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时钟

介绍​

准确地模拟时间依赖行为对于验证应用程序的正确性至关重要。使用 时钟 功能，开发人员可以在测试中操作和控制时间，从而能够精确验证诸如渲染时间、超时、计划任务等功能，而不会受到实时执行的延迟和变化的影响。

该 时钟 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：初始化时钟，并允许您
    • pauseAt：在特定时间暂停时间。
    • fastForward：快进时间。
    • runFor：运行特定时间段的时间。
    • resume：恢复时间。
  • setSystemTime：设置当前系统时间。

建议的方法是使用setFixedTime将时间设置为特定值。如果这并不适合您的用例，您可以使用install，它允许您稍后暂停时间、快进时间等等。setSystemTime仅推荐用于高级用例。

注意

page.clock 覆盖与时间相关的本机全局类和函数，允许手动控制它们

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

使用预定义时间进行测试​

通常您只需要伪造Date.now，同时保持计时器运行。这样时间就会自然流动，但Date.now始终返回一个固定值。

<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值不随时间变化时会感到困惑。在这种情况下，您可以在测试时安装时钟并快进到感兴趣的时间。

<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("https://127.0.0.1:3333")

# 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")

测试不活动监视​

不活动监视是 Web 应用程序中的一项常见功能，它会在用户一段时间不活动后注销用户。测试此功能可能很棘手，因为您需要等待很长时间才能看到效果。借助时钟，您可以加快时间并快速测试此功能。

<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("https://127.0.0.1:3333")
# 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()

手动逐个时间段地计时，一致地触发所有计时器​

在极少数情况下，您可能希望手动逐个时间段地计时，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("https://127.0.0.1:3333")
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")