Testing Express routes with Supertest + Jest

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

describe('POST /projects', () => {
  it('returns 400 for invalid payload', async () => {
    const res = await request(app).post('/projects').send({ name: '' });
    expect(res.status).toBe(400);
    expect(res.body.error).toBe('VALIDATION_ERROR');
  });
});

Route tests give me fast feedback about the API contract without needing a full browser. I structure the app so I can import an app instance without binding a port, then use supertest to make requests. The key detail is determinism: stub time and randomness, and use a test database (or a transaction that rolls back) so tests don’t leak state. I assert on both status code and response shape because clients depend on both. When a bug slips in, a focused route test is often the cheapest way to lock in the fix. It’s not a replacement for end-to-end tests, but it covers a lot of ground quickly and keeps regressions from creeping back.

Mateo Rodriguez

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Testing Express routes with Supertest + Jest

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