Improve Test Coverage

[tarecord]

This handles setting up code coverage measuring and improves our test coverage quite a bit.

You can verify this locally with Slic.

First, you'll need to start XDebug to use it as a driver with:

slic xdebug on

Then you can run the tests and generate the coverage report in the tests/_output directory:

slic run --coverage-html tests/_output

[tarecord]

There's a lot more tests to cover now that the core class has tests (which reveals all the rest of the classes in the library). I've done about all I can do for now.

Testing is a never-ending endeavor, but this should provide a good base to build on when features are added or refactored.

[ChrisMKindred]

This is great @tarecord ! What are the chances you could do a walk-through on testing for the Biweekly sometime?