I'm for this package conceptually, but I don't like:
* Use of SimpleTest means that this package can't be easily integrated into the pear wide test suite (Either phpunit or pear's run-tests are the options I like to push here)
* Code needs cleanup & PHPCS.
* The use of the 'final' keyword - if a unit test wants to mock out something out, you are blocking it from happening.
* Encouraging singletons (if you only need one instance of an object, inject it; singleton makes testing a PITA)