def METHOD_NAME(compute_project, manager, port_manager):
    aux = port_manager.get_free_tcp_port(compute_project)
    port_manager.release_tcp_port(aux, compute_project)
    node = DockerVM("test", "00010203-0405-0607-0809-0a0b0c0d0e0f", compute_project, manager, "ubuntu", aux=aux)
    assert node.aux == aux
    node.aux = None
    assert node.aux is None