Also fuzz tests! I cannot stress enough how important fuzz tests are if your security model solely relies on your C++ being memory safe (a lot of code should be

Also fuzz tests! I cannot stress enough how important fuzz tests are if your security model solely relies on your C++ being memory safe (a lot of code should be sandboxed as well but that's another discussion...). Even when using modern stuff correctly on a mature codebase fuzz testing will find bugs. So if you don't fuzz test and someone evil has your binary then they'll fuzz test for you...