I gotta wonder how you got to this solution, I honestly love the way that second for loop works by iterating through the elements behind the current index. That if else statement really had me tripped up at first but now I am wondering how I missed that idea myself, it's a great way to ensure that even if the signature or n have mismatched sizes that the data gets copied over regardless. Great job!

Time: 227ms Passed: 9 Failed: 1
Test Results:
✔ Test Passed
✔ Test Passed
✔ Test Passed
✔ Test Passed
✔ Test Passed
✔ Test Passed
✔ Test Passed
✔ Test Passed
✔ Test Passed
✘ ['EAST'] should equal ['e']

I don't need your code. Please post only the output of the failing test and if you want post for which input too.
1230 guys passed the Python kata and I don't see what kata error you could have.

The two spelling are permitted. "string" is an alias of "String".

The kata is meant to be simple. The description doesn't say to handle numbers, so numbers shoudn't be handled. That's fine.

In C# the input is listed as String[]

This should be string[]

minor, but thought I'd mention it.

Include some words with numbers. The definition of word in the kata does not include alphanumeric. Some Regex Solutions would fail.

For example assertEquals("int12n13n", abbr.abbreviate("int12nationalization"));