The windshield wipers appear to be functioning properly.
A few images, plus a windshield-wiper-in-action GIF, capture the Tesla Model 3 out on the test track at Tesla's Fremont factory.
The Imgur uploader added some notes to describe what was seen.
"They kept removing the driver interior door panel and then putting it back on before driving a few laps. Also kept measuring the windshield wiper range/coverage."
"Side profile view. Had to zoom in quite a bit with my iPhone (sorry for the quality)"
*Note: There are two images embedded above. Click the Next arrow to scroll through.
Kittyburritoeater apparently snapped the shots and posted them along with this to Reddit:
"Decided to take a nice Saturday drive to the Tesla Fremont factory. Found the test track and peeked through the covered chain link fence to see the Model 3! Super exciting since I had never seen one before despite living in the Bay Area. Looks like they were testing the windshield wipers."
The Model 3 will be unveiled to select individuals on June 2, followed by a full public reveal sometime in July. Interestingly, we recently saw the Model 3 out testing in Cincinnati, getting some "wiper action" in a heavy rain.