text: try:
      from cStringIO import StringIO
  except ImportError:
      from StringIO import StringIO
  
  from django.core import management
  from django.contrib.auth.models import User
  from django.test import TestCase
  
  from models import Person, Group, Membership, UserMembership
  
  
  class M2MThroughTestCase(TestCase):
      def test_everything(self):
          bob = Person.objects.create(name="Bob")
          jim = Person.objects.create(name="Jim")
  
          rock = Group.objects.create(name="Rock")
          roll = Group.objects.create(name="Roll")
  
          frank = User.objects.create_user("frank", "frank@example.com", "password")
          jane = User.objects.create_user("jane", "jane@example.com", "password")
  
          Membership.objects.create(person=bob, group=rock)
          Membership.objects.create(person=bob, group=roll)
          Membership.objects.create(person=jim, group=rock)
  
          self.assertQuerysetEqual(
              bob.group_set.all(), [
                  "<Group: Rock>",
                  "<Group: Roll>",
              ]
          )
  
          self.assertQuerysetEqual(
              roll.members.all(), [
                  "<Person: Bob>",
              ]
          )
  
          self.assertRaises(AttributeError, setattr, bob, "group_set", [])
          self.assertRaises(AttributeError, setattr, roll, "members", [])
  
          self.assertRaises(AttributeError, rock.members.create, name="Anne")
          self.assertRaises(AttributeError, bob.group_set.create, name="Funk")
  
          UserMembership.objects.create(user=frank, group=rock)
          UserMembership.objects.create(user=frank, group=roll)
          UserMembership.objects.create(user=jane, group=rock)
  
          self.assertQuerysetEqual(
              frank.group_set.all(), [
                  "<Group: Rock>",
                  "<Group: Roll>",
              ]
          )
  
          self.assertQuerysetEqual(
              roll.user_members.all(), [
                  "<User: frank>",
              ]
          )
  
      def test_serialization(self):
          "m2m-through models aren't serialized as m2m fields. Refs #8134"
  
          p = Person.objects.create(name="Bob")
          g = Group.objects.create(name="Roll")
          m =Membership.objects.create(person=p, group=g)
  
          pks = {"p_pk": p.pk, "g_pk": g.pk, "m_pk": m.pk}
  
          out = StringIO()
          management.call_command("dumpdata", "m2m_through_regress", format="json", stdout=out)
          self.assertEqual(out.getvalue().strip(), """[{"pk": %(m_pk)s, "model": "m2m_through_regress.membership", "fields": {"person": %(p_pk)s, "price": 100, "group": %(g_pk)s}}, {"pk": %(p_pk)s, "model": "m2m_through_regress.person", "fields": {"name": "Bob"}}, {"pk": %(g_pk)s, "model": "m2m_through_regress.group", "fields": {"name": "Roll"}}]""" % pks)
  
          out = StringIO()
          management.call_command("dumpdata", "m2m_through_regress", format="xml",
              indent=2, stdout=out)
          self.assertEqual(out.getvalue().strip(), """
  <?xml version="1.0" encoding="utf-8"?>
  <django-objects version="1.0">
    <object pk="%(m_pk)s" model="m2m_through_regress.membership">
      <field to="m2m_through_regress.person" name="person" rel="ManyToOneRel">%(p_pk)s</field>
      <field to="m2m_through_regress.group" name="group" rel="ManyToOneRel">%(g_pk)s</field>
      <field type="IntegerField" name="price">100</field>
    </object>
    <object pk="%(p_pk)s" model="m2m_through_regress.person">
      <field type="CharField" name="name">Bob</field>
    </object>
    <object pk="%(g_pk)s" model="m2m_through_regress.group">
      <field type="CharField" name="name">Roll</field>
    </object>
  </django-objects>
          """.strip() % pks)
  
      def test_join_trimming(self):
          "Check that we don't involve too many copies of the intermediate table when doing a join. Refs #8046, #8254"
          bob  = Person.objects.create(name="Bob")
          jim = Person.objects.create(name="Jim")
  
          rock = Group.objects.create(name="Rock")
          roll = Group.objects.create(name="Roll")
  
          Membership.objects.create(person=bob, group=rock)
          Membership.objects.create(person=jim, group=rock, price=50)
          Membership.objects.create(person=bob, group=roll, price=50)
  
          self.assertQuerysetEqual(
              rock.members.filter(membership__price=50), [
                  "<Person: Jim>",
              ]
          )
  
          self.assertQuerysetEqual(
              bob.group_set.filter(membership__price=50), [
                  "<Group: Roll>",
              ]
          )
  
  class ThroughLoadDataTestCase(TestCase):
      fixtures = ["m2m_through"]
  
      def test_sequence_creation(self):
          "Check that sequences on an m2m_through are created for the through model, not a phantom auto-generated m2m table. Refs #11107"
          out = StringIO()
          management.call_command("dumpdata", "m2m_through_regress", format="json", stdout=out)
          self.assertEqual(out.getvalue().strip(), """[{"pk": 1, "model": "m2m_through_regress.usermembership", "fields": {"price": 100, "group": 1, "user": 1}}, {"pk": 1, "model": "m2m_through_regress.person", "fields": {"name": "Guido"}}, {"pk": 1, "model": "m2m_through_regress.group", "fields": {"name": "Python Core Group"}}]""")
  