public void testPropertySetMonth() {
        YearMonth test = new YearMonth(1972, 6);
        YearMonth copy = test.monthOfYear().setCopy(12);
        check(test, 1972, 6);
        check(copy, 1972, 12);
        
        try {
            test.monthOfYear().setCopy(13);
            fail();
        } catch (IllegalArgumentException ex) {}
        try {
            test.monthOfYear().setCopy(0);
            fail();
        } catch (IllegalArgumentException ex) {}
    }