# File lib/nanoc/extra/checking/checker_cli.rb, line 111
    def run_checkers(classes)
      puts
      checkers = []
      issues = Set.new
      length = classes.map { |c| c.identifier.to_s.length }.max + 20
      classes.each do |klass|
        print format("%-#{length}s", "Running #{klass.identifier} checker… ")

        checker = klass.new(site)
        checkers << checker
        checker.run
        issues.merge checker.issues

        # TODO report progress

        puts issues.empty? ? 'ok'.green : 'error'.red
      end
      issues
    end