How to create Jest mock function with Promise?

Question

I am trying to mock an axios module by create this Promise function

// __mocks__/axios.js
export default function axios() {
  return new Promise((resolve) =>          


        

Answer 1

It looks like you are trying to mock the default export for axios to be a mock function that returns a resolved Promise.

In that case you can create your mock for axios like this:

__mocks__/axios.js

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

...and you can use it in a test like this:

import axios from 'axios';

const func = () => axios();

test('func', async () => {
  const promise = func();
  expect(axios).toHaveBeenCalledTimes(1);  // Success!
  await expect(promise).resolves.toEqual({ data: {} });  // Success!
})

Answer 2

In my tests, I usually just mock axios like this:

import axios from "axios";

jest.mock("axios");
const mockAxios = axios as jest.Mocked<typeof axios>;

Then in your describe block:

beforeEach(() => {
  mockAxios.request.mockImplementationOnce(
    (): Promise<any> => Promise.resolve({ hello: "world" })
  );
});