Before a test, you need to make sure you are prepared and mentally ready for it because during the test, if you aren't either of those, then you, my friend, will have a tough time completing that test.
1. Eat a snack. Eating food can calm your nerves, making you feel full and ready for a test. Eat a granola snack, yogurt, or something small that would be okay to bring to school.
2. A day before, have some fun. Make sure you've studied enough before you do this. Have some fun as a reward for studying. Maybe go for a walk or treat yourself to a nice gaming session.
3. Breathing exercises. Breathe in. Breathe out. Breathe in. Breathe out. Those words aren't useless mumbo jumbo. Breathing is a good way to relax your body and let go of all your worries.
4. Drink something ice cold. Refresh yourself, the coldness of the drink will run down the back of your throat making you feel just delightful!
There are surely more tips, but these are a few more well-known. If you need more tips, look some up on the internet.