I feel like i’ve missed the boat with this, but the “first class” unit testing support that has been added to BizTalk Server 2009 is terrific. Unit testing with BizTalk Server up to this point, has always been very painful and custom.

Setting this to true, instructs the BizTalk MSBuild tasks that take our precious BizTalk artefacts like orchestrations, maps, pipelines and so on and parses and compiles them into MSIL, to add an extra layer of inheritance between for example, our pipeline and the real BizTalk pipeline base class. A whole family of these new “intermediate” testable classes live in the Microsoft.BizTalk.TestTools.dll assembly (available under c:\Program Files(x86)\Microsoft BizTalk Server 2009\Developer Tools\) such as Microsoft.BizTalk.TestTools.Pipeline.TestableReceivePipeline and Microsoft.BizTalk.TestTools.Map.TestableMap.