An interesting mental picture - "Programming is like exploring a dark house. You go from room to room and writing the test is like turning on the light. Then you can avoid the furniture and save your shins (the clean design resulting from refactoring). Soon you're ready to explore the next room."

Here is a need of an adjective which means "can be made to work in one step" Atomic? Achievable? Progressive?. At the different stages of the cycle, you are solving different problems, so the aesthetics change: Write a test - What should the API be? Make it compile-do as little as possible to satisfy the compiler. Make it run-get back to green so you have confidence. Refactor-remove duplication to prepare for the next test.