testing: after serveShellRequest serves a router, dispatch on the same router stops 308-redirecting a trailing-slash URL #1107

What happens

In a unit test, after serveShellRequest has served a router, calling dispatch on the same router with a trailing-slash URL no longer answers with the 308 redirect to the canonical URL. The route matches and renders instead. A fresh router gives the expected 308.

Reproduced with a plain server route, not only with clientUrls(), so it isn't specific to client routes.

Reproduction

import { serveShellRequest, dispatch } from "@rangojs/router/testing";

const router = createRouter({ /* a route at /products */ });

await serveShellRequest(router, "/products");          // any shell request first

const res = await dispatch(router, "/products/");      // trailing slash
// expected: res.status === 308, location: /products
// actual:   the route matches and renders (200)

With a separate router for the dispatch call, the 308 is returned as expected.

Expected

dispatch behaves the same whether or not the router was served by serveShellRequest before: a trailing-slash URL redirects with 308 to the canonical URL.

Notes

• The likely cause is per-router state that serveShellRequest sets, for example on the matcher or the trailing-slash handling, leaking into later dispatches. This isn't verified.
• Found while extending the testing helpers to serve clientUrls() modules. The new test works around it by using a separate router for its dispatch case.