There is a user zztest defined in the system.

This user can be used for testing.  His password is set to '******'.

Note that if you ever need to force the ordering system to think that zztest has no Subscription Date set, you can set the year of the Subscription Date to 1900 and the 'Run Keygen' conditional action code - see http://www.openvpms.org/admin/store/ca/2/edit/actions - will treat this as null Subscription Date.