title: Access Docker image in Heroku CI
body: <p>I'm trying to get <a href="https://devcenter.heroku.com/articles/heroku-ci" rel="nofollow noreferrer">Heroku CI</a> setup so that, upon code checkin, I can start a server running my app and then run Webdriver tests against it to confirm that the new code change is valid.</p>
  
  <p>Locally, I run my tests using a <a href="https://github.com/SeleniumHQ/docker-selenium" rel="nofollow noreferrer">selenium/standalone-chrome-debug</a> Docker image. </p>
  
  <p>The Heroku docs <em>seem</em> <a href="https://devcenter.heroku.com/articles/app-json-schema#image" rel="nofollow noreferrer">to suggest</a> that it may be possible to use a Docker image during Heroku CI runs, but I'm not sure if this is actually possible.</p>
  
  <p>My current app.json looks like this:</p>
  
  <pre><code>{
   "name": "Test",
   "environments": {
   "test": {
    "env": {
    },
    "scripts": {
      "test-setup": "docker run -d --name se-chrome-debug -p 5900:5900 -p 4444:4444 selenium/standalone-chrome-debug",
      "test": "npm run test"
    },
    "image": "selenium/standalone-chrome-debug",
    "buildpacks": [
      {"url": "heroku/nodejs"},
      {"url": "https://github.com/heroku/heroku-buildpack-google-chrome.git"},
      {"url": "https://github.com/heroku/heroku-buildpack-chromedriver"}
    ]
  }
  </code></pre>
  
  <p>}
  }</p>
  
  <p>During the 'test-setup' phase on Heroku, I see the buildpacks (which I think I probably don't need) being installed, but there's no mention of anything relating to the Docker image.</p>
  
  <p>Then when my 'test-setup' command "docker run ..." runs, it fails because the Docker CLI is not available. </p>
  
  <pre><code>bash: docker: command not found
  </code></pre>
  
  <p>Is this even a valid approach to using Heroku CI? If so, how can I start the Docker image?</p>