anchor.diff:        .readAsStringSync();
     var expectedFile =
         new File.fromUri(Platform.script.resolve('expected/$outputname'));
  -  String expected = expectedFile.existsSync()
  -    ? expectedFile.readAsStringSync() : '';
  +  String expected = '';
  +  if (expectedFile.existsSync()) {
  +    expected = expectedFile.readAsStringSync()
  +      .replaceAll(new RegExp('^//.*\n', multiLine: true), '')
  +      .trim();
  +  }
  +
     var match = elementNameRegExp.firstMatch(source);
     var elementName = match?.group(1);
   
  
positive.code:       Expect.isTrue(result.isSuccess);
        CompilerImpl compiler = result.compiler;
        if (expected != null) {
          String output = elementName == null
              ? _getCodeForMain(compiler)
              : _getCodeForMethod(compiler, elementName);
          // Include the input in a comment of the expected file to make it easier
          // to see the relation between input and output in code reviews.
          found = '// Expectation for test: \n'
              '// ${source.trim().replaceAll('\n', '\n// ')}\n\n'
              '$output\n';
        }
      } catch (e, st) {
        print(e);
  
negative.code:     }
      if (expected != found) {
        if (update) {
          // Include the input in a comment of the expected file to make it easier
          // to see the relation between input and output in code reviews.
          String comment = source.trim().replaceAll('\n', '\n// ');
          expectedFile.writeAsStringSync('// Expectation for test: \n'
              '// ${comment}\n\n${found}\n');
          print('INFO: $expectedFile was updated');
        } else {
          Expect.fail('Unexpected output for test:\n  '
              '${_formatTest(files).replaceAll('\n', '\n  ')}\n'
              'Expected:\n  ${expected.replaceAll('\n', '\n  ')}\n\n'
              'but found:\n  ${found?.replaceAll('\n', '\n  ')}\n'
              '$regenerateCommand');
        }
  