Don't know why yours is downvoted -- it's helpful

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You're mutating s1 (changing the expected values), and even if you don't do it, your code will timeout. Find another way.

I think the reference solution somehow bugs on [4,5].

Thanks for your time solving the kata and being the first one in solving it in the ruby version.
I changed the test [6] for this one: [3,3], a valid one that has length higher than 1 and, of course, with result 0.

'(()'

I believe it would return the following test case as true: validParentheses("())()(()")

but that test case is not a valid use of parenthesis.

true. I did it in one iteration.