Give access to a network time kept in the variation service.

chrome/browser/metrics/variations/network_time_tracker_unittest.cc

+// Copyright (c) 2013 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#include <math.h>
+
+#include "chrome/browser/metrics/variations/network_time_tracker.h"
+#include "testing/gtest/include/gtest/gtest.h"
+
+namespace {
+
+// These are all in milliseconds.
+const int64 kLatency1 = 50;
+const int64 kLatency2 = 500;
+
+// Can not be smaller than 15, it's the NowFromSystemTime() resolution.
+const int64 kResolution1 = 17;
+const int64 kResolution2 = 177;
+
+const int64 kPseudoSleepTime1 = 500000001;
+const int64 kPseudoSleepTime2 = 1888;
+
+class NetworkTimeTrackerTest : public NetworkTimeTracker {

[Alexei Svitkine (slow), 2013/02/05 02:29:07]

Nit: NetworkTimeTrackerTest -> TestNetworkTimeTracker

The NetworkTimeTrackerTest implies that it's an actual test case class (e.g.
extends an existing test class that has things like SetUp() and TearDown()
methods), whereas this is just a test version of the NetworkTimeTracker class.

[MAD, 2013/02/05 15:56:00]

Done.

+ public:
+  NetworkTimeTrackerTest() : now_(base::Time::NowFromSystemTime()) {
+  }
+
+  void AddToTicksNow(int64 ms) {
+    ticks_now_ += base::TimeDelta::FromMilliseconds(ms);
+  }
+
+  base::Time now() const {
+    return now_ + (ticks_now_ - base::TimeTicks());
+  }
+
+  void ValidateExpectedTime() {
+    base::Time network_time;
+    base::TimeDelta uncertainty;
+    EXPECT_TRUE(GetNetworkTime(&network_time, &uncertainty));
+    EXPECT_LE(fabs(static_cast<double>(now().ToInternalValue() -
+                                       network_time.ToInternalValue())),
+              static_cast<double>(uncertainty.ToInternalValue()));
+  }
+
+ protected:
+  virtual base::TimeTicks GetTicksNow() const { return ticks_now_; }

[Alexei Svitkine (slow), 2013/02/05 02:29:07]

Nits:

- OVERRIDE
- put method body on a new line
- add a blank line before the variable decl

[MAD, 2013/02/05 15:56:00]

Done.

+  base::TimeTicks ticks_now_;
+  base::Time now_;
+};
+
+}  // namespace.
+
+TEST(NetworkTimeTrackerTest, ProperTimeTracking) {
+  NetworkTimeTrackerTest network_time_tracker;
+
+  // Should not return a value before UpdateNetworkTime gets called.
+  base::Time network_time;
+  base::TimeDelta uncertainty;
+  EXPECT_FALSE(network_time_tracker.GetNetworkTime(&network_time,
+                                                   &uncertainty));
+
+  network_time_tracker.UpdateNetworkTime(
+      network_time_tracker.now(),
+      base::TimeDelta::FromMilliseconds(kResolution1),
+      base::TimeDelta::FromMilliseconds(kLatency1));
+  network_time_tracker.ValidateExpectedTime();
+
+  // Fake a wait for kPseudoSleepTime1 to make sure we keep tracking.
+  network_time_tracker.AddToTicksNow(kPseudoSleepTime1);
+  network_time_tracker.ValidateExpectedTime();
+
+  // Update the time with a new now value and kLatency2.
+  network_time_tracker.UpdateNetworkTime(
+      network_time_tracker.now(),
+      base::TimeDelta::FromMilliseconds(kResolution2),
+      base::TimeDelta::FromMilliseconds(kLatency2));
+
+  // Fake a wait for kPseudoSleepTime2 to make sure we keep tracking still.
+  network_time_tracker.AddToTicksNow(kPseudoSleepTime2);
+  network_time_tracker.ValidateExpectedTime();
+}