Add tests for wallet withdrawal: ensure exception is thrown for insuf…

…ficient funds and balance is decreased on valid withdrawal

E_Wallet/Models/Wallet.cs

@@ -1,4 +1,3 @@
-
 namespace E_Wallet.Models;
 
 public class Wallet
@@ -40,20 +39,14 @@ public void Deposit(decimal amount)
     {
         // TODO -- ***is it ok to check on zero values**
         if (decimal.IsNegative(amount) || amount == decimal.Zero)
-        {
             NegativeBalanceException.Throw(amount);
-        }
-
         Balance += amount;
     }
 
     public void Withdraw(decimal amount)
     {
         if (Balance < amount)
-        {
             InsufficientFundsException.Throw(amount);
-        }
-
         Balance -= amount;
     }
 

Wallet_Tests/Wallet_Wallet_Tests.cs

@@ -43,6 +43,7 @@ public void Should_Throw_Exception_If_InitialBalance_Is_Under_Limit(string code,
     [InlineData(-10)]
     [InlineData(-200.9)]
     [InlineData(0)]
+    [InlineData(null!)]
     public void Should_Throw_Exception_When_Deposit_Amount_Is_Negative_Or_Zero(decimal amount)
     {
         var currency = Currency.Create("USD", "United States Dollar", 1.99m);
@@ -61,4 +62,25 @@ public void Should_Increase_Balance_When_Deposit_Amount_Is_Positive()
         wallet.Deposit(amount: 100);
         wallet.Balance.Should().Be(200);
     }
+
+
+    [Fact]
+    public void Should_Throw_Exception_When_Balance_Is_Lower_Than_Withdrawal_Amount()
+    {
+        var currency = Currency.Create("USD", "United States Dollar", 1.99m);
+        var wallet = Wallet.Create(balance: 100, currency);
+        wallet.Withdraw(amount: 100);
+        wallet.Balance.Should().Be(0).And.BePositive();
+        ;
+    }
+
+
+    [Fact]
+    public void Should_Decrease_Balance_When_Withdrawal()
+    {
+        var currency = Currency.Create("USD", "United States Dollar", 1.99m);
+        var wallet = Wallet.Create(balance: 100, currency);
+        var withdrawal = () => wallet.Withdraw(amount: 101);
+        withdrawal.Should().ThrowExactly<InsufficientFundsException>();
+    }
 }