Jest Mock 计时器

发表 admin at 2024年8月26日

类别

未分类

标签

测试超时的最大障碍之一是等待超时。Jest提供了一种解决方法。

运行所有定时器

假设您正在测试一个程序，该程序会在一段时间后发出一个事件，但您不想等待该事件实际发出的时间太长。Jest 为您提供了通过setTimeout函数立即运行设置的回调的选项jest.runAllTimers。

// This has to be called before using fake timers.
jest.useFakeTimers();

it('closes some time after being opened.', (done) => {
  // An automatic door that fires a `closed` event.
  const autoDoor = new AutoDoor();
  autoDoor.on('closed', done);
  autoDoor.open();
  // Runs all pending timers. whether it's a second from now or a year.
  jest.runAllTimers();
});

运行定时器到时间

但如果你不想运行所有计时器怎么办？如果你只想模拟一些时间流逝？runTimersToTime就在这里等着你。

jest.useFakeTimers();

it('announces it will close before closing.', (done) => {
  const autoDoor = new AutoDoor();
  // The test passes if there's a `closing` event.
  autoDoor.on('closing', done);
  // The test fails if there's a `closed` event.
  autoDoor.on('closed', done.fail);
  autoDoor.open();
  // Only move ahead enough time so that it starts closing, but not enough that it is closed.
  jest.runTimersToTime(autoDoor.TIME_BEFORE_CLOSING);
});