Improving the fake clock and using it to fix a flaky STUN timeout test.

webrtc/base/timeutils_unittest.cc

 /*
  *  Copyright 2004 The WebRTC Project Authors. All rights reserved.
  *
  *  Use of this source code is governed by a BSD-style license
  *  that can be found in the LICENSE file in the root of the source
  *  tree. An additional intellectual property rights grant can be found
  *  in the file PATENTS.  All contributing project authors may
  *  be found in the AUTHORS file in the root of the source tree.
  */
 
@@ skipping 341 matching lines @@
 
   Thread worker;
   worker.Start();
 
   // Post an event that won't be executed for 10 seconds.
   Event message_handler_dispatched(false, false);
   auto functor = [&message_handler_dispatched] {
     message_handler_dispatched.Set();
   };
   FunctorMessageHandler<void, decltype(functor)> handler(functor);
-  worker.PostDelayed(10000, &handler);
+  worker.PostDelayed(60000, &handler);
 
   // Wait for a bit for the worker thread to be started and enter its socket
-  // select().
+  // select(). Otherwise this test would be trivial since the worker thread
+  // would process the event as soon as it was started.
   Thread::Current()->SleepMs(1000);

[tommi, 2016/06/02 07:59:01]

A whole second seems like a lot.  Can we synchronize somehow instead?

[Taylor Brandstetter, 2016/06/02 17:19:54]

I picked a long time so that it's guaranteed to be long enough for a thread to
start. There's no way to synchronize unless we expose more of the thread's
current state; the goal is to make sure it's in a socket select(), but there's
no easy way to tell that.

 
   // Advance the fake clock, expecting the worker thread to wake up
-  // and dispatch the message quickly.
-  clock.AdvanceTime(TimeDelta::FromSeconds(10u));
-  message_handler_dispatched.Wait(Event::kForever);
+  // and dispatch the message instantly.
+  clock.AdvanceTime(TimeDelta::FromSeconds(60u));
+  EXPECT_TRUE(message_handler_dispatched.Wait(0));
   worker.Stop();
 
   SetClock(nullptr);
 
-  // The message should have been dispatched long before the 10 seconds fully
-  // elapsed.
+  // The message should have been dispatched long before the 60 seconds fully
+  // elapsed (just a sanity check).
   int64_t real_end_time_ms = TimeMillis();
-  EXPECT_LT(real_end_time_ms - real_start_time_ms, 2000);
+  EXPECT_LT(real_end_time_ms - real_start_time_ms, 10000);
 }
 
 }  // namespace rtc