Is it AC or DC sol? What voltage?
Are they single coil or double coil?
There are two things that usually go wrong with solenoids, that is the coil burns out or the spool sticks.
You can test by applying the correct voltage or test to see if voltage is present.
You can push the spool over manually usually to test the air/hydraulics.
If it is AC sol, Be careful not to push the solenoid over manually when one side is energized as you will burn out the coil or blow a fuse. DC is OK to do.