Added missing testing config

fixes #1302

docs/testing.rst

@@ -98,7 +98,9 @@ test method to our class, like this::
 
         def setUp(self):
             self.db_fd, flaskr.app.config['DATABASE'] = tempfile.mkstemp()
+            flaskr.app.config['TESTING'] = True
             self.app = flaskr.app.test_client()
+            with flaskr.app.app_context():
                 flaskr.init_db()
 
         def tearDown(self):