Phys.org's Europa Clipper high-gain antenna undergoes testing says:
The full-scale prototype antenna, which at 10 feet (3 meters) tall is the same height as a standard basketball hoop, is in the Experimental Test Range (ETR) at NASA's Langley Research Center in Hampton, Virginia. Researchers from NASA's Jet Propulsion Laboratory in Pasadena, California, the Johns Hopkins University Applied Physics Laboratory in Laurel, Maryland, and Langley are testing the prototype in the ETR in order to assess its performance and demonstrate the high pointing accuracies required for the Europa Clipper mission.
The ETR is an indoor electromagnetic test facility that allows researchers to characterize transmitters, receivers, antennas and other electromagnetic components and subsystems in a scientifically controlled environment.
It uses the image described in JPL's Space Image page Europa Clipper Antenna Prototype shown below.
You can also see it in Engadget's NASA is testing Jupiter moon probe's data-beaming antenna
Notice that there is a projection screen with an image of Jupiter and presumably Europa being projected on to it.
Kudos for "keeping an eye on the prize" but I am not sure how the projections could be part of the testing of the antenna. Perhaps the image is there to improve the attractiveness of the photo-op for publication, but that wouldn't explain the presence of the screen or the rojector.
Are there optical tests of imagers or star cameras done in this site as well perhaps?