public void Add_of_two_numbers_should_calculate_correct_sum()
        {
            // Arrange
            calculator.Enter(50);
            calculator.Enter(70);

            // Act
            calculator.Add();

            // Assert
            calculator.Result.Should().Be(120);
        }
 public void Given_I_have_entered_NUMBER_into_the_calculator(int number)
 {
     calculator.Enter(number);
 }