go down the road and stamp on the stop pedal as hard as you can and listen for the digga digga digga digga and feel for it through the pedal?
the other way, drive onto a bit of grass and put it in 1st rev up and drop the clutch and watch for the light and listen for the same digga digga digga noise and your rev counter dropping down the scale while on full throttle.
then go back and clean up the mess you made of the grass .
repeat with the button pressed to turn off vsa and see the difference.
a fault code will usually come up for abs/vsa, once that has come up it is disengaged (as i found out in the snow last year!)