public void RGBtoHSL_ArgumentNullException()
 {
     Assert.Throws <ArgumentNullException>(() => ColorModelConverter.RGBtoHSL(null));
 }
        public void RGBtoHSL_CorrectCalculation(RGB rgb, HSL expected)
        {
            HSL result = ColorModelConverter.RGBtoHSL(rgb);

            Assert.That(result, Is.EqualTo(expected));
        }