Tell me if now it is more clear and/or if you wish to suggest further :)

This is a good idea.

I see your point, but maybe it is better if I update the description to be extra clear and follow the author's will.

In most languages as well as in math, operations on list/set are correctly defined for list/set of one element,
including e.g. javascript's redudce and Haskell's product.

It requires the product of any amount of numbers, see above the discussion with Jolaf.

That was no doubt the hardest Kata I have completed so far. Excellent job. The randomized test cases certainly kept me on my toes!

The problem description here leaves a lot out. It is unclear what exactly the program ought to do with examining the (thankfully well written) test cases.

The Python test cases are broken.