Can I use my friend’s car for driving test UK?
There is no reason why you cannot take your own car or someone else's car to a driving test. However there are a couple of things that you need to be aware of. It needs to be suitable, road worthy (legal) and insured.
Can I use my friends car in UK?
Technically, yes, you can—at least, as long as you're covered by insurance. If you're going to be learning regularly in their car, then you should look at getting added as a named driver on their policy. Alternatively, short-term cover might be more cost-effective.
Can someone drive my car if they are not on my insurance UK?
It might be an emergency or you may have permission from the car owner, but that doesn't mean it's legal. Unless you're a 'named driver' on their car insurance, you almost certainly won't be insured. And both the driver and car owner can run into trouble if caught without the necessary cover.