Testing for Steroids

I’ve been pondering this for awhile now and finally its gotten on my nerves enough too actually ask this question…

when they do test’s to see if a competitor(for example well use olympics) is on steroids after winning the gold…does this test only pick up if your currently on a cycle? or if you’ve ever done a cycle?..how long does it take in a drug test before it wont show up?

i hope I’ve worded this question correctly, if not thanks for reading anyway

cheers

p.s i realize this is a complete newb question, no I’m not juicing im just generally interested…

depends on the drug as to how long it remains traceable in your system.