diff -r 000000000000 -r 6474c204b198 xpcom/tests/TestObserverArray.cpp
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/xpcom/tests/TestObserverArray.cpp	Wed Dec 31 06:09:35 2014 +0100
@@ -0,0 +1,146 @@
+/* -*- Mode: C++; tab-width: 2; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
+// vim:cindent:ts=4:et:sw=4:
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+#include "TestHarness.h"
+#include "nsTObserverArray.h"
+
+using namespace mozilla;
+
+typedef nsTObserverArray<int> IntArray;
+
+#define DO_TEST(_type, _exp, _code)                                   \
+  do {                                                                \
+    ++testNum;                                                        \
+    count = 0;                                                        \
+    IntArray::_type iter(arr);                                        \
+    while (iter.HasMore() && count != ArrayLength(_exp)) {            \
+      _code                                                           \
+      int next = iter.GetNext();                                      \
+      int expected = _exp[count++];                                   \
+      if (next != expected) {                                         \
+        fail("During test %d at position %d got %d expected %d\n",    \
+             testNum, count-1, next, expected);                       \
+        rv = 1;                                                       \
+      }                                                               \
+    }                                                                 \
+    if (iter.HasMore()) {                                             \
+      fail("During test %d, iterator ran over", testNum);             \
+      rv = 1;                                                         \
+    }                                                                 \
+    if (count != ArrayLength(_exp)) {                             \
+      fail("During test %d, iterator finished too early", testNum);   \
+      rv = 1;                                                         \
+    }                                                                 \
+  } while (0)
+
+int main(int argc, char **argv)
+{
+  ScopedXPCOM xpcom("nsTObserverArrayTests");
+  if (xpcom.failed()) {
+    return 1;
+  }
+
+  int rv = 0;
+
+  IntArray arr;
+  arr.AppendElement(3);
+  arr.AppendElement(4);
+
+  size_t count;
+  int testNum = 0;
+
+  // Basic sanity
+  static int test1Expected[] = { 3, 4 };
+  DO_TEST(ForwardIterator, test1Expected, { /* nothing */ });
+
+  // Appends
+  static int test2Expected[] = { 3, 4, 2 };
+  DO_TEST(ForwardIterator, test2Expected,
+          if (count == 1) arr.AppendElement(2);
+          );
+  DO_TEST(ForwardIterator, test2Expected, { /* nothing */ });
+
+  DO_TEST(EndLimitedIterator, test2Expected,
+          if (count == 1) arr.AppendElement(5);
+          );
+
+  static int test5Expected[] = { 3, 4, 2, 5 };
+  DO_TEST(ForwardIterator, test5Expected, { /* nothing */ });
+
+  // Removals
+  DO_TEST(ForwardIterator, test5Expected,
+          if (count == 1) arr.RemoveElementAt(0);
+          );
+
+  static int test7Expected[] = { 4, 2, 5 };
+  DO_TEST(ForwardIterator, test7Expected, { /* nothing */ });
+
+  static int test8Expected[] = { 4, 5 };
+  DO_TEST(ForwardIterator, test8Expected,
+          if (count == 1) arr.RemoveElementAt(1);
+          );
+  DO_TEST(ForwardIterator, test8Expected, { /* nothing */ });
+
+  arr.AppendElement(2);
+  arr.AppendElementUnlessExists(6);
+  static int test10Expected[] = { 4, 5, 2, 6 };
+  DO_TEST(ForwardIterator, test10Expected, { /* nothing */ });
+
+  arr.AppendElementUnlessExists(5);
+  DO_TEST(ForwardIterator, test10Expected, { /* nothing */ });
+
+  static int test12Expected[] = { 4, 5, 6 };
+  DO_TEST(ForwardIterator, test12Expected,
+          if (count == 1) arr.RemoveElementAt(2);
+          );
+  DO_TEST(ForwardIterator, test12Expected, { /* nothing */ });
+
+  // Removals + Appends
+  static int test14Expected[] = { 4, 6, 7 };
+  DO_TEST(ForwardIterator, test14Expected,
+          if (count == 1) {
+            arr.RemoveElementAt(1);
+            arr.AppendElement(7);
+          }
+          );
+  DO_TEST(ForwardIterator, test14Expected, { /* nothing */ });
+
+  arr.AppendElement(2);
+  static int test16Expected[] = { 4, 6, 7, 2 };
+  DO_TEST(ForwardIterator, test16Expected, { /* nothing */ });
+
+  static int test17Expected[] = { 4, 7, 2 };
+  DO_TEST(EndLimitedIterator, test17Expected,
+          if (count == 1) {
+            arr.RemoveElementAt(1);
+            arr.AppendElement(8);
+          }
+          );
+
+  static int test18Expected[] = { 4, 7, 2, 8 };
+  DO_TEST(ForwardIterator, test18Expected, { /* nothing */ });
+
+  // Prepends
+  arr.PrependElementUnlessExists(3);
+  static int test19Expected[] = { 3, 4, 7, 2, 8 };
+  DO_TEST(ForwardIterator, test19Expected, { /* nothing */ });
+
+  arr.PrependElementUnlessExists(7);
+  DO_TEST(ForwardIterator, test19Expected, { /* nothing */ });
+
+  // Commented out because it fails; bug 474369 will fix
+  /*  DO_TEST(ForwardIterator, test19Expected,
+          if (count == 1) {
+            arr.PrependElementUnlessExists(9);
+          }
+          );
+
+  static int test22Expected[] = { 9, 3, 4, 7, 2, 8 };
+  DO_TEST(ForwardIterator, test22Expected, { });
+  */
+  
+  return rv;
+}