public void Test_Excecute_Null()
 {
     ExceptionAssert.ThrowsArgumentException <ArgumentNullException>(() =>
     {
         TwoColorThreshScript.Execute(null);
     }, "input");
 }
        private void Test_Execute(string input)
        {
            string inputFile = GetInputFile(input);
            string output    = input.Replace(".jpg", ".gif");

            using (var image = new MagickImage(inputFile))
            {
                using (var scriptOutput = TwoColorThreshScript.Execute(image))
                {
                    TestOutput(scriptOutput, output);
                }
            }
        }