Self-tuning systems are inherently complex and opaque. Execution tends to be non-deterministic and irreproducible, and so the burden of testing is far greater.

Self-tuning systems are inherently complex and opaque. Execution tends to be non-deterministic and irreproducible, and so the burden of testing is far greater. It takes some discipline to write elegant, loosely coupled code that is self-tuning. I work on scientific software, where reproducibility and reusability is (…or at least should be) paramount, and where black boxes are evil. It's hard not to build black boxes when you're writing self-tuning software.