it's wrong solution, because result contains numbers only! is's against the rules of the kata.

it's wrong solution, because uuid4 contains numbers! is's against the rules of the kata.

i think need to add test case n=21,5 for example, because some variants of function returns wrong results in this case, for example this:
def test_even(n)
n.round.even?
end

if you take n=21.5 then your test_even returns true, but this is false!