well, a doa which make me feel comfortable when the exam is just around the corner is ;
Allahuma La Sahla illa Ma Jaaltahu Sahla, Waanta Taj alul hazna iza shi'ta sahla
Oh God, There Is No Ease, Except What You make Easy, And You Make Difficult Easy, If You Wish.
try it, no joke but it somehow help your confidence level :)
remember, thou shall not cheat, because;
Whoever Cheats Us Is Not From Amongst Us - Prophet Mohammad SAW