MSW Patterns

Quick Guide: MSW intercepts requests at the network layer, so application code never learns it is mocked. One handler set serves both environments — setupWorker from msw/browser in development, setupServer from msw/node in tests — and the two are not interchangeable. Keep response bodies in their own module so each variant (default, empty, error) is reusable and typed against your API's generated types.

Detailed Resources:

• examples/core.md — mock data modules, variant handlers, server setup and test lifecycle, per-test overrides, runtime variant switching, simulated latency
• examples/browser.md — browser worker setup and app integration for client-rendered and server-rendered entry points

Which path applies

Handlers are shared; only the setup module and the lifecycle differ.

• Browser, during development — setupWorker from msw/browser, awaited before the app renders, with runtime variant switching to walk the UI through its states. Follow examples/browser.md.
• Node, in tests — setupServer from msw/node, listening for the suite and reset between tests, with server.use() for one-test overrides. Follow examples/core.md.