assertTrue("expected an XMLStreamException", ex.getCause() instanceof XMLStreamException);
// let's make sure our test string is unmarshallable, just for a good sanity check
JAXBContext testcontext = JAXBContext.newInstance(AddNumbers.class);
Unmarshaller testunmarshaller = testcontext.createUnmarshaller();
AddNumbers testresponse =
(AddNumbers)testunmarshaller.unmarshal(new ByteArrayInputStream(xmlWithDTD.getBytes()));
assertEquals("we could not unmarshal the test xml", 99999999, testresponse.getArg0());
}