class MiniTest::Mock

def expect(name, retval, args=[])
  n, r, a = name, retval, args # for the closure below
  @expected_calls[name] = { :retval => retval, :args => args }
  self.class.__send__ :remove_method, name if respond_to? name
  self.class.__send__(:define_method, name) { |*x|
    raise ArgumentError unless @expected_calls[n][:args].size == x.size
    @actual_calls[n] << { :retval => r, :args => x }
    retval
  }
  self
end