Add XML helper

src/CuteUtils.Tests/Misc/XmlHelperTests.cs

@@ -0,0 +1,69 @@
+using CuteUtils.Misc;
+
+namespace CuteUtils.Tests.Misc;
+
+[TestClass]
+public class XmlHelperTests
+{
+    public class TestModel
+    {
+        public string? Name { get; set; }
+        public int Age { get; set; }
+        public NestedModel? Child { get; set; }
+    }
+
+    public class NestedModel
+    {
+        public string? Value { get; set; }
+    }
+
+    [TestMethod]
+    public void SerializeDeserialize_RoundTrip_RetainsData()
+    {
+        TestModel model = new TestModel
+        {
+            Name = "Alice",
+            Age = 30,
+            Child = new NestedModel { Value = "Inner" }
+        };
+
+        string xml = XmlHelper.Serialize(model);
+        Assert.IsFalse(string.IsNullOrWhiteSpace(xml), "Serialized XML should not be empty.");
+        Assert.Contains("Alice", xml, "XML should contain the Name value.");
+        Assert.Contains("30", xml, "XML should contain the Age value.");
+        Assert.Contains("Inner", xml, "XML should contain the Nested Value.");
+
+        TestModel? deserialized = XmlHelper.Deserialize<TestModel>(xml);
+        Assert.IsNotNull(deserialized, "Deserialized object should not be null.");
+        Assert.AreEqual(model.Name, deserialized!.Name);
+        Assert.AreEqual(model.Age, deserialized.Age);
+        Assert.AreEqual(model.Child?.Value, deserialized.Child?.Value);
+    }
+
+    [TestMethod]
+    public void Serialize_OmitsNamespaceDeclarations()
+    {
+        TestModel model = new TestModel { Name = "Bob", Age = 25 };
+        string xml = XmlHelper.Serialize(model);
+
+        // Expect no namespace attributes like xmlns or common schema prefixes
+        Assert.DoesNotContain("xmlns", xml, "XML should not contain namespace declarations.");
+        Assert.DoesNotContain("xsi:", xml, "XML should not contain xsi prefix.");
+        Assert.DoesNotContain("xsd:", xml, "XML should not contain xsd prefix.");
+    }
+
+    [TestMethod]
+    public void Deserialize_NullXml_ThrowsArgumentNullException()
+    {
+        _ = Assert.ThrowsExactly<ArgumentNullException>(() => XmlHelper.Deserialize<TestModel>(null!));
+    }
+
+    [TestMethod]
+    public void GetXmlSchema_ReturnsSchemaContainingTypeName()
+    {
+        string schema = XmlHelper.GetXmlSchema<TestModel>();
+        Assert.IsFalse(string.IsNullOrWhiteSpace(schema), "Schema should not be empty.");
+        Assert.IsGreaterThanOrEqualTo(0, schema.IndexOf("schema", StringComparison.OrdinalIgnoreCase), "Schema should contain 'schema' element.");
+        Assert.Contains("TestModel", schema, "Schema should reference the TestModel type.");
+    }
+}