✅ Fix tests (missed one)

jh0ker · jh0ker · commit 69bfb85298fa · 2017-02-27T15:35:57.000+01:00
python-telegram-bot#494
diff --git a/tests/test_audio.py b/tests/test_audio.py
@@ -59,7 +59,7 @@ def setUp(self):
     def test_send_audio_required_args_only(self):
         message = self._bot.sendAudio(self._chat_id, self.audio_file)
 
-        self.assertEqual(message.caption, '')
+        self.assertEqual(message.caption, None)
 
         audio = message.audio
 
