👀 Views: 478 💬 Answers: 1 📅 Created: 2025-07-11

jest node.js mongodb JavaScript

I recently switched to I'm maintaining legacy code that I tried several approaches but none seem to work. I'm currently working with an scenario while writing unit tests for my Node.js API using Jest. My API has an endpoint that retrieves user data from a MongoDB database. The question arises when I try to test the async function that handles this request. I'm getting the behavior: `TypeError: want to read property 'username' of undefined`. Here’s a simplified version of the code for my API handler: ```javascript const getUser = async (req, res) => { const userId = req.params.id; const user = await User.findById(userId); res.json({ username: user.username }); }; ``` In my test file, I mock the database call as shown below: ```javascript const getUser = require('./path/to/getUser'); const User = require('./path/to/userModel'); jest.mock('./path/to/userModel'); describe('GET /user/:id', () => { it('should return user data', async () => { const req = { params: { id: '123' } }; const res = { json: jest.fn() }; User.findById.mockResolvedValueOnce({ username: 'testuser' }); await getUser(req, res); expect(res.json).toHaveBeenCalledWith({ username: 'testuser' }); }); }); ``` I expected the test to pass since I mocked the `findById` method to return a user object. However, I keep getting the behavior, which suggests that my mocked return value might not be reaching the API handler correctly. I’ve double-checked the path for my mock and the import statements in the test file, and they seem fine. Am I missing something in the way I’m mocking the model or structuring the test? Any insights would be appreciated! For context: I'm using Javascript on Linux. How would you solve this? I'm working in a Windows 11 environment. I'm working in a Debian environment. What's the correct way to implement this?