> Give me one project and I'll send you a test suite that "tests" 100% of executable lines.

I don’t think you can do that with every project. For example, a function f may do:

  if (p == null) {
    abort();
  }

If all callers also do that test, there’s no way to hit that abort() line in the program. Your test suite may not be able to hit it either. Maybe f is a private function, or that test occurs on one of its intermediate values, or f accidentally has two identical tests:

  if (p == null) {
    abort(“p is null”);
  }
  if (p == null) { // copy-paste bug
    abort(“q is null”);
  }
  if (r == null) {
    abort(“r is null”);
  }

Even if it is possible to hit that line, finding a path through the code that passes in a null value can be extremely hard.

As a simple contrived counterexample, try getting 100% coverage on a function that does if(secure_hash(foo) == 0) bar();