Thank you for improving. I added this test case.

foldr' is required to be lazy.

I added a line a to clarify this. Apparently if you get stuck at the part where this is tested, the whole thing just breaks down without showing the describe block: foldr should allow lazy evaluation.

You're right, the description can be polished a bit more. However, everything that is needed to complete the kata is present in the description and being under polished doesn't stop anyone from successfully completing it. I feel modifying the description to be more eloquent won't add to the validity of the kata so in that regard, I'm not too bothered with updating it. Thanks for your feedback tho.