On the test system we enable the Reroute Email module. This is installed on production but not enabled.
To enable the mail re-routing use Site Configuration|Reroute Email|Settings or http://test.openvpms.org/admin/settings/reroute_email/settings
Set like the following:
You MUST enable rerouting - so notification and other emails are not sent out to users. You SHOULD change the email address from its default of admin[at]openvpms[dot]org so that only the you (ie the person doing the testing) gets the re-routed emails.