Personally, I wouldn't waste my time with a woman who is spending an evening alone with another guy when she already has a boyfriend. Any woman who's worth your time will know that's not acceptable behavior and she wouldn't agree to it. Maybe OP wasn't acting masculine, or maybe she's just a cheater, but either way it doesn't matter. That kind of behavior from a woman is not acceptable.
In my opinion, this does not qualify as a **** test and is simply her getting ready to dump you but is too afraid of not having a guy's attention that she doesn't dump you before going after other guys. A **** test is her feigning interest so she has a chance to see you be confident, or not. You call her, she doesn't answer, and you don't contact her again until she contacts you. She wants to make sure you're confident enough not to chase her and that she wants you just a little bit more than you want her. Her going out with other guys alone? That's not a **** test, that's just cheating.
IMO OP, dump her right now, tell her straight up you're not interested in a woman who wants to go out with other guys. Keep it short, simple, then walk away. There's way too many worthwhile women out there to meet, so don't waste another second on a cheater. Don't ignore warning signs of a woman who isn't LTR material if an LTR is what you're looking for.