Tests using Jest and Supertest

1. What is a Local Test?

A local test is a small script that runs on your computer inside your terminal (using npm test) to automatically test your code without needing a browser, Postman, or any cloud server.

Right now, if you want to check if your backend works, you might:
1. Start your server (node server.js).
2. Open Postman or your browser.
3. Send a request to http://localhost:3000/todo.
4. Manually look at the JSON response to see if it's correct.

There are Main two Tools we use

Jest (The Test Engine & Runner)

• Manages running your test files.
• Provides test structure syntax like test(...) and assertions like expect(response.status).toBe(200).

Supertest (The Fake HTTP Client)

• Acts like Postman inside your code
• Sends fake HTTP requests (GET, POST, PUT, DELETE) directly into your Express app.

Example Code
const request = require('supertest');
const app = require('./app'); // Your Express app

describe('GET /todo', () => {
  test('should return status 200 and a list of todos', async () => {
    // 1. Supertest sends a fake GET request to /todo
    const response = await request(app).get('/todo');

    // 2. Jest checks (asserts) the result
    expect(response.statusCode).toBe(200);
    expect(Array.isArray(response.body)).toBe(true);
  });
});

CI/CD

• CI/CD is a software development practice that automates the process of testing, building, and delivering/deploying code.
• two main parts:
  • Continuous Integration (CI)
  • Continuous Delivery / Deployment (CD)

CI

• Whenever developers push or merge code, an automated pipeline checks whether the new code works correctly.

Code pushed
    ↓
Checkout code
    ↓
Install dependencies
    ↓
Build
    ↓
Run tests
    ↓
Pass / Fail