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>

1 files changed, 4 insertions, 7 deletions

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