text: import { WildDuck, DuckLearnFly, FlyWithWings } from '../behavioral/strategy';
  describe('', () => {
    test('should delegate', () => {
      let duck = new WildDuck();
      expect(duck.performFly()).toBe('I can fly with wings');
    });
    test('should change behavior', () => {
      let duck = new DuckLearnFly();
      expect(duck.performFly()).toBe("I can't fly");
      duck.setFlyBehavior(new FlyWithWings());
      expect(duck.performFly()).toBe('I can fly with wings');
    });
  });
  