good-power-plant.scala

import scala.concurrent.ExecutionContext.Implicits.global
import scala.concurrent.Future

trait WaterSupply {
  def turnOn(): Future[Unit]
}

trait PowerPlant {
  def waterSupply: WaterSupply

  def increaseVolumeControl(): Future[Boolean]

  def turnOn(): Future[Boolean] = {
    waterSupply.turnOn().flatMap { _ =>
      increaseVolumeControl()
    }
  }
}