Will one line of cocain test positive?

I'm going to assume you're talking about a drug test and not a pregnancy test, because I'm not too familiar on the latter. Lol. Anyways yes, one line CAN show up on a drug test, but some factors play into it. Coke as well as some other 'party drugs' coke/X/Mollie, can be out of your system in 2-4 days, or as long as 7 or more. It really depends on your hydration level before and after you blew, the purity of the coke and your natural metabolism, and if you're a repeated user, I would say at least 3 or more times a month. If you've been clean and just did one line of average grade blow I would say with plenty of hydration, it should be out in about 3 days. One other thing to think about is that the test itself doesn't even look for the drug, it looks for the chemical your body produces by metabolizing it. That being said most employers pick only a few things to test for, because it would be just too expensive to test everyone for everything. ;) Hope that helps.