We need to run a real-world test at the earliest opportunity, in which our partners in Japan make test donations through our prototype Express Checkout integration. There's a moderate risk that the documentation is incorrect, and we will still not be able to fundraise in Japan, so we should work towards proving this is safe as a early milestone.
Update on the TY bug I mentioned in email: These contributions actually *will* be imported into Civi by the listener, so the donors are recorded and will get a thank you letter. Tech will still get a fail mail when the DI message is rejected.
We're creating a situation that'll be annoying to clean up as these test transactions come in. I'm not sure how to distinguish between the gateways after the fact, other than log scraping.
Inconclusive. The basic functionality worked, but we encountered an incompletely explained credit card funds error which might indicate that the JPY rails still don't work for us. We'll need higher volume to test.