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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.
The thing is that the test environment expects that you throw an error, but you can't really tell it what kind of error it's looking for, so it thinks that the ReferenceError is the one it wants. That's just a quirk with the test environment.