diff -r 000000000000 -r 6474c204b198 js/src/tests/test262/ch11/11.13/11.13.2/S11.13.2_A4.4_T1.4.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_T1.4.js	Wed Dec 31 06:09:35 2014 +0100
@@ -0,0 +1,50 @@
+// 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_T1.4.js
+ * @description Type(x) and Type(y) vary between primitive string and String object
+ */
+
+//CHECK#1
+x = "1";
+x += "1";
+if (x !== "11") {
+  $ERROR('#1: x = "1"; x += "1"; x === "11". Actual: ' + (x));
+}
+
+//CHECK#2
+x = new String("1");
+x += "1";
+if (x !== "11") {
+  $ERROR('#2: x = new String("1"); x += "1"; x === "11". Actual: ' + (x));
+}
+
+//CHECK#3
+x = "1";
+x += new String("1");
+if (x !== "11") {
+  $ERROR('#3: x = "1"; x += new String("1"); x === "11". Actual: ' + (x));
+}
+
+//CHECK#4
+x = new String("1");
+x += new String("1");
+if (x !== "11") {
+  $ERROR('#4: x = new String("1"); x += new String("1"); x === "11". Actual: ' + (x));
+}
+
+//CHECK#5
+if ("x" + "1" !=="x1") {
+  $ERROR('#5: x = "x"; x += "1"; x === "x1". Actual: ' + (x));
+}
+
+//CHECK#6
+x = "1";
+x += "x";
+if (x !== "1x") {
+  $ERROR('#6: x = "1"; x += "x"; x === "1x". Actual: ' + (x));
+}
+