# File lib/minitest/unit.rb, line 69
    def self.diff
      @diff = if WINDOZE
                "diff.exe -u"
              else
                if system("gdiff", __FILE__, __FILE__)
                  "gdiff -u" # solaris and kin suck
                elsif system("diff", __FILE__, __FILE__)
                  "diff -u"
                else
                  nil
                end
              end unless defined? @diff

      @diff
    end