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+# Phase 4: Queue, Config & Player Tests - Context
+
+**Gathered:** 2026-03-03
+**Status:** Ready for planning
+
+<domain>
+## Phase Boundary
+
+Write unit tests for three packages: queue operations (SetQueue, Next, Previous, shuffle, repeat, persistence), config roundtrip (load/save, validation, defaults), and player pure logic (volume conversion, state mapping). These tests characterize current behavior and serve as a safety net for Phase 6-7 refactoring. No production code changes except adding test files.
+
+</domain>
+
+<decisions>
+## Implementation Decisions
+
+### Test fixture strategy
+- Per-test inline setup for queue — each test creates its own audio_file FK rows with minimal fields. Verbose but self-contained; a test failure tells you everything.
+- t.TempDir() for config filesystem tests — real filesystem via Go's test temp dirs, auto-cleaned, tests actual TOML read/write.
+- Simple mock TrackLoader struct defined locally in queue_test.go — only queue tests need it, keep it local.
+- Player tests are pure logic only — no NewTestDB, no persistence round-trips. Volume conversion, clamp, state mapping only. Player persistence deferred to integration tests.
+
+### Player logic extraction
+- Test existing pure logic in place — volume.go (UserVolume, Volume, clampVolume) is already cleanly separated. Write volume_test.go against it. No extraction from player.go.
+- Include stateToMediaControls() — it's pure and trivial but documents the state mapping. Characterization value.
+- Format detection tested in metadata package, not player — the code lives in metadata/decoder.go, tests belong there (decoder_test.go or similar).
+- Do NOT extract anything new from player.go — lock-sensitive code must not be touched. Test what's already pure.
+
+### Coverage depth vs breadth
+- Queue: edge cases first — empty queue, single track, last track, first track, remove current track. These are where bugs hide and refactoring breaks.
+- Queue: dedicated move test cases — move forward, move backward, move current track, move to boundaries, move multiple tracks. MoveQueueTracks has the most complex index arithmetic.
+- Queue: test InsertTracksAt index shifts — insert before/at/after current index, verify currentIndex adjusts correctly. Common off-by-one bug source.
+- Queue: verify generateShuffleOrder() properties — all indices present, current track at index 0, no duplicates. Property-based validation.
+- Queue: full persistence round-trip — SaveState → new Queue → RestoreState → verify all fields match (shuffle order, repeat mode, current index, track list). Critical for Phase 7 optimization safety.
+- Config: test both sub-config validators independently AND the composed Config.Validate(). Pinpoints failures to specific validators.
+- Config: include library.Config.Validate() path with t.TempDir() — test both valid directory (real temp dir) and invalid directory (nonexistent path).
+- Player: 5-6 tests is sufficient — volume roundtrip, boundary values, clamp, state mapping. Quality over quantity.
+
+### Test organization
+- Internal test packages (package queue, package config, package player) — queue tests need access to unexported fields (shuffleOrder, currentIndex, tracks) for setup and assertions.
+- Mirror source file names — navigation_test.go tests navigation.go, persistence_test.go tests persistence.go, queue_test.go tests queue.go. Easy to find tests for any function.
+- Sub-config tests in their respective packages — theme/config_test.go, tracklist/config_test.go, favorites/config_test.go, library/config_test.go. Config package tests the composed Config.
+- t.Parallel() everywhere — NewTestDB gives isolated DB instances, pure logic tests have no shared state. Matches existing coverart/metadata convention.
+
+### Claude's Discretion
+- Exact test case names and table-driven subtest structure
+- How to organize table-driven tests vs individual test functions (per complexity)
+- Specific assertion messages and error formatting
+- Whether to use subtests within a single Test function or separate Test functions per behavior
+
+</decisions>
+
+<specifics>
+## Specific Ideas
+
+- Queue persistence round-trip is the highest-priority safety net — Phase 7 (PERF-01) will change queue persistence from full table rewrite to incremental INSERT/DELETE. These tests must catch any data loss.
+- Mock TrackLoader should be minimal — just enough to satisfy the interface. LoadFile/Play/UnloadTrack can be no-ops, IsPlaying returns false, CurrentPositionSeconds returns 0.
+- Queue tests need to insert audio_file rows before queue_tracks (FK constraint). Also need file_type rows since audio_files FKs to file_types.
+- Player's existing player_test.go is an integration test guarded by YELLOWJACKET_INTEGRATION env var — new unit tests are separate and should always run.
+- Existing test conventions: table-driven subtests with t.Run(), t.Parallel(), standard library testing only (no testify), no assertion libraries.
+
+</specifics>
+
+<deferred>
+## Deferred Ideas
+
+None — discussion stayed within phase scope.
+
+</deferred>
+
+---
+
+*Phase: 04-queue-config-player-tests*
+*Context gathered: 2026-03-03*