Tests are the final gate: why comprehensive test coverage is how humans accept AI

As AI agents take over more of software development, human review of individual code changes becomes impractical. The argument here is that comprehensive test suites must become the primary acceptance mechanism for AI-generated code. Tests serve as machine-executable specifications: they encode requirements from compliance documents, contracts, and institutional knowledge that AI cannot access from code alone. Most current test suites were built for regression detection, not for verifying organizational requirements, leaving a dangerous gap. The post examines the 'human-on-the-loop' shift, the circular problem of AI-generated tests, legacy migration challenges (COBOL, behavioral equivalence testing), and real-world failures from inadequate gates. The structural answer proposed is to inventory requirements before AI-assisted work begins and encode them as tests, rather than relying on code review at scale.