class-scoped fixtures VS test subclasses

[MRigal]

Hi,

I'm trying to build a base class to hold a common test setup and assumptions, that I want to enable in subclasses (inspired by this article) having the fixture-powered setup be dependent on class variables. However this approach clashes with class-scoped fixtures which are not run in subclasses of test classes, so any effect or class variables initialized there are not available. I don't know if it's a feature or a bug.

I wonder if this is a bug, if the fixtures should be called in __init_subclass__() for example. Or maybe if an additional "subclass" scope would be of interest or just legit to have?

Here a concrete example, modifying the code from the docs https://docs.pytest.org/en/stable/how-to/fixtures.html#running-multiple-assert-statements-safely

I'm also open to any other suggestion to get a similar result. Passing fixtures as subclasses variable was also not successful.

# contents of tests/end_to_end/test_login.py
from unittest.mock import MagicMock
from urllib.parse import urljoin
from uuid import uuid4

import pytest

Chrome = MagicMock()
AdminApiClient = MagicMock()
User = MagicMock()
LandingPage = MagicMock()
LoginPage = MagicMock()


@pytest.fixture(scope="class")
def admin_client(base_url, admin_credentials):
    return AdminApiClient(base_url, **admin_credentials)


@pytest.fixture(scope="class")
def user(admin_client):
    _user = User(name="Susan", username=f"testuser-{uuid4()}", password="P4$$word")
    admin_client.create_user(_user)
    yield _user
    admin_client.delete_user(_user)


@pytest.fixture(scope="class")
def driver():
    _driver = Chrome()
    yield _driver
    _driver.quit()


@pytest.fixture(scope="class")
def landing_page(driver, login):
    return LandingPage(driver)


class TestLandingPageSuccessBase:

    __test__ = False  # Hide from test discovery

    def __init_subclass__(cls, **kwargs):
        super().__init_subclass__(**kwargs)
        cls.__test__ = True  # Enable test discovery for subclasses

    api_version: str  # To be defined in subclasses

    # Unfortunately, login is not called in subclasses!!!
    @pytest.fixture(scope="class", autouse=True)
    def login(self, driver, base_url, user):
        driver.get(urljoin(base_url, f"/{self.api_version}/login"))
        page = LoginPage(driver)
        page.login(user)

    def test_name_in_header(self, landing_page, user):
        assert landing_page.header == f"Welcome, {user.name}!"

    def test_sign_out_button(self, landing_page):
        assert landing_page.sign_out_button.is_displayed()

    def test_profile_link(self, base_url, landing_page, user):
        profile_href = urljoin(base_url, f"/profile?id={user.profile_id}")
        assert landing_page.profile_link.get_attribute("href") == profile_href


class TestLandingPageSuccessV1(TestLandingPageSuccessBase):

    api_version: str = 'v1'


class TestLandingPageSuccessV2(TestLandingPageSuccessBase):

    api_version: str = 'v2'

Running locally on Python 3.14.0 and pytest 8.4.2.

[The-Compiler]

Could you please show a complete, standalone example which can actually be run to reproduce the problem you describe? For starters, base_url and admin_credentials are undefined in yours, and a more minimal example works just fine:

import pytest

@pytest.fixture(scope="class")
def data():
    return []


class TestBase:

    __test__ = False  # Hide from test discovery

    def __init_subclass__(cls, **kwargs):
        super().__init_subclass__(**kwargs)
        cls.__test__ = True  # Enable test discovery for subclasses

    value: int  # To be defined in subclasses

    @pytest.fixture(scope="class", autouse=True)
    def fixt(self, data):
        data.append(self.value)

    def test_base(self, data):
        assert data == [self.value]


class Test42(TestBase):

    value: int = 42

[MRigal]

Hi @The-Compiler

Thanks for the quick answer and sorry for the bad example, I thought to take something close to what is in the pytest docs to overcome the complexity of my example, but it was not standalone. Thanks also for the example you gave that shows me another way to probably achieve what I want.

A first, based on yours, example that shows what do not work currently would be the following:

import pytest


@pytest.fixture(scope="class")
def base_value():
    return 5


class TestBase:

    __test__ = False  # Hide from test discovery

    def __init_subclass__(cls, **kwargs):
        super().__init_subclass__(**kwargs)
        cls.__test__ = True  # Enable test discovery for subclasses

    value: int  # To be defined in subclasses
    new_value: int  # Also leaving this out does not change the result

    @pytest.fixture(scope="class", autouse=True)
    def fixt(self, base_value):
        self.new_value = self.value + base_value

    def test_base(self, base_value):
        assert self.new_value == self.value + base_value


class Test42(TestBase):

    value: int = 42

[MRigal]

So to phrase it differently: thanks for your approach @The-Compiler ! I was able to do what I wanted using "data-holding fixtures" how you showcased them!

If others are interested, as in real-life you will use subclasses in different test files, the "data" fixture needs to be specified in conftest.py to be available everywhere.

I still wonder if the first approach which I intended to achieve is supposed to work or not, but saving some state, query result or whatever from a "setup" fixture on the class does not work on subclasses.