diff -r 000000000000 -r 6474c204b198 js/src/jit-test/tests/collections/WeakMap-clear.js
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/js/src/jit-test/tests/collections/WeakMap-clear.js	Wed Dec 31 06:09:35 2014 +0100
@@ -0,0 +1,42 @@
+var key = {};
+var wm = WeakMap();
+
+assertEq(wm.has(key), false);
+// Clearing an already empty WeakMap
+wm.clear();
+assertEq(wm.has(key), false);
+
+// Clearing a WeakMap with a live key
+wm.set(key, 42);
+assertEq(wm.has(key), true);
+wm.clear();
+assertEq(wm.has(key), false);
+
+// Clearing a WeakMap with keys turned to garbage
+wm.set(key, {});
+for (var i = 0; i < 10; i++)
+    wm.set({}, {});
+assertEq(wm.has(key), true);
+wm.clear();
+assertEq(wm.has(key), false);
+
+// Clearing a WeakMap with keys turned to garbage and after doing a GC
+wm.set(key, {});
+for (var i = 0; i < 10; i++)
+    wm.set({}, {});
+assertEq(wm.has(key), true);
+gc();
+assertEq(wm.has(key), true);
+wm.clear();
+assertEq(wm.has(key), false);
+
+// More testing when the key is no longer live
+wm.set(key, {});
+key = null;
+wm.clear();
+gc();
+var key2 = {};
+wm.set(key2, {});
+key2 = null;
+gc();
+wm.clear();