This project has added a quite a bit of complexity in order to support Groovy for test files.

I wonder, is this really worth it? Maybe I'm missing something, but I see only 3 .groovy files being used in the entire project.

Besides the complexity vs usage, is it really a good idea to have tests in totally different formats? I would argue it's better for consistency to have all tests in the same format using the same testing system and same language.