This line arr[i] = static_cast(rand() * 1.0 / (static_cast(RAND_MAX) + 1.0) * 21 - 10); can be std::uniform_int_distribution⩽int⩾ randomNumber(-9, 10). In this case you can rid off ctime header and include the mersenne twister engine with random device std::mt19937 mt{ std::random_device{}() }. The final result would be more convenient arr[i] = randomNumber(mt)
Please remove using namespace std from Test Cases/Sample Test Cases

Wouldn't it be better to write ExtraMessage("Wrong answer for arr={" + s_arr + "}" instead of string s_arr("Wrong answer for arr={");

Lol, insane, I missed it for Java and now missed it again.

Fixed

That's only the case with test suites like Python, as in those languages the function might be accessible from the solution. (https://docs.codewars.com/languages/python/authoring/#reference-solution)
In Rust you need to declare a function with pub to make it accessible from outside, which isn't the case.

However, for the sake of encapsulation, I will agree that it would make more sense to have the function as part of the tests module.

What kind of kata name is "Don't use!"?

I fixed it.

Хорошо

How many tests approx do you want me to do?

How to delete this kata?

you cannot, once any other user solved it. The only thing you can do is to unpublish it. Then the kata will sit in your draft section (...just like it is right now, in fact. So you already did all that you could do)

Yes, it's un publish and similar problem with deleting.

It's Un publish, but similar problem.

How to delete this kata?

duplicated issue. Closing. @LeoVaider: read the docs linked in the message below.

How?

Because 2 * 13 + 1 = 27