There are no prescribed du`aas/supplications in the sources for this, but you can make use of any general prayers/supplications from the Qur’an and the Sunnah and any other general supplications you say for this purpose. At the same time, you are recommended to prepare yourself for the test seeking the help of friends and more experienced people in this field.
You can make use of the following supplications:
Hasbiya allaahu laa ilaaha illaahuwa `alayhi tawakkaltu wahuw rabbu al-arshi al-azheem
(Allah is sufficient for me; there is no other god but He; in Him alone I place all my trust; He is the Lord of the Mighty Throne).
Rabbanaaaatinaafi ad-dunyahasanatanwafi al-aakhiratihasanatanwaqinaaadhaaba an-naar
(Our Lord, grant us good in this world and good in the next world and save us from the torments of the Hellfire).