Tests on Django Q object assertion helper

test_assert_q_equal.py

# encoding: utf-8

import pytest
from django.db.models import Q


def assert_q_equal(left, right):
    """
    Simply test two Q objects for equality. Does is not match commutative.

    Args:
        left (Q)
        right (Q)

    Raises:
        AssertionError: When -
            * `left` or `right` are not an instance of `Q`
            * `left` and `right` are not considered equal.
    """
    assert isinstance(left, Q), f'{left.__class__} is not subclass of Q'
    assert isinstance(right, Q), f'{right.__class__} is not subclass of Q'
    assert str(left) == str(right), f'Q{left} != Q{right}'


# --- Matches ---

def test_eq_self():
    """
    Matching is reflexive, matches self
    """
    q_a = Q(location='London')

    assert_q_equal(q_a, q_a)


def test_eq():
    """
    Matching Q objects matches their internal
    """
    assert_q_equal(Q(location='北京市'), Q(location='北京市'))


def test_eq_multi_and():
    """
    assert_q_equal matches multi Qs
    """
    assert_q_equal(Q(direction='north') & Q(speed=12), Q(direction='north') & Q(speed=12))
    assert_q_equal(Q(direction='north') | Q(speed=12), Q(direction='north') | Q(speed=12))


# Non-matches


def test_neq_simple():
    """
    assert_q_equal spots that Q filters do not match
    """
    q_a = Q(location='北京市')
    q_b = Q(location='北京')

    with pytest.raises(AssertionError):
        assert_q_equal(q_a, q_b)


def test_neq_multi_and():
    """
    assert_q_equal matches multi Qs
    """
    q_a = Q(direction='north') & Q(speed=13)
    q_b = Q(direction='north') & Q(speed=12)

    with pytest.raises(AssertionError):
        assert_q_equal(q_a, q_b)


def test_neq_multi_not_commutative():
    """
    assert_q_equal does not match commutative: A & B != B & A
    """
    q_a = Q(speed=12) & Q(direction='north')
    q_b = Q(direction='north') & Q(speed=12)

    with pytest.raises(AssertionError):
        assert_q_equal(q_a, q_b)


def test_neq_type_a():
    """
    assert_q_equal raises if either q is not of type Q, left side
    """
    q_a = 1
    q_b = Q(location='New York')

    with pytest.raises(AssertionError):
        assert_q_equal(q_a, q_b)


def test_neq_type_b():
    """
    assert_q_equal raises if either q is not of type Q, right side
    """
    q_a = Q(location='New York')
    q_b = "(AND: ('location', u'New York'))"

    with pytest.raises(AssertionError):
        assert_q_equal(q_a, q_b)