Почему Unit тесты Django работают по отдельности, но падают вместе в одном файле?

Question

[alex-shef]

class PostModelTest(TestCase):
    @classmethod
    def setUpTestData(cls):
        user = User.objects.create_user(username='testuser', password='testpassword')
        Post.objects.create(title='Test Post', slug='test-post', author=user, body='This is a test post',
                            publish=timezone.now(), status='published')

    def test_title_max_length(self):
        post = Post.objects.get(id=1)
        max_length = post._meta.get_field('title').max_length
        self.assertEqual(max_length, 250)


class CommentModelTest(TestCase):
    @classmethod
    def setUpTestData(cls):
        user = User.objects.create_user(username='testuser', password='testpassword')
        post = Post.objects.create(title='Test Post', slug='test-post', author=user, body='This is a test post',
                                   publish=timezone.now(), status='published')
        Comment.objects.create(
            post=post,
            name='John Doe',
            email='[e-mail]',
            body='Test comment',
            created=timezone.now(),
            updated=timezone.now(),
            active=True
        )

    def test_comment_str_representation(self):
        comment = Comment.objects.get(id=1)
        expected_str = 'Comment by John Doe on Test Post'
        self.assertEqual(str(comment), expected_str)

Ошибка raise self.model.DoesNotExist(
blog.models.Post.DoesNotExist: Post matching query does not exist.

Выполняю в Docker

Answer 1

[deepblack]

Документация

After each test, Django calls flush to reset the database state. This empties all tables and emits the post_migrate signal, which recreates one content type and four permissions for each model. This operation gets expensive proportionally to the number of models.

Setting reset_sequences = True on a TransactionTestCase will make sure sequences are always reset before the test run

class TestsThatDependsOnPrimaryKeySequences(TransactionTestCase):
    reset_sequences = True

    def test_animal_pk(self):
        lion = Animal.objects.create(name="lion", sound="roar")
        # lion.pk is guaranteed to always be 1
        self.assertEqual(lion.pk, 1)

UPD:
Инфа выше для понимания происходящего, но видимо не до всех доходит.
Вот еще пример со stackoverflow, но вобще есть несколько различных вариантов решения.

Comments

[alex-shef]

спасибо, но не помогло

[alex-shef]

Спасибо, я сам не нашел этот пример со stackoverflow. Всё заработало.