I think this thread highlights the need for more tests , or restrictions to the input advertised in the kata description.

I'd like to propose the addition of Groovy to the list of available languages. A sandbox mode is feasible, it is done on http://groovyconsole.appspot.com/ with the code available on GitHub

I also think so, it's a minor quality duplicate. For this version, it would have been nice to include in the kata description the implementation of the Node, Edge, etc .