test: move firstInvalidFD() out of common module

common.firstInvalidFD() is used in only one test. Move it out of the
common module and into the one test that uses it.

PR-URL: nodejs#17781
Reviewed-By: Michaël Zasso <targos@protonmail.com>
Reviewed-By: Gireesh Punathil <gpunathi@in.ibm.com>
Reviewed-By: Benjamin Gruenbaum <benjamingr@gmail.com>
Reviewed-By: Colin Ihrig <cjihrig@gmail.com>
Reviewed-By: Timothy Gu <timothygu99@gmail.com>
Reviewed-By: Jon Moss <me@jonathanmoss.me>
Reviewed-By: Luigi Pinca <luigipinca@gmail.com>
Reviewed-By: James M Snell <jasnell@gmail.com>
Reviewed-By: Ruben Bridgewater <ruben@bridgewater.de>

test/common/index.js

@@ -851,12 +851,3 @@ exports.hijackStdout = hijackStdWritable.bind(null, 'stdout');
 exports.hijackStderr = hijackStdWritable.bind(null, 'stderr');
 exports.restoreStdout = restoreWritable.bind(null, 'stdout');
 exports.restoreStderr = restoreWritable.bind(null, 'stderr');
-
-let fd = 2;
-exports.firstInvalidFD = function firstInvalidFD() {
-  // Get first known bad file descriptor.
-  try {
-    while (fs.fstatSync(++fd));
-  } catch (e) {}
-  return fd;
-};

test/parallel/test-http2-respond-file-fd-invalid.js

@@ -3,8 +3,10 @@
 const common = require('../common');
 if (!common.hasCrypto)
   common.skip('missing crypto');
-const http2 = require('http2');
+
 const assert = require('assert');
+const fs = require('fs');
+const http2 = require('http2');
 
 const {
   NGHTTP2_INTERNAL_ERROR
@@ -18,7 +20,16 @@ const errorCheck = common.expectsError({
 
 const server = http2.createServer();
 server.on('stream', (stream) => {
-  stream.respondWithFD(common.firstInvalidFD());
+  let fd = 2;
+
+  // Get first known bad file descriptor.
+  try {
+    while (fs.fstatSync(++fd));
+  } catch (e) {
+    // do nothing; we now have an invalid fd
+  }
+
+  stream.respondWithFD(fd);
   stream.on('error', common.mustCall(errorCheck));
 });
 server.listen(0, () => {