public void CheckSortNatural()
        {
            var result = new List <string>();

            FilePathUtility.Sort(source_paths, result);

            var sb = new StringBuilder();

            sb.Append("sorted path = [\n");
            foreach (var path in result)
            {
                sb.Append($"  {path}\n");
            }
            sb.Append("]\n");
            Debug.Log(sb);

            Assert.IsTrue(CheckEquals(result,
                                      new string[] { "02file_4_sample_00.dat",
                                                     "02file_10_sample_00.dat",
                                                     "data777_pattern2.csv",
                                                     "data00777_pattern2.csv",
                                                     "data777_pattern2.csv2",
                                                     "data777_pattern2.csvext",
                                                     "file_008_sample_2.dat",
                                                     "file_8_sample_011.dat",
                                                     "file_012_sample_11.dat",
                                                     "file_44_sample_11.dat" }));
        }
        private void CheckSortWithFilter(string filter, string[] reference)
        {
            var result = new List <string>();

            FilePathUtility.Sort(source_paths, filter, result);

            var sb = new StringBuilder();

            sb.Append($"filter = {filter}\n");
            sb.Append("sorted path = [\n");
            foreach (var path in result)
            {
                sb.Append($"  {path}\n");
            }
            sb.Append("]\n");
            Debug.Log(sb);

            Assert.IsTrue(CheckEquals(result, reference));
        }