'Create an in-memory I/O system and set up a L{TuntapPort} against it.'

def setUp(self):

    self.name = 'tun0'
    self.system = MemoryIOSystem()
    self.system.registerSpecialDevice(Tunnel._DEVICE_NAME, Tunnel)
    self.protocol = self.factory.buildProtocol(TunnelAddress(self.helper.TUNNEL_TYPE, self.name))
    self.reactor = FSSetClock()
    self.port = TuntapPort(self.name, self.protocol, reactor=self.reactor, system=self.system)
