feat(player): add verified USB bit-perfect PCM output

android/app/src/androidTest/kotlin/com/zarz/spotiflac/UsbBitPerfectPluginTest.kt

@@ -0,0 +1,63 @@
+package com.zarz.spotiflac
+
+import android.media.AudioDeviceInfo
+import android.media.AudioManager
+import androidx.test.ext.junit.runners.AndroidJUnit4
+import androidx.test.platform.app.InstrumentationRegistry
+import io.flutter.embedding.engine.FlutterEngine
+import io.flutter.plugin.common.MethodCall
+import io.flutter.plugin.common.MethodChannel
+import java.util.concurrent.CountDownLatch
+import java.util.concurrent.TimeUnit
+import org.junit.Assert.assertEquals
+import org.junit.Assert.assertNull
+import org.junit.Assert.assertTrue
+import org.junit.Assume.assumeTrue
+import org.junit.Test
+import org.junit.runner.RunWith
+
+@RunWith(AndroidJUnit4::class)
+class UsbBitPerfectPluginTest {
+    @Test
+    fun unsupportedRouteReturnsFallbackAndEngineDetachesCleanly() {
+        val instrumentation = InstrumentationRegistry.getInstrumentation()
+        val context = instrumentation.targetContext
+        val manager = context.getSystemService(AudioManager::class.java)
+        assumeTrue(manager.getDevices(AudioManager.GET_DEVICES_OUTPUTS).none {
+            it.type == AudioDeviceInfo.TYPE_USB_DEVICE || it.type == AudioDeviceInfo.TYPE_USB_HEADSET
+        })
+        lateinit var engine: FlutterEngine
+        lateinit var plugin: UsbBitPerfectPlugin
+        instrumentation.runOnMainSync {
+            engine = FlutterEngine(context)
+            plugin = UsbBitPerfectPlugin()
+            engine.plugins.add(plugin)
+        }
+        try {
+            fun invoke(method: String, arguments: Map<String, Any>? = null): Any? {
+                val done = CountDownLatch(1)
+                var value: Any? = null
+                var failure: String? = null
+                instrumentation.runOnMainSync {
+                    plugin.onMethodCall(MethodCall(method, arguments), object : MethodChannel.Result {
+                        override fun success(result: Any?) { value = result; done.countDown() }
+                        override fun error(code: String, message: String?, details: Any?) {
+                            failure = "$code: $message"
+                            done.countDown()
+                        }
+                        override fun notImplemented() { failure = "not implemented"; done.countDown() }
+                    })
+                }
+                assertTrue("Native method timed out", done.await(10, TimeUnit.SECONDS))
+                assertNull(failure)
+                return value
+            }
+            val result = invoke("prepare", mapOf("path" to "/unopened.flac", "token" to 1)) as Map<*, *>
+            assertEquals(if (android.os.Build.VERSION.SDK_INT >= 34) "no_usb" else "android_version", result["reason"])
+            assertNull(result["ready"])
+            invoke("stop")
+        } finally {
+            instrumentation.runOnMainSync { engine.destroy() }
+        }
+    }
+}