test: refactor test-fs-watch-stop-async

* use common.mustNotCall() to confirm callback is not invoked * blank line after common module per test writing guide PR-URL: #13661 Reviewed-By: Refael Ackermann <[email protected]> Reviewed-By: Richard Lau <[email protected]> Reviewed-By: Colin Ihrig <[email protected]> Reviewed-By: James M Snell <[email protected]> Reviewed-By: Luigi Pinca <[email protected]>

Author: Trott

test/parallel/test-fs-watch-stop-async.js

@@ -1,9 +1,10 @@
 'use strict';
 constcommon=require('../common');
+
 constassert=require('assert');
 constfs=require('fs');
 
-constwatch=fs.watchFile(__filename,common.noop);
+constwatch=fs.watchFile(__filename,common.mustNotCall());
 lettriggered;
 constlistener=common.mustCall(()=>{
 triggered=true;