We don't just throw stuff at prod. Google has a culture of testing and code review, so code review, unit testing and integration tests are the first line of defense. Then we do QA testing, where a lot of problems not caught by tests are found, which then inform us where tests may be lacking. We also roll out to internal dogfood first, given Google's number of employees this is kind of like a pre-canary.

The point of the canary is it gives you one last real world test where you can limit the damage if anything goes wrong. Without it, you'll have to assume your tests are perfect, and I doubt that's ever achieved in practice in a real environment, except maybe in avionics and space control systems.