Как установить Firefox и Chrome на Travis

.travis.yml

sudo: required
dist: trusty
language: node_js

env:
  global:
    - FF_BETA_PATH: './firefox/firefox'

node_js:
  - 'stable'

addons:
  # From some tests it seems you can only have one firefox addon.
  # Adding two results in the last one defined being the one installed.
  firefox: latest
  apt:
    sources:
      - google-chrome
    packages:
      - google-chrome-stable
      - google-chrome-beta

before_install:
  # Get firefbox beta and extract to tar for the test runner to use.
  - wget 'https://download.mozilla.org/?product=firefox-beta-latest&lang=en-US&os=linux64' -O firefox-beta.tar.bz2 && tar xvjf firefox-beta.tar.bz2

# Read more here: https://docs.travis-ci.com/user/gui-and-headless-browsers/#Using-xvfb-to-Run-Tests-That-Require-a-GUI
before_script:
  - "export DISPLAY=:99.0"
  - "sh -e /etc/init.d/xvfb start"