Method changeToNextCD of CDPlayer tested checking the effect -> loadedCDShouldNotReturnNull.

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

@@ -158,7 +158,7 @@ public class CDPlayer implements Device {
         if(activeSource.equals("CDDrive")){
             throw new ChangeCDOnlyOnCDWechselerException();
         }
-
+        this.loadedCD=cdWechseler.getCDList()[1];
     }
 
     //Getters, Setters und SupportMethods

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

@@ -431,14 +431,31 @@ class CDPlayerTest {
     @ParameterizedTest
     @MethodSource("changeToNextCDData")
     void changeToNextCDTest(String testName,String cases, CDPlayer _cdPlayer,Exception exception) {
+        if(cases.equals("Case1")) {
             Exception newException = assertThrows(exception.getClass(), () -> _cdPlayer.changeToNextCD());
             assertEquals(ChangeCDOnlyOnCDWechselerException.class, newException.getClass());
         }
+        if(cases.equals("Case2")) {
+            CD actualCD=_cdPlayer.getCD();
+            _cdPlayer.changeToNextCD();
+            CD nextCD=_cdPlayer.getCD();
+            assertThat(nextCD).describedAs(testName).isNotEqualTo(null);
+        }
+    }
     static Stream<Arguments> changeToNextCDData () {
         CDPlayer cdPlayer1 = new CDPlayer();
 
+        CDPlayer cdPlayer2 = new CDPlayer();
+        cdPlayer2.changePlaySource();
+
+        String[] audioPlayList=new String[]{"Audio 01","Audio 02","Audio 03","Audio 04","Audio 05"};
+        CD audioCD1=new CD("Audio",audioPlayList);
+        cdPlayer2.loadCDWechseler(audioCD1,0);
+        cdPlayer2.loadCDWechseler(audioCD1,1);
+
         return Stream.of(
-                Arguments.of("[changeToNextCD() by CDWechselerNotSelected ] => shouldThrowAnException", "Case1", cdPlayer1,new ChangeCDOnlyOnCDWechselerException())
+                Arguments.of("[changeToNextCD() by CDWechselerNotSelected ] => shouldThrowAnException", "Case1", cdPlayer1,new ChangeCDOnlyOnCDWechselerException()),
+                Arguments.of("[changeToNextCD()  checking the effect ] => loadedCDShouldNotReturnNull", "Case2", cdPlayer2,null)
         );
     }