I was working on an app with the latest 1.2.9 release and all was well until I started to use ngMockE2E's $httpBackend to do some backend-less development. Once angular-mocks.js was included on the page my animations would no longer work. What's interesting is removing ngMockE2E as a dependency for my app is not enough to get animations working again, angular-mocks.js must be removed entirely. Here's some fiddles to help illustrate the issue:

angular-mocks not included (works as expected):
http://jsfiddle.net/8y3Ey/

angular-mocks included (animations appear to start but halt on enter):
http://jsfiddle.net/q8SQg/

Current workarounds are to either remove animation classes from elements (don't use animations) or to refrain from including angular-mocks.js (don't use ngMock/ngMockE2E). There's been quite a few releases since I last used angular mocks so it's possible that I'm just doing something incorrectly.