From f3efaeed35de4cbb445c107dda57cb2dda279a6f Mon Sep 17 00:00:00 2001
From: abouthiroppy <git@about-hiroppy.com>
Date: Mon, 23 Jan 2017 22:27:00 +0900
Subject: [PATCH] test: increase coverage for stream's duplex

Make use of Arrow function.
Add a small test and this file's coverage is 100%.
https://github.com/nodejs/node/blob/a647d82f83ad5ddad5db7be2cc24c3d686121792/lib/_stream_duplex.js#L25
Coverage: https://coverage.nodejs.org/coverage-067be658f966dafe/root/_stream_duplex.js.html

PR-URL: https://github.com/nodejs/node/pull/10963
Reviewed-By: Colin Ihrig <cjihrig@gmail.com>
Reviewed-By: Anna Henningsen <anna@addaleax.net>
Reviewed-By: Italo A. Casas <me@italoacasas.com>
Reviewed-By: James M Snell <jasnell@gmail.com>
Reviewed-By: Michael Dawson <michael_dawson@ca.ibm.com>
Reviewed-By: Luigi Pinca <luigipinca@gmail.com>
Reviewed-By: Matteo Collina <matteo.collina@gmail.com>
---
 test/parallel/test-stream-duplex.js | 9 +++++----
 1 file changed, 5 insertions(+), 4 deletions(-)

diff --git a/test/parallel/test-stream-duplex.js b/test/parallel/test-stream-duplex.js
index 85438c09fdff88..0b71b3d9a50569 100644
--- a/test/parallel/test-stream-duplex.js
+++ b/test/parallel/test-stream-duplex.js
@@ -5,27 +5,28 @@ const Duplex = require('stream').Transform;
 
 const stream = new Duplex({ objectMode: true });
 
+assert(Duplex() instanceof Duplex);
 assert(stream._readableState.objectMode);
 assert(stream._writableState.objectMode);
 
 let written;
 let read;
 
-stream._write = function(obj, _, cb) {
+stream._write = (obj, _, cb) => {
   written = obj;
   cb();
 };
 
-stream._read = function() {};
+stream._read = () => {};
 
-stream.on('data', function(obj) {
+stream.on('data', (obj) => {
   read = obj;
 });
 
 stream.push({ val: 1 });
 stream.end({ val: 2 });
 
-process.on('exit', function() {
+process.on('exit', () => {
   assert.strictEqual(read.val, 1);
   assert.strictEqual(written.val, 2);
 });