discogs: add tests for medium, medium_total

Add three tests for the setting of tracks' medium and medium_total on
the discogs plugin. test_parse_medium_numbers_single_medium is meant
to fail due to beetbox#587.

test/test_discogs.py

@@ -92,6 +92,44 @@ def test_parse_media_for_tracks(self):
         self.assertEqual(t[0].media, d.media)
         self.assertEqual(t[1].media, d.media)
 
+    def test_parse_medium_numbers_single_medium(self):
+        release = self._make_release_from_positions(['1', '2'])
+        d = DiscogsPlugin().get_album_info(release)
+        t = d.tracks
+
+        self.assertEqual(d.mediums, 1)
+        self.assertEqual(t[0].medium, 1)
+        self.assertEqual(t[0].medium_total, 1)
+        self.assertEqual(t[1].medium, 1)
+        self.assertEqual(t[0].medium_total, 1)
+
+    def test_parse_medium_numbers_two_mediums(self):
+        release = self._make_release_from_positions(['1-1', '2-1'])
+        d = DiscogsPlugin().get_album_info(release)
+        t = d.tracks
+
+        self.assertEqual(d.mediums, 2)
+        self.assertEqual(t[0].medium, 1)
+        self.assertEqual(t[0].medium_total, 2)
+        self.assertEqual(t[1].medium, 2)
+        self.assertEqual(t[1].medium_total, 2)
+
+    def test_parse_medium_numbers_two_mediums_two_sided(self):
+        release = self._make_release_from_positions(['A1', 'B1', 'C1'])
+        d = DiscogsPlugin().get_album_info(release)
+        t = d.tracks
+
+        self.assertEqual(d.mediums, 2)
+        self.assertEqual(t[0].medium, 1)
+        self.assertEqual(t[0].medium_total, 2)
+        self.assertEqual(t[0].medium_index, 1)
+        self.assertEqual(t[1].medium, 1)
+        self.assertEqual(t[1].medium_total, 2)
+        self.assertEqual(t[1].medium_index, 2)
+        self.assertEqual(t[2].medium, 2)
+        self.assertEqual(t[2].medium_total, 2)
+        self.assertEqual(t[2].medium_index, 1)
+
     def test_parse_track_indices(self):
         release = self._make_release_from_positions(['1', '2'])
         d = DiscogsPlugin().get_album_info(release)