@Test
@Ignore // 暂时忽略，测试不通过，add by 芋艿
public void testGetDayBegin() {

    Assert.assertNull(DateUtil.getDayBegin(null));
    Assert.assertEquals(new Date(1_515_542_400_000L),
            DateUtil.getDayBegin(new Date(1_515_585_600_000L)));
}