An RSpec "undefined method" oddity

undefined_method_oddity_spec.rb

class UndefinedMethodOddity
  def foo
    bar 1
    bar 2
  end
  
  def bar(arg)
  end
end

describe UndefinedMethodOddity do
  describe '#foo' do
    it "correctly complaints 'expected: 1 time, received: 2 times'" do
      subject.should_receive(:bar)
      subject.foo
    end

    it "strangely complains about 'undefined method `bar' for #<UndefinedMethodOddity'" do
      subject.stub(:bar)
      subject.should_receive(:bar).with(1)
      subject.foo
    end
  end
end