issue not reproducible with the OP's C# code

haha that is exactly what I spoke out loud when I looked at this...

Yeah, your right.

I did that in other languages translations, it is less boring to vary a bit...

Of course.You are right!Thank you for your suggestion!

Thanks! No harm done:-)

Again how can both be string[2] when expected string length is 5 and actual is 4?

I am not responsible for this, it is the output done by the NUnit.Framework.

Are you sure you're not modifying the input or something?

Look at the top of the page: 1544 people passed the C# kata. I just try some solutions and all worked fine. I suppose you mutate the input.

Over 1000 people have completed the C#. It is near impossible to know if your code has a problem or is correct if you don't post your code with markdown (use a spoiler tag).