Why is testing mock behavior considered a red flag?

Testing mock behavior verifies that your test setup works rather than the actual code. This leads to tests that pass even when the real component is broken or fail when the implementation changes but the behavior remains correct.

What are testing anti-patterns?

Testing anti-patterns are common but suboptimal practices, such as testing if a mock exists rather than verifying real application logic, which results in fragile and unhelpful test suites.

Can I use this with any testing framework?

Yes. While the documentation provides examples in TypeScript and Vitest, the core principles and logic gates apply to any language or testing framework including Jest, Pytest, or JUnit.

How does this skill prevent production code pollution?

It provides strict Gate Functions that require you to verify if a method is only used for tests; if so, it guides you to move that logic into dedicated test utilities rather than the production class.

Testing Anti-Pattern Guardrails

Name: Testing Anti-Pattern Guardrails
Author: NickCrew

byNickCrew

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Security & Testing

Prevents common testing mistakes by enforcing strict rules against mock-testing, production code pollution, and incomplete test doubles.

About

This skill provides a comprehensive framework for writing robust, maintainable tests by identifying and blocking common anti-patterns like testing the behavior of mocks instead of real components or adding test-only methods to production classes. It integrates structured 'Gate Functions' that force a pause and reflection before mocking dependencies, ensuring developers understand side effects and maintain the integrity of their production codebase through disciplined TDD practices. By following these rules, developers can avoid fragile test suites that break during refactoring or provide false confidence in system stability.

Key Features

Mock behavior detection to ensure tests verify real logic
Prevention of test-only method pollution in production classes
Complete mock object validation to prevent silent failures
7 GitHub stars
Dependency analysis gate functions to avoid over-mocking
TDD-based workflow enforcement and red-flag identification

Use Cases

Refactoring legacy codebases with fragile or over-complex test suites
Preventing accidental production leaks of test-specific utilities
Ensuring high testing standards during team onboarding and PR reviews

What are Skills?·How to Install

Install with 🐟 Skill.Fish

npx skillfish add nickcrew/claude-cortex testing-anti-patterns

For use in Claude.ai and ChatGPT

Download Skill

GitHub