角度异步无法解决超时

Question

看起来 @angular/core/testing 中的 Angular 的 async 在 async 的测试中没有解决超时问题，而 beforeEach 也有 async。 不幸的是，我无法在任何类型的 Plunkr 或 JSFiddle 上重现此错误。

重新创建它的最简单方法是简单地创建一个全新的 Angular CLI 应用并将此代码粘贴到 app.component.spec.ts 中：

import { async } from "@angular/core/testing";

describe("test async", () => {

   let count: number = 0;

   beforeEach(async(() => {
       count++;
       console.log('async before test ' + count);
       setTimeout(() => {
           console.log('timeout before test ' + count);
       }, 1000);
   }))

   it("async test 1", async(() => {
       console.log('starting test 1');
       setTimeout(() => {
           console.log('test 1 finished');
           console.log('expected count: 1, actual count: ' + count);
           expect(count).toBe(1, "should be test 1");
       }, 2000);
   }));

   it("async test 2", async(() => {
       console.log('starting test 2');
       setTimeout(() => {
           console.log('test 2 finished');
           console.log('expected count: 2, actual count: ' + count);
           expect(count).toBe(2, "should be test 2");
       }, 2000);
   }));

   it("async test 3", async(() => {
       console.log('starting test 3');
       setTimeout(() => {
           console.log('test 3 finished');
           console.log('expected count: 3, actual count: ' + count);
           expect(count).toBe(3, "should be test 3");
       }, 2000);
   }));
});

如果您随后运行此测试，您应该会看到如下输出：

async before test 1
timeout before test 1
starting test 1
async before test 2
timeout before test 2
starting test 2
async before test 3
test 1 finished
expected count: 1, actual count: 3
timeout before test 3
starting test 3
test 2 finished
expected count: 2, actual count: 3
test 3 finished
expected count: 3, actual count: 3

但这在我的理解中是不正确的，因为测试中的超时应该在下一个测试开始之前完成，这就是异步的全部意义。

这是正常工作时的输出结果：

async before test 1
timeout before test 1
starting test 1
test 1 finished
expected count: 1, actual count: 1
async before test 2
timeout before test 2
starting test 2
test 2 finished
expected count: 2, actual count: 2
async before test 3
timeout before test 3
starting test 3
test 3 finished
expected count: 3, actual count: 3

任何帮助将不胜感激，谢谢！

Answer 1

在撰写本文时，这是 Angular 的一个错误。我发现 2 张票可以确认这一点：#16647 和 #12115

Answer 2

来自 @angular/core/testing 的异步无法解决异步测试中的超时问题，而 beforeEach 也具有异步功能

async 只解析 Promise 而不是 setTimeout。您可以将 setTimeout 包装在延迟函数中

const delay = (ms) => new Promise(res => setTimeout(res,ms));