# File lib/test/unit/diff.rb, line 414
        def diff(options={})
          @result = []
          operations.each do |tag, from_start, from_end, to_start, to_end|
            case tag
            when :replace
              diff_lines(from_start, from_end, to_start, to_end)
            when :delete
              tag_deleted(@from[from_start...from_end])
            when :insert
              tag_inserted(@to[to_start...to_end])
            when :equal
              tag_equal(@from[from_start...from_end])
            else
              raise "unknown tag: #{tag}"
            end
          end
          @result
        end