How to break the database access class of a Repository

问题

I have the following tightly coupled database access class (repository), that is hard to unit test:

class EmployeesRepository : IEmployeeRepository ...

public IEnumerable<Employee> GetAllEmployees()
{
    List<Employee> list = new List<Employee>();

    try
    {           
        string connectionString = _secureConfig.Value.MyDbSetting;
        
        string sql = "select id, firstname, lastname, entrydate, email from empoyees";
        using SqlConnection connection = new SqlConnection(connectionString);
        using SqlCommand command = new SqlCommand(sql, connection);
        connection.Open();

        using SqlDataReader reader = command.ExecuteReader();
        while (reader.Read())
        {
            list.Add(new Employee
            {
                Id = reader.GetString(0),
                FirstName = reader.GetString(1),
                LastName = reader.GetString(2),
                EntryDate = reader.GetDateTime(3),
                Email = (reader.IsDBNull(4) ? null : reader.GetString(4))
            });
        }
    }
    catch (Exception ex)
    {
        _log.LogError(ex, "An error is caught when getting all employees");
    }
    return list;
}

sometimes the same code uses command.ExecuteNonQuery(), there are also sometimes connection.BeginTransaction()...

My question is what is the pattern should be used to decouple this class into logical units, in order to facilitate integration testing.

来源：https://stackoverflow.com/questions/65599782/how-to-break-the-database-access-class-of-a-repository