@Test
public void getTrackGroups_returnsTrackGroups() throws Exception {

  prepareDownloadHelper(downloadHelper);
  TrackGroupArray trackGroupArrayPeriod0 = downloadHelper.getTrackGroups(/* periodIndex= */ 0);
  TrackGroupArray trackGroupArrayPeriod1 = downloadHelper.getTrackGroups(/* periodIndex= */ 1);
  assertThat(trackGroupArrayPeriod0).isEqualTo(trackGroupArrays[0]);
  assertThat(trackGroupArrayPeriod1).isEqualTo(trackGroupArrays[1]);
}