Django管理与使用on_delete = PROTECTED的单元测试之间的结果不一致

Question

我正在Django中制作一个“简单”的零件清单应用程序。

我以此为模型。

from django.db import models


# Create your models here.
class Site(models.Model):
    create_date = models.DateField(auto_now_add=True)
    name = models.TextField(max_length=150,  null=False, unique=True, verbose_name="Site name")
    update_date = models.DateField(auto_now=True)

    def __str__(self):
        return self.name


class Location(models.Model):
    create_date = models.DateField(auto_now_add=True)
    name = models.TextField(max_length=150,  null=False, unique=False)
    site = models.ForeignKey(Site, null=False, on_delete=models.PROTECT)
    update_date = models.DateField(auto_now=True)

    @property
    def site_name(self):
        try:
            return self.site.name
        except Exception as ex:
            return 'Unknown'

    def __str__(self):
        return self.name


class Part(models.Model):
    create_date = models.DateField(auto_now_add=True)
    name = models.TextField(max_length=150, null=False, unique=True)
    verbose_name = models.TextField(max_length=150, null=True)
    update_date = models.DateField(auto_now=True)

    def __str__(self):
        return self.name


class PartLocation(models.Model):
    create_date = models.DateField(auto_now_add=True)
    location = models.ForeignKey(Location, null=False, on_delete=models.PROTECT)
    number_of_parts = models.IntegerField(null=False)
    part = models.ForeignKey(Part, null=False, on_delete=models.PROTECT)
    update_date = models.DateField(auto_now=True)

    @property
    def site(self):
        try:
            return self.location.site.name
        except Exception as ex:
            return 'Unknown'

    def __str__(self):
        return f'{self.part.name}/{self.location.name}/{self.site}/{self.number_of_parts}'

我添加了一个看起来像这样的admin.py：

from django.contrib import admin
from .models import Location, Part, PartLocation, Site


class PartLocationAdmin(admin.ModelAdmin):

    ordering = ('id', 'location', 'part', 'location__site__name', 'number_of_parts',)
    list_display = ('id', 'part', 'get_part_verbose_name', 'location', 'site', 'number_of_parts',)
    list_filter = ('id', 'part', 'location', 'location__site__name', 'number_of_parts',)
    search_fields = ('id', 'part__name', 'location__name', 'location__site__name', 'number_of_parts',)

    def get_part_verbose_name(self,obj):
        if obj.part.verbose_name is None:
            return "-"
        return obj.part.verbose_name
    get_part_verbose_name.command_order_field  = 'Verbose name'  #Allows column order sorting
    get_part_verbose_name.short_description = 'Verbose name'  #Renames column head


class LocationAdmin(admin.ModelAdmin):
    ordering = ('id', 'name', 'site',)
    list_display = ('id', 'name', 'site',)
    search_fields = ('id', 'name', 'site__name',)


class PartAdmin(admin.ModelAdmin):
    ordering = ('id', 'name', 'verbose_name')
    list_display = ('id', 'name', 'verbose_name')
    search_fields = ('id', 'name', 'verbose_name')


# Register your models here.
admin.site.register(Site)
admin.site.register(Location, LocationAdmin)
admin.site.register(Part, PartAdmin)
admin.site.register(PartLocation, PartLocationAdmin)

然后我在tests.py中添加了单元测试：

from django.test import TestCase, TransactionTestCase
import django.db.utils
from .models import Location, Part, PartLocation, Site
from django.db.models import ProtectedError


class ModelTestCases(TransactionTestCase):

    def add_and_delete(self):
        '''
        In this test we will add a site, location, part and partlocation information into the database.
        Then we will ensure that one cannot delete a site until all sub records have also been deleted.
        :return:
        '''

        # Let's create a site.
        site_1 = Site.objects.create(name='site_1')

        # Let's demostrate that you cannot create a location without a cite.
        try:
            loc_1 = Location.objects.create(name='loc_1')
        except django.db.utils.IntegrityError as ex:
            self.assertEqual('null value in column "site_id" violates not-null constraint', ex.args[0].split('\n')[0])

        # Create a Location at site_1
        loc_1 = Location.objects.create(name='loc_1', site=site_1)

        # Create a Part
        part_1 = Part.objects.create(name='part_1', verbose_name='Part One')

        # Let's add inventory or part_1 in loc_1.
        part_loc_1 = PartLocation(location=loc_1, part=part_1, number_of_parts=5)

        # Let's demostrate that one cannot remove site_1 because it has a location.
        try:
            site_1.delete()
            self.fail('Deletion of site not prevented.')
        except ProtectedError as ex:
            pass

        # Let's demostrate that one cannot remove loc_1 because it has a PartLocation record.
        try:
            loc_1.delete()
            self.assertEqual(0, Location.objects.count())
            self.fail('Deletion of location not prevented.')
        except ProtectedError as ex:
            pass

如果我转到管理面板中的“位置”列表，则会看到此信息...

...，然后单击“转到”按钮以删除所选位置，我看到以下内容：

这是我想要的行为。但是我的单元测试允许删除包含零件的位置并引发此错误。

AssertionError: Deletion of location not prevented.

为什么我的管理代码阻止删除，而我的单元测试没有阻止删除？

我的Django版本是：

django.VERSION
(2, 1, 7, 'final', 0)

Answer 1

DOH！我总是犯这个错误！在我的单元测试中，我有这个：

part_loc_1 = PartLocation(location=loc_1, part=part_1, number_of_parts=5)

当我应该写这篇文章的时候：

part_loc_1 = PartLocation.objects.create(location=loc_1, part=part_1, number_of_parts=5)