How to write automated tests and how to write them well.
- 55-minute presentation "Unit Testing by Example" at PHP UK Conference 2017.
- 80-minute video course "Unit Testing with PHPUnit". This is available with a paid subscription to Pluralsight. I highly recommend this service. Their content quality is unmatched, and I use it myself. There is also a free trial.
- Short video: Test Doubles with PHPUnit
- Short video: Cyclomatic Complexity
- Article: Randomizing Test Data is a Bad Idea
- Article: Lessons Learned from Testing and Refactoring Legacy