fix: advance playback after track completion

tests/test_music_player.py

@@ -93,6 +93,16 @@ class MusicPlayerQueueTest(unittest.IsolatedAsyncioTestCase):
         self.assertEqual(state.index, 1)
         self.assertEqual(state.current.id, "b")
 
+    async def test_initial_playback_callback_advances_from_zero_token(self):
+        _, voice_client, state = await self._queue_abc()
+
+        voice_client.after(None)
+        await asyncio.sleep(0.01)
+
+        self.assertEqual(state.index, 1)
+        self.assertEqual(state.current.id, "b")
+        self.assertEqual(state.queue[0].plays_left, 4)
+
     async def test_loop_track_replays_same_index(self):
         player, _, state = await self._queue_abc()
         await player.play_next(GUILD, advance=True)
@@ -118,11 +128,24 @@ class MusicPlayerQueueTest(unittest.IsolatedAsyncioTestCase):
         self.assertIsNone(state.current)
         self.assertEqual(state.index, 3)
 
+    async def test_queue_end_is_not_active_even_if_voice_client_lags(self):
+        player, voice_client, state = await self._queue_abc()
+        state.index = 2
+        await player.play_next(GUILD, advance=True)
+
+        self.assertIsNone(state.current)
+        self.assertFalse(voice_client.is_playing())
+        self.assertFalse(player.is_active(GUILD))
+
+        await player.enqueue(GUILD, FakeTrack("new"))
+
+        self.assertEqual(state.current.id, "new")
+
     async def test_jump_after_queue_end_plays_selected_track(self):
         player, voice_client, state = await self._queue_abc()
         state.index = 2
         await player.play_next(GUILD, advance=True)
-        voice_client.playing = None
+        voice_client.playing = state.queue[2]
 
         await player.jump(GUILD, 0)