private void btnConvertInt_MouseUp(object sender, MouseEventArgs e)
 {
     lblOutput.Text = NumberFormatter.Spell(txtUnsignedInt.Text);
 }
 private void btnConvertString_MouseUp(object sender, MouseEventArgs e)
 {
     lblOutput.Text = NumberFormatter.Spell(txtString.Text);
 }
        public void Spell(int input, string expected)
        {
            string actual = NumberFormatter.Spell(input.ToString());

            Assert.Equal(expected, actual);
        }