This test suite had grown too big to manage, and a lot of the testing

patterns being used are far from ideal. With more work on the horizon,

we want to split this up and make it easier to maintain a test suite.
This change simply splits the tests.py into a series of test_*.py

files. No logic or documentation has been changed, though module-level

docstrings were added. Cleanup would happen in another change.

Unit tests passed.