The increasing complexity of software requires increasingly sophisticated means of ensuring its correctness -- "just" testing is not necessarily good enough, depending on the domain in which the software is used. Formal specification, verification and proof is a field with a long tradition in computer science that is gaining more (practical) relevance these days; and in this episode, we cover the basics. Our guest is Benjamin Pierce, professor of computer science at UPenn. We discuss the nature of (good) specifications, how verification and proof is different from testing, and where and how these techniques are successfully used today.