在angular2测试中,fakeAsync的tick()和done()有什么区别？

我正在试图弄清楚fakeAsync的tick()方法与done()的区别,正如堆栈溢出上的某些 answers所建议的那样.

使用tick()我们可以模拟超时,但我们可以使用done()完成相同的操作吗？

为什么angular将它视为使用异步或伪同步？

举个例子.

这个方法对我有用……

it("Should display names",(done:any) => {
        component.names = [
            {
                "firstname": "abc","lastname": "max"
            },{
                "firstname": "def",];
        done();
        fixture.detectChanges();
        let wrapBox = fixture.debugElement.queryAll(By.css('.wrapBox'));
        console.log(wrapBox);
});

但是以下方法返回’6个计时器仍在队列中’错误…

it("Should display names",fakeAsync(() => {
        component.names = [
            {
                "firstname": "abc",];
        tick();
        fixture.detectChanges();
        let wrapBox = fixture.debugElement.queryAll(By.css('.wrapBox'));
        console.log(wrapBox);
}));

注意：

>数组名称的数据是异步的,因为它是使用“get”操作从后端检索的.但在这里我嘲笑数据.
>迭代数组中的数据并传递给另一个子组件,该子组件在视图中显示它.

解决方法

这两件事没有任何共同之处.

完成只是一个回调,让你的测试运行器知道异步操作何时完成.

例如：

it('should wait for this promise to finish',done => {
  const p = new Promise((resolve,reject) =>
    setTimeout(() => resolve(`I'm the promise result`),1000)
  );

  p.then(result => {
    // following will display "I'm the promise result" after 1s
    console.log(result);

    // this let your test runner know that it can move forward
    // because we're done here
    // the test will take 1s due to the setTimeout at 1000ms
    done();
  });
});

您也可以使用异步(只是为了避免手动调用)：

it(
  'should wait for this promise to finish',async(() => {
    const p = new Promise((resolve,reject) =>
      setTimeout(() => resolve(`I'm the promise result`),1000)
    );

    p.then(result =>
      // following will display "I'm the promise result" after 1s
      console.log(result)
    );

    // notice that we didn't call `done` here thanks to async
    // which created a special zone from zone.js
    // this test is now aware of pending async operation and will wait
    // for it before passing to the next one
  })
);

现在,fakeAsync可以让你随着时间的推移控制(这真的很强大),所以你可以用同步方式编写测试,并模拟时间过去以避免等待setTimeout,例如：

it(
  'should wait for this promise to finish',fakeAsync(() => {
    const p = new Promise((resolve,1000)
    );

    // simulates time moving forward and executing async tasks
    flush();

    p.then(result =>
      // following will display "I'm the promise result" **instantly**
      console.log(result)
    );

    // notice that we didn't call `done` here has there's no async task pending
  })
);

所以要清楚一点,在上一个例子中使用fakeAsync,如果setTimeout设置为10s,测试仍然会立即执行.