"""Unit tests for slot-related functionality."""
import pytest
from pympler.asizeof import asizeof

import attr


@attr.s
class C1(object):
    x = attr.ib(validator=attr.validators.instance_of(int))
    y = attr.ib()


@attr.s(slots=True)
class C1Slots(object):
    x = attr.ib(validator=attr.validators.instance_of(int))
    y = attr.ib()


def test_slots_being_used():
    """Test whether the class really is using __slots__."""
    non_slot_instance = C1(x=1, y="test")
    slot_instance = C1Slots(x=1, y="test")

    assert "__dict__" not in dir(slot_instance)
    assert "__slots__" in dir(slot_instance)

    assert "__dict__" in dir(non_slot_instance)
    assert "__slots__" not in dir(non_slot_instance)

    assert asizeof(slot_instance) < asizeof(non_slot_instance)

    non_slot_instance.t = "test"
    with pytest.raises(AttributeError):
        slot_instance.t = "test"