The desirable qualities of good tests

I often say that learning test-driven development is comparable to learning a whole other programming language. The practice of TDD is a mirror world of depth and trade-offs. Kent Beck underscores that depth in listing all [the desirable qualities of good tests], some of which are at tension with each other. Tests aren’t the easiest thing to get right, but there’s no better way to improve your design skills than to wrestle with the feedback loop of writing tests for the code you’re currently working on.