Question

测试错误和承诺。我有类似下面的情况：

public myUtilityMethod(): Promise<string> {
  // some synchronous stuff
  console.log('bla bla');
  // some asynchronous stuff
  return Promise.resolve('ok');
}
public async doSomething(): Promise<void> {
  let promise;
  try {
    promise = this.myUtilityMethod();
  } catch (e) {
    throw new MyError('I knew it', e, {});
  }
  await Promise.all([promise]);
  return Promise.resolve();
}

我想测试一下，当myUtilityMethod的同步部分出现问题时，抛出一个MyError，所以我写了下面的测试

it('should throw MyError when something goes wrong in the synchronous part of myUtilityMethod', fakeAsync(() => {
  // given
  const error = new Error('something went wrong');
  component.myUtilityMethod = sinon.stub().throws(error);
  // when
 expect(() => {
   component.doSomething();
   flushMicrotasks();
 }).toThrow(jasmine.any(MyError));
}));

测试失败，因为

        Error: Expected function to throw <jasmine.any(MyError)>, but it threw Error: Uncaught (in promise): MyError: {"message":"i knew it","nativeError":{},"context":{}}.

我是否遗漏了一些明显的东西？

Answer 1

我认为你的说法是不正确的。您在嘲笑 doSomething 会抛出 new Error('something went wrong')，但您期待的是 MyError。

我会存根 myUtilityMethod 抛出 Error，这样它就会进入您的 catch 块和要遍历的 throw new MyError('I knew it', e, {})。

it('should throw MyError when something goes wrong in the synchronous part of myUtilityMethod', fakeAsync(() => {
  // given
  const error = new Error('something went wrong');
  component.myUtilityMethod = sinon.stub().throws(error); // make myUtilityMethod throw the error
  // when
 expect(() => {
   component.doSomething(); // once myUtilityMethod throws the error, doSomething's catch block will run
   flushMicrotasks();
 }).toThrow(new LabelGenerationError('I knew it', error, {}));
}));

编辑：查看新错误后：

// change this line to back to how it was
.toThrow(jasmine.any(MyError));
// to this
.toThrow(new LabelGenerationError('I knew it', error, {}));

Answer 2

async 函数将它们的所有内容都包装在一个承诺中，因此即使在遇到任何“等待”之前抛出错误，所发生的情况也是承诺拒绝而不是抛出错误。以下测试通过：

  it('test test', (done) => {
    const error = new Error('something went wrong');
    component.myUtilityMethod = sinon.stub().throws(error);

    component.doSomething().catch((e) => {
      expect(e).toEqual(jasmine.any(MyError));
      done();
    });
  });

用茉莉花测试错误和承诺

2 个答案: