Do you have access to your curriculum guide yet? If so, that's where I would start. See what they are required to know by the end of the year, and create a test based on that material. If you don't know what's required, you can test them over proofreading/editing skills (punctuation, capitalization, spelling, usage...), vocabulary, reading skills (main idea, fact/opinion, cause/effect, summary, inferencing...)
I do have a pretest that I created some years ago, but I won't have access to it until I go back for inservice on the 20th.