Why Jest don't exit correctely?

Question

I'm testing a UDP server, and to do that, I created a UDP client within the test. However, despite the test passing, Jest exits with the following message:

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

It points to the line where I declared the UDP socket.

I tryed the following code:

const dgram = require('node:dgram');

describe("udp client", () => {
    let testClient = dgram.createSocket('udp6');
    test('test', ()=>{
        let popo = false
        expect(popo).toEqual(false); 
    })
    
});

But sitll I am getting the same problem:

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

  ●  UDPWRAP

      2 |
      3 | describe("udp client", () => {
    > 4 |     let testClient = dgram.createSocket('udp6');
        |                            ^
      5 |     test('test', ()=>{
      6 |         let popo = false
      7 |         expect(popo).toEqual(false);

      at createSocket (test/test_udp.test.js:4:28)
      at Object.describe (test/test_udp.test.js:3:1)

That is not a serious problem, but i like to know what is going on.

Answer 1

Jest is kept "alive" by an open socket, which you have to close explicitly by calling socket.close() . A good place to do it is in afterEach() or afterAll() hook.