anchor.diff:          'a/b/c/var3/foo',
         ];
         for (String asset in assets) {
  -        fs.file(asset)
  +        fs.file(fixPath(asset))
             ..createSync(recursive: true)
             ..writeAsStringSync(asset);
         }
  
positive.code:         expect(utf8.decode(await bundle.entries[asset].contentsAsBytes()), asset);
        }
  
        fs.file('a/b/c/foo').deleteSync();
        bundle = AssetBundleFactory.instance.createBundle();
        await bundle.build(manifestPath: 'pubspec.yaml');
  
  
negative.code: import 'dart:convert';
  
  import 'package:file/file.dart';
  import 'package:file/memory.dart';
  
  import 'package:flutter_tools/src/asset.dart';
  import 'package:flutter_tools/src/base/file_system.dart';
  import 'package:flutter_tools/src/base/platform.dart';
  import 'package:flutter_tools/src/cache.dart';
  
  import 'src/common.dart';
  import 'src/context.dart';
  import 'src/pubspec_schema.dart';
  
  void main() {
    String fixPath(String path) {
      // The in-memory file system is strict about slashes on Windows being the
      // correct way so until https://github.com/google/file.dart/issues/112 is
      // fixed we fix them here.
      // TODO(dantup): Remove this function once the above issue is fixed and
      // rolls into Flutter.
      return path?.replaceAll('/', fs.path.separator);
    }
  
    group('AssetBundle asset variants', () {
      FileSystem testFileSystem;
      setUp(() async {
        testFileSystem = new MemoryFileSystem(
          style: platform.isWindows
            ? FileSystemStyle.windows
            : FileSystemStyle.posix,
        );
        testFileSystem.currentDirectory = testFileSystem.systemTempDirectory.createTempSync('flutter_asset_bundle_variant_test.');
      });
  
      testUsingContext('main asset and variants', () async {
        // Setting flutterRoot here so that it picks up the MemoryFileSystem's
        // path separator.
        Cache.flutterRoot = getFlutterRoot();
        writeEmptySchemaFile(fs);
  
        fs.file('pubspec.yaml')
          ..createSync()
  