testfixture_withtest.cs

public class given_an_instance_of_calculation_controller
{
  [Fact]
  public void assert_that_given_two_numbers_the_result_returned_is_the_correct_sum()
  {
    // arrange
    var controller = new CalculationController();
    var viewModel = new TwoNumberViewModel
    {
      FirstNumber = 10,
      SecondNumber = 20
    };
    
    // act
    var result = controller.Add(viewModel) as OkObjectResult;
    
    // assert
    Assert.NotNull(result);
    Assert.Equal("30", result.Value.ToString());
  }
}