Very simple version of Isolates.

tests/isolate/nested_spawn_stream2_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 spawn other isolates and
-// that the nested isolates can communicate with the main once the spawner has
-// disappeared.
-
-library NestedSpawn2Test;
-import 'dart:isolate';
-import '../../pkg/unittest/lib/unittest.dart';
-
-void _call(IsolateSink sink, msg, void onreceive(m, replyTo)) {
-  final box = new MessageBox();
-  sink.add([msg, box.sink]);
-  sink.close();
-  box.stream.single.then((msg) {
-    onreceive(msg[0], msg[1]);
-  });
-}
-
-void _receive(IsolateStream stream, void onreceive(m, replyTo)) {
-  stream.single.then((msg) {
-    onreceive(msg[0], msg[1]);
-  });
-}
-
-void isolateA() {
-  _receive(stream, (msg, replyTo) {
-    expect(msg, "launch nested!");
-    IsolateSink sink = streamSpawnFunction(isolateB);
-    sink.add(replyTo);
-    sink.close();
-    stream.close();
-  });
-}
-
-String msg0 = "0 there?";
-String msg1 = "1 Yes.";
-String msg2 = "2 great. Think the other one is already dead?";
-String msg3 = "3 Give him some time.";
-String msg4 = "4 now?";
-String msg5 = "5 Now.";
-String msg6 = "6 Great. Bye";
-
-void isolateB() {
-  stream.single.then((mainPort) {
-    // Do a little ping-pong dance to give the intermediate isolate
-    // time to die.
-    _call(mainPort, msg0, ((msg, replyTo) {
-      expect(msg[0], "1");
-      _call(replyTo, msg2, ((msg, replyTo) {
-        expect(msg[0], "3");
-        _call(replyTo, msg4, ((msg, replyTo) {
-          expect(msg[0], "5");
-          replyTo.add(msg6);
-          replyTo.close();
-        }));
-      }));
-    }));
-  });
-}
-
-main() {
-  test("spawned isolate can spawn other isolates", () {
-    IsolateSink sink = streamSpawnFunction(isolateA);
-    _call(sink, "launch nested!", expectAsync2((msg, replyTo) {
-      expect(msg[0], "0");
-      _call(replyTo, msg1, expectAsync2((msg, replyTo) {
-        expect(msg[0], "2");
-        _call(replyTo, msg3, expectAsync2((msg, replyTo) {
-          expect(msg[0], "4");
-          _call(replyTo, msg5, expectAsync2((msg, replyTo) {
-            expect(msg[0], "6");
-          }));
-        }));
-      }));
-    }));
-  });
-}