diff --git a/src/System.Windows.Forms.Design/tests/UnitTests/System/Windows/Forms/Design/MaskedTextBoxDesignerTests.cs b/src/System.Windows.Forms.Design/tests/UnitTests/System/Windows/Forms/Design/MaskedTextBoxDesignerTests.cs
index 9e0b26a8987..8925716b5f1 100644
--- a/src/System.Windows.Forms.Design/tests/UnitTests/System/Windows/Forms/Design/MaskedTextBoxDesignerTests.cs
+++ b/src/System.Windows.Forms.Design/tests/UnitTests/System/Windows/Forms/Design/MaskedTextBoxDesignerTests.cs
@@ -1,43 +1,138 @@
 // Licensed to the .NET Foundation under one or more agreements.
 // The .NET Foundation licenses this file to you under the MIT license.
 
+#nullable enable
+
+using System.ComponentModel;
+using System.ComponentModel.Design;
+using System.Globalization;
+using Moq;
+
 namespace System.Windows.Forms.Design.Tests;
 
-public sealed class MaskedTextBoxDesignerTests
+public sealed class MaskedTextBoxDesignerTests : IDisposable
 {
-    [Fact]
-    public void SnapLines_WithDefaultMaskedTextBox_ShouldReturnExpectedCount()
+    private readonly MaskedTextBox _maskedTextBox = new();
+    private readonly MaskedTextBoxDesigner _maskedTextBoxDesigner = new();
+
+    public MaskedTextBoxDesignerTests()
     {
-        using MaskedTextBoxDesigner maskedTextBoxDesigner = new();
-        using MaskedTextBox maskedTextBox = new();
-        maskedTextBoxDesigner.Initialize(maskedTextBox);
+        _maskedTextBoxDesigner.Initialize(_maskedTextBox);
+    }
 
-        maskedTextBoxDesigner.SnapLines.Count.Should().Be(9);
+    public void Dispose()
+    {
+        _maskedTextBox.Dispose();
+        _maskedTextBoxDesigner.Dispose();
     }
 
+    [Fact]
+    public void SnapLines_WithDefaultMaskedTextBox_ShouldReturnExpectedCount() => _maskedTextBoxDesigner.SnapLines.Count.Should().Be(9);
+
     [Fact]
     public void SelectionRules_WithDefaultMaskedTextBox_ShouldReturnExpectedValue()
     {
-        using MaskedTextBoxDesigner maskedTextBoxDesigner = new();
-        using MaskedTextBox maskedTextBox = new();
-        maskedTextBoxDesigner.Initialize(maskedTextBox);
-
         SelectionRules selectionRules;
         using (new NoAssertContext())
         {
-            selectionRules = maskedTextBoxDesigner.SelectionRules;
+            selectionRules = _maskedTextBoxDesigner.SelectionRules;
         }
 
         selectionRules.Should().Be(SelectionRules.LeftSizeable | SelectionRules.RightSizeable | SelectionRules.Moveable | SelectionRules.Visible);
     }
 
     [Fact]
-    public void Verbs_WithDefaultMaskedTextBox_ShouldReturnExpectedCount()
+    public void Verbs_WithDefaultMaskedTextBox_ShouldReturnExpectedCount() => _maskedTextBoxDesigner.Verbs.Count.Should().Be(1);
+
+    [Fact]
+    public void Verbs_WithDefaultMaskedTextBox_ShouldContainSetMaskVerb()
     {
-        using MaskedTextBoxDesigner maskedTextBoxDesigner = new();
-        using MaskedTextBox maskedTextBox = new();
-        maskedTextBoxDesigner.Initialize(maskedTextBox);
+        DesignerVerbCollection verbs = _maskedTextBoxDesigner.Verbs;
+
+        verbs.Should().NotBeNull();
+        verbs.Count.Should().BeGreaterThan(0);
+        DesignerVerb? firstVerb = verbs.Count > 0 ? verbs[0] : null;
+        firstVerb.Should().NotBeNull();
+        firstVerb!.Text.Should().Be(SR.MaskedTextBoxDesignerVerbsSetMaskDesc);
+    }
+
+    [Fact]
+    public void GetDesignMaskedTextBox_WithNullInput_ShouldReturnDefaultMaskedTextBox()
+    {
+        using MaskedTextBox designMaskedTextBox = MaskedTextBoxDesigner.GetDesignMaskedTextBox(null!);
+        designMaskedTextBox.Should().NotBeNull();
+        designMaskedTextBox.Mask.Should().BeEmpty();
+        designMaskedTextBox.Text.Should().BeEmpty();
+    }
+
+    [Fact]
+    public void GetDesignMaskedTextBox_WithMaskedTextBox_ShouldCloneProperties()
+    {
+        using MaskedTextBox maskedTextBox = new()
+        {
+            Text = "123",
+            ValidatingType = typeof(int),
+            BeepOnError = true,
+            InsertKeyMode = InsertKeyMode.Overwrite,
+            RejectInputOnFirstFailure = true,
+            CutCopyMaskFormat = MaskFormat.IncludePrompt,
+            Culture = new CultureInfo("en-US")
+        };
+
+        using MaskedTextBox designMaskedTextBox = MaskedTextBoxDesigner.GetDesignMaskedTextBox(maskedTextBox);
+        designMaskedTextBox.Should().NotBeNull();
+        designMaskedTextBox.Text.Should().Be("123");
+        designMaskedTextBox.ValidatingType.Should().Be(typeof(int));
+        designMaskedTextBox.BeepOnError.Should().BeTrue();
+        designMaskedTextBox.InsertKeyMode.Should().Be(InsertKeyMode.Overwrite);
+        designMaskedTextBox.RejectInputOnFirstFailure.Should().BeTrue();
+        designMaskedTextBox.CutCopyMaskFormat.Should().Be(MaskFormat.IncludePrompt);
+        designMaskedTextBox.Culture.Should().Be(new CultureInfo("en-US"));
+    }
+
+    [Fact]
+    public void ActionLists_WithDefaultMaskedTextBox_ShouldReturnExpectedCount()
+    {
+        IServiceContainer serviceContainer = new Mock<IServiceContainer>().Object;
+        ITypeDiscoveryService typeDiscoveryService = new Mock<ITypeDiscoveryService>().Object;
+        IUIService uiService = new Mock<IUIService>().Object;
+        ISite mockSite = new Mock<ISite>().Object;
+
+        Mock<IServiceContainer> mockServiceContainer = new();
+        mockServiceContainer.Setup(s => s.GetService(typeof(ITypeDiscoveryService))).Returns(typeDiscoveryService);
+        mockServiceContainer.Setup(s => s.GetService(typeof(IUIService))).Returns(uiService);
+
+        Mock<ISite> mockMockSite = new();
+        mockMockSite.Setup(s => s.GetService(typeof(IServiceContainer))).Returns(mockServiceContainer.Object);
+        mockMockSite.Setup(s => s.GetService(typeof(ITypeDiscoveryService))).Returns(typeDiscoveryService);
+        mockMockSite.Setup(s => s.GetService(typeof(IUIService))).Returns(uiService);
+
+        _maskedTextBoxDesigner.Component.Site = mockMockSite.Object;
+
+        DesignerActionListCollection actionLists = _maskedTextBoxDesigner.ActionLists;
+        actionLists.Count.Should().Be(1);
+    }
+
+    [Fact]
+    public void ActionLists_WithDefaultMaskedTextBox_ShouldReturnExpectedType()
+    {
+        IServiceContainer serviceContainer = new Mock<IServiceContainer>().Object;
+        ITypeDiscoveryService typeDiscoveryService = new Mock<ITypeDiscoveryService>().Object;
+        IUIService uiService = new Mock<IUIService>().Object;
+        ISite mockSite = new Mock<ISite>().Object;
+
+        Mock<IServiceContainer> mockServiceContainer = new();
+        mockServiceContainer.Setup(s => s.GetService(typeof(ITypeDiscoveryService))).Returns(typeDiscoveryService);
+        mockServiceContainer.Setup(s => s.GetService(typeof(IUIService))).Returns(uiService);
+
+        Mock<ISite> mockMockSite = new();
+        mockMockSite.Setup(s => s.GetService(typeof(IServiceContainer))).Returns(mockServiceContainer.Object);
+        mockMockSite.Setup(s => s.GetService(typeof(ITypeDiscoveryService))).Returns(typeDiscoveryService);
+        mockMockSite.Setup(s => s.GetService(typeof(IUIService))).Returns(uiService);
+
+        _maskedTextBoxDesigner.Component.Site = mockMockSite.Object;
 
-        maskedTextBoxDesigner.Verbs.Count.Should().Be(1);
+        DesignerActionListCollection actionLists = _maskedTextBoxDesigner.ActionLists;
+        actionLists[0].Should().BeOfType<MaskedTextBoxDesignerActionList>();
     }
 }