test: refactor test-child-process-pass-fd

Add a comment explaining the test (especailly why it forks 80 processes. Use destructuring and an arrow function callback. PR-URL: #17596 Reviewed-By: Khaidi Chu <[email protected]> Reviewed-By: Ruben Bridgewater <[email protected]> Reviewed-By: Colin Ihrig <[email protected]> Reviewed-By: Minwoo Jung <[email protected]>

Author: Trott

test/sequential/test-child-process-pass-fd.js

@@ -1,11 +1,20 @@
 'use strict';
 constcommon=require('../common');
+
+// On some OS X versions, when passing fd's between processes:
+// When the handle associated to a specific file descriptor is closed by the
+// sender process before it's received in the destination, the handle is indeed
+// closed while it should remain opened. In order to fix this behavior, don't
+// close the handle until the `NODE_HANDLE_ACK` is received by the sender.
+// This test is basically `test-cluster-net-send` but creating lots of workers
+// so the issue reproduces on OS X consistently.
+
 if((process.config.variables.arm_version==='6')||
 (process.config.variables.arm_version==='7'))
 common.skip('Too slow for armv6 and armv7 bots');
 
 constassert=require('assert');
-constfork=require('child_process').fork;
+const{fork }=require('child_process');
 constnet=require('net');
 
 constN=80;
@@ -46,14 +55,14 @@ if (process.argv[2] !== 'child'){
 process.on('message',common.mustCall());
 
 constserver=net.createServer((c)=>{
-process.once('message',function(msg){
+process.once('message',(msg)=>{
 assert.strictEqual(msg,'got');
 c.end('hello');
 });
 socketConnected();
 }).unref();
 server.listen(0,common.localhostIPv4,()=>{
-constport=server.address().port;
+const{port }=server.address();
 socket=net.connect(port,common.localhostIPv4,socketConnected).unref();
 });
 }