added play() and first test for first saved station

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

@@ -149,7 +149,7 @@ public class RadioPlayer implements Device {
 
     @Override
     public String play() {
-        return null;
+        return ("Radio is playing station: 0"+(Playlist.indexOf(playTrack)+1)+ " "+this.playTrack);
     }
 
     public String showStationInfo() {

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

@@ -164,10 +164,20 @@ class RadioPlayerTest {
     @Test
     void chooseOption() {
     }
+*/
+@ParameterizedTest
+@MethodSource("testPlayOptions")
+void testPlay(String testName, RadioPlayer testRp, String expectedResult) {
+    String playedStation = testRp.play();
+    assertThat(playedStation).describedAs(testName).isEqualTo(expectedResult);
+}
 
-    @Test
-    void play() {
+    static Stream<Arguments> testPlayOptions() {
+        RadioPlayer rp1 = new RadioPlayer();
+
+        return Stream.of(
+                Arguments.of("Test for playing first station on saved playlist", rp1, "Radio is playing station: 01 YouFM")
+        );
     }
 
- */
 }