It is possible but there are conditions, for example if you have two 
interfaces each configured with an IP address that happen to be on the 
same subnet, while you will be able to receive communication on both 
interfaces transmission will work from only one interface since as you 
can't have duplicate entries in the routing table. In such a case, you 
would need an instance of io-pkt per interface so you have two routing 
tables.

You could get away with creating an alias, so giving an interface a 
second IP address and this can be on the same subnet. When you transmit 
the packets aren't going to get sent over the wire (so layer 2) they get 
forwarded from one queue to the next within the stack. Depending on your 
requirements though this might not be sufficient for a self test.

Wouldn't pinging another host on the network be a sufficient test to 
demonstrate connectivity?