High Quality Content by WIKIPEDIA articles! Matz`s Ruby Interpreter or Ruby MRI (also called CRuby) is the reference implementation of the Ruby programming language. As there is currently no specification of the Ruby language, the MRI implementation is considered the de facto reference. The RubySpec project has created a large test suite that captures 1.8.6/1.8.7/1.9 behavior as a reference conformance tool. Ruby MRI 1.9.2 currently passes over 99% of RubySpec.