Jameleon - Jagacy Plug-in
The Jagacy Plug-in uses a commercial library as a 3270 emulator. It has a GUI that displays the test case behavior as the test is executing.
The library that comes with the Jagacy plug-in is a trial version that limits the number of screens in a session. To get a full license, be sure to visit the Jagacy Site. I have been given full permission to redistribute the trial version of Jagacy. However, this permission is limited to Jameleon.