Testing public exports can be done using the bundle, as the example d3-plugin does, but this does not let you test internal functions.
reify lets you use ES6 modules in nodejs.
Run the tests using npm test.
Check the tests run!
Bump the version with npm version {major | minor | patch} as appropriate.
Edit the changelog in the README.md to move the "unpublished" items into a new section, and amend the version commit.
Publish the new version to npm with npm publish.