Coupon is TESTANDCODE
I had already used it before realising it was one or the other, honestly its one of the better TLD’s IMO, too bad Cloudflare doesn’t support it yet.
Edit: I should have mentioned, you have to make a tentative payment of 1 USD, which is reverted.
I’ve used them for years, never had any issues and I’d say they are very reasonably priced.