An RSpec "undefined method" oddity

gistfile1.txt

ubuntu-desktop-x64 :: ~/Code » rspec 2274040/undefined_method_oddity_spec.rb
FF

Failures:

  1) UndefinedMethodOddity correctly complaints 'expected: 1 time, received: 2 times'
     Failure/Error: subject.should_receive(:bar)
       (#<UndefinedMethodOddity:0x000000010b7c68>).bar(any args)
           expected: 1 time
           received: 0 times
     # ./2274040/undefined_method_oddity_spec.rb:17:in `block (2 levels) in <top (required)>'

  2) UndefinedMethodOddity strangely complains about 'undefined method `bar' for #<UndefinedMethodOddity'
     Failure/Error: subject.should_receive(:bar).with(1)
       (#<UndefinedMethodOddity:0x00000001d85af8>).bar(1)
           expected: 1 time
           received: 0 times
     # ./2274040/undefined_method_oddity_spec.rb:22:in `block (2 levels) in <top (required)>'

Finished in 0.00098 seconds
2 examples, 2 failures

Failed examples:

rspec ./2274040/undefined_method_oddity_spec.rb:16 # UndefinedMethodOddity correctly complaints 'expected: 1 time, received: 2 times'
rspec ./2274040/undefined_method_oddity_spec.rb:21 # UndefinedMethodOddity strangely complains about 'undefined method `bar' for #<UndefinedMethodOddity'

undefined_method_oddity_spec.rb

class UndefinedMethodOddity
  def foo
    self.bar 1
    self.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.should_receive(:bar).with(1)
      subject.foo
    end
  end
end