Software is complex stuff. Even relatively straightforward applications that do only a few things can have a dizzying number of possible “journeys” for users to take. Ideally, every one of those journeys is tested under all possible circumstances to ensure the software works as expected and doesn’t crash, pop-up useless error messages, or provide wrong answers.

If you’ve ever been using a piece of software that crashed or went into some catatonic state for no apparent reason, your first thought, probably, was “why didn’t they test this?” followed by some choice words for the developers.