I've got malformed and unsupported FR10 responses in our dashboard tests now. Missed a simpler sequence: valid reading followed by a failed poll. The old reading stays green. What should I ask the developer to show about its age?
Show last successful reading time separately from the latest attempt. Then test valid, failed, failed, valid with expected display states. Stale data shouldn't look freshly confirmed, even if the old value happens to remain correct.