How do you check and see if something is wrong with the power steering pump?

See if the belt turns the pulley right. listen to it when it idles vs. when you turn the wheel. Of course it has fluid. The tires are up to pressure. max amount is on the tire sidewall. You can turn the wheels left and right by hank when jacked up. Hydraulic tests require high pressure simulator equipment. Dealers have them. Report your findings so far.

by hand, (not hank) excuse me. Yours has an integral gear? or a rack and pinion steering gear?

Does your reservoir of power steering fluid areate (fill with little bubbles) when you cycle lock to lock? Howling noise or whine?

If you are noticing it turns easy one way but stiff the other way, you may have a bad steering box. My '89 4x4 steering box went bad. Will warn you ahead of time, don't go to Toyota for a replacement if you find that's the issue. They are more new than the truck is worth. They wanted $2300 for a new one at the dealer! Order one from Meridian. You will have to send in your old one for a core. Only cost me $300 for a rebuild. http://www.meridianautoparts.com/

Yes they encourage repair and or rebuild steering gears because they offer those parts in many markets. Using new creates much waste, so, they price it to where only basic warranty and insurance would use a brand new one...... But back to the system prechecks, when you define the problem, is it noise related, lack of lubrication maintenance? low tire pressure? vehicle hit something ? Does the fluid aerate in the reservoir?