diff --git a/BasicBlockChain.Core/Block.cs b/BasicBlockChain.Core/Block.cs
index 3ef9b2b..0bc8d2e 100644
--- a/BasicBlockChain.Core/Block.cs
+++ b/BasicBlockChain.Core/Block.cs
@@ -11,10 +11,12 @@ namespace BasicBlockChain.Core
         public int Index { get; set; }
         public DateTime Date { get; set; }
         public string PreviousHash { get; set; }
-        public List<Transaction> Transactions { get; } = new List<Transaction>();
+        public List<Transaction> Transactions { get; set; } = new List<Transaction>();
         public string Hash { get; set; }
         public int Nonce { get; set; }
 
+        public Block() { }
+
         public Block(DateTime date, Block previousBlock, IList<Transaction> transactions)
         {
             Index = (previousBlock?.Index ?? -1) + 1;
diff --git a/BasicBlockChain.Core/BlockChain.cs b/BasicBlockChain.Core/BlockChain.cs
index e6a6a49..a4b0303 100644
--- a/BasicBlockChain.Core/BlockChain.cs
+++ b/BasicBlockChain.Core/BlockChain.cs
@@ -7,7 +7,7 @@ namespace BasicBlockChain.Core
     public class BlockChain
     {
         public List<Transaction> PendingTransactions { get; } = new List<Transaction>();
-        public List<Block> Chain { get; } = new List<Block>();
+        public List<Block> Chain { get; set; } = new List<Block>();
         public int Difficulty { get; set; } = 2;
         public int Reward { get; set; } = 1_000_000;
 
@@ -23,6 +23,10 @@ namespace BasicBlockChain.Core
                 }
                 return _users;
             }
+            set
+            {
+                _users = value;
+            }
         }
 
         private void InitUsers()
@@ -65,6 +69,8 @@ namespace BasicBlockChain.Core
             }
         }
 
+        public BlockChain() { }
+
         public BlockChain(DateTime? genesisDate = null, int difficulty = 2, int reward = 1_000_000)
         {
             Block genesisBlock = new Block(genesisDate ?? DateTime.UtcNow, null, null);
diff --git a/BasicBlockChain.Core/Transaction.cs b/BasicBlockChain.Core/Transaction.cs
index e0f4ef6..8e1beae 100644
--- a/BasicBlockChain.Core/Transaction.cs
+++ b/BasicBlockChain.Core/Transaction.cs
@@ -9,6 +9,8 @@ namespace BasicBlockChain.Core
         public long MicroCoinAmount { get; set; }
         public DateTime Date { get; set; }
 
+        public Transaction() { }
+
         public Transaction(string sender, string receiver, long microCoinAmount, DateTime date)
         {
             Sender = sender;