Linux.com - https://www.linux.com/news/test-knowledge
Software testing is a form of learning. A set of tests can be considered a set of questions. The most obvious question a unit test poses is “Does the code pass?” to which there are two simple answers: yes or no. A test allows us to move from belief to knowledge — for example, to move from merely believing something works to knowing that, in a particular case, it does or does not.