The driving license is split into two tests: theory and practical. Theory is about laws and rules, you have to pass a multiple choice test.
Failure rate is pretty high, something around 35 - 50% ... but that might be due to brain dead legislations which could be simplified and put down to more general more basic rules.
Practice tests vary greatly from driving school to driving school.
However there are ofc the MUST PASS tests: parking, U turning on a road, never pass a red light or stop sign, never take the right of way of another car or threaten a pedestrian.
Ofc the judge will also try to figure your general attention/awareness to the traffic etc.
But I guess failures are far below 50% ... I passes my car and my motorcycle license on first attempt.
OTOH I heard about a record in the USA where a woman needed something like 30+ attempts for the practical driving license.
20 years ago you had to make an so called "Idiots test" if you failed more than 3 times in any of the theory or practical tests.
However those got abolished for ordinary driving licenses, but not if you got caught 2x drunk (pretty low limit in most nations) while driving.
This was germany :D Now, next state of the EU?