A great test is to pitch your tent in the backyard and hit it with a spray nozzle. Have someone you trust spry it with you in it. The idea isn't to try to get you soaked, it's to find out where the weaknesses in your setup are, if any of the seams leak, and to get experience with the guying requirements.
I understand that. I have a couple of tents which have always done the job for me. I was just curious in which tent Litespeed survived, completely dry, in the middle of what he called a shallow stream.