To start a study of proofs, you could try looking here
But the topic comprises a course, in and of itself. I would suspect that the point of this Compass test is to see what you have learned, versus what you need to learn. Since you need to know about proofs (hence the advisory about this topic) and since you do not, this means that the placement test would detect this, and then place you in a course appropriate to your current level of knowledge: high enough that you're challenged, but low enough that you're prepared and can pass.
Trying to "fool" the placement test
doesn't usually end well.