Testing Anti-Patterns

This skill teaches how to identify and avoid the five major anti-patterns that undermine effective testing practices. The core principle: "Test what the code does, not what the mocks do."

The Three Iron Laws

1. Never verify mock behavior
2. Never add test-only methods to production classes
3. Never mock without understanding dependencies

Five Major Anti-Patterns

1. Testing Mock Behavior - Verifying mocks exist rather than actual functionality
2. Test-Only Methods in Production - Adding cleanup methods that only tests call
3. Mocking Without Understanding - Over-mocking that eliminates necessary side effects
4. Incomplete Mocks - Partial mocks that hide structural assumptions
5. Integration Tests as Afterthought - Testing after implementation instead of before

Prevention Strategy

Writing tests first through TDD forces examination of actual behavior before mocking, catching these anti-patterns early. This skill works best in combination with Test-Driven Development practices.