anchor.diff:  	Input = "AWS4-HMAC-SHA256 Credential=RANDY_ACCESS_KEY/20140224/us-east-1/dynamodb/aws4_request, SignedHeaders=content-length;content-type;host;user-agent;x-amz-date;x-amz-target, Signature=81f71d83f35b3b2be9589f9ec0f5edca95b14d602f639b183e729d1fd1e3308c",
   	Actual = dynamo_user(Input),
   	Expected = <<"RANDY_ACCESS_KEY">>,
  -	?assertEqual(Expected, Actual).
  +	?assertEqual(Expected, Actual),
  +	?assertEqual(undefined, dynamo_user(undefined)).
   
   dynamo_op_test() ->
   	TargetHeader = "DynamoDB_20120810.ListTables",
   	Actual = dynamo_op(TargetHeader),
   	Expected = {"ListTables", "DynamoDB_20120810"},
  -	?assertEqual(Expected, Actual).
  +	?assertEqual(Expected, Actual),
  +	?assertEqual({undefined, undefined}, dynamo_op(undefined)).
  +
   
   -endif.
   
  
positive.code: content_types_accepted(ReqData, Context) ->
  	{[{"application/json", accept_json}, 
  	  {"application/x-amz-json-1.0", accept_json}], ReqData, Context}.
  
  %% TODO, validate request?
  malformed_request(ReqData, Context) ->
  
negative.code:     service_available/2,
      allowed_methods/2,
      content_types_accepted/2,
      content_types_provided/2,
      malformed_request/2,
      resource_exists/2,
      process_post/2,
  