Modified unittest to use new argument syntax.

tests/html/websocket_test.dart

 #library('WebSocketTest');
 #import('../../pkg/unittest/unittest.dart');
 #import('../../pkg/unittest/html_config.dart');
 #import('dart:html');
 
 main() {
 
   useHtmlConfiguration();
 
+  var isWebSocket = predicate((x) => x is WebSocket, 'is a WebSocket');
+
   test('constructorTest', () {
       var socket = new WebSocket('ws://localhost');
-      Expect.isTrue(socket != null);
-      Expect.isTrue(socket is WebSocket);
+      expect(socket, isNotNull);
+      expect(socket, isWebSocket);
   });
 }