MSW + client-js Fixtures: Primary Testing Strategy Core Principle Drive the real transport, mock the network. Tests in and MUST be written as Vitest tests that exercise the real SDK, the real React Query cache, and the real component/hook code paths. The only seam we mock is the network boundary, via MSW. This catches contract drift between the playground and at typecheck time and at test time — something style tests cannot do. Priority Order When you write or refactor a test for these packages, choose in this order: 1. MSW + typed client-js fixtures (THIS SKILL) — for hooks, pages, routes, d…