Implement everything in test Future-class to avoid analyzer warnings.

tests/lib/async/future_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.
 
 library future_test;
 
 import 'package:async_helper/async_helper.dart';
 import "package:expect/expect.dart";
 import 'dart:async';
 
@@ skipping 1117 matching lines @@
 // An evil future that completes with another future.
 class UglyFuture implements Future<dynamic> {
   final _result;
   UglyFuture(int badness) :
       _result = (badness == 0) ? 42 : new UglyFuture(badness - 1);
   Future then(action(value), {onError(error, StackTrace stack)}) {
     var c = new Completer();
     c.complete(new Future.microtask(() => action(_result)));
     return c.future;
   }
-  Future catchError(onError, {test}) {}  // Never an error.
+  Future catchError(onError, {test}) => this;  // Never an error.
   Future whenComplete(action()) {
     return new Future.microtask(action).then((_) => this);
   }
+  Stream asStream() {
+    return (new StreamController()..add(_result)..close()).stream;
+  }
+  Future timeout(Duration duration, {onTimeout()}) {
+    return this;
+  }
 }