How to use the webtest.debugapp.debug_app function in WebTest

def setUp(self):
        self.s = http.StopableWSGIServer.create(debug_app)
        self.s.wait()
        self.application_url = self.s.application_url.rstrip('/')

def test_repr(self):
        def _repr(v):
            br = repr(v)
            if len(br) > 18:
                br = br[:10] + '...' + br[-5:]
                br += '/%s' % len(v)

            return br

        app = webtest.TestApp(debug_app)
        res = app.post('/')
        self.assertEqual(
            repr(res),
            '<200 OK text/plain body=%s>' % _repr(res.body)
        )
        res.content_type = None
        self.assertEqual(
            repr(res),
            '<200 OK body=%s>' % _repr(res.body)
        )
        res.location = 'http://pylons.org'
        self.assertEqual(
            repr(res),
            '<200 OK location: http://pylons.org body=%s>' % _repr(res.body)
        )

def test_mustcontains(self):
        app = webtest.TestApp(debug_app)
        res = app.post('/', params='foobar')
        res.mustcontain('foobar')
        self.assertRaises(IndexError, res.mustcontain, 'not found')
        res.mustcontain('foobar', no='not found')
        res.mustcontain('foobar', no=['not found', 'not found either'])
        self.assertRaises(IndexError, res.mustcontain, no='foobar')
        self.assertRaises(
            TypeError,
            res.mustcontain, invalid_param='foobar'
        )

def test_url_without_fragments(self):
        app = webtest.TestApp(debug_app)
        res = app.get('http://localhost/')
        self.assertEqual(res.status_int, 200)

def test_get_extra_environ(self):
        app = webtest.TestApp(debug_app,
                              extra_environ={'HTTP_ACCEPT_LANGUAGE': 'ru',
                                             'foo': 'bar'})
        res = app.get('http://localhost/')
        self.assertIn('HTTP_ACCEPT_LANGUAGE: ru', res, res)
        self.assertIn("foo: 'bar'", res, res)

        res = app.get('http://localhost/', extra_environ={'foo': 'baz'})
        self.assertIn('HTTP_ACCEPT_LANGUAGE: ru', res, res)
        self.assertIn("foo: 'baz'", res, res)

def test_url_with_fragments(self):
        app = webtest.TestApp(debug_app)
        res = app.get('http://localhost/#ananchor')
        self.assertEqual(res.status_int, 200)

def test_post_extra_environ(self):
        app = webtest.TestApp(debug_app,
                              extra_environ={'HTTP_ACCEPT_LANGUAGE': 'ru',
                                             'foo': 'bar'})
        res = app.post('http://localhost/')
        self.assertIn('HTTP_ACCEPT_LANGUAGE: ru', res, res)
        self.assertIn("foo: 'bar'", res, res)

        res = app.post('http://localhost/', extra_environ={'foo': 'baz'})
        self.assertIn('HTTP_ACCEPT_LANGUAGE: ru', res, res)
        self.assertIn("foo: 'baz'", res, res)