def test_len():
    anm = NetworkModel()
    """ default overlays are:
    input, phy, _dependencies, graphics
    """
    assert (len(anm) == 4)
    anm.add_overlay("test")
    assert (len(anm) == 5)
def test_init():
    anm = NetworkModel()
    print anm
def test_init():
    anm = NetworkModel()
    assert (anm.has_overlay(("phy")) is True)
    assert (anm.has_overlay(("test")) is False)