A mechanism for testing signals in Ruby processes.

ruby_process.rb

class RubyProcess
  WAIT_HELPER = <<-EOS
    # Top-level method to signal the parent process
    # and wait for an interrupt.
    def wait_for(seconds)
      # Signal parent we are ready.
      Process.kill('USR1', Process.ppid)

      # Wait for interrupt.
      sleep(seconds)
    end
  EOS

  def initialize(code, *args)
    cmd = ['ruby'] + args
    @io = IO.popen(cmd, 'w+', err: [:child, :out])
    @io.write(WAIT_HELPER)
    @io.write(code)
  end

  attr_reader :io, :status

  def run_and_send(signal)
    # Prefer to do this without trap, but $? does't get set when
    # inside a rescue for some reason. Maybe use fork to avoid cleanup?
    usr1_handler = trap('USR1') do
      Process.kill(signal, io.pid)
    end

    io.close_write
    @pid, @status = Process.waitpid2(io.pid)
  ensure
    trap('USR1', usr1_handler)
  end

  def output
    io.readlines
  end
end

if $0 == __FILE__
  ruby = RubyProcess.new <<-EOS
    trap('INT') { exit }
    wait_for 1.0
  
    # Fail if no interrupt is received.
    raise 'No Interrupt received'
  EOS
  
  ruby.run_and_send('INT')
  
  puts ruby.status
  puts ruby.output
end