authorize_net table config conflicts with testing mode

When in testing mode the primary key on the column anid in the ec_autorize_net table only allows one transaction to be tested. Authorize.net servers always return 0 for the anid when testing mode is on. On the second transaction in testing mode the module attempts to insert 0 to anid the data base returns a duplicate key error.

What should we do here? reconfigure the data base so that anid is not a primary key?