Formal methods have been verifying real world systems using ACL2 for a long time. Also, sqlite has 730 times amount of test code https://sqlite.org/testing.html

Formal methods have been verifying real world systems using ACL2 for a long time. Also, sqlite has 730 times amount of test code https://sqlite.org/testing.html https://sqlite.org/testing.html . Formal verification is not a magic bullet but it doesn't make your systems bullet proof though.