[MaulingMonkey]

This works fine on small scales.

When dealing with millions of lines of code, I do not have the time to read the whole thing and internalize it's whole state. Understanding the call graph can help, but diving through every abstract interface and callback and abstraction is a non-starter. Even if I had time to read the entire codebase line by line, I wouldn't be able to fit it all in my head, and I often have enough coworkers that changes are occuring faster than I can read and understand them all.

Even the codebases I work on are dwarfed by much larger ones.