**Course Title:** Testing Frameworks: Principles and Practices **Section Title:** Integration Testing **Topic:** Create integration tests for a multi-component application (Lab topic) ### Overview In this lab, we will explore how to create integration tests for a multi-component application using a testing framework. We will use a real-world scenario to demonstrate the process of writing integration tests and debugging them. ### Prerequisites - Familiarity with a programming language (e.g., JavaScript, Python, Java) - Basic understanding of testing frameworks (e.g., Jest, Mocha, JUnit, NUnit) - Understanding of integration testing and its importance - Prior experience with writing integration tests is a plus ### Project Overview We will use a sample e-commerce application with three components: 1. **Product Service**: Responsible for managing products 2. **Order Service**: Handles order processing 3. **Payment Gateway**: Integrates with payment processors Our goal is to write integration tests that verify the interactions between these components. ### Step 1: Setting up the Testing Environment For this lab, we will use Jest as our testing framework and Node.js as our runtime environment. ```bash npm install jest --save-dev npm install @jest-mock/express --save-dev ``` Create a new test file `integration.test.js` in the root directory of your project. ```javascript // integration.test.js const request = require('supertest'); const app = require('./app'); // Import your express app describe('Integration Tests', () => { it('should test the product service', async () => { // Write your test here }); it('should test the order service', async () => { // Write your test here }); it('should test the payment gateway', async () => { // Write your test here }); }); ``` ### Step 2: Writing Integration Tests In this step, we will write integration tests for each component of our e-commerce application. **Product Service Test** ```javascript it('should retrieve a list of products', async () => { const response = await request(app).get('/api/products'); expect(response.status).toBe(200); expect(response.body.length).toBeGreaterThan(0); }); ``` **Order Service Test** ```javascript it('should create a new order', async () => { const orderData = { productId: 1, quantity: 2, }; const response = await request(app).post('/api/orders').send(orderData); expect(response.status).toBe(201); expect(response.body.orderId).toBeGreaterThan(0); }); ``` **Payment Gateway Test** ```javascript it('should process a payment', async () => { const paymentData = { orderId: 1, amount: 10.99, }; const response = await request(app).post('/api/payments').send(paymentData); expect(response.status).toBe(200); expect(response.body.paymentStatus).toBe('success'); }); ``` ### Step 3: Mocking Dependencies In integration testing, it's essential to isolate the component under test by mocking its dependencies. We can use Jest's `jest.mock` function to mock our dependencies. ```javascript jest.mock('./productService', () => ({ getProducts: jest.fn(() => [ { id: 1, name: 'Product 1', }, { id: 2, name: 'Product 2', }, ]), })); ``` ### Step 4: Running Integration Tests To run our integration tests, execute the following command: ```bash jest integration.test.js ``` ### Conclusion In this lab, we learned how to create integration tests for a multi-component application using Jest. We covered setting up the testing environment, writing integration tests, mocking dependencies, and running tests. With this knowledge, you can now write effective integration tests for your applications. ### Resources - [Jest Documentation](https://jestjs.io/docs/getting-started) - [SuperTest Documentation](https://www.npmjs.com/package/supertest) **Leave a comment or ask for help** if you have any questions or need further clarification on any of the steps. Next Topic: [Understanding End-to-End Testing](https://www.example.com/end-to-end-testing)