Change package scheduled_test to throw TestFailures rather than strings.

pkg/scheduled_test/test/descriptor/directory_test.dart

Index: pkg/scheduled_test/test/descriptor/directory_test.dart
diff --git a/pkg/scheduled_test/test/descriptor/directory_test.dart b/pkg/scheduled_test/test/descriptor/directory_test.dart
index a8051cc58dabadc8ae62557a16068e399c55a9cf..2607ed0a8dff9ccdbab4dab0c35fe3beee2004a8 100644
--- a/pkg/scheduled_test/test/descriptor/directory_test.dart
+++ b/pkg/scheduled_test/test/descriptor/directory_test.dart
@@ -300,9 +300,9 @@ void main() {
         d.file('name.txt', 'contents')
       ]);
 
-      expect(dir.load('subdir').toList(),
-          throwsA(equals("Couldn't find a readable entry named 'subdir' within "
-              "'dir'.")));
+      expect(dir.load('subdir').toList(), throwsA(predicate(
+          (x) => x.toString() == "Couldn't find a readable entry named "
+                                 "'subdir' within 'dir'.")));
     });
   });
 
@@ -331,9 +331,9 @@ void main() {
     test('test', () {
       var dir = d.dir('dir', [d.file('name.txt', 'contents')]);
 
-      expect(dir.load('not-name.txt').toList(),
-          throwsA(equals("Couldn't find a readable entry named 'not-name.txt' "
-              "within 'dir'.")));
+      expect(dir.load('not-name.txt').toList(), throwsA(predicate(
+          (x) => x.toString() == "Couldn't find a readable entry named "
+                                 "'not-name.txt' within 'dir'.")));
     });
   });
 
@@ -345,9 +345,9 @@ void main() {
         d.file('name.txt', 'contents')
       ]);
 
-      expect(dir.load('name.txt').toList(),
-          throwsA(equals("Found multiple readable entries named 'name.txt' "
-              "within 'dir'.")));
+      expect(dir.load('name.txt').toList(), throwsA(predicate(
+          (x) => x.toString() == "Found multiple readable entries named "
+                                 "'name.txt' within 'dir'.")));
     });
   });
 
@@ -412,4 +412,4 @@ void main() {
       expect(d.dir('dir').describe(), equals('dir'));
     });
   });
-}
+}