I've added some custom ErrorDocument stuff to Apache but I'm a bit stumped about how to test it. I can test my custom 404 handler easily, but what about 403 and 500? Is there a standard way to test that sort of thing?
You can easily make them appear:
error 500 - make a none executable script in your cgi-bin and browse to it;
error 403 - try to browse your cgi-bin directory - it should have directory indexing forbidden;
There are 10 types of people in this world, those who understand binary and those who don't