test+productive code for case:3 of method prev in CDPlayer created.

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

@@ -53,7 +53,13 @@ public class CDPlayer implements Device {
     @Override
     public void prev() {
         List<String> playList =  Arrays.asList(loadedCD.getPlayList());
-        this.actualPlayTrack=playList.get(playList.indexOf(actualPlayTrack)-1);
+        int actualIndex=playList.indexOf(actualPlayTrack);
+        if(actualIndex>0){
+            actualIndex-=1;
+        }else{
+            actualIndex=0;
+        }
+        this.actualPlayTrack=playList.get(actualIndex);
     }
 
     @Override

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

@@ -202,16 +202,13 @@ class CDPlayerTest {
     void prevTest(String testName,String testDirection, CDPlayer _cdPlayer,int anzClicks, String expectedResult){
         if(testDirection.equals("StartingBySecondSong")) {
             _cdPlayer.next();
-            for (int i = 0; i < anzClicks; i++) {
-                _cdPlayer.prev();
-            }
         }
         if(testDirection.equals("StartingByThirdSong")) {
             _cdPlayer.next();
             _cdPlayer.next();
-            for (int i = 0; i < anzClicks; i++) {
-                _cdPlayer.prev();
-            }
+        }
+        for (int i = 0; i < anzClicks; i++) {
+            _cdPlayer.prev();
         }
         assertThat(_cdPlayer.getActualPlayTrack()).describedAs(testName).isEqualTo(expectedResult);
     }
@@ -225,10 +222,10 @@ class CDPlayerTest {
         cdPlayer1.setCD(audioCD);
         cdPlayer1.tapOnCdFlap();
 
-
         return Stream.of(
                 Arguments.of("[getActualPlayTrack() after 1x prev() starting by secondSong] => FirstSongSelected", "StartingBySecondSong", cdPlayer1, 1, cdPlayer1.getSongByNumber(0)),
-                Arguments.of("[getActualPlayTrack() after 2x prev() starting by thirdSong] => FirstSongSelected", "StartingByThirdSong", cdPlayer1, 2, cdPlayer1.getSongByNumber(0))
+                Arguments.of("[getActualPlayTrack() after 2x prev() starting by thirdSong] => FirstSongSelected", "StartingByThirdSong", cdPlayer1, 2, cdPlayer1.getSongByNumber(0)),
+                Arguments.of("[getActualPlayTrack() after 1x prev() starting by firstSong] => FirstSongSelected", "StartingByFirstSong", cdPlayer1, 1, cdPlayer1.getSongByNumber(0))
         );
     }
 }