@Test
  public void itReturnsAudioUrl() {
    Episode episode =
        new Episode() {
          @Override
          protected Audio getAudio() {
            return new Audio() {
              @Override
              public String getUrl() {
                return "audio.mp3";
              }
            };
          }
        };

    assertThat(episode.getAudioUrl(), is(episode.getAudio().getUrl()));
  }
  @Test
  public void itReturnsEmptyUrlWhenAudioIsNull() {
    Episode episode = new Episode();

    assertThat(episode.getAudioUrl(), is(""));
  }