Method addToFavoriteSongs of CDPlayer tested on addingDuplicatedSong -> SongShouldNotBeAdded.

src/main/java/device/cdPlayer/CDPlayer.java

@@ -167,8 +167,10 @@ public class CDPlayer implements Device {
         this.loadedCD=CDList.get(nextIndex);
     }
     public void addToFavoriteSongs(String song){
+        if(!(favoriteSongs.contains(song))) {
             favoriteSongs.add(song);
         }
+    }
 
     //Getters, Setters und SupportMethods
     public void setCD(CD _loadedCD) {

src/test/java/device/cdPlayer/CDPlayerTest.java

@@ -494,10 +494,18 @@ class CDPlayerTest {
     @ParameterizedTest
     @MethodSource("addToFavoriteSongsData")
     void addToFavoriteSongs(String testName,String cases, CDPlayer _cdPlayer,Exception exception) {
-        String myFavoriteSong=_cdPlayer.getCD().getPlayList()[0];
+        if(cases.equals("Case1")) {
+            String myFavoriteSong = _cdPlayer.getCD().getPlayList()[0];
             _cdPlayer.addToFavoriteSongs(myFavoriteSong);
             assertThat(_cdPlayer.getFavoriteSongs().get(0)).describedAs(testName).isEqualTo(myFavoriteSong);
-
+        }
+        if(cases.equals("Case2")) {
+            String myFavoriteSong1 = _cdPlayer.getCD().getPlayList()[0];
+            String myFavoriteSong2 = _cdPlayer.getCD().getPlayList()[0];
+            _cdPlayer.addToFavoriteSongs(myFavoriteSong1);
+            _cdPlayer.addToFavoriteSongs(myFavoriteSong2);
+            assertThat(_cdPlayer.getFavoriteSongs().size()>1).describedAs(testName).isNotEqualTo(true);
+        }
     }
     static Stream<Arguments> addToFavoriteSongsData () {
         String[] audioPlayList = new String[]{"Audio 01", "Audio 02", "Audio 03", "Audio 04", "Audio 05"};
@@ -510,7 +518,8 @@ class CDPlayerTest {
         cdPlayer1.loadCDWechseler(audioCD2, 1);
 
         return Stream.of(
-                Arguments.of("[addToFavoriteSongs() by addingOneSong] => favoriteSongsShouldReturnsThatAddedSong", "Case1", cdPlayer1, null)
+                Arguments.of("[addToFavoriteSongs() by addingOneSong] => favoriteSongsShouldReturnsThatAddedSong", "Case1", cdPlayer1, null),
+                Arguments.of("[addToFavoriteSongs() by addingDuplicatedSong] => SongShouldNotBeAdded", "Case2", cdPlayer1, null)
         );
     }