Added test for default value (not reset on ChangeColumn)

Author: JaBistDuNarrisch

src/Migrator.Tests/Providers/Generic/Generic_ChangeColumnTestsBase.cs

@@ -1,4 +1,7 @@
+using System;
+using System.Collections.Generic;
 using System.Data;
+using System.Linq;
 using DotNetProjects.Migrator.Framework;
 using Migrator.Tests.Providers.Base;
 using NUnit.Framework;
@@ -30,4 +33,41 @@ public void ChangeColumn_NotNullAndNullToNotNull_Success()
         Assert.That(column1.ColumnProperty.HasFlag(ColumnProperty.NotNull), Is.True);
         Assert.That(column2.ColumnProperty.HasFlag(ColumnProperty.NotNull), Is.True);
     }
+
+    [Test, Ignore("Not yet implemented. See issue https://github.com/dotnetprojects/Migrator.NET/issues/139")]
+    public void ChangeColumn_RemoveDefaultValue_Success()
+    {
+        // Arrange
+        var tableName = "TableName";
+        var column1Name = "Column1";
+        var column2Name = "Column2";
+
+        var testTime = new DateTime(2025, 5, 5, 5, 5, 5, DateTimeKind.Utc);
+
+        Provider.AddTable(tableName,
+            new Column(name: column1Name, type: DbType.Int32, property: ColumnProperty.NotNull),
+            new Column(name: column2Name, type: DbType.DateTime2, property: ColumnProperty.Null, defaultValue: testTime)
+        );
+
+        // Act
+        Provider.Insert(table: tableName, [column1Name], [1]);
+        Provider.ChangeColumn(table: tableName, column: new Column(name: column2Name, type: DbType.DateTime2, property: ColumnProperty.Null));
+
+        // Assert
+        Provider.Insert(table: tableName, [column1Name], [2]);
+
+        using var cmd = Provider.CreateCommand();
+        using var reader = Provider.Select(cmd: cmd, table: tableName, columns: [column1Name, column2Name]);
+
+        List<(int, DateTime)> records = [];
+
+        while (reader.Read())
+        {
+            records.Add((reader.GetInt32(0), reader.GetDateTime(1)));
+        }
+
+        Assert.That(records.Count, Is.EqualTo(2));
+        Assert.That(records.Single(x => x.Item1 == 1).Item2, Is.EqualTo(testTime));
+        Assert.That(records.Single(x => x.Item1 == 2).Item2, Is.Null);
+    }
 }

src/Migrator.Tests/Providers/SQLServer/SQLServerTransformationProvider_ChangeColumnTests.cs

@@ -8,7 +8,7 @@ namespace Migrator.Tests.Providers.SQLServer;
 
 [TestFixture]
 [Category("SqlServer")]
-public class SQLServerTransformationProvider_ChangeColumnTests : Generic_AddIndexTestsBase
+public class SQLServerTransformationProvider_ChangeColumnTests : Generic_ChangeColumnTestsBase
 {
     [SetUp]
     public async Task SetUpAsync()