Modern Vespa

Is there a way with a NON battery scoot to test all the functionality without starting it (ie, connect a 5v battery and test brake lights etc.

Bonus question- can you check spark without starting the scoot?

you can hook up a battery yes and checking spark is always done without the scoot running. Pull the plug out, put the spark cable back on and try to kick start it while holding the spark plug against the frame. If you see a spark you're kosher.

Remember that an all AC system turns off the circuit by shorting it so you can tell the brake light, for instance, works with the pedal down but when it's up you will be shorting the battery which could fry a wire. There's other nonsense as well like the horn grounding through the lights on some systems. You might be better off with a circuit tester.

Yah, you would think that but I found that to not be the case. I would have spark when kicking it over with the plug touching the engine but it would not spark when in the cylinder (confirmed with timing light). I had the flywheel remagnetized, new points, new condenser (even replaced the condenser), new coil, plug wire, plug cap, and still nothing. It was a 1978 P125X so I replaced the points with electronic ignition and now she runs like a top. The only thing I can figure at this point is the HV coil needed to be replaced or rewound as that was the only part I had not replaced.