def test_xor_combinations(self):
        assert_equal((volA ^ volB),
                     volume.UnionVolume(
                         volume.CVDefinedVolume(op_id, -0.5, 0.25),
                         volume.CVDefinedVolume(op_id, 0.5, 0.75)
                     ))
        assert_equal((volA ^ volA2),
                     volume.SymmetricDifferenceVolume(volA, volA2))