Breed it to your snow. A snow is an animal that is homozygous for BOTH amelanism AND anerythrism. So, if you breed it to your snow (and your anery is het for amel), 50% of the babies should be snows, proving that your anery is het amel.
However, these are ONLY the expected percentages, and that may not be what actually takes place in any given clutch of babies. Let's say that your anery is het for amel, and you breed it to your snow. Your anery could throw 0, 1, 50%, 0r 100% snow babies. It's just like flipping a quarter. The odds are 50% that it will come up heads or tails on any given throw. However, it is entirely possible to flip that quarter and have it come up heads 95 times in a row! It's all a matter of chance.
So, if you breed your snow to your anery, and NONE of the babies are snows, you know two things: Your babies are all anery het amel (snow), AND your anery is probably not het amel. It could be that it is het amel and you were just unlucky, but that possibility decreases the more babies you produce and none of them are snows. However, if you ever produce even one snow baby out of that anery, you can know for certain that it IS het for amel. Just like it only takes one flip of "tails" to prove that the quarter does have both sides to it.
Now, assuming I haven't made this even more confusing for you . . .
I hope this helps. Good luck with your corns!