def test_empty_volume(self):
        """Empty volume is well-behaved"""
        empty = volume.EmptyVolume()
        test = 0.1
        assert_equal(empty(test), False)
        assert_equal((empty & volA)(test), False)
        assert_equal((volA & empty)(test), False)
        assert_equal((empty | volA)(test), True)
        assert_equal((volA | empty)(test), True)
        assert_equal((empty & volA).__str__(), "empty")
        # assert_is: logical combos with empty should return same obj
        assert_is((empty - volA), empty)
        assert_is((volA - empty), volA)
        assert_is((volA | empty), volA)
        assert_is((empty | volA), volA)
        assert_is((volA & empty), empty)
        assert_is((empty & volA), empty)
        assert_is((empty ^ volA), volA)
        assert_is((volA ^ empty), volA)
        assert_equal((~ empty).__str__(), "all")