TDD Quick tip: “What test should I choose next?”

When test-driving your code, you shift between red (write a failing test), green (write the code needed to make the test pass) & refactor (clean up). But how do you kickstart this loop? What heuristics can you use to guide selection of the next test you write? This article summarizes the most common heuristics and highlights the one I use predominantly:

Pick the test that forces you to add one (and only one) new facet.