public void Chain_of_Responsibility_Pattern_Test()
        {
            var first  = new FirstStep();
            var second = new SecondStep();
            var third  = new ThirdStep();

            first.Next(second).Next(third);

            Assert.IsTrue((bool)first.Handler(NumberEnum.One));
            Assert.IsTrue((bool)first.Handler(NumberEnum.Two));
            Assert.IsTrue((bool)first.Handler(NumberEnum.Three));
            Assert.IsNull(first.Handler(NumberEnum.Four));
        }