I m getting error State object has no attribute implementation with FastAPI test code. My source: # tests/example_test.py import pytest from httpx import AsyncClient from webserver import app @pytest.mark.anyio async def test_get_value(): async with AsyncClient(app=app) as client: response = await client.get( /api/get_value ) assert response.status_code == 200 assert response.json() == { value : 0, } # webserver.py from fastapi import FastAPI from fastapi import Request from httpx import AsyncClient from contextlib import asynccontextmanager from implementation import Implementation @asynccontextmanager async def lifespan(app: FastAPI): async with AsyncClient(app=app) as client: implementation = Implementation() yield { implementation : implementation} implementation.shutdown() app = FastAPI(lifespan=lifespan) @app.post( /api/increment ) async def api_increment( request: Request, ): implementation: Implementation = request.state.implementation implementation.increment() return {} @app.get( /api/get_value ) async def api_get_value( request: Request, ): implementation: Implementation = request.state.implementation value = implementation.get_value() return { value : value, } # implementation.py class Implementation(): def __init__(self) -> None: self.current_value = 0 self._initialized = True print(f Implementation starts ) def shutdown(self) -> None: A function which must be called to cleanup resources before exit self._initialized = False print(f Implementation stops ) def increment(self) -> None: In reality this would do something like read/write to a file, db etc self.current_value += 1 def get_value(self) -> None: return self.current_value How to fix? FYI: This synchronous test works: from fastapi.testclient import TestClient def test_get_value_synchronous(): with TestClient(app) as client: response = client.get( /api/get_value ) assert response.status_code == 200 assert response.json() == { value : 0, }