protected void AddNumbers(object sender, EventArgs e)
        {
            if (IsValid)
            {
                var     number1 = double.Parse(numberInput1.Value);
                var     number2 = double.Parse(numberInput2.Value);
                var     number3 = double.Parse(numberInput3.Value);
                Sumator sumator = new Sumator(number1, number2, number3);

                lblResult.Text    = sumator.GetSum().ToString();
                lblResult.Visible = true;
            }
        }
 public void When_SumatorIsInstanciatedWithThreeNumbers_Then_ShouldReturnTheirSum()
 {
     Assert.AreEqual(sumator.GetSum(), 9);
 }