Jeep Repair: alternator

Question
i have 2003 jeep liberty the check engine light came on a few miles down the road the battery light came on when i got to where i was going shut car off tried to start had to jump after jumping which was about an hour after shutting car off the lights were out battery and altenator showed good on amp meter started home about a mile down the road the lights came on took to parts store to have them check lights low battery and not charging took home next day took altenator out of car to be bench tested and it tested good is this a computer problem or a diode on the voltage regulator in the  altenator going out when it gets warm

Answer
sounds like the alternator issue.   
Here is why  
1 when u take off the alternator more then likely u messed with the brushed inside and allowed it to work for a little while.
2 unless the battery light is on at teh time  the alternator is working correctly so any test will show good.

when they get hot they will tend to show up being bad more often