OK.
You said you recently upgraded Katalon Studio from old 5.3 to 5.7. In between these two versions, there were a few significant design changes around TestObject. I suppose you should do ‘clean build’ from source to binary classes in order to make your project in sync with KS5.7 platform.
How to do ‘clean build’ ? It’s easy. Do as follows.
- stop your Katalon Studio
- in Windows Explorer, identify the /bin folder
- delete the bin folder
- restart Katalon Studio
- open your project
- run test in you project ---- all of Groovy sources will be re-compiled to generate new binaries