diff -r 000000000000 -r 6474c204b198 js/src/tests/ecma_6/Math/atanh-exact.js
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/js/src/tests/ecma_6/Math/atanh-exact.js	Wed Dec 31 06:09:35 2014 +0100
@@ -0,0 +1,35 @@
+// Properties of Math.atanh that are guaranteed by the spec.
+
+// If x is NaN, the result is NaN.
+assertEq(Math.atanh(NaN), NaN);
+
+// If x is less than −1, the result is NaN.
+assertEq(Math.atanh(-ONE_PLUS_EPSILON), NaN);
+assertEq(Math.atanh(-Number.MAX_VALUE), NaN);
+assertEq(Math.atanh(-Infinity), NaN);
+
+for (var i = -5; i < -1; i += 0.1)
+    assertEq(Math.atanh(i), NaN);
+
+// If x is greater than 1, the result is NaN.
+assertEq(Math.atanh(ONE_PLUS_EPSILON), NaN);
+assertEq(Math.atanh(Number.MAX_VALUE), NaN);
+assertEq(Math.atanh(Infinity), NaN);
+
+for (var i = +5; i > +1; i -= 0.1)
+    assertEq(Math.atanh(i), NaN);
+
+// If x is −1, the result is −∞.
+assertEq(Math.atanh(-1), -Infinity);
+
+// If x is +1, the result is +∞.
+assertEq(Math.atanh(+1), Infinity);
+
+// If x is +0, the result is +0.
+assertEq(Math.atanh(+0), +0);
+
+// If x is −0, the result is −0.
+assertEq(Math.atanh(-0), -0);
+
+
+reportCompare(0, 0, "ok");