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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 hidden specs you run at the end (when you submit a solution) have a bug...or perhaps your instructions do. :)
The first two specs use the same list object, but if the reduce implementation modifies the list (for example, by slicing off the first value to use as the intial value) then the second spec fails.
I suppose you could argue that this means you shouldn't modify the list; in that case, I'd want an explicit test for that, rather than this implied one, i.e.,