diff --git a/src/System.Windows.Forms.Design/tests/UnitTests/System/Windows/Forms/Design/MaskedTextBoxTextEditorDropDownTests.cs b/src/System.Windows.Forms.Design/tests/UnitTests/System/Windows/Forms/Design/MaskedTextBoxTextEditorDropDownTests.cs
new file mode 100644
index 00000000000..8ffbfab8941
--- /dev/null
+++ b/src/System.Windows.Forms.Design/tests/UnitTests/System/Windows/Forms/Design/MaskedTextBoxTextEditorDropDownTests.cs
@@ -0,0 +1,59 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+
+#nullable enable
+
+namespace System.Windows.Forms.Design.Tests;
+
+public class MaskedTextBoxTextEditorDropDownTests
+{
+    [Fact]
+    public void Value_ReturnsNull_WhenCancelled()
+    {
+        using MaskedTextBox maskedTextBox = new();
+        using MaskedTextBoxTextEditorDropDown dropDown = new(maskedTextBox);
+        dropDown.TestAccessor().Dynamic._cancel = true;
+
+        dropDown.Value.Should().BeNull();
+    }
+
+    [Fact]
+    public void Value_ReturnsText_WhenNotCancelled()
+    {
+        using MaskedTextBox maskedTextBox = new("00000");
+        maskedTextBox.Text = "12345";
+        using MaskedTextBoxTextEditorDropDown dropDown = new(maskedTextBox);
+        dropDown.TestAccessor().Dynamic._cancel = false;
+
+        dropDown.Value.Should().Be("12345");
+    }
+
+    [Fact]
+    public void ProcessDialogKey_SetsCancel_WhenEscapePressed()
+    {
+        using MaskedTextBox maskedTextBox = new();
+        using MaskedTextBoxTextEditorDropDown dropDown = new(maskedTextBox);
+        bool processDialogKey = dropDown.TestAccessor().Dynamic.ProcessDialogKey(Keys.Escape);
+        bool cancel= dropDown.TestAccessor().Dynamic._cancel;
+
+        cancel.Should().BeTrue();
+        processDialogKey.Should().BeFalse();
+    }
+
+    [Fact]
+    public void MaskInputRejected_SetsError_WhenInputRejected()
+    {
+        using MaskedTextBox maskedTextBox = new("00：00");
+        using MaskedTextBoxTextEditorDropDown dropDown = new(maskedTextBox);
+        using ErrorProvider errorProvider = dropDown.TestAccessor().Dynamic._errorProvider;
+
+        // No error when setting a correct format value.
+        MaskedTextBox dropDownMaskedTextBox = dropDown.TestAccessor().Dynamic._cloneMtb;
+        dropDownMaskedTextBox.Text = "12：20";
+        errorProvider.GetError(dropDownMaskedTextBox).Should().Be(string.Empty);
+
+        // Incorrectly formatted values will result in the error "Error at position 0: expected number".
+        dropDownMaskedTextBox.Text = "invalid";
+        errorProvider.GetError(dropDownMaskedTextBox).Should().Contain(SR.MaskedTextBoxHintDigitExpected);
+    }
+}