new_contents: #!/usr/bin/env python
  # -*- coding: utf-8 -*-
  
  from main import TornadoApp
  from tornado.testing import AsyncHTTPTestCase, gen_test
  
  
  class TornadoAppTest(AsyncHTTPTestCase):
      def get_app(self):
          return TornadoApp()
  
      @gen_test
      def test_app(self):
          response = yield self.http_client.fetch(self.get_url('/'))
          self.assertEqual(str(response.body, 'utf-8'), "Hello, world")
  
subject: Add tornado test