test: fix http-writable-true-after-close flakyness

Ref: #15404
Fixes: #15505

test/parallel/test-http-writable-true-after-close.js

@@ -7,29 +7,36 @@ const { get, createServer } = require('http');
 // res.writable should not be set to false after it has finished sending
 // Ref: https://github.com/nodejs/node/issues/15029
 
+let internal;
 let external;
 
-// Http server
-const internal = createServer((req, res) => {
- res.writeHead(200);
- setImmediate(common.mustCall(() => {
- external.abort();
- res.end('Hello World\n');
- }));
-}).listen(0);
-
 // Proxy server
 const server = createServer(common.mustCall((req, res) => {
  get(`http://127.0.0.1:${internal.address().port}`, common.mustCall((inner) => {
- res.on('close', common.mustCall(() => {
+ const listener = common.mustCall(() => {
  assert.strictEqual(res.writable, true);
- }));
+ });
+
+ // on CentOS 5, 'finish' is emitted
+ res.on('finish', listener);
+ // everywhere else, 'close' is emitted
+ res.on('close', listener);
+
  inner.pipe(res);
  }));
 })).listen(0, () => {
- external = get(`http://127.0.0.1:${server.address().port}`);
- external.on('error', common.mustCall((err) => {
- server.close();
- internal.close();
- }));
+ // Http server
+ internal = createServer((req, res) => {
+ res.writeHead(200);
+ setImmediate(common.mustCall(() => {
+ external.abort();
+ res.end('Hello World\n');
+ }));
+ }).listen(0, () => {
+ external = get(`http://127.0.0.1:${server.address().port}`);
+ external.on('error', common.mustCall((err) => {
+ server.close();
+ internal.close();
+ }));
+ });
 });