more fun with nil marshal

test.rb

class User
  def _dump(level)
    ""
  end

  def self._load(*args)
    nil
  end
end

user1 = User.new
user2 = User.new
s = "string"

arr = [user1, user2, s, s]
arr_dump = Marshal.dump(arr)

p Marshal.load(arr_dump)