Tornado AsyncHTTPTestCase client doesn't handle Cookies within itself thus can't be used to test session based scenarios. This code provides basic support for that.

LoginTest.py

TEST_URL='/resource'
LOGIN_URL='/login'
LOGOUT_URL='/logout'
					
application = tornado.web.Application([
			(LOGIN_URL, LoginHandler),
			(LOGOUT_URL, LogoutHandler),
			(TEST_URL, ResourceHandler),
			], cookie_secret='cookie_secret', login_url=LOGIN_URL)
			
class LoginTest(tornado.testing.AsyncHTTPTestCase):
	def __init__(self, *rest):
		self.cookies = Cookie.SimpleCookie()
		tornado.testing.AsyncHTTPTestCase.__init__(self, *rest)
		
	def get_app(self):
		return application
		
	def _update_cookies(self, headers):
		'''
		from
		https://github.com/peterbe/tornado-utils/blob/master/tornado_utils/http_test_client.py
		'''
		try:
			sc = headers['Set-Cookie']
			cookies = escape.native_str(sc)
			self.cookies.update(Cookie.SimpleCookie(cookies))
			while True:
				self.cookies.update(Cookie.SimpleCookie(cookies))
				if ',' not in cookies:
					break
				cookies = cookies[cookies.find(',') + 1:]
		except KeyError:
			return
			
	def setUp(self):
		tornado.testing.AsyncHTTPTestCase.setUp(self)
		resp = self.fetch(TEST_URL, follow_redirects=False)
		self.assertEqual(302, resp.code) # redir to LOGIN_URL
		
	def fetch(self, url, *r, **kw):
		if 'follow_redirects' not in kw:
			kw['follow_redirects'] = False
		header = {}
		hs = self.cookies.output()
		if hs != '':
			hs = hs.split(':')[1]
			header['Cookie'] = hs
			#print "URL: {}, Cookie: {}".format(url, header['Cookie'])
		resp = tornado.testing.AsyncHTTPTestCase.fetch(self, url, headers=header, *r, **kw)
		self._update_cookies(resp.headers)
		return resp
		
	def test_login(self):
		resp = self.fetch(LOGIN_URL, method='POST', body=urllib.urlencode({'u' : 'user', 'p' : 'pass'}), follow_redirects=False)
		self.assertEqual(200, resp.code)
		resp = self.fetch(TEST_URL, follow_redirects=False)
		self.assertEqual(200, resp.code)
		resp = self.fetch(LOGOUT_URL, follow_redirects=False)
		self.assertEqual(200, resp.code)