EXECUTE: Open beans.xml editor and select 'Interceptors' node in 'Tree' tab.
EXECUTE: Call from context menu 'Add Class' wizard, input 'MyClass' and finish.
ASSERT: Node 'MyClass' appears.
EXECUTE: Repeat second step with the same 'MyClass' input.
ASSERT: Wizard disables finish and displays error message ''Interceptors' already contains class MyClass.'.
FAILURE: Wizard allows to push 'Finish', writes error message with stack trace into the log and remains open.
The same steps work for nodes 'Decorators' and 'Alternatives'.