If it's just for testing then I concur language strings do not need not be added. I'm more thinking about the XML files and G3Ds, though.
The point I'm coming from is that, ideally, no errors would be logged if it is an expected issue, or they would become warnings somehow. For G3Ds and images this could be achieved by referencing generic models / animations / images which only indicate what would be seen here if this model / animation / image was in place. For example, for an upgrading building, display an up arrow. Those could then be referenced in the XML files so that no errors would occur if it is known and acceptable that a dedicated model / animation / image is not available.
But this is really just a nice-to-have for Shibboleth then.