Gracefully handle tests that print.

test/runner/isolate_listener_test.dart

 // 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.
 
 @TestOn("vm")
 
 import 'dart:async';
 import 'dart:isolate';
 
 import 'package:unittest/src/backend/invoker.dart';
@@ skipping 244 matching lines @@
         }, (error) {
           expect(error, isRemoteException("three"));
         }, (error) {
           expect(error, isRemoteException("four"));
         }]);
 
         return liveTest.run();
       });
     });
   });
+
+  test("forwards a test's prints", () {
+    return _isolateTest(_printTest).then((liveTest) {
+      expect(liveTest.onPrint.take(2).toList(),
+          completion(equals(["Hello,", "world!"])));
+
+      return liveTest.run();
+    });
+  });
 }
 
 /// Loads the first test defined in [entryPoint] in another isolate.
 ///
 /// This test will be automatically closed when the test is finished.
 Future<LiveTest> _isolateTest(void entryPoint(SendPort sendPort)) {
   return _spawnIsolate(entryPoint).then((receivePort) {
     return receivePort.first;
   }).then((response) {
     expect(response, containsPair("type", "success"));
@@ skipping 98 matching lines @@
   IsolateListener.start(sendPort, () => () {
     test("multiple errors", () {
       Invoker.current.addOutstandingCallback();
       new Future(() => throw "one");
       new Future(() => throw "two");
       new Future(() => throw "three");
       new Future(() => throw "four");
     });
   });
 }
+
+/// An isolate entrypoint that defines a test that prints twice.
+void _printTest(SendPort sendPort) {
+  IsolateListener.start(sendPort, () => () {
+    test("prints", () {
+      print("Hello,");
+      return new Future(() => print("world!"));
+    });
+  });
+}
+