Just thought I'd add something to this.
When I took the celica for its first MOT under my ownership, I'd done everything I thought needed doing in terms of safety, including new discs and pads etc.
I got a call to say the brake pipes had actually burst on the rollers during the test. Not the bits you can see, but the bit where they go under the plastic cover halfway down the car. Now, your average guy would be hard pressed to visually spot that.
If it hadn't been picked up at the MOT when would it have gone? The first time i broke heavily at motorway speeds? If someone pulled out on me?
I'm really glad the MOT test did what it was supposed to there.