Django db connection inconsistent between tests and view

[Subaku]

Hello,

I just found a workaround to my problem but wanted to see if anyone has had this issue and might have suggestions. I'm using Django purely for its ORM feature with my Postgres DB but FastAPI for everything else. Note I'm not doing anything async.

Take a simple pytest using django-pytest:

import pytest

from my_django_models import Asset

@pytest.mark.django_db
class TestAssets:
...

    def test_response(self):
        assets = AssetFactory.create_batch(2)
        print(Asset.objects.all())
        resp = self.client.get('/assets')

The view:

from fastapi import APIRouter

from my_django_models import Asset

router = APIRouter()

@router.get('/assets')
def assets():
    print(Asset.objects.all())
    ...

The output:

[<Asset: Asset object (1)>, <Asset: Asset object (2)>]
<QuerySet []>

So the view has access to the db but it's not actually getting my data for some reason as if it has a bad or incorrect connection.
Now if I inherit from Django's TransactionTestCase class and continue using Starlette's TestClient it works... But I don't understand why. So for now that's what I'm doing but wanted to maybe get some clue into why this is the case.

As another note I have made sure I'm pointing at the right settings module and made sure django.setup() was called though I think django-pytest does this for me.

Appreciate any info.

[adambudziak]

I currently have the same problem. Interestingly, when I debug the app I can see that the connection is still fine when FastAPI validates POST request data, i.e. a query ModelName.objects.all() test inside

• test definition ✅
• Pydantic model validator method ✅
• a view itself ❌

However, I performed a little experiment and created a dependency in my view, something like this:

def get_query():
    return ModelName.objects.all()

and if I pass it as a dependency for the view, then it again does not work. ❌

Also, I use pytest without any classes (i.e. plain test_ functions)

[adambudziak]

It seems that the problem can also be mitigated by using pytest.mark.django_db(transaction=True) instead of plain pytest.mark.django_db

[penoux]

I have the same issue, while migrating all my Django views to FastAPI. The view is working OK at runtime, but I encounter database access issues between pytest and a FastAPI dependency.

test_func.py

"""
pytest fixtures : 
  fastapp (FastAPI initialized app with routers)
  test_client (FastAPI TestClient instance)
  auth (User in DB + API credentials)
"""
def test_func(fastapp, test_client, auth):
    user = User.objects.get(username=auth.username)  # works
    user.check_password(auth.password) # works
    authenticate(username=auth.username, password=auth.password) # works

    response = test_client.get('/', auth=auth) # fails (see comments below)
    ...


router.py

@router.get("/")
def get_foo(user: User = Depends(get_current_user):
    ...


dependencies.py

basic = HTTPBasic()

def get_current_user(credentials: HTTPBasicCredentials = Depends(basic)) -> User:
    # fails (see comments below)
    user = authenticate(username=credentials.username, password=credentials.password)
    ...

Test cases :

1. sqlite in-memory database : access to ORM (User) ok in the test, fails with no such table: auth_user in the FastAPI dependency
2. sqlite in-memory database + @pytest.mark.django_db(transaction=True) annotation on test : access to ORM (User) ok in the test, fails with no such table: auth_user in the FastAPI dependency
3. sqlite file database : access to ORM (User) ok in the test, fails with database table is locked: auth_user in the FastAPI dependency
4. sqlite file database + @pytest.mark.django_db() annotation on test : access to ORM (User) ok in the test, fails with database table is locked: auth_user in the FastAPI dependency
5. sqlite file database + @pytest.mark.django_db(transaction=True) annotation on test : access to ORM (User) ok in the test, also OK in the FastAPI dependency

I expected the simplest case (sqlite in-memory database) to work, as it was the case with Django test client. Is there a threading issue there ?

[bameda]

I have the same problem with postgresql. Tests only work using transactional_db fixture or pytest.mark.django_db(transaction=True) or extending the class django.test.TransactionTestCase with my test functions.

It seems that the db is empty in "view" functions even if you create items with the ORM before the call to client.get function.