Flask-login pytest how to test logout

Question

I am building a test suite for a flask app's auth blueprint.

I've successfully built tests for user registering and login in, but I am having some trouble to test my logout route.

This is my logout route in the flask app:

@auth_blueprint.route("/logout", methods=["GET"])
def logout_route():
    if current_user.is_authenticated:
        logout_user()
        
    return redirect(url_for("auth.login_page"))

When the user GETs the /users/logout endpoint, he is first logged out, if he is authenticated and then redirected to a different page.

I am currently utilizing the following fixtures for the test:

import pytest
import os
from decimal import *
import hashlib

from mongoengine import connect
os.environ["CONFIG_TYPE"] = "config.TestingConfig"

from app import create_app, socketio
from app.utilities import get_utc_now_func
from app.models import *

@pytest.fixture(scope='module')
def create_flask_app():
    #drop all records in testDatabase before strting new test module
    db = connect(host=os.environ["MONGODB_SETTINGS_TEST"], alias="testConnect")
    for collection in db["testDatabase"].list_collection_names():
        db["testDatabase"].drop_collection(collection)
    db.close()
    
    # Create a test client using the Flask application configured for testing
    flask_app = create_app()
    return flask_app

@pytest.fixture(scope='function')
def test_client(create_flask_app):
    """
    Establish a test client for use within each test module
    """
    with create_flask_app.test_client() as testing_client:
        with create_flask_app.app_context():
            yield testing_client 

And running the following test:

def test_logout_page_get(create_flask_app, test_client):
    """
    GIVEN a logout_route view function
    WHEN a user submits GET to '/users/logout'
    THEN check that the user is logged out and redirected correctly if logged in
    """
    @create_flask_app.login_manager.request_loader
    def load_user_from_request(request):
        return User.objects(username="test_register_user")[0]
    assert isinstance(current_user, User)

    response = test_client.get('/users/logout', follow_redirects=True)
    assert response.status_code == 200
    assert not isinstance(current_user, User)

The test first logs in a user and asserts that such user is logged in. Then the test calls the logout endpoint and asserts a 200 HTTP response and that no user is logged in anymore.

But I'm receiving the following error:

_________________________________________________________________ test_logout_page_get _________________________________________________________________

create_flask_app = <Flask 'app'>, test_client = <FlaskClient <Flask 'app'>>

    def test_logout_page_get(create_flask_app, test_client):
        """
        GIVEN a logout_route view function
        WHEN a user submits GET to '/users/logout'
        THEN check that the user is logged out and redirected correctly if logged in
        """
        @create_flask_app.login_manager.request_loader
        def load_user_from_request(request):
            return User.objects(username="test_register_user")[0]
>       assert isinstance(current_user, User)
E       assert False
E        +  where False = isinstance(current_user, User)

tests/functional/test_auth.py:116: AssertionError

The current_user object is still referencing the user that I had logged in, meaning that the route didn't execute the logout command.

Any idea why that is happening?