2002 Chevrolet Prizm with Fault code: P0446

My girlfriend's car has had the check engine light on for some time. She took it to a cheap repair place and it failed emissions. The guy said she'd need a whole bunch of stuff that totalled $500. We went to auto zone, had the guy clear the code, drove around for about 80 miles over the last 24 hours and the light is still out. What will happen when we take the car back in for emissions testing? Here's some info:

2002 Chevrolet Prizm
Fault code: P0446

It's a clone of a Toyota Corolla if that helps.
When you take it back for testing, it may show that a code has been erased and a monitor is not in a readiness state. If so, fails again.

Being way2old is why I need help from younger minds So how long do you have to drive for the sensor to, for lack of a better word, ready itself again? Is it possible for advance/auto zone employees to test for that state? I'd like for it not to fail a second time to avoid paying for another test.
I LIVE IN ILLINOIS AND HERE IM PRETTY SURE THEY JUST MAKE SURE THE LIGHT ISNT ON. IF IT IS - U FAIL IF NOT THEY WILL TEST IT. IF THATS THE CASE - RUN IT THROUGH AND SEE WHAT HAPPENS. IVE HAD SOME PRETTY HORRIBLE EXPERIENCES WITH THOSE PEOPLE SO GOOD LUCK!