By “users” I assume you mean persons in CME who are not agents. If so you do not need to synchronise to get these people into WFM.
Just go the the Security Roles/Users object in the User Security Module, select the Users tab and move the people you want to add from the right hand pane into the left.
Some objects like agent, skill etc. in WFM database are identified by the same identifiers (DBID) as in configuration database. So when you move WFM production DB to test platform integrity of WFM database is broken. As synchronization process is using these unique identifiers it won’t work correctly.
I met with the same issue few years ago. The solution was to move both databases - WFM and Configuration - to Test platform. It isn’t easy task as you have to modify Configuration database manually to work properly. I did it by using set of SQL update queries but today it’s possible to use SDK to do the same job.
I can see the DBID of the configuration DB cannot connect to WFM DB but my problem is I cannot move config DB to the test platform because the configuration of the test platform will be using for another project as well. I will try to reconfig WFM in the test platform
Another way is to add an extra server to the production enviroment, and install a new set of paralell WFM apps for test purposes there.
In this way the agent dbid’s will always be correct, and all production like testing can be done.
Of cource you have to keep in mind that you cannot remove agents in CME etc for testing purposes, but you will have real statistics collected, and therefore the possiblity to run extensive testing.