How can I write a Tornado unit test that tests concurrency

Question

I'm interested in my Tornado handlers not blocking, so I would like to write some unit tests as a health check.

I mean a handler that sleeps asynchronously for 2 seconds. In the test, I want to call this handler twice to simulate "simultaneous" requests.

If I am not mistaken, both of these requests should work simultaneously and, thus, be completed in less than 4 seconds. The problem is that I'm not sure how to make 2 simultaneous requests in my application through AsyncHTTPTestCase.

Here is what I still have:

class SyncSleepHandler(tornado.web.RequestHandler):
    def get(self):
        time.sleep(2)


class AsyncSleepHandler(tornado.web.RequestHandler):
    @gen.coroutine
    def get(self):
        yield gen.sleep(2)


class SleepTest(AsyncHTTPTestCase):
    def get_app(self):
        return Application([(r'/sync', SyncSleepHandler),
                            (r'/async', AsyncSleepHandler)], debug=True)

    def test_async_sleep(self):
        start = time.time()
        resp1 = self.fetch(r'/async', method='GET')
        resp2 = self.fetch(r'/async', method='GET')
        diff = time.time() - start
        self.assertTrue(2 < diff < 4, msg="Difference is {:}".format(diff))

Answer 1

AsyncHTTPTestCase.fetch IOLoop , , self.http_client @tornado.testing.gen_test IOLoop:

@gen_test
def test_async_sleep(self):
    start = time.time()
    resp1, resp2 = yield [
        self.http_client.fetch(self.get_url('/async')),
        self.http_client.fetch(self.get_url('/async')),
    ]
    diff = time.time() - start