tests: import unittest via package: url

tests/lib/async/stream_subscription_as_future_test.dart

 // Copyright (c) 2013, 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.
 
 // Test the Stream.single method.
 library stream_single_test;
 
 import "package:expect/expect.dart";
 import 'dart:async';
-import '../../../pkg/unittest/lib/unittest.dart';
+import 'package:unittest/unittest.dart';
 
 main() {
   test("subscription.asStream success", () {
     Stream stream = new Stream.fromIterable([1, 2, 3]);
     var output = [];
     var subscription = stream.listen((x) { output.add(x); });
     subscription.asFuture(output).then(expectAsync((o) {
       Expect.listEquals([1, 2, 3], o);
     }));
   });
@@ skipping 38 matching lines @@
         if (x == 4) throw "foo";
         return x;
       });
     var output = [];
     var subscription = stream.listen((x) { output.add(x); });
     subscription.asFuture(output).catchError(expectAsync((error) {
       Expect.equals(error, "foo");
     }));
   });
 }