no power steering!!!

My steering got very hard to turn. I checked the serp belt the powersteering fluid and all looks good. All I know of is a pump and rack wonder which one is bad?
How do you check them?
TIA

I had my pump blow a hose on my 96 grand am and the steering was still fine the only way I knew that the steering pump was out was because at first I thought I had a oil leak but found the busted hose. now that was a relief
just replaced the hose added fluid and kept going no system bleed down .