There is not a sample test, but you can download a pdf of the Tasks and Objectives that might covered on the test <a href="http://volt.ni.com/niwc/common.jsp?page=custed_cecp">here</a>. Look for the "Certified LabVIEW Developer" heading, then click the Tasks and Objectives link. There is also other information available on that page.
I didn't take the prep course, but a co-worker did and he did pass the test after taking it. Ed