test_case_with_user_factory_shortened.py

@pytest.fixture(scope='function')
def session(connection):
    transaction = connection.begin()
    session = Session(bind=connection)
    UserFactory._meta.sqlalchemy_session = session # NB: This line added
    yield session
    session.close()
    transaction.rollback()
    
def my_func_to_delete_user(session, user_id):
    session.query(UserModel).filter(UserModel.id == user_id).delete()

def test_case(session):
    user = UserFactory.create()
    assert session.query(UserModel).one()

    my_func_to_delete_user(session, user.id)

    result = session.query(UserModel).one_or_none()
    assert result is None