Fixed flaky StunRequestTests which depended on the wall clock

webrtc/p2p/base/stunrequest_unittest.cc

Index: webrtc/p2p/base/stunrequest_unittest.cc
diff --git a/webrtc/p2p/base/stunrequest_unittest.cc b/webrtc/p2p/base/stunrequest_unittest.cc
index 5fb34a85d263e1ec90e74dd59711e3cb9d97557a..47583b90e8e9072b36a18a3ecfd4059303cb2dda 100644
--- a/webrtc/p2p/base/stunrequest_unittest.cc
+++ b/webrtc/p2p/base/stunrequest_unittest.cc
@@ -9,6 +9,7 @@
  */
 
 #include "webrtc/p2p/base/stunrequest.h"
+#include "webrtc/base/fakeclock.h"
 #include "webrtc/base/gunit.h"
 #include "webrtc/base/helpers.h"
 #include "webrtc/base/logging.h"
@@ -17,12 +18,6 @@
 
 using namespace cricket;
 
-// STUN timeout (with all retries) is 9500ms.
-// Add some margin of error for slow bots.
-// TODO(deadbeef): Use simulated clock instead of just increasing timeouts to
-// fix flaky tests.
-static const int kTimeoutMs = 15000;
-
 class StunRequestTest : public testing::Test,
                         public sigslot::has_slots<> {
  public:
@@ -150,18 +145,19 @@ TEST_F(StunRequestTest, TestUnexpected) {
 // Test that requests are sent at the right times, and that the 9th request
 // (sent at 7900 ms) can be properly replied to.
 TEST_F(StunRequestTest, TestBackoff) {
+  const int MAX_TIMEOUT_MS = 10000;
+  rtc::ScopedFakeClock fake_clock;
   StunMessage* req = CreateStunMessage(STUN_BINDING_REQUEST, NULL);
 
   int64_t start = rtc::TimeMillis();
   manager_.Send(new StunRequestThunker(req, this));
   StunMessage* res = CreateStunMessage(STUN_BINDING_RESPONSE, req);
   for (int i = 0; i < 9; ++i) {
-    while (request_count_ == i)
-      rtc::Thread::Current()->ProcessMessages(1);
+    EXPECT_TRUE_SIMULATED_WAIT(request_count_ != i, MAX_TIMEOUT_MS, fake_clock);
     int64_t elapsed = rtc::TimeMillis() - start;
     LOG(LS_INFO) << "STUN request #" << (i + 1)
                  << " sent at " << elapsed << " ms";
-    EXPECT_GE(TotalDelay(i + 1), elapsed);
+    EXPECT_EQ(TotalDelay(i), elapsed);
   }
   EXPECT_TRUE(manager_.CheckResponse(res));
 
@@ -174,13 +170,15 @@ TEST_F(StunRequestTest, TestBackoff) {
 
 // Test that we timeout properly if no response is received in 9500 ms.
 TEST_F(StunRequestTest, TestTimeout) {
+  rtc::ScopedFakeClock fake_clock;
   StunMessage* req = CreateStunMessage(STUN_BINDING_REQUEST, NULL);
   StunMessage* res = CreateStunMessage(STUN_BINDING_RESPONSE, req);
 
   manager_.Send(new StunRequestThunker(req, this));
-  rtc::Thread::Current()->ProcessMessages(kTimeoutMs);
-  EXPECT_FALSE(manager_.CheckResponse(res));
+  // Simulate the 9500 ms STUN timeout
+  SIMULATED_WAIT(false, 9500, fake_clock);

[honghaiz3, 2016/09/06 22:00:00]

In case that this takes too long to run, it may be OK to use AdvanceTime by
100ms every time, although this is closer to the original test. 

 
+  EXPECT_FALSE(manager_.CheckResponse(res));
   EXPECT_TRUE(response_ == NULL);
   EXPECT_FALSE(success_);
   EXPECT_FALSE(failure_);