diff -r 000000000000 -r 6474c204b198 browser/metro/base/tests/unit/test_util_extend.js
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/browser/metro/base/tests/unit/test_util_extend.js	Wed Dec 31 06:09:35 2014 +0100
@@ -0,0 +1,41 @@
+"use strict";
+
+Components.utils.import("resource:///modules/ContentUtil.jsm");
+let Util = ContentUtil;
+
+function run_test() {
+  do_print("Testing Util.extend");
+
+  do_print("Check if function is defined");
+  do_check_true(!!Util.extend);
+
+  do_print("No parameter or null should return a new object");
+  let noArgRes = Util.extend();
+  do_check_true(noArgRes && typeof noArgRes == "object");
+
+  let nullRes = Util.extend(null);
+  do_check_true(nullRes && typeof nullRes == "object");
+
+  do_print("Simple extend");
+  let simpleExtend = {a: 1, b: 2};
+  let simpleExtendResult = Util.extend(simpleExtend, {b: 3, c: 4});
+
+  do_check_true(simpleExtend.a === 1 && simpleExtend.b === 3 && simpleExtend.c === 4);
+  do_check_true(simpleExtendResult === simpleExtend);
+
+  do_print("Cloning");
+  let cloneExtend = {a: 1, b: 2};
+  let cloned = Util.extend({}, cloneExtend);
+
+  do_check_true(cloneExtend.a === cloned.a && cloneExtend.b === cloned.b);
+  do_check_true(cloneExtend !== cloned);
+
+  do_print("Multiple extend");
+  let multiExtend1 = {a: 1, b: 2};
+  let multiExtend2 = {c: 3, d: 4};
+  let multiExtend3 = {b: 5, e: 6};
+  let multiExtend4 = {e: 7, a: 8};
+  let multiResult = Util.extend({}, multiExtend1, multiExtend2, multiExtend3, multiExtend4);
+
+  do_check_true(multiResult.a === 8 && multiResult.b === 5 && multiResult.c === 3 && multiResult.d === 4 && multiResult.e === 7);
+}