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, 4 deletions

diff --git a/test/parallel/test-stream-pipe-without-listenerCount.js b/test/parallel/test-stream-pipe-without-listenerCount.js
index 872be6d7be..c2b73c74b1 100644
--- a/test/parallel/test-stream-pipe-without-listenerCount.js
+++ b/test/parallel/test-stream-pipe-without-listenerCount.js
@@ -12,8 +12,6 @@ w.on('pipe', function() {
   r.emit('error', new Error('Readable Error'));
   w.emit('error', new Error('Writable Error'));
 });
-r.on('error', common.mustCall(noop));
-w.on('error', common.mustCall(noop));
+r.on('error', common.mustCall());
+w.on('error', common.mustCall());
 r.pipe(w);
-
-function noop() {}