The best way to test binoculars is to take them hunting for 10 years and see how they hold up. Since I didn't have time for that, I did the following: To see if a glass was "waterproof," I dropped it in a bucket of warm water and watched for bubbles. If it bubbles, it's leaking. Then I stuck it in the freezer overnight, took it out, and let it thaw. If there's condensation on the interior of the lenses, it's leaked.