    @Test
    public void testContentJAXB() throws Exception {

        assertEquals("<customer id=\"0\"><age>0</age></customer>",
            $.content(new Customer()).content());
        assertEquals($(new Customer()).toString(), $.content());
        assertEquals("<customer id=\"0\"><customer id=\"0\"><age>0</age></customer></customer>",
            $.find("customer").content(new Customer()).parent().content());

        assertEquals("<document/>", $.content((Object) null).toString());
    }