The reviews/tests.py file was getting large, and an upcoming change was

about to increase the size considerably. Along with this, it's become a

bit cluttered and disorganized in places. This all makes it harder for

new contributors (and us old-timers) to contribute new unit tests in a

consistent way.
This change is the first in a series that will clean up these unit

tests. This change simply splits the tests.py file into a handful of

individual files, based on the area of responsibility.
The code has simply moved in this change, without modern code standards

being applied. This is intentional, to help with backporting to other

branches. Future changes will clean up the test suite.

Unit tests pass.