I have done this many times with customers databases that they have provided to us. As long as you have network separation and you are using an SA account for SQL you shouldn't have an issue. If you are not using an SA account or are using a different password for SA in the test environment you will have to edit core/config to update the database credentials.
Many customers do this to replicate their production ePO to their test and staging environments.
I was able to successfully to a DR test of backing up our production ePO and restoring to a virtual machine. I read the documentation as inferring the DR Snapshot as being a SQL Server only feature, but it works well with SQL Server Express (assuming you have enough free space in your database). The only issue I ran into was not being able to control the SQL Server's TCP port when installing ePO in the virtual machine. For some reason our port number is different than the default and the installer does not let you change this port (you can change all of the other ports). The work-around was to only install the software needed, change the TCP port and then complete the recovery. It was not too difficult, but I thought I would post the steps I followed for the restoration:
Note: All of these steps were performed with ePO 5.1.3. We're hoping to upgrade to ePO 5.3.x later this year now that we feel very confident that we could recover if we have issues.