This video show you the Contoso HR sample app. The Submit Application workflow coordinated database updates, sending of email and multiple web service calls. How can you unit test a workflow like this? You don't want to update databases and send email when testing but you want to be sure that the conditions and correlation queries are correct.
The WorkflowTestHelper project now features XamlInjection which allows you to inject mock activities into XAML when testing. Ron Jacobs show you how he tested Submit Application workflow using XamlInjection.