code: function fixedSaveCookies(res) {
      const cookies = res.headers['set-cookie'];
  
      if (cookies) {
          const fixedCookies = cookies.reduce(
              (cookies, cookie) => cookies.concat(cookie.split(/,(?!\s)/)),
              []
          );
          this.jar.setCookies(fixedCookies);
      }
  }
docs: Fixes jest's set-cookie behavior. Jest normally sets the cookie as a single string instead of an array.
  This function splits the string and transforms it into an array the way it should be.
  @param {Response} res
  @api private