diff --git a/src/main/java/device/Device.java b/src/main/java/device/Device.java
index a2a8c3f..276e029 100644
--- a/src/main/java/device/Device.java
+++ b/src/main/java/device/Device.java
@@ -7,6 +7,7 @@ public interface Device {
 	int getVolume();
 	void next();
 	void prev();
+	String play();
 	//get deviceName, Album and current Item
 	String getInfoText();
 	//get a list of public methods
@@ -15,6 +16,8 @@ public interface Device {
 	String chooseItem(int itemNr);
 	// get the actual album
 	String[] getItemList();
-	String play();
-
+	//mute the Volume and returns an Info.
+	String mute();
+	//unmute the Volume and returns an Info.
+	String unmute();
 	}
diff --git a/src/main/java/device/cdPlayer/CDPlayer.java b/src/main/java/device/cdPlayer/CDPlayer.java
index bdf1995..f5f93cc 100644
--- a/src/main/java/device/cdPlayer/CDPlayer.java
+++ b/src/main/java/device/cdPlayer/CDPlayer.java
@@ -90,6 +90,16 @@ public class CDPlayer implements Device {
         return loadedCD.getPlayList();
     }
 
+    @Override
+    public String mute() {
+        return null;
+    }
+
+    @Override
+    public String unmute() {
+        return null;
+    }
+
     @Override
     public String play() {
         if(isCdFlapOpen()){
diff --git a/src/main/java/device/radioPlayer/RadioPlayer.java b/src/main/java/device/radioPlayer/RadioPlayer.java
index 858cf13..2bd5401 100644
--- a/src/main/java/device/radioPlayer/RadioPlayer.java
+++ b/src/main/java/device/radioPlayer/RadioPlayer.java
@@ -166,6 +166,16 @@ public class RadioPlayer implements Device {
         return null;
     }
 
+    @Override
+    public String mute() {
+        return null;
+    }
+
+    @Override
+    public String unmute() {
+        return null;
+    }
+
 
     @Override
     public String play() {
diff --git a/src/main/java/device/usbPlayer/UsbPlayer.java b/src/main/java/device/usbPlayer/UsbPlayer.java
index bf403d6..b1440e3 100644
--- a/src/main/java/device/usbPlayer/UsbPlayer.java
+++ b/src/main/java/device/usbPlayer/UsbPlayer.java
@@ -160,6 +160,16 @@ public class UsbPlayer implements Device {
         return null;
     }
 
+    @Override
+    public String mute() {
+        return null;
+    }
+
+    @Override
+    public String unmute() {
+        return null;
+    }
+
 
     @Override
     public String play() {
diff --git a/src/test/java/device/cdPlayer/CDPlayerTest.java b/src/test/java/device/cdPlayer/CDPlayerTest.java
index 56646dc..3bcc1db 100644
--- a/src/test/java/device/cdPlayer/CDPlayerTest.java
+++ b/src/test/java/device/cdPlayer/CDPlayerTest.java
@@ -2,6 +2,7 @@ package device.cdPlayer;
 
 import device.Device;
 import device.cdPlayer.exceptions.*;
+import org.junit.jupiter.api.Test;
 import org.junit.jupiter.api.extension.ExtendWith;
 import org.junit.jupiter.params.ParameterizedTest;
 import org.junit.jupiter.params.provider.Arguments;
@@ -249,10 +250,7 @@ class CDPlayerTest {
             for (int i = 0; i < interfaceMethods.length; i++) {
                 assertThat(deviceMethods.contains(interfaceMethods[i].getName())).describedAs(testName).isEqualTo(true);
             }
-
         }
-
-
     }
     static Stream<Arguments> getOptionsTestData () {
         CDPlayer cdPlayer1 = new CDPlayer();
@@ -263,6 +261,15 @@ class CDPlayerTest {
         );
     }
 
-
+    @Test
+    void getVolumeReturnValueBetween0And100(){
+        CDPlayer cdPlayer1 = new CDPlayer();
+        boolean volumeIstInValueRange=false;
+        int volume=cdPlayer1.getVolume();
+        if(volume>=0 && volume <=100){
+            volumeIstInValueRange=true;
+        }
+        assertThat(volumeIstInValueRange).isEqualTo(true);
+    }
 
 }
\ No newline at end of file