public void Fibonacci_ShouldReturn_CorrectIndex_FromSeries()
{
var expectedResult = 21;
_calculations.GetFibonacciNumber(Arg.Any <long>()).Returns(expectedResult);
var actionResult = _valuesController.Fibonacci(8);
var contentResult = actionResult as OkNegotiatedContentResult <string>;
Assert.IsNotNull(contentResult);
Assert.AreEqual(Convert.ToInt64(contentResult.Content), expectedResult);
}