rule.rb

class NoPoopInString < Base
  extend AutoCorrector
  MSG = 'Where did you learn that?'
  def on_str(node)
    bad = '💩'
    return unless node.source.include?(bad)

    add_offense(node) do |corrector|
      corrector.replace(node, node.source.tr(bad, '🌈'))
    end
  end
end