public void OnAlienDeath()
        {
            //arrange
            int lives = 1;
            //int score=10;
            ScoreAndLife sl = new ScoreAndLife(lives, laserFactory, bombFactory);

            //act
            sl.OnAlienDeath(20);
            int result = sl.Score;

            //assert
            Assert.AreEqual(20, result); //expected, actual
        }