I've got a little test program that checks to make sure my protocol behaves correctly. Each function returns a deferred, and sets the next function as the callback, and some common function as errback. This seems to work great -- the test runs through all the test funcs when working properly, and halts at the problem point if not. But now I want to verify that I get errors (errbacks) in all the places I should. I was hoping to do the same thing as before, only now swap the function of the errbacks with that of the callbacks. This doesn't seem to work. Returning a deferred from an errback still results in its parent errbacks getting called, terminating the test program prematurely. Whats the right way to test conditions that should trigger errbacks? I couldn't see a tutorial or doc that covered this. Thanks, Gary