Very simple version of Isolates.

tests/standalone/io/testing_server.dart

Index: tests/standalone/io/testing_server.dart
diff --git a/tests/standalone/io/testing_server.dart b/tests/standalone/io/testing_server.dart
index c8bd2b65352d6a2a71e5467bf33810ff58665fc6..76eba423bbf82ffb01520e66478b448b1ee3e94a 100644
--- a/tests/standalone/io/testing_server.dart
+++ b/tests/standalone/io/testing_server.dart
@@ -19,48 +19,24 @@ abstract class TestingServer {
     Expect.fail(msg);
   }
 
-  void dispatch(message, SendPort replyTo) {
-    if (message == INIT) {
-      ServerSocket.bind(HOST, 0).then((server) {
-        _server = server;
-        _server.listen(
-            onConnection,
-            onError: errorHandlerServer);
-        replyTo.send(_server.port, null);
-      });
-    } else if (message == SHUTDOWN) {
-      _server.close();
-      port.close();
-    }
-  }
-
-  ServerSocket _server;
-}
-
-abstract class TestingServerTest {
-
-  TestingServerTest.start(SendPort port)
-      : _receivePort = new ReceivePort(),
-        _sendPort = port {
-    initialize();
-  }
-
-  void run();  // Abstract.
-
-  void initialize() {
-    _receivePort.receive((var message, SendPort replyTo) {
-      _port = message;
-      run();
+  SendPort get closeSendPort => _closePort.sendPort;
+
+  Future<int> init() {
+    _closePort = new ReceivePort();
+    _closePort.first.then((_) { close(); });
+    return ServerSocket.bind(HOST, 0).then((server) {
+      _server = server;
+      _server.listen(
+          onConnection,
+          onError: errorHandlerServer);
+      return _server.port;
     });
-    _sendPort.send(TestingServer.INIT, _receivePort.toSendPort());
   }
 
-  void shutdown() {
-    _sendPort.send(TestingServer.SHUTDOWN, _receivePort.toSendPort());
-    _receivePort.close();
+  void close() {
+    _server.close();
   }
 
-  int _port;
-  ReceivePort _receivePort;
-  SendPort _sendPort;
+  ServerSocket _server;
+  ReceivePort _closePort;
 }