You can download by solution from here https://github.com/bparanj/ruby-koans-edgecase.
This took me 5.5 hours to complete. I broke this down into 11, 30 minutes sessions over a period of two weeks.
Things that I learned:
1. It was a "aha" moment when I worked through a series of tests that described the behavior of a class. You have to do the exercises to get the feel for describing the behavior or specification of a class.
2. It helps you to find your strengths and weakness so you will know where to focus your learning efforts.