How to use TestClient with requests_mock?

Suppose I have a route in my API that creates an http request to an external resource using requests package. When creating a starlette TestClient, it creates four adapters for ws, wss, http and https, so that it can handle all requests to the API. This is problematic since if I want to mock a route with requests_mock.Mocker() for requests to use, all the adapters created by TestClient get overwritten and do not get matched anymore resulting in NoMockAddressError.

I want to create a test with a mocked response for the address I use in my tested API route, so that the route actually sends the request, gets the response and returns it. How do I go about using TestClient along with requests_mock.Mocker? Can I somehow extend TestClient’s http matchers or should I do it differently? Below is an example of a test that is not working for me:

queue.py

import fastapi
import requests

router = fastapi.APIRouter()
@router.get('/queue/')
def queue_messages():
    return requests.get('http://test-url/stats').json()

conftest.py

import fastapi
import pytest
import starlette.testclient

from source import queue

@pytest.fixture(scope='function')
def test_server():
    app = fastapi.FastAPI()

    app.include_router(queue.router, prefix='/api')

    return starlette.testclient.TestClient(app)

test_queue.py

def test_queue_get(requests_mock, test_server):
    stats = { ... }
    requests_mock.get('http://test-url/stats', json=stats)

    response = test_server.get('/api/queue/')
    assert response.json() == {'messages': 45}

[madispp]

I got it working by adding client.base_url to exceptions (real_http=True) for the requests_mock’s fixture. I keep my TestClient in the module scope but have to override requests_mock in its function scope:

@pytest.fixture(scope="module")
def module_client():
    with TestClient(app) as c:
        yield c

@pytest.fixture
def client(module_client, requests_mock):
    test_app_base_url_prefix_regex = re.compile(fr"{re.escape(module_client.base_url)}(/.*)?")
    requests_mock.register_uri(ANY, test_app_base_url_prefix_regex, real_http=True)
    return module_client

[four43]

It works fine for me (on FastAPI) even without real_http :

This doesn’t seem to work anymore due to the TestClient using a base_url of http://testserver? I keep getting

> requests_mock.exceptions.NoMockAddress: No mock address: GET http://testserver/route

../../../.venv/lib/python3.9/site-packages/requests_mock/adapter.py:261: NoMockAddress