Mock aiohttp http request

handler.py

from aiohttp import web, ClientSession


async def handler(request):
    async with ClientSession() as session:
        async with session.post("http://service/path", json={"key": "value"}) as response:
            if response.status in [200, 201]:
                data = await response.json()
                result = data.get("result", False)

                await session.close()
                
                return web.json_response({"result": result})

test_call_other_service.py

from asynctest import CoroutineMock, patch
from aiohttp import web, ClientResponse
from aiohttp.test_utils import TestClient


@patch("aiohttp.ClientSession.post")
async def test_call_other_service(mock: CoroutineMock, aiohttp_client: TestClient) -> None:
    """
    Mock calling aiohttp HTTP request
    """
    returned_data = {"key": "value"}
    mock.return_value.__aenter__.return_value.json = CoroutineMock(
        side_effect=lambda: returned_data
    )

    app = web.Application()
    web_client = await aiohttp_client(app)

    response: ClientResponse = await web_client.get("/path")
    assert response.status == 200

    assert mock.called
    assert mock.call_count == 1