diff -r 000000000000 -r 6474c204b198 xpcom/tests/unit/test_bug325418.js
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/xpcom/tests/unit/test_bug325418.js	Wed Dec 31 06:09:35 2014 +0100
@@ -0,0 +1,61 @@
+const Cc = Components.classes;
+const Ci = Components.interfaces;
+
+// 5 seconds.
+const kExpectedDelay1 = 5;
+// 1 second.
+const kExpectedDelay2 = 1;
+
+var gStartTime1;
+var gStartTime2;
+var timer;
+
+var observer1 = {
+  observe: function observeTC1(subject, topic, data) {
+    if (topic == "timer-callback") {
+      // Stop timer, so it doesn't repeat (if test runs slowly).
+      timer.cancel();
+
+      // Actual delay may not be exact, so convert to seconds and round.
+      do_check_eq(Math.round((Date.now() - gStartTime1) / 1000),
+                  kExpectedDelay1);
+
+      timer = null;
+
+      do_print("1st timer triggered (before being cancelled). Should not have happened!");
+      do_check_true(false);
+    }
+  }
+};
+
+var observer2 = {
+  observe: function observeTC2(subject, topic, data) {
+    if (topic == "timer-callback") {
+      // Stop timer, so it doesn't repeat (if test runs slowly).
+      timer.cancel();
+
+      // Actual delay may not be exact, so convert to seconds and round.
+      do_check_eq(Math.round((Date.now() - gStartTime2) / 1000),
+                  kExpectedDelay2);
+
+      timer = null;
+
+      do_test_finished();
+    }
+  }
+};
+
+function run_test() {
+  do_test_pending();
+
+  timer = Cc["@mozilla.org/timer;1"].createInstance(Ci.nsITimer);
+
+  // Initialize the timer (with some delay), then cancel it.
+  gStartTime1 = Date.now();
+  timer.init(observer1, kExpectedDelay1 * 1000, timer.TYPE_REPEATING_PRECISE);
+  timer.cancel();
+
+  // Re-initialize the timer (with a different delay).
+  gStartTime2 = Date.now();
+  timer.init(observer2, kExpectedDelay2 * 1000, timer.TYPE_REPEATING_PRECISE);
+}