My favourite sport is boxing. I do sit on the side of the argument that it's innocent until proven guilty but at the same time I have my suspicions that they're all on
something it's just the idiots that mess up their cycles get caught. Victor Conte, who helped many athletes juice and evade detection, has a lot of interesting things to say on the subject.
It's also things like VADA/UKAD while they need to know where you are at all times there's some weird loophole where they can only visit between certain times. So if you're micro-dosing EPO or whatever designer juice there is, it has a half life of a few hours so by the time they could theoretically test, it should be out of your system. It's obviously a lot more complicated than that.
The drug detection labs are in a constant game of trying to keep up with the designer drugs but they're always a step behind. Though I know the IOC keep blood samples for ~8 years so when they have the ability to detect a new substance in the future historical people can still be popped.
Though, if they're all on something like I believe, then it's a level playing field and it's irrelevant.
Edit:
Funnily enough, Victor Conte actually released a video last night! Odd timing but makes sense with the Olympics around the corner.