public void ConstantTestGetExpressionWithOtherConstants()
        {
            Constant constant = new Constant();
            string input = "x = 12 + 12";
            constant.ChangeExpression(input);
            constant.GetExpression();
            constant.ChangeExpression("y = x + 2");
            int expected = 26;

            Assert.AreEqual(expected, constant.GetExpression());
        }
        public void ConstantTestGetExpressionWithIncorrectValues()
        {
            string input = "x = y + 1";
            Constant constant = new Constant(input);
            int expected = 5;

            Assert.AreEqual(expected, constant.GetExpression());
        }
        public void ConstantTestGetExpressionWithOneThingOneRightSide()
        {
            Constant constant = new Constant();
            string input = "x = 12";
            constant.ChangeExpression(input);
            int expected = 12;

            Assert.AreEqual(expected, constant.GetExpression());
        }
        public void ConstantTestGetExpression()
        {
            string input = "x = 12 + 12";
            Constant constant = new Constant();
            constant.ChangeExpression(input);
            int expected = 24;

            Assert.AreEqual(expected, constant.GetExpression());
        }
 static void Main(string[] args)
 {
     Console.WriteLine("Calculator");
     int count = 0;
     string input;
     Constant constant = new Constant();
     while (true)
     {
         Console.Write("[{0}]> ", count);
         input = Console.ReadLine();
         if(input == "exit" || input == "quit")
         {
             Console.WriteLine("loggin out");
             break;
         }
         ProcessInput PI = new ProcessInput(input);
         try
         {
             Evaluate ev = new Evaluate(PI.GetFirstInputNumber(), PI.GetOperator(), PI.GetSecondInputNumber());
             Console.WriteLine("   = " + ev.Operate());
         }
         catch
         {
             constant.ChangeExpression(input);
             try
             {
                 Console.WriteLine(constant.GetExpression());
             }
             catch
             {
                 Console.WriteLine("Error! Try again . . .");
             }
         }
         count++;
     }
 }
        public void ConstantTestIfReturnsValueOfConstant()
        {
            Constant constant = new Constant();
            constant.AddToConstants('x', 12);
            constant.ChangeExpression("x");

            Assert.AreEqual(12, constant.GetExpression());
        }