I found really weird stuff when I was building my test project.
I subclassed my own test from AndroidTestCase, and implemented several test cases inside. Some cases didn't run at first, however, there was no exceptions. After I just changed the name of these cases, they got invoked by test runner and all passed.
I've no idea if there's any naming convention.
These are the tests naming conventions in Android: https://source.android.com/setup/contribute/code-style#javatests-style-rules