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时钟

引言

准确模拟时间相关的行为对于验证应用程序的正确性至关重要。利用时钟 (Clock) 功能,开发人员可以在测试中操纵和控制时间,从而能够精确验证渲染时间、超时、计划任务等功能,而无需经历实时执行的延迟和可变性。

时钟 (Clock) API 提供了以下控制时间的方法:

  • setFixedTime: 设置 Date.now()new Date() 的固定时间。
  • install: 初始化时钟并允许你
    • pauseAt: 在特定时间暂停时间。
    • fastForward: 快进时间。
    • runFor: 按特定持续时间运行时间。
    • resume: 恢复时间。
  • setSystemTime: 设置当前系统时间。

推荐的方法是使用 setFixedTime 将时间设置为一个特定值。如果这不适用于你的用例,你可以使用 install,它允许你稍后暂停时间、快进时间、使其前进(tick)等等。setSystemTime 仅推荐用于高级用例。

注意

page.clock 覆盖原生全局类和函数,使其相关的时间行为可以手动控制

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

如果在测试中的任何时候调用 install,该调用*必须*发生在任何其他时钟相关调用(参阅上面的注意列表)之前。按错误的顺序调用这些方法将导致未定义的行为。例如,你不能先调用 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。

使用预定义时间进行测试

通常你只需要模拟 Date.now,同时让计时器正常运行。这样时间会自然流逝,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

有时你的计时器依赖于 Date.now,并且当 Date.now 的值不随时间变化时会感到困惑。在这种情况下,你可以在测试时安装时钟并快进到你感兴趣的时间。

<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("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 Web 应用程序中的常见功能,用于在用户不活动一段时间后将其注销。测试此功能可能很棘手,因为你需要等待很长时间才能看到效果。借助时钟,你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("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()

手动推进时间,一致地触发所有计时器

在极少数情况下,你可能希望手动推进时间,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")