Not that hard. It coming up random means either you're required to travel to a place within a time limit (certainly possible to get a "doctor" to drain and refill you with clean piss) or you are at a place where the test will take place / be escorted straight there, which you could just refill before going there. If you really think random drug screenings are where they show up and say "right now, whip it out and piss in this cup!".
And that is the problem. Random means there is some kind of time between when the person is picked and when they are tested, so there is time to find ways around popping positive. The alternative is scheduled testing, which is just as easy, if not more so, to get around.
And, thinking we are going to eliminate all PEDs from sports is just plain ridiculous.
And, that is only with urine tests, which are the cheapest. If they switched to blood tests, I would imagine it would be much harder to get around, but still possible.There was a murder trial I recall years back where the defendant was a doctor and his DNA didn't match that found at the scene. It was only after some diligence from the sister that she obtained the doctors DNA (stolen) and had it compared on her own that she got the case reexamined and they discovered the doctor had surgically implanted a rubber vein filled with someone else's blood to fool the DNA test. He was able to convince them to not take it from his hands, as he couldn't have open wounds and perform his job (surgery or something) and got it from the arm he put the 'fake' blood in. Was pretty brilliant.