Robolectric is a unit testing framework and it is important that Robolectric itself be very well tested. All classes should have unit test classes. All public methods should have unit tests. Those classes and methods should have their possible states well tested. Copied Android source should at least have “smoke tests” that assure the copied functionality is wired up correctly. Pull requests introducing untested functionality should not accepted, and reviewers should give appropriate feedback to the submitter.
“When appropriate” is subjective. In an effort to avoid complexity, copying Android source as the basis for Shadow object functionality is discouraged. That said, sometimes the functionality is complex and the Android implementation is what is needed. Contributors and reviewers should use their best judgement: should a 3000-line Android class be copied to gain access to a boolean getter and setter? It depends.
This is essentially the IntelliJ default Java style.