gitlab CI

Question

我在gitlab CI共享跑步者上运行聚合物测试时遇到了问题。在运行chromedriver时我被困在Selenium error: no such session。它没有出现在运行firefox上。如何使用xvfb-run -a聚合物测试在gitlab CI中运行聚合物测试以在chrome浏览器中运行？

这是我的.gitlab-ci.yml文件：

image: node:6.9.5
before_script:
  - wget -q -O - https://dl-ssl.google.com/linux/linux_signing_key.pub | apt-key add -
  - echo "deb http://dl.google.com/linux/chrome/deb/ stable main" > /etc/apt/sources.list.d/google.list
  - echo "deb http://ppa.launchpad.net/webupd8team/java/ubuntu xenial main" | tee /etc/apt/sources.list.d/java-8-debian.list
  - echo "deb-src http://ppa.launchpad.net/webupd8team/java/ubuntu xenial main" | tee -a /etc/apt/sources.list.d/java-8-debian.list
  - apt-key adv --keyserver keyserver.ubuntu.com --recv-keys EEA14886
  - echo oracle-java8-installer shared/accepted-oracle-license-v1-1 select true | /usr/bin/debconf-set-selections
  - apt-get update -yqqq
  - apt-get install -y oracle-java8-installer
  - apt-get install -y google-chrome-stable
  - apt-get install -y iceweasel
  - apt-get install -y xvfb
  - npm install -g bower
  - npm install -g polymer-cli
  - bower install --allow-root
stages:
  - build
  - test
  - deploy
testing:
  stage: test
  script:
    - xvfb-run -a polymer test
  only:
    - develop
  tags:
    - docker

这是错误报告： http://pastebin.com/wsVMLc83

谢谢。