In our product we get the occasional HMAC Validation Error when we do end of month processing. It's only 1 out of every 1,000 or so transactions. I'm trying to simulate the error in my test app using the sandbox and I can't get it to fail even when I put obvious garbage in.
The sequence: I am getting a token and then making a purchase. This is stuff I've done a couple of hundred times. I change the nonce so it's a different value from what generated my HMAC. So I have the HMAC that I've generated and purposely given an incorrect nonce in the header in Token Purchase.
It *NEVER* returns an error. I think it should. So maybe the sandbox is not working properly? Or maybe it is I'm not doing the right thing.
How do I simulate an HMAC Validation error in the sandbox?