separate business layer from infrastructure layer before service.spec.js with jest mocks

service.spec.js

import {jest} from '@jest/globals'

import Service from './service';

test('teams with disqualified players cannot check-in', async () => {
  const playerDisqualificationsFindToArray = jest.fn()
    .mockResolvedValueOnce([
      {
        teamID: 'some team id',
        reason: 'was a big meanie'
      }
    ]);
  const playerDisqualificationsFind = jest.fn()
    .mockReturnValueOnce({
      toArray: playerDisqualificationsFindToArray
    });
  const checkInsUpdateOne = jest.fn();
  const db = {
    collection(collection) {
      switch (collection) {
        case 'playerDisqualifications': {
          return {
            find: playerDisqualificationsFind
          };
        }
        case 'checkIns': {
          return {
            updateOne: checkInsUpdateOne
          };
        }
      }
    }
  };

  const service = Service(db);
  await expect(service.checkIn('some team id')).rejects.toThrow();
  expect(playerDisqualificationsFind).toHaveBeenNthCalledWith(1, {teamID: 'some team id'});
  expect(playerDisqualificationsFindToArray).toHaveBeenCalled();
  expect(checkInsUpdateOne).not.toHaveBeenCalled();
});