He doesn't have to take another medical test as long as his contract and RP will be renewed BEFORE EXP DATE.
otherwise he will have to do it, even if it's for the same company.

another thing is, that even when he will go to check if he is HIV positive on his own, i think the clinic will have to report it anyway.

and yes, as long as he is not local they will ask his to leave the country- this might be post some kind of questioning how he got it in the first place, for safety reasons.

All the best to him and hopefully he is perfectly healthy and will be wiser the next time, if he had done sth stupid without proper protection.