I recommend that you use Tomas Restrepo’s excellent Pipeline Testing Library which allows you to write unit tests for your pipelines.
Further information can be found on his website at http://www.winterdom.com/weblog/2006/04/24/TestingPipelineComponents.aspx and you can download the library from GitHub at http://github.com/tomasr/pipelinetesting/tree/master
I also did a write up on the library over at my blog: http://www.modhul.com/2008/03/11/testing-pipeline-components-the-pipeline-testing-library/
Rgds, Nick.