Yes, if the vehicle up to 3.5 tonnes has test-drive plates and is used on Swiss motorways, it must have a valid vignette.
Any vehicles and trailers over 3.5 tonnes are subject to the LSVA / PSVA.
Related articles:
Where can I buy the Swiss motorway vignette?
Are shorter term Swiss motorway vignettes available (daily/weekly/monthy)?
What happens if I drive without a Swiss vignette?