We do not have a sandbox we can use for testing DupeBlocker. Is there a way to "test" DupeBlocker in production without affecting my users?
When DupeBlocker is installed in Production and a scenario is deployed, the scenario will trigger for all users. This is true even if the application is undeployed.
To "test" DupeBlocker in production without effecting all users, the best option is to add a "Current User" filter to any deployed scenario specifying that the scenario will only trigger for users with a specific profile, role, or user id. This could be based on the System Administrator profile or the user id for the specific user doing the testing. Once testing is complete the filter can be deleted so that the scenario will now fire for ALL users.
More information on how to create Scenario Filters can be found here.
NOTE: DupeBlocker will trigger for all users regardless of whether or not the application is deployed. However, visibility to the DupeBlocker Warnings, Potential Duplicates and Scenarios will be limited to just System Administrators until the application is deployed.