diff -r 000000000000 -r 6474c204b198 xpcom/tests/TestPriorityQueue.cpp
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/xpcom/tests/TestPriorityQueue.cpp	Wed Dec 31 06:09:35 2014 +0100
@@ -0,0 +1,96 @@
+/* -*- Mode: C++; tab-width: 2; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
+/* vim:set ts=2 sw=2 sts=2 et cindent: */
+/* 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 "nsTPriorityQueue.h"
+#include <stdio.h>
+#include <stdlib.h>
+
+template<class T, class Compare>
+void
+CheckPopSequence(const nsTPriorityQueue<T, Compare>& aQueue,
+                 const T* aExpectedSequence, const uint32_t aSequenceLength)
+{
+  nsTPriorityQueue<T, Compare> copy(aQueue);
+
+  for (uint32_t i = 0; i < aSequenceLength; i++) {
+    if (copy.IsEmpty()) {
+      printf("Number of elements in the queue is too short by %d.\n",
+          aSequenceLength - i);
+      exit(-1);
+    }
+
+    T pop = copy.Pop();
+    if (pop != aExpectedSequence[i]) {
+      printf("Unexpected value in pop sequence at position %d\n", i);
+      printf("  Sequence:");
+      for (size_t j = 0; j < aSequenceLength; j++) {
+        printf(" %d", aExpectedSequence[j]);
+        if (j == i) {
+          printf("**");
+        }
+      }
+      printf("\n            ** Got %d instead\n", pop);
+      exit(-1);
+    }
+  }
+
+  if (!copy.IsEmpty()) {
+    printf("Number of elements in the queue is too long by %d.\n",
+        copy.Length());
+    exit(-1);
+  }
+}
+
+template<class A>
+class MaxCompare {
+public:
+  bool LessThan(const A& a, const A& b) {
+    return a > b;
+  }
+};
+
+int main()
+{
+  nsTPriorityQueue<int> queue;
+
+  NS_ABORT_IF_FALSE(queue.IsEmpty(), "Queue not initially empty");
+
+  queue.Push(8);
+  queue.Push(6);
+  queue.Push(4);
+  queue.Push(2);
+  queue.Push(10);
+  queue.Push(6);
+  NS_ABORT_IF_FALSE(queue.Top() == 2, "Unexpected queue top");
+  NS_ABORT_IF_FALSE(queue.Length() == 6, "Unexpected queue length");
+  NS_ABORT_IF_FALSE(!queue.IsEmpty(), "Queue empty when populated");
+  int expected[] = { 2, 4, 6, 6, 8, 10 };
+  CheckPopSequence(queue, expected, sizeof(expected) / sizeof(expected[0]));
+
+  // copy ctor is tested by using CheckPopSequence, but check default assignment
+  // operator
+  nsTPriorityQueue<int> queue2;
+  queue2 = queue;
+  CheckPopSequence(queue2, expected, sizeof(expected) / sizeof(expected[0]));
+
+  queue.Clear();
+  NS_ABORT_IF_FALSE(queue.IsEmpty(), "Queue not emptied by Clear");
+
+  // try same sequence with a max heap
+  nsTPriorityQueue<int, MaxCompare<int> > max_queue;
+  max_queue.Push(8);
+  max_queue.Push(6);
+  max_queue.Push(4);
+  max_queue.Push(2);
+  max_queue.Push(10);
+  max_queue.Push(6);
+  NS_ABORT_IF_FALSE(max_queue.Top() == 10, "Unexpected queue top for max heap");
+  int expected_max[] = { 10, 8, 6, 6, 4, 2 };
+  CheckPopSequence(max_queue, expected_max,
+      sizeof(expected_max) / sizeof(expected_max[0]));
+
+  return 0;
+}