Add code coverage for UpDownBase.UpDownBaseAccessibleObject

src/test/unit/System.Windows.Forms/System/Windows/Forms/AccessibleObjects/UpDownBase.UpDownBaseAccessibleObjectTests.cs

@@ -0,0 +1,49 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+
+namespace System.Windows.Forms.Tests.AccessibleObjects;
+
+public class UpDownBase_UpDownBaseAccessibleObjectTests : IDisposable
+{
+    private readonly TestUpDownBase _upDown;
+    private readonly UpDownBase.UpDownBaseAccessibleObject _accObj;
+
+    public UpDownBase_UpDownBaseAccessibleObjectTests()
+    {
+        _upDown = new();
+        _accObj = new(_upDown);
+    }
+
+    public void Dispose() => _upDown.Dispose();
+
+    [WinFormsFact]
+    public void GetChild_WithValidIndices_ReturnsExpectedChildren()
+    {
+        _accObj.GetChild(0).Should().BeSameAs(_upDown.TextBox.AccessibilityObject.Parent);
+        _accObj.GetChild(1).Should().BeSameAs(_upDown.UpDownButtonsInternal.AccessibilityObject.Parent);
+    }
+
+    [WinFormsTheory]
+    [InlineData(-1)]
+    [InlineData(2)]
+    [InlineData(100)]
+    public void GetChild_WithInvalidIndices_ReturnsNull(int index) =>
+        _accObj.GetChild(index).Should().BeNull();
+
+    [WinFormsFact]
+    public void GetChildCount_WithCustomParents_ReturnsTwo() =>
+        _accObj.GetChildCount().Should().Be(2);
+
+    [WinFormsFact]
+    public void Role_WithCustomParents_ReturnsSpinButton() =>
+        _accObj.Role.Should().Be(AccessibleRole.SpinButton);
+
+    private class TestUpDownBase : UpDownBase
+    {
+        public TestUpDownBase() : base() { }
+
+        public override void DownButton() => throw new NotImplementedException();
+        public override void UpButton() => throw new NotImplementedException();
+        protected override void UpdateEditText() => throw new NotImplementedException();
+    }
+}