diff -r 000000000000 -r 6474c204b198 services/sync/tests/unit/test_fxa_startOver.js
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/services/sync/tests/unit/test_fxa_startOver.js	Wed Dec 31 06:09:35 2014 +0100
@@ -0,0 +1,63 @@
+/* Any copyright is dedicated to the Public Domain.
+ * http://creativecommons.org/publicdomain/zero/1.0/ */
+
+Cu.import("resource://testing-common/services/sync/utils.js");
+Cu.import("resource://services-sync/identity.js");
+Cu.import("resource://services-sync/browserid_identity.js");
+Cu.import("resource://services-sync/service.js");
+
+function run_test() {
+  initTestLogging("Trace");
+  run_next_test();
+}
+
+add_task(function* test_startover() {
+  let oldValue = Services.prefs.getBoolPref("services.sync-testing.startOverKeepIdentity", true);
+  Services.prefs.setBoolPref("services.sync-testing.startOverKeepIdentity", false);
+
+  ensureLegacyIdentityManager();
+  yield configureIdentity({username: "johndoe"});
+
+  // The boolean flag on the xpcom service should reflect a legacy provider.
+  let xps = Cc["@mozilla.org/weave/service;1"]
+            .getService(Components.interfaces.nsISupports)
+            .wrappedJSObject;
+  do_check_false(xps.fxAccountsEnabled);
+
+  // we expect the "legacy" provider (but can't instanceof that, as BrowserIDManager
+  // extends it)
+  do_check_false(Service.identity instanceof BrowserIDManager);
+
+  Service.serverURL = "https://localhost/";
+  Service.clusterURL = Service.serverURL;
+
+  Service.login();
+  // We should have a cluster URL
+  do_check_true(Service.clusterURL.length > 0);
+
+  // remember some stuff so we can reset it after.
+  let oldIdentity = Service.identity;
+  let oldClusterManager = Service._clusterManager;
+  let deferred = Promise.defer();
+  Services.obs.addObserver(function observeStartOverFinished() {
+    Services.obs.removeObserver(observeStartOverFinished, "weave:service:start-over:finish");
+    deferred.resolve();
+  }, "weave:service:start-over:finish", false);
+
+  Service.startOver();
+  yield deferred.promise; // wait for the observer to fire.
+
+  // the xpcom service should indicate FxA is enabled.
+  do_check_true(xps.fxAccountsEnabled);
+  // should have swapped identities.
+  do_check_true(Service.identity instanceof BrowserIDManager);
+  // should have clobbered the cluster URL
+  do_check_eq(Service.clusterURL, "");
+
+  // we should have thrown away the old identity provider and cluster manager.
+  do_check_neq(oldIdentity, Service.identity);
+  do_check_neq(oldClusterManager, Service._clusterManager);
+
+  // reset the world.
+  Services.prefs.setBoolPref("services.sync-testing.startOverKeepIdentity", oldValue);
+});