Replying to both of you so replying to myself -- I know all of the arguments for why testing improves maintainability; that has nothing to do with what I'm aski

Replying to both of you so replying to myself -- I know all of the arguments for why testing improves maintainability; that has nothing to do with what I'm asking. It was my mistake for muddying my question with my own anecdote. I'm asking: is there scientific proof (i.e., in a study) that testing and maintainability are at least positively correlated in a reasonably universal fashion?