public void testParsePeriod_simple() {
        Period expect = new Period(1, 2, 3, 4, 5, 6, 7, 8);
        assertEquals(expect, f.parsePeriod("P1Y2M3W4DT5H6M7.008S"));
        
        try {
            f.parsePeriod("ABC");
            fail();
        } catch (IllegalArgumentException ex) {}
    }