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?
. . . [A]ccording to [Stack Exchange] poster Uri Dekel (handle: Uri), a Google software engineer.
“There’s a serious move towards formal verification rather than random functional testing. Government agencies like NASA and some defense organizations are spending more and more on these technologies. They’re still a PITA [pain in the ass] for the average programmer, but they’re often more effective at testing critical systems.”
Written by Michael Byrne, Motherboard Editor
http://motherboard.vice.com/read/how-is-critical-life-or-death-software-tested