anchor.diff:  class _FailingTest {
     const _FailingTest();
   }
  +
  +/**
  + * A marker annotation used to annotate a test class to run it using
  + * [solo_group].
  + */
  +class _SoloTest {
  +  const _SoloTest();
  +}
  
positive.code:  * for the annotated classes.
   */
  const ReflectiveTest reflectiveTest = const ReflectiveTest();
  
  /**
   * Is `true` the application is running in the checked mode.
  
negative.code:         });
        }
      });
    }
    String className = MirrorSystem.getName(classMirror.simpleName);
    if (_hasAnnotationInstance(classMirror, soloTest)) {
      solo_group(className, runMembers);
    } else {
      group(className, runMembers);
    }
  }
  
  bool _hasAnnotationInstance(DeclarationMirror declaration, instance) =>
  