Every module writer should use this module. There is nothing worse than uploading your beautiful module and seeing hundreds of test failures emailed back to you. My only complaint is that you actually have to temporarily edit the files to test with it. I rather suspect that there is no alternative but sadly I cannot give it 5/5 on ease of use on account of this.
This module is short and simple and solves a (somewhat common) need in testing. From the time I found it on CPAN to when I used it to verify that my tests performed correctly was just a couple minutes. It's a very handy addition to the toolbox.