Is it normal for a mechanic to take a car home hoping it breaks down on the way so he can analyse what caused it to do so? That's what is happening with my Holden Cruze. I thought with the cars of today it could be done with a computer.
If there is no error code showing on the computer — and that's common — you're probably getting better service if they're prepared to drive it in search of the fault instead of waiting for it to break down