This is what you do to unlock the following license tests.

Test	How to unlock
A License Tests	Reach level 3 and complete the B license tests.
B License Tests	Buy your first car.
International A License Tests	Reach level 12 and complete the International B license tests.
International B License Tests	Reach level 9 and complete the International C license tests.
International C License Tests	Reach level 6 and complete the A license tests.
S License Tests	Reach level 15 and complete the International A license tests.