Decouple command execution from command creation to allow full unit testing of each.

CommandExecutor.cs

using System.Data;

public interface ICommandExecutor
{
	void ExecuteNonQuery(IDbCommand command);
}

public class CommandExecutor : ICommandExecutor
{
	public void ExecuteNonQuery(IDbCommand command)
	{
		command.ExecuteNonQuery();
	}
}

SqlRepository.cs

using System.Data.SqlClient;

public class SqlRepository
{
	private readonly ICommandExecutor _commandExecutor;
	private readonly string _connectionString;

	public SqlRepository(string connectionString, ICommandExecutor commandExecutor)
	{
		_commandExecutor = commandExecutor;
		_connectionString = connectionString;
	}

	public void Save(SomeObject obj)
	{
		using (var connection = new SqlConnection(_connectionString))
		using (var command = connection.CreateCommand())
		{
			//setup command object
			_commandExecutor.ExecuteNonQuery(command);
		};
	}
}

Delegates command execution to a class designed to execute commands. Allows full testing of repository classes without actually executing commands.