def test_empty_cpt(self):
        bn = BayesianNetwork()
        from primo2.nodes import DiscreteNode
        n1 = DiscreteNode("a")
        n2 = DiscreteNode("b")
        bn.add_node(n1)
        bn.add_node(n2)
        bn.add_edge(n1,n2)
        ft = FactorTree.create_jointree(bn)
        res = ft.marginals(["a"])
        np.testing.assert_array_almost_equal(res.get_potential(), np.array([0.0, 0.0]))