anchor.diff:    'ffi': 'const LibraryInfo("ffi/ffi.dart")',
     'html': 'const LibraryInfo("html/dart2js/html_dart2js.dart")',
     'io': 'const LibraryInfo("io/io.dart")',
  +  'isolate': 'const LibraryInfo("io/isolate.dart")',
     'math': 'const LibraryInfo("math/math.dart")',
   };
   
  
positive.code:       '''
  library dart.io;
  
  abstract class Directory implements FileSystemEntity {
    factory Directory(String path) {
      throw 0;
  
negative.code:   static FileSystemEntityType typeSync(
      String path, {bool followLinks: true}) => throw 0;
  }
  
  enum ProcessStartMode {
    normal,
  }
  
  abstract class Process {
    external static Future<Process> start(
      String executable,
      List<String> arguments, {
      String? workingDirectory,
      Map<String, String>? environment,
      bool includeParentEnvironment: true,
      bool runInShell: false,
      ProcessStartMode mode: ProcessStartMode.normal,
    });
  
    external static Future<ProcessResult> run(
      String executable,
      List<String> arguments, {
      String? workingDirectory,
      Map<String, String>? environment,
      bool includeParentEnvironment: true,
      bool runInShell: false,
      Encoding? stdoutEncoding,
      Encoding? stderrEncoding,
    });
  }
  ''',
      )
    ],
  );
  
  final MockSdkLibrary _LIB_ISOLATE = MockSdkLibrary([
    MockSdkLibraryUnit(
      'dart:isolate',
      '$sdkRoot/lib/isolate/isolate.dart',
      '''
  library dart.isolate;
  
  abstract class SendPort {}
  
  class Isolate {
    external static Future<Isolate> spawnUri(
      Uri uri,
      List<String> args,
      var message, {
      bool paused = false,
      SendPort? onExit,
      SendPort? onError,
      bool errorsAreFatal = true,
      bool? checked,
      Map<String, String>? environment,
      @deprecated Uri? packageRoot,
      Uri? packageConfig,
      bool automaticPackageResolution = false,
      String? debugName,
    });
  }
  ''',
    )
  ]);
  
  final MockSdkLibrary _LIB_MATH = MockSdkLibrary(
    [
  