A bit of personal experience, although minor.
Nearly 30 years ago I took my VN V8 to a well-known windscreen repairer to get a chip fixed. An employee took the keys, and gunned it into the workshop, at the same time as one of their vans was backing out. I watched as they collided, inside the workshop.
I just went to the manager and told him (calmly) that his employee had pranged my car and his business van inside the workshop, which had a sign clearly displayed "no admittance to workshop" for customers.
Damage was a headlight, grille, bar, bonnet and guard. A couple of days later, I was able to collect it from the panel shop that was only 50 metres away, at no cost to me. Windscreen also fixed, no cost, all good.
A couple of months later I received a letter from QBE wanting me to sign a waiver, stating that my car was being driven by person who had my permission to drive the car.
This was, to me, an attempt to make me responsible for the cost of the repairs, and therefore being made to claim on my insurance.
I refused to sign, replying with the sequence of events and that I was not allowed to drive it into the workshop.
A few more months, and another letter with the same demand, and that I should take note that my refusal would result in the repairs not being carried out. Big deal, the car had been fixed, and I was only inconvenienced by a couple of days. Letter returned to them, unsigned, with the same explanation.
This went on for a while, and all their subsequent letters were binned, no further action from me. Then, no more letters.
About 18 months later, I received a cheque in the mail, for the cost of the repairs being in full settlement of my claim. I hadn't made any claim.
Took the cheque to the panel shop, who told me that they had been paid at the time of the repair.
Took the cheque to the windscreen repairers ................ new staff, no knowledge of incident, so I said the cheque is yours, you sort it out.
I could have cashed the cheque myself, kept the money, and maybe nobody would have noticed.
My point ................. if a mechanic prangs your car while road testing it, don't sign anything that makes you liable for making a claim against your own insurance. And if that is part of their disclosure propaganda in fine print at the bottom of the page, tell them that you don't agree to be responsible for any damage caused by them.