trackShape.test.ts: songToTrack mapping (required, optional, replayGain
flattening, missing-block fallback, no invented flags); resolveReplayGainDb
precedence (disabled, track, album, auto with prev/next neighbour match,
missing albumId fallback, both gains missing); shuffleArray (non-mutating,
preserves multiset, copies, empty/single, deterministic under mocked RNG).
queue.test.ts: enqueue / enqueueAt (auto-added separator placement,
queueIndex shift, index clamping), playNext (playNextAdded tag, position,
empty input), clearQueue (state reset, audio_stop call), reorderQueue
(splice, currentTrack-id-following queueIndex), removeTrack (clamp on
shrink, keep when after cursor), undo / redo (empty stacks return false,
rollback, replay, new edit drops pending redo).
Adds a 5-line test-only export _resetQueueUndoStacksForTest in playerStore.ts
because the undo/redo arrays live at module scope outside the Zustand state
graph; storeReset.ts now calls it so resetPlayerStore is fully complete.
playerStore.ts coverage 4.76% -> 18.1% lines. PR 2b + 2c push further toward
the F1 floor of 50%.
Frank Stellmacher