@Test
void scheduleNext() {

    FixedRateTask task = new FixedRateTask(null, null, Duration.ofSeconds(30));
    ZonedDateTime start = ZonedDateTime.now();
    task.scheduledTime = start;
    ZonedDateTime next = task.scheduleNext();
    assertThat(Duration.between(start, next)).isEqualTo(Duration.ofSeconds(30));
}