Facade.ts

class EngineSystem {
    activate() {
      console.log('Activate the engine');
    }
  }
  
  class MonitorSystem {
    check() {
      console.log('Check system situations');
    }
  }
  
  class OxygenSystem {
    generate() {
      console.log('Oxygen will be generated');
    }
  }
  
  class RocketTestingOperation {
  
    private _engineSys: EngineSystem;
    private _monitorSys: MonitorSystem;
    private _oxygenSys: OxygenSystem;
  
    constructor() {
      this._engineSys = new EngineSystem();
      this._monitorSys = new MonitorSystem();
      this._oxygenSys = new OxygenSystem();
    }
  
    operationStart() {
      this._monitorSys.check();
      this._oxygenSys.generate();
      this._engineSys.activate();
  
    }
  }
  
// USAGE:
const operation = new RocketTestingOperation();
operation.operationStart();
// OUTPUT:
// "Check system situations"
// "Oxygen will be generated"
// "Activate the engine"