Unfortunately there aren't any practice tests or sample questions as of yet. The User Assistance team here at Skuid is still hard at work to build that module out.
Until then, my best advice to you is to familiarize yourself with the existing components, and complete as much of the current documentation on http://help.skuid.com/. If you can confidently come up with use cases around each of the components, then you should be well-prepared to take the exam. Good luck!