Question 177075 in Javascript Question posted in
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Can Jest & Typescript mock a named export from a local file & verify the mock is called?

I’m trying to test a custom hook, that fetches some token from the API.
The ../api is my own module. Both files are in the same directory

// useTokenHook.tsx
import { getToken } from '../api';

const someVariable = useSelector();
useEffect(() => {
  const asyncWrapper = async () => {
    const token = await getToken()
    // do some stuff with token
  }
  asyncWrapper();
}, [someVariable]);

I’m trying to test it using jest and RTL

// useTokenHook.test.tsx
const getTokenMock = jest.fn();

jest.mock('../api', () => ({
  getToken: () => getTokenMock,
}));

describe('x', () => {
  it('should work', () => {
    renderHook(() => { useTokenHook(); },{ wrapper });

    expect(getTokenMock).toBeCalledTimes(1);
  });
});

I get the error:

    Expected number of calls: 1
    Received number of calls: 0

Without the mock, I can see that the original getToken method gets called. I would assume the mock should also be called, but at least jest doesn’t say so.
I tried adding async to it() callback but the result is the same

Tags:

2

Answers


  1. Chosen as BEST ANSWER
    0

    Based on RAllen answer I came up with the following:

    // useTokenHook.test.tsx
import * as api from '../api';

jest.mock("../api");

describe('x', () => {
  it('should work', () => {
    const getTokenSpy = jest.spyOn(api, 'getToken')

    renderHook(() => { useTokenHook(); },{ wrapper });

    expect(getTokenSpy).toBeCalledTimes(1);
  });
});

    Which solves my problem


  2. 0

    Try to use the following approach. Notice that there is no wrapper around getToken call. The code is obviously not tested but the concept should work.

    // useTokenHook.tsx
import { getToken } from '../api';

const someVariable = useSelector();
useEffect(async () => {
    const token = await getToken()
    // do some stuff with token
}, [someVariable]);

    And then the test:

    // useTokenHook.test.tsx
import * as api from '../api';

jest.mock("../api");
api.getToken = jest.fn().mockImplementation(() => {
 return "the token";
});

describe('x', () => {
  it('should work', () => {
    renderHook(() => { useTokenHook(); },{ wrapper });

    expect(api.getToken).toBeCalledTimes(1);
  });
});
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