diff -r 000000000000 -r 6474c204b198 js/src/tests/test262/ch11/11.13/11.13.2/S11.13.2_A4.4_T2.2.js
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/js/src/tests/test262/ch11/11.13/11.13.2/S11.13.2_A4.4_T2.2.js	Wed Dec 31 06:09:35 2014 +0100
@@ -0,0 +1,38 @@
+// Copyright 2009 the Sputnik authors.  All rights reserved.
+// This code is governed by the BSD license found in the LICENSE file.
+
+/**
+ * The production x += y is the same as x = x + y
+ *
+ * @path ch11/11.13/11.13.2/S11.13.2_A4.4_T2.2.js
+ * @description Type(x) is different from Type(y) and both types vary between Number (primitive or object) and Null
+ */
+
+//CHECK#1
+x = 1;
+x += null;
+if (x !== 1) {
+  $ERROR('#1: x = 1; x += null; x === 1. Actual: ' + (x));
+}
+
+//CHECK#2
+x = null;
+x += 1;
+if (x !== 1) {
+  $ERROR('#2: x = null; x += 1; x === 1. Actual: ' + (x));
+}
+
+//CHECK#3
+x = new Number(1);
+x += null;
+if (x !== 1) {
+  $ERROR('#3: x = new Number(1); x += null; x === 1. Actual: ' + (x));
+}
+
+//CHECK#4
+x = null;
+x += new Number(1);
+if (x !== 1) {
+  $ERROR('#4: x = null; x += new Number(1); x === 1. Actual: ' + (x));
+}
+