The test is perfectly valid since the kata does not specify any constraints on character range, a.k.a any character is to be expected and handled gracefully

This is not a performance or advanced version, so no need such tests with such huge inputs & different languages have different overflow boundaries so unapplicable.

The he/she would need to make sure it doesn't overflow. Also the code for the challange would have to be rewritten a but.
Tho, it would be cool to have as an extre or something you can use in the test like if it was // out at the start.