First you buy or lease a code coverage tool. Then running through it, usually, you add markers to the source code and recompile the application. Then you run all of your tests and the code coverage tool will analyze the paths through the application and provide you with detailed reports on what paths are not being tested and maybe even where too much traffic is passing through a node.
Is this what you had in mind?
You could spend a lifetime analyzing the path structure and test coverage manually. Now Test Coverage is a different story.
Success is the ability to go from one failure to another with no loss of enthusiasm.
~ Winston Churchill ~