Thanks for all the comments. Let me distilled what I have learned. Correct me
if I am wrong.

In Smalltalk:
Production environment and development environment are very similar if not
identical.
Runtime and debug modes are identical. So, debugging is instantaneous
available.
Debugging occurs at the context of the exception itself - not in a handler
or somewhere else.
Debugger, nah, the whole environment allows doit's, code changes and resumes
always.
Reflection is constantly available for debugging and logging.

Can we coin a term for these capabilities/properties? Can we define a
standard to gauge programming environments?