public void GetCalculatedSizeNoImageTest()
        {
            // given: calculator
            var calc = new PercentageSizeCalculator();

            // when: getting size with no image
            // then: ArgumentNullException
            Assert.That(() => calc.GetCalculatedSize(null), Throws.ArgumentNullException);
        }
        public void GetCalculatedSizeTest()
        {
            // given: image and calculator
            using (var img = new Image(128, 128))
            {
                var calc = new PercentageSizeCalculator
                {
                    Percentage = 0.5
                };

                // when: getting size
                var size = calc.GetCalculatedSize(img);

                // then: size correct
                Assert.That(size.Width, Is.EqualTo(img.Width * calc.Percentage));
                Assert.That(size.Height, Is.EqualTo(img.Height * calc.Percentage));
            }
        }