Jest spyOn not works

Question

So I have a file that consists of a couple of functions. And I wrote a test for getOpeningHours.

• The getOpeningHours use isLocationOrderAheadAvailable function
• The isLocationOrderAheadAvailable function is not using getOpeningHours so it's not a circular dep issue
• Both getOpeningHours and isLocationOrderAheadAvailable are exported functions
• Both functions came from same file.

import * as locationUtils from './location';
import {
    isLocationOrderAheadAvailable,
    getProductItemsFromMenu,
    resolveOpeningHours,
    getOpenedTimeRanges,
    getOpeningHours,
} from './location';


describe('getOpeningHours', () => {
        it('should return same locationHours if isLocationOrderAheadAvailable is false', () => {
            jest.spyOn(locationUtils, 'isLocationOrderAheadAvailable').mockImplementation(
                jest.fn().mockReturnValue(false)
            );

            const openingHours = getOpeningHours(validLocationEntry);
            expect(openingHours).toEqual(locationHours);
        });
});

So eventually the isLocationOrderAheadAvailable not been mocked at all. The wired thing is that I did exactly the same in a different test and it worked.

Sorry, I can't give a working example of this.

Answer 1

Changing from export function isLocationOrderAheadAvailable(...) to export const isLocationOrderAheadAvailable = (...): => makes jest.spyOn work.

But I still don't understand why. I think it might be connected with JS hoisting but I don't know how jest interacts with it.