public void testFactory_standardDaysIn_RPeriod() {
        assertEquals(0, Days.standardDaysIn((ReadablePeriod) null).getDays());
        assertEquals(0, Days.standardDaysIn(Period.ZERO).getDays());
        assertEquals(1, Days.standardDaysIn(new Period(0, 0, 0, 1, 0, 0, 0, 0)).getDays());
        assertEquals(123, Days.standardDaysIn(Period.days(123)).getDays());
        assertEquals(-987, Days.standardDaysIn(Period.days(-987)).getDays());
        assertEquals(1, Days.standardDaysIn(Period.hours(47)).getDays());
        assertEquals(2, Days.standardDaysIn(Period.hours(48)).getDays());
        assertEquals(2, Days.standardDaysIn(Period.hours(49)).getDays());
        assertEquals(14, Days.standardDaysIn(Period.weeks(2)).getDays());
        try {
            Days.standardDaysIn(Period.months(1));
            fail();
        } catch (IllegalArgumentException ex) {
            // expeceted
        }
    }