How to test chained promises in a jest test?

Question

Below I have a test for my Login actions. I'm mocking a firebase function and want to test if the signIn/signOut functions are called.

The tests pass however I do not see my 2nd console log. Which is this line console.log('store ==>', store);.

it('signIn should call firebase', () => {
  const user = {
    email: '[e-mail]',
    password: 'abd123'
  };

  console.log('111');
  return store.dispatch(signIn(user.email, user.password)).then(() => {
    console.log('222'); // does not reach
    expect(mockFirebaseService).toHaveBeenCalled();
  });
  console.log('333');
});

● login actions › signIn should call firebase

TypeError: auth.signInWithEmailAndPassword is not a function

Action being tested

// Sign in action
export const signIn = (email, password, redirectUrl = ROUTEPATH_DEFAULT_PAGE) => (dispatch) => {
  dispatch({ type: USER_LOGIN_PENDING });

  return firebase
    .then(auth => auth.signInWithEmailAndPassword(email, password))
    .catch((e) => {
      console.error('actions/Login/signIn', e);
      // Register a new user
      if (e.code === LOGIN_USER_NOT_FOUND) {
        dispatch(push(ROUTEPATH_FORBIDDEN));
        dispatch(toggleNotification(true, e.message, 'error'));
      } else {
        dispatch(displayError(true, e.message));
        setTimeout(() => {
          dispatch(displayError(false, ''));
        }, 5000);
        throw e;
      }
    })
    .then(res => res.getIdToken())
    .then((idToken) => {
      if (!idToken) {
        dispatch(displayError(true, 'Sorry, there was an issue with getting your token.'));
      }

      dispatch(onCheckAuth(email));
      dispatch(push(redirectUrl));
    });
};

Full Test

    import configureMockStore from 'redux-mock-store';
import thunk from 'redux-thunk';

// Login Actions
import {
  // onCheckAuth,
  signIn,
  signOut
} from 'actions';

import {
  // USER_ON_LOGGED_IN,
  USER_ON_LOGGED_OUT
} from 'actionTypes';

// String Constants
// import { LOGIN_USER_NOT_FOUND } from 'copy';

const middlewares = [thunk];
const mockStore = configureMockStore(middlewares);

// Mock all the exports in the module.
function mockFirebaseService() {
  return new Promise(resolve => resolve(true));
}

// Since "services/firebase" is a dependency on this file that we are testing,
// we need to mock the child dependency.
jest.mock('services/firebase', () => new Promise(resolve => resolve(true)));

describe('login actions', () => {
  let store;

  beforeEach(() => {
    store = mockStore({});
  });

  it('signIn should call firebase', () => {
    const user = {
      email: '[e-mail]',
      password: 'abd123'
    };

    console.log('111');
    return store.dispatch(signIn(user.email, user.password)).then(() => {
      console.log('222'); // does not reach
      expect(mockFirebaseService).toHaveBeenCalled();
    });
    console.log('333');
  });

  it('signOut should call firebase', () => {
    console.log('signOut should call firebasew');
    store.dispatch(signOut()).then(() => {
      expect(mockFirebaseService).toHaveBeenCalled();
      console.log('store ==>', store);
      expect(store.getActions()).toEqual({
        type: USER_ON_LOGGED_OUT
      });
    });
    console.log('END');
  });
});

Answer 1

You have 2 issues here,

The tests pass however I do not see my 2nd console log. Which is this line console.log('store ==>', store);.

That is because the test is not waiting for the promise to fulfill, so you should return it:

it('signOut should call firebase', () => {
    console.log('signOut should call firebasew');
    return store.dispatch(signOut()).then(() => { // NOTE we return the promise
      expect(mockFirebaseService).toHaveBeenCalled();
      console.log('store ==>', store);
      expect(store.getActions()).toEqual({
        type: USER_ON_LOGGED_OUT
      });
      console.log('END');
    });

  });

You can find examples in redux official docs.

Secondly, your signIn test failing because you have mocked wrong firebase:

jest.mock('services/firebase', () => new Promise(resolve => resolve(true)));

That should probably look more like:

jest.mock('services/firebase', () => new Promise(resolve => resolve({
    signInWithEmailAndPassword: () => { return { getIdToken: () => '123'; } }
})));

Answer 2

Login actions › signIn should call firebase

TypeError: auth.signInWithEmailAndPassword is not a function

This tells that your store.dispatch(signIn(user.email, user.password)) fails, thus your second console.log won't go into your then chain, use catch or second callback argument of then instead.