diff --git a/src/main/java/device/usbPlayer/UsbPlayer.java b/src/main/java/device/usbPlayer/UsbPlayer.java
index 1c18978..2dac1b0 100644
--- a/src/main/java/device/usbPlayer/UsbPlayer.java
+++ b/src/main/java/device/usbPlayer/UsbPlayer.java
@@ -76,7 +76,7 @@ public class UsbPlayer implements Device {
 
         for (int i = 0; i < Playlist.size(); i++) {
             song = Playlist.get(i).substring(Playlist.get(i).length() - 4);
-            if (song.equals(".mp3") | song.equals(".mp4") ) {
+            if (song.equals(".mp3") | song.equals(".mp4")| song.equals(".m4a") ) {
                 flag = true;
             } else {
                 flag = false;
diff --git a/src/test/java/device/usbPlayer/UsbPlayerTest.java b/src/test/java/device/usbPlayer/UsbPlayerTest.java
index 37acd4a..fc121f7 100644
--- a/src/test/java/device/usbPlayer/UsbPlayerTest.java
+++ b/src/test/java/device/usbPlayer/UsbPlayerTest.java
@@ -3,6 +3,7 @@ package device.usbPlayer;
 import org.junit.jupiter.params.ParameterizedTest;
 import org.junit.jupiter.params.provider.Arguments;
 import org.junit.jupiter.params.provider.MethodSource;
+
 import java.util.stream.Stream;
 import java.util.ArrayList;
 
@@ -48,12 +49,12 @@ class UsbPlayerTest {
     }
 
 
-@ParameterizedTest
-@MethodSource("louderOptions")
-void louderTest(String testName, UsbPlayer inputPlay, int expectedResult) {
-    int volumeNum = inputPlay.getLautstaerke();
-    assertThat(volumeNum).describedAs(testName).isEqualTo(expectedResult);
-}
+    @ParameterizedTest
+    @MethodSource("louderOptions")
+    void louderTest(String testName, UsbPlayer inputPlay, int expectedResult) {
+        int volumeNum = inputPlay.getLautstaerke();
+        assertThat(volumeNum).describedAs(testName).isEqualTo(expectedResult);
+    }
 
     static Stream<Arguments> louderOptions() {
         UsbPlayer up11 = new UsbPlayer();
@@ -149,7 +150,7 @@ void louderTest(String testName, UsbPlayer inputPlay, int expectedResult) {
 
         UsbPlayer up2 = new UsbPlayer();
         for (int i = 0; i <= 3; i++) {
-          up2.Louder_10();
+            up2.Louder_10();
         }
         up2.quieter_10();
 
@@ -162,6 +163,7 @@ void louderTest(String testName, UsbPlayer inputPlay, int expectedResult) {
                 Arguments.of("Volume was 100, should stay 100 ", up3, 100)
         );
     }
+
     @ParameterizedTest
     @MethodSource("quieter_10_Options")
     void quieter_10_Test(String testName, UsbPlayer inputPlay, int expectedResult) {
@@ -194,10 +196,10 @@ void louderTest(String testName, UsbPlayer inputPlay, int expectedResult) {
     @MethodSource("FindSongOptions")
     void findSongTest(String testName, int inputPlay, int expectedResult) {
         //first case: the song is not in the Album
-       // int songLoc1 = inputPlay.findSong("song 4");
+        // int songLoc1 = inputPlay.findSong("song 4");
         assertThat(inputPlay).describedAs(testName).isEqualTo(expectedResult);
         //Second Case: the song is in the album
-       // int songLoc2 = inputPlay.findSong("Musik 02");
+        // int songLoc2 = inputPlay.findSong("Musik 02");
         assertThat(inputPlay).describedAs(testName).isEqualTo(expectedResult);
 
     }
@@ -245,21 +247,30 @@ void louderTest(String testName, UsbPlayer inputPlay, int expectedResult) {
     @ParameterizedTest
     @MethodSource("isAllAudioOptions")
     void isAllAudioTest(String testName, boolean inputTestResult, boolean expectedResult) {
-       // String current_Track = inputPlay.getPlayTrack();
+        // String current_Track = inputPlay.getPlayTrack();
         assertThat(inputTestResult).describedAs(testName).isEqualTo(expectedResult);
     }
 
     static Stream<Arguments> isAllAudioOptions() {
         UsbPlayer up1 = new UsbPlayer();
-        UsbPlayer up2=new UsbPlayer();
+
+        UsbPlayer up2 = new UsbPlayer();
         ArrayList<String> Pl = new ArrayList<String>();
         Pl.add("Musik 01.mp4");
         Pl.add("Musik 02.mp4");
         Pl.add("Musik 03.mp4");
         up2.setPlaylist(Pl);
+//m4a
+        UsbPlayer up3 = new UsbPlayer();
+        ArrayList<String> Pl1 = new ArrayList<String>();
+        Pl1.add("Musik 01.m4a");
+        Pl1.add("Musik 02.m4a");
+        Pl1.add("Musik 03.m4a");
+        up3.setPlaylist(Pl);
         return Stream.of(
-                Arguments.of("Go to Song : Musik 03.mp3 ", up1.isAllAudio(), true),
-                Arguments.of("Go to Song : Musik 03.mp3 ", up2.isAllAudio(), true)
+                Arguments.of("Check if the Files are .mp3 ", up1.isAllAudio(), true),
+                Arguments.of("Check if the Files are .mp4 ", up2.isAllAudio(), true),
+                Arguments.of("Check if the Files are .m4a ", up3.isAllAudio(), true)
 
         );
     }