public void CleanFolder() { var folder = "C:\\Test\\ArchiveTest"; var file1 = $"{folder}\\TestDelete1.xlsx"; var file2 = $"{folder}\\TestDelete2.xlsx"; var file3 = $"{folder}\\TestDelete3.xlsx"; var daysOld = 5; Directory.CreateDirectory(folder); if (Directory.Exists(folder)) { Directory.GetFiles(folder, "*.*", SearchOption.TopDirectoryOnly).ToList().ForEach(f => File.Delete(f)); } var fileStream1 = File.Create(file1); var fileStream2 = File.Create(file2); var fileStream3 = File.Create(file3); fileStream1.Close(); fileStream2.Close(); fileStream3.Close(); File.SetLastWriteTime(file1, DateTime.Now.AddDays(-3)); File.SetLastWriteTime(file2, DateTime.Now.AddDays(-4)); File.SetLastWriteTime(file3, DateTime.Now.AddDays(-5)); FileUtilities.CleanFolder(folder, daysOld); var files = Directory.GetFiles(folder); Assert.AreEqual(files.First(), file1); Assert.AreEqual(files.Last(), file2); Assert.IsFalse(files.Contains(file3)); }