The methodology for testing unpublished rules in DTM varies based on the type of hosting used. The type of hosting can be viewed from within the 'embed' tab in the property.
If Akamai hosting is used, then testing can be done from the web console.
Testing with DTM Switch Plug-in:
Testing can be most easily accomplished by leveraging the DTM switch plug-in discussed here: https://marketing.adobe.com/resources/help/en_US/dtm/search_discovery_plugins.html
Testing manually in the console:
If using library download, FTP delivery, or there isn't a testing environment available, testing unpublished rules can be more difficult. The easiest approach is to use a Proxy tool such as Charles to dynamically replace the production DTM code snippet with the staging DTM code snippet.