chore: run the basics server tests against Server.respond

[Nic-Polumeyv]

The server tests in basics never needed a browser: they assert on status, headers and body. Running them through Playwright with JavaScript off meant a preview server and a browser per project, repeated in every no-js leg of the matrix, and a 1 to 2 minute loop to run one of them locally. The file said so itself (server.test.js:33, "this would ideally be a unit test of Server").

80 of the 93 now run under vitest against the built app served in-process with getRequest/setResponse from @sveltejs/kit/node, the adapter-node path. The whole file runs in ~2 s after a build, with pnpm test:unit, no browser or port involved, and failures come back as a plain response diff instead of a Playwright trace. Each test also stops being repeated across the six no-js legs and the async/resolution variants.

13 stay in Playwright: 3 assert dev-server behaviour, 10 need the static-asset and prerendered-page serving that adapters and vite preview do around Server. Anything that only talks to Server can follow the same path with no new plumbing.

[pkg-svelte-dev]

Install the latest version of @sveltejs/kit from 2c0208d:

pnpm add https://pkg.svelte.dev/@sveltejs/kit/c/2c0208d60571bac7ae29dace6cbaa0456779077b

Open in pkg.svelte.dev: https://pkg.svelte.dev/repos/kit/pr/16872

[changeset-bot]

⚠️ No Changeset found

Latest commit: 2c0208d

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[svelte-docs-bot]

Preview: https://svelte-dev-git-preview-kit-16872-svelte.vercel.app/

[Rich-Harris]

Noodling on some tweaks in #16879. One thing neither PR covers AFAICT: the existing setup tests the dev server as well as the prod build, but this only tests the latter IIUC?

[Nic-Polumeyv]

Dev is back on 535985a, a second vitest project runs the same spec through Vite in middleware mode. 79 build / 67 dev, 12 skipped where Playwright skipped them too.