diff -r 000000000000 -r 6474c204b198 js/src/tests/ecma_6/Math/acosh-exact.js
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/js/src/tests/ecma_6/Math/acosh-exact.js	Wed Dec 31 06:09:35 2014 +0100
@@ -0,0 +1,26 @@
+// Properties of Math.acosh that are guaranteed by the spec.
+
+// If x is NaN, the result is NaN.
+assertEq(Math.acosh(NaN), NaN);
+
+// If x is less than 1, the result is NaN.
+assertEq(Math.acosh(ONE_MINUS_EPSILON), NaN);
+assertEq(Math.acosh(Number.MIN_VALUE), NaN);
+assertEq(Math.acosh(+0), NaN);
+assertEq(Math.acosh(-0), NaN);
+assertEq(Math.acosh(-Number.MIN_VALUE), NaN);
+assertEq(Math.acosh(-1), NaN);
+assertEq(Math.acosh(-Number.MAX_VALUE), NaN);
+assertEq(Math.acosh(-Infinity), NaN);
+
+for (var i = -20; i < 1; i++)
+    assertEq(Math.acosh(i), NaN);
+
+// If x is 1, the result is +0.
+assertEq(Math.acosh(1), +0);
+
+// If x is +∞, the result is +∞.
+assertEq(Math.acosh(Number.POSITIVE_INFINITY), Number.POSITIVE_INFINITY);
+
+
+reportCompare(0, 0, "ok");