A mock test gives you a realistic picture of how you drive when there is less help from the instructor. It shows whether your routines hold up when you have to make decisions independently.
The aim is not just to collect faults. The aim is to understand patterns: late observations, rushed positioning, weak mirror checks, hesitation, speed choice, or inconsistent planning at junctions.
After a mock test, focus on the few habits that caused most of the problems. Fixing those habits usually improves several parts of your driving at once.