Unit Testing Pipeline Components

It seems like all I ever post about is pipeline components, but I've got some pretty heavy pipeline work to do over the next few months, so I knocked up a simple pipeline component unit testing framework. 
Its a lot easier than I could have hoped to spoof the executing context of a BTS2004 pipeline.  My initial plan was to decompile pipeline.exe in the SDK (as it does exactly what I want - runs a pipeline out of BTS), but it became immediately obvious that everything I needed was provided and nicely exposed by PipelineObjects.dll in it's root folder.  So that concrete implementation of IPipelineContext and IBaseMessage that was going to be so crucial in fooling a standard pipeline component to run Execute(IPipelineContext, IBaseMessage) was just a new away.
 
The rest wrote itself really.  I'm left with a class that takes an instatiated Pipeline component, and calls Validate() on it to check you've also remembered to set all its props.  It then passes a string you give it as a message, and lets you know the output for unit testing.  Its proper bo!