Add a VmListener and IsolateTest class for running tests in other isolates.

lib/src/vm_listener.dart

Index: lib/src/vm_listener.dart
diff --git a/lib/src/vm_listener.dart b/lib/src/vm_listener.dart
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+++ b/lib/src/vm_listener.dart
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+// Copyright (c) 2015, 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.
+
+library unittest.vm_listener;
+
+import 'dart:isolate';
+import 'dart:async';
+
+import 'declarer.dart';
+import 'remote_exception.dart';
+import 'suite.dart';
+import 'test.dart';
+
+/// A class that runs tests in a separate isolate and communicates the results
+/// back to the main isolate.
+class VmListener {
+  /// The test suite to run.
+  final Suite _suite;
+
+  /// Extracts metadata about all the tests in [main] and sends information
+  /// about them over [sendPort].
+  ///
+  /// Once that's done, this starts listening for commands about which tests to
+  /// run.
+  static void start(SendPort sendPort, main()) {
+    var declarer = new Declarer();
+    runZoned(main, zoneValues: {#unittest.declarer: declarer});
+    new VmListener._(new Suite("VmListener", declarer.tests))
+        ._listen(sendPort);
+  }
+
+  VmListener._(this._suite);
+
+  /// Send information about [_suite] across [sendPort] and start listening for
+  /// commands to run the tests.
+  void _listen(SendPort sendPort) {
+    var tests = [];
+    for (var i = 0; i < _suite.tests.length; i++) {
+      var test = _suite.tests[i];
+      var receivePort = new ReceivePort();
+      tests.add({"name": test.name, "sendPort": receivePort.sendPort});
+
+      receivePort.listen((message) {
+        assert(message['command'] == 'run');
+        _runTest(test, message['reply']);
+      });
+    }
+
+    sendPort.send(tests);
+  }
+
+  /// Runs [test] and send the results across [sendPort].
+  void _runTest(Test test, SendPort sendPort) {
+    var liveTest = test.load(_suite);
+
+    liveTest.onStateChange.listen((state) {
+      sendPort.send({
+        "type": "state-change",
+        "status": state.status.name,
+        "result": state.result.name
+      });
+    });
+
+    liveTest.onError.listen((asyncError) {
+      sendPort.send({
+        "type": "error",
+        "error": RemoteException.serialize(
+            asyncError.error, asyncError.stackTrace)
+      });
+    });
+
+    liveTest.run().then((_) => sendPort.send({"type": "complete"}));
+  }
+}