Refer to the document below, I can do unit test using Python, but I found there is no way to pass the environment variables (i.e. config properties) when calling setup_fn_call().
@pytest.mark.asyncio
async def test_parse_request_without_data():
call = await fixtures.setup_fn_call(handler)
content, status, headers = await call
assert 200 == status
assert {"message": "Hello World"} == json.loads(content)