Will someone test positive for drugs use through sexual intercourse with an illegal drugs user?

You shouldn't test positive for drugs if you've been having sexual intercourse with someone who is using them. Drugs can't really do much to someone else while having sex.

In case of doubt, the best thing to do would be to

1. Use protection

2. Get yourself an at home drug kit, they sell them over the counter at most pharmacies. Test yourself within an hour or two after sex to see what the results are. If they're positive and you haven't done any sort of drugs, please edit this question.