diff --git a/Week 10 - Account Library/Account.cs b/Week 10 - Account Library/Account.cs
index 13fb71d..11d26ca 100644
--- a/Week 10 - Account Library/Account.cs	
+++ b/Week 10 - Account Library/Account.cs	
@@ -8,20 +8,29 @@ namespace Week_10___Account_Library
 {
     public class Account
     {
+        
         private decimal _balance;
         private decimal _overdraftLimit;
 
         public decimal Balance => _balance;
         public decimal OverdraftLimit => _overdraftLimit;
+        public AccountState StateOfAccount { get; }
 
-        void Deposit(decimal amount)
+        private bool ValidateAmount(decimal amount)
         {
-            _balance += amount;
+            return amount >= 0;
         }
 
-        void Withdraw(decimal amount)
+        public void Deposit(decimal amount)
         {
-            _balance -= amount;
+            if (ValidateAmount(amount))
+                _balance += amount;
+        }
+
+        public void Withdraw(decimal amount)
+        {
+            if (ValidateAmount(amount))
+                _balance -= amount;
         }
 
         public Account(decimal balance, decimal overdraftLimit)
@@ -30,4 +39,12 @@ namespace Week_10___Account_Library
             _overdraftLimit = overdraftLimit;
         }
     }
+
+    public enum AccountState
+    {
+        Safe,
+        InOD,
+        ODLimit,
+        None
+    }
 }
diff --git a/Week 10 - TDD Tests/TDDTests.cs b/Week 10 - TDD Tests/TDDTests.cs
index 276a86b..db247a1 100644
--- a/Week 10 - TDD Tests/TDDTests.cs	
+++ b/Week 10 - TDD Tests/TDDTests.cs	
@@ -1,15 +1,43 @@
 using Microsoft.VisualStudio.TestTools.UnitTesting;
 using System;
+using Week_10___Account_Library;
 
 namespace Week_10___TDD_Tests
 {
     [TestClass]
     public class TDDTests
     {
-        [TestMethod]
-        public void TestMethod1()
+        private Account account;
+        [TestInitialize]
+        public void InitTests()
         {
+            account = new Account(1000, 500);
+        }
 
+        [TestMethod]
+        public void DepositAmount()
+        {
+            account.Deposit(200);
+            Assert.AreEqual(1200, account.Balance);
+        }
+
+        [TestMethod]
+        public void WithdrawAmount()
+        {
+            account.Withdraw(200);
+            Assert.AreEqual(800, account.Balance);
+        }
+
+        [TestMethod, ExpectedException(typeof(ArgumentOutOfRangeException))]
+        public void WithdrawNegative()
+        {
+            account.Withdraw(-200);
+        }
+
+        [TestMethod, ExpectedException(typeof(ArgumentOutOfRangeException))]
+        public void DepositNegative()
+        {
+            account.Deposit(-200);
         }
     }
 }