added first test case for chooseItem() & and added productive code for RadioPlayer

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

@@ -158,7 +158,8 @@ public class RadioPlayer implements Device {
 
     @Override
     public String chooseItem(int itemNr) {
-        return null;
+        playedStation = savedPlaylist.get(itemNr - 1);
+        return ("Radio is playing station: 0" + (savedPlaylist.indexOf(playedStation) + 1) + " " + this.playedStation + " from saved playlist");
     }
 
     @Override

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

@@ -171,11 +171,24 @@ class RadioPlayerTest {
         @Test
         void getOptions() {
         }
-
-        @Test
-        void chooseOption() {
-        }
     */
+
+    @ParameterizedTest
+    @MethodSource("chooseItemOptions")
+    void testChooseItem(String testName, RadioPlayer testRp, String expectedResult) {
+        String playedStation = testRp.playedStation;
+        assertThat(playedStation).describedAs(testName).isEqualTo(expectedResult);
+    }
+
+    static Stream<Arguments> chooseItemOptions() {
+        RadioPlayer rp = new RadioPlayer();
+        rp.chooseItem(2);
+
+        return Stream.of(
+                Arguments.of("Test select station to play with nr isn`t bigger than playlist size", rp, "Teddy")
+        );
+    }
+
     @ParameterizedTest
     @MethodSource("testPlayOptions")
     void testPlay(String testName, RadioPlayer testRp, String expectedResult) {