Sorry, I honestly didn't mean to be snarky. It was a genuine question. I couldn't really see the real-case justification for testing a clock that slowed down, s

Sorry, I honestly didn't mean to be snarky. It was a genuine question. I couldn't really see the real-case justification for testing a clock that slowed down, sped up, or went backwards. But you're right, malfunctioning clocks would be an example.