As long as the car can pass the tests set out for humans, there really shouldn't be need for government involvement. We already have defined standards that we find acceptable. It is not like humans are perfect and the machine has to match that, though I do hope that the machines can exceed those existing expectations.
We've defined standards for humans that we find acceptable, in part because there is much that is implicit in the operator being a human. For example, a cop at an intersection, holding his hand up, then pointing left to redirect traffic is not something we test in a driver's test, but is something we expect human drivers to understand and obey. Perhaps the cars can handle this already, but there are likely hundreds, if not thousands, of these scenarios that are going to be necessary to think about now.
There is also a lot of legal work that will begin as these roll out, especially dealing with liability, and these things take time that simply selling millions of these cars in 3-4 years will not allow for.
Its probably a little more difficult than making the car take what we know as a driving test but it could probably be boiled down to some reasonable number of city and highway miles in various conditions (hard rain, snow, fog) and a small number of situations to make sure it doesn't run down pedestrians and deer at random. In that respect, the endpoints of a journey would likely be harder to deal with than anything else (ie. driveways). When it comes down to it though, humans are an amazingly low bar so while it would be nice to have perfect cars, it wouldn't be hard to save a few lives.