a === b -> identical(a, b)

tests/standalone/io/http_server_socket_test.dart

 // Copyright (c) 2012, the Dart project authors.  Please see the AUTHORS file
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.
 
 #import("dart:io");
 #import("dart:isolate");
 #import("dart:math");
 
 class ExpectedDataOutputStream implements OutputStream {
   ExpectedDataOutputStream(List<int> this._data,
                            int this._cutoff,
                            bool this._closeAsError,
                            SocketMock this._socket);
 
   void set onNoPendingWrites(void callback()) {
     _onNoPendingWrites = callback;
   }
 
   void set onError(void callback(e)) {
     _onError = callback;
   }
 
   bool write(List data, [bool copyBuffer = true]) {
     _onData(data);
     return true;
   }
 
   bool writeFrom(List data, [int offset = 0, int len]) {
-    if (len === null) len = data.length - offset;
+    if (len == null) len = data.length - offset;
     _onData(data.getRange(offset, len));
     return true;
   }
 
   void close() {
     _socket.close(true);
   }
 
   void _onData(List<int> data) {
     // TODO(ajohnsen): To be removed, since the socket should not be written to
@@ skipping 184 matching lines @@
       "GET / HTTP/1.1\r\nKeep-Alive: False\r\n\r\n",
       "HTTP/1.1 200 OK\r\ntransfer-encoding: chunked\r\nconnection: close"
       "\r\n\r\n0\r\n\r\n");
 
   server.close();
 }
 
 void main() {
   testSocketClose();
 }