foolproof test?
Read the back, if it says "Brooks" it is a good saddle.

You can also do it like this fool and spend half the riding season trying different saddles and being afraid of the pain of long rides. Then by chance ride a borrowed bike with Brooks saddle (no fit adjustment or anything) and have the most comfortable 60 mile ride. Instant convert bought Brooks saddle and happy as ever, don't even know there is a butt.