Some devices have a working "Cable test" feature, which shows status (normal/open/short, and measured length) for each of the 4 cable pairs.
Some of these devices actually have only 10/100 (not gigabit) ports, but cable test in Winbox still shows 4 pairs, so what does it really mean?
For example, DISC Lite5 accessed over the radio, powered by PoE but with no wired connection to any other device, cable test shows "open" and the same cable length for all 4 pairs. But this device only has a 10/100 port and comes with a 10/100 PoE injector which shorts the other two (PoE 45+/78-) pairs.