A: Gently shake the cheesecake. If the cheesecake looks nearly set and only a small circle in the center jiggles slightly, it is done. (The center will firm up during the cooling time.) Using a knife to test a cheesecake may create a crack in the top and will not work for cheesecakes made with a large amount of sour cream because it won't give an accurate test. Cheesecakes made with sour cream should jiggle a little more and will have a larger soft spot in the center.