I've just uploaded a new version of my PipelineTesting library. This one contains just a few minor modifications: A few improved unit tests, and new methods to make it easier to create multi-part messages to use as pipeline inputs.
Here's an example of the last one:
IBaseMessage message = MessageHelper.Create(
"This is the body part (part1)",
"This is the part2",
"This is the part3"
The new MessageHelper.Create() method takes a params array of strings as argument. Each one will get loaded as a separate message part, with the first one being marked as the body part. There's also a second overload which takes a params array of Stream objects.
As usual, you can download the code from here: PipelineTesting.zip.