I'm going to embed a scripting engine in our application, which is basically is a GUI testing f/w. Since some scripts are going to be relatively big and complex (100-200 lines) i need to provide a support for debugging (step-by-step execution and locals watches at least). I think I will create a simple editor for this, or maybe reuse some existing if possible - Eclipse+plugin maybe? Which of the popular engines is most suitable for this task? I will appreciate any comments, if someone did same thing already.