Very simple version of Isolates.

tests/isolate/cross_isolate_message_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.
 
 // Dart test program for testing that isolates can communicate to isolates
 // other than the main isolate.
 
 library CrossIsolateMessageTest;
 import 'dart:isolate';
 import '../../pkg/unittest/lib/unittest.dart';
 
-void crossIsolate1() {
-  port.receive((msg, replyTo) {
-    SendPort otherIsolate = msg;
-    ReceivePort receivePort = new ReceivePort();
-    receivePort.receive((msg, replyTo) {
-      otherIsolate.send(msg + 58, null);  // 100.
-      receivePort.close();
-    });
-    replyTo.send(['ready', receivePort.toSendPort()]);
-    port.close();
+/*
+ * Everything starts in the main-isolate (in the main-method).
+ * The main isolate spawns two isolates: isolate1 (with entry point
+ * 'crossIsolate1') and isolate2 (with entry point 'crossIsolate2').
+ *
+ * The main isolate creates two isolates, isolate1 and isolate2.
+ * The second isolate is created with a send-port being listened on by
+ * isolate1. A message is passed along this from isolate2 to isolate1.
+ * Isolate1 then sends the result back to the main isolate for final checking.
+ */
+
+void crossIsolate1(SendPort mainIsolate) {
+  ReceivePort local = new ReceivePort();
+  mainIsolate.send(["ready1", local.sendPort]);
+  local.first.then((msg) {
+    // Message from crossIsolate2
+    expect(msg[0], "fromIsolate2");
+    mainIsolate.send(["fromIsolate1", msg[1] + 58]);  // 100.
   });
 }
 
-// crossIsolate2 is nearly the same as crossIsolate1, but contains a
-// different constant.
-void crossIsolate2() {
-  port.receive((msg, replyTo) {
-    SendPort mainIsolate = msg;
-    ReceivePort receivePort = new ReceivePort();
-    receivePort.receive((msg, replyTo) {
-      mainIsolate.send(msg + 399, null); // 499.
-      receivePort.close();
-    });
-    replyTo.send(['ready', receivePort.toSendPort()]);
-    port.close();
-  });
+void crossIsolate2(SendPort toIsolate1) {
+  toIsolate1.send(["fromIsolate2", 42]);
 }
 
 main() {
-  test("share port, and send message cross isolates ", () {
-    SendPort port1 = spawnFunction(crossIsolate1);
-    SendPort port2 = spawnFunction(crossIsolate2);
-    // Create a new receive port and send it to isolate2.
-    ReceivePort myPort = new ReceivePort();
-    port2.call(myPort.toSendPort()).then(expectAsync1((msg) {
-      expect(msg[0], "ready");
-      // Send port of isolate2 to isolate1.
-      port1.call(msg[1]).then(expectAsync1((msg) {
-        expect(msg[0], "ready");
-        myPort.receive(expectAsync2((msg, replyTo) {
-          expect(msg, 499);
-          myPort.close();
-        }));
-        msg[1].send(42, null);
-      }));
-    }));
+  test("send message cross isolates ", () {
+    ReceivePort fromIsolate1 = new ReceivePort();
+    Isolate.spawn(crossIsolate1, fromIsolate1.sendPort);
+    var done = expectAsync0((){});
+    fromIsolate1.listen((msg) {
+      switch (msg[0]) {
+        case "ready1":
+          SendPort toIsolate1 = msg[1];
+          Isolate.spawn(crossIsolate2, toIsolate1);
+          break;
+        case "fromIsolate1":
+          expect(msg[1], 100);
+          fromIsolate1.close();
+          break;
+        default:
+          fail("unreachable! Tag: ${msg[0]}");
+      }
+    }, onDone: done);
   });
 }