fixed (bug) Audio output device not switching

tests/test_audio.cpp

@@ -11,6 +11,29 @@ TEST(AudioTest, FriendlyDeviceNameMapping) {
     EXPECT_EQ(mapToFriendlyDeviceName(""), "Default Audio Output");
 }
 
+TEST(AudioTest, ResolvePlaybackDeviceNameHandlesSentinels) {
+    // The sentinel and 0 mean "system default" and never correspond to a real
+    // enumerated playback device, so they resolve to the empty (default) name.
+    EXPECT_EQ(AudioManager::resolvePlaybackDeviceName(0), "");
+    EXPECT_EQ(AudioManager::resolvePlaybackDeviceName(SDL_AUDIO_DEVICE_DEFAULT_PLAYBACK), "");
+}
+
+TEST(AudioTest, GetPlaybackDevicesFallsBackWithIdZeroWhenNone) {
+    AudioManager am;
+    auto devices = am.getPlaybackDevices();
+    // Headless hosts (CI) expose no playback devices, so expect the synthetic
+    // fallback entry that carries id 0 (the "system default" marker).
+    if (devices.empty()) {
+        // No devices and no fallback would be a contract violation.
+        FAIL() << "getPlaybackDevices() returned an empty list without fallback";
+    }
+    for (const auto& d : devices) {
+        if (d.raw_name.empty()) {
+            EXPECT_EQ(d.id, 0u);
+        }
+    }
+}
+
 TEST(AudioTest, AudioManagerVolumeClamping) {
     radiantwave::config::ConfigManager config;
     std::string temp_path = (std::filesystem::temp_directory_path() / "test_rw_audio_cfg.yaml").string();