javascript - Jest : How to mock a promise on the same file for resolve and reject options?

Question

所以我试图测试我的实现的积极和消极方面。如果我这样做:

jest.mock('./apiClient', () => ({
  get: jest.fn((url: string) => Promise.resolve({ data: mockData }))
}));

jest.mock('./apiClient', () => ({
  get: jest.fn().mockImplementation((url: string) => {
    console.log('error result');
    return Promise.reject(mockError);
  })
}));

然后唯一通过的测试将是最后一个声明的。在上述情况下，reject 情况将通过，第一个 mock 将被忽略。

这是我的整个测试:

// @ts-ignore
import ApiClient from './apiClient';
import ApiService from './apiService';

const mockData = {};
const mockError = { message: 'Smth Bad Happened' };

const firstCallback = jest.fn((data: any) => data);
const secondCallback = jest.fn((data: any) => data);

jest.mock('./apiClient', () => ({
  get: jest.fn((url: string) => Promise.resolve({ data: mockData }))
}));

jest.mock('./apiClient', () => ({
  get: jest.fn().mockImplementation((url: string) => {
    console.log('error result');
    return Promise.reject(mockError);
  })
}));

describe('apiService', () => {
  it('should call callbacks consequently', done => {
    ApiService.makeApiCall('testUrl', firstCallback, secondCallback).then(() => {
      expect(firstCallback).toBeCalledTimes(1);
      expect(firstCallback).toBeCalledWith(mockData);

      expect(secondCallback).toBeCalledTimes(1);
      expect(secondCallback).toBeCalledWith(firstCallback(mockData));
      done();
    });
  });

  it('should handle error', done => {
    console.error = jest.fn();
    ApiService.makeApiCall('testUrl', firstCallback, secondCallback).then(() => {
      expect(firstCallback).toBeCalledTimes(0);
      expect(secondCallback).toBeCalledTimes(0);
      expect(console.error).toBeCalledTimes(1);
      expect(console.error).toBeCalledWith('ApiClient testUrl', mockError);
      done();
    });
  });
});

就目前而言，测试通过是 should handle error 这是第二个，但是如果我从

切换位置

jest.mock('./apiClient', () => ({
  get: jest.fn((url: string) => Promise.resolve({ data: mockData }))
}));

jest.mock('./apiClient', () => ({
  get: jest.fn().mockImplementation((url: string) => {
    console.log('error result');
    return Promise.reject(mockError);
  })
}));

到

jest.mock('./apiClient', () => ({
  get: jest.fn().mockImplementation((url: string) => {
    console.log('error result');
    return Promise.reject(mockError);
  })
}));

jest.mock('./apiClient', () => ({
  get: jest.fn((url: string) => Promise.resolve({ data: mockData }))
}));

然后测试通过将是应该调用回调，那么我可以做些什么来模拟 reject 和 resolve 而不会相互干扰？

Answer 1

我在寻找一个好的做法时遇到了这个问题，因为我遇到了同样的问题，但我找到了解决方法来解决这个问题。尽管我想您已经解决了这个问题，但我还是将我的临时解决方案留在这里供 future 的读者使用。

基本上，我在我想拒绝 promise 的测试中覆盖了该方法的模拟实现。

所以我会去掉 describe 声明之前的 reject 实现，并将其添加到 'should handle error' 测试中方式:

ApiClient.get: jest.fn().mockImplementation((url: string) => {
    console.log('error result');
    return Promise.reject(mockError);
})

您的最终测试将如下所示:

// @ts-ignore
import ApiClient from './apiClient';
import ApiService from './apiService';

const mockData = {};
const mockError = { message: 'Smth Bad Happened' };

const firstCallback = jest.fn((data: any) => data);
const secondCallback = jest.fn((data: any) => data);

jest.mock('./apiClient', () => ({
  get: jest.fn((url: string) => Promise.resolve({ data: mockData }))
}));

describe('apiService', () => {
  it('should call callbacks consequently', done => {
    ApiService.makeApiCall('testUrl', firstCallback, secondCallback).then(() => {
      expect(firstCallback).toBeCalledTimes(1);
      expect(firstCallback).toBeCalledWith(mockData);

      expect(secondCallback).toBeCalledTimes(1);
      expect(secondCallback).toBeCalledWith(firstCallback(mockData));
      done();
    });
  });

  it('should handle error', done => {
    ApiClient.get: jest.fn().mockImplementation((url: string) => {
        console.log('error result');
        return Promise.reject(mockError);
    });
    console.error = jest.fn();
    ApiService.makeApiCall('testUrl', firstCallback, secondCallback).then(() => {
      expect(firstCallback).toBeCalledTimes(0);
      expect(secondCallback).toBeCalledTimes(0);
      expect(console.error).toBeCalledTimes(1);
      expect(console.error).toBeCalledWith('ApiClient testUrl', mockError);
      done();
    });
  });
});

我认为这不是最好的方法，但一点也不差，应该适用于这个例子。

我会继续寻找更智能的解决方案。