Over the course of WordPress's existence, the practice of writing PHP has evolved. With modern coding principles it is possible to make easy-to-read, easy-to-debug, and easy-to-upgrade plugins. Unfortunately, much of core WordPress and hundreds of plugins did not evolve at the same pace. I'd like to show you how just making your plugins testable can give you cleaner code, faster improvements, and fewer bugs.
You can view these slides here:
https://sirbrillig.github.io/writing-testable-plugins-slides/