testing-anti-patterns

Testing mock behavior creates false confidence without verifying actual functionality. Instead, test real component interactions and dependencies; mocks should stand in for external services, not replace the logic you're validating. This Skill identifies when tests verify mock setup rather than production code behavior.

Test-only methods pollute production classes, increase maintenance burden, and blur the line between testable design and test infrastructure. Production code should be designed for real use; if you need special test methods, redesign dependencies and interfaces instead.

Brittle tests mock without understanding their dependencies, leading to tests that pass when production fails. Correct mocking requires understanding what external behavior to isolate and what internal behavior to verify, preventing false confidence in test suites.

Review for three core violations: testing mock behavior instead of real behavior, adding test-specific methods to production classes, and mocking without understanding dependencies. This Skill enforces gate checks during test development and review to catch these patterns early.

Use mocks in unit tests to isolate the code under test from external dependencies; use integration tests to verify real component interaction. In both cases, never test the mock's behavior itself—always verify that your production code correctly uses the mocked interface.