In my experience, this usually ends with Bill continuing to do what he's always done and you & Fred trying to continue refactoring and adding tests but getting

In my experience, this usually ends with Bill continuing to do what he's always done and you & Fred trying to continue refactoring and adding tests but getting frustrated because more untested mega code keeps getting added so your target keeps expanding. If you're lucky, you'll reach critical mass and be able to start enforcing coverage or lint checks at the build step (at which point you can tell Bill "oh yeah you just need to add test coverage and it will pass" when he comes to you trying to figure out why is build failed), but more often than not you won't be able to keep up and you'll just get burnt out & cranky.