diff -r 000000000000 -r 6474c204b198 js/src/tests/ecma_6/Math/log2-approx.js
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/js/src/tests/ecma_6/Math/log2-approx.js	Wed Dec 31 06:09:35 2014 +0100
@@ -0,0 +1,8 @@
+for (var i = -10; i < 10; i++)
+    assertNear(Math.log2(Math.pow(2, i)), i);
+
+assertNear(Math.log2(5), 2.321928094887362);
+assertNear(Math.log2(7), 2.807354922057604);
+assertNear(Math.log2(Math.E), Math.LOG2E);
+
+reportCompare(0, 0, "ok");