test: improve the code in test-pipe.js

* use const and let instead of var
* use common.mustCall to control functions executions
* use assert.strictEqual instead of assert.equal
* use assert.ifError to handle errors
* use arrow functions
* remove console.log and process.stdout.write

PR-URL: https://github.com/nodejs/node/pull/10452
Reviewed-By: James M Snell <jasnell@gmail.com>
Reviewed-By: Luigi Pinca <luigipinca@gmail.com>
Reviewed-By: Brian White <mscdex@mscdex.net>

test/sequential/test-pipe.js

@@ -1,110 +1,96 @@
 'use strict';
-var common = require('../common');
+const common = require('../common');
-var assert = require('assert');
+const assert = require('assert');
-var http = require('http');
+const http = require('http');
-var net = require('net');
+const net = require('net');
 
-var webPort = common.PORT;
+const webPort = common.PORT;
-var tcpPort = webPort + 1;
+const tcpPort = webPort + 1;
+const bufferSize = 5 * 1024 * 1024;
 
-var listenCount = 0;
+let listenCount = 0;
-var gotThanks = false;
+let gotThanks = false;
-var tcpLengthSeen = 0;
+let tcpLengthSeen = 0;
-var bufferSize = 5 * 1024 * 1024;
 
 
 /*
  * 5MB of random buffer.
  */
-var buffer = Buffer.allocUnsafe(bufferSize);
+const buffer = Buffer.allocUnsafe(bufferSize);
-for (var i = 0; i < buffer.length; i++) {
+for (let i = 0; i < buffer.length; i++) {
   buffer[i] = parseInt(Math.random() * 10000) % 256;
 }
 
 
-var web = http.Server(function(req, res) {
+const web = http.Server(common.mustCall((req, res) => {
   web.close();
 
-  console.log(req.headers);
+  const socket = net.Stream();
-
-  var socket = net.Stream();
   socket.connect(tcpPort);
 
-  socket.on('connect', function() {
+  socket.on('connect', common.mustCall(() => {}));
-    console.log('socket connected');
-  });
 
   req.pipe(socket);
 
-  req.on('end', function() {
+  req.on('end', common.mustCall(() => {
     res.writeHead(200);
     res.write('thanks');
     res.end();
-    console.log('response with \'thanks\'');
+  }));
-  });
 
-  req.connection.on('error', function(e) {
+  req.connection.on('error', (e) => {
-    console.log('http server-side error: ' + e.message);
+    assert.ifError(e);
-    process.exit(1);
   });
-});
+}));
+
 web.listen(webPort, startClient);
 
 
-var tcp = net.Server(function(s) {
+const tcp = net.Server(common.mustCall((s) => {
   tcp.close();
 
-  console.log('tcp server connection');
+  let i = 0;
-
-  var i = 0;
 
-  s.on('data', function(d) {
+  s.on('data', (d) => {
-    process.stdout.write('.');
     tcpLengthSeen += d.length;
-    for (var j = 0; j < d.length; j++) {
+    for (let j = 0; j < d.length; j++) {
-      assert.equal(buffer[i], d[j]);
+      assert.strictEqual(buffer[i], d[j]);
       i++;
     }
   });
 
-  s.on('end', function() {
+  s.on('end', common.mustCall(() => {
-    console.log('tcp socket disconnect');
     s.end();
-  });
+  }));
 
-  s.on('error', function(e) {
+  s.on('error', (e) => {
-    console.log('tcp server-side error: ' + e.message);
+    assert.ifError(e);
-    process.exit(1);
   });
-});
+}));
-tcp.listen(tcpPort, startClient);
 
+tcp.listen(tcpPort, startClient);
 
 function startClient() {
   listenCount++;
   if (listenCount < 2) return;
 
-  console.log('Making request');
+  const req = http.request({
-
-  var req = http.request({
     port: common.PORT,
     method: 'GET',
     path: '/',
     headers: { 'content-length': buffer.length }
-  }, function(res) {
+  }, common.mustCall((res) => {
-    console.log('Got response');
     res.setEncoding('utf8');
-    res.on('data', function(string) {
+    res.on('data', common.mustCall((string) => {
-      assert.equal('thanks', string);
+      assert.strictEqual('thanks', string);
       gotThanks = true;
-    });
+    }));
-  });
+  }));
   req.write(buffer);
   req.end();
-  console.error('ended request', req);
 }
 
-process.on('exit', function() {
+process.on('exit', () => {
   assert.ok(gotThanks);
-  assert.equal(bufferSize, tcpLengthSeen);
+  assert.strictEqual(bufferSize, tcpLengthSeen);
 });