The testing team follows Software Testing Life Cycle (STLC) which is similar to the development cycle followed by the development team. There are following six phases in every Software development life cycle model: Requirement gathering and analysis. Design.
If you simply deleted an XLS file, DiskInternals Excel Recovery will look up the file system to find all XLS files that were deleted recently, and test each file for the possibility of successful recovery.
You can also try other methods to recover workbook data when repairing a workbook is not successful. As a preventive measure, you may want to save your workbook often and create a backup copy every time that you save it. Or you can specify that Excel automatically creates a recovery file at specific intervals.