How do I test axios in jest

I have this action in react

export function fetchPosts() {
    const request = axios.get(`${WORDPRESS_URL}`);
    return {
        type: FETCH_POSTS,
        payload: request
    }
}

How do I test axios in this case? Jest have this use case on there site for async code where they use a mock function but I don't know if I can do this with axios? ref: https://facebook.github.io/jest/docs/tutorial-async.html

I have done this so far to test that it is returning the correct type

it('should dispatch actions with the correct type', () => {
    store.dispatch(fetchPosts());
    let action = store.getActions();
    expect(action[0].type).toBe(FETCH_POSTS);
});

I have no idea how to pass in mock data and test that it returns however, has anyone got any ideas?

Thank you in advance

Answers:

Answer

I used axios-mock-adapter. In this case the service is described in ./chatbot. In the mock adapter you specify what to return when the API endpoint is consumed.

import axios from 'axios';
import MockAdapter from 'axios-mock-adapter';
import chatbot from './chatbot';

describe('Chatbot', () => {
    it('returns data when sendMessage is called', done => {
        var mock = new MockAdapter(axios);
        const data = { response: true };
        mock.onGet('https://us-central1-hutoma-backend.cloudfunctions.net/chat').reply(200, data);

        chatbot.sendMessage(0, 'any').then(response => {
            expect(response).toEqual(data);
            done();
        });
    });
});

You can see it the whole example here:

Service: https://github.com/lnolazco/hutoma-test/blob/master/src/services/chatbot.js

Test: https://github.com/lnolazco/hutoma-test/blob/master/src/services/chatbot.test.js

Answer

Without using any other libraries:

import * as axios from "axios";

// Mock out all top level functions, such as get, put, delete and post:
jest.mock("axios");

// ...

test("good response", () => {
  axios.get.mockImplementation(() => Promise.resolve({ data: {...} }));
  // ...
});

test("bad response", () => {
  axios.get.mockImplementation(() => Promise.reject({ ... }));
  // ...
});

It is possible to specify the response code:

axios.get.mockImplementation(() => Promise.resolve({ status: 200, data: {...} }));

It is possible to change the mock based on the parameters:

axios.get.mockImplementation((url) => {
    if (url === 'www.example.com') {
        return Promise.resolve({ data: {...} });
    } else {
        //...
    }
});

Jest v23 introduced some syntactic sugar for mocking Promises:

axios.get.mockImplementation(() => Promise.resolve({ data: {...} }));

can be simplified to

axios.get.mockResolvedValue({ data: {...} });

There is also an equivalent for rejected promises: mockRejectedValue.

See Jest mocking docs for more info. This GitHub discussion explains about the scope of the jest.mock("axios") line.

Answer

I could do that following the steps:

  1. Create a folder __mocks__/ (as pointed by @Januartha comment)
  2. Implement an axios.js mock file
  3. Use my implemented module on test

The mock will happen automatically

Example of the mock module:

module.exports = {
    get: jest.fn((url) => {
        if (url === '/something') {
            return Promise.resolve({
                data: 'data'
            });
        }
    }),
    post: jest.fn((url) => {
        if (url === '/something') {
            return Promise.resolve({
                data: 'data'
            });
        }
        if (url === '/something2') {
            return Promise.resolve({
                data: 'data2'
            });
        }
    }),
    create: jest.fn(function () {
        return this;
    })
};
Answer

I've done this with nock, like so:

import nock from 'nock'
import axios from 'axios'
import httpAdapter from 'axios/lib/adapters/http'

axios.defaults.adapter = httpAdapter

describe('foo', () => {
    it('bar', () => {
        nock('https://example.com:443')
            .get('/example')
            .reply(200, 'some payload')

        // test...
    })
})
Answer

For those looking to use axios-mock-adapter in place of the mockfetch example in the redux documentation for async testing, I successfully utilized the following

actions.test.js:

describe('SignInUser', () => {
  var history = {
    push: function(str) {
        expect(str).toEqual('/feed');
    }
  }

  it('Dispatches authorization', () => {
    let mock = new MockAdapter(axios);
    mock.onPost(`${ROOT_URL}/auth/signin`, { 
        email: '[email protected]', 
        password: 'test'
    }).reply(200, {token: 'testToken' });

    const expectedActions = [ { type: types.AUTH_USER } ];
    const store = mockStore({ auth: [] });

    return store.dispatch(actions.signInUser({ 
      email: '[email protected]', 
      password: 'test',
    }, history)).then(() => {
        expect(store.getActions()).toEqual(expectedActions);
  });

});

In order to test a successful case for signInUser in actions/index.js:

export const signInUser = ({ email, password }, history) => async dispatch => {
  const res = await axios.post(`${ROOT_URL}/auth/signin`, { email, password })
    .catch(({ response: { data } }) => {
        ...
  });

  if (res) {
    dispatch({ type: AUTH_USER });                 // test verified this
    localStorage.setItem('token', res.data.token); // test mocked this
    history.push('/feed');                         // test mocked this
  }
}

Given that this is being done with jest, the localstorage call had to be mocked. This was in src/setupTests.js:

const localStorageMock = {
  removeItem: jest.fn(),
  getItem: jest.fn(),
  setItem: jest.fn(),
  clear: jest.fn()
};
global.localStorage = localStorageMock;

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