Sorry for the delay, u/No_Literature_8903. I kept writing and getting interrupted. It's been quite a few days... weeks... anyways. For refactoring, I think Refactoring: Improving the Design of Existing Code is the one on my eventual to-buy list. Unit Testing Principles, Practices and Patterns is what I had in mind for unit testing. Really, combing through the Manning catalog of books could provide a lot of great options. Design Principles is excellent, Clean Code & Clean Architectureare also classics (which I mentioned before but can actually provide links to this time).