Open handles when starting and stopping an http server in a test.

🐛 Bug Report

Starting an http server results in an open handle despite closing the server down after tests ran.

To Reproduce

Steps to reproduce the behavior:

Create the following file named demo.test.js:

const http = require('http');

describe('demo', () => {
    let server;

    beforeAll(() => {
        server = http.createServer((req, res) => {
            res.write('ok');
            res.end();
        });
        server.listen();
    });

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

    test('my test', async () => {

    });
});

Running with jest produces the following output

$ npx jest --detectOpenHandles .
 PASS  ./demo.test.js
  demo
    ✓ my test (2ms)

Test Suites: 1 passed, 1 total
Tests:       1 passed, 1 total
Snapshots:   0 total
Time:        1.759s
Ran all test suites matching /./i.

Jest has detected the following 1 open handle potentially keeping Jest from exiting:

  ●  TCPSERVERWRAP

      10 |             res.end();
      11 |         });
    > 12 |         server.listen();
         |                ^
      13 |     });
      14 | 
      15 |     afterAll(() => {

      at Object.listen (demo.test.js:12:16)

Expected behavior

No open handles should be left.

Run npx envinfo --preset jest

Paste the results here:

$ npx envinfo --preset jest
npx: installed 1 in 1.938s

  System:
    OS: Linux 4.15 Ubuntu 18.04.1 LTS (Bionic Beaver)
    CPU: x64 Intel(R) Core(TM) i7-4510U CPU @ 2.00GHz
  Binaries:
    Node: 10.8.0 - ~/.nvm/versions/node/v10.8.0/bin/node
    npm: 6.2.0 - ~/.nvm/versions/node/v10.8.0/bin/npm
  npmPackages:
    jest: ^23.5.0 => 23.5.0 

[pascalopitz]

Just to follow this up, should anybody read this because they’re testing with supertest and express. The following leaves no open handles.

import supertest from 'supertest';
import express from 'express';
import http from 'http';

describe('demo test', () => {
    let appp, server;

    beforeAll(done => {
        app = new express();
        server = http.createServer(app);
        server.listen(done);
    });

    afterAll(done => {
        server.close(done);
    });

    it('returns 500', async () => {
        const response = await supertest(app).get('/');
        expect(response.status).toBe(500);
    });
});

[SimenB]

That’s because you don’t wait for it to close down. The http API is callback based, not promise.

This successfully closes down without a warning from detectOpenHandles:

const http = require('http');

describe('demo', () => {
  let server;

  beforeAll(done => {
    server = http.createServer((req, res) => {
      res.write('ok');
      res.end();
    });
    server.listen(done);
  });

  afterAll(done => {
    server.close(done);
  });

  test('my test', async () => {});
});