test: refactor test-http-client-readable

* var -> const
* remove function names where V8 inference is as good or better
* add function names where there is no V8 inference
* assert.equal -> strictEqual
* move assertion from exit handler to response end handler

PR-URL: #9344
Reviewed-By: Colin Ihrig <cjihrig@gmail.com>
Reviewed-By: James M Snell <jasnell@gmail.com>
Reviewed-By: Gibson Fahnestock <gibfahn@gmail.com>
Reviewed-By: Luigi Pinca <luigipinca@gmail.com>

test/parallel/test-http-client-readable.js

@@ -1,21 +1,21 @@
 'use strict';
 const common = require('../common');
-var assert = require('assert');
-var http = require('http');
-var util = require('util');
+const assert = require('assert');
+const http = require('http');
+const util = require('util');
 
-var Duplex = require('stream').Duplex;
+const Duplex = require('stream').Duplex;
 
 function FakeAgent() {
   http.Agent.call(this);
 }
 util.inherits(FakeAgent, http.Agent);
 
-FakeAgent.prototype.createConnection = function createConnection() {
-  var s = new Duplex();
+FakeAgent.prototype.createConnection = function() {
+  const s = new Duplex();
   var once = false;
 
-  s._read = function _read() {
+  s._read = function() {
     if (once)
       return this.push(null);
     once = true;
@@ -27,11 +27,11 @@ FakeAgent.prototype.createConnection = function createConnection() {
   };
 
   // Blackhole
-  s._write = function _write(data, enc, cb) {
+  s._write = function(data, enc, cb) {
     cb();
   };
 
-  s.destroy = s.destroySoon = function destroy() {
+  s.destroy = s.destroySoon = function() {
     this.writable = false;
   };
 
@@ -40,17 +40,15 @@ FakeAgent.prototype.createConnection = function createConnection() {
 
 var received = '';
 
-var req = http.request({
+const req = http.request({
   agent: new FakeAgent()
-}, common.mustCall(function(res) {
-  res.on('data', function(chunk) {
+}, common.mustCall(function requestCallback(res) {
+  res.on('data', function dataCallback(chunk) {
     received += chunk;
   });
 
-  res.on('end', common.mustCall(function() {}));
+  res.on('end', common.mustCall(function endCallback() {
+    assert.strictEqual(received, 'hello world');
+  }));
 }));
 req.end();
-
-process.on('exit', function() {
-  assert.equal(received, 'hello world');
-});