[mattvanhorn]

I think far too many people fail to make the distinction between designing an algorithm and designing a program (which implements it).

This is why I have to watch co-workers create dozens of useless error classes and utility functions, and totally ignore YAGNI, before actually taking a single step towards a working program.

If you don't know the algorithm, and haven't figured out the abstractions, then just slinging some implementation code is the easiest (and laziest) thing you can do. It's basically a way of avoiding having the necessary conversations. In this case, the question that needed answering before beginning TDD was: "How does one efficiently solve a sudoku puzzle (as opposed to just manipulating one)"

[mathattack]

Very important point. It can also be viewed as the difference between research and development. It's hard to get through with testable and measurable development until you've done the fuzzier creative work first.