db_url parameter is initializer is ignored and db passed in register_tortoise is used instead

I'm trying to create a test with pytest for my FastAPI + Tortoise ORM app.
To start, I am using the example provided in the documentation.

main.py:

from typing import List
from pydantic import UUID4
from fastapi import Depends, FastAPI, HTTPException, Request
from . import crud, models, schemas, auth
from tortoise.contrib.fastapi import HTTPNotFoundError, register_tortoise
from fastapi_users import FastAPIUsers
from .config import JWT_SECRET, ADMIN_PW
from .workers import selenium, jobs

app = FastAPI()

...

register_tortoise(
    app,
    db_url="sqlite://./db.sqlite3",
    modules={"models": ["app.models"]},
    generate_schemas=True,
    add_exception_handlers=True,
)

My test.py:

# mypy: no-disallow-untyped-decorators
# pylint: disable=E0611,E0401
import asyncio
from typing import Generator

import pytest
from fastapi.testclient import TestClient
from .. import models
from ..main import app

from tortoise.contrib.test import finalizer, initializer


@pytest.fixture(scope="module")
def client() -> Generator:
    initializer(modules=["app.models"], db_url="sqlite://./test_db.sqlite3")
    with TestClient(app) as c:
        yield c
    finalizer()


@pytest.fixture(scope="module")
def event_loop(client: TestClient) -> Generator:
    yield client.task.get_loop()


def test_create_user(
    client: TestClient, event_loop: asyncio.AbstractEventLoop
):  # nosec
    response = client.post(
        "/auth/register",
        json={
            "email": "test@test.com",
            "password": "string",
            "is_active": True,
            "is_superuser": False,
            "is_verified": False,
        },
    )
    assert response.status_code == 201, response.text
    data = response.json()
    assert data["email"] == "test@test.com"
    assert "id" in data
    user_id = data["id"]

    async def get_user_by_db():
        user = await models.UserModel.get(id=user_id)
        return user

    user_obj = event_loop.run_until_complete(get_user_by_db())
    assert user_obj.id == user_id

Yet, the data is written to db.sqlite3 in the root folder and even not cleaned at the end of the test (the data remains in the database).
I have also tried using sqlite://:memory: but to no avail. It always defaults to db.sqlite3.

Is this a bug or am I doing something wrong?

Inspect the register_tortoise call in main.py alongside the initializer and finalizer fixtures in test.py. Reproduce the behavior with the shown pytest setup, then trace which database configuration the application uses during the test. Done means the test writes to test_db.sqlite3 or the in-memory database rather than db.sqlite3, and cleanup removes the test data.