public HttpResponse execute(HttpUriRequest req) throws IOException, ClientProtocolException {
   String digest = req.getLastHeader("Digest").getValue();
   String ticket = TICKET;
   String userId = USER;
   HttpResponse response =
       new DefaultHttpResponseFactory()
           .newHttpResponse(new ProtocolVersion("1.1", 1, 1), 200, null);
   // validate the ticket
   try {
     String checkdigest =
         LocalDigestValidator.SHA(SHARED_SECRET + ticket, ENCODING, HASH_FUNCTION);
     if (checkdigest.equals(digest)) {
       String responsedigest =
           LocalDigestValidator.SHA(SHARED_SECRET + ticket + userId, ENCODING, HASH_FUNCTION);
       response.setEntity(
           new StringEntity(successResponse.replace("${digest}", responsedigest)));
     } else {
       // return error
       response.setEntity(new StringEntity(failResponse));
     }
   } catch (NoSuchAlgorithmException e) {
     // TODO Auto-generated catch block
     e.printStackTrace();
   }
   return response;
 }
 @Test
 public void serviceReturnsDigest() throws Exception {
   String digest = LocalDigestValidator.SHA(SHARED_SECRET + TICKET, ENCODING, HASH_FUNCTION);
   String result = client.validateDigest(digest, TICKET, "myserviceurl", USER);
   String responsedigest =
       LocalDigestValidator.SHA(SHARED_SECRET + TICKET + USER, ENCODING, HASH_FUNCTION);
   assertEquals(responsedigest, result);
 }