Well, if the test will be done "traditionally", you can get the piss from somebody else... but it in a small bottle, wrap it in one of those heating pads, and when you're in the bathroom, take out the bottle and use that piss.

If the test is administered with somebody watching, either A- be very handy, or B- tell them to fuck off.

It's against the law to watch as you take the test if there isn't a SPECIFIC claim to have you watched. Don't be an asshole... know your rights.