implementing Jest testing and mocking a Node.js service using axios with TypeScript
Hey everyone, I'm running into an issue that's driving me crazy. I'm following best practices but I'm having trouble testing a service in my Node.js application that makes HTTP requests using axios. My service is written in TypeScript and I'm using Jest for testing. The service looks something like this: ```typescript import axios from 'axios'; export class ApiService { async fetchData(url: string): Promise<any> { const response = await axios.get(url); return response.data; } } ``` I want to write a test for the `fetchData` method, but when I try to mock axios, I'm running into issues. Here's what I've written for the test: ```typescript import { ApiService } from './ApiService'; import axios from 'axios'; jest.mock('axios'); describe('ApiService', () => { it('should fetch data from API', async () => { (axios.get as jest.Mock).mockResolvedValue({ data: { message: 'success' } }); const apiService = new ApiService(); const data = await apiService.fetchData('https://example.com/api/data'); expect(data).toEqual({ message: 'success' }); }); }); ``` However, when I run the test, I get the following behavior: `TypeError: want to read properties of undefined (reading 'get')`. It seems like the mock for axios is not being applied correctly. I've tried updating my Jest configuration and using `jest.clearAllMocks()` before each test, but nothing seems to fix the scenario. I'm using Jest v27.0.6 and TypeScript v4.5.2. Any suggestions on how to properly mock axios in this context and ensure that my tests work as expected? This is for a CLI tool running on CentOS.