anchor.diff:  
     @override
     Future<List<int>> getArchiveBytes(String package, String version) async {
  -    final archive = ArchiveBuilder();
  +    return _archives.putIfAbsent('$package/$version', () {
  +      final archive = ArchiveBuilder();
   
  -    final isFlutter = package.startsWith('flutter_');
  -    final pubspec = json.encode({
  -      'name': package,
  -      'version': version,
  -      'environment': {
  -        'sdk': '>=2.6.0 <3.0.0',
  -      },
  -      'dependencies': {
  -        if (isFlutter) 'flutter': {'sdk': 'flutter'},
  -      },
  +      final isFlutter = package.startsWith('flutter_');
  +      final pubspec = json.encode({
  +        'name': package,
  +        'version': version,
  +        'environment': {
  +          'sdk': '>=2.6.0 <3.0.0',
  +        },
  +        'dependencies': {
  +          if (isFlutter) 'flutter': {'sdk': 'flutter'},
  +        },
  +      });
  +      archive.addFile('pubspec.yaml', pubspec);
  +      archive.addFile('README.md', '# $package\n\nAwesome package.');
  +      archive.addFile('CHANGELOG.md', '## $version\n\n- updated');
  +      archive.addFile(
  +          'lib/$package.dart', 'main() {\n  print(\'Hello.\');\n}\n');
  +      archive.addFile(
  +          'example/example.dart', 'main() {\n  print(\'example\');\n}\n');
  +      archive.addFile('LICENSE', 'All rights reserved.');
  +      return archive.toTarGzBytes();
       });
  -    archive.addFile('pubspec.yaml', pubspec);
  -    archive.addFile('README.md', '# $package\n\nAwesome package.');
  -    archive.addFile('CHANGELOG.md', '## $version\n\n- updated');
  -    archive.addFile('lib/$package.dart', 'main() {\n  print(\'Hello.\');\n}\n');
  -    archive.addFile(
  -        'example/example.dart', 'main() {\n  print(\'example\');\n}\n');
  -    archive.addFile('LICENSE', 'All rights reserved.');
  -    return archive.toTarGzBytes();
     }
   
     @override
  
positive.code: 
  /// Generates data based on random seed, without any network (or file) access.
  class _AutoGeneratedImportSource implements ImportSource {
    @override
    Future<List<ResolvedVersion>> resolveVersions(TestProfile profile) async {
      final versions = <ResolvedVersion>[];
  
negative.code: 
    /// Creates a source that generates data based on random seed, without any
    /// network (or file) access.
    static ImportSource autoGenerated() => _autoGeneratedImportSource;
  }
  
  /// Resolves and downloads data from pub.dev.
  