I have 2 bathrooms that have a total of 3 outlets from the same power source. When I press the test button on one of GFCI outlet, it will not only cut off its own power but it will also trip the AFCI breaker. Is this normal? It is rather inconvenient because I have to go to the main panel at night to reset it.
I will post an answer as I believe others will run into similar problem.
The issue is that the wiring has neutral wires from multiple circuits connected together. While this works with older breakers. It will not work with newer AFCI breaker. The solution is to clean up the wiring such that the hot and neutral pairs are isolated to individual breakers and not mixed with other breakers.
This is normal when you have them wired in a series like that. I've seen GFCIs do that as well. I found that the GFCI in my bathroom was wired downstream from a GFCI in another bathroom. If I use my GFCI tester it always pops the one closest to the breaker (which, in your case, is the breaker itself).
Note that they do make combination AFCI/GFCI breakers. You could replace the breaker and just put in a normal outlet to avoid the problem (test just the breaker instead of the breaker AND outlet)