public void testFactory_parseYears_String() {
        assertEquals(0, Years.parseYears((String) null).getYears());
        assertEquals(0, Years.parseYears("P0Y").getYears());
        assertEquals(1, Years.parseYears("P1Y").getYears());
        assertEquals(-3, Years.parseYears("P-3Y").getYears());
        assertEquals(2, Years.parseYears("P2Y0M").getYears());
        assertEquals(2, Years.parseYears("P2YT0H0M").getYears());
        try {
            Years.parseYears("P1M1D");
            fail();
        } catch (IllegalArgumentException ex) {
            // expeceted
        }
        try {
            Years.parseYears("P1YT1H");
            fail();
        } catch (IllegalArgumentException ex) {
            // expeceted
        }
    }