test,benchmark: stabilize child-process

also some cleanup

PR-URL: https://github.com/nodejs/node/pull/13457
Refs: https://github.com/nodejs/node/issues/12817
Reviewed-By: Tobias Nießen <tniessen@tnie.de>

benchmark/child_process/child-process-exec-stdout.js

@@ -1,41 +1,42 @@
 'use strict';
 const common = require('../common.js');
+const { exec, execSync } = require('child_process');
+const isWindows = process.platform === 'win32';
 
 var messagesLength = [64, 256, 1024, 4096];
-// Windows does not support that long arguments
-if (process.platform !== 'win32')
-  messagesLength.push(32768);
-const bench = common.createBenchmark(main, {
+// Windows does not support command lines longer than 8191 characters
+if (!isWindows) messagesLength.push(32768);
+
+const bench = common.createBenchmark(childProcessExecStdout, {
   len: messagesLength,
   dur: [5]
 });
 
-const child_process = require('child_process');
-const exec = child_process.exec;
-function main(conf) {
+function childProcessExecStdout(conf) {
   bench.start();
 
-  const dur = +conf.dur;
+  const maxDuration = conf.dur * 1000;
   const len = +conf.len;
 
-  const msg = `"${'.'.repeat(len)}"`;
-  // eslint-disable-next-line no-unescaped-regexp-dot
-  msg.match(/./);
-  const options = {'stdio': ['ignore', 'pipe', 'ignore']};
-  const child = exec(`yes ${msg}`, options);
+  const cmd = `yes "${'.'.repeat(len)}"`;
+  const child = exec(cmd, { 'stdio': ['ignore', 'pipe', 'ignore'] });
 
   var bytes = 0;
-  child.stdout.on('data', function(msg) {
+  child.stdout.on('data', (msg) => {
     bytes += msg.length;
   });
 
-  setTimeout(function() {
+  setTimeout(() => {
     bench.end(bytes);
-    if (process.platform === 'win32') {
-      // Sometimes there's a yes.exe process left hanging around on Windows...
-      child_process.execSync(`taskkill /f /t /pid ${child.pid}`);
+    if (isWindows) {
+      // Sometimes there's a yes.exe process left hanging around on Windows.
+      try {
+        execSync(`taskkill /f /t /pid ${child.pid}`);
+      } catch (_) {
+        // this is a best effort kill. stderr is piped to parent for tracing.
+      }
     } else {
       child.kill();
     }
-  }, dur * 1000);
+  }, maxDuration);
 }