It seems logical to me that if you have a dependency graph of your source code (tree showing call stack of all functions in your code base) you should be able to save a tremendous amount of time doing functional and integration tests after each release.

Essentially you will be able to tell the testers exactly what functionality to test as the rest of the features remain unchanged from a source code point of view.

If for instance you change a spelling mistake in once piece of the code, there is no reason to run through your whole test script again "just in case" you introduced a critical bug.

My question, why are dependency trees not used in software engineering and if you use them, how do you maintain them? What tools are available that generate these trees for C# .NET, C++ and C source code?