Github user paul-rogers commented on the issue:
https://github.com/apache/drill/pull/978
@jinfengni, sorry my description was a bit ambiguous. This PR has two goals:
1. Clean up the contexts based on what has been learned recently.
2. Evolve the contexts to allow "sub-operator" unit testing without mocks.
Drill has many tests that use mocks and these are unaffected by the change.
The PR simply allows new tests to do sub-operator testing without mocks, when
convenient. ---
