You can specify sub-branches of the tree as a way of limiting which tests are executed during a test run. The JavaTest harness walks the tree starting with the sub-branches or tests you specify and executes all the tests that it finds. This feature is very useful when you want to run only a portion of the test suite. For example, if you run the test suite and only a few of the tests fail, you can limit subsequent test runs to only the tests that failed.
If you wish to specify selected sections of the test tree answer "Yes". You will be presented with a tool in the next editor panel with which you can choose tests and test branches for execution.