Report failing and unexpected passed tests after run

[awvwgk]

Currently the test status is only printed when the tests are run, but there is no summary in the end. Having a list of all failed unit tests after the run would be quite helpful in practice.

[lewisfish]

I wanted a summary count of tests failed and passed so have thrown together a minimal working example of this on my fork.
It currently just tracks the amount of tests failed, passed, unexpected passes, skipped, and expected to fail.

I'm happy to open a pull request and work on this further with input from folk if this is a good starting point for what you envision?