They will most likely not test for it.
There is a drug panel they run to screen you for certain things (pot, coke, heroin, ecstacy, PCP, meth, etc) and anabolic steroids are not included in the screen.
However, you will be subject to a series of questions and I think also a lie deector test. They will ask if you have ever used recreational/illegal drugs. If you have, (and are caught lying about it) then you will be automatically disqualified.
Although the drug compounds in these are technically legal, so there is no issue there. If you use them after they are made illegal (even if you bought them while legal), then you would be lying if you said "no".