test: add unit tests for PackageRegistration to verify package addition and default state in ShellDocsOptions

Author: Shewart

tests/ShellDocs.Tests/PackageRegistrationTests.cs

@@ -0,0 +1,30 @@
+using ShellDocs.Components;
+using Xunit;
+
+namespace ShellDocs.Tests;
+
+public class PackageRegistrationTests
+{
+    [Fact]
+    public void AddPackage_FluentChain_AppendsInOrder()
+    {
+        var options = new ShellDocsOptions()
+            .AddPackage("core",       "Core",       "Foundation.",  "/docs/core")
+            .AddPackage("components", "Components", "Widgets.",     "/docs/components", iconPath: "M0 0h10v10H0z");
+
+        Assert.Equal(2, options.Packages.Count);
+        Assert.Equal("core",       options.Packages[0].Id);
+        Assert.Equal("Core",       options.Packages[0].Title);
+        Assert.Equal("/docs/core", options.Packages[0].RootUrl);
+        Assert.Null(options.Packages[0].IconPath);
+        Assert.Equal("components",         options.Packages[1].Id);
+        Assert.Equal("M0 0h10v10H0z",      options.Packages[1].IconPath);
+    }
+
+    [Fact]
+    public void Packages_DefaultToEmpty_SoSelectorHides()
+    {
+        var options = new ShellDocsOptions();
+        Assert.Empty(options.Packages);
+    }
+}