test: refactor test-stream2-readable-wrap.js

Use common.mustCall() where appropriate, var to const/let,
assert.equal() -> assert.strictEqual(), explicit time provided to
setTimeout()

PR-URL: nodejs#10551
Reviewed-By: Rich Trott <rtrott@gmail.com>
Reviewed-By: Gibson Fahnestock <gibfahn@gmail.com>

test/parallel/test-stream2-readable-wrap.js

@@ -1,77 +1,63 @@
 'use strict';
-require('../common');
+const common = require('../common');
 const assert = require('assert');
-
 const Readable = require('_stream_readable');
 const Writable = require('_stream_writable');
 const EE = require('events').EventEmitter;
 
-var testRuns = 0, completedRuns = 0;
 function runTest(highWaterMark, objectMode, produce) {
-  testRuns++;
 
-  var old = new EE();
-  var r = new Readable({ highWaterMark: highWaterMark,
-                         objectMode: objectMode });
-  assert.equal(r, r.wrap(old));
+  const old = new EE();
+  const r = new Readable({ highWaterMark: highWaterMark,
+                           objectMode: objectMode });
+  assert.strictEqual(r, r.wrap(old));
 
-  var ended = false;
-  r.on('end', function() {
-    ended = true;
-  });
+  r.on('end', common.mustCall(function() {}));
 
   old.pause = function() {
-    console.error('old.pause()');
     old.emit('pause');
     flowing = false;
   };
 
   old.resume = function() {
-    console.error('old.resume()');
     old.emit('resume');
     flow();
   };
 
-  var flowing;
-  var chunks = 10;
-  var oldEnded = false;
-  var expected = [];
+  let flowing;
+  let chunks = 10;
+  let oldEnded = false;
+  const expected = [];
   function flow() {
     flowing = true;
     while (flowing && chunks-- > 0) {
-      var item = produce();
+      const item = produce();
       expected.push(item);
-      console.log('old.emit', chunks, flowing);
       old.emit('data', item);
-      console.log('after emit', chunks, flowing);
     }
     if (chunks <= 0) {
       oldEnded = true;
-      console.log('old end', chunks, flowing);
       old.emit('end');
     }
   }
 
-  var w = new Writable({ highWaterMark: highWaterMark * 2,
-                         objectMode: objectMode });
-  var written = [];
+  const w = new Writable({ highWaterMark: highWaterMark * 2,
+                           objectMode: objectMode });
+  const written = [];
   w._write = function(chunk, encoding, cb) {
-    console.log('_write', chunk);
     written.push(chunk);
-    setTimeout(cb);
+    setTimeout(cb, 1);
   };
 
-  w.on('finish', function() {
-    completedRuns++;
+  w.on('finish', common.mustCall(function() {
     performAsserts();
-  });
+  }));
 
   r.pipe(w);
 
   flow();
 
   function performAsserts() {
-    assert(ended);
     assert(oldEnded);
     assert.deepStrictEqual(written, expected);
   }
@@ -81,10 +67,5 @@ runTest(100, false, function() { return Buffer.allocUnsafe(100); });
 runTest(10, false, function() { return Buffer.from('xxxxxxxxxx'); });
 runTest(1, true, function() { return { foo: 'bar' }; });
 
-var objectChunks = [ 5, 'a', false, 0, '', 'xyz', { x: 4 }, 7, [], 555 ];
+const objectChunks = [ 5, 'a', false, 0, '', 'xyz', { x: 4 }, 7, [], 555 ];
 runTest(1, true, function() { return objectChunks.shift(); });
-
-process.on('exit', function() {
-  assert.equal(testRuns, completedRuns);
-  console.log('ok');
-});