Battery light comes on and off randomly

My car has a battery that’s only about a year old. There is a little or corrosion on the terminal but I cleaned off as best I can and I can’t remove the terminal because it’s hard to get off. I recently replaced the belt because it was cracked. The light comes on randomly and sometimes doesn’t come on at all while driving. For example I went about 95 and got no warning light using the radio and everything. I left where I was and the light came in after about 15 miles and went off for another 10 and then proceeded to come on and off every 10-15 minutes. I’m not sure if it’s a wiring issue or the alternator. I had the battery tested with the car off and the charge is good. Had the battery tested car on and same thing. I had the alt tested and it’s read 14.3v so it passed. I’m really not sure what it is but I don’t want to spend money to replace the alt just for this issue to continue. Does anyone have any better guesses?