Mocks network-level API requests using MSW 2.x to create deterministic and resilient frontend tests.
The MSW Mocking skill empowers Claude Code to implement sophisticated, network-level API simulations for frontend testing environments. It leverages Mock Service Worker (MSW) 2.x to intercept REST, GraphQL, and WebSocket traffic, allowing developers to test complex UI states, error handling, and loading behaviors without relying on live backend services or brittle mocks that target implementation details. By using service workers to capture traffic, it ensures that your tests remain decoupled from your specific data-fetching library.
Key Features
01Simulation of network latency and server error states
02Real-time WebSocket connection and event mocking
0369 GitHub stars
04Dynamic response overrides for specific test scenarios
05Standardized integration templates for Vitest and modern test runners
06Network-level interception for REST and GraphQL APIs
Use Cases
01Developing frontend features in isolation before the backend API is fully implemented
02Simulating API failure states like 404 or 500 errors to verify frontend error boundaries
03Testing UI loading indicators and race conditions by injecting artificial network delays
