TEVV is a structured process for checking that a system works as intended and meets required safety, security, and performance goals. Testing finds defects, evaluation measures how well the system performs, verification checks that it matches specifications, and validation confirms that it solves the real-world problem it was built for.
In cyber security, TEVV matters because failures can create direct attack paths. A model or application that is not well evaluated may leak data, follow malicious prompts, mis-handle permissions, or trigger unsafe automated actions. Defenders use TEVV before deployment and after changes to catch regressions, stress-test edge cases, and confirm controls like access limits, logging, and abuse detection still work. Attackers also benefit when systems skip TEVV: weak validation can leave exposed APIs, brittle agent workflows, and unsafe trust assumptions that are easy to exploit.