class FakeFS::File

def self.chown(owner_int, group_int, filename)
  file = FileSystem.find(filename)
  if owner_int && owner_int != -1
    owner_int.is_a?(Integer) || raise(TypeError, "can't convert String into Integer")
    file.uid = owner_int
  end
  if group_int && group_int != -1
    group_int.is_a?(Integer) || raise(TypeError, "can't convert String into Integer")
    file.gid = group_int
  end
end