element-plus/packages/components/virtual-list/__tests__/scrollbar.spec.ts

import { nextTick } from '@vue/runtime-core'
import { mount } from '@vue/test-utils'
import Scrollbar from '../src/components/scrollbar'
import { ScrollbarDirKey } from '../src/defaults'

describe('virtual scrollbar', () => {
  async function testInlineStyle(layout = 'vertical') {
    const wrapper = mount({
      template: `<scrollbar visible layout="${layout}"></scrollbar>`,
      components: {
        Scrollbar,
      },
    })
    await nextTick()
    const scrollbar = wrapper.findComponent(Scrollbar)
    const styles = getComputedStyle(scrollbar.vm.$el)

    Object.entries({
      display: 'block',
      position: 'absolute',
      width: 'vertical' !== layout ? '100%' : '6px',
      height: 'vertical' !== layout ? '6px' : 'auto',
      [ScrollbarDirKey[layout]]: '2px',
      right: '2px',
      bottom: '2px',
      'border-radius': '4px',
    }).forEach(([key, value]) =>
      expect(`${key}: ${styles.getPropertyValue(key)}`).toBe(`${key}: ${value}`)
    )
  }

  it('vertical inline style', async () => {
    testInlineStyle('vertical')
  })

  it('horizontal inline style', () => {
    testInlineStyle('horizontal')
  })

  it('click track', async () => {
    const wrapper = mount({
      template: `
        <div
          style="
            height: 100px;
            position: relative;
            border: 1px solid red;
          "
        >
          <scrollbar
            layout="vertical"
            :total="100"
            :ratio="25"
            :client-size="100"
            :scroll-from="0 / 300"
            :visible="true"
            ref="scrollbar"
          />
        </div>
      `,
      components: {
        Scrollbar,
      },
    })

    await nextTick()

    const scrollbar = wrapper.findComponent(Scrollbar)
    const el = scrollbar.vm.$el

    // layout: vertical; width: auto; height: 100px; scrollHeight: 400px;
    // thumb ratio: (100 / 400) * 100 -> 25   // (clientHeight / scrollHeight) * 100
    // thumbSize: 33   // scrollbar.ts computed thumbSize
    // thumb translateY: (0 / (400 - 100)) * (100 - 25) -> 0  // (scrollTop / (scrollHeight - clientHeight)) * (clientHeight - thumbSize)
    const initializeStyle =
      'height: 33px; transform: translateY(0px); webkit-transform: translateY(0px); width: 100%;'

    expect(wrapper.find('.el-scrollbar__thumb').attributes('style')).toContain(
      initializeStyle
    )

    const e = document.createEvent('MouseEvents')
    const clientY = 20
    e.initMouseEvent(
      'mousedown',
      false,
      false,
      null,
      0,
      0,
      0,
      0,
      clientY,
      false,
      false,
      false,
      false,
      0,
      null
    )
    el.dispatchEvent(e)

    await nextTick()

    expect(
      wrapper.find('.el-scrollbar__thumb').attributes('style')
    ).not.toContain(initializeStyle)
  })
})