One of the neat things about TestNG is the ability to annotate individual tests as belonging to zero or more groups. At execution time, it is possible to tell the test runner to run all tests in a particular group. In addition, tests in certain groups can be excluded so you can run all tests in a particular group except for those that are marked as broken.

The Apache Harmony project apparently uses TestNG. On their wiki, they describe their testing conventions for using groups. They have groups to identify tests that are operating system specific, processor architecture specific, feature specific, environment requirements, current state and test type. Worth checking out.