test-fidelity-over-coverage

Prioritize test fidelity over coverage percentage. A test that exercises real code paths and makes meaningful assertions is worth more than ten tests that assert true == true to inflate coverage metrics.

Context

Coverage metrics create perverse incentives. Teams optimize for the number rather than the quality of assertions. 100% coverage with weak assertions gives false confidence.

Antipattern

Writing tests that call functions but never assert on meaningful output. Testing implementation details instead of behavior. Mocking so aggressively that the test only exercises the mock.

Rationale

Test fidelity is the probability that a passing test suite means the system works correctly. High coverage with low fidelity is worse than moderate coverage with high fidelity because it creates false confidence.