Add code coverage for DataGridViewButtonColumn (#12814)

related #10453

Proposed changes
Add unit tests for DataGridViewButtonColumn.cs to test its methods & properties

src/System.Windows.Forms/tests/UnitTests/System/Windows/Forms/DataGridViewButtonColumnTests.cs

@@ -0,0 +1,205 @@
+// 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.Drawing;
+
+namespace System.Windows.Forms.Tests;
+
+public class DataGridViewButtonColumnTests : IDisposable
+{
+    private readonly DataGridView _dataGridView;
+    private readonly DataGridViewButtonColumn _column;
+
+    public DataGridViewButtonColumnTests()
+    {
+        _dataGridView = new();
+        _column = new();
+    }
+
+    public void Dispose()
+    {
+        _dataGridView?.Dispose();
+        _column?.Dispose();
+    }
+
+    [Fact]
+    public void DataGridViewButtonColumn_FlatStyle_GetSet_ReturnsExpected()
+    {
+        _column.FlatStyle.Should().Be(FlatStyle.Standard);
+
+        _column.FlatStyle = FlatStyle.Flat;
+        _column.FlatStyle.Should().Be(FlatStyle.Flat);
+
+        _column.FlatStyle = FlatStyle.Popup;
+        _column.FlatStyle.Should().Be(FlatStyle.Popup);
+
+        _column.FlatStyle = FlatStyle.System;
+        _column.FlatStyle.Should().Be(FlatStyle.System);
+    }
+
+    [Fact]
+    public void DataGridViewButtonColumn_FlatStyle_SetWithDataGridView_UpdatesRows()
+    {
+        _dataGridView.Columns.Add(_column);
+
+        using DataGridViewRow row = new();
+        row.Cells.Add(new DataGridViewButtonCell());
+        _dataGridView.Rows.Add(row);
+
+        _column.FlatStyle = FlatStyle.Flat;
+        ((DataGridViewButtonCell)row.Cells[0]).FlatStyle.Should().Be(FlatStyle.Flat);
+
+        _column.FlatStyle = FlatStyle.Popup;
+        ((DataGridViewButtonCell)row.Cells[0]).FlatStyle.Should().Be(FlatStyle.Popup);
+    }
+
+    [Fact]
+    public void DataGridViewButtonColumn_FlatStyle_SetNullButtonCellTemplate_ThrowsInvalidOperationException()
+    {
+        _column.GetType().GetProperty("CellTemplate")!.SetValue(_column, null);
+
+        Action action = () => { var flatStyle = _column.FlatStyle; };
+        action.Should().Throw<InvalidOperationException>();
+    }
+
+    [Fact]
+    public void DataGridViewButtonColumn_Text_Set_GetReturnsExpected()
+    {
+        _column.Text.Should().BeNull();
+
+        _column.Text = "Test";
+        _column.Text.Should().Be("Test");
+    }
+
+    [Fact]
+    public void DataGridViewButtonColumn_UseColumnTextForButtonValue_Set_GetReturnsExpected()
+    {
+        _column.UseColumnTextForButtonValue.Should().BeFalse();
+
+        _column.UseColumnTextForButtonValue = true;
+        _column.UseColumnTextForButtonValue.Should().BeTrue();
+    }
+
+    [Fact]
+    public void DataGridViewButtonColumn_UseColumnTextForButtonValue_SetWithDataGridView_UpdatesRows()
+    {
+        _dataGridView.Columns.Add(_column);
+
+        using DataGridViewRow row = new();
+        using DataGridViewButtonCell cell = new();
+        row.Cells.Add(cell);
+        _dataGridView.Rows.Add(row);
+
+        ((DataGridViewButtonCell)row.Cells[0]).UseColumnTextForButtonValue.Should().BeFalse();
+
+        _column.UseColumnTextForButtonValue = true;
+        ((DataGridViewButtonCell)row.Cells[0]).UseColumnTextForButtonValue.Should().BeTrue();
+    }
+
+    [Fact]
+    public void DataGridViewButtonColumn_UseColumnTextForButtonValue_SetNullButtonCellTemplate_ThrowsInvalidOperationException()
+    {
+        _column.GetType().GetProperty("CellTemplate")!.SetValue(_column, null);
+
+        Action action = () => { bool useColumnTextForButtonValue = _column.UseColumnTextForButtonValue; };
+        action.Should().Throw<InvalidOperationException>();
+    }
+
+    [Fact]
+    public void DataGridViewButtonColumn_Clone_ReturnsExpected()
+    {
+        _column.Text = "Test";
+        _column.FlatStyle = FlatStyle.Flat;
+        _column.UseColumnTextForButtonValue = true;
+
+        var clone = (DataGridViewButtonColumn)_column.Clone();
+        clone.Text.Should().Be("Test");
+        clone.FlatStyle.Should().Be(FlatStyle.Flat);
+        clone.UseColumnTextForButtonValue.Should().BeTrue();
+    }
+
+    [Fact]
+    public void DataGridViewButtonColumn_Clone_WithDifferentType_ReturnsExpected()
+    {
+        CustomDataGridViewButtonColumn customColumn = new()
+        {
+            Text = "Test",
+            FlatStyle = FlatStyle.Flat,
+            UseColumnTextForButtonValue = true
+        };
+
+        var clone = (CustomDataGridViewButtonColumn)customColumn.Clone();
+        clone.Text.Should().Be("Test");
+        clone.FlatStyle.Should().Be(FlatStyle.Flat);
+        clone.UseColumnTextForButtonValue.Should().BeTrue();
+    }
+
+    [Fact]
+    public void DataGridViewButtonColumn_ToString_ReturnsExpected()
+    {
+        _column.ToString().Should().Be("DataGridViewButtonColumn { Name=, Index=-1 }");
+
+        _column.Name = "TestColumn";
+        _column.ToString().Should().Be("DataGridViewButtonColumn { Name=TestColumn, Index=-1 }");
+    }
+
+    [Fact]
+    public void DataGridViewButtonColumn_DefaultCellStyle_GetSet_ReturnsExpected()
+    {
+        DataGridViewCellStyle style = _column.DefaultCellStyle;
+        style.Alignment.Should().Be(DataGridViewContentAlignment.MiddleCenter);
+
+        DataGridViewCellStyle newStyle = new DataGridViewCellStyle { Alignment = DataGridViewContentAlignment.BottomRight };
+        _column.DefaultCellStyle = newStyle;
+        _column.DefaultCellStyle.Alignment.Should().Be(DataGridViewContentAlignment.BottomRight);
+    }
+
+    [Fact]
+    public void DataGridViewButtonColumn_CellTemplate_SetInvalidType_ThrowsInvalidCastException()
+    {
+        Action action = () => _column.CellTemplate = new DataGridViewTextBoxCell();
+        action.Should().Throw<InvalidCastException>();
+    }
+
+    [Fact]
+    public void DataGridViewButtonColumn_CellTemplate_SetValidType_GetReturnsExpected()
+    {
+        using DataGridViewButtonCell cell = new();
+        _column.CellTemplate = cell;
+        _column.CellTemplate.Should().Be(cell);
+    }
+
+    [Fact]
+    public void DataGridViewButtonColumn_Clone_CopiesProperties()
+    {
+        _column.Text = "Test";
+        _column.FlatStyle = FlatStyle.Flat;
+        _column.UseColumnTextForButtonValue = true;
+        _column.DefaultCellStyle = new DataGridViewCellStyle { Alignment = DataGridViewContentAlignment.BottomRight };
+
+        var clone = (DataGridViewButtonColumn)_column.Clone();
+        clone.Text.Should().Be("Test");
+        clone.FlatStyle.Should().Be(FlatStyle.Flat);
+        clone.UseColumnTextForButtonValue.Should().BeTrue();
+        clone.DefaultCellStyle.Alignment.Should().Be(DataGridViewContentAlignment.BottomRight);
+    }
+
+    [Fact]
+    public void DataGridViewButtonColumn_ShouldSerializeDefaultCellStyle_ReturnsExpected()
+    {
+        dynamic accessor = _column.TestAccessor().Dynamic;
+
+        bool result = accessor.ShouldSerializeDefaultCellStyle();
+        result.Should().BeFalse();
+
+        _column.DefaultCellStyle.BackColor = Color.Red;
+        result = accessor.ShouldSerializeDefaultCellStyle();
+        result.Should().BeTrue();
+    }
+
+    private class CustomDataGridViewButtonColumn : DataGridViewButtonColumn
+    {
+    }
+}