> What do you mean it mismatches? Also what do you mean by self-checking? > It passes all the unit tests for me. I think he meant that it doesn't throw exceptions on error. This is the wrapper I used to make it conform with the provided tests: class JSONParser def initialize @parser = JsonParser.new end def parse(text) rv = @parser.parse(text) if rv return rv.value else raise RuntimeError end end end Regards, Thomas.