diff -r 000000000000 -r 6474c204b198 toolkit/components/places/tests/expiration/test_pref_interval.js
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/toolkit/components/places/tests/expiration/test_pref_interval.js	Wed Dec 31 06:09:35 2014 +0100
@@ -0,0 +1,144 @@
+/* -*- Mode: C++; tab-width: 2; indent-tabs-mode: nil; c-basic-offset: 2 -*-
+ * vim: sw=2 ts=2 et lcs=trail\:.,tab\:>~ :
+ * This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+/**
+ * What this is aimed to test:
+ *
+ * Expiration relies on an interval, that is user-preffable setting
+ * "places.history.expiration.interval_seconds".
+ * On pref change it will stop current interval timer and fire a new one,
+ * that will obey the new value.
+ * If the pref is set to a number <= 0 we will use the default value.
+ */
+
+// Default timer value for expiration in seconds.  Must have same value as
+// PREF_INTERVAL_SECONDS_NOTSET in nsPlacesExpiration.
+const DEFAULT_TIMER_DELAY_SECONDS = 3 * 60;
+
+// Sync this with the const value in the component.
+const EXPIRE_AGGRESSIVITY_MULTIPLIER = 3;
+
+// Provide a mock timer implementation, so there is no need to wait seconds to
+// achieve test results.
+const Cm = Components.manager.QueryInterface(Ci.nsIComponentRegistrar);
+const TIMER_CONTRACT_ID = "@mozilla.org/timer;1";
+const kMockCID = Components.ID("52bdf457-4de3-48ae-bbbb-f3cbcbcad05f");
+
+// Used to preserve the original timer factory.
+let gOriginalCID = Cm.contractIDToCID(TIMER_CONTRACT_ID);
+
+// The mock timer factory.
+let gMockTimerFactory = {
+  createInstance: function MTF_createInstance(aOuter, aIID) {
+    if (aOuter != null)
+      throw Cr.NS_ERROR_NO_AGGREGATION;
+    return mockTimerImpl.QueryInterface(aIID);
+  },
+
+  QueryInterface: XPCOMUtils.generateQI([
+    Ci.nsIFactory,
+  ])
+}
+
+let mockTimerImpl = {
+  initWithCallback: function MTI_initWithCallback(aCallback, aDelay, aType) {
+    print("Checking timer delay equals expected interval value");
+    if (!currentTest)
+      return;
+    // History status is not dirty, so the timer is delayed.
+    do_check_eq(aDelay, currentTest.expectedTimerDelay * 1000 * EXPIRE_AGGRESSIVITY_MULTIPLIER)
+
+    do_execute_soon(runNextTest);
+  },
+
+  cancel: function() {},
+  initWithFuncCallback: function() {},
+  init: function() {},
+
+  QueryInterface: XPCOMUtils.generateQI([
+    Ci.nsITimer,
+  ])
+}
+
+function replace_timer_factory() {
+  Cm.registerFactory(kMockCID,
+                     "Mock timer",
+                     TIMER_CONTRACT_ID,
+                     gMockTimerFactory);
+}
+
+do_register_cleanup(function() {
+  // Shutdown expiration before restoring original timer, otherwise we could
+  // leak due to the different implementation.
+  shutdownExpiration();
+
+  // Restore original timer factory.
+  Cm.unregisterFactory(kMockCID,
+                       gMockTimerFactory);
+  Cm.registerFactory(gOriginalCID,
+                     "",
+                     TIMER_CONTRACT_ID,
+                     null);
+});
+
+
+let tests = [
+
+  // This test should be the first, so the interval won't be influenced by
+  // status of history.
+  { desc: "Set interval to 1s.",
+    interval: 1,
+    expectedTimerDelay: 1
+  },
+
+  { desc: "Set interval to a negative value.",
+    interval: -1,
+    expectedTimerDelay: DEFAULT_TIMER_DELAY_SECONDS
+  },
+
+  { desc: "Set interval to 0.",
+    interval: 0,
+    expectedTimerDelay: DEFAULT_TIMER_DELAY_SECONDS
+  },
+
+  { desc: "Set interval to a large value.",
+    interval: 100,
+    expectedTimerDelay: 100
+  },
+
+];
+
+let currentTest;
+
+function run_test() {
+  // The pref should not exist by default.
+  try {
+    getInterval();
+    do_throw("interval pref should not exist by default");
+  }
+  catch (ex) {}
+
+  // Use our own mock timer implementation.
+  replace_timer_factory();
+
+  // Force the component, so it will start observing preferences.
+  force_expiration_start();
+
+  runNextTest();
+  do_test_pending();
+}
+
+function runNextTest() {
+  if (tests.length) {
+    currentTest = tests.shift();
+    print(currentTest.desc);
+    setInterval(currentTest.interval);
+  }
+  else {
+    clearInterval();
+    do_test_finished();
+  }
+}