Certainly it's fun from the pure engineering perspective but I guess also somewhat tedious. On the other hand, if a billion dollars depend on your code working

Certainly it's fun from the pure engineering perspective but I guess also somewhat tedious. On the other hand, if a billion dollars depend on your code working or not, or in other cases human lives like in space rockets, you don't get a second chance. If you fuck up, lots of important things get flushed down the toilet, usually including your job. So you have 3 teams do in parallel to be 99.999999999% certain that it'll work as advertised. It's also sorta why banks are slow to adopt new changes since they want to be sure that whatever is going on, it'll work and not flush down Grandma's rent.