 ev.clientY = 0;
      el.dispatchEvent(ev);
      for (var i = 0; i < 5; i++) {
        ev = new CustomEvent('mousemove', options);
        ev.clientX = 10 * i;
        ev.clientY = 10 * i;
        // left button until move 4
        ev.buttons = (i > 3) ? 2 : 1;
        el.dispatchEvent(ev);
      }
      el.dispatchEvent(new CustomEvent('mouseup', options));

      // down, <skipped>, track:start, track:track, track:track, track:end, up
      assert.equal(el.stream.length, 6);
      assert.equal(el.strea