Change package scheduled_test to throw TestFailures rather than strings.

pkg/scheduled_test/lib/src/descriptor/directory_descriptor.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 descriptor.directory;
 
 import 'dart:async';
 import 'dart:io';
 
 import 'package:path/path.dart' as path;
@@ skipping 24 matching lines @@
     });
   }, 'creating directory:\n${describe()}');
 
   Future validate([String parent]) => schedule(() => validateNow(parent),
       'validating directory:\n${describe()}');
 
   Future validateNow([String parent]) {
     if (parent == null) parent = defaultRoot;
     var fullPath = path.join(parent, name);
     if (!new Directory(fullPath).existsSync()) {
-      throw "Directory not found: '$fullPath'.";
+      fail("Directory not found: '$fullPath'.");
     }
 
     return Future.wait(contents.map((entry) {
       return new Future.sync(() => entry.validateNow(fullPath))
           .then((_) => null)
           .catchError((e) => e);
     })).then((results) {
       var errors = results.where((e) => e != null);
       if (errors.isEmpty) return;
       throw _DirectoryValidationError.merge(errors);
@@ skipping 14 matching lines @@
 
       var requiresReadable = split.length == 1;
       var matchingEntries = contents.where((entry) {
         return entry.name == split.first && (requiresReadable ?
             entry is ReadableDescriptor :
             entry is LoadableDescriptor);
       }).toList();
 
       var adjective = requiresReadable ? 'readable' : 'loadable';
       if (matchingEntries.length == 0) {
-        throw "Couldn't find a $adjective entry named '${split.first}' within "
-            "'$name'.";
+        fail("Couldn't find a $adjective entry named '${split.first}' within "
+             "'$name'.");
       } else if (matchingEntries.length > 1) {
-        throw "Found multiple $adjective entries named '${split.first}' within "
-            "'$name'.";
+        fail("Found multiple $adjective entries named '${split.first}' within "
+             "'$name'.");
       } else {
         var remainingPath = split.sublist(1);
         if (remainingPath.isEmpty) {
           return (matchingEntries.first as ReadableDescriptor).read();
         } else {
           return (matchingEntries.first as LoadableDescriptor)
               .load(_path.joinAll(remainingPath));
         }
       }
     }));
@@ skipping 32 matching lines @@
 
   _DirectoryValidationError(Iterable errors)
       : errors = errors.map((e) => e.toString()).toList();
 
   String toString() {
     if (errors.length == 1) return errors.single;
     return errors.map((e) => prefixLines(e, prefix: '  ', firstPrefix: '* '))
         .join('\n');
   }
 }