How to effectively test asynchronous functions in Jest with mocked API calls?
I'm working on a project and hit a roadblock. I've been banging my head against this for hours. I'm currently working on a Node.js application using Express and I need to test an asynchronous function that makes a call to an external API. I'm using Jest for my unit tests, and I've run into some issues with mocking the API calls correctly. Here's a simplified version of my function: ```javascript const axios = require('axios'); async function fetchData(url) { const response = await axios.get(url); return response.data; } ``` And here's how I'm trying to test it: ```javascript jest.mock('axios'); const { fetchData } = require('./path/to/your/module'); test('fetchData returns data successfully', async () => { const data = { data: 'some data' }; axios.get.mockResolvedValue(data); const result = await fetchData('https://api.example.com/data'); expect(result).toEqual('some data'); }); ``` However, when I run the test, I get the following behavior: ``` TypeError: want to read properties of undefined (reading 'data') ``` It seems like the `axios.get` mock is not returning the expected structure. I've tried different variations of the mock return value but nothing seems to work. I also checked that the Jest version is up to date (`27.0.6`), and I'm using `axios` version `0.21.1`. I would appreciate any guidance on how to properly mock the API response to avoid this behavior and ensure that my test passes. Has anyone else encountered this?