What is the difference between mocks and spies in this skill?

Mocks are used to replace a dependency entirely with a controlled version, while spies (jest.spyOn) allow you to track calls to real methods without necessarily overriding their original behavior.

How does this skill help with testing React components?

It provides standardized patterns for combining Jest with React Testing Library, covering component rendering, user event simulation, and waiting for asynchronous DOM updates.

Does it support testing asynchronous code?

Absolutely. The skill includes patterns for async/await assertions, promise resolutions/rejections, and the use of fake timers to handle timeouts and intervals.

Can I use this for mocking external API calls?

Yes, it includes specific patterns for module mocking (e.g., Axios) and function-level mocks to ensure your tests don't rely on actual network requests.

Jest Testing Patterns

Name: Jest Testing Patterns
Author: TheBushidoCollective

byTheBushidoCollective

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Security & Testing

Simplifies the creation of robust JavaScript and TypeScript tests using standardized Jest patterns for unit testing, mocking, and assertions.

About

This skill provides Claude with a comprehensive framework for implementing high-quality test suites using Jest. It enables the generation of maintainable test structures, advanced mocking strategies for modules and functions, and sophisticated assertion patterns for both synchronous and asynchronous code. Whether you're testing React components, API integrations, or complex business logic, this skill ensures consistent application of best practices like proper setup/teardown, spy implementation, and snapshot testing to achieve high code coverage and reliability.

Key Features

Comprehensive Matcher library for equality, truthiness, and exceptions
72 GitHub stars
Snapshot and Inline Snapshot testing for UI and data structures
Asynchronous Testing Patterns including async/await and fake timers
Standardized Test Suite Organization using describe and it blocks
Advanced Mocking strategies for modules, functions, and partial exports

Use Cases

Writing unit tests for complex business logic and utility functions with high coverage.
Mocking external dependencies like Axios or database clients to isolate service logic.
Implementing React component tests using React Testing Library and user event simulations.

About

Key Features

Comprehensive Matcher library for equality, truthiness, and exceptions
72 GitHub stars
Snapshot and Inline Snapshot testing for UI and data structures
Asynchronous Testing Patterns including async/await and fake timers
Standardized Test Suite Organization using describe and it blocks
Advanced Mocking strategies for modules, functions, and partial exports

Use Cases

Writing unit tests for complex business logic and utility functions with high coverage.
Mocking external dependencies like Axios or database clients to isolate service logic.
Implementing React component tests using React Testing Library and user event simulations.