Method getInfoText of CDPlayer tested on shouldThrowReturnValueNullException.

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

@@ -14,6 +14,7 @@ public class CDPlayer implements Device {
     private int CdDriveContent=0;
     private int CdFlap=0;
     private int volume = 0;
+    private String infoText=null;
     private List<String> supportedFormats = new ArrayList<String>(Arrays.asList(new String[] {"Audio","MP3","WMA","AAC"}));
 
     private String actualPlayTrack="";
@@ -66,7 +67,10 @@ public class CDPlayer implements Device {
 
     @Override
     public String getInfoText() {
-        return null;
+        if(infoText==null){
+            throw new ReturnValueNullException();
+        }
+        return infoText;
     }
 
     @Override
@@ -157,4 +161,7 @@ public class CDPlayer implements Device {
         return actualPlayTrack;
     }
 
+    public void setInfoText(String intoText) {
+        this.infoText=intoText;
+    }
 }

src/main/java/device/cdPlayer/exceptions/ReturnValueNullException.java

@@ -0,0 +1,9 @@
+package device.cdPlayer.exceptions;
+
+public class ReturnValueNullException extends RuntimeException{
+
+    public ReturnValueNullException() {
+        super("Method should not return a Null-Value.");
+    }
+
+}

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

@@ -7,6 +7,7 @@ import org.junit.jupiter.api.extension.ExtendWith;
 import org.junit.jupiter.params.ParameterizedTest;
 import org.junit.jupiter.params.provider.Arguments;
 import org.junit.jupiter.params.provider.MethodSource;
+import org.mockito.Mockito;
 import org.mockito.junit.jupiter.MockitoExtension;
 
 import java.lang.reflect.Method;
@@ -17,6 +18,8 @@ import java.util.stream.Stream;
 
 import static org.assertj.core.api.Assertions.assertThat;
 import static org.junit.jupiter.api.Assertions.*;
+import static org.mockito.Mockito.when;
+
 @ExtendWith(MockitoExtension.class)
 class CDPlayerTest {
 
@@ -272,4 +275,19 @@ class CDPlayerTest {
         assertThat(volumeIstInValueRange).isEqualTo(true);
     }
 
+    @ParameterizedTest
+    @MethodSource("getInfoTestData")
+    void getInfoTest(String testName, CDPlayer _cdPlayer,Exception exception , String expectedResult){
+        Exception newException=assertThrows(exception.getClass(),()->_cdPlayer.getInfoText());
+        assertEquals(ReturnValueNullException.class, newException.getClass());
+    }
+    static Stream<Arguments> getInfoTestData () {
+
+        CDPlayer cdPlayer1 = new CDPlayer();
+
+        return Stream.of(
+                Arguments.of("[getInfoText() by infoText=null ] => shouldThrowReturnValueNullException", cdPlayer1,new ReturnValueNullException(),"")
+        );
+    }
+
 }