In the last couple of weeks, I have written quite a few articles about what Java developers should learn in 2022 like programming languages, libraries, and frameworks, but if you have just one thing to improve or learn then that must be your testing skills. Testing is one of the disciplines which separates professional developers from amateur ones. It's not about following Test-driven development (TDD), Business Driven Development (BDD), or whatever testing methodologies but at the very minimum level, you must write code to test your code automatically. Many Java developers write unit tests and integration tests that automatically run during build time, mostly by using continuous integration tools like Jenkins or TeamCity.