How to stop my stomach from growling in tests?

You shouldn't skip breakfast! And yes, you do need a lot of food, as long as you aren't stuffing yourself, or else you feel nauseated, so be careful with that. One way to eat only a little bit is to eat fiber, right before the test. I realize you don't like to eat before tests, but just a little of fiber can fill you up for a while. Good luck!