- Queue operations: SetQueue, AddTrack, InsertTracksAt, MoveQueueTracks, RemoveTrack, Clear, ToggleShuffle, CycleRepeat - Navigation: nextIndex/previousIndex in all repeat modes (off/all/one) - Shuffle: generateShuffleOrder properties (no duplicates, current at [0]), shuffle navigation - Mock TrackLoader and seedAudioFiles helper for DB-backed tests - 23 tests total (14 core + 9 navigation) all passing with -race