chromium/components/system_cpu/pressure_test_support.h

// Copyright 2021 The Chromium Authors
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.

#ifndef COMPONENTS_SYSTEM_CPU_PRESSURE_TEST_SUPPORT_H_
#define COMPONENTS_SYSTEM_CPU_PRESSURE_TEST_SUPPORT_H_

#include <stdint.h>

#include <optional>
#include <type_traits>
#include <utility>
#include <vector>

#include "base/functional/callback_forward.h"
#include "base/memory/weak_ptr.h"
#include "base/synchronization/lock.h"
#include "base/test/test_future.h"
#include "base/thread_annotations.h"
#include "base/time/time.h"
#include "components/system_cpu/cpu_probe.h"
#include "components/system_cpu/cpu_sample.h"

namespace system_cpu {

// Test double for platform specific CpuProbe that stores the CpuSample in
// a TestFuture.
template <typename T,
          typename = std::enable_if_t<std::is_base_of_v<CpuProbe, T>>>
class FakePlatformCpuProbe : public T {
 public:
  template <typename... Args>
  explicit FakePlatformCpuProbe(Args&&... args)
      : T(std::forward<Args>(args)...) { … }
  ~FakePlatformCpuProbe() override = default;

  // Tests the internals of each platform CPU probe by calling Update() directly
  // instead of using the public interface.
  std::optional<CpuSample> UpdateAndWaitForSample() { … }

 private:
  base::test::TestFuture<std::optional<CpuSample>> sample_;
};

// Test double for CpuProbe that always returns a predetermined value.
class FakeCpuProbe final : public CpuProbe { … };

// Test double for CpuProbe that produces a different value after every
// Update().
class StreamingCpuProbe final : public CpuProbe { … };

}  // namespace system_cpu

#endif  // COMPONENTS_SYSTEM_CPU_PRESSURE_TEST_SUPPORT_H_