The best way to test boots for ice fishing is to dress in the gear you plan to use and try going outside in the snow, slush, and ice to see how they hold up. You can use them while shoveling the driveway to see how they hold up. See if your feet remain dry even if you're in a few feet of snow. The next test is to then try sitting outside for an extended period. Maybe, after shoveling and exerting yourself so your blood is flowing and heating all of your extremities, then try sitting for a while to let yourself settle. This is a good way to test how long the boots will be able to retain heat even while you're not moving.