If I don't have a crank, I pull the bottom cover from the flywheel off underneath, and use a pry bar on the flywheel teeth to lever the engine around. If it turns at all, in any direction, it's not locked up.
I suggest turning at least a full turn of the crank (maybe two turns of the crank to give a full cycle of the valve train). I have met one 235 that seemed to turn just fine - for maybe 300 degrees - but wouldn't do a full turn. I haven't ripped into it to see the cause but am glad I was turning by hand rather than power to reduce possible damage.
