anchor.diff:    assert.AreEqual('2234567890', phone.Clean);
   end;
   
  +procedure PhoneNumberTests.Valid_when_11_digits_and_starting_with_1_even_with_punctuation;
  +var phone: IPhoneNumber;
  +begin
  +  phone := NewPhoneNumber('+1 (223) 456-7890');
  +  assert.AreEqual('2234567890', phone.Clean);
  +end;
  +
   procedure PhoneNumberTests.Invalid_when_11_digits_does_not_start_with_a_1;
   var phone: IPhoneNumber;
   begin
  
positive.code: uses
    DUnitX.TestFramework;
  
  type
  
    [TestFixture]
  
negative.code:   assert.AreEqual('', phone.Clean);
  end;
  
  procedure PhoneNumberTests.Invalid_if_area_code_starts_with_0;
  var phone: IPhoneNumber;
  begin
    phone := NewPhoneNumber('(023) 456-7890');
    assert.AreEqual('', phone.Clean);
  end;
  
  procedure PhoneNumberTests.Invalid_if_area_code_starts_with_1;
  var phone: IPhoneNumber;
  begin
    phone := NewPhoneNumber('(123) 456-7890');
    assert.AreEqual('', phone.Clean);
  end;
  
  procedure PhoneNumberTests.Invalid_if_exchange_code_starts_with_0;
  var phone: IPhoneNumber;
  begin
    phone := NewPhoneNumber('(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;
  
  