fix(test): isolate content-encoding chain limit tests with per-test servers

Each test in the chain limit describe block now creates its own server
via createChainServer(). This eliminates intermittent ECONNRESET on
macOS where an aborted connection's async RST delivery from a reject
test could corrupt shared server state for the allow test.

Also removes the keepalive: false no-op (undici's fetch documents
this flag as a noop outside of browser context).

Author: samayer12

test/fetch/encoding.js

@@ -99,35 +99,32 @@ describe('content-encoding chain limit', () => {
   // Similar to urllib3 (GHSA-gm62-xv2j-4w53) and curl (CVE-2022-32206)
   const MAX_CONTENT_ENCODINGS = 5
 
-  let server
-  before(async () => {
-    server = createServer({
-      noDelay: true
-    }, (req, res) => {
+  async function setupChainServer (t) {
+    const server = createServer({ noDelay: true }, (req, res) => {
       const encodingCount = parseInt(req.headers['x-encoding-count'] || '1', 10)
       const encodings = Array(encodingCount).fill('identity').join(', ')
-
       res.writeHead(200, {
         'Content-Encoding': encodings,
         'Content-Type': 'text/plain'
       })
       res.end('test')
     })
     await once(server.listen(0), 'listening')
-  })
-
-  after(() => {
-    server.closeAllConnections?.()
-    server.close()
-  })
-
-  test(`should allow exactly ${MAX_CONTENT_ENCODINGS} content-encodings`, async (t) => {
+    t.after(async () => {
+      server.closeAllConnections?.()
+      server.close()
+      await once(server, 'close')
+    })
     const client = new Client(`http://localhost:${server.address().port}`)
     t.after(() => client.close())
+    return { server, client }
+  }
+
+  test(`should allow exactly ${MAX_CONTENT_ENCODINGS} content-encodings`, async (t) => {
+    const { server, client } = await setupChainServer(t)
 
     const response = await fetch(`http://localhost:${server.address().port}`, {
       dispatcher: client,
-      keepalive: false,
       headers: { 'x-encoding-count': String(MAX_CONTENT_ENCODINGS) }
     })
 
@@ -137,13 +134,11 @@ describe('content-encoding chain limit', () => {
   })
 
   test(`should reject more than ${MAX_CONTENT_ENCODINGS} content-encodings`, async (t) => {
-    const client = new Client(`http://localhost:${server.address().port}`)
-    t.after(() => client.close())
+    const { server, client } = await setupChainServer(t)
 
     await t.assert.rejects(
       fetch(`http://localhost:${server.address().port}`, {
         dispatcher: client,
-        keepalive: false,
         headers: { 'x-encoding-count': String(MAX_CONTENT_ENCODINGS + 1) }
       }),
       (err) => {
@@ -154,13 +149,11 @@ describe('content-encoding chain limit', () => {
   })
 
   test('should reject excessive content-encoding chains', async (t) => {
-    const client = new Client(`http://localhost:${server.address().port}`)
-    t.after(() => client.close())
+    const { server, client } = await setupChainServer(t)
 
     await t.assert.rejects(
       fetch(`http://localhost:${server.address().port}`, {
         dispatcher: client,
-        keepalive: false,
         headers: { 'x-encoding-count': '100' }
       }),
       (err) => {