In some integration tests in my Node.js, I use pg to perform some cleanup of the Postgres tests database after the test have run. I call this in the afterAll():

afterAll(() => {

  const { Pool } = require('pg')
  const connectionString = 'postgresql://' + PG_USER + ':' + PASSWORD + '@' + HOST + ':' + PG_PORT + '/' + DATABASE_TEST;
  const pool = new Pool({
   connectionString,
   })

   pool.query('TRUNCATE someTable RESTART IDENTITY CASCADE;', (err, res) => {
       pool.end();
   })

When I run Jest tests in my Node.js app, I'm getting the error:

Jest did not exit one second after the test run has completed.

This usually means that there are asynchronous operations that weren't stopped in your tests. Consider running Jest with `--detectOpenHandles` to troubleshoot this issue.

When I add --detectOpenHandles to my npm test script in package.json, I then get the following:

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

  ●  TCPWRAP

> 259 |   pool.query('TRUNCATE someTable RESTART IDENTITY CASCADE;', (err, res) => {
      |        ^
  260 |       
  261 |       pool.end();
  262 |   })

If I move the connection to the database into a separate file (outside of the __tests__ folder), the Jest tests still don't exit (with the same error).

If I use a pg Client and do this, I get a similar issue with the client.connect()

  client.connect()
  client
    .query('TRUNCATE someTable RESTART IDENTITY CASCADE;')
    .then(() => client.end())

Can anyone explain what's actually going on here? Does Jest try to close after the final test, but the operation in afterAll() is preventing this? What do I need to do to allow the tests to exit? None of the solutions in other similar SO questions apply to my case.

Update

I tried the suggestion by @Estus Flask, but it still doesn't fix the issue. Using the following (which passes done as the callback function, so that the afterAll won't complete until done() is called (which I call when the pool.end() promise resolves):

afterAll( done => {

  const { Pool } = require('pg')
  const connectionString = 'postgresql://' + PG_USER + ':' + PASSWORD + '@' + HOST + ':' + PG_PORT + '/' + DATABASE_TEST;
  const pool = new Pool({
   connectionString,
   })

   pool.query('TRUNCATE someTable RESTART IDENTITY CASCADE;', (err, res) => {
     pool.end().then(done());
   })
  })
});