how to to Mock a Function in Jest Due to Module Circular Dependency
I'm wondering if anyone has experience with I'm experiencing a circular dependency scenario while trying to unit test a module in my Node.js application using Jest... My setup includes two modules, `userService.js` and `notificationService.js`, where `userService` imports `notificationService` to send notifications when users are created. However, when I try to mock `notificationService` in my tests for `userService`, I keep getting a `ReferenceError: want to access 'notificationService' before initialization` behavior. Here’s a simplified version of my code: ```javascript // notificationService.js class NotificationService { sendNotification(user) { // Logic to send notification console.log(`Notification sent to ${user.name}`); } } module.exports = new NotificationService(); ``` ```javascript // userService.js const NotificationService = require('./notificationService'); class UserService { createUser(user) { // Logic to create user NotificationService.sendNotification(user); } } module.exports = new UserService(); ``` In my test file for `userService.js`, I'm trying to mock `sendNotification` like this: ```javascript // userService.test.js const UserService = require('./userService'); const NotificationService = require('./notificationService'); jest.mock('./notificationService'); describe('UserService', () => { it('should send notification when user is created', () => { const user = { name: 'John Doe' }; UserService.createUser(user); expect(NotificationService.sendNotification).toHaveBeenCalledWith(user); }); }); ``` When I run the tests, I get the circular dependency behavior mentioned above. I tried restructuring my imports and using dynamic imports, but the scenario continues. How can I properly mock `notificationService` in my tests without running into this circular dependency question? Any best practices or workarounds would be greatly appreciated! My team is using Javascript for this desktop app. Has anyone dealt with something similar? This is happening in both development and production on Windows 10. I'd love to hear your thoughts on this.