如何模拟 ManyToMany 字段？

Question

我有这些模型要测试：

# models.py (simplified, name is a costum multilanguage field)
class NameType(models.Model):
    name = models.CharField(_('nome'), max_length=25, unique=True)

class NameLanguage(models.Model):
    name = models.CharField(_('nome'), max_length=25, unique=True)
    syntax = models.ManyToManyField(
        NameType, related_name='syntax_name',
        verbose_name=_('sintassi'))

为了隔离我要使用的测试mock()（我已经测试过NameType）

# test_models.py
class NameLanguageTest(TestCase):
    def test_language_created(self):
        self.name = Mock(spec=NameType)
        self.surname = Mock(spec=NameType)
        self.romans = NameLanguage.objects.create(name='Romans')
        self.romans.syntax.add(self.name)
        self.romans.syntax.add(self.surname)
        self.assertEqual(NameLanguage.objects.all().count(), 1)
        self.assertEqual(
            list(NameLanguage.objects.get(name='romans').syntax.all()),
            [self.name, self.surname]
        )

但是当我尝试将 self.name 和 self.surname 添加到 M2M syntax 时，它给了我这个错误：

Traceback (most recent call last):
  File "E:\progetti\ElencoNomi\lists\tests\test_models.py", line 79, in test_language_created
    self.romans.syntax.add(self.name)
  File "e:\progetti\envs\ElencoNomi\lib\site-packages\django\db\models\fields\related_descriptors.py", line 938, in add
    through_defaults=through_defaults,
  File "e:\progetti\envs\ElencoNomi\lib\site-packages\django\db\models\fields\related_descriptors.py", line 1039, in _add_items
    if not router.allow_relation(obj, self.instance):
  File "e:\progetti\envs\ElencoNomi\lib\site-packages\django\db\utils.py", line
280, in allow_relation
    return obj1._state.db == obj2._state.db
  File "E:\Python\Python37\lib\unittest\mock.py", line 593, in __getattr__
    raise AttributeError("Mock object has no attribute %r" % name)
AttributeError: Mock object has no attribute '_state'

我还应该使用self.name 和self.surname（就像我在上面的代码中所做的那样）还是只使用name 和surname？有区别吗？

谢谢

编辑：就像我在评论中建议的那样添加

    self.name._state = Mock()
    self.surname._state = Mock()

但它给出了这个错误：

Traceback (most recent call last):
  File "E:\progetti\ElencoNomi\lists\tests\test_models.py", line 81, in test_language_created
    self.romans.syntax.add(self.name)
  File "e:\progetti\envs\ElencoNomi\lib\site-packages\django\db\models\fields\related_descriptors.py", line 938, in add
    through_defaults=through_defaults,
  File "e:\progetti\envs\ElencoNomi\lib\site-packages\django\db\models\fields\related_descriptors.py", line 1042, in _add_items
    (obj, self.instance._state.db, obj._state.db)
ValueError: Cannot add "<Mock spec='NameType' id='86024648'>": instance is on database "default", value is on database "<Mock name='mock._state.db' id='93279176'>"

编辑：

我很惊讶我不能模拟一个简单的 m2m 字段，无论如何使用 factory_boy 都可以（也许，请检查）：

# factories.py:
class NameTypeFactory(factory.DjangoModelFactory):
    class Meta:
        model = NameType

# test_models.py
class NameLanguageTest(TestCase):
    def test_language_created(self):
        self.name = NameTypeFactory()
        self.surname = NameTypeFactory()
        self.romans = NameLanguage.objects.create(
            name_en='Romans', name_it='Romani')
        self.romans.syntax.add(self.name)
        self.romans.syntax.add(self.surname)
        self.assertEqual(NameLanguage.objects.all().count(), 1)
        self.assertEqual(
            list(NameLanguage.objects.get(name_it='romani').syntax.all()),
            [self.name, self.surname]
        )

但这真的是我想要的吗？

Answer 1

Django 使用模型和表来运行测试，还有更复杂的库可以全面模拟您的数据（如果需要，甚至在数据库中创建它），例如 factory_boy

你可以做类似的事情

import factory, factory.django
from . import models

class NameTypeFactory(factory.django.DjangoModelFactory):
    class Meta:
        model = models.NameType 

class NameLanguageFactory(factory.django.DjangoModelFactory):
    @factory.post_generation
    def groups(self, create, extracted, **kwargs):
        if create and extracted:
            # A list of groups were passed in, use them
            for group in extracted:
                self.groups.add(group)