The Agent Test Pyramid: Why the 70/20/10 Split Breaks Down for Agentic AI
Every engineering organization that graduates from "we have a chatbot" to "we have an agent" hits the same wall: their test suite stops making sense.
The classical test pyramid — 70% unit tests, 20% integration tests, 10% end-to-end — is built on three foundational assumptions: units are cheap to run, isolated from external systems, and deterministic. Agentic AI systems violate all three at once. A "unit" is a model call that costs tokens and returns different answers each time. An end-to-end run can take several minutes and burn through API budget that a junior engineer's entire sprint's tests couldn't justify. And isolation is nearly impossible when the agent's intelligence emerges precisely from interacting with external tools and state.
