test: use mustCall() for simple flow tracking

Many of the tests use variables to track when callback functions
are invoked or events are emitted. These variables are then
asserted on process exit. This commit replaces this pattern in
straightforward cases with common.mustCall(). This makes the
tests easier to reason about, leads to a net reduction in lines
of code, and uncovered a few bugs in tests. This commit also
replaces some callbacks that should never be called with
common.fail().

PR-URL: https://github.com/nodejs/node/pull/7753
Reviewed-By: Wyatt Preul <wpreul@gmail.com>
Reviewed-By: Minwoo Jung <jmwsoft@gmail.com>
Reviewed-By: Ben Noordhuis <info@bnoordhuis.nl>

1 files changed, 3 insertions, 11 deletions

diff --git a/test/parallel/test-net-dns-error.js b/test/parallel/test-net-dns-error.js
index eed59cddeb..b36d84d3e9 100644
--- a/test/parallel/test-net-dns-error.js
+++ b/test/parallel/test-net-dns-error.js
@@ -1,12 +1,9 @@
 'use strict';
-require('../common');
+const common = require('../common');
 var assert = require('assert');
 
 var net = require('net');
 
-var expected_bad_connections = 1;
-var actual_bad_connections = 0;
-
 var host = '*'.repeat(256);
 
 function do_not_call() {
@@ -14,17 +11,12 @@ function do_not_call() {
 }
 
 var socket = net.connect(42, host, do_not_call);
-socket.on('error', function(err) {
+socket.on('error', common.mustCall(function(err) {
   assert.equal(err.code, 'ENOTFOUND');
-  actual_bad_connections++;
-});
+}));
 socket.on('lookup', function(err, ip, type) {
   assert(err instanceof Error);
   assert.equal(err.code, 'ENOTFOUND');
   assert.equal(ip, undefined);
   assert.equal(type, undefined);
 });
-
-process.on('exit', function() {
-  assert.equal(actual_bad_connections, expected_bad_connections);
-});