It's not that hard in practice either. Besides mutation testing (which becomes a rather slow affair when your codebase is of significant size) you can just do c

It's not that hard in practice either. Besides mutation testing (which becomes a rather slow affair when your codebase is of significant size) you can just do coverage checks. If you have a simple branch coverage, that alone can guarantee (in most situations) which methods are used and which aren't in your tests.