anchor.diff:  
   FileSystemAccess _fileSystemAccess;
   
  +/**
  + * Sets the used FileSystemAccess class, allowing overriding versions of the
  + * filesystem
  + */
   void setMockFilesystemAccess() {
     assert(_fileSystemAccess == null || _fileSystemAccess.root == null);
     _fileSystemAccess = new MockFileSystemAccess();
   }
   
  +/**
  + * Returns the current FilesystemAccess
  + */
   FileSystemAccess get fileSystemAccess {
     if (_fileSystemAccess == null) {
       _fileSystemAccess = new FileSystemAccess._();
  
positive.code: }
  
  /**
   * Provides abstracted access to all filesystem functions
   */
  class FileSystemAccess {
    ProjectLocationManager _locationManager;
    ProjectLocationManager get locationManager => _locationManager;
  
    LocationResult location;
  
    ws.WorkspaceRoot _root;
    ws.WorkspaceRoot get root {
      if (_root == null) {
        if (location != null) {
          _root = getRootFor(location);
        }
      }
  
  
negative.code:     DirectoryEntry rootParent = fs.createDirectory("rootParent");
  
      rootParent.createDirectory("root").then((DirectoryEntry root) {
        _location = new LocationResult(rootParent, root, false);
      });
    }
  
  