How Is Critical 'Life or Death' Software Tested?

Your average scripter likely isn't writing a whole lot of proofs or going through the rigors of formal program verification, generally. Which is fine because your average scripter also isn't writing software for jet airliners or nuclear power plants or robotic surgeons. But somebody is—and the odds are pretty good that your life has been in their hands very recently. How do you know they're not a complete hack? Well, you don't really. Which prompts the question: How is this sort of code tested?

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