如何使用 axios 模拟假 url 进行单元测试？

Question

Context

The URL in this app is only accessible in production and it is not able to access via local. When doing unit tests, I need to mock the response of that url.

What I got

Follow this tutorial

Code I have

saga.js

import {all, call, put, takeEvery} from 'redux-saga/effects';
import axios from 'axios';

async function myfetch(endpoint) {
  const out = await axios.get(endpoint);
  return out.data;
}

function* getItems() {
  //const endpoint = 'https://jsonplaceholder.typicode.com/todos/1';
  const endpoint = 'http://sdfds';
  const response = yield call(myfetch, endpoint);
  const items = response;

  //test
  console.log('items', items);

  yield put({type: 'ITEMS_GET_SUCCESS', items: items});
}

export function* getItemsSaga() {
  yield takeEvery('ITEMS_GET', getItems);
}

export default function* rootSaga() {
  yield all([getItemsSaga()]);
}

You can see that I made endpoint as const endpoint = 'http://sdfds'; , which is not accessible.

saga.test.js

// Follow this tutorial: https://medium.com/@lucaspenzeymoog/mocking-api-requests-with-jest-452ca2a8c7d7
import SagaTester from 'redux-saga-tester';
import mockAxios from 'axios';
import reducer from '../reducer';
import {getItemsSaga} from '../saga';

const initialState = {
  reducer: {
    loading: true,
    items: []
  }
};

const options = {onError: console.error.bind(console)};

describe('Saga', () => {
  beforeEach(() => {
    mockAxios.get.mockImplementationOnce(() => Promise.resolve({key: 'val'}));
  });

  afterEach(() => {
    jest.clearAllMocks();
  });

  it('Showcases the tester API', async () => {
    const sagaTester = new SagaTester({
      initialState,
      reducers: {reducer: reducer},
      middlewares: [],
      options
    });

    sagaTester.start(getItemsSaga);

    sagaTester.dispatch({type: 'ITEMS_GET'});

    await sagaTester.waitFor('ITEMS_GET_SUCCESS');

    expect(sagaTester.getState()).toEqual({key: 'val'});
  });
});

axios.js

const axios = {
  get: jest.fn(() => Promise.resolve({data: {}}))
};
export default axios;

I was hopping this will overwrite the default axios

Full code here

Summary

Need to overwrite default axios' return response.

Answer 1

In order to replace a module, you need to save your mock module in a specific folder structure: https://jestjs.io/docs/en/manual-mocks#mocking-node-modules

So it seems that in your project - https://github.com/kenpeter/test-saga/blob/master-fix/src/ tests /saga.test.js - you need to move the __mocks__ folder the root, where package.json is. Then import axios normally like import mockAxios from 'axios' , and jest should take care of replacing the module.