Awesome question, @dinlovetter! I’ve put this in its own topic so it can get the attention it deserves 
The sun sigil Kasie shared is an awesome spell to help pass an exam. In addition to the sun sigil, you might also consider:
Before you go to take the test, you may want to consider casting Magic Armor over yourself.
If you like crystals, I recommend bringing a piece of Amethyst with you (in a bag or maybe your pocket) to help bring good luck whie also boosting courage and creativity.
You can many more good luck spells by clicking the picture below- look through them, and know that is okay to adjust ingredients to suit what you have on hand. Remember that the most important element in any spellwork is your own personal intent!
I wish you the best of luck with your exam- blessed be! 