This was once part of the hiring process for a company I used to work for. They no longer use it, and I no longer work for them, so it's no longer particularly relevant, and is only still up for reference purposes.
Each problem consists of a class to implement, and a test suite which must pass. You should only edit the file defining the class.
Tests developed by Jim Lindley (@jlindley on GitHub) and Mark Josef (@mark on GitHub)