I have removed this test because is not working.

Solved

I hope it is better now.

Double check the string you're returning on the last line. Is it the same as in the instructions?

It seems the tests print out that message when you return an empty string. It's probably some string comparing issue, but I'm not sure. I'm not a java expert, and I am definitely not familiar with how junit works on codewars.

The reason your code is generating this error this error is because your code almost always returns an empty string. You might want to go back and debug a little more :)

This test error message was also reported by another user, but I haven't been able to replicate it yet. Would you mind sharing what code you have? You can mark the comment as a spoiler and it will stay hidden.

Do you have problems with "Code timed out" or similar? Then optimize your code.
I had a correct solution that "worked on my machine", but it was too slow. After optimization author's test cases run in 3 seconds.

Each time I create a chain list with a loop and you a to find the loop's size

Thanks @abudjakov, I'll try your kata later.

Aw, I had to cheat it :[

And you rejected my recursive solution with this new test ^_^ The most effective solution among present here :)