Here is the setup. I am taking salsa lesson, currently doing level 2, its lots of fun. Okay so every exercise the girls rotate guys. The girls rotate to the left. Okay so this is what happened next.

She is the nicest looking girl in the class HB9. I think she was enjoying dancing with me, or she just wanted to prove she is the hottest. An exercise ended, I exchanged a few words with the next girl (partner) to the right of me (HB7). As the instructor is explaining the next exercise I am standing between two girls HB9 and HB7. Then the instructor says okay rotate, my old partner HB9 does not move. The girl which was suppose to be my new partner, HB7, has to go around her and go to the next guy. There was a weird moment there of confusion, but the HB9 was right in front of me so she got more eye contact.

My gut feeling was telling me, why did I not just move towards my next partner HB7, I actually like dancing with her. Instead I just stood there, and decided the girls to figure things out. Following that exercise the HB9 rotated. And I felt disappointed I did not get a chance to dance with the HB7. Do you guys think that was a shit test? Or did the HB9 wanted to validate herself as hotter? Did I fail?

Pretty controlling move on her part, and definitely a shit test; you were her pawn. Too bad she shat on that poor HB7, must have been humiliating for her... especially for an activity with crazy potential for embarrassment like salsa. At least it happened fast, and hopefully not too many people noticed.

The correct frame for you in this case would have been similar to "hands off the goods, honey."

I know it's hard when you are caught off-guard. I would of pretended I was reading a dictionary in my hand and looked at her and said..

"Rotate: Verb. The act of moving to the next location of desire"

*ahem cough*

A shit test is a demand or comment, i was under the impression that a shit test has to be vocal, but i suppose does'nt have to be. But i see this as more of a complience test.
This one is a very difficult one to answer. Who did you think was testing you?
I would'nt worry about this too much, youre probly just over analysing things or maybe it was just the jelously between the two of them competing. Now just focus on getting the girl to meet up with you sometime or after the class.

To me it seemed like she was testing /playing both of us, proving her dominance/control, she is a very confidant woman, at least from the first impression and the way she dances. I think she wanted to prove to the other girl that I will choose to dance with her again, because she is hotter better/whatever ego boost she needs. And I just stood there, damn it, I want to teach her a lesson.
Heck yeah, It happened quite quick, but regardless it happened. My gut feeling after the class was that HB9 is such a bitch\hog. I know I don't feel good about it, and it’s not my regular class either. So it will be awkward to bring it back up to the HB7 when I see her again if ever, 2 weeks, 3 weeks from now dunno. But the salsa scene is a small community. Or should I say something like, listen I know what happened last class was not kewl, and I want to make it up to you with a hot chocolate. BTW the HB7 has a boyfriend so I would not really try to game her.