Using PyTest to create and run tests within Docker container

I'm trying to create a fixture that can take existing test files and execute them within a docker container. I just can't seem to wrap my head around it.

Non working code for reference.

test_foo.py

class TestClass:

    def test_example(self):
        a = 1
        b = 2
        assert a + b == 3

conftest.py

import docker as docker_py
import pytest


docker = docker_py.from_env()


@pytest.fixture(autouse=True, scope="class")
def generate_container(request):
    """ Create a container for all tests within class to run inside of """

    con = docker.containers.run(image="test_image", tty=True, detach=True)
    request.cls.container = con
    

@pytest.fixture(autouse=True, scope="function")
def run_tests_in_container(request):
    """
    Not sure how to get the contents of request.function 
    to execute inside of the docker container
    """

    output = request.cls.container.exec_run( ??? ) 

    exit_code = output[0]
    assert exit_code == 0
   

Ideally I'd like the test to only run inside the container. I think with my current approach the test will run inside the container and then run again on the host (unless I add in pytest.skip but that seems wrong)