Cache songs on get playlist details

tests/adapter_tests/filesystem_adapter_tests.py

@@ -98,12 +98,27 @@ def test_caching_get_playlist_details(
 
     # Ingest an empty list (for example, no playlists added yet to server).
     cache_adapter.ingest_new_data(
-        FilesystemAdapter.FunctionNames.GET_PLAYLIST_DETAILS, ('1', ),
-        SubsonicAPI.PlaylistWithSongs('1', 'test1', songs=[]))
+        FilesystemAdapter.FunctionNames.GET_PLAYLIST_DETAILS,
+        ('1', ),
+        SubsonicAPI.PlaylistWithSongs(
+            '1',
+            'test1',
+            songs=[
+                SubsonicAPI.Child(
+                    '1', 'Song 1', duration=timedelta(seconds=10.2)),
+                SubsonicAPI.Child(
+                    '2', 'Song 2', duration=timedelta(seconds=20.8)),
+            ],
+        ),
+    )
 
     playlist = cache_adapter.get_playlist_details('1')
     assert playlist.id == '1'
     assert playlist.name == 'test1'
+    assert playlist.song_count == 2
+    assert playlist.duration == timedelta(seconds=31)
+    assert (playlist.songs[0].id, playlist.songs[0].title) == ('1', 'Song 1')
+    assert (playlist.songs[1].id, playlist.songs[1].title) == ('2', 'Song 2')
 
     with pytest.raises(CacheMissError):
         cache_adapter.get_playlist_details('2')