Each mock should be wrapped in jest.fn

[erheron]

Why it is needed?

Currently, in mock, functions are mocked like this:

export const getCalendar = () => "gregorian"; // the calendar identifier you want
...

So every mock is just a simple function, not e.g. a jest mock
It makes it really hard to overwrite values of those mocks, cause one is unable to write a code like this:

import { getCalendar } from `react-native-localize';

describe('Test how `getCalendar` values influence my function foo', () => {
 beforeEach(jest.resetAllMocks);

 test('If `getCalendar` returns 'gregorian', we return "cool", () => {
   getCalendar.mockImplementation(() => "cool");
   expect(foo()).toEqual("awesome");
 });


 test('If `getCalendar` returns 'chinese', we return "nice", () => {
   getCalendar.mockImplementation(() => "chinese");
   expect(foo()).toEqual("nice");
 });
});

The issue here is that getCalendar is not a mock, but a function, so getCalendar.mockImplementation will not exist in runtime. In our project, we've found that we should either split two tests above to each be in a separate file, and use jest.mock at that file top-level (which you imagine is a bit weird way to write collocated tests), or that we need to overwrite provided mock with code like this put at the top of the file:

jest.mock('react-native-localize', () => {
   const actualMock = jest.requireActual('react-native-localize/mock');
   return {
      ...actualMock,
      getCalendar: jest.fn()
   }
}

and then proceed as above, which is also not desired (although it works)

Why don't we simply wrap every mock function in jest.fn?
I can see that you maybe don't want to have a dependency on jest and allow people to use other test runners as well -- is that the reason?

Possible implementation

That would be really simple -- we'd just need to make changes like this across mock/index.ts
If there's a support for this, I can submit a PR

-- export const getCurrencies = () => ["USD", "EUR"]; // can be empty array
++ export const getCurrencies = jest.fn(() => ["USD", "EUR"]); // can be empty array

This was also mentioned in another issue -- see here

Code sample

See above

[erheron]

Hey @zoontek btw, I think we've met in Paris last year, for drinks with Matthias and your female friend from work 😆

[zoontek]

No problem, open a PR, I will release it.

[erheron]

Hey @zoontek please see #267