A while a go I wrote some posts about unit testing Windows Workflow foundation Activities, you can find the posts here and here. Fortunately I am not the only one who thinks unit testing is important as you can find various other blog posts about it like this one from Ron Jacobs.
But Cliff Simpkins has taken this one step further and just blogged about a new MSDN virtual lab “Using Test-First Development with WF”! Excellent work and I recommend doing the lab, I know I did! And while you are at it, there are a number of other interesting labs you can do.