1 files changed, 25 insertions, 0 deletions
diff --git a/js/src/jit-test/tests/collections/for-in.js b/js/src/jit-test/tests/collections/for-in.js
new file mode 100644
index 000000000..b46de15e2
--- /dev/null
+++ b/js/src/jit-test/tests/collections/for-in.js
@@ -0,0 +1,25 @@
+// for-in loops on Maps and Sets enumerate properties.
+
+var test = function test(obj) {
+    assertEq(Object.keys(obj).length, 0);
+
+    var i = 0, v;
+    for (v in obj)
+        i++;
+    assertEq(i, 0);
+
+    obj.ownProp = 1;
+    assertEq(Object.keys(obj).join(), "ownProp");
+
+    for (v in obj)
+        i++;
+    assertEq(i, 1);
+    assertEq(v, "ownProp");
+
+    delete obj.ownProp;
+};
+
+test(Map.prototype);
+test(new Map);
+test(Set.prototype);
+test(new Set);