Add test for MySql.Data bug 109476.

Author: bgrainger

docs/content/tutorials/migrating-from-connector-net.md

@@ -296,3 +296,4 @@ The following bugs in Connector/NET are fixed by switching to MySqlConnector. (~
 * [#108756](https://bugs.mysql.com/bug.php?id=108756): Can't insert negative number using prepared statement with MySqlDbType.Int24]
 * [#108970](https://bugs.mysql.com/bug.php?id=108970): `MySqlConnectionStringBuilder.ContainsKey` method gives wrong result
 * [#109141](https://bugs.mysql.com/bug.php?id=109141): Insert of data into a table results in `System.ArgumentException`
+* [#109476](https://bugs.mysql.com/bug.php?id=109476): `TransactionScope.Dispose` throws "Connection must be valid and open to rollback"

tests/IntegrationTests/TransactionScopeTests.cs

@@ -683,6 +683,24 @@ public void CommitTwoTransactions()
 		Assert.Equal(new[] { 3, 4 }, values2);
 	}
 
+	[SkippableTheory(MySqlData = "https://bugs.mysql.com/bug.php?id=109476")]
+	[MemberData(nameof(ConnectionStrings))]
+	public void TransactionScopeNullReference(string connectionString)
+	{
+		// see https://bugs.mysql.com/bug.php?id=107110
+		using var scope = new TransactionScope();
+		using var connection = new MySqlConnection($"{AppConfig.ConnectionString};{connectionString}");
+		connection.Open();
+
+		using var command = connection.CreateCommand();
+		command.CommandText = "SELECT * from INFORMATION_SCHEMA.TABLES LIMIT 1; SELECT SLEEP(5);";
+		command.CommandTimeout = 1;
+		if (connection.ServerVersion.IndexOf("MariaDB") == -1)
+			command.ExecuteNonQuery();
+		else
+			Assert.Throws<MySqlException>(() => command.ExecuteNonQuery());
+	}
+
 	[SkippableFact(MySqlData = "Multiple simultaneous connections or connections with different connection strings inside the same transaction are not currently supported.")]
 	public void RollBackTwoTransactions()
 	{