diff -r 000000000000 -r 6474c204b198 js/src/jit-test/tests/basic/emulates-undefined.js
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/js/src/jit-test/tests/basic/emulates-undefined.js	Wed Dec 31 06:09:35 2014 +0100
@@ -0,0 +1,18 @@
+function test() {
+    var values = [undefined, null, Math, objectEmulatingUndefined()];
+    var expected = [true, true, false, true];
+
+    for (var i=0; i<100; i++) {
+        var idx = i % values.length;
+        if (values[idx] == undefined)
+            assertEq(expected[idx], true);
+        else
+            assertEq(expected[idx], false);
+
+        if (null != values[idx])
+            assertEq(expected[idx], false);
+        else
+            assertEq(expected[idx], true);
+    }
+}
+test();