The school uses a syllabus, you should have been given a copy.
Review the items to be covered.
If your instructor thinks you’re ready you’re ready most of the time.
A stage check is meant as an additional set of eyes and is partially to check if your instructor taught you what you needed to learn for the stage you’re in.
Its also an evaluation of your skills by a person you are not familiar with.
So it ups the stress levels a little bit which emulates the increased stress levels when you fly alone or when you a flight with the examiner.
Its not about being perfect at this stage in the game, it’s about being safe.
Yes I’ve conducted hundreds or stage checks.
Enjoy the journey and don’t forget to have fun.