How do you know when you're ready to take a CLEP?

[WaltzJump413]

I have been working on IC (just studying for one test, US History II) for 3 weeks now. I feel like I have a much better grasp of events than I formerly did, but am not sure if I am actually ready to take the final test.

Is there a baseline I can go by to gauge when it's time? IC said to "try to get 90% at least 3 times in a row". Should I go through each subset of flashcards several times and check my score based on that? Or is there another way to figure this out?

Thank you!