Last updated at 7:16 pm UTC on 12 October 2019
From the class comment:
An ObjectTracer can be wrapped around another object, and then give you a chance to inspect it whenever it receives messages from the outside. For instance...
(ObjectTracer on: Display) flash: (50@50 extent: 50@50)
will give control to a debugger just before the message flash is sent.
Obviously this facility can be embellished in many useful ways.