Advanced JS Mocking Patterns

概要

This skill provides specialized guidance and implementation patterns for JavaScript testing using Jest and Vitest. It equips Claude with the expertise to handle sophisticated mocking requirements, such as isolating external dependencies, managing mock lifecycles to prevent state leakage, and simulating time-sensitive logic with fake timers. By enforcing best practices like proper mock restoration and avoiding implementation-detail testing, this skill ensures that test suites remain clean, reliable, and maintainable across both frontend and backend projects.

主な機能

• Full and partial module mocking for Jest and Vitest frameworks
• Precise function spying and call tracking using spyOn
• Sequential and conditional mock implementations for complex logic branching
• Fake timer implementation for testing debounces, timeouts, and delays
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• Automated mock lifecycle management with clear, reset, and restore patterns

ユースケース

• Testing time-dependent features like auto-saving or rate-limiting without waiting
• Verifying that specific callbacks are triggered within complex UI components
• Isolating network requests or database modules during unit testing