Add next_track and tests

mopidy/backends/__init__.py

@@ -117,3 +117,13 @@ class BasePlaybackController(object):
 
     def next(self):
         raise NotImplementedError
+
+    @property
+    def next_track(self):
+        if self.current_track is None:
+            return None
+        try:
+            return self.backend.current_playlist.playlist.tracks[
+                self.playlist_position + 1]
+        except IndexError:
+            return None

tests/backends/basetests.py

@@ -249,3 +249,15 @@ class BasePlaybackControllerTest(object):
         self.assertEqual(playback.state, playback.STOPPED)
         self.assertEqual(playback.current_track, tracks[-1])
         self.assertEqual(playback.playlist_position, len(tracks) - 1)
+
+    @populate_playlist
+    def test_next_track_before_play(self):
+        # FIXME should next_track reflect which track is about to be played?
+        tracks = self.backend.current_playlist.playlist.tracks
+        self.assertEqual(self.playback.next_track, None)
+
+    @populate_playlist
+    def test_next_track_during_play(self):
+        tracks = self.backend.current_playlist.playlist.tracks
+        self.playback.play()
+        self.assertEqual(self.playback.next_track, tracks[1])