test: WIP, fix an issue when passing year event.

tests/HeadlessTest.Ursa/Controls/DateTimePicker/CalendarYearButtonTests.cs

@@ -0,0 +1,96 @@
+using System.Globalization;
+using Avalonia;
+using Avalonia.Controls;
+using Avalonia.Headless;
+using Avalonia.Headless.XUnit;
+using Avalonia.Input;
+using Ursa.Controls;
+
+namespace HeadlessTest.Ursa.Controls.DateTimePicker;
+
+public class CalendarYearButtonTests
+{
+    [AvaloniaFact]
+    public void SetContext_YearMode_SetsContentToAbbreviatedMonthName()
+    {
+        var button = new CalendarYearButton();
+        var context = new CalendarContext(null, 5);
+        button.SetContext(CalendarViewMode.Year, context);
+        Assert.Equal("May", button.Content);
+    }
+    
+    [AvaloniaFact]
+    public void SetContext_YearMode_SetsContentToAbbreviatedMonthName_Chinese()
+    {
+        CultureInfo.CurrentCulture = new CultureInfo("zh-CN");
+        var button = new CalendarYearButton();
+        var context = new CalendarContext(null, 5);
+        button.SetContext(CalendarViewMode.Year, context);
+        Assert.Equal("5月", button.Content);
+    }
+
+    [AvaloniaFact]
+    public void SetContext_DecadeMode_SetsContentToYear()
+    {
+        var button = new CalendarYearButton();
+        var context = new CalendarContext(2023);
+        button.SetContext(CalendarViewMode.Decade, context);
+        Assert.Equal("2023", button.Content);
+    }
+
+    [AvaloniaFact]
+    public void SetContext_CenturyMode_SetsContentToYearRange()
+    {
+        var button = new CalendarYearButton();
+        var context = new CalendarContext(null, null, 1900, 1999);
+        button.SetContext(CalendarViewMode.Century, context);
+        Assert.Equal("1900-1999", button.Content);
+    }
+
+    [AvaloniaFact]
+    public void SetContext_InvalidYear_DisablesButton()
+    {
+        var button = new CalendarYearButton();
+        var context = new CalendarContext(null, null, -1);
+        button.SetContext(CalendarViewMode.Decade, context);
+        Assert.False(button.IsEnabled);
+    }
+    
+    [AvaloniaFact]
+    public void SetContext_Month_Mode_DisablesButton()
+    {
+        var button = new CalendarYearButton();
+        var context = new CalendarContext(1, 1);
+        button.SetContext(CalendarViewMode.Month, context);
+        Assert.False(button.IsEnabled);
+    }
+    
+    [AvaloniaFact]
+    public void OnPointerReleased_RaisesItemSelectedEvent()
+    {
+
+        var button = new CalendarYearButton();
+        var context = new CalendarContext(2023, 5);
+        button.SetContext(CalendarViewMode.Year, context);
+        int eventRaised = 0;
+        CalendarContext? eventContext = null;
+        void OnItemSelected( object? sender, CalendarYearButtonEventArgs args)
+        {
+            eventRaised++;
+            eventContext = args.Context;
+        }
+        button.ItemSelected += OnItemSelected;
+        Window window = new Window();
+        window.Content = button;
+        window.Show();
+        window.MouseUp(new Point(10, 10), MouseButton.Left);
+        Assert.Equal(1, eventRaised);
+        Assert.Equal(context, eventContext);
+        button.ItemSelected -= OnItemSelected;
+        eventContext = null;
+        window.MouseUp(new Point(10, 10), MouseButton.Left);
+        Assert.Null(eventContext);
+        Assert.Equal(1, eventRaised);
+
+    }
+}