How can a doctor check the ability of a man to have ?

How the doctor check-up a man to prove his ability to have with a girl and lead a successful married life. please help. The scenario is - in a court wife claims that husband has no ability for . But he claims that he has the ability and wife is putting up false allegations. So, how can he prove it medically, any procedure - please explain. Can a man check his ability for without actually doing it? Is it true that all masturbating male can have successful with girls? Please help.