unit-testing - Mock axios with axios-mock-adapter get undefined resp

Question

I created an axios instance ...

// api/index.js

const api = axios.create({
  baseURL: '/api/',
  timeout: 2500,
  headers: { Accept: 'application/json' },
});
export default api;

And severals modules use it ..

// api/versions.js

import api from './api';

export function getVersions() {
  return api.get('/versions');
}

I try to test like ..

// Test
import { getVersions } from './api/versions';

const versions= [{ id: 1, desc: 'v1' }, { id: 2, desc: 'v2' }];
mockAdapter.onGet('/versions').reply(200, versions);

getVersions.then((resp) => { // resp is UNDEFINED?
  expect(resp.data).toEqual(versions);
  done();
});

Why resp is undefined?

Answer 1

Two things to try here:

1. Maybe you already have this elsewhere in your code, but be sure to set up mockAdaptor:

import axios from 'axios';
import MockAdapter from 'axios-mock-adapter';

const mockAdapter = new MockAdapter(axios);

2. I haven't found a way to get the mock adapter working when the function you are testing uses 'axios.create' to set up a new axios instance. Try something along the lines of this instead:

// api/index.js

const api = {
  get(path) {
    return axios.get('/api' + path)
    .then((response) => {
        return response.data;
    });
  }
}
export default api;

Answer 2

For anyone still struggling with this.

You need to make sure you iniatilise your MockAdapter outside a test body.

ie. ❌ Incorrect ❌</p>

it('should do a thing', () => {
    const mockAdapter = new MockAdapter(axios);
})

✅ Correct ✅</p>

const mockAdapter = new MockAdapter(axios);

it('should pass' () => {})

Answer 3

according to James M. advice, I updated my api/index.js , not using the axios.create...

api/index.js

import http from 'axios'

export default {

  fetchShoppingLists: () => {
    console.log('API FETCH SHOPPINGLISTS')
    return http
      .get('http://localhost:3000/shoppinglists')
      .then(response => {
        return response
      })
      .catch(error => {
        console.log('FETCH ERROR: ', error)
      })
  }
}

Answer 4

You don't need axios-mock-adapter. Here is how I mock my axios:

// src/__mocks__/axios.ts

const mockAxios = jest.genMockFromModule('axios')

// this is the key to fix the axios.create() undefined error!
mockAxios.create = jest.fn(() => mockAxios)

export default mockAxios