public void testPropertySetMonth() {
        YearMonthDay test = new YearMonthDay(1972, 6, 9);
        YearMonthDay copy = test.monthOfYear().setCopy(12);
        check(test, 1972, 6, 9);
        check(copy, 1972, 12, 9);
        
        test = new YearMonthDay(1972, 1, 31);
        copy = test.monthOfYear().setCopy(2);
        check(copy, 1972, 2, 29);
        
        try {
            test.monthOfYear().setCopy(13);
            fail();
        } catch (IllegalArgumentException ex) {}
        try {
            test.monthOfYear().setCopy(0);
            fail();
        } catch (IllegalArgumentException ex) {}
    }