What H2testw does is write files that contain a test pattern that will fill up any unused space on a disk drive. This means that it will work on SD cards, USB drives, or even hard drives (especially SSDs.). If it writes successfully then it will read the files back and verify the data.
I tried it on an 8GB SanDisk microSD that I had. It tested successfully. The complete test took about 40 minutes.
When the application completes you'll need to delete the .h2w files.
It also reports the writing and reading speeds.