Are you 100% sure @barks is available as an instance variable of dog and not just an attribute?

I really like the idea of making sure attributes don't bleed across instances. I just need to figure out exactly how to word it in the instructions. Also, I think this may increase the difficulty...what do you think the ranking should be with this new test added?

Update: I have added the test, but left the ranking as is for now.

I think the description leads you to believe that you're looking for words (as in separated by whitespace) and not just substrings.

:alpha strings contain the word "alpha"