test: check fd 0,1,2 are used, not access mode

Don't do a write on stdout/stderr because that checks for their
writability. But fd=1 could legitimately be opened with read-only
access by the user. All this test needs to ensure is that
they are used at startup.

PR-URL: #10339
Fixes: #10234
Reviewed-By: Sam Roberts <vieuxtech@gmail.com>
Reviewed-By: Gibson Fahnestock <gibfahn@gmail.com>
Reviewed-By: Ben Noordhuis <info@bnoordhuis.nl>
Reviewed-By: James M Snell <jasnell@gmail.com>

test/parallel/test-stdio-closed.js

@@ -2,28 +2,15 @@
 const common = require('../common');
 const assert = require('assert');
 const spawn = require('child_process').spawn;
+const fs = require('fs');
 
 if (common.isWindows) {
   common.skip('platform not supported.');
   return;
 }
 
 if (process.argv[2] === 'child') {
-  try {
-    process.stdout.write('stdout', function() {
-      try {
-        process.stderr.write('stderr', function() {
-          process.exit(42);
-        });
-      } catch (e) {
-        process.exit(84);
-      }
-    });
-  } catch (e) {
-    assert.strictEqual(e.code, 'EBADF');
-    assert.strictEqual(e.message, 'EBADF: bad file descriptor, write');
-    process.exit(126);
-  }
+  [0, 1, 2].forEach((i) => assert.doesNotThrow(() => fs.fstatSync(i)));
   return;
 }
 
@@ -32,5 +19,5 @@ const cmd = `"${process.execPath}" "${__filename}" child 1>&- 2>&-`;
 const proc = spawn('/bin/sh', ['-c', cmd], { stdio: 'inherit' });
 
 proc.on('exit', common.mustCall(function(exitCode) {
-  assert.strictEqual(exitCode, common.isAix ? 126 : 42);
+  assert.strictEqual(exitCode, 0);
 }));