These are tests for the Raku programming language in addition to the official "roast" tests.
This is a place to test aspects of the Raku programming language that might not be so well covered by the roast tests. You might think of it as a test-bed for new tests.
This is intended to have a lower barrier to entry than the official tests-- feel free to ask to be added to the Contributors.
The Raku project settled on the idea that "The tests are the spec." That philosophy has a few issues, one of which is that it raises the barrier to entry for additional tests-- any attempt at improving coverage might inadvertanly change the definition of the language.