Merge commit '77768e5230a252ffb2657e59465d5df7cded6c61' into HEAD

src/main/java/device/usbPlayer/UsbPlayer.java

@@ -118,7 +118,12 @@ public class UsbPlayer implements Device {
 
     @Override
     public void prev() {
-
+        int currentIdex = Playlist.indexOf(playTrack);
+        int nextIndex = Playlist.size() - 1;
+        if (currentIdex != 0) {
+            nextIndex = (currentIdex - 1);
+        }
+        playTrack = Playlist.get(nextIndex);
     }
 
     @Override

src/test/java/device/usbPlayer/UsbPlayerTest.java

@@ -114,4 +114,27 @@ void louderTest(String testName, UsbPlayer inputPlay, int expectedResult) {
         );
     }
 
+    ////////////////
+    @ParameterizedTest
+    @MethodSource("PrevOptions")
+    void PrevTest(String testName, UsbPlayer inputPlay, String expectedResult) {
+        String current_Track = inputPlay.getPlayTrack();
+        assertThat(current_Track).describedAs(testName).isEqualTo(expectedResult);
+    }
+
+    static Stream<Arguments> PrevOptions() {
+        UsbPlayer up1 = new UsbPlayer();
+        up1.prev();
+        UsbPlayer up2 = new UsbPlayer();
+        for (int i = 1; i < up2.getPlaylist().size(); i++) {//3
+            up2.prev();
+        }
+
+
+        return Stream.of(
+                Arguments.of("From first-Song to last-Song : Musik 03.mp3 ", up1, "Musik 03.mp3"),
+                Arguments.of("From first-Song to second-Song(Backward) : Musik 02.mp3 ", up2, "Musik 02.mp3")
+        );
+    }
+
 }