In the spirit of http://rubykoans.com/, but to learn how to use compensations.
In the long term we should use a Java EE Koan 'runner'. In the short term, try using Arquillian with some broken tests. We could do something to intercept logs for an appropriate error message to present the user.
Might also be worth having Arquillian stop on a failed test to prevent too many failures swamping the user.