title: How to get uri_for with webapp2 in unit test?
body: <p>I'm trying to unit test a handler with webapp2 and am running into what has to be just a stupid little error.</p>
  
  <p>I'd like to be able to use webapp2.uri_for in the test, but I can't seem to do that:</p>
  
  <pre><code>    def test_returns_200_on_home_page(self):
          response = main.app.get_response(webapp2.uri_for('index'))
          self.assertEqual(200, response.status_int)
  </code></pre>
  
  <p>If I just do <code>main.app.get_response('/')</code> it works just fine. </p>
  
  <p>The exception received is:</p>
  
  <pre><code>   Traceback (most recent call last):
    File "/Library/Frameworks/Python.framework/Versions/2.7/lib/python2.7/unittest/case.py", line 318, in run
      testMethod()
    File "tests.py", line 27, in test_returns_200_on_home_page
      webapp2.uri_for('index')
    File "/Users/.../webapp2_example/lib/webapp2.py", line 1671, in uri_for
      return request.app.router.build(request, _name, args, kwargs)
    File "/Users/.../webapp2_example/lib/webapp2_extras/local.py", line 173, in __getattr__
      return getattr(self._get_current_object(), name)
    File "/Users/.../webapp2_example/lib/webapp2_extras/local.py", line 136, in _get_current_object
      raise RuntimeError('no object bound to %s' % self.__name__)
  RuntimeError: no object bound to request
  </code></pre>
  
  <p>Is there some silly setup I'm missing?</p>