anchor.diff:       ?_assertEqual(ok, validate_request(ValidRequest2)),
        ?_assertEqual({error, {invalid, contact_must_be_sips}}, validate_request(InvalidRequest2)),
        ?_assertEqual(ok, validate_request(ValidRequest3)),
  -
   
        % Response validation
        ?_assertEqual(ok, validate_response(ValidResponse)),
  
positive.code:     InvalidResponse2 = create_response(ValidRequest2, 200),
      ValidResponse2 = append_header(contact, sip_headers:address(<<>>, <<"sip:alice@localhost">>, []), InvalidResponse2),
  
      % Record-Route is SIPS, so Contact must be sips
      InvalidResponse3 = ValidResponse2,
  
      [% Request validation
  
negative.code:      ?_assertEqual(Response2, create_response(Request, 201, <<"Very Ok!">>))
       ].
  
  -spec create_ack_cancel_test_() -> list().
  create_ack_cancel_test_() ->
      ReqHeaders = [{via, <<"SIP/2.0/UDP pc33.atlanta.com;branch=z9hG4bKkjshdyff">>},
                    {via, <<"SIP/2.0/UDP bob.biloxi.com;branch=z9hG4bK776asdhds">>},
                    {to, <<"Bob <sip:bob@biloxi.com>">>},
  