Use Python Fixtures in Classes

TL;DR: use scope, @pytest.mark.usefixtures and request.cls to define your fixture as attribute of the class.

With pytest you can use fixtures to have a nice delimitation of responsibilities within your test modules, sticking to the Arrange-Act-Assert pattern:

import pytest

@pytest.fixture()
def get_some_data():
    yield "get some data"

def test_reading_data(get_some_data):
    assert get_some_data == "get some data"

If the following code works, what about if you want to organize your tests functions within classes? Naively you would assume the following to be a fair implement:

import pytest

@pytest.fixture()
def get_some_data():
    yield "get some data"

class TestDummy(unittest.TestCase):

    def test_dummy(self, get_some_data):
        assert get_some_data() == "get some data"

Running poetry run pytest -vvvs tests/path/to/test_module.py will return the following error in the traceback:

E       TypeError: TestDummy.test_dummy() missing 1 required positional argument: 'get_some_data'

In order to use python fixture within a class, you need to edit the above snippet for the following as you cannot call fixtures directly:

import pytest

@pytest.fixture()
def get_some_data():
    yield "get some data"

class TestDummy(unittest.TestCase):

    @pytest.fixture(autouse=True)
    def _get_some_data(self, get_some_data):
        self.get_some_data = get_some_data

    def test_dummy(self):
        assert self.get_some_data == "get some data"

Note that _get_some_data will be called once per test by default which is inconvenient if you have to perform request through the network e.g. requests.get("https://www.google.com"). You can change this behaviour by adapting the scope:

@pytest.fixture(scope="module")
def get_some_data():
    yield "get some data"

@pytest.fixture(scope="class")
def define_get_data_attribute(request, get_some_data):
    request.cls._get_some_data = get_some_data

@pytest.mark.usefixtures("define_get_data_attribute")
class TestDummy(unittest.TestCase):

    def test_dummy(self):
        assert self._get_some_data == "get some data"

Note that the request object gives access to the requesting test context such as the cls attribute. More here.