alt Hacker NewsTesting is so important for development.
Even more so when coding with agents. I think it is the probably the biggest lever to keep AI in guardrails.
(It's also why I wrote my latest book, Effective Testing, because I routinely find that my clients are very poor at treating.)
Having thought heavily and even presenting on exactly the same topics, looking at the ToC, your book seems to cover the basics well.
However, since we are talking about effectiveness, applying a lot of these principles might lead to a non-maintainable codebase — for humans and LLMs alike.
When any change causes 500 tests to break, or it causes nothing to break (see monkey-patching and/or mocking), you've gotten to a point where your testing approach is ineffective.
Most start applying principles of just enough tests and testable architectures too late, yet I believe they are fundamental.
Do you cover these in your book?