would you mind to use async/await in the test?

thanks @mcollina.
I try use async/await, while when I modify code below it, show error for it tapError: incorrect number of tests, plan test is 2, I dig it for a while, but not solved. please told me where is errors.

test('Cannot be reopened the closed server has listen callback', async t => {
  t.plan(2)
  const fastify = Fastify()

  await fastify.listen(0)
  await fastify.close()

  fastify.listen(0, (err) => {
    t.is(err.code, 'FST_ERR_REOPENED_CLOSE_SERVER')
    t.ok(err)
  })
})

you must write

try{
  await fastify.listen(0)
}catch(err){
    t.is(err.code, 'FST_ERR_REOPENED_CLOSE_SERVER')
    t.ok(err)
}

(the promise of the test ends, so it is resolved as undefined and the callback of the fastify.listen is ignored even if it is executed)

Hey @Eomm thanks for the answer.

The test unit is listen has callback . if I follow the code about 👆，I don't test code logic. https://github.com/fastify/fastify/pull/2415/files#diff-c945a46d13b34fcaff544d966cffcabaR138.

Ops 😅

Then you can just wrap the callback in a new Promise 👍🏼

thanks @Eomm, I got it