How to test Async SQL Databases with Encode/Databases(Package) in FastAPI

Question:

- How to run tests in isolation that don't create entries in database.- Also, How we can use the isolated user that is created during the test for other endpoint testing

Some minimal code:

from contextlib import asynccontextmanagerimport databasesimport sqlalchemyfrom fastapi import FastAPI, HTTPExceptionfrom pydantic import BaseModel, EmailStrDATABASE_URL = "postgresql://user:password@postgresserver/db"database = databases.Database(DATABASE_URL)metadata = sqlalchemy.MetaData()users = sqlalchemy.Table("users",    metadata,    sqlalchemy.Column("id", sqlalchemy.Integer, primary_key=True, index=True),    sqlalchemy.Column("first_name", sqlalchemy.String, nullable=True),    sqlalchemy.Column("last_name", sqlalchemy.String, nullable=True),    sqlalchemy.Column("email", sqlalchemy.String, index=True,                      nullable=False, unique=True),    sqlalchemy.Column("password", sqlalchemy.String,                      index=True, nullable=False),)engine = sqlalchemy.create_engine(    DATABASE_URL)metadata.create_all(engine)class UserBase(BaseModel):    first_name: str | None    last_name: str | None    email: EmailStrclass UserCreate(UserBase):    password: strapp = FastAPI()@asynccontextmanagerasync def lifespan(app: FastAPI):    await database.connect()    yield    await database.disconnect()app = FastAPI(lifespan=lifespan)class UserRepository:    async def create(self, obj_in: UserCreate):        query = users.insert().values(            first_name=obj_in.first_name,            last_name=obj_in.last_name,            email=obj_in.email,            password=obj_in.password,        )        await database.execute(query=query)        return obj_in    async def get_by_email(self, email: str):        query = users.select().where(email == users.c.email)        return await database.fetch_one(query=query)user_repository = UserRepository()@app.post("/", response_model=UserBase)async def create_user(    payload: UserCreate,):    if await user_repository.get_by_email(payload.email):        raise HTTPException(            status_code=400,            detail="The user with this username already exists in the database.",        )    return await user_repository.create(payload)##### Testing import pytestfrom fastapi.testclient import TestClient@pytest.fixture()def client():    with TestClient(app) as c:        yield c@pytest.fixture(scope="session")async def db():    database = databases.Database(DATABASE_URL, force_rollback=True)    await database.connect()    yield database    await database.disconnect()async def test_create_user_endpoint(client: TestClient):    user_data = UserCreate(        first_name="John",        last_name="Doe",        email="JohnDoe@example.in",        password="pass123",    )    response = client.post("/", json=user_data.dict())    assert response.status_code == 200    created_user = response.json()    assert created_user["first_name"] == "John"    assert created_user["last_name"] == "Doe"

The issue at involves unexpected behavior when running a FastAPI test multiple times using Pytest. The intention is to ensure test isolation by utilizing the force_rollback=True option in the test database fixture. However, despite using this option, the test fails on subsequent runs, indicating that the user already exists in the database.