anchor.diff:  test_add_list_devices( Server ) ->
   	DeviceCount = 2,
   	StartDeviceOk = fun( ) ->
  -		{ ok, DeviceId } = start_device( Server, <<"dummy">>, [ ] ),
  +		{ ok, DeviceId } = start_device( Server, test_driver_config() ),
   		DeviceId
   	end,
   	DeviceIds = [ StartDeviceOk( ) || _N <- lists:seq( 1, DeviceCount ) ],
  
positive.code: 
  -type device_id() :: reference().
  
  -spec start_device( pid(), binary(), [ binary() ] ) -> { ok, device_id() }.
  start_device( Server, Driver, Parameters ) ->
  	gen_server:call( Server, { start_device, Driver, Parameters } ).
  
  -spec stop_device( pid(), device_id() ) -> ok.
  stop_device( Server, Id ) ->
  
negative.code: % API functions
  -export(
  	[ start/0, start_link/0, stop/1
  	, start_device/2, stop_device/2, list_devices/1
  	] ).
  
  % gen_server callbacks
  