def METHOD_NAME(test_name, original_size, modified_size):
  """Generate a report for a single test."""
  if original_size >= 0:
    # Both files exist, so compare their sizes.
    size_percent = (modified_size / float(original_size)) * 100
    note = "unchanged" if size_percent == 100 else "%.1f%%" % (
        size_percent - 100)
  else:
    # The original file doesn't exist, this is a new result.
    size_percent = 100
    note = "new"
  row_format = size_format + " %s (%s)\n"
  message = row_format % (original_size, modified_size, test_name, note)
  return (size_percent, message)