diff -r 000000000000 -r 6474c204b198 services/sync/tests/unit/test_forms_tracker.js
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/services/sync/tests/unit/test_forms_tracker.js	Wed Dec 31 06:09:35 2014 +0100
@@ -0,0 +1,58 @@
+/* Any copyright is dedicated to the Public Domain.
+   http://creativecommons.org/publicdomain/zero/1.0/ */
+
+Cu.import("resource://gre/modules/Log.jsm");
+Cu.import("resource://services-sync/engines/forms.js");
+Cu.import("resource://services-sync/service.js");
+Cu.import("resource://services-sync/util.js");
+
+function run_test() {
+  _("Verify we've got an empty tracker to work with.");
+  let engine = new FormEngine(Service);
+  let tracker = engine._tracker;
+  // Don't do asynchronous writes.
+  tracker.persistChangedIDs = false;
+
+  do_check_empty(tracker.changedIDs);
+  Log.repository.rootLogger.addAppender(new Log.DumpAppender());
+
+  function addEntry(name, value) {
+    engine._store.create({name: name, value: value});
+  }
+  function removeEntry(name, value) {
+    guid = engine._findDupe({name: name, value: value});
+    engine._store.remove({id: guid});
+  }
+
+  try {
+    _("Create an entry. Won't show because we haven't started tracking yet");
+    addEntry("name", "John Doe");
+    do_check_empty(tracker.changedIDs);
+
+    _("Tell the tracker to start tracking changes.");
+    Svc.Obs.notify("weave:engine:start-tracking");
+    removeEntry("name", "John Doe");
+    addEntry("email", "john@doe.com");
+    do_check_attribute_count(tracker.changedIDs, 2);
+
+    _("Notifying twice won't do any harm.");
+    Svc.Obs.notify("weave:engine:start-tracking");
+    addEntry("address", "Memory Lane");
+    do_check_attribute_count(tracker.changedIDs, 3);
+
+    _("Let's stop tracking again.");
+    tracker.clearChangedIDs();
+    Svc.Obs.notify("weave:engine:stop-tracking");
+    removeEntry("address", "Memory Lane");
+    do_check_empty(tracker.changedIDs);
+
+    _("Notifying twice won't do any harm.");
+    Svc.Obs.notify("weave:engine:stop-tracking");
+    removeEntry("email", "john@doe.com");
+    do_check_empty(tracker.changedIDs);
+
+  } finally {
+    _("Clean up.");
+    engine._store.wipe();
+  }
+}