diff -r 000000000000 -r 6474c204b198 services/sync/tests/unit/test_tab_tracker.js
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/services/sync/tests/unit/test_tab_tracker.js	Wed Dec 31 06:09:35 2014 +0100
@@ -0,0 +1,98 @@
+/* Any copyright is dedicated to the Public Domain.
+   http://creativecommons.org/publicdomain/zero/1.0/ */
+
+Cu.import("resource://services-sync/engines/tabs.js");
+Cu.import("resource://services-sync/service.js");
+Cu.import("resource://services-sync/util.js");
+
+let clientsEngine = Service.clientsEngine;
+
+function fakeSvcWinMediator() {
+  // actions on windows are captured in logs
+  let logs = [];
+  delete Services.wm;
+  Services.wm = {
+    getEnumerator: function() {
+      return {
+        cnt: 2,
+        hasMoreElements: function() this.cnt-- > 0,
+        getNext: function() {
+          let elt = {addTopics: [], remTopics: []};
+          logs.push(elt);
+          return {
+            addEventListener: function(topic) {
+              elt.addTopics.push(topic);
+            },
+            removeEventListener: function(topic) {
+              elt.remTopics.push(topic);
+            }
+          };
+        }
+      };
+    }
+  };
+  return logs;
+}
+
+function run_test() {
+  let engine = Service.engineManager.get("tabs");
+
+  _("We assume that tabs have changed at startup.");
+  let tracker = engine._tracker;
+  tracker.persistChangedIDs = false;
+
+  do_check_true(tracker.modified);
+  do_check_true(Utils.deepEquals(Object.keys(engine.getChangedIDs()),
+                                 [clientsEngine.localID]));
+
+  let logs;
+
+  _("Test listeners are registered on windows");
+  logs = fakeSvcWinMediator();
+  Svc.Obs.notify("weave:engine:start-tracking");
+  do_check_eq(logs.length, 2);
+  for each (let log in logs) {
+    do_check_eq(log.addTopics.length, 5);
+    do_check_true(log.addTopics.indexOf("pageshow") >= 0);
+    do_check_true(log.addTopics.indexOf("TabOpen") >= 0);
+    do_check_true(log.addTopics.indexOf("TabClose") >= 0);
+    do_check_true(log.addTopics.indexOf("TabSelect") >= 0);
+    do_check_true(log.addTopics.indexOf("unload") >= 0);
+    do_check_eq(log.remTopics.length, 0);
+  }
+
+  _("Test listeners are unregistered on windows");
+  logs = fakeSvcWinMediator();
+  Svc.Obs.notify("weave:engine:stop-tracking");
+  do_check_eq(logs.length, 2);
+  for each (let log in logs) {
+    do_check_eq(log.addTopics.length, 0);
+    do_check_eq(log.remTopics.length, 5);
+    do_check_true(log.remTopics.indexOf("pageshow") >= 0);
+    do_check_true(log.remTopics.indexOf("TabOpen") >= 0);
+    do_check_true(log.remTopics.indexOf("TabClose") >= 0);
+    do_check_true(log.remTopics.indexOf("TabSelect") >= 0);
+    do_check_true(log.remTopics.indexOf("unload") >= 0);
+  }
+
+  _("Test tab listener");
+  for each (let evttype in ["TabOpen", "TabClose", "TabSelect"]) {
+    // Pretend we just synced.
+    tracker.clearChangedIDs();
+    do_check_false(tracker.modified);
+
+    // Send a fake tab event
+    tracker.onTab({type: evttype , originalTarget: evttype});
+    do_check_true(tracker.modified);
+    do_check_true(Utils.deepEquals(Object.keys(engine.getChangedIDs()),
+                                   [clientsEngine.localID]));
+  }
+
+  // Pretend we just synced.
+  tracker.clearChangedIDs();
+  do_check_false(tracker.modified);
+
+  tracker.onTab({type: "pageshow", originalTarget: "pageshow"});
+  do_check_true(Utils.deepEquals(Object.keys(engine.getChangedIDs()),
+                                 [clientsEngine.localID]));
+}