What is Supertest and how is it used?

Short answer: 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');

Example code

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(); }); }); });

Real-world example (ShopNest)

A ShopNest BFF in Node.js aggregates catalog and price APIs for the React storefront.

Say this in the interview

1. Define — one clear sentence (the short answer above).
2. Example — relate it to a project like ShopNest or your real work.
3. Trade-off — when you would not use it.