What are the tests for wilson disease?

It depends. Serum ceruloplasmin is often used and it is a poor choice as it misses about 30% of cases. Urine copper is my choice. If there's a family history or the diagnosis seems obvious, or urine copper is high, test the ATP7B gene.
Not perfect. Tests are not perfect but in the clinical setting where wilson disease is suspected, serum ceruloplasmin and serum copper levels may be helpful. Also, if the eye shows a kayser-fleicher ring or sunflower cataract, that would be indicative of possible wilson disease.