### Question:
Minute extends RegularTimePeriod implements Serializable { @Override public RegularTimePeriod next() { Minute result; if (this.minute != LAST_MINUTE_IN_HOUR) { result = new Minute(this.minute + 1, getHour()); } else { Hour nextHour = (Hour) getHour().next(); if (nextHour != null) { result = new Minute(FIRST_MINUTE_IN_HOUR, nextHour); } else { result = null; } } return result; } Minute();  Minute(int minute, Hour hour);  Minute(Date time);  Minute(Date time, TimeZone zone, Locale locale);  Minute(int minute, int hour, int day, int month, int year); Day getDay(); Hour getHour(); int getHourValue(); int getMinute(); @Override long getFirstMillisecond(); @Override long getLastMillisecond(); @Override void peg(Calendar calendar); @Override RegularTimePeriod previous(); @Override RegularTimePeriod next(); @Override long getSerialIndex(); @Override long getFirstMillisecond(Calendar calendar); @Override long getLastMillisecond(Calendar calendar); @Override boolean equals(Object obj); @Override int hashCode(); @Override int compareTo(TimePeriod o1); static Minute parseMinute(String s); static final int FIRST_MINUTE_IN_HOUR; static final int LAST_MINUTE_IN_HOUR; }### Answer:
@Test public void testNext() { Minute m = new Minute(30, 1, 12, 12, 2000); m = (Minute) m.next(); assertEquals(2000, m.getHour().getYear()); assertEquals(12, m.getHour().getMonth()); assertEquals(12, m.getHour().getDayOfMonth()); assertEquals(1, m.getHour().getHour()); assertEquals(31, m.getMinute()); m = new Minute(59, 23, 31, 12, 9999); assertNull(m.next()); }