Am I unlucky or testing SD cards wrong?

I have bought 6 different SD cards and each one was corrupted through testing with h2testw. I did test an older SD card just to make sure the test was valid and it came through as working which makes sense as I have used it. I got the files for h2testw from a 3ds modding website which I believe to be valid. The ones that fail the test I have tried to put random files in and they are unable to copy over so it would appear that the test is right that the SD cards are defective.

I've bough Amazon Basic, Sandisk 2x, Samsung, and Microcenter 2x. The one I have that worked is Lexar. Once it fails the test, I have tried reformatting it to exFAT and tested again which it fails again. The old card was FAT32 and all the new ones are exFAT but I've been told that doesn't make a difference.

If anyone knows another way to verify storage integrity of SD cards or if I am doing something wrong, please let me know.