For me the best battle test was to set up a re-establishing vpn-pptp (or was it lptp?). The issue was that the daemon, name long forgotten, used a default route to establish a VPN connection, then rewrote it with an in-channel ip received at the handshake. But when it crashed or stalled, the default route didn't exist in the segment anymore and you had to re-dhcp it, somehow automagically detecting the situation.
Wonder if it solved it. If not, what's the fuss.