How do we test human readiness for driving? We give them a driving test, which takes all of 40 minutes. This is possible only because we know a lot about what it means to be a human. To test self-driving technology we need to understand a lot about the AI that is behind it, which is an active area of research with much progress. Moreover, there is adversarial testing in simulation and on raw sensor data, which can tell you a lot about your system before any large scale real world testing begins, including when it might be safe to start real-world testing. Real-world testing at such large scales is neither a practical nor a necessary component to validating self-driving systems.