Quid.
The anti-skid is tested well before we start engines. There are 2 anti-skid test function buttons, 1 each for both the hydraulic systems.
The test button is pushed in and the anti-skid "fault" and "inop" annunciators both illuminate. After 4 seconds, the "inop" annunciator extinguishes after which we release the button. After a further 10 seconds, the "fault" should extinguish also. This confirms the system is servicable. If any part of the anti-skid system is u/s, one or both annunciators will remain illuminated.
As I said, this begs the question whether the system can be tested correctly if all the parameters are not measurable i.e not connected etc.