text: // Copyright 2020 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/browser/ash/process_snapshot_server.h"
  
  #include <memory>
  
  #include "base/run_loop.h"
  #include "base/time/time.h"
  #include "content/public/test/browser_task_environment.h"
  #include "testing/gtest/include/gtest/gtest.h"
  
  namespace ash {
  namespace {
  
  // -----------------------------------------------------------------------------
  // TestObserver:
  
  class TestObserver : public ProcessSnapshotServer::Observer {
   public:
    explicit TestObserver(base::TimeDelta desired_refresh_time)
        : ProcessSnapshotServer::Observer(desired_refresh_time) {}
    ~TestObserver() override = default;
  
    base::Time last_refresh_time() const { return last_refresh_time_; }
  
    void WaitForRefresh() {
      if (!refresh_received_) {
        run_loop_ = std::make_unique<base::RunLoop>();
        run_loop_->Run();
        run_loop_.reset();
      }
      refresh_received_ = false;
    }
  
    // ProcessSnapshotServer::Observer:
    void OnProcessSnapshotRefreshed(
        const base::ProcessIterator::ProcessEntries& snapshot) override {
      last_refresh_time_ = base::Time::Now();
      refresh_received_ = true;
  
      if (run_loop_)
        run_loop_->Quit();
    }
  
   private:
    base::Time last_refresh_time_;
    std::unique_ptr<base::RunLoop> run_loop_;
    bool refresh_received_ = false;
  };
  
  // -----------------------------------------------------------------------------
  // ProcessSnapshotServerTest:
  
  class ProcessSnapshotServerTest : public testing::Test {
   public:
    ProcessSnapshotServerTest() = default;
    ProcessSnapshotServerTest(const ProcessSnapshotServerTest&) = delete;
    ProcessSnapshotServerTest& operator=(const ProcessSnapshotServerTest&) =
        delete;
    ~ProcessSnapshotServerTest() override = default;
  
    ProcessSnapshotServer* server() const { return ProcessSnapshotServer::Get(); }
  
   private:
    content::BrowserTaskEnvironment task_environment_;
  };
  
  TEST_F(ProcessSnapshotServerTest, FirstObserverTriggersImmediateRefresh) {
    constexpr base::TimeDelta kDesiredDelay = base::Seconds(20);
    TestObserver observer(kDesiredDelay);
  
    server()->AddObserver(&observer);
    observer.WaitForRefresh();
    EXPECT_LT(base::Time::Now() - observer.last_refresh_time(), kDesiredDelay);
  
    server()->RemoveObserver(&observer);
  }
  
  TEST_F(ProcessSnapshotServerTest, AddRemoveObservers) {
    constexpr base::TimeDelta kDelay1 = base::Seconds(10);
    constexpr base::TimeDelta kDelay2 = base::Seconds(5);
    constexpr base::TimeDelta kDelay3 = base::Seconds(20);
    TestObserver observer1(kDelay1);
    TestObserver observer2(kDelay2);
    TestObserver observer3(kDelay3);
  
    server()->AddObserver(&observer1);
    const auto& timer = server()->GetTimerForTesting();
    EXPECT_TRUE(timer.IsRunning());
    EXPECT_EQ(kDelay1, timer.GetCurrentDelay());
  
    // Adding an observer with a smaller delay updates the timer.
    server()->AddObserver(&observer2);
    EXPECT_EQ(kDelay2, timer.GetCurrentDelay());
  
    // Adding an observer with a larger delay should not change the timer delay.
    server()->AddObserver(&observer3);
    EXPECT_EQ(kDelay2, timer.GetCurrentDelay());
  
    // Removing observers with delay larger than the minimum one shouldn't change
    // the timer delay.
    server()->RemoveObserver(&observer3);
    EXPECT_EQ(kDelay2, timer.GetCurrentDelay());
  
    // Removing the observer with the minimum delay will pick the next minimum.
    server()->RemoveObserver(&observer2);
    EXPECT_EQ(kDelay1, timer.GetCurrentDelay());
  
    // Removing the last observer should stop the timer.
    server()->RemoveObserver(&observer1);
    EXPECT_FALSE(timer.IsRunning());
  }
  
  }  // namespace
  }  // namespace ash
  