It’s recommended that you don’t cut meat to test if it’s cooked. The simple reason is this. The food cooked in an air fryer tends to come out crispy on the outside, and tender and juicy on the inside. If you slice the food to test if it’s cooked, it will dry the food on the inside as well.  If you must test it, I would recommend getting a good meat thermometer such as a thermopop. They are expensive but very quick, accurate, and really good.  Here’s a link so you can check it out.  Any meat thermometer will do, but the faster it is, and the more accurate it is, the better your food will be. Here’s an Amazon link to a Thermopop.