Well, unfotrtunately in world where steroids can be sold on the Black market for up to 30 times what it costs to make them, everything has been faked at some point. You just need to get a supplier who you can trust and looks after you......
Typically new products are difficult to counterfit shortly after introduction into the market. For example, BD Primo...been out for a couple of months.
I would say test and dbol are the least faked. They're so damn cheap, it's not worth faking them. Also, you'll get obvious sides like water retention using them. Anavar is quite often faked, tren is faked sometimes too, i'd say test and dbol are the least faked out of gear.