Django 抽象模型 + DB 迁移：测试抛出“无法更改表，因为它有待处理的触发事件”

Question

我想编写一个抽象模型 mixin，我可以用它来建立 OneToOne - 与用户模型的关系。这是我的代码：

from django.conf import settings
from django.db import models


class Userable(models.Model):
    user = models.OneToOneField(
        settings.AUTH_USER_MODEL,
        on_delete=models.CASCADE
    )

    class Meta:
        abstract = True

我为此模型编写了以下测试：

class TestUserable(TestCase):

    mixin = Userable

    def setUp(self):
        user = User.objects.create_user(
            email="testuser@test.com",
            name="Test User",
            password="test1234test"
        )
        self.user = user
        self.model = ModelBase(
            '__TestModel__' + self.mixin.__name__, (self.mixin,),
            {'__module__': self.mixin.__module__}
        )

        with connection.schema_editor() as schema_editor:
            schema_editor.create_model(self.model)

    def test_user(self):
        self.model.objects.create(user=self.user)
        self.assertEqual(self.model.objects.count(), 1)

    def tearDown(self):
        with connection.schema_editor() as schema_editor:
            schema_editor.delete_model(self.model)

我的问题是，tearDown() 方法中的这个测试会引发以下错误：

django.db.utils.OperationalError: cannot DROP TABLE "core___testmodel__userable" because it has pending trigger events

这可能是什么原因？我确实运行了 python manage.py makemigrations 和 python manage.py migrate，但没有待处理的迁移（正如预期的那样，因为这是一个抽象模型）。

编辑：它似乎与 OneToOneFields 或 ForeignKeys（关系）有关。如果我将此代码用于常规字段（如 CharFields 或 IntegerFields），则它可以工作。

EDIT2：如果您有另一种更好的方法来测试使用 ForeignKeys 的抽象基础模型，请告诉我！

Answer 1

测试抽象模型的常见做法是为测试创建实际模型

这是model-utils项目https://github.com/jazzband/django-model-utils/blob/master/tests/test_models/test_timestamped_model.py中的示例

from tests.models import UserableTest

class TestUserable(TestCase):
    def setUp(self):
        user = User.objects.create_user(
            email="testuser@test.com",
            name="Test User",
            password="test1234test"
        )
        self.user = user

    def test_user(self):
        UserableTest.objects.create(user=self.user)
        self.assertEqual(UserableTest.objects.count(), 1)

在这个项目中他们有单独的设置DJANGO_SETTINGS_MODULE = tests.settingshttps://github.com/jazzband/django-model-utils/blob/master/tests/settings.py

INSTALLED_APPS = (
    'model_utils',
    'tests',
)
DATABASES = {
    'default': {
        'ENGINE': 'django.db.backends.sqlite3'
    }
}
SECRET_KEY = 'dummy'

并且模型在https://github.com/jazzband/django-model-utils/blob/master/tests/models.py中有描述

from myapp.models import Userable

class UserableTest(Userable):
    pass

Answer 2

试试下面的代码。我已经测试过它可以正常工作。

requirements.txt

Django==1.11.13
pkg-resources==0.0.0
pytz==2018.4

models.py

from django.conf import settings
from django.db import models


class Userable(models.Model):
    user = models.OneToOneField(
        settings.AUTH_USER_MODEL,
        on_delete=models.CASCADE
    )

    class Meta:
        abstract = True

tests.py

# -*- coding: utf-8 -*-
from __future__ import unicode_literals
from django.test import TestCase
from .models import Userable
from django.db import connection
from django.db.models.base import ModelBase
from django.contrib.auth.models import User


class TestUserable(TestCase):

    def setUp(self):
        user = User.objects.create_user(
            username="testuser@test.com",
            password="test1234test"
        )
        self.user = user
        self.model = ModelBase(
            Userable.__name__,
            (Userable,),
            {'__module__': Userable.__module__}
        )

        with connection.schema_editor() as schema_editor:
            schema_editor.create_model(self.model)

    def test_user(self):
        self.model.objects.create(user=self.user)
        self.assertEqual(self.model.objects.count(), 1)

    def tearDown(self):
        with connection.schema_editor() as schema_editor:
            schema_editor.delete_model(self.model)