I wanted to test a pipeline component that is executed after a resubmit via de ESB Portal. My standard approach is to add the assembly with the pipeline component to the GAC, reset IIS and then attach the debugger to the process. For some reason the breakpoints in code are not always hit. What you can also do, is add the following code at the beginning of the method to be debugged.
#if DEBUG
Debugger.Launch();
#endif