Factor common test patterns into reusable utilitiesHEADmain

Refactor duplicated test setup/teardown code into shared fixtures:
- test_math_helpers.h: Float comparison (test_near, test_near_vec3)
- AudioTestFixture: RAII wrapper for AudioEngine lifecycle
- EffectTestFixture: Combined WebGPU + AudioEngine + MainSequence

Migrated 9 test files (3 math, 6 audio) to use fixtures.
Net reduction: 54 LOC (178 insertions, 232 deletions).

All 34 tests passing.

Co-Authored-By: Claude Sonnet 4.5 <noreply@anthropic.com>

6 files changed, 106 insertions, 147 deletions

diff --git a/src/tests/audio/test_audio_engine.cc b/src/tests/audio/test_audio_engine.cc
index 3b29dcd..72c1653 100644
--- a/src/tests/audio/test_audio_engine.cc
+++ b/src/tests/audio/test_audio_engine.cc
@@ -4,6 +4,7 @@
 #include "audio/audio_engine.h"
 #include "audio/tracker.h"
 #include "generated/assets.h"
+#include "../common/audio_test_fixture.h"
 #include <assert.h>
 #include <stdio.h>
 
@@ -13,19 +14,13 @@
 void test_audio_engine_lifecycle() {
   printf("Test: AudioEngine lifecycle...\n");
 
-  AudioEngine engine;
-  printf("  Created AudioEngine object...\n");
-
-  engine.init();
-  printf("  Initialized AudioEngine...\n");
+  AudioTestFixture fixture;
+  printf("  Created and initialized AudioEngine...\n");
 
   // Verify initialization
-  assert(engine.get_active_voice_count() == 0);
+  assert(fixture.engine().get_active_voice_count() == 0);
   printf("  Verified voice count is 0...\n");
 
-  engine.shutdown();
-  printf("  Shutdown AudioEngine...\n");
-
   printf("  ✓ AudioEngine lifecycle test passed\n");
 }
 
@@ -33,16 +28,15 @@ void test_audio_engine_lifecycle() {
 void test_audio_engine_music_loading() {
   printf("Test: AudioEngine music data loading...\n");
 
-  AudioEngine engine;
-  engine.init();
+  AudioTestFixture fixture;
 
   // Load global music data
-  engine.load_music_data(&g_tracker_score, g_tracker_samples,
-                         g_tracker_sample_assets, g_tracker_samples_count);
+  fixture.load_music(&g_tracker_score, g_tracker_samples,
+                     g_tracker_sample_assets, g_tracker_samples_count);
 
   // Verify resource manager was initialized (samples registered but not loaded
   // yet)
-  SpectrogramResourceManager* res_mgr = engine.get_resource_manager();
+  SpectrogramResourceManager* res_mgr = fixture.engine().get_resource_manager();
   assert(res_mgr != nullptr);
 
   // Initially, no samples should be loaded (lazy loading)
@@ -51,8 +45,6 @@ void test_audio_engine_music_loading() {
   printf("  ✓ Music data loaded: %u samples registered\n",
          g_tracker_samples_count);
 
-  engine.shutdown();
-
   printf("  ✓ AudioEngine music loading test passed\n");
 }
 
@@ -60,14 +52,13 @@ void test_audio_engine_music_loading() {
 void test_audio_engine_manual_resource_loading() {
   printf("Test: AudioEngine manual resource loading...\n");
 
-  AudioEngine engine;
-  engine.init();
+  AudioTestFixture fixture;
 
   // Load music data
-  engine.load_music_data(&g_tracker_score, g_tracker_samples,
-                         g_tracker_sample_assets, g_tracker_samples_count);
+  fixture.load_music(&g_tracker_score, g_tracker_samples,
+                     g_tracker_sample_assets, g_tracker_samples_count);
 
-  SpectrogramResourceManager* res_mgr = engine.get_resource_manager();
+  SpectrogramResourceManager* res_mgr = fixture.engine().get_resource_manager();
   const int initial_loaded = res_mgr->get_loaded_count();
   assert(initial_loaded == 0); // No samples loaded yet
 
@@ -89,8 +80,6 @@ void test_audio_engine_manual_resource_loading() {
   assert(spec1 != nullptr);
   assert(spec2 != nullptr);
 
-  engine.shutdown();
-
   printf("  ✓ AudioEngine manual resource loading test passed\n");
 }
 
@@ -98,13 +87,12 @@ void test_audio_engine_manual_resource_loading() {
 void test_audio_engine_reset() {
   printf("Test: AudioEngine reset...\n");
 
-  AudioEngine engine;
-  engine.init();
+  AudioTestFixture fixture;
 
-  engine.load_music_data(&g_tracker_score, g_tracker_samples,
-                         g_tracker_sample_assets, g_tracker_samples_count);
+  fixture.load_music(&g_tracker_score, g_tracker_samples,
+                     g_tracker_sample_assets, g_tracker_samples_count);
 
-  SpectrogramResourceManager* res_mgr = engine.get_resource_manager();
+  SpectrogramResourceManager* res_mgr = fixture.engine().get_resource_manager();
 
   // Manually load some samples
   res_mgr->preload(0);
@@ -115,10 +103,10 @@ void test_audio_engine_reset() {
   assert(loaded_before_reset == 3);
 
   // Reset engine
-  engine.reset();
+  fixture.engine().reset();
 
   // After reset, state should be cleared
-  assert(engine.get_active_voice_count() == 0);
+  assert(fixture.engine().get_active_voice_count() == 0);
 
   // Resources should be marked as unloaded (but memory not freed)
   const int loaded_after_reset = res_mgr->get_loaded_count();
@@ -126,8 +114,6 @@ void test_audio_engine_reset() {
          loaded_before_reset, loaded_after_reset);
   assert(loaded_after_reset == 0);
 
-  engine.shutdown();
-
   printf("  ✓ AudioEngine reset test passed\n");
 }
 
@@ -136,25 +122,22 @@ void test_audio_engine_reset() {
 void test_audio_engine_seeking() {
   printf("Test: AudioEngine seeking...\n");
 
-  AudioEngine engine;
-  engine.init();
+  AudioTestFixture fixture;
 
-  engine.load_music_data(&g_tracker_score, g_tracker_samples,
-                         g_tracker_sample_assets, g_tracker_samples_count);
+  fixture.load_music(&g_tracker_score, g_tracker_samples,
+                     g_tracker_sample_assets, g_tracker_samples_count);
 
   // Seek to t=5.0s
-  engine.seek(5.0f);
-  assert(engine.get_time() == 5.0f);
+  fixture.engine().seek(5.0f);
+  assert(fixture.engine().get_time() == 5.0f);
 
   // Seek backward to t=2.0s
-  engine.seek(2.0f);
-  assert(engine.get_time() == 2.0f);
+  fixture.engine().seek(2.0f);
+  assert(fixture.engine().get_time() == 2.0f);
 
   // Seek to beginning
-  engine.seek(0.0f);
-  assert(engine.get_time() == 0.0f);
-
-  engine.shutdown();
+  fixture.engine().seek(0.0f);
+  assert(fixture.engine().get_time() == 0.0f);
 
   printf("  ✓ AudioEngine seeking test passed\n");
 }
diff --git a/src/tests/audio/test_silent_backend.cc b/src/tests/audio/test_silent_backend.cc
index 8daacf7..cc98139 100644
--- a/src/tests/audio/test_silent_backend.cc
+++ b/src/tests/audio/test_silent_backend.cc
@@ -6,6 +6,7 @@
 #include "audio/audio_engine.h"
 #include "audio/backend/silent_backend.h"
 #include "audio/synth.h"
+#include "../common/audio_test_fixture.h"
 #include <assert.h>
 #include <stdio.h>
 
@@ -80,8 +81,7 @@ void test_silent_backend_tracking() {
   SilentBackend backend;
   audio_set_backend(&backend);
 
-  AudioEngine engine;
-  engine.init();
+  AudioTestFixture fixture;
 
   // Initial state
   assert(backend.get_frames_rendered() == 0);
@@ -105,7 +105,6 @@ void test_silent_backend_tracking() {
   assert(backend.get_frames_rendered() == 0);
   assert(backend.get_voice_trigger_count() == 0);
 
-  engine.shutdown();
   audio_shutdown();
 
   printf("SilentBackend tracking test PASSED\n");
@@ -116,8 +115,7 @@ void test_audio_playback_time() {
   SilentBackend backend;
   audio_set_backend(&backend);
 
-  AudioEngine engine;
-  engine.init();
+  AudioTestFixture fixture;
   audio_start();
 
   // Initial playback time should be 0
@@ -137,7 +135,6 @@ void test_audio_playback_time() {
   float t2 = audio_get_playback_time();
   assert(t2 >= t1); // Should continue advancing
 
-  engine.shutdown();
   audio_shutdown();
 
   printf("Audio playback time test PASSED\n");
@@ -148,8 +145,7 @@ void test_audio_buffer_partial_writes() {
   SilentBackend backend;
   audio_set_backend(&backend);
 
-  AudioEngine engine;
-  engine.init();
+  AudioTestFixture fixture;
   audio_start();
 
   // Fill buffer multiple times to test wraparound
@@ -164,7 +160,6 @@ void test_audio_buffer_partial_writes() {
   // no audio callback to consume from the ring buffer
   audio_update(); // Should not crash
 
-  engine.shutdown();
   audio_shutdown();
 
   printf("Audio buffer partial writes test PASSED\n");
@@ -175,8 +170,7 @@ void test_audio_update() {
   SilentBackend backend;
   audio_set_backend(&backend);
 
-  AudioEngine engine;
-  engine.init();
+  AudioTestFixture fixture;
   audio_start();
 
   // audio_update() should be callable without crashing
@@ -184,7 +178,6 @@ void test_audio_update() {
   audio_update();
   audio_update();
 
-  engine.shutdown();
   audio_shutdown();
 
   printf("Audio update test PASSED\n");
diff --git a/src/tests/audio/test_tracker.cc b/src/tests/audio/test_tracker.cc
index 6be2a8d..1112e91 100644
--- a/src/tests/audio/test_tracker.cc
+++ b/src/tests/audio/test_tracker.cc
@@ -5,6 +5,7 @@
 #include "audio/gen.h"
 #include "audio/synth.h"
 #include "audio/tracker.h"
+#include "../common/audio_test_fixture.h"
 // #include "generated/music_data.h" // Will be generated by tracker_compiler
 #include <assert.h>
 #include <stdio.h>
@@ -17,15 +18,12 @@ extern const uint32_t g_tracker_patterns_count;
 extern const TrackerScore g_tracker_score;
 
 void test_tracker_init() {
-  AudioEngine engine;
-  engine.init();
+  AudioTestFixture fixture;
   printf("Tracker init test PASSED\n");
-  engine.shutdown();
 }
 
 void test_tracker_pattern_triggering() {
-  AudioEngine engine;
-  engine.init();
+  AudioTestFixture fixture;
 
   // At time 0.0f, 3 patterns are triggered:
   // - crash (1 event at beat 0.0)
@@ -37,31 +35,30 @@ void test_tracker_pattern_triggering() {
   // drums_basic:
   //   0.00, ASSET_KICK_1
   //   0.00, NOTE_A4
-  engine.update(0.0f, 0.0f);
+  fixture.engine().update(0.0f, 0.0f);
   // Expect 2 voices: kick + note
-  assert(engine.get_active_voice_count() == 2);
+  assert(fixture.engine().get_active_voice_count() == 2);
 
   // Test 2: At music_time = 0.25f (beat 0.5 @ 120 BPM), snare event triggers
   //   0.25, ASSET_SNARE_1
-  engine.update(0.25f, 0.0f);
+  fixture.engine().update(0.25f, 0.0f);
   // Expect at least 2 voices (snare + maybe others)
   // Exact count depends on sample duration (kick/note might have finished)
-  int voices = engine.get_active_voice_count();
+  int voices = fixture.engine().get_active_voice_count();
   assert(voices >= 2);
 
   // Test 3: At music_time = 0.5f (beat 1.0), kick event triggers
   //   0.50, ASSET_KICK_1
-  engine.update(0.5f, 0.0f);
+  fixture.engine().update(0.5f, 0.0f);
   // Expect at least 3 voices (new kick + others)
-  assert(engine.get_active_voice_count() >= 3);
+  assert(fixture.engine().get_active_voice_count() >= 3);
 
   // Test 4: Advance to 2.0f - new patterns trigger at time 2.0f
-  engine.update(2.0f, 0.0f);
+  fixture.engine().update(2.0f, 0.0f);
   // Many events have triggered by now
-  assert(engine.get_active_voice_count() > 5);
+  assert(fixture.engine().get_active_voice_count() > 5);
 
   printf("Tracker pattern triggering test PASSED\n");
-  engine.shutdown();
 }
 
 int main() {
diff --git a/src/tests/audio/test_tracker_timing.cc b/src/tests/audio/test_tracker_timing.cc
index 9f15197..7295de3 100644
--- a/src/tests/audio/test_tracker_timing.cc
+++ b/src/tests/audio/test_tracker_timing.cc
@@ -7,6 +7,7 @@
 #include "audio/backend/mock_audio_backend.h"
 #include "audio/synth.h"
 #include "audio/tracker.h"
+#include "../common/audio_test_fixture.h"
 #include <assert.h>
 #include <cmath>
 #include <stdio.h>
@@ -14,9 +15,10 @@
 #if !defined(STRIP_ALL)
 
 // Helper: Setup audio engine for testing
-static void setup_audio_test(MockAudioBackend& backend, AudioEngine& engine) {
+static AudioTestFixture*
+setup_audio_test(MockAudioBackend& backend) {
   audio_set_backend(&backend);
-  engine.init();
+  return new AudioTestFixture();
 }
 
 // Helper: Check if a timestamp exists in events within tolerance
@@ -66,10 +68,9 @@ void test_basic_event_recording() {
   printf("Test: Basic event recording with mock backend...\n");
 
   MockAudioBackend backend;
-  AudioEngine engine;
-  setup_audio_test(backend, engine);
+  AudioTestFixture* fixture = setup_audio_test(backend);
 
-  engine.update(0.0f, 0.0f);
+  fixture->engine().update(0.0f, 0.0f);
   const auto& events = backend.get_events();
   printf("  Events triggered at t=0.0: %zu\n", events.size());
 
@@ -78,7 +79,7 @@ void test_basic_event_recording() {
     assert(evt.timestamp_sec < 0.1f);
   }
 
-  engine.shutdown();
+  delete fixture;
   printf("  ✓ Basic event recording works\n");
 }
 
@@ -86,25 +87,24 @@ void test_progressive_triggering() {
   printf("Test: Progressive pattern triggering...\n");
 
   MockAudioBackend backend;
-  AudioEngine engine;
-  setup_audio_test(backend, engine);
+  AudioTestFixture* fixture = setup_audio_test(backend);
 
-  engine.update(0.0f, 0.0f);
+  fixture->engine().update(0.0f, 0.0f);
   const size_t events_at_0 = backend.get_events().size();
   printf("  Events at t=0.0: %zu\n", events_at_0);
 
-  engine.update(1.0f, 0.0f);
+  fixture->engine().update(1.0f, 0.0f);
   const size_t events_at_1 = backend.get_events().size();
   printf("  Events at t=1.0: %zu\n", events_at_1);
 
-  engine.update(2.0f, 0.0f);
+  fixture->engine().update(2.0f, 0.0f);
   const size_t events_at_2 = backend.get_events().size();
   printf("  Events at t=2.0: %zu\n", events_at_2);
 
   assert(events_at_1 >= events_at_0);
   assert(events_at_2 >= events_at_1);
 
-  engine.shutdown();
+  delete fixture;
   printf("  ✓ Events accumulate over time\n");
 }
 
@@ -112,11 +112,10 @@ void test_simultaneous_triggers() {
   printf("Test: SIMULTANEOUS pattern triggers at same time...\n");
 
   MockAudioBackend backend;
-  AudioEngine engine;
-  setup_audio_test(backend, engine);
+  AudioTestFixture* fixture = setup_audio_test(backend);
 
   backend.clear_events();
-  engine.update(0.0f, 0.0f);
+  fixture->engine().update(0.0f, 0.0f);
 
   const auto& events = backend.get_events();
   if (events.size() == 0) {
@@ -150,18 +149,17 @@ void test_simultaneous_triggers() {
     printf("  ℹ Only one event at t=0.0, cannot verify simultaneity\n");
   }
 
-  engine.shutdown();
+  delete fixture;
 }
 
 void test_timing_monotonicity() {
   printf("Test: Event timestamps are monotonically increasing...\n");
 
   MockAudioBackend backend;
-  AudioEngine engine;
-  setup_audio_test(backend, engine);
+  AudioTestFixture* fixture = setup_audio_test(backend);
 
   for (float t = 0.0f; t <= 5.0f; t += 0.5f) {
-    engine.update(t, 0.5f);
+    fixture->engine().update(t, 0.5f);
   }
 
   const auto& events = backend.get_events();
@@ -172,7 +170,7 @@ void test_timing_monotonicity() {
     assert(events[i].timestamp_sec >= events[i - 1].timestamp_sec);
   }
 
-  engine.shutdown();
+  delete fixture;
   printf("  ✓ All timestamps monotonically increasing\n");
 }
 
@@ -183,8 +181,7 @@ void test_seek_simulation() {
   audio_set_backend(&backend);
 
   audio_init();
-  AudioEngine engine;
-  engine.init();
+  AudioTestFixture fixture;
 
   // Simulate seeking to t=3.0s by rendering silent audio
   // This should trigger all patterns in range [0, 3.0]
@@ -194,10 +191,10 @@ void test_seek_simulation() {
   float t = 0.0f;
   const float step = 0.1f;
   while (t <= seek_target) {
-    engine.update(t, step);
+    fixture.engine().update(t, step);
     // Simulate audio rendering
     float dummy_buffer[512 * 2];
-    engine.render(dummy_buffer, 512);
+    fixture.engine().render(dummy_buffer, 512);
     t += step;
   }
 
@@ -214,7 +211,6 @@ void test_seek_simulation() {
     assert(evt.timestamp_sec <= seek_target + 0.5f);
   }
 
-  engine.shutdown();
   audio_shutdown();
 
   printf("  ✓ Seek simulation works correctly\n");
@@ -226,12 +222,11 @@ void test_timestamp_clustering() {
   MockAudioBackend backend;
   audio_set_backend(&backend);
 
-  AudioEngine engine;
-  engine.init();
+  AudioTestFixture fixture;
 
   // Update through the first 4 seconds
   for (float t = 0.0f; t <= 4.0f; t += 0.1f) {
-    engine.update(t, 0.1f);
+    fixture.engine().update(t, 0.1f);
   }
 
   const auto& events = backend.get_events();
@@ -249,7 +244,6 @@ void test_timestamp_clustering() {
     }
   }
 
-  engine.shutdown();
   printf("  ✓ Timestamp clustering analyzed\n");
 }
 
@@ -260,11 +254,10 @@ void test_render_integration() {
   audio_set_backend(&backend);
 
   audio_init();
-  AudioEngine engine;
-  engine.init();
+  AudioTestFixture fixture;
 
   // Trigger some patterns
-  engine.update(0.0f, 0.0f);
+  fixture.engine().update(0.0f, 0.0f);
   const size_t events_before = backend.get_events().size();
 
   // Render 1 second of silent audio
@@ -276,13 +269,12 @@ void test_render_integration() {
   assert(backend_time >= 0.9f && backend_time <= 1.1f);
 
   // Trigger more patterns after time advance
-  engine.update(1.0f, 0.0f);
+  fixture.engine().update(1.0f, 0.0f);
   const size_t events_after = backend.get_events().size();
 
   printf("  Events before: %zu, after: %zu\n", events_before, events_after);
   assert(events_after >= events_before);
 
-  engine.shutdown();
   audio_shutdown();
 
   printf("  ✓ audio_render_silent integration works\n");
diff --git a/src/tests/audio/test_variable_tempo.cc b/src/tests/audio/test_variable_tempo.cc
index bbc9ebf..da056c5 100644
--- a/src/tests/audio/test_variable_tempo.cc
+++ b/src/tests/audio/test_variable_tempo.cc
@@ -6,6 +6,7 @@
 #include "audio/audio_engine.h"
 #include "audio/backend/mock_audio_backend.h"
 #include "audio/tracker.h"
+#include "../common/audio_test_fixture.h"
 #include <assert.h>
 #include <cmath>
 #include <stdio.h>
@@ -13,11 +14,13 @@
 #if !defined(STRIP_ALL)
 
 // Helper: Setup audio engine for testing
-static void setup_audio_test(MockAudioBackend& backend, AudioEngine& engine) {
+static AudioTestFixture*
+setup_audio_test(MockAudioBackend& backend) {
   audio_set_backend(&backend);
-  engine.init();
-  engine.load_music_data(&g_tracker_score, g_tracker_samples,
-                         g_tracker_sample_assets, g_tracker_samples_count);
+  AudioTestFixture* fixture = new AudioTestFixture();
+  fixture->load_music(&g_tracker_score, g_tracker_samples,
+                      g_tracker_sample_assets, g_tracker_samples_count);
+  return fixture;
 }
 
 // Helper: Simulate tempo advancement with fixed steps
@@ -47,14 +50,13 @@ void test_basic_tempo_scaling() {
   printf("Test: Basic tempo scaling (1.0x, 2.0x, 0.5x)...\n");
 
   MockAudioBackend backend;
-  AudioEngine engine;
-  setup_audio_test(backend, engine);
+  AudioTestFixture* fixture = setup_audio_test(backend);
 
   // Test 1: Normal tempo (1.0x)
   {
     backend.clear_events();
     float music_time = 0.0f;
-    simulate_tempo(engine, music_time, 1.0f, 1.0f);
+    simulate_tempo(fixture->engine(), music_time, 1.0f, 1.0f);
     printf("  1.0x tempo: music_time = %.3f (expected ~1.0)\n", music_time);
     assert(std::abs(music_time - 1.0f) < 0.01f);
   }
@@ -62,9 +64,9 @@ void test_basic_tempo_scaling() {
   // Test 2: Fast tempo (2.0x)
   {
     backend.clear_events();
-    engine.reset();
+    fixture->engine().reset();
     float music_time = 0.0f;
-    simulate_tempo(engine, music_time, 1.0f, 2.0f);
+    simulate_tempo(fixture->engine(), music_time, 1.0f, 2.0f);
     printf("  2.0x tempo: music_time = %.3f (expected ~2.0)\n", music_time);
     assert(std::abs(music_time - 2.0f) < 0.01f);
   }
@@ -72,14 +74,14 @@ void test_basic_tempo_scaling() {
   // Test 3: Slow tempo (0.5x)
   {
     backend.clear_events();
-    engine.reset();
+    fixture->engine().reset();
     float music_time = 0.0f;
-    simulate_tempo(engine, music_time, 1.0f, 0.5f);
+    simulate_tempo(fixture->engine(), music_time, 1.0f, 0.5f);
     printf("  0.5x tempo: music_time = %.3f (expected ~0.5)\n", music_time);
     assert(std::abs(music_time - 0.5f) < 0.01f);
   }
 
-  engine.shutdown();
+  delete fixture;
   printf("  ✓ Basic tempo scaling works correctly\n");
 }
 
@@ -87,8 +89,7 @@ void test_2x_speedup_reset_trick() {
   printf("Test: 2x SPEED-UP reset trick...\n");
 
   MockAudioBackend backend;
-  AudioEngine engine;
-  setup_audio_test(backend, engine);
+  AudioTestFixture* fixture = setup_audio_test(backend);
 
   float music_time = 0.0f;
   float physical_time = 0.0f;
@@ -97,7 +98,7 @@ void test_2x_speedup_reset_trick() {
   // Phase 1: Accelerate from 1.0x to 2.0x over 5 seconds
   printf("  Phase 1: Accelerating 1.0x → 2.0x\n");
   auto accel_fn = [](float t) { return fminf(1.0f + (t / 5.0f), 2.0f); };
-  simulate_tempo_fn(engine, music_time, physical_time, 5.0f, dt, accel_fn);
+  simulate_tempo_fn(fixture->engine(), music_time, physical_time, 5.0f, dt, accel_fn);
 
   const float tempo_scale = accel_fn(physical_time);
   printf("    After 5s physical: tempo=%.2fx, music_time=%.3f\n", tempo_scale,
@@ -107,14 +108,14 @@ void test_2x_speedup_reset_trick() {
   // Phase 2: RESET - back to 1.0x tempo
   printf("  Phase 2: RESET to 1.0x tempo\n");
   const float music_time_before_reset = music_time;
-  simulate_tempo(engine, music_time, 2.0f, 1.0f, dt);
+  simulate_tempo(fixture->engine(), music_time, 2.0f, 1.0f, dt);
 
   printf("    After reset + 2s: tempo=1.0x, music_time=%.3f\n", music_time);
   const float music_time_delta = music_time - music_time_before_reset;
   printf("    Music time delta: %.3f (expected ~2.0)\n", music_time_delta);
   assert(std::abs(music_time_delta - 2.0f) < 0.1f);
 
-  engine.shutdown();
+  delete fixture;
   printf("  ✓ 2x speed-up reset trick verified\n");
 }
 
@@ -122,8 +123,7 @@ void test_2x_slowdown_reset_trick() {
   printf("Test: 2x SLOW-DOWN reset trick...\n");
 
   MockAudioBackend backend;
-  AudioEngine engine;
-  setup_audio_test(backend, engine);
+  AudioTestFixture* fixture = setup_audio_test(backend);
 
   float music_time = 0.0f;
   float physical_time = 0.0f;
@@ -132,7 +132,7 @@ void test_2x_slowdown_reset_trick() {
   // Phase 1: Decelerate from 1.0x to 0.5x over 5 seconds
   printf("  Phase 1: Decelerating 1.0x → 0.5x\n");
   auto decel_fn = [](float t) { return fmaxf(1.0f - (t / 10.0f), 0.5f); };
-  simulate_tempo_fn(engine, music_time, physical_time, 5.0f, dt, decel_fn);
+  simulate_tempo_fn(fixture->engine(), music_time, physical_time, 5.0f, dt, decel_fn);
 
   const float tempo_scale = decel_fn(physical_time);
   printf("    After 5s physical: tempo=%.2fx, music_time=%.3f\n", tempo_scale,
@@ -142,14 +142,14 @@ void test_2x_slowdown_reset_trick() {
   // Phase 2: RESET - back to 1.0x tempo
   printf("  Phase 2: RESET to 1.0x tempo\n");
   const float music_time_before_reset = music_time;
-  simulate_tempo(engine, music_time, 2.0f, 1.0f, dt);
+  simulate_tempo(fixture->engine(), music_time, 2.0f, 1.0f, dt);
 
   printf("    After reset + 2s: tempo=1.0x, music_time=%.3f\n", music_time);
   const float music_time_delta = music_time - music_time_before_reset;
   printf("    Music time delta: %.3f (expected ~2.0)\n", music_time_delta);
   assert(std::abs(music_time_delta - 2.0f) < 0.1f);
 
-  engine.shutdown();
+  delete fixture;
   printf("  ✓ 2x slow-down reset trick verified\n");
 }
 
@@ -157,34 +157,33 @@ void test_pattern_density_swap() {
   printf("Test: Pattern density swap at reset points...\n");
 
   MockAudioBackend backend;
-  AudioEngine engine;
-  setup_audio_test(backend, engine);
+  AudioTestFixture* fixture = setup_audio_test(backend);
 
   float music_time = 0.0f;
 
   // Phase 1: Sparse pattern at normal tempo
   printf("  Phase 1: Sparse pattern, normal tempo\n");
-  simulate_tempo(engine, music_time, 3.0f, 1.0f);
+  simulate_tempo(fixture->engine(), music_time, 3.0f, 1.0f);
   const size_t sparse_events = backend.get_events().size();
   printf("    Events during sparse phase: %zu\n", sparse_events);
 
   // Phase 2: Accelerate to 2.0x
   printf("  Phase 2: Accelerating to 2.0x\n");
-  simulate_tempo(engine, music_time, 2.0f, 2.0f);
+  simulate_tempo(fixture->engine(), music_time, 2.0f, 2.0f);
   const size_t events_at_2x = backend.get_events().size() - sparse_events;
   printf("    Additional events during 2.0x: %zu\n", events_at_2x);
 
   // Phase 3: Reset to 1.0x
   printf("  Phase 3: Reset to 1.0x (simulating denser pattern)\n");
   const size_t events_before_reset_phase = backend.get_events().size();
-  simulate_tempo(engine, music_time, 2.0f, 1.0f);
+  simulate_tempo(fixture->engine(), music_time, 2.0f, 1.0f);
   const size_t events_after_reset = backend.get_events().size();
 
   printf("    Events during reset phase: %zu\n",
          events_after_reset - events_before_reset_phase);
   assert(backend.get_events().size() > 0);
 
-  engine.shutdown();
+  delete fixture;
   printf("  ✓ Pattern density swap points verified\n");
 }
 
@@ -192,8 +191,7 @@ void test_continuous_acceleration() {
   printf("Test: Continuous acceleration from 0.5x to 2.0x...\n");
 
   MockAudioBackend backend;
-  AudioEngine engine;
-  setup_audio_test(backend, engine);
+  AudioTestFixture* fixture = setup_audio_test(backend);
 
   float music_time = 0.0f;
   float physical_time = 0.0f;
@@ -215,7 +213,7 @@ void test_continuous_acceleration() {
     physical_time += dt;
     const float tempo_scale = accel_fn(physical_time);
     music_time += dt * tempo_scale;
-    engine.update(music_time, dt * tempo_scale);
+    fixture->engine().update(music_time, dt * tempo_scale);
     if (i % 50 == 0) {
       printf("    t=%.1fs: tempo=%.2fx, music_time=%.3f\n", physical_time,
              tempo_scale, music_time);
@@ -232,7 +230,7 @@ void test_continuous_acceleration() {
          music_time);
   assert(std::abs(music_time - expected_music_time) < 0.5f);
 
-  engine.shutdown();
+  delete fixture;
   printf("  ✓ Continuous acceleration verified\n");
 }
 
@@ -240,8 +238,7 @@ void test_oscillating_tempo() {
   printf("Test: Oscillating tempo (sine wave)...\n");
 
   MockAudioBackend backend;
-  AudioEngine engine;
-  setup_audio_test(backend, engine);
+  AudioTestFixture* fixture = setup_audio_test(backend);
 
   float music_time = 0.0f;
   float physical_time = 0.0f;
@@ -256,7 +253,7 @@ void test_oscillating_tempo() {
     physical_time += dt;
     const float tempo_scale = oscil_fn(physical_time);
     music_time += dt * tempo_scale;
-    engine.update(music_time, dt * tempo_scale);
+    fixture->engine().update(music_time, dt * tempo_scale);
     if (i % 25 == 0) {
       printf("    t=%.2fs: tempo=%.3fx, music_time=%.3f\n", physical_time,
              tempo_scale, music_time);
@@ -267,7 +264,7 @@ void test_oscillating_tempo() {
          physical_time, music_time, physical_time);
   assert(std::abs(music_time - physical_time) < 0.5f);
 
-  engine.shutdown();
+  delete fixture;
   printf("  ✓ Oscillating tempo verified\n");
 }
 
diff --git a/src/tests/audio/test_wav_dump.cc b/src/tests/audio/test_wav_dump.cc
index 85b168d..9175153 100644
--- a/src/tests/audio/test_wav_dump.cc
+++ b/src/tests/audio/test_wav_dump.cc
@@ -5,6 +5,7 @@
 #include "audio/audio_engine.h"
 #include "audio/backend/wav_dump_backend.h"
 #include "audio/ring_buffer.h"
+#include "../common/audio_test_fixture.h"
 #include <assert.h>
 #include <stdio.h>
 #include <string.h>
@@ -38,8 +39,7 @@ void test_wav_format_matches_live_audio() {
   audio_init();
 
   // Initialize AudioEngine
-  AudioEngine engine;
-  engine.init();
+  AudioTestFixture fixture;
 
   // Create WAV dump backend
   WavDumpBackend wav_backend;
@@ -59,7 +59,7 @@ void test_wav_format_matches_live_audio() {
   float music_time = 0.0f;
   for (float t = 0.0f; t < duration; t += update_dt) {
     // Update audio engine (triggers patterns)
-    engine.update(music_time, update_dt);
+    fixture.engine().update(music_time, update_dt);
     music_time += update_dt;
 
     // Render audio ahead
@@ -76,7 +76,6 @@ void test_wav_format_matches_live_audio() {
 
   // Shutdown
   wav_backend.shutdown();
-  engine.shutdown();
   audio_shutdown();
 
   // Read and verify WAV header
@@ -192,8 +191,7 @@ void test_clipping_detection() {
   const char* test_file = "test_clipping.wav";
 
   audio_init();
-  AudioEngine engine;
-  engine.init();
+  AudioTestFixture fixture;
 
   WavDumpBackend wav_backend;
   wav_backend.set_output_file(test_file);
@@ -225,7 +223,6 @@ void test_clipping_detection() {
   printf("  Detected %zu clipped samples (expected 200)\n", clipped);
 
   wav_backend.shutdown();
-  engine.shutdown();
   audio_shutdown();
 
   // Clean up