class RSpec::Expectations::Differ

def diff_as_string(input_data_new, input_data_old)
  encoding = pick_encoding input_data_new, input_data_old
  output = matching_encoding("", encoding)
  data_old = input_data_old.split(matching_encoding("\n", encoding)).map! { |e| e.chomp }
  data_new = input_data_new.split(matching_encoding("\n", encoding)).map! { |e| e.chomp }
  diffs = Diff::LCS.diff(data_old, data_new)
  return output if diffs.empty?
  oldhunk = hunk = nil
  file_length_difference = 0
  diffs.each do |piece|
    begin
      hunk = Diff::LCS::Hunk.new(
        data_old, data_new, piece, context_lines, file_length_difference
      )
      file_length_difference = hunk.file_length_difference
      next unless oldhunk
      # Hunks may overlap, which is why we need to be careful when our
      # diff includes lines of context. Otherwise, we might print
      # redundant lines.
      if (context_lines > 0) and hunk.overlaps?(oldhunk)
        if hunk.respond_to?(:merge)
          # diff-lcs 1.2.x
          hunk.merge(oldhunk)
        else
          # diff-lcs 1.1.3
          hunk.unshift(oldhunk)
        end
      else
        output << matching_encoding(oldhunk.diff(format).to_s, encoding)
      end
    ensure
      oldhunk = hunk
      output << matching_encoding("\n", encoding)
    end
  end
  #Handle the last remaining hunk
  output << matching_encoding(oldhunk.diff(format).to_s, encoding)
  output << matching_encoding("\n", encoding)
  color_diff output
rescue Encoding::CompatibilityError
  if input_data_new.encoding != input_data_old.encoding
    "Could not produce a diff because the encoding of the actual string (#{input_data_old.encoding}) "+
    "differs from the encoding of the expected string (#{input_data_new.encoding})"
  else
    "Could not produce a diff because of the encoding of the string (#{input_data_old.encoding})"
  end
end