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

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

@@ -52,7 +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);
     }
 
     @Override

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

@@ -197,4 +197,27 @@ 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();
+
+        return Stream.of(
+                Arguments.of("[getActualPlayTrack() after 1x prev() starting by secondSong] => FirstSongSelected", "FirstSongSelected", cdPlayer1, 1, cdPlayer1.getSongByNumber(0))
+        );
+    }
 }