> The problem arises because usually one or some of the points are unfulfilled. An important idea of TDD is that it allows you to discover those "unfulfilled p

> The problem arises because usually one or some of the points are unfulfilled. An important idea of TDD is that it allows you to discover those "unfulfilled points" in the tests. When writing code (the tests) that use an API, instead of when writing the actual API. When writing code that uses objects, methods, interfaces and so on, you are in a mindset of writing "what a user of the code would wish there was". This is probably the best place, mindset and moment to define those specs in detail.