How to resolve promise and spy on a function inside axios

Question

function getusers(config){
     const {successCB} = config;
     return axios.get(url, params)
      .then(response => {
        successCB(response.data, config);
      });
}

************************ UT ******************************

const mock = new MockAdapter(axios);
const successCB = jest.fn();

mock.onGet(url).reply(200, 'success');
const axiosSpy = jest.spyOn(axios, 'get');
const successCBSpy = jest.spyOn(config, 'successCB');

getUsers({successCB});

axiosSpy is success from below code

expect(axiosSpy).toHaveBeenCalled();

But it's not reaching inside to resolve with results for successCB

expect(successCBSpy).toHaveBeenCalled();

Throwing error as: successCB never called

What am I doing wrong and what should I expect here?

I am only able to use ES6 solutions only.

Answer 1

Make sure you return the Promise from getusers so you can await it in your test.

Here is a complete working example:

const axios = require('axios');
const MockAdapter = require('axios-mock-adapter');

const url = 'test-url';
const params = {};

function getusers(config) {
  const { successCB } = config;
  return axios.get(url, params)  // <= return the Promise
    .then(response => {
      successCB(response.data, config);
    });
}

test('getusers', async () => {  // <= async test function
  const mock = new MockAdapter(axios);
  const successCB = jest.fn();

  mock.onGet(url).reply(200, 'success');
  const axiosSpy = jest.spyOn(axios, 'get');

  await getusers({ successCB });  // <= await the Promise

  expect(axiosSpy).toHaveBeenCalled();  // Success!
  expect(successCB.mock.calls[0][0]).toBe('success');  // Success!
})

Update

If async/await syntax is not an option then you can do the assertions in a then callback and return the resulting Promise from the test so Jest knows to wait for it:

test('getusers', () => {
  const mock = new MockAdapter(axios);
  const successCB = jest.fn();

  mock.onGet(url).reply(200, 'success');
  const axiosSpy = jest.spyOn(axios, 'get');

  return getusers({ successCB }).then(() => {
    expect(axiosSpy).toHaveBeenCalled();  // Success!
    expect(successCB.mock.calls[0][0]).toBe('success');  // Success!
  });
})