Can we test robocars the way we tested regular cars?

I've written a few times that perhaps the biggest unsolved problem in robocars is how to know we have made them safe enough. While most people think of that in terms of government certification, the truth is that the teams building the cars are very focused on this, and know more about it than any regulator, but they still don't know enough. The challenge is going to be convincing your board of directors that the car is safe enough to release, for if it is not, it could ruin the company that releases it, at least if it's a big company with a reputation. We don't even have a good definition of what "safe enough" is though most people are roughly taking that as "a safety record superior to the average human." Some think it should be much more, few think it should be less.