Generally, in a Geometry test, you'd need to test proofs (Prove that triangle XYZ and ABC are congruent).
On the other hand, proofs depends depends on theorems which depend on postulates, which are annoying (and ultimately useless) to memorize.
For example, when I learned Geometry, I had to memorize that postulate 13 is called the "Parallel Postulate" (If there is a line and a point not on the line, then there is exactly one line through the point parallel to the given line.)
Note, I didn't remember any of that, I had to Google it. That's why I feel that learning Geometry like this is useless. On the other hand, you do need to somehow document your steps.
How do others do it?