Car bogs down when idle or at stop sign battery light comes on n off randomly

I have had battery n alt tested three diff places no one thinks it is it but that's what I thought to but would hate to spend $339 and then find out that's not the issue

where did you have it tested and did they load test alt,it may be an intermitent issue.

Put a new alternator in last night since car completely died out every light came on dash I just made it to my driveway thankfully now car is still bogging down when idle. When you put car from park to drive you can feel it bog down idle going way too low but doesn't stall. Battery light hasn't come back on yet though. When use AC & radio car gets really rough vibrates whole car...