What is ng-bullet?
For a complete and detailed answer please read my article at meduim.
For a library description with some useful examples and performance comparison please go to bullet's project repo.
Update
Please excuse me, but it seems like I don't have time to invest into this library anymore. This being said please let me provide you with an even better alternative in my opinion - spectator, backed by Netanel Basal. It should provide you a similar technique to speed up your tests, plus many more useful tools to improve testing of your application. Excuse me once again for inconvenience.