Let me start with some contexts in the form of a quote from JUnit Test Infected: Programmers Love Writing Tests:
Every programmer knows they should write tests for their code. Few do. The universal response to "Why not?" is "I'm in too much of a hurry." This quickly becomes a vicious cycle- the more pressure you feel, the fewer tests you write. The fewer tests you write, the less productive you are and the less stable your code becomes. The less productive and accurate you are, the more pressure you feel.
I am working as a Test Engineer for three (five developer sized) Scrum teams. I cannot do all of their testing work. Therefore I am training them to become better testers and continuously improve their process.
I firmly believe part of being a good software developer is being a good tester.
-- John Sonmez
This leads to my question:
I am looking for methods I haven't tried are unaware of. Preferable one method per answer, unless they cannot be used a single method. (This way we can vote for which we think are the best or most promising methods to try, certainly for a single tester in larger teams.)