When you need to contribute a new library or framework, you might try to write test and 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. In this talk, I explain the details of the CRuby test suite and contribution protips for CRuby's development for beginners.