test: add common.noop, default for common.mustCall()

Export a new common.noop no-operation function for general use.
Allow using common.mustCall() without a fn argument to simplify
test cases.

Replace various non-op functions throughout tests with common.noop

PR-URL: https://github.com/nodejs/node/pull/12027
Reviewed-By: Jeremiah Senkpiel <fishrock123@rocketmail.com>
Reviewed-By: Richard Lau <riclau@uk.ibm.com>
Reviewed-By: Gibson Fahnestock <gibfahn@gmail.com>
Reviewed-By: Teddy Katz <teddy.katz@gmail.com>
Reviewed-By: Colin Ihrig <cjihrig@gmail.com>
Reviewed-By: Franziska Hinkelmann <franziska.hinkelmann@gmail.com>

1 files changed, 2 insertions, 2 deletions

diff --git a/test/parallel/test-event-emitter-once.js b/test/parallel/test-event-emitter-once.js
index d440947ed2..bbd29c8437 100644
--- a/test/parallel/test-event-emitter-once.js
+++ b/test/parallel/test-event-emitter-once.js
@@ -26,7 +26,7 @@ const EventEmitter = require('events');
 
 const e = new EventEmitter();
 
-e.once('hello', common.mustCall(function(a, b) {}));
+e.once('hello', common.mustCall());
 
 e.emit('hello', 'a', 'b');
 e.emit('hello', 'a', 'b');
@@ -45,7 +45,7 @@ e.once('e', common.mustCall(function() {
   e.emit('e');
 }));
 
-e.once('e', common.mustCall(function() {}));
+e.once('e', common.mustCall());
 
 e.emit('e');