SpecFlow MathIdiot 01

using System;
using TechTalk.SpecFlow;
using Microsoft.VisualStudio.TestTools.UnitTesting;

namespace MyNamespace {
    [Binding]
    public class StepDefinitions {
        public int NumberToAdd { get; private set; }

        private StepDefinitions() {
            NumberToAdd = 0;
        }

        [Given(@"I have entered (.*) into the calculator")]
        public void GivenIHaveEnteredIntoTheCalculator(int numberToAdd) {
            NumberToAdd += numberToAdd;
        }

        [When(@"I press add")]
        public void WhenIPressAdd() {
           //nothing to do
        }

        [Then(@"the result should be (.*) on the screen")]
        public void ThenTheResultShouldBeOnTheScreen(int expectedSum) {
            Assert.AreEqual(expectedSum, NumberToAdd);
        }
    }
}