Tests as data: ensuring AI-generated code does what we want

· Martin Fowler · Nov. 11, 2026, 3:18 p.m.
Summary
Automated testing in the age of AI coding assistants is problematic: when AI agents write both production and test code, developers risk losing the assurance that automated tests protect against functional errors. Matteo Vaccari makes three claims: (1) when AI writes the code, developers become its customers; (2) therefore customer tests, not developer tests, become the primary contract between humans and AI; (3) moving that contract into test data rather than test...