public void Result_WhenUnsupportedOperatorProvided_ShouldThrowException()
        {
            // Arrange
            var post = new PostfixCalc();

            // Act, Assert
            post.Result("4,2,^");
        }
        public void Result_WhenTheFirstInputValueIsNotInteger_ShouldThrowException()
        {
            // Arrange
            var post = new PostfixCalc();

            // Act, Assert
            post.Result(",1,4+");
        }
        public void Result_WhenThereIsNoInput_ShouldThrowException()
        {
            // Arrange
            var post = new PostfixCalc();

            // Act, Assert
            post.Result(string.Empty);
        }
        public void Result_ShouldCalculate_ExpectedOutput()
        {
            // Arrange
            var post = new PostfixCalc();

            // Act
            var output = post.Result("3,5,+");

            // Assert
            Assert.AreEqual(8, output, "Should be 8.");
        }