unit testing a unit of work

new to unit testing. I have a unit of work that I am trying to unit test. I am probably missing something simple here. I am trying to unit test the Commit method. I am using nunit and moq.

public class  UnitOfWork : IUnitOfWork
{
    private readonly DbContext _context;
    public UnitOfWork(DbContext ctx)
    {
        _context = ctx;
    }

    public void Commit()
    {
        _context.SaveChanges();
    }
}

What do I need to do to test this?