diff -r 000000000000 -r 6474c204b198 js/src/tests/ecma_6/Math/tanh-exact.js
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/js/src/tests/ecma_6/Math/tanh-exact.js	Wed Dec 31 06:09:35 2014 +0100
@@ -0,0 +1,19 @@
+// Properties of Math.tanh that are guaranteed by the spec.
+
+// If x is NaN, the result is NaN.
+assertEq(Math.tanh(NaN), NaN);
+
+// If x is +0, the result is +0.
+assertEq(Math.tanh(+0), +0);
+
+// If x is −0, the result is −0.
+assertEq(Math.tanh(-0), -0);
+
+// If x is +∞, the result is +1.
+assertEq(Math.tanh(Number.POSITIVE_INFINITY), +1);
+
+// If x is −∞, the result is -1.
+assertEq(Math.tanh(Number.NEGATIVE_INFINITY), -1);
+
+
+reportCompare(0, 0, "ok");