It will all come down to what it fails on, whether its dangerous or not, your not gonna hurt anyone driving around with a small chip in zone A of the wondscreen, but knowingly driving around with defective brakes is another story.

Even if you get a pass, and an advisory that says for example, that "one of your tyres requires attention" and you ignore it and have an accident. If the insurance assessor can apportion blame to your tyre they could "walk" away as you were "knowingly" driving a car with a defect.
As far as i'm aware insurance companies will have access to MOT details (pass/fail and advisories)
Regards
Dave
ps - good question - needs answering !!