Viewing github.com/django/django-stable-4.1.x/tests/m2m_through

```
from io import StringIO
```

from django.contrib.auth.models import User

```
from django.core import management
```
```
from django.test import TestCase
```

from .models import Car, CarDriver, Driver, Group, Membership, Person, UserMembership

```
class M2MThroughTestCase(TestCase):
```
```
    @classmethod
```
```
    def setUpTestData(cls):
```

        cls.bob = Person.objects.create(name="Bob")

        cls.jim = Person.objects.create(name="Jim")

        cls.rock = Group.objects.create(name="Rock")

        cls.roll = Group.objects.create(name="Roll")

        cls.frank = User.objects.create_user("frank", "[email protected]", "password")

        cls.jane = User.objects.create_user("jane", "[email protected]", "password")

```
        # normal intermediate model
```

        cls.bob_rock = Membership.objects.create(person=cls.bob, group=cls.rock)

        cls.bob_roll = Membership.objects.create(

            person=cls.bob, group=cls.roll, price=50

```
        )
```

        cls.jim_rock = Membership.objects.create(

            person=cls.jim, group=cls.rock, price=50

```
        )
```

        # intermediate model with custom id column

        cls.frank_rock = UserMembership.objects.create(user=cls.frank, group=cls.rock)

        cls.frank_roll = UserMembership.objects.create(user=cls.frank, group=cls.roll)

        cls.jane_rock = UserMembership.objects.create(user=cls.jane, group=cls.rock)

    def test_retrieve_reverse_m2m_items(self):

        self.assertCountEqual(self.bob.group_set.all(), [self.rock, self.roll])

    def test_retrieve_forward_m2m_items(self):

        self.assertSequenceEqual(self.roll.members.all(), [self.bob])

    def test_retrieve_reverse_m2m_items_via_custom_id_intermediary(self):

        self.assertCountEqual(self.frank.group_set.all(), [self.rock, self.roll])

    def test_retrieve_forward_m2m_items_via_custom_id_intermediary(self):

        self.assertSequenceEqual(self.roll.user_members.all(), [self.frank])

    def test_join_trimming_forwards(self):

```
        """
```

        Too many copies of the intermediate table aren't involved when doing a

```
        join (#8046, #8254).
```
```
        """
```
```
        self.assertSequenceEqual(
```

            self.rock.members.filter(membership__price=50),

```
            [self.jim],
```
```
        )
```

    def test_join_trimming_reverse(self):

```
        self.assertSequenceEqual(
```

            self.bob.group_set.filter(membership__price=50),

```
            [self.roll],
```
```
        )
```

class M2MThroughSerializationTestCase(TestCase):

```
    @classmethod
```
```
    def setUpTestData(cls):
```

        cls.bob = Person.objects.create(name="Bob")

        cls.roll = Group.objects.create(name="Roll")

        cls.bob_roll = Membership.objects.create(person=cls.bob, group=cls.roll)

```
    def test_serialization(self):
```

        "m2m-through models aren't serialized as m2m fields. Refs #8134"

```
        pks = {
```
```
            "p_pk": self.bob.pk,
```
```
            "g_pk": self.roll.pk,
```
```
            "m_pk": self.bob_roll.pk,
```

            "app_label": "m2m_through_regress",

```
        }
```
```
        out = StringIO()
```
```
        management.call_command(
```

            "dumpdata", "m2m_through_regress", format="json", stdout=out

```
        )
```
```
        self.assertJSONEqual(
```
```
            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.assertXMLEqual(
```
```
            out.getvalue().strip(),
```
```
            """
```
```
<?xml version="1.0" encoding="utf-8"?>
```
```
<django-objects version="1.0">
```

  <object pk="%(m_pk)s" model="%(app_label)s.membership">

    <field to="%(app_label)s.person" name="person" rel="ManyToOneRel">%(p_pk)s</field>

    <field to="%(app_label)s.group" name="group" rel="ManyToOneRel">%(g_pk)s</field>

    <field type="IntegerField" name="price">100</field>

```
  </object>
```

  <object pk="%(p_pk)s" model="%(app_label)s.person">

    <field type="CharField" name="name">Bob</field>

```
  </object>
```

  <object pk="%(g_pk)s" model="%(app_label)s.group">

    <field type="CharField" name="name">Roll</field>

```
  </object>
```
```
</django-objects>
```
```
        """.strip()
```
```
            % pks,
```
```
        )
```
```
class ToFieldThroughTests(TestCase):
```
```
    @classmethod
```
```
    def setUpTestData(cls):
```

        cls.car = Car.objects.create(make="Toyota")

        cls.driver = Driver.objects.create(name="Ryan Briscoe")

        CarDriver.objects.create(car=cls.car, driver=cls.driver)

        # We are testing if wrong objects get deleted due to using wrong

        # field value in m2m queries. So, it is essential that the pk

```
        # numberings do not match.
```

        # Create one intentionally unused driver to mix up the autonumbering

        cls.unused_driver = Driver.objects.create(name="Barney Gumble")

        # And two intentionally unused cars.

        cls.unused_car1 = Car.objects.create(make="Trabant")

        cls.unused_car2 = Car.objects.create(make="Wartburg")

```
    def test_to_field(self):
```

        self.assertSequenceEqual(self.car.drivers.all(), [self.driver])

```
    def test_to_field_reverse(self):
```

        self.assertSequenceEqual(self.driver.car_set.all(), [self.car])

    def test_to_field_clear_reverse(self):

```
        self.driver.car_set.clear()
```

        self.assertSequenceEqual(self.driver.car_set.all(), [])

```
    def test_to_field_clear(self):
```
```
        self.car.drivers.clear()
```

        self.assertSequenceEqual(self.car.drivers.all(), [])

    # Low level tests for _add_items and _remove_items. We test these methods

    # because .add/.remove aren't available for m2m fields with through, but

    # through is the only way to set to_field currently. We do want to make

    # sure these methods are ready if the ability to use .add or .remove with

    # to_field relations is added some day.

```
    def test_add(self):
```

        self.assertSequenceEqual(self.car.drivers.all(), [self.driver])

        # Yikes - barney is going to drive...

        self.car.drivers._add_items("car", "driver", self.unused_driver)

```
        self.assertSequenceEqual(
```
```
            self.car.drivers.all(),
```

            [self.unused_driver, self.driver],

```
        )
```

    def test_m2m_relations_unusable_on_null_to_field(self):

```
        nullcar = Car(make=None)
```
```
        msg = (
```

            '"<Car: None>" needs to have a value for field "make" before this '

            "many-to-many relationship can be used."

```
        )
```

        with self.assertRaisesMessage(ValueError, msg):

```
            nullcar.drivers.all()
```

    def test_m2m_relations_unusable_on_null_pk_obj(self):

```
        msg = (
```

            "'Car' instance needs to have a primary key value before a "

            "many-to-many relationship can be used."

```
        )
```

        with self.assertRaisesMessage(ValueError, msg):

            Car(make="Ford").drivers.all()

```
    def test_add_related_null(self):
```

        nulldriver = Driver.objects.create(name=None)

        msg = 'Cannot add "<Driver: None>": the value for field "driver" is None'

        with self.assertRaisesMessage(ValueError, msg):

            self.car.drivers._add_items("car", "driver", nulldriver)

```
    def test_add_reverse(self):
```

        car2 = Car.objects.create(make="Honda")

        self.assertCountEqual(self.driver.car_set.all(), [self.car])

        self.driver.car_set._add_items("driver", "car", car2)

        self.assertCountEqual(self.driver.car_set.all(), [self.car, car2])

```
    def test_add_null_reverse(self):
```

        nullcar = Car.objects.create(make=None)

        msg = 'Cannot add "<Car: None>": the value for field "car" is None'

        with self.assertRaisesMessage(ValueError, msg):

            self.driver.car_set._add_items("driver", "car", nullcar)

    def test_add_null_reverse_related(self):

        nulldriver = Driver.objects.create(name=None)

```
        msg = (
```

            '"<Driver: None>" needs to have a value for field "name" before '

            "this many-to-many relationship can be used."

```
        )
```

        with self.assertRaisesMessage(ValueError, msg):

            nulldriver.car_set._add_items("driver", "car", self.car)

```
    def test_remove(self):
```

        self.assertSequenceEqual(self.car.drivers.all(), [self.driver])

        self.car.drivers._remove_items("car", "driver", self.driver)

        self.assertSequenceEqual(self.car.drivers.all(), [])

```
    def test_remove_reverse(self):
```

        self.assertSequenceEqual(self.driver.car_set.all(), [self.car])

        self.driver.car_set._remove_items("driver", "car", self.car)

        self.assertSequenceEqual(self.driver.car_set.all(), [])

class ThroughLoadDataTestCase(TestCase):

```
    fixtures = ["m2m_through"]
```
```
    def test_sequence_creation(self):
```
```
        """
```

        Sequences on an m2m_through are created for the through model, not a

        phantom auto-generated m2m table (#11107).

```
        """
```
```
        out = StringIO()
```
```
        management.call_command(
```

            "dumpdata", "m2m_through_regress", format="json", stdout=out

```
        )
```
```
        self.assertJSONEqual(
```
```
            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"}}]',

```
        )
```