CSA exam will test your in depth knowledge about their various services. You should have good understanding in the basic concepts of AWS. The questions are little tricky so you have read it twice before answering.
I think whizlabs has to update the their practice exam now. Because AWS have introduced STS and API gatetway services in their exam. Nearly 3 to 4 questions. Other than that whizlabs is the best place to check your knowledge before going in to the exam. And also i can find 5 to 10 questions same as whizlabs in the CSA exam.