Our readingWhat is a korrent?
A test checks a handful of examples; a proof settles an infinite state space, which is why formal methods can say things testing never can.
Drawn from what Martin Kleppmann said
What these subjects mean
formal proof Machine-checked mathematics: proof assistants such as Lean, and what changes when correctness is certified rather than refereed.
software quality Whether a program is any good and how anyone would know: tests, review, debt, and what a suite cannot cover.