[mdr] Add audio test

youtube_dl/extractor/mdr.py

@@ -20,6 +20,17 @@ class MDRIE(InfoExtractor):
         # MDR regularily deletes its videos
         'url': 'http://www.mdr.de/fakt/video189002.html',
         'only_matching': True,
+    },  {
+        # audio
+        'url': 'http://www.mdr.de/kultur/audio1312272_zc-15948bad_zs-86171fdd.html',
+        'md5': '64c4ee50f0a791deb9479cd7bbe9d2fa',
+        'info_dict': {
+            'id': '1312272',
+            'ext': 'mp3',
+            'title': 'Feuilleton vom 30. Oktober 2015',
+            'duration': 250,
+            'uploader': 'MITTELDEUTSCHER RUNDFUNK',
+        },
     }, {
         'url': 'http://www.kika.de/baumhaus/videos/video19636.html',
         'md5': '4930515e36b06c111213e80d1e4aad0e',