Add HTML parser implementation with tokenizer, factory, and unit tests

Agent-Logs-Url: https://github.com/webexpress-framework/WebExpress.WebCore/sessions/7e93c55c-79fd-4d3c-ac96-9948c1ec6d5a

Co-authored-by: ReneSchwarzer <31061438+ReneSchwarzer@users.noreply.github.com>

Author: Copilot

src/WebExpress.WebCore.Test/Html/Parser/UnitTestHtmlElementFactory.cs

@@ -0,0 +1,117 @@
+using WebExpress.WebCore.WebHtml;
+using WebExpress.WebCore.WebHtml.Parser;
+
+namespace WebExpress.WebCore.Test.Html.Parser
+{
+    /// <summary>
+    /// Unit tests for the <see cref="HtmlElementFactory"/> class.
+    /// </summary>
+    [Collection("NonParallelTests")]
+    public class UnitTestHtmlElementFactory
+    {
+        /// <summary>
+        /// Known tags are resolved to their specific subclass.
+        /// </summary>
+        [Fact]
+        public void KnownTag_Div_ReturnsCorrectType()
+        {
+            var element = HtmlElementFactory.Create("div");
+
+            Assert.IsType<HtmlElementTextContentDiv>(element);
+        }
+
+        /// <summary>
+        /// Known tags are resolved to their specific subclass.
+        /// </summary>
+        [Fact]
+        public void KnownTag_Span_ReturnsCorrectType()
+        {
+            var element = HtmlElementFactory.Create("span");
+
+            Assert.IsType<HtmlElementTextSemanticsSpan>(element);
+        }
+
+        /// <summary>
+        /// Known tags are resolved to their specific subclass.
+        /// </summary>
+        [Fact]
+        public void KnownTag_Img_ReturnsCorrectType()
+        {
+            var element = HtmlElementFactory.Create("img");
+
+            Assert.IsType<HtmlElementMultimediaImg>(element);
+        }
+
+        /// <summary>
+        /// Known tags are resolved to their specific subclass.
+        /// </summary>
+        [Fact]
+        public void KnownTag_Input_ReturnsCorrectType()
+        {
+            var element = HtmlElementFactory.Create("input");
+
+            Assert.IsType<HtmlElementFieldInput>(element);
+        }
+
+        /// <summary>
+        /// Known tags are resolved to their specific subclass.
+        /// </summary>
+        [Fact]
+        public void KnownTag_Table_ReturnsCorrectType()
+        {
+            var element = HtmlElementFactory.Create("table");
+
+            Assert.IsType<HtmlElementTableTable>(element);
+        }
+
+        /// <summary>
+        /// Factory is case-insensitive – upper-case tag names resolve correctly.
+        /// </summary>
+        [Fact]
+        public void CaseInsensitive_UpperCase_ReturnsCorrectType()
+        {
+            var element = HtmlElementFactory.Create("DIV");
+
+            Assert.IsType<HtmlElementTextContentDiv>(element);
+        }
+
+        /// <summary>
+        /// An unknown tag name returns a generic <see cref="HtmlElement"/>.
+        /// </summary>
+        [Fact]
+        public void UnknownTag_ReturnsGenericElement()
+        {
+            var element = HtmlElementFactory.Create("x-custom-widget");
+
+            Assert.IsType<HtmlElement>(element);
+        }
+
+        /// <summary>
+        /// <see cref="HtmlElementFactory.IsKnown"/> returns <c>true</c> for known tags.
+        /// </summary>
+        [Fact]
+        public void IsKnown_KnownTag_ReturnsTrue()
+        {
+            Assert.True(HtmlElementFactory.IsKnown("div"));
+        }
+
+        /// <summary>
+        /// <see cref="HtmlElementFactory.IsKnown"/> returns <c>false</c> for unknown tags.
+        /// </summary>
+        [Fact]
+        public void IsKnown_UnknownTag_ReturnsFalse()
+        {
+            Assert.False(HtmlElementFactory.IsKnown("x-unknown"));
+        }
+
+        /// <summary>
+        /// Passing <c>null</c> to <see cref="HtmlElementFactory.Create"/> throws an
+        /// <see cref="System.ArgumentNullException"/>.
+        /// </summary>
+        [Fact]
+        public void NullTagName_Throws()
+        {
+            Assert.Throws<System.ArgumentNullException>(() => HtmlElementFactory.Create(null));
+        }
+    }
+}