There's a hell of a lot of testing that needs to be done to not only get to fully-autonomous cars, but to even have the sort of technology that a lot of modern cars have today like radar-guided cruise control and active braking systems. This is how they test them. Youtuber Tom Scott went up to Thatcham Research, a British insurance industry-funded non-profit that looks into how to prevent car crashes, and he took a look at their foam-bot car known as the Global Vehicle Target. The foam-bot replicates a real car to automotive sensors, with the added benefit of being made out of, well, foam. They can even re-assemble the whole thing, after you've plowed right into it, in about 15 to 20 minutes.