feat(io): MusicController + MusicBackend (testable music logic)

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

Semesterprojekt/src/test/java/thb/jeanluc/adventure/io/MusicControllerTest.java

@@ -0,0 +1,87 @@
+package thb.jeanluc.adventure.io;
+
+import org.junit.jupiter.api.Test;
+
+import java.util.ArrayList;
+import java.util.List;
+
+import static org.assertj.core.api.Assertions.assertThat;
+
+class MusicControllerTest {
+
+    /** Records backend calls for assertions. */
+    private static final class FakeBackend implements MusicBackend {
+        final List<String> calls = new ArrayList<>();
+        public void fadeTo(String track, float gainDb) { calls.add("fadeTo:" + track); }
+        public void fadeOut() { calls.add("fadeOut"); }
+        public void setGainDb(float gainDb) { calls.add("setGain:" + gainDb); }
+        public void shutdown() { calls.add("shutdown"); }
+    }
+
+    @Test
+    void firstRoomWithTrackPlaysAtDefaultLevel() {
+        FakeBackend b = new FakeBackend();
+        new MusicController(b).room("a");
+        assertThat(b.calls).containsExactly("fadeTo:a");
+    }
+
+    @Test
+    void sameTrackDoesNotRestart() {
+        FakeBackend b = new FakeBackend();
+        MusicController c = new MusicController(b);
+        c.room("a");
+        b.calls.clear();
+        c.room("a");
+        assertThat(b.calls).isEmpty();
+    }
+
+    @Test
+    void differentTrackSwitches() {
+        FakeBackend b = new FakeBackend();
+        MusicController c = new MusicController(b);
+        c.room("a");
+        c.room("b");
+        assertThat(b.calls).containsExactly("fadeTo:a", "fadeTo:b");
+    }
+
+    @Test
+    void nullOrBlankRoomFadesToSilence() {
+        FakeBackend b = new FakeBackend();
+        MusicController c = new MusicController(b);
+        c.room("a");
+        c.room(null);
+        c.room("  ");
+        assertThat(b.calls).containsExactly("fadeTo:a", "fadeOut");
+    }
+
+    @Test
+    void offStopsAndIgnoresRooms() {
+        FakeBackend b = new FakeBackend();
+        MusicController c = new MusicController(b);
+        c.room("a");
+        c.level(MusicLevel.OFF);
+        b.calls.clear();
+        c.room("b");
+        assertThat(b.calls).isEmpty();
+    }
+
+    @Test
+    void levelChangeSetsGain() {
+        FakeBackend b = new FakeBackend();
+        MusicController c = new MusicController(b); // default MEDIUM
+        c.level(MusicLevel.HIGH);
+        assertThat(b.calls).containsExactly("setGain:" + MusicLevel.HIGH.gainDb());
+    }
+
+    @Test
+    void turningOffThenOnReplaysOnNextRoom() {
+        FakeBackend b = new FakeBackend();
+        MusicController c = new MusicController(b);
+        c.room("a");
+        c.level(MusicLevel.OFF);   // fadeOut
+        c.level(MusicLevel.MEDIUM); // setGain
+        b.calls.clear();
+        c.room("a");               // current was reset → plays again
+        assertThat(b.calls).containsExactly("fadeTo:a");
+    }
+}