Sorry if this is an obvious question:

How does one perform a compression test with the engine rotated for service?
Or, more precisely - How do you get the starter motor to turn with engine rotated?

Don't see how you can do it with the engine in position so you could do it warm etc due to plug access.

I've wired the starter motor directly to the battery with the starter and solenoid energised, battery not connected: Result - a few random lights on dash. No response from starter motor.

Your thoughts much appreciated.