How to use the @better-scroll/core/src/__tests__/__utils__/layout.mockDomOffset function in @better-scroll/core

it('observe without MutationObserver', () => {
    const bs = createBS()
    const obDom = new ObserveDom(bs)

    jest.advanceTimersByTime(1000)
    expect(bs.refresh).not.toBeCalled()

    mockDomOffset(bs.scroller.content, {
      width: 400
    })
    jest.advanceTimersByTime(1000)
    expect(bs.refresh).toBeCalledTimes(1)
    // destroy
    bs.hooks.trigger('destroy')
    mockDomOffset(bs.scroller.content, {
      width: 500
    })
    jest.advanceTimersByTime(1000)
    expect(bs.refresh).toBeCalledTimes(1)
  })

it('should have right info for no page info', () => {
    const bscroll = bscrollHorizon().partOfbscroll
    const sliderDom = bscroll.scroller.content
    const wrapperDom = bscroll.scroller.wrapper
    mockDomOffset(sliderDom, {
      width: 0,
      height: 0
    })
    mockDomOffset(wrapperDom, {
      width: 0,
      height: 0
    })
    pagesPos = new PagesPos(bscroll as BScroll, {})
    expect(pagesPos.xLen).toBe(0)
    expect(pagesPos.yLen).toBe(0)
    expect(pagesPos.getNearestPage(0, 0)).toBeUndefined
  })
})

it('should have right info for no page info', () => {
    const bscroll = bscrollHorizon().partOfbscroll
    const sliderDom = bscroll.scroller.content
    const wrapperDom = bscroll.scroller.wrapper
    mockDomOffset(sliderDom, {
      width: 0,
      height: 0
    })
    mockDomOffset(wrapperDom, {
      width: 0,
      height: 0
    })
    pagesPos = new PagesPos(bscroll as BScroll, {})
    expect(pagesPos.xLen).toBe(0)
    expect(pagesPos.yLen).toBe(0)
    expect(pagesPos.getNearestPage(0, 0)).toBeUndefined
  })
})

fillDom(start: number, end?: number, height = TOMBSTONE_HEIGHT): this {
    if (!end) {
      end = this.list.length
    }

    for (let i = start; i < end; i++) {
      const dom = document.createElement('div')
      mockDomOffset(dom, { height })
      Object.assign(this.list[i], { dom, height, pos: -1 })
    }

    return this
  }