No default tests.
That is bad.

If kata can't be solved without clicking "Submit" button (because of incorrect method name), it is an issue.
This is not a puzzle task, not a bugfix task, it is just simple 8 lvl kata, so it needs to be shaped accordingly.

As you can see, I was able to solve this kata.
But it was like fixing of someone's buggy code, not like the following the well defined task.

C# version is completely broken.
For example, it have incorrect name of the method and no default test cases.

So it's a problem not with kata.
Marking this as solved.
(But I will add another message soon)

No, I mean "Validate the input!" is not enough description for making correct solution (without clicking submit button).

Please fix the encoding in the tests.
"αβγδεζηθικλμνξοπρστυφχψω" is not a Greek alphabet.

C++ tests needs correction.
First parameter of Assert::That must be an actual value.

I think you should describe the validation step in more detail.

Are you saying that empty array is an integer? That's strange.

Incorrect tests for booleans and empty arrays:

Testing against [[],23,7]
Expected: 0237, instead got: 0

Testing against [true,true,false,15]
Expected: 10001, instead got: 0

Initial tests are missing.

Can you add to description that subtracted numbers will be only positive or zero?

So it is possible for you to accept this translation then?