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时钟

简介​

准确模拟时间相关行为对于验证应用程序的正确性至关重要。利用Clock功能，开发者可以在测试中操纵和控制时间，从而无需实时执行的延迟和变异性，就能精确验证诸如渲染时间、超时、计划任务等特性。

Clock API 提供以下方法来控制时间：

  • setFixedTime: 为Date.now()和new Date()设置固定时间。
  • install: initializes the clock and allows you to:
    • pauseAt: 在特定时间暂停计时。
    • fastForward: 快速前进时间。
    • runFor: 运行特定时长的时间。
    • resume: 恢复时间。
  • setSystemTime: 设置当前系统时间。

推荐的方法是使用setFixedTime将时间设置为特定值。如果这不适用于您的用例，您可以使用install，它允许您稍后暂停时间、快进时间、计时等。setSystemTime仅推荐用于高级用例。

note

page.clock 覆盖了与时间相关的原生全局类和方法，使它们可以被手动控制：

  • Date
  • setTimeout
  • clearTimeout
  • setInterval
  • clearInterval
  • requestAnimationFrame
  • cancelAnimationFrame
  • requestIdleCallback
  • cancelIdleCallback
  • performance
  • Event.timeStamp

warning

如果在测试中的任何时刻调用install，该调用必须在所有其他与时钟相关的调用之前进行（参见上文的注意事项列表）。不按顺序调用这些方法将导致未定义的行为。例如，您不能先调用setInterval，然后调用install，再调用clearInterval，因为install会覆盖时钟函数的原生定义。

使用预设时间进行测试​

通常你只需要模拟Date.now而保持计时器继续运行。这样时间会自然流逝，但Date.now始终返回固定值。

<div id="current-time" data-testid="current-time"></div>
<script>
  const renderTime = () => {
    document.getElementById('current-time').textContent =
        new Date().toLocaleString();
  };
  setInterval(renderTime, 1000);
</script>

一致的时间和计时器​

有时您的计时器依赖于Date.now，当Date.now值随时间推移不发生变化时会感到困惑。在这种情况下，您可以安装时钟并在测试时快进到感兴趣的时间点。

<div id="current-time" data-testid="current-time"></div>
<script>
  const renderTime = () => {
    document.getElementById('current-time').textContent =
        new Date().toLocaleString();
  };
  setInterval(renderTime, 1000);
</script>
# Initialize clock with some time before the test time and let the page load
# naturally. `Date.now` will progress as the timers fire.
page.clock.install(time=datetime.datetime(2024, 2, 2, 8, 0, 0))
page.goto("http://localhost:3333")

# Pretend that the user closed the laptop lid and opened it again at 10am.
# Pause the time once reached that point.
page.clock.pause_at(datetime.datetime(2024, 2, 2, 10, 0, 0))

# Assert the page state.
expect(page.get_by_test_id("current-time")).to_have_text("2/2/2024, 10:00:00 AM")

# Close the laptop lid again and open it at 10:30am.
page.clock.fast_forward("30:00")
expect(page.get_by_test_id("current-time")).to_have_text("2/2/2024, 10:30:00 AM")

测试不活动监控​

不活动监控是网页应用程序中的常见功能，它会在用户一段时间不活动后自动注销。测试这一功能可能会比较棘手，因为您需要等待很长时间才能看到效果。借助时钟功能，您可以加快时间流逝，快速测试这一功能。

<div id="remaining-time" data-testid="remaining-time"></div>
<script>
  const endTime = Date.now() + 5 * 60_000;
  const renderTime = () => {
    const diffInSeconds = Math.round((endTime - Date.now()) / 1000);
    if (diffInSeconds <= 0) {
      document.getElementById('remaining-time').textContent =
        'You have been logged out due to inactivity.';
    } else {
      document.getElementById('remaining-time').textContent =
        `You will be logged out in ${diffInSeconds} seconds.`;
    }
    setTimeout(renderTime, 1000);
  };
  renderTime();
</script>
<button type="button">Interaction</button>
# Initial time does not matter for the test, so we can pick current time.
page.clock.install()
page.goto("http://localhost:3333")
# Interact with the page
page.get_by_role("button").click()

# Fast forward time 5 minutes as if the user did not do anything.
# Fast forward is like closing the laptop lid and opening it after 5 minutes.
# All the timers due will fire once immediately, as in the real browser.
page.clock.fast_forward("05:00")

# Check that the user was logged out automatically.
expect(page.get_by_text("You have been logged out due to inactivity.")).to_be_visible()

手动逐步推进时间，一致触发所有计时器​

在极少数情况下，您可能需要手动推进时间，在此过程中触发所有计时器和动画帧，以实现对时间流逝的精细控制。

<div id="current-time" data-testid="current-time"></div>
<script>
  const renderTime = () => {
    document.getElementById('current-time').textContent =
        new Date().toLocaleString();
  };
  setInterval(renderTime, 1000);
</script>
# Initialize clock with a specific time, let the page load naturally.
page.clock.install(
    time=datetime.datetime(2024, 2, 2, 8, 0, 0, tzinfo=datetime.timezone.pst),
)
page.goto("http://localhost:3333")
locator = page.get_by_test_id("current-time")

# Pause the time flow, stop the timers, you now have manual control
# over the page time.
page.clock.pause_at(datetime.datetime(2024, 2, 2, 10, 0, 0))
expect(locator).to_have_text("2/2/2024, 10:00:00 AM")

# Tick through time manually, firing all timers in the process.
# In this case, time will be updated in the screen 2 times.
page.clock.run_for(2000)
expect(locator).to_have_text("2/2/2024, 10:00:02 AM")