在React中使用Jest模拟Axios - 模拟函数未被调用

Question

我正在尝试使用Jest进行单元测试。部分测试是模拟Axios，但由于某种原因它没有被调用。

这是我的/__mocks__/axios.js代码：

export default {
  post: jest.fn(() => Promise.resolve({})),
};

这是我的测试代码：

import mockAxios from 'axios';
import { registerUser } from '../../actions/auth';
import user from '../fixtures/user';


describe('Register User', () => {
  test('Should call register API and redirect to login', async () => {
    const historyMock = { push: jest.fn() };

    mockAxios.post.mockImplementationOnce(() => Promise.resolve());

    await registerUser(user, historyMock);

    expect(mockAxios.post).toHaveBeenCalledTimes(1);

  });
});

这里还有registerUser代码：

export const registerUser = (user, history) => dispatch => axios
  .post('/users/register', user)
  .then(() => history.push('/login'))
  .catch((err) => {
    dispatch(handleError(err));
  });

但由于某种原因，我继续得到错误：

Register User › Should call register API and redirect to login

    expect(jest.fn()).toHaveBeenCalledTimes(1)

    Expected mock function to have been called one time, but it was called zero times.

      35 |     await registerUser(user, historyMock);
      36 | 
    > 37 |     expect(mockAxios.post).toHaveBeenCalledTimes(1);

任何想法为什么模拟不起作用？

Answer 1

正如@jonrsharpe在评论中指出的那样，registerUser函数正在返回函数：

dispatch => axios
  .post('/users/register', user)
  .then(() => history.push('/login'))
  .catch((err) => {
    dispatch(handleError(err));
  });

因此，为了使其工作，我不得不使用redux-mock-store npm模块来模拟商店。新的测试代码如下：

import mockAxios from 'axios';
import configureMockStore from 'redux-mock-store';
import thunk from 'redux-thunk';

import { setCurrentUser, registerUser } from '../../actions/auth';
import user from '../fixtures/user';

const defaultStoreState = { errors: {}, auth: { isAuthenticated: false, user: {} } };
const createMockStore = configureMockStore([thunk]);

describe('Register User', () => {
  test('Should call register API and redirect to login', (done) => {
    const mockStore = createMockStore(defaultStoreState);
    const historyMock = { push: jest.fn() };

    mockStore.dispatch(registerUser(user, historyMock)).then(() => {
      expect(mockAxios.post).toHaveBeenCalledTimes(1);
      expect(historyMock.push).toHaveBeenCalledTimes(1);
      expect(historyMock.push).toHaveBeenCalledWith('/login');

      done();
    });
  });
});

这给了一个通过测试。

Answer 2

我认为你没有正确设置模拟。

mockAxios.post.mockImplementationOnce

应改为

mockAxios.post = jest.fn().mockResolvedValueOnce('bloofblurg');

然后你可以仔细检查post被调用一次并解决了预期值。

expect(mockAxios.post).resolves.toBe('bloofblurg');

看到

1. https://jestjs.io/docs/en/mock-function-api#mockfnmockresolvedvalueoncevalue
2. https://jestjs.io/docs/en/expect#resolves