Thank you for this suggestion. I have added a random generated test to this kata.

I fixed the compiling errors.

You are right that the description is inconsistent about what you have mentioned so far. I will need some additional time to extend it a bit.

edit:
i overthought the whole thing and added the corresponding description. It is a bit different than before, but i think thats what i wanted.

Now i got the hang of it. I fixed this.

Thank you for your feedback.

It is my first Kata and some stuff is not that clear to me (probably its just me), so I am still learning how to do it effectively.

=> Compile error: Hopefully fixed it.
=> It is not a bug fixing Kata ^^" Can you get into detail if you are saying buggy and / or not conforming to the description?
=> Haven't thought about edge cases. Should be added!
=> Problem statement is well packaged :-) (thanks ^^)

Oh man, you are right. Now that i think about it ...
I am really sorry for being blind ^^"
I give it a second try.

Thanks for the input!

Okay, i try to be more specific:

Target language: C#
Running Sample Tests, i get the following error

Assert.AreEqual(414, Kata.NextBiggerNumber(144)); => Expected: 414 But was: -1
4 and 4 is the same, it should return -1, since it has already the "biggest possible" value.

Same goes for the "final" attempt. I dont know which are the original values, but here are my errors:

Expected: 1234567908
But was: 1234567809
My guess is that the original value is 1234567908 and it should be xxx80. Cannot say.

Expected: 93892937
But was: 93892739

The task can be completed if the tests would be updated and present the solutions as it is expected. Can't submit it with inconsistent logic.