'L{TuntapPort.startListening} opens the tunnel factory character special
device C{"/dev/net/tun"} and configures it as a I{tun} tunnel.'

def test_startListeningOpensDevice(self):

    system = self.system
    self.port.startListening()
    tunnel = self.system.getTunnel(self.port)
    expected = (((system.O_RDWR | system.O_CLOEXEC) | system.O_NONBLOCK), ('tun0' + ('\x00' * (_IFNAMSIZ - len('tun0')))), self.port.interface, False, True)
    actual = (tunnel.openFlags, tunnel.requestedName, tunnel.name, tunnel.blocking, tunnel.closeOnExec)
    self.assertEqual(expected, actual)
