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>

test/README.md

@@ -324,7 +324,7 @@ Gets IP of localhost
 
 Array of IPV6 hosts.
 
-### mustCall(fn[, expected])
+### mustCall([fn][, expected])
 * fn [<Function>](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Function)
 * expected [<Number>](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Number_type) default = 1
 * return [<Function>](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Function)
@@ -333,6 +333,8 @@ Returns a function that calls `fn`. If the returned function has not been called
 exactly `expected` number of times when the test is complete, then the test will
 fail.
 
+If `fn` is not provided, `common.noop` will be used.
+
 ### nodeProcessAborted(exitCode, signal)
 * `exitCode` [<Number>](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Number_type)
 * `signal` [<String>](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#String_type)
@@ -340,6 +342,18 @@ fail.
 
 Returns `true` if the exit code `exitCode` and/or signal name `signal` represent the exit code and/or signal name of a node process that aborted, `false` otherwise.
 
+### noop
+
+A non-op `Function` that can be used for a variety of scenarios.
+
+For instance,
+
+```js
+const common = require('../common');
+
+someAsyncAPI('foo', common.mustCall(common.noop));
+```
+
 ### opensslCli
 * return [<Boolean>](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Boolean_type)
 

test/addons/async-hello-world/test.js

@@ -6,5 +6,5 @@ const binding = require(`./build/${common.buildType}/binding`);
 binding(5, common.mustCall(function(err, val) {
   assert.strictEqual(err, null);
   assert.strictEqual(val, 10);
-  process.nextTick(common.mustCall(function() {}));
+  process.nextTick(common.mustCall());
 }));

test/addons/heap-profiler/test.js

@@ -5,7 +5,7 @@ const common = require('../../common');
 const binding = require(`./build/${common.buildType}/binding`);
 
 // Create an AsyncWrap object.
-const timer = setTimeout(function() {}, 1);
+const timer = setTimeout(common.noop, 1);
 timer.unref();
 
 // Stress-test the heap profiler.

test/common.js

@@ -35,6 +35,9 @@ const execSync = require('child_process').execSync;
 const testRoot = process.env.NODE_TEST_DIR ?
                    fs.realpathSync(process.env.NODE_TEST_DIR) : __dirname;
 
+const noop = () => {};
+
+exports.noop = noop;
 exports.fixturesDir = path.join(__dirname, 'fixtures');
 exports.tmpDirName = 'tmp';
 // PORT should match the definition in test/testpy/__init__.py.
@@ -429,6 +432,13 @@ function runCallChecks(exitCode) {
 
 
 exports.mustCall = function(fn, expected) {
+  if (typeof fn === 'number') {
+    expected = fn;
+    fn = noop;
+  } else if (fn === undefined) {
+    fn = noop;
+  }
+
   if (expected === undefined)
     expected = 1;
   else if (typeof expected !== 'number')
@@ -525,9 +535,9 @@ util.inherits(ArrayStream, stream.Stream);
 exports.ArrayStream = ArrayStream;
 ArrayStream.prototype.readable = true;
 ArrayStream.prototype.writable = true;
-ArrayStream.prototype.pause = function() {};
+ArrayStream.prototype.pause = noop;
-ArrayStream.prototype.resume = function() {};
+ArrayStream.prototype.resume = noop;
-ArrayStream.prototype.write = function() {};
+ArrayStream.prototype.write = noop;
 
 // Returns true if the exit code "exitCode" and/or signal name "signal"
 // represent the exit code and/or signal name of a node process that aborted,

test/debugger/test-debugger-client.js

@@ -150,7 +150,7 @@ addTest(function(client, done) {
 
 let connectCount = 0;
 const script = 'setTimeout(function() { console.log("blah"); });' +
-               'setInterval(function() {}, 1000000);';
+               'setInterval(common.noop, 1000000);';
 
 let nodeProcess;
 
@@ -193,7 +193,7 @@ function doTest(cb, done) {
         console.error('>>> connecting...');
         c.connect(debug.port);
         c.on('break', function() {
-          c.reqContinue(function() {});
+          c.reqContinue(common.noop);
         });
         c.on('ready', function() {
           connectCount++;

test/message/unhandled_promise_trace_warnings.js

@@ -1,5 +1,5 @@
 // Flags: --trace-warnings
 'use strict';
-require('../common');
+const common = require('../common');
 const p = Promise.reject(new Error('This was rejected'));
-setImmediate(() => p.catch(() => {}));
+setImmediate(() => p.catch(common.noop));

test/parallel/test-assert.js

@@ -20,7 +20,7 @@
 // USE OR OTHER DEALINGS IN THE SOFTWARE.
 
 'use strict';
-require('../common');
+const common = require('../common');
 const assert = require('assert');
 const a = require('assert');
 
@@ -505,22 +505,22 @@ a.throws(makeBlock(a.deepEqual, args, []));
 // check messages from assert.throws()
 {
   assert.throws(
-    () => { a.throws(() => {}); },
+    () => { a.throws(common.noop); },
     /^AssertionError: Missing expected exception\.$/
   );
 
   assert.throws(
-    () => { a.throws(() => {}, TypeError); },
+    () => { a.throws(common.noop, TypeError); },
     /^AssertionError: Missing expected exception \(TypeError\)\.$/
   );
 
   assert.throws(
-    () => { a.throws(() => {}, 'fhqwhgads'); },
+    () => { a.throws(common.noop, 'fhqwhgads'); },
     /^AssertionError: Missing expected exception: fhqwhgads$/
   );
 
   assert.throws(
-    () => { a.throws(() => {}, TypeError, 'fhqwhgads'); },
+    () => { a.throws(common.noop, TypeError, 'fhqwhgads'); },
     /^AssertionError: Missing expected exception \(TypeError\): fhqwhgads$/
   );
 }

test/parallel/test-async-wrap-check-providers.js

@@ -39,35 +39,33 @@ function init(id, provider) {
   keyList = keyList.filter((e) => e !== pkeys[provider]);
 }
 
-function noop() { }
-
 async_wrap.setupHooks({ init });
 
 async_wrap.enable();
 
 
-setTimeout(function() { }, 1);
+setTimeout(common.noop, 1);
 
-fs.stat(__filename, noop);
+fs.stat(__filename, common.noop);
 
 if (!common.isAix) {
   // fs-watch currently needs special configuration on AIX and we
   // want to improve under https://github.com/nodejs/node/issues/5085.
   // strip out fs watch related parts for now
-  fs.watchFile(__filename, noop);
+  fs.watchFile(__filename, common.noop);
   fs.unwatchFile(__filename);
   fs.watch(__filename).close();
 }
 
-dns.lookup('localhost', noop);
+dns.lookup('localhost', common.noop);
-dns.lookupService('::', 0, noop);
+dns.lookupService('::', 0, common.noop);
-dns.resolve('localhost', noop);
+dns.resolve('localhost', common.noop);
 
 new StreamWrap(new net.Socket());
 
 new (process.binding('tty_wrap').TTY)();
 
-crypto.randomBytes(1, noop);
+crypto.randomBytes(1, common.noop);
 
 common.refreshTmpDir();
 
@@ -75,14 +73,14 @@ net.createServer(function(c) {
   c.end();
   this.close();
 }).listen(common.PIPE, function() {
-  net.connect(common.PIPE, noop);
+  net.connect(common.PIPE, common.noop);
 });
 
 net.createServer(function(c) {
   c.end();
   this.close(checkTLS);
 }).listen(0, function() {
-  net.connect(this.address().port, noop);
+  net.connect(this.address().port, common.noop);
 });
 
 dgram.createSocket('udp4').bind(0, function() {
@@ -99,7 +97,7 @@ function checkTLS() {
     key: fs.readFileSync(common.fixturesDir + '/keys/ec-key.pem'),
     cert: fs.readFileSync(common.fixturesDir + '/keys/ec-cert.pem')
   };
-  const server = tls.createServer(options, noop)
+  const server = tls.createServer(options, common.noop)
     .listen(0, function() {
       const connectOpts = { rejectUnauthorized: false };
       tls.connect(this.address().port, connectOpts, function() {

test/parallel/test-async-wrap-disabled-propagate-parent.js

@@ -1,6 +1,6 @@
 'use strict';
 
-require('../common');
+const common = require('../common');
 const assert = require('assert');
 const net = require('net');
 const async_wrap = process.binding('async_wrap');
@@ -28,8 +28,6 @@ function init(uid, type, parentUid, parentHandle) {
   }
 }
 
-function noop() { }
-
 async_wrap.setupHooks({ init });
 async_wrap.enable();
 
@@ -41,7 +39,7 @@ const server = net.createServer(function(c) {
     this.close();
   });
 }).listen(0, function() {
-  net.connect(this.address().port, noop);
+  net.connect(this.address().port, common.noop);
 });
 
 async_wrap.disable();

test/parallel/test-async-wrap-propagate-parent.js

@@ -1,6 +1,6 @@
 'use strict';
 
-require('../common');
+const common = require('../common');
 const assert = require('assert');
 const net = require('net');
 const async_wrap = process.binding('async_wrap');
@@ -28,8 +28,6 @@ function init(uid, type, parentUid, parentHandle) {
   }
 }
 
-function noop() { }
-
 async_wrap.setupHooks({ init });
 async_wrap.enable();
 
@@ -41,7 +39,7 @@ const server = net.createServer(function(c) {
     this.close();
   });
 }).listen(0, function() {
-  net.connect(this.address().port, noop);
+  net.connect(this.address().port, common.noop);
 });
 
 

test/parallel/test-async-wrap-throw-from-callback.js

@@ -43,7 +43,7 @@ if (typeof process.argv[2] === 'string') {
   d.on('error', common.mustNotCall());
   d.run(() => {
     // Using randomBytes because timers are not yet supported.
-    crypto.randomBytes(0, () => { });
+    crypto.randomBytes(0, common.noop);
   });
 
 } else {

test/parallel/test-async-wrap-throw-no-init.js

@@ -1,6 +1,6 @@
 'use strict';
 
-require('../common');
+const common = require('../common');
 const assert = require('assert');
 const async_wrap = process.binding('async_wrap');
 
@@ -17,9 +17,9 @@ assert.throws(function() {
 }, /init callback is not assigned to a function/);
 
 // Should not throw
-async_wrap.setupHooks({ init: () => {} });
+async_wrap.setupHooks({ init: common.noop });
 async_wrap.enable();
 
 assert.throws(function() {
-  async_wrap.setupHooks(() => {});
+  async_wrap.setupHooks(common.noop);
 }, /hooks should not be set while also enabled/);

test/parallel/test-async-wrap-uid.js

@@ -1,6 +1,6 @@
 'use strict';
 
-require('../common');
+const common = require('../common');
 const fs = require('fs');
 const assert = require('assert');
 const async_wrap = process.binding('async_wrap');
@@ -8,7 +8,7 @@ const async_wrap = process.binding('async_wrap');
 // Give the event loop time to clear out the final uv_close().
 let si_cntr = 3;
 process.on('beforeExit', () => {
-  if (--si_cntr > 0) setImmediate(() => {});
+  if (--si_cntr > 0) setImmediate(common.noop);
 });
 
 const storage = new Map();

test/parallel/test-buffer-includes.js

@@ -1,5 +1,5 @@
 'use strict';
-require('../common');
+const common = require('../common');
 const assert = require('assert');
 
 const Buffer = require('buffer').Buffer;
@@ -278,7 +278,7 @@ for (let lengthIndex = 0; lengthIndex < lengths.length; lengthIndex++) {
 const expectedError =
   /^TypeError: "val" argument must be string, number, Buffer or Uint8Array$/;
 assert.throws(() => {
-  b.includes(() => {});
+  b.includes(common.noop);
 }, expectedError);
 assert.throws(() => {
   b.includes({});

test/parallel/test-child-process-bad-stdio.js

@@ -5,7 +5,7 @@ const assert = require('assert');
 const cp = require('child_process');
 
 if (process.argv[2] === 'child') {
-  setTimeout(() => {}, common.platformTimeout(100));
+  setTimeout(common.noop, common.platformTimeout(100));
   return;
 }
 

test/parallel/test-child-process-disconnect.js

@@ -78,7 +78,7 @@ if (process.argv[2] === 'child') {
   }));
 
   // the process should also self terminate without using signals
-  child.on('exit', common.mustCall(function() {}));
+  child.on('exit', common.mustCall());
 
   // when child is listening
   child.on('message', function(obj) {

test/parallel/test-child-process-fork-ref2.js

@@ -20,7 +20,7 @@
 // USE OR OTHER DEALINGS IN THE SOFTWARE.
 
 'use strict';
-require('../common');
+const common = require('../common');
 const fork = require('child_process').fork;
 
 if (process.argv[2] === 'child') {
@@ -29,7 +29,7 @@ if (process.argv[2] === 'child') {
 
   setTimeout(function() {
     console.log('child -> will this keep it alive?');
-    process.on('message', function() { });
+    process.on('message', common.noop);
   }, 400);
 
 } else {

test/parallel/test-child-process-kill.js

@@ -25,9 +25,9 @@ const assert = require('assert');
 const spawn = require('child_process').spawn;
 const cat = spawn(common.isWindows ? 'cmd' : 'cat');
 
-cat.stdout.on('end', common.mustCall(function() {}));
+cat.stdout.on('end', common.mustCall());
 cat.stderr.on('data', common.mustNotCall());
-cat.stderr.on('end', common.mustCall(function() {}));
+cat.stderr.on('end', common.mustCall());
 
 cat.on('exit', common.mustCall(function(code, signal) {
   assert.strictEqual(code, null);

test/parallel/test-child-process-send-type-error.js

@@ -1,10 +1,8 @@
 'use strict';
-require('../common');
+const common = require('../common');
 const assert = require('assert');
 const cp = require('child_process');
 
-function noop() {}
-
 function fail(proc, args) {
   assert.throws(() => {
     proc.send.apply(proc, args);
@@ -22,4 +20,4 @@ fail(target, ['msg', null, 'foo']);
 fail(target, ['msg', null, 0]);
 fail(target, ['msg', null, NaN]);
 fail(target, ['msg', null, 1]);
-fail(target, ['msg', null, null, noop]);
+fail(target, ['msg', null, null, common.noop]);

test/parallel/test-child-process-spawnsync-kill-signal.js

@@ -1,10 +1,10 @@
 'use strict';
-require('../common');
+const common = require('../common');
 const assert = require('assert');
 const cp = require('child_process');
 
 if (process.argv[2] === 'child') {
-  setInterval(() => {}, 1000);
+  setInterval(common.noop, 1000);
 } else {
   const { SIGKILL } = process.binding('constants').os.signals;
 

test/parallel/test-child-process-spawnsync-validation-errors.js

@@ -2,7 +2,6 @@
 const common = require('../common');
 const assert = require('assert');
 const spawnSync = require('child_process').spawnSync;
-const noop = function() {};
 
 function pass(option, value) {
   // Run the command with the specified option. Since it's not a real command,
@@ -31,7 +30,7 @@ function fail(option, value, message) {
   fail('cwd', false, err);
   fail('cwd', [], err);
   fail('cwd', {}, err);
-  fail('cwd', noop, err);
+  fail('cwd', common.noop, err);
 }
 
 {
@@ -47,7 +46,7 @@ function fail(option, value, message) {
   fail('detached', __dirname, err);
   fail('detached', [], err);
   fail('detached', {}, err);
-  fail('detached', noop, err);
+  fail('detached', common.noop, err);
 }
 
 if (!common.isWindows) {
@@ -64,7 +63,7 @@ if (!common.isWindows) {
       fail('uid', false, err);
       fail('uid', [], err);
       fail('uid', {}, err);
-      fail('uid', noop, err);
+      fail('uid', common.noop, err);
       fail('uid', NaN, err);
       fail('uid', Infinity, err);
       fail('uid', 3.1, err);
@@ -85,7 +84,7 @@ if (!common.isWindows) {
       fail('gid', false, err);
       fail('gid', [], err);
       fail('gid', {}, err);
-      fail('gid', noop, err);
+      fail('gid', common.noop, err);
       fail('gid', NaN, err);
       fail('gid', Infinity, err);
       fail('gid', 3.1, err);
@@ -105,7 +104,7 @@ if (!common.isWindows) {
   fail('shell', 1, err);
   fail('shell', [], err);
   fail('shell', {}, err);
-  fail('shell', noop, err);
+  fail('shell', common.noop, err);
 }
 
 {
@@ -121,7 +120,7 @@ if (!common.isWindows) {
   fail('argv0', false, err);
   fail('argv0', [], err);
   fail('argv0', {}, err);
-  fail('argv0', noop, err);
+  fail('argv0', common.noop, err);
 }
 
 {
@@ -137,7 +136,7 @@ if (!common.isWindows) {
   fail('windowsVerbatimArguments', __dirname, err);
   fail('windowsVerbatimArguments', [], err);
   fail('windowsVerbatimArguments', {}, err);
-  fail('windowsVerbatimArguments', noop, err);
+  fail('windowsVerbatimArguments', common.noop, err);
 }
 
 {
@@ -154,7 +153,7 @@ if (!common.isWindows) {
   fail('timeout', __dirname, err);
   fail('timeout', [], err);
   fail('timeout', {}, err);
-  fail('timeout', noop, err);
+  fail('timeout', common.noop, err);
   fail('timeout', NaN, err);
   fail('timeout', Infinity, err);
   fail('timeout', 3.1, err);
@@ -179,7 +178,7 @@ if (!common.isWindows) {
   fail('maxBuffer', __dirname, err);
   fail('maxBuffer', [], err);
   fail('maxBuffer', {}, err);
-  fail('maxBuffer', noop, err);
+  fail('maxBuffer', common.noop, err);
 }
 
 {
@@ -198,5 +197,5 @@ if (!common.isWindows) {
   fail('killSignal', false, typeErr);
   fail('killSignal', [], typeErr);
   fail('killSignal', {}, typeErr);
-  fail('killSignal', noop, typeErr);
+  fail('killSignal', common.noop, typeErr);
 }

test/parallel/test-child-process-stdin.js

@@ -43,11 +43,11 @@ cat.stdout.on('data', function(chunk) {
   response += chunk;
 });
 
-cat.stdout.on('end', common.mustCall(function() {}));
+cat.stdout.on('end', common.mustCall());
 
 cat.stderr.on('data', common.mustNotCall());
 
-cat.stderr.on('end', common.mustCall(function() {}));
+cat.stderr.on('end', common.mustCall());
 
 cat.on('exit', common.mustCall(function(status) {
   assert.strictEqual(0, status);

test/parallel/test-cluster-basic.js

@@ -103,7 +103,7 @@ if (cluster.isWorker) {
   }));
 
   //Kill process when worker is killed
-  cluster.on('exit', common.mustCall(() => {}));
+  cluster.on('exit', common.mustCall());
 
   //Create worker
   const worker = cluster.fork();

test/parallel/test-cluster-disconnect-leak.js

@@ -6,19 +6,17 @@ const common = require('../common');
 const net = require('net');
 const cluster = require('cluster');
 
-const noop = () => {};
-
 cluster.schedulingPolicy = cluster.SCHED_NONE;
 
 if (cluster.isMaster) {
   const worker = cluster.fork();
 
   // This is the important part of the test: Confirm that `disconnect` fires.
-  worker.on('disconnect', common.mustCall(noop));
+  worker.on('disconnect', common.mustCall());
 
   // These are just some extra stuff we're checking for good measure...
-  worker.on('exit', common.mustCall(noop));
+  worker.on('exit', common.mustCall());
-  cluster.on('exit', common.mustCall(noop));
+  cluster.on('exit', common.mustCall());
 
   cluster.disconnect();
   return;

test/parallel/test-cluster-eaccess.js

@@ -35,10 +35,10 @@ if (cluster.isMaster) {
   const worker = cluster.fork();
 
   // makes sure master is able to fork the worker
-  cluster.on('fork', common.mustCall(function() {}));
+  cluster.on('fork', common.mustCall());
 
   // makes sure the worker is ready
-  worker.on('online', common.mustCall(function() {}));
+  worker.on('online', common.mustCall());
 
   worker.on('message', common.mustCall(function(err) {
     // disconnect first, so that we will not leave zombies

test/parallel/test-cluster-http-pipe.js

@@ -38,7 +38,7 @@ if (cluster.isMaster) {
   worker.on('message', common.mustCall((msg) => {
     assert.strictEqual(msg, 'DONE');
   }));
-  worker.on('exit', common.mustCall(() => {}));
+  worker.on('exit', common.mustCall());
   return;
 }
 

test/parallel/test-cluster-rr-domain-listen.js

@@ -29,10 +29,10 @@ const domain = require('domain');
 
 if (cluster.isWorker) {
   const d = domain.create();
-  d.run(function() { });
+  d.run(common.noop);
 
   const http = require('http');
-  http.Server(function() { }).listen(common.PORT, '127.0.0.1');
+  http.Server(common.noop).listen(common.PORT, '127.0.0.1');
 
 } else if (cluster.isMaster) {
 

test/parallel/test-cluster-setup-master-emit.js

@@ -43,5 +43,5 @@ function emitAndCatch2(next) {
 }
 
 emitAndCatch(common.mustCall(function() {
-  emitAndCatch2(common.mustCall(function() {}));
+  emitAndCatch2(common.mustCall());
 }));

test/parallel/test-cluster-worker-destroy.js

@@ -38,8 +38,8 @@ if (cluster.isMaster) {
   worker2 = cluster.fork();
 
   [worker1, worker2].forEach(function(worker) {
-    worker.on('disconnect', common.mustCall(function() {}));
+    worker.on('disconnect', common.mustCall());
-    worker.on('exit', common.mustCall(function() {}));
+    worker.on('exit', common.mustCall());
   });
 } else {
   if (cluster.worker.id === 1) {

test/parallel/test-cluster-worker-wait-server-close.js

@@ -11,7 +11,7 @@ if (cluster.isWorker) {
   const server = net.createServer(function(socket) {
     // Wait for any data, then close connection
     socket.write('.');
-    socket.on('data', function discard() {});
+    socket.on('data', common.noop);
   }).listen(common.PORT, common.localhostIPv4);
 
   server.once('close', function() {
@@ -20,7 +20,7 @@ if (cluster.isWorker) {
 
   // Although not typical, the worker process can exit before the disconnect
   // event fires. Use this to keep the process open until the event has fired.
-  const keepOpen = setInterval(function() {}, 9999);
+  const keepOpen = setInterval(common.noop, 9999);
 
   // Check worker events and properties
   process.once('disconnect', function() {

test/parallel/test-console-instance.js

@@ -43,7 +43,7 @@ assert.throws(() => {
 
 // Console constructor should throw if stderr exists but is not writable
 assert.throws(() => {
-  out.write = () => {};
+  out.write = common.noop;
   err.write = undefined;
   new Console(out, err);
 }, /^TypeError: Console expects writable stream instances$/);

test/parallel/test-crypto-pbkdf2.js

@@ -98,7 +98,7 @@ assert.doesNotThrow(() => {
 });
 
 assert.throws(() => {
-  crypto.pbkdf2('password', 'salt', 8, 8, function() {});
+  crypto.pbkdf2('password', 'salt', 8, 8, common.noop);
 }, /^TypeError: The "digest" argument is required and must not be undefined$/);
 
 assert.throws(() => {

test/parallel/test-crypto-random.js

@@ -38,7 +38,7 @@ const expectedErrorRegexp = /^TypeError: size must be a number >= 0$/;
 [crypto.randomBytes, crypto.pseudoRandomBytes].forEach(function(f) {
   [-1, undefined, null, false, true, {}, []].forEach(function(value) {
     assert.throws(function() { f(value); }, expectedErrorRegexp);
-    assert.throws(function() { f(value, function() {}); }, expectedErrorRegexp);
+    assert.throws(function() { f(value, common.noop); }, expectedErrorRegexp);
   });
 
   [0, 1, 2, 4, 16, 256, 1024].forEach(function(len) {

test/parallel/test-debug-brk.js

@@ -3,7 +3,7 @@
 const common = require('../common');
 const spawn = require('child_process').spawn;
 
-let run = () => {};
+let run = common.noop;
 function test(extraArgs, stdoutPattern) {
   const next = run;
   run = () => {

test/parallel/test-dgram-bind-shared-ports.js

@@ -25,8 +25,6 @@ const assert = require('assert');
 const cluster = require('cluster');
 const dgram = require('dgram');
 
-function noop() { }
-
 if (cluster.isMaster) {
   const worker1 = cluster.fork();
 
@@ -51,8 +49,8 @@ if (cluster.isMaster) {
     });
   });
 } else {
-  const socket1 = dgram.createSocket('udp4', noop);
+  const socket1 = dgram.createSocket('udp4', common.noop);
-  const socket2 = dgram.createSocket('udp4', noop);
+  const socket2 = dgram.createSocket('udp4', common.noop);
 
   socket1.on('error', (err) => {
     // no errors expected

test/parallel/test-dgram-close-is-not-callback.js

@@ -11,4 +11,4 @@ socket.send(buf, 0, buf.length, common.PORT, 'localhost');
 // if close callback is not function, ignore the argument.
 socket.close('bad argument');
 
-socket.on('close', common.mustCall(function() {}));
+socket.on('close', common.mustCall());

test/parallel/test-dgram-close.js

@@ -33,8 +33,8 @@ let socket = dgram.createSocket('udp4');
 const handle = socket._handle;
 
 socket.send(buf, 0, buf.length, common.PORT, 'localhost');
-assert.strictEqual(socket.close(common.mustCall(function() {})), socket);
+assert.strictEqual(socket.close(common.mustCall()), socket);
-socket.on('close', common.mustCall(function() {}));
+socket.on('close', common.mustCall());
 socket = null;
 
 // Verify that accessing handle after closure doesn't throw

test/parallel/test-dgram-oob-buffer.js

@@ -30,12 +30,11 @@ const dgram = require('dgram');
 const socket = dgram.createSocket('udp4');
 const buf = Buffer.from([1, 2, 3, 4]);
 
-function ok() {}
+socket.send(buf, 0, 0, common.PORT, '127.0.0.1', common.noop); // useful? no
-socket.send(buf, 0, 0, common.PORT, '127.0.0.1', ok); // useful? no
+socket.send(buf, 0, 4, common.PORT, '127.0.0.1', common.noop);
-socket.send(buf, 0, 4, common.PORT, '127.0.0.1', ok);
+socket.send(buf, 1, 3, common.PORT, '127.0.0.1', common.noop);
-socket.send(buf, 1, 3, common.PORT, '127.0.0.1', ok);
+socket.send(buf, 3, 1, common.PORT, '127.0.0.1', common.noop);
-socket.send(buf, 3, 1, common.PORT, '127.0.0.1', ok);
 // Since length of zero means nothing, don't error despite OOB.
-socket.send(buf, 4, 0, common.PORT, '127.0.0.1', ok);
+socket.send(buf, 4, 0, common.PORT, '127.0.0.1', common.noop);
 
 socket.close();

test/parallel/test-dgram-send-empty-buffer.js

@@ -43,6 +43,6 @@ client.bind(0, common.mustCall(function() {
 
   const buf = Buffer.alloc(0);
   const interval = setInterval(function() {
-    client.send(buf, 0, 0, port, '127.0.0.1', common.mustCall(function() {}));
+    client.send(buf, 0, 0, port, '127.0.0.1', common.mustCall());
   }, 10);
 }));

test/parallel/test-dgram-udp4.js

@@ -46,7 +46,7 @@ server.on('listening', common.mustCall(() => {
               message_to_send.length,
               port,
               'localhost');
-  client.on('close', common.mustCall(() => {}));
+  client.on('close', common.mustCall());
 }));
-server.on('close', common.mustCall(() => {}));
+server.on('close', common.mustCall());
 server.bind(0);

test/parallel/test-dns-lookup.js

@@ -24,7 +24,7 @@ assert.throws(() => {
     hints: 100,
     family: 0,
     all: false
-  }, () => {});
+  }, common.noop);
 }, /^TypeError: Invalid argument: hints must use valid flags$/);
 
 assert.throws(() => {
@@ -32,7 +32,7 @@ assert.throws(() => {
     hints: 0,
     family: 20,
     all: false
-  }, () => {});
+  }, common.noop);
 }, /^TypeError: Invalid argument: family must be 4 or 6$/);
 
 assert.doesNotThrow(() => {

test/parallel/test-dns.js

@@ -20,7 +20,7 @@
 // USE OR OTHER DEALINGS IN THE SOFTWARE.
 
 'use strict';
-require('../common');
+const common = require('../common');
 const assert = require('assert');
 
 const dns = require('dns');
@@ -55,8 +55,6 @@ assert.doesNotThrow(() => {
   dns.setServers(servers);
 });
 
-function noop() {}
-
 const goog = [
   '8.8.8.8',
   '8.8.4.4',
@@ -93,7 +91,7 @@ assert.doesNotThrow(() => dns.setServers([]));
 assert.deepStrictEqual(dns.getServers(), []);
 
 assert.throws(() => {
-  dns.resolve('test.com', [], noop);
+  dns.resolve('test.com', [], common.noop);
 }, function(err) {
   return !(err instanceof TypeError);
 }, 'Unexpected error');
@@ -102,25 +100,25 @@ assert.throws(() => {
 const errorReg =
   /^TypeError: Invalid arguments: hostname must be a string or falsey$/;
 
-assert.throws(() => dns.lookup({}, noop), errorReg);
+assert.throws(() => dns.lookup({}, common.noop), errorReg);
 
-assert.throws(() => dns.lookup([], noop), errorReg);
+assert.throws(() => dns.lookup([], common.noop), errorReg);
 
-assert.throws(() => dns.lookup(true, noop), errorReg);
+assert.throws(() => dns.lookup(true, common.noop), errorReg);
 
-assert.throws(() => dns.lookup(1, noop), errorReg);
+assert.throws(() => dns.lookup(1, common.noop), errorReg);
 
-assert.throws(() => dns.lookup(noop, noop), errorReg);
+assert.throws(() => dns.lookup(common.noop, common.noop), errorReg);
 
-assert.doesNotThrow(() => dns.lookup('', noop));
+assert.doesNotThrow(() => dns.lookup('', common.noop));
 
-assert.doesNotThrow(() => dns.lookup(null, noop));
+assert.doesNotThrow(() => dns.lookup(null, common.noop));
 
-assert.doesNotThrow(() => dns.lookup(undefined, noop));
+assert.doesNotThrow(() => dns.lookup(undefined, common.noop));
 
-assert.doesNotThrow(() => dns.lookup(0, noop));
+assert.doesNotThrow(() => dns.lookup(0, common.noop));
 
-assert.doesNotThrow(() => dns.lookup(NaN, noop));
+assert.doesNotThrow(() => dns.lookup(NaN, common.noop));
 
 /*
  * Make sure that dns.lookup throws if hints does not represent a valid flag.
@@ -133,7 +131,7 @@ assert.doesNotThrow(() => dns.lookup(NaN, noop));
  */
 assert.throws(() => {
   dns.lookup('www.google.com', { hints: (dns.V4MAPPED | dns.ADDRCONFIG) + 1 },
-             noop);
+             common.noop);
 }, /^TypeError: Invalid argument: hints must use valid flags$/);
 
 assert.throws(() => dns.lookup('www.google.com'),
@@ -142,49 +140,49 @@ assert.throws(() => dns.lookup('www.google.com'),
 assert.throws(() => dns.lookup('www.google.com', 4),
               /^TypeError: Invalid arguments: callback must be passed$/);
 
-assert.doesNotThrow(() => dns.lookup('www.google.com', 6, noop));
+assert.doesNotThrow(() => dns.lookup('www.google.com', 6, common.noop));
 
-assert.doesNotThrow(() => dns.lookup('www.google.com', {}, noop));
+assert.doesNotThrow(() => dns.lookup('www.google.com', {}, common.noop));
 
-assert.doesNotThrow(() => dns.lookup('', {family: 4, hints: 0}, noop));
+assert.doesNotThrow(() => dns.lookup('', {family: 4, hints: 0}, common.noop));
 
 assert.doesNotThrow(() => {
   dns.lookup('', {
     family: 6,
     hints: dns.ADDRCONFIG
-  }, noop);
+  }, common.noop);
 });
 
-assert.doesNotThrow(() => dns.lookup('', {hints: dns.V4MAPPED}, noop));
+assert.doesNotThrow(() => dns.lookup('', {hints: dns.V4MAPPED}, common.noop));
 
 assert.doesNotThrow(() => {
   dns.lookup('', {
     hints: dns.ADDRCONFIG | dns.V4MAPPED
-  }, noop);
+  }, common.noop);
 });
 
 assert.throws(() => dns.lookupService('0.0.0.0'),
               /^Error: Invalid arguments$/);
 
-assert.throws(() => dns.lookupService('fasdfdsaf', 0, noop),
+assert.throws(() => dns.lookupService('fasdfdsaf', 0, common.noop),
               /^TypeError: "host" argument needs to be a valid IP address$/);
 
-assert.doesNotThrow(() => dns.lookupService('0.0.0.0', '0', noop));
+assert.doesNotThrow(() => dns.lookupService('0.0.0.0', '0', common.noop));
 
-assert.doesNotThrow(() => dns.lookupService('0.0.0.0', 0, noop));
+assert.doesNotThrow(() => dns.lookupService('0.0.0.0', 0, common.noop));
 
-assert.throws(() => dns.lookupService('0.0.0.0', null, noop),
+assert.throws(() => dns.lookupService('0.0.0.0', null, common.noop),
               /^TypeError: "port" should be >= 0 and < 65536, got "null"$/);
 
 assert.throws(
-  () => dns.lookupService('0.0.0.0', undefined, noop),
+  () => dns.lookupService('0.0.0.0', undefined, common.noop),
   /^TypeError: "port" should be >= 0 and < 65536, got "undefined"$/
 );
 
-assert.throws(() => dns.lookupService('0.0.0.0', 65538, noop),
+assert.throws(() => dns.lookupService('0.0.0.0', 65538, common.noop),
               /^TypeError: "port" should be >= 0 and < 65536, got "65538"$/);
 
-assert.throws(() => dns.lookupService('0.0.0.0', 'test', noop),
+assert.throws(() => dns.lookupService('0.0.0.0', 'test', common.noop),
               /^TypeError: "port" should be >= 0 and < 65536, got "test"$/);
 
 assert.throws(() => dns.lookupService('0.0.0.0', 80, null),

test/parallel/test-domain-crypto.js

@@ -37,7 +37,7 @@ global.domain = require('domain');
 
 // should not throw a 'TypeError: undefined is not a function' exception
 crypto.randomBytes(8);
-crypto.randomBytes(8, function() {});
+crypto.randomBytes(8, common.noop);
 crypto.pseudoRandomBytes(8);
-crypto.pseudoRandomBytes(8, function() {});
+crypto.pseudoRandomBytes(8, common.noop);
-crypto.pbkdf2('password', 'salt', 8, 8, 'sha1', function() {});
+crypto.pbkdf2('password', 'salt', 8, 8, 'sha1', common.noop);

test/parallel/test-domain-exit-dispose.js

@@ -43,7 +43,7 @@ function err() {
   function err2() {
     // this timeout should never be called, since the domain gets
     // disposed when the error happens.
-    setTimeout(common.mustCall(() => {}, 0), 1);
+    setTimeout(common.mustNotCall(), 1);
 
     // this function doesn't exist, and throws an error as a result.
     err3(); // eslint-disable-line no-undef

test/parallel/test-domain-timers.js

@@ -51,4 +51,4 @@ immediated.run(function() {
   });
 });
 
-const timeout = setTimeout(function() {}, 10 * 1000);
+const timeout = setTimeout(common.noop, 10 * 1000);

test/parallel/test-domain.js

@@ -22,7 +22,7 @@
 'use strict';
 // Simple tests of most basic domain functionality.
 
-require('../common');
+const common = require('../common');
 const assert = require('assert');
 const domain = require('domain');
 const events = require('events');
@@ -261,7 +261,7 @@ const fst = fs.createReadStream('stream for nonexistent file');
 d.add(fst);
 expectCaught++;
 
-[42, null, , false, function() {}, 'string'].forEach(function(something) {
+[42, null, , false, common.noop, 'string'].forEach(function(something) {
   const d = new domain.Domain();
   d.run(function() {
     process.nextTick(function() {

test/parallel/test-event-emitter-check-listener-leaks.js

@@ -20,7 +20,8 @@
 // USE OR OTHER DEALINGS IN THE SOFTWARE.
 
 'use strict';
-require('../common');
+
+const common = require('../common');
 const assert = require('assert');
 const events = require('events');
 
@@ -28,40 +29,40 @@ let e = new events.EventEmitter();
 
 // default
 for (let i = 0; i < 10; i++) {
-  e.on('default', function() {});
+  e.on('default', common.noop);
 }
 assert.ok(!e._events['default'].hasOwnProperty('warned'));
-e.on('default', function() {});
+e.on('default', common.noop);
 assert.ok(e._events['default'].warned);
 
 // symbol
 const symbol = Symbol('symbol');
 e.setMaxListeners(1);
-e.on(symbol, function() {});
+e.on(symbol, common.noop);
 assert.ok(!e._events[symbol].hasOwnProperty('warned'));
-e.on(symbol, function() {});
+e.on(symbol, common.noop);
 assert.ok(e._events[symbol].hasOwnProperty('warned'));
 
 // specific
 e.setMaxListeners(5);
 for (let i = 0; i < 5; i++) {
-  e.on('specific', function() {});
+  e.on('specific', common.noop);
 }
 assert.ok(!e._events['specific'].hasOwnProperty('warned'));
-e.on('specific', function() {});
+e.on('specific', common.noop);
 assert.ok(e._events['specific'].warned);
 
 // only one
 e.setMaxListeners(1);
-e.on('only one', function() {});
+e.on('only one', common.noop);
 assert.ok(!e._events['only one'].hasOwnProperty('warned'));
-e.on('only one', function() {});
+e.on('only one', common.noop);
 assert.ok(e._events['only one'].hasOwnProperty('warned'));
 
 // unlimited
 e.setMaxListeners(0);
 for (let i = 0; i < 1000; i++) {
-  e.on('unlimited', function() {});
+  e.on('unlimited', common.noop);
 }
 assert.ok(!e._events['unlimited'].hasOwnProperty('warned'));
 
@@ -70,26 +71,26 @@ events.EventEmitter.defaultMaxListeners = 42;
 e = new events.EventEmitter();
 
 for (let i = 0; i < 42; ++i) {
-  e.on('fortytwo', function() {});
+  e.on('fortytwo', common.noop);
 }
 assert.ok(!e._events['fortytwo'].hasOwnProperty('warned'));
-e.on('fortytwo', function() {});
+e.on('fortytwo', common.noop);
 assert.ok(e._events['fortytwo'].hasOwnProperty('warned'));
 delete e._events['fortytwo'].warned;
 
 events.EventEmitter.defaultMaxListeners = 44;
-e.on('fortytwo', function() {});
+e.on('fortytwo', common.noop);
 assert.ok(!e._events['fortytwo'].hasOwnProperty('warned'));
-e.on('fortytwo', function() {});
+e.on('fortytwo', common.noop);
 assert.ok(e._events['fortytwo'].hasOwnProperty('warned'));
 
 // but _maxListeners still has precedence over defaultMaxListeners
 events.EventEmitter.defaultMaxListeners = 42;
 e = new events.EventEmitter();
 e.setMaxListeners(1);
-e.on('uno', function() {});
+e.on('uno', common.noop);
 assert.ok(!e._events['uno'].hasOwnProperty('warned'));
-e.on('uno', function() {});
+e.on('uno', common.noop);
 assert.ok(e._events['uno'].hasOwnProperty('warned'));
 
 // chainable

test/parallel/test-event-emitter-get-max-listeners.js

@@ -1,5 +1,5 @@
 'use strict';
-require('../common');
+const common = require('../common');
 const assert = require('assert');
 const EventEmitter = require('events');
 
@@ -15,5 +15,5 @@ assert.strictEqual(emitter.getMaxListeners(), 3);
 
 // https://github.com/nodejs/node/issues/523 - second call should not throw.
 const recv = {};
-EventEmitter.prototype.on.call(recv, 'event', function() {});
+EventEmitter.prototype.on.call(recv, 'event', common.noop);
-EventEmitter.prototype.on.call(recv, 'event', function() {});
+EventEmitter.prototype.on.call(recv, 'event', common.noop);

test/parallel/test-event-emitter-listener-count.js

@@ -1,15 +1,15 @@
 'use strict';
 
-require('../common');
+const common = require('../common');
 const assert = require('assert');
 const EventEmitter = require('events');
 
 const emitter = new EventEmitter();
-emitter.on('foo', function() {});
+emitter.on('foo', common.noop);
-emitter.on('foo', function() {});
+emitter.on('foo', common.noop);
-emitter.on('baz', function() {});
+emitter.on('baz', common.noop);
 // Allow any type
-emitter.on(123, function() {});
+emitter.on(123, common.noop);
 
 assert.strictEqual(EventEmitter.listenerCount(emitter, 'foo'), 2);
 assert.strictEqual(emitter.listenerCount('foo'), 2);

test/parallel/test-event-emitter-max-listeners-warning-for-null.js

@@ -18,5 +18,5 @@ process.on('warning', common.mustCall((warning) => {
   assert.ok(warning.message.includes('2 null listeners added.'));
 }));
 
-e.on(null, function() {});
+e.on(null, common.noop);
-e.on(null, function() {});
+e.on(null, common.noop);

test/parallel/test-event-emitter-max-listeners-warning-for-symbol.js

@@ -20,5 +20,5 @@ process.on('warning', common.mustCall((warning) => {
   assert.ok(warning.message.includes('2 Symbol(symbol) listeners added.'));
 }));
 
-e.on(symbol, function() {});
+e.on(symbol, common.noop);
-e.on(symbol, function() {});
+e.on(symbol, common.noop);

test/parallel/test-event-emitter-max-listeners-warning.js

@@ -18,5 +18,5 @@ process.on('warning', common.mustCall((warning) => {
   assert.ok(warning.message.includes('2 event-type listeners added.'));
 }));
 
-e.on('event-type', function() {});
+e.on('event-type', common.noop);
-e.on('event-type', function() {});
+e.on('event-type', common.noop);

test/parallel/test-event-emitter-max-listeners.js

@@ -25,7 +25,7 @@ const assert = require('assert');
 const events = require('events');
 const e = new events.EventEmitter();
 
-e.on('maxListeners', common.mustCall(function() {}));
+e.on('maxListeners', common.mustCall());
 
 // Should not corrupt the 'maxListeners' queue.
 e.setMaxListeners(42);

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');
 

test/parallel/test-event-emitter-remove-all-listeners.js

@@ -36,28 +36,26 @@ function expect(expected) {
   return common.mustCall(listener, expected.length);
 }
 
-function listener() {}
-
 {
   const ee = new events.EventEmitter();
-  ee.on('foo', listener);
+  ee.on('foo', common.noop);
-  ee.on('bar', listener);
+  ee.on('bar', common.noop);
-  ee.on('baz', listener);
+  ee.on('baz', common.noop);
-  ee.on('baz', listener);
+  ee.on('baz', common.noop);
   const fooListeners = ee.listeners('foo');
   const barListeners = ee.listeners('bar');
   const bazListeners = ee.listeners('baz');
   ee.on('removeListener', expect(['bar', 'baz', 'baz']));
   ee.removeAllListeners('bar');
   ee.removeAllListeners('baz');
-  assert.deepStrictEqual(ee.listeners('foo'), [listener]);
+  assert.deepStrictEqual(ee.listeners('foo'), [common.noop]);
   assert.deepStrictEqual(ee.listeners('bar'), []);
   assert.deepStrictEqual(ee.listeners('baz'), []);
   // After calling removeAllListeners(),
   // the old listeners array should stay unchanged.
-  assert.deepStrictEqual(fooListeners, [listener]);
+  assert.deepStrictEqual(fooListeners, [common.noop]);
-  assert.deepStrictEqual(barListeners, [listener]);
+  assert.deepStrictEqual(barListeners, [common.noop]);
-  assert.deepStrictEqual(bazListeners, [listener, listener]);
+  assert.deepStrictEqual(bazListeners, [common.noop, common.noop]);
   // After calling removeAllListeners(),
   // new listeners arrays is different from the old.
   assert.notStrictEqual(ee.listeners('bar'), barListeners);
@@ -66,8 +64,8 @@ function listener() {}
 
 {
   const ee = new events.EventEmitter();
-  ee.on('foo', listener);
+  ee.on('foo', common.noop);
-  ee.on('bar', listener);
+  ee.on('bar', common.noop);
   // Expect LIFO order
   ee.on('removeListener', expect(['foo', 'bar', 'removeListener']));
   ee.on('removeListener', expect(['foo', 'bar']));
@@ -78,7 +76,7 @@ function listener() {}
 
 {
   const ee = new events.EventEmitter();
-  ee.on('removeListener', listener);
+  ee.on('removeListener', common.noop);
   // Check for regression where removeAllListeners() throws when
   // there exists a 'removeListener' listener, but there exists
   // no listeners for the provided event type.
@@ -88,12 +86,12 @@ function listener() {}
 {
   const ee = new events.EventEmitter();
   let expectLength = 2;
-  ee.on('removeListener', function(name, listener) {
+  ee.on('removeListener', function(name, noop) {
     assert.strictEqual(expectLength--, this.listeners('baz').length);
   });
-  ee.on('baz', function() {});
+  ee.on('baz', common.noop);
-  ee.on('baz', function() {});
+  ee.on('baz', common.noop);
-  ee.on('baz', function() {});
+  ee.on('baz', common.noop);
   assert.strictEqual(ee.listeners('baz').length, expectLength + 1);
   ee.removeAllListeners('baz');
   assert.strictEqual(ee.listeners('baz').length, 0);

test/parallel/test-event-emitter-remove-listeners.js

@@ -112,7 +112,7 @@ function listener2() {}
   const listener3 = common.mustCall(() => {
     ee.removeListener('hello', listener4);
   }, 2);
-  const listener4 = common.mustCall(() => {});
+  const listener4 = common.mustCall();
 
   ee.on('hello', listener3);
   ee.on('hello', listener4);
@@ -140,7 +140,7 @@ function listener2() {}
 {
   const ee = new EventEmitter();
 
-  assert.deepStrictEqual(ee, ee.removeListener('foo', () => {}));
+  assert.deepStrictEqual(ee, ee.removeListener('foo', common.noop));
 }
 
 // Verify that the removed listener must be a function
@@ -152,7 +152,7 @@ assert.throws(() => {
 
 {
   const ee = new EventEmitter();
-  const listener = () => {};
+  const listener = common.noop;
   ee._events = undefined;
   const e = ee.removeListener('foo', listener);
   assert.strictEqual(e, ee);

test/parallel/test-event-emitter-special-event-names.js

@@ -5,7 +5,7 @@ const EventEmitter = require('events');
 const assert = require('assert');
 
 const ee = new EventEmitter();
-const handler = () => {};
+const handler = common.noop;
 
 assert.deepStrictEqual(ee.eventNames(), []);
 

test/parallel/test-event-emitter-subclass.js

@@ -34,7 +34,7 @@ function MyEE(cb) {
   EventEmitter.call(this);
 }
 
-const myee = new MyEE(common.mustCall(function() {}));
+const myee = new MyEE(common.mustCall());
 
 
 util.inherits(ErrorEE, EventEmitter);
@@ -62,6 +62,6 @@ MyEE2.prototype = new EventEmitter();
 const ee1 = new MyEE2();
 const ee2 = new MyEE2();
 
-ee1.on('x', function() {});
+ee1.on('x', common.noop);
 
 assert.strictEqual(ee2.listenerCount('x'), 0);

test/parallel/test-event-emitter-symbols.js

@@ -6,7 +6,7 @@ const assert = require('assert');
 
 const ee = new EventEmitter();
 const foo = Symbol('foo');
-const listener = common.mustCall(function() {});
+const listener = common.mustCall();
 
 ee.on(foo, listener);
 assert.deepStrictEqual(ee.listeners(foo), [listener]);

test/parallel/test-events-list.js

@@ -5,6 +5,7 @@ const EventEmitter = require('events');
 const assert = require('assert');
 
 const EE = new EventEmitter();
+// Do not use common.noop here, these need to be separate listener functions
 const m = () => {};
 EE.on('foo', () => {});
 assert.deepStrictEqual(['foo'], EE.eventNames());

test/parallel/test-fs-assert-encoding-error.js

@@ -1,14 +1,13 @@
 'use strict';
-require('../common');
+const common = require('../common');
 const assert = require('assert');
 const fs = require('fs');
 
 const options = 'test';
-const noop = () => {};
 const unknownEncodingMessage = /^Error: Unknown encoding: test$/;
 
 assert.throws(() => {
-  fs.readFile('path', options, noop);
+  fs.readFile('path', options, common.noop);
 }, unknownEncodingMessage);
 
 assert.throws(() => {
@@ -16,7 +15,7 @@ assert.throws(() => {
 }, unknownEncodingMessage);
 
 assert.throws(() => {
-  fs.readdir('path', options, noop);
+  fs.readdir('path', options, common.noop);
 }, unknownEncodingMessage);
 
 assert.throws(() => {
@@ -24,7 +23,7 @@ assert.throws(() => {
 }, unknownEncodingMessage);
 
 assert.throws(() => {
-  fs.readlink('path', options, noop);
+  fs.readlink('path', options, common.noop);
 }, unknownEncodingMessage);
 
 assert.throws(() => {
@@ -32,7 +31,7 @@ assert.throws(() => {
 }, unknownEncodingMessage);
 
 assert.throws(() => {
-  fs.writeFile('path', 'data', options, noop);
+  fs.writeFile('path', 'data', options, common.noop);
 }, unknownEncodingMessage);
 
 assert.throws(() => {
@@ -40,7 +39,7 @@ assert.throws(() => {
 }, unknownEncodingMessage);
 
 assert.throws(() => {
-  fs.appendFile('path', 'data', options, noop);
+  fs.appendFile('path', 'data', options, common.noop);
 }, unknownEncodingMessage);
 
 assert.throws(() => {
@@ -48,11 +47,11 @@ assert.throws(() => {
 }, unknownEncodingMessage);
 
 assert.throws(() => {
-  fs.watch('path', options, noop);
+  fs.watch('path', options, common.noop);
 }, unknownEncodingMessage);
 
 assert.throws(() => {
-  fs.realpath('path', options, noop);
+  fs.realpath('path', options, common.noop);
 }, unknownEncodingMessage);
 
 assert.throws(() => {
@@ -60,7 +59,7 @@ assert.throws(() => {
 }, unknownEncodingMessage);
 
 assert.throws(() => {
-  fs.mkdtemp('path', options, noop);
+  fs.mkdtemp('path', options, common.noop);
 }, unknownEncodingMessage);
 
 assert.throws(() => {

test/parallel/test-fs-empty-readStream.js

@@ -33,11 +33,9 @@ fs.open(emptyFile, 'r', common.mustCall((error, fd) => {
 
   const read = fs.createReadStream(emptyFile, { fd });
 
-  read.once('data', () => {
+  read.once('data', common.mustNotCall('data event should not emit'));
-    common.fail('data event should not emit');
-  });
 
-  read.once('end', common.mustCall(function endEvent1() {}));
+  read.once('end', common.mustCall());
 }));
 
 fs.open(emptyFile, 'r', common.mustCall((error, fd) => {
@@ -48,13 +46,9 @@ fs.open(emptyFile, 'r', common.mustCall((error, fd) => {
 
   read.pause();
 
-  read.once('data', () => {
+  read.once('data', common.mustNotCall('data event should not emit'));
-    common.fail('data event should not emit');
-  });
 
-  read.once('end', function endEvent2() {
+  read.once('end', common.mustNotCall('end event should not emit'));
-    common.fail('end event should not emit');
-  });
 
   setTimeout(common.mustCall(() => {
     assert.strictEqual(read.isPaused(), true);

test/parallel/test-fs-make-callback.js

@@ -12,7 +12,7 @@ function test(cb) {
 }
 
 // Verify the case where a callback function is provided
-assert.doesNotThrow(test(function() {}));
+assert.doesNotThrow(test(common.noop));
 
 process.once('warning', common.mustCall((warning) => {
   assert.strictEqual(

test/parallel/test-fs-mkdir.js

@@ -77,4 +77,4 @@ common.refreshTmpDir();
 
 // Keep the event loop alive so the async mkdir() requests
 // have a chance to run (since they don't ref the event loop).
-process.nextTick(function() {});
+process.nextTick(common.noop);

test/parallel/test-fs-options-immutable.js

@@ -63,12 +63,14 @@ if (!common.isAix) {
   // https://github.com/nodejs/node/issues/5085 is fixed
   {
     let watch;
-    assert.doesNotThrow(() => watch = fs.watch(__filename, options, () => {}));
+    assert.doesNotThrow(() => {
+      watch = fs.watch(__filename, options, common.noop);
+    });
     watch.close();
   }
 
   {
-    assert.doesNotThrow(() => fs.watchFile(__filename, options, () => {}));
+    assert.doesNotThrow(() => fs.watchFile(__filename, options, common.noop));
     fs.unwatchFile(__filename);
   }
 }

test/parallel/test-fs-read-file-assert-encoding.js

@@ -1,6 +1,6 @@
 'use strict';
-require('../common');
 
+const common = require('../common');
 const assert = require('assert');
 const fs = require('fs');
 
@@ -8,6 +8,6 @@ const encoding = 'foo-8';
 const filename = 'bar.txt';
 
 assert.throws(
-  fs.readFile.bind(fs, filename, { encoding }, () => {}),
+  fs.readFile.bind(fs, filename, { encoding }, common.noop),
   new RegExp(`Error: Unknown encoding: ${encoding}$`)
 );

test/parallel/test-fs-read-stream-double-close.js

@@ -5,7 +5,5 @@ const fs = require('fs');
 
 const s = fs.createReadStream(__filename);
 
-s.close(common.mustCall(noop));
+s.close(common.mustCall());
-s.close(common.mustCall(noop));
+s.close(common.mustCall());
-
-function noop() {}

test/parallel/test-fs-read-stream-inherit.js

@@ -39,7 +39,7 @@ let paused = false;
   });
 
 
-  file.on('end', common.mustCall(function() {}));
+  file.on('end', common.mustCall());
 
 
   file.on('close', common.mustCall(function() {
@@ -139,7 +139,7 @@ let paused = false;
   let file7 =
     fs.createReadStream(rangeFile, Object.create({autoClose: false }));
   assert.strictEqual(file7.autoClose, false);
-  file7.on('data', function() {});
+  file7.on('data', common.noop);
   file7.on('end', common.mustCall(function() {
     process.nextTick(common.mustCall(function() {
       assert(!file7.closed);
@@ -169,8 +169,8 @@ let paused = false;
 {
   const options = Object.create({fd: 13337, autoClose: false});
   const file8 = fs.createReadStream(null, options);
-  file8.on('data', function() {});
+  file8.on('data', common.noop);
-  file8.on('error', common.mustCall(function() {}));
+  file8.on('error', common.mustCall());
   process.on('exit', function() {
     assert(!file8.closed);
     assert(!file8.destroyed);
@@ -181,8 +181,8 @@ let paused = false;
 // Make sure stream is destroyed when file does not exist.
 {
   const file9 = fs.createReadStream('/path/to/file/that/does/not/exist');
-  file9.on('data', function() {});
+  file9.on('data', common.noop);
-  file9.on('error', common.mustCall(function() {}));
+  file9.on('error', common.mustCall());
 
   process.on('exit', function() {
     assert(!file9.closed);

test/parallel/test-fs-read-stream.js

@@ -159,7 +159,7 @@ pauseRes.pause();
 pauseRes.resume();
 
 let file7 = fs.createReadStream(rangeFile, {autoClose: false });
-file7.on('data', function() {});
+file7.on('data', common.noop);
 file7.on('end', function() {
   process.nextTick(function() {
     assert(!file7.closed);
@@ -182,13 +182,13 @@ function file7Next() {
 
 // Just to make sure autoClose won't close the stream because of error.
 const file8 = fs.createReadStream(null, {fd: 13337, autoClose: false });
-file8.on('data', function() {});
+file8.on('data', common.noop);
-file8.on('error', common.mustCall(function() {}));
+file8.on('error', common.mustCall());
 
 // Make sure stream is destroyed when file does not exist.
 const file9 = fs.createReadStream('/path/to/file/that/does/not/exist');
-file9.on('data', function() {});
+file9.on('data', common.noop);
-file9.on('error', common.mustCall(function() {}));
+file9.on('error', common.mustCall());
 
 process.on('exit', function() {
   assert(file7.closed);

test/parallel/test-fs-read-type.js

@@ -13,7 +13,7 @@ assert.throws(() => {
           expected.length,
           0,
           'utf-8',
-          () => {});
+          common.noop);
 }, /Second argument needs to be a buffer/);
 
 assert.throws(() => {

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

@@ -3,7 +3,7 @@ const common = require('../common');
 const assert = require('assert');
 const fs = require('fs');
 
-const watch = fs.watchFile(__filename, () => {});
+const watch = fs.watchFile(__filename, common.noop);
 let triggered;
 const listener = common.mustCall(() => {
   triggered = true;

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

@@ -1,9 +1,10 @@
 'use strict';
-require('../common');
+
+const common = require('../common');
 const assert = require('assert');
 const fs = require('fs');
 
-const watch = fs.watchFile(__filename, () => {});
+const watch = fs.watchFile(__filename, common.noop);
 watch.once('stop', assert.fail);  // Should not trigger.
 watch.stop();
 watch.removeListener('stop', assert.fail);

test/parallel/test-fs-watchfile.js

@@ -15,7 +15,7 @@ assert.throws(function() {
 }, /"watchFile\(\)" requires a listener function/);
 
 assert.throws(function() {
-  fs.watchFile(new Object(), function() {});
+  fs.watchFile(new Object(), common.noop);
 }, /Path must be a string/);
 
 const enoentFile = path.join(common.tmpDir, 'non-existent-file');

test/parallel/test-fs-write-stream-double-close.js

@@ -8,7 +8,5 @@ common.refreshTmpDir();
 
 const s = fs.createWriteStream(path.join(common.tmpDir, 'rw'));
 
-s.close(common.mustCall(noop));
+s.close(common.mustCall());
-s.close(common.mustCall(noop));
+s.close(common.mustCall());
-
-function noop() {}

test/parallel/test-fs-write-stream-end.js

@@ -31,7 +31,7 @@ common.refreshTmpDir();
   const file = path.join(common.tmpDir, 'write-end-test0.txt');
   const stream = fs.createWriteStream(file);
   stream.end();
-  stream.on('close', common.mustCall(function() { }));
+  stream.on('close', common.mustCall());
 }
 
 {

test/parallel/test-global-console-exists.js

@@ -35,8 +35,8 @@ const old_default = EventEmitter.defaultMaxListeners;
 EventEmitter.defaultMaxListeners = 1;
 
 const e = new EventEmitter();
-e.on('hello', () => {});
+e.on('hello', common.noop);
-e.on('hello', () => {});
+e.on('hello', common.noop);
 
 // TODO: Figure out how to validate console. Currently,
 // there is no obvious way of validating that console

test/parallel/test-handle-wrap-close-abort.js

@@ -22,7 +22,7 @@
 'use strict';
 const common = require('../common');
 
-process.on('uncaughtException', common.mustCall(function() {}, 2));
+process.on('uncaughtException', common.mustCall(2));
 
 setTimeout(function() {
   process.nextTick(function() {

test/parallel/test-handle-wrap-isrefed.js

@@ -87,7 +87,7 @@ const strictEqual = require('assert').strictEqual;
 // tcp
 {
   const net = require('net');
-  const server = net.createServer(() => {}).listen(0);
+  const server = net.createServer(common.noop).listen(0);
   strictEqual(Object.getPrototypeOf(server._handle).hasOwnProperty('hasRef'),
               true, 'tcp_wrap: hasRef() missing');
   strictEqual(server._handle.hasRef(),
@@ -112,7 +112,7 @@ const strictEqual = require('assert').strictEqual;
 
 // timers
 {
-  const timer = setTimeout(() => {}, 500);
+  const timer = setTimeout(common.noop, 500);
   timer.unref();
   strictEqual(Object.getPrototypeOf(timer._handle).hasOwnProperty('hasRef'),
               true, 'timer_wrap: hasRef() missing');

test/parallel/test-http-abort-client.js

@@ -59,6 +59,6 @@ server.listen(0, common.mustCall(function() {
     });
 
     // it would be nice if this worked:
-    res.on('close', common.mustCall(function() {}));
+    res.on('close', common.mustCall());
   }));
 }));

test/parallel/test-http-client-aborted-event.js

@@ -13,6 +13,6 @@ server.listen(0, common.mustCall(function() {
     headers: { connection: 'keep-alive' }
   }, common.mustCall(function(res) {
     server.close();
-    res.on('aborted', common.mustCall(function() {}));
+    res.on('aborted', common.mustCall());
   }));
 }));

test/parallel/test-http-client-defaults.js

@@ -1,24 +1,23 @@
 'use strict';
-require('../common');
+
+const common = require('../common');
 const assert = require('assert');
 const ClientRequest = require('http').ClientRequest;
 
-function noop() {}
-
 {
-  const req = new ClientRequest({ createConnection: noop });
+  const req = new ClientRequest({ createConnection: common.noop });
   assert.strictEqual(req.path, '/');
   assert.strictEqual(req.method, 'GET');
 }
 
 {
-  const req = new ClientRequest({ method: '', createConnection: noop });
+  const req = new ClientRequest({ method: '', createConnection: common.noop });
   assert.strictEqual(req.path, '/');
   assert.strictEqual(req.method, 'GET');
 }
 
 {
-  const req = new ClientRequest({ path: '', createConnection: noop });
+  const req = new ClientRequest({ path: '', createConnection: common.noop });
   assert.strictEqual(req.path, '/');
   assert.strictEqual(req.method, 'GET');
 }

test/parallel/test-http-connect-req-res.js

@@ -33,7 +33,7 @@ server.listen(0, common.mustCall(function() {
     path: 'example.com:443'
   }, common.mustNotCall());
 
-  req.on('close', common.mustCall(function() { }));
+  req.on('close', common.mustCall());
 
   req.on('connect', common.mustCall(function(res, socket, firstBodyChunk) {
     console.error('Client got CONNECT request');

test/parallel/test-http-connect.js

@@ -49,7 +49,7 @@ server.listen(0, common.mustCall(function() {
     path: 'google.com:443'
   }, common.mustNotCall());
 
-  req.on('close', common.mustCall(() => {}));
+  req.on('close', common.mustCall());
 
   req.on('connect', common.mustCall((res, socket, firstBodyChunk) => {
     // Make sure this request got removed from the pool.

test/parallel/test-http-end-throw-socket-handling.js

@@ -49,4 +49,4 @@ server.listen(0, common.mustCall(() => {
   }
 }));
 
-process.on('uncaughtException', common.mustCall(() => {}, 10));
+process.on('uncaughtException', common.mustCall(10));

test/parallel/test-http-eof-on-connect.js

@@ -20,7 +20,8 @@
 // USE OR OTHER DEALINGS IN THE SOFTWARE.
 
 'use strict';
-require('../common');
+
+const common = require('../common');
 const net = require('net');
 const http = require('http');
 
@@ -28,7 +29,7 @@ const http = require('http');
 // It is separate from test-http-malformed-request.js because it is only
 // reproduceable on the first packet on the first connection to a server.
 
-const server = http.createServer(function(req, res) {});
+const server = http.createServer(common.noop);
 server.listen(0);
 
 server.on('listening', function() {

test/parallel/test-http-invalidheaderfield.js

@@ -1,5 +1,6 @@
 'use strict';
-require('../common');
+
+const common = require('../common');
 const assert = require('assert');
 const EventEmitter = require('events');
 const http = require('http');
@@ -28,7 +29,7 @@ server.listen(0, function() {
         port: server.address().port,
         headers: {'testing 123': 123}
       };
-      http.get(options, function() {});
+      http.get(options, common.noop);
     },
     function(err) {
       ee.emit('done');

test/parallel/test-http-parser-bad-ref.js

@@ -4,7 +4,7 @@
 
 // Flags: --expose_gc
 
-require('../common');
+const common = require('../common');
 const assert = require('assert');
 const HTTPParser = process.binding('http_parser').HTTPParser;
 
@@ -39,7 +39,7 @@ function demoBug(part1, part2) {
     console.log('url', info.url);
   };
 
-  parser[kOnBody] = function(b, start, len) { };
+  parser[kOnBody] = common.noop;
 
   parser[kOnMessageComplete] = function() {
     messagesComplete++;

test/parallel/test-http-pause-resume-one-end.js

@@ -43,6 +43,6 @@ server.listen(0, common.mustCall(function() {
       });
     }));
 
-    res.on('end', common.mustCall(function() {}));
+    res.on('end', common.mustCall());
   }));
 }));

test/parallel/test-http-pipeline-flood.js

@@ -46,7 +46,7 @@ function parent() {
     res.end();
   });
 
-  server.on('connection', common.mustCall(function(conn) {}));
+  server.on('connection', common.mustCall());
 
   server.listen(0, function() {
     const spawn = require('child_process').spawn;

test/parallel/test-http-server-reject-chunked-with-content-length.js

@@ -25,5 +25,5 @@ server.listen(0, () => {
     // close the connection without returning any data.
     common.fail('no data should be returned by the server');
   });
-  client.on('end', common.mustCall(() => {}));
+  client.on('end', common.mustCall());
 });

test/parallel/test-http-set-timeout-server.js

@@ -52,7 +52,7 @@ test(function serverTimeout(cb) {
     // just do nothing, we should get a timeout event.
   });
   server.listen(common.mustCall(function() {
-    http.get({ port: server.address().port }).on('error', function() {});
+    http.get({ port: server.address().port }).on('error', common.noop);
   }));
   const s = server.setTimeout(50, function(socket) {
     caughtTimeout = true;
@@ -81,7 +81,7 @@ test(function serverRequestTimeout(cb) {
   server.listen(common.mustCall(function() {
     const port = server.address().port;
     const req = http.request({ port: port, method: 'POST' });
-    req.on('error', function() {});
+    req.on('error', common.noop);
     req.write('Hello');
     // req is in progress
   }));
@@ -104,7 +104,7 @@ test(function serverResponseTimeout(cb) {
   });
   server.listen(common.mustCall(function() {
     const port = server.address().port;
-    http.get({ port: port }).on('error', function() {});
+    http.get({ port: port }).on('error', common.noop);
   }));
 });
 
@@ -132,7 +132,7 @@ test(function serverRequestNotTimeoutAfterEnd(cb) {
   });
   server.listen(common.mustCall(function() {
     const port = server.address().port;
-    http.get({ port: port }).on('error', function() {});
+    http.get({ port: port }).on('error', common.noop);
   }));
 });
 

test/parallel/test-http-upgrade-server.js

@@ -20,7 +20,8 @@
 // USE OR OTHER DEALINGS IN THE SOFTWARE.
 
 'use strict';
-require('../common');
+
+const common = require('../common');
 const assert = require('assert');
 
 const util = require('util');
@@ -37,7 +38,7 @@ function createTestServer() {
 }
 
 function testServer() {
-  http.Server.call(this, function() {});
+  http.Server.call(this, common.noop);
 
   this.on('connection', function() {
     requests_recv++;

test/parallel/test-https-close.js

@@ -31,7 +31,7 @@ server.on('connection', function(connection) {
 });
 
 function shutdown() {
-  server.close(common.mustCall(function() {}));
+  server.close(common.mustCall());
 
   for (const key in connections) {
     connections[key].destroy();
@@ -49,7 +49,7 @@ server.listen(0, function() {
   };
 
   const req = https.request(requestOptions, function(res) {
-    res.on('data', function(d) {});
+    res.on('data', common.noop);
     setImmediate(shutdown);
   });
   req.end();

test/parallel/test-https-set-timeout-server.js

@@ -69,7 +69,7 @@ test(function serverTimeout(cb) {
     https.get({
       port: this.address().port,
       rejectUnauthorized: false
-    }).on('error', function() {});
+    }).on('error', common.noop);
   }));
 });
 
@@ -90,7 +90,7 @@ test(function serverRequestTimeout(cb) {
       method: 'POST',
       rejectUnauthorized: false
     });
-    req.on('error', function() {});
+    req.on('error', common.noop);
     req.write('Hello');
     // req is in progress
   });
@@ -111,7 +111,7 @@ test(function serverResponseTimeout(cb) {
     https.get({
       port: this.address().port,
       rejectUnauthorized: false
-    }).on('error', function() {});
+    }).on('error', common.noop);
   });
 });
 
@@ -119,7 +119,7 @@ test(function serverRequestNotTimeoutAfterEnd(cb) {
   function handler(req, res) {
     // just do nothing, we should get a timeout event.
     req.setTimeout(50, common.mustNotCall());
-    res.on('timeout', common.mustCall(function(socket) {}));
+    res.on('timeout', common.mustCall());
   }
   const server = https.createServer(serverOptions, common.mustCall(handler));
   server.on('timeout', function(socket) {
@@ -131,7 +131,7 @@ test(function serverRequestNotTimeoutAfterEnd(cb) {
     https.get({
       port: this.address().port,
       rejectUnauthorized: false
-    }).on('error', function() {});
+    }).on('error', common.noop);
   });
 });
 

test/parallel/test-https-socket-options.js

@@ -58,7 +58,7 @@ server_http.listen(0, function() {
   });
   // These methods should exist on the request and get passed down to the socket
   req.setNoDelay(true);
-  req.setTimeout(1000, function() { });
+  req.setTimeout(1000, common.noop);
   req.setSocketKeepAlive(true, 1000);
   req.end();
 });
@@ -82,7 +82,7 @@ server_https.listen(0, function() {
   });
   // These methods should exist on the request and get passed down to the socket
   req.setNoDelay(true);
-  req.setTimeout(1000, function() { });
+  req.setTimeout(1000, common.noop);
   req.setSocketKeepAlive(true, 1000);
   req.end();
 });

test/parallel/test-instanceof.js

@@ -1,10 +1,11 @@
 'use strict';
-require('../common');
+
+const common = require('../common');
 const assert = require('assert');
 
 
 // Regression test for instanceof, see
 // https://github.com/nodejs/node/issues/7592
-const F = () => {};
+const F = common.noop;
 F.prototype = {};
 assert(Object.create(F.prototype) instanceof F);

test/parallel/test-net-connect-options-ipv6.js

@@ -36,7 +36,7 @@ let localhostTries = 10;
 
 const server = net.createServer({allowHalfOpen: true}, function(socket) {
   socket.resume();
-  socket.on('end', common.mustCall(function() {}));
+  socket.on('end', common.mustCall());
   socket.end();
 });
 

test/parallel/test-net-connect-options-port.js

@@ -159,7 +159,8 @@ function syncFailToConnect(port, regexp, optOnly) {
 }
 
 function canConnect(port) {
-  const noop = () => common.mustCall(function() {});
+  const noop = () => common.mustCall();
+
   // connect(port, cb) and connect(port)
   const portArgBlocks = doConnect([port], noop);
   for (const block of portArgBlocks) {

test/parallel/test-net-listen-close-server-callback-is-not-function.js

@@ -4,7 +4,7 @@ const net = require('net');
 
 const server = net.createServer(common.mustNotCall());
 
-server.on('close', common.mustCall(function() {}));
+server.on('close', common.mustCall());
 
 server.listen(0, common.mustNotCall());
 

test/parallel/test-net-listen-error.js

@@ -26,4 +26,4 @@ const net = require('net');
 const server = net.createServer(function(socket) {
 });
 server.listen(1, '1.1.1.1', common.mustNotCall()); // EACCESS or EADDRNOTAVAIL
-server.on('error', common.mustCall(function(error) {}));
+server.on('error', common.mustCall());