chore: import upstream snapshot with attribution

tests/fetch-utils.test.ts

@@ -0,0 +1,51 @@
+import { describe, it, expect, afterEach } from 'vitest'
+import { createServer, type Server } from 'node:http'
+import { type AddressInfo } from 'node:net'
+
+import { fetchWithTimeout } from '../src/fetch-utils.js'
+
+let server: Server
+
+afterEach(async () => {
+  await new Promise<void>(resolve => server?.close(() => resolve()))
+})
+
+function listen(handler: (respond: () => void) => void): Promise<string> {
+  return new Promise(resolve => {
+    server = createServer((_req, res) => handler(() => res.end('{"ok":true}')))
+    server.listen(0, '127.0.0.1', () => {
+      const { port } = server.address() as AddressInfo
+      resolve(`http://127.0.0.1:${port}/`)
+    })
+  })
+}
+
+describe('fetchWithTimeout', () => {
+  it('aborts when the server never responds, within the timeout window', async () => {
+    // Accept the request but never reply — the half-open-network case.
+    const url = await listen(() => { /* never respond */ })
+
+    const start = Date.now()
+    await expect(fetchWithTimeout(url, {}, 150)).rejects.toMatchObject({ name: 'TimeoutError' })
+    const elapsed = Date.now() - start
+
+    // Fails fast at ~the timeout, not hanging indefinitely.
+    expect(elapsed).toBeLessThan(2000)
+  })
+
+  it('returns the response when the server replies before the timeout', async () => {
+    const url = await listen(respond => respond())
+
+    const res = await fetchWithTimeout(url, {}, 2000)
+    expect(res.ok).toBe(true)
+    expect(await res.json()).toEqual({ ok: true })
+  })
+
+  it('still aborts on timeout when the caller also passes a signal', async () => {
+    const url = await listen(() => { /* never respond */ })
+    const controller = new AbortController()
+
+    await expect(fetchWithTimeout(url, { signal: controller.signal }, 150))
+      .rejects.toMatchObject({ name: 'TimeoutError' })
+  })
+})