public void SetUp()
        {
            _file = new [] { "Console.WriteLine()" };

            _existingLicense = new Mock <ILicense>();
            _existingLicense.Setup(x => x.RemoveFrom(_file)).Returns(_file);

            _newLicense = new Mock <ILicense>();
            _newLicense.Setup(x => x.AddTo(_file)).Returns(_file);

            var subject = new ChangedSource(_file, _existingLicense.Object, null);

            _result = subject.Add(_newLicense.Object);
        }