anchor.diff:      fileName = '${tmpDir.path}/fuzz.dart';
       runner1 = TestRunner.getTestRunner(mode1, top, tmpDir.path, env);
       runner2 = TestRunner.getTestRunner(mode2, top, tmpDir.path, env);
  +    isolate = 'Isolate (${tmpDir.path}) '
  +        '${runner1.description} - ${runner2.description}';
  +
       numTests = 0;
       numSuccess = 0;
       numNotRun = 0;
  
positive.code:   void reportDivergence(
        TestResult result1, TestResult result2, bool outputDivergence) {
      numDivergences++;
      print('\n\nDIVERGENCE $version:$seed : ${runner1.description} vs. '
          '${runner2.description}\n');
      if (outputDivergence) {
        print('out1:\n${result1.output}\n\nout2:\n${result2.output}\n');
      }
    }
  
  
negative.code:   String fileName;
    TestRunner runner1;
    TestRunner runner2;
    String isolate;
    int seed;
  
    // Stats.
  