base.py 文件源码

def test_cycle(self):
        # Simple cycle
        a = Place.objects.create(name='a')
        a.parent = a
        with self.assertRaisesMessage(
                InternalError, 'Cannot set itself or a descendant as parent.'):
            with transaction.atomic():
                with self.assertNumQueries(1):
                    a.save()

        # Complex cycle
        b = Place.objects.create(name='b', parent=a)
        c = Place.objects.create(name='c', parent=b)
        d = Place.objects.create(name='d', parent=c)
        a.parent = d
        with self.assertRaisesMessage(
                InternalError, 'Cannot set itself or a descendant as parent.'):
            with transaction.atomic():
                with self.assertNumQueries(1):
                    a.save()