API Testing with Supertest: practical guide

What is Supertest?

Supertest is a library for testing HTTP APIs in Node.js. It integrates with any testing framework (Jest, Vitest, Mocha) and lets you make HTTP requests to your application without starting a real server.

Basic setup

import request from 'supertest';
import { app } from '../app';

describe('GET /api/health', () => {
  it('should return 200', async () => {
    const res = await request(app).get('/api/health');
    expect(res.status).toBe(200);
    expect(res.body).toEqual({ status: 'ok' });
  });
});

Testing different methods

await request(app).post('/api/users').send(userData).expect(201);
await request(app).put(`/api/users/${id}`).send(updateData).expect(200);
await request(app).delete(`/api/users/${id}`).expect(204);

Simulating authentication

Use the set() method to add authentication headers:

const token = generateTestToken();
await request(app)
  .get('/api/protected')
  .set('Authorization', `Bearer ${token}`)
  .expect(200);

Response validation

Supertest integrates with Jest matchers. Validate status, body, headers, and timing.

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