anchor.diff:      {bool debug: false,
       bool verbose: false,
       List<String> options: const <String>[]}) async {
  -  Directory dir = new Directory('.');
  -  new File('test.dart').writeAsStringSync(annotatedCode.sourceCode);
  +  Directory dir = Directory.systemTemp.createTempSync('stepping_test');
  +  String path = dir.path;
  +  String inputFile = '$path/test.dart';
  +  new File(inputFile).writeAsStringSync(annotatedCode.sourceCode);
  +  String outputFile = '$path/js.js';
     List<String> arguments = <String>[
  -    '--out=js.js',
  -    'test.dart',
  +    '--out=$outputFile',
  +    inputFile,
       Flags.disableInlining,
     ];
     if (config == kernelMarker) {
  
positive.code:     d8output.forEach(print);
    }
    checkD8Steps(dir.path, d8output, annotatedCode, debug: debug);
  }
  
negative.code:   Expect.isTrue(compilationResult.isSuccess);
    List<String> scriptD8Command = [
      'sdk/lib/_internal/js_runtime/lib/preambles/d8.js',
      outputFile
    ];
    ProcessResult result = runD8AndStep(dir.path, annotatedCode, scriptD8Command);
    List<String> d8output = result.stdout.split("\n");
  