He won't get tested unless something seriously warrants the suspicion (ie - he beats the shit out of his wife and kids) Seriously.
The Army is suppose to test 100% of their personnel at least twice a year (usually after the 4th of July and New Years). They are also suppose to test 10% of their personnel monthly. Does this always happen? Nope. Do they ever randomly test for AS? Nope.
I've been around awhile and I hold some clout (as far as rank is concerned). Tell your friend, never smuggle shit on leave. If he must, have it mailed to him. I presuming to think he's over in Europe. If he's near the sand, if he's not able to find anything local - he's not looking hard enough