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, 15 deletions

diff --git a/test/parallel/test-stream2-readable-legacy-drain.js b/test/parallel/test-stream2-readable-legacy-drain.js
index b41de6a38e..8a0687a6eb 100644
--- a/test/parallel/test-stream2-readable-legacy-drain.js
+++ b/test/parallel/test-stream2-readable-legacy-drain.js
@@ -1,5 +1,5 @@
 'use strict';
-require('../common');
+const common = require('../common');
 var assert = require('assert');
 
 var Stream = require('stream');
@@ -12,10 +12,7 @@ r._read = function(n) {
   return r.push(++reads === N ? null : Buffer.allocUnsafe(1));
 };
 
-var rended = false;
-r.on('end', function() {
-  rended = true;
-});
+r.on('end', common.mustCall(function() {}));
 
 var w = new Stream();
 w.writable = true;
@@ -32,11 +29,7 @@ function drain() {
   w.emit('drain');
 }
 
-
-var wended = false;
-w.end = function() {
-  wended = true;
-};
+w.end = common.mustCall(function() {});
 
 // Just for kicks, let's mess with the drain count.
 // This verifies that even if it gets negative in the
@@ -46,8 +39,3 @@ r.on('readable', function() {
 });
 
 r.pipe(w);
-process.on('exit', function() {
-  assert(rended);
-  assert(wended);
-  console.error('ok');
-});