Not entirely true. Armstrong in 1999 Tour De France on 4 occasions submitted samples which contained traces of steroids. He claimed it was due to medication he was using for saddle sores and got his corrupt doctor to falsify the date it was prescribed. That along with other tests between that were clean were enough to convince the authorities his lies where the truth. So the anti-doping program of any sport is only as good as the governing bodies that regulate them and obviously in boxing more so than in perhaps any other sport the governing bodies are a joke. But your point is valid. The anti-doping program in boxing in general is awful. VADA is seen as some gold standard but as it's not true random 24/7, 365 days per year random testing then in reality it's just a PR stunt to make boxing look cleaner than it actually is, as a whole it's ineffective. I'm sure plenty of boxers are doping and enrolled in VADA.