Refactor to eliminate unneeded BasketQueryService

tests/UnitTests/ApplicationCore/Entities/BasketTests/BasketAddItem.cs

@@ -1,8 +1,8 @@
 using System;
-using System.Linq;
-using Microsoft.eShopWeb.ApplicationCore.Entities.BasketAggregate;
-using Xunit;
-
+using System.Linq;
+using Microsoft.eShopWeb.ApplicationCore.Entities.BasketAggregate;
+using Xunit;
+
 namespace Microsoft.eShopWeb.UnitTests.ApplicationCore.Entities.BasketTests;
 
 public class BasketAddItem
@@ -72,4 +72,4 @@ public class BasketAddItem
 
         Assert.Throws<ArgumentOutOfRangeException>(() => basket.AddItem(_testCatalogItemId, _testUnitPrice, -2));
     }
-}
+}

tests/UnitTests/ApplicationCore/Entities/BasketTests/BasketTotalItems.cs

@@ -0,0 +1,35 @@
+using Microsoft.eShopWeb.ApplicationCore.Entities.BasketAggregate;
+using Xunit;
+
+namespace Microsoft.eShopWeb.UnitTests.ApplicationCore.Entities.BasketTests;
+
+public class BasketTotalItems
+{
+    private readonly int _testCatalogItemId = 123;
+    private readonly decimal _testUnitPrice = 1.23m;
+    private readonly int _testQuantity = 2;
+    private readonly string _buyerId = "Test buyerId";
+
+    [Fact]
+    public void ReturnsTotalQuantityWithOneItem()
+    {
+        var basket = new Basket(_buyerId);
+        basket.AddItem(_testCatalogItemId, _testUnitPrice, _testQuantity);
+
+        var result = basket.TotalItems;
+
+        Assert.Equal(_testQuantity, result);
+    }
+
+    [Fact]
+    public void ReturnsTotalQuantityWithMultipleItems()
+    {
+        var basket = new Basket(_buyerId);
+        basket.AddItem(_testCatalogItemId, _testUnitPrice, _testQuantity);
+        basket.AddItem(_testCatalogItemId, _testUnitPrice, _testQuantity*2);
+
+        var result = basket.TotalItems;
+
+        Assert.Equal(_testQuantity*3, result);
+    }
+}