Support re-running tests while debugging.

lib/src/backend/live_test.dart

Index: lib/src/backend/live_test.dart
diff --git a/lib/src/backend/live_test.dart b/lib/src/backend/live_test.dart
index 00b0d11cf2a748bac3dac79410b59be89de4d114..60dc3699e3f1f101b62f5bde5b647ee12ee1d5e3 100644
--- a/lib/src/backend/live_test.dart
+++ b/lib/src/backend/live_test.dart
@@ -115,6 +115,9 @@ abstract class LiveTest {
     return test.name.substring(group.name.length + 1);
   }
 
+  /// Loads a copy of this [LiveTest] that's able to be run again.
+  LiveTest copy() => test.load(suite, groups: groups);
+
   /// Signals that this test should start running as soon as possible.
   ///
   /// A test may not start running immediately for various reasons specific to