At the bottom of the Learning at Ada: 02 Problem Solving page, there is a section 'Optional readings'. The link What Is a Good Test Case? (Cem Kaner, J.D., Ph.D.) on the page no longer seems to work and could probably be updated to the link below.
https://profinit.eu/wp-content/uploads/2016/03/WhatIsGoodTestcase.pdf
