;
      data.b = () => data.a + 1;

      sb.watch('b', (v) => test(v === 3, 'watch 3 working'));
      sb.watch('b', (v) => test(typeof v === 'number', 'watch 4 working'));
      data.a = 2;

      sb.unwatch('b');
      delete data.b;
      data.a = 3;

      sb.watch('b', (v) =>
        test(v === 4 || v === undefined, `watch 5 (${v}) is working`)
      );

      data.b = 4;
      delete data.b;
      sb.unwatch();
      delete data.a;
    </script>

    <div id="l1">
      <red-p sb-mark="l1.#"></red-p>