Not very well. You could search Google for
EICAR-STANDARD-ANTIVIRUS-TEST-FILE
and then attach it to an email to yourself. If Avast is
setup properly, it should send EICAR to the virus vault.
If you can't get into the virus vault then Avast isn't
setup properly or RPCSS is not enabled.
All AVs will react to this 70 byte file unless they are
totally dead. I keep a dozen or so virus/worms/trojans on
a floppy for when I want to test a new AV or version change.