This tests all methods (private and public), as well as number of sub-cases for some methods.

Still need to confirm what's needed to run test suite other than `pytest`.

The "cleanup" test is broken because the DiskQueue's implemention is also broken (it's not clearing vars properly).

Had to re-build BaseOptions inside each test, lest it's vars/files get squashed or shared between test functions.

You previously had to be in the `tests` directory, but that wasn't going to work with some future changes (code coverage reporting)

Can now generage test result HTML and Junit reports, as well as code coverage reports.
https://pypi.org/project/pytest-cov/
https://pypi.org/project/pytest-html/

Can now mark tests as bugs, versus just having them fail (or xfail) before. https://pypi.org/project/pytest-bug/

Can now add test dependencies (Test A only runs if Test B passes): https://pypi.org/project/pytest-depends/

Not tested, but should work well.

The 'retry' tests have both Disk and Redis tests, so those were broken down into two steps, such that you could tell which one was failing.

Previously, asserts were being done against their values individually, but now both drivers are being compared against eachother *and* the desired value

Previously, asserts were being done against their values individually, but now both drivers are being compared against eachother *and* the desired value