How to Mock a Method with Conditional Logic in Jest for Unit Testing?
I'm maintaining legacy code that I'm writing unit tests and Hey everyone, I'm running into an issue that's driving me crazy... After trying multiple solutions online, I still can't figure this out. I'm working on a React application using Jest for unit testing, specifically trying to test a component that relies on a method with conditional logic. The method fetches user data based on a user ID and returns different structures based on the user's role. My current implementation looks like this: ```javascript // userService.js export const getUserData = (userId) => { // Assume this function fetches user data from an API const user = fetchUserFromAPI(userId); if (user.role === 'admin') { return { ...user, permissions: 'all' }; } else { return { ...user, permissions: 'limited' }; } }; ``` My test case in Jest is as follows: ```javascript // userService.test.js import { getUserData } from './userService'; import { fetchUserFromAPI } from './api'; jest.mock('./api'); describe('getUserData', () => { it('should return admin user data with all permissions', async () => { fetchUserFromAPI.mockReturnValue({ role: 'admin', name: 'Alice' }); const result = await getUserData(1); expect(result).toEqual({ role: 'admin', name: 'Alice', permissions: 'all' }); }); it('should return regular user data with limited permissions', async () => { fetchUserFromAPI.mockReturnValue({ role: 'user', name: 'Bob' }); const result = await getUserData(2); expect(result).toEqual({ role: 'user', name: 'Bob', permissions: 'limited' }); }); }); ``` However, I'm working with an scenario where the test for the admin user fails with the following message: ``` Expected: { role: 'admin', name: 'Alice', permissions: 'all' } Received: { role: 'admin', name: 'Alice' } ``` It seems like the method is not returning the permissions field in the mock result. I've confirmed the logic in `getUserData` is correct and returns the expected object when called directly. I've tried debugging with console logs and the permissions field is indeed being added, but not in the test. I've also tried using `jest.clearAllMocks()` before each test to ensure I'm not running into state issues between tests, but it hasn't resolved the question. What could be causing this discrepancy in the unit test? Any insights on how to mock this properly or test this conditional logic effectively would be greatly appreciated! My development environment is Windows. This is part of a larger application I'm building. Any help would be greatly appreciated! Thanks for any help you can provide! I'm coming from a different tech stack and learning Javascript.