We could leave the testing center to grub. As long as we didn't violate the alloted break time, we could do whatever. The testing center had no place to take a break...I'm glad they didn't hold us hostage there.
You are free during your break time to do anything. If your testing center tells you anything else, they are violating your rights as a test taker. The only thing you're not supposed to do during break is talk to an outside person and report the contents of the exam. (Although there's nothing stopping you from even doing that.)