@Test
public void testEventCount() {

  assertThat(emptySubtitle.getEventTimeCount()).isEqualTo(0);
  assertThat(simpleSubtitle.getEventTimeCount()).isEqualTo(4);
  assertThat(overlappingSubtitle.getEventTimeCount()).isEqualTo(4);
  assertThat(nestedSubtitle.getEventTimeCount()).isEqualTo(4);
}