diff -r 000000000000 -r 6474c204b198 xpcom/tests/TestExpirationTracker.cpp
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/xpcom/tests/TestExpirationTracker.cpp	Wed Dec 31 06:09:35 2014 +0100
@@ -0,0 +1,204 @@
+/* -*- 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 <stdlib.h>
+#include <stdio.h>
+#include <prthread.h>
+#include "nsExpirationTracker.h"
+#include "nsMemory.h"
+#include "nsAutoPtr.h"
+#include "nsString.h"
+#include "nsDirectoryServiceDefs.h"
+#include "nsDirectoryServiceUtils.h"
+#include "nsComponentManagerUtils.h"
+#include "nsXPCOM.h"
+#include "nsIFile.h"
+#include "prinrval.h"
+#include "nsThreadUtils.h"
+
+namespace TestExpirationTracker {
+
+struct Object {
+  Object() : mExpired(false) { Touch(); }
+  void Touch() { mLastUsed = PR_IntervalNow(); mExpired = false; }
+
+  nsExpirationState mExpiration;
+  nsExpirationState* GetExpirationState() { return &mExpiration; }
+
+  PRIntervalTime mLastUsed;
+  bool           mExpired;
+};
+
+static bool error;
+static uint32_t periodMS = 100;
+static uint32_t ops = 1000;
+static uint32_t iterations = 2;
+static bool logging = 0;
+static uint32_t sleepPeriodMS = 50;
+static uint32_t slackMS = 20; // allow this much error
+
+static void SignalError() {
+  printf("ERROR!\n");
+  error = true;
+}
+
+template <uint32_t K> class Tracker : public nsExpirationTracker<Object,K> {
+public:
+  Tracker() : nsExpirationTracker<Object,K>(periodMS) {
+    Object* obj = new Object();
+    mUniverse.AppendElement(obj);
+    LogAction(obj, "Created");
+  }
+
+  nsTArray<nsAutoArrayPtr<Object> > mUniverse;
+
+  void LogAction(Object* aObj, const char* aAction) {
+    if (logging) {
+      printf("%d %p(%d): %s\n", PR_IntervalNow(),
+             static_cast<void*>(aObj), aObj->mLastUsed, aAction);
+    }
+  }
+
+  void DoRandomOperation() {
+    Object* obj;
+    switch (rand() & 0x7) {
+    case 0: {
+      if (mUniverse.Length() < 50) {
+        obj = new Object();
+        mUniverse.AppendElement(obj);
+        nsExpirationTracker<Object,K>::AddObject(obj);
+        LogAction(obj, "Created and added");
+      }
+      break;
+    }
+    case 4: {
+      if (mUniverse.Length() < 50) {
+        obj = new Object();
+        mUniverse.AppendElement(obj);
+        LogAction(obj, "Created");
+      }
+      break;
+    }
+    case 1: {
+      obj = mUniverse[uint32_t(rand())%mUniverse.Length()];
+      if (obj->mExpiration.IsTracked()) {
+        nsExpirationTracker<Object,K>::RemoveObject(obj);
+        LogAction(obj, "Removed");
+      }
+      break;
+    }
+    case 2: {
+      obj = mUniverse[uint32_t(rand())%mUniverse.Length()];
+      if (!obj->mExpiration.IsTracked()) {
+        obj->Touch();
+        nsExpirationTracker<Object,K>::AddObject(obj);
+        LogAction(obj, "Added");
+      }
+      break;
+    }
+    case 3: {
+      obj = mUniverse[uint32_t(rand())%mUniverse.Length()];
+      if (obj->mExpiration.IsTracked()) {
+        obj->Touch();
+        nsExpirationTracker<Object,K>::MarkUsed(obj);
+        LogAction(obj, "Marked used");
+      }
+      break;
+    }
+    }
+  }
+  
+protected:
+  void NotifyExpired(Object* aObj) {
+    LogAction(aObj, "Expired");
+    PRIntervalTime now = PR_IntervalNow();
+    uint32_t timeDiffMS = (now - aObj->mLastUsed)*1000/PR_TicksPerSecond();
+    // See the comment for NotifyExpired in nsExpirationTracker.h for these
+    // bounds
+    uint32_t lowerBoundMS = (K-1)*periodMS - slackMS;
+    uint32_t upperBoundMS = K*(periodMS + sleepPeriodMS) + slackMS;
+    if (logging) {
+      printf("Checking: %d-%d = %d [%d,%d]\n",
+             now, aObj->mLastUsed, timeDiffMS, lowerBoundMS, upperBoundMS);
+    }
+    if (timeDiffMS < lowerBoundMS || timeDiffMS > upperBoundMS) {
+      if (timeDiffMS < periodMS && aObj->mExpired) {
+        // This is probably OK, it probably just expired twice
+      } else {
+        SignalError();
+      }
+    }
+    aObj->Touch();
+    aObj->mExpired = true;
+    DoRandomOperation();
+    DoRandomOperation();
+    DoRandomOperation();
+  }
+};
+
+template <uint32_t K> static bool test_random() {
+  srand(K);
+  error = false;
+ 
+  for (uint32_t j = 0; j < iterations; ++j) {
+    Tracker<K> tracker;
+
+    uint32_t i = 0;
+    for (i = 0; i < ops; ++i) {
+      if ((rand() & 0xF) == 0) {
+        // Simulate work that takes time
+        if (logging) {
+          printf("SLEEPING for %dms (%d)\n", sleepPeriodMS, PR_IntervalNow());
+        }
+        PR_Sleep(PR_MillisecondsToInterval(sleepPeriodMS));
+        // Process pending timer events
+        NS_ProcessPendingEvents(nullptr);
+      }
+      tracker.DoRandomOperation();
+    }
+  }
+  
+  return !error;
+}
+
+static bool test_random3() { return test_random<3>(); }
+static bool test_random4() { return test_random<4>(); }
+static bool test_random8() { return test_random<8>(); }
+
+typedef bool (*TestFunc)();
+#define DECL_TEST(name) { #name, name }
+
+static const struct Test {
+  const char* name;
+  TestFunc    func;
+} tests[] = {
+  DECL_TEST(test_random3),
+  DECL_TEST(test_random4),
+  DECL_TEST(test_random8),
+  { nullptr, nullptr }
+};
+
+}
+
+using namespace TestExpirationTracker;
+
+int main(int argc, char **argv) {
+  int count = 1;
+  if (argc > 1)
+    count = atoi(argv[1]);
+
+  if (NS_FAILED(NS_InitXPCOM2(nullptr, nullptr, nullptr)))
+    return -1;
+
+  while (count--) {
+    for (const Test* t = tests; t->name != nullptr; ++t) {
+      printf("%25s : %s\n", t->name, t->func() ? "SUCCESS" : "FAILURE");
+    }
+  }
+  
+  NS_ShutdownXPCOM(nullptr);
+  return 0;
+}