ter b (computed) delete');

      data.c = 0;
      let w = 0;
      const w1 = (nv) => test(nv === 1, 'watch 1 working');
      const w2 = () => w++;

      sb.watch('c', w1);
      sb.watch('c', w2);

      data.c = 1;
      test(w === 1, 'watch 2 ran');

      sb.unwatch('c', w1);
      data.c = 5;
      test(w === 2, 'watch 2 ran again');

      sb.unwatch('c', w2);
      data.c = 1;
      test(w === 2, 'watch 2 removed');

      delete data.c;
      delete data.b;
      delete data.a;

      data.a = 1