public void CheckGetLast()
        {
            StackStorage stack = new StackStorage();

            stack.addMathToStack("4 + 3");
            stack.addMathToStack("23 + 23");

            string expectedResult = "23 + 23";
            string actualResult   = stack.getLastProblem();

            Assert.AreEqual(expectedResult, actualResult);
        }
        public void CheckIfAddingToStack()
        {
            StackStorage stack = new StackStorage();

            stack.addMathToStack("4 + 3");

            string expectedResult = "4 + 3";
            string actualResult   = stack.Stack.Peek().ToString();

            Assert.AreEqual(expectedResult, actualResult);
        }