How to isolate unit tests from external API calls in a Node.js application using Jest?
After trying multiple solutions online, I still can't figure this out. I'm collaborating on a project where Quick question that's been bugging me - I'm working on a Node.js application that interacts with an external API to fetch user details. I've implemented unit tests using Jest, but I'm struggling with how to isolate these tests from making real API calls, as they lead to flaky tests and increased execution time. In my test, I want to mock the API response instead of hitting the actual endpoint. Here’s a snippet of my code that makes the API call: ```javascript const axios = require('axios'); async function getUserData(userId) { const response = await axios.get(`https://api.example.com/users/${userId}`); return response.data; } ``` For the test, I originally tried to mock the Axios module like this: ```javascript const axios = require('axios'); const { getUserData } = require('./user'); jest.mock('axios'); test('fetches successfully data from an API', async () => { const userId = 1; const userData = { id: 1, name: 'John Doe' }; axios.get.mockResolvedValue({ data: userData }); const result = await getUserData(userId); expect(result).toEqual(userData); }); ``` But I keep working with the behavior `TypeError: want to read property 'get' of undefined`. I’ve ensured that Jest is properly mocking Axios but still need to figure out why it’s undefined. I’ve also checked that I’m not importing Axios in a different way. I’m using Jest 27.0.6 and Axios 0.21.1. Is there a specific Jest configuration I might be missing, or perhaps I need to structure my imports differently to avoid this scenario? Any guidance on isolating these tests would be much appreciated! My development environment is Linux. What am I doing wrong? I'm using Javascript 3.9 in this project. For reference, this is a production web app. Any suggestions would be helpful.