Gracefully handle tests that print.

test/backend/invoker_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.
 
 import 'dart:async';
 
 import 'package:fake_async/fake_async.dart';
 import 'package:unittest/src/backend/invoker.dart';
 import 'package:unittest/src/backend/metadata.dart';
 import 'package:unittest/src/backend/state.dart';
@@ skipping 475 matching lines @@
 
       expectErrors(liveTest, [(error) {
         expect(lastState.status, equals(Status.complete));
         expect(error, new isInstanceOf<TimeoutException>());
       }]);
 
       liveTest.run();
       async.elapse(new Duration(seconds: 30));
     });
   });
+
+  test("a test's prints are captured and reported", () {
+    expect(() {
+      var liveTest = _localTest(() {
+        print("Hello,");
+        return new Future(() => print("world!"));
+      }).load(suite);
+
+      expect(liveTest.onPrint.take(2).toList(),
+          completion(equals(["Hello,", "world!"])));
+
+      return liveTest.run();
+    }, prints(isEmpty));
+  });
 }
 
 LocalTest _localTest(body(), {tearDown()}) =>
     new LocalTest("test", new Metadata(), body, tearDown: tearDown);