old_contents: #!/usr/bin/env python
  import pytest
  import echo_server
  import echo_client
  
  
new_contents: #!/usr/bin/env python
  import pytest
  import echo_server
  from threading import Thread
  import socket
  
  
  def dummy_client():
      message = "Christian Bale is a terrible actor."
      port = 50000
      address = '127.0.0.1'
      client_socket = socket.socket(
          socket.AF_INET,
          socket.SOCK_STREAM,
          socket.IPPROTO_IP)
      client_socket.connect((address, port))
      client_socket.sendall(message)
      client_socket.shutdown(socket.SHUT_WR)
  
      return client_socket.recv(1024)
  
  
  def test_connection():
      thread = Thread(target=echo_server.main)
      thread.start()
      assert dummy_client() == "Christian Bale is a terrible actor."
  
subject: Add test_connection unit test. This single test seems to cover it.