Flesh out the docs for BaseTestCase and clean up some code.
Review Request #11076 — Created July 8, 2020 and submitted
BaseTestCaseis complex, with a lot of arguments required for some
methods, and a lot of terminology that's required for understanding how
it all works. Most of this was undocumented, and some argument names
weren't as clear as they could be.
In preparation for some upcoming work, this change cleans up a lot of
this, adding docs that explain arguments better, reworking some function
calls to pass explicit keyword arguments to help make code more
self-documenting, and renaming some arguments to make their intentions
Unit tests pass.