## Popup boxes to unit test each of file inputs ##

        popup('My first number is: ' + myNum1)
        popup('My second number is: ' + myNum2)
        popup('My selection is: ' + userSelection)

        if myNum1.isnumeric() and myNum2.isnumeric():
            if userSelection == "Add":
                myResult = MathFunctions.addTwoNumbers(myNum1, myNum2)
                popup(returnMessage())
            #Use the print statements to show that the program continues
            elif userSelection == "Subtract":
                myResult = MathFunctions.subtractTwoNumbers(myNum1, myNum2)
                popup(returnMessage())
            elif userSelection == "Multiply":
                popup(
                    returnMessage2(
                        MathFunctions.multiplyTwoNumbers(myNum1, myNum2)))
            elif userSelection == "Divide":
                if int(myNum2) == 0:
                    popup("You can't divide by Zero!")
                else:
                    myResult = MathFunctions.divideTwoNumbers(myNum1, myNum2)
                    popup(returnMessage())
        else:
            popup("Please check the file")

    ## Thank the user to signify the end of the application run ##
    popup("Thank you for using the simple calculator")