Take a store. Change one thing. Watch agents shop it.
Make your own copy of a reference store and change one thing: ranking, product data or agent instructions. You get two private stores, A and B. Point any agent at them and see what each store recorded.
Your own copyReference stores never change; you work on a private copy.
One change per testA and B differ in exactly one setting.
Test money onlyReal protocols, test cards, nothing ships.