Refactoring, or improving and refining code without changing functionality, is a key skill in any programmer's toolbox. Over the past few years, one of the most eloquent refactoring experts has been Ben Orenstein of thoughtbot. In this course, Ben takes the code written in a previous Play by Play and refactors both its tests and its implementation.
Play by Play is an opportunity to watch experts work (not a step by step tutorial), but you'll learn about many topics. Ben starts by looking at the code and giving us a tour of his text editor (Vim), extensive shell customization, and tooling workflow. Ben then reads and understands the test code, then rewrites it to be clearer and more maintainable. He then sets his sights on the implementation code where he changes a bit of the API, then tackles a particularly terse method. The result is a dozen insights into when, where, and how to refactor code confidently. This isn't a rehearsed presentation, but a live discovery of code for the first time. If you're not confident with refactoring, you'll learn a ton from this video. If you are, you'll see how another expert does it.