test: check this value for nextTick()

Depending on how many arguments are provided, `nextTick()` may run its
callback with `this` set to `null` or not. Add assertions for
both cases.

PR-URL: #14645
Reviewed-By: Luigi Pinca <luigipinca@gmail.com>
Reviewed-By: Matteo Collina <matteo.collina@gmail.com>
Reviewed-By: James M Snell <jasnell@gmail.com>
Reviewed-By: Refael Ackermann <refack@gmail.com>

test/parallel/test-next-tick.js

@@ -21,6 +21,7 @@
 
 'use strict';
 const common = require('../common');
+
 const assert = require('assert');
 
 process.nextTick(common.mustCall(function() {
@@ -40,8 +41,23 @@ const obj = {};
 process.nextTick(function(a, b) {
   assert.strictEqual(a, 42);
   assert.strictEqual(b, obj);
+  assert.strictEqual(this, undefined);
 }, 42, obj);
 
+process.nextTick((a, b) => {
+  assert.strictEqual(a, 42);
+  assert.strictEqual(b, obj);
+  assert.deepStrictEqual(this, {});
+}, 42, obj);
+
+process.nextTick(function() {
+  assert.strictEqual(this, null);
+}, 1, 2, 3, 4);
+
+process.nextTick(() => {
+  assert.deepStrictEqual(this, {});
+}, 1, 2, 3, 4);
+
 process.on('exit', function() {
   process.nextTick(common.mustNotCall());
 });