public IList <string> GenerateRandomFiles(string directoryRoot = "TestData", int subFolderCount = 2, int filesInFolderCount = 2)
        {
            List <string> files = new List <string>();

            string fileNamePrefix = "file";
            string fileExt        = "txt";

            for (int i = 0; i < subFolderCount; i++)
            {
                string fullFolder = Path.Combine(directoryRoot, $"folder{i}");
                Directory.CreateDirectory(fullFolder);

                for (int j = 0; j < filesInFolderCount; j++)
                {
                    string fileName     = $"{fileNamePrefix}{j}.{fileExt}";
                    string fullFileName = Path.Combine(fullFolder, fileName);
                    string text         = GuidUtils.NewGuid().ToString();
                    File.AppendAllText(fullFileName, text);

                    files.Add(fullFileName);
                }
            }

            return(files);
        }