public void testToLocalDate() {
        YearMonth base = new YearMonth(2005, 6, COPTIC_UTC);
        LocalDate test = base.toLocalDate(9);
        assertEquals(new LocalDate(2005, 6, 9, COPTIC_UTC), test);
        try {
            base.toLocalDate(0);
            fail();
        } catch (IllegalArgumentException ex) {}
    }