public void throws_when_input_data_is_null() //assert
        {
            //arrange
            double[] inputData = null;
            //act
// ReSharper disable ExpressionIsAlwaysNull
            Assert.Throws <ArgumentNullException>(() => AbsoluteReturnMeasures.GainMean(inputData));
// ReSharper restore ExpressionIsAlwaysNull
        }