What are you trying to achieve?
Change to a different tab by call I.switchToPreviousTab() or I. switchToNextTab()
What do you get instead?
The target page still in the background
  async _setPage(page) {
    page = await page;
    this._addPopupListener(page);
    this.page = page;
    if (!page) return;
    page.setDefaultNavigationTimeout(this.options.getPageTimeout);
    this.context = await this.page.$('body');
    if (this.config.browser === 'chrome') {
      await page.bringToFront();
    }
  }