My gym does the test by appointment. You have to ask questions of the person testing though. Make sure they took classes on it. I had one guy say "24%, thats not too bad". Too bad it was actually 8.5%.
Testing yourself will give you an idea of what you are... a ballpark of sorts. I would recomend getting it done professionally. They can give you a printout with all the site measurements etc. It is easy to keep a log that way too!
Let us know if you find a good online site!
Good luck too!