Inheritance: ISevenDigitalId
 public bool Equals(SevenDigitalId other)
 {
     if(ReferenceEquals(null, other))
     {
         return false;
     }
     if(ReferenceEquals(this, other))
     {
         return true;
     }
     return other._id == _id;
 }
 public void SetUp()
 {
     _sevenDigitalId = new SevenDigitalId(132456);
     _expectedMapping = new Mapping
     {
         SevenDigital = _sevenDigitalId
     };
     _loadedList = new List<IMapping>
     {
         _expectedMapping
     };
     _subject = new Repository(_loadedList);
 }