This creates a Docker image capable of running rspec tests for OpenStack puppet modules. I use it like this when working with puppet-keystone:

docker run --rm -it \
  -e SPEC_OPTS='--fail-fast --format documentation' \
  -v /tmp/rspec:/var/cache/rspec \
  -v $PWD:/module \
  -w /module \
  larsks/rspec \
  run-rspec

The run-spec script will copy the contents of the current directory (/module because of -w /module in the above command) into a temporary location, and then proceed to run:

bundle install
bundle exec rake spec_prep
bundle exec rake spec_standalone

It runs the tests in a temporary location because otherwise it will drop root-owned content into your current directory and artifacts into your .git directory.

The -v /tmp/rspec:/var/cache/rspec preserves the gems and other artifacts that are installed to support the tests, which means that subsequently I can run:

docker run --rm -it \
  -e SPEC_OPTS='--fail-fast --format documentation' \
  -v /tmp/rspec:/var/cache/rspec \
  -v $PWD:/module \
  -w /module \
  larsks/rspec \
  run-rspec --standalone

The --standalone flag skips the bundle install and bundle exec rake spec_prep steps, which means the tests will start running immediately.