Add support for TestCase annotation

[bilderbuchi]

Would you consider adding support for the standardised TestCase annotation in scope?
This would enable testing packages like https://github.com/xogeny/XogenyTest, which uses those annotations in its test suite (although an old draft form, apparently), and would also allow other packages to use TestCase in their test suite (e.g. to define tests that should fail).

[casella]

Absolutely!