test+productive code for case:1 of method prev in CDPlayer created.

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

@@ -52,6 +52,8 @@ public class CDPlayer implements Device {
 
     @Override
     public void prev() {
+        List<String> playList =  Arrays.asList(loadedCD.getPlayList());
+        this.actualPlayTrack=playList.get(playList.indexOf(actualPlayTrack) -1);
 
     }
 

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

@@ -197,4 +197,29 @@ class CDPlayerTest {
         );
     }
 
+    @ParameterizedTest
+    @MethodSource("prevTestData")
+    void prevTest(String testName,String testDirection, CDPlayer _cdPlayer,int anzClicks, String expectedResult){
+        for (int i = 0; i < anzClicks; i++) {
+            _cdPlayer.prev();
+        }
+        assertThat(_cdPlayer.getActualPlayTrack()).describedAs(testName).isEqualTo(expectedResult);
+    }
+    static Stream<Arguments> prevTestData () {
+
+        String[] audioPlayList=new String[]{"Audio 01","Audio 02","Audio 03","Audio 04","Audio 05"};
+        CD audioCD=new CD("Audio",audioPlayList);
+
+        CDPlayer cdPlayer1=new CDPlayer();
+        cdPlayer1.tapOnCdFlap();
+        cdPlayer1.setCD(audioCD);
+        cdPlayer1.tapOnCdFlap();
+        cdPlayer1.next();//1x nach Vorne
+
+       return Stream.of(
+               Arguments.of("[getActualPlayTrack() after 1x prev() starting by firstSong] => FirstSongSelected","FirstSongSelected", cdPlayer1, 1, cdPlayer1.getSongByNumber(0))
+               );
+
+    }
+
 }