code:     public void testHandleNoInitialResponseNull() throws Exception
      {
          final AuthenticationResult result = _negotiator.handleResponse(null);
          assertEquals("Unexpected authentication status", AuthenticationResult.AuthenticationStatus.CONTINUE, result.getStatus());
          assertArrayEquals("Unexpected authentication challenge", new byte[0], result.getChallenge());
  
          final AuthenticationResult firstResult = _negotiator.handleResponse(VALID_RESPONSE.getBytes());
          assertEquals("Unexpected first authentication result", _expectedResult, firstResult);
      }
  