anchor.diff:    assert.AreEqual('', phone.Clean);
   end;
   
  +procedure PhoneNumberTests.Invalid_if_area_code_starts_with_1_on_valid_11_digit_number;
  +var phone: IPhoneNumber;
  +begin
  +  phone := NewPhoneNumber('1 (123) 456-7890');
  +  assert.AreEqual('', phone.Clean);
  +end;
  +
   procedure PhoneNumberTests.Invalid_if_exchange_code_starts_with_0;
   var phone: IPhoneNumber;
   begin
  
positive.code:     procedure Invalid_if_exchange_code_starts_with_1;
  
      [Test]
      [Ignore('This is a bonus test')]
      procedure Extract_area_code;
  
  
negative.code:   assert.AreEqual('', phone.Clean);
  end;
  
  procedure PhoneNumberTests.Invalid_if_exchange_code_starts_with_0_on_valid_11_digit_number;
  var phone: IPhoneNumber;
  begin
    phone := NewPhoneNumber('1 (223) 056-7890');
    assert.AreEqual('', phone.Clean);
  end;
  
  procedure PhoneNumberTests.Invalid_if_exchange_code_starts_with_1;
  var phone: IPhoneNumber;
  begin
    phone := NewPhoneNumber('(223) 156-7890');
    assert.AreEqual('', phone.Clean);
  end;
  
  procedure PhoneNumberTests.Invalid_if_exchange_code_starts_with_1_on_valid_11_digit_number;
  var phone: IPhoneNumber;
  begin
    phone := NewPhoneNumber('1 (223) 156-7890');
    assert.AreEqual('', phone.Clean);
  end;
  
  