Originally published at tddbuddy.com.
Related reading: The Bar for TDD Just Moved sets the floor this post extends; Just-in-Time Tests Are What You Get When You Gave Up argues for persistent suites; Where the Review Point Moved is the human-review companion to this test-architecture argument.
The test pyramid was a price chart, not a quality model.
That is the part everyone forgot. The pyramid arrived as a memorable shape with strong claims about where tests should live (many at the bottom, few at the top), and the shape got passed down as a quality principle. It was never a quality principle. It was a cost-structure argument made under the constraints of a specific era: unit tests were cheap to write and fast to run, so the math worked out in their favor. Integration tests were expensive to write and slow to run, so the math punished them. End-to-end tests were both, so the math killed them. The shape was the math, rendered in a triangle.
Agents broke the math.
