"PED tests aren't drug tests, they're IQ tests" is a common refrain. Some substances take longer to clear the system or have obvious effects that will trigger the average person watching will lose their suspension of disbelief (The Rock's HGH traps for example) but traditional testosterone as a PED has you cycle on and off of it so if you're doing it under proper scheduling rarely will tests prove anything.

Once you're famous enough to get sponsorships they probably fast track you to the personal doctors who greenlight all the sketchy shit you want which every rich person seems to have access to.