gistfile1.rb

class Updater
  def self.update_total_points(employee)
    employee.total_points = employee.rocket_actions.sum(:points)
    gateway.persist_employee_total(employee)
  end
  
  def gateway
    if defined? Rails
      rails gateway
    else
      mem gateway
    end
  end
end

AR
Updater.update_total_points(Employee.find(1))
expect(employee.total_points).to eql(123)

Mem
employee = OpenStruct.new({
    :total_points => 0,
    :rocket_actions => [
        OpenStruct.new({ :points => 123 })
      ]
  })
Updater.update_total_points(employee)
expect(employee.total_points).to eql(123)