test: Added integrations tests from WinUI for CalendarView and Calend…

…arDatePicker

src/Uno.UI.RuntimeTests/Helpers/DateTimeOffsetExtensions.cs

@@ -0,0 +1,12 @@
+using System;
+
+namespace Uno.UI.RuntimeTests.Helpers
+{
+	internal static class DateTimeOffsetExtensions
+	{
+		internal static long UniversalTime(this DateTimeOffset dto)
+		{
+			return dto.UtcTicks;
+		}
+	}
+}

src/Uno.UI.RuntimeTests/Helpers/ListExtensions.cs

@@ -0,0 +1,18 @@
+using System.Collections.Generic;
+
+namespace Uno.UI.RuntimeTests.Helpers
+{
+	internal static class ListExtensions
+	{
+		// Helpers for WinUI code compatibility
+		internal static T GetAt<T>(this List<T> list, int index) => list[index];
+
+		internal static T GetAt<T>(this IList<T> list, int index) => list[index];
+
+		internal static T GetAt<T>(this IReadOnlyList<T> list, int index) => list[index];
+
+		internal static void SetAt<T>(this IList<T> list, int index, T value) => list[index] = value;
+
+		internal static void Append<T>(this IList<T> list, T item) => list.Add(item);
+	}
+}