This provides a container for running cms-builder inside.

1. Unless/until it gets rolled into the main cms-builder, you'll need this fork. Download it somewhere, uncomment the docker-compose.yml volumes line

   # - 'path/to/cms-builder/on/host:/opt/cms-builder
   

   and set the first path to the relative or absolute location of the custom cms-builder.
2. Ensure the site project has the following snippet in its .platform-project.local.settings.php file.

   // Configuration when running drush commands from inside a docker container.
   if (getenv('CMS_BUILDER_DOCKER')) {
     $cmd = "docker inspect --format='{{.NetworkSettings.Networks.bridge.IPAddress}}' {{ container_name }}";
     $ip = trim(shell_exec($cmd));
   
     // Update the host and port if running inside a container.
     $databases['default']['default'] = array(
       'host' => $ip,
       'port' => '3306',
     ) + $databases['default']['default'];
   }

3. Create a directory called test in this project root that is owned by 33:33 (sorry, I realise that's not uber-portable). It can be improved I suspect (:
4. Supply environment variables by command line or in .env.
   • SSH_KEY_FILE: the path to a private key with access to the git repo; this should be a deployment key, not a personal one! chown to 33:33 and chmod to 600.
   • PROJECT_ROOT: The absolute path to the project root. It gets directly mapped into the container running cms-builder (lovely, I know). Files will be checked out directly into this folder.
   • REPO_URL: The URL for the project repository. Must be accessible within the container.
   • REPO_BRANCH: (optional) The repo branch to checkout.
   • CMS_BUILDER_SITE: (optional) The site argument to specify to cms-builder build.
   • CMS_BUILDER_USER: (optional) The user that will be running cms-builder; defaults to 33 (www-data on Debian and derivatives).
5. In theory you can just run docker-compose up and the tests will run. It's untested. Alternatively if you need an interactive terminal you can run docker-compose run -u www-data php run-tests or just do things manually by running docker-compose run -u www-data php /bin/bash.

# Quickstart (uses sudo)
git clone XXX
cd cms-builder-docker
mkdir test
sudo chown 33:33 test
cat << ENV > .env
SSH_KEY_FILE={{path to deployment private key}}
CMS_BUILDER_PROJECT_ROOT={{path to project root}}
CMS_BUILDER_SITE={{site to build}}
REPO_URL={{repo url}
REPO_BRANCH={{branch}}
ENV
docker-compose run -u www-data php run-tests