Well to have a valid scientific test, you can only change ONE variable, because if you change more than one variable you cannot know which of the variables (or multiple) caused the changes.
This is why most all audio testing is invalid as truly scientific testing, because knowledge about the equipment being changed could of course affect your perceptions on a psychological basis. You probably REALLY WANT that new $6400 Anthem AVM 70 + ATI 525NC combo to sound at least "$5300 better" than the old Denon AVR-X3600H...even if, well, it really just sounds never but not better.
My suggestion for testing in general is yes having someone invisibly change the cables or streamer or amp or whatever while you ar, etc.e out of the house, each day you don't know if they did or not, you just make notes. Each day you decide if the system sounds different or not, then you compare to their record of when they actually made changes. This wipes any "A/B/X testing is too pressured/hurried" "switching is not a natural way to listen" complaints.