mocking store.getState()

Question

I want to assert that when a function gets my redux state value using store.getState(), it does various things based on the conditions of that state. How am I able to assert / mock what I want the state value to be for certain tests using the store.getState() method? Thanks.

sampleFunction.js:

import { store } from './reduxStore';

const sampleFunction = () => {
  const state = store.getState();
  let result = false;
  if (state.foo.isGood) {
    result = true;
  }

  return result;
};

export default sampleFunction;

sampleFunction.test.js:

import sampleFunction from './sampleFunction.js';

test('sampleFunction returns true', () => {
  // assert that state.foo.isGood = true
  expect(sampleFunction()).toBeTruthy();
});

Answer 1

What you can do to mock your store is

import { store } from './reduxStore';
import sampleFunction from './sampleFunction.js';

jest.mock('./reduxStore')

const mockState = {
  foo: { isGood: true }
}

// in this point store.getState is going to be mocked
store.getState = () => mockState

test('sampleFunction returns true', () => {
  // assert that state.foo.isGood = true
  expect(sampleFunction()).toBeTruthy();
});

Answer 2

import { store } from './reduxStore';
import sampleFunction from './sampleFunction.js';


beforeAll(() => {
jest.mock('./reduxStore')

const mockState = {
  foo: { isGood: true }
}

 // making getState as mock function and returning mock value
 store.getState = jest.fn().mockReturnValue(mockState)

});

afterAll(() => {
 jest.clearAllMocks();
 jest.resetAllMocks();
});

test('sampleFunction returns true', () => {
  // assert that state.foo.isGood = true
  expect(sampleFunction()).toBeTruthy();
});