diff -r 000000000000 -r 6474c204b198 js/src/jit-test/tests/collections/Map-constructor-2.js
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/js/src/jit-test/tests/collections/Map-constructor-2.js	Wed Dec 31 06:09:35 2014 +0100
@@ -0,0 +1,6 @@
+// The Map constructor can take an argument that is an array of pairs.
+
+var arr = [["zero", 0], ["one", 1], ["two", 2]];
+var m = Map(arr);
+for (var [k, v] of arr)
+    assertEq(m.get(k), v);