added second test case for changeToSavedPlaylist() & and added productive code

src/main/java/device/radioPlayer/RadioPlayer.java

@@ -203,6 +203,11 @@ public class RadioPlayer implements Device {
     }
 
     public String changeToSavedPlaylist() {
+        if(regionPlaylist.contains(playedStation)) {
+            playedStation = savedPlaylist.get(0);
+            regionPlaylist.clear();
+            return "Playlist switched now playing station: 0" + (savedPlaylist.indexOf(playedStation) + 1) + " " + this.playedStation + " from saved playlist";
+        }
         return "You are already in saved Playlist!";
     }
 }

src/test/java/device/radioPlayer/RadioPlayerTest.java

@@ -255,9 +255,13 @@ class RadioPlayerTest {
     static Stream<Arguments> changeToSavedPlaylistOptions() {
         RadioPlayer rp = new RadioPlayer();
         rp.changeToSavedPlaylist();
+        RadioPlayer rp1 = new RadioPlayer();
+        rp1.changeRegion("BY");
+        rp1.changeToSavedPlaylist();
 
         return Stream.of(
-                Arguments.of("Test for change to saved playlist when you already in saved playlist", rp, "YouFM")
+                Arguments.of("Test for change to saved playlist when you already in saved playlist", rp, "YouFM"),
+                Arguments.of("Test for change to saved playlist when in regional playlist", rp1, "YouFM")
 
         );
     }