInfo();
-  let pwlogin2 = new nsLoginInfo();
-
-  pwlogin1.init("http://mochi.test:8888", "http://mochi.test:1111", null,
-                "", "1234");
-
-  pwlogin2.init("http://mochi.test:8888", "http://mochi.test:8888", null,
-                "", "1234");
-
-
-  Services.logins.addLogin(pwlogin1);
-  Services.logins.addLogin(pwlogin2);
+  // Note: the second login is deleted at the end of the test.
+  await addLoginsInParent(
+    ["http://mochi.test:8888", "http://mochi.test:1111", null, "", "1234"],
+    ["http://mochi.test:8888", "http://mochi.test:8888", null, "", "1234"]
+  );
+  await startTest();
 });
-
-let DEFAULT_ORIGIN = window.location.origin;
 </script>
 <p id="display"></p>
 
 <div id="content" style="display: none">
 </div>
 
 <pre id="test">
 <script class="testbody" type="text/javascript">
+const DEFAULT_ORIGIN = window.location.origin;
 
 /** Test for Login Manager: password-only logins **/
 async function startTest() {
-  let win = window.open("about:blank");
+  const win = window.open("about:blank");
   SimpleTest.registerCleanupFunction(() => win.close());
   await loadFormIntoWindow(DEFAULT_ORIGIN, `
     <!-- simple form: no username field, 1 password field -->
     <form id='form1' action='http://mochi.test:1111/formtest.js'> 1
         <input type='password' name='pname' value=''>
diff --git a/toolkit/components/passwordmgr/test/mochitest/test_bug_627616.html b/toolkit/components/passwordmgr/test/mochitest/test_bug_627616.html
--- a/toolkit/components/passwordmgr/test/mochitest/test_bug_627616.html
+++ b/toolkit/components/passwordmgr/test/mochitest/test_bug_627616.html
@@ -75,36 +75,35 @@
 
     var pendingTests = [{expectedDialogs: 2, test: testNonAnonymousCredentials},
                         {expectedDialogs: 1, test: testAnonymousCredentials},
                         {expectedDialogs: 0, test: testAnonymousNoAuth}];
 
-    let mm = runInParent(() => {
+    const mm = runInParent(() => {
       const { classes: parentCc, interfaces: parentCi } = Components;
 
-      let {NetUtil} = ChromeUtils.import("resource://gre/modules/NetUtil.jsm");
+      const {NetUtil} = ChromeUtils.import("resource://gre/modules/NetUtil.jsm");
 
-      let channel = NetUtil.newChannel({
+      const channel = NetUtil.newChannel({
         uri: "http://example.com",
         loadUsingSystemPrincipal: true,
       });
 
-      let pps = parentCc["@mozilla.org/network/protocol-proxy-service;1"].
+      const pps = parentCc["@mozilla.org/network/protocol-proxy-service;1"].
                 getService(parentCi.nsIProtocolProxyService);
       pps.asyncResolve(channel, 0, {
-        onProxyAvailable(req, uri, pi, status) {
-          let mozproxy = "moz-proxy://" + pi.host + ":" + pi.port;
-          let login = parentCc["@mozilla.org/login-manager/loginInfo;1"].
+        async onProxyAvailable(req, uri, pi, status) {
+          const mozproxy = "moz-proxy://" + pi.host + ":" + pi.port;
+          const login1 = parentCc["@mozilla.org/login-manager/loginInfo;1"].
                       createInstance(parentCi.nsILoginInfo);
-          login.init(mozproxy, null, "proxy_realm", "proxy_user", "proxy_pass",
+          login1.init(mozproxy, null, "proxy_realm", "proxy_user", "proxy_pass",
                      "", "");
-          Services.logins.addLogin(login);
 
-          let login2 = parentCc["@mozilla.org/login-manager/loginInfo;1"].
+          const login2 = parentCc["@mozilla.org/login-manager/loginInfo;1"].
                        createInstance(parentCi.nsILoginInfo);
           login2.init("http://mochi.test:8888", null, "mochirealm", "user1name",
                       "user1pass", "", "");
-          Services.logins.addLogin(login2);
+          await Services.logins.addLogins([login1, login2]);
 
           sendAsyncMessage("setupDone");
         },
         QueryInterface: ChromeUtils.generateQI([parentCi.nsIProtocolProxyCallback]),
       });
@@ -114,31 +113,31 @@
           getService(parentCi.nsIHttpAuthManager).
           clearAll();
         sendAsyncMessage("prepareForNextTestDone");
       });
 
-      let modalType = Services.prefs.getIntPref(
+      const modalType = Services.prefs.getIntPref(
         "prompts.modalType.httpAuth"
       );
-      let authPromptIsCommonDialog =
+      const authPromptIsCommonDialog =
         modalType === Services.prompt.MODAL_TYPE_WINDOW
           || (modalType === Services.prompt.MODAL_TYPE_TAB
             && Services.prefs.getBoolPref(
         "prompts.tabChromePromptSubDialog",
         false
       ));
 
-      let dialogObserverTopic = authPromptIsCommonDialog
+      const dialogObserverTopic = authPromptIsCommonDialog
         ? "common-dialog-loaded" : "tabmodal-dialog-loaded";
 
       function dialogObserver(subj, topic, data) {
         if (authPromptIsCommonDialog) {
           subj.Dialog.ui.prompt.document
           .getElementById("commonDialog")
           .acceptDialog();
         } else {
-          let prompt = subj.ownerGlobal.gBrowser.selectedBrowser
+          const prompt = subj.ownerGlobal.gBrowser.selectedBrowser
             .tabModalPromptBox.getPrompt(subj);
           prompt.Dialog.ui.button0.click(); // Accept button
         }
         sendAsyncMessage("promptAccepted");
       }
diff --git a/toolkit/components/passwordmgr/test/mochitest/test_case_differences.html b/toolkit/components/passwordmgr/test/mochitest/test_case_differences.html
--- a/toolkit/components/passwordmgr/test/mochitest/test_case_differences.html
+++ b/toolkit/components/passwordmgr/test/mochitest/test_case_differences.html
@@ -9,20 +9,10 @@
   <script type="text/javascript" src="pwmgr_common.js"></script>
   <link rel="stylesheet" type="text/css" href="/tests/SimpleTest/test.css" />
 </head>
 <body>
 Login Manager test: autocomplete due to multiple matching logins
-
-<script>
-runChecksAfterCommonInit(false);
-
-let origin = window.location.origin;
-addLoginsInParent(
-  [origin, "https://autocomplete:8888", null, "name", "pass", "uname", "pword"],
-  [origin, "https://autocomplete:8888", null, "Name", "Pass", "uname", "pword"],
-  [origin, "https://autocomplete:8888", null, "USER", "PASS", "uname", "pword"]);
-</script>
 <p id="display"></p>
 
 <!-- we presumably can't hide the content for this test. -->
 <div id="content">
 
@@ -35,10 +25,11 @@
 
 </div>
 
 <pre id="test">
 <script class="testbody" type="text/javascript">
+runChecksAfterCommonInit(false);
 
 /** Test for Login Manager: autocomplete due to multiple matching logins **/
 
 const uname = getFormElementByName(1, "uname");
 const pword = getFormElementByName(1, "pword");
@@ -48,10 +39,18 @@
   uname.value = "";
   pword.value = "";
   uname.focus();
 }
 
+add_setup(async () => {
+  const origin = window.location.origin;
+  await addLoginsInParent(
+    [origin, "https://autocomplete:8888", null, "name", "pass", "uname", "pword"],
+    [origin, "https://autocomplete:8888", null, "Name", "Pass", "uname", "pword"],
+    [origin, "https://autocomplete:8888", null, "USER", "PASS", "uname", "pword"]
+  );
+})
 
 add_task(async function test_empty_first_entry() {
   /* test 1 */
   // Make sure initial form is empty.
   checkLoginForm(uname, "", pword, "");
@@ -63,11 +62,11 @@
   popupState = await getPopupState();
   is(popupState.selectedIndex, -1, "Check no entries are selected");
   checkAutoCompleteResults(items, ["name", "Name", "USER"], "example.com", "initial");
 
   // Check first entry
-  let index0Promise = notifySelectedIndex(0);
+  const index0Promise = notifySelectedIndex(0);
   synthesizeKey("KEY_ArrowDown");
   await index0Promise;
   checkLoginForm(uname, "", pword, ""); // value shouldn't update
   synthesizeKey("KEY_Enter");
   await promiseFormsProcessedInSameProcess();
diff --git a/toolkit/components/passwordmgr/test/mochitest/test_form_action_javascript.html b/toolkit/components/passwordmgr/test/mochitest/test_form_action_javascript.html
--- a/toolkit/components/passwordmgr/test/mochitest/test_form_action_javascript.html
+++ b/toolkit/components/passwordmgr/test/mochitest/test_form_action_javascript.html
@@ -10,25 +10,21 @@
 <body>
 Login Manager test: form with JS submit action
 <script>
 runChecksAfterCommonInit(() => startTest());
 
-runInParent(function setup() {
-  let jslogin = Cc["@mozilla.org/login-manager/loginInfo;1"].createInstance(Ci.nsILoginInfo);
-  jslogin.init("http://mochi.test:8888", "javascript:", null,
-               "jsuser", "jspass123", "uname", "pword");
-  Services.logins.addLogin(jslogin);
-});
-
-let DEFAULT_ORIGIN = window.location.origin;
+const origin = window.location.origin;
 
 /** Test for Login Manager: JS action URL **/
 
 async function startTest() {
-  let win = window.open("about:blank");
+  await addLoginsInParent(
+    [origin, "javascript:", null, "jsuser", "jspass123", "uname", "pword"]
+  );
+  const win = window.open("about:blank");
   SimpleTest.registerCleanupFunction(() => win.close());
-  await loadFormIntoWindow(DEFAULT_ORIGIN, `
+  await loadFormIntoWindow(origin, `
     <form id='form1' action='javascript:alert("never shows")'> 1
       <input name="uname">
       <input name="pword" type="password">
 
       <button type='submit'>Submit</button>
diff --git a/toolkit/components/passwordmgr/test/mochitest/test_munged_values.html b/toolkit/components/passwordmgr/test/mochitest/test_munged_values.html
--- a/toolkit/components/passwordmgr/test/mochitest/test_munged_values.html
+++ b/toolkit/components/passwordmgr/test/mochitest/test_munged_values.html
@@ -8,55 +8,55 @@
   <script src="pwmgr_common.js"></script>
   <link rel="stylesheet" href="/tests/SimpleTest/test.css" />
 </head>
 <body>
 <script type="application/javascript">
-let readyPromise = registerRunTests();
+const readyPromise = registerRunTests();
 
 const DEFAULT_ORIGIN = window.location.origin;
 
 function removeAllUserFacingLoginsInParent() {
   runInParent(function removeAllUserFacingLogins() {
     Services.logins.removeAllUserFacingLogins();
   });
 }
 
-function add2logins() {
+async function add2logins() {
   removeAllUserFacingLoginsInParent();
-  addLoginsInParent([DEFAULT_ORIGIN, DEFAULT_ORIGIN, null, "real••••user", "pass1", "", ""], [DEFAULT_ORIGIN, DEFAULT_ORIGIN, null, "user2", "pass2", "", ""]);
+  await addLoginsInParent([DEFAULT_ORIGIN, DEFAULT_ORIGIN, null, "real••••user", "pass1", "", ""], [DEFAULT_ORIGIN, DEFAULT_ORIGIN, null, "user2", "pass2", "", ""]);
 }
 
-function addSingleLogin() {
+async function addSingleLogin() {
   removeAllUserFacingLoginsInParent();
-  addLoginsInParent([DEFAULT_ORIGIN, DEFAULT_ORIGIN, null, "real••••user", "pass1", "", ""])
+  await addLoginsInParent([DEFAULT_ORIGIN, DEFAULT_ORIGIN, null, "real••••user", "pass1", "", ""])
 }
 
 /**
  *  For any test including the character "!", generate a version of that test for every known munge
  *  character.
  **/
  function generateTestCases(test) {
   const MUNGE_CHARS = ["*", ".", "•"];
 
-  let nothingToReplace = Object.values(test).every(value => typeof value !== "string" || !value.includes("!"));
+  const nothingToReplace = Object.values(test).every(value => typeof value !== "string" || !value.includes("!"));
   if (nothingToReplace) {
     return test;
   };
 
   return MUNGE_CHARS.map(char => {
-    let newTest = {};
-    for (let [propName, val] of Object.entries(test)) {
+    const newTest = {};
+    for (const [propName, val] of Object.entries(test)) {
       if (typeof val === "string") {
         newTest[propName] = val.replace(/!/g, char);
       } else {
         newTest[propName] = val;
       }
   };
   return newTest;
 })};
 
-let loadPromise = new Promise(resolve => {
+const loadPromise = new Promise(resolve => {
   document.addEventListener("DOMContentLoaded", () => {
     resolve();
   });
 });
 
@@ -99,44 +99,44 @@
     testName: "test_combinedMungeCharacters",
     username: "*.•*.•*.•*.•*.•*.•",
     expected: "*.•*.•*.•*.•*.•*.•",
   },
 ].flatMap(generateTestCases);
-  for (let tc of TEST_CASES) {
+  for (const tc of TEST_CASES) {
     info("Starting testcase: " + JSON.stringify(tc));
     // Create a new window for each test case, because if we instead try to use
     // the same window and change the page using window.location, that will trigger
     // an onLocationChange event, which can trigger unwanted FormSubmit outside of
     // clicking the submit button in each test document.
-    let win = window.open("about:blank");
-    let html = `
+    const win = window.open("about:blank");
+    const html = `
       <form id="form1" onsubmit="return false;">
         <input  type="text"       name="uname" value="${tc.username}">
         <input  type="password"   name="pword" value="thepassword">
         <button type="submit" id="submitBtn">Submit</button>
       </form>`;
     await loadFormIntoWindow(DEFAULT_ORIGIN, html, win);
     await SpecialPowers.spawn(win, [html], function(contentHtml) {
-      let doc = this.content.document;
-      for (let field of doc.querySelectorAll("input")) {
-        let actualValue = field.value;
+      const doc = this.content.document;
+      for (const field of doc.querySelectorAll("input")) {
+        const actualValue = field.value;
         field.value = "";
         SpecialPowers.wrap(field).setUserInput(actualValue);
       }
     });
     await SpecialPowers.spawn(win, [tc], function(testcase) {
-      let doc = this.content.document;
+      const doc = this.content.document;
       Assert.equal(doc.querySelector("[name='uname']").value, testcase.username, "Checking for filled username");
     });
 
     // Check data sent via PasswordManager:onFormSubmit
-    let processedPromise = getSubmitMessage();
+    const processedPromise = getSubmitMessage();
     await SpecialPowers.spawn(win, [], function() {
       this.content.document.getElementById("submitBtn").click();
     });
 
-    let { data } = await processedPromise;
+    const { data } = await processedPromise;
     info("Got submitted result: " + JSON.stringify(data));
 
     if (tc.expected === null) {
       is(data.usernameField, tc.expected, "Check usernameField");
     } else {
@@ -175,38 +175,38 @@
       password: "*.•*.•*.•*.•",
       shouldShowPrompt: true,
     },
   ].flatMap(generateTestCases);
 
-  for (let tc of TEST_CASES) {
+  for (const tc of TEST_CASES) {
     info("Starting testcase: " + tc.testName)
     // Create a new window for each test case, because if we instead try to use
     // the same window and change the page using window.location, that will trigger
     // an onLocationChange event, which can trigger unwanted FormSubmit outside of
     // clicking the submit button in each test document.
-    let win = window.open("about:blank");
-    let html = `
+    const win = window.open("about:blank");
+    const html = `
       <form id="form1" onsubmit="return false;">
         <input  type="text"       name="uname" value="username">
         <input  type="password"   name="pword" value="${tc.password}">
         <button type="submit" id="submitBtn">Submit</button>
       </form>`;
     await loadFormIntoWindow(DEFAULT_ORIGIN, html, win);
     await SpecialPowers.spawn(win, [html], function(contentHtml) {
-      let doc = this.content.document;
-      for (let field of doc.querySelectorAll("input")) {
-        let actualValue = field.value;
+      const doc = this.content.document;
+      for (const field of doc.querySelectorAll("input")) {
+        const actualValue = field.value;
         field.value = "";
         SpecialPowers.wrap(field).setUserInput(actualValue);
       }
     });
     await SpecialPowers.spawn(win, [tc], function(testcase) {
-      let doc = this.content.document;
+      const doc = this.content.document;
       Assert.equal(doc.querySelector("[name='pword']").value, testcase.password, "Checking for filled password");
     });
 
-    let formSubmitListener = SpecialPowers.spawn(win, [], function() {
+    const formSubmitListener = SpecialPowers.spawn(win, [], function() {
       return new Promise(resolve => {
         this.content.windowRoot.addEventListener(
             "PasswordManager:ShowDoorhanger",
             event => {
               info(`PasswordManager:ShowDoorhanger called. Event: ${JSON.stringify(event)}`);
@@ -218,11 +218,11 @@
 
     await SpecialPowers.spawn(win, [], function() {
       this.content.document.getElementById("submitBtn").click();
     });
 
-    let dialogRequested = await formSubmitListener;
+    const dialogRequested = await formSubmitListener;
 
     is(dialogRequested, tc.shouldShowPrompt, "Verify 'show save/update prompt' message sent to parent process");
 
     win.close();
     await SimpleTest.promiseFocus(window);
@@ -230,59 +230,59 @@
 });
 
 add_task(async function test_no_autofill_munged_username_matching_password() {
   // run this test with 2 matching logins from this origin so we don't autofill
   await add2logins();
-  let allLogins = await LoginManager.getAllLogins();
-  let matchingLogins = Array.prototype.filter.call(allLogins, l => l.origin == DEFAULT_ORIGIN);
+  const allLogins = await LoginManager.getAllLogins();
+  const matchingLogins = Array.prototype.filter.call(allLogins, l => l.origin == DEFAULT_ORIGIN);
   is(matchingLogins.length, 2, "Expected number of matching logins");
 
-  let bulletLogin = matchingLogins.find(l => l.username == "real••••user");
+  const bulletLogin = matchingLogins.find(l => l.username == "real••••user");
   ok(bulletLogin, "Found the real••••user login");
 
-  let timesUsed = bulletLogin.timesUsed;
-  let guid = bulletLogin.guid;
+  const timesUsed = bulletLogin.timesUsed;
+  const guid = bulletLogin.guid;
 
-  let win = window.open("about:blank");
-  let html =
+  const win = window.open("about:blank");
+  const html =
     `<form id="form1" onsubmit="return false;">
       <input  type="text"       name="uname" value="">
       <input  type="password"   name="pword" value="">
       <button type="submit" id="submitBtn">Submit</button>
     </form>`;
   await loadFormIntoWindow(DEFAULT_ORIGIN, html, win);
   await SpecialPowers.spawn(win, [html], function(contentHtml) {
-    let doc = this.content.document;
-    for (let field of doc.querySelectorAll("input")) {
-      let actualValue = field.value;
+    const doc = this.content.document;
+    for (const field of doc.querySelectorAll("input")) {
+      const actualValue = field.value;
       field.value = "";
       SpecialPowers.wrap(field).setUserInput(actualValue);
     }
   });
   await SpecialPowers.spawn(win, [], function() {
-    let doc = this.content.document;
+    const doc = this.content.document;
     Assert.equal(doc.querySelector("[name='uname']").value, "", "Check username didn't get autofilled");
     SpecialPowers.wrap(doc.querySelector("[name='uname']")).setUserInput("real••••user");
     SpecialPowers.wrap(doc.querySelector("[name='pword']")).setUserInput("pass1");
   });
 
   // we shouldn't get the save password doorhanger...
-  let popupShownPromise = noPopupBy();
+  const popupShownPromise = noPopupBy();
 
   // Check data sent via PasswordManager:onFormSubmit
-  let processedPromise = getSubmitMessage();
+  const processedPromise = getSubmitMessage();
   await SpecialPowers.spawn(win, [], function() {
     this.content.document.getElementById("submitBtn").click();
   });
 
-  let { data } = await processedPromise;
+  const { data } = await processedPromise;
   info("Got submitted result: " + JSON.stringify(data));
 
   is(data.usernameField, null, "Check usernameField");
 
-  let updatedLogins = await LoginManager.getAllLogins();
-  let updatedLogin = Array.prototype.find.call(updatedLogins, l => l.guid == guid);
+  const updatedLogins = await LoginManager.getAllLogins();
+  const updatedLogin = Array.prototype.find.call(updatedLogins, l => l.guid == guid);
   ok(updatedLogin, "Got the login via guid");
   is(updatedLogin.timesUsed, timesUsed + 1, "timesUsed was incremented");
 
   await popupShownPromise;
 
@@ -293,59 +293,59 @@
 
 add_task(async function test_autofill_munged_username_matching_password() {
   // only a single matching login so we autofill the username
   await addSingleLogin();
 
-  let allLogins = await LoginManager.getAllLogins();
-  let matchingLogins = Array.prototype.filter.call(allLogins, l => l.origin == DEFAULT_ORIGIN);
+  const allLogins = await LoginManager.getAllLogins();
+  const matchingLogins = Array.prototype.filter.call(allLogins, l => l.origin == DEFAULT_ORIGIN);
   is(matchingLogins.length, 1, "Expected number of matching logins");
 
   info("matched login: " + matchingLogins[0].username);
-  let bulletLogin = matchingLogins.find(l => l.username == "real••••user");
+  const bulletLogin = matchingLogins.find(l => l.username == "real••••user");
   ok(bulletLogin, "Found the real••••user login");
 
-  let timesUsed = bulletLogin.timesUsed;
-  let guid = bulletLogin.guid;
+  const timesUsed = bulletLogin.timesUsed;
+  const guid = bulletLogin.guid;
 
-  let win = window.open("about:blank");
-  let html =
+  const win = window.open("about:blank");
+  const html =
     `<form id="form1" onsubmit="return false;">
       <input  type="text"       name="uname" value="">
       <input  type="password"   name="pword" value="">
       <button type="submit" id="submitBtn">Submit</button>
     </form>`;
   await loadFormIntoWindow(DEFAULT_ORIGIN, html, win);
   await SpecialPowers.spawn(win, [html], function(contentHtml) {
-    let doc = this.content.document;
-    for (let field of doc.querySelectorAll("input")) {
-      let actualValue = field.value;
+    const doc = this.content.document;
+    for (const field of doc.querySelectorAll("input")) {
+      const actualValue = field.value;
       field.value = "";
       SpecialPowers.wrap(field).setUserInput(actualValue);
     }
   });
   await SpecialPowers.spawn(win, [], function() {
-    let doc = this.content.document;
+    const doc = this.content.document;
     Assert.equal(doc.querySelector("[name='uname']").value, "real••••user", "Check username did get autofilled");
     doc.querySelector("[name='pword']").setUserInput("pass1");
   });
 
   // we shouldn't get the save/update password doorhanger as it didn't change
-  let popupShownPromise = noPopupBy();
+  const popupShownPromise = noPopupBy();
 
   // Check data sent via PasswordManager:onFormSubmit
-  let processedPromise = getSubmitMessage();
+  const processedPromise = getSubmitMessage();
   await SpecialPowers.spawn(win, [], function() {
     this.content.document.getElementById("submitBtn").click();
   });
 
-  let { data } = await processedPromise;
+  const { data } = await processedPromise;
   info("Got submitted result: " + JSON.stringify(data));
 
   is(data.usernameField, null, "Check usernameField");
 
-  let updatedLogins = await LoginManager.getAllLogins();
-  let updatedLogin = Array.prototype.find.call(updatedLogins, l => l.guid == guid);
+  const updatedLogins = await LoginManager.getAllLogins();
+  const updatedLogin = Array.prototype.find.call(updatedLogins, l => l.guid == guid);
   ok(updatedLogin, "Got the login via guid");
   is(updatedLogin.timesUsed, timesUsed + 1, "timesUsed was incremented");
 
   await popupShownPromise;
 
diff --git a/toolkit/components/passwordmgr/test/mochitest/test_primary_password.html b/toolkit/components/passwordmgr/test/mochitest/test_primary_password.html
--- a/toolkit/components/passwordmgr/test/mochitest/test_primary_password.html
+++ b/toolkit/components/passwordmgr/test/mochitest/test_primary_password.html
@@ -21,43 +21,32 @@
 "use strict";
 
 // Force parent to not look for tab-modal prompts, as they're not used for auth prompts.
 modalType = Ci.nsIPrompt.MODAL_TYPE_WINDOW;
 
-var exampleCom = "https://example.com/tests/toolkit/components/passwordmgr/test/mochitest/";
-var exampleOrg = "https://example.org/tests/toolkit/components/passwordmgr/test/mochitest/";
+const exampleCom = "https://example.com/tests/toolkit/components/passwordmgr/test/mochitest/";
+const exampleOrg = "https://example.org/tests/toolkit/components/passwordmgr/test/mochitest/";
 
 gTestDependsOnDeprecatedLogin = true;
-var chromeScript = runChecksAfterCommonInit();
-
-runInParent(() => {
-  var nsLoginInfo = new Components.Constructor("@mozilla.org/login-manager/loginInfo;1", Ci.nsILoginInfo);
-
-  var login1 = new nsLoginInfo();
-  var login2 = new nsLoginInfo();
+const chromeScript = runChecksAfterCommonInit();
 
-  login1.init("https://example.com", "https://example.com", null,
-              "user1", "pass1", "uname", "pword");
-  login2.init("https://example.org", "https://example.org", null,
-              "user2", "pass2", "uname", "pword");
-
-  Services.logins.addLogin(login1);
-  Services.logins.addLogin(login2);
-});
-
-let win = window.open("about:blank");
+const win = window.open("about:blank");
 SimpleTest.registerCleanupFunction(() => win.close());
 
 add_setup(async () => {
+  await addLoginsInParent(
+    ["https://example.com", "https://example.com", null, "user1", "pass1", "uname", "pword"],
+    ["https://example.org", "https://example.org", null, "user2", "pass2", "uname", "pword"]
+  );
   ok(await isLoggedIn(), "should be initially logged in (no PP)");
   enablePrimaryPassword();
   ok(!await isLoggedIn(), "should be logged out after setting PP");
 });
 
 add_task(async function test_1() {
   // Trigger a MP prompt via the API
-  var state = {
+  const state = {
     msg: "Please enter your Primary Password.",
     title: "the title",
     textValue: "",
     passValue: "",
     iconClass: "authentication-icon question-icon",
@@ -68,17 +57,17 @@
     checkMsg: "",
     checked: false,
     focused: "passField",
     defButton: "button0",
   };
-  var action = {
+  const action = {
     buttonClick: "ok",
     passField: LoginTestUtils.primaryPassword.primaryPassword,
   };
-  var promptDone = handlePrompt(state, action);
+  const promptDone = handlePrompt(state, action);
 
-  var logins = await LoginManager.getAllLogins();
+  const logins = await LoginManager.getAllLogins();
 
   await promptDone;
   is(logins.length, 3, "expected number of logins");
 
   ok(await isLoggedIn(), "should be logged in after MP prompt");
@@ -86,11 +75,11 @@
   ok(!await isLoggedIn(), "should be logged out");
 });
 
 add_task(async function test_2() {
   // Try again but click cancel.
-  var state = {
+  const state = {
     msg: "Please enter your Primary Password.",
     title: "the title",
     textValue: "",
     passValue: "",
     iconClass: "authentication-icon question-icon",
@@ -101,23 +90,23 @@
     checkMsg: "",
     checked: false,
     focused: "passField",
     defButton: "button0",
   };
-  var action = {
+  const action = {
     buttonClick: "cancel",
   };
-  var promptDone = handlePrompt(state, action);
+  const promptDone = handlePrompt(state, action);
 
-  var logins = await LoginManager.getAllLogins().catch(() => {});
+  const logins = await LoginManager.getAllLogins().catch(() => {});
   await promptDone;
   is(logins, undefined, "shouldn't have gotten logins");
   ok(!await isLoggedIn(), "should still be logged out");
 });
 
 add_task(async function test_3() {
-  var state = {
+  const state = {
     msg: "Please enter your Primary Password.",
     title: "the title",
     textValue: "",
     passValue: "",
     iconClass: "authentication-icon question-icon",
@@ -128,17 +117,17 @@
     checkMsg: "",
     checked: false,
     focused: "passField",
     defButton: "button0",
   };
-  var action = {
+  const action = {
     buttonClick: "ok",
     passField: LoginTestUtils.primaryPassword.primaryPassword,
   };
-  var promptDone = handlePrompt(state, action);
+  const promptDone = handlePrompt(state, action);
 
-  var fillPromise = promiseFormsProcessed();
+  const fillPromise = promiseFormsProcessed();
 
   info("Load a single window to trigger a MP");
   await SimpleTest.promiseFocus(win, true);
   win.location = exampleCom + "subtst_primary_pass.html";
 
@@ -148,12 +137,12 @@
   info("filled");
 
   // check contents of win fields
 
   await SpecialPowers.spawn(win, [], function() {
-    var u = this.content.document.getElementById("userfield");
-    var p = this.content.document.getElementById("passfield");
+    const u = this.content.document.getElementById("userfield");
+    const p = this.content.document.getElementById("passfield");
     Assert.equal(u.value, "user1", "checking expected user to have been filled in");
     Assert.equal(p.value, "pass1", "checking expected pass to have been filled in");
     u.value = "";
     p.value = "";
   });
@@ -162,11 +151,11 @@
   logoutPrimaryPassword();
   ok(!await isLoggedIn(), "should be logged out");
 });
 
 add_task(async function test_4() {
-  var state = {
+  const state = {
     msg: "Please enter your Primary Password.",
     title: "the title",
     textValue: "",
     passValue: "",
     iconClass: "authentication-icon question-icon",
@@ -177,25 +166,25 @@
     checkMsg: "",
     checked: false,
     focused: "passField",
     defButton: "button0",
   };
-  var action = {
+  let action = {
     buttonClick: "none",
   };
-  var promptDone = handlePrompt(state, action);
+  const promptDone = handlePrompt(state, action);
 
   // first part of loading 2 MP-triggering windows
   await SimpleTest.promiseFocus(win);
   win.location = exampleOrg + "subtst_primary_pass.html";
   // The MP prompt is open but don't take any action yet.
   await promptDone;
 
   // check contents of win fields
   await SpecialPowers.spawn(win, [], function() {
-    var u = this.content.document.getElementById("userfield");
-    var p = this.content.document.getElementById("passfield");
+    const u = this.content.document.getElementById("userfield");
+    const p = this.content.document.getElementById("passfield");
     Assert.equal(u.value, "", "checking expected empty user");
     Assert.equal(p.value, "", "checking expected empty pass");
   });
 
   ok(!await isLoggedIn(), "should be logged out");
@@ -206,14 +195,14 @@
   // This should detect that there's already a pending MP prompt, and not
   // put up a second one.
 
   // Since the Primary Password prompt is open, we can't focus another tab
   // to load the second form. Instead, we load the same form into an iframe.
-  let url = exampleOrg + "subtst_primary_pass.html";
+  const url = exampleOrg + "subtst_primary_pass.html";
   await SpecialPowers.spawn(win, [url], async function(urlF) {
-    let iframe = this.content.document.querySelector("iframe");
-    var loadPromise = new Promise(resolve => {
+    const iframe = this.content.document.querySelector("iframe");
+    const loadPromise = new Promise(resolve => {
       iframe.addEventListener("load", function onload() {
         resolve();
       }, { once: true });
     });
     // Use the same origin as the top level to ensure we would autofill
@@ -227,12 +216,12 @@
   await new Promise(resolve => {
     // Testing a negative, wait a little to give the login manager a chance to
     // (incorrectly) fill in the form.  Note, we cannot use setTimeout()
     // here because the modal window suspends all window timers.  Instead we
     // must use a chrome script to use nsITimer directly.
-    let chromeURL = SimpleTest.getTestFileURL("chrome_timeout.js");
-    let script = SpecialPowers.loadChromeScript(chromeURL);
+    const chromeURL = SimpleTest.getTestFileURL("chrome_timeout.js");
+    const script = SpecialPowers.loadChromeScript(chromeURL);
     script.addMessageListener("ready", _ => {
       script.sendAsyncMessage("setTimeout", { delay: 500 });
     });
     script.addMessageListener("timeout", resolve);
   });
@@ -240,23 +229,23 @@
   // iframe should load without having triggered a MP prompt (because one
   // is already waiting)
 
   // check contents of iframe fields
   await SpecialPowers.spawn(win, [], function() {
-    let iframe = this.content.document.querySelector("iframe");
-    let frameDoc = iframe.contentDocument;
-    var u = frameDoc.getElementById("userfield");
-    var p = frameDoc.getElementById("passfield");
+    const iframe = this.content.document.querySelector("iframe");
+    const frameDoc = iframe.contentDocument;
+    const u = frameDoc.getElementById("userfield");
+    const p = frameDoc.getElementById("passfield");
     Assert.equal(u.value, "", "checking expected empty user");
     Assert.equal(p.value, "", "checking expected empty pass");
   });
 
   // XXX check that there's 1 MP window open
   ok(!await isLoggedIn(), "should be logged out");
 
   // Ok, now enter the MP. The MP prompt is already up.
-  var fillPromise = promiseFormsProcessed(2);
+  const fillPromise = promiseFormsProcessed(2);
 
   // fill existing MP dialog with MP.
   action = {
     buttonClick: "ok",
     passField: LoginTestUtils.primaryPassword.primaryPassword,
@@ -270,26 +259,26 @@
   // processing the form.
   ok(await isLoggedIn(), "should be logged in");
 
   // check contents of win fields
   await SpecialPowers.spawn(win, [], function() {
-    var u = this.content.document.getElementById("userfield");
-    var p = this.content.document.getElementById("passfield");
+    const u = this.content.document.getElementById("userfield");
+    const p = this.content.document.getElementById("passfield");
     Assert.equal(u.value, "user2", "checking expected user to have been filled in");
     Assert.equal(p.value, "pass2", "checking expected pass to have been filled in");
 
     // clearing fields to not cause a submission when the next document is loaded
     u.value = "";
     p.value = "";
   });
 
   // check contents of iframe fields
   await SpecialPowers.spawn(win, [], function() {
-    let iframe = this.content.document.querySelector("iframe");
-    let frameDoc = iframe.contentDocument;
-    var u = frameDoc.getElementById("userfield");
-    var p = frameDoc.getElementById("passfield");
+    const iframe = this.content.document.querySelector("iframe");
+    const frameDoc = iframe.contentDocument;
+    const u = frameDoc.getElementById("userfield");
+    const p = frameDoc.getElementById("passfield");
     Assert.equal(u.value, "user2", "checking expected user to have been filled in");
     Assert.equal(p.value, "pass2", "checking expected pass to have been filled in");
 
     // clearing fields to not cause a submission when the next document is loaded
     u.value = "";
diff --git a/toolkit/components/passwordmgr/test/mochitest/test_prompt.html b/toolkit/components/passwordmgr/test/mochitest/test_prompt.html
--- a/toolkit/components/passwordmgr/test/mochitest/test_prompt.html
+++ b/toolkit/components/passwordmgr/test/mochitest/test_prompt.html
@@ -45,48 +45,19 @@
 let prompter1 = new PrompterProxy(prompterParent);
 
 const defaultTitle = "the title";
 const defaultMsg = "the message";
 
-function initLogins() {
-  var login1, login2A, login2B, login2C, login2D, login2E;
-  login1  = Cc["@mozilla.org/login-manager/loginInfo;1"].
-            createInstance(Ci.nsILoginInfo);
-  login2A = Cc["@mozilla.org/login-manager/loginInfo;1"].
-            createInstance(Ci.nsILoginInfo);
-  login2B = Cc["@mozilla.org/login-manager/loginInfo;1"].
-            createInstance(Ci.nsILoginInfo);
-  login2C = Cc["@mozilla.org/login-manager/loginInfo;1"].
-            createInstance(Ci.nsILoginInfo);
-  login2D = Cc["@mozilla.org/login-manager/loginInfo;1"].
-            createInstance(Ci.nsILoginInfo);
-  login2E = Cc["@mozilla.org/login-manager/loginInfo;1"].
-            createInstance(Ci.nsILoginInfo);
-
-  login1.init("http://example.com", null, "http://example.com",
-              "", "examplepass", "", "");
-  login2A.init("http://example2.com", null, "http://example2.com",
-               "user1name", "user1pass", "", "");
-  login2B.init("http://example2.com", null, "http://example2.com",
-               "user2name", "user2pass", "", "");
-  login2C.init("http://example2.com", null, "http://example2.com",
-               "user3.name@host", "user3pass", "", "");
-  login2D.init("http://example2.com", null, "http://example2.com",
-               "100@beef", "user3pass", "", "");
-  login2E.init("http://example2.com", null, "http://example2.com",
-               "100%beef", "user3pass", "", "");
-
-  Services.logins.addLogin(login1);
-  Services.logins.addLogin(login2A);
-  Services.logins.addLogin(login2B);
-  Services.logins.addLogin(login2C);
-  Services.logins.addLogin(login2D);
-  Services.logins.addLogin(login2E);
-}
-
 add_setup(async () => {
-  runInParent(initLogins);
+    await addLoginsInParent(
+    ["http://example.com", null, "http://example.com", "", "examplepass", "", ""],
+    ["http://example2.com", null, "http://example2.com", "user1name", "user1pass", "", ""],
+    ["http://example2.com", null, "http://example2.com", "user2name", "user2pass", "", ""],
+    ["http://example2.com", null, "http://example2.com", "user3.name@host", "user3pass", "", ""],
+    ["http://example2.com", null, "http://example2.com", "100@beef", "user3pass", "", ""],
+    ["http://example2.com", null, "http://example2.com", "100%beef", "user3pass", "", ""]
+  );
 });
 
 add_task(async function test_prompt_accept() {
   state = {
     msg: "the message",
diff --git a/toolkit/components/passwordmgr/test/mochitest/test_prompt_http.html b/toolkit/components/passwordmgr/test/mochitest/test_prompt_http.html
--- a/toolkit/components/passwordmgr/test/mochitest/test_prompt_http.html
+++ b/toolkit/components/passwordmgr/test/mochitest/test_prompt_http.html
@@ -22,53 +22,22 @@
 // Let prompt_common know what kind of modal type is enabled for auth prompts.
 modalType = authPromptModalType;
 
 const AUTHENTICATE_PATH = new URL("authenticate.sjs", window.location.href).pathname;
 
-runInParent(() => {
-  let login3A, login3B, login4;
-  login3A = Cc["@mozilla.org/login-manager/loginInfo;1"].
-            createInstance(Ci.nsILoginInfo);
-  login3B = Cc["@mozilla.org/login-manager/loginInfo;1"].
-            createInstance(Ci.nsILoginInfo);
-  login4  = Cc["@mozilla.org/login-manager/loginInfo;1"].
-            createInstance(Ci.nsILoginInfo);
-  let httpUpgradeLogin = Cc["@mozilla.org/login-manager/loginInfo;1"].
-                         createInstance(Ci.nsILoginInfo);
-  let httpsDowngradeLogin = Cc["@mozilla.org/login-manager/loginInfo;1"].
-                            createInstance(Ci.nsILoginInfo);
-  let dedupeHttpUpgradeLogin  = Cc["@mozilla.org/login-manager/loginInfo;1"].
-                                createInstance(Ci.nsILoginInfo);
-  let dedupeHttpsUpgradeLogin = Cc["@mozilla.org/login-manager/loginInfo;1"].
-                                createInstance(Ci.nsILoginInfo);
-
-
-  login3A.init("http://mochi.test:8888", null, "mochitest",
-               "mochiuser1", "mochipass1", "", "");
-  login3B.init("http://mochi.test:8888", null, "mochitest2",
-               "mochiuser2", "mochipass2", "", "");
-  login4.init("http://mochi.test:8888", null, "mochitest3",
-              "mochiuser3", "mochipass3-old", "", "");
-  // Logins to test scheme upgrades (allowed) and downgrades (disallowed)
-  httpUpgradeLogin.init("http://example.com", null, "schemeUpgrade",
-                        "httpUser", "httpPass", "", "");
-  httpsDowngradeLogin.init("https://example.com", null, "schemeDowngrade",
-                           "httpsUser", "httpsPass", "", "");
-  // HTTP and HTTPS version of the same domain and realm but with different passwords.
-  dedupeHttpUpgradeLogin.init("http://example.org", null, "schemeUpgradeDedupe",
-                              "dedupeUser", "httpPass", "", "");
-  dedupeHttpsUpgradeLogin.init("https://example.org", null, "schemeUpgradeDedupe",
-                               "dedupeUser", "httpsPass", "", "");
-
-
-  Services.logins.addLogin(login3A);
-  Services.logins.addLogin(login3B);
-  Services.logins.addLogin(login4);
-  Services.logins.addLogin(httpUpgradeLogin);
-  Services.logins.addLogin(httpsDowngradeLogin);
-  Services.logins.addLogin(dedupeHttpUpgradeLogin);
-  Services.logins.addLogin(dedupeHttpsUpgradeLogin);
+add_setup(async () => {
+  await addLoginsInParent(
+    ["http://mochi.test:8888", null, "mochitest", "mochiuser1", "mochipass1", "", ""],
+    ["http://mochi.test:8888", null, "mochitest2", "mochiuser2", "mochipass2", "", ""],
+    ["http://mochi.test:8888", null, "mochitest3", "mochiuser3", "mochipass3-old", "", ""],
+    // Logins to test scheme upgrades (allowed) and downgrades (disallowed)
+    ["http://example.com", null, "schemeUpgrade", "httpUser", "httpPass", "", ""],
+    ["https://example.com", null, "schemeDowngrade", "httpsUser", "httpsPass", "", ""],
+    // HTTP and HTTPS version of the same domain and realm but with different passwords.
+    ["http://example.org", null, "schemeUpgradeDedupe", "dedupeUser", "httpPass", "", ""],
+    ["https://example.org", null, "schemeUpgradeDedupe", "dedupeUser", "httpsPass", "", ""]
+  );
 });
 
 add_task(async function test_iframe() {
   let state = {
     msg: "This site is asking you to sign in.",
@@ -280,11 +249,11 @@
   await checkEchoedAuthInfo({user: "httpUser", pass: "httpPass"},
                             iframe);
 });
 
 add_task(async function test_schemeDowngrade() {
-  let state = {
+  const state = {
     msg: "This site is asking you to sign in. Warning: Your login information " +
       "will be shared with example.com, not the website you are currently visiting.",
     title: "Authentication Required",
     textValue: "", // empty because we shouldn't downgrade
     passValue: "",
@@ -296,26 +265,26 @@
     checkMsg: "",
     checked: false,
     focused: "textField",
     defButton: "button0",
   };
-  let action = {
+  const action = {
     buttonClick: "cancel",
   };
-  let promptDone = handlePrompt(state, action);
+  const promptDone = handlePrompt(state, action);
 
   // The following tests are driven by iframe loads
 
-  let iframeLoaded = onloadPromiseFor("iframe");
+  const iframeLoaded = onloadPromiseFor("iframe");
   iframe.src = "http://example.com" + AUTHENTICATE_PATH +
                "?user=unused&pass=unused&realm=schemeDowngrade";
   await promptDone;
   await iframeLoaded;
 });
 
 add_task(async function test_schemeUpgrade_dedupe() {
-  let state = {
+  const state = {
     msg: "This site is asking you to sign in. Warning: Your login information " +
       "will be shared with example.org, not the website you are currently visiting.",
     title: "Authentication Required",
     textValue: "dedupeUser",
     passValue: "httpsPass",
@@ -327,18 +296,18 @@
     checkMsg: "",
     checked: false,
     focused: "textField",
     defButton: "button0",
   };
-  let action = {
+  const action = {
     buttonClick: "ok",
   };
-  let promptDone = handlePrompt(state, action);
+  const promptDone = handlePrompt(state, action);
 
   // The following tests are driven by iframe loads
 
-  let iframeLoaded = onloadPromiseFor("iframe");
+  const iframeLoaded = onloadPromiseFor("iframe");
   iframe.src = "https://example.org" + AUTHENTICATE_PATH +
                "?user=dedupeUser&pass=httpsPass&realm=schemeUpgradeDedupe";
   await promptDone;
   await iframeLoaded;
   await checkEchoedAuthInfo({user: "dedupeUser", pass: "httpsPass"},
diff --git a/toolkit/components/passwordmgr/test/mochitest/test_prompt_noWindow.html b/toolkit/components/passwordmgr/test/mochitest/test_prompt_noWindow.html
--- a/toolkit/components/passwordmgr/test/mochitest/test_prompt_noWindow.html
+++ b/toolkit/components/passwordmgr/test/mochitest/test_prompt_noWindow.html
@@ -19,25 +19,17 @@
 
 // Let prompt_common know what kind of modal type is enabled for auth prompts.
 modalType = authPromptModalType;
 
 add_setup(async () => {
-  let loginAddedPromise = promiseStorageChanged(["addLogin"]);
-
-  runInParent(() => {
-    let login = Cc["@mozilla.org/login-manager/loginInfo;1"].
-                createInstance(Ci.nsILoginInfo);
-    login.init("http://mochi.test:8888", null, "mochitest",
-               "mochiuser1", "mochipass1", "", "");
-    Services.logins.addLogin(login);
-  });
-
-  await loginAddedPromise;
+  await addLoginsInParent(
+    ["http://mochi.test:8888", null, "mochitest", "mochiuser1", "mochipass1", "", ""]
+  );
 });
 
 add_task(async function test_sandbox_xhr() {
-  let state = {
+  const state = {
     msg: "This site is asking you to sign in.",
     title: "Authentication Required",
     textValue: "mochiuser1",
     passValue: "mochipass1",
     iconClass: "authentication-icon question-icon",
@@ -48,25 +40,25 @@
     checkMsg: "",
     checked: false,
     focused: "textField",
     defButton: "button0",
   };
-  let action = {
+  const action = {
     buttonClick: "ok",
   };
-  let promptDone = handlePrompt(state, action);
+  const promptDone = handlePrompt(state, action);
 
-  let url = new URL("authenticate.sjs?user=mochiuser1&pass=mochipass1", window.location.href);
-  let sandboxConstructor = SpecialPowers.Cu.Sandbox;
-  let sandbox = new sandboxConstructor(this, {wantXrays: true});
+  const url = new URL("authenticate.sjs?user=mochiuser1&pass=mochipass1", window.location.href);
+  const sandboxConstructor = SpecialPowers.Cu.Sandbox;
+  const sandbox = new sandboxConstructor(this, {wantXrays: true});
   function sandboxedRequest(sandboxedUrl) {
-    let req = new XMLHttpRequest();
+    const req = new XMLHttpRequest();
     req.open("GET", sandboxedUrl, true);
     req.send(null);
   }
 
-  let loginModifiedPromise = promiseStorageChanged(["modifyLogin"]);
+  const loginModifiedPromise = promiseStorageChanged(["modifyLogin"]);
   sandbox.sandboxedRequest = sandboxedRequest(url);
   info("send the XHR request in the sandbox");
   SpecialPowers.Cu.evalInSandbox("sandboxedRequest;", sandbox);
 
   await promptDone;
diff --git a/toolkit/components/passwordmgr/test/mochitest/test_prompt_promptAuth.html b/toolkit/components/passwordmgr/test/mochitest/test_prompt_promptAuth.html
--- a/toolkit/components/passwordmgr/test/mochitest/test_prompt_promptAuth.html
+++ b/toolkit/components/passwordmgr/test/mochitest/test_prompt_promptAuth.html
@@ -14,15 +14,12 @@
 <div id="content" style="display: none">
 </div>
 
 <pre id="test">
 <script class="testbody" type="text/javascript">
-var state, action;
-var isOk;
-
-var level = Ci.nsIAuthPrompt2.LEVEL_NONE;
-var authinfo = {
+const level = Ci.nsIAuthPrompt2.LEVEL_NONE;
+const authinfo = {
   username: "",
   password: "",
   domain: "",
 
   flags: Ci.nsIAuthInformation.AUTH_HOST,
@@ -31,19 +28,19 @@
 };
 
 // Let prompt_common know what kind of modal type is enabled for auth prompts.
 modalType = authPromptModalType;
 
-let prompterParent = runInParent(() => {
+const prompterParent = runInParent(() => {
   const promptFac = Cc["@mozilla.org/passwordmanager/authpromptfactory;1"].
                     getService(Ci.nsIPromptFactory);
 
-  let chromeWin = Services.wm.getMostRecentWindow("navigator:browser");
-  let prompter2 = promptFac.getPrompt(chromeWin, Ci.nsIAuthPrompt2);
+  const chromeWin = Services.wm.getMostRecentWindow("navigator:browser");
+  const prompter2 = promptFac.getPrompt(chromeWin, Ci.nsIAuthPrompt2);
   prompter2.QueryInterface(Ci.nsILoginManagerAuthPrompter).browser = chromeWin.gBrowser.selectedBrowser;
 
-  let channels = {};
+  const channels = {};
   channels.channel1 = Services.io.newChannel("http://example.com",
                                              null,
                                              null,
                                              null, // aLoadingNode
                                              Services.
@@ -61,62 +58,39 @@
                                              null, // aTriggeringPrincipal
                                              Ci.nsILoadInfo.SEC_ALLOW_CROSS_ORIGIN_SEC_CONTEXT_IS_NULL,
                                              Ci.nsIContentPolicy.TYPE_OTHER);
 
   addMessageListener("proxyPrompter", function onMessage(msg) {
-    let args = [...msg.args];
-    let channelName = args.shift();
+    const args = [...msg.args];
+    const channelName = args.shift();
     // Replace the channel name string (arg. 0) with the channel by that name.
     args.unshift(channels[channelName]);
 
-    let rv = prompter2[msg.methodName](...args);
+    const rv = prompter2[msg.methodName](...args);
     return {
       rv,
       // Send the args back to content so out/inout args can be checked.
       args: msg.args,
     };
   });
-
-  let login1, login2A, login2B, login2C, login2D, login2E;
-  login1  = Cc["@mozilla.org/login-manager/loginInfo;1"].
-            createInstance(Ci.nsILoginInfo);
-  login2A = Cc["@mozilla.org/login-manager/loginInfo;1"].
-            createInstance(Ci.nsILoginInfo);
-  login2B = Cc["@mozilla.org/login-manager/loginInfo;1"].
-            createInstance(Ci.nsILoginInfo);
-  login2C = Cc["@mozilla.org/login-manager/loginInfo;1"].
-            createInstance(Ci.nsILoginInfo);
-  login2D = Cc["@mozilla.org/login-manager/loginInfo;1"].
-            createInstance(Ci.nsILoginInfo);
-  login2E = Cc["@mozilla.org/login-manager/loginInfo;1"].
-            createInstance(Ci.nsILoginInfo);
-
-  login1.init("http://example.com", null, "http://example.com",
-              "", "examplepass", "", "");
-  login2A.init("http://example2.com", null, "http://example2.com",
-               "user1name", "user1pass", "", "");
-  login2B.init("http://example2.com", null, "http://example2.com",
-               "user2name", "user2pass", "", "");
-  login2C.init("http://example2.com", null, "http://example2.com",
-               "user3.name@host", "user3pass", "", "");
-  login2D.init("http://example2.com", null, "http://example2.com",
-               "100@beef", "user3pass", "", "");
-  login2E.init("http://example2.com", null, "http://example2.com",
-               "100%beef", "user3pass", "", "");
-
-  Services.logins.addLogin(login1);
-  Services.logins.addLogin(login2A);
-  Services.logins.addLogin(login2B);
-  Services.logins.addLogin(login2C);
-  Services.logins.addLogin(login2D);
-  Services.logins.addLogin(login2E);
 });
 
-let prompter2 = new PrompterProxy(prompterParent);
+const prompter2 = new PrompterProxy(prompterParent);
+
+add_setup(async () => {
+  await addLoginsInParent(
+    ["http://example.com", null, "http://example.com", "", "examplepass", "", ""],
+    ["http://example2.com", null, "http://example2.com", "user1name", "user1pass", "", ""],
+    ["http://example2.com", null, "http://example2.com", "user2name", "user2pass", "", ""],
+    ["http://example2.com", null, "http://example2.com", "user3.name@host", "user3pass", "", ""],
+    ["http://example2.com", null, "http://example2.com", "100@beef", "user3pass", "", ""],
+    ["http://example2.com", null, "http://example2.com", "100%beef", "user3pass", "", ""]
+  );
+});
 
 add_task(async function test_accept() {
-  state = {
+  const state = {
     msg: "This site is asking you to sign in.",
     title: "Authentication Required",
     textValue: "inuser",
     passValue: "inpass",
     iconClass: "authentication-icon question-icon",
@@ -127,11 +101,11 @@
     checkMsg: "",
     checked: false,
     focused: "textField",
     defButton: "button0",
   };
-  action = {
+  const action = {
     buttonClick: "ok",
     textField: "outuser",
     passField: "outpass",
   };
   authinfo.username = "inuser";
@@ -140,20 +114,20 @@
 
   promptDone = handlePrompt(state, action);
   // Since prompter2 is actually a proxy to send a message to a chrome script and
   // we can't send a channel in a message, we instead send the channel name that
   // already exists in the chromeScript.
-  isOk = prompter2.promptAuth("channel1", level, authinfo);
+  const isOk = prompter2.promptAuth("channel1", level, authinfo);
   await promptDone;
 
   ok(isOk, "Checking dialog return value (accept)");
   is(authinfo.username, "outuser", "Checking returned username");
   is(authinfo.password, "outpass", "Checking returned password");
 });
 
 add_task(async function test_cancel() {
-  state = {
+  const state = {
     msg: "This site is asking you to sign in.",
     title: "Authentication Required",
     textValue: "outuser",
     passValue: "outpass",
     iconClass: "authentication-icon question-icon",
@@ -164,23 +138,23 @@
     checkMsg: "",
     checked: false,
     focused: "textField",
     defButton: "button0",
   };
-  action = {
+  const action = {
     buttonClick: "cancel",
   };
   promptDone = handlePrompt(state, action);
-  isOk = prompter2.promptAuth("channel1", level, authinfo);
+  const isOk = prompter2.promptAuth("channel1", level, authinfo);
   await promptDone;
 
   ok(!isOk, "Checking dialog return value (cancel)");
 });
 
 add_task(async function test_pwonly() {
   // test filling in password-only login
-  state = {
+  const state = {
     msg: "This site is asking you to sign in.",
     title: "Authentication Required",
     textValue: "",
     passValue: "examplepass",
     iconClass: "authentication-icon question-icon",
@@ -191,30 +165,30 @@
     checkMsg: "",
     checked: false,
     focused: "textField",
     defButton: "button0",
   };
-  action = {
+  const action = {
     buttonClick: "ok",
   };
   authinfo.username = "";
   authinfo.password = "";
   authinfo.realm    = "http://example.com";
 
   promptDone = handlePrompt(state, action);
-  isOk = prompter2.promptAuth("channel1", level, authinfo);
+  const isOk = prompter2.promptAuth("channel1", level, authinfo);
   await promptDone;
 
   ok(isOk, "Checking dialog return value (accept)");
   is(authinfo.username, "", "Checking returned username");
   is(authinfo.password, "examplepass", "Checking returned password");
 });
 
 add_task(async function test_multipleExisting() {
   // test filling in existing login (undetermined from multiple selection)
   // user2name/user2pass would also be valid to fill here.
-  state = {
+  const state = {
     msg: "This site is asking you to sign in.",
     title: "Authentication Required",
     textValue: "user1name",
     passValue: "user1pass",
     iconClass: "authentication-icon question-icon",
@@ -225,30 +199,30 @@
     checkMsg: "",
     checked: false,
     focused: "textField",
     defButton: "button0",
   };
-  action = {
+  const action = {
     buttonClick: "ok",
   };
   authinfo.username = "";
   authinfo.password = "";
   authinfo.realm    = "http://example2.com";
 
   promptDone = handlePrompt(state, action);
-  isOk = prompter2.promptAuth("channel2", level, authinfo);
+  const isOk = prompter2.promptAuth("channel2", level, authinfo);
   await promptDone;
 
   ok(isOk, "Checking dialog return value (accept)");
   ok(authinfo.username == "user1name" || authinfo.username == "user2name", "Checking returned username");
   ok(authinfo.password == "user1pass" || authinfo.password == "user2pass", "Checking returned password");
 });
 
 add_task(async function test_multipleExisting2() {
   // test filling in existing login (undetermined --> user1)
   // user2name/user2pass would also be valid to fill here.
-  state = {
+  const state = {
     msg: "This site is asking you to sign in.",
     title: "Authentication Required",
     textValue: "user1name",
     passValue: "user1pass",
     iconClass: "authentication-icon question-icon",
@@ -260,32 +234,32 @@
     checked: false,
     focused: "textField",
     defButton: "button0",
   };
   // enter one of the known logins, test 504+505 exercise the two possible states.
-  action = {
+  const action = {
     buttonClick: "ok",
     textField: "user1name",
     passField: "user1pass",
   };
   authinfo.username = "";
   authinfo.password = "";
   authinfo.realm    = "http://example2.com";
 
   promptDone = handlePrompt(state, action);
-  isOk = prompter2.promptAuth("channel2", level, authinfo);
+  const isOk = prompter2.promptAuth("channel2", level, authinfo);
   await promptDone;
 
   ok(isOk, "Checking dialog return value (accept)");
   is(authinfo.username, "user1name", "Checking returned username");
   is(authinfo.password, "user1pass", "Checking returned password");
 });
 
 add_task(async function test_multipleExisting3() {
   // test filling in existing login (undetermined --> user2)
   // user2name/user2pass would also be valid to fill here.
-  state = {
+  const state = {
     msg: "This site is asking you to sign in.",
     title: "Authentication Required",
     textValue: "user1name",
     passValue: "user1pass",
     iconClass: "authentication-icon question-icon",
@@ -297,32 +271,32 @@
     checked: false,
     focused: "textField",
     defButton: "button0",
   };
   // enter one of the known logins, test 504+505 exercise the two possible states.
-  action = {
+  const action = {
     buttonClick: "ok",
     textField: "user2name",
     passField: "user2pass",
   };
   authinfo.username = "";
   authinfo.password = "";
   authinfo.realm    = "http://example2.com";
 
   promptDone = handlePrompt(state, action);
-  isOk = prompter2.promptAuth("channel2", level, authinfo);
+  const isOk = prompter2.promptAuth("channel2", level, authinfo);
   await promptDone;
 
   ok(isOk, "Checking dialog return value (accept)");
   is(authinfo.username, "user2name", "Checking returned username");
   is(authinfo.password, "user2pass", "Checking returned password");
 });
 
 add_task(async function test_changingMultiple() {
   // test changing a password (undetermined --> user2 w/ newpass)
   // user2name/user2pass would also be valid to fill here.
-  state = {
+  const state = {
     msg: "This site is asking you to sign in.",
     title: "Authentication Required",
     textValue: "user1name",
     passValue: "user1pass",
     iconClass: "authentication-icon question-icon",
@@ -334,32 +308,32 @@
     checked: false,
     focused: "textField",
     defButton: "button0",
   };
   // force to user2, and change the password
-  action = {
+  const action = {
     buttonClick: "ok",
     textField: "user2name",
     passField: "NEWuser2pass",
   };
   authinfo.username = "";
   authinfo.password = "";
   authinfo.realm    = "http://example2.com";
 
   promptDone = handlePrompt(state, action);
-  isOk = prompter2.promptAuth("channel2", level, authinfo);
+  const isOk = prompter2.promptAuth("channel2", level, authinfo);
   await promptDone;
 
   ok(isOk, "Checking dialog return value (accept)");
   is(authinfo.username, "user2name", "Checking returned username");
   is(authinfo.password, "NEWuser2pass", "Checking returned password");
 });
 
 add_task(async function test_changingMultiple2() {
   // test changing a password (undetermined --> user2 w/ origpass)
   // user2name/user2pass would also be valid to fill here.
-  state = {
+  const state = {
     msg: "This site is asking you to sign in.",
     title: "Authentication Required",
     textValue: "user1name",
     passValue: "user1pass",
     iconClass: "authentication-icon question-icon",
@@ -371,21 +345,21 @@
     checked: false,
     focused: "textField",
     defButton: "button0",
   };
   // force to user2, and change the password back
-  action = {
+  const action = {
     buttonClick: "ok",
     textField: "user2name",
     passField: "user2pass",
   };
   authinfo.username = "";
   authinfo.password = "";
   authinfo.realm    = "http://example2.com";
 
   promptDone = handlePrompt(state, action);
-  isOk = prompter2.promptAuth("channel2", level, authinfo);
+  const isOk = prompter2.promptAuth("channel2", level, authinfo);
   await promptDone;
 
   ok(isOk, "Checking dialog return value (accept)");
   is(authinfo.username, "user2name", "Checking returned username");
   is(authinfo.password, "user2pass", "Checking returned password");
diff --git a/toolkit/components/passwordmgr/test/mochitest/test_prompt_promptAuth_proxy.html b/toolkit/components/passwordmgr/test/mochitest/test_prompt_promptAuth_proxy.html
--- a/toolkit/components/passwordmgr/test/mochitest/test_prompt_promptAuth_proxy.html
+++ b/toolkit/components/passwordmgr/test/mochitest/test_prompt_promptAuth_proxy.html
@@ -90,11 +90,11 @@
       sendAsyncMessage("initDone");
     }
     onStopRequest(request, status) {}
   }
 
-  function initLogins(pi) {
+  async function initLogins(pi) {
     mozproxyURL = `moz-proxy://${pi.host}:${pi.port}`;
 
     let proxyLogin = Cc["@mozilla.org/login-manager/loginInfo;1"].createInstance(
       Ci.nsILoginInfo
     );
@@ -107,11 +107,11 @@
       "proxpass",
       "",
       ""
     );
 
-    Services.logins.addLogin(proxyLogin);
+    await Services.logins.addLoginAsync(proxyLogin);
   }
 
   let resolveCallback = {
     QueryInterface(iid) {
       const interfaces = [Ci.nsIProtocolProxyCallback, Ci.nsISupports];
@@ -124,12 +124,12 @@
         throw Components.Exception("", Cr.NS_ERROR_NO_INTERFACE);
       }
       return this;
     },
 
-    onProxyAvailable(req, uri, pi, status) {
-      initLogins(pi);
+    async onProxyAvailable(req, uri, pi, status) {
+      await initLogins(pi);
 
       // I'm cheating a bit here... We should probably do some magic foo to get
       // something implementing nsIProxiedProtocolHandler and then call
       // NewProxiedChannel(), so we have something that's definately a proxied
       // channel. But Mochitests use a proxy for a number of hosts, so just
diff --git a/toolkit/components/passwordmgr/test/mochitest/test_username_focus.html b/toolkit/components/passwordmgr/test/mochitest/test_username_focus.html
--- a/toolkit/components/passwordmgr/test/mochitest/test_username_focus.html
+++ b/toolkit/components/passwordmgr/test/mochitest/test_username_focus.html
@@ -10,31 +10,15 @@
   <script type="text/javascript" src="pwmgr_common.js"></script>
   <link rel="stylesheet" type="text/css" href="/tests/SimpleTest/test.css" />
 </head>
 <body>
 <script>
-let readyPromise = registerRunTests(5);
-let chromeScript = runInParent(function chromeSetup() {
-  let login1A  = Cc["@mozilla.org/login-manager/loginInfo;1"].
-                 createInstance(Ci.nsILoginInfo);
-  let login2A  = Cc["@mozilla.org/login-manager/loginInfo;1"].
-                 createInstance(Ci.nsILoginInfo);
-  let login2B  = Cc["@mozilla.org/login-manager/loginInfo;1"].
-                 createInstance(Ci.nsILoginInfo);
-
-  login1A.init("http://mochi.test:8888", "http://username-focus-1", null,
-               "testuser1A", "testpass1A", "", "");
-
-  login2A.init("http://mochi.test:8888", "http://username-focus-2", null,
-               "testuser2A", "testpass2A", "", "");
-  login2B.init("http://mochi.test:8888", "http://username-focus-2", null,
-               "testuser2B", "testpass2B", "", "");
-
-  Services.logins.addLogin(login1A);
-  Services.logins.addLogin(login2A);
-  Services.logins.addLogin(login2B);
-});
+ const readyPromise = addLoginsInParent(
+    ["http://mochi.test:8888", "http://username-focus-1", null, "testuser1A", "testpass1A", "", ""],
+    ["http://mochi.test:8888", "http://username-focus-2", null, "testuser2A", "testpass2A", "", ""],
+    ["http://mochi.test:8888", "http://username-focus-2", null, "testuser2B", "testpass2B", "", ""]
+  ).then(() => registerRunTests(5));
 </script>
 
 <p id="display"></p>
 <div id="content">
   <!-- first 3 forms have a matching user+pass login -->
@@ -109,40 +93,40 @@
   ok(readyPromise, "check promise is available");
   await readyPromise;
 });
 
 add_task(async function test_autofilled() {
-  let usernameField = getFormElementByName("-autofilled", "uname");
+  const usernameField = getFormElementByName("-autofilled", "uname");
   info("Username and password already filled so don't show autocomplete");
   await noPopupBy(() => usernameField.focus());
 
   removeFocus();
   usernameField.value = "testuser";
   info("Focus when we don't have an exact match");
   await popupBy(() => usernameField.focus());
 });
 
 add_task(async function test_autofilled_prefilled_un() {
-  let usernameField = getFormElementByName("-autofilled-prefilled-un", "uname");
+  const usernameField = getFormElementByName("-autofilled-prefilled-un", "uname");
   info("Username and password already filled so don't show autocomplete");
   await noPopupBy(() => usernameField.focus());
 
   removeFocus();
   usernameField.value = "testuser";
   info("Focus when we don't have an exact match");
   await popupBy(() => usernameField.focus());
 });
 
 add_task(async function test_autofilled_focused_dynamic() {
-  let usernameField = getFormElementByName("-autofilled-focused-dynamic", "uname");
-  let passwordField = getFormElementByName("-autofilled-focused-dynamic", "pword");
+  const usernameField = getFormElementByName("-autofilled-focused-dynamic", "uname");
+  const passwordField = getFormElementByName("-autofilled-focused-dynamic", "pword");
   info("Username and password will be filled while username focused");
   await noPopupBy(() => usernameField.focus());
   info("triggering autofill");
   await noPopupBy(() => passwordField.type = "password");
 
-  let popupState = await getPopupState();
+  const popupState = await getPopupState();
   is(popupState.open, false, "Check popup is closed");
 
   removeFocus();
   passwordField.value = "test";
   info("Focus when we don't have an exact match");
@@ -150,56 +134,56 @@
 });
 
 // Begin testing forms that have multiple saved logins
 
 add_task(async function test_multiple() {
-  let usernameField = getFormElementByName("-multiple", "uname");
+  const usernameField = getFormElementByName("-multiple", "uname");
   info("Fields not filled due to multiple so autocomplete upon focus");
   await popupBy(() => usernameField.focus());
 });
 
 add_task(async function test_multiple_dynamic() {
-  let usernameField = getFormElementByName("-multiple-dynamic", "uname");
-  let passwordField = getFormElementByName("-multiple-dynamic", "pword");
+  const usernameField = getFormElementByName("-multiple-dynamic", "uname");
+  const passwordField = getFormElementByName("-multiple-dynamic", "pword");
   info("Fields not filled but username is focused upon marking so open");
   await noPopupBy(() => usernameField.focus());
 
   info("triggering _fillForm code");
   await popupBy(() => passwordField.type = "password");
 });
 
 add_task(async function test_multiple_prefilled_un1() {
-  let usernameField = getFormElementByName("-multiple-prefilled-un1", "uname");
+  const usernameField = getFormElementByName("-multiple-prefilled-un1", "uname");
   info("Username and password already filled so don't show autocomplete");
   await noPopupBy(() => usernameField.focus());
 
   removeFocus();
   usernameField.value = "testuser";
   info("Focus when we don't have an exact match");
   await popupBy(() => usernameField.focus());
 });
 
 add_task(async function test_multiple_prefilled_un2() {
-  let usernameField = getFormElementByName("-multiple-prefilled-un2", "uname");
+  const usernameField = getFormElementByName("-multiple-prefilled-un2", "uname");
   info("Username and password already filled so don't show autocomplete");
   await noPopupBy(() => usernameField.focus());
 
   removeFocus();
   usernameField.value = "testuser";
   info("Focus when we don't have an exact match");
   await popupBy(() => usernameField.focus());
 });
 
 add_task(async function test_multiple_prefilled_focused_dynamic() {
-  let usernameField = getFormElementByName("-multiple-prefilled-focused-dynamic", "uname");
-  let passwordField = getFormElementByName("-multiple-prefilled-focused-dynamic", "pword");
+  const usernameField = getFormElementByName("-multiple-prefilled-focused-dynamic", "uname");
+  const passwordField = getFormElementByName("-multiple-prefilled-focused-dynamic", "pword");
   info("Username and password will be filled while username focused");
   await noPopupBy(() => usernameField.focus());
   info("triggering autofill");
   await noPopupBy(() => passwordField.type = "password");
 
-  let popupState = await getPopupState();
+  const popupState = await getPopupState();
   is(popupState.open, false, "Check popup is closed");
 
   removeFocus();
   passwordField.value = "test";
   info("Focus when we don't have an exact match");
diff --git a/toolkit/components/passwordmgr/test/mochitest/test_xhr.html b/toolkit/components/passwordmgr/test/mochitest/test_xhr.html
--- a/toolkit/components/passwordmgr/test/mochitest/test_xhr.html
+++ b/toolkit/components/passwordmgr/test/mochitest/test_xhr.html
@@ -60,26 +60,15 @@
   });
 });
 
 let prompter1 = new PrompterProxy(prompterParent);
 
-add_task(function setup() {
-  runInParent(function initLogins() {
-    let nsLoginInfo = Components.Constructor("@mozilla.org/login-manager/loginInfo;1",
-                                             Ci.nsILoginInfo, "init");
-    let login1 = new nsLoginInfo("http://mochi.test:8888", null, "xhr",
-                                 "xhruser1", "xhrpass1");
-    let login2 = new nsLoginInfo("http://mochi.test:8888", null, "xhr2",
-                                 "xhruser2", "xhrpass2");
-
-    try {
-      Services.logins.addLogin(login1);
-      Services.logins.addLogin(login2);
-    } catch (e) {
-      assert.ok(false, "addLogin threw: " + e);
-    }
-  });
+add_setup(async () => {
+  await addLoginsInParent(
+    ["http://mochi.test:8888", null, "xhr", "xhruser1", "xhrpass1"],
+    ["http://mochi.test:8888", null, "xhr2", "xhruser2", "xhrpass2"]
+  );
 });
 
 add_task(async function test1() {
   let state = {
     msg: "This site is asking you to sign in.",
diff --git a/toolkit/components/passwordmgr/test/unit/test_LoginManagerPrompter_getUsernameSuggestions.js b/toolkit/components/passwordmgr/test/unit/test_LoginManagerPrompter_getUsernameSuggestions.js
--- a/toolkit/components/passwordmgr/test/unit/test_LoginManagerPrompter_getUsernameSuggestions.js
+++ b/toolkit/components/passwordmgr/test/unit/test_LoginManagerPrompter_getUsernameSuggestions.js
@@ -1,6 +1,6 @@
-let { LoginManagerPrompter } = ChromeUtils.importESModule(
+const { LoginManagerPrompter } = ChromeUtils.importESModule(
   "resource://gre/modules/LoginManagerPrompter.sys.mjs"
 );
 
 const TEST_CASES = [
   {
@@ -108,44 +108,43 @@
   registerCleanupFunction(() => {
     Services.prefs.clearUserPref("signon.capture.inputChanges.enabled");
   });
 }
 
-function _saveLogins(logins) {
-  logins
-    .map(loginData => {
-      let login;
-      if (loginData.isAuth) {
-        login = TestData.authLogin({
-          origin: loginData.origin ?? "https://example.com",
-          httpRealm: "example-realm",
-          username: loginData.username,
-          password: loginData.password,
-        });
-      } else {
-        login = TestData.formLogin({
-          origin: loginData.origin ?? "https://example.com",
-          formActionOrigin: "https://example.com",
-          username: loginData.username,
-          password: loginData.password,
-        });
-      }
-      return login;
-    })
-    .forEach(login => Services.logins.addLogin(login));
+async function _saveLogins(loginDatas) {
+  const logins = loginDatas.map(loginData => {
+    let login;
+    if (loginData.isAuth) {
+      login = TestData.authLogin({
+        origin: loginData.origin ?? "https://example.com",
+        httpRealm: "example-realm",
+        username: loginData.username,
+        password: loginData.password,
+      });
+    } else {
+      login = TestData.formLogin({
+        origin: loginData.origin ?? "https://example.com",
+        formActionOrigin: "https://example.com",
+        username: loginData.username,
+        password: loginData.password,
+      });
+    }
+    return login;
+  });
+  await Services.logins.addLogins(logins);
 }
 
 function _compare(expectedArr, actualArr) {
   Assert.ok(!!expectedArr, "Expect expectedArr to be truthy");
   Assert.ok(!!actualArr, "Expect actualArr to be truthy");
   Assert.ok(
     expectedArr.length == actualArr.length,
     "Expect expectedArr and actualArr to be the same length"
   );
   for (let i = 0; i < expectedArr.length; i++) {
-    let expected = expectedArr[i];
-    let actual = actualArr[i];
+    const expected = expectedArr[i];
+    const actual = actualArr[i];
 
     Assert.ok(
       expected.text == actual.text,
       `Expect element #${i} text to match.  Expected: '${expected.text}', Actual '${actual.text}'`
     );
@@ -157,19 +156,19 @@
 }
 
 async function _test(testCase) {
   info(`Starting test case: ${testCase.description}`);
   info(`Storing saved logins: ${JSON.stringify(testCase.savedLogins)}`);
-  _saveLogins(testCase.savedLogins);
+  await _saveLogins(testCase.savedLogins);
 
   if (!testCase.isLoggedIn) {
     // Primary Password should be enabled and locked
     LoginTestUtils.primaryPassword.enable();
   }
 
   info("Computing results");
-  let result = await LoginManagerPrompter._getUsernameSuggestions(
+  const result = await LoginManagerPrompter._getUsernameSuggestions(
     LOGIN,
     testCase.possibleUsernames
   );
 
   _compare(testCase.expectedSuggestions, result);
@@ -181,9 +180,9 @@
   LoginTestUtils.clearData();
 }
 
 add_task(async function test_LoginManagerPrompter_getUsernameSuggestions() {
   _setPrefs();
-  for (let tc of TEST_CASES) {
+  for (const tc of TEST_CASES) {
     await _test(tc);
   }
 });
diff --git a/toolkit/components/passwordmgr/test/unit/test_context_menu.js b/toolkit/components/passwordmgr/test/unit/test_context_menu.js
--- a/toolkit/components/passwordmgr/test/unit/test_context_menu.js
+++ b/toolkit/components/passwordmgr/test/unit/test_context_menu.js
@@ -250,13 +250,11 @@
  * Tests if the LoginManagerContextMenu returns the correct login items.
  */
 async function runTestcase({ formOrigin, savedLogins, expectedItems }) {
   const DOCUMENT_CONTENT = "<form><input id='pw' type=password></form>";
 
-  for (let login of savedLogins) {
-    Services.logins.addLogin(login);
-  }
+  await Services.logins.addLogins(savedLogins);
 
   // Create the logins menuitems fragment.
   let { fragment, document } = createLoginsFragment(
     formOrigin,
     DOCUMENT_CONTENT
diff --git a/toolkit/components/passwordmgr/test/unit/test_legacy_empty_formActionOrigin.js b/toolkit/components/passwordmgr/test/unit/test_legacy_empty_formActionOrigin.js
--- a/toolkit/components/passwordmgr/test/unit/test_legacy_empty_formActionOrigin.js
+++ b/toolkit/components/passwordmgr/test/unit/test_legacy_empty_formActionOrigin.js
@@ -39,28 +39,31 @@
 
 /**
  * Adds a login with an empty formActionOrigin, then it verifies that no other
  * form logins can be added for the same host.
  */
-add_task(function test_addLogin_wildcard() {
+add_task(async function test_addLogin_wildcard() {
   let loginInfo = TestData.formLogin({
     origin: "http://any.example.com",
     formActionOrigin: "",
   });
-  Services.logins.addLogin(loginInfo);
+  await Services.logins.addLoginAsync(loginInfo);
 
   // Normal form logins cannot be added anymore.
   loginInfo = TestData.formLogin({ origin: "http://any.example.com" });
-  Assert.throws(() => Services.logins.addLogin(loginInfo), /already exists/);
+  await Assert.rejects(
+    Services.logins.addLoginAsync(loginInfo),
+    /already exists/
+  );
 
   // Authentication logins can still be added.
   loginInfo = TestData.authLogin({ origin: "http://any.example.com" });
-  Services.logins.addLogin(loginInfo);
+  await Services.logins.addLoginAsync(loginInfo);
 
   // Form logins can be added for other hosts.
   loginInfo = TestData.formLogin({ origin: "http://other.example.com" });
-  Services.logins.addLogin(loginInfo);
+  await Services.logins.addLoginAsync(loginInfo);
 });
 
 /**
  * Verifies that findLogins, searchLogins, and countLogins include all logins
  * that have an empty formActionOrigin in the store, even when a formActionOrigin is
diff --git a/toolkit/components/passwordmgr/test/unit/test_legacy_validation.js b/toolkit/components/passwordmgr/test/unit/test_legacy_validation.js
--- a/toolkit/components/passwordmgr/test/unit/test_legacy_validation.js
+++ b/toolkit/components/passwordmgr/test/unit/test_legacy_validation.js
@@ -14,67 +14,67 @@
 // Tests
 
 /**
  * Tests legacy validation with addLogin.
  */
-add_task(function test_addLogin_invalid_characters_legacy() {
+add_task(async function test_addLogin_invalid_characters_legacy() {
   // Test newlines and carriage returns in properties that contain URLs.
   for (let testValue of [
     "http://newline\n.example.com",
     "http://carriagereturn.example.com\r",
   ]) {
     let loginInfo = TestData.formLogin({ origin: testValue });
-    Assert.throws(
-      () => Services.logins.addLogin(loginInfo),
+    await Assert.rejects(
+      Services.logins.addLoginAsync(loginInfo),
       /login values can't contain newlines/
     );
 
     loginInfo = TestData.formLogin({ formActionOrigin: testValue });
-    Assert.throws(
-      () => Services.logins.addLogin(loginInfo),
+    await Assert.rejects(
+      Services.logins.addLoginAsync(loginInfo),
       /login values can't contain newlines/
     );
 
     loginInfo = TestData.authLogin({ httpRealm: testValue });
-    Assert.throws(
-      () => Services.logins.addLogin(loginInfo),
+    await Assert.rejects(
+      Services.logins.addLoginAsync(loginInfo),
       /login values can't contain newlines/
     );
   }
 
   // Test newlines and carriage returns in form field names.
   for (let testValue of ["newline_field\n", "carriagereturn\r_field"]) {
     let loginInfo = TestData.formLogin({ usernameField: testValue });
-    Assert.throws(
-      () => Services.logins.addLogin(loginInfo),
+    await Assert.rejects(
+      Services.logins.addLoginAsync(loginInfo),
       /login values can't contain newlines/
     );
 
     loginInfo = TestData.formLogin({ passwordField: testValue });
-    Assert.throws(
-      () => Services.logins.addLogin(loginInfo),
+    await Assert.rejects(
+      Services.logins.addLoginAsync(loginInfo),
       /login values can't contain newlines/
     );
   }
 
   // Test a single dot as the value of usernameField and formActionOrigin.
   let loginInfo = TestData.formLogin({ usernameField: "." });
-  Assert.throws(
-    () => Services.logins.addLogin(loginInfo),
+  await Assert.rejects(
+    Services.logins.addLoginAsync(loginInfo),
     /login values can't be periods/
   );
 
   loginInfo = TestData.formLogin({ formActionOrigin: "." });
-  Assert.throws(
-    () => Services.logins.addLogin(loginInfo),
+  await Assert.rejects(
+    Services.logins.addLoginAsync(loginInfo),
     /login values can't be periods/
   );
 
   // Test the sequence " (" inside the value of the "origin" property.
   loginInfo = TestData.formLogin({ origin: "http://parens (.example.com" });
-  Assert.throws(
-    () => Services.logins.addLogin(loginInfo),
+  await Assert.rejects(
+    Services.logins.addLoginAsync(loginInfo),
     /bad parens in origin/
   );
 });
 
 /**
diff --git a/toolkit/components/passwordmgr/test/unit/test_logins_change.js b/toolkit/components/passwordmgr/test/unit/test_logins_change.js
--- a/toolkit/components/passwordmgr/test/unit/test_logins_change.js
+++ b/toolkit/components/passwordmgr/test/unit/test_logins_change.js
@@ -21,18 +21,21 @@
  *        nsILoginInfo corresponding to an invalid login.
  * @param aExpectedError
  *        This argument is passed to the "Assert.throws" test to determine which
  *        error is expected from the modification functions.
  */
-function checkLoginInvalid(aLoginInfo, aExpectedError) {
+async function checkLoginInvalid(aLoginInfo, aExpectedError) {
   // Try to add the new login, and verify that no data is stored.
-  Assert.throws(() => Services.logins.addLogin(aLoginInfo), aExpectedError);
+  await Assert.rejects(
+    Services.logins.addLoginAsync(aLoginInfo),
+    aExpectedError
+  );
   LoginTestUtils.checkLogins([]);
 
   // Add a login for the modification tests.
   let testLogin = TestData.formLogin({ origin: "http://modify.example.com" });
-  Services.logins.addLogin(testLogin);
+  await Services.logins.addLoginAsync(testLogin);
 
   // Try to modify the existing login using nsILoginInfo and nsIPropertyBag.
   Assert.throws(
     () => Services.logins.modifyLogin(testLogin, aLoginInfo),
     aExpectedError
@@ -85,20 +88,21 @@
 // Tests
 
 /**
  * Tests that adding logins to the database works.
  */
-add_task(function test_addLogin_removeLogin() {
+add_task(async function test_addLogin_removeLogin() {
   // Each login from the test data should be valid and added to the list.
-  for (let loginInfo of TestData.loginList()) {
-    Services.logins.addLogin(loginInfo);
-  }
+  await Services.logins.addLogins(TestData.loginList());
   LoginTestUtils.checkLogins(TestData.loginList());
 
   // Trying to add each login again should result in an error.
   for (let loginInfo of TestData.loginList()) {
-    Assert.throws(() => Services.logins.addLogin(loginInfo), /already exists/);
+    await Assert.rejects(
+      Services.logins.addLoginAsync(loginInfo),
+      /This login already exists./
+    );
   }
 
   // Removing each login should succeed.
   for (let loginInfo of TestData.loginList()) {
     Services.logins.removeLogin(loginInfo);
@@ -181,77 +185,83 @@
  * be strictly equal to null, and the other must not be null or an empty string.
  *
  * The legacy case of an empty string in formActionOrigin and a null value in
  * httpRealm is also supported for storage at the moment.
  */
-add_task(function test_invalid_httpRealm_formActionOrigin() {
+add_task(async function test_invalid_httpRealm_formActionOrigin() {
   // httpRealm === null, formActionOrigin === null
-  checkLoginInvalid(
+  await checkLoginInvalid(
     TestData.formLogin({ formActionOrigin: null }),
     /without a httpRealm or formActionOrigin/
   );
 
   // httpRealm === "", formActionOrigin === null
-  checkLoginInvalid(
+  await checkLoginInvalid(
     TestData.authLogin({ httpRealm: "" }),
     /without a httpRealm or formActionOrigin/
   );
 
   // httpRealm === null, formActionOrigin === ""
   // TODO: This is not enforced for now.
-  // checkLoginInvalid(TestData.formLogin({ formActionOrigin: "" }),
+  // await checkLoginInvalid(TestData.formLogin({ formActionOrigin: "" }),
   //                   /without a httpRealm or formActionOrigin/);
 
   // httpRealm === "", formActionOrigin === ""
   let login = TestData.formLogin({ formActionOrigin: "" });
   login.httpRealm = "";
-  checkLoginInvalid(login, /both a httpRealm and formActionOrigin/);
+  await checkLoginInvalid(login, /both a httpRealm and formActionOrigin/);
 
   // !!httpRealm, !!formActionOrigin
   login = TestData.formLogin();
   login.httpRealm = "The HTTP Realm";
-  checkLoginInvalid(login, /both a httpRealm and formActionOrigin/);
+  await checkLoginInvalid(login, /both a httpRealm and formActionOrigin/);
 
   // httpRealm === "", !!formActionOrigin
   login = TestData.formLogin();
   login.httpRealm = "";
-  checkLoginInvalid(login, /both a httpRealm and formActionOrigin/);
+  await checkLoginInvalid(login, /both a httpRealm and formActionOrigin/);
 
   // !!httpRealm, formActionOrigin === ""
   login = TestData.authLogin();
   login.formActionOrigin = "";
-  checkLoginInvalid(login, /both a httpRealm and formActionOrigin/);
+  await checkLoginInvalid(login, /both a httpRealm and formActionOrigin/);
 });
 
 /**
  * Tests null or empty values in required login properties.
  */
-add_task(function test_missing_properties() {
-  checkLoginInvalid(
+add_task(async function test_missing_properties() {
+  await checkLoginInvalid(
     TestData.formLogin({ origin: null }),
     /null or empty origin/
   );
 
-  checkLoginInvalid(TestData.formLogin({ origin: "" }), /null or empty origin/);
+  await checkLoginInvalid(
+    TestData.formLogin({ origin: "" }),
+    /null or empty origin/
+  );
 
-  checkLoginInvalid(TestData.formLogin({ username: null }), /null username/);
+  await checkLoginInvalid(
+    TestData.formLogin({ username: null }),
+    /null username/
+  );
 
-  checkLoginInvalid(
+  await checkLoginInvalid(
     TestData.formLogin({ password: null }),
     /null or empty password/
   );
 
-  checkLoginInvalid(
+  await checkLoginInvalid(
     TestData.formLogin({ password: "" }),
     /null or empty password/
   );
 });
 
 /**
  * Tests invalid NUL characters in nsILoginInfo properties.
  */
-add_task(function test_invalid_characters() {
+add_task(async function test_invalid_characters() {
   let loginList = [
     TestData.authLogin({ origin: "http://null\0X.example.com" }),
     TestData.authLogin({ httpRealm: "realm\0" }),
     TestData.formLogin({ formActionOrigin: "http://null\0X.example.com" }),
     TestData.formLogin({ usernameField: "field\0_null" }),
@@ -259,11 +269,11 @@
     TestData.formLogin({ passwordField: "field\0_null" }),
     TestData.formLogin({ username: "user\0name" }),
     TestData.formLogin({ password: "pass\0word" }),
   ];
   for (let loginInfo of loginList) {
-    checkLoginInvalid(loginInfo, /login values can't contain nulls/);
+    await checkLoginInvalid(loginInfo, /login values can't contain nulls/);
   }
 });
 
 /**
  * Tests removing a login that does not exists.
@@ -276,25 +286,24 @@
 });
 
 /**
  * Tests removing all logins at once.
  */
-add_task(function test_removeAllUserFacingLogins() {
-  for (let loginInfo of TestData.loginList()) {
-    Services.logins.addLogin(loginInfo);
-  }
+add_task(async function test_removeAllUserFacingLogins() {
+  await Services.logins.addLogins(TestData.loginList());
+
   Services.logins.removeAllUserFacingLogins();
   LoginTestUtils.checkLogins([]);
 
   // The function should also work when there are no logins to delete.
   Services.logins.removeAllUserFacingLogins();
 });
 
 /**
  * Tests the modifyLogin function with an nsILoginInfo argument.
  */
-add_task(function test_modifyLogin_nsILoginInfo() {
+add_task(async function test_modifyLogin_nsILoginInfo() {
   let loginInfo = TestData.formLogin();
   let updatedLoginInfo = TestData.formLogin({
     username: "new username",
     password: "new password",
     usernameField: "new_form_field_username",
@@ -307,11 +316,11 @@
     () => Services.logins.modifyLogin(loginInfo, updatedLoginInfo),
     /No matching logins/
   );
 
   // Add the first form login, then modify it to match the second.
-  Services.logins.addLogin(loginInfo);
+  await Services.logins.addLoginAsync(loginInfo);
   Services.logins.modifyLogin(loginInfo, updatedLoginInfo);
 
   // The data should now match the second login.
   LoginTestUtils.checkLogins([updatedLoginInfo]);
   Assert.throws(
@@ -322,11 +331,11 @@
   // The login can be changed to have a different type and origin.
   Services.logins.modifyLogin(updatedLoginInfo, differentLoginInfo);
   LoginTestUtils.checkLogins([differentLoginInfo]);
 
   // It is now possible to add a login with the old type and origin.
-  Services.logins.addLogin(loginInfo);
+  await Services.logins.addLoginAsync(loginInfo);
   LoginTestUtils.checkLogins([loginInfo, differentLoginInfo]);
 
   // Modifying a login to match an existing one should not be possible.
   Assert.throws(
     () => Services.logins.modifyLogin(loginInfo, differentLoginInfo),
@@ -338,11 +347,11 @@
 });
 
 /**
  * Tests the modifyLogin function with an nsIPropertyBag argument.
  */
-add_task(function test_modifyLogin_nsIProperyBag() {
+add_task(async function test_modifyLogin_nsIProperyBag() {
   let loginInfo = TestData.formLogin();
   let updatedLoginInfo = TestData.formLogin({
     username: "new username",
     password: "new password",
     usernameField: "",
@@ -365,11 +374,11 @@
     /No matching logins/
   );
 
   // Add the first form login, then modify it to match the second, changing
   // only some of its properties and checking the behavior with an empty string.
-  Services.logins.addLogin(loginInfo);
+  await Services.logins.addLoginAsync(loginInfo);
   Services.logins.modifyLogin(
     loginInfo,
     newPropertyBag({
       username: "new username",
       password: "new password",
@@ -403,11 +412,11 @@
   // The login can be changed to have a different type and origin.
   Services.logins.modifyLogin(updatedLoginInfo, differentLoginProperties);
   LoginTestUtils.checkLogins([differentLoginInfo]);
 
   // It is now possible to add a login with the old type and origin.
-  Services.logins.addLogin(loginInfo);
+  await Services.logins.addLoginAsync(loginInfo);
   LoginTestUtils.checkLogins([loginInfo, differentLoginInfo]);
 
   // Modifying a login to match an existing one should not be possible.
   Assert.throws(
     () => Services.logins.modifyLogin(loginInfo, differentLoginProperties),
@@ -507,11 +516,11 @@
 });
 
 /**
  * Tests handling when adding a login with bad date values
  */
-add_task(function test_addLogin_badDates() {
+add_task(async function test_addLogin_badDates() {
   LoginTestUtils.clearData();
 
   let now = Date.now();
   let defaultLoginDates = {
     timeCreated: now,
@@ -522,11 +531,11 @@
   let defaultsLogin = TestData.formLogin();
   for (let pname of ["timeCreated", "timeLastUsed", "timePasswordChanged"]) {
     Assert.ok(!defaultsLogin[pname]);
   }
   Assert.ok(
-    !!Services.logins.addLogin(defaultsLogin),
+    !!(await Services.logins.addLoginAsync(defaultsLogin)),
     "Sanity check adding defaults formLogin"
   );
   Services.logins.removeAllUserFacingLogins();
 
   // 0 is a valid date in this context - new nsLoginInfo timestamps init to 0
@@ -535,11 +544,11 @@
       Object.assign({}, defaultLoginDates, {
         [pname]: 0,
       })
     );
     Assert.ok(
-      !!Services.logins.addLogin(loginInfo),
+      !!(await Services.logins.addLoginAsync(loginInfo)),
       "Check 0 value for " + pname
     );
     Services.logins.removeAllUserFacingLogins();
   }
 
@@ -549,11 +558,11 @@
       Object.assign({}, defaultLoginDates, {
         [pname]: -1,
       })
     );
     Assert.ok(
-      !!Services.logins.addLogin(loginInfo),
+      !!(await Services.logins.addLoginAsync(loginInfo)),
       "Check -1 value for " + pname
     );
     Services.logins.removeAllUserFacingLogins();
   }
 
@@ -562,12 +571,12 @@
     let loginInfo = TestData.formLogin(
       Object.assign({}, defaultLoginDates, {
         [pname]: MAX_DATE_MS + 1,
       })
     );
-    Assert.throws(
-      () => Services.logins.addLogin(loginInfo),
+    await Assert.rejects(
+      Services.logins.addLoginAsync(loginInfo),
       /invalid date properties/
     );
     Assert.equal(Services.logins.getAllLogins().length, 0);
   }
 
@@ -581,35 +590,37 @@
   LoginTestUtils.clearData();
 
   let defaultsLogin = TestData.formLogin({
     username: "defaults",
   });
+  await Services.logins.addLoginAsync(defaultsLogin);
 
   // -11644473600000 is the value you get if you convert Dec 31 1600 16:07:02 to unix epoch time
   let timeCreatedLogin = TestData.formLogin({
     username: "tc",
     timeCreated: -11644473600000,
   });
+  await Assert.rejects(
+    Services.logins.addLoginAsync(timeCreatedLogin),
+    /Can\'t add a login with invalid date properties./
+  );
 
   let timeLastUsedLogin = TestData.formLogin({
     username: "tlu",
     timeLastUsed: -11644473600000,
   });
+  await Assert.rejects(
+    Services.logins.addLoginAsync(timeLastUsedLogin),
+    /Can\'t add a login with invalid date properties./
+  );
 
   let timePasswordChangedLogin = TestData.formLogin({
     username: "tpc",
     timePasswordChanged: -11644473600000,
   });
-
-  await Services.logins.addLogins([
-    defaultsLogin,
-    timeCreatedLogin,
-    timeLastUsedLogin,
-    timePasswordChangedLogin,
-  ]);
-
-  // none of the logins with invalid dates should have been added
-  let savedLogins = Services.logins.getAllLogins();
-  Assert.equal(savedLogins.length, 1);
+  await Assert.rejects(
+    Services.logins.addLoginAsync(timePasswordChangedLogin),
+    /Can\'t add a login with invalid date properties./
+  );
 
   Services.logins.removeAllUserFacingLogins();
 });
diff --git a/toolkit/components/passwordmgr/test/unit/test_logins_decrypt_failure.js b/toolkit/components/passwordmgr/test/unit/test_logins_decrypt_failure.js
--- a/toolkit/components/passwordmgr/test/unit/test_logins_decrypt_failure.js
+++ b/toolkit/components/passwordmgr/test/unit/test_logins_decrypt_failure.js
@@ -26,13 +26,11 @@
 /**
  * Resets the primary password after some logins were added to the database.
  */
 add_task(async function test_logins_decrypt_failure() {
   let logins = TestData.loginList();
-  for (let loginInfo of logins) {
-    Services.logins.addLogin(loginInfo);
-  }
+  await Services.logins.addLogins(logins);
 
   // This makes the existing logins non-decryptable.
   resetPrimaryPassword();
 
   // These functions don't see the non-decryptable entries anymore.
@@ -55,13 +53,11 @@
 
   // The function that counts logins sees the non-decryptable entries also.
   Assert.equal(Services.logins.countLogins("", "", ""), logins.length);
 
   // Equivalent logins can be added.
-  for (let loginInfo of logins) {
-    Services.logins.addLogin(loginInfo);
-  }
+  await Services.logins.addLogins(logins);
   LoginTestUtils.checkLogins(logins);
   Assert.equal(
     (await Services.logins.getAllLoginsAsync()).length,
     logins.length,
     "getAllLoginsAsync length"
@@ -90,11 +86,11 @@
 });
 
 // Bug 621846 - If a login has a GUID but can't be decrypted, a search for
 // that GUID will (correctly) fail. Ensure we can add a new login with that
 // same GUID.
-add_task(function test_add_logins_with_decrypt_failure() {
+add_task(async function test_add_logins_with_decrypt_failure() {
   // a login with a GUID.
   let login = new LoginInfo(
     "http://www.example2.com",
     "http://www.example2.com",
     null,
@@ -118,39 +114,39 @@
     "form_field_password"
   );
   loginDupeGuid.QueryInterface(Ci.nsILoginMetaInfo);
   loginDupeGuid.guid = login.guid;
 
-  Services.logins.addLogin(login);
+  await Services.logins.addLoginAsync(login);
 
   // We can search for this login by GUID.
   let searchProp = Cc["@mozilla.org/hash-property-bag;1"].createInstance(
     Ci.nsIWritablePropertyBag2
   );
   searchProp.setPropertyAsAUTF8String("guid", login.guid);
 
   equal(Services.logins.searchLogins(searchProp).length, 1);
 
   // We should fail to re-add it as it remains good.
-  Assert.throws(
-    () => Services.logins.addLogin(login),
+  await Assert.rejects(
+    Services.logins.addLoginAsync(login),
     /This login already exists./
   );
   // We should fail to re-add a different login with the same GUID.
-  Assert.throws(
-    () => Services.logins.addLogin(loginDupeGuid),
+  await Assert.rejects(
+    Services.logins.addLoginAsync(loginDupeGuid),
     /specified GUID already exists/
   );
 
   // This makes the existing login non-decryptable.
   resetPrimaryPassword();
 
   // We can no longer find it in our search.
   equal(Services.logins.searchLogins(searchProp).length, 0);
 
   // So we should be able to re-add a login with that same GUID.
-  Services.logins.addLogin(login);
+  await Services.logins.addLoginAsync(login);
   equal(Services.logins.searchLogins(searchProp).length, 1);
 
   Services.logins.removeAllUserFacingLogins();
 });
 
diff --git a/toolkit/components/passwordmgr/test/unit/test_logins_metainfo.js b/toolkit/components/passwordmgr/test/unit/test_logins_metainfo.js
--- a/toolkit/components/passwordmgr/test/unit/test_logins_metainfo.js
+++ b/toolkit/components/passwordmgr/test/unit/test_logins_metainfo.js
@@ -80,13 +80,13 @@
 
 /**
  * Tests the behavior of addLogin with regard to metadata.  The logins added
  * here are also used by the following tests.
  */
-add_task(function test_addLogin_metainfo() {
+add_task(async function test_addLogin_metainfo() {
   // Add a login without metadata to the database.
-  Services.logins.addLogin(gLoginInfo1);
+  await Services.logins.addLoginAsync(gLoginInfo1);
 
   // The object provided to addLogin should not have been modified.
   Assert.equal(gLoginInfo1.guid, null);
   Assert.equal(gLoginInfo1.timeCreated, 0);
   Assert.equal(gLoginInfo1.timeLastUsed, 0);
@@ -102,35 +102,35 @@
   Assert.equal(gLoginMetaInfo1.timePasswordChanged, creationTime);
   Assert.equal(gLoginMetaInfo1.timesUsed, 1);
 
   // Add a login without metadata to the database.
   let originalLogin = gLoginInfo2.clone().QueryInterface(Ci.nsILoginMetaInfo);
-  Services.logins.addLogin(gLoginInfo2);
+  await Services.logins.addLoginAsync(gLoginInfo2);
 
   // The object provided to addLogin should not have been modified.
   assertMetaInfoEqual(gLoginInfo2, originalLogin);
 
   // A login with the provided metadata should have been stored.
   gLoginMetaInfo2 = retrieveLoginMatching(gLoginInfo2);
   assertMetaInfoEqual(gLoginMetaInfo2, gLoginInfo2);
 
   // Add an authentication login to the database before continuing.
-  Services.logins.addLogin(gLoginInfo3);
+  await Services.logins.addLoginAsync(gLoginInfo3);
   gLoginMetaInfo3 = retrieveLoginMatching(gLoginInfo3);
   LoginTestUtils.checkLogins([gLoginInfo1, gLoginInfo2, gLoginInfo3]);
 });
 
 /**
  * Tests that adding a login with a duplicate GUID throws an exception.
  */
-add_task(function test_addLogin_metainfo_duplicate() {
+add_task(async function test_addLogin_metainfo_duplicate() {
   let loginInfo = TestData.formLogin({
     origin: "http://duplicate.example.com",
     guid: gLoginMetaInfo2.guid,
   });
-  Assert.throws(
-    () => Services.logins.addLogin(loginInfo),
+  await Assert.rejects(
+    Services.logins.addLoginAsync(loginInfo),
     /specified GUID already exists/
   );
 
   // Verify that no data was stored by the previous call.
   LoginTestUtils.checkLogins([gLoginInfo1, gLoginInfo2, gLoginInfo3]);
diff --git a/toolkit/components/passwordmgr/test/unit/test_logins_search.js b/toolkit/components/passwordmgr/test/unit/test_logins_search.js
--- a/toolkit/components/passwordmgr/test/unit/test_logins_search.js
+++ b/toolkit/components/passwordmgr/test/unit/test_logins_search.js
@@ -88,14 +88,12 @@
 // Tests
 
 /**
  * Prepare data for the following tests.
  */
-add_task(function test_initialize() {
-  for (let login of TestData.loginList()) {
-    Services.logins.addLogin(login);
-  }
+add_setup(async () => {
+  await Services.logins.addLogins(TestData.loginList());
 });
 
 /**
  * Tests findLogins, searchLogins, and countLogins with basic queries.
  */
diff --git a/toolkit/components/passwordmgr/test/unit/test_module_LoginCSVImport.js b/toolkit/components/passwordmgr/test/unit/test_module_LoginCSVImport.js
--- a/toolkit/components/passwordmgr/test/unit/test_module_LoginCSVImport.js
+++ b/toolkit/components/passwordmgr/test/unit/test_module_LoginCSVImport.js
@@ -249,13 +249,11 @@
  */
 add_task(async function test_import_from_firefox_various_latest() {
   await setupCsv([]);
   info("Populate the login list for export");
   let logins = LoginTestUtils.testData.loginList();
-  for (let loginInfo of logins) {
-    Services.logins.addLogin(loginInfo);
-  }
+  await Services.logins.addLogins(logins);
 
   let tmpFilePath = FileTestUtils.getTempFile("logins.csv").path;
   await LoginExport.exportAsCSV(tmpFilePath);
 
   await LoginCSVImport.importFromCSV(tmpFilePath);
diff --git a/toolkit/components/passwordmgr/test/unit/test_notifications.js b/toolkit/components/passwordmgr/test/unit/test_notifications.js
--- a/toolkit/components/passwordmgr/test/unit/test_notifications.js
+++ b/toolkit/components/passwordmgr/test/unit/test_notifications.js
@@ -49,11 +49,11 @@
     expectedNotification = null; // ensure a duplicate is flagged as unexpected.
     expectedData = null;
   },
 };
 
-add_task(function test_notifications() {
+add_task(async function test_notifications() {
   let testnum = 0;
   let testdesc = "Setup of nsLoginInfo test-users";
 
   try {
     let testuser1 = new LoginInfo(
@@ -86,11 +86,11 @@
     testnum++;
     testdesc = "addLogin";
 
     expectedNotification = "addLogin";
     expectedData = testuser1;
-    Services.logins.addLogin(testuser1);
+    await Services.logins.addLoginAsync(testuser1);
     LoginTestUtils.checkLogins([testuser1]);
     Assert.equal(expectedNotification, null); // check that observer got a notification
 
     /* ========== 3 ========== */
     testnum++;
@@ -126,11 +126,11 @@
     testnum++;
     testdesc = "removeAllLogins (again)";
 
     expectedNotification = "addLogin";
     expectedData = testuser1;
-    Services.logins.addLogin(testuser1);
+    await Services.logins.addLoginAsync(testuser1);
 
     expectedNotification = "removeAllLogins";
     expectedData = null;
     Services.logins.removeAllLogins();
     Assert.equal(expectedNotification, null);
diff --git a/toolkit/components/passwordmgr/test/unit/test_search_schemeUpgrades.js b/toolkit/components/passwordmgr/test/unit/test_search_schemeUpgrades.js
--- a/toolkit/components/passwordmgr/test/unit/test_search_schemeUpgrades.js
+++ b/toolkit/components/passwordmgr/test/unit/test_search_schemeUpgrades.js
@@ -53,14 +53,12 @@
 }
 
 /**
  * Prepare data for the following tests.
  */
-add_task(function test_initialize() {
-  for (let login of TestData.loginList()) {
-    Services.logins.addLogin(login);
-  }
+add_setup(async () => {
+  await Services.logins.addLogins(TestData.loginList());
 });
 
 /**
  * Tests searchLogins with the `schemeUpgrades` property
  */
diff --git a/toolkit/components/passwordmgr/test/unit/test_storage.js b/toolkit/components/passwordmgr/test/unit/test_storage.js
--- a/toolkit/components/passwordmgr/test/unit/test_storage.js
+++ b/toolkit/components/passwordmgr/test/unit/test_storage.js
@@ -32,18 +32,18 @@
     username: String.fromCharCode(533, 537, 7570, 345),
     password: String.fromCharCode(421, 259, 349, 537),
     usernameField: "field_" + String.fromCharCode(533, 537, 7570, 345),
     passwordField: "field_" + String.fromCharCode(421, 259, 349, 537),
   });
-  Services.logins.addLogin(loginInfo);
+  await Services.logins.addLoginAsync(loginInfo);
   await reloadAndCheckLoginsGen([loginInfo]);
 
   // Store the string "test" using similarly looking glyphs.
   loginInfo = TestData.authLogin({
     httpRealm: String.fromCharCode(355, 277, 349, 357),
   });
-  Services.logins.addLogin(loginInfo);
+  await Services.logins.addLoginAsync(loginInfo);
   await reloadAndCheckLoginsGen([loginInfo]);
 });
 
 /**
  * Tests addLogin with newline characters in the username and password.
@@ -51,26 +51,26 @@
 add_task(async function test_storage_addLogin_newlines() {
   let loginInfo = TestData.formLogin({
     username: "user\r\nname",
     password: "password\r\n",
   });
-  Services.logins.addLogin(loginInfo);
+  await Services.logins.addLoginAsync(loginInfo);
   await reloadAndCheckLoginsGen([loginInfo]);
 });
 
 /**
  * Tests addLogin with a single dot in fields where it is allowed.
  *
  * These tests exist to verify the legacy "signons.txt" storage format.
  */
 add_task(async function test_storage_addLogin_dot() {
   let loginInfo = TestData.formLogin({ origin: ".", passwordField: "." });
-  Services.logins.addLogin(loginInfo);
+  await Services.logins.addLoginAsync(loginInfo);
   await reloadAndCheckLoginsGen([loginInfo]);
 
   loginInfo = TestData.authLogin({ httpRealm: "." });
-  Services.logins.addLogin(loginInfo);
+  await Services.logins.addLoginAsync(loginInfo);
   await reloadAndCheckLoginsGen([loginInfo]);
 });
 
 /**
  * Tests addLogin with parentheses in origins.
@@ -86,10 +86,8 @@
     TestData.authLogin({ origin: "http://parens(.example.com" }),
     TestData.authLogin({ origin: "http://parens).example.com" }),
     TestData.authLogin({ origin: "http://parens(example).example.com" }),
     TestData.authLogin({ origin: "http://parens)example(.example.com" }),
   ];
-  for (let loginInfo of loginList) {
-    Services.logins.addLogin(loginInfo);
-  }
+  await Services.logins.addLogins(loginList);
   await reloadAndCheckLoginsGen(loginList);
 });
diff --git a/toolkit/components/passwordmgr/test/unit/test_telemetry.js b/toolkit/components/passwordmgr/test/unit/test_telemetry.js
--- a/toolkit/components/passwordmgr/test/unit/test_telemetry.js
+++ b/toolkit/components/passwordmgr/test/unit/test_telemetry.js
@@ -109,28 +109,28 @@
 
 /**
  * Enable local telemetry recording for the duration of the tests, and prepare
  * the test data that will be used by the following tests.
  */
-add_task(function test_initialize() {
+add_setup(async () => {
   let oldCanRecord = Services.telemetry.canRecordExtended;
   Services.telemetry.canRecordExtended = true;
   registerCleanupFunction(function() {
     Services.telemetry.canRecordExtended = oldCanRecord;
   });
 
   let uniqueNumber = 1;
+  let logins = [];
   for (let loginModifications of StatisticsTestData) {
     loginModifications.origin = `http://${uniqueNumber++}.example.com`;
-    let login;
     if (typeof loginModifications.httpRealm != "undefined") {
-      login = TestData.authLogin(loginModifications);
+      logins.push(TestData.authLogin(loginModifications));
     } else {
-      login = TestData.formLogin(loginModifications);
+      logins.push(TestData.formLogin(loginModifications));
     }
-    Services.logins.addLogin(login);
   }
+  await Services.logins.addLogins(logins);
 });
 
 /**
  * Tests the collection of statistics related to login metadata.
  */
diff --git a/toolkit/components/passwordmgr/test/unit/test_vulnerable_passwords.js b/toolkit/components/passwordmgr/test/unit/test_vulnerable_passwords.js
--- a/toolkit/components/passwordmgr/test/unit/test_vulnerable_passwords.js
+++ b/toolkit/components/passwordmgr/test/unit/test_vulnerable_passwords.js
@@ -8,15 +8,15 @@
 });
 
 add_task(async function test_vulnerable_password_methods() {
   const storageJSON = Services.logins.wrappedJSObject._storage.wrappedJSObject;
 
-  let logins = TestData.loginList();
+  const logins = TestData.loginList();
   Assert.greater(logins.length, 0, "Initial logins length should be > 0.");
 
-  for (let loginInfo of logins) {
-    Services.logins.addLogin(loginInfo);
+  for (const loginInfo of logins) {
+    await Services.logins.addLoginAsync(loginInfo);
     Assert.ok(
       !storageJSON.isPotentiallyVulnerablePassword(loginInfo),
       "No logins should be vulnerable until addVulnerablePasswords is called."
     );
   }
@@ -26,21 +26,21 @@
 
   Assert.ok(
     storageJSON.isPotentiallyVulnerablePassword(vulnerableLogin),
     "Login should be vulnerable after calling addVulnerablePassword."
   );
-  for (let loginInfo of logins) {
+  for (const loginInfo of logins) {
     Assert.ok(
       !storageJSON.isPotentiallyVulnerablePassword(loginInfo),
       "No other logins should be vulnerable when addVulnerablePassword is called" +
         " with a single argument"
     );
   }
 
   storageJSON.clearAllPotentiallyVulnerablePasswords();
 
-  for (let loginInfo of logins) {
+  for (const loginInfo of logins) {
     Assert.ok(
       !storageJSON.isPotentiallyVulnerablePassword(loginInfo),
       "No logins should be vulnerable when clearAllPotentiallyVulnerablePasswords is called."
     );
   }