Please help this ruby idiot mock something

gistfile1.rb

def MPQ path
  path
end

class ReplayFile
  def initailize path
    @archive = MPQ(path)
  end
end

# how do I mock MPQ in the context of ReplayFile's initializer?
# is trying to do this obviously stupid?

# this works (needs bang version), but not inside the initializer
# stub!(:MPQ).and_return("stub says hi")

# in a static language I would change the code to:

# class ReplayFile
#   def initialize archive
#     @archive = archive
#   end
# end

# but like, my god, its ruby, I want to bend the universe to my will

:\ dependency injection. do you hear about it? m>