Emil & Justin : :

When I created WP Test 8 months ago at WordCamp Atlanta 2013, there was nothing quiet like it. And there were (and still are) several reasons why it was needed.

The official WordPress theme unit test data had gone over a year without any updates and there were several key tests missing, especially with the responsive web revolution. Equipped with what I had learned from 3.5 years of being QA for 8BIT in building Standard, I created WP Test with all the things that tripped us up along the way.

Chip Bennett and others have since incorporated a majority of WP Test's data into the official WordPress theme unit test data. Which is awesome! I am glad to help strengthen WordPress themes and plugins either through WP Test and / or the unit test data. WordPress as a whole is better for it.

But WP Test still covers some things that the official WordPress theme unit test data chose not to incorporate, such as true non-breaking text tests in all areas it can be used, for just one example.

While WP Test has been dormant for longer than I would have hoped, Tom McFarlin and I are in active dreaming and planning of the next iteration of WP Test, which will include even more ease of use, uncovered tests, and far greater transparency and ease of contribution to the test data.

Thanks for the great question! Hopefully this provides some clarification.