public Contract Create()
 {
     Contract newContract = new Contract
     {
         Name = GenerateRandomString(),
         Supplier = GenerateRandomString(),
         Purchaser = GenerateRandomString(),
     };
     int maxItems = random.Next(1, 5);
     for (int i = 0; i < maxItems; i++)
         newContract.Add(RandomStorableFactory());
     return newContract;
 }