public void Retrieve_ValidNumberOfDays_ForecastReturned()
        {
            //Arrange
            var sut          = new WeatherForecastController(null);
            var numberOfDays = 7;

            //Act
            var result = sut.Retrieve(numberOfDays).ToList();

            //Assert
            Assert.IsNotNull(result);
            Assert.AreEqual(numberOfDays, result.Count);
        }