Firstly, I have zero confidence in Autozone's testing abilities. They tested an alternator of mine (off the car), and promptly failed it. Turns out the alternator was fine... my charging issue was down to damaged insulation, that old 200 series issue.

So, how are the dash warning lights behaving? When the ignition is on but engine off, is the alternator light on? Are the lights dim? If so, I strongly suspect the wiring. It's really not a big deal to fix, there's a harness repair kit from IPD for about 20 bucks. You could be encountering an intermittent issue, that might only become apparent during driving because of vibration, varying load, etc.