Add a testOn parameter to test() and group().

lib/src/backend/test.dart

Index: lib/src/backend/test.dart
diff --git a/lib/src/backend/test.dart b/lib/src/backend/test.dart
index cfc0c30072182714e13ca4db3a024b29d3f1ee48..bbf14348ef48ab3d5d2361bf2378587975de5899 100644
--- a/lib/src/backend/test.dart
+++ b/lib/src/backend/test.dart
@@ -5,6 +5,7 @@
 library unittest.backend.test;
 
 import 'live_test.dart';
+import 'metadata.dart';
 import 'suite.dart';
 
 /// A single test.
@@ -16,6 +17,9 @@ abstract class Test {
   /// The name of the test.
   String get name;
 
+  /// The metadata for the test.
+  Metadata get metadata;
+
   /// Loads a live version of this test, which can be used to run it a single
   /// time.
   ///