First off, link -
http://mikelab.kiev.ua/index_en.php?page=PROGRAMS/chkflsh_enIt's a tiny program that requires no installation. You can use it to test any USB drive, whether that's a flash drive, SD card or USB HDD. There are several different options or tests that can be run, but the primary purpose is to write data to the device, then read it back and check for any errors. This can be useful not only to diagnose a failing drive, but to test if your flash drive is the correct capacity - there are fake drives circulating, that report a capacity of say 64GB but in reality are only 2GB and thus anything written over 2GB gets corrupted.
Chkflash will also report read and write speeds, and although there are better programs for this purpose (Atto, crystaldiskmark, HDTune to name a few depending on the drive and what you need to know) it's a nice feature to have as it just reports the speeds alongside the current operation. Right now I'm testing a 32GB USB3 drive I picked up, it's been running for 10 minutes, current speed 11.45MB/s, 33 minutes till the end of the test. That's just a write test - after this, I'll use the program to verify the written data and make sure it's all OK. The option is there to run one complete pass, one cycle, a specified number of cycles, or until an error is detected (possibly useful for write endurance tests).
There are other programs that do the same thing, I just wanted to make a recommendation for this one as it's so tiny, yet does everything those others do. It's not something everyone will have a sue for, but it's worth keeping on one side just in case.
A word of warning - writing to the entire drive will obviously destroy any data on the drive. It's intended for use with a blank drive to avoid data loss, so ensure the drive is either blank, or you don't care about the data currently on it.
