test: refactor test-next-tick-error-spin

* use common.mustCall()
* setTimeout() -> setImmediate()
* assert() -> assert.strictEqual()
* var -> const
* remove unneeded console.log()
* remove commented-out code

PR-URL: https://github.com/nodejs/node/pull/9537
Reviewed-By: Michael Dawson <michael_dawson@ca.ibm.com>
Reviewed-By: Colin Ihrig <cjihrig@gmail.com>

test/sequential/test-next-tick-error-spin.js

@@ -1,24 +1,23 @@
 'use strict';
-var common = require('../common');
-var assert = require('assert');
+const common = require('../common');
+const assert = require('assert');
 
 if (process.argv[2] !== 'child') {
-  var spawn = require('child_process').spawn;
-  var child = spawn(process.execPath, [__filename, 'child'], {
+  const spawn = require('child_process').spawn;
+  const child = spawn(process.execPath, [__filename, 'child'], {
     stdio: 'pipe'//'inherit'
   });
-  var timer = setTimeout(function() {
+  const timer = setTimeout(function() {
     throw new Error('child is hung');
   }, common.platformTimeout(3000));
-  child.on('exit', function(code) {
-    console.error('ok');
-    assert(!code);
+  child.on('exit', common.mustCall(function(code) {
+    assert.strictEqual(code, 0);
     clearTimeout(timer);
-  });
+  }));
 } else {
 
-  var domain = require('domain');
-  var d = domain.create();
+  const domain = require('domain');
+  const d = domain.create();
   process.maxTickDepth = 10;
 
   // in the error handler, we trigger several MakeCallback events
@@ -40,10 +39,8 @@ if (process.argv[2] !== 'child') {
   }
 
   f();
-  setTimeout(function() {
+  setImmediate(function() {
     console.error('broke in!');
-    //process.stdout.close();
-    //process.stderr.close();
     process.exit(0);
   });
 }