depends upon your location... different countries and locations have different ways of diagnosing. for example if you were here in america yes there are diagnostic tests that are done. here its called a psychiatric evaluation. many tests and an interview with a psychiatrist.

to find out if your location has a uniform diagnostic process you would need to contact your own treatment providers or ask the person in question if you can have contact with their treatment providers. dont be offended though if your friend says no. many people dont want their friends and family to have access to their psychiatrists, therapists and doctors. its a right of privacy and confidentiality thing. like you wouldnt want just anyone to be able to talk with your doctors about you and whether they think you are in your right mind or not right.. well others also dont want that kind of invasion of privacy.

my suggestion since this isnt about you,and you have no control over who this person can see for their treatment providers is to voice your opinion with your friend and then leave it up to your friend to take care of their self and their own mental/ physical health problems and treatment providers.