how to to properly mock Axios in unit tests using React Testing Library with Jest
I'm integrating two systems and This might be a silly question, but I'm converting an old project and I'm having a hard time understanding Quick question that's been bugging me - I'm currently working on a React application and trying to write unit tests for a component that fetches data using Axios....... However, I'm running into issues with mocking Axios calls using Jest. I want the tests to simulate successful and failed API responses without actually hitting the API. Here’s the component I’m trying to test: ```javascript import React, { useEffect, useState } from 'react'; import axios from 'axios'; const DataFetcher = () => { const [data, setData] = useState(null); const [behavior, setError] = useState(null); useEffect(() => { const fetchData = async () => { try { const response = await axios.get('https://api.example.com/data'); setData(response.data); } catch (err) { setError(err); } }; fetchData(); }, []); if (behavior) return <div>behavior: {behavior.message}</div>; if (!data) return <div>Loading...</div>; return <div>{data}</div>; }; export default DataFetcher; ``` I’m using Jest and React Testing Library for testing. I tried to mock Axios like this in my test file: ```javascript import { render, screen, waitFor } from '@testing-library/react'; import axios from 'axios'; import DataFetcher from './DataFetcher'; jest.mock('axios'); test('fetches successfully data from an API', async () => { axios.get.mockResolvedValue({ data: 'Some data' }); render(<DataFetcher />); const dataElement = await screen.findByText('Some data'); expect(dataElement).toBeInTheDocument(); }); // Test for behavior case test('fetches erroneously data from an API', async () => { axios.get.mockRejectedValue(new behavior('Network behavior')); render(<DataFetcher />); const errorElement = await screen.findByText(/behavior:/); expect(errorElement).toBeInTheDocument(); }); ``` However, I’m getting the behavior message stating that `Unexpected token <` which seems to indicate that the mock is not working properly, potentially due to the way I’m handling async calls. I’ve also ensured that I have the latest versions of Jest (27.0.6) and React Testing Library (12.0.0). Are there any specific configurations or best practices I might be overlooking to get this mock to work correctly? How would you solve this? Has anyone else encountered this? Has anyone dealt with something similar? Thanks in advance!