Lab tests if drug is confisicated by customs

For example, if one were to put tabs in a vitamin bottle and if customs take it away saying that they want to check what's really in it, is it easy for them to find out exactly what compound it is? Lets say one puts anavars or winny tabs into a vitamin C bottle and when asked, you claim that it is vitamin C but he doesn't believe you and say that they need it checked and you can come collect it later. In this case, just wondering how much trouble they would go through to guess what that compound is. Meaning, if they suspect it is anavar, would it be easier for them to check than if they had no idea what it was?

Just wondering because if it is too costly or troublesome to check, most likely is that they won't. OR they could just make sure that it isn't recreational drugs. I am not talking about US customs, more like asian countries......

Not to long ago there was a member on here that got some powder nabbed by customs and in the letter it said how much of each compound was nabbed, and it was exactly correct to what he had ordered. Not sure if it was tested, but I would guess they did.

Yes they will tell you exactly what it is once they arrest you and then they will make you pay for the lab testing. Not the best route to go about testing product.