diff -r 000000000000 -r 6474c204b198 js/xpconnect/tests/unit/test_js_weak_references.js
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/js/xpconnect/tests/unit/test_js_weak_references.js	Wed Dec 31 06:09:35 2014 +0100
@@ -0,0 +1,45 @@
+/* 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/. */
+
+/* See https://bugzilla.mozilla.org/show_bug.cgi?id=317304 */
+
+function run_test()
+{
+  // Bug 712649: Calling getWeakReference(null) should work.
+  try {
+    var nullWeak = Components.utils.getWeakReference(null);
+    do_check_true(nullWeak.get() === null);
+  } catch (e) {
+    do_check_true(false);
+  }
+
+  var obj = { num: 5, str: 'foo' };
+  var weak = Components.utils.getWeakReference(obj);
+
+  do_check_true(weak.get() === obj);
+  do_check_true(weak.get().num == 5);
+  do_check_true(weak.get().str == 'foo');
+
+  // Force garbage collection
+  Components.utils.forceGC();
+
+  // obj still references the object, so it should still be accessible via weak
+  do_check_true(weak.get() === obj);
+  do_check_true(weak.get().num == 5);
+  do_check_true(weak.get().str == 'foo');
+
+  // Clear obj's reference to the object and force garbage collection. To make
+  // sure that there are no instances of obj stored in the registers or on the
+  // native stack and the conservative GC would not find it we force the same
+  // code paths that we used for the initial allocation.
+  obj = { num: 6, str: 'foo2' };
+  var weak2 = Components.utils.getWeakReference(obj);
+  do_check_true(weak2.get() === obj);
+
+  Components.utils.forceGC();
+
+  // The object should have been garbage collected and so should no longer be
+  // accessible via weak
+  do_check_true(weak.get() === null);
+}