message: test(CountDown): fix test warning
diff: -import { nextTick } from 'vue';
  +import { KeepAlive, nextTick } from 'vue';
  import CountDown from '..';
  import { mount, later } from '../../../test';
  @@ -178,11 +178,13 @@ test('should format S milliseconds correctly', () => {
  test('should pause counting when deactivated', async () => {
  const wrapper = mount({
  - template: `
  - <keep-alive>
  - <van-count-down v-if="render" ref="countDown" time="100" />
  - </keep-alive>
  - `,
  + render() {
  + return (
  + <KeepAlive>
  + {this.render ? <CountDown ref="countDown" time="10000" /> : null}
  + </KeepAlive>
  + );
  + },
  data() {
  return {
  render: true,
  