this  attach interface not found case is almost the same as the one of v api test  so how about defining not found case exception exc httpnotfound in interfaceattachtestsv class and defining not found case exception exc httpbadrequest in interfaceattachtestsv  class and replacing self assertraises exc httpbadrequest self assertraises self not found case exception  in  attach interface not found case of interfaceattachtestsv 