Close server and db connect after tests

I have koa server with mongo connection and use supertest to mock server and send requests, jest as test framework.

const app = new Koa()
...
export default app.listen(PORT, (err) => {
  if (err) console.log(err)

  if (!IS_TEST) {
    console.log(`Server running on port: ${PORT}`)
  }
})

After success finish test or fail server connection steel works, how close koa server connection after test ?

Test example:

import supertest from 'supertest'
import mongoose from 'mongoose'
import server from '../../../app/server'
import User from '../../../app/models/user'

const r = supertest.agent(server.listen())

afterEach(async (done) => {
  await mongoose.connection.db.dropDatabase()
  done()
})

describe('Authorization', () => {
  describe('POST /signup', () => {
    const userData = {
      email: 'test@test.com',
      password: 111111,
    }

    test('success create user', (done) => {
      r
        .post(`/api/auth/signup`)
        .send(userData)
        .expect(200)
        .expect({
          data: {
            email: userData.email,
          },
        })
        .end(done)
    })

    test('fail of user create, password required', (done) => {
      const userData = {
        email: 'test@test.com',
      }

      r
        .post(`/api/auth/signup`)
        .send(userData)
        .expect(400)
        .expect({
          errors: {
            password: 'Password required',
          },
        })
        .end(done)
    })
  })
})