public void testWithers() {
        YearMonthDay test = new YearMonthDay(1970, 6, 9);
        check(test.withYear(2000), 2000, 6, 9);
        check(test.withMonthOfYear(2), 1970, 2, 9);
        check(test.withDayOfMonth(2), 1970, 6, 2);
        try {
            test.withMonthOfYear(0);
            fail();
        } catch (IllegalArgumentException ex) {}
        try {
            test.withMonthOfYear(13);
            fail();
        } catch (IllegalArgumentException ex) {}
    }