mock tornado's AsyncHTTPClient().fetch - coroutine

fetch_mock_coroutine.py

#!/usr/bin/env python

from tornado import gen
from tornado.ioloop import IOLoop
from tornado.httpclient import AsyncHTTPClient
from tornado.httpclient import HTTPRequest
from tornado.httpclient import HTTPResponse

import mock
import StringIO

def setup_fetch(fetch_mock, status_code, body=None):
    @gen.coroutine
    def side_effect(request, **kwargs):
        if request is not HTTPRequest:
            request = HTTPRequest(request)
        buffer = StringIO.StringIO(body)
        response = HTTPResponse(request, status_code, None, buffer)
        raise gen.Return(response)

    fetch_mock.side_effect = side_effect

@gen.coroutine
def main():
    client = AsyncHTTPClient()
    with mock.patch.object(client, 'fetch') as fetch_mock:
        setup_fetch(fetch_mock, 200, 'hello')
        response = yield gen.Task(client.fetch, 'http://google.com')
        print response.body

IOLoop.instance().run_sync(main)