diff --git a/TDDLesson.BankAccount.Tests/BankAccountTests.cs b/TDDLesson.BankAccount.Tests/BankAccountTests.cs
index 99508d3..ef29aa3 100644
--- a/TDDLesson.BankAccount.Tests/BankAccountTests.cs
+++ b/TDDLesson.BankAccount.Tests/BankAccountTests.cs
@@ -2,7 +2,117 @@
 
 using FluentAssertions;
 
+/*
+ * - Добавление на счет денеждых средств
+ * - Снятие средств со счета
+ */
+
+
 [TestClass]
 public sealed class BankAccountTests
 {
+    [TestMethod]
+    public void ShouldBe20OnAccount_When20Added()
+    {
+        // Arrange
+        var balance = 20;
+        var account = new BankAccount(0);
+        
+        // Act
+        var newAccount = account.Add(balance);
+        
+        // Assert
+        newAccount.Balance.Should().Be(balance);
+    }
+    
+    [TestMethod]
+    public void ShouldBe50OnAccount_When20AddedAnd30Was()
+    {
+        // Arrange
+        var balanceBefore = 30;
+        var balanceAdded = 20;
+        var account = new BankAccount(balanceBefore);
+        
+        // Act
+        var newAccount = account.Add(balanceAdded);
+        
+        // Assert
+        newAccount.Balance.Should().Be(50);
+    }
+    
+    [TestMethod]
+    public void ShouldThrow_WhenNegativeValueAdded()
+    {
+        // Arrange
+        var balanceBefore = 30;
+        var balanceAdded = -20;
+        var account = new BankAccount(balanceBefore);
+        
+        // Act
+        var newAccount = () => account.Add(balanceAdded);
+        
+        // Assert
+        newAccount.Should().ThrowExactly<ArgumentException>();
+    }
+    
+    [TestMethod]
+    public void ShouldBe20OnAccount_When10Withdrawn()
+    {
+        // Arrange
+        var balanceBefore = 30;
+        var balance = 10;
+        var account = new BankAccount(0, balanceBefore);
+        
+        // Act
+        var newAccount = account.Withdraw(balance);
+        
+        // Assert
+        newAccount.Balance.Should().Be(20);
+    }
+    
+    [TestMethod]
+    public void ShouldThrow_WhenNegativeValueWithdrawn()
+    {
+        // Arrange
+        var balanceBefore = 30;
+        var balanceWithdrawn = -20;
+        var account = new BankAccount(0, balanceBefore);
+        
+        // Act
+        var newAccount = () => account.Withdraw(balanceWithdrawn);
+        
+        // Assert
+        newAccount.Should().ThrowExactly<ArgumentException>();
+    }
+    
+    [TestMethod]
+    public void ShouldThrow_WhenWithdrawnMoreThanOnAccountIncludingOverdraft()
+    {
+        // Arrange
+        var balanceOverdraft = 10;
+        var balanceBefore = 30;
+        var balanceWithdrawn = 50;
+        var account = new BankAccount(0, balanceBefore);
+        
+        // Act
+        var newAccount = () => account.Withdraw(balanceWithdrawn);
+        
+        // Assert
+        newAccount.Should().ThrowExactly<InvalidOperationException>();
+    }
+        
+    [TestMethod]
+    public void ShouldBeMinus50OnAccount_WhenWithdrawn50AndZeroOnAccount()
+    {
+        // Arrange
+        var balanceBefore = 10;
+        var balanceWithdrawn = 50;
+        var account = new BankAccount(0, balanceBefore);
+        
+        // Act
+        var newAccount = account.Withdraw(balanceWithdrawn);
+        
+        // Assert
+        newAccount.Balance.Should().Be(-40);
+    }
 }
\ No newline at end of file
diff --git a/TDDLesson.BankAccount/BankAccount.cs b/TDDLesson.BankAccount/BankAccount.cs
index cdc2e4e..a8d565e 100644
--- a/TDDLesson.BankAccount/BankAccount.cs
+++ b/TDDLesson.BankAccount/BankAccount.cs
@@ -1,13 +1,19 @@
 namespace TDDLesson.BankAccount;
 
-public sealed class BankAccount
+public record BankAccount(int Overdraft, int Balance = 0)
 {
-    public int Balance { get; private set; }
+    public int Balance { get; private set; } = Balance;
 
-    public void Add(int money)
+    public BankAccount Add(int money)
     {
-        if (money < 0) throw new InvalidOperationException();
-        
-        Balance = money;
+        if (money < 0) throw new ArgumentException();
+        return new BankAccount(Balance + money);
+    }
+    
+    public BankAccount Withdraw(int money)
+    {
+        if (money < 0) throw new ArgumentException();
+        if (Balance + Overdraft - money <  0) throw new InvalidOperationException();
+        return new BankAccount(Balance + Overdraft - money, Overdraft);
     }
 }
\ No newline at end of file