Usually recipes tell you to insert a toothpick and if it comes out clean, the cake is done. That is fine for a 2 inch deep cake pan, but barely makes a dent in a Bundt cake or loaf pan. I have a 6 inch cake tester that I use for deep cakes, but it is not necessary to buy one. In fact, I often lose my skinny cake tester in a kitchen drawer. When I do I grab a skewer or a piece of uncooked spaghetti and insert it into the cake to see if it is done.