--- a/services/common/tests/unit/head_helpers.js
+++ b/services/common/tests/unit/head_helpers.js
@@ -152,21 +152,8 @@ function installFakePAC() {
   fakePACCID = MockRegistrar.register("@mozilla.org/system-proxy-settings;1",
                                       PACSystemSettings);
 }
 
 function uninstallFakePAC() {
   _("Uninstalling fake PAC.");
   MockRegistrar.unregister(fakePACCID);
 }
-
-// Many tests do service.startOver() and don't expect the provider type to
-// change (whereas by default, a startOver will do exactly that so FxA is
-// subsequently used). The tests that know how to deal with
-// the Firefox Accounts identity hack things to ensure that still works.
-function ensureStartOverKeepsIdentity() {
-  Cu.import("resource://gre/modules/Services.jsm");
-  Services.prefs.setBoolPref("services.sync-testing.startOverKeepIdentity", true);
-  do_register_cleanup(function() {
-    Services.prefs.clearUserPref("services.sync-testing.startOverKeepIdentity");
-  });
-}
-ensureStartOverKeepsIdentity();

--- a/services/fxaccounts/tests/xpcshell/head.js
+++ b/services/fxaccounts/tests/xpcshell/head.js
@@ -1,15 +1,16 @@
 /* Any copyright is dedicated to the Public Domain.
  * http://creativecommons.org/publicdomain/zero/1.0/ */
 
 var {classes: Cc, interfaces: Ci, results: Cr, utils: Cu} = Components;
 
 "use strict";
 
+Cu.import("resource://gre/modules/Services.jsm");
 Cu.import("resource://gre/modules/XPCOMUtils.jsm");
 
 (function initFxAccountsTestingInfrastructure() {
   do_get_profile();
 
   let ns = {};
   Cu.import("resource://testing-common/services/common/logging.js", ns);
 

--- a/services/fxaccounts/tests/xpcshell/test_accounts.js
+++ b/services/fxaccounts/tests/xpcshell/test_accounts.js
@@ -1,15 +1,14 @@
 /* Any copyright is dedicated to the Public Domain.
  * http://creativecommons.org/publicdomain/zero/1.0/ */
 
 "use strict";
 
 Cu.import("resource://services-common/utils.js");
-Cu.import("resource://gre/modules/Services.jsm");
 Cu.import("resource://gre/modules/FxAccounts.jsm");
 Cu.import("resource://gre/modules/FxAccountsClient.jsm");
 Cu.import("resource://gre/modules/FxAccountsCommon.js");
 Cu.import("resource://gre/modules/FxAccountsOAuthGrantClient.jsm");
 Cu.import("resource://gre/modules/Promise.jsm");
 Cu.import("resource://gre/modules/Log.jsm");
 
 // We grab some additional stuff via backstage passes.

--- a/services/fxaccounts/tests/xpcshell/test_accounts_device_registration.js
+++ b/services/fxaccounts/tests/xpcshell/test_accounts_device_registration.js
@@ -1,15 +1,14 @@
 /* Any copyright is dedicated to the Public Domain.
  * http://creativecommons.org/publicdomain/zero/1.0/ */
 
 "use strict";
 
 Cu.import("resource://services-common/utils.js");
-Cu.import("resource://gre/modules/Services.jsm");
 Cu.import("resource://gre/modules/FxAccounts.jsm");
 Cu.import("resource://gre/modules/FxAccountsClient.jsm");
 Cu.import("resource://gre/modules/FxAccountsCommon.js");
 Cu.import("resource://gre/modules/Promise.jsm");
 Cu.import("resource://gre/modules/Log.jsm");
 
 initTestLogging("Trace");
 

--- a/services/fxaccounts/tests/xpcshell/test_loginmgr_storage.js
+++ b/services/fxaccounts/tests/xpcshell/test_loginmgr_storage.js
@@ -5,17 +5,16 @@
 
 // Tests for FxAccounts, storage and the master password.
 
 // Stop us hitting the real auth server.
 Services.prefs.setCharPref("identity.fxaccounts.auth.uri", "http://localhost");
 // See verbose logging from FxAccounts.jsm
 Services.prefs.setCharPref("identity.fxaccounts.loglevel", "Trace");
 
-Cu.import("resource://gre/modules/Services.jsm");
 Cu.import("resource://gre/modules/FxAccounts.jsm");
 Cu.import("resource://gre/modules/FxAccountsClient.jsm");
 Cu.import("resource://gre/modules/FxAccountsCommon.js");
 Cu.import("resource://gre/modules/osfile.jsm");
 Cu.import("resource://services-common/utils.js");
 Cu.import("resource://gre/modules/FxAccountsCommon.js");
 
 // Use a backstage pass to get at our LoginManagerStorage object, so we can

--- a/services/fxaccounts/tests/xpcshell/test_oauth_grant_client.js
+++ b/services/fxaccounts/tests/xpcshell/test_oauth_grant_client.js
@@ -1,16 +1,15 @@
 /* Any copyright is dedicated to the Public Domain.
  * http://creativecommons.org/publicdomain/zero/1.0/ */
 
 "use strict";
 
 Cu.import("resource://gre/modules/FxAccountsCommon.js");
 Cu.import("resource://gre/modules/FxAccountsOAuthGrantClient.jsm");
-Cu.import("resource://gre/modules/Services.jsm");
 
 const CLIENT_OPTIONS = {
   serverURL: "http://127.0.0.1:9010/v1",
   client_id: "abc123"
 };
 
 const STATUS_SUCCESS = 200;
 

--- a/services/fxaccounts/tests/xpcshell/test_push_service.js
+++ b/services/fxaccounts/tests/xpcshell/test_push_service.js
@@ -1,17 +1,16 @@
 /* Any copyright is dedicated to the Public Domain.
  * http://creativecommons.org/publicdomain/zero/1.0/ */
 
 "use strict";
 
 // Tests for the FxA push service.
 
 Cu.import("resource://gre/modules/Task.jsm");
-Cu.import("resource://gre/modules/Services.jsm");
 Cu.import("resource://gre/modules/Promise.jsm");
 Cu.import("resource://gre/modules/FxAccountsCommon.js");
 Cu.import("resource://gre/modules/Log.jsm");
 
 let scope = {};
 Services.scriptloader.loadSubScript("resource://gre/components/FxAccountsPush.js", scope);
 const FxAccountsPushService = scope.FxAccountsPushService;
 

--- a/services/fxaccounts/tests/xpcshell/test_storage_manager.js
+++ b/services/fxaccounts/tests/xpcshell/test_storage_manager.js
@@ -1,17 +1,16 @@
 /* Any copyright is dedicated to the Public Domain.
  * http://creativecommons.org/publicdomain/zero/1.0/ */
 
 "use strict";
 
 // Tests for the FxA storage manager.
 
 Cu.import("resource://gre/modules/Task.jsm");
-Cu.import("resource://gre/modules/Services.jsm");
 Cu.import("resource://gre/modules/FxAccountsStorage.jsm");
 Cu.import("resource://gre/modules/FxAccountsCommon.js");
 Cu.import("resource://gre/modules/Log.jsm");
 
 initTestLogging("Trace");
 log.level = Log.Level.Trace;
 
 const DEVICE_REGISTRATION_VERSION = 42;

--- a/services/sync/modules/service.js
+++ b/services/sync/modules/service.js
@@ -826,27 +826,16 @@ Sync11Service.prototype = {
     Svc.Prefs.resetBranch("");
     this._ignorePrefObserver = false;
     this.clusterURL = null;
 
     Svc.Prefs.set("lastversion", WEAVE_VERSION);
 
     this.identity.deleteSyncCredentials();
 
-    // If necessary, reset the identity manager, then re-initialize it so the
-    // FxA manager is used.  This is configurable via a pref - mainly for tests.
-    let keepIdentity = false;
-    try {
-      keepIdentity = Services.prefs.getBoolPref("services.sync-testing.startOverKeepIdentity");
-    } catch (_) { /* no such pref */ }
-    if (keepIdentity) {
-      Svc.Obs.notify("weave:service:start-over:finish");
-      return;
-    }
-
     try {
       this.identity.finalize();
       // an observer so the FxA migration code can take some action before
       // the new identity is created.
       Svc.Obs.notify("weave:service:start-over:init-identity");
       this.status.__authManager = null;
       this.identity = Status._authManager;
       this._clusterManager = this.identity.createClusterManager(this);

--- a/services/sync/tests/unit/test_bookmark_duping.js
+++ b/services/sync/tests/unit/test_bookmark_duping.js
@@ -44,17 +44,16 @@ async function setup() {
 
   Svc.Obs.notify("weave:engine:start-tracking");   // We skip usual startup...
 
   return { server, collection };
 }
 
 async function cleanup(server) {
   Svc.Obs.notify("weave:engine:stop-tracking");
-  Services.prefs.setBoolPref("services.sync-testing.startOverKeepIdentity", true);
   let promiseStartOver = promiseOneObserver("weave:service:start-over:finish");
   Service.startOver();
   await promiseStartOver;
   await promiseStopServer(server);
   await bms.eraseEverything();
 }
 
 function getFolderChildrenIDs(folderId) {