It's probaby because you can get the same number as int, long, string or whatnot. Check it with Console.WriteLine(n.GetType()) to know for sure.

Shouldn't the first line have index on first_name + last_name and last_name + first_name instead of 2 times first_name + last_name?

Accidentally submitted. This one may fail or succeed randomly, i was trying to understand why it was random and hit submit instead of attempt.

(The cause turned out to be negative indices that should be treated as positive indices, something that wasn't even mentioned in the description or initial tests).

Oh right, i can print that, i forgor 💀.

My regex is wrong, i know it, i just couldn't figure out why it was failing one of the tests. Now that i printed it, i see that it was the test for 253 total characters limit (and that it's not 7th, it's #8 out of 10 length tests...).

Thanks for the assist.

My solution [python] is passing all of the tests except one and i have no idea what is wrong because all it says is "value is not what was expected". But what was expected? I only know it's something about length, but i already tried every "missed by one" possible errors and no luck.

What does the 7th test in the length group test for?

Oops, you are right.

Changed the name back to s in solution setup and in description.

Yeah, but the idea is to see some example before   you press Train button. Makes the task clearer.

Example in the description is a good idea because you can't see test cases before starting kata.
And the problem with data1 is that it's not used anywhere.

Description needs to have examples of input, more clear output example. Also i don't understand why even there's data1 string.