public void testAdd_RP4() {
        MutablePeriod test = new MutablePeriod(1, 2, 0, 4, 5, 6, 7, 8, PeriodType.yearMonthDayTime());
        try {
            test.add(new Period(1, 2, 3, 4, 5, 6, 7, 8));  // cannot set weeks
            fail();
        } catch (IllegalArgumentException ex) {}
        assertEquals(1, test.getYears());
        assertEquals(2, test.getMonths());
        assertEquals(0, test.getWeeks());
        assertEquals(4, test.getDays());
        assertEquals(5, test.getHours());
        assertEquals(6, test.getMinutes());
        assertEquals(7, test.getSeconds());
        assertEquals(8, test.getMillis());
    }