NestJS e2e "supertest ... ECONNREFUSED" (app not initialized) in CI

By Daniel Zoghalchali·Latchkey

supertest hit a connection refused because the Nest application was not initialized before the request, or the test targeted a hardcoded host/port instead of the in-memory app instance.

What this error means

An e2e spec fails with "Error: connect ECONNREFUSED 127.0.0.1:3000". The HTTP server the test expected was never started or bound.

Error: connect ECONNREFUSED 127.0.0.1:3000
    at TCPConnectWrap.afterConnect [as oncomplete] (node:net:1494:16)

Common causes

app.init() was not awaited before requests

supertest was passed the HTTP server before await app.init() completed, so nothing is listening yet.

The test targets a URL string instead of the app

Passing request('http://localhost:3000') requires a separately running server; the in-memory app never bound that port.

How to fix it

Init the app and pass its HTTP server

1. Create the app from a compiled TestingModule.
2. Await app.init() in beforeAll before any request.
3. Pass app.getHttpServer() to supertest so no real port is needed.

beforeAll(async () => {
  const moduleRef = await Test.createTestingModule({ imports: [AppModule] }).compile();
  app = moduleRef.createNestApplication();
  await app.init();
});

it('/health', () => request(app.getHttpServer()).get('/health').expect(200));

Close the app after the suite

Call await app.close() in afterAll so a leaked server does not affect later suites.

afterAll(async () => { await app.close(); });

How to prevent it

• Always pass app.getHttpServer() to supertest, never a URL.
• Await app.init() in beforeAll and close in afterAll.
• Avoid hardcoded ports in e2e tests.

Frequently asked questions

Related guides

References

• Node.js documentation
• npm CLI documentation
• GitHub Actions documentation