From your linked article:

  Andrew: A story states that you once entered a programming
  contest at Stanford (I believe) and you submitted the winning
  entry, which worked correctly after a single compilation. Is
  this story true? In that vein, today’s developers frequently
  build programs writing small code increments followed by
  immediate compilation and the creation and running of unit
  tests. What are your thoughts on this approach to software
  development?

  Knuth: As to your real question, the idea of immediate
  compilation and "unit tests" appeals to me only rarely, when
  I’m feeling my way in a totally unknown environment and need
  feedback about what works and what doesn’t. Otherwise, lots of
  time is wasted on activities that I simply never need to
  perform or even think about. Nothing needs to be "mocked up."

Amusing given the link prompting this whole thread.