public void testFactory_parseHours_String() {
        assertEquals(0, Hours.parseHours((String) null).getHours());
        assertEquals(0, Hours.parseHours("PT0H").getHours());
        assertEquals(1, Hours.parseHours("PT1H").getHours());
        assertEquals(-3, Hours.parseHours("PT-3H").getHours());
        assertEquals(2, Hours.parseHours("P0Y0M0DT2H").getHours());
        assertEquals(2, Hours.parseHours("PT2H0M").getHours());
        try {
            Hours.parseHours("P1Y1D");
            fail();
        } catch (IllegalArgumentException ex) {
            // expeceted
        }
        try {
            Hours.parseHours("P1DT1H");
            fail();
        } catch (IllegalArgumentException ex) {
            // expeceted
        }
    }