If "the design in your head" involves classes or functions, or any programming language dependent ideas, then it you are not doing TDD. I call this style test-

If "the design in your head" involves classes or functions, or any programming language dependent ideas, then it you are not doing TDD. I call this style test-first, or pseudo TDD. But if the design in your head is an algorithm that can be expressed in natural language, then TDD will let you take that and make a loosely coupled, maintainable program out of it. Good post on the difference here: http://cumulative-hypotheses.org/2011/08/30/tdd-as-if-you-meant-it/ http://cumulative-hypotheses.org/2011/08/30/tdd-as-if-you-me...