Add unit tests for Category creation in Catalog module

Introduce tests to ensure Category creation throws exceptions for null, empty, and whitespace names. Also, verify correct Category creation with valid name.

src/Modules/Products/Modules.Catalog.Tests/CatalogTests.cs

@@ -0,0 +1,51 @@
+using FluentAssertions;
+using Modules.Catalog.Categories.Domain;
+
+namespace Modules.Catalog.Tests;
+
+public class CatalogTests
+{
+    [Fact]
+    public void Create_ShouldThrowException_WhenNameIsNull()
+    {
+        // Arrange
+        Action act = () => Category.Create(null!);
+
+        // Act & Assert
+        act.Should().Throw<ArgumentException>();
+    }
+
+    [Fact]
+    public void Create_ShouldThrowException_WhenNameIsEmpty()
+    {
+        // Arrange
+        Action act = () => Category.Create(string.Empty);
+
+        // Act & Assert
+        act.Should().Throw<ArgumentException>();
+    }
+
+    [Fact]
+    public void Create_ShouldThrowException_WhenNameIsWhiteSpace()
+    {
+        // Arrange
+        Action act = () => Category.Create(" ");
+
+        // Act & Assert
+        act.Should().Throw<ArgumentException>();
+    }
+
+    [Fact]
+    public void Create_ShouldReturnCategory_WhenNameIsValid()
+    {
+        // Arrange
+        var name = "ValidName";
+
+        // Act
+        var category = Category.Create(name);
+
+        // Assert
+        category.Name.Should().Be(name);
+        category.Id.Should().NotBeNull();
+    }
+}