[pron]

If we look at practices that fall under formal methods, I would include things like TLA+ (or Alloy) specifications and concolic testing (https://en.wikipedia.org/wiki/Concolic_testing) (which is sometimes used as a step in the process of automatic test generation).

Practices that are not usually considered formal methods include clever semi-blackbox fuzzing (like Antithesis) and mutation testing to improve test quality.