Django 测试：匹配的查询不存在

Question

我一直在开发一个博客应用程序，它具有三个常规模型：Post、Category和Comment。现在我正在尝试为这些模型编写一些测试。当我单独运行测试时，它们会顺利通过。但是当我对 test_models.py 作为一个整体运行测试时，我收到四个错误，告诉我我Comment/Category matching query does not exist.明白这个错误意味着 django 无法id在运行测试时创建的数据库中找到我想要的。我的问题是，为什么仅当我对 test_model 文件运行测试时才会出现这些错误，而当我单独对测试类运行测试时却不会出现这些错误？

python manage.py test blog.tests.test_models.TestPostModel -v 2 # this command doesn't cause errors
python manage.py test blog.tests.test_models -v 2  # but this one causes 4 errors in TestPostModel

测试模型.py

from blog.models import Post, Category, Comment, Recipient
from django.test import TestCase

class TestPostModel(TestCase):
@classmethod
def setUpTestData(cls):
    Post.objects.create(title="creation of the first post", body="i am the body of the first post.")

    for i in range(1, 11):
        Category.objects.create(name=f"post_category{i}")

    for i in range(1,11):
        Comment.objects.create(name=f"user{i}", email=f"user{i}@email.com", comment=f"i am comment number {i}.") 

def test_post_str_method(self):
    post = Post.objects.get(id=1) 
    self.assertTrue(isinstance(post, Post)) 
    self.assertEqual(post.__str__(), post.slug) 

def test_post_get_absolute_url(self):
    post = Post.objects.get(id=1) 
    first_post_url = f"/blog/{post.slug}" 
    self.assertEqual(first_post_url, post.get_absolute_url())  

def test_adding_categories_to_post(self):
    post = Post.objects.get(id=1) 
    for i in range(1, 11):
        post.categories.add(Category.objects.get(id=i)) # Error 1: Category matching query does not exist.
    self.assertEqual(post.categories.count(), 10)

def test_deletting_categories_from_post(self):
    post = Post.objects.get(id=1)
    for i in range(1, 11):
        post.categories.add(Category.objects.get(id=i)) # Error 2: Category matching query does not exist.

    for i in range(1, 6):
        Category.objects.filter(id=i).delete()
    self.assertEqual(post.categories.count(), 5) 

def test_adding_comments_to_post(self):
    post = Post.objects.get(id=1)
    comment =""
    for i in range(1,11):
        comment = Comment.objects.get(id=i) # Error 3: Comment matching query does not exist.
        comment.post = post
        comment.save()

    comments = Comment.objects.filter(post=post)
    self.assertEqual(comments.count(), 10)  

def test_deletting_comments_from_post(self):
    post = Post.objects.get(id=1)
    comment =""
    for i in range(1,11):
        comment = Comment.objects.get(id=i)  # Error 4: Comment matching query does not exist
        comment.post = post
        comment.save()

    Comment.objects.filter(id__in=[1, 2, 3]).delete()
    self.assertEqual(Comment.objects.count(), 7) 

class TestCategoryModel(TestCase):
@classmethod
def setUpTestData(cls):
    Category.objects.create(name="first_category")

def test_category_str_method(self):
    category = Category.objects.get(id=1)
    self.assertTrue(isinstance(category, Category)) 
    self.assertEqual(category.__str__(), category.name) 

def test_category_get_absolute_url(self):
    category = Category.objects.get(id=1)
    first_category_url = f"/blog/hashtag/{category.name}" 
    self.assertEqual(first_category_url, category.get_absolute_url())      

class TestCommentModel(TestCase):
@classmethod
def setUpTestData(cls):
    Comment.objects.create(name=f"user", email=f"user@email.com", comment=f"i am a comment.")

def test_comment_str_method(self):
    comment = Comment.objects.get(id=1)
    self.assertEqual(comment.__str__(), comment.comment) 

多谢。

Answer 1

Django 不会为每个测试用例重置自动 ID 字段。所以当你运行时TestCommentModel，TestCategoryModel创建的对象的 id 不等于 1。

您可以在方法中保存新的对象 IDsetUpTestData并在测试用例中使用它：

class TestCategoryModel(TestCase):
    @classmethod
    def setUpTestData(cls):
        cls.obj_id = Category.objects.create(name="first_category").pk

    def test_category_str_method(self):
        category = Category.objects.get(id=self.obj_id)
        self.assertTrue(isinstance(category, Category)) 
        self.assertEqual(category.__str__(), category.name) 

    def test_category_get_absolute_url(self):
        category = Category.objects.get(id=self.obj_id)
        first_category_url = f"/blog/hashtag/{category.name}" 
        self.assertEqual(first_category_url, category.get_absolute_url())