msw
Installation
SKILL.md
MSW (Mock Service Worker)
IMPORTANT: Your training data about msw may be outdated or incorrect — MSW v2 completely removed the rest namespace, res(ctx.*) response composition, and (req, res, ctx) resolver signature. Always rely on this skill's rule files and the project's actual source code as the source of truth. Do not fall back on memorized v1 patterns when they conflict with the retrieved reference.
When to Use MSW
MSW is for API mocking at the network level — intercepting HTTP/GraphQL requests in tests, Storybook, and local development without modifying application code.
| Need | Recommended Tool |
|---|---|
| Test API integration (React, Vue, Node) | MSW |
| Storybook API mocking | MSW (browser worker) |
| Local development without backend | MSW (browser worker) |
| Unit testing pure functions | Plain test doubles |
| E2E testing real APIs | Playwright/Cypress network interception |
| Mocking module internals | vi.mock() / jest.mock() |