_run_parallel

# File lib/test/unit.rb, line 570
      def _run_parallel suites, type, result
        if @options[:parallel] < 1
          warn "Error: parameter of -j option should be greater than 0."
          return
        end

        # Require needed things for parallel running
        require 'thread'
        require 'timeout'
        @tasks = @files.dup # Array of filenames.
        @need_quit = false
        @dead_workers = []  # Array of dead workers.
        @warnings = []
        @total_tests = @tasks.size.to_s(10)
        rep = [] # FIXME: more good naming

        @workers      = [] # Array of workers.
        @workers_hash = {} # out-IO => worker
        @ios          = [] # Array of worker IOs
        begin
          # Thread: watchdog
          watchdog = start_watchdog

          @options[:parallel].times {launch_worker}

          while _io = IO.select(@ios)[0]
            break if _io.any? do |io|
              @need_quit or
                (deal(io, type, result, rep).nil? and
                 !@workers.any? {|x| [:running, :prepare].include? x.status})
            end
          end
        rescue Interrupt => ex
          @interrupt = ex
          return result
        ensure
          watchdog.kill if watchdog
          if @interrupt
            @ios.select!{|x| @workers_hash[x].status == :running }
            while !@ios.empty? && (__io = IO.select(@ios,[],[],10))
              __io[0].reject! {|io| deal(io, type, result, rep, true)}
            end
          end

          quit_workers

          unless @interrupt || !@options[:retry] || @need_quit
            @options[:parallel] = false
            suites, rep = rep.partition {|r| r[:testcase] && r[:file] && r[:report].any? {|e| !e[2].is_a?(MiniTest::Skip)}}
            suites.map {|r| r[:file]}.uniq.each {|file| require file}
            suites.map! {|r| eval("::"+r[:testcase])}
            del_status_line or puts
            unless suites.empty?
              puts "Retrying..."
              _run_suites(suites, type)
            end
          end
          unless @options[:retry]
            del_status_line or puts
          end
          unless rep.empty?
            rep.each do |r|
              r[:report].each do |f|
                puke(*f) if f
              end
            end
            if @options[:retry]
              @errors   += rep.map{|x| x[:result][0] }.inject(:+)
              @failures += rep.map{|x| x[:result][1] }.inject(:+)
              @skips    += rep.map{|x| x[:result][2] }.inject(:+)
            end
          end
          unless @warnings.empty?
            warn ""
            @warnings.uniq! {|w| w[1].message}
            @warnings.each do |w|
              warn "#{w[0]}: #{w[1].message} (#{w[1].class})"
            end
            warn ""
          end
        end
      end