You have space at the end...

The kata seems to be tricky at best, or even underspecified.
Your solution most probably returns incorrect answer for inputs like int[] { 21, -10, 212 }.

I did everything according to the instructions and generated code that measures the length of the string. The tests go fine, but when I press "Attempt", it throws an error- "expected: <1874011478> but was: <-1974269008>"

Ok.

I needed time to solve this task.
I had created a solution so that the basic test was gone but the total thrown error
Well, I've come to the conclusion that I haven't read the description completely, which clearly states that "case insensitive" must be followed, which also led me to success.