Mocking with Generic Repository / UnitOfWork

I'm newbee in Unit Testing and i want to ask how i can test Insert Method from Generic repo and service i have this generic repo

IEnumerable<TEntity> Get(
    Expression<Func<TEntity, bool>> filter = null,
    Func<IQueryable<TEntity>, IOrderedQueryable<TEntity>> orderBy = null,
    string includeProperties = "");

TEntity GetById(object id);

IEnumerable<TEntity> GetAll();

void Insert(TEntity entity);

void Delete(object id);

void Delete(TEntity entityToDelete);

void Update(TEntity entityToUpdate);

this unit of work:

IGenericRepository<Department> DepartmentRepository { get; }

and this service

public void Insert(string depName, List<Post> posts = null)
        {
            try
            {
                var department = new Department(depName, posts);
                unitOfWork.DepartmentRepository.Insert(department);
                unitOfWork.Save();
            }
            catch (Exception ex)
            {
                ErrorSignal.FromCurrentContext().Raise(ex);
                return;
            }
        }

and i'm want to test this service method with Rhino.Mock

 var mocks = new MockRepository();
            IUnitOfWork unitOfWork = mocks.Stub<IUnitOfWork>();
            var dep = new Department("TestDep2");
            var deps = new List<Department>
            {
                new Department("TestDep"),
                new Department("FizMat"),
                new Department("MainTest"),
            };
            unitOfWork.Stub(svc => svc.DepartmentRepository.GetAll()).Return(deps);

            DepartmentService depService = new DepartmentService(unitOfWork);
            // Act
            mocks.ReplayAll();
            depService.Insert(dep.Name);
            var result = depService.GetAll();

            //Assert

And always i got errors can any help me?