shitty situation bro. Luckily the job i work at just tested once before i started to work and never again, so i haven't had to worry about all the things you are worried about.

It seems like your current process is working, so why fix something that is broken?
now that you are back to random testing, dont that mean you can take less precautions?
what does random testing mean at your job? once they tell you that you are being randomly tested, does that mean you have to do it on the spot, or do they make an appointment at some place the same/next day?