It really depends on which application. In the past few years I've been mainly writing server-side infrastructure libraries and services with no GUI at all. In

It really depends on which application. In the past few years I've been mainly writing server-side infrastructure libraries and services with no GUI at all. In those cases I'm writing stuff bottom-up anyway, so while I'm writing the bottom layers (data structures, interfaces, algorithms), I'll be testing them and playing with them with no big app wrapping them. It's both faster to write the bottom layers like that, and eventually you end up with pretty solid tests. So it's not a compromise for me in these cases.