When you need to understand a new library or framework, you might try to invoke the test suite with "rake test" or "rake spec". CRuby also has a test suite like many libraries and frameworks, written in Ruby. But, It's different from typical ruby libraries. Therefore many Rubyists don't know how to run the CRuby test suite.
This is because CRuby's test suite has historical and complex structures. In this talk, I explain the details of the CRuby test suite and protips for CRuby's testing technology.