Display which nested tasks are running when an error occurs in a scheduled test.

pkg/scheduled_test/lib/src/task.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.
 
 library task;
 
 import 'dart:async';
 import 'dart:collection';
 
 import 'future_group.dart';
@@ skipping 72 matching lines @@
 
     // If the parent queue experiences an error before this task has started
     // running, pipe that error out through [result]. This ensures that we don't
     // get deadlocked by something like `expect(schedule(...), completes)`.
     queue.onTasksComplete.catchError((e) {
       if (state == TaskState.WAITING) _resultCompleter.completeError(e);
     });
 
     // catchError makes sure any error thrown by fn isn't top-leveled by virtue
     // of being passed to the result future.
-    result.whenComplete(() {
-      _state = TaskState.DONE;
+    result.then((_) {
+      _state = TaskState.SUCCESS;
+    }).catchError((e) {
+      _state = TaskState.ERROR;
+      throw e;
     }).catchError((_) {});
   }
 
   /// Run [fn] as a child of this task. Returns a Future that will complete with
   /// the result of the child task. This task will not complete until [fn] has
   /// finished.
   Future runChild(fn(), String description) {
     var task = new Task._child(fn, description, this);
     children.add(task);
     if (_childGroup == null || _childGroup.completed) {
@@ skipping 13 matching lines @@
 }
 
 /// An enum of states for a [Task].
 class TaskState {
   /// The task is waiting to be run.
   static const WAITING = const TaskState._("WAITING");
 
   /// The task is currently running.
   static const RUNNING = const TaskState._("RUNNING");
 
-  /// The task has finished running, either successfully or with an error.
-  static const DONE = const TaskState._("DONE");
+  /// The task has finished running successfully.
+  static const SUCCESS = const TaskState._("SUCCESS");
+
+  /// The task has finished running with an error.
+  static const ERROR = const TaskState._("ERROR");
 
   /// The name of the state.
   final String name;
 
+  /// Whether the state indicates that the task has finished running. This is
+  /// true for both the [SUCCESS] and [ERROR] states.
+  bool get isDone => this == SUCCESS || this == ERROR;
+
   const TaskState._(this.name);
 
   String toString() => name;
 }