What is Supertest and how is it used?

Supertest is a library for testing HTTP APIs, especially Express apps.

It allows you to simulate HTTP requests and assert on responses.

Example:

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

describe('GET /users', () => {

it('should return 200 and a list of users', (done) => {

request(app)

.get('/users')

.expect(200)

.expect('Content-Type', /json/)

.end((err, res) => {

if (err) return done(err);

done();

});

});

});