Applicants for Fine Art are not required to register for a test. There is no written test.
However, if you are invited to interview in Oxford, there will be a practical test, where you are asked to complete a piece of work in a variety of media from a question chosen from two options. You do not need to make any special arrangements for the test, as this will be organised for you by the Ruskin School of Art.
For more information on how to apply for Fine Art, please see the relevant course page.