diff -r 000000000000 -r 6474c204b198 js/src/jit-test/tests/collections/Set-iterator-remove-6.js
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/js/src/jit-test/tests/collections/Set-iterator-remove-6.js	Wed Dec 31 06:09:35 2014 +0100
@@ -0,0 +1,20 @@
+// Removing many Set entries does not cause a live iterator to skip any of the
+// entries that were not removed. (Compacting a Set must not be observable to
+// script.)
+
+load(libdir + "iteration.js");
+
+var set = Set();
+for (var i = 0; i < 32; i++)
+    set.add(i);
+var iter = set[std_iterator]();
+assertIteratorNext(iter, 0);
+for (var i = 0; i < 30; i++)
+    set.delete(i);
+assertEq(set.size, 2);
+for (var i = 32; i < 100; i++)
+    set.add(i);  // eventually triggers compaction
+
+for (var i = 30; i < 100; i++)
+    assertIteratorNext(iter, i);
+assertIteratorDone(iter, undefined);