the fan tested on a stopped engine is useless as the fluid enters the working chamber under gravity. The only way to test is to spin it up.

cold start test
fan engaged for 5 to 20 seconds then freewheels - good - stopping engine at this time would cause the fan to pinwheel to a stop.
fan has no engagement at all when dead cold on stopped engine and you can pinwheel it by hand - bad
noise from bearing - bad


hot test - engine temperature approximately 95 or 100C, hood closed after a drive - pop hood to test, fan should blow a gust of air on acceleration of engine. - good - at this point of time, shutting down the engine will stop the fan dead or about 1 blade pitch rotation.

hold engine at max pedal and see the fan decouple (start to freewheel) at above 3400 rpm - fan good.

no coupling when 95-100C - engine area blazing hot - bad clutch, most likely may also be bad radiator.

__________________
2012 BMW X5 (Beef + Granite suspension model)

1995 E300D - The original humming machine (consumed by Flood 2017)
2000 E320 - The evolution (consumed by flood 2017)