BaseTimeline { static Long decrementMaxId(Long maxId) { return maxId == null ? null : maxId - 1; }    }
@Test public void testDecrementMaxId_positive() { final Long correctedId = BaseTimeline.decrementMaxId(TEST_ID); assertEquals((Long) (TEST_ID - 1L), correctedId); }
@Test public void testDecrementMaxId_nullId() { assertNull(BaseTimeline.decrementMaxId(null)); }