A common migration pattern when moving to docker includes running some systems (e.g. dev, staging or a prod canary) on your docker image while the production app is still running your traditional tgz artifacts (e.g. your node app with node_modules)
Let's create a travis build that creates two artifacts: (1) your docker image and (2) a tgz from the docker container.
Let's assume you have a basic dockerfile with your app.js and a package.json. The key is that the app is built into
RUN mkdir -p /usr/src/app