Implemented ScopedFakeTime, faking rtc::TimeNanos.

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.
  */
 
 #include "webrtc/base/common.h"
 #include "webrtc/base/gunit.h"
 #include "webrtc/base/helpers.h"
 #include "webrtc/base/thread.h"
 #include "webrtc/base/timeutils.h"
+#include "webrtc/base/faketime.h"
 
 namespace rtc {
 
 TEST(TimeTest, TimeInMs) {
   int64_t ts_earlier = TimeMillis();
   Thread::SleepMs(100);
   int64_t ts_now = TimeMillis();
   // Allow for the thread to wakeup ~20ms early.
   EXPECT_GE(ts_now, ts_earlier + 80);
   // Make sure the Time is not returning in smaller unit like microseconds.
@@ skipping 172 matching lines @@
       EXPECT_TRUE(rtc::TmToSeconds(tm) == t);
 #endif
     }
   }
 };
 
 TEST_F(TmToSeconds, TestTmToSeconds) {
   TestTmToSeconds(100000);
 }
 
+TEST(FakeTime, TestScoping) {
+  static const uint64_t kMaxDuration = rtc::kNumNanosecsPerSec;
+  uint64_t before = rtc::TimeNanos();
+  {
+    test::ScopedFakeTime fake_time(10000);
+    EXPECT_EQ(rtc::TimeNanos(), 10000u);
+    fake_time.AdvanceTime(15);
+    EXPECT_EQ(rtc::TimeNanos(), 10015u);
+  }
+  {
+    test::ScopedFakeTime fake_time;
+    uint64_t t = rtc::TimeNanos();
+    EXPECT_LE(before, t);
+    EXPECT_LE(t, before + kMaxDuration);
+    fake_time.AdvanceTime(17);
+    EXPECT_EQ(rtc::TimeNanos(), t + 17);
+  }
+
+  uint64_t after = rtc::TimeNanos();
+  EXPECT_LE(before, after);
+  EXPECT_LE(after - before, kMaxDuration);
+}
+
 }  // namespace rtc