chrome/common/thread_profiler_unittest.cc

// Copyright 2018 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 "chrome/common/thread_profiler.h"

#include "base/macros.h"
#include "base/test/bind_test_util.h"
#include "base/time/time.h"
#include "testing/gtest/include/gtest/gtest.h"

TEST(ThreadProfilerTest, PeriodicSamplingScheduler) {
  // Initialized to the "zero" time.
  const base::TimeTicks start_time;
  const base::TimeTicks artificial_now =
      start_time - base::TimeDelta::FromSeconds(1000);
  double rand_double = 0.0;
  const base::TimeDelta sampling_duration = base::TimeDelta::FromSeconds(30);
  const double fraction_of_execution_time_to_sample = 0.01;

  const base::TimeDelta expected_period =
      sampling_duration / fraction_of_execution_time_to_sample;

  class Scheduler : public PeriodicSamplingScheduler {
   public:
    Scheduler(base::TimeDelta sampling_duration,
              double fraction_of_execution_time_to_sample,
              base::TimeTicks start_time,
              const base::TimeTicks* now_value,
              const double* rand_double_value)
        : PeriodicSamplingScheduler(sampling_duration,
                                    fraction_of_execution_time_to_sample,
                                    start_time),
          rand_double_value_(rand_double_value),
          now_value_(now_value) {}

    double RandDouble() const override { return *rand_double_value_; }
    base::TimeTicks Now() const override { return *now_value_; }

   private:
    const double* rand_double_value_;
    const base::TimeTicks* now_value_;

    DISALLOW_COPY_AND_ASSIGN(Scheduler);
  };

  Scheduler scheduler(sampling_duration, fraction_of_execution_time_to_sample,
                      start_time, &artificial_now, &rand_double);

  // The first collection should be exactly at the start time, since the random
  // value is 0.0.
  EXPECT_EQ(base::TimeDelta::FromSeconds(1000),
            scheduler.GetTimeToNextCollection());

  // With a random value of 1.0 the second collection should be at the end of
  // the second period.
  rand_double = 1.0;
  EXPECT_EQ(base::TimeDelta::FromSeconds(1000) + 2 * expected_period -
                sampling_duration,
            scheduler.GetTimeToNextCollection());

  // With a random value of 0.25 the second collection should be a quarter into
  // the third period exclusive of the sampling duration.
  rand_double = 0.25;
  EXPECT_EQ(base::TimeDelta::FromSeconds(1000) + 2 * expected_period +
                0.25 * (expected_period - sampling_duration),
            scheduler.GetTimeToNextCollection());
}