角度测试:使用 fakeAsync 和 async/await

问题描述

Angular Material 提供用于测试的组件线束，让您可以与其交互await 承诺的组件，像这样:

Angular Material provides component harnesses for testing, which lets you interact with their components by awaiting promises, like this:

  it('should click button', async () => {
    const matButton = await loader.getHarness(MatButtonHarness);
    await matButton.click();
    expect(...);
  });

但是如果按钮点击触发延迟操作怎么办?通常我会使用 fakeAsync()/tick() 来处理它:

But what if the button click triggers a delayed operation? Normally I would use fakeAsync()/tick() to handle it:

  it('should click button', fakeAsync(() => {
    mockService.load.and.returnValue(of(mockResults).pipe(delay(1000)));
    // click button
    tick(1000);
    fixture.detectChanges();
    expect(...);
  }));

但是有什么办法可以在同一个测试中同时做这两项吗?

But is there any way I can do both in the same test?

将 async 函数包装在 fakeAsync() 中给我错误:代码应该在 fakeAsync 区域中运行以调用此函数"，大概是因为一旦它完成一个 await，它不再是我传递给 fakeAsync() 的同一个函数.

Wrapping the async function inside fakeAsync() gives me "Error: The code should be running in the fakeAsync zone to call this function", presumably because once it finishes an await, it's no longer in the same function I passed to fakeAsync().

我是否需要做这样的事情——在等待之后启动一个 fakeAsync 函数?或者有更优雅的方式吗?

Do I need to do something like this -- starting a fakeAsync function after the await? Or is there a more elegant way?

  it('should click button', async () => {
    mockService.load.and.returnValue(of(mockResults).pipe(delay(1000)));
    const matButton = await loader.getHarness(MatButtonHarness);

    fakeAsync(async () => {
      // not awaiting click here, so I can tick() first
      const click = matButton.click();
      tick(1000);
      fixture.detectChanges();
      await click;
      expect(...);
    })();
  });

推荐答案

fakeAsync(async () => {...}) 是一个有效的结构.

此外，Angular Material 团队是 明确测试此场景.

Moreover, Angular Material team is explicitly testing this scenario.

it('should wait for async operation to complete in fakeAsync test', fakeAsync(async () => {
        const asyncCounter = await harness.asyncCounter();
        expect(await asyncCounter.text()).toBe('5');
        await harness.increaseCounter(3);
        expect(await asyncCounter.text()).toBe('8');
      }));

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