This time a posting from Mark Seemann has raised a slew of comments.
One of them is a note from Colin Jack about the annoyance of producing interface/implementation pairs all the time. My first response is that that sounds to me a bit like a problem with style. Maybe it's just wordplay, but usually I don't extract interfaces from classes, I implement interfaces that I've already discovered in some previous test.
My second response is to wonder how much this is a tools issue. I don't believe there's anything in the .Net world that yet matches the responsiveness of the usual Java IDE's. It makes a difference as to what's plausible. I remember the huge shift in perception when first VisualAge for Java and then JetBrains' Idea came out. In retrospect, I always spent more on time on rework than many people I worked with 1 but it sure took a lot more time in emacs (and I was pretty good at it), even if I was working in a better language.
1) which is not to say who was right, I'm just wired that way...