anchor.diff:  	meck:new( lurch_driver_port, [ ] ),
   	meck:expect( lurch_driver_port, start_driver,
   				 fun( _Driver, _Parameters ) -> { ok, port_mock } end ),
  +	meck:expect( lurch_driver_port, stop_driver,
  +				 fun( Port ) -> ok end ),
   	Pid.
   
   
  
positive.code: start_device( Server, Configuration ) ->
  	gen_server:call( Server, { start_device, Configuration } ).
  
  -spec stop_device( pid(), device_id() ) -> ok.
  stop_device( Server, Id ) ->
  	gen_server:call( Server, { stop_device, Id } ).
  
  
negative.code: 
  
  handle_call( { stop_device, DeviceId }, _From, State ) ->
  	case orddict:find( DeviceId, State#state.devices ) of
  		{ ok, Device } ->
  			lurch_driver_port:stop_driver( Device#device.port ),
  			NewDevices = orddict:erase( DeviceId, State#state.devices ),
  			NewState = State#state{ devices = NewDevices },
  			{ reply, ok, NewState };
  		error -> {reply, { error, no_such_device }, State }
  	end;
  
  
  handle_call( list_devices, _From, State ) ->
  