I am trying to run an ExecuteScript that should be taking in a json message and parsing the fields for further processing but I cannot get this to work. I ran a tester for ExecuteScript created by this author:
Everything you need to know and more is included in that 3 part series.
My other advice is to create and test your script directly in command line. Then start to work with it in the context of ExecuteScript. While working with the NiFi Processor you should also be tailing the nifi log file(s) as they will possibly contain more information than you see in the NiFI UI errors.