public void TestMulardDuck()
        {
            Duck mulard = new Duck(new IStrategyCall_Qual());

            Assert.AreEqual("Qual", mulard.Call());
        }
        public void TestPlainDuck()
        {
            Duck regularDuck = new Duck(new IStrategyCall_Quack());

            Assert.AreEqual("Quack", regularDuck.Call());
        }