Ajax 无法删除是为啥~

blade

$('.unwant').click(function() {
            $.ajaxSetup({headers: {'X-CSRF-TOKEN': $('meta[name="csrf-token"]').attr('content')}});
            $.ajax({
                url: "{{ route('usertestsfav.destroy', [$isfav['id']]) }}",
                type: "DELETE",
                success:function(data){
                    if(data['status'] == 'success') {
                            $('.iswant i').removeClass('fas text-warning');
                            $('.iswant i').addClass('far');
                        }
                }
            })
        });

route

Route::resource('/usertestsfav', 'UserTestFavsController', ['only' => ['store', 'destroy']]);

controller

public function destroy(UserTestFav $usertestfav)
    {
        if($usertestfav->delete()) {
            return response()->json(["status"=>"success"])->setStatusCode(201);
        } else {
            dd($usertestfav->delete());
        }
    }

结果是null，是为啥呢