There is a profile called "CZ: Publication Lookup Mode". When you launch Configurator from a hosting application (e.g. Order Management), the value of the publication model profile is sent as an initialization parameter in order to determine a publication for your model. So, you can technicallly, publish the same model to a single instance with the same effectivity dates and application parameters. In one case, you can have mode = PRODUCTION and then a second publication = TEST. You control which publication is rendered to the user by the value of their profile setting.
In general, you will always want to publish with mode = PRODUCTION --- regardless of whether you are publishing to a PROD, TEST or DEV environment. Only publish to mode = TEST if you intend on retaining the existing PRODUCTION publication while you perform an isolated test of the TEST publication. For the user that needs to access the TEST publication, they will need to update the profile value.
Just to give a little background on the utility of the 'Test' Publication Mode...it provides companies that don't have separate test instances the ability to do system testing on their production instance without impacting production users. The idea is that you can define test users on the production instance (whose 'CZ: Publication Lookup Mode' profile option value is 'Test') who will see 'Test' mode Publications, while all other users continue to see the existing 'Production' mode Publications.
If you have a separate test instance where system testing is performed, there's no reason to ever use 'Test' Publication Mode.