Adding test to fix of duplicate _order fields (#22720)

from django.test import TestCase

from django.db import models

from .models import Post, Question, Answer

        Post.objects.create(title="2.1", parent=p2)

        p1_3 = Post.objects.create(title="1.3", parent=p1)

        self.assertEqual(p1.get_post_order(), [p1_1.pk, p1_2.pk, p1_3.pk])

    def test_duplicate_order_field(self):

        class Bar(models.Model):

            pass

        class Foo(models.Model):

            bar = models.ForeignKey(Bar)

            order = models.OrderWrt()

            class Meta:

                order_with_respect_to = 'bar'

        count = 0

        for field in Foo._meta.local_fields:

            if isinstance(field, models.OrderWrt):

                count += 1

        self.assertEqual(count, 1)