Dave tests the Stellar Phoenix Mac Data Recovery 5.0 software by intentionally unmounting one of his drives using Disk Utility. The software is then able to successfully scan and recover files from the unmounted 32GB USB drive. Dave previews the recovered files and verifies they are the original files by opening them. He is able to save the recovered files back to his Mac hard drive, demonstrating the software's ability to retrieve inaccessible data from an unmounted drive.