Lemme tell ya about the benches they use at Autozone and other chain stores...
They check voltage output. Yes, voltage output is controlled by a voltage regulator - but it's not what's critical, and what should be getting measured. It's current that you're interested in.
In a roundabout way (cf. Ohm's Law,) the voltage regulator works to regulate current output of the alternator - which sounds odd, until you realise that voltage and current are mathematically related in a closed system. Once you see that, it makes more sense.
Why is this a problem? Because the benches at AZ/AA/PB/... don't put a heavy load on the alternator to stimulate current output - they check for 12VDC at something like 1/2 to 1 Ampere. Yeah - not much. I have flashlights that draw more than that (SureFire pushes the filaments in their bulbs like you wouldn't believe!) 12VDC@1A won't even power a decent fan - Hell, the HVAC blower fan is good for 20-25A at full tilt, and around 12A or so at low speed!
So, how do we qualify that test? Say it with me kids: "Useless." My suggestion to you is to find a shop that does naught but alternators & starters (they're out there. I know they're out there, I've got one I've been dealing with for about fifteen years now, and I talked him into doing mail-order a few years ago...) and take your alternator in for him to put on his bench - since he's likely to be able to not only put a high-current load on your alternator, but tell you just how much current you can get out of your alternator and still get nominal system voltage (13.6VDC or so @ however many amperes.) And, if it turns out you'll need a replacement - get it from him! Yes, AA/AZ/PB/... offer "Lifetime Warranties" on their parts - catch is, you usually end up needing them. The big chains get most of their parts by the large Conex box from China, testing at the factory is a hit-or-miss proposition at best, and I've told you about the test at the shop. That Lifetime Warranty is little more than playing the odds.
You get it from the little shop, and you'll be talking to the guy that does the building and testing. He's going to wring it out on his bench before he gives it to you, and chances are quite good he can tell you exactly what your alternator will be capable of. And, pricing should be comparable.
The little guy might only give you a one-year warranty, but the best warranty is the warranty you don't need. I'd take a one-year warranty that I won't need over a Lifetime warranty that I damn sure will need any day of the week, without thinking.
