Looks like there are 2 main kinds (at least that I have.) One doesn’t give you much to go on the other has lots of test points. This is obviously the latter.
Jumper T-H for manual run
multimeter:
V-N voltage for water valve during run
L-N standby voltage 120V
L-H test heater ~72 ohms
L-M timer motor ~4400 ohms
N-V water valve ~150-300 ohms
T-L thermostat 0 ohms with ice