public void CreateTest()
        {
            var factory = new CalculateHandlerFactory();
            var handler = factory.Create();

            Assert.AreEqual(1 + 2 + 3, handler(1, 2, 3));
        }
        public void TestDelegateFactory()
        {
            IFactory <CalculateHandler> factory = new CalculateHandlerFactory();
            CalculateHandler            handler = factory.Create();

            Assert.AreEqual <int>(1 + 2 + 3, handler(1, 2, 3));
        }