what is commutative testimony?

I'm sorry, but "commutative testimony" does not appear to be a commonly discussed concept. It is possible that you might be referring to a term or concept that is not widely known or used.

To get a better understanding of the term "commutative testimony," it would be helpful to provide more context or clarify where you encountered this term. Additionally, if you meant something else, please provide more information so I can try to assist you better.