What -vert Are You? (Myers-Briggs)
Check out the Myers-Briggs test if you haven't already. This is basically a copy of it, except with only ambivert, introvert, and extrovert as results.
Disclaimer: I'm not gonna lie to you so you'll take this, I'm going to tell you the truth. This isn't very accurate. Sure, it might work for some people, but it's not going to work for everyone.