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Collections are a way for you to organize kata so that you can create your own training routines. Every collection you create is public and automatically sharable with other warriors. After you have added a few kata to a collection you and others can train on the kata contained within the collection.
Get started now by creating a new collection.
Probably a Codewars bug; refresh the page and you should be good. If not, it might be your code which I'd be happy to look at. The test cases seem to work fine for me.