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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.
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In my opinion the test cases should include partial numbers such as "12.test". And/or the test details amended to indicate whether these values should be accepted or return null (I would suggest null).