[icegreentea2]

Yes, this stuff is nice.

But it is worth noting that these control loops can often have some sort of memory, so you normally need to test over multiple cycles - you usually have a test vector to load in, and watch for the response vector.

Trivial example would be if you had a PID controller implemented into your main loop. Your main loop would be storing the integral and "previous" error term.

[bagels]

Equivalent to handling an additionaanl sensor input and an additional output, no?

[icegreentea2]

Yes, you could in principle convert any memory within a given loop into a separate unit. You just gotta pick between the tradeoffs between having more I/O and software/hardware units, versus having more memory within specific software/hardware units.

You just gotta find a balance that works for your requirements and constraints. In my application (it was medical devices), we found that stateful loops fit nicely.

[EmielMols]

True, but you do want to test the emergent control system.

[jcims]

That's the irony of closed loop control systems. They appear to be simple but the emergent behavior, particularly when there is a hierarchy of control loops, is incredibly complex.