proof of the pudding

[ proof uhv thuh pood-ing ]

noun

1. the true value or quality of something, as seen when it is experienced, tried, or put to use:

   The proof of the pudding for a business is what customers say about it.

Word History and Origins

Origin of proof of the pudding¹

First recorded in 1600–20; from the proverb “The proof (i.e., test) of the pudding is in the eating”