new_contents: from butter.eventfd import Eventfd
  from butter.fanotify import Fanotify
  from butter.inotify import Inotify
  from butter.signalfd import Signalfd
  from butter.timerfd import Timerfd
  import pytest
  import os
  
  @pytest.fixture(params=[Eventfd, Fanotify, Inotify, Signalfd, Timerfd])
  def obj(request):
      Obj = request.param
      o = Obj.__new__(Obj)
      
      return o
  
  @pytest.mark.eventlike
  @pytest.mark.unit
  def test_fd_closed(obj):
      """Ensure you cant close the same fd twice (as it may be reused"""
      old_close = os.close
      os.close = lambda fd: None
      obj._fd = 1
      
      obj.close()
      with pytest.raises(ValueError):
          obj.close()
  
  
      os.close = old_close
  
subject: Check closing the same file twice