### Question:
TimelineUtilities { public static TimeSpan getYesterday() { return TimeSpan.get(Days.ONE, get0000().getTimeInMillis()); } private  TimelineUtilities(); static void addDuration(Calendar calendar, Duration duration); static Calendar get0000(); static Calendar get0000(Date aDate); static List<TimeSpan> getIntervalsForSpan(Date startDate, TimeSpan span, int spanType); static Calendar getNext0000(Date aDate); static TimeSpan getPartialWeek(); static TimeSpan getPrecedingMonths(Date reference, int months, boolean includeThisMonth); static TimeSpan getPrecedingMonths(int months, boolean includeThisMonth); static TimeSpan getPrecedingWeeks(Date reference, int numWeeks, boolean includeThisWeek); static TimeSpan getPrecedingWeeks(int numWeeks, boolean includeThisWeek); static Map<Duration, List<DateDurationKey>> getTableOfLegalDates(TimeSpan span, Duration duration); static TimeSpan getThisDay(Date time); static TimeSpan getThisMonth(Date time); static TimeSpan getThisWeek(Date time); static TimeSpan getToday(); static TimeSpan getYesterday(); static boolean isAt0000(Date aDate); static boolean isDayWeekMonth(TimeSpan span); static boolean isDay(TimeSpan span); static boolean isWeek(TimeSpan span); static boolean isMonth(TimeSpan span); static boolean isRounded(Date time, Duration duration); static Calendar roundDown(Date date, Duration interval); static Calendar roundUp(Date date, Duration interval); static TimeSpan scale(TimeSpan span, double factor);  }### Answer:
@Test public void testGetYesterday() { TimeSpan yesterday = TimelineUtilities.getYesterday(); Assert.assertTrue(Days.ONE.compareTo(yesterday.getDuration()) == 0); Assert.assertTrue(TimelineUtilities.isAt0000(yesterday.getStartDate())); Assert.assertTrue(yesterday.getStart() < System.currentTimeMillis()); Assert.assertTrue(TimelineUtilities.isAt0000(yesterday.getEndDate())); Assert.assertTrue(yesterday.getEnd() < System.currentTimeMillis()); }