Refs #17876: enhanced new test to actually test underlying function, not just...

        obj.save()

    def test_defer_proxy(self):

        # using select related and only should not result in Exception

        for obj in ChildProxy.objects.all().select_related().only('id'):

            continue

        """

        Ensure select_related together with only on a proxy model behaves

        as expected. See #17876.

        """

        related = Secondary.objects.create(first='x1', second='x2')

        ChildProxy.objects.create(name='p1', value='xx', related=related)

        children = ChildProxy.objects.all().select_related().only('id', 'name')

        self.assertEqual(len(children), 1)

        child = children[0]

        self.assert_delayed(child, 1)

        self.assertEqual(child.name, 'p1')

        self.assertEqual(child.value, 'xx')