Why is testing mock behavior considered an anti-pattern?

Testing a mock only verifies that the mock works, not the code. This leads to tests that pass even when the real component is broken, providing a false sense of security.

Can this skill help with incomplete API mocks?

Yes, it includes specific checks to ensure that mocks mirror the complete data structure of the real API, preventing silent failures when downstream code accesses fields that were omitted in a partial mock.

How does it prevent production code pollution?

It identifies methods created solely for testing purposes and directs the user to move that logic into dedicated test utilities, keeping production classes clean and focused on their primary lifecycle.

What are the 'Iron Laws' enforced by this skill?

The skill enforces three core rules: never test mock behavior, never add test-only methods to production classes, and never mock without fully understanding the underlying dependencies.

Testing Anti-Pattern Guard

Name: Testing Anti-Pattern Guard
Author: martin-janci

bymartin-janci

•

セキュリティとテスト

Prevents common software testing mistakes by enforcing strict principles against mock misuse and production code pollution.

Testing Anti-Pattern Guard empowers Claude to identify and avoid the most frequent pitfalls in software testing, such as asserting on mock behavior instead of real logic, polluting production classes with test-only methods, and creating incomplete mocks that lead to silent integration failures. By applying rigorous Test-Driven Development (TDD) principles and specific 'Gate Functions,' this skill ensures your test suite remains robust, maintainable, and focused on verifying actual application behavior rather than implementation details.

主な機能

01Enforces structural completeness for mocks to prevent downstream integration errors

02Provides gate functions to validate the necessity and scope of mocks

03Identifies assertions that mistakenly test mock existence instead of component behavior

041 GitHub stars

05Flags and prevents the addition of test-only methods to production classes

06Promotes strict TDD workflows to catch architectural issues early in development

ユースケース

01Refactoring legacy test suites that rely on fragile or over-complicated mocks

02Conducting automated code reviews to catch production code pollution before deployment

03Guiding the development of new features using clean, TDD-aligned testing patterns

What are Skills?·How to Install

Install with 🐟 Skill.Fish

npx skillfish add martin-janci/claude-marketplace testing-anti-patterns

For use in Claude.ai and ChatGPT

Download Skill