Method chooseItem of CDPlayer tested on notSetCD.

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

@@ -18,7 +18,7 @@ public class CDPlayer implements Device {
     private List<String> supportedFormats = new ArrayList<String>(Arrays.asList(new String[] {"Audio","MP3","WMA","AAC"}));
 
     private String actualPlayTrack="";
-    private CD loadedCD;
+    private CD loadedCD=null;
 
     @Override
     public void louder() {
@@ -86,6 +86,9 @@ public class CDPlayer implements Device {
 
     @Override
     public String chooseItem(int itemNr) {
+        if(this.loadedCD==null){
+            throw new ReturnValueNullException();
+        }
         return null;
     }
 

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

@@ -327,4 +327,17 @@ class CDPlayerTest {
         );
     }
 
-}
+    @ParameterizedTest
+    @MethodSource("chooseItemTestData")
+    void chooseItemTest(String testName,String cases, CDPlayer _cdPlayer,Exception exception , String expectedResult) {
+        Exception newException = assertThrows(exception.getClass(), () -> _cdPlayer.chooseItem(1));
+        assertEquals(ReturnValueNullException.class, newException.getClass());
+    }
+    static Stream<Arguments> chooseItemTestData () {
+        CDPlayer cdPlayer1 = new CDPlayer();
+        return Stream.of(
+                Arguments.of("[chooseItem() by notSetCD ] => shouldThrowReturnValueNullException","Case1", cdPlayer1,new ReturnValueNullException(),"")
+        );
+    }
+
+    }